Note: Descriptions are shown in the official language in which they were submitted.
ICIA 1317
DETONATOR ACTUATOR
:
TECHNICAL FIELD
This invention relates to an actuator to be
used with a detonator and to a detonator-actuating
system for use in blasting.
BACKGROUND ART
__
A conventional blasting system comprises a
series of explosive charges which are detonated by
detonators which are wired to a remote command source.
~ 10 In order to prevent breakage of the wiring connecting
; detonators set to go off late in the blasting by
earlier explosions, the detonators are provided with
delays, such that the last detonator to explode has
received its firing signal prior to the explosion of
the first. Recent improvements in the system have
included electronic delays (replacing the older, less
precise pyrotechnic delays), and the ability to
program such delays in situ. German Offenlegungsschrift
~ v~
-- 2
3301251 provides an example of the versatility of
which these systems are capable.
There has recently been provided in my co-
pending Australian Patent Application Number PH1255 a
detonator which comprises conditioning means which
renders fusehead conductors incapable of carrying a
voltage or current capable of firing the detonator
prior to the altering of the conditioning means from
a "normal" (incapable of being fired) state to an
"armed" state. This provides a considerable safety
factor not previously present in detonators.
DISCLOSURE OF INVE~TION
I have now found that it is possible to
maximise this safety factor by using such detonators
; 15 in combination with a particular actuating system. I
therefore provide, according to the present invention,
an actuator for a detonator, characterised in that
the actuator comprises control circuitry which is
responsive to input signals from the control device
applied to inputs thereof, said control circuitry
, being operable, on receipt of at least one predetermined
- input si~nal, to (i) generate an output arm signal
which is applied in use to the detonator and render
it capable of being acutated and (ii~ generate an
output actuate signal which is applied to the detonator
after a predetermined delay relative to said
predetermined input signals to cause explosive
actuation of the detonator.
By "actuator" I mean a unit whose function is
to receive signals from a control device, and to
actuate a detonator. The type of detonator with
which an actuator of the type used in this invention
is associated may be one which must be armed before it
can be detonated. An especially preferred type is
described in Canadian Patent Application No. 512,676.
However, the actuators according to my invention may be used
in association with conventional detonators by, for example,
connecting the detonator with the actuator such that only the
actuate signal is transmitted to the detonator. By
"associated", I mean that the detonator and the actuator may
be connected in some way such that signals may be passed from
actuator to detonator. This may be achieved for example, by
wiring the two components together, or by incorporating the
actuator within the detonator. However, in a preferred
embodiment, the actuator and detonator are in modular
housings, and are simply connected together prior to putting
into a blasthole. In this case, all the appropriate
electrical connections are made by the connection of the
modular housings.
The actuator for use in this invention incorporates the
delay which is so important in large-scale commercial
blasting. The specific length of delay may be built into the
actuator during manufacture, but I prefer to have the delay
programmable; this confers considerable versatility on the
system. Thus, an actuator may be programmed electronically
prior to its being inserted in a blasthole. Even more
versitility is conferred by having the actuator programmable
when the detonator is in place i~ the ~lasthole via the means
through which the input signals are transmitted. Thus, a
blast pattern can be altered at will and in complete safety
up to the time of sending of the input arm and input actuate
signals.
The electronic circuitry within the actuator stores
delay information and acts on an appropriate signal or
appropriate signals from the control device to generate
output arm and output actuate signals separated by a
selected delay time. Preferably, the ~
_.~
~l2~783
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circllitry will comprise a microcomputer with a memory
which stores at least both an arm code and an actua-te
code and preferably also the selectecl delay -time.
The microcomputer analyses input signals, and
when it identifies a predetermined signal or pre-
determined signals it then causes to be generated
appropriate corresponding output arm and actuate
signals.
The nature of the signal received by the
actuator may be any suitable signal known to the art.
It may be, for example, a single signal, and the
circuitry of the actuator may be such that this signal
can cause the generation, by reference to the arm and
actuate codes and the predetermined delay stored in
the actuator circuitry, of both arm and actuate
signals, separated by a predetermined delay. A
typical signal of this typ~ is a voltage which is in
excess of a predetermined level. Other signals may
comprise both an arm code and an actuate code, or
example, a voltage step signal wherein the leading
edge of the signal comprises an arm signal and the
trailing edge an actuate signal. I prefer, however,
that both arm and actuate signals be digital signals.
This has a number of advantages. It means that if
the actuator is conditioned to recognise certain
digital codes, it will act only on those codes.
Accidental or unauthorised firing can thus be almost
completely eliminated.
The nature of the signal or signals transmitted
by the actuator to the detonator may be any convenient
signal suitable for the purposes of actuating the
detonator. In the case of a conventional detonator,
it may be a simple voltage or current suitable for
causing the ignition of a flashing mixture and the
consequent explosion of the detonator. However, the
signal preferably comprises multi-bit digital code;
1272~8~
when such a signalling system is used with a preferred
detonator as described in Canadian Patent Application No.
512,676, it permits of degrees of security and safety not
attainable with known detonating systems.
The power to drive the actuator and the detonator itself
may be provided by any convenient means, consistent with the
fact that a detonator set to explode late in a series of
blasts should not be prone to failure by the breakage by an
earlier explosion of a wire connection thereto. The power
source *or the arming and actuating of the detonator should
therefore be in close proximity to the actuator and
pre~erably either enclosed within the actuator housing or
- capable of being connected to it. The power source may be a
battery, or preferably a temporary power source such as a
capacitor which is charged by signals from the surface. In
an especially preferred embodiment of my invention, the
capacitor is housed in a separate modular unit which can be
attached to the detonator and actuator units, such that they
form an integral unit with internal wiring and connections
appropriately joined by the act of joining together the
individual modular units.
The actuator receives its signals from a control device
on the surface. This may be a remote exploder box of the
type well known to the art. However, when the actuators of
my invention are used in conjunction with a selected control
device, the result is a detonator actuating system of
remarkable versatility and safety. I therefore also provide
a detonator actuating system comprising
(a) an actuator as hereinabove described associated with a
detonator which has an explosive charge;
and
33
-- 6 --
(b) a control device for controlling by means of
signals to the actuator the operation of the
detonator;
the system being further characterised in that the
control device comprises a microcomputer having a
memory which stores at least an arm code and an
actuate code, and wherein the microcomputer has an
arm key which upon actuation by a user causes
generation and emission to the actuator of an arm
signal derived from the arm code, and an actuate key
which upon actuation by a user causes generation and
emission of an actuate signal derived from the actuate
code, the microcomputer being such that the actuate
key must be actuated within a predetermined period
after actuation of the arm key otherwise the actuate
signal is not transmitted to said actuator.
My invention additionally provides a control
device suitable for use in a detonator actuating system
; as hereinabove described, and a method of blasting
using such a system.
The control device which acts in concert with
the actuator is adapted to control a plurality of
detonators. It comprises a microcomputer with at
least arm and actuate codes, and arm and actuate keys
~5 which, when operated, act to generate arm and actuate
signals and send them to the actuator. The microcomputer
is such that the actuator key must be operated within
a predetermined period after operation of the arm
key, otherwise no actuate signal is transmitted.
This feature adds a further useful margin of safety to
an already very safe system.
Preferably the memory additionally stores a
reset code and the microcomputer operates to generate
an output reset signal derived from the reset code
if the actuate key is not ~ctuated within the
~2~3
-- 7
predetermined period after actuation of the arm key,
the output reset signal rendering the detonators
incapable of being explosively actuated until a
predetermined sequence of output arm and actuate
siynals is received. It follows of course, that the
actuator must have appropriate circuitry which permits
of this resetting function.
In a further preferred embodiment, the delay
of the actuator unit may be calibrated from the
control device. This may be achieved by having an
actuator unit which is responsive to calibrate
signals and the microcomputer of the control device
is arranged to generate an output calibrate signal in
response to actuation of a calibrate key or a programmed
instruction whereupon timing means in the control
circuitry of the actuator unit is actuated for a
period terminated by a control signal from the control
device, the output of the timing means being stored
in the control circuitry whereby a delay period
stored therein can be calibrated on a time basis
relative to the control device. It is possible to
incorporate the calibration function in the control
device such that it is automatically carried out when
the arm key is operated.
As hereinabove stated, it is possible not only
to calibrate the delay times for accurate detonation
but also to program them from the surface. This can
be done from a suitably equipped control device.
~ further considerable advantage o my invention is
that the calibration may be carried out only seconds
before the actual blast, and the calibration signals
may be part of the blast signal itself. This allows
the use of low-cost components and reduces costs
considerably.
In one preferred embodiment of my invention,
the actuator may be equipped with a transducer unit
which is couplable thereto such that all the appropriate
~7Z:783
~ 8 --
electrical connections are made by the coupling. As
is well known in the art, a transducer i5 an electronic
device which is responsive to a preselected physical
parameter (for example, pressure or temperature) and
which produces corresponding condition signals which
ma~ then be sent, for example, to a measuring instrument
or to an apparatus affected by the parameter so as to
modi~y its behaviour. In this case, information from
a transducer may be used to vary the calibration of
the actuator, and any variation is communicated back
to the control device at the surface, which control
device is capable of receiving such signals. The
actuator can thus "talk back" to the control device
and this permits much tighter control over blasting
operations.
In some embodiments, the control device may
include a connector which enables direct connection
with the control circuitry of the actuator units so
as to read ~ata stored in the actuator unit. That
data might for instance comprise an identity code o
the user, a code number assigned to a particular
blast, and the delay period programmed into the
detonator control circuitry. The control device may
include a display such as an LCD display or a VDU for
displaying this information to the user. In a further
emboaiment of my invention, the detonators may be
receptive to control signals which prevent them from
operating, and the control device may comprise circuitry
which sends to the detonators a continuous stream of
control signals which prevents any accidental or
inadvertent firing. Suitable circuitry is described
in my co-pending Australian Patent Application No~
PH1258.
The invention will now be further described with
reference to the following drawings:
~2'727~33
_ 9 _
BRIEF DESCRIPTION_OF DRAWINGS
F.igure 1 is a schematic view of a quarry having
a plurality o charges arranged to be activated by
remote control;
Figure 2 is a similar view but showing an
arrangement in which the charges are set off by a
direct wire connection;
Figure 3 is a side view of a detonator assembly;
Figure 4 is a schematic sectional view through
the detonator assembly of Figure 3;
Figure 5 is a schematic view of lines in a
communication bus;
Figure 6 shows the circuitry of one embodiment
of a conditioning means according to the invention;
Figure 7 shows the circuitry of another
embodiment of a detonator unit;
Figure 8 is a schematic circuit diagram for an
embodiment of a detonator actuator unit;
Figure 9 is a connection table showing the
connections of the components of Figure 8;
Figure 10 is a flow diagram illustrating the
operation of the detonator actuator unit of Figure 8;
Figure 11 is a schematic circuit diagram for
another embodiment of a detonator actuator unit;
71~3
].o
Fi.gure 12 i8 a connection table showing the
connections of the components of Fi.gure 10;
;: Figure 13 is a schematic circuit diagram for an
embodiment oE a transducer unit'
Figure 14 is a flow diagram for the operation
of a transducer programme;
Figure 15 is a schematic circuit diagram of
part of a detonator controller;
Figure 16 is a connection table showing the
connections of the components of Figure 15.
Figure 17 is a flow diagram illustrating the
operation of the controller,
Figure 18 is a sectional view through an
embodiment of a detonator assembly;
,~
Figure 19 is a schematic circuit diagram for
an embodiment of a detonator actuator unit suitable
with assemblies as shown in Figure 18;
Figure 20 is a connection table showing the
connections of the components of Figure 19,
Figure 21 is a flow chart illustrating the
operation of the circuit shown in Figure 19,
Figure 22 is a schematic circuit diagram for
an embodiment of a detonator actuator unit;
Figure 23 is a connection table showing the
connections of the components of Figure 22.
Figure 24 is a flow diagram illustrating the
operation of the detonator actuator circuit shown in
Figure 22.
MODES OF CARRYING OUT T~E INVENTION
.
~igure 1 shows a quarry face 2 anc a number of
charge holes 4 drilled into the gro~nd behind the face.
A detcn~tor assembly 6 is located in each hole 4 and the
remainder of the hole is filled with a bulk charge 8
such as ammonium ni~rate fuel oil mixture which is
supplied as a powder or slurry, in aceordance with known
practice. The detonator assemblies 6 are connected by
conductors 10 to an antenna 11 or a radio transceiver
12 located in one or more of the assemblies 6. The
transceiver 12 receives control signals from a
15 controller 14 via ~ transceiv~r 15 so that the detonator
assemblies oan be actuated by rcmote control. A site
safety unit 16 may also be provided to provide
additional ~afety during layins of the charges. The
unit 16 is preferably located near the ~ntenna ll so as
20 to be likely to pick up all signals received by the
antenna ll. The safety unit 16 includes a loudspeaker
18 which is operated in emergency oonditions and prior
to a blast. The detonator assemblies 6 are arranaed to
be ac~uated at a~ accurately determined time after the
25 controller 14 has transmitted signals for the blas~ to
c~mmence. The detonator assemblies 6 can be arranged to
be ac~ivated in a precisely defined time sequence so
' that efficient use is made of the blasting materials.
The number o~ blast holes 4 can of course be ~ery
30 considerable. ~or instance, in some large scale mining
and quarrying ~perations up to 2000 holes are sometimes
required in a single blasting operation.
- 12 -
Figure 2 shows an arrangement which is similar to
Figure 1 except that communication from the controller
14 to the detonator assemblies 6 is via a wire 20
extending from the controller 14 to the conductors 10.
In this case the safety unit 16 is not recuired because
of the hard wire connection between the controller 14
anc' the detonator assemblies 6, but it could be coupled
to the wires 20 so as to sound an alarm when signals are
detected for causing actuation of the detonator
assemblies.
Figure 3 shows ~he detonator assembly 6 in more
detail. As will be described hereinafter, it com~rises
a number of interconnected modules which can be varied
in accordance with requirementsO In the illustrated
15 arrangement the modules comprise a detonator unit 22, an
actuator unit 24, a transducer unit 26, a battery unit
38, an expander unit 40 and a connector unit 42. The
units themselves can be made with various modifications
as will be explained hereinafter. Generally speaking
20 however a detonator assembly 6 in a useful configuration
will include at least the following units: a detonator
unit 22, an actuator unit 24, a battery unit 38 and a
connector unit 42.
Figure 4 shows a longitudinal cross section through
25 the detonator assembly 6 revealing in schematic form the
physical layout of the components.
The detonator unit 22 comprises a tubular housing
44 which ~or instance mi~ht be forme~ from aluminium, or
a resilient material which is a conductor such as
30 carbonised rubber. The housing 44 is provided with
transverse partitions 46 and 48 press fit into the
727~3
- 13 -
housing 44~ A first chamber 50 is formed between the
partitions 46 and 48 and a second chamber 52 is fGrmed
between the partition 46 and the closed end wall 54 of
the housing. Extending into the second chamber 52 are
two fusehead conductors 56 and 58 separated by an
insulati.ng block 60. The conductors 56 and 58 are
connected to a fusible element 62 located within a
flashing mixture charge 64. The remainder of the second
chamber 52 is filled or partly filled with a base charge
10 66 of explosive material. The conductors 56 and 58
include insulated portions 68 and 70 which extend
through ~n opening 72 in the partition 46 and into the
first chamber 50.
Located within the first chamber 50 is a circuit
: 15 board 74 which mounts electronic and/or electric
: components. The board 74 is supported by tabs 76 and 78
pressed from ~he partitions 46 and 48. The partion 48
also supports a multiport connector 80 for a bus 82.
.
The bus 82 has multiple lines which enable
20 elec~rical interconnection of the various modular units
although not all of the lines are required for the
functioning of particular unitsO Figure 5 shows
schematically the vari~us lines in the bus 82 for the
illustrated arrangement. In thi-C case there are 11
25 lines 84, B6, 88, 90, 92, 94, 96, 98, 100, 102 and 104,
some of which are required for the operation of the
circuitry on the board 74 of the detonator unit 22.
i
~ igure 6 illustrates diagrammatically a circuit 106
which is mounted on the board 74 of the unit 22. The
30 circuit 106 includes a connector 108 which allows
~'72~3
connection to selected lines in the bus 82. In the
illustrated arrangement, the line 84 is a voltage supply
line and the line 86 is a ground line for the supply.
The lines g4 and 96 carry, at appropriate times, high
5 currents which enable fusing of the fusing element 62.
The line lQ4 carries clock pulses whereas the line 102
carries an ARM signal which places the detonator unit 22
in a "armed" state so that it can be activated on
receipt of appropriate driving currents on the lines 94
10 and 96. In the illustrated arrangement, the signals and
currents on the lines 94, 96, 1~2 and 104 are derived
from the actuator unit 24. The power supply lines 84
and 86 are coupled to receive power from the battery
unit 38.
The circuit 106 includes a relay 110 having a
driving coil 112, normally closed contacts 114 and
normally open contacts 116 which are connected to
conductors 113 ~nd 115 which are connected to the lines
94 and 96 via connector 108. The normally closed
20 contacts 114 are connected by means of conductors 117 to
the aluminium housing 44 so that both sides of the
fusible elements 62 are shorted directly to the housing.
This is an important safety factor because the detonator
unit 22 cannot be activated unless the relay 110 is
25 operated. This protects the unit 22 from unwanted
operation caused by stray currents or radlo frequency
electromagnetic radiation. In the illustrated
arrangement, the relay 110 is not operated until jus~
before signals are delivered to the lines 94 and 96 for
30 activa~ion of the detonator unit. The arrangement
therefore has ~he advantage that until just prior to
when the detonated unit 22 is activated, the fuse head
conductors 56 and 58 cannot receive any electromagnetic
~ 72783
- 15 -
or electrostatic charges which might inadvertently fuse
the element 62.
The operating coil 112 cf the relay is connected to
a logic circuit 118 which receives input from lines 102
5 ana 104. The preferred arrangement is that th~ circuit
118 must receive an AR~ signal comprising a two part
four ~it code on the line 102 in order to produce an
output on line 120 which activates the relay.
The circuit 118 includes a 74164 eight bit shift
10 register 122 having eight output lines Qo-Q7~ The
circuit further includes four exclusive OR gates 124,
126, 128 and 130 connected to pairs of outputs from the
shif~ register 122. The ou~puts of the exclusive OR
gates are gated in a four input AND gate 132, the output
15 of which is in turn connected to one input of a three
: inpu~ high current AND gate 134. The circuit further
includes a f~ur input N~ND gate 136 connected to the
first four outputs of the register 122 and a second NAND
gate 138 connected to the second four outputs of the
20 register 122. The outputs from the NAND gates 136 and
138 are connected to the remainîng two inputs of the AND
gate 134. The configuration of the gates connected to
the outputs Qo~Q7 of the register 122 is such that only
selected eight bit signals on the line 102 will cause a
2S 6ignal to appear on the output 120 for activating the
relay. The signal must be such that the first four bits
are exactly the complement of the second four bits and
further the first four bits cannot be all l's or all
0's. The la~ter requirements are important in practice
30 because it prevents erroneous operation of the circuit
118 in the event that a circuit fault causinq a high
level or short circuit to be applied to the line 102.
~%~72}7~3
- 16 -
The circuit ~06 illustrated above is given by way of
example only and it would be apparent that many
alternatlve circuits could be used. If at any time a
signal is received on line 102 which is not an ARM
5 signal the output line 120 will go low and deactivate
the relay 110. The controller 14 may generate RES~T
signals for ~his purpose. In any event the logic
circuitry 118 will cause the output 12G to go low if any
signal other than an ARh signal is received. The
10 following are examples of valid ARM signals
00011110
1 0 0 0 0 1 1 1
01001011 .
~urther, the circuit 10~ could be integrated if
15 required, except for the relay.
~ igure 7 illustrates an alternative circuit 140 for
the detonator unit 22. The inputs from the bus 82 to
the connector 108 are the same as for the circuit 106
and the logic circuitry 118 is also the same as for the
20 circuit 106. An alternative arrangement is however
employed to ensure that ~he lines 94 and 96 are not
electrically connected to the fusible element 62 until
just prior to actuation on receipt of a correc~ly coded
signal ~o the logic circuitry 118. In this arrangement,
25 the circuit includes ~wo solid state relays 142 and 144.
The relays have electrodes 146 and 148 which are
permanently connected to ground. The relays include
electrodes 15Q and 152 which are connected to the
insulated portions of the conductors 56 and 58 leading
30 to ~he fusible element 62. The relays are such that the
clec~rodes 146 and 150 and the electrodes 148 and 152
~%72:7~3~
- 17 -
are in~ernally connected so that both conductors 56 and
58 are grounded and connected to the housing 44. The
relays include electrodes 154 and 156 which are
connected to the lines 94 and 96 via conductors 113 and
5 115. When the relays receive triggering signals on
~rigger electrodes 158 and 160 the internal connections
change so that the electrodes 150 and 154 and the
electrodes 152 and 156 are internally connected. In
this case the conductors 56 and 58 are nc longer
l~ grounded and are electrically connected to the lines 94
and 96 in readiness for activa~ion of the fusible
element 62. Triggering of the relays depends upon the
output line 120 from the logic circuitry 118 as will
hereinafter be explain~d.
The output line 120 from the circuitry 118 is
connected to the input of an amplifier 162 which is
connected to the junction 164 of three fusible links
166, 168 and 170 via a resistance 172. The circuit
includes an AND gate 174 one input of which is connected
20 to the output line 120 and the other input of which is
connected to the jllnction 164. Output from the gate 174
is connected to the trigger terminals 158 and 160 of the
relays. The arrangement is such that during normal
operation both inputs to the gate 174 are low so that
25 the relays are not triggered. When h~wever a correctly
coded signal is present on the line 102, the output line
120 of the circuitry ll8 will go high to a sufficien~ j
extent whereby the f~sible links 1~4, 166 and 168 will
rupture. When all links have been ruptured the junc~ion
164 will be high and hen~e the gates 174 will go high
and the relays will be triggered. ~his couples the
conductors 56 and 58 to the lines 94, 96 in readiness
for actuation. It will be appreciated that until the
~%~83
lo~ic circuitry 118 detects a correctly coded signal,
the fusible element 62 is protected by the fusible links
166, 168 and 170. The arrangement prevents inadvertent
charges or currents being developed in the conductors 56
5 and 58 due to stray electromagnetic or electrosta~ic
fields.
The detonator actuator 24 illustrateà in ~igures 3
and 4 includes a tubular housing 176 preferably formed
from aluminium. The unit includes partitions 178 and
10 18Q ~hich define a chamber 190 in which a circuit board
1~2 for electric andtor electronic components are
mounted. The board 192 is supporte~ by tabs 194 and 196
pressed from the par~itions. The bus 82 extends ~hrough
the chamber 190 and is connected at either end to
15 connectors 198 and 200. One end of the housing 176 is
formed with a keyed reduced diameter spigot portion 202
which in use is received in the free end of the housing
: 44 of the detonator unit 22. The arrangem~nt is such
that when the spigot portion 94 is interlocked with the
20 housing 44 the connectors 198 and 108 establish
appropriate connections for ~he various lines of the bus
82. The actuator unit ~4 may include an LE~ 204 which
can be mounted so as to be visible when illuminated from
the exterior of the actuator unit 24.
The actuator unit 24 performs a variety of
functions in the detonator assembly 6. Generally
speaking, it ensures that the detonator uni~ 22 is
actuated only in response to correctly received signals
from the controller 14 and at an exactly defined instant
30 of time~ Other functions of the actuator unit 24 are to
ensure correct operation of the other units in the
~ ~72~ 3
- 19 -
assembly on interconnection of the various units and to
control the operatlon of the transducer unit 26.
Figure 8 shows in schematic form one arran~ement
for the circuitry 206 mounted on the board 192 in the
5 actuator unit 24. The circuitry 206 generally speaking
includes a microcomputer with memory to store programmes
and data for correct operation of the unit 24 as well as
the other u~its of the assembly. The data includes data
relative to the precise delay required for actuation of
10 the detonator unit 22 followinq generation of a blast
commence signal (or BOOM command) from the controller
19. ~urther, the s~ored programme provides for
calibration of a crystal clock in the circuitry 206 by
the controller 14 just prior ~o operationO This ensures
15 a high level of accuracy of all the time based functions
of the assembly 6 which is ~herefore no~ dependent upon
accurately selec~ed components in the circuit 206.
~urther the accuracy would not be influenced by
temperatures and pressures in the blast holes 4 at a
20 blasting site.
The circuit 206 includes an 8085 CPU 208, an 8155
input~output unit 210, a 2716 EPRO~s 212, a 74123
monostable retriggerable multivibrator 214 and a 7437
eight bit latch 216. The components are connected
: 25 together as indicated in the connection table (Figure 9) so
as to function as a microcomputer, a~ known in the art.
Figure 10 shows schematically a flow chart of some
of the prvgramme functions which are carried out by the
microcomputer 206. When power is supplied to ~he
30 circuit by connection of the battery unit 38 in the
detonator assembly 6 a power supply voltage and ground
1%'72783
.- 20 -
are established on the lines %4 and 86. The
: ~ultivibrator circuit 214 ensures that the CPV 208 is
reset on power up. The first programming function
performed by the microcomputer is to ensure that the
5 detonator units 22 are made safe. This is accomplished
by sending eight consecuti~e zeros fro~, pin 32 of the
input/output de~ice 210, the pin 32 being connected to
the line 1~2. This ensures that the register 122 in the
detonator 22 is initialised to zero and accordingly the
10 unit 22 cannot be activa~ed because of the arrangement
of the logic circuitr~ 118. This step is indicated by
the functional block 218 in ~igure 10.
After initialisation, the microcomputer waits for a
command Xrom the controller 14 as indicated by
15 programming step 220. Commands from the controller 14
are received by the connector unit 42 and are then
transmit~ed on the line 88 of the bus 82. The command
signals on line 88 preferably comprises eight bit codes
J in which different ~it patterns represent different
20 commands. Typical command signals would be for (a) a
: request for information from the transducer unit 26, (b)
a CALIBRATE command to commence calibration procedures,
(c) a BLAST code for arming the detonator units 22, (d)
: a BOOM com~and for exploding the units 22, or a P~ESET
25 command for resetting the units 22. Accordingly, ~igure
shows a question box 222 which determines whether the
signal on the line 88 is a re~uest for information from
the transducer unit 26. If the signal is the
appropriate signal the programme will then en~er a
30 sub-routine indicated by programme step 224 to execute
the transducer interrogation and transmission programme.
A flow chart for this programme is shown in Figure 14.
After execution of the transducer programme, the main
~L~72~1~3
-- 21 -
pro~ramme returns to the question box 222. The signal
on the line 88 will ~hen no longer be a request for
information from the transducer. The pxogramme will
then pass to the next question box 226 which determines
5 whether a signal is on the line 88 is a CALIBRATE
co~mand appropriate for commencement of calibration
procedures. This is indicsted in the flow chart by
question box 226. If the signal is not a C~LIBRATE
commanQ, the programme returns and waits for an
10 appropriate command. Receipt of an incorrect command at
any time returns the programme to the start.
When the controller 14 transmits a CALIBRATE
com~.and, this will be recognized by ~he programme which
then co~mences calibration of timing of pulses derived
15 from the crystal clock 228 connected to pins 1 and 2 of
the CPV 208, as indicated by step 230 in ~igure 10. ~he
program~e then waits for a further signal on line 8B to
stop counting of the pulses a~d to record the number of
pulses counted. This is indicated by step ~32 in Figure
20 10. T}.ese programmin~ steps enable the clock rate of the
CPU 208 to be accurately correlated to the signals
generated by the con~roller 14 and transmitted on the
line 88 so that the ~ctuator unit 24 can be very
accurately calibrated relative tc the controller 14.
25 The controller 14 can be arranged to h~ve a precisely
defined time base so that it therefore is able to
accurately calibrate a multiplicity of actuators 24
which do not have accura~e~v selected components and
would therefore not necessarily have a very accurately
30 ~nown time base.
MoreoYer, the cali~ration procedures can be carried
out just prior to despatch of signals to activate the
. _ .. . . . .. . . . . .
~.2~27133
- 22 -
detonator uni~s so ~s to minimize the possibility of
; errors owing to changing concli~ions of temperature and
pressure or the like.
In the preferred arrangement, the signal on the
5 line 88 to stop the timer is in fact another BLAST code
generated by the controller 14, the BLAST code being
; selected so as to be identifiable with the particular
blast e.g. user identity, date, sequential blast number,
etc. The question box 234 in E`igure I0 indicates the
10 required progra~ning step. If the next signal received
on the line 88 is not a correct BLAST code, the
programme returns to the start so that recalibration
will be required before the detonator unit 22 can be
armed.
If on ~he other hand the BL~ST code is correct the
programme then calculates the exact delay required by
the actuator 24 prior to generating signals for
explosively activating the detonator unit 22. This is
indicated by the programming step 236 in Figure lO. For
20 instance, the actuator unit 24 may be required to
actuat~ the detonator unit 22 precisely lO ms after a
: precise predetermined delay from commencement of the
blasting sequence which is initiated by generation of a
BOO~ command by the controller 14. The information
25 r~garding the particular delay is stored in the EPRO~
212 and the programme is then able ~o calculate the
exact number of clock cycles for the microcomputer 206
required to give the precise delay. The calibration
information h~s in the meantime been stored in RAM
- 30 within the input~output device 210.
~L~7~7~3
- 23 -
Following this step, the actuator unit 24 may
signal to the controller 14 that it is functio~ing
correctly and ~hat appropriate signals have been
received. Signals for transmission back to the
controller 14 are carried by line 90 which i5 coupled tc
pin 4 of the CPU 208. This is indicated by step 238 in
~igurel0. The arming of the detonator unit 22 is
indicated by step 240 in which an ARM sîgnal is
generated on pins 31 and 32 of input/output unit 210.
The programme then is arranged to set a predetermined
period say 5 seconds in which i~ mus~ .receive a BOOM
command signal on the line 88 from the controller 14 for
activation of the detonator unit 22. If the BOOM
command signal is not received within the 5 second
15 period, the programme returns to the start so that
recalibration procedures etc. will be required in order
to again be in readiness for actuation of the detonator
unit 22. These programming steps are denoted 242, 244
and 24S in Figure 10- The BOOM con~and signal on line 88
20 ~ust be a correct eight bit pattern of signals o~herwise
the programme will again return to the start, as
indicated by the question box 248. If the BOOM command
is correct, the required delay is retrieved from the RAM
. in the input/output unit 210 ancl the delay is ~aited, as
25 indicated by progran~ins steps 250 and 252. At the end
of the delay period, a signal is passed to the
input/output unit 210 the output pins 29 and 30 of which
~, go high. These output.pins are connected by current
drivers 254 and 256 to the li~es 96 and 94 and the
30 current drivers supply a fusehead actua~ing current, say
1.5 amps, required to fuse the element 62 and ignite the
~, flashing charge 64 and thus actuate the detonator unit
22. This is indica~ed by the programming step 258.
Actuation of ~he detonator unit 22 of course destroys
,
i
~. .,
:
, .. . .. . . .. .. . . .. .
12~2~7~33
- 24 -
the detonator sssembly 6 so that the controller 14 will
be aware of successful operation o~ the detonator
assembly by its silence. If however there has been a
malfunction, the programme includes a auestion box 26C
which determines whether the CPU is still func~ioning
and if so this information is communicated to line 90
: for transmission to the controller l4. The programme
then returns to the start whereup~n the detona~or unit
is ag2in made safe, this being i~dicated by programming
~teps 260 and 262.
~ igure ll illustrates alterna~ive circuitry for the
actuator unit 24. In this arrangement, the power supply
lines 84 and ~6 are used for communication from the
controller 14 to the actuator assembly 6.
15 The same lines may be utilised for communications in the
reverse dir~ction if a transducer unit 26 is utilised.
Alternatively the line 90 may be used for that purpose
if required as shown in Figu~e ll. The circuit of
: ~igure ll essentialiy comprises a microcomputer 490
20 comprising and 8085 CPU 492, a 2716 EPROM 494, sn 8155
input/output unit 496, a 74123 triggerable monostable
multivibrator 498 and a 74377 eight bit latch 500.
These components are connected toge~her as indicated in
.
27~3
25 -
the connection table (Figure 12) so as to function as a
microcomputer as is known in the art. The principle
function of the microcomputer 450 is to carry o~t the
programming steps indicated diagramatically in Figure 10
as well as Figure 14 where a transducer unit 26 is
employed.
Power supply for the detonator assembly 6 is
derived from the valtage applied to the line 84 by the
controller 14 vi~ the conductors 10 and wires 20 of
~igure 2. The voltage is stored in a storage capacitor
S04. The diode 502 ensures the capacitor 504 cannot
discharge itself back along the path to pin 5 of the CPU
492, or to ~he controller 14 along conductors 10 and 20.
The norm~l level applied to the line 84 is selected to
15 be 2.4 volts which is sufficient to charge the capacitor
504 and maintain the CPU 492 but insufficient to
generate a response on the input pin S of the CPU 492
which is connected ~o the line 84~ ~hen signals are
required to be transmit~ed to the assembly 6 from the
controller, the controller is arranged to send a pulsed
waveform the peak voltages of which are say 5 volts
which is above the threshold level for a positive input
to the pin 5 of the CPV 492. By this means, various
coded signals can be sent from the controller 14 to the
25 assemblies. The output pin 4 could be used to apply
voltages to the line 84 for communication from the
assembly 6 to the controller, pro~ided the time
sequencing were correctly arra~g~d. Alternately, the
output pin 4 could be connected to the return
communication line 90 of the bus.
~L272~783
- 26 -
Returning now to Figures 3 ~nd 4, the transducer
unit 26 comprises a tubular housing 264 preferably of
aluminium and formed with a spi~ot portion 266 which
interlocks with the open end of the housing 17S of the
5 actuator unit 24. The shape is such that it cannot mate
with the unit 22. The housing has partitions 268 and 270
which define a chamber in which a circuit board 272 for
electronic and~or electrical components is located. The
: partitions 26~ an~ 270 can be used to support the board
10 272 as well as supporting electrical connectors 2?2 and
2?4 for the bus ~2. The housing 264 has an opening to
per~it access to a transducer element 276 which is
sensitive to ~urrounding temperature, pressure, humidity
or other parameters as required. ~or temperature
15 sensi~g the elemen~ 2~6 could be ~onded to the inner
surface of the housing 264. The transducer unit 26 may
have several ~ransduc~r elements and so be responsive to
a number of different parameters. When the spigot
. .
... . ~ .. ... . . . _ ... .... . ~ .. . . .
~L~?'~ a3
- 27 -
port.ion ~66 i~ interl~cked with the end of the actuator
un.it 24 t the connector 272 mates with the connector 200
so that the bus 82 extends through the respecti~e units.
In its simplest configuration, the board 272 would
5 simply carry any circuitry which might be necessary for
c~rrect operation of the transducer element 276 and for
co~ing of its output for application to lines 98 and 100
of the bus 82.
Figure 13 shows an example of one such circuit. In
10 this arrangement the output 278 of the transducer
element 276 is connected to the input of a voltage to
frequency converter 280 which may comprise an LM 331
circuit. The resistors and capacitors connected to ~he
converter 2~0 are well known and need not be described
15 in detail. Qutput from pin 3 of the converter 280 is
connected to the line 98 of the bus, the line 100 being
ground. The frequency of the si~nal on the line 98 will
~e proportional to the output of the transducer element
276 and thus be proportional to the temperature pressure
20 humidity etc. to which the element 276 is exposed. The
signal on the line 98 is applied to the CPU 208 for
conversion to digital form and outputted on pin 4 which
: is coupled to line 90 of the bus for transmission to the
controller 14.
Pigure 14 shows schematically a flow chart for
processing by the microcomputer 206 of the variable
fre~uency output ~ignals of the tr~nsducer unit 26. The
flow chart of Figure 14 is an example of the programme
denoted by 224 in ~igure 10. ~he first step in the
30 programme is ~o clear a timer, as indicated by programme
step 282. The timer may be located in the input/output
unit ~10. The programme then waits for the rising edge
.. .. . . . ...... . .. .. . .. .
~L27~:~7~;3
- 28 -
of the first received pulse on the line 98, as indicated
b~ step 284. ~h~ programme then starts ~he timer and
waits for a falling edge of the same pulse, as indicated
by steps 286 and 288. The timer is then stopped and its
5 value is indexed into a conversion table stored in the
EPROM 212, as indicated by steps 290 and 292. The
progra~me then l~oks up the value of the parameter such
as temperature, pressure, etc. an~ sends ar.
appropr ately encoded signal to the controller 14 via
10 line 90, as indicated by steps 294 and 2g6. The
programme then returns to the main cor.trol programme of
the actuator unit 24, as indicated in ~igure 10.
In circumstances where communication from the
detonator assemblies 6 to the controller 14 is not
required, the connector unit 42 need only be capable
of r~ceiving signals from the controller 14 and does
not need to transmit signals thereto. Thus, the unit
42 need only include a radio receiver for use wi th radio
: controlled arrangements as in Figure 1, or line connectors
for use in wire systems as shown in Figure 2.
Returning once again to ~igures 3 and 4, ~he
battery unit 38 comprises a tubular housing 298 with a
spigot portion 300 which is interlockable with the open
end of the housing 264 of the transducer unit 26. The
25 spigot 300 is also shape~ so that it can be plugged
directly into the housing 176 of the actuator unit 24 in
instances where the transducer 26 is not required. The
shape of the spigot 300 is such that it cannot be
inserted into the open end of the housing 44 of the
30 detonator unit 22. The unit 38 includes partitions 302
.. , . . . , .. . . ..... , ..... ~ .. . . .. .. . . .... . . . . .... .. . .. .. . . . . . . . .
~72~7 !33
~9
~nd 304 which define a chamber within which a bat~ery
306 is mou~ted. The battery pro~ides the power supply
on lines 84 and 86 of the bus for the other units in the
assem~ly. In some arrangements, the battery unit 38 may
be omitted by arranging for one or more of the other
5 units such as the actuator 24 to have an inbuilt battery
or to be provided with energy storage means such as a
capacitor for powering the units or to have power
supplied by the controller 14 itself, as on lines 86 and
84 via the lines 20. The battery unit 38 has connectors
10 308 and 310 to provide interconnections of the bus 82
through the unit.
~ igures 3 and 4 also show the expander unit 40 in
more detail. The expander unit comprises a tubular
housing 312 formed with a spigot 319 which can be
15 inserted into the housings of the units 38, 26 and 24 as
required. The housing has partitions 316 and 318 which
define a chamber in which a terminal block 320 is
mounted. ~he partitions also support connectors 322 and
324 for the bus 82. Extending from the terminal block
20 320 through an openin~ in the housing 312 are lines 326
which can be used to connect a number of detonator
assemblies in parallel, as shown in Figures 13 and 14.
~igures 3 and 4 also illustrate the connector unit 42.
The ~nit 42 comprises a tubular housin~ 328 with ~
25 closed end wall 330. The housing has a partition 322
which defines a chamber within which a circuit board 334
is mounted. The partition 332 also ~npports a connec~or
336. The housin~ 328 is formed with a spigot portion
338 which is insertable in any one of the ~nits 40, 38,
30 26 and 24 and the arrangement is such that the connector
336 mates with the complementary connector of the unit
.
-
~27~3
- 30 -
to which lt is connected. The unit 42 is not however
directly insertable in the detonator unit 22,
The circuit board 334 in the unit 42 may comprise a
connection block which connects the wires 20 from the
5 controller 14 to the assemblies 6, as in the arransement
shown in Figure 2. This is ~he simplest arrangement for
: the unit 42.
In another alternative arrangement for the unit 42,
the board 334 may include an electronic ~lock and si~nal
10 generator to enable activation of the actuator unit 24
i~dependently oS the controller 14. In this arrangement
(not shownJ the clock would control a signal generator
which would gener2te signals for actuator unit 24 via
the line 88 which signals would normally be generated by
15 the control ler 14.
In a further alternative arrangement, the unit 42
may include the radio transceiver 12 which receives
siqnals radiated by the transmitter 15 or the safety
unit 16, as in the arrangement of Figure 1. ~n this
20 instance, the lines 340 which comprise the input to the
circuitry ~n the board 334 would comprise or be
connected to ~n antenna for receipt of radio si~nals.
i
~igure 15 illustrates in ~ore detall part ~f the
circuitry ~or the controller 14. The circuitry
25 essentially comprises a micrOCQmputer 342 comprisin~ an
r
. . . , .. . . " . ,, _ . . . _ _ _ " . , _ ~ _ ... ~ ... . _ . _ _ . _ .. . _ . _ .. _ .. ~ _ .. . ~ . . . .
.. . . ~ ~
~7~7~33
- 31 -
8085 CPU 344, a 2716 EPROM 346, an 8155 input/output device
348, a 74123 monostable triggerable multivibrator 352 and a
74377 eightbit latch 350. These components are connected
together as indicated by the connection table (Figure 16) and
so that they function as a microcomputer as is known in the
art. The principal function of the microcomputer 342 is to
generate control signals which are used to control the
datonator assemblies 6. The microcomputer also interprets
information sent to the controller 14 by the various
detonator assemblies 6, input and output to the CPU 344 is
Vi2 pins 5 and 4 respectively. The circuitry includes a
keyboard unit 354, the keyboard having control switches S~,
S2, S3 and S4 which are operated in order to perform various
steps reguired for activation of the detonator assemblies 6.
The microcomputer includes three LED devices 356, 358 and 360
which provide a visual indication as to which signals have
been despatchsd by the computer 342 to the detonator
assembli~s 6. The programmes for the microcomputer 342 are
stored in the EPROM 346.
Figure 17 is a flowchart illustrating the important
programming steps which are carried out by the computer 342.
on power up, the multivibrator 352 ensures that the CPU 344
is correctly initialised and the programme waits for one of
the control keys Sl to S4 to be actuated, as indicated by
step 362. The programme then has four question boxes 364,
366, 368 and 370 which determine which if any of the switches
S1-S4 have been pressed. The switches can be arranged to
generate signals within the CPU 344 corresponding to
different COMMAND signals to be transmitted to the assemblies
6. For instance, the switch S1 can be made to represent
selection of a first BLAST code in which case the CPU
~L2'727~3
- 32 ~
344 generates the appropriate BLAST code. The progra~me
then arranges for the BL~ST code to be sent to the
detonator assemblies 6, as indicated by programme step
372. It follows that those detonators which have the
first BLAST code will be armed in readiness for
operation. After that signal is sent, the programme
returns to the start. The switch S2 may represent a
second BLAST code which will cause a different BLAST
code to be generated by the CPU 444 and sent to the
detonator assemblies 6, as indicated by step 374. Those
assemblies which have actuator units 24 progra~ned to
respond to the second BLAST code will thereby be armed.
The switch S3 if pressed causes the CP~ 334 to
generate a signal causing the armed actuator units 24 to
actuate the detonator units 22 connected thereto. These
i signals comprise the BOOM command and are distinguished
I by the question box Z48 in Figure 9. The despatch of a
~OOM command is indicated by programme step 376 in
Figure 13.
The switch S~ represents a reset switch which can
be activated by an operator at any stage during the
programme and if pressed a RESET command will be
generated by the CPU 344, as indicated by step 378.
Receipt of a RESET command by the actuator units 24
25 causes them to return to the start of their operating
pr~gramme, as indicated in ~igure 10. The reset signal
need not be a specially encoded signal, t;-,e actuator
units 24 ~eing progra~med to automatically reset if any
signals other than known sequence of predetermined
30 commands are received. Resetting the actuators 24 will
consequently make the detonator units 22 safe so that
~hey cannot be inadvertently exploded. Of course, a
.. . . . .. . . . . . ...
33
- 33 -
detonator unit 2' with fusible links as ~hown in Figure
7 cannot reconnect the fusehead ccnductors 56 and 58 via
the fusible links, but will remain safe while power is
available to maintain the solid state relays 142 and 144
5 on.
The controller programme has a question box 380
which is responsive to a manual or progra~me generated
input to commence calibration procedures. The
arrangement shown in Pigure 16 shows a step 382 for
10 generation and transmission of a CALIBR~E command to
start calibration. This com~,and is the input to box 226
in Figure lO.The programme then wai~s ~or a
prédetermined peri~d say one second which is accurately
,. known because care is taken to ensure that the crystal
15 ~scillator 386 and associated components connected to
p~ns l and 2 of the CPV 344 are ~ccurately selected
whereby the timing o~ the CPU 344 is accurately known.
At the end of the predetermined period, an END ~alibrate
command is generated as indicated by the step 38~. This
20 may be effecteà by generation of a valid BLAST code.
Many variations and enhancements would of course be
available in the software for the microcomputer 342.
~ igure 18 shows a detonator ~ssembly 434 comprising
a detonator unit 22, actuator unit 24 and connector unit
42. In this arrangement the connector unit 42 is
arranged for connection to the controller 14 by the
conductors 10 and wires 20, as in ~igure ~. Th~
detonator assembly 434 receives power directly from the
controller 14 and to be actuated at a predetermined
interval after voltage has been disconnected from the
wires 20. In a blast using these assemblies, i~ would
not matter if the wire 20 or c~nductors lO were broken
.. . , . . . . .. . . . ... .. . . ~ ..... . . .. . . . .. . . . . . . .
1272783
- 34
by actuation of assemblies which have been actuated
earlier since the assemblies have their own power supplies
and will be actuated at a predetermined period after the
voltage has been disconnected regardless of whether the
conductors 10 or wires 20 remain intact.
Figure 19 illustrates in more detail the circuitry
for the actuator unit 24 of assembly 434. The circuitry
essentially comprises a microcomputer 436 comprising an
8085 CPU 438, a 2176 EPROM 440, an 8155 input/output device
442, a 7~123 triggerable multivibrator 444, and a 74377
eight bit l~tch 446. These components are connected
together as indicated by the connection table (Figure 20~ so
that they function a~ a microcomputer as is known in the art.
The principle function o~ the microcomputer 436 is to
generate control signals which are used to control the
detonator assembly 436. In this arrangement, the power
supply line 84 and ground line 86 are connected to the
conductors 10 so as to establish direct connection to the
controller 14. The voltage on -the power supply line 84
charges a storage capacitor 450. The diode 448 ensures that
the "power sense" line 5 can detect the discontinuation of
power from the controller 14 on line 84 even while the
capacitor 450 maintains the actuator 436 on. The capacitor
450 is chosen so that it will have sufficient charge to power
the circuitry for the micorcomputer 436 after the voltage
supply level has been removed from supply line 84. As soon
as the multivibrator 444 operates after power on, it will
properly initialise the CPU 438. The input pin 5 of the CPU
is connected to the line 84 so as to indicate a "power up".
After power up, the microprocessor 436 will operate to
generate an ARM command which is communicated via pins
31 and 32 of the - -
- 35 -
unit 472 to the detonator unit 22. The CPU ~38 will
then wait until the voltage falls to zero or below a
predetermined level on line 84, and, after a
predetermined period, the fusehead actuatin~ current
5 will be generated to initiate the flashing charge 64 via
pins 29 and 30 to cause activation thereof.
Figure 21 is a flowchart illustra~ing the important
progra~ming steps which are carried out by the
microcomputer 436. The programme starts on power up and
10 then immediately generates an A~M command, as indicated
by step 452, for the detonator unit 22. The ARM command
will then wait for a predetermined period say 0.25
seconds before taking any other action. This prevents
premature operation of the system as the result of
lS transients or the like which might occur shortly after
po~er up, and allows time for mechanical relays in the
detonator unit 22 to switch. This step is indicated by
programming step 454. The programme then waits for the
voltage to fall on line 84, as indicated by step 456.
When the voltage on line 84 falls to zero or below a
pre-determined level the CPU will then wait a
pre-determined delay so that the detonator assembly 434
will be actuated in the correct sequence relative to
other assemblies. This is indicated by programming
steps 458 and 460 representing retrieval of the delay
period from the EPROM 44~ and thereafter waiting the
delay period. At the end of the delay period, ~he
programme then causes generation of the fusehead
ac~uating current for actuation of the detonator unit
22, as indicated by step 462. The programme then passes
to a question box 464 which ascertains whether the
programme is ~till operating indicatins whether the
.
.. . . . .. . ~ . ..
'~7~3~
- 36 -
detondtor unit 22 has been ~uocessfully actu2ted or not.
I~ ic has ~ot, it will return to ~he 6tep 452.
Fi$ure 22 shows an altern~tive circuit for use in
~he actuator unit 24 o' ~he asser~iv 436, show~ in
S Figure 19. In this ar- ngement the de~onator assem~ly
434 is arranqed to ~e actuateZ a prede~ermined perio~
after power has been applied thereto via the conduc~ors
10 and ~ires 20 of the arranqemen~ shown ir. Figure 2.
The circuit of Figure 22 essentially comprises a
mic~ocompu~er ~66 comprising an 8085 CPU 468, 2 2176
E~RO~ 470, and 8155 inpu~/output unit 472, a 7412'
monostable triggerable multi~ibra~or 474, and a 74~77
e~ght bit latch 476. These comp~nents are connected
toge~her ~s indicated by ~he co~ectioA table(Fig~ 23) so
that they fu~ction as a microprocessor as is kaown i~
the ar~. The microcomputer has programmes s~ored in its
EPROM ~70 for car~ying out primærily the pro~ramme ~hown
dia~ramatically in the flowohart of Fiqure 24 .
On the application of a volta~e above a
preae~ermined l~vel, e.g. 2 . 4 volts, on the supply line
R4, the ~ulti~ibrator 474 will reset the CPU 468 and
various circuit and progr~in~ func~cions are properly
: initialised. The C~U 468 will ~hen start run~ing and
its first fu~ction will be .~o generate an AR~: comman~ on
pins 31 and 32 of the ~nit 472 for the detonator unit
22. This is indicated by the programming step 478 of
Figure 24. The programme the~ waits a fixed delay
pexiod 2S indicated by step 480. The fix~d delav period
... .
~l~72~7~3
- 37 -
6ay 0.25 ~ec~n~s, is provided ~o as to prevent
inadvertent operation c~used by transients or the like
which might occur shortly sfter power up, and allow time
for relays to switch. All of the detvnator assemblies
for a particular blast would have the same fixed delay
5 period. The programme then reads a pre-selected delay
from the EPROM 470, as indicated by programme step 482.
~he pre-selected delay can be different for particular
actuator units 24 so ~hat a predetermined blast ~equence
can be established. The progra~me then w~its for the
10 preselected delay period, as indicated by programme step
~82 then causes generation of the fusehead actuating
current via pin~ 29 and 39 of the unit 472 as indica~ed
by ~tep 486. The BOOM command appears on pins 29 and 30
of the unit 472. The BOOM command causes the deto~ator
15 unit 22 to explode.
I the unit 22 fails to explode, the programme will
pass to question box 488 which will return the pro~ramme
to ~he start if the microcomputer 466 has remained in
tact.
2~ ~any ~odifications will be ~ppar~nt to those
skilled in the art. For instance, integration
techniques could be used to integrate circuits which are
~hown in non-integrated form~
INDUSTRIAL APPLICABILITY
.
25 The blas~ing system according to my invention is useful
in commercial blasting. The system offers higher
degrees of versatility, safety and security than are
attainable by systems currently known to and used by
the art. The components of the blasting system can be
30 easily manufactured u~ing equipment and techniques
known to the explosives and electronics industries, and
their use in the field is straightforward.
.. ~ ..... .. . . . . . . . . .. . . . . . . . . . .. . . .
