Note: Descriptions are shown in the official language in which they were submitted.
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¦I The present invention relates to control devices re-
sponsive to infrared radiation and, more particularly, to devices
responsive to heat emanating from a human body for controlling
an auxiliary current line.
¦¦ Control devices responsive to heat emanating from a
¦¦human body are known and are often used to provide a signal
activating such items as security alarms when a person penetrates
a secured area. These control devices, however, are often
difficult to install, particularly in existing buildings, and typ-
~lically lack adaquate discrimination to prevent false triggering.
¦jMoreover, many of the known control devices simply produce a sig-
nal activating an alarm or the like when a person first enters a
¦ particular area, and thus cannot be adapted readily for other
!Idesirable uses.
¦ One of these desirable uses is the con~rol of auxiliary
¦¦current lines powering such items as room air conditioners and
¦linterior lighting. These items often waste energy by being left
on needlessly when no one is actually within the area served by
¦these items.
¦ Consequently, it is an object of the present invention
¦to provide a device controlling a current line in response to the
¦¦presence or absence of a human body.
It is a further object of the present invention to pro-
vide such a device having good discrimination so as to minimize
Ifalse triggering.
An additional object of the present invention is to pro-
vide such a device which is relatively easy to install even in
existing structures.
; Another object of the present invention is to provide
such a device which is compact, and can be manufactured simply
and easily.
Accor~ing to the present invention, the device comprises
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¦ detection means including an infrared detector preferably comprised
¦l of a thermopile formed by thin-film techniques for producing
detection signals in response to infrared radiation in the fre-
l¦~uency spectrum emitted by the human body. These detection signalc
5 ¦1 are amplified by a suitable circuit which also produces reset sig-
nals for those detection signals resulting from actual movements
of a body emanating the detected infrared radiation. The reset
signals are received by a timing circuit which produces a control
signal opening the controlled current line after failing to re-
¦ ceive a reset signal for a predetermined time period. In this way,the current line is opened only when movement of a human body is
, not detected by the device within a predetermined time period.
Preferably, inhibiting means are cor.nected to the timing circuit
for activation by the control signal for maintaining the current
line open until a reset signal is again produced to thus turn the
item powered by the current line back on when a person enters the
area served by the item.
, The thermopile of the detector is preferably housed ~ :
¦ within a container having a small opening having a diameter of,
¦ for example, 0.18 inches and being covered by a filter formed of
¦ infrared-transparent germanium coated to pass only a narrow band
¦ containing the frequency spectrum. The container may be fitted
¦I w1thin a housing having an outer window including such materials
Il as potassium bromide or silver chloride so as to-be infrared
transparent and spaced from the detector to prevent convective
heat transfer thereto.
The circuit of the device receiving the detection
siynals preferably includes a plurality of amplifier stages laving !
~ respective filters eliminating detection signals changing at a
,, frequency below a predetermined value. By these means, the circuit
retains only higher fre~uency signals corresponding to movement
of a body emanating in~rared radiation in the desired spectrum.
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~dditionally, the circuit may include a preamplifier stage having
'a pair of transistors formed on the same substrate and coupled
, together through their respective emitters for reducing adverse
Ijtemperature effects. Preferably, respective capacitors are
,¦connected across the base-emitter junction of each transistor
of this pair and the collectors of the transistors are connected
¦to respective inputs of an amplifier having a gain of, for example,
573.5.
More particularly, -the circuit may include a second
lamplifier stage including a second amplifier receiving the output
from the preamplifier stage and containing a filter having a cut- ¦
off frequency for eliminating low frequency signals as noted above.
¦Preferably, the cut-off frequency is approximately 0.129 Hz and
jthe second amplifier has a gain of approximately 14. Additionaly,
a third amplifier stage may ~e used, and it includes a third
amplifier having a gain and filter similiar to those of the second
I amplifier. The circuit also may include an encoding circuit
connected to the output of the last amplifier stage for producing
¦Ithe reset signals. The preferred encoding circuit would include
¦ two parts, the first of which would produce a reset signal in
¦ response to a signal from the third amplifier stage becoming more
¦¦positive, and the second part would produce a reset signal in
¦response to a signal from the third amplifier stage becoming more
negative.
li
~~ In preferred form, the timing circuit includes a clock
producing a train of clock pulses directed to a counter producing
the control signal after a predetermined nul~ber of clock pulses
;has been counted. The counter may also include a reset port
'receiving the reset signals in order to start the counting of the ,
clock pulses over. The counter may include a plurality of outputs
each producing a respective control signal after counting a
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l,different number of clock pulses. In this way, a particular output
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may be selected for adjusting the time period.
When using the timing circuit described above, the
- , inhibiting means may include a counter yate interposed between the
'I clock and the counter. This counter gate would have a first input
ll receiving the clock pulses and a control input adapted to receive
a block signal in response to the control signal from the timing
¦rneans for blocking the counter gate.
~j The electronic circuitry of the device of the present
!l invention is preferably housed in a housing having a depending
Ineck portion holding the infrared detector in its lower portion
and including the outer window noted above. The housing further
includes a retaining element adapted to be secured to the lower
~portion of the neck portion so that the device can be installed to
la ceiling or wa'l by inserting the neck portion through an opening
in the ceiling or wall and securing the retaining element to the
lower portion of the neck portion. The neck portion may further
~ include a separate locator fitting axially therein and having a
,Irecess in its end portion for receiving the infrared detector.
Structures are formed on the upper portion of the loca-tor for
mating with complementary structures on the nec}~ portion. In this
way, the infrared detector can be positioned accurately in place
n qulte a simple manner. These complementary structures may,
in preferred form, include longitudinally e~tending ribs protruding
l¦from the locator and longitudinal recesses formed in the neck
portion.
Preferably, the end portion of the neck portion is
generally circular in cross sec~ion and includes a bottom wall
having a central opening therethrough. The outer window of the
housing lies over this central opening and has an O-ring lying
thereover. The O-ring is held in place against the outer window
by a rim portion of the locator. Further, the opening in the
bottom wall of che neck portion is preferably in the form of a
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conical frusturl flaring outwardly at an angle of between
approximately 'i0 and 120. Also, the retaining element would
I have an openincJ therein formed as a conical frustum and adapted
Il to align with the opening in the bottom wall of the neck portion.
1~ Other features, advantages and objects of the present
invention will become apparant from the following description of
i a preferred embodiment thereof taken in conjunction with the
Il following drawings, in which:
¦I Fig. 1 is a block diagram illustrating electronic
l1 components of a preferred embodiment of the present invention;
¦ Fig. 2 is a sectional view of the structural aspects of
the preferred embodiment;
Fig. 3 is a top plan view of portions of the housing
I taken along line 3-3 of Fig- 2, absent the locator 16 and detector 26
l Fig. 4 is a side plan view of the locator shown in
Fig. 2; and
Fig. 5 is a diagram illustrating the circuit of a
preferred embodiment of the present invention.
¦ The control device of the illustrated embodiment includes
t ~ ~ ~ S
~ a housing 1 formed of a synthetic material such as Aa~rcopolomer
plated with a metallic finish by known vacuum techniques. The
housing includes a generally rectangular base portion 2 having a
¦~ central recess area 3 surrounded by a peripheral seat portion 4.
I The peripheral seat portion carries a plurality of spacers 5 1ying
1 oppositely to spacers 6 carried by the back plate 7 of the housing.
A printed circuit board 8 is held between aligned spacers 5 and 6
and carries the majority of the electronic components of the
il device. Depending from the central recess area 3 is a depending
neck portion 9 adapted to receive a retaining element 10 on its
;, lower portion as will be explained more fully below.
The electronic components of the device are illustrated
generally in the block diagram of Fi~. 1 and include a detector
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25 able to produce detection signals in response to infrared
radiation in the frequency spectrum emitted by the human body.
The ~etector includes a heîmetically sealed container 26 fitted
Il within the lo~-er portion of the neck portion 9 and having a small
¦¦ opening of the order of 0.18 inches covered by a filter of infrarec _
transparent germanium coated to pass only a narrow band of infrare
radiation containing the frequency spectrum emitted by the human
body. This band preferably includes radiation having only wave-
ll lengths between 8 microns and 13-l/2 microns so the filter thus
il serves as an optical filter narrowing the spectral sensitivity of
the detector. Within the container 26 is a small multijunction
,~ thermopile formed from evaporated bismuth and antimony by known
thin-film techniques. A suitable detector is the model 2M
~~ thermopile detector sold by ~exter Research Center of Dexter,
1I Michigan.
~¦ ~he signals produced by the infrared detector 25 are
- ' first amplified to a workable level by a preamplifier 30 and then
passed to a series of amplifier stages 40 and 50 hav;ng respective !
Il low pass filters for eliminating those signals changing at a
li frequency below a predetermined value. The infrared detector will
respond with relatively low frequency signals to changes in temper-
~l ature of a stationary object within its field of view, an~ will
¦¦ respond with higher frequency signals to movements within the
I field of view of an object having a relatively constant temperature
level. Consequently, the low pass filters sill serve as elec-
tronic filters eliminating signals produced by mere temperature
; change of a stationary object, such as those produced by incident
radiation from a carpet being warmed or cooled from sunlight or
' an incandescent light bulb, and retain the higher frequency signals
corresponding to movement of a body emanating radiation in the
desired spectrum.
The signals emerging from the amplifier stage 50 are
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converted to a binary voltage level by an encoding circuit 60
divided into two parts. Part 60a responds to those signals be-
I coming more positive so that motion of the infrared source towards
¦I the detector will be converted to a binary voltage level, and part
¦ 60b responds to those signals becoming more negative to therebyprovide a similiar binary voltage level for motion of the infrared
isource away from the detector.
The binary voltage level from the encoding circuit 60 is
llpassed to the reset port oE a time-delay circuit 80 which produces
ll a control signal after failing to receive a signal at its reset
I port for a predetermined period of time. This control signal is
¦Isent to a control unit 100 including a relay for opening a current
iline to be controlled so that the current line will be opened
'whenever movement of a human body is not detected within the time
period set by the time-delay circuit 100.
l The circuit diagram of Fig. 5 illustrates the preferred
¦ circuitry in more detail. A regulated power source 11 is formed
by the one amp bridge rectifier lla connected through the 470
I~Kohm resistor llb across the 35 microfarad filter capacitor llc
¦¦ and three terminal 12V regulator lld. The regulated voltage from
¦the power source is divided by the two 390 Kohm resistors 12a and
12_ and sent to the splitter formed by amplifier 13. Amplifier 13
may be one of the group of four amplifiers designated A2 and pro-
~ ~ vided by a single integrated circuit such as the LM324N sold by
~iNational Semiconductor. In such case, pins 12 and 13 of the int~-
grated circuit wou~d serve as the inputs of amplifier 12 and pin
14 would serve as its output. Amplifier 12 provides a 6V supply
of proper impedance to the detector 25. The preamplifier 30
includes a pair of NPN transistors Ql and Q2 formed on a common
substrate and coupled together through theil~ respective emittels.
The two transistors will thus be at the same temperature to rc~cluc~-
~internal noise, and receive a push-pull input from the detecto~-
g~
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Il 25 to reduce the undesirable effects of ternperature drift and the
¦l like. The transistors have a common emitter resistor 31 preferabl~
of 249 Kohms and respective 150 picofarad dipped silvered capaci-
I tors 32 and 33 connected across the base-emitter junction of each
1 transistor for bypassing undesirable noise. The collectors of
! transistors Ql and Q2 are connected to respective inputs of
amplifier 34 and thus amplifier 34 will sense any difference in th~
potential drop across the 349 Kohm resistors 35 and 36 connected
to the respective collectors of transistors Ql and Q2~ Amplifier
34, in a manner similiar to amplifier 13, may be one of a group of
four amplifiers designated Al provided on a single lntegrated
circuit LM324N and could be provided by usiny pins 2 and 3 as the
inputs leading off the collector resistors and pin 1 as the output.
Resistors 37 and 38 are selected so as to set the closed loop gain
of the preamplifier 30 to 573.5 and, preferably, would be 390 Kohm
and 820 Kohms, respectively.
The amplifier stage 40 includes an amplifier 42 receiving
the output from the preamplifier 30 through resistor 43 of prefer-
~lably 82 Kohms and has a gain of approximately 14 set by resistors
45 and 46. Resistors 45 and 46 may thus be of 390 Xohms and 27
Kohms, respectively. Amplifier 42 may be formed from the Al group-
ing of amplifiers and is formed by using pins 5 and 6 as the input~
and pin 7 as the output. Capacitor 48, a 15 microfarad tantalum
¦Icapacitor, operates with resistor 43 to provide the low-pass filter
1I which will thus have a cut-off frequency of 0.129 Hz. The amplifi~
er stage S0 is similiar to amplifier stage 40 and includes an
amplifier 52 formed by connecting the pin 10 of the A2 grouping to
the output of amplifier stage 40 through r`esistor 53 of preferably
, 82 Kohms. The gain of the amplifier stage 50 is also 14 and is
provided by resistors 55 and 56 connected to input pin 9 of the A2
grouping. Capacitor 58 is similiar to capacitor 48 and thus pro-
vides with resistor 63 a low-pass filter having a cut-off frequency~
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of 0.129 ~z.
The output of amplifier stage 50 is provided at pin 8 of
l! the A2 grouping and is directed to the encoding circuit 60. In
¦Ipreferred form, the encoding circuit includes two parts each com-
j prised of respective slope detectors. The first slope detector is
made up of resistors 62, 63 and 64 and capacitor 66 toyether with
amplifier 68 provided by using pins 2 and 3 of the A2 grouping as
¦inputs and pin 1 as the output. This first slope detector produces
l a binary output signal in response to an output from amplifier
stage 50 becoming more negative. The second slope detector in-
cludes resistors 72, 73 and 74 connected with capacitor 76 to
amplifier 78 and produces a binary ou-tput signal in response to an
¦output of pin 8 of the A2 grouping becoming more positive. Ampli-
fier 78 is also provided from the A2 grouping by using pins 5 and ¦
6 as the inputs and pin 7 as the output. Preferably, resis-tors
62 and 72 are of 3.9 megaohms and resistors 63 and 73 are 27 Kohms.
Further, resistors 64 and 74 may be 390 Kohms and capacitors 66
and 76 may be 2.2 microfarad tantalum capacitors.
The output of either of the slope detectors is passed to
the time-delay 80 and, more particularly, to the reset port of
counter 82. The counter receives as its input a train of clock
pulses generated in a clock circuit comprised by an astable oscil-
lator formed by inverters 84 and 86 and the one megaohm resistor
l¦87 and 0.1 microfarad capacitor 88. The pulses from the inverter
11 84 are directed to one input of a counter gate fGr~ed by NAND
circuit 90 which together with inverter 92 provides an inhibitor
to be described more fully below. Since the NAND circuit 90 is to
~be used, the inverters 84, 86 and 92 may also be constituted by
' NAND circuits having their respective inputs connected. In this
way, a single integrated circuit having four NAND gates, such as
the CMOS quad NAND circuit 4011B, may be effectively used.
The counter 82 is preferably the CMOS circuit 4040B
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Il binary counter which has a plurality of outputs. In the preferred
il embodiment, output pins 13 and 14 are used which develope an
¦¦ output pulse 4 minutes and 8 minutés, respectively, after a pulse
¦ is received at the reset pin 11. In this way, pins 13 and 14 may
1l alternatively be selected to thereby provide a 4 minute or 8
minute delay. Of course, other delay periods can be obtained by
selecting different output pins or changing the frequency of the
astable oscillator by varying the values of resistor 87 and
capacitor 88.
The inverter 92 receives the output pulse from the counter
82 to provide a "low"output to one control input of the counter
gate to thereby block the pulses leading from the astable oscil-
lator to the counter. In this way, the output signal from the
counter will be maintained until a signal is again received at the
reset port of the counter, presumably by a person entering the
field of view of the infrared detector.
The output from the counter is used as the control signal¦
to the control unit 100. The control unit includes an NPN switch-
ing transistor 101, such as a 2N3471, having its base connected
through a 15 Kohm resistor 102 to the selected output of the count-
er 82. The control signal turns transistor 101 on to activate a
relay adapted to control an auxiliary current line, preferably
through a step-up transformer.
The control device may be installed easily even in exist-
ing buildlng structures and the like due in large part to the de-
pending neck portion carrying the infrared detector in its lower
portion. The base portion 2 may be placed behind an opening 14a
,in a ceiling or wall unit 1~ or the like with suitable resilient
spacing elements 15 placed between the base portion and ceiling
~lunit. The neck portion 9 may then be inserted through the opening~
~ a until its lower portion protrudes into the service area of the
Il _
litem controlled by the auxliary current line. The retaining
ll
element 10 will then be tightened down on the protruding lower
portion to secure the control device in place. The retaining
element 10 preferably is threaded onto the lower portion of the
llneck portion, but may be secured in other ways, such as by being
Ipress-fitted or snapped into place through resilient locking tabs.
The neck portion 9 is generally circular in cross-section
~and receives a locator 16 fitting axially therein and having a
,Irear surface 17 secured to the printed circuit board 8 by deform-
, able posts 17a fixed within mating aperatures in the board. In
i its end portion, the locator 16 has a recess 18 surrounded by a
rim portion 19. The back wall 18a of the recess receives and
holds the container 26 of the infrared detector. The u~per portion
of the locator 16 has a plurality of longitudinally extending ribs~
1119 spaced circumferentially therearound. These ribs 19 are comple
¦ mentary with longitudinal recesses 20 formed in the inner wall of ¦
l the neck portion 9. In this way, the locator will be easily placed
¦ and held within the neck portion to position the detector accu- i
Irately within the control device.
¦ The end portion of the neck portion 9 includes a bottom
¦wall 21 having a central opening 21a therethrough. An outer
window 22 lies over this central opening and is held in spaced
~relation from the detector 25 by an O-ring 23 compressed between
the rim ~ortion 19 of the locator and the outer window 22. The
outer window prevents air currents from reaching the surface of the
r 25 j detector container 26 to thereby reduce false triggering of the
detector by convective heat transfer. The outer window 22 must,
of course, be transparent to infrared radiation and preferably
would include such materials as potassium bromide or silver
chloride.
The field of view of the detector 25 is defined by the
geometry of the opening 21a in the bottom wall of the neck portion
li and the opening 24 formed in the retaining element 10. The
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openings 21a and 24 are each preferably in the form of a conical
frustum flaring outwardly -to provide a conical field of view
having an angle of between 90 and 120 at its apex.
ll As an optional feature, the control device may be pro-
!i vided with a cover member fitting over the entire housing and
adapted to be mounted to a wall or ceiling unit. In this way,
Il the device rnay be mounted directly to the outer surface of the
¦I wall or ceiling unit without -the need ror providing a hole
therethrough. Such a cover could be snapingly engaged with the
I housing and would, of course, have a small opening aligned with
the detector.
From the above, lt is apparent that the present invention
includes important features in both its circuitry and structural
relationships. The control device may be installed readily and
includes both optical and electronic filters to provide a high
descrimination. Further, the device can be adapted for many uses I
and, as set forth above, can be made to close a current line to
interior lighting or the like whenever someone enters the field
of view of the detector, and will keep the current line closed as
long as even slight motion,such as simple hand motions or even
writing at a desk, is made within the detector's field of view.
Thereafter, the control device will open the current line soon
after no motion is sensed within the detector's field of view,
I i.e. after all persons have left the field of view, and will re~
j' close the current line should someone again re--enter the field.
These and other impcrtant features may be employed in
forms other than those described for the preferred embodiment and
still incorporate the substance of the invention which is intended
' to be defined by the appended claims.
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