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Патент USA US2403609

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July 9, 1946.
" Filed Dec. 19; 1942
u I»
Patented July 9, 1946
Theodore B. Perkins, West Orange, N. J ., assign
or to Radio Corporation of America, a corpora
tion of Delaware
Application December 19, 1942, Serial No. 469,757
7 Claims.
This invention relates to relay systems, and
more particularly to an automatic photoelectric
relay for: controlling the operation of a device
in response to a sudden change of light intensity,
substantially independently of the actual light
Photoelectric relays are widely used to detect
changes in‘ light intensity for the purpose of
giving alarm, starting‘ or stopping various mech
(Cl. 250-415)
is connected to the junction of the resistor RI‘!
and the capacitor C I 9.
The anode circuit of the tube I5 includes'a re
sistor R25 and a relay 21. The relay 21 is con
nected to one side of an A.-C. supply 29, and
through a resistor RBI to the cathode of the tube
I5. The other sidev of the A.-C. supply 29 is con
nected through a switch 33 to the resistor RZI.
A stepdown transformer 35 is provided for ener
anisms, controlling: operations in manufacturing, 10 gizing the heater of the tube I5. A switch 31
and. 80.1011.
is included between the junction point II and
One dif?culty which‘ frequently arises is caused
the adjustable tap 23. The adjustment and op
by changes in the ambient illumination which
eration of the circuit is as follows:
may produce false operation of the relay. In gen
The output of the photo cellv I is applied to
eral, the more sensitive the system is made to 15 both the, grid and the cathode of the tube I5
small changes in light intensity. the more seri
ousthis-e?ect becomes.
through circuits of different time constants,
Bil-C9 and RI"I—CI9 respectively; With the
It has been proposed to provide relays of this
proper adjustments of these time constants, slow
type’ with such characteristics that they respond
ly varying light will not establish a potential
only to the. rate of change of light intensity, 20 which will ionize the gas in the tube I5 because
rather than to the intensity itself. This enables
the potentials applied to the grid and cathode
the system to be made extremely sensitive to
are equal. The time constant of the circuit
variations which take place at greater than a
RI'I—CI9 and of the circuit R'l—-C9 may be ad
predetermined rate, without encountering dii?
justed to determine the fastest and slowest varia
culties due to the relatively much slower ambient 25 tion, of light to which the circuit will respond.
variations caused by daylight and darkness,
The relativetime constants of the circuits RH
clouds, etc.
CI9 and R'I—C9 in combination with the po
Accordingly it is the principal object of the
larity of the phototube, its polarizing battery and
present invention to provide an improved‘ method
the initial condition of the gas tube, I5, as de
of. and.‘ means. for providing. response to change in 30 termined by the setting of the tap 23, determine
illumination, independently of the degree of light
whether a decrease or an increase in light will
energize or deenergize the relay. For example:
A further object is to provide an improved pho
For the polarity of the phototube and polarizing
toelectric relay circuit arranged to enable con
battery shown in the sketch, and theadjustment
venient adjustment of the rate of change of light
of the tap 23 such as not to ?re tube I5 with
intensity to which response will occur.
switch 3'! closed, when RI 'I—-C I 9 is of higher time
These and other and incidental objects will
constant than that of R9—C9 a decrease in light
become apparent to those skilled in the art upon
will operate the relay. When the time constant
consideration of the following description, with
ratio is reversed an increase of the light will
reference to the accompanying drawing, which 40 operate the relay. A reversal of the phototube
is a schematic circuit diagram of an embodiment
and polarizing battery will cause the effects of
of the invention.
the ‘time-constant ratio to be reversed. Initial
A photoelectric cell I is connected to a direct
adjustment of the tap 23 such as to ?re the tube
current source such as a battery, 3, through a
I5 with switch 3'! closed will necessitate reversed
load resistor, R5. A resistor R‘! and a capacitor 45 time constant ratios on phototube and polarizing
C9 are connected in series across the load re
battery polarity, as described above to cause de
sistor R5. The junction II between the resistor
energization of the relay.
R1 and capacitor C9 is connected through a re
The resistor RI3 is included to prevent the re
sistor RI 3 to the control grid of the gas ?lled
lay from “holding” subsequent to its actuation.
discharge tube I5. The tube I5 may be an 50
Without this resistance the capacitors C9 and
RCA 2051 or equivalent type. A second network,
CI9 will charge, whenever the gas in the tube
comprising a resistor RI1 and a capacitor CI9
I5 is ionized, and will remain charged during the
is connected across the load resistor R5. The
negative half cycles of plate voltage, re-ionizing
cathode circuit of the tube I5 includes a resistor
the gas with each positive half cycle. If this type
RZI, provided with an adjustable tap 23, which
of operation is required, the resistor RI3 may be
omitted. The switch 31 is provided ‘to equalize
the changes of the capacitors C9 and CI!) to
posite sides of the input circuit 01 said discharge
means, said connections including time delay net
restore normal starting conditions if necessary.
Suppose that the variable tap, 23, on the re
sistor RZI is adjusted until the tube l5 does not
?re upon application of plate voltage. Then if
Rl'l--Cl9 is of higher time constant than R'I—C9
when light falls on the phototube the gas dis
works of di?ering time constants, each of said
networks including an input terminal connected
to said source and an output terminal connected
to both input and output circuits, said common
terminals being connected together to the other
charge tube 15 will still be non-conductive and
side of said source.
will gradually acquire a grid bias determined by
the drop in the resistor R2 |. With slowly varying
light such as daylight changes, the grid to cath
ode potential will remain constant. Upon the
sudden interruption of the light the capacitor C9
discharges much‘ more rapidly than the capacitor
Cl9 resulting in a positive bias on the grid of the
tube l5, causing the gas to ionize and operate the
relay 21.
Thus the invention has been described as an
improved photoelectric relay including means to
provide response to variation in light intensity in
dependent of the actual intensity itself. This is
accomplished by applying the output of a photo
to said discharge means, and a terminal common
3. A relay circuit including a discharge tube
provided with a control grid, a cathode and an
anode, a source of control voltage, means apply
ing the output of said source in the same polarity
to both said grid and said cathode, and delaying
the application of said output to said cathode
with respect to the application of said output to
said control grid.
4. A relay circuit including voltage responsive
discharge means having two input terminals, a
source of control voltage having two output ter
minals, a resistor connected between one of said
output terminals and one of said input terminals,
a second resistor connected between said one out
put terminal and the other of said input termi
electric cell to both the grid and the cathode of
a gaseous discharge tube through the delay net 25 nals and capacitors connected from each of said
input terminals to the other of said output ter
works of differing constants. The delay in the
minals, the numerical product of the values of
cathode and grid networks are adjusted to deter
said resistor and said capacitor connected to one
mine the slowest change and the fastest change
of said input terminals being greater than the
to which this system will respond. Adjustments
numerical product of the values oi! said resistor
oi the relative time constants at the grid and
and said capacitor connected to the other or said
cathode networks together with the polarity of
input terminals.
the phototube and battery as well as the adjust
5. A system for producing, in response to a
ment at the initial grid bias at the tube will de
varying voltage, a voltage substantially propor
termine whether the relay is energized or de
energized upon an increase or decrease of light, 35 tional in magnitude to the rate of change of said
varying voltage, including two low pass ?lter sec
The device may be operated to hold inde?nitely
tions of di?erent time constants, means applying
after actuation or reset automatically by a simple
said varying voltage to the inputs of said ?lter
change in the circuit.
sections in the same polarity, and means combin
I claim as my invention:
1. A photoelectric relay device including a gas 40 ing the outputs of said ?lter sections in opposite
eous discharge tube provided with a control grid,
6. The invention as set forth in claim 5, where
a cathode and an anode, a pair of time delay net
in the inputs of said ?lter sections are connected
works having different delay constants, and each
in parallel and the outputs of said ?lter sections
having an input circuit and an output circuit,
are connected in series.
said output circuits being connected in series be
'7. The invention as set forth in claim 5, where
tween said control grid and said cathode, and a
in each of said ?lter sections, as viewed from its
photoelectric cell connected to said input circuits
output circuit, includes a series resistor and a
in parallel.
shunt capacitor.
2. A relay circuit including voltage responsive
discharge means, a source of control energy, and 50
connections from one side of said source to 0D
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