This project is an automatic PIR sensor
Project is based on Holtek’s IC HT7610A, which is a
CMOS LSI chip designed for use in automatic PIR
lamp, flash or buzzer control. It can operate in
3-wire configuration for relay applications. In our
project we have used relay instead of Traic to
connect any kind of load in output, HT7610B IC is
suitable for traic and HT7610A for Relay
application. The chip is equipped with operational
amplifiers, a comparator, timer, a zero crossing
detector, control circuit, a voltage regulator, a
system oscillator, and an output timing oscillator.
Its PIR sensor detects infrared power variations
induced by the motion of a human body and transforms
it to a voltage variation. If the PIR output voltage
variation conforms to the criteria (refer to the
functional description), the lamp is turned on with
an adjustable duration. The circuit doesn’t required
step down transformer and can work directly by
applying 110V AC or 220V AC (Capacitor C7 needs to
change for 220V AC (0.33uF/275V) and 110V AC
- Supply Input 110V or 220V AC ( Capacitor Value
needs to Change)
- No Step Down transformer
- IC Operating voltage: 5V~12V
Load Current 80mA when relay is on.
current of the IC: 100uA
- On-chip regulator
- Adjustable output duration
- 40 second warm-up
- ON/AUTO/OFF selectable by MODE pin
- Auto-reset if the ZC signal
disappears over 3 seconds
- On Board Relay to
connect output Buzzer or Flash
- On Board LDR to
Detect Day/Night operation
- J1 to Set the Mode
- PR1 to set the Sensitivity of the sensor
to set the output Turn On Duration
- CDS R11 for
Auto Day/Night detection
- (HIGH Voltage On
Board) Do Not touch the PCB while power is on
click for full resolution
Mode (Jumper J1):
This project offers three operating modes (ON, AUTO,
OFF) which can be set through the MODE pin. While
the chip is working in the AUTO mode the user can
override it and switch to the TEST mode or manual ON
mode, or return to the AUTO mode by switching the
power switch. J1 Jumper is to set the desired modes.
Output is always
On: Output is high RELAY ON
Output is Always
Off: Output is low RELAY OFF
Outputs remain in
the off state until activated by a valid PIR
input trigger signal. When working in the
mode, the chip allows override
control by switching the ZC signal.
CDS-LDR (Light Dependent Resistor):
CDS is a CMOS Schmitt Trigger input structure. It is
used to distinguish between day time and night time.
When the input voltage of CDS is high the PIR input
is enabled. On the other hand, when CDS is low the
PIR input is disabled. The input disable to enable
debounce time is 5 seconds. Connect this pin to VDD
when this function is not used. The CDS input is
ignored when the output is active.
OSCD is an output timing oscillator input pin. It is
connected to an external RC to obtain the desired
output turn-on duration. Variable output turn-on
durations can be achieved by adjusting variable
resistor or setting various values of RC.
The PIR signal amplifier requires a warm up period
after power-on. The input should be disabled during
this period. In the AUTO mode within the first 10
seconds of power-on initialization, the circuit
allows override control to enter the test mode.
After 40 seconds of the initial time the chip allows
override control between ON and AUTO. It will remain
in the warm up period if the total initial time has
not elapsed after returning to AUTO. In case that
the ZC signal disappears for more than 3 seconds,
the chip will restart the initialization operation.
However, the restart initial time is always 40
seconds and cannot be extended by adding CRST to the
RST pin as shown in the circuit.
The HT7610A offers mask options to select the output
flash (3 times) when changing the operating mode.
The output will flash 3 times at a 1Hz rate each
time it changes from AUTO to another mode and flash
3 times at a 2Hz rate when it returns to the AUTO
mode. However the output will not flash if the mode
is changed by switching the MODE switch. Options for
effective override: Once or twice Off/On operation
of power switch within 3 seconds. Options for output
flash to indicate effective override operation.
Flash for the circuit.
Test mode control
Within 10 seconds after power-on, effective ZC
switching will force the chip to enter the test
mode. During the test mode, the outputs will be
active for duration of 2 seconds each time a valid
PIR trigger Signal is received. If a time interval
exceeds 32 seconds without a valid trigger input,
the chip will automatically enter the AUTO mode
- The output is activated
if the trigger signal conforms to the following
- More than 3 triggers within 2
- A trigger signal sustain duration
0.34 seconds >/2 trigger signals within 2 seconds
with one of the trigger signal sustain 0.16 seconds.
- The effective comparator output width is
selected to be 24ms.
- The output duration is
set by an external RC that is connected to the OSCD
When the chip is working in an AUTO mode
(MODE=open), the output is activated by a valid PIR
trigger signal and the output active duration is
controlled by an OSCD oscillating period. The lamp
can be switched always to ON from the AUTO mode by
either switching the MODE pin to VDD or switching
the ZC signal by an OFF/ON operation of the power
switch (OFF/ON once or twice within 3 seconds by
mask option). The term override refers to the change
of operating mode by switching the power switch. The
chip can be toggled from ON to AUTO by an override
operation. If the chip is overridden to ON and there
is no further override operation, it will
automatically return to AUTO after an internal
preset ON time duration has elapsed.
This override ON time duration is 8 hours. The chip
provides a mask option to determine the output flash
times (3 times) when changing the operating mode. It
will flash 3 times at a 1Hz rate each time the chip
changes from an AUTO mode to another mode or flash 3
times at a 2Hz rate when returning to the AUTO mode.
But if the AUTO mode is changed by switching the
MODE switch it will not flash.