Here is one simple circuit of a general-purpose white LED security light with Passive Infrared (PIR) Motion sensing mechanism. At the heart of the circuit is a PIR sensor module SB0061. SB0061 is a pyroelectric sensor module which developed for human body detection. A PIR detector combined with a fresnel lens are mounted on a compact size PCB together with an analog IC, SB0061, and limited components to form the module. High level (3.3V) output of variable width is provided.
In this security light circuit, High level (3.3V) output from SB0061 is used to switch on six 5mm white straw hat LEDs through a solid-state switch realized using transistors T1 & T2. PIR sensor modules usually have a 3-pin connection: Vcc (+) , Output, and Ground (-) . The pinout may vary, so it is recommend to check the manufacturer’s datasheet to confirm the pins. Besides PIR sensor module also has a 3-pin jumper selection for single or continuous trigger output mode.
The two positions have labels H and L. When the jumper is at H position, the output remains high when the sensor is re-triggered repeatedly. In position L, the output goes high and low every time the sensor is triggered. So a continuous motion will give repeated high/low pulses in this mode.
The PIR LED light security circuit can be powered from a compact 9V rechargeable battery. Note that the battery charger circuit is not included with the circuit schematic. You can use any suitable external 9V battery charger to re-charge the battery pack.
PIR LED Security Light Circuit Schematic
- The PIR sensor requires an initial stabilization time of about 10 to 60 seconds in order to function properly. During this time, the sensor gets familiar with the surrounding environment, and any motion in its field of view should be avoided.
- As stated above, the PIR Module needs a “warmup” period of about 10 to 60 seconds, during which time it’s adapting to ambient conditions and may trigger randomly. So anyone using this simple circuit needs to be prepared to accept random triggering for a while after startup.
- Due to the high sensitivity of PIR sensor device, it is not recommended to use the module in the following or similar condition:
- in rapid environmental changes
- in strong shock or vibration
- in a place where there are obstructing material (eg. glass) through which IR cannot pass within detection area.
- exposed to direct sun light
- exposed to direct wind from a heater or air condition
- A 9V /250mAh NI-MH Rechargeable battery is used to test the prototype. If possible, try to use a 9V type with higher current capacity.
- Value of R3-R4-R5 is optimised for the white LEDs used in the prototype. This needs a “re-touch”, based on the type of white LEDs used in your circuit.