PIR - LED Circuit Trouble
invictuz
Posts: 1
Hi, I'm currently working on a project to create a circuit to activate 4 LEDs in series with a 555-28027 PIR motion sensor.
I have a 12V 1.5A power source that powers a string of 4 white LEDs (3.2 V, 20mA) and the motion sensor (which has a 5V volt regulator to prevent it from frying).
The output of the motion sensor goes to the gate of a MOSFET n-channel semiconductor, with anywhere between a 500K - 100K resistor between the two.
The drain lead on the MOSFET is connected to the ground end of the LED series chain and the source goes to ground.
When I apply power to the circuit, the LEDs light up and the motion sensor blinks red when it sees an IR spike, but it doesn't interrupt the LED circuit like it's supposed to.
Additionally, I've tried using a normal NPN transistor in place of the MOSFET and I've tried using a 12V, 2A power source.
Any ideas?
Thanks a bunch,
Zach
I have a 12V 1.5A power source that powers a string of 4 white LEDs (3.2 V, 20mA) and the motion sensor (which has a 5V volt regulator to prevent it from frying).
The output of the motion sensor goes to the gate of a MOSFET n-channel semiconductor, with anywhere between a 500K - 100K resistor between the two.
The drain lead on the MOSFET is connected to the ground end of the LED series chain and the source goes to ground.
When I apply power to the circuit, the LEDs light up and the motion sensor blinks red when it sees an IR spike, but it doesn't interrupt the LED circuit like it's supposed to.
Additionally, I've tried using a normal NPN transistor in place of the MOSFET and I've tried using a 12V, 2A power source.
Any ideas?
Thanks a bunch,
Zach
Comments
You noted that when power is applied, the LEDs turn on - correct? If that's the case, then the FET is already "on".
The PIR is supposed to turn off the FET, and consequently the LEDs?
IIRC, the PIR outputs a positive level when it sees IR motion. In the case of using an NPN transistor, then I can see why the LEDs stay on (are not interupted).
Sounds like you may need an inverter between the PIR and FET/Xistor.
Any chance of a schematic on how things are currently connected?
I have this very type of setup working with a mosfets. I'm currently testing everything installed on breadboard. I have six zone of LED strips. 5 zones 1 - 5 are controlled by motion sensors (5) and zone 6 is controlled by sonar and a motion.
zone 1 - 5, I do not have with the Stamp because the BS2 is limited (single thread) so, I'm learning the propeller. My zone six is controlled by a BS2 for the distance detection of the sonar and the motion to activate the LED.