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Really noob power question!!

silence00

Aug 28, 2019
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Hi there, I'm trying to light my kitchen with under cabinet colour changing led strip, but I would like to add a PIR sensor so that when you walk in the kitchen the lights automatically slowly fade up, when you leave they fade down.

The problem is with the PIR sensor, it's a 5A PIR, and my strip is 12V 2A, my power supply, which came with the strip is also 12V 2A output, when I have the sensor in line, it doesn't work, however I can still turn the strip on and off with the IR remote, (there is a mini controller with DC connection built in at the start of the strip).

I'm assuming the sensor doesn't work because the power supply isn't rated high enough, would I be right thinking I need a 12v 7a PSU, to power both the strip and sensor?

Any help is greatly appreciated, thank you.
 

Harald Kapp

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I'm assuming the sensor doesn't work because the power supply isn't rated high enough, would I be right thinking I need a 12v 7a PSU, to power both the strip and sensor?
No.
The 5 A rating on the sensor is the max. amperage it can control (switch on/off). The sensor by itslef will require only a few mA.
The controller for the LED strip probably outputs not a steady 12 V DC but a PWM signal which will interfere with the operation of the sensor. You will need a steady 12 V supply. The pir sensor alone, however, usually will turon the lights on and off hard, without fading.

Another trick you can try is: put the PIR sensors switched output in line with the LED controller on the mains side.

Show us datasheets of the parts you use and add a schematic of your circut for further analysis.
 
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