Customer:
I want to connect an HC-SR501 PIR sensor directly to a LED strip light, but I’m unable to figure out the wiring diagram. I have a single-colored 12V LED strip with only + and – terminals. I plan to run this strip through a 12V 5A driver. I need a wiring diagram for this setup - the goal is to turn on under-cabinet kitchen lights when a drawer is opened.
Originally submitted via email support on 27 June 2024. Migrated to the forum for community visibility.
Soldered Support:
You can follow the tutorial at https://soldered.com/learn/how-to-use-hc-sr501/ which includes a code example. To control the LED strip, you would need to use the HC-SR501 output to trigger a relay or MOSFET switch that controls the 12V power to your LED strip. The motion sensor triggers digitalWrite logic on the microcontroller, which then activates the relay to turn the strip on and off for a set duration.
Customer:
I built a test circuit based on this configuration and it works, but the brightness of the LED strip is only around 5% of maximum. What should I change?
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Soldered Support:
You appear to be using a MOSFET as a switch. Here’s the correct schematic for this configuration: https://www.electronics-tutorials.ws/transistor/tran_7.html
In this setup, the LEDs should be powered directly from your power supply through the MOSFET, which should be more than enough to provide full brightness well above 5%. Does the LED strip reach full brightness when you power it directly from the power supply without the MOSFET circuit?
If the issue persists, please share a schematic of your circuit and I can review it to help identify the problem.