Sep 10, 2026Povilas Dumcius1 min read
Build ideas: Light Dependent Resistor

Build ideas: Light Dependent Resistor

I've used light sensors for years and never really watched what happens to the signal as the light changes. So, this week I made three things with one.

An LDR is basically a resistor whose resistance changes with light. Shine more light on it and the resistance drops. Cover it up and the resistance rises. The board turns that change into a voltage it can measure, giving you a simple number for how bright or dark the room is.

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LDR Desktop Visualizer

The AX22-0005 is a light-dependent resistor that plugs into any Genesis port. Unlike a fixed resistor, its resistance changes with the amount of light hitting it. More light lowers the resistance, less light raises it, giving the board a simple analog signal it can measure.

 

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LDR Display Visualizer

The next project puts the LDR data on an IPS display. Instead of watching the value in the browser, the Genesis reads the sensor continuously and shows the current light level directly on the screen, updating in real time as the lighting changes.

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LDR Automatic Lights

The final project turns it into an automatic light. The LDR measures the room, the rotary encoder sets the light threshold, and the 5×5 LED display switches on automatically when it gets dark enough.

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Fork it

All three are in Studio. Open them, change how the light level is displayed, set a different threshold, or turn the automatic light into something else entirely. If you build something with it, send me a photo!

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