LED Driver - Capacitive dropper light sensitive.

255

04:08:27

Simple capacitive dropper to drive LEDs. Uses a PNP transistor and LDR to turn the LEDs on or off.
Pot is a light sensor.

published 9 years ago

rich11292000

9 years ago

The only thing missing is a series resistor before the bridge to help aid the capacitor. For similar reasons of why a led is ALWAYS in series with resistor. A pure resistance has a linear v-i curve, a led has a exponential v-i curve, a capacitor has a logarithmic v-i curve. The v-i curves of led and cap have REACTANCE with your unpredictable mains, full of harmonics. From your source you have series capacitor, two series diodes, capacitor in parallel, these are all components that have frequency dependent reactance.

RootZero

9 years ago

Thanks, I was just reproducing a circuit I'd seen recently. That didn't have a series resistor from what I noticed. I added a 1k, is that a reasonable value?

RootZero

9 years ago

Decided to leave it as is.

RootZero

9 years ago

This is from a cheap Chinese product so it's extremely minimal.

add comment in editor

EveryCircuit is an easy to use, highly interactive circuit simulator and schematic capture tool. Real-time circuit simulation, interactivity, and dynamic visualization make it a must have application for professionals and academia. EveryCircuit user community has collaboratively created the largest searchable library of circuit designs. EveryCircuit app runs online in popular browsers and on mobile phones and tablets, enabling you to capture design ideas and learn electronics on the go.