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I took this little remote controlled RGB LED circuit out of a fake candle and want to re-use it to drive several RGB LEDs.
The LED on the circuit is common anode and I'm using common anode as well.

The circuit is designed to drive one LED, so simply connecting 10 to 20 additional LEDs will probably ruin it as it would draw a lot more current.
So my idea was to remove the LED from the circuit and use the power that it's getting from the remote control circuit to switch transistors (one per color) on my circuit that switch my LEDs.

However, I can't figure out how to achieve this.
If it were a common cathode LED, I would simply connect the cathode to ground and connect each color anode to the base of a transistor, but I don't understand how to do this with the LEDs being common anode and the color pin being negative voltage.

In the example circuit, I focus just on one LED color (let's say the Red ones). If anyone can explain me how to switch D1 - D10 in my circuit using the Red cathode on the remote control circuit, that would help me out.

schematic

simulate this circuit – Schematic created using CircuitLab

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    \$\begingroup\$ Have you considered using a PNP transistor instead of a NPN? \$\endgroup\$ – brhans Nov 29 '16 at 21:24
  • \$\begingroup\$ First you need to examine the candle and determine whether the LED is connected to V+ or ground. \$\endgroup\$ – WhatRoughBeast Nov 29 '16 at 21:33
  • \$\begingroup\$ @brhans Can I hook up a PNP transistor with the Red pin connected to the base, 5v+ connected to emitter, my own RGB led's common anode to the collector and its cathode to ground (same ground as the remote control circuit), correct? \$\endgroup\$ – Ruud van Falier Nov 29 '16 at 21:37
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    \$\begingroup\$ Why not replace the LED for another LED of an optocoupler? The opto can then drive a transistor, etc.. \$\endgroup\$ – Wesley Lee Nov 29 '16 at 22:08

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