dissecting an IR remote-controlled color change LED

Okay, I bought one of those remote-controlled color changing LED candle things.  I want to get its guts as small as possible.  My knowledge level is basically "LED + battery = glowy" so I need some help figuring it out.  I've attached a pictured.  I tested and it will work with 3 volts.  I get that obviously I need the RGB LED, the IR receiver, and the control chip thingy... but what is everything else?  I'm figuring resistors and capacitor/transistor, but I don't understand these and why I need them, and why so many?!  Any chance some of them are just for lowering the voltage down to 3, and now that I'm using only 3 they are no longer needed?


Picture of dissecting an IR remote-controlled color change LED
If any of the components where not needed they wouldn't be there. All the bits with 3 leads are transistors. The 2 small parts near the IR receiver are capacitors. All the other 2 lead black parts are resistors. The large cylinder is a capacitor. The cylinder next to the IC is the clock crystal for the IC. Obviously the circle in the middle is the LED and the black deal on the right is the IR receiver. There are no voltage regulators.

The capacitor is there to help smooth out the voltage coming into the circuit. The power comes into the unit and through the capacitor on the positive lead. Chances are there is a common ground on the back side of the board. Looks like the RGB LED uses a common Anode (positive voltage). The negative lead goes through the 3 larger resistors and to there respective transistors. Then on into the LED. Like all LEDs you need current limiting resistors which is why they are there. The 3rd leg of the transistors go into the IC. The positive and negative also go to 2 of the leads of the IR receiver the 3rd to the IC. The 2 small capacitors are likely tied into the IR receiver and/or the clock crystal to help regulate the power to the devices. The clock crystal is there to keep the IC in time with the IR signal that will be received by the unit. The IC generates a PWM (Pulse Width Modulation) signal. Basically a signal that is turning on and off very rapidly. It is sending that signal out to the transistors turning the power on and off to the Red, Blue and Green elements in the LED. The transistors are needed because the IC's PWM signal isn't able to output the power needed to drive the LED directly. The transistors are able to turn on and off vary rapidly allowing the voltage and current from the battery to flow through them.

Removal of any of these parts will cause the circuit to not function anymore. You can't do anything to make this device any smaller. Unless you can figure out a better and more efficient way to lay out the PCB so it fits in a smaller area.
aliasjanedoe (author)  mpilchfamily4 years ago
Wow, that is a really thorough answer. Thank you so much! :)