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Flashing LED problem? Answered

Hi everyone. I mess around with HO scale slot cars and have had decent success lighting them with LEDs using track voltage and simple resistors to power them. I have ventured into the use of full wave rectifiers to smooth out the power and a small capacitor to eliminate the flicker. The problem I am having is when trying to use multiple blinking LEDs. Single blinking LEDs haven't caused any problems and I've had good results with them. The problem starts when I use more than one. I can get a pair of them to work on the bench with out any problem at all, but when they are soldered to the slot car chassis they might work for 3-5 minutes and then they stop blinking, and usually get hung up on one LED staying lit. What is even stranger is if I take a piece of brass rod and touch the anode of the dead LED, it will light up momentarily (and the other will go out). I only have so much room to work with so flashing circuits, large capacitors and voltage regulators are out of the question. Keep in mind, these cars are the size of a hot wheels or matchbox car, and the chassis uses up most of the internal space. Any help would be greatly appreciated!!!


I suspect its brush noise upsetting them. How much capacitance have you added ?

I've been using 0.1uf (100000pf). I was wondering if the magnets might be a suspect too. I normally light up T jets (the old chassis from the 60's), but the car these are going in are from a newer type car with a huge amount of magnetic down force. I will give bigger caps a shot!!! Thank you for your response!!

Yes, I'd add a 100uF capacitor - you can get very small ones AND the 0.1uF in parallel with it.


Thank you for the reply!! I'm ordering them today!! I have my fingers crossed!! :)

If you are using classic controllers, I assume your speed control is entirely from the voltage you apply to the track ? I wonder if the LEDs get upset by the supply going up and down too !

Try the caps and lets see !