Trying to replace LED’s in my Halloween inflatables. Whenever I touch the bare wires coming out of the fan (that previously connected to the dim LED’s) to the new LED, the fan shuts off. What’s going on here? *Edited to include previous research

Submitted by boeckman t3_ye0r1z in DIY

Whenever I touch the bare wires coming out of the fan (that previously connected to the dim LED’s) to the new LED, the fan shuts off. What’s going on here? My earlier post was removed, so here is the research I've already done: I've looked around for videos/instruction on how to do this, and the creators use LED's already mounted in little housings, which I guess must include the resistors/capacitors others mentioned in my post that was removed - all I can find are bare LED's, at least in white/clear. I've Googled "LED's with capacitor built in" and "LED's with resistor built in." I did find an aliexpress entry that I think is what I need, but they were only available in a $60 lot. Also a lot of automotive lights. The ones with the two wires sticking out attached to the bulb, I don't think I can make work because I need to connect multiple bulbs with a wire, running up the inside of the inflatable, and I'm not sure how to do that without contacts on either side of a housing to solder the wires to. And besides, I don't seem to see a white/clear one of those for some reason.

I have switched the positive/negative wires around - one way makes the light come on but cuts the fan, one way keeps the fan on but lights the light. The comments I was able to see in the other post indicated the LED's I have may be drawing too much power, causing the fan to shut off, and that using one with a capacitor or resistor may do the trick. As mentioned above, I'm having trouble knowing what/where to look for something like that.

I apologize for my earlier post, which I guess violated the rules since I didn't appear to have tried to find answers on my own, but I was just trying to keep the post concise.

2

Comments

You must log in or register to comment.

tuckedfexas t1_itvjdov wrote

I’m bad with electrical but the new lights are using more power and some safety feature cuts the power of it exceeds the amount it’s setup for maybe?

1

Ex-maven t1_itvozr9 wrote

You may be getting a into electronics here. LEDs often require a driver circuit to provide the correct voltage and current. If the system was sized for a certain voltage drop and current draw, and the new LEDs are requiring something else, the power supply may not function properly.

Unfortunately, I am no expert in this so I don't think I can offer much more (my work with LEDs is limited to relatively simple circuits and repair of a couple LED desk lamps...but I was able to educate myself through various internet sources just enough to solve my particular issue).

1

Diligent_Nature t1_itvx48p wrote

A capacitor won't help at all. Look for "5V LED" or "12V LED" or whatever the supply is. The resistor has to be matched to the supply voltage.

1

lorfeir t1_itvzes0 wrote

My first recommendation is to get a multimeter, if you don't already have one, and check the voltage on those wires coming off the fan when the fan is running. LEDs have an operating voltage. That is, when an LED is lit, there will be a particular voltage drop across the LED. The exact value depends on the details on how the LED is made, but a typical white LED will be around 3 volts. If you put a white LED in parallel with a fan, and the fan needs 5 volts to operate, the LED will end up clamping the voltage to 3 volts, and the fan won't run. (The LED will also run pretty hard and won't last long.)

One important thing... are these inflatables battery operated or powered off the mains? If off the mains be SUPER careful about the wires when you check the voltage. Treat them as if they could be live. While the voltage might be 5 volts, you don't know if there is proper protection on that, and you could get a nasty shock off them. Don't touch the wires while the thing is plugged in, and don't let them come in contact with each other or anything conductive.

So, check the voltage across the fan and see what it's running at. I'd guess it's running at 5 or 6 volts or possibly 12. If it's 5 volts, put a resistor (100 ohm 1/4 watt should be fine) in series with the LED and the two of them together across the wires:

WIRE----RESISTOR---LED---WIRE

If it's 6 volts, you can do two LEDs in series (maybe with a small resistor in series as well):

WIRE---LED---LED---WIRE

If it's 12 volts, you can try four in series. Make sure the LEDs are wired in the same way, since they're polarized.

Another possibility is to get LED tape. You can probably find LED tape that will match the voltage of the leads without much fuss.

Finally, you can order resistors online. I don't know what country you're in, but in the U.S. you can order resistors from various places: Adafruit, Digikey, Mouser. You can even get starter kits that have various resistors in them.

EDIT: After I posted this, I got to worrying about my response. Frankly, if these things are powered off the mains, I wouldn't recommend messing with them. It isn't just the shock risk while you're working on them, it's the risk of a short and/or fire while they're operating at night. They'll be outside, where they could get damp and so on. That's really not a serious problem for something that works off batteries, but for something that's mains powered, it could turn bad. You want to be sure of what you're doing before messing with something like that.

1

boeckman OP t1_itw77bk wrote

Replying to lorfeir (#242,734)

This is solid gold, thank you so much! I'll go looking for a multimeter and resistors after work.

It is powered off mains, and I have been VERY careful not to touch the bare wires while it's plugged in. The fire hazard is definitely noted, as well. At this point, I just want to solve the "mystery" so I'm all the wiser going forward!

Oh, and that EXACT thing you mentioned happened with one of the types of LED's I tried - blinding light from the LED, then it wouldn't light anymore.

1

dad_called_me_beaker t1_itwkuan wrote

Replying to Ex-maven (#241,378)

One other electronics 101 point--LEDs are diodes. That means they only allow electricity to travel through them in one direction, and they work with DC. If the wires from the fan are AC, the fan may not work because half the cycles will get blocked. If they're DC and you put the LED in series, it will only work if the diode is oriented correctly. Try switching which pins connect to which wire.

1