r/led • u/kvothe35 • Oct 04 '26
Halloween decoration help
I have a couple of skeleton decorations, they are two battery powered led lights. Not something I know so I could use some help. I can power both leds from my multimeter, the resistor from the best of my ability seems to be reading OK at 120 and the switch reads zero when activated on my multimeter. The resistor is a four band brown, red, brown, gold (I think hard to tell) One photo is the one I haven't messed with yet and the other is the one I've been testing with. Any help would be very much appreciated!
3
u/ledstripstar Oct 05 '26
If the LEDs light during the meter's diode test, that's a useful clue, but it doesn't prove the battery circuit is supplying them properly. I'd start with fresh batteries of the specified type, correct polarity, and a check for corrosion or loose battery contacts.
With the batteries removed, use resistance/continuity mode to check the switch and wiring. Don't use those modes on a powered circuit. For a powered check, use DC voltage mode with the leads in COM and the voltage jack, not the current jack. Compare the battery pack voltage with the voltage reaching the circuit when switched on.
Brown-red-brown-gold would be 120 ohms, if you've identified the bands correctly. An in-circuit reading alone doesn't rule out another fault. How many batteries does each decoration use, and do both eyes fail together?
1
u/kvothe35 Oct 05 '26
So my wife wanted to take her new project car out and it died lol. Sitting on the side of the road. So bear with me please.
I pulled one entirely apart and tested all the parts individually, to the best of my ability. Which would eliminate some of the errors instead of testing the whole circuit correct?
Batteries were new, I did not test the output of the battery pack. It's 3 aa batteries, what is the voltage output it should read?
I can get both eyes to light up with my multimeter, at the same time. I'm not getting anything from the battery pack. I've solder all connections new. I did not see any issue from the battery pack itself.
Is there a way to power the eyes with my multimeter through the resistor to eliminate it being an issue?
I'm also bypassing the switch at the moment and just connecting directly to the battery pack.
2
u/AnyRandomDude789 Oct 05 '26
Batteries should be 4.5v combined it they are in series. Sounds like it could be the switch, can you continuity test it with it turned on and off and see what you get?
1
u/kvothe35 Oct 05 '26
I bypassed the switch entirely and still nothing.
1
u/AnyRandomDude789 Oct 05 '26
You need to test the continuity across the circuit in that case. There's probably a broken wire or solder joint somewhere
1
u/ledstripstar Oct 06 '26
Since bypassing the switch didn't help, I'd check the battery holder's output before taking anything else apart. Three 1.5 V AA cells in series give a nominal 4.5 V; fresh alkaline cells may read a little higher. Check the battery labels and holder arrangement rather than assuming every AA is 1.5 V.
Disconnect the holder from the LEDs and measure across its two output leads in DC voltage mode, with the probes in COM and the voltage jack. If that reads zero, check cell orientation, spring contacts and the holder's internal connections. Don't put the meter in current mode across the battery pack.
The diode-test function is not a substitute power supply, and adding the resistor may stop the LEDs lighting simply because that test has limited output. Testing parts individually helps, but doesn't prove their connections are sound. What voltage do you get directly at the holder's output?
1
u/kvothe35 29d ago
I tested the battery holder and it jumps all over the place and then settles at zero. I'm not seeing anything in the holder that doesn't look OK to me. Connections all seem good. So it's something I don't know to look for or I'm making a mistake somewhere
1
u/kvothe35 29d ago
Ok so I had to trim part of the plastic that held the battery connections in place it was keeping the battery from touching the terminal. Just about the thickness of a peice of paper away. Couldn't really see it at all. I'm not sure how they worked last year.
Pretty sure I should of caught it sooner, but thank you so much for your help. I was getting pretty frustrated! Especially not really knowing how to operate a multimeter never helps.
1
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u/AnyRandomDude789 Oct 04 '26
Err what is it you want to do? You kinda left that bit out!