New to wiring LEDS - what am I doing wrong?

Thread Starter

debb1985

Joined Feb 16, 2022
19
I like to make things and I had an ambitious idea to make a small scale Griswold house and needed to wire together 100 1.5V 100mA (AC and DC compatible) pre-wired bulbs that are typically used for hobby train use. I am a complete newbie to anything that has to do with lights and wiring, but my husband had me solder them together in parallel and when I test them on a battery they light up. I bought a battery holder with switch that I was them going to solder to my lights. I did this and it does not work. I am hoping someone can help me to know what I did wrong and help me fix it.
 

djsfantasi

Joined Apr 11, 2010
8,323
If you briefly reverse the leads from the battery, do they light up?

Normally, I’d be very sure of my answer. LEDs are sensitive as to which lead goes to the positive side of a DC power supply. But one thing you said has me a little confused and I have to see the description and specifications for the lights. The confusing part is you stated they were DC and AC compatible. The latter is inconsistent with LEDs. Unless since you said they were for hobby train use, they need a custom power supply. Like Woodland Scenics plug and play lights…

Can you provide a link to the lights?
 

Ya’akov

Joined Jan 27, 2019
5,657
Welcome to AAC.

Could you provide some photos of what you have done, as well as the part number or link to the lamps you are using?

I am sure it can be made to work but we need more information.
 

Ya’akov

Joined Jan 27, 2019
5,657
If you briefly reverse the leads from the battery, do they light up?

Normally, I’d be very sure of my answer. LEDs are sensitive as to which lead goes to the positive side of a DC power supply. But one thing you said has me a little confused and I have to see the description and specifications for the lights. The confusing part is you stated they were DC and AC compatible. The latter is inconsistent with LEDs. Unless since you said they were for hobby train use, they need a custom power supply. Like Woodland Scenics plug and play lights…

Can you provide a link to the lights?
If they really draw 100mA, that's going to be 10A, which is a lot. If they are AC/DC compatible, I assume that have a diode in there to half-wave rectify the supply. Unless they have a bridge which is certainly possible but doesn't seem as likely.
 

MrSalts

Joined Apr 2, 2020
1,762
It should look like this. The resistor may be included in the Flexible wire of one LED.
Some people want to position the switch differently when they start out in electronics and somehow out it parallel with the battery. But make sure the switch is in series with the battery similar to the drawing below...

A39A74ED-0E7F-4129-B535-A18B76E9A5E5.jpeg
 

djsfantasi

Joined Apr 11, 2010
8,323
If they really draw 100mA, that's going to be 10A, which is a lot. If they are AC/DC compatible, I assume that have a diode in there to half-wave rectify the supply. Unless they have a bridge which is certainly possible but doesn't seem as likely.
Exactly! You include if and unless in your reply. Which is why I want to see the light specs.

Woodland Scenics make a popular line of hobby train lighting. It is designed to be used with their hub, which is designed to make wiring simple. But for off catalog use, you need the specs.
 

Tonyr1084

Joined Sep 24, 2015
6,884
I bought a battery holder with switch that I was them going to solder to my lights. I did this and it does not work.
You DID say they worked when you hooked them directly to the battery, so I'm sure the battery can carry the load.
If you briefly reverse the leads from the battery, do they light up?
I suspect the same thing. If they worked when connected directly to the battery and not after you installed a battery case (with switch built in I'm assuming) they don't work, then the only common point is the connections to the battery case. Just make sure you put the batteries in the holders properly. I've seen that too. Done that too.
 

Ya’akov

Joined Jan 27, 2019
5,657
So, if the TS is talking about these it would explain some things. The LED equivalents seem to be 12V so it appears these are incandescent lamps. I don't think you could reasonably expect to run 100 of them on a single 1.5V cell for very long. I also hope that the battery case is either a single cell or parallel.

1645034807675.png
 

ThePanMan

Joined Mar 13, 2020
367
needed to wire together 100 1.5V 100mA (AC and DC compatible) pre-wired bulbs that are typically used for hobby train use.
These are not LED's; they're incandescent bulbs. LED's work only on DC. They're commonly rated to work on a max of 30mA, with a suggested current of 20mA or less. Some super bright LED's can be run on as little as 5mA. If you're putting a whole bunch of those in parallel you have a very very heavy current draw. 100 of them would draw 10,000mA (100A). It's doubtful your little 1.5V battery could supply that kind of current.
my husband had me solder them together in parallel and when I test them on a battery they light up.
Then they're not incandescent. If they worked before then either the battery is hooked up backwards. Just because they can be powered from DC or AC, AC is alternating current, meaning half the time the current is forward and half the time the current is reversed. The LED will only turn on when the current is going forward through the LED. When it tries to go reversed it blocks the current. LED's are not strong in blocking reverse current and can be damaged. But you're hooking them up to a battery, so the current will only pass one way through. Provided you have them hooked up the right way.

Since they worked without the battery holder, try it again. Make sure they still work. Chances are good they still do. But I can't be sure because you don't say what battery voltage you're using. You only hinted that you bought a battery holder. Didn't say what size batteries or how many. Like your non-lit LED's we're in the dark.
 

Thread Starter

debb1985

Joined Feb 16, 2022
19
Ok so here are the lights I bought and the battery holder with switch. I tried to find a single D battery holder with switch, but had no luck so I tried the 2 AA one only because someone in the reviews for the lights said they needed 3v to get good light (?). When I reverse the leads from the battery holder to the lights it doesn't do anything still. I also attached some pics of my soldered lights. Be kind if I totally messed it up lol. I am happy to learn how to fix this if I can.

GPW02W 50PCS Clear 3mm 1.5V 100mA Miniature Pre-Wired Grain of Wheat Bulbs Warm White for Model Train Layout or Architectural Project https://smile.amazon.com/dp/B07DW9B...t_i_Y6768GVYRVZ9RJPWWT9V?_encoding=UTF8&psc=1

QTEATAK 5Pcs 2X 1.5V AA Battery Holder Case with On/Off Switch and Wire Leads https://smile.amazon.com/dp/B08119T...t_i_4KB4BKHPTKXWXB90T9D6?_encoding=UTF8&psc=1
 

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Ya’akov

Joined Jan 27, 2019
5,657
OK, sorry for the plodding along with questions but to troubleshoot a problem effectively we need to ensure we are not going down a blind alley.

As an aside, I suspect those lights will not last very long on a single D cell. Once you get it working it might be worthwhile to find a better power source, possibly even something you plug in.

But, back to the problem. Can you show us some photos of the battery holder and its connections? Also, if you have a part number or link to it, that would help.
 

Boggart

Joined Jan 31, 2022
13
That battery is doing pretty well, they are small incandescent bulbs, not LEDs, so total current would indeed be several amps.

I expect the problem is with the battery holder, I've seen some designs where the battery doesn't quite fit in properly and the +ve terminal of the battery doesn't connect.

It's also possible that the switch isn't wired up or has a faulty solder joint, it happens with cheap chinese battery holders.

Also, the switch will be a small slide switch, they are usually rated for half an amp or so at most, they won't last long with several amps running through them.

So basically, the issue is that you selected the wrong voltage and device type. You should have gone with LEDs as they can run from just a few milliamps each. Because white LEDs need around 3V to light, you need to use at least that voltage. Prewired LEDs are common in 5V, 9V and 12V versions, and you can run the higher voltage versions on a lower voltage, they just get less current and so are not quite as bright.

For example, run 12V LEDs on 5V and they will draw only a few milliamps per LED, so you can parallel a hundred of them and still be well under 1 amp of current, although even at those lower currents, a single AA battery isn't going to last long.
 

Ya’akov

Joined Jan 27, 2019
5,657
I came back to add, as @Boggart said just after me, that they are not LEDs and the distinction is very important. LEDs have peculiar electrical characteristics and so it is very misleading to call them that.

As a term of art, they are "grain of wheat bulbs" and if you call them that, a knowledgeable person would understand exactly what you've got. If they didn't recognize that term (possibly due to insufficient age) "miniature incandescent lamps" is the purely technical description.
 

Thread Starter

debb1985

Joined Feb 16, 2022
19
The battery pack works properly as I tested it on a strand of cut fairy light LEDs I had and it lit them up no problem. I didn't realize what I had was not an LED until this forum. My husband didn't even know either. Like I said this was an ambitious project for me. At this point I would be happy doing a plug in option if necessary if someone can guide me on what to do. The house I made is out of cards took so I want to make sure I am not making a fire death trap either! I did post the battery pack link in my previous post that also had the lights in it if that helps.
 

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