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gointern 03-29-2011 05:01 AM

Requirements for transformer
Hello everybody,

My first post and question about specifications for transformer.

I have 60 candles powered by 4 AA batteries each. I would like to connect them to a circuit and power everything with a transformer however, I am not sure what kind of transformer to look for.

I've been trying to calculate amps and power needed to power everything but my math skills with electrical units is bad.

Anybody have any advice? Thanks!

mpoulton 03-29-2011 05:56 AM

You need a 6VDC adapter, capable of at least 500mA or so. Each AA battery is 1.5V, and there are four in each candle for a total of 6V. Each candle should use under 10mA, assuming they are normal flickering LED candles. So with 60 candles, the total current should be less than half an amp (500mA). Just wire them all in parallel, with keeping the positive and negative correct, and it will work just fine.

Do It Right 03-29-2011 05:58 AM

Need the wattage of the candles to determine the current draw.
We know each one works at 6 volts.
You would need a small tramsformer to step down the voltage from what is available to what you need.
You would also have to add a rectifier to get DC.

If you can change the light bulbs to AC type, you could get away without the rectifier.

It sounds like you're looking for someone to help you with your science homework.

nap 03-29-2011 08:59 AM

Not saying the others are wrong but I think you need to check to see how the batteries are arranged. Since LEDs typically run on less than 6 volts (more like 2-3.3) it could be possible the batteries are arranged to provide 3 volts, or even 1.5 volts (very low powered LED maybe) and arranged as such to provide more amp hours (for longer run time).

gointern 03-29-2011 10:47 AM

Its not a homework :) I just dont know a lot about the power calculations.

The candle is this, how would I connect it in parallel?

Do It Right 03-29-2011 11:18 AM

Parallel means not end-to-end like Christmas lights.
Picture an extension ladder, one side would be + (hot,feed)
the other side - (neutral,return) the lights would connected as the "rungs" with one wire connected to each side.

That looks like a PITA to accomplish. Do they sell something like these that plug-in?

gointern 03-29-2011 11:30 AM

The candles that plug in to the power? There are kits that can have multiple candles connected in the row, they just cost way too much. Since I already have the candles, I would rather spend a few hours connecting them then buying a special kit.

nap 03-29-2011 12:15 PM

I cannot tell how those batteries are connected. That would have to be determined in order to figure out how to move forward. Maybe one of the other guys can see something there I'm not.

davido30093 03-29-2011 12:55 PM


Need the wattage of the candles to determine the current draw.
We know each one works at 6 [COLOR=blue !important][COLOR=blue !important]volts[/COLOR][/COLOR].
You would need a small tramsformer to step down the voltage from what is available to what you need.
You would also have to add a rectifier to get DC.
I think that this is the most likely senereo, however you would need to look at the battery hookup to be sure. Also, although regular light bulbs do not care whether the voltage is AC or DC, ALL electronic devices (like yours) work on DC. i.e. as stated above, your supply MUST be DC. The direct output of ALL transformers is AC, hence the need for the rectifier, either built into the transformer case or externally. So, if you are looking to try one of the small wall transformers, be sure that the output is DC. They come in both "flavors".

gointern 03-29-2011 02:11 PM

Would this 6V/1800mA AC-to-DC Power Adapter from radioshack ( be good enough? Says its 1800mA, mpoulton mentioned only 500mA is needed.

Could I also split candles on multiple power adapters? If there are 60 candles with 4 batteries each, I can get 3 of these power adapters and put 20 candles on each adapter?

davido30093 03-29-2011 03:00 PM

Yep, that should work fine. Just remember to wire the lights in parallel as described above and remember that this is DC so polarity MUST be observed. Look at how the lights are wired to the
+ and - terminals of the battery holders and it should be easy to follow.

davido30093 03-29-2011 03:06 PM

I just went back and re-read your first post. I noticed that you said you had 60 of these and each one has 4 batteries. Now that is a lot of batteries. Before you commit to how many of the power adapters you need, you should calculate the total amount of current needed. Each one should have a decal or sticker with some information on it or you can hook up a meter in series with one of them and see how much current it draws. Then see just how many of the lights you can hook to each of the power supplies.

mpoulton 03-29-2011 05:16 PM

I can't tell from the pictures how the batteries are connected. I'm not confident that they are all in series. The two batteries on each side of the battery holder are definitely in series (3V), but it looks like the two sets of two batteries may be in parallel. Can you post better pictures of the battery wiring?

gointern 03-29-2011 10:39 PM

I've connected two candles and used kill-a-watt device to measure amps. It showed 0.09 when one candles was connected and the same when two candles were connected. Not sure how accurate that device is but that's all I had to measure amps with.

The power adapter I got is Enercell 3-7.5V 2A

Here are some more pictures of battery wiring. The candle works when one or both black wires are connected to the power. Should I use only one black cable for power? The candle seemed to give more light when both cables were joined.

mpoulton 03-29-2011 11:25 PM

The two pairs of two batteries each are in parallel, so the device uses 3V not 6. The kill-a-watt cannot measure power consumption here, since this is not an AC circuit, not at 120V, and also far below the minimum power the kill-a-watt could possibly measure. You would need a multimeter to measure DC milliamps. You can be quite confident that each candle will require less than 30mA, and rather confident that it's actually less than 10mA.

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