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So I bought a few letters light that works with 2X AAA batteries and i am trying to connect them together to one AC source instead of using batteries. I opened one of them and there is nothing but the lights and the power on/off switch. Can I connect all the positives together and all negatives together? if so, how much AC power do I need? is it 3V or the total of the used batteries? I have 14 letters that's mean I need 28 batteries. enter image description here

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  • Are the individual lights incandescent bulbs or LEDs? Incandescents run on AC or DC. LEDs typically require current-limited DC, otherwise they change to DEDs. The 12 lamps in your example "A" wouldn't be wired in series, but are they wired in parallel or a series-parallel combination? – HABO Mar 27 at 13:19
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Interesting question: Yes, you can connect all the letters in parallel. But be careful here. You're talking about both AC (mains powers) and DC (batteries). Measuring DC current is more difficult than AC. with AC you can just put a DM with an amp clamp around a wire and whamo samo, you have a current reading. Measuring DC current is less common, possible, but just less common requiring a specialized meter.

Also, your power supply must convert from mains power to 3 volt DC, preferably with some capacitors to smooth out the supply. your lights might not work right or flicker without a high end power supply.

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  • We haven't established whether the lights require DC or would function on AC. Aside: Using a clamp-on an AC circuit often involves separating a wire from a cable, i.e. you can't just put a line cord in the clamp. Most DMMs will measure DC current, though the meter needs to be inserted in the circuit under test. My AC/DC current clamp, a vintage ES 695, is "my favorite tool that shouldn't exist". Very handy for diagnosing charging problems in vehicles without disturbing connectors. – HABO Mar 27 at 21:45
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    @habo. Yeah, I knew that about the amp clamp, which is why in other posts suggested making up a short "extension cord" with separate wires, but I missed mentioning that here...DOH! Although in my defense, I did say "wire" not "cable". Thanks for clarifying, I guess I was in a hurry when I first posted! – George Anderson Mar 27 at 22:30
  • Thank you George for the clarification. – Amjad Ali Mar 27 at 23:56
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you can connect the letters in parallel to a single 3V supply.

The current requirement is going to add up so I can't guess how many amps you will need. is there anything written on the lamps? (if they unscrew on the metal part)

You could use a multimeter to measure how much each letter needs (I expect that I uses less than W) and add those up.

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  • Thank you Jasen, unfortunately there is nothing written on the letters or the box. I will try to look online and see if I can find anything or just use multimeter like you suggested. Thank you again – Amjad Ali Mar 27 at 13:14
  • if they are filament type lamps they will unscrew and have a rating stamped into the metal part, if not you'll have to measure or guess from how long batteries last for, – Jasen Mar 29 at 1:47

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