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Old Jan 31, 2016, 04:54 PM
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Hot wire cutter help

I bought a 12 volt 6 amp car battery charger with the intent to use it as a hot wire cutter attached to a wooden bow and some nickel coated electric guitar string (E). However the charger refused to create the circuit when all attached and would just turn off, unfortunately i bought a car charger with reverse polarity protection which is what I think is causing it.
I've taken it apart in the hope I can recycle some of the components into a working power supply however I lack the knowledge to do this alone.
Any help or suggestions would be greatly appreciated!
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Old Jan 31, 2016, 06:20 PM
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Remove the circuit board, connect the battery clip wires to the transformer output wires and add a light dimmer 'tween the transformer and mains.

Be careful, pay attention.
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Old Feb 01, 2016, 11:05 AM
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Thank you, really appreciate the help!
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Old Feb 03, 2016, 08:45 AM
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Have to notice something... where is the fuse? It should be on the board, on the place marked with F1. Try with car fuse, 10A.
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Old Feb 03, 2016, 04:25 PM
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This thread might be more suitable for DIY electronics forum.

The battery charger I have has a battery sense circuit along with short circuit protection. The output will not turn ON unless the leads are connected to a battery and that almost makes it useless for hot wire cutter. I'm assuming your battery charger does not have these "features"

Are you sure the transformer is not dead? Have you measured output voltage at the transformer? It could be that the transformer is OK and that you blew off the fuse?

If the transformer indeed is OK and is rated for 12V/6A, using a dimmer might be the easiest solution. In which case, you don't even need the bridge rectifier.

However, if you plan to use a brushed ESC for current control I'd think you'll need the bridge.

You might also want to pay attention that the total power draw should not exceed 72W.
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Last edited by elewon; Feb 03, 2016 at 04:38 PM.
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Old Feb 05, 2016, 05:21 AM
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Hi chinger yes you are precisely right and I had already taken the fuse out to take it apart, it was a 7.5 amp fuse i think.

Thanks for the info elewon, I took a gamble because it was cheap and I'm supporting my girlfriend through university right now so money is tight especially when hobbies are concerned! So I have to work with what I have i guess. My work gets a heck of a lot of these big polystyrene boxes so I thought i'd try my luck making a plane. As far as I know its all working and the plan is to attach a dimmer as soon as I find one suitable for it.

Again, thank you guys I really appreciate the replies and support.
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