12.6 v - 2a Transformer question

Thread Starter

SO$hocking

Joined Jan 1, 2012
4
I made a hot wire foam cutter with Radio Shack 12.6v-2a transformer, single pole dimmer switch and a guitar string.

Q: Do I really need a fuse box?
Do I need to hook the black middle wire on the transformer up?
Will I blow this transformer with full dimmer on?

Thanks. I'm new here and really like this forum already!!:)

ps. sorry about my scematic pic.
Transformer specs are wrong on it.
 

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SgtWookie

Joined Jul 17, 2007
22,210
It would be a good idea to put a fuse in the mains side, in case there is a fault in the transformer.

No, you don't need to connect the center tap.

As far as the transformer burning up if you turn the dimmer all the way up - hard to say, as we have no clue how much resistance your guitar string has. I think they are generally a type of stainless steel, but resistance would depend upon length, diameter, how much it's corroded, etc.

If you add a slow-blow fuse on the secondary to, say, 1.5x the transformer's rating, that should take care of it.
 

Thread Starter

SO$hocking

Joined Jan 1, 2012
4
Its a 16 gauge guitar string(i think it refers to thousands of an inch).
21" long
I don't have access to a slow burn fuse right now(nor any fuse), but i want to cut foam. BADLY!!!
Think I can risk it without a fuse for a little while?
 

bountyhunter

Joined Sep 7, 2009
2,512
If the transformer load is a guitar string, you are probably severely overloading the transformer and exceeding the current rating. An easy way to tell is stick a series Amp meter in and see the current.
 

Thread Starter

SO$hocking

Joined Jan 1, 2012
4
If the transformer load is a guitar string, you are probably severely overloading the transformer and exceeding the current rating. An easy way to tell is stick a series Amp meter in and see the current.
I don't have a series Amp meter. I just cut some foam for a couple minuets. The transformer hummed. also stayed cool at the dimmer half way up.
 

SgtWookie

Joined Jul 17, 2007
22,210
Well, if the music wire is stainless steel (which I believe it is something similar), and it's 16 mils (same as 0.016", or 16/1000 of an inch), then a 21" length of it should measure roughly 3.79 Ohms. 12.6v / 3.79 Ohms = 3.32 Amperes.

Do you have a multimeter that can measure AC volts? It would be helpful to know what the transformer measures with no output load on it.
 
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