# Attempt at fairly simple circuit

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#### ScuzZ

##### New Member
I'm attempting to build a circuit that will result give me a result of, [email protected] - 10amps(regulated).

I'm thinking AC step down transformer (10:1 or 20:1), bridge rectifier, current regulator then voltage regulator.

I'm wondering:

1. The maximum amps I can pull from the grid is 10amps, by using a step down transformer from 240volts to say 18 or 20 volts, do I also get the same increase in amperage? Say 20:1 transformer, will I end up with like 200amps?

More questions to come...

##### Banned
Only if your transformer can handle it.

Use an ATX power supply, nothing to build, it's all right there.

#### ScuzZ

##### New Member
I would use a power supply, but I've been so out of practise that I feel I need to build something to get my eye/brain back in.

So you're saying that if I use a 20:1 transformer and pull 10amps from the grid, I'll get 200amps on the 'down' side?

#### birdman0_o

##### Active Member
Yes, when voltage decreases over a transformer amperage increases, and vice versa.

##### Banned
No that is dead wrong, it should be that way but the wire thickness and actual magnetics going on will limit the current draw WELL bellow the 20:1 turns ratio, of 10 amps to 200 amps. It depends WHOLLY on the transformer being used.

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#### ScuzZ

##### New Member
So I understand that I'm going to get an increase in amperage, maybe in a perfect world you'd get the 20:1 increase, but still.

Another question:

1. I'm thinking about using LM338T as the current and voltage regulator as these are relatively inexpensive and very easy to come by.

There are stated as being 5 amps.

Is there a way of using these to produce 10amps or will I have to find another regulator?

#### dougy83

##### Well-Known Member
You can buffer the current with one or more pass transistor(s). The details for such a circuit may be found in e.g. 7805 regulator datasheet.

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