# Transformer output voltage

Discussion in 'General Electronics Chat' started by jachete, Jan 27, 2007.

1. ### jachete Thread Starter New Member

Jan 27, 2007
3
0
I am building my first electronic project: a smart NiCD batter charger. The circuit requires either 16 or 24VAC input. I have found transformers that say they produce 2 x 12V.
Question 1: Can I simply connect the 2 12V secondary connectors to my circuit to get 24 VAC?
Question 2: Where would I put a fuse and how to calculate the rating?

Any help would be great; sorry if this is a really stupid question.
Jac

2. ### beenthere Retired Moderator

Apr 20, 2004
15,815
282
Hi,

You should be able to tie the secondaries together for a 24 VAC output. The fuse should go in the primary circuit. Figure the value by the current draw of the charger times the 24 volts for the power used. Divide that by 120 volts to get the primary current. Select the next larger standard fuse value for circuit protection. You might want to use a slow blow fuse so a start-up surge doesn't pop the fuse when there's no fault condition.

Jan 10, 2006
613
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the 2 secondaries should be connected In series, and In Phase....

4. ### jachete Thread Starter New Member

Jan 27, 2007
3
0
Hi! Thanks for all the advice. So, I should connect the two 12v outputs in series? That's easy. But how to be sure that they are in phase?

I thought that connecting the two 12 v ac outputs in parallel would ensure that with the sin curve, I got 24 Vac?

Is that not true?

5. ### beenthere Retired Moderator

Apr 20, 2004
15,815
282
Hi,

No, in parallel means 12 VAC with more current ability.

If you don't have a wiring diagram of the transformer, then just connect a wire from each secondary together and check the voltage on the remaining unconnected wires. If it's 24 VAC, you guessed right. If not, trade wires from one of the secondaries and check again.