Transformer sizing advice needed....

Thread Starter

Gearbreaker

Joined May 23, 2019
24
I have a project with a 6.3 vac 60hz supply voltage available. I need to isolate it and (although not 100% necessary) step it up to at least 12 volts. I need less than 100ma on the output side and was hoping to use a small audio transformer. The small size and price are both necessary.

Can I use a small audio transformer for this application? I am open to any suggestions.
 

MrChips

Joined Oct 2, 2009
19,753
You cannot use an audio transformer. It is not designed for power applications at 60Hz.
Your lowest priced source for a low power transformer is your local second hand store. Get the voltage and current you require.

Are you looking for DC regulated output?
If you are going to add a three-terminal linear regulator, make sure you include the dropout voltage plus a little extra overhead. If you go too high you will need heatsink on the regulator.
 

Thread Starter

Gearbreaker

Joined May 23, 2019
24
You cannot use an audio transformer. It is not designed for power applications at 60Hz.
Your lowest priced source for a low power transformer is your local second hand store. Get the voltage and current you require.

Are you looking for DC regulated output?
If you are going to add a three-terminal linear regulator, make sure you include the dropout voltage plus a little extra overhead. If you go too high you will need heatsink on the regulator.
Thank you very much for the info. Yes, I will need to rectify and regulate the output. I have been looking at triad iron core units but they are too big to fit into the space. Perhaps a torroidal would be smaller? It was wishful thinking to think I may have been able to use an audio transformer.
 

dendad

Joined Feb 20, 2016
3,168
If you can find an old unregulated 6V plug pack, or even a 9V or 12V one, and it has a center tapped transformer with only 2 diodes, you can feed the 6.3V into the center tap and one end of the transformer secondary, then across the ends of the secondary, you will have 12.6V. BUT be sure to leave the primary wires unconnected, and insulate then as mains level voltage will be there.
Run it as an "auto transformer"
 

Thread Starter

Gearbreaker

Joined May 23, 2019
24
If you can find an old unregulated 6V plug pack, or even a 9V or 12V one, and it has a center tapped transformer with only 2 diodes, you can feed the 6.3V into the center tap and one end of the transformer secondary, then across the ends of the secondary, you will have 12.6V. BUT be sure to leave the primary wires unconnected, and insulate then as mains level voltage will be there.
Run it as an "auto transformer"
Thank you for the reply. Great idea but space is a concern. I can't fit a transformer from a gutted wall wart into my enclosure. Also, I am looking for isolation. However, I may be able to separate the two six volt windings depending on the transformer design. Certainly great food for thought though.
 

Thread Starter

Gearbreaker

Joined May 23, 2019
24
I actually got the Chinese to make me a run of exactly what I need. That part of the puzzle is solved. Thank you all again for your replies.
 
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