AC to DC

[R1agan]

hi, i am building a project and i was going to use a transformer to supply 9 and 12V/AC and i then reliased i need 9V/AC for one and 12V/DC for another what would be the easiest and cheapest way to convert ac to dc for this kit?

Thanks R1agan

 

[stevez]

If I had this project the first place I'd start is to understand the current requirements as well as the voltage requirements.

Start with this thought - that 9 x 1.414 = 12.7 volts. That suggests that if you rectify 9 vac and filter it with a capacitor that you might end up with something close to 12 vdc. A single transformer with a 9 vac secondary might work.

Another thing to consider - that the 9 vac load might tolerate 10 vac - that allows you to go up a tiny bit on the secondary. You might even consider a slightly higher secondary voltage and us a resistor if the 9 vac load can tolerate shifts in voltage as loads vary.

The same thing might be true of the 12 vdc load - it might work ok on slightly less.

I do realise that none of this gives you a firm answer and the right answer is quite dependent on your situation.

Other options could include a special transformer with multiple windings. As it happens I do have a transformer sitting on my bench at this moment with a 9-0-9 vac secondary. The 9 vac is easy - one leg of the transformer to the center tap and that's 9 vac. Take the 18 volts, recitify, filter and follow with a regulator and you get the 12 volts.

Anyway, I hope this helps.

 

[R1agan]

Take the 18 volts, recitify, filter and follow with a regulator and you get the 12 volts.

Sounds good any chance you know what recitify, filter and regulator i should use?

Thanks R1agan

 

[stevez]

Those choices are quite dependent on a few things:

How precise and stable you want the voltage, ripple, etc.
How much current you need.
Load characteristics
Stability of AC primary source does affect this.

That said, not everyone goes to great lengths to specify and thoroughly design a power supply. Often a simple supply is good enough - though the voltage and current limits do matter.

Share more about what you are doing so I can provide a better response.

 

[R1agan]

Those choices are quite dependent on a few things:

How precise and stable you want the voltage, ripple, etc.
How much current you need.
Load characteristics
Stability of AC primary source does affect this.

That said, not everyone goes to great lengths to specify and thoroughly design a power supply. Often a simple supply is good enough - though the voltage and current limits do matter.

Share more about what you are doing so I can provide a better response.

ok i need 9V to run 2 sound level meters and 12V/DC to run a neon tube sound display kit