Most Economical way to Turn 120v AC to 30-40v DC

[VicMac]

Hi! I'm looking to build a dc power supply for electrolysis. I have built a constant current (.25ma) circuit that I currently power from a couple of rechargeable 9v batteries. It works great, except I'm having to recharge the batteries every few days. The BC547 transistor I'm using needs to see less than 45 volts.

What is the most economical way to turn 120v ac to dc of 30 to 40 volts? Another requirement for this project is that it is physically small... And finally, I should be able to source the parts from a well known internet auction site...

Thanks in advance for your help! ! !

 

[ronv]

Power Supply

**broken link removed**

 

[crutschow]

**broken link removed**

That apparently has an AC output so you could add a bridge rectifier and capacitor filter to give about a 32Vdc output.

 

[Pommie]

At 1/4 of a milliamp your batteries should last around 1200 hours which is 20 days. Did you mean 25mA and not 0.25mA?

Mike.

 

[KJ6EAD]

There are lots of 18-19VDC switch mode power supplies made for ink jet printers. Get two and wire the outputs in series.

 

[VicMac]

Hi Mike! The OUTPUT of the constant current circuit is.25ma, but the current flowing from the batteries is 3.5ma, which mean my 100ma rechargeable 9 volt batteries last a little longer than 24 hours. I need a way to step down 120v ac to 20-40volts and then run it through a bridge rectifier so the constant current circuit will be happy. I think you can see my previous posts, and if you can find my first one (It is titled: Can a LM723 Be Used To Regulate Current Between .25ma And 1ma? ), at the end of the thread you can see the circuit I'm using for constant current. If that could be modified to run on 120v ac, that would work as well.

Thanks for your reply!

Victor