Low Voltage AC Supply from Wall wart?

[Bzap]

Hi - I'm just starting to build a few basic circuits and am looking to get easy access to a low voltage ac power supply. I pulled apart a power brick, and it only has 4 diodes, a cap, and a transformer. If I pull out the cap and the diodes and solder the cord to the leads on the transformer, I should get a pretty safe low voltage ac power source, right? What kind of fuse should I add, if any?

 

[berkeman]

Hi - I'm just starting to build a few basic circuits and am looking to get easy access to a low voltage ac power supply. I pulled apart a power brick, and it only has 4 diodes, a cap, and a transformer. If I pull out the cap and the diodes and solder the cord to the leads on the transformer, I should get a pretty safe low voltage ac power source, right? What kind of fuse should I add, if any?

Yes, that should work fine. You can add a fuse that is rated a bit above what you will be pulling from the transformer. What are the input and output ratings on the unit you have?

BTW, you can get AC wall warts too, not just DC wall warts.

 

[Bzap]

120 vac, 3.3vac

 

[berkeman]

120 vac, 3.3vac

I meant input and output power ratings, not just the voltage ratings. You asked about fusing -- you need to know what kind of power the transformer is designed for, before picking a good fuse value.

 

[Bzap]

Says it's rated for 350 ma dc.

 

[berkeman]

Says it's rated for 350 ma dc.

350mA at 3.3Vdc? That's a pretty small wall wart...?

I'd fuse the AC output a bit below the rated DC output current. That should have reasonable margin.

 

[Bzap]

It is a pretty small wall wart. It was to a very old USB hub, I think. I'll set this stuff up and let you all know if it works tomorrow.

350mA at 3.3Vdc? That's a pretty small wall wart...?

I'd fuse the AC output a bit below the rated DC output current. That should have reasonable margin.

 

[Bzap]

Yep, works! Thanks!