What did I do wrong!

tnegun

Hey guys I'm a novice but have built simple circuits with arduino boards so not completely incapable! I've put together a project with an arduino Leo, Ethernet shield and 4 channel relay board to interface with my boiler controls.

The project works well but I'm having problems powering it. I wanted to dispense with the wall wart adaptor and use a 230v to 12v dc transformer and then a 12v to 5v switching psu.

I've used the 12v to 5v switching psu from 12v DC batteries and it's worked fine but connecting them to the 230/12v transformer just cooks them in a couple of mins!

I've burned 2 so don't want to loose any more am I doing something fundamentally wrong?

Chet T16

Are you sure it's 12v dc coming out?

tnegun

Chet T16 wrote: »

Are you sure it's 12v dc coming out?

I couldn't get a reading on the multi meter I've got 2 230/12v transformers so when the first blew I tried the second with the same result and thought it unlikely that both 230/12v transformers where faulty and must be my design but I did salvage both from electronics destined for the bin!

Chet T16

If they're actual transformers then they'll be ac output which is why your meter can't read a dc voltage. You'll need to rectify that output and stick a cap across it before sending it to your 12v -> 5v circuit

tnegun

That would make sense I had drawn power from one before but it was still plugged into an alarm panel at the time so I guess the panel had a rectifier built in. Thanks for the help!