I tried to make an AC / DC power supply and it worked perfectly fine,by changing the switch it would either provide DC from the middlle wires or AC from the wires on the sides.Here is a picture of the circuit: diagram1 http://8pic.ir/images/kmwfgdyppyvsex9o1ire.jpg

I wanted to have only two output wires so I added another switch to totally disconnect the capacitor and the bridge rectifier like so: diagram2 http://8pic.ir/images/3alk4npyh1synwqriomn.jpg

While I switch it to DC it still works just fine.Then I discharged capacitor and changed the switchs positions to AC and powered it up again,this time the diodes started to heat up really fast despite the bridge was disconnected and I also noticed that the capacitor was charged again.

Am I missing something here? Why is there current in the DC part of the circuit and why is there not an AC output? Im a bigginer so please explain in simplest way possible


You've wired your capacitor up the wrong way round: -

enter image description here

I've marked the correct polarity in red. Some electrolytic caps may work once with the wrong polarity but a 2nd time probably not.

Alternatively, and using your own words: -

While I switch it to DC it still works just fine.Then I discharged capacitor and changed the switchs positions to AC

That would certainly cause problems - discharging the cap before disconnecting the bridge is really not the thing to do.

So, given the two errors so far there's every possibility that you've wired the switch up incorrectly or made some other wiring error.....

Yes, there it is in your 2nd picture - you just CANNOT cross-wire a bridge rectifier like that: -

enter image description here

This will put AC on the capacitor.

  • \$\begingroup\$ Messed up the drawing but the bridge and cap work fine ( believe me they are in correct polarity) but even that doesnt expain why it works one way but heats up the other way \$\endgroup\$ – OM222O Jul 16 '16 at 16:19
  • \$\begingroup\$ I added some more text while you were posting the comment. \$\endgroup\$ – Andy aka Jul 16 '16 at 16:21
  • \$\begingroup\$ I cannot answer that. \$\endgroup\$ – Andy aka Jul 16 '16 at 16:35
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    \$\begingroup\$ I would delete the top SPST switch, and use a DPDT switch at the bottom to switch both output terminals between the AC leads and the DC leads. \$\endgroup\$ – Peter Bennett Jul 16 '16 at 16:42
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    \$\begingroup\$ Perhaps this will help: i.imgur.com/tdFSGVI.png \$\endgroup\$ – zeffur Jul 16 '16 at 17:32

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