Hi All,

I am new into electronics and this is my 2nd post on this forum.
I have a basic question on step down transformer. One of my DIY circuit need 12 volt regulated dc supply so i have purchased a 12-0-12 500 ma transformer and build the circuit as in the below URL.

http://tinypic.com/view.php?pic=n1fs6v&s=8

My question is what to do with the middle winding of the transformer highlighted in red. The transformer is marked as 12-0-12 and i need only 12 volt regulated supply. I read some post and it sounds like if i did not connect it properly then it may produce 24 volt and burn my connect circuit so i am worried.

Thanks
Shan

 

One thing to add here... i dont want to add any more component in the circuit and just wanted to follow the same circuit for regulated 12v dc but with 12-0-12 transformer.

circuit diagram is taken from below URL.

http://www.circuitstoday.com/wp-content/uploads/2011/03/

 

Use the bottom, left drawing.

 

Use the bottom, left drawing.

Thank you for your response.

Can I use the same full wave bridge circuit which I have indicated in my initial post with 12 0 12 transformer?
Actually I already solders all components and now just looking for correct wiring with transformer

Thanks
Shan

 

Can I use the same full wave bridge circuit which I have indicated in my initial post with 12 0 12 transformer?

If your initial post was correct, I would not have told you to use a different circuit. You have started out with 24 VAC into a bridge rectifier which will get you about 32 VDC. Do what I said and you will get about 16.3 VDC.

 

Here is how to salvage your existing tranny and full-wave-bridge: Note the filtering required for a nominal 1A output current.

 

If you want a negative voltage for any reason, the unused output of the bridge labeled NC on Mike's circuit can be filtered to give -16.3Vdc.

 

If you want a negative voltage for any reason, the unused output of the bridge labeled NC on Mike's circuit can be filtered to give -16.3Vdc.

Thank you all for your response. i will try #12 and mike suggestion this weekend.
one more question, what if i use the first and middle winding of secondary coil of 12-0-12 transformer with full bridge rectifier with 7812 IC
and leave the third winding as is without connected anywhere? will i get approx 12 v regulated output?

i am not sure if this make sense but just my thought.

Thank you
Shan

 

That will get you about 15.6 peak volts at the first capacitor. Allowing 2 volts for the regulator, you have 1.4 volts left for ripple voltage @ 1500uf. You will be able to use 0.31 amps because you are only using half the transformer. The way I told you to do it in the first response would get you 0.5 amps with 1300 uf.

 

#12, I have made the bridge with 2 diode as u mentioned earlier and the circuit works fine.
Thanks for you help.