How to build a single 12V DC supply from AC mains

[jasonhanjk 0]

Important: You'll be touching the 230V main supplies if you follow this instruction, I'll not be liable in causing your death or loss of property. If you agree to my term, please read on.

 

This is just a basic instruction on how to build a high quality DC power supply. The construction cost would be around S$10. If you want to build a 24V supply, you need to increase the electrolitic cap only C5 to 50V and C6 to 25V.

 

Items:

 

1. 230V to 12V ac transformer, power 5VA. You can also get those transformer with labels like 6-0-6 on the secondary side.

2. 0.22uF AC line filter cap 230V, this is to be mount on the secondary side.

3. 4 X Ultra fast recovery diode, 50V DC reverse voltage, rated 1A. http://sg.farnell.com/jsp/endecaSearch/par...KU=366924&N=401

4. 4 X Wima film cap, 1uF, 50VDC.

5. 4 X 1 ohm resistor, 0.5W.

6. 1 X 4700uF electrolitic cap, 25VDC.

7. LM7812 & heatsink. http://sg.farnell.com/jsp/endecaSearch/par...?SKU=413215&N=0

8. 1 X 4700uF electrolitic cap, 16VDC.

9. AC plugs and cable.

 

 

Instructions:

 

1. If you walk around Sim Lim tower, you'll see the transformer having wordings on the primary side. 0V, 120V and 230V. For our AC supply, connect the brown (live) to the 230V and blue (neutral) to the 0V. Some steps will be skip because I assume you'll be very experience in building such circuit.

 

2. Attach the schemactic diagram, build it.

 

3. Use electrical tape to cover both the primary and secondary of the transformer.

 

4. Power up and test it using DMM. You should get 12V +-1% DC at the output. Or you might see fire works if you connect wrongly.

 

5. Do not ground the 0V to earth.

 

Enjoy with Cmoy or Cmoy 2!!!!

Edited April 16, 2005 by jasonhanjk

[jasonhanjk 0]

Another 15VDC supply.

 

DC socket --> rectifier (4 diode) --> big cap --> regulator --> small cap

Edited April 16, 2005 by jasonhanjk

[siriuz 0]

been waiting awhile for this

 

approx how much do the components cost?

 

edit: oops, read your post and saw that its supposed to cost $10..

Edited April 16, 2005 by siriuz

[heady 0]

Thanks Jason, how about info re: the diode number and where to get the diodes and regulator chip. Just the thing to learn to do. Any changes if I make a 18V DC power supply?

[skyskraper 0]

please remember to be very very very very careful working with 240v mains wiring people! if you are unsure of your mains capabilities, ask someone to help you! its always better to get someone to show you how to do it properly, then to kill yourself.

[jasonhanjk 0]

Modified to answer your question...

 

Those are examples

[Firefox 0]

Hehe... Spotted a miniscule mistake... The rectifier in the picture is a half-wave rectifier which is equivalent to 2 diodes, not 4 diodes as with full-wave rectifiers.

[jasonhanjk 0]

I am not very sure too myself. I tried to use my osciloscope but I can't remember how does a half-bridge waveform look like. 2ms per division.

[jtfoo 0]

I am not very sure too myself. I tried to use my osciloscope but I can't remember how does a half-bridge waveform look like.    2ms per division.

Nice scope pic, what's the veritcal scale? (volt/div)..

 

This is before or after the regualtor?

Edited April 17, 2005 by jtfoo

[jasonhanjk 0]

After the cap and before the regulator input. A few mV per div, didn't take note.

 

So long didn't see you around.

[jtfoo 0]

If a few mV then it's normal ripple after the rectifier & cap.. Anyway been busy on other non-headamp project so had to spend time on other forums for a while.