[S3am]

Hello. I want to build my first (working) cmoy. And I want to make it non_portable. So i'll just want to build PS + CMOY Board and on next step i'll just swap CMOY pcb with better one.

If I will use Talema (Amveco) transformer like here:

(but 7VA 2*12V), how can i get Gnd line?
As i can see, trafo has two secondary and none GND windings. Can anybody explain me how can i get GND in this case (pict scheme if it's posible)?

Thanks.

 

[linuxworks]

I'm not sure what you're asking.

the transformer has 2 secondaries. there is no center tap and each secondary is its own winding. you can join the 'top' and 'bottom' wires to form a center tap. THAT can be your ground if you use the typical design of 1 full wave bridge and 2 regulator chips with the center tap being ground/common.

you can also use a ground 'rail splitter' and feed that from the total of the 2 windings (in series) and have the rail splitter 'form' a virtual center ground for you.

 

[S3am]

Thank you for answer. I think using virtual ground is not good idea. Then:
Quote:

Originally Posted by linuxworks /img/forum/go_quote.gif you can join the 'top' and 'bottom' wires to form a center tap. THAT can be your ground if you use the typical design of 1 full wave bridge and 2 regulator chips with the center tap being ground/common.

Yes I'm planning to use 2 regulator chips (7909 and 7809). But i can't imagine how to get the ground in this case, because i have a little experience with simple +\- transformer and +\+\gnd, but no exp with subj.

Can you draw simple scheme, please?

 

[tangent]

Just Google for dual power supply. What you're asking to do is very generic. You should be able to find dozens of schematics.

 

[deltaydeltax]

There are four pins on the secondary side. The two in the middle closest together get wired together and that becomes your ground.

There are also four pins on the primary side. They get either paralleled for 110-120V, or you connect the two middle ones and attach a plug to the two outter ones for ~220V.

 

[S3am]

deltaydeltax
Wow, great! Thanks!