24Vdc DIY power supply?

[Grainger49]

The first one.  

You are right, the schematic is wrong.  I should have the line to the center of the two bridges eliminated.  I'll correct it and change the link.  (OOOoooo  I get to use my erasing shield again after all these years, I was trained on a drawing board, then Intergraph, Cadam and AutoCad). 

Thanks!

 

[audioclass]

Well I think you have it on there correctly, but looks like there might be some eraser marks there and it made it difficult to tell.  No biggy thanks for the quick reply and of course thank you for drawing up the schematic for me in the first place!

 

[audioclass]

Is this along the lines of what I'm looking for in a transformer?

http://www.digikey.com/product-detail/en/241-5-24/595-1056-ND/952926

 

[Paul Joppa]

You only need one bridge (four diodes).

 

[audioclass]

I'm no EE so could you elaborate on that a bit?  I'm going off of Grainger's design here using a 12-0-12 transformer and my knowledge bank is pretty empty beyond understanding some BASIC (just enough to troubleshoot simple circuits) DC theory and reading schematics.

 

[Grainger49]

Paul is saying you can use a 24V transformer and create a virtual ground.  A pair of matched 1/2 Meg ohm resistors, in series between the two DC legs will create a virtual ground.  Then attach the capacitors and regulators to the positive and negative rails, ground is between them.

Your transformer is 24V rated at 1/2 amp.  So if that is enough current for the load it is fine.

 

[audioclass]

This is the design then?  Are there any disadvantages to using this method to rectify instead of the two bridges?

 

[Grainger49]

Ok, I looked up the unit and it uses a chip that draws 4.2mA quiescent.  So any power supply you build will be more than it needs.  The above transformer you linked will do well.

What you have drawn will be fine.  The dual rectifiers might have more separation, might not.

 

[audioclass]

Oh wow, so I could go to a smaller transformer in an attempt to save some space then?  Say 100mA or less?  The 500ma would be considered overkill then most likely?

As for the bridges, maybe I'll build both and see which sounds better.  I'm sure I could find a buyer for the second one

 

[Paul Joppa]

The dual bridges will go up in smoke. You don't need a "virtual ground" - the center tap is the ground, assuming you are looking for +12v and -12v.

I can't believe it - I googled a half dozen different sets of keywords and couldn't find the simple design - and found lots of incorrect stuff. It's crazy.

Here's the circuit.

 

[jrebman]

Do you even need a bipolar supply?  I thought the cmoy had a chip that provided a virtual ground and plus/minus rails internally to the board.  I know my omega micro dac has one of these Ti split rail chips in it because the current draw is so low and it simplifies the external power supply design.

Just asking because it's been a long time since I even looked at the cmoy.

-- Jim

 

[audioclass]

I just need a 24v linear regulated PS.  The specs don't specify +24v vs +12v/-12v.

 

[jrebman]

That's what I figured.

-- Jim