Newbie- Will this PSU blow something up?

[georgeburns]

Okay... gave up on my last idea for dropping the big transformers voltage to power the fans.

Added a second transformer which is a low voltage 12.

The attached pdf is my first attempt at trying to document anything electrical... hope it looks okay.

I cranked it up and tested the voltages with my multimeter. They all look great without load. They all looked great with a 12V fan load on the 12V output. No components got hot after 20 minutes on time.

When I hook this up to my CNC4PC BOB, Gecko 203s and Steppers... will anything cause problems?

[vger]

I looked at your drawing and have a few questions.

Are your rectifiers full wave bridge modules or discrete diodes ?

Are the capacitors on the high voltage supply in series because the voltage rating on them is too low ?

Did you include small capacitors across the output of the 7812 and 7805 to keep them from oscilating ?

Why is there a jumper straight from the bridge to the +5 volt output ?

Steve

[Al_The_Man]

Originally Posted by vger Are your rectifiers full wave bridge modules or discrete diodes ? Why is there a jumper straight from the bridge to the +5 volt output ? Steve

I think these are drawing errors, the bridge is just drawn wrong and would not work the way shown, also the regulators are drawn as 2 terminal devices instead of three.
Al.

[georgeburns]

Originally Posted by vger I looked at your drawing and have a few questions. Are your rectifiers full wave bridge modules or discrete diodes ? Are the capacitors on the high voltage supply in series because the voltage rating on them is too low ? Did you include small capacitors across the output of the 7812 and 7805 to keep them from oscilating ? Why is there a jumper straight from the bridge to the +5 volt output ? Steve

Thanks for the response.

The rectifiers are full wave.
The capacitors are in series to be extra safe, 65V was enough to handle a 50V output, but I read somewhere to ensure that they were rated at least 20 percent more than the output.
No capacitor across the output of the 7812 and 7805... is oscillating bad in this case and what type of capacitor would resolve it?
Jumper from bridge to +5volt output is a drawing error.

Thanks again.

[martinw]

Originally Posted by georgeburns Thanks for the response. No capacitor across the output of the 7812 and 7805... is oscillating bad in this case and what type of capacitor would resolve it? .

Dear georgeburns,

It is a good idea to put something like a 1uF tantalum (electrolytic) capacitor between the regulator output and ground. Make sure this capacitor is close to the output pin, and make sure you get the polarity correct. They go off with a sharp crack if you get it wrong.

If the PSU filter capacitor is far away from the regulator input, you should put a tantalum between the input and ground ... say 0.33uF. Observe the same precautions as above.

Best wishes,

Martin