How much current does this 12V input require, because that will dictate what you can use to achieve the delay & turn on. Is there a threashold voltage for this input?

 

I have a bit of a challenge that I need help with.

The PSU for my in-car computer (for playing MP3) outputs the standard AT voltages (+5, +12, -5, -12)

My motherboard needs all these, plus a further input at 12v when the PSU is happy and ready to supply a steady voltage for everything.

The PSU doesn't give this. So I've tried putting 12v straight into this, and occasionally it boots, occasionally it doesn't.

What I need is some way of delaying the supply to that pin.

Is there an electronic component that would do this for me? I am thinking that a capacitor and resistor may work, but it may be a bit too simple. Is there such a thing as a "delay relay"???

 

I'm no electronics expert, but I know that you could use a 555 and a transistor to do it..., Im sure you could do it with a capacitor and when the capacitor is charged... Ill ask my dad tonight how to do it...

David

 

I'm no electronics expert, but I know that you could use a 555 and a transistor to do it..., Im sure you could do it with a capacitor and when the capacitor is charged... Ill ask my dad tonight how to do it...

David

 

im also no expert.. at posting!

 

Cheers David, any help would be most appreciated!

Nick.

 

It's a footling amount of current, can't tell you what the threshold voltage is unfortunately.

 

Voltage regulator?

or Relay after the 555 circuit - 555 should provide enough current to switch a relay?

 

Assuming you're talking about the powergood signal. I thought it went to +5V after the PSU stabilised not +12 (certainly does on the one I've just measured).

Take a look at

 

Using the example on the web page given by Silent Monkey may work but its a bit of a dirty fix. The voltage on the Power Good output will ramp up from 0 to 5 volts. If the equipment connected to the output draws a bit of current the voltage may never rise to 5 volts.

This is the hack....
<BLOCKQUOTE><font size="1" face="Verdana, Arial">code:<HR><pre>
+5V-------///-------To Power Good
1k |
-- +
-- 100µF/16V
|
GND--------------------GND
</pre><HR></BLOCKQUOTE>
If you want something a bit more clever drop me an email.

[This message has been edited by orbv (edited 13 October 2001).]

 

That's the bunny - it's the power good. I'll try it - if it all goes quiet, don't worry I've not blown myself, I'm just all over the place this week!

 

Sounds like great advice.

In this situation there is only one bit of advice I ever use.

"ASK PAT!"

He knows everything when it comes to electronics and is a bloody whizz.

Nick, if you want help on this, drop me a line if/when :P you dont get it sorted and I will see what I can forward you to.