howardb

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?

chiark

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"???

David_Wallis

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

David_Wallis

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

David_Wallis

im also no expert.. at posting!

chiark

Cheers David, any help would be most appreciated!

Nick.

chiark

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

john banks

Voltage regulator?

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

Silent Monkey

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

orbv

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).]

chiark

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!

Adam M

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.