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Delay Circuit Problems - Need Help

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Kinsy

New Member
Hi.

Im currently building a couple of circuits based on the following:
Here are the components used:-
1 220uf 16v Capacitor
1 1N4001 Diode
1 9v Zener Diode
1 1k Resistor
1 10k Resistor
1 DPDT Relay (Omron G6P-2214P)
1 NPN Transistor (BC108C)
This is what the circuit looks like complete.

The circuits job is to delay the current on the PC floppy connector's 12v and 5v rails for 1-4s. This is so i dont get a voltage spike and the PC's PSU shuts down. It in effect is designed to replace me holding the floppy connector out of my ATi 9800SE AIW graphics card, turning on the PC, counting to 3, and then plugging the connector in, in order that the PC boots.

However its not working. Here is something i worked up in illustrator which has all the components laid out.

Can anyone tell me whats wrong with the circuit, and why its not working?

Thanks in advance.
 

Kinsy

New Member
Er, its at the top. I cant get the IMG code to work. Just copy and paste into your browser.

I cant provide anything else, because i dont have anything else, and im asking people to fill in the gaps.
 

Roff

Well-Known Member
Don't use IMG codes, use URL. It will look like this:
.
Code:
[url=http://iownjoo.com/freeimghost/kinsy/Delay%20Circuit.GIF]delay circuit[/url]
.
Embedding this in the text, it looks like this:
delay circuit
I simulated the circuit, and it worked, but it is marginal - it requires a fairly high beta transistor.
You can make it really snap on by adding some positive feedback, and make it more tolerant in the process. Connect a 10k resistor from the collector of the NPN to the base of a PNP. Connect the emitter of the PNP to +12v, and the collector to the capacitor. This also allows you to use a smaller cap and a larger timing resistor, such as 100uF and 22k.
 

Kinsy

New Member
Could you make me a diagram detailing what i have to do, and an additional parts list?

Thanks
 

Roff

Well-Known Member
Kinsy said:
Could you make me a diagram detailing what i have to do, and an additional parts list?

Thanks
Do you really need that degree of hand holding? The additional parts are a 2N3906 and a 10k resistor. I described how to hook them up. You should be able to add them to the schematic you have. If you can't, tell me why and we'll go from there.
 
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