Beginers Question

Hi All,
Im not very knowledgable about electronics at all and hoping someone may be able to advise me as to what component (if there is one) will do the job.
I have an old laptop that wouldnt boot so for fun I thought id try and fix it, mainly through good luck I seem to have stumbled on a way to get it to boot, but id isnt a bad component I can find. But I have found that if at the right time I short from a component to ground then it starts up perfectly.
To simplify... I have a wire that when I power on gives 3v, if I hold it to earth then start the laptop then nothing happens at all but if I wait for around 2 or 3 seconds after I press the power button then touch the wire to earth then the laptop starts.
The question- is there some kind of component that would do this ?
maybe a relay of some kind but then i need a trigger for it.
Any suggestions would be appreciated.
Cheers
Steve.

Are you holding the laptop in reset for a couple seconds to maybe let an old slow hard drive spin up enough to boot?

Hi mramos,
No this isnt a delay for a hard drive. Just wont boot unless it can be earthed at the right time. I imagine from what Ive read I could use a mosfet but id need to find a supply on the MB that gives power at just the right time, and wasnt sure if there is any kind of component that would give a delayed connection.
Cheers
Steve.

I know in the old days there was a sony playstation MOD that was what you want for a PIC I think, it grounded a power line (for msecs, but you can change that) and you can add a couple resistors and an FET and to it that way. google for sony playstation mod ship source code. It was a long time ago. Think it was a 12C508 or 509. You can mod it to the 12F629..

mramos,
Ill take a look.
The delay is really only needed at start up and then could stay grounded as long as the laptop runs so long as it disconnects when turned off ready for the next power on cycle.
Cheers
Steve.

It all looks a little complicated for me mramos....do you think there is a simpler way ?
I was hoping I may be able to find a single component that might do what i need.
Cheers
Steve.

OK tell all again what you need.

When you turn the computer on, you short a wire to what voltage for how long. And it works?? Give exect details (volts and time) and I am sure someone will pop in with an answer.

Ok mramos, when I turn on.from the moment I hit the button I get 3v from the wire, when the screen lights up about 2.5 secs after I hit the button I ground the wire and the laptop starts, if I do it before the screen lights the laptop doesnt start, once the laptop is running I can leave the connection grounded for as long as the laptop runs if i want to but need to disconnect it when I shut the laptop down so that it isnt connected when I restart it again as I need to delay the connection every time I start it up.
Cheers
Steve.

Hi Steve

I only wonder whether you are not resetting the thing- and it is comming up !!!

mvs sarma, no Im not resetting it.
This is on my part also an experiment, there may be other ways of fixing the laptop or I could take it to an electronics shop but that defeats the purpose.
The problem I have isnt a laptop that doesnt start .. the problem is how to delay the connection of the wire.
Cheers
Steve.

please fill in your location.. Also, be detailed and short with your posts.

Like:

I have 3VDC for power, 2.5 seconds after power is turned on I need to ground a signal line. It would also be nice if I could adjust the time. Can I do this with an RC circuit? A 555 or microcontroller?

My quick answer would be:
I would pull out a PIC (12F625), FET and two resistors (write a small program) and be done. But you need to have all the equipment to do that.

You can look at RC curcuits, and charge a cap to drive the gate of an FET? Maybe google for "555 one shot"

Hi Steve

PLease try a capacitor ( say 4.7uF/16V or 25V )in place of the said wire observing proper polarity.. After a moment the capacitor shold not conduct any more. the Laptop could behave.

mvs sarma,
That sounds more within my capabilities, but would that not work in reverse to what I need by giving the connection from power on then cutting it ?
Excuse my questions as I have very little understanding of electronics.
Cheers
Steve.