Computer Keep On Circuit

Wendy

Joined Mar 24, 2008
22,181
Looks like one of my kludges.

I've been running a BBS / print server for around 20 years, using a really old computer, the kind with a push on / push off power button. I also use it as a file server, it is handy for backups. The only reason I suggested a relay way back when is you don't want to inject voltages into an unknown circuit like the motherboard switch, and both MOSFETs and transistors must be biased correctly. With a relay, it doesn't matter, and relays can be very small indeed.

I gather you have your own vision what you want. I'll respect that. If you want any more input from me just PM me.
 

mkbutan

Joined Sep 30, 2008
296
Looks like one of my kludges.

I've been running a BBS / print server for around 20 years, using a really old computer, the kind with a push on / push off power button. I also use it as a file server, it is handy for backups. The only reason I suggested a relay way back when is you don't want to inject voltages into an unknown circuit like the motherboard switch, and both MOSFETs and transistors must be biased correctly. With a relay, it doesn't matter, and relays can be very small indeed.

I gather you have your own vision what you want. I'll respect that. If you want any more input from me just PM me.



no no no why PM this thread came up to hear we all would like to know the perfect solution after all we came upto #83 and +++++++++
so pl. no PM its an request :cool::(
 

Wendy

Joined Mar 24, 2008
22,181
Actually this is the OPs call, drawing schematics is work, and I've already done one custom drawing. I wasn't happy with it, I think a three minute timer delay is what is called for in this case.

I think the OP is convinced he can do this without solid state components however, so he'll has to ask me for help or I'll go on to my other projects, of which I stay swamped. It is his problem to figure out, and part of the fun of electronics is problem solving. Who am I to deny anyone the fun?

What I think I'm seeing here is a problem called brainstorming. Everyone feeds ideas into the bucket, which in turn can generate new ideas.
 

R!f@@

Joined Apr 2, 2009
9,734
no, that's a momentary toggle switch. my old button broke so i just put a new switch on to replace the button
like one of these but a momentary version so it pulls back down when you release
A toggle switch. seems to be a relay at the first glance. :confused:

To OP : I asked u something.
 

Thread Starter

Kool1zero

Joined Feb 13, 2012
24
ahhh so far i haven't had time to prototype anything. but i've got all the pieces listed for bills circuit except the relay for now i just grabbed a couple leds and some resistors for them. I've been leaving school and heading to work, get home, work on some homework, sleep, and head back to school the next day so i've not had much time
 
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R!f@@

Joined Apr 2, 2009
9,734
Gimme a list of the components u have or better yet show us if u can.
I'll be around tonight and tomorrow. So may be I can start something for ya ..
 

Thread Starter

Kool1zero

Joined Feb 13, 2012
24
i have a lab full of electronics components at my college, they said i could have as many discrete components and more common chips like 555s no problem. they wont let me have any relays though, so i've got to find time to drop by radioshack or get one on order
 

R!f@@

Joined Apr 2, 2009
9,734
Fine then.
After dinner and some head banging on a Monitor, I will wip up something that I would actually use in such a case.

Ur's or mine I dunno whose luck but I do have a IBM open under my feet for such kinda odd things.
 

R!f@@

Joined Apr 2, 2009
9,734
U know when I doodled the circuit came out much simpler :D

Try making it, then I will tell u how to connect it.
The unmarked capacitor C and Resistor R has to be determined by you. The combination gives u the delay between Off time to On time. Capacitor voltage can be 10V

I tried with 100uf and 100K and it gave me the delay needed to test it. It was around 1 to 2 minutes.

The Relay should be a 5V type and just one set of NO contacts will do.
Q1 is based on the relay current and can be any thing suitable for ur relay.
T1 should be capable of handling 500mA or more if you decide to use larger values for C. as this transistor is used to discharge the cap when the sense line is active.
All R's can be low power types.

Once you finished it, I will tell u how to implement it safely.

hint...
U know I think I can get rid of the relay too. But for this you need to do some DMM probing for me.
 

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Brownout

Joined Jan 10, 2012
2,390
You'll only expect a Beta of around 10 from Q1. It'll probably need a driver transistor. That will also help with turn on from your RC network.
 
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