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Main => Main Forum => Topic started by: jimmy2x2x on July 05, 2011, 01:33:57 pm

Title: Simple 12v delay circuit?
Post by: jimmy2x2x on July 05, 2011, 01:33:57 pm: I was wondering if there is a simple circuit I could build to delay 12v from a pc power supply molex for 5 seconds when power is applied, after 5 seconds it should remain continuous.
Title: Re: Simple 12v delay circuit?
Post by: boardjunkie on July 05, 2011, 01:42:29 pm: A 555 timer circuit driving a relay (via transistor switch) should work fine.
Title: Re: Simple 12v delay circuit?
Post by: jimmy2x2x on July 05, 2011, 01:43:52 pm: excellent, could you translate into spazomatic for me please?

(uk parts links would be very welcome)

I have no idea!
Title: Re: Simple 12v delay circuit?
Post by: Bender on July 05, 2011, 01:51:02 pm: I don't know about making one but they make such a device for car custom a/v installs
can't remember what they're called off the the top of my head though, used one to delay the monitor coming on

ahh, here is the thread where I asked a similar question (http://forum.arcadecontrols.com/index.php?topic=98288.0)
Title: Re: Simple 12v delay circuit?
Post by: WindDrake on July 05, 2011, 03:14:11 pm: Here's my try at it, assuming my memory serves right!

10nF Cap - ECQ-V1H103JL
Diode on Relay - 1N4004
Relay - G5LE-1 DC12
BJT NPN Transistor - TIP29C
555 Timer - LM555C
4.7k Resistor (1/4 Watt, 5%) - Get it anywhere!
1000uF Capacitor - ECA-1EM102B

Here's the schematic. As with anything you see, check it for sanity! (I'm at work and rushed. :P)

(http://www.booguild.net/winddrake/schematics/12v_555_5sec.gif)
Title: Re: Simple 12v delay circuit?
Post by: bkenobi on July 05, 2011, 06:35:13 pm: This might be useful. I've wondered how to set the delay on a 555 before but never checked. This is a calculator.

http://clarkson-uk.com/555-timer/operation/frames3.html (http://clarkson-uk.com/555-timer/operation/frames3.html)

It looks like a set capacitor value with a rheostat would provide a variable delay. Find an appropriate sized capacitor for the rheostat you want to use and you're good to go, right?
Title: Re: Simple 12v delay circuit?
Post by: BadMouth on July 05, 2011, 07:40:46 pm: http://www.crutchfield.com/S-nH1bbdA6HFz/tech/kb327.html (http://www.crutchfield.com/S-nH1bbdA6HFz/tech/kb327.html)
Title: Re: Simple 12v delay circuit?
Post by: boardjunkie on July 05, 2011, 10:25:52 pm: Quote from: bkenobi on July 05, 2011, 06:35:13 pm
This might be useful. I've wondered how to set the delay on a 555 before but never checked. This is a calculator.

http://clarkson-uk.com/555-timer/operation/frames3.html (http://clarkson-uk.com/555-timer/operation/frames3.html)

It looks like a set capacitor value with a rheostat would provide a variable delay. Find an appropriate sized capacitor for the rheostat you want to use and you're good to go, right?

10k resistor with a 470u cap gives a time of 5.1 secs.
Title: Re: Simple 12v delay circuit?
Post by: Gray_Area on July 10, 2011, 07:10:45 pm: What are the details of the application?
Title: Re: Simple 12v delay circuit?
Post by: jimmy2x2x on July 10, 2011, 07:29:46 pm: Quote from: Gray_Area on July 10, 2011, 07:10:45 pm
What are the details of the application?

Postpone power switching to TV, so I can apply power to all devices at once, postpone switching for a couple of seconds, then apply power to select correct scart channel.

Looks like there are some great solutions here, I have not had chance to experiment yet.