Here's a kit: http://www.proaxis.com/~iguanalabs/555kit.htm
Hi, I want to wire up a relay that goes from normally open to normally closed for around an hour then back to normally open, with the switch being a wire that goes from 0V to 12V.
I was thinking about doing this with a IC 555 timer, but I don't know what the schematic would be for it.
Could anyone point me in the right direction?
All the sites say that the trigger works by having the V go low,
But my source is opposite. It goes from 0V to 12V.
Ahh so a 12V to 0V will trigger it? Is it ok that the 0V will not go back to 12V for more than an hour?
I'm planning on using my ECU which goes from 0 to 12V when the key is in the ignition.
So if I drive for less than an hour, the 555 will be on for an hour and go off.
If I drive for more than an hour, the 555 will be on for an hour and go off.
Get a standard 5 pin relay, and wire it up, whatever you want to be on to the NO and off to the NC. Then, do some crap that will wait an hour and put +5 on the positive terminal. (I suck)
Quick! To the Popemobile!
Originally Posted by BiohazrD
Will the 12V to 0V drop trigger the 555? Does it matter that the trigger may not return to 12V until after the 1 hour?
No. What you want is a relay with NO -Normally Open and NC - Normally closed on it. This is what BiohazrD is talking about.Originally Posted by phita23
You hook up your 555 timer trigger to the NC pins. When the relay is energized, it will OPEN those pins, and you'll get a change in state from 12 volts to 0. This will trigger your timer.
I understand that. My question is... I've read that, usually, the trigger needs to go back to 12V before the pulse is over.
That is, if the pulse length is 1 hour, the trigger needs to reset before 1 hour.
Is that true?
Ah! I get what you're asking. I don't actually know the answer to that, but I do have a 555 timer circuit kit that does what I think you're asking about.
I needed a timer that delayed turning power on for 10 seconds after the computer started. I looked at 555 circuits but ended up buying this 555 kit instead:
It has 8 modes, one of which is to instant on, stay on for a user programmable period (1 second to 2550 minutes) and then turns off. There's a PDF of the instructions so you can read about it if you want. Best of all, the input is 9-12 volts.
It includes a relay (NO and NC) so you can wire something up to it. I bought the kit because by the time I calculated the cost of Radio Shack parts I was practically at the price of the kit and I was still short a couple items -like a circuit board.
You have to solder it up yourself but it's no big deal if you've done a little bit of soldering before.