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Timing circuit for A/C.

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fordrule

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Hello, Its been a while a since ive dealt with circuits.
I want to make a Timing Circuit to use with AC power (im in Australia, 240V, if it makes a difference) .

Here was my idea, trigger (push button) a 555 timer to close a relay for a period of time.
Would this work? as in, can a 555 hand the AC input (with the use of something to bring the input amps down)? I was thinking of having the relay switch to the off state after 1/2hour-1hour. Could the 555 handle this?

Also does anyone know of schematics available to help me so i dont have to come up with it all on my own? Like how i can attach the 555 to the relay, im looking for my old notes and circuits but i cant find them anywhere.

Please help, thank you all.
 
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This would go better if you explained the project in detail. Also, the 555 is not well suited to long timing applications. It sounds like what you are after is called a one shot, where when triggered the output will change state for a period of time then return to it's original state. That signal would drive a relay to switch an AC load. Something like that what you are after?

Ron
 
A 555 requires a low voltage DC supply. It is not good on its own for time periods greater than a few minutes, but can be used to clock a counter IC to give much greater periods (hours, if needed).
 
I have attached a timer that could be adapted for 30 min or 60 min.

This is a variant on the timer I built for my garage door opener. It keeps the light on for about 3 min after the door has been opened or closed.

However, RC timing only provides approximate timing. eg. say 30 +/- 5 minutes.

If you want a more accurate timer, then you would need a counter as someone suggested.

I look for a counter timer later. Have to go out now.
 

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Not a bad little timer kit there KISS.

Maintaining my tradition of off the shelf if I had 220 VAC mains (or whatever) and wanted to switch mains voltage AC with a respectable current I would get one of these. Easy to program just like the kit. DPDT output with 10 amp contacts. Simple push button (or whatever) to start the cycle and they work forever in my experience. Then too, they carry about a $100 USD price tag. :)

Ron
 
That one doesn't look too bad either. I need to replace an SSAC Delay on Break 120 VAC timer for a bathroom fan, but I don't know how I wired it 20+ years ago. It's mounted in the attic. 122 F isn't so bad. I need 20 minutes.
 
Here is an analogue timer that will operate a relay for about 1 hour.

If you want it to be 30 minutes, change the capacitors to either 33 or 27 uF.
 

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Ron:

I found one of those relays (120 VAC) for $30 ppd and I ordered it, BUT I think I need a 120 VAC trigger. The thing is burried and I have to move a lot of stuff to get to it in the attic.

Since you have used them, do you have any idea what the "Start Switch" equivalent circuit might be like? Is there a DC voltage present there, AC? Current drawn? Maximum Resistance that is considered closed? Anything useful?

I want to know if I have any other options besides another 120 VAC relay to isolate the "Start switch" and trigger from a 120 VAC source.
 
Hi Kiss

The start switch is just a matter of a N/O push button across pins 5 & 6. That is about it. :)

The NCC ones I use have an 11 pin base so you need a socket. If you need a socket let me know. I have a bucket of them lying around. They have about 5 functions. Repeat, 1- Shot, Delay on Break, Delay on Make, and Interval. Hell, a little late but if you want I could send you the whole thing after Christmas.

Ron
 
$25 with DIN rail socket, not $30 ppd.

I need to make the NO button, 120 VAC activated, I'm pretty sure.
So, I need a 120 VAC coil pilot duty relay that mounts easily (e.g. DIN rail).

That button circuit could be AC or DC. We know a contact works, but will a transistor work (e.g. optocoupler), will FET work? (optocoupler). Will and SCR work (optocoupler). The are all potential less. Will a 200 ohm resistor work? or a 20 ohm resistor? 10, 5, 1?
 
Bathroom fan correct? OK, enter bathroom and turn on light & fan. Set up timer for DOB (Delay on Break). Set time for 30 min (or whatever you want). Fan runs off the relay so after light is turned off fan will run an additional 30 min.

Got to get my ass going to work. I'll post more later from work. :)

Ron
 
I have a broken www.ssac.com device there. I forget which model. I think it's like this one, but longer: http://www.ssac.com/product.php?pid=800&catid=55 May even be obsolete.. I forget what size J-box it's in even. 6" x 6" is my guess. The SSAC device is much smaller. I THINK it uses a 120 V trigger. 14 AWG wire, pigtailed to stranded, 1/4" Fast-ON terminals. Those Right angle screw to fast-on things will help.

The bath has a duplex switch: 1) Light, 2) Fan w/ delay on break (~20 minutes). It also has a mechanical timer for the heat lamp.

Right now, fan has a mind of it's own. It doesn't always come on or stay on.
 
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