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[on:]

I live full time in an RV and there is a ventilation fan that I would like to enhance with a timer. The ultimate goal is to push a button and have the fan run for a short time (15-30 minutes..?) or push another button to cause it to run for maybe an hour. Of course there would need to be a button or other means of cancelling the timer function if necessary.

I was thinking that an ATtiny85 might be a good route to go.  Any thoughts or suggestions would be greatly appreciated.

[Reply #1 on:]

You could get some ideas from this:

http://www.forkrobotics.com/2012/05/relay-control-over-i2c/

[Reply #2 on:]

An ATTiny will do it fine and is what I'd recommend. You don't even need a crystal if you don't mind being a few seconds off in your timing.

[Reply #3 on:]

Exactly, and I agree: I don't think he would need the precision in his timing with fan.

Anyway, good luck with your project!!!

[Reply #4 on:]

I live full time in an RV

Likewise, great lifestyle eh?

I concur with the above, a tiny85 will perform that function easily.

_______
Rob

[Reply #5 on:]

Thanks for all the input folks! I appreciate it. Yes, full-timing in a RV is great!  I'm still trying to put this project together.. Being retired, I don't get in a big hurry to do anything these days    So I now have a couple of ATiny85's ... one to practice with (and potentially let the smoke out of) and one for after I have the bugs worked out. I'm figuring on taking the RVs 12vdc and a 5 volt regulator (plus a couple of caps on the input & output) to bring it down to 5v for the ATiny..  I have relays that are for 12 vdc operation (both the coil as well as the contact side. I also have some small(-ish) arcade-style buttons that are backlit with some LEDs for the timer function. Again, I want to push one and have the fan run for a shorter time (10-15 minutes..?) and another one will turn it on for longer.. around an hour. No crystal since it really doesn't matter if it runs 15 minutes versus 16.5 minutes, etc.  I'll breadboard this all up this weekend and see what happens. Next is the code for the ATiny.. I'm planning to use my Arduino Uno for that.. I have already found the code I can use to go that route.  So.. any input on circuit configuration or components (instead of, in addition to what I have already mentioned).. would certainly be appreciated.