I can see that the trick to this is going to be getting the on/off adjustable to the second. There are lots of timers, but they are limited to on/off by minute.

I control my peristaltic pumps to the second with my Aquatronica...but I'm sure you don't want to go that extreme.

Something to look into maybe what they call "repeat cycle" or "percentage cycle" timers.

Some links you can try exploring (look at page 2 of this thread):
http://www.canreef.com/vbulletin/sho...d.php?t=43323&

Happy hunting though .. I don't imagine you'll find these timers at your average hardware store.

The only programmable timer I can find with a minimum setting of 1 sec is the Mist King timer I use on my viv.
It only has 8 programs so it might not be enough for you.
There are repeat cycle timers that go down to 5 sec and I think I saw some that were min 1 sec. Check out the hydroponic stores.

there are many electronic timmers that are for industrial and commercial use, just check with an electrical supply store and see what they can get you.
I think Omron makes a fully programable down to the second 24hr timer
i have one at work that can be programed down to the second in a full year period, just needs to be wired up and then programmed

Those are the timers I am talking about. Omron H3scr's have On delay, Off delay, repeat, and other featires built in. BUT, the repeat is the same on/off time. SO, if you set a 5 sec time, it will be 5 sec on/5 sec off. You need 2timers One in ON delay, on in OFF delay.

That price is also a bit high I think. Check eBay for some smokin deals too. Omron makes timers 1/4 the side of that one too. The one in your link is 1/16 DIN Sized. THey make smaller ones, 1/32 DIN I think?

Heres one $20
http://cgi.ebay.com/H3CR-A8-OMRON-Ti...3%3A1|294%3A50



Here is the PDF file on the omron H3CR series timers

http://www.omron247.com/doc/pdfcatal...9H3CRA0302.pdf