go to pet store...like petrus and go to iquana/reptile area.

they have what is called a day/night timer, or*wave-maker timer.(*you can place power heads at different angles in a pool to create cross turbulence, or something like that.)

anyway...It costs about 28 bucks and you can set on/off every 15 minutes, furthermore what is cool...the day/night function allows you to have 3 seperate way to control a grow-room from a single timing device.
1st. It has 4 constant power inputs...
the 24 hour timer has 2 day and 2 night inputs.
So, I use mine like this.
I put my 24 hour on appliances...i.e. airpumps are on 24/7
Fans...
then I put my nutrient rez pump on the daytime timer.

The daytime side is yellow inputs and will turn on/off every 15 minutes or one time in a 12 hour period, or whatever...MInimum 15minute settings....I use 15 on 15 off for clones...45 on and 15 off for growing.

someone with ebb and flow might turn their pumps on 15 minutes then off for anywhere from 2 hours to 12 hours...depending on medium used. Sorry, I didn't mean to rant, but I just started typing and all this came out.

the blue inputs for night turn on an off when the lights are out...co2 or automated night foliar feeding...ooooooooohhH,
got you thinking now, HUH? Anything you can think of

Oh yeah fans can also be put into this On the constant 4 input side or on the timers...so The big one can be off most of the night photoperiod.

OK, enough of this rant...give somebody else a chance...

No, I can't STTtttooooopppp, Just kidding. LOL

good buddage. Kaliorange-skunk

I gotta go! lw