looking for a timer that will change fan settings.

i want my fan to kick on 90% when my lights come on and stay there, when they go off i'd like it to go down to 20% to maintain negative pressure so my house doesn't smell like the inside of a stash box. i've looked and the only things i've found have been expensive, complicated things that look like they're designed to run a furnace.
Anyone know of something like this? right now i'm considering buying another controller, setting it at 20%, splicing another plug onto my fan cord, and running the thing with two synced digital timers.

This may help you. I run my fans and a heater of it. I set it at 19 on the temp the room runs prefect. When the room gets to 19 the fans will come on. Lower then that and the heater come on its the best way. I have been using a thermostat for years

SMSCom 4.5-Amp Twin Fan Speed Temp Controller (don't bother with the cheaper older 4 amp version which apparently hums).

Only works on 240v though (made in the Netherlands). They come with cable glands to hard wire or EU/UK plug sockets. Supposed to be a great bit of kit.

Not sure if anything like that exists with US plugs or 110v though. A DIY alternative would be something like this:

http://www.ebay.co.uk/itm/261717417309

Wire up a 20% variac to the "heating" plug and a 90% variac to the "cooling" plug. Have them both wired to the same fan. Then make it switch between "heating" and "cooling" depending on a preset temp. Not quite as elegant but it should work the same. (Disclaimer: I haven't tried that device myself)

the thing is i don't really care about the temperature...as far as this goes (of course i care about the temp., but with the fan on 90% i know what its going to be anyway, with the fan pulling the 72 degree air from my house in it stays at 76-77.) i have my lights and fan coming on at 8:30 am so the school kids (and their parents )who get on the bus right outside my house won't hear it.
the lights go off at 8:30 pm, and right now the fan does as well. i'd like the fan to stay on at 20% power to keep a negative air pressure so my house doesn't smell. the little carbon scrubber i made works well, but not if its not getting air pulled through it.

In that case...

Use a timer and a DPDT relay. "Normally open" circuit goes to a Variac set to 90%. "Normally closed" circuit goes to a Variac set to 20%.

When your timer is powered on the fans run at 90%. When your timer is powered off the fans run at 20%.

hmmmm.....i'll definitely look into this, thnx

well what you suggest is possible, but i was hoping for something in the 50 dollar range, maybe 100, this would take close to 200 to make, and thats with my engineer friend buying the parts and putting it together for me. your suggestion is good, my budget isn't.

I just really assumed i would be able to go to ebay or amazon and find one with little effort, spent hours looking there then all over the web, only ones i found had been discontinued, and they looked shady anyway.

All the ones I've ever found were based on temp control.

Consider mounting another exhaust fan with low cfm?

i give up. i just ordered a 6 inch 440 cfm fan, which i will run through the light with a carbon filter when its on, and i'll use the 4 inch 190 cfm i have now when the light goes off to vent the box through a separate carbon filter and keep the smell down.
apparently i think of things that don't exist, unfortunately it seems like im the only one that wants it.