This week i built a timer for my grinder...
It has a switch and a timer relay...very simple!
The relay is made by dayton, and has accuracy to the 100th of a second under 10 seconds and 10ths of a second 10 seconds and over. It runs in line like the darkroom timers (it plugs into the wall, and the grinder plugs into it), and it adjusts with little push-buttons that advance the digits one number up or down. The model number of the relay is Dayton 6A855 if you want to see it. I bought it at Grainger for $75. Total the project could be done for under $125 with tax if you are handy. The cheapest darkroom timer i saw was around $200 + shipping. I can give more details if anyone is interested!