I've only recently set up my new darkroom from bits and peices given to me secondhand. I don't have a timer on my old Zenith enlarger, which means I have to reach round the back to switch it on/off and count the seconds down on the clock - which is quite clumbersome, perticulary if I'm trying to shade areas of the image at the same time.

Since money is a bit tight I'm considering building my own exposure timer to controll my enlarger. I wondered if anyone else has any experance of this and could point me to some circuits.

The best one I've found so far is:


Thanks in advance,