Darkroom computer - photometer, temperature meter and process timer

10-30 — elektor october 1982 darkroom computer darkroom computer Readers who have already read the "instructions for use" in the previous issue, will have a pretty good idea of the capabilities of the darkroom computer. However, before all the available features can be used the necessary accessories have to be constructed. In this case there are three such circuits; to measure light, temperature and a time/ sequence indicator. The processor timer is little more than a box containing a series of LEDs in a line giving an optical indication of the passing of time. After all, it is nice to know how much longer a particular photograph has to remain in the devel- opment tank of bath, rather than panic at the last moment when the acoustic alarm is heard. The rows of LEDs, in efect, indicate the amount of time that has elapsed since the start button was pressed. How long each LED remains lit and at which point the buzzer sounds is determined by the computer. The alarm can sound after 15...