This is one of those so trivial problems that shouldn't need advice but, as so often with me, I have over researched to the point where Ic an't make a decision. Since I am not going to get a smart electricity meter real soon now I intend to build my own power monitor. The meter has a red LED which flashes 1000 times per kWh and the key to the project is measuring the time between flashes. But I can't decide the best way to detect the flashing LED. CDS photo resistor followed by a Schmit trigger; photo transistor followed by a transimpedance amp. There should be no problem excluding ambient light and the LED flashes for about 1/2 second. __________________________________________ David C Brown 43 Bings Road Whaley Bridge High Peak Phone: 01663 733236 Derbyshire eMail: dcb.home@gmail.com SK23 7ND web: www.bings-knowle.co.uk/dcb *Sent from my etch-a-sketch* --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .