In all the energy monitor projects I remember seeing I've not seen a CdS cell used, not that I think there is anything wrong with that idea, they've all used a phototransistor or photodiode, I seem to remember one that used an LED... The late John Becker had one or two published in EPE that were Pic based, might be worth seeking those out? On 20 Feb 2018 10:29, "David C Brown" wrote: > 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 ti= me > 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* > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=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 .