Em 12/9/2011 11:35, Michael Watterson escreveu: > Isaac Marino Bavaresco wrote: >> Em 12/9/2011 10:34, Michael Watterson escreveu: >> =20 >>> Forrest Christian wrote: >>> =20 >>>> I'm struggling with coming up with a circuit which I actually like for= =20 >>>> measuring AC line voltage and current. The goal is to be able to rea= d=20 >>>> the voltage of AC line within a volt or two within a microchip PIC....= =20 >>>> For obvious reasons I'd like something where in normal operation the A= C=20 >>>> line is isolated from the PIC side of the circuit. >>>> =20 >>>> =20 >>> Neon and a photo transistor? Should work at about 200uA on mains side? >>> Voltage varies the current thus brightness due to large series resistor= ..=20 >>> Better suited maybe to 230V AC than 110V AC. >>> >>> Hall effect sensor to measure line current. >>> =20 >> >> It seems that my suggestion got lost in the list: >> >> "You could make a circuit with a small PIC (8 pins) with A/D converter, >> connected directly to the AC line, powered by a transformerless power >> supply and using a resistive divider to measure the line voltage. Then >> transmit the result of the measurement to the other side of an >> opto-coupler to a circuit that implement the remaining functionalities >> of your appliance. This way you can read as many different signals as >> you wish." >> >> >> Isaac >> >> =20 > I thought that a good idea. But I thought he objected to current draw of= =20 > the LED in the coupler? Can you go less than 1mA? It seems that the OP is worried about power dissipation (heat), not exactly current consumption. The capacitive power supply is mostly reactive, not resistive, so the power dissipation is small even for moderate currents. If he uses a power resistor to drop the line voltage, then a few mA generate a lot of heat, but with the capacitive power supply the power dissipation is very small. Isaac --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .