voltage/current detector

[jabss]

Hello,

I have a microcontroller controling some home appliances (220v) with some relays.
When each relay is closed, these apliances may be consuming power or not, because each one of them have their own switch (some are floodlights with presence detector, water boiler with its own thermostat, etc.).

I'd like to know when the appliances are really on (consuming power), because turning it on with the relay cannot tell me for sure (the internal switch may be on or off). For each appliance I have a ucontroller output port, driver and relay, and will have an input port that will tell if the appliance is consuming or not.

I have initially aproached this problem with a current detector and ADCs, but in some cases the current flow is so low that it wasn't detecting the difference.

I believe I need to aproach this problem differently. Any suggestions?

Basically I need a circuit that detects that the appliance circuit is closed (relay and internal switches) and then puts a ucontroler pin at "1".

Any suggestion?

Thanks,
Jabss

 

[ronsimpson]

What "current detector" did you try?
What current range? Current maximum = 20A, Current minimum=0.5A.

 

[alec_t]

With the right current sensor you should be able to detect currents down to just mA easily.

 

[jabss]

Hi,

I used some ACS712 kits connected to a PCF8591 (I was planning to know if the appliances were on/off by reading the value on each ADC port). There are kits of 5, 10 and 20A. I tested a 5A kit, the datasheet says it will increase 185mv per Ampere. The appliance I tested is a 20w Led floodlight and therefore consumes arruound 90mA (220v AC). This means the ACS712 would increase 16mV when ON, which is difficult for the PCF8591 to notice any difference (8 bits). Also, since I'm using AC, the output of the ACS712 is also variable (50 Hz).

Because of this, I decided to abandon the use of current detector. I was wondering if there is any other (and easier) way of identifying if there is power passing by...

I saw some ideias in the web with phototransistors, like the TLP620, but I don't think it would support voltages like 220V AC.


Any ideas?

Thanks,
Jabss