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measure the current flowing in the wire

jsotola
– jsotola

2020年10月28日 02:01:54 +00:00
Commented Oct 28, 2020 at 2:01
2

R -----/\/\/\---|>|----- W ... perhaps a high value resistor in series with an LED .... it is possibe that a small amount of current could pass without activating the heater ... the LED would actually be emitter part of an optocoupler ... when the heater is off, the LED is on ... the thermostat contacts short out the LED when they close, which causes the LED to turn off

jsotola
– jsotola

2020年10月28日 02:11:17 +00:00
Commented Oct 28, 2020 at 2:11
@jsotola Your opto solution worked! I have used an optocoupler in series with a 22k resistor and it does not trigger the heater. I measured the resistance between emitter and collector terminals of the optocoupler. Heater on → 0 (shorted) Heater off → 17Mohm I hope I hooked it up correctly to Arduino to detect it.

zip85
– zip85

2020年10月28日 03:29:35 +00:00
Commented Oct 28, 2020 at 3:29
1

You should add a diode in reverse in parallel with the LED of the optocoupler. At the moment you're halving the power delivered to the heater. Also the optocoupler may die from the reverse voltage of AC. That is if it really is AC - you say +24VAC which makes no sense - there is no + in AC, only DC.

Majenko
– Majenko

2020年10月28日 21:41:40 +00:00
Commented Oct 28, 2020 at 21:41
1

@Majenko added D1 but it was working anyway. The heater has a relay so it's on or off. Also added pull-down R2.

zip85
– zip85

2020年10月29日 06:05:48 +00:00
Commented Oct 29, 2020 at 6:05

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