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Topic: Testing coil (Read 318 times) previous topic - next topic


I've got a device similar to this
or this: http://patentimages.storage.googleapis.com/US6249417B1/US06249417-20010619-D00000.png

It has a coil in it switched by a triac.
I opened it up and found a 47ohm NFR was blown, so I replaced it with a 47ohm resistor.

I'm not sure if it's working (switching coil on /off), I'm looking for a test to discover that.

If I were to meter the mains for frequency, I wouldn't likely see the coil switching as it still is 50Hz (they claim it uses electromotive force to disrupt noise on the cable to deter pests).
I did feel the coil after around 10 mins of running and it was midly warm, which I think would happen if it was switching, but then.. what happens if you have a coil with active on one side and open for a long period?
I checked the MOV inside the device, it's got very high resistance across it (normal).
I checked the IC (a 14 bit counter) for frequency output to the triac, and this was 1.5Hz.
I checked resistance across coil at 4.7kOhm.

Any thoughts on how you'd test it was working?


The best way is to look at the voltage across the triac with an oscilloscope.
You could try and wind a pick up coil with an LED across it and see if it lights when you bring it close to the coil.

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