I need some advice on protecting the micro controller when measuring an AC power line (300VAC max). I do not have much experience in this matter.
My circuit is supplied with a fly-back switcher because of high power requirements. The supply to the micro controller is isolated.
I now want to measure the voltage, phase and freq at the input of the fly-back switcher (directly on the AC power line). I'm using a resistor and 2 clamping diodes to protect the I/O pin.
Is this enough protection? But the circuit is not isolated anymore, except on the switcher side.
How do I go about isolating the measuring part without using a transformer. Can I use an opto-coupler?
Or is it unnecessary to isolate the measuring part while the supply is isolated?
The circuit must conform to standards for commercial use (SABS - South African Bureau of Standards).
Please any good information will help.
Regards
Protection and safety design of this kind is not something that one learn at Engineering School. It is something that one learn through experience in the industry.
I am by no means a novice to this kind of work and just asked for some ideas. Hopefully somebody with some experience could have given a useful input rather than putting me down (At least Erik did). Thanks!
I am qualified to do this and have 5 years experience in electronic design (Not that it is that much but it counts).
But thanks for your help, concern and positive responses.
Have you looked for a linear optocoupler yet?