I've found this schematic and from looking at the modules they sell, it looks almost like a dead ringer. I was wondering what you guys think. I know there was some concern for the the dropping resistor (820K) in another thread, i'm going to update that to a 1/2W thru hole.
What is the AC mains voltage you intend to measure?
120V, 220-240V?
120V, on multimeter in socket I get 121.3V
The 820K was intended for 220-240V applications.
You want to choose a resistor that gives you about 1 mA of current through the transformer.
So R=E/I, R=120V/1mA, R=120K.
The power is I^2xR, P=1mA^2 x120K, P=0.12W. A 1/4W SMD would be OK
The Peak voltage is 1.414x120=170V, so choose a resistor that has a working voltage of 200V or more.
Hth:
In that diagram @ruilviana provided, in Figure 4, they are using a 100K pot and some of the cap values are different, 100pf instead of 1nf. Otherwise it's basically the same as the one I posted from what I can tell.
@jim-p I had a feeling that value was off. Thanks for showing me the math to determine!
I'll have to change the values Im using on the breadboard circuit and see what comes of it, I'm trying to take the ZMPT101B module and build it into a PCB.
One other issue i'm having a problem with, is there is no marking for Pin 1 on the ZMPT101B module or the crappy datasheet. Is Pin 1 on the top left with the writing on the module facing you so you can read it?
Does that matter with a 1:1 transformer? Both windings are the same.
You can figure out the winding pins from the footprint. Spacing is not the same.
Leo..
I realized that was a stupid question when I remembered it was a 1:1 transformer. D'oh
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