Hi guys. I'm trying to make a VA Meter by getting real time data from a rectifier using a microcontroller. The circuit uses a voltage divider to get voltage (A0 Pin) and the drop accross the shunt resistor for current (A1 Pin). When I apply a rectifier though only the A1 Pin gives a signal, I don't get a reading from A0.
Any idea on why this is?
I attached a snap shot of the circuit, it's pretty basic.
Thanks for your help!
Edit: i attached the image
The description of what you are doing is vague. It appears that when you say "1A read 2A" it means that 2 amperes are measured flowing through the .47 Ohm (R3) resistor. In other words, using OHm's law .47 Ohms times 2 Amps equals .94 volts across R3. Is this what you are measuring ???
Again using Ohm's law, A0 would then read ' .94 volts times 100k divided by 105k equals .895 volts ' ???
It would help if you could tell what you are measuring ( volts, Amps, Ohms) and how you are measuring it (with a meter ??).
Sorry it took me a while to reply. What type of microcontroller are you using? Can we see a snippet of the code? Your system looks very simple, which makes me assume that your issue might actually be a coding problem. . .
Instead of doing RTM on the system, you might just do an intterupt that periodically samples and records the voltage and curent on pin A0 and A1. . .
If you can tell me the controller/code or both, I can only reccommend checking your code to make sure your not lossing the voltage data.
Not to leave the uanswered questions about what was being measured hanging. The point is: That there is nothing wrong. If current was being measured at A0, then 0 is the measurement that a meter would show, if it was on the same setting used to measure the 2 amps at the .47 Ohm shunt resistor, since only .00000895 amps would be flowing through the 100k resistor.