Electronics > Beginners
AC measurement circuit question
(1/5) > >>
Tom18991:
Please see the schematic below, which is one of many similar versions on the internet for measuring AC voltage on a microcontroller.  If the AC source is independent of the microcontroller's power input (for example, the AC is coming from a sensor that generates its own signal and the microcontroller is powered with a 9v battery), then how can the microcontroller measure the DC voltage on the output of this circuit?

Benta:
Don't do this. You have 230 V live voltage on your MCU and display, it's potentially lethal.
Tom18991:
Thanks and no worries.  I don't play with that kind of power.  :)   I'm borrowing the concept to measure the voltages off a variable reluctance sensor.  The volts might climb up to 20-30v, but without the current of a power line.  I see there's a ground at the bottom of the circuit, which I presume is tied to the arguido ground, which probably explains my confusion.  I'll try it on a (safe) function generator and see how I get on...
Kleinstein:
The circuit is a crude form of a peak detector. It's slow and temperature dependent.

With a decent ADC inside the µC and only mains frequency it is usually better to do direct AC sampling and that do RMS calculation in software. Even a 8 Bit µC with 10 Bit ADC like 8 bit AVR can do that surprisingly well.
Tom18991:
Mains frequency?  Meaning the frequency of the 220v?  My actual project involves a low-current ac sensor, and the waveform is not a sign wave.  I'll play with various circuits, and am looking for something cheap :) without the need to be all that accurate -- +/- 5% is plenty good enough for my purpose.  I was just confused how this could even work, but probably just missed the fact that the sensor circuit appears tied to the Arduino ground plane.
Navigation
Message Index
Next page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod