soundboy Posted November 12, 2004 Report Share Posted November 12, 2004 Hi... I have a simple question, yet for some reason I'm blocked and can't figure out how to do this.I have a system which generates a variable AC current . What I need to do is measure this AC current and somehow feed it back to a microcontroller (passing through a ADC first). In order to do this, I guess I need to take the AC current and obtain from it a proportional DC voltage level which I cand send back to the microcontroller.Can anyone help me find the best way to achieve this?Thank you! Quote Link to comment Share on other sites More sharing options...
Kevin Weddle Posted November 12, 2004 Report Share Posted November 12, 2004 What you will find is that you already have a circuit. The AC is divided across whatever elements you have and the voltage divided by the resistance is the current. In the case of a single element, you don't have a voltage divider. But you still have the voltage and resistance and thus the current. What you are guessing at is the theoretcal situation in which you have a variable load with an AC source. Maybe a light activated resistor. But I think that even an ammeter uses the voltage over the known resistance to calculate the current. Quote Link to comment Share on other sites More sharing options...
soundboy Posted November 13, 2004 Author Report Share Posted November 13, 2004 I understand, but what I need to know is how to obtain a variable DC voltage level, which is proportional to the variable AC waveform I'm feeding into my system. Quote Link to comment Share on other sites More sharing options...
Dazza Posted November 13, 2004 Report Share Posted November 13, 2004 Hi soundboy, I know very little, but maybe you can use a hall effect sensor for measuring the current, then feed the signal from that to a frequency to voltage converter. Quote Link to comment Share on other sites More sharing options...
trigger Posted November 17, 2004 Report Share Posted November 17, 2004 use a coil and opamp circuit, you can convert AC current to DC voltages. Quote Link to comment Share on other sites More sharing options...
audioguru Posted November 17, 2004 Report Share Posted November 17, 2004 I understand, but what I need to know is how to obtain a variable DC voltage level, which is proportional to the variable AC waveform I'm feeding into my system.Hi Soundboy,You described the function of a rectifier circuit.It can be a simple, half-wave rectifier using only one diode but will have a 0.7V loss and won't rectify signals below 0.7V peak. It could also be a full-wave "absolute value" rectifier circuit using a couple of opamps, without any loss (can even have gain) and can rectify signals as low as millivolt levels.Your choice. Quote Link to comment Share on other sites More sharing options...
soundboy Posted November 17, 2004 Author Report Share Posted November 17, 2004 That's just what I needed.Thank you! Quote Link to comment Share on other sites More sharing options...
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