I am currently doing EMG using arduino to capture the waveform. I used duel power supply opamp +5 - > -5 V to get the signal but arduino can only handle 0 -> +5 V. So i built a basic diode bridge to convert the signal, but the voltage drop a bit instead of 0-5V it is -2 -> 5v. How can i solve this problem ?
NeedToKhow:
How can i solve this problem ?
Show us all your parts and whatever schematics depict your current circuit.
After that is, you read and fully understand the posting instructions.
Assuming you mean "electromyography", is value more important than time?
If value is most important the best way to convert a bipolar signal to unipolar signal is a precision rectifier. If a half cycle is acceptable you can easily make your opamp into a precision rectifier by the addition of a rectifier in series with the opamp output (before the feedback resistor).
How do you plan on sampling the output with the Arduino? Are you looking for the Peak, RMS or Average value? Or do you plan on sampling the signal at multiple points and doing some other analysis?
Tell us more about your goal and circuit and we can help more.
Google precision rectifier - a circuit using an op amp with diodes in the feedback loop to eliminate that voltage drop .
why not just apply a positive offset and then sample the output of a divider?
NeedToKhow:
I am currently doing EMG using arduino to capture the waveform. I used duel power supply opamp +5 - > -5 V to get the signal but arduino can only handle 0 -> +5 V. So i built a basic diode bridge to convert the signal, but the voltage drop a bit instead of 0-5V it is -2 -> 5v. How can i solve this problem ?
Simple voltage divider will convert -5V..+5V range to 0V..5V The 5V rail is the base of the divider for this,
not ground. Rectification is definitely not the right approach.
Thank you all, I tried out precision full wave rectifier, it work out very well