2

I guess its a dumb question but couldnt find anything about it online. I know its possible to supply the AREF pin with 3.3 V to increase the ADC resolution.

For the project i am working on the analog voltage i will be reading will be between 0 and 2.2 and the increased resolution is a must.

I know i can use another board that has a 12 bit resolution but i really would like to make do with Uno. So i wonder if i can set an analog pin to output 2.3 V and feed it to the Aref pin.

If thats not possible please let me know why, so i can increase my knowledge

Improve this question

2 Answers 2

Reset to default
3

With an input voltage between 0 and 2.2 V, you can use a 2:1 voltage divider to cut the voltage in half. In your code, use analogReference(INTERNAL) to set the analog reference voltage to 1.1 V. The 1.1 V internal reference voltage is created by a bandgap circuit so is reasonably accurate.

To make the voltage divider, put two equal resistors (eg 10KΩ each) in series; connect one end of the series to your input voltage, the other end to ground, and the mid-point to an analog input pin.

Improve this answer
2
  • Once you set the analog voltage to the internal bandgap voltage source, you can measure the actual voltage on the AREF pin using a multimeter. You can use that voltage to "calibrate" that arduino.
    – Gerben
    Aug 24, 2016 at 18:32
  • @Gerben That seems like easiest option, thanks for the further explanation. I also checked the oversampling, which i have never heard of before. It also seems quite valid. Again thanks for the heads up
    – Firat.Berk.Cakar
    Aug 24, 2016 at 20:47
0

The output voltage of the "analog outputs" (which are actually PWM) are dependent on supply voltage and so are not a good choice where precision is required. Consider using either an integrated voltage reference (e.g. TL431) or a constant-current source feeding a zener diode instead.

Improve this answer
2
  • Thanks for the quick reply! The things is i really try to refrain from using another circuit, allthough its relatively easy to use, the target users will have no idea how to set it up. The resolution i need is not that much, just 2.5 V /1024 instead of 5 V / 1024. sadly 3.3 V wouldnt do. Is the way i suggested still too unreliable in these conditions ? And if it is do you have any other suggestion that would not require another component ? thanks in advance!
    – Firat.Berk.Cakar
    Aug 24, 2016 at 14:14
  • @Firat.Berk.Cakar You could try oversampling to get better resolution.
    – Gerben
    Aug 24, 2016 at 18:33

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.