# Voltage Scaling with a Hall Sensor...

OK Hopefully someone might be able to give me a little guidance here as I am have been researching information on all sorts of different methods of adjusting voltage and haven't really found anything that my brain is processing to be applicable to what I am trying to do..

Anyway I am trying to use a Teensy LC to read an analog input from a Hall Sensor using a Magnet with a higher Range on the ADC.

The Hall sensor works on the 3.3V with the Static center voltage of 1.64V. The HALL Sensor is a 2 Way Sensor but I really only wish to use one direction. the Low Read with a magnet right up against the sensor is .84V or a little more than Half range of the one side of the Hall but it relates to only about a 1/4 of the ADC's 10 bits or about 256 steps. That would be OK but I would like more.. I was able to get more by voltage dividing to the AREF @ 1.65V which then of course shuts off the reverse direction of the HALL and moved me 512 steps from the HALL as it never reaches 0 and use half the range.

My issue is though that in my project the Magnet is NEVER far enough away from the HAL sensor to not have some degree of Pull on the Sensor which causes its Nominal Low voltage on the one side to start at about 1V which of course causes the range on the Sensor to be between 1V and .85V which gives me a VERY small Range of input on the ADC. apron 50ish steps I calculate.

I am trying to find a simple way to expand the range of input to the ADC on the analog pin without exceeding the 3.3V limit. I have been looking at amplification and offsets, as well as dividing and offsets but I am getting myself lost.

As I was writing this I did realize that I can just alter the AREF to 1V instead of 1.6V and that would expand the range to about 154 steps which is better but I would still like to have more of the 10bit range. as the 1V to .85V is 15% of the range.

I might be able to possibly find a closer field magnet but it might not work as well (I don't know that would be an experiment)

Anyway any help or just direction of what to look at doing would be greatly appreciated.

gilshultz:
This is a very common problem that is relative easy to solve if you understand what you are doing. If you add a rail to rail op-amp in a non inverting configuration you can increase the voltage range. Please realize it will also amplify the zero offset, but many will operate on a single ended power supply such as 5V.