PIC negative voltage analog read

[Karolina_1]

Hi everyone
I have an output which changes from -15 to +15 and i need to display it on the LCD display using PIC18F45k22 and mikroC pro language has been used. But the problem is that 15V is too high and it cant read negative values. What is the best way of doing it. I really appreciate any help or idea.
Thank you

 

[KlausST]

Hi,

A frequently asked question .... with many discussions and solutions... in this forum .... and even more in the internet.

The solution depends on:
* ADC input range
* desired precision
* signal frequency
...

Please do a search, read through the search results...
Then give enough informations and ask a more detailed question....best if you give documents, links...which you refer to.

Klaus

 

[j33pn]

a shortened link to an opamp schematic on https://www.falstad.com/circuit/circuitjs.html , a simulator applet.

https://tinyurl.com/y9b3ruc3

...contingent on issues raised by the esteemed KlauseST

- - - Updated - - -

 

[FvM]

The Falstad applet is a good example of a circuit that simulates correctly with an ideal OP model but never works with a real OP. OP inputs need to be flipped, feedback must be negative.

A simple 5k:1k voltage divider with Vref = 3V does essentially the same, don't necessarily need an OP, unless you want higher input resistance.

 

[j33pn]

corrected: https://tinyurl.com/ybx9nvf6