Wireless transmitters (pic16f1825 has a 5 bit DAC)

Thread Starter

Ian Rogers

Joined Dec 12, 2012
800
On my wireless transmitters I use 3v batteries... I then connect a voltage divider consisting of 2 10k resistors to the battery terminal to ground and read middle... BUT!! I use and internal reference of 1.5v.. (pic16f1825 has a 5 bit DAC) My system needs 1.8V to function so my percentage is 1.8v -> 3.2v. I just read the voltage which should be 1.5v max to 0.9v min.
 

upand_at_them

Joined May 15, 2010
475
On my wireless transmitters I use 3v batteries... I then connect a voltage divider consisting of 2 10k resistors to the battery terminal to ground and read middle... BUT!! I use and internal reference of 1.5v.. (pic16f1825 has a 5 bit DAC) My system needs 1.8V to function so my percentage is 1.8v -> 3.2v. I just read the voltage which should be 1.5v max to 0.9v min.
You can simplify this *and* use less power by reading the internal fixed voltage reference, which will of course give a result dependent on your Vdd (the battery). Use a lookup table to return the result. Microchip have an app note about it, including calibration.
 

Thread Starter

Ian Rogers

Joined Dec 12, 2012
800
ou can simplify this *and* use less power by reading the internal fixed voltage reference, which will of course give a result dependent on your Vdd (the battery). Use a lookup table to return the result. Microchip have an app note about it, including calibration.
True.... But nowadays I throw a solar panel on and charge a lithium cell... Never needed to monitor the battery since..
 

Thread Starter

Ian Rogers

Joined Dec 12, 2012
800
We also use the MCP73831 when using the larger 18650 batteries... As these will last months without sunlight, then they charge quite rapidly... We use the SOT version Only a prog resistor and two external caps needed
 

upand_at_them

Joined May 15, 2010
475
Ian, are you using a charge controller? I'd be worried about weird charge effect, or poor charging, due to clouds-sun-clouds-sun... Any problem with that?
 
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