Wanted - PIC based LVC for 3S Lipo

[Bearded Flyer]

I have built the voltage comparator based lvc from another thread in this forum but it refuses to work for me. I want to run a 3S Lipo (my first one and currently in the post) on a non-lipo friendly esc. I have a few 16F88/877/84 PICs lying around and wondered if anybody had a circuit and code to use one of these as a lvc. When the battery voltage drops to 9v I want to pull the motor signal line to ground through a resistor and thus stop the motor. I have programmed PICs before to fire my AP camera shutter when the motor is turned off but I have not done anything with the A/D inputs.

Richard

[Mr.RC-CAM]

A PIC would be fun, but this project would be easily solved with a simpler analog based solution. Take a peek at the MAX8211 -- Long ago I used it in a similar app (took one 8-pin IC, about 4 res, a cap or two, and a pot).

[Bearded Flyer]

Thanks for the info but a MAX8211 is difficult to obtain cheaply over here.

Richard

[Mr.RC-CAM]

The MAX chip was just offered as a simple canned example. For sure, there are other hassle free analog solutions out there too. For example, a lowly LM358 could be used. Again, just an example of software free components for creating simple voltage detection designs.

Don't get me wrong -- I am a big promoter of using PIC's (a huge understatement). But, if you do use a microcontroller, then take advantage of it and add other useful features while you are at it (ie, failsafe, glitch counter, voltage reporter, LMA, etc.)

Unless your chosen PIC has an internal precision VRef source in it then you will have to add one to your design. This is the same issue with the analog solutions, so there is often no advantage in that regard to either method. Beyond that, using the A/D module in the PIC is simple and fully described in the data sheet.

[TheAdrian]

... a MAX8211 is difficult to obtain cheaply over here.
Richard

There are some ICL8211s going on Ebay UK. I decided not to bid for
them myself because I was going to use a PIC for mt project.

[Bearded Flyer]

I have chickened out for the time being and ordered a commercial version. I want to get the plane back in the air! I hate to be beaten and enjoy making things work but this has taken up far too much flying time already. I will experiment a bit more when time permits. I will not be beaten :)

Thanks again
Richard

[Chippie]

Richard, you could try and obtain the Max ic from Maxim as a free sample...

I've had 712s and 713s from them for free... ;)