16F690-Potentiometer Shorting Out??

[JDR04]

Having completed the flowcahrt with the kind help of this forums members, I have strated to build the circuit on a breadboard.

I have connected up the 10K Linear potentiometers as per the method in my attached schematic. However, while experimenting, one of the pots shorted/burnt out when on its minimum setting.

Could somebody tell me where I have gone wrong in connecting up my potentiometers please and a better way of doing it.

I also plan on using 4 X 1.5 AA batteries for power but will insert a diode for two reasons;

To drop 6V down to within the 16F690 required specification for power supply.
To prevent any accidental damage to the controller by accidental wrong polarity connection.

I would appreciate any advice/comments on how I can improve what I have done so far.....Thanks a ton, John

[medelec35]

Hi John I would guess your pots could be burning out because they are connected to ICSP data and ICSP clock connections.
All you will need to do to stop pots from burning out is connect a 10K resistor between each wiper and microcontroller i/p connections.
The ICSP connections connect directly to the microcontroller pins.
So effectively there is a 10k resistance between the pot wipers and programmer/microcontroller pins.
This will also prevent damage to microcontroller/pots if you have pot on min or max resistance and you accidentally configure pins connected to pots as an output.
It will also prevent damage to your programmer.

Another issue I have spotted is you have a yellow LED connected to pin A3
A3 is MCLR pin which will be an input only pin.
Besides during programming this pin can go over 10V.
Twice the normal 5V
So you will need to connect yellow LED to a different pin.

Martin

[JDR04]

Thanks Martin, seems to have done the trick. Been running for 24 hours now and no wisp of smoke.

Thanks again.....John

[medelec35]

Hi John,

Been running for 24 hours now and no wisp of smoke.

Phew that's a relief.
Thanks for the update

Martin