O
ozzy
- Jan 1, 1970
- 0
Hi all,
I've been trying to get a value going from 0 to 100 on an LCD display
using a PIC micro controller (VCC- 5v, VEE - 0V) with AtoD (10 bit -
but converted to 8 bit in software). The hardware used is a simple
non-inverting op amp (LMC660 single supply) with non inverting pin
connected to a voltage divider of 0.05v (my step voltage). I have a
10K linear pot (wiper connected to output) acting as the feedback
resistor along with a 100 ohm resistor to ground.
My problem is that although I get movement of numbers from 0 to 100
there is always slight jumps. E.g if number is set to 6 it will jump
from ~ 3 to 9. At first I thought it was capacitance of the POT leads
so I trimmed that down to a minimum - but still the problem remains.
I have thought about using a current mirror to set the current, but the
circuit described above is using that principle. And anyway the pot
value would have to be high to avoid offset voltage errors.
beginning to feel I've turned full circle....any help on this issue
would be much appreciated.
Regards,
Ozzy.
I've been trying to get a value going from 0 to 100 on an LCD display
using a PIC micro controller (VCC- 5v, VEE - 0V) with AtoD (10 bit -
but converted to 8 bit in software). The hardware used is a simple
non-inverting op amp (LMC660 single supply) with non inverting pin
connected to a voltage divider of 0.05v (my step voltage). I have a
10K linear pot (wiper connected to output) acting as the feedback
resistor along with a 100 ohm resistor to ground.
My problem is that although I get movement of numbers from 0 to 100
there is always slight jumps. E.g if number is set to 6 it will jump
from ~ 3 to 9. At first I thought it was capacitance of the POT leads
so I trimmed that down to a minimum - but still the problem remains.
I have thought about using a current mirror to set the current, but the
circuit described above is using that principle. And anyway the pot
value would have to be high to avoid offset voltage errors.
beginning to feel I've turned full circle....any help on this issue
would be much appreciated.
Regards,
Ozzy.