To stabilize the voltage i used a zener diode of 12V (5W) connected on the base of a 2N3055 transistor,
followed by a LM2940T-5.0 regulator.
Another problem that a i have to solve it is to eliminate the electromagnetic influences. This can be done beginning with the design of the circuit/pcb . It is important to:
a) place the controller in to a metallic box
b) all the conductors (power and signal) must be shielded.
c) the pcb must designed with ground plane and components must be SMD if it is possible.
d) avoid ground loop.
I change the controller 16F876 with 18F2550 which has same layout (28pins). The 16F876 has some difficulties at memory access because the memory are split in banks. The 18F2550 memory can be allocated withowt problems. Another advantage of 18F2550 is 32K program memory.
