Harry Tenopoulos wrote:
>
> Hello everybody
>
> I have designed a PCB for the company i work for which is used on an
> automatic machine..
> The board has 3 PICs on it (2 16C54 and 1 16C55)
>
> This board interfaces with 3 external power relays.These relays are
> signaled from 3 other reed relays on the board which are
> opto-isolated from the signaling PIC.
>
> When the power relays operate alone (not connected to the machine's
> motor) there is no problem. But when they are connected problems
> start. These three relays control a two speed bi-directional  220V
> motor. At the change of speed or direction the electronic circuit
> seems to be reset (it happens about once in 10 changes).
>
> Can anyone tell me what is happening ?
>
> Harry

I've had similar problems with DC motor control
I have not had time to find the problem yet but I
was very sloppy with earth returns and decoupling

I did find a mention in the pic16c84 data sheet ds30081A
"6.3.3 Operating in a noisy environment" page 32
says that "register contents can get corrupted due to noise
spikes.The on-chip watchdog timer will take care of all situations
involving program sequence "lock-ups." however,if an I/O control
register gets corrupted, "............... you get the idea

My lock-up problem is on a 16c56 but I must assume that the
registers on all the pic's are similar and therefore all
are prone to this problem

--
Peter Cousens
email: peter@cousens.her.forthnet.gr
snailmail: Peter Cousens, karteros, Heraklion, Crete, 75100, Greece,
phone: + 3081 380534,    +3081 324450   voice/fax