AVR-Chat

As I remember MOV's do wear, you might want to
consider this. What is voltage rating for them?

>I also left in the Int0 interrupt disable before
> switching the 
> relays on.

this doesn't seem to me a proper solution, you should
better have fixed the problem with other cautions, so
that you can free your mind from this.

> 2) Added diodes across the relay coils - no
> difference

when working with inductive loads, these clamping
diodes are always needed, this is why most designs
include them. The ULN2803 driver ICs, IRF530 like
transistors for example do include them internally,
because most people use them with inductive loads, and
integrating them was so natural.




--- Joe <joet@attg.net> wrote:
> Thanx to everybody that contributed to the Thread.
> I got good ideas and the problem is solved.
> 
> I think the main fixes were:
> 1) MOV's across the relay contacts
> 2) 6.2v zeiner across VCC to ground
> 3) .01uf caps at the LCD+, AVR power pins
> 
> I also changed:
> 1) Removed the cap across the switch - no difference
> 2) Added diodes across the relay coils - no
> difference
> 3) I also left in the Int0 interrupt disable before
> switching the 
> relays on.
> 
> I tried changing the resistor on the Int0 but a
> lower value did not 
> pull the VCC down far enough. I will try to post an
> updated schematic.
> 
> JoeT 
> 
> 


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