AVR-Chat

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

 I used v150la20, 150v (22mm) MOV's. I am still researching 
 the correct values. I may put them on the contactors 
 instead of the PCB next time.


>>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.

 It did get it to work without disabling the Int0. I left 
 it in because it did not seem to affect the operation
 and was insurence against the problem.


>> 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.

 This is why adding the diodes did not help and the
 unit worked with its own relays and not the contactors.

 I am making a second unit that will control more. I will
 include what I have done and experiment some more.

 Thanx 
JoeT


--- 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 
> 
> 


__________________________________
Do you Yahoo!?
Yahoo! Finance: Get your refund fast by filing online.
http://taxes.yahoo.com/filing.html



 
Yahoo! Groups Links