AVR-Chat

John Samperi wrote:
> At 10:28 AM 20/07/2006, you wrote:
>>  but in this case I can't.  (The solenoid is connected
>> remotely)
> 
> How remote is remote? A few cm or a few metres? Remember that
> the wire going to the solenoid becomes an antenna radiating
> electrical noise if the back emf is not suppressed somehow.
> 
> 
> Regards
> 
> John Samperi

When I worked in access control systems, we used to use solenoids up to 
1.5A current (direct) all bigger loads were through relays. We had a 
good on board protection network, but STILL PUT DIODES ACROSS EVERY COIL 
. Stopped strange problems like opening 1 door and all the doors in that 
  cabinet opening (some of the electro magnets drew up to 20A if the 
keeper plate did not make contact :( and when you broke the supply, it 
would give a nice spike. I built up a rig in the workshop to simulate 
this, one old big electro magnet, with the keeper spaced at the point 
where I would get the maximum voltage spike. IF my gear drove it and did 
not fail, I knew it was VIRTUALLY bullet proof (still had a few where 
the load destroyed the network (I had to use polly fuses, as standard 
fast fuses were not allowed by the building owners for insurance reasons)

-- 
Regards,

Kat.
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