[chbot] Opto isolated triacs - Digikey account anyone?

[Mark Atherton]

Robin,

Any chance of a PDF schematic ?

If you are happy moving to optos, then that has the possibility of 
fixing all manner of issues in one-fell-swoop.

Still might be worth taking a look at coil current before and after 
just to be sure that a) the DC offset is actually causing the issue, 
and ii) the new solution resolves the issue.

I am still having a hard time understanding how even a 20% DC content 
can physically burn out solenoid windings (if this is the correct 
failure mechanism) - sounds more like a high current impulse problem 
- again, measuring coil current with a scope + resistor may be useful.

Have you measured AC current of the energized solenoid using a DMM 
(try the same test on DC amps) ?

Also, any chance of unwinding a busted solenoid, and measuring how 
much current is actually required to fuse the single-strand conductor ?

-mark

>There is another issue - with 24VAC, peaking at 34V plus the 12V driver
>voltage, the common round the garden and paddocks is up at 46V on occasion
>which is enough to tingle when kneeling in wet grass and working on wiring
>with with soggy fingers!!
>
>Using the opto isolation would allow me to ground the centre tap of the
>24VAC transformer which would make the whole system safer.