The opto isolator gets it's dcv for it's input side by rectifying the 7.0
vac at the cold end of the fil choke. Run through a FWB, then some series
diodes to dump some excess voltage, then a 100 ohm bleeder (1/4 watt diss)
ensures there is 50 ma of bleeder current at all times..and ensures the
diodes are always turned on, and forward biased. What's left if 5.0 vdc to
run the opto isolator. The opto is 5 vdc rated, and will handle anything
from 2.5-8 vdc. You can also get 15 vdc versions, that will handle
anything from 9-16 vdc. Last one in the ODC series is the 24 vdc version,
which will run on anything from 18-32 vdc. The output on this opto is
rated at 200 vdc @ 1 amp CCS. You can also get them with a 60 vdc @ 3 amp
CCS output. They all turn on in < 100 usecs..... and turn off in <
750usecs. 4 kv isolation between the input + output side. No moving
parts, stupid fast, and an industry standard. Output of opto is used to key
the sped up 4 x vac relays.
Later Jim VE7RF
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