piclist 2002\10\29\132805a >
Thread: Speeding up a relay - zero crossing detection
face BY : Wagner Lipnharski email (remove spam text)

What about using two relays?

The first idea was to feed power to the load only when Relay#1 is not
energized and Relay#2 is energized, power would flow by both relays
contacts, so, energizing Relay#1 (that you can do in 4ms), will cut power
to the load and would release Relay#2 from auto-sustain.  This would be
something like Set/Reset flip-flop using relays. But here you need a
zero-crossing detector to sync the operation.

The second idea was to use the Relay#1 to switch Relay#2 coild feed power
from DC to AC rectified non filtered lower voltage, so, when Relay#1
energizes, the Relay#2 will still energized (auto-sustainned) as long the
semi-senoid holds power to it.  When the senoid drops its voltage to a very
low level (around 160 degrees or less), Relay#2 will release armature and
also will interrupt its own sustain. With some sort of luck it could
release power from the load very close to zero-crossing without any
external sync.  You could call this a "line sync shut off".


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See also: www.piclist.com/techref/io/motors.htm?key=relay
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Subject (change) Speeding up a relay - zero crossing detection

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