 "Solid State" Variac HELP
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Curtis
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Sun Aug 31 2008, 04:44AM
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Registered Member #883
Joined: Sat Jul 07 2007, 01:02PM
Location:
Posts: 16
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Hello all,
I was just wondering. In Steve Connor's Solid State Variac, pin 5 on the 555timer that controls the firing angle is tied to Vcc thru a 220microfarad Electrolytic. In every monostable i can think of, its tied to Ground thru a small decoupling cap. Why is his tied to Vcc? Also when i crunch the numbers i seem to get a delay that is adjustable from 100milliseconds to 10 milliseconds. I was thinking for a 50 Hz line that a delay of about 4milliseconds to about 10 milliseconds would be ideal. That would turn on just before the crest for full power and just before zero crossing for little power. 60Hz lines should have about 3mS for big power and just <8mS for small power.
Doc Connor, if your out there, please set me straight.
Edit: I guess in reality the Solid State should not have quotes and the variac should as it is truly solid state but is not really a variac. Just an afterthought
Double Edit: I recrunched the numbers and it turns out that 91k in parrallel with 0k is 0k. that make the delay adjustable from .1mS to 10mS. Just what it should be for a 50 Hz line. Damn that Connor is good. But i am still wondering why pin 5 is tied to Vcc. I know that the cap keeps DC out. so it shouldnt affect the timing. but still WHY?
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