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fading red eyes - triac

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gazza1966

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Hi folks

Ive just built the fading red eyes project from Bill Bowdens diagram and all works fine.
Im running the circuit from a reactive supply (1uf cap, resistor, diodes, zener, 470uf smoothing cap)
I am trying to get the circuit to fade 1.5M of 240v led ropelight via a 5mA gate triac but having no luck getting it smoothly fading.
When the circuit is fired up I get: full on - half faded (flickering) - off so not really fading at all.
I have used the exact Bowden circuit and used the cathode of the led straight to the gate of the triac which switches the neutral line.
I cant remember the part number of the triac as Im not near the circuit at the moment but I have used this triac with micro controllers for dimming 1.5m of ropelight and they work fine so I dont think there is a gate current issue.
If anyone has any ideas on how to get this working smoothly then please let me know as I'm at a dead end with it at the moment. :eek:

Thanks in advance

Gaz
 

kchriste

New Member
Forum Supporter
Well, if you've used the triac with a micro, you'll remember that a triac dimmer circuit works by delaying the triac turn on from the zero cross point.
Bowden's circuit doesn't do that. It simply varies the amplitude of the voltage driving the LEDs because it is designed to drive a transistor in a DC circuit. His varying brightness AC lamp would be a better circuit to adapt.
 
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