If I use a triac as a simple on-off switch to control a lamp at mains voltage, do I need a snubber across the triac? Say the lamp is 10 meters away from the triac, mains-rated LED or 100W incandescent (not CFL, mercury, neon, etc.), and the switchig is via an optoisolator without zero-cross sensing. Thanks in advance.
Snubber for triac light switch?
Feb 03, 2010
4 Replies
If your LED lamps use any kind of transformer, the triac switch can be a DC source under some trigger conditions, which will blow fuses or expensive LEDs. In the incandescent lamp case, the snubber would mainly be of use to prevent RF emissions.
"whit3rd" "pawihte"
If your LED lamps use any kind of transformer, the triac switch can be a DC source under some trigger conditions,
** Only in the case of phase control and ONLY if the gate is *pulse fired* at a 100/120 Hz rate.Which is not what the OP is doing.
which will blow fuses or expensive LEDs.
** DC in a transformer primary burns out the transformer.In the incandescent lamp case, the snubber would mainly be of use to prevent RF emissions.
** Only a single current spike when the lamp comes on and none as it goes off - cos the current then is close to zero.So any RFI is much less than regularly generated by ordinary light switches.
..... Phil
No. No phase control. Just a simple on-off function.
But that won't happen with a full-cycle on-off function, will it? The switching cycle wil be at least several seconds.
Thanks.
If your mains leds are just a series string with no transformer or other inductor then yeah, you can use a triac for on-off control. incandescant lamps are fine too, NE2 indicator lamps also.
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