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RegistrerenLLDB3-TP trigger diode (Algemeen)
door Jordan22xx 
, 14-10-2025, 19:57 (1 dag en 5 uur geleden)
Gewijzigd door Forumbeheer, 14-10-2025, 20:21
Hey everyone,
I’m still pretty new to electronics, and I’ve been learning by building small AC control circuits lately. I just found an LLDB3-TP trigger diode and I’m curious if it’s a good choice for a simple lamp dimmer project I’m trying to make for school.
From what I’ve read, it’s a diac that helps trigger a TRIAC at around 30V, but I’m still not sure how stable it is in real setups. Does the trigger voltage change much over time or temperature? And if the circuit picks up noise from the mains, can that cause random firing or flickering?
I’m planning to mount it close to the TRIAC on a small perf board, but I’m not sure if that’s ideal. Any tips on placement or wiring would be super helpful. If anyone here has used the LLDB3-TP (or a similar diac) in dimmer or AC motor control circuits, I’d love to hear how it performed and what I should watch out for.
I’m trying to learn by doing, so any advice from you guys who’ve been at this longer would really help!
Thanks!!!
LLDB3-TP trigger diode
door Maarten Bakker 
, Haarlem/Delft, 14-10-2025, 20:23 (1 dag en 4 uur geleden) @ Jordan22xx
Gewijzigd door Forumbeheer, 14-10-2025, 20:33
Hi Jordan!
The type number LLDB3 suggests it's the SMD version of the very common DB3 from ST. Trigger diodes (diacs) are pretty much standardised. One isn't better or worse than the other. You could try measuring the trigger voltage under different conditions (different temperatures is probably the easiest). That might be a nice addition for a school project. And then see if this has any influence on the brightness of the bulb or if it's negligeble.
When working on perf board, you might want to get a through-hole diac, for example the DB3.
Flickering from mains pollution is a bit more complicated. Maybe someone else can explain better.
LLDB3-TP trigger diode
door RAAF12 , contreien, 15-10-2025, 20:02 (5 uur en 4 minuten geleden) @ Jordan22xx
I have never seen flickering from man made noise in the circuit. Normaliter there is an effective suppressor in in a household dimmer with CE marking in Europe. It consist of ferrite and condensators. But the DIAC will last, no problem.
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RAAF12