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somewhere near 50mA or more, forget about using a TRIAC because you're not going to meet it's holding current requirements. Use a relay instead, and the relay will need to be snubbed too.
worry about the holding current. How often does a bell get turned on/off an yway? Driving one EM with another EM device is a more harmonious and simpli fied fit.
Not for the kind of engineering you do...
.What was he using to drive TRIAC?
--sp
You risk breaking the insulation on the coils, as it is prepared to get only 100V across the coil.
Well they've since tested good at 240VAC, so that's that AFAIC. :->
Whoosh!
I'm not familiar with that manufacturer. Can you provide a link?
I know you now have a triac but here are two possible ways to use two SCRs whereby one is slaved to the other and triggering is referenced to one supply rail:
piglet
Thank you for that, Piglet. I shall take a good, hard look at it for future reference.
That is an interesting concept. But you can also connect two SCRs in series, cathode to cathode, with anti-parallel diodes across each, and drive both gates from a single source. Here's an LTSpice simulation:
Paul
======================================================
XU1 N006 N005 0 MCR8SN V1 gate 0 PULSE(0 5 50m 10u 10u 100m 200m 1) R2 gate N002 50 R3 N005 gate 50 .model D D .lib C:\PROGRA~2\LTC\LTSPIC~1\lib\cmp\standard.dio .tran 0 200m 0 1u startup uic .inc MCR8SN.sub .backanno .end
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es,
========================= =====
and you can do the same with fets, except then you can skip the diodes and you can turn off when ever you want
I've used it as a fast "fuse" switch off to protect a number of triac contr olled output from shorts
-Lasse
Good idea! ...Jim Thompson
[snip LTSpice ASCII]
Thanks. The disadvantage is having the diode drop along with the forward voltage drop of the SCR. Most SCR based SSRs and high power SCR controllers use two SCRs connected anti-parallel, so you eliminate two diodes and their voltage drop. But the gate control becomes more complex, usually requiring trigger transformers, opto-isolators, and DC-DC converters.
The systems I work with operate on 480 VAC mains and often draw currents well over 1000 amps for short durations. The load is a transformer with a
6-20 volt output connected to large industrial circuit breakers up to 6000 amp frame and instantaneous trip of 10x or more. For such highly inductive loads it is necessary to trigger the SCRs initially at about 60 to 90 degrees to reduce current surges from DC offset. And for very light loads or open circuit conditions the gates must be driven with continuous DC, so pulse transformers don't work.Paul
Good Lord!!
Those were used in PBX phone systems for decades. I still have a couple good spares., and one five line system with the KTU cards.
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