I'm trying to use a Triac to fire the "latch" side of an eletromechanical latching relay. The relay is 24vac. The signal I have available is only present for 2-3 milliseconds - not long enough for the relay to switch. I figure something solid state is needed. If I use the Triac, I should be able to get a half cycle which may be enough time. Otherwise, is there a way to get the Triac to latch itself on after the initial 2-3 millisecond pulse? Thanks for any feedback.
Mike
Unless you can synch your firing signal to the ac source, you aren't going to average anything like a half cycle - you could easily get nowt. There is a possibility you may not have enough current through the triac to hold it on, before the trigger pulse disappears - particularly with your inductive load.
A simple retrigerable monostable fired from your pulse can stretch it to the relay response time. You can use that stretched pulse to enable a free-running pulse generator that can keep supplying firing pulses to the triac to operate the relay - irrespective of the phase relationship of the supply. This isn't exactly latching the triac on - it is making sure that it will conduct when current is available.
One advantage of using a free-running pulse generator is that you can then use a standard pulse transformer with the triac. This will give you electrical isolation - which may be useful and also is pretty good at avoiding the domino effect, should the triac fail. Multiple windings on the transformer can be pretty useful too and often designers don't seem to consider the possibilities..
PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.