Snubber capacitor suggestion
Snubber capacitor suggestion
(OP)
I have a relay design, where the relay switches AC 240V/10A (Phase Line). Sometimes during switching the LCD on the board goes blank. Similar problems have been reported on various other forums too.
Suggestion was that the switching of the relay produces spikes and a snubber cap of 0.1uF/1KV will arrest the spike. I haven't had the opportunity to check if it works as the circuit where this happens is not with me right now it is in field and i don't have direct access to it. Will test it when i get my hands on it.
I have attached a pdf of the circuit. (Just the relay part)
Any suggestion or improvement in design is welcome so that i can implement it in future design.
Suggestion was that the switching of the relay produces spikes and a snubber cap of 0.1uF/1KV will arrest the spike. I haven't had the opportunity to check if it works as the circuit where this happens is not with me right now it is in field and i don't have direct access to it. Will test it when i get my hands on it.
I have attached a pdf of the circuit. (Just the relay part)
Any suggestion or improvement in design is welcome so that i can implement it in future design.
Thanks
Regards
Gokkul





RE: Snubber capacitor suggestion
I'm not sure that the added capacitor across the contacts would solve whatever the problem actually is. If the contacts are arcing due to an inductive load, then maybe.
I assume that the load wires are dressed away (routed in accordance with EMI best practice) from the uC signals?
RE: Snubber capacitor suggestion
What is the best snubber solution to prevent contact arcing. It is this arcing that generates spikes that corrupt the LCD module.
Thanks
Regards
Gokkul
RE: Snubber capacitor suggestion
RE: Snubber capacitor suggestion
If more, then use a varistor instead of the RC combination.
Select a varistor with 275 V rated voltage (230 V is too tight) and large enough to carry the coil current for a few milliseconds. I use Siemens S10K275 for most applications. It can handle most contactor coils easily.
Question: Does the relay really switch 10 A? Or is that the contact rating? If it really switches 10 A, then I would use an S20K275 instead.
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Snubber capacitor suggestion
If the EMI design is correct, arcs and uC can coexist.
I don't think it's the wee little arc itself, it's probably the noise (generated by the wee little arc) on the load wiring.
RE: Snubber capacitor suggestion
RE: Snubber capacitor suggestion
Yes the relay really does switch 10A. The relay is rated for 30A. And also the Voltage is AC (just reminding
In the choice of varistor instead of 275V rating can i go for anything even higher like S14K1000 or S20K1000?
Yes you are right its the noise from the arc that causes problem. But to eliminate the noise i have to eliminate the arc at least minimize it. Also the arcing reduces the life of contacts (that is what most say in forums).
Thanks
Regards
Gokkul
RE: Snubber capacitor suggestion
RE: Snubber capacitor suggestion
RE: Snubber capacitor suggestion
Sorry mate, but yes that will be expensive for this particular design, on a tight budget. Also i might need to completely reroute the PCB. So it may not work here. But do appreciate the suggestion :)
Will these varistor do the trick S14K1000 or S20K1000.
Thanks
Regards
Gokkul