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A zoom image of the recommended transformer on your original link indeed shows 40VA 24Vac
If you are sensing remote contacts with low current and these contacts are not rated for <2A (i.e. gold plated) then they will oxidize and fail sooner than you expect.
My solution which works well is low ESR or tantalum cap across the remote sense contact closure to "wet" the oxide insulation on the contact closure on each use. 10uF or so. with R pullup to Vcc . Then use twisted pair. and ferrite bead around pair if Murphy's Law creates an IRQ.
If you are sensing remote contacts with low current and these contacts are not rated for <2A (i.e. gold plated) then they will oxidize and fail sooner than you expect.
My solution which works well is low ESR or tantalum cap across the remote sense contact closure to "wet" the oxide insulation on the contact closure on each use. 10uF or so. with R pullup to Vcc . Then use twisted pair. and ferrite bead around pair if Murphy's Law creates an IRQ.
That's a bummer if it's a bad transformer...
Sunnysky, I will look into that transformer instead of what I have. Gosh, it sure seems weird that a damn relay would need that much current to engage the contacts. I'm really scratching my head on that one. Waste of energy it seems.
Oh, and btw, I'm a technical guy in my field and now I know what I sound like to the noobs.
"My solution which works well is low ESR or tantalum cap across the remote sense contact closure to "wet" the oxide insulation on the contact closure on each use. 10uF or so. with R pullup to Vcc . Then use twisted pair. and ferrite bead around pair if Murphy's Law creates an IRQ"
...this statement will take me a bit of time to decipher. I'll be back in a week! haha
Sunnysky, I will look into that transformer instead of what I have. Gosh, it sure seems weird that a damn relay would need that much current to engage the contacts. I'm really scratching my head on that one. Waste of energy it seems.
Oh, and btw, I'm a technical guy in my field and now I know what I sound like to the noobs.
"My solution which works well is low ESR or tantalum cap across the remote sense contact closure to "wet" the oxide insulation on the contact closure on each use. 10uF or so. with R pullup to Vcc . Then use twisted pair. and ferrite bead around pair if Murphy's Law creates an IRQ"
...this statement will take me a bit of time to decipher. I'll be back in a week! haha
Back in #13 you said your tranny was 20va ...???
Anyhow, why muck around , you have 110v (or 240 for that matter) with an isolation relay on the micro, so why not use that on a similarly powered pair of contactors.
Just a noter that contactor coils are like motors, large inrush currents at startup so if not enough juice, the 24vac will drop like a rock.
Anyhow, why muck around , you have 110v (or 240 for that matter) with an isolation relay on the micro, so why not use that on a similarly powered pair of contactors.
Just a noter that contactor coils are like motors, large inrush currents at startup so if not enough juice, the 24vac will drop like a rock.
Well, my trans is 20VA, but that is because I was using what I had...and I'm showing my lack of attention to detail on that portion. Frankly, it blows me away that it would need that much current to make the electromagnet work. I erroneously read that relay coils require very little.
I got these two contactor relays from researching what I could find. I am seeing a lot more now that time has gone further. I really liked your suggestion. I was able to find this. Would you recommend me swapping these for my current units?
As I've said, I'm learning a ton from this project, so I can absolutely see where major efficiencies in my design can be made.
I got these two contactor relays from researching what I could find. I am seeing a lot more now that time has gone further. I really liked your suggestion. I was able to find this. Would you recommend me swapping these for my current units?
As I've said, I'm learning a ton from this project, so I can absolutely see where major efficiencies in my design can be made.
Just wondering if I've missed you actually confirming your transformer can power the second contactor on its own?
I'd hate to think you were accidentally using the wrong terminals.
Contactors and relays are different in many respects. The power required to switch a contactor, while large compared to a small relay is still small compared to the power the contactor itself can switch.
I'd hate to think you were accidentally using the wrong terminals.
Contactors and relays are different in many respects. The power required to switch a contactor, while large compared to a small relay is still small compared to the power the contactor itself can switch.
I've been thinking a lot about your response, Bluejets. "Why in the heck didn't I purchase a 11V relay coil relay to begin with?" Well, honestly, I had such a hard time finding a 220V, 2-pole relay that I basically got whatever I could find. Now, I'm seeing sources for more of them.
I'd like to avoid the extra step of the 24VAC transformer altogether. Do all of you agree that I should swap it out w/ the one I mentioned in my previous post? (link was embedded) That way, I can use the 110V I already have in that NEMA enclosure and just switch in the 110V to the relay coil w/ the existing design I already have.
One last question. Do I need a current limiting component to this design? Right now, there's nothing. I read somewhere I can use an inline cap and resistor between the hot and neutral, but I don't quite understand why and how that works. That's the last part I'm concerned about...
Thanks.
I'd like to avoid the extra step of the 24VAC transformer altogether. Do all of you agree that I should swap it out w/ the one I mentioned in my previous post? (link was embedded) That way, I can use the 110V I already have in that NEMA enclosure and just switch in the 110V to the relay coil w/ the existing design I already have.
One last question. Do I need a current limiting component to this design? Right now, there's nothing. I read somewhere I can use an inline cap and resistor between the hot and neutral, but I don't quite understand why and how that works. That's the last part I'm concerned about...
Thanks.
Contactors are designed to switch higher power at higher voltages than relays. If your load is inductive and a reasonably high power then the contactor is a safe option.
Measure the resistance of the coil of the working contactor and then measure around the various connections on the other one (looking for some similar resistance) to make sure you haven't accidentally wired up the wrong connections.
Measure the resistance of the coil of the working contactor and then measure around the various connections on the other one (looking for some similar resistance) to make sure you haven't accidentally wired up the wrong connections.
None needed.
I told you so, several posts back. That was the only thing that made sense, given your readings and the description of the behavior.
Bob
CDRIVE
Hauling 10' pipe on a Trek Shift3
I've been out of town vacationing in the surf. Didn't bring my laptop and don't do smart phones. I have enough addictions already.
Anyway, I told you way back in this thread to monitor the 24VAC output of the transformer with your DMM while connecting the contactor coils to it. This test would have shown you that either the transformer is underrated or that one of the contactor coils is shorted.
Chris
Anyway, I told you way back in this thread to monitor the 24VAC output of the transformer with your DMM while connecting the contactor coils to it. This test would have shown you that either the transformer is underrated or that one of the contactor coils is shorted.
Chris
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