Humming relay question

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Nova wrote:

The relay is a Cutler-Hammer C25DND330T. You can get formal specs here:
http://www.famousparts.com/c23pol30amp2.html
No idea if that seller is any good, they were the first Google hit that had what I wanted. It's a 3 pole because that's all my local electrical supply place had; I'm just not hooking up the third pole. It's listed on that page as:
Coil Voltage Rating: 24 Volts AC
The doorbell tranformer is definitely 24 V AC output.
Everything's within spec - either this is normal for this setup (George's opinion, I believe) or something's wrong. I suppose it's also possible this setup is not just inadvisable, but Wrong.
-BAT
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wrote:

snip
What is the current draw for the solenoid coil? Could it be that your wire size (#26?) is too small to hold the current and that you are possibly experiencing too much voltage drop to hold the coil?
Just a thought.
Allyn
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Allyn Vaughn wrote:

Thanks for the thought. I'm running 20 gauge wire, and, for my test setup, my single estop switch is about three feet away.
Also, to be clear, the coil seems to be *holding*, it just hums while it's doing so and I want to make sure it's OK that it does so (and/or learn if there's some way to make it not hum that I don't know).
-BAT
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It _may_ be relatively 'mormal' for that relay.
Converting to _DC_ power (a whole $10, or so) could make for a signficant noise reduction. NOTE: 'AC' coil relays _will_ work just fine on DC power (the 'other way around' can be problematic :)
visit your neighborhood Radio Shack.
Look for a "bridge rectifier", rated for "at least" 24V -- 50V ones are fairly common -- at a couple of amps.
Also a capacitor. rated at _at_least_ 50V, and at least 200 microfarad ("uf").
The bridge rectifier should be a 'little black box', with a lead at each corner. one will be marked "+", the one opposite it will be marked "-", and the other two will either be not labelled, or will have a sort-of "~". Those last two are the AC input, connect one to each wire from the transformer.
Connect the capacitor across the other two leads. making sure that the "+" side of the capaitor is connected to the "+" output from the rectifier, and "-" to "-". Then run connect the existing wiring to the switch/relay to the "+" and "-", as well.
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