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Humidifier Without Humidistat

Thread starter #1
My roommate is currently using an ultrasonic humidifier which does not have any means of turning it off when the room reaches the humidity level he wants. Is there any product out there that can be added to the humidifier to do the job. Or do I have to create my own? I ask in this forum because I want to be able to create a portable humidistat, which would be similar to the timers people use to turn lights on and off. Basically I want to have the humidistat where I can plug it in to an outlet, then plug the humidifier into the humidistat, so that when he slides the lever it will turn the humidifier off at a certain level. Can anyone help?


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Honeywell, among others, offers a line of humidistats. You would need to know the current and voltage requirements of your humidifier and compare to the contact ratings on the humidistat to see if you need a relay. Google "Honeywell humidistat" and you'll find some.

Keep in mind that if you are working with line/mains voltage that there are significant safety/law issues - possibly very easy for some yet a serious challenge for others.

It would be great if you could find a pre-wired package that is UL/other approved but it doesn't sound familiar.
Thread starter #3
The humidifier is an ultrasonic one. Not a whole house humidifier. So any humidistats made would not work. Humidistats that get wired into the house wiring would not work. Which is why I think I will have to create a humidistat that can plug into the wall socket and then plug his humidifier into that.
I'd use a timer, but the only indoor ones I've seen are designed for turning lights and such on and off. And all I'd want is one that can be turned to a time limit, like two hours, just before going to bed so that it shuts off after that time frame. Closest timer is an outdoor one that will turn on at dusk and turn off 2-4-6-8 hours after dusk.

Thanks anyway for the help.
+1 on the honeywell sensors - have used them many times. Many are programmable with set points that will set a pin high/low. As has already been noted, however, you would need to get that single low voltage line up to switching the humidifier on/off.

They do, indeed, make such devices that might work for you. Here is one, for example. Of course, it would help if you gave the model of the humidifier with it's ratings.
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Old thread revived by a spammer (deleted and banned).



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Oh, I'm so disappointed that I didn't see what he was selling.
  • A plug in relay triggered by a humidistat
  • A wet sponge on a balance that monitored by a microcontroller - turns off when rate of weight loss decreases.
  • An electronic "sling psychrometer" with two mercury thermometers - one wearing a wet sock - and a row of IR sensors along each thermometer to sense where the mercury level may be - all spinning on an old phonograph turntable set to 78 to create the air flow needed across the wet sock to reduce the temp of that thermometer to the current dew point

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