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Nice job on this! Incredible documentation / plans. Is this related to SARE Project FNC14-975? chriscallahanuvm Saturday, November 1, 2014 - 7:39am Saturday, November 1, 2014 - 7:39am 0

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Hi Josh, nice work. I'd love to see the more complete posts at your site ( with pictures. The pictures don't seem to be loading? -Chris (
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<p> Hi BuffaloDan, Fantastic work on this and thanks for sharing it with such excellent documentation.&nbsp; Also, all 6 of your photos did upload and users can see them if they click on the primary photo above.&nbsp; We're working on the photo gallery presentation so that becomes more obvious.&nbsp; Again, nice work with this system, I'm likely to do a replicate soon.</p> <p> -Chris</p>
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<p> testing</p>
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<p> Great job Stephan.</p>
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The originator of the post / tool will have to answer that. I'd suspect purchasing 3" won't be that much more expensive and will be on the safe side. But don't have exact dimensions of 32" diam. drainage pipe in front of me. if you have the pipe, measure it and add in the batten board thickness.

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The McMaster-Carr motor included in the prints can be found here: It is a 1/2 hP, 1725 RPM motor.

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I added a wiring schematic. Please review it and let me know if anything seems wrong.

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Thanks for the nudge, Noah. I'll post a wiring schematic this weekend.

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Hi Ben,

Yes, this could definitely be used for freezers as well as coolers. Lower set-points, of course, but same principle. In fact, one of the challenges with using outside air for coolers is that the inlet area of the outside are is prone to freezing on very cold days. So routing of the inlet air and distribution / diffusion can be important.


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Hi Jenna and Louis,

Thanks for the feedback.

Arduino - Certainly could do this with an Arduino board. I opted for an off the shelf PID control, which available with a remote bulb thermocouple and solid state relay cost about the same as an Arduino Uno. The control portion of the BOM is EITHER a PID OR a thermostat, so you don't need both. The PID does the job very nicely, is quite versatile, and they have become quite inexpensive (less than a thermostat). They also have an auto-tune function which adjusts the PID tuning variables by algorithm. Makes life simple. And no additional programming or electronics labor was required. The benefit of the Arduino would be additional I/O, I suppose.

Relative Humidity Control - The PID in this system could take an RH sensor as input as well. My experience has been RH measurement in low temp and high humidity environments is not well done with generally available sensors. Louis and I have discussed this and I have been cooking something up here as a prototype that I think will help address this need.

Energy Use - Sorry, haven't measured electrical kWhr consumption yet. Fundamentally, this is no different from a conventional humidifier. The energy required is that needed to raise the temperature of incoming water to the setpoint and then to evaporate it into the air. Conventional humidifiers do this as well. The difference is a matter of evaporation (humidification) capacity and rate. This design allows for high rates of humidification which requires high rates of evaporation which requires greater energy input. But it can also do lower rates and I would expect the energy use to be comparable to other humidifiers. The only difference being, perhaps, greater heat loss through the surface area of the bucket. But I think that will be minor. My first attempt at this involved hacking an existing humidifier to try to make it simply auto-fill. They are actually pretty complex little machines. In that case, the reservoir was held by the machine at slight vacuum which made controlled auto-filling difficult even with a fancier fill valve.

I also need to post a schematic and some build photos. 2nd generation build coming soon.