Temp and RH Monitoring


 
A

Aaron Patterson

New member
Hi everyone! I've been working on a temperature and humidity monitoring system for my curing box, and I thought I would share my progress. I've built it using an msp430 launchpad and a humidity an temperature sensor.

On the left is the board, and the right is the sensor:

7291060952_49b6fd48f0_z.jpg


Again with my temporary wiring in to the microcontroller:

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The chip has an onboard temperature sensor, so I was able to gather ambient temperature measurements as well as measurements inside the curing box. I did notice that the onboard temp sensor was pretty inaccurate though so I had to calibrate it with the external sensor. I'm considering purchasing another external sensor for monitoring ambient conditions.

Here is a graph of two hours worth of data I collected:

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I have my box set at 58F, and the RH set at 70%. I've only monitored overnight, so I'm not totally sure how ambient temperature impacts the box temperature. It's interesting to see the RH drop when the fridge turns on, but I guess that's expected since the water should condense on the cooling plate. I'm not sure why the RH rises up to 75%. My current guess is that the first spike is when the humidifier shuts off, but then condensed water starts to evaporate.

Anyway, the project cost me about $18 (including shipping). The sensor was $10, and the microcontroller was $5. It took me a couple days to write the software (I'm new at microcontrollers), but I'd be happy to share it if other people are interested in building this.

When I get more time, I'll post detailed instructions for building this thing. Hope you all enjoy!
 
Second on the nice work. I plan on building a curing chamber and having a way to log the conditions would be great.

I wonder, do you have a heat source in the chamber? Some people suggest using a low watt bulb on a dimmer to add heat into the system to get the fridge to turn on more frequently. They claim it helps "smooth out" the fluctuations in RH (shorter but more frequent times that fridge is on) but I've never seen any logged data that would support the claim.

Thanks
 
I don't have any heat sources in my curing chamber, but I'd be happy to add a heat source and log the data (on my next batch). I'm not sure that increasing the frequency would result in more time at the desired RH. You can see from my graphs that as soon as the pump shuts down, the RH bounces back fairly quickly.

This graph is 30 minutes of samples:

um3ya.png


It takes less than 6 minutes to recover to my setting of 70% RH, and about 1 min for the cooler to get the RH below 70%. In 2 minutes, it's at 60% (dropped 15%!). The period on the cooling wave seems to be about 26 min. My guess is that even if you shorten the period of the wave, the average RH is going to be pretty similar. I am excited to try it out and report results!

My next step is to add a sensor to the door, and a sensor to the pump. Then I can get more accurate data about when the pump turns on and off, and how door open and closure impacts the box environment.
 
awesome! I love diy stuff but I'm so deficient in electronics I could never figure something like this out.

How are you controlling your humidifier?
 
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Aaron Patterson:
I've got a Dayton Controller inside my box. If I can get this embedded processor to be more stable, I may just use it rather than the Dayton. </div></BLOCKQUOTE>

I've got the Dayton too and see fluctuations of about +/- 5% RH around the Set Point. I'm OK with that though, 75-85% RH is fine for early curing and 65-75% is fine for the later stages of drying.
 
A Crane "Drop" ultrasonic/cool mist humidifier, like this one:

opFzr.jpg


http://www.amazon.com/Crane-Dr...difier/dp/B005PK7RW4

It's a 1 gallon reservoir and when plugged into the control unit that reservoir lasts at least 3 weeks.

The one in the curing cabinet works fine, but we got another one for my baby's nursery and it failed after only a few weeks of nightly use, so YMMV. Crane customer service has indicated they will send a replacement but it's a pain...
 
Been researching this for quite a while and when it's time I think I'm going to give this a try. I'm comfortable enough with the electronic part of things but don't have a burning desire to learn code writing.
 
Marc that's a cool solution and it wouldn't be too hard to implement it with some rudimentary wiring not dissimilar to my sous vide setup.

The best part about it is that you can set it up use the included sensor to control the humidifier plug from that computer box outside the curing chamber, rather than having mains electricity inside the curing chamber (like with the Dayton controller) which honestly makes me feel slightly nervous with the water in there.
 
Not really, between my exterior (dry Colorado) air venting and the compressor drawing moisture from the air, in combination with the Dayton the humidity overshoots only to about 80% RH at most.

Sorry for the hijack, Aaron.
 
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