My new DIY wireless curing chamber!

Air dried cured Meat Techniques

My new DIY wireless curing chamber!

Postby Jonathan_Hudds » Sat Jun 10, 2017 6:27 pm

Hi all, I'm a long time lurker on this forum but have only just registered as I wanted to share my new DIY curing chamber with you.

I've been curing/drying small pieces in my kitchen fridge for a while but the temperature/humidity is far from ideal and I was only able to work with small pieces due to lack of space in an already cramped fridge! And as I don't a suitable 'natural' location to dry meat I figured the only way to go was to use a dedicated fridge where I could control the environment.

Conveniently, a friend at work was looking to get rid of an under-counter fridge after a kitchen refurb so I claimed it, cleaned it up (after it sat outside for 3 weeks) and put it in my garage (which gets hot in summer and freezing in winter!) I then got to work with the electronics/electrical elements. Now I should point out at this stage that I'm a bit of an electronics/electrical/software nerd in my spare time, so there is a bit more to this then I'm stating here, but I thought I'd give you the summary and if there's interest from other members, then I can expand and provide more detail.

So essentially here's what I added:
- Ultrasonic humidifier
- 40W tubular heater
- 5V fan for air circulation internally
- 2 x 12v PC fans at the top of the fridge to extract air
- 2 x 3" circular holes at the bottom of the fridge to act as air intakes (intake air filtered via dust masks!)
- Plastic enclosure filled with silica gel sachets with a motorised lid (controlled via a servo)
- Temperature/relative humidity sensors inside and outside the fridge
- Arduino microcontroller with a few add-ons to control everything

So without going into too much detail here, I wrote some software for the Arduino microcontroller that executes the following loop:
- Check the temperature of the fridge, turn on the heater or turn on the fridge to get the temperature into an acceptable range
- Wait 10 minutes for the environment inside the fridge to stabilise
- Check the humidity of the fridge. If humidity is low then run the humidifier periodically with fan circulation until it's in an acceptable range. If humidity is low then open the silica gel enclosure (this is then closed again later when the humidity is in range as the silica gel acts slowly)
- Wait 5 minutes for the environment inside the fridge to stabilise
- Correct temperature again
- Wait 10 minutes again
- Ventilate the fridge with fresh air using the PC fans for 5 mins or until the temperature gets too high (i.e. if the fresh air is too warm)
- Repeat the loop.....

The benefit of this control method compared to most of the other DIY curing chambers I've seen online is that in this case it cant 'fight' against itself. I control the temperature then let everything settle, then control humidity and let everything settle then provide ventilation and let everything settle. I'm generalising here, but essentially this is the most economic way I can come up with to control a drying environment. Like I said above, I don't have anywhere even remotely close to a natural drying environment so this is my solution!

So with a bit of tweaking, what I now have is a fridge in my garage that controls temperature, humidity and at least simulates a fresh air 'breeze'.

This all works great but I added 2 additional features:
- The garage was the best place I had to install this but its still not ideal as I use the garage for occasional DIY projects. So I added a switch to the outside of the fridge that when switched on will disable the external air circulation to effectively seal off the environment if I'm sanding or just generally making a mess. Then once the mess is clean, I flick the switch and ventilation resumes.
- I added wireless communications to the controller which allows it to transmit all of the conditions of the fridge to a wireless receiver. This receiver sits in my kitchen (and looks noticeably better than the fridge itself) and displays temperature/humidity and operational status every 60 seconds. It also has an alarm built in and can notify me of temperatures/humidities out of range, sensor failures, ventilation inhibit switch left on, communications failures etc.

Here's a few pics:

Note: The clip lock food tub was never intended as a wiring enclosure. But for a budge working prototype, on this occasion it does the trick!....For now.

And a little demo of the silica box opening and closing followed by the controller showing it's alarm conditions and then receiving status info:
phpBB [video]

So although this is all working just fine, I am going to refine it moving forward. I'll add some switches to the remote receiver so I can alter the temperature/humidity set points easily and also tweak the software to improve the control and show more info on the screen (long term averages for example). It's currently just a working prototype after all.

Onto the cost, I already had a lot of these parts myself which kept things cheap, but omitting cable/connectors/tools etc etc, it works out roughly like:

Fridge - £0 - There's always someone looking to get rid of a fridge
Arduino microcontrollers, relay board, wireless transmitters, LCD screen, sensors and alarm sounder (all ebay): £37
Humidifier: £14
Fan: £6
Silica gel: £6
Heater: £11

Everything else you see in the pics was either scavenged or already in my parts supply, either way, there's nothing expensive there.

So there it is, I appreciate some may see this as overcomplicated for somewhere to dry meat but considering that I don't have a natural drying environment at my disposal plus the fact that electronics/software is a bit of a hobby for me, I've actually found this a really enjoyable little project and now I can dry larger pieces of meat conveniently under a controlled environment and I have my kitchen fridge back in all it's glory!

I'd welcome any questions and if there's demand then I'm sure I can come up with some diagrams if anyone wants to build one themselves.

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Re: My new DIY wireless curing chamber!

Postby Jonathan_Hudds » Sat Jun 10, 2017 8:52 pm

hhmm, so it looks like youtube video shortcuts don't work on this forum unless I'm missing something? I also can't see a link to edit my initial post so I'm responding instead to provide a link to the video I wanted to show:

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Re: My new DIY wireless curing chamber!

Postby RodinBangkok » Sun Jun 11, 2017 11:00 am

Looking good , you may want to consider adding pid control algorithms, they are readily available for Arduino.
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I am the captain of my soul.

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Re: My new DIY wireless curing chamber!

Postby wheels » Tue Jun 13, 2017 10:44 pm

Jonathan_Hudds wrote:hhmm, so it looks like youtube video shortcuts don't work on this forum unless I'm missing something? I also can't see a link to edit my initial post so I'm responding instead to provide a link to the video I wanted to show:


Hi Jonathan,

I think that there may be problems with the BB code for video on the site following a server move. Please bear with it by linking how you have.

Many of us are very interestested in what you've done.

Many of us have similar chambers ourselves.

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Re: My new DIY wireless curing chamber!

Postby Jonathan_Hudds » Mon Jun 19, 2017 8:38 pm

Thanks Phil, I'd assumed it was a technical issue, so thanks for the clarification.

Well I thought I'd post a quick update. It's been about 10 days since I started this post and TBH the following 2-3 days had me a little concerned!

I'd had no appearance of mould whilst curing in the fridge over the past 2-3 months, which I'm assuming is because of the low temperature and low humidity. But I also knew that whilst this environment was passable for small pieces (duck breasts, small steaks, small bacon slabs etc), I knew that it would start to compromise the end product as I was moving on to larger pieces (i.e. the two pork leg pieces were circa 1kg each when they went in). Hence the fabrication of this curing chamber.

So anyway, after approx 2 days in the new chamber at a set temp of 12C and set centrepoint humidity of 70%, the two pork pieces developed multiple plumes of white, developing to green, mould. It started off looking fine/granular and so I thought it may be penicillium (easy mistake to make as I hadn't seen it before!) However it was soon evident that it wasn't penicillium.

My controller was doing a great job in maintaining the set values that I'd given it. And when I say great I mean that the 12 hour rolling average vales were 12C and 68% humidity. But I did notice that on the ventilation cycles where 'fresh' air was being brought in for 5 mins, the temperature was peaking at around 18-19C (obviously depends on the garage temperature at the time). In addition to this, it would seem that the humidity cycle did not have enough time to recover from the artificially low humidity reading that resulted from a cooling cycle and so was adding humidity unnecessarily.

So I used white vinegar to treat the undesirable mould (which by this point was starting to show on the flesh of my 'plain' duck breast and also just slightly on my peppered duck and peppered beef rump, albeit through the muslin).

Long story 'kinda' short, I made some changes to the software last Wednesday (14th June) which was also the same day that I added in two pieces of bresaola (approx 800g each) just out of their 5 day wine bath after a 4 day salt cure and I then left the house empty for 5 days to visit relatives!

So with all expectation of returning to fridge full of mould today, what I actually found was this:

This has gotta be penicillium, fine/white/powdery, but I'd welcome opinions from other members:

No further outward signs of mould plumes on my peppered duck and beef:

No further outbreaks on the pork leg:

Duck breast ready to eat, I did find a few small patches of undesirable mould on the beef after it was unwrapped so I've treated them and will give it a few days to settle down in the kitchen fridge and then dig in!:
Image Image

Also, the 'plain' duck which i unashamedly devoured before I left on my trip and thoroughly enjoyed! Despite the fact that in all my excitement I managed to slice along the grain instead of against it!:

Image Image Image

I'm sure there's more to come here as the pork gets closer and the bresaola develops. I'm also hoping to get hold of a whole deer leg from a deer stalking friend of mine, so this may become my first bone in whole joint cure! I've also obtained a 3D printer recently so I might have a go at producing a more aesthetic enclosure for the 'receiver' element of this whole endevour as one of my first printing projects.

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