Humidor Project

Big post coming soon. I've been working with the Honeywell HIH6130 humidity sensor. I enjoy the occasional cigar but I'm terrible at keeping it humid. I'm going to use the sensor to display a LED when the humidity drops lower than the preferred range. It will cover some bit twiddling and I2C communication. This was a great project to get me more comfortable with both topics.

Burrrrr.....It's not that cold

Went ahead and tried a little experiment this weekend with putting my peltier chiller to a test. I took a medium sized foam cooler, modified the top of the cooler and hot glued the fan and cut some intakes out. The fan pushes cool air away from the cooling surface of the peltier.

I haven't bought the materials to make to create the larger chamber to fit my 3 gallon fermentor because I want to get an idea on how one peltier device will perform. I placed the sensor in the box and cut a small hole for the cables to run through. I didn't add any other insulation nor did I seal the holes I made for wiring so it wasn't air tight. Rather than controlling the temperature in this case, I simply let the cooler run to see how cool it got. After about an hour, I didn't see anymore reduction in chamber temperature. Room temp when I started was about 75 F. After about an hour, it stayed pretty steady between 62-64 F which is over 10 F cooler than ambient. If I had a larger chamber, I'd have some more losses and it would take longer to even get near this chamber. I may try plugging up a few of the cracks and seal the lid to see how much impact that makes. This was a quick crude test. My plan was to use thick 2" thick insulation surrounded by a wood frame which will have better insulating properties than my cheap cooler. Made a graph of the temperature versus time.

I didn't loose hope but I think its important to do small scale tests to ensure your making progress. I still learned quite a bit from doing this project even up to this point so I'll try a few more things with my setup.

• Insulate/seal the chamber better
• Let it run longer

Chiller Control Board Up and Running

I went ahead and double checked all my connections for my hand wiring on the underside of the board with my multimeter. I got a bunch of beeps which is good news. I went ahead and used jumpers to connect to the 4 pins I'm using on the Raspberry Pi at this time. There may be more parameters I end up measuring later. The temperature sensor hooked up to the three pin terminal. All the "high power" electronics including the fans and Peltier are wired into one terminal since they are all the same operating voltage and it just draws more current. They are hooked in parallel to be precise. I did use larger wire when wiring these lines because there was going to be more than 5A running through these. After I wired everything it up, I powered it through another screw terminal and the board, sensors and fan all functioned properly. The RasPi didn't do anything odd because I powered through a convertor and had no issues controlling the MOSFET. I tried to power it simply from a 12V to 5V convertor only with some capacitors wired in but the Pi didn't function properly.

Peltier Wired Up

In the program, a temperature range is set where you'd like to ferment. The Peltier turns off and on based on that temperature reading. I want to make it a little more intelligent when it comes turning off and on. I don't want it to run continually simply because it doesn't have to.

Wired Setup

I am pretty pleased with how it is coming together. Before I go ahead and build the chamber, I think i may do a test just in a cardboard box to see how cool it gets with one device. I'd figure out the losses and predict the temperature but I do that in my day job so I'll wing this one.

Fermentation Control Board

I wired all the components from a schematic I made. Took a few steps to get to the finished product. Below is a circuit demonstrating the concept and it incorporates a few things.

• A power jack
• NPN Transistor
• Peltier Device
• Digital temperature sensor
• x2 Fans
• One to cool the heat sink
• One to circulate the chamber

The Raspberry Pi reads the temperature and switches the MOSFET from another GPIO pin. The x2 fans and Peltier device are all on the same MOSFET since they need to turn on at the same time.

Schematic of Diagram

I ended up with a large power block that operates at 12 V and is capable up to 10 Amps. The Peltier can pull up to 5 A and the fans about 1 A and the Raspberry Pi another amp probably. My goal was to power everything from one source so I didn't have all these power cords and I could easily mount it to the top of the cooler. Due to the large current draw on some components, I didn't design a PCB board for this. Instead I went with a perfboard. All the components are 12 V except for the Raspberry pi so to power that, I purchased a small buck power converter for a few bucks on Amazon. It works very well and steps down the 12V to 5V and the raspberry pi can be powered via USB then. I mounted this directly to the board itself.

I laid it out on a piece of "perfboard paper" which makes it very easy to plan how to mount the components. If you Google for it you can find it easily online. I drew the layout some-what to scale on the size board I was using and labeled everything.

Perfboard Layout on Piece of Paper

After I laid everything out on the board, I went ahead and wired the components with wires on the bottom. I used lower gauge wire for higher amp lines and just used some 22 gauge for the smaller stuff. Pins on the left hook to Raspberry Pi and I have 3 terminals.

• Temp Sensor Terminal
• Fan and Peltier Terminal
• Power Terminal

Wired Perf Contorl Board

After I confirm all connections, I'll go ahead and test it out!

Still Here...

It has been awhile but I've been pretty busy. I got some work to post on the fermentation controls fo sho.