e-zombie craft - incubator build part 1

I've completed the first step in the electronics setup for my incubator, which I'm building after the DIY model developed by Andrew Pelling (Pelling Lab) while he was researcher-in-residence at SymbioticA. You can see his setup and excellent instructions here for the entire incubator build.

The first part of the electronics build is the fan, which will circulate air inside the incubator and distribute CO2 and heat, which cells need to stay alive. Andrew Pelling's clear instructions for that build (with very helpful photos) are here and here. My experiment and comments (including additions to his instructions) are below.

Parts:
Inside PC towers are power supply boxes such as the two below (one on the left is in tact after I ripped it out of the tower, and one on the right is then further ripped open to reveal its guts).

It's not an easy process to wedge your way into the interior of these solidly-built, metal-encased things - but with the right tools and persistence, you can hack it open and find the treasures you seek. There are a lot of zip ties everywhere inside to clip off, and a lot of hidden screws to unscrew in order to get to the gold. The 'gold' in this case is a 12V fan. Let me clarify - it's a 12V fan with TWO wires (positive and negative). There are plenty of other fans inside the PC tower that are more easily accessible than ripping open the power supply, BUT those fans all have 3 or 4 wires and therefore are more complicated than what you need. I discovered on an online forum that I could find a simple 2-wire 12V fan inside the power supply. I must admit, I do get joy from the process of destruction when I know I'm going to be upcycling obsolete technology (which, by the way, I found on the curb near to my place). My living room floor was a mess, but a joyful mess.

Maybe you can find compressed air for cheaper than $10.99.

One thing that Andrew doesn't mention, but which I feel is important to know, is that when you're scavenging parts out of the insides of old computers, they will be very dirty and dusty. You will have to clean them, particularly in this case since an incubator is supposed to be a sterile environment, or at least the possibilities for bacterial contamination minimized as much as possible. So, prep yourself with a can of compressed air, some rubbing alcohol and cotton swabs. Compressed air is great for cleaning dust and crap out of tiny spaces. Rubbing alcohol will finish the job and sterilize things to a certain point. *Ultimately, asepsis is a whole other issue.

I was pretty grossed out by the filth inside the computer towers I took apart (there were four of them). Your other option is to simply go to a computer repair shop and ask for a 12V fan with two wires. They must have tons. It likely won't be free, but then again, it might be.

See that little white adapter on the ends of the fan cables? You can clip that off with wire cutters so that you can poke the ends directly into a breadboard. Or you can plug jumper cables directly into the adapter. I chose to clip it off.
I cleaned the fan blades like the obsessive perfectionist that I am, two or three times with rubbing alcohol, until no more caked on dust was to be seen.

Now, before you snicker about my wiring, I want to qualify that I am an artist, and I like the aesthetics of bare DIY electronics, and using excessive wiring is intentional. It was an awesome artist named Erin Sexton who showed me how to appreciate the aesthetics of excessive wire, gave me permission to get messy and stringy (and, being a textile artist, I clutched onto that idea for my own use). I could make neat little bridges in my circuitry, but I chose to have large, looping wires. And besides, this is the prototype, not the soldered unit that will go on the incubator - but the soldered unit will likely be loopy, too.

Here is the breadboard wired up with the fan (fan is barely visible in the background to the right):

Honestly, I wouldn't recommend designing your wiring from looking at mine. Andrew Pelling has much better photos with neat and tidy wiring that makes more visual sense. Mine is a jumble.

Fan schematic.

One thing Andrew forgot to include in his list of components needed: a 1N4007 diode. He does include the diode in his schematic.
That component is mentioned in the Instructable that Andrew refers to (well, the Instructable uses a 1N4004 but I used a 1N4007, since that is what is in the schematic). So, the revised list of components needed:
1x TIP120 transistor, 1x 1kOhm resistor, 1x 100uF cap, 1N4007 diode, 12V DC Fan, 12V power supply.

What I have here that Andrew doesn't show in his photos is this sweet little YwRobot power supply for the breadboard. You can get a similar one here. It even has an on/off switch, so you don't have to unplug your power source every time you want to change the wiring, code, whatever. Great for prototyping. My Arduino is running off the power supply to the breadboard (blue and yellow wires). This power adapter is for 5V, but my 12V fan is running just lovely with it. I've plugged a 12V power supply into it to test it out and it all works. Maybe it'll burn out faster, I'm not sure, but I'm not worried about it right now. The power source I'm using (the power cable I've got plugged into that breadboard power adapter) is an old cable from my Zip drive from many years ago. Sometimes it pays to hoard the obsolete tech! At this point, I have an electronics junkyard growing in my living room.

Here's another look - it's on and the fan is moving:

So, why not just plug directly into the Arduino to power the fan? Because technically it's a 12V power supply you want for the fan, and the Arduino can handle max 5V.  For my prototype, though, I am running the fan on 5V. Ultimately, that might even be enough to circulate the heat and CO2. More testing will happen once the rest of the incubator is built.

This is what your IDE should look like, when uploading the fan test code to the Arduino:
(I think there's a newer version IDE available on the Arduino website, but anyway...)
This is the code I copied directly from Andrew Pelling's github and pasted into the Arduino IDE. And by the way, IDE stands for Integrated Development Environment in case you were wondering.

I've been playing with my new fan all day, happy to see life in my build. There is a clear and definite connection between something alive electronically and a biological system, something which I was only able to fully appreciate when I began working with both simultaneously. There is a huge amount of pride in making a system work, or building something that functions well. The process of building that system, whether hacking a biological system or an electronics/digital system, is akin to craft. Craft is making something that works. In the case of this fairly basic project, I've brought obsolete things back to life: electronics zombies! Then, shall we call this e-zombie craft for fun?