Stir Plate update, or how I let the smoke out of two sets of components

soldiered board

This stir plate project has been on the drawing board for a _very_ long time. When I spotted a post by a peer from my homebrew club offering a set of components to build one last spring I jumped at the opportunity. The kit was all the required electronics, including circuit board, heat sink, even the thermal compound. I only needed to find a Neodymium magnet, pc fan, power supply, and a project box. The required tools are pretty simple too, just a soldering iron. The only thing I needed to buy was a project box, the rest I was able to scrounge from an old pc, old hard drive, and old cell phone charger. Sounds pretty simple eh?

IMG 2028Easier said than done. My first attempt was a crazy mess. As you can see to the left. I managed to nearly ruin the board, how you ask? I couldn’t 

figure out how to bridge two contacts and ended up just dragged solder around. After reviewing some youtube tutorials before attempting to continue, I figured out my problem. I wasn’t bridging the contacts with the wires, I was just trying to connect it with solder. This should be a straight forward task. It’s five components, 3 pairs of wires, and it appears to be a very simple circuit design.

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After sorting out the bridging, attaching the fan and power supply was simple enough. I plugged it in, and it even seemed to be functional. However when I attached the magnet to the fan, the fan didn’t have enough power to spin it. A little research showed I needed to increase the voltage, more voltage, more rpm’s. The fan is rated for 12v, and I was only pushing 5v. I decided to replace the 5v power supply with a 9v one. Doing so resulted in a smoked a capacitor. I’m guessing it was wired wrong, and therefore the added voltage was enough to blow the capacitor. Not sure why I didn’t just remove it, and replace it. The board was ugly, but mostly functional. I even had the spare parts.

So, I decided to tear the board down, and started again from scratch. Not sure why I didn’t just leave it assembled as an example. My second attempt was equally filled with fail. I managed to get all the pieces on the board, some what neater than the first attempt, but it was still quite messy. Once all hooked up, the potentiometer began to spark and smoke. I just don’t get it, there seems to be only two directional components in the diagram, and I can’t believe I’ve managed to put them in wrong twice. I am really struggling to figure out how to read the diagram, and apply it to the components.

Just when you think I’ve done all the wrong things I have done, this last attempt is even more incredulous. All I was going to do was to swap the potentiometer out, and swap the poles on the wiper and positive. However I wanted to change the solder iron tip. I was using a chisel tip which was the recommended tip, but I think my 20w iron is too hot, or I was using too thick solder. So I was having trouble being accurate. However when I went to change it, it was stuck solid. I tried to twist it cool, then I heated it up a bit, and tried a bit more, then it snapped right off. I can’t believe I managed to break the tip off in the iron.

This project has been a gigantic fail!

There is good news on the horizon. I spoke to my friend who shared the parts, spent a whopping $10, and bought 5 more sets of parts. I should have enough to get a working set, and still pay it forward. Because I want someone else to share in the joy I’ve had with this project. Status: Unknown. Maybe rewiring the potontiometer, Mounting the magnet to the fan, and putting the parts in the box, this project is all but done.

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