Like a lot of us here, I was looking into buying a stir plate, and after seeing what they were going for I scrounged around and found some items to put my own together. I'm sharing what I did here. FYI - I have zero electronic experience, I read a bunch of posts and sites and took the best of everything. In fact, I wondered why Radio Shack even existed, now I know why.
WARNING: Be careful with electricity, messing with it can be dangerous. Follow at your own risk.
Step 1: Scrounge and procure something like this.
- Found a Linksys router lying around that wasn't being used, even had the 12v cord.
- Had multiple PC case fans lying around, luckily as the first one didn't work.
- Found an old hard drive to get the magnets from.
Step 2: Spend some cash - about $15 bucks or improvise.
- Buy a $2.99 SPDT black flip switch from Radio Shack (catalog: 275-711)
- Buy a $1.99 Communications style knob from Radio Shack (catalog: 274-402) - in hind sight, i would have bought a smaller prettier knob (lol).
- Buy a $3.99 25-Ohm 3-watt Rheostat (catalog: 271-265)
- Buy a $5.97 pack of #8-32 x 1-1/4" machine screws with nuts from Home Depot (can probably find something cheaper, depending on your fan you can just use screws that fit, had some for the first fan but it didn't work.
Step 3: Linksys router
- On mine there were rubber grommets hiding the screws, peel those back and unscrew the router.
- Pull out the circuit board and separate the top, bottom, and siding which contains the ethernet ports etc.
- With a pair of scissors or pliers, cut the plastic bits (used for mounting router to wall etc.) that stick up from the bottom panel completely off.
- With your screws or Home Depot machine screws with nuts secure your 12v case fan to the bottom panel using the existing holes that you cut away to get access to. It may be slightly crooked depending on your case fan, but that beats drilling new holes.
Step 4: Wiring
- I used existing holes in the back of the router to place my Radio Shack parts so i'll describe that but feel free to change it up a bit, drill your own holes or what not. You may want to wire it first to make sure it works, then place it how you want. I also soldered my wires but you could probably get away without soldering by twisting or using wire connectors.
- Your case fan should have a black and red wire (if it has another ignore it), strip these.
- Cut the power plug portion off your case fan, then cut off about 4 inches of both the black and red wire, keep the black and lose the red (don't worry, you'll have plenty)
- In the Internet port, i put in my 25-Ohm 3-watt Rheostat (catalog: 271-265), just take the washer and nut off, slip it in, put the washer/nut back on. I had the prongs facing towards the right (knob positioned at left corner, prongs facing right).
- I put the switch in the ethernet 4 port, this switch comes with two plastic bits, i discarded one as it wants to fit snuggly on the switch, since I had the holes already, i just screwed in the round piece all the way.
- Cut the power end off your router cord (or use another cord you have lying around) and strip the ends. Slip the ends through the power port on the router.
- Connect the positive (red) from the power supply to the red wire on the fan.
- Connect the negative (black) from the power supply to the middle prong on your switch.
- Connect the black wire from the fan to the top prong on your Rheostat
- With the piece of black wire you collected from your fan earlier (when you discarded the red), connect that to the middle prong of the Rheostat to one of the end prongs on your switch.
Step 5: Test
- Wiring is done, time to test it.
- Make sure your case fan works, plug the power in and flip the switch.
- If fan spins, you're good to go. If not, check the black/red is correct from your power supply to fan and middle prong on switch.
Step 6: Magnets
- Affix the hard drive magnet in the middle of the fan using super glue (you'll see I put it off to the side in the pic, i changed this later). If you have issues, you may need both of the magnets on top of each other.
Step 7: Finish up
- Screw the top back on, make sure the middle part of the router is facing the right way or it won't line up with the screws.
- Plug it in again and power it up, put a flask or whatever on it with your stir bar.
- If it doesn't spin around like it should, experiment with spacing and speed. Mine tended to work better at slower speeds. I experimented with spacing using an O-ring but it was too high up on this particular enclosure.
Next steps:
- Might want to cover those holes in the top of the router, probably don't want any water accidentally getting in there. I was thinking of custom fitting a thin mouse pad over the top.
Good luck, let me know if you have any questions or want the individual images.
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