Sisterlimonpot

My Diy Stirrer Plate (lots of videos)

I dose alkalinity and calcium to my tank via a bubble magus dosing pump. However, despite the fact that it’s said that after mixing soda ash and calcium carbonate powder with distilled water into their respective container they are supposed to stay mixed, I have had quite the opposite experience. Although there isn’t sediment resting at the bottom of the containers, the liquid is more concentrated throughout different areas, making constant tank parameters hard to achieve.

So I decided to get a couple stir plates for the containers that have the alkalinity and calcium but realized right away I wasn’t going to pay $100+ for a stir plate. So I started the research and came across an easy way to make a stir plate using a computer fan. I started to experiment (videos below) with various ways of doing this but always came to the conclusion that the fan speed was too fast to keep the magnet centered.

That’s where I came up with the idea that I would just make a simple circuit using a pulse width modulation to vary the speed of the DC motor.

So here’s my attempt.

Here it is completed and if you want to see how I made it continue on below.



I have a bunch of these little earth magnets, I fear that they will be too small to achieve what I want though, we’ll see.


The fan with the stir stick on it.


I glued the magnets to the fan, they rest right on the edge of the inner hub of the fan.

I ended up attaching 2 magnets to each side, north up on one side and south up on the other

This is an old cell phone charger that I found in a box, I clipped the connector off the wire and exposed the 2 power wires.




Now that it’s all set up I put the fan underneath a flat surface.


Cup of water directly over top.


Dropped the stir bar in.


And here’s a video of my first attempt



I bought new magnets because the ones I had from the beginning were way too weak, the new magnets are rated at lifting 8 lbs each so they should do the job well.

The only problem that I had was that the magnets were so strong that the motor couldn't spin because they were holding the fan still. So I cut some acrylic circles and glued them to the center of the fan



Here’s the schematic of what I came up with for the pulse width modulation.



I ordered all the electronic parts from mousers website but couldn't wait for shipping, so I went to Fry's and grabbed everything that I needed. They didn't have the same exact parts that I ordered which isn't a big deal. I really only went there to get a blank circuit board because I forgot to order one, but instead I grabbed one of each and headed to the register (BTW ordering online is a lot cheaper even with shipping... California taxes!!!). After getting home I got started soldering.
First the 14 pin IC socket was soldered on:



Then the 2 capacitors:



The 2 diodes:



The 10K ohm potentiometer and resistor:



The transistor went on next:



Here's the underneath, I still have to solder a bunch of jumper wires but I will do that in a few:



here it is all wired up:



Next step was to put a container over the magnets and stir some water for a day to see if anything needs to be heat sinked.

In action:



I ran the motor for a few days to make sure nothing happened within that timeframe, I started to have fun with it. This is a video of me adding food coloring to the mixer



Hope this inspires some of you to put on that Diy hat and try this. It has been in use for 2 days now and everything is working as expected. I’m pretty confident that there isn’t going to be any problems with it in the future.