DIY Kalk Stirrer


New member

Thought I would post a few pics of a DIY Kalk Stirrer project I completed awhile back. Originally I had a maxi-jet pump sealed in the chamber to mix the Kalk on a timer every couple hours.

Worked ok, but it ate impellers because of the high PH. Decided to make a stirrer using some spare parts I had on hand. A Powermax II stepper motor and a split coupler, some acrylic etc.

Stepper motor is connected to a split coupler to a 3/8" acrylic shaft. The end of the shaft sits in a short piece of 1/2" acrylic tube at the bottom of the chamber to act as a bushing, but more importantly to keep the stir rod true when rotating and keep it from wandering.

The stepper motor is powered by a Pololu stepper motor driver. The stepper driver is driven by a PIC 18f14K50 programmed using Microchip C18 and MPLabX. I did not want a LCD display or buttons, so I use a terminal program to program the unit from the pc via a Bluetooth module.

RPM is variable from 0-20 rpm
Has a fast stir rate every set number of hours 1-24 hours to give the kalk a good stir. The rate for the fast stir is variable from 20-100 rpm and from 0-60 seconds

So far has been running perfectly for the last couple months, I do find I have to turn it off and on every once in awhile becasue the PC looses connection with the Bluetooth module.

Need to modify the paddle as it could probably stir better, but making the paddle more agressive will require more torque from the stepper.

YouTube video of it running


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New member
very nice, question though, is the loud humming coming from the unit?
if so, that would drive me nuts!
what was the overall cost of this build?


New member
The unit has little noise, camera was just amplifying it for some reason. Sometimes the top acrylic piece will resonate, a little nudge stops it.

Can't put a price on it as most of it was from my parts bin.
very nice built i was planning to built mine with 110v slow rpm motor from ebay and then built a box the side for permanent 7 day digital timer on it. and that it. it will be simple design and i can have motor come on every 1 min 10 min or 1 hr depends on my requirement.


New member
Thanks, was going to go the route of the synchronous AC motors commonly used for bbq etc, but wasn't sure if the set speed of these motors would be optimum. I don't think you need to put it on a timer as they can be pretty much be run 24/7.


New member
i have used micro wave motors and disco ball motors both are a good speed. but with the plastic gears in them...well they wear out after a few months of 24/7 use. use a timer..doesnt need to be running all the time!! it at the same time as your top off pump. that should be enough times during the day