By Aimee O'Driscoll, 24 April 2021
A magnetic stirrer is a handy item to have at hand for a range of applications, including agitation, dispersion, and dissolution. Professionally-manufactured magnetic stirrers usually aren’t very pricey, but if you need multiple, the costs soon add up.
If you’re on a tight budget, you may be wondering if you can create your own DIY stirrer out of easily accessible materials. We did some digging to find out and discovered there are quite a few viable options available. While a home-made stirrer is unlikely to give you the power and speed control of professional-grade equipment, it could be sufficient for some applications.
An online search will provide you with several different types of magnetic stirrer designs. We take a look at some of those here, making note of some of the advantages and drawbacks of each design.
Most of the designs here are fairly simplistic, but we’ll start with perhaps the most straightforward design. This set of instructions uses a fan-based setup. The main component of the stirrer is an old computer fan with magnets glued to it.
Here are the materials needed:
One of the trickiest tasks is mounting the magnets correctly. One magnet should have its north facing upwards and the other its south facing upwards. The magnets should be positioned directly across from each other. Because the motor contains magnets, it can be difficult to align the two magnets such that there is minimal vibration when you switch the fan on.
Spacers are needed to sit between the fan and the flat top due to the extra height created by the magnets. Something as simple as coins can be used here, but the creator used small pieces of plexiglass, the same material that is used for the plate of the stirrer.
The creator mentions that you can choose from a range of voltage sources as long as the fan is rated to it. You just need to make sure that at the rated speed, the coupling between the magnet and the stir bar is strong enough. Too high speeds could lead to uncoupling. Three AAA batteries were used in this case.
In this set of instructions, the stir bar is made from two magnets housed in moldable plastic. One issue with this concept is that you can’t stir hot liquids as the moldable plastic won’t hold its shape.
This is another simplistic model which uses a cooling fan housed inside a plastic container. While some designs simply use the fan as is, this goes a step further by using a wire cutter to snip off the blades to limit resistance. A dremel tool is used to sand down the remainder of the blades.
The creator used a mini drill as a routing tool to cut a hole in the plastic container for the switch. Hot glue is used to hold it in place. Another hole is cut on the other side of the container to house a DC jack.
One downside is a soldering iron is needed for the wiring to connect the fan, switch, and DC jack. There is no option of speed control with this model.
This project has several different components to those above, the primary one being that it uses a DC motor instead of a cooling fan. It also uses a 9V battery as the power source and has a speed control option. This design uses a simple steel wire (essentially a reformed paper clip) as a stir bar.
The housing of this model is a little more refined with the magnets being inserted into a custom plywood construction. The corrugated card makes for an easy-to-build platform, but it wouldn’t hold up well against spills.
This is another design that uses a fan as the main component. The housing for this model makes for a neat aesthetic and is very simple to construct from a few pieces of wood. The wiring for this model is a little different to others. It uses a female power adapter DC barrel to screw plug jack connector to connect the fan wires to a power brick.
A hole in the platform strengthens the coupling between the stir bar and the magnets. The creator has forgone glue in favor of tape to hold the magnets in place. This is a good idea in case you don’t get the alignment right the first time. The stir bar used in this instance comprises four magnets, a small piece of plastic, and some tape.
If you’re looking for a more refined aesthetic and have access to a 3D printer, this could be the model for you. The basics of this stirrer are similar to some of those above, using magnets mounted on a PC fan. Additional parts include a female power jack and a 12V motor speed controller with LCD.
There are three 3D-printed parts in total: the main stirrer housing, a stir bar with slots to hold two magnets, and a mount for the fan with four slots for magnets. The additional slots in the mount are there in case you need to use a large stir bar and want to space magnets farther apart.
If a 3D printer isn’t available or you simply want to save time, a project box can give you an equally clean aesthetic. In fact, this stirrer almost looks professionally made.
This design provides a fairly high-speed stirrer, but the creator suggests that adding a voltage regulator could allow you to reduce the minimum speed if necessary.
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