Who we are & What we do

We like to invent things and make improvements to existing products - this is how Stir-Plate.com came about. We were originally interested in purchasing a couple of stir plates for yeast propagation but quickly discovered that a commercial stir plate can cost $300.00 or more! Then we did some chasing on the net and discovered that a lot of people were building their own stir plates using an old PC cooling fan, used hard drive magnets and were using a variety of methods to vary the fan motor speed. We built a few stir plates based on designs off the net but we really weren't happy with any of them - each one had "issues".

Stir Plate Development

06/09/2009 - First Working stir plate

After a little bit of work, we produced our first working stir plate.

06/10/2009 - Finalizing Design

While working on the prototype, we were also designing the circuit card, sourcing parts and deciding which magnets and stir bars would work best for our stir plates.

We chose FR4 material with 1 ounce copper for the controller card. This is industry standard for any high end equipment and the circuit card is rugged enough to last many years of service.

Another view populated with the components. Notice the large part on the right with the metal fin? Some might think this is a LM317 regulator. It is not, it is a power transistor. Also note that we do not use a heat sink. Our stir plate controller does not need one. The transistor fin does not even get warm.

We consulted with a major magnet distributor before deciding which magnets to use for our stir plates. They suggested Neodymium Rare Earth Magnets. Notice that the magnets seem to be stacked with some space between them? The space is nylon spacers that were put between the magnets at the factory. Without these spacers, it would be impossible to pull the magnets apart!

06/13/2009 - Prototype in initial Box

We sourced an initial box to build the next prototype in, including mounting the speed control, power switch and power on indicator.

06/18/2009 - Final Version in Production Box

We found a box we like. It's compact enough to not take up much space but large enough to contain everything.

Prototype and production boxes side by side.	Final product with 2000 ml flask
	10/5/09 Our latest design improvements The most obvious change from the outside is the absence of a power switch. We have incorporated the power switch into the speed control knob. Now you turn the knob all the way counter clockwise and "click", it turns off. Then you just turn the knob back clockwise to turn the power back on. On the inside We were using 4 machine screws and nuts to mount the motor but an early customer return convinced us to come up with a better solution. The motor had loosened up with use. Now we mount the motor with 4 aluminum rivets. Since the rivets are not threaded, they can-not loosen and the motor stays tightly fastened to the frame. We discovered that changes in line voltage could change the speed of our stir plate so we switched to an energy star rated regulated 12 VDC power supply. These supplies cost a few dollars more than an unregulated 12 VDC power supply but now changes in line voltage have no affect on our stir plate speed setting.
Jan 2010 Manufacturing Issues With help from our distributor, we identified a manufacturing issue with our stir plates. The bond between the motor and magnet cross bar was not strong enough to survive rougher than usual shipping. We have changed our manufacturing process to solve this issue and all new product is OK, but there may still be some failures in the field. If you bought your stir plate from one of our resellers and the stir bar has stopped spinning you can return the stir plate to them for replacement. For even faster service, we'd rather you return your stir plate directly to us. We will repair your stir plate and ship it directly back to you the next business day. Note: Repaired stir plates will be shipped back with the accessories they were shipped in with. In other words, only ship us the actual stir plate and we will only return the repaired stir plate to you.
	1/12/2010 40 Stir plates that have passed run-in & final test and are ready to ship to our distributor These have all been modified to prevent the cross bar from separating from the motor in shipping.

Now, watch us on YouTube!

[ Home ]

Copyright © 2009 Stir-Plate.com
Last modified: 10/09/09