Hot Plate & Magnetic Stirrer / IKA C-Mag HS 7


I found this baby rotting in the E14 loading dock. As sturdy a piece of hardware that ever walked–yanking the tork screws out this was an exercise unto itself.


Looking classy in blue. This is a piece of lab-grade experimentation equipment, used for simultaneously heating and agitating fluids. Get yours for only $515.


Both the top and bottom of the clamshell case are sturdy metal–heavy, almost like cast-iron. Only a couple of deep screws held the two halves together and were easily accessible from the bottom side. The wire linking the two grounds the whole deal.


Here are the basics of the electronic guts. You can see the control board, the motor beneath the heating plate, and the PCBs that the potentiometers are mounted to. The PCB attached beneath the motor housing is a reflective optical sensor for monitoring just how fast the motor is spinning–a nice closed-loop system.


The transformer is the blue box. The fat capacitor next door is conditioning the supply, smoothing out the hiccups in a high-power system. The board is crammed with really nice components, at least so sayeth the wise.


The ceramic heating element, turned on its dear little head. You can see two pairs of wires tracing out of it–the big ones go to a heating element and are coated with some dusty asbestos stuff that came off on my fingers. I hope it wasn’t asbestos. The little ones go to a thermocouple sensor.


The heating element and the thermocouples.


Giblets. The power switch is enclosed on plastic in the side. Looking at the connectors, here, which are slide-fit tabs–it’s clear that the pieces are handwired together. You can see from the routing (above), that someone just tucked the wires beneath those plastic tabbed discs.


Lovely spring-loaded connectors for hooking up the motor. The accept bare twisted wire-ends, suggesting that someone is just wiring the thing together on a bench. I’m guessing this is a fairly low-volume item.


The motor. The spindle is attached to a powerful magnet (that black ovoid). The gear-looking component beneath it is actually just a toothed-disk that’s used to measure the speed that the motor is turning. The reflective IR sensor (I already took it off) can tell just how quickly the disk is spinning by measuring the reflection ratio of tooth-to-gap.


And wouldn’t you know, it just pops apart. This is what’s called a ‘Shaded Pole Motor.’ I don’t know what that means, but it’s something like a single-coil stepper. The armature is a multipole permanent magnet and the coil is pulsed to rotate the shaft. Here’s a bit of info. They seem fairly unusual.

This is the reflective photo sensor. You can see the IR LED in the sensor, as well as the receiver–a phototransistor of some kind, I guess. It’s a CNY-70 (datasheet). You can get one for a few bucks, though probably not mounted on this lovely breakout board. The board is even labeled ‘photosensor’, as are many of the other components.


Here’s the board in detail. You can see how many of the headers and such are labeled: heating, heater, photocoupler, thermocouple, motor, and heater.


A whole array of dip switches on the control board. The purpose of these seems at first mysterious — though an attached instruction panel gives instructions on how to set them for various models. The stirrer comes in a range of sizes and they must all use the same control board. I’m not sure why using dip switches was the best way of setting the different behaviors — or who the target audience of such setting are. It’s hard to imagine even the most informed consumer switching the board from the guts of one machine to the other, but who knows? I would do the same with a solder jumper or similar.


Here are the switching options. They could have represented the same range with half as many bits–and notice, the configuration of the board (above) doesn’t match any of these. Are there unpublished values? Or perhaps this is why it was being thrown out in the first place? An errant dip switch?


The LCD display board PCB, as well as the potentiometers used to adjust the speed and temperature of the plate. The little broken teeth on these boards suggest that they were ordered as part of some kind of mega board and snapped off.


And it passed a five-point quality control inspection. The marks are all different–does that mean that five different people checked it?

Part Breakdown

  • Custom-cast top and bottom enclosures
  • Custom-molded and coated ceramic upper plate
  • AC Electric Motor
  • Main control board
    • All kind’s of fancy parts.
  • Temperature control PCB (pot)
  • Speed control PCB (pot)
  • Display PCB (LTS-4801WC-08T 7-segment numerical display)
  • IR sensor motor PCB (CNY-70, $1.18 apiece on mouser)
  • Heating element
  • Thermocouple


The custom boards were manufactured and stuffed automatically, possibly by a robot-device. That’s where the automation ends, though, I think. It appears that all of the PCBs are from the same manufacturer, RU–or at least, that’s what the logo looks like. Additionally, the IKA component number is also printed on the back. I am guessing they order these parts in large quantities, but do not do any of the assembly of them themselves.

Then, all of the parts were screwed in and mounted by hand. All of the connectors None of the final components are particularly small and all are well-labeled–probably as much for the workers putting these things together as for the tinkering end-consumer. It even says “bottom” on the underside of the PCB.

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