Replace stepper motor for bidet

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1

Hi,
I have discovered a leak in my bidet toilet seat and appears the water has got into the stepper motor and caused corrosion. The motor controls the rod which now doesn’t extend or retract properly.
When powered on via 240v wall plug, the unit goes through a start sequence control/reset process and triggers the motor to move the rod back into correct position, however, the spindle barely turns. So I’ve decided to replace it.

The motor is stamped with the specs, but due to age and damaged, some is illegible. I can’t scratch under the red wrapper without losing the stamp also.
What I can see is:
RoSH
ST28-…
12vDC 130…
…604…

Not sure what comes after the ST28 - maybe a “54” (which could allow it to be “548”… maybe?)
And looks like the Ohm symbol after the 130
and maybe the last line is 160412 - some kind of product code (but not one I can find online)
Images following:

IMG_9793
IMG_97931920×2560 192 KB

IMG_9799
IMG_97991920×2560 87.4 KB

I found a possible replacement with

Most of the dimensions match except the spacing between mounting holes. original is 40mm, new is 35mm (which I could probably make work)

But I see there’s a difference in Ohms

  • original says 130, and this new one is 280.

Is this going to be acceptable, or a showstopper?

2

Hi Cam,

That ohm difference means that (inductive effects aside) half the current will flow through the new motor compared to the old for a given voltage, however this depends on the type of stepper driver used.

If it’s a “chopper” type, it will be able to overcome this extra resistance by increasing the duty cycle of the supply voltage to the coils, but considering that low-power appliances are often powered by 12V, I’d assume it’s just a H-bridge driving it.

You could give the 280 ohm motor a go, but you may find it has less torque and doesn’t possess enough power to extend the rod. In that case you’ll have to try the broader internet for a closer match.

3

Thanks James. The rod is very light with low friction resistance, so the torque might not be an issue. So i will give this 280 ohm motor a try. Greatly appreciate your input.!