| Electronics > Repair |
| Washing machine main control knob. Is it a rotary encoder? |
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| Chris Wilson:
My Hoover washing machine has failed a few times with no display and no action at all. Turning the mains off and on again has returned it to life. Today it failed again mid cycle so I removed the control board PCB and examined it carefully for obvious issues and dry joints / failed joints. All seemed good. I put it back together agin and now, by CAREFULLY fiddling with the main control rotary knob that has 15 positions including the off position it once again came back to life. The two wire cable and two pin connectors are sound, low resistance and making good contact with the control board PCB and the tiny PCB of the control that I am assuming IS an encoder. However mid cycle once again the display disappeared and it stopped. No coaxing it back to life at all now... The main knob has what looks like it may be a rotary encoder, with detents, but I think the detents are mechanical and external to the encoder itself. in a plastic housing that the encoder is held on to. surprisingly to me, only two of the three pins on the encoder are used. How might this work? Is it likely to be a rotary encoder or something else, and is there a way to safely fool the control board to "do something -- anything in fact to prove this rotary device is the culprit? I will Google rotary encoders, but a brief look shows most have at least five contacts.... Thanks and a very happy Christmas and a healthy and prosperous New Year to all members. |
| coromonadalix:
well photos would help, some bands are using the pcb as the encoder traces, and only dial contacts goes over the traces, and yes some have real encoders with real encoder or else you have examples on the web or youtube videos who explain the 3 pins detection, forward or reverse .... on how an mcu detect the rotation Some encoders have : say 12 detents and other have 24 detents etc .. and some called enter press in pushing the center shaft witch is the 2 supplemental pins for a 5 pins total count, some have more ... and maybe you're dealing with customized one too ? the dial could be ok and your problem(s) could be mcu, supply issues etc ... |
| ebastler:
Without photos and/or the exact model number of your machine, this amounts to crystal-ball gazing. A standard (cheap) encoder seems unlikely since it would only be able to detect relative movements of the knob, not its absolute position. And a two-pin cable seems unlikely too. What does it connect to? A PCB with just the "encoder" on it? Are there additional power supply connections? Are the displays on a separate circuit board? |
| Gyro:
The only type of absolute position control knob I can think of that has only 2 pins would be a resistive one. In repair terms, hopefully this would be in the form of PCB segments, a wiper and smd resistors, rather than a printed resistive track. With the appropriate complimentary resistor and ADC input on the controller PCB, this would provide sufficient resolution for a reasonable number of fixed positions. This method used to be used fairly extensively for the buttons on things like VCRs. Maybe it still is. Agreed, photos are needed to confirm what is going on and avoid confusion. |
| Chris Wilson:
Thanks for the replies, as my wife is panicking and seems to have forgotten that we did not all go around in filthy clothes before the invention of the washing machine I have ordered a new "switch". Agitating washing in a sink seems total anathema to her :) However I am nonetheless keen to understand how this thing works with just two wires to the controller board PCB which is all surface mount. Both the controller board PCB and the switch have fingers for three wires, only two (the outermost ones) are used. Here's a link to the rotary control itself. Thanks again. https://www.espares.co.uk/product/es1802455?utm_source=google+shopping&utm_medium=shopping&utm_campaign=google+shopping&gad_source=1&gclid=CjwKCAiA65m7BhAwEiwAAgu4JDV9ZXfPC4x0E9MSFZffmX0MRbi4Nlo2ZpOQ1izYLcEWGo_WiV1PYhoCwIwQAvD_BwE |
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