Please help identify and source a replacement rotary encoder (for digital oven) - Page 1
Forum section: electronics / repair

author: Enlargee79
author_rank: Contributor
timestamp: February 27, 2022, 02:25:16 pm
content: I have a digital oven, which means all the controls/temp/cooking modes are controlled by relays/etc. with a microcontroller PCB.It has two rotary controls, which I have so far worked out to be simple rotary encoders, and they are identical. Even the PCBs are identical with the same identifying numbers/codes, and both say "R-KNOB" on them.One of the encoders is clearly faulty, and no longer has the feeling of moving between detents. Also when I (gently!) pulled it apart, the detent wheel had completely fallen to pieces [sad trombone.wav].The control knobs have a push in mechanism (push the knob in, and it sits flush, push again to activate it). However, this does NOT have a push-button effect as far as the control board is concerned, it's just probably some kind of style/child protection feature).These are the features I've been able to figure out:24 detents per revolution, each detent produces a change in setting, so that appears to be 24 PPR.mechanical with (I think) 2 channels - Common in the centre, A and B on the outer pins -> continuity beeps briefly while holding probes between either outer pin and the center pin while rotating the knob, stays continuously beeping if held between detentsThe shaft length from PCB mount base to tip of the actuator is 25mm, but the actual shaft is ~12mm, or 20mm to flush with the top surface of the component (see pic)The shaft diameter is 6mm, with a 4.5mm flattened (D-shape, slotted top)The pitch between the 3 through hole pins is ~4mm, the space between the outer 2 pins is close enough to 10.2mm, which is what apppears on data sheetsI have found what appears to be the appropriate replacement:https://au.rs-online.com/web/p/mechanical-rotary-encoders/7295804/Data Sheet:https://docs.rs-online.com/1497/0900766b80f4c3d5.pdfI am reasonably confident that this is a proper match for the broken component. I can't find any spare parts, or even the any mention of the board anywhere online (except in Russia, and I don't think going there is a good idea at the moment!).Is this the right component or am I getting something horribly wrong?

author: floobydust
author_rank: Super Contributor
timestamp: March 01, 2022, 03:07:17 am
content: This is your usual Alps rotary encoder that is copied to something generic. But most of them have a metal collar and shaft - this would be a safety issue if the oven control board is at mains potential. Very slim chance but check the board's power supply is isolated, usually they are- but I don't know this oven.I think you've got the right replacement part Alps EC12E24204A9. It looks like anAlps EC12E series.Bourns also make rotary encoders, likePEC12Rmaybe a PEC12R-4225F-N0024 but RS only offer the PEC12R-4225S-N0024 that has a pushbutton switch.

author: Enlargee79
author_rank: Contributor
timestamp: March 01, 2022, 06:12:50 am
content: The 240V part of the board is isolated, yes. It's on a separate board with the power control relays and a small transformer for the presumably 12V supply for the control board. I know to keep well enough away from the 240V side of things. The connections for the rotary encoder are on thin little traces, which route back to an ATMEGA or similar microcontroller on the same board so I'd be very surprised if there was any 240V going through the board or the encoders.

author: floobydust
author_rank: Super Contributor
timestamp: March 01, 2022, 09:34:40 am
content: I wasn't sure why it's all plastic, Midea must be a little cheap. A $2 part causes so much hassle.

author: Enlargee79
author_rank: Contributor
timestamp: March 09, 2022, 12:39:01 pm
content: Just a little update to this thread, in case anyone else is having the same problem and comes across it.This worked just fine. The EC12E24204A9 of couse has 5mm total spread between the 3 pins, and a different pinout. I had to swap two of the pins over, and route them to different traces on the board, but after doing that (and a few swear words when I first thought the part wouldn't work), it's working just fine and is nice and clicky with fresh new detents.And the best part is, wifey has started baking all kinds of interesting things now that she can properly set different temperatures on the oven.