Encoder Switch Replacement - Page 1
Forum section: electronics / projects

author: bostonman
author_rank: Super Contributor
timestamp: January 07, 2024, 04:29:07 pm
content: I obtained a Korad KA3305P power supply.Looks like the front took a hit because the current adjustment knob is broken off, shaft for the encoder switch is snapped off, and three banana plug terminals are broken off.The power supply works fine, so replacing these broken pieces will be nice. From my measurements (using the voltage adjustment encoder switch that didn't break), looks like it's 24 clicks for a full revolution, detent type (each position clicks), and, pushing on the shaft appears to be a momentary open (or closed) switch. The issue I'm having is the sizing. Just about all the ones I found have a base size of 12.4mm x 13.4mm. Mine measures 12.65mm x 13.3mm.Although this isn't a big difference in size, and probably this will fit (most likely shaft length/size is the most important as far as mechanical), I always find myself feeling that the exact one must exist since these are what is being used.A few other measurements: shaft length measures approx. 9.55mm, 6mm diameter with a flat side, it's horizontal mount (I think this is the correct mounting type), and not threaded (not sure of the terminology). I'll post a picture shortly for a visual.Also, due to losing the plastic knob, I'll need the associated knob. I haven't looked for the plastic knob yet, so maybe it's fairly straight forward, but uncertain if the knob usually associated with the switch as a matching pair. If need be, I can replace the good knob so both match if I find one that's slightly different.Later I'll need to figure out the banana jack too because these are a specific size that fit through the plastic front panel.

author: tooki
author_rank: Super Contributor
timestamp: January 07, 2024, 09:27:04 pm
content: The critical mechanical specs are the pin locations, the height of the housing, the type of bushing (plain, threaded, etc) if used (in many designs it doesn’t matter), the shaft style, and the shaft length. (Beware that some encoder models measure shaft length from the PCB, others from the top of the housing!This is even within a single manufacturer. So pay close attention when ordering, study the datasheet very carefully first! #LFMF)The knob is not included with the encoder. Get encoders with whatever shaft style you prefer, to match whatever knobs you like.I’d probably replace both the encoders, since even the encoder that’s not broken off may have suffered some strain that shortens its lifespan. They’re so cheap anyway, and by replacing both you can choose whatever knob type you want (not just ones that fit the old encoder).

author: PCB.Wiz
author_rank: Super Contributor
timestamp: January 07, 2024, 09:43:30 pm
content: Quote from: bostonman on January 07, 2024, 04:29:07 pmDid the one you removed have any part codes underneath ?You have a lot of room there, so almost any shaft encoder could be coaxed to fit, with some bending and 'copper rod' craft work.That lets you focus on the shaft length and knob interface, which are what the operator sees and feels.

author: bostonman
author_rank: Super Contributor
timestamp: January 08, 2024, 01:30:30 am
content: QuoteI always manage to leave out some key item in my questions/responses. Unfortunately I didn't see a single mark/number on it. Using the filter on DigiKey, I narrowed things down based on the few features I knew, but it didn't seem to get an exact match (as I mentioned, the physical size is different).Good to know some manufactures measure shaft length from the PCB; I'll keep an eye out. You're correct, replacing both is a safe bet. Usually when I order parts, if they are cheap enough, I'll order several just to keep as spares or if it gets damaged while replacing. In this case, I'll plan to use the spare(s) to replace both.I'm uncertain how to electrically measure this. The easiest are the two pins which appears to be the switch. When I press the shaft (until it clicks), the two pins short, release, and the pins open.The three pins I assume are the encoder itself. They all appear open, but, if I turn the shaft so it sits between clicks, I measure shorts on the pins. The shorting is probably fed back and the micro (?) determines the shaft is turning, but too many pins are shorted together for this to make sense.On the datasheets I looked at, they showed the pins, but from my analysis, the circuit may be designed around the signals shown on the datasheet since it shows the pulses in the CW direction.Does a certain spec exist that would tell me if the pins and/or shaft rotation (CW versus CCW) may not work in this design?

author: PCB.Wiz
author_rank: Super Contributor
timestamp: January 08, 2024, 01:46:38 am
content: Quote from: bostonman on January 08, 2024, 01:30:30 amIf you are unlucky, I think just swapping the quadrature pins will reverse CCW/CW.

author: bostonman
author_rank: Super Contributor
timestamp: January 09, 2024, 04:12:34 am
content: QuoteSorry, I didn't exactly mean "included" as in sold as a pair, I meant it more as: does a typical datasheet suggest knobs that compliment that particular encoder shaft. It was really a silly question on my part because, as expected, a plethora of knobs exist. Also, you already answered it including that I discovered the answer as I dug deeper into datasheets.Having looked on DigiKey and Mouser for knobs, I'm finding some very basic ones. Is the original knob (shown in the picture in my original post) something that may be a special design or a COTS that I just haven't located yet?QuoteThanks, this was a help as it seems the one I found does measure from the PCB. I somewhat did a double check by measuring from the top of the housing to the shaft end, and that length wasn't listed. The length listed was the one I measured from the PCB to the top of the shaft (and what the datasheet diagram showed).Also, one last (hopefully) question: the filters show detents and another for pulses. Mine clicks 24 times for a full turn, this tells me it's 24 for detents, and 24 for pulses, correct? Would a case exist where these would not be equal?

author: PCB.Wiz
author_rank: Super Contributor
timestamp: January 09, 2024, 04:22:08 am
content: Quote from: bostonman on January 09, 2024, 04:12:34 amIf you want instrument knobs, you could expand your search to include collet knobs. Not cheap, but they grip a shaft well, with some height adjust.

author: bostonman
author_rank: Super Contributor
timestamp: January 09, 2024, 04:30:57 am
content: That term seemed to have got a few results closer, but looks like I'll search elsewhere as DigiKey didn't seem to have one close to this.It won't matter if I replace both knobs anyway. It's more about fitting correctly and somewhat looking like a normal knob that matches the unit.

author: coromonadalix
author_rank: Super Contributor
timestamp: January 09, 2024, 11:41:50 am
content: you have 12 and 24 click per turn ...

author: bostonman
author_rank: Super Contributor
timestamp: January 09, 2024, 01:27:45 pm
content: Not sure I understand. Do you mean 12 clicks and 24 pulses?

author: bostonman
author_rank: Super Contributor
timestamp: January 10, 2024, 03:20:07 pm
content: I may be ordering the switches in the next few days and wanted to clarify what you meant by 12 and 24.I tried getting samples, but the company hasn't responded yet, so I may resort to DigiKey if I don't get a response on the samples soon.

author: bostonman
author_rank: Super Contributor
timestamp: January 10, 2024, 06:12:17 pm
content: I didn't realize the datasheet showed the names of the three pins. After doing some research and finding a great visual on how the switch works, I grasp the concept of how these work.Also, the company responded and said they'd send samples. I ordered a few varieties including 12 and 24, a slightly longer shaft, etc...

author: tooki
author_rank: Super Contributor
timestamp: January 10, 2024, 08:41:07 pm
content: Quote from: bostonman on January 09, 2024, 04:12:34 amI’ve never seen an encoder manufacturer sell or recommend knobs. Maybe some does it, but none of the three big name brands (Alps, Bourns, and Panasonic) does.Quote from: bostonman on January 09, 2024, 04:12:34 amYes, there are ones like that. Not sure why you’d want it, but they exist.

author: bostonman
author_rank: Super Contributor
timestamp: January 16, 2024, 03:52:46 am
content: Bournes should be sending some encoder switch samples to me; hopefully this week. I spoke to the sales rep because originally I ordered a variety including a 12/24 combination (the order was placed before I got a better understanding of them in this thread), and he explained typically they come 12/12 or 24/24, but a combination can be made as a special order.Obviously I don't have a need for a 12/24 or 24/12 combination, so I'm getting the regular ones but in different shaft lengths.On another note, I contacted the power supply company in hopes they would/could supply part numbers for the plastic (collet) knob and banana jacks, or the cost for replacement parts (shipping cost was too high for this option to be considered). The first reply included a part number (EC12S-H6.5-P24-AL20F7) and she informed me this is for the knob combination. Also, the banana jacks are a standard 4mm, but she didn't provide a part number.I responded stating that part number only provides the encoder switch and not the knob. Also, the banana jacks may be a standard size, however, they mount differently than what I'm finding.The two follow up responses resulted in going in circles. I politely re-requested part numbers for two items: plastic knob and banana jacksUnfortunately it's either a language barrier causing communication issues (they are China based) or they are reluctant to provide more accurate part numbers.I've searched quite a bit for the plastic collet knobs. I'm not finding the correct diameter (too large and it will block the writing on the panel) and zero luck finding banana jacks that have PCB mounting in the size/type these are.My search will continue, but may result in making some modifications.

author: tooki
author_rank: Super Contributor
timestamp: January 16, 2024, 11:11:13 am
content: The knobs are almost certainly a custom part, not something you can buy off the shelf.

author: bostonman
author_rank: Super Contributor
timestamp: January 16, 2024, 02:23:26 pm
content: I agree and also believe these banana jacks are custom too. She stated they are standard size, but I think she has some confusion between the front input size and the actual part that screws into the PCB.Thingiverse has some knobs, however, they are around 30mm in diameter and these are around 17mm (as mentioned, a larger diameter will block the print on the front panel). Also, most likely my 3D printer will not accurately print the 6mm D shaft so it properly fits.The option for knobs is basically go with ones that will be visibly different due to (smaller) size, have a position notch/line, and style, but I'll have a working adjustable power supply as an addition to my collection.

author: PCB.Wiz
author_rank: Super Contributor
timestamp: January 16, 2024, 08:40:34 pm
content: Quote from: bostonman on January 16, 2024, 02:23:26 pmDid you try places like thishttps://www.don-audio.com/Control-Knobs_s2or RS show a small collet knobRS PRO 14.7mm Black Potentiometer Knob for 6mm Shaft Screw Fix RS Stock No.: 463-8514Elma Rotary Collet Knob for use with Rotary switch RS Stock No.: 224-2270 Knob Diameter 14.5mm

author: bostonman
author_rank: Super Contributor
timestamp: January 17, 2024, 02:25:13 am
content: Believe I came across that site already; and the others you recommended in your post.Since the face doesn't have indicator numbers, I felt a knob with an indicator line (or part of the knob protruding out) wouldn't go with the function of the knob. At this point I may begin making exceptions.The site isn't very informative, but, if I understand correctly, they sell covers. One knob that stuck out was KN-TATTO-S-15 (15mm diameter), it's a bit smaller, but close enough. It's a silver knob, 15mm, but, their covers are "for" 14.5mm and don't list silver. In either case, the knob doesn't state if the cover is removable, but the covers don't come in silver anyway.Eventually I'll make some exception and pull the trigger.

author: themadhippy
author_rank: Super Contributor
timestamp: January 17, 2024, 02:29:44 am
content: Quotemake the hole smaller than wanted,heat up the shaft and push it in.Dont try this with a plastic shaft

author: tooki
author_rank: Super Contributor
timestamp: January 17, 2024, 01:44:54 pm
content: I wouldn’t do that with a metal shaft, either… I’d be worried about conducting excessive heat into the encoder body and damaging it. (Not an issue with ones designed for SMD reflow, I guess.)

author: bostonman
author_rank: Super Contributor
timestamp: January 17, 2024, 04:01:20 pm
content: I agree with not using heat. Also, it would probably cause the knob to go off center and become annoying to turn.

author: bostonman
author_rank: Super Contributor
timestamp: January 17, 2024, 04:33:38 pm
content: Sales rep just contacted me about the encoders.They will ship from Taiwan on 2/2, so I won't know if they are good replacements until then. Also gives me a bit of time to search for a knob and banana jacks.