KP184  - Rotary Encoder Issues - Page 1
Forum section: electronics / testgear

author: Ziggo
author_rank: Contributor
timestamp: October 26, 2021, 06:08:24 am
content: I bought three KP184 electronic loads in 2019, but didn't use them much until recently. I am experiencing issues with entering values using the knob/rotary encoder. It's difficult to get the values to change smoothly. The values will go up or down even when the knob if being turned only one way. The values will also jump between the various digit positions.One unit is mostly OK if I turn the knob slowly. Another can be made to work by turning in very small increments (less than a "notch"). The third is nearly unusable so I try to keep it set to a certain value.I use them for battery capacity testing and they work fine in other respects. No issues with the buttons or the actual load testing. I'm not sure if a firmware update would help or is even possible.I wanted to see of others had experienced this issue and had found a solution.Thanks

author: voltsandjolts
author_rank: Unknown
timestamp: October 26, 2021, 10:11:28 am
content: The rotary encoders are often of poor quality in this type of far east stuff.It's probably a standrd footprint so I would start by replacing it withsomething better.

author: Peabody
author_rank: Super Contributor
timestamp: October 26, 2021, 03:03:25 pm
content: It sounds like typical low-quality or dirty encoders. If they worked properly in the beginning, you might be able to restore proper function by taking them apart and cleaning them. Of course that's hit or miss, but I've had some luck doing that.If you decide to replace them, you need to remove one and see what you'll need to order. There are basically two kinds of mechanical encoders - those with the same number of pulses as detents per revolution, and those with half as many pulses as detents. A "pulse" is one complete cycle of both switches. So the first kind always comes to rest at a detent with both switches open. The second kind can be either both-open or both-closed at a detent. You need to get the right kind because the firmware will be written for that kind of encoder.

author: Ziggo
author_rank: Contributor
timestamp: October 28, 2021, 10:39:20 am
content: Thanks for the suggestions. I'll try cleaning the encoder on the worst unit. Today, the other two units were working OK, but one was still barely usable.

author: interflexo
author_rank: Regular Contributor
timestamp: October 29, 2021, 06:30:14 am
content: You can also control it by software and forget the whole ordeal for now.

author: aristarchus
author_rank: Regular Contributor
timestamp: October 29, 2021, 09:08:17 am
content: Quote from: Ziggo on October 28, 2021, 10:39:20 am@ZiggoIf possible, please give us a photo of the pcb that has the encoder's circuit, it could reveal if the design is filtering noise on encoder's contacts or not.

author: Ziggo
author_rank: Contributor
timestamp: November 06, 2021, 02:08:06 am
content: OK, I'll open one of the units up and get some pics. But not today. I want to fix other things with my test equipment, not fix my test equipment. The encoder issues are back on all three units and an additional issue popped up.I couldn't start a battery discharge at 9A (40V). I had to lower it to 5A before it would start. Then, I could increase it to 9A without issue (other than the issue of the rotary encoders being flaky). I tried lowering the ramp up/down rate but couldn't find a solution. Same problem on two different units.

author: interflexo
author_rank: Regular Contributor
timestamp: November 07, 2021, 06:40:01 pm
content: Quote from: Ziggo on November 06, 2021, 02:08:06 amThat's why I suggested the full software control for now and you don't have to touch the Kunkin operating panel again.If you have a suitable USB to serial adapter at hand you may have a go with it:https://www.eevblog.com/forum/testgear/serial-to-usb-on-kunkin-kp184-electronic-load/msg3787289/#msg3787289

author: Ziggo
author_rank: Contributor
timestamp: November 10, 2021, 06:06:20 am
content: Thanks for the link to that thread. I had tried to use the KP184 software from the mfg in 2019 but couldn't get it to run. I'll try again.

author: torch
author_rank: Frequent Contributor
timestamp: July 22, 2025, 08:38:50 pm
content: Mine has started acting the same recently. Were you able to resolve it or replace it?

author: torch
author_rank: Frequent Contributor
timestamp: July 25, 2025, 11:37:07 am
content: No response in this old thread. Oh well.For the next guy who finds this through the search function, I took mine apart. No sign of a part number anywhere. It is a contact type, apparently incremental design with 3 terminals. While it has detents, fortunately there were no tiny springs and balls waiting to jump out on disassembly.I sprayed the interior with DeOxit D5 and reassembled. It's working better now -- not perfect, but better. It is still occasionally skipping or doubling (ie: rotating CCW one detent from a displayed digit of, say, 5, may result in a displayed digit of 5, 4 or 3) but at least it is always going in the right direction now (ie: CCW to decrease, CW to increase).I'm going to have to do more research on rotary encoders to see if I can figure out the specs for a replacement. Sounds like a winter project...

author: torch
author_rank: Frequent Contributor
timestamp: July 25, 2025, 11:42:12 am
content: Oh, one last thing:I have been using interflexo's "Modbus" software for some time now. It works well, especially for automated tasks like battery load testing. But sometimes I just want to do a fast manual test or observe how a circuit behaves as things are changed, etc. so I really want the panel controls to work properly too.

author: Peabody
author_rank: Super Contributor
timestamp: July 25, 2025, 04:17:17 pm
content: Ziggo never posted a picture of the encoder. Can you do that, plus give us:Anything on the encoder that might be a part numberThe number of detents per revolutionWith the power off: on each detent, are both switches always open, or are they sometimes both closedI'm assuming you would be able to replace the old encoder if you could order the right one.

author: torch
author_rank: Frequent Contributor
timestamp: July 25, 2025, 11:09:29 pm
content: Ok, you asked for it!There is absolutely no sign of a part number. There are 24 detents per revolution. On each detent, everything is open -- they are closed partway between detents (more about that below).Pictures:(note the piece of tape on the shaft. That there is a factory applied feature. Without it the knob falls off.. I'm also really curious what "Right 1" might have been for. )(I'm guessing the extra holes mean the original design had a different encoder -- one with a push-button for something)(I'm not sure if that melted corner was a factory applied feature or a by-product of the de-soldering process. I use a de-soldering station with vacuum pump so it doesn't usually need a lot of extra heat, but those tabs took a bit more).Note in the image above, the circle of contacts is divided into 3. The solid section is connected to the centre terminal -- I'll call that common. The next third (individual pads) is connected to one of the outside terminals, the final third (also individual pads) is connected to the final terminal.I connected the centre terminal to +1vdc or so, and each of the two remaining to two separate scope channels. PS and scope grounds were all connected, like so:I was able to confirm that one side leads the other and the order reverses when the direction of rotation is reversed:Clockwise:Counter-clockwise:

author: Peabody
author_rank: Super Contributor
timestamp: July 26, 2025, 12:22:22 am
content: As far as I can tell, it's a standard mechanical (as opposed to optical) rotary encoder with 24 detents per revolution and 24 pulses per revolution. Take a look at the Bourns PEC12R models:https://www.bourns.com/docs/Product-Datasheets/PEC12R.pdfIt will be a question of finding the right type of encoder which fits the holes in the board. The datasheet has detailed measurements of the various models. I don't know if the PEC12R is the right size, but if it isn't, you will have to go to Digikey or Mouser and try to find one that fits. Just make sure it's 24 detents per revolution and 24 pulses per revolution. And you'll want to be sure the shaft is the right type and length. I'm not sure it matters about the pushbutton. It looks like you don't need it, but I don't think it would hurt if it was there. You can always just cut the pins if the switch is a problem.It shouldn't matter what the inside looks like. There's a variety of designs, but they all produce the same output. So the detents, pulses, and size are the main things to get right.Edit: On another look at the pictures, I'm a bit puzzled by the three spring contacts. Not sure how they work. But the main thing is whether your encoder produces the standard quadrature output as shown in the datasheet, in both directions, for a full revolution. If it does, then the inside design doesn't matter. Typically the middle pin of the three is the common. The outside pins connect to the middle pin as each switch closes.

author: torch
author_rank: Frequent Contributor
timestamp: July 26, 2025, 01:45:10 am
content: Quote from: Peabody on July 26, 2025, 12:22:22 amThere's 3 pairs of wipers stamped from a single disk of metal and spaced equidistantly. So one pair is in contact with the common pin's third at all times, one pair makes contact with the left outside pin's contacts and the third with the final set of contacts, respectively. I assume that there is a degree or two physical difference in the location of the contacts in each zone relative to the axis of rotation, to ensure that one leads the other as each detent is crossed and that the order is reversed when the direction of rotation is reversed.I'm not sure why they are in pairs. Mechanical de-bounce?

author: Peabody
author_rank: Super Contributor
timestamp: July 26, 2025, 01:55:23 am
content: Yes I think so. Two contacts would make it more likely that at least one of them would be connected.

author: torch
author_rank: Frequent Contributor
timestamp: July 26, 2025, 08:37:12 am
content: Quote from: Peabody on July 26, 2025, 12:22:22 amI had to take it apart again to measure the overall length, but based on the datasheet above the Bourns version is:PEC12R-4217F-N0024In stock at Digi-key, Mouser, etc.Now, all that said, does it really matter if it's 12 or 24 detents? I mean this is just a control, we're not monitoring a rotation speed or orientation where the circuit needs to monitor the shaft position. So long as the number of pulses = the number of detents the circuit won't know or care, right? It seems to me that a 12 detent encoder would be a little less touchy to operator input -- understanding it would take twice as many rotations to achieve the same result.A 12 detent encoder would be PEC12R-4117F-N0012. Also readily available.

author: Peabody
author_rank: Super Contributor
timestamp: July 26, 2025, 01:32:13 pm
content: I think that's right. But I've never used a 12-detent encoder, so I don't know if there are any other differences that you would notice. I think it depends on how often you'll need to go through a big change of setting - that could be tiresome with a 12-detent encoder. One thing we do in the Arduino world where I usually hang out is a hyper-responding encoder depending on how fast the knob is turning. It's normally one tick per detent, but could be 2, or 4, or even more if the knob is turned fast. If that kind of thing is used in your device's firmware, then a 12-detent encoder could really slow you down.Well, you know, you could get one of each. They're a couple bucks, and shipping will cost more than the parts anyway. But I don't see a 12-detent in stock at Digikey, even with a switch.

author: torch
author_rank: Frequent Contributor
timestamp: July 26, 2025, 02:18:14 pm
content: Quote from: Peabody on July 26, 2025, 01:32:13 pmHuh. Maybe it's a regional thing. The Canadian site shows over 1,900 in stock:https://www.digikey.ca/en/products/detail/bourns-inc/PEC12R-4117F-N0012/4699275