Integrated Encoders only work when moving really fast

So I’ve seen this problem a few times, usually with IEMs, but still haven’t found a solution or cause to the issue. Basically my Integrated Encoder will only change if the motor is moving really fast. If anybody else had encountered this problem and found a fix, please help. Thank you for reading and hopefully responding. If you need any more detail, I’ll happily give it.

@ZachDaChampion How are you testing this? Just reading the debugger as you apply motor power thru a joystick? If the testing is indeed this simple, then I have no idea, this is news to me, however if you are seeing this problem happening within your competition code, then it is probably a coding problem, not hardware. Hope that makes sense.

Have you attempted to switch the two wires on the two ports with eachother? Have you attempted trying to use a potentiometer instead as well?

I think you are thinking of Quad Encoders and
not integrated encoders.

I am wondering if it has to do with the black and white flywheel. If it is loose on its axel it may slip until the motor gets up to speed causing you to get inaccurate results.

Another thought is that the sensors reading the flywheel could be dirty.

You may want to pull the motor apart and inspect.

@ZachDaChampion Does this happen with only one particular IME on one particular motor, or do you see it across multiple devices (motors and/or IMEs)?

I’d say if this happens across multiple devices on the same robot, it may be a programming issue.

If it’s just limited to one specific IME/motor combination (and other IME/motor combinations are working fine), it’s probably a device issue. If this is the case:

  1. [Easiest option, by far] I have seen people recommend not screwing the black caps on too tight, or else it puts too much pressure on the black & white gear and keeps it from spinning properly. Try loosening the motor screws on the IME end and see what happens.

  2. Do the lights on the IME register the way they should, depending on what the robot is doing? (when idle, it should do 2 quick green flashes, then off for 2-3 seconds, then repeat; when the motor is running, the green light should flash on/off constantly, in proportion to how fast the motor is spinning (slow motor, slow on/off; fast speed, fast blinking on/off)

  3. Lights OK? Move on to the basic “sniff test” – take off the IME

  • look at the electronics on the inside of the cap; is there any white corrosion or does it look damaged?
  • does the black & white gear look scratched on the top side or dirty?
  • does the black & white gear have any broken or worn teeth, on either set (the big ring or the little ring)?
  1. If that all looks OK, go through this testing tree:
  • keep the motor on the robot & slap on a brand new IME and black&white gear (or one from another motor that you know works fine)
  • same problem happening? then it’s probably something with the motor.
  • problem gone? then you had a problem with that first IME and/or black & white gear. Look at them both really closely for damage (again), and compare them to the one that works.
  • still have the same problem? try this new IME/black&white gear AND a new motor. Maybe you were really unlucky and had problems on both the motor AND IME.
  1. After that, I got nada.

Hope this helps.

Leslie Peters, Coach
Renegade Robotics, Team 1666

Our team had a lot of problems this season using IME’s I think gyroscopes are a way better alternative but if you get them to work then I would use them

@Chad and @ZachDaChampion – I have, coincidentally written 2 extensive blog posts recently, one on the gyro sensor and one on IMEs, linked here, intended to be a reference manual of sorts for other teams. I’ve collected up all of the information from a zillion disconnected Forum threads into one place, combined with my team’s experiences with each of these sensors. Please check them out if you’re interested.

They gyro sensor, in particular, I wanted to be a central repository of information that people could use, since there is NO central repository of information or instruction sheet, or diddly squat about this sensor from VEX On High.

Since the title of the IME post is “Why I’ll never use IMEs again…” you can guess what I concluded after connecting the dots between my team’s disastrous results this season and the technical information I garnered doing research for this post.

I’d recommend both posts for anyone interested in an all-in-one-place, easy-to-read synthesis of lots of useful information from the Forum, including the helpful info from people like @jpearman (plus links back to the originals, in case people want to hear it from the horse’s mouth).

Cheers -

LP