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Well, it looks like I have a faulty JRK?

Discussion in 'Motor actuators and drivers' started by Barry, Jan 28, 2018.

  1. Barry

    Barry Active Member

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    My Motion Simulator:
    3DOF, DC motor, JRK
    After all the months of planning and wiring I finally got to fire up some power to my sim today. I plugged in all my JRKs and double and triple checked all my connections and installed the JRK drivers and the JRK utility to set up the motors.

    First thing I did was disconnect the levers so I didn't have anything connected to the motors. A little common sense as these things can really kick.

    Then I started to go through the settings as per Robbies step by step guide. First motor, set up perfect, went to the input tab of the utility and I can move the motor lever no problem and set it's position, second motor, just the same, no problems there. Then the third JRK and motor.....

    I set up the range of motion, no problems there, I do the motor direction check and the motor kicks. All good there, I flick through all the tabs to ensure I hadn't missed anything as I did with the first 2 and it's all fine. Back to the input tab to use the 'set target' button, i move the slider and click target and the motor shaft moves, I move the slider again and click set target again...... then all hell breaks loose. Clicking, shuddering, juddering back and forwards, looks like the motor has thrown a wobbly. I quickly shut the power off and remove the USB lead so I don't have any voltage spikes back into the PC. as I'm checking my connections I notice that the JRK was pretty hot. The other controllers had no problems, no excessive heat at all. They'd only been on for about 10 minutes max. All wiring was good. After around 20 minutes I went back and ran the utility again. First 2 controllers and motors are working fine. 3rd one has all the settings, everything looks normal, the readings from the potentiometer are showing as they should but there's no movement from the motor at all. I try setting the target, nothing at all, the motor direction test does nothing.

    After swapping 2 JRKs completely including motors and usb cables and pots, it appears the JRK simply isn't putting any power to the motor at all. It appeared to work for all of about 10 seconds, then died.

    Is it fixable? As i've had the controllers far a long time they're obviously out of warranty so i don't thing pololu would be interested.
  2. Ads Master

    Ads Master

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  3. noorbeast

    noorbeast Xsimulator Race Director Staff Member Moderator Race Director

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    My Motion Simulator:
    3DOF, DC motor, JRK
    First off can you step back through the basics.

    I am presuming the JRKs have heatsinks and fans, if you run them without you definitely risk damaging one.

    Double check all wiring and soldered pins.

    In the menu reset the problem JRK to defaults.

    Loosen the pot and using the graph in the JRK utility ensure the pot line is mid way in the top graph when the lever is level.

    Rerun the setup.

    Report back what happens and post pictures of all of your settings.

    Worst case it is still worth contacting Pololu, they will often give a discount on a replacement.
    • Informative Informative x 1
  4. Barry

    Barry Active Member

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    My Motion Simulator:
    3DOF, DC motor, JRK
    Heatsinks are on yes, fans are not installed yet as I don't intend to run the sim just yet. This was really just to set up the software to make sure everything was connected and ready to go.

    I'll have a go and resetting it and see where I get to. It might be tomorrow evening before I get a chance to post the results but i'll try and get screenshots of everything.
    • Like Like x 1
  5. Nick Moxley

    Nick Moxley Well-Known Member

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    My Motion Simulator:
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    Dont invest in more JRK's Discount or not........Get a Sabertooth 32 (worth the extra $$) and put a working seat JRK on the TL, keep the spare JRK for the TL if you ever have issues,

    JRK's are Not up to the job of running out sims Flat out, ..Sure soft slower motion's and it'll survive for years , But Having been through 3 now in 4 + years of Aggressive heavy use....they eventually give up the ghost and go weak, Run motor driven errors and get so weak there not able to hold you up while racing.
    • Informative Informative x 1
  6. Barry

    Barry Active Member

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    My Motion Simulator:
    3DOF, DC motor, JRK
  7. Barry

    Barry Active Member

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    My Motion Simulator:
    3DOF, DC motor, JRK
    So i've been in touch with Pololu and they've been very helpful. I explained my situation and they've given me a few suggestions to help with any potential problems. I purchased my JRKs about 3 years ago but they've generously offered a half price replacement which I think is pretty fair. Here is the reply from pololu.



    Hello, Barry.

    Thank you for the additional information. It is not clear to me what
    caused the damage to your jrk, but if you would like to try again with a
    new jrk, we can help you out with a 50% discount toward a replacement. I
    have set up coupon code XXXXXXXX for you to access this special
    discount through our website.

    It looks like your motor is rated for around 15A. The page you linked to
    does not specify what this rating actually is, but if that is a nominal
    rating, it could draw many times this amount when starting up or
    switching directions. To help reduce the potential for large current
    spikes, you might consider adding some acceleration limiting and maybe
    limiting the maximum duty cycle, if your application allows for it. You
    might also double check that your large heat sink wasn't shorting
    anything out on the board.

    Additionally, we have recently been looking into potential problems with
    using switching PSUs like that with the jrk controllers due to voltage
    spikes generated by the motor. From your description, it does not sound
    like this caused the problem with your first jrk, but to help prevent
    damage to your PSU or controllers in the future, you might consider
    adding a TVS or Zener diode from the power input of each driver to
    ground.
    • Like Like x 1
  8. Barry

    Barry Active Member

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    My Motion Simulator:
    3DOF, DC motor, JRK
    Also, I know the sabertooths are the smart upgrade in this situation but if the JRKs get me up and running properly. I can use them for seatbelt tensioners or other less strenuous tasks in future upgrades.
    • Agree Agree x 1