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DHB-10 rate — Parallax Forums

DHB-10 rate

JuliussssssJuliussssss Posts: 12
in Accessories
Apologies for new post, I failed to find this specific question asked before.
But what is the control loop rate of the DHB-10 ? How often is the encoder read and how often the motor input updated? Did not find this info in the doc :/

Thanks

Comments

  • Duane DegnDuane Degn Posts: 10,588
    The default firmware has a 50Hz control cycle but (I think) the firmware uses encoder ticks from the previous half a second to compute speed.

    I think the half second speed interval is needed when low resolution encoders (like the ones with Arlo) are used.

    If you had a motor/encoder combo with lots of encoder ticks per second, you could more precisely control the speed over a shorter interval of time.

    Do you have an application in mind? What sort of motor/encoders do you want to use with the DHB-10?

  • JuliussssssJuliussssss Posts: 12
    Thank you !
    You say default? Implying that it can be changed?
    How would one need to go about that? Would I need to build from source somehow and flash it?

    I'm buying the off the shelf Arlo ones. Nominal speeds are really slow, hopefully the half second delay won't be too much of an issue.
  • Duane DegnDuane Degn Posts: 10,588
    edited 2017-03-29 19:52
    Juliussssss wrote: »
    You say default? Implying that it can be changed?
    How would one need to go about that? Would I need to build from source somehow and flash it?

    The firmware of the DHB-10 can be changed by using a Prop Plug or other USB to serial device.

    The firmware is available from the DHB-10 product page.

    I haven't used my DHB-10 a lot but the code looks a lot like the original Eddie code used with the predecessor of the Arlo.

    I modified the original Eddie code to work on a Propeller Activity Board (PAB) in conjunction with the now discontinued HB-25 motor controllers. I posted videos of some of my experiments in the thread about converting the firmware. This post includes a video showing my robot driving a 1m x 2m rectangle to test the dead reckoning capability of the new firmware.

    I haven't performed the same sort of test with the DHB-10 but I'd expect the DHB-10 is capable of the same sort of dead reckoning done with the PAB/HB-25 combo.

    If you plan to use the DHB-10 with Arlo hardware, I don't you'll need to change the firmware. You'll likely just need to change some of the configuration parameters as explained in the board's documentation.

    What are you using as the main processor for your robot? Are you using the DHB-10 with computer or are you using a microcontroller to control the DHB-10?

    Edit:
    Juliussssss wrote: »
    hopefully the half second delay won't be too much of an issue.

    The half second time period is used for monitoring the speed of the wheels. The DHB-10 is continuously monitoring inputs and can respond to new commands in about 20ms.

  • JuliussssssJuliussssss Posts: 12
    Ah I see, so its not that encoder is read at 2Hz, but the 'sliding window' to get the encoder cound derivative is 500ms wide.

    ye, my main main main computer is an actual PC running linux. I thiiiiink I will be using maybe a lower level baord like raspi zero to control the DB-10s . probably 'outsource' some lower level, fast loop controls to that raspi too and only keep the high level stuff for pc.

    Thanks for your help, this makes sense now.
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