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Step-n-Roll: locked rotor after throwing me twice


alfu

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With less than 10 minutes total on the pedals of my newbie Step-n-Roll (generic Chinese 14" wheel), recently I mounted the unit and attempted forward navigation, and the machine pitched me forward violently. Shutting down and restarted, the motor jerked to full speed, the emergency stop activated, the motor stopped, and the beep turned on.
On opening the controller panel, I found a loose terminal in the yellow wire connector that I assume comes from the wheel phase encoder. I pushed it back in, made sure all the connections are tight, and powered up again.
BAM! Same thing. Needless to say, that was frustrating.

170524_step-n-roll_connector.jpg

I looked at Youtube and learned about calibration.
 

170524_rebalance_connector_j3.jpg

Here is a picture of the full mainboard, which I think is probably pin compatible with Airwheel X3 mainboard:
 

EUC_labeled_mainboard.thumb.jpg.afc6373d852c5bdb4b5a2f784e8d2eff.jpg

Update 170525: J3 is the calibration port. I soldered the loose wires together, and after a few false starts (at first the wheel froze up, then the wheel was tilted at startup) the calibration worked and I thought I could go on gently bruising myself! The jumper stored easily on one of the screw pillars:
 

cal_jumper_storage.jpg

 

Update 170526: After working for a day, the damn Step-n-Roll (more appropriately named "Stand-n-Deliver") threw me again. Repeated calibrations seem to progress normally, but don't fix it. Here's what I know (battery unplugged):

  • The board-to-hall effect sensor adapter cable and connectors & motor leads seem to be good; else motor would not run correctly during calibration
  • Ohmed out with a multimeter, all three hall sensor leads show a discernable capacitance to both the power wires (red and black)
  • All three phases of the delta-wired motor produce about 15VAC when the wheel is spun manually

And powered up:

  • Normal power up beep, battery charge indicators lit (170527: unit no longer beeps)
  • Wheel rotor is now electrically locked up on startup
  • Extreme angles of pitch and roll do not trigger an error condition

Edit 170528: Since the hardware is intact, is it possible a theft-prevention or protection software mode, that is neither activated nor documented on this entry-level model, has been inadvertently entered in this wheel? It appears that the mainboard is provisioned with connectors that are not used, perhaps for features that are implemented in a more premium model? Might one of them be for a Bluetooth adapter? Is there a way to reset to factory default on these boards?

I watched a Youtube video that suggested opening the continuity of the calibration jumper just after startup. Doing so resulted in 2 new behaviors, neither of which is repeatable or useful:

  1. A sudden jerk, then the wheel free-wheels powered up, but does not balance
  2. A gradual increase in speed in one direction, then I shut it off
  3. The locked rotor, however, predominates

 

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If you didn't already, disconnect the 6-pin connector with the 5 wires (with the wheel turned off of course ;)) and check that the wires are ok in the pins and that the pins make good contact when reconnecting. It's the hall-sensor wires, apparently at least at start-up and slow speeds, the motor position is read from them. Hopefully the pin(s) just got knocked loose from the connector.

As for the level calibration, those could be the right wires, but it's impossible to say for sure (according to 1RadWerkstatt, there are at least 50 variants of the generic mainboards).

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  • 4 weeks later...

I'll bet shorting T (universal symbol for level or it could be Trim level I don't know) to GND right next to it on the board will enter into calibration mode.  Be sure to have the wheel leveled out and the wheel free to spin before shorting and turning on.  Allow the cycle to complete before turning off and disconnect T from GND.  :whistling:  Or it could blow up.  Hard to say.   If it starts beeping with a count down, cut the blue wire!  :efee96588e:  (just a joke - watched too much of The Hurt Locker)

Disclaimer:  I have no idea except that the generic boards I have seen including mine seem to place the calibration jumper on the edge of the PCB.  Try it at your own risk, I'm just taking a wild, semi-edumacated guess really.  Maybe confirm with the seller of the board.

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16 minutes ago, Hunka Hunka Burning Love said:

I'll bet shorting T (universal symbol for level or it could be Trim level I don't know) to GND right next to it on the board will enter into calibration mode.

I had already thought of that, of course. Shorting it (with the wheel on the calibration stand) results in the same behavior as it open: the wheel responds to tilt and starts pulsing the beeper if tilted too much. BTW, try as I might, I could not find anything on the board that 'T' connected to. It seems to be floating.

Confirming anything with either the seller of this replacement board, or the original vendor of the wheel, is as you might expect, useless. I've tried; it's like talking to a wall.

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Could you verify your sequence?  Is it the following:

1. Wheel powered off, place on calibration stand.

2. Short the calibration jumper contacts (solder points on board T and GND) and keep shorted during calibration cycle.

3.  Turn on wheel.  Do not touch it or tilt it.

4.  Wheel should spin in one direction then reverse a few times then signal a beep that it is done.

5.  Power down wheel.

6.  Remove calibration jumper.

7.  Power on wheel on floor to test balance level.

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18 hours ago, Hunka Hunka Burning Love said:

Could you verify your sequence?  Is it the following: [snip]

 

Thank you! That's the sequence, exactly. Placing the shorting jumper on the T to GND header results in no change from standard power up. Placing the header on JN8 with the same protocol results in a sustained pulsed beep and flash of the POWER ON LED that apparently indicates an error and does not stop until shutdown. Removing the jumper during the beeping results in no change.

BTW, I have not yet updated the controller image, but I think JN4 is for communicating with the CPU via I2C.

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18 hours ago, electric_vehicle_lover said:

Maybe find the pin that does calibration on older board and try the same on the new one? I mean the pin of the STM32F103

All the CPU pins I mapped out in reverse-engineering the controller were different from the old board, and different from any on-line documentation I have been able to scrounge, but sure, I'll give that a whack, and get back to you on that.

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19 hours ago, Hunka Hunka Burning Love said:

Disclaimer:  I have no idea except that the generic boards I have seen including mine seem to place the calibration jumper on the edge of the PCB.  Try it at your own risk...

I soldered a 330 ohm resistor into my shorting jumper to reduce risk, but still allow a logic '0'. However, JN8 places a 10K resistor in series with the CPU pin, so no harm likely there.

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How bad is the level currently?  Can you ride the wheel as is?  When you turn it on, does it self-balance in the forwards and backwards direction?  Or does it beep an error constantly?  You haven't described things completely so there may be some missing information.  Does it function normally, but the shell/pedals are not level?

According to this page, the board comes in vertical or horizontal orientations.  Are you sure you have the vertical version?

https://detail.1688.com/offer/43245285971.html

With my hoverboards, a long press of the power button activates the calibration routine.  Maybe with this version of board they have incorporated that functionality into the power switch?  Maybe try placing it on your calibration rig with the wheel allowed to spin freely and try long pressing the power button.

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22 hours ago, Hunka Hunka Burning Love said:

With my hoverboards, a long press of the power button activates the calibration routine.  Maybe with this version of board they have incorporated that functionality into the power switch?

I doubt it. The power switch on this wheel is a toggling push-ON push-OFF switch. The battery power (+64V) is mechanically supplied through the switch to the controller logic. At any rate, the conversion is now a success. I will be happy to answer anyone's questions who wants to do a similar conversion.

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8 minutes ago, Hunka Hunka Burning Love said:

So how did you end up calibrating it and getting it to work?

I updated the graphic above to include cal procedure. I discovered it by turning it on after doing some final mounting and connecting of the controller. It was grossly tilted, and it had been level on first startup! So I must have inadvertently calibrated it previously. Put it back on the level stand and tried again, and presto-changeo, it was calibrated.

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