Jump to content


Full Members
  • Content Count

  • Joined

  • Last visited

Community Reputation

59 Excellent

1 Follower

About trevmar

  • Rank
    Advanced Member
  • Birthday 11/14/1948

Profile Information

  • Gender
  • Location

Recent Profile Visitors

155 profile views
  1. No, I disagree, from a design engineer's point of view you are simplifying the situation too much. The Ninebot design team wrote an excellent blog detailing the safety margins upon which the MiniPRO was built. You can find it with Google Translate in the Chrome Browser at http://bbs.ninebot.cn/forum.php?mod=viewthread&tid=4100&extra=page%3D1%26filter%3Dtypeid%26typeid%3D43 1/23 Truth is that the current firmware still has flaws which can, and do, result in the rider being thrown forward and run over. It happened to me. After reading the designer's blog I formed the opinion (as a design engineer) that many of the current speed and weight limitations were based on requirements by the various country's safety authorities, rather than on limitations of the platform. Additionally, when Ninebot was forced to used high-quality LG batteries by the hoverboard-fires scandal, the amount of power the motors had available was actually increased significantly (see my post on battery peak-power testing). This was never exploited to improve the carrying ability of the platform, and hence its safety margin. All firmware versions have the same balance capabilities, that is how they were designed. Finally, in answer to your question, the current being drawn, and rotational speeds of the motors are what the firmware uses to regulate the power it delivers.The current sensing resistors can be clearly seen at the top of the control board (R004 or R008 SMD power-resistors) If you want to explore this further, MRN76 has produced an app which allows any of the major Ninebot firmware revisions to be programmed into any MiniPRO, and the original firmware replaced after testing. Search here for "JTAG" to find my posts on implementing those changes. You can learn a heck of a lot about the device by looking at the progression of the designers' thought-processes as the device went to market, and was changed through to its current state (v1.4.1) Hope that helps...
  2. Nope. No news. Except for those few trusted dealers who were given a copy of the JTAG firmware, and are programming customers' units with that, none of the rest of us have gotten anything working. My excitement at the news of this potential breakthrough has faded...
  3. When you have ridden 50Km several limits are removed from maximum speed and maximum torque. That made a big difference for me...
  4. It was designed to keep lawyers and bureaucrats happy. Here is the chinese blog written by its design team. View it in Chrome, or run it through Google translate. It explains each of the steps of the designers. The executives, bureaucrats and lawyers then crippled it to provide the "safety margins" http://bbs.ninebot.cn/forum.php?mod=viewthread&tid=4100&extra=page%3D1%26filter%3Dtypeid%26typeid%3D43 1/23
  5. @ChriullFor me the speed increase is not important. Two other things make the MiniPRO critically unsafe 1. When you get to a point where the MiniPRO thinks you are pushing it too hard it slows down by pushing you backwards, which does result in me falling and crashing (turning off the track). It also beeps, but there is no way to tell it you are a responsible driver, and that beeping is all it needs to do (and 'please don't push me off'). This pushback occurs at varying speeds dependent on terrain, and on the streets around my home it occurs at 10-12Kph which is not much faster than a walking pace. It is very,very hard to keep your balance at these slow speeds when the pushback occurs. This is a safety problem, not a speed problem. Better to manually ride slow than get pushed off without warning, but the Ninebot firmware doesn't give you this choice. 2. As the battery empties the speed at which you can move is reduced by the controller firmware. The batteries can actually supply just as much current at low charge levels, yet the machine pushes me back at even lower speeds than the 10-12Kph mentioned above. I think this behavior allows Ninebot to use cheaper Lithium Ion cells than the LG cells they actually ended up using. My suspicion is that they were forced to drop the cheaper cells, for which this firmware was written, due to their propensity to catch fire. The Swallowbot software allows more of the LG battery to be used, if necessary, only slowing you down when the charge is almost gone (and charge has therefore become a safety issue). This forum is being used to share thoughts about these issues, and others, and is a HOT TOPIC because these are REAL PROBLEMS Does the Swallowbot software do what it is supposed to do? What about the Chinese firmware hack, does it work properly? These are the topics you will find in this forum, along with the "How do I get this to try on my MiniPRO" which is such a focus at this point in time.
  6. @Chriull Ah - I see the confusion now. There is no way this discussion has been an advertisement. It was started by a member alerting other members to the firmware 'Swallowbot.' There was much discussion before MRN76 joined in. In my opinion, MRN76 was very careful not to advertise his or Alexei's work. Recently MRN76 actually posted: " I do not know why this topic was created. I did not want to advertise it until the bluetooth application was made" Please allow us to continue formulate and test this major development. Push-back is so very unsafe when going up hills. When you are struggling up a slope, and pushback occurs at only 10Kph, it is very hard to avoid crashing. I myself could not walk on my left ankle for over a month after being thrown while going up a hill....
  7. Alex_from_NZ, I suspect it is all a big mistake - @Chriull not understanding the safety problems in the design of the Ninebot MiniPRO, and thinking that MRN76's motivation here was to sell something. I bet @Chriull doesn't even know MRN76 and Alexei have already produced a stream of totally free software to help those of us who are worried about the MiniPRO's safety. The discussion about those free programs was not curtailed, AFAIK. I think TPTB were attracted by the optics of Alexei wanting much-deserved recompense this time, which IMO is reasonable, considering the magnitude of what he has achieved. However, even a casual reader will note the discussion from our Taiwanese members about the Chinese attempts on TaoBao to work towards what Alexei and MTN76 have achieved. What is being done here is not so much related to 'firmware modification' as it is to 'solving a problem.' The discussions here have been technical and balanced. Hopefully the mistake will be corrected before it does too much more damage.
  8. *** YOU ARE SORRY???. Rubbish, you don't care about the hours I have spent participating in this thread, nor do you care about me losing contact with members who have only ever posted in this thread. You have made a decision that all this work will RETROSPECTIVELY disappear, without any warning to me, or the other participants. Please at least be honest with us...
  9. For the next 24hours the '2018 US Model' N3M260 MiniPRO (with the mini battery) is selling on Amazon for $335, including Prime shipping. https://www.amazon.com/Balancing-Transporter-10-5-Inch-Pneumatic-Customizable/dp/B0749956JC They obviously did not sell many at Black Friday's price of $479..
  10. An update, since I have been busy over the Thanksgiving holidays. I realized that one of the biggest problems I had with my CPU soldering was the surface coating Ninebot put over all components on the control board. Even though it had been dissolved by the methylene chloride, a semi-fluid residue (looking like water) was left around which my circuit board solvents were not removing. This stuff was interfering with the flux during soldering. All this only became visible when I used my binocular microscope, which I normally only use for really,really, small stuff. After two re-soldering of the Swallowbot CPU (and two more power MOSFETs, which blew each time I tried using the CPU) I decided it could have been damaged, and so I soldered a brand new STM32F103RCT6 CPU (STmicro, I usually buy them from from DigiKey to avoid the Chinese clones) onto the board. This time nothing misbehaved (by comparison with what I remember from previous experience with the MiniPROs, all the LEDs illuminated with an error code which beeped two long, nine short, error 29. I had this code once before when I had programmed the 1.1.7 firmware from a different MiniPRO into mine, and I knew it was a serial number mismatch (the Segway firmware is locked to a unique ID within each CPU chip). Darn - I had thought I had swapped in the new ID Anyway, MRN76 kindly sent me the specific patching instructions for the Binary files and I realized that I had thought the data would be little-Endian while it was actually literal. Oh well... After fixing Error 29 the MiniPRO rebooted to error 12, at which point I relaxed as I have fixed that one before (loose wires in the plug from the motor sensor). I will continue the debug after Thanksgiving, but am confident that I soldered the CPU in properly this time, using the Microscope on every lead, and am pretty confident everything will come back to life again from this point... And, on the plus side, those special Chinese Power-MOSFETs they use will be pretty neat for some of my other projects. I bought plenty of spares
  11. No. We were also taught how to design bridges, radars, etc Those were the days before microcomputers, when Engineers were just trained how to design stuff. Then came the microprocessor (late '70s) and everything changed... Getting back to pneumatic tyres, however, the job of the air is to act as a cushion, a balloon to absorb impact. The inflation of that balloon, and the rigidity of its 4-ply polymer walls (in the case of the INNOVA 90/65-6.5) is therefore important. A tyre is typically a key part of the resonant system involving machine/rider mass, and elasticity. Reducing inflation pressure, rather than building lighter tyres, does increase the resonance problem, it is much better to produce tyres specifically designed for the lighter loads it will be bearing. But in the case of miniPRO tyres we are repurposing tyres designed for pocket-bikes, lawnmowers etc. The stiff-wall-thin-web design approach taken by Ninebot was quite radical, since it departed from the 'balloon' concept in a quest (I assume) for perceived 'safety' and longer battery life.
  12. I was taught pneumatic tyre design when I studied Engineering at University in the '60s. Let me share some of what I learned.. When I look at the wall of my Knobbly INNOVA tyres on my MiniPRO I can see the load rating on each is 189Kilogram at 50psi, so when properly loaded, two tyres would be able to carry 189x2=378Kg. Now there is a possibility that on extreme cornering a lot of this weight might shift to one tyre or the other, but tyres are rated to allow for that. So let's assume two tyres might have to carry the 15Kg of the MiniPRO plus 100KG of a heavy rider, = 115Kg. You can see these tyres are over-kill for a MiniPRO. We can generally make the tyres operate well at a lesser weight by under-inflating them from the 50psi maximum pressure. In 'normal' use the pressure we would need is 50 x (115/378), or 15psi. Now we can understand why the Segway model X2 tyres are rated at 4psi, and the I2 at 15psi. Obviously those vehicles were designed by a mechanical engineer
  13. An impedance mismatch? Yes, indeed, but the chip (NRF51822) can handle an infinite SWR. Maximum output power is only 4milliwatts in BLE. A couple of milliamps change in chip current when transmitting. There is no way the chip will be damaged by my modification to its antenna. I am not saying your power interruption is not a better mod, as long as the control CPU Firmware can be trusted to operate with non-functional Bluetooth. I chose the antenna method as the control CPU will never know anything has happened with this mod
  14. I just found a video from Denis Hagov, showing off his Swallowbot. Videos like this keep me convinced that all the effort needed to get Swallowbot running will be worthwhile.. I need that improved battery management...
  15. Your English is excellent, MRN76, the mistake about Alexei's priorities was mine. Please don't be worried about this