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esaj last won the day on June 1

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About esaj

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  1. Power mosfet should be fine, the only thing that occurred to me is that you need more than 5V to make IRF540 or similar "fully conductive". It will start to conduct after the gate voltage (Vgs) is above something like 4-5V, but it's still in the linear region (partially conducting), and dropping voltage (ie. the "resistance" of the mosfet is higher). The currents are small here (<1A, probably even <0.5A), so it's probably not that big of an issue, but you might want to take a look at some logic-level mosfets (these have much lower Vgs requirement for full conduction, specifically meant to be used with "logic-level" voltages, like 3.3V or 5V), especially if you make any changes requiring higher current draw. Placing a small PTC-fuse or normal fuse in series before the circuit might also be a smart move, in case something goes wrong, the fuse would trigger / burn, saving the wheel USB-port (and possibly the 5V regulation before it, which might be shared as the hall-sensor power). Arduino Nano draws something like <20mA while in operation (much less in sleep-states), but the LEDs might use much more, so you need to calculate or measure the entire current draw to size the fuse accordingly.
  2. ASD The motor is noisy (electrically), but if the noise isn't too wide amplitude, it shouldn't trigger the inputs. Running a separate ground from the sensor might help. If you're using the wheel USB to power your circuit, they already share a common ground through that (I doubt it would work very well even laying on the side if there wasn't some common ground). Nice work! I guess you mean based on this: I never really finished it though
  3. esaj

    New to forum

    I think the speed limit hack is only for Ninebot Mini Pro (the two-wheeled thingamabob), although not sure. The max speed for Ninebot Ones is around 20km/h (about 12-13mph). The Ninebots use non-"standard" voltage (well, there really isn't any standard as such, but most wheels use 16S / 67.2V max / 59.2V nominal or 20S / 84V max / 74V nominal batteries), you need the specific charger for Ninebot's 15S (63V max / 55.5V nominal) batteries. The plug is different from most unicycles to prevent anyone from accidentally plugging in a charger with wrong voltage. Depending how it was stored, the batteries may have degraded and may not hold full charge anymore. Lithium-ion batteries should not be stored fully charged or empty. The "sweet spot" voltage for storing is somewhere between 30-50%. If the battery is stored full, it will permanently lose capacity over time. The batteries cannot be "rejuvenated" through cycling, like some other chemistries (NiMH/NiCd?). If the battery is stored empty and drops to low enough voltage, it will start forming metallic deposits (dendrites) inside the cells and ruin the battery completely (it will short-circuit over time and drop the voltage to 0V). Trying to charge a battery with dendrites may cause a fire or explosion, but the BMS (Battery Management System) -board should prevent charging if the voltage has dropped to too low (whether it actually does on Ninebot, I don't know). If there is a "hack" for Ninebot Ones, I'm not aware of it, but maybe someone else knows. Get the original charger, maybe @Jason McNeil carries Ninebot chargers, or maybe eBay / Aliexpress have chargers with correct plug, polarity and voltage, although you can never be 100% sure whether they're up to par with the originals. You can't use a car charger, it has too low voltage, lithium-ion charging requires a basic CC/CV (Constant current / constant voltage -modes) charger with correct voltage.
  4. esaj

    Inmotion V10 fire.

    So it's not just 3 wheels, but about 20 in France alone + however many others in other countries? Or did you mean 20 wheels needing the seal upgrades? I was going to play down that one earlier reported incidence as an isolated case, but if you mean 20 wheels have caught fire, then it's a very serious issue.
  5. esaj

    Inmotion V10 fire.

    Wasn't there at least one other V10 that had burned in the V10 thread? Caught fire during charging?
  6. Firstly, check the voltage the wheel uses on the sensors (it's probably 5V, but better make sure). To my knowledge, the hall-sensors used in the wheel motors are the kind which output their own voltage from the output (if VCC = 5V, high = 5V, low = 0V, +-something, might not go all the way to rails), but there are other kinds that for example have an open drain/collector -output (it connects the output to ground internally, or floats it in the other state). For measuring the sensors, see what @hobby16 said: AFAIK, if the voltage is 5V, you can bring the output of the hall sensor (one is enough, although you could use 2 or all 3) in parallel to a digital input of the Arduino / ATMega328P. If it's 3.3V, check the datasheet what is the minimum voltage for the digital input pins at 5V VCC to read the state as high. If it's higher (some hall-sensors work with voltages from around 3 up to 30V), you need to level-shift it for the Arduino, maybe using something like a (logic-level) N-channel mosfet or something. Only the ground needs to be common. Simple schematic: I have no idea if A1101ELHL is even the same kind of hall sensor as your wheel motor uses, but the general idea is just to bring the output of the hall-sensor directly to a digital-input pin (don't use the internal pull-up resistor). I chose D2 as an example, because it has separate interrupt, and it should be quite straightforward to write a simple interrupt handler counting the pulses and changing them to wheel revolutions and to speed.
  7. esaj

    New Inmotion V10 (V8 Fast)

    Check that the screws holding the mainboard are tight. If they're loose, the mainboard can shake around when the wheel takes a hit, and since the IMU is connected to the mainboard, it will shake with it, causing the wheel trying to reach balance by accelerating and decelerating back and forth as the mainboard is moving.
  8. esaj

    New Inmotion V10 (V8 Fast)

    I'm not sure what you actually mean by gyro here, some kind of a flywheel? To my knowledge, the "gyros" in the wheels are 6-axis electronic IMUs (inertial measurement units , https://en.wikipedia.org/wiki/Inertial_measurement_unit ), that contain both 3-axis gyroscope (detecting rotational rate) and 3-axis accelerometers (detecting linear acceleration), similar to what smartphones have. I think at least some older wheels may have used for example MPU6050's ( https://www.invensense.com/products/motion-tracking/6-axis/mpu-6050/ ), probably newer wheels use a similar 6-axis IMU, but different manufacturers / models. Both are used in detecting the "lean" of the wheel, as the combined information ("sensor fusion") is more accurate and can be used to overcome the "drift" in both. The information is then used by the CPU of the microcontroller of the wheel with probably in some form of a PD- or PID-loop to control the motor acceleration/deceleration.
  9. This tutorial now should contain enough information to get normal 1-sided boards done without much hassle. Also removed some notes and some other off-topic stuff (mostly by me) to clean this up a bit, and some off-topic from other people, sorry about that I'll try to get around to write about the more special cases (engraving, 2-sided boards, multiple boards in one go) at some point.
  10. Could be a problem with one or both battery packs. I haven't tried it, but if the wheel works with one battery only, you could try which battery (or both) causes the problem. Of course if it's still under warranty and you don't want to dig in yourself, best to contact your reseller and see what they can do. I knew the KS16S has a three-pin connector on the batteries, and suspected that the third line is used for some sort of data communication, this confirms it (and also that it's a serial communication, not just some form of "all ok/problem" high/low -state).
  11. esaj

    MSuper X vs. KS18L: Has Gotway become 'safe enough'?

    Yeah, like I said, " slamming to a wall or other rigid object at 30mph (48km/h) or pavement head first (without a helmet) could be pretty deadly ". Sure you would probably roll or slide or whatever, and with protective gear likely "just" get some minor or less major injuries, but in the worst case, like slamming to the side of a heavy van that pulled in front of you "out of nowhere", it's pretty close to a vertical fall. Slamming your head to the pavement without a helmet is bad, even falling from standstill, but the forces become greater with speed. "It's not the speed that kills you, but the sudden stop" (or more like, the very fast rate of deceleration). Most newer wheels are safer, yeah, sort of, at least in the sense that it seems they no longer cut out at high speeds (or appropriately warn of getting near the edge) or with low battery, which is a good thing, but no matter how reliable the wheel is, it's not going to help on a rider error or someone else making a mistake around you (car pulling in front or such). I still ride while fully aware that it might kill me if I fall or crash badly enough, despite the protective gear, even on a wheel that's capable of "only" 22mph (well, more if you ride the tilt-back). Then again, I might also die reaching for stuff on the high shelves while standing on a swiveling office chair, choke on a piece of chicken or a weird lawnmover accident
  12. esaj

    MSuper X vs. KS18L: Has Gotway become 'safe enough'?

    Thank you, Captain Obvious
  13. esaj

    My Z10 Triumphs, Tribulations, and Failures

    Firewheel or the generic didn't have warnings (or then I never noticed them) for overcharge, but the KS's would beep if going down faster and then braking stronger with full battery. A quick glance on height maps says it rises about 10 meters vertically in about 110 meters of horizontal travel, so not particularly steep (about 9%, if I calculated correctly, the steepest bikelane around here is a long uphill one at the edge of the town with parts going up to 18%). The asphalt is cracked and there are lots of bumps in the road caused by ground frost, so I don't usually ride it down very fast anyway.
  14. The 75A rating for TO-220 is some sort of (de facto?) industry standard, I've seen it quoted many times as limit for the TO-220's legs. But that's sustained (continuous) current, to actually "blow" (melt very fast) the leg, the momentary current is much, much higher. EUC Extreme blew off the legs of a mosfet in his MSuper V2 boards with RC-LiPo batteries, capable of very high currents. A short circuit with caps dumping their charge through can cause very high (momentary) current if the voltage is high and the resistance is small enough (kiloamperes, that is, 1000's of A). Yeah, but the transistors can't even handle 170A continuous current in reality. The number in the datasheet is theoretical maximum value, assuming infinite heatsinking capability. If you work the numbers "backwards" from the actual thermal resistances of the entire system & ambient temperature, you get nowhere near the rated maximum current of the datasheet before the junction temperature has raised to critical levels and the component dies. But, for switching-mode systems, like the wheels are for example, the momentary currents can get very high, it's the average power dissipation of the part that counts (assuming the momentary currents when switched on aren't anything completely "insane"). The absolute maximum rating of the HY3712 for pulsed current is given as 585A when the case is at 25C (again a theoretical number).
  15. esaj

    MSuper X vs. KS18L: Has Gotway become 'safe enough'?

    Depends, protection, how you land, what surface etc. I'd think that slamming to a wall or other rigid object at 30mph (48km/h) or pavement head first (without a helmet) could be pretty deadly: A fall off a 3.3 feet desk results in a speed at impact of 10 m.p.h. A 10 m.p.h. change in speed (Delta-V) in a motor vehicle collision is equivalent to falling off a desk. Similarly, a 15 m.p.h. change in speed is equivalent to falling 7.5 feet - off a step ladder. A 20 m.p.h. change in speed is equivalent to falling 13.4 feet - off the roof of a one story building. A 25 m.p.h. change in speed is equivalent to falling 20.5 feet - off a two-story building. A 30 m.p.h. change in speed is equivalent to falling 30 feet - off a three-story building. Newer wheels may be more reliable, but that doesn't make you invulnerable.