esaj

Moderators
  • Content count

    3,675
  • Joined

  • Last visited

  • Days Won

    127

esaj last won the day on July 12

esaj had the most liked content!

Community Reputation

5,059 Excellent

About esaj

Profile Information

  • Gender
    Not Telling
  • Location
    Finland

Recent Profile Visitors

5,142 profile views
  1. Not an expert, but I think you should be able to use another mosfet, if you change them all and get something that has similar (or higher) Vds & Id, at least as low Rds(on) and same or lower gate charge (depending on the gate drive -circuitry, it could work with higher charge too if the gate drives can switch it on and off fast enough)? Looking at the STP100N8F6 specs: Vds: 80V Rds(on) max: 9 milliohms (0.009 ohms) Id: 100A Total gate charge (typical, max is not listed): 100nC A quick search on Digikey with as high or higher Vds, as low or lower Rds(on) etc. came up (just us an example) with TI's CSD19501KCS: https://www.digikey.com/product-detail/en/texas-instruments/CSD19501KCS/296-37286-5-ND/4701488 Half the gate charge (max, lower for typical), lower input capacitance, same Vds & Id, 6.6 milliohms Rds(on) max with 10V gate drive. This was just at a quick glance, with those search parameters (and TO-220 -casing), it gave me about 30+ options. But, like said, I'm not an expert, so there might be something I'm overlooking, and things I don't know (like, if the original gate driver is "matched" to 100nC gate charge, can the gate start ringing if driving a lower charge gate with high current?).
  2. With the speeds and pressures used in the wheels, it probably won't matter, at least for hydroplaning. For general grip & tire wear, I have no idea whether the tread pattern direction is meaningful... There's a myriad of reasons that can cause you to fall or lose traction, but I doubt hydroplaning is very high up in the list In about 3000km, I've never had the tire skid on pavement (wet or dry), but loose gravel and soft mud can cause "nice" skidding (usually sideways ).
  3. You can start worrying about hydroplaning when the wheels go 150-200km/h, or something along those lines... I read that for bicycles, the speed was something like 200+km/h before the tread pattern starts to matter and the tire can hydroplane. For cars and other vehicles with wide tires and large contact patch, it's a different matter. EDIT: Still had to check... on both my KS16B & KS16S, the rotation direction is correct with the buttons in front
  4. The BMS is there "just" for balancing the cells and for protections (like discharge short-circuit / overcurrent / overdischarge and charging overvoltage monitoring / reverse polarity protection). When the protections are not active during discharge, yes, it works just as a 16-cell battery with the BMS adding just a little bit of extra resistance (probably negligible in comparison to the total internal resistance of the cells themselves). Without the balancing mechanism, the cells can start to charge/discharge to different voltages over time, and an imbalance will occur. This can lead to some cells reaching too high voltage during charging or getting overdischarged during riding. Overcharged cells can catch fire or explode, overdischarged cells will age, lose capacity and drop the voltage faster and can even reverse their polarity. A large series battery pack with no BMS is a fire hazard, especially if there are no charging side protections. The typical reason for the hoverboard fires seems to have been caused by the cells overcharging (catching fire during charging), maybe they had bad BMSs?
  5. I used this sizing chart when buying mine a couple years back: EDIT: Note that "width" is measured as the circumference of your hand. I ended up in the lower right "M"-section, and that's what I ordered. Never tried other sizes, but the fit was right.
  6. I just moved the original pieces to the sides of the shell instead of the pedals, so they aren't in the way of my foot.
  7. "Normal" household tweezers can be horrible to work with, if that's what you have and need to occasionally work with SMDs, get a basic SMD-tweezer set from eBay or similar, and/or a suction tool (see below) if you work with larger ICs. They're cheap and most likely the tweezers will be better than what you currently have. The chips usually have a small dot next to pin 1, or if not, the datasheets should show some way of identification, for example, some small ICs with pins on two sides have (also or only) a notch at the other end or a slant on one side: Hate the slanted ones, on small packages the slant can be hard to see, plus I'm not sure if it's always on the side with the pin 1 or could be the opposite, need to check the datasheets. Larger IC-packages can be hard to handle with tweezers, they're mostly good for the smaller "basic" components like resistors and capacitors in standard smaller SMD-packages (1206, 0805, 0603, SMA/SMB/SMC etc) and smaller ICs (like *SOP/SOIC and whatever that MPU-6050 one is above), a suction-cup style tool might be more useful for the larger packages (BGA, higher pin-count *QFPs etc) where you have enough surface area on top to grab onto: I have one of these "manual" ones, plus one that attaches to the fume removal -port of the station for continuous suction. So far I've liked it. The soldering iron's 75W, so it heats up really fast, and while I was annoyed a bit with the fume extractor tube getting in the way of wiping the tip on sponge, I've kept it there, since the extraction works pretty well. The iron uses a "normal" rotatable potentiometer knob on the station front panel for setting the heat (and shows the set heat also on a 7-segment, as well as the actual tip temperature when not adjusting), the pump speed for the hot air also has a rotatable pot, but the hot-air temperature uses separate up/down/reset -buttons, and is much slower to set to wanted heat. The hot-air always starts at 90 degrees Celsius after the machine is turned on and you need to keep the "up" -button pressed for a good while before it rolls up into the 300's which I usually use. Not really a big issue, but I hope they'd have used similar pot for that too. I've also used the tweezers that can be attached instead of the iron for replacing basic 2-pin components like resistors when trying stuff out (or have to remove a shorted component that's already soldered on both ends): So much easier just to grab the component from the ends with the tweezers and lift it out. Soldering new ones back in with the tweezers themselves isn't that easy, have to be fast as they're heating the component from the moment you pick it up and would destroy it before long, so I prefer to use the normal iron for that, but for removal the tweezers are really handy. Only minor annoyance with them is having to screw out the soldering iron and screw in the tweezers, then wait for the tweezers to heat up (they're much slower than the iron). Having two GX16-5 -ports and a switch to select between the tweezers and the normal iron would be handier. I still need to practice more with the hot-air, the largest IC I've removed so far was something like 208-pin QFP with small pin-pitch on the DVD-drive I dismantled for the sled, I just used the board for practice. I don't think the IC survived, it took several minutes to heat up the pins enough for the chip to come off, and at that point the surface already was "warped" a bit, meaning it must have gotten really hot. Not that I'd have had any use for the chip anyway, as it was some special purpose optical drive -control chip. Gotta dig up more broken stuff with SMD-parts for practice before I face a situation where I have to remove a large chip without destroying it, and maybe also get the special purpose hot-air nozzles for QFPs (quad flat package). Only problem is, you need a separate nozzle for each QFP-size... I tried a BGA (ball-grid array) -nozzle but it heats up the center too much, QFP-nozzles direct the airflow to the sides only: Well, maybe not lazy, but easily distracted by other projects, and then ending up with lots of unfinished stuff? Blu-tack might work, I have some in the drawers. Usually the board moving is not an issue, as they're at least slightly larger than the blinker-boards, the white surface seen in the microscope-video is my silicone soldering mat, which typically has enough friction to prevent the boards from moving around. For SMD-work, I need to rotate the board around to get better "angle of attack" at the sides of the components all the time, so "helping hands" or anything that sticks "too much" is not good either. Maybe I should do a rotatable & quick lockable stand next? Glad you liked it
  8. Thanks, although I've had a lot of practice since I started using SMDs late last year and I (still) don't work with the really small sizes like 0402's (but working my way there, slowly ). Good tweezers help a lot with handling the small parts, I'd say they're about the most important tool when working with SMDs by hand, you can easily get by with a cheapo soldering iron with a basic 0.8mm chisel-tip, but not with crappy tweezers. I did OK(ish) on an Aliexpress SMD-tweezer set, which wasn't that bad, but bought better (and expensive, for tweezers, around 15€ on sale) early this year, and have been using those almost exclusively: http://ideal-tek.com/scheda.php?m=0&f=8&l=3&c=Smd Tweezers&idp=856 There's a huge selection of different tweezers out there, TME was having -25% off from the normal prices for tweezers, and while I did look through the selection for a long time (I think they already carried something like 200 different models, probably something like Mouser or Digikey has much larger selection ), not having the possibility to try any almost made give up. I picked those (Ideal-Tek SM108.SA, also known as Lindstrom SM108.SA, as IdealTek is OEM for Lindstrom) simply based on a couple of threads in some electronics forums, and they seemed to be one of the most popular ones and good for general use, people have used those down to 0402 -sizes (so less than a quarter of those 0805-resistors I use in the video, as length is halved and width is slightly less than half), and somebody posted a picture of the heads after 10 years of use: https://www.eevblog.com/forum/reviews/best-tweezers-etc/msg1194495/#msg1194495 That was the second blinker-board I made (I didn't shoot a video of the first one), the board & the video was done in one go, but I did edit it down to make it shorter, cut the first few minutes, as there are lots of pauses and not much is happening, as well as cutting out the pauses between getting the next component from a sample book and such (5-20 seconds clips here and there). As the video was still 15 minutes, I then just sped it up in Youtube. A board like that can be put together in 15-20 minutes (the one in the video took 25 minutes total with all the pauses), maybe even faster if you have all the components lined up (and don't mix them ) so you can just pick and go all the time (and with a real PCB fabrication-house made board, there's be no need to check for shorts to surroundings), but that's barring any bigger mistakes, it can easily take double that if things go wrong (like a short-circuit under a component after all legs are soldered). One of the board also had bad cuts (there was some hard to see copper stuck at the bottom of the cut), so it took a lot longer as I was wondering where the short-circuit was for a good while. I made 9 of those boards in a single waste bakelite-board with fast feed & single-pass cut, the kind of settings that destroy the V-bit in seconds with FR4, so the cut quality is a bit iffy But these were mostly for practice anyway Btw, it's been 21.5 hours for the slower blinker and about 16 hours for the dual-board setup, and the blinkers are still happily going, the average current must be a few tens of microamps...
  9. Finally learned to solder watching the microscope view from the screen instead of looking at the board and using 0805's, and it does help a lot. I've done a bunch of other stuff (a frequency meter & some PWM mosfet-drivers, motorized stand for the microscope from a broken DVD-drive, new power distribution board for the next rack-front panel and some small stuff) over the past week, but today I made a bunch of hastily designed & cut led-blinker boards, mostly for practice: The board's 18mm across (0.7 inches), the cap and the led on the board are 1206-size, the resistors are 0805's (so the next smaller size from the 1206's to which I'm used to), transistors are SOT-23, so although small, nothing really small. Although the other stuff (the microscope stand & the frequency meter) might be more interesting than a blinking led, I thought of writing about this (at least for now). This is a self-oscillating "micro-power" blinker (average current is in the microamperes-range, µA, millionth of an ampere), it's run by a 1.5F / 5.5V supercapacitor, should blink it a good while (15-20 hours, even more?) on one charge, recharges in about 20 seconds It blinks around twice per second, but taking a picture just when it blinks is of course next to impossible. The first one I made has been going for over 12 hours now, another with usb-charging & two boards in parallel and faster blink rate (so higher current usage) on a single cap has been running for over 7 hours... Not sure what real use these are though, maybe attach to clothes during winter time when it's dark? On a lithium (primary, non-rechargeable) coin-cell, which is about 150mAh, it could theoretically run for half a year, and some people have managed to make ones that use around 6µA on average, reaching over two and a half years of run-time on a coin-cell. Or if enough light is available often enough, a supercap (or rechargeable lithium cell or some other type of battery) can charge from a small solar-panel and run until it breaks down (10-20 years? I don't know how long supercaps last in use...). Shot a video of making one of the boards, but of course it didn't go "perfectly" (nothing ever does when shooting a video ), although not really bad either. Not sure if anyone wants to watch it though, there's no audio and it's long and pretty boring, so I sped it up to 4x to get it down to less than 4 minutes (original was about 15 minutes even with parts cut out): It's a bit tricky to solder a board this small, as it isn't attached to anything and is so light that it easily moves around by accident. Also need to check for short circuits all the time with milled boards, as it's easy to slip a bit of tin into the cuts as there are no solder-masks. The blink at the end doesn't look that bright, but it's easier to "fool" naked eye than camera, especially in darker conditions.
  10. But you've got Jason!
  11. Judging by size/packaging only, the gyro/accelerometer-chip is likely U3, seen on left middle next to the MCU. No need to support it separately, it's sitting there pretty tightly
  12. But most wheels use GX-16's anyway, maybe with a different number of pins, but they seem to always just use 2 pins, whether it's 3/4/5-pin GX-16... I think 1RadWerkstatt used either different connectors or two or more GX-16's in parallel for their high-power chargers, at least I recall that at some point they had 8A charger for the old MSuper V2, but it required two charge ports?
  13. Not to mention the port... even if you replace the wires with thicker gauge, the GX-16's are rated for 5A max (7A according to some sources, ie. Aliexpress sellers, but that sounds like pushing it). Above that, the charge port may overheat, melt the plastics and short.
  14. LTSpice: http://www.linear.com/designtools/software/#LTspice
  15. They seem pretty low cost... Lizardmech pointed out that they've even skipped proper gate-driver chips and built them from discrete components instead. Saves maybe a buck or two per board? Apparently no current sensors either, only shunt-resistors, the chips next to them might be something like op-amps for measuring the voltage drop over the resistors? Bluetooth-chip is on a breakout (the kind you get for $2 from Aliexpress), but that seems to be the case with pretty much all wheels... the gyro/accelerometer is on a breakout too, I bought some MPU-6050 -breakouts for maybe 2-3€/piece, but those are not the same as the NB1-board. But, in general, they've seemed to hold pretty good, many people have got thousands of kilometers on their NB1's...