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esaj

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Everything posted by esaj

  1. An EE once told me that usually handling an assembled board shouldn't be an issue, since there are resistances and capacitances etc. on the boards that can sink the energy from the usual static discharges. Mostly it comes down to handling individual components during assembly, there the danger is much higher, and the worse kind are the "walking dead/walking wounded"-components, ie. such that have been damaged by ESD, but that don't "show" it right away, instead they'll fail hours or days of use later, but it seems quite rare. Someone here in the forums (pico?) mentioned that they used to do a "burn-in" running the devices 48 hours at full load / maximum stress to see that things work like they should, but I guess it's rare with EUCs. KS does do some sort of a running test (shown in their videos where the wheels are being run on treadmills of sorts), but no idea how long or if each and every wheel goes through this. Some components are more sensitive to ESD-spikes than others (mosfet gates come to mind, it doesn't take that much to break the insulation between the gate and the channel).
  2. The world has changed due to a lot of things being digital nowadays... In software-world, all kinds of copy protections have been used for a good while, from the old "input the word from page X paragraph Y of the game manual" to more complex schemes, like dongles that need to be connected to the computer to use the software and to on-line check of license validity and tying it to keys calculated from hardware things like network MAC-addresses these days and whatnot. Probably all of these will get broken in a matter of days or weeks after software release. I get that people/companies making the product or producing the "content", be it software, literature, movies or whatever should get compensated for their work, but it seems just weird that once you pay for a book or movie, you'd have to jump through hoops to make sure you can read/watch it again X years or decades from now should you want to. It's like selling the same content that you've already paid for again. I don't get reimbursed when someone uses a software I made years ago (granted that I was just an employee back then and the rights belong to the company I worked for at the time, but you get the idea) Nowadays, a lot of things seem to be selled based on some sort of "subscription". It's not a completely bad thing, I love Netflix for example, back when I was a poor student a long time ago, I dreamed someone would make a monthly-paid service where I could watch movies and series, and that's exactly what it does, and does well. But should they cancel my subscription for some reason, or once a series or movie gets removed from the catalogue, I can't access it. And I don't "own" any of the content there, but have a "license" to watch it. I guess it works better for movies and series than books. Slightly off tangent, the IOT-craze on the other hand seems just bizarre to me, I can see the use in industrial-settings and such (remote monitoring/control, fleet tracking, handling huge amounts of remote sensor data and such), but at least most of the stuff for normal consumers is not something they really need, if not downright dangerous, like remotely activated kettles or other high power devices that could cause a fire. And do you really need to do that remotely? A lot of these seems to be tied to some sort of subscription, rather than that you'd buy the device and "own" and use it for as long as you like (or as long as it works? ). The stupidest idea someone was trying to sell me some number of years back on the IOT-things was "smart thermostats" for the house. The idea was that they sell you the thermostats for relatively low price/margin, but you have no control over them manually. Instead, you need to login to their web-service to adjust the thermostats, and you pay monthly for the service. I then asked the guy what happens if there's no network? "The thermostats will automatically adjust to 21C". What if your company goes bankrupt? "I guess the thermostats will stay at 21C forever then". Considering that I really rarely have any need to adjust them, and can do so just by going to thermostat and doing the adjustment manually, I can't get who would really need these in a normal household... You have to be pretty lazy to need something like that, or you're obsessed with controlling the temperature room-by-room Maybe if you have something like a cottage out in the woods that you visit seldomly, and want to set the heating up while heading there, so it's nice and warm by the time you get there, but otherwise I don't get it. On a quick Google search, I couldn't find the company anymore. But there are other companies with "smart thermostats", and they do have manual control...
  3. Do you leave it charging (sometimes) until the current has dropped to zero? Did you measure the output voltage with a multimeter or just by the display on the charger? The displays look like the cheapo chinese voltage/current meters that aren't exactly precise, or at least drift over time. I have Firewheel charger that outputs around 67.6V, I initially assumed it was to overcome a reverse protection diode in the BMS, but later on learned that probably the reverse protection is done with mosfets ("ideal diode"), and it's just off... nevertheless, I've used it at times to fully charge the battery (current dropping to near zero) to make sure the cells get balanced. Never had issues with overcharging even with slightly too high voltage, probably the balancing circuits in the BMSs can handle the slight overvoltage. If you leave the "dumb charger" on until the current drops to zero, do you reach full 67.2V (or thereabouts)? If looking just at the wheel app (requiring the wheel to be turned on), it might show 67.1V just because of the current required to run the MCU & other things on the mainboard, and keep the wheel balanced on its own. Checking that the voltage is correct with a multimeter and then allowing the charge to run until (near) zero current should allow the batteries to charge all the way to full voltage. I start my rides with less than 100m of going straight and then a more steep downhill for a couple of hundred of meters, followed by more gradual decline for maybe about half a kilometer. Never had the wheels warn me of overcharge there, although it might push the voltage somewhat above 67.2V. I've done this for years, never had to do any really hard braking though. Charging the batteries all the way every now and then (say, every 10-20 charges for example?) is a good practice to make sure that the cells get balanced. For longevity, charging to less than full (most of the time) is good, also if you need to store the wheels for a longer time (I do, for about 6-7 months every year over the winter), discharge them down to something like 30-40%. If stored for longer while at full charge, the batteries lose maximum capacity much faster. If stored "empty" for a longer while and the voltage drops too much, internal short circuits will ruin the cells. Last winter, the wheels (at that time, I still had both the KS16S & KS16B) were both run down to 3 leds before putting them to "sleep", I didn't even bother checking the wheels or voltages over the winter. The voltage drop over about 7 months wasn't enough to drop a single led from the side panels (both KS16's set to show the battery state with the side leds when not moving) Ninebot Z-series is different, the vampire drain requires the wheels to be charged monthly or so.
  4. I replaced the caps for the charger today, and all I can say is that this charger ("Gojusin", apparently the manufacturer) isn't "exactly high quality". Removing the old solder from the (remaining) capacitor legs, I actually lifted of all of the capacitor pads and some of the traces! All of them! I haven't had a pad lift off since I was using some very cheap dot-matrix boards I bought from Aliexpress (and maybe too much heat) years ago. I had to bend the capacitor legs to nearest component legs on the same trace to make sure that a good enough contact is made... Many of the traces are "topped off" with solder, probably because the copper (assuming it even is copper) layer seems to be really, really thin, maybe to prevent the traces from burning out just by normal operating current. I don't know how it's attached to the substrate, by super glue? Now I kind of wish I hadn't used so "good" caps on this (120uF / 450V long life United Chemi-Con, about 3€ per piece), they'll probably outlast the charger
  5. Sounds like the fast charger output voltage is too low. I adjusted a friends' fast charger (bought from Wheelgo, Jason McNeil's UK-company before he moved to US) a couple of years back because the output voltage had dropped to too low, it was around 66V or even a little bit below, don't remember exactly anymore. It's normal for the battery voltage to drop a bit after removing the charger, to get "full" 67.2V after removing the charger, you have to wait until the charging current drops to near zero (which can take hours after the charger light already turns green) and all the cells have charged to full. Even the relatively small current required to run the electronics and keep the wheel upright at standstill (when it's own) can drop the voltage somewhat. With KS's and other wheels having reverse protection for the batteries, you can't measure the battery voltage directly from the charge port (and Charge Doctor won't turn on when plugged to the wheel without the charger plugged to power outlet), what you see during the charging in CD or similar, or in the charger itself, if it has voltage display, is the charger output voltage, which is higher than the actual battery voltage as long as current is flowing (once they reach the same voltage, the current has dropped to 0).
  6. You'd think so, but... Year or two ago (I've actually forgotten whether it was the summer of 2018 or 2017) I was riding around with a childhood friend visiting from another town, and we went to her big sister's house for a barbeque. Turns out, the big sis's husband is actually a local police officer. Over the course of the evening I talked with him about the legal situation about the wheels (they're legal up to 25km/h / 1kW, but KS16S already breaks both restrictions), and in summary, what he said was that A "normal" police officer won't know about those details, if they even know whether they're legal or not They're not usually interested in the wheels (at least in professional sense), as long as you behave and don't do anything crazy / endanger the public, they've got better things to do Even if they know the limitations otherwise, they won't know which model goes how fast or has how much nominal power They won't be able to test ride the wheel to see how fast it can go, and they can't force you to do that Finally, they're reluctant to give out tickets without a very good reason, because if they can't cite the exact laws and how they were broken, and there are some technicalities, the person receiving the ticket can "challenge" (well, that's not the right word exactly, but couldn't think of a better one right now) the ticket in court, which means they have to show up in court to give a testimony So here, your "basic" normal police officer is unlikely to stop you or give you a ticket, unless you're riding recklessly or certainly going much faster than 25km/h (think of something like riding 40+km/h or causing possible danger in sidewalks or crowds or something) and they can prove that.
  7. Yeah, that seems to be the nature of "digital" things nowadays, when you buy something, you don't own it, what you own (or have) is a license granting you the rights to use said product (with certain restrictions). I don't have a Kindle or such, but I wouldn't be too surprised if at least some of those services won't let you read the books you "bought" unless they can (at least every few days or something) check that your license is still "valid". Same goes for a lot of software.
  8. The low-side mosfet stopping the charging seems to be an IRF540, which has an absolute maximum Vds of 100V, so at least that would need to be changed to a higher voltage variety. Similar looking current/voltage-meters as what is used in Charge Doctor come in 100V and 200V -varieties, I don't know which hobby16 used (if it even is the same), but it's possible the meter cannot handle 100V and change, if it's the absolute maximum rating, but I don't know. Usually the absolute maximums are something to stay away from, ie. I wouldn't use a 100V max Vds mosfet for 100V input voltage, but maybe up to 90-95V max to leave some "headroom". Running something right at the limit at least drops the lifetime of the component, if not cause an outright failure. Still, it's also possible that the 100V & 200V -models are the same device, but just use a different voltage divider and software-values for measuring the voltage, and the circuitry otherwise works just fine with higher voltages (might need a protection diode in the measurement divider to prevent overvoltage at the MCU ADC-input). It could work, but the risk is that you'll burn your CD and/or damage your charger if it gets shorted over the failing CD. I don't want to test on mine I started polling for interest in a CD-like device some time ago, currently looking into going to open-source hardware/software-route, and maybe selling kits/pre-built devices at some point, but unfortunately the price (even just for the components + board + encasing, if building by yourself) is going to be much higher than the original CD. The current idea is to support voltages up to (around) 105V, so it can work with the 24S-wheels, OLED-display, BT-communication so a mobile app could be used and separate adapter-cables, so the same device can be used with wheels having different connectors.
  9. Yeah, I figured early that fixed connectors would become an issue, seeing that many people have more than one wheel, and quite often they may have completely different connectors, even if the voltages are the same. XT60 was just used as an example to explain the idea, I don't like it because it's "too tight", yanking the connectors off from each other can get difficult, and if the other end is board mounted, in the worst case you end up ripping the connector off the board before they loosen Molex might have some good candidates, for example Mini-Fit series has connectors where the connectors are locking (won't come off by accident, easier to detach than XT60) and the pins are rated up to 13A, and if need be, multiple pins could be used for both positive and negative (ground). I don't know what's going on with hobby16, I haven't tried to contact him. Maybe he got tired of making Charge Doctors. I'll try to keep the component costs down, but unfortunately, the "more special" components (meaning mostly the >100V switcher controller) seem to be quite pricey in low quantities, also the nRF54-SoC is about three times the price a non-BT device would need (+ it needs an antenna, but on a quick glance they're relatively cheap). Also, if the device is to end up in the hands of others, I'd rather spend more money on quality components and proper protections than "cut corners" just to keep the price down. Still can't say how much it will cost in total, as there's lots of things that are still in the air regarding the overall design, and I don't know what Seba's going to cook up, he might come up with a superior design. I was calculating the characteristics and external component values for the LT3638 last night, and it occurred to me, that while having the "support" for up to 24S (around 101V) -wheels is a good thing, not that many people have those really, most are 84V or below. Spending a bit more board space, it would be possible to add another (cheaper, but still good) lower voltage SMPS controller to the board, so that a <100V model could be made with the same board and save a bit in the component costs. Of course only one or the other controller (<100V or the LT3638) would be installed on the board, but people who don't want to pay extra for the wider input voltage range could build it/get it slightly cheaper.
  10. esaj

    18L Shakes!!!

    There are so-called "sensorless" motor driving algorithms that rely on the voltage and phase current measurements to timing the motor drive, but I don't know much about the details of motor control algorithms or if such is used in any wheel: All I remember is reading somewhere is that it's pretty hard to get right because of the precise timing requirements on the voltage measurement, and as usual with complex motor algorithms, the math gets somewhat hairy fast... Might be able to test by doing what you suggest, using some sort of a jig to hold the tire off the ground with the mainboard visible, speed it up to high speed by gently tilting and then yanking off the hall-sensor -connector, but I doubt anyone really wants to try that For science?
  11. Agree, probably the best bet is checking that the battery charges to full voltage (as said above), and if it doesn't, figuring out whether it's a faulty battery or a charger with too low voltage. Unfortunately at least with most wheels checking the battery pack health further isn't easy for a layman (even trying to decipher whether the voltage values are normal or not may not be easy), and not many people will want to unwrap the pack and start measuring individual cell voltages. Even less exchanging faulty cells. There should at least be some type of internal monitoring that can warn the user (through app or blinking lights or warning sound or whatever) if the battery voltage/behavior seems abnormal (ie. very little or no current running through the motor but the voltage drops faster than expected, tracking charge and discharge to detect energy "disappearing" from the pack or something...). Hopefully this will change in the future.
  12. I don't know about InMotion specifically, but most stock chargers are 2A or thereabouts. The maximum charge and discharge currents are usually rated with so-called "C-rates" ( https://batteryuniversity.com/learn/article/what_is_the_c_rate ), for most lithium-chemistries, the recommended charging rate is 0.5 (2 hour charge) or 1C (1 hour charge). Faster charging stresses the cells and drops their lifespan. With multiple packs in parallel, more current could be used than 2A safely, for example, the 16S4P / 840Wh uses 3.5Ah cells, 4 in parallel, meaning 14 amphours. Theoretically, the paralleled packs could be charged with even up to 3.5A per pack (14A total), but the charge port, wiring and possibly components in BMS might overheat / melt at that high current, so not really recommended. For wheels with big batteries, 5A should usually still be safe. The wheels with dual-ports can maybe be charged with even higher currents safely (10A?), but better check the wire gauges and that the BMS can handle that on the charging side, to prevent damage. Using low-side cut-off with low Rds(on) -mosfets, this could be handled, but it again pushes the prices of the components up, but not horribly. On a quick glance, for example 120V N-channels with Rds(on) around 10milliohm can be had for about 1.50€/piece, pushing 10A through one of those would "only" dissipate about 1W, which isn't difficult to deal with (for example, PowerPAK SO-8 has 20C/W maximum junction-to-ambient, 1.2C/W maximum junction-to-case, stick it to double-sided plane and stitch with thermal vias, it shouldn't warm up hardly at all, shouldn't even need much board space?). The downside is that the ADC-resolution is limited, so using higher current range (I was originally thinking up to 5A), some resolution is lost. But for 12-bit ADC (assuming the entire voltage range could be used, but depending on commonly available sense-resistor values and fixed gain current sense amplifier, it might not be), this would mean 10A / 4096 = 0,00244... A or about 2.5mA per bit, so not that bad Actual accuracy will likely not be that high, although oversampling might be able to keep the resolution high. Also, the limiting factor may be the wheel wiring, charge port or BMS, as mentioned above. If the two charger were separately connected to the device, they could be measured separately (ie. "only" 5A per channel), keeping the resolution higher, but this would make the device bigger and maybe somewhat more complex, at least more expensive, as certain parts would be duplicated. I'm not sure if @Seba still started to design anything, he might have his hands pretty full with other stuff. Unless he's going to do the design, I'll try to get started soon...ish, likely I'll go with one of the LTC363x buck-controllers mentioned before, at least for the time being, unfortunately they're a bit expensive (likely more than 10€ with the inductors and capacitors, possibly a diode if using the non-synchronous version). Things can always be of course changed later on as needed. There are likely parts where I'll need help, like for example I have no idea how the BT-antenna dimensions are calculated, if using a PCB-antenna, or of impedance matching if using chip-antenna, although probably there are good resources available for both, and it's not the first thing I'm going to be tackling anyway.
  13. Looking at the list on that topic, Finland's information is wrong. EUCs are not "mopeds", they're bicycles. 25km/h maximum allowed speed, 1000W maximum nominal power.
  14. Some of the info here might be already outdated, but it's a place to start:
  15. Yeah, can't be the board if it still occurs after replacement, so either motor- or battery-related. @JBinBalt: Can you convince Lutalo to switch packs between your and his wheel, if it still occurs with known-working battery packs, then it's definitely either the hall sensors or the motor itself. And if not, then it's the batteries (or at least one of them). Of course it's a bit of a hassle taking apart the wheels and switching the packs...
  16. No idea if it works with the newer wheels, but I've kept on using the old(est) green app if I need to change some settings: https://www.electricunicycles.eu/kingsong_ks14ks16_electric_unicycles_mobile_app-c__162 If I remember correctly, you still need to (possibly manually, at least with some phones) to give it permission for location for it to work, but it doesn't ask for any really suspicious permissions. Usually I don't use the apps (even Wheellog) at all.
  17. But doesn't KS already produce their own BMS's, along with everything else (electronics-wise)? Prior to self balancing scooters business, King song has been engaged in developing and producing power bank protection board, all of the control boards of king song scooters are made by our own SMT factory, which is one of our advantage compared to our competitors, we can be more flexible and gurrantee quality of core components. Also, doesn't Ninebot Z-series show the individual cell voltages in the app?
  18. AFAIK, at least most if not almost all sellers ship worldwide... Aliexpress is an "e-commerce"-site or whatever they're called, like eBay / Amazon with multiple sellers, so they just provide the platform, the sellers are separate companies.
  19. That's actually pretty fast, if using the cheapest (or free) shipping option in Aliexpress. Of course it might be different for UK in general. Usually my orders have taken more like 3-6 weeks to arrive, maybe once or twice it has arrived in two weeks or less. The longest one was over 3 months... A few never arrived (I think I have way more than 1000 orders in Ali, but a single order from one seller is usually something small and cheap, like 1€ chip or whatever). EDIT: Oh right, the CNC came with DHL, that was 9 days in transit (+ a few days before that it even left China)
  20. Yes, MP174 is different. Look at the manufacturer list you linked to: https://www.monolithicpower.com/en/products/ac-dc-power-conversion/hv-buck-regulators-lt-10w.html 175 is 85V AC minimum. I didn't find a mention of minimums in its datasheets, but all the graphs start from 85V and the example circuit at the end of the datasheet shows 85~265VAC input.
  21. Good points, I originally dismissed the AC/DC -converters, because Mouser lists them as "85VAC minimum input", but that could be just laziness or mistake on their part. Have to take a closer look into those. Some of them may rely on the input voltage "pulsing" though (even half-wave rectified, it goes down if there's no capacitors on the input). And at least some do have minimum input voltages to work, the LinkSwitch-TN2 family was looking promising until this: "Adequate DC Rail Voltage – Check that the minimum DC input voltage does not fall below 70 VDC at maximum load, minimum input voltage" Many don't talk about the minimum requirement, but most datasheets never mention powering them from anything except rectified 85-240V AC or such. EDIT: In the end, I didn't find any AC/DC -controllers that are available in Mouser and that would work certainly also with low enough voltages. Even with the MP174 (that's non-stocked and not on order) that's marked to work down to 20VAC, the datasheet says: "Avoid a minimum DC voltage below 70V; a low DC input voltage can cause thermal issue.". So, it looks like it's back to MP9488 (if it becomes available again at some point in low quantities), LTC3639 or LTC3638, unless someone knows any other good choices or knows a better way than DC-DC buck regulation. I was thinking of a "flying capacitor" / "step-down charge pump" - style circuit to drop the voltage before regulation to use lower voltage parts, but a project that may enter the hands of others is probably not the place to start playing around with ideas and things I'm really not familiar with
  22. If it was "recently acquired", shouldn't it still be under warranty? 1RadWerkstatt (in Germany) could probably build you high-quality pack(s), but it's not going to be cheap... Don't know of much other sources, ordering from somewhere like eBay or Aliexpress is a gamble, plus the batteries cannot be airlifted, so it'll take a longer while to arrive and the shipping costs can be high(ish).
  23. Do you have any recommendations or ideas on the high voltage step-down? Seems that above 100V the "simpler" solutions get scarce... I earlier found this: https://eu.mouser.com/datasheet/2/277/mp9488_r1.0-1384072.pdf (MP9488, 450Vin max / 300mA max step-down regulator, non-synchronous), and it was "only" 2.17€ <10pcs, 1.75€ 10-99 pieces (without VAT), but, it's out of stock now and the minimum order quantity is 2500 pieces (for <1€ per piece, but I'll never have need for that many in my lifetime, and the total price would still be something like closer to 3000€ with VAT ), and the lower quantity option has vanished from the catalog, so maybe they will only sell higher quantities in the future. Out of stock on Digikey also, minimum order quantity 100 pieces. The next options I found so far would be either LTC3639 (150Vin max / 100mA, synchronous) or LTC3638 (140Vin max / 250mA, non-synchronous), but the price goes up a lot (over 7€ + VAT per piece for either when buying <10). There are some cheaper controllers for flyback-topologies, but I've never designed a flyback-converter (one SEPIC though, which is pretty close, but was a bitch to get my head around), and suspect that the transformer / coupled inductor would make it as "expensive". The 0.96" OLED-displays should pull about 30mA if all pixels are lit, and I've used 20mA as a "conservative" value for the SoC (it should use less, but better leave some headroom + other components will draw some current too), the datasheet for nRF52811 ( https://www.nordicsemi.com/-/media/DocLib/Other/Product_Spec/nRF52811PSv10pdf.pdf , chapter 5.2.1) seems to only give typical values, not maximums. So 50mA or more for everything to leave headroom. Another option would be simply not to support the 24S wheels (slightly over 100V), as there are more options if the input voltage maximum is 100V (usually the next step seems to be 80V max, which is already too low for 20S). For low currents, something like TL783 could work (linear regulator, 125V max), but it's still going to heat up considerably even with efficient cooling (dropping directly to 3.3V from 101V even with 50mA of current -> almost 5W of power dissipation!).
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