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Forum section: electronics / projects

author: Anonymous.Engineer
author_rank: Newbie
timestamp: March 09, 2015, 05:35:55 pm
content: .

author: eneuro
author_rank: Super Contributor
timestamp: March 10, 2015, 06:46:28 pm
content: Quote from: kristapsdreija on March 09, 2015, 05:35:55 pmI do not like breadboards-it is easy to make mistake-it is better draw schematics and make # home PCB prototype-it costs a few hours with old school transfer method, but we have something usable and PCb software checks for bad connectionsFrom A3930 datasheet:QuoteI do not like such brakeing at allQuoteIt's is hopelessPrefere connect additionl resistive load and disipate motor energy as a heat, but not in motor windings.This A3930 doesn't support regenarative brakeing?Anyway, I never used A3930, but quick view into its datascheet and this brakeing method completlly do not fit my needs in any EV project, while regenarative brakeing with battery overvoltage protection and additional power resistors to disipate heat outside motor has top priority in my requirements, so yep testing right now my new galvanic insulated gate drivers and never tried messing with charge pumps in EV projects for made @ home use where a few $es more doesn't matter since those modules are also reused in other projects, so I prefere spend more time on one module test it independent of other subsystems and build driver from reusable blocks in custom motor driver

author: Siwastaja
author_rank: Super Contributor
timestamp: March 10, 2015, 07:07:16 pm
content: The net is literally full of application notes and example codes of running a BLDC motor on special MCUs optimized for exactly motor control - every manufacturer provide those, starting from PIC or AVR, to more modern and powerful ARM MCU's. Those things cost something like $1 and are much better suited for most cases, because you are not locked up to one (probably buggy or lacking) chip design and its limitations. You can also integrate any user logic into the same chip. BLDC control is something MCU manufacturers are very committed to, and provide a lot of resources.IMO, the lack of regen braking is a total showstopper. This chip is clearly for something else, not for electric traction.Motor control is not completely trivial and there is always quite a bit of processing, conditioning, a lot of inputs and outputs, and you always need more flexibility than you originally thought. CPU is great for this kind of task.Integrated bootstrap FET drivers are of course a nice touch, but still, they are pretty off-the-shelf stuff so no big deal having those separate as you do with an MCU.

author: eneuro
author_rank: Super Contributor
timestamp: March 10, 2015, 07:17:04 pm
content: It looks like there are many ways and many double checks to run this A3930 chipQuoteNow, I'm prety sure that a way to forget about charge pumps and play only with galvanic insulated gate driver PSUs was not so bad and maybe not such expensive, since a lot of time can be saved while no need to mess with things like bootstrap capacitor selection-just design small PSU for gate driversYep those ICs can be really good, but everything have to be corretly wired else sometime not so easy find a hardware bug-mistaken connection.I use clasic MPUs with a few kV optoisolated pins when iterfacing gate drivers and high voltage stuff.Anyway, probably a lot of people uses A3930, so they will help you.Do not give up-just wanted to make quick view into its datascheet to see if it could be usdable maybe in another non EV project where small battery powered machine with two BLDCs need to be controlled and this IC might work for me if wanted go to higher volume as commercial product.BTW: You can try also connect something smaller to this controller to ensure it works-DVD or hard disks has nice BLDCs, but DVD had analog Hall sensors output and this is how I rotated my first BLDC motor... without any driver... manuallyI do not remember if had also protective glassesNote: On this crappy multimeter is output of one of those analog Hall sensors from this DVD BLDC.

author: Siwastaja
author_rank: Super Contributor
timestamp: March 10, 2015, 08:13:03 pm
content: Bootstrap drivers are damn easy. So easy that they are THE go-to solution pretty much everywhere for low cost and easy design.It's just normal in engineering that every single approach always has downsides and you always find yourself engulfed in analysis and math, and application notes are always published...Isolated drive is nice, but normally not worth the hassle and bigger, more expensive components, when you do just fine with a tiny little capacitor and diode.The secret behind the bootstrap lies in the modern IC integration. Bootstrap really requires some relatively "complex" stuff like UVLO, but it's all in the driver chip, and it's a proven solution.I have always approximated the bootstrap capacitor as 100x total gate capacitance. Or just use a 1 uF cap for everything expect some very large IGBT bricks, and use 10 uF for those... No big deal here. There surely are corner cases and possible pitfalls out there, but no solution is free of those.And I have trouble understanding why you'd need near 100% duty cycle in an AC motor (such as BLDC) controller.

author: eneuro
author_rank: Super Contributor
timestamp: March 11, 2015, 07:30:58 pm
content: Quote from: Siwastaja on March 10, 2015, 08:13:03 pmThere are many subsystems in EV or high power applications where I do not like mess with something different than galvanic insulated gate driver and PSU to be able get without any thinking about it 100% duty cycle-for example mentioned disipation of heat during battery overvoltage protection when electrodynamic brakeing is enabled, synchronous rectification, etc.This simple fet gate driver with 24VAC galvanic insulated from PSU easy outputs +/-12V and quite bulky 100uF caps for +12V and -12V driver output provide huge amount of charge to fully switch ON/OFF fet gate between -12Vgs..12VgsThis was designed for 2 layer PCB, testing on single layer made @ home prototype before sending for manufacturing, so a few bypasses and elements soldered on bottom side with THT holes to easy check all points in this circuit.Everything works fine from first run, while it was designed in simple circuit simulator and for given switching frequency range from 0Hz , no supprise nice -12Vgs when gate driver optoisolator has no input currentsSince this thing is easy to test, lets manufacture hundreds of such quite small PCBs in the terms for bigger EV which are in my interest and this fet gate driver will be also reused in my recent desulfator project in AC mosfets switch, as well as other projects where no tiny PCB needed and cost it is not everything.Anyway if we buy tens, hundreds of similar components we get much better lower elements prices, PCB cost is low, so I see no reason to mess with other gate drivers, but it will depend of someone preferences and project requirements.Building bigger systems from small well tested modules and usually nothingwhile I know limits and performace data and limits of all of those designed modules, so can quite quickly figure out what is going on in whole system if something goes wrong

author: eneuro
author_rank: Super Contributor
timestamp: March 12, 2015, 01:20:35 pm
content: Quote from: kristapsdreija on March 11, 2015, 07:51:40 pmNot a great RDSON for this quite low 60V voltage, so if you put them in series for high and low side in your H bridge, probably too much losses, even if we try to put a few of them in parallel for each switch, so I'd rather dismiss them, but maybe other people there, more experienced in commercial applications have different point of view

author: eneuro
author_rank: Super Contributor
timestamp: March 12, 2015, 03:04:36 pm
content: Quote from: kristapsdreija on March 12, 2015, 01:26:25 pmIt depends how much space do you have for your ebike controler, but automotive things have to deal with diffrent kind of vibrations, so a lot of mechanical stuff to make this thing strong to survive differetn kind of stresses during drivingAnyway, in this video 3 phase ebike PCB designed in... Corel Draw

author: eneuro
author_rank: Super Contributor
timestamp: May 17, 2015, 05:42:09 pm
content: Quote from: kristapsdreija on May 15, 2015, 08:31:38 pmTry to run it as generator than check if it output any voltages eg. using 3 phase bridge with 6 diodes and try to power up low power light bulb eg. 12V 5W or better use osciloscope to see three motor wires waveforms

author: Alfie
author_rank: Newbie
timestamp: October 19, 2015, 08:39:36 pm
content: Hi, how did you get on? I am using A3930 chips and finding them reasonably tolerant. Tips: Things I noted is that if you get phasing wrong, the motor still runs (especially if you give it a little spin), but just very badly. It even does this with a hall line off or one phase off. The A3930 is "very" easily blown. Once in a good circuit, they are almost indestructible, but the slightest hint of a voltage in the wrong place at the wrong time, and no more. I found it best to keep the hall power well away from the A3930, so I gave it a separate regulator. The 100K pull ups to drive the 74HC14 seem a little light, but I don't know. My 90W BLDC motor has it's halls connected direct to the A3930. The Bootstrap caps seem a little light at 10nF. Mine are 1uF (I have no idea how to calculate it .. the sheet is baffling/annoying, but I read elsewhere someone uses 1uF for most things). Ensure the reset and coast lines are high. A simple test to check the A3930 is to apply BRAKE and see if it stiffens up the motor. Would be great to hear how you got on. Alfie