pinout puzzle on big BLDC drivers (repurposed automotive motors) - Page 1
Forum section: electronics / projects

author: mtraven
author_rank: Newbie
timestamp: November 30, 2019, 02:26:49 am
content: got 2 of these motors from a surplus store, they told me they had tried to test one and let out some smoke, but for $10ea, I bought the pair. from the remains, I can tell they connected 12v to the one plug(pigtail) that had been left with the motors. I am reasonably certain this was a signal line that wants to see 0-5v (maybe -5 to 5), but def not 12v. Polarity may also have been reversed, hard to tell at this point. These were power steering motors from a 2007 land rover and I don't have a specific purpose in mind just yet. They seem pretty beefy, I would like to get them spinning and see what I have. I think these were setup kind of like a computer fan-give it 12v and a signal and the driver takes care of the rest.My goal is to use the destroyed driver to workout the pinout for the good one and then design a BLDC driver for the bad one. So in response I am looking for any info on the motor, how it was originally implemented and suggestions on where to begin on a new BLDC drive.full photo set here: http://"https://photos.app.goo.gl/fFFZnPuG3wyVfVfp7After ripping the driver apart & spending countless hours researching, here is everything I know:-I see one chip blown up. I can only read the last few digits on that chip (?9072c3) a few digits of the manufacturer are : ???ANXDTG4 and the G is underlined. I cant get anywhere in IDing this chip.-The other 64pin chip is an infineon-TLE7189QK (3 phase BLDC driver)-The largest IC, presumably a microprocessor, is d70f3485gj(a2). Not Found any info on that.-power steering (full asm) part #: 80-30278ORPINOUT:-main power connection is obvious (giant spades)-from the single row header(left), the cable was still with it & only had connections on 4 & 5 (contacts in blue)-from the photos of this motor in its asm., it looks like the 2 row header also has just 2 connections. One going to each row of the header, reasonably sure pin 6 is the one on the inside row. The second one looks like pin #2, but very well could be #1.edit: fixed broken link

author: jhpadjustable
author_rank: Frequent Contributor
timestamp: November 30, 2019, 06:10:46 am
content: Quote1. You need to look at the whole picture, and not ignore the small stuff. For example, that SOIC-8 at the center right is a TJA1051 CAN transceiver which strongly suggests that this motor is meant to be a node on a CAN network, where status information and possibly control will be exchanged.2. Reverse-engineering "in these uncertain times" has a lot more to do with "open source intelligence gathering" as the spies call it. A bit of web searching seems to confirm that some Land Rovers do indeed have electrically assisted power steering controlled via the CAN bus, and that the head unit plays a role in translating steering angle into torque commands to these motors.Anyway, you're going to need some sort of CAN interface to work the unmodified device. An "ELM327" OBD-II reader might do. You'll also need some software to view and generate CAN messages, which is a matter of taste and budget. Then you'll need to identify the higher-layer protocol in use, then try to figure out how to send messages to the motor controller to get the desired results of torque. Here's a free ebook that might help you get started:http://opengarages.org/handbook/ebook/Or, you could dispense with the existing controllers entirely as needless complications and build your own BLDC controller. If you want results, and not a crash course in CAN (see what I did there?), you'll probably prefer this option.

author: mtraven
author_rank: Newbie
timestamp: November 30, 2019, 11:16:27 am
content: Quotemy knowledge base is rather limited, so its more like I am blind to the small stuff...I could have starred at that board for hours & never figured that out. thats why I reached out for help, and thank you for that, makes the decision to just start from scratch easy. I had hoped it would be as simple as a couple of analog input voltages, oh well. And if that board is that specific, I wonder if its not purpose build for the sort of back-and-forth action it would see steering a car vs the more continuous manor I would probably use it in. There has to be a PID loop in there right? at very least, I would think that would be tuned differently. All things I would have control over in a custom driver...alright I am sold.In looking at the OEM board, creating my own version is a bit intimidating, but something I have wanted to tackle for a while now. I like the idea of having the logic separate from the power stage (it seems some IC's are both)...that may be the only option for a motor of this size anyways. I have been playing with a samd21 dev board, that seems more than capable of timing and sensing and prototyping circuits is easy. On the other hand, there is no shortage of purpose built BLDC driver chips, with all sorts of features...I don't even know where to start...and that pretty much requires a custom pcb. which is fine once I come up with a final circuit, but I am going to want to play with/test that circuit before having them printed.then on the power size, how might I size the mosfets? I have seen a method for setting up a virtual ground to measure the resistance of the coils then ohms law it from there? and if I am building my own, if the motor will tolerate it, I would love to run that voltage up...maybe 24v? 48?edit: a quick search showed breakout boards are available, so if a smt BLDC driver chip is the better option, I should be able to prototype on one of those boards just fine.Are there any well documented guides or tutorials you would recommend on the subject?

author: jhpadjustable
author_rank: Frequent Contributor
timestamp: November 30, 2019, 12:33:06 pm
content: That's fair. Anyway, the moral of that story is don't forget to look up the little chips too, as they might hold critical clues to some aspect of the system under study. (Yes, sometimes even the little SOT23 as in the lower left might hold something important.) A couple of analog voltages would not have been the automotive way. Those guys like to see robustness against noise, local intelligence and diagnostics, and not running extra wires without a good reason. Silicon is cheaper than copper, especially by the hundred-thousand.QuoteSurely it is. Since they come in pairs, it might be reasonable to assume that each one pushes in its own single direction The lack of multiple power MOSFETs seems to confirm that the driver there only runs one way. Maybe that means you would be ill-advised to use it for propulsion, or should observe a duty cycle limitation and not try to go all the way to town and back on it. Or, maybe it'd be fine. Lots of possibly hidden mechanical details, which I don't claim as my wheelhouse (no pun intended).The control is probably implemented by the big processor at lower left. There might be more to it than one simple PID loop, since road surfaces do vary. For that matter, the PID loop may be distributed over the network.QuoteThey sort of did. I speculate that inductor and MOSFET at the upper right is a constant-current driver they use to apply measured torque.QuoteIt appears they used a 55A, 40V device (upper right). A steering motor would need to maintain torque into a 0rpm condition, so I'd think they would size it generously. You might as well follow suit at minimum. MOSFETs are pretty cheap. But maybe it's not brushless after all, if there's only the one power driver transistor?QuoteYou're on your own there. I'm more of an industrial networks guy who happens to sort of know a few dribs and drabs about motors. I can only say that, due to the presence of that buck converter-like arrangement in the corner, I wouldn't be 100% sure it's meant to run even at the full 12V for any great length of time. Again, motors aren't really my specialty, so hopefully someone else with more domain expertise can weigh in on that and on the finer points of drivers.

author: max_torque
author_rank: Super Contributor
timestamp: November 30, 2019, 05:30:03 pm
content: These EPAS motors are not that useful in traction or continuous operation because they are only rated for short term operation, for steering assist, which on a road car is a very part time duty cycle. The driver is also fairly limited in terms of continous current. The large mosfet will be used as a primary power switch, to enable the power to the motor to be shut off for fail safe no matter what happens to the 3 phase driver itself. As steering systems as "safety critical" they tend to include dual switching capability and often dul processors, with one operating as a equizzer / monitor to check the performance of the system is appropriate.It will definitely be CAN controlled, but the majority of the functionality is within the embedded micro, and the assistance and inertia negation functionality is hard baked into that device. EPAS racks typically include a column torque sensor which is an analogue or phase shift device to indicate to the control micro how much torque needs to be applies by the rack mounted motor.The motors are pretty high performance and low inertia, but as mentioned have a poor thermal co-effiicient, but you may have more headroom in your application because these systems are validated to run in a 85 degC engine bay and still meet their performance targets.In all cases, it will be far easier to just use a pre-existing universal 3 phase motor controller to drive the motor. What you will need to check for is the motor position feedback signals to see how those are arranged. Often these use a bipolar magnet on the end of the rotor shaft, and a small (typically SO-8) sensor ic on the pcb that reads the rotor position.

author: mtraven
author_rank: Newbie
timestamp: November 30, 2019, 10:07:06 pm
content: The mosfets are on a separate board, there are a couple pics in the photo alum I linked to (which I now realize, the link didn't work, fixed now) here is a direct link to a pic of the mosfets:https://photos.app.goo.gl/uGeDoRrHR3NX34MJA. Plus when the driver is completely removed, I have 3 spades to the coils and one of the chips I was able to identify is a BLDC driver.....so yes, I am confident it is a BLDC. Unfortunately, there are NO markings on the mosfets, so that's of no help in sizing new ones.Quoteman I have been trying, but I find it very challenging to ID some of this stuff...there is a sot23 chip near the right set of headers, all it has on it is "n 7" and then a 42 written perpendicular to the "n 7". I spent like an hour trying to figure that out, finally got fed up and came on here for help.Quotethere definitely is a bipolar magnet on the rotor shaft...I have looked extensively, and I can't seem to find the actual sensor(presumably a hall sensor)...in fact, there dont seem to be any electronic comps in close proximity to that magnet. If I am making my own, I will need to replicate that sensor or switch to an EMF feedback system...could also add an external encoder I suppose.Quoteare you saying buy the whole thing (driver & power stage)? or start with a driver IC and go from there? I am not looking for the easiest way to get the motor running, I don't even have a particular use for it yet. This is more of a learning project. Not to mention, a robust enough driver is probably hundreds of dollars, not really inline with the 10$ i spent on the motors.As for it duty cycle....I had been thinking it might make a decent motor for a small lathe, if I cannot find a way to run it continuously, maybe it will be put to use on a rotary table or to drive a leadscrew on a future CNC conversion. With respect to extending the duty cycle, it seems like I will need a more robust driver (bigger mosfets) and address / monitor motor temp...maybe even water cooling. I am just thinking out loud here.can anyone give me a ball park of the horse power on one of these things?thanks so much for your help, made more progressing reading your responses than I did in a day and half of frustrating "open source intelligence gathering".

author: mtraven
author_rank: Newbie
timestamp: November 30, 2019, 11:47:54 pm
content: Quote from: max_torque on November 30, 2019, 05:30:03 pmI wondered if there wasn't some redundancy built in, that makes sense on such a safety critical system. I understand the term EPAS to refer to column mounted systems, which these were not. These were rack mounted with a 1:1 pulley driving a ball screw(pulley/nut). Just 1 per axle. I think most of your assertions about the duty cycle are still sound, just wanted to clarify.

author: james_s
author_rank: Super Contributor
timestamp: December 01, 2019, 12:27:52 am
content: Brushless motor controllers for RC models are cheap and readily available up into the kilowatts, in the larger sizes there are also controllers for e-bikes and scooters. I'd scrap the existing controllers and look at those.

author: mtraven
author_rank: Newbie
timestamp: December 01, 2019, 08:41:37 am
content: Quote from: james_s on December 01, 2019, 12:27:52 amI will be scrapping the OEM drivers, that decision is made. But I will most likely be building one myself. there is no learning in buying one off the shelf. also you need to qualify "cheap", but I doubt there is anything premade, in my price range, that would drive these motors. lastly, if I have made something, I can modify it and that's valuable to me.I did a bit of investigative work into the motor coils. here is a peak inside:https://photos.app.goo.gl/RBqyGp9k8UgNNSdc6So i set up a kelvin connection to measure the resistance of the coils. I first confirmed the measurement setup with some known resistors and then measured the coils. Call them A, B & C. AB =AC =BC both in theory & then measured to be 0.058 ohms. since the resistance through any 2 coils is equal, I think I can infer that coils are intact and each coil is 0.029ohms. But the driver is always energizing 2 coils at a time right? So using the "full" 2 coil resistance and Vsup=12v, ohms law says I=206A. That would put power at 2472 watts. Gotta be honest, those numbers kind of shocked me, so I was hoping someone could check my math and also tell me exactly what that number is.....is that peak current? start current? surely it wont draw 200+A free spinning? Or maybe I have just done this all wrong....please advise.the enamel wire measures 0.065", so I am gonna call that 14 guage? That seems a bit small to take 200A through it, but maybe the "pulsed" nature of a bldc allows for those high currents

author: max_torque
author_rank: Super Contributor
timestamp: December 01, 2019, 05:31:16 pm
content: I'd bet the position sensor is the SO-8 component, smack bang in the middle, on the "back" of the main pcb, as shown in the 10th pic (sorry can't seem to link direct to pic in question)Regarding power, EPAS racks typically are rated at around 1.2 to 1.4 kW peak (100 amps peak supply current at between 12 and 14 volts) and will usualy have a continuou rating of around 300 wattsIf you can get the datasheet for the driver IC, then you can reverse engineer the drive signals to the packageless fets, and keep using those (because they are obviously well matched to the motor)If you add a large fan driven heatsink or water cooling system to the outside body of the motor, you will be able to signifciantly increase the continuous rating of the unit.These motors are designed to be low inertia, because they try to drive the rack without adding additional inertia and hence damping into the steering system, so they would make a good servo motor :-)

author: james_s
author_rank: Super Contributor
timestamp: December 01, 2019, 05:40:54 pm
content: If you want the fun of building something then you'll certainly learn more by designing something yourself. You won't save any money over buying a mass produced brushless ESC though, there's no way. It's been a couple years since I've built an airplane but I was paying $20-$30 for a decent quality 300-400W ESC. I just checked and you can get a 100A controller for $44, there are some under $30 but I've used several of these Turnigy Plush models and they do work significantly better than the cheapest ones I've tried.https://hobbyking.com/en_us/turnigy-plush-32-100a-speed-controller-w-bec.html

author: max_torque
author_rank: Super Contributor
timestamp: December 01, 2019, 05:41:38 pm
content: Quote from: mtraven on November 30, 2019, 11:47:54 pmThere is no electrical redudancy, because the fail safe state is to simply de-power the driver. The steering column is still the primary mechanical link, so it's just important that should control of the motor be lost, the system can be effectively switched off.. Worst case would be the motor turning when uncommanded, but also if the driver mosfets fail short, the motor can fail locked.. Either case is, er non optimum in a car being driven at speed along a road!

author: mtraven
author_rank: Newbie
timestamp: December 01, 2019, 08:35:36 pm
content: QuoteYES! good eye! that has been bugging me for a while now, but that chip is in fact a KMZ49-magnetic field sensor.Quoteis that consistent with the measured resistance of the coils(0.058ohms)? Sorry to do this, but I have to go back to, this is not an EPAS, steering column mounted motor. Everyone of those I have seen are much smaller motors driving a worm gear with a bit of planetary gearing to prevent the lock up scenario you described since wormgears don't back-drive.Quoteoh how I would love to have that datasheet...the driver seems to be made by a company called "hella." I sent them an email about a week ago and have gotten no response. Good to know that those are called packageless FETs, i thought they were a bit goofy looking. Are those able to handle more current/ cool better since there is no package? While I agree those FET's are obviously well matched to the motor, I destroyed the connections between the two boards and that whole thing is covered in this clear goo, so I am not even sure I could get it clean enough to solder new leads.Quotei agree and I see no reason not to do that...I can also spread out and better cool the FET'sQuotethats fascinating, I would have thought you'd want some dampening to replace the dampening normally done by a hydraulic steering rack. good to know.suppose I was to use these as servos, I would need to add a proper encoder to properly position, correct?QuoteI hear ya, and have experienced that many times. I look at it like this: if the DIY cost is less than the premade cost + cost of course work to learn the topic, I still come out ahead. But in this particular situation, there is a good chance I can do it cheaper. I while back I bought the inventory of an electronics shop that had gone out of business, so I have boxes and boxes of electronic components..got a whole crate of high power NPN's / mosfets ect.Thank you for the recommendation, I will certainly look into those. I do have my doubts that a 100a controller is even enough, but that's just a hunch based on the resistance of the coils. Then we get into repair...suppose I burn out a premade driver...if its something simple like the FETs I can replace them, but if its anything else, without a schematic, the board is probably shot....whereas if I have designed it, I can more effectively diagnose and repair problems.

author: max_torque
author_rank: Super Contributor
timestamp: December 01, 2019, 09:04:36 pm
content: The measured phase resistance of the coils means nothing. In order to build a high efficiency motor, that motor needs to be substantially reactive rather than resistive, ie to have a high inductance and a low resistance. For a motor controlled by an "Inverter" there is no such thing as "short circuit current" (i'm ignoring active short circuit functionality here) and phase current is controlled dynamically at all times.A EPAS system in order to provide the maximum fidelity must provide torque assistance to the driver, ideally without imposing any inertial or drag forces on the steering system, ie be completely transparent in its operation. Therefore the motor is designed for low inertia, and high peak current so it can very quickly change its velocity to match that of the steering system. EPAS simply means "Electrical Power Assisted Steering" and there is no relevance to how that assistance is provided, or the architecture of the system. Early, low power, high inertia systems were mounted directly on the steering column, but they were bulky, noisy, and very poor performing often having truely shocking steering "feel". A few "city" cars used them for a while, but the gen2 systems such as the ZF/Hella system you have moved to a rack mounted high performance brushless motor, with only the driver demand torque sensor mounted inline in the column itself.The rotor of the motor must be low intertia because it inertia is referenced to the rack by the overall gear ratio, which needs to be as practically large as possible to provide the greatest assistance force from the smallest (cheapest) motor!You won't get any info from Hella regarding the driver IC, as that is a proprietry automotive chipset, so you'd have to sign an NDA with them before they will release it to you.Realistically, peak motor currents of around 100 amps are used, perhaps as high as 150 amps for a few seconds, but the resistance of a lead acid battery starts to become limiting, ie the supply voltage falls with increasing current, limiting the power you can pull from the battery to a couple of kW at peak.If you have a look at the phase current measurement system, you may be able to get an idea of the peak phase current used, it may use one of three different phase current measurement techniques:1) Voltage drop across the power silicon2) Voltage drop across resistive current shunts3) A hall effect non contact magnetic based measurement systemThere is also a possibility it doesn't actually directly detect phase current, just measures supply current and ratio metrically calculates the phase current from the effective duty cycle ratio

author: max_torque
author_rank: Super Contributor
timestamp: December 01, 2019, 09:06:09 pm
content: PS, the sytems try to be mechancially transparent, so that damping and inertia compensation can be calibratable parameters and allow the system to be tuned to the necessary atributes for the particular application

author: mtraven
author_rank: Newbie
timestamp: December 02, 2019, 03:31:07 am
content: Quotewell shit that's a useful piece of information. Would measuring the inductance be of any use to me?Quotewhile I very much appreciate your detailed explanation, all I was really trying to say was the column mounted, wormgear style assist systems get away with a smaller motor because of the huge reduction in a worm gear. I just didn't want people to think it was one of those smaller ones. and that is enough on that.QuoteI didn't even ask for a schematic, just a pinout and what the pins were expecting...but they didn't even bother send a "no" ...seems a bit unprofessional if ya ask me.Quoteso based on that, how much current should my mosfets be rated for? 150? 200?your comment about a limited supply from a battery got me thinking, what the hell kind of power supply and I gonna need to run this thing. I made a spot welder a few years back that supplies 1200-1500amps, but that's just a few seconds..thats going to need some serious consideration.On a related note, I have just learned one of the methods for controlling speed (maybe the only?) is to regulate the supply voltage feeding the mosfets. Do I have that right? So that is another big ass mosfet(or set of mosfets) correct? I had just assumed the gates of the Fets would be driven by a variable input that would determine speed. I am sure there is a reason they don't do it that way, any idea what that reason is?

author: james_s
author_rank: Super Contributor
timestamp: December 02, 2019, 04:41:21 am
content: Something I forgot to mention, there is an open source firmware called BLHeli, and another one the name of which escapes me. Those and the associated hardware notes are a treasure trove of information on driving BLDC motors.

author: oPossum
author_rank: Super Contributor
timestamp: December 02, 2019, 05:03:34 am
content: Quote from: james_s on December 02, 2019, 04:41:21 amSimonK is one of the others. I think they both are derived from an earlier firmware.edit: Derived from Bernhard Konze's tp-18a firmwareThere is also the more comprehensive VESC firmware (unrelated to the previous).