BLDC board for RC car?

Hi guys, i’ve got the following problem:
I inherited a student project using an RC car with 2x GM3506 BLDCs, and a dead custom made motorcontroller. I’m looking for a new, off the shelf controller to get it running again.
I’m by no means an expert regarding electronics, so please excuse me if this seems stupid/trivial/etc.

Maybe you know a board that’ll fit my criteria, i’d be very thankful for any insights.
-Support for 2x GM3506 BLCD → 5.57 Ohms, 1A max. constant current
-Onboard chip that supports SimpleFOC (or any other library that allows me to control the motors easily)
-Ability to communicate with the board (i2c would be perfect, but other methods may work as well)
-Ability to drive the motors precisely on low speeds without losing lots of torgue (possible with current sensing?)
-Small footprint (the SimpleFOC Shield looks nice, but it would be quite huge)
-A nice extra would be the option to drive a simple DC motor for steering as well, but this is optional

The old board used AS5048A rotation encoders, but it seems like you can go either via encoders or via current sensing.

Does anyone know of such a board?

I’ve looked at the Storm32 BGC, which should be able to handle my 2 BLDC’s (and a DC motor with a bit of tinkering). The Storm32 v1.31 uses the DRV8313, which was also used as the driver on the custom board, so the motors should hold up. I’m really not sure about these kind of specs, though. Also, is there any way to communicate with the board?

So yeah, i’m kind of lost here, and any advice would be greatly appreciated.

Hello and welcome to the board!

Check recent threads, there are a few efforts but you need to order the boards yourself. Look for Dagor, Mosquito and Lepton.

May be others can suggest, too.


Thanks Valentine!
I had a look at your suggestions, but it seems like Dagor and Mosquito aren’t open for orders and Lepton seems like a FLiR board?
Do you know of any gimbal-specific boards with communication possibilities?

They all are gimbal capable boards. You need to approach @David_Gonzalez directly.

The Mosquito and Lepton are also gimbal capable motors, I’m the designer. Also, there is the HackJammer board, but that one is expensive to order.

You need to order your own boards from an online manufacturing facility such as PCBWay or JLCPCB. What you can get here is the hardware designs, then you put in an order, upload the design files, and the facility will SMD and mail you the boards.

Also, I believe you are confusing the FLiR Lepton with the Lepton board I designed some time ago

Hi @p-rott

I’m going to chime in here on your original questions regarding the Storm32 boards…

For your size of motor this driver will work fine.
The difficulty with this board is that there is no SPI connection to connect magnetic sensors to get closed loop control. You can make SPI work by soldering onto one of the LEDs, but then its not that “off the shelf” any more… One solution could be to use encoders with A/B type outputs, those should work on any IO pin, of which there are several available.
If you’re happy with open loop control, then you don’t care about this.

The board has several I2C ports which you can use for comms, it also has serial and USB.

So if you’re really looking for an off-the-shelf board, that one could be good.

Another nice multi-motor board that might suit you is the STEVAL-GMBL-02 which would offer SPI without any soldering, but can’t handle as much power and costs more.

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Thanks for your input, but i think I’d prefer something proven. Not that i don’t trust your designs, but I’m just not knowledgeable enough to solve any occurring issues regarding hardware etc.

Hello @runger, thank you very much for your insights! Soldering just once shouldn’t be a huge issue, so thats nice to know. Since my first goal is to just get the car running again, I’ll start with an open loop solution. Are you sure the SPI connection would work with my encoders? Closed loop would be the long term goal. Using one of the drivers to drive a simple DC motor shouldn’t be an issue as well, right?

I’ve seen that there’s also a T-STorM32 setup, that uses NT controllers that combine the encoder and motor. Would this be a better idea for me? It seems like it utilises many more components, so I’d be more likely to mess something up.

For the STEVAL board, could you elaborate what you mean by it not being able to handle as much power? Would I be able to drive my motors with it? It looks quite nice, and I’d be able to get it delivered much faster.

Thanks again for your patience!

It’s not for a first time soldering experience, but for someone with a little practice its not too hard.

The AS5048A is an SPI sensor, but it depends on the exact PCB board its on. Many of them only output the PWM signal from the sensor, which is not nearly as good.

You mean unidirectionally? Bi-directional control would need 2 half-bridges, so two of the channels/drivers. But yes, no reason it shouldn’t work in principle, within the current-limits of the drivers. Keep in mind that brushed motors are a lot “noisier” than brushless, and the board might not be adequately protected for this use.

Its not a fair comparison, I think - the Storm32 designs are several years old, and the versions on Amazon or AliExpress are inexpensive versions of the original design. The T-STorM32 with the NT controllers is Ollie’s current design. For your described purpose the integrated board (i.e. old Storm32) sounds sufficient, and simpler.

A 3506 gimbal motor with 5.6Ω will be easy to drive with any driver. If unloaded, a few hundred milliamps will get it moving without problems. The actual consumption (when using FOC, i.e. closed loop control) will depend on the load and torque/speed desired.

I don’t know the weight of your RC car, but if it isn’t heavy, then 1A will be more than enough to move it, even in open loop (which is far less efficient). To even get 1A through the motor you’d have to use about 6V or more. If you’re planning to run at 24V, then the current could rise to 4A or more, you will have to apply a voltage limit in software.

The Storm32 boards come in driver or MOSFET versions. The driver versions handle about 2A (per driver/phase), the MOSFET versions handle a little more.
The ST-Micro board uses the STSPIN-233, which handles 1.2A continuously.

The 3506 motor can’t handle even 1A for a long time without extra cooling- it will get very very hot.

So really, I’d have to know more about your use case to judge, but if we’re talking about a small, not too heavy RC car, if the drive-train doesn’t have too much friction, etc, then 1A should move it just fine.

You won’t reach great speeds with this type of motor, but I assume that’s not the goal or it would not have been chosen in the first place…

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I don’t trust my own designs, either. That’s why there is a substantial amount of testing I do before I post anything.

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Whats about using B-G431B-ESC1: small footprint, supports SimpleFOC, current sensing, i2c

Assuming you want to use this motors as hub/direct drive. I’m currently designing a rc-car with two hub motors in the back tires using B-G431B-ESC1.

-Ability to drive the motors precisely on low speeds without losing lots of torgue (possible with current sensing?)

It is possible but not simple, like shown in this video: High Performance Sensorless Control for E-Scooter Applications - SMCT - YouTube
I also got contact with the smc guys and they reassured me that it is possible with the B-G431B-ESC1 board cause it has a powerful chip on it which you need for high torque sensor-less control

You will need liquid cooling.

I drove my rc car with a Skystars Slim40A 40A ESC, which is even smaller than the B-G431B-ESC1 and it doesn’t get hot, only a bit warm without any cooling.

here is a video

I want sensor-less low torque at startup so I’m experimenting with the B-G431B-ESC1 but i cant get to work. Will update soon if i get it to work. On all my tests the board gets really warm even with very little load. So there are two options i do something compliantly wrong or the board is bullshit

Thanks, that helps a lot! Turns out, my time on this project is ticking, so I’ll need to figure out what board will work and is in store in Europe, as i don’t have time to wait 4-6 weeks for shipping. The STEVAL is available, as is the B-G431B-ESC1, with the latter being 1/5 the price.

@Lukas_Pfitscher I’ll probably give the B-G431B-ESC1 a shoot, as it’s cheap and deliverable soon. I’ll let you know how I’m doing when it arrives. I’ll need two boards to drive both motors, right? I checked your repo, but there’s another ESC listed

Yeah right you need two of them.

But after two days of testing, i can’t get it to run without getting extremely warm.
i searched for issues and i found this FETs are connected to V+ with a single Via

Which if true would be a total fail but could also be me not knowing how to test this esc, here is what i did. I will write to STM directly, maybe they can help

Wow, that would be a severe design flaw, if that’s the case… :-/ just goes to show even big companies make mistakes, and you should always double-check everything!

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You might want something like Odrive or VESC.
Thats more reliable and mature.

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IIRC ST said they fixed the flaw back in Feb 2021 and produced a new batch with C1 revision. Could it be you either got an old revision, or they haven’t really fixed it?

Also, a plugged via carries 2A to 3A depending on diameter, but still it was a problem.

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Not having anything against those, I’m sure they are good for the original purpose. I tried both and then chose to go for a custom designed board and SimpleFOC with some extra custom code on top. Opaque firmware, and insufficient support are their two top issues. Also the support is more or less non-existent for a commercial solution (online board forum).

I keep saying this but there is a reason a commercial BLDC board from a proven manufacturer as Siemens or the likes costs a couple thousand $ compared to $100 odrive or vesc board.

Again, depending on your use case, they may work great.

Caveat emptor.


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Also take a look at Moteus, if considering ODrive/VESC… Moteus is also pretty nice.

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I’m not sure where to look for revision number

by feeling the temperature with my finger it is in the area where the via is.
But it is really strange that the ESC just can handle 1A, without any switching of the mos fets, just set output to high(tested it)