JMC integrated servo teardown

Just if anyone is interested some pictures of the insides of a JMC integrated servo, it seems to use a optical encoder and aditionally 3 hall sensors. if anyone has any questions i havent put it back toghter yet.


Thank you this is really nice. Is this an stm32f103rct6?
Also it is very educational to see the connectors. Excellent hardware porn.
Also notice how all I/O lines are protected.

yes the MCU is a stm32f103rct6

I’m actually thinking about switching my design over to stm32 because the esp32 is quite limited with gpio, it’s doable but it’s more complicated.

Based on my experience with stm32, and after I designed a few boards, I am pretty happy. By no means I consider myself an expert but so far I have not met any issue I could not solve. The hardware and software ecosystem is massive and, support is excellent. The only problem now is the chip shortage, it’s kicking serious butt. Even the small F0 chips are out.

Why do you say it’s complicated?

Yeah I saw that stm32 is sold out everywhere that’s why I wanted to use esp32 because it’s available.
My problem is the limited gpio pins, my plan now is to have a master esp32 that does IO from the outside and then a slave esp32 that drives the igbt measures the current and so on. The slave MCU has simplefoc on it. And master and slave are isolated from another. Encoder, bldc driving, breaking resistor controll and DC bus voltage are all on the slave that is connected via SPI to master Wich gets the signals to the outside world and does temp monitoring and stuff.

Did you allready put it together? I would be interessted in more detailed pictures of the IO´s. The pictures you uploaded are good but is it possible to make a picture on which we can see the markings of Q1-Q4, U1, U4 and U3? Thank you very much.

It’s still apart in a box somewhere, tomorrow i can post some more pictures

Thank you very much!

@Paule2002 sorry i didn’t have time today to make the pictures, i set me a reminder for tomorrow when I have some time.


If you need anything else, let me know. But I’m not available from Wednesday/Thursday for two or three weeks.

Thank you very much! I will take a closer look. Ther is no stress. So don´t hurry.
Thank you again.

I have a slightly different version here.
iHSV57-S V3.2 20191204 (top PCB), the actual driver PCB has the same revision.

JMC does not seem to provide any after service/repair service for their motors. The main voltage regulator seems to be burned on my side. So I’m waiting for some spare parts to fix it.
Is there any plan to support simplefoc with this?

I’m slowly tracing down all the internal connections here.

While the controller is well designed, there are some small gaps on the controller which allow chips to enter the electronic housing (mounting the controller downwards is recommended to avoid things entering the housing).
I’ve had a small aluminium chip below the RS232 chipset killing the RS232 + STM32F1 chipset here.
I have desoldered those 2 defect parts and I’m slowly jumpwiring it with an STM32F4 nucleo board (it’s a small side project now).

The HALL sensors enter the chip with 5V (the inputs are 5v tolerant). There’s some nice filtering done before it enters the chip already.

if anyone has a defect motor (with another defect other than the STM32F1) just let me know I’m certainly interested to get my motor back into my system.

Next on the list would be to interface the encoder and current sensors (so far I have interfaced the pre-drivers + hall sensors only)

@MRx Where are you located? I don’t need the PCB from my motor, but I think it has the older firmware 5.xx on it.

Taiwan, hm I’d prefer the 6.x firmware…

I was talking again with them seems like they can get some spare parts to us.