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A100S

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TechAUmNu
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A100S

Following on from my A50S I posted a month or so back. I have been working on a slightly larger board for 2-22S at 50A continuous.



This is the A100S, 42x40x20mm (1/3 size of a VESC6). 



So far I have managed to cram quite a lot into the tiny board. Still going through testing prototypes.

  • Micro USB
  • 12x 2.4mOhm 100v Mosfets
  • 2x 0.5mOhm shunts
  • TVS protection for all voltage rails 
  • BMI160 IMU (same as on the Vesc6 Mk4)
  • Sensor connector with TVS protection
  • Enable input for a power switch
  • PPM Input with TVS protection
  • CNC machined Hard black anodised heatsink with laser etching

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A100S Top_0.jpg

A100S Bottom_0.jpg

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First prototype had bit of a meltdown at 16S, the 5V buck regulator decided to go away :D

 

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vadicus
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That's a lot of fireworks for the 5v buck. Seems like mosfets shorted. I noticed that the shunt amplifier is rated for up to 26v common mode. Wouldn't that be a problem for 22s? 

TechAUmNu
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Nah the mosfets and gate driver were fine, the buck blew its lid and a pin off the package. I actually think it might have been caused by some ceramic caps that had large cracks in them as they exploded rather violently. The big sparks was the tracks on the back of the board fusing and the ceramic caps. There was also a tantalum on the RX board I had plugged into it that blew. 

Have since done thermal testing on the buck and it correctly goes into thermal shutdown. So have added the diode + caps in front of it to stop it seeing any high dv/dt.

The shunts are low side so I could use a cheap dual amp and get costs down. Seems to still work perfectly fine for everything I have tested it with... not exactly sure why we all have phase shunts tbh.

 

GeorgS
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Damn, if this had CAN, It would be perfect! Did you not include it to save space and cost at the same time?

TechAUmNu
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Yeah the CAN chip is massive! I might have a look if I can maybe find some way to have an add-on board that adds CAN.

 

I did some more testing with the new design, seems to be less explodey now lol.

 

 

So far manages about 45A continuous without the case. So once the case arrives that should improve things.

 

Designed a slide in fan duct so you can cool it with a standard 36-40mm fan. I like the SanAce36 as they are stupid powerful in a tiny size.

district9prawn
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Omg I wants it.

mystamo
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My Man,

 

You do some cool work. We should be friends. Lol

 

Mo

TechAUmNu
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Oh look a wild CANbus transceiver appeared?! Now idea how that got there!!

In other news I am currently redoing the layout to include this hilarious 20 pin Pico-Clasp connector. Which lets me put all the IO you could ever need on this thing.

mystamo
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You're just having too much fun. So am I and I have a lot of digikey boxes kick'n around and an angry wife.

 

Mo

GeorgS
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Siccc, man this thing is going to be epic! Looking forward to getting one once its ready... I sincerely hope you are going to sell them, not only here to tease us lol? 

bauck
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Hi Euan,

Really cool project, cant wait for it to be available on your website!

Couple of questions from looking at the pictures:

- Looks like you only use 0402 resistors in your design? 0402 resistors are often only rated for 50Vdc, so for voltage readings (where almost the whole voltage is across the resistors) this may be a problem, or maybe you use 2x 0402 resistors in series (3 in total for voltage dividers)?

- I cant see a crystal/oscillator. Do you run the stm off the internal RC oscillator/clock? I could not see any information on the forum or in the firmware (probably did not look deep enough) if this is possible, only a comment from benjamin that the usb could cause some problems if you are unlucky. IMO it should be possible and I dont see why the oscillator is there in all the vesc designs (besides for maybe precise usb clock), many motor controllers runs without any external crystal/oscillator. The bluetooth module probably has a precise clock, maybe you use this in some way?

bauck
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Just saw this option in the firmware:

#define HW_USE_INTERNAL_RC

So I guess it works in some way. Still curious if it causes any problems though.

TechAUmNu
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Hey,

Yeah I kinda forgot to change that when switching to 0402!! Just fixed that mistake now, thanks for pointing it out :)

Yeap runs off the internal HSI oscillator. Its plenty accurate for our purposes, my A50s, A100s and A200s all run without it and no problems so far. USB works fine. USB spec says 0.25%, but I think almost all usb devices support up to like 4% or something. Alternative is an external one like below, but that adds 2 more parts to the board which don't seem to help in any way.

https://lcsc.com/product-detail/SMD-Oscillators-XO_Shenzhen-SCTF-Elec-S3...