VESC HW Redesign (VESC Mini?)

General topics and discussions about the VESC and its development.
ekman
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Re: VESC HW Redesign (VESC Mini?)

Postby ekman » 09 Feb 2016, 21:58

Nice Andreas, do you have the project posted anywhere like on Github or something so we can follow along with the files and make adjustments perhaps?

Andreas
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Location: Switzerland
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Re: VESC HW Redesign (VESC Mini?)

Postby Andreas » 10 Feb 2016, 17:00

Thanks, ekman.
No, i have no Git or similar repository. Currently CircuitMaker is my repository, since it has basically Altiums vault release management integrated into the software.

I plan to make a different repo once the project is complete, so everyone can access the files without registration with Altium and a massive circuitmaker download just to see the files.
If you go with me with circuitmaker, you can basically pull a Fork of my work right now and start to mess with everything as you please, or join the project for a more collaborative aproach.

Actually, i do plan to change some functions around on the interface side after a discussion about the project with a coworker:
New interface will be added for satellite RC receivers. The way i see it now, PD2 can be mapped to UART5_RX, so i guess that would be my input pin, connector would feature 3.3V, GND and signal connection with the JST ZR connector. Plan is that it works for Spektrum receivers for now (i only have spektrum rc stuff).
The servo input will probably be simplified (no galvanic isolation) and it should be bidirectional or fixed output. The idea here is that you could basically hook the steering servo directly to the MiniVESC and use the signal from the satellite receiver to directy drive motor and steering like that. :geek:

jaroslavnovotny
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Re: VESC HW Redesign (VESC Mini?)

Postby jaroslavnovotny » 16 Feb 2016, 13:42

Hello Andreas,

very nice thing you are doing!

I have just one suggestion and it's the connectors. I don't like much how they are facing the top direction, I think it would be much better to have them to the side and maybe surface mounted (just like the usb connector on VESC).

This would make the design much flatter when connected with wires. You could also stack these boards on top of each other better. What I am imagining is something like this design:

Image

I also hope there will be screw mounts similar as on the big VESC, fingers crossed:)

When you are trying to save space I suppose the STM32F4 microcontroller can handle more than 1 DRV8302. You could probably make 2 VESCs on a single PCB sharing one microcontroller with a much smaller footprint than both original VESCs. This would be great for robotics and drones!

Andreas
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Joined: 04 Feb 2016, 19:02
Location: Switzerland
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Re: VESC HW Redesign (VESC Mini?)

Postby Andreas » 17 Feb 2016, 10:44

Hello jaroslav
Thanks for your inputs. There are two reasons why i went with top facing connectors. First, the are just smaller than horizontal connectors in general. And second, i was not thinking about stacking the ESCs on top of each other if i would need more than one. It seems to me that this could restrict the airflow and cooling of the FETs too much. Putting them side by side makes much more sense to me for cooling, and for that, having the connectors go vertical is better, because you don't need as much space on the side of the board for the connectors/wires to exit.

The reason why i went with thru hole connectors is pretty simple: Thru hole connectors are just way stronger. I've had too many "toys" and gadgets on my desk to repair where there was just some SMD-connector to resolder that was ripped away. In RC cars there are usually a lot of vibrations, so thru hole is definately the more reliable choice. I know it is way easyer and cheaper for the manufacturing process if you use SMD connectors you can place by robot and reflow with the rest of the board in one go instead of having to set up another soldering process after reflow where you have to possibly manually place the connectors (the right way!), and run the board over a solder wave or do manual soldering. But i'm planning this revision to be mostly hand assembled anyway, so thru hole connectors are the better choice for now.

Screw mounts are something i should probably consider, yes. I'll see if i can make room for that somewhere. I was already considering to add some holes around the FETs to screw on a little heatsink.

Actually i'm just "turning" a lot of stuff on the board upside down right now, because i originally had the FETs on top and the driver on the bottom layer, but i want to change it so they are both on the same side of the board. The idea is that i can reflow them in the oven at the same time and don't have to use glue to hold the bottom side component in place. I am planning to populate and reflow one side in the oven, then do the other side of the board just with a hot-air (or infrared) soldering iron by hand.

jaroslavnovotny
Posts: 49
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Re: VESC HW Redesign (VESC Mini?)

Postby jaroslavnovotny » 17 Feb 2016, 13:24

I do agree that thru-hole connectors are better, that's a good point with vibrations. I don't longer vote for the surface mounted:)

I suppose then it doesn't matter and it's everyone's business which ones they solder into the holes..

The top facing ones make the mounting space of the board taller which for me is a bigger negative than having a larger foot-print with cables to the sides and slimmer mounting space. For someone else it could be vice-versa.

The cooling is actually one of the reasons that side connectors might be good because without wires coming up you could sandwich the whole VESC between 2 bigger heat-sinks. With some spacers such heat-sinks could use the mounting holes so no extra needed. This however assumes the side thru-hole connectors are not taller than the FETs. The only thing just a bit taller than FETs is currently the coil but with thermal pads the heat-sink fits above the coil.

If it happens there is no room for the mounting holes perhaps there could be just half-circle indents on the sides of PCB.

dpetrillo
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Re: VESC HW Redesign (VESC Mini?)

Postby dpetrillo » 17 Feb 2016, 18:14

I'm not trying to hijack your thread here or anything but I think this is relevant. The motor control boards out of self balancing scooters usually run on an ARM STM32F103 and have an inverter circuit for each motor. From this pic it also looks like there might be a SWD port too. It would be a huge task but if someone were to port Ben's firmware over to this hardware it would make a nice affordable controller. The scooters also have a second micro on a separate board, which would lead you to believe you could figure out what inter board communication they use and build your own controller for adding in CAN or Encoders or whatever you like on top of that. The board runs at 36V and at least 10A and supports hall sensors.

If for nothing else, boards like this are notorious for making interesting cost saving shortcuts in their designs that are worth a look for inspiration.

Image


Andreas
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Re: VESC HW Redesign (VESC Mini?)

Postby Andreas » 17 Feb 2016, 21:20


Jacobbloy
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Re: VESC HW Redesign (VESC Mini?)

Postby Jacobbloy » 19 Feb 2016, 22:38

The better thing to do would be port a scaled down version of the vesc firmware onto a f103 chip but I think you could loose foc. But it would make the vesc cheaper and with smaller lower voltage fets it could be a very small package. But I would prefer to just move to a BGA version of the f405, I messed with it but it would be a 6 layer pcb with crazy small vias, and trace gaps that you would spend $100 on 1 pcb

fertito
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Joined: 26 Feb 2016, 14:01
Location: Grenoble
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Re: VESC HW Redesign (VESC Mini?)

Postby fertito » 26 Feb 2016, 14:11

Hello,
I found pour project recently, Nice piece of work.
I would like to build myself a 2-4 motor esc based on 1 processor,
Do you use special feature of the f405 (DSP) or could that be ported on a big f103z?
I'm used with these 2 chips but can easely access to the f103 at low cost.
Thanks.
Roman

Jacobbloy
Posts: 7
Joined: 05 Feb 2016, 05:38
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Re: VESC HW Redesign (VESC Mini?)

Postby Jacobbloy » 10 May 2016, 14:27

are you using the same shunts as the original or have you gone for some thing els? the original shunts are great but are big they probably stand taller then the mosfets that you are using.


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