Kliment Conversations

1

Great to hear from you, thanks for responding. You can see more about our work at this TED talk. Our immediate need is 2.5A and up for serious stepper motors for CNC Torch Table Prototype II (prototype I was shown in the TED talk)

http://opensourceecology.org/wiki/File:Table_Frame.JPG

I would like this to be 1-off producible via CNC circuit mill, such as the open source Shapeoko (I'd like to know if you know of any better off-shelf open source variants of a CNC circuit mill?). That is our preferred route for rapid prototyping, until the point where we stabilize a design. In any case, our goal is to make something designed for an off-shelf CNC circuit mill to enable full control of the technology by the user.

Interestingly, I looked up the driver chip and found this immediately - it appears to be open source -

http://www.thingiverse.com/thing:40540

With fully-assembled board available:

https://shop.germanreprap.com/en/Powerlolu-Stepper-Motor-Driverup-to-10A

Can you help us design a prototype driver equivalent of the above that we can mill with a CNC circuit mill? It appears that the component cost would be about $20 per channel in single units?

2

Yep, that's actually based on a design of mine called STOMP that is GPLv3 licensed, so yes, it is open source. I'm not entirely happy with the lack of link to source on the product page, but at least it's available. The 10A is optimistic, and the current is highly dependent on the current sense resistors, so it's not going to do anything like a 2A-10A range. You have to pick a fairly small range of coil currents and match the current sense resistor value to those. So I'll need to know what motors you plan to use it with. It's a very limited chip in that sense, but the price is right.

Can you help us design a prototype driver equivalent of the above that we can mill with a CNC circuit mill? It appears that the component cost would be about $20 per channel in single units?

Component cost can be less than that, the bulk of cost other than the chip and FETs are connectors. I can definitely try to make a single-layer version of it, but it's likely to end up using many jumpers. What sort of trace/space can you get on a shapeoko? Toner transfer might be a better way for prototyping with chips spaced this densely.