Thoughts on designing a new controller

Actually this is the smd part for the GPIO port -

https://www.digikey.com/product-detail/en/amphenol-icc-fci/20021321-00040T4LF/609-3779-ND/2209124

Thank you

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This is another excellent suggestion. We also re-home the z-axis pretty regularly so position holding when powered off is less of an issue there as well. That’s a fantastic idea.

The surface mount headers are a really good point. They would need to be on the bottom of the board which is still a little complicated, but removing through hole aspect is still a win.

I get what everyone is saying around some price increase being tolerable, but going to a four motor design is already going to increase the price somewhat. I know for a lot of people a price increase wouldn’t be a big deal, but I know for me and some people it would be. If possible I would like to offer the lowest possible price point for a viable machine with the option to upgrade easily. I’ve got some simplifications in mind that should partly offset the cost increase of going to four motors so if it is possible to keep the cost low I would like to try.

I found some guys at the local maker space who run a business around integrating raspberry pi type things into products and they agreed to let me buy them dinner in exchange for picking their brains about what the best options are. I will bring up all the things everyone has said and see if they have any new suggestions to offer.

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One of the advantages to including an RPI in a product is that it could then support optical calibration. I don’t know of any “arduino” that can readily run OpenCV. However, you could always run the optical calibration portion on a PC (Windows, Mac, whatever) and communicate the results (i.e., detected location of sled) to the controller.

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@bar I’m not very familiar with the 4 motor configuration. Do you know of any good threads that talk about it to learn more?

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My musings on the topic are here:

And @madgrizzle being the amazing being that he is is building one here:

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@bar, @Gero thank you both, I have some reading to do! Seems very interesting.

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I don’t think the RPI has enough PWM pins to run a motor controller directly (not even sure it has enough GPIO for all the encoder pins needed for a four motor design) so if you have an RPI as part of the design, it needs some sort of “intelligent” controller it can talk to since it won’t be able to talk directly to the TLE5206/whatever chips and motor encoders. That’s why I like the idea of incorporating a microcontroller directly on the motor controller (4 dc brushed motors + stepper) and just making that microcontroller do really basic work like managing the PID loop and reporting errors. Leave all the complicated stuff to the RPI (e.g., processing gcode, UI, etc.) so you seldom, if ever, have to update the firmware of the microcontroller.

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Here is some detail on the Pi GPIO pins: https://www.raspberrypi.org/documentation/usage/gpio/

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So, this would look something like the Einsy Rambo with a Rasberry Pi Zero W, used in the 3D printing world?

image
[Edit - photo courtesy of Prusa Printers blog The Rpi zero W is used to run OctoPrint]

https://reprap.org/wiki/EinsyRambo

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I’m using 10 pwm pins an 10 gpio at the moment in my four motor design. I guess you might be able to rework the pwm with the tle5206 to just use one pwm pins and do something different for the z axis or maybe use softpwm but not sure if that would work for the application.

+1 on that.

While I understand the market concepts/dynamics that @JWoody18 and others were referring to.
Even near $500 is a big ask for many. That can be hard to justify for one tool no matter how useful and amazing.
Not everyone is looking to use this for business/income. For many of us it would be just for hobby.

I was on the fence for some time and missed the opportunity for the first one. Still trying to justify the price on the current offerings.

If it was $700+ I would not even consider it much like traditional CNC router machines.

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In the very beginning when it was introduced to me, I might not have either, honestly. I will say that it feels like a majority of people, at least the ones active on this forum, seem to tinker enough over time and add upgrades slowly, pushing their all-in costs way past the advertised price point. EDIT: myself included!! :slight_smile:
Maybe we can have the best of both worlds by having easy upgrade options, as bar said above. If that continues to be the mission, I do feel that communication to new users, who are in the buying phase, about the existing “stock” options and “upgrade” options, could be improved.

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Good point, on lower price entries into tech such as this. Overall costs can well exceed the initial price.

The tough sell is that first price.
As @bar alluded to above, I think it’s important to keep the initial “kit” price low to get people into these that may otherwise avoid the tech and miss out on the joys and benefits.

3D printing was like that for me, It wasn’t until good printers were in the sub $300 range that I took the plunge and got one.
Now that I like it and understand the value of that tool, I can see and rationalize the benefit of adding a quality extruder that is near the initial price of the whole printer.

Exactly, for many (me included) its better to keep the initial cost down even if much more is spent over time to upgrade. It lessens any single impact on the pocketbook. For others who know that they want it and can afford it, I can see the benefit of getting a completely upgraded unit with all the bells and whistles.

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This is part of my point about improving communication on options. I’m not sure if new, inexperienced users could know if a certain kit would be right for them, if “this” piece of hardware is better than “that” piece of hardware and why.

What I’m thinking about is: how to inform the new user, who has the money, that there are upgrades that could be done straight away, instead of buying the “stock” option and then saying “well ‘that’ part doesn’t work well, wish I would have known about ‘the other part’? My felling is that this scenario is frustrating and off putting to the “Maslow brand”.

before we get too worked up in different options, I’ll point out that we don’t
have anyone who is producing a ultra reliable/precision kit yet. I think the
problems are more on the software side now than the hardware side, but in a year
we have not put together a good comparison of the different triangulation kits,
let alone any of the other options.

We do know the Z axis can be improved significantly, but there’s no comparison
between the different Z options (other than they are all better, and mostly more
expensive or harder to build, than the stock Z option)

frame angle, we know that 20 degrees is too much and 5 degrees to little, is 15
degrees right or would be be better going closer to vertical?

a 12’ top beam seems better and it may be good to define that as the default,
ith 10’ or shorter being a fallback (including just a little more chain in the
kits). this would be close to zero cost

it seems pretty clear now that weights instead of bungees improve the machine,
this is pretty much a zero cost upgrade

it’s only the more drastic differences (4-motor, gantry) that add a really
significant extra cost. Even more expensive electronics would not be a huge
cost.

David Lang

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@dlang, @Metalmaslow is producing a very nice laser cut metal kit, although the first unit arrived today and we don’t have “data” on its performance, by watching the video of it cutting, I’m pretty optimistic and confident in its performance. In my opinion, their kit options are a step improvement for the community.

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The best way to keep costs down is to make all parts available for people to buy themselves. Right now the motors used are realistically only obtainable in large quantities easily and unless you are a skilled electrical person same thing for motor controller.
There are other Chinese motor companies. Aslong is one that make similar motors and sell them in small quantities.

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I’m planning to use SPI to talk to both the encoders and the motor controllers. That would give us more information to work with (like real time current measurements) and should ultimately use fewer GPIO pins.

Based on everyone’s discussions about the price point, I agree with the idea that keeping the cost to get a machine as low as possible should be the goal, with optional upgrades. I’ve been playing around with the esp32 and it seems like a great replacement for the Arduino at a lower price. The point about having a clear list of what is available and what the benefits are is a good one. It could be a little bit difficult with multiple people selling different things, but I will work on that.

Great point about the motors. Using a motor which can be bought in smaller quantities would be a big step towards making the kit more open. Do you have any recommended motors which are available in smaller quantities? For the next version I am planning to use an external encoder so the motor does not need to have an integrated encoder.

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That looks like it’s readily available, how would you calibrate it? The
non-linerity is prety significant (0.8 to 1.2 degrees depending on temp and
magnet placement being off by 0.5mm) I’m thinking of the problems you had with
the makesmith magnetic sensor.

David Lang