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Motors for Makers: A Guide to Steppers, Servos, and Other Electrical Machines (2015)

motorsformakers.com

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Re: Motors for Makers: A Guide to Steppers, Servos, and Other Electrical Machines (2015)

#91

Post by conductr »

atonse wrote: post #85

Wow this is AMAZING! There are a whole set of projects I’ve just not tinkered with because of my lack of knowledge about motors. For example, I want to make my bicycle hook system run on a motor. But winches are too strong. Don’t need something to pull 1500 lbs. just 100 lbs. All I know is that it should probably be low rpm and higher torque. Another is to play with something like curtain opening motors but as long a…

> Don’t need something to pull 1500 lbs. just 100 lbs.

I suspect with a smart pulley design you could get that down significantly as well

Re: Motors for Makers: A Guide to Steppers, Servos, and Other Electrical Machines (2015)

#92

Post by balfirevic »

marcosdumay wrote: post #78
GeorgeTirebiter wrote: post #59

Earlier quoted context omitted.

This was PRECISELY the problem that led me to get a 3D printer. I have successfully printed many gears using PETG for my projects. Now, they are physically bigger than metal gears for the same strength, but that hasn't been an issue in my applications. Using the wishbone-style gear teeth with 3D printing is remarkably sturdy. Of course the other way is: buy motors with (metal) gears that are close to your need - then…

> Of course the other way is: buy motors with (metal) gears that are close to your need - then you only need to 'transform' that motion a little bit. Buy overpowered motors close to your need, and 'transform' them by software.

Unfortunately, that only works if weight is not a concern - direct drive applications will have worse torque/weight ratio.

Re: Motors for Makers: A Guide to Steppers, Servos, and Other Electrical Machines (2015)

#93

Post by conductr »

dragontamer wrote: post #30
CubsFan1060 wrote: post #11

For someone wanting to get into "making",is there a good set of starter resources like this? Software I'm comfortable with, but I'm not really familiar with all of the physical components or how to put them together, when you might use each, etc...

My issue with motors is that all of their problems seem mechanical in nature to me. I don't think anyone will really have a problem wiring up an H-bridge or whatever to run a motor. I'm personally wondering how to use the physical properties of a motor to like, move Magic The Gathering cards around, or other real world tasks. It very quickly becomes a mechanical levers / pullies / motion kinda problem, rather than el…

This is a great point and where I spend most my time and 3D printing. The coupling between motor and desired function is 90% of any project for me.

Re: Motors for Makers: A Guide to Steppers, Servos, and Other Electrical Machines (2015)

#94

Post by Youden »

rq1 wrote: post #54
Youden wrote: post #32

Earlier quoted context omitted.

Assuming you're talking about AC servos typically used for industrial equipment (and not the DC kind used for robots or RC aircraft), there are kind of two routes you can go. On the easy hobbyist route, you can get the parts from a nice online store with email support like DamenCNC [0]. You'll need to read the spec sheet to find the speed/torque/resolution though. On the harder route, you collect a bunch of spec shee…

Thank you for this comprehensive comment. I appreciate it. I did the drawings of several drones and robot arms, and accurately computed the needed torque. I target specific precisions for several applications. I’m a mathematician so the math is straightforward to me though as you said, it’s super easy to overlook something without the appropriate experience, especially since it’s cross disciplinary (ME, EE, SE… etc.…

Those motors are just closed-loop steppers. I'd say they're inappropriate for robot arms because they can only apply their specified torque when the angle happens to be in proximity to a full step [0].

Proper AC servo motors like the A3 series from Delta are - as far as I understand - able to apply their specified torque with "infinite" resolution, in practice limited primarily by the encoder.

In robotics though, BLDC motors are often used. You might want to look into ODrive [1].

Make sure you're choosing an appropriate gearbox too. A planetary gearbox has some amount of backlash associated with it, often around 10 arcmin from what I've seen in data sheets. If that's inappropriate for you, look into harmonic drive. Much more expensive but for a reason.

[0]: https://www.machinedesign.com/archive/article/21812154/micro...

[1]: https://odriverobotics.com/

Re: Motors for Makers: A Guide to Steppers, Servos, and Other Electrical Machines (2015)

#95

Post by iancmceachern »

convolvatron wrote: post #87
iancmceachern wrote: post #40

Earlier quoted context omitted.

The key, if you can, is to choose a NEMA standard motor, there are tons of suppliers you can get a nema gearbox from. They get pretty small, but if it's amaller than the smallest nema size I'd go to a place like stock drive components which stocks thousands of gears. The challenge is that gear tooth geometry is often more than 2d, so laser cutting may not be the best solution for longevity. For a quick and dirty prot…

standalone gear boxes also seem to be really really expensive what i would really love is a set of compatible gears that work from the same shank and would allow easy construction of 1:2 or 1:4 or 1:8 and i could compose. maybe some 1:1 bevels too

Check automation direct, eBay, Ali express. I recently bought a nema 23 50:1 gearbox for a project for $50

Re: Motors for Makers: A Guide to Steppers, Servos, and Other Electrical Machines (2015)

#96

Post by rq1 »

Youden wrote: post #94
rq1 wrote: post #54

Earlier quoted context omitted.

Thank you for this comprehensive comment. I appreciate it. I did the drawings of several drones and robot arms, and accurately computed the needed torque. I target specific precisions for several applications. I’m a mathematician so the math is straightforward to me though as you said, it’s super easy to overlook something without the appropriate experience, especially since it’s cross disciplinary (ME, EE, SE… etc.…

Those motors are just closed-loop steppers. I'd say they're inappropriate for robot arms because they can only apply their specified torque when the angle happens to be in proximity to a full step [0]. Proper AC servo motors like the A3 series from Delta are - as far as I understand - able to apply their specified torque with "infinite" resolution, in practice limited primarily by the encoder. In robotics though, BLD…

Thank you for your reply.

Proper servos with high torque are quite expensive. I wanted to keep the project under a certain amount to scale it.

With the springs to compensate the static loads (gravity) I can use weaker servos but I didn’t yet completed the “sensitivity table” of the generated angular momentums.

Yes indeed, the ~10arcmin should represent something like 5mm at about 1m distance. Plus the ~30mm of the 1.8deg/step again at 1m or 3mm with 10:1 gearbox.

I thought I could tackle it by using more expensive parts (but weaker) at the end part of the arm for instance and write a software to orchestrate all the 6motors together.

I didn’t know about the harmonic drive I’ll look into it.

Thank you again for the references.

Re: Motors for Makers: A Guide to Steppers, Servos, and Other Electrical Machines (2015)

#97

Post by dTal »

As an aside that might be of interest to some - if you want to build a machine out of steppers, servos, digital output pins etc, and you want it to operate under tight timing constraints, and you want to avoid getting your hands dirty with finicky embedded programming, the Klipper project - nominally a 3D printer system - is sufficiently modular to be an excellent base. The developer documentation isn't perfect, but it's pretty straightforward to write new modules for it, all in Python, and it performs extremely well.

Re: Motors for Makers: A Guide to Steppers, Servos, and Other Electrical Machines (2015)

#98

Post by atonse »

conductr wrote: post #91
atonse wrote: post #85

Wow this is AMAZING! There are a whole set of projects I’ve just not tinkered with because of my lack of knowledge about motors. For example, I want to make my bicycle hook system run on a motor. But winches are too strong. Don’t need something to pull 1500 lbs. just 100 lbs. All I know is that it should probably be low rpm and higher torque. Another is to play with something like curtain opening motors but as long a…

> Don’t need something to pull 1500 lbs. just 100 lbs. I suspect with a smart pulley design you could get that down significantly as well

So the problem is that I don't even know where to start... where to buy, where to experiment.

Say I want to hoist a 30 lb bicycle to hang on a 10 foot ceiling. The winch just needs to pull the rope (the pulleys are already installed).

For that, how to go about finding the smallest motor needed (that's also quiet, I love when motors are generally quiet and don't whine). DC Stepper motors seem like the right solution there.

Re: Motors for Makers: A Guide to Steppers, Servos, and Other Electrical Machines (2015)

#99

Post by relaxing »

dragontamer wrote: post #30
CubsFan1060 wrote: post #11

For someone wanting to get into "making",is there a good set of starter resources like this? Software I'm comfortable with, but I'm not really familiar with all of the physical components or how to put them together, when you might use each, etc...

My issue with motors is that all of their problems seem mechanical in nature to me. I don't think anyone will really have a problem wiring up an H-bridge or whatever to run a motor. I'm personally wondering how to use the physical properties of a motor to like, move Magic The Gathering cards around, or other real world tasks. It very quickly becomes a mechanical levers / pullies / motion kinda problem, rather than el…

>I'm personally wondering how to use the physical properties of a motor to like, move Magic The Gathering cards around

I would use a suction gripper on a 2-axis CNC platform.

> How do I study that stuff?

Take a printer apart to see how it works. The pros do it, too.

Re: Motors for Makers: A Guide to Steppers, Servos, and Other Electrical Machines (2015)

#100

Post by relaxing »

sbierwagen wrote: post #70
gwynplaine wrote: post #64

I feel like there's a gap in the hobbiest motor market. On the one hand there are stepper motors which can withstand lots of radial load thanks to steel shafts and bearings. They also provide some relative position control and no absolute position feedback (at hobbiest prices). On the other there are servos, which typically have weak components. Plastic gears, shafts and bushings which cannot withstand radial load. B…

>However I can't find them anywhere at hobbiest prices. Might put this higher up in your comment. Dynamixel robotics servos exist, but at Dynamixel prices. Weird stuff has weird prices. If anyone made a useful home robot that sold millions of units then robotics servos would get rapidly cheaper, but that hasn't happened yet.

iRobot has sold millions of Roombas. Wonder if there's been any economy of scale bleed-over from that work.
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