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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)

#31

Post by acomms »

philote wrote: post #26
pitched wrote: post #5

The second Google result for this book is a chapter preview from the publisher: https://ptgmedia.pearsoncmg.com/images/9780134032832/samplep... The first result is entire PDF though. I remember back in the old days being a poor student trying to save money spending hours trying to find scans of texts (or making scans in the library). Now it’s the first result in Google! Here’s hoping none of us need to make money thr…

The PDF version is directly downloadable via the original site posted ( http://www.motorsformakers.com/downloads/mfm.zip ). They're making money by selling a print version.

That zip doesn't include a PDF (Arduino and Py files code/design files).

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

#32

Post by Youden »

rq1 wrote: post #20

Does anybody have an address where to shop servos and gearboxes online? Or at least find references through filtering for specific torque/rpm/power/driver resolution... etc.? I hardly can find something worth looking at outside of ebay. A lot of websites don't have public price lists but ask you to fill forms and receive quotes, but I don't want to order thousands of these (yet?)...

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 sheets, figure out what features you want, come up with a list of SKUs, find a seller on Alibaba, AliExpress or eBay and ask them for a quote. Not all of them will be responsive but I didn't find it too hard.

For a vague idea of the price, you can usually get the order of magnitude from the listings on the sites I mentioned.

Ultimately though, servos are treated as industrial equipment and take a lot of work for a hobbyist to figure out. If you're not buying a pre-made kit sold by a hobby store, my suggestion is that you should know the manual like the back of your hand and be able to clearly visualise the full installation process step-by-step before you buy anything, as there's a lot of stuff that can trip you up and a lot of ways you can even kill yourself. Servo drivers don't have nice AC wall plugs for example, they have screw terminals, so you need to be able to wire mains voltage electricity without giving yourself an electric shock or causing a fire. The manuals usually say you should get a professional electrician to handle it. All the cables are non-standard and usually per-series so you need to make sure you buy the right ones. The list goes on...

"Surely I just feed it electricity and it spins" you might think but unfortunately it's not that simple. These motors are deceptively complex things.

As others have mentioned though, Teknic is a thing. Those motors are much simpler, they're designed as drop-in replacements for stepper motors and they have an easy to use online store.

I'm not a fan though, for a similar dollar amount and several orders of magnitude more stress and time, you can have high-end A3 servos from Delta with more features than you'll ever need. The encoder is 24-bit! You'll never be able to accurately use that resolution without precision engineering and temperature control but it's nice to know it's there.

[0]: https://www.damencnc.com/en/ac-servo-drive-400w-asd-a2-0421-...

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

#33

Post by _spduchamp »

If you are looking for a super easy way to put a motor with closed loop motion control, I highly recommend Vertiq (https://www.vertiq.co/) modules. They have a built-in position sensor and microcontroller. They have firmware based anti-cogging for smooth motion. I use them in making computer controlled musical instruments by just hooking up the serial interface to an ESP32 and using the Vertiq API to handle all the hard stuff of controlling motors. They really lowered the barrier to working with motors for me. Just be sure you get the right Kv for your project and use voltage limiting for an extra layer of safety.

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

#34

Post by opwieurposiu »

One thing to note about steppers, If you take them apart they will loose half their torque.

In the factory they magnetize them after assembly. If you take them apart the lower permeability of air causes the rotor to somehow lose much of it's magnetic field. Physicists please chime in, IDK why this happens.

We discovered this after machining some stepper backshells to accept optical encoders.

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

#35

Post by abakker »

Youden wrote: post #32
rq1 wrote: post #20

Does anybody have an address where to shop servos and gearboxes online? Or at least find references through filtering for specific torque/rpm/power/driver resolution... etc.? I hardly can find something worth looking at outside of ebay. A lot of websites don't have public price lists but ask you to fill forms and receive quotes, but I don't want to order thousands of these (yet?)...

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…

I'll say for completeness here (having mentioned Clearpath servos in another comment) that DC clear path servos are totally fine for "semi" industrial uses. I have them on a bed mill I am restoring, and with a good ballscrew I can easily move a 300lb Z axis at 200inches/minute without torque saturation.

That said, they are simple because they are limited. They give you only 3 inputs: Enable, Step, Direction. they give you one output called "High level feedback" and BOY OH BOY is it high level. it is basically only useful for basic error detection. In the software you have pretty cool tuning options - a visual oscilloscope, the RAS feature (which is really good for DIY CNC machines), and encoder resolution selection.

A DMM, or especially a Delta, will give you a lot more IO to the motors, and a lot more stuff to play with. E.g. direct access to the encoder position (even if the motor is not active), many more error states, warnings, etc. and some more condition specific tuning.

Last bit on clearpaths. I've been talking about the SDSK series motors. those are controlled from an external controller through pulses like stepper motors. They have other series of the same motors that interface differently. Specifically, they have some motors designed to interface with microcontrollers and have a really nice set of C libraries for doing all the basic motor control stuff. If you are building things like conveyor belt automations or material handling stuff, the clearpaths are very much an "easy button" compared to nearly every other kind of motor on the market IMO.

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

#36

Post by oakwhiz »

opwieurposiu wrote: post #34

One thing to note about steppers, If you take them apart they will loose half their torque. In the factory they magnetize them after assembly. If you take them apart the lower permeability of air causes the rotor to somehow lose much of it's magnetic field. Physicists please chime in, IDK why this happens. We discovered this after machining some stepper backshells to accept optical encoders.

This is fascinating, I hope someone knows the answer.

Is it possible that they magnetized the teeth of the rotor as a Halbach array?

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

#37

Post by dekhn »

_spduchamp wrote: post #33

If you are looking for a super easy way to put a motor with closed loop motion control, I highly recommend Vertiq ( https://www.vertiq.co/ ) modules. They have a built-in position sensor and microcontroller. They have firmware based anti-cogging for smooth motion. I use them in making computer controlled musical instruments by just hooking up the serial interface to an ESP32 and using the Vertiq API to handle all the…

Do you know if this would be appropriate in, for example, a microscope stage? I use steppers (open loop) to move a stage on bearings, and I would prefer to have closed-loop with position sensing (not movement- actual position- because a single dropped step will ruin an acquisition).

I already work with ESP32 and have done closed-loop DC motor stuff before, so I'm just curious if this is something I could drop in and be happy with.

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

#38

Post by FatActor »

One problem I always run into with rotary motion: gearing. Finding gears of the right diameter, thickness, and thread pitch is always such a stumbling block for me. Most sites that sell gears to fit their motors have a small selection, and sites that sell gears are very hard to navigate (only to find out they don't sell in quantities <1,000 units). I end up having them laser cut out of HDPE online. Wish there was an easier solution.

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

#39

Post by jerzmacow »

opwieurposiu wrote: post #34

One thing to note about steppers, If you take them apart they will loose half their torque. In the factory they magnetize them after assembly. If you take them apart the lower permeability of air causes the rotor to somehow lose much of it's magnetic field. Physicists please chime in, IDK why this happens. We discovered this after machining some stepper backshells to accept optical encoders.

Perhaps when you slide the rotor past the stator lamination, it demagnetises it a bit? Like those screwdriver demagnetizers

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

#40

Post by iancmceachern »

FatActor wrote: post #38

One problem I always run into with rotary motion: gearing. Finding gears of the right diameter, thickness, and thread pitch is always such a stumbling block for me. Most sites that sell gears to fit their motors have a small selection, and sites that sell gears are very hard to navigate (only to find out they don't sell in quantities <1,000 units). I end up having them laser cut out of HDPE online. Wish there was an…

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 prototype it's certainly fine.

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