[HN Gopher] Motors for Makers: A Guide to Steppers, Servos, and ...
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Motors for Makers: A Guide to Steppers, Servos, and Other
Electrical Machines (2015)
Author : teleforce
Score : 213 points
Date : 2023-01-25 10:21 UTC (12 hours ago)
(HTM) web link (www.motorsformakers.com)
(TXT) w3m dump (www.motorsformakers.com)
| frankus wrote:
| VESC (vesc-project.org) is worth checking out if you need (low)
| triple digit watts and a PMSM/BLDC motor is suitable.
|
| You can interface via UART and CAN and a bunch of other
| analog/digital options as well
| mvidal01 wrote:
| The url is https://vesc-project.com/ I think. vesc-project.org
| didnt work.
| WJW wrote:
| One of my projects for this year will be getting a slightly
| bigger AC motor (say a 0.5-1 HP asynchronous motor) and
| integrating that into a more well-finished project. I have a
| decent grasp of the software parts and have done some projects
| with servos and steppers, but using bigger motors has eluded me
| so far.
| waynesonfire wrote:
| how does one protect the microprocessor from the back EMF? Do you
| need an optoisolator?
| gwynplaine wrote:
| That answer would depend on the type of motor.
|
| For a DC motor, they are rarely connected directly to the
| microcontroller. But you can put a diode across the motor
| terminals to minimise any back EMF.
|
| A stepper would typically have a driver circuit between the
| microcontroller and the motor.
|
| A small servo would usually just need one signal connection to
| the microcontroller, there's no back EMF via that path. You
| would of course also need common ground.
| frowin wrote:
| in case the author is reading this:
|
| I would suggest to add an affiliate tag to the Amazon link. I
| once heard that authors make more from the affiliate program than
| from the book itself. Maybe a modern anecdote but yeah... costs
| you nothing. As you don't get rich by the book itself, atleast
| you get some few dollars through the link!
| FatActor wrote:
| 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.
| mstudio wrote:
| I came here to say exactly the same thing. I'd love to find a
| kit or gearbox than can gear up/down a simple stepper motor for
| Arduino projects. The HDPE laser cut is a good idea though,
| I'll give that a try.
| GeorgeTirebiter wrote:
| 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
| you only need to 'transform' that motion a little bit.
|
| I also can cut involute gears on the (mini-) lathe or mill. You
| want to practice this skill because being off just a little
| means you have a useless part. I have found 3D printing more
| convenient and forgiving.
| marcosdumay wrote:
| > 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.
| [deleted]
| Animats wrote:
| Stock Drive Products and Berg are the classic US small gear,
| bearing, and accessories suppliers. I've used those two. KHK
| (Kohara Gear Industry Co., Ltd, Japan) is now active in the US.
|
| The classic Boston Gear Gearology course is no longer online at
| Boston Gear, but there's a copy here.[1] This gives a quick
| overview of the minimum you need to know about specifying
| gears.
|
| [1] https://www.me.psu.edu/sommer/me360/gearology.pdf
| iancmceachern wrote:
| 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.
| doctorwho42 wrote:
| It really comes down to the fact that gear shaping/cutting
| machines are quite specialized machines. Therefore demand a
| higher cost to buy (machines cost) and setup (tooling cost).
|
| For example a single gear shaper cutter is on average
| $700-$1000, and that's for a pretty standard and brand new
| cutter.
|
| So without taking into account actual time to set up the
| machine, program it, and feed it material. You are already
| having a high overhead. So the only real way to deal with that
| cost is in volume or cost.
|
| But when looking at the hobby market, volume is out of the
| question (who wants to buy >1000 of one gear for a personal
| project) and cost is out of the question ( if it's so
| expensive, I might as well 3D print or laser cut or waterjet
| some)
|
| So it's an odd market to get into.
| Steltek wrote:
| If you watch enough tool teardowns (AvE, etc), most gears are
| sintered metal or plastic. I'm sure large industrial
| applications use machined gears but it looks like consumer-
| prosumer space goes for much cheaper fare.
| abakker wrote:
| standard gear cutting arbors aren't that expensive, but are
| often for standard module gears and the gear form is an
| approximation that applies to a given range of gears.
|
| e.g. https://www.amazon.com/EVNSIX-Involute-Cutters-Milling-
| Machi...
| dsfyu404ed wrote:
| The "frequently bought together" set there is a
| surprisingly good combo for an algorithmic pick.
| abakker wrote:
| Belt drives are also very annoying. Naming conventions are
| inconsistent and obtuse. Parts materials differ, and a whole
| lot of stuff seems to be custom.
|
| in Servos and steppers, there are also weird mixes of metric
| and standard sizes - e.g. Nema 34 motors often have 1/2"
| (12.7mm) shafts with 5mm keyways. No idea why.
|
| Finding gears or pulleys for my purposes has 100% of the time
| resulted in some machining and lathe work to take off the shelf
| parts and make them work for my applications.
| [deleted]
| TheRealWatson wrote:
| Another good resource is Jeremy Fielding's YT channel.
| asddubs wrote:
| I was going to post this too! He's got a great series on motors
| schaefer wrote:
| I agree, I had a custom controller board for a pair of huge
| electric motors go bad. I was able to bring the machine back to
| life using only what I learned form Jeremy Fielding's channel.
| fumoto wrote:
| [dead]
| pitched wrote:
| 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 through writing...
| sugarkjube wrote:
| > Here's hoping none of us need to make money through
| writing...
|
| i'd assume pretty soon hardly anybody can still make money
| through writing as it's easy to ask chatgpt "write me a book
| titled Motors for makers: A Guide to Steppers, Servos, and
| Other Electrical Machines".
|
| or maybe i lack vision, maybe soon chatgpt can answer "should i
| use a stepper or a servo for my robot arm", or "how do i wire
| up stepper xyz on CNC machine ABC", or even "design a 3d
| printer with parts <$100 on ali express".
| sugarkjube wrote:
| seems i lack vision.
|
| should i use a stepper or a servo for the robot arm i'm
| designing ?
|
| Stepper motors are best for precise, open-loop control
| applications where position and speed can be accurately
| controlled. They are also a good choice for low-speed, high-
| torque applications. However, they tend to be less efficient
| than servo motors and can generate more heat.
|
| Servo motors are best for closed-loop control applications
| where precise position, speed, and torque control are
| required. They are also more efficient than stepper motors
| and generate less heat. However, they tend to be more
| expensive and less precise than stepper motors.
|
| Therefore, if precise control and speed of the arm are the
| most important factors, a stepper motor may be the better
| choice. But if overall efficiency and cost are more
| important, a servo motor may be a better option.
| abakker wrote:
| This advice is not good.
|
| Robot arms should use harmonic drive gearboxes and servos,
| IMO. In practice, if the loads are not massively high, the
| important thing is closed loop steppers or servos, with
| accurate homing routines and good error handling.
| diydsp wrote:
| Agreed. It sounds like a junior engineer bs-ing an
| interview after reading lots of amateur forums.
| jakzurr wrote:
| Maybe they _really did_ ask chatgpt?
| Animats wrote:
| It depends on the kind of load and the job. Harmonic
| drives tend to shear teeth if they get a shock load. It's
| good to have a back-driveable gear train, so that if the
| arm hits something or is overloaded, the forces push back
| to the motor, and the controller can see them and stop or
| deal with the problem. For something like a pick and
| place machine, you don't need that, but if you're trying
| to put screws into holes and might miss, you do.
|
| 3-phase servomotors (which used to be called "brushless
| DC servomotors") are much more available than they used
| to be. Drone motors are tiny 3-phase motors, and can be
| controlled as servomotors. The drone industry has done a
| lot to make such motors cheaper. The controllers are much
| smaller and cheaper now, too. They used to be the size of
| a book or worse. But they're still more expensive than
| they should be. I was once at a trade show talking to a
| rep from a motor company I'd used, and noticed they now
| sold controllers, too. He said, yes, they had to get into
| the business because others were selling controllers for
| 10x the cost of the motor, and they cost about the same
| to make.
|
| For a long time, you had to bolt the encoder on the back
| of the motor, and encoders cost way too much. Motors with
| built-in encoders have become more common.
|
| "RC servos" from model aircraft are cheap, but crappy
| actuators. They're advancing from 1970s pulse width
| modulation control to 1980s serial, and for under $20 you
| can now get some force feedback.
| abakker wrote:
| Very good point about harmonic drives and
| backdriveability. I had forgotten that problem.
| GeorgeTirebiter wrote:
| When we build actuators in the Leg Lab, every actuator
| had some electrical feedback element. For example, leg
| length actuator had a resistive strip that was as long as
| the leg's travel. A fixed 'wiper' allowed us to therefore
| have a potentiometer, giving a leg-length-proportional
| voltage on the wiper when top and bottom were driven by a
| constant current source. This was used in a 500Hz
| (sometimes 1 kHz) servo loop for position control.
|
| (somewhat related): We also had a velocity sensor on the
| legs -- a simple coil of wire and a magnet (but COTS).
| This gave us a Velocity signal directly -- rather than
| differentiating the position measurements. Velocity
| estimates made by differencing position measurements tend
| to be noisy, and filtering esp FIR filters introduces
| phase delay -- things you do not want. Lesson was: If at
| all possible, get a sensor that senses the quantity you
| want to sense, so you do not have to integrate or
| differentiate to get your desired quantity. It's the same
| reason we had a REAL gyroscope, and not a rate gyro (as
| in most MEMs IMUs -- in IMUs they call them 'gyroscopes'
| but they are actually 'rate gyroscopes' -- they only
| directly measure "theta-dot").
| Animats wrote:
| > Velocity estimates made by differencing position
| measurements tend to be noisy, and filtering esp FIR
| filters introduces phase delay
|
| Yes. Which is why you see encoders for sale with a
| zillion points per rev. Not because the position is that
| precise, but so that you get enough events per second to
| calculate velocity. Actual tachometers, which are little
| DC generators, are sometimes used in servo systems, but
| not often. The last time I saw one, it was on a mainframe
| tape drive.
|
| You do want velocity and force feedback if you're doing
| anything beyond pick and place in a totally controlled
| environment. Simple preprogrammed blind movement is most
| of industrial robotics, though. There are fancier
| systems, but most of them don't sell, because the
| engineering cost exceeds the value add. Sometimes you see
| a little force feedback to get something inserted
| properly, but more often you see some mechanical spring
| setup to get the same result.
|
| I used to be into legged locomotion, but there's no
| profitable market. Many of the technical problems have
| been solved, though. The sensors and actuators are good
| enough. Electric motors finally are strong enough. (It's
| sad that Schaft went under. Google bought them and dumped
| them.)
| philote wrote:
| 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.
| acomms wrote:
| That zip doesn't include a PDF (Arduino and Py files
| code/design files).
| boredemployee wrote:
| man back in my college days (2006-2012), it was a pain in the
| ass to have books (materials science) and find stuff online.
| anyway, i was known as "the king of pdfs". because i always
| knew how to search things. but now the game is in a whole
| another level and my fame would fall into oblivion!
| cpp_frog wrote:
| My trick was searching +"index of" on Google or something
| like that, I could find all sorts of books that way. What
| were your tricks?
| cpach wrote:
| filetype:pdf
|
| These days, Libgen is much more convenient.
|
| With that said, I personally prefer buying an official book
| if available, so that the author can get their royalties.
| Many publishers even offer DRM-free ebooks.
| dsfyu404ed wrote:
| When I can't find a pdf I like buying old editions on
| eBay for $10 or whatever. I find that having to browse
| through more info to actually find what I'm trying to
| reference leads to better ancillary knowledge and
| understanding than CTRL+Fing a pdf.
| rq1 wrote:
| 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?)...
| Youden wrote:
| 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-...
| rq1 wrote:
| 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. All at once yeah!)
|
| I found these for instance on eBay:
|
| * https://www.ebay.com/itm/393967889048
|
| * https://www.ebay.com/itm/275442630163
|
| I can get from them more than 120Nm with the appropriate
| planetary gearbox without sacrificing too much speed and even
| more with gas springs compensating the static loads...
| theoretically... but I'm a bit skeptic about the announced
| 12Nm and the 51200microsteps/rev resolution for instance.
|
| I think it's better (in my case) to have access to maximum IO
| on the encoder side.
|
| I'll double check the electrical installation with a pro for
| sure, I already did a mistake in the past that almost
| destroyed the house boiler in the middle of the winter...
| lesson learned.
| abakker wrote:
| 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.
| iancmceachern wrote:
| I agree, love their motors for simple applications where
| you don't want to write software
| krisoft wrote:
| > Does anybody have an address where to shop servos and
| gearboxes online?
|
| Depends on what kind you are looking for.
|
| In the hobby sphere I know about Servocity, Hobbyking, Pololu,
| adafruit.
|
| If I were looking for something bigger, more professional range
| I would check if maybe Farnell or RS Components have it.
| iancmceachern wrote:
| I second teknik motors, also check automation direct,misumi, or
| even ebay/Ali express
| abakker wrote:
| If you are doing servos and not well versed in these things, I
| highly recommend clearpath servos from teknic. The wiring is
| easy and their tuning support is very good (if the auto tune
| doesn't work). If you need more power, or AC servos, I suggest
| DMM Dyn4 drives and servos.
|
| Finally, if you need gearboxes, stepper online has good ones
| that have held up well for me.
|
| Source: have built/converted several CNCs.
| jbay808 wrote:
| I'll second DMM. Unlike most servo companies, they post their
| pricelist, making it easy to figure out which tradeoffs you
| need to make to stay on budget: https://dmm-
| tech.com/pricing.html
| abakker wrote:
| Another thing as a hobbyist: AC servos can save you money
| vs high performance DC power supplies. they also simplify
| some kinds of wiring.
|
| in a typical 3 axis mill with 3 motors of hobby scale, you
| might buy a teknic IPC5 power supply and a a power hub and
| a bundle of cables and a backup 24v din rail supply for
| about $370 after tax/shipping. for a DMM DYN 4 setup, you
| just run AC power to drives with standard wire and
| terminals.
|
| If your control box is tight, it can also pay to use AC
| servos because then you don't have the power supplies in
| your box. They may be more expensive / motor but can be way
| easier to deal with later.
| slicktux wrote:
| Try servocity...
| diydsp wrote:
| https://www.omc-stepperonline.com/
|
| https://www.pololu.com/
| opwieurposiu wrote:
| 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.
| oakwhiz wrote:
| This is fascinating, I hope someone knows the answer.
|
| Is it possible that they magnetized the teeth of the rotor as a
| Halbach array?
| adrian_b wrote:
| Any permanent magnet demagnetizes partially whenever it is
| taken out of a closed magnetic circuit.
|
| If the magnet is made from a material with very high
| coercivity, the demagnetization may be negligible, but it is
| always recommended to store permanent magnets only with a
| piece of soft iron in contact with their N and S poles.
|
| To reach the maximum remanence possible for a given material,
| a permanent magnet must always be magnetized after being
| assembled in the final magnetic circuit.
| GeorgeTirebiter wrote:
| What about, say, Neodymium magnets?
| https://www.kjmagnetics.com/neomaginfo.asp
|
| What I'm asking is: are Neodymium magnets NOT used in these
| applications?
| jbay808 wrote:
| They are used in these applications, typically very high
| grade, unless you're buying a legacy product line.
|
| In, say, a hybrid stepper the magnet is usually a wide
| thin round disc, sandwiched between two steel rotor
| lamination stacks. With the link below you can examine
| the BH curve and load line for a O20 mm N52 disc magnet,
| 2mm thick, at 20 degrees C. (It's not exact because this
| assumes a magnet in free space and neglects the steel of
| the rotor - but it's an illustration).
|
| https://www.kjmagnetics.com/bhcurves.asp
|
| You'll notice that the load line (which assumes the
| magnet is in free air) is already landing within the
| "knee" where the intrinsic magnetization starts dropping
| rapidly. That's working too far along the hysteresis
| curve, where the poles are already starting to flip and
| demagnetize.
|
| However, if that magnet were surrounded by the steel of
| the stator, the high permeability of the magnetic circuit
| would put the load line at a steeper angle, where the
| magnetic field through the magnet would be much higher.
| Small changes in permeability around that point would not
| damage the magnet, but allowing it to fall all the way
| down below the knee-point would. It would not be
| completely demagnetized by that, but it would lose some
| of its original strength.
| jerzmacow wrote:
| Perhaps when you slide the rotor past the stator lamination, it
| demagnetises it a bit? Like those screwdriver demagnetizers
| jbay808 wrote:
| If you're familiar with electronics: Imagine you have a current
| source, driving 1 amp through a variable resistor set to a very
| low resistance. It only takes less than a volt to sustain that
| current, so your current source is quite happy to do this.
| Then, without turning off the current source, you increase the
| resistance: now the current source needs a lot more voltage to
| sustain that current.
|
| From the current source's point of view, the voltage across the
| resistor looks indistinguishable from a voltage source pushing
| back against it. Even though that voltage is coming from the
| resistive load, even though that voltage only exists across the
| resistor because of the 1 amp that the current source is itself
| driving, the load acts the same as a voltage source fighting to
| drive current _backwards_ into the current source.
|
| Imagine that your current source is not ideal: it has voltage
| limits. If you want to squeeze the most power out of your
| current source, you'll set the resistance up such that the
| resulting output voltage is near the limit of what your current
| source can handle while still supplying 1 amp. If you increase
| the resistance further, you'll exceed the voltage rating and
| possibly damage your current source. Then even if you return
| the resistance to a low level after that, you might not get 1
| amp anymore from that damaged source.
|
| All of this has been an analogy. Permanent magnets are a lot
| like non-ideal sources that cannot turn off. To squeeze the
| very most out of the magnet, you want to configure the load
| such that it's driving the magnet to its limits. When you
| remove the rotor from the stator, it now has to push magnetic
| field through air, rather than through steel. This increases
| the effective demagnetizing load working against the magnet
| (known as "reluctance", analagous to resistance). It's no
| different from the magnet's point of view than if you'd looped
| an electromagnet wire around it fighting against its
| magnetization. Permanent magnets are magnetized through a
| hysteresis process, and with a strong enough demagnetizing
| field, the internal domains can flip and the magnet gets
| demagnetized.
| _spduchamp wrote:
| 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.
| sbierwagen wrote:
| (Price starts at $130)
| iancmceachern wrote:
| Another product in this vein, Teknik motors. They're fully
| integrated, give them power and Connect to them via USB amd
| program it. Once you program it you can just use the gpio pins
| on the motor to wire up switches or other types of control.
| Super easy
| HeyLaughingBoy wrote:
| Another plug for Teknik. Only used them once, but it was the
| easiest closed-loop DC servo I've ever used: entire project
| was done in less than a day.
|
| Contrast with Advanced Motion Controls where it took days of
| coding before I could even talk to the controller. Not to
| knock a-m-c: their product is very fast and precise, just far
| less software help to get going. Manuals are complete but
| extremely dense reading.
| dekhn wrote:
| 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.
| iancmceachern wrote:
| Yes it would
| gwynplaine wrote:
| 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. But they do allow control of absolute
| position.
|
| For many robotics projects, a hobbiest has to choose between
| servos which are physically weak, or steppers which can tear the
| project apart if they don't home correctly. And of course the
| hobbiest has to roll their own safety/endstop system every time.
|
| I'd love something physically like a Nema 14/17 stepper but with
| a servo interface. However I can't find them anywhere at hobbiest
| prices. Why are there thousands of good value steppers and
| thousands of models of servos, but nothing in between, I wonder?
| jbay808 wrote:
| It's worth distinguishing between two completely different
| types of "servos": RC hobby servos, and industrial-type servos
| which are robustly built like steppers but significantly more
| fast, accurate, efficient, and powerful. They are hard to find
| in Nema 14/17 sizes but not impossible.
|
| RC servos typically have an analog or PWM signal interface.
| That would usually not be accurate enough for an industrial
| servo in positioning mode. Industrial servos, like steppers,
| have a digital interface which might be a serial format or
| STEP/DIR pulse train. Some drives will accept a -10V to +10V
| analog signal for velocity or torque control mode.
|
| Anyway, here are some Nema 14/17-sized industrial servos with
| online pricing, which might be what you're looking for?
|
| https://en.nanotec.com/products/2262-smart-servos-motors-wit...
|
| https://catalog.orientalmotor.com/viewitems/l-categories-ser...
|
| Or many companies offer stepper motors with built-in encoders
| and controllers to prevent missed steps:
|
| https://catalog.orientalmotor.com/viewitems/az-series-absolu...
|
| https://www.zaber.com/products/stepper-motors/X-NMS-E
| gwynplaine wrote:
| Thanks, lots of helpful links there. Much appreciated.
| Although quickly checking, I suspect they could be over an
| order of magnitude more expensive than the hobbiest
| equivalents.
| fest wrote:
| Somewhere between 1 and 2 orders of magnitude more
| expensive though not without a reason- increased demands
| for design, manufacturing, testing, reliability and having
| to support the product for several decades costs money.
|
| The cheapest of RC servos have a lifetime of a couple
| hundred hours max, even at less than half of their max
| torque (if their manufacturers would even specify what is
| the rated torque). I have one fail after two days of
| operation with a full rotation every 15 seconds with very
| light load. There are of course properly built RC servos-
| with serial communication for feedback, metal gearbox,
| brushless motor- but those start at ~50EUR-100EUR.
|
| IMO the best bet for hobbyist is NEMA17/14 motor with a
| driver that has rotary magnetic encoder on them- there are
| cheap and open source options for that.
|
| Next best thing would probably be a BLDC motor (optionally-
| geared) with SimpleFOC.
| sbierwagen wrote:
| >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.
| HeyLaughingBoy wrote:
| This is an important point. The low prices of a lot of
| hobbyist-grade motors and motor controls are driven by their
| use in consumer electronics. I can buy an entire 4-axis
| stepper motor controller with drivers for under $100 because
| they are made by the thousands for laser cutters and 3D
| printers. OTOH a similar professional controller will set me
| back at least a few hundred $$, if not a few thousand due to
| being designed for a harsher environment and for higher
| reliability.
| CubsFan1060 wrote:
| 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...
| conductr wrote:
| I've been diving in the past few years. You end up having to
| learn a lot of things. And need a lot of tools. Id compare it
| to woodworking. You can't really "just start" woodworking one
| day without buying some tooling and supplies. I've amassed a
| big little workshop over the last few years.
|
| I find the best way to get started is to have an idea of
| something you want to make, then just buy what is needed for
| that.
|
| Pick a microcontroller first. Arduino is popular and well
| documented. Raspberry Pi is overkill in my opinion. I find I
| like the NodeMCU. The mini D1 specifically as it as an ESP8266
| for Wi-Fi support. If you need Bluetooth or whatever look for
| the ones you need. And use the Arduino IDE to program and code
| it. From there, most motors need a motor drive and there's a
| million of those and it's typically a separate board (breakout
| board). You want to stock up on breadboarding supplies.
|
| Openbuilds.com store is great if you have the need and budget
| for this type of items. You can get anything to build most any
| type of contraption and generally know it's going to fit
| together if you plan correctly.
|
| YouTube is your best resource. I like reading text when it
| comes to software but reading electrical diagrams is hard for
| me and it's so much easier if I can watch someone else. They
| often tell you the little gotchas too.
|
| Amazon is good for almost everything else. If you're like me
| you'll end up placing 50 orders in the first 2 months. The
| hardest part is no retail store, even hobby shops, stock these
| types of items.
|
| I will say I don't find kits particularly helpful. They can be
| fun, but at the end of it you've just followed the directions
| and didn't really learn anything. It's like putting an ikea
| dresser together, if you're trying to learn how to build
| furniture it's not very helpful.
| dragontamer wrote:
| 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 electrical. And I have no idea how
| to study mechanical engineering.
|
| -------
|
| Like: how does a damn printer pick up just one piece of paper?
| Yeah yeah, there is a motor involved, but it's not the hard or
| interesting part.
|
| There has to be little rotating mechanical fingers, the shape
| of the basin, the winding path the paper takes internally. Who
| designed that? How do I study that stuff?
| sacrosancty wrote:
| A lot of that stuff is internal industry knowledge that
| people learn by working for a company that already does it.
| It probably started out with people experimenting. You don't
| learn that in a mechanical engineering degree.
|
| Though printers use rubber rollers on the top sheet in the
| pile so the friction between the rollers and sheet is greater
| than the friction between sheets and therefore only the top
| sheet is fed by the rollers.
| HeyLaughingBoy wrote:
| ...and often a second roller on the underside, slightly
| forward and running in the opposite direction to strip off
| any sheets that adhere to the top one.
| HeyLaughingBoy wrote:
| > Like: how does a damn printer pick up just one piece of
| paper?
|
| Ah, the task of Singulation! The answer is "with a lot of
| difficulty" :-)
|
| I used to work for a large corp whose specialty is building
| high-speed paper handling machines for offices and industry.
| It is a far harder task than it seems on the surface.
| fellowmartian wrote:
| IMO buying a hackable 3D printer is the best way to get
| practical experience with kinematics, motors, stepper
| controllers, etc. The standard recommendation is to buy an
| Ender 3, but it's very slow by today's standards. I'd recommend
| Flsun V400, it prints almost as fast as the state of the art,
| but has no proprietary components, and comes (almost) pre-
| assembled.
| bartlettD wrote:
| EE is my day job so I may be biased towards more formal
| resources.
|
| Sparkfun, Adafruit, etc have some good stuff to get you off the
| ground and building projects almost right away. I think they're
| great "taster" in how circuits work and what some of the
| components are for.
|
| Khan Academy has a course for EE, I haven't used it but I've
| used the site for other stuff like brushing up of my math.
|
| Manufacturers actually make some really nice training
| materials, if you like analogue stuff, TI's Precision Labs
| series is a great resource for that. Analog Devices has an
| intro to electronics wiki series too.
| https://wiki.analog.com/university/courses/electronics/text/...
|
| For a deeper look, an undergraduate electronics textbook will
| hold your hand from the very basics through to more advanced
| concepts. You can ignore some of the more advanced stuff like
| AC analysis and non-linear components for the most part (Unless
| they interest you!)
|
| I learned from this book (https://www.pearson.com/en-
| gb/subject-catalog/p/electronics-...) and found it quite
| approachable in how it laid out the basics before
| contextualising them as systems.
|
| Theres also the famous Art of Electronics which is a good book
| but personally feels a bit dated (even with the new edition)
| and really analogue heavy. A good reference manual though.
| [deleted]
| piotrrojek wrote:
| Am I missing something? It doesn't seem like this book is
| available online to read, just TOS and link to Amazon to buy
| paperback version.
| unwind wrote:
| Also it seems to be from 2015, which makes it almost more
| strange to post (especially without tagging the year).
|
| Perhaps it is just being ackowledged as a time-less epic
| classic, I don't know.
| pca006132 wrote:
| Doesn't seem so, classics will probably not have dedicated
| chapters for showing how to control motors with Arduino and
| such. I think it is nice to know the differences between
| different motors, but I would rather read an article about
| this instead of buying a book.
| qwertox wrote:
| Felt like an ad, even though I could imagine that someone would
| want to post this out of normal interest.
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