remix logo

Hacker Remix

How Servo Motors Work

106 points by kaycebasques 1 day ago | 25 comments

viraptor 19 hours ago

> Understanding the technical aspects of a servo motor and how it works

I don't feel like the article explains that at all. They explain the control signal and what the servo does as a result. The "how" in between is completely missing though. How is that pulse translated? How does the feedback work? What are the safety mechanisms involved?

gsf_emergency_2 18 hours ago

MarkSweep 6 hours ago

I think this is a pretty good overview of how motors work and how you can write algorithms to control how much torque they generate by varying the PWM:

https://www.actronic-solutions.de/files/actronic/FTPROOT/Fie...

relaxing 19 hours ago

That’s because the control circuit is hidden in a monolithic IC. If you’re really curious, here’s a datasheet for an old fashioned design with a block diagram and theory of operation described that should give you some hints. https://www.meditronik.com.pl/doc/plus/zn409.pdf

If that sort of thing interests you, there’s a whole field of control theory to study.

dcrazy 1 day ago

I’ve noticed that distributors (Jameco, Mouser, etc) have a surprising number of introductory education articles. I’ve seen this pattern on websites for car dealerships and HVAC installers, so I assumed it was for SEO purposes. But electronic parts distribution seems like a much more niche audience; why bother with SEO?

analog31 1 day ago

I think it's just a tradition in the electronics world to write and publish hobby and educational articles. It dates back to well before the the Internet. People enjoy this interaction, and the distributors give them space for it.

People like HVAC installers -- I've seen most of that on YouTube, where there's a chance of monetizing the content. I've repaired nearly every appliance in my house, thanks to blogs and videos posted by strangers.

dcrazy 1 day ago

Indeed. Vancouver Carpenter got me through a minor drywall repair job.

larrywright 21 hours ago

He's fantastic. I still suck at drywall work, but I suck way less after watching a bunch of his videos.

MisterTea 1 day ago

It brings you to their site as well as advertises a specific component or range of components from a manufacturer.

The Digikey articles I've come across are well written. This article however is artificially inflated using SEO style writing. I mean after they supposedly explained servo motors you'll find this ugly sentence further down: "Still, how does a servo motor work?" I mean holy shit man, do you even care about your writing or the subject? Likely not. And really, the article is so light on details its barely technical and only talks about the RC servo. This is pretty much junk.

HeyLaughingBoy 23 hours ago

Electronics distributors have published educational material for decades. Knowing how something works and how to choose the best option reduces their support burden and itself a form of marketing.

Omega Engineering used to (still does?) publish a set of absolutely massive hardcover catalogs on sensors and industrial controls that contained detailed tutorials and theory of operation. In some cases, they published entire books devoted to teaching you how stuff worked. Their Temperature Sensors Handbook always had a place on my bookshelf for many years.

cbhl 24 hours ago

If I recall correctly these pages are useful for teachers and students, and Jameco has relatively high-touch education sales (for example, their kitting program: https://www.jameco.com/Jameco/workshop/education-center/educ...).

I want to say that I remember seeing this page in high school in the late 00s, although the Internet Archive only seems to go back to 2012 for this exact URL.

Animats 20 hours ago

It's about how radio control toy servos from the 1970s work. Annoyingly, those pre-computer dumb devices with no feedback output still dominate the low end of mechanical output devices.

HeyLaughingBoy 2 hours ago

Yeah, but they're cheap and basically trivial to use. Cheap enough and trivial enough that they can replace solenoids in a lot of use cases.

One of my most amusing applications was the client who put an R/C servo on the choke cable of a carbureted generator motor instead of spending more money to buy the fuel-injected version. Servo cost about $5 and we were already measuring air temperature and had a PWM output available.

namibj 17 hours ago

Makes me wonder if the generic servos of the described kind are really close enough to the performance a cheap-class servo can have, or if modern advances in monolithic power stage ICs could allow a servo free of sliding movement (no brushes, no wiper potentiometer (maybe a capacitively coupled differential sensing of angle, or the tricks of the cheap digital calipers with their iirc nonius-like scale read through several parallel tracks of non-touching capacitive electrodes?), instead just a clever chip digitally controlling a brushless electric machine using the feedback sensing available to it).

Being able to run an even just very simple digital controller allows things like severely dropping negative feedback gain at a resonance frequency of the larger system. And so much more.

Animats 15 hours ago

The nice thing about using a potentiometer for position sensing is that you don't have to home the thing.

There are lots of alternative sensors, but most are bigger, heavier, or more expensive. If 1% precision is good enough, pots are fine. The next step up is Dynamixel servos, which have a nice daisy-chain digital interface, encoders, about the same form factor as toy-type servos, at about 10x the price.[1]

[1] https://www.robotis.us/dynamixel/

arbitrandomuser 10 hours ago

I just want to put this hack here which enables the toy servos with a very high accuracy and repeatability

https://youtu.be/ECLrLupFW10?si=dQPSq-hjMTaVGuQS