paper: Build your own PWM signal generator for testing motors and servos

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#1

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Build your own PWM signal generator for testing motors and servos
by: WDB

Instructions on how to build a PWM signal generator to test motors and servos. Relatively low-cost components make this project affordable and fun for the electrical team.

This project uses easy to find and affordable components to construct a Pulse Width Modulation signal generator that can be used to test motors and servos. The ability to bench test motors, subsystems, or prototypes without the need for RoboRIO or special software can save time. It is also a fun and and interesting project for the electrical team!

Building a PWM signal generator.pdf (2.8 MB)

#2

Thanks for sharing !

#3

This looks very interesting, but you might be better served buying a standard RC PWM generator for a couple dollars, or at least sourcing components from places like Ebay or Aliexpress to save on costs.
I do like the addition of a small battery though, very useful to have that on there! Definitely beats powering it from an Anderson connector.

#4

Yes, thanks for providing info on this!

One minor question:

This is the program used for our device. It’s not perfect, nor is it intended to be.

Looks like clean code to me! Why not strive for greatness? :slight_smile:

#5

Can you be more specific, like a buy link? I can’t find the component or board you’re talking about.

I did find a forum of EEs talking about hacking something together out of a set of 555’s, but that’s way harder for me to do than program a cheap microcontroller.

#6

If you google “Servo Tester” you’ll find a lot of different options for cheap (less than $10). I’ve used a generic one (don’t remember where I got it from), and it worked pretty much as expected with PWM motor controllers. If you can find it on CD, I think Ether posted something about one that he recommended a year or two ago.

#7

My bad, I should have posted a link:
https://www.ebay.com/itm/Multi-RC-Digital-ESC-Servo-Tester-3CH-ECS-Consistency-Speed-Controler-Power-HK/223007104269?epid=2148788103&hash=item33ec425d0d:g:RY4AAOSwLIhZg2dU
There’s also a trendier version:
https://www.ebay.com/itm/HJ-Digital-Servo-Tester-ESC-Consistency-Tester-for-RC-Helicopter-Aircraft-Car/332389104848?epid=1874292685&hash=item4d63ef3cd0:g:9E0AAOSw9gRZ5Zwr

#8

Why does there always have to be a Negative Nellie :mad: every time someone presents a cool unique solution to a problem that they have.

It would have been extremely prudent to have actually read ::rtm:: the document and just maybe one would have found this statement:

Building a DIY PWM driver also offered a great opportunity for the electrical team to gain a little more experience in designing a functional solution, sourcing quality components, programming a microcontroller, and some human-machine interface development experience.

FIRST is all about technology, learning, applying what’s been learned.

#9

I did read through the document, and I liked what I saw. I wanted to implement it on our team for electrical trainings (we have been looking for “fun projects” for a while now) and so I liked the look of this. But a $50 price tag is too high to spend on trainings for just a couple of people.
If you look through my old images, you’ll see that I’ve built a DIY PWM generator for FRC before, and I know what these things can cost. There’s no harm in swapping out some of the pricier components for cheaper alternatives.

#10

Thank you!!

I’ve been thinking about building OP’s box for a couple years, but had never found those devices before - the power of the right search term!

Whoa :eek: slow your roll buddy - suggestions of improvements are a sign of respect around these parts. :]

#11

Wow! $50 is too much for training a “couple” of people?? So sad!

I feel real bad for your students.

SMH!

#12

Improvement?? Respect?? You’ve got to be kidding!

Anytime there is a “but” it’s all negative from there no matter what else is tacked on as an alleged suggestion for improvement.

Once you’ve tossed in a “but,” you’ve shot down the idea, caused dismay that the idea is unworthy and anything further stated in the message isn’t received. Furthermore, a “but” does not convey respect. It conveys a “you are lacking” message.

Being a cheapskate and always looking for the cheap way out does not teach anything useful nor anything productive.

They came up with a plan, it had a purpose, they obviously can afford it, they were not looking for cheaper alternatives and y’all immediately stomped on their project. That is NOT respect!

Education, knowledge costs time and money to acquire. The less you have of one, the more you need of the other.

#13

Thanks for your interest, but we don’t see it that way. One of our most valuable assets is the feedback and criticism we actively solicit… Lessons learned are treasure to an effective iterative development effort. Please don’t stand in the way of our learning.

#14

Your right, too many teams these days are going the cheap and easy way out and sacrificing the learning experience of students. That’s why we have our students mine all the raw bauxite and then refine it, smelt it and extrude it into aluminium box tube. We don’t need no fancy vex pro pre-drilled stuff. Our students get the knowledge they need in the real world.

#15

Serious question, how do you account for that on the CAW? We’ve got some trees that were planted by students and they are big enough now that we have been debating using them for bumper wood but we’re not sure how to account for the CAWst. Is it just the price of the seed or sapling? Do you think we need to include the cost of the full packet of seed or just the per seed cost, which I think is less than $5? I’m not sure.

#16

Buying enough land for a bauxite mine for under $4k sounds tight, unless they’re a sponsor.

R14 must be a real bear as well.

#17

Depends, is the sun a mentor and/or sponsor?

#18

Sol is registered as a sponsor.

I’m not sure we account for our rent on the space we’re in now… hmm…

#19

This is a nice post, but I like your shirt.

#20