Need help with a motor and electronic stuff!

An Electronic Resource for Miniature Builders!

@tjleasa made such an incredibly timed post becasue just yesterday I spent a solid 5 hrs trying to sort out servo motors, step motors, arduino boards etc, and while I have a tiny bit more clue, it aint enough to get what I need. So I’ll take tjleasa’s cool resource post as a sign I should figure this out and work on the concept that’s been floating around my head for years, and was the very idea that prompted me to get a GF in the first place. So if anyone knows enough to take pity and help me figure it all out, I would be so grateful. I am not electronically inclined and every time I try to figure out how to go about it, I get so frustrated I just give up for another year.

I know I need the motor and maybe a control board, and I now have a very general understanding of how an arduino board works, but that’s about it. What I’m looking for is a motor that can spin a 6" disk of thin acrylic or wood, and I want to have it mounted in a frame behind the disk. I want to power it via a regular plug or usb with just a simple on off switch. It can’t spin too fast and one speed is fine, but in a perfect world it could have a knob to control the speed. (I can live without that though.)

-Which would be best; a step motor, servo or maybe a little brush motor?
(What I’d really love is to figure out using a servo so I can make more complicated kinetic sculptures and automata, but I’ll start off small first lol.)

-What size motor would I need; how do I know what power/torque I’d need?

-If I need a motor with a control board, does the power and on/of switch work off the same board, or is the board only for programming the motor?

-What exact components would I need? (Board, wires, switches?)
or
-Anyone know where to just get a kit that has it all together or a place that lists exactly what components go together so beginners like me can sort it out? (I couldn’t find any, but I don’t know what I’m looking for, so… :woman_shrugging:t2:)

I make it this far, but then it all turns into Greek and I don’t know what I need or which kits may apply.

Here’s what I’m trying to spin


image

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See if this helps

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So there are a whole ton of options to solve this but let’s start with two easy solutions (super simple first and slightly less simple second)

You can buy a motor called a “gear motor” which for a given dc voltage will spin at a specific speed (obviously no load). it just is an on-off thing (there are fancier gear motors on their site, go up a level and go to planetary gear motors). This means you simply need a power source/switch (they often draw a lot of current so you need a relay, easiest way with an Arduino is a relay shield (there are way more sophisticated relay/switching methods but let’s go super simple). Now do you need a relay shield vs a naked relay? No, but if you aren’t careful it is easy to fry an output on the Arduino powering even a micro relay.

Favorite site for motors, etc, Motors:
https://www.servocity.com/standard-spur-gear-motors/

Arduino compatible relay:

Pros:

  • It is an on-off thing, the motor automatically goes in the direction of the DC (reverse the leads and it goes backwards)
  • it goes at the listed speed
  • this sounds about your level of circuit building (no offense)
  • you don’t need the Arduino at all (a switch works fine here with the dc power supply/battery)

cons:

  • only runs at that speed
  • there is no possibility for closed loop speed control (if something drags it down the motor just goes slower)
  • you can’t vary the speed based on an input
  • you can’t rotate to a specific angle on command

Ok second option (fancier, but bigger learning curve). So now you can dive in to the world of stepper motors or continuous motion servos. This absolutely requires a controller of some form (whoever is about to jump in that you can use a 555, pipe down). So for this a shield that “knows” how to control these is your friend. I love adafruit’s one and have many of them (for both Arduino and raspberry pi). Now it can control up to 16 of them (fine just ignore all those)

The shield I use is:

Note with that shield you can pick stepper or servo. Now why one vs. the other? Steppers are easier in many ways. They move forward based on a given number of pulses (some number of degrees per pulse). But they’re “dumb” in that they are unaware whether they accomplished the number of degrees you asked (some controllers can sense a failed pulse) or you can put a rotary encoder to figure out how far it’s moved. The advantage of Steppers is really simple programming (the tutorials are easy on the adafruit site)

Now why a servo? Well unlike a stepper you specify a specific angle to rotate to (conceptually) and so you say go to 60 degrees and the stepper knows where it is, and will keep trying to get to 60. The advantage is if it gets bumped it will still work to hold that location. But you want this to spin so you can modify a servo to be “continuous” so it kinda works like a gear motor. The servo city site has a wide variety of servos and steppers. If you decide servos I would absolutely go with a “digital” servo (not mandatory, just easier). Be very careful with both servos and steppers as it is super easy to smoke the shield’s controller FET (ask me how I know) if you decide you need a stepper capable of powering a giant crane. Both servos and steppers would allow you to go forward/backwards in some specific pattern.

Note that shield can also take a basic DC motor (hobby motor) and control it via the built in h-bridge where the Arduino will provide speed control. That’s easy and cheap but not nearly as versatile.

No matter what you will need an external power supply that matches the voltage/current of whatever motor you pick. Make sure the motor you pick isn’t more current than the shield/relay can handle.

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I have done this type of thing before. I would use a DC gearmotor. They are available on Amazon and on Pololu. You can easily drive it with a power supply. Put a rheostat inline with the motor and you can control the speed. This is the most simple. You have the power supply, the rheostat, and the motor as your only components. Maybe a power switch if you don’t want to use the rheostat as the power control also. If you want to get more complex and use a microcontroller you can, but you will need a driver, usually MOSFET based. You cannot drive a motor directly from a microcontroller. (Very few exceptions)
Next step would be a stepper motor. Easy to set up, but needs a driver and a microcontroller. Probably the most adaptable to different applications and can be fitted with position feedback in a variety of ways.
Most complex would be a servo since they must be modified or specially sourced for continuous rotation. Needs a microcontroller and maybe a driver depending on the model and application.

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@eflyguy Thank you! The info about pulse and voltage divider was interesting and I was able to follow it, but honestly, the rest of it is just way over my head. :stuck_out_tongue: It’s sending me down another rabbit hole and I’m watching all his build videos though.

@henryhbk @ben1 The Gear motor info is super helpful and I think it’s totally the way to go for this! (Or planetary if it gets too heavy and I need more torque.) I also think it’s best to just skip any microcontrollers etc. and the simpler, the better. (And @henryhbk, you couldn’t offend me if you tried, and even some of what you explained is over my head. I’m good at a lot of things, but electronics isn’t one of them and I need it explained like I’m five year old. lol)

So can you guys point me to everything I’d need so I get it right? I don’t need to know if they’re the best choices or the exact ones I’d need or anything, but it’d help to see visual examples so I know what I’m looking at.

For example, would these be the things I need?

Or this

And then the on/off switch with maybe a speed controller like this?

or

(Or if there a controller like these that can turn on two different motors at once so I could have two disks spinning at different rpms? :thinking:)

So how/what products do I need to connect a power cord to it?


And in my search with the info you guys provided I came across this, and it’s exactly the kind of jumping motion I’d like to play with. I think starting with a simple spinning movement would be easiest to learn with, but I envision having several objects “jump” out from behind a piece of wood. (Kinda like a rabbits jumping out of a hole.) To find an example of how I could achieve that is exciting for me!

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The only thing you are missing here is a power supply. Looks like the motor needs 12V 500ma which is well within those speed controllers’ current rating. So all looks good… I have a similar collection of motor+controller I use for a video slider (slides the camera along a rail). No microcontroller needed.

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I would look hand cranked automata it might lend itself to your artwork and give you chance to the mechanics right first.

From a very talented artist.

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A turnkey solution with the right RPM and torque is great. I looked at these solutions when I was making my coin sorter. But that’s it, finding the right RPM and torque and being happy with that with a power supply and simple controller easily connected.

But I couldn’t be satisfied and that’s what sent me to a stepper motor and arduino since I had to tweak the speed of the disk to get it to sort correctly. But man, it takes a bit if you haven’t done much with microcontrollers. There are great tutorials these days and so many solutions. I’ve been figuring out servo motors for my exhaust valve and I do believe I broke a few brain cells. It seems that every tutorial is close to what I need, but not quite enough. Part of it was using a platform for and ESP32 that didn’t have an adequate library for controlling servos.

I’m looking at the geared DC motors for doing some automation on blinds. I was surprised at what this guy did with the ubiquitous [8BYJ-48 Stepper Motor] but hacked them a bit to make them a bit more versatile. But this definitely requires a bit more resources. Cheap in the long run, but lots of investment in time and skill.

I am sure interested in what you decide. I’m still puzzled by all the options.

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This place and its people are awesome.

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The way I would proceed if I were hired to do this project is:

  1. Determine and set the physical requirements of your moving parts. If you know the material and dimensions of what you are spinning, you can calculate the torque required to move it. Find or decide what speed or speed range you need.
  2. Use the requirements to locate a gearbox that will do what you need. If you only need 2 once-inches of torque, don’t spend the money on a 2 foot-pound gearmotor.
  3. Use the motor to size the controller, be it a 0.5 amp controller or a 3 amp controller. Also check that your motor controller is compatible with your motor. Note that the motor will only pull what it needs, so you can run a 1/2 amp motor on a 3 amp controller safely, but putting a 1 amp motor on a 1/2 amp controller will burn out the controller unless the power supply amp rating is less than the controller amp rating, in which case the power supply will either be damaged or will either limit the current or shut down to prevent overheating.
  4. Find the power supply you need based on the motor and controller specifications and add 15%.

As @henryhbk noted, the parts you have chosen already will work, but may not be optimized. For a first unit that may be fine, but if you make more than one you will want to start looking at cutting the cost by only buying what you need. Through optimization you may also find the parts that you need are smaller and easier to package than the parts you have chosen for the first one.

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So is this the kind of stuff I’d need to power it?

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Yes, I’ve spent a lot of time researching automata and I’ve practiced with some basic designs, so that’s not the part I’m struggling with. I just want an art pice to hang on the wall where it wouldn’t be conducive to a hand crank, and I struggle with the electrical part of it. :slight_smile:

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Exactly this. I’ve spent countless hours looking for a basic way to achieve the mechanics I want, but having to learn something like this from absolute scratch just sucks all the joy out of the build for me. A couple of times a year I see something that sparks my desire to try again, and then hours later I just give up again. But I think getting one made with a simple DC gear motor will be just the ticket to get the juices flowing again.

And man, that video helps so much!

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Aww man, this is so, so helpful! It’s understanding amps and voltage etc and what parts can go together that trips me up and I’d totally settle for something that won’t burn my house down versus something that’s elegant and optimized! :laughing: And I know I want it to spin between 15 and 25 Rpm, so now I’ll figure out the torque I need to sort out which motor would work and that’ll give me a great starting point. And if you and @henryhbk don’t mind, if I pick out the components and have a question about compatibility, can I have you guys double check them for me?

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First impression: There is a very long history of kinetic sculptures and automata long before even electricity. To call it a deep rabbit hole is a severe underestimation, and just when you think you have a handle on it, you find that the Japanese totally blew out the concept enough that you really want to learn Japanese to try and follow.

@bill.m.davis and @pubultrastar have a number of such projects that do not involve motors and the making of their own gear trains.

but I digress into crazy man rant, so will stop it mid-sentence, and let those who can help, do so.

That said the ocean of electronic carp around here is only exceeded by the Glowforge scrap carp and indeed trying to “organize” things a bit I discover I have about a cubic foot of wall warts that I have no idea what they go to with dozens of plug types with little or no standardization or even notation of what they came with. The tools etc have the brand names splattered prominently even three or four times but the wall wart? Nothing!

Sometimes there are differently colored wires, often they are all black, and I suppose proper gadgets and soldering could solve many issues, as well as a carp load of connectors, etc. and all that before even thinking about programming or Bluetooth stuff.

I know for many folk here all of those mountains are molehills, and many do not remember a time when there was no internet, and robots were only Sci-Fi

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@bwente took my hand-crank marble run and added a motor to it. So I would heed his advice. I do not have much experience with motors; just played with them a little.

I have been dreaming of making clockwork automata. But I feel like I need to find good clock spring or a way to make one.

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You have access to a fantasy land for doing this sort of work on the west side of Winter Park called Skycraft. They sell a few things on eBay but the most and best is only sold in-house.

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Yep, although it’s a bit further now. They moved to a new location last month.

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The power supply is overkill by about 7 amps, but yes, you are headed in the right direction.

Yes, once you have everything picked out I am happy to look it over for you.

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