I'm a teacher at a highschool in Belgium (Europe). Our senior students are going to make various projects with Arduino. But...
Much of this projects are going to be made with steppermotors, servomotors, DC-motors (with encoder),... And to be honest, I have no idea with to order for my students in the field of hardware. There is so much you can buy... So many different websites, so many different steppers, servos, ... And with that so many questions (is everything compatible with each other? ...) ....
In our class we have already used smaller microservos etc, that's not the problem. But for their projects, the students would like to use bigger steppermotors (NEMA 17) and servo's..
The projects are the folowing:
And automated bridge with two steppers the lift the bridge (made of lasercutted MDF) and two servos for 3D printed barrier.
An elevator with two steppermotors and possibly a servo for the elevator door.
A CNC router with 4 steppermotors with a dremel router
A robotic arm made out of PLA parts with four stepper/servos (which is the best?)
An modelhouse with various automated parts (temperature, humidity, ventilator, servos,...
All of this projects would be controlled with an Arduino UNO or MEGA.
But can someone help me with what steppers, servos, motor-shields, powersupply, Arduino UNO/MEGA,... i would best buy for my students?
With regards,
Hans Vertongen
Teacher at GO! Campus De Brug - Belgium
Ask your students for the requirements for their projects. I note you do not have a background in engineering because you are wanting to design some projects from the end, towards the beginning. You will not know what to order until you know the requirements.
Advice:-
Never try an learn stuff from the Instructable web site. It is written in the main by people with an inflated idea of there own skills. So unless you can spot the errors that exist in almost all of them then it is nest to steer clear of it.
You would be better off with a nice glass of Gueuze rather than wine.
Having presented my credentials note that there are basically two types of stepping motor. A monopole motor and a bipolar motor. Both need drivers to connect them to an Arduino or any other processor.
It is possible to wire some motors to be of either type.
Stepping motors are great for moving to any position, but the zero step point is where ever the motor is when you turn it on. That is why many projects need some sort of calibration when you first switch it on. This is normally done by moving the motor in one direction until it triggers a switch either mechanical or optical.
Most stepping motor projects require at least 12 to 24 Volts even if the stepping motor says it can run off just 5V.
You include stepper motors, but neglect what they will move. Will they move lead screws that need bearings on each end as well as a way to connect the stepper to the lead screw. Then what will the lead screw move? Are you going to direct drive or use a pulley and belt? Will the lead screw have a nut that follows the lead screw with something connected to the nut? What type of rail will will be used with the lead screw/nut to make the device track back and forth?
There are no dummy proof solutions, unless the class also has a shop to create the missing parts.
Stepper motor drivers are easy to destroy, even if you are careful, know what you are doing and are aware that you will personally have to pay to get new ones. Consequently, they are a nightmare to let students loose on. Stepper motors are more resilient, but I have faith in the folks you'll be teaching - they can find a way to melt them!
Servos are easy, over-volt them a (fair) bit and the magic smoke will come out.
So I suggest that your purchasing is going to be budget constrained and that you will need a lot more parts than is initially apparent. Look at the hardware used in typical 3D printer projects using Ramps. They generally use the ubiquitous NEMA 17 cubical little steppers and A4988 drivers from Pololu. Choose projects that fit these to start with. Ramps can give you hints about power too - they often use PC power supplies. Oh, guess what, your students will find ways to burn these out too.
For servos, get a lot because well, no need to keep flogging that dead horse. TowerPro are popular but be aware that their stuff is counterfeited a lot - use a reputable supplier. You may want to consider the more durable metal geared ones because students. Get some digital ones that can report their position too but keep them locked away until there's a project that really needs them.
Servos need their own power - an Arduino can't provide it reliably - forget what you see on tutorials. An AC supply that can supply an Amp per servo at 6V or so is what is required.
Edit: For clarity, servos need DC, but you can use an AC transformer in phone charger format to provide it. Typically though, anything for charging phones will only be sufficient for a single servo if that.
Do you have some links to website of the stuff you just mensioned?
Especially the stuff that is compatible with each other.
In that way I can compared the hardware with everything from our suppliers.
For servos, compatibility isn't much of an issue - they're intended to be standard so you can swap them out in your RC models and for the most part, they are. However, they don't all accept the same range of voltage (though it's close), don't all move through the same range of angles and the manufacturers are pretty tight lipped about how much current they pull under load. Best therefore to pick one model for classroom work.
Here's a typical example: Standard servo but I expect that you will want a supplier in Europe.
Adafruit carries steppers too. Note that NEMA 17 refers to the dimensions of the faceplate used to mount the motor. You can get many different motors sizes with different torque that are still NEMA 17.
I'd give you a link to the Pololu stepper driver, but their site is down. Again, I doubt you'll be ordering from them but they have good documentation on what driver for what stepper.
Adafruit, the company wildbill linked to, has distributors in Belgium. I've personally had great experiences with Adafruit, but I live in the US and order direct. They have good support for their products. Sorry to shill for them, but they've helped me through many issues my inexperience has caused.
An FYI, many companies will give discounts for school purchases because the students will buy from a known source in the future. I know my company did that. So, be sure to identify your school when ordering and ask for a discount!
Are you planning to fit "shields" to the Arduinos? Shields are ready-made PCB with a similar shape to Uno/Mega and plug on top of them. Shields could contain motor drivers or other circuits, but the choice is limited. If so, Uno/Mega is a good choice.
Are you planning to have your students build circuits on breadboard, or solder circuits on protoboard or stripboard? If so then Uno/Mega are a bad choice because they are not breadboard/stripboard compatible. Arduino Nano 3, Pro Mini, Pro Micro etc would be a better choice.
I was thinking about using DC-motors (maybe with encoders for a bit speed control) with the bridge?
Also for the elevator I could use the DC-motors?
Are their sort of medium servos that could be used for a robot arm? So that the student have a bit of choice how "big" they want to make the robot arm...
The things I have already found are shield for using steppers, servos and dc-motors. The problem is, that I have a week to get to know this stuff and order things that my studens would be able to use for their project.
It's kind of a "here are some materials and what can you make with them" kind of projects.
I'm a big fan of shield, because the studens can just "click" the shields on their Arduino. But for example with the bridge, they don't only need motors. They would also need to be able to use the DI/DO and AI/AO. And I don't know right know if that is possible with a shield.
I'm also not looking for the most perfect sollution (if their is a perfect sollution), just a working sollution. I'm looking for a way that my students can make this work. They are so motivated right know about their work and I don't want them to be demotivated.
Because of the fact that I've not already order something, I'm open to any suggestions for what I would best order.
So... What do you thing that would be a good option for my students? Because I only have a week, I'm kinda relying on what you guys tell me here....
Yes, DC motors which can drive a threaded shaft is a possibility. You may not need encoders if you use microswitches as limit/position sensors. You would probably not need encoders for speed control, I don't think precise speed control is critical for bridges/evelators. Speed can adjusted with any motor controller. Linear servos/actuators is another possibility for raising a bridge and maybe an elevator, if there are only a few storeys.
Normally shield is stackable, that is you can put one on top of another. So in general pins that are unused on the shield can be passed through to another or to jump wires.
This is a web site you might like to look at:-
You can pay in Euros or GB pounds, and when I have ordered stuff ( in £) they seem to be dispatched from this side of the Atlantic.
Pretty much any motor driver will be compatible with Arduino. Avoid drivers that use the ancient L293/L298 chips. More modern alternatives like TB6612, DRV88XX... You should choose a driver once you know what motor you want to drive.
You can get a variety of DC motors with a choice of gearboxes to give different speeds/torques.
Mean Well brand power supplies. I worked in what are called "the national labs" - DoD research facilities. we designed our own test gear, because nobody makes commercial gear to measure what we are doing, because our research is "out there". don't ask. we used Mean Well power supplies exclusively, because we knew they are reliable as an anvil. I got paid to do maker things.*
