Hi all,
I am very new to Arduino and for a school project I want to be able to control a 12v servo motor using my Arduino.
What components do I need to source? How do I set up the circuit?
And help is much appreciated. Thanks!
I'm not sure what you mean by "12v servo motor" - post a link to its datahsheet.
Most hobby servos work at 4.8v to 6v so you may have something very different.
...R
Hi, thanks for your reply
Here is a link to the motor im looking at - https://uk.rs-online.com/mobile/p/servo-motors/9213747/
Strange thing! Everything looks like in an ordinary dc motor, not a servo. Could it be that this motor is designed to be used in more complex servos, which would mean that it fits to a separate gearbox equipped with the potentiometer or rotary encoder and some circuit which reads the servo signals and drives this motor?
I agree. That seems to be an expensive DC motor.
...R
Although the vendor calls it a servo motor, the manufacturer's datasheet to which they link, just calls it a dc motor.
You can afford 70 quid for a school project?
Luckily I'm not paying and the school is! If you could recommend a reasonably powerful servo at a better price and how to set it up that would be great!
You need to define what you want to do with it: in the Arduino world, basically hobbyland ;), a servo is one of these where the arm moves a linkage say to open and close a door or direct the output of a chute, that kind of thing.
Since the motor you linked to seems to be more of a dc motor than a servo, to make it act like a servo as we know it here, you'll need to add position control and gearing as mentioned above, and that's a whole new kettle of fish.
You'll get better advice if you say what it is you're wanting to do, then someone will likely have a good anser for you.
Hi,
Welcome to the forum.
Can you tell us your electronics, programming, Arduino, hardware experience?
Thanks.. Tom.. 
I have been tasked with designing an ankle exerciser. My idea was to have a servo motor moving a footplate back wards and forwards that the users foot is strapped to. I have a very small amount out electronic experience but am keen to learn! I also would like to have a smart phone app to control the speed of the motor and the range of movement. Any addition advice on that would be greatly appreciated!. Thanks
Seateam:
My idea was to have a servo motor
Before we go any further it would be good to get a common understanding of the terminology being used.
What do YOU mean by "servo motor"?
I presume you mean something different from a simple DC motor, but different in what way?
A simple diagram of the machine you propose to make would be a big help. A photo of a pencil drawing will be fine.
...R
I have a quick sketch! How do I post it on the forum?
The design brief is to design and engineer an ankle exerciser that can be used for injured servicemen with leg cages. The product must attach to the end of the leg cage and be electronically powered and controlled to move the foot backwards and forwards. It's not a great sketch but hopefully you can tell out that I have a box behind the foot where I plan to keep the electronics, 2 motors with axle running between them and the axle attached to the foot plate. Then I have a mechanism at the top to attach it all to the frame. My understanding of a servo motor is it like a motor but with constant feed back meaning it's position can be controlled. I'm just really confused on how I'm going to get this to work but I really want to give it a go!
What I was hoping you would show in your diagram is the proposed mechanical arrangement so we could understand how you propose to use the motors
And you did not answer my question "What do YOU mean by "servo motor"?"
...R
I haven't really decided what arrangement I will use yet. Maybe this is something you could advise me on? Really what I'm looking for is a set up similar to a cars windshield wipers, they move backwards and and forwards and aloe the user to adjust the speed and the gap between their movements. I also need to be able to control the range of movement. Sorry for not giving an answer to your question. To me a servo motor is a motor that you can control the position of, so I has constant feed back. I don't know if that is correct but if you can let me know that would be great! Thanks, I much appreciated all the help!
This is your project so you need to propose the sort of mechanical system.
Making something move up and down at varying speeds and with varying intervals between movements should be straightforward. A motor driving a crank would do that.
But if you want the amount of movement to vary the system becomes a lot more complex and there are many different ways that it might be done. Maybe you should investigate linear actuators.
If this were a model a hobby servo would do the job nicely. But a mechanism that operates like that with the sort of forces needed for a person's foot is a whole other ball game.
If you can figure out the mechanics the programming should not cause a problem.
...R
Get a kik drum foot pedal and use a bigger spring DONE !!!!!!!!!!
You are much better off with a linear actuator considering the torque needed. A motor without significant gear reduction as you plan would have to be huge as it would face high stall currents.
But frankly amateurs have no business making devices that will be used with another individual's well-being is at stake.
I have nursing experience and know firsthand that working stiff atrophied joints can require so much force that I've literally feared breaking a bone before extension of a joint. If you are addressing foot drop, you really need to seek advice from someone with some medical knowledge. You're not just working an ankle, you're working with leg muscles.
If your device is aiming to actually be used, you really must've misrepresented your abilities or whoever tasked you with cobbling together a device is an oblivious moron unaware of the liabilities involved.
INTP has a good point. Take it seriously. After that, if you go further, figure out the mechanics. Shafts, rods, hinges, axes...
A back and forth movement can be achieved with a wind shield wiper motor, which rotates continuously. The amplitude can be adjusted with a linear actuator or a stepper motor with timing belt to adjust shaft length.