really simple project

Hello, I need guidance regarding the choice of hardware. I need to command a step by step motor that will drive the focus of my camera objective. I need the setup to be light, small but precise. I think this is all I need : - arduino board (or even the nano one) - 9V battery - step by step motor - control command.

What motor would you advice me ? It does not have to have a lot of force. What control can I use ? I thought about using midi controller but I wonder this is necessary, can I just use electric ones ? and then which one ? I guess I would prefer a wheel rather that two buttons or a joystick. The whole thing might be wired but any advice on HF would also be good. Thanks a lot for your great help. Alex

I think this is all I need :

  • arduino board (or even the nano one)
  • 9V battery
  • step by step motor
  • control command.

Dump that choice of battery right now. Before you even get started.

What motor would you advice me ? It does not have to have a lot of force.

Well, I’d advise a small one, then. One that does not have a lot of torque.

I thought about using midi controller but I wonder this is necessary

For what? Is the camera focus somehow related to music?

can I just use electric ones ?

You need a stepper motor driver, if you are planning on driving a stepper motor. Midi controllers and relay controllers are not suitable substitutes.

I guess I would prefer a wheel rather that two buttons or a joystick.

What will this wheel, or two buttons, do?

The whole thing might be wired but any advice on HF would also be good.

What do you mean by HF? Until you get a lot more experience, stick with wires.

Thanks for the reply

PaulS: For what? Is the camera focus somehow related to music?

Not related to music no, I want to set the point of the focus of the camera with a motor. Instead of turning it by hand.

You need a stepper motor driver, if you are planning on driving a stepper motor. Midi controllers and relay controllers are not suitable substitutes.

Ok thanks for that info. But I meant a sort of physical wheel. I want the system to be independant. I don't want to control the motor from the computer.

What will this wheel, or two buttons, do?

Idealy I would like to turn the wheel to turn the focus. So If I turn the wheel 10° left, the motor will go backward to achive a 10° turn on the camera focus (I'd have to work on the scale but that does not have to be degree precise since I will do it visually)

What do you mean by HF? Until you get a lot more experience, stick with wires.

Sorry HF I meant wireless. So what kind of battery will I need ? Why is 9V not suitable because of amperage ?

This motor and this driver should be sufficient. The motor has the power to provide 2.5 ounces of force at 1 inch distance from the shaft. To interface to it you just need to set one line high or low to tell it what direction to turn and then pulse a second line for each step you want it to move.

A 9V battery has a capacity of about 400mah (400 milliamps over the course of one hour). This motor pulls 600ma, so with active use your 9V battery would only last an evening or so. A small sealed lead acid battery would probably be best.

The type of control you're looking for -- a type of knob you could spin continuously -- would be referred to as a rotary encoder. Offhand I'm not aware of any that are low cost with enough resolution for a project like yours.

I would like to turn the wheel to turn the focus. So If I turn the wheel 10° left, the motor will go backward to achive a 10° turn on the camera focus

like this? http://www.youtube.com/watch?v=o13CuoY6ZWY

here is how to do it:- http://arduino.cc/en/Tutorial/MotorKnob