We seem to get a lot of these inquiries as many people seem to want to make a similar setup themselves. We are happy you posted it here and we hope this becomes “the” thread relating to DIY motorized sliders. We foresee the following parts are required and comment on each. We will update this post as we bring in more parts and encourage the community to provide their feedback, questions and experiences.
Rail
The rail needs to be straight and supported either its entire length or at the ends. The IGUS rails seem to run from about $38 per meter and up, though there are many possibilities and variations online. The site 8020.net also offers some very attractive extrusions which can easily be used as rails.
Slider
The slider must have a way to remain horizontal and as such needs at least a line and point contact or two line contacts (for example supported by two rails; one rail and an offset wheel, 3/4 wheels etc.). Some less expensive sliders use Delrin, while others can use rollers. There needs to be some way to attach the timing belt below to the slider. Usually you would purchase the rail and slider from the same company to ensure they fit together.
You need to decide in advance if you want the motor to be located on the slider, or connected to the rail. Having all the motors and electronics on the slider increases its weight substantially, but also allows for much longer track, and ease of construction / design.
Timing belt
The circumference of the timing belt needs to be about twice as long as the rail, plus the circumference. You can either try to measure it exactly or have one of the pulleys adjustable so you can tension it.
Pulley
The bore of the pulley should ideally match the diameter of the output shaft of the motor you will choose below. The pulley does not need to be very large, but proportional to the rail and the belt. If you have a long track and the belt is under tension, you should support the free end of the motor’s shaft.
End pieces
This usually needs to be custom made - try to design them to be identical; you can use the same motor at either end to prevent having to design a setup for an “idler” pulley and also have the ability to purchase two smaller motors instead of one larger one. This end piece can usually be made out of bent metal or machined plastic.
Travel Motor
You should get an idea of the speed at which you want the slider to move. Use the equation v=ω*r, where v is the speed of the slider, and r is the radius of the drive pulley. This will allow you to calculate ω (omega), the angular velocity of the pulley. Note that ω is in radians per second, not revolutions per minute (rpm). You can choose a DC gear motor or perhaps a stepper motor.
To know the torque required, see if the manufacturer of the rail/slider system provides a value for the force require to move the basic slider along the rail. This will be your minimum value. Ideally the manufacturer will have a force versus weight curve, but this is rarely the case. To get a better idea, you need to experiment a bit, which means purchasing the rail/slider system, adding weights and using a force gauge to pull it along the track. Once you know this value, use the equation F= Τ*r where Τ (Tau) is the motor’s torque, r is the radius of the pulley and F is the force needed to move the pulley. When you get T, multiply it by a “safety factor” since static friction is always higher than kinetic friction (the force needed to start the slider is greater than the force needed to keep it in motion).
Travel Motor Controller
Once you have found the right motor based on torque and rpm (and ideally matching the bore of the pulley) you can use the voltage and continuous current to find the motor controller. You will also need to determine at this point how you want to control the slider; manually using a knob (potentiometer), remotely using an R/C system or using a microcontroller or computer. If you are using a motor at either end you can still use one controller, just use double the required current of one of the motors as your criteria.
Pan/tilt for camera
The size of the pan/tilt depends on the weight of the camera, as well as the angle at which you plan to tilt it. The force required when holding a camera vertically is far less than the force required if you point the camera straight down; it’s like holding a weight above your head versus straight out. If you don’t plan to tilt the camera much, you can get away with a smaller pan/tilt. However, to be safe, you should consider a power gearbox setup.
Controller for pan/tilt
Almost all pan/tilt systems are based on servo motors, with a few exceptions being DC gear motors. Servos allow for position control which is usually needed in camera systems. As such, you will likely need a standard servo controller. Choose the controller based on the size of the servos in the pan/tilt (some smaller servo controllers cannot handle high current), and also the control method you want. In most cases the servo controller will be able to control far more servos than you actually plan to use. Note that if you chose an R/C motor controller above, you can also connect it to a servo controller.
A device like the 4-servo recorder/playback controller allows you to control the servos while the controller records the motions, and then play them back. In order to use this, you need an R/C motor controller for the travel motor.
Alternative:
Linear gear rack and drive sprocket; this keeps the propulsion system entirely on the slider, allowing you to more easily vary the length of the track.
Alternative
Cut timing belt, affixed at either end, and use the timing pulley to move along, similar to a linear gear rack and sprocket.
Alternative:
Chain and sprocket. The downside here is that there will likely be sag since chain is heavier than a rubber belt in most cases. You could also affix the chain to the rail and have the sprocket move along it, again like the linear gear rack.
