Stepper or low RPM DC motor for my timelapse rig?

Other Hardware Motors, Mechanics, Power and CNC
1

Hi all,

Over the next few months im going to be putting together a time lapse rail for a DSLR camera. I've got a lot of it planned already, but am currently at a decision point with regards to motor. The basic hardware of this requires a slow moving carriage along a guide rail, similar to this.

http://uk.rs-online.com/web/p/linear-guides-rails/3113711/.

The carriage will hold a DSLR camera (weighing around a couple of kilos potentially) and may move along the rail at an incline of up to 45 degrees. For either motor choice, i'll be running a timing belt mechanism to shift the carriage along the rail.

The primary considerations of this are

  • The mechanism requires a "move, stop, shoot, move, stop, shoot" process
  • The whole rig must run on external power and run for a relatively long period (in the region of hours) between charges.

Ideally, id like to use a stepper motor as this covers off the ability to set the speed and do the "move/stop/shoot" process.

However, my concern is with the amount of power a stepper motor will take compared to a normal low RPM (15) geared DC motor. From what i have read on steppers, they require power to hold position whereas I could "pulse" a normal DC motor and it will rest un-powered without the carriage moving (have seen this done in other examples of timelapse rails but im not sure its as controllable as i need it to be).

All of the timing and movement will be ATMega driven.

I'm pretty new to the hardware side of things so if someone could recommend motors/power sources i would be extremely grateful.

My initial thoughts for DC motor are this one

And stepper motor (i know i need a controller too)

http://www.ebay.co.uk/itm/NEMA-14-Hybrid-Stepper-Motor-2-Phase-1-8-Degree-For-CNC-RepRap-Prusa-3D-Printer-/252462173763?hash=item3ac7eb0e43:g:4DsAAOSwyKxXhlnR

Many thanks

Mark

2

I could "pulse" a normal DC motor and it will rest un-powered without the carriage moving

Maybe. A motor without gearing won't. Otherwise depends on the gearing.

How far does the carriage need to travel? You may be better off with a screw/worm drive instead of a belt. With the right threading and a geared motor you can hold position unpowered. Add an encoder and you can attain precision.

  • Scotty
3

For portability, it will be at most 3 ft long. I've got to be able to carry the rig through the Himalayas, so weight is also an issue (but probably not an issue in terms of the difference between a timing belt and worm driven mech)

I'll look into encoders (no experience there) . If you have any recommendations, that would be great.

4

This might interest you. You could contact Servo City and ask about a motor to serve your needs. - Scotty

5

the stepper motor does not really use that much power you will need 50- 60 oz/in for a couple kilos and a 12 volt rechargeable battery motorcycle or a ups battery about half that size stepper 42byghw609 nema 17 56oz-in <$20 and a A4988 stepper driver and arduino would work and belt rail and pulley 2020 v rail a modified tripod one leg holes rail other two give the elevation sounds easy

6

A stepper driver like this can reduce the standstill current to 25% so not so much heat and power waste.

Also, if you use a DC motor you will need either a brakemotor or some kind of clamping mechanism to hold the carriage on an incline.