Time lapse has become a popular technique in photography and video production. Different types of rails are used to make the timelapse movie more dynamic. The web is full of different home made solutions, from simple to very advanced. I wanted to make my own version of a rail based on Arduino control. For those not familiar to Arduino Uno this is a microcontroller, about 7×5 cm in size, able to control LEDs, motors and other external hardware. It can take inputs and can be programmed by an ordinary computer through USB interface. The programming language can be downloaded from the Arduino website. It is open source. Programming can be difficult, but many “sketches” can be downloaded from the web. The microcontroller is battery powered and can be supplied voltage in the range 5-12 V. The current consumption is quite high, and when driving motors it is even higher. I was planning to use a 14.4 V electric drill battery (Li-ion, 3.0 Ah). This is a higher voltage than recommended, but Arduino is supposed to handle up to 20 V.
The rail can be home made but I decided to buy a ready made rail. The company ASI in Drammen, Norway, is selling aluminum rails (100 cm, 40 ‘) from the producer Igus for NOK 1990.-. They are well made and sturdy but they are heavy. Mine has a weight of 2850 g including carriage, motor, belt and pulleys. So for hiking photography it is better to look for a lighter solution. Fig. 1 shows the finished rail. In addition to the weight comes the electronic box (light) and the drill battery (650 g).
The pulleys, stainless steel shaft and the timer belt were purchased from eBay. The stepper motor (Mercury Motor SM-42BYG011-25, 12 V bipolar, 1.8 degrees/step) was purchased from youBlob, Sandnes, Norway. The motor pulley (20-toooth) was mounted on the motor shaft (5 mm) as the shaft was taken trough a hole at the end of the rail. The motor was mounted directly on the rear side of the rail with four screws and some rubber gasket in between (Fig. 2).
The smooth timing pulley (ball-bearing) was mounted on a 5 mm stainless steel shaft sitting in a bore hole in the other end of the rail. A 90 degree angle steel was mounted to stabilize the pulley, as some force will pull on the belt from the carriage holding the camera. To reduce friction some nylon washers were inserted between metal sufaces (Fig. 3).
The timing belt has to be attached to the carriage, and the belt should not have too much slack to ensure a stable operation. I came up with a rather nice solution here, a belt holder made from a plywood piece. The key is to make a longitudinal slot in the plywood, just wide enough for two lengths of belt, put together teeth-against-teeth. One small piece of belt is cut to the same length as the longitudinal slot, and then glued in the slot with teeth free. The two open ends of the belt can then be put into the slot and will be locked in position by the glued belt piece, unable to slip because of the tightness of the slot. Two nuts can be glued in corresponding holes in the plywood. These are used for attaching the belt holder to underside of the carriage by screws (Figs. 4 and 5).
The mechanical part of the rail is now complete. I will return to the electronic part in a separate tech tip.