No Arduino, No Software, No Relay, just a simple low power, four chip, Auto Reverse Circuit!!! Micro-processors and Relays will consume much more power then this simple Ckt.
Here you see the Simplified Logic Diagram that controls the H-Bridge Ckt. The Timer’s Cap and Resistor (C1 and R3 in the schematic, step 1) determine the motor’s stop or pause time. With a 10uF Cap and a 47k Resistor you get about 1/2 Seconds pause before the motor reverses (33k = about 1/3 Second, 22k about ¼ Second, and so on).
Basically the slider on your powered Camera Slider hits a micro-switch (one at each end), pauses the motor, and then reverses its travel. This Ckt will allow the slider to continue back and forth all day or all night. And, you can add a PWM Controller to control the slider's speed.
This Ckt (with the LEDs turned off, using CMOS) is an extremely low power ckt for remote photo shoots!!
Here is the schematic (updated 3/27/2017)... I bread boarded this ckt... and it's and working like a champ. I used all CMOS Logic for my setup, including a 7555 timer chip. The LEDs are optional, but make for an interesting display to see what is happening. Be sure to tie any unused inputs to Vcc (outputs just float). It’s always a good idea to add small caps at Vcc for each chip to remove any supply spikes. The "Timer Control Input" box is for a control ckt I am building for control of the motor, for nighttime photography, a series of several hundred long exposure photos of the Milky Way as the Milky Way moves across the night sky (move, pause, take picture).
Here is the H-Bridge setup, configured with my PWM Controller. Again, works great to control the motor's speed. Be sure to pay attention to the RED and adjacent Black wire coming from the PWM board (H-Bridge sensitive to polarity connections). The other two Black Wires (from the "Manual Revers Switch) simply pass through the PWM Controller Board and go out to the Motor. Another way to say this is that I spliced the H-Bridge Ckt into the cable that comes from the PWM Controller and goes to the Manual Revers Switch. The particular PWM Controller that I am using (see photo in upper-left corner) makes it easy to splice in the H-Bridge, Note: the Speed Control (Rheostat) is mounted on the board and the Manual Reverse Switch is on four short wires that plug into the PWM board (available via Amazon or Ebay). The Red and Green LED (not shown in the schematic) are optional, but again make for an interesting display, connected in parallel across the Motor. The Power Supply is 12v DC, the "-" is the same as ground.