switches, each light is on for approximately 12 seconds
and does not duplicate the normal short on time for the
yellow light in a regular traffic light. A future modification
might be to design a different cam and/or different switch
locations so the yellow light is on for a shorter duration.
This might be accomplished by having an upper and lower
cam with the limit switches at different heights.
The controller could also be used for sequencing
Christmas light decorations or attention-getting advertising
booth chaser lights. The unit cost for parts for the finished
controller was $13.82 when I purchased enough parts for
This interesting mechanical design using limit switches
provided a cost-effective solution for an entertaining
March 2015 35
■ FIGURE 8. Controller with new square hub
and plastic cam.
Resource 1 www.amazon.com/TurboCAD-Windows%C2%AE-8-7-Vista-
Resource 2 www.surpluscenter.com/Electric-Motors/AC-Gearmotors/AC-Gearmotors/50-RPH-115-VAC-INLINE-
Resource 3 www.allelectronics.com/make-a-store/item/SMS-309/10A-SNAP-ACTION-SWITCH/1.html
Resource 4 www.pololu.com/product/1993
Resource 5 www.allelectronics.com/make-a-store/item/mts-4/spdt-on-on-mini-toggle-switch/1.html
Resource 6 www.newark.com/molex/05-06-0301/unknown/dp/54H5270