The cam was originally
mounted on a Pololu mounting
hub #1993 which added about $4
(Resource 4). Again, I used
TurboCad 18 to lay out a new hub
and had the local high school
Career Center machine shop class
fabricate hubs to the TurboCad 18
drawings shown in Figure 6 and
Figure 7. The schematic shows
that a switch is in series with the
gearmotor to allow it to be turned
off (Resource 5).
This allows the operator to
turn on just one light and leave it
on all the time (Figure 8). I have a
friend who stated that if he
displayed a continuous green light,
that meant that it was okay to visit
his man-cave; a continuous red
light meant to stay away.
Lugs to connect to the switches
and to the terminals in the traffic light
housing can be obtained from Newark
Because of the symmetry of the
cam and the spacing of the limit
34 March 2015
■ FIGURE 6. Dimensions to make the square hub.
■ FIGURE 7. A 3D model of the hub.