extreme care should be exercised. Once
the unit is closed up, the metal enclosure
protects everyone. The lighting scheme
may include metal boxes which need to
be grounded back to the cabinet and to
the incoming AC cord.
only gets done once or twice a year.
The cabinet was staked to the lawn
using two lengths of EMT conduit
attached to the cabinet base. The same
technique was used for the mini-tree
bases. Alternatively, the cabinet can be
mounted on a wall.
■ FIGURE 5
Anyone attempting to construct and
use this equipment should be aware of a
few safety issues. AC power is conducted
through both PCBs and when the cover
is off, there is a deadly shock hazard, so
■ FIGURE 6
Holiday lights are prone to failure,
possibly by damage to the wiring or breakage of the bulbs. Some 120V bulbs may
short out when the filament breaks, and
this can cause a current surge. Each I/O
card is protected by a five amp fuse, as is
the controller card’s power transformer. I
hard-wired the mini-lights on each of my
trees, cutting off the original plugs. Note
that these had fuses installed in the plugs,
and that protection is continued by the
fuses on the I/O cards as just noted.
In theory, all channels could be
turned on at the same time and a total of