46 SERVO 06.2010
The last step is to attach the project into
your existing power supply project. Drill four
holes to the power supply cover to attach the
main board with 4-40 hardware. Now
permanently solder the wires that come from
the display to the board. The display assembly
is best attached to the main cover with Velcro™
tape which allows repositioning for the best
viewing angle. After you have finished, it
should look something like Figure 5.
Locate the power supply board on the
main filter capacitor for the fixed output. It will
be several thousand µFs and rated 12 to 16
volts. On its terminals, verify that you have a
raw DC voltage in the 8. 5 to 12 volt range.
Solder the cables to the plug that connects to
J4, observing polarity.
Attach the fan(s) and temperature sensor
to the heatsink as shown in Figure 6. A two-part epoxy works well for this purpose. Just
make sure that you don’t glue the fan’s blades
shut! Depending on the actual heatsink, you
may need one or two fans. In this particular
heatsink configuration, two small fans were
better than a single large one. They are wired
in parallel. Just remember to observe the 350
mA total current limit.
Lastly, cut the wires that go from the
power supply’s board to the output banana
jacks about halfway. The trick here is that we’ll
re-route the output wires to be in series with
the project’s main board. Refer to Figure 7
which will help make this clearer. Please note
that the ground (common) path is not broken,
but referenced to both boards. Also note that
since the +5V fixed output sources a higher
current, the contacts are “doubled up.”
The wires are soldered together and
insulated with heat shrink tubing. Again, please
use color-coded wires to prevent confusion.
Final Tests and
After carefully inspecting your wiring,
power-up the unit. After a brief delay, the
topmost screen in Figure 8 will appear. Adjust
the variable supplies; you’ll see the display
changing which is useful to set the proper
voltage before actually powering the circuit.
Verify that none of the outputs have any
voltage with your multimeter.
Now connect a 10 to 20 ohm, three watt
load to the fixed output terminals. Press the