Nuts and Volts - September 2014

at the exact same time to produce the flame effect.)

Take your hacked power supply and with the cover removed, drill some small holes in the bottom of the case. Be careful not to drill through anything but the case itself. Now, place the power supply inside of the enclosure (we have a lower shelf installed in ours to attach this to). The power supply needs to be securely mounted. We also need to place the electrical box inside the enclosure as far away as possible from the power supply. Set the electrical box aside for now.

We need to mount the power switch to the side of the enclosure. Since we’re only going to have one power cord coming out of the prop, we cut the cord to the power supply about one foot from the plug end, stripped the wire back, and tinned all of it to prep for soldering (Figure 14).

We now need to run all the wiring into the electrical box so we can solder it all together. On the top and bottom of the electrical box are little knockouts. We’ll need to remove these on one side and feed the cut ends from the power supply through one of the knockouts, then run the two black and white wires from the lighting harnesses through the other knockout and into the electrical box as shown (Figures 15A, 15B, and 15C).

Next, take the white wires from the two light harnesses and solder them together with the two common wires: one from the plug end that we cut off and one from the cord running to the power supply. Shrink wrap all these wires once they are soldered. (The common wire is the one coming from the wide spade on the power plug. Of course, not all power supply cords are the same and might have different colored wire for the common.) To connect the black wires from the lighting harness and hot wires together, we will make a pigtail. Cut a piece of black wire about three inches long and solder it together with the two black wires from the lighting harness and the hot wires from the power supply cord. Shrink wrap all of this together, leaving just the end of the new black wire hanging out; this is the pigtail.

The pigtail will need to have a terminal ring added by using crimpers, then crimping the ring to the wire. The ring will attach to the switch, so make sure the ring is the right size for the switch’s screw.

So, now you should have three wires left; two of them are ground wires from the power supply cord. They can be soldered together and shrink wrapped since we won’t be using them. The third wire from the plug end of the power supply cable will be used to connect to the switch. Attach a terminal ring to this wire (it should be the hot wire coming from the plug end that we cut from the power supply cord).

The switch we used is a double pull/double throw and has six screws on it. We will need to take a short piece of black wire (about two to three inches long) and use it as a jumper wire. This will connect to the two end screws so that when the switch is flipped in either direction, it will turn on the prop.

Attach the blue terminal ring from the black pigtail wire to one of the end screws, and attach the red terminal ring from the hot wire coming from the plug to the middle screw. All the wires will be attached on the same side. Do not attach any wires to the other side of the switch. It should look like Figure 16 when wired correctly.

Be sure you make room for the switch! We did run into a problem here. The switch we picked did not have enough threads to go all the way through the side of our wood enclosure. This required us to notch out an area the size of the switch to recess it from the inside of the enclosure and have enough threads stick out to put the nut on to mount the switch.