The Schwartzvolcker Conception

The firing system is planned starting backwards from the point of e-match ignition. Known factors include:

• Anticipated 75-100' distance from control unit to ground zero.
• 12v circuit preferred due to readily available parts & battery.
• 350mA+ current to ignite e-matches.
• E-matches are 6' in length.
• Ground zero will have a radius of about 8'.
• Keep costs to a minimum.

The final point is important. My budget will be around $60, tops. So looking around the garage, I have some switches, resistors and LEDs that can be used. I have access to a large amount of scrap CAT5e cable which can also be incorporated. 18, even 20 gauge wire costs $0.10 to $0.15/ft; running up to 20 cues could potentially mean a half-mile of wire costing upwards of $375. The CAT5 is 8 individual 24ga wires. Over a potential 200' run, this could present a mild risk of melting when a larger amount of current is applied. It is best to be safe, so the plan is to double up into pairs, and cut the resistance in half.

I start out with a few hand sketches of the planned circuitry, again working backwards with the known factors. The easy thing about planning DC circuits it to follow the directional path of power in a complete loop - provided the function of each device in the circuit is understood. I finally get a rough draft of what I think will work after reading a few highly educational posts on this subject by "JoeRatman" at PyroUniverse (Thanks Joe). Among them, the use of cheap speaker terminals to easily field-wire e-matches to cue slats, the part numbers of some diodes necessary in the circuit, and how handy it is to have a lower current circuit run beneath the firing current to visually display continuity (and therefore readiness) of each e-match prior to ignition.

Final draft sketched.

The idea of a junction box of sorts is introduced; this will decrease the amount of cable needed by about 75%. In theory, the control unit will be in the lap of the operator, with two CAT5 cables leading 75-100' away to the junction box. The junction box will split the signal to five separate cue slats, themselves up to 20' away from the junction box. From the cue slats will go the e-matches - up to six feet away. 

There will now be seven separate parts to the system - Control unit, junction box and five cue slats (sets) each with four pairs of clip-downs for e-matches. A rotatory switch will be used on the ground return wire to toggle between the sets. Four additional cues are added in parallel to the last set (E) since it is closer to the finale in the show, when there are often at least two items being ignited at a time.

Each part of the system is planned to be easy to set up and dismantle. Ideally, cables can be pulled out and wrapped up for next use. To keep costs down I plan to hard-wire the CAT5 into each set, though their connections into the junction box will be removable.

The sketch detail, along with notes made after reviewing several times, is entered into MS Visio. This program is meant for flow charting, but has a library of electrical symbols that are handy to draw circuits. At this point some calculations are made to determine the resistor values needed to run the continuity circuit, and proper location of diodes. A single cue, test circuit is also added, to facilitate e-match testing without setting up the junction box or set slats, and perhaps to ignite a close-by fountain or wheel.

When it comes time to save the file, I name it 'Schwartzvolcker'. Really, for no other reason than it sounds bad-ass German, invoking feelings of sturdy, robust engineering...

A dead 'furnace efficiency meter' is chosen to be the base for the Schwartzvolcker. It comes in a small latched case, and the face swings open for access to the inner workings. Not sure the battery will fit into the unit, however.

Now everything is on paper. Using the completed drawing, a parts list is created. The next step will be sourcing parts and starting the build.