The bus controller and all the SmartRails are powered by standard 9V batteries, one per each unit. The cheapest 9V batteries I can find cost less than $0.50 each. Even those will provide power all day if necessary. In practice though, the batteries are only installed if we need to do a continuity test or to fire the show. Otherwise, I keep them in storage for safety.

Firing circuit

The ultimate goal of the SmartRail is to fire electric matches. Manufacturer specifications for these matches vary as do their recommendations for how to fire them. A very conservative approach is to supply 1 Amp for 40 msec to each match that has nominally 2 Ohms of resistance.

The basic core of the design is the firing circuit that provides this current. I opted for a capacitive discharge design like many others with one exception. I use a very low 5 Volt design.

Some in the pyrotechnics industry will be surprised by that, because their experience is almost exclusively with 12/24 Volt battery powered systems or high-voltage (200+ Volts) capacitive discharge systems.

This 5 Volt design does work, it is a simple matter of Ohm's Law. The key is that the power source has to be located close to the electric matches to minimize the amount of wire and associated resistance. In my design there is a huge (1 Farad) capacitor on each SmartRail and less than 0.5 Ohms of wire resistance between the capacitors and the matches, including the leads of the matches themselves.

The capacitor is charged over a 15 minute period from the 9V battery via a 5 Volt regulator. Once fully charged it can deliver 16 separate pulses of 1 Amp and 50 msec duration each to the 16 cues on the SmartRail. The cues cannot fire exactly simultaneously on this one SmartRail. They must fire sequentially, separated by at least 50 msec. All 16 cues can fire in 800 msec total.

Note: The 50 msec separation between cues applies only to cues on the same SmartRail. Cues on two different SmartRails are completely independent and can indeed fire simultaneously.