How Many E-matches Can You Fire at Once?
Whether you are conducting a fireworks display or launching a high-power rocket with a cluster of engines, there is obviously a limit on the number of electric matches you can fire on one circuit of an electrical firing system. To be clear, we are not talking about using a firing computer to fire multiple circuits at the same perceived time, we are talking about a single firing circuit. Imagine you have to plug all your ematches into one terminal. There are many factors that play into this number, a couple of the most important ones are the electric match resistance, internal firing system resistance, and the order in which you wire them. Ematches can be wired in many different series parallel combinations, which will each allow different amounts of current to flow through them. To understand this, let’s walk through some definitions first.
Series or Parallel?
How do you wire in Series? How do you wire in Parallel?
Series
Three Electric Matches in Series
Standard: No more than 5 ematches in series on one circuit
Parallel
Three Electric Matches in Parallel
Standard: Electrically, no more than 5 is desirable; however, we use no more than 3 in parallel as a general rule, to take into consideration care of the electronics terminals, so as to not cram to many wires into a single one.
Series-Parallel Wiring
What if I need to shoot more than five electric matches from a single circuit? This can be achieved through special series-parallel wiring. See below for an equivalent circuit diagram as well as a cartoon drawing of what the electric match wiring would look like for an example configuration of 3 sets of 4 parallel electric matches. The three sets are in series. So in other words, you have 4 electric matches in parallel, then you take those parallel sets and tie them in series.
3 sets of 4 Parallel Electric Matches
Equivalent Circuit
3 sets of 4 Parallel Electric Matches
Physical Wiring
How Much Current Does it Take to Fire an Ematch?
This table shows how much current it takes to fire electric matches from two different manufacturers. The all-fire current is the metric relevant to this discussion. The all-fire current is the minimum electrical current needed to reliably set off the electric match 100% of the time.
The Ultimate Series-Parallel EMatch Chart
The following graphs show how much current is passing through each ematch for different series-parallel combinations. By comparing this current to the “All Fire Current” given by the manufacturer’s data sheets, you can determine if your electric matches will have enough current to fire when wired in that particular order. This will allow you to find the maximum number of electric matches you can fire per cue. There are two graphs, each assumes an internal firing system resistance of 4 ohms. One plot is for ematch resistance of 2 Ohms and the other for 2.6 Ohms. and a different electric match resistance. Each of these values is at the top of each graph. Download the paper we published in the Journal of Pyrotechnics, which comes with the mathematics, experimental test results, and other technical info.
Current per Electric Match – Ematch Resistance of 2 Ohms
Current per Electric Match – Ematch Resistance of 2.6 Ohms
How to Read the Ultimate Electric Match Plots
These examples utilize the plots that assume an electric match resistance of 2.6 Ohms
How to find 1 ematch, 5 in parallel, and 5 in series
How to find combinations that yield 1 A per ematch
Examples Using the Ultimate Ematch Chart
These examples utilize the plots that assume an electric match resistance of 2.6 Ohms and that 0.55 A is above the All-Fire Current
Problem: I need to shoot 10 e-matches on one cue
Problem: I need to shoot 48 e-matches on one cue
Real-life Use – On Mythbusters!
The data above was used to simultaneously set off 47 rocket engines (twice!) for the Discovery Channel Show “Mythbusters” in the episode titled “Ming Dynasty Astronaut” using a 24V firing system. For more information and pictures on this event, visit our television and movie pyro page.
Mike Tockstein making the final firing system connections to the 47 black powder bamboo rockets that are strapped to the chair buster is sitting in
The first shot, utilizing 47 black powder bamboo rockets ignited simultaneously, ending in a spectacular explosion
47 high power “I” rocket motors, each capable of 50 lbs of thrust, strapped to the chair for the second shot
Buster the dummy rocketing into the ground with the force of 2,350 lbs of thrust behind him, with the second shot ending in a spectacular crash
Mythbusters signed and left one of the destroyed chairs to the pyro team
Mike Tockstein along with the hosts of Mythbusters, Jamie Hyneman and Adam Savage
How Ematches Work
If you haven’t seen it yet, be sure to watch our video on how electric matches work!