Lexan panel, 0.220" thick, 21"× 36" A 30"× 36" sheet
is about $40 from Home Depot.
Perf board, about 3"× 4"
Lego klaxon alarm sound brick item #55206c03
from BrickLink ( bricklink.com)
Toggle switches with red safety covers ( 2) I used
MPJA ( mpja.com) parts #12219 and #16100.
SPDT key switch for the Power switch
7805 5V DC voltage regulators ( 2) All Electronics
( allelectronics.com) part #7805T
555 timer IC chip All Electronics #LM555
Yellow LED and 150Ω resistor, ¼W or ½W
(optional) for an Arm switch indicator light
100kΩ potentiometer All Electronics #POS-104A
Quick-connect wire connectors with headers:
4-pin ( 3), 10-pin ( 1) All Electronics #CON-244
Angle brackets ( 6)
10-wire, 22-gauge bundle cable, 25' for the launch
bar firing cable; All Electronics #10CS22
14-gauge insulated wire, 30' for the launch bar
22-gauge hookup wire, 150'
Large 12V battery I used a lawn tractor battery
from a discount store, about $20.
Lamp cord for connecting battery to circuit
Spring clamps ( 2) for connecting battery to circuit
2× 6 ( 1½"× 5½") pressure-treated lumber, 8'
2× 3 ( 1½"× 2½") lumber, 12'
¾" plywood scrap, about 2' square
13mm bolts, at least 2" long, with matching
wing nuts ( 2)
Cabinet hinges ( 2)
Typical workshop stuff: epoxy, screws, hot glue,
zip ties, heat-shrink tubing, bolts
Time: 1–2 Weekends Complexity: Moderate
Photography by Douglas Desrochers
FOR THE 10 LAUNCH PADS:
2-outlet electrical box cover plates, steel ( 10) from
hardware or home improvement stores
Metal rods, 1"× 3' ( 10) from a hardware store
Momentary push-button switches ( 10) to fit the
1N4004 blocking diodes ( 10)
LEDs, ultra bright, clear lens ( 10) All Electronics
510Ω resistors, ½W ( 10)
Mini alligator clip jumpers ( 10) MPJA #16434
Drill press and bits, including #9, 1",
and Forstner bits
Hot glue gun
The mega-launcher consists of a 10-rocket launch
bar and its control station connected a safe distance away by a 25' cable. The control station fits
on 2 long folding tables arranged end to end, with
firing stations 1–3 on the left, 8–10 on the right, and
4–7 on the control console in the middle (Figure A).
The console (Figure B) carries the system-wide
Power, Arm, and Mega-Launch switches. For safety,
the main power switch on the control console is
a key switch; this lets you pull the key to prevent
overly excited scouts from firing rockets while
someone is still working at the launch bar.
Turn on the power, and a row of 10 continuity
LEDs tells you which launch pads have igniters in
place that are ready to fire. Flip up the Arm switch
and the klaxon sounds, signaling that the firing station and Mega Launch buttons are now enabled!
The system is powered by a 12V battery, and continuity to each igniter is ensured by an LED that’s