W9YA Elegant Launch Controller

The Rocketeer's favorite Launch Controller System

Parts List;

- 16 Gauge (Light Duty), 3 Conductor Electrical Extension Cord, 100 foot lengths as needed.
- 16 Gauge (Light Duty), 3 Conductor Electrical Extension Cord, 50 foot length
- Leviton R40-115PR Vacuum Cleaner 2 Conductor Electrical Plug - Used for the igniter leads removable connection.(Will need to be modified)
- Leviton or Cooper Standard 115v/15amp Duplex Electrical Outlet
- Leviton (or other) Standard Duplex Outlet Cover - U.S General (Harbor Freight) Battery Cut-Off Switch, Model #92688 - Used for the safety switch in the Relay/Pad Unit.
- Harbor Freight Model #97350 Toggle Switch w/ Carbon Fiber Cover - Used for the Standalone switch on the optional Extension box.(Will need to be modified.)
- Harbor Freight Model #42292-2VGA 12v Float Charger
- Harbor Freight Model #37957-4VGA Electrical Clip assortment
- Radio Shack Model 275-0001 12v/40Amp Automotive Relay
- Radio Shack Model 274-679 12 Position, European Style, Terminal Strip - Relay/Pad Unit
- Radio Shack Model 275-0601 Spst Panel Mount Toggle Switch with Safety Cover - Use this for the Arm/Disarm switch on the Relay/Pad Unit. (Will need to be modified)
- Radio Shack Model 275-609 Spst Momentary Pushbutton Switches (2 per package) - Use one for the launch switch on the Remote Unit and one for the Test switch on the Relay/Pad Unit.)
- Radio Shack Model 273-060 OR 273-060A 12v DC Piezo Buzzer (Steady tone) ** 2 REQUIRED
- Radio Shack Model 273-066 12v DC Piezo Buzzer (Pulsing tone)
- Radio Shack Model 276-1104 1N4005 Diodes ** 5 REQUIRED
- Radio Shack Model 270-1803 5x2.5x2 Project Enclosure (Remote Unit)
- Radio Shack Model 270-1807 7x5x3 Project Enclosure (Relay/Pad Unit)
- Radio Shack Model 270-015 Mini-Blade fuse holder (In-Line style)
- Radio Shack Model 274-0252 1/4" Mono Phone Jacks - Used as the stationary part of the RSO's Interlock switch.
- Radio Shack Model 274-1536 1/4" Mono Phone Plugs (Will need to be modified by shorting the two connections together inside the plug's plastic cap.) - Used as the removable part of the RSO's Interlock switch.
- 14 gauge stranded jacketed electrical/electronic wire (Typically copper or tinned copper), 15 feet - Used for connections inside the boxes.
- Misc spare fuses, 15 amp recommended
- Gel cell for battery source. 12volt DC and 7 amp (12v/7a) is o.k. 10 to 20 amp preferred.


One of the more interesting aspects of this design is that it can be changed easily once understood. One thing I could not find easily at the local stores was a small keyswitch that would fit the Remote Unit's project box size I chose. I could have elected to do without this popular style interlock switch and just use a missile-launch-style switch with a disarming guard cover. If I felt the need to assure the switch isn't operated from the Remote/LCO position when I am at the Pad end of things I can always easily unplug the Remote Panel/Box and carry it out to the pad much like the key from the keyswitch can be hand carried out to the pad area to assure no unexpected launches when working near the rockets. Tom Beach suggested that I use a phone plug as the safety switch, and so I modified one by shorting a 1/4 inch two-conductor one internally and that works quite well.

I elected to use a 12.5 amp/hour gel-cell battery to power the unit so I used 14 gauge wiring and a 15 amp fuse and appropriate holder. If you decide to use a bigger battery to ignite your large clusters, be sure to upgrade the fuse, the wire gauge for the current, and your alligator clips for battery connection. If you need a tremendous amount of current (more than 40 amps,) you will also need a higher current relay and perhaps higher rated toggle and pushbutton switches. Above 60 amps you will need to examine every part in this unit. What you will need to upgrade will depend on how far above 60 amps you want to go.

You can choose to change the size of the boxes, use metal toggle switches for extra long life, and so forth. I recommend not removing the access cover from the arming switch as this can be used as an immediately accessed safety by simply closing the cover. Whatever you decide to do that modifies the parts used or the design itself is your decision, but if you change the design or the parts used YOU assume liability for any resulting loss is safety. Please be careful not to downgrade the ratings on any parts. The high-current safety switch used on the pad/relay box should NOT be replaced as this is a robust and very high current switch and you might run into safety problems by switching this for something smaller. (Fortunately this launcher's design and test procedure will alert you during pre-flight testing if there are welded switch contacts as a result of using an underrated switch !)

I was told that Radio Shack no longer offers the three buzzer parts from their website. However Radio Shack merely changed the numbers associated with these parts. Nonetheless substitutions can be made HOWEVER be sure to get units that do NOT use more than 4 ma current in operation and that will reliably operate over a range of at least 4 to 24 volts. Successful alerts and the low current operational features of this unit are dependent on proper substitution of these critical parts.

Rocket Graphics courtesy of the Crystal Space Community.