I used to make rockets as a kid, but haven't made any in probably the last 15 years. So to get back in the spirit this is what I came up with. (I made this slideshow as an afterthought, so sorry to say no build pictures).The first time my wife saw it she asked me if I was about to rob a bank (Thus the name BDC, Bomb Detonation Controller) , so I'm pleased with the very detonatoresque way it looks.
The breakdown of the whole system is relatively simple. I'm sure most of you can figure it out by just looking at the wiring, but I will break it down to individual components. Total cost of parts was probably around $15 (versus $25 for a store bought controller). This whole project runs from a single 9V battery.
- First is the project box. I just picked it up from Radioshack to enclose all of the components. its the medium sized box
- Next is the interlock safety switch, also from Radioshack. It has a safety cover to prevent accidental engagement and an indicator light which I use as an "ARMED" light. The positive of the 9V battery is soldered to the "power" lead of the interlock switch. The negative of the 9V is soldered to the "ground" lead of the switch. Another ground wire is soldered from the ground lead to the black binding post.
- The ACC lead from the interlock switch is soldered to the momentary ON switch that is used as a "FIRE" button on the controller. Which is then wired to the red binding post.
The circuit, in essence, is a very simple switch circuit. Flip the saftey cover up, flip the "ARMED" switch, and press the "FIRE" button to launch your rocket! I made the wires that lead to the rocket out of some 22 gauge speaker wire and some solder on alligator clips. The wire needs to be at least 15 feet long to keep the user far enough from the rocket to prevent injury. The ends of the speaker wire are stripped so they can be attached to the binding posts.
Note: When I installed the binding posts, they have a metal thread instead of a plastic one that goes through the project box. I had to insulate the threads, with heatshrink tubing, to prevent the hotlead from grounding out on the case.
**This launch controller follows the NAR (National Association of Rocketry) guidelines for an ignition launch controller. Directly from the NAR website: "Ignition System. I will launch my rockets with an electrical launch system and electrical motor igniters. My launch system will have a safety interlock in series with the launch switch, and will use a launch switch that returns to the "off" position when released."**