Estes Launch Controller

Homebuilt 9-volt Launch Controller
Here is my homebuilt 9-volt launch controller for Estes type rockets. Below is the schematic I used to build this controller. It comes from the Estes version with a second switch added. Also it uses a 9-volt battery that will fire CopperHead® igniter's from Aerotech. Building this controller assumes that you know how to read schematics and solder electrical parts together. I will not be held responsible for misuse or mis-constructed devices that may cause harm, damage or injury. Please get help to put this device together from someone who has experience with electronic construction if you do not. In order to use this controller, you must use a high quality 9-volt battery like a Duracell or Energizer battery. Regular 9-volts will not fire even Estes igniter's. It is a simple device that gives you a continuity test with one switch. When switch one is pushed the LED will light up if there is continuity. In order to fire the rocket, switch one and switch two must be pushed at the same time. Also note that no power can get to the igniter while the safety key is out.

I will list the parts used but I don’t have part numbers for Radio Shack. I built this with items I already had in my electric junk box. All parts should be available at Radio Shack.
Here is the parts list:
One project box with 9-volt battery access cover
One NO (Normally Open) push button switch with black button
One NO (Normally Open) push button switch with red button
One 2.2K ohm resistor 1/8 watt
One orange LED (Light Emitting Diode)
One 9-pin serial connector male or 1/8-1/4 phono-jack male
One 9-pin serial connector female or 1/8-1/4 phono-jack female
Some 20 gauge wire for internal wiring
35 feet of 18 gauge speaker wire
2 small alligator tips

Here are the tools I used to put this together with:
Drill with drill bits for drilling holes
Hot Glue gun for gluing in LED
Soldering iron to connect electric part together
Solder for the soldering iron
Heat shrink for exposed wire connections
Wire cutters for cutting wire
Wire strippers for stripping wire insulation
Lighter or small torch to melt heat shrink
A small saw to cut out the key hole (rectangle hole)

The box I used is a small project box that had a 9-volt battery slot and cover already built in. All I needed to do to the case was to drill holes for the two switches, led, safety key and wire leads to igniters. I decided to put the safety key and one push switch on the top of the box. This moves the key away from the launch button. Both switches must be pushed in order for the current to pass onto the igniter. By having a switch on top and one on the side, this prevents an accidental fire of the rocket if the controller is dropped on the side with the launch button down. The key you want to have can be a simple 1/8 or ¼ phono plug and phone jack. You will have to solder a wire across the terminal inside of the plug for it to work. Switch one is the switch with the black button and switch 2 is the switch with the red button. See picture for placement. Please make sure you read all instructions before you begin to put this together. Make sure all parts will fit in the place you want them to go.

Putting it together
I started off with drilling the hole for the LED. I drilled it just big enough for the top part to fit. LED’s usually have a small ridge at the base. This ridge is what keeps the LED from going all the way through the hole. Glue the LED into place. Next drill holes for the safety key, both switches and for the wires to come through the top. You may have to check to make sure the parts will fit where you want them to go. It depends on the part sizes you get. Next install both switches as per the picture. Install your female safety key connector or jack.
It is time to hook up all the wires as per the schematic. The only thing you have to worry about is hooking up the LED. It only works one way. If you hook it up backwards, it will not work, but the controller can still fire rocket igniter's this way. Please test before using on a rocket. Make sure you have a hole for the wire leads. Tie a small knot in the speaker wire at the end buy the controller. Then feed the leads out the hole you made for the leads. The knot will keep the wire from being pulled out of the end on the controller. Once all the wiring is soldered you can solder on the alligator ends.
The resistor that is put in before the LED is used to limit the amount of current sent to the LED and igniter from the battery. All lamps and LED’s can allow some current to flow through the motor igniter to test continuity. If too much current goes through, it can light the igniter and fire the rocket motor unexpectedly. I tested mine to be around 17mA. To test the continuity light, install the battery and attach both alligator leads together. If everything is right, push the black button switch one and the LED should light up. If not reverse the LED leads. If it does light up, you have a good path for current to flow and ignite you rocket motors. I would also suggest that you test the controller for lighting actual Estes and Copperhead igniter's. First make sure that you are outside and no rocket motor or flammable things are around. Next hook up an igniter and set it on a piece of wood or on the ground. Push the black button to check continuity. If the LED lights up, while holding the black button down, push the red button and the igniter should glow red and flash. This is what happens inside the rocket motor. If it did not work, but you got the LED to light, you may what to verify that you have a name brand high output 9-volt battery. Hope this helps.
I had all the parts already lying around so it did not cost me anything but my time. You should be able to do this project for about $10-12 dollars. Good Luck.