Return to contents.

An Inexpensive Flasher for Night Launches

by Bill Orvis, LUNAR #309

I have been toying with some ideas for creating inexpensive locators for our rockets to make them easier to find in the dark. It turns out that if you have one of those disposable flash cameras laying around, you can modify the flash unit so it flashes about once every 6 seconds. It is not difficult for anyone who can solder a wire. I did the same modification on a Fuji and a Kodak unit, so I expect that you should be able to do the same thing with other brands as well.

The Fuji unit made the smallest flasher, which would fit in the clear nose cone of an Estes Magnum (1.6 inches diameter). You might be able to make it smaller, but you would have to get real creative cutting and folding your circuit board.

  1. After shooting all the film, open the film door (usually with a screw driver) and remove the film cartridge (a standard looking 35mm can). As you take pictures, the film is wound into the can, so when you are done, the film is all in the can and does not need to be rewound. This is just the opposite of a normal camera.

  2. Separate the front and back of the camera to expose the circuit board. It is usually held together with plastic clips, so you just snap it apart (or break it, you are not going to put it back together, just don't break the circuit board).

    BE CAREFUL - Do not touch the leads of the photoflash capacitor. It is a cylinder about an inch long and one half of an inch in diameter with two wires coming out of one end. It can be charged up to 250 Volts and bites. Imagine a rat on PCP and you get the idea. I speak from experience here. It will not kill you, but it is not pleasant.

  3. Clip a wire across the photoflash capacitor to short the two leads together. If the capacitor was charged, it will make a spark when you apply the wire, so be sure to use a wire with insulated clips. This discharges the capacitor, making it safe to touch. It also makes it impossible to short the capacitor across the oscillator transistor and blow it out. I blew out two before I started being more careful.

  4. Remove the circuit board from the camera.

  5. Remove the battery.

  6. Locate the charging switch. This is the one you press to charge up the flash. Solder a wire across this switch so it is always on.

  7. Locate the trigger switch that is closed when you take a picture.

  8. Solder two neon bulbs in series across that switch. One bulb might work, but it will stop after the bulb ages a little. Two bulbs provide a 140 volt trigger pulse that seems to work every time.

  9. Remove the shorting wire from the capacitor and insert the battery to see if it works. It should charge for about 6 seconds, the neon bulb will flash and the photoflash will flash. It will then charge again, flashing about every 6 seconds.

  10. If it works, now you have to get it to fit into the transparent nose cone of a rocket. I guess you could tape it to a fin, or tie it to the shock cord, but it will be safer if it is in a clear plastic nose cone. {Actually, taping it to a fin with the capacitor exposed might be a good way to convince all the kids who run to catch your rocket for you to leave it alone. :-) }

  11. Remove the battery and apply the shorting wire to the capacitor (big spark and a loud noise; I'm glad that was not my finger again).

  12. Figure out where you are going to have to cut the circuit board to get it to fit in your nose cone. Pay close attention to the traces on the circuit board. You will have to solder wires to reconnect any traces you have to cut. Also pay attention to which end of the battery connects to which trace on the circuit board.

  13. Cut the circuit board in half and cut away any non-essential parts of the circuit board, such as the battery clip.

  14. Arrange the two parts of the circuit board so they will fit as a unit into your nose cone. Glue or tape the parts in place (not in the nose cone). Make sure none of the wires on the circuit board touch.

  15. Solder short pieces of wire to reconnect any traces you had to cut. You do not need to solder the wires to the exact points where the traces were cut. Anywhere on a trace will do.

  16. Solder a wire to each end of a AA battery. Don't let the battery get too hot while you are doing this.

  17. Solder one of the two wires to the trace on the circuit board where the battery clip connected. Be sure to attach the correct end of the battery to the right trace.

  18. Solder another wire (not the one connected to the other end of the battery) to the trace where the other end of the battery connected. You should be left with two unconnected wires, one from the battery and one from the circuit board. These two wires are your switch for turning the unit on and off.

  19. Remove the shorting wire from the capacitor and connect the two switch wires together to see if the unit still works. If it does not, check to see that you have reconnected all cut traces and that you have the polarity of the battery right.

  20. Disconnect the battery and reattach the shorting wire (Ooh, another big spark and loud noise.)

  21. Fit the battery and circuit board into your nose cone, making sure that you do not short any wires in the process. Use electricians tape to cover any wires that might short during launch. Bring the two wires (from the battery and circuit board) to the outside.

  22. Remove the shorting wire and insert the nose cone.

When you are ready to launch, twist the two wires together to make the flasher start working and fly the thing. One AA battery should last for more than enough time to find your rocket.

Some other options I have been playing with are old children's toys that have flashing lights and sounds (There are a lot around my house so the kids will never miss one or two -- Not!). The best is the super-deluxe, galaxy class blaster, with flashing lights that run around it and a noise that is guaranteed to drive off evil spirits (or parents). After you remove all the plastic, you are left with a little circuit board with a couple of attached watch batteries. Add wires to the pads where the buttons were so you can turn it on and off by twisting the wires together. These units should fit in the smaller rockets, giving them an audible locator.

Anybody else got some inexpensive ideas for locators? If anyone needs help, you can contact me, Bill Orvis at or

Copyright © 1997 by LUNAR, All rights reserved.

Information date: September 14, 1997 lk