Coil Gun Kit Instructions

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Introduction

These step-by-step instruction were designed for the coil gun kit offered on the Stuff for Sale page. If you purchased this kit, you should have all the necessary parts to complete this project with the exception of tools and other building equipment.

Step 1. Winding up a Coil

With a bit of super glue, secure a section of the magnet wire to the pipette leaving a few inches of extra wire sticking out as a connection point. The placement of this coil should be near one end of the pipette, allowing easy access to it for positioning the projectile. Now wind a single layer of the coil neatly up the pipette, approximately 0.5 inches long. Now secure this layer of the coil in place with a dab more super glue. When the glue is dry, wind the next layer on top of the first layer back towards where the first one started. Repeat this until there are 5 layers of windings. Glue everything in place and cut the wire leaving a few inches of extra for connection to the circuit. You may also want to wrap the entire coil with some electrical tape to make sure everything stays put. Now take a sharp knife and scrape off the enamel insulation from the two leads that you have left for connection. Sometimes the enamel coating is clear, so it may be difficult to determine if it is gone. To find out, try measuring continuity (ohms) across your coil's leads. If you have removed adequate insulation and made good contact, the resistance should be only and ohm or two.

Step 2. Modifying the Camera Circuit

Essentially all the circuitry for this project can be found (and used) already made inside a typical disposable camera flash circuit. The camera brand/model will vary with the kit, but operation is the same for all. Start off by CAREFULLY removing the back cover from the camera. There should be a few plastic tabs around the perimeter of the camera that you would need to pry loose with a flat-head screwdriver. Once the back cover is off, you need to remove the battery. It is important that you do this first if you do not want to be shocked. Once the battery is removed, you need to manually discharge the capacitor to ensure that it doesn't have a stored charge on it. This is done by taking a screwdriver with an insulated handle and shorting the leads together. Now it is time to remove the entire circuit board from the plastic casing.

Once you have removed the circuit board, try to figure out how the circuit worked in the camera i.e. charging up the and make the flash work. Usually, there is a "charge" button on the front of the camera (red arrow) which when pressed begins the charging cycle. As for triggering the flash there is generally a mechanical switch in the camera so that when the shutter flings open it somehow triggers the flash. But now we have no shutter, so we must jumper these switch terminals (short them together) to make the flash go. These two terminals are usually some bulk metal pieces (black arrows in photo) that used to attach to the shutter system. So put your battery back in (carefully) and test charging and discharging the flash. If you can't get it to work here, it will never work in the completed project. Once you are satisfied with this, remove the battery and short out the capacitor with your screwdriver again. You may want to solder an actual switch in the place of the old shutter mechanism to trigger the flash, buy you don't have to.

Step 3. Connecting the Coil to the Camera Flash Circuit

There is only one simple connection to the camera flash circuit. Carefully unsolder one of the leads that connect to the ends of the flash tube. Now take this lead and solder to one of your coil leads that you stripped. Solder your other stripped lead to the flash tube end that you unsoldered from before. Now when you test your charging and discharging, you should see that the coil in the circuit has little influence on the flash operation.

Connecting the coil this way allows us to use the existing flash tube as a "trigatron" to switch the high voltage and current. If we were to use a regular switch, the switch wouldn't last very long.

Step 4. Adding additional Capacitors

If you purchased the optional capacitors with the kit, you may use them for a multi-stage gun (not covered here) or you can put one or more of them in parallel with the capacitor in the camera flash circuit for more powerful single stage coil gun. These capacitors are electrolytic, which means that they have polarity requirements. They have a positive and a negative terminal. To add them in parallel, simply hook the positive terminal to the positive terminal of the flash capacitor and the same for the negative terminal. The flash capacitor should have some sort of marking on it indicating which is the positive terminal. Often times it is marked with a stripe printed on the side of the capacitor leading to the negative terminal.

Step 5. Testing Out Your Coil Gun

If you have followed the above steps and everything has worked out right, now it is time to fire off you coil gun! Take the projectile and place it inside the pipette so that the end of it is just poking inside the end of the coil. This will be the back end of the gun, the projectile will be pulled toward and through the coil so point it in a good direction. Now charge the circuit and hit the fire switch. You projectile should be launched through the barrel and out the other end. You may have to play with the projectile starting position a bit to reach optimal launching speeds. Keep in mind that this is a relatively low power system. If you are using all three of the optional capacitors charged to three hundred volts, the energy stored in this system is approximately 20 joules.

So What's Next?

Well this is only the beginning. Once you have made a single stage device you know most of the principles involved in building a higher power multi-stage device. Sensor controlled switching, silicon controlled rectifiers, velocity and timing circuits. This project can keep you busy for a long long time!

DISCLAIMER

The author assumes no liability for any incidental, consequential or other liability from the use of this information. All risks and damages, incidental or otherwise arising from the use or misuse of the information contained herein are entirely the responsibility of the user, have a nice day!

Last updated: 06/22/03
Copyright 2003, Greg Miller
http://www.angelfire.com/80s/sixmhz/cgkit.html