Overview:
My cousin Jason and I decided to build an electromagnetic coil gun. In principal, it draws a metal object into an electromagnet at a high speed, then the magnet is shut off and the projectile continues to move at a high velocity. Simple enough right?
Technical specs and schematic:
Our device is a single stage gauss gun, that means there is only one electromagnet, and only one instance of acceleration. This is a less efficient, but infinitely simpler method. We tried 12V and found acceleration was lousey, so we moved to 120V, much better, but the AC just jiggled things around violently inside rather than throwing the object. Finnally we settled on charging a Cap bank with 120V rectified and releasing it through the coil (roughly 170V although minor power surges have on one occasion brought it all the way up to 192V!
Getting 180V is very
common at my cousins house but I never get higher than 178V.) The
gun is charged with a light switch allowing current to pass through a
resistor and rectifier. Our first resistor was a jar of salt
water (when the bubbles stopped, it was done charging,) and our first
rectifier was two microwave oven diodes in parallel (hey, it was what
we had convienent at the time.) The gun was then fired by closing
hte first light switch, and opening another one allowing the cap banks
to flow from one side to the other through the coil.
We quickly decided that higher voltage was better, and then decided that we were not satisfied with 120V. I devised a method using switches to charge two cap banks in parallel (to full voltage) and then flip some switches to rearrange them in series (using peak voltage 170V this was 340V!) That was fun for like 4 hours straight. Then we got hungry for more power again and realized that a gazillion switches was going to be problematic, so we tried MOSFETs and when they blew up, we used relays for 4 cap banks. Plugging in peak voltage that is 680V. With a sharpened projectile we can punch through a can without denting it! We use 7000 uF (a number we choose based on other designs, although we varied it and found it was indeed the best for our coil.) We still need light switches to handle the shock of switching the cap banks to series, but we eliminated all the charging switches with relays; not bad eh?
Results:
The results are sweet! We spent very little on this project, roughly $150 and the gun will shoot our projectile (2.5in*.25in steel of unknow mass) approximately 60 feet into the air when shot straight up. It is especially good a powning soda cans. We plan on upgradimg to six stages soon, as well as tweaking the position of the projectile in the barrel for maximum thrust (if you put it in too far, it will hit the center of the magnet too quickly and waste energy trying to slow itself down.
My cousin Jason and I decided to build an electromagnetic coil gun. In principal, it draws a metal object into an electromagnet at a high speed, then the magnet is shut off and the projectile continues to move at a high velocity. Simple enough right?
Technical specs and schematic:
Our device is a single stage gauss gun, that means there is only one electromagnet, and only one instance of acceleration. This is a less efficient, but infinitely simpler method. We tried 12V and found acceleration was lousey, so we moved to 120V, much better, but the AC just jiggled things around violently inside rather than throwing the object. Finnally we settled on charging a Cap bank with 120V rectified and releasing it through the coil (roughly 170V although minor power surges have on one occasion brought it all the way up to 192V!
We quickly decided that higher voltage was better, and then decided that we were not satisfied with 120V. I devised a method using switches to charge two cap banks in parallel (to full voltage) and then flip some switches to rearrange them in series (using peak voltage 170V this was 340V!) That was fun for like 4 hours straight. Then we got hungry for more power again and realized that a gazillion switches was going to be problematic, so we tried MOSFETs and when they blew up, we used relays for 4 cap banks. Plugging in peak voltage that is 680V. With a sharpened projectile we can punch through a can without denting it! We use 7000 uF (a number we choose based on other designs, although we varied it and found it was indeed the best for our coil.) We still need light switches to handle the shock of switching the cap banks to series, but we eliminated all the charging switches with relays; not bad eh?
Our charging
resistor/rectifier is a thing of beauty, my cousin Jason is to be
credited with it's design and creation.
I will have a proper shcemait up here soon guys, just be patient for now!
I will have a proper shcemait up here soon guys, just be patient for now!
The results are sweet! We spent very little on this project, roughly $150 and the gun will shoot our projectile (2.5in*.25in steel of unknow mass) approximately 60 feet into the air when shot straight up. It is especially good a powning soda cans. We plan on upgradimg to six stages soon, as well as tweaking the position of the projectile in the barrel for maximum thrust (if you put it in too far, it will hit the center of the magnet too quickly and waste energy trying to slow itself down.
Scott Bogard, 2008