The Electromagnetic Projectile Launcher

"Rules of Engagement"

Sat, 31 Jan 2009 16:18:00 -0800

… Lethal Force!

well, not really ‘lethal’, it’s only lethal if you get shocked by the capacitors…

So I finally did my first day of single stage testing (using a push button to trigger shot). I got it to shoot through 2 layers of cardboard and almost through a can. Right now, I’m shooting at around 320V, and hopefully I’ll be able to push this up to 380V later on (I’m just to lazy/scared to test right now). I’m just glad I got it to fire without frying a part. Turns out a simple sugar-cube relay could handle the burst of voltage & current. I’m using a SPDT relay, but a SPST should suffice. But if I want it to automatically turn off the charging unit, I should get a DPDT.

What next?

I guess I should start on building my optical triggers, and start building my second stage.

I should also purchase my turrent/pan tilt kit soon.

EDIT:

Actually I just examined the can, most noteably the upper rim where my projectile hit. The material up there (and the bottom) is actually thicker and harder than the middle of the can. I’m thinking theoretically, if I hit the middle of the can.. it would’ve punctured straight through, seeing that it almost went through at the top of the can.

almost through a can! (320V)

Sat, 31 Jan 2009 16:09:59 -0800

almost through a can! (320V)

straight through two layers of cardboard! (320V)

Sat, 31 Jan 2009 16:09:17 -0800

straight through two layers of cardboard! (320V)

Wii Nunchuck, Arduino & Servos!

Fri, 30 Jan 2009 14:30:06 -0800

Wii Nunchuck, Arduino & Servos!

i finally got it to shoot! at the cost of an IGBT. proof of...

Fri, 30 Jan 2009 01:20:07 -0800

i finally got it to shoot! at the cost of an IGBT. proof of concept that it works.

i loaded the projectile ~1/4 or 1/6th of the way into the coil.. charged the caps to ONLY 100V

triggered the IGBT, and out goes the projectile hitting the box what it looks like to be almost perfectly square on. the box actually had two layers of really good cardboard so it didn’t puncture the box completely… and it knocked the box over and the projectile bounced back to the wall..

the coolest part: SILENCE leaving the barrel… on firing.. you just can barely see it exit.. and the next thing you know.. a pop (when the projectile hit the box) and the box tumbling over in front of you…

pretty cool @ only 100V..

i’m gonna pick up a relay from jesse tomorrow to see if that will suit my needs as a trigger… we’ll see. (for the second stage though i think i would still need and SCR/IGBT as a relay wouldn’t trigger fast enough)

this is what a 200V spark did… (note to self: jesse was...

Thu, 29 Jan 2009 01:24:40 -0800

this is what a 200V spark did… (note to self: jesse was right.. i need saftey glasses)

—

what happened:

i tested the coil that I made with a 1.5V (D-sized) battery (pictured below with the coil) to make sure it was magnetic. (it was =]).. (btw, the measured resistance of the coil is inbetween 3-4ohms)

i then bought an SCR and wired the anode/cathode in series with the coil with the capacitors in parallel. the gate was connected to a wire which i would manually connect to a 12V line in series with a 1k resistor.

i charged up the capacitors to 250 volts.. turned off my charing circuit… loaded my projectile into the proper location (1/8 of the way entering into the coil). and connected the gate of the SCR….

NOTHING..

i examine the circuit… everything is in order.. i check the voltage over the caps to make sure they’re still charged and they are… i wonder what went on… i unplugged the + on the caps connecting it to the boost converter and accidently left it hanging.. and second later while examining the circuit… a HUGE spark and a HUGE noise (sounded like a really big high pitched firework)..

i got discouraged and stopped working for the night..

this is the damage it left on the breadboard.. the hanging +’ve line scrapped against the ground… and it STILL left a 50V charge over the caps…

It took me forever to properly wind magnet...

Thu, 29 Jan 2009 01:16:04 -0800

It took me forever to properly wind magnet wire…

—

This is how I did it… (with the stuff I had in my room)

I took a screw, used a hacksaw to chop of the end of the screw.

I then wraped some duct tape over the screw so that it would provide support for the barrel as the screw is around a hundreths of an inch too small to be a perfect fit.. (the problem i was running into before caused my wrapping to compress the barrel and therefore causing more friction and my projectile to get stuck inside the tube)

I then cut my tube/barrel to the size of my desired coil, slipped it over the duct tape (forcefully, if it didn’t take force.. i think the tube would’ve been compressed again).. and then wrapped the barrel with 2 pieces of regular notebook paper so that i could slip the tube off and stick it on my real barrel..

i had two washers on the side that fit on my barrel perfectly…

then had to end thingys that acted as lockwashers…

weeee, i made a coiling jig without having to goto the hardware store..

to wrap.. i just wrap as tightly as possible and the picture is what you get!

i wrapped 8 layers and is ~>1inch in length

Boost Converter, perfect test! 360V is less than a couple...

Thu, 15 Jan 2009 22:03:44 -0800

Boost Converter, perfect test! 360V is less than a couple seconds.

Boost Circuit testing!

Thu, 15 Jan 2009 22:02:35 -0800

Boost Circuit testing!

Perfect 555 timer waveform, double checked with oscilloscope.

Thu, 15 Jan 2009 22:00:39 -0800

Perfect 555 timer waveform, double checked with oscilloscope.

Booster Circuit in progress: 15V Regulator working (Denoted by...

Wed, 14 Jan 2009 21:33:00 -0800

Booster Circuit in progress:

15V Regulator working (Denoted by top left LED, verified by DMM)
555 Timer Blink Test Working (The middle LED is actually blinking)
LM311 Op Amp Comparator Working (Last LED turns on and off depending on -‘ve/#2 input voltage

And to the right is one of multiple large caps I’m planning to charge.

Things needed to complete the circuit:

Diode/Inductor/IGBT connections that actually charge.
Replace TS555 with NE555

I’m due for another trip to MarVac tomorrow (thank EECS70B for showing that place to us engineers =])

Overall, decently productive day… I have parts all over my desk…

—

things to do in lab tomorrow:

-use oscilloscope to check freq of 555 output
-demo joystick/arduino to jesse
-if booster converter complete, try to charge 1 400V 470uF cap
-ask jesse about his eaglecad/pcb slides

things to do for fun tomorrow:

-play with new soldering tools! weee

ATX Power to Bench Power Supply OH YEAH! Initial test works! ...

Wed, 14 Jan 2009 21:29:13 -0800

ATX Power to Bench Power Supply OH YEAH!

Initial test works! Combined the -12 and +12V rails to get close to 24V swing (I know this PSU sucks, but I’m to lazy to pull a decent one out of an older computer, this one I found laying around in my closet).

NE555 Calculator/Equations via Instructables

Wed, 14 Jan 2009 21:27:11 -0800

NE555 Calculator/Equations via Instructables:

just useful information for me to calculate how to tweak the 555 timer.

Note to self: buy a NE555 timer, (I accidently bought a TS555 which is rated lower for amps)

How to Convert an ATX PSU to a Lab Power Supply - wikiHow

Tue, 13 Jan 2009 15:26:00 -0800

How to Convert an ATX PSU to a Lab Power Supply - wikiHow:

looks like i have a side project to do… where can i find something to drill holes through metal?

simple snapshot of progress: nunchuck w/ arduino and code from...

Tue, 13 Jan 2009 00:32:00 -0800

simple snapshot of progress: nunchuck w/ arduino and code from instructables.

(taken with iPhone!)

Progress...

Mon, 12 Jan 2009 12:45:00 -0800

I’m not sure what problem I had before, but it seems to be resolved now. Initially when I stripped off the end of the nunchuck (before I found: http://store.fungizmos.com/index.php?main_page=product_info&cPath=69&products_id=212), and stripped the individual wires, the arduino would stop responding to my computer via USB. During the weekend, I soldered the stripped wires so that the braided wire would be easier to connect to the arduino directly or through a breadboard. I believe this fixed my problem. Possibly something was shorting… stupid Nunchuck wires.

—

Progress report:

~~Wii Nunchuck communicates with ardunio~~

Waiting on parts to arrive (TAKING FOREVERS, and my new soldering station http://www.circuitspecialists.com/prod.itml/icOid/7307)

Plan for tomorrow:

Hopefully the parts will arrive, and I’ll be able to initially start on the boost converter.

In the mean time:

I’m trying to find an old PSU to see if I can turn it into a power supply for this project (and future projects!).

Instructable Control Your Robot Using a Wii Nunchuck

Mon, 12 Jan 2009 12:12:00 -0800

Instructable Control Your Robot Using a Wii Nunchuck:

Okay, using this (and proper connections), I finally got the Wii Nunchuck to communicate with the Arduino and can detect all movements for Joystick, Accelerometer, and Buttons!