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Quick coilgun project: Single stage SCR V-switch coilgun pistol

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LAN_403

TheMerovingian

Thu Jul 06 2006, 11:55AM

Registered Member #14 Joined: Thu Feb 02 2006, 01:04PM
Location: Prato/italy
Posts: 383

During these days i have built a pexiglass cased coilgun pistol.

Technical details:
Model: EMP090S1SDR
Exit speed:23 m/s (71mfeets/s)
Armature mass: 6g
Kinetic Energy: 1,6J joules
Starting voltage: 310V
End voltage:150V
Capacitance: 1900uF
Efficiency: 2,29%
Impactivity (P/surface): 4,9 Tons m^-1 s^-1

Charging circuit: 10W 300V Tl494-controlled boost converter (d2pak 600V fairchild igbt)
Capacitors: 1900uF worth of photoflashes
Display: lm3914

Pointer: 5mw laser pointer with screw-spring adjusting
switching: high side v-switch with GDT and magnetic sensing (coil on projectile entrance)
Snubbing: 30A ultrafast fairchild diode + 1,2ohms 10W wiredoun resistor

Coil: 98uH, 250mOhms
Power supply: 12V 1,2AH SLA

Charges in 9 seconds

pierces through cans.
blunt projectile with no gyroscopic stabilization.

Note: a feet is 30,5cm and mfeet is 32,8 cm

WaveRider

Thu Jul 06 2006, 01:06PM

Registered Member #29 Joined: Fri Feb 03 2006, 09:00AM
Location: Hasselt, Belgium
Posts: 500

Pretty E1ite gun you've got there! How did you come up with the model number? Are the LEDs for indicating the state of capacitor charge...

I like it...

Maz

Thu Jul 06 2006, 04:45PM

Registered Member #111 Joined: Fri Feb 10 2006, 01:04AM
Location: Menasha,Wisconsin
Posts: 65

actually it is more like 73h 1337012Z!!!!111!!11oneone!

but some things just dont jive the way they should to me.

doing the electronics would have taken me at least a day of soldering (im a slow worker)
doing measurements, and cutting out the pattern for the gun must have taken a while as well.

so if you invested that much time into it, it pains me that you chose to use silicone caulk to hold it together and not Weld-on or glue of the sort...

either way, great work, keep it up!

TheMerovingian

Thu Jul 06 2006, 07:14PM

Registered Member #14 Joined: Thu Feb 02 2006, 01:04PM
Location: Prato/italy
Posts: 383

model number stands for:

EMx-yyyy-Szz-xx-Py-Tz

x= P (Electromagnetic Pistol) or R (Electromagnetic rifle)
yyyy = Start capacitor energy (joules)
zz = stages
xx = type (HB = halfbridge, SC = SCR, SDR = scr-vswitch, ID = igbt-diode, IDR = igbt-diode resistor, MD = mosfed diode, MDR = mosfet diode resistor)
y= number of pre stages (if 0, omit)
z= tyming type (A= analog, D= digital, if absent , omit)

The glue is hot glue, ideal for construction.

The leds indicate the voltage in divisions of 30V each

Note: on the chassis 1,2J 20m/s are written, to respect the firearm legal limit (in italy 1.35J).

rupidust

Fri Jul 07 2006, 01:02AM

Banned
Registered Member #110 Joined: Fri Feb 10 2006, 12:23AM
Location: Banned City
Posts: 85

You may be cheating yourself out some feet per second. How are you converting m/s to f/s? Should be 1 m/s = 3.28 f/s. If you are then calculating joules based on f/s you could be having a slightly higher joule rating than you think.

TheMerovingian

Fri Jul 07 2006, 03:35PM

Registered Member #14 Joined: Thu Feb 02 2006, 01:04PM
Location: Prato/italy
Posts: 383

mmm actually you are right, but i used for my speedtrap a 2/10 of a "feet" taking it 6,56 cm of sensor spacing instead of 3,05. So the conversion unit from feets to meters is 1 feet = 0,328 meters

they arent actually feets but mfeets (merovingian feets

)

a real international feet is 30,5 cm and a metre is 3,28 feets

so the meter x second are ok

1 mfeet = 1,09 real feets

so the speed in feets x second is 66

The sensor spacing is 6.56 centimeters
so
the projectile travelling at 23m/s
takes 2,85ms to trigger both sensors.
Since it is taken as 20% of the unit 0,2/0,00285 = 70mfeets/s
70mfeets/s = 22,95 m/s

6,56 / 0,2 , an mfeet is 32,8 cm
despite a feet is 30,5 cm

williamn

Fri Jul 07 2006, 10:31PM

Registered Member #55 Joined: Thu Feb 09 2006, 04:56AM
Location:
Posts: 149

Very cool Mero! I have one on the way too, you beat me too it :)
What type of sense coil did you use, this is something I have been playing around with, and results are pretty good.

William

Marko

Fri Jul 07 2006, 10:34PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

If someone wants t be really 1337 he should build a small railgun like such

I don't know if anyone actually got such a miniature (in 100's of joules range) railgun to work and give some significant thrust..

FastMHz

Thu Jul 13 2006, 06:55PM

Registered Member #179 Joined: Thu Feb 16 2006, 02:08AM
Location: Hagerstown, Maryland - Close to Prime Outlets
Posts: 287

Nice work...and good efficiency too.

TheMerovingian

Fri Jul 14 2006, 11:44AM

Registered Member #14 Joined: Thu Feb 02 2006, 01:04PM
Location: Prato/italy
Posts: 383

The sensor is a bit atypic. It works on the v-switch principle, using two scr-s.
THe first is triggered by a gdt (and the trigger), the second is triggered from the induced voltage when the projectile exits the small coil, of course clamped by a 6V zener. The snubbing network is a 1.2ohm 10W wirewound resistor and a 30A Ultrafast fairchild diode to damp the field faster. A higher walue would be possible (approx 2.5 ohms) but in this case the simulation shows that the field damps too fast losing the chance to further accelerate the projectile during turn-off phase. The result is that the projectile is very fast, able to punch through a wall of a can full of water and seriously damaging the opposite wall, despite the friction of water. The projectile impact on a ferrous object damages it. A projectile bulged a bit and jammed upon fire in the launch tube, needing a screwdriver to get it out and lots of patience. It is dangerous for windows and peoples even with blunt projectiles.

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