Quick coilgun project: Single stage SCR V-switch coilgun pistol
TheMerovingian, Thu Jul 06 2006, 11:55AMDuring 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
Re: Quick coilgun project: Single stage SCR V-switch coilgun pistol
WaveRider, Thu Jul 06 2006, 01:06PM
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...
WaveRider, Thu Jul 06 2006, 01:06PM
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...
Re: Quick coilgun project: Single stage SCR V-switch coilgun pistol
Maz, Thu Jul 06 2006, 04:45PM
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!
Maz, Thu Jul 06 2006, 04:45PM
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!
Re: Quick coilgun project: Single stage SCR V-switch coilgun pistol
TheMerovingian, Thu Jul 06 2006, 07:14PM
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).
TheMerovingian, Thu Jul 06 2006, 07:14PM
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).
Re: Quick coilgun project: Single stage SCR V-switch coilgun pistol
rupidust, Fri Jul 07 2006, 01:02AM
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.
rupidust, Fri Jul 07 2006, 01:02AM
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.
Re: Quick coilgun project: Single stage SCR V-switch coilgun pistol
TheMerovingian, Fri Jul 07 2006, 03:35PM
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
TheMerovingian, Fri Jul 07 2006, 03:35PM
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
Re: Quick coilgun project: Single stage SCR V-switch coilgun pistol
williamn, Fri Jul 07 2006, 10:31PM
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
williamn, Fri Jul 07 2006, 10:31PM
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
Re: Quick coilgun project: Single stage SCR V-switch coilgun pistol
Marko, Fri Jul 07 2006, 10:34PM
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..
Marko, Fri Jul 07 2006, 10:34PM
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..
Re: Quick coilgun project: Single stage SCR V-switch coilgun pistol
FastMHz, Thu Jul 13 2006, 06:55PM
Nice work...and good efficiency too.
FastMHz, Thu Jul 13 2006, 06:55PM
Nice work...and good efficiency too.
Re: Quick coilgun project: Single stage SCR V-switch coilgun pistol
TheMerovingian, Fri Jul 14 2006, 11:44AM
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.
TheMerovingian, Fri Jul 14 2006, 11:44AM
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.
Re: Quick coilgun project: Single stage SCR V-switch coilgun pistol
williamn, Fri Jul 14 2006, 06:05PM
Hi Mero
So the V-switch you implemented is the type devloped by Evgeny Vasiljev? I have looked at his website in the past and am now intreged to try this topology. I always figured I would get the same if not better control with IGBTs, but your results are very good and are tempting me to have a go at it.
williamn, Fri Jul 14 2006, 06:05PM
Hi Mero
So the V-switch you implemented is the type devloped by Evgeny Vasiljev? I have looked at his website in the past and am now intreged to try this topology. I always figured I would get the same if not better control with IGBTs, but your results are very good and are tempting me to have a go at it.
Re: Quick coilgun project: Single stage SCR V-switch coilgun pistol
TheMerovingian, Fri Jul 14 2006, 08:42PM
basically yes. It is the E.V. v-switch except that i would a small coil around the launch tube instead of using a ferrite stick placed near the coil. Used zeners to clamp spikes and a toroidal GDT for the work SCR, since they are high sided (Cap+ , SCRS , LOAD, ground) so the gates float a 300V. The key to the success is to wire the sensing coil in the right way (otherwise both scrs will trigger at start, and the current will not turn off) and chosing appropriate damping resistor
following 2 simple guidelines:
1) avoid that the induced voltage go higher than your scr rating , in my case 800V( for worst case use Ipeak * Rdamp + V@peak, need a rcl simulator), or the SCR will latch back on.
2) Calculate the proper resistor value to have a not-too fast or not-too slow damping.
calculate the time that takes for the projectile from turn off to reach the coil center, subtracting the scr turn off time (approx 40us) obtaining the time toff. Calculate the current in the coil after turn off with an LR model with this formula I= Ioff* e^(-toff*R/L) and make sure it falls in the 1-10A range.
3) Size the second damper resistor (the one on the small cap bank) 3-4 times the main damper resistor
TheMerovingian, Fri Jul 14 2006, 08:42PM
basically yes. It is the E.V. v-switch except that i would a small coil around the launch tube instead of using a ferrite stick placed near the coil. Used zeners to clamp spikes and a toroidal GDT for the work SCR, since they are high sided (Cap+ , SCRS , LOAD, ground) so the gates float a 300V. The key to the success is to wire the sensing coil in the right way (otherwise both scrs will trigger at start, and the current will not turn off) and chosing appropriate damping resistor
following 2 simple guidelines:
1) avoid that the induced voltage go higher than your scr rating , in my case 800V( for worst case use Ipeak * Rdamp + V@peak, need a rcl simulator), or the SCR will latch back on.
2) Calculate the proper resistor value to have a not-too fast or not-too slow damping.
calculate the time that takes for the projectile from turn off to reach the coil center, subtracting the scr turn off time (approx 40us) obtaining the time toff. Calculate the current in the coil after turn off with an LR model with this formula I= Ioff* e^(-toff*R/L) and make sure it falls in the 1-10A range.
3) Size the second damper resistor (the one on the small cap bank) 3-4 times the main damper resistor
Print this page