Coil Gun

[maxfoo]

The BUZ11 mosfet, cheap but deadly.

http://jlnlabs.imars.com/vpexp/

 

[Anthony Fremont]

The BUZ11 mosfet, cheap but deadly.

http://jlnlabs.imars.com/vpexp/

Seems an odd way to have the coil for an electromagnet, I used the innards
of a Ford starter solenoid. I used an 400V 820uF cap charged to about 300V.
I used a PIC (of course ;-) to generate the PWM signal and measure the cap
charge thru a resistive divider. For the switching transistor, I used an
IGBT. An SCR dumped the charge into the solenoid. On a good launch, it
would throw a computer case screw across the room.

 

[Roger Hamlett]

Seems an odd way to have the coil for an electromagnet, I used the
innards of a Ford starter solenoid. I used an 400V 820uF cap charged to
about 300V. I used a PIC (of course ;-) to generate the PWM signal and
measure the cap charge thru a resistive divider. For the switching
transistor, I used an IGBT. An SCR dumped the charge into the solenoid.
On a good launch, it would throw a computer case screw across the room.

The 'fun' bit comes, when you have multiple coils, and capacitors, and add
opto-detection of the projectile, to fire the next coil. Once the speed
gets up to a few hundred m/sec, the timings begin to get quite critical.
Large flash-gun capacitors work quite well.

Best Wishes

 

[Jan Panteltje]

Seems an odd way to have the coil for an electromagnet, I used the innards
of a Ford starter solenoid. I used an 400V 820uF cap charged to about 300V.
I used a PIC (of course ;-) to generate the PWM signal and measure the cap
charge thru a resistive divider. For the switching transistor, I used an
IGBT. An SCR dumped the charge into the solenoid. On a good launch, it
would throw a computer case screw across the room.

Or use a slingshot, like the Tijuana police:
http://www.nbc4.tv/news/10833857/detail.html
hehe

 

[Sven Wilhelmsson]

Seems an odd way to have the coil for an electromagnet, I used the innards
of a Ford starter solenoid. I used an 400V 820uF cap charged to about 300V.
I used a PIC (of course ;-) to generate the PWM signal and measure the cap
charge thru a resistive divider. For the switching transistor, I used an
IGBT. An SCR dumped the charge into the solenoid. On a good launch, it
would throw a computer case screw across the room.

The reason I can see for using ferrite cores this way would be to
protect the mosfet, as they moderate the current a bit. Apart from the
fact that a simple solenoid wouldn't look that impressive!

 

[Anthony Fremont]

The reason I can see for using ferrite cores this way would be to
protect the mosfet, as they moderate the current a bit. Apart from the
fact that a simple solenoid wouldn't look that impressive!

I'm referring to direction of the wrapping with the core being parallel to
the windings instead of perpendicular. AFAIR, I have never seen an
electromagnet constructed this way.

 

[Sven Wilhelmsson]

I'm referring to direction of the wrapping with the core being parallel to
the windings instead of perpendicular. AFAIR, I have never seen an
electromagnet constructed this way.

They are not exactly parallel. So there will be an effect, but not better
than a single turn the usual way, except from the moderation.

 

[ian field]

Or use a slingshot, like the Tijuana police:
http://www.nbc4.tv/news/10833857/detail.html
hehe

Wheelnuts as projectiles - great deterrent to rampaging hoodies.

 

[maxfoo]

The 'fun' bit comes, when you have multiple coils, and capacitors, and add
opto-detection of the projectile, to fire the next coil. Once the speed
gets up to a few hundred m/sec, the timings begin to get quite critical.
Large flash-gun capacitors work quite well.

Best Wishes

Here's a guy shooting 30 caliber projectiles with his coil gun.

Interesting 16 Stage Optically Triggered Prototype with opto-sensors.
http://www.coilgun.eclipse.co.uk/16_stage_opto_prototype.html