Portable Coilgun

20, November  2006:     ACG 85P  2 Stage Configurable Semi-Automatic Pistol
10, January     2006:      ACG 300P  3 Stage Configurable Pistol
25, July            2005:      ACG 130   Update
22, June           2005:     ACG 130  2 Stage Pistol Fully PIC Microcontroller Controlled
15, Sept           2004:     Still "portifying" the ACG 750
04, Sept           2004:     Onto "portifying" the ACG 750
09, Aug            2004:     All 8-stages completed
29, July            2004:     Almost there...  The ACG 750 reaches 570
01, July            2004:     Benchtop inception of ACG 750
20, May            2004:    Second portable version a success   ACG 375
17, April           2004:    Benchtop version for now
08, April           2004:
13, March        2004:    Portable version a success   ACG 188
07, March        2004:

20, November 2006: ACG 85P 2 Stage Configurable Semi-Automatic Pistol

    First portable semi-automatic coilgun pistol finaly complete.  This long overdue project started out 6 months ago.  Initial the pistol was designed for a lower bank and energy shot level just to demonstrate 5 shots per second at 2 joules.  As time passed and parts perished, the orginal designed transformed into a higher shot level and lower rate of fire.  The next design will more than compensate for it all.

* 1 Injector + 2  Coil stages
* 3 SCRs and 3 clamp Diodes.
* 3 Capacitor banks, 12.5J for Injector, 37J for Stage 1, 50J for Stage2
* Boost converter power using 32v AAA Rechargable batteries, Inductor, 1 IGBT, 1 Relay, and diodes.
* Interface: Fire button, Infra-Red Module Rx, Shot Level switch, Configure switch, Main Power switch, and Status LED.
* PCBoard Embedded in to bottom surfac of the pistol.  This board is both the controller and the charger in one.
* Schematic

Preliminary:  Demonstrations

Preliminary 1 End Assembly

Preliminary 2 1 Shot Close Up

1 Target Escaped

3 Targets

4 Targets

10, January 2006: ACG 300P 3 Stage Configurable Pistol

    At last!! A functioning example of the combined wants in a coilgun pistol.  You always see posts for this and that, read how if it could do such and such and the inevitable plans on doing whatever.
The wish list follows.---
"Fast Charger and be small enough to fit in a pistol", yep.  "Charger automatically charges upto the voltage I want, stops, then regulates", yep.  "Controllable fire sequence, I want to use a computer to test by adjusting on/off times to the microsecond", yep.  "Holds a magazine and is retractable along with a retractable battery power source", I say yes to this too.  "Dual energy shot levels, full power and partial power, by charging to a lower voltage and loading a different timing sequence", yes and you need but to flip a switch the pistol will handle the rest.    ---These concepts have now evolved into a physical reality.

* 3 Coil stages with 3 SCRs and 3 clamp Diodes.
* 3 Capacitor banks, each 100J using 8 x 12.5J 330v @ 230uF Photo Flash. The system is using 660v from series capacitors.
* Circuitry as a whole. PIC and 3 Dual Mosfet drivers. 1 Driver for booster. 2 Drivers for 3 stages.
* Boost converter power using 22v AA. Inductor, 2 IGBTs and diodes.
* Up close of PIC, Fire button, and Infra-Red Module (little black dot). The other black dot is the transistor powering the IR transmitting LED.
* Plywood body construction.
* Preliminary: Majority of paint and body work completed.
* PCBoard Embedded in to handle of pistol.  This board is both the controller and the charger in one.
* Schematic
25, July 2005:    ACG 130 Update

The output energy, 130J supply, has increased from 4.0 Joules to 4.7 Joules 32m/s | 105 f/s ( 3.1% to 3.6%) due to an exchange of the barrel meterial.  The original slotted brass tube caused a small exposure in the coils center windings.  The exposure led to coils shorting across each another at discharge time.  A make shift barrel ended up being the permenent barrel.  I defaulted to my old tube forms using rolled layers of transparency film.  Added preliminary videos.

Quick Videos:
#65  4.7 Joules  2 boxes   Low Res

Foundation    Handle     Loading    Breach    Trigger
22, June 2005:   2 Stage Pistol Fully PIC Microcontroller Controlled  ACG 130
   This is a 2 stage, 3% 4 Joules out at 30 meters/second 9 gram load electromagnetic pistol.  No miraculous kinetic or velocity, but just proof of coilguning evolution. 
    I have bounced around between different design methods of coilguns.  Each of the designs had operated in segmented functional block models: charging, detecting, switching.  The responsibility of the functional blocks were delegated to different components.  Charging done by either mains powered cascade multipliers or LM555 timer/boost converter and relay control.  Detecting implemented with optics and LM339/LM393 comparators, detecting both projectile position and capacitor voltage levels.  Switching done by either electro-mechanical contact, optics, and temporal control.   During these variations, microcontrollers were present, doing a little here and there while taking care of timing issues, yet the microcontroller was just another component in the mix.
   The next step is to centralize.  Omit all those peripheral components if it not be of absolute necessity.  The PIC Microcontroller will be charged with the full responsibility of the charging, detecting, and switching functional blocks.  Any buffer/driver components of absolute necessity will remain because microcontrollers are not designed for amplified voltage/current use. 

  Boost converters are my voltage accumulators of choice.  Rapidly drive an inductor on and off with a switch while the inductor's residual energy during the off times is dumped into a capacitive load via a high voltage diode. 
  The accelerator coils for this ACG130 is temporally sequenced; hence, Infra-red diodes and photo transistors are omitted.  Instead,  a fixed time is programmed into the PIC to tell it when to fire the second accelerator stage.  The timing was derived through experimentation. 
  Can you say PIC?  Its obvious the PIC does this as well.  All which culminated to the end result is not easy, but here after the operation is simple.

PIC code:
ASM: acg130
Include: Shorts

Schematics: BreadBoard Development
PC Board
ACG-130J Page 1 As a whole SCR driver As a whole
ACG-130J Page 2 Board close up SCRs and clamp diodes Side thickness view
ACG-130J Page 3 RS-232 and PIC16F628 2 Capacitor Banks 660v test SCR board

Power switch and regulator 2 Coil stages Logic/Booster no PIC brains

IGBT High / Low side booster
Logic/Booster with PIC brains
15, Sept 2004:   Still "portifying" the ACG 750

   Fabrication of the rifle continues.  In this order this is how I plan the construction:
1.    -  Glue together the Coil/Barrel as free form rod.  The barrel is removable while coils remain rigid.
2.   -  Solder leads to the Capacitor banks.              
3.   -  Bond Coil banks to Capacitor banks.              
4.   -  Design PCB schematics Num 1, Num 2, Num 3, and Num 4, PCB layouts 1 animated and 2 animated, etch PCB, 
             and install the components.
5.  -  Connect Capacitors and Coils to PCB, and run test shots, tweak, test and tweak, then test some more.
6. -   Install magazine load and battery load.

7. WIP -  Form the rifle body and paint the body.

04, Sept 2004:  Onto "portifying" the ACG 750

   Fabrication of the rifle continues.  In this order this is how I plan the construction:
1.    -  Glue together the Coil/Barrel as free form rod.  The barrel is removable while coils remain rigid.
2.   -  Solder leads to the Capacitor banks.              
3.   -  Bond Coil banks to Capacitor banks.              
4.   -  Design PCB schematics Num 1, Num 2, Num 3, and Num 4, PCB layouts 1 animated and 2 animated, etch PCB, 
             and install the components.
5.  -  Connect Capacitors and Coils to PCB, and run test shots, tweak, test and tweak, then test some more.

6.  WIP   -   Install magazine load and battery load.
7.  Form the rifle body and paint the body.

09, Aug 2004:  All 8-stages completed

   Fabrication of the rifle begins.  In this order this is how I plan the construction:
1.  Glue together the Coil/Barrel as free form rod.
2.  Solder leads to the Capacitor banks.
3.  Bond Coil banks to Capacitor banks.
4.  Design PCB layout, etch PCB, and install components.
5.  Connect Capacitors and Coils to PCB, and run test shots, tweak, test and tweak, then test some more.
6.  Install magazine load and battery load.
7.  Form the rifle body and paint the body.

29, July 2004:  Almost there...  The ACG 750 reaches 570

    The efficiency per stage remains fairly constant.  From 1 to 6 stages, I am achieving 3% with 95 Joules each stage.  This is a good sign and edges me forward to completing all 8 stages for an 18 to 22 Joule output portable rifle version.  The goal of 20J will be met with even a small decrease of the last stages for a total system efficiency of 2.6%.

  So far I have beaten 2 of my personal best records, kinetic output and size.  Three stages of the ACG 750 release more kinetic energy then the ACG 375.  That is 285J versus 375J with outputs of  9J versus 8J, respectively.  The coils of the ACG 750 are 33% smaller in outer diameter than that of the ACG 375, and also fire much quieter. 

Closed/Opened Loop  switching with SCR Clarification
  What is the primary purpose of a closed loop design?  The question is better posed as “Which is the primary purpose of a closed loop design: verification alone or error correction?”  If the choice is error correction, then it must be concluded that the main-stream idea of using optics alone is not correct according to definition of closed loop stated below.

Closed Loop
  This method consist of two acts, the act of verifying and the act of correcting.  The act of verifying is equal to that of the opened loop.  Optics or another transducer detects the existence of the projectile.  The act of correction here is defined as: processing the current projectile velocity, and adjusting the discharge times for the next stages accordingly.  The governing discernment is “active”.  A status is recorded, compared, then corrected if so needed.
Opened Loop
  As for optics alone, the only discernment from a closed loop method is the optic's singular discernment of “verification”.  Without a controller, whether it be a microcontroller, RC/Crystal timer, or logic counter-timer, optics only possess the ability to verify the existence of a projectile during its traversal through successive stages.  Contrary to a closed loop, optics alone will not perform error correction because their timings are hard coded in the form of gaps between coil stages.  Hence, any undesired condition which alters the timing away from the optimum velocities of the beginning stages induces a lowered efficiency of the system as a whole.  The extent of the deficiency is dependent on the degree of the initial alteration.  The same is true for coilguns controlled by temporal switching.  Since a temporal switching method operates under the definition of an opened loop and suffers the same effects here, then passive optical switching should be considered as an open loop design as well.

01, July 2004:  Benchtop inception of ACG 750
    The beginning of this coilgun marks the end of stage detection.  Mechanical and optical sensors functioned well for previous designs, actually still do.   The dilemma is space as in the necessary gap between coils.  The greater the number of stages the greater the distance between stages.  Since my objective is to build a rifle model of coil barrel no longer than 50 cm (20 inches), I decided to put prior methods to pasture.

   Temporal triggering is now being implemented.  A PIC 16F628 microcontroller outputs a sequence of pulses to buffer/drivers.  Drivers in turn relay the sequence of small signal pulses as amplified pulses to each SCR stage.  From this implementation, the gab between coils stages are now acceptable and fulfill my barrel requirements.

PIC source files:  cg-stage.asm   shorts.inc

07, March 2004: Here to play games. As Joda would say, "To play games here I am"

   Testing. Achieved 2.1 % efficiency, 4 Joules kinetic output from 188 Joules input. Achieved 3% efficiency, 6 Joules output from 203 Joules input, when capacitors are overcharged near the surge voltage. Constructed the body and assembled the circuit onto a copper padded perf-board.

   I have made many printed circuit boards of closely packed components. This time this board by far is the most densely packed board to date. Three SCRs are soldered in parallel for each bank; therefore 2 of these stacks are juxtaposed with the closest proximity allowable. The 555 timer is under a 12V regulator and this is under (2) 1000V @ 30A diodes. All high current wires are 18 AWG while low currents consist of 24 AWG wrapping wire.
13, March 2004:  Portable version a success

    Fully assembled the functioning hand held electromagnetic accelerator.  It fully charges within 5 seconds via the manual push button switch.  Because the charging is manual and not controlled by logic, the electromagnetic accelerator may repeat a propulsion within 2 seconds, but at the expense of lowered kinetic output.  An LED is the charging indicator and illuminates when the capacitors are charged to 500 VDC.  Projectile is held in position by a wad of printer paper and held in place by a small round Neodymium magnet inside the wad.

     Portable named:  Throw Away
    The Throw Away is born from the festering piles of discarded possibilities.  Time and space may have separated the piles, but that did not prevent their meek yet effective coalition. Capacitors were found in a mal-shaped unmarked box from a swap meet. Coils were made from wire spools that laid dead like on the floor of my nearest Fry's Electronics as it avoided the many bustling feet of customers and employees alike.  The masking tap, responsible for holding it all together, was the last windings around its spool of which I invested about an hour to find.   It was hastily assembled, no It was thrown together.  Its appearance suggest that either I recently found it along side some road or I am about to chuck it into the trash.  So I dubbed thee Throw Away.

8, April 2004: 

     A double the power 376 Joules (source) pistol is the current work in progress project.  A system efficiency of 2% will yield 8 Joules @ 42 meters/sec  :   square root [ 8 joules / (.5*.009kgrams) ] = 42.2 meters/sec

   Delays come from a few decisions such as magazine fabrication and attachment, deciding whether to place the magazine in the battery pack, in the rear, or using an internal revolver loading scheme.  I have finally built a magazine using plastic as a spring.  Plastic, yes the right plastic is a great compression spring.  Coincidence?; the plastic tie raps used to hold down coils to the coil-mount is the very same plastic springs for the magazines.  Turns out a magazine will be reserved for a rifle. 
17, April 2004:  Benchtop version for now

   Achieved a system efficiency greater than the goal of 2%.  It is presently at 2.33% efficiency, 8.7 Joules kinetic output from 375 Joules input desktop model.  Velocity is at 44 meters/sec.   These results at 500v are actually lower than those when fired at a slightly lower voltage.  Fired at 475v yields a 2.41% efficiency.  Will perform passive attempts to raise the results by carefully spacing apart the coils one stage at a time.  First get maximum efficiency with 2 stages, then 3 stages, and finally the 4th stage.  The arrangement is 4 stages, 1 capacitor bank per stage, 1 pushbutton trigger, and 3 electrical contact triggers.  The next portable coilgun may now get underway.
20, May 2004: ACG 375  Second portable version a success

s the website name says, another coilgun has been assembled.  This is the same 375 Joules with 8 Joules of kinetic output stated in the previous news update.  The longest stage in building this one was in designing the PCB layout.  Physically there are 3 boards but  basically 2 circuit board functions divided into accumulator board and discharge board.  The energy and velocity results are the same as the benchtop version, so I will append new videos of the portable version in action.

ACG375 Dissection

Accumulator board layout     -->  generates up to 500VDC for the capacitor loads. 
Three functions:
1.  30 kHz square wave signal generator.         3.  (4) channel voltage monitor.
2.  Inductor-IGBT-Diode boost converter.         

Discharger board layout      -->  electronically switches the charged capacitors to the accelerator coils.
                    schematic 1      schematic 2
                    dissection 1      dissection 2
Two functions:
1.  receive trigger pulses and sends to SCR gates.
2.  clamps/snubbs the coil back EMF with reversed diodes.

Since the coilgun has 4 stages and 2 stages are controlled by 1 discharge board, I have a total of 2 discharge boards.  I did this bisection because the length of a single board design would have been longer than the coilgun.

Quick videos:
#34 ACG 375 Can


Total:               375 Joules
Bank 1:             250v + 250v = 500v @ 750 uF
Bank 2:            
250v + 250v = 500v @ 750 uF
Bank 1:             250v + 250v = 500v @ 750 uF
Bank 1:             250v + 250v = 500v @ 750 uF

8 capacitors connected in series parallel configurations

ACG 188
Dubbed  -  Throw Away
Source Energy:     188 Joules
Capacitors:            250v @ 1,500 uF, Qty 4
Bank 1:                  250v + 250v = 500v @ 750 uF
Bank 2:                 
250v + 250v = 500v @ 750 uF

Kinetic Energy:      4 Joules    -      2.1%
Projectile:              9 grams, 3.0 cm, 8 mm dia.
Velocity:                 30 m/s (98ft/s)

Drives :                  2 coils
Charge time:         5 seconds
Power supply:       24v NiMH battery  AA

ACG 300
Source Energy:     300 Joules
Capacitors:           330v @ 230uF, Qty 24
Bank 1:                  660v @ 460uF = 100J
Bank 2:                  660v @ 460uF = 100J
Bank 3:                  660v @ 460uF = 100J

Kinetic Energy:      11.0 Joules    -      3.7%
Projectile:              10.5 grams, 3.0 cm, 8 mm dia.
Velocity:                 45 m/s (150 ft/s)

Drives :                  3 coils
Charge time:         6 seconds,  50 Watt Charger
Power supply:       22v NiMH battery 18-AA

Mass:                    960 grams + 580 magazine.
Dimensions:         11" long, 6.5" high, 2.75" girth
Capacity:              10 rounds magazine
ACG 85
Source Energy:     87 Joules
Capacitors:           330v @ 230uF, Qty 8
Bank 1:                  330v @ 230uF = 12J
Bank 2:                  330v @ 690uF = 37J
Bank 3:                  330v @ 920uF = 50J

Kinetic Energy:      4.5 Joules    -      5.1%
Projectile:              10.5 grams, 3.0 cm, 8 mm dia.
Velocity:                 29 m/s (95 ft/s)

Drives :                  1 Injector coil + 2 coils
Charge time:         1 second,  100 Watt Charger
Power supply:       32v NiMH battery 26-AAA

Mass:                    1,030 grams + 122 magazine.
Dimensions:         10.5" long, 6.5" high, 2.0" girth
Capacity:              10 rounds magazine
ACG 375
Source Energy:     375 Joules
250V @ 1,500 uF, Qty 8
Bank1:              250V + 250V = 500V @ 750 uF
Bank1:              250V + 250V = 500V @ 750 uF
Bank1:              250V + 250V = 500V @ 750 uF
Bank1:              250V + 250V = 500V @ 750 uF

Kinetic Energy:      8.7 Joules    -      2.3%
Projectile:              9 grams, 3.0 cm, 8 mm dia.
Velocity:                 42 m/s (138ft/s)

Drives :                  4 coils
Charge time:         8 seconds, 46 Watt Charger
Power supply:       30v NiMH battery  AAA

The responsible components were a 555 timer to generate a frequency, an IGBT to be driven from this frequency, and a relay to remove the main power from the inductor else power is dumped into the capacitive load when the 555 idles off.  Now the ACG130 's PIC performs the frequency generation.  The bulky relay is replaced with another IGBT as a main power switch, which is also controlled by the PIC.  What is interesting is how the PIC controls both IGBTs.  Not only does one IGBT (booster) receives a frequency signal, a static voltage level of 25v - 30v is also generated to drive the other IGBT (main power) connected on a High Side at the same time and from the actual signal being sent to the booter IGBT.
* Removed the 555 timer.
* Removed the bulky relays.
The actual transferring of time data is done with the PIC's RS-232 communication to my proprietary PC application named Another Coilgun Acquisition.  ACG Acquisition, the PIC, and my Velocity traps enable me to easily perform velocity and energy test while sending and receiving stage enabling commands and stage timings.  Stage timing data is stored into the PIC's EEPROM to facilitate modifications without actually hard coding the data at burn time.  Other than coil sequencing, capacitor bank voltage levels need to be monitored.  A standard LM339/LM393 comparator was responsible for preventing a cap bank from over charging by disabling the main power relay.  The PIC replaces this comparator with its own internal comparator.  Not only does the PIC has its own comparator, it is also capable of generating its own reference voltage.  If programmed to stop charging at 100v, 200v, 300v, 350, or more, it will do so as long as the cap bank has the proper voltage divider.  No more potentiometer adjustments.
* Removed the comparators.
* Removed the Vref voltage dividers  resistors.
Monitor Charge and Fire buttons.  If Charge button is pressed, then charge to programmed cap voltage.  If Fire button is pressed, then fire stage 1, do timing delay, then fire stage 2.  Loop.  In effect this tells the 4017 decade timers to take a hike, and forces 555 one-shots, PWMs, and all those other peripheral components of yeaster year out of a job.  All from a neat little < $3.00 (18) pin package dubbed PIC16F628.
* Removed one-shot timers.
* Removed comparators for optics.
* Removed optics.

ACG 130
Source Energy:     130 Joules
Capacitors:            330v @ 600uF, Qty 4
Bank 1:                  330v @ 1200uF = 65J
Bank 2:                  330v @ 1200uF = 65J

Kinetic Energy:      4.7 Joules    -      3.6%
Projectile:              9 grams, 3.0 cm, 8 mm dia.
Velocity:                 32 m/s (102ft/s)

Drives :                  2 coils
Charge time:         8 seconds, 16 Watt Charger
Power supply:       15v NiMH battery  AAA

Mass:                    700 grams
Dimensions:         7.5" long, 6" high, 2.25" girth
Capacity:              10 rounds magazine

ACG 130 Foundation

The capacitors are the building foundation of the pistol.    After the capacitors are mounted to the handle with quick wood putty, the pistol is done.  All other parts are just covers to hide wires and increase visual aestetics.

* Coils mounted to wood
* Wood mounted to capacitors
* Capacitors mounted to handle

ACG 130 Handle

   In the handle resides majority of the electronics.  Utilizing this space lowers the overall pistol size.

 *Batteries on the left
* Projectile magazine in the center
* PCB on the right.

ACG 130 Loading

   Projectiles are displaced from the magazine into the coil breach.  The glide has two functioning parts.  In its center is a steel rod to push on the projectile.  The rod is magnetized from a neodymium glued at the rear.  On the glide's sides are rubberbands to aid in the glid firing position.

ACG 130 Breach

Close in view of how the magnetized rod holds the projectile in firing position.

  Projectile must be in a position away from the remaining projectiles in the magazine else the firing characteristics will be perturbed by the presence of excess iron.  The magnet pull of the magnet affixed to the rear of the rod is balanced to be strong enough to hold a projectile against gravity when facing south yet at the same time not causing tug against the accelerator coil.

ACG 130 Trigger

   The Trigger is a spring loaded momentary electronics switch.  When pressed, code inside the PCB waits until the trigger is released, then branches to the firing sequence routine. 

    Trigger is covered with a layer of stainless steel sheet metal.  The spring built into the momentary switch smoothly slides the stainless steel cover back into ready position after firing.