coil gun
rp181, Wed Jun 11 2008, 12:31AMI've been working on a coil gun. I am working on them for a science fair project in determining the best way to affect effeciency. I hope to get 5kJ worth of Capacitors, but im still working on getting them. Ile update as i get items/construct.
Parts i have:
3x ST180S12POV (SCR's) - Datasheet:
4x Fast recovery diodes: R6021225HSYA -
5x 300 watt, 1000ohm bleeder resistors
1' x .5" Hymu-80 rod - will become proectiles
Parts i need:
Capacitors - 6x 400v 2900uf -- Shipping --
Plans/Pics:
The SCR's and Diodes, with AA for comparison:
Bleeder resistors
fairly big, larger than expected
Heres some renderings done on Rhino of the railgun and coilgun. Capacitor bank is shown on railgun, and railgun is ghost rendered. Each little sqare is 1/4in, and each big square (marked by darker lines) is 1in.
Coilgun:
Specs:
14 in long, 3 coils. AWG wire - 12
624J each stage
I have decided on using a quad comparator and phototransistors to trigger.
Update
After a long delay, started project again. I ditched the railgun, and im using 624J X 3 for a multistage coilgun. Heres the coil gun:
Capacitors are shipping. My charging will be a voltage multiplier for 110 to ~600v. Capacitors will be in sets of 2 for each stage.
Update 2
Ive mounted everything on a base and wired the anti-parrallel diodes and SCR's together. Now i am just lacking the capacitors and triggering system. I have started making a triggering system using a LM339 Quad-Comparator. If you look at earlier pic, you can see the that the IR Emitter/Reciever are built in. Ive got the basic LM339 working, but i gotta make it work with a 2SB772 NPN transistor for it to switch the SCR's.
Heres a pic:
The empty space will be where the Capacitors will go. The (+) of the cap bank will connect to the studs of the SCR's and the (-)'s will connect to the Diode (screwed down part). In the upper right is my LM339 triggering system prototype. The Aluminum thing right after the CG is a simple set of IR Emitter/Recievers i will use with my PC to chrono the projectile. Ferroxcube, chtechnology, and Powerohm logos are on there to show who donated parts.
Re: coil gun
ea6b607, Wed Jun 11 2008, 01:15AM
how's your machining facilities/ tools/
ea6b607, Wed Jun 11 2008, 01:15AM
how's your machining facilities/ tools/
Re: coil gun
rp181, Wed Jun 11 2008, 01:55AM
a 1/3rd horsepower Drill O.o
Doing it at school,so table saw, radial arm saw, drill press, band saw, metal bandsaw, horizontal bandsaw, drum sander, belt/disc sander, scroll saw, spot welder, mig welder, arc welder, and a foundry O.o.
rp181, Wed Jun 11 2008, 01:55AM
a 1/3rd horsepower Drill O.o
Doing it at school,so table saw, radial arm saw, drill press, band saw, metal bandsaw, horizontal bandsaw, drum sander, belt/disc sander, scroll saw, spot welder, mig welder, arc welder, and a foundry O.o.
Re: coil gun
Lakeowner, Wed Jun 11 2008, 08:53AM
Why are you using resistors in series with your coil? I think they decrease performance considerably.
Lakeowner, Wed Jun 11 2008, 08:53AM
Why are you using resistors in series with your coil? I think they decrease performance considerably.
Re: coil gun
rp181, Wed Jun 11 2008, 02:08PM
The inductor and resistor represents the coil, as it will have resistance and inductance.
rp181, Wed Jun 11 2008, 02:08PM
The inductor and resistor represents the coil, as it will have resistance and inductance.
Re: coil gun
Bjørn, Wed Jun 11 2008, 02:12PM
The resistor is usually implied. When you draw it like that people will think you have added an external resistor.
Bjørn, Wed Jun 11 2008, 02:12PM
The resistor is usually implied. When you draw it like that people will think you have added an external resistor.
Re: coil gun
rp181, Wed Jun 11 2008, 03:41PM
Updated schematic, would that triggering work?
rp181, Wed Jun 11 2008, 03:41PM
Updated schematic, would that triggering work?
Re: coil gun
Andyman, Wed Jun 11 2008, 05:51PM
If I recall, it's best if you have a resistor of about 1k on the gate of the fire scr, if you're running straight from a 9v battery.
P.S. What program did you use for the schematic?
edit:(on a random side note, 100th post!)
Andyman, Wed Jun 11 2008, 05:51PM
If I recall, it's best if you have a resistor of about 1k on the gate of the fire scr, if you're running straight from a 9v battery.
P.S. What program did you use for the schematic?
edit:(on a random side note, 100th post!)
Re: coil gun
rp181, Wed Jun 11 2008, 06:10PM
The program is microcap (evaluation).
I will be using a laptop power supply (14.5v) with a resistor to trigger. I tested it and it works. The gate max is 20v, so it should be fine.
Also works without resistor, but just to leave a wide saftey margin.
rp181, Wed Jun 11 2008, 06:10PM
The program is microcap (evaluation).
I will be using a laptop power supply (14.5v) with a resistor to trigger. I tested it and it works. The gate max is 20v, so it should be fine.
Also works without resistor, but just to leave a wide saftey margin.
Re: coil gun
Electroholic, Wed Jun 11 2008, 06:52PM
use max gate current to calculate resistance, u want a good kick to the gate.
Electroholic, Wed Jun 11 2008, 06:52PM
use max gate current to calculate resistance, u want a good kick to the gate.
Re: coil gun
rp181, Wed Jun 11 2008, 08:07PM
max gate current is 3amp, resistance of the gate is 15ohm according to my mulltimeter, but the supply still shorts, so its wrong. since its shorting, it means its giving 4.5amps short pulse into gate.
rp181, Wed Jun 11 2008, 08:07PM
max gate current is 3amp, resistance of the gate is 15ohm according to my mulltimeter, but the supply still shorts, so its wrong. since its shorting, it means its giving 4.5amps short pulse into gate.
Re: coil gun
Electroholic, Thu Jun 12 2008, 03:56AM
gate of an SCR doesn't have a resistance, it has a voltage drop.
Edit:
well, I'm not saying it's a superconductor, but you get what i mean.
Electroholic, Thu Jun 12 2008, 03:56AM
gate of an SCR doesn't have a resistance, it has a voltage drop.
Edit:
well, I'm not saying it's a superconductor, but you get what i mean.
Re: coil gun
rp181, Thu Jun 12 2008, 02:30PM
Ahh, i get what you mean. About 5 ohms on the supply will be good then.
rp181, Thu Jun 12 2008, 02:30PM
Ahh, i get what you mean. About 5 ohms on the supply will be good then.
Re: coil gun
Dr. Drone, Thu Jun 12 2008, 04:06PM
Dr. Drone, Thu Jun 12 2008, 04:06PM
Re: coil gun
rp181, Mon Jun 16 2008, 03:16PM
a capacitor company said they could donate capacitors, they just need a letter from my school =)
rp181, Mon Jun 16 2008, 03:16PM
a capacitor company said they could donate capacitors, they just need a letter from my school =)
Re: coil gun
rp181, Tue Jun 17 2008, 05:22PM
Resistors and transducer arrived today, updated first post
rp181, Tue Jun 17 2008, 05:22PM
Resistors and transducer arrived today, updated first post
Re: coil gun
OZZY, Tue Jun 17 2008, 07:23PM
Hi rp181
It`s nice to see someone building a multistage coilgun, they can be much more efficient than single stage.
I hope you will forgive me but I do not understand your schematic. I do not think it will work as a trigger because you have the SCR connected between the output and discharge pins. If you want a detailed discusion on triggering it may be wise to take it to the accelerators board.
Ozzy
OZZY, Tue Jun 17 2008, 07:23PM
Hi rp181
It`s nice to see someone building a multistage coilgun, they can be much more efficient than single stage.
I hope you will forgive me but I do not understand your schematic. I do not think it will work as a trigger because you have the SCR connected between the output and discharge pins. If you want a detailed discusion on triggering it may be wise to take it to the accelerators board.
Ozzy
Re: coil gun
rp181, Tue Jun 17 2008, 11:24PM
I just tooke the schematic from the website posted in original post. When the beam is broken, the 555 sends the signal through output, and discharge acts as ground (0v)?
rp181, Tue Jun 17 2008, 11:24PM
I just tooke the schematic from the website posted in original post. When the beam is broken, the 555 sends the signal through output, and discharge acts as ground (0v)?
Re: coil gun
OZZY, Wed Jun 18 2008, 11:40AM
Hi rp181
There is a transistor between the discharge pin and ground, when the output is high the discharge transistor is off and when the output is low the discharge transistor is on. The output of the 555 is only rated for 200mA, in an earlier post you were talking about currents of several Amps. I would suggest you use an amplifier stage after the 555 to get more current.
When the beam is broken the reset pin is taken high but the 555 will not trigger because the trigger pin is held high by C4 (the trigger is active low). This site has good information on NE555 circuits Electronics Club or you could try searching for datasheets and application notes for the NE555.
Good luck with the coilgun and railgun projects.
Ozzy
OZZY, Wed Jun 18 2008, 11:40AM
Hi rp181
There is a transistor between the discharge pin and ground, when the output is high the discharge transistor is off and when the output is low the discharge transistor is on. The output of the 555 is only rated for 200mA, in an earlier post you were talking about currents of several Amps. I would suggest you use an amplifier stage after the 555 to get more current.
When the beam is broken the reset pin is taken high but the 555 will not trigger because the trigger pin is held high by C4 (the trigger is active low). This site has good information on NE555 circuits Electronics Club or you could try searching for datasheets and application notes for the NE555.
Good luck with the coilgun and railgun projects.
Ozzy
Re: coil gun
rp181, Thu Jun 19 2008, 01:13AM
Good point ozzy, i forgot that to open fully/fastest it needs ~3A. do you think a MJE3055T (from fairchild) will work?
UPDATE:
I wired all the resistors in parrallel, giving combined resistance of 200ohms. So at 400v, it will draw ~400W, well below the 1500W rating of the bank, And WELL below the rating of 15KW for 10sec.
I was looking at fairchild's infrared diodes, and im confused by all the options/ properties. Which properties should i look for in a detector beam?
rp181, Thu Jun 19 2008, 01:13AM
Good point ozzy, i forgot that to open fully/fastest it needs ~3A. do you think a MJE3055T (from fairchild) will work?
UPDATE:
I wired all the resistors in parrallel, giving combined resistance of 200ohms. So at 400v, it will draw ~400W, well below the 1500W rating of the bank, And WELL below the rating of 15KW for 10sec.
I was looking at fairchild's infrared diodes, and im confused by all the options/ properties. Which properties should i look for in a detector beam?
Re: coil gun
ea6b607, Thu Jun 19 2008, 03:26AM
still below your rating, but isn't that 800watts? E^2/R
1600/200=800watts
ea6b607, Thu Jun 19 2008, 03:26AM
still below your rating, but isn't that 800watts? E^2/R
1600/200=800watts
Re: coil gun
rp181, Thu Jun 19 2008, 12:54PM
oh ya, it will draw 2amps (assuming i get capacitors 400v), so yes, 800watt.
rp181, Thu Jun 19 2008, 12:54PM
oh ya, it will draw 2amps (assuming i get capacitors 400v), so yes, 800watt.
Re: coil gun
Bust_A_Cap, Tue Jun 24 2008, 12:03PM
have you made any decision as far as how you'll be injecting the projectile? I'm always interested to see what people come with for this.
Also do you have designs for both a rail and coil setup because your going to use the same bank for both or what?
Bust_A_Cap, Tue Jun 24 2008, 12:03PM
have you made any decision as far as how you'll be injecting the projectile? I'm always interested to see what people come with for this.
Also do you have designs for both a rail and coil setup because your going to use the same bank for both or what?
Re: coil gun
rp181, Wed Jun 25 2008, 01:17AM
Well someone on spudfiles mentioned a electrothermal gun for injection, i was thinking 1KJ electrothermal gun, mabey more. My only worry is heat, what plastic should i layer it with to reflect/insulate from flame/heat? I was thinking carbonfiber or UHMW polyethylene.
They will be one main bank for the railgun, and another for the coilgun. It wont really be a bank for coilgun, as one cap is ~500J, and i dont plan on going high (unless they give me the bigger ones, they need to see if its in stock, there 1.2KJ each capacitor).
rp181, Wed Jun 25 2008, 01:17AM
Well someone on spudfiles mentioned a electrothermal gun for injection, i was thinking 1KJ electrothermal gun, mabey more. My only worry is heat, what plastic should i layer it with to reflect/insulate from flame/heat? I was thinking carbonfiber or UHMW polyethylene.
They will be one main bank for the railgun, and another for the coilgun. It wont really be a bank for coilgun, as one cap is ~500J, and i dont plan on going high (unless they give me the bigger ones, they need to see if its in stock, there 1.2KJ each capacitor).
Re: coil gun
rp181, Fri Jul 25 2008, 02:48AM
havn't updated this thread for good reason. Ive been talking to my school district lawyer and a capacitor company, the company wanted a letter from the school so they can donate capacitors for a capacitor bank, but the district said by writing the letter and accepting the "gift" liabilty would become theres, so they cant do it =(
That means railgun wont happen, just the coilgun.
rp181, Fri Jul 25 2008, 02:48AM
havn't updated this thread for good reason. Ive been talking to my school district lawyer and a capacitor company, the company wanted a letter from the school so they can donate capacitors for a capacitor bank, but the district said by writing the letter and accepting the "gift" liabilty would become theres, so they cant do it =(
That means railgun wont happen, just the coilgun.
Re: coil gun
rp181, Mon Oct 06 2008, 10:45PM
BUMP! Im finally starting this project again. Capacitors were ordered yesterday, and ile be able to start testing.
rp181, Mon Oct 06 2008, 10:45PM
BUMP! Im finally starting this project again. Capacitors were ordered yesterday, and ile be able to start testing.
Re: coil gun
rp181, Thu Oct 09 2008, 01:37AM
updated
rp181, Thu Oct 09 2008, 01:37AM
updated
Re: coil gun
aonomus, Thu Oct 09 2008, 03:14AM
This thing looks like its going to have some serious kick...
Friendly suggestion: use a better photo host like imagebucket that doesn't force you to view ad pages...
aonomus, Thu Oct 09 2008, 03:14AM
This thing looks like its going to have some serious kick...
Friendly suggestion: use a better photo host like imagebucket that doesn't force you to view ad pages...
Re: coil gun
rp181, Thu Oct 09 2008, 03:25AM
Can do, ile make an account now.
Thanks for saying that, made me think of recoil. havn't thought about that. To keep it mounted, there are 2 screw hooks on either side of the barrel, with a hose clamp.
Ile be ramping up the power by 50v, so if the force becomes too much, ile figure something out.
rp181, Thu Oct 09 2008, 03:25AM
Can do, ile make an account now.
Thanks for saying that, made me think of recoil. havn't thought about that. To keep it mounted, there are 2 screw hooks on either side of the barrel, with a hose clamp.
Ile be ramping up the power by 50v, so if the force becomes too much, ile figure something out.
Re: coil gun
rp181, Thu Oct 09 2008, 09:22PM
Capacitors arrived today. I threw together a quick test setup, one capacitor charged to 400v shot a screw 10ft. Pretty good considereing the large dead space, probable saturation, and the huge sparking at my aligator clip connections =). Bus bars are aluminum, cut them, just need to drill them.
rp181, Thu Oct 09 2008, 09:22PM
Capacitors arrived today. I threw together a quick test setup, one capacitor charged to 400v shot a screw 10ft. Pretty good considereing the large dead space, probable saturation, and the huge sparking at my aligator clip connections =). Bus bars are aluminum, cut them, just need to drill them.
Re: coil gun
aonomus, Fri Oct 10 2008, 02:33AM
Not to hijack but is there a difference between copper and aluminum buss bars? I've only built one sizable coilgun but I used copper buss bars made from flattened water pipe. I suppose the aluminum would be easier to drill holes into though.
aonomus, Fri Oct 10 2008, 02:33AM
Not to hijack but is there a difference between copper and aluminum buss bars? I've only built one sizable coilgun but I used copper buss bars made from flattened water pipe. I suppose the aluminum would be easier to drill holes into though.
Re: coil gun
uzzors2k, Fri Oct 10 2008, 12:32PM
Aluminium is about 60% more resistive than copper, so you would need more of it to get the same resistance in your buss bars.
uzzors2k, Fri Oct 10 2008, 12:32PM
Aluminium is about 60% more resistive than copper, so you would need more of it to get the same resistance in your buss bars.
Re: coil gun
rp181, Fri Oct 10 2008, 08:39PM
alu. is cheaper though, and more commonly available in flat stock.
One of my SCR's somehow wont work, closed circuit both ways with no signal.
rp181, Fri Oct 10 2008, 08:39PM
alu. is cheaper though, and more commonly available in flat stock.
One of my SCR's somehow wont work, closed circuit both ways with no signal.
Re: coil gun
Backyard Skunkworks, Thu Oct 16 2008, 08:37PM
Although aono is right that the recoil will be a lot more than the average coilgun, it still won't be anything huge.
I'd just reccomend adding weight to the gun, maybe a bit of padding. Even if you get near 10% energy conversion, you will still only have the energy of a 9mm pistol.
Backyard Skunkworks, Thu Oct 16 2008, 08:37PM
Although aono is right that the recoil will be a lot more than the average coilgun, it still won't be anything huge.
I'd just reccomend adding weight to the gun, maybe a bit of padding. Even if you get near 10% energy conversion, you will still only have the energy of a 9mm pistol.
Re: coil gun
rp181, Thu Oct 16 2008, 09:01PM
well, all my SCR's are damaged in someway. One was my fault, and the other 2 seem like manefacturing defects. I can't complain though, they were free.
In other news, I may be getting 6 SCR's with rating's of 3.6kV and 10.9kA surge for 10ms in a 3in puk package! They will be free if my school doesn't come up with some liability excuse like with the capacitors...
I was reading a website (forgot which one) about encasing coils in A iron powder and epoxy mix, which got him 10% effeciancy! How do i find out a good mixture of epoxy vs. iron powder?
rp181, Thu Oct 16 2008, 09:01PM
well, all my SCR's are damaged in someway. One was my fault, and the other 2 seem like manefacturing defects. I can't complain though, they were free.
In other news, I may be getting 6 SCR's with rating's of 3.6kV and 10.9kA surge for 10ms in a 3in puk package! They will be free if my school doesn't come up with some liability excuse like with the capacitors...
I was reading a website (forgot which one) about encasing coils in A iron powder and epoxy mix, which got him 10% effeciancy! How do i find out a good mixture of epoxy vs. iron powder?
Re: coil gun
rp181, Thu Oct 23 2008, 11:19PM
Update:
I am getting 6 puk SCR's, rated for 3.6kV constant and 10.9kA surge for 10ms free of charge,brand new (donated by westcode semi)! I can actually start doing this project again! I have everything ready, just need to add SCR's.
Heres a datasheet:
rp181, Thu Oct 23 2008, 11:19PM
Update:
I am getting 6 puk SCR's, rated for 3.6kV constant and 10.9kA surge for 10ms free of charge,brand new (donated by westcode semi)! I can actually start doing this project again! I have everything ready, just need to add SCR's.
Heres a datasheet:
Re: coil gun
Killa-X, Sat Oct 25 2008, 03:43AM
Looking good, I was considering a multi-stage gun after i get my single stage fully working, Since I hear timing sucks! Also, those are BIG bleeding resistors. Geehz, What are the specs of those things? lol
Killa-X, Sat Oct 25 2008, 03:43AM
Looking good, I was considering a multi-stage gun after i get my single stage fully working, Since I hear timing sucks! Also, those are BIG bleeding resistors. Geehz, What are the specs of those things? lol
Re: coil gun
rp181, Sat Oct 25 2008, 07:45PM
there 1000ohm, 300W to actually bleed, all 5 in parrallel are fast. I orignally got these for a bigger bank for my planned railgun project.
rp181, Sat Oct 25 2008, 07:45PM
there 1000ohm, 300W to actually bleed, all 5 in parrallel are fast. I orignally got these for a bigger bank for my planned railgun project.
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