Coilgun Handgun

Step 3 Coils, Capacitors, and Results

Coils, Capacitors, and Results
All measurement are taken from velocity test with chronograph and are maximum achieved.

22 gauge:
-UM:7 Layer, 33mm L, 6.5mm InDia 1320uF 330V E.37m/s 4g(11*330V 120uF)
-8 Layer, 30mm L, 8mm InDia 960uF 350V 24m/s 8g(8*330V 120uF) 3.9%
-12 Layer, 30mm L, 8mm InDia 600uF 350V 12m/s 8g(5*330V 120uF) 1.57%
-12 Layer, 30mm L, 8mm InDia 470uF 450V 27m/s 8g(1*400V 470uF) 6.1%
-16 Layer, 30mm L, 8mm InDia 470uF 450V 28m/s 8g(1*400V 470uF) ****Best results 6.6%
-UM:12 Layer, 30mm L, 8mm InDia 470uF 800V E.>50m/s 8g(4*400V 470uF)

20 gauge:
-UM:12 Layer, 29mm L, 8mm InDia 940uF 400V 31m/s 8g(2*400V 470uf)
-UM:12 Layer, 12mm L, 8mm InDia 1200uF 350V 26m/s 8g(10*330V 120uf)
-8 Layer, 12mm L, 8mm InDia 880uF 450V 13m/s 9.0g(4*400V 220uF)
-Ferrite Surrounded-8 Layer, 12mm L, 8mm InDia 880uF 450V 14m/s 9.0g(4*400V 220uF)
-8 Layer, 30mm L, 8mm InDia 1100uF 450V 33.0m/s 9.0g(5*400V 220uF) SCR Switched 4.4%

E.=Estimated Velocity-The velocity here is estimated based on visual comparison to the other results, they are Not measured.
UM=Unmaximized- Coil not experimented with to achieve maximum results

If you do not have access to a chronograph the method HERE is relatively accurate.
If you use this method to get velocity results make sure your coil is perfectly horizontal and don't fire to the ground, fire at a piece of foam that is a meter or so away.

Also HERE is an optical velocity measurement set up. I have not done it my self so I do not know how accurate it is.

Even at best the shown results are + or - 20% correct, this is because most electrolytic capacitors capacitance rating is within the + or - 20% region. In order to get the results above you may have to test several different capacitors to match whatever value mine might have actually been.

My projectiles and speed measurements are close to 100% accurate so + or - 20% is the maximum offset.

Comments

[hunter566]

can i use 220uF 400V capacitors and still  get enought power to shoot omething a couple feet away

[eggman]

 absolutely.  throw a few of those in parallel, and you've got yourself a formidable coilgun.  depending on whats available to you, i'd aim for 5 or 6 of those capacitors in parallel.

[hunter566]

if i used 7 how many cameras do you think i would need

[eggman]

 that puts you at 1540uF  i would use 6 or 7 chargers running on 4 D batteries at 3V.

[Jduhl]

4 D batteries would put you at 6 volts

[TehMessiah]

erm.... no... if in series it would, but in a hybrid of both this is how i'd look
|[-+]-[-+]|
|[-+]-[-+]|
|- + 3vdc, so then it has twice the power of a 3vdc in series :D lol this is an old comment but still...

[eggman]

2 batteries in series gives 3V. connected in parallel to two more in series stays at 3V but doubles the amperage.

[magiccowy]

What about the really big 400v caps you can get out of computer power boxes. How many would i need for the same power as him. Thanks

[eggman]

 well his caps probably came from a computer PSU, along with yours.  i have a few 400V 220uF caps that came from PSU's.  if yours have a different capacitance, let me know.   otherwise, you'll probably have about the same power.

[magiccowy]

Thanks what would be the best cap to use and how many chargers would i need

[eggman]

 use whatever caps you have with the EXACT same voltage rating to add up to 1000-1500uF.  same amount of chargers.

[magiccowy]

Thank you

[GakkenGod]

If i may ask your opinionI have capacitors ranging from 6800uf 75V to 22uf 250 volts as well as various smaller ones.... what capacitors uf number and volt number should i use? I have read your instructable on this matter and cannot figure out what capacitors i should use. Thank you,

[eggman]

the comments almost have more info than the instructable. you need at least 330V. the capacitance ranges but a good start is 1000uF per stage.

[zattifier]

I need some help with charging circuit theory. I have built a decent coilgun whic doesn't actually shoot THAT far. With 1.3V (drained 1.5V) it will make a dent in the side of a tissue box and with the extra 0.1V (1.4V) it will nearly break through. I wanted to know if I could regulate a 2V into the charging circuit, which would charge the capacitors at about 360-380V (they are rated at 400V). Also, I would like to know if I could use multiple charging circuits, so as not to destroy the capacitors by feeding to much voltage, but to decrease charging time, thanks guys.

[hunter566]

I need some help Im confused on how to wind the coil because i dont no if i should finish a coil then cut it then start a new layer or just go back and forth

[moshee]

 Back and forth.

[tim.vrakas]

I have some old NP1 12v batterys how do i make them work

[Milesla]

This is probly the sweetest thing ive ever seen

[alvaromanuel]

could you please tell me the diameter of the wire(not in Gauge)

[rwilsford07]

Check out this link for gauge to diameter comparisons. http://www.powerstream.com/Wire_Size.htm

[krooq]

So how do you have your batteries wired? like my pic-? and whats the max voltage for the kodak circuts? also what is the point of having more batteries with one circuit, it would do nothing is they were all at 1.5V right ? i live in australia and it is near impossible to find used dispossable cameras, damn digital and noone sells capacitors here. how much are your DC to HV convertors it looks a bit difficult to make

[moshee]

that last bit of wire on the left side is not needed (actually it creates a short circuit). kodak circuits output 500v from 3v i think, more batteries in parallel gives more capacity (longer battery life). capacitors are available online (farnell seems to be popular down there) and the charger circuits on http://futureexperimentalsystems.googlepages.com/productsandservices are $75

[alvaromanuel]

400v from 3 v

[moshee]

(that's rwilsford's website)

[krooq]

What did you use to charge this one? 16 Layer, 30mm L, 8mm InDia 470uF 450V 28m/s 8g(1*400V 470uF) ****Best results 6.6%

[rwilsford07]

6 Charger circuits in parallel + 8 C Batteries at 3V (4 banks connected in parallel of 2 bank series connected C's) ~50W output

[planeboy95]

will the uF be shown on the capacitor? and how do you get 330V out of a battery

[jondo huang]

the capacitance rating is usually labeled on all electrolytic capacitors. In order to make 1.5 v from a battery become 300+ volts you must use a voltage amplifier circuit involving a 'step up' voltage transformer.

[rwilsford07]

Usually in photoflash capacitors the uF will not be shown, but on any bought or scavenged there will be a shown rating. the charger circuits convert you battery input into the high voltage needed to charge your capacitors.

[planeboy95]

i dont get the chart above. how do i make the projectile go the fastest

[rwilsford07]

With coilguns all you can do is trial and error, simulation trial and error, or replicating a working system, ie a specific coil, capacitance, voltage, projectile, etc. Working systems are shown in step 3 in the chart listing the systems properties.