A few questions in the field of coilguns

[mondeluz]

Greetings!

So Im making a coilgun for my science project at school,ofcourse my physics teacher thinks im insane.

I would like to build a 4 stage coilgun with 20 capacitors in total. We were already sucesfull in assembling a single stage coilgun that used a ''ready'' circuit board from a disposable camera that already had a 330v 120uf capacitor attached to It. For the final version im planing to use 20x capacitors wich are either the same or with the same voltage and higher capacity.

my questions are:

1)How do i mount the stages togeather? Because I couldnt find any ''real'' explination anywhere on the web. I know that it requiers a sensor of some sort or calculation.

2)Could someone recomend a website besides ebay where i could get a light barrier or a similar sensor unit that would be nice for for a coilgun online?

Im asking for online because im preaty sure noone is selling what i need atleast in 200km radius.

[davidivad]

there are many ways to time coils together.

you could manually calculate the coil timing.

this could cause untold problems due to nonconstrained variables in your experiment.

it is best to let your first coil gun decide the best time by position.

you can do this with light bulbs or leds and cds cells available at radio shack still i believe.

if you put a hood on the front of the cds cell, you can block out all but a straight shot from your light bulb or led.

a simple circuit with only a few parts will do.

your cds cell will change value when the light is blocked and can be set up to switch power to the coil in question.

i would say that for small projects, better efficiency will be found with a single coil and a large pulse equivelent to the amount of force required to accelerate your projectile to the desired speed.

 

OR...

instead of using a dc coil or two, why not create a linear ac motor?

it only reqires a shunt winding to offset the field temporarily and create positive movement.

not only is this a more efficient design by removing components not needed (fewer places for loss), but you can decrease the size of the field windings and core material by multiplying your frequency...

in other words 120 hertz is better than 60 hertz.

this is one reason ac motors are so important to the future of electric cars.

they are more efficient and you can make them with a higher power to weight ratio because you can increase the frequency.

just like using more energy to find smaller particles in accelerators it is the frequency that determines its kick.

http://www.alliedelec.com/ if you do not like radio shack. too bad you couldnt get one of those twenty dollar raspberry pi cards as it is in essence a smart controller...

[mondeluz]

there are many ways to time coils together.

you could manually calculate the coil timing.

this could cause untold problems due to nonconstrained variables in your experiment.

it is best to let your first coil gun decide the best time by position.

you can do this with light bulbs or leds and cds cells available at radio shack still i believe.

if you put a hood on the front of the cds cell, you can block out all but a straight shot from your light bulb or led.

a simple circuit with only a few parts will do.

your cds cell will change value when the light is blocked and can be set up to switch power to the coil in question.

i would say that for small projects, better efficiency will be found with a single coil and a large pulse equivelent to the amount of force required to accelerate your projectile to the desired speed.

 

OR...

instead of using a dc coil or two, why not create a linear ac motor?

it only reqires a shunt winding to offset the field temporarily and create positive movement.

not only is this a more efficient design by removing components not needed (fewer places for loss), but you can decrease the size of the field windings and core material by multiplying your frequency...

in other words 120 hertz is better than 60 hertz.

this is one reason ac motors are so important to the future of electric cars.

they are more efficient and you can make them with a higher power to weight ratio because you can increase the frequency.

just like using more energy to find smaller particles in accelerators it is the frequency that determines its kick.

http://www.alliedelec.com/ if you do not like radio shack. too bad you couldnt get one of those twenty dollar raspberry pi cards as it is in essence a smart controller...

Thank you for your reply.

Now I have a question about capacitors.

Im thinking about buying elektrolytic capacitors as shown here (http://www.ebay.com/itm/Aluminium-Elektrolytic-Capacitors-Screw-Terminal-Snap-In-Multi-Pin-/311154114632?pt=AU_Electronics_Wholesale_Electronics&var=&hash=item48723b0048)

There are other electrolytical capacitors out there as well,however i chose thease,because of their high capacity at nearly similar voltage,the shipping is free and Germany is closer then China.

However I am a bit confused now.

1) Is it possible to use a 5-pin capacitor for a coilgun?

2) I've red that electrolytical capacitors can explode.Can thease as well? And if they can what do i use so they don't?

3)Are thease type of capacitors ''mountable'' to a disposable camera circuit?

Im planing to buy 470/470 uf,385v 5pin(only available) 85*C capacitors (4-5 capacitors in total)

The original capacitor wich was attached to the camera was a 330v 120uf cap.

[davidivad]

to be honest, you will not need caps.

746 watts is about one horsepower.

a 30 amp outlet can produce quite a kick that you will not get from a cap.

you can add resistance and slow down the discharge but will not make up for an adequate power supply.

i would invest in relays instead and run full current through the full length of each stage instead of a dwindling charge.

the price of a relay compared to a cap of decent size is small.

 

caps are useful but they must first charge up through a charging circuit which is additional components.

they do not put out full power across the discharge either which relays do.

if you do use caps, make sure to have more than you might consider needing.

if you have enough charge depth to your cap banks, you can set the gun up to only use the top end of the charge.

this actually helps because the caps are already partially chargted for the next projectile.

 

if you have any issues with your sensor set up, you can always whisker switches. this will slow your projectile slightly but i doubt you are shooting for escape velocity.

[mondeluz]

to be honest, you will not need caps.

746 watts is about one horsepower.

a 30 amp outlet can produce quite a kick that you will not get from a cap.

you can add resistance and slow down the discharge but will not make up for an adequate power supply.

i would invest in relays instead and run full current through the full length of each stage instead of a dwindling charge.

the price of a relay compared to a cap of decent size is small.

 

caps are useful but they must first charge up through a charging circuit which is additional components.

they do not put out full power across the discharge either which relays do.

if you do use caps, make sure to have more than you might consider needing.

if you have enough charge depth to your cap banks, you can set the gun up to only use the top end of the charge.

this actually helps because the caps are already partially chargted for the next projectile.

 

if you have any issues with your sensor set up, you can always whisker switches. this will slow your projectile slightly but i doubt you are shooting for escape velocity.

Thank you for your answer.

This is all werry helpful,however i have one more question about caps.

1)I will build a coilgun with capacitors simply because there is no time left. However could you tell me if I will be able to use capacitors with 5 pins? and If yes how will i be able to tell wich one is positive wich one is negative?

2)Is it possible for thease caps to explode?

 

(P.S. Im talking about caps which were shown in previous link)

Edited November 25, 2014 by mondeluz

[davidivad]

 

here is a five lead cap. it should have the information on the pins available from the retailer. give them a call.

caps can explode if they are severely overcharged. i doubt you will run into this problem.

in class, i used to plug caps into outlets by thier leads. smells horrid when it starts to leak and will pop with enough juice.

Edited November 25, 2014 by davidivad

[mondeluz]

 

here is a five lead cap. it should have the information on the pins available from the retailer. give them a call.

caps can explode if they are severely overcharged. i doubt you will run into this problem.

in class, i used to plug caps into outlets by thier leads. smells horrid when it starts to leak and will pop with enough juice.

Thank you for your cooperation. Now im at final stages of building the device. And i have a question. Can i use 9v batery to charge the capacitors? Because i've seen on some vids and pictures of devices with even multiple 9v bateries.

[Harold Squared]

Fantastic topic, let us know how it turns out, please.

[mondeluz]

Fantastic topic, let us know how it turns out, please.

Very well, perhaps you could assist with my question? Can I use a 9v batery?