A coil gun missing part problem

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Terminator Electricity

Joined: 02 Feb 2006
Posts: 150

25 Mar 2006 22:33 toy car coil mechanism

this is a circuit 4 a coil gun

but there is a part that i couldnt find it anywhere

it is : SCR S6025L

Any way

I am plannig 4 my project to be an ejection seat

could a lower cost simpler coil gun do the trick ?

(using ofcourse a toy car and a toy seat)

and if it does , can anybody help me with a comlete design or help me make my

own design ?

10x , Very Happy

[/img]

IanP

Joined: 05 Oct 2004
Posts: 6661
Helped: 1577
Location: West Coast

26 Mar 2006 1:33 lorentz coilgun

The S6026L thyristor is a general purpose 600V SCR (with isolated tab) rated for 25A, see table below .. http://www.darisus.de/Elektonikshop/Datenblaetter/TECCOR/S2006D.pdf ..
It can be replaced by any other SCR rated for similar voltage and current, for example, BT152-600, 25TTS08, and so on ..

I don't think there is anything wrong with this design .. go for it ..

Regards,
IanP

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Terminator Electricity

Joined: 02 Feb 2006
Posts: 150

26 Mar 2006 10:33 A coil gun missing part problem

would BT151 work as well?

IanP

Joined: 05 Oct 2004
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Location: West Coast

26 Mar 2006 11:31 Re: A coil gun missing part problem

The BT151-XXX are rated for 12A, but in this application I can't see any reason why not ..

Regards,
IanP

Terminator Electricity

Joined: 02 Feb 2006
Posts: 150

26 Mar 2006 11:38 A coil gun missing part problem

ur help is very much appriciated , 10x

one more question plz

wat type of coil i should use : length , diameter, number of turns ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

for the transistors used in this circuit, can i used any transistors ?

IanP

Joined: 05 Oct 2004
Posts: 6661
Helped: 1577
Location: West Coast

26 Mar 2006 11:54 Re: A coil gun missing part problem

Try to construct a coil as per attached picture ..
More details you can find at: http://www.oz.net/~coilgun/mark2/home.htm

Regards,
IanP

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Terminator Electricity

Joined: 02 Feb 2006
Posts: 150

26 Mar 2006 11:57 A coil gun missing part problem

wat is meant by washers ?

IanP

Joined: 05 Oct 2004
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Helped: 1577
Location: West Coast

26 Mar 2006 12:00 Re: A coil gun missing part problem

As far as the NPN transistors are concerned, any general purpose NPN will be OK ..
P2222, 2N2222, BC107, BC .. , ZTX .. and so on ..

Regards,
IanP

Terminator Electricity

Joined: 02 Feb 2006
Posts: 150

26 Mar 2006 12:16 A coil gun missing part problem

ok , 10x , but should i separate the 3 coils by distance or 2 be continues?

IanP

Joined: 05 Oct 2004
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Helped: 1577
Location: West Coast

26 Mar 2006 12:18 Re: A coil gun missing part problem

The iron washers will just increase the magnetic field strength of the coil ..
If you don't want to, you may not use them, but they can help ..

Regards,
IanP

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Terminator Electricity

Joined: 02 Feb 2006
Posts: 150

26 Mar 2006 12:59 A coil gun missing part problem

does the diameter of the coil have to be at certain

ammount or any diameter would do the trick ?

would it melt if it was too thin ?

Buriedcode

Joined: 06 May 2004
Posts: 330
Helped: 34
Location: London

26 Mar 2006 16:26 Re: A coil gun missing part problem

Quote:

would it melt if it was too thin ?

I doubt it. What the circuit does it charge a capacitor (5000uF) and then this is shorted through the coil via the SCR. The discharge will be very quick, and some of the diodes will prevent oscillation (also known as 'ringing') where the energry is dumped into the coil, from the cap, and then the coil dumps some energy back into the cap...just like an LC circuit.

The discharge will be very quick, under a ms. But....if you were to use a massive capactior and some very thin wire, there is a small chance the wire in the coil could explode. You're ok with a 5000uF cap.

Quote:

does the diameter of the coil have to be at certain
ammount or any diameter would do the trick ?

I don't think there are any 'rules', you're just creating a massive magnetic field for a very short period. I'm unsure of how you are going to 'eject' your seat? Most coil guns, have a projectile placed just outside the coil, when the coil is enegised, the projectile it strongly attracted to the centre of the coil, but the pulse has stopped by the time it gets there, so it just goes through the coil, and out the other end.

Some designs, that can be more efficient, use the Lorentz force. Put simply, any coil nearby your coil, will have a current induced in it, of opposite polarity. If this secondary coil is closed (like a ring of aluminium) then current will flow in it, producing its own magnetic field.....which again, is opposite to the first coils polarity....the effect? They repel like theres no tomorrow Very Happy

Also, because the secondary coil is simply a 'ring' (a single turn on a transformer) the voltage from the first coil is stepped down....by *1st coil turns : 1* And the current is stepped up. Because magnetic field strength is determined by current flow, this makes the effect quite impressive.

Anyway, I'm just ranting now....sorry, back to your problem.
The coil would simply require experimentation. From school, the properties of a coil that determine field strength are:
-Diameter of wire (you want it fairly thick)
-Some sort of 'core' (iron probably, or some sort of ferrite material)
-Number of turns in the coil

And obviously current. You might not want to have too many windings....more windings = higher resistance = less current flow. But anything under 500 turns should be OK.

Hope this helps, at least in some way :/

Finally, your SCR. I'm sure it will be fine, but I built a 'pulser' a while back, very similar design to yours...used for Xenon Tubes, Coil guns, rail guns etc.. And the SCR nearly always 'latched'. That is, once fired, the SCR remained 'on' and could not be turned off. It was rated at 800v and peak of 120A. Think I blew it.
If you want a substitute SCR....check the max Voltage, and peak current. It won't be conducting all the time, so av. current is meaningless.

Regards,

BuriedCode.

IanP

Joined: 05 Oct 2004
Posts: 6661
Helped: 1577
Location: West Coast

27 Mar 2006 2:58 Re: A coil gun missing part problem

I am not sure if Buriedcode used protective diodes (see picture below) around the coil when blew his SCR, but in your case all three diodes make sure that you are protected against positive (D5 -->C3 path) and negative (D3 and D6) spikes at both sides of the coil ..

Regards,
IanP

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Terminator Electricity

Joined: 02 Feb 2006
Posts: 150

29 Mar 2006 12:57 A coil gun missing part problem

10x ,

could I ask one more question ?

wat could be the transformer current ?

another thing , I couldnt find the 24 CT

how can i use two transformers instead ?

10x again

IanP

Joined: 05 Oct 2004
Posts: 6661
Helped: 1577
Location: West Coast

29 Mar 2006 13:08 Re: A coil gun missing part problem

The transformer's current won't be high .. After all the 5000µF caps are charged through 1kΩ resistors .. I would say, if a transformer is rated for more than 100mA it will work ..

I don't think you need two transformers .. Try to use one 24V transformer .. The 7805 regulator can handle voltages up to 35V so all what you may need is a small heatsink for the 7805 ..

Regards,
IanP

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Terminator Electricity

Joined: 02 Feb 2006
Posts: 150

29 Mar 2006 13:38 A coil gun missing part problem

heatsink ?????????????????????

wat do u mean by that ?

For the transformer , i couldnt find any 24 v CT

so i was advised to use two transformers(12v) instead , but i dont know how 2 connect them together

Added after 1 minutes:

and yeah,, aslo wat fuse current i should use ?

10x ,

IanP

Joined: 05 Oct 2004
Posts: 6661
Helped: 1577
Location: West Coast

30 Mar 2006 4:58 Re: A coil gun missing part problem

I suggested heatsink for the voltage regulator if you ran it of full 24Vac ..
If you have two 12V transformers you will not need it ..

As far as the transformers are concerned, connect their primary windings in parallel, so both primary winding will be fed of the mains, and connect the secondary windings in series, so where they are connected together is the CT point ..

Depending on the power rating of your transformers, the primary fuse may be sized at 250% of transformer primary current, for example, 10VA transformer running at 120Vac and full rating load will draw ≈85mA .. use 250mA slow-blow fuze ..

Regards,
IanP

Terminator Electricity

Joined: 02 Feb 2006
Posts: 150

31 Mar 2006 15:03 A coil gun missing part problem

Another question plz , i have finished connecting the circuit

how much distance is barable between the emmiter and the reciever in order to still have a signal ?

IanP

Joined: 05 Oct 2004
Posts: 6661
Helped: 1577
Location: West Coast

31 Mar 2006 17:22 Re: A coil gun missing part problem

The best thing to do is to build a simple test circuit ( see picture below ) and test them ..
I don't think you can estimate that distance just by reading data shits ..

Regards,
IanP

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Terminator Electricity

Joined: 02 Feb 2006
Posts: 150

06 Apr 2006 19:25 A coil gun missing part problem

hey, i have tried the coil gun

how much does it take 4 the capacitors to fully charge ?

if it took 4ever 2 charge , what could be the problem ?

Added after 2 hours 27 minutes:

Another thing , the capacitors r not charged !!!!!

the voltage accross the first one is 21.7 v

the others each has a voltage of 0.7 v

plz answer fast

cuz i am trying the circuit right now

10x,

IanP

Joined: 05 Oct 2004
Posts: 6661
Helped: 1577
Location: West Coast

07 Apr 2006 1:43 Re: A coil gun missing part problem

To fully charge 5000µF capacitor through 1kΩ resistor you will need roughly 5 * R * C = 25s .. see picture below ..

If there is no voltage on one or more of these caps check SCRs as they may be ON and current through 1kΩ resistor will be enough to keep them ON .. If you have an oscilloscope take a look at C5 (SCR2) and C8 (SCR3) on power on ..
BTW, which caps are not charged: C3 or C6/C7?

Try this: disconnect SCRs (anode) and measure voltage on caps ..

Regards,
IanP

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Terminator Electricity

Joined: 02 Feb 2006
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07 Apr 2006 12:19 A coil gun missing part problem

hey man , one more question

if we decided to weld the project

where can we find the circuit suitable for welding

in order 2 print it on the board ?

IanP

Joined: 05 Oct 2004
Posts: 6661
Helped: 1577
Location: West Coast

07 Apr 2006 12:28 Re: A coil gun missing part problem

"welding" <=> "soldering"
Is this what you have in mind?

Regards,
IanP

Terminator Electricity

Joined: 02 Feb 2006
Posts: 150

07 Apr 2006 12:49 A coil gun missing part problem

yes man

i have told that i should have a circuit buid on eagle or something in order to print it on a board

but i dont know how 2 do it

how can i have it ?

Terminator Electricity

Joined: 02 Feb 2006
Posts: 150

08 Apr 2006 15:48 A coil gun missing part problem

any one ??!!!!!

Terminator Electricity

Joined: 02 Feb 2006
Posts: 150

09 Apr 2006 13:54 A coil gun missing part problem

plz i need a help with the coil gun

wen i press the trigger , the capacitor is discharged , but the projectile (nail) is not even moving

wat could be the problem

i used the coil at 4 cm long , one turn

note : the capacitor charges untill 27 v

plz help me fast , the engineering day is approaching

IanP

Joined: 05 Oct 2004
Posts: 6661
Helped: 1577
Location: West Coast

09 Apr 2006 14:12 Re: A coil gun missing part problem

Was the cap charged to 27V?

If it was, and you had discharged it through that coil and nothing happened then somethnig has to be wrong with the coil ..
5000µF at 27V is a lot of energy ..

Regards,
IanP

Terminator Electricity

Joined: 02 Feb 2006
Posts: 150

09 Apr 2006 14:31 A coil gun missing part problem

my coil was 4 cm long with one layer

the diameter was about 1 mm

is there any thing wrong with that ?

Buriedcode

Joined: 06 May 2004
Posts: 330
Helped: 34
Location: London

09 Apr 2006 16:40 Re: A coil gun missing part problem

Hi,

Quote:

my coil was 4 cm long with one layer

the diameter was about 1 mm

is there any thing wrong with that ?

Not entirely sure what you mean. With that cap charged, as IanP siad, thats a fair bit of energy. What determines how powerful the magnetic field is is current and number of turns. Although, even a few turns around a plastic tube should make a nail near it twitch.

The more turns you have, the more resistance the coil has, the less current can flow (I=V/R). Its a careful balance, so thick wire would be a good idea, to lower the resistance, and allow for lots and lots of turns. Maybe gauge #28?

1mm diameter? of the wire? or of the entire coil? Thats VERY small for a coil in this sort of application. I would put together a simple 'test' coil to check that your circuit is working correctly......THEN you can design a coil for your app.

An obvious thing to check would be, is your projectile magnetic? Most nails are iron, so that shouldn't be a problem. Also, connect your coil to a 12V supply, keep the current low, say, 1A. Now you have a solenoid, move some iron things around it to check if the field is there/how strong it is, you also might want to check that the coil is actually conducting Very Happy

If you've tried the above, and it makes a good solenoid, a decent electromagnet, then the problem is with your circuit. The cap may be disacharging via some other path.

Is the coil wrapped around a non-magnetic former? I can only assume you want a hollow coil, with a nail just outside of it, so that when you discharge your cap through the coil, the nail is pulled into the coil and thrown out the other side. I once used a spool of gauge 28, I bought from an electronics shop. Its the spool the wire came on, I just soldered the wires to my circuit and let her rip.

Some examples of what your coil should look-like/do:
http://www.global-defence.com/1997/High-speed/CoilgunLG.jpg
http://mix.hive.no/~nayrn/Martyrium/pics/coilgun_pri.jpg
http://www.sampson-jeff.com/rsoh/010420/rsoh05.jpg

So, just to recap, some simple checks you can do:
Check continuity of coil.
Check power of magnetic field with the coil carrying DC
Check if projectile is magnetic (although, an aluminium ring WILL move)
Check diodes around the coil, one might have blown and be shunting the power, bypassing the coil.

Once you have a working circuit, that can create a magnetic pulse, then you can worry about your 'ejecter seat' mechanism.

I hope this helps in some way. I'm sorry if I'm asking questions that are obvious, or have been asked before, but once I get a good idea of what you want, and what your coil looks like, then I can try and help you solve your problems.