Coil gun

[zachtheterrible]

I've been wanting to make one for quite some time, and since I'm making an order I figure I might as well get the components. I just wanted to make sure that my idea is ok.

I'm going to get 10 3900uf 160V capacitors. I'm getting 10 because of the price break from digikey. I'm getting 160v so that I can operate this directly from mains without the need for a transformer. Not having to buy a transformer will save me a good bundle as I don't have one laying around.

Just wanted to get everyone's opinion before I go through with it.

 

[Roff]

I've been wanting to make one for quite some time, and since I'm making an order I figure I might as well get the components. I just wanted to make sure that my idea is ok.

I'm going to get 10 3900uf 160V capacitors. I'm getting 10 because of the price break from digikey. I'm getting 160v so that I can operate this directly from mains without the need for a transformer. Not having to buy a transformer will save me a good bundle as I don't have one laying around.

Just wanted to get everyone's opinion before I go through with it.

Don't forget that rectified line voltage is about 170 volts, and that you can easily kill yourself with 120 volts, especially without a transformer.

 

[zachtheterrible]

Rectified is 170?? really? What is the simplest way of lowering it down to 120 or so?

 

[Oznog]

Yes, 120v is the RMS value. The diodes in a rectifier will charge a cap all the way up to the peak value of the waveform which is the RMS value times the square root of 2 for any sine wave.

You don't need a big transformer, a smaller power source only means it will take longer to cycle and you probably won't want to- nor could you, due to limitations in other components- cycle rapidly.

A variac is a non-isolated high current transformer that you can adjust to the voltage you need. Note that line voltage varies so what setting was 160v may yield 180v later.

There are many links describing coilgun projects on the web. Some use fairly low voltage, others use HV camera flashes which gives you not only a HV cap made to sustain large discharges AND a charging circuit to boot.

 

[zachtheterrible]

Well I guess I'll do some more research before I go buying a bunch of stuff I don't need

 

[Someone Electro]

Try not to get killed on mains.

And also a discharged cap is almost like an short so i wod limit the curent whith somting resistive.

An SCR can also be handy for trigering it.

You will also need magnet wire for the coil.You may try to take an big tranformer apart to get it.

The barrel can be anything noncondutive.As for the projetiles you can use big nails.

good luck.

 

[audioguru]

I suppose you could take the two-phase 120VAC from a dual kitchen outlet, that is actually 240VAC center-tapped, and make a grounded full-wave rectified 170VDC with a couple of rectifiers and a 200V filter cap. It would be "safe".
With a full-wave bridge rectifier you could make plus and minus 170VDC.
The zero volts connection would be grounded through the neutral wire if the outlets are wired correctly. :lol:

I should try connecting two-phase 120VAC (actually 240VAC) to the florescent lights I have that don't start. Their filaments glow, but I must flick the switch many times or touch the tubes with static electricity to make them start with only 120VAC. I don't want to replace them again, they look like new without being black at the ends.
Naw, they would blow-up!

These old florescent lights are inefficient and are being phased-out:
1) Their filaments glow and waste power for the entire duration the light is on. The filaments are needed only to start the tube, when warm they aren't needed. If they worked, I would add a 555 timer and relay to disconnect the filament current after a minute.
2) Florescent tubes are replaced when a filament has burned-out. More waste and expense. They would last "forever" if the filaments weren't powered all the time.

 

[Nigel Goodwin]

These old florescent lights are inefficient and are being phased-out:
1) Their filaments glow and waste power for the entire duration the light is on. The filaments are needed only to start the tube, when warm they aren't needed. If they worked, I would add a 555 timer and relay to disconnect the filament current after a minute.
2) Florescent tubes are replaced when a filament has burned-out. More waste and expense. They would last "forever" if the filaments weren't powered all the time.

I don't know if flourescent lights are different over there?, but in the UK the heaters are only brought on from cold for a short time - that's what the 'starter' is for.

 

[Someone Electro]

Yep same here.

Flagments,the coil and the starter in seris to fire it up.

 

[Nigel Goodwin]

Yep same here.

Flagments,the coil and the starter in seris to fire it up.

But you've got 230V mains like the UK 8)

 

[audioguru]

We don't use starters but I've seen them.
The filaments in a florescent tube are fed about 5VAC at 2A for each end of the tube continuously. The 4' tubes used to be 40W but now are energy-saving 34W. Since they waste 20W, do they use only 14W for light? :?:

 

[Someone Electro]

No we have 220V mains here.

That must be a lot of wasted power.

How about those mini flurescent light bulbs that you can screw in an normal light bulb socket.Do those also waste so much power for the filamets? I know they use an solid state way of fireing it up.

 

[Nigel Goodwin]

No we have 220V mains here.

You've not joined the EU yet then?, the EU has standardised the mains supply at 230V throughout the EU.

That must be a lot of wasted power.

How do they get the low voltage supply then?.

How about those mini flurescent light bulbs that you can screw in an normal light bulb socket.Do those also waste so much power for the filamets? I know they use an solid state way of fireing it up.

They don't usually use the heaters, electronic starters strike the tube by providing it with a far higher initial voltage.

 

[Someone Electro]

Well we joined in the EU but they didnt change the mains,well etlest not yet.

Do those 10V realy mather?

We also didnt charge our curency from SIT to Euro (€)yet.

 

[Nigel Goodwin]

Well we joined in the EU but they didnt change the mains,well etlest not yet.

They might not have told you :lol:

Do those 10V realy mather?

The UK was 240V, and the rest of Europe 220V, so it was changed to 230V right across the EU. In actual fact the UK cheated!, the spec for the rest of Europe is 230V +/-5%, the UK changed the tolerance to something like +7%/-3%, so our old 240V falls in that range :lol:

It's quite possible other countries did the opposite, but in any case appliances are now designed for 230V.

We also didnt charge our curency from SIT to Euro (€)yet.

We don't have the Euro yet either - I don't know if it's a good thing or a bad thing?.

 

[audioguru]

My 120VAC regular large (4') florescent lamp tubes use an inductive ballast with 2 filament windings for each tube.

Compact florescent bubs use rectified and filtered mains to drive a push-pull oscillator (about 40kHz) which switches its output across the tube.
The filaments are in series with each other so receive a fairly high current before the lamp lights. When the lamp lights, it has only about 100V across it which reduces the current in the filaments. :lol:

 

[Oznog]

I'm really interested in new uses for high freq CCFL tube drivers. They're easily available surplus or even Fry's since they drive the tubes used to make computer cases glow neat colors.

I made a 12v strobe based on one of those that uses 450v caps. You need high freq rectifier diodes and something to guaranteed to shut off the voltage when it charges to the right voltage, but it's pretty darn powerful powerful. Charged up 300uF to 450v in about 6 sec I believe.

It's of course still quite dangerous, but not so dangerous as power mains! And the current output is limited so catastrophic shorts aren't so catastrophic. At least you're isolated from the power mains AND ground, though you may need to reestablish a common ground between output and input in order to make it shut off when the cap voltage is maxed out.