Nice idea !

are microphones fast enough for that?

@@justfasial01 Yes. They do >40000 samples/second. That is plenty for measuring projectiles slower than speed of sound. As a teen, I used to measure softair velocities that way.

very interesting @@HL65536

Why not just put a scope on the last light detector? You know the length of the projectile, so just measure the length of the pulse?

Uh that would be nice. Unfortunately those are very expensive. But it would be nice to see how the acceleration changes from coil to coil.

The Boom himself 💥

Yo Slomo Guys....where you at lads?!

@@ELECTRONOOBS there are companies that let you rent them, so it might be worth looking around.

i know

Personally I'd probably layer rubber, metal, then a shoulder piece of rubber for added comfort of it does backfire. Initial rubber absorbs the shock of the round, the metal stops it, then you have the shoulder piece to absorb the rest of the shock. I don't have loads of experience with electronics but all that force knocking this back makes me think a bad solder connection or something could become dislodged

yep got the same idea

You're right that its possibly that happens but it should only have the power from the first stage, doubtful that has any kind of penetration power for most materials better than paper. Even cardboard could stop it. Something would have to go really wrong in the circuit for it to travel to the other end and then full recharge to fire in opposite order.

right, to optimize for efficiency, precise calculations would be necessary, coils, capacitors and projectile should all be balanced.

Yep. Also the earlier coils should probably use lower capacity capacitors, and last stages higher... But, meh, coilguns are useless and will probably forever will be regardless so what's a difference of extra 10-20 m/s, which is the most you'll get from any and all tinkering?

interesting point about the air - I wonder if a small ducted blower blowing across the face of the tube might (venturi effect) cause a small vacuum in the tube and help with that.

Yes, you could (and should imo) reverse the current direction of the coil, as soon as the projectile hits the center. This way most of the remaining energy of the coil gets fed back into the system. It would require current sensing and H bridges on each of the stages though. And that would be an order of magnitude more complex than what he has right now.

@amos9274 My thoughts... Order of magnitude? Perhaps 10% more. Seems like it would require an extra MOSFET and diode (and the removal of an optical sensor). Perhaps a 10% increase in the component count per stage. Here is why I don't think reversing current will help. Coils take time to charge and discharge - reversing the current inside a coil will also take time - and during that time you will be pushing power against near-infinite resistance. All you would get for your effort is heat. But if you disconnect coil 1 from power at the same time you connect coil 2 to power and capture back EMF from coil 1 through a diode into capacitor 2. I think the position of the coils would need to be tuned based on segment firing times - if you put the later coils too close together they will not fully charge before the projectile moves through them. Their minimal distance would cause linear acceleration- implying they should be spaced to inverse square... I think I like designing things more than I like building them :)

@@JohnBoen Yes, what you need to do in the end is lower the current, as the projectile is going through. The more/the faster, the better. If you hooked the coil up in reverse to a common capacitor bank, it would not only return most of the energy, it would also discharge the fastest (U= I'*L). To implement that though you'd need some additional circuitry. If you want to trigger based off the induced voltage of a projectile, you'd face the issue of it being proportional to the speed (which means it wont work from a standstill) but also, even more measurement circuitry. Like you proposed, it would also work to dump the energy into just the next single capacitor with an extra diode. First of all, you'd have to replace the thyristor with something more sophisticated for that to work, second of all that would just overcharge that next capacitor (and if not, why not apply a higher voltage in the first place). So, you'd have to start activating the next coil while the other coil is still active, to dump the energy somewhere afterwards. To do that, you'd need to coordinate between the two coils which would in turn require even more circuitry.

@amos9274 Thanks for the talk - I think triggering based on the current direction change is such a fundamentally better design that it is worth a little more effort. am a bit rusty. I haven't built any electronics in about 15 years. So I am not getting my point across. I also may think some things areI possible when they really are not. I think an optical trigger that cannot be adjusted is bad design (it triggers off a side effect) - this trigger would be nearly optimal in timing. The design referenced here leaves prior coils on, which means your ball is often moving between two magnets that are both on. This is just a bad design... Turning off the prior coil is an important part of this... . I think this would work -tell me what you think: Assuming a projectile is moving toward or away from the coil.,the induced current will be in opposite directions. As it passes through the center, the current flow moves.from highly positive.to highly negative. I think this would be trivially easy to detect with an OpAmp. This is a comparator operation that you could perform with a commercially4 available OpAmp IC. These operate at 200+ khz, which should be well past any realistic circuit needs. A 100 m/s 10 cm ball would not need 20 khz. Use the comparators to drive MOSFETs. I did a little hand waving on the OpAmp logic, but this is literally what they are designed to do - so I figure there are dozens of digital and analog solutions to this problem. And since Udio frequencies are sufficient we probably have a whole bunch of low-cost and high-power audio chips available. Blah blah blah...

I would like to have your Altium design PCB design file

Thanks :)

​@@ELECTRONOOBS Altium designer looks like EasyEDA on steroids.

I would like to have your Altium design PCB design file@@TheUnknownCatWarrior

I would like to have your Altium design PCB design file@@ELECTRONOOBS

I have one. Is not more powerful than my station. Is still not enough for those big pads...

​@@ELECTRONOOBS Ah I see, that's a lot of copper then lol

your idea is really cool, but for a noob like me, do you know any links to explain that, or with concrete examples with downloads of gerbers etc.. it already looks so complicated without your idea LOL thx for your comment.

Oh such a good idea!!! I have like 5-6 old tattoo machines, each with 2 coils... Thanks!

I would like to have your Altium design PCB design file

Not really, rifling works with powder weapons because the lead making the projectile is kinda soft, and the insane acceleration makes the bullet expand into the rifling and spin. However lead isn't ferromagnetic and thus can't be used as a projectile. Ferromagnetic projectiles are too hard to fit in a rifling. That's actually one reason armies aren't that seriously working on magnetic rifles

You could use Ferris metal dipped in lead, then use a CNC machine to make the projectiles the correct diameter then add rifling then you would lose the tumble

Yes, without the 3D enclosure the PCB can't hold itself, is too heavy. The enclosure ads support!

Those caps and coils gotta have a fair bit of gravity to em!

I would like to have your Altium design PCB design file

Is just a stainless steel rod cut into 15mm long bits...

I've tried all the ways... :/

Maybe even something of a clip like the Crossman does for some of their air rifles. It would also be somewhat beneficial to possibly slightly magnetize the bolt to hold the projectile at its most efficient starting point or design a tight fitting single or multi shot clip.

Check here: ae01.alicdn.com/kf/Sef89e3bafc0b4aae8597e65c02f84f802/Inversor-Boost-Step-up-Board-de-500W-1000W-DC-12V-a-AC-220V-380V-420V-transformador.jpg_.webp Just connect the 380V to your couldun high voltage input...

I don't have them. Only Blender project, sowy...

A lot of MOSFETs are not able to handle the amount of current when firing so Thyristors are used as they can do the job well. It's also cheaper to buy thyristors instead of MOSFETs suited for the application. The current flowing through each coil is calculated with this formula: V÷R

@@ThinkingFurry thank you for that answer !

Thyristors are more suited for these applications than IGBTs. Also it might be more expensive to buy an IGBT for this application than a Thyristor.

I think each coil is turning on and off independently and not all at once

Not at all!