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Coil-Gun controller made from TTL chips (show-off your controller too!)

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muller

Tue Apr 04 2006, 07:18PM

Registered Member #363 Joined: Mon Apr 03 2006, 07:16PM
Location: San Carlos, CA, USA
Posts: 4

This is a 3-stage Coil-Gun timer made from basic SSI TTL chips made for McFluffin. I built this from 15 year old parts I found in my dads garage including wire and breadboard. I have to pick up a few replacement dip switches as 2 of them are faulty. I might post up my schematics for kicks if people wanna see them.

5f5b8633

Now all we have to do is build the 3-stage Coil-Gun.

Madgyver

Tue Apr 04 2006, 08:01PM

Registered Member #177 Joined: Wed Feb 15 2006, 02:16PM
Location: Munich, Germany
Posts: 214

So....

first, what does the board do?
second, what does this thread do in computer science?

Steve Conner

Tue Apr 04 2006, 10:30PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Third, does it work?
Fourth, what is this thread doing in General Science, I reckon it should be in EM Projectile Launchers.

rupidust

Wed Apr 05 2006, 09:13AM

Banned
Registered Member #110 Joined: Fri Feb 10 2006, 12:23AM
Location: Banned City
Posts: 85

What is the question, problem, or need?

Appears to be 3 pulse timers with or without optics. Are the dip switches for loading 8-bit parallel binary numbers into 8-bit counters? Are the stage drivers included such as darlingtons, mosfet drivers...? You have to start from somewhere, so these descrete combinational logic circuits are a good starting point. I started out with a love of interfacing all TI's 7400 logic with BCD counters, 7-segment drivers, static ram, shift registers, ..etc.. to build all kinds of circuits. Once building these kinds of circuits becomes easy and successfull, a true appreciation grows for alternative (in those days, but mandatory now adays) low chip count reconfigurable microprocessing control.

For instance, the below image is of a multistage coil-gun controller of PIC core. The code supports 4 stage for this 18 pin IC but the image is only displaying the circuit for a 2-stage coil-gun. There is only one logic chip, the PIC '819. All other ICs are mosfet drivers to switch the SCR/IGBT devices and drive the onboard boost converter.

Charger

Yes, send them schematics.

ragnar

Wed Apr 05 2006, 01:52PM

Registered Member #63 Joined: Thu Feb 09 2006, 06:18AM
Location:
Posts: 1425

wrote ...
What is the question, problem, or need?

Some people post just to pimp stuff, too

How long did it take you to find the DIP switches were faulty?

Barry

Wed Apr 05 2006, 03:44PM

Registered Member #90 Joined: Thu Feb 09 2006, 02:44PM
Location: Seattle, Washington
Posts: 301

Nice looking layout. I see the little '555 oscillator chip almost in the center. It all looks like an open-loop coil timer, where each stage is turned on/off according to a selectable time count. If so, it is very much like my Mark 1 coilgun. A great idea if I do say so myself.

I found the outcome was not too successful because a simple timer-based coilgun does not adjust itself for minor changes from shot to shot. With the high accelerations involved, this magnifies any timing error in each subsequent stage. It takes only a coil or two until the timing is too far off to be helpful.

Those DIP switches make an easy circuit to adjust (assuming the switches work!) and play around with. You might even consider overlapping coil times to see if two-coils-turned-on-together can improve the accelerations. However I think most people will find that closed-loop controllers with position detectors will permit more stages and higher acceleration.

Cheers, Barry
May the electromagnetic force be with you.

[Edit: Go here

to learn how to post pictures.]

Wed Apr 05 2006, 07:58PM

Registered Member #85 Joined: Thu Feb 09 2006, 01:22PM
Location:
Posts: 21

As this thread is a good place to to show off with coilgun controllers, I will also do so.

This 12 stage optical controller is a good examle of how simple an SCR coilgun controller can be because it needs no timing circuits whatsoever.

rupidust

Wed Apr 05 2006, 08:59PM

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Registered Member #110 Joined: Fri Feb 10 2006, 12:23AM
Location: Banned City
Posts: 85

EN wrote ...

This 12 stage optical controller is a good examle of how simple an SCR coilgun controller can be because it needs no timing circuits whatsoever.

No circuits never the less timing is inevitable. The optics is the timing. Proper spacing distance between successive coil stage and sensor have to be adjusted for optics. You cannot place the optical sensors at the same fixed position for all stages and expect the results to be better compared to the optics being placed slightly further away for each stage. If optics are at the same fixed position for each stage, then the coil/optic assembly would be in need of distance adjustment as above. This physical placment/adjustment is in essence a form of timing. Alter either the slug mass, start position, cap voltage, or coil winding, and the conscequence is the repositioning of the optic sensors.

muller

Thu Apr 06 2006, 12:22AM

Registered Member #363 Joined: Mon Apr 03 2006, 07:16PM
Location: San Carlos, CA, USA
Posts: 4

Wow, thanks everyone for the great responce!

Before I continue I would like to clarify that I fixed a mistake In my first post. I accidently left out the word "timer" after coil-gun. so yeah this is not the coil-gun. But I assume everyone figured that out.

I probably should've had some more explanation with this.
But yeah, Barry hit what I had pretty much spot on.

Basically I have a 555 driving an 8-bit counter. I then compare the counter to the dip switches. Some j/k's lock the signal high so that the coils fully discharge. The stray wire at the top is my counter & j/k reset(I really need to go to jameco and get some switches).

I didn't take very long to find out the dip switches were faulty. I tested each section as I went along with my o-scope(you never know with 15-20 year old chips you find in buckets). Right now the 555 is slow enough that I can visibly see the voltage spike on my o-scope.

If anyone is wondering what the mess of wires on the left-most rail is I'll tell you. I ran out of comparitor chips so I jurry rigged one. I XOR each bit, invert them, and and them all together for an equals circuit.

The output of the circuit are the 3 brown wires coming from j/k's in the right-ish bottom-ish corner.

People have given me some great advice on what I should do If I build another controller (the need for sensors mabye). But I realize that right now I lock my output to high until a reset. I did this to make sure that there was enough time for the coils to charge. Is this wise? From a recent experiment I realized I might need some sort of cut-off time so that the projectile doesn't get sucked backwards.

Those controllers all look cool and have given me some real insight!

McFluffin

Thu Apr 06 2006, 01:28AM

Registered Member #119 Joined: Fri Feb 10 2006, 06:26AM
Location: USA
Posts: 114

Nice job Muller. Now we just need to wine the other coil gun stages and get your DIP switches and the driver for the SCRs, and some optical sensors. I need to check what most people use for those. I hear people use lasers, but I figure simple IR sensors would work too. Glad to hear you are getting some use out of my scope.

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