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Bjørn

Sat Sept 15 2007, 10:10AM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

If you have a PC with a sound card you can make fairly accurate measurements of frequency.

Steve Conner

Sat Sept 15 2007, 10:23AM

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

Bah, if you're serious about electronics, get an oscilloscope. Troubleshooting electronic circuits without one is like playing golf without clubs. I've seen the old 20MHz Hitachi and Hameg ones go for $20 on Ebay. Or use a scope in the electronics lab at college.

phil

Thu Nov 08 2007, 04:22AM

Registered Member #314 Joined: Mon Mar 13 2006, 03:12AM
Location:
Posts: 52

I'm in the process of using the schools equipment. Took a little convincing after i mentioned that i was building a boost converter(and Electrical engineering professors don't like to "waste" time on a Mech E major). Right now i'm just going to test the 555 timer circuit to make sure it's outputting the proper frequency. The next step after that is to set up a MOSFET driver and MOSTFET to get the boost converter working.....

I decided to make my first project a coilgun as it does not require an injection system. So the next step after a boost converter would be on to the PIC microcontroller for the triggering. I don't know if i'm going to do more of a "dead reckoning" by just calculating the time before the coils need to be turned on and shut off(thinking of making 2-3 stages), or if i'm going to use an IR trigger. Anyone have any input on which they prefer?

EDIT:I also failed to mention that i now have full access to the Schools machine shops, which includes a CNC plasma cutting table, so building the rails for a railgun just got a heck of alot easier to make =). It's just the whole projectile welding itself to the rails thats preventing me from making at the moment; not to mention i'd have to carry the damned thing around or write a proposal to the school
for a place to keep it.

EDIT2: An idea just popped into my head, what if I used a coil to accelerate the slug into the railgun rails instead of using air? A 1 stage coil might be enough to get the projectile up to speed, but then again i could just make a larger coil gun. any thoughts?

badastronaut

Mon Nov 12 2007, 06:44AM

Registered Member #222 Joined: Mon Feb 20 2006, 05:49PM
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Posts: 96

Railguns do not need an injector. Magnetic forces alone are enough to overcome friction. If you have problems with the projectile welding to the rails, then you have designed the railgun very badly and an injector will not help at all.

phil

Mon Nov 12 2007, 10:16PM

Registered Member #314 Joined: Mon Mar 13 2006, 03:12AM
Location:
Posts: 52

So if i was to make a railgun, could i make the rails out of something like carbon steel. And what would i make the projectile out of, aluminum?

Eric

Mon Nov 12 2007, 11:59PM

Registered Member #69 Joined: Thu Feb 09 2006, 07:42AM
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Posts: 116

Steel is a bad choice for rails. Use copper, hard copper if possible, C110 or C102.

Check out Rapp's info on Railguns above. You'll need to translate it in google but the ideas are good.

phil

Tue Nov 13 2007, 07:34PM

Registered Member #314 Joined: Mon Mar 13 2006, 03:12AM
Location:
Posts: 52

Ahh ok, thank you for linking that site. i can see what Steve was talking about with the plexi + wire projectile now.

EDIT: Pulled one of the toroidal inductors from one of the dead ATX power supplies i have. Tried running the boost converter from the breadboard circuit i have set up but my bench top power supply can't put out enough power to run the damned thing. I've been given permission to use some of the school equipment to tune my 555 timer circuit to the right freq, I'm going to try to get it close to 1KHZ for now.

When i tried running the boost converter using my benchtop power supply the voltage on the meter would rise until it got to 4volts and then drop back to zero, taking about 3-4 seconds to get to the 4volts. I just assumed i wasn't getting enough power from the supply. Any other thoughts about why this is happening?

phil

Thu Nov 15 2007, 05:42AM

Registered Member #314 Joined: Mon Mar 13 2006, 03:12AM
Location:
Posts: 52

Tested the 555 timer circuit today in the lab, put out complete garbage. Redid the circuit based on "anothercoilgunsite" and it's now outputting a nice square wave. Now i just have to tune it to 1Khz, unfortunately i didn't have enough time to do it today. I'm also trying to start this as a research project at Stony Brook university, if any of you go to school there let me know.

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