Timing Current Lapses

First of all, I apologize if this is the wrong group or if this question has been addressed in the FAQ.

I've been interested in circuitry for a while, and am now trying to design them. One thing in particular I want to do is create a setup where, after a given time, the circuit *breaks*. This is to trigger capacitors, which are connected to solenoids. I think you can guess (or is it guass?) where I'm trying to go with this.

The 555 timer seems to be popular, but from what I understand it rapidly flips between a low and high current. What would be a good way to do what I intend?

Thanks in advance, Bill

Reply to
Bill Wayne
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No, I can't guess right now what you want to do. I am sitting here with a glass of wine, thinking out the wonders of the applications of the LM555. Life is truely amazing there must be a million ways you can wire up a 555 to do a million different things. Among them are various circuits that oscillate and make single pulses. Some of these puses are high and can be used to tuen on a MOSFET for a brief time others are low.

I predict that if you can be more specific, many people will give you many suggestions. Among them will be some that will work, perhaps after you decide to put a bypass capacitor on pin 5.

There will also be some folks suggesting that your application would be better served by a PIC. Although these people are well meaning, you should ignore them for that way leads to maddess. The only microprocessor anyone should ever consider using is the 8051.

Reply to
MooseFET

Guessing is useless, so most won't even bother.

What are you actually trying to accomplish?

Thanks, Rich

Reply to
Rich Grise

Gauss gun. I thought the pun made it clear.

Reply to
Bill Wayne

First of all, I'd like to say that I'm planning on building a coilgun. It seems the pun wasn't as obvious as I had hoped.

In any case, it seems that what I planned won't exactly work out. A better option instead seems to be using 555 circuits so that after time N, the output switched from low to high and completes the capacitor circuit that runs through the solenoid. Would this work? Assuming it does, what would be an efficient way to recharge the capacitor after it discharges?

Bill

Reply to
Bill Wayne

Probably not. I wouldn't put a 555 withihn 10 feet of a coilgun. You use a pushbutton to fire the first coil, then optical interruptors and SCRs to time the ensuing pulses based on the position of the slug.

I'd also physically space out the coils to account for acceleration along the barrel, that simplifies your timing requirements.

A power supply? Use enough series resistance so that your power supply doesn't blow a fuse, and charge them as fast as you need to to be ready for your next shot. But whichever way you do it, over the long run you'll be expending pretty much the same amount of watt-hours.

Good Luck! Rich

Reply to
Rich Grise

I think I understand how that would work. I was already planning on spacing the coils to optimize the end velocity, but I can see how that would help with timing.

I'm trying to imagine how this would look in practice, though. As I see it, some distance before each capacitor is an photodiode connected to an SCR gate. When the sensor detects the projectile has passed over it (probably either by detecting sparks caused by friction or by modifying the projectile), it supplies electricity to gate and allows the capacitor to conduct through the SCR. That seems much less complicated than either other setup, at least in theory.

So the supply would be connected to each capacitor. I had imagined that could cause the gun to fire preemptively, but it seems your recommended capacitor setup solves that problem, too.

Thanks! Bill

Reply to
Bill Wayne

No, it's by interrupting the light beam from your emitter to your detector.

I need to make a disclaimer here - I've never actually done anything like this, it's just sort of a seat-of-the-pants "that's the way I'd do it" kind of stuff.

But if I've helped you build a coil gun, that'd be a feather in my cap! :-)

Thanks, RIch

Reply to
Rich Grise

Yes, I see how that would make much more sense.

Same. Most of the calculations I've been making have been for optimization, and all the circuit designs I've been designing are more intuition based.

I'll be sure to properly attribute it. :-)

Bill

Reply to
Bill Wayne

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