Switching Circuit

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About: Student @ University of North Texas working towards a Mechanical and Energy Engineering Major. I do all kinds of fun little projects. I'm currently trying to scavenge old pictures so I can publish a few more...

In this Instructable (my first) I have posted the circuit design that I am currently fiddling with for its eventual use in my coilgun. When it is finished it will serve as the activation switch for a second coil. Like I said; I am still modifying the circuit and I'm currently looking for a bit of advice, so any ideas would be helpful.

Continue on to the next page for a few more details.

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Step 1: The Parts

Of course with any electronics project you have to have a parts list. Here it is so far.

3904NPN Transistor
3906PNP Transistor
Diode (not needed)
LDR (Highest Ohm rating I could find @ radioshack)
3-16V Buzzer

The buzzer is on the circuit in place of the relay that will eventually be used to short out my capacitor bank.

Step 2: Schematic

The idea of my circuit consists of an LED, LDR, relay, and a digital switch. when put togeather the LED and LDR will be placed on opposite sides of my coilguns barrel and the digital switch will turn ON and stay on when the projectile passes between the light and the light detector. My current problem (current...lol) is that the switch does just the opposite. When the light is introduced, the circuit is turned OFF and stays off.

Step 3:

Basically what this Instructable is an attempt to do is create an SCR without having to buy one through some online electronics superstore. I'm so close, but I'm definitely stumped at this point. If I have left out any info that would help you help me, feel free to message me. Ill be back with an answer ASAP.

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    11 Discussions

    None
    randofo

    10 years ago

    This project looks awesome but there isn't enough documentation of you actually making it to be a full Instructable. There are two things which you could do. 1) If you happen to have images of you making your project you can create some more steps, add those additional photos into your Instructable and then republish your Instructable. 2) If you don't have any more pictures of you working on your project, that's ok too. That just means that your project is better suited to be submitted as a slideshow. Your images are already in your library, and you can use the same text that you have already written for your Instructable so it should only take a few minutes to create your slideshow and show the world what you made! Thanks for your submission and let me know if you have any questions along the way.

    None
    admin

    10 years ago

    This project looks awesome but there isn't enough documentation of you actually making it to be a full Instructable. There are two things which you could do. 1) If you happen to have images of you making your project you can create some more steps, add those additional photos into your Instructable and then republish your Instructable. 2) If you don't have any more pictures of you working on your project, that's ok too. That just means that your project is better suited to be submitted as a slideshow. Your images are already in your library, and you can use the same text that you have already written for your Instructable so it should only take a few minutes to create your slideshow and show the world what you made! Thanks for your submission and let me know if you have any questions along the way.

    None
    theblindferrengi

    10 years ago on Step 2

    cany tou just wire the relay in so the turning off [of the relaycoil] will close the circut,

    None
    sabre

    10 years ago on Introduction

    Wow. Thanks for the input. Thats what I was looking for when I posted this.

    None
    MacDynamo

    10 years ago on Introduction

    I probably sound noobish to most hobbyists, but for my own and other viewers benefits, what's an LDR? The schematic almost makes it look like a photosensitive cell for detecting light and dark.

    None
    d-lite

    10 years ago on Introduction

    The first thing you should do is learn about photo-transistors. The LDR is totally unsuitable for anything that requires precision, and, a rail gun needs milli-second timing at the very least! For the same reason, forget about SCRs - use MOSFETs instead!

    None
    Muscelz

    10 years ago on Step 2

    aye mate, that aint a coil gun circuit. delete the Instructable ur making urself look stupid lol. buy urself a SCR, they're pretty cheap, and stop trying to reinvent them, because no NPN or PNP setup would be able to cope with hundreds of amps

    2 replies
    None
    sabreMuscelz

    Reply 10 years ago on Step 2

    your definitely right. its not the main circuit for my coilgun, but it is a piece of circuitry that I was planning on using for my coilgun. Also I don't intend this setup to conduct the amount of voltage that would be put through my coil. This circuit simply opens/closes a relay represented by the buzzer. Its been a while since I have actually worked on this design. The only reason I have left it up is to see what other people think about the concept.

    None
    Muscelzsabre

    Reply 10 years ago on Step 2

    oh! well ur reason is understandable, soz about sayin dat b4 :), kool as