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microcontroller for a coilgun

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LAN_403

Reid

Wed May 13 2009, 09:05PM

Registered Member #2064 Joined: Sat Apr 04 2009, 09:26PM
Location: NJ, USA
Posts: 16

Hey, guys
I'm looking at using a microcontroller to operate multiple SCRs for a quad stage coil gun instead of using hard-wired logic.
Yes, I will be using photogates, not electronic timing.

I was just wondering if you could recommend one microcontroller over another.
PIC?
BASIC stamp?
Arduino?

I am currently planning on the Arduino simply for its price, but I would like to hear what you would recommend.
thanks in advance

big5824

Wed May 13 2009, 09:22PM

Registered Member #1687 Joined: Tue Sept 09 2008, 08:47PM
Location: UK, Darlington
Posts: 240

Iv only used PICAXE's, but they perform great for me and are programmed in basic. So far iv used them to build an electronic lawn mower, a chronograph, and soon my 9KJ gun

Bjørn

Wed May 13 2009, 09:39PM

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

PICAXE

is a good and cheap solution.

I reccomend that you use PIC and do it in assembly, that way you will learn more. Basic Stamps are probably the least suitable of the ones mentioned. For $25 you can also get a very fast 32 bit ARM controller.

MachineShop

Thu May 14 2009, 02:41AM

Registered Member #2107 Joined: Mon May 04 2009, 05:02AM
Location:
Posts: 12

i understand the advantage just suppose u get the circitry wrong thats a wate o f 50 dollas if u fry the circuit...

Killa-X

Thu May 14 2009, 03:16AM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039

I personally only used AVR by Atmel. I own a 2kb attiny2313 and a 64kb atmega644p, with 20mhz set built-in clk speed. I fond these handy and easy to program with Atmels programmers. I've done LCD screens for projects on my colgun once such as setting a voltage stop point. Instead of 2 resistors for a voltage divider to trigger an SCR. I used digtal pots. I can program it in assem. But I rather C. I've also used my mega to controll my TV for a game with sound. Hopes this helps you!

uzzors2k

Thu May 14 2009, 12:14PM

Registered Member #95 Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308

I second AVR, it's assembly code is easy to use, comparable to BASIC IMO. I like bringing up this quote when the PIC VS AVR discussion comes up:

Overall, I've written some asm for both processors and I hate to break it to PIC users but writing assembly for PIC is akin to stabbing myself in the face. (Except its not even that efficient, cause you have to more the knife into the working register first (movlw KNIFE), and then you can stab yourself (movwf FACE).

The rest of the site is good for clearing up the differences.

TheMerovingian

Thu May 14 2009, 01:45PM

Registered Member #14 Joined: Thu Feb 02 2006, 01:04PM
Location: Prato/italy
Posts: 383

I have used PIC16f876a for both interface and timing, written the code in PBPpro.

I'm redesigning the thing using the PIC16F876a for interface and charging/firing control, connected to a PIC16f88 (SPI interface) that is used ONLY for timing (don't want to use interrupts since i'm using LCD's, so it would screw up the display). At beginning the "master" pic will send the activation command to the "slave" that has own values of pulse times. The master comunicates changes of pulse time in the usual SPI way.

Bjørn

Thu May 14 2009, 02:00PM

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

A PIC is a dedicated simple microcontroller and it is pretty good at it. The main advantage is that it is simple and you can spend most of your time figuring out how to use it well. The main disadvantage with the 16Fxx chips is the banking which can be quite bad unless you make a real effort to keep it under control. The 18Fxxx series does not have that problem.

The AVR is more like a normal 8 bit CPU turned into a microcontroller, so it is much better for writing complex programs which does not really apply here since we are talking about a simple control application.

If you want to learn for the future or make a something complex then you are better off with an ARM.

hotcrazyfruit

Thu May 14 2009, 08:07PM

banned on 5/26/2009
Registered Member #1877 Joined: Mon Dec 22 2008, 02:03AM
Location:
Posts: 147

i am going to be building this one. it seems pretty simple.

big5824

Thu May 14 2009, 08:33PM

Registered Member #1687 Joined: Tue Sept 09 2008, 08:47PM
Location: UK, Darlington
Posts: 240

Use a single potentiometer for the threshold resistors (wiper connected to comparator, other two pins to + and 0v). I used a 100 turn high accuracy one, lets me tune the frequency to 0.01v (probably more, but my multimeter doesnt go that accurate)

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