My latest 'gun' project lot's of pics, but...update #1 post 22 - video

This is a discussion on My latest 'gun' project lot's of pics, but...update #1 post 22 - video within the General Firearm Discussion forums, part of the Related Topics category; This isn't a gun project per se, but it certainly has to do with guns. In one of my other threads, it came up about ...

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    My latest 'gun' project lot's of pics, but...update #1 post 22 - video

    This isn't a gun project per se, but it certainly has to do with guns. In one of my other threads, it came up about how to range 'in the field'. I thought just about everybody these days used a laser range finder for that. Some however, use the scope reticle and some math and/or tables to calculate range and then use another table to determine bullet drop for the load you are using at the range you have estimated.

    First, let's be very clear about this method - it is an estimation - it is not as accurate as a laser range finder, not even close to it. Range finders typically measure range within a yard. Of course there are times you simply can't use a laser range finder so you have to use the scope.

    Using the scope for ranging is based on two very inaccurate parameters: the number of MOA or MRADs the target covers on the scope reticle and estimating the size of the target. I'll leave it at that, only to add that if you want to see how difficult it can be to pick out small, black dots or marks in the scope reticle against a dark target, perhaps in subdued lighting....

    None the less I wanted a microcontroller project to build and I thought why not build all this into electronic tables and just dial in the parameters. It doesn't make the estimation any more accurate, but it does make it easier, funner, and less error prone. So as soon as you've dialed in the target size in MOA or MRADS (you get to pick which) and the target size in inches, feet, yards or meters, it instantly gives you the range in yards or meters and the drop of your specific load at the estimated range and the number of clicks to make to your elevation. Here's the prototype. By prototype, I mean an unfinished, conceptual model - working of course.



    The pic is poor, but what you're looking at is a four line by 20 character LCD display (I bought that) and a microcontroller board I designed and built around the Atmel Mega 88A microcontroller. I will be adding a quadrature phase encoder with a switch to enter all the data, but this is where I am right now.

    It will be powered by two CR 2032 coin cells. I'm powering it with a battery eliminator right now.

    Here's what the display looks like and it's actually doing some stuff. Here's the details I hardwired in for now, but they will be entered by the user when I get there.

    estimated target size in yards - 0.5
    MRADs target covers in scope - 2.5
    Load - Federal .223 55 gr Soft Point Power Shok with a drop of 6.9" at 250 yards - I'm supplying this for now - load selection will be built in and selected by the user.
    Zero: 100 yards
    Scope: Mildot with 0.1 MRads per click

    Calculations it actually does now:
    Calculates range from MRADs and target size in yards
    Calculates the number of clicks (i.e. number of 0.1 mrad clicks) needed to put the POI dead on

    The pic is not sharp, but readable. Given all that, here's what it calculated:



    The 'clicks' are 7.5 actually so I suppose it should read 8 clicks since we can't dial 7.5 clicks into the scope. I don't have the round off correction in place yet.

    But, it basically shows if you have a target estimated to be 18" (0.5 yards) at an unknown distance that takes up 2.5 mildots in the scope, you are 250 yards from the target (calculated) and if zeroed at 100 yards, the drop will be 6.79 inches at 250 yards (built in ballistics) and you should adjust your scope up 7 clicks (calculated).

    Well, this will be fun for me to develop, but I've got a ways to go yet - and oh - it just broke - that's the problem with prototypes sometimes.

    Well, I got my last set of final papers graded so I've got a little time to add some construction pics:

    Here's the printed circuit board pattern (on the light box), printed fresh off my computer onto transparency.



    Here's a better view of the light box with a blank photosensitive board on top of the transparency.



    After developing and etching, the board looks like this and is ready for drilling:



    And here I am with my powerful seeing glasses drilling the board - ugh this is tedious!



    Kind of a neat close up. That drill bit is a .029" - less than 1/32". The holes are spaced 0.10" apart and for the IC and programming header, the holes have to be pretty well lined up or the socket and header won't fit.



    Time to mount the components and solder them in. You can see an important construction fluid in the white cup - coffee of course.



    One war story. I actually worked for days, not some each day, most of the days because I couldn't get the LCD display to initialize. It takes a fairly complicated sequence to get it going and it just would start. I checked the circuit, the wiring, connections, made continuity checks - anything and everything I could think of. Then this morning I did one more continuity test straight from the pins coming out of the IC (14 of those things to check) over to the LCD connections. Pin 28 of the IC showed an open circuit. I finally discovered the 28 pin socket I used didn't have a connection on the 28 th pin - the whole thing was just not there. I had to de-solder the socket, remove it, and put another one in its place. You can be sure I checked the socket thoroughly this time.

    Anyway that fixed it and it's worked from then on, well until one of the small connecting wires broke, but that's easy to fix.
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    I'm impressed.

    But...

    You have WAY too much time on your hands.
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    I just wish I had half your skills.

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    Darned engineers. Always doing stuff and making the rest of us look lazy.
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    Nice project you have there. It is a bit like the way that we do the range finding for the OCAT System, although we have automated the target side of it. The only thing you have to set is the scope zoom level for it to give you the range.

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    Quote Originally Posted by RoadRunner71 View Post
    I'm impressed.

    But...

    You have WAY too much time on your hands.
    Hey man, this is what I do. I teach this stuff. I'd much rather be doing this than sitting at school with little to do. Plus, I needed a project to 'update' myself.
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    Quote Originally Posted by OutWestSystems View Post
    Nice project you have there. It is a bit like the way that we do the range finding for the OCAT System, although we have automated the target side of it. The only thing you have to set is the scope zoom level for it to give you the range.
    Can you tell me a bit more about this? It kinda sounds like a Burris Eliminator scope???
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    Very cool. Having etched some circuit boards that came out total crap, I'm *really* impressed with yours! I've given up trying to do that part of the process; given the prices of the online fan houses it just made no sense for me to keep beating my head against that particular wall...

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    wow great work! I would love to be able to watch a project like this come together.
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    Quote Originally Posted by Tangle View Post
    Hey man, this is what I do. I teach this stuff. I'd much rather be doing this than sitting at school with little to do. Plus, I needed a project to 'update' myself.
    Please don't get me wrong. I really AM impressed. My amusements are generally quite a bit less useful. I never seem to have time to devote to fun "projects". My "projects" usually consist of things like fixing the leaky faucet or replacing the brakes on the car.

    Keep on, keeping on, Tangle. I always enjoy your stuff - I've even learned a thing or two from them.
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    Quote Originally Posted by RoadRunner71 View Post
    Please don't get me wrong. I really AM impressed. My amusements are generally quite a bit less useful. I never seem to have time to devote to fun "projects". My "projects" usually consist of things like fixing the leaky faucet or replacing the brakes on the car.

    Keep on, keeping on, Tangle. I always enjoy your stuff - I've even learned a thing or two from them.
    No worries RR, I didn't take it offensively at all. I have had extra time at school because of the last week and this week is finals and I'm really down to the minimum, so it was a good time for a filler project.

    Actually on the way home today I got to thinking about using a graphic display instead of the character display to get more information on the 'screen'. That's the problem with this stuff, if you don't watch it, it can grow rapidly into a project that takes forever - or you never get done with it.
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    Dang. That's a lot more complicated and probably a lot more accurate than my thumb-at-arm's-distance range estimator.
    - Sideways thumb (looking at thumbnail): Adult male as tall as my thumb is wide = ~60 yards. Half as tall = ~120yds... etc. At long ranges, I turn my thumb 90 degrees (thumbnail down) and double.
    - Closer ranges: Vertical thumb: Close left eye, line up left edge of thumb on left edge of shoulder. Switch eyes and estimate # of shoulder-widths my thumb moves. Multiply by 5 = number of yards away. Works better with bigger targets like vehicles (average car about 15' long) - multiply apparent distance jump x width of target x 10'.

    Sounds like something you could sell.

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    Brother, this is cool beyond words!
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    That's a tool to take over the world
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    Twenty years of aircraft avionics and I still don't like electronic things. I prefer the Russian version of a $1,000,000 space pen--a pencil.
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