Self-Adjusting Reflex Bow Sight


The original intention of this project was to make a new sight for bows which would be able to adjust based upon the distance to target. The sight would be a reflex sight with it’s mirror attached to a servo which would adjust the angle of the mirror (and subsequently the vertical position of the “dot”) based upon input from a range finder. The advantages of this over traditional bow sights is that it would be able to be sighted in for any distance and the user would only have to look at a single dot, as opposed multiple pins.


The first thing that I did was build a basic Reflex Sight (red dot sight) as a proof of concept for myself. Essentially, a reflex sight works by bouncing light from a laser (or LED) off of a mirror and onto a clear object, be it glass, plastic, or whatever happens to be handy. Below are photos and a circuit diagram for my proof of concept.

IMG_2235 IMG_2236 IMG_2237 Red Dot Diagram

Next, I started working with circuits to actually code up the project and get it running with an adjustable mirror. For this, I used a Sparkfun Redboard, which is essentially an Arduino Uno, along with a mini servo, LCD display screen and a few push-buttons for controls.

Final Result:

The final result was not quite the complete product that I had wished for. It is too big to actually be mounted on a bow, and because of cost factors, I was unable to purchase a rangefinder with adequate range. So, the final result was more a proof of concept than anything else. It had the ability for the user to key in distance manually, as well as adjust the angle of the mirror at each distance. This angle is stored in non-volatile memory, so it remains the same after the sight is turned off and restarted. Below are images of the sight, as well as a video demonstration of it being used.

IMG_2258 IMG_2259 IMG_2260 IMG_2261 IMG_2262 IMG_2263 IMG_2266


If you would like to see my code, or a circuit diagram, follow this link to my GitHub account where all of that can be found:

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