Need help or ideas

Thread Starter

greg webb

Joined Sep 12, 2013
So I am very new to this site and my electrical skills and knowledge are Farley sub par. I am currently invested in a project but unfortunately iv hit a brick wall.

The project is a double 7 segment display that tells you how many rounds you have in the magazine of an AR 15 style rifle. The display would simply mount to the top or side.

Iv got the 7 seg figured out, partially. I understand I need a micro controller to act as the brain, and I have read about the BCD decoder. My first question is what does this decoder look like and how do I program it. Or do I even need to program it. And where can I find them? I looked at radio Shaquille and frys and I feel like I'm looking right at them but all the small black chips look the same if they have the same number of pins.

Ok next, and this is the biggest problem, I can't figure out what method of sensing I would use in a magazine. Iv racked my brain, considered position sensors, variable resisters, photo transistors, ect. The idea would be for the micro to respond to the different levels of resistance by sending a code to the decoder which would then illuminate the display accordingly.

So I'm trying to figure out a very low profile sensing method that can sense possibly 40 different positions and then communicate that to the microcontroller.

Final question. Would it be possible to make the sensor communicate wirelessly, and if so would I need a second micro controller to do so?

I know that's a lot. Any help or advice would be greatly appreciated. Thank you!!!


Joined Mar 24, 2008
The Completed Projects Forum is for Completed Projects only. It is meant to allow members to show plans for projects they built so other members can duplicate them if desired. New threads are also automatically moderated per Moderator review for this reason. Your thread does not belong in this forum, and was moved here.


Joined Mar 31, 2012
Forget about how you are going to display the result or communicate the information until you have a plan for sensing the number of rounds in the magazine -- how you do that may place restrictions (or provide opportunities) for doing the other things.

You need to consider what your constraints are and then what your possible sensing options are within those constraints.