JSI Ammo Counters

Follow our progress on the JSI LED Ammo Counter here!

--April 7-- 
Still working with the coding for the Arduino, trying to debug the Interupt Service Routine (ISR) function for cycling through modes. Prottype circuit is complete, just need the code to debug before battle testing and the imminent design minimization as well as final design considerations for production can begin. Cost is looking like it will be around ~$30ish (USD) per unit, and requires basic wiring knowledge for DIY install (switch mounting to shell and wire cutting to shorten excess).

--Feb. 5--
Worked with the Arduino Mini Pro some, and got a working code/circuit for counting down from 35 --> 00 on a 2 digit 7-segment display. Just need to get the cycling through mag sizes and reset features added, and we'll be in business.

Documentation for the microcontroller board: (5v-12v 16MHz Version)

So far, it's looking like this:
-Arduino Pro Mini (clone)
-Microtivity 2 digit 7 segment display
-Master On/Off throw-switch or push-switch (non-momentary style)
-Magwell lever-switch (non-roller) for sensing mag release (to reset counter)
-Trigger push-button (momentary) switch for decrementing the counter
-Tertiary manual decrement push-button switch (momentary) (for non-full mags) (optional)
-Push-button switch (momentary) to cycle between all 5 standard mag sizes

Still debating the onboard battery selection (3x AAs vs. 1x 9v).

More to come later, hoping to have a full prototype by the end of the weekend.

Based on preliminary costs, a DIY install kit may run around $35-$40. We'll see how much a full production unit costs in the end.

--Jan. 27--
Ordered some Arduino Mini Pro boards, should hopefully have a semi-working prototype by the end of the weekend. 

--Oct. 29--

We haven't forgotten about these, we promise!

--May 29--

Trying to rework with an Arduino Mini microcontroller unit [5v-12v 16MHz Version],

Pros: More than enough processing power, compact, still runs on 5v, can be burn away form Purdue
Cons: More expensive, must rewrite entire code, must redesign schematic
Will update later.

--Prior to May 4--

Design Considerations:
-Variable mag size select via DIP Switch
-Dual 7-segment display: possibly 00 through 99
-2x common-anode 7-segment LED displays (available in many colors)
-Manual decrement select
-Trigger or plunger clocking
-Reset on mag release
-Master On/Off switch

Originally opted for Lattice Semiconductor GAL 22V10 24-pin logic chip - 22v10 Data Sheet

This type of chip can be burned by a Dataman Universal ISP Programmer unit, readily available to Jake in the Purdue ECE labs.

Pros: Easy to burn at Purdue, cheap, simple, not overkill for features
Cons: Can't burn/prototype away from Purdue

Schematic [v1]:

Note: This is not the original hand-drawn schematic and may be missing some considerations. This was recreated from memory and original design considerations.
ABEL Code [v1]: ABEL source code v1
This is a the original iteration of the ABEL source code for the ammo counter. It should technically work, but has a few looping termination flaws. I would like to rewrite it to incorporate Moore states instead of a single truth table and decoding lines. It is written to compile on Lattice Semiconductor ispLever Classic 5 and sync to the chip via the above mentioned Dataman programmer unit.
Abstract-ish blurb:

The goal is to create a singular-enclosed unit (chip, LEDs, DIP switch) that will control everything except the trigger clocking and magwell release (which are two other switches) and the master switch (which may get integrated on the DIP switch anyways). The DIPs will form a cascading 5-switch "don't care" decoder, where the highest activated switch from left to right (regardless of lower switch positions) will select either 6, 12, 18, 25 or 35 rounds to reset to. The counter will auto-reset to the selected amount on magwell release.

Another possible feature may be the ability to individually decrement the counter for non-full mags via one of the extra DIP switches.


  1. WHen will the ammo counters be ready?

    1. We've been on hiatus for quite some time, this may be a project that never gets realized.