Ammo Counter with Optical Sensor


This kit comes ready to install and will add a functioning ammo counter to your project.

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The Ammo Counter MkIV was designed in collaboration with Nathaniel Deal of to be the ultimate Nerf Ammo Counter. Customers have also had success installing in airsoft and paintball.

This ammo counter is small enough to be added to a variety of builds. I have have been making Ammo Counter Kits since 2009 and have sold hundreds of circuit kits. I pride myself on making the smallest available ammo counter.

* Ammo Counter Circuit
* 3xAAA Battery Holder
* Optical Sensor

The battery and optical sensor will be pre-wired for you. A solder iron is still recommended so you can adjust the wire lengths in your build.




* Do I want a Lever Switch or Optical Sensor? That depends on your project. The optical sensor works best for full auto low speed projectiles, like nerf. The lever switch only works for semi-auto, but is much more reliable at counting small high speed shots.

* Where should I mount the Optical Sensor? You can mount in the barrel or action assembly.

* What are the dimensions of the optical sensor? 20mm x 10mm x 8mm / 0.8″ x 0.4″ x 0.3″

* Can I wire the ammo counter into my blaster’s battery pack? Yes. Add a note to your order, request a step down voltage circuit instead of the included 3xAAA battery pack.

* How do I attach the color sheet to my display? Recommended method is to laminate with clear packing tape or pinch within a bezel. 3D Models below.

* Can I have clip detection? Typical usage is to let the Ammo Counter auto-reload, or press either button to reset. However, Yes, there is an unwired connector that will reset the ammo counter when shorted. Recommend using a Normally Closed Reed Switch with a magnet in the clip.


* Smallest Ammo Counter Circuit!
* Selectable Clip Sizes 6, 10, 12, 15, 18, 22, 25, 35. Can be customized using on screen menu.
* Compatible with Normally Open Switches / Normally Closed Switches / Analog Optical Sensors
* Configurable Auto Reset

Physical Specifications:
* PCB Dimensions: 26.3 x 27.0 x 14.0 mm
* Display Dimensions: 25.0 x 19.2 x 7.2 mm
* Screen color is white, can be tinted using gel sheets. Select your color when you Add to Cart.
* Circuit requires 3-5V, 3xAAA or AA are recommended. Can also be wired into 6V-40V battery pack when using a step down voltage circuit.
* The two buttons on the front are used to reset the count, change clip sizes, and configure additional options. See user guide.

3D Printed Housings:
Designed by Nathaniel Deal, these cases print reliably on a Prusa Mk3s


Housing Assembly:


Ammo Counter User Guide

Basic Usage:

* Change ammo clips: Click left or right to cycle between the clips.
* Change ammo count: Hold right button until the display is flashing, then click left/right to change the ammo. Press and hold right to save the setting.
* Advanced menu: Hold left to access the advanced menu. Press left right to navigate the settings. Hold left to exit the advanced menu. Hold right to edit a setting / save a setting.

Settings Menu:
* Press and hold the left button to enter the settings menu.
* Press left or right to change the menu pages.
* Press and hold right to select a setting.
* Press left or right to edit the setting.
* Press and hold left to save and exit, or press and hold right to save and return to the menu.

* Auto Reset (A0 – A9) : Number of seconds after 00 is reached before auto reset.
* Brightness Level (B1 – B5) : Adjust the brightness of the LED display.
* Calibrate (C0 – C9) : Ignore this. The digital optical sensor does not need calibration.
* Low Ammo Warning (L0 – L9) : Set the counter to blink when the ammo is low.
* Fire Detector Type (F0 – F2): Rising Edge / Falling Edge / Analog Voltage Threshold

Other info:
* The fire mode can be set to 0, 1, or 2 to support different types of input sensors and switches.
* Setting the clip size to 00 puts the ammo counter into “count up” mode.
* Setting A0 / L0 will disable auto reset / low ammo warning.

Additional information

Kit Contents

Ammo Counter Circuit, 3xAAA Battery Holder, Lever Switch or Optical Sensor


Smallest Ammo Counter Circuit!, Selectable Clip Sizes 6, 10, 12, 15, 18, 22, 25, 35. Can be customized using on screen menu., Compatible with Normally Open Switches / Normally Closed Switches / Analog Optical Sensors, Configurable Auto Reset


PCB Dimensions: 26.3 x 27.0 x 14.0 mm, Display Dimensions: 25.0 x 19.2 x 7.2 mm


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