Custom EOTech Reticle with an Arduino Inside

Steve Johnson
by Steve Johnson

A TFB reader purchased a damaged EOTech very cheaply, then gutted the internals and replaced them with custom electronics. This video shows the result:

The possibilities are endless. Rangefinders, shot counters, timers etc. could be easily integrated and the data shown on the Heads Up Display (HUD).

It was built using a Arduino Pro Mini (about $7 on Amazon), a small variant of the popular Arduino micro controller board, which was squeezed into the battery compartment. The Arduino was wired to the EOTech’s switches and to a cheap I2C OLED display (about $5, search eBay for “i2c oled”). The OLED display replaces the laser module to provide the HUD/reticle. One neat advantage of using the OLED is that the HUD can extend “beyond” the users field of view, allowing the user to look through the scope at an angle and see additional information. The downside of the OLED is that it is not nearly as bright as the EOTech’s laser module and is faint in direct sunlight. A field ready version of this hacked EOTech would need a significantly brighter display.

I asked the reader if he was willing to share the custom code he wrote which runs on the Arduino, but he said it was very rough around the edges and not worth sharing with the world.

Steve Johnson
Steve Johnson

I founded TFB in 2007 and over 10 years worked tirelessly, with the help of my team, to build it up into the largest gun blog online. I retired as Editor in Chief in 2017. During my decade at TFB I was fortunate to work with the most amazing talented writers and genuinely good people!

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  • Bp_sti Bp_sti on Aug 27, 2014

    This could be done with a custom pcb stuffed to the brim with interesting bits. Think compass, gyros (the fancy kind or sandwich kind, your call), temp, altimeter, hygrometer, even GPS or other radios. Just look at the teensy 3.1 for an idea of how cheaply you can stuff a decent amount of CPU power into a tiny space (it's a ARM Cortex M4 at 72mhz and can run arduino code). A better choice. As for the screen, I've seen a few other options that might work. A dot matrix style VFD panel would be very bright but who knows how reliable it would be in such a rough environment. A simple LED matrix. It's small enough you should still be able to find some led displays of reasonable density that are still just LED and not LCD. A 128x96 or something might work.

  • Ryan Arendt Ryan Arendt on Aug 31, 2014

    Anyone want to make some money changing my recital? PM me on Facebook and we'll talk.