If you are looking for the ABSOLUTLY lowest cost way to get an electronic target, then FreeETarget Minimalist is the way to go! This project is a bare bones Arduino and microphone setup that has an estimated cost of $30US for the electronics. Once assembled and programmed, the FreeTarget Minimalist gives you many of the features of the Version 3 hardware.
Here is the target’s project from the original author.
Background
I came across the frETagret just before the holiday season and was intrigued by the effort which has gone into this community projects and the quality of the product. Living in Europe, I decided it would be too late to order and receive the specific parts to build one before the break and so I investigated a solution which would only depend on locally available parts.
The Arduino mega board is broadly available, and there are many sources for the common microphone boards KY-038 (and 037). This board offers an analog and digital output, with an adjustable trigger level.
Looking at the timer infrastructure of the ATmega2560, the chip has 6 timers, with 4 of them offering a 16-bit input capture unit (ICU). This allows to record a timestamp based on a pin change – exactly what we need. So I started analyzing the existing code. It only used two timers, one for PWM (timer2) and one for timing all processes (timer1). Since process timing does not require 16-bit resolution, I shifted that code over to the 8-bit timer0 and added one bit in software to achieve the 1 ms ticks. This freed up timer 1,3,4,5 and I implemented the ICU code on these.
The next obstacle: The Arduino mega board does not connect all processor pins to the pin headers. And two of the ICU pins fall into this category. Since the pin spacing is quite small, I decided to look into options to connect the pins to adjacent ones not in use. This was achieved and testing on the bench could start.
Using a multi-channel pulse generator I developed and tested the code to ensure it functioned as designed- which it did.
Hooking up the microphones and starting the first tests were successful. Since the trigger level has to be adjusted manually using the multi-turn trim pots for each mic this took some time. Obviously, the original freETarget software solution is more elegant…
So this was it. Took a few hour programming in Visual Studio Code (thanks for the original developers for the clean and documented code) and few hours on the bench. It was a fun project and I like the result :-).
GITHUB
The source files and other information you need can be found on GitHub at