Chronograph

This is for a simple chronograph using a microcontroller that times the breaking of two foil strips then reports the velocity and keeps a running average.

Mega 2650 or Arduino Uno

16x2LCD screen

Wires

Aluminum foil

Box or frame for the aluminum foil strips, I used a box that 3d printing filament comes in

Box or frame for the microcontroller( If you are using the mega R2650 you can 3d print my box):

https://www.thingiverse.com/thing:6960830

200ohm Resistor or potentiometer for the LCD screen

Small self-tapping screws, I use this set:

https://www.amazon.com/dp/B07ZH9GJWP?ref=ppx_yo2ov_dt_b_fed_asin_title

The case I made is for a Mega 2650, print at 20% infill and use a high enough resolution to keep the sensor labels intact. I used 6mm long self tapping M2 screws to hold it in place. You could probably get away with some drops of hot glue. The 2 wires for the foil strips will sit right next to their respective connections. You will have to ream them out with a pen just a little bit. Leave it wide enough for a tight fit. The 2 wires for the ground will sit just above them.

The lid holds a 16x2 LCD screen and 2 buttons. The hole is for a switch that I Intend to use for a future function.

Youll have to shave down the holes for the buttons just a little bit, but when you push them in, they should sit tightly. Solder the wires on after pressing them in. I used 4: m1.7x5mm screws to hold the LCD screen in place.

This is the basic setup. I've used a Mega 2650 because that's what I have, But the pin layout should be the same for an Arduino Uno. The 200 ohm resistor controls the brightness of the screen but more or less maybe be better depending on your screen and outdoor lighting. I used a mini breadboard to save space inside the case. A shield for the board would definitely be better. The Mega 2650 has 2x5V ports so I plugged those pins directly into them to keep it simpler.

Here, the mini breadboard is connecting all the pins that would go to ground, including the sensors and buttons

Takes a little fiddling and folding but all the wiring with the mini breadboard should fit.

Takes a little fiddling and folding but all the wiring with the mini breadboard should fit.

https://github.com/HenryData/Henrys-chronograph-V1

Open the file, change distanceIn to the length between your foil strips in inches, and upload.

When you shoot through the 2 holes of the box, the projectile should break the pieces of foil and give a reading for the velocity calculated from the distance between the 2 strips and the time it took to go from sensor 1 to sensor 2. Theoretically it can go fairly high into the tens of thousands for velocity readings, but I really only trust it for 5000 fps and below. Which should be fine for any caliber.

When you shoot through the 2 holes of the box, the projectile should break the pieces of foil and give a reading for the velocity calculated from the distance between the 2 strips and the time it took to go from sensor 1 to sensor 2. Theoretically it can go fairly high into the tens of thousands for velocity readings, but I really only trust it for 5000 fps and below. Which should be fine for any caliber.

I poked the wires through precut strips of foil and folded the slack back over the top of the box, adding a little tear near the middle can help small calibers or pellets fully break the foil.

Resetting and what the buttons do

The button on the left (with the buttons on top) will accept a reading and use it for the running average. The button on the right will reject the reading. Either one will take a few seconds, display the current average, and then wait for setup. Once the system senses its been reset by reestablishing a connection between the foils, it will display” waiting for shot.”

This would definitely be worth returning to with some optical or motion sensors, I’ve seen alot of chronographs online and I think it would be worth having someone put together a relatively cheap “ultimate version” using the most common parts for the best possible version. Huge credit to Tim "The Mad Brewer" Slice for the chronograph he posted, which this is heavily based off of.