Latest Version of Chronograph - AirChrony-S3

Update on the Latest version of the DIY Chronograph, the PCBs have arrived, I've populated them, assembled the chronograph and done some basic testing, so far so good.

All design files can be found on Github at www.github.com/gadjet 

Detector PCB

Emitter PCB

Top View with Xiao ESP32 S3

3D printed case parts

Also, to help assemble the detector and emitter PCBs with the detectors/LEDs I made a helper jig, this makes sure that the distance between the lenses on the detectors/LEDs are spaced exactly 50mm apart to match the tube.

Jig usage

New version of the Chronograph

Latest project update for 2026 here

Yes I continue to find new ways to do the same thing again ..... and again, this time I wanted to learn how to program the ITEAD Nextion display which I got when they were on Kickstarter some time ago.
I have a couple of these 2.4" screens but not really got around to doing much with them so I thought about having a small touch screen chronograph remote connected to my pellet sensor fitted to the end of the rifle.
About the screen
The screens, made by ITEAD, come in various sizes and use resistive touch screens (Capacitive also available) and come with a full editor to allow you to design you whole interface layout including screens, buttons etc. on the PC and then download it to the screen.   The interaction/control can then be done via the serial port by an Arduino or other MCU.

I have a Brocock Compatto air rifle that has a picatinny rail under the front end of the stock and I planned to mount the screen on that rail.

For this project I started on the hardware first rather than my usual approach of starting with the software first.
The Hardware
I designed the hardware in Tinkercad making a front, rear, picatinny mount and the tube to hold the IR LED sensor assembly it looks like this

In the rear half of the case the battery, Nano and power PCB are mounted the front houses the display and also forms the mounting bracket to  secure to the Picatinny rail adapter.

DIY Chronograph Revisited

This project is still a work in progress as I am waiting for PCBs and parts to be delivered, so details like the 3D-printed enclosure and software will probably evolve. I will create a GitHub repository once I am happy with how everything is working.

It has been over 10 years since my first blog entry on my DIY chronograph (https://gadjetsblog.blogspot.com/2013/02/air-rifle-chronograph.html), which used an Arduino Nano and a Bluetooth transmitter. That setup connected to an app on my phone and transmitted the elapsed time between trigger 1 and trigger 2. The app then used that time, along with the entered pellet weight, to calculate the muzzle velocity and kinetic energy of the rifle/pistol.

I have built a few projects since then. Although I enjoy designing hardware, writing software is not my strong suit. Like many others, I have started using AI—specifically Google Gemini—to help write code not only for the microcontroller hardware, but also for the web-based user interface.

I realised that I could modernise the DIY Chronograph using an ESP32, my favourite being the Seeed Studio XIAO ESP32-S3. Running at 240 MHz, it is substantially faster than the older Arduino Nano. Because it features built-in Wi-Fi and web server capabilities, the entire user interface can now be hosted directly on the chronograph itself. You simply open a web browser on your phone, tablet, or laptop to interact with the device.

Hardware

The core concept remains similar to the original design: two optical IR emitter/detector pairs are spaced 50 mm apart, creating two infrared beams. When a pellet passes through and breaks each beam, high-speed hardware interrupts measure the travel time across that 50 mm distance to accurately calculate the projectile's velocity.

 

The outer casing is printed in two halves that slide over the electronics and aluminium barrel tube. They lock securely together using two 2 mm alignment dowels and an M3 screw.

One interesting challenge was "how to package the FPC antenna" this proved to be a bit tricky so in the end I went for a single wire antenna 31mm long.

This solution allowed me to feed the antenna back into a hole inside the casing and it works perfectly well in the 2 or 3m range needed to work with your phone.

Power is currently supplied via a USB-C cable from a 5V power bank, with the option to add an internal LiPo battery later. *(Note: The USB-C connector head must be slim enough to fit into the 11.5 mm × 6.5 mm housing recess).*

Unlike the original design, where raw timing data was sent over Bluetooth for the phone app to process, all calculations are now performed locally on the ESP32. 

To view the live dashboard, simply connect your phone or PC to the **"AirChrony-S3"** Wi-Fi access point and navigate to **`http://192.168.4.1`** (or `http://chronograph.local`) in your browser.

User interface

When opened, the dashboard immediately displays the **"Live Chrono"** tab showing the latest shot's speed, muzzle energy, rolling averages, and a velocity progression graph. 

Additional tabs include:

• Pellet Profiles:** Save custom pellet profiles with brand names, calibers, and weights (in grains or grams) to automatically calculate muzzle energy (Joules or ft-lbs).
• Saved Strings:** Store, recall, and export previous shooting sessions directly to CSV or JSON from the ESP32's onboard flash memory.
• Settings & Diagnostics:** Customise speed units (FPS / m/s), toggle between dark and light themes, configure sensor spacing, test beam alignment, and enable spoken voice callouts (e.g. shot count and velocity spoken aloud through your phone or Bluetooth ear defenders).

The project is constantly evolving as new ideas arise, and you are welcome to use AI to tailor the firmware and interface to your own setup!

Testing LoRA transmitters and receivers

I've wanted to have a play with 868MHz LoRA transmitters for some time now but never got around to it until,  a while ago, I did an hardware design and PCB for someone wanting a prototype remote sensor as part of a security system to monitor inclination levels and transmit them over longer distances than WiFi can reasonably achieve.

I chose the Seedstudio Wio-E5 for the prototype connected to an ESP32 S3 and it was succesful as a testbed for further development. 

I know some of you reading this will be saying that you can just buy the HELTEC modules and similar modules but, as usual, I want to learn myself and also use up some of the modules I've bought in the past and never got around to using.

For my own design I wanted a simpler solution that I could use for outbuildings (shed) to monitor the status of the door and also the ambient temperature, the requirements were: -

• Cheap to build
• Last a very long time on a battery
• Have a good range, relative to WiFi
• Not using Meshtastic just sending a datapacket when triggered
• Use a DS18B20 Temp sensor
• Have an I2C connection for other sensors or a screen
  

For the power control I used the same trigger logic  circuitry I used on my WiFi window/Door sensor  which means that the LDO is enabled when the reed switch opens or closes and when the code is finished sending the datapacket it shuts off the power to itself using a GPIO.

I have made three different variants of the PCB to use different processors: -

• An adapter PCB to connect an Xiao ESP32-C3 or S3 (or other Xiao module?)

• A transmitter using an ATMEGA328p

• An adapter to connect the Wio-E5 to a Waveshare 1.47" Display module based on an ESP32-C6

The other thing I'm testing out for these projects is AI, I've tried ChatGPT for writing Arduino code for ESP32s etc. without much success but I thought I'd try out the new Google Gemini Canvas AI and I was blown away with the code it generated, it's not 100% perfect but unlike ChatGPT it remembers it's mistakes and doesn't make them twice.  It's not a cheap option at £18.99 ($25) per month but you also get 2TB of storage.

Within a couple of hours (total prompt writing time)  I had working code for all three options, the AI sometimes needed help with the different pins used on the different ESPs for serial connections and there were a couple of inconsistencies between the transimitter and receiver code when I switched on encryption of the data packets but by pasting the debug serial code from the PC into the prompt window the AI was able to track down it's mistake and fix it.

One of the biggest time saving things about using the AI to generate the code is that once the screen setup is complete it lays out all the text for you, no more counting pixels to determine where everything goes and when the screen refreshes it creates the code to draw a rectangle over the existing code to clear out any left over bits of text if the newer text is shorter in length.

I also added a web page option to the receiver by just asking the AI to include a web page with the same information that's displayed on the screen.

I will post the code and the PCB details on my GitHub page in the next few days, I'm making some corrections to the ATMEGA 328p version before I publish it to GitHub.

Updates for my Commarker B4 30W fibre Laser

 Second Mod - Add external buttons and an automated height controller

******* PLEASE NOTE *********

I did this with my B4 30W laser unit, I cannot guarantee that it will be the same for your laser and you may break something if you attempt this. I am not responsible for anything you do to your laser if you follow my instructions.

This Blog article will give an overview of the project and all the files will be made available in my Github account www.github.com/gadjet

The github files will follow on after this blog post so please be patient if they aren't there yet.

While I was moving the Stepper controller inside the main body of the Commarker B4 30W laser I decided that I could tap into the lift buttons on the front of the unit and using the now spare 5 way cable, that used to connect to the stepper controller, connect to some external buttons to move the head up and down.

This was a good idea for me because the orientation of the laser unit means that I have to face it from the side and I can't see the buttons easily.

3D Printed enclosure for the external buttons

When I changed the 5 way connector on the back of the laser (old stepper controller connection) and replaced it with a 4 way connector (from the original stepper controller enclosure) I was able to use the redundant 5 way connector in a spare, unused,  hole at the rear of the laser to plug in the external buttons.

How the current buttons work

The front buttons on my B4 30W are connected to a motor controller module that switches the polarity of the DC motor depending which button is pressed to drive the laser head up or down.

The Module has two relays to control the polarity of the motor, at rest (no buttons pressed) both motor connections are connected via the relays to ground, this shorts the motor so it would be difficult to move.

When the UP button is pressed one of the relays switches one of the motor connections to positive causing the motor to move the head up, if the other button is pressed the opposite motor connection is connected to positive and the motor moves the headDOWN.

When the button is released the motor connections are then grounded again bringing the motor to a quick stop.  This is know a an H-Bridge arrangement.

Motor direction control example circuit

The addition of the external buttons

To enable the external controller to activate the motor I tapped in parallel with the buttons so that they would still work if the external buttons were not plugged in.

The drawing below shows how the external buttons were connected in parallel to the existing buttons, I have kept the wire colours as I found them inside the Laser.  The external buttons connector has the pins shorted out so that the internal buttons will also work, if the external buttons are disconnected then they will stop working and a shorting plug would be required.  The interconnecting cable is the one that was provided witht the external stepper controller which I placed inside the laser and was no longer required.

The addition of the height controller

Main components

The last stage of my modification was to add an external controller that could move the Galvo head to a known height that could be entered on my PC.

To achieve this I needed a method of detecting the position of the laser head relative to the base of the laser, after looking into to some laser distance measuring devices that used IR lasers and detectors using TOF (Time Of Flight) measurements to detect range I realised that the accuracy and repeatability for the reasonably priced detectors was not good enough.

I settled on using a Linear scale, a device used on lathes and milling machines to accurately and reliably measure distance for linear movement.

Linear Scale - sourced from Aliexpress

These devices come in different lengths and I chose 550mm.  The Linear scale is secured to the top and bottom of the Z height tower of the laser using some 3D printed brackets I designed and the moving sled is attached to the Galvo head and moves up and down with the head.  The signals from the linear scale are fed into two interrupt pins of an ATMega328P (as used in the Arduino UNOs) 

As the Linear scale is a relative measuement method rather than absolute we need a way to define a reference point at a known measurement, to do this I used an inductive sensor that can detect the presence of the metal in the laser head unit and feedback to the controller when the head reaches a known position.

Inductive Sensor - Sourced from Amazon

These sensors are also used to stop the motor movement at the extremes of the Z height range.  One thing to note is that these sensors come with a wide voltage supply range but typically start at 6V but I've found that mine work fine at 5V, make sure your choice of sensor does work at 5V.

Component overview

The rendering below shows the position of the components added to the Z height tower (without the tower in the picture)

The controller

OK so the next thing is to connect all the parts to the controller, the controller is a custom PCB based on an Atmel Mega328p 8 bit processor (Arduino UNO) but you could use an Ardunino UNO, Nano, ESP based processor or any other with suitable IO.

I chose the 328P because it is relatively cheap and available at JLCPCB where I get my PCBs made.

I also included a serial to USB interface so the controller could be connected to a computer and interact with the user via the custom application.

The code I run is, apart from a couple of tweaks, generated by the Google Gemini Canvas AI.

The PCB has the ISP programming connector because the chips have no bootloader code as supplied so this need flashing before you can load a sketch.  There are also connectors for some of the spare GPIOs and the I2C bus so a display could be connected or even a laser distance measuring device if you like but please note that the voltage is 5V and NOT 3.3V.

Although initially the hardware was created with the intention of driving a stepper motor controller I've currently configured the code to drive the DC motor controller in the Laser unit, therefore Down for the motor uses the "DIR" connection and the Up uses the "STEP" connection

In this second version I added all the screw terminal connections so that each sensor could be connected, you can connect directly to the screw terminals or, like I did, use aircraft type connectors 

• 2 off 4 pin 12mm connectors for the Limit Switches and the Linear scale
• 2 off 5 pin 16mm connectors for the external buttons and the motor wires to the laser unit.

PC Software

The PC software is a work in progress and is written in Visual Studio/Visual Basic and connects to the controller via USB allowing 2 way communication, the application displays the mm of movement as the laser head moves up and down and is also used to trigger a fixed distance movement up or down and to calibrate the position of the laser head to a known distance from the base.

The current functions of the PC application: -

• Display the available comm ports and connect/disconnect
• Display the position of the laser head in mm
• Calibrate the distance from the top limit switch to the base
• Measure the distance from the head to the base and set the height to that value
• Trigger a fixed distance move in mm from the current position
• Setup some pre-defined positions on the three configurable buttons
• Focus position for each lens?
• Display the text data recieved from the controller in the console window

All the 3D files, Sketch and PC software will be available on my Github within the next couple of weeks.

Please note that this project is a work in progress and may change in functionality as time moves on also I make no guarantees on the functionality and/or safety of this software, use at your own risk.

Updates for my Commarker B4 30W fibre Laser

First Mod - move the Stepper controller inside the main unit.

I recently bough a 30W fibre Laser from Commarker and it's great peice of kit for marking and etching metal, something my Creality Diode Laser isn't so good at doing

The fibre laser is a Galvo based laser that uses mirrors to control where the laser lands on the material being etched and is very particular about the focus distance from the lens to the material being etched.

Depending of the lens that is fitted to the Galvo head both the etching area and the focus distance changes, the supplied 110mm x 110mm on my laser has a focus distance of 197mm from the base of the Galvo housing to the top surface of the material being etched, this means that sepending on the thickness of the material the height of the Galvo needs adhusting.

A 500mm ruler is supplied with the laser for you to measure the required distance as well as two focus laser pionters that are angled to meet together when the correct focus distance is acheived.

B4 30W Fibre Laser

   

Focus point lasers

I also bought the add on option of the rotary chuck that links to the laser and allows you to hold a cylindrical object and mark/etch around it, the laser rotates the object whilst etching resulting in allround coverage.

The rotary addon is supplied in two parts, the actual Stepper controlled rotary chuck and the Stepper controller, mounted inside its own aluminiun box. which is connected to the laser main unit with a cable.

So, my first update was to place the stepper controller inside the Laser main unit as the 30W version comes in a tall enclosre and there's loads of room inside to include the stepper controller.

Step1

Remove the Stepper controller from the seperate black box it comes in and make a note of the wire colour connections.

Stepper Controller Wiring

Step2

After removing the galvo assembly and then the Z height tower in a reverse of the assembly process when first put together.

Remove the six hex screws that hold the top on the case and remove the top remembering that the motor for the z height is still attached, place the lid to the side of the box and secure it so it doesn't pull on the wires.

Then de-solder the wires from the 5 pin stepper motor control connector on the back of the laser unit and connected them directly to the Stepper Controller connector.

The Black, Green and Yellow go into one connector and the power wires Blue and Red go into the other two way terminal.

Step3

Remove the 4 way connector from the original stepper controller box and extend the wires so they will reach the other 4 way screw terminal connector on the controller.

Replace the original 5 pin connector with the new 4 pin connector.

DON'T forget to feed the wires through from the rear of the case and add the nut and washer before connecting them to the terminal block.

Step4

Secure the Stepper controller to the base of the main unit with an M4 screw, I used just one at end of the controller nearset the motor controller.

M4 threaded hole to secure the stepper controller

You should now have a single 4 pin connector on the rear of you main laser unit which you connect your rotary chuck to.

While I had the unit apart I also took the opportunity to use the two spare 5 pin connectors to add external access to control the Z height lift motor, details of this mod will be in the next post.

 

 Time for another post.

A while ago I bought a new Oscilloscope, a RIGOL DHO914, but this scope doesn't have WiFi built in just a LAN connector on thre rear, luckily, as the Scope runs on Android someone has figured out how to get WiFi by using a TP-Link USB WiFi Dongle which, you can plug in the single USB port on the front of the scope.

I found this Youtube video explaining how to enable the WiFi using a plugin TP-link WiFi dongle.

Unfortunately it only has one USB port, you can plug in a WiFi dongle, mouse, keyboard or memory stick but only one at a time.

Now the problem is that I wanted to have the WiFi dongle and a mouse plugged in at the same time so I needed a USB gateway to do this but it's a bit ungainly so I thought I would have a go at making my own USB gateway that fits in with the layout of the scope (I know that they can be bought from Aliexpress for a couple of pounds but where's the fun in that!).  This will allow more than one thing to be  plugged in at the same time.

I found the FE1.1S chip that was a 4 port USB hub controller and JLCPCB had them in stock for $0.55 (£0.41) so I set about designing my own USB HUB.

JLCPCB Part Link

First Attempt

Two port hub

As usual I couldn't wait to get the design done and ordered from JLCPCB  but those eagle eyed amongst you will notice that this device gives me a problem for the DHO914 in that it blocks the Logic Analyser connection port, on the DHO800 series this would be fine as they don't have the Logic Analyser port but for me it will be a problem when I get the Logic Analyser option.

So on to design number 2....

Having proven out that I could make a working USB hub I decided to try and make a design that would better suit the DHO900 Series of scopes, this time I decided on a three port hub with the ports horizontal and below the Logic Analyser port.

Design Render

This design will plug into the single port and still allow the Logic Analyser to plug in although as of today I've not tried it with a Logic Analyser.

The design comprises two PCBs, one for the male USB plug and the other for the three USB sockets, they are connected together using some normal wires (ignore the PCB labels in the render as they are incorrect).  The cover holds the Male USB PCB in place and is screwed from the rear and sides to secure all the parts together.

With the front cover off

All the files including STLs and PCB gerbers etc. are available on Printables.com here.