New Accessories for the AirChrony S3

With the increasing abilities of AI it has become so much easier to take an idea to a finished, working item in a really short time.

I was thinking about the next teps for the AirChrony S3 and I had two ideas, an addon battery holder so that I didn't need to plug it into a USB powerbank and a remote monitor so that I could use it without my phone.

Addon Battery Carrier

I wanted to be able to have the option of using the USB powerbank or a dedicated supply that attached to the Chronograph, to this end I designed a sleeve that slid over the chronograph body and secured it using the the existing screw.  The battery slot was sized for an 620mAh LP602248 Li-Ion rechargeable pouch cell.

3D Render of the battery Sleeve

Actual assembled device

Sectional View from the Right Side

Due to the fact that the IR Detectors require a 5V supply to operate reliably I needed to supply 5V to the Xaio ESP32 rather that include a cell inside the device so I used a DC/DC step-up converter to increase the 3.7V cell voltage to 5V, the buck converter was very small and had the same connection pads as a USB C PCB connector I had and they soldered together perfectly, I soldered on a 2mm PH JST socket to the DC/DC conveter input to connect the batery to then slid the whole assembley into a 3D printed sleeve that fits into the USB connector entry of the Chronograph.

USB C Plug/DC/DC Buck Converter Assembly

 The above assembly in the 3D printed Sleeve

Remote Viewer Screen

The second accessory was a remote viewing screen that would connect to the Chronograph instead of the mobile phone and allow the viewing of the shot data and other functions.

I had an ESP32-S3 based display module that I'd bought from Aliexpress, this had a 2.8" capacitive touch screen, speaker output, battery charging circuit and SD card slot.  I designed an enclosure to house the display, speaker and an 1100mAh Pouch cell.

Whenever a shot is registered the display will beep (optional).

3D Rendering of the case

Actual Screen Layout

All the code for the display was written using Gemini Antigravity AI in a couple of hours, it's stil a work in progress with more functions to be added but so far it all seems to be working.

When I'm happy with the final version I'lI will post all the files/code on my github www.github.com/gadjet

DIY Chronograph Accuracy testing

Latest project update for 2026 here

A few people have attempted the DIY chronograph build, at least one person improved the design and made an excellent version of his own.

I had a a question asked about the accuracy of the chronograph so I setup some testing over the weekend to try and determine if it was as accurate as others out there.

I don't have access to a calibrated air rifle or similar, if something like that even exists?? so I decided to use a good quality Oscilloscope (Picoscope automotive), which connected to my laptop via USB and do a comparison with the output from the Nano (in uSeconds).

For each measurement I took a screenshot of the waveform from the Oscilloscope and the serial data from the Nano, this shows the correlation between the actual time between the first beam being broken and the second.

There is also a google sheet showing the data that was recorded during the test here you can view the data and make your own decisions, for the last few shots I added a Chrony F1 about 3m away from the rifle to see what result that gave me.

The Chrony was set up in the garage with the lights off (florescent's) because the Chrony doesn't like florescent lights, instead I had a couple of cheap battery powered LED lights on top of the diffusers.

The conclusion is that although the data for each shot was different between the oscilloscope and Nano, over the 23 shots the average from both was exactly the same 10.57 ftLbs, this compares well to the 10.48 ftLbs when I had it checked at a shop a couple of years ago.

So I'm happy to use my DIY chrono with the understanding that there's always margin for variation and if I was getting 11.9 ftLbs that would be too close for comfort but 11.5 would give me 4% 'ish headroom.

DIY Chronograph - Nokia display

Latest project update for 2026 here

The Acrylic case arrived on Saturday for the Chrono using the Nokia 5110 display.

I just wired up the display to an Arduino Mini Pro and put the case together to make sure it all fit together.

The Nokia display is on top, the battery on the bottom with the Arduino Mini Pro in the middle.

No I have to fashion a joystick extension, sort out a power switch, build up the sensor tube and figure out to re-charge the battery with out taking it all apart.

Sketch can be downloaded here.

Sketchup and EPS files for the case are here.

DIY Chrono Shopping list

Latest project update for 2026 here

A few people have expressed interest in making a DIY chronograph so I said I'd put together a shopping list.

There are quite a few options for the display type so I try to give the pros and cons at each step.

Firstly, the processing power.
All my projects are done using the Arduino family, including the many clones out there, I've used original Arduinos and Clones from China all without any problems. (A PIC Micro will do just as well with the same hardware)

Arduino Mini Pro	Arduino Nano
These are available in 5V 16MHz and 3.3V 8MHz versions, I used the 5V versions @ 16MHz to get the best uSecond resolution, I believe that the 5V versions can be run at 3.7V and still run at 16MHz. This device needs an external USB to serial adapter to allow programming but, once progr ammed, can be fed from a 7V source via the on-board regulator (RAW input) or a regulated 3.3 to 5V supply on the VCC pin. I bought mine on Ebay from here for less than £3 but it took 27 days to arrive. Others on Ebay search	These are the boards I've been using, mainly due to the USB connector for both programming and supplying 5V.  I use an Eveready unit that uses 2x AA batteries and steps up the voltage to 5V, I connect this with a standard micro USB lead. Apart from the on-board USB and the in-circuit programming connector (far right) the specs are the same as the Mini Pro. These can be bought on Ebay for around £4 from China and around £10 from the UK, they're a little more expensive due to the on-board USB. Ebay search.
Display Options
This is the top of the range display £7 from China but has the advantages of being colour and also touch screen. I didn't go very far with this display but I think it would be good in a larger Chronograph that has a large detection curtain.
	This is an I2C connected display and can come in yellow, blue, white and red. This is my choice for my portable sensor. It's very easy to program and is a similar size the the sensor tube so is a good fit, see this post. You can only really display one value, I chose FPS because that doesn't require you to input the pellet weight, you can generate a little look up chart for you pellets.
I dug out an old Nolia 5110 phone display that was set into an Arduino UNO shield and added it to the DIY Chronograph family, it works pretty well and has a very good contrast for outside readability and the 5 way switch at the bottom centre allows for a menu system to enter the pellet weight. I can't get the shields any more but the screen can be bought off Ebay for a couple of quid from China and around £7 from the UK, these displays not on the shield work on 3.3V only so require some level shifting when used with a 5V arduino.
	A cheap and cheerful display that can be bought in many webstores an Ebay, they're nearly all the same connection standards and have Arduino Libraries readily available and can come with or without backlighting.
Similar to the 2 line 16 character display just a bit smaller, easier to package and can come with and without backlight, the non backlight versions tend to use an LCD technology that means they're a good contrast  and can be good in sunlight.
	Fancy using your Android smartphone as the display then this is what you need, available from £5 in China to £15 in the UK. Be careful, this board comes with and without the back PCB, without it is a bit fiddly to use and works of 3.3V only. Ebay search
Other parts
	I chose Aluminium tube because I wanted to thread it to fit my 1/2" UNF silencer adapters on my rifle and pistol but you could use any tubing you liked, depending on how you want to fix it. I bought mine on Ebay from here. You will need to get it cut to length and threaded if you want to do as I did. Maybe you have an old silencer that you could modify.  See this post for assy. details
The sensor LEDs were bought from RS components, they are available on Ebay but at a huge markup Photo sensor - OPL-550a Ebay Farnell RS components IR Emitter LED OP240A Ebay Farnell RS Components
Software
Arduino	Android
I have quite a few version of the various sketches so if you would like a particular version just request it in the comments and I sort out a link. Nokia 5110 shield sketch Nano with 7 segment display Chrono with 8x2 LCD	Here Aptoide store download

Finally the DIY Chronograph meets Android

Latest project update for 2026 here

Yes, I finally got a Bluetooth serial adapter to connect to my Arduinos.

I bought it off Ebay for £5, just search for HC-06 Bluetooth adapter but be aware that it comes with and without the mounting PCB.  The one in the picture comes with the back PCB which handles the level shifting from 5 to 3.3V as the transceiver itself is 3.3V not 5V and the connections are a bit small and difficult to solder to.

The connections are 5V, GND, TX and RX, the baud rate comes set to 9600 but can be changed using a terminal console and AT commands also the name and pass code can be changed, the default pass code is 1234.

Once this was connected to my Arduino I put together a little sketch to simulate some shot data, a loop counting from 300 - 340 incrementing by one every 5 seconds (saved a lot of pellets ;-))

I've did attach the transceiver to the sensor tube (as seen in part6) for a quick trial with the pistol and it worked fine.

Next came a couple of days writing the Android app using the App Inventor site, this is what it looks like

First you power up the transceiver and pair it to your phone, the same way you would any other device then enter the data: pellet weight, the distance between the sensors, pellet name and then press calculate.

Once the calculations have been done and stored you can press the top right button to select the paired device, it shows up as "invor" or similar, if you've not renamed it, I renamed mine "Chrono1"

Once selected press the top left button to connect, when connected the shot data should appear in the Shot, FPS and FPE boxes with the average and max. data showing below.

If you tick the speech box then the FPE value will be spoken out loud to you by your phone, the quality of this function may vary between phones.

Also, I'm not an App developer, this is my first App therefore there could be other issues like screen resolution etc. I wrote this for my Galaxy S4 and haven't tried it on any other phones so I'm interested in any feedback.

It can be downloaded here.

1st Feb 2016 - Link to the AI2 aia file here and the APK file here.

I found another AI2 project I did, the only problem is that when you first start it there is an error but if you press the back button and add the settings and then exit it works OK the next time. you can try it here, AI2 Gallery link to app here

I intend to add other features in the future like multiple speech options and logging shot data to memory etc. it depends how popular it is.

Chronograph update

Latest project update for 2026 here

When I made the smaller screw on sensor that connected to the PC and fed the timing into a PC application, it got me thinking about different types of display that could be used and after a a good look around the net I came across a couple of options.

The first was a 7 segment LED display, these come in different shapes and sizes and could still be quite portable when added to the sensor.

The only problem with these displays is the amount of IO needed to drive them as each of the segments require driving. I then came across the Adafruit 7 display backpack, which takes all the hard work out of controlling the 7 segment displays.

The backpack details can be found here

The device is based on an Holtek HT16K33 chip that controls the LED segments and connects to the Arduino via the I2C bus and has a library that makes sending data to the display easy.

I bought one of the displays from Ebay and stuck it on the side of the sensor tube then added the code to the sketch to send the value for feet/second to the display after sending the uSecond value to the PC.

This would allow the chronograph to be used in conjunction with the PC via the USB lead or remotely with a battery pack, just reading the Feet/Second value.

Showing the feet/Second would require a lookup table to get the power from the velocity and the weight of the pellet, I suppose with a couple of small buttons added you could enter the pellet weight after power-up but before the first shot it could then alternate between the FPS and the power reading every 10 seconds?.

I then tried it out using my CP Sport Co2 pistol and it looks good.

I then used some of that PVC heatshrink, normally used for battery packs, it's really good as it shrinks using a hair drier and is quite hard when cool but can easily be removed with a pair of scissors or a knife.

Ideally I would have liked to use some clear but I only have red or white but surprisingly the LED shows through the PVC quite well.

Things to think about: -

• Writing the shot data to EEPROM for later retrieval
• Adding buttons to allow pellet weight to entered
• put together a battery pack for remote usage
• Think about power saving schemes
• Display battery power on power-up?
• Who knows?

Nano Sketch can be downloaded here you can use it with or without a PC, if you want the PC application let me know in the comments, it's still very BETA.

Fritzing file here.

More about the second option I found later.....

Chronograph - Part 6

Latest project update for 2026 here

Working on this project has really got me thinking and now I have my air rifle I needed to get something finished and usable ASAP before I started to tune the rifle, I don't want to go over the legal limit.

Whilst thinking about the total cost of the parts to make a usable chronograph, the one most people buy is £50, I had the idea of removing the LCD and just using the serial link to the PC.

So I thought about strapping an Arduino Nano to an aluminium tube with a 1/2" UNF thread so that it would fit on the standard silencer adapter, this would make it very stable.
I decided to use the Nano because there wouldn't be the need for a battery to power it, the USB lead would carry power and data back to the PC, people would also be able to programme them without having to buy the serial/USB interface.

Marking out the sensor distance

Tube screwed into the silencer adapter for my rifle

Fully assembled prototype with a foam spacer

Finished part attached to the Air Rifle

I used some thin but very tough heat shrink sleeving the same as that used to hold battery packs together on remote control cars

Below is a screen grab of the PC software (Ignore the FPS value, I'd forgot to change the calculation to 60mm spacing instead of 100mm)

Now for some more testing.

Chronograph - Part 5

Latest project update for 2026 here

Files
Here are the various files etc. if you want to make your own Chronograph.

Rar file with the files required to make the PCB using Seeedstudio.com are here

A copy of the sketch I'm currently using with my PCB is here, please note it's definitely a work in progress, use at your own risk.

Please note that the connections to the LCD are not the standard ones, I have changed them to suit my PCB requirements.

Items needed
8x2 LCD (16x2 can be used, just modify the code to suit) from here
5V Step-up converter from here
Arduino Mini Pro clone from here (check the pin out is the same prior to buying)
Switches from here

Circuit diagram

PCB

Chronograph - Part 4

Latest project update for 2026 here

The PCBs arrived, at last!

They look good and after assembling the parts, the design works, well I've not tested the 868MHz transceiver yet but the LCD display connected to the Arduino Mini Pro clone works fine and when connected to the sensor fitted to the gun all seems to be OK.

I used a scope to check the calibration of the value sent from the Arduino and it looks pretty good.

Front View - LCD and switches

Back View - the Mini Pro plugged in

Various part plugged in

The PCB is essentially a carrier board for the processor and the display and the 5V step-up converter.

Using an oscilloscope I fired some pellets with my pistol through the sensor tube and compared the timing reported by the Arduino, via serial to the PC, with the measurements taken with the scope.

Scope display showing time between pulses

As you will see from the picture the timings are not exactly the same but this could be due to rounding or the fact that the Arduino only has a 4uS resolution for the micros() function.  I will do some calculations to see what the effect on the final FPS or FPE values would be.

Chronnograph - Part 3

Latest project update for 2026 here

A bit slow going but I've got a bit further with the Chronograph, I had to enlarge the hole at one end by about 1 mm so it would fit over the end of the barrel (thanks Les), then I actually fired some pellets through it and so far it looks to be making reasonably sensible measurements, of course until I can compare it to another chronograph then I can't be completely certain of the accuracy.

As usual, I end up thinking of all the different ways I could achieve my goal .... and then have a go at most of them at the same time: -

1. Remote transmitter attached to the rifle, using a receiver with a graphical LCD to display the results.
2. Remote transmitter with a normal 16x2 LCD receiver.
3. Remote transmitter with a Jeelink/Jeenode connected to a PC running an VB application to display the data.
4. As no. 2 but with a smaller 8x2 LCD.
5. As no. 4 but with  no transmitter and the whole thing mounted on the sensor tube.

I've had a dabble at most of the above with some good results, the Jeelink connected to the PC and using a VB application worked quite well.

Images below showing the received data from the Jeelink.  I also receive the transmitter's battery voltage level.

To determine the energy generated by the rifle/pellet you need to know the weight of the pellet in Grains, this can be adjusted to cater for the .177 pistol or the .22 rifle or different types of pellets.

Results from my 34 year old Diana air rifle

Results from my CPS CO2 air pistol with fresh Cartridge

I saw a discount offer on Hobytronics for their display range, this gave me an idea for the Arduino Nano I had laying around in a drawer, I bought an 8x2 LCD and connected it the Nano, a bit of a mess but it worked OK for a prototype.

Arduino Nano connected to an 8x2 LCD

This was linked to the sensors and also two buttons to allow for the pellet weight to be adjusted up or down prior to the first shot being taken.

This package was quite neat and small so I got to thinking about mounting the whole thing on the aluminium tube using a step up converter so I could run the Nano Mini Pro (Smaller) at 5V (16MHz) from one, or two 1.5V cells or a small lithium ion cell.

To do this as neatly as possible I decide to dust off the Eagle PCB layout tools and do a PCB, after all it's only around £10 for 10 off 5cm x5cm PCBs.

Rendered view of the PCB with LCD

Rendered view of the back of the PCB showing the Mini Pro and RFM12B

It's a bit of a squeeze but I got the LCD on one side the Arduino Mini Pro on the other and even got an RFM12B 868MHz transceiver on there, I couldn't help myself, I also added a couple of spare switches at the bottom of the display and a space for a temp. sensor (DS18B20) this will give me some alternative uses, remote temp monitoring/display etc.

There is also the 5V step-up converter on there, it's one of these.

More to come ....