OperatingInstructions:  Maybe you are one of he lucky people that just got a larryrocktimer system fully assembled and all you want to do is start using it.  So skip all the construction and programming stuff and go right to the setup and operation page.  Have fun.

How It Works:

Set up a backline assembly unit and a laser beam shining into the light sensor at the back line; and set up a hog line assembly unit with laser at the hog line.  Arm the system at the back line with the Infrared Sensor using your hand or broom head.  Breaking the laser beams starts and stops a timing system to act like a stop watch to give you split times AND the speed at the hog line.  Great for Practicing specific weight shots.  The system is very easy to set up and use; and gives you immediate feedback on how hard you throw a shot.   Can set up with either 1 or 2 hogline "sender" units.

MULTIBEAM SYSTEM.

The larryrocktimer system will let you “Know what you throw”™ between as many lines as you want.  Typically curlers will use this for measuring split times from back line to near hog line; and then from hog line to hog line.  However, the options are literally endless (ha ha curling joke) and the new system can measure interval times and speeds at as many locations as you want; although the software I send out with a system is for only up to two beams.  Choosing one or two beams is done at startup using the IR sensor.  If you want more beams, a simple software change is needed for a custom system.

For a three beam system use two of the hog line units.  Most people will use this to get the back line to near hog line split time and then the Hog to Hog interval time.  Having the far hog line set up diagonally to the back line unit might improve the reliability of the system--some people have reported this while others say it doesn't matter.  It might depend on the particulars of the ice rink.

For a two hog line system, hold your hand behind the IR sensor at the end of the 5 second start up test and the system will set itself for two hog lines.  For just a single hog line system, remove your hand at the end of the startup test.  

INTRODUCTION

This project is a cheap DIY curling stone timing system.  

A pair of laser/phototransistor photogates measure the interval time from the back line to the near Hog line.  Also, the speed through the hog line is measured. My system uses 3D printed parts (designed with Autodesk Fusion360), small laser diodes, a couple of phototransistors and ESP32 microcontrollers that communicate with each other over the ESP-NOW communications protocol.  No wifi or bluetooth is needed (but see note below about andy's better rock timer).  The timer is "armed" with an infrared sensor and the time is displayed on a small OLED display panel after the stone is delivered.  

I use this system to practice and will say that it has helped improve my draw weight significantly.  Muscle memory is acquired for specific interval times.  I can get myself calibrated to throw certain weights and have a lot more confidence when trying to throw a specific shot.

A little soldering will be needed to build this--to connect the battery to the laser diode (and you could just twist the wires together).  Otherwise it takes less than 30 minutes to put the parts together once the housings are 3D printed.  The trickiest part is programming the ESP32's.  If you have never done that type of thing, the first time is going to take a while; but it WILL work.  Installing the IDE software, the drivers and everything takes some patience.  There are lots of good tutorials online for this; you can do it too!  In fact, the following two sources have helped me tremendously and inspired me to make this project available for anyone interested at no cost.

https://randomnerdtutorials.com/projects-esp32/

or

https://dronebotworkshop.com/esp32-intro/

Good curling!!

Overview of the operation...

The files and software are all FREE.  Do whatever you want with them.  I hope somebody out there smarter than me will improve the system and pass it on to others.

It will cost around $40 in parts and plastic to build my system with two pieces that will give the interval time from backline to hog line; and it also gives the Hog Line speed (in feet per second) through the hogline photogate so that it can be determined if the curler is pushing or pulling the stone on their release.  It's just a little more for the multibeam system with the second hogline system (another esp32 and phototransister and battery).  A three beam system actually works out great for buying as you can easily find esp32C3 packs of 3 from seeedstudio and phototransistor packs of 3 from amazon.  

Some useful information regarding rock timing is here..http://www.curlingschool.com/timingRocks.html#:~:text=Interval%20timing%20is%20a%20scientific,the%20rest%20of%20the%20way.

The following is a rough example of split times a sweeper will look for on draws.  NOTE:  These are just copied from the above source....I, personally, have done some math modeling on curling times and have not verified these numbers myself.  The rock/ice friction dynamic is quite complicated so this oversimplification hides what is really going on--but good enough.

Ice Speed Hog -Tee Ice Speed Hog-Hog Interval Time

(like what us old curlers

used to time)

23.0 seconds 13.5 3.70

23.5 seconds 13.8 3.75

24.0 seconds 14.0 3.80

24.5 seconds 14.2 3.85

25.0 seconds 14.5 3.95

25.5 seconds 14.8 4.00

26.0 seconds 15.0 4.10(seems like 4.05 would fit the pattern)

For takeouts, on "normal" ice, the interval splits might look like the following numbers for different weight takeouts.

Weight Split Target

Hack 3.40

Control 3.15

Normal 3.00

Peel 2.75

Peel + 2.50 or lower

SOFTWARE--IGNORE THIS VERSION 1.0 information.  Go to the 2.0 version.  I just haven't deleted this information yet.

Software for Version2.0 is here

There are two arduino IDE software sketches.  One for the HogLine, one for the BackLine.   The arduino IDE 2.3.3 does NOT compile correctly with the older original software that was for the 30 pin esp32.  There is an issue with the ESP NOW setup commands.  I have documented this in the new software.  So new software and old arduino IDE will need some changes to make it compile.  The new Boards manager for the esp32 are causing me lots of problems on some other projects.  I hope it is just a simple fix for the rock timer. 

 Don't worry about any of this if you are using the ESP32-C3 Xiao from SeeedStudio--the recommended build by Larry of larryrocktimer. 

Here is the setup that I have been using for the XiaoESP32-C3 and everything works.  I am careful to NOT allow updates to my system after having lots of problems with new software.

The video below shows the installation process...

Arduino IDE 2.3.4  (Possibly good with IDE 2.3.6 on 8/30/25.  It worked on my new Dell Computer)

Gyver OLED library 1.6.4

esp32 boards manager from espressif v3.0.7

esp-now.h v5.1

A suggestion from someone else building a system...Kudos to DB for this idea:

"If you search esp32 in the board manager, install an older version of the esp32 by Espressif Systems module, I used 2.0.12, the software compiles and uploads just fine"

A purchased kit will have the software installed.   Click to download only if you want to mess with these programs.

Current Software as of 2/11/25

XIAO ESP32-C3 Software:

BackLine2Beam software for the Xiao ESP32-C3

HogLine software for the Xiao ESP32-C3.  

Be sure to put the correct MAC Address for the Backline ESP32-C3.  I have had some intermittent problems printing the Mac address to the serial port monitor with these new Xiao esp32-c3s.  So I just install the Backline software first and get the mac address from the display screen on startup.  It's actually a little more efficient this way as I just need to install one program.  If you want to run a separate mac address reader sketch, there are many online--or download the one I use.

30 Pin  ESP32  Software:  Maybe someone wants the old stuff so here it is.

Backline as of 11/4/2024

Hogline as of 11/4/2024

I am cleaning up the webpage so am removing some of the older systems that I doubt will ever be used.  Here's the links if you want to explore them. They work and might be good for certain applications.

LarryGameTimer

If you want a super cheap and easy way to create a countdown game timer, use one these esp32-c3 and set up a webpage that has a countdown clock.  LarryGameTimer might be just what you need.