Combat Reflex Timer For Martial Artist

Hi All

I’m new here and know absolutely nothing about electronics so if Ive posted this in the wrong place , forgive me.

I want to build a combat reflex timer like that shown in this video

Ive found a sparkfun project that almost gives me what I want here

However I’m looking to make the following change

Inside of hitting the button when it lights up to stop the timer I want to be able to hit a sandbag or a focus mitt as in the video above.

what I need help with is:

  1. What materials would I need ( apart from the materials needed for the sparkfun project above) to wire up a switch inside a sand bag or focus mitt to act as the impact point that stops the timer when hit instead of the button. So the only change from the sparkfun project is the impact point to stop the timer is a sandbag/ focus mitt, everything else stays the same.
    The material acting as the switch inside the sandbag/focus mitt would have to be able to withstand hard impact punches.

  2. Would I have to change the sparkfun project coding in anyway? if so, what changes would I have to make?

  3. If I wanted to add a auditory part to the reaction timer such as a beeper and be able to switch between the visual stimulus ( the light button) and the auditory stimulus ( the beeper) what materials would I need and what changes would I need to make to the sparkfun project above in terms of wiring and coding

Thank you


Hey David,

Welcome to the forum, quite an interesting project!!

  1. I’d have a look at using some sort of pressure sensitive material such as velostat: Pressure-Sensitive Conductive Sheet (Velostat/Linqstat) Australia
    It would be best to pad it up a bit between the hitting surface and the sensor.

  2. There wont be an answer straight away, it will depend on what parts you go for and how you want everything to work together.

  3. I’d go for a piezo buzzer and a toggle switch. throwing a big if statement around everything should handle the logic.

Before you start coding it would be worth making a flowchart of how you want it to work. From there you can figure out how to implement each ‘block’ into the Arduino.


Hi Liam120347

Thanks for the heads up about velostat.

As for the parts I will use…basically I will use everything listed to build the sparkfun project and then whatever materials needed to make the pressure switch to be placed into/behind a sandbag/focus mitt the only difference between the sparkfun project and my combat reaction timer being that the impact area used stop the reaction timer is the sandbag/focus mitt pressure switch instead of the big button.

so how do I want everything to work together …basically as in the video…timer is powered on…at a random time light will flash…punch delivered to sandbag/focus mitt…timer stops/shows reaction time…timer resets itself and everything starts again.

Will look into the piezo buzzer and toggle switch

and the coding aspect…really have no clue!

Again thanks for taking the time to help me out I appreciate it


Hey David,

Sounds awesome! I’m keen to see how it goes :smiley:

I’d check out the Core tutorial on coding with Arduino:

If you want to change things up a bit micropython/python spoils you, a lot easier to write with and the Pico (A micropython enabled microcontroller) is a lot cheaper than an Arduino:


Thanks Liam will look into both.

Let me ask your opinion…on a scale of 1 to 10…and taking into account that I will be using the materials and follwing the directions given for the sparkfun project here
how difficult will this project be, and making the changes for the combat reaction timer, for a complete and utter noob to electronics and coding


Hey David,

Making comparisons to other projects isn’t really the best metric but for a beginner there are a couple of tricky bits that have to work together, which is why breaking them down makes them sooooo much easier!! All projects will have some catch or roadblock - also known as integration hell so don’t get worried if you get bogged down, also Stuff Made Here is an awesome channel.

Each part individually shouldn’t be too bad though, probably in the realm of 3 or 4, if you need a hand have a google around to see if you can figure it out (sooo much more rewarding imo, you learn a ton more) if you don’t have any luck the forum is definitely here to help.


Thanks mate really appreciate your time and help


No worries at all David!!

I’m sure everyone will love to see what you come up with!