From Ideas to Prototype. I have a ton of ideas and I love to…
By: Thomas Roccia
Tags: DIY, Code, CrossFit, Electronics, Timer

The Idea

In early 2020, many countries were locked down due to the Covid. Gym have also closed. A lot of people had to do their training at home, including me. Having a timer is especially handy if you are doing HIIT exercises. I was using my phone as a timer but it never came in handy, it is always on standby, you always get a notification from every apps and you can break it.

With that in mind, I started to imagine a portable timer that includes the same features as a normal timer such as the one below.

I also searched the internet and found a DIY timer https://www.instructables.com/DIY-Garage-Gym-Timer/.

But what I wanted was something portable that I can use wherever I go as a stopwatch with multiple workout programs.

Proof Of Concept

The best way to start something when you have an idea is to start small.

In other words, try to make a fairly early version with what you have in your lab.

In my case, I had an Arduino and some electronic parts that I got from an old box to start electronics. The first step I did was create a basic timer that works with an Arduino and a seven segment display. I coded a simple POC with a breadboard.

POC timer

Notice in the photo that in this version I already had 4 buttons and a buzzer. The V0.1 only included the Arduino and the 7 segments.

Great! We had our initial version of the timer. Now is the time to think about how to have it portable.

Sketch

Before going any further, I decided to try to sketch out what I had in mind. The sketch below shows you the kind of things I imagined.

First sketch

At that point, I realized that maybe my 7 segments were too small for my goal. So I decided to buy a bigger one online. I bought the Adafruit 1.2" 4-Digit 7-Segment Display w/I2C Backpack — Red. With the new segment received, I had to redo another sketch.

Second Sketch

In this second sketch, you can see what the final prototype will look like roughly.

Hardware & Code

With the new 7 segments received and a pretty good idea of ​​what I wanted, I started to code all the programs and make the connection between the components. The link to the Github project will be added at the end of the article.

New 7 segment

I ended up with 600 lines of code and 4 programs:

Simple timer

Tabata training — Interval (30 sec / 10 sec)

EMOM — Interval (every minute)

Pomodoro timer — Time management method

Demo

I was pretty happy with the result but needed a built-in battery so after chatting with a few people and seeing what I can do I just decided to use an old power bank.

The list below shows you the material I used:

Arduino Uno for the initial version

Arduino Nano for the final prototype

A piezzo buzzer

4 buttons for selection

A power button with LED

An old power bank

Magnets

The image below shows the prototype with the external battery that I soldered on later.

Power bank connection

For the power button I used a simple button with LED.

Power button

The final diagram looked like the following image:

Diagram

3D Modeling the Case

Once I had all the code and hardware ready I designed the case on Fusion 360. I own a 3D printer so I did some testing before I found the perfect setting.

First 3D printed case

As you can imagine, the initial test was unsuccessful and the next and the next...

I did a lot of testing and something I hadn’t thought of was organizing the inside of the timer. To do this, I made another sketch.

Sketch of the inside

Okay, it wasn’t perfect but it was enough for me to move forward.

With a better view of how to organize the electronics inside the case, I returned to Fusion 360 to model another. In the screenshot below you can see some of my essays.

3D Printed case

As you can see, it comes close to the original idea.

Finally the final model is as follows.

Final Sketch

You can see specific locations inside the box for electronics, but also to add magnets to hang it on a board for example.

Assembly

After finding the right setting for the case, it was time to put everything in place. The first step was to glue the magnets and finish the welding.

Magnets Assembly

Finally I glued everything in the case.

Final Assembly

Final Prototype

After all of this process, it was time to close the case. The images below show the final prototype.

Final Prototype

Final Prototype

Final Prototype

Final Prototype Working

What next?

I wanted to take it a step further and see how much it can cost to have a marketable end product. So I contacted a company specializing in this type of prototype. The price was over 4000 euros just for the design of the PCB.

In the end, I just wanted to have something useful for myself, so I decided to publish it for free, so that everyone can make their own portable timer.

Conclusion

The whole process was really interesting, it took me over 2 weeks to have this final prototype (minus the delivery time for each part). It was interesting to think about the design of the object but also to do the various tests. Along the way, I had some failures and had to 3D print about 7 cases.

I’m pretty happy with the end result and currently use it in my own training.

Hope you enjoyed this blog, I created it during my #100DayOfCodeChallenge. If you want to make your own portable timer, you can download everything from my Github.