Simple tamper-resistant countdown timer

Thread Starter


Joined Jun 21, 2019
Hi everyone!

First of all Im not really a DIY-type of guy, so please be gentle with me, Im new to all this :)

For a summer camp game I need to have some kind of mobile, tamper resistant countdown timer.
Since I couldn't find anything like that ready to buy, I decided I might have to try and build them myself (please tell me if im crazy for trying this).

Here's what I'd like to achieve:
- A small, mobile device (easily carried around in one hand), that counts down a fixed time (10 minutes) and then makes a noise (think alarm clock)
- Once the countdown is started, it shouldn't be possible to stop or reset it (except for removing the battery obviously)
- The device should have some kind of clock displaying the remaining time
- For budget reasons a single device can not cost more than 12€ (I plan on using 10 devices, 120€ budget)

Any help would be much appreciated!


Joined Mar 14, 2008
Building such a device from scratch is likely more than someone that's "not really a DIY-type of guy" can readily do. ;)

The easiest might be just to buy a countdown kitchen timer or stopwatch, which includes the display and buzzer, and mount it in a locked box with the buttons inaccessible and display visible, but with one added external button (with perhaps a small amount of added circuitry) that can only start the timer but not stop it.

Thread Starter


Joined Jun 21, 2019
Ah well, I was afraid I'd get that answer.

Anyway, thank you for taking the time to reply and I'll see what I can do with modifiying some cheap timers!