Knock To Open Trasure Chest

The finished box

Preface

My daughter asked me to build her a treasure chest that she could use to store her most valuable things. Obviously she demanded it to have some kind of a locking mechanism so only she could open the box.

First thought was to use a keypad but then her grandfather bought her a diary with a secret code. So I had to come up with something else. On adafruit’s tutorials I came across the Secret Knock Activated Drawer Lock. Use a secret combination of knocks to open the box… An idea I instantly liked a lot. Another great thing about this drawer lock was that it was programmable, which means you can change the knock sequence to anything you like. Continue reading

Balance board

Here some photos from a project I did a few months ago:


Unfortunately I didn’t have any camera available in my workshop so there are only pictures of the finished boards. I used plywood for the platform. I created myself a sliding carriage to attach a router to it to mill the form.
To find a wooden semi sphere was a hard task. I could not find any (affordable) one with a diameter > 40mm. I ended up buying a semi sphere off ebay that originally was intended as a coordination toy. It had a diameter of 140mm.

Cash register for kids with Arduino

Ever since I started with Arduino I wanted to create a cash register for my girl.
My requirements:

  • A “scanner” that triggers a buzzer and displays a (random) value on a LCD.
  • A keyboard where numbers can be pressed and calculated.


For the scanner I thought it would be a good idea to use a LDR (Photo resistor). Initially I hard coded a threshold value and when the value returned from the LDR was over that value, it triggered a buzzer. I then realized that working with the LDR depended a lot on the light – meaning it really mattered if I tested at day or at night with no daylight. I decided to add a potentiometer with which I can fine tune the threshold value later instead of uploading new code to the Arduino just to change a constant.
I also added a LED to the scanner that is on most of the time but turns off when the LDR value goes over the threshold value, ie when it is dark.

Scanner complete

Scanner complete

Continue reading