Protection grid

These instructions outline how to make the protection grid that the top secret Super Massive Nerd Sweet Device sits atop. The protection grid is essentially an electronic circuit that is closed when the Super Massive Nerd Sweet Device sits on top of it.

Key details

• Uses radio group 1 and sends the following messages:
  • alarm - triggers the alarm
• Uses radio group 2 and sends the following messages:
  • disabled - notifies that the protection grid is disabled.
  • enabled - notifies that the protection grid is enabled.
• Uses radio group 2 and receives the following messages:
  • one - turns off corner 1.
  • two - turns off corner 2.
  • three - turns off corner 3.
  • four - turns off corner 4.
• Buttons A+B - resets the protection grid.

Bill of materials

• BBC micro:bit; a V1 micro:bit is fine.
• BBC micro:bit battery power box.
• 2 crocodile clips.
• Materials to make a box and "switch".

Click here for the completed code.

Here is an example of the protection grid using a 3D printed back plate (here) mounted to a plastic box. The Nerds box is itself a plastic box with a large washer screwed to the bottom.

Whilst the above box works nicely, it is also possible to make the same type of system using the minimals materials of paper, foil (or copper tape). Simply use foil to make the two contacts of the switch and connect the BBC micro:bit to both pieces of foil via the crocodile clips. Then the vessel representing the Super Massive Nerd Sweet Device can have foil or copper tape attached to its underside so that when it sits on the paper, it closes the switch.

Explanation

This is a very simple device that can be applied to many different scenario. We pull pin 2 high so that by default it returns the digital value 1. Crocodile clips are then used to connect pins 2 and pin GND to contacts.

When the Super Massive Nerd Sweet Device sits atop the protection grid, it closes the contacts connected to pins 2 and GND. This "connects" the two pins and forces pin 2 low so that it returns a digital value 0. Therefore, when the Super Massive Nerd Sweet Device is present on the protection grid, a digital value 0 is read from pin 2 but when the Super Massive Nerd Sweet Device is absent, a digital value 1 is read from pin 2. This is how the protection grid determines if the Super Massive Nerd Sweet Device is present or not.

Instructions

Setup the following variables:

Add the following code:

Add the following code:

Extensions

The protection grid is easy to extend. Try these ideas:

• Play a sound when the device is removed from the protection grid.
• Make a beeping sound whilst the protection grid is active.