My NXTLOG ‘Crazy Contraption’ Entry    Send article as PDF   
Many robots are designed to do simple tasks in an efficient way to make our lives easier. But what if robotic machines did simple tasks in an over-complicated way? This is the type of Machine that ‘Rube Goldberg‘ envisaged for his weird world. Below is an example of a ‘Rube Goldberg Light Switch’. I have attempted emulate this crazy idea of Goldberg’s, with my very own over complicated LEGO Mindstorms NXT based ‘Light Switch’.

Rube Goldberg Cartoon
‘Rube Goldberg’s Light Switch’

The Contraption uses two LEGO Mindstorms NXT’s to control it. I could have just use the one, by using a couple of extra long Home-brew NXT Cables. The two NXT’s control the six modules involved with making this Crazy Contraption turn on your ‘Table Lamp’:

  1. The (random) distance measuring unit [NXT 1]
  2. The Keyboard for inputting you distance guess [NXT 1]
  3. Ball Dispenser [NXT 1]
  4. Trigger Unit [NXT 2]
  5. Light Switch Target [NXT 2]
  6. The Mains Voltage Appliance Controller [NXT 2]
  7. The Table Lamp [NXT 2]

‘Rube Goldberg Type Light Switch’

To operate my NXTLOG ‘Crazy Contraption’ Entry, you first need to know how to subtract! No basic maths. No light to read by!

My NXTLOG ‘Crazy Contraption’ Entry

When the first NXT’s program is run,  the measuring target is positioned a random distance from the Ultrasonic Sensor at the extreme left of the gantry. The user’s goal is to get the Trolley with the ‘Red Plate’ to move along the gantry until it is 100mm from the Ultrasonic Sensor. If you go closer than 100mm, you are forced to start again.

Gantry and Keyboard
RCX Touch Sensor Mux
NXT – 8 Input RCX Touch Sensor Multiplexer Unit

The user Input to the first NXT is via an 8 Input RCX Type Touch Sensor Mux. The Mux is a fully compatible I2C Bus Type Sensor, based on a Philips PCF8574 remote I/O expander. It’s a single integrated circuit that includes eight pins that are used for Touch Sensor inputs.

Ordering System Keyboard
Crazy Contraption’s Data Entry Keyboard.

These 8 inputs are used on the Keyboard for:

  1. Clear Entry (Large Red Key)

  2. Number 1 (Red Key)

  3. Number 2 (Yellow Key)

  4. Number 3 (Grey Key)

  5. Number 4 (Blue Key)

  6. Enter Your Total (Large White key)

  7. Number 7 (Gantry Home Position)

  8. Number 8 (Ball Dispenser Home Position)

Ball Dispenser

When you managed to have the Trolley 100mm from the Ultrasonic Sensor, you win and a ‘Ball’ is dispensed. The ball drops onto a ‘Trigger Mechanism’ which fires 2x ‘Darts’ at the Black and red target which then triggers a Touch Sensor attached to the second NXT. Once the Touch Sensor has been depressed, the second NXT sends a signal to the Mains Voltage Appliance Controller which in turn turns the ‘Reading Lamp’ ON!

‘Light Switch Trigger and Lamp Switch’

NXC Source Code:


Source Code for Slave NXT:
Download the Source Code and Sound Files.<


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