Wednesday, 19 October 2016

Robot Car V1.0

Robot Car V1.0

A few months ago we created a cardboard framed "robot" that moved forward when three sensors on the front were covered. The wheels were made out of milk tops and chiseled wood. The batteries were so heavy we had to hold them behind the car as it drove.

It wasn't fit for purpose but was a great proof of concept. We decided to start creating the robot for real. I'm going to document in parts the progress we are making.

Initial Design
On the back of a "beer mat" we sketched our rough idea.

Parts To Buy

4 Arduino Smart Car Robot Plastic Tire Wheel with DC 3-6v Gear Motor - £5 to £8
Aluminium offcuts - £0 (up to £14)
Arduino Uno r3 - £2.40 to £8
2 9v Rechargable Batteries - £12 - £30
4 channel 5v relay module board - £1.83 to £6
6+ Photo resistors - £1.50 to £3
Various Jumper Wires - £2 to £4
Total Cost: £24.73 to £73

  Our first task was to create a prototype so we knew how to cut the offset of metal we had. The idea based on the above diagram was to have a flat piece of aluminium with a slight protrusion either end. The plan is for bi-directorional movement of the robot so it will eventually move in both directions with no clear "front".

Cardboard Prototype With Part Placement
  The prototype measured at 19cm x 9cm with the tops coming in by 1cm either side. We also measured some brackets that could be used to hold the motors and therefore the wheels in place.       
  These were 11.5cm in length. We then cut these out of the aluminium offcuts we had.

Lesson 1: Don't do this in a shed on an allotment with no lights at 8pm in October
Lesson 2: If you need 4 equal length pieces... measure them correctly

Having cut two of the metal pieces a little short we decided to make a smaller two wheeled car as it was too dark to cut more aluminium strips.

  The next step was to bend the metal strips that would hold the motors and to solder wire to the motors using red for positive charge and black for ground.

  Once the wheels were in place we secured them by drilling a hole where there was a small plastic dial on the gears plastic. This allowed the gear to sit comfortably. After riveting the holder together the gear was solidly in place and each of the two sides were connected to a long metal strip which connected them.
  At the centre of this we sellotaped one of the 9v batteries and connected wires from each of the two motors to the batteries positive and negative.

  Having both the positive wires from the motor go to the negative on the battery and vice-versa meant the affect was for the robot to spin around in a circle. However having the two motors positive and negative wired to opposing positions on the battery will have made it go straight.

  Just for good luck we added a tail to one of the sides. This stopped the motors wires from dragging on the floor. The video below shows it in action.
In Action:

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