Robot Car V2.0

  A few weeks ago, we created the first version of our new and slowly improving robot car. For version 2 we added the front wheels, the body and a relay to control both sides from a single 9v battery.

  Continuining from the back of a "beer mat" design below we continued to implement.

Initial Design

Our parts list can be found here

  The first task to do was to re-cut and bend the wheel brackets, this aluminium was to be 11.5cm in length. The width was 2cm and each needed a hole drilling to allow the gears wheel connector to poke through and allow the wheel itself to sit on it.

  Once this was achieved we drilled out the rivets attaching the two wheels together from V1.0 and attached them to the larger frame using more rivets.

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Lesson 1: Make sure you have measured the rivet locations correctly or you will have wonky wheels

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   At this point we wanted to be able to thread the motor wires to the upper body to attach to the relay/battery etc. To do this we drilled two holes either side of the frame and attached grommets to them before threading through the motor wires - two to a side.

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Lesson 2: Loose wires on a flimsy motor will easily break. SECURE them

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  As can be seen in lesson 2. The wires being loose underneath the frame caused them to turn and pull whilst manoeuvring them. This lead to the wires coming off the motors and needing urgent soldering surgery. To secure them, we have now added cable ties that attach the wires tort at the base of the motor.

  Once the wires were threaded through we attached we placed the relay on the frame on top of a piece of cardboard to reduce the chances of the relay etc. shorting out.

Ready to wire

  For V2.0 we decided we would just directly connect the motors to the relays switches as well as the battery. The wiring system we chose can be seen in the image below. We are currently researching a system diagram creator (software). Any suggestions would be greatly appreciated!

Current confusing wiring diagram - wired connectors between NC and NO

  As you can see/not see in the diagram above, red wires show positive energy flow, black wired show ground and the blue wires are just connectors. The blue boxes are motors, yellow box is battery, the centre grey circle is a wire connector and the orange box is the relay module with the grey boxes inside being each switch.

  It's quite obvious that this form of drawing diagrams is going to be quickly untenable. But we live and learn.

Tidy and Smart wiring

  This wiring allows the robot to go in a straight line. With slight moving of wires you can make the car go in a circle but I'll leave you to play to make that happen. Below is a video of the robot in motion. We move onwards.

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In Action:

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

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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

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Total Cost: £24.73 to £73

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  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.

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Lesson 1: Don't do this in a shed on an allotment with no lights at 8pm in October

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Lesson 2: If you need 4 equal length pieces... measure them correctly

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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.

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In Action: