Let's Make Robots!


Arduino demo bot

These robots were created as a small demo of how easy it can be to get up and running. It's a Magician chassis with an Arduino Uno and L293D. We're probably the biggest consumer of Magician chassis - we've got about 30 at the moment and I'm just requested another 20. They're relatively inexpensive and easy for small hands to assemble, though we do find the motor wires have a habit it of breaking. I'm hoping to move to a 3D printed design in February.

They were originally simply named "demo bots" but after a typo in an email became known as Demon bots. The original versions use LDRs for photophillic and photophobic behaviour. They were shown on s4c when we appeared at the Urdd Eisteddfod with a variety of toys.

They are essentially Braitenberg vehicles, though we have made various adaptations - such as attaching a pen so that a path can be programmed in s4a then drawn in the real world.


Parts & Construction

The original design:

All of the tools and components are common place; they should be easy to find online or in electronics shops.

  • L293D H-Bridge (approx. £2.50)
  • Arduino Uno (approx. £20)
  • Magician Chassis including a 4xAA battery pack and 2xDC motor & wheel sets (approx. £14)
  • 3x LDRs (aprox £1.50)


The “Magician” chassis we used is an affordable and easy kit, but we recognise it is only available through certain suppliers. An alternative chassis could be created from scratch using two 15x20cm pieces of 3-5mm acrylic plastic, held with 3cm high struts. Motors would be attached to the base (with glue or an acrylic bracket) slightly forward of the centre of gravity. In lieu of a castor wheel, a curved piece of strong wire could be attached to the rear to support the vehicle and reduce friction.




I'll post updates as we try new things out with these bots. Any suggestions of enertaining demonstrations we might do with these robots would be greatly appreciated.

Currently we are working on two versions - a drawing robot (once programmed in s4a a servo mounted pen will draw a line on the ground) and battle bots which have detatchable parts that will fall off on impact, when they all fall off the robot stops moving.




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Nice work! 

Since you've worked with this chassis a lot maybe you can help me with the issues I'm having.  I bought 3 of these kits as a simple robot project with my kids. The idea was to use a breadboard with a Picaxe 18m2 and an L293D motor driver. I wired it all up with sensors and LEDs included and it wouldn't go anywhere. After hours of testing and rewiring I found that the motors draw about 2 amps each. At that power draw it seems there is nothing left for the picaxe so it essentially shuts down.  I've found that I'm going to have to add a second battery pack so that the Picaxe and sensors can be powered separately from the motors. Is this the expected configuration? Did you run into this issue with the many robots you've built?  Since it came with a single battery pack I designed the circuitry around a single power source and a single power switch.