Easily programmable remote-control cars
Class: Year 10 Electronics
Teacher: Andrew Calder
Shirley Boys' High School
Shirley Boys' High School electronics teacher Andrew Calder uses battery-driven remote-control cars bought cheaply from megastore retail outlets to create a teaching tool for his PICAXE programming lessons that has his Year 10 class captivated right from the start.
Out-of-the-box, the cars are linked to a handheld control unit by a wire lead. Andrew replaces this control system with an onboard control unit of his own design. The unit is linked to a touch sensor mounted on the front of each car and the motor and gearbox at the rear.
At the heart of the control unit is a programmable PICAXE chip. Students (working in teams of two or three) are asked to program this chip to perform a repertoire of simple functions – to move a car forward and backwards for set distances, turn it, and have it react to a collision when its sensor is tripped. When the class has completed their programming, Andrew trials the results by staging what he terms a 'dressage', in which each car must perform the pre-determined series of moves.
The approach offers several benefits. The cars are cheap – as little as $7. The PICAXE chips used have lots of extension capacity, which means additional functions, such as radio-control, may be added to the cars at a later date. And the cars immediately engage the Year 10 boys, who are instantly captivated and excited by the notion of robotics and automobiles. (Background lessons in PICAXE programming using chips plugged into breadboards aren't nearly so engaging, Andrew notes.)
Modifying the cars isn't that complicated, and Andrew uses the construction of the (unprogrammed) cars as an extension exercise for his keen Year 10 students, who have finished their course work.
Andrew credits his predecessor at Shirley Boys' High, Peter Wilson, with the original idea of modifying toy cars to create a teaching tool. Andrew extended the idea by developing the programmable unit.
The schematic for the unit was designed using EAGLE (Easily Applicable Graphical Layout Editor) freeware. EAGLE shows the footprint of each component as it will appear on the completed circuit board. The circuit diagram produced by EAGLE is transferred to small copper-coated plastic circuit boards for etching using the toner transfer process.
This involves using a laser printer to print the circuit (see sample [pdf, 86kb]) on to glossy photographic paper and then using heat from an iron to bind the printer toner, defining the wiring, to the copper face of the circuit board. Subsequent etching removes the uncoated copper from the board. A YouTube video of the process is available at www.youtube.com/watch?v=urv6jArKp6M. Here, also, is set of instructions (pdf, 64kb).
The approach to making circuit boards has several advantages over the older photo-etching system, which involves relatively expensive specially-prepared photosensitive circuit-board material and the inconvenience of having to work with light-sensitive chemicals. "The new method is simpler, faster, and about four times cheaper. It's also something keen students could do at home."
Andrew is keen to extend the use of the cars as a teaching tool to teach aspects of radio control. And, interestingly, one of the school's biology teachers saw the modified cars in action and said they could be used to demonstrate the workings of a primitive nervous system.
RESOURCES
Making a Printed Circuit Board (PCB) using the Toner Transfer process (pdf, 64kb)
Printout of circuit (pdf, 86kb)
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