Generally writing about sensors make the subject appear complex. Using sensors, particularly with the Roamer, is much easier than it may seem, and the more you practice, the easier it gets! Marcus Topham continues his look at Roamer Sensors.
Roamer’s sensor system is just like that of humans: the act of switching on a lamp (stimulus) is detected by a light sensor that transmits a signal to the Roamer’s microprocessor brain.
If the Roamer recognises the signal it will respond by executing a sense procedure. A sense procedure is like any other Roamer procedure except that it is referred to in a sense instruction and should not be used as part of the GO Program.
Marcus was a Bradford teacher who was part of a small group who sat in Tom Stonier’s Bradford University office patiently providing advise on the design of the Valiant Turtle and Classic Roamer. He went on to run a CDT in Bradford before moving into Digital Management at Bradford Council.
The Roamer sense instruction needs to tell Roamer which type of signal to recognise and then which sense procedure to execute. To enter a sense instruction, press S followed by a number from 1 and 5 for the type of input signal to recognise and a number betwen 1 and 99 for the sense procedure.
The sense instruction can be used anywhere in the GO Program.
When the Roamer executes a sense instruction, it remembers what type of signal to recognise and what procedure to execute if the signal occurs. It then continues to execute the GO Program. If it receives the correct signal, it immediately stops executing the GO Program and executes the sense procedure. Once the sense procedure has been executed, the Roamer returns to where it left the GO Program and executes the remaining instructions. If the correct signal occurs again the Roamer will execute the sense procedure again and then return once more to the GO Program.
A signal in electronic parlance is a change of voltage from a High level to a Low level or vice versa.
Roamer uses High/Low terminology for programming Inputs and Outputs. Note: Roamer’s Input line is normally High.
Sensors react in different ways: some light sensors will cause a High to Low signal when a light is switched on and other designs will cause a Low to High signal. You need to find out how the particular sensor you are using acts. In the examples here it is assumed that the sensor causes a High to Low signal when a change from dark to light occurs.
The new Roamer Inputs do not use the electronic ideas involved in the Classic Roamer. While it simplifies the human readability of the coding, it does not diminish the potential of the educational challenges. In fact it makes the use of sensors accessible to the youngest children.
|1||A High to Low signal (e.g. a dark to light change).|
|2||A Low to High signal (e.g. a light to dark change).|
|3||Either a High to Low or a Low to High signal (e.g. a dark to light or a light to dark change).|
|4||Roamer will recognise if the Input line is Low when the sense instruction is executed or if a High to Low signal occurs (e.g. if it is light when the sense instruction is executed or if it changes from dark to light).|
|5||Roamer will recognise if the Input line is High when the sense instruction is executed or if a Low to High signal occurs (e.g. if it is dark when the sense instruction is executed or if it changes from light to dark).|
All good stuff! Explaining how to use sensors always appears more difficult than actually using them – which is why we have simplified in with the newest Roamer. The practical programming of the following examples should help develop an understanding of the basic ideas.
The object of this activity is to program Roamer to find its way through a doorway. Play acting the activity can be valuable. Blindfold the pupil and ask him or her to find the doorway. They are only allowed to walk forward, backward or turn 90° left or right; that is, they are not allowed to ‘side-step’
Make the Roamer into a car with a pair of headlights and fit it with a light sensor. Put the Roamer car in a room with daylight blocked out. The room lights should be on. Program the Roamer car to turn on its headlights when the room lights are switched off. (Note: the headlights are made from two lamps connected into Output 1 of the Control Box).