Light sensor

The Smart Sense light sensor will measure light levels over a wide range. The sensor connects to any one of the analogue sensor inputs. Once connected the Smart Move software will display the name of the sensor and label the appropriate input ‘LIGHT’. The screen will display the current light level as a value on a scale from 0, very dark to 255, very bright.

Responding to the sensor

The sensor can be used as an input device to a system which responds to changes in light level. An example might be an automatic lighting system which switches on when the light level falls below a certain value. The procedure "Auto" shown below will switch on a bulb connected to output 0 when the light level falls below 50.

Procedure: Auto

REPEAT
IF LIGHT IS LESS THAN 50 THEN SWITCH ON 0 ELSE SWITCH OF
FOREVER

How it works

The REPEAT...FOREVER loop repeats the second line of the procedure. This takes a reading from the sensor and either switches on or off output 0 depending on the current light level.

Counting

The second example "Counter" uses the light sensor as a counter to detect whenever a light beam is broken. As supplied, the sensor will detect light falling on it from a wide angle. For this type of use the sensor will perform more accurately if the sensor is mounted at the end of a tube with a light source, for example a torch, pointing at it from some distance away.

Procedure: Counter

number = 0
PRINT "Press the space bar to stop counting"
REPEAT
WAIT UNTIL LIGHT IS LESS THAN 50
LET number=number+1
WAIT UNTIL LIGHT IS GREATER THAN 75
UNTIL INKEY=32
PRINT number

Recording light levels

The readings from the light sensor can be stored to a disk file. This data can then be analysed using a spreadsheet. Procedure "Night" records the average light level every 5 minutes during the night. The recording starts when the light falls below a certain level at dusk, 150 in this example, and stops as the sun rises and the sensor reading rises above 200.

Procedure: Night

FILE 1,"Data"
WAIT UNTIL LIGHT IS LESS THAN 150
START CLOCK
REPEAT
RESET CLOCK
AVERAGE CLEAR
REPEAT
AVERAGE LIGHT
UNTIL TIME IS GREATER THAN :5:0:00
STORE 1,AVERAGE
UNTIL LIGHT IS GREATER THAN 200
CLOSE 1