Table of Contents
A reflection sensor is most of the time a sensor that uses (infrared) light to detect the precence of an object.
TCND5000 the demonstrated sensor
Upper left: The TNCD5000 is a sensitive photo diode and an infrared led in one case.
Upper right: A sketch of the TCND5000 driver.
Lower left: Five sensors mounted on Cosey's PCB.
Lower Right: Piece of schematics of the Cosey robot, note that the resistor values have changed!
Function: REFLECTION ( adc -- +n ) Read adc input 'adc' leave the reading '+n' Function: FLOOR ( adc -- +s ) Read adc input 'adc' and leave the scaled result '+s' Function: RAVINE ( -- 0|1|2|3 ) Read the three adc inputs from the front of a robot. Translate the results to the numbers 0 to 3, indicating which sensor(s) where fired. Zero means non. Function: BACKWARD? ( -- flag ) Test the sensor on the backside of a robot, leave true if the sensor is fired, otherwise false
\ Reflection sensor example as used with the Cosey robot \ \ Each sensor output is connected to an ADC input with 12-bit resolution \ \ Words with hardware dependencies: \ : **BIS ( mask addr -- ) tuck @ or swap ! ; \ : **BIC ( mask addr -- ) >r invert r@ @ and r> ! ; \ : BIT** ( mask addr -- 0|b ) @ and ; \ \ Needed an ADC routine like this one for the MSP430FR5949: \ \ We need to clear the ENC bit before setting a new input channel \ ADC can be used with VCC and VREF (2.5V) as reference voltage \ : ADC ( adc fl -- +n ) \ 02 800 **bic \ ADC12CTL0 Clear ENC \ 100 and >r \ Use VREF when fl is true \ 1F and r> or 820 ! \ ADC12MCTL0 Select input \ 03 800 **bis \ ADC12CTL0 Set ENC & ADC12SC \ begin 1 802 bit** 0= until \ ADC12CTL1 ADC12 busy? \ 860 @ ; \ ADC12MEM0 Read result \ \ Activate an output on a PCA9632 I2C led output driver \ The routine /MS waits in steps of 0.1 milliseconds \ It is used here to give the sensor time to settle \ : >ON ( b -- ) 8 >pca 1 /ms ; \ b = 1, 4, 10 or 40 \ Read sensor level from input 'adc' using VCC as reference : REFLECTION ( adc -- +n ) 0 adc ; \ FLOOR sensor result is scaled and gives a number from 0 to 10 : FLOOR ( adc -- s ) reflection 180 / ; \ Examples (Cosey's advanced commands): \ 0 = No ravine Table edge detection \ 1 = ravine at left \ 2 = ravine in front \ 3 = ravine at right : RAVINE ( -- 0|1|2|3 ) 01 >on 01 floor 5 < if 3 exit then \ Right sensor 04 >on 02 floor 5 < if 2 exit then \ Middle sensor 10 >on 05 floor 5 < if 1 exit then \ Left sensor 0 ; \ No floor sensor at all triggered \ True if reflection sensor on the backside goes over the edge : BACKWARD? ( -- f ) 10 >on 0E floor 5 < ;
More info look at specific implementations, if any.