Forth-eV Wiki

User Tools

Site Tools

You are here: Forth Wiki » Forth-ev Wiki » pfw » Reflection sensors
Trace:
en:pfw:reflection-sensors

Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revisionPrevious revision
en:pfw:reflection-sensors [2023-09-04 18:18] – gelöscht - Externe Bearbeitung (Unbekanntes Datum) 127.0.0.1en:pfw:reflection-sensors [2023-09-04 18:18] (current) – ↷ Seite von pfw:reflection-sensors nach en:pfw:reflection-sensors verschoben uho
Line 1: Line 1:
 +{{pfw:banner.png}}
 +====== Reflection sensors ======
 +
 +===== Idea =====
 +
 +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 =====
 +
 +|{{https://user-images.githubusercontent.com/11397265/154144243-3562aae3-f703-405f-9148-8460dfb92e05.jpg?400|TCND5000}}                                |{{https://user-images.githubusercontent.com/11397265/154144262-307428fa-ce24-453f-a98e-5db9d4db09f9.jpg?400|Sketch schematics}}           |
 +|{{https://user-images.githubusercontent.com/11397265/154559970-26f69aa7-d06c-43a0-a1d3-ee4ff6014d69.jpg?400|Cosey floor sensors on the front side sm}}|{{https://user-images.githubusercontent.com/11397265/154144288-a7196a4c-be4e-4c2a-8405-c2779fa51ce2.jpg?400|Reflection sensor schematics}}|
 +
 +**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!
 +
 +
 +----
 +
 +===== Pseudo code =====
 +
 +<code>
 +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
 +</code>
 +
 +===== Generic Forth =====
 +
 +<code forth>
 +\ 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 < ;
 +</code>
 +
 +More info look at specific implementations, if any.
 +
 +**Cosey robot V1.0** {{https://user-images.githubusercontent.com/11397265/154557981-a7b3d33a-0dc0-47c8-b40c-a01395871c94.jpg|Cosey V1 0}}