LED Light detector

jgjonola · 2009-07-02 01:07

Hi everyone, I am just getting back in to playing with SX/B (its been a few years.) I was playing around with making an LED light detector. So i have an led hooked between RB.1 and RB.2 with a resistor in series. Here is the code:

'PWM.SXB
DEVICE         SX28, OSC4MHZ, TURBO, STACKX, OPTIONX
FREQ         4_000_000

led2 PIN RB.2
led1 PIN RB.1
led7 PIN RB.7
light VAR Word
time CON 2000


'Code

PROGRAM Start
Start:

led1 = 1
led2 = 0
DO
  OUTPUT led2
  OUTPUT led1

  RCTIME led1, 1, light

  IF light = 0  THEN 
    led7 = 1 
  ELSE 
    led7 = 0
  ENDIF

PAUSE time
LOOP

I have another LED connected to RB.7 that is supposed to turn on if the value of light is 0. Not seeming to work. I copied this from similar code i found from the basic stamp and it worked fine with my stamp. I just made a few changes for the SX and no go...

Here is the code i used as a base for the Stamp:

'{$PBASIC 2.5}
'file:LED_Emitter_Detecter.bs2
'Clark Radcliffe
'Michigan State University
'July 30, 2007
'Requires an LED in series with a 220 Ohm resister
'between pin 1 and the LED connected to pin 2
'Declarations
Pin2 PIN 2
Pin1 PIN 1
light VAR Word
time CON 2000
'Code
DEBUG "Start test...", CR
DO
DEBUG "LED is a detecter (LED off and charging)", CR
Pin1 = 1
Pin2 = 0
PAUSE 10
RCTIME pin1, 1, light
DEBUG "Light measured = ", DEC light, CR
PAUSE time
LOOP

Thanks!
John G

Benoit · 2009-07-02 01:17

John,

I don't see in your code where RB.7 is set as an output. It could be that the pin is set as an input.

-Benoit

Zoot · 2009-07-02 01:19

Your code examples are not exactly the same; in the SX version you are presuming you will get an RCTIME of 0 -- seems unlikely as there will probably always be *some* capacitance.

Your Stamp code debugs out the value; for the SX, use WATCH and then run the program in DEBUG mode with your Key connected. Then try it out and see what values you get for various light intensities -- once you have a decent threshold number established, then you can have an LED turn on and off based on that threshold.

Then, shouldn't the loop turn the led back on (and maybe pause) to charge up the capacitance again?

'PWM.SXB
DEVICE         SX28, OSC4MHZ, TURBO, STACKX, OPTIONX
FREQ         4_000_000

led2 PIN RB.2 OUTPUT
led1 PIN RB.1 OUTPUT
led7 PIN RB.7 OUTPUT
light VAR Word
time CON 2000

someThreshold CON 100 ' or whatever a good number ends up being

WATCH light

'Code

PROGRAM Start
Start:


DO
  'OUTPUT led2
  'OUTPUT led1 

  'led1 = 1
  'led2 = 0

  HIGH led1 ' makes high and output
  LOW led2

  PAUSE time

  RCTIME led1, 1, light  ' also automatically makes led1 an input

  IF light < SomeThreshold  THEN 
    led7 = 1 
  ELSE 
    led7 = 0
  ENDIF

LOOP

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Post Edited (Zoot) : 7/2/2009 1:26:56 AM GMT

jgjonola · 2009-07-02 20:19

Zoot,
That was it. Thanks! It works perfectly now.

John Gjonola

LED Light detector

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