Here is an amusing project, which my main
      purpose was to first - use up the last three PIC12F675 processors
      I had in my parts drawers, and second - to experiment with a
      tricolor RGB LED. The final project took about a week in spare
      time after work to produce, and produces a very brilliant, and
      very pure light for each color. So much fun in the dark at night!

      
Here are some images,
      schematic, and code in CCS-C for this interesting piece of hardware.
      I built it into a strong metal enclosure, and it runs nicely
      on two 9v batteries. The functional description follows in each
      panel.



      

The
      box is a strong cast aluminum enclosure four inches wide, painted
      wrinkle black. (Allied Electronics) When the power switch is
      ON, the knobs adjust the individual brightness of each 1 watt
      color LED in the lamp, for a total of 3 watts when all are on.
      The range is off to full brightness with each knob. The little
      tab at the top? Thats so you cant see the side of the super bright
      LED and have it blast you with its side light. (You will see
      purple spots for a while)
 

      

End
      on view of 3W LED. There are three chips in one bubble lens,
      and the output is a full 180 degrees producing a flood effect.
      By mounting the unit directly on the metal box, we heat sink
      the back and keep all cool since 3w is pretty hot in such a small
      package!
 

      

Inside
      the box. Two batteries at the top for power, and below is the
      circuit board with the 3 PIC's, a voltage regulator for them,
      three TIP120 power darlingtons (my favorites), some filter caps,
      and the power resistors. (2W). The black foam is to keep everything
      inside from rattling. On the left are the three 100k pots. I
      would have preferred 10k pots, but thats all I had in the junk
      drawer...
 

      


      
Schematic - CLICK
      TO ENLARGE.

      
Theory of Operation:
      The PIC's read the pot and digitize to 10 bit. Then put out a
      PWM signal at 1khz period that varies from about 10uS to full
      on in response. The TIP120s are a high gain power Darlington
      NPN transistor which drive the series R's to drive both the on
      board small red LED's and onward to the power resistors to drive
      the 3W RGB Led. The LED was obtained from Adafruit. (adafruit.com)


      
Fun in the Dark!

      
Here are some tests
      in the house at night to show the effects of separate and combined
      light colors on a planter we have near the kitchen.  This is
      the very same plants our autonomous robot has been watering for
      nearly a year now, and are growing well. They are bell pepper
      plants. The entire room lights up when you turn those LED's on.
      I used a hand held camera to take these!

      
The first
      image is in RED light:

      


      
Next,
      we turn on only the GREEN light:

      


      
Finally
      we use only the BLUE light:

      


      
Now here
      is the color of a typical plant lamp - RED + BLUE (Wow, look
      at the color of those leaves!)

      


      
Looking
      closer, we can see the leaves are black. This is because all
      of the magenta light is absorbed. Pretty cool, ay?

      




      
Code
      for this project: CCS-C Compiler

      
//****************************************************************************

      //Chris Schur

      //Project Name here: 12F675 NO xtal LED PWM

      //Date: 9/23/16

      //****************************************************************************

      
/*Description of
      this Program: This program Will use the 100k pot and vary the

      PWM out put from near zero on time to near 100% on time at a
      pulse period of

      1ms. Works great!*/

      
//I/O Designations
      ---------------------------------------------------

      // A0 (GPIO0): An0 = Potentiometer Input 

      // A1 (GPIO1): X (An1) 

      // A2 (GPIO2): Digital Output to LED

      // A3 (GPIO3): X (can ONLY be input)

      // A4 (GPIO4): X (An3) 

      // A5 (GPIO5): X

      
//--------------------------------------------------------------------

      
//Include Files:

      #include <12F675.h> //Normally chip, math, etc. used is
      here.

      //Directives and Defines:

      
#device ADC=10
      //This directive will only work if put RIGHT HERE first...

      
#fuses NOPROTECT,NOMCLR

      #use delay(internal=4MHz)

      #use fast_io(A)

      
//****************************************************************************

      //-- Main Program

      //****************************************************************************

      
void main(void)
      {

      
// Set TRIS I/O
      directions, define analog inputs, compartors:



      set_tris_A(0b101001); //sets port directions



      //(analog inputs digital by default)

      setup_adc_ports(sAN0);

      setup_adc(ADC_CLOCK_DIV_2);

      set_adc_channel(0);

      

      
//Initialize variables
      and Outputs: --------------------------------------



      int16 result; //0 - 1023 out of ADC

      int16 on_pulse; //LED high pulse width in uS

      int16 off_pulse;



      //----------------------------------------------------------------

      
//MAIN LOOP:

      
while (true) {

      
//First read ADC

      result = read_adc(); //0 - 1023



      //calculate pulse width:

      on_pulse = (result); //for a range of 0 to 1023uS

      off_pulse = (1023 - on_pulse);





      //next send pulse to servo output:



      if (on_pulse > 20) { //The fastest you can on off is like
      20us. so we do this



      output_high(PIN_A2); //LED out = 1 

      delay_us(on_pulse); //high time

      output_low(PIN_A2); //turn off pulse 



      delay_us(off_pulse); //remainder of 1ms PWM pulse max



      } //if



      } //while

      
} //main


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