Nuts and Volts - February 2011

C:\Program Files\Mecanique\MCS\FLICKERING CANDLE.pbp

■ FIGURE 5

'**************************************************************** '* Name : flickering candle * '* Author : Russ Kincaid * '* Date : 10/22/2010 * '* Version : 1.0 * '* Notes : A SINGLE LED IS VARIED IN BRIGHTNESS RANDOMLY * '* : WHILE THE RATE OF BRIGHTNESS IS VARIED RANDOMLY * '****************************************************************

REM REM DEVICE = 12F675

CMCON = 7 'SETS DIGITAL MODE ANSEL = 0 'GPIO.0 TO GPIO. 3 SET AS DIGITAL TRISIO = 0 'ALL OUTPUTS BUT GP3 (PIN4) IS INPUT ONLY VRCON. 7 = 0 'TURN OFF VOLTAGE REFERENCE TO SAVE POWER DEFINE DEFINE OSCCAL_1K 1 'TO SAVE OSCILLATOR CALIBRATION d VAR VAR BYTE BYTE 'DUTY CYCLE OF PULSE, 127=50% t VAR VAR VAR VAR BYTE BYTE 'SPEED OF FLICKERING J VAR VAR AR AR BYTE BYTE BYTE BYTE 'CONTROL VARIABLE START: RANDOM d RANDOM RANDOM d 'DOUBLED TO MAKE IT MORE RANDOM RANDOM t FOR FOR J = 50 TO TO d STEP STEP 5 'STEP 1 WAS TOO SLOW PWM PWM GPIO.0,J,1

PAUSE PAUSE PAUSE PAUSE t 'MILLISECONDS PER STEP, UP TO 255 NEXT NEXT J FOR FOR FOR FOR J = d TO TO 50 STEP STEP - 5

PWM GPIO.0,J,1

PAUSE PAUSE t NEXT NEXT J RANDOM d 'SINGLE TO BE DIFFERENT RANDOM OM t FOR FOR J = 50 TO TO T d STEP STEP 5 'STEP 1 WAS TOO SLOW PWM PWM GPIO.0,J,1

PAUSE PAUSE t 'MILLISECONDS PER STEP, UP TO 255

NEXT NEXT NEX NEX J FOR FOR FO FO J = d TO TO TO TO 50 STEP STEP - 5 PWM PWM GPIO.0,J,1

PAUSE SE t NEXT XT J GOTO START END

■ FIGURE 6

■ FIGURE 7

railroad runway for an airport (see Figure 5). Quick explanation: First, I want to use one 4017 chip, but I need a 20 LED strobe light for the runway, and only have very limited space on the board. So, I was thinking why not use the 4017 twice for the 20 LEDs.

I figured pin 12 goes high for 10 counts, and then it goes low for another 10 counts. While thinking about this, how about putting a FF such as a 4013 coming from pin 12 of the 4017. This should give me what I want — a 20 step strobe effect. My question is will this work? If so, what do I do with the other pins of the 4013 which is 1/2 used?

— Craig Kendrick Sellen

■ FIGURE 8

AThe only change I made to your schematic is to connect the D input of the 4013 to the notQ output so that the FF toggles. Good job. The unused inputs of the 4013 are grounded.