Electronic Circuits and Projects Forum

Originally Posted by ljcox

Yes, you can do what you like with the programme.

Have you tried to simulate it in MPLAB?

Yes, I was intending to suggest that you start a new thread in the Microprocessor section as more people with PIC expertise will see it there & be able to help you.

I haven't put it into MPLAB but will be doing so tomorrow. Then I will study it and follow up in a new thread in the desired section with any questions and as for now i'm gonna leave this thread alone.
Thanks for the response.

Response to EDIT:
Yes I do and will look at that.

After some thought about the PIC programme, I have made some minor changes to the circuit in order to make the programme simpler.

Tom,
Here is another simple programme that you may find of interest.

I wrote it some years ago for a friend who wanted a device that would switch a fan on for 1, 2, 3 or 4 hours - as set by a rotary switch.

The PIC is driven by a 32.768 kHz crystal. Therefore the PIC is operating at 8192 instructions per second.

The basic timing is done by TMR0. The prescaler is set to 256. So TMR0 is being incremented every 256/8192 = 31.25 ms.

TMR0 is loaded with the complement of the value required and it counts up. The overflow flag is set when it goes from FF to 00.

When the programme detects the overflow flag, it counts the event & and reloads TMR0.

So for a delay of 4 seconds, TMR0 is loaded with the complement of 128 (128 = 4/0.03125).

Code :

;Programme function - Operate a relay & release it after 1, 2, 3 or 4 hours.
;The timing is set by a rotary switch. Switch changes are detected by the 
; RB change interrupt function & cause the timer to restart from 0.
;Oscillator frequency = 32.768 kHz, Instruction rate = 32768/4 = 8192 Hz.
;TMR0 prescale = 256, so the frequency input to the TMR0 is 8192/256 = 32 Hz.
;If TMR0 is set to the complement of 16 (decimal) then it will overflow after
; approx 16/32 = 0.5 seconds.  
;If TMR0 is set to the complement of 128, it will overflow after 128/32 = 4 sec.
 
              LIST   P=PIC16F84,	F=INHX8M
            include "p16f84.inc"
             __CONFIG 0x3FF0	;32.768 kHz Crystal Oscillator, WDT off, Power up reset on
 
porta	equ	05	;input/output pins RA0 ~ RA4
portb	equ	06	;input/output pins RB0 ~ RB7
 
cblock 0x10				
	count1	;minutes counter (4 sec increments)
	count2	;hours counter (60 sec increments)
	temp
endc
 
#define relay	portb, 0	;relay connected to RB0
 
#define	tmr0_of	INTCON, 2	;TMR0 overflow flag
#define	sw_ch	INTCON, 0	;switch change (RB change flag)
 
	ORG	0x00		;set programme counter to 0
 
	call	init
 
	bsf		relay		;operate relay
 
restart 		;Starts from here after a switch change is detected
	bcf		sw_ch		;clear RB change flag
 
	call	delay_500m		;call 0.5 second delay to allow switch contacts to settle
 
	movlw	d'240'		;4 hour
 
	btfsc	portb, 4	;is rb4 high?
	movlw	d'60'		;1 hour
 
	btfsc	portb, 5	;is rb5 high?
	movlw	d'120'		;2 hour
 
	btfsc	portb, 6	;is rb6 high?
	movlw	d'180'		;3 hour
 
	movwf	count2		;count2 = 60, 120, 180 or 240
;the code below uses count1 & count2 to determine the relay on time.
 
loopb
	movlw	d'15'		
	movwf	count1		;4 sec * 15 = 1 minute
 
loopa
	call	delay_4s
 
	btfsc	sw_ch		;has a switch changed?
	goto	restart		;yes - restart to determine the new time setting
 
	decfsz	count1		;decrement count1 by 1, skip if 0
	goto	loopa		;count1 is not 0, so repeat
 
	decfsz	count2		;count1 is 0 , so decrement count2
	goto	loopb		;count2 is not 0, so repeat
 
	bcf		relay		;count2 is 0, so release relay
 
	sleep	;PIC goes into low power mode & does nothing
	NOP
 
;sub routines
 
delay_4s
	movlw	d'127'		;4 second delay @ 32.768 kHz
	goto 	$+2
 
delay_500m
	movlw	d'15'		;0.5 second delay @ 32.768 kHz
	movwf	temp		
	comf	temp, w
	movwf	TMR0
	bcf		tmr0_of
 
	btfsc	sw_ch		;has a switch changed?
	return				;yes - exit loop
 
	btfss	tmr0_of		;await TMR0 overflow
	goto	$-1
	return
 
init
	bsf		STATUS, 5	;selects BANK 1
 
	clrf	TRISA		;make RA0:4 outputs
 
	movlw	b'01110000'	
	movwf	TRISB       ;RB0:3,7 outputs  RB4:6 inputs
 
	movlw	b'10000111'	;sets prescaler to 256, internal clock
	movwf	OPTION_REG	
 
	bcf		STATUS,5	;selects bank 0
 
	clrf	INTCON
	clrf	porta		;clears porta
	clrf	portb		;clears portb
 
	bsf		INTCON, 3	;RB change enable
	bsf		INTCON, 5	;TMR0 overflow enable
	return
 
	end

Very good.

Now I can see what it does.

There is a lot in the .asm files that I have not used or knew was possible, eg. Macros & if functions.

Originally Posted by ljcox

Very good.

Now I can see what it does.

There is a lot in the .asm files that I have not used or knew was possible, eg. Macros & if functions.

Thank you Len.

I am studying them now, they are something new to my self too.

Talk later

Tom

Hi,

I noticed that there is still some current running through the rows and maybe the columns so I increased the inline resistors from 1K0 to 2K0 and still see real faint flicker when leds are not supposed to be on.

Anyone know what may be a solution to this? You may have to watch ((((MY VIDEO)))) from post #25 to understand.

PS. attachment below of the schematic below.

Anyone know what may be a solution to this?

Try adding a respective resistor (say 10 x the base resistor value) between base and emitter of each transistor, to ensure turn-off.

Originally Posted by alec_t

Try adding a respective resistor (say 10 x the base resistor value) between base and emitter of each transistor, to ensure turn-off.

That should not be necessary since the PIC outputs switch between V+ & Gnd.

I study your circuit further & post later.