PIC circuit to hold a relay on when input is removed - Page 2 - Electronic Circuits Projects Diagrams Free

dougy83 · 7th July 2009, 12:32 PM

I've no idea why you insist on using a pic. If you had a look at the circuit I posted above, you'd see that your task is very simple using a single 555.

Anyway, for a pic12F508, the following code should work. Use MPASM to assemble.

Code:

#include "p12f508.inc"

	__CONFIG _MCLRE_OFF & _WDT_OFF &_IntRC_OSC
	radix dec
	
inpin 	equ 0
outpin 	equ 1
sec90	equ	10
cnta	equ 11
cntb	equ 12
cntc	equ 13

	org 0
start:
	movlw	0
	option
	movlw 	255-(1<<outpin)
	tris 	GPIO
	
main:
	btfsc	GPIO,inpin		; wait for inpin low
	goto	main
	
	call	delay

	btfsc	GPIO,inpin		; make sure inpin is actually low
	goto	main
	
waitloop90:
	bsf		GPIO,outpin		; output high
	
	call	delay
	
	incf	sec90			; 1 second has passed
	btfss	GPIO,inpin
	clrf	sec90			; reset count if inpin is still low
	
	movfw	sec90			; test for 90 seconds past
	xorwf	90
	
	btfss	STATUS,Z		; quit after 90 seconds
	goto	waitloop90		; otherwise keep going
	
	bcf		GPIO,outpin		; reset output
	goto	main
	
; delay for a second
delay:
	movlw	6
	movwf	cntc

dloop0:
	movlw	216
	movwf	cntb
		
dloop1:
	clrf	cnta

dloop2:
	decfsz	cnta
	goto	dloop2

	decfsz	cntb
	goto	dloop1

	decfsz	cntc
	goto	dloop0
	
	retlw 	0

	END

MrDEB · 7th July 2009, 12:55 PM

all the trees are in the way
KEEP IT SIMPLE!
use the 555/556 circuit I posted
It works in multisim so it should? work for your app.
BUT learn something
BREAD BOARD the circuit then discover how and why it works.
Your opening yourself up for failure by getting the simple task to complex.

larrybeaty · 7th July 2009, 02:44 PM

I use PICs to improve my programming "skills". The more i work with them, the more macros or canned programs i collect.
I only suggest one way to solve the problem. A 555 is a good simple way to solve the problem. There are other ways depending on what parts you have on hand.
Enjoy the challange!
Larry

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7th July 2009, 12:55 PM	#17
MrDEB	He can't see the forrest because all the trees are in the way KEEP IT SIMPLE! use the 555/556 circuit I posted It works in multisim so it should? work for your app. BUT learn something BREAD BOARD the circuit then discover how and why it works. Your opening yourself up for failure by getting the simple task to complex.

7th July 2009, 02:44 PM	#18
larrybeaty	I use PICs to improve my programming "skills". The more i work with them, the more macros or canned programs i collect. I only suggest one way to solve the problem. A 555 is a good simple way to solve the problem. There are other ways depending on what parts you have on hand. Enjoy the challange! Larry