Electronic Circuits and Projects Forum

I wrote these codes in PIC16F84a

Code :

    list      p=16F84A             ; list directive to define processor
    #include <p16F84a.inc>         ; processor specific variable definitions
 
    __CONFIG   _CP_OFF & _WDT_OFF & _PWRTE_ON & _XT_OSC
 
org 0x0
	cblock 0x0c	
	d1,d2,d3
	endc
 
		bsf		STATUS,RP0
		movlw	b'00000'
		movwf	TRISA
		bcf		STATUS,RP0
 
START	movlw	b'11111'
		movwf	PORTA
		call 	Delay2msec
		movlw	00h
		movwf	PORTA
		call 	Delay18msec
		goto	START
 
Delay18msec
			;17993 cycles
	movlw	0x0E
	movwf	d1
	movlw	0x0F
	movwf	d2
Delay18msec_0
	decfsz	d1, f
	goto	$+2
	decfsz	d2, f
	goto	Delay18msec_0
 
			;3 cycles
	goto	$+1
	nop
 
			;4 cycles (including call)
	return
 
Delay2msec
			;1993 cycles
	movlw	0x8E
	movwf	d1
	movlw	0x02
	movwf	d2
Delay2msec_0
	decfsz	d1, f
	goto	$+2
	decfsz	d2, f
	goto	Delay2msec_0
 
			;3 cycles
	goto	$+1
	nop
 
			;4 cycles (including call)
	return
 
 
	END

The motor goes to the desire angle but it shake every 0.5second and stop shaking for 1second then shake for 1/2second and doing it again and again Anyone know why?

Put your scope on the servo pin or run it through MPLABs simulator.

I finish my testing and I know the working range of my servo motor its between 0.8ms and 2.1ms the angle don't know still need to get it soon .

About shaking i will do as you said bill.

You think the control wire consume alot of current? More than the PIC can handle ? Or I am thinking too much?

Thanks in advance

Hello again,

I did the oscilloscope test it fine I can see nice square wave.
I am using the same power supply for the servo and the PIC you think that has to do something with it?

BUT the skaking is still there

Thanks in advance

The servo control wire draws very little current. Many servo controllers have 100ohm resistor in series anyway.

THanks everyone for replying,

Q1> I have PIC16F877, HOw many servo motor can be controlled using it?
Q2> I need to send same command to 3 servo motor at the same time, do i hook up the RB0 to 3 servo motor?

A skilled programmer could drive as many servos as there are output pins.

One Output pin per servo

Stop worrying about servos till you unterstand the PIC and MPLAB better.

I am trying to design a power supply for my servo motor.
Number of servo = 18
Servo specification
Torque: 347 oz/in @ 4.8V, 403 oz/in @ 6V
Speed: .19 sec/60° @ 4.8V, .15 sec/60° @ 6V
Current rating i heard it is 2.5A at max not sure ....

Any idea how my power supply should be or ratting ?