Servo control not sooo bad but...

Ok, so on Friday night I began testing out the servo motor more. I got the motor to move both from a program and from a potentiometer.

After taking the code from the website to make the servo move to the left then to the right I wanted to add in some buttons to control the direction. This took some figuring out but eventually I understood that the pulsewidth that the PIC is sending out must stay between two constants: minPulse and maxPulse. While I'm not totally sure if this is correct but pretending the pulseWidth is a degree element 0 degrees to 200 degrees (more like 180) it was easier to see how the variable referred to position.

here's the code for the button servo action.

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INPUT portd.1
INPUT portd.0
OUTPUT portc.3

start:

pulseWidth VAR BYTE
' set up constants with the minimum and maximum pulsewidths
minPulse CON 50
maxPulse CON 250
' set up a constant with the time between pulses:
refreshPeriod CON 20

' set an initial pulsewidth:
pulseWidth = minPulse

main:
' change the angle for the next time around:
IF (pulseWidth <= maxPulse) AND (portd.1=1) THEN
pulseWidth = pulseWidth+1
GOSUB move
HIGH portd.2
ELSE
pulseWidth = pulseWidth
LOW portd.2
ENDIF

' change the angle for the next time around:
IF (pulseWidth >= minPulse) AND (portd.0=1) THEN
pulseWidth = pulseWidth-1
GOSUB move
HIGH portd.3
ELSE
pulseWidth = pulseWidth
LOW portd.3
ENDIF
GOTO main

move:
'take the output pin low so we can pulse it high
LOW PORTC.3
' pulse the pin
PULSOUT PORTC.3, pulseWidth
' pause for as long as needed:
PAUSE refreshPeriod
RETURN


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and a button servo picture.



I got the code for the servo to be controlled by a potentiometer and tried it out.
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' Define ADCIN parameters
DEFINE ADC_BITS 10 ' Set number of bits in result
DEFINE ADC_CLOCK 3 ' Set clock source (3=rc)
DEFINE ADC_SAMPLEUS 50 ' Set sampling time in uS

sensorValue VAR WORD ' Create variable to store result

TRISA = %11111111 ' Set PORTA to all input
ADCON1 = %10000010 ' Set PORTA analog and right justify result
PAUSE 500 ' Wait .5 second

pulseRange VAR WORD
pulseWidth VAR BYTE
' set up constants with the minimum and maximum pulsewidths
minPulse CON 50
maxPulse CON 250
' set up a constant with the time between pulses:
refreshPeriod CON 20

' set an initial pulsewidth:
pulseWidth = minPulse
pulseRange = maxPulse - minPulse

main:
ADCIN 0, sensorValue
'take the output pin low so we can pulse it high
LOW PORTC.3
' pulse the pin
PULSOUT PORTC.3, pulseWidth
' pause for as long as needed:
PAUSE refreshPeriod


pulseWidth = minPulse + (pulseRange * (sensorValue/10)) / 100

' change the angle for the next time around:
'IF pulseWidth > maxPulse Then
' pulseWidth = minPulse
'Else
' pulseWidth = pulseWidth + 1
'Endif

GOTO main

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I have another project from sustainable energy that I am working on that involves solar panels. I will post some information about that later on but think about charging a capacitor from a solar panel and then releasing it when it reaches a desired voltage. It makes a project very organic in the sense that it totally depends on the sun for life. I think these will make incredibly interesting opportunities for advocating alternative energies.

See you all in class.