Comparator circuit thoughts....

[mackrackit]

At this point I would say whatever you have laying around. The 88 is good for starters. Might run out of memory or pins later but might not.

But how are you writing code if you have not picked a PIC?

[kevlar129bp]

I have opted to write the code for the '88. Hopefully I don't run out of space . I'll keep you posted on that one.

[kevlar129bp]

Major stupid question...
If I declare something like Number var BYTE...
Then I do: Number = 1.01567
Does that get truncated to 1, or something else, or rejected altogether?

Wow, I feel like a moron for asking! Sorry.

Chris

[mackrackit]

No problem with the questions.....
Unless you get into floating point routines we are stuck with integer math.
But if You need to be more accurate there are ways to do so. Basically mutiply by a power of ten and ...... Well you get the idea.

So it would become 1.

The PBP manual has a good section about the math.

[kevlar129bp]

Cool... I guess I'll put this mess up for you to take a look at. Mark it up at will. Thanks a ton....and here goes

'   Name    : THC.BAS                                      
'   Author  : Me                                                
'   Notice  : Copyright (c) 2009 None                           
'          : All Rights Reserved                               
'   Date    : 10/20/2009                                        
'   Version : 1.0                                               
'   Notes   : 
'                                                                                          
'
include "MODEDEFS.BAS"
'
'\\\\ADC DEFINES////
DEFINE ADC_BITS 8       'Number of bits in ADCIN result
DEFINE ADC_CLOCK 3      'ADC clock source (rc = 3)
DEFINE ADC_SAMPLEUS 50  'ADC sampling time in microseconds
CVRCON = 143            'Reference on, not tied to pin, set to 3.59vdc
ANSEL = 64              'Enable analog select, select channel 6
CMCON = 7
'
'\\\\SERIAL PORT SETUP////
DEFINE HSER_RCSTA 90h   'Enable serial port 
define HSER_TXSTA 24h   'Enable transmit 
define HSER_SPBRG 25    'Set baudrate to 9600                   
DEFINE HSER_CLOERR 1    'Automatic clear overrun error
INTCON = 64             'Enable peripheral interrupts
PIE1 = 32               'Enable AUSART receive interrupt
'
'\\\\PINS SETUP////
TRISB.0 = 0             'Up LED Output
TRISB.1 = 1             'Enable THC Input
TRISB.3 = 0             'LCD Pin
TRISB.4 = 0             'Dn LED Output
TRISB.6 = 0             'THC Enabled LED Output
TRISB.7 = 1             'Scaled Torch Voltage Analog Input
'
'\\\\VARIABLE DECLARATIONS////
TargetVDC var byte      '000-256 Allowed
TargetVDCDiv var byte
TorchPin var PORTB.0
TorchVoltsNow var byte
TorchDown var PORTB.4
TorchUp var PORTB.0
EnableIn var PORTB.1
TorchVoltsFull var byte
'
'
'
'\\\\POWER UP STARTS HERE////
Pause 500               'Wait for LCD to startup
TargetVDC = 120         'Start up target volt value
'
'
'\\\\LOOK FOR SERIAL DATA ON AUSART RX PIN////
on interrupt goto NewSerialData
'
NewSerialData:
hserin [wait ("V"),DEC3 TargetVDC]
TargetVDCDiv = TargetVDC / 256
goto mainloop
'
'\\\\START MAIN PROGRAM LOOP HERE////
Mainloop:
TargetVDCDiv = TargetVDC / 256
    IF Enablein = 1 then
        ADCIN 6,TorchVoltsNow
        if torchvoltsnow > TargetVDCDiv then
            high torchup    'Turn off TorchUp Pin
            low torchdown   'Turn on TorchDown Pin
        else
            high Torchdown  'Turn off TorchDown Pin
            Low torchup     'Turn on TorchUp Pin
        endif
    TorchVoltsFull = TorchVoltsNow * 256
    '\\\\SEND STATUS OUT TO LCD////
    LCDOUT $FE, 1
    LCDOUT $FE, 2
    LCDOUT "PLASMA VDC : "TorchVoltsfull
    PAUSE 50
    LCDOUT $FE, $C0
    LCDOUT "TARGET VDC : "TARGETVDC
    PAUSE 50    
    HSEROUT TorchVoltsFull
else
    LCDOUT $FE, 1
    LCDOUT $FE, 2
    LCDOUT "---CONTROL IS---"
    PAUSE 50
    LCDOUT $FE, $C0
    LCDOUT "----DISABLED----"
    PAUSE 50
ENDIF
Goto mainloop

Don't be cruel....newbie with ambition!

Thanks a ton!

Chris

[kevlar129bp]

Typo in:
TorchPin var PORTB.0
Change to
TorchPin var PORTB.7

[mackrackit]

This is for comparators

CVRCON = 143

you want

ADCON1 = %00100000 'Pin #2 is voltage reference

The LCD lines and HSEROUT line should be something like

LCDOUT "TARGET VDC ", #TARGETVDC
HSEROUT [#TorchVoltsFull]

The divide by multiply by 256 should not be there. The 8bit ADC goes from 0 to 255. As we talked before withe the voltage divider feeding the ADC and using using the reference voltage. Well it worked pretty neat for you. The torch voltage will be the same "number" as the ADC value.

Other than that it should do something

Now I will toss something else at you.
Think how fast the torch move up and down. Those few line of code before the ADC is read could mean trouble. You may want to increment the movement.