LED Machine Tach For Tired Eyes

[Archangel]

Hello,
I am trying to make a tachometer for my lathe and milling machines. I have joined M E Labs 7 segment example to some code I was experimenting with a year ago or so. The code does count and return a value, I have not attempted to make it return any useful numbers yet, as I am not at all satisfied with what it displays, 1: the portA.3 output is much brighter than the other 3, all switched with 2n3906 transistors, and the less bright displays are too dim. I decreased the initial pause directly after T1CON to increase the loop speed so as to make the display flash faster than my eyes can see,This makes the displays brighter too, I think however I will never be able to make enough pulses to use this as anything but an RF freq. counter with this setting. What I am contemplating is to add TTL latches to the ABCDEFG and DIG ports to freeze the LEDs on between cycles. Does anyone have better Ideas?
Thank You
Joe S.

oh BTW PIC 16F876A and 2" tall LED 7 Segment displays

@ __config  _HS_OSC & _WDT_OFF & _PWRTE_ON & _LVP_OFF  & _BODEN_OFF
define OSC 20
CMCON  = 7
ADCON0 = 0
ADCON1 = 7


TrisA = %00000000
TrisB = %00000000
TrisC = %00000001
Segments Var	PORTB
Digits	 Var	PORTA
PORTC = %00000011
PAUSE 500
PORTC = %00000000

CounterTotal var word
RPM          VAR WORD 
i	           Var Byte
n	           Var Byte

RPM = 0
T1CON = %00000111 ' bits 0, 1, 2 set high, prescaler to 1:1



                                                                                        
START:
TMR1L = 0
TMR1H = 0


mainloop:

counterTotal.lowbyte=TMR1L
counterTotal.highbyte=TMR1H
TMR1L = 0
TMR1H = 0 

T1CON.0=1
pause 5   <font color = red>' the greater the delay the slower the display flashes</font color>
rpm = (CounterTotal * 2) 'no attempt has been made here to get accurate numbers


	GoSub display	' Display the value
T1CON.0=0	
	GoTo mainloop		' Do it forever


' Subroutine to send the number (0 - 9999) in Value to LEDs
display:
	For i = 0 To 3		' Loop through 4 digits
		n = RPM Dig i	  ' Get digit to display
		GoSub display1	' Display the digit
				      ' Leave it on 2 millisecondS
	Next i			      ' Do next digit
	
	Return


' Surboutine to display one digit on LED
'  i = digit number
'  n = number to display
display1:
	'Digits = $ff		' All digits off to prevent ghosting

	' Convert binary number in n to segments for LED
	Lookup n, [$40, $79, $24, $30, $19, $12, $02, $78, $00, $18,$7f], Segments
  ' logic low complements
	' Set digit pin i to 0 (on) and the rest of the pins to 1 (off)
	Digits = ~Dcd i
  Pause 2<font color = red> Increase to make digits brighter and flicker worse</font color>
	Return
	
	end

[skimask]

Feed your individual digits into a few 74LS373 (or 74LS573) latches, kicks the latch pin, have the output from the 393's drive ULM2803's which connect directly to your 7 segment LEDs. Or might not even need the ULN2803, could probably drive the LEDs directly from the '373...

Set everything up, set the output enables high, set the output latches high...

Pull the output enable pin on the first '373 high, put the first number for output on PortA, toggle the first '373 latch pin, pull the first '373 output enable pin low, leave it
Put the output enable pin on the second '373 high, put the second number for output on PortA, toggle the second '373 latch pin, pull the second '373 output enable pin low, leave it. Since you didn't trigger the latch enable pin on the 1st '373, it won't do squat but sit there and output for you...thereby stay sitting still.

Wash, lather, rinse, repeat, all the way down the line...


Or even easier, buy up one of those 'large-ish' backlit LCDs.

[George]

I did a similar counter several years back with some 4" tall digits I just over drive the LEDs, for example if you have 4 digits and each segment is 20mA, pump each segment to 80mA. I also found it necessary to put a resistor to each of the 7 outputs to the LED segments rather than just a common resistor - else I found that a 1 was much brighter than anything else - and of course the 8 was quite dim.

[Darrel Taylor]

Hi Joe,

I think the problem is in the pauses.
The first 3 digits are on for 2ms each, then the last digit is on for 7ms (2ms + 5ms in the main loop). So the dutycycles are around 15% for the 3 digits and over 50% for digit 4.

Removing the 5ms pause in the Mainloop should make them all the same brightness with 25% duty.

But you still need a Time Base if you want to read RPM, and you'll need to do some math to convert the result which will cause small variances in the brightness as the delays thru the loop change.

This sounds like the perfect job for Instant Interrupts.

I just happen to have some hardware available, that's hooked up the same way as the meLabs 7-segment demo.
http://www.picbasic.co.uk/forum/show...?p=58076#58076

Feel like trying it a different way?
<br>

[Archangel]

Hi Joe,

I think the problem is in the pauses.
The first 3 digits are on for 2ms each, then the last digit is on for 7ms (2ms + 5ms in the main loop). So the dutycycles are around 15% for the 3 digits and over 50% for digit 4.

Removing the 5ms pause in the Mainloop should make them all the same brightness with 25% duty.
<br>

That answered a question I didn't exactly know how to ask.

But you still need a Time Base if you want to read RPM, and you'll need to do some math to convert the result which will cause small variances in the brightness as the delays thru the loop change.
<br>

I thought the pause was the time base! In the example it was 500.

This sounds like the perfect job for Instant Interrupts.

I just happen to have some hardware available, that's hooked up the same way as the meLabs 7-segment demo.
http://www.picbasic.co.uk/forum/show...?p=58076#58076

Feel like trying it a different way?
<br>

OH HECK YES . . . I was getting ready to output BCD into some 4511s so as to have a latch to get brightness without flicker . . . In fact to that end I ordered some common cathode LEDs last night, I already have common anode ones here.<h2><b>LEAD THE WAY MASTER</h2></b>Thank You Darrel.

[Archangel]

Hello again,
M E Labs has a lot of code samples, many of you have examples there, and here is a sample from mister_e that I believe will do what I need without all the overhead associated to using latches. I am posting it here as the download from ME Labs has some cut paste errors, specificly duplicate IF THEN loop which upset my compiler's little tummy I modified mister_e's code only enough to port it to a 16F628A, . . . Great piece of work Steve ! Thank You !

' Pulse counter
' =============
'
' File name : Count_Display.bas
' Company : Mister E
' Programmer : Steve Monfette
' Date : 27/12/2004
' Device : PIC16F84A-20/P
'
'
' This program display to 3 x 7 segments dislay the result of
' pulses count on PORTA.4 pin/sec.
'
' Hardware connection :
' ---------------------
'      1. 3 X 7 segments display on PORTB<7:0>
'      2. 3 X PNP transistor on PORTA<3:0> to drive common anode
'         of each 7 segments display
'
'
' Programming mode and PIC define
' -------------------------------
'
@ __config _HS_OSC & _WDT_ON & _PWRTE_ON & _LVP_OFF
CMCON=7       ' ADDED FOR PIC16F628A   
DEFINE OSC 20 ' use 20 MHZ oscillator


    ' I/O Definition
    ' --------------
    '
TRISA = %11111000 ' PORTA  : <2:0> outputs to common Anode of 7 segment
                      '                1. PORTA.0 More significant
                      '                2. PORTA.2 Less significant
                      '        : PORTA.4 input for signal
                      '
TRISB = 0         ' PORTB connected to 7 segments
                  '       B0 : segment a
                  '       B1 : segment b
                  '       B2 : segment c
                  '       B3 : segment d
                  '       B4 : segment e
                  '       B5 : segment f
                  '       B6 : segment g
                  '       B7 : segment decimal dot
                      

' Internal EEPROM definition
' --------------------------
'
data @0,192,249,164,176,153,146,130,248,128,144 ' table to convert
                                                ' numbers to 7 segments
                                                ' pattern output when
                                                ' drive invert
                                                    


' Interrupt and register definition
' ---------------------------------

OPTION_REG = %1111000   ' TMR0 clock source : RA4/T0CKI
                        ' increment on low to high transition
                        ' Prescaler assign to WDT
                        ' WDT rate 1:1
                        '
INTCON = %10100000      ' Enable global interrupt
                        ' Disable EE write interrupt
                        ' Enable TMR0 overflow interrupt

        
    ' Variable definition
    ' -------------------
    '
DisplayPort  var PORTB   ' Port for 7 Segments
ClockInput   var PORTA.4 ' Input pin for signal
_7Seg1       con 14      ' enable more significant 7 segment display
_7Seg2       con 13      ' enable mid significant 7 segment display
_7Seg3       con 11      ' enable less significant 7 segment display
Digit_1          var byte    ' Hundreds digit
Digit_2          var byte    ' Tenth digit
Digit_3          var byte    ' Unit digit
ToBeDisplay  var word    ' Result of count to be send to 7 segment display
Display      var byte    ' Temp variable
DisplayLoop  var byte    '
Delay        var word    ' Variable for Delay loop
OverFlowVar  var word        '
Thousands    var bit         ' Flag for count >= 1000 & < 10 000
TenThousands var bit         ' Flag for count >= 10 000

    ' Variable and software initialisation
    ' ------------------------------------
    '
tobedisplay = 0 ' set initial value of count
TMR0 = 0        ' reset prescaller
On interrupt GoTo SetVarToBeDisplay
    
MainLoop:

    ' MainLoop
    ' ---------
    '
    ' 1. display the result of the count on RA4 pin
    ' 2. refresh display
    ' 3. reset Timer0
    ' 4. reload prescaler.
    '
    ' Duration of the procedure : 1 sec
    '           fine tuned by DelayBetweenEachDisplay Sub
    '
    ' Looping 1 sec and get results of the pulse count in
    ' TMR0 + OverFlowVar
    '
DisplayRefresh:
        '
    ' Testing amount of count
    ' -----------------------
    '
    ' Get the result of count and place decimal point flag
    ' on the according 7 segments
    '
    If tobedisplay>= 1000 Then
    tobedisplay = tobedisplay / 10
    Else
        tenthousands = 0
           thousands = 1
EndIf
     
    '
    ' convert digit to 7 segment output pattern
    ' -----------------------------------------
display=ToBeDisplay dig 2 ' Read hundreds digit
read display, digit_1     ' Convert hundreds
     if thousands==1 then digit_1=digit_1 & $7F ' enable decimal dot
                                                   ' by clearing PORTB.7

    display=ToBeDisplay dig 1 ' Read tenths digit
    read display, digit_2     ' Convert tens
        if tenthousands==1 then digit_2=digit_2 & $7F ' enable decimal dot                          '
                                                  ' by clearing PORTB.7
                                                  
        display=ToBeDisplay dig 0 ' Read units digit
        read display, digit_3     ' Convert units
    '
    '
    ' Send digit to 7 segments
    ' ------------------------
    For displayloop = 0 To 111 ' loop for about 1 sec

        ' display hundreds
        ' ----------------
        PORTA=_7seg1        ' enable hundreds 7 segment
        displayport = digit_1 ' display
        GoSub DelayBetweenEachDigit
        
        ' display tenth
        ' -------------
        PORTA=_7seg2        ' enable tenth 7 segment
        displayport = digit_2 ' display
        GoSub DelayBetweenEachDigit
        
        ' display units
        ' -------------
        PORTA=_7seg3        ' enable unit 7 segment
        displayport = digit_3 ' display
        GoSub DelayBetweenEachDigit
        
    Next
    tobedisplay = OverFlowVar + TMR0
    OverFlowVar = 0 ' Reset OverFlowVar
    TMR0 = 0        ' reset prescaller
    GoTo DisplayRefresh


DelayBetweenEachDigit:

    ' DelayBetweenEachDigit
    ' ---------------------
    ' Produce delay of about 3 mSec
    '
    ' Fine tuned with MPLAB StopWatch to get MainLoop = 1 sec
    '
        For delay = 1 To 307
            @ nop
        Next
        @ nop
        @ nop
        @ nop
        @ nop
        @ nop
        @ nop
        @ nop
    Return


    disable
SetVarToBeDisplay:
    '
    ' SetVarToBeDisplay
    ' -----------------
    ' interrupt routine of TMR0 overflow
    '
    ' Reset prescaller
    ' Reset overflow flag
    '
    OverFlowVar = OverFlowVar + 256
    INTCON.2 = 0 ' clear overflow flag
    TMR0 = 0     ' reload TMR0
    Resume
    enable

END

[Darrel Taylor]

That's a "Straw", I'm a "Camel", and my back is broken.

2 days of work, and as I'm posting it I see ... "Nevermind, I'll use mister-e's program".
Arrrrghhh.

Enjoy.

[Archangel]

That's a "Straw", I'm a "Camel", and my back is broken.

2 days of work, and as I'm posting it I see ... "Nevermind, I'll use mister-e's program".
Arrrrghhh.

Enjoy.

No NO NO NO Don't be that way Darrel, I really want to see what you have come up with! You and Mister_e, Melanie, and a few others all write really sweet code, and I am humbled, that you have made this effort. I thought you were standing by to see what I could come up with (I know, there I go thinkin' again). I just really thought this example needed to be "showcased"as a lot of NOOBS may have tried unsucessfuly to use it, due to aforementioned . . . misprint? For sure I have no intent to offend Professor Rex Nexus Taylor of the Crownhill University. I'm like an old hound dog with a bone, keep on shakin' it and shakin' it till I get the marrow out of it, now for steak . . . as for you being a Camel, yea like Secretariate was huh?