LED Machine Tach For Tired Eyes

[Archangel]

Hey Joe,

I've been real busy with other things and meant to update this sooner.

The tach is working just fine, I have milled the PCB and installed one in my SC machine and it's great. I did switch to shielded wire and had to use a 1K resistor (I already had a 10K in place and that didn't work) and a .01 uf to ground.

When I get some more time I'm going to order two more of the 4 digit displays from Sure Electronics and add them to my lathe and CNC mill.

So again, I really appreciate you providing the code (I've learned from it too) and your help.

I'll post a pic of the tach in operation later. Also, if anyone would like the schematic and PCB layout from Eagle I'll provide that.

Best regards

Hi Sam,
I appreciate the feedback! Thanks!

[Sam]

Here it is in operation ! It's doing a fine job, very happy with it.

Also a pic of the pickup coil embedded in epoxy inside a plastic tube, the magnet is epoxied to the shaft.

[DanPBP]

First, I would like to say thanks to Sam for sending me the code and the schematic.

Second, I have a question: what is the maximum RPM this circuit/code can read?

Thanks!

Daniel.

[Archangel]

First, I would like to say thanks to Sam for sending me the code and the schematic.

Second, I have a question: what is the maximum RPM this circuit/code can read?

Thanks!

Daniel.

Hi Daniel,
I added this line:

if displays > 9999 then displays = 9999

to keep the display from rolling over 9999. What use do you have for this tach? I do not think I would try it on a turbine, as it updates too slowly, but it was written for a lathe. It will go over 9999 without that line, the max is unexplored. Perhaps someone who is skilled at math could tell you. The displays can be cascaded, if you feel adventurous.

[DanPBP]

What use do you have for this tach?

I have a few brushless R/C trucks, they have an optic sensor on the transmission and I would like to read the RPM. They go up to 50.000 RPM! I'll give it a try.

[Archangel]

I have a few brushless R/C trucks, they have an optic sensor on the transmission and I would like to read the RPM. They go up to 50.000 RPM! I'll give it a try.

Cool, keep us posted, I am curious as to the limits of count. I am thinking the variable might overflow if RPM goes too high, and you might have to alter the sampling rate or use some form of prescaler.

[fratello]

I try to use code from post #1 to my thermometer with 16F628A, DS18B20 and LED display ( like in : http://melabs.com/resources/articles/ledart.htm fig.6). To another topic, I receive one working code, from one user (thanks !).
But, I am still disappointed, because MY code don't work. Please, what's wrong with him ? Thank you !

@ DEVICE pic16F628A, intOSC_osc_noclkout, WDT_OFF, PWRT_ON, MCLR_OFF, LVP_OFF, CPD_OFF, PROTECT_OFF    
TRISA= %11110000                   ' RA0..3=Outputs RA4=Input
TRISB= %00000000 			             ' RB0..RB7=Outputs
CMCON=7                            ' Disable comparators


    
    DQ          VAR PORTA.4
    DS18B20_12bit 	CON %01111111           ' 750ms,   0.0625°C       
    I           VAR BYTE
    SIGN        VAR BIT
    TEMPERATURE     VAR WORD ; TEMPERATURE REGISTER
    n			var byte
segments 		var portb
digits		    var porta
value			var word



   
MAINloop :   
        OWOUT DQ ,1,[$CC,$44]
      
WaitLoop: 
While not DQ
Wend
        
        OWOUT DQ ,1,[$CC,$BE]
        OWIN  DQ ,2,[TEMPERATURE.LOWBYTE , TEMPERATURE.HIGHBYTE]
        
        IF TEMPERATURE.15 = 1 THEN
            TEMPERATURE = (65535 - TEMPERATURE) + 1
            SIGN = 1
        ELSE
            SIGN = 0
        ENDIF
        
        value = (TEMPERATURE * 10)/16


        gosub display
        
goto mainloop


' Subroutine to send the number (0 - 9999) in Value to LEDs
display:
	For i = 0 To 3		' Loop through 4 digits
		n = value 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 1 'Increase to make digits brighter and flicker worse
	Return
	
	end