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Author Topic: LED Tachometer design Ideas....  (Read 5091 times)
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wanderingmoose
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« on: May 04, 2008, 06:22:41 06:22 »

Hi
I have been working on a 20 LED tach for my motorcycle.
Build a good unit, but looking for more ideas.
The circuit I am using has a 555 timer as a frequency to voltage converter, and two LM3914 as the display drivers.
I like what I have built, but with using LM3914 as the LED drivers, it can be a little slow to respond the changes in RPM.

He hardest part so far is finding a good housing that would compliment my motorcycle.
At this time I am using a 12 volt 50 watt chrome driving light holder. Found this on Ebay.
Uses the same bulb as the halogen house lighting. MR16

So looking for any other design ideas.
Using a PIC or Huh?

Would also be interested in seeing the Silicon Chip Tachometer articles from Issue 217(PT1: Oct 11 2006) and 218 (PT2: Nov 29, 2006) that show a larger tach with LED's and 7 segment display. Like the idea of a remote display.

Thanks for your time
WM


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zuisti
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« Reply #1 on: May 04, 2008, 10:05:29 10:05 »

I have been working on a 20 LED tach for my motorcycle.
The circuit I am using has a 555 timer as a frequency to voltage converter, and two LM3914 as the display drivers.
I like what I have built, but with using LM3914 as the LED drivers, it can be a little slow to respond the changes in RPM.

Hi wanderingmoose,
I think the slow responding is caused by your F/U converter (because you must integrate the pulses), NOT by the led drivers.
Please post here your schematic to discuss it (and make it faster :-).

Other:
At my mind the 'analog' display using 20 (or more) leds is far better in this case as a digital display using 7 segment numbers.

I think it's possible also a solution using a PIC but I'm not sure that will be plainer (and cheaper) to you...  google it!
Cheers
zuisti
 
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sputnik
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« Reply #2 on: May 20, 2008, 05:19:32 05:19 »

It can be done very easy with a pic and the proton complier.

I just built one for my bike.

Here is simple code using 16F628A, a counter to count pulses in 100ms, multiply that by 10 to get frequency (pulses per second), multiply that by 60 to get RPM.

VERY EASY!!!

Quote

Device 16F628A
 XTAL = 4
 
 Config INTRC_OSC_NOCLKOUT , WDT_OFF , PWRTE_ON , BODEN_OFF , CP_OFF, MCLRE_OFF ,LVP_OFF
 
 
 ALL_DIGITAL = true
 
 Dim rpm As Word
 Dim rpm2 As Word
 
  TRISB = %00000000
  TRISA = %00001100 
  PORTB = %00000000
 
 DelayMS 100
 

 GoTo Mode1

 
'''''''''''''''''''''''''''''''''''''''''''''''
 
 Mode1:
 rpm = Counter PORTA.3 , 100
 DelayMS 5
 rpm = rpm * 10
 rpm2 = rpm * 60

 
 Select rpm2

  Case 500 To 1499
   PORTB = %00000001
 
  Case 1500 To 2499
   PORTB = %00000011

  Case 2500 To 3499
   PORTB = %00000111
   
  Case 3500 To 4499
   PORTB = %00001111
   
  Case 4500 To 5499
   PORTB = %00011111
   
  Case 5500 To 6499
   PORTB = %00111111
   
  Case 6500 To 7499
   PORTB = %01111111
   
  Case 8500 To 9499
   PORTB = %11111111
   
  Case 9500 To  10000
   PORTB = %11111111
   PORTA.1 = 1
   PORTA.0 = 0
   
  Case > 10001
   PORTB = %11111111
   PORTA.1 = 1
   PORTA.0 = 1

  Case < 500
   PORTB = %00000000
   PORTA.0 = 0
   PORTA.1 = 0

 EndSelect
 GoTo Mode1     
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bbarney
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« Reply #3 on: May 20, 2008, 05:40:04 05:40 »

I have that article someplace and I'LL LOOK FOR IT Grin
sputnik maybe you can post a schematic for him so he can see how much simpler it look's
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wanderingmoose
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« Reply #4 on: May 21, 2008, 06:30:00 06:30 »

thanks for the replies.
I found the articles yesterday on the site and was able to dl.
Strange on what one will find when they are not looking.
I am waiting for 12F683 pics I ordered for a dual servo laser cat toy I am working on, to try the pic idea.

I love this site, alot of ideas and with enough people surfing the net the answers do come together.

Thanks for the replies and thoughts.
WM


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"There is a theory which states that if ever anyone
 discovers exactly what the universe is for and why
it is here, it will instantly disappear and be replaced
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