Need circuit to multiply tach signal for use with other tach

Discussion in 'The Projects Forum' started by Dr Evil, Aug 24, 2011.

  1. Dr Evil

    Thread Starter New Member

    Aug 24, 2011
    8
    0
    I tried searching and found some similar issues, but nothing that I found answered my questions completely. Please forgive if this is a common subject and I missed it on search.

    What I am trying to do:

    I have a Moto Guzzi that I am customizing. The Guzzi uses two separate ignition circuits with two separate 6v coils, points, etc. I would like to use an aftermarket tach on my project, but all of the ones I see that I like are car related and thus allow for customization to 4, 6, 8, 10 cyl. As such, I believe that I need to multiply the single fire signal x4 to utilize these gauges. Correct? There are costly products out there that do similar to this, but still not exactly what I need with out some serious massaging. As such, I would rather build what I image would be an easy circuit to solve this issue. I have built mega jolts, sparks, and squirts, but the programming was always a PITA as I was self teaching.

    Dose anyone have any guidance?

    A little background on me:
    3 years of electronics in HS (back in early 90s), 4 years as an avionics tech in the USCG (12 years ago). I can read a schematic, order parts, understand basics, but I am a little rusty. Solid state stuff is my weakest point so I may ask some simple questions.

    Thanks for your help :)
     
  2. jaclement

    Active Member

    Apr 15, 2009
    34
    0
    Don Lancaster had the solution to your problem in his book " CMOS Cookbook".You use a phase-locked loop with the proper division to give the number of pulses so that your readout is correct.
     
  3. Dr Evil

    Thread Starter New Member

    Aug 24, 2011
    8
    0
    Interesting book. I may have to add it to my library. Thanks for the tip and the direction to search, PLL. Looking into it and it looks like the deal. I will see if I can figure out how to program one/hook one up.
     
  4. wayneh

    Expert

    Sep 9, 2010
    12,126
    3,048
    Not sure it would work, but you might consider just rectifying the pulses. Kinda depends what signal the tach is looking for - it may not work if it needs a zero-crossing.
     
  5. Dr Evil

    Thread Starter New Member

    Aug 24, 2011
    8
    0
    Any info on where to buy this PLL and hook it up? Or is it an IC that I need to source and buy based on inputs and desired output? Is it a circuit I have to build with a CMOS?
     
  6. Dr Evil

    Thread Starter New Member

    Aug 24, 2011
    8
    0
    Some answer here. http://ecelab.com/circuit-pll-osc.htm

    Now I think the cook book will help me figure out how to time the thing to put out 4:1 signal. Unless anyone wants to take a stab at it.
     
  7. Dr Evil

    Thread Starter New Member

    Aug 24, 2011
    8
    0
  8. Dr Evil

    Thread Starter New Member

    Aug 24, 2011
    8
    0
    What about a buffer amplifier?
    http://www.tpub.com/neets/book9/35h.htm

    Will this only quadruple a base frequency that is stable, or will it multiply all them in the RPM band of the engine?

    (Never mind, I see that the tank will only be set to the harmonic of a specific reference freq and thus is static. So, this wont work.)
     
  9. Dr Evil

    Thread Starter New Member

    Aug 24, 2011
    8
    0
    Being that I am playing around in the 8.33Hz-166.67Hz range, I am finding it difficult to find a circuit that will operate in this band. I may be misunderstanding.
     
    Last edited: Aug 26, 2011
  10. Dr Evil

    Thread Starter New Member

    Aug 24, 2011
    8
    0
Loading...