Best way to pick up electrical pulse?

Discussion in 'The Projects Forum' started by wannaBinventor, Nov 12, 2010.

  1. wannaBinventor

    Thread Starter Member

    Apr 8, 2010
    179
    4
    I may be buying an old Nighthawk motorcycle this weekend that has a broken tach. Tachs on this bike can run 250+ on ebay. I could buy and aftermarket tachometer, but there is no fun in that!

    What's the best way to actually pick up a signal from the spark plug wire?

    I've seen other people do it with wraps of wire, but that honestly sounds unreliable and prone to problems.

    Any other ideas on that one?
     
  2. guitarguy12387

    Active Member

    Apr 10, 2008
    359
    12
    I don't understand what
    means.

    What are you trying to do with the spark?
     
  3. t06afre

    AAC Fanatic!

    May 11, 2009
    5,939
    1,222
    You pick up the signal on the low voltage side as a starter.
     
  4. wayneh

    Expert

    Sep 9, 2010
    12,126
    3,048
    That approach (inductive pick-up) actually works just fine. The only negative is the nuisance of have a small wire wrapped around your sparkplug wire. I think the traditional automotive tach was connected to the ignition coil primary and detected a zero-crossing each time the points opened. So a tach had to matched to the cylinder count.
     
  5. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
    312
    A hall effect sensor shrink-wrapped to the spark plug wire should do the trick.
     
Loading...