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Spark plug digital tachometer help — Parallax Forums

Spark plug digital tachometer help

lucplucp Posts: 4
edited 2019-12-16 17:13 in BASIC Stamp
Sorry I posted my question in the activity entry, hope it will work better here
Hi, I am new here and would like to have someone help me figure out this for me please. I bought a spark plug tachometer RL-HM011A V7 an the spark plug wire came out of the device. I opened it but can't figure out where it was connected. I have two wires in the spark plug cable, one black and one red. I guess that both were on the same terminal, but I could be wrong. I just have little knowledge on electronics. I contacted the manufacturer but never answered. I noticed a terminal with SIN stamped beside it could that be it. thank you for any help
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Comments

  • kwinnkwinn Posts: 8,697
    Typical setup would be for the red wire to be the signal in and the black wire to go to ground, and the connections would usually be close together. My guess would be that the red should go to "Sin" and the black wire to the terminal above and slightly left of Sin in your picture if there is nothing else connected to it. A picture of the other side of that area would help decide if that is correct.
  • lucplucp Posts: 4
    Is this better? and the other end of the spark plug wire has no connections, just wrap around the ignition wire couples of turns
    20191216160832.jpg
    2592 x 1944 - 2M
  • kwinnkwinn Posts: 8,697
    lucp wrote: »
    Is this better? and the other end of the spark plug wire has no connections, just wrap around the ignition wire couples of turns

    Just having the wire wrapped around the ignition wire is normal. The end of the wire that wraps around the ignition wire should go to Sin. The other wire most likely goes to the terminal directly below it. If that does not work then try the terminal to the left of it.
  • lucplucp Posts: 4
    Thanks Kwinn, I will try that, and just to make it clear both the red and black are in the same cable that wraps around the ignition, but I will put the red on "SIN" and the black on the lower connection.
  • kwinnkwinn Posts: 8,697
    lucp wrote: »
    Thanks Kwinn, I will try that, and just to make it clear both the red and black are in the same cable that wraps around the ignition, but I will put the red on "SIN" and the black on the lower connection.

    That makes a difference. It may be that you only need the red wire soldered on so try that first. Then solder the black one on if red only does not work.
  • lucplucp Posts: 4
    ok I soldered the red on the SIN and it is working, it seem low on the rpm but I will check with a good tach to see if it's different.
    thanks for your appreciated help
  • Capt. QuirkCapt. Quirk Posts: 872
    edited 2019-12-19 17:07
    Did it work correctly?

    Your tach appears to be a "Tiny Tach" clone. If it is, the Tiny Tach uses an
    inline ceramic capacitor on the positive lead. Then a resistor, and a transistor
    just like your picture.

    The difference in rpm may be from a mode setting. Usually 2 stroke or 4 stroke.

    Bill M.
  • kwinnkwinn Posts: 8,697
    Capt. Quirk wrote: »
    Did it work correctly?

    Your tach appears to be a "Tiny Tach" clone. If it is, the Tiny Tach uses an
    inline ceramic capacitor on the positive lead. Then a resistor, and a transistor
    just like your picture.

    The difference in rpm may be from a mode setting. Usually 2 stroke or 4 stroke.

    Bill M.

    Thanks for the correction and jogging my memory. It's been decades since I was seriously into automotive electronics and forgot about having to set the tachometer for 2/4 stroke and the number of cylinders.
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