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Help with audible shift light system

Discussion in 'Automotive Electronics' started by BSinnott, Mar 26, 2017.

  1. BSinnott

    BSinnott New Member

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    Hi - I race a 1991 Lola T91/90 Sports 2000, it's a sports racer powered by an engine originally used in the Ford Pinto. The car is much sexier than I'm making it sound! The motor revs to about 7000rpm, and at the moment I use shift lights on the dash to help time the upshifts. I'm sure everyone has seen the lights, anywhere between 3 and 12 of them, different colors, usually run left to right, and they light at 200 rpm increments. Last one goes on at 7000rpm. Lots of products available (search shift lights). Now in the heat of the moment it's easy to miss the lights, and glancing down in a racecar more frequently than required is a bad idea. So I've been trying to find an audible shift system, where instead of lights a series of beeps or a tone is transmitted to an earpiece worn inside the helmet. No one seems to make one. So I'd like to build one, or have one built for me. Any thoughts on where to start? Car has a coil, and most shift light system take the RPM input from there.

    Any help greatly appreciated!
     
  2. MikeMl

    MikeMl Well-Known Member Most Helpful Member

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    I fight alternator whine in aircraft stereo entertainment systems. Sounds like you purposely want to hear alternator whine that I fight so hard to get out.

    Hint: the frequency of alternator whine is directly proportional to engine rpm...
     
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  3. alec_t

    alec_t Well-Known Member Most Helpful Member

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    A kit such as this might be the basis for an audio mod. Any DIY version is going to need calibration. How would you do that?
    Is the "coil" you mention an ignition coil or is it some pickup coil on the engine?
    I like Mike's hint, though.
     
    Last edited: Mar 27, 2017
  4. dave

    Dave New Member

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  5. BSinnott

    BSinnott New Member

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    The (tach) signal comes off the ignition coil. I think perhaps modifying a product like below would be easiest, but it would have to feed an earpiece rather than a beeper. You need the system to have gradations that are easy to hear over the noise and vibration of the car and this one does. If it was a varying tone it might be hard. Keep in mind that the motor revs quickly in low gears so the time between beeps is short.

    http://www.modifry.com/index.php?route=product/product&path=18_66&product_id=66index.htm

    So how about if I cut the wires to the buzzer and spliced in the wires from my Apple Earbuds? What would happen? Clearly I know very little about electronics and am really appreciative of any help.
     
  6. alec_t

    alec_t Well-Known Member Most Helpful Member

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    Did you read this bit in the link? "It is NOT designed to work with ignition systems that use a distributor and points, as these generate high-voltage spikes that can damage the shift beeper module." Does that rule it out?
    Depends if the buzzer is one which only needs a DC supply to make it work (most likely), or one which needs a tone signal to drive it. The latter should work with earbuds (plus a current-limiting resistor), but the former wouldn't work.
     
  7. mojozoom

    mojozoom New Member

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    Does the car have an MSD? You can do alot with their RPM Activate Switch.

    How about an Arduino, Bluetooth module, and a Bluetooth earpiece?

    I'd think you might be overall better served to move the shift light into your helmet. Then you don't have to worry about hearing the beep when you're ear is in direct shot of someone's exhaust header. Again the Aduino would do the work, and the output would be either wired, or something more elaborate and wireless.
     

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