sequential shift light

Discussion in 'The Projects Forum' started by xcaliber, Jun 9, 2009.

  1. xcaliber

    Thread Starter New Member

    Jun 9, 2009

    I am trying to make a sequential shift light like you'd see on a formula 1 car. The basic design I would like is 7 LEDs to light up at specific RPMs (1000, 2000, 3000, ... ,7000 which is redline for my car). They would all stay on until the RPMs drop below the respective RPM also. I would like the first 4 lights which come on to be green, then 2 reds at 5000 and 6000, then a blue at 7000. I also need the LEDs to be about a meter away from the rest of the wiring so I can put the lights in the dash somewhere and keep all the wiring under the dash or somewhere.

    There are a few other things that I would like but are not completely necessary. First, to have 14 LEDs that come on 2 at a time and converge to each other. Also, to have all 7 (or 14) LEDs flash three or four times at or just after the 7000RPM redline.

    I have done some research and seen some diagrams but I dont have much experience with circuits or circuit diagrams so I dont really understand them. From what I gather, I need a frequency to voltage converter chip I've seen people use this one a few times "LM2917". I then use the voltage output to power the LEDs. As the RPMs and input frequency increase, the voltage output increases. So I would need to make the LEDs come on one at a time as the voltage increases.

    That is pretty much where I come to a stop. I'm not sure I've got the right idea or even on the right track so I dont want to try anything that might mess up my car. Also, I don't understand what goes where into and out of the LM2917 chip.

    Any information would be very helpful and appreciated. What would really be helpful would be a circuit diagram and an explanation of exactly what goes where and what everything is in the diagram. Or an explanation of what everything is in that chip and what they all connect to.

    Again any information, suggestions, tips or references would be greatly appreciated. If you need to email me you can at

    Last edited by a moderator: Jun 9, 2009
  2. Externet

    AAC Fanatic!

    Nov 29, 2005
    I suggest you generate some voltage with a magnet(s) attached to the front pulley and stationary coil(s), filter as much as possible to obtain DC, and use a single chip LM3914 for up to 10 leds of your color choice.
    The IC data sheet has the application notes schematic and explanations.
    Put your efforts on generating a voltage proportional to the rpm.
  3. SgtWookie


    Jul 17, 2007
    Attaching magnets to the front pulley is a dangerous idea; if they came off at high RPM's they would have a significant amount of kinetic energy, likely causing damage or injury.

    An LM2907-8/LM2917-8 running from the tach signal would be a much safer bet. There are circuits shown in the datasheet for producing a reasonably linear voltage over an RPM range.

    Combine that with an LM3914 or two using the schematics in the datasheet, and you have what you're looking for.