Can a LM2907 be used to show higher/lower than center frequency ?

Discussion in 'The Projects Forum' started by Externet, Sep 6, 2014.

  1. Externet

    Thread Starter AAC Fanatic!

    Nov 29, 2005
    The intention is to use a LM2907 that will turn a LED on when frequency is 60Hz +/- 5Hz and two more leds for frequency being lower and higher.
    Does the LM2907 has any pin useable to tell if input is under or over the center frequency ?

    It is for a adjusting the engine governors in portable generators, to be built in a wall wart case.
  2. SgtWookie


    Jul 17, 2007
    The LM2907 simply takes an input frequency and outputs a voltage that is relative in amplitude to the input frequency, depending upon component selection. I suppose you could add a window comparator to trip at the desired voltages/frequencies.

    Your application simply screams for a microcontroller, used as a frequency counter. You could drive 7-segment LEDs to show what the actual frequency is. Or, you could use something like a bargraph LED to show more of a range.

    See this link for a PIC16F628-driven 5-digit frequency counter:
    Last edited: Sep 6, 2014