AC supply frequency measurement

Discussion in 'The Projects Forum' started by onlyvinod56, Dec 15, 2008.

  1. onlyvinod56

    Thread Starter Senior Member

    Oct 14, 2008
    Hi everyone
    Iam working over a project in which i want to display the supply frequency on a 7 segment display. Somebody suggested to use LM2907(f-v converter) and ICL7107(a-d converter cum 7 segment display driver).

    My problems are:
    1. How can i interface the f-v converter to the mains 230v, 50HZ supply.
    2. Suppose if i get the output of f-v converter as 5v for 50Hz frequency,
    how can i calibrate the ICL7107 to display 50Hz?

    Can anybody help me with a schematic to calibrateICL7107 and to interface LM2907.

    I had a circuit got in the net. I'm not getting how to modify the circuit to display 50Hz. Here iam attaching it.
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    First of all, you need to isolate your project from the mains. Use a step down transformer to obtain a useful voltage, like 12. You can produce your power supply voltage from that.

    It is generally accepted that mains frequency is extremely accurate. If you really want to do the project, simply follow the LM2907 data sheet for obtaining whatever voltage you wish from the 50 Hz input. The ICL7107 is a digital voltmeter, so no modification to it is necessary.
  3. Audioguru


    Dec 20, 2007
    The OP is from India. Whenever the electricity there works its frequency is wrong. They ask for quartz crystal clocks because their electric clocks are always wrong. I think he wants to measure the inaccuracy of his electrical frequency.