3-digit frequency meter

Flow sensors are useful tools for collecting data on the rate of liquid usage, but they need a device to display the data they collect. This three digit frequency meter was designed by [Turbokeu] to do just that, converting a Swissflow SF800 flow sensor’s square wave signal (similar to fan RPM signals) into an numerical expression of liters per minute on a 3 digit LCD. Fan RPM is

[Turbokeu] provides detailed schematics of different configurations for the frequency meter as well as schematics of the layouts of the two PCBs that are used. Even if you don’t have an immediate use for a frequency meter, his clean and readable schematics are worth a look in their own right. The display is installed on front of a tower case along side a CPU speed display.

[via YourITronics]


  1. dane says:

    end of paragraph 1: Fan RPM is…..

    otherwise, good to see some pure logic hackery

  2. ... says:

    If you want to make one tht doesn’t use such hard to find chips I found a few designs that only use basic logic chips
    http://4hv.org/e107_plugins/forum/forum_viewtopic.php?24079 and a more complicated but more stable (not that it matters if you are building a 3 digit counter)

  3. Eizu says:

    I’m surprised you didn’t mention the utility this could have if converted to work in an automobile dashboard. It would enable all those “hyper-miling” idiots to stare at their dashboard and watch the precise volume of dinosaur sauce going into their engine.

  4. J. Peterson says:

    I wonder why it did it with old-school logic…this would be trivial to implement with a single PIC/AVR.

  5. miked says:

    i approve of this post

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