Voltage to Frequency

Discussion in 'General Electronics Chat' started by Tobias, May 23, 2011.

  1. Tobias

    Thread Starter Active Member

    May 19, 2008
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  2. beenthere

    Retired Moderator

    Apr 20, 2004
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  3. Jaguarjoe

    Active Member

    Apr 7, 2010
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    Study the data sheet for the TC4900 part. It shows how to use it with a single ended positive supply. Also note the caveats for the -5v supply if you choose to go that way:

    http://ww1.microchip.com/downloads/en/DeviceDoc/21483d.pdf

    The data sheet has a few incomplete sentences in it which wouldn't be expected from a company with more than 1 person like Microchip. Also, one of the circuits (I think its fig. 4.3) shows a 0.1 ohm resistor and a 0.2 ohm rheostat as part of the circuit that makes no sense.
     
  4. Tobias

    Thread Starter Active Member

    May 19, 2008
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    Attached is the schematic for the board I built. It does give a pulse out. I am struggling with getting the offset to work correctly. The pulse out will stop when Vin is less than 4v. At 4V the FO/2 is 10hz. My understanding from the schematic was I should be able to adjust the OFFSET pot to get the pulse to start at 10hz at around 0.200mv.

    I modeled my schematic off this link
    http://ecelab.com/circuit-9400-vf-conv-2.jpg

    I am using a 5K pot to adjust the Vin.
     
  5. Adjuster

    Well-Known Member

    Dec 26, 2010
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    Taking the frequency all the way down to 0Hz may be rather problematic, depending what you want the signal for. In particular, it takes a relatively long time to determine a low frequency, so if you are representing a voltage in this way, the effective bandwidth gets less at low voltages.
     
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