voltage clamp

Discussion in 'The Projects Forum' started by roro36, Sep 28, 2011.

  1. roro36

    Thread Starter Member

    Sep 7, 2010
    52
    0
    I have an application that upon adjusting a pot regulates the air pressure into a system. At a certian point a pressure switch will kick in, say 7V. Now I want to, by using the signal from the pressure switch not allow the voltage to be turned up any higher, max is 10V. So the pot, even if turned higher will have no effect on the voltage. I thought of having two pots, and switch from one to the other at the pressure point and then setting the second pot to that point. Then when the pressure is reached by turning the first pot, the second pot is brought in and it is set to the same value, and non adjustable. The problem is that when the first pot is then turned down, it won't have an eefect on the air line which will mean the pressure will never be reduced.
    What i need is for when the pot is turned to give the right pressure, it must be capped here and only be allowed to be turned down.:confused:
     
  2. roro36

    Thread Starter Member

    Sep 7, 2010
    52
    0
    What I can think of is to have 2 pots in series and then set both to maximum. Turning the top pot down until the pressure switch comes on will set the max of the second pot to what I want still allowing the 2nd pot to turn the voltage down, but limiting to the voltage of the first pot. Is there a better way?
     
  3. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    If this has anything to do with safety, you need to ask yourself what will happen when the potentiometer fails?

    Let's say that the connection between the wiper and ground fails, and so the wiper gets pulled up to 10v. What happens then?
     
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