Voltage Clamp

Discussion in 'The Projects Forum' started by goldfingerfif, Jul 28, 2006.

  1. goldfingerfif

    Thread Starter New Member

    Jul 28, 2006
    2
    0
    I am trying to make a voltage clamp. It is for automotive and 3 wires run to a sensor 5v, gnd, and signal 0-5v. I am looking to clamp the voltage between 4.2v-4.5v as in it will have to be adjustable because different settings depending on weather and such. I know I can use a zener diote and potentiometer I believe but not sure on wiring it up. I saw this thread:
    http://forum.allaboutcircuits.com/showthread.php?t=2647

    But still confused on wiring it as there is no pictures and no very good description. From what I understand one wire on the potentiometer gets spliced into 5v and the other end to GND and the middle signal wire would get wired to the zener diode and then SPLICED into the signal wire. I don't get how splicing would clamp the voltage because I made a test circuit but no matter what the LED gets 5v. I am using a 4.5v zener diode.

    [​IMG]
     
  2. mrmeval

    Distinguished Member

    Jun 30, 2006
    833
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  3. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
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    Do you know what the resistance of the sensor is? It's difficult to clamp a low-resistance source.
     
  4. goldfingerfif

    Thread Starter New Member

    Jul 28, 2006
    2
    0
    Is a resistor a good way to lower voltage?
     
  5. Gadget

    Distinguished Member

    Jan 10, 2006
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    only if you have a constant current draw
     
  6. pebe

    AAC Fanatic!

    Oct 11, 2004
    628
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    If you are refering to my post, The circuit got lost when the board format was changed. I've tried to attach it again, but without success, so I'll try to describe it.

    An NPN transistor is connected across the voltage rail that needs to be clamped. Collector to +ve and emitter to -ve. Connect a pot end contacts across the rail and wiper to transistor base. The rail will be clamped at a voltage where the slider is ~0.7v higher than emitter.
     
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