Voltage adjustment

Discussion in 'The Projects Forum' started by Mnemoseck, Apr 19, 2013.

  1. Mnemoseck

    Thread Starter New Member

    Apr 18, 2013
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    I am about 10 years removed from Circuit design so pardon me for being a bit rusty. I have a 6vdc to 40vdc signal that I want to clip at a 0 - 24vdc signal to trigger a relay. This is coming from the auxiliary port on a desk phone and I wanted to convert this into a "line in use" light. If I can get the voltage down I can connect to a relay and then I 'm good from there. I however am confused which direction to go and which components to pick. If I can get started on the right path I should be ok, if anyone can give a few suggestions.
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,156
    3,063
    Does the signal have enough current to trigger your relay directly? There are solutions that could use the signal to trigger a comparator, for instance, that would then control the relay. But that would would require a DC power supply to power the circuit.

    If you have enough juice at your trigger and the relay doesn't require too much, I'm thinking you could use a current-limiting resistor and a zener to cap the input to the relay.
     
  3. #12

    Expert

    Nov 30, 2010
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    6,840
    Here's an idea: Why activate a relay coil when they require so much more energy than an LED? Why not just add a resistor and a light?
     
  4. wayneh

    Expert

    Sep 9, 2010
    12,156
    3,063
    Good point, who needs a relay just to light a bulb ?!
     
  5. Mnemoseck

    Thread Starter New Member

    Apr 18, 2013
    2
    0
    You're right with the LED. The only benefit of doing a relay is that I can trigger anything, like a 120Vac Desk lamp. There is enough current draw. I can trigger the realy but the voltage doesn't drop low enough to releas it. I also have a controller at my desk that I can read the voltage into and incorporate it into a program for various other functions if it was scaled properly. I could simplify it down to an LED, and that would defiantly serve my purposes for now. Over complicating it also helps refresh my memory on alot of aspects.

    Thanks.
     
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