High Voltage Detection device

Discussion in 'The Projects Forum' started by dhosinski, May 27, 2009.

  1. dhosinski

    Thread Starter Active Member

    Dec 6, 2007
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    Hello, I am working on a new project and we need to know when High Voltage is present and when it's safe to operate. Our current supply is 400VDC (for a BEV project). Upon "key-off" the supply is suppose to bleed down in a matter of about 20 secs. We want to confirm that the voltage has infact come down which will tell us our resistor is good at the traction motor controller.

    Since it's high voltage I believe the circuit is going to be more complex than just a couple of diodes and transistor. Any suggestions?

    Thanks
     
  2. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
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    If your bleeder resistor is instead a voltage divider, one may more safely measure across the smaller resistor in the divider.
     
  3. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    "BEV"?

    Ken
     
  4. gerty

    AAC Fanatic!

    Aug 30, 2007
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    I would use a ne2 neon indicator bulb, with the proper series resistor.
     
  5. dhosinski

    Thread Starter Active Member

    Dec 6, 2007
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    BATTERY ELECTRIC VEHICLE
     
  6. dhosinski

    Thread Starter Active Member

    Dec 6, 2007
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    thanks I'll check into them...
     
  7. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    At best a neon will only tell you that the voltage has dropped below ~90VDC. Still can be lethal.

    Ken
     
  8. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    U need a discharge circuit to discharge the out put caps ( if used any ) or the filter caps if mains are used.
    It can be automatic like when the power is off it will activate and discharge what ever u need to discharge to a safe value.
    Simple.
     
  9. dhosinski

    Thread Starter Active Member

    Dec 6, 2007
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    A discharge resistor is already in place to draw the caps down, but we want to be able to identify if the voltage (60volts or better) still exists. That's why I'd like to have a detection system in place.
     
  10. PRS

    Well-Known Member

    Aug 24, 2008
    989
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    Could it be that you might use a high voltage rotary relay with an indicator dial on its shaft? Experimentally find the place where the indicator points to, say, 35 volts, and mark it?
     
  11. CDRIVE

    Senior Member

    Jul 1, 2008
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    Ever thought of using a panel meter? Why complicate a simple task?
     
  12. dhosinski

    Thread Starter Active Member

    Dec 6, 2007
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    We'd like to have something that's not going to put a continuous draw on our traction battery. I only need to know when the high voltage is present. It would be nice to be able to say when it's safe to work on the vehicle.
     
  13. dhosinski

    Thread Starter Active Member

    Dec 6, 2007
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    Can I get a meter that is cheap? If I can design some type of LED circuit that will identify the presence of HV, then I can build that at a fraction of the cost.
     
  14. StayatHomeElectronics

    Well-Known Member

    Sep 25, 2008
    864
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    How about a voltage divider run into a comparator. It compares your divided down voltage to a set point to indicate the transition between high and low. The comparator drives the LED.
     
  15. tkng211

    Well-Known Member

    Jan 4, 2008
    65
    2
    You may try the attached simple circuit. Change the value of R2 or the zener voltage to get the satisfied indication if required.
    The listed values of the parts may result in lighting up the red LED when the high voltage is above 40V.
     
    Last edited: May 28, 2009
  16. Wendy

    Moderator

    Mar 24, 2008
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    Anyone ever see the little yellow screwdriver with the neon built in?
     
  17. CDRIVE

    Senior Member

    Jul 1, 2008
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    Is there a low voltage suppy (like 12V) available in your traction motor system? If not, are you willing to add a dry cell to your monitoring circuit?
     
  18. DickCappels

    Moderator

    Aug 21, 2008
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    How about just using a diode and a resistor. Connect the cathode of the diode (with appropriate PIV rating) to the supply output you want to monitor. Use a pull-up resistor (to whatever voltage you want, for example, to +5 volts) and connect it to the anode of diode and a high impedance logic input. You may want to add a capacitor from the anode to ground if your power supply has a fast rise time.
     
  19. dhosinski

    Thread Starter Active Member

    Dec 6, 2007
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    Yes, we have a 12V supply as well.
     
  20. dhosinski

    Thread Starter Active Member

    Dec 6, 2007
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    That sounds close to what I am looking for. The voltage divider is also interesting. The goal is to notify the user that HV is present. We do have a discharge resistor inside of our controller (motor) to discharge the CAPS, but if for some reason the resistor isn't working we'd like know that the high voltage is present.
     
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