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Voltage spike protection

Discussion in 'Electronic Design' started by Efthimios, Nov 19, 2008.

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  1. Efthimios

    Efthimios Guest

    Imagine a device working at 1 Volt.

    I what to protect it from a voltage spike of 50 to 100 Volts.

    Does any know how to do this in a cheap way???

    Efthimios
     
  2. Rich Webb

    Rich Webb Guest

    You'll need to define your requirements for "protect." No over-voltage
    protection can react in zero time to clamp the voltage to (V-limit plus
    exactly 0 volts).
    Knowing how to do it cheaply requires more knowledge of what device and
    in what environment. Guessing the operating and maximum allowable
    parameters of an arbitrary device isn't productive.
     
  3. limit the current into the device to a safe value
     
  4. Efthimios

    Efthimios Guest

    -The spike has a duration of 0.2 to 0.3 seconds.
    -The device to be protected is a sensor with operation voltage of 1
    Volt and maximum allowed 1.5 Volts.
    -The sensor draws a less than 0.1 milliamp.
    -The device works under normal room temperature and humidity
    conditions
    -Cost preferably about a dollar.
     
  5. Rich Grise

    Rich Grise Guest

    Yes, but we frown on doing people's homework for them. Maybe check the
    other side of google for "transient protection" or so.

    Good Luck!
    Rich
     
  6. Eeyore

    Eeyore Guest

    TVS (transient voltage suppresor) if the energy is high otherwise a
    zener plus series R.

    Graham
     
  7. Eeyore

    Eeyore Guest

    But of what ENERGY ? That's critical. And source impedance ?

    Plus, that's a bugger of a voltage range to protect as it happens !

    Graham
     
  8. Eeyore

    Eeyore Guest

    Student you reckon ? Sounds too intelligent a question for that to me !

    Graham
     
  9. legg

    legg Guest

    Protection of power rails and signal lines pose differing problems.
    You'd have to be more specific about the actual node on the specific
    device that was threatened.

    RL
     
  10. Rich Grise

    Rich Grise Guest

    Well, it's homework season again on the NG. Haven't you noticed about a
    dozen new googlies, mostly obvious homework? (or, more likely, mid-terms.)

    I guess I should give him the benefit of the doubt. but at least I
    gave him a search term. :)

    Cheers!
    Rich
     
  11. Eeyore

    Eeyore Guest

    Yes, can't fault that one other than possible junction capacitance. The OP
    doesn't say how fast the signal is.

    Graham
     
  12. Jasen Betts

    Jasen Betts Guest


    ---+---[DEVICE]-+---[fuse]---
    | |
    +-->|--->|---+
    | |
    +--|<---|<---+

    4X silicon rectifier diodes
     
  13. whit3rd

    whit3rd Guest

    So, you need to put a network between the source and the sensor
    that passes 1V and 0.1 milliamp accurately (so less than 10 mV drop
    and less than 1 uA current error), but protects a sensor that
    undergoes
    some kind of failure at 1.5V, against inputs in the 100V range.

    Is that +100V? or could it be -100V?

    Usually, one would put a triggerable shunt across the sensor,
    and a small triac (or pair of SCRs) might do it. Most packaged
    surge protectors operate at much higher voltages, though,
    and sense-with-an-amplifier schemes have a few microseconds
    of delay.
     
  14. Jamie

    Jamie Guest

    If 1.5 volt is the max allowed, why not use the simple components
    that are out there already?
    2 sets of diodes to form 1.5 average break down joined back to back.

    this gives you a nice bi-directional clamp via some components that
    should be able to handle that through some kind of current limiting
    source, like a resistor.

    They also make TVS diodes...

    http://webpages.charter.net/jamie_5"
     
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