HV nanopulse generation

Discussion in 'General Electronics Chat' started by ariemeir, Jun 20, 2013.

  1. ariemeir

    Thread Starter Member

    Jun 24, 2011
    Hi guys,

    My question is regarding a generating a very high voltage pulse
    for a period of say 10-500 ns.

    The goal is a scientific experiment - seeing how these kind of pulses affect plants - they are hypothesized to stimulate growth.

    I recently got a taser from ebay which claims it produces 15,000,000 volt.
    The sparks are very impresive, but i have 2 questions:

    1. how can i measure such a high voltage , even to an order of magnitude accuracy.

    2. how can i engineer some sort of an electronic switch which will allow me to discharge the pulse into an external load for a controlled amount of time : on the order of ns. I can see how i can generate a nanosecond pulse using a PIC (even arduino at the high end of the range: high NS),
    but i am wondering - what kind of transisor could tolerate such voltages even for a short amount of time. Overall the power that is generated is not high, so i am wondering what should i be looking at in the transistor datasheet.

    Thanks in advance,
  2. Austin Clark

    Active Member

    Dec 28, 2011
    Have you considered possibly just using a transistor and a monostable switch to momentarily connect the taser to its power source? You might not be able to get very consistent or short enough pulses, but it's worth a shot.
    That way you won't have to worry with the HV side, you'd just have to work on the low voltage side.
  3. ariemeir

    Thread Starter Member

    Jun 24, 2011
    Austin, thanks for the reply, i'll look into it, i have not used monostable switches before, i guess i could simply generate a one shot short pulse using a fast micro-controller (1ghz raspberry pi ? )

    BTW, based on a dielectric strength of air, no way my taser generates 15e6V, it should have sparked to a much larger distance if it did.

  4. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    I think a 'pulse' from a taser will produce a current strength far in excess of those seen to be useful in prominent experiments in this field. The suggested approach is to create a corona type discharge in the near field vicinity of the plant and allow the ionized air to conduct a very low level current through the plants. A direct ZAP, I fear will be harmful, and produce effects that weaken the plant, much like they do a criminal suspect who is exposed to such a discharge.

  5. ariemeir

    Thread Starter Member

    Jun 24, 2011
    thank you Kermit2 !
  6. crutschow


    Mar 14, 2008
    But likely not as impressive as such a voltage would predict. 15 million volts will arc about 15 feet through air at normal temperature and pressure. I think the voltage is more likely 15,000 volts. :rolleyes:
    ariemeir likes this.
  7. Papabravo


    Feb 24, 2006
    The basic problem you have is overcoming the inductance of wire, and charging and discharging the capacitance of the load. In order to get a pulse that is 20 ns wide you need edges that are say 2 ns rise time or fall time. As you must know the inductive reactance of a piece of a piece of wire is ωL where ω is the radian frequency (2πf) of the signal and L is the inductance.
    ariemeir likes this.
  8. Shagas

    Active Member

    May 13, 2013
    Not more likely , but definately!
    Them *ssholes in e-shops have a knack of adding an order of magnitude or a few to the output voltages/currents of a product.
    I also see this in handheld lasers :
    'HOLY CRAP 10000MW LASER , CAN BURN A CRATER ON THE MOON, MUST BUY' , and in reality it's 100mW. (and probably doesn't work either)