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Making noise

Discussion in 'Electronic Basics' started by V8TR4, Oct 9, 2003.

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  1. V8TR4

    V8TR4 Guest

    Hi everyone,

    I am working with a lot of TTL circuits in a lab enviroment and noise is
    always a huge issue. Mostly noise from ION souces and Electron beam guns
    when they short out. I am looking for a way to test my circuits in an
    enviorment like this. Currently I find I get good results from unplugging a
    transformer with a load on it. The inductive kick can be seen rattling the
    shift registers. I was wondeirng what other things I could do to bring some
    noise into my circuits. I am thinking right now to simply use a 208 to 24v
    (60amp) transformer I have extra and put a good 12 volt load on it since I
    will only be inputting 110. I will put a relay or switch to break the
    circuit.

    Should I break both poles or is just disconnecting one pole good enough?

    Any other means out there to create noise for testing circuits from noise?

    Thanks,

    Oliver
     
  2. Tom Woodrow

    Tom Woodrow Guest

    heat guns, old ac drill motors, spark gaps, these are just a few that
    come to mind from the early 70's when were testing Commodore desktop
    calculators.

    Tom Woodrow
    www.dacworks.com
     
  3. I have many times used a few different sized relays wired up as buzzers.
    Dont grab them powerleads though, give you a nice tingle. Good for the odd
    practical joke on the apprentice!!
     
  4. default

    default Guest

    Tesla coil.
     
  5. Turning on a mobile phone and placing it in close proximity of the circuit.

    Using a lighter - the ones that light up with a piezo (I think) pushbutton

    Cheers

    Klaus
     
  6. An old electric coffee grinder, with the filter caps (if any) removed.
     
  7. Fred

    Fred Guest

    Many years ago I had a very noisy neighbour and he would listen to what was
    then Radio 2 on the long wave, 198m. I got a triac, a diac and a 1.0uF
    polypropylene(?) capacitor and generated some massive spikes on the mains.
    Completely drowned out the radio. The spikes were so harsh that you could
    see a horizontal ripple on a TV.

    I was thinking of using a thyristor next since these turn on faster in the
    centre of a bridge diode but never got round to it :-(
     
  8. JeffM

    JeffM Guest

    relays wired up as buzzers

    Yup. Very cheap. Very effective.

    The bigger, the better.
     
  9. R.Legg

    R.Legg Guest


    Weller WTCP soldering irons. I like them and find their magnetic
    regulator and transformer on-off switch to be excellent spike
    generators, at less than ten paces.

    If you are serious, and have a spec and a budget, It's best to
    characterize the fields for which you intend to provide immunity and
    test your equipment using suitable calibrated EM field generators.

    RL
     
  10. tim kettring

    tim kettring Guest

    Maybe a "plasma globe" that used to be popular around in the late 1980s .

    tim
     
  11. I sometimes plug a DIY drill into nearby mains socker and switch it
    on/off a few times. Alternatively, my old vacuum cleaner.
     
  12. If you actually want to *test* something, as opposed to kicking the tyres so
    to speak, you need to have some reliable setup that will create the same
    conditions on each test. Otherwise you will not know whether you are solving
    problems or just got lucky passing the test.

    When I did EMI trouble-shooting, we used a high frequency generator to
    inject RF signals into the wires connected to the equipment and a power
    meter to measure via a current transformer what the injection level was.
    Then we swept the frequency across a defined band, noted any
    responses/deviant behaviour from the equipment, increased the power for a
    new sweep etc.

    Boring and Tedious, but we did find and fix enough problems to totally
    eliminate the "random failures" and "strange behaviour" seen in the
    equipment.

    PS:
    It is not worth the effort to test for EMI sensitivity on a circuit on
    itself; because you designed it correctly in the first place!?
    One has to test the unit in the situation it is supposed to be used in to
    get any meaningful results.
     
  13. Guy Macon

    Guy Macon Guest

    I use a Jacobs Ladder and a Tesla Coil not only do they generate lots
    of noise, they also impress the managers.
     
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