Variable Time Delay

Discussion in 'The Projects Forum' started by ckong, Feb 2, 2009.

  1. ckong

    Thread Starter New Member

    Feb 2, 2009
    3
    0
    Hi,

    I'm a 3rd year student working on a project which requires variable time delay of a pulse to a LED to that of a transducer. I'm currently generating waveforms using Arbitrary Waveform Generator, and using that to pulse my LED as well. Another option available to me is the use of Handyscopes, but I'm not at all sure if this is possible using Handyscopes with Matlab.

    The variable delay that I need is in the range of nanoseconds to microseconds. The pulse width for the LEDs are about 50 ns. Please advice on the feasibility of using Matlab and Handyscopes, or any suggestions on what circuit/instruments I need. It's much appreciated.

    Kinds Regards

    CK
     
  2. Skeebopstop

    Active Member

    Jan 9, 2009
    358
    3
    throw the output of a square wave relaxation oscillator through a high speed buffer for your clock into a counter, which when anded with inputs you provide, decides whether to turn on the LED or not. The input you provide could be 8 bits or something, so you can provide the 'count up' flag.

    Depending on how long the LED must stay on, you may need to latch the output. Most any IC, including latches/flip flops will have enough driving power for an LED.
     
  3. Skeebopstop

    Active Member

    Jan 9, 2009
    358
    3
    The only thing matlab could do for you is write code for a micro for you. Otherwise it woudl be windows based software trying to control something fast, and seemingly real-time. Something windows will never do for you.

    I have no idea what handyscopes are, but I assume a module of matlab.

    Windows finest resolution timer is 1mS, as with most any user based system, so simple jobs like the parallel port etc.. are out.

    Do you have any supporting hardware? NI-DAQ or anything? I know NI has some fancy software to get you 10,000 or so samples a second, but even that falls short of what you are after.
     
  4. ckong

    Thread Starter New Member

    Feb 2, 2009
    3
    0
    Thanks for the ideas, and sorry for the late reply.

    I probably should give a more detailed description it.

    An Arbitrary Waveform Generator (AWG) generates a burst of sine waves, and at the beginning of each burst, sends out a trigger.

    The trigger is an output of square waveform pulse, 500 microsecond period, 50% duty cycle, and +3V.

    This pulse then triggers a separate AWG to generate a burst of pulses that flashes my LED each time a trigger pulse is received. The input into the AWG 2 should be of +2.5V to +5V, pulse width > 1 microsecond.

    The connector used is BNC type connectors.

    I need to introduce a variable delay of the trigger pulse from AWG 1 to AWG 2. I've been looking at some circuits, and attempted to build a power-on delay circuit using a LM 555 ic timer.

    [​IMG]

    Please advice
     
  5. ckong

    Thread Starter New Member

    Feb 2, 2009
    3
    0
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