Pulse Generator with 10 and 100 microsecond outputs

Discussion in 'Digital Circuit Design' started by dori123, Mar 16, 2019.

  1. dori123

    Thread Starter New Member

    Mar 14, 2019
    18
    0
    I am quite a novice in this field, and was looking for a circuit for pulse generator with 10 and 100 microsecond outputs. I found the circuit attached from this website, and would like to implement it.

    I am seeking advice on the circuit.

    Also, do I need(have) to add some components like resistor and capacitor somewhere around or between the ICs, ground or 20MHz crystal?

    Thank you for any suggestions and advice.
     
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  2. ericgibbs

    Moderator

    Jan 29, 2010
    8,494
    1,709
    hi dori,
    Welcome to AAC.
    How precise do want the 10uSec and 100uSec pulses.?
    Do you want to to generate say one pulse when you press a switch or do you want a continuous pulses.?
    E
     
  3. Picbuster

    Well-Known Member

    Dec 2, 2013
    977
    125
    it might work but it's a lot of connections.
    Use a pic mpu (nearly any type will do) and a few component.
    High accuracy needed? add xtal.

    Program in C.
    This takes you a few hours to understand programming principle and a few hours to make it to run.
    You will roll into holes, get pissed off, want to burn the lot , getting angry, blaming the world being round.
    BUT ..>> keep going, defeat the problems and build a beautiful generator.
    End up being proud!!

    Advantage :
    1:gaining knowledge (The meaning of live)
    2:end up with a universal generator.
    3:the so gained knowledge allows you implement other things quickly.

    But ...........> you have the 'all about circuit' people to help you.
    Use their shoulders.

    Remember: electronics is fun but Programming gives you Control over the hardware!!

    Picbuster
     
  4. DickCappels

    Moderator

    Aug 21, 2008
    5,724
    1,794
    Use a .01 uf capacitor across the Vdd and Vds pins on each chip. Avoid Z5U capacitors.

    Put 47 to 100 uF from Vdd to Vss somewhere near the chips.

    If you are using a crystal oscillator module follow the manufacturer's power supply bypassing suggestion.

    If you are't planning to use a crystal oscillator module you can look around on the web for a design based on gates. You would have to provide load capacitors for the crystal and a .01 uF bypass capacitor.
     
  5. pmd34

    Active Member

    Feb 22, 2014
    366
    154
    I'm with picbuster, its an awful lot of work for making a few pulses. I would look at using a 555 timer IC or a MIC1555.. Not sure I would quite reach for my microcontrollers.. but it depends what you want to do with the pulse afterwards, and how much control you want.
     
  6. danadak

    Distinguished Member

    Mar 10, 2018
    3,463
    778
    Below module driven by a pic or ATTINY85 (this could be done in Bascom basic) or
    the pic in picaxe visual programming or the ATTINY85 in Ardublock visual
    programming.

    Or Arduino board...

    https://github.com/tardate/LittleArduinoProjects/tree/master/playground/AD9833/BasicDemoCycle

    https://forum.arduino.cc/index.php?topic=467320.0




    https://www.ebay.com/itm/AD9833-DDS...752143&hash=item58f68520e9:g:tg0AAOSwigla3VCq

    [​IMG]
    The AD9833 is a low power, programmable waveform generator capable of producing
    sine, triangular, and square wave outputs. Waveform generation is required in various
    types of sensing, actuation, and time domain reflectometry (TDR) applications. The
    output frequency and phase are software programmable, allowing easy tuning. No
    external components are needed. The frequency registers are 28 bits wide: with a 25
    MHz clock rate, resolution of 0.1 Hz can be achieved; with a 1 MHz clock rate, the
    AD9833 can be tuned to 0.004 Hz resolution.

    The AD9833 has a standard serial interface that allows the part to interface directly
    with several microprocessors. The device uses an external serial clock to write the
    data or control information into the device.


    Regards, Dana.
     
    Last edited: Mar 17, 2019
  7. dori123

    Thread Starter New Member

    Mar 14, 2019
    18
    0
    Thank you for all the feedback.
    What I need is a circuit generating 10uSec, 100uSec pulse widths, +- 10% accuracy. Continuous pulses.
    The schematic attached here is using 20MHz crystal, 74HCT390, two CD4017B and CD4013B.
    This also uses 74HCT32 and 74HCT08 to get 10uSec.
    My question is how to get 100uSec as well.
     
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  8. pmd34

    Active Member

    Feb 22, 2014
    366
    154
    You could simply add another C4017 to count your 10uS pulses..
     
  9. BobTPH

    Senior Member

    Jun 5, 2013
    1,923
    530
    What does continuous pulses mean? There has to be some gap between the pulses. Do you mean a square wave?

    Bob
     
  10. dori123

    Thread Starter New Member

    Mar 14, 2019
    18
    0
    I mean the pulse generator is feeding two pulses, 10uSec and 100uSec, continuously to two MOSFET drivers respectively, not switching between them back and forth.
     
  11. dori123

    Thread Starter New Member

    Mar 14, 2019
    18
    0
    Instead of adding CD4017B, can I use another OR gate(74HCT32) to get 100uSec?
     
  12. pmd34

    Active Member

    Feb 22, 2014
    366
    154
    Use one where?
     
  13. AnalogKid

    AAC Fanatic!

    Aug 1, 2013
    8,077
    2,285
    Your question still is not clear.

    Pulse width and pulse frequency are two entirely different things. You want one of your outputs to be a 10 us pulse. OK, how often? One pulse every second? One pulse every week? One pulse every millisecond? How often do you want the pulses to reoccur? What are the *frequencies* of the two output pulse signals?

    It would help to know more about what you are trying to achieve, what the relationship is between the two pulses (Are the leading edges aligned? Trailing edges? Centers?). Do you want ten 10 us pulses for every one 100 us pulse?

    PLEASE post a sketch of the two pulse signals to show their relationship. Make the timeline long enough to show at least two of each pulse.

    And, what the output transistors are connected to.

    ak
     
    Last edited: Mar 17, 2019
  14. dori123

    Thread Starter New Member

    Mar 14, 2019
    18
    0
    I apologize for my lack of understanding. Please forget about my previous question.

    My project is 10kHz pulsed laser module with 1% duty cycle.
    So the circuit I attached is supposed to generate 10kHz pulse frequency with 1% duty cycle.
    Please advise what part should be modified to meet the requirement and how to modify, or reinvent the circuit..
     
  15. AnalogKid

    AAC Fanatic!

    Aug 1, 2013
    8,077
    2,285
    That sounds like a 10 kHz square wave with a 1 us "up time". A 1 us pulse every 100 us. If yes, that is much easier than the schematic in post #1.

    One - 1.000 MHz clock oscillator

    Two - CD4017 Johnson counters in series, as in post #1.

    Delete U10. Drive the U1 clock input with the 1 MHz signal directly.

    U3 Carry output drives the U4 clock. U4 "D" input tied to Vcc. In this way, a 1 is latched into the flipflop every 100 cycles of the 1 MHz clock.

    Connect O1 output of U1 to the U4 CLR input. The U4 Q output drives the external laser circuits.

    Delete all of that other output gating goop.

    The idea here is that the flipflop output is clocked to a 1 state every 100 us, and then is reset back to a 0 state 1 us later. The CLR input is hit 99 more times before the next output cycle starts, and the flipflop clock input remains high for another 49 us. Don't care. All that matters is the U4 CLR signal immediately before and after the positive-going clock input edge.

    Where are you located?

    ak
     
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  16. dori123

    Thread Starter New Member

    Mar 14, 2019
    18
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    ak - Thank you for the detailed feedback. I am in New Jersey.

    I followed the steps and added the MOSFET driver part.
    Please take a look and let me know.
     
  17. AnalogKid

    AAC Fanatic!

    Aug 1, 2013
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    2,285
    Not quite. At U4:

    Q- is disconnected and floating. D is tied to Vdd.

    Remove the GND connection at the PRE pin.

    Remove the connection from PRE to Vdd. Connect PRE to GND.

    ak
     
  18. dori123

    Thread Starter New Member

    Mar 14, 2019
    18
    0
    When you say Q is disconnected and floating, which one of U4 is connected to the laser driver?

    dj
     
  19. dori123

    Thread Starter New Member

    Mar 14, 2019
    18
    0
    Please disregard my previous post.
     
  20. dori123

    Thread Starter New Member

    Mar 14, 2019
    18
    0
    I changed again and attached it.
    I am wondering if this logic is good to be implemented on the PCB, or there still needs to add some components like resistors and capacitors to the logic to protect the circuit and for its practical use.
    Thank you again

    dj
     
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