Generate a square wave signal of different frequency

Discussion in 'The Projects Forum' started by Cerkit, Jan 20, 2009.

  1. Cerkit

    Thread Starter Active Member

    Jan 4, 2009
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    What can I use to generate square waves of different frequencies??

    I need the signals in order to input them through an LCR circuit. I know the possible resonance frerquencies but need to create the signals of different frequencies put them through and see for which one the output voltage drops significantly.

    This circuit will be placed on a buggy so obviously I can't just use a lab signal generator!.
     
  2. DickCappels

    Moderator

    Aug 21, 2008
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    Try a 74HC4066 for multiple, harmonically-related frequencies.

    If you are even more specific about your requirements, we can be even more specific about solutions.

    What frequencies?
     
  3. Cerkit

    Thread Starter Active Member

    Jan 4, 2009
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    The frequencies I need to be able to create are as follows

    17576,19300,21268,23215,25485,27705,30629,33932,37513,41094,45944,50329

    Need to test all frequencies therefore will require for me to swop from one to the other.
     
  4. mik3

    Senior Member

    Feb 4, 2008
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    What is that? Write it clearer.
     
  5. Wendy

    Moderator

    Mar 24, 2008
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    Do you need them simultaniously? If not a simple 555 w/ pot connected to a freq counter would do it.
     
  6. Cerkit

    Thread Starter Active Member

    Jan 4, 2009
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    Do not need them simultaneosly. Need the frequency change to be done without physically altering hardware. Do you think I could use the 555 in conjunction with software to try each frequency in turn. Need the change to be unmanned as it is on a buggy and on trial it needs to run on its own.
     
  7. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    Why not use an MCU and step through them based on whatever input you want to use?

    John
     
  8. Cerkit

    Thread Starter Active Member

    Jan 4, 2009
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    I wish I was allowed to do that unfortunately there's a budget on what I put on the buggy so that would be out of the question. I have vhdl and c programming at my disposal and any other small chips that might be useful ie 555, but that is all!!
     
  9. mik3

    Senior Member

    Feb 4, 2008
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    You can use a 555 and vary its frequency with a variable resistor. Another option is to use the 555 as an astable at a fixed frequency and then use fast decade counters to divide that frequency.
     
  10. Cerkit

    Thread Starter Active Member

    Jan 4, 2009
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    How about the 555 timer and and instead of variable resistor find the resistances which give the frequencies I want then use a multiplexer and through software select the individual resistors to be used in turn to give the desired frequencies??
     
  11. mik3

    Senior Member

    Feb 4, 2008
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    That is possible too.
     
  12. RiJoRI

    Well-Known Member

    Aug 15, 2007
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    Price it out: This is where a "jelly-bean" micro would shine. For example, an Atmel ATTiny15 is around $1.32. There are also other uCs such as the PIC, and 8051 which come in a small package. Check the price of them, and do not forget the price of a crystal for the micro, and other chips needed for the 555. And do not be afraid to say, "There is no way to do this within budget."

    --Rich
    P.S., If you use a micro, you can modify the frequencies* generated by simply reprogramming it: no easy way to do that with a 555.

    *In the Real World, Marketing always wants changes. Reprogramming is a LOT cheaper than rebuilding / modifying the hardware.
     
  13. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    By budget, do you mean that you cannot use an MCU by rule, because of space, or because of cost?

    I don't see how space or cost could favor a 555 solution over something like a 12F509 ($1.20 each at Digikey) vs. NE555 at $.42 each. The NE555 will require more peripherals to get to the same result.

    If it is by rule, then I can understand.

    John
     
  14. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    One other thing, your list of frequencies implies you need 5 significant figures. You aren't going to get that level of reproducibility with a 555 circuit.

    John
     
  15. Cerkit

    Thread Starter Active Member

    Jan 4, 2009
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    My idea of MCU was different from yours but I understand what your saying now. The ATTiny15 seems like the best thing for the job. What kind of programming language is required for this chip??
     
  16. hgmjr

    Moderator

    Jan 28, 2005
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    You have your choice of AVRSTUDIO4 if Assembly Language is the way you would like to go. If you prefer C-Language programming you will want to install WINAVR as a add-on to the AVRSTUDIO4. The good news is that both of these software packages are free. You can get AVRSTUDIO4 from www.atmel.com and you can get WINAVR from www.sourceforge.net.

    hgmjr
     
  17. Wendy

    Moderator

    Mar 24, 2008
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    The point about accuracy on the 555 is valid. It can be a VCO with extreme ease however.
     
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