Connect with us

50Mhz Square wave generation.

Discussion in 'General Electronics Discussion' started by Hoobbyy_Engineer, Jun 14, 2017.

Scroll to continue with content
  1. Hoobbyy_Engineer

    Hoobbyy_Engineer

    13
    0
    May 21, 2017
    Hi,
    I am trying to generate a square wave of frequency 50Mhz.What is the best way(also cheap way) to get a 50Mhz decent square wave which does not vary much with temperature?

    Thanks
     
  2. Arouse1973

    Arouse1973 Adam

    5,164
    1,080
    Dec 18, 2013
  3. Harald Kapp

    Harald Kapp Moderator Moderator

    10,025
    2,138
    Nov 17, 2011
  4. Hoobbyy_Engineer

    Hoobbyy_Engineer

    13
    0
    May 21, 2017
    Hi,
    Thanks for the replies.But I am not looking for any IC that can generate a square wave. I am in need of an analog circuit to get 50Mhz.

    Regards
     
  5. davenn

    davenn Moderator

    13,589
    1,872
    Sep 5, 2009
    I hope you are not going to put an antenna on that, you will upset a lot of people !

    why ??
    Harald gave you a whole page of excellent choices what is wrong with them ... specifically

    you understand that a square wave that you asked for is basically a digital signal, aye ?

    You had better explain clearly what you are trying to achieve
     
    Arouse1973 likes this.
  6. Hoobbyy_Engineer

    Hoobbyy_Engineer

    13
    0
    May 21, 2017
    I am trying to make a capacitive soil moisture sensor.
    The concept is to charge the capacitor( sensor) with a square wave and measure the peak voltage stored in it. So as the moisture content of soil changes , the capacitance of sensor will change,resulting in change in peak voltage.So does it really require an ic?(I want to keep costs as low as possible)

    Regards,
    Nilesh
     
  7. davenn

    davenn Moderator

    13,589
    1,872
    Sep 5, 2009
    it's the best way to satisfy your bracketed comment
     
  8. AnalogKid

    AnalogKid

    2,361
    659
    Jun 10, 2015
    Does it really require 50 MHz? Can you post a justification for this requirement?

    Please read post #1.

    If this is for a product, you just volunteered for a ton of certification and compliance testing.

    ak
     
  9. Hoobbyy_Engineer

    Hoobbyy_Engineer

    13
    0
    May 21, 2017
    Hi,
    Higher the frequency, more it is insensitive towards minerals and salts.

    Nope, it is for personal use.I am going to use it in my grapeyard.
     
  10. davenn

    davenn Moderator

    13,589
    1,872
    Sep 5, 2009
    beware that you don't cause your signal to go too far ..... 50MHz is a commercial and also an amateur radio frequency in most countries
    as I said earlier, you could upset a lot of people .... 50MHz will radiate 1000's of km's when the propagation is right

    what power level were you looking at using ?
     
  11. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,387
    2,773
    Jan 21, 2010
    A colleague of mine has built a soul moisture probe based on a capacitive sensor.

    The major problem is protecting your sensor from the environment. If you don't, your readings will drift over time.
     
  12. duke37

    duke37

    5,361
    767
    Jan 9, 2011
    To measure capacitance you do not need a square wave, a sine wave would do.
    To get a square wave you need lots of odd harmonics so if only going to the 5th harmonic, the circuit must be able to handle 250MHz without phase distortion.
     
    Harald Kapp likes this.
  13. Hoobbyy_Engineer

    Hoobbyy_Engineer

    13
    0
    May 21, 2017
    It will be about 50mW. The whole sensor will be underground so I don't think it will cause any problems.
     
  14. Hoobbyy_Engineer

    Hoobbyy_Engineer

    13
    0
    May 21, 2017
    Yep, I am using a layer of epoxy to isolate it from corrosive environment.

    That is interesting. Can you explain how it is done.

    Thanks
     
  15. Harald Kapp

    Harald Kapp Moderator Moderator

    10,025
    2,138
    Nov 17, 2011
    How is the sensor to measure humidity if it is isolated by epoxy from the environment?

    You know Google? -> https://meettechniek.info/passive/capacitance.html
     
  16. AnalogKid

    AnalogKid

    2,361
    659
    Jun 10, 2015
    My guess is that he is by measuring the capacitor voltage after a fixed charge time (shunt mode). With a sine wave you could measure the capacitor impedance (series mode) in a half-bridge. Either way, changing soil moisture content might change the dielectric properties enough to affect the capacitance value, even if isolated by epoxy, but the change will be very small.

    ak
     
  17. Hoobbyy_Engineer

    Hoobbyy_Engineer

    13
    0
    May 21, 2017
    If water comes in contact with the uncoated capacitor it will not simply remain a capacitor! Here we are measuring the parasitic capacitance, similar to capacitive touch sensors.

    Here is a circuit diagram that I found on https://wemakethings.net/2012/09/26/capacitance_measurement/
    [​IMG]
    In this case the clock is 8 Mhz. I want to replace it with 50Mhz.
     
  18. Arouse1973

    Arouse1973 Adam

    5,164
    1,080
    Dec 18, 2013
    :)
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-