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230v relay switching problem with rf

Discussion in 'Radio and Wireless' started by VIJAYAKUMAR P, Dec 18, 2014.

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  1. VIJAYAKUMAR P

    VIJAYAKUMAR P

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    Dec 18, 2014
    230v relay switching problem with rf
    Hi,

    I'm facing relay switching problem by using RF.I'm using the relay in RF Receiver side.I tried with RC snubber circuit in relay coil and relay contacts.But i can't find any solution for that.Relay switching time differs for snubber circuit(tried with different R and C combinations).

    I couldn't switch the relay for right timing through RF receiver. Pls give solutions for this......

    [​IMG]

    - - - Updated - - -

    hi,

    Here i'm using industrial gong bell as a load.


    RF input is given to transistor base.
     
    Last edited: Dec 18, 2014
  2. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    Hi there and welcome to Electronics Point :)

    I don't think I understand your question. Are you using the relay contacts to switch an RF (radio frequency) signal? It looks like you are using them to switch mains power ON and OFF.

    And you mentioned an industrial bell as a load. I don't see how this relates to RF.

    You haven't explained what the actual problem is. Is it something to do with the timing of the switching? Relays do not respond immediately, and relay turn-off will be delayed by the presence of the diode across the coil, but if you're switching AC mains, you won't get accurately timed control anyway.

    If the slow turn-off of the relay is the problem, you can replace the inductive kickback suppression diode with a diode and a resistor in series, or a diode and a zener diode in series, to allow the flyback voltage to be higher. This will speed up the relay's turn-off.

    Alternatively you could try an SSR (solid state relay).

    You need to explain what you're trying to do, and exactly what the problem is.
     
  3. VIJAYAKUMAR P

    VIJAYAKUMAR P

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    Dec 18, 2014
    hi,

    Thanks for your reply.
    RF input is given to the base of the transistor.
     
  4. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    Why?!

    A relay can switch around 100 times per second. An RF signal alternates at least 100,000 times per second.

    What are you trying to do?
     
  5. VIJAYAKUMAR P

    VIJAYAKUMAR P

    3
    0
    Dec 18, 2014
    I'm trying to switch on/off the relay through rf signal.Relay perfectly works when without load.When i connect the load,relay switched on perfectly if receives RF signal but it couldn't turn off at right time through rf.
     
  6. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    Please answer @KrisBlueNZ questions. Why are you using RF and what is the RF signal. What frequency and amplitude.
    Adam
     
  7. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    So do you want the relay to turn ON when RF is present, and turn OFF when it isn't?

    As Adam asked, what is the frequency and amplitude of the RF? How are you getting the RF into that circuit?

    You say the relay doesn't turn off "at the right time". Can you explain? Does it turn off too late? How much too late? Or does it not turn off at all?

    Please tell us all about the project. Don't just answer our specific questions.

    We are not here to play guessing games! (https://en.wikipedia.org/wiki/Guessing_game)
     
  8. Frenoy Osburn

    Frenoy Osburn

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    Nov 20, 2014
    I think he means he wants to control the relay remotely, using RF. But then again it's just my guess. We would have to wait for him to get back.
     
    davenn likes this.
  9. davenn

    davenn Moderator

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    Sep 5, 2009
    Yes, that's the way I interpreted it too


    I would hope that he is rectifying the received RF and using that rectified DC to switch t he transistor
    If he is receiving the RF signal and feeding that directly to the base of the transistor, then yes transistor operation is going to be spasmodic

    Dave
     
  10. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    You talk about "RF Receiver side" without specifying what signal you are intercepting from the "RF Receiver". Is there an "RF Transmitter side" too? Are you trying to actuate the relay when the transmitter signal is received by the "RF Receiver side?"

    What are the timing requirements for the relay? Would this be your first attempt at designing an antenna transmit/receive switch?

    Wonderful! Gong bell should get someone's attention. Is that the final load, or just something you happened to have available for testing? Please tell us exactly what "RF input" signal looks like: frequency, amplitude, modulation (if any), and source impedance.
     
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