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Reed Relay Replacement

Discussion in 'General Electronics Discussion' started by New122, Jan 29, 2013.

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  1. New122

    New122

    10
    0
    Jan 29, 2013
    Hello Expets,

    Currently We have reed relay in our one of board. Now we are wondering to have opto isolator.Can you suggest me what information I have to look in opto isolator for appropriate replacement.

    Thanks in Advance,
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,838
    Jan 21, 2010
    If the reed relay coil uses 10 to 20 mA then you'll be able to power the LED inside the optocoupler. You will almost certainly need an appropriate resistor in series with it.

    What are the contacts of the reed relay connected to? Can we see a (possibly partial) schematic? You may need to use the optocoupler to switch another transistor.
     
  3. New122

    New122

    10
    0
    Jan 29, 2013
    Re

    Steve,

    Currently we have Reed Relay design with Sensor. Relay coil(3&5) energize by sensor. and NO contact(1&7) worked in series with Flip Flop. So do i have to find opto coupler which had 10-20mA to operate LED.Please advice.
    Please let me know if i am still missing some inputs.
     
  4. New122

    New122

    10
    0
    Jan 29, 2013
    Re

    Steve,

    Currently we have Reed Relay design with Sensor. Relay coil(3&5) energize by sensor. and NO contact(1&7) worked in series with Flip Flop. So do i have to find opto coupler which had 10-20mA to operate LED.Please advice.
    Please let me know if i am still missing some inputs.
     
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,838
    Jan 21, 2010
    Can you show me your schematic (possibly just a partial one) showing the way you're currently driving the reed relay, and what the contacts are being used for.
     
  6. New122

    New122

    10
    0
    Jan 29, 2013
    Re

    Steve,

    Please find attachment. I would like to connect OptoCoupler at Input side. The Output will go to input for Flip Flop. Please review and let me know if this works. I am planning to use 4N35-X Opto, with atleast 1080 ohm at LED side and atleast 960 ohm at Transistor side.

    Also I am planning to use same type of Opto for output to interlock. So i am planning to connect PWM output to LED in series with Resistor and other end with 0/+3.3V?Is that possible?

    Thanks in Advance
     

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  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,838
    Jan 21, 2010
    OK, so you have switch contacts that pull J2.2 to ground? And you want a logic level as an output?

    You can do it the way you have drawn it, but there are also optocouplers with logic level outputs which may be even more suited to your circuit. (Here's 2842 of them)

    One thing to address. Is J2.2 connected to a switch? If so you'll get contact bounce to some extent and that will make it's way through the optocoupler so you get a train of pulses prior to the solid change of state.

    Is that an issue?
     
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