Do I need a current limiting resistor with this relay?

And do I need a diode across the coil like a normal relay?



I mean do I need a resistor on control circuit side?

3 Answers

  • Bony
    Lv 5
    1 decade ago
    Favorite Answer


    Operating current of 10 mA, with V drop of 1.7V for

    . the LED. Calculate to drop any voltage above this

    across the limiting resistor, also carrying 10mA. Example,

    for 12v Supply, Rlimit = ( 12- 1.7) / 0.01 = 1030 ohms (=1k ).


    No diode required, because there is no coil to give back-emf.

    Output when Fully ON, voltage drop across

    transistors is 0.5V max, and can carry 1 Amp,

    Connect load in series with this solid state switch.

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  • Robin
    Lv 4
    4 years ago

    You must select a suitable circuit breaker to connect in series with the relay. A circuit breaker may be rated at 6 amp for example but requires a certain length of time to operate. The higher the current then the quicker it will operate. You could use a fuse but would need to keep on replacing it whereas a breaker would only need to be reset. Even a breaker has a limited number of operations before it to would need replacing but may be several thousand operations. Check that the voltage is compatible with your circuit. If the circuit is fed from a higher voltage you could insert the breaker there.

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  • 1 decade ago

    Yes, you want to limit the driving current into the LED.

    No, the diode is to prevent voltage spikes due to the collapsing field of a inductor (relay coil) which can destroy the driving transistor.

    Source(s): EE
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