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electrical relay vs mechanical relay

Discussion in 'Misc Electronics' started by [email protected], May 21, 2005.

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  1. Guest

    Just a very basic question:

    Can anyone share with me what's the benefit of using transistor as an
    electrical relay compared to mechanical relay when the incoming signal
    is from a computer?

    Is it related to pricing, input voltage/current, power rating and etc?

    Pls help.


  2. A digital IO typically can't drive a mechanical relay directly. A
    transistor is needed to amplify the current and/or the voltage, so that
    the relay can operate. Also, look at optocouplers. They're often used.
    So it ain't a benefit. It is a must. No fuckin' way you can handle a
    mechanical relay from a computer...
  3. Jerry G.

    Jerry G. Guest

    Both mechanical relays, and solid state relays both have their
    particular characteristics. They both have their particular
    requirements, and may not necessarily be directly able to be
    substituted for each other.

    Solid state relays however, are extremely fast switching with their
    speed of response. The circuit design for one or the other, has to be

    Most any transistor can work as a switch. There are however,
    transistors that are designed specificaly for swithing applications.

    Most of the time, solid state relays are opticaly isolated. There are
    however some types that do not use optical design for their isolation.
    There are also some types that may not be isolated for various reasons.

    Web page from a distributor for solid state relays:

    Examples of spec sheets:

    Jerry G.
  5. Ahh, maybe just I that haven't came across them yet... I either use
    transistors to drive DC low-voltage load, or, for light bulbs and so, a
    solid state relay, and for some stuff, I let the solid state relay feed
    a mechanical heavy duty relay, esp. when controlling engines.

    Besides, I'm sceptical to hook up impedances to a computer...;)
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