electrical relay vs mechanical relay

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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.

Thanks.

Albert

 

[Vidar Løkken]

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?

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...

 

[Jerry G.]

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
specific.

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:
http://www.vishay.com/solid-state-relays/

Examples of spec sheets:
http://relays.tycoelectronics.com/datasheets.asp



Jerry G.
======

 

[R. Steve Walz]

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...

--
MVH,
Vidar

www.bitsex.net

 

[Vidar Løkken]

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...