What are Relays used for

[walters#1]

What are Relays used for?

I seen Relays used for Switching inputs , outputs, grounds

The relays used to Isolate the grounds how do design engineers do this?

[Tomi Engdahl]

A relay is a simple electromechanical switch made up of an electromagnet and a set of contacts. Relays are found hidden in all sorts of devices.
The relays are typically used when you want to control some higher current / voltage with a low voltage/current control signal.
With a suitable relay it is easy to control pretty high power (for example 230V AC 8-16A) with pretty low power control signal (for example 12V 50 mA). Relays provide isolation between the control side and the output.

You can find lots of relay information at
http://www.epanorama.net/links/componentinfo.html#relay

[walters#1]

thanks for the information

I seen this Design tech. take a regular preamp and eq circuit before it had no relays and then he added like 40 or more relays to do all the switching,grounding,isolation

How do you use relays to do isolation?
i think he used relays like isolation transformer

How do you use relays to isolate the ground from circuit ground from
The lighting panel grounds to run lights from the relays them self have to have another grounding so you don't hear the clicky cheater coming up from the ground

I know to use a isolation transformer to with alot of secordary isolation
terminal to use it to seperate all the grounds

How do most most design tech modify a circuit that has No relays and
then adds alot of relays to do all the switching,grounding,isolation?

The switch on the front panel would be a DC voltage going to the relay?
and the relay would handle all the switching,grounding,isolation?

[HWman]

I seen this Design tech. take a regular preamp and eq circuit before it had no relays and then he added like 40 or more relays to do all the switching,grounding,isolation

Can you give more specific information on this particular appication you are referring. There is nobody else than you (and maybe that desighn tech) that could understand the application based on your exmplantion you gave.

Can you post a circuit diagram of the application, and then we are talking...

How do you use relays to do isolation?

Relays are normally used to isolate electrical load from the control circuitry. The control current on coil of the relay can turn the output contact on or off, but there is no electrical contact between the relay coil and output switch contacts. In many applications relay isolation eliminates surges from affecting host PC/PLC/microcontroller in various test, control, monitor, and measurement applications

i think he used relays like isolation transformer

Most propably not.

Relay is not like transformer. A normal relay is a "binary" device. The outptu of a relay is either on or off, dependign on the control signal (if it is on or off).

How do most most design tech modify a circuit that has No relays and then adds alot of relays to do all the switching,grounding,isolation?

This depends on the application.

In many automation applications where the original device was origially controlled with push buttons or switches that switch the current going to various parts of device, the origianl operation of those switch/button controls are simulated with relays. For example a relay output contact could be wired in the place of the original button/switch contacts, or on some cases to series or parallel to the original control button/switch.

The switch on the front panel would be a DC voltage going to the relay? and the relay would handle all the switching,grounding,isolation?

Usually many control panels with lots of controls are built in such way that the controls (buttons, swiches, electronic controlling devices etc..) operate at low voltage and low currents. The control paner control would control if low voltage (usually 5-24V) AC or DC (usually currents below 100 mA) goes to relay coil or not. Typical voltages used in this kind of applications are 12V DC, 24V DC and 24V AC.

The relays at possibly physically at some other location than the control panel itself (for example placed near the load or installed inside electrical distribution panel) then control the power going to the load. The load is connected to the relay output contacts. The signals from control panel are wired to relay coil inputs.