Help understanding switch relays

[gtrscott]

Hi,

I'm a newbie builder and have built one amp with much help from a friend. I'm going to add a second master volume but I don't really understand the switching portion. I think I've figured out the places to break the circuit but I don't know how to setup the relay(s), diode(s) etc to perform the switching.

I assume that 2 pins on the relay are power and the rest are contacts that open or close.

I'm hoping for a simple switching example/experiment to get me going on the basics so I can understand the concepts.

Thanks for any help!!!

Scott

[Enzo]

A relay is a switch with an electromagnet to activate it. That's it.

The switch contacts come out the end of the relay so you can connect to them. The magnet coil leads come out the end of the relay so you can connect to them.

When you run current through the magnet coil, it moves the switch contacts - they open or close.

Relay coils have ratings just like light bulbs or something. 5v, 12v, 24v, 48v, 120v. They come in AC or DC current. The switch part doesn;t care about the coil part. Select the switch type for your needs, and get the coil voltage that makes most sense in your amp. No point in using 5v relaus when there is a 12v power source in teh amp, for example.

To energize a relay coil and switch its contacts, apply voltage across the voil. If it is a 24v DC relay, then connect 24v to one end and ground to the other and the coil comes on. switching the relay contacts. To control the relay, insert a switch or button or controlling transistor in series with the coil. The wiring is exactly no more comlpex than a table lamp.

We generally install a reverse biased diode across the coil leads to reduce noises in the amp.

Go to the web site of relay makers and see what tutorial data there are. The pin wiring arrangements should be on any data sheet, and on most relays it is printed right on the relay itself.

[gtrscott]

Ahh, that makes sense now.

Thanks very much for the plain english explanation.

One question, by reverse biased diode, you mean that the diode is oriented to prevent any voltage going back acoss the relay?

Thanks again!!!!

[Enzo]

NO, the diode is oriented so the relay power supply does not conduct through it. If a relay runs on +24VDC then the cathode of the diode would be at the +24v end of the coil. ANd of course -24v means the anobe of the diode is at the -24v end.

The diode is there for when power is romved from the coil. The coil inductance wants to keep the current flowing. that diode shunts that current back to the other end of the coil,.

[gtrscott]

Thank you very much for your help!!!