vocabulary precisions about relays...

[artsinbloodshed]

hey guys!
As many folks around here i'm building my switching system, involving relays and all.I must say that i'm a bit lost amng the sum of info available..
already read articles at geofex (like this one:http://www.geofex.com/article_folders/rmtswtch/rmtsw.htm) and elsewhere.
In order to make my researches about relays more efficient I need some hints about what's  what...especially concerning what I'd like to build.
so, what does latching relay means!
my aim is to build an amp channel switching system (2 channels).
Do I need a flip flop relay design? a latching one?
i'm confused..
thanks!
J.

[R.G.]

so, what does latching relay means!

There is a whole article on audio relays and what they are, how they work, at geofex.com

However;
Normal or non-latching relays are momentary switches moved by an electromagnet. If there is no current in the coil, they sit on one position all the time. They are also called "one-side stable".  The no-coil-current position is stable with nothing done to the coil at all. If you put enough current into the coil, the electromagnet makes the switch flip to the other position. It stays in the energized position only as long as there is enough current flowing through the electromagnet coil. When the current quits, it goes back to the no-current position. So if you want it to stay "on", you have to provide coil current all the time.

A "latching" relay or "two-side-stable" relay has a mechanical and/or magnetic setup much like a light switch. It is stable in either position with no current in the coil. But to get it to flip to the opposite condition, you have to put enough current into the coil in the right direction to make it flip to the other position. After it flips, the coil current can be reduced to zero, and it will stay there.

Do I need a flip flop relay design? a latching one?

Let's ignore relays for a minute and think just about the switches. There are momentary footswitches and "alternate action" footswitches. Momentary footswitches stay in one condition all by themselves, and only go to the opposite condition when you push on them with your foot. If you remove your foot, they go back. Alternate action footswitches stay in whatever condition they are in, but when you push on them, they go to the opposite condition and stay *there* until you push again to make them go back.

This is exactly the same as relays, except you use electricity to make the relays change. For a non-latching (that is, momentary!) relay, the relay changes away from the no-current condition as long as the electricity flows in the coil, just like the momentary switch only stays switches while your foot is on the pushbutton. For a latching relay, each pulse of current makes it change to the opposite condition, just like your foot pressing the button makes an alternate action switch change to "opposite" until you press it again.

So the answer to your question is tied up in what you want your footswitches to do. Do you want them to be momentary? Then you can use a nonlatching relay.

If you want them to change when you press the button and only change back when you press the button again, you need either (1) an electronic flipflop to make the "momentary" relay stay changed until you change it again or (2) a latching relay to make the relay itself remember where to stay after you change it.