Where to buy non-latching relays?

[spargo]

I'm looking for a small footprint DPDT or 3PDT non-latching relay to use for a momentary switch (the smaller the better!).  Smallbear only seems to carry latching relays.  Any ideas on where to find non-latching ones?  I'm new to relays, so I'm at a bit of a loss on mouser or digikey with a billion choices.

[defaced]

I used the Omron G5V series in my amps (as do alot of other amp builders) - these are all non latching. These come in SPST, DPDT and various voltages and sensitivities (current draw).  With those parameters, you should be able to get something that'll work well in your setup. These can be found through Mouser or other big supply houses.  

http://www.mouser.com/Electromechanical/Low-Signal-Relays-PCB/_/N-5g38?Keyword=omron+g5v&FS=True

[spargo]

I'm new to relays.  Anything particular I should be looking for?  The box will have a standard 9V supply available.  The smaller the horizontal footprint the better (but it can be taller).  From my understanding, relays are basically mechanical switches so I'm not sure this makes a difference, but if there is any resistance in the switch connection from point A to point B I need one with as little resistance as possible.  I'm trying to make a connection that shorts two wires, and the connection needs to be strong and direct.

[defaced]

A relay is made of two things, one is just a normal set of switch contacts, the other is a coil that becomes an electromagnet when you energize.  If there's any resistance in the switching contacts, it's not going to be any different than a regular switch with switching contacts made of the same material.  I'm going to assume you're switching a signal, which is why I pointed you to the G5V series because these relays are intended are a low signal relay. Signal relays are different than relays intended to switch power which have contacts made of different material (not surprisingly this is the same for regular switches, just no one really cares unless they have a need to).  As for size, the G5V-s (DPDT) are the size of a 16 pin DIP chip, the SPST versions are smaller, I think 10 pin DIP but check the data sheet to be sure.  I would advise socketing the relays like you do ICs. They are mechanical and can fail, and really suck to unsolder if you have to replace them. 

So, open that page I linked to and you'll see alot of selection boxes in the middle of the page.  You're working with 9v, so select 9v from the "Coil Voltage" box.  
That leaves you with 5 choices, of which three are in stock.  
Of these five, the G5V-1 are SPST, the G5V-2 are DPDT.
Download the data sheets for both and start reading.  You'll see that Omron offers different sensitives (current draw) for their relay coils.  If this is battery powered, you probably want the highest sensitivity you can find because that will be the relay with the lowest current draw.  This is in the "Coil Data" table.  

Presto, you've selected a relay for your application.  If you don't like what Omron has to offer, then go back to Mouser (or wherever you want to shop), and start over with a different manufacturer.  You know enough now to select a relay for what you're doing from scratch.  

[spargo]

Cool, thanks for the help.  You can get a lower coil voltage can't you?  If I get one that's 5V and send 9V to it, it'll switch, correct?  It just needs to be at least that much.  Is the coil resistance what I was talking about?  The lower voltage ones have a lower coil resistance.

I'm concerned about the resistance because I've tried the switching with a CD4053 and there is resistance somewhere in there that didn't make a strong connection between the two points being switched, and the signals were not fully shorted (which is what I'm trying to do, short two points together).  That's why I'm looking into relays.

[defaced]

The CD4053 is an electronic switch, so yes, there will be some "on" resistance.  This is probably what was kicking your ass with that approach. 

However, I think you're a little confused on how a relay works because the coil resistance has nothing to do with the resistance switch contacts - which is what you really care about if you're shorting two wires together.  So looking at the data sheet and saying "Hey, the 5v coil one has lower resistance, that will make better switch contact" won't get you what you're after because the coil and the switch are completely different parts of the relay. 

The switching part of a relay is exactly like a mechanical switch, so inside there are two pieces of metal that will touch.  Whatever resistance there is between those two contacts is probably negligible (unless you're dealing with very high currents) and very difficult to measure (meaning, fractions of an ohm). 

The coil is basically a wire wound resistor.  It has a resistance, and when a specified voltage is applied to it, a desired amount of current flows, and that current creates a magnetic field that moves the relay switch contacts.  If you supply this coil with too much voltage, too much current can flow and the wire can fuse open.  This is why it's a bad idea to use a 5v relay with a 9v supply.  In the case of the G5V, you can run the relay at 180% of its listed voltage.  That puts you right at 9v, so any over voltage and your relay's coil can fuse open.  (Side note, a new 9v battery is about 9.6v)

In the world of switching for our applications, a relay is the closest you can get to a perfect short and is the only what I know of to get a perfect open contact.

Once you see the guts of a relay, it'll make more sense: http://en.wikipedia.org/wiki/Relay

[spargo]

Awesome, thanks for the help!  It all makes sense now.  I just need to find good sockets that will fit and I'm set.

[defaced]

If you decide to order the relays from Mouser, check out the Mill-Max DIP IC Sockets (these will be under "Interconnects" and then under the sub heading "Socket" in the catalog which you can download). Sockets from Mouser will be more expensive than if you buy them elsewhere, but of the sockets Mouser carries, I remember Mill-Max being the least expensive.  I have used them and they are good quality. 

[spargo]

Any idea of a good socket to go with this one? http://www.mouser.com/ProductDetail/Omron-Electronics/G5V-2-H1-DC9/?qs=sGAEpiMZZMs3UE%252bXNiFaVDVuZJnAgzXjQhkBI%252bCseqE%3d

It doesn't seem like a regular 8-pin DIP socket would work since the last two pins seem to be a bit farther apart from the others.

[defaced]

I have used the 24v version of that relay.  They're spaced perfectly for a 16 pin DIP socket.  If you look at the foot print data, the pins are numbered the same on these as they would be on a regular 16 pin DIP IC. 

[spargo]

Ooohh, that makes sense. It's a bit more in perspective now as far as size goes. Thanks!