5v DPDT relay channel switching double check

[TheKT88KilledJFK]

So I've started incorporating DPDT relays like the one found for sale on this site into my projects and I'm trying to make sure I understand the Switching logic of the relay itself.  I've attached a pic outlining a potential configuration.  Essentially, it looks like the middle pin (9 in this case) is set default to pin 10.  When 5v is applied to the relay, it switches pin 9 to pin 8?  This operation is mirrored for the other side where the middle pin switches between the outside pins?

I know it probably seems obvious but I like double checking the operation of these things!

[shooter]

looks correct,
relay contacts are typically labeled N/C or N/O, normally Closed, or normally Open, meaning that is the state they are in laying on the table, no power applied.  Also there is typically a diode across the relay coil, Anode to -  Cathode to +

[TheKT88KilledJFK]

looks correct,
relay contacts are typically labeled N/C or N/O, normally Closed, or normally Open, meaning that is the state they are in laying on the table, no power applied.  Also there is typically a diode across the relay coil, Anode to -  Cathode to +

Thanks again shooter!

[PRR]

It gets "obvious" *after* the first time you work it out.

A relay is a push-button switch(es) and an electromagnet to "push the button".

The drawings are somewhat conventionalized for drawing simplicity; most relay users know the convention.

In relays and in switches, what Shooter said: "NO" is Normally Open; "NC" is Normally Closed, where "Normal" is no push/coil-current.

A plain house door-bell button is Normally Open. No push, no path from battery to bell, no ring.

A home furnace has a 24V (for safety) thermostat switch and a 24V relay at the furnace. If it is warm-enough (or the thermostat wires break), the NO function ensures the furnace does not run.

My car has a headlight high/low relay. Normally headlight power (from yet another relay!) flows through the NC contacts to the Low beam lights. When I click the thingie, the hi/lo relay coil is energized and now the NC contacts open, the NO contacts close, the High beams come on and the low beams go off.

You can re-verify these thoughts with a continuity checker for the contacts and an appropriate battery for the coil.

I would not say a diode is "typical". Many/most relays do not have one. But a lot of 5VDC relays do, because they are typically run from logic chips, which need the protection, and an on-board diode saves a penny in assembly. Check for this and be sure you get it right way round!

[sluckey]

Be careful when wiring that relay! The pic you show of a JQX-115F relay is ***NOT*** the same as the OMRON relay that Hoffman sells. The pin out is totally different. Here's the info on Hoffman's relay...

[TheKT88KilledJFK]

It gets "obvious" *after* the first time you work it out.

A relay is a push-button switch(es) and an electromagnet to "push the button".

The drawings are somewhat conventionalized for drawing simplicity; most relay users know the convention.

In relays and in switches, what Shooter said: "NO" is Normally Open; "NC" is Normally Closed, where "Normal" is no push/coil-current.

A plain house door-bell button is Normally Open. No push, no path from battery to bell, no ring.

A home furnace has a 24V (for safety) thermostat switch and a 24V relay at the furnace. If it is warm-enough (or the thermostat wires break), the NO function ensures the furnace does not run.

My car has a headlight high/low relay. Normally headlight power (from yet another relay!) flows through the NC contacts to the Low beam lights. When I click the thingie, the hi/lo relay coil is energized and now the NC contacts open, the NO contacts close, the High beams come on and the low beams go off.

You can re-verify these thoughts with a continuity checker for the contacts and an appropriate battery for the coil.

I would not say a diode is "typical". Many/most relays do not have one. But a lot of 5VDC relays do, because they are typically run from logic chips, which need the protection, and an on-board diode saves a penny in assembly. Check for this and be sure you get it right way round!

I always feel like I'm playing catch up with conventions in this industry! 

So the diode is there to protect the logic chip.  I'm just using a foot switch so I don't really think it needs the diode, then.  I might put a low pass RC network behind the switch in case there is bouncing action but I have a feeling the relays aren't fast enough to care. 

Be careful when wiring that relay! The pic you show of a JQX-115F relay is ***NOT*** the same as the OMRON relay that Hoffman sells. The pin out is totally different. Here's the info on Hoffman's relay...

Thanks!  I decided to go with the other one because the pcb footprint is readily available in the limited software I use (easy eda).  For future convenience, I'm actually hoping they're the same footprint and there's some sort of 5VDC relay package standard these companies try to comply with. 

[sluckey]

So the diode is there to protect the logic chip.  I'm just using a foot switch so I don't really think it needs the diode, then.

Any time a DC coil relay de-energizes (switch off) there will be a big reverse polarity voltage spike created. Yes, this spike can harm the relay driver. This same spike will cause a very noticeable "pop" in a sensitive audio circuit. The diode will prevent this pop. A cheap 1N4148 is the most commonly used diode with low voltage relay coils. All commercial, industrial, and military electronics use diodes. You probably won't find diodes under the hood of your car. I highly recommend using a diode in electronic circuits.

Hoffman's relay fits a standard 16 pin DIP footprint. I can't find info on the footprint of that JQX-115F relay.

[TheKT88KilledJFK]

So the diode is there to protect the logic chip.  I'm just using a foot switch so I don't really think it needs the diode, then.

Any time a DC coil relay de-energizes (switch off) there will be a big reverse polarity voltage spike created. Yes, this spike can harm the relay driver. This same spike will cause a very noticeable "pop" in a sensitive audio circuit. The diode will prevent this pop. A cheap 1N4148 is the most commonly used diode with low voltage relay coils. All commercial, industrial, and military electronics use diodes. You probably won't find diodes under the hood of your car. I highly recommend using a diode in electronic circuits.

Hoffman's relay fits a standard 16 pin DIP footprint. I can't find info on the footprint of that JQX-115F relay.

The 5v power isn't going to be on any lead carrying audio signals so I assume you are saying it will still cause a pop across the otherwise isolated signal pins.  Well I guess the diode is going back in!  I was already trying to address channel popping but I was just going to use some high value resistors shunt to ground on the signal pins.     

I'm going to try to use the omron unit anyways.  Edit:  I found a pcb foot print for it so I'll used that instead.

[TheKT88KilledJFK]

Another consideration is that I am using one of these relays to switch between cathode-follower-driven tone stacks, so it has well over a couple hundred volts DC on the contacts.  I might have to find another solution altogether, maybe LDR.