I want to make some kind of relay plug

[Syntaxvgm]

So here's what I want- when an outlet goes off, as in has no power, it powers a plug from another source, but ONLY when the first plug is off. 

I have a plug on a lightswitch (where the lights are obviously), and I want some stuff that's on only when the lights are off. (Unnecessary detail, I will run the power source battery backup so I have lighting during power loss) 

Easiest way to go about this? 

[Enderman]

Something like this:

https://www.grainger.com/product/FUNCTIONAL-DEVICES-INC-RIB-Enclosed-Pre-Wired-Relay-2ERZ5?functionCode=P2IDP2PCP

 

Coil volts is 120VAC so you can wire it directly into the your first wall plug.

 

Then it is SPDT switch so from the other 3 wires (there are 5 total) when power goes out two of them will be connected, so you just put that in line with the stuff you want to turn on when power goes out.

Keep in mind that this relay in only 10A, there are other models that can do more if you need.

[Syntaxvgm]

9 minutes ago, Enderman said:

Something like this:

https://www.grainger.com/product/FUNCTIONAL-DEVICES-INC-RIB-Enclosed-Pre-Wired-Relay-2ERZ5?functionCode=P2IDP2PCP

 

Coil volts is 120VAC so you can wire it directly into the your first wall plug.

 

Then it is SPDT switch so from the other 3 wires (there are 5 total) when power goes out two of them will be connected, so you just put that in line with the stuff you want to turn on when power goes out.

Keep in mind that this relay in only 10A, there are other models that can do more if you need.

third wire ground? Do I just ground the box somehow? 

[Enderman]

21 minutes ago, Syntaxvgm said:

third wire ground? Do I just ground the box somehow? 

No, these are what the three wires are for:

[Mihle]

Endermans solution only works when you manually switch the light switch.

 

Normally closed relay, would work even if for example the fuse went (if the other source isn't connected to the same fuse).

 

Aka, when it's activated, it's open. So when it's activated, what's connected to it will be off.

 

Btw, doing this, 100v+ stuff would be illegal in my country without Bering an electrician.

Edited August 23, 2017 by Mihle

[mariushm]

The easiest would be to use a microcontroller, an optical isolator and a couple of relays.

 

Use a capacitive dropper (resistor and capacitor in a certain layout) to reduce the 110v AC from the lamp to something the optical isolator can accept (for example 5v). As long as theres power, the isolator sends "1" on the other side to the microcontroller.

 

Micro keeps monitoring the signal from the isolator. If there's no 1s for a few seconds (configurable), disconnect the relay which connects your devices to same circuit with the lamp, wait a second or so (because you don't want both connections active at same time and you don't know how many ms it takes for relay to disengage) and then turn on the other relay.

Then, continue monitoring and when you get 1s again for at least a few seconds do the same thing the other way.

 

If you want uninterrupted power, you'd have to use an UPS after this switcher or use an inverter.. There's nothing cheap you can buy which would switch instantly between power circuits

[Pixel5]

13 hours ago, mariushm said:

The easiest would be to use a microcontroller, an optical isolator and a couple of relays.

 

Use a capacitive dropper (resistor and capacitor in a certain layout) to reduce the 110v AC from the lamp to something the optical isolator can accept (for example 5v). As long as theres power, the isolator sends "1" on the other side to the microcontroller.

 

Micro keeps monitoring the signal from the isolator. If there's no 1s for a few seconds (configurable), disconnect the relay which connects your devices to same circuit with the lamp, wait a second or so (because you don't want both connections active at same time and you don't know how many ms it takes for relay to disengage) and then turn on the other relay.

Then, continue monitoring and when you get 1s again for at least a few seconds do the same thing the other way.

 

If you want uninterrupted power, you'd have to use an UPS after this switcher or use an inverter.. There's nothing cheap you can buy which would switch instantly between power circuits

the idea is not bad but it can be done much simpler, all you need is a  relay module with two relays on it and a 5V power supply.

 

you connect whatever you need to have powered to the relay, one powersource to NO and the other to NC, one relay for life and one for neutral.

then you just wire the module directly to the 5v power and whenever the power goes out the relay will switch to the NC contact where you need to connect you secondary power source.

 

this way it is impossible for both power sources to be on at the same time and they will switch at the same time within a few milli seconds.

 

[Enderman]

17 hours ago, Mihle said:

Endermans solution only works when you manually switch the light switch.

 

Normally closed relay, would work even if for example the fuse went (if the other source isn't connected to the same fuse).

 

Aka, when it's activated, it's open. So when it's activated, what's connected to it will be off.

 

Btw, doing this, 100v+ stuff would be illegal in my country without Bering an electrician.

No it also works when the power goes off, why do you think I told him to get SPDT??

Do you not understand what double throw means?

 

He wants the second circuit to be connected when he either shuts off the first circuit (with a light switch) or power goes out.

This relay does exactly that.

 

15 hours ago, mariushm said:

The easiest would be to use a microcontroller, an optical isolator and a couple of relays.

This is a massive overcomplication of a simple problem.

Only a single relay is necessary to achieve all that, no other electronics.

[mariushm]

3 hours ago, Pixel5 said:

you connect whatever you need to have powered to the relay, one powersource to NO and the other to NC, one relay for life and one for neutral.

then you just wire the module directly to the 5v power and whenever the power goes out the relay will switch to the NC contact where you need to connect you secondary power source.

 

this way it is impossible for both power sources to be on at the same time and they will switch at the same time within a few milli seconds.

 

 

Whenever you use two relays and only one of them must be active at any point, there must be some delay between them.  It takes a few ms for the coil in the relay to energize and turn on a relay, and it also takes some time for the coil to lose its energy and for the magnetic field to go down enough to disconnect a relay.

So from time to time, it may happen that both relays will be ON or in some in-between state and you'll have energy from 2nd circuit flow through the relays into the first circuit and turn on the lamp.

 

1 hour ago, Enderman said:

He wants the second circuit to be connected when he either shuts off the first circuit (with a light switch) or power goes out.

 

Ah see? I missed that initially...

 

So he actually needs to

* check if there is voltage on the circuit

* check if there is a switch on or off  (you could probably simplify it to "is there at least this many mA of current flowing?" )

 

It seems like he wants the gizmo to switch to other circuit if there's no voltage on the first circuit  OR   if user hits the switch (therefore no current flows but there's still voltage)

Maybe I over-complicate it.

 

Measuring the current flow would be super easy, just a hall effect sensor or a current transformer on the AC wires before the switch. If the switch is off, naturally there's no current flow, so you know to connect the device to the other circuit.

 

[Enderman]

8 minutes ago, mariushm said:

It seems like he wants the gizmo to switch to other circuit if there's no voltage on the first circuit  OR   if user hits the switch (therefore no current flows but there's still voltage)

Maybe I over-complicate it.

I am pretty sure he means that he wants to wire it AFTER the switch, such that it will activate when the power goes out, or he can manually override it by flipping the switch off, which basically simulates the power going out.

 

There is no need to measure current or anything, simply plug the relay into the wall outlet controlled by the switch.

Then it will activate when he either shuts the switch off or power goes out.

[Pixel5]

35 minutes ago, mariushm said:

 

Whenever you use two relays and only one of them must be active at any point, there must be some delay between them.  It takes a few ms for the coil in the relay to energize and turn on a relay, and it also takes some time for the coil to lose its energy and for the magnetic field to go down enough to disconnect a relay.

So from time to time, it may happen that both relays will be ON or in some in-between state and you'll have energy from 2nd circuit flow through the relays into the first circuit and turn on the lamp.

 

 

you dont need two relays because you use one to switch powerline one off and then switch power line two on.

you need two relays because we are dealing with AC and you need to connect and disconnect both life and neutral in order to keep both power sources separate.

 

i fritzt together a little overview, on the left the two power sources the regulator stands for the 5V powersupply, one line from each powersource goes to one on the relays which are switched to the normally open position as long as there is power on 5v

 

if power goes out on the upper power line the relays turn of all at once and automatically switch both neutral and life wires to the 2nd power source.

 

the LED stands as a replacement for the actual load, i know that LEDS wont like 120V AC just like that.

 

[Mihle]

3 hours ago, Enderman said:

No it also works when the power goes off, why do you think I told him to get SPDT??

Do you not understand what double throw means?

 

He wants the second circuit to be connected when he either shuts off the first circuit (with a light switch) or power goes out.

This relay does exactly that.

I think I got confused with the symbols you posted with the symbols I have learned... 

But just a normal Normally closed relay in parallel with the main circuit would work just fine...

Not that switching relay thing.

EDIT: realized now he probably ment switching to a different source in the same light and not a second light... my mistake.

[Enderman]

7 minutes ago, Mihle said:

I think I got confused with the symbols you posted with the symbols I have learned... 

But just a normal Normally closed relay in parallel with the main circuit would work just fine...

Not that switching relay thing.

EDIT: realized now he probably ment switching to a different source in the same light and not a second light... my mistake.

A relay IS a switch...

DT means that you have both the options of using it as normally closed or normally open.

 

Holy crap why are the people in this thread complicating everything so much...

This is a simple circuit...

Now when power goes out or he flips the switch, his devices will turn on (assuming the other 120vac line still has power).

[Mihle]

1 hour ago, Enderman said:

A relay IS a switch...

 

Ofc I know a relay is a switch controlled with electricity, Do you really think I am that stupid?

[Enderman]

2 minutes ago, Mihle said:

Ofc I know a relay is a switch controlled with electricity, Do you really think I am that stupid?

 

Then why did you say this...

 

"just a normal Normally closed relay in parallel with the main circuit would work just fine...

Not that switching relay thing"

[Mihle]

43 minutes ago, Enderman said:

 

Then why did you say this...

 

"just a normal Normally closed relay in parallel with the main circuit would work just fine...

Not that switching relay thing"

Bad words on my part, I was tired. I write bad when I am tired.
But I ment that that one you posted is basically a normal open AND normal closed relay. 

Just stop. please.

[Mihle]

And that's a product that isn't used here.

[Enderman]

8 minutes ago, Mihle said:

Just stop. please.

This is something you could have done a long time ago.

I can't believe I needed to draw a picture of what I explained in my first post in order for people to understand how simple this is.

 

Just now, Mihle said:

And that's a product that isn't used here.

Are you talking about double throw? Double throw switches are literally everywhere...

[Mihle]

4 minutes ago, Enderman said:

This is something you could have done a long time ago.

I can't believe I needed to draw a picture of what I explained in my first post in order for people to understand how simple this is.

 

Are you talking about double throw? Double throw switches are literally everywhere...

Not that spesific product.

[Enderman]

3 minutes ago, Mihle said:

Not that spesific product.

Oh look, thousands of SPDT relays also available in norway. What a coincidence!

http://no.mouser.com/Electromechanical/Relays/_/N-5g31

[Mihle]

7 minutes ago, Enderman said:

Oh look, thousands of SPDT relays also available in norway. What a coincidence!

http://no.mouser.com/Electromechanical/Relays/_/N-5g31

Not the exact same product.

I got confused.

Stop.

[Enderman]

1 minute ago, Mihle said:

Not the exact same product.

Stop.

It's a relay, they all do the same thing.

I never said he needed to get that exact same product, I was giving an example of the type of product that would do what he wants.

 

Notice the first three words of my initial post:

Quote

Something like this

 

[Mihle]

5 minutes ago, Enderman said:

It's a relay, they all do the same thing.

I never said he needed to get that exact same product, I was giving an example of the type of product that would do what he wants.

 

Notice the first three words of my initial post:

 

Just stop. I know it's a relay. I got confused at first, as I said.

[Pixel5]

12 hours ago, Enderman said:

A relay IS a switch...

DT means that you have both the options of using it as normally closed or normally open.

 

Holy crap why are the people in this thread complicating everything so much...

This is a simple circuit...

Now when power goes out or he flips the switch, his devices will turn on (assuming the other 120vac line still has power).

how should that circuit switch between two AC sources?

 

the source on the left powers the coil of the relay so you can switch between the NC and NO contact so the circuit is able to turn the power coming from the right on or off but it will never switch to the power from the left.

Its essentially a switch that is controlled by turning of the power on another outlet instead of switching to that outlet.

[Enderman]

6 hours ago, Pixel5 said:

how should that circuit switch between two AC sources?

It doesn't.

OP never said he wanted to switch between two sources.

6 hours ago, Pixel5 said:

Its essentially a switch that is controlled by turning of the power on another outlet instead of switching to that outlet.

Yes, this is what he wants, look at what he said:

"when an outlet goes off, as in has no power, it powers a plug from another source, but ONLY when the first plug is off."

 

For example, maybe you have some LED strips underneath your table, but you only what them on when your room lights are off.

Or you have a special emergency lighting system and you only want it to turn on when there is a power outage (in which case the second circuit will need to be battery powered, such as a UPS)