Yes you are 
Thanks. I see that these contactors ( with 4 pins) are very expensive. Are there any other cheaper alternatives?
Can a relay also work the other way around, like high voltage circuit driving a low voltage circuit? If so, please provide me a link to such a product.
The one in the link that I've included before is at 12 euros that is mostly the lowest that you can found, the price are related to the contact rate. The contactors are relays, is a just a different name used to indicate devices that has 230V coil rather relays are typically at lower voltages.
If you have a lot of lamps to control and don't want to spend too much money, you can always connect the wall switch to the arduino directly and let it control the lamp, and maybe use the scheme that I've proposed only for some main lights.
A middle way is changing your wall switch with double poles one, they are cheaper a smaller than a contactor and has two poles. These are think for breaking both phase and neutral to a device and are not common for light, rather are used for high power devices.
In that case, you have the switch and two poles, so you can use the same scheme without the contactor in between.
Regards,
Dario.
I considered the double throw relay as a possible solution to knowing the state of a latching relay until I saw the cost. When you spend as much on a relay as the rest of the circuitry, it gets a little silly. That's why I've been researching how to sense that current is flowing in combination with voltage being available.
What I want to do is power the electronics of a switch with the power that's available in the switch box (no batteries or separate power supply) This means that I have to have a tiny power supply that takes mains voltage (110 for me) and gives me 5V to run the circuitry. On a multi-switch setup, where there are both SPDT and DPDT switches in the chain, finding power and knowing the state of the latching relay can become quite a task without rewiring the switches.
draythomp:
I considered the double throw relay as a possible solution to knowing the state of a latching relay until I saw the cost. When you spend as much on a relay as the rest of the circuitry, it gets a little silly. That's why I've been researching how to sense that current is flowing in combination with voltage being available.What I want to do is power the electronics of a switch with the power that's available in the switch box (no batteries or separate power supply) This means that I have to have a tiny power supply that takes mains voltage (110 for me) and gives me 5V to run the circuitry. On a multi-switch setup, where there are both SPDT and DPDT switches in the chain, finding power and knowing the state of the latching relay can become quite a task without rewiring the switches.
If this is your job, the cheapest solution is a double pole wall switch (7 $) and no additional space or power supply required as the one that I've linked before.
If you want to sense the 110V you have to build a capacitive transformer, but it will require an isolation, otherwise you may risk to burn your board.
Regards,
Dario.
npadma:
@TorremolinosThanks for the reply. I did go through your project, but couldn't really find anything related to controlling and monitoring the current status of the light in existing 2-way switch circuits. Please provide me a link or additional info, if I did miss on something.
Hello everybody.
I am sorry. I have not read the forum for some days and I was not able to answer.
Anyway, I can explain the concept of the schematic and its aim. The basic concept is to make a "3 relays circuit". First relay to change between manual and remote mode, second one to let pass the current from the fase cable, and the third one works as "inversal" relay, detecting the change of state of the switch connected to the fase cable.
Why to use this concept? Ok. For me it was essential two things:
1- manual mode has preference over remote mode, so if the state of the switch is changed, by internal programming at Arduino board, the remote mode is always disconnected (this can be changed for emergency modes, as it is controlled by Arduino)
2- If the PCB has a problem and it does not work, all the PCBs are a cable. The current will arrive directly from the fase cable that it pass through the switch. It always work in manual mode. Without current at relays the only way to work is manual mode.
I hope that I have been able to answer the concept of my circuit.
im not sure if your question has been answered, so ill just cut to the chase...
you can set your relay like a 3 way switch. NC and NO of the relay will serve as the traveler leads, with the C as the common. Therefore, you will need a 4 way switch between your relay and a 3 way switch. This will allow your to control your lights from 3+ locations simultaneously.