relaytransistors
I have some remotely controlled sockets and I would like to rip open the remote control (3v DC) and connect it to the rooms lighting switch (240V AC) so the sockets are triggered when the light is switched on.
Any idea what type of relay I would need to do this (240v trigger with a 3v load) ? Would it be small enough to conceal in the backbox of a light switch?
Thanks!
There are multiple reasons you want to do this in your case the reasons I can think of are:
1) The relay needs 12V on the input to turn on. An Arduino GPIO only outputs 5V. A transistor in between will allow a 5V signal from the Arduino to switch a 12V signal via the transistor to the relay - thus turning it on.
2) The transistor provides protection. In the event of a back emf voltage spike or some other undesired event only your transistor will be blown, instead of the entire Arduino.
3) Using a transistor should provide marginally faster switch times because the transistor can source more current than the few mA that an Arduino can - thus saturating the coil faster.
Read this info sheet (http://www1.electusdistribution.com.au/images_uploaded/relaydrv.pdf). and pay attention to these images in particular. They show you what a good switching circuit would be and explain how to implement them.
Just want to post the resolution in case anyone else ends up here with the same issue.
First, I have to admit I was being lazy because I didn't want to remove the camera from its mount to bring it to a place where I could do tests.
I checked the voltage across camera pins 2 and 4. I found 5VDC. I connected camera pins 2 and 4 to the relay pins DC+ and DC-. Resulted in green "power" LED illuminated.
Next, I connected camera pin 1 to relay pin "IN." To test, I went to the camera setup page and changed the digital output state from NO to NC. No effect. I then moved the relay jumper from low to high. At that point, I was able to change relay by changing the digital output state on the camera.
Calling it solved. Now I just need to decide where to mount the relay and how to make the connections.
Thanks for all the assistance. I love this site!
Best Answer
If you have 3V to drive the relay, then you can possibly use a Solid State Relay. It seems to be just barely enough to turn it on.
However I feel that if you are asking this kind of question, you shouldn't be modifying the AC wiring in your home just yet. It could possibly kill you and others either by electrical shock or fire.
Please be careful and research a bit more, possibly for other kinds of controllable lights which you can also modify and hack.