Automated Plug-In Appliances

The title may sound a little daunting, but this is probably one of the most simple instructables you could make. Here I will show you how to switch on and off appliances such as TV's, lamps, Christmas lights, or anything that plugs into an AC wall jack, with a microcontroller or any other computerized source.

WARNING: When creating this device, you will be dealing with ~120V AC. This is considered HIGH VOLTAGE, which as many know, can be lethal. Be careful when working with high voltage; NEVER work on this when it is plugged in. Make sure all connections are how they should be, and verify that they are fully insulated and won't short each other out, or you could cause a fire. Also, be aware of what is going on around you, be alert, and never work on with high voltage if you feel you can't devote enough concentration towards what you are doing. And lastly, if you ever have to service the connections inside this device, ALWAYS unplug it before doing so.

Step 1 Theory

Basically, all you need for a low-power microcontroller or any form of computer to switch high-voltage is either a relay or an SCR (solid-state type switching device).

Comments

[purpulhaze]

How would I triggered another computer to turn on? I have a server I would like to make this for but the power switch is a momentary push button. Holding the button down longer than a few seconds will cause it to shut down. I guess what I'm trying to find out is if the relay used is one that will return to its original state. Kinda like a momentary push button.

[pastaking]

Not sure if this will help, but on some computers I have used, the computer will power itself up when power is connected. An even easier way would be to configure the server to automatically hibernate/sleep, and use the 'wake on LAN' function on the network card. That way, when the server is not being used, it automatically goes into a low-power state, but is easy to access when needed. The only drawback to this would be the fact that you can't use the computers alias/network name to refer to it, as the computer does not broadcast its status when it is in standby.

[purpulhaze]

(removed by author or community request)

[mortaldoom780]

Using PWM with a incandescent bulb is probably not a good idea if you want it to last long! You could dim it with fixed resistors on different relays or solid-state switching devices, yes. You would use ONE SPST relay for power, and ONE SPDT relay for the dimmer, connected in conjunction with the appropriate resistor. Or you could go fancy and but a digital potentiometer from Maxim, for example.

[mattotone]

The latest dimmer packs used in theaters all use PWM sinewave dimmers. quiet as a mouse with no crap on the mains. All they do is PWM the power, and then filter to make it smooth.

[purpulhaze]

Okay, I'm so use to working with DC. With the fixed resistors I would need a different resistor and relay for every varying light level. I also know that it would generate a lot of heat. I'm going to check out the digital pots. I'm trying to get into home automation and seeing that it's probably a lot easier to just buy ready made modules.

[account3r2]

what number gauge should I use?

[evilwon]

 I don't get it. After you make this thing how do you control it (specifics)?

[purpulhaze]

I purchased a Solid State relay  pretty cheap from China off of ebay and got the other parts from the hardware store.

[mortaldoom780]

Very nice. I should have used solid state instead of this giant, noisy relay haha

[eecharlie]

Any particular reason you chose relays over a triac or pair of SCRs? If you used a triac, I think you should be able to accomplish PWM, although it's a little complicated and requires synchronizing your PWM signal with the AC line phase. But, PWM with relays means clicky sounds and can't approach the frequencies you'd need to dim lights etc.

[mortaldoom780]

Yea, I was hoping to do it that way, but I couldn't find any schematics online of that type of circuit, and these relays were readily available. If you have a good example schematic let me know.

[gibson_se]

Personally, I do my high voltage safety the other way around. "Always keep the device plugged in". It keeps you on your toes, and lets you know when you made a mistake. ;-)

[blackwellj]

what relays would you suggest for uk 240V 13A ac power and 3-5V trigger Voltage form arduino

[Kallan]

Just a note, 120VAC is no where near high voltage ;) But still deadly.

[kikiclint]

this ible needs some more details about how to interface with a computer or microcontroller. Labeling some more of the components in the pictures would also help.

[imakethings]

NC is normally closed NO is normally open

[Mr. Smart Kid]

NC means normally closed "connected" NO means normally closed "not connected"