Checking Voltage

First of all, I'm almost completely an electronics n00b. My knowledge goes as far as connecting an LED or small DC motor to a battery :-)

I'm very interested in buying either a basic stamp or arduino. Apparently the arduino is better (and cheaper :D) so I think I will go with that, but I am unsure if it can do what I want it to!

I'd like to create an automatic changeover switch for my house & generator.

I would get a regular changeover switch installed, and somehow mount a solenoid onto it. That way, I'm not dealing with mains power directly.

I understand that I would need a relay connected to the arduino in order to control a solenoid. I would run the arduino off a 12v battery, constantly hooked up to a charger, so that gives me the power for the arduino, and 12v for things (like relays & solenoids) for when the power is off.

I dont know how much power a solenoid draws, but would a 5v solid state relay connected to an Output, and the ground on the arduino be able to turn a solenoid on and off using things like digitalWrite(pin, 1)?

Or would I need a 5v solid state relay to turn on another (solid state, or mechanical) relay to control the solenoid?

(Reason for this method is because I am not comfortable with making my own relays that have protection etc).

Also, I would need a fairly decent relay to start the generator... Hmm actually I could rip apart the key wiring and just use that. So would I need just two 5v solid state relays, or something else, is the question. :P

That is one side of it, the other is: How should I check that there power - on the mains and on the generator.

I suppose I will need a power point on the other side of the changeover switch which is stepped down to 5v to plug into the arduino, so that it can tell when the power is back on.

And also one on the generator to tell that it is started and producing electricity.

How would this connect to the arduino though? Where would the + and - of the 5v go on the arduino? I cant connect them both to input pins. But I dont want and power to go into the arduino that might hurt it!

So, anyone up for helping a complete n00b out? :D

I also have another project I want to try, but I'll leave that to another thread :D


do you have the specs for the changover switch? My suspicion is that a solenoid big enough to move such a switch would be about the size of an average chicken. :)

I haven't got the changeover switch yet - I didn't think it would be so big, and I thought solenoids had alot of power. Apparently not? Perhaps a small DC motor would be better instead!

solenoids take scads of current to do anything meaningful... you'd be best to find a suitable changeover switch first, and see what that looks like specification-wise. Maybe you can find something that can take a low-voltage, low-power signal to switch the 220V for the house, instead of modifying it for solenoid operation? Safer too.

I've been searching around, but anything for "automatic change over switch" brings up a whole device, including the computer to change it over :s

My knowledge goes as far as connecting an LED or small DC motor to a battery :-)

You know, given what you say above, maybe building a circuit to control and activate a switch that moves 20KW (!!twenty-two-thousand-watts!!Yikes!!) around is maybe not the best choice for a first project. You're talking modifying a switch to control lethal voltages and currents... I wouldn't touch that stuff myself. Not to mention the fact that your house insurance wouldn't touch it either :)

Which is why I just wanted an electrician to install a regular changeover switch, which I can plug some kind of mechanical level straight onto = Safe, and insurance-friendly!

well, if you are "dead set" on it :D ;D :D,

then the thing to do is find a changeover switch and see how much physical force it will take to move it. I'm guessing it's a lot. Design-wise though I would guess that the Arduino stuff will cost you under $150 and the changeover switch will be $1000-2000, so it might be more cost effective and less life-threatening to just buy an automated changeover switch. Something to think about.

Oh-- don't forget to get some rubber boots. ;D

Heh. I'm sure changeover switches aren't that expensive! All they are is a double-throw switch!

At any rate, I'll investigate it further and post my findings and if I go ahead with it.

Hey seriously, working with such power levels on the hobby level (20,000 Watts for the average house) is a VERY bad idea, for your health, safety, personal property and your insurance.

One bad line of code in your cool Arduino 20KW controller and you might find out what happens when that 20KW gets sent somewhere it shouldn't be!

I've just found this image:

See, it can only be between house & mains, or house & generator - NEVER generator & mains.

It would be a proper transfer switch! All this will do is automate switching it on and off! - That has to be safe :P P.S: Generator is only 6000kVA.