Wiring a simple switch

hi all,

I'm wishing to wire up my arduino and ethernet shield to a control switch (image attached) so that when I turn on the switch via my web panel it will do so via the arduino.

Just wondering if there are any tutorials about this type of thing.


Not sure what you want to do here. That looks like a mains switch, do you want your arduino to physically click over the switch?

Hi sorry I should have explained it a little better.

I'd like to replicate the functionality of the switch so either wire it up to replace the switch or to wire it up to this unit and replicate the switching function.

I should have explained it a little better.

Getting close but no coconut yet. What is the switch carrying? Is it mains? If so how much current?

The switch itself is attached through a small snow machine unit.

The snow machine is mains powered (230v)

so how much current?

Without knowing this it is imposable to tell you what size of SSR to get.

Maybe it would be better if you took a image of the machine, and a close up of the label on it...

That switch has a single wire, so it’s hard to tell what its function really is. Perhaps it’s mains AC. Perhaps something else.
I suggest you open the case of the switch, and show a picture of the insides. You should also take a multimeter to the switch, and measure the voltage across the switch when it’s off, and if possible, the current through the switch when on. Just don’t touch any live wires with your body!

Let’s assume the switch is mains AC, and that it runs something less than 900 Watts (so it’s < 8 A for 120, or < 4 A for 240). Further, let’s assume it’s a simple SPST switch that just turns “on” and “off.”
In this case, you can bridge the switch using a relay – either a simple mechanical relay with appropriate current/voltage rating, or a solid state relay (“SSR”).
SSRs can be driven directly by an Arduino. For example, this guy, plus a 180 Ohm resistor, will work fine:
http://search.digikey.com/us/en/products/S108T01F/425-2395-5-ND/720455 (about $5)
(This is the 120 V / 8A version; it comes in higher voltage/currents too for about a dollar or two more – I’m using it myself and I love it)
An alternative is a mechanical relay, which then also needs a MOSFET or other buffer from the Arduino, because the relay coil draws too much current.

Now, wire a 180 ohm resistor from Ardy output pin to “+” side of the SSR, wire “-” side to ground, wire a 47 kOhm pulldown between the ardy pin and ground for good measure. When you drive the output pin “high,” then the relay will conduct AC across the AC-marked pins. Connect those AC pins across the switch on the inside of that black box, and you have what you need!