I want to use one an push button with an led in middle, similar to this one on eBay. The push button has a 12v input I want to hook it up to an Aduino Uno or Nano.
Is there a way to hook it up and receive the signal?
Specifications from the eBay page:
- Latching type, push it—on, push it again — off
- Switch Rating: 3A/250VAC
- LED voltage: 12V only
- Contact Configuration: 1NO1NC
- Pin Number: 5
Most likely, there will be a push button, and on separate wires, there is a light. If this is the case, you can hook the push button part up to the arduino. You can test this - find two random wires, test the resistance with a multimeter, then press the button and see if the resistance changes. Keep trying until you find two wires that change when you press the button.
Once you find the pair, you can hook one of those two to a digil pin on the Arduino, and via a resister (large, anything 10kilo-ohm or larger is fine) to ground (GND). Then, connect the other side of your pushbutton to 5V. See http://arduino.cc/en/tutorial/button for photos and a circuit diagram - their wiring is more complicated than it needs to be, and their button has 4 pins in two pairs (left pair, and right pair in the picture with the breadboard; the left-top and left-bottom are permanently connected, and the right-top and right-bottom are permanently connected). Have a look at the circuit diagram - that's a lot simpler. The zig-zag at the top is the resistor, and the disconnected looking thing is the switch (open). There is sample code there too.
Note that push buttons typically "bounce" - that is, when you push them, they will go (starting off) on-off-on-off-on-off-on, so if you're counting the number of pushes you will get a result which is way too high. If you delay long enough in between (10ms?) then you won't get these. The code I linked to already has debounce built in.
The other part is the light. This is a little more tricky. The light will probably use too much current for the arduino to supply directly. You will need a transistor and a resistor (again, at least 10 kiloOhm is good).
The transistor should be an NPN transistor, and should look like the top one in http://www.reprise.com/host/circuits/transistor_pinouts.asp. The easiest one is the base - this is the middle one. Connect this via your resistor to another digital pin on your arduino (pin 13 is great for testing this, because it will also light up the led on the Arduino). Next, connect your emitter to ground (GND). Then, IF YOUR POWER SUPPLY IS NO MORE THAN 12 VOLT! you can connect VIN to the + side of the light, and the - side of the light to the collector.
Next, load a sketch - the "blink" sketch is good to test this. Adjust the pin as necessary.
Note that, these switches have a resistor already built in to the light; if you want to do the same with an ordinary led, you will have to add one yourself. Check out http://ledcalc.com/ to tell you which resistor you need.
