Keyboard LED Indicator

Hi everyone !

I'm back with this second Instructable to show you guys how I added an LED to my keyboard.

I was always asking myself whether my keyboard was on or off, and I was so angry that they didn't put any indicator... So I decided to add one myself !

Come with me in this very simple Instructable, perfect for beginners. You'll get your hands on drilling, soldering, dimensioning components and using a multimeter.

First thing first, you need to gather some tools and few components to improve your wireless keyboard !

Tools :

• A dremel (or anything to make a small hole)
• A soldering iron
• A glue-gun (or any strong glue)
• A multimeter (or only voltmeter)
• Pewter
• Electrical tape or shrinking tube
• A screwdriver

Components :

• A green LED
• A 100 Ohm resistance
• Wires

And of course, you need a keyboard !

You are now ready for step 2 !

First, you need to remove every screw to access the back of your keyboard. Then you'll probably see a board near the batteries (see picture 2).
You'll also find a switch on the board. It's important to find it because we'll connect our LED to the GND of the batteries and the "+" to the switch. That way, when switch is ON, our LED receives current.

Next step will be to see how much voltage we have and to what pin to connect on the switch.

First, you can test the voltage of the batteries by putting your multimeter on both connection comming from the batteries (picture 1). By doing that, I get around 3V. (If you get a negative value it means that you have just switched between + and GND)

Next is to find the pin of the switch that will vary depending on its position. By keeping my black pike on GND with switch on ON postion, I'll move the red pike to find 3V. Now if it's the right pin, when switching OFF, you should get 0V. By looking at the route comming from the switch you can also find the right pin.

Now that you now where to connect your LED, you can choose its spot. That's what we'll do in the next step.

I chose to drill a hole near the spot of the board to minimize cable length. Try to find a spot where there's enough room for the led and wires.

You have the hole, and you now where is GND and + on the board. What is left is to connect the LED.
But first, we need to set the current we need for the LED.

A normal LED requires ~20mA wich is 0.02A at 2-3volts. We found previously that the voltage between + and GND was 3V, thanks to Ohm's law we have : U = R*I (with U voltage, R resistance, I current).
We already know the voltage and the current we want, so we need to find the right resistance. So, we have R = U/I => R = 3/0.02 => R = 150 Ohm. Because I only have 100 Ohm resistances I chose to go with it.
If you want to be precise, the LED will receive I = U/R => I = 3/100 => I = 0.03A or 30mA. Wich I decided to be acceptable.

If you look at the last image, you find that the ANODE is the longest pin of the LED, wich will conect to + (the switch) and the other to the GND. You'll put the resistance in serie between the LED and the switch or GND and the switch. Make sure to put electrical tape or shrinking tubes to hide any conductive part.

Finally, solder to the board and it should work fine !

You have now an LED indicating if your keyboard is ON or OFF.

You'll never let it run for the entire day for nothing ;)

I hope you enjoyed this simple instructable. If yes, don't hesitate to comment, subscribe... :D
See you soon !