At home we rent out the free rooms that were my brothers', so most of the time there's people with different schedules living in the same house. We have an alarm, so the last one leaving is supposed to put it on when he leaves but it's often difficult to know who's last, and if you are leaving at 9.30 you don't always feel like storming through all the rooms to see if anyone is home...

I had been thinking a long time about building something to show who is home and who is not, so one day I finally got up and grabbed a friend who knows more than i do about electronics (which is easy ;-) ) and he helped me with the diagrams. Big thanks to Lufe! :)

What this does, is light up green or red leds when you press the push button, depending on who is home (or who forgot to change his switch to "away" ;-) ). That way, when you are about to leave and you see all other red LEDs lighting up, you know you should put the alarm on.

It doesn't require any special knowledge, just very basic soldering skills and being able to use a drill.

Step 1: Material List

For this project I bought (i don't know if the names are right in english...feel free to correct me):

- 1 Battery holder for 4 AA batteries.
- 1 Project Box
- 7 Green LEDs
- 7 Red LEDs
- 14 LED holders
- 7 Resistors (470 Ohm)
- 7 Switches
- 1 Push Button (Default open)
- Cable

Step 2: Diagrams

Sooooo, here are the diagrams I used to build this. The main picture shows how I ended up building it, the second one is another way which maybe makes the connections a bit clearer and the last one uses official symbols but doesn't have any nice colours ;)

It's pretty self-explaining, but I'm going to explain it for dummies like me: the anode (positive pole, red cable) gets out of the battery holder, first it gets interrupted by the push button, then it goes to all the middle pins of the switches. Each remaining pin from one switch is connected to the positive end (the round one, long pin) of one led. From the negative pin of the LED it goes to the resistor, and from there to the cathode (negative pole) of the battery holder.

Step 3: Marking and Drilling

I decided I wanted the switch to be in the middle and the leds on the sides, so I marked where the holes would go according to the size of the switch and the LED holders. The LED holders aren't really that necessary, but they give it a better finish and you don't have to glue the LEDs to the box. And they are cheap, always a plus ;)

So first I marked the holes with a pencil so I could erase everything, which I later promptly forgot to do.

For the center holes (for the switches) I used a 6mm wood drill bit which I found at home, and for the LED holders I used an 8mm wood drill bit. I did it nice and slow and it worked quite well.

The lonely hole on the side you see in the last picture is for the push button, also 6mm.

Step 4: Setting Stuff in the Holes.

So when you are done drilling, put in all the components and admire how nice it is starting to look :)

I know its not perfectly aligned, but that's an artistic thing, don't worry about it.

Step 5: Start Connecting

I started by connecting the positive pins of the LEDs to the side pins of the switches, seeing that they were already pretty close and practically asking for it.

Step 6: Solder Away!

Solder everything together following the diagrams as good as possible, as always, you might have to improvise to find out what works best.

I also hot glued the battery holder to the top of the box so it wouldn't bounce around. As funny as electronics usually are, when I checked everything before glueing the holder, it worked. When I checked it again afterwards, it didn't. When I ripped it off, it worked again. And when I finally glued it down again, it worked. I think I tired it out. Now it comes running when I whistle ;)

If you compare the picture with the diagrams, you might even find coincidences.

The only thing I noticed afterwards is that maybe I bought the wrong type of switches, as with this layout, the LED looking away from the switch lights up, instead of the LED the switch is facing. I would have to change the positive poles of the LEDs to the other pin, but I got tired and it isn't THAT bad this way. (See step 7).

It's probably also a good idea to isolate the connections so you don't get any shortcircuits, but I was lazy and it wasn't going to get tossed around too much, so I just hoped it was going to work. And it does :-)

Step 7: Finish It Up

Write the names of the people living there on name tags so that everyone gets one switch assigned.

The first picture shows how it looks when you are not pressing anything and the second one shows it in action. You can also see what i meant in step 6 when i said that the LED facing away from the switch lights up.

Step 8: Be Happy!

Proudly present your project to all your housemates and explain how it works. Place it somewhere near the door, so people don't forget to change their status when they leave. Be happy about finally managing to build something.