Introduction: Who's Home?

Picture of Who's Home?

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

Picture of 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

Picture of 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

Picture of 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.

Picture of 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

Picture of 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!

Picture of 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

Picture of 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!

Picture of 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.


cvxdes (author)2008-03-30

nice. Looks really clean too. Looks like the LEDs light up on the red side instead of green, when the switch is pointed towards the green, I guess that could be confusing. I'd switch the sides of the switch, so right green turns on when the switch faces it.

I'd switch the way the switch is switched so you don't get confused on how the switch is switched when its switched on.

Indeed, exactly what I said! haha


I'm glad that somebody actually understands me. It's just been so long since somebody understood me like that. I can stop listening to emo music now.. my god, what a glorious day! Will you marry me?


How romantic. lmao

SABBaS (author)cvxdes2008-03-30

yup, that's what I meant in step 6 and how I initially wanted it to be... but it was way too much work for the time it was to desolder and solder 14 connections again... maybe if i get bored soon, I'll fix that. :)

GorillazMiko (author)2008-03-23

Smart, done very nicely! I might just do this for something else-- just to see if anybody is home once I get home from school or something. Amazing Instructable, done SO neatly. +1 rating. (added to favorites)

SABBaS (author)GorillazMiko2008-03-24

Yup, it's always nice to know if you are alone or not without having to shout "HELLOOOO" (which also works, btw)

yeah but my mom is EXTREMELY lazy about answering me, even if she hears me.

eeeXsmart (author)2008-04-16

awesome instructable!!!!! ;) great idea

T3h_Muffinator (author)2008-03-30

Integrate sub-epidermal RFID tags and you've got yourself one hell of a product. Sweet Idea, even more interesting would be RFID tracking throughout the house, with a floorplan map on the box - as someone moves, different rooms light up so that you can see where they are. Never lose your friends again!

SABBaS (author)T3h_Muffinator2008-03-30

Now THAT is cool... but I'm not really sure how my friends would react if i greet them with a syringe at the door... ;)

mightywombat (author)SABBaS2008-03-31

Put an RFID tag on their keychain. That would also help if they lost their keys. The board would say where they were.

Oh, and nice job!

cvxdes (author)T3h_Muffinator2008-03-30

Overkill, much? haha I'm sure that would be somehow illegal too.

T3h_Muffinator (author)cvxdes2008-03-30

I don't think it'd be illegal, but probably overkill =P

mightywombat (author)2008-03-31

This is a really neat project. I made something like this (out of paper) to keep track of whether our cats were inside or outside so the last person to go to bed would set the indicators and the first person to get up in the morning would know what was up. Hey, it answered a need. I think on this project, since I know my memory is atrocious and I'd never remember to flip my switch, I might have made a key hanger that lit up when there were no keys on it, but then some people might not want their keys hanging up by the door, and if there are keys then you really don't need the awesome LEDs I guess...

chu11 (author)2008-03-31

Real cool amazing idea _!!!
Great work and thank you so much for sharing it =)

Ahmedqatar (author)2008-03-27

Impressive .. but what if any one forgot to switch on??

SABBaS (author)Ahmedqatar2008-03-27

In that case, they appear as away (or as home, depending which side they forgot to switch to)... i know it's not 100% foolproof, but it does a good job :)

cvxdes (author)SABBaS2008-03-30

you should hook it up with kipkay's laser house defense project, except, a quieter speaker, and maybe a beeping noise, not an alarm. The box could beep when somebody walks in, to remind them.

SABBaS (author)cvxdes2008-03-30

That is also a VERY good idea, ill look it up, but maybe the energy cost goes up a bit... but i'll definitely check it out!

Tarps (author)2008-03-30

This is a huge waste of electricity. All you need is some paper or cardboard arrows on a thumbtack that can be pointed at "home" or "away."

PKM (author)Tarps2008-03-30


Let's assume that the LEDs have zero resistance, so the circuit resistance is 470 / 7 = 67 ohms. With a 6V power supply this would equate to about 90ma or 0.53W power consumption.

Let's then assume that each of the seven people in the house goes out three times a day, and checks the board for one second on their way. This equates to 0.53 * 21 = 11 watt seconds (or 0.003 WH) of electricity per day. Leaving your computer on for literally the blink of an eye uses this much electricity, so if you leave your computer on for, say, 30 seconds you will use as much electricity as this device does in an entire year.

Also, a device like this is a lot more memorable and novel than the usual "in"/"away" sliders, so people are more likely to use it. I think 11 watt seconds a day is a small price to pay for people remembering to check the board, turn on the alarm and not having all your stuff stolen :)

I'd be tempted to add a couple of external contacts that fire a buzzer in the box for a moment when you open the door, to remind people to flick their switch and check the alarm. If more than three people lived in my house and we had an alarm I'd totally make one.

darkmuskrat (author)2008-03-26

Very professional looking :D

Thorax (author)2008-03-24

Haste toll gemacht, aber brauchst du wirklich ne alarmanlage? Wohnste in so ner gefährlichen gegend?

SABBaS (author)Thorax2008-03-24

Tja, die Gegend ist OK, passieren aber immer Sachen, bei Nachbarn wurde manchmal eingebrochen, etc... wusstest du eigentlich dass ich Deutsch spreche? translation: Thorax: Well done, btu do you really need an alarm? Do you live in such a dangerous area? SaBBaS: Well, the area is ok, but stuff always happens, some neighbours have suffered robberies, etc...

Thorax (author)SABBaS2008-03-24

Wann man mit Leuten zusammenwohnt, die Gerhard, Kerstin und Bettina heißen sollte man wohl zwangsläufig ein wenig Deutsch können, selbst wenn man in Spanien wohnt ;)

lawizeg (author)Thorax2008-03-25

Ah. Dutch. i think.

Thorax (author)lawizeg2008-03-25

nope, German ;)

lawizeg (author)Thorax2008-03-25

Oh, i thought so at first, but i didn't see the things with 2 dots on top, so i figured it was dutch.

Thorax (author)lawizeg2008-03-25

the things with the two dots on top end up in being shown as ö and ä :)

lawizeg (author)Thorax2008-03-25

thanks! i now know one more thing! You never know when i might need that info...

ll.13 (author)2008-03-24

Looks Good! =)

thebboy (author)2008-03-24

sweet, i'd like to try this sometime with my dad. +1

Weissensteinburg (author)2008-03-23

This is a really neat idea that I think could potentially sell well in stores. Nice job!

SABBaS (author)Weissensteinburg2008-03-24

Thanks, I hadn't thought about it, I'm going to change the license to all rights right now ;) (just kidding)

struckbyanarrow (author)2008-03-23

ya gr8 idea and well put together instructable and very neat and clean soldering +1

SABBaS (author)struckbyanarrow2008-03-24

Maybe it's because the pictures are a bit blurry, but I was kinda embarrassed to put them on the internet, i thought they were crappy. Thanks!! :D

Noodle93 (author)2008-03-24

Whilst it would probably be hard, it'd be awesome to have some sort of automatic version of this, wireless of course.

SABBaS (author)Noodle932008-03-24

Yup, I guess it could use something like those chips they use in the robotic (domotic?) houses, where lights, music, etc, turn on or off when you enter or leave the room... but that escapes my knowledge ;)

w00ty32 (author)2008-03-23

well done!

joejoerowley (author)2008-03-23

Cool! Well Executed! Looks great!

bumpus (author)2008-03-23

very smart, kudos

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