Picture of Broken nose preventer
There are three doors in my house that open outwards, and I have personal experience how easy it is to walk into the edge of one of them in the dark. After doing this a few times, I decided to build a device for providing a flashing LED embedded in the edge of the door to warn you that it is open.

This is really simple to make, and saves getting blood on the bedroom carpet

Step 1: Step 1. Make the circuit

Picture of Step 1. Make the circuit
The circuit came from my stash of ancient electronics relics, I have no idea where it originated. It will run off a single AA penlight dry battery, although I used a bigger C size battery. The original unit has been running in my house 24/7 for around 5 years so far with no sign of giving up yet.

I etched the circuit board myself and soldered the parts to it. I used BC107 transistors for TR1 and TR2, and a 2N3906 pnp transistor for TR3, but pretty much any npn transistors will do for the first pair, and any pnp for the third one. The LEDs I used are 5 volt types, but I’m not sure that they need to be, and I suspect any standard LED (and any colour you like) would work just fine.
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Yeah - you think you're so clever except one of these nights it will be the Terminator looking at you and not your soft little blinky door light. Then you'll all be sorry for laughing at me and my crooked nose.

If this were like Facebook, I would hit the like button. Hey Instructables you should create a LIKE button.
We sent John Connor your address so he could ambush it.

You and your crooked nose are safe with us!

The Cylon Support Network
You make me sooooo happy.
We also like your crooked nose.
johnfrog3 years ago
Very cool! Back in remote antiquity (c.1980) there used to be a little IC (LM 3909, I think) that did the same sort of thing - would run an LED forever on a 1.5v battery with only a timing/storage capacitor. Good if you're pushed for space or (like me) too lazy to make PCBs. Nice instructable; brings back old memories! :-)
I believe it's a 555 timer your thinking of.
dwosullivan3 years ago
A photoelectric switch would work pretty well here too!
Nicely done.
Hate to disagree, but no it wouldn't.

This instructable is only useful at night, when there is little light, exactly the same as when you have the door closed and covering the switch.
True. My Bad.
It could at least be used to have it turned off when it sees light, i.e. when the door is open during the day, then the LED would only light when the door is closed or its night time. It would be worthwhile even if using a reed switch so if the door is open during the day the light won't shine.

I guess this is getting more complicated than its worthwhile, Its a great idea, It looks like it works well and the author doesn't seem to have any problem with battery life. well done!
A reed switch would however.
Remag12343 years ago
Obviously you have too much time on your hands. A simple Night Light would do and a hellva lot easier.
grizelli (author)  Remag12343 years ago
Yep, I just retired, so plenty of time to do stuff like this. You ain't seen nothin' yet :-)
Good, I'm retired and it's tough because every day is a day off. ;-)
MandingaRes3 years ago
Buen proyecto grizelli ! y muy buenos proyectos los de tu blog.

(Bien dicho bstevenson1!! Cada uno hace de su tiempo lo que se le canta!!!)
grizelli (author)  MandingaRes3 years ago
Muchas gracias! Keep watching the blog, loads more stuff is coming soon!
lambsb3 years ago
All usefulness or purpose aside, It is a nice looking circuit and nicely built. As for anyone who might use this to warn of an open door..... (I would prefer blue LED's, they're cool) we always need new excuses to build LED projects. How can you resist? The 3909 IC will flash an led but I prefer to use a 555, you can get many different pulse patterns from it just by changing the rc circuit values.

There is also a circuit from Radio Shacks optoelectronics projects book I use from time to time that is a dual led flasher, that uses 2 2n2222 transistors and I think 2 2n3906's. (Like a school bus or railroad crossing flasher). Maybe useful to someone.
e5frog3 years ago
There are LEDs with a built in flashing circuit, no need for 13 something components when three is enough. Flashing LED, resistor and battery. Possibly some switch to turn it on/off as well.

Stop walking around in the dark, would probably help.
vroom3503 years ago
Simple make LED box with reed switch magnet just put on top door with use double tape without hard hand and/or drill hole. More life save battery when closed the door.
madfreet3 years ago
Easier still ...just fit a door closer
grizelli (author)  madfreet3 years ago
Not much fun in that though, is there? Unless you can get them with LEDs on? :-)
And doors should be kept closed..(ever heard of fire) not
much fun being burned alive either
Also ...if your staggering around in the darkness...a closed door
represents just as much a hazard as an open one...now
lets consider the stairs...assuming you have stairs that is....
ie darkness, staircase...fall...broken neck....yep id happily
take the open door and broken nose : )....lets have some
LEDS on that staircase please...flashing ones. Now youve just
picked yourself up from the fall down stairs, broken neck takes
your mind of your broken nose...still pich black and you bump into
someone !!! well you get my drift lol...just turn on the light
grizelli (author)  madfreet3 years ago
You must be a mind reader. I already have LEDs installed on every step of the stairs with a PIR to turn them on when it sees a warm body approaching from either the top or bottom of the staircase. I'll post this on here as well shortly. I like LEDS :-)
I see from your pic that you have the danger of
walking out of the window solved lol : )
Javin0073 years ago
I need to make one of these for the leg of my damned bed. I've broken my little toe on that thing TWICE already.
May I humbly suggest a thin strip of glow in the dark paint?
I know it's not got that tech-cool, but I'm sure it'd do the job.
But then I wouldn't get to use my power tools...
So how would you get your power tools to light up when your toe got close?


Let's say you have your saber saw welded to your oak bed leg.

You get too close and it turns on, the sound would alert you of impending pegleg disaster.

This would be great for blind people who couldn't see a red light.
Granted, glow in the dark paint wouldn't need power tools to apply. However, you could use power tools to make a corner cover (L in cross section) painted in glow in the dark paint to do the same job. Also has the advantage of being easily removed with the right adhesive.

Of course you could also just paint the legs in 5 minutes and then use the remaining build time to make something else entirely... and that could be far more power-tool hungry than this. :D
"...easily removed with the right adhesive."

Make that "If attached with the right adhesive it also has advantage of being easily removed."
vincent75203 years ago
I don't get it.
Why don't you just get rid of your doors. As you've got only three I guess you place is somewhat small : you wouldn't believe the feeling of roominess when you trips the doors of a small apartment !…
OK , I'm joking, but it is true : I don't have doors in my house (except a sliding panel for the bathroom).
EvilRSA3 years ago
I really like the idea of the a pin switch, and as long as we're talking about drilling through the door to get to the hinge side for the switch, why not drill to the top of the door instead, put the switch there and add a photo cell too, so when the door is open the led only fires when it's dark enough that you wouldn't be able to see the door, and no visible distraction during the day when you can see the door. Plus keeping the switch and photo cell on the top, you wouldn't have to see them either, keeping a nice clean look....actually, you can put all the of the circuit in the top of the door, and just run the LED down the door, and actually combine the LED with the exiting latch hardware....now that would be a slick and clean look, with extra function.
grizelli (author)  EvilRSA3 years ago
Good idea, especially putting all the electrics in the top of the door and running just the LED in the lock plate. I have to fit another one of these to a french window, thats probably how I will do it, thanks for the suggestion
vidakk3 years ago
You could also implement a reed switch and put magnet in doorframe, so the circuitry sitches off when door is closed.
frickelkram3 years ago
Works great!
Low battery voltage leads to more frequent flashes. It is easy to see that the battery needs to be changed. I am using BC547c and BC557c and a high power red led. I used a 470uF capacitor instead of a 100uF. Because the 10k resistors where out of stock I am using 12k, these work as well. The circuit operates from nearly 1V up to 6V. If you go above 3V the flashing frequency gets very low and the led starts glowing right before the flash pulse. Best operation is with 1.5V alkaline cells as grizelli recommended.
I have'nt made any long term test, because I just built it one day ago. It runs on a 1.1Ah NiMH battery since then, without problems.
The way the shematic was drawn reminds me of German magazine called Elektor or Elrad ...
Your instruct able made me burst out laughing, I could see myself doing the exact same thing! Thanks for the laugh! Great idea!
starlored3 years ago
Ever heard of a light switch!!!
Alternatively, you can buy LEDs with a flasher circuit built into them, with these, you just hook them up to 3v and the flash. An elegant and simple solution though, I like it.
Ther we go! thats what I was taking about. Lest money, smaller and easy to install!
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