Broken Nose Preventer





Introduction: Broken Nose Preventer

About: Trained in mechanical engineering, discovered computers in the late seventies, been collecting junk and making stuff all my life. Recently retired, I now have the time to get to all those projects that I've...

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

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.

Step 2: Step 2. Assemble to the Mounting Plate

The LED leads are left long and the LED itself is glued into an alloy plate that is recessed into the edge of the door so that the circuit board just hangs off the LED leads. A space chiseled out of the door behind the plate houses the circuit and battery, there is just enough room inside the door to fit the standard C type torch battery.

The power consumption can be reduced even more if the circuit is switched on and off by means of a pin switch (like the ones used on a car hood to trigger the alarm) embedded in the hinge edge of the door so that when the door is closed the flasher is turned off and uses no juice at all.



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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.


    3 replies

    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.

    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! :-)

    1 reply

    I believe it's a 555 timer your thinking of.

    A photoelectric switch would work pretty well here too!
    Nicely done.

    3 replies

    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.

    Obviously you have too much time on your hands. A simple Night Light would do and a hellva lot easier.

    2 replies

    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. ;-)

    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!!!)

    1 reply

    Muchas gracias! Keep watching the blog, loads more stuff is coming soon!

    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.

    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.

    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.

    Not much fun in that though, is there? Unless you can get them with LEDs on? :-)