Virtual Rotating LED Beacon (Rundumlicht)




Here is my first very small *virtual* rotating LED beacon. And my first instructable too!

It's build from 4 x 0603 SMD LEDs. They only need a room about 2,5 mm3.

To make the round tripping light looking more realistic I wrote a program on a PIC12F629. It drives each LED with a PWM signal.

See the "virtual" rotating effect in the video...

Maybe next time I try it with 0402 LEDs ;-)

The Idea behind that project is to build a realistic looking rotating beacon for a small (1:87) police, fire or ambulance car. Normally they use only a single flashing LED.
(The examples on the following link are not build by me! RC Feuerwehrfahrzeug in 1:87 )

And now lets go to my Part... ;-)

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Step 1: Make a Tiny Workbench

We need a square hole about 2.5mm. I use 4 old SMD chips and solder them on a PCB together.

First you should solder only one pin. Then bend the chip in the right position and solder one or to other pins to fix the chip.

Be sure that there is one hole of the PCB in the center of the 4 chips. We need this hole later!

Step 2: Insert LEDs

Now place the 4 SMD LEDs (Size 0603) inside the 4 chips.

Make sure that the anode from each LED is on the upper side!

Cut 3 small pieces of paper for isolation between the LEDs. (You can see them in the picture)

Paper Size:
- 1 x 2mm x 2mm
- 2 x 2mm x 1mm

Step 3: Solder the First Wire

Now here is one of the tricky parts. ;-)

Use a very thin isolated copper wire.

Remove the isolation on about 3mm.

Bend a small ring like shown in the first picture.

Put the wire in the middle of the 4 SMD LEDs and place the ring on top. (Sorry no picture before soldering.)

Solder fast and carefully all 4 LEDs and the wire ring together. (second picture)

Now you can remove the 4 LEDs out of the "tiny workbench". (third picture)

Step 4: Solder the 4 Cathodes

Now put the 4 LEDs upside down back into the "workbench".

Solder all 4 cathodes from the 4 LEDs to 4 wires.

If you finished this very tricky part you become a multi LED with 5 contacts.

1 Anode and 4 Cathodes.

Step 5: PWM or Not PWM That Is the Question!

The PWM driven version looks much more realistic than the simple on/off one...
In my case I build an 4 channel 8 Bit PWM signal generator with PIC 12F629.

If you don't have a PIC, Atmel or whatever CPU or no programmer or not the right skills you can say I don't need PWM.

Then you can build an easy 4 step counter from a 4017 CMOS decimal counter. Driven by a 555 oscillator.

Things to come: Build some sort of housing for the LEDs. I think about an 3mm LED. I have to make two of them with blue LEDs and place them on a small Police car (1:87).

Thank you for reading my basic english and have fun. ;-)
If you build your own "SMD LED rotating beacon" please show me a picture of it.

take care

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    20 Discussions


    6 years ago on Introduction

    I want to program PIC12F629 with readymade .hex code. Which programmer should I use? I would like to know the best and cheapest programmer available. I bought PICKIT2 clone from India but I had very bad experience with it. I couldn't program with it.
    Can you please suggest me good programmer?


    7 years ago on Introduction

    Hi, I was just wondering if the code for this project was ever published?
    Many thanks for any help provided.

    KT Gadget

    11 years ago on Introduction

    will a ATTINY13 work the same as the PIC12F629? cause i have a spare ATTINY and i want to see if that will work. btw great instructable. im gonna see if i can get it to blink everytime it hits a certain volume level on music like the synchronized lights at a concert.

    1 reply
    KT GadgetKT Gadget

    Reply 11 years ago on Introduction

    oh one more question, will it work if i put 6 or 8 of the smds instead of just 4 and still program it to spin?


    11 years ago on Introduction

    Can you post the code please so that we can make this very cool project thanks

    Thank you! I am very busy today building our own house. ;-) If I had time left I search for the latest source and post it here. A few things left to build into the source. 1. Speed up and down the rotation. 2. "Switch on" and the "motor" rises the speed. 3. "Switch off" and the LEDs should glow off a little like a real light bulb.


    Reply 11 years ago on Introduction

    Thank you! The schematics are as easy as you can see it on the picture. I use the internal oscillator so there are 6 I/Os left. 4 of them I use as outputs to the LEDs. Two I use as input pins for selecting algorithms. Later I want to use them for selecting start/stop rotating and light etc.. The two 2k2 resistors only for two extra test inputs. I can select different algorithms for easy comparing best results.


    11 years ago on Introduction

    That is one of the coolest projects I have seen. I model trains in N scale and I was tinking the same could be done with SMD 0402 leds. These are 1mm by .5 mm and should scale nicely to 160th scale. With an SOIC 8 PIC12F508 one could make it stand alone in the vehical Thanks Again. Steve

    3 replies

    Reply 11 years ago on Introduction

    Thank you for the interesting comment! Yes, that's the idea behind. My Bush Ambulance model car in the picture below is 1:87. I see two ways to make it smaller. 1. Carefully sand down the edges of the 0603 LEDs without destroying the inner structure is possible. That is enough for 1:87. 2. Yes, for 1:160 you need 0402 LEDs. That could be very tricky! But I have some orange & red 0402 ready to try. I only need more free time to do it. ;-) In the 2nd, 3rd and 4th picture in this Instructable you can see how small those 0402 are in comparison to the wire I use. Would it be nice to use 0402 and the 6-Pin SOT-23 PIC 10F2xx with 4 I/O-pins! That is one target! ;-) The other part I have to work on is the usage of the two left I/O-Ports on the PIC. I want use one of them for a smart start & stop signal and the other for left-right rotation or different speeds. 1. start: "bulb lamps" are faster than the "rotating motor". 2. stop: "rotating motor" stops immediately and the "bulb lamps" fade out a little longer. WattSekunde


    Reply 11 years ago on Introduction

    Yes. I assume you used 30ga wire wrap wire for the connections . I think your choice of the 10F2xx is miss guided. You have only 4 IO's and 1 of them must be an input. I think you could use the 12F508 with 6 IO's to do what you want and with fading and all. Use PWM on the LEDs for current limiting all the time and to fade it just increase the pulse width. As far as starting and stopping and right and left once you used 4 outputs for the 4 LED's you still have 2 inputs to play with. This solution also saves the use of current limiting resisters which I know can be even smaller but when you are talking about putting this thing in an N scale car space is by definition limited. I just ordered a bunch of LED's tonight from Kingbright and when I get them I will start playing. I also did the calculations and these 0402 leds are perfect for street traffic light's. By law the lenses on traffic lights have to be 300mm in diameter for traffic traveling at 35mph or more so that make the lens 1.4mm in n scale. Then one only needs to build a traffic light controller and one can have working 4 way lights at each intersection. I will post when I build my first traffic light and see if anyone is interested in it.


    Reply 11 years ago on Introduction

    Nice! I can't wait to see the results. ;-) You are right with the 10F2xx there is no input available for start, stop, etc.. But at power on the light can also start slowly "rotating" is possible and power off is only off. ;-) But for really small designs the 10F2xx could be the right answer. The 4 resistors on the experimental board I only needed in the early days of writing and testing the PWM routine. My 4-Channel PWM routine also has an 8-Bit resolution. For the LED fading 5-Bit resolution is enough. The LED brightness responses in a logarithmic way.


    Reply 11 years ago on Introduction

    Thank you! For a model car I have to build it with blue LEDs too. But for the first try I decided to use the cheaper red LEDs. Your "LED Bouncie" gives me the idea to combine a SMD PIC CPU with these 4 LEDs and 3Volt battery and place it inside a diffuse thing like a bouncie. The Picture shows a model car that I want to completely light up with LEDs

    Busch - Ford E350 Mercy 1.jpg

    11 years ago on Introduction

    FLAGAFIED! no one here will ever play that game, so go put your dumb ads somewere else