Chaotic Lighthouse

A circuit sculpture to participate in the 2023 op amp challenge.

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When I read about the op amp challenge and there about chaotic circuits, I thought that I should build another sculpture.

I remembered how it was to sail the baltic sea at night and navigate using light houses. But now, with GPS,... they appear somehow superfluous. What would happen if one of them got mad...?

So the idea of using a chaotic circuit as the basis for the sculpture was born. I found Sprott's chaotic jerk circuit and thought that it was reasonable simple. And to make it a bit more "chaotic", I decided to use it three times in my sculpture, as my lighthouse has three legs to have a stable base. With slightly different time constants in each of the legs.

Since the circuit itself oscillates somewhere in the range of 100Hz I wanted to make use of the envelope of the oscillation for my blinking. So I incorporated a peak detector to somehow get it. Some signal conditioning and in the end generating a PWM signal for the LEDs. That's it. Sounds easy, but took me quite some time to play around with everything on a breadboard to find out suitable values for the resistors and capacitors.

In total it's 46cm high.

Watch the videos in the files section to see it in all its beauty!

P.S. The component list is not correct for the resistors, caps and diodes. I just mentioned the values. Counting can be done based on the schematics. And I used many of the 1N41418s and 10Ms just for rigidity.

MPEG-4 Video - 46.01 MB - 05/26/2023 at 20:40



The lighthouse as it shows its chaotic signals.

MPEG-4 Video - 30.45 MB - 05/26/2023 at 20:09



Seen from above. All LEDs can be seen.

MPEG-4 Video - 32.60 MB - 05/26/2023 at 20:02


  • 14 × LM 358
  • 2 × LM 324
  • 1 × 1N4148 Discrete Semiconductors / Diodes and Rectifiers
  • 10 × 1N4004 Discrete Semiconductors / Diodes and Rectifiers
  • 1 × 680, 1k, 10k, 22k, 33k, 100k, 220k, 10M

View all 8 components

  • It works!

    MaBe4205/27/2023 at 15:53 0 comments

    It works right from the beginning. Testing after more or less each step paid off.

    Many basic op amp circuits are used in this sculpture: integrators and differentiators in the chaotic circuits, buffers and amplifiers in the signal conditioning, a very dirty triangle signal generator, a peak detector, building the difference between signals and converting analog to PWM. Best practices were not always applied. But in this project it's not about signal quality in the first place. The idea was to use the op amps to make the lighthouse blink in a non-repetitive way. This would also be possible with a micro controller and a few lines of code - but much less fun!

  • Putting the parts together

    MaBe4205/27/2023 at 15:43 0 comments

    This was again a job where two hands are not enough, I chose to build a structure out of 10 diodes (1N4004 are more stable than 1N4148) to form the interface between the round base and the pentagonal tower.

    I mounted the diodes with glue tack on a circle on paper, soldered the tower to them and then put it onto the base.

  • Testing

    MaBe4205/27/2023 at 15:38 0 comments

    With so many solder joints, I decided to test the functionality quite often during the build. It was sometimes quite messy.

  • The upper tower

    MaBe4205/27/2023 at 15:35 0 comments

    The upper tower is a rather simple structure with a pentagonal cross-section. All made from brass wire, V+ in the center, diodes building a roof-like structure and some 10M resistors and diodes (some are SMD) to provide mechanical stability.

  • The central part

    MaBe4205/27/2023 at 14:36 0 comments

    In the central part, the virtual ground is generated and also a kind of a triangular signal (very quick and dirty) which is needed for the conversion of the analog signal to PWM for the LEDs. Finally, the signals A, B and C from the legs are either directly used to drive the LEDs or differences are generated to have six different rhythms.

    For the orange LED I took a 680R resistor instead the 1k to have it a bit brighter.

    The FETs are not really necessary since the LEDs consume only about 5mA. But when I designed everything I was not yet sure how many LEDs I would need to drive.

    The large caps look cool and are needed to reduce some 50Hz ripple I had observed on some of the signals.

  • Building the legs

    MaBe4205/27/2023 at 08:07 0 comments

    In each leg there is one of Sprott's chaotic circuit, a peak detector and some signal conditioning:

    To facilitate soldering I had designed a little jig and 3d printed which helped a lot getting the job done:

    In the background, a plan can be seen where I had "translated" the schematic into a design for soldering.

    For assembling the triangular leg (each brass wire is a supply (V+, V- and virtual ground) I had another jig. This time more "ad hoc" using my favourite tool: glue tack.

    After building of each leg: testing!

    As you can see, I added some 1N4148s for rigidity and a small cap as protective/isolating foot.

    Putting the three legs together made me wish I was an octopus. But again a little jig and some glue tack helped a lot.

  • The chaotic circuit

    MaBe4205/26/2023 at 20:49 0 comments

    The circuit is Sprott's chaotic jerk circuit.

    The schematic is linked from the above website. I use the signal 'x' for my lighthouse.
    Let's label the resistor from top to bottom and then to the right. So the topmost is R1 and the rightmost is R6.
    Caps labelled from left to right.

    In my circuit all op amps are 1/2 of LM358 driven from a single 12V supply (which requires generating a virtual ground).
    D = 1N4148
    R1 = R2 = R3 = 1k
    C1 = 1u
    R4 = 10k
    are always the same.

    My three legs have all different combinations of the other components:
    C2 = 1u / 680n / 680n
    C3 = 680n / 1u / 680n
    R5 = 22k / 33k / 22k
    R6 = 33k / 22k / 33k

  • First build on a breadboard

    MaBe4205/26/2023 at 20:39 0 comments

    I build the circuit on a breadboard to play around with the resistors and caps which influence the blinking of the LED. Looks quite chaotic. But there is a system in the colours of the wires.

    There is also a video showing this circuit in operation.

View all 8 project logs

Enjoy this project?



MaBe42 wrote 06/06/2023 at 16:38 point

Thanks to both of you!

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Kuba Sunderland-Ober wrote 05/30/2023 at 13:28 point

This is beautiful work!

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Dr. Cockroach wrote 05/27/2023 at 10:23 point

Yeah, if I were sailing late at night and saw that I would think WHAT??? Cool looking build :-)

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