• The digital chaos alternative

    Keith • 04/15/2025 at 23:33 • 0 comments

    https://www.desmos.com/calculator/pjq3vwytqs is an online interactive model of a chaos generator, written in Javascript. It certainly is chaotic, and I would not be able to tell any difference from the analogue circuit. By their very nature, any analogue simulation would diverge from other ones due to tiny differences in their starting conditions.

    The Microchip PIC12HV752-I-P has a DIP8  package and a £1.07 price tag. It only needs three output to PWM control the RGB LED. Yes I know it is not a real analogue chaotic system but it is chaotic and probably more accurate than the AD633 allows. 

    Programming the PIC series of microcontrollers isn't trivial, I know because I have done it. I might try a test run with a R-Pi or something easier to program.

    https://colab.research.google.com/github/REsteche/REsteche_blog/blob/master/_notebooks/2021-10-20-Lorenz_animation.ipynb is a chaos generator written in python. It has some limitation, in that the 

    The 3-D graph has colour enhancement. However, I now notice that the x, y, z values range from positive to negative. One cannot have negative light intensity. It is true that colours have 'negative' colours, on the opposite side of the 'colour wheel', but negative red would be cyan, which is green plus blue. Perhaps the best way is to add an offset so that 

    -x = 0% red,     +x = 100% red,
    -y = 0% green, +y = 100% green,
    -z = 0% blue,   +z = 100% blue.

    It would be interesting to take this python program and adjust it also show the RGB LED colour changes.

    While analogue signals have effectively no resolution limit and the chaos curve never passes the same point twice (being a fractal), digital signals will be rounded to the nearest LSB and have a finite number of states. Therefore it will eventually repeat. With 8 bits per primary colour signal, there are  (2 ^ 8)^ 3 = 16,777,216 states. You could use floating point for more realistic chaos.

  • The analogue chaos circuit

    Keith • 04/15/2025 at 00:15 • 0 comments

    The Elektor article uses 9 dual op amps. That could be reduced to 5 quad op-amps. I have plenty of TL074 chips. 

    The only rare component is the AD633 multiplier. This is available from Digikey at £16.97, Farnell at £18.83 which others have remarked is insanely overpriced. DigiKey have a range of multipliers, the cheapest being £2.73 in packs of 85.

    At this point I feel it would be simpler and cheaper to have a microcontroller doing the maths.