DIY All-Transistor Addressable Pixel

By now most readers should be used to addressable LEDs, devices that when strung out in a connected chain can be individually lit or extinguished by a serial data stream. Should you peer at one under a microscope you’ll see alongside the LED dies an integrated circuit that handles all the address decoding. It’s likely to be quite a complex device, but how simply can its functions be replicated? It’s a theme [Tim] has explored in the TransistorPixel, and addressable LED board that achieves addressability with only 17 transistors.

It uses a surprisingly straightforward protocol, in which a pulse longer than 500ns enables the LED while a shorter one turns it off. Subsequent pulses in a train are passed on down the line to the next device. A 20µs absence of a pulse resets the string and sets it to wait for the next pulse train. Unlike the commercial addressable LEDS there is only a single colour and no suport for gradated brightness, but it’s still an impressive circuit.

Under the hood is some very old-school RTL logic, a monostable to detect the pulse and a selection of gates and a latch to capture the state and forward to the chain. It’s laid out on a PCB in order of circuit function, and while we can see that maybe it’s not a practical addresssable LED for 2021, it’s likely that it could be made into a much smaller PCB if desired.

Perhaps unsurprisingly given the ready availability of addressable LEDs, we’ve not seen many home made ones. This addressable 7-segment display may be the closest.

36 thoughts on “DIY All-Transistor Addressable Pixel

      1. Uh. The 555 contains two comparators, which are quasi-digital (they have analog inputs and digital outputs), an S-R flip-flop, which is digital, and a switch transistor. Which is digital. RTL is an inherently analog process (common-emitter amplifiers) that is used to implement digital functions. Also, have you no idea what a joke is? Hint: any mention of the 555 in Hackaday comments IS one.

  1. Die or dice, not dies. In over half a century of exposure to the semiconductor manufacturing industry, I never heard of a “diesing” saw, but a dicing saw, yeah, those exist.

    Is this a spell check issue or a style guide issue? Or both?

    Perhaps this is just post-modern newspeak that shuns historical reference.

        1. In this case it seems to me that what Jenny wrote is correct:
          “you’ll see alongside the LED dies an integrated circuit…”
          as she refers to three (R, G, B) LED dies here. Not sure what the commenters above are raging about.

      1. Die (noun)

        plural dies : any of various tools or devices for imparting a desired shape, form, or finish to a material or for impressing an object or material: such as
        a(1) : the larger of a pair of cutting or shaping tools that when moved toward each other produce a desired form in or impress a desired device on an object by pressure or by a blow
        (2) : a device composed of a pair of such tools

        tool and die


        tool and die (plural tools and dies)

        (chiefly attributive) One of the cutting tools and forming dies used by machine tools.

        The toolmakers are employed in tool and die jobbing shops.
        Wage rates for tool and die makers differ in various regions of the country.
        The manufacture of tools and dies is on the critical path of automobile development programs.

        1. No, I don’t think so. You are using the “tool and die” meaning. When referring to the plural of “die” meaning a small, square gaming device, “dice” is the correct plural. Integrated circuit chips are named after their resemblance to the gaming devices, not for being tools.

          On the other hand, this may be somewhat similar to “fish”, where the plural is “fish” if they’re of the same species, or “fishes” if more than one. For chips, it may be “dies” when referring to chips in general, as in “CPU dies range from 1mm^2 to 20mm^2”, but what you get when you score and bend a wafer, are dice.

          1. Actually, from what I can tell, Integrated circuits were named based on using a chunk of gallium or silicon as a die, not a dice.

            “A die, in the context of integrated circuits, is a small block of semiconducting material on which a given functional circuit is fabricated.”

            Apparently, the “dice” usage is relatively limited, and came from a specific vendor referring to its integrated circuits as DICs, (Digital Integrated Circuits). The “other” obvious epithet not being printable, they got referred to as “dice”.

            However, “die” (plural “dies”) is both the older usage and the much more common current usage.

          2. “When referring to the plural of “die” meaning a small, square gaming device”

            There are NO dice that are square. There are many that are cubes. There are some that are not cubes (Dungeons & Dragons?)

            “Integrated circuit chips are named after their resemblance to the gaming devices” Sez you. I think you are just making stuff up.

    1. When a word has multiple meanings, it is not unusual for the different usages to have different plurals. Here’s what Wiktionary has to say about it – it’s pretty definite:


      die (plural dies)

      The cubical part of a pedestal; a plinth.
      A device for cutting into a specified shape.
      A device used to cut an external screw thread. (Internal screw threads are cut with a tap.)
      A mold for forming metal or plastic objects.
      An embossed device used in stamping coins and medals.
      (electronics) (plural also dice) An oblong chip fractured from a semiconductor wafer engineered to perform as an independent device or integrated circuit.
      Any small cubical or square body.


      die (plural dice)

      (plural dies nonstandard) An isohedral polyhedron, usually a cube, with numbers or symbols on each side and used in games of chance.

      Most dice are six-sided.

      I roll the die and moved 2 spaces on the board.

      (obsolete) That which is, or might be, determined, by a throw of the die; hazard; chance.

      (electronics) (plural also dies) An oblong chip fractured from a semiconductor wafer engineered to perform as an independent device or integrated circuit.

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