discrete transistors

9 Articles

Transistor Logic Clock Has 777 Transistors

June 1, 2016 by 23 Comments

Sometimes, the parts list says it all. 777 transistors, 1223 resistors, 136 LEDs, 455 crimp connectors, 41 protoboards and 500 grams of solder. That’s what went into this transistor logic clock build.

While additional diodes and capacitors were tolerated in this project, a consequent implementation of a discrete transistor logic clock, of course, does not contain a quarz oscillator. Instead, it extracts its clock signal from the mains frequency in its power supply. Because mains frequency is slow, it can be stepped down to a clock-applicable 1 Hz by a simple counter unit which already spreads its discrete transistors across 4 protoboards.

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A 4-bit Computer From Discrete Transistors

November 22, 2014 by 23 Comments

Anyone reading this uses computers, and a few very cool people have built their own computer out of chips, [zaphod] is doing something even cooler over on hackaday.io: he’s building a computer from discrete transistors.

Building a computer from individual components without chips isn’t something new – Minecraft players who aren’t into cheaty command blocks do it all the time, and there have been a few real-life builds that have rocked our socks. [zaphod] is following in this hallowed tradition by building a four-bit computer, complete with CPU, RAM, and ROM from transistors, diodes, resistors, wire, and a lot of solder.

The ROM for the computer is just a bunch of 16 DIP switches and 128 diodes, giving this computer 128 bits of storage. the RAM for this project is a bit of a hack – it’s an Arduino, but that’s only because [zaphod] doesn’t want to solder 640 transistors just yet. This setup does have its advantages, though: the entire contents of memory can be dumped to a computer through a serial monitor. The ALU is a 4-bit ripple-carry adder/subtractor, with plans for a comparison unit that will be responsible for JMP.

The project hasn’t been without its problems – the first design of the demux for the ROM access logic resulted in a jungle of wires, gates, and connections that [zaphod] couldn’t get a usable signal out of because of the limited gate fan-out of his gates. After looking at the problem, [zaphod] decided to look at how real demuxes were constructed, and eventually hit upon the correct way of doing things – inverters and ANDs.

It’s a beautiful project, and something that [zaphod] has been working for months on. He’s getting close to complete, if you don’t count soldering up the RAM, and already has a crude Larson scanner worked out.