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.
[Pyrow] wanted to upgrade his garage door opener remote. It worked just fine, but changing those tiny batteries out can be an inconvenience. Plus, the remote control was taking up valuable storage space and would always rattle around while driving. [Pyrow] decided to make use of an Omron E2K-F10MC2 capacitive touch sensor to fix these issues.
[Pyrow’s] circuit still makes use of the original remote control. He just added some of his own components to get it to do what he wanted. The circuit is powered by the car’s battery, so it never needs a battery replacement. The circuit is protected with a fuse and the power is regulated to prevent electrical spikes from burning up the original remote control. The actual circuit is pretty simple and uses mostly discrete components. It’s all soldered onto proto board to keep it together. He only had to solder to three places on the original remote control in order to provide power and simulate a button press.
Next, [Pyrow] took his dash apart. He used double-sided tape to attach the touch sensor to the back of the dash. After securing the electronics in place with tape, he now has a working hidden garage door opener. Full schematics are available in the writeup linked above. Also, be sure to watch the demonstration video below.
Continue reading “Capacitive Garage Door Opener Hides Behind Your Dash”
By now we’ve all seen the ‘Three Fives’ kit from Evil Mad Scientist, a very large clone of the 555 timer built from individual transistors and resistors. You can do a lot more in the analog world with discrete parts, and [Shane]’s SevenFortyFun is no exception: it’s a kit with a board, transistors, and resistors making a very large clone of the classic 741 op-amp, with all the parts laid bard instead of encapsulated in a brick of plastic.
[Shane] was inspired by the analog greats – [Bob Pease], [Jim Williams], and of course [Bob Widlar], and short of mowing his lawn with goats, the easiest way to get a feel for analog design was to build some analog circuits out of individual components.
[Shane] has a few more kits in mind: a linear dropout and switching regulators are on the top of the list, as is something like the Three Fives kit, likely to be used to blink giant LEDs.
We never bought an RFID reader because it seems too simple to be all that much fun. But [Abdullah] really caught our eye with his latest project. It’s an RFID reader built from discrete parts, and that’s an adventure we can get behind!
His write-up dives right into the theory of the device. He wrapped his own coil, which measure about one microhenry, then shares an equation used to calculate the appropriate capacitor pair for it. This is fed by a 125 kHz oscillator and works as the most basic reader. In practice this needs more components for rock-solid operation and he quickly moves to a marginally more complicated circuit which still does exactly the same thing.
He is now able to detect RFID tag data by reading this circuit with an oscilloscope. But the signal is very very weak. The rest of the post focuses on how to best utilize an OpAmp to increase signal quality and on/off time.
If you’re looking to recreate his reader [Abdullah] included a Kicad schematic and board layout.
You’re going to want to do some stretching before undertaking a soldering project like this one. We’re betting that the physical toll of assembling this 4-bit discrete processor project is starting to drive [SV3ORA] just a bit crazy. This small piece of electronic real estate is playing host to 62 transistors so far, and he’s not done yet.
It’s one thing to build some logic gates in Minecraft (and then turn then into a huge 16-bit ALU). But it’s another thing to actually commit to a physical build. [SV3ORA] does a great job of showing the scope of the project by posting a tight shot of one inverter, then three in a row, then the entire 8-bit address and display system. These gates are built on the copper side of the board, with the power feed, LEDs for displays, and jumpers for control on the opposite side. We’re excited to see where he goes with this project!
But hey, if you don’t want to do that much soldering there’s a lot you can do on a few breadboards.
[Caleb] is hard at work on a driving game based on 7400 series logic chips. This will be his entry in the Open 7400 Logic Competition, and it really outlines why this contest is especially tricky.
The concept behind the game is quite simple. You’re the driver of a car (the red dot at the bottom of the display square seen above) and need to navigate the curves in the road as you drive along. It’s the same game as we saw played on receipt paper back in June. [Caleb’s] using and LED matrix as the display, and we’re confident that if we grabbed our favorite microcontroller we could have this up and running on an 8×8 bi-color display in an afternoon. But doing it without the crutch of a programmable chip really brings out the clever engineer inside of you.
The circuit seen above is a Logisim proof-of-concept that [Caleb] went on to test on the breadboard. He thought he had everything figured out until he realized that his Data Flip-Flops were very occasionally not powering up in the same state as he predicted. Don’t worry, he found a solution to the problem. But we can’t wait to see what other hurdles he encounters as he pushes on toward completing the project.
Here’s another chance to ply your hacking skills for cash and prizes. Dangerous Prototypes has just announced the Open 7400 Logic Competition. First prize is $100 and a bunch of hacking goodies. But even better is that since it was announced, more sponsors have stepped up to increase the kitty, and the number of entries that will get prizes.
The parameters for entry are wide open. You can design anything you want, with emphasis on originality. Make sure you take plenty of pictures and document the project along the way. Their judging will take into consideration the amount of detail posted about the project (hence the ‘Open’ in the contest title).
Need some ideas to get you started? We enjoyed the useless machine that used a 7400 NAND gate. You could always build a time piece of some sort like this no-microcontroller clock. Perhaps hardware control like this stepper motor driver is more to your liking?