Single Board Relay Computer

September 18, 2017 by Brian Benchoff 26 Comments

We all know you can build a computer out of relays, and if you’re a regular reader of Hackaday, you’ve probably seen a few. Actually designing and fabricating a computer built around relays is another thing entirely, and an accomplishment that will put you right up there with the hardware greats.

The newest inductee of the DIY microcomputer hall of fame is [Jhallen]. He’s built a microcomputer ‘trainer’ out of relays. It’s got more click and clack than the Tappet family, and is a work of art rendered in DPDT relays.

The biggest consideration in designing a relay computer is the memory. You can implement a CPU in a few dozen relays, but even a small amount of memory is still hundreds of additional components. In this computer, [Jhallen] is sort of cheating. The memory is implemented as 256 32-bit words on a microcontroller alongside a controller for the front panel. The CPU is still all relays, with support for self-modifying code, a bunch of instructions for conditional jumps, and an ‘increment and jump if not equal to zero’ instruction.

Below, you can check out a very in-depth video of the relay computer in action, starting off with some satisfying click and clack of Euclid’s algorithm and a demonstration of the variable clock rate. The video goes on to demonstrate the assembly language of the relay computer itself and a bit of the overall architecture. This is really one of the most educational demo videos for vintage computing we’ve ever seen.

[Jhallen] assembled a few of these boards and he’s selling some of the extras. If you have $600, you can pick one up over on Tindie (standard Hackaday / Tindie disclosure statement). Considering the amount of soldering required to assemble this board, we’re going to guess that’s a very fair price.
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Relay Computer: You Can Hear It Think

September 11, 2017 by Inderpreet Singh 29 Comments

Modern digital computers have complex instruction sets that runs on state-of-the-art ALUs which in turn are a consequence of miniaturized logic gates that are built with tiny transistors. These tiny transistors are essentially switches. You could imagine replacing with electromagnetic relays, and get what is called a relay computer. If you can imagine it, someone’s done it. In this case, [jhallenworld].

The Z3 was the first working programmable, fully automatic digital computer designed by Konrad Zuse. The board employs modern semiconductor devices such as memory and microcontrollers, however, the CPU is all relays. A hexadecimal keyboard allows for program entry and a segment display allows tracking the address and data. The program is piped into serial to the parallel decoder and fed to the CPU where the magic happens. Since the core is electromechanical it is possible to connect the output to peripherals such as a bell as demonstrated near the end of the video.

This project is a good balance of retro and modern to be useful to anyone interested in mechanical computers and should be a lot of fun for the geek kind. Hacking this computer to modify the instruction set should be equally rewarding and a good exercise for students of computing theory.

There is a SourceForge page dedicated to the project with the details on the project including the instruction set and architecture. Check out the video below and if you are inspired by the project, be sure to check out the [Clickity Clack]’a Videos on designing a relay computer bit by bit.

Switching: From Relays To Bipolar Junction Transistors

September 7, 2017 by Sean Boyce 28 Comments

How many remote controls do you have in your home? Don’t you wish all these things were better integrated somehow, or that you could add remote control functionality to a random device? It’s a common starting point for a project, and a good learning experience for beginners.

A common solution we’ve seen applied is to connect a relay in parallel to all the buttons we want to press. When the relay is triggered, for example by your choice of microcontroller, it gets treated as a button press. While it does work, relays are not really the ideal solution for the very low current loads that we’re dealing with in these situations.

As it turns out, there are a few simple ways to solve this problem. In this article, we’re going to focus on using common bipolar junction transistors instead of relays to replace physical switches. In short, how to add transistors to existing electronics to control them in new ways.

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Have Alexa Open Your Garage Door

September 3, 2017 by John Baichtal 17 Comments

[yoyotechKnows] built an Alexa-controlled garage door opener after his Liftmaster stopped working. Now all he has to do is holler at his mobile phone and he can raise and lower his garage doors at will.

His project is based around a Photon WiFi kit, with a pair of LCC 120 digital relays triggering the two doors, reed switches, and a serial-equipped LCD to display door status, with Alexa, IFTTT, and OpenHab to process the commands. You can find his code in the project writeup.

Currently he has a LCD display informing him of the status of each door, hot glued a reed switch to keep track of whether each one is closed. This might seem a little bit extraneous since he can also just look at the doors from within the garage. However, he’s thinking about putting the display inside his house. But couldn’t he just ask Alexa?

We love us our home automation here at Hackaday, with everything from swimming pools to chicken coops rigged for app control and datalogging.

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Fight Mold And Mildew With An IoT Bathroom Fan

September 2, 2017 by Dan Maloney 24 Comments

Delicious sheets of wallboard coated with yummy latex paints, all kept warm and moist by a daily deluge of showers and habitually forgetting to turn on the bathroom exhaust fan. You want mildew? Because that’s how you get mildew.

Fed up with the fuzzy little black spots on the ceiling, [Innovative Tom] decided to make bathroom ventilation a bit easier with this humidity-sensing IoT control for his bathroom exhaust fan. Truthfully, his build accomplishes little more than a $15 timer switch for the fan would, with one critical difference — it turns the fan on automatically when the DHT11 sensor tells the WeMos board that the relative humidity has gone over 60%. A relay shield kicks the fan on until the humidity falls below a set point. A Blynk app lets him monitor conditions in the bathroom and override the automatic fan, which is handy for when you need it for white noise generation more than exhaust. The best part of the project is the ample documentation and complete BOM in the description of the video below, making this an excellent beginner’s project.

No bathroom fan? Not a problem — this standalone humidity-sensing fan can help. Or perhaps you have other bathroom ventilation needs that this methane-sensing fan could help with?

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Spoiler Alert! Repairing A Race Car Can Get Complicated, Fast.

August 28, 2017 by James Hobson 37 Comments

[Big Fish Motorsports] has a vehicle with an adjustable rear spoiler system that broke in the lead up to a big race. The original builder had since gone AWOL so the considerable talents of [Quinn Dunki] were brought to bear in getting it working again.

Cracking open the black control box of mystery revealed an Arduino, a ProtoShield and the first major road block: the Arduino remained stubbornly incommunicado despite several different methods of trying to read the source code. Turns out the Arduino’s ATMega324 was configured to be unreadable or simply fried, but an ATMega128 [Quinn] had proved to be a capable replacement. However, without knowing how the ten relays for this spoiler system were configured — and the race day deadline looming ever larger — [Quinn] opted to scrap the original and hack together something of her own design with what she had on hand.

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Keep Pedaling To Keep Playing

August 8, 2017 by Bryan Cockfield 12 Comments

It’s been said that the best way to tackle the issue of childhood obesity would be to hook those children’s video game consoles up to a pedal-powered generator. Of course, this was said by [Alex], the creator of Cykill. Cykill interfaces an Xbox to an exercise bike, so to keep the video game going you’ll have to keep pedaling the bike.

While there is no generator involved in this project, it does mimic the effect of powering electronics from a one. The exercise bike has a set of communications wires, which are connected to a relay on the Xbox’s power plug. When the relay notices that the bike isn’t being pedaled enough, it automatically cuts power to the console. Of course, the risk of corrupting a hard drive is high with this method, but that only serves to increase the motivation to continue pedaling.

The project goes even further in order to eliminate temptation to bypass the bike. [Alex] super-glued the plug of the Xbox to the relay, making it extremely difficult to get around the exercise requirement. If you’re after usable energy instead of a daily workout, though, there are bikes out there that can power just about any piece of machinery you can imagine.