OpenDog Version 3 Is Ready To Go Walkies

December 18, 2021 by Dave Rowntree 12 Comments

We’ve been following [James Bruton]’s open dog project for a little while now, and with his considerable pace of work – pandemic or no pandemic – development has been incredibly rapid. The latest milestone is the public release of version 3 (Video, embedded below.) This upgrade to the system adds 3D printed cycloidal gearboxes, removing the previous belt drives. [James] had immense fun tuning the motor controller parameters for these and admits they’re not completely dialed in yet. He notes that the wider gearbox body means that the robots geometry needed to change a little, and the previous belt-drive version may have a bit of an edge, but he’s confident he can make it work (and given his incredible previous robotics builds, we totally believe he’ll nail it!)

Silicone overmolding around a 3D printed former, using a 3D printed mould

Older versions struggled with slippery plastic feet; the advantage of a predictably smooth contact shape of a rounded foot is somewhat offset by the limited contact patch size, and that means not so much grip on some surfaces. [James] solution was obvious enough – just learn how to make 3D printed silicone moulds and cast a nice rubber foot around a plastic former, and problem solved! Unfortunately he neglected to add some recesses for a lever to get in between the mould halves, so it was a bit of a struggle to separate after curing. A beginner’s mistake that won’t be repeated, we’re sure.

Full source for openDogV3 is now available on the GitHub page. Here’s the playlist for the whole project, as well as direct links for the cycloidal drive development (part1, part2, part3.) But before you all go diving in to start 3D printing your own pooch, [James] tells us that the total cost would be around $2000 all in, with the bulk of that being the motors and ODrive units, so this one for the serious builder only!

We’ve covered robot dogs a fair bit, a particularly nice example is The Dizzy Wolf, and if you’re wondering just why on earth you’d want a robot dog, then Ask Hackaday has you covered as well.

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ESP8266 Based WiFi Game Boy Cartridge Browses WikiPedia

December 18, 2021 by Dave Rowntree 8 Comments

[Sebastian Staacks] came across his old Game Boy and was wondering (as you do) what happened to recent attempts at getting a WiFi interface wedged into a standard cartridge. After a while the conclusion was that people had been scuppered by approaching the problem in a way that made it too hard. Obviously that meant it was necessary to follow through and build something, which is precisely what he did with his WiFi Game Boy Cartridge.

A trend lately has been to hook up a fast microcontroller to a bus, then move the whole interfacing shenanigans into software. This works fine in some circumstances, but for the GB interface, it’s not so easy. The GB is powered by the Sharp LR35902, running at a smidge over 4 MHz, but its machine cycle takes four clocks giving an instruction rate of only 1 MHz. The cartridge interface presents the raw CPU bus directly. This is both good and bad. It’s good, because it enables all kinds of expansion modules, like cameras, printers, and other custom peripherals, but it’s bad because the burden of interfacing with the CPU, at its full speed, lies squarely in the cartridge’s remit.

Rather than trying to hook this bus directly to a fast microcontroller, [Staacks] has taken a different approach; by decoding the address bus with discrete logic, it was easy to derive chip selects for an embedded ESP8266 as well as a socketed EEPROM. The clock for the former was also gated and sent into the ESP8266, generating an interrupt to wake it up. The EEPROM stores a simple application whose job is to present an OSD keyboard and send requests to Wikipedia, via the ESP8266 WiFi stack. The resulting text is then displayed on the 160×144 dot matrix display. The interrupt latency of the ESP8266 was mitigated by the application simply discarding the first data byte sent to it, and retrying the access. This way the ESP8266 could spend the majority of its time dealing with wireless duties, only pausing to swap a byte now-and-then with the application. A simple solution which appears to actually work! If you’re up for building one of these and writing your own applications, you can wander over to GitHub, clone yourself a copy and crack on!

We’ve seen a few attempts at doing this before, [davedarko] tried with this project, and if you search hackaday.io you’ll get loads of GB hacks to browse. Finally a recent twitter thread also points to another effort to do something similar with Wi-Fi, but development is still ongoing. We’ll check back later!

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A Well Documented BreadBoard Computer Shows Dedication

December 18, 2021 by Dave Rowntree 11 Comments

These pages have not been exactly devoid of home-built computers, with those constructed on solderless breadboard less frequent, but still not rarities. But what is more of a rarity is this ground-up 8-bit 74xx logic-based computer (video, embedded below) with full source, an emulator, assembler and test suite. [JDH] spent a solid couple of weeks working late into the night to build this, and the results show for themselves.

The new JDH-8 is now a figment of reality.

The architecture is a traditional 8-bit load/store microcoded processor with the microcode stored in easily programmable AT28C64 EEPROMs for ease of tweaking. The address bus is 16-bits, which is quite ample for this, and puts it in line with (admittedly more sophisticated) 8-bit micros of old such as the 6502. There is also a hardware stack, and a discrete-logic ALU as well! Finally, since that wasn’t enough work already, he added in his own discrete logic video controller.

Wise people simulate before prototyping something like this

There are sixteen instructions covering memory access, ALU operations and I/O operations. One of the great things about this project is that [JDH] readily admits the mistakes made along the way, and how the architecture didn’t need to be this complex. One example is that hardware stack wasn’t really necessary as it could just have been implemented in software. Also, due to the implementation, memory accesses were so fast compared with the achievable cycle time, that there really was no point to using load/store architecture at all! Still, [JDH] had fun building and programming it!

It was interesting to see the use of LogiSim-Evolution to debug first a high level model of the architecture and then the translation into TTL chips. This scribe wasn’t aware of that tool (the shame!) but is going to try this out real soon.

All code for the software side of things can be found on the project GitHub. Perhaps the hardware design will appear there as well, be at the time of writing we couldn’t seem to find it.

Can’t get enough breadboard computers? (We can’t) check this out from last year. Stuck for a suitable enclosure for your latest bread breadboard computer? How about a bread bin.

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The Second Worst CAD Package Ever

December 17, 2021 by Dave Rowntree 28 Comments

A while back, [Heavydeck] remembered stumbling across the worst CAD package ever, which is a schematic editor whose existence was purely intended for use to make quick circuit sketches for documentation, presentations and the like. All good. But, being based on low quality JPEG graphics, which when blown up to projector size on a big screen, they look really rough. After deciding that the original nasty, clunky interface was just nasty and clunky enough, [Heavydeck] then proceeded to reimplement the idea over the course of an afternoon, and came up with Kludge (possibly the second worst CAD package ever) making an actually useful tool even more useful.

You see, whether you make website content, YouTube tutorials, or just need to write technical reports, if you’re in the electronics business, you’re going to need to make high-quality editable schematic images at some point, and Kludge might well solve some problems for you. Kludge lets you do so many things; you can save a schematic, you can load a schematic, you can even export it to an SVG file. Actually, that’s all you can do, but it is actually just enough. Once you’ve got an image as an SVG, you can whack that into Inkscape to add some more details and you’re done. We demonstrate this with the image above, which was not annoying at all to create.

So here’s to Kludging your way around a problem, and hoping that the somewhat limited symbol library may expand a little more in the future!

Implementing A CPU Using 555 Timers And Logic Synthesis

December 17, 2021 by Dave Rowntree 26 Comments

There is many a comment on these here pages along the lines of “Why did you use a microcontroller, when you could just have easily used a 555 timer!” And, yes, we sometimes agree with the sentiment, but when a chance comment seen by Hackaday.io user [Tim Böscke] suggested turning it around and building a microcontroller out of 555 timers, the gauntlet was well and truly thrown down. Now let’s be clear, this is not the first time we’ve come across this idea, there was a breadboard 555 based build ten years ago, but this is the first time we’ve seen it done by leveraging open source synthesis targeting a PCB!

The first logic element was a simple inverter, constructed by tying the TRIGger and THReShold pins together.

LTSpice model of a NAND gate implemented with 555 and diodes

From there it was a simple matter of adding a few diode-resistor networks to the input, to effect a NAND2 gate and a NOR2 gate. Development was speeded up a bit by modeling the logic circuits in LTSpice, to find the best combination of part values. From these simple elements, all further logic functions could be implemented. Next a memory element was needed. As luck would have it, the 555 has a RS flip flop as part of its circuit, fed by dual comparator inputs. All that was needed was to bias the THRS input at Vdd/2 and then feed the data in via a pass transistor, and hey presto! a serviceable, albeit slow latch.

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DIY Semi Auto Grinder Builds Itself (Sort Of)

December 14, 2021 by Dave Rowntree 12 Comments

[JSK-koubou] is no stranger to making tools to improve their work, and this latest video is yet another in a long list of such builds, just checkout their YT channel to see the many other examples. The tool being highlighted this time is a semi-automatic grinder (Video, embedded below) which could be very handy in many situations.

Many of us struggle a little to get straight cuts with an angle grinder, especially with softer materials, as it is sometimes hard to get a good ‘feel’ of how the cut is proceeding. Once the cut is started, thin blades will tend to ‘track’ in the slot, so if it starts off a little bit, the whole cut will be off. Most annoying. Anything to help keep things straight and square would help a lot, with the extra feature of a motorized drive enabling a constant cut rate, and presumably giving an increase in the cut quality.

Using the part completed rig to cut its own leadscrew

Since operation is hands-off, you could set it up, and leave it to do its thing, whilst you step aside, away from flying sparks, noise and the remote possibility of getting a splintered blade in your face, should the unthinkable happen. All good things.

The detailed build video shows what looks like a pretty solid construction, there are plans available on the accompanying website, but they do request a small donation of ¥1000 (less than $10 USD) to download them. Given the usefulness of the tool, this seems like a small price to pay. We quite liked some sections of the build video, where the tool is used to cut its own components, as it is built-up sequentially. Clever stuff! Another interesting technique to see was the use of a flame-heated (Stanley) knife blade as a drive belt end-jointer. Somewhat tough on the blade, but it’s a consumable item and gets the job done, so that’s good enough for us!

Parts wise, there’s nothing special at all here, with most easily sourced via the usual mechanical suppliers, but we reckon you’d be able to find most of it on eBay as well. We think this is exactly the sort of build that would work well in your local Makerspace, so perhaps give that a thought?

Bored with manually cutting off? Need an overkill solution for a mundane job? How about an Automatic Cut-Off Saw? If you need some defense against the mighty angle grinder, then perhaps Proteus is just the ticket?

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Self balancing wheeled robot with auto-righting arms lofted high

A Self Righting Balancing Robot Configured The Easy Way

December 13, 2021 by Dave Rowntree 2 Comments

Norwegian electronics hacker [Hans Jørgen] aka [time expander] on YouTube, has a clear interest in robotics, and for his latest effort, decided that it was time to build a custom controller platform. Since [Hans] had a pile of Dynamixel servo motors lying around to test it with, a good first project for the platform was a simple self-balancing wheeled robot. (Video, embedded below)

We say ‘simple’ but that isn’t really the case, as there is a fair bit going on to get this to work. The first problem, is sensing, which was quickly solved with the excellent BMO055 IMU chip. Next, what to do when it falls over? Simply adding some servo-controlled arms, allowed the robot to flip itself back upright. Control is covered with a ESP32-WROOM-32D module from our friends at Espressif, which enables remote firmware uploading over the air (OTA update) as well as parameter tuning. In order to implement the latter, [Hans] chose to use bonjour/mDNS which is an implementation of zero-configuration networking. This gets the ESP32 onto the WiFi, but it isn’t immediately obvious how to connect to it, without a little digging around. To simply connection, [Hans] implemented a dynamic QR code via the connected OLED. This is just one of the those tiny 0.96″ displays that you see touted all over our corners of the internet.

Simply by scanning the QR code with any compatible device to hand brings up a simple configuration web page, allowing one to tweak the PID controller parameters, and get that balancing robot into check. Great stuff!

The PCB was designed in Eagle, firmware for the ESP32 is available, 3D models for the plastic are designed with fusion 360, and [Hans] is even currently working on some preliminary Alexa integration. What a fun project!

All the above, albeit an early cut (look out for bugs!) is available on the project GitHub for your viewing pleasure.

We’re no stranger to self-balancing 3D-printed bots, whilst you’re here, why not checkout A problematic Self-Balancing Sonic the Hedgehog? If wheeled bots aren’t your cup-of-tea, there’s a not-at-all freaky one-legged bouncing bot that may be of interest.

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