Dealing with all the wiring can quickly become a challenge on robots, especially the walking variety which have actuators everywhere. [Eric Yufeng Wu] sidestepped the wiring issue by creating Q8bot, a little quadruped where all the components, including the actuators, are mounted directly on the PCB.

[Eric] uses a custom PCB as the spine of the robot, and the eight servos plug directly into connectors on the PCB. With their bottom covers removed, the servos screw neatly into a pair of 3D printed frames on either side of the PCB, which also have integrated 14500 battery holders. The PCB is minimalist, with just the XIAO ESP32C3 module, a boost converter circuit to drive the servos, and a battery fuel gauge. Each SCARA-style leg consists of four SLS 3D printed segments, with press-fit bearings in the joints.

The little one moves quickly, and can even do little jumps. For this prototype, most of the control processing is done on a laptop, which sends raw joint angles to the onboard ESP32 via the ESP-Now protocol. We think this little robot has a lot of development potential, and fortunately [Eric] has made all the hardware and software files available for others to build their own.

Non-contact infrared (IR) thermometers used to be something of an exotic tool, but thanks at least in part due to the COVID-19 pandemic, they’re now the sort of thing you see hanging up near the grocery store checkout as a cheap impulse buy. Demand pushed up production, and the economies of scale did the test. Now the devices, and the sensors within them, are cheap enough for us hackers to play with.

The end result is that we now have projects like this ultra compact IR thermometer from [gokux]. With just a handful of components, some code to glue it all together, and a 3D printed enclosure to wrap it all up, you’ve got a legitimately useful tool that’s small enough to replace that lucky rabbit’s foot you’ve got on your keys.

If this project looks familiar, it’s because the whole thing is closely related to the LiDAR rangefinder [gokux] put together last month. It shares the same Seeed Studio XIAO  ESP32-C3 microcontroller, 0.49 inch OLED display, and tiny 40 mAh LiPo battery. The only thing that’s really changed, aside from the adjustments necessary to the 3D printed enclosure, is that the LiDAR sensor was replaced with a MLX90614 IR temperature sensor.

[gokux] has put together some great documentation for this build, making it easy for others to recreate and remix on their own. Assembly is particularly straightforward thanks to the fact that both the display and temperature sensor communicate with the ESP32 over I2C, allowing them to be wired daisy chain style — there’s no need for even a scrap of perfboard inside the case, let alone a custom board.

While we are used to USB WiFi adapters, embedded devices typically use SDIO WiFi cards, and for good reasons – they’re way more low-power, don’t take up a USB port, don’t require a power-sipping USB hub, and the SDIO interface is widely available. However, SDIO cards and modules tend to be obscure and proprietary beyond reason. Enter ESP-Hosted – Espressif’s firmware and driver combination for ESP32 (press release)(GitHub), making your ESP32 into a WiFi module for either your Linux computer (ESP-Hosted-NG) or MCU (ESP-Hosted-FG). In particular, ESP-Hosted-NG his turns your SPI- or SDIO-connected ESP32 (including -S2/S3/C2/C3/C6 into a WiFi card, quite speedy and natively supported by the Linux network stack, as opposed to something like an AT command mode.

We’ve seen this done with ESP8266 before – repurposing an ESP8089 driver from sources found online, making an ESP8266 into a $2 WiFi adapter for something like a Pi. The ESP-Hosted project is Espressif-supported, and it works on the entire ESP32 lineup, through an SDIO or even SPI interface! It supports 802.11b/g/n and even Bluetooth, up to BLE5, either over an extra UART channel or the same SDIO/SPI channel; you can even get BT audio over I2S. If you have an SPI/SDIO port free and an ESP32 module handy, this might just be the perfect WiFi card for your Linux project!

There are some limitations – for instance, you can’t do AP mode in the NG (Linux-compatible) version. Also, part of the firmware has blobs in it, but a lot of the firmware and all of the driver are modifiable in case you need your ESP32 to do even more than Espressif has coded in – this is not fully open-source firmware, but it’s definitely way more than the Broadcom’s proprietary onboard Raspberry Pi WiFi chip. There’s plenty of documentation, and even some fun features like raw transport layer access. Also, of note is that this project supports ESP32-C6, which means you can equip your project with a RISC-V-based WiFi adapter.

Title image from [zhichunlee].

Hacker Hotel is a small Dutch hacker event that takes place, as its name suggests, in a hotel. It’s a welcome high point in the damp of a north-west-European winter, and attendees come to its setting in the wooded Veluwe region in the centre of the country from far and wide. As is the custom with such events it has an electronic badge, and this year’s one had a rather unusual interface. Instead of a keyboard for text input, it replicates a 19th century Crook and Wheatstone telegraph, replacing the five needles of the original with a diamond-shaped grid of LEDs.

At its heart is an Espressif ESP32-C6 microcontroller which provides both a processor powerhouse and the usual array of wireless connectivity. Paired with that is a much more modest CH32V003 microcontroller to handle I/O tasks, and an e-paper screen using displays salvaged from surplus German supermarket shelf labels. That interface is handled by an array of five-way switches, and in a stroke of genius there’s a small relay on board which does nothing but provide a satisfying tactile “click”. Expansion is seen to by an SAO connector, Qwiic, and a USB-C socket. The software meanwhile is a combination of a non-volatile nametag, a complex set of puzzles used in the on-site competition, and a messaging system using the C6’s 802.15.4 mesh networking. A particularly neat feature of this was a Battleships game that could be played with another badge.

While this isn’t the first Hacker Hotel badge with an e-paper display, we like this one for its novel interface, for the mesh connectivity, and for that clicky relay. We’ll definitely be using ours as a name badge for some time to come.

[Minikk], aka [Athul] is about to enter 10th grade and reports that they and their contemporaries are eschewing boring mobile games for 90s stuff and old games like PONG. Well, we already knew the 90s were back, but it’s nice to see that even older stuff is coming along with it. The kids are alright.

Whether you want to play alone or with a friend, it’s a classic to have in your pocket for sure. The brains behind this 70s-era operation is a Seeed Xiao ESP32-C3, which takes input from the two potentiometers and outputs the game on a 128 x 64 OLED. There’s also a small buzzer for when the ball hits the paddle, or you or your friend slips one past the goalie.

Our favorite part of this build has to be the DIY rivets that hold the OLED in place. [Athul] built posts into the enclosure that get heat-smashed into place with a soldering iron. Pretty neat, huh?

PONG is a specific thrill, certainly. How can it be more thrilling? Maybe with LEDs instead of a screen? Just a thought.

If you have mischievous children or forgetful elderly in your life, you might want to build a couple of these tiny motion detection alarms to help keep them out of harm’s way. Maybe you want to keep yourself out of the cookie jar. We say good for you.

But you could always put one of these alarms on a window, a drawer, or anything else you don’t want opened or moved. The MPU6050 3-axis IMU makes sure that any way the chosen item gets jostled, that alarm is going off.

As you may have guessed, there isn’t much more to this build — the brain is a Seeed Xiao ESP32-C3, and there’s a buzzer, a battery, a switch, and a push button to program it.

The cool thing about using an ESP32-C3 is that [gokux] can use these for other things, like performing a task when motion is detected. If you do want to build yourself a couple of these, here are step-by-step instructions.

If you’d rather detect motion in the vicinity, here’s a PIR-based solution.

[James Stanley] likes to spend time making puzzles and gadgets for escape rooms, and decided for a change to try their hand at a bit of magic. The idea was to construct a ‘magic box’, in which a coin can be placed in one of a number of slots, and then be able to remotely be able to determine the slot by means unseen. Obviously, this is an electronics hack, with a neat package of sensor and radio comms hidden inside a stack of CNC-milled wood. Coin locations are transmitted via Bluetooth to a Bangle.js smartwatch, which vibrates according to the slot occupied, allowing [James] to predict where the coin was placed.
The sensor uses capacitive sensing, with a plate below each coin slot acting as one electrode of a capacitor and a copper-clad board hidden in the upper plate acting as the second. The presence of a coin is detected as a change in the capacitance of one of the sensors due to the fact that the plate separation will now be less for that one position. A simple PCB was CNC routed from a piece of plain clad board, with a cut out to solder down a Seeed Studio XIAO-ESP32-C3 module which runs the show and provides Bluetooth connectivity via an external PCB antenna module. Handily this module also handles the lithium battery management.

The software stack seems to be Arduino, with a very simple capacitance testing routine based on measuring charge times. Overall this is very nicely executed, even if [James] reckons there’s a bit more to being a show magician than just being able to construct the hardware. Magical hacks are a bit of a rarity around these parts, but we found a couple, like this magic opening box, and whilst not a magic trick, being able to hide from surveillance cameras could be actually helpful.