Mini Wireless Thermal Printers Get Arduino Library (and MacOS App)

September 21, 2021 by Donald Papp 23 Comments

[Larry Bank]’s Arduino library to print text and graphics on BLE (Bluetooth Low Energy) thermal printers has some excellent features, and makes sending wireless print jobs to a number of common models about as easy as can be. These printers are small, inexpensive, and wireless. That’s a great mix that makes them attractive for projects that would benefit from printing out a hardcopy.

It’s not limited to simple default text, either. Fancier output can be done using Adafruit_GFX library-style fonts and options, which sends the formatted text as graphics. You can read all about what the library can do in this succinct list of concise functions.

But [Larry] hasn’t stopped there. While experimenting with microcontrollers and BLE thermal printers, he also wanted to explore talking to these printers from his Mac using BLE directly. Print2BLE is a MacOS application that allows dragging image files into the application’s window, and if the preview looks good, the print button makes it come out of the printer as a 1-bpp dithered image.

Small thermal printers make for neat projects, like this retrofitted Polaroid camera, and now that these little printers are both wireless and economical, things can only get easier with the help of a library like this. Of course, if that’s all starting to look a little too easy, one can always put the thermal back in thermal printing by using plasma, instead.

Self Balancing Robot Needs A Little Work

September 20, 2021 by Al Williams 6 Comments

A self-balancing robot isn’t a new idea, but we liked the aesthetics of [Maker ATOM’s] build. The use of a breadboard and a printed bracket looks good, as you can see in the video, below.

Like most first-time projects, though, there were some lessons learned. The power supply needs a little work and the range of balance compliance didn’t meet expectations. But those problems are soluble and, as usual, you often learn more from working through issues like these.

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Optical Theremin Makes Eerie Audio With Few Parts

September 19, 2021 by Donald Papp 6 Comments

[Fearless Night]’s optical theremin project takes advantage of the kind of highly-integrated parts that are available to the modern hacker and hobbyist in all the right ways. The result is a compact instrument with software that can be modified using the Arduino IDE to take it places the original Theremin design could never go.

The design is based on a ‘Blue Pill’ STM32 MCU development board and two Avago APDS-9960 gesture sensor breakout boards, along with a few other supporting components. Where the original Theremin sensed hand proximity using two antenna-like capacitive sensors to control note frequency and volume, this design relies on two optical sensors to do the same job.

[Fearless Night] provides downloads for the schematic, code, parts list, and even 3D models for the enclosure. PCB files are also included for a convenient assembly, but since the component count is fairly low, a patient hacker should be able to get away with soldering it up by hand without much trouble.

This project creates the audio using the STM32’s Direct Digital Synthesis (DDS) capability and a simple low-pass filter, and has several ways to fine-tune the output. What’s DDS? Our own Elliot Williams explains it in terms of audio output for microcontrollers, and if you’d like a more comprehensive overview, Bil Herd will happily tell you all about it.

Line Following Robot Uses PID For Speed

September 18, 2021 by Al Williams 19 Comments

While a line-following robot may not be the newest project idea in the book, this one from [Edison Science] is a clean build using modern components and gets a good speed thanks to PID control feedback instead of the more traditional bang-bang control you see in low-end robots.

Of course, PIDs need tuning and that seems to be the weak link — you’ll have to experiment with the settings. The sensors also require calibration, but we bet both of those issues could be fixed pretty easily.

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RoboTray Is A Secret Tea Butler

September 17, 2021 by Kristina Panos 10 Comments

How far would you go for your cup of tea? [samsungite]’s missus doesn’t like clutter on her countertops, so away the one-cup kettle would go back into the cupboard for next time while the tea steeped. As long as there’s room for it in there, why not install it there permanently? That’s the idea behind RoboTray, which would only be cooler if it could be plumbed somehow.

RoboTray went through a few iterations, most importantly the switch from 6mm MDF to 4 mm aluminum plate. A transformer acts as a current sensor, and when the kettle is powered on, the tray first advances forward 7 cm using a 12 VDC motor and an Arduino. Then it pivots 90° on a lazy Susan driven by another 12 VDC motor. The kettle is smart enough to turn itself off when finished, and the Arduino senses this and reverses all the steps after a ten-second warning period. Check it out in action after the break.

If [samsungite] has any more Arduinos lying around, he might appreciate this tea inventory tracker.

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Harp Uses Frikin’ Lasers

September 14, 2021 by Al Williams 12 Comments

We aren’t sure if you really need lasers to build [HoPE’s] laser harp. It is little more than some photocells and has an Arduino generate tones based on the signals. Still, you need to excite the photocells somehow, and lasers are cheap enough these days.

Mechanically, the device is a pretty large wooden structure. There are six lasers aligned to six light sensors. Each sensor is read by an analog input pin on an Arduino armed with a music-generation shield. We’ve seen plenty of these in the past, but the simplicity of this one is engaging.

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Robert Dunn holds a button in his hand for controlling a spot welder

Gorgeous Battery Welder Hits The Spot

September 14, 2021 by Ryan Flowers 32 Comments

Raise you’re hand if you’ve ever soldered directly to a battery even though you know better. We’ve all been there. Sometimes we get away with it when we have a small pack and don’t care about longevity. But when [Robert Dunn] needed to build a battery pack out of about 120 Lithium Ion cells, he knew that he had to do it The Right Way and use a battery spot welder. Of course, buying one is too simple for a hacker like [Robert]. And so it was that he decided to Build a Spot Welder from an old Microwave Oven and way too much mahogany, which you can view below the break.

A Battery Cell with a spot welding tab attached — Spot Welding leaves two familiar divots in the attached tab, which can be soldered or welded as need.

For the unfamiliar, a battery spot welder is the magical device that attaches tabs to rechargeable batteries. You’ll notice that all battery packs with cylindrical cells have a tab with two small dimples. These dimples are where high amperage electricity quickly heats the battery terminal and the tab until they’re red hot, welding them together. The operation is done and over in less than a second, well before any heat damage can be done. The tab can then be soldered to or spot welded to another cell.

One of the most critical parts of spot welding batteries is timing. While [Robert Dunn] admits that a 555 timer or even just a manual switch and relay could have done the job, he opted for an Arduino Uno with a 4 character 7 segment LED display that shows the welding time in milliseconds. A 3d printed trigger and welder handle wrap up the hardware nicely.

The build is topped off by a custom mahogany enclosure that is quite a bit overdone. But if one has the wood, the time, the tools and skills (and a YouTube channel perhaps?) there’s no reason not to put in the extra effort! [Robert]’s resulting build is almost too nice, but it’ll certainly get the job done.

Of course, spot welders are almost standard fare here at Hackaday, and we’ve covered The Good, The Bad, and The Solar. Do you have a battery welder project that deserves a spot in Hackaday’s rotation? By all means, send it over to the Tip Line!

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