Using Motors As Encoders

If you have a brushless motor, you have some magnets, a bunch of coils arranged in a circle, and theoretically, all the parts you need to build a rotary encoder. A lot of people have used brushless or stepper motors as rotary encoders, but they all seem to do it by using the motor as a generator and looking at the phases and voltages. For their Hackaday Prize project, [besenyeim] is doing it differently: they’re using motors as coupled inductors, and it looks like this is a viable way to turn a motor into an encoder.

The experimental setup for this project is a Blue Pill microcontroller based on the STM32F103. This, combined with a set of half-bridges used to drive the motor, are really the only thing needed to both spin the motor and detect where the motor is. The circuit works by using six digital outputs to drive the high and low sided of the half-bridges, and three analog inputs used as feedback. The resulting waveform graph looks like three weird stairsteps that are out of phase with each other, and with the right processing, that’s enough to detect the position of the motor.

Right now, the project is aiming to send a command over serial to a microcontroller and have the motor spin to a specific position. No, it’s not a completely closed-loop control scheme for turning a motor, but it’s actually not that bad. Future work is going to turn these motors into haptic feedback controllers, although we’re sure there are a few Raspberry Pi robots out there that would love odometry in the motor. You can check out a video of this setup in action below.

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GTA: San Andreas Radio Earns Six-Star Wanted Level

[Raphaël Yancey] wanted to be able to jam to Bounce FM and Radio:X all the time, without having to steal a car or a street sweeper in San Andreas. As people who like to put on the sad piano building music from The Sims and write Hackaday posts, we can totally relate.

But this isn’t just another one of those jam-a-Pi-into-a-vintage-radio-and-call-it-a-sandwich projects (not that there’s anything wrong with those). This thing acts like a real radio. All the stations play continuously whether you’re tuned in or not, and they bleed into each other as you go up and down the dial.

After much trial and error, [Raphaël] found a Python mixer that would work, but it was no longer maintained. He forked it, squashed a bug or two, and wrote a module for KY040 rotary encoders to make them play nice with the Pi. The snake charming doesn’t stop there: the rock star of this project is [Raphaël]’s virtual radio software, which handles the audio blending as he tunes between stations. A step-by-step tutorial is coming soon, so watch [Raphaël]’s site for updates. Tune past the break to give it a listen.

Adventures in Raspi radio-ing don’t have to be one-way. Here’s how you can turn one into an AM/FM+ transmitter using a DVB-T dongle and SDR.

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Stepper Motor? Encoder? It’s Both!

We always think it is interesting that a regular DC motor and a generator are about the same thing. Sure, each is optimized for its purpose, but inefficiencies aside, you can use electricity to rotate a shaft or use a rotating shaft to generate electricity. [Andriyf1] has a slightly different trick. He shows how to use a stepper motor as an encoder. You can see a video of the setup below.

It makes sense. If the coils in the stepper can move the shaft, then moving the shaft should induce a current in the coils. He does note that at slow speeds you can miss pulses, however. Again, the device isn’t really optimized for this type of operation.

The circuit uses an opamp-based differential amplifier to read the pulses from the coil. Two opamps on two coils produce a quadrature signal just like a normal encoder. When the shaft turns in one direction, one pulse will lead the other. In the other direction, the lead pulse will be reversed.

There’s code to let an Arduino read the pulses. And here’s plenty of code that will read quadrature on an Arduino or other processors. We’ve seen similar hacks done with hard drive motors which are quite similar, by the way.

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Rotary Encoders Become I2C Devices

Rotary encoders are the bee’s knees. Not only do you get absolute positioning, you can also use a rotary encoder (with a fancy tact button underneath) for an easy UI for any electronics project. There’s a problem with rotary encoders, though: it’s going to use Gray code or something weird, and getting a rotary encoder to work with your code isn’t as easy as a simple button.

For his Hackaday Prize project, [fattore.saimon] has come up with the solution for using multiple rotary encoders in any project. It’s a board that turns a rotary encoder into an I2C device. Now, instead of counting rising and falling edges, adding a rotary encoder to a project is as easy as connecting four wires.

The project is built around the PIC16F18344, a small but surprisingly capable microcontroller that reads a rotary encoder and spits data out as an I2C slave device. Also on board are a few pins for an RGB LED, general purpose pins, the ability to set all seven bits of the I2C address (who wants 127 rotary encoders?), and castellated holes for connecting several boards together.

This project is an update of [fattore]’s earlier I2C Encoder, and there are a lot of improvements in the current version. It’s slightly smaller, has better connectors, and uses a more powerful microcontroller. That’s just what you need if you want a ton of rotary encoders for all those cool interactive projects.

Dumb Down Your Xiaomi Smart Lamp With A Custom Firmware

Undoubtedly, the ESP8266’s biggest selling point is its WiFi capability for a ridiculously low price. Paranoid folks probably await the day its closed-source firmware bits will turn against humanity in a giant botnet, but until then, hobbyists and commercial vendors alike will proceed putting them in their IoT projects and devices. One of those devices is the Yeelight desk lamp that lets you set its color temperature and brightness via mobile app.

[fvollmer] acquired such a lamp, and while he appreciated its design and general concept, he wasn’t happy that it communicates with external servers. So he did the only reasonable thing and wrote his own firmware that resembles the original functionality, but leaves out the WiFi part. After all, the ESP8266 has still a lot to offer in its core essence: a full-blown 32-bit microcontroller with support for the most common, hobbyist-friendly SDKs.

The lamp’s color temperature and brightness are set with a rotary encoder / push button combo switch, and the LEDs themselves are controlled via PWM. All things considered, it’s a rather straightforward endeavour, for which [fvollmer] chose the standalone C SDK. And in the end, it’s not like he’s unreasonably cautious to keep some control over his household items.

Tiny Function Generator on the ATtiny85, Complete with OLED

It’s easy to have a soft spot for “mini” yet perfectly functional versions of electronic workbench tools, like [David Johnson-Davies]’s Tiny Function Generator which uses an ATtiny85 to generate different waveforms at up to 5 kHz. It’s complete with a small OLED display to show the waveform and frequency selected. One of the reasons projects like this are great is not only because they tend to show off some software, but because they are great examples of the kind of fantastic possibilities that are open to anyone who wants to develop an idea. For example, it wasn’t all that long ago that OLEDs were exotic beasts. Today, they’re available off the shelf with simple interfaces and sample code.

The Tiny Function Generator uses a method called DDS (Direct Digital Synthesis) on an ATtiny85 microcontroller, which [David] wrote up in an earlier post of his about waveform generation on an ATtiny85. With a few extra components like a rotary encoder and OLED display, the Tiny Function Generator fits on a small breadboard. He goes into detail regarding the waveform generation as well as making big text on the small OLED and reading the rotary encoder reliably. His schematic and source code are both available from his site.

Small but functional microcontroller-based electronic equipment are nifty projects, and other examples include the xprotolab and the AVR-based Transistor Tester (which as a project has evolved into a general purpose part identifier.)

Roll Your Own Magnetic Encoder Disks

[Erich] is the middle of building a new competition sumo bot for 2018. He’s trying to make this one as open and low-cost as humanly possible. So far it’s going pretty well, and the quest to make DIY parts has presented fodder for how-to posts along the way.

One of new bot’s features will be magnetic position encoders for the wheels. In the past, [Erich] has used the encoder disks that Pololu sells without issue. At 69¢ each, they don’t exactly break the bank, either. But shipping outside the US is prohibitively high, so he decided to try making his own disks with a 3D printer and the smallest neodymium magnets on Earth.

The pre-fab encoder disks don’t have individual magnets—they’re just a puck of magnetic slurry that gets its polarity on the assembly line. [Erich] reverse-engineered a disk and found the polarity using magnets (natch). Then got to work designing a replacement with cavities to hold six 1mm x 1mm x 1mm neodymium magnets and printed it out. After that, he just had to glue them in place, matching the polarity of the original disk. We love the ingenuity of this project, especially the pair of tweezers he printed to pick and place the magnets.

Rotary encoders are pretty common in robotics applications to detect and measure wheel movement. Don’t quite recall how they work? We’ll help you get those wheels turning.

via Dangerous Prototypes