Tiny Function Generator On The ATtiny85, Complete With OLED

March 2, 2018 by Donald Papp 4 Comments

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

January 30, 2018 by Kristina Panos 32 Comments

[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

Man-in-the-Middle Jog Pendant: Two Parts Make Easier Dev Work

January 11, 2018 by Donald Papp 7 Comments

In a project, repetitive tasks that break the flow of development work are incredibly tiresome and even simple automation can make a world of difference. [Simon Merrett] ran into exactly this while testing different stepper motors in a strain-wave gear project. The system that drives the motor accepts G-Code, but he got fed up with the overhead needed just to make a stepper rotate for a bit on demand. His solution? A grbl man-in-the-middle jog pendant that consists of not much more than a rotary encoder and an Arduino Nano. The unit dutifully passes through any commands received from a host controller, but if the encoder knob is turned it sends custom G-Code allowing [Simon] to dial in a bit acceleration-controlled motor rotation on demand. A brief demo video is below, which gives an idea of how much easier it is to focus on the nuts-and-bolts end of hardware when some simple motor movement is just a knob twist away.

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DIY Capacitive Rotational Encoder On The Cheap With FR4

November 17, 2017 by Donald Papp 15 Comments

Rotary encoders are critical to many applications, even at the hobbyist level. While considering his own rotary encoding needs for upcoming projects, it occurred to [Jan Mrázek] to try making his own DIY capacitive rotary encoder. If successful, such an encoder could be cheap and very fast; it could also in part be made directly on a PCB.

First prototype, two etched plates with transparent tape as dielectric material. Disc is 15 mm in diameter.

The encoder design [Jan] settled on was to make a simple adjustable plate capacitor using PCB elements with transparent tape as the dielectric material. This was used as the timing element for a 555 timer in astable mode. A 555 in this configuration therefore generates a square wave that changes in proportion to how much the plates in the simple capacitor overlap. Turn the plate, and the square wave’s period changes in response. Response time would be fast, and a 555 and some PCB space is certainly cheap materials-wise.

The first prototype gave positive results but had a lot of problems, including noise and possibly a sensitivity to temperature and humidity. The second attempt refined the design and had much better results, with an ESP32 reliably reading 140 discrete positions at a rate of 100 kHz. It seems that there is a tradeoff between resolution and speed; lowering the rate allows more positions to be reliably detected. There are still issues, but ultimately [Jan] feels that high-speed capacitive encoders requiring little more than some PCB real estate and some 555s are probably feasible.

This project is a reminder that FR4 (whether copper-clad, etched, or blank) shows up in clever applications: copper tape and blank FR4 can be used to quickly prototype RF filters, PocketNC built an entire small CNC tool around FR4, and our own [Voja] wrote a full guide on making beautiful enclosures from FR4.

Reading 16 Rotary Encoders At The Same Time

October 21, 2017 by John Baichtal 19 Comments

We’re digging these daisy-chainable encoders built by [fattore.saimon]. Each module consists of a rotary encoder attached to a PCB with a PIC16F15386 on the back. As we’ve covered in the past, the Microchip released their feature-rich PIC16 microprocessor just this year, and it’s great to see them start to crop up in projects. With 4 address jumpers on the back of each PCB, [fattore.saimon] is able to connect up to 16 of the encoders on the bus. The modules also have male and female plugs so he can connect them physically as well, to simplify wiring. Each module also has a PWMable bicolor LED for keeping track of each encoder’s setting.

If you’re interested in making your own you can buy the PCBs from Tindie or download the project files from the creator’s GitHub, including an Arduino library.

We love encoders here on Hackaday — building DIY encoders, as well as using them in projects like this precision cutting jig. And definitely read our colleague [Al]’s great piece on encoders.

Fifty Shades Of Gray Code

January 25, 2017 by Al Williams 77 Comments

Some years back, a museum asked me to help them with an exhibit a contractor had built for them. It was a wheel like the one on Wheel of Fortune, but smaller and mounted on the wall instead of the floor. You would spin the wheel, it would stop on some item, and a computer would play a short video about the item. Physically and mechanically, it was a beautifully built exhibit. The electronics, though, left something to be desired.

In principle, this is pretty simple computer task. Measure the position of the wheel, and when it stops moving, play a video based on the position. The problem was the folks who created the artistic mechanics didn’t think hard about the electronics behind it. Sometimes–but not often–the wheel would play the wrong video. Sometimes it wouldn’t play at all.

The Prime Suspect

My immediate suspicion turned out to be correct. I took the wheel off its mount to discover copper foil tape on the back of it. Each pie wedge had foil in different areas and there were two brushes in each area. When the wheel stopped, two of the brushes would be shorted together and the rest were open. The way they detected that was bizarre, but that wasn’t the problem. (It involved a cannibalized PS/2 keyboard.)
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Encoders Spin Us Right Round

January 11, 2017 by Al Williams 44 Comments

Rotary encoders are great devices. Monitoring just a few pins you can easily and quickly read in rotation and direction of a user input (as well as many other applications). But as with anything, there are caveats. I recently had the chance to dive into some of the benefits and drawbacks of rotary encoders and how to work with them.

I often work with students on different levels of electronic projects. One student project needed a rotary encoder. These come in mechanical and optical variants. In a way, they are very simple devices. In another way, they have some complex nuances. The target board was an ST Nucleo. This particular board has a small ARM processor and can use mbed environment for development and programming. The board itself can take Arduino daughter boards and have additional pins for ST morpho boards (whatever those are).

The mbed system is the ARM’s answer to Arduino. A web-based IDE lets you write C++ code with tons of support libraries. The board looks like a USB drive, so you download the program to this ersatz drive, and the board is programmed. I posted an intro to mbed awhile back with a similar board, so if you want a refresher on that, you might like to read that first.

Reading the Encoder

The encoder we had was on a little PCB that you get when you buy one of those Chinese Arduino 37 sensor kits. (By the way, if you are looking for documentation on those kinds of boards, look here.; in particular, this was a KY-040 module.) The board has power and ground pins, along with three pins. One of the pins is a switch closure to ground when you depress the shaft of the encoder. The other two encode the direction and speed of the shaft rotation. There are three pull-up resistors, one for each output.

I expected to explain how the device worked, and then assist in writing some code with a good example of having to debounce, use pin change interrupts, and obviously throw in some other arcane lore. Turns out that was wholly unnecessary. Well… sort of.

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