Continuity Tester Uses The ATtiny85’s Comparator

November 25, 2017 by Anool Mahidharia 11 Comments

There’s an inside joke among cyclists – the number of bikes you need is “n+1”, where “n” is your current number of bikes. The same probably also applies to the number of tools and equipment a hacker needs on their workbench. Enough is never enough. Although [David Johnson-Davies] has a couple of multimeters lying around, he still felt the urge to build a stand-alone continuity tester and has posted details for a super-simple ATtiny85 based Continuity Tester on his blog. For a device this simple, he set himself some tall design goals. Using the ATtiny85 and a few SMD discretes, he built a handy tester that met all of his requirements and then some.

The ATtiny85’s Analog Comparator function is perfectly suited for such a tester. One input of the comparator is biased such that there is a 51 ohm resistor between the input and ground. The output of the comparator toggles when the resistance between the other input and ground is either higher or lower than 51 ohms. Enabling internal pullup resistors in the ATtiny85 not only takes care of proper biasing of the comparator pins, but also helps reduce current consumption when the ATtiny85 is put to sleep. The test current is limited to 100 μA, making the tester suitable for use in sensitive electronics. And enabling the sleep function after 60 seconds of inactivity reduces standby current to just about 1 μA, so there is no need for a power switch. [David] reckons the CR927 button cell ought to last pretty long.

For those interested in building this handy tester, [David] has shared the Eagle CAD files as well as the ATtiny85 code on his Github repository or you could just order out some boards from OSHpark.

Snail Is Actually Cleverly Strange Geocaching Waypoint

November 11, 2017 by Donald Papp 12 Comments

Basic geocaching consists of following GPS coordinates to a location, then finding a container which is concealed somewhere nearby. Like any activity, people tend to add their own twists to keep things interesting. [Jangeox] recently posted a video of the OLED Snail 2.0 to show off his most recent work. (This is a refinement of an earlier version, which he describes in a blog post.)

Another of [Jangeox]’s Electronic Waypoints

[Jangeox] spices up geocaching by creating electronic waypoints, and the OLED Snail is one of these. Instead of GPS coordinates sending someone directly to a goal, a person instead finds a waypoint that reveals another set of coordinates and these waypoints are followed like a trail of breadcrumbs.

A typical waypoint is an ATTINY85 microcontroller programmed to display an animated message on the OLED, and the message reveals the coordinates to the next waypoint. The waypoint is always cleverly hidden, and in the case of the OLED Snail 2.0 the enclosure is the shell of a large snail containing the electronics encased in resin. This means that the devices have a finite lifespan — the battery sealed inside is all the power the device gets. Fortunately, with the help of a tilt switch the electronics can remain dormant until someone picks it up to start the show. Other waypoints have included a fake plant, and the fake bolt shown here. Video of the OLED Snail 2.0 is embedded below.

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ESP8266 As A Tape Drive

November 3, 2017 by Rich Hawkes 25 Comments

1976 was the year the Apple I was released, one of several computers based on the MOS 6502 chip. MOS itself released the KIM-1 (Keyboard Input Monitor) initially to demonstrate the power of the chip. The single board computer had two connectors on it, one of which could be used for a tape recorder for long-term storage. When [Willem Aandewiel] went to the Apple Museum Nederland in 2016, he saw one and felt nostalgic for his youth. He was able to get a replica, the microKIM, and build it but he wanted to use new technology to interface with this old technology, so he decided to use an ESP8266 as a solid state tape recorder.

One of the reasons the KIM-1 was so popular when it was released was that there was lots of documentation available. [Willem] used this documentation to figure out how the KIM-1 saves data to the recording device. An ATTiny85 is used to decode the pulse stream that the KIM-1 sends when saving because the timing was too tight to both “listen” and decode the bits as well as convert and store them. For loading programs, the data can be sent digitally as 1’s and 0’s to the KIM-1. This means that the ATTiny is only used for decoding and doesn’t have to re-encode the data. Because of this, saving is slow, but loading is very quick.

To complete the project, [Willem] added four buttons, one each for rewind, record, play and fast-forward, and a screen so you can see which program is currently selected and can go from one program to another. As a nice throwback touch, record and play have to be pressed at the same time when saving. For more 6502 projects, check out this 6502 based DIY computer, or this 6502 built from discrete parts.

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DIY Pyrography Power Supply

November 2, 2017 by Kristina Panos 25 Comments

Ever wanted to try your hand at wood burning? If you already threw away your first soldering iron—you know the one: plugged straight in to the wall, no temperature control, came with a thick piece of tin foil to rest it on—don’t despair. Pyrography pens don’t cost that much. The variable power supply they plug into, though: that’s another story. Those cost more than they probably should.

[td0g] took the plunge into pyrography a while back, and wanted to build his own controller from an old ATX power supply. Why not? It should be more than capable of doing the job. Even the most heavy-duty pyrography pens only draw 10A, and the 3.3V line showed to be rated for 30A. All [td0g] had to do was add a PWM with a MOSFET and a ‘Tiny85.

The project nearly became Fail of the Week fodder after [td0g] saw huge voltage spikes across the MOSFET. A 47kΩ resistor took care of those, and a heat sink salvaged from the junk bin will prolong the transistor’s life. [td0g] added a push button that cycles through five heat settings, and an LED to show the status. After that, all he had to do was add a male RCA input to connect the pens he already has.

Okay, so you wouldn’t be caught dead dropping money on some fancy power supply for this new hobby. Don’t want to buy pens, either? Roll your own from a plasma arc lighter.

LAMEBOY Is Handheld Gaming On The ESP8266

September 30, 2017 by Mike Szczys 11 Comments

We’ve had our eye on [davedarko’s] LAMEBOY project for a while now, a handheld setup in roughly the same form factor as the classic Nintendo Game Boy. It’s remarkable how approachable portable electronic design has become, and that’s really what makes this interesting. The design is beautiful, and the closer you look, the more respect you have for what [dave] is doing.

Right now his proof of concept has a 3D printed enclosure whose face is the printed circuit board. We love how the lower left corner of the PCB slips under a pocket in the case, which makes it possible to use just one screw to secure the two together in the upper right.

The LAMEBOY is built around an ESP8266 module. Anyone who has used one knows this chip contains a fair amount of horsepower, but very little I/O. [Dave] has a lot going on with an LCD screen, six user buttons, a USB to I/O chip, and an SD card slot. He took two approaches to solve this dilemma. First he grabbed a PCF8574 port expander, and second he’s offloaded the color control of the screen backlights to an ATtiny85 (running a BlinkM clone).

Below you can see some early game tests on the perfboard prototype. We haven’t seen game play on the most recent prototype (there is a screen color test video in his latest project log) but it sounds as though [dave] plans to make use of the Gamebuino framework. This should mean that there will be no shortage of cool ROMs to load.

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Customizable PCB Business Card

September 22, 2017 by John Baichtal 19 Comments

[Corey Harding] designed his business card as a USB-connectable demonstration of his skill. If potential manager inserts the card in a USB drive, open a text editor, then touches the copper pad on the PCB, [Corey]’s contact info pops up in the text box.

In addition to working as a business card, the PCB also works as a Tiny 85 development board, with a prototyping area for adding sensors and other components, and with additional capabilities broken out: you can add an LED, and there’s also room for a 1K resistor, a reset button, or break out the USB’s 5V for other uses. There’s an AVR ISP breakout for reflashing the chip.

Coolly, [Corey] intended for the card to be an Open Source resource for other people to make their own cards, and he’s providing the Fritzing files for the PCB. Fritzing is a great program for beginning and experienced hardware hackers to lay out quick and dirty circuits, make wiring diagrams, and even export PCB designs for fabrication. You can download [Corey]’s files from his GitHub repository.

For another business card project check out this full color business card we published last month.

Mini Tetris Game Packs A Tiny85

August 2, 2017 by John Baichtal 5 Comments

[dombeef] originally built pocketTETRIS as a Father’s Day gift for his Tetris-loving pops. However, having finished the project he’s decided to share it with the universe, and it’s looking rather sweet.

He made the game the smallest he could make, with size limitations imposed by a 0.96” OLED display, the coin-cell battery pack, and his desire for a durable 3D-printed case. It uses a ATtiny85 for the brains, mounted on a custom PCB that [dombeef] designed in KiCad. The Arduino code was modified from Andy Jackson’s ATtinyArcade code, giving it three-button capability instead of two. [dombeef] has details on the project page on Hackaday.io as well as 3D-design and PCB-design files on the project’s code repository on GitHub.

We’ve published a fair number of Tetris posts in the past, including skyscraper Tetris, playing Tetris on a soldering iron, and Tetris in 446 bytes. What’s the smallest Tetris you’ve seen?