Here are two brand new boards for faster prototyping. These are especially useful for these one-off projects that need to be more permanent than on a breadboard. And they save time as most of the standard components as reset button or ISP header are already on board. Only the custom part of the project has to be soldered on the proto area. They come in two flavors, one for ATtiny25 and one for ATtiny2313 Atmel microcontrollers.

Even a 3 AA cell battery holder with on/off switch is included in the kit. There also two new how-tos with detailed step-by-step instructions, Tiny25 Proto Board Howto and Tiny2313 Proto Board Howto.

You can grab a full kit at the Tinker Store, if you like.

A couple of months ago, some nice guys of the IFISC (Institute for Cross-Disciplinary Physics and Complex Systems) contacted me. They saw the Synchronizing Fireflies and wanted them to demonstrate how simple rules can make patterns emerge from chaos. The main research of the institute is in Nonlinear Physics and Complex Systems.

But why would they want electronic gimicks? Every year, there is a science fair, the “Fira de la ciència” in Palma de Mallorca. The fair is aimed at young students, to introduce them to science with many hands-on projects and experiments. The IFISC is part of this fair and decided to use my fireflies as a demonstration of self organizing systems for one of their projects.

It took a while to figure out how to present the fireflies best. Here are two pictures of the palm tree to which the fireflies are tied. Great idea and it came out really beautiful.

For the fair they built a small cubicle with the palm tree inside. The cubicle was neccessary because the fireflies need an almost pitch back environment to see each other flashes.

As the fair was at Palma de Mallorca, I couldn’t resist to see it in person. Last week my girlfriend and I took some days off and travelled to Mallorca. We visited the fair and met some really nice staff members of IFISC. And there it was, a tiny black cube with a palm tree and fireflies within. Wohoo!

After all I have to say thank you all so much for the warm welcome and showing and explaining all your projects. Thanks for the cool t-shirt, I feel almost as a IFISC member now
And especially thanks to Pep for pushing this project further and further and making it possible. It has been a fantastic experience. You guys rock.

Links

• 64 Synchronizing Fireflies
• Synchronizing Firefly Kit
• Some more videos of the test setup, done by Pep
• IFICS (Instituto de Física Interdisciplinar y Sistemas Complejos)
• Fira de la ciència

It took a while since I first posted about the new ATmega header board but finally, here it is.

The board is great for prototyping on a solderless breadboard. It is compatible with the common 28-pin AVR controllers like ATmega48, ATmega88, ATmega168 and ATmega328. On plus it is Arduino compatible.

Some of the features:

• Space efficient, occupies only on more row than the controller itself
• Has no voltage regulator on board, so you choose, at which voltage you want to run it
• It has SMD resistors and LEDs (size 1206) to make it a great starting point to learn how to hand solder SMD
• Has a sticker to tell which pin is what. Thanks Tod!
• Blinks blue!

Check out the detailed howto page and grab a kit at the shop, if you like.

It’s Advent season. And what do you do to let your geek shine? An LED Advent wreath of course.

The idea came to me after seeing Sprite’s minimalistic version of the Hackaday’s Flickering LED circuit. It’s a simple circuit that flickers LEDs and detects darkness. I thought that this could make a great little Advent wreath. My version should have 4 LEDs and should be support first, second, third and fourth Advent.

Parts and Schematic

The parts list is rather short:

• ATtiny13V, 8-bit microcontroller, 1k flash RAM, 64 bytes SRAM
• 4 * 3mm LEDs, yellow or orange, forward voltage ~ 2.0 V
• CR2032 coin cell, 3 V, 230 mAh
• Paperclip

There are no current limiting resistors in this circuit. Normally operating LEDs without them is not advisable because the LEDs will get damaged. But under certain conditions the resistors can be left out. For more on this topic, see Sprite’s computation or mine here.

How does it work

The nice thing about this circuit is, that it needs no special components to detect darkness. It uses an LED for that. An LED is also a photodiode that can detect light of the same wavelength it emits. See here for more details. Sprite used an available ADC of the ATtiny13 instead of the “Reverse Bias” method.

Software

The software is heavily based on Sprite’s version. Things I’ve changed:

• Added support for four LEDs.
• Removed calibration, replaced with hard wired values.
• Added a bit sampling to the light measurements, because the values were a bit erratic.
• Added a mode for first, second, third and fourth Advent, stored in EEPROM. Gets incremented at every reset.
• Modified the watchdog code a bit to keep it generating interrupts instead of resets.

After power up, the watchdog gets enabled to generate an interrupt every two seconds. Then the current mode (0-3) is read from EEPROM, incremented and stored back. Then the endless loop is entered, where random values are used to flicker the LEDs. The ISR checks the ambient lighting and if it is higher than a certain level, sets a sleep flag. This flag is monitored in the main loop. If set it sends the controller in to power down mode to save battery power. The next interrupt will wake up the main loop.

Assembly

This circuit is soldered in “free form”, so no PCBs. It takes some time to get it done but it’s worth it.
All cathodes of the LEDs are connected to form the ring. The anodes are bent inwards to be soldered to pin 2, 3, 6 and 7 of the ATtiny13. A short piece of wire is connected to the common cathode and soldered to the GND pin.

The microcontroller lies “dead bug” style on the coin cell. The GND pin is bent to the top, now connecting to GND of the battery. The VCC pin is bent to the bottom and soldered to the coin cell holder. The coin cell holder works as a clip, pressing the microcontroller onto the cell.

Some random notes:

• Be patient.
• Use as less solder as possible.
• Don’t heat the pins of the controller for too long.
• Be gentle while bending the controller pins. They come off easily. I added a tiny bit of solder.
• BE patient

The Result

If you make one, please let me know. Send me a picture or post it on the tinkerlog flickr pool.

Happy third Advent …

Downloads and Links

• Source advent.zip
• Minimalistic flickering LEDs at Spritesmods
• Flickering LED circuit at Hackaday
• LED Menorah, also free form at Evil Mad Science

Again a Braitenberg vehicle. This one is even smaller, than the previous one and comes on a custom PCB. It weighs 17 gramms, is driven by two pager motors, powered by a small lipo cell and controlled by an 8-pin ATtiny25V.

Schematic and parts

This tiny robot has a very low component count. At least for a robot, based on a microcontroller. That has, of course, some implications. It can handle only two sensors and the motors run only in one direction. A full H-bridge for both motors would need 8 transistors and more lines to control it.

So I decided to just use a single transistor to drive the motor. That means it can only run forward. Not a big deal for a Braitenberg vehicle.

Here is the parts list. Most parts are very common.

• ATtiny25V, 2 kB flash RAM, ATTINY25V-10PU-ND
• MPC1700 3.3 voltage regulator, MCP1700-3302E/TO-ND
• 2 * light dependent resistors (LDR)
• 2 * 10 kOhm resistor
• 2 * 470 Ohm resistor
• 2 * 2n3904 transistor
• 2 * 1n4148 diode
• 100n capacitor
• 100u capacitor
• Lithium-polymer battery, 3.7 V, 100mAh, HobbyCity
• 2 * fuse holder
• 2 * pager motor
• heat shrink tubes
• rubber tube
• custom PCB
• 6-pin ISP header

A bit tricky was to find the right rubber tube to build the wheels. I found these, which are normally used to connect tiny motors to a model stern tube. Because the inner diameter is a bit to wide, I used short pieces of cable isolation as an adaptor.

If you have pager motors with an attached weight on their shaft, you may want to take a look at the RobotRoom for instruction on how to get rid of the weights. I had no locking pliers, maybe that’s the reason why I ruined at least three motors. Mostly by twisting the shaft while trying to pull off the weight.

Software and programming

The software is straigt forward. Reading two inputs, the light sensors, and driving two ouput lines accordingly with a PWM signal.

But it turns out, that the software needs a lot of adjustments. First you have to figure out in what range the light sensors report values. Next, check at what PWM level the robot starts to move. Maybe even adjust the directional stability.

Programming the robot in circuit via the 6-pin ISP header didn’t work out in the first place. The programmer was not able to set the lines to high that were driving the transistors. So I soldered a socket in place and can now pull off the two 470 Ohm resistors. After programming I can re-insert the resistors. Can be seen on the left critter on the picture above. A bit awkward, but it works.

Demo

You should have a very clean surface for them to run on. If you put them on a table, as I did, be sure to have very good reflexes or put a kind of fence around them. Mine dropped off the table a couple of times. Mostly no dramatic damage, but the sensors got twistet and the motors sprung out of their holders.

Depending on the ambient light, the light source itself and the nature of the surface you may have to adjust the light sensors. As an example, if the surface is white and diffuses the light, then you would have to bend the sensors away from the surface, because the surface looks bright, even if the robot turns away from the light source.

Issues and conclusion

There are still a couple of issues to resolve.

• Software improvements, use ADC in free running mode and use hardware PWM to drive the motors
• Place the skid in the middle of the PCB.
• There is no protection of deep discharging the battery, no idea how to solve this.
• Add a small power switch.

Someone wanting to volunteer for some private beta testing and helping with improvements?

Besides these issues, these two critters are fun. There was a lot of testing, reprogramming and re-adjustment needed, to get them doing, what I thought they should do. But hey, that’s the way to learn something.

Links and downloads

• Braitenberg vehicle with Arduino mini
• Arduino powered Braitenberg vehicle
• Formica, swarm bots
• Source code and Eagle CAD files, really BETA, tiny_braitenberg.zip

Last week I invested some time to solder 64 Firefly boards. Only 2.432 solder joints later I was ready for some videos.

Every firefly acts completely autonomously, it has its own tiny controller, eye and luminary. They are all connected for power supply only.

Here are some different configurations.

Links

• See how it’s done in the Synchronizing Firefly Howto
• Grab a Firefly kit at the Tinker Store

Often, when I am tinkering with a controller on a breadboard, I have to open up the according datasheet, only to look up the pinout. So I designed a simple page with all of of the pinouts that I use most. It has:

• 8-pin AVRs, ATtiny25/ATtiny45/ATtiny85
• 20-pin AVR, ATtiny2313
• 28-pin AVRs, ATmega48/ATmega88/ATmega168/ATmega328
• Arduino to ATmega mapping
• ISP header, 6-pin and 10-pin
• FTDI-cable

Maybe it’s helpful for others as well. You can download it as:

• micro-cheat-sheet.pdf
• micro-cheat-sheet.svg

If you like it, you will also like the Tod’s cool Arduino chip sticker.

Update 2010/01/24

The new version includes the pinout of the Bus Pirate. Thanks Philipp for the update.

This is another breadboard compatible header board, that I am working on. This one is for all 28-pin AVR devices, ATmega48, ATmega88, ATmega168 and the latest ATmega328. Component count is low and there is no voltage regulator on board. That makes it easy to power it from various sources.

As a bonus, this board is a hybrid of through hole and SMT components. It has two SMD LEDs under the hood. Great to learn how to solder surface mounted devices.

It has also an FTDI-connector and runs with a 16 MHz resonator, which makes it Arduino compatible. The jumper is used to select between different power sources.

Yikes, SMD soldering. This is my first attempt at hand soldering 1206 SMT components. 1206 is only 3.2 mm × 1.6 mm! But these are about the largest SMT components available. Most commonly used are way smaller, 0805, 0603 or 0402. My soldering still looks ugly, but with a bit of practice I think I can do much better.

The space on the board is a bit limitted, so there is no room to mark all pins. That’s why I have a little cheat sheet around, while wiring things up.

If you want to play some retro arcade games, you will install the amazing MAME and run your favorite ROM. One of my best-of-all-times is Bomb Jack.

But you have to play it with the keyboard. Bah!

Or an USB game pad. Better, but still — bah!

Nothing compares to real arcade controls. And with a bit of tinkering, you can get a tiny step closer to the real gaming experience.

USB HID

HID stands for Human Interface Device class. Common devices of this class are keyboards, mice and joysticks. The great thing, that this interface brings in, is, the devices don’t need a specific device driver. If they behave according to the USB HID spec, then they are automatically recognized by all OSs. Every device sends a report, in which it states, which kind of device it is and how it wants to report its data.

The next great part is the fantastic USB driver V-USB that is developed by Objective Development. This driver can be run on most of all Atmel AVR controllers, even on ATtinys. It does not require any other chip, only a couple of standard components. The library is licensed under GPL, a commercial license is available as well.

Needed components

I ordered my arcade controls at ArcadeShop.de, a german shop for Arcade parts. The joystick is great. Heavy and solid. And makes nice clicks.

The buttons, that I ordered are ok. They are working fine but seem to be a bit too small. They have a diameter of 27 mm. Next time I would take bigger ones.

Nothing special about the rest of the needed parts. A breadboard, an ATmega48 and a couple of resistors, capacitors and diodes. And of course a plastic box as enclosure. Keeps the electrons fresh. BTW, mine is not Tupperware, but super cheap IKEA.

The circuit

The circuit is almost one of the standard setups, that Obdev recommends. I used 47 Ohm instead of 68 Ohm for R2 and R3 because I had them laying around. The two 1N4148 diodes reduce the supply from 5 V to about 3.6 V. This is a “poor mans” voltage regulator. A better solution would be a low drop 3.3 V voltage regulator. But for prototyping the two diodes will do the job.

First I tried to run it with a 16 MHz crystal. I thought that it should be enough to change the F_CPU setting, but that didn’t work out. The device was not recognized. When I switched to the 12 MHz crystal it worked almost at once.

All controls, the stick and the buttons, are connected to the controller and to ground. Therefor the internal pull-up resistors have to be enabled.

Firmware

The firmware is based on the examples provided at the V-USB page. Two projects, that I played with are the HIDKeys example and the SNES-Joypad. The first one is used to build a simple keyboard. The second was made to play emulated SNES games with a SNES pad.

The biggest problem was to find a matching USB HID report descriptor. This descriptor is used to tell the PC, what kind of device is attached to the USB port and what kind of data it sends. At the moment I am using the “Game Pad” device class.

Conclusion

This is a work in progress. The plastic box works but is way too wobbly. It was more of a joke. The next version should have a more sturdy enclosure. And the circuit should be more permanent and not that place consuming.

I am planning to have a two player version (Gauntlet!). For that I am still unsure, if I should switch to the USB-HID keyboard class. Or maybe implement two gamepads with one controller. We will see.

Over all, it’s great to play some of the old games again. Even if this is nothing compared to a real cabinet.

Links and Downloads

• Firmware: mame_controller.zip
• MAME, Multi Arcade Machine Emulator
• V-USB (formerly know as AVR-USB) developed by Objective Development
• SNES-Joypad using V-USB (german)
• USB HID page at USB.org
• Arcade controls at ArcadeShop.de

Jonathan bought a 64pixels kit and modded it into a green version. The three solar cells, that he uses are rated with: 2.7 volts (open circuit) @ 15mA (short circuit). He writes, it works well in bright sun light. His desktop lamp shines with 60 Watts and that seems to work as well.

He also used a socket to be able to pop out the controller, whenever he wants to program new messages or animations.
Well done!