Sunday, November 25, 2012

ATtiny Breakout/Programmer

Introducing the eeZee Tiny

To make it easier to prototype ATtiny-based circuits like my lost model alarm I made a breakout / programmer board for ATtiny13 pin-compatible chips. I call it the eeZee Tiny. It's a surface mount version of an existing open source project.

(The list of compatible chips includes the ATtiny11, ATtiny12, ATtiny13, ATtiny13A, ATtiny25, ATtiny45, ATtiny85)

The board has a 6-pin AVRISP header so I don't have to keep looking up pinouts, a reset switch and breadboard friendly header pins. Supply power to pins 4 and 8 and you're set.

I can either use the board to prototype the next project or embed them in projects permanently.

LED flashy test using ATtiny13A
I made a few extras in hopes that it'll help out others. They're on sale at Tindie at the moment and for Cyber Monday you can use coupon code 8F7CD17 to get 25% off the regular price.


  • Works with ATtiny13,13A, ATtiny25,45,85, ATtiny11, ATtiny12
  • Tiny 1-square-inch board
  • Perfect for breadboarding
  • 0.1uF and 10uF filtering capacitors pre-soldered
  • Compact AVRISP connector for easy programming
  • All 8 pins exposed for breadboarding
  • Reset switch and pull-up resistor included


Here are the Eagle files and example code so you can make your own. I had my boards done by and they turned out great as always.
Parts list includes a standard 6mm square tactile switch with 4 pins, one 0603 0.1uF ceramic cap, a 1206 10uF tantalum, a 0603 1K resistor, an 8PDIP socket, a 2x3 pin header, and a 1x8 (or two 1x4) pin header.

Additional details here.

Thursday, November 22, 2012

Happy Thanksgiving!

RoboTurkey says
"Happy Thanksgiving to
robots and humans alike!"
Happy Thanksgiving!

Wanted to let you now Pololu is doing their Black Friday sale again. Here's the details.

Pololu Robotics and Electronics is having its biggest Black Friday sale yet, starting this Thursday.  You can get up to $30 off your entire order in addition to saving up to 60% on dozens of selected products, including the Pololu 3pi Robot, our new Zumo Robot Kit for Arduino, Wixel wireless modules, Maestro Servo Controllers, Simple Motor Controllers, MinIMU-9 9-channel IMU, sensors, chassis, actuators, and more!  For details, visit: 

Windows, OS X, Linux for the Roboticist

Call me a luddite, my main geek system is running XP despite being an OS X fanboy. The Windows upgrade path looks torturous. Windows 7 is a train wreck of confusion and delay. Trying to find My Documents and navigate around is like running in a pool. Windows 8 sounds like a nightmare, too. Swell.

I can't stay with XP forever. If I ditch Windows, what's the replacement? OS X? Linux? Everything runs on Windows but not everything runs on the other two. Here's a sample of some of my favorite tools.

LTSpice IV
CadSoft Eagle

MPLAB 8.xx

AVR Studio

Arduino IDE
Processing IDE
Google Earth
IAR Embedded Workbench

Flash Magic

Propeller Tool
Google SketchUp

AVR Studio and LTSpice are tools I really like and use often. Ugh.

Picasa is my go-to image manager/editor for this blog. Going without it may suck.

One can use Wine or VirtualBox to run Windows stuff. Since I first wrote this I've actually done it and both are looking promising.

Replacement tools are possible for some of these. Maybe I'd rather use TurboCAD or Blender.

Friday, November 16, 2012

Soldering Accessories

Here's my recommendations on what to use when you solder.


I really like Radio Shack 0.015" silver bearing solder (64-035) for detail work. It flows well and it's really thin diameter so you can carefully control the amount of solder applied to small surface mount components. I've used it to solder 0.5mm pitch TQFP and larger/coarser parts, 0603 passives, SOT23 packages, and similar.

I've been using Radio Shack 0.032" 60/40 rosin core solder for bigger parts, particularly pin headers and it works ok, but mine is pretty old so it probably doesn't work as well as it used to.

As much electronics work as I do, it still takes forever to get through a spool of solder. Best to buy in small quantities so it stays fresh.

Solder Braid

The last two rolls of solder braid were Radio Shack (64-2090) 5' rolls and it worked ok for removing a number of parts from junk electronics or for cleaning up solder bridges on fine pitch QFP parts. It worked even better if you apply a flux pen to it just before use.

I've recently tried Stanley Supply Services 0.100" x 10 ft. rosin solder wick (410-115). It's wider, with finer braid, quicker action, more thorough wicking, and it's cheaper. You get twice as much braid for about half the total cost.


I discovered the magic of flux when I first started using Radio Shack (64-022) rosin flux paste. It works well to improve solder flow but it is really messy and hard to clean. It gets gooey and liquidy in hot garages in summer and hard as a rock in cool garages in winter.

Then I tried a flux pen. It happened to be a Kester #2331-zx pen. I found it easy to apply, relatively clean, and solder flow was out of this world. This is my go-to flux pen.

For giggles I recently tried a Kester no-clean flux pen, #951, and found it to be clean at the cost of slightly decreased flow. When you first apply it, it appears to dry out, then wets up again when you apply heat and solder. Weird. I notice that if I let it sit on the board too long it doesn't work as well. Best to apply it as you go.

Tip Cleaner

For awhile I was using the sponge on my Weller WES51 station. Keeping the sponge wet was kind of a pain, kind of messy.

I thought I'd try a brass wool tip cleaner so I picked up one from Aoyue. It works brilliantly! A few quick dips of the tip and it comes out shiny as a mirror. No mess, no fuss. I can't say enough good things about this.

Your Turn

What are your favorite accessories, solder, flux, etc?

Tuesday, November 13, 2012

NXP LPC800, a tiny, amazing ARM

LPC800 image from NXP
reproduced for
educational purposes
The first ARM in 8-PDIP form factor!

"NXP Revolutionizes Simplicity with LPC800"

It will also comes in SO20, TSSOP20, TSSOP16. It's a full-on 32-bit ARM Cortex M0.

You may wonder how so few pins could be of any use? The Flexible Switch Matrix. You can assign any peripheral to nearly any pin using software on the PC (YouTube demo).

The chip also features a very flexible timer/compare/match/pwm peripheral, basically two 16-bit PWMs with capture inputs and match outputs.

Here's the product data webpage. Here's the datasheet.

Apparently there will be an LPCXpresso for this chip, too (YouTube).

The wait for this thing is going to be excruciating.

Friday, November 9, 2012

RC Lost Model Alarm

rc plane lost model alarm top view

rc plane lost model alarm bottom view


Previously I built a tiny, lightweight lost model alarm for ultra-micro RC planes. I was contacted by a reader to design and produce a lost model alarm suitable for use in big, expensive RC planes.

My recently acquired SIG Kadet with 60" wingspan


The large version features a much louder 100dBA piezo speaker and a circuit board that can accommodate a much larger 350mAH LiPo battery providing about two weeks of continuous run time. The basic code and hardware is the same.
  • Standalone, no connections or external power
  • LiPo power source
  • Loud enough to hear downed plane in a backyard while standing on the curb
  • After 15 minutes, beep morse "W" for low battery warning
  • After 30 minutes, beep morse "SOS" assuming the plane is lost
  • Beep every 10 seconds for a total of two weeks
  • When LiPo voltage is nearing depletion, increase beep interval to 60 seconds
  • Easily mountable inside the plane flush with exterior skin
  • remote on/off switch
  • remote LiPo charge port


An ATtiny13 controls the timing and chirping and uses a voltage divider to measure voltage against an internal reference and chirps out the battery voltage upon startup.
rc plane lost model alarm top, render

After an initial delay period, the device chirps 'W' in morse code to suggest fuel or battery are depleted and that it is time to land.

After another reasonable delay, the unit chirps morse code SOS every 10 seconds to assist in locating the plane if it is lost.

Once battery voltage gets to dangerously low levels, the chirping interval increases to eke out a little extra audio location time.

A socketed 8-PDIP ATtiny13 is used for easy replacement and reprogramming.

rc plane lost model alarm bottom, render
Rendering of an older interim design
The initial version of this Big LMA seems to work well, but there are a few revisions planned for the next version that will make it a little easier for the hobbyist to install.

Power Conservation

It delays using a deep sleep mode to conserve power, and uses the watchdog timer interrupt to very briefly wake up every second.

As with the Ultra Micro version, this version also runs at a very low clock rate to conserve power. The PUI Audio piezo speaker (datasheet, pdf) is efficient drawing only 9mA at 100dBA.

Software and Schematics

Firmware (for AVR Studio 4)
Hardware (Eagle files)

Thursday, November 1, 2012

WheelEncoderGenerator 0.2-beta

Announcing version 0.2-beta of WheelEncoderGenerator, the open source, cross-platform application for quickly generating and printing wheel encoder discs. Download here.