Free PCB coupon via Facebook to 2 random commenters

in Free PCBs by DP | 0 comments


Every Friday we give away some extra PCBs via Facebook. This post was announced on Facebook, and on Monday we’ll send coupon codes to two random commenters. The coupon code usually go to Facebook ‘Other’ Messages Folder . More PCBs via Twitter on Tuesday and the blog every Sunday. Don’t forget there’s free PCBs three times every week:

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More awesome DoorBell control

in DIY by DP | 0 comments


Felix of LowPowerLab posted an update on his DoorBell Mote project  we covered previously:

My first DoorBell Mote prototype was working nicely and it allowed monitoring the door bell (while also triggering it remotely – toddlers love it). But I wanted more. On weekends the family likes to get a well deserved nap during the day and often those pesky solicitors ring the bell and wake everyone up. So naturally the doorbell has to be disabled also, without major effort or any disconnected wires. Sounds like the perfect addition to the Door Bell Mote. So I made a new revision and a proper PCB for this, below is the schematic with the changes and the proto PCB from OSHPark. Actually I made more changes to the schematic after putting together the PCB, so there are some differences. I’ve tried a LTV814H optocoupler for AC detection instead of the more expensive H11AA11, it works just as well, but both can be used on this PCB

Details at LowPowerLab site.

Interfacing a chord keypad to Papilio Duo FPGA board

in DIY by DP | 0 comments


Ken writes:

This is a simple chord style keypad that I made up a few years ago.  It is loosely based on the Microwriter – an early UK designed portable keypad / notewriter.
The five main keys are located under the fingertips and thumb of the right hand, plus an additional shift key that can be held down with the thumb.  This combination allows up to 64 key combinations  – which is enough for simple ascii, alphas and numerals.
However, this time the application is not for text entry, but to allow very rapid access to menu items, tools and colour options for a CAD program – without having to break concentration and use the keyboard.

Project info at Ken’s SustainableSuburbia blog.

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STM32 Nucleo and DFU USB bootloading

in programmers, tools by DP | 0 comments


MrMobileWill writes:

Over the last few months I have been playing with the Nucleo development boards from STMicroelectronics. If you’re unfamiliar with them, they are fast, mbed and Arduino (headers) compatible. This makes it easy like an Arduino to program and use. What sets them apart is that they are 32bit and have, depending on the model, tons of memory and flash. The Nucleo boards maintain the Arduino footprint but also have headers for the extra pins which gives this board plenty of GPIO for your projects.  In turn, you end up with multiple buses such as SPI, I2C, and UARTs for your consumption. They are priced very well and come in different flavors based on your needs. Each flavor is based on different ARM Cortex architectures such as M0, M3, and M4. One of the best features is real debugging via ST-Link/V2-1. The unfortunate thing due to the nature of mbed, you can only use the debugging features using a full desktop IDE such as Keil or some of the other free alternatives. But mbed allows you to export your code from the online IDE to the project format for those IDE’s. So there’s that.

More details at MobileWill’s project page.

Programmable 8-character LCD module and digital voltmeter

in project logs by DP | 5 comments


A programmable 8-character LCD module and digital voltmeter project from Tuxgraphics:

Our 3 digit LED digital voltmeter module has been quite successful over the years. This new LCD module is basically an advanced version with a lot more capabilities. You can power it with the same voltage source that your signal is derived from. You can load your own code into this module but it has even some nice features for people who just need a voltmeter module and don’t want to play with C-code.

Project info at Tuxgraphics.

Files and source code are available at

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Wireless Dallas iButton reader

in software, wireless by DP | 0 comments


Ondřej Karas writes:

This article describes simple wireless Dallas one-wire device ROM reader. It is intended as a base code for some more sophisticated access control system. We try some kind of access system in followings articles. Now, we are going to read 1-wire ROM code.
We use DDC-SE-01-dallas.c from DDC examples as a template for our project. In fact, we use functions for one-wire handling only and throw away the rest of the code. The main code periodically checks one wire device presence on DQ pin of IQRF module (PC3). If device is present, it checks, if previous readings was more than 1s ago, and then it reads ROM code, which is sent to another module. At the end of reading, startDelay(100) is executed and flag released = FALSE; is set. It’s protection against multiple reading.

Project details at DoItWireless site.

Review: Dirty Circuits Done Dirt Cheap

in by DP | 2 comments


DirtyPCBs detailed review by Gee_Rabid_Inventor:

 Often design and research is and expensive business, especially when dealing with technology that your are unfamiliar with. A big proportion of this is PCB manufacture and I have spend a few years looking for a low cost reliable method for PCB production.
The most cost effective method is to have the boards produced overseas but then you won’t be sure of the quality of the boards until they return. This is where Dirty PCB step in.

Details at Gee’s blog.

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App note: Anatomy of a high-quality meter

in app notes by DP | 4 comments


An application note from Fluke on best characteristics of a high-quality multimeters. Link here

The hazards of working with electricity aren’t new, of course. But as electronic and electrical systems become increasingly complex, the dangers of measuring its flow have increased and unprepared technicians can suddenly be faced with a simple job gone bad.
The key is selecting a meter with a high level of safety capabilities.


Posted in app notes | Tagged , , | 4 Comments

Free PCB Sunday: Pick your PCB

in Free PCBs by DP | 47 comments


We go through a lot of prototype PCBs, and end up with lots of extras that we’ll never use. Every Sunday we give away a few PCBs from one of our past or future projects, or a related prototype. Our PCBs are made through Seeed Studio’s Fusion board service. This week two random commenters will get a coupon code for the free PCB drawer tomorrow morning. Pick your own PCB. You get unlimited free PCBs now – finish one and we’ll send you another! Don’t forget there’s free PCBs three times every week:

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Posted in Free PCBs | Tagged | 47 Comments

App note: Ten dumb things smart people do when testing electricity

in app notes by DP | 6 comments


Tips from Fluke on things we could not resist doing or forgetting when doing electricity works. Link here.

Anyone who makes their living by working with electricity quickly develops a healthy respect for anything with even a remote chance of being “live.” Yet the pressures of getting a job done on time or getting a mission-critical piece of equipment back on line can result in carelessness and uncharacteristic mistakes by even the most seasoned electrician.

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App note: Use and calibration of the internal temperature indicator

in app notes by DP | 0 comments


Use and calibration of the internal temperature indicator (PDF!), an application note from Microchip:

Many PIC16 family devices include an internal temperature indicator. These devices include the PIC16F72X device family, PIC16F1XXX device family, and the PIC12F1XXX device family. The temperature indicator is internally connected to the input multiplexer of the ADC (Figure 1). Refer to the specific device data sheet for more details.
These devices incorporate an internal circuit which produces a variable output voltage with temperature using internal transistor junction threshold voltages. The indicator can be used to measure the device temperature between -40°C and +85°C. The circuit must be calibrated by the user to provide accurate results, as the equation coefficients will vary between devices.

Valve’s “Lighthouse” optical tracking system

in gadget, infrared by DP | 0 comments


Travis stumbled across an interesting project at Bay Area Maker Faire, the Lighthouse Optical Position Tracking by Alan Yates of Valve. He writes:

While walking around the Bay Area Maker Faire this weekend, I stumbled across an amazing piece of technology: Valve’s “Lighthouse” tracking system. Valve’s demos were (supposedly) a major contributor to Oculus’ fundraising efforts and ultimate sale to Facebook, and this device may have been a key piece of those demos. I’d heard rumors about this system for many months. It was designed for augmented and virtual reality — namely, for head and controller tracking, where it needs to have some insane specifications for positional accuracy, angular accuracy, and especially(!!!) latency. Honestly, the rumors didn’t do it justice: it’s really elegant! This solution is exceedingly simple, low-cost, light weight, and performant.  It’s much (much!) better than the image processing techniques I’ve seen to date. Most importantly…. I think this technology could be a “big deal” for robotics too.  I had a chance to speak with Valve’s Alan Yates about how the Lighthouse system works; I didn’t get all the specifications, but I did get some interesting information — so read on!

Details at Travis’ Hizook blog.

Nixie tube clock

in DIY by DP | 2 comments


Pete Mills has written an article detailing the build of his Nixie tube clock:

 Fortunately, not all nixie tube clocks are implemented the same.  In fact, look around at all the schematics for nixie clocks, and you will realize there are more permutations in methodology than there are models of nixie tubes.  This is how it should be.  We ( DIY electronics people ) like to put our own spin on things.

My version of the Nixie Clock has a few of its own nifty features.  The list includes:

  • Single microcontroller design
  • Software based RTC
  • Software driven boost converter for ~175 V DC supply
  • Time, Date, and behavior configuration via USB
  • Windows application for clock configuration
  • Time, Date, Temperature, and AC Power line frequency display

Project info at Pete’s blog.

Posted in DIY | Tagged | 2 Comments

Free PCB coupon via Facebook to 2 random commenters

in Free PCBs by DP | 2 comments


Every Friday we give away some extra PCBs via Facebook. This post was announced on Facebook, and on Monday we’ll send coupon codes to two random commenters. The coupon code usually go to Facebook ‘Other’ Messages Folder . More PCBs via Twitter on Tuesday and the blog every Sunday. Don’t forget there’s free PCBs three times every week:

Continue reading →

Posted in Free PCBs | Tagged | 2 Comments

A GUI and CLI utility for EFM32’s UART bootloader

in ARM, AVR by DP | 1 comment


Mario writes:

I’ve been doing mostly sensor-based systems and I think these microcontrollers are the perfect fit. ARM Cortex (they go from M0 to M4, and their series seem to keep growing), an architecture that was specially designed for low-power sensor-based embedded systems, allowing to measure “stuff” while the CPU is stopped, a nice set of peripherals (OPAMP, 12bit DAC and ADC), great support for GCC ARM Embedded (which makes them really ease to use or getting started to) and a factory-programmed UART bootloader.
The bootloader uses XMODEM-CRC protocol and TeraTerm may be used for uploading. However if you want a command-line tool (like “avrdude” for AVR microcontrollers), there’s anything you can use. So, I built one.

Source code is on Github.

Via the forum.

Project details at Mário Ribeiro’s blog.

Posted in ARM, AVR | Tagged , , | 1 Comment

Soldering station to drive HAKKO 907 handles

in DIY, tools by DP | 2 comments


Dilshan Jayakody published a new build:

To keep it simple we choose LM358 dual operational amplifier IC to monitor the 907’s thermocouple and drive the TRIAC. The entire control circuit of this soldering station is powered by single rail 5V DC power supply. To drive both handle and station we use 12V-0-12V 8A step down transformer.
Once calibrated, we may be able to regulate temperature of the soldering iron between 210 °C to 450 °C. As shown in the photograph we construct our final version of soldering station in slightly modified old ATX power supply casing. For this entire project we spent only 25USD, which is roughly 3000LKR at the time of writing.

Project files are available at

More details at Dilshan’s blog.

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USB Host Library 3.0-Alpha

in library, USB by DP | 0 comments


Oleg over at Circuits@Home writes:

The alpha of the third revision of USB Host library has been posted on GitHub. The code has been extensively re-organized to make it modular and generic; as a result, it is now possible to run it on more Arduino compatibles and also use native USB Host hardware on some of them. At the time of this writing, USB Hub and Mass Storage classes are supported, the work on migrating the rest of device drivers is in progress.
The code is to be used with Arduino IDE 1.6.1 or newer, please upgrade before attempting to compile it. Also, please read the README file for more details. If you encounter any issues, post them in the issue tracker on GitHub.

The credit for this commit goes to Andrew Kroll – thank you!

Available at Github.

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