Free PCB coupon via Facebook to 2 random commenters

in Free PCBs by DP | 1 comment


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. More PCBs via Twitter on Tuesday and the blog every Sunday.

Don’t forget there’s free PCBs three times every week:

Continue reading →

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5W stereo audio amplifier

in project logs by DP | 1 comment


Another project from Rajkumar Sharma of Electronics Lab a 5W Stereo Audio amplifier based on BA5406:

5W Stereo Audio Amplifier project based on BA5406 IC which is suitable for application like stereo radio cassette player, stereo components systems etc.
The Heart of the project, BA5406 is a dual OTL monolithic power IC with two built-in, high output speaker amplifier circuits. High output of 5W×2 can be produced when VCC=12 V and RL=3Ω, and 2.8 W×2 when VCC=9V and RL=3Ω. The BA5406, which uses a high allowable power dissipation package, has a simple heat-sink design.

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Week in (p)review October 31, 2014

in week in review by DP | 0 comments


Here’s a summary of major developments over the last week. Free PCB Friday is coming up soon.

Coming up:

  • Free PCBs via Facebook on Friday
  • App notes on the weekend
  • Free PCB Sunday
  • Free PCBs via Twitter on Tuesday
  • Weekly roundup and preview every Friday

ArTICL: Arduino TI Calculator Linking Library

in library by DP | 0 comments


KermMartian over at Cemetech writes:

The ArTICL library (pronounced “article”) lets Arduino programs send and receive TI link protocol-formatted packets at a low level. In addition, it includes a CBL2 class that lets the calculator emulate either a CBL2 device or a calculator speaking the CBL2 protocol (thanks to Cemetech member CVSoft for helping to make this possible). This means that you can use the Send() and Get() commands on your graphing calculator to control the Arduino, including turning LEDs and motors on and off, reading the state of buttons and switches, and performing measurements with sensors. You could even use the ArTICL library to control a Norland Research robot with an Arduino.

Check out the video after the break. Continue reading →

DS3231 RTC control and theory with the Bus Pirate

in Bus Pirate by DP | 0 comments


@omwah tweeted, “Article I wrote on controlling the Maxim DS3231 RTC with the Bus Pirate

The Maxim DS3231 is an accurate, yet relatively expensive real time clock (RTC). It has an integrated temperature compensated crystal and communicates over I2C.

Get an assembled Bus Pirate for $30, including world-wide shipping. Also available from our friendly distributors.

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Modification of the Lexmark E260 for direct laser printing of printed circuit boards – MCU version

in hacks, tutorials by DP | 0 comments


mlerman writes:

After trying several brands and models of laser printer, the printer I have settled on is the Lexmark E260. I use it because:

1 – It has an excellent Local Printer Utility that allows almost every printing parameter to be adjusted.
2 – It is readily and reasonably available on Ebay or Craig’s List. I paid $45 for each of the last two I bought on Ebay, including shipping.
3 – The drum is separate from the toner cartridge and is relatively inexpensive (<$30), so it can be replaced if it does become damaged.
4 – The printer has a manual feed slot in front so the paper path can be “flattened” with reasonable effort to pass PCBs.
5 – The charge on the drum seems to provide for essentially perfect transfer of toner to grounded metal sheets.

Complete step-by-step instructions here.


Portable bluetooth-enabled scrolling LED matrix display

in Arduino, LEDs by DP | 0 comments


An open-source cascadable 8×8 LED matrix module using Arduino and MAX7219 from Embedded Lab:

Easy Matrix is a cascadable 8×8 LED matrix module with the MAX7219 chip on board, which allows to control the display with only 3 I/O pins from microcontroller. Multiple Easy Matrix modules can be easily cascaded to make a bigger-size display through precisely aligned male and female headers on opposite sides of the display. It is compatible with Mark Ruys’ Max72xxPanel (Adafruit’s GFX library is also required) and MaxMatrix libraries for Arduino platform.

This project is available on Tindie.

Check out the video after the break.

Continue reading →

New MurchLabs TinyLoadr Shield

in Arduino, AVR, programmers by the machinegeek | 0 comments

Jeff Murchison has released a new version of my TinyLoadr Shield, which was used for programming ATmegas and ATtinys using your Arduino.

The new version is just a USBtinyISP-based programmer with a ZIF socket for DIP microcontrollers and 10 and 6-pin ICSP headers for programming target boards.

More information can be found at MurchLabs.

Via the contact form.

Voice echo project

in project logs by DP | 1 comment


voice echo module with build-in amplifier project by Rajkumar Sharma of Electronics Lab:

A project has been designed around Holteks Ht8970 voice echo IC. Project can be used in various audio systems karaoke, toys, animatronics, show, display, exhibitions, and sound equipment’s.
The HT8970 is an echo/surround effect processor. It is designed for various audio systems including karaoke, television, sound equipment’s, etc. The chip consists of a built-in pre-amplifier, VCO or Voltage Control OSC, 20Kb SRAM, A/D and D/A converters as well as delay time control logic.

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Back to the mc-17 remote control

in hacks, Logic Pirate by DP | 0 comments


Tim writes:

After the Maker Faire, I went back to the Graupner mc-17 remote control.
The Arduino library from tronixstuff for the KTM-S1201 LCD which is also using a mPD7225 controller was a good starting point. But to get the LCD up and running, it took quite a bit of fiddling and logic sniffing.
Once the controller allowed me to switch on individual segments of the LCD, I needed to adapt my implementation to this specific display, as it offers remote control specific elements unusual for normal LCDs. With a proper mapping of bits and bytes to their respective LCD elements, it was easy to implement the usual alpha-numerical characters. Each of the digits is controlled by a word / two bytes. For each byte, one bit is used to control one of the additional symbols like colons, dots, or remote controls specific texts.

A look inside a ’70s voltage and current standard

in Teardowns by DP | 0 comments


SQKYBeaver did a teardown of a Techtron Standards type 51 voltage and current standard:

Absolutely amazing inside! The wires to the front panel look like the were loomed by a professional Spacecraft mechanic. every one individually numbered it must have taken hours. only 4 rc4136 quad opamps for all this functionality, two dating back to 1973.

OpenSprinkler Firmware 2.1.0 released

Ray Wang from RaysHobby announces the release of OpenSprinkler Firmware 2.1.0.

OpenSprinkler is an open-source, Arduino-based, web-connected sprinkler controller. This new firmware is a major upgrade that introduces a number of new features, including automatic weather-based watering adjustment (using real-time data from, timezone and DST detection, logging, and a new unified mobile interface. It also now supports 17 different languages (thanks to many users who contributed to the translations).

Details can be found in Ray’s blog post. The OpenSprinkler source code is available on GitHub.

Via the contact form.

#FreePCB via Twitter to 2 random RTs

in Free PCBs by DP | 0 comments


Every Tuesday we give away two coupons for the free PCB drawer via Twitter. This post was announced on Twitter, and in 24 hours we’ll send coupon codes to two random retweeters. Don’t forget there’s free PCBs three times a every week:

  • Hate Twitter and Facebook? Free PCB Sunday is the classic PCB giveaway. Catch it every Sunday, right here on the blog
  • Tweet-a-PCB Tuesday. Follow us and get boards in 144 characters or less
  • Facebook PCB Friday. Free PCBs will be your friend for the weekend

Some stuff:

  • Yes, we’ll mail it anywhere in the world!
  • Check out how we mail PCBs worldwide video.
  • We’ll contact you via Twitter with a coupon code for the PCB drawer.
  • Limit one PCB per address per month please.
  • Like everything else on this site, PCBs are offered without warranty.

We try to stagger free PCB posts so every time zone has a chance to participate, but the best way to see it first is to subscribe to the RSS feed, follow us on Twitter, or like us on Facebook.

DIRTY TUESDAY: A bumpy road to streamlined service

in by Ian | 15 comments


A few months ago we started a private PCB website so our team can get cheap PCBs from a fab in China. Someone spilled the beans, and it hit Hack a Day, Hacker News, etc. We almost shut it down, but it was too much fun to hack and refine the process. Dirty Tuesday is a weekly post about our misadventures accidentally starting a PCB service. As a design shop with Seeed Studio doing fulfillment, we’ve never been on this side of the fence and want to share the terrifying experience.

DirtyPCBs. A site named to manage expectations. We’re not a PCB company, we’re a couple hackers with access to a cheap board house in China helping out other geeks. The cheapest board house, really. It’s no secret, rank Taobao results by price and you have our supplier list. Despite our flippant attitude and dirty board house, we do our best to offer extremely good service. Here’s some highlight of our comedic attempts to overlay first class service on top of China’s cheapest PCB manufacturer.

Sorting orders

Briefly mentioned last week, our original goal was to make cheap prototype PCBs without adding annoying little numbers to the silkscreen. Our solution: stickers! The board house must already have a way of tracking boards through production, so we’d have them put an order number sticker on each pack.

The factory agreed to do this, no problem. We printed shiny metallic stickers on a trusty Postek C168 (far superior to the G3106) acetate transfer label printer and sent them to the factory via SF (UPS of China). The first batch of boards with labels arrived a few days later and we mailed them out.

A week after we start getting emails with variations of “not my PCBs”. Apparently the factory applied the labels randomly to any board of similar size and color. At the time we didn’t have an image of each board to reference before shipping, and we placed all our trust in color and size. We ended up replacing a few dozen boards at our own expense.

Solution: we gave up and added the PCB ID to the silkscreen of each board.

Colors and Quantity

Dirty board house doesn’t charge for colors, and neither do we. However, sometimes the board house sends boards in the wrong color. From their perspective it’s a cheap PCB for the Chinese market, it works (100% e-test), it didn’t cost more, better luck next time.

The board house is supposed to send 10 of each board, as advertised on their Taobao page. Most of the time they send 12 or more PCBs. We’ve even seen 50 of a medium board, and 200 of a tiny board panelized for free into a 10x10cm order. About 1-2% of the time, they send only 8 or 9 PCBs. Once or twice we’ve even seen just 7. As with colors the board house doesn’t care or want to replace them. Our sales rep argued extensively that most people only want one or two anyways, and they gave us extra PCBs in other orders. We mostly agree, but that doesn’t fly with buyers outside China.

Dirty customers are awesome. We email explaining the situation, and most people have no problem with fewer PCBs. Getting the wrong color is more disappointing but not the end of the world. As the volume of boards going through DirtyPCBs increased this because a huge time sink. Counting each order, writing emails, and tracking replies was so frustrating that we shut the site on several occasions.

Solution: the “protopack”. Instead of selling quantity 10, we market the service as a prototype PCB package with + or – 10 boards. Usually you get more, sometimes you get a few less. If you really need ten, you can choose quantity 10 for 25% more money to pay for the increased hassle. To date nobody has paid extra to guarantee 10, and there have been no more emails about too few boards.

Rush orders

Most board houses in China offer 48 hour and 24 hour board processing options. Usually this works pretty well, but it isn’t guaranteed. It just means your boards won’t be held in queue until they can be done with a huge batch of other boards. This is great if you’re doing prototypes in China as a board really can be delivered the next day if you time it right.

Depending on the board house load, rush service can cut a week or more off normal processing time. It really can speed development at a cost way less than having a rush order made and shipped from a US-based board house. However, we’re not actually the manufacturer – boards still have to ship to us, we have to pack them, and then hand them off to logistics. This led to some angry emails early on when buyers thought their boards would ship in 24 hours or less.

Solution: we label the 48 hour service “rush (2-3 days)”, and the 24 hour service “emergency (1-2 days)”. The extra day is absolutely needed for the boards to be delivered to us (same or next day).

4 layer board house

4 layer boards are not so dirty and come from a different cheap board house found on Taobao. While the 2 layer house loves working with us, the 4 layer board house is completely indifferent.

Each order has to be uploaded to the 4 layer board house website. The zip file cannot have the same name as anyone’s previous order. Once you tackle that lovely bit of poorly thought out code, you fill in all the specs and wait.

Within a day an engineer verifies the board and then calls to confirm it. Each and every one. If there’s an error, upload new gerbers (can’t be named the same!) and start over. When all is good, login again and pay via Alipay.

This process drives everyone nuts. We’re fully integrated with the 2 layer board house. We send an email with attachments and a spreadsheet in their internal factory format. From there boards pop out on the other end with minimal handling. We asked the 4 layer board house about better integration. The sales guy said “it only takes 10 minutes a board”, and “our big clients just hire someone to enter boards all day”. Lovely.

While the 2 layer board house allows panelizing, the 4 layer board house doesn’t. In fact, they charge more to process a panelized board than it costs to do the panelized designs separately in individual orders.

The 4 layer board house has rush (72 hour) and emergency processing (48 hours) for 4 layer boards. However, you can’t combine that with a color or ENIG coating.  Gottcha!

Solution: future tour to get around sales reps and talk to an actual manager about production line integration. Apply cognac or tea liberally and see what happens. We’ll post pics, promise!

Missing boards

Sometimes boards just don’t show up. Our dirty backend system shows the age of each order and we nag about it as needed. Many times the board house simply forgot about them, sometime their system says they’ve shipped already.

Our system is simple and redundant. For each batch of boards we print a packing list and keep them in dated files. When boards arrive we scan a barcode on the packing list to load images of the order. We we compare the boards for design, color and coating, then scan the barcode again to mark it shipped. At this point the shipping label is printed and placed on the box. If the database says a board has not been shipped, and the packing label is still on file, its highly likely we didn’t receive it.

Solution: if DirtyPCBs gets another update before we pull it offline, it will auto-nag the board house about all orders past 7 days. The auto-nag will include the missing boards as attachments so they can skip asking for the files again if they were lost.

Queued shipping

Very recently we noticed that boards started coming only once or twice a week. Usually Tuesday and Friday. Three or four giant boxes would show up, so heavy that I felt genuinely bad that Xiao Tang had to drag them up seven flights of stairs (and then back down for shipping).

The Tang had to process half a week of boards in a few hours and then lug them up to espeed logistics in giant bags. The rest of the time he was bored. There’s nothing worse than a bored Tang.

A quick call to the board house confirmed that they were holding our orders for a few days so that we could save $1-$2USD per batch on shipping. They seemed rather proud to have given us this excellent money saving opportunity, but we explained that people want their boards fast and we’d rather pay more.

Boards started arriving more frequently again but not every day. Including rush orders, we should get 2-3 parcels every day. After some digging we found out the cheap delivery company was batching up our deliveries so they didn’t have to come every day.

Solution: all orders, stencils, etc are now shipped by SF. In China SF is like UPS or Fedex, but much cheaper and faster. It costs twice as much to have boards delivered now, but the service is much more reliable.


Running DirtyPCBs has been a first hand look at dealing with suppliers, customers, and logistics. Each bump in the road was a traumatic yet fun chance to hack a system. It’s been a great experience to get a taste of this side of the industry, but it also reenforces our desire to have Seeed Studio and our fantastic distributors handle all this stuff for our projects.

The cover image is PCB etching and drilling equipment. In a pile. In a parking lot. In the rain. Just chilling. Photos from our factory tour soon.

Classic NES played using a Kinect

in hacks by DP | 0 comments


Control your classic NES console with the Kinect V2 sensor by Paul DeCarlo:


  • An NES console with game to test
  • An NES controller OR some wiring skills and a CD4021BE 8-bit shift register
  • 12 strands of wire, recommend Kynar
  • 8 1k resistors (technically any value from 1k to 50k should suffice)
  • 2 3.6k resistors (again higher not necessarily bad)
  • IoT board capable of running Firmata, Intel Galileo or Arudio Uno etc.
  • Kinect V2 Sensor for Windows OR recently announced Kinect V2 Adapter and existing Xbox One Kinect Sensor
  • Machine capable of running the Kinect V2 SDK

Via Hacked Gadgets.


Check out the video after the break. Continue reading →

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