Inside the Intel 1405: die photos of a shift register memory from 1970

in Teardowns by DP | 0 comments


Ken writes:

In the Datapoint 2200, each memory board had 32 shift registers, providing 2K of storage. The processor board used a counter to keep track of the shift register position, and would stop processing until the right bits were available. (Kind of like a cache miss in modern processors.)
I got a display board from a Datapoint 2200, which uses Intel 1405 shift registers for the display storage. This board uses 14 shift registers and holds 896 bytes. Shift-register memory was convenient for a video display board, since the circuitry needed to access each character in sequence to display it.

Details can be found on Ken Shirriff’s blog.

Free PCB Sunday: Pick your PCB

in Free PCBs by DP | 66 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:

Continue reading →

Posted in Free PCBs | Tagged | 66 Comments

App note: Design considerations for single-sided sensing applications of reflective assemblies

in app notes by DP | 0 comments


App note from TT Electronics on reflective assemblies and the surfaces they need to effectively detect/sense.

A reflective sensor provides a major mounting advantage to the designer because only one side of a sensing surface is required. However, there are a number of design variables that need to be considered to assure detection of the object or target. They include the type or size of the reflective surface, the distance to the reflective surface, variation of surface reflectivity, sensor variation and contrast ratio.

App note: Designing encoder elements for two channel optical interrupters

in app notes by DP | 0 comments


An app note from TT Electronics on design and getting information out of encoder elements of two channel optical interrupters.

Rotational direction of a shaft can be readily determined by utilizing the two channels of a dual optical interrupter, an encoder disc with a number of openings around the circumference, and some simple electronics. The speed and relative shaft location information is available as a by-product and requires some additional electronics.

App note: Introduction to USB Power delivery applications

in app notes by DP | 0 comments


Another application note from Microchip, an introduction to USB Power delivery applications (PDF!):

This document is designed for systems and hardware engineers seeking the information necessary to begin to integrating USB Power Delivery (under Power Delivery Specification Rev 1.0) into their designs using the Microchip UPD1001 or UPD1002 USB Power Delivery Controllers

App note: Microchip dedicated slave devices in I2C systems

in app notes by DP | 0 comments


An app note on Microchip dedicated slave devices in I2C systems (PDF!):

Microchip supplies dedicated slave devices that include a two-wire serial interface that is System Management Bus (SMBus) and I2C™ compatible. The SMBus specification is based on the I2C serial communications protocol, but with some differences.

This document describes the key differences that may affect successful application of Microchip two-wire serial interface dedicated slave devices in systems that are designed with an I2C master interface.
This application note assumes that the reader is familiar with reading and writing registers in I2C or SMBus slave devices and has access to the following documents:
• The I2C-bus and how to use it, Philips
Semiconductors document #98-8080-575-01.
• The System Management Bus Specification
Version 2.0. Appendix B provides details of the
major differences between SMBus and I2C.



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 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 →

PCB for Raspberry Pi WH1080 weather station

in PCBs, R-Pi by DP | 0 comments


PCB for Raspberry Pi WH1080 weather station by Andy Ayre of BritishIdeas:

Previously I wrote about using a Raspberry Pi to receive 433MHz signals from a WH1080 weather station. This is the mess of wiring I came up with.
This worked fine until it stopped. I probably didn’t crimp a wire properly and too many knocks resulted in unreliable operation. To solve this I designed a PCB that connects the radio receiver, pressure sensor and an antenna to a Raspberry Pi.

Eagle vs. KiCad revisited

in tools by DP | 3 comments


Steve Chamberlin of Big Mess o’ Wires writes:

Four and a half years ago, I wrote a mini-review of Eagle vs. KiCad, two of the most popular software tools for hobbyists creating custom circuit boards. I concluded that while KiCad had lots of promise, it was too full of quirks and bugs to recommend, and Eagle was the better choice for most people.

This week I had an opportunity to try KiCad again. Although nothing had fundamentally changed, I found that my overall impression of the program was much more favorable. KiCad still has lots of annoying issues, but frankly so does Eagle. And with 4 1/2 years more design experience, I can now appreciate how some of what I originally saw as flaws in KiCad were actually just different design decisions, whose value I can now appreciate.

Posted in tools | Tagged , , | 3 Comments

MeArm – Pocket sized industrial robotics for everybody

in open source, robotics by DP | 19 comments

Here’s an interesting open source project on Kickstarter the MeArm, a pocket size robot Arm by Benjamin Gray:

Low cost, easy to build and simple to control, MeArm is designed to make learning with robotics accessible for everyone.

MeArm is a pocket size robot arm. It was conceived to make robotics, electronics and programming accessible – by driving down the cost of robot arm ownership. The ultimate aim is to make something low cost that you can build with nothing but a screwdriver and enthusiasm.

Apart from being something that’s small, cool and attractive the MeArm is a miniature version of an industrial robot arm. So while it’s simple enough to build and use with a child on a rainy Sunday afternoon – it can also be used at more advanced levels of education to teach real robotics.

Design and code files are available on Github.

Oops – Again

in dev boards, DIY, Sick of Beige by DP | 11 comments


Sjaak likes to design (and build) PCBs in his spare time. This has a big downside as he has a busy daytime job, which makes him a bit less focussed during the design process. He used a small crystal of which he didn’t had a proper footprint of. No problem as it is a few clicks away in eagle. Unfortunately the datasheet he used had two versions of the crystal; one ‘regular’ and a reversed one.

Sjaak is recently being acused of being a soldering alien and he gets his trusty old soldering iron and removed the crystal, flipped it over and resolder it using some small wires. After the quick fix it worked as expected. The board has some other minor nuisances (prolly because of the late night design) so expect a new revision soon. It is BTW an ESP8266 breakout, which uses a custom 1200×1200 mil PCB (loosely based on 30x30mm SOB). Using mils instead of mm make it easier to place imperial stuff more symmetrical.

Programming an Arduino via WiFi with the ESP8266

in Arduino, project logs by DP | 0 comments


Gary Servin has been working on a new project a method to flash an Arduino via WiFi using the ESP8266.  He wrote a post on his blog detailing the process:

I’ve been working on a new robot called RoDI for a summer course at my Alma mater. RoDI is a low cost wireless robot to teach robotics and programming I started developing last year (reminder to self: I still need to post about it), but it wasn’t until a month ago that I started to work on it more often.
The first version used a HC-06 Bluetooth module to communicate with the computer. I wanted to to use WiFi, but the cost of the WiFi modules was a problem, since the idea was that the entire robot would cost less than 30 USD. Then, I read about the ESP8266 WiFi modules on Hackaday, and started working on a new version of RoDI, this time with WiFi :D. I wanted to be able to flash the atmega328 inside the robot via WiFi because the robot doesn’t have a USB to Serial converter.

Via the project log forum.


Running LED dice

in LEDs by DP | 1 comment


Raj over at Embedded Lab has published a new build, a running LED dice using PIC12LF1822 microcontroller:

This project is about a similar LED dice but with a slightly different output form. It uses 6 LEDs which are arranged in a circular pattern and are labeled 1 through 6. They create a chasing effect when the dice is rolled. The chasing effect slows down gradually, and eventually stops at one of the six LEDs. The rolling is done by a gentle shaking of the dice horizontally. The LED dice is powered with a 3V coin cell battery and uses PIC12LF1822 microcontroller to generate a random number and drive the output LEDs.

Check out the video after the break.

Continue reading →

Posted in LEDs | Tagged , | 1 Comment

#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.

OpenSprinkler Firmware 2.1.1 new feature: Control remote power sockets

in open source, RF by DP | 0 comments

We previously covered Ray’s OpenSprinkler. Now it has added a new feature to remotely toggle radio frequency power sockets:

This allows OpenSprinkler to not only switch sprinkler valves, but also easily control powerline devices such as lights, heaters, pumps, fans. Looking for a programmable way to control Christmas lights? Look no further!
This feature is implemented by installing an RF transmitter to OpenSprinkler and assigning the remote signal code as a station name. The remote signal code can be obtained by using either an RFToy or simply an Arduino+RF receiver. The firmware automatically recognizes the code and sends out signal through the transmitter to turn on/off remote sockets. With OpenSprinkler’s mobile web interface and flexible timer programming, this enables automated control of almost any device that can be plugged into a power socket.

Arduino-based inductance meter

in Arduino, measurement by DP | 0 comments


Lukas of Soldernerd built a DIY Arduino-based inductance meter:

I’ve just finished a little Arduino project. It’s a shield for the Arduino Uno that lets you measure inductance. This is a functionality that I found missing in just about any digital multi meter. Yes, there are specialized LCR meters that let you measure inductance but they typically won’t measure voltages or currents. So I had to build my inductance meter myself.

Via the contact form.

A web configurable Xively logger, build on AVR ATmega328

in AVR by DP | 0 comments


Here’s an ATmega configurable Xively logger platform by Davide Gironi:

Xively (formerly Cosm and before that Pachube) is a platform devoted to simplifying the interconnection of devices and data with applications on the Internet of Things. It is an on-line database service allowing developers to connect sensor-derived data (e.g. energy and environment data from objects, devices & buildings) to the Web and to build their own applications based on that data.

This embedded platform is a modular and configurable Xively data logger, built on an ATmega328 micro, usefull to send datapoints to your xively feed.

You can check out the project details on David’s blog.

Check out the video after the break. Continue reading →

Posted in AVR | Tagged , | Leave a comment

How to drive a latching relay

in tutorials by DP | 0 comments


Kerry Wong writes:

Latching relay (a.k.a. impulse relay) can be turned on and off by momentarily applying a voltage across the relay coil. The relay would maintain in its last switched state without the need to maintain the coil current. In this post, I will show a simple circuit which can be used to drive such relays. In the video towards the end, I also included more explanations and some demonstrations.
The relay I am using here is a latching RF relay. It is used to switch the input signal between its two outputs. For this particular relay, the input has an APC-7 connector. One side of the output has an N connector and the other side is 50 Ohm terminated. Although this relay is an RF relay, the method I described below is applicable to any latching relays.
Many dedicated ICs (such as MAX4820, MAX4821) can be used for driving such relays. Because of nature of the latching relay, no H-bridge is needed (although you can definitely use an H-bridge, but it would be wasteful).

DIY smart RGB strip with BLEduino

in project logs by DP | 0 comments



Kevenlaker over at ElecFreaks has shared a Smart RGB LED strip with BLEduino project in the forum:

Smart RGB LED Strip is based on the development of our BLEduino, using the Bluetooth 4.0, and the sample code written by EF men, by mobile phone APP, to control the switch of RGB LED strip, and the RGB LED color changing. The main principle is that using BLEduino mega328P chip three PWM pins respectively to control the RGB LED strip of R G B three colors. When the phone APP and BLEduino bluetooth pairing connection succeed, phone APP can control mega328P chip three PWM pins output value, then control the the color of the RGB LED strip
This project is very easy – making, as long as with three things of BLEduino, BLE mobile phone APP, RGB LED Strip, we can complete it, which enable more Arduino starters to participate in this project. What’s more, we can apply this project to finish a Christmas tree with smart RGB LED Strip.

Via the project log forum.

Details and codes can be found on ElecFreaks’ website.

App note: Photologic

in app notes by DP | 1 comment


Photologic components and applications from TT Electronics.

Historically, optoelectronic components such as phototransistors have been analog output devices. The application engineer had to design with an output current from the phototransistor generated by a given input bias circuit. The advent of the integrated circuits and microprocessors has required the electronics world to turn digital. The sophisticated electronics today communicate by logic levels of 1’s or 0’s. This means that the application engineer must now convert the analog light current of the phototransistor to a voltage level in order to communicate the sensing function to downstream processing electronics. This signal represents additional system cost in components and performance specification guard banding which can be reflected in the unit pricing of the optoelectronic component or assembly.

Photologic discrete components consist of an input photodiode, an amplifier (with gain), a high speed comparator (with or without hysteresis), and a power output device. The photologic sensor is used in many applications to convert input light to a logical high or low output. Its current applications include encoder, non-contact reflective object sensing, non-contact interruptive sensing, assembly line automation, machine safety, end of travel sensing, object sensing and paper sensing.