App note: DMX512 isolated receivers using digital capacitive-isolation technology

Here is an app note from Texas Instruments describing in depth how DMX512 protocol functions, and how to build isolated DMX512 receivers. Their new isolated transceivers use digital capacitive-isolation technology, which has proven to be more reliable, and resilient,  then the opto-isolation that was common in DMX512 devices.

This type of isolation has been tested at data transfer rates of over a 100Mbps. While the voltage isolation threshold is around 560V of continuous charge, and 4kv peak charge.

A DMX512 network utilizes a multidrop topology similar to RS-422, where a single  controller (master node) sends repetitive control data to multiple receivers (slave nodes)…

A DMX512 controller transmits packets of asynchronous serial data at 250 kbps (see  Figure 3). A data packet starts with a break (logic low) and is followed by a mark (logic high), a sequence known as mark-after-break (MAB). Following MAB is a time slot consisting of a start bit, eight data bits, and two stop bits. The entire packet consists of a maximum of 513 time slots, 512 of which are actual data slots. The first slot, known as the  start code, specifies the type of data in the packet.

Free PCB Sunday: Pick your PCB

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:

  • Tweet-a-PCB Tuesday. Follow us and get boards in 144 characters or less
  • Facebook PCB Friday. Free PCBs while you wait for the weekend
  • Free PCB Sunday, right here on the blog

Continue reading “Free PCB Sunday: Pick your PCB”

App note: Comprehensive manual for SMD components

Here is a comprehensive manual for SMD components. It covers most common SMD components used in the electronics industry today. Package dimensions as well as markings are covered.

This brochure brings a help and clearance for a newcomer and moreover should help a service technician to start a repair of the instruments made with the SMD components. It presents most of the SMD components available at the 1998 end with pin-outs and encoding comparison tables: SMD / classic and classic / SMD. The SMD does not present a “new technique”, it is only a miniaturisation of the components. But this components requires a different processing technology.

Via the forum. Thanks Fcobcn!

How to read several infrared sensors using one MCU pin


Oscar has written an article describing a technique he’s used for reading multiple analog sensors with one MCU ADC pin. He was designing a line-following robot and wanted to read several infrared sensors without having to dedicate an analog read pin for each. His solution uses “a Schmitt trigger inverter whose output has resistors connected in a series of different values attached to a common point. From this point the voltage value is measured, which will be different depending on the active sensor, being able to know the position of the robot.”

You can find the complete explanation of Oscar’s project on his website. Note that this is a multi-lingual post.

Via the contact form.

App note: High precision temperature measurement with thermocouples

The sensitivity of modern thermocouple is around o.1C over a range which spans from -270C to 1750C. Here is an app note from Maxim on how to built high precision temperature acquisition systems based on thermocouple sensors.

One examples uses a 24bit ADCs for high precision measurement. Another example use a MAX31855 thermocouple-to-SPI converter for designs that don’t require high precision.

Thermocouples are used in a wide range of temperature-sensing applications. Recent developments in thermocouple designs, as well new standards and algorisms, have greatly extended their temperature ranges and precision. Accuracies up to ±0.1°C are now possible over a very wide -270°C to +1750°C range. To utilize all the new thermocouple capabilities, high-resolution thermocouple temperature-measurement systems are required. A low-noise, 24-bit, delta-sigma analog-to-digital converter (ADC) with the ability to resolve very small voltages perfectly fits this task.

Simple MCU speaker boost


Bryan Duxbury offers a tip to get more volume from a weak MCU output pin.

This may be an obvious trick to some, but I just did a short writeup on a really simple way to get more volume out of a speaker attached directly to a weak microcontroller pin – like those on the Arduino – without any complicated audio amplifier ICs. If all you’re doing is playing square waves, you can use nothing but one transistor to get the maximum volume! Now that buzzer in your project can *really* annoy your cat.

Via the contact form.

App note: Understanding ADC specifications and attributes

Here is an app note from Microchip explaining how to interpret various analog to digital converter specifications. This article covers how attributes of ADCs are calculated and how they apply to it’s performance and precision.

The purpose of this application note is to describe the
specifications used to quantify the performance of A/D
converters and give the reader a better understanding
of the significance of those specifications in an application.

SPICY Schematics: A schematic editor and SPICE simulator for iPad

SPICY is an electronics schematic editor and SPICE simulator for the iPad. A free version is available at iTunes.

SPICY is fast, intuitive, and allows you to literally draw circuits with your fingers. Create, save, edit, share, simulate, export and send screenshots to email, SPICY is a must have for students and working engineers alike.

Via Electronics-Lab

28C3: Driving high power LEDs


Here’s a brief video from the recently concluded 28C3 hacker conference hosted by Chaos Communication Congress in Berlin, Germany. Jonathan Foote of rotormind.com covers some ways to drive high power LEDs without burning them up, including the latest technology current source circuits and ICs.

This was one of the “lightning talks” which are are part of the pre-scheduled program, so no CCC documentation page is available.

Free PCB coupon via Facebook to 2 random commenters


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 a every week:

  • Free PCB Sunday. The classic. Every week, get free PCBs right here on the blog comments
  • Tweet-a-PCB Tuesday. Follow us and get boards in 144 characters or less
  • Facebook PCB Friday. Free PCBs while you wait for the weekend

You can get a Bus Blaster v2 for $34.95

Continue reading “Free PCB coupon via Facebook to 2 random commenters”

Preview: Open source soldering iron driver v1.5

Today we sent our updated soldering iron driver v1.5 PCB to be fabricated. This is a 100% through-hole reroute of Arhi’s latest gen 3 design. The ground plane is broken into power supply, analog, and digital sections to help reduce noise. PCBs will be available in the free PCB drawer soon if you’d like to test it.

Version 1 was based on the gen2 driver designed by Arhi in the forum. Since v1 many bugs were found and ironed out. Version 1.5 is based on, and totally compatible with, Arhi’s gen3 driver and firmware. Here’s a list of updates in v1.5:

  • An 1mA constant current now drives PTC type sensors, clearing out the noise.
  • The DC/DC converter features an output filter, contributing to a cleaner power supply and more accurate ADC measurements.
  • The board is a two layer design, and ground layers have been separated between the power, analog, and digital sections.
  • Some footprints have been changed to more easily available packages.
  • Pins were reassigned to make V1.5 compatible with Arhi’s firmware.
  • There are now 6 I/O pins. 3 are reserved for the rotary encoder or interface buttons. The other 3 are free for development. Two of those are Interrupt-on-Change pins, and one is connected to the PWM peripheral’s output.

Week in (p)review: January 20, 2012

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

Coming up:

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

What are you hacking this week?

High-voltage arcs using a flyback transformer from a monitor

Hak8or uploaded a gallery of high voltage arc pictures. The setup was salvaged from an old CRT monitor. He suspects the flyback transformer produces around 30 kV.

I found some old pictures of me playing around with a flyback, and I wanted to test out this awesome gallery thing I found, so I mushed them together, and well, here they are!

The full size pictures are around 2MB each, so users with slow internet connection be advised.

Via the forum.

Digital light intensity meter with a calibrated LDR

Shawon made a light intensity meter using an ATmega microcontroller to read a light-dependent-resistor and display the values on a 2X16 character display. To calibrate his LDR he used a digital light meter and a dimmable light source. This allowed him to plot the sensor output and properly calibrate his device.

This project is about a microcontroller based light intensity meter where an LDR light sensor is calibrated against an external photometer to obtain the intensity of incoming light in the unit of lux. The lux is the SI unit of illuminance and luminous emittance, and measures lumens per square meter (lm/m2). The microcontroller used in this project is ATMega8L and its firmware is written using mikroElektronika’s MikroC Pro for AVR compiler.

Measuring hexacopter rotor speed with Logic Sniffer


Philip Peter has made a somewhat unconventional use of the Open Bench Logic Sniffer.

Recently we suspected that one motor of our hexacopter had been damaged in a crash. Since removing the motor requires almost the complete disassembly of the copter I started thinking of ways to test the motor in place.

In this article he describes a technique he used to measure the rotational speed of the blades of the hexacopter using a red laser as a sending unit and a photodiode and variable resistor connected to the Logic Sniffer adjusted to provide a 1 volt/2 volt dividing line between the photodiode’s dark and light states. He conducted the whole experiment using the stock OLS software jawi.

Via the contact form.

DIY music box with PIC32

Markus built a DIY music box from some old speakers and a PIC32 microcontroller. The uC generates the sound, and the amplifier that’s integrated into the speakers amplifies it.

being inspired by another project of ChaN I decided to build my own music box. The theory is described in detail on ChaN’s page, so I won’t repeat it here. Instead of an ATtiny, mine uses a PIC32 and has therefore enough processing power to play up to 64 notes simultaneously

Via the forum.

Check out the video after the break.

Continue reading “DIY music box with PIC32”

Electrochemically plated vias for homemade PCBs

By electrochemically plating vias, Bearmos takes home-etched PCBs to the next level. His constant current source, with we covered earlier, is used in the process.

I just finished writing up some of the details on DIY plated through holes. This is what the simple constant current source was designed for. This process was slightly adapted from Think and Tinker – a really great site for DIY PCB fab. The overall process is:
1. Drill holes in the PCB
2. Coat the holes with a mixture of water-proof ink and finely powdered graphite
3. Cure the ink so it doesn’t rub off
4. Dunk the PCB in the electroplating tank, apply current, and let chemistry do the rest of the work.

Via the forum.

Arduino-controlled espresso machine


Gleb Polyakov and Igor Zamlinsky of Atlanta, GA have designed this proportional-integral-derivative (PID) controlled espresso machine. Based upon their observations after reverse engineering a number of espresso units, the pair worked on developing a machine which would be reasonably priced, open source, be espresso pod compatible and have a PID controller. Temperature and pressure are controlled by an Arduino.

The resulting machine is expected to retail for $400, and the project has been fully funded on Kickstarter.

Here’s a link to their video demonstrating this project.