Workshop Update for February 4th, 2013

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Got solder paste dispenser working with .1 second interval and about 50 psi. Solder paste makes a big difference. Sparkle paste we tried first was almost impossible to dispense and harder to control. A cheapie tub of “Mechanic” paste from eBay (thanks Sjaak!) works great though.

We did have to up the reflow oven temperature from 200c to 210c to fully cook a big board, but it didn’t scorch or brown the silk this time.

Plotting for Maker Faire Shenzhen, China, which is most likely first weekend of April. Will we fly Aeroflot? Looks like it…

PCB a Week 7: Mains log sensor

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Mats continues his challenge of designing one PCB every week. In week 7 he designed a voltage and frequency logger for household mains power supply. The device is designed around the ATtiny45 microcontroller which records the frequency and voltage, and passes measurements through an onto-coupler to an isolated logging board.

This week I’ll just finalize and order a board that I started on earlier. It’s the sensor board for the mains (wall power) logger that will collect statistics about voltages and exact frequencies over a period of time.

The project will be split up to two pcb’s. The first board is this PAW – the sensor board that makes the actual measurements and sends the data to the second board. The second board that I’ll do in a later PAW will handle the storing, calculation and display of the received data.

Via the forum.

Open source DIY friendly Li Ion battery charger

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Miceuz designed 2 open source single sided boards for Li Ion battery chargers. He used the MAX1555 and MCP73831 ICs as the charging controller, power is provided through USB. We especially like his battery holder rig.

For a long time I wanted to enter the 21st century by stopping using NiCad or NiMH batteries and upgrading to Lithium accumulators as they provide more power per volume and are cool in general. Constant flow of obsolete cell phones provides a nice source of reasonably high-performance batteries for free – I felt compelled to tap into this resource for my battery operated projects.

Via the forum.

ATX breakout board bench power supply back in stock

The ATX breakout board bench power supply is back in stock at Seeed Studio. This board recycles an old computer PSU into a handy bench tool with 3.3/5/12/-12 volt supplies.

You can get one for $14 at Seeed Studio.

You can also get a Sick of Beige case for your ATX breakout board for $4 at Seeed.

App Note: Capacitors and their parasitic components

As with all electronics components capacitors can never be ideal, there are always parasitic components that have to be considered as well. With capacitors the most prominent parasitics are Equivalent series resistance (ESR), and Equivalent series inductance (ESl).

The video recorded by Texas Instruments describes 3 most common capacitor technologies, (ceramic, aluminum electrolytic, and aluminum polymer) and the parasitics that need to be considered when designing with them.

Free PCB Sunday: Pick your PCB

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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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VHDL tutorial using Xilinx CPLD

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We’re always looking for good information on programmable logic devices, projects and tutorials. In our quest we discovered this tutorial on VHDL programming by the crew from StartingElectronics. The course is geared toward beginneers and provides a good introduction to the VHDL language through a series of tutorials that demonstrate the use of VHDL running on a Xilinx CPLD. Each lesson contains a good balance of code, the circuit designed, and the logic theory the project implements.

The tutorial focuses on the XC9536XL CPLD from Xilinx as implemented on the tutorial author’s homebrew CPLD board. Since the XC9536XL is a smaller version of the XC9572XL used in our CPLD Development Board, the tutorial can be used with the DP board as well.

You can get your own CPLD Development board for $15 and start learning VHDL programming.

App Note: Single phase energy meter using XMEGA A

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Here is a reference design from Atmel describing how to build a single phase energy meter using a XMEGA A microcontroller. The circuit is attached to a mains line, and moniters the energy consumption of it, as well as being powered by it. Each part of the circuit and the firmware is carefully analyzed.

The heart of the meter is the MCU, which calculates active, reactive and apparent energy based on voltage and current measurement. The ADC samples the analog input voltage, current signals and converts into digital form. The digital samples are given to MCU for calculating energy. The MCU accumulates the products of voltage and current samples
over a time. The active power is calculated by dividing this accumulated value by the  number of samples. Multiplying the active power by time gives the active energy consumed.

 

Raspberry Pi supercomputer


The crew at the University of Southhampton have been working on a Raspberry Pi based supercomputer. “The machine, named ‘Iridis-Pi’ after the University’s Iridis supercomputer, runs off a single 13 Amp mains socket and uses MPI (Message Passing Interface) to communicate between nodes using Ethernet. The whole system cost under £2,500 (excluding switches) and has a total of 64 processors and 1Tb of memory (16Gb SD cards for each Raspberry Pi). Professor Cox uses the free plug-in ‘Python Tools for Visual Studio’ to develop code for the Raspberry Pi.” The racks holding the components are made from Legos!

They’ve published links to their detailed build instructions on the Raspberry Pi at Southhampton website.

App Note: Boost converter that works with voltages down to 0.5v

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EDN Network covers the design of a very low voltage boost converter. The circuit in question is an LED flashlight designed to power 2 LEDs from voltages as low as 0.5V. The circuit uses an integrated constant current boost converter LT192, though for a cheaper design look no further than the Joule Thief.

Via Electronics Lab.

Workshop Update for February 1st, 2013

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Unboxed yet more tools. One TM220A pick and place is ordered and on the way. We’re trying to negotiate a deal for an additional 6 for people in the forum. Found a good heat profile for the reflow oven that doesn’t scorch PCBs and leave the silk screen clean. Added new Tools of the Trade forum to track experiences with new tools.

LED light intensity logger

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The light intensity of LED’s drops over time. Bogdan wanted to figure out exactly by how much the light intensity of his LED strips dropped, so he build a light intensity logger. It’s basically a closed box with an LED strip and a light intensity sensor inside. An Arduino reads the sensor and stores the reading in its EEPROM.

Via Hacked Gadgets.

ATX Breakout Board V1.1 Acrylic case V1 back in stock

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The ATX Breakout Board v1.1 Sick of Beige case is back in stock at Seeed Studio. This case is designed to be simple, cheap, and easy to assemble. The ATX Breakout Board is sandwiched between two laser-cut acrylic sheets, and the whole assembly is held together with aluminum screws and standoffs.

This is a minor update with the secondary ground and -5volt post holes cut, and a ventilation opening over the big resistor.

Check out our tutorial on how to customize Sick of Beige cases.

You can get one for $4 at Seeed Studio.

Arduino based stereo 7 band equalizer display

Here’s a tutorial describing how to design a stereo 7 band equalizer display using an Arduino and two MSGEQ7 ICs. The MSGEQ7 does most of the work by reading the input signal and outputting 7 voltage levels depending on the strength of their respective bands in the signal. The output is time multiplexed, meaning you read them one after the other, and control the timing through  the strobe and reset pins.

 

Free PCB coupon via Facebook to 2 random commenters

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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:

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Corpsman Up vitals monitor using Propeller chip

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Here’s a project for remote monitoring of heart rate (and potentially other medical/sensor info) using Propeller chips and XBee modules. Nick Ernst has published his plans and code for the Corpsman Up Vitals Monitoring System on the Parallax website. The system consists of two units: a base which is equipped with a Parallax Propeller MCU and a uOLED information display, A/D converter and three corresponding LEDs that indicate battery life of the unit. The remote units are designed using the Propeller Spin Stamp MCU which takes the sensor reading from a Polar T34 Heart Rate Monitor and receiver unit and relays it to the base using an Xbee RF module. (We note that Parallax indicates the Spin Stamp module is in the end-of-life production stage.)