#FreePCB via Twitter to 2 random RTs

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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.

Hacking a UART where there never was before

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Thanks to Andrew for sharing – check out the full post on their blog, MOAM Industries.

As part of a prototype developed 12 months ago I was tasked with reading measurements from a blood pressure cuff [sphygmomanometer] in real time. Not surprisingly there are no consumer level devices that have a serial interface because what ‘normal’ person would want such a thing!
Initially we considered our own interface for a blood pressure cuff. Just run the pump and take the readings with our own processor and pressure sensor, how hard can it be. Rather difficult it seems, the processing and knowledge required to develop a device to perform even rudimentary readings would have completely blown the time budget. Instead we looked to hack an existing device, enter the Omron RS8.

Details at MOAM Industries blog.

Via the contact form.

BeagleBone Black GPIO Benchmark

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Joonas Pihlajamaa from Code and Life writes, ” I’ve previously made a GPIO benchmark of Raspberry Pi 1 and 2, and have always wanted to see how BeagleBone Black would stack against the Pis. I recently got one so the obvious thing to do was to see how fast the little thing could go.  Turns out, the little thing needed a bit more work than the Pi, but the results were quite interesting.”

More details at Code and Life homepage.

Via the contact form.

48″ T8 Cree LED tube teardown

Electronupdate has posted a teardown video of 48″ T8 Cree LED tube:

LED based replacements for old T8 fixtures are finally becoming reasonably priced. I see two old competitors back at it again: CREE, and Philips. Both bulbs attractively priced, both 4000K.
I tore down the Cree 1st. Longest circuit board that I have ever seen……

More details at Electronupdate blog.

Capacitive battery charger

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Marcus Jenkins made a capacitive battery charger using Dirty Board PCB’s to revive rechargeable batteries:

This is really a basic, bare-bones circuit. I’ve prepared the PCB with a view that it could be used as a module in a rather more-sophisticated charging system. You could imagine using a microcontroller (e.g. Arduino, PIC, etc.) to monitor the battery voltage and disconnect the mains input to the charger module when voltage reaches a user-selectable limit. The microcontroller could also have a thermistor probe to attach to the side of the battery with elastic – a basic precaution to try and automatically disconnect in the case unreasonable temperature rise while charging.

Project info at Marcus Jenkins’ blog.  You can order PCB’s for this project here.

Bus Pirate v3.8 free PCB build

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@joseluisalcoba tweeted picture of his free Bus Pirate v3.8 PCB build. The Bus Pirate is an open source hacker multi-tool that talks to electronic stuff.

If you build a free PCB we’ll send you another one! Blog about it, post a picture on Flicker, whatever – we’ll send you a coupon code for the free PCB drawer.

Get your own handy Bus Pirate for $30, including world-wide shipping. Also available from our friendly distributors.

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:

Continue reading “Free PCB Sunday: Pick your PCB”

110v temperature controlled soldering station build no. 2

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Mike Doughty from PCB Smoke shared his DIY 110v temperature controlled soldering station in the project log forum:

This project is build number 2 of a 110v temperature controlled soldering station. It is a follow-up post to the project that I was working on last October.
Blog post with complete details here.
This version has a couple of improvements over the first build. This new soldering iron is a better unit and was less expensive than the first one.
A chisel tip plus a selection of other tips was available for this soldering iron instead of being limited to a conical tip only.

More details at PCB Smoke project page.

Via the forum.

Check out the video after the break. Continue reading “110v temperature controlled soldering station build no. 2”

ESP8266 controlled with Android app (MIT App Inventor)

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Rui Santos from Random Nerd Tutorials has posted a detailed tutorial on how to build an Android app using the MIT App Inventor software that allows you to control the ESP8266 GPIOs:

More details at Random Nerd Tutorials homepage.

Check out the video after the break. Continue reading “ESP8266 controlled with Android app (MIT App Inventor)”

USB curve tracer for NPN transistors

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Dilshan Jayakody documented his USB port base NPN transistor curve tracer project:

Curve tracer is an electronic test instrument to analyze the characteristics of transistors and other discrete semiconductors. In this post we construct USB base curve tracer to analyze properties of NPN transistors. This curve tracer is build around Microchip’s PIC18F4550 MCU and it use simple Windows based GUI application to plot captured data of a transistor.
In this design PIC18F4550 MCU is used to establish USB connectivity, perform voltage readings and control current/voltage flow into the test subject. To minimize the cost and to make it simple, we use R2R ladder circuit to generate discrete collector-emitter voltage levels for the transistor on test. In each scan session collector-emitter voltage level get increase from 0V to 7.5V in 256 steps. In this design, “tracer” scans the transistor for 7 base current levels which are in between 7µA to 60µA. In viewer application collector-emitter voltage levels are plotted on x-axis and collector current is plotted on y-axis.

More details at Dilshan Jayakody’s blog.

Project files available at sourceforge.net.

App note: The LED versus LCD decision

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Choosing between two display types, LED and LCD discussed in this application note from Murata. Link here (PDF)

Users of contemporary digital panel meters (DPMs) have a variety of options available to them. While options are nice, they invariably mean more choices have to be made. After determining what meter resolution one requires, the next most basic decision is usually which type of display to use liquid crystal or light emitting diode?
Traditionally, liquid crystal displays (LCDs) have been the obvious choice for outdoor/daylight applications and/or for applications requiring extremely low power consumption (current drains less than 15mA). Light emitting diode (LED) displays, with their comparatively low light intensities and relatively high current drains, have been excluded from these more demanding applications.
Recent DATEL innovations, most notably the introduction of extremely low-power LED displays, have complicated the once straightforward, LED/LCD decision.

App note: EFM32 Energy Modes

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Application note from Silicon Labs on their EFM32 energy saving microcontrollers, some interesting points are discussed how these type of microcontrollers can conserve power. Link here (PDF)

In battery powered microcontroller applications, energy saving is essential. By reducing the current consumption, the mean time between battery charging / replacement can be significantly increased. Following these principles will drastically reduce the current consumption:
• Use appropriate Energy Modes
• Exploit low energy peripherals
• Turn off unused modules / peripherals
• Disable clocks to unused modules / peripherals
• Reduce clock frequency
• Lower the operating voltage
The EFM32 supports extensive usage of all these principles.

 

Radionova 1 frequency synthesizer

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Vasily Ivanenko has written up documentation on his Radionova 1 frequency synthesizer project:

Frequency synthesizer for my Jupiter receiver — Радионова 1 — [ Radionova 1 ]
Greetings! Most of my future homebrew radio projects will focus on building radio astronomy gear.
Radio astronomy offers much fun + learning for the radio homebuilder — example topics include how to design and make antennas, LNAs, receivers, and frequency synthesizers from HF to microwave. Further we may craft op-amp analog integrators to remove background noise, and/or ADCs, plus write software to store and analyze our data. Avid radio astronomers enjoy a strong understanding of noise measurement/physics, plus a whole lot of really cool science. I’ve already made new friends and feel inspired by the dedicated, skillful folks who listen to signals from space on stuff they craft in their home labs. In radio astronomy, Dx might mean receiving signals from 590 million kilometers away. I’m in!

Project info at QRP HomeBuilder blog.

Slider controller with auto-reverse and variable speed control

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Paulo built a DIY electronic camera slider controller based on a small PIC microcontroller. It supports auto-reverse and variable speed:

These motorized sliders share a common electronic controller design that provides speed control for the gear motor and also an auto-reverse feature using limit switches. In this article , I’ll go over the electronics and software for this slider controller and show how you can build your own.

Project info at paulorenato.com.

Check out the video after the break. Continue reading “Slider controller with auto-reverse and variable speed control”

Force FTDI FT232 USB to serial converters to use a single Windows COM port

Ever notice that each new FT232 inserted into each USB port is assigned a unique COM port number under Windows? When we’re developing hardware with lots of prototypes flying around Windows quickly hits COM 100. Each FT232 has a unique serial number and the driver creates a new COM port for each by default.

FTDI has a quick knowledge base item  about editing a registry key to disable this and stick with a single COM number.

“For a default FTDI device ID (VID 0x0403, PID 0x6001), add the following registry REG_BINARY value set to 01:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\UsbFlags\IgnoreHWSerNum04036001 ”

It’s not difficult to do, but it is impossible to find with Bing* so we’re posting it here for reference.

*Bing is the most reachable English search engine in China at the moment, though reachable doesn’t infer quality search results.

Reverse engineering the popular 555 timer chip (CMOS version)

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Ken Shirriff wrote an article on reverse engineering a 555 timer chip,  He writes:

This article explains how the LMC555 timer chip works, from the tiny transistors and resistors on the silicon chip, to the functional units such as comparators and current mirrors that make it work. The popular 555 timer integrated circuit is said to be the world’s best-selling integrated circuit with billions sold since it was designed in 1970 by analog IC wizard Hans Camenzind[1]. The LMC555 is a low-power CMOS version of the 555; instead of the bipolar transistors in the classic 555 (which I described earlier), the CMOS chip is built from low-power MOS transistors. The LMC555 chip can be understood by carefully examining the die photo.

Details at Ken Shirriff’s blog.

Temperature controlled fan

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Lukas Fassler from Soldernerd has written up documentation on his DIY fan controller project:

I’m currently mainly working on my new anemometer design but once in a while I get distracted. For example when my Keysight E3645A lab power supply was making so much noise that I could hardly concentrate. That’s when the idea of this fan controller was born.

More details at Soldernerd project page.