Olympus RS-24 foot pedal mod

in Arduino, hacks by DP | 0 comments


Rupert Hirst writes:

For a while now, I have been toying with the idea of modifying a transcriber foot pedal into a programmable HID device. This could be useful for those complicated keyboard macros , Push to Talk  or even for a more natural feel in racing type games, although not with proportional control.
Your feet are generally wasted whilst sat at the computer, other than tapping to a beat. With a whole industry and trend built from standing desks and the health issues in the media regarding sitting for hours at a time, maybe it’s time to get a free leg exercise.
Meet the Olympus RS-24 foot pedal… sporting three proprietary software driven functions, rewind, fast forward and listen, all your secretary could ever dream of.

Project info at Rupert’s RunawayBrainz blog.

Specan, a reboot of the W7ZOI/K7TAU spectrum analyzer

in DIY by DP | 0 comments


Ashhar Farhan blogged about his spectrum analyzer build:

The Specan is actually a very simple but robustly built receiver. it is, in essence, a double conversion superhet receiver with 112 Mhz and 12 Mhz Intermediate frequencies. The first mixer uses an Si570 as the local oscillator. The second oscillator is a crystal controlled at 100 MHz; built with a common microprocessor crystal of 20 MHz. Unlike most radio receivers, the second IF has two filters : a narrow band crystal filter with 1 Khz bandwidth and a wide band LC filter with 300 Khz bandwidth. The detector converts the tuned signals into a log scale. The detector output is a decibel measure of the incoming signal.
The Specan is controlled with an Arduino board. The Arduino controls the Si570, handles the front panel, talks to the computer over the USB port, reads the detector and switches the filters.
In a very simple usage, the Specan can be tuned around like a regular radio. Instead of listening to the signals, you read their strength on the LCD display.

Check out the video after the break.

Project info at Farhan’s VU2ESE’s radio experiments blog.

Via SolderSmoke blog.

Continue reading →

Calculator for audio output transformers

in hacks by DP | 0 comments


Dilshan Jayakody  writes:

    Audio output transformers are heavily used in vacuum tube and some (older) transistor base audio power amplifiers, but these days output transformer are quiet hard to find and expensive item. For homebrew projects the best option is to construct those transformers by ourselves and this script helps to calculate winding parameters for those transformers.
This “AF output transformer calculator” script is written using Python and it works with most of the commonly available Python interpreters.

The script is available at elect.wikispaces.com.

Details at Dilshan’s blog.

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Therm: a Tiny PID controller

in hacks by DP | 0 comments


A tiny PID controller project from Ethan Zonca:

Therm is a very small PID controller with an OLED display, thermocouple interface, and USB port. It can switch an external solid-state relay for driving large loads, or a transistor for driving small loads. When attached to a computer, it enumerates as a USB serial port for easy control and logging of data. The design is based around a STM32F0 microcontroller and the MAX31855 thermocouple-to-digital IC (note: an RTD version of therm is in the works).

Project info at Protofusion site.

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Unbrick a Teclast X98 BIOS with Bus Pirate 4 and Flashrom

in BP v4, tutorials by DP | 0 comments


cosmok82 has posted a tutorial on how to unbrick a Teclast X98 BIOS with Bus Pirate 4 and Flashrom:

Sometimes you put your feet out of bed and a bad day comes. In all these days C/D is close to you! Enjoy our guide, step by step to unbrick your Teclast X98 tablet.

First of all.
Be very careful, you can damage your tablet if you make an hardware variation or a version of BIOS not in conformity with your tablet model. I take absolutely no responsibility in both cases. If you haven’t the right know-how to make the circuit by yourself, you have to ask help to a technician!
This is the first guide to unbrick this particular BIOS with Bus Pirate 4 around the world. It was designed for BP4’s header connection, for the version 3.6 of Bus Pirate the situation with the connections is a bit different, take care!

More details at CreativitySlashDesign blog.

Via the forum.

You can get a Bus Pirate v4 for $40, including worldwide shipping.

Simple scalar network analyzer

in Arduino, hacks by DP | 8 comments


rheslip blogged about his simple scalar network analyzer project:

The principle is to stimulate an electrical network with a sinewave and measure the magnitude of the response. If we sweep over a range of frequencies and measure the power transmitted through the network we can determine its frequency response.  Transfer from the input port (1) to the output port (2) is called the network’s S12 S-parameter response. By using a return loss bridge or coupler we can measure the reflected power – the S11 response. A Vector Network Analyzer is a much more complex piece of gear that measures the phase response of the network as well.
In practical terms, a Scalar Network Analyzer allows you to test and characterize crystal filters, attenuators, highpass/lowpass/bandpass filters, cable losses, and antennas among other things. Its also useful as a signal generator and the power detector can be used on its own for power measurements.

Source code is on github.  Project info at rheslip’s blog.

Check out the video after the break.

Continue reading →

Posted in Arduino, hacks | Tagged , , | 8 Comments

#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.

Tutorial: Using GNU profiling (gprof) with ARM Cortex-M

in tutorials by DP | 0 comments


Erich Styger of MCUonEclipse writes, “I have published a Sneak Preview how GNU gprof profiling looks for an embedded target ARM Cortex-M in an earlier post.
This tutorial explains how to profile an embedded application (no RTOS needed) on ARM Cortex-M devices with GNU gprof. Additionally I explain the inner workings to generate the data necessary for gprof.”

An Android reflow controller that anyone can build

in Android, DIY by DP | 0 comments


Andy Brown published a new build, an Android reflow controller:

 The only surface mount device on this PCB is the MAX31855 and it has a low number of generously spaced pins. I eschewed my hot air gun, previous reflow oven and hot plate in favour of a plain old iron and the tack-soldering method because I wanted to show how easy it is to assemble this PCB and you can see me soldering the MAX31855 in the video that accompanies this article. No laughing at the back please; it’s hard to solder from behind a video camera!

Project info at Andy’s blog.

Check out the video after the break. Continue reading →

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App note: Overview of USB battery charging revision 1.2 and the important role of charger detectors

in app notes by DP | 1 comment


Ever wonder why USB connector’s power are longer than the D+ D- pads?  Here’s an app note from Maxim Integrated about these detection proccess and their importance. Link here (PDF)

This application note explains details of the USB Battery Charging Specification 1.2, and the role of charger detection. With the use of charger detection ICs, the USB connector on a portable device becomes a versatile component. The built-in BC1.2 compliance keeps the implementation clean and simple to use.
When designing a compact and portable product, the wealth of features accompanying charger detection ICs make them an extremely attractive integrated circuit.

Free PCB Sunday: Pick your PCB

in Free PCBs by DP | 41 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 | 41 Comments

App note: Get a constant +5V output by switching between a +5V input and a single-cell LI+ rechargeable cell

in app notes by DP | 0 comments


App note from Maxim Integrated on providing smooth power from two sources. Link here (PDF)

Design provides a simple method for maintaining an uninterrupted +5V even while switching between the external +5V supply and a rechargeable single-cell Li+ battery.

App note: Low drop fixed and adjustable positive voltage regulators

in app notes by DP | 1 comment


Low drop fixed and adjustable positive voltage regulators application note (PDF!) from ST:

The LD1117A is a low drop voltage regulator able to provide up to 1 A of output current, available also in adjustable versions (VREF = 1.25 V). In fixed versions, the following output voltages are offered: 1.2 V, 1.8V, and 3.3 V. The device is supplied in: SOT-223, DPAK and TO-220. Surface mounted packages optimize the thermal characteristics while offering a relevant space saving advantage. High efficiency is assured by an NPN pass transistor. Only a very common 10 μF minimum capacitor is needed for stability. Chip trimming allows the regulator to reach a very tight output voltage tolerance, within ± 2% at 25 °C.

Posted in app notes | Tagged | 1 Comment

Windows 10 IoT core controlling a Raspberry Pi 2 robot

in R-Pi, robotics by DP | 0 comments


Windows 10 IoT Core running a Raspberry Pi 2 robot by Scott Hanselman:

Starting with a Raspberry Pi 2, walk through the setup instructions here. You do need to have a Windows 10 today to installing Windows 10 IoT Core but at least it’s gotten a lot easier with the latest build for IOT. There’s an app that does all the work and you don’t need to go to the command line. Also get Visual Studio 2015 Community and the Windows IoT Core Project Templates. Basically just follow these step-by-step instructions.

Project info at Scott’s blog.

Check out the video after the break. Continue reading →

Free PCB coupon via Facebook to 2 random commenters

in Free PCBs by DP | 2 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 to two random commenters. The coupon code usually go to Facebook ‘Other’ Messages Folder . More PCBs via Twitter on Tuesday and the blog every Sunday. Don’t forget there’s free PCBs three times every week:

Continue reading →

Posted in Free PCBs | Tagged | 2 Comments

Simple pendulum tiltmeter

in project logs by DP | 0 comments


Jbeale shared his tiltmeter project in the forum:

Apparently the most popular sensor for this purpose is an “electrolytic tilt sensor”, basically a bubble level with internal electrodes. These are not exactly consumer items. I tried building a simple pendulum tiltmeter using a split-photodiode, Optek OPR2100 (about $10 from Mouser) and LF411 opamp. The pendulum is a 0.064 x 3/4″ x 12″ strip of brass (K&S Metals #8247). Light from a 3W LED shines through a slit at the bottom of the pendulum into the detector. I have the photodiodes in zero-bias mode, wired anode-to-cathode so in balance, the current from one photodiode circulates through the other photodiode. This way the opamp only sources or sinks current (into the photodiodes, through feedback resistor Rf = 1 Mohm) when there is an imbalance in the photodiode current (= light level). I used a LF411 at +/- 15 V because I had it handy; I guess a more modern design would use a 5V single supply opamp and generate a 2.5V midpoint reference somehow. The pendulum will swing a long time unless damped, so I used a magnet assembly from an old hard disk drive for damping (eddy currents in the brass pendulum provide the force), this worked nicely.

Via the project log forum.