Moteino IoT sprinkler controller automation

in hacks by DP | 0 comments


Felix of LowPowerLab writes:

Another node type is now available on the Gateway automation interface: a sprinkler controller. This is achievable through a board I designed to be able to control many outputs. I call this board IOShield and it features two 74HC595 serial to parallel shift registers.
The IOShields are daisy chainable and can take 24VAC through a buck regulator. Wireless control is done with a regular Moteino or MoteinoUSB and in a daisy chain only the first board would need the regulator and Moteino.

Project details at LowPowerLab blog.

Check out the video after the break. Continue reading →

How to control your ESP8266 from anywhere in the world

in tutorials, wireless by DP | 0 comments


Rui Santos shared a tutorial on how to control your ESP8266 from anywhere in the world:

The most common questions I get about the ESP8266 WiFi Modules are: “Is it possible to control my ESP8266 from anywhere in the world?” and “How can I control my ESP8266 from anywhere?”.
I’m happy to announce today that I have a solution for that problem.
With the new version of Home Automation Server you can add an ESP8266 to your dashboard and control your ESP8266 GPIOs from anywhere in less than 5 minutes!

More details at Rui’s Random Nerd tutorials site.

Check out the video after the break.

Via the contact form.

Continue reading →

Vulcan-74: A 6502 Retro MegaProject

in hacks by DP | 0 comments


Radical Brad over at the forum has been working on this cool 7400 logic VGA video game system, Vulcan-74:

The Goals…

  • Video must be perfectly stable VGA, putting out 256 colors at a resolution of 400×300 using an 8 bit color space divided into RRR-GGG-BB
  • Video must include full 256 color 400×300 bitmapped screens with a seamless double buffer for high speed animations and high detailed images
  • The GPU system will include a high speed (20MHz) blitter system capable of dealing with moving variable sized bitmaps from a dedicated 1MB memory bank to the back buffer independent of the 6502 CPU. The entire GPU must be made ONLY of 7400 logic parts
  • The sound system will be minimum 4 independent digital sound channels, and include its own 1MB independent sample SRAM. Much like the Amiga, the sound system is independent of the CPU, and again all made with 7400 logic parts
  • The completed system must be capable of impressive games (Amiga quality), not just some simple tile engine. All games will load only from an external EEPROM (cartridge) via onboard 7400 logic based loader. No external processing will be allowed
  • The CPU will be a 65C02 only. No 65C16, as this is too new for my system! The 6502 will run at 16MHz minimum, using whatever IO decoding tricks I see fit. Bus pirating illegal opcodes, etc. Prelimanry tests have shown stable operation at 20MHz using a ROMless system running from 10ns SRAM

Project info at forum.

Check out the video after the break.

Via the contact form.

Continue reading →

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App note: How to successfully apply low dropout regulators

in app notes by DP | 1 comment


Application note regarding proper usage of LDO from Analog Devices. Link here (PDF)

A low dropout (LDO) regulator is capable of maintaining its specified output voltage over a wide range of load currents and input voltages, down to a very small difference between input and output voltages. This difference, known as the dropout voltage or headroom requirement, can be as low as 80 mV at  2 A.
Current portable devices often require up to 20 low dropout linear regulators. Many of the LDOs in today’s portable devices are integrated into multifunction power management ICs (PMICs), highly integrated systems with many power domains for audio, battery charging, housekeeping, lighting, communications, and other functions.
As portable systems rapidly evolve, however, the integrated PMIC cannot keep up with peripheral power requirements. Dedicated LDOs must be added in the later stages of system development to power such optional items as camera modules, Bluetooth®, WiFi®, and other bolt-on functions. LDOs have also been used to reduce noise, to solve voltage-regulation problems caused by electromagnetic interference (EMI) and printed circuit board (PCB) routing, and to improve system power efficiency by switching off unneeded functions.
This application note reviews the basic LDO topology, explains key specifications, and shows the application of low dropout voltage regulators in systems.

Posted in app notes | Tagged , , | 1 Comment

Free PCB Sunday: Pick your PCB

in Free PCBs by DP | 49 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 | 49 Comments

App note: Isolating USB with SPI

in app notes by DP | 1 comment


Old but still good technical note from Analog Devices on USB isolation. Link here (PDF)

Currently, iCoupler® digital isolation technology is capable of transferring data at rates ranging from DC to about 150Mbps, which is adequate for transferring serial data to support low (1.5Mbps) and full (12Mbps) speed modes of USB. There are three places where isolation could be introduced, in the differential transmission lines D+/D–, between the controller and the transceiver, and between the controller and the system controller.  Unfortunately, the trend toward higher levels of integration incorporates the transceiver and controller interfaces into the system controller, leaving only D+/D– data lines available outside of the controller for isolation.
This is an extremely challenging place to try isolation because there is no flow of control signals, and data is a combination of single ended and digital signaling.  With current isolation technology, the most practical place to isolate is between the system controller and a stand-alone USB controller/transceiver where signals can be unidirectional and logic level.  In many cases this means bypassing inboard controllers and adding a discrete USB controller.

App note: Triacs – How to calculate power and predict Tjmax

in app notes by DP | 0 comments


An application note (PDF!) from NXP on how to calculate the power dissipated by the triac:

This Application Note describes how to calculate the power dissipation for triacs and Silicon Controlled Rectifiers. Thermal calculations are also included to help the circuit designer to predict the maximum junction temperature or calculate the required heatsink thermal resistance. Four
worked examples ensure that all the power and thermal questions that arise during the design process are covered.

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 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 →

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

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.”