Simple crystal tester

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Dilshan Jayakody build a simple crystal tester based on Colpitts oscillator. He writes:

This is simple Colpitts oscillator to test commonly available passive crystals which range between 2MHz to 27MHz. This unit must connect to an oscilloscope and/or frequency counter to get the frequency of the crystal. This circuit is design to work around 9V to 12V DC power source. Both 2SC930 transistors can replace with any high speed NPN transistor such as 2SC829, 2SC933, etc.

Simple crystal tester – [Link]

DS1307 RTC Module

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The module based on DS1307, The DS1307 serial real-time clock (RTC) is a low-power, full binary-coded decimal (BCD) clock/calendar plus 56 bytes of NV SRAM. Address and data are transferred serially through an I²C, bidirectional bus. The clock/calendar provides seconds, minutes, hours, day, date, month, and year information. The end of the month date is automatically adjusted for months with fewer than 31 days, including corrections for leap year. The clock operates in either the 24-hour or 12-hour format with AM/PM indicator. The DS1307 has a built-in power-sense circuit that detects power failures and automatically switches to the backup supply. Timekeeping operation continues while the part operates from the backup supply.

Specifications

  • Supply 5V DC
  • Completely Manages All Timekeeping Functions
  • Real-Time Clock Counts Seconds, Minutes, Hours, Date of the Month, Month, Day of the Week, and Year with Leap-Year Compensation Valid Up to 2100
  • 56-Byte, Battery-Backed, General-Purpose RAM with Unlimited Writes
  • Programmable Square-Wave Output Signal
  • Simple Serial Port Interfaces to Most Microcontrollers

DS1307 RTC Module – [Link]

Using a Current Shunt with a Panel Meter / Ammeter scale change

This video gives you the basics of how to calculate and use a simple resistive current shunt with an analog panel meter to change the current that is needed for a full scale deflection. The notes page for this video can be found here.

Using a Current Shunt with a Panel Meter / Ammeter scale change – [Link]

ulibSD – a library for use SD cards in SPI mode with uControllers

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electronictechnician.wordpress.com has published a library for use SD cards in SPI completely written in C.

It’s a library for use SD cards in SPI mode with uControllers, entirely written in C. This library can work with SD cards and also has the possibility to emulate the behavior in a PC file (GNU/Linux) using the macro _M_IX86. It’s for debugging purposes. The data transfer is oriented to 512 byte size, remember this.

ulibSD – a library for use SD cards in SPI mode with uControllers – [Link]

Hacking a UART on a blood pressure cuff

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moamindustries.com hacked an Omron RS8 blood pressure cuff by adding a UART interface to it.

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.

Hacking a UART on a blood pressure cuff – [Link]

WISP – Wireless Identification and Sensing Platform

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WISP, the Wireless Identification and Sensing Platform, is a family of sensors that are powered and read by UHF RFID readers.

WISP, the Wireless Identification and Sensing Platform, is a family of sensors that are powered and read by UHF RFID readers. WISPs do not require batteries since they harvest their power from the RF signal generated by the reader. The WISP is an open source, open architecture EPC Class 1 Generation 2 RFID tag that includes a fully programmable 16 bit microcontroller, as well as arbitrary sensors.

WISP – Wireless Identification and Sensing Platform – [Link]

Hacking home weather station transmitter

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Bob hacked a home weather station transmitter and made a home thermometer from it. He writes:

Recently I’ve found this piece of electronic on the dumpster, it was looking interesting – compact case with battery holder, LCD display, temperature and humidity sensor. It has also radio transmitter, but I’m not interested in it since I don’t have the receiver station. I decided to bring it back to life.

Hacking home weather station transmitter – [Link]

3W Stereo Audio Amplifier using TDA7266D

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Tiny stereo audio amplifier board has been designed around SMD TDA7266D IC from ST. The TDA7266D is a dual bridge amplifier specially designed for Portable Audio, LCD TV/Monitor, PC Motherboard, and TV applications. This circuit provides high quality audio output of 3W approx. on each channel with standard audio signal input. The circuit works with 3.5V to 5V. Due to low supply input this amplifier is suitable for small size audio gadgets and portable audio applications like MP3 player, Voice messaging system, Warning signals, Annunciator etc.

Specifications

  • Supply voltage range 3.5 to 5v (maximum supply 5v due to small pcb and small thermal area)
  • Output power 3+3w @thd = 10%, rl = 8ω, vcc = 3.7v (3w approx.)
  • Single supply
  • Minimum external components no svr capacitor no bootstrap no boucherot cells internally fixed gain
  • Mute functions (jumper close)
  • Short circuit protection
  • Thermal overload protection

3W Stereo Audio Amplifier using TDA7266D – [Link]

RELATED POSTS

Raspberry Pi Web Server using Flask to Control GPIOs

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In this article “Rui Santos” shows us how to configure Raspberry Pi as server and use it to toggle two LEDs over the internet.

In this project you’ll create a standalone web server with a Raspberry Pi that can toggle two LEDs. You can replace those LEDs with any output (like a relay or a transistor). In order to create the web server you will be using a Python microframework called Flask.

Raspberry Pi Web Server using Flask to Control GPIOs – [Link]