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20 Mar 2014

This is another common device people use everyday, in which a circuit drives the motor found in our watches or clocks to determine the time.

The circuit is mainly operated by PCA1462U IC, specially suited for battery-operated quartz-crystal controlled wrist watches. The quartz crystal is used to input an oscillated signal to the PCA1462U IC then produces an output of pulses that drives the stepping motor ON.

The IC used in this circuit is specialized for this application featuring an amplitude regulated 32KHz oscillator, with excellent frequency stability resulting in a high immunity from oscillator-to-leakage currents. The loss of motor steps is not possible because of an on-chip detection on the induced motor voltage, this output is applicable for different types of bipolar stepping motors. This IC also has a very low current consumption; typically 170 nA, and the time calibration of the pulses is electrically programmable and reprogrammable (via EEPROM).


  • PCA1462U CMOS integrated circuit
  • 1.55V dc power source
  • Quartz Crystal Oscillator
  • Stepper Motor

Quartz-crystal Controlled Wrist Watch - [Link]

19 Dec 2012


This project is “NanoUtils Xtal” – a crystal oscillator breakout board. The board is designed to be interfaced with microcontrollers that have their oscillator pins next to a ground pin. [via]

This board is a breakout containing a SMD crystal, two caps and a resistor meant to be used in breadboards when building something with an Atmel ATmega or a Microchip PIC that have the two crystal pins next to a GND pin. For instance the atmega328 or pic18f2550.

Crystal oscillator breakout - [Link]

30 Mar 2012

Atmel describes how to select and test 32.768 kHz quartz crystals [PDF!] for real-time clocks. The basic tips on layout apply to any microcontroller project, not just those with AVRs. [via]

This application note summarizes the crystal basics, PCB layout considerations, and how to test a crystal in your application. A crystal selection guide shows recommended crystals tested by experts and found suitable for various oscillator modules in different Atmel AVR families. Test firmware and test reports from various crystal vendors are included.

Selecting and testing 32kHz crystal oscillators - [Link]

12 Feb 2012

adafruit.com writes:

Learning to design your own PCBs and being able to put together a schematic to solve a specific problem is both a valuable and rewarding skill. There are a number of resources out there to help you avoid common mistakes, but it isn’t always obvious to know where the values of certain common components come from, particularly common parts like resistors and capacitors. Figuring this out is part of the learning process, but it isn’t always easy to know where to look since you first need to know exactly the right terms to search for.

Choosing the Right Crystal and Caps for your Design - [Link]

15 May 2011

hackersbench.com writes:

There are many projects that require an accurate 1Hz clock signal, most involving the measurement of time, or controlling something based on time. There are timers, time clocks, nixie and other real time clocks, and many others. In my case, I wanted to build a very simple frequency counter. That circuit, in essence, simply counts how many pulses happen within 1 second. To make the counter as accurate as possible I needed my 1 second counting period to be as accurate as possible.

Crystal Controlled 1Hz Time Base - [Link]

3 Jan 2011

IPenguin shows how to verify a crystal oscillator is working using the Logic Sniffer. This should work with the crystal circuit on many microcontrollers. [via]

Verify an oscillator with the Logic Sniffer - [Link]

23 May 2010

Transistor Q1, a 2N3563, and its associated components form an oscillator circuit that will oscillate if, and only if, a good crystal is connected to the test clips. The output from the oscillator is then rectified by the 1N4148 signal diode and filtered by C3, a 100pF capacitor.

Simple Crystal Tester - [Link]

7 Jul 2009

A common challenge when working with embedded systems is keeping track of real time. Luckily, most microcontrollers have timers that can be used with a precision quartz crystal — already present for the CPU clock — to keep track of real time. In this video tutorial, we show how you can use the timer interrupts on an ATMega168 chip to make a simple timer. Building off of this, it is possible to make your own reasonably accurate alarm clock, create systems to perform timed automated tasks, or create a multitude of other projects.

Crystal Real Time Clock - [Link]

1 Jun 2008

If a crystal radio is the distilled essence of a radio, this transmitter is the matching distilled essence of transmitters. The transmitter goes together in about 10 minutes, and is small enough to fit in the palm of your hand. Depending on the antenna, the transmitter can send voice and music across the room, or across the street. [via]

Building a very simple AM voice transmitter - [Link]

17 May 2008

This is a really cheap and probably illegal shortwave transmitter, don’t build it. It just feeds the output from an LM386 audio amplifier directly into the power pin of a crystal oscillator can to produce AM-modulated shortwave radio frequencies. This works better than one might expect — this particular oscillator seems to provide a stable waveform with voltages anywhere from 2.0v to 5.0v! [via]

Cheap Shortwave Transmitter - [Link]





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