Tag Archives: crystal

The top 10 crystal oscillators from SnapEDA

Elizabeth Bustamante @ snapeda.com lists the top 10 crystal oscillators used today. She writes:

A crystal oscillator is an electronic circuit that generates an electrical signal with a very precise frequency. To achieve this, it uses the mechanical resonance of a vibrating crystal made of piezoelectric material.

The first crystal oscillator was invented in the late 1920s by Walter Guyton Cady who was interested in submarine detection with ultrasonic waves. He suggested that a piezoelectric resonator could be used as a frequency reference, a coupling device between circuits, or a filter.

The top 10 crystal oscillators from SnapEDA – [Link]

CH340E, A New Small Serial to USB Chip

WCH, a Chinese integrated circuits manufacturer, has just released a new serial to USB chip called CH340E. Unlike other CH340 chips, it doesn’t require an external crystal and also needs less PCB space and BOM.

CH340 is a 3x3mm tiny chip comes in MSOP10 package and has 10 pins. Although it is smaller than other alternatives, it is a little more expensive than them. But considering other components and PCB size needed, the total cost of the BOM may be lower.

According to Electrodragon, it needs only two external parts to build a full function circuit. They also tested it with up to 150,000 baud rate to flash an ESP8266 chip. Most features and technical specifications are the some for CH340 family including CH340E, so the same drivers will work with it.

CH340E features

  • Full-speed USB device interface, compatible with USB V2.0.
  • Emulation standard serial port used to upgrade the original serial peripherals or add additional serial port via USB.
  • Computer applications under the Windows operating system serial port are fully compatible, without modification.
  • Hardware full duplex serial port, built-in send and receive buffer, support communication baud rate 50bps ~ 2Mbps.
  • Support common MODEM contact signal RTS, DTR, DCD, RI, DSR, CTS.
  • Through the additional level conversion device, providing RS232, RS485, RS422 and other interfaces.
  • Software compatible CH341, CH341 driver can be used directly.
  • Support 5V supply voltage and 3.3V supply voltage or even 3V supply voltage.
  • Built-in clock, no external crystal.
  • Available in SOP-16 and SSOP-20 and MSOP-10 lead – free packages, RoHS compliant.

The chip costs about 42 cents with a minimum order of 5 pieces on Eelectrodragon store. There is also an option to get a small board featuring the CH340E for about $1, and maybe cheaper in the future. Finally, the most powerful feature of this chip is that you can easily add USB connectivity to your own design.

Source: CNX-software

Simple crystal tester


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]

Ovenized crystal oscillator frequency stability


E. Schrama @ ejo60.wordpress.com uses an Arduino and a DCF77 time signal receiver to test the stability of an ovenized crystal oscillator running at 1 MHz.

In this experiment I will use an Arduino and a DCF77 time signal radio receiver to measure the stability of an ovenized crystal oscillator running at 1 MHz. It demonstrates that 50ppb (or 50 milliHerz) can be achieved on the short term, whereby an aging effect of 0.1 ppb per day is demonstrated with a 18 month long dataset. The output of the 1MHz oscillator is fed into a 248 counter and six 74HC165 parallel in, serial out (piso) conversion ICs that are controlled by an ATMEGA 2560, the circuit is described here. With this setup running at 1 MHz you get a rollover every 10 years, the resolution is 1 microsecond. In principle you could do this also with an Arduino but I decided for this set-up since I already had most of the components left over from an earlier experiment.

Ovenized crystal oscillator frequency stability – [Link]