Building a crystal oven

Radio communications depend on stable oscillator frequencies and with that in mind, [Scott Harden] built a module to regulate temperature of a crystal oscillator. The process is outlined in the video after the break but it goes something like this: A small square of double-sided copper-clad board is used as a base. The body of the crystal oscillator is mounted on one side of this base. On the other side there is a mosfet and a thermister. The resistance of the thermister turns the mosfet on and off in an attempt to maintain a steady temperature.

This is the first iteration of [Scott’s] crystal oven. It’s being designed for use outdoors, as his indoor setup uses a styrofoam box to insulate the oscillator from ambient temperatures. He’s already working on a second version, and mentioned the incorporation of a Wheatstone bridge but we’ll have to wait to get more details.

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Using videotape tape as a controller

Behold the Bodystick, an instrument built and demonstrated by [Erich Lesovsky]. It’s a bit like a string bass but instead of strings there is a strip of VHS tape. Apparently not all VHS tape will work, but if you have the right kind you can run voltage through it and then change the resistance with a touch of your finger. It seems that the hand not touching the tape needs to be touching a conductive pad, completing the circuit. The resulting resistance changes the oscillator values on a CD40106 CMOS chip. This project is a bit out there (just like [Erich’s] Mega-Tape-O-Phone), and in keeping with its peculiarity is the demo video after the break. Enjoy!

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Pure TTL based clock

We’ll just say, [Kenneth] really likes clocks. His most recent is a pure 7400 series TTL based one, ie no microcontroller as seen in the past, here, here, and here. The signal starts out as a typical 32,768 crystal divided down to the necessary 1Hz, which is then divided again appropriately to provide hours and minutes.

As far as TTL clocks go, this is nothing too original; until it comes to his creative button interface. By using a not as sexy as it sounds multivibrator, he can produce a clean square wave instead of the figity signals produced from buttons to advance and set the time. Like always, he also provides us with a thorough breakdown of his clock, after the jump. Continue reading “Pure TTL based clock”

Parts: 133MHz-16.2kHz programmable oscillator (DS1077)

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The DS1077 is a 5volt, 133MHz to 16kHz programmable clock source. The internal frequency divider is configured over a simple I2C interface, and the chip requires no external parts. Not bad for under $2. We used the Bus Pirate to test this chip before using it in a project. Grab the datasheet (PDF) and follow along. Continue reading “Parts: 133MHz-16.2kHz programmable oscillator (DS1077)”

How-To: Make a digital synthesizer

This week’s How-To comes from our newest contributor: Logan Williams.

This simple guide will show you how to build a digital synthesizer that generates and manipulates square waves. Your synthesizer will have one oscillator, which produces a variable pitch controlled by a potentiometer, as well as an LFO which modulates that pitch at a variable frequency. The part count for this project is quite low, and it can be built for under $20.

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