Gain wizardly knowledge about crystals

Make sure your test equipment is handy, then give this video series about crystal oscillators a spin. [Shahriar] of the Signal Path Blog put together a four-part video blog post totaling about an hour. In the discussion he covers the ins and outs of crystal oscillators and ring oscillators. His focus is on how these parts are used as timekeeping devices for microcontrollers. This isn’t a lecture that skims the surface of the topic, it takes you down the rabbit hole, discussing theory, how the devices are built, how to use them, and the pitfalls of doing so.

Our favorite part is in the fourth segment when [Shahriar] measures the effect that temperature has on crystals by spraying them with an inverted compressed air canister. We always thought we were just screwing around when freezing stuff like that. It didn’t occur to us that we were conducting serious experiments.

We’ve embedded the first segment of the video after the break. [Read more...]

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.

[Read more...]

Wristwatch board with throwback digits

This wristwatch circuit board has some pretty interesting digits. They’re older components that give a classic look to your wristwatch display. On board you’ll find a PIC 16F628A running with an external clock crystal. The display isn’t always illuminated (kind of like Woz’s watch) in order to save the batteries, but can be woken up for a short time with the push of a button. The steam-punk-ish body seen to the left is the just first try. This guy has four more boards left so it should be fun to see what he comes up with.

[Via Hackaday Flickr Pool]

Hack Your Crystal’s Frequency

[Drone] tipped us off about [Joachim]‘s efforts to alter a crystal’s frequency. Through a process called penning, a crystal’s resonant frequency is lowered by painting the crystal with an indelible ink marker. Our curiosity piqued, we went off  and found more information about penning crystals. It turns out this technique has been around for nearly as long as there have been amateur radio operators. Outside of your local oscillator, and radio jammer, how might you best use a hacked crystal?

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. [Read more...]

3D video with consumer cameras


While perusing our photos from the Hooptyrides, Inc. tour you may have noticed [Eric Kurland]‘s two handed stereoscopy rig. It’s constructed from two consumer grade Sony DV cameras. The problem with using two separate cameras to make stereo images or video is that a lack of clock sync will make objects appear out of their true position because of differences in framerate. To solve this problem Damir Vran?i? developed the 3D LANC Master. It reads the crystal frequency from one of the cameras and writes to the ram of the other camera using Sony’s LANC protocol. This constant monitoring keeps the clocks within +/- 3ms. The control box also has buttons to power on, zoom, and record in sync. The 3D LANC Master plans are completely open source and work with a large number of Sony cameras. We have more photos of Eric’s rig after the break.

[Read more...]