Crystal

Quartz Crystal Windup Wall Clock

Last year, I found a 31 day pendulum wall clock (dissambled) in a box of parts at a swap meet and decided to try and put it together and regulate it with a quartz crystal oscillator. The escapement part that rocks back and forth and drives the pendulum was missing and had to be made from a couple razor blade pieces and heavy copper wire. The razor blade escapement worked well but only allowed the movement to advance as the pendulum swung, and would not sustain the pendulum motion by itself. But this wasn't a problem since the quartz crystal divider circuit provides energy to the pendulum with an electromagnet to keep it swinging with only a 5 second error per day. ..

Oscillator using crystal

Below are a couple circuits you can use to produce a 32.768 KHz square wave from a common watch crystal. The output can be fed to a 15 stage binary counter to obtain a 1 second square wave. The circuit on the left using the 4069 inverter is recommended over the transistor circuit and produces a better waveform. ..

Crystal Oscillator counter

Using a 50 Khz crystal, a count of 50000 is detected when the appropriate counter bits that add up to 50000 are all high. This corresponds to bits 15 (32768) + 14 (16384) + 9 (512) + 8 (256) + 6 (64) + 4 (16). Bits 14 and 15 are the 3rd and 4th stages of the second counter, bit 0 is the first stage of the first counter (Q1, pin 9). To use a 100 Khz crystal, each bit would be moved one to the right so the total would be (65536 + 32768 + 1024 + 512 + 128 + 32 = 100,000). Using a 1 Mhz crystal, the following bits would be needed:..

7 MHz VFO

A 7 MHz oscillator with a variable crystal oscillator (VXO) operates very stably, but it allows only a small frequency variation (approx. 5 kHz). In contrast, a VFO with an LC resonant circuit can be tuned over a range of several hundred kHz, but its frequency stability will depend upon its construction. The use of a ceramic resonator as frequency-determining component fulfills both requirements. The following oscillator circuit, which uses a ceramic resonator, offers a tuning range of 35 kHz with good frequency stability. The somewhat unusual resonant LC circuit at the collector of VT1 has two functions. It improves the shape of the output signal and at the same time compensates the amplitude drop starting at approximately 7020 kHz. ..

Crystal Clock Generators

Here exist a small collection from three generators, what using crystal for basic production of oscillations. Each generator uses different topology of circuit for the production of oscillations. ..

Crystal Oscillator

Crystal Oscillators are usually, fixed frequency oscillators where stability and accuracy are the primary considerations. For example it is almost impossible to design a stable and accurate LC oscillator for the upper HF and higher frequencies without resorting to some sort of crystal control. Hence the reason for crystal oscillators. The transistor could be a general purpose type with an Ft of at least 150 Mhz for HF use. A typical example would be a 2N2222A. The turns ratio on the tuned circuit depicts an anticipated nominal load of 50 ohms...

50MHz crystal bug

This bugg is based on my previous 3-transistor transmitter. This bugg unit has many advantage. The transmitter use a crystal 46.515MHz to hold a steady frequency. The frequency can be fine-tuned by some 100kHz. The transmitter can send data and audio-signal with +/- 10kHz FM modulation. The output power is about 10mW into 50 ohm. The crystal I used is a 3:th overtone crystal. The coil L1 is a slug tuned coil. The primary winding is 8 turns and the second winding is 2 turn. The inductance in the primary winding is about 800nH. L1 and C1 should be in resonance at 47MHz. The number of turns is dependent on type of coil you have. You will have best performance when the "ferrite tuning slug" is at the bottom of the CAN, because you will then have the best couppling between the two windings. ..

Collection of Crystal Oscillators

On following pages circuits are shown for 3rd overtone crystals 15 to 65MHz and 5th overtone crystals 60 to 105 MHz operating in their series resonant mode. In both of these circuits with the crystal short circuited, the oscillator should operate at or near the required frequency. With the crystal in circuit L1 should be adjusted for either (a) minimum voltage across the crystal or (b) for the exact frequency required. Ideally, these two points would coincide but they rarely will due to the need for a manufacturing tolerance on crystal frequency. If L1 is of incorrect size it is possible for the oscillator to operate on a different order of overtone, for this reason it is important to accurately check the output frequency. ..

Crystal Filter

n the view of the dramatic drop in the price of crystals used in color TV sets, they now represent an economical way of building an SSB filter. The circuit shown in the diagram is for a filter with a 6 DB band width of roughly 2.2 KHz. By terminating the input and output with a 1 K Ohms resistor in parallel with an 18 pf trimming capacitor, passband ripple can be tuned down to 2 DB. All crystals used in the circuit are 4.433 MHz. Collect all the six crystals from same manufacture with same serial number...

The circuit is an VXO with buffered output. It operates on 20-meter amateur radio band with the output voltage about 0.2 Vp-p. The crystal frequency is pulled by tuning the variable capacitor CV1 about 36Khz with only one crystal (Y1), and 250Khz by using two crystals Y1 and Y2. The first configuration stability is much better than using two crystals. However, if you need more frequency variation, use two crystals and you have to pay the cost by getting less stability. ..

This crystal oscillator is designed to operate with fundamental crystals with less than 1 mW dissipated in the crystal. The signal current is filtered by the crystal and develops a voltage across a capacitor with about 500 ohm of reactance. The resulting sinewave has low distortion and phase noise. A JFET buffer is included to drive lower impedance loads. Further buffering with an emitter follower and a voltage step-down transformer or matching network is recommended for driving 50 ohm loads...

This converter allows reception of six metre signals on a two metre receiver. It should therefore be useful for those with single or dual band sets that do not cover 50 MHz. To eliminate the need to obtain a special crystal, the local oscillator is a computer crystal oscillator module operating near 48 MHz. The output of these modules is rich in harmonics. In this case two tuned circuits are being used to pick off the second harmonic near 96 MHz...

Using the circuit in Fig 1, a 68HC11 µP`s stop instruction can put the µP`s external RC-oscillator clock, as well as the µP itself, into a low-power mode. On receiving an interrupt, the µP will exit the stop condition and enable the RC clock. The RC clock, being a low-Q circuit, will start up immediately. Crystal oscillators, on the other hand, can waste precious milliseconds coming up to speed and stabilizing...

One of the nicest features of the 8-bit KX8 microcontroller (manufactured by Freescale Semiconductor) is that it includes an internal clock generator (ICG). This allows the chip to run without the trouble and expense of an external crystal or canned oscillator...

Bugdozer is an autonomous mini-Sumo robot. Her main board consists of a MC68HC908GP32 microcontroller along with input/output support chips, a voltage regulator, a crystal oscillator, and the usual assortment of resistors, capacitors, and switches. All chips are socket mounted. I`m not experienced at soldering, so soldering the sockets avoided damage that could have resulted from soldering the chips directly. Also, if a chip becomes damaged in battle, it can be replaced easily...