A Crystal Oscillator Module is a self contained Crystal Controlled Oscillator, housed in a sealed metal can. It is powered by a 5V DC supply, and usually produces a TTL (Transistor-Transistor-Logic) compatable square wave output signal at a nominated frequency. Some Modules that operate at very high frequencies (usually above 100 MHz) produce an ECL (Emitter-Coupled-Logic) compatable output clock. The frequency of operation is either printed, or stamped on the top of the metal can.
The pinout of the device can be referenced to a standard 8 pin DIP package where pins 8 and 4 are Power (VCC) and Ground (GND) connections, while Pin 5 is the clock output. Pin 1 (shown with a dot next to it) is normally not used, but is sometimes configured as an output enable control line (active low). The device is normally leaded, and thus described as a through hole component, however the leads can be carefully bent to form a J-lead configuration for SMT (Surface Mount Technology) applications, if required.
Most Electronic Technicians, and Engineers would consider a Crystal Oscillator Module to be functional if it produced a stable output clock within its frequency tolerance. Unfortunately, this is not always the case! Crystal Oscillator Modules are notorious for suffering from mechanical stress issues, due to poor quality practices in the Manufacturing process. As the Crystal Oscillator Module works within specification – ‘most of the time’, being able to identify functional failures can be extremely challenging. In the final product,Crystal Oscillator Module failures are readily seen during mechanical vibration tests on a Vibration table. However, adding to this issue – most Organizations don’t have access to a Vibration table, and Vibration Testing is not usually part of the Final product Integration plan.
To help provide rapid identification of intermittent Crystal Oscillator Modules in a Repair or Manufacturing operation – I would recommend the construction of a simple Test Rig made up of five D-type Flip Flops (74XX74 Series). These components are packaged as 14 pin devices (DIP or SOIC), with two D-type FF in each package. In other words, this design requires three IC’s (designated U1 to U3). This design could be reduced down to only two IC’s however it is easier to find 8 MHz Crystal Oscillator Modules than 4 MHz parts.
The wiring list for each component node is as follows:
8 MHz Crystal Oscillator Module pin 5 to U1 pin 3. (this is not the DUT, ‘Device Under Test’)
8 MHz Crystal Oscillator Module pin 8 to VCC.
8 MHz Crystal oscillator Module pin 4 to GND.
U1 pins 1,4,10,13,14 to VCC.
U1 pin 7 to GND.
U1 pin 2 to U1 pin 6.
U1 pin 5 to U1 pin 11.
U1 pin 12 to U1 pin 8.
U1 pin 9 to U2 pin 3, U2 pin 11.
U2 pins 2,4,10,14 to VCC.
U2 pin 7 to GND.
U2 pin 1 to U2 pin 13, 10K Ohm PUP (Pull Up Resistor 1), Yellow Test Lead.
U2 pin 5 to U2 pin 12.
U2 pin 8 to 1K Ohm Resistor 1 lead 1.
1K Ohm Resistor 1 lead 2 to Green LED Anode.
Green LED Cathode to GND.
U2 pin 9 to U3 pin 3.
U3 pins 1,14 to VCC.
U3 pins 2,7 to GND.
U3 pin 4 to 10K Ohm PUP (Pull Up Resistor 2), 100nF Capacitor lead 1, SPST Momentary Contact Switch lead 1.
100nF Capacitor lead 2 to GND.
SPST Momentary Contact Switch lead 2 to GND.
U3 pin 5 to Red LED Cathode.
Red LED Anode to 1K Ohm Resistor 2 lead 1.
1K Ohm Resistor 2 lead 2 to VCC.
To Test a Crystal Oscillator Module for Mechanical Stress Issues:
1. Apply power to the Test Rig. Confirm that the Green LED is lit.
2. Common the Ground. The DUT and Test Rig Grounds are connected together.
2. Connect the Yellow Test Lead to the clock output of the DUT. If the Red LED is lit, press the Momentary Contact Switch.
3. With a small wooden handle – tap the adjacent area to the DUT. Do not directly tap the Crystal Oscillator Module, as this may fracture the crystal wafer inside the device. If the Red LED comes on as a result of tapping, then replace the Crystal Oscillator Module.
4. To retest the DUT, press the Momentary Contact Switch then repeat Step 3.
To be thorough, additional Functional Test Procedures would also incorporate the following steps:
1. Using a Frequency Counter with a High Impedence input, measure the frequency of the DUT at U2 pin 1 (Test Rig).
2. Using an Oscilloscope, measure the Voltage Amplitude and Rise/Fall time of the output clock (U2 pin 1). It should conform to TTL or ECL specifications.
3. Perform step 2 under different temperature conditions.
Body Weight Training Retractable Awning
The idea is that this board functions as a controller for a central, 4-way traffic light, that is attached to a post, creating a realistic street intersection. Parts list: 1 ATmega8 (could have done it with an even simpler processor, but..) 1 7805 5V regulator 2 red LEDs 2 yellow LEDs 2 green LEDs 6 330 ohm resistors (SMD 0805 used here) 3 100nF capacitors (SMD 0805) 1 330nF capacitor (SMD 0805) 6-pin male header (ISP programming connector) 1 JST plug pair (battery connection to screw terminal, optional) 1 screw terminal (pair) The PCB was etched. 
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