Wiring Diagram

The IC ELM446 is an 8 pin digital divider integrated circuit, that provides both 50Hz and 1Hz outputs from a common 3.58MHz NTSC colourburst crystal. Externally, the designer need only provide the crystal and two appropriate loading capacitors, as well as a suitably bypassed power supply. Internal Oscillator circuits then use this reference frequency to precisely derive a stable 50Hz signal. For convenience, a complementary 50Hz signal is also provided. This signal is then further divided to provide a 1Hz signal output. By ELM Electronics

This is a circuit of sine wave oscillators covering a frequency range of 15 to 150kHz in four switched steps. Two conditions exist for a sinusoidal oscillator. Regenerative or positive feedback, and a closed loop gain of unity. The losses in the wien feedback circuit, are such that the open-loop gain of the amplifier must also exceed 3.

The circuit gain is provided by a FET type op-amp (LF351), but LF351 may be difficult to obtain, for a replacement you can use TL071CN or TL081CN. The Maplin order codes are RA67X and RA70M respectively. The wien network is a parallel combination of resistors and capacitors, in series with a series RC network. Regenerative feedback is applied from the op-amp output, to the serail RC input and continues. Stabilization is required to prevent the otherwise Uncontrolled oscillation from building up and becoming unstable.

This is circuit for accurate time-base generation using the readily available 3.5795MHz crystal commonly used in telecommunication equipment. Crystal-based oscillator with divider IC chain or a similar circuit in the form of an ASIC is used for time-base generation. The 3.5795MHz crystal is used in conjunction with a CD4060-based crystal oscillator- cum-divider (IC1). The crystal frequency is divided by 512 by IC1, which is further divided by 7 by CD4017 (IC2). IC2 is reset as soon as its Q7 output goes high.

Thus the crystal frequency is divided by 3584, giving the final output frequency of around 998.8 Hz. This frequency can be trimmed to exactly 1 kHz with the help of trimmer capacitor VC1 as shown in the figure. The 1kHz signal can be further divided using decade counters to generate the required time period. EFY lab note.