This is a switch selectable dual output `re-hashed` version of my previous (2007) design, and uses a field programmed EPROM for generating both versions of the ringing sequence. AC mains is stepped down to about 10 v AC and fed to the familiar bridge rectifier, filter capacitor and 3 terminal voltage regulator. However a series diode is inserted b
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etween the + terminal of the bridge rectifier and the filter capacitor. Therefore at the anode end of this diode will be a pulsating 100Hz unidirectional sinusoid which is used as an accurate "clock" (Cathode end being filtered DC voltage) This positive going sinusoid is fed to a 4093 Schmitt trigger, its action produces a fast rise (and fall) square wave output necessary to clock following logic IC`s. A clamping diode b/w the Schmitt input (pin 2) and the Vcc rail precludes the input from rising greater than one diode drop above Vcc, excess voltage being dropped across 1K resistor. It was found by experiment that a 22K "bleed" resistor was needed at the gate input to prevent "lock-up" due to some sort of "charge storage" effect. This cleaned-up 100Hz "clock" signal is now fed to a 4013 D type flip-flop which divides the signal by 2 and also gives a 50 Hz equi` mark/space signal. This then feeds the 7490 where another divide by 2 gives; 25Hz (for ringing frequency) and further divide by 5 give 5Hz or a 200mS interval suitable for producing the correct ring cadence. The sequential outputs of the 4040 are connected to the address lines of a 2716 eprom which has been field programmed to provide a serial output bit-stream of 200mS interval used as a gating signal to enable on and off the 25Hz ringing signal. For each 200mS clock pulse the output of the eprom moves to the next sequential address. The first 64 locations contain...
This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,....
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
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