Following a power interruption, all relays assume their previous state before the power interruption. (relay states and PIN are stored in non-volatile memory) An Motorola MC145436 DTMF decoder is used, this IC is clocked with a common 3. 58Mhz NTSC colour burst crystal and supplies a divide by 8 clock output (about 450 Khz) which is used as the clo
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ck for the Atmel AT90S2313 microcontroller. As this MCU does not have a "brown out detector" feature, a MC34064 is used as a reset generator to prevent possible EEPROM corruption at abnormally low supply voltages. Audio from the radio RX is fed to pin 7 of the DTMF decoder. When the DTMF decoder detects a valid DTMF tone, it outputs a nibble representing the tone on pins 1, 2, 13 & 14 and it drives pin 12, it`s Data Valid output, high, which drives pin 11 on the mcu high. This wakes the mcu up from sleep mode, and the mcu samples the nibble on it`s input pins 2, 3, 6 & 7. Depending on the sequence of DTMF tone data supplied to the mcu, the mcu uses it`s pins 12 - 19 as outputs to control the relays, these outputs are fed to a ULN2803 open collector driver IC, which drives the output lines. All DTMF commands sequences start with a [*] and end with a [#]. Decoded DTMF tones are stored in a tone buffer, the command in this buffer is executed when the DTMF tone for the [#] key is received. Reception of the DTMF tone for the [*] key will clear the buffer without executing it. When a relay is pulsed, it will change state (XOR operation), wait about one second, then change back to it`s original state and if more than one pulse is being generated, there will be an approximately one second delay between each pulse. During pulse output, the controller is deaf to incoming DTMF tones and you must wait for the end of the pulse sequence...
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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