Remotely Programmable RTC-Interfaced Microcontroller for Multiple Device Control

  
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This project based on Atmel AT89C52 and Dallas real-timeclock (RTC) chip DS12887 can be used to control and remotely program the switching operation of 24 electrically operated devices. The devices can be switched on/off at precise times repeatedly every day, every month. The microcontroller can be programmed for device control using a normal Phil
Remotely Programmable RTC-Interfaced Microcontroller for Multiple Device Control - schematic

ips TV remote control. The Philips IR format makes use of RC5 code, which is also known as bi-phase coding. ` In RC5-coded signals (Fig. 2), each bit has a uniform duration. A transition in the middle of the time interval assigned to each bit encodes its logical value (0` or 1`). A high-to-low transition assigns the bit a logic value of 0, ` and a low-to-high transition assigns the bit a logic value of 1. ` We need additional transitions at the beginning of each bit if a stream of equal bits is sent. However, there is no need of additional transitions if the The first two bits are start` bits, which are used to adjust and synchronise the receiver. These bits are used to calculate and analyse the bit length of the other bits. The third bit is a toggle` bit, which is toggled every time a button ispressed at the remote control. This bit is used to identify whether the button is really pressed or whether an obstacle came in between the IR path of the remote and the IR receiver. The five bits (A4 through A0) immediately following the toggle bit are used to identify the device (see Table III). So, a maximum of 32 devices can be identified to and respond individually to the same type of coding without any disturbance, i. e. , one among the 64 devices can be identified uniquely. Addresses of some of the remotes are shown in Table III. The six bits (C5 through C0) immediately following the five address bits are the control/command...



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