Web-Based programmable logic control (PLC)

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Today there are very rapid development of technology and progress, these developments require humans to continue to innovate to create tools that can help in performing daily activities.

Many activities to do outside the home who sometimes have to leave home until the days and – days. Usually we always turn out the lights when leaving the house empty. This could cause the waste of electrical energy consumption for lighting during the day alive, and will also lead to vulnerability to theft because the house is seen in a state of no activity. To overcome this, the authors sought to create control systems electrical installations are cheap and easy to apply.
This application which will manage all electrical systems to manipulate the situation as if uninhabited, except that this application will replace our work in the light turn on and off every day. Therefore, the authors tried to examine and make the “Applications Web-Based Control Electrical Equipment OpenWRT”.
OpenWRT is an operating system (actually more properly called Firmware) that can be installed (more precisely planted / in-embedded) on a wireless radio device. OpenWRT is to replace the function of a PC is usually used in the application of programmable logic control (PLC), as an OpenWRT operating system can be installed with various applications such as web server and PHP. With this capability makes the “Applications Web-Based Control Electrical Equipment OpenWRT” is very flexible and low cost. Another capability of this application is able to control your home from anywhere are, as long as it can be connected to the internet.

Author : puguh

Copyright: Puguhwah@yahoo.com



RS232 to RS485 Converter

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EIA-485 only specifies electrical characteristics of the driver and the receiver. It does not specify or recommend any communications protocol. EIA-485 enables the configuration of inexpensive local networks and multidrop communications links. It offers data transmission speeds of 35 Mbit/s up to 10 m and 100 kbit/s at 1200 m. Since it uses a differential balanced line over twisted pair (like EIA-422), it can span relatively large distances (up to 4,000 feet (1,200 m)). A rule of thumb is that the speed in bit/s multiplied by the length in meters should not exceed 108. Thus a 50 meter cable should not signal faster than 2 Mbit/s.

In contrast to EIA-422, which has a single driver circuit which cannot be switched off, EIA-485 drivers need to be put in transmit mode explicitly by asserting a signal to the driver. This allows EIA-485 to implement linear topologies using only two wires. The equipment located along a set of EIA-485 wires are interchangeably called nodes, stations and devices.

The recommended arrangement of the wires is as a connected series of point-to-point (multidropped) nodes, a line or bus, not a star, ring, or multiply connected network. Ideally, the two ends of the cable will have a termination resistor connected across the two wires. Without termination resistors, reflections of fast driver edges can cause multiple data edges that can cause data corruption. Termination resistors also reduce electrical noise sensitivity due to the lower impedance, and bias resistors (see below) are required. The value of each termination resistor should be equal to the cable impedance (typically, 120 ohms for twisted pairs).

Star and ring topologies are not recommended because of signal reflections or excessively low or high termination impedance. But if a star configuration is unavoidable, such as when controlling multiple pan-tilt-zoom video cameras from a central video surveillance hub, special EIA-485 star/hub repeaters are available which bidirectionally listen for data on each span and then retransmit the data onto all other spans.

Download RS232 to RS485 Schematic

RJ45 Connector Tester Circuit

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This circuit work with IC 555 and IC 4017. IC 555 as monostable mode, the 555 timer acts as a “one-shot” pulse generator. The pulse begins when the 555 timer receives a signal at the trigger input that falls below a third of the voltage supply. The width of the output pulse is determined by the time constant of an RC network, which consists of a capacitor (C) and a resistor (R). The output pulse ends when the charge on the C equals 2/3 of the supply voltage. This Pulse drive IC 4017 decimal decade. first step pin 2 will high, next pin 3,4,7. so led will on at the end of the cable.