Sms Controlled Relay Board (8 Relays)

Project code:-E64 Project Cost:- INR:- Rs.11000/- USD:- 275$

Sms Controlled Relay Board (8 Relays)

With the advancement in technologies in wireless communication many products are available in the market to make the human life more comfortable.One of my friend asked me to design a project for him .His only requirement was to switch ON/OFF his irrigation pump ,which is two km away from his house. I could not find the radio module which could cover this distance So I decided to design sms controlled project. I used sim300 gsm module which is readily available in the electronic market. His only requirement was to switch ON/OFF single pump.

Sms Controlled Relay Board Block DiagramSms Controlled Relay Board (8 Relays) Block Diagram

I designed a relay circuit using 89c51 microcontroller Which could be switched on by single mis call to the device and can also be switched off by another miscall. It saves my talktime and money Then it gave me a thought to design the present project which could be used in various application areas depends upon the individual requirement in the field of agriculture ,lighting,security,telecommunication,access and safety both industrial,commercial and in residential area.

Designed for control and sensing applications, this project provides 8 relay outputs and 4 optically isolated inputs. It can be used in various applications including load contact closure and external voltage sensing. Connection to the isolated inputs and relay outputs is via “pluggable type” screw terminal blocks The project presented here is based on world’s most powerful intel’s mcs-51 family of microcontroller atmel at89c51.In this project we are using AT 89C2051 microcontroller,since this controller has two ports are more than enough for our project

Application area: the project can be used for various application wherever you require control using pc.
1 hotel power management
2.street light management
3.home automation
4.load shedding
5. High voltage grid control
6. Industrial automation
7.electro,hydrolic and pneumatic valve control
8. Robotic control and many more

All the above operation are possile from the any mobile phone by sms

The circuit is connected to gsm modem through rs232 cable to Dshall 9 pin connectror connected on both sides. ic max 232 is a level conver ter ic to convert ttl level data to +12v and –12v level for complete details on this ic, refer to manufacturer’s data sheet ASSEMBLY INSTRUCTIONS Follow the component overlay on the PCB, starting with the resistors then diodes, IC sockets and crystal. Next fit the ceramic and monobloc capacitors, followed by the small electrolytic capacitors. Electrolytic capacitors are polarised, the positive lead is marked on the overlay, the negative is marked on the body of the capacitor. Leave the large electrolytic until later.Fit the regulator next and use the 3mm screw and nut to attach the heatsink. All that remains is to fit the DC jack and D9 connector, followed by the relays and finally the large electrolytic capacitor.

Do not insert any ICs yet. Connect a power supply to the DC jack (centre positive) and measure the regulator output (5V). If OK disconnect the power and insert the ICs. Take care that the ICs are the correct way around and none of the leads are bent under the body of the IC.

Circuit explanation: diodes d1 to d4 are power recifire diodes connected in bridge circuit c1 is a filter capacitor .input to the bridge rectifire is 9v 1 ampere transformer. Out put of the bridge rectifire and capacitor is 12v dc. All our relays are operated by 12v dc. Relay output can be connected to any 250v 7 ampere load.please donot cross this limit other wise you will damage the relay circuit.
Ic1 is 7805 regulater gets it’s input from the 12v dc power through d5 and dropping resistance r1 d5 is connected to avoid reverse polarity.5v dc is available at pin no 3 of this ic c2 and c3 are filter capacitors ld1 is a power indication led gets the voltage through current and voltage limiting resistor r2.
Ic2 is atmel at 89c2051 microcontroller. It has two ports port1 pin number 12 to 19 and port 3 pin number 2,3,6,7,8,9 and 11. This controller has inbuilt uart(universal synchronous,asynchronous receiver transmitter, and pin no 2 is rx pin and pin number 3 is tx pin of the uart. Through these two pins microcontroller is able to communicate with the ibm pc comport. Communication boud rate is 9600 bits per second.

Port 1 controlls all our relays.out pot of this port is pulled hifh through pullup resistors
R28 sil arrays(single in line resistor array) hense the outout of pin no 12 to 19 are by default high( at 5v logic) ALL relays stays off on power up. All the relay driver circuits are similar I will explain one of then here .

Q1 to q16 all are npn general purpose transisters. Npn transister will become on when base is high.
If you refer circuit diagram q1 base is driven by r4 connected to pin no 12 of the ic2 as this pin is at logic high , q1 is on(conducting) and it’s collector remains at low logic(transister acts as switch,very low resistance between emitter and collector),resulting base of the transister is low and transister q2 is in off state(non-conducting). To switch on Q2, we have to switch off q1. To switch off the q1 the program inside the microcontroller must bring the logic at pin number 12 to low logic. q1 will become off and q2 base will get high logic through r12 and will become on relay coil of rl1 will get energised as the current will pass through coil , q2 transister collector and emitter to ground. Normally open contact will close the connection. Load should be connected to the out put of the contacts on CON1.diode d6 connected across the relay coil is to proctect the circuit from the induced emf generated by the relay coil during on/off operation.ld2 ic relay ON indication led r20 is a voltage dropping resistor.
All the relay circuit works in the same manner.

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