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. I used to get the sms from the moter starter contactor panel when it actullay becomes on, that gives me confirmation that the motor is on.
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
Port 3.0 is rxd pin to receive data serially and port3.1 is to transmit data serially
Circuit is driven by 9v 1 AMP transformer connected to pcon1
Diode d1-d4 forms bridge circuit c1 ,c2,c3 and c4 are filter capacitors
Ic1 7805 is 5v regulator ic to give stablised supply to microcontrollerLD1 LED is a power indication led. Crystal gives the necessary clock to micro-controller.
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.
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 micro-controller is able to communicate with the ibm pc comport. Communication boud rate is 9600 bits per second.
Port 1 controlls all our relays.out put of this port is pulled high through pullup resistors
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 r3 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 micro-controller must bring the logic at pin number 12 to low logic. q1 will become off and q2 base will get high logic through r4 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 d5 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 r5 is a voltage dropping resistor.
All the relay circuit works in the same manner.
Ic3 max 232 ic is a level converter ic. IBM pc com port is designed for telephone network which works on 12v dc where as our controller logic is at 5v we need to convert this data to +12 &-12 logic before it is sent to pc this ic has transreceiver level converter. Transmitter
part convert the TTL logic to com port logic and receiver part convert the signals coming from pc to TTL level before it is given to micro-controller.
All the components connected around this ic is as per the application notes given in the datasheet by the manufacturer..
Capacitor c5 and r1 gives the required reset pulse to microcontroller.Crystal x1 along with capacitor c6 and c7 gives the required clock pulse to microcontroller.
Resistances connected to indication leds are current limiting resistors.
Four isolated inputs are connected through opto couplers ic4 to ic7. output of the opto-coupter are connected to p3.2,p3.3,p3.4 and p3.7 respectively. In1 to in4 are connected to the normally open contact of the device(sensor controller) you want to monitor . when ever contact is made led inside the opto coupler will glow and collector inside will pull the microcontroller pin to logic low, this is the active state of the device. You can test this by shorting in1 to in4 pins by a piece of wire and give command from your computer you will get the proper response as mentioned in the command section.
OPERATION
To switch on devices, You can send sms to the device as ON1,ON2,ON3 and so on .T0 switch off devices send sms as OFF1,OFF2,OFF3 and so on . to get the response from the actuating device if connected to the input terminals you will receive sms on your mobile phone like ‘device1 is on’ or ‘device2 is off ’ etc.
Commnication between SIM300 modem and microcontroller takes place via serial port Using Sim300 AT command set. Which can be downloaded from the official SIMCOM site.
Some are given here ,can be tried on pc using hyperterminal.
SIM300 AT Command Set
SMS commands
Demonstration Syntax Expect Result
Set SMS system into text mode, as
opposed to PDU mode.
AT+CMGF=1 OK
Send an SMS to myself.
AT+CMGS=”+861391
818xxxx”
>This is a test
+CMGS:34
OK
Unsolicited notification of the SMS
arriving
+CMTI:”SM”,1
Read SMS message that has just arrived.
Note: the number should be the same as
that given in the +CMTI notification.
AT+CMGR=1 +CMGR: “REC UNREAD”,
“+8613918186089”, ,”02
/01/30,20:40:31+00”
This is a test
OK
Reading the message again changes the
status to “READ” from ”UNREAD”
AT+CMGR=1 +CMGR: “REC READ”,
“+8613918186089”, ,
“02/01/30,20:40:31+00”
This is a test
OK
Send another SMS to myself. AT+CMGS=”+861391
818xxxx”
>Test again
+CMGS:35
OK
Unsolicited notification of the SMS
arriving
+CMTI:”SM”,2
Listing all SMS messages.
Note:”ALL” must be in uppercase.
AT+CMGL=”ALL” +CMGL: 1,”REC
READ”,”+8613918186089”,
, “02/01/30,20:40:31+00”
This is a test
+CMGL: 2,”REC
UNREAD”,” ”,”+861391818
6089”,
, “02/01/30,20:45:12+00”
Test again
OK
Delete an SMS message. AT+CMGD=1 OK
List all SMS messages to show message
has been deleted.
AT+CMGL=”ALL” +CMGL: 2,”REC READ”,
“+8613918186
089”,”02/01/30,20:45:12+00
”
Test again
OK
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