This project is an Application/extension of Digital Pulse Counter.
Transmitter Part: The transmitter circuit (see Fig. 1) is built around timer NE555 (IC1), which is wired as an astable multivibrator producing a frequency of about 38 kHz. The infrared (IR) beam is transmitted through IR LED1.
HERE A is +9V and B is GND.
Receiver Part: There are two 7 segment displays driven by two CD4026B (CMOS DECADE COUNTER/DIVIDER) used here to count up to 99. Seven Segment display used are common cathode type(see fig below).
Moving ahead when the transmitted signal is cut, Pulses are generated by the IR receiver TSOP1738. The output of TSOP1738 is then fed to monostable multivibrator circuit made using NE555. Then the controlled stable pulse of 250ms (T=1.1*R*C) is fed to CD4026B which will drive the unit place display to make it count from 0 to 9. When it overflows, carry is generated by this IC and this carryout is fed to another CD4026B driving Tens Place display . Thus making the whole circuit count 0 to 99. Similar CD4026 circuit can be added to increase the number of counts.
This Circuit has various applications such as spring oscillation counting, Counting no of people entering through door(one way), as a bugular alarm, etc.
Here you can download the PDF Schematic of the receiver part.
The range of this FM transmitter is around 100 metres at 9V DC supply.
Fig. 1: FM transmitter
The circuit comprises three stages. The first stage is a microphone preamplifier built around BC548 transistor. The next stage is a VHF oscillator wired around another BC548. (BC series transistors are generally used in low-frequency stages. But these also work fine in RF stages as oscillator.) The third stage is a class-A tuned amplifier that boosts signals from the oscillator. Use of the additional RF amplifier increases the range of the transmitter.
Coil L1 comprises four turns of 20SWG enamelled copper wire wound to 1.5cm length of a 4mm dia. air core. Coil L2 comprises six turns of 20SWG enamelled copper wire wound on a 4mm dia. air core.
Fig. 2: Pin configurations of transistors BC548 and C2570
Use a 75cm long wire as the antenna. For the maximum range, use a sensitive receiver. VC1 is a frequency-adjusting trimpot. VC2 should be adjusted for the maximum range. The transmitter unit is powered by a 9V PP3 battery. It can be combined with a readily available FM receiver kit to make a walkie-talkie set as shown in Fig. 3
Fig. 3: Walkie-talkie arrangement
I have used earphone speakers in replacement for condenser mic providing more portability.
COURTESY: ELECTRONICS FOR YOU
Here is a simple water level alarm circuit using 555 timer that will produce an audible alarm when the water level reaches a preset level. The circuit can be powered of a 3V battery and is very handy to use.
The circuit is based on an astable multivibrator wired around IC1 (NE 555).
FIG 1. WATER LEVEL ALARM CIRCUIT USING NE555 TIMER
The operating frequency of the astable multivibrator here will depend on capacitor C1, resistances R1,R2 and the resistance across the probes A&B. When there is no water up to the probes, they will be open and so the multivibrator will not produce oscillations and the buzzer will not beep.When there is water up to the level of probes, some current will pass through the water, the circuit will be closed to some extend and the IC will start producing oscillations in a frequency proportional to the value of C1,R1,R2 and the resistance of water across the probes. The buzzer will beep to indicate the presence of water up to the level of the sensing probes.
The circuit can be powered by a 3-12V battery.
Many of the current security and monitoring systems available till now requires manual intervention and not all of them real time and don’t support 24 hour monitoring. Where the manual intervention is, there will be little pinch for errors. The GSM based Automation system provides easy accessibility and complete automation of the system. The mobile network is on the path of continual improvement. The betterment of this system for the end user is the main aim of the project. As the mobile has become an integral part of our lives, the choice of this project seems all the more logical.
Automated system with GSM module is an effort to satisfy these events.
The block diagram show above contains blocks before the signal conditioning block and these blocks are
- Fire sensor: In this project we have used ionization type smoke detector which will continuously check for fire in the place of its installation.
- Temperature control: In this project we have used LM35 as temperature sensor which will continuously check the temperature and give its output to micro-controller through ADC. Two relays will switch the heater and the cooler respectively according to temperature preset.
- Anti theft device: In this project we have used keypad based locking system, where in the user has to enter the pre-defined password to open the door. User gets 3 attempts to enter correct password.
- Light control: In this project we have used LDR (light dependent resistor) to control the lighting of the room based on the intensity. Lights will switch ON-OFF according to some predefined intensity level.
- For GSM module we are using Nokia 3310 with an F-bus cable and it serves the purpose of GSM interface with microcontroller.
- For purpose of display we are using 16*2 LCD display which gives information about various activities happening in the microcontroller and peripheral devices.
- Micro-controller used here is Philips P89C51.
- Buzzer is used to bring to attention some undesirable event that is going to take place.
CIRCUIT DESCRIPTION & WORKING:
The above circuit shows the interfacing of the microcontroller with different
components. The components which are interfaced are LCD, ADC, Keypad, Relays, Smoke sensor, LM35.
- LCD: The LCD is connected to the Port 1 of the microcontroller. The pins P1.5 to P1.8 are the data lines. P1.2 to P1.4 are control lines. P1.2 is connected to WR (write) pin, P1.3 is connected to RD (read) pin and P1.4 to enable pin.
- ADC: ADC is used to convert the input analog signal to digital signal. It is connected to the Port 0 of the microcontroller. The ADC gets the analog signal from the temperature sensor and LDR. Timer is used to provide clock pulses to ADC used in the conversion of analog signals to digital signals.
- Keypad: Keypad is a component useful in the Anti Theft system. It is connected to the Port 2 of the microcontroller. The user uses keypad to enter the password. The user must enter the correct password in order to enter the house. The keypad used here is 3*3 keypad.
- Smoke detector: Smoke detector used is an ionization type detector. It is connected to port 2.3 of microcontroller.
- LM 35: It is temperature sensor used to constantly monitor temperature inside the room. It is connected to channel 2 of ADC 0809.
- LDR: it is used for automatic light controlling and continuously senses for change in light intensity. It is connected to channel 1 of ADC.
The system we have designed works as a real time system which keeping on scanning the current condition with the one which is preset in the micro-controller to check if there is any undesirable condition. If there is any undesirable condition it takes corrective action accordingly for e.g. if the temperature passes the set range of 20-40 and it goes down to say 18 in this case we have predefined to turn ON the cooler till temperature becomes greater than or equal to 20 i.e. bringing it back to pre defined range.
Similarly we have done it for automatic lighting where if the intensity of light falls below dome predefined range the micro-controller switches on the relay and hence the light thus compensating for fall in intensity of light.
We have used a smoke sensor to continuously monitor if the house is safe from any fire hazardous. The sensor used is an ionic type sensor whose working is explained in detail in section 3.13. The sensor checks for hazardous condition and immediately brings it to notice of the owner if there is any breakthrough.
Similar sort of arrangement is made for security by using keypad based locking of the door which acts as burglar alarm system. Only genuine user can enter the room who has the correct password. The user gets 3 attempts to enter correct password if he fails to enter it correctly the buzzer starts to ring and immediately this is brought to notice of the owner by sending him a warning message.
This is how the entire system works. For more details download the PDF (BLACK BOOK) and zip of PCB LAYOUTS for more circuit details.
The Programming part is included in Software zip. Programming is easy on PHILIPS 89C51 as it has (In System Programmable (ISP) with a boot loader. Details can be seen in datasheet.
ISP Programming software can be found at http://www.atmel.com/products/microcontrollers/8051architecture/flash_isp in_system_programmable.aspx
Program is written in Embedded C and is well commented so you can make necessary changes and it can be reused as per need. Folder doesn’t contains hex file, it can be made using Keil Compiler. Make your own and use it :).