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Monday, 15 March 2010

Color Sensor

Click here for the circuit diagram

Colour sensor is an interesting project for hobbyists. The cir- cuit can sense eight colours, i.e. blue, green and red (primary colours); magenta, yellow and cyan (secondary colours); and black and white. The circuit is based on the fundamentals of optics and digital electronics. The object whose colour is required to be detected should be placed in front of the system. The light rays reflected from the object will fall on the three convex lenses which are fixed in front of the three LDRs. The convex lenses are used to converge light rays. This helps to increase the sensitivity of LDRs. Blue, green and red glass plates (filters) are fixed in front of LDR1, LDR2 and LDR3 respectively. When reflected light rays from the object fall on the gadget, the coloured filter glass plates determine which of the LDRs would get triggered. The circuit makes use of only �AND� gates and �NOT� gates.
When a primary coloured light ray falls on the system, the glass plate corresponding to that primary colour will allow that specific light to pass through. But the other two glass plates will not allow any light to pass through. Thus only one LDR will get triggered and the gate output corresponding to that LDR will become logic 1 to indicate which colour it is. Similarly, when a secondary coloured light ray falls on the system, the two primary glass plates corres- ponding to the mixed colour will allow that light to pass through while the remaining one will not allow any light ray to pass through it. As a result two of the LDRs get triggered and the gate output corresponding to these will become logic 1 and indicate which colour it is.
When all the LDRs get triggered or remain untriggered, you will observe white and black light indications respectively. Following points may be carefully noted :
1. Potmeters VR1, VR2 and VR3 may be used to adjust the sensitivity of the LDRs.
2. Common ends of the LDRs should be connected to positive supply.
3. Use good quality light filters.
The LDR is mounded in a tube, behind a lens, and aimed at the object. The coloured glass filter should be fixed in front of the LDR as shown in the figure. Make three of that kind and fix them in a suitable case. Adjustments are critical and the gadget performance would depend upon its proper fabrication and use of correct filters as well as light conditions

Magnetic proximity sensors

Click here for the circuit diagram

Here is an interesting circuit for a magnetic proximity switch which can be used in various applications.
The magnetic proximity switch circuit, in principle, consists of a reed switch at its heart. When a magnet is brought in the vicinity of the sensor (reed switch), it operates and controls the rest of the switching circuit. In place of the reed switch, one may, as well, use a general-purpose electromagnetic reed relay (by making use of the reed switch contacts) as the sensor, if required. These tiny reed relays are easily available as they are widely used in telecom products. The reed switch or relay to be used with this circuit should be the �normally open� type.
When a magnet is brought/placed in the vicinity of the sensor element for a moment, the contacts of the reed switch close to trigger timer IC1 wired in monostable mode. As a consequence its output at pin 3 goes high for a short duration and supplies clock to the clock input (pin 3) of IC2 (CD4013�dual
D-type flip-flop). LED D2 is used as a response indicator.
This CMOS IC2 consists of two independent flip-flops though here only one is used. Note that the flip-flop is wired in toggle mode with data input (pin 5) connected to the Q (pin 2) output. On receipt of clock pulse, the Q output changes from low to high state and due to this the relay driver transistor T1 gets forward-biased. As a result the relay RL1 is energised.

Super simple stepper motor controller

Click here for the circuit diagram

The circuit shown above can be used to control a unipolar stepper motor which has FOUR coils (I've swiped it off an old fax machine). The above circuit can be for a motor current of up to about 500mA per winding with suitable heat sinks for the SL100. For higher currents power transistors like 2N3055 can be used as darlington pair along with SL100. The diodes are used to protect the transistor from transients.

Activating sequence:-

Inputs

Coils Energised

D0

D1

0

0

A,B

0

1

B,C

1

0

C,D

1

1

D,A

To reverse the motor just reverse the above sequence viz. 11,10,01,00.

Alternately a 2bit UP/DOWN counter can also be used to control the direction , and a 555 multi-vibrator can be used to control the speed

Automatic Speed Controller for fans & Coolers

Click here for the circuit diagram

During summer nights, the temperature is initially quite high. As time passes, the temperature starts dropping. Also, after a person falls asleep, the metabolic rate of one�s body decreases. Thus, initially the fan/cooler needs to be run at full speed. As time passes, one has to get up again and again to adjust the speed of the fan or the cooler.The device presented here makes the fan run at full speed for a predetermined time. The speed is decreased to medium after some time, and to slow later on. After a period of about eight hours, the fan/cooler is switched off.Fig. 1 shows the circuit diagram of the system. IC1 (555) is used as an astable multivibrator to generate clock pulses. The pulses are fed to decade dividers/counters formed by IC2 and IC3. These ICs act as divide-by-10 and divide-by-9 counters, respectively. The values of capacitor C1 and resistors R1 and R2 are so adjusted that the final output of IC3 goes high after about eight hours.The first two outputs of IC3 (Q0 and Q1) are connected (ORed) via diodes D1 and D2 to the base of transistor T1. Initially output Q0 is high and therefore relay RL1 is energised. It remains energised when Q1 becomes high. The method of connecting the gadget to the fan/cooler is given in Figs 3 and 4.

Car anti theft wireless alarm.

Click here for Circuit Diagram.

This FM radio-controlled anti- theft alarm can be used with any vehicle having 6- to 12-volt DC supply system. The mini VHF, FM transmitter is fitted in the vehicle at night when it is parked in the car porch or car park. The receiver unit with CXA1019, a single IC-based FM radio module, which is freely available in the market at reasonable rate, is kept inside. Receiver is tuned to the transmitter's frequency. When the transmitter is on and the signals are being received by FM radio receiver, no hissing noise is available at the output of receiver. Thus transistor T2 (BC548) does not conduct. This results in the relay driver transistor T3 getting its forward base bias via 10k resistor R5 and the relay gets energised. When an intruder tries to drive the car and takes it a few metres away from the car porch, the radio link between the car (transmitter) and alarm (receiver) is broken. As a result FM radio module gene-rates hissing noise. Hissing AC signals are coupled to relay switching circ- uit via audio transformer. These AC signals are rectified and filtered by diode D1 and capacitor C8, and the resulting positive DC voltage provides a forward bias to transistor T2. Thus transistor T2 conducts, and it pulls the base of relay driver transistor T3 to ground level. The relay thus gets de-activated and the alarm connected via N/C contacts of relay is switched on. If, by chance, the intruder finds out about the wireless alarm and disconnects the transmitter from battery, still remote alarm remains activated because in the absence of signal, the receiver continues to produce hissing noise at its output. So the burglar alarm is fool-proof and highly reliable.

water level controller

Making double layer PCBs at home

LIST OF MICROCONTROLLER BASED PROJECTS AT-89C51 BASED

MICROCONTROLLER AT-89C51 BASED METRO TRAIN
PROTOTYPE USING LCD: The project shows resemblance as
you are traveling in metro train. It will display three station at LCD
and a stepper motor to rotate clock or anti-clock wise.(with or
without vehicle)
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MICROCONTROLLER AT-89C51 BASED VOTING
MACHINE: The voting system for four candidates with memory
backup to restore the results to be viewed with password.
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MICROCONTROLLER AT-89C51 BASED TEXT EDITOR
CUM MOVING MESSAGE DISPLAY: The project comprises 30
keys to edit any message in English.One can restore the message in
memory IC. The 16 characters at a time can be view in running
mode.
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MICROCONTROLLER AT-89C51 BASED FULL FUNCTION
STEPPER MOTOR CONTROLLER :The project will operate
the stepper motor in almost all modes viz. clock, anticlock, speed
and frequency control with time duration for both directions.
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MICROCONTROLLER AT-89C51 BASED WATER LEVEL
CONTROLLER CUM MOTOR PROTECTOR: It can indicates
the level and control the water pump at top level filling.
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MICROCONTROLLER AT-89C51 BASED SIMPLE
STEPPER MOTOR CONTROLLER: A simple stepper motor
controller circuit with direction change only.
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MICROCONTROLLER AT-89C51 BASED CALL
MONITORING SYSTEM: An economical room monitoring
system for eight channels and with buzzer indication and seven
segment display provides feed back to the caller.
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MICROCONTROLLER AT-89C51 BASED INDUSTRIAL
FAULT MONITORING SYSTEM: It will check the faults like
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over temperature, humidity, power failure, over voltage etc. at the
monitor. One can link this with RF data encoders/decoder for
wireless link.
MICROCONTROLLER AT-89C51 BASED SAFETY GUARD
FOR BLIND: This embedded safety guard system with voice
processor to play the prerecorded message in case of any obstacle is
detected by the blind person.
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MICROCONTROLLER AT-89C51 BASED FASTEST
FINGER FIRST: Useful for Quiz games, dumb charades. It
display the player no. along with the beep for seven players.
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MICROCONTROLLER AT-89C51 BASED TEMPERATURE
METER: It will display the room temperature on LCD and one can
set the desired value to indicate the alarm or control at a desired
teperature. It uses an ADC to interface with LM-35 sensor.
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MICROCONTROLLER AT-89C51 BASED INFRARED
REMOTE CONTROLLED SWITCH BOARD: (4
APPLIANCES):One can operate (on/off) four electrical devices
with TV remote syncronised with circuit independently.
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MICROCONTROLLER AT-89C51 BASED RANK DISPLAY
SYSTEM FOR RACE & QUIZ COMPETITION WITH LCD:
It can resolve the time difference(may be few milliseconds) and
indicate the correct ranking between the individuals denoted A to H
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MICROCONTROLLER AT-89C51 BASED AUTO GEAR
SHIFTING SYSTEM: The circuit shows the demo of auto shifting
of gears using stepper motor with the change in speed of vehicle.
One can change the speed of DC motor as actual vehicle running
wheel.
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MICROCONTROLLER AT-89C51 BASED AUTO SPEED
LIMITER/GOVERNER WITH AUTO BREAKING: The
project is to read the rpm of a automobile and according to that it
limits the speed as Speed Governor. One can change the speed with
variable control.
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MICROCONTROLLER AT-89C51 BASED LINE
FOLLOWER ROBOT: A Robotic car that follows the black line
at the floor area based on IR sensors with transmitters and receivers.
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MICROCONTROLLER AT-89C51 BASED ‘YES MASTER’
FOLLOWER : A robotic car that follows his master who is
sending an IR transmission always.
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MICROCONTROLLER AT-89C51 BASED OVER CURRENT
RELAY: The circuit senses the over current and limit the relay .
MICROCONTROLLER AT-89C51 BASED VOLTAGE/
POWER FACTOR / FREQUENCY METER: The project check
the electrical input factors as multifunction meter.
MICROCONTROLLER AT-89C51 BASED DATA DRIVEN
DISPLAY : It shows how you can use the controller to drive an
LCD module and in turn use it as a handheld device to set the
parameters of the control unit through RS-232 serial link. It
comprises two units – Control unit and a LCD module unit. Any
wired or wireless link like IR can be used to display the unit.
MICROCONTROLLER AT-89C51 BASED TELEREMOTE
SWITCH: The project can is to remotely control four electrical
devices using a landline or mobile to be connected with the circuit.
MICROCONTROLLER AT-89C51 BASED TRIPPING SEQUENCE
CODE INDICATOR: The electrical utility project that indicates the MCB
tripped on the first if short circuit arises and the sequence for total eight
areas.
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MICROCONTROLLER AT-89C51 BASED RFID ATTENDENCE
MONITOR: The project will show the names of person who had pressed
the RFID key on LCD. One can use DATA encoder/decoder circuit.
MICROCONTROLLER AT-89C51 BASED LED LIGHT CHASER: With
the help of this one can display 5 different effects for running lights for 24
lights. One can change the speed also.
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