Wednesday, November 13, 2013

Automatic Darkness-Controlled Lighting System

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Make tubelights automatically switch on at night and switch off in daytime using this automatic control system. Automatic darkness-controlled lighting system means that whenever there is darkness, light source like bulb or tubelight glows automaticly.

Fig. 1: Circuit of automatic darkness-controlled lighting system
The circuit works off regulated 5V and uses triac BT136, NOT gate 7404 and light-dependent resistor (LDR).

Operation of the circuit is simple. During daytime, low resistance of LDR1 makes pin 1 of gate N1 low and its output pin 2 goes high. This high output is applied to input pin 3 of gate N2. As a result, the output of gate N2 goes low. Hence no gate signal is applied to triac BT136 (triac 1) and it acts as an open circuit and the bulb does not glow.

Fig. 2: Pin configuration andsymbol of triac BT136
At night, the high resistance of LDR1 makes pin 1 of gate N1 high and its output pin 2 goes low. This low output is applied to input pin 3 of gate N2. As a result, the output of gate N2 goes high, which is applied to the gate of triac BT136 (triac 1) and it acts as a short circuit and the bulb start glowing.

Assemble the circuit on a general-purpose PCB and keep at a suitable place. Keep LDR1 at such a place that enough light falls on it in day-time. You can also use this circuit as a street light controller.

Shadow Detector Alarm

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This is also known as Sun up alarm, in this circuit you can set the LDR’s sensitivity by 100k potentiometer, you can set it with any lamp around your room (tube light, bulb, LED etc) by varrying the 100k potentiometer. We can also control the buzzer time by 1M potentiometer ;) 
You can Enhance this project and set the sensitivity of the LDR with a lazer light and keep it on the way of any door circuit at one side and lazer at other side of the door and a then you can make this project to buzz as soon as some one enters in a room ;)
I personally set this project in my room with sensitivity of tube light and whenever i came in and turn my room’s tube light on
Parts Required:
  1. 555 Timer
  2. 100k & 1M potentiometers 
  3. 10k, 1Mx(3), 47k
  4. 0.1mF, 0.01mF & 10mF
  5. LDR
  6. BC337 transistor
  7. Beeper/Buzzer
  8. 9v Battery Supply
   Circuit Diagram:

Bread board Arrangement:     Strip Board Version:


Simple Electronic Lock Project

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There are six (or more) push switches. To 'unlock' you must press all the correct ones at the same time, but not press any of the cancel switches. Pressing just one cancel switch will prevent the circuit unlocking. When the circuit unlocks it actually just turns on an LED for about one second, but it is intended to be adapted to turn on a relay which could be used to switch on another circuit.
Please Note: This circuit just turns on an LED for about one second when the correct switches are pressed. It does not actually lock or unlock anything!
This project uses a 555 monostable circuit.

Parts Required

  • resistors: 470, 100k ×2, 1M
  • capacitors: 0.1µF, 1µF 16V radial
  • red LED
  • 555 timer IC
  • 8-pin DIL socket for IC
  • on/off switch
  • push-switch ×6 (or more)
  • battery clip for 9V PP3
  • stripboard 12 rows × 25 holes

Stripboard Layout

Stripboard layout for simple electronic lock

Circuit diagram

Circuit diagram for simple electronic lock

Line Following Robot using BC108 Transistors

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Rookie electronicsThis is a Line Following Robot and is simplest possible electronic circuit to make your first robot. The key to success of this Circuit is totally depended upon DC geared Motor. Make sure, it is Geared motor. I also first ignored this, and I made whole circuit and fixed it in the structure of the robot, and in the end the RPM and Torque of my non-geared simple dc motors was not proper to move robot efficiently on line. In this robot I have not used any chaster wheel & Strip Sensor part, which are used almost in all line followers. This make this Robot simplest Line Following Robot Ever!! =)

Circuit Diagram:
Parts Required:
  1. BC 108 Transistors x (2)
  2. N4148 Diode x (2)
  3. 10K potentiometer x (2)
  4. LDR x (2)
  5. DC geared Motors x (2)
  6. 9V Battery
Bread Board Arrangement:
Simple LFR

One of the most disadvantage of making this circuit is that with only transistors its difficult to control speed of motors. The most common, efficient and reliable method of controlling motor’s speed is through PWM(pulse width modulation) which make the transistor rapid on/off switch. Click here to see: PWM based Line Following Robot using three 555 timers.
Step by Step Procedure to make this Circuit:

Stripboard Version:
Black Line Follower
By taking advantage of this small and easy circuit, dont miss to make a Strip board version. And by making this little easy solding circuit you will be able to reduce the structure of your robot and make it precise. Best part is, when you use these jumpers then you dont have to make the sensor strip which is commonly made and used in LFRs. I also added a ON/OFF switch in this strip board, so that I have to plug in and plug out the Battery while tuning the sensitivity of LDRs. The reason I left the space beside the circuit is for keeping the 9V battery over it =) 
The motor used in this video is a simple DC motor, I used this one just to show you the output. You have to use the DC geared motor, like ones shown in this figure. The reason for using DC geared motor is that, Geared DC motors have low RPM and high Torque. And they are commonly famous by Robot Motors =) so must Use Geared DC motors for your first robot.
In our case, the method we are using is called as “differential drive steering method”. It is Jerky and shaggy but still works fine! Here is the picture taken from which defines this differential drive method properly.
The BC108 transistors are designed to be used in their linear region so that the collector current passed through the DC motors will vary according to the base current, which is controlled by LDR+10k trimpot. And like this, DC motor will be given current according to the light intensity received by LDR.
The trimpot is used to adjust the DC motor speed, and N4148 is used to protect the BC108 from EMF generated by motor inductor when it switches off.
The material in the for the track might be different for every other roboticist. So we can always have different track’s route by simply varrrying the 10k 

Zero 2 Nine counter

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This is a sequential circuit design, Mod10 means it will count from 0-9. This would be probably your first long circuit, but don’t worry because you have a breadboard arrangement ;)
555 timer is in astable mode and it will produce a clock pulse, which is controlled by 100k potentiometer.
This clock pulse is input to 74LS90 which is a decade 0-9 ripple counter. Kindly use the 74LS90 if some one tell you that you can alternatively use 74LS93.. so let me tell you though they have same pin configuration and work same but the thing is 74LS93 is 0-15 ripple counter, so you will face some garbage outputs after counting up 0-9 which you don’t want. I tried my best to use 74LS93 and use reset pins to make it Mod 10
well, 74LS90 is a BCD counter but as we are showing a display on 7 segment so we need a driver IC
74LS90 is cascaded to 74LS47 which is a BCD to 7-segment display driver
and at last the seven outputs of 74LS47 are connected to 7 segment display.
Parts Required:
  1. 100k(potentiometer), 47k & 1k
  2. 0.1mF & 2.2mF
  3. 555 Timer
  4. 74LS90
  5. 74LS47
  6. 7 Segment Display Common Anode
  7. 9V battery with clip
Circuit Diagram:
Bread board Arrangement:
Pin Confiiguration:

Line Following Robot Using 555 timer

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