Saturday, August 14, 2010

make line follower robot (analog)-simple

LM358- Low Power Dual Operational Amplifiers


This line follower is based on the concept of light detection by a photo diode. When the photodiode is introduced with black surface, the light produced by LED is absorbed by the surface and there is no conduction in photo diode, which sets the comparator output to a positive voltage. Due to this positive voltage the transistor gets triggered by this voltage and N2907 transistor comes in on state being a NPN transistor and hence the motor turns ON.
The same mechanism rotates the another motor by the working of another photo diode.Now for the turn or to maintain its path, as soon as any photodiode gets influenced by the light reflected by the white surface the respective motor stops and the another motor automatically turns the line follower to its right path. And again the both motor starts there functioning and the line follower travels in a straight path.
Similarly, when N is replaced by 2N2222, the photodiode turns on in white light. Hence comparator produces negative output, which further triggers the transistor. This turns the motor ON. Rest of the mechanism of turning is same as above.
General Description
The LM358 series consists of two independent, high gain, internally frequency compensated operational amplifiers which were designed specifically to operate from a single power supply over a wide range of voltages. Operation from split power supplies is also possible and the low power supply current drain is independent of the magnitude of the power supply voltage. Application areas include transducer amplifiers, dc gain blocks and all the conventional op amp circuits which now can be more easily implemented in single power supply systems. For example, the LM358 series can be directly operated off of the standard a5V power supply voltage which is used in digital systems and will easily provide the required interface electronics without requiring the additional g15V power supplies.
Unique Characteristics
  • In the linear mode the input common-mode voltage range includes ground and the output voltage can also swing to ground, even though operated from only a single power supply voltage.
  • The unity gain cross frequency is temperature compensated.
  • The input bias current is also temperature compensated.
  • Two internally compensated op amps in a single package
  • Eliminates need for dual supplies
  • Allows directly sensing near GND and VOUT also goes to GND
  • Compatible with all forms of logic
  • Power drain suitable for battery operation
  • Internally frequency compensated for unity gain
  • Large dc voltage gain 100 dB
  • Wide bandwidth (unity gain) 1 MHz (temperature compensated)
  • Wide power supply range: Single supply 3V to 32V or dual supplies g1.5V to g16V
  • Very low supply current drain (500 mA) essentially independent of supply voltage
  • Low input offset voltage 2 mV
  • Input common-mode voltage range includes ground
  • Differential input voltage range equal to the power supply voltage
  • Large output voltage swing 0V to Vab 1.5V.

N2907 Transistor:

The 2N2907 also known as the PN2907 is a small PNP BJT Transistor used for general purpose low power amplifying or switching applications. It is designed for low to medium current, low power; medium voltage and can operate at moderately high speed.
It is a 1amp, 50v, 300mW transistor capable of operating up to 100 MHz it is used in variety of analog application and switching application.

Pin Out Diagram of LM358


Bottom view

Alignment of DC gear head Motors

Top View

One more by

ANALOG Line tracer

Components Used:

  • · IC LM358.
  • · N2907/2n2222 Transistors.
  • · 10k Resistors.
  • · 10k Presets.
  • · Photo Diode with LED Sensor
  • · DC Gear Head Motor.
  • · 9v power supply/battery.


  1. I have a query.....
    where is the LED used which transmits light on the surface and then this reflected light from the surface is detected by photodiode?

  2. use a set of 2 or 4 led and same number of ldr( or photo diode) in front of the bot. if 2, set them up at a distance that is a touch more than the width of the given line. if 4, add the other two along with the previous two in a square or rhombus formation(such that the new ones form two tips of one diagonal of the square, while the old ones the other two tip)....for any other query call...09883332014(soumik).....
    happy bot-ing.....

  3. photo diode is reverse or forward bias

  4. where led goes??????