Easier Approach to Electronic Projects

LFR using BC108 Transistors


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!! =)

 

Parts Required:

  1. BC 108 Transistors x (2)
  2. N4148 Diode x (2)
  3. 1M potentiometer x (2)
  4. 1K Resistors x (2)
  5. Bright White LEDs x (2)
  6. LDR x (2)
  7. DC geared Motors x (2)
  8. 9V Battery
          




Circuit Diagram:

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 emicro.com 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 Trimpot


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