Help with Line Follower Robot

Discussion in 'General Electronics Chat' started by amruth11, Mar 5, 2012.

  1. amruth11

    Thread Starter Member

    May 24, 2011
    Hi there, i came up with a circuit for a line follower robot which follows a black line. In the circuit i have used a voltage divider using a LDR as the sensor which goes through a 50k variable resistor to the base of a TIP 122 transistor and then to the motor from there. The 50k between the base and the sensor is for regulating the voltage going to the base and to control motor speed and sensitivity. There is another 50k between 2 LEDs and VCC to control brightness of the LEDs. The robot works from 6v to 9v. I have attached a diode to the motor but havent mentioned it in the circuit. I have attached the circuit but really sry for the bad drawing cause i did it in paint. I would like to know is there any mistake in the circuit and whether any changes can be done. Thx in advance and waiting eagerly for replies. :)
    Last edited: Mar 6, 2012
  2. Potato Pudding

    Well-Known Member

    Jun 11, 2010
    Your description might be made to work, in fact I have seen similar designs elsewhere.

    Your drawing shows the transistors connected wrong = not at all how you described. You should want to educate yourself on how transistors are used. Look through the information available on this site.

    Two more circuits that you will need on each side I think.

    The design would benefit from signal amplification of the LDR voltage level.

    Your motors will work better and more efficiently if you use a pulse width modulation system to control them.

    Linear control of the type you want to use with the power transistors can cause plenty of problems.

    A Line Follower ROBOT is a fairly advanced project, so you might want to come back to this after you have built some simpler circuits for practice.
  3. amruth11

    Thread Starter Member

    May 24, 2011
    Hi, thx for the advice, the transistors are connected correctly, they are shown like that cause the TIP 122 B=left C=middle E=right when seen from the front. Thats why i drew it like that. here is the datasheet

    I dont want to use PWM for the motors because i want to keep it simple as much as i can but i know that the efficiency is reduced.

    I dont get the linear control u said can u explain it to me. And the other circuit, which amplification will be better op-amps or transistors.
    Thx for the help. :)