The Simplest Line Follower [Updated]


Alright! First robotics project on the site :-)! This is a robot I made for a workshop, which I conducted under my college’s IEEE chapter. The robot is the simplest line follower you can make and I feel everyone who wants to start with robotics and does not know how to, should begin with this one. It does not need a microcontroller or any complex digital logic circuit. So you don’t have to worry about writing code in C and Assembly. You don’t need to worry too much about the design either. This robot is based on another line follower I had learned at a workshop (conducted at M. S. Ramaiah Institute of Technology, Bangalore). There is a difference of just one IC. The change was due to that fact that my robot uses 12V motors while their’s used 5V motors (with a gear system). Basic idea remains the same.
Note: If you are interested in a microcontroller based line follower I suggest checking this out http://www.kmitl.ac.th/~kswichit/LFrobot/LFrobot.htm
Before we begin. lets see the robot work!
Notice that the track is very simple.

Construction

Alright. Lets first look at the circuit for the robot (Click to enlarge).

Here are the parts you will need:
Sr. No. Part Description
1. R1, R2 220Ω 1/4W Resistors.
2. RV1, RV2 20KΩ Potentiometers (Use presets)
3. LDR1, LDR2 Light Dependent Resistors
4. LED1, LED2 White LEDs
5. V1 Use four 1.5 V batteries. With this you will get 6V. Alternatively you can use four 1.2V batteries to get 4.8V
6. V2 Use a 9V battery
7. L293D The L293D is a motor driver. See http://focus.ti.com/lit/ds/symlink/l293.pdf for the datasheet. Also use a 16-pin IC base if you are soldering the circuit on a PCB.
8. M1, M2 DC Motors. I used 200rpm DC motors. (12V, 2A)
9. Breadboard or PCB A general purpose PCB can be used to solder the components. Alternatively you can also use a breadboard. I’ve used a PCB
The circuit can be constructed on a bread board or soldered on to a general purpose PCB. Make sure that the wires connecting the LEDs and LDRs are long enough since they need to “look” at the line which the robot will follow. Solder the 16-pin IC base to the PCB and then fix the L293D to that.
Here’s a photograph of the circuit excluding the LEDs and LDRs:
The two connectors on the left are for the motors. I did not solder the connections to the motors directly. Instead, I used 2-pin female RMC connectors for the motors. On the PCB I connected the outputs on the L293D to berg strips (use two pairs of pins – one for each motor). With this you can change the polarity of the motors if needed.
Once the circuit is done, you will need to put the motors, wheels and circuits together. Here’s what you will need:
  1. Chassis – I used a base from a Meccano Set. You could choose any appropriate material you like (maybe a thin sheet of wood).
  2. Wheels (see the photograph of the robot below).
  3. Caster Wheel (spherical) – This is a free moving wheel fixed to the front of the robot.
  4. Spacers.
  5. Clamps – To fix the motors to the chassis.
In addition to this, I covered the LEDs and LDRs using plastic LED holders. This protects the LDRs from the light of the room (LDRs are extremely sensitive). Next I paired an LED with an LDR and taped the two together. This is what the sensor section looks like:
The sensors were mounted using two cardboard strips. I made two grooves on each strip – one for each LED-LDR pair.
Fix the motors using clamps and then fix the wheels on to them. Next place the PCB on the top of the base. If you are using a metal base, make sure you insulate the bottom of the PCB with some tape. Fix the caster wheel at the front using spacers between the chassis and the wheel. Finally place the batteries and you’re done.
Here are photographs of the completed robot:
It shouldn’t take you more then a few hours to finish if you are not new to soldering components. In the workshop I conducted, there were participants who were soldering for the first time and they were able to complete the robot successfully in 9 hours (spread over two days).

How Does It Work?

First, lets understand how the sensors work. For that, we need to first look at how an LDR changes its resistance depending on how much light falls on it.
The LDR is basically a semiconductor. If you have studied about semiconductors, you will be familiar with the Band Model. We know that a semiconductors crystal has two main energy bands where electrons (or holes) can exist. These are the valence band and the conduction band. The electrons must exist in the conduction band for conduction to take place. However, an Energy gap prevents electrons from moving to the conduction band freely. The electrons need energy to jump to the conduction band. This energy is usually given in the form of electrical energy i.e. by connecting the semiconductor across a voltage source. The energy gap and the number of electrons in the conduction band define the resistance of the material. When light falls on an LDR, the electrons gain energy from this light and move into the conduction band causing the resistance to decrease.
Thats how the LDR works. Light falls on the LDR when light from the LED is reflected off the white surface. Little or no light falls when the sensors are on the black line since reflection won’t take place. Now lets see how we can use this as a sensor. Take a look at the circuit again. The LDR and the potentiometer form a voltage divider system:
The voltage at the point between the potentiometer and LDR is connected to the L293D IC. Lets look at two cases.
  1. Case 1: When the sensor is placed over the black line, no light falls on the LDR. It thus has a very high resistance, typically in the MΩ range. Suppose the resistance of the LDR is 1MΩ. Thus the voltage at the node is:
  2. Case 2: When the sensor is placed over the white line, light falls on the LDR. Therefore its resistance is quite low, possibly 1 or 2Ω. Thus the voltage at the node is equal to:

Hence the sensors give a Logic 0 when they are above the black line and a Logic 1 when on the white surface.

Finally, lets look at the L293D IC. Here’s a schematic of the chip:
Ignore the insides of the chip. Lets look at what the pins are for. The pins EN1, IN1, IN2, OUT1 and OUT2 control one of the motors while the pins EN2, IN3, IN4, OUT3 and OUT4 control the other. Here’s how it works -
  1. EN1 and EN2 are enable pins. Setting these to Logic 1 (i.e. 5V) enables control to the motor. If these are kept at Logic 0, the motors will not run.
  2. IN1 and IN2 control the motors direction of rotation. If IN1 = 1 and IN2 = 0, the motor will rotate in one direction and if the inputs are switched, the motor will rotate in the opposite direction. The control signals to the motors are given through OUT1 and OUT2. If IN1 = IN2 = 0 then OUT1 and OUT2 will both have 0V and the motor is free to run. This means that if the robot is moving while this signal is given, it will still move due to its inertia. However, if IN1 = IN2 = 1, OUT1 and OUT2 will both have 10V and the motor is prevented from rotating. This can be used for a braking action.
  3. The pin Vcc is connected to 5V and Vss is connected to 10V. The latter is used to drive the motor. The L293D has four ground connections.
Suppose EN1, IN1, IN2, OUT1 and OUT2 control the left motor and EN2, IN3, IN4 and OUT3 and OUT4 control the right one. Since the robot isn’t going to perform any complicated line following, we’ll make sure that the motors always cause the robot to move forward. For this we have set IN1 and IN4 to Logic 1 and IN2 and IN3 to logic 0. Connect the EN1 and EN2 pins to the voltage divider system formed by the LDRs and the potentiometers. The left sensor is connected to EN1 while the right sensor is connected to EN2.
Having understood how one can use an L293D, lets see how the robot actually follows a line. When the black line turns towards the right, the right sensor moves on the black line. This causes the sensors to give a Logic 0 at EN2 causing the right motor to stop. The left motor continues running. This causes a right turn. The turning causes the robot to align itself on the line again and now both sensors will be on the white surface and both motors will now run causing the robot to move forward.
Thats how this line follower works. Simple isn’t it? Try it yourself and feel free to comment if you have any questions, suggestions or videos/pictures of your own robots. I have attached the presentation I made for the workshop (check the sidebar on the right). Hope you have fun building it :)

Update 1:

Here is what you do if you want the robot to work on a white line – You add a NOT gate before sending the signal to the chip. So the schematic will change to the following:

 Note the two NOT gates (triangles with a small circuit at the apex). Here is how this works. A NOT gate basically reverses it’s input. If you give a value of 5V, the gate will output 0V. Similarly giving a value of 0V will output a value of 5V. So in this case, the motors will move when the sensors are on the black surface. The motors will stop when the sensors are over the white line (that is, reverse/NOT of the original circuit).

Update 2:

I have made an improved version of this robot. This one requires you to make your own PCB. It is also a stronger design. Check it out here: http://wp.me/pRhUf-d0

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125 Responses to The Simplest Line Follower [Updated]

  1. Pingback: Best links for Begginers!!!! « Manoj Kumar S

  2. Pingback: Finally, Details on Obstacle avoiding Robot. « Manoj Kumar S

  3. nannu says:

    nice explanation but i want some more explanation in ic connection thanks

  4. Ashwith says:

    Can you be more specific on what kind of explanation you want? Isn’t this self explanatory?
    http://ashwith.files.wordpress.com/2010/03/proteus-schematic11.jpg

    • nannu says:

      the ic is 16 pin and 14 pin is connected. which 2 pin is not connected
      and plz explane every pin of ic’s connection plz sir plz i bought every things for this project. plz

      • Ashwith says:

        Pins 4, 5, 12 and 13 are connected to ground. The two “GND” connections shown in the circuit diagram actually refer to these four pins. So there are 16 connections. Details on each pin of the IC is well explainied in the datasheet:
        http://focus.ti.com/lit/ds/symlink/l293.pdf

        I’ve explained whatever pins are relevant in the blog post.

        Please comment without using short forms like “plz” and you don’t have to refer to people around the internet as “sir”.

  5. nannu says:

    sorry for short forms. the upper ic numbering and ” focus .ti.com……” ic numbring is different
    please explane with diagram . this project so important for me i have to complete in three days i hope you explane me please.

  6. nannu says:

    i have completed this but moter is not moving when it is on the surface and when i put in the air its working i have 12volt dc moter its rpm is 2400. the 200 rpm moter is not avaiable

    • Ashwith says:

      The RPM is too high. Your motor must be having very low torque, You need motors with gears. The 200 rpm motors I have are actually of high rpm. But they have gears inside to increase torque. You get such motors in vega robo kits. If you’re from mumbai or nearby, check out lamington road. If you’re from Bangalore, you’ll find motors in SP road.

  7. Nat says:

    Hello I dont see a ground connection in your circuit schematic,(assume bottom horizontal line).
    How did you connect ground on PCB ?

    • Ashwith says:

      Hi Nat,

      Well I guess I forgot to put the ground sign there. The ground connection is the wires where the GND pins of L293D are connected. They all go to the negatives of the batteries (both 9V and 5V sources’ grounds are shorted).

  8. Jyothinath says:

    Can i please get the pcb layout of this circuit ??

    • Ashwith says:

      Hi Jyothinath

      I did not make a PCB for this. There are general purpose PCBs available (whose layout is similar to a bread board). Thats what I used.

      • Jyothinath says:

        ok..but my software doesnot have this l293d for taking the layout. Can u pls try to get its simple layout ..?

      • Ashwith says:

        I’m not sure I can find it out. What software are you using? Maybe you could look at the datasheet and create your own footprint for the l293d based on the dimensions given.

    • msharmavikram says:

      you can create your own label in eagle if you are using that software for pcb design.

      • Ashwith says:

        How do I print it on to the PCB?

      • msharmavikram says:

        you have create both label and schematic. Eagle supports both. After creating the label, create schematic separately. Then create your own lib and attach both together. however make sure that pin description match. Suraj know perfectly. he can tell how to do it for smd to…

      • Ashwith says:

        I managed to do something different for now.
        For the labels, I made only the required layers visible for the PCB design. Then I printed the mirror image. I ironed this on the plastic side of the PCB. It looked pretty neat. :) I will try this next time.

  9. SaNgEeTh says:

    Hi,i’ve succesfully cmpletd d lfr basd on ur ckt diagram..nw i want to use an obstacle sensr in it.d sensor i usd is the amplified versn here: http://www.societyofrobots.com/schematics_infraredemitdet.shtml.cud u pls modify dat ckt such that its o/p switches btwn high and low,so that i can interface it with my lfr.pls do reply

  10. hardik sharma says:

    i didn’t understand that on which ground i have to connect vs

    • Ashwith says:

      Hi Hardik
      Allow me to clear one point first. Ground is just our reference for zero potential. All that matters is that we use the same reference throughout our circuit. In this case, the negative terminals of all voltage sources is considered as this reference.
      Now lets look at the circuit. “Vs” is a 10V source. You can see that this is the source “V1″ (the one on the right). The positive terminal of this source has been connected to the L293D IC’s Vs input. The negative terminal goes to the long horizontal line at the bottom. You can also see that the 5V voltage source’s negative (The one on the left) terminal goes to this horizontal line. So this becomes my zero potential reference i.e. ground. Hope this clears things up. Let me know if you have any more doubts and I’ll be glad to help :)

  11. hardik sharma says:

    can you give me a simple circuit of line follower using phototransistor and with obstacle detection without using microcontroller andalso a h-bridge driver but using any dual camparator ic.

  12. hardik sharma says:

    i want a line follower using comparator ic

  13. SS says:

    But what happens if there’s some kind of overlaping?

    • Ashwith says:

      This robot cannot handle that. It’ll probably go straight ahead at the intersection. This is meant to be a very very basic robot for a simple track.

      • SS says:

        Well, I think I can solve that problem. Last question, what happens if EN1 = EN2 = 0? I mean, would the motors be in “brake” mode or in “free to run” mode?

      • Ashwith says:

        Free run mode. Setting an EN to 0 will disable the amplifiers (see the diagram for L293D). This in turn will cause INs to have no effect.

  14. SS says:

    BTW, isn’t there a mistake with the LEDs and the LDR in the schematic? I mean, shouldn’t the current flow into the anodes?

  15. sushant says:

    we hav 2 pair led-ldr 2gether…so is der need 2 prevent led’d light 2 fall on ldr???
    ie, do we hav to create a partition betn led n ldr???

    • Ashwith says:

      I don’t think a partition between the LED and the LDR is necessary. The LED should give a directed beam of light so it won’t fall on the LDR unless it reflects off the white surface. You still need to cover the LDR however. This because, there will be light in the room and this will cause problems.

  16. sushant says:

    wht shud b potentiometer values???
    i mean whr shud v keep d potentiometer knob???

    • Ashwith says:

      Hi Sushant,

      The values are 20k. These are not the big potentiometers that most are familiar with. What I’ve used are called presets. Its the blue and white component you see in the first picture. You can solder it directly to the PCB. Ask for 20 kilo ohm presets at your electronics store.

  17. sushant says:

    how to control dc motor rpm to 200???
    it has abt 23000 rpm…

  18. sushant says:

    i got dat 200 rpm 12 v dc…
    nw i want 2 ask 1 thing…
    preset hav 3 terminals…so which 2 v hav 2 use???
    another thing…
    frm whr does pin no start in L293d???
    lastly, does polarity matters in d case of dc motor???

  19. sushant says:

    arey yaar…
    i hav made whole ckt…
    bt nw its nt working
    even led doent light up…
    when i connect batteries, jst one motor rotates…irrespective of led ldr…
    plz help me out…

    • Ashwith says:

      The LEDs should should light up. Its just a simple circuit where the battery is connected to the LEDs through a resistor.

      1. Check if the polarity of the LEDs is correct.
      2. Use a multimeter to check voltages at various part of the circuit:
      a. The LED anode should have 5V
      b. Check the following voltages at L293D:
      i. Pin1 = 5V
      ii. Pin2 = 0V
      iii. Pin10 = 5V
      iv. Pin15 = 0V
      v. Pin16 = 5V
      vi. Pin8 = 9-10V
      3. Also check for short circuits that may of happened while soldering.

  20. sushant says:

    i think frm ckt diagram,
    it seems dat pin 2 shud hav 5 volts w.r.t ground…
    nd all d others also shud b reversd 0 instead of 5
    isnt it???

    • Ashwith says:

      Sorry. I didn’t check my circuit correctly. I counted Pin1 as “IN1″. Here is the correct set:

      Pin2: 5V
      Pin7: 0V
      Pin10: 0V
      Pin:15: 5V

      • sushant says:

        ohhhkkk…with ur help i hav made d ckt…
        der were few loose connections…
        bt finally got it…
        working properly…
        jst remain 2 assemble as a car…
        thnk u so much…
        i want more projects…
        i saw cookie, bt it seems very hard…
        can u suggest me…

      • Ashwith says:

        Its not all that hard. Give it a shot :-)

  21. sushant says:

    cant we make some mods in dis ckt only, for edge follower or obstacle avoider???

    • Ashwith says:

      The edge follower requires a program. This circuit doesn’t use a mirco controller so you cannot write a program for it. An obstacle avoider requires a program as well.

  22. sushant says:

    bro i hav 1 problem…
    ckt is working properly, bt im not able to build led-ldr pairs…
    i mean sensors are not working properly due light problem…
    plz help me out…
    aft dis my project will b ready…

  23. arsalan says:

    yr ye circuit white line sense kare ga ya sirif black kare ga….plz tell me buddy…..

    • Ashwith says:

      This circuit will work only on a black line.

      For a white line you need only a simple modification. Don’t connect the LDR circuit directly to the L293D chip. Pass it through a NOT gate.

      • Xavier Romagosa says:

        There is a simpler solution. Swap the position of LDR and potentiometer, and you will just have the reverse signals. (LDR to ground, pot to +5V)

  24. arsalan says:

    i dnt understand plz tell me cleraly …plz

  25. arsalan says:

    yr plz bata do easy wordings main mujha karna hai kam white line sense karwane hai…..

  26. arsalan says:

    thanks buddy……

  27. Pingback: The Simplest Line Follower – Upgraded! « Ashwith

  28. arsalan says:

    hi ashwith bro…..plz tell me kah ap ne jo white line follower circuit diagram hai us main jo not gate use kya hai woh diode hai ya IC……sign tho diode ka bana hua hai……

  29. arsalan says:

    k but ic bohat garam ho jati hai…..or phir kharab hojati hai…..why

  30. arsalan says:

    l293d getting hot…..not 7404

  31. V.Rahul says:

    sir how do i identify where to connect which pin in the ic and can i use a 9volt battery in V1 and if i so can i use a single battery with both the one and should the motor should be only 12V can i use a toy motor
    this is very important for me please give me exact details of the pins of the ic

  32. faraz shahid says:

    where is the third pin of the potentiometer is connected…

    is it ground?

  33. faraz shahid says:

    The gear motors are very expansive ,,,is there any way to use simple dc motors ………

    • Ashwith says:

      You’ll need to use gears. The simple DC motors do not give enough torque to push the robot. If you use toy motors, you’ll need to build your own gears. Either way, gears are needed.

  34. Rahul says:

    hey Ashwith,
    I am Rakesh’s your classmate’s brother Rahul.
    i had a doubt in the circuit diagram,should pin 15 and pin 2 be connected to pin 16.And should all the components like R1,LDR1,R2,LDR2 be connected to pin 16.please help.I have finished the circuit but i have only this doubt, if you help me in this it will be over.please answer as soon as possible

    • Ashwith says:

      Hi Rahul,

      Look at the circuit diagram carefully again. Those components are all connected to the 5V supply on the left. The thing is, pin 16 is also connected to 5V. That is why you see all of them connected like that.

      Similarly, pins 4, 5, 12 and 13 are ground connections. In this case, you need to connect the negative terminal of the battery to these pins. The remaining components also need to connected to ground so that is why you see them all connected together. I should I have used a GND symbol while making the circuit.

      Was I able to clear your doubts?

  35. Rahul says:

    should all the components like LED,RV1,RV2 be connected to pin 4,5,12,13. please help.

  36. Mitash says:

    your project is a stupid project which does not work and i tried it from another site and it worked.
    DONT DELETE THIS POST because others should know it does not works

    • Ashwith says:

      Mitash,

      As you wish, I won’t delete your comment however I must respectfully disagree with you.

      1. I designed this robot based on another one which I learned at a workshop. I then taught my design to 25 teams at another workshop where 17 teams got it working straight away. This workshop was conducted again two more times with higher success rates. The design of the robot has been the same. I’ve even posted about these workshops. The robot works. I have a working version at home.

      2. There could be mistakes in my post. If you look through the comments, there have been people who were kind to point out errors and I’ve fixed them immediately.

      3. I do appreciate constructive criticism but what you’ve done is plain rude. If you have nothing useful to say please be respectful at the very least. I don’t get paid for writing these posts. I do this for free so that I can share what I learn.

      I’m glad you managed to get it to work either way. That’s what really matters in the end.

      Best Regards
      Ashwith

  37. Satish M says:

    when are u going to do digital power power amplifier in fpga…
    btw good article…

  38. prachi says:

    nice project, but can i get report on this project?

    • Ashwith says:

      Yes of course you can! :-) I used a metal chassis too. Just make sure it’s insulated properly so that the PCB’s doesn’t touch it directly.

  39. sushil says:

    Nice work !
    but i am not able to understand the use of preset or potentiometer. Why cant we use just a 20 k resistor?

    • Ashwith says:

      The potentiometer is used to vary the threshold of the comparator. This threshold sets the range of the sensor. That’s why we use a potentiometer. It’s needed for fine adjustments.

  40. gautham says:

    keepppppppppppppppppppppppp ittttttttttttttttt upppppppppp aswith you are great robotic boyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy good jobbbbbbbbbbbbbbbb

  41. Wayne says:

    Hi Ashwith

    This might be a silly question but why the motor must be 200rpm,12v,2A?

    Thanks

    • Ashwith says:

      No question is silly! :-)

      2A because those are the motors that were available so I picked them. I didn’t want to use toy motors as those would require some gears for sufficient torque and complicate things a little. I wanted this to be as simple as possible. My target audience were students in their first year of engineering. I picked 200 rpm because the higher one was 500, which was too fast for me – the robot would overshoot the line. It does even with these 200 rpm motors if I’m not careful. For the workshop (I built this robot for a workshop), we actually put 100 rpm motors in the kits to make it easier for the participants.

  42. Ankit Maurya says:

    Hi, Ashwith
    I made It very easlly 1st time and its work properly.
    But i want to know the circuits of IC 7404.
    How it work as a NOT gate.??
    Please…

    • Ashwith says:

      Ankit,

      There are a couple of way to create a NOT gate. Search for “BJT inverter”, “FET inverter” and “CMOS inverter”.

      • Ankit Maurya says:

        ohh, Yes I perform these Experiment BJT & CMOS Inverter In my Last Semester.
        I understand Clearly.
        Thanx Ashwith For Your suppourt.
        Thanku Very Much :) :) .!!

  43. Abhishek says:

    hey Aswith,
    I dnt want the wheel to stop when the sensor senses the black line..instead I want d wheel to rotate backwards so that the robo turns instantly with zero degree rotation…I knw it can be done using ic 7404..but how???

    • Ashwith says:

      It’s simple. I won’t describe everything here (experimenting is a LOT more fun and I don’t have an L293D to test right now).

      In the robot, I have said that we need to connect the IN1, IN2, IN3, IN4 inputs of the L293D to fixed values. Next we connect the sensors to the EN12 and EN34 pins to start and stop the motors when needed.

      Your requirement needs a different approach. You need to connect the sensors to IN1, IN2, IN3 and IN4 with some logic. I don’t think just 7404 will be enough. You’ll probably need AND/OR gates as well. I suggest that you write down a truth table and use the Boolean expression you get out of it.

      • Abhishek says:

        thnx fr d reply..but i found d solution within hours of posting here..it was simple..nd ya we dnt need AND/OR gate fr it..nly not gate is sufficient..:)

  44. sivabalan says:

    i’v 1 doubt wt program used in L293

  45. Srikanth Karney says:

    I want the connecting details of preset of 20k which u have used which pin I should leave and which pins of potentiometer should I connect can u pls mail me the details

    • Ashwith says:

      The preset is nothing but a potentiometer. All I’m doing is using it as a variable resistor. To do this, I use the middle pin and one of the other pins.

      The point of this part of the circuit is to have a voltage divider which you can ‘tune’. The voltage divider consists of an LDR and the preset. You can alter the preset to (slightly) tweak the voltage across the LDR when there is light and when there isn’t.

  46. HARMANAN says:

    CAN U PLEASE PROVIDE A BLOCK DIAGRAM FOR THIS WITHOUT INVOLVING MICROCONTROLLER

    • Ashwith says:

      This project doesn’t use a micro controller.

      • harmanan says:

        So can u please provide block diagram

      • Ashwith says:

        The block diagram should be simple enough. I would just use three blocks: Sensors > Logic + Motor Driver > Motor

        Usually the logic and motor driver steps would be separate but the L293D chip performs both functions.

      • harmanan says:

        Can u pls Provide the description of block diagram too in 8-10 lines.As I m in 12th I need this its a 40 marks project
        Sorry to give u problem

      • Ashwith says:

        I’m sorry I cannot do that for you. A project is meant for you to learn so do it yourself. In class 12th I built and documented my project on my own. The purpose of my tutorials is to help learn, not help do assignments and projects for you.

  47. gautam says:

    can we make this without using ic and simply using transistor]

    • Ashwith says:

      I imagine it should be possible. You’ll need to use transistors capable of driving about 500mA – 1A of current (depending on the motor). Look for H-Bridge circuits.

  48. Hemant says:

    nic explanation but I want a proper veiw of connections on pcb.I can’t understand how to connect the circuits.

    • Ashwith says:

      I’m sorry but it’ll be hard to explain that here. You’ll need to look at the circuit diagram and figure out the connections.

      You could buy a breadboard and first practise rigging up a few simple circuits (and testing them). You can then rig up the robot’s circuit and test it. Once you’re confident, you can use a PCB. You get general purpose PCBs which have a layout similar to a breadboard (that’s the one I used).

      If you can fabricate your own PCBs, constructing this robot will be easier: http://ashwith.wordpress.com/2012/04/22/the-simplest-line-follower-upgraded/

  49. Harmanan says:

    can we use 20k ohms resistors in place of presets

  50. ajs says:

    Bro can u plz tel me how to set potentiometer???

  51. ajs says:

    Plz tel me how u creat pcb of ua own

  52. Hashir says:

    Hello, I have a question about the materials. How much does it cost for the whole robot set and is there any way I can buy it from one place. Thanks

    • Ashwith says:

      I bought the materials from shops at SP road Bangalore. You’ll need to check with a local electronics shop. Cost of the materials would be around Rs. 800 – 900. But if you don’t have any of the tools (soldering iron, etc), it could go up – but that extra bit would be a non-recurring cost.

  53. suraj says:

    Hello Ashwith I appreciate for your work.I just want to know can we use IR sensor in place of LDR. Also can we directly connect resistance of 20k instead of preset pot, will it make a difference?

    • Ashwith says:

      Yes an IR sensor will work (with the white LEDs changed to IR ones of course). In fact an IR sensor will have less of the ambient light problem. You can check out one of the possible IR circuits on my table follower robot. Using a TSOP sensor with a modulated IR source will make it even better against ambient light (but it might be an overkill for a simple project like this).

      I use a preset because it gives me the option to tune the sensor’s (i.e. the voltage divider’s) threshold level. I recommend that you keep that if you’re going to solder the circuit. If the 20k is too much/too little (it’s probably too much), you cannot change the resistance easily.

      • Xavier Romagosa says:

        If it isn’t for comunications (remote), is beter not to use TSOP receivers, don’t work well with simple modulated IR. Use instead TSSP4038 ( http://www.vishay.com/docs/82458/tssp4038.pdf ) I’m using it for break beam sensors to triger a camera. It’s intended for this use.

        But still…. It’s overkill for reflectance, you will need to dimm the emiter to faint to get some meaningfull result.

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