Build Your Own Transistor Based Mobile Line Follower Robot (LFR)

[meshgheru]

I use a double gearbox instead that 2 micromotor and I change the 2n3904 with BC 639.

And the bot doesn't run! :( If one transistor is burned or fail,the circuit will work? I ask this because I thing one of that 2 transistor is broken.

[ermicroinfo]

@meshgheru, usually a double gearbox (e.g. tamiya) need more current in order to work compare to the micromotor (or the GM2 geared motor from solarbotics). This LFR circuit is designed to work with a small current (less then 100 mA). You could read more information on ermicroblog website shown on the video

[srikings]

boss can you get me the circuit and its components list. pls mail to: pdodlavssa@gmail.com

[geanfilms]

ADOREI SEU ROBÔ.PARABÉNS PELO VÍDEO!!!

[iceberg789]

very nice and simple, thanks !! :)

[geonylove]

am facut acest robot si sincer merge!!! multumesc pt postare tino tot asa



[zaiban03329777747]

can i use more leds if yes then it must be use on same transistor or system or build another symstem....

[ermicroinfo]

@zaiban03329777747, yes you could add the LED, but only two LDR allowed.

[zaiban03329777747]

@ermicroinfo i have made one and it is working beutifully thanks for sharing the idea and circuit , very simple circuit design....i have one more question can i use 12 v insteat of 5 v>>>.thanks

[ermicroinfo]

@zaiban03329777747, Congratulate! You could try to experiment with 12 volt, pay attention to the transistor if it getting to hot than you have to lower the voltage. With more voltage means the LFR will run more faster and it could become difficult to navigate the black line properly.

[asdfgghjklpoiuytr]

Pardon me,i forgot to answer if the 3mm led for the sensor must be superbright(high intensity) or normal one.

[ermicroinfo]

@asdfgghjklpoiuytr, yes you could use it

[asdfgghjklpoiuytr]

@ermicroinfo Any idea to increase the torque of the motors?



[ermicroinfo]

@asdfgghjklpoiuytr, there are two ways to increase torque, the first one is to use the geared DC motor and the second one to increase the DC motor voltage.

[asdfgghjklpoiuytr]

@ermicroinfo what if i use 9volt battery to increase torque and 2x 50k pots instead of 10k or something like that to control low the amperes?

[ermicroinfo]

@asdfgghjklpoiuytr, you could always experiment with it

[asdfgghjklpoiuytr]

I built it eventually,but i have some problems.First of all the dc motors(from a cd/dvd player) haven't enough torque to move the whole vehicle when their speed is low.I used two white leds from a torch and i don't now how many watts they are.The weaker light the better response?

Can i make any change to improve the torque without increase the speed?

[ermicroinfo]

@asdfgghjklpoiuytr, you need to use the geared DC motor

[asdfgghjklpoiuytr]

Can i use 5mm white leds?

[ermicroinfo]

@asdfgghjklpoiuytr, yes you can

[karthik1065]

how to make an abstacle avoider using diz bot

[ermicroinfo]

@karthik1065, no you can not.

[dyctvz]

what if i'll use about 12v motor?

[ermicroinfo]

@dyctvz, You could not use this circuit anymore, because most of 12 volt motor will draw more current that exceed the 2N3904 specification.

[abpccpba]

Nice simple crisp construction. Simple Circuits. It is great. Thanks for showing your work. Have become a Subscriber.

[asdfgghjklpoiuytr]

Sorry for the double post...The motors aren't stepper,it was my fault.They are dc motor for cd/dvd player ~3500 rpm and they consume 30mA max.

[ermicroinfo]

@asdfgghjklpoiuytr, yes you can give it a try

[asdfgghjklpoiuytr]

@ermicroinfo

Thank you very much for your reply!I have one more question for you.

Can i use a pair of 2 small toy wheels or i need a little bit bigger as those on the video?

[ermicroinfo]

@asdfgghjklpoiuytr, you need to use a geared DC motor, not an ordinary DC motor.

[asdfgghjklpoiuytr]

@ermicroinfo

Can i use 2x 5mm white leds instead of 3mm?Also can i supply the circuit with 4x AA batteries?

[asdfgghjklpoiuytr]

Can i use a stepper motor like this from a dvd player qualified with a proper gearbox to reduce the rpm?

[meshgheru]

Hello!I made your robot,but I had a problem.The LDR doesn't respond to dark,i mean,he's giving curent to spin that motor's

.What i can do?

To replace the LDR?

Sorry for my english,but I am from Romania.

[ermicroinfo]

@meshgheru, Make sure you check your circuit connection especially the transistor terminals (i.e. base, collector, and emitter). You could simply check the LDR using ohmmeter, it will give you high resistance (more than 100 K Ohm) output when in the dark and low resistance when in the bright light (less than 5 K Ohm). 

[ramiister01]

Hi!

Nice robot! Very neat work.

I want to build one myself, but I have a question:

Can I use a phototransistor instead of the LDR and the 2N3904? (Like replacing the 2N3904 with the phototransistor and just getting rid of the LDR and the trimpot)

If so, what model of phototransistor should I use for this project?

Thanks

[ermicroinfo]

@ramiister01, you need a phototransistor that could provide sufficient current to the DC geared motor. The other option is to use the phototransistor with 2N3904 transistor in Darlington configuration.

[ramiister01]

@ermicroinfo I googled Darlington configuration (cause I didnt know what it was).

From what I understand, for the Darlington config, I would replace only the LDR with the phototransistor and have it feeding the base of the 2N3904. Right?

I'll try both anyway!

Again, really cool robot, that is the kind of line follower I was looking for, cause I don't have programming skills.

Thanks

[ermicroinfo]

@ramiister01, That's right you could visit the ermicroinfo website (ermicroblog) for more information about the Darlington configuration in "Using Transistors as Switch" article or perhaps more advanced LFR project in "LM324 Quad Op-Amp Line Follower Robot" project.

[MrArunsinghbaghel]

Dear Sir,

The Motor is of the same specification as stated and works well on 5v when not connected in circuit but after it is connected in circuit it does not stir without 9v current .

changing amount of light recieved by ldr is not making any change in speed of motors please help

[ermicroinfo]

@MrArunsinghbaghel, it's mean your DC motor draw more current as it required by the circuit. Use the DC geared motor with this specification: Operating voltage 4 - 6 volt, unloaded RPM < 50, unloaded current: < 50mA (e.g. solarbotics GM2 DC geared motor)

[MrArunsinghbaghel]

Hi,

I got the robot working only on 9v after circuit is complete but motor can also run in 5 v when not connected in circuit i cannot get the robot to follow black line please help

[ermicroinfo]

@MrArunsinghbaghel, Becaue the LFR used a very simple circuit you need to follow the specification required. First the most important is the DC geared motor, you need to use DC geared motor which is rated 5 volt, unloaded RPM < 50, unloaded current: < 50mA and secondly is the sensor LDR should give you 2 ~ 5K Ohm on bright light and 100K Ohm on dark.

[dsgregg]

Love the music. 

[ermicroinfo]

@St4xxx, You could get more information on the website address shown in the video!

[neil7416]

i can't find a DC geared motor with a low rpm. what can i do to decrease the revolution of a typical toy dynamo?

[ermicroinfo]

@neil7416, you need to use a gear to reduce the DC motor RPM. The principal is similar to the gear used in many tamiya racing car but with more gears so the DC motor RPM become lower.

[rahulsriram43]

thanks

[francisroan]

there is a problem the ldr is not detecting the light from the led.................so what will i do??????any way when i point the led at the ldr it works otherwise no!help pls

[ermicroinfo]

@francisroan, Read detail information about LED and LDR sensor position at the blog website address shown on video.

[francisroan]

is there any program?

[ermicroinfo]

@francisroan, no programming. For detail information about building this robot you could visit the blog website address shown on video.

[francisroan]

will any ldr work?

[ermicroinfo]

@francisroan, Yes any LDR will work... experiment with it.

[ermicroinfo]

Connect the QRD1114 using darlington pair with 2N3904. For the reference you could read my blog "Using Transistor as Switch", you could also visit djhesit8 channel and watch the video of the QRD1114 version.

[MomochiZab]

Hello rwb, i have read your blog and it is very helpful, like djhesit8 iam also using a reflective object sensor without the comparator. I was wondering what calculation are needed to make the circuit work, e.g. take the QRD1114 photo transistor datasheet values, to find what resistance values are needed for the sensor side and the emitter side of the phototransistor. What other calculations do you think needs to be performed? Also i was wondering could you relate it to the QRD1114 datasheet.

[MomochiZab]

@MomochiZab Much appreciated emircoinfo

[djhesit8]

ok its working... added your page :D at my video descripion... but... can I use QRD1114 without comparator for this too, right?

[ermicroinfo]

@djhesit8, Nice work ! Yes you could experiment with it by connecting the QRD1114 photo transistor using darlington pair with 2N3904.

[djhesit8]

thats right but it has no load.... by the way I checked the soldering and there was the problem :D

[djhesit8]

hi... sorry again for disturbing... I made my circuit etc, i got gm2... works fine but... if I reduce the trimpots to 0... when I start up both motors runs and everything is fine except that an LED instead of white is green lol... if I fully close the trimpots... a motor won't start... the same motor which way the LED is green... what's the problem? sometimes the same tranzistor is heating up

[ermicroinfo]

@djhesit8, when you fully close the trimport (i.e. 10K) then the base current will be smaller and it will effect the collector current (Ic = hFE x Ib). Trimport is used to adjust the transistor's base current; therefore by adjusting the trimport we could adjust how the motor responds toward the light (LDR). The transistor heating up because when the motor is stalled (more load on it) it draw more current compared to when it operate without the load.

[djhesit8]

ok... as I promised... I'll future you somewhere... so I'll have a conference meeting at my university... I'll present my work and add links to your pages and you'll be featured in this: "ANNALS OF THE ORADEA UNIVERSITY. Fascicle of Management and Technological Engineering"... :) if interested later I'll send the link :D

[ermicroinfo]

@djhesit8, Thank you.

[djhesit8]

@ermicroinfo it is a problem using 6V instead of 4.5V?

[ermicroinfo]

@djhesit8, it should work with 6 volt.

[djhesit8]

ok :) breadboarded it and it is working fine... btw... I used some motors from CD_ROM and they are not working... the 2N2222 is overheating... :| but with pager motors it just works fine... whats the problem? I ordered 2 GM8 gear motors from robotshop... would it be ok?

[ermicroinfo]

@djhesit8,

The overheating mean the current to drive the CDROM motor near the maximum collector current allowed by 2N2222 (max 800mA). Remember that we operate the transistor in its linear region. The GM8/GM10 DC geared motor; I think it will be work fine.

[djhesit8]

@ermicroinfo your information is really valuable... thank you really much... I promise I'll feature your project on facebook or something :D I was thinking about making a forum too but need to promote it.... btw... I really enjoyed your assamble C for avr... if you'll add more tutorials, It will be cool...

[ermicroinfo]

@djhesit8, Thank you.

[djhesit8]

thanks for your fast respond... I would really apreciate if you help me making a small fairchild based line follower... only transistor based... I'll really love a diagram if you could help me out with this... At leas I can even use an ATmega8-16PU but it will be hard to program it cause I have only the controller :(

[ermicroinfo]

@djhesit8,

I will reconsider it and put on my project list for the non microcontroller IR reflective base line follower robot

[djhesit8]

@ermicroinfo that would be great... I allready bookmarked your blog :D some cool info there

[djhesit8]

and please... can you make a wiring diagram for PCB-s? :D I want to make it on PCB so lot of cables will disappear... later I'll be trying making out a small one, like a keyring with CR2032 batteries... would you help me?

[ermicroinfo]

Because this circuit its very simple, I only made it on the prototype board (no PCB drawing) as shown on the video.

[djhesit8]

@ermicroinfo can you send me some more photos about how to wire up the trimpots? I don't want to trow this away again :( please I'll really apreciate it

[ermicroinfo]

@djhesit8

I will put the picture on the project website (shown on the video). You could visit the project website to get more detail information.

[djhesit8]

this is nice :) soon I'll go to buy materials... but by the way... I want a faster robot... I was thinking on IR LED emitter and reciever... I have 5-5 each of hem... 5mm LEDs... could you please update the diagram? ;;) I will have a compatition in 7 May :D please help

[ermicroinfo]

For more advanced line follower robot you could watch the "Build Your Own Microcontroller Based PID Control Line Follower Robot (LFR) " project on the YouTube ermicroinfo channel and visit the ermicroinfo project blog shown on each video for the detail project description.

[djhesit8]

@ermicroinfo yeah but I don't want to spend a lot of money... my ideea... keep it simple :D no microcontroller I want... now I'll use 2N2222 the only 2N's I can get here :( 1$... I got two... I wanted to make 4 transistor 4 LED based diagram, the transistor hooked up like collector to emmiter, the two base should be going to two different LDRs... and 2-2 on sides... for better performance :D

but what I want is, using QRD1114 instead of LDR... do I need LM324 amplifier?

[ermicroinfo]

If you want to use the Farchild QRD1114 IR reflective sensor, its better to use the comparator such as LM339, you could read more information about the comparator on the blog's website "Working with the Comparator"

[BADelectRonique]

if you want to view my portions of robot you can tell me! no probleme

[BADelectRonique]

aim a studying that's why i cant repond you very quikly !! but i love all circuits electronics!! LOL

[BADelectRonique]

aim very satisfied of your expensive answers!!

[BADelectRonique]

now the support of leds and LDRs is completed with the supporte of the RBOT!aim waiting just a good test for the circuit before use !

[BADelectRonique]

yes ! i will do when i finish this project with pictures of curse! but i have worry for the power of motors! this morning a had a test of circuit and i think the power of motors is low . so i think they cant move an heavy robot!

[ermicroinfo]

I will glad to hear it from you, again you could find more technical information about building this robot in the blog shown on the video.

[BADelectRonique]

i tell you when i finish my first robot fllower.

[BADelectRonique]

great idea ! thank you again for your attention .you are very interesseng

[ermicroinfo]

Yes you could use a fix value resistor instead of 10K variable resistor, try start with a small value and slowly increase it (e.g. 560, 1K, 1K5,...); observe the behavior until you get the best result.

[BADelectRonique]

one more question please! can i use a simple resistor fo 10K or oder Kohm instead of potentio-metre of 10K?? thanks alot

[ermicroinfo]

Yes you can use 2N2222 as the replacement for 2N3904

[BADelectRonique]

hi !! can you tell me please?? can i use two npn transistors 2N2222 insteaf of 2N3904? i need your hel please!!

[ermicroinfo]

It's 220 Ohm.

[salvoo8]

the resistance is 220k or 220ohm?

thanks.