Introduction: Easy Robot: Light Follower

Picture of Easy Robot: Light Follower

No programming or microchips!

Robots, the most awesome thing there is, especially when allot of people can build it!
I got this robot from a friend as a present. thank you Rudolf.

Anyway, this robot uses 2 Light dependent resistors to sense light and drive toward it.

Soldering iron->hot->hurts

That said, lets start

the reason this is green: the battery's i used are rechargable, one battery can load 1000 times so i save 1998 battery's in this instructables

PS: you have to have SOME electric knowledge for this.

Step 1: Electrical Materials

Picture of Electrical Materials

R1-4 4 100 ohm resistor

R5-6 2 220 ohm resistor

SW1 1 Switch

RV12 2 10k variable resistors

T12 2 Transistors BC557C

T34 2 Transistors BC547C

LD12 2 LEDs

LDR12 2 Light Dependent Resistors

1 IN4007 Diode (note: can be replaced by a paperclip, it supports the wheel XD)

*Note: I got this as a present from a friend. Some of the parts can be different, I dont know.

Step 2: Rest Materials

Picture of Rest Materials

Box to put everything in and a piece of cardboard so you pieces dont go flying / PCB**
Some wires if you dont have a PCB.
Some electric components
Battery holder
Some motors, I got some open chassis motors
Soldering iron
File / sanding paper
A small screw
Something to make the motors have more grip (heatshrink?)

** : I dont have a digital version of the pcb , as I told you I got it from a friend. If someone has the tools to make a digital version please do.

Step 3: The Building Of.

Picture of The Building Of.

1. resistors
2. transistors
3. switch
4. LEDs, these are supposed to bend a bit (looking like bug eyes) i bent them about 90 degrees.
5. light dependent resistors, these are supposed to point forward. (solder them on and then bend them until they lyon the pcb.
6. variable resistors point them forward and next to eachother, that looks fun
7. AAA holder
8. motors, file them down so you can solder/glue them to your pcb/box. put these under an angle so the axis of the motor acts as a wheel
9. put some heatshrink on the motor. this wil get some extra grip and makes it go faster.

Step 4: Operate It

Picture of Operate It

When I just finished the robot i didn't quite know what to do with it, yes i knew it drives towards light but then what do the variable resistors do?

Turns out that the resistors say how sensitive a light dependent resistor is.
if you turn the one close to the left LDR then the left LDR will become less sensitive. and thus the RIGHT motor will not turn as fast.

PS: you can get this kit at:


AkiraNic (author)2014-08-08

1) is there a way to build this without transistors?

2) If I connected the left LDR to the left motor, and the right LDR to the right motor, is it going to turn to the side with less light?

3) Will the LED interfere with the LDRs?

AkiraNic (author)AkiraNic2014-08-09

4) Is there a way to combine this with BeetleBot?

5) How to make it go slower? I've seen one in a video and it runs like mad. I wanted it to be slow.

Pranjal Joshi (author)2011-12-18

are u connected left side motor to right LDR or left LDR??

Pranjal Joshi (author)2011-12-18

how wil it turns if light only falls on one side of LDR??

dynaso7 (author)2011-10-11

Hi, can you show me how this robot work ? (Share the video)
And this robot does not need wheels?

thenmozhi (author)2009-03-14

can u plz explain me how this circuit works

Bongmaster (author)thenmozhi2009-07-08

just lok at the circuit and u should be able to see how it works ;) i knew nothing of circuits til i bought this very kit and once i examined the diagram i understood what was going on :)

Gerrles (author)Bongmaster2010-11-03

can u help me i dont understand the diagram and do u have to have that circuit board???

dunnos (author)Gerrles2010-11-03

I can try to explain how the circuit works... What do you know about electronics right now? Do you know how transistors work? And what do you mean by do you have that circuit board?

Gerrles (author)dunnos2010-11-03

yea i know how transistors work and for the circuit board i mean that do u need a bread board

Gerrles (author)Gerrles2010-11-03

can u post some pictures of connecting the transistor and stuff if u do that will really help

dunnos (author)Gerrles2010-11-03

what exactly do you want to see? do you want to know wich pins go where?

Gerrles (author)dunnos2010-11-03

yea which pin goes where thnx

dunnos (author)Gerrles2010-11-04

Let me make this a learning experience:
for the pins of the bc557c: click here

for the pins of the bc547c: click here

Gerrles (author)dunnos2010-11-04

u know im only 12 im doing this for my project and i dont know the bc557c or the bc547c because my PDF donesn't have english

dunnos (author)Gerrles2010-11-05

What do you mean with: my pdf donesn't have english? you mean you can't read an english datasheet? Or is adobe reader not cooperating?

also, do you have the kit or are you doing this on a breadboard?

flat side facing you:

BC557C: the leftmost pin is the collector
the middle pin is the base
the rightmost pin is the emitter

Same goes for the BC547C.
On the image the flat side is the bas
the line going right and up is the collector
de line on the right downside is the emitter.

Can you figure it out now?

Gerrles (author)dunnos2010-11-05

adobe reader is not cooperating and i dont have kit or breadboard. Im building it free hand and not really, can u try the diagram from step 16

dunnos (author)Gerrles2010-11-06

I already built that one, I really liked that build :) I suggest the beetlebot V2.

Gerrles (author)Gerrles2010-11-04

so if u just put picture of which pin to which pin would be fine and my teacher keeps saying im not talented

dunnos (author)Gerrles2010-11-05

What a nice teacher you have -_-

dunnos (author)Gerrles2010-11-03

you can use a breadboard if you want, you can also buy the kit or do it freehand, whatever your preference is.

Gerrles (author)2010-11-02

HELP i dont know how to read the diagram

cupnoodles2 (author)2010-09-28

Hey wsup i was wondering u asked for 4 transistors but u only used 2 on the diagram. Is there anything wrong with the diagram or is it just me that i cant understand it? thanks for replying

srinandhana (author)2010-08-27

could u explain the circut ahd u can give the source code.......for light following robot

srinandhana (author)2010-08-27

could u explain the circut ahd u can give the source code.......for light following robot

salahaddam (author)2010-01-09

 There's a BEAM type similar to this at

freerunnin1 (author)2009-12-22

i got this from maplin and made it in 4 mins :P lol

AndyGadget (author)2009-12-11

I've just linked this Instructable from 'answers' so here's a bit of info as to how the circuit works . . .

The variable resistor should be adjusted so the motor is just below the point of turning on in normal light.  When a light is shined on LDR1, it's resistance drops and a current begins to flow in the base of T3 causing it to start to turn on and draw a current from the base of T1 (through R3).  This in turn, causes a larger current to flow through T1 and into the motor M1.  The LED (LD1) will also begin to light up.  The brighter the light on the sensor, the more the transistors will turn on and the faster the motor will spin.
The full robot is two identical circuits, and each half turns on the motor on the other side of the robot, so if, for example, the LHS sensor sees light, the RHS motor will spin and the robot will turn towards the light. 
If the light is equal on both sensors, both motors will turn and the robot will go straight towards the light.

Kiteman (author)2009-03-01

I've tidied up the keywords for you, and moved the project into Tech rather than Craft.

(One thing you forgot to mention is where other people can buy the same kit.)

dunnos (author)Kiteman2009-03-01

thank you for doing that, i am quite bad at keywords. and i must've been half asleep putting it into craft O_o

i put in where to find it in step 4

dunnos (author)dunnos2009-03-01

oh, and could you tell me what you thought of this instructable? please? =]

derbert (author)dunnos2009-09-19

now the video's gone, it's not an instructable.

dunnos (author)derbert2009-09-19

OMG could you just SHUT UP!?

Kiteman (author)dunnos2009-03-01

It's OK - a bit lacking in actual instructions, though. Tips on soldering, ways to position components, what needs trimmed to size etc. would have been useful.

dunnos (author)Kiteman2009-03-01

yes, but soldering can be fouund in other articles, i have given some tips but i guess not enough(positioning) and i can't quite get what you mean by trimming to size

but thanks, i like it when people can say these kind of things without going all: this sux and this is **** and you *** ****** and**** know what i mean? (of course not on instructables due to the be nice policy but still)

dunnos (author)dunnos2009-03-01

there, i have some more about positioning. you could check it out, if you have the time (hint hint) =]

Kiteman (author)dunnos2009-03-01

That's better - these things come with instructions, but there's always something they forget to tell you.

Bongmaster (author)Kiteman2009-06-04

it is a good kit tho :) 1st time i actually understood what the circuit was doing, it was that simple :3 great for beginner robot makers that actually want to understand the basics and not just buy a kit that is far too advanced for them to know whats going on :P especially if there is programming involved ;)

Kiteman (author)dunnos2009-03-01

When I said trimming, I have seen the kit, and it's clear that some components need their leads trimmed to size and others don't.

dunnos (author)Kiteman2009-03-01

.. i believe that lead trimmming is part of the soldering, did you EVER when soldering on a pcb let the leads stay theyre original length?

derbert (author)dunnos2009-08-05

CRAZY FOOL!!! your videos don't work. FIX IT!!

dunnos (author)derbert2009-08-05

uhm... aren't we supposed to be nice to eachother on instructables? anyway, i kinda removed my youtube account...

derbert (author)dunnos2009-08-05

Yes we are supposed to be nice. Have you got it posted anywhere else?

dunnos (author)derbert2009-08-05

No, i am sorry.

freerunnin1 (author)Kiteman2009-08-02

you can get them from maplins :P

Wesley666 (author)2009-08-25


derbert (author)2009-08-04

couldn't i just use photodiodes. i have a couple lying around...

krogie (author)2009-07-04

does this actually work.??

dunnos (author)krogie2009-07-05

yes, totally

Bongmaster (author)2009-03-01

I had this same kit :) i got mine from Maplins Electronics
this one right here

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