Let's Make Robots!

Transistor based line follower

follows a black line on a white surface

Hi guys....



Finally today arrived the last order for this robot... the wheels and the caster....


I took me 2 night of CAD-ing...


This is  my first entry and I hope that you'll like this... I made this robot based on ermicro schematic and tutorial...  http://www.ermicro.com/blog/?p=1097


I used near the same things excepting the transistor... I'm using two 2N2222 transistor which allows 800mA on its collector... So the basic ideea is to follow a black line on a white surface... The principle of working is simple... I used a white LED to illuminate the surface... and one LDR as reciever/sensor.... when the white light contacts a white surface it will be reflected so the LDR lower his voltage opening the transistor... as the transistor is opening, the gearmotor gets more curent and will spin faster making it to turn...





unfortunatly I get tired with setting the trimpots every time when the illuminance changed... this way I was going to use QRD1114 fairchild sensor... and finally it's working... no more white light... :D just IR...


the only problem is that when my trimpots are at 0 Ohm, my LED isn't glowing :( the blue flashing LED :(

Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.

I think it will work without it... sometimes I'll use them with new battery but when the battery goes low... no reason to use them...

Thanks for the info, I am goin to attempt to build one myself.


hello , i liked the circuit and will integrate it in my tank as another feature ! :)

here is the circuit i drew , its 1-1 ratio and self explanatory , 2 parts break apart .

Rubbish circuit design ! , i threw away the POTs and the diodes , put in an L293D motor driver to be able to drive the tamiya dual gearbox fitted inside my tank , functioning gr8 now .

anyway do you have a video?

dunno... mine working fine... don't need an L293D for this... just the diode is rather enough... i use GM2

your is more simple :D but don't know what goes where... btw... :D I'll show up the drawing later... don't have windows now... realpcb is only for windows :(

ok...replaced the LED and LDR.. with 2 QRD1114 :D working perfect :D

   Next step, give it a brain.

Maybe... but later.... This should be the cheapest robot I've ever made... didn't want to spend a lot of money on it