Best Christmas gift ever!!! 🎁🎅

Hi. We’ve got the best christmas gift ever! In this video I will show what it is and tear it down to the schematic and see how it works.

See the video about it on YouTube.

Santa brought my little boy the best christmas gift ever! It is a little line following robot. It is fun to play with. I plan to buy another one, as it is more fun to compete with two of them. You can also get one. See the link below! Although it is very cheap, it brings a lot of joy! It follows the 15mm wide black line. Rudi soldered the kit together with my help in about 20 minutes.
The attached track is only letter-sized paper, so we drew more tracks and printed them. You can download them. See the description below. Well, I will let it drive across the track and show you how the robot looks like closely.

Well, it looks very simple. Few elements, two batteries, two motors.
How it works? There are two leds and two photo resistors. White surface reflects light and changes photo-resistance. They are connected to two operational amplifiers and further on to two transistors. Each transistor drives a motor. The thresholds of opamps are set by two trimmers. That’s it. Let’s see schematics.
As we see the inputs to opamps are both phototransistors. One detecting line contains trimmer, resistor and phororesistor. Trimmer adjusts voltage to the opamp. Detecting lines are connected to opamp. What opamp does is compare the both inputs and gives an output. If the + is higher, the output will be +. And vice versa.
At the output of opamps we have two PNP transistors. What does that mean? I will simplify the whole thing. If I can understand it and I am a MD by education, so can you.
Simplified, transistor is a sort of a switch. PNP means it will switch on, if we draw the current on the input from it. You can remember PNP as Points iN. And NPN transistor as Never Point iN. So, if input is connected to ground, it will conduct and the motor will get its power supply.
Going back in reverse. If we look at upper opamp, motor 1 will run, if we pull Q1 input to ground. Opamp will do that, if its “minus” input is higher voltage than its “plus” input. Minus input will be higher, if the resistance of R14 is high or the R2 trimmer is set to minimum. If you want a more detailed explanation, comment below, and I will make another video about it.
Resistors. As you maybe don’t know the resistor color code, see the resistor color calculator in the description below. You can also use this video to help you.

If you like this video, don’t forget to subscribe to my channel, hit like and share it with your friends. Did you make your own tracks? Comment below!

We’ve got the best christmas gift ever! A line following robot! I will show you how it works! It’s a DIY kit. It is a half hour easy project for beginners. Meanwhile I will play with it. Additional tracks can be found on my homepage (link below). I made them with free Inkscape. See links below.

Line following robot: (cheap)
Soldering iron: (cheap, but good)

Resistor color calculator:
Nice opamp simulator:

Robot maps: Robot MAPS


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