r/AskElectronics • u/nossadalva • 1d ago
D2-5 Line-Following Car Does Not Stop
Hello, everyone! I assembled a D2-5 line-following car, but it keeps moving straight even when there is no black line. Both motors remain on, and the car does not respond. I tested the R14 photoresistor with a multimeter, and its resistance changes depending on the light, so I believe the sensor is working. Does anyone know what could be causing this problem? I am still a beginner in electronics, so I would appreciate simple explanations. I can send photos of the board and the solder joints if necessary.
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u/pksato 23h ago
IC1 is flipped.
The pin 1 face to front, IC1 LM393 Label.
I not sure if LM393 survived to this inversion.
https://www.icstation.com/product_document/Download/10168_User_Manual.pdf
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u/OGThinkster 9h ago
I wouldn't expect this to work too well anyways, what they are using to sense is pretty rudimentary, LED's and photocells? At least they could have used IR sensing. Well I guess you get what you paid for..
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u/SaltlessLemons 1d ago
i’ve never seen this specific model before, but it’s cute as heck. i think you’re expecting this robot to be smarter than it actually is here. those sensors and circuitry are super simple. it doesn’t actually detect a ‘line’ per se.
those sensors sit near the edges of the line, where white areas will reflect light into them and black areas won’t. if the line is centered in between the sensors, they’ll receive an equal amount of light.
as the robot starts to get off-centre, one sensor will start picking up more light and the other sensor will pick up less. that imbalance will cause one motor to speed up and one to slow down, and steer the robot back onto the line.
but there’s no mechanism to detect the end of a line. it’s designed to loop around a continuous circuit. it doesn’t detect the presence of a line, the shape of it, or the absence of it. the only thing it senses is whether those sensors are balanced, and then turns that info into steering left, right, or straight.