KEY WORDS(line tracing robot,line follower,autonomous robot,homemade robot from junk.building your line tracing robot)This is my first autonomous robot project .This robot has got no brains.It works on the principle that black color reflects less than 2% of its incident light and white color whereas reflects more than 50% of its incident light.You can also use some dark colors instead of black color and light colors instead of white colors.This principle applies to all wavelengths of light infrared,visible and laser.
The circuit diagram is quite simple .I have used two light sensors ,you can use either an light dependent resistor (LDR) or an photo diode in revers bias .when light falls on LDR the resistance of LDR reduces en the range of kilo ohms where as when placed in dark its resistance increases to tens of kilo ohms.A 100 ohm ,5 v relay is used in this circuit a relay is basically a electronic switch which gets closed when voltage across it exceeds 5 volts.BC 547 transistor is used to amplify the change in resistance of LDR. A 10k variable potential divider is used to set the biasing voltage Vbe i.e. the sensitivity of the circuit.When light reflects and falls on the LDR its resistance of LDR decreases and base current increases and as base current increases Ie =Hfe(gain)*Ib increase .Hence Vce decreases and voltage across relay increases which switches the relay.The components requiered for this circuit are as follows-10 potential divders-2BC 547-2LDR -2(larger the surface area and the 'S' design of the LDR larger the sensitivity)connecting wires5v,100 ohms relay-2printed circuit board-1dc (china) moters -2
THE CHASSIS
Well this is mechanical part of this robot.I have used two shatter proof rulers,one cell holder.two small plastic ear buds(ya they fit tightly to the moter axle )and dont remove the cotton on it they provide grip.one omni directional wheel some polystyrene (thermocol) cello tape.Its construction is well explained in the diagram below.
If you want to increase the sensitivity with small LDR's then you can use convex lens which will converge the reflected light .More the area of the lens more is its sensitvity.
If you want to increase the sensitivity with small LDR's then you can use convex lens which will converge the reflected light .More the area of the lens more is its sensitvity.
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