Let's Make Robots!

Line Follower Robot (Without Microcontroller)

This is a simple line follower robot that is designed for the purpose of applying pwm control with opamps without using any microprocessor. 5 CNY70 reflective optical sensors and 4 NE555 opamps are used. To drive the motors I've used two mosfets (IRFZ44).

If you want to see my other robot projects you can visit my web site.


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Cool bot. It is certainly an effective line follower. I like how smooth the motion is.

You said you used PWM.  Do you have a schematic or block diagram you can post?

I haven't prepared a circuit diagram yet. But I can draw a Proteus ISIS circuit schema and post here soon.

Very nice! And without a MCU! Congratulations!


I think quality of picture was bad I post a better one.

can u plz send me the proteus diagram and logic table of sensors ?
plz plz plz....i will be very thankful :)

my email id is

I don't have his diagram, but I can take some guesses about his circuit.

Power looks like it is from two 9V batteries in parallel. The large chip with the heat sink is probably a voltage regulator to provide clean power for the logic chips like the 74hc14. The big electrolytic capacitor is probaby part of the power circuit too.

He said he is driving the motors with some IRFZ44 MOFSETs. Since he doesn't need to run the motors in reverse, he just uses one to drive each motor. No h-bridge required. I suspect the diodes near these two MOSFETS are to prevent back-EMF from the motors.

The 74hc14 is a schmitt trigger hex inverter. This chip can be used to create a PWM signal. Dave's Robot Room is an informative site, and has this article showing how the 74hc14 chip can be used in this way. However, each PWM output for this circuit required two capacitors and two diodes. I don't see that here. I think the two diodes on the lower boards are for back-EMF protection on the motors, as stated above. There is a resistor near the 74hc14; if there is a capacitor hiding somewhere too, he could be using that chip to set up a clock pulse for timing.

He said he used five CNY70 sensors and five NE555 timers. I can only see four 555 chips, so I'm not sure what's going on there. The diodes, capacitors and resistors  and trim potentiometers near each 555 are clearly part of their control circuit. The 555 is a very flexible chip, so I'm not sure how he is using them. I strongly suspect each 555 is associated with a CNY70.

It looks like there are also four smaller transistors on the top board, one near each 555. So I think each 555 circuit provides an input to a transistor, and the output of the transistors provides control for the motors via the MOSFETS in some way.

Hopefully, some of these guesses (right or wrong) will provide you with insight for your own investigation and experimentation.


Hello, it was an old project, I will send you the circuit diagram when I find it within my old folders. 74HC14 was used to convert the analog signal coming from the CNY70 sensors into 1-0 values, not as a PWM converter. for PWM signals I have used 555 opamps.