Line follower robot without a microcontroller

[ahsrabrifat]

If you are ever asked to make a line follower robot without a microcontroller, how will you proceed?

 

[rjenkinsgb]

A light source aimed downwards and two photo sensors - LDRs, phototransistors etc., with appropriate bias or load resistors.

Use tubes around the sensors to make them directional and "aim" them down near the centreline of the robot, each just slightly to it's own side (left or right), mounted as far forward as possible.

If the robot is centred on the line, the two signals from the sensors should be equal, seeing the line. As it starts to drift off centre, one sensor or the other will start to leave the line.

Use the sensor balance or imbalance (such as a differential amplifier) to steer the robot. Equal signals means straight, if one signal start to drop steer proportionally towards the opposite side.

Add a two pole changeover switch to swap the sensor output, if you may need it to follow a black line rather than a white line.

(I built stuff like that back in the 70s).

 

[danadak]

Simple Line Follower Circuit – Making Easy Circuits

makingcircuits.com

Simple Line Follower Circuit

Are you interested in robotics and electronics? If so, you might be familiar with the concept of a "line-follower robot"—a simple yet fascina

www.circuits-diy.com

 

[AnalogKid]

That is the same circuit on two different sites, and the circuit has issues.

1. This circuit places a large reverse voltage across the Q1 and Q2 base-emitter junctions. IIRC, this voltage exceeds the datasheet limits, and will lead to device failure.

2. The relay coils *must* have suppression diodes across the coils

3. There is no power supply decoupling across the IC.

4. The circuit places a large reverse voltage across the LEDs. Depending on the part, they might go into reverse breakdown. There could be some illumination in the "off" state.

If you don't want to mess with a two-battery circuit, it can be modified for operation on only one battery. Also, the output relays can be replaced with small power MOSFETs.

al

 

[MaxHeadRoom78]

This was done on industrial trace cutting machines that followed a printed pattern shape. in order for a attached cutting torch to cut out the shape.
A light beam was used to oscillate/vibrate across and follow a line by recieving the reflected signal back and stay on track on the line.

 

[danadak]

Of course the circuits could be modified with adding simple diodes in series,
1 in series with each current limiting R, for the LEDs and output transistor base
drive limiting R's.

 

[ahsrabrifat]

This was done on industrial trace cutting machines that followed a printed pattern shape. in order for a attached cutting torch to cut out the shape.
A light beam was used to oscillate/vibrate across and follow a line by recieving the reflected signal back and stay on track on the line.

What was the main processor in such a circuit? Timer IC or something else?

 

[ahsrabrifat]

Simple Line Follower Circuit – Making Easy Circuits

makingcircuits.com

Simple Line Follower Circuit

Are you interested in robotics and electronics? If so, you might be familiar with the concept of a "line-follower robot"—a simple yet fascina

www.circuits-diy.com

Thank you, sir. Did you ever try any of these circuits personally?

 

[ahsrabrifat]

A light source aimed downwards and two photo sensors - LDRs, phototransistors etc., with appropriate bias or load resistors.

Use tubes around the sensors to make them directional and "aim" them down near the centreline of the robot, each just slightly to it's own side (left or right), mounted as far forward as possible.

If the robot is centred on the line, the two signals from the sensors should be equal, seeing the line. As it starts to drift off centre, one sensor or the other will start to leave the line.

Use the sensor balance or imbalance (such as a differential amplifier) to steer the robot. Equal signals means straight, if one signal start to drop steer proportionally towards the opposite side.

Add a two pole changeover switch to swap the sensor output, if you may need it to follow a black line rather than a white line.

(I built stuff like that back in the 70s).

Did you use any motor driver IC?

 

[MaxHeadRoom78]

What was the main processor in such a circuit? Timer IC or something else?

In this case it was an A to D convertor input to an industrial (MG) plasma cutting machine.

 

[rjenkinsgb]

Did you use any motor driver IC?

No, just a couple of darlingtons as emitter followers, from what I remember.