A Mini Op-Amp Based Line Following Robot


There’s no denying it. Super small robots are just cool. [Pinomelean] has posted an Instructable on how to create a mini line following robot using only analog circuitry. This would make a great demo project to show your friends and family what you’ve been up to.

Analog circuitry can be used instead of a microcontroller for many different applications, and this is one of them. The circuit consists of two op-amps that amplify the output of two phototransistors, which control each motor. This circuit is super simple yet very effective. The mechanical system is also quite cool and well thought out. To keep things simple, the motors drive the wheel treads, rather than directly through an axle. After the build was completed, the device needed to be calibrated by turning potentiometers that control the gain of each op-amp. Once everything is balanced, the robot runs great! See it in action after the break.

While not the smallest line follower we have seen, this robot is quite easy to reproduce. What little robots have you build lately? Send us a tip and let us know!

[via Embedded Lab]

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Protoboard line following robot


We love a good line-following robot project and this really hits the spot. It’s got sharp edges, gobs of solder bridging, and look at all those jumper wires! Despite its appearance it puts in a performance that won’t disappoint.

It uses a dsPIC33 to read from half a dozen analog sensors on the bottom of the board. We’re not all that familiar with the chip’s features, but [Exapod] says it’s got an auto-scan feature he uses to read the sensors. This allows him to sample with 12-bit resolution from all six of them at about 30 kHz. No wonder the thing is so responsive in the demo video embedded below. The track he’s using is just some white printer paper with a fat circuit of black electrical tape placed in a somewhat squiggly pattern.

This is also a fun challenge with toys. Here’s one that hacks a hexapod to follow the lines.

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Line-follower is an homage to [Homer]; plans to infringe copyrights

The Chief Knock-a-Homer robot is [Psycho Freaky's] shout out to The Simpsons. The robot design appeared in an episode where [Homer] built [Bart] a fighting robot. Since he’s not robot builder, [Homer] actually climbed inside the shell and dished out sweet vengeance while suffering some severe injuries at the same time.

But [Psycho] has the skills necessary to make this autonomous and keep it looking just like the TV show at the same time. He has a friend with a CNC mill, and used it to cut out case parts from Masonite which were assembled with hot glue. A pair of small servos drive two wheels at the rear of the base, with a ball-bearing universal wheel centered in the front. There are also two downward-pointing sensors which lend it the ability to follow a line as seen in the video after the break.

We love the paint job, it really polishes the look. But [Pyscho] isn’t quite done yet. He plans to add an audio circuit that will give the robot the ability to play back classic sound clips.

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Easy rotary encoding for your projects

Want to monitor how much a wheel has turned in your project? Then you need a rotary encoder! Here’s a way to add rotary encoding without changing the mounting method of your wheels (translated). [Jorge] added it as a way to improve the functionality of this line-following robot. It uses a paper encoder wheel which is monitored by an optical sensor.

The paper wheel consists of alternating white and black pie pieces. You can make this with a felt-tipped marker, or use a tool like the one we featured a couple of years ago to print out a disc rendered to your own specifications. This is glued to the inside of the wheel and monitored by a CNY70 reflective sensor (the same one used in that electric keyboard retrofit).

The homemade board which holds the sensor can be seen mounted on top of each wheel’s motor. It requires three wires, voltage, ground, and data. The data line is connected to the output of the phototransistor in the CNY70 package so it can be used with a microcontroller interrupt for easy integration with the firmware driving the robot.

[Jorge] goes into some detail about how the added data helps to improve the speed performance seen in the clip after the break.

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Update: Tiny line-follower and more

This tiny line-following robot is quite impressive. It’s [Ondrej Stanek's] second take on the design, which he calls PocketBot 2. Just like the earlier version, this robot is small enough to fit in a matchbox, but it’s received several upgrades in this iteration.

The coin cells that ran the previous version have been replaced by a rechargeable Lithium Ion cell. The ATmega8 which controlled the first robot has been swapped out for an ATmega128 running at 32 MHz. You won’t find an IR receiver on this one either, it’s been traded for a Bluetooth module which adds a quantum leap in functionality. For instance, the graph in the upper left of this photograph shows the reflective sensor data readings used to follow the line.

There’s all kinds of great engineering in this design, which is shown off in the video after the break. One of our favorite parts is that the axles are attracted to the center of the robot by one rare-earth magnet. This keeps the rubber tires pressed against the motor spindles rather than use a gearing system.

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A collection of quick line-followers

Here’s a nice collection of line-following robots (translated). They’re fast and they stay on track even through sharp turns. They center around a Baby Orangutan board which features an ATmega328 microcontroller and two motor driver channels. These drive the geared motors and use optical sensors to track a dark line on a light surface. There’s plenty of build and testing information (translated) if you’re interested in the gory details. Or just jump past the break to see the red on doing its thing.

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