One of the most exciting aspects of robotics is that you can somtimes see beautifully intricate behaviours emerging out of relatively simple mechanisms. Don't get me worng, I love overcomplicating my designs as much as the next engineer, but it's still nice to appreciate simple, elegant ideas every once in a while.

This instructable will introduce some of the simplest and most elegant robotics conepts I have ever seen. The concept came from a book called Vehicles : experiments in synthetic psycology by a guy named Valentino Braitenberg, and appropriately, robots based off of this concept have come to be known as braitenberg vehicles.

These braitenberg vehicles can be built using nothing but a pair of motos, a pair of sensors, a battery, and a power opp amp, but they are able to move in ways that seem so biological that braitenberg chose to attribute them to emotions.

"Robots that emote? this is not possilbe" you say, and you're probably right, but I've made a short video to demonstrate the robots and show you what I mean.

This tutorial will explain ho to make the robot in the video above.
what you will need:

- two dc motors with wheels. (best if they are rated to run at around 4.5 volts)
- two light sensitive resistors
- a power op-amp (preferably either an lm272 or one of the copycats)
- assorted resistors (2x 1k, 2x 10k, 2x matching your light sensitive resistors)
- a breadboard + jumper wires
- a nine volt abttery
- a baseplate (I used a book cause I'm fancy)

## Step 1: Step 1 - the electronics

We will start by contructiong two of the circuits shown here: one for the left side of the robot and one for the right.

as you can see it's just a voltage divider feeding into a non inverting op amp. for the resistor R1, you can either use a trimmer like I did, or you can use a resistor that matches the resistance of your light sensitive resistor (LSR) when it is fully saturated with light. as the light levels surrounding the LSR increase, it's resistance will go down. In the current configuration, the voltage measured across the light sensitive resistor will be 9v*R1/(Rlsr+R1). As such, when no light is sent to the LSR it's resistance will be very high relative to R1 so the voltage sent to the motor will be almost zero. In contrast, if the light sensor is fully saturated the voltage sent to the motor will be half of the supply voltage (4.5v). This explains why the figure above is labeled excitation - the more light it sees, the faster the motor will turn.

To switch the motor out of excitation mode and into inhibition mode, all you have to do is swap R1 and the LSR as shown in the second figure. This will cause the motors to spin fast in the dark, but slow down as the light increases.

It would be nice if we could connect our motors directly to our voltage dividers, but motors need too much current for that to work. To make sure that our motors have plenty of current to nom on, we'll put some beefy op-amps in between them and the voltage dividers.  The lm272 is a great choice for this sort of application. It can put up up to 1 amp of current, and it doesn't need a negative voltage supply. In addition to the connections shown in the figure above, you will also need to connct the op-amp to power and ground. the resistor values shown in the figure above will set the gain relating our input voltage to our output voltage to about 1.1 (1+1k/10k).

Once you've completed your circuit, your robot should look a little somthing the breadboard in the third figure.
<p>Would this work for the op-amp: http://www.maplin.co.uk/p/tl081cn-ra70m ?</p>
<p>That would depend on the motors you use, but the op amp that you linked can output only 40mA per channel, so you do not have a lot to work with. You might be able to run a small pager motor off of it - This one </p><p>https://solarbotics.com/product/rpm2/</p><p> for example has a free run current of only 22 mA. It will not be able to support much of a load, but it would at least run. For most motors you are going to want an op-amp that can output at least 1A of current.</p>
<p><a href="http://electronics.stackexchange.com/questions/198845/components-needed-to-build-a-braitenberg-robot" rel="nofollow">http://electronics.stackexchange.com/questions/198...</a></p><p>May you have a look at that?</p>
<p>Your explanation is fantastic. Factual and fun to listen to... Not often those can be combined so eloquently. Well done!</p>
your dialog is like a very cool poem that pulls in a listener... kinda like the robot... :-) HEY maybe that could become a haiku! excellent 'ible! <br>-stu
Very nicely made video, I found it engaging and thought provoking. Thank you very much.
Thanks, I figured that a video would be the best way to explain how the robot works and why it's interesting. I also just like making videos.