Robotics

To use a photodiode in its photoconductive mode, the photodiode is reverse-biased; the photodiode will then allow a current to flow when it is illuminated.

LEDs can be used as photodiodes

FLEDs are light-sensitive, and so flash faster in brighter light

智能不仅仅局限于大脑。在整个控制过程中，大脑，执行器以及传感器都对产生我们认为是智能的行为有着非常重要的意义。这就意味着，在定义机器人的行为时，你机器人的尺寸也要被考虑进去

在Nordin博士的实验室里，机器人已经开始像婴儿一样开始学习爬行，慢慢开始学会平衡以及走路，甚至爬楼梯。而且机器人还开始研究放在它们面前的物体，甚至会归纳出物体的属性，并且开始玩弄它们，就像小孩一样。一个4足机器人在不小心损坏一只脚的情况下，能够慢慢学习如何使用3只脚来保持平衡并且有效的行走。在实验室里，类似的项目还有很多。

The current through a photodiode is directly proportional to the light intensity

The photodiode and phototransistor can be both photovoltaic (generators of potential difference) and photoconductive (modifiers of an electric current), depending on the application.

A reverse-biased photodiode operates in what is called photoconductive mode, since the conduction of the semiconductor junction varies with the illuminating light intensity.  If the reverse-biased voltage is relatively large (i.e. several volts) the reverse-biased photodiode will have a very fast response time (much faster than an LDR) and is suitable for detecting light signals that vary down to a time scale of a fraction of a microsecond.

The robots do not build a model of their world they simply act in response to the things they encounter whilst existing there.

This form of robotics has proved to be successful in environments that are unknown to the robot, environments that are busy or noisy such as a place with moving objects or people

An important part of the behaviour based theory is "embodiment" This means that a robot must be embodied, have a presence (it is an entity in itself).  In order to react the robot must be surrounded by the real world.

Large diameter wheels give your robot low torque but high velocity. So if you already have a very strong motor, then you can use wheels with larger diameters.

But if your motor is weak (such as if it does not have any gearing), you want to use a much smaller diameter wheel. This will make your robot slower, but at least it has enough torque to go up a hill!

Wheel width. You do not want it too wide as it causes increased resistance to rotating the wheel on a surface.

The only time you will need this term is when acceleration plays a big factor with your robot. If your robot is really heavy, or gravity is not on it's side (such as steep hills), then you will need the integral term.

The sampling rate is the speed at which your control algorithm can update itself.

To increase sampling rate, you want an even faster update of sensor readings, and minimal delay in your program loop.

The Sharp IR Range Finder works by the process of triangulation. A pulse of light (wavelength range of 850nm +/-70nm) is emitted and then reflected back (or not reflected at all). When the light returns it comes back at an angle that is dependent on the distance of the reflecting object. Triangulation works by detecting this reflected beam angle - by knowing the angle, distance can then be determined.

The IR range finder reciever has a special precision lens that transmits the reflected light onto an enclosed linear CCD array based on the triangulation angle.

The Sharp IR has a non-linear output. This means that as the distance increases linearly (by set increments), the analog output increases/decreases non-linearly.

This chip is great for building robots because it has extensive input/output hardware built right into the chip. This reduces the need for external components.

Reverse bias induces only little current (known as saturation or back current) along its direction. But a more important effect of reverse bias is widening of the depletion layer (therefore expanding the reaction volume) and strengthening the photocurrent. Circuits based on this effect are more sensitive to light than ones based on the photovoltaic effect and also tend to have lower capacitance, which improves the speed of their time response. On the other hand, the photovoltaic mode tends to exhibit less electronic noise.

Photodiodes can be used under either zero bias (photovoltaic mode) or reverse bias (photoconductive mode)

It's simply a Phototropic BiCore driving two small motors

I had to add resistors across the motor leads to slow them down! I got this idea from Ben Hitchcock's Fred Troubleshooting Page -- "D) If the motor fires strongly once..."