The Nv neuron circuit may look familiar as it is found in most
CMOS data handbooks as an example of a simple edge detector or one-shot
or mono-stable circuit application.
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.
When
light shines on the LDR, it has low resistance and allows current to flow. When light does not shine on it, the LDR has
a very high resistance, and a much smaller current will not flow through it.
The suspended bicore is the core of most BEAM devices. It's unique structure makes it very easy to customize for a wide range of uses. These uses vary from blinking LED's to servo-drivers to walkers.
Many BEAMbots are based on bicores (2-Nv neuron "loops") in some fashion or another (and there are two main kinds of bicores -- but more on that later). Even if you're not building a bicore-based BEAMbot, studying how bicores work will help
The quadcore, or 4-Nv net, is by far the most-common variant of Nv net. You will sometimes also hear this circuit referred to as the "Microcore" -- although this term should strictly be used in reference to a "fully dressed" quadcore,