Erica Synths EDU DIY Dual VCA Eurorack Module Kit - Manual (Page 35)

DIODES
Diodes are basically like one way valves . Current
can only pass through in one direction – from anode
to cathode . That direction is indicated by the arrow in
the diode symbol, and by a black stripe on the diode’s
casing. So any current trying to move in the opposite
direction is blocked from flowing.
There are a few quirks here, though. For one, the diode
will only open up if the pushing force is strong enough.
Generally, people say that that’s 0.7 V
, but in reality, it’s
usually a bit lower. Also, diodes don’t open up abruptly
– they start conducting even at much lower voltages,
although just slightly.
There are a lot of di ff erent diode types: zener, schottky,
rectifier, small signal etc. They all have their unique
properties and ideal usage scenarios – but usually, a
generic 1N4148 small signal diode will get the job done.
SCHMITT TRIGGER INVERTERS
You can think of a schmitt trigger inverter as two
separate things
. On the left, there’s a sensor that
measures the pressure inside an attached pipe . On
the right, there is a water pump . This pump’s
operation is controlled by the sensor. Whenever the
pressure probed by this sensor is below a certain
threshold, the pump will be working. If the pressure is
above a second threshold, the pump won’t be working.
Here’s a quick graph to visualize that. The squiggly line
represents the voltage at the input, while the dotted line
shows the voltage at the output. So every time we cross
the upper threshold on our way up, and the lower one
on our way down, the output changes its state. One
thing that’s very important to keep in mind: no current
flows into the sensor! It’s really just sensing the voltage
without a
ff ecting it.
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