We’re going to talk about weird resistors. Yes,
you’ve heard me. The resistor is one of the
most underrated components in electronics.
This article is the first of a series about weird
resistors. True to our theme of Squishy Tech, in
this issue we’ll start by playing with our food.
WHAT IS A RESISTOR?
Electricity is measured by three quantities or
properties: voltage, current, and resistance. If
you’ve spent any time working with electronics,
you’ve heard of Ohm’s law, which says that the
electric current through a conductor is directly
proportional to the voltage, and the resistance
is used to control that relationship. This can be
described mathematically as:
• Voltage = current × resistance
• Current = voltage / resistance
• Resistance = voltage / current
This means that by knowing the value of two
components, you can determine the third.
Controlling resistance is key, and the resistor
is the component that does it. It’s something
you will need to do in so many circuits to limit
the current and prevent your components from
burning out.
Often resistors are made by winding a resistive
wire around an insulated form and covering it
with an insulator, or by applying a thin layer of
resistive material onto an insulated form. These
techniques ensure that the resistor is — roughly
— the right value.
We can check the value of a resistor a few
ways. The most common is to read the colored
lines painted on most resistors — check the
“resistor color code” online or in your Maker’s
Notebook (makershed.com/collections/
notebooks-writing).
Another way is to use a multimeter to read
the value. Just turn the knob to the resistance
range you desire to read on the ohms (Ω) portion
of the dial and touch the leads or probes to either
side of the resistor. You’ll notice that it might
not measure exactly the indicated value; that’s
normal, as most resistors have a tolerance of 5%
or 10%, and some can vary up to 20% (Figure
A
).
Resistor values are organized into a
standardized series of values, the E-series,
Build an Atari Punk synth circuit
— then get fruity with it!
A
spaced so that their tolerance ranges do not
overlap. So not all resistors are created equal!
You can buy a package of resistors with a
variety of values and use them for all kinds of
projects. Using resistors to control the properties
of a circuit can change the output, or be used to
make decisions.
WHAT’S A VARIABLE RESISTOR?
It’s easiest to think of resistors as having a static
value. But we actively use variable resistors all the
time in the form of knobs or slides. As you twist or
move the knob, the resistance changes. If you’ve
ever turned up the volume using a knob, you’re a
variable resistor user!
These variable resistors, known as
potentiometers, work mechanically, by moving a
conductive piece along a resistive surface, forcing
the electricity to go through more or less of the
resistive material. We’ll explore this mechanic
more in Weird Resistors Part 2.
Any material that conducts electricity also has
a resistance; even copper wire has a very low
resistance that can accumulate over distances.
EXPERIMENTING WITH RESISTANCE
Now it’s time for the fun! I’ve experimented with
a variety of fruits and foods to better understand
their resistance, and how we can play with them
inside circuits. You’ll notice that dry foods will
have a very high resistance (water is a pretty
good conductor), and depending on the qualities
and freshness of the food, the values can vary
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