Circuit Locution

Resistors

Symbol for Resistor

Resistors are used to limit current, in accordance with Ohm’s law. Not coincidentally, a resistor’s ability to limit current is measured in Ohms (Ω). The higher a resistor’s Ohm rating, the less current is allowed through it at a particular voltage.

Resistors are a key component in circuitbending, and nearly all electronic devices use them. Most notable are clockspeed resistors, used by some CPUs (nearly all black blob devices, and some 80s-era devices) to set their internal clockspeeds. Resistors are also used in keyboard matrices, as they allow just enough current through a given circuit path to set a connection to read as ‘on’ or ‘off’ to a CPU, until overridden by a keypress connecting the path through less resistance. (More on this in Button Matrices, later.)

Resistors in series are additive – that is, putting a 50k Ω resistor in series with a 200k Ω resistor results in 250k Ω of total resistance.

In parallel, resistor math is a little more complicated:

For example, in the following diagram, there are two resistors in parallel, R1 and R2:

The total resistance between points A and B is 6666Ω.

The upshot is that two resistors in parallel will always provide resistance lower than the lowest of the group.

Body contacts

The human body acts as a resistor, too, which has lead circuitbenders to bring parts of a circuit outside the case of an instrument. Touching these contacts adds an unpredictable resistor, either in series or parallel, to the circuit – as the musician increases pressure on the contacts, resistance decreases further.

Resistor values

Most resistors are printed with color bands to indicate their values. The first two bands represent the significant digits, the third band the x10 multiplier. A fourth band, either gold or silver, indicates the precision of the resistor – a gold band means the value may be off by 5%, whereas a silver band means it may be off by 10%.

In the picture at the top of the page, the top resistor reads “Blue, Brown, Red, Gold”, meaning its Ohm value is 61 x 10², or 6200 Ω with a possible variance of 5%. Likewise, the middle resistor is “Red, Red, Orange, Gold”: 22 x 10³ or 22k Ω.