Signals and controls
Resistors
Limit current, define input states, and divide voltages.
What it does
Resistance opposes current. Ohm’s law relates voltage, current, and resistance: I = V/R. Two resistors can form a divider when its output is lightly loaded.
Connections and compatibility
Values and quantities are specified by each tutorial. A 1 kΩ series resistor suits the indicator examples; a 10 kΩ pull-down keeps a transistor off during reset.
Choosing one
A through-hole assortment containing 330 Ω, 1 kΩ, 2.2 kΩ, 10 kΩ, and 100 kΩ covers many small projects. 1/4 W parts are usually sufficient for these signal circuits.
Common mistakes
A resistor divider is not a power supply. Resistor values matter; color alone is unreliable under poor lighting.
Use it in a tutorial
- Analog and PWM signals — Use a potentiometer to control an indicator, and learn how analog measurements differ from PWM outputs.
- Blinking an LED — Wire a low-current status indicator and blink it without blocking the rest of your program.
- Shift registers — Use a 74HC595 to drive eight low-current indicators with three controller pins.
- Transistors — Build a low-side transistor switch, then learn what changes when the load becomes a motor or relay.