Chapter 1: Your First Circuit
Closed circuits and when current can flow How Chapter 1 works →
Chapter 2: Series and Parallel
How current and voltage change in series and in parallel How Chapter 2 works →
- 2-1The Story of SeriesLight two LEDs brightly with one resistor★★
- 2-2The Story of ParallelLight two LEDs with a 3V battery★★
- 2-3A Dim LEDMake it glow softly, like a night-light★★
- 2-4Three LED ColorsLight red, green, and blue LEDs at about the same brightness (current)★★★
- 2-5Combined ResistanceGet just the right LED brightness using only 1kΩ resistors★★★
- 2-6Better EfficiencyLight three LEDs equally while using as little battery power as possible★★★
Chapter 3: Switches and Logic
Building conditions with switches (AND, OR, while pressed, changeover) How Chapter 3 works →
- 3-1Two Switches: ANDLight it only when both S1 and S2 are ON★★
- 3-2Two Switches: ORLight it when either S1 or S2 is ON★★
- 3-3Push ButtonMake a power lamp, and a call lamp that lights only while the button is held down★★
- 3-43-Way SwitchesTurn the light on and off from both the bottom and the top of the stairs★★★
- 3-5Traffic LightUse two SPDT switches to light just one of red, yellow, and green★★★★
Chapter 4: Reading Voltages
Voltage dividers, potentiometers, input pins, and sensors How Chapter 4 works →
- 4-1Measure VoltageUse voltmeters to measure the voltage across the LED and across the resistor★★
- 4-2Voltage DividerMake about 3.3V from 5V★★
- 4-3Set a Voltage with a KnobTurn the potentiometer's knob to make both 1.5V and 4.0V★★
- 4-4Brightness with a KnobBuild a dimmer that makes the LED brighter or dimmer with a knob, and that doesn't burn it out even at the end of the knob★★★
- 4-5Pull-DownBuild an input circuit that reads HIGH when the button is pressed and LOW when it is released★★★
- 4-6Pull-UpBuild an input circuit that reads LOW when the button is pressed, without wasting the battery's current★★★
- 4-7Read the TemperatureUse a thermistor to turn temperature into a voltage the microcontroller can read★★★
- 4-8HIGH When It Gets DarkBuild a light sensor that makes the microcontroller input HIGH when it gets dark★★★★
Chapter 5: Capacitors
Timing with charging and discharging How Chapter 5 works →
- 5-1Store ChargeStore charge in the capacitor and raise its voltage to 4.5V★★
- 5-2Delayed LightingMake the LED light a little while after you turn on the switch★★
- 5-3AfterglowKeep the LED glowing for a while after you turn off the switch★★★
- 5-4Choose the CapacitancePick a capacitor so the LED lights 1–2 s after you turn on the switch★★★
- 5-5Two-Step LightingWhen you turn on the switch, make L1 light first and L2 a little later★★★★
Chapter 6: Motors
How motors behave (stall current, direction, speed), groundwork for driving them with semiconductors in Chapter 8
- 6-1Spin the MotorSpin the fan motor in the right direction★★
- 6-2Voltage and SpeedUse two 1.5V batteries to spin the motor fast★★
- 6-3Safe Even When StalledKeep the current safe even when you hold the motor still with your finger★★★
- 6-4Forward and ReverseUse two SPDT switches so the motor can spin both forward and backward★★★★
- 6-5Two-Speed FanUse an SPDT switch to change the fan between High and Low★★★★
Chapter 7: Switching with Transistors and FETs
Output stages that let a microcontroller pin switch big loads
- 7-1Safe Even If It's BackwardKeep the microcontroller board safe even if the battery goes in backward★★
- 7-2More Than a Pin Can GiveUse a transistor to switch three LEDs that need more current than a microcontroller pin can give★★★
- 7-3A Floating Gate MisbehavesKeep the LEDs from turning on by themselves, even right after the microcontroller starts up★★★
- 7-4Pick a FET for 3.3VChoose a FET that lets a 3.3V microcontroller switch a 12V lamp★★★★
- 7-5Drive a RelayDrive a relay from the microcontroller to switch a 12V lamp on a separate supply★★★★
- 7-6Switch the + SideKeep the lamp's − on GND and switch its 12V + side from a 5V pin★★★★★
Chapter 8: Controlling Motors (PWM and H-Bridges)
Changing a motor's speed (PWM) and direction (H-bridge) with semiconductors, while protecting the circuit from stall current, back-EMF, and shoot-through
- 8-1Survive a StallDrive a 12V motor from the microcontroller with a circuit that survives even when the motor is held still★★★
- 8-2Speed Control with PWMRun a 3V-rated motor at 5,000–8,000 rpm from a 6V battery without wasting the battery★★★
- 8-3Half-BridgeWith one pin, switch the motor between running and a quick stop (brake)★★★
- 8-4H-Bridge: Forward and ReverseWith two pins and four FETs, spin the motor forward and backward, and stop it quickly from either★★★★
- 8-5A 12V H-BridgeDrive a 12V motor forward and backward from two 5V pins, with no shoot-through in any combination★★★★★
- 8-6A Motor Driver ICWire a motor driver IC as its datasheet says, and control a 12V motor's direction and speed★★★
Chapter 9: More Outputs with Digital ICs (7-Segment and 74HC595)
A logic IC's power and inputs, sourcing and sinking outputs, and a shift register with a latch to show a digit from just a few wires
- 9-1Light Up a 7-Segment DisplaySwitch the 7-segment display between "1" and "7" with S1, at the same brightness★★
- 9-2Power and Inputs of an ICUse a NOT-gate IC so the LED is on while the button is released and off while it's pressed★★★
- 9-3Source and SinkUse one output to swap between L1 and a "1" on the 7-segment display★★★
- 9-4Eight Outputs from Two WiresSend 1s and 0s with just DATA and CLK: light L1 and L2, then only L3★★★★
- 9-5LatchSwitch the LED pattern only when you press LATCH, without showing the bits on their way★★★★
- 9-6Send a Digit to the DisplayShift 8 bits into the 74HC595 with the buttons to show "3", then "7"★★★★★
Chapter 10: Reading Sensors with Analog ICs
Turning slow, small sensor signals into usable ones with comparators, a timer, and op-amps, and finally protecting a motor from overcurrent
- 10-1Compare Two VoltagesBuild a temperature switch with a comparator that tells the microcontroller HIGH once it's hotter than 40 °C★★★
- 10-2No Flicker at DuskBuild a streetlight that turns on when it gets dark and doesn't flicker when the light wavers a little★★★★
- 10-3Blink Without a MicrocontrollerUse a 555 timer to blink an LED every 1–2 seconds, lit for 55–70% of each cycle★★★★
- 10-4Make a Small Signal BiggerAmplify a temperature-sensor IC's small voltage with an op-amp so the microcontroller's ADC can read it finely★★★
- 10-5Stop When It StallsBuild a protection circuit that measures the current, cuts the FET when the motor is held still, and keeps it off until START is pressed★★★★★
Chapter 11: Building Power Supplies
Making the steady 5 V a circuit needs from batteries, a car, and AC: regulator heat and dropout, switching between sources, rectifying and smoothing
- 11-1Make 5 VRun a 5 V microcontroller board from a 9 V battery, even after the battery drops to 7 V★★★
- 11-2Heat and DropoutMake 5 V at 0.5 A from a car's 12 V system—both at 6 V while cranking the engine and at 14 V while driving★★★★
- 11-3USB or BatteriesKeep U1 running—from USB when it's plugged in, from the batteries when it isn't★★★
- 11-4AC to DCMake the LED light in both directions of a source that keeps flipping (AC)★★★★
- 11-5Smooth, Then RegulateMake 5 V for the microcontroller from AC—and hold it for 3 seconds without a single dip★★★★★
Chapter 12: Charging Batteries
Charging a lithium-ion cell at a set current (CC) and stopping at 4.20 V (CV), and keeping voltage, current, and temperature in range with charger and protection ICs
- 12-1Set the currentKeep 20 mA flowing through the LEDs even as the supply voltage and the number of LEDs change★★★
- 12-2Stop at the right voltageA lithium-ion cell is charging at constant current—stop it at 4.20 V and fill it up★★★★
- 12-3Use a charger ICFill a 500 mAh cell at 0.5C or less with a charger IC, and show the state with red and green LEDs★★★★
- 12-4Don't charge when it's too hotWatch the battery pack's temperature on the TEMP pin and stop charging outside 0–45 °C★★★★
- 12-5Protect the batteryGuard the cell against a short circuit and a broken charger with a protection IC and two FETs★★★★★