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Electronics and Signals

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Electronics and Signals: 0% done

Module 1 · Charge, current and voltage

Electricity is charge on the move

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1 / 390 · Charge, current and voltage

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, 1 to practiseElectricity is charge on the move
The water analogy, and where it breaks
, 1 to practiseCurrent is charge per second
, 2 to practiseElectrons crawl; the signal flies
, 1 to practiseVoltage is energy per charge
, 1 to practiseA first circuit: a battery, a resistor and an LED
, 1 to practiseTune it: keep the LED in its safe range
, 1 to practiseOpen and short circuits
, 1 to practisePower is voltage times current
, 1 to practiseEnergy and battery capacity: Wh and mAh
, 2 to practiseSI prefixes, and how values are written
, 1 to practiseSafety: mains, stored energy and lithium cells
, 3 to practisePractice problems
Recap: charge, current and voltage

, 1 to practiseResistance, and Ohm’s law
, 1 to practiseOhm’s law picks an LED’s resistor
, 1 to practiseResistivity: wires and traces have resistance too
, 2 to practiseA resistor turns power into heat
, 2 to practiseReading a resistor: the colour code
, 1 to practiseStandard values: the E-series
Tolerance, and the kinds of resistor
, 1 to practiseSeries: one path, the voltages add
, 1 to practiseParallel: many paths, the currents add
, 1 to practiseThe voltage divider
, 2 to practiseTune it: 3.3 V from 12 V
, 1 to practiseLoading a divider
, 3 to practisePractice problems
Recap: resistance and Ohm’s law

, 1 to practiseReading a schematic
, 1 to practiseThe multimeter: measuring voltage
, 1 to practiseMeasuring current: the meter goes in series
, 2 to practiseResistance, continuity and the diode test
, 1 to practiseThe bench supply: set the current limit first
, 1 to practiseThe breadboard, and its traps
, 1 to practiseSoldering through-hole parts
, 1 to practiseSoldering surface-mount parts, and rework
, 1 to practiseWire and connectors
, 1 to practiseESD, and safety at the bench
The starter kit
Build it on the bench: an LED, measured three ways
, 2 to practiseWhat the first build should read
Recap: the bench

, 2 to practiseKirchhoff’s current law: what flows in flows out
, 1 to practiseKirchhoff’s voltage law: round any loop, the voltages sum to zero
, 1 to practiseNodal analysis: one equation per node
, 2 to practiseNodal analysis is a matrix equation
, 1 to practiseMesh analysis: one equation per loop
, 2 to practiseSuperposition: one source at a time
, 1 to practiseThévenin: any two terminals are a source and a resistor
, 2 to practiseMeasuring a Thévenin equivalent on the bench
, 1 to practiseNorton: a current source and a resistor
, 2 to practiseMaximum power transfer: match the load
, 1 to practiseSource resistance and loading
, 2 to practiseDependent sources: how amplifiers are modelled
, 2 to practiseThe Wheatstone bridge: measuring by balance
Recap: analysing circuits

, 2 to practiseA capacitor stores charge
, 1 to practiseA capacitor’s current is how fast its voltage changes
, 1 to practiseAn inductor’s voltage is how fast its current changes
, 2 to practiseBoth store energy, and it has to go somewhere
, 1 to practiseReal capacitors: a ceramic loses capacitance under voltage
, 1 to practiseReal parts: ESR, ripple current and saturation
, 1 to practiseAn RC circuit moves in time constants
, 2 to practiseHow long to reach a threshold
, 1 to practiseAn RL circuit is the same, with current
, 1 to practiseAdd a capacitor and it can ring
, 2 to practiseTune it: settle fast without ringing
, 2 to practiseInterrupt an inductor and it bites back
Build it on the bench: an RC timer you can watch
Recap: capacitors, inductors and transients

, 1 to practiseA sinusoid has an amplitude, a frequency and a phase
, 2 to practiseRMS: the AC voltage that heats like DC
, 1 to practisePhase is a delay, measured in degrees
, 1 to practiseComplex numbers are arrows that multiply by turning
, 1 to practiseA phasor is a sine as an arrow
, 2 to practiseImpedance: Ohm’s law for R, L and C at a frequency
, 1 to practiseAC analysis is DC analysis in complex numbers
, 1 to practiseImpedances in code
, 1 to practiseAC power: real, reactive and apparent
, 2 to practiseTune it: correct a motor’s power factor
, 2 to practiseMains, and three phases
, 1 to practiseBuild it on the bench: voltages that don’t add up
Recap: AC, phasors and impedance

, 2 to practiseDecibels measure ratios on a log scale
, 1 to practiseA Bode plot: gain and phase against frequency
, 1 to practiseTune it: a 1 kHz corner
, 2 to practiseSwap R and C: a high-pass
, 1 to practiseLoading: the next stage changes the last
, 1 to practiseFind the corner by bisection
, 1 to practiseAn RLC resonates, and Q says how sharply
, 1 to practiseSecond-order low-pass: −40 dB a decade, and peaking
, 1 to practiseA notch cuts one frequency
, 1 to practiseSpecifying a filter: bands, attenuation and order
Build it on the bench: a Bode plot by hand
Recap: frequency response and filters

, 1 to practiseDoped silicon, and a junction that conducts one way
, 1 to practiseThe diode equation: current grows exponentially
, 2 to practiseDiode models, from ideal to exponential
, 1 to practiseA half-wave rectifier, smoothed
, 2 to practiseA bridge rectifier uses both halves
, 2 to practiseDesigning for ripple
, 1 to practiseClippers and clamps
, 2 to practiseA Zener diode holds a voltage
, 2 to practiseAn LED needs a resistor
, 1 to practiseSchottky, fast and TVS diodes
, 2 to practiseDesign review: a junior’s supply board
Build it on the bench: an LED, measured
Build it on the bench: a bridge rectifier
Recap: semiconductors and diodes

, 1 to practiseA small base current controls a large collector current
, 2 to practiseOff, active or saturated
, 1 to practiseA transistor as a switch: saturate it, with margin
, 2 to practiseTune it: saturate the switch, and spare the pin
, 1 to practiseAn inductive load needs a flyback diode
, 1 to practiseBias it so that β doesn’t matter
, 3 to practiseDesigning a bias point
, 1 to practiseThe common-emitter amplifier
, 2 to practiseThe emitter follower, and the Darlington
, 1 to practiseA current mirror copies a current
, 1 to practiseSolve a bias point in code
, 2 to practiseDesign review: a relay driver
Build it on the bench: a relay driver
Recap

, 1 to practiseA voltage on the gate opens a channel
, 1 to practiseFully on, a MOSFET is a small resistor
, 1 to practiseA low-side switch from a microcontroller pin
, 2 to practiseTune it: drive a standard MOSFET hard enough
, 1 to practiseThe gate is a capacitor: switching takes charge
, 2 to practiseWhere a MOSFET’s heat comes from
, 1 to practiseHigh-side switches
, 1 to practiseAn H-bridge drives a motor both ways
, 1 to practiseThe body diode, and reverse-polarity protection
, 1 to practisePWM: control power by switching it
, 1 to practisePWM in firmware
, 2 to practiseDesign review: a heater driver
Build it on the bench: a PWM LED dimmer
Recap

, 1 to practiseAn op-amp: enormous gain, tamed by feedback
, 1 to practiseThe inverting amplifier
, 2 to practiseThe non-inverting amplifier and the follower
, 1 to practiseThe difference amplifier, and why its resistors must match
, 1 to practiseThe instrumentation amplifier
, 2 to practiseThe integrator
, 1 to practiseActive filters: the Sallen–Key low-pass
, 1 to practiseComparators and the Schmitt trigger
, 1 to practiseReal limits: gain-bandwidth and slew rate
, 2 to practiseReal limits: offset, bias current, rails and output current
, 1 to practiseSingle-supply design, decoupling and stability
, 3 to practiseDesign review: a sensor buffer
Build it on the bench: a non-inverting amplifier
Recap

, 1 to practiseEvery design starts with a power budget
, 1 to practiseFrom the mains: transformer, rectifier and reservoir
, 1 to practiseA linear regulator burns the difference
, 2 to practiseHeat: thermal resistance and heatsinks
, 1 to practiseThe buck converter switches its way down
, 2 to practiseChoosing the inductor and the capacitor
, 1 to practiseThe boost converter, and buck-boost
, 2 to practiseLinear or switching?
, 1 to practiseWorst-case design: vary the parts
, 1 to practiseBatteries, and charging a Li-ion cell
, 1 to practiseProtection: fuses, reverse polarity, surges and inrush
, 3 to practiseDesign review: a 5 V rail
Build it on the bench: a buck module’s efficiency
Recap

, 1 to practiseDigital signals use two levels, with a gap between them
, 3 to practiseBinary and hexadecimal count in bits
, 1 to practiseGates compute truth tables
, 1 to practiseBoolean algebra simplifies logic
, 2 to practiseDe Morgan’s laws, and why NAND can build anything
, 2 to practiseA Karnaugh map groups the 1s into the simplest form
, 2 to practiseAdders add one bit and a carry at a time
, 2 to practiseA multiplexer chooses an input; a decoder picks one output
, 2 to practiseWhat counts as 0 and 1: input and output levels
, 1 to practiseMixing 3.3 V and 5 V logic
, 2 to practiseFan-out, open-drain outputs and pull-ups
, 1 to practiseBuild it: an XOR from one 74HC00
, 2 to practiseDesign review: a logic board
Recap: digital logic

, 1 to practiseFeedback gives a circuit memory
, 1 to practiseA D flip-flop takes its input on the clock’s rising edge
, 1 to practiseRegisters hold words; shift registers move bits along
, 2 to practiseCounters count clock edges and divide frequencies
, 1 to practiseA state machine is states, inputs and a rule for the next state
, 2 to practiseThe traffic light in two flip-flops and four gates
, 1 to practiseThe same machine in firmware
, 2 to practiseEvery state machine needs a known start
, 1 to practiseSetup, hold and the fastest clock
, 2 to practiseMetastability, and the two-flip-flop synchroniser
, 1 to practiseHDLs and FPGAs: hardware you describe in code
, 1 to practiseBuild it: a 74HC595 drives eight LEDs
, 2 to practiseDesign review: a decade counter
Recap: sequential logic

, 1 to practiseA microcontroller is a computer and its peripherals on one chip
, 3 to practiseA GPIO pin: pull-ups for inputs, limits for outputs
, 2 to practiseButtons bounce; an RC and a Schmitt trigger smooth them
, 2 to practiseInterrupts and timers do the waiting
, 1 to practiseDebouncing in firmware, from a timer
, 2 to practisePWM: an average voltage from a digital pin
, 3 to practiseAn ADC turns a voltage into a number
, 3 to practiseUART: a start bit, eight data bits and a stop bit
, 2 to practiseSPI: a clock, data each way, and a chip select
, 1 to practiseI²C: two shared wires and an address
, 3 to practiseSizing I²C pull-ups: current against rise time
Build it: a Pico dims an LED, one press at a time
, 2 to practiseDesign review: a microcontroller board
Recap: microcontrollers and interfacing

, 1 to practiseA sensor turns a quantity into a signal
, 1 to practiseA thermistor’s resistance falls steeply as it warms
, 2 to practiseA divider turns the thermistor into a voltage
, 2 to practiseStrain gauges and RTDs: small changes, read with a bridge
, 2 to practiseLight, magnetic field and current
, 1 to practiseDigital sensors do their own conditioning
, 2 to practiseConditioning: fit the signal to the ADC, and protect it
, 1 to practiseA DC motor, and an H-bridge to drive it both ways
, 2 to practiseMotors, relays and solenoids kick back
, 2 to practiseSteppers, servos and brushless motors
, 2 to practiseIsolation: optocouplers and digital isolators
Build it: a Pico reads an SHT31 and a thermistor
, 2 to practiseDesign review: a sensor and actuator board
Recap: sensors and actuators

, 1 to practiseFirmware: a program that never ends
, 2 to practiseThe super-loop: never wait, check the clock
, 1 to practiseState machines: firmware that remembers where it is
, 2 to practiseInterrupts and shared data: volatile and critical sections
, 2 to practiseA ring buffer: from an interrupt to the main loop
, 1 to practiseAn RTOS: tasks, priorities and queues
, 2 to practisePriorities: rate-monotonic, and priority inversion
, 4 to practiseLow power: sleep, wake, and the average current
, 2 to practiseWatchdogs and brown-out: surviving a hang
, 1 to practiseBootloaders, safe updates and CRCs
, 2 to practiseDebugging: a probe, a pin and a logic analyser
Build it on the bench: watch your firmware run
, 4 to practiseDesign review: firmware that works on the desk and fails in the field
Recap: embedded systems and firmware

, 1 to practiseA signal carries information; a system changes it
, 1 to practiseThe step, the impulse and the exponential
, 2 to practiseEnergy signals and power signals
, 2 to practiseLinear, time-invariant, causal and stable
, 1 to practiseThe impulse response tells you everything
Convolution: flip, slide, multiply, add
, 3 to practiseThe convolution sum, by hand and in code
, 2 to practiseThe step response is the running integral of the impulse response
, 1 to practiseTune it: a time constant from a step response
, 2 to practiseA discrete system: the exponential moving average
, 1 to practiseStable systems: bounded in, bounded out
Build it on the bench: an RC’s step and impulse responses
, 3 to practiseDesign review: does the test measure the system?
Recap: signals and systems

, 1 to practiseEvery periodic signal is a sum of sines
, 1 to practiseThe Fourier series: each coefficient is an average
, 1 to practiseA square wave, built harmonic by harmonic
, 1 to practiseGibbs: the overshoot that never goes away
, 1 to practiseTriangles and sawtooths: jumps make slow-falling harmonics
, 1 to practiseA pulse train’s spectrum follows a sinc
, 1 to practiseThe Fourier transform: spectra of signals that don’t repeat
, 2 to practiseBandwidth, and the spectrum of a digital edge
, 2 to practiseFiltering in frequency: multiply the spectrum
, 2 to practiseParseval: the power is the same counted either way
, 2 to practiseModulation moves a spectrum: AM, and FM in brief
Build it on the bench: a square wave’s harmonics
, 3 to practiseDesign review: where the harmonics go
Recap: Fourier series and transform

, 1 to practiseThe Laplace transform turns calculus into algebra
, 1 to practiseA transfer function is the system, written in s
, 2 to practiseBack to time: partial fractions
, 1 to practisePoles and zeros: a map of the system
, 3 to practiseSecond-order systems: ζ, ωn and overshoot
, 1 to practiseFeedback: measure, compare, correct
, 3 to practiseSteady-state error, from the final-value theorem
, 1 to practisePID control: proportional, integral, derivative
, 1 to practiseTune a PID on a heater, in simulation
, 2 to practiseGain and phase margin: how far from oscillating
, 3 to practiseOscillators: feedback that is meant to be unstable
Build it on the bench: PID temperature control
, 3 to practiseDesign review: loops that ring and loops that wind up
Recap: Laplace, feedback and control

An ADC measures at instants, and rounds
, 1 to practiseSample faster than twice the highest frequency
, 2 to practiseAbove Nyquist, a frequency folds back
, 1 to practiseFilter first: the anti-aliasing filter
, 1 to practiseOne pole is rarely enough
, 1 to practiseQuantising adds noise: 6.02N + 1.76 dB
, 3 to practiseENOB: the bits you really get
, 2 to practiseFlash, SAR and sigma-delta
, 2 to practiseThe reference sets the scale
, 2 to practiseOversampling buys bits
, 1 to practiseBack out: DACs, steps and the sinc
Build it on the bench: aliasing on a Pico
, 2 to practiseDesign review: a logger’s analogue input
Recap

, 1 to practiseA digital filter is arithmetic on samples
, 2 to practiseThe moving average, and where its nulls fall
, 2 to practisez⁻¹ is a delay: poles inside the circle
, 1 to practiseWindowed sinc: the ideal low-pass, cut short
, 2 to practiseHow many taps: the window and the transition
, 1 to practiseIIR filters: poles near the circle resonate
, 1 to practiseThe bilinear transform, and its warping
, 1 to practiseA biquad by the cookbook
, 2 to practiseThe DFT, the FFT, and one bin by Goertzel
, 1 to practiseWindowing and leakage
, 2 to practiseFixed point: Q15 on a microcontroller
, 3 to practiseA biquad in fixed point, as firmware
Build it on the bench: a digital low-pass on a Pico
Recap

, 1 to practiseWhen a wire becomes a transmission line
, 1 to practiseCharacteristic impedance: what a line looks like to a wave
, 1 to practiseA mismatch reflects: Γ, VSWR and return loss
, 1 to practiseThe Smith chart: every impedance on one disc
, 2 to practiseAn L-network matches two resistances at one frequency
, 1 to practiseMatching, simulated: all the power at one frequency
, 1 to practiseA match has a bandwidth, and S-parameters measure it
, 1 to practiseAntennas: dipoles, monopoles and PCB antennas
, 4 to practiseLink budgets: dBm in, dBm out
, 1 to practiseModulation: putting bits on a carrier
, 1 to practiseUse a certified module
, 1 to practiseRegulations in brief: bands, power and duty cycle
Build it on the bench: measure a link budget
Recap

From schematic to board: the flow
, 1 to practiseThe schematic is the source of truth, and ERC checks it
, 1 to practiseFootprints: copper that must fit the real part
, 1 to practiseDesign rules: set them first, check them last
Placement first: most of a layout is decided here
, 2 to practiseDecoupling at the pins: it is the inductance that matters
, 1 to practiseGround is a plane, and return current follows the signal
, 2 to practiseTrace width for current: IPC-2221
, 1 to practiseClearance for voltage, and vias
, 1 to practiseFabrication outputs, and ordering
, 2 to practiseAssembly, and a BOM you can actually buy
, 2 to practiseDesign review: spot the layout mistakes
, 1 to practiseBuild it: your first ordered board
Recap

, 1 to practiseA board that works on the bench can still fail
, 1 to practiseEdges, not clock rates, set the bandwidth
, 2 to practiseA trace is long when its delay is a fair part of the rise time
, 2 to practiseReflections, and a resistor that stops them
, 2 to practiseCurrent comes back under its trace: keep the loop small
, 2 to practiseNoise you can’t remove: thermal, shot and 1/f
, 1 to practiseEvery watt leaves through a thermal resistance
, 2 to practiseDerate: run every part well inside its ratings
, 2 to practiseTolerances: the worst case, and what builds really do
On the bench: measure how real parts spread
, 3 to practiseESD and faults: protect every connector
, 3 to practiseRead a datasheet like a sceptic
, 2 to practiseDesign review: a junior’s sensor board
Recap: boards that work

, 1 to practiseFrom boards in a box to a product
, 1 to practiseLook and measure before you power
, 1 to practiseFirst power-on: the current limit is your fuse
, 1 to practiseBring up one block at a time, rails before chips
, 2 to practiseFault-finding is a method, not a hunch
, 1 to practiseHunting a short with millivolts
, 4 to practiseDiagnose it: what do you measure next?
, 2 to practiseDesign for test: make every board quick to prove
, 2 to practiseDesign for manufacture: let the factory build it right
, 2 to practiseCertification: what is tested, and how to pass first time
, 2 to practiseRevision control: know exactly what every board is
, 1 to practiseReview the design before you order
, 1 to practiseBuild it on the bench: a fault-finding drill
Recap

, 3 to practiseHow an expert attacks a circuit problem
, 3 to practiseDiagnose: a battery reading 9% low
, 2 to practiseDesign: a MOSFET switch for an LED string
, 2 to practisePredict: what a relay coil does when it’s let go
, 1 to practisePredict: two RC stages, with and without a buffer
, 2 to practiseDesign: a sensor to fill a 3.3 V ADC
, 3 to practiseDesign: a regulator from 12 V, and a battery budget
, 2 to practisePredict: does the path meet its clock, and is the input safe?
, 2 to practiseDiagnose: a 50 Hz hum that isn’t mains
, 1 to practiseCode: a low-pass that doesn’t stall
, 2 to practisePredict: a speed loop’s step from its poles
, 2 to practiseDesign: will the sensor’s radio reach?
, 3 to practiseCheck a board: tolerances and a long trace
, 2 to practiseReview a design, then bring it up
What you can do now

What you’ll build, and the kit
, 2 to practiseStep 1: the architecture, and the decision that sets the battery life
, 2 to practiseStep 2: the charger’s current and its heat
, 2 to practiseStep 2: the regulator’s dropout, and what the ADC can see
, 2 to practiseStep 2: the switch that turns the RP2040 off
, 2 to practiseStep 3: the sensor’s bus, with pull-ups fast enough
, 1 to practiseStep 3: reading the SHT31, and checking every word
, 3 to practiseStep 4: the log record and its CRC-16
, 2 to practiseStep 5: where the next record goes, and when
, 2 to practiseStep 6: measuring the cell, and how long it lasts
, 1 to practiseStep 7: the schematic in KiCad
, 1 to practiseStep 8: the layout, placement first
, 1 to practiseStep 9: order the boards, and assemble them
, 2 to practiseStep 10: bring it up, and test it against the spec