Computer Peripherals

Hardware
Audio
Video
Published

August 17, 2015

Modified

October 12, 2022

Motherboard

Main circuit board to connect different build components of a computer.

  • Also known as mainboard, system board, abbreviated to MB
  • System Clock (CMOS Battery)
  • Front Panel, connectors for external devices (i.e. USB, HDMI, Audio)
  • BIOS (Basic Input/Output System)
    • Performs hardware check after power on
    • Configurable with a system settings menu (boot devices, power settings, etc.)
  • Chipset
    • Determines which components are compatible
    • Dictates future expansion options
    • Enables overclocking of CPUs, RAM
    • Single-chip on modern systems directly connected to the CPU
    • Intel Platform Controller Hub (PCH), Direct Media Interface (DIM)
    • AMD Fusion Controller Hub (FCH), Unified Media Interface (UMI)
  • VRM (Voltage Regulator Module)
    • Senses the CPU voltage requirements
  • SATA storage controller

Connectors

  • CPU Socket
  • Memory Slots
  • Expansion Slots
  • Storage Connectors (SATA ports, M.2)
  • I/O Interfaces (on board)
  • Front panel connectors
    • USB 2 8 pin
    • USB 3
    • Audio connector
  • 3/4 pin fan connectors (4 pin is backwards compatible to accommodate 3 pins)
  • RGB Connection

Form Factor

Size of the motherboard:

  • ATX
    • 305x244mm
    • Full/Mid tower cases
    • Most common, de facto standard
    • Up to 7 expansion slots
    • Up to 8 memory slots
  • Micro-ATX, UATX
    • 244x244mm
    • Less expensive
    • Max. 4 expansion slots
    • 2-4 memory slots
  • Mini-ITX
    • 170x170mm
    • Even less expensive
    • 1 expansion slot
    • Up to 2 memory slots

Power Connectors

ATX 24 pin 12V (ATX v2.2 standard)

  • Connects the board to the PCU (Power Supply Unit)
  • Molex 39-01-2240, often called a Molex Mini-fit Jr.
  • ATX 20+4 for backwards compatability

ATX/EPS 8 pin 12V (EPS12V) - Powers the processor voltage regulator - Dedicated CPU power supply - Molex 39-28-1083 - Not to confuse with 8 pin PCIe connectors

P4 4 pin ATX 12V

  • Additional power connector (older boards)
  • Molex 39-28-1043
  • 8 pin connectors are backward compatible and are two 4-pin connectors connected to each other that can be separated.

CPU Socket & Chipset

Motherboards need to match/support the CPU!

Following a couple of introduction material on Youtube:

Selection of chipset is relevant to overclocking and customization.

List of current sockets with corresponding chipset and CPU compatibility:

Expansion Slots

Expansion slots need to support the expansion card!

Following a couple of introduction material on Youtube:

Motherboards support PCI Express (PCIe) slots:

  • PCIe x16 (de facto standard for video cards, GPUs)
  • PCIe x1 (network, audio, I/O interfaces)
  • Replaces PCI, and AGP

x{1,4,8,16} indicates the number of parallel lanes.

Slots are downwards compatible (physical protection for wrong slotting)

GPU expansion cards need to match the PCI generation for max. performance.

PCIe generations:

Year Version Speed (per lane)
2010 3.0 985MB/s
2017 4.0 1.97GB/s

I/O Interfaces

Connectivity varies widely on motherboards, and have a huge impact on prices.

Located on the rear (or back) I/O panel, and on the motherboard surface

  • USB for mouse, keyboard, microphones, cameras, storage, etc
  • NIC typically Ethernet
  • Sound input/output for headphones, and a microphone
  • Some motherboards support integrated video (DisplayPort, HDMI)
  • Some motherboards include Wifi, and Bluetooth

Keyboard

Configuration

# list input devices
cat /proc/bus/input/devices | grep -P '^[NH]: ' | paste - -
# monitor keystrokes
evtest                      # select from the list of devices
evtest /dev/input/event$n   # select a specific device
# monitor keystrokes in a virtual console
showkey --keycodes
# monitor keystrokes in X
xev | awk -F'[ )]+' '/^KeyPress/ { a[NR+2] } NR in a { printf "%-3s %s\n", $5, $8 }'
# or
xbindkeys --defaults > ~/.xbindkeysrc
xbindkeys --multikey

Layouts

Configuration Files:

# default keyboard layout
/etc/default/keyboard
# virtual console keymap configuration
/etc/vconsole.conf
# keymap files (usually corresponds to one keyboard)
find /usr/share/kbd/keymaps/ -type f

loadkeys loads or modifies the keyboard driver’s translation tables

# set german keyboard for current console
loadkeys de

X Keyboard Extension (XKB) handles keyboard settings and layouts in X11

# list of keyboard models known to XKB
/usr/share/X11/xkb/rules/base.lst
# list available toggle keys
grep "grp:.*toggle" /usr/share/X11/xkb/rules/base.lst

setxkbmap for non-permanent changes:

# get current keyboard layout
setxkbmap -query | grep layout
# set the keyboard layout, i.e. to `de` (german)
setxkbmap de
# toggle keyboard layout with ALT+SHIFT
setxkbmap -layout us,de -option grp:alt_shift_toggle

Add a permanent keyboard configuration:

sudo mkdir -p /etc/X11/xorg.conf.d
cat << EOF | sudo tee /etc/X11/xorg.conf.d/00-keyboard.conf
Section "InputClass"
    Identifier "keyboard-all"
    Driver "evdev"
    Option "XkbLayout" "us,de"
    Option "XkbModel" "pc104"
    Option "XkbOptions" "grp:alt_shift_toggle"
    MatchIsKeyboard "on"
EndSection
EOF

Displays

Physiological aspect of the human eye:

  • Visual field: approx. 200°, 120° binocular overlap
  • Retinal resolution 0.3 to 0.7 arc minutes (depends on task/luminance)
  • Temporal resolution: approx 50Hz (increases with luminance)
  • Three types of photoreceptors:
    • Blur (450nm +/-30)
    • Green (550nm +/-40)
    • Red (600nm +/-35)

Display device is an output device to present information.

Electronic visual display (informally screen) technologies:

  • CRT (cathode ray tube)
  • Segment display
  • LCD (liquid crystal display)
    • TFT (thin-film transistor) LCD
    • LCD with LED backlit
  • OLED (organic light-emitting diode display)
  • Plasma (plasma display panel)
  • QLED (quantum dot LED)

Displays emitting light called active.

Displays modulating available light (reflection/transmission) called passive.

Modern displays are basically giant grids…

  • …each gird elements represented by a bit value encoding the color information
  • individual gird elements are referred to as pixel

Addressing Scheme

Three different addressing schemes for display devices:

  • Direct
    • Individual control signals to each pixel
    • m×n pixels, require m×n control signals (considered inefficient)
  • Raster
    • Scanning across display in sequence
    • Modulating control signal to activate each pixel
    • Pixels fade-out until the scan visits that pixel again
  • Vector displays
    • Display line by line, specified by endpoints
    • Directly control the electron beam of a CRT (cathode ray tube)
    • Periodical refresh required
  • Matrix
    • Control signals only to the rows and columns
    • m×n pixels, require m+n control signals
    • Active matrix: external capacitor maintain the state of the cell
    • Passive matrix: cell itself bistable, no additional capacitor

Resolution

Number of pixels from left-to-right & top-to-bottom determines the screen resolution. Monitor resolution describes the visual dimensions of any given display.

width x height abbr. marketing term
1280x720 720p HD
1920x1080 1080p FHD
2560x1440 1440p QHD 2k
3840x2160 2160p UHD 4k
5120x2160 5k
7680x4320 8k

Aspect ratio describes the correlation between width and height

  • 4:3 (640x480, 1024x768, 1600x1200) traditional screen resolutions
  • 16:9 (1920x1200, 2560x1440, 3840x2160) widescreen

PPI (pixels per inch) describes a monitor screen’s pixel density…

  • …how fine-grained the individual pixels are
  • The higher the PPI the better image quality will appear to the human eye
  • similar to DPI (dots per inch) for printers

Synchronization

Reduces screen tearing, and improves input lag:

  • Occurs if the video feed is not synced to the display refresh rate)
  • Solved by driving the screen refresh with the graphic device

G-Sync (Nvidia), or FreeSync (AMD) operate with VRR (variable refresh rate)

Color

HDR (High Dynamic Range)…

…take advantage of higher contrast ratios and higher overall luminance

  • …contrast ratio between the darkest black and the brightest white
  • …increased luminance or light output

…increase the number of bits used to represent Red, Green, and Blue

  • HDR10 (10 bits) set intensities of red,green, and blue between 0 and 1023
  • …over a billion possible colors

Technology

LCD

  • Works by adjusting the amount of light blocked
  • Array of liquid crystal segments (containing organic molecules)
    • Organized in a random pattern when not electric field is applied
    • Within an electric field crystals align perpendicular to a light source
    • Crystals “gate” the amount of light that can pass through
  • A light source - backlight - needs to drive light through the crystals
  • TFT type of an LCD with a thin film transistor attached to each pixel
    • Amplifies each pixel (higher contrast ratio)
    • Pixel hold electrical state
    • Pixel more rapidly switched (faster response time (25ms))

Color filters allow the generation of colors (RGB) at a segment:

  • Three segments required to generate a real world color
  • Light passes individually through red/grenn/blue filter segments
  • These segments for a group, RGB pixel

I.e. a 320x240 RGB display is formed by 960 columns and 240 rows

OLED

Use organic materials that emit light when electricity is applied

  • …rather then blocking light like LCDs
  • Series of organic thin films between two conductors
  • Emissive displays that do not require backlight, or color filters
  • Only an “on” pixel consumes power

Improvements over LCDs:

  • Ultra-thin form factor: Plastic, organic layers of an OLED are thinner, lighter and more flexible than the crystalline layers in an LED
  • Because the light-emitting layers of an OLED are lighter:
    • Substrates can be plastic rather than the glass used for LEDs
    • Substrate of an OLED can be flexible (fold, roll, stretch) instead of rigid
  • Lower power consumption
  • Better durability (broader temperature range)
  • Long-lasting lifetime, up to 55.000 hours
  • Improved resolution up to <5 micrometer pixel size
  • Improved display refresh rates between 1 to 10 microseconds
  • OLEDs are brighter than LEDs, with better contrast
  • Large fields of view, about 170 degrees
  • Wider color range

Disadvantages overt LCDs:

  • (currently) More expensive manufacturing costs
  • Over time, moisture can react with the organic layers, cause degradation and defects in an OLED display
  • Harder to see in direct sun-light

Manufacturing

Vacuum Deposition or Vacuum Thermal Evaporation (VTE)

  • Vacuum evaporation of small organic molecules onto a substrate
  • Evaporation through a slow heating process…
  • …followed by a thin film condensing onto the cooled substrate
  • Inefficient, expensive, limited up to 15” diameter
  • Crystallization process shortens lifespan and reliability

Organic Vapor Phase Deposition (OVPD)

  • Use of a carrier gas to transfer films of organic material…
  • … onto substrate in a hot-walled, low-pressure chamber
  • Better control film thickness, lower material cost

Polymer OLEDs, Inkjet Printing

  • OLEDs sprayed onto substrate through inkjet printing…
  • …under ambient conditions
  • Low cost, deposit of multiple layers simultaneously
  • Fabrication of large screen sizes
  • Problems
    • Substrate surface properties affect uniformity of the film thickness
    • Layer shift due to drying and evaporation process

Types

PMOLED (passive matrix OLED)

  • Cheaper manufacturing compared to other OLED types
  • Large driving current to achieve adequate average brightness…
  • …limits display size (<3”), resolution by max. input voltage
  • …increased power dissipation, excess flicker, shortened lifespan
  • Most efficient for text (most pixels off)
  • Still more power efficient the LCDs

External circuitry control each row in the display sequentially:

  • Strips of cathode, organic layers and strips of anode
  • Anode strips are arranged perpendicular to the cathode strips
  • Intersections of the cathode/anode makes the pixels (light is emitted)
  • External circuitry applies current to selected strips of anode and cathode
  • Brightness of pixels proportional to driving current

AMOLED (active matrix OLED)

  • Use (active-matrix) TFT array with storage capacitor
  • Consume less power than PMOLEDs (internal TFT more efficient)
  • Faster refresh rate (suitable for video)
  • Efficient enough to support larger high-resolution displays

Internal TFT array circuitry determines which pixels get turned on:

  • Full layers of cathode, organic molecules and anode
  • Anode layer overlays a thin film transistor (TFT) array forming a matrix

QLED

QLED (quantum dot light emitting diodes):

  • Light emitters, cadmium selenide (CdSe) nano-scale crystals
    • Quantum dots (QD): conducting nano-crystals with 2nm to 10nm diameter
    • Color of light produced or filtered by a dot is based on its diameter
  • Sandwiched between electron-transporting & hole-transporting organic materials
  • Applied electric field causes electrons and holes to move into the quantum dot layer, where they are captured to emit photons.

Improvements over OLED:

  • 30-40% luminance efficiency advantage over OLED
  • Up to 50% less power consumption the over OLED

Audio

Sound System…

  • PCM (Pulse-Code-Modulation)
    • Digital audio encoding
    • Represents amplitude of a signal at uniform intervals
  • MIDI (Musical Instrument Digital Interface)
    • Control electronic musical instruments

OSS (Open Sound System)…

  • …old sound card support system up to Linux 2.4
  • Still used for old sound cards not ported to ALSA, marked as deprecated
  • Designed for standard devices system calls read(), write(), etc.
  • Write to /dev/dsp for playback
  • Reading from /dev/dsp to capture (record)
  • Limitations…
    • No support for software mixing (limited to a single application)
    • Play/record at the same time not possible
    • No hardware MIDI support
/dev/dsp        # D/A and A/D converter device, generate/read audio
/dev/mixer      # mainly for controlling volume
/dev/audio      # Sun compatible digital audio
/dev/sequencer  # audio sequencer (MIDI)

Making Sense of The Audio Stack On Unix (2021)
https://venam.nixers.net/blog/unix/2021/02/07/audio-stack.html

DAC Interface

External DAC (Digital Audio Converter) aka audio interfaces

  • Passing audio from the outside world into your computer and back
  • Conversion between digital and analog audio and interface with external devices
    • Speakers, headphones and microphones
    • Direct instrument inputs (guitar, keyboard, etc.)
  • Connectivity with USB, Firewire, Thunderbolt or PCIe
  • Analog and digital connections typically include XLR, 1/4” TRS, and RCA

Studio Monitors

Loudspeakers giving an accurate reproduction of the tonal qualities of the source audio(flat frequency response), no relative phase shift of particular frequencies.

  • Used for audio mixing and mastering, enable audio engineers to create sound pleasing on the widest range of playback systems used by regular listeners
  • Nearfield monitors design for close proximity to the listener
    • I.e. sitting on a desk infront of the monitor, equilateral triangle arrangement
    • Hear primarily the direct sound coming from the speakers (minimized reflections from room surfaces)
    • Compact two-way systems, tweeter and a moderately-sized (4-8”) second driver
    • Good for small rooms and/or challenging room acoustics
  • Midfield monitors (more powerful than nearfield)
    • Beefier power amplifiers provide more bass extension and proper mid- and high-frequency dispersion at greater distances
    • Have larger woofers (8-10”), sometimes three-way designs (with a dedicated midrange driver)
    • Can fill larger rooms with high-quality sound for multiple listeners positioned further away
    • Larger monitoring sweet spot, more volume (“bigger” sound)
  • Active monitors including one or more internal power amplifier(s)
  • Bi-amplified, separate low- and high-frequency amplifiers
    • Low-frequency part is routed to a woofer
    • High-frequency part is routed to a tweeter
  • Input:
    • Stereo RCA connectors for soundcards
    • Stereo 1/8” TRS (3.5mm Klinkenstecker) for CD/MD/Phones
    • 1/4” TRS (6,35mm Klinkemstecker) for microphone, keyboards, etc..
    • XLR balanced audio interconnection (found on professional equipment)
  • Output: 1/8” TRS for headphones

Power Amplifier

Audio power amplifier (amp) reproduces low-power electronic audio signals for driving (loud)speakers or headphones.

  • Typical loudspeaker has an impedance of between 4Ω and 8Ω
  • Amps supply high peak currents to drive the low impedance speaker

Classes, broad indication of an amplifier’s characteristics and performance:

  • Amount of the output signal over one cycle of operation (by a sinusoidal input signal)
  • A, B, AB and C for analog designs
  • D, E, F, G, S, T etc switching designs (use digital circuits and pulse width modulation (PWM))
  • Trade-off between power efficiency (class D up to 90%) and audio fidelity
  • Class T, inexpensive, efficient, lightweight, digital amplifiers
    • Real time control of the switching frequency depending on the input signal and amplified output
    • low distortion signal levels (of class AB) and power efficiency (of class D)
    • Use DSP (Digital Signal Processing)

Microphones

Dynamic microphones used for live broadcast, podcasts, voice-over:

  • Passive (does not need an extra power source)
  • Durable (can handle very loud sound)
  • Good at background noise rejection
  • Low sensitivity, low output level
  • Usually no full frequency response

Condenser microphones provide a more natural sound and are used in studios for music recording:

  • Powered (requires a power source connection) aka phantom power
  • Fragile (can be over-driven by loud sound)
  • Wider range of frequency response
  • Higher sensitivity, higher output level
  • Require a controlled environment (no background noise)

Additional equipment for desk recording:

  • Microphone stand
  • Shock mount
  • Pop filter or wind screen

Noise Suppression

RNNoise: Learning Noise Suppression
https://jmvalin.ca/demo/rnnoise
https://gitlab.xiph.org/xiph/rnnoise

Real-time Noise Suppression Plugin
https://github.com/werman/noise-suppression-for-voice
https://github.com/josh-richardson/cadmus

NoiseTorch
https://github.com/lawl/NoiseTorch

Communication

Serial Communication

Serial data transmission (one single bit at a time) between digital devices:

  • Umbrella word for all that is time division multiplexed (data sent spread over time)
  • Opposite of parallel data transmission (multiple bits at the same time)
  • Basic serial communication require one wire, typically 2 wires are used (never more than four)

Synchronous or asynchronous serial interface:

  • Synchronous, pairs data line(s) with clock signal
    • All devices on the serial bus share a common clock
    • Faster serial transfer, requires (at least) one extra wire
    • Common clocked serial protocols: SPI, I2C
  • Asynchronous, no common clock signal
    • Data stream includes synchronization information
    • Minimize required wires and I/O pins
    • Common clock-less serial protocols:

Commonly “serial” is used synonymously with asynchronous serial.

Serial hardware implementation:

  • Send data over an communication channel
  • Data transmitted sequentially over a single channel
  • Data send/receive as electrical pulses
    • 0V for logic zero and nowadays 5V (or 3.3V) as logic one
    • Cf. TTL transistor-transistor logic level, and RS-232

The baud rate defines speed of communication in bps (bits per second)

  • Determines how long the transmitter holds a serial line high/low
  • Baud rate missmatch happens when communication devices use different transmission speeds
  • Standard baud rates: 1200, 2400, 4800, 9600, 19200, 38400, 57600, and 115200

Synchronous

SPI (Serial Peripheral Interface):

  • Master sends a clock signal, each clock pulse shifts one bit to the slave (out), and one bit from the slave (in)
  • Signal names:
    • SCK clock, MOSI master out slave in, and MISO master in slave out
    • SS slave select, master controls more than one slave on the serial bus

I2C (Inter-Integrated Circuit), pronounced “I squared C”:

  • 2 wires, clock (SCL) created by the master, data (SDA) master and slave share the same wire
  • Devices have a 7 bit address, with a maximum of 127 devices on the bus
  • read/write bit indicates data direction of the next byte(s), 0 to acknowledge reception

Atmel uses TWI (2-wire interface) which is exactly same as I2C

Asynchronous

An asynchronous serial protocol requires mechanisms to ensure robust, error-free data transfer:

  • Uses data frames (packets) to encapsulate a data block (chunk) to transfer
  • The data block has a variable size (typically 5 to 9 bit), i.e. 7 bit for ASCII
  • Each data frame includes synchronization bits (start/stop bit(s)) and parity bits
  • 2 wires for communication RX receiver, TX transmitter, and GND ground
  • RX/TX with respect to the device, transmitter wired to the receiver
  • Full duplex means both communication partners send/receive data simultaneously

UART (Universal Asynchronous Receiver/Transmitter), physical circuit (dedicated IC, or integrated within a MCU) implementing serial communication:

  • UARTs communicate directly with each other (not a protocol like SPI or I2C)
  • Converts parallel (8 bit) data from a controlling device (MCU/CPU) into serial data and vice versa
  • More advanced UARTs use a buffer for received data (FIFO)
  • USART (Universal Synchronous/Asynchronous serial Receiver/Transmitter)

Lighting

Part of the electromagnetic spectrum that is perceived by our eyes

Wavelength between 380 and 780 nm

Light has a triple effect:

  • Visual illumination (glare-free and convenient)
  • Emotional perception (creating mood and comfort)
  • Biological effects (circadian rhythm, stimulation or relaxing)

Sources

Incandescent lamps (Glühlampe)

  • Sends electric current through a thin wire called a filament
  • The filament is mostly of tungsten (Wolfram)
  • Resistance heats the filament until it glows producing light & heat

Halogen lamps are a more efficient incandescent lamps

Fluorescent lamps (a type of gas discharge lamp)

  • I.e. mercury vapor emits ultraviolet to excite phosphor which emits light
  • More expensive, longer life, less energy (than an incandescent lamps)

LED (light-emitting diode)

  • Semiconductor device that produces light from electricity
  • Less expensive (more efficient), longer life (than all other sources)

Parameters

Name Symbol Unit
Luminous flux Lichtstrom Φ (Phi) lm (Lumen)
Luminous intensity Lichtstärke Ι cd (Candela)
Illuminance Beleuchtungsstärke E lx (Lux)
Luminance Leuchtdichte L cd/m²
Luminous efficiency Lichtausbeute lm/W (Lumens per Watt)
  • Luminous intensity
    • Quantity of light radiated in a particular direction
    • Represented by the luminous intensity distribution curve (LDC)
  • Illuminance - Quantity of luminous flux falling on a surface
  • Luminance - Brightness that is perceived by the eye

Luminous Flux

Measure of quantity of light emitted…

  • …by a light source (accounts for the sensitivity of the eye)…
  • …weighting the power at each wavelength with the luminosity function
Source Lumen (lm)
Simple LED diode <1
Candle 10
Kerosene lantern 100
Incandescent light bulb (40W,230V) 430
High-output white LED (7W) 450
Fluorescent tube (30W,895mm) 1600
Xenon bulb (35W) >2200
Sun 3.7·10²⁸

Luminous Efficacy

Ratio of the luminous flux to the electrical power consumed (lm/W)

Source lm/W
Tungsten incandescent light bulb 12.5-17.5
Halogen lamp 16-24
Mercury vapor lamp 35-65
Fluorescent lamp 45-75
LED lamp 80-100
Metal halide lamp 75-100
High pressure sodium vapor lamp 85-150
Low pressure sodium vapor lamp 100-200

It is a measure of a light source’s economic efficiency

Light Colour

Colour Temp. Appearance Association
up to 3300K reddish warm
3300-5300K white neutral
more than 5300K bluish cool

Melanopic effect of light:

  • Blue light suppresses the sleep hormone melatonin
  • Melatonin is responsible for a good sleep at night
  • Right light controls the circadian rhythm (circadiane Rhythmik)…
  • ..thus a healthy waking and sleeping behaviour

Bulb Sockets

Standard socket for interior lighting is called Edison screw:

  • Right-hand threaded metal bases (caps) which…
  • …screw into matching threaded sockets (lamp holders)
  • Thread connected to neutral, buttom tip connected to main phase

Countries with 220–240V use typically use

  • Edison screw-mounts: E27 (27mm) & E14 (14mm)
  • Type G Bi-post (pin) lamp bases: GU10 (10mm)

Batteries

NiMH

NiMH (nickel–metal hydride) batteries:

  • Provide approximately 75% of the capacity of alkaline AA batteries
  • Low drain rates, can surpass alkaline performance in high drain applications
  • Significantly higher capacity than NiCd batteries
  • Expected life of 2 to 5 years
  • Do not have a “memory effect” like NiCd

Capacities:

Type Size Capacity
Non-LSD AA up to 2700mAh
AAA up to 1100mAh
LSD AA up to 2500mAh
AAA up to 950mAh
C up to 5000mAh
D up to 9500mAh

Handling

  • Don’t mix batteries:
    • Of different manufacturers
    • Of different capacity
    • Of different chemistries (i.e. NiCd, Lithum)
  • Don’t exposes the battery to cold or extreme heat
  • Remove the batteries when warm to the touch from a device/charger

Cycle Life, factor effecting charge/discharge:

  • Capacity
  • Temperature
  • Discharge depth
  • Charge/discharge current
  • Exposer to over charge/discharge
  • Age

Charging

Rated Voltage:

  • A full charged AA cell should have a voltage of ~1.4V (at 20 degrees C)
  • Fully charged cell supplies an average 1.25V during discharge

Continuous low rate charge (aka overnight charging)

  • Slow charge generally good for battery life
  • Under these conditions several hundred battery cycles are possible
  • Modern cells have an oxygen recycle catalyst to prevent damage on over-charge if the charge rate is less of equal to C/10
  • 0.1C (C/10) or below 10% of the rated capacity over 12 to 14 hours
  • Cheap charger with user management of the charge time

Smart charger (aka faster charging)

  • The charger monitors the battery voltage change and prevent over-charging
  • Moderate rate recommended C/3.33 for 5 hours
  • Fastest charging
    • In 1.5 hours at 1C
    • Temperature monitoring recommended, cells should stay below 45 degrees C
    • Impacts battery longevity
  • Maintenance trickle charge rate < 0.025C (C/40) recommended (reduces negative effects of over-charging)

Discharge

Over-discharge can push the battery into cell reversal (reversing polarity of the terminals) which permanently damages the battery. Therefore don’t discharge below 1.0–1.1V per cell.

Self-discharge can deplete a common NiMH cell within several month:

  • Depends on the environment temperature (lower temperature, slower discharge)
  • 5–20% on the first day, stabilizes around 0.5–4% per day at room temperature

LSD (low self-discharge) NiMH batteries

  • Typically maintain >75% of charge after 1 year
  • Marketed under “Pre-charged”, “Ready to use” or “Hybrid” since normal NiMH cells require to be charged before the first use

Storage

  • Store:
    • With open circuit (removed from the device) to eliminate loaded storage effects
    • In Fully charged condition
    • Clean, dry, protected environment to minimize physical damage
    • Use first in, first out to reduce time batteries spend in storage
    • Can generate high currents if shorted, sufficient to ignite flammable material
  • After storage for extended periods of time multiple cycles required to attain pre-storage capacities
  • Batteries stored under load for a prolonged time:
    • Deterioration caused by gas generation in the battery (activation of the safety vent)
    • Small quantities of electrolyte seep out around the seals or the safety vent
    • Creep leakage may result in the formation of crystals of potassium carbonate, can result in corrosion of batteries

LiPo

  • LiPo (Lithium Polymer battery), high energy density, very high discharge and charge rates
    • Fairly flat discharge rate until 10% remaining capacity, followed by a sharp voltage drop
    • Never discharge below 80% capacity, eg. 850mAh * 0.2 = 170mAh
  • Pack Configuration
    • S number of serial cells (raises voltage)
    • P number of parallel cells (raises capacity)
    • “1S” single cell, 3.7V
    • “3S” three serial cells, 11.1V (3x 3.7V)
  • Capacity measured in mAh (milli-Amp-hour), 1/1000th of an Ah

Balancing

  • Allows monitoring and manipulation of each battery cell in a battery pack individually
  • Cell imbalance
    • Damages the cell, results in a fire in extreme cases (e.g. over-charging)
    • Goal: Make all cells in a pack the same voltage
  • Majority of cell packs come with a Cell Balancer
  • Requires a Balancing Charger
    • Monitors individual cell voltage
    • Discharges high voltage cells in order to balance the pack
  • Balance Connector, break out connector to access all individual cells
  • Vendor specific wiring of the balancing connector
    • Plugs may be the same, but differ in the wiring
    • Types: TP (Thunder Power), JST-XH, Hyperion (Polyquest)
    • Balance-Adapter: single use adapter, adapter board

C-Value

  • C tied to the capacity
    • Continuous discharge at 1C depletes the battery in 1 hour
    • Similar charging at 1C takes 1 hour
    • 2C cuts time to 1/2, 3C to 1/3, etc.
  • Calculating C, e.g.:
    • 2200mAh/1000=2.2Ah (drop “h”) C=2.2A
    • 850mAh C=.85A
    • only the capacity is used to determine C
    • number of cells S/P has no impact

Rates

  • Calculate Charge Rate
    • 1C (1*C) 1*2.2A=2.2A
    • 2C 2*2.2A=4.4A
    • 5C 5*2.2A=11A
  • Charging rates beyond 1C is considered fast charging
  • C-Rating output capability
    • 25C/40C continuous discharge rating/burst discharge rating
  • Calculate Maximum Continuous Discharge Rate
    • 25C 25 * C = 25 * 2.2A = 55A
    • 30C 30 * C = 30 * 5A = 150A

Handling

  • Shelf time in “sleep” state
    • 3.85V per cell
    • Chemical stabilizer lost when cells are cycled
  • “Break in” process during the first few cycles
    • Charge slowly 1C
    • Gently discharging to 50% capacity for the first 5 flights
    • “loosens” cells for normal duty
  • Battery Log
    • Discharge & charge date
    • Battery cycles
    • mAh replace during charge
    • Battery IR (Internal Resistance) to monitor health

Safety & Longevity

  • Pick up on the body, not the connection wires (prevents breaking solder points)
  • Keep away from objects which can penetrate the cell wall (leads to fire)
  • Internal Temperature
    • Stay below 130F/60C
    • Rule of thumb: if a lipo is too warm to hold tightly in your hand, it is too hot
  • Internal Resistance (IR)
    • Used to determine the quality/health of a pack
    • the lower the IR the easier current flows

Charging

  • Goal: Charge to a specific voltage, number of cells multiplied by 4.2V
    • Resting Voltage: Checked to determine charge state
    • During this process the resting voltage rises
  • DON’T
    • Charge if the battery is sill hot from resent use
    • Never leave the charger unattended!
    • Explosion of a LiPo possible due to over-charging (wrong charger configuration, cell count)
    • Never charge above 4.2V per cell (full charge voltage)
  • DO
    • Charge in something flameproof, e.g. safe-bag (bath-tube, oven, etc.)
    • Choose appropriate charge rate
    • Charge up to 4.1V, eventually up to 4.2 immediately before use
    • Double check charger configuration before start, and once during charge cycle
    • Failure response: unplug charger, prepare (outdoor) save place for the LiPo
    • Have a fire extinguisher at hand

Discharge

  • 80%-rule (never discharge below 80% of its rated capacity (mAh))
  • Never discharge below 3.6V (cells below 3V minimum voltage may defect)

Storage

Storing long term >week at 40-50% capacity (never fully charged)

  • Voltage: 3.7-3.75V per cell, check regularly (every month), recharge eventually
  • Store in LiPo Safe-Bag
  • Environment: Cold, dry, away from flammable objects (ammo can, metal tool box, fire proof safe)
  • Use a charger with storage charge feature and a discharge feature
  • Battery Monitor
    • Device that plugs into the balance leads
    • Beep when voltage of the battery gets low
    • Some include a display to show voltage of individual cells

Damage

  • Damage
    • Physically damages LiPos should be disposed immediately
    • This includes punctured, crushed or swollen cells/packs
    • Disconnected wires should be fixed by an expert!
  • Crashing, quickly approach vehicle and inspect battery for visible damage
    • Check the temperature of the battery, heat indicated an internal short
    • Internal short: Battery builds up heat, and could “go off” (can happen within seconds, or after several minutes)
    • Remove the Lipo from the vehicle if not to hot
    • Pick up by the wires and put battery at the ground were it safely can burn down
    • LiPo batteries are non-toxic, and can be disposed in thrash after burn-out
  • “Go off”, burn-out
    • In multi cell LiPos each cell can go off separately
    • Cell expands, eventually breaks (pops)
    • Very hot smoke streams out of a broken cell, may lit on fire

Disposal

  • Many hobby shops properly dispose LiPo batteries
  • Fully discharge to 0V (zero volts)
    • Use a discharging device, e.g. light bulbs
    • Discharge on a small current e.g. 1/10C
    • During the process heat is generated
    • Potential for swelling, even fire is possible
    • Submerge battery in a bucket of sand during full discharge
  • Check for 0V before cutting the connector, and twisting the wires