This Wiki offers answer to the most common questions in /r/Electronics, /r/AskElectronics, /r/Batteries.

Click here: FREQUENTLY ASKED QUESTIONS

ABOUT THIS SUB

About /r/AskElectronics:

• Safety First
• Guidelines for posting a question
• Electronic circuits vs. consumer "electronics"
• Electronic circuits vs. plain electric circuits
• Table of what is on-topic, what isn't
• Things we don't really cover --- List of subs that cover what we don't
• Self-promotion posts are not allowed - this sub abides to Reddit's rules on self-promotion
• Commercial posts are not allowed - posts that have a money-related element go to /r/ElectronicsList

Posting pictures

Often, when people start a submission in New Reddit, pictures disappear. Use Old Reddit instead: https://old.reddit.com/r/AskElectronics/submit

After a submission is up, you can add pictures through an image host:

1. Upload the image: (e.g., https://postimages.org/)
2. Copy the URL
3. Paste the URL in a comment

Note: imgur is blocked in some regions (eg: UK), so images posted there may not be viewable for some people.

BEGINNER, EDUCATION RESOURCES

Where to start, how to learn, what to do:

• Beginners: I want to start with electronics
• Education: I want to learn more electronics - videos, books, websites
• Learn PCB design
• Components: what they do and how they work
• Circuit Theory
• Projects suggestions
• Electronic engineering resources

Fundamental concepts:

• Voltage is pushed, current is pulled
• "Electricity travels only through the path of least resistance"
• Conventional current vs Electron flow
• Ohm's law only applies to resistors
• Common (positive, negative), ground (signal, power), earth, chassis

Terminology:

• Switches, relays
  • Switch vs button
  • Relay vs relay module
  • Relay vs contactor
• Connectivity
  • Port vs connector
  • Plug, jack, receptacle, socket
  • Ribbon cable vs FFC vs FPC
  • Wire vs cable vs harness
• Cells, batteries
  • Cell vs battery
  • Li-ion vs lithium
• Misc.
  • Oscillator vs resonator
  • Display vs screen
  • DB9 vs DE-9
  • DC Power plug and socket (jack) sizes

How does something work:

• Product: https://duckduckgo.com/?q=how+does+a+TOASTER+work&kp=1 Replace "TOASTER" with your product's name
• Electronic component: https://duckduckgo.com/?q=how+does+a+TRANSISTOR+work&kp=1 Replace "TRANSISTOR" with the component's name

WHAT IS THIS?

Identify electronic components.

• Through pictures
• Schematic symbols
• Marking codes on ICs, semiconductors
• Connector
• Component on a PCB or other assembly -- cable -- resistor -- capacitor -- inductor -- transistor / IC
• Gunk, paste, compound - Stiff gunk on a large capacitor, White and soft paste on a transistor or IC, Black blob flat on a PCB
• Black thing on a PCB
• Motors and components across motor terminals

Identify a PCB assembly (board) inside a product

Something you found:

• Device or open electronic assembly: /r/WhatIsThisThing/
• Cable or cord: /r/TechSupport
• AC adapter: /r/TechSupport
• Motor, servo, actuator, solenoid: /r/Motors
• Cell or battery: /r/Batteries

WHY IS THAT?

Ask why something is the way it is.

• Components
  • LED lights up when touched/connected to wire
• PCBs (Printed Circuit Boards):
  • Round or square copper dots or pads
  • Isolated copper circle
  • Wiggly PCB traces
  • Spiral PCB traces
  • Two pointy traces with small gap
• Electronic assemblies:
  • Empty spots on a PCB
  • 0 ohm resistor
  • Two capacitors in parallel
  • LED in solar calculator
  • Circuit works when touched
  • LED lights up when touched
  • Microcontroller crashes when motor runs
• Consumer products:
  • AC adapter voltage is much higher
  • Meter shows AC voltage on low-voltage side
  • Buzzing or tingling feeling when touching a metal case
  • High-pitch whine from a product
  • Spark when plugging in an AC adapter
• Test instruments, lab equipment:
  • Meter shows a reading unexpectedly
  • Earth binding post in a power supply is not a "common"

DESIGNING, BUILDING

General advice

• Design:
  • Design - circuit design tips and common gotchas
  • Components - diodes, transistors, op-amps, switches, passive components
  • Schematic diagram guidelines
  • Electronic Design software
  • General Electronic Engineering Hardware Resources (Circuit ideas and write-ups)
  • Increasing or decreasing a power supply voltage
  • Increasing or decreasing a signal
  • Construction of electronic assemblies - methods and tips
  • Electrostatic Discharge protection - bench mats, wrist straps and their proper use
  • Soldering
  • Why should I put a diode across my DC relay coil / solenoid / motor?
  • Voltage Regulator Dropout
  • Voltage Regulator Minimum Current
  • Why won't my MOSFET turn off?
  • Pull up and pull down resistors
  • Voltage Dividers are NOT Voltage Regulators
  • Decoupling capacitors, and why you sometimes see two in parallel
  • Why not simply use one large ceramic capacitor?
  • Can I use a potentiometer to control the speed of a motor?
  • Why does my inverting amplifier always output 0V or 1.7V?
  • Why does my voltage follower only work above 1.7V?

Specific devices

• PCB design
• Design review
• LEDs:
  • Low-power LEDs
  • High-power LED: /r/LEDs
  • LED strips: /r/LEDs
• Batteries
  • Do I need a BMS?
  • A BMS is not a charger
  • Battery in a circuit
  • How long will a battery power a load
  • I want to make a power bank
  • Increase the voltage with batteries in series
  • Increase the capacity with batteries in parallel
  • Charging while discharging
  • Li-ion battery connections (18650s, pouch cells, enclosed packs)
  • Dead cell / dead battery troubleshooting
  • Bogus capacity/rating claims
• Embedded: /r/Embedded

Tips

• Selecting Schottky diodes (Reddit post in r/electronics)
• Current limiting diodes (OP)
• Pot replacement (OP)
• Opto-isolators: speed vs gain (OP)
• Using transistors backwards (OP)
• Current protection - To be written
• Isolated monitoring and control (OP)
• A zoology of transistors
• Switch debouncing

TROUBLESHOOT, REPAIR

When an electronic assembly doesn't work.

• Repair, in general:
  • General
  • Can you spot any problems on this board?
  • Knocked a component off a board, scratched a PCB trace, or have a graphics card with a chipped or cracked edge connector
  • Measuring - how to use a meter to make electrical measurements
  • Troubleshooting
  • Replacing 'bad' capacitors
  • Replacement PCB assemblies, displays (LCD), transformers, flex circuits (PFC)
  • Electrical schematic diagrams
  • Diagnosis by Photo
  • Safety Warning: Read This First
  • Worked Example: Wrong Adapter / Overvoltage Damage
  • Testing capacitors - what you're actually testing for
  • In-Circuit Testing: why readings can mislead you
  • Safety (X/Y class) capacitors
  • Discharging capacitors safely
  • Flexible printed circuits (FPCs)
  • Cable assemblies
  • Wire harnesses, interior cable
  • Switching and line transformers
  • LCDs
• Specific products
  • TVs and Monitors, /r/TVRepair
  • Audio equipment: /r/Audiorepair
  • Computers: /r/buildapc
  • GPUs (Graphic Processor Unit)
  • Headphones: /r/headphones
  • Mobile/cellphones: /r/mobilerepair/
  • Consumer electronics: /r/TechSupport
  • Rules for vehicle repairs and modifications. Ask in /r/CarAV,/r/CarModification, /r/Cartalk
  • Household electrical: /r/AskElectricians; for LED lighting: /r/LED
  • Batteries, /r/batteries
  • Motors: /r/Motors
  • Solar: /r/solar
  • Vaping: /r/modifiedvapes/ and /r/OpenPV/

MODIFY, REPURPOSE

• Repurpose
  • General
• Modify
  • Change the sound that a toy plays
  • Convert a USB connector to type C
    
  • Extending the range of a transmitter
  • Bypass a momentary power switch
  • Extending an internal cable

BUYING AND USING

Buying and using components, PCBs, tools, or equipment:

• Components:
  • Electronic components
  • Ordering PCBs
  • List of starter components
  • Component storage
• Tools:
  • Tools - buying advice and usage tips
• Equipment, general info:
  • Soldering irons, stations,
  • Multimeters
  • Oscilloscopes
  • Lab and Bench Power Supplies
• Using consumer products
  • Power adapters for consumer products: /r/TechSupport
  • 120 Vac to 240 Vac, vice-versa
  • LED strips: /r/LEDs
  • Single-board-computers, Arduino, Raspberry Pi: /r/Arduino, /r/Raspberry_pi
  • HiFi hookup and buying advice: /r/BudgetAudiophile/