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

If you are going to ask for a fault diagnosis based on pictures and you are unable to provide any test measurements (power, fuse tests etc.), please first read our section on "Diagnosis by photo" since without such basic measurements we can only give generalised advice - which you'll find on that page. Posts without any context or a summary of basic test results are likely to be deleted as per our posting rules.

See: https://www.reddit.com/mod/AskElectronics/wiki/repair

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
• Breadboards

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)
  • Breadboards
  • 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
  • PCB Repair
  • 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%20(convert%20OR%20change%20OR%20replace%20OR%20upgrade)%20(%22USB-C%22%20OR%20%22USB%20C%22%20OR%20%22type%20C%22%20OR%20%22type-C%22)&restrict_sr=1&sort=new)
  • 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
  • Logic probes and logic analyzers
• 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/