Hot answers tagged

81 votes

What does this symbol mean on my Samsung travel adapter?

That's the Ukrsepro mark. It means the product has passed the certification of UkrSEPRO, the safety certification requirement symbol for trading in the Ukraine region. Scope of products covered by ...
  • 9,041
44 votes
Accepted

What is the reason for yellow tape on top of USB mini-B?

The official name is Pick and Place Pad. While this can refer to hard parts added to bigger or irregular shaped parts for pick and place, it also refers to the tape used for picking. The tape a high ...
  • 71.8k
30 votes

Why do laptops need larger transformers than mobile phones?

Laptops and cell phone both use switching power supplies so the adapters are not simple transformers. For a given technology there is a relationship between power capability (measured in watts) and ...
24 votes
Accepted

What is the purpose of oscilloscope-probe-to-BNC adapters?

I use these quite a lot. When making a circuit where any high-frequency signals need to be measured with minimal disruption to the circuit, placing a cheap BNC jack as a test point is a very easy way ...
  • 22.8k
22 votes

Why do laptops need larger transformers than mobile phones?

Actually, neither laptops or cell phones use a transformer, per se. What they use, instead, is called a "Switched-Mode Power Supply" that rectifies the 110 or 220V AC input into a DC capacitor, then ...
20 votes
Accepted

Difference between these RF adapters

This: is a simple BNC splitter, it has no real circuit inside, all ground/shields are directly connected and so are the signal pins. There is only a straight wire between all pins. This BNC splitter ...
  • 79.4k
20 votes

What is the reason for yellow tape on top of USB mini-B?

It's to give the pick and place machine a flat surface to pick it up by, when it's transferring the part from its tape to the PCB.
  • 123k
16 votes

Fuse keeps blowing on AC/DC Adapter

The answer is clear: Buy a new supply and find something else much simpler to "learn" on. Switching power supplies are outrageously complex and not something you're gonna be able to wrap ...
  • 4,361
15 votes

DIP to SOIC-8 Adapter

duckduckgo.com turned up the following for me: https://www.cimarrontechnology.com/product/browndog-201202-8-pin-dip-to-soic-8-adapter It's a little PCB that holds the DIP. It solders to a SOIC ...
  • 1,122
13 votes
Accepted

Why are these traces shaped in such way?

What are those parallel soldered-traces on the PCB traces? They are traces where some of the soldermask has been removed in order to allow solder to build up to improve the current capacity of the ...
  • 166k
12 votes

What is the purpose of oscilloscope-probe-to-BNC adapters?

One further use: connecting to BNC T-splitters to measure a signal going between two devices: Connecting another 50 ohm terminated cable would make the total termination impedance 25 ohms, and would ...
  • 5,450
12 votes

In AC/DC adapters, why can't the DC cable be detached from the adapter?

Because it would cost more since you now need two more connectors. The AC side is detachable because different countries use different outlets. ADDITION BY HEARTH: ...and the DC side isn't, because ...
  • 51k
10 votes

Electric shock from outdoor security cameras

It's not a strong electric shock else you'd be shouting that from the rooftops so, I am presuming you mean something more like an irritating tingle. Based on that assumption I would suggest that the ...
  • 404k
10 votes

DIP to SOIC-8 Adapter

As noted in this response from Ian M. to the thread that Mat mentioned in the question comments, Winslow makes a couple of adapters that place the DIP on a PCB "platform" above the SOIC pad. ...
  • 657
9 votes

Why are these traces shaped in such way?

What are those parallel soldered-traces on the PCB traces? When you are designing a PCB with high current traces, you want to keep the trace resistance as low as possible. You can do this by multiple ...
  • 7,616
9 votes
Accepted

Why would a USB-C adapter have a pull-up resistor?

TL;DR Adapters with Type-C male to Type-A female connections advertising a 56 kΩ resistor value are wrong. The resistor tells the Type-C downstream-facing port (DFP) whether the connected device is ...
  • 29k
9 votes

Why does dropping my laptop's AC adapter in the floor make it work again?

There must be a solder joint of a component which is broken. A mechanical shock moves the component and it makes contact again. That could be a fire hazard, not to mention more components coming loose ...
  • 104k
9 votes
Accepted

DIP to SOIC-8 Adapter

That's benign in speed. How much tinkering is OK? I'd probably bend the DIP pins inwards (maybe 30° or so), then bend the "tips" of the pins to form an "L" shape that happens to ...
7 votes
Accepted

Why a high voltage AC always present in SMPS AC to DC power adapters

The internal transformer used to step down (and isolate) the power voltage has capacitance between primary and secondary - this can be around 10pF to 1nF depending on construction and size and is ...
  • 404k
7 votes
Accepted

What is the purpose of all these resistors and capacitors in this power supply?

Resistors have voltage ratings, as well as power ratings, and in SMT parts these can be surprisingly low. Part of the reason for series chains is UL requirements, part is just seeking a high enough ...
  • 16.4k
7 votes
Accepted

Increasing voltage, but same current

The load determines the ratio of current to voltage at its terminals. If you control the voltage you supply, it determines the current. If you control the current you supply, it determines the ...
  • 148k
7 votes

Fuse keeps blowing on AC/DC Adapter

Powering up with a random component removed is a bad idea unless you know its function and understand what will happen without it in the circuit. It could be part of a clamp that prevented overvoltage ...
  • 21k
7 votes
Accepted

How do I protect the power supply from a short circuit inside a device?

A simple way to address this is to use a polyfuse inside your device. These work by detecting an overcurrent condition, then 'tripping' to limit the current to a lower value until the power is removed,...
  • 44.4k
6 votes

How can I adapt a 3-pin PC fan connector to a 4-pin connector?

This solved my problem: Cited from 3pin to 4pin fan adapter(Chinese) Explanation: two fast-switch triodes (2N-2907 and 13003) utilize PWM control over 12v power. diode protects the fan from voltage ...
  • 161
6 votes
Accepted

How to convert a device pluggable to a car lighter, changing to a regular home socket

Get yourself a cheap power supply with a built in 13.8 VDC port. I have an old one from Radio Shack that I bought 20 years ago, and still use for exactly this purpose. Your cigarette lighter plug ...
6 votes
Accepted

3.5mm to DB9 connector (differences)

You have two cables, one works and another does not. What is similarity and what is the difference? Similarity: both are black cables, looking like the same; both are having DB9 (male or female - ...
  • 6,656
6 votes

Replaced 4x AA battery with 6V 3A DC adapter, but device won't work

So I pulled the cover off one of these a couple of months ago with the same plan in mind, this is our second door, and the batteries only last 3-4 months. The system seems to run the batteries both ...
  • 61
6 votes

How do I protect the power supply from a short circuit inside a device?

Put a fuse inside the device you are designing. You know the power and the voltage and current so select a suitable fuse with sufficient headroom and fast or slow blow as applicable.
  • 5,512
6 votes
Accepted

Can I use this US extension cord in Europe?

You could get as many “no” as “yes” answers. Will it work? Sure. Should you use it? Probably not. No, this product is not CE marked, its importation is actually illegal. Yes, it is rated for 30 A, ...
  • 1,266
6 votes
Accepted

What adapter do I need to replace 4 AA batteries?

The power source has to provide the peak current needed to operate the lock as well as the quiescent current. The short-circuit current of an alkaline AA battery could be as much as ~10A so it's ...

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