Component Identification Question Guidelines

Question

Following this poll, the EE.SE community has determined that component identification questions should be allowed, though we need some better guidelines. This post contains guidelines on how to ask a good component identification question, and what to do when they're not good.

In general, most people will only look at a component identification question once, so make sure you have all the information in place before you post your question.

Rules for Asking:

• Include a clear picture of the part in question, including a ruler if possible for scale.
• Type out any text on the part. Many parts have text that is difficult to read from a picture.
• Include any information about the surrounding circuit, or any knowledge on the type of system your component came from.
• Include the identification tag.

What helps:

• Make sure the picture of your component is clear, focused, and has something to compare dimensions with (e.g. a ruler)
• Add a second image that shows where the component is located in the board/system
• Show a schematic if you have it, or a tracing of the PCB traces if possible.
• If you know what the package is, or what the specific dimensions are, that can also help (e.g. a 24-pin SOIC)

Ground Rules:

• Only one component per question. Questions with more than 1 component will probably be closed as "Too Broad"
• "Components" includes connectors, batteries, battery cells and packs, single active devices, passive devices or networks, integrated circuits, and other parts that an EE would use in a design or prototype.
• "Components" does not include: printed circuit boards (bare PCBs), whole circuit boards with components installed (PCB assemblies), parts that fall in another domain (wall outlets or spark plugs), or lawn mowers.
• Parts that were intentionally obfuscated (e.g. the board manufacturer sanded off the part number) will not be considered. This also includes chip-on-board with an opaque epoxy.

Answer 1

I think these guidelines generally make sense. However, this part needs some adjustment:

Parts that were obfuscated (e.g. the board manufacturer sanded off the part number) will not be considered. This also includes chip-on-board with an opaque epoxy, and parts that are burned beyond recognition.

We've had some legitimate questions where a part was burned beyond recognition, and the OP was trying to figure out what it might have been. Obviously just a picture is not good enough then, but this can be a good question if the schematic is shown, and we understand what the unit as a whole is intended to do.

A picture might show a blown diode was in SMA package, and from the schematic we can see that it is a rectifier that needs to handle 30 V in reverse, and carry under 1 A. That's enough information to know what to replace the blow part with.

Conversely, the picture could be the same, but the schematic shows a zener diode used as a 5.6 V source. Again, good and useful answers can be written.

These example do run the risk of being repair questions. The distinction is between "What do I replace this part with?", and "How do I use this information to infer the part specs?". That distinction won't be obvious to everyone, but that doesn't mean good questions of this type can't be asked.

Answer 2

One thing that I think should be a requirement:

The question title should be a short description of the component

Instead of What is this component? the title should be What is this blue plastic cylinder with two wires?.

The former is very annoying on the front page, because every identification question looks the same so it is difficult to remember if you have seen it before.

Answer 3

I recommend making the photography instructions contain more specific guidance, since many people don't have experience with taking good technical photos. I would say:

• Well lit. Details should be crisp, not noisy from lack of light. There should be no overexposure (white blobs) hiding colors and details. (Using a basic photo editor to improve contrast afterward may be worthwhile, too, but it can't improve what wasn't there to start with.)
• In focus. Edges should be sharp. After you take the picture, zoom in on it to check; don't just judge it from the tiny phone/camera screen. A camera mount or leaning your elbows on the table while you take the picture can help, as will providing good lighting.
• Cropped so as to show the component at a reasonable size when displayed in the question. Consider including an original or second photo with an overview of the board or other surrounding components. Avoid painting a thick box around a component on a board as this may hide relevant information of how it is wired up.

Answer 4

Regarding "Type out any text on the part.":

It would perhaps be useful to remind OP to actually search for the text themselves before posting, noting that the downvote button popup includes the text This question does not show any research effort.

If the result is confusing, at least mention this in the question. Cutting off just the right part of the IC markings to get a good result is something of an art, but mostly It Just Works™.

Answer 5

Another thing that really helps is:

• If they know something about the voltages on any of the pins around the part, ie which pins are ground or Vcc.
• Probe the part with a meter, especially if it could be a transistor or a diode with a meter in diode mode