25
votes
Accepted
How were standard serial port baud rates chosen?
The first modems I ever worked with were 110 baud, but the Bell 103 modem set the mainstream speed ball rolling with a 300 baud FSK setup. This was the best which could reliably be achieved at the ...
- 8,271
20
votes
USB A mechanical orientation?
Yes. The receptacle tab goes on the top.
According to the USB specification, section 6.5.1 there are guidelines on orientation for USB-A receptacles:
6.5.1 USB Icon Location
The USB Icon is embossed, ...
- 1,598
19
votes
Rules and guidelines for drawing good schematics
R100, R101, R102 Instead of R1, R2, R3
I would like to share my experience in assigning names for components.
Identify the blocks of circuits according to the functions. Even if it is a complex ...
15
votes
‘One for all’ standardized land pattern v.s. specified land pattern in datasheet
The correct footprint to use for a component land is 'one that works'.
This isn't so flip as it sounds.
What does a land pattern have to do in order to 'work'?
a) it must connect each component ...
- 174k
15
votes
Why are there no 12V/5A USB PD chargers/batteries?
The reason is USB Power Delivery standard. You cannot make a product that is against a standard and the standard does not allow it.
Also, as per the name, it is a standard for delivering power, it is ...
- 172k
14
votes
Accepted
Standard Volt and Ampere
This all brings me to wonder, how much of what we use is calibrated to
someone else's meter. And how many of those meters, are calibrated to
yet someone else's.. and on and on. Seems like one big ...
- 5,841
12
votes
Accepted
Are USB 2.0, Type-A, Male-Male cables compliant with USB specification?
Technically, it depends how the cable is built. In USB 2 standard these cables are not allowed at all, and USB 3 standard allows these cables only if they are build according to the standard.
They are ...
- 172k
11
votes
Accepted
‘One for all’ standardized land pattern v.s. specified land pattern in datasheet
In my experience, you can safely stick to the IPC standards, which by the way also suggest three different footprints for each part: Least, Most, and Nominal. It is up to you which one to select, ...
- 2,827
10
votes
Accepted
Medical electronic devices quality
The only 'grade' that is sometimes specific to medical components is encapsulation. Stuff that is going to be used "in people" has different encapsulation requirements than stuff that is going to be ...
- 4,622
9
votes
Accepted
What standard defines the number of stop bits in RS-232?
Nothing, there is no such standard that says how data should be sent over an RS-232 interface.
RS-232 is only a physical, mechanical, and electrical standard; it does not even define a protocol for to ...
- 172k
9
votes
How were standard serial port baud rates chosen?
The short version
300 baud is the maximum rate that the telephone line could support using modulation and demodulation technology that was easily available at the time. The specific number is, ...
- 501
9
votes
Is there a standard which requires a high voltage warning label on a PCB?
IEC61010: Safety requirements for electrical equipment for measurement, control, and
laboratory use
PCBs with hazardous voltages should be protected with an enclosure, and should not be reachable ...
- 9,666
8
votes
Are pins supposed to have the same thickness by some standard?
The DHT-22 has 0.5mm nominal leads, which is similar to other through-hole parts. For example, the 1N4148 (JEDEC DO-35) has leads that are between 0.46 and 0.55mm (so about 0.5mm nominal).
The female ...
8
votes
Accepted
Is there a "standard connector" for SPI, in a similar way to the "standard Qwiic connector" for I2C?
No, there are no standards for I2C or SPI connectors and their pinouts.
What you are referring to would be manufacturer specific.
If you just want something that is commonly used like Qwiic, take a ...
- 172k
8
votes
Rs485 A & B Labels being used inconsistently
RS-485 standard defines the A line as negative and B line as positive, as can be seen from here:
The RS-485 differential line consists of two signals:
A, which is low for logic 1 and high for logic ...
- 38.5k
8
votes
Are USB 2.0, Type-A, Male-Male cables compliant with USB specification?
They don't follow the USB specification. The USB 1.2 and 2.0 specify that the ends of the connectors define whether a connection is a host or a device. The male to male A connectors would be host to ...
- 88.8k
8
votes
Is there a standard which requires a high voltage warning label on a PCB?
Generally there should be a protective element preventing general public, machine operators and service personnel from getting into contact with a live part.
That means that the PCB should be ...
- 3,704
7
votes
Medical electronic devices quality
There is no defined grade for medical. There are only norms defining what a medical product must comply with.
Some manufacturer may have e a special product series of a part such as military, space ...
- 819
7
votes
Accepted
If there is a cable and jack standard for I2C?
I2C specification does not specify any connector, as it is not a specification for an external interface. Many technologies that are based on I2C do specify a connector and pinout for an external ...
- 172k
7
votes
Accepted
Creepage between layers on a PCB
Do I need to consider the distance towards the board outline, up/down
to the other layer and to the component
Yes you do but, path 2 in your diagram doesn't represent this; it appears to show the ...
- 473k
7
votes
Accepted
Is there a specific definition for the tolerance value of a resistor?
AFAIK, no there is not. This is done manufacturer to manufacturer, the distribution can vary considerably depending on the manufacturer. It's generally understood to be an upper and lower bound. A ...
- 88.8k
6
votes
Accepted
Is there some kind of official standard for signal measurements?
There is no standard for exactly what rise and fall times mean. Even if there were, good documentation defines its terms.
In the case of rise and fall time of a digital signal, the appropriate ...
- 315k
6
votes
Australian 3-Phase Colour Code Standard
It seems these are the new colour standards for equipment, based on the most recent National Electrical Standards as of 2010 thru 2017. I have confirmed they are accurate.
New cable colour code for ...
- 148k
6
votes
Accepted
Why does my router have a power on/off switch?
It's largely for convenience.
Not having to crawl under desks to plug and unplug things you aren't using isn't exactly my favourite pastime, and I assume it wouldn't be yours either.
Adding a switch ...
- 1,764
6
votes
Accepted
Are pins supposed to have the same thickness by some standard?
There are many standards.
Wires, jumpers, sockets, and other parts made for use with solderless breadboards are made to fit together. I don't know if there's an official standard for them, but the ...
- 73.6k
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, ...
- 2,184
6
votes
Accepted
What are the hole dimensions for 0.1" pitch headers?
For less standard machined-pin headers from companies like preci-dip or mill-max, you can get the information fairly easily--for instance, mill-max's 801 series headers (which accept standard 25 mil ...
- 38.5k
5
votes
Are there standards for digital sensor links?
In avionics (particularly flight safety critical) it is not unusual to see the usual comms (SPI, I2C) within a box, but externally it is usually going to be ARINC 429 (civil) or MIL-STD-1553B (...
- 22.6k
5
votes
Rules and guidelines for drawing good schematics
A few more:
(1) Draw on normal grid.
I really hate having to deal with other people’s work that’s drawn on half-grid. It’s a huge waste of time and doesn’t add any value to the drawing.
(2) Use ‘...
Only top scored, non community-wiki answers of a minimum length are eligible