Tutorial on part selection when requirements are simple

[tcort]

How does Dave Jones choose a pull-up resistor for a project? I'm curious to know what an engineer thinks about when choosing from thousands of parts that could do the job.

[Simon]

erm 1-10K does the jobs depends on how much power you can piss away. I think your question really is, what are the common jelly bean parts

[Rerouter]

probably somethign along the lines of most people designing something, know which supplier your getting most of your parts from, list all of the value your interested in and find the cheapest in the size your looking,

even for more specific passives, its generally just putting a temp coeficient or a tolerance before the price a little, and in general what even works within your error budget

i will say from my own recent escapades, that powers of 10 seem to be a bit cheaper than the other values, e.g.a precision 100K is 14c (one of), but 180K can be far higher, on the order of approaching 50-60c

[EEVblog]

How does Dave Jones choose a pull-up resistor for a project? I'm curious to know what an engineer thinks about when choosing from thousands of parts that could do the job.

It's easy. You start with 10K, which is:
a) A nice round value you are likely using elsewhere in your design
b) Not too low in value to be pissing away current (5V/10K=500uA), or cause grief to any puny driver.
c) Not too high in value to let in any noise or be a problem with line capacitance.

So in a typical design the "pull-up of choice" would be 10K, with maybe 100K or 1M for more power sensitive designs if required.
Or a lower value (like 2K2) for say an I2C bus that needs a lower value because of the line capacitance and open collector design.

It's a surprisingly interesting topic when you get into the detail!

Dave.

[hans]

Yes there are both lower and higher limits.

The lower limit is determined by the amount of current each open collector(transistor that pulls down to GND) can sink. Sure you can have a pull-up of 470 ohms, but at 5V that's ~10mA. Can every I2C or 1-wire device handle that?
The higher limit depends on the bus situation , speed, etc. A bus will gather capacitance and with a too high value it won't be able to rise fast enough (because the pull-up resistor has to charge this 'capacitor'). Either lower the speed or lower the pull-up resistor.
Noise is also something involved in this (in the end the bus becomes more of a high impedance state in pulled up condition).
And then there is low-power requirements..

Would make for an educational video indeed.