Special annotations in schematic? - Page 1
Forum section: electronics / general

author: joeyjoejoe
author_rank: Frequent Contributor
timestamp: December 04, 2018, 12:05:48 am
content: I have a schematic which is starting to have quite a few components. A few are fairly "of interest" when it comes time to assembly, and that'll probably be 4 weeks out since I'm ordering from China.Realizing I'm a hobbyist, and can do whatever I want, I'd still prefer some inputThere's a few resistors that I'd like to annotate differently instead of R3, R17 and R22.Two are for leaving options as to what to measure with the single ADC input.I feel like this annotation would help clue in at assembly time like "Hey, only one of these should have a 0-ohm resistor attached!"Likewise, I have another which adjusts the gain of a receiver. I'd like to call this R_AGC, although it's less critical as that can be found by cross referencing the schematic.Is this done ever in "real" production? Or it's always the standard designation and a number (R3, C5, L3)

author: T3sl4co1l
author_rank: Super Contributor
timestamp: December 04, 2018, 12:50:16 am
content: Production doesn't... well,isn't supposed tocare if it's "R3" or "R_RSSI" or "Gary", as long as it has a MFG and PN attached, and where to put it (if not a centroid list, or the PCB file if supported, then best guess by silkscreen). If it's not to be "put", label it "DNP" or the like, quantity zero.No idea what assembly variants and parameters Eagle supports, but that's the way to do it in enterprise software, set the part as DNP and generate the BOM accordingly.Tim

author: Gribo
author_rank: Frequent Contributor
timestamp: December 04, 2018, 02:11:51 pm
content: Isn't supposed to care is the ideal situation. From my experience, if you have weird reference designators, the assembly house will complain because one of their parsing scripts couldn't handle it.

author: joeyjoejoe
author_rank: Frequent Contributor
timestamp: December 04, 2018, 09:20:35 pm
content: So generally, not really accepted.DNP would apply not all the time though, it would depend on the circumstance for DNP...

author: chrisl
author_rank: Regular Contributor
timestamp: December 05, 2018, 08:16:17 am
content: Quote from: joeyjoejoe on December 04, 2018, 12:05:48 amI have seen it but not common tho.

author: AndyC_772
author_rank: Super Contributor
timestamp: December 05, 2018, 08:35:08 am
content: It's kind to Production not to surprise them.Leave the reference designators as R1, R2, R3 etc. That won't confuse anyone building the board by hand, or programming a P&P machine.By all means annotate your schematic to say what each one does, if it's not obvious. I'm surprised how few schematics are marked up with notes as to why things are done a particular way; I do it all the time to indicate nominal voltages, the meanings of hardware revision bits, the meanings of the signals available on test points, and so on.Also consider putting notes on the silk screen of the PCB, even if it's just "GAIN SET" and a box around the parts which are relevant.If certain parts are likely to be changed frequently - perhaps during development, or to customise a design for different applications, then consider using a larger size for them. For example, I have a design which is mostly built using 0402 passives, but a couple of resistors are 0603 because they're easier to rework, and the part is marked with the value.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: January 29, 2019, 06:11:30 pm
content: It's just a string of text to KiCad.Why would anyone else treat it differently?As a hobbyist you also probably jus want to order a PCB with a silkscreen, and do the component placement yourself.In the gerber files it's just "artwork" and even text is probably built out of separate lines.