Schematic Information - Page 1
Forum section: electronics / general

author: Wilksey
author_rank: Super Contributor
timestamp: April 25, 2016, 01:19:06 am
content: I am curious to know how many of the circuit designers on here put actual part numbers on their schematics?Do you prefer to put generic component values, such as 100nF / 50V Capacitor, or do you also add say for example, a DigiKey part number?I've heard mixed feelings regarding the information added, personally I add part numbers as extra info but hide it from the main schematic print view, so the information is not visible on print out but I can still add the info to a BOM generation script, the argument against is what if the part goes obsolete, but I feel the part number on the schematic shouldn't override the latest BOM, which has an exact part number on in any case, and with respect of obsolescence will be superseded with a new BOM issue.Just interested to know your thoughts / company procedures for schematic information displayed.

author: Richard Crowley
author_rank: Super Contributor
timestamp: April 25, 2016, 01:28:11 am
content: I always put component designations (R1, C3, L2), etc. and values (1 ohm, 10nF, -18V, etc.) on my schematics.Conversely, I never put vendor part numbers on a schematic. That is what the BOM is for.The designations are for convenience in reading, referencing the schematic.The part values are an integral part of the circuit design.OTOH, vendor ordering numbers are NOT part of the circuit design.They are part of aparticular implementationof the circuit.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: April 25, 2016, 01:35:37 am
content: All schematics are a conversation. What needs to be in that conversation depends on the audience and on how the conversation is going on. In many cases the schematic goes to people who are only interested in how the circuit works, not how to build or repair it. A different document, often a BOM goes to the people building it, and maybe even a third document to those repairing it.In other cases the schematic is either the only document generated, or the only one distributed to people who will be maintaining and repairing the item. If that is the case, all possible information is valued.I don't think there is a general answer to your question. The answer depends on your situation.

author: Wilksey
author_rank: Super Contributor
timestamp: April 25, 2016, 09:37:28 am
content: More curiosity rather than after advice to be honest, the vendor P/N isn't displayed but it's in the symbol so I can use it in the BOM generation, if someone wanted to open the project files they can see the P/N but the PDF / print out it will just display ref designator and value. I have seen some schematics with vendor part numbers on, and seen arguments for and against doing so, I don't, I keep that for the BOM that way if the part changes I don't have to update a perfectly good schematic!

author: Karel
author_rank: Super Contributor
timestamp: April 25, 2016, 10:29:59 am
content: Not in the schematic directly. I put information like manufacturer, partnumber, ordercodes of Farnell, Mouser, Digikey, RS, etc.in so called atttributes. Those attributes are part of a device which are in the libraries.

author: AndyC_772
author_rank: Super Contributor
timestamp: April 25, 2016, 10:39:14 am
content: My view is that a schematic should contain all the information necessary to show which parts are required by a design and how they are connected, but should not try to prescribe commercial or logistical details which have no bearing on the finished product.For passive components, I'll typically refer to them by a short description, like C/CERSM 10n 10% 50V X7R 0603. There's enough information to know exactly what's needed, but on the other hand, it doesn't prescribe the use of any particular manufacturer or distributor, because those things don't matter in the context of the schematic.If a particular customer or manufacturer always uses, say, Murata capacitors in reels of 3000, and buys them from Avnet, that's nothing to do with the schematic - but it may well be information that goes into the same central database as my BoM.Similarly, if I know for a fact that a Murata cap isn't suitable in a given design but a Taiyo Yuden is, then I'll include the TY part number instead of the description.In either case, the schematic will show "10n 50V" for brevity. In the case of unusual properties which matter, they'll be shown too, eg. "10n 50V 125C" for a high temperature part.For semiconductors I'll usually specify the exact, complete part number - say, Microchip PIC16F1723-E/ML - but omitting any details which relate only to the method of packaging (ie. tubes vs T&R) or pack quantity. Once again, it's about ensuring every important technical detail is captured, but not factors which are entirely down to the preference of the assembler.