naming schemes for components on PCBs?

It's common to have the components named such that, e.g., C1 is in the upper left-hand corner and, e.g., C21 is in the lower right-hand corner and the designators increment from left to right, top to bottom. This makes it easy to find some random component such as C16, which is especially useful on prototypes that are hand-loaded.

Most PCB packages can perform this sorting automatically and will then back-annotate your schematic to match.

Your idea of using CA, CB, CC etc. could be useful if you have many capacitor types that use identical or similar footprints, although it'll probably be momentarily confusing to the casual observer. I've made PCBs that have "J23" and "IJ7" where the Js are for connectors -- jumpers -- to the outside world whereas IJs are for internal jumper between boards within the same unit.

---Joel Kolstad

We name parts according to the military convention (R for resistor, K for relay, Q for transistor, no weirdies like RV or TR or RN or MOV3) and our PCB software resequences them sequentially in a nice geometric pattern, so it's easy to find, say, C46. That means there's no correlations or groupings of like parts, which is what the parts list is for.

John

An excellent idea which I shall immediately adopt.

However, the effect will be negligible because I have been transferred to the firmware group and I am no longer allowed to do hardware designs.

I do much the same thing, but since my products generally have small enough boards, I use R1 through R99 (C1 through C99 ...) for parts that are mounted on the chassis, R100-199 for PC Board #1, R200-299 for PC Board #2 and so on. THe one time I ran out of resistor numbers, it became R199, RA100, RA102 etc.

Poor bugger got taken from hardware heaven and dumped onto the Dark Side of firmware.

Jim

What do you use for diodes? CR?

We use D. So court-martial us.

(Actually, D means Dynamotor, but we don't surface-mount many of them these days.)

John

We use PADS, and it resequences automatically and back-annotates the schematic.

John

I assign a range per page of schematics; page 1 has R100 through R199 (for resistors, C for caps, T for transistors, U for ics, etc), page 2 has R200 through R299, etc. Since both the schematics and board tend to be grouped by function, this seems to work OK for me.

So if I'm looking for C305 I look on the part of the board where I put the group of components for page 3.

The only thing I sometimes do is group all the values with the same part together. So when stuffing the board you can do C1..10 100n, C11..15 10uF etc. Of course this breaks down if you have to change a value. For large boards one can groups parts geographically, so that they can be found more easily. So that as one goes from R1, R2, R3 you are progressing along the board in a particular direction.

It is probably best to avoid more than single letter prefixes to keep the length of text down. Especially important if you want to have idents on SMT boards. My last such was particularly packed such that I considered getting rid of the letters altogether, so the parts would be called 1,2,3 etc. I decided against that in the end and made room somehow...

Neither do we. It makes big ugly messes that take more time to fix than it ever saved. We "pre-route": arrange placement and pinouts - especially big stuff like FPGAs and RAMs - so all the signals flow with mimimum vias and crossovers. Then routing is a snap.

John

Few ppl really take this very far.

I've used CD for decoupling capcitor in the past to distinguish them from signal caps but no more than that. Your idea has more value with regard to parts lists or stock numbering.

Graham

Where the hell did CR come from anyway ?

Not to mention U or Q !

We use D, IC and TR. As do most Europeans.

Graham

IEEE-315 says D or CR can be used for a diode. Dynamotor is MG which can be surface mounted on a concrete slab. That reminds me, I need to remove the rotary 2-phase to 3-phase converter sitting in the back of my car. Don't know if I'm strong enough to lift the bloody thing out!

Doesn't this resequencing leave your board out of step with your schematic?

(I was wondering about the O/P's schematic part numbering too)

Exactly how I do it. It's something I picked up from a service manual for some gear twenty-odd years back. I tend to break the overall schematic into logical blocks (eg power distribution, on-board SMPS etc as one sheet with one leading digit group). Sometimes this means distributed parts from a group eg bypass caps around the board, but it also makes their function more obvious.

It makes backtracking to the schematic soooo easy.

Hmmm... maybe I should update some of my reference books.

We just bought (I think Don Lancaster gave us the link) a few surplus

John

ACK! And besides, the available space for reference designators is getting very tight these days.

John

I believe I remember an IEEE standard on reference designations. I am afraid I don't recall the number at present. If I remember correctly it does not address schemes for meaningful designations within a board, but it would discourage the use of "CA1, CA2" etc.

Or for part numbers ( or any meaningful identification) on the parts.