Lack of BOMs on OSHW projects is frustruating....

[george graves]

One thing I've been really frustrated with is how few people include actual part number in their documentation of their OSHW projects.

For example...a year ago, I wanted to make a standalone arduino built exactly as an arduino, then of course my circuit around it. Maybe I missed it, but there is no place I could find the exact part numbers for things like the SMD crystal, and loading caps. I wanted to use the EXACT part numbers as the original arduino. I didn't trust myself to try and find the one part out of 10,000's on mouser that would work, or be the right spec.

It's not just arduino. It's something I've noticed on most(?) OSHW projects.

Should all OSHW project include a detailed BOM with actual, real part numbers? Not just "0.1uF cap"...but an actual manufacture part number? Something like a cap isn't that big of a deal, but some of the more crazy parts, and be really hard to track down. Why not just include a real BOM!?!?!?!? (end rant)

Thoughts?

[BruceF]

I agree that being specific would be handy if parts don't change much, but I could also see it being a pain in the posterior region for both the list creator and user if parts do change. If the part list says they're using a Multilayer Ceramic Capacitors (MLCC) - SMD/SMT 6.3volts 2.7uF X5R 10% (C1206C275K9PACTU) and it's non-stock when you get around to ordering, are you then going to feel comfortable picking your own substitute, like perhaps a C1206C275K9RACTU? You'd probably end up with a forum full of posts about that kind of problem. I guess the kit designer could just say, "this is what I ordered, have at it - amongst yourselves!" and avoid taking on too much extra work.

Slight digression, but I have this kit idea (hey, who doesn't have a few of them?) that I figure in the 1% chance I get around to producing, I would want to sell as a board, enclosure and a shared project on Mouser's site. People could then drop parts they already have, change parts, or try to copy everything to a distributor closer to them.

My other thought was that if I could design the enclosure as a set of snap-together layers I might be able to produce it on a MakerBot in the style of one of those flat, injection moulded rectangular frames full of bits that you then snick apart and assemble, which may allow me to ship the kit in a bubble pack envelope with just first class letter postage. An IKEA flat pack electronic kit, if you will.

Clearly I'd have to be motivated to maintain that BOM well or people couldn't be expected to build my kit. It would kind of align my interest as a kit seller with yours as a kit bender.

[cstratton]

For something of the volume of arduino, it's likely they maintain several sources for most parts (except the atmegas) and consider themselves free to buy whichever is cheapest this week. Surely they do not primarily shop at digikey or mouser as you would.

Perhaps what we haven't seen yet are substantial community contributions to the hardware side of an open hardware design - ie, the originator may not care about sourcing the BOM from a prototype/pilot-run scale parts supplier, but someone in the community such as yourself very well could, and might go work out a solution. On a software project, that's the kind of addition that might be submitted back upstream for the project owner to consider incorporating into the official tree - presumably the same thing could be done with an open hardware project, it just seems that most open hardware projects have relatively few community "patches" in their official tree. Maybe the idea hasn't gotten to that point yet.

[mikeselectricstuff]

It's a waste of time listing part numbers for generic parts like resistors, caps etc. There are so many alternates, and different specific parts will have different availability and pricing from different suppliers.

What is much more useful is to list the important parameters, e.g. where dielectric types of caps matter, current ratings of inductors etc. A note as to why certain parameters is even more useful for the less experienced.

It is certainly worth it for parts which are more specific like connectors, where dimensions and footprints can be different, so at least you can reference the original to compare others. Also exact part numbers for semics, so you know you have the right package, speed etc.

If you can't figure out how to order things as basic as resistors and capacitors you should probably be buying a complete unit instead of trying to make one

[lyndon]

A "suggested" or sample BOM would be a good idea though.

A problem I sometimes have is needing more of a part I bought years ago. e.g., I need a D-sub 9 female right angle connector. I may vaguely remember that I paid $0.50 each for 100 of them 2 years ago, but a Digikey, Mouser, etc search only brings up units that cost $2.50 each at that quantity. So what am I missing in my search? Thumbing through the catalog, I'll eventually find the cheap one (or else I give up and find some at a surplus dealer), but often knowing the vendors part # means I can use their description as a search term on other sites and find what I need.

My current solution to this problem is to always save the label on the package. A longer term solution is to write a simple database app to record this stuff.

[FightCube]

George, I hear you bro! I fully agree that the lack of BOMs is a blatant issue and seriously affects the ability of "the community" to reproduce your work.

If you at least start with a BOM that has all of the MFGs part numbers at the time you designed your product, others at least have a starting point to compare to for substitutions. If you have no starting point, you are only guessing. Sure you can guess correctly for most commodities, but why should you have to guess and peck and hunt at all?

I had the exact same problem when I set off to reproduce the Arduino Pro Mini. I had a board made at Dorkbotpdx, and ordered all parts with Digikey. I found them all through lots of scouring. It was no easy task, and if you are not an engineer like me... good luck.

Lots of information can be built into a base number of a part, such as a 2N4401 transistor. If you search for that, or "4401" and know it's a SOT-23 package.. your searching will end quickly. However it REALLY doesn't hurt to just put down that it's a MMBT4401 in SOT-23 package. I have even started doing this in schematics just to keep the number of documents needed fewer. Put down the power rating of resistors, and voltage ratings for caps and zeners on schematics as well, just to name a few.

Here's my Arduino Pro Mini in purple, with yellow tants and blue leds and high power hungry 328(no p) Silkscreen on this run was low dpi, but the board works great.

Reproduced Arduino Pro Mini

Arduino_Pro_Mini.jpg (463.93 KiB) Viewed 3423 times

[cstratton]

Just a note, I don't think you are supposed to silkscreen "Arduino" on a board that you produce.

The design might be freely available, but the brand name is not.

[FightCube]

You are correct. I made that one just for my own personal use, so it's no big deal. I will definitly brand it appropriately when I make it my own for sale. It will likely be completely different at that time, because I'm not about to compete with Sparkfun apples to apples.

[electrotek]

Hmmm,

I didn't read Fightcube's post as "i'm duplicating arduino's board and trying to compete with sparkfun". I think that it should be understood that unless you are a masochist, no one would try to rip off a design as their own AND put the other people's logo on it. Why think the worst of people? It was a great visual aid in making his point. Just my .02

Electrotek

[FightCube]

I just created a spreadsheet for my Arduino Pro Mini v12/v13 (5V) BOM. If you are interested check it out here:
https://docs.google.com/spreadsheet/ccc ... mE1YlN5MUE

[inventorjack]

Good stuff FightCube. I've just been using a text file for my BOM, but I may switch to a simple spreadsheet like you have there.

I think a BOM is critical for any hardware project. I'm so forgetful that if I didn't keep a detailed BOM, I'd quickly be lost after any sort of hiatus.

Here's an excerpt from my BOM from a project in progress:

Code: Select all

DISPLAY DRIVER (x3 per board)
-------
Mfg Part:            AS1107WL
URL:               http://search.digikey.com/us/en/products/AS1107WL-T/AS1107WL-TCT-ND/2334782
Package:            24-SOIC
Supply Voltage Range:   2.7 to 5.5V
Brightness Control:      Digital and Analog
DigiKey O/H:         2,385
DigiKey Price @1500:      $4.07
DigiKey O/H:         2000 (1000/reel)
DigiKey Price @1000:      $3.33
Future Electronics O/H:   850 (1000/reel)
FE Price @1000:         $3.49
Used for:            LED Matrix driving


CAPACITOR TANTALUM 10uF 10V 20% 1206 SMD
-------
Mfg Part:      TCJA106M010R0300
URL:         http://search.digikey.com/us/en/products/TCJA106M010R0300/478-3127-1-ND/827213
         http://search.digikey.com/us/en/products/TCJA106M010R0300/478-3127-2-ND/827200
ESR:         300 mOhm
DigiKey O/H @1000:   18,829
Price @1000:      $0.38745
DigiKey O/H @2000:   18,000
Price @1000:      $0.274
Used for:      Supply filtering



CAPACITOR CERAMIC 0.1UF 50V 10% X7R 1206 SMD
-------
Mfg Part:      GRM319R71H104KA01D
URL:         http://search.digikey.com/us/en/products/GRM319R71H104KA01D/490-1775-2-ND/586815
DigiKey O/H:      310439
Price @12000:      $0.0134
Used for:      Power In/Out, Decoupling, etc


etc...

(It looks better in NotePad, lol. Formatting tabs on the web sucks)

Anyway, a good BOM helps your customers or end-users find the parts they need, but also helps the designer keep things straight.

[westfw]

Why not just include a real BOM!

Well, for instance, freeduino was designed without specific parts in mind, and the prototypes were built largely with "surplus" components of unknown part numbers and usually unknown manufacturer (and not always matching the schematic. I have a partial reel of 9.19k resistors that were used in place of the 10k reset pullup on the 1206 version, and a big bag of .22uF and .33uF ceramic caps that I used instead of .1uF bypass caps. You're lucky the schematic values aren't "bypass cap" and "pullup resistor" (Hmm. I think I actually did "LED current limiting resistor" rather than specifying an actual value.))
It's a FEATURE of a hobbyist open source design that the parts used are generic and widely substitutable, but it makes it really annoying (for the developer as well as the would-be builder) to track down REAL part numbers. (I suppose I could look up part numbers in a catalog, but if I'm going to go to that level of detail, it would probably be nice to actually TEST those actual parts, right?) (What? Spend REAL money?)

That said, I do like the Adafruit projects whose parts lists point to actual mouser/digikey parts OR specifically specify "generic." And a surprising number of parts DO have specific limitations that ought to be mentioned somewhere (like the power supply electrolytics on a TH freeduino should be "short" (5mm, 7mm), or the shields won't fit right.)

I'm not really very fond of BOMs that have meaningless manufacturer part numbers instead of calling out the important features of the part (very common in manufacturer "reference designs.")

I suppose that somewhere there is a happy medium.

(Meanwhile, if you build something based on an OSHW design, using all new parts with known part numbers, it probably IS a good thing to contribute back to the community. Also negative result info: "don't use a 1/8W resistor here, because it's actually dissipating more than 1/8W!") FIghtCube's example is great. (well, almost great; it looks like the links don't work (digikey's fault for tying "search" to a session?)) I do notice that it apparently took several months to put together!)

[FightCube]

I'm not really very fond of BOMs that have meaningless manufacturer part numbers instead of calling out the important features of the part (very common in manufacturer "reference designs.")

Well I say, start with the "meaningful" mfg part number AT LEAST... so you can go look up the spec sheet.

Knowing what the design requires would take a little more then a 10 word description, more like a circuit design description. Good luck getting that for an OSHW design. It's hard enough to get engineers to do this work when they are being paid fat stacks.

Also negative result info: "don't use a 1/8W resistor here, because it's actually dissipating more than 1/8W!")

If you just make a habit of designing CORRECTLY... and labeling all parts in the schematic for power dissipation and voltage rating... "negative" warning type comments would not be necessary

FIghtCube's example is great. (well, almost great; it looks like the links don't work (digikey's fault for tying "search" to a session?)) I do notice that it apparently took several months to put together!)

I just fixed the links... so click on through.
https://docs.google.com/spreadsheet/ccc ... li=1#gid=0

It took about an hour or so to put the spreadsheet I had up online and get all of the links initially added. I just never published it back when I first posted my Arduino Pro Mini picture here because this is not really a PROJECT on my website.

[inventorjack]

Why not just include a real BOM!

Well, for instance, freeduino was designed without specific parts in mind, and the prototypes were built largely with "surplus" components of unknown part numbers and usually unknown manufacturer (and not always matching the schematic. I have a partial reel of 9.19k resistors that were used in place of the 10k reset pullup on the 1206 version, and a big bag of .22uF and .33uF ceramic caps that I used instead of .1uF bypass caps. You're lucky the schematic values aren't "bypass cap" and "pullup resistor" (Hmm. I think I actually did "LED current limiting resistor" rather than specifying an actual value.))

I still think a BOM is useful in the circumstance you mention here. You could easily mention on your BOM that values between X and Y are acceptable for this part, and the size needs to be Z mm to fit on the board.

In fact, I'm going to start doing that on my own BOMs.

[inventorjack]

I just created a spreadsheet for my Arduino Pro Mini v12/v13 (5V) BOM. If you are interested check it out here:
https://docs.google.com/spreadsheet/ccc ... mE1YlN5MUE

I liked your idea enough to start building something similar for my own projects. If anyone finds it useful, feel free to use and adapt to your needs:
https://docs.google.com/spreadsheet/ccc ... jY0LW8xRWc