So I am about to begin some new projects, and have my BOM for each and realize there are quite a few different parts to order, and wondered if anyone had any tricks or techniques for placing a large order I have never placed an order like this.
I am putting together a spreadsheet with information on each part I need and where to get it... aside from that, I am curious what the more experienced folk do when ordering large orders for several projects at once. Thanks in advance.
I am putting together a spreadsheet with information on each part I need and where to get it... aside from that, I am curious what the more experienced folk do when ordering large orders for several projects at once. Thanks in advance.
Usually anyone who does a lot of projects keeps most parts in stock. It's much cheaper buying in bulk. Small signal transistors and resistors are dirt cheap when you buy 100 at a time. Larger items usually come considerably cheaper in multiples of 25. There aren't a lot of different devices used in audio.
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I usually use RS Components or Farnell.
For more than one project I just add components as I go along.
If the same component comes up twice I simply "add" more of that component to the list.
I usually print off parts lists and tick off as I order each part.
For more than one project I just add components as I go along.
If the same component comes up twice I simply "add" more of that component to the list.
I usually print off parts lists and tick off as I order each part.
I keep some basic stuff around, and only usually shop for project specific stuff. E12-series resistors in 0,6 and 2 watt forms, some usual suspect caps, stuff like that. I never buy a single resistor, or a diode or a zener. At least ten at a time.
And still it's some kind of a rule of physics, that for every project you have to go to the component store at least three times. For my currently active project (a tube preamp) I've bought stuff from at least five stores, plus the places I've been to get stuff for the chassis. And the boards done. But usually three times per project is 'nuff.
Not much help, I guess...
And still it's some kind of a rule of physics, that for every project you have to go to the component store at least three times. For my currently active project (a tube preamp) I've bought stuff from at least five stores, plus the places I've been to get stuff for the chassis. And the boards done. But usually three times per project is 'nuff.
Not much help, I guess...
I try to stick to some basic components.
i.e. MPSA42 MPS92 transistors for amplifier front ends, VAS and Vbe multiplier..
Good little high voltage general purpose transistors.
i.e. MPSA42 MPS92 transistors for amplifier front ends, VAS and Vbe multiplier..
Good little high voltage general purpose transistors.
With Digikey you can include a comment for each component which will appear on the printed labels.
What I do with multiple orders if the orders are big enough is make a separate order for each project.
Then when the orders arrive mark on each box or jiffy bag the name of the project.
I also put the name of the project on any pcb's I order.
Any pcb's I make also have a BOM file with the same name as the pcb but with a different file extension.
Then when the orders arrive mark on each box or jiffy bag the name of the project.
I also put the name of the project on any pcb's I order.
Any pcb's I make also have a BOM file with the same name as the pcb but with a different file extension.
Many of the sites like mouser and Digikey have BOM upload ordering. Should make it easier.
Also, this is why a lot of designers use the same parts across designs, even if it's a tad more expensive. It simplifies ordering and can actually make the design cheaper in the long run due to higher qty ordered.
Keeping track of parts and parts requirements is a LOT of detailed work no matter how you do it. After "evaluating alternatives", a design engineer's most valuable trait is "attention to details".
I use an Excel spreadsheet to help monitor parts requirements. I have attached a screenshot - there are real-life samples of the actual Excel file in the project documentation I posted to the "Discrete Opamp Open Design" thread a while back. The file shown in this image was taken from post #2909 at: http://www.diyaudio.com/forums/anal...screte-opamp-open-design-291.html#post3485352 ; there's another sample at :
http://www.diyaudio.com/forums/anal...screte-opamp-open-design-271.html#post3374536 . You'll have to download the archive file " Post2885_Docs_Edited_Part1_B.zip " from that post, and extract the Excel spreadsheet.
The spreadsheet is organized as two pages. The first is in "Parts List" (PL) format - one line for each component reference-designator in the project. As I develop a project's schematic and PWB layout I identify suitable components - and an alternative, if possible - and record the information in the spreadsheet's first page. You may think of this as the "Engineer's page", telling the principal characteristics of each part used in the design.
The second page is in "Bill of Materials" (BOM) format - one line for each component part number in the project. It shows the net requirements for each component - so-many 470 ohm, quarter watt resistors; so-many BC560 transistors; etc. You may think of it as the "Purchasing agent's page" (or "Storeroom clerk's page"). Consolidating the information from the first page onto the second page is a totally manual operation I perform when the design is close to complete and I'm getting ready to order parts. Yeah, it takes some concentration to avoid mistakes, and you must remember to update the second page whenever you make a change on the first page. (Some VBA whizz can probably write a program to automate the process. I'm a circuits guy at heart, not a programmer.) The same process can be used to consolidate the parts lists from several projects into a single BOM.
In this form it's fairly easy to pick off all the parts you want to order from a particular supplier, copy the relevant columns to another spreadsheet (or spreadsheet page) and use it to compose an order. Many suppliers have on-line order pages that can read an Excel spreadsheet directly, saving you the tedium of entering each line individually.
(The seminal origins of this spreadsheet are in what I considered the "best practices" of design documentation and configuration control at several former employers, adjusted for the typical practices of several small-time clients I did freelance work for. Like anything else you find on the internet, you are free to use, berate, modify, improve, simplify, enhance, praise, curse, bend, fold, spindle or mutilate this file to your heart's content. Karma is alive and well.)
I agree with the advice about purchasing in quantity. Unless it's a high-cost, or very specialized, item I never buy only one, and seldom purchase the exact quantity required for a project. Especially in development and prototyping stages you will need to deal with changes and mistakes, and a stash of useful parts can simplify the effort. (A couple months ago I got the pin order turned around on some PCB patterns for LP2950's. Fortunately I had ordered 5 of them to cover the 2 units I needed to build. As for the guy who published a datasheet showing the pins of a TO-92 package from the TOP view . . . . )
As for organizing, cataloging, and storing all those accumulated bits and pieces, that's a separate - and non-trivial - problem. Old threads on the subject include
http://www.diyaudio.com/forums/parts/226898-parts-storage.html and
http://www.diyaudio.com/forums/parts/231133-how-do-you-keep-invertory-your-parts.html
Dale
I use an Excel spreadsheet to help monitor parts requirements. I have attached a screenshot - there are real-life samples of the actual Excel file in the project documentation I posted to the "Discrete Opamp Open Design" thread a while back. The file shown in this image was taken from post #2909 at: http://www.diyaudio.com/forums/anal...screte-opamp-open-design-291.html#post3485352 ; there's another sample at :
http://www.diyaudio.com/forums/anal...screte-opamp-open-design-271.html#post3374536 . You'll have to download the archive file " Post2885_Docs_Edited_Part1_B.zip " from that post, and extract the Excel spreadsheet.
The spreadsheet is organized as two pages. The first is in "Parts List" (PL) format - one line for each component reference-designator in the project. As I develop a project's schematic and PWB layout I identify suitable components - and an alternative, if possible - and record the information in the spreadsheet's first page. You may think of this as the "Engineer's page", telling the principal characteristics of each part used in the design.
The second page is in "Bill of Materials" (BOM) format - one line for each component part number in the project. It shows the net requirements for each component - so-many 470 ohm, quarter watt resistors; so-many BC560 transistors; etc. You may think of it as the "Purchasing agent's page" (or "Storeroom clerk's page"). Consolidating the information from the first page onto the second page is a totally manual operation I perform when the design is close to complete and I'm getting ready to order parts. Yeah, it takes some concentration to avoid mistakes, and you must remember to update the second page whenever you make a change on the first page. (Some VBA whizz can probably write a program to automate the process. I'm a circuits guy at heart, not a programmer.) The same process can be used to consolidate the parts lists from several projects into a single BOM.
In this form it's fairly easy to pick off all the parts you want to order from a particular supplier, copy the relevant columns to another spreadsheet (or spreadsheet page) and use it to compose an order. Many suppliers have on-line order pages that can read an Excel spreadsheet directly, saving you the tedium of entering each line individually.
(The seminal origins of this spreadsheet are in what I considered the "best practices" of design documentation and configuration control at several former employers, adjusted for the typical practices of several small-time clients I did freelance work for. Like anything else you find on the internet, you are free to use, berate, modify, improve, simplify, enhance, praise, curse, bend, fold, spindle or mutilate this file to your heart's content. Karma is alive and well.)
I agree with the advice about purchasing in quantity. Unless it's a high-cost, or very specialized, item I never buy only one, and seldom purchase the exact quantity required for a project. Especially in development and prototyping stages you will need to deal with changes and mistakes, and a stash of useful parts can simplify the effort. (A couple months ago I got the pin order turned around on some PCB patterns for LP2950's. Fortunately I had ordered 5 of them to cover the 2 units I needed to build. As for the guy who published a datasheet showing the pins of a TO-92 package from the TOP view . . . . )
As for organizing, cataloging, and storing all those accumulated bits and pieces, that's a separate - and non-trivial - problem. Old threads on the subject include
http://www.diyaudio.com/forums/parts/226898-parts-storage.html and
http://www.diyaudio.com/forums/parts/231133-how-do-you-keep-invertory-your-parts.html
Dale
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Agree, I can buy individual resistors for 10-15 cents each or 100 of the same type for a dollar or two. And then I have plenty of that value for the next few projects. Small signal transistors in 100 lot are a few cents each.
I also make a spread sheet, but I do it with pen and paper. Columns for my favorite suppliers, and lines for each part. The thing to do is look at the big picture. I might find Digikey has a part costing half as much as at Mouser, but the rest of my list is much cheaper at Mouser. I will go ahead and pay the higher price for that one part just to get the savings of all the other parts, plus I don't have to pay shipping twice from two suppliers.
I also make a spread sheet, but I do it with pen and paper. Columns for my favorite suppliers, and lines for each part. The thing to do is look at the big picture. I might find Digikey has a part costing half as much as at Mouser, but the rest of my list is much cheaper at Mouser. I will go ahead and pay the higher price for that one part just to get the savings of all the other parts, plus I don't have to pay shipping twice from two suppliers.
Thank you all for the advice. I was a bit apprehensive about posting such a thread, as it seemed to me like a bit of a stupid question, but its really given me lots to think about. Definitely see the sense in ordering 100 resistors like that.
My spreadsheet is starting to look really organized and knowing I can add comments to my parts orders makes me feel much more confident in placing a large order. I know I hate going to the store for resistors and little things to walk away with $1.25 in parts that throw a wrench into things. The advice here will hopefully keep me from having to make those same mistakes again.
Many thanks, and feel free to keep the tips coming 😀
My spreadsheet is starting to look really organized and knowing I can add comments to my parts orders makes me feel much more confident in placing a large order. I know I hate going to the store for resistors and little things to walk away with $1.25 in parts that throw a wrench into things. The advice here will hopefully keep me from having to make those same mistakes again.
Many thanks, and feel free to keep the tips coming 😀
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