DFH - Defacto FreeEMS Hardware in KICAD

[jharvey]

I'm thinking of adding fields to the schematic symbols. I'm thinking of using field1 as digikey thru hole, field2 as digikey SMD, field3 as vendorX thru, field4 as vendorX SMD.

Any thoughts? Any recommended part numbers for digikey, or perhaps a default second vendor for vendorX?

[jharvey]

with an extremely poor editor like notepad. Those using a decent editor like VIM or textpad or whatever will have no problems with this. In fact, even wordpad does it right

I typically use emacs, but for some reason I can't get it to copy and paste from putty, so I have to open with notepad or word, then copy paste, then open with emacs. I used to find notepad would do it correctly, but word wouldn't. Now I find both wordpad and notepad fail. Damn MS.

That MS comment works on so many levels doesn't it.

[Fred]

Yes, MS is the definition of fail. Click. That suddenly sounds a little harsh, I meant MS = MicroSoft, but now that I think about it...

I'm thinking of adding fields to the schematic symbols. I'm thinking of using field1 as digikey thru hole, field2 as digikey SMD, field3 as vendorX thru, field4 as vendorX SMD.

Any thoughts? Any recommended part numbers for digikey, or perhaps a default second vendor for vendorX?

I don't understand what you mean, can you explain the benefit?

One thing I will say is that I really hate the way the MS BOM is. I strongly believe that the BOM should be location independent, and not some particular companies part number. if we have 1/4 220 Ohm 1% as the thing on the BOM then we can have separate lists made up by other users for the company they prefer and post links to them from the main BOM web page.

So if that's what you meant, I think you should save the effort and have it external to the design where it belongs considering a digikey list is pretty much US only.

Fred.

[jharvey]

I was planning on putting the digikey values in the schematic symbols so I can keep track of the footprints. I guess we could keep track of the important parameters rather then simply linking to a part number. For a resistor we would need capacitance/inductance, watts, footprint, LxWxH. I think it's easier to keep track of a part number though. The internals of a resistor can have significant variations of inductance, or capacitance based on whether it's a wire-wound, carbon film, or carbon composition, ceramic composition, ect. All can come in the same package we are so used to.

The BOM is exported to a text file, so the only way you know these are matched together is to open it with KICAD and go several clicks deep until you have found the field1 property.

I don't object to someone using other components, however I have seen many times when a tantalum was planned for, and an electrolytic was subbed, causing all sorts of havoc.

[Fred]

I guess we could keep track of the important parameters rather then simply linking to a part number.

I think you might be making the important parameters a larger group than it needs to be. I'm all for quality and repeatability, but a large number of users will be buying their stuff NOT in the USA, including some important ones like Dave and Me Me Me!! :-) Plus, there are 10 places or more to get your stuff in the states. Specifying "digikey xyz" is a bad way to do it because the person then HAS to use digikeys (poor) website to find the actual specs which they may not even interpret correctly before they can go shopping at their outfit of choice. They should have the specs up front and then go and find the parts from their supplier of choice.

eg a page on the main site like this :

Parts List

• D1 diode 1 amp 400 volts
• R1 resistor 1k ohm 1% MF
• C1 capacitor tantalum 2uF 25 volts
• C2 capacitor ceramic X7R 0.22uF 50 volts

Supplier specific BOM lists

• Farnell list
• Jaycar list
• DigiKey list
• RadioSpares list

[links aren't real just yet...]

The internals of a resistor can have significant variations of inductance, or capacitance based on whether it's a wire-wound, carbon film, or carbon composition, ceramic composition, ect.

This is true, but if you nail down what they are supposed to be using a bit then they will be pretty much OK.

I don't object to someone using other components, however I have seen many times when a tantalum was planned for, and an electrolytic was subbed, causing all sorts of havoc.

I don't think people who deviate significantly from the specified parts should get much in the way of help do you?

EG, we are going to say "use an autoFET with at least 5A current limiting and at least 40V voltage clamp and cmos drive capability" and if someone sticks some ordinary device in or one with lower V or A rating then they are on their own?

Ditto, we'll spec "tantalum X Volts Y uF" and if they stick in an electro, they can go jump.

For a resistor we would need capacitance/inductance, watts, footprint, LxWxH.

For resistors we need to spec value, power rating, package, tolerance and construction. The obvious one is : Metal Film 1% 1/4 body 1/4+ power.

Reality is that most of the stuff on this board is happening at or near audio frequencies so there isn't going to be a significant difference between my MF resistor and yours. Provided the value is right we are good to go. Again, if someone uses a 5% carbon film unit then they are on their own.

The worst thing will be people wiring the things into the car badly, again, if you can't show us how mint your wiring is, fix it till you can and then do so. 95% of the time that will mean they don't have a problem before they come sulking about how it doesn't work with 50ga wire twisted together at the ends...

It's a bit hard lined, but if you ever supported MS at all, you would understand, the cheap nature of it brings predominantly cheap tin arse people and they aren't afraid to take dodgy short cuts. These short cuts inevitably cause major issues with their installs and thus the support load on the knowledgeable members becomes excessive.

Jean might have a few things to chime in on here. Perhaps I'm being overzealous (again)? I know my installs problems (short lived) came down to use of inappropriate wire for something that wasn't carrying any current (and I knew it) so I used light wire, but reality is it needs to be significant just to survive some vibration etc. Ditto mops install, heaps of VR issues from bad wiring and board and sensor bracket. Ditto most of the issues that crop up. Reality is that users that "do it right" don't have many problems. (that wire breaking on the inside after less than 15 minutes driving was my only issue).

Fred.

[jharvey]

We have fields1 through 8 to work with, perhaps we can have 2 vendors for both SMD and thru hole, then use the remaining 4 fields for other specs? What 2 vendors are cover the largest area, or perhaps who are the two easiest to work with via the web. I've used digi, mouser, and newark. I've liked newark the best so far, then mouser. Any of you out there toss in your top two picks, and lets see what we come up with for a list.

Listing a vendor will fill in gaps we have have missed. Sub um if you got um. Attached is a PDF with a possible layout for the fields.

[davebmw]

RS are very good, only sell good quality stuff but a bit expensive, but delivery is THE best always on time and free.

Farnell are also good, slightly less enthusiastic about the delivery service though.

Rapid Electronics are very good here in the UK regarding delivery and prices I use them often for components as they have a good selection of PIH parts.

I will be getting most of my bits from RS because I have more confidence in them working first time.

[Fred]

so already we have you wanting mouser, gearhead wanting digi, Dave wanting RS, me wanting a mix of farnell/dse/jaycar/current stock held and what about the guy that lives Argentina? If you want the two biggest areas, thats india and china, who is the "average" supplier there?

Doing it with supplier specific part numbers is a recipe for maintenance issues and local specific problems. This is how MS does it. I honest do not like and have never liked the way they do that. I have emails from 3 years ago trying to get Lance to change the listing to actual component specs such as 1n4004 for diodes etc etc. Inside the schematic is not the place for this detail, it belongs in a document outside of the schematic.

The schematics purpose in life is to describe the circuit, the pcb layout to describe how to assemble it, and a BOM to show what parts you need to use, NOT where to get them from and how to order!

Use the fields to describe the components themselves in a supplier independent way please, pretty please? With sugar on top? It just does not make sense in an international context to do anything else. I'm not convinced it makes sense to do anything else anyway, but that's another story.

end rant/

Fred.

[jharvey]

I have no problem supplying non vendor specific information and I have no problem considering that info more important then part numbers. I do think we should supply a vendor option to help fill in any blanks that might be left out. I don't see why everyone should have to create their own order BOM just because we can't make one BOM to fit them all. I also think 4 fields will allow us to cover the non vendor specific info. Wow what a collection of fragmented sentences.

When you tell KICAD to export a BOM you can select what you want exported, so someone from a remote island in Africa, can print it with fields 1,2,3,4 but for me I can print it with fields 5. What ever allows you to get'er done.

I also think I won't consider field4 as Newark, instead I'll consider it thru hole vendor 1. The vendor can be found by the part number. Fore example part numbers that end with "-nd" will come from digikey, and you'll have to know that. See revised PDF w/ examples.

[Delta]

From an electronic engineering point of view I have to agree with Fred here. We have always been told that a layout should contain only the footprint of the devices and that a separate BOM should be produced. We were always told that part numbers are NOT to be supplied even if the company we work for only buys from one source. The reason for this is simple - Part numbers change and get removed from circulation after a reasonably short period of time. In general however listing something like

R1 100ohm 1% Metal Film 1/4W
D1 1N4004 Power Diode

Means that an alternative part can be sourced easily - all the info you need is there. Any competent engineer will know whats going on and be able to help. If however you embed part numbers from various places what invariably happens is that after the part can't be found the engineer will look at the schematic and make an assumption - sometimes not a good one.

The best way to achieve a newark/mouser/rs/jaycar/whatever BOM is to maintain one outside the schematic. As you say it takes several clicks per part to update things - this is not acceptable in terms of maintainance if you ask me. When part numbers invariably change, you will have to go back to the schematic and make lots of changes. Better to have it external in an easy to change text file or even a database. Then a BOM for a new company can be made by someone else and they don't have to release a full set of schematics with the part numbers in them.