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How is Chipageddon affecting you?
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tom66:

--- Quote from: peter-h on January 04, 2023, 06:05:29 am ---You can always tell a novice working without supervision. The circuit is full of 9.1k resistors :) A lot of Honeywell avionics are like that e.g. the KFC225 autopilot - hundreds of weird component values which are so obviously pointless.

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When you're making an avionics system, the pick and place cost is probably a fraction of what you sell it for.  So it just doesn't come into it.  Maybe the engineer chose 9.1k because it gave the best Vol/Voh in a certain application, or because it was used in a previous design.  But BOM rationalisation isn't really an issue in that type of product.

Strangely enough Maxim has been one of the best suppliers during the chip shortage, so they've won a few design ins.
peter-h:
With 2x to 3x price exploitation...
mikeselectricstuff:

--- Quote from: Kasper on January 04, 2023, 06:12:15 am ---
--- Quote from: T3sl4co1l on January 04, 2023, 05:38:14 am ---
--- Quote from: peter-h on January 04, 2023, 05:20:20 am ---
--- Quote ---add more BOM line items
--- End quote ---

Do some companies have such a rule? It would be utterly bizzare. Resistors and caps and common transistors are always available, and are always cheap. Using commodity parts to replace a unique chip, especially a weird thing like that, is always a good idea.

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Yes? Most of them? More line items means more reel changes on the PnP, more labor required, more production cost. :-+

Tim

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I'm not really familiar with PnP but I've heard removing an item can have extra impact if for example their PnP has 20 reel slots and your BOM has 21 or 41 line items.

I'm not sure how many slots my assemblers have or how much that difference actually costs.

I just know that's more items for me and everyone else to deal with and I prefer to have less.

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Another factor is that by  minimising your BOM, it may also reduce your total parts cost, as you will be buying a larger quantity, e.g. 1 full reel vs. two half-reels of different values will usually be cheaper.
VK3DRB:
I noticed TI's Webench and their datasheets often choose obscure resistances. Sometimes odd-ball values do make sense, but sometimes they do not. For feedback voltages another combination of common "preferred" values will work just as well very close to the nominal, especially taking into account tolerances. I have seen pull-up resistors on digital lines like 10.1k, when 10k will work fine. Why they do that, I have no idea. I have also used a network of common resistors if the real estate is plentiful. For example, 2 x 10k in parallel, when a 4k7 is not used anywhere else. Less parts means less chance of a wrong part being loaded, less chance of overflowing the number of feeders in a placement machine, and potentially lower cost because vendors look at the number of unique parts in their quoting.

During Chipageddon about 18 months ago, obscure resistors were hard to get and expensive, especially precision resistors used for current sensing. I think that has calmed down a bit since.
peter-h:
Yes; to design manufacturable products you need to understand electronics, and why and where a 10k will do when a calculator says 9.1k :)
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