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Building a SMD inventory
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Building a SMD inventory

by inches on Thu Mar 09, 2017 2:45 pm

I went through the through-hole and SMD Eagle tutorials on Sparkfun and I'm really enjoying building circuit boards. I have one off to OSH Park and another one off shortly.

I want to continue, but I'm wondering about how hobbyists manage parts. Should I just buy an assortment of SMD resistors/caps of all sizes? Or just buy the ones I need for each project at a time?

I see the SMD books here at Adafruit, but should I get several sizes, or just pick a size I want to work with and build my boards only using those?

inches
 
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Re: Building a SMD inventory

by adafruit_support_mike on Fri Mar 10, 2017 1:18 am

Start with 0805 and build out from there. It's one of the most common sizes, and is easy to work wtih. When you get comfortable with that, you can move to 0603 and then to 0402 if you're feeling obsessive enough. ;-)

Component kits are a good way to pick up an initial inventory, then you can buy in quantity when you need to restock. My last refill of 0805 resistors from Mouser cost 70c per hundred, so I generally tack a few values onto orders for other parts.

I've found that it's good to have seven decades of E6 series values: 1.0, 1.5, 2.2, 3.3, 4.7, 6.8, with multipliers of 1 ohm to 1M for resistors, and 10pF to 10uF for capacitors. With that you can build just about any new circuit without having to order parts and wait. When you start to feel limited with those values, you can expand to the E12 series by adding the values 1.2, 1.8, 2.7, 3.9, 5.6, 8.2. I got those one decade at a time while I was building out my own inventory.

Along the way, you'll pick up special values as you need them.

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Re: Building a SMD inventory

by inches on Fri Mar 10, 2017 12:59 pm

So either of these two pretty much cover everything then, right? https://www.adafruit.com/products/441 or https://www.aliexpress.com/store/produc ... .34.KpmONj

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I was working on an FDTI project that required polarized caps so that's what started my confusion. I needed 10nF and 4.7uF pol. Are electrolytic SMD components things you stock up on too, or just buy as needed?

Right now I'm sitting next to a board I pulled from a TV that has what I need for the FTDI project, so maybe not?
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inches
 
Posts: 94
Joined: Sat Jan 16, 2016 3:33 pm

Re: Building a SMD inventory

by adafruit_support_mike on Sat Mar 11, 2017 2:13 am

Either kit should give you a good initial selection of parts.

WRT electrolytic caps, I keep 1, 2.2, and 4.7 values in the 1uF, 10uF, and 100uF decades, plus 1000uF.

There are about nine different ways to make devices that fall under the general heading of 'capacitors', each of which has different strengths and weaknesses. Electrolytics have the worst performance in almost every way, but they're dirt cheap compared to anything else with the same capacitance and voltage ratings. Their tolerances are generally +/-20%, and they're generally used in places where you can say, "enh.. close enough" about the values. The range above covers everything below serious power supply smoothing.

The other kinds of capacitors are things you'll buy when you need them, and you'll know what specific properties you need by the time you do buy them.

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Re: Building a SMD inventory

by inches on Sat Mar 11, 2017 12:02 pm

Ok, thanks a lot for your guidance. I'll pick up a mixed book.

Can 0805's be used in place of 0603's on board designs I might come across? Are they within a tolerable size range for soldering?

inches
 
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