Re: Getting a stock of basic components

On Fri, 2 Mar 2007 20:16:52 -0000, "Simon"
<simon@xxxxxxxxxxxxxxxxxxxxxx> wrote:

"Arthur Rhodes" <arhodes@xxxxxxxxxx> wrote in message
news:R_qdnX2PtOQg0HjYnZ2dnUVZ_t2tnZ2d@xxxxxxxxxxxxxx
I'm just getting started, hoping to build some things with
microcontrollers. It would be nice to have a good assortment
of basic components on hand, so I don't have to go online and
spend $10 on shipping and wait a week every time I need a resistor.
How do most people acquire a good basic stock of resistors, capacitors,
etc.?

There's a fellow in town who has a set of components organized in about
8 of those storage boxes with arrays of drawers. There are something
like 25 or 50 each of a couple dozen resistor types, an assortment
of capacitors, and some miscellaneous other stuff, like dip switches,
knobs, IC sockets, etc. The stuff is left over from a business that
built rack mountable electronic devices. The components probably
reflect to some extent the specific boards they made. For instance,
there's a bunch of IC's included, but I assume they'd probably be very
little use to me. He wants $150 for the lot.

Does the $150 sound reasonable? Is there a better way for me to get
a basic stock of components?

I'm pretty much a novice and was wondering the same thing. So far my
approach has been that whenever I need few of a cheap component such as a
resistor or diode I buy 10 or even 100 of them, as the unit price falls
rapidly with quantity, and I'll probably want more in future.

I haven't seen folks talking about what I used to do (and it made
somewhat more sense, I suppose, then.) That's cannibalizing TVs (I
think radios are a little too IC'd up, these days, but most TVs have
some parts to snarf in them. Used to go in with a pair of dikes and
cut away or work out the parts. Usually can find some nice inductors,
capacitors (ceramic and electrolytic), a few transistors (large and
small), and various resistors (up to a few watts worth.)

I'd like to ask a related question - are there any component types that it
doesn't make sense to over-buy in anticipation of future use? How about
electrolytic capacitors - do they have a finite shelf life? Do mechanical
components such as switches and relays deteriorate if left on the shelf for
a few years? Presumably some kinds of cheap ICs are likely to be superseded
by even cheaper and better models in future so it wouldn't make sense to
stockpile them. I've got some diodes that have been in storage for 15 years
and the leads are mottled and dark rather than shiny - I'm not sure whether
I should try to clean them up or just discard them.

Over-buy the cheap stuff. New 1/4 watt resistors will be about 2-3
cents each -- get a whole range of values at that price. Make it
10-20 of each value. Then you only need to refill the ones you use
up, later. Capacitors, I'd look for grab bags specifying large
numbers of parts. They will be divided into ceramics in one grab bag,
electrolytics in another. But focus on cheap. You can always just
buy the polyprops when you actually know you'll need one, so don't
bother with pre-buying a wide range of expensive parts like that.
Transistors like the 2N3904 and 2N3906 should be in the range of 1 to
3 to maybe 5 cents each. If you can find a bag of 1000 at $10, go for
it. It happens sometimes. Otherwise, look for those in as cheap a
bag as you can find. They are good transistors. The 2N2222 would be
okay, but it usually isn't quite as cheap. Also, you may find some
mosfets of the 2N7000/2N7001/2N7002/2N7003 types, but don't pay more
than 8-10 cents each. Look for a nickel each.

Other than that, perhaps just buy or find what you need. I usually
also get a tube of one of one or two different kinds of cheap micros
and keep those around, as well. Of the roughly 18-pin dip variety.

Jon
.

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