Re: SMD Group Build


Diver Martin <diver.martin@...>
 

Another option would be to make the kits yourself, if you wanted to market them to your club.  Use E3 resistor values (explanation here, http://www.radio-electronics.com/info/data/resistor/e-series-e3-e6-e12-e24-e48-e96.php), with basically from 1 ohm up to 1M ohm of values 1.0, 2.2 and 4.7 (So 1.0 ohms, 2.2 ohms, 4.7 ohms, 10 ohms, 22 ohms, 47 ohms, 100 ohms, etc).  Account for 7 ranges, that's 21 values.

Caps, I'd do E6 in the ranges from 10p to 100nF (5 ranges, 6 per range = 30), and then 1uF, 4.7uF, and 10uF electrolytics at 50V a pop, roughly.  If you want to build 50 kits, using the 1k 1206 as a reference, it's $16 per reel of 5000 parts (50 kits x 100 pcs per kit).  That's $0.32 per value.  21 values in resistors, 30 values in caps, and 3 values in electrolytics, you can make a pretty good kit.  The resistors would only cost you $6 per kit with 100 parts per value.

The problem with caps is that you have multiple factors / degrees of freedom.  1) Value, naturally, about 30 values would get you there 2) Material.  X7R?  NP0?  Electrolytic?  Tantalum? Some are good for RF, some are horribad, but great for bypassing power supplies.  I generally have NP0 below 1000p, and X7R above, though I do have some 10nF NP0's for specific applications 3) Voltage.  Higher voltage = larger capacitor = more material = more cost.  You don't want to spec 30 values all at 1kV, but 50V might not be good enough for all applications.  My tuner though uses 1kV NP0 caps.

I would generally say 50V is usually useful for most low power and filtering applications though, so 10->1000p @ NP0, 50V, 1000p -> 100nF @ 50V X7R.

On Wed, Jan 24, 2018 at 9:29 PM, Martin Held <diver.martin@...> wrote:

On Wed, Jan 24, 2018 at 9:23 PM, Jack Purdum via Groups.Io <jjpurdum@...> wrote:
I wish someone would put together an assortment of, say, 40 common values, quantity 100 of each value and market it for some reasonable markup for resistors and caps. For the club build, I'd prefer 1206 since this is a huge step for some of the club members.

BTW, today I just got 40 clear plastic 1.25"x0.75" cosmetic sample jars (eBay #332506418787). Tomorrow I'm going to Target and buy Velcro sticky tape "dots" and place one half on the bottom of the jar, and the other on a piece of plywood which hangs on the wall. Now if somebody has an assortment of 40 common values, they go into the jar and I'm ready to go. Each jar will have a small Avery label on it.

Jack, W8TEE



From: Diver Martin <diver.martin@...>
To: BITX20@groups.io
Sent: Thursday, January 25, 2018 12:09 AM

Subject: Re: [BITX20] SMD Group Build

Jack,

Just as a point of reference:  Going for 5% tolerance 1k ohm resistors, and buying 1000 at a time, a quick search on digikey gives me:

1000x 0603 resistors:  $2.07
1000x 0805 resistors:  $3.03
1000x 1206 resistors:  $4.63

For reference
1000x axial TH resistors: $7.29.

At a half penny a pop, the cost of 1206 vs 0603 I'm betting isn't going to be a noticable difference.  (At 100qty, they're about 2x as much, ~$0.01 each, or $1 for 100).  You can really sneeze hard and not loose a lot of money.



On Wed, Jan 24, 2018 at 8:20 PM, Jack Purdum via Groups.Io <jjpurdum@...> wrote:
I can barely see a 0603! I would prefer 1206 if I can find them and am not too worried about the cost differential.
Jack, W8TEE


From: Clark Martin <kk6isp@...>
To: BITX20@groups.io
Sent: Wednesday, January 24, 2018 9:15 PM
Subject: Re: [BITX20] SMD Group Build


Clark Martin
KK6ISP

On Jan 24, 2018, at 5:56 PM, Diver Martin <diver.martin@...> wrote:

Mouser & Digikey are my go-to for SMT parts.  They carry just about everything.  If you have other oddball SMT stuff, and either one are out, head to findchips.com.  There are alternate suppliers, but those two always have what I need, either in the exact specified part number, or an equivalent.  Other places will source 1206's and stuff, but might only sell by the full reel (which I have yet to need, except maybe 0.01uF caps or 0.1uF caps across multiple, multiple projects).

SMD resistors/caps (0603, 5% in my case) are usually cheap enough that I buy them in 1000-piece quantity, because $2 of parts for life or $0.5 for the parts I need for the project, and to always have them on hand, is easy.


I’ve only bought from Digikey a few times but I use Mouser all the time.  Also there are Newark and Allied for such supplies.

I bought a set of 0805 resistors (from 0 ohm through several Mohms) and a set of 0805 caps (10s of pF through 1µF).  They came on cards that fit a day planner binder.  There are between 1 and four strips of 25 each for each value (depending on expected usage levels).  I have little trouble working with 0805 parts and they  fit nicely on .1” grid perfboard (with plated through holes).  

When I use up a strip I buy a new strip of 25 at a local electronics shop (Silicon Valley still has a few).

I haven’t done any PCB fabricating yet but that is in the plans.

SMD diodes and transistors of most any size are easily soldered to perfboard.

I’ve also soldered up to 8 pin SOICss buy putting alternate pins on the perfboard pads and tack soldering leads to the other pins.

It definitely makes for smaller boards.





--
Martin Held - AE7EU
http://ae7eu.com/
-------------------------------------------------------------------------------
If there aren't any questions, then what is there to learn?





--
Martin Held - AE7EU
http://ae7eu.com/
-------------------------------------------------------------------------------
If there aren't any questions, then what is there to learn?



--
Martin Held - AE7EU
http://ae7eu.com/
-------------------------------------------------------------------------------
If there aren't any questions, then what is there to learn?

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