Re: SMD Group Build
Diver Martin <diver.martin@...>
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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: