Capacitor values

[hstewart]

Hi,

Searching through the forum I found a recent explanation regarding how to choose a voltage for capacitors. I think I'll be fine ordering some 25V capacitors for the led and pic circuits that I'm playing with.

The problem is searching digikey and mouser, I see a wide price range on what appears to be basically the same item. We're not talking a lot of money each, .06-.21 each but when ordering say 50 of each value, and about 8 different values, that can add up and I don't want to waste money on useless parts.

For simple led/4017/pic types of circuits I'm thinking about ordering say 50 each .1µF, 1µF, 4.7µF, 10µF, 22µF, 47µF, 100µF, 220µF. I understand that specific areas of interest will dictate parts and values but does that seem like a decent list of general use capacitors?

I keep coming across parts that I don't have so I'll place another order and try to use the bulk(100 or so) price to get more for less. Below is what I've gathered so far and if there are any other "must have" items that I should order, by all means let me know.

1000 1/4w resistors in different values
10- 40MHZ crystals
5- 20MHZ crystals
25- 32.768 crystals
25- 1000µF 25V aluminum electrolytic capacitors
100- 100µF 10V " "
50- 10µF 25V " "
Single row headers
10- LM723CN programmable regulator
50- 7809CT
10- 2N3055 NPN transistor
100- 2N3906 PNP transistor
100- 2N3904 NPN transistor
100- PN2222ATA NPN transistor
100- 1N5819 Schottky Barrier
100- 1N4007 Rectifier
100- 1N4148-T diode
100- 1N4002 rectifier
100- 1N4001 rectifier
2500 led (I like the lights )
5- 555 timers
25- 4017 decade counter
Misc battery packs
Bag full of potentiometers and a box full of "stuff" from Electronics Goldmine.
4 or 5 different PICs in DIP and you can imagine my dismay when I received the first order from Microchip to realize I had ordered about fifteen 40 pin QFN PICs.

 

[Diver300]

Don't bother with

1N4007

and

1N4002

and

1N4001

they only differ in maximum voltage rating and so marginally in cost that it is not worth having anything other than the 1N4007s. Reduce the problems of storage and have just one type.

It is only when you are buying thousands for production that it might be worth saving the fractions of a cent and buying the ones exactly rated for the job.

 

[hstewart]

Thats a perfect example of why I had posed the question about the capacitors since I already have all those diodes so I guess I've got quite a supply huh?

 

[Dean Huster]

(50) 7809s but only (5) 555 timers? I'd gather up a few more 555s and a few 7805 and 7812 regulators. Don't be afraid to salvage old audio equipment for capacitors rather than buying new.

Here's the philosophy I used when I wanted to increase my stock of 1% resistors (that's 96 values per decade over 5 or 6 decades and I had no intention of ordering 10 each of 500 values): If a project needed 4 different values of 1% resistors, I ordered a bulk package of 100 (or was it 200?) of those 4 values only, figuring that if I needed them then, I might need some later -- maybe. But I also ordered 100 of 100, 1K, 10K, 100K and 1M to have as base resistors for voltage dividers and attenuators. You could apply similar logic for other parts. Don't order 100 of some value of cap unless you plan to use it. Let salvaged parts fill in your stock for all those little-used or not-used values.

It took me a couple of decades to build up my parts stock and I have more stock than any Radio Shack ever thought of having, albiet many as used stock rather than new. 90% of my parts were salvaged.

Dean

 

[fernando_g]

For the crystals, you will also need those low-picofarad caps. Depending on the crystal you got, they will be anywhere from 10 to 22 pf. Check the datasheet.
Also , IMHO, I would also stock some low power N-chan Mosfets, which in certain apps are better than its bipolar counterparts. The 2N7000 is a good candidate in a TO92 package.

And unless you are planning the "all digital" route, please do stock some dual opamps and/or quad comparators. Everyone has its own favorite, but general purpose devices like the LM358 and LM339 are dirt cheap and extremely useful.

 

[Hero999]

My advice is to look for a mixed bag of resistors and capacitors.

An E12 set of carbon resistors between 10R and 1M should be good for most applications. You'll probably want to get extra common values, i.e 150R, 220R (for powering LEDs off 5V), 10k (general purpose pull-up) and 1M (for biasing crystal oscillators).

An E3 set of capacitors between 10pF and 10µF plus all powers of 10 up to 10,000µF are good enough for most things. Again you'll need extra common values, 22pF for crystal oscillators, 1nF and 100nF for decoupling IC pins, and 10µF for audio.

When I talk of E3 or E12 values I'm talking about the standard set of preferred values for components:

E3
10, 22, 47

E6
10, 15, 22, 33, 47, 68

E12
10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82

E24
10, 11, 12, 13, 15, 16, 18, 20, 22, 24, 27, 30, 33, 36, 39, 43, 47, 51, 56, 62, 68, 75, 82, 91


For example an E3 resistor set with values between 1k and 100k will consist of: 1k, 2k2, 4k7, 10k, 22k, 47k 100k.

When I mean powers of ten I mean 10, 100, 100 etc.

 

[hstewart]

Thanks for all the advice.

It seems I keep running into items that I don't have to do a few given projects which is starting to be a PITA.

I guess I may just concede to the fact that I'm going to have to keep placing orders as I come across different projects to try and I'll just order extras of the items that cause me to place the orders.

I'll have to check digikey, newark and mouser to see if they have the E3-E24 sets available so I don't have to spend an hour putting it together in the shopping cart.

 

[Hero999]

Velleman sell E12 and E3 resistor kits. I recommend buying a packet of each.

Velleman Components n.v.
Velleman Components n.v.

They also sell E4 capacitor kits:

10pF to 220nF ceramic
Velleman Components n.v.

1:mu:F to 1000:mu: electrolytic.
Velleman Components n.v.

Again I recommend buying both.

 

[hstewart]

This may seem stupid but I've looked a few times now and I still don't see any way to buy them from their(Velleman) site. Do you buy direct from Velleman or one of the dealers?

Granted, I didn't start calling all the dealers listed but I didn't see anything on the line card for the 10 or so dealers that I did look at.

On a side note... I did find some capacitor kits on the Mouser site but lets just say the chance of me paying $975 for an assortment is slim to none and leaning heavily towards the none side.

 

[Hero999]

Go to your nearest dealer.
**broken link removed**

 

[Dean Huster]

It seems I keep running into items that I don't have to do a few given projects which is starting to be a PITA.

Maybe the cure is that I offer my entire collection of electronic parts for say, $8000. A bargain that includes any passive component of any value you could ever want, digital and analog ICs, transistors, diodes, fuses, wire, junk circuit boards for scavenging, connectors, LEDs, crystals, coils, transformers, lamps, vacuum tubes ..... Hey, 40 years of collecting adds up. Double the price and I can throw in some high-end test and measurement equipment.

Dean

 

[hstewart]

Maybe the cure is that I offer my entire collection of electronic parts for say, $8000.

Dean

I appreciate the offer but if I were to lay out $8000 in one lump sum for another hobby, I may find myself participating in an intervention soon after.