Common Capacitor Values
NWCCTV
Posts: 3,629
Several years ago I purchased a Capacitor kit that I thought would come in handy. I have not used a single one of them since buying it. So, What are the most common Capacitors that might be used In various Propeller projects? I do not need to be specific but rather than buying a few at a time I would like to buy another kit but with values I will actually use.
Comments
The full range kitted values tend to be a waste of money.
For capacitors, it is a bit more difficult as there are a wide variety of kinds with different attributes. You might have the right value and the right voltage capacity, but desire something that has more ideal qualities for the frequency that you are targeting.
Having said that
Having a lot of 0.1mfd to 0.33mfd capacitors for by-pass in the 25 volts or less range is optimal.
Having some 10mfd to 33 mfd might be useful for filtering linear voltage regulators.
In the world of resistors, I find that most I need pull-up resistors, LED current limiters, and i/o pin protection
For pull-up resistors, 10K ohms is generally acceptible and maybe 3.3K to 20K will work
For LED current limiters - different values for 3.3v and 5.0v. But between 220 and 470 ohms are useful.
For i/o pin protection - ON the Propeller, jumps from 5 to 3.3 volts are best protected by 3.3K ohms.
and general i/o current limiting by 120 to 220 ohms for things like the base of the transistors.
I'd say the main thing is to avoid the extremes in values that you might rarely use.
In capacitors, you won't be using 500V capacitors unless you are working with tube amps and motor starters. These get big. And you won't like be needing 50,000mfd and above unless you are building power supply filters.
In resistors, you won't be using a lot of 1 watt, 2 watt, or 5 watt resistors. And you really won't need mega-ohm values unless you are dealing with op amp designs. Even then, high mega-ohm resistors are almost never needed.
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In other areas
Basic transistors can be limited as well. I usually have 2n2222 and 2n2907 for almost everything.
MOSfets have changed rapidly to get smaller and better, so it is harder to say what one should keep on hand. I do have a few 2n7000 for general stuff.
Of course there are items for the curious...
SuperBeta transistors, super capacitors, big power darlingtons, and I have dummy resistor loads for 20 watts at 8 ohms for audio work.
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It gets silly to stock all and everything. You usually use up the most popular values and have the odd ones sitting around forever.
And then there are diodes.....
(Just trying to keep things ON TOPIC).
Once you have a junk box of components you can start filling a junk closet and work your way up to a junk room.
Your wish is Parallax's command!
http://www.parallax.com/product/751-00012
picofarad values like 6 pF, 22 pF, 33 pF, and 0.1 uF
get a ton of 0.1 uF ceramics for bypassing chips, 0.1 inch lead spacing to fit in two adjacent rows on a solderless breadboard.
Aluminum electrolytic (50V or even bettter 100V):
microfarad values of 1 uF, 10 uF, and 100 uF
yes these guys wear out but are super cheap, Nichicon are the best (watch out for knockoffs)
Beyond this are the RF and extreme voltage spike abuse tolerant kind of capacitors, but again you'll probably never use them.
(things like epoxy dipped mica capacitors, max 2000V, and other kinds of film capacitors)
I haven't seen a need for tantalum in hobby circuits: they're expensive and don't ever dare reverse their polarity or exceed the max voltage even once.
If you're scared about aluminum electrolytic capacitors (going to have a circuit powered constantly on for years and years) then the new guys on the block are Aluminum Organic Polymer capacitors. High values like 220 uF, but low max voltage though... 10V, 16V, 6.3V etc... But great in switching power supplies and general ripple reduction. Most are going to be surface mount, but versions with leads do exist.
Socking up can be fraught with dangers...
At one point, I decided to stock up on 10K, 5K, and 1K resistors. When I got home, I found that someone at the store had stocked these with 10M, 5M, and 1M respectively. Of course, it wasn't worth a trip back to return them, so they will likely sit in my Megaohm baggie for all eternity, unless I get into some high volt applications.
Often, buy 5V-10V rated capacitors might leave you short. I try to buy at least 25V ratings unless I am sure about what I need less for.
Why so? Well, not all ICs are 5V, 10V or less. For instance, I bought come ML339 comparitors intended for 3.3V and 5V use, but they can operate up to 36VDC. Now I see that I can use one for LED indicators for my gel cell charger and it will be operating at 13.8VDC and maybe a bit higher. I guess that being an IC, it needs a by-pass capacitor between power and ground regardless of the higher voltage.
At one point, I thought that tantalum were the best for all and everything, but I soon found that they are polarized. There are times that this doesn't matter, and there are times that this does and you blow up the capacitor if it is reversed. Electrolitics tend to be polarized as well, but there are non-polarized ones as well.
Like I said above... it is hard to stock exactly what you want in capacifors. But non-polarized and between 25 and 100VDC might be the most handy.
Found a dead LCD monitor and decided to bring it back from the dead.
Turns out 25 volt 1000 mF and 25V 470 mF electrolytic capacitors are used quick a lot on LCD monitor pwer supplies.
They say the electrolytic capacitors dry out when they get hot, and the monitor dies. Appearantly if we replace the non-105c caps with 105c versions, the monitor works again, and is less likely to die from heatstroke.
And it turns out that buying 10 costs the same as buying 1, when buying from ebay. So i got 10 each of the 105c 25volt 1000 mF and 470 mF electrolytic capacitors for like $8. Which would be enough for two monitors.
I have not completed this experiment yet, I chose cheapest shipping from china, to keep the cost below the prince of a new monitor.
Man, too bad this topic didn't come up three days earlier. The capacitors in the monitor that went bad are in fact CapXon. I thought the issue was the heat (the circuit board is visibly golden brown in the area of the bulging capacitors), I didn't even think that the caps themselves would be shoddy. I thought the bad caps thing was solved years ago. I guess some gifts keep giving.
What about brand SAMXON? Are they worth trying? That's whats on the way, the 105C version to replace the regular version.
1000 mF 25V
and
470 mF 25V
would 10 @ 47 mF = 470 mF ?
Jameco has tantalum caps 4.7 mF 35volt. for $0.59. Could I put 100 of these on a board and have it work? It would look silly, but it would still cost less than a new monitor.
http://www.ebay.com/itm/10-25V-470uF-10x10mm-SMD-Aluminum-Solid-Capacitor-SANYO-/351097100294?pt=LH_DefaultDomain_0&hash=item51bf049806
They are the wrong physical size, but I don't mind modifying the case.
If you're concerned about life, I'd just go with a good quality, regular aluminum electrolytic with a decently long working life rating. I've been using the Panasonic FR series.
http://www.mouser.com/ProductDetail/Panasonic/EEU-FR1E102/?qs=sGAEpiMZZMtZ1n0r9vR22eOLaseCUKTaHMz177co6pA%3d
That way, over time, you'll build up an inventory of the exact values that you've used in the past, which in my experience is a pretty good indicator of what you'll need in the future.
So for a 1000mfd at 25vdc, I would try to get something like a 1500mfd at 35vdc. I suspect that might run a bit cooler and longer.
I did have a TV tuner for my monitor that went bad due to bad filter caps. The replacements lasted another 3 years and then the whole thing went seriously haywire.
Sometimes though, it is too late to just replace the capacitors and the device has down stream damage from the power not being clean.
When you see some that are bad, you really should replace all of them. The remaining ones may look good and even test good, but they have aged and been stressed.
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Fake capacitors are a reality in the audio world and they do come out of Asia. I wanted some 2N3055 transistors for an audio project and even those can be phoney. My fakes have the logo 90 degrees out from the real Motorola devices and the M is certainly not the true Motorola logo. These could be anything... not even transistors, but broken voltage regulators that have been relabled.