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Hi! I'm starting to study electronics but I still don't know much. I'm about to make my first order. Since below 60$ I have to pay 25$ shipping, I'm going to make a 60$ order.
I don't need a lot of stuff to begin playing, since I have a couple tools (multimeter, prototyping boards, soldering iron) from when my dad messed with this stuff decades ago (I know they're all very cheap so eventually I'll invest in the real deal).
The bulk of my order will be resistor and maybe capacitors, just to pad to 60$. I was thinking I'd buy at 1% tolerance something like this (more or less, values will follow standard values):
20
resistors
21 resistors
22 resistors
2... resistors
2k resistors
this way I should be able to make any value I want... more or less, tolerance considered.
PS: while I wait to make the order and for the stuff to get here, I'm building the jankiest modular storage system that could still be considered suitable for storing things. Like in electronics, I literally have no idea what I'm doing but I'm trying to have fun in my free time.
EDIT: to be clear, I'm looking to buy several thousands of (probably smd) resistors. -
I'll recommend you to buy a "resistor kit" instead, like this, you'll never know when you'll need a specific value, even with those kits you'll have to put some of those in series/parallel for a non-standard value, then you see what values you use most and order those apart, kits like this are also for ceramic and electrolytic capacitors too, a diodes kit it's also useful.
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Resistors and capacitors are made in standard values, which roughly follow a geometric progression, which repeats every decade. In the E12 series, each value next up is around 5% larger, than the previous. This means selecting the nearest value to the ideal, will always give 5% tolerance. See the Wikipedia link:
https://en.wikipedia.org/wiki/E-series_of_preferred_number
Resistors values in the E24 series are most common, E96 (1% tolerance) is widely available and E192 (0.5% tolerance) less so. Non-standard values are also available but aren't quite as common.
Capacitors values in the E3 series are fairly common, E6 is still widely available, E12 less so, with E24 reserved for precision values.
Note, that it's possible to get 1% tolerance and better resistors in all the E24 values.
I started with 25 of each E12 resistor values from 1R to 10M, with E24 values from 10R to 1M and is enough for most applications.
If you really are on a limited budget, then you can get away with just the E6 series, which can be used to make any E24 value.
The good thing about the E24 values is that they can be used to make and E96 value. -
@rpv
Unfortunately that doesn't help. As I said, I'm padding a 60$ digikey order with resistors. I can include several thousands. That's 50 resistors for 80 values. I was thinking more along the lines of 250 resistors for 20 values. Using my proposed values, that's about 1ohm to 1Mohm
If I understand digikey's results, I can get 250 resistors for about 2.5$. I want to be able to understand the datasheets of what I'm buying before placing the order, but I think I'm looking at the right stuff.
@Hero999
Thanks for all that useful info! My budget for these resistors is 50$+. I have to order more than 60$ to avoid 20$ shipping, so I want to buy lots of the most common stuff that I will probably need in the future (and since I'm beginning just now I'm not really equipped to understand what the most common stuff is). -
When it comes to resistors, you should buy an entire "series" ( https://www.electronics-notes.com/articles/electronic_components/resistors/standard-resistor-values-e-series-e3-e6-e12-e24-e48-e96.php )
E12 contains all the values you will use _a lot_, and E24 should get you covered for pretty much 99% of your needs.
Keep in mind that the series also contains "decades", so when it says "2.2", they mean:
2.2ohm, 22ohm, 220ohm, 2.2Kohm, 22Kohm, 220Kohm, 2.2Mohm (I think some resistor-kits go into the Gohm range, but that's very rarely used)
E12 = 12 values, 7 decades = 84 different kinds of resistors
E24 = 12 values, 7 decades = 168 different kinds of resistors
As for capacitors, I'm not sure if there exists series like that, but your usage would vary _a lot_ by what you're building.
Since I do mainly digital stuff, I mainly use just a few values:
* 10-22pF ( For crystals )
* 0.1uF ( Decoupling. I use _a lot_ of these, like 10+ per board )
* 10uF ( Bulk capacitance, a few per board )
* 0.8pF 1.0pF, 1.5pF, 2.2nF ( Matching network for 2.4GHz )
Now, if you were doing audio-work, you'd probably have a whole different set of capacitors laying around.
And finally.. Have you thought about how you're going to keep all of this organized? That's not as easy as it sounds.. -
@stmdude
Wow, thanks! That's exactly what I wanted to know. No bulk caps then.
As for the organizing part, I'm building a modular storage system. It has boxes with sides multiple of 10cm I can arrange however I want by attaching and detaching them, and I will also make a rack with rails, kind of like a server rack but made of wood and way worse, haha. -
For a beginner, this chart may be easier to understand : http://www.vishay.com/docs/28372/e-series.pdf
You pick a series and then you either divide values by 10 or multiply by 10.
For example, a beginner will do just fine with E12 which should be easily available in 5% tolerance or 1% tolerance.
If you divide by 10, you have 1 ohm , 1.2 ohm , 1.5 ohm and so on...
If you multiply by 10, you have 100, 120 ohm, 150 ohm and so on...
If you need some in-between values you can use two resistors in parallel and you get 1/R = 1/R1 + 1/R2 ... so 1/R = (R1+R2) / R1xR2 .,. therefore, R = R1xR2 / (R1+R2)
So for example, a 120 ohm in parallel with a 150 ohm will give you R = 120*150 / (120+150)= 18000 / 270 = ~ 66 ohm .. which is almost 68 ohm, another E12 value
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Thanks all! This is great information. I'm going to get the E12 series. Since E12 is a subset of E24, when I need to get more I can just order the values between what I already have.
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As for capacitors, I'm not sure if there exists series like that, but your usage would vary _a lot_ by what you're building.
Capacitors are the exact same way and you can buy kits of standard values just like with resistors. For general purpose work, you can usually get away with 1.0, 2.2, and 4.7 for capacitors with the lower values in C0G ceramic, medium values in plastic film, and higher values in electrolytic up to 100uF. Then add in the intermediate standard values as needed.
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@rpv
Be prepared to pay a bit more for the fact that they're sorted into a kit.
Unfortunately that doesn't help. As I said, I'm padding a 60$ digikey order with resistors. I can include several thousands. That's 50 resistors for 80 values. I was thinking more along the lines of 250 resistors for 20 values. Using my proposed values, that's about 1ohm to 1Mohm
If I understand digikey's results, I can get 250 resistors for about 2.5$. I want to be able to understand the datasheets of what I'm buying before placing the order, but I think I'm looking at the right stuff.
@Hero999
Thanks for all that useful info! My budget for these resistors is 50$+. I have to order more than 60$ to avoid 20$ shipping, so I want to buy lots of the most common stuff that I will probably need in the future (and since I'm beginning just now I'm not really equipped to understand what the most common stuff is).
Velleman do some component kits and they're available from Rapid Electronics, a UK distributor.
E12 carbon film resistors:
https://www.rapidonline.com/velleman-e12-series-610-piece-carbon-film-resistor-kit-74262
E3 carbon film resistors:
https://www.rapidonline.com/velleman-e3-series-480-piece-carbon-film-resistor-kit-74263
I'd buy a pack of both of the above, if I was starting out again and on a budget. The only downside is they're carbon film, which is only 5% but is still good enough for most things.
They also do capacitor kits.
Ceramic 10pF to 220nF
https://www.rapidonline.com/velleman-k-cap1-224-piece-ceramic-capacitor-kit-13-0206
Aluminium electrolytic 1µF to 1000µF
https://www.rapidonline.com/velleman-k-cap2-electrolytic-capacitor-kit-120-piece-13-0221
If you build audio circuits, then ceramic capacitors aren't ideal. They can be microphonic (generate a signal when vibrated) and cause distortion due to dielectric absorption, so a film capacitor kit is a good idea:
https://www.rapidonline.com/miniature-polyester-capacitor-kit-100pcs-13-0215 -
In Europe, TME.eu has imho quite good prices, you may want to check them out.
You'd have to buy 100pcs of each resistor, but for carbon film 1/4w 5%, that costs you maybe 0.7$ for each resistor value (in 100pcs quantity, cheaper for higher quantities). As a beginner, you'd only need values between 1ohm and 1kohm, and maybe a few like 3.3kohm , 4.7 kohm and 10kohm - anything else you'd be able to create by using two resistors in series or in parallel.
Here's a link to start from: http://www.tme.eu/en/katalog/resistors_100299/#id_category=100009&page=1&s_field=niski_prog&s_order=ASC
So with around 25$ plus shipping, you'd have around 40 different resistor values times 100 pcs. Beats paying ~10$ for 610 pcs in a tiny box.
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I was planning to buy around that amount but 1%. Also dang, TME's search is pretty cool.
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I forgot to ask what kind of power rating I should get (I'm getting smd). I think the thing I'll be doing most is audio: modular synths, touch keyboard, guitar pedals.
So if I'm not really mistaken, from 100ohm this isn't really a problem, but below that I need some pointers. I'll include my reasoning below so you can correct me if I have some misconceptions.
I'm writing this 50% to ask and 50% so I can think a bit about it. Let's see if I understand the first couple of pages of my book :PQuote"pro" and "prosumer" audio line level is +4dBu, which is 1.228 volts RMS. That is 3.473 volts peak-to-peak. Modular audio levels typically are 10 volts p-p (3.536 volts RMS).
I found this on another forum. I think I have to calculate my power requirements using the RMS but I'll use both to be sure.
I also found somewhere else the typical voltages for guitar pedals, and they're lower, so I'll use these.
I am including the typical RMS and peak to peak power draw, and assuming I should pick at least double.
>1ohm: I don't think I'll have to use these with this much voltage. 3.5W/10W, which I would assume would be in the power resistor range.
>10ohm: 0.35W/1W. If I have to use these with these voltages I'll need beefy resistors, but these might not cost me an eye and leg.
>100ohm: 0.035/0.1W. If this is correct, these ratings should be pretty common and so from here on I don't have to worry about it. -
I'm aware the OP has decided to choose E12 series resistors; a choice that I totally agree with. However, I don't think the flaw with his/her original plan (20, 21 , 22 , 2... , 2k resistors) has been clearly put forward.
Firstly, most designs that you find online have E12 values, because E12 values are commonly encouraged. It's circular reasoning, but it's valid circular reasoning.
Moreover, consider a 1 kiloohm resistor (which is an extremely commonly specified value, because it is on the E12 series). Now, of course the OP could have constructed 1000 ohms with a string of 512 + 256 + 128 + 64 + 32 + 8 ohms. But that string of 6 resistors in a row is a bit... unwieldy. 47k resistor? No problem, just join 32768 + 8192 + 4096 + 1024 + 512 + 256 + 128 + 16 + 8!
So, not so practical in the real world.
But, don't be discouraged: the E12 series is a geometric series just like the OP's original proposal, it's just that the ratio is (the 12th root of 10) instead of (2).
BTW, if you want a value in between E12 values; there are tools online to find simple 2-resistor series and parallel combinations of E12 values that will get you there. So in practice, you may achieve all of the accuracy* you were hoping to achieve with your binary expansion; but with far fewer parts.
(* since you're limit by tolerances anyway.) -
Moreover, consider a 1 kiloohm resistor (which is an extremely commonly specified value, because it is on the E12 series). Now, of course the OP could have constructed 1000 ohms with a string of 512 + 256 + 128 + 64 + 32 + 8 ohms. But that string of 6 resistors in a row is a bit... unwieldy. 47k resistor? No problem, just join 32768 + 8192 + 4096 + 1024 + 512 + 256 + 128 + 16 + 8!
I might not have thought that through... any thoughts about my last power rating question?
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Firstly: in SMD resistors, power rating is intimately related to size. See the table here.
You are correct that if you put 3.473V across an 0805-sized (0.125W rating typical) 1 ohm resistor, you'll dissipate 12.06 Watts and you'd blow up the resistor.
However, why would you just be putting 3.473V straight across a 1 ohm resistor? If you were ever using a 1 ohm resistor, you'd be much more likely to be using it as a current-measuring shunt. In that application, the P = I^2 * R equation becomes far more relevant; if you want to measure 100 milliamps with a 1 ohm resistor, you'll develop a 0.1 Volt drop and produce 0.01W of dissipated power; which is absolutely fine.
0805-sized resistors are my favourite, and the power rating of 0.125W is fine for most applications. Sure you occasionally have one or two resistors in your design that are particularly power-hungry, but you know that in advance and buy special resistors accordingly. Others like the compactness of 0603 resistors, I personally find them a little bit too fiddly. You're more likely to get written markings on 0805 resistors, maybe. My point here is that you should probably be thinking about picking the size of resistor you want; power rating is something that you worry about at the design stage (when you're figuring out which one or two of the 50 resistors on your design might use more than 0.125W and special-ordering those as required.) -
I forgot to ask what kind of power rating I should get (I'm getting smd). I think the thing I'll be doing most is audio: modular synths, touch keyboard, guitar pedals.
I'm not sure what you're asking and the comment quote about audio, seems irrelevant here, unless you're using the resistor as a dummy load.
So if I'm not really mistaken, from 100ohm this isn't really a problem, but below that I need some pointers. I'll include my reasoning below so you can correct me if I have some misconceptions.
I'm writing this 50% to ask and 50% so I can think a bit about it. Let's see if I understand the first couple of pages of my book
Quote"pro" and "prosumer" audio line level is +4dBu, which is 1.228 volts RMS. That is 3.473 volts peak-to-peak. Modular audio levels typically are 10 volts p-p (3.536 volts RMS).
I found this on another forum. I think I have to calculate my power requirements using the RMS but I'll use both to be sure.
I also found somewhere else the typical voltages for guitar pedals, and they're lower, so I'll use these.
I am including the typical RMS and peak to peak power draw, and assuming I should pick at least double.
>1ohm: I don't think I'll have to use these with this much voltage. 3.5W/10W, which I would assume would be in the power resistor range.
>10ohm: 0.35W/1W. If I have to use these with these voltages I'll need beefy resistors, but these might not cost me an eye and leg.
>100ohm: 0.035/0.1W. If this is correct, these ratings should be pretty common and so from here on I don't have to worry about it.
The actual power dissipated in the resistor, depends on the current and voltage and can be calculated using good old Ohm's law. Often lower resistor values need to have a higher power rating, because the current flowing through them is higher, thus the power dissipated is greater.
Obviously physically larger resistors can dissipate more power, than smaller ones. It might be a good idea to have a higher wattage rating for the values 10R and below, but I don't see any point in going over a couple of watts for general purpose use. If you need a higher power rating, several resistors can be connected in series and parallel, for example take four resistors, of the same value, connect them in two pairs in series, then in parallel and you'll have the same resistance value, but quadruple the power rating. -
You may want to check ebay for "smd sample books" which will give you assortment of resistors and capacitors. You can get sample books with just capacitors or just resistors 0603 & 0805 types
https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2380057.m570.l1313.TR0.TRC0.H0.Xsmd+sample+books%27.TRS0&_nkw=smd+sample+books%27&_sacat=0