Knowing How to Source Components

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MrBiggs
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Post by MrBiggs » Fri Jan 21, 2011 10:08 am

The problems I've had as a noob at this, is too much choice on, say, Mouser and not enough on Small Bear. Mouser will give me thirty versions of what seems like the same thing. It has that system for narrowing the choice down but more often than not the categories are what seems like very esoteric things that I have no idea, and with no images I don't know what it's referring to. And then, also more often than not, the thing that is important, like the physical size of a cap as frozenkore mentions, may not even be one of the choices. I've looked at a lot of data sheets in the last few months. And I've also written a lot of emails to Flight and others asking "will this or that work?"

Small Bear is a huge relief, but so often lacks any details at all about his items. No links to data sheets, no sizes, etc. I've been frustrated enough times that I've either driven to Radio Shack, or contemplated just buying the whatever module I'm trying to build. I can't believe how many hours I've spent putting together a $20 order.
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Paradigm X
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Post by Paradigm X » Fri Jan 21, 2011 10:24 am

/\/\

Me too!

I spent about 2 hours putting my first order together, and besides forgetting stuff, i also got some wrong bits. :mad:

I really struggle with switches, any advice as to the most commonly used/needed types are? I have real problems visualising the connections. :(

Just for example, what would you need for;

a - a switch for 2pole/4pole or high/low ?
b - a switch to change 4 states? Eg HP/LP/BP/AP?
c - a true bypass switch?
d - number of steps for a 8 step sequencer?

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Post by cornutt » Fri Jan 21, 2011 10:22 pm

A quick tutorial on switches: They classify switches by the number of "poles" and the number of "throws". (Note that "poles" in this context has nothing to do with filters.) The number of "throws" is the number of lever or button positions in which the switch completes a circuit. The simplest switch is a "single pole single throw", which has two contacts. When the switch is on, it completes the circuit between the two contacts; when the switch is off, it's open. A "single pole double throw" switch has three contacts and two "on" positions. If you name the contacts 1, 2, and 3, and 1 is the common, then in one position the switch completes a circuit between 1 and 2, and in the other position it completes a circuit between 1 and 3. If it's a toggle switch it may be specified with a "center off" position in which it makes no circuit.

A "double pole" switch is basically two separate switches connected to the same lever or button. The "double pole double throw" is pretty widely used. It has a total of six contacts -- a 1, 2, and 3 for each half of the switch. There is no connection between the two halves.

Some catalogs describe the positions of a switch using a different notation, for example, a single-pole single-throw switch is described as "on-off" and a double throw is described as "on-on". A double throw with a center off is "on-off-on". If the switch is spring loaded in one position, such that it snaps back when released, that position is shown in parentheses, so a "on-off-(on)" is a double-throw switch with center off and one of the on positions spring-loaded.

If you need a switch with more than three selections, you need a rotary switch. Rotary switches usually have 6, 8, or 12 on positions; it's possible to get double-pole rotaries which basically are two switch bodies on the same shaft. Most rotaries have a stop mechanism you can set so that if your circuit doesn't use all of the available positions, you can prevent it from being turned to the unused positions.
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Post by russma » Fri Jan 21, 2011 10:45 pm

Clear and concise. Nice post, Cornutt.

:tu:
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Post by JRock » Sat Jan 22, 2011 2:38 am

I've spent days and days putting orders together (for multiple projects) and still missed stuff! I certainly am a little faster now. That's it. It's a lot easier to just do it than to think about it. It seems a little overwhelming in thought, but in reality you'll get it if you just do it. You'll make a couple mistakes then learn from them and not do them again. 8_)

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Post by Paradigm X » Tue Jan 25, 2011 7:56 am

russma wrote:Clear and concise. Nice post, Cornutt.

:tu:
Quite right.

Many thanks.

Quick query; on the on off on version, is that 3 distinct options, or only two plus an off (nothing connected).

I thought buying a switch would be easy, theres about 20 options even for toggle switches... :deadbanana: :lol:

Cheers

:)

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Post by Luka » Tue Jan 25, 2011 8:06 am

:)


Image

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Post by doctorvague » Tue Jan 25, 2011 8:37 am

MrBiggs wrote:The problems I've had as a noob at this, is too much choice on, say, Mouser and not enough on Small Bear. Mouser will give me thirty versions of what seems like the same thing. It has that system for narrowing the choice down but more often than not the categories are what seems like very esoteric things that I have no idea, and with no images I don't know what it's referring to. And then, also more often than not, the thing that is important, like the physical size of a cap as frozenkore mentions, may not even be one of the choices. I've looked at a lot of data sheets in the last few months. And I've also written a lot of emails to Flight and others asking "will this or that work?"

Small Bear is a huge relief, but so often lacks any details at all about his items. No links to data sheets, no sizes, etc. I've been frustrated enough times that I've either driven to Radio Shack, or contemplated just buying the whatever module I'm trying to build. I can't believe how many hours I've spent putting together a $20 order.
Your post sums up my DIY frustration perfectly.
Rather than caps my biggest frustration comes from headers, IC's and pots. There are an incredible number of TL074 variations in the Mouser catalog - it's mind-numbing! I made it through the pot minefield mostly but never did figure out headers and many times wanted to drop-kick the Mouser catalog out the window.

Starting out with Blacet kits was a great way to get acquainted with this stuff for me. I admire you guys that just jumped right into DIY'ing your whole synth- that seems super-human to me!

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Post by e-grad » Tue Jan 25, 2011 8:46 am

doctorvague wrote:There are an incredible number of TL074 variations
Unless the BOM makes a difference: Just ignore the suffixes. They often refer to the temperature range i.e. stating that chip in question will work below minus 20 degree Celsius.

Just make sure you're ordering DIP (or SIP in some occasions) unless you're going SMT.
doctorvague wrote:Starting out with Blacet kits was a great way to get acquainted with this stuff for me.
:tu: Great kits! Great modules! The Time Machine was my start into DIY.

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Post by EATyourGUITAR » Tue Jan 25, 2011 11:11 am

Peake wrote:Please also be aware that transistors can lead to confusion...one company's version of a transistor might have a different pin configuration than another company's version; same name, same behaviour, different connections. You'll notice a little "f" on a unit for the manfacturer, Fairchild, and you can google for the Fairchild datasheet for your specific trannie...or if you have a tester it won't reveal any useful data until you seat the trannie correctly; make note of its pinout (ECB, etc.).

Welcome to DIY! There is a learning curve that never seems to end, but it's a wonderful love/hate relationship :)
thats why I got a atlas DCA55 component tester. it tells me the gain and pinout of any transistor. also tells me npn or pnp and makes a guess if its germanium. it $70 shipped.
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Post by Peake » Tue Jan 25, 2011 6:38 pm

Good stuff. Should get one of those... I have a tiny VOM with HFE testing, and I use it to determine pinout on unknown trannies.

I also had to build my VBE tester (the original Moog design) to allow for these unusual pinouts..

I'll tell you, going through 100 vintage 2N5172 to get FOUR matched pairs (HFE plus VBE)...now I know why vintage gear cost so much and why designers dropped everything for early opamps :lol: Especially when changing room temperature obsoletes your transcribed values, WHILE YOU TEST. Oh dear...

Love/Hate. Definitely.
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Post by paults » Tue Jan 25, 2011 11:31 pm

a) let's hope they didn't violate my patent on auto-transitor ID checking (#5,355,082). :deadbanana:

It expires this October. I'm gonna SUE!!!!!!!! (ooppsss. It's owned by Tandy, they're gonna sue!!!!!! Sure. Hey, the CEO quit today.)

b) About MLCC caps (and the axial AVX 'SpinGuard' types as well):

There is a 'dirty little secret' that is buried (if that) on datasheets: the capacitance of a MLCC drastically decreases with applied DC voltage. If at ALL possible, use 50V caps so that the value you *think* is there is really there.

A C0G/NPO cap is not as bad as a X5R/X7R. The other dielectrics that are cheaper (Z5U, etc) are to be AVOIDED AT ALL COSTS.

For example, a 1uf cap that is used in a 5V power bypass, if rated 10V, is really like 0.4uf at applied +5V bias.. A 25V 1uf at 5V bias is like 0.8uf. A 1uf 6.3V cap at 5V bias is like 0.1uf (1/10th of actual value).

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Post by Dave Kendall » Wed Jan 26, 2011 12:59 pm

I don't think you can ever have too many 100k resistors - get a load of 1% resistors in bulk, and save in the long run. Other common values are 1K and 10k.

some more common stuff;
100K linear pots
100nF (ceramic) and 10uF (electrolytic, 35V or higher) PSU decoupling caps
TL072 and TL074 opamps
Ferrite beads (for CGS)
1N4148 or 1N914 diodes
Knobs and sockets (3.5mm sockets if you are in euro format)

IIRC, there was a list of common components for synth diy posted on the [sdiy] list a while back. It was based on the components needed for a whole bunch of CGS and some other modules. If I find it , I'll post it, unless someone else has it to hand. It seemed to be a good starting point IMO.

@paradigmx - in the UK Rapid electronics are pretty hard to beat price-wise for many things - they do Alpha-type pots pretty cheap, 1% metal film 1/4 watt resistors are around 1p each for a hundred (less vat) and shipping is free if spending over 30 quid. They have actual humans on the end of the phone too!

cheers,
Dave
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Post by iopop » Wed Jan 26, 2011 1:33 pm

Dave Kendall wrote:IIRC, there was a list of common components for synth diy posted on the [sdiy] list a while back. It was based on the components needed for a whole bunch of CGS and some other modules. If I find it , I'll post it, unless someone else has it to hand. It seemed to be a good starting point IMO.
Think its this one you're thinking about, http://www.teaser.fr/~amajorel/misc/sdiy-parts.txt

That list is so fascinating. There's a modular planner for Eurorack, someone should do a BOM-planner for DIY modules. I have a few ideas, but I code for a living, so I rather solder on my spare time.

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Post by Dave Kendall » Wed Jan 26, 2011 1:39 pm

That's it!
Nice one iopop :)

cheers,
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Post by cornutt » Wed Jan 26, 2011 10:59 pm

paults wrote: There is a 'dirty little secret' that is buried (if that) on datasheets: the capacitance of a MLCC drastically decreases with applied DC voltage.
I didn't know that! What kind of range are we talking about? I wonder if you could use one as a varactor...
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Post by cornutt » Wed Jan 26, 2011 11:10 pm

MrBiggs wrote:The problems I've had as a noob at this, is too much choice on, say, Mouser and not enough on Small Bear. Mouser will give me thirty versions of what seems like the same thing.
Here's a tip for handling that: Set up the search filters to eliminate the types you know you can't use, for example, getting rid of all the SMT types (assuming that you're doing thru-hole). Then, sort by price, starting with the lowest. Take a look at the top 4-5 to see if there is any reason to eliminate any (for example, minimum order quantity, wrong voltage range, etc.) and then you can choose more or less at random from the set that's left. The higher-priced listings for a given part are nearly always "over-qualified" parts that you don't need, such as extended temperature range or mil-spec qualification.

Another tip about Mouser: They are in the process of trying to clear non-RoHS parts out of their inventory. Unless you are in Europe, or you are using lead-free solder for some reason, there is absolutely no reason why you must have RoHS parts for a DIY project. Often you can find the non-RoHS parts going cheap. The catch is that they are limited to quantities remaining in inventory, but if you only need a few, it's usually not a problem.
Sequence 15 -- sequence15.blogspot.com

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Post by Peake » Thu Jan 27, 2011 6:09 pm

And once you source a good component, check to see if its in its last days or is becoming vintage. If so, stock up! I've passed up on certain transistors at .70cents each, that are now over $6.00 each. In the period of only a couple of years. It goes that way!
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Post by Peake » Fri Jan 28, 2011 2:55 pm

Just as I was saying about different pinouts on different makes of the same transistor...THREE of the trannies on a DIY project I'm in are Different from the board layout, much twisting of legs was enjoyed by everyone...
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Post by MrBiggs » Fri Jan 28, 2011 3:23 pm

Peake wrote:Just as I was saying about different pinouts on different makes of the same transistor...THREE of the trannies on a DIY project I'm in are Different from the board layout, much twisting of legs was enjoyed by everyone...
heh heh heh. He said "trannies" and "twisting of legs." Heh heh.
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Peake
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Post by Peake » Fri Jan 28, 2011 3:41 pm

My favorite is from the prosoundweb early days...someone characterized the highly audible artefacts of RealAudio streaming as "swimmies".

Someone posted "you said swimmies". :lol:

At least my project is now functional; trannie leg-twisting was the only remaining issue!
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Post by decaying.sine » Fri Jan 28, 2011 3:47 pm

Question for y'all.

I am getting some switches for my two Double Dekka builds. They require single pole 6-throw type. I assume it's okay to use either shorting or non-shorting as it is not specified in the build doc. Does that sound okay?

Also, it's fine if I have a SP-7T even SP-12T, right? I just wouldn't connect the other solder lugs or do they need to be shorted/grounded or something?

Thanks.
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Post by iopop » Fri Jan 28, 2011 4:24 pm

Using a SP-12T would be fine. Some of them are adjustable so you can set it to use 2 - 12 positions. If that is not possible, just solder up the unused positions to give the same result as if set on first or last position.

Cant answer the shorting / non-shorting issue..

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Post by Paradigm X » Tue Feb 01, 2011 9:21 am

thanks to all youve replied in this thread, very helpful :)

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Post by frozenkore » Tue Feb 01, 2011 10:44 am

One thing I forgot to mention in finding parts. I was "fixing" my M28 and needed 330k(?) resisters. I didn't want to place an order for two resisters and pay :75: shipping. I hopped on ebay and got 100 for $5 (shipped). So if you need something here and there, ebay can sometimes get you it fast, large quantities, and cheep.
Cheers!
Brian

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