Author Topic: From no parts to decent stockpile, best approach?  (Read 61382 times)

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Offline CharlieWorton

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Re: From no parts to decent stockpile, best approach?
« Reply #175 on: June 09, 2017, 02:18:28 PM »
For new parts, AliExpress or BangGood are both good sources.  I have more success (lower prices, better selection) with AliExpress.  Both companies are equally reputable, I've never had a problem with either.  For used stuff, run a free ad in a local advertiser offering free pickup and disposal of unwanted electronics - old computers, printers, whatever.  There are decent stepper motors in some printers, the power supplies in old computers still work well (usually).  If you have more time than money, this can be a decent way to acquire some unusual stuff.  In addition, you might be able to repair and sell some broken electronics, if you're so inclined.
 

Offline brainwash

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Re: From no parts to decent stockpile, best approach?
« Reply #176 on: June 11, 2017, 08:34:02 AM »
Not sure if this is new, it was probably discussed above, but stockpiling needs an organised approach:
- stockpile base components (capacitors, resistors, LM324, 74*, 555, resonators, fuses, SMD 0805, ....)
- do not stockpile 'best and greatest' components. That includes any ARM chip, any PIC chip, ADCs, FPGAs, ...
- stockpile connectors - they are likely to be needed at any time: USB, mini-USB, micro-USB male, USB cables, Sub-9, ...
- stockpile wires - any size, any number of conductors under the insulation, any color (preferably all, including dual-color)
- stockpile base logic: breadboards, Arduino Uno [clones], Digistamp [clones], BT, ESP8266

The above would let you fix a lot of issues if you have broken device. It will also let you prototype almost any idea.
Avoid buying into the latest and greatest, unless you are a technical head at some company. Most of the time, the things you will know how to use will be the ones that are the cheapest and people tend to use the most (ATMega328, ESP8266).
I have a pile of TI and Microchip stuff that I've rarely used. At least TI can be used with Energia, but most of the times you want to fail fast and fail often. This means you don't want to be wasting 1-2 days to get a chip working only to prove that your idea is wrong.

Aside from that, a good digital scope (or a mediocre analog one and a mediocre digital one) will get you far. You'll use the multimeter a lot more than those. You'll use your soldering station more. You'll use clips and clamps and wires even more. You'll use a digital analyzer, a hot-air station and signal generator a few times per year, at most. That is, considering your question. So plan your stockpile according to that.
 
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Offline schmitt trigger

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Re: From no parts to decent stockpile, best approach?
« Reply #177 on: June 24, 2017, 10:35:59 AM »
This thread is loooong, and I essentially skimmed thru it.

But I think relays have not been mentioned. If you would like to control lights, motors, etc., in a safe and straightforward manner, relays are the way to go.
Get 5v-coil relays for the smaller sizes, and 12v-coil relays for the larger sizes.

From time to time you will find that your regulator, transistor, Triac, etc are overheating. Get some small TO220 heatsinks. It is surprising how much more power you can dissipate from a device with even a small heatsink, as compared to stand alone.
 

Offline brainwash

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Re: From no parts to decent stockpile, best approach?
« Reply #178 on: June 24, 2017, 10:47:34 AM »
Cheap relays can be found from the scrapyard, you can get at least 10 for 1$. Some of them are timing relays (for example diesel heater) so not so easy to use. Anyway, most of the manufacturers these days have went the MOSFET way, and for a good reason: the old relays are both unreliable and fail in an uncontrolled way.
Still the cheapest and simplest way to get DPDT, if you need it. But in my experience relays tend to fail both randomly and in strange ways (i.e. one contact working 90% of the time).
 

Offline Jellysfish

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Re: From no parts to decent stockpile, best approach?
« Reply #179 on: August 18, 2017, 03:34:57 AM »
My local melvac sometimes sells general electronics in a grab bag--slightly more expensive than online but at least these parts are more likely to be new
 

Offline TheDane

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Re: From no parts to decent stockpile, best approach?
« Reply #180 on: August 26, 2017, 05:22:27 PM »
Recycling old equipment is also a nice way to get components.

Instead of 'throwing' out old/broken stuff, I usually keep it around for scraps - and when I need something I don't have already in my assortments - I will take a look at the old junk, and surprisingly I often find what I am looking for.  :-+
 
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Offline kobaz

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Re: From no parts to decent stockpile, best approach?
« Reply #181 on: September 26, 2017, 03:07:42 AM »
Adding a question to the pool.

For capacitors and the like I get the importance of quality.  It's good to avoid the exploding type, etc.

Things like transistors.  How important is it to get high quality transistors from known brands?

For example if I wanted a PNP 2N3906:
https://www.digikey.com/products/en/discrete-semiconductor-products/transistors-bipolar-bjt-single/276?k=2N3906&k=&pkeyword=2N3906&v=497&pv69=80&mnonly=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=500

These are 44 cents each USD.  Versus:
https://www.amazon.com/dp/B06Y49GB3F

I can get 675 transistors at 2 cents each on amazon.  Are they going to catch my bench on fire?  Are they going to produce excessive noise?  Anyone familiar with these?

 

Offline JoeN

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Re: From no parts to decent stockpile, best approach?
« Reply #182 on: September 26, 2017, 08:24:18 AM »
For example if I wanted a PNP 2N3906:
https://www.digikey.com/products/en/discrete-semiconductor-products/transistors-bipolar-bjt-single/276?k=2N3906&k=&pkeyword=2N3906&v=497&pv69=80&mnonly=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=500
These are 44 cents each USD.

3904/3906's can be 2 cents each if you buy in bulk/know where to look. 

http://www.newark.com/micro-commercial-components/2n3906-ap/bjt-pnp-40vdc-to-92/dp/69R6840

The SMT versions can be one cent each. 

http://www.newark.com/on-semiconductor/mmbt3906lt3g/bipolar-transistor-pnp-40v-sot/dp/98H0752

I would think the people building kits are getting components from sources that are buying in huge quantities.  The Chinese seem to do it that way (small guys knowing a big guy and getting in on orders so they can get big guy prices for kits to sell on eBay, etc.).  All the other transistors offered, I don't know, not much is as cheap as a 3904/3906.
« Last Edit: September 26, 2017, 08:32:52 AM by JoeN »
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Offline TheUnnamedNewbie

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Re: From no parts to decent stockpile, best approach?
« Reply #183 on: September 28, 2017, 02:10:26 AM »
Adding a question to the pool.

For capacitors and the like I get the importance of quality.  It's good to avoid the exploding type, etc.

Things like transistors.  How important is it to get high quality transistors from known brands?


To be honest, that seems like a very high price for a that transistor. Just a quick search on Farnell shows me that I can get them for a few cents each. I got most of my small-signal transistors for breadboarding from auction sales, but I know that you can order from farnell or RS here through the local component store or the local university. I wouldn't suggest getting unknown devices - when you are prototyping and debugging a circuit, the last thing you need is a shady transistor that might cause the problem.


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Offline adras

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Re: From no parts to decent stockpile, best approach?
« Reply #184 on: October 11, 2017, 12:48:59 AM »
As a start I would buy everything in China. Of course it takes some time to arrive. But if you buy everything at once, after two weeks the first packages arrive. And almost everytime you come home there's a new surprise package waiting for you :). When you're done with prototyping and start with final production it makes sense to buy brand components.

  • To get started I suggest an Arduino kit, these kits have a lot of stuff. IR-Sensors, gyro sensors, more sensors, a breadboard, resistors etc, basically everything you need for a first small project.
  • Next comes the "Assorted XXX" search term. Great to get a stock of all kinds of resistors, diodes, capacitors etc
  • Breadboard jumper cables, you can never have enough of them, pretty cheap
  • Wire, from AWG? to AWG? from small to big - I'm always buying the wrong ones, even after looking at the datasheet :D
  • Maybe a cheap oscilloscope kit and a signal generator. Don't expect too much, but it's a start
  • Of course a soldering Iron and solder. And pretty important: Solder flux paste, makes soldering way more easy. I use a Rosin based flux since it's more healthy than some other stuff. I had one which may give you cancer, makes you impotent, and other stuff so I through it away right after opening the package.
  • One of those cutting mats. Great to save your bench from damage.
  • Maybe one of those ESD armbands, although I never managed to fry anything yet. But every professional considers those as mandatory

I think that's all you need to start, everything else can be bought on demand.

The header of the next links is the search term I used, and the link is what the result may look like.

Arduino kit
http://www.ebay.com/itm/ULTIMATE-UNO-R3-Starter-Kit-for-Arduino-Keypad-RTC-1602LCD-Servo-Motor-Gas-Relay-/152145710940?epid=730831715&hash=item236c974f5c:g:tAUAAOSwhQhY7sYK

Assorted Resistors
http://www.ebay.com/itm/300x-30-Values-1-4W-1-Metal-Film-Resistors-Assorted-Resistance-Kit-Set-New-/112341051881?epid=735028540&hash=item1a280c69e9:g:gE4AAOSw4GVYJYyO

Assorted Capacitors
http://www.ebay.com/itm/60pcs-12-Values-1uF-470uF-Assorted-Electrolytic-Capacitor-Assortment-Kit-Radial-/192063668173?epid=1879167269&hash=item2cb7e2ffcd:g:D9oAAOSw5cNYYPFB

Assorted XXX is a great way to get the common parts, resitors, diodes, capacitors etc. Very cheap. Make sure there are values on the paper that holds resistors, otherwise you have to look at each color code to sort them which is a huge pain to me.

Breadboard
https://www.ebay.com/sch/i.html?_odkw=assorted+capacitors&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR1.TRC0.A0.H0.Xbreadbord.TRS0&_nkw=breadbord&_sacat=0

breadboard jumper
https://www.ebay.com/sch/i.html?_odkw=breadbord&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR0.TRC0.H0.Xbreadbord+jumper.TRS1&_nkw=breadbord+jumper&_sacat=0

oscilloscope kit
http://www.ebay.com/itm/Assembled-DSO138-2-4-TFT-Digital-Oscilloscope-Kits-DIY-Parts-1Msps-Probe-/162200576235?var=&hash=item25c3e860eb:g:r7wAAOSw2gxYuMrU
DSO 138 cheap oscilloscope, better than nothing. As a kit a very good practice for SMD soldering

signal generator kit
https://www.ebay.com/sch/i.html?_odkw=oscilloscope+kit&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR0.TRC0.H0.Xsignal+generator+kit.TRS0&_nkw=signal+generator+kit&_sacat=0
cheap as the oscilloscope, better than nothing. There are apps for your smartphone as well

Soldering iron
I've got a cheap chinese one. It's still working, and has a temperature control, awesome! Not imported, bought in Germany so I have warranty.

I'd also pick up some Mosfets. Are these some cheap "general purpose" high current Mosfets?
IRF9540N - P-Channel https://www.infineon.com/dgdl/irf9540n.pdf?fileId=5546d462533600a401535611caa31dc6
FQP30N06L - N-Channel http://cdn.sparkfun.com/datasheets/Components/General/FQP30N06L.pdf
RFP30N06LE - N-Channel http://www.sparkfun.com/datasheets/Components/General/RFP30N06LE.pdf
 

Online james_s

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Re: From no parts to decent stockpile, best approach?
« Reply #185 on: October 11, 2017, 04:12:13 AM »
I buy a lot of parts from China, you can get some good stuff but you have to be careful. Some of it is junk, especially older or more exotic parts are often counterfeit. A part that is fake or substandard can lead to great frustration when a project doesn't work.
 

Offline Old Don

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Re: From no parts to decent stockpile, best approach?
« Reply #186 on: October 11, 2017, 06:30:45 AM »
If as you have stated taxes are high in Norway, a way to get cheap parts is to get free broken electronics stuff. Printers, dead computers and other circuit boards obtained from local sources that in many cases are glad to get rid of their E waste since they may have to pay to have it recycled. Strip them for their parts. A cheap hot air gun can strip a board quickly. Sensors and motors from printers can be used for robots. Better than a hot air gun is to invest in a hot air rework station for future BGA circuit work and with/without a large nozzle it with also strip a board. Also, check with local companies and they might have inventory reduction sales of components that they no long need.

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Offline VEGETA

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Re: From no parts to decent stockpile, best approach?
« Reply #187 on: October 11, 2017, 04:34:42 PM »
For me I bought stuff from Aliexpress but it is slow which is acceptable for the price. One thing I like about banggood is that they have warehouses for their stuff, so they are not just a frontend like Aliexpress.

One great benefit of that is that you get all your parts together, unlike Aliexpress where you get them one by one because they are from different sellers.

BTW, how do you sort your components and store them at the bench?

I need a good and cheap way to do it, since I live in Jordan and buying heavy storage tools is pricey.

Offline Awesome14

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Re: From no parts to decent stockpile, best approach?
« Reply #188 on: October 12, 2017, 06:02:19 AM »
I'd build your stock slowly. I only say that because building a stock of everything you might need is a naive dream.  However, one of the least time consuming means to build a stock is from salvaged PCBs using a solder pot:
« Last Edit: October 18, 2017, 02:10:12 PM by Awesome14 »
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Online asmi

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Re: From no parts to decent stockpile, best approach?
« Reply #189 on: October 14, 2017, 01:04:56 PM »
I tend to stockpile only parts that I use in many projects (things like connector strips, LEDs of different colors), and I accumulated many "one extra" parts, which came from following my rule of thumb (buy the amount of parts you need + 1 in case you mess something up). Also since buying powered vacuum pickup, reflow oven and stereo microscope I started using a lot of 0402 passives, so I slowly build up an inventory of them as they are very cheap if you buy them in reels - a 10K reel of 1% 0402 resistors is 10 CAD for almost all values on Mouser, 0402 caps are a bit more expensive, but in many cases you can find 10K reel for 30-40 CAD per reel), and a single reel will last till the end of times for me, and I don't have to worry about bumping one or two off my work table during assembly. Reels are very easy to store too - just put them on a metal rod of some kind.
Basically now whenever I need a value I still don't have, I buy a reel of that value in 0402 package unless any of this is true:
- the passive in question is a resistor which need to dissipate more power than 0402 package can handle
- I know for fact that I will have to de-solder and re-solder this part several times (for example voltage-setting resistors for DC-DC converters). In this case I use 0805 parts because most manufacturers put value label of them - so I can later easily identify values (0402 and most of 0603 parts don't have any labels)
- the component with that value actually exists in 0402 package - this is for caps, which have limits on capacitance and voltage
 

Offline iontodirel

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Re: From no parts to decent stockpile, best approach?
« Reply #190 on: October 19, 2017, 08:16:52 PM »
I personally recommend buying/stocking on a need basis only, don't get something if you don't think you'll need, and categorize components per projects; get components for multiple projects, IMHO you can wait a week for parts from digikey if you want to experiment with something new or work on a new project
« Last Edit: October 19, 2017, 08:18:45 PM by iontodirel »
 

Offline Mr. Scram

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Re: From no parts to decent stockpile, best approach?
« Reply #191 on: October 19, 2017, 11:58:31 PM »
I personally recommend buying/stocking on a need basis only, don't get something if you don't think you'll need, and categorize components per projects; get components for multiple projects, IMHO you can wait a week for parts from digikey if you want to experiment with something new or work on a new project
I've poured some money into a basic collection of classic jellybean parts and components. It has reached the point where I can build a PoC for most ideas with what's around. They are generally not the best performing parts for the job, but they will keep me entertained until I can draw up a schematic and order "real" parts.
 

Online paulca

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Re: From no parts to decent stockpile, best approach?
« Reply #192 on: November 06, 2017, 07:28:15 PM »
Interesting thread.

Different hobby, but in the radio controlled space I was in for a few years I found over-buying parts in advance caused issues.  I would order stuff, sometimes in bulk, say buying 32 AA NiMh cells, then I discovered with a voltage regulator I could use much more convenient LiPos for that application, so I bought a bunch of pairs of those each and never used the NiMhs ever again.  I still have a bunch of 2000mAh AA cells around, but they aren't even useful for clocks or TV remotes due to their lower 1.2 voltage and high dissipation they only last a few months.

The other issue with over stocking is that stock management comes into play.  You order a whole assortment of stuff, use about 10% of it, then forget exactly what the other 90% was.  6 months down the road you need a particular component, either don't remember you have some or don't remember where exactly they would be and end up ordering more.  Of course after you hit "Buy Now" at checkout you remember where the stock pile is.   Battery connectors were an example.  I think I ordered bags of bullet connectors three times and now have about 200 of them.  Being meticulous about organising things into labelled parts trays and boxes would help, but that's not me.

Shipping cost tends to come into play and aggravate this.  If you are ordering 2 x 555 timer chips the postage is probably more than the chips by an order of magnitude.  You get a better price if you order 10 of them.  So you spend an evening "magpie-ing" around the online store going "one of them, two of those, three of that thing" to lower the differential between cost and shipping.  Then you realise if you order a few more expensive things you get free shipping.  You spend £100 randomly.  The stuff arrives, you flick through it and throw it in a box, happy with yourself.  You don't use much of it for 6 months and then have no idea what you actually have or where you put it all.  So you order it again.

I have plastic tubs and boxes full of RC electrical parts, high amp connectors, low amp JSTs, servo adaptors, battery charge adaptors and splitters, load testers, volt/ammeters, discharge loads, wall warts, you name it.  Most of it still in the plastic bags they came in.

Case in hand.... my ExTech multimeter hasn't arrived yet.  I did some bread boarding yesterday, building logic gates from transistors, figured I must have a volt/amp meter somewhere for RC stuff, but couldn't find anything after an hour going through boxes of stuff.... I'm sure it's there somewhere though.....  back to LEDs, trial and error, and screwing around with my phone camera on zoom to read resistor values.  Still managed to successfully build, ANDs, ORs, NOTs etc.  Though I nearly cooked a few transistors and without a multi-meter couldn't tell that I was driving the full power supply current though the base of the NPN.  No NPNs died though.

Yet, I don't learn my lesson.  I'm currently looking at assorted part kits.  Like a 2600 piece resistor pack.  1000 piece cap pack and still trying to find a sensible assorted pack of logic ICs.
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Offline schenkzoola

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Re: From no parts to decent stockpile, best approach?
« Reply #193 on: November 13, 2017, 10:17:50 AM »
I would recommend creating an inventory database of your IC's and more expensive passives.  This can be done with a simple spreadsheet, or a service like partsbox.io.  I find this useful if I am wanting to do a proof of concept, and want to quickly figure out if I have everything I need.

If you start building a commercial project, you will find that the inventory management skills you have developed on the way are invaluable.
 


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