Help me harvesting general purpose transistors (with pictures) - Page 1
Forum section: electronics / projects

author: zapta
author_rank: Super Contributor
timestamp: January 12, 2014, 05:58:23 pm
content: Our local surplus store (Halted) has hundreds of SMD reels with resistors, transistors, caps, diodes, LEDS, connectors and so on. They give you a pair of scissors, you go around, pick whatever you like and pay a few pennies per part. Just like those pick-your-own-cherries farms. This works well with caps and resistors but with transistors, it is hard to find what you want without a parametric search.I am looking for general purposes NPN, PNP, N-Chan, and P-Chan switching transistors, nothing special, let's say 40V and 250ma to use with 5V logic. In my last visit I took pictures (with permission of course) of some of the transistor shelves and started to lookup the datasheets at home but this is very tedious.Can you identify in the pictures any good candidate? Larger versions of the pictures are available herehttp://imgur.com/28CPYst,8HXnOKe,9tch3r2,6bjauex,0EeqsOA,XU8tS7i,NsmcpRp

author: Macbeth
author_rank: Super Contributor
timestamp: January 12, 2014, 06:21:26 pm
content: What a cool shop! Why don't we have that around here? I am jealous. Just use your phone with something like farnell or RS.

author: calexanian
author_rank: Super Contributor
timestamp: January 12, 2014, 06:32:52 pm
content: As yes. Halted, or Haltek depending on how old you are! What info do you need exactly. Every one I tried came up with a data sheet. Do you work for them and are just looking for business?

author: zapta
author_rank: Super Contributor
timestamp: January 12, 2014, 08:02:05 pm
content: Quote from: calexanian on January 12, 2014, 06:32:52 pmNo interest with them whatsoever.I started to look datasheets one by one but hoped that somebody with a good memory of parts numbers can just scan the pictures on suggest a few part numbers to check first.

author: Macbeth
author_rank: Super Contributor
timestamp: January 12, 2014, 08:58:03 pm
content: If they are so cheap why not cut off ten of each and make a nice little access database for them, attaching pdfs as you find them and make your own parametric and warehouse search? I end up having to do this with all parts anyway! That place looks like a treasure trove - buy first, ask questions later! :lol:

author: LukeW
author_rank: Frequent Contributor
timestamp: January 12, 2014, 10:48:19 pm
content: There's a box of 2N7002 N-channel MOSFETs there, they're a useful general purpose small FET if you don't mind working with SOT23s.

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: January 13, 2014, 01:58:06 am
content: Hi,I have been to Halted also known as HSC.I can tell you what I have in my collection:NPN General PurposeMMBT2222A 40V 1A NPN switching transistor (2N2222A)MMBT3904 40V 200mA NPN Switching transistor (2N3904)NPN Fast switchingMMBT2369A 15V 200mA NPN transistor very fast, equivalent to 2N2369APNP General PurposeMMBT3906 40V 200mA PNP transistor (2N3906)MMBT2907A 60V 800mA PNP transistor (2N2907A)High voltage NPNMMBTA42 300V 300mA High voltage NPNHigh voltage PNPMMBTA92 300V 300mA High voltage PNPSmall signal MOSFETsBSS123 100V 6 Ohm N Channel MOSFETOR2N7002 60V 7.5 Ohm N Channel MOSFETSmall Signal diodesMMBD4148 small signal diodesBAT54 small Schottky diodes, these come in various versions singles and dualsAll these parts are available in SOT23 packages.this is a good general purpose list. Halted should have most, if not all, of these.Be sure to keep them separate if you cut them from the reels. There is only room on these packages for a couple of characters. You need to bag and tag them.Good luck !!Jay_Diddy_B

author: zapta
author_rank: Super Contributor
timestamp: January 13, 2014, 01:58:36 am
content: Quote from: LukeW on January 12, 2014, 10:48:19 pmThanks. Yes, this is a keeper. I spend today some time looking up datasheets and came with this list. Will pick it up on Monday. All those transistors codes look arbitrary to me.

author: zapta
author_rank: Super Contributor
timestamp: January 13, 2014, 02:01:24 am
content: Jay_Diddy_B, out posts just crossed the wires ;-)Thanks for the list. I will update mine.

author: calexanian
author_rank: Super Contributor
timestamp: January 13, 2014, 02:38:51 am
content: HSC has been around since the early days of the PC. Many of the pioneers at apple used to get parts there.

author: dannyf
author_rank: Super Contributor
timestamp: January 13, 2014, 03:34:06 am
content: i would limit myself to a few types: 5551/5401, 3906/3904, 7002 (really is a npn). They will be sufficient for 90% of what most people will need.Buy them in hundreds and you are done.

author: TerraHertz
author_rank: Super Contributor
timestamp: January 13, 2014, 09:39:03 am
content: Those pics make me very jealous. F*ck this stupid country called Australia, where such a shop is inconceivable.My though on your choice problem - why don't you just go in with a laptop, open a text editor, and write down *every* part number they have on their shelves. How many can that be?Then you have a searchable list, and also you can go datasheet hunting at leisure at home.

author: miceuz
author_rank: Frequent Contributor
timestamp: January 13, 2014, 10:32:55 am
content: Welcome to a brave new world of part sourcing and specification. As far as I can tell, you often spend the most of your project time browsing what's available, checking datasheets and browsing available parts again ab nauseum untill you find a part that's suitable for your project and is available at your source. It's not uncommon to change the design according to what's available. Wait till you have to choose an opamp!

author: amyk
author_rank: Super Contributor
timestamp: January 13, 2014, 11:04:02 am
content: Those who are jealous have probably never been tothe SEG in Shenzhen...

author: Macbeth
author_rank: Super Contributor
timestamp: January 13, 2014, 06:22:19 pm
content: Quote from: amyk on January 13, 2014, 11:04:02 amOh I totally agree! But I would need the guiding hand of someone as experienced as yourself to get my head around it all, and avoid the fakers and charlatans. I really need to book a Chinese vacation, and use theexcellent guide linked to on your blog, if I can't partner up with a pro!

author: zapta
author_rank: Super Contributor
timestamp: January 13, 2014, 07:36:55 pm
content: Quote from: miceuz on January 13, 2014, 10:32:55 amThat's the reason I diverted my career from mostly electronics to mostly software. At the time I was working at Motorola designing one-off system, doing about 70% hardware and 30% software (I learned electronics at high school, it was a special program). I got tired of all the logistics, second source, component qualification etc and appreciated the simplicity of software (all you need is a computer and a creative brain) so when I went to college I picked CS/Math over EE. Professional EE is much more than a clever design and a working prototype.

author: nctnico
author_rank: Super Contributor
timestamp: January 13, 2014, 07:47:38 pm
content: Quote from: Macbeth on January 12, 2014, 06:21:26 pmNow you know what Farnell looks like on the insideI'd just buy what I need. No need to hoard components. They'll most likely end up rotting away in your drawer. I still have transistors I bought 25 years ago.The Chinese electronics market looks nice BTW but it is like many shopping malls in Asia. Often an entire building is specialised in one kind of goods.And yes, electronics is about logistics. The first thing I do in a project is adding the new components to my database so the part numbers, symbols and footprints match.

author: LukeW
author_rank: Frequent Contributor
timestamp: January 13, 2014, 08:13:54 pm
content: There's a box there with a reel or two labelled as MIC520xx3.3 (I can't read the whole thing.) Those are probably a 3.3V LDO, probably handy to get some of those. But read the whole part number and check the datasheet first.

author: TerraHertz
author_rank: Super Contributor
timestamp: January 14, 2014, 01:35:38 am
content: Speaking of salvaging components, with pictures... this was a bunch of PC power supplies.Alas, poor Ozu. A cat with a fine sense of humour. He is no longer with us.

author: dannyf
author_rank: Super Contributor
timestamp: January 14, 2014, 02:14:54 am
content: QuoteThe going rate for those little "rooms" where the lady sit is about 30 million YMB (about $5 million).Next time you belittle those ebay sellers from China, remember that they can easily buy you multiple times over.

author: calexanian
author_rank: Super Contributor
timestamp: January 14, 2014, 05:11:52 am
content: We used to have a place here in Fresno called Cut Rate Electronics. They closed for regular business in the late 80's and the place sat for years until a wholesaler cleaned it out. I got in there for a day to make up a pile of goodies to buy off of him. Lots of good transformers and germanium transistors. (Rhodes pianos of early years used 4 Delco branded TO3 germaniums in the output and i was seeing quite a few of those in for repair at the time and they had a coffee can of them.) also lots of nice heatsinks and the like. IT was about 15000 feet of floor to ceiling parts, all old. Apex electronics is just a faint image of what Cut Rate was. That sort of thing will never be here in the states again as we are just simply not doing the volume to lead to that much surplus.

author: zapta
author_rank: Super Contributor
timestamp: January 14, 2014, 05:54:07 am
content: Thanks everybody for your help. I went today to the store and picked the components. I think I start to understand their system, the shelves are organized by category (transistor, diode, zeners) and then by base part numbers. If you are looking for MMBT2222A, look for 2222 in the transistor section. Overall got 30 X 11 kinds = 450 components for a total of $15 (~4c each).They also have bulk components, I mean really bulk, for example this box with tiny diodes. When you play with it it feels almost like sand, sand of silicon diodes. Could make an hourglass with it.

author: codeboy2k
author_rank: Super Contributor
timestamp: January 14, 2014, 07:03:41 am
content: Nice score !I loved going to halted .. now you make me wish I was still near them , and Fry's... and the swap meetsNow I am back in Canada and we have nothing like it... at least I haven't found it yet(yes, I'm jelly now)Cheers!

author: zapta
author_rank: Super Contributor
timestamp: January 14, 2014, 07:12:59 am
content: Quote from: codeboy2k on January 14, 2014, 07:03:41 amAvailability of cheap SMD components is important but not the only criteria for quality of life ;-)

author: Macbeth
author_rank: Super Contributor
timestamp: January 14, 2014, 06:47:27 pm
content: Quote from: dannyf on January 14, 2014, 02:14:54 amI didn't see any "belittling" going on. The opposite in fact. In the west we would LOVE ladies with the contacts set up shops like this. In my part of the UK, it is the chip shops of the fried potato and battered cod kind that they are successful at, and I love my local chippy and the lovely chinese woman and family who runs it.It would be amazing to have a cheap Aladdins cave type of chip shop, and from the sounds of it FAR FAR cheaper to rent one over here too.

author: dannyf
author_rank: Super Contributor
timestamp: January 14, 2014, 08:36:06 pm
content: BAT54s are not terribly useful due to their fairly large junction capacitance. They are great, however, for clamping + AF work.

author: zapta
author_rank: Super Contributor
timestamp: January 14, 2014, 09:25:22 pm
content: Quote from: dannyf on January 14, 2014, 08:36:06 pmThat's was my intention, using them for signal protection. What would you use instead?Sent from my Nexus 5 using Tapatalk

author: calexanian
author_rank: Super Contributor
timestamp: January 14, 2014, 10:30:02 pm
content: Quote from: Macbeth on January 14, 2014, 06:47:27 pmI bet many people in Asia wish they had a good Fish and Chips shop! Or a friendly little pub to go to.

author: Macbeth
author_rank: Super Contributor
timestamp: January 14, 2014, 10:55:24 pm
content: Quote from: calexanianChippyANDPub. In the UK (at least oop North) there is always a Chippy within walking/staggering distance of the Pub! Also home is then within staggering distance too, so your curry sauce and chips are still nice and hot when you get back. My battered cod is also much bigger and far cheaper than anything the cheapest supermarkets can do and fresher too.If we could get Won Hung Lo over here to sort out logistics for IC's, components, etc, then Farnell and RS will die of culture shock and real competition. But at a cost... (some of my "cod" I am sure was "river cobbler". Did I care? Nope - it was advertised as generic Fish, it was delicious too!)

author: ivaylo
author_rank: Frequent Contributor
timestamp: January 15, 2014, 02:10:04 am
content: Thanks for doing the work on this. I've always avoided those shelfs of reels at Halted as being one big mess. Being a lazy copy cat went there today and kinda replicated your list. Didn't get this lucky with the prices though. Mostly convinced the guy on the $0.04/piece price but he got stuck up on NDC651N being $0.30. Whatever, paid and left. Thanks to you this was my shortest visit there...

author: zapta
author_rank: Super Contributor
timestamp: January 15, 2014, 02:43:30 am
content: Quote from: ivaylo on January 15, 2014, 02:10:04 amYes, they are intimidating but once you get the system it's manageable. They have veritical shelves for transistors, diodes and zeners and on each vertical shelf, the parts are sorted by the numeric part of name.My guy asked for 8c for the 'mosfets'. I marked the part numbers on the cut tapes so he could see the exact part numbers.BTW, Dave had a video on a surplus store in southern califroniabut Halted seems to be more useful.

author: calexanian
author_rank: Super Contributor
timestamp: January 15, 2014, 05:26:17 am
content: I get to Apex once a month. Unfortunately you are only seeing about half of what they have. Don the owner has another warehouse and behind the wall where the transformers are is another store room with some pretty cool crap but its so dangerous they don't let anybody back there. Ask at the counter for what you are looking for and they will go get it, or tell you to come back in a day or two and they will unearth it. Much of the cool Apollo era stuff has been pilfered lately because several companies are making docudramas about the Apollo program right now so prop departments are gobbling the stuff up. I get so mad when I see those guys. They are all asses and so pushy. hey will literally take something out of your hands. Fortunately I have a good report with the guys there so they let me screw with those guys. Big them up at the counter and such.