Buying components early on.

[paulca]

I know we have the sticky thread, but I thought this different enough to create a new thread.

I got one of those cheap "discover" kits on ebay and so far it's been fine.  It has a few dozens of resistors, LEDs, caps, half a dozen NPNs and a shift register IC (presumably to make an LED chaser).

Surprisingly it did not have a 555 timer.

So I went to farnel and 10x CMOS 555s are like £1.50.  Then I thought about a bunch of digital logic ICs ... but trying to work out which are commonly used and handy to have would take hours and hours.

What I basically need is another "kit" type thing with a bunch more ICs and stuff.  I don't want to just buy a load of stuff I'll never use.

Is there such a thing as intermediate / advanced digital electronic kits available with assorted ICs and components?

I see Chinese IC packs with varying series and contents of a few dozen assorted ICs in those series... are these any good or cheap and nasty chips nobody wants so they are off loading them?

I'm assuming I can't go much wrong buying the multi-thousand resistor and cap packs for £5 each?  Presumably someone does NPN packs too.

[bd139]

Interesting questions.

As a beginner I would really avoid buying packs of components from China etc via ebay. They don't always live up to the expectations you will have of them. As a beginner you will have trouble working out if it's your fault or the parts. Plus the prices locally aren't actually that bad. In fact some are insanely cheap! Want to buy some 10k resistors? 6p for 10 including free next day delivery by parcel force! http://uk.rs-online.com/web/p/through-hole-fixed-resistors/7077745/

For your situation, I'd keep quantities low and just buy what you need on demand. These guys are pretty good when it comes to that: https://www.bitsbox.co.uk - parts are reasonable quality, delivery is usually next day and if there's a single problem, they will sort it instantly. They sell component packs too if you really want to go down that route but beware; most of them will never get used.

Personally, I just buy what I need on demand from RS and Farnell. I spent probably around £6-10 a week on parts (not much!) for projects I have on the go. Speculative parts purchasing gets expensive and requires storage and management which is hell (I've been there with about 100kg of crap jammed in cupboards)

To keep costs down I have switched mainly to SMD parts. You can spend 30p on 100x good quality branded metal film 1% 0805 resistors and they will last a long time. I don't buy any generic / unbranded parts now or have to worry about the supply chain or if they're going to work or not.

[tszaboo]

I don't want to just buy a load of stuff I'll never use.

Haha... Half of my dev boards that I got never got powered up.

Is there such a thing as intermediate / advanced digital electronic kits available with assorted ICs and components?

No there isn't discrete logic is used as glue logic today. You dont build a circuit for a 74hc153 you use that if you have a problem with another circuit and this is the solution.

Presumably someone does NPN packs too.

Why would they? So you can use different transistor with different Beta? Or use a 45V part instead of the 35V one? This is not the 80's. Everyone uses a BC807 and BC817 to solve 95% of the problems in circuits.

[bd139]

On the subject of discrete logic vs microcontrollers you should definitely actually play around with discrete logic! You might never use it in a project (not true - I use the stuff all the time) but that's what the microcontroller is made of so it helps you rationalise how stuff works.

[bd139]

On the subject of discrete logic vs microcontrollers you should definitely actually play around with discrete logic! You might never use it in a project (not true - I use the stuff all the time) but that's what the microcontroller is made of so it helps you rationalise how stuff works.

Yes, that's true. But I still maintain it is not a good set of parts to stockpile.

Agree. Get some 74hc00's and build a few composite gates, then a couple of flip flops, then buy some real flip flops, then make a counter or two, then buy a real counter or two, then learn about buses and multiplexers, build a state machine or two then instantly forget it all and use a CPLD and microcontroller (i.e. follow "Learning the art of electronics")

Edit: to give you an idea of how bad an idea it is to stockpile, I once had about 200 tubes of 74LS TTL floating around... used about 15 ICs in total building a Z80 SBC that was inferior to a PIC16F84 at the time.

[paulca]

Thanks guys.  I will probably want to follow up on a few discrete points above, but I'm in work and my boss is hovering.

Remember that I am learning, so I have already built ANDs and ORs from a few PNPs.  I'd like to build the rest of the gates too.  Then I would like to move up to using discrete gates to build more complex gates like latches (are SR latches not standard sub-circuits for control buttons etc even in analogue electronics?)  So while I agree that with MCs being so cheap and available and easily programmed today, why would I want discrete logic gates at all, but, I'm a software engineer if I go down that route I would just plug the raspberry pi in, attach a few output pins to stuff and do everything in software.  Great, but it won't teach me all that much about electronics.

So the stuff you might only expect in a school is the stuff I will probably be looking for.

The other thing is that while a given project might then require me to buy components for it, at this early stage the inspiration can almost as easily work the other way too.  For example the shift register in this pack I got, I'm curious to see if I can build a small project to set it up.  It's "tool orientated design", I have a hammer, now I have to find a nail.  This is why I asked about intermediate component packs etc.  maybe they will include stuff that I will want to figure out.

I signed up for TronClub, but it looks like the first pack will take a while (if at all) so I'm thinking I need to do a Farnell order.

I want to make a 555 timer with transistors as a project.  Then replace it with an actual 555 and back and forth between the two to learn a few things.

Not sure where to go after that.

[paulca]

So here is an example of my pains.

I used this as a reference for what parts I need to build a 555: http://www.instructables.com/id/Build-Your-Own-555-Timer/

Going to Farnell the transistors were easy enough, ordered 25 of them, though I probably won't use 25 PNPs (ever?) so I might drop that to 10.

Then I thought about stocking up on some branded resistors and I got bogged down.  This kit would require 3 different resistors, but I can't decide on which type I want.

I assume, through-hole, 1/4 or 1/2 watt ,ideally not the blue ones as I can't read them, even my resistor camera scanner can't read them.  So as these are common ohms, 1k, 10k, 4k7 I thought I'd add 100 each and bang there is £9 in resistors.  I can order a resistor pack on ebay that contains 2600 resistors with 26 different values for £10.  What I need to find is a resistor pack on branded resistors with a few dozen different common sizes for £20 or so.  Same for caps.

Also, breadboard jumpers.  The little kit I bought has a selection but I get a feeling there are probably better quality selections out there.  Or ... what are the solutions for buying single core wire and snips + stripper to make them to length?

(sorry so many questions)

[bd139]

Good project.

For what you need to do I'd hit bitsbox: https://www.bitsbox.co.uk  ... not ebay! Ebay is full of non bargains.

Good "beginner" resistors are generic 1/4W 5% carbon film. You can see them, read them and they are cheap. You don't need a massive range of values. Buy any non standard ones if you need them. You can make up other values easily with two other resistors:

1.2k - 1k+220R
900R - 1K || 10k

etc etc.

Some suggestions:

resistor kit (30ea common values £3.49): https://www.bitsbox.co.uk/index.php?main_page=product_info&cPath=272_274&products_id=1997
bc547 NPN transistors (20 for 1.60p): https://www.bitsbox.co.uk/index.php?main_page=product_info&cPath=140_151_152&products_id=998
bc557 PNP transistors (10 for 80p): https://www.bitsbox.co.uk/index.php?main_page=product_info&cPath=140_151_153&products_id=1003
wire for jumpers (10m for £1.60 - yellow so you can see it): https://www.bitsbox.co.uk/index.php?main_page=product_info&cPath=200_201&products_id=1449
postage £1.75

capacitors: depends what you need - buy them individually. Not worth stocking a kit. I'd stock:

Electrolytics: 10x 10uF, 10x 1uF, 5x 100uF, 1x 1000uF (bulk / coupling / decoupling)
Polybox: 10x 1nF, 10x 10nF, 10x 100nF (timing / filters etc)
Ceramic: 10x 100pF, 30x 100nF (get through lots of these - decoupling / frequency compensation)

Breadboard jumpers - all the dupont wired ones like the one in that article are total crap. Fall to bits and sometimes dont even work to start with! Buy some decent wire strippers (I use these - expensive but worth it: http://uk.rs-online.com/web/p/cable-strippers/0243112/ ) and some wire as above.

Also a killer: get a decent breadboard. Wisher from CPC. A lot of failed projects are from crappy breadboards.

[woody]

These :

http://nl.farnell.com/pro-signal/psg-jws-65/jumper-wire-set-65pc/dp/2503764

are not too expensive and not too shabby.

My most-used breadboard jumpers are 10 cm long, green, solid wire, pre-stripped on both sides. I got maybe a kg for a guilder from a Philips factory surplus where I worked 35 years ago. Still have some left 

[paulca]

So I went for:
BB: Pro's Kit 800 slot w/ rails. http://uk.farnell.com/webapp/wcs/stores/servlet/ProductDisplay?catalogId=10001&langId=44&urlRequestType=Base&partNumber=2503746&storeId=10151
Resistors: WELWYN MFR4 500mW 1% Metal foil (x10 each of the sizes), probably overkill, but I figured they would maybe be larger and easier to deal with on a breadboard
Caps: MULTICOMP 100uF 50V Aluminium Electrolytic  x5
NPN: ON SEMICONDUCTOR 2N3904BU x 25
PNP: MULTICOMP 2N3906 x10

And because I'll use them else where: TEXAS INSTRUMENTS NE555P x5

Jumpers I'll stick with what I have from the cheap kit for now.  The hard jumper kits on Farnell don't seem overly different to what the cheap kit gate me.

I have a 3.3/5V dual rail power module for the breadboard that runs on a wall wart, so I think I have everything I need for now anyway.  Of course I will have forgotten one thing, but it looks like Farnell might be next day delivery.

There are probably a few nights worth of tinkering in this.  Build a compactor, build the latch, build both together, test it.  I'm wondering if I should break out the DIP pins like the article so I can plug in either my breadboard version or the real chip.  (Implementation behind interface in software design)

Do you UK guys get the £3.95 handling charge or is that just us over in Northern Ireland?  It might cause me to buy in larger orders as in this case it came out at close to 20% of the total!

Thanks for the pointer to bitsbox, I'll check them out.

[bd139]

We get shafted for the £3.95 charge as well. If you spend £20 ex VAT it's free though. Farnell are next day (sometimes UPS screw up but that's rare)

[paulca]

I did forget something, but I can order it from bitsbox.  Not really related to the 555 project but...

Potentiometers.  When I going through the theory of stuff like transistors and diodes it's impossible to observe what happens at what voltage when you are stuck swapping resistors in and out of a divider.

Which reminds me for some experiments I would ideally need 2 or more voltmeters.  I have invested in an Extech EX350, but what are you guys thoughts on little panel meters for such things?  I seen some from the US designed for breadboards, but can anyone suggest a cheap 0.1V resolution LED panel meter that costs a couple of quid and multiples could be inserted into breadboards at various locations?

Also, I forgot plunger clips (or crocs) for the multi-meter.  Extech do a probe kit for £17 ...  Sticking the multimeter up against the legs of components and trying to hold both probes with one hand is getting old.

[bd139]

I use trimmers for the job instead of potentiometers. Bitsbox sell ones you can finger adjust (the blue ones!) and will fit in the breadboards without killing them. 

I can’t speak for multimeters as I have lots of them and none of them were particular cheap. Any cheapish one will do for low voltage. Watch out because some of them load the circuit heavily. You will need more than 0.1v resolution so aim for proper DMMs. This is a big area for contention on this forum

Farnell sell leads which are made by Pomona but they are £4 a pop. They have a minigrabber at one end and a 4mm plug for your meter at the other. These are the most convenient and last a long time. You can get away with croc to croc leads attached to your circuit and the probe ends worst case.

[paulca]

Do you think these will work?
https://www.bitsbox.co.uk/index.php?main_page=product_info&products_id=1722

They don't state the input... is it likely to be a probe or a 4mm banana plug?

On meters.  As you say, it's low voltage and I might not be using them for any particular reference, so would it be that much of a sin to buy 2 or 3 £5 DMMs for this purpose? 
eg: https://www.bitsbox.co.uk/index.php?main_page=product_info&cPath=243_270&products_id=1986

[bd139]

Those are just the bare ends. You'll have to buy 4mm plugs and cable to connect to them and a soldering iron etc.

Those meters are "ok" for a first but do not ever stick them near the mains or anything that can shift more than an amp or two. The input impedance is 1M which isn't great and can cause loading problems. 10M is normal these days. Also there is no low AC range which limits usefulness. You can get them for less with free delivery over £5 ex VAT at CPC: http://cpc.farnell.com/duratool/d03046/multimeter-digital/dp/IN07220

Really min spec these days seems to be around the £40 mark. Not sure what your budget is. I've got a couple of these: https://www.amazon.co.uk/dp/B00L7R1G4E/ (measure frequency, AC volts, capacitance etc as well. Again, not the best for mains use but an order or two of magnitude better.

[ChrisLX200]

I would not dismiss Ebay as a source of components so readily, of course you need to be selective what/where/whom you buy and consider where the parts originate, but as an example I've bought some good stuff from (one example) http://stores.ebay.co.uk/HFO-Elektronik?_trksid=p2047675.l2563 who is a Polish dealer.

[bd139]

I've bought from them as well a few times. Problem is check the postage on anything that weighs more than a 100g or so is a bit scary and it's a pick and mix shop. TME (in Poland) is sometimes a good deal. Next day DHL for £8 or so. My Keysight meter is coming from there next week.

[paulca]

Those are just the bare ends. You'll have to buy 4mm plugs and cable to connect to them and a soldering iron etc.

Those meters are "ok" for a first but do not ever stick them near the mains or anything that can shift more than an amp or two. The input impedance is 1M which isn't great and can cause loading problems. 10M is normal these days. Also there is no low AC range which limits usefulness. You can get them for less with free delivery over £5 ex VAT at CPC: http://cpc.farnell.com/duratool/d03046/multimeter-digital/dp/IN07220

Really min spec these days seems to be around the £40 mark. Not sure what your budget is. I've got a couple of these: https://www.amazon.co.uk/dp/B00L7R1G4E/ (measure frequency, AC volts, capacitance etc as well. Again, not the best for mains use but an order or two of magnitude better.

Thanks.  They were 49p, but I added a batch of 10 doubled ended crocodile leads anyway.  It's all these little things that add up.  I have dozens of connectors for radio controller stuff, but it's all high amp bullet/barrel connector stuff, I don't have a single 4mm bannana connector to my name. 

My main multi-meter is the Extech EX350, which I gather is about bare minimum spec.  I procrastinated over the cheapest (supposed to be China only) Fluke at £85, but worried about fakes etc.

I just want a few voltage or current meters I can clip into the circuit and see (without a scope) what happens to voltages.  Scope is a way off yet and I might start with a USB gizmo first.

I figured if I need more I can always go round the corner to "Pound Land" and buy their rubbish meter for £5.  When I don't need them anymore I'll do a quick video of "Will it microwave".

On ebay and cheap Chinese stuff I'm fairly experienced in spotting trash.  Though I would say that most of it works and does about 90% of what it's supposed to and often that 90% is all you need.  However there is usually something less optimal about it.  The little blue metal foil resistors for example have wire thats a bit too thin for breadboards and they are completely illegible.  Using a meter or component tester every time I want to reuse one is getting old as well.

[ChrisLX200]

I bought 5 of these 4-digit voltmeters a couple months ago: https://www.amazon.co.uk/gp/product/B00MUMN58K/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1 and found them to be accurate down to their LSD - which is remarkable given they only cost £1.72 each. They use separate sense and power lead and I power them from 12v. For simply monitoring voltage with no special accuracy requirement you could do a lot worse..

[bd139]

All sensible 

Always worth keeping an eye on eBay for decent quality second hand flukes. One of my flukes (8024B) is about 35 years old and works perfectly. Think I paid £8 for it.

The cheap Chinese resistors you have to watch it with as sometimes they are marked up wrong or well out of spec.

Some of those voltmeters aren’t floating - be careful or stuff will blow up.

[paulca]

Some of those voltmeters aren’t floating - be careful or stuff will blow up.

Funny story    I needed a 13A PWM voltage limiter for my home brew boiler to calm it down a bit and stop it raining beer in the kitchen (literally!).  I followed a guide on a forum that built a nice little box with air holes drilled in it and a small volt/amp meter on the front panel.  All high grade 15A mains flex the whole heap.

The 40A rated PWM circuit works fine, huge heat sink, huge caps, but when I went to wire up the meter the instructions where not very clear.  The connectors on the board where not labelled and it was a matter of assumption as to where they went.  I googled it.  Turns out there were two versions of the unit and the second batch were wired differently but shipped with the old instructions.

I was fairly sure I had a new model and wrong instructions as the 240V connected to something like a 9V battery wire, but a voice in my head said, "If you ignore the instructions that came with it and follow something off google and it blows up you will be right embarrassed."  So I followed the instructions that came with it.

I have a rule.  When I switch on something dodgy that is connected to the mains I make sure I am not holding or touching it and the only thing that comes near me is the mains switch.  I also have my fingers position so I can quickly turn it off again.

PUFFFF!!  Big cloud of magic smoke.... and 4 lovely little circular burn marks in my carpet later and I realised I should have followed the instructions off google.  I'm pretty sure I put 240V through low voltage sense side and from the colour of the debris I think a capacity exploded spraying flames and cooper coloured goo all over the inside of the box and the carpet.

Surprisingly the 40A "dimmer" still works fine, though I treat it like it's got small pox when it's plugged in.  Still smells of magic smoke though.  The hole where the meter was adds cooling, but could also provide a way to put your fingers in and get zapped.

Do I get a "Dodgy cowboy" badge?  If that doesn't get me the badge, when I was 14 I took a CRT monitor apart and wondered what was under the sucker on the back of the tube, so I tried to pry it off with my fingers.  BANG!  I was launched clean across the room and slid down the wall shaking like a leaf.  Of course I now know that is the 50KV pull up and the capacity it was connected to was nearly the size of a coke can!  At least I lived to tell the tale.

[bd139]

Nearly killing yourself a few times is a rite of passage. If it involves smoke and fire, it’s more interesting 

My most famous fuck up was plugging in a valve radio chassis I bought from a jumble sale in the 80s. I was 9.  Three seconds later the kitchen lino was on fire and there was only a gap about 2 feet between the floor and the ceiling when there wasn’t any smoke. Turns out the caps and gone short and the fuse replaced with a piece of thick wire. Transformer stood no chance

[ChrisLX200]

As a kid I had a good idea for listening to 'Top of the Pops' at greater volume, I would wire the speaker terminals from the TV to the input on my 30w valve guitar amp. Didn't realise there was 240v on the speaker terminals.

[paulca]

Nearly killing yourself a few times is a rite of passage. If it involves smoke and fire, it’s more interesting 

I read somewhere that some people are more susceptible to dying from electrical shocks that others.  I think I'm immune but damn does it hurt.

My favourite is 50Hz AC mains.  It hurts like hell but you just can't let go.

Funniest one was talking my brother into touching an electric fence with his tongue.  He'll not do that again.

BE WARNED KIDS THE FIRST SHOCK CAN AND DOES KILL!  DO NOT PLAY WITH THE MAINS.

[alexanderbrevig]

As the creator of said sticky my advice, even though I did not take it at the time I asked for it, limit your stock.

Personally, when I have an idea I simulate first. LTSpice and TINA is my stockpile.
For must solve today, I've never grabbed anything but caps, resistors, the odd diode and a transistor. I currently only keep a small selection of these in THT.  Everything else I simulate, order some parts, wait a day or two, test, design a prototype,order PCB wait two weeks and build.

For an intermediate and advanced kit, check the listing for Art of Electronics. Will probably showcase everything you need to know. I find every 'simulation works, why not my prototype then' valuable.
I'm still a beginner, always will be I think.