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.

[trys]

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

Many many years ago, I read or heard somewhere:

"Volts jolts, and Mills kill"

(The "Mills" referring to milliamps).

I've had two electric shocks in my life. Both were my own stupid fault, nobody else's.

One was building a variable PSU using a LM317T (about thirty or more years ago). It was an incredibly useful kit. I brushed the back of my hand past the live fuse connector.

Luckily enough it was the back of my hand, so my hand clenched and got away from it (a muscle will stay contracted towards an AC shock).

One tip with mains is to do all "hot" work one-handed (keep one in a pocket) so that if any current does pass it's less likely to pass through your heart and stop it. The other one is to pre-plan all the steps. The best tip of all is to avoid doing it.

As a result, it put me off mains work (until last week, 30+ years on) to build my second PSU project. I've built it and it will stay built, I'm not going to fiddle with it any more. I promise.

Trys

[SkrillBill]

When you buy components from say digikey or mouser, add a couple extra of the part you want and throw in a couple of others. Over time, you'll build up a decent stock of parts. Another way you can acquire parts (and practice desoldering) is by removing parts from old PCBs. Power supplies, oldder radios, really any pcb with through-hole components. This is what i did / still do and it works out pretty good. You will eventually have to buy something, so always make it worth the shipping. Someplaces even have free shipping above $xx.xx, so if you can afford it build up a cart to that amount to get free shipping.

[bd139]

Also with parts, if you can afford to wait a couple of weeks, these guys are pretty good: http://www.taydaelectronics.com

Stick to the royal ohm resistors though; the other ones are spindly shit - rest of the parts are good!

If you stick $100 worth of stuff in an order it'll fly through customs with a pre-printed jiffy bag with "$7 commercial samples" on it 

[nes999]

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.

I just ordered the art of electronics. It was a pricey bugger!

Sent from my VS988 using Tapatalk

[Brumby]

It's all these little things that add up.

Yeaaaah.

Do yourself a favour .... don't add up what you spend over a year.  Your workbench will never seem to reflect the value of what you've put into it.


+1 on not "stocking up" on parts you hope will be useful.  Last week I came across a tube of 7400 (not HC or LS - just regular TTL) from more than 30 years ago ... and that's just one example.

[trys]

I just ordered the art of electronics. It was a pricey bugger!

Good book. Get the other lab one too.

[KL27x]

Very few things you would want to stock up on. Over the course of some years, you may find you move from thru hole to smd. From logic chips to micros (and micros to newer micros). Everything you stock up on is potentially (more like probably) garbage to you in the future. There is very little that you will be happy to have on hand. In Digikey's warehouse, it has value. In your possession, it is just junk that will be thrown away when you die, if not sooner. It's like how a car loses 20% of its value as soon as you drive it off the lot, except it's more like 99%.

[nes999]

I just ordered the art of electronics. It was a pricey bugger!

Good book. Get the other lab one too.

What is the lab one?

Sent from my VS988 using Tapatalk

[thermistor-guy]

When you buy components from say digikey or mouser, add a couple extra of the part you want and throw in a couple of others. Over time, you'll build up a decent stock of parts. Another way you can acquire parts (and practice desoldering) is by removing parts from old PCBs. Power supplies, oldder radios, really any pcb with through-hole components. This is what i did / still do and it works out pretty good. You will eventually have to buy something, so always make it worth the shipping. Someplaces even have free shipping above $xx.xx, so if you can afford it build up a cart to that amount to get free shipping.

Yeah, I do this. I scavenge parts from broken gear before throwing it out, if it's not economical to repair. Connectors, terminal blocks, heatsinks, ceramic spacers. Unusual components or materials that are rated for high power, high voltage, or high temperature. Useful materials like Mylar film or copper sheet. Cables and fasteners from old PCs, useful for building and modding new ones. Magnets from failed disk drives, for magnetizing the tips of screwdrivers (handy when repairing laptops). 2.5 mm and 3mm dia. shafts from old DVD drives, useful as accurate punches for sheet metal, to make temporary housings.

There is a wealth of technology in the stuff people throw out.

[ChrisLX200]

I would hazard a guess that most folk are limited by space anyway, certainly I am, so I could not store a large selection of components even if I wanted to. I have a good mix of parts recovered over the years from scrap PCBs, some enclosures, a lot of logic ICs (which have never been used for anything other than experiments), switches, connectors and so on. I have recently topped off with a few new electrolytic caps, and some SMD collections (cheap and don't take up much space). I figure I'm in a good position to tackle repairs for the most part without needing to wait for a parts order.

[bd139]

Very limited space here as well. I have two small CPC boxes and a couple of binders of parts and that's it. All the loose stuff is compacted in ziplock bags.

I don't bother recovering anything these days as it takes up too much space now on the off chance that I might need some of it. When I eventually drop dead, I don't want my family to have to clear out a hoarder. I'd rather just order some new bits of RS for next day

[woody]

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

I know that there's a nice T-shirt quote in there somewhere 

[woody]

So I had to look up "Jesus stick"

https://www.urbandictionary.com/define.php?term=jesus%20stick

I certainly hope you mean something different

[paulca]

I work with 3 parallel banks of 8P2S 8uF, 4kV caps (totally 96uF, charged to 7.5kV, 2.7kJ). I treat them like death himself.
I have a normally closed fail safe relay for slow discharging, a manual 100Ohm fast discharging rod with long handle, and for the worst case, a Jesus stick.
I was bitten by 33nF, 25kV once, and a couple times by up to 100nF, 1kV, and once by 47uF, 300V. I don't plan to dump 2.7kJ through my body, though.

Ouch.  I'm not sure how many uF a 15" CRT has in it's tube charge caps but it certainly hurt and as it's DC it threw me clean across the room and left me shaking.

It's worth adding to my warning:  "EVEN WHEN ITS OFF!"  as a lot of main gear has got large caps inside and so even if it's switched off and unplugged when you open it there are still VERY dangerous potential currents in there you could unwittingly unleash on yourself.... and the hurt a lot.

On an aside and in defense for "don't buy cheap chinese rubbish".  I have got a shock off a PC power supply after unplugging it.  I literally switched it off at the PSU, switched the mains off and pulled the plug, then I promptly got a rather unexpected and sore shock off the Live/Earth pins on the plug, spark and all.  I gather they did not have reverse protection on the power caps and that allowed my hand to discharge them to earth.  Dodgy.

[paulca]

So I had to look up "Jesus stick"

https://www.urbandictionary.com/define.php?term=jesus%20stick

I certainly hope you mean something different

What will you shout if you just shorted a huge capacitor and turned a few kJ of energy to acoustic energy and a bright flash?

Can you get a Holy good f**k stick?

[alanb]

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)

CPC-Farnell have free delivery on orders over £5 (3-5 day)
You can get next day with a payment of 2.99 +Vat

[nes999]

I volunteer at a dog obedience school and I also do the majority of their maintenance. I was changing out a fluorescent light fixture. I shut off the breaker, power to the ring is cut. You should have seen the other volunteers when a cloud of sparks rained down. It was get power from somewhere, just not enough to light anything.



Sent from my VS988 using Tapatalk

[paulca]

So the stuff all arrived.  "Mail bag!", LOL

I even created a box with resistors laid out by size. 
10R, 100R, 1K, 10K, 100K, 1M
22R, 220R, 2K2, 22K, 220K
47R, 470R, 4K7, 47K, 470K
Assorted others.

Also built the trigger comparator for the 555 and was somewhat surprised and a little disappointed that it worked first time!  When a bit of code I spend 2 hours writing works on the first run I feel similar surprise, disappointment and a moderate amount of suspicion.  I'll do the other one on Saturday.

One thing I bought of theBay that is invaluable I find, is a "Nail painting light".... relax I'm not painting my nails, it's just a circular flourescent with a 8X magnifier lens.  Makes reading ICs and fiddling with breadboards so much easier.

[paulca]

Feeling pretty good with myself as I got the full 555 timer circuit working.  Learnt quite a bit as me, the instructions and my understanding of them parted company once the individual sub circuits were built.  I had to work it out bit by bit by retesting each component, finding a few things backwards and finally tinkering until annoyingly surprisingly the LED started to flash.

It's mickey mouse stuff, but for me this is my first circuit involving more than a few components.

Next project might be replacing the comparators with op amps.  Haven't worked out what I can replace the flip-flop/latch with yet. 

Can anyone suggest a basic logic IC with at least one flip/flop or SR latch on it?

[bd139]

Nice one 

I'd get a couple of 74LS00's (they are just 2-input NAND gates) and learn how to build a couple of different types of flip flops first. There are quite a few with different characteristics. You could get 74HC00's but they are CMOS and therefore a little easier to blow up just by looking at them funny.

Then move to 74LS74 which is a D-type flip flop.

When you start with this you will need "debounced" switches as inputs.

[TheDane]

Buying components early on can be tricky.

Passives are a must to stock. Unfortunately there's a ton of different kinds, once you get into it. (Filters for one, fast and slow blow fuses, poly-fuses, multiples components into one device/arrays, different physical sizes and leaded/smd, power ratings, voltage rating - don't use a 50V rated tantal cap in a 5V circuit - that can be bad as it self-heals when voltage ratings are correct, crystals and oscillators can have different load values and of course frequencies, etc.)

Active devices can be really hard; you can stock up on e.g. leaded components - and when you do a layout you learn there's no room, so you have to go SMD - or choose a different version, with different pin layouts. A 5V device that runs 16MHz, but running at 3v3 it will only run 5MHz and so on. Easy to miss in the datasheet when quickly glanced over - it's usually hidden far from page 1/2.

Stock also grows 'x-tra' legs, and tends to disappear on its own over time. You know you have had it, but now it' gone, not to be found. 

Then there's the supplier New Featured Product Update Announcements, telling you that there's a new part which is much better, smaller, cheaper, etc. Hard not to keep using what you have, and not adding to your already growing stockpile.

Doing homework, reading datasheets and comparing various manufacturers can be a lengthy process - and it can take up more time than 'just doing the design' and buying all combined + a few items extra most likely to blow up during testing and development.

Waiting, trial and error, stock issues and other not so fun stuff can make the homework worth it though.
Usually having some R&D stock for developing, and then down-scaling for production is a good idea.
Some companies also require you to have 2.nd sources on everything, if not 3 sources. Then you go by inventory, and take the fight ONLY when you absolutely need the new item.

The best thing, I found, is that you know the ins and outs of the devices if and when you use them. Buy lots, and you become an expert on that device. Then they go obsolete, and you're in for some more schooling/shopping.

Happy shopping and reading - its a never ending story 

[trys]

I just ordered the art of electronics. It was a pricey bugger!

Good book. Get the other lab one too.

What is the lab one?

The lab one is called "Learning The Art of Electronics" "A Hands-On Lab Course" by Thomas C Hayes with the assistance of Paul Horowitz.
ISBN 978-0-521-17723-8

Excellent gook. It can be read independently of The Art of Electronics too.

Trys

[paulca]

I'd get a couple of 74LS00's (they are just 2-input NAND gates) and learn how to build a couple of different types of flip flops first. There are quite a few with different characteristics. You could get 74HC00's but they are CMOS and therefore a little easier to blow up just by looking at them funny.

Interesting.  I ordered x5 of these, then I looked up an SR Latch and realised it was made from NOR gates.  I ordered some NOR gates... then I realised that the 555 timer latch is (?) active low and probably should be NAND gates.  Aww well I have both now anyway, whichever way it works out.

Then move to 74LS74 which is a D-type flip flop.

The D FlipFlop requires a rising clock pulse.  I found this quite profound to use a 555 timer to control a gate in a 555 timer circuit.

When you start with this you will need "debounced" switches as inputs.

As above, again I could get recursive and use a 555 timer in monostable mode to debounce the switch


Is there a useful cheat sheet for selecting the common/beginner logic gate ICs?  I thought I could simply look for the 74LS range, but it turns out it's not that simple.  It seems that searching for these on CPC etc can lead you down a rabbit hole or ending up purchasing an expensive IC for more specific requirements when an IC a tenth the price was available elsewhere.

[bd139]

TTL Cookbook by Don Lancaster is the goto book for this stuff. There's a ton of databooks available but they're all rather large and unwieldy.

You can make any gate with NAND gates

[paulca]

You can make any gate with NAND gates

Yes, but you can also slide down a concrete slope in your underpants.  It's entirely possible but not very comfortable

In a Computing HNC I did we had to power a single 7 segment display from a 4 bit number using only NAND gates.  I think it ended up with 30 or 40 gates.  (I prefer  Ben Eater's approach of using an EPROM lookup table)

[trys]

In a ScienceFair (Intertan / Tandy / Radio Shack) "300 in One" Electronic Project Lab it comes with the following Digital ICs:

QUAD 2 Input NAND GATE 4011 (2 off)
QUAD 2 Input NOR GATE 4001 (2 off)
4 BIT PRESETTABLE UP-DOWN COUNTER 4029
BCD to 7 SEGMENT DECODER 4511
J-K FLIP FLOP 4027

(It also comes with a bunch of other compoents too, but as you were asking which series of logic ICs to perhaps get I thought I'd type this up, in case it helps).

Edited to add: They are all in stock at CPC as I type this, and the above bunch would come to £3.06 (incl VAT)

Trys

[paulca]

I found this list of the 7400 series: https://en.wikipedia.org/wiki/List_of_7400_series_integrated_circuits

But I am wondering if some of these are more suitable in other series.

[trys]

And here's about  the 4000 series: https://en.wikipedia.org/wiki/4000_series

The list itself:
https://en.wikipedia.org/wiki/List_of_4000_series_integrated_circuits

[bd139]

4000 series is mostly pretty dead now apart from a few parts.  There are 74HC series which have replaced it basically. You can get 74HC4xxx series which are much faster ICs compared to their original 4000 counterparts.

Also 74HC are quite fragile static-wise.

[trys]

The 4000 series are easier to work with as far as supply voltages go.

As far as them being pretty much dead, well yes you are right, and so are the 74 series or discreet logic chips generally. Broadly speaking. Which one is deader than the other is a bit immaterial really. Microcontrollers have taken care of that in the main (yes, I'm aware of lots of exceptions!).

As I said, the 4000 series are available at CPC (as are the 74 series too).

As far as cutting your teeth on logic circuits, then just take your pick.

[paulca]

So I got my NOR gates (SN74HC02 quad NOR gate)  and wired up an SR Latch.  It works, but, it's a bit of a faff.

I had mind to check the datasheet before I hung LEDs on the outputs and they claim to only provide a max of 25mA current with a max across the chip of 50mA.

I don't have a datasheet for my LEDs, but I'm sure they are 20-30mA.

So I created single NPN drivers for them, but of course to prevent the NPN drawing current through the base I needed resistors between the logic outputs and the base.

It works, but... surely it's a bit of faff having to use transistors to drive the LEDs.  Also the inputs all needed pulled down with resistors or the gates wouldn't function.

I have watched all of Ben Eaters 8-bit computer videos and he typically hangs 8 or more LEDs off a logic circuit.

Am I being overly pedantic and it would probably be fine driving a few LEDs or is Ben Eater risking burning out his logic gates?  Am I reading the data sheet wrong?  Have I got highly sensitive gates? 

[paulca]

Also on buying stuff...  I decided to get a bench power supply and got the Tenma 30V 5A model, it's cheap, but I've seen a few torture and tear down reviews and it seems to be worth the money.

It's a bit noisy when I put it under some load charging a 3S LiPo at 5A, and the fan is still considerably audible on minimum.  Someday I'm probably like to mod it to turn the fan off under 1A.

[trys]

It works, but... surely it's a bit of faff having to use transistors to drive the LEDs.  Also the inputs all needed pulled down with resistors or the gates wouldn't function.

Good on ya for persevering with that despite it being a right faff.

You will probably find that your LEDs will light with just 1mA, so you're looking at a series resistor of 4K7 (or something like that) if the outputs are at 5V. They won't be bright, but you'll be able to see them.

The mA draw of LEDs is usually quoted as maximums to stop us lot frying them. An LED fed with 20mA gives a good bright light.

Trys

[bd139]

Actually if you build yourself a current source as a project, you can see what colours red LEDs go above 20mA or so. It's quite interesting. Wear safety goggles though as the no brand chinese ones tend to explode.

[paulca]

Actually if you build yourself a current source as a project, you can see what colours red LEDs go above 20mA or so. It's quite interesting. Wear safety goggles though as the no brand chinese ones tend to explode.

I found out that a unlimited green LED turns Amber before the Raspberry PI it's connected to dies when it's cobbler is wired backwards.  Thankfully it wasn't my PI, it was a work owned one.  The LED didn't light when connected sensibly, so bring a little flippant I stuck it across the +- rail of the breadboard.  It went bright amber, then dimmed and the PI went off with the LED.  Neither worked again.

I never did check to see what I pulled the current through or into when the cobbler header was wired backwards.  Something that didn't like killing an LED, I suspect.

On torturing LEDs, I think the Tenma PSU will do 10mA increments, actually think will let me set 1mA increments, but the spec says 10mA resolution (I believe).  That should be enough to destroy an LED or two.  Don't have safety glasses though, but I can use a plastic screen.

[StillTrying]

you can see what colours red LEDs go above 20mA or so. It's quite interesting. Wear safety goggles though as the no brand chinese ones tend to explode.

It must be the heat, in my light experiments, for 10us/4ms I've had 600mA through a 5mm 20mA red LED, and didn't see any colour change.

[bd139]

The ones I tried were a bag of 250 of them from Rapid Electronics circa 1995. We connected them to a relatively hefty HP supply with CC support and cranked them up to about 80-100mA. Bright orange following by a radiant shade of black

More recently, these ones go with a satisfying snap, especially the blue ones. I bought a whole bag just to blow up: https://www.aliexpress.com/item/500pcs-lot-F5-10-Colors-5MM-Round-Green-Yellow-Blue-White-Red-Warm-White-Orange-Purple/32597550934.html

[TheDane]

A bit of caution regarding blowing up LED's:

Some components contains poisonous chemicals, and most LED's contain Gallium arsenide.
https://en.wikipedia.org/wiki/Gallium_arsenide - which is rated

High frequency transmitter amplifiers can contain large amounts, and if they blow - the magic smoke can kill quickly - be well..... get outside a.s.a.p. and don't breathe in on the way. Ventilate - Wear a respirator, be safe.
I know, one LED - small. 100kW solid state amplifier - huge.

A ham - not to be eaten 

[paulca]

Some components contains poisonous chemicals, and most LED's contain Gallium arsenide.
https://en.wikipedia.org/wiki/Gallium_arsenide - which is rated

Yes, but you need to eat a plate of the stuff to have a 50% chance of death:

https://wcam.engr.wisc.edu/Public/Safety/MSDS/Gallium%20Arsenide.pdf

Toxicological impact on health:
Gallium arsenide is considered as acutely non-toxic.
 Animal tox. (for GaAs):
 LD50 (mouse) = 4,700 mg/kg (intraperitoneal)
 LD30 (rat) = 10 g/kg (intraperitoneal)
 LD50 (rat) = 10 g/kg (oral, dermatological)
 That means:
 Classification criteria for hazardous substances do not apply. There is no evidence that inhalation,
ingestion of or skin contact with gallium arsenide (compound semiconductor) has an acute
toxicological impact on health.

So if I weigh 100Kg (I don't), I would need to eat/inhale/drink 470g of the stuff to have a 50% chance of fatal dose.  As a gas at STP that would be many, many litres of pure magic smoke.  There are probably worse things in magic smoke than that.  So I don't recommend putting transistors in a bong.

It's interesting that the Wiki article flags it as Toxic, but then links to a safety data sheet which disagrees.

[bd139]

Big ass transmitters are usually full of mercury and beryllium oxide which is where the problems are.

[paulca]

So update on the 555 project.  It's now gone from 2 breadboards and 19 transistors + 1 test breadboard to 1 small breadboard and a test breadboard.

2xOpAmp comparators and 2xNOR gates on one IC + output and discharge drivers.  Haven't wired the reset, but I'm 50/50 that I just need to jump one of the latch outputs Q or !Q to the reset pin via a trannie to do that.

It works and is a LOT mores stable than the trannie version.

I could go one more step and replace the opamps with actual comparators, but meh.

I'll collect the images I have and make a summary post soon.  It might help another newbie who fancies doing similar.

[trys]

Cross posting by paulca on the LED current issue:

https://www.eevblog.com/forum/beginners/driving-leds-from-logic-circuits/