Is Digilent breadboard has high quality? - Page 1
Forum section: electronics / general

author: quaternion00
author_rank: Contributor
timestamp: April 04, 2019, 11:59:14 am
content: Hi Guys. I am planning to buy a digilent breadboard . Is the quality good? Thanks

author: tggzzz
author_rank: Super Contributor
timestamp: April 04, 2019, 01:08:54 pm
content: If you mean a solderless breadboard then, as withanysolderless breadboard, be prepared to spend as much time debugging the breadboard as your circuit.From long experience, I refuse to even look at any circuit that has been put together on a solderless breadboard; I regard them as the work of the devilBetter to use manhattan and rat's nest construction techniques.

author: quaternion00
author_rank: Contributor
timestamp: April 04, 2019, 11:31:33 pm
content: Thanks for the reply. Sure, rat's nest beats breadboard. I mean the quality of digilent solderless breadboard compared to other solderless breadboards.

author: ebclr
author_rank: Super Contributor
timestamp: April 05, 2019, 07:46:58 am
content: It's good quality, but isn't premium one?

author: tggzzz
author_rank: Super Contributor
timestamp: April 05, 2019, 08:04:28 am
content: Quote from: quaternion00 on April 04, 2019, 11:31:33 pmI cannot make any useful comment about the relative merits of two "unhelpful" products.As for "rats nest", have a look at Appendix F of this justly famous application notehttp://cds.linear.com/docs/en/application-note/an47fa.pdf"High Speed Amplifier Techniques, A Designer’s Companion for Wideband Circuitry".Don't fall into the trap of thinking that "my digital signal is only 1kHz, and that is only a low frequency" - because that is completely false and it could have significant energy above 1GHz.

author: Richard Crowley
author_rank: Super Contributor
timestamp: April 05, 2019, 12:13:07 pm
content: If I wanted something reliable I would only buy 3MWho knows what "Digilent" is? Is it just another random brand-name applied to some random product from an anonymous factory in China?

author: ebastler
author_rank: Super Contributor
timestamp: April 05, 2019, 12:40:47 pm
content: Quote from: Richard Crowley on April 05, 2019, 12:13:07 pmAnd even the 3Ms are not perfect -- if we assume that "Assembly Specialist" is their OEM and sells the same quality under their own name:https://www.eevblog.com/forum/chat/3m-breadboards-for-cheap/

author: Hemi345
author_rank: Contributor
timestamp: April 05, 2019, 03:47:40 pm
content: I ordered some Digilent formed jumper wires for breadboard work from Mouser (LINK) and what I got was some generic product without a Digilent logo on them anywhere. I wouldn't put much weight in the Digilent name but rather go on recommendations for something else folks have used and like.

author: NorthGuy
author_rank: Super Contributor
timestamp: April 06, 2019, 01:49:15 am
content: Breadboards are very inconsistent. You can buy ten of them from the same source and all of them might be of different quality. I buy them mostly from China. The ones I bought in Canada are probably somewhat better, but not dramatically. The difference in prices is not dramatic neither. If you want to get the absolutely best breadboard, buy several from different places and pick up the best. Otherwise, I wouldn't worry much and would buy what fits.If I want a big one, I buy a plastic clipboard and glue standard breadboard pieces onto it - they're self-adhesive on the bottom. Works great.

author: tggzzz
author_rank: Super Contributor
timestamp: April 06, 2019, 08:02:20 am
content: Quote from: NorthGuy on April 06, 2019, 01:49:15 amI don't disagree with your observations, but my conclusion is different: don't use solderless breadboards, do use better techniques that are used by experienced people. Manhattan and rats nest both work predictably.

author: NorthGuy
author_rank: Super Contributor
timestamp: April 07, 2019, 04:37:19 pm
content: Quote from: tggzzz on April 06, 2019, 08:02:20 amNothing is as fast to build circuits as solderless breadboards. You can build a test circuit in minutes. They're also very easy to change, say to try different resistor values, different configurations etc. Once done, you just pull everything off and you can reuse it again. And last, but not least, they don't produce any fumes.

author: frogg
author_rank: Regular Contributor
timestamp: April 07, 2019, 06:24:16 pm
content: I love solderless breadboards. I don't think I could build anything without them.Not sure I understand the hate, but then again, you know what they say about opinions.As for digilent vs any other brand - I use four cheap-o no-name brand Amazon specials and all have worked fine for me. These aren't gigabit ethernet controllers. They're just pieces of plastic with some metal bits inside. YMMV.

author: tggzzz
author_rank: Super Contributor
timestamp: April 07, 2019, 07:00:35 pm
content: Quote from: frogg on April 07, 2019, 06:24:16 pmNot hate, merely a refusal to waste my life when there are cheaperand betteralternatives.QuoteNope. They are capacitors and the interconnecting wires are inductors, and the connections are variable non-linear resistors. Any of those "parasitic" elements can be significant in circuits that beginners are likely to build.

author: chickenHeadKnob
author_rank: Super Contributor
timestamp: April 08, 2019, 07:05:45 am
content: Quote from: NorthGuy on April 07, 2019, 04:37:19 pmThere is a very non-linear knee in terms of total effort when prototyping with breadboards. Prototypes with less than 5 components say, or characterizing/testing a single through hole component then the breadboard wins handsdown. Once a certain circuit complexity is reached, and particularly if you fuss with part placement and beauty wiring, then breadboards fall behind. Those folks building a multi breadboard ttl monstrositys with a rats nest of wires are crazy masochists.

author: tooki
author_rank: Super Contributor
timestamp: April 08, 2019, 06:27:56 pm
content: Quote from: tggzzz on April 07, 2019, 07:00:35 pmHow is soldering things cheaper than a breadboard, where you just unplug the components for later reuse?Quote from: tggzzz on April 07, 2019, 07:00:35 pmJust what do you think beginners begin with?!? Like... we start with lighting LEDs and making buzzers out of relays. Circuits where parasitics become an issue come along... later.

author: tggzzz
author_rank: Super Contributor
timestamp: April 08, 2019, 06:42:25 pm
content: Quote from: tooki on April 08, 2019, 06:27:56 pmCheaper in money: no breadboard. Cheaper in time: no debugging the breadboard.As for "unplug for later reuse" - just unsolder for later reuse. That's worked for me for 45 years, and I still got some of those components to prove itQuoteLook at photos of what people use breadboards for: far more than LEDs and buzzers.Yes, solderless breadboards aren't too bad for an LED plus resistor (bad connections notwithstanding!), but they are no better than manhattan/rats nest. But when the LED is one of the tricolour LEDs controlled by a micro - you aren't in the realm of simple circuits anymore.Yes, of course, with skill and experience to recognise and avoid traps, you can use solderless breadboards for complex circuits. You can also travel to India on a bicycle.But beginners don't have that skill and experience.

author: tooki
author_rank: Super Contributor
timestamp: April 08, 2019, 07:07:31 pm
content: No, they don’t. But a breadboard makes it a lot easier and faster to gain it. And there’s a lot to be said for instant gratification, in that quick experimentation is rewarding and engaging. Soldering takes a LOT longer.

author: tggzzz
author_rank: Super Contributor
timestamp: April 08, 2019, 07:19:41 pm
content: Quote from: tooki on April 08, 2019, 07:07:31 pmYou can also get instant disillusionment, when you don't notice your one transistor amplifier hooting at 100MHz, or when trying to debug pattern-sensitive glitches in digital circuits.The soldering is a small part of the time, when you include the time spent getting all the components and equipment in place, measuring, thinking, debugging.

author: tooki
author_rank: Super Contributor
timestamp: April 08, 2019, 10:01:37 pm
content: Again... what you’re describing isn’t really true beginner stuff, man...

author: tggzzz
author_rank: Super Contributor
timestamp: April 08, 2019, 10:09:02 pm
content: Quote from: tooki on April 08, 2019, 10:01:37 pmWhat? A one transistor amplifier isn't beginner stuff?Or is this a "there's no such thing as a true Scotsman" argument?

author: NorthGuy
author_rank: Super Contributor
timestamp: April 08, 2019, 10:54:59 pm
content: Quote from: tggzzz on April 08, 2019, 07:19:41 pmNot looking too far, just this morning I was working with an MCU. At some point, I decided to swap it for a different MCU and see what happens. It took me 10 seconds to swap them on my breadboard, then 10 seconds to swap back. If I had to re-solder, I'd have to remove the MCU with hot air, then clean, then solder a new one in its place, then wait until it cools down, then clean again, perhaps. It was SSOP-28, so it would probably take me 15 minutes to replace, then 15 minutes to replace back. 30 minutes for re-soldering compared to 2 hours I spent working with the program is probably not very bad. But, if I had to spend half-an-hour soldering every time I need to change MCUs, it would be total nightmare. Not to mention that constantly heating parts with hot air would have damaged them in the end.

author: tggzzz
author_rank: Super Contributor
timestamp: April 08, 2019, 11:09:13 pm
content: Quote from: NorthGuy on April 08, 2019, 10:54:59 pmWhy did you decide to swap MCUs? Did you think it had been damaged?Using IC sockets is not unusual in the early stages of bringing up a design, especially when used with Manhattan or rats nest techniques.. It (usually) works because ICs are inserted a very limited number of times, and the pin dimensions are constant - unlike resistor, capacitor, hookup wire dimensions.But guess what happens in solderless breadboards!

author: tooki
author_rank: Super Contributor
timestamp: April 08, 2019, 11:29:10 pm
content: Quote from: tggzzz on April 08, 2019, 10:09:02 pmHonestly, no, that’s not what most beginners are gonna start with these days.

author: tggzzz
author_rank: Super Contributor
timestamp: April 08, 2019, 11:48:57 pm
content: Quote from: tooki on April 08, 2019, 11:29:10 pmSo it is a "there's no such thing as a true Scotsman" argument. Not enlightening.

author: tooki
author_rank: Super Contributor
timestamp: April 08, 2019, 11:56:37 pm
content: More enlightening than your fingers-in-the-ears-crying-LALALA refusal to acknowledge that breadboards do work for a great many situations, especially those beginners find themselves in, and that breadboards have many advantages over soldering for quickly lashing together a circuit.It’s, like... stop always coming to piss on everyone’s parade. You found a solution that works for you, great. But stop being, frankly, a bully about how soldering is always better and breadboards always suck and acting like everyone else is dumb for not believing you. You come and whine in every damned thread about breadboards. Just drop it, man, OK?! Let. It. Go.

author: tggzzz
author_rank: Super Contributor
timestamp: April 09, 2019, 12:08:01 am
content: I've outlined the basic theory for some of the problems in other threads; with digital circuits "ground bounce" is a good term for googling.Beginners make mistakes that are newto them, even though more experienced people know that they are going down an unwise path. To what extent should we allow people to make predictable mistakes, especially given that...I have seen many beginners frustrated by "failures" in their early circuits on solderless breadboards. When they rebuilt them using techniques with more predictable characteristics, the circuit "magically" started working.

author: tooki
author_rank: Super Contributor
timestamp: April 09, 2019, 12:17:49 am
content: Yes, but you remain obstinately oblivious to the advantages of breadboards, and to the fact that they work fine for most things a hobbyist does.It’s not as though soldered circuits work 100% of the time, either, and they don’t lend themselves to experimenting the way breadboards do.So you’re warning people away from breadboards because of pitfalls that they stand a small chance of running into (in a way that causes things to fail), even though this means depriving them of the learning benefits of experimenting quickly.

author: tooki
author_rank: Super Contributor
timestamp: April 09, 2019, 12:19:50 am
content: But my point is this: there’s nothing wrong with letting people know that breadboards have limitations. (Every tool does.) It’s your sanctimonious attitude that they suck, and only suck, and have no value whatsoever, which is both unhelpful and irritating.

author: NorthGuy
author_rank: Super Contributor
timestamp: April 09, 2019, 02:23:22 am
content: Quote from: tggzzz on April 08, 2019, 11:09:13 pmThe part didn't perform to the specs, so I swapped it to a different part which I had working before.However, it is immaterial. The point is that it's easy to swap things on the breadboard and I use this feature all the time.Quote from: tggzzz on April 08, 2019, 11:09:13 pmBreadboards sometimes have poor contact problems. For example, if you insert something thin, such as a lead of a watch crystal, the contact will not be very reliable. So, you simply build an adapter for such things. Thick things, such as adapter pins never have problems. Resistors and capacitors usually work well. Since you only need it for few hours (few days at most), it's not a big deal.However, SI is not that bad on the breadboards. There was a post recently, where a guy tried working with 1080p HDMI signals on a breadboard. This looked crazy to me, so I decided to investigate if I can pass fast digital signals through the breadboard. It actually worked much better than I ever thought. I even decided to write a blog about it:https://www.northguyblog.com/2019/02/19020901.htmhttps://www.northguyblog.com/2019/02/19020902.htm

author: tggzzz
author_rank: Super Contributor
timestamp: April 09, 2019, 07:27:52 am
content: Quote from: NorthGuy on April 09, 2019, 02:23:22 amDo you have an eye diagram? That's a traditional way of assessing signal integrity.Then repeat when there are other signals using the breadboard.

author: tooki
author_rank: Super Contributor
timestamp: April 09, 2019, 09:04:36 am
content: ::whoosh::That's the sound of the point whizzing over your head.

author: tggzzz
author_rank: Super Contributor
timestamp: April 09, 2019, 09:28:27 am
content: Quote from: tooki on April 09, 2019, 09:04:36 amNope.NorthGuy claims success, but IMNSHO only considers a trivial unrepresentative case and doesn'tshowexperimental results demonstrating adequate signal integrity.

author: tooki
author_rank: Super Contributor
timestamp: April 09, 2019, 09:38:43 am
content: Exactly. That comment is precisely why I say you missed the point: a breadboard isn't about signal integrity. It's about rapid experimentation.

author: tggzzz
author_rank: Super Contributor
timestamp: April 09, 2019, 10:33:38 am
content: Quote from: tooki on April 09, 2019, 09:38:43 amYou didn't makethatpoint; I quite reasonably assumed that you were pointing to NorthGuy's results as an indication that solderless breadboard were acceptable for modern digital signals.I prefer not to do experiments where the limitations of the experimental technique dominate any validity that might be inferred from the experimental results. For me, "I got lucky this time" is not an acceptable result!Other (obvious) points about NorthGuy's results w.r.t. beginners use of solderless breadboards are thatHDMI has low voltage swings, and they are differential / balancedmost solderless breadboards are used for normal voltage swings and are single-ended / unbalancedthose two are very different, especially with suboptimal parasiticsbeginners won't be using HDMI

author: NorthGuy
author_rank: Super Contributor
timestamp: April 09, 2019, 01:42:06 pm
content: Quote from: tggzzz on April 09, 2019, 10:33:38 amApparently, you haven't read it, because it uses single-ended 3.3V CMOS. Everything else is quite breadbordish too, such as long-legged resistors.Of course, analog eye diagram on PRBS data would be the best, but it would require a multi-GHz scope. And since the capacitance is only 5 pF, you would also need an active low-capacitance probe. I don't have that. So, I used an FPGA to do 12.5 GS/s digital ETS, which worked quite well to capture the results IMHO.If someone has adequate scope and probes and want to test it and present eye diagrams, I'll be happy to publish it.

author: ebastler
author_rank: Super Contributor
timestamp: April 09, 2019, 02:08:58 pm
content: I don't understand why this needs to be a matter of fundamental controversy.Personally, I do not like breadboards much. I have preconceptions against them which date back to my first ventures in electronics as a kid, and had not touched them for decades. I recently wanted to prototype a circuit (5 MHz 74HC series, plus some analog signals) where I expected a fair bit of back-and-forth in the circuit design. So I decided to give breadboards another try. Spent some $60 on a 3M (Assembly Specialist) breadboard and wires, but unfortunately found my preconceived notions confirmed:Not as easy to build and modify circuits as I would have liked. Contacts were too tight, forcing me to jam in wires with pliers much of the time.At the same time, external connections -- especially thin coax -- kept slipping out of the contacts, despite various attempts to secure them.Signal integrity at 5 MHz was already less than ideal, and I could not stop a fast comparator from oscillating. (Yes, I did add hysteresis, and soldered decoupling caps directly to its pins...)Hence, personally I am going back to soldering wires on perfboard (with a ground plane where needed). And I'm happy to share my experience about the above problems.But at the same time, I see that breadboards do lower the barrier of entry for beginners (who want to build blinking-LED circuits, attach some peripherals to an Arduino board, or the like), and can also be handy for more experienced amateurs (who know the limitations of breadboards). Hence, why not use them, within these limitations?No need to turn this into a religious debate, IMO.

author: tggzzz
author_rank: Super Contributor
timestamp: April 09, 2019, 03:20:36 pm
content: Quote from: ebastler on April 09, 2019, 02:08:58 pmYup, that mirrors my experience.My concern is that beginners get put offfor the wrong reasonswhen their circuits don't work, and that debugging solderless breadboards is a futile task.But yes, where solderless breadboards worksatisfactorially, use them - but recognise such situations are more limited than beginners can understand.My preference is to start with a groundplane and then, whereever I happen to need to make a connection between components, glue an island (i.e. a bit of a cut-up PCB) onto the ground plane.Examples (not mine), with and without an enclosure:And when building a system incrementally is desirable:

author: rdl
author_rank: Super Contributor
timestamp: April 09, 2019, 04:42:33 pm
content: I tried to find something wrong with a 3M breadboard and failed. They seem to be fine up to around 10 MHz or even higher. I've been using them for 30 years and have never had a bad connection. I have had a few broken wires hiding inside the insulation give me a headache, but that could happen for any build type.Here is a square wave before and after passing through about 17" of breadboard rails. The blue is the original.

author: 2N3055
author_rank: Super Contributor
timestamp: April 09, 2019, 05:13:51 pm
content: I newer use breadboards. They are fiddly, and it honestly takes as much time to just wire up something on perfboard and if you do it right than it is actually a working circuit and sometimes good enough to put in a box. If I fell a need to swap ICs I just put a socket in there...If I'm doing something sensitive or faster than solid plane PCB and Manhattan style..I also sometimes just wire it up in the air if something simple..

author: tggzzz
author_rank: Super Contributor
timestamp: April 09, 2019, 05:51:11 pm
content: Quote from: rdl on April 09, 2019, 04:42:33 pmWhy 10MHz when modern digital signals have significant energy in the UHF band, and many have energy above 1GHz?QuoteThat the easy example. Now do it with NEXT, FEXT, and ground bounce - and multiple signals.Google for those terms; I can't be bothered to reproduce them here.Alternatively, look at TAoE3 section 12.9.1, including but not limited to "And if the chip happened to be an octal buffer, with simultaneous transitions on a half dozen outputs, the ground spike would be over a volt; refer back to Figure 10.99.".I can assure you that a 1V ground spikewillupset your circuit's operation.

author: tooki
author_rank: Super Contributor
timestamp: April 09, 2019, 06:23:53 pm
content: Quote from: tggzzz on April 09, 2019, 10:33:38 amI have emphasized this point in one reply after another. You just aren't getting it.So no, I didn't make any claims about acceptability for "modern" digital signals. But it boggles the mind that you think eye diagrams for HDMI is something beginners would be dealing with at all.

author: tggzzz
author_rank: Super Contributor
timestamp: April 09, 2019, 06:32:31 pm
content: Quote from: tooki on April 09, 2019, 06:23:53 pmYet another strawman argument. Beginners are unlikely to be fiddling with HDMI.But if you don't think beginners (try to) use solderless breadboards for modern digital signals, then (a) you are mistaken and (b) what do you think they use them for and (c) what you think they shouldn't use them for?

author: tooki
author_rank: Super Contributor
timestamp: April 09, 2019, 06:36:10 pm
content: Straw man? YOU are the one who asked for an eye diagram and performance characterization...As for what I think beginners do -- I stated my views long ago. Plus, I've said this before: learning the limitations of your tools and techniques is a key part of learning any skill.You're extremely annoying to "discuss" with since you ignore what I say, then ask antagonistic questionsthe answers to which I've already stated.I'll repeat: Get off your damned high horse and accept that breadboards DO have a place in many people's labs.

author: tggzzz
author_rank: Super Contributor
timestamp: April 09, 2019, 06:55:44 pm
content: Quote from: tooki on April 09, 2019, 06:36:10 pmA strawman argument is where one person argues about a point that the other person is not making; when done deliberately it is used to deflect an argument. While you are doing the former, I do not believe you do it for that latter reason.We seem to be unable to have a constant conversation where one person makes their point clear to the other. There is no reason to believe that will change. I suggest we drop this discussion.

author: tooki
author_rank: Super Contributor
timestamp: April 09, 2019, 06:59:59 pm
content: I've made my position, and my objections to your position, crystal clear. YOU are the one who keeps arguing things I didn't say, and dodging my point over and over. At no point did I engage in straw man argument with you. You only perceive it that way because of your inability to actually read what I write.

author: tggzzz
author_rank: Super Contributor
timestamp: April 09, 2019, 07:14:21 pm
content: Quote from: tooki on April 09, 2019, 06:59:59 pmMirror.This conversation serves no purpose.

author: NorthGuy
author_rank: Super Contributor
timestamp: April 09, 2019, 07:15:21 pm
content: Quote from: tggzzz on April 09, 2019, 05:51:11 pmCrosstalk shouldn't be a big problem with breadboards. It is basically a matter of proximity. The worst case is when you lay long traces too close together on PCB (which may be hard to avoid when fanning out BGAs for example). The wires on breadboards are typically much further apart, so crosstalk should be less of a problem.Not sure why you think that breadboards should exacerbate ground bounces.

author: tggzzz
author_rank: Super Contributor
timestamp: April 09, 2019, 08:05:51 pm
content: Quote from: NorthGuy on April 09, 2019, 07:15:21 pmThe inductance of the wires used to connect to the "gnd" and Vcc. See the reference I gave in TAoE3; it isn't a case of my thinking it, it is physics.

author: NorthGuy
author_rank: Super Contributor
timestamp: April 09, 2019, 08:52:01 pm
content: Quote from: tggzzz on April 09, 2019, 08:05:51 pmHow the inductance of wires in breadboards is different from the inductance of wires in any other setting? Why can't you install bulk/bypass capacitors on the breadboard as needed?

author: tggzzz
author_rank: Super Contributor
timestamp: April 09, 2019, 09:21:29 pm
content: Quote from: NorthGuy on April 09, 2019, 08:52:01 pmThe wires are longer on solderless breadboards, so the inductance is higher.Do the arithmetic to see the consequences!Read the references I gave, or find the information from many other sources. I was taught all the necessary physics at school (i.e. before university), so it isn't difficult. The only "magic" number you need to keep in mind is that 1mm of wire is about 1nH inductance.Yes, lead inductance was a problem back in the 80s,and it has only got worse. Back then amelioration techniques included:or the datasheet athttp://www.farnell.com/datasheets/22715.pdfOr for a quick outline seehttps://www.eevblog.com/forum/beginners/simple-cheap-1hz-oscillator-low-accuracy-fine/msg1293248/#msg1293248

author: NorthGuy
author_rank: Super Contributor
timestamp: April 09, 2019, 09:38:24 pm
content: Quote from: tggzzz on April 09, 2019, 09:21:29 pmI don't think they're too long to cause any significant problem. Also, this is partly compensated by the parasitic capacitance. I worked a lot with breadboards and I've never encountered the problem. At any rate, if you do experience the problem, why can't you simply increase the number or value of bypass capacitors?

author: tggzzz
author_rank: Super Contributor
timestamp: April 09, 2019, 09:56:35 pm
content: Quote from: NorthGuy on April 09, 2019, 09:38:24 pmThat is so wrong on so many levels, I don't know where to begin.What's the first phenomenon you (should)think of if you have an inductor and a capacitor? What happens when you "hit" it with a step change in voltage or current?Look, if you can't be bothered to read the references I've given, then you aren't going to learn no matter how much of my time I spend trying to enlighten you.

author: NorthGuy
author_rank: Super Contributor
timestamp: April 09, 2019, 10:44:26 pm
content: Quote from: tggzzz on April 09, 2019, 09:56:35 pmBegin with your brain. Try to think a little. Crunch some numbers. Estimate the switching current. Calculate what wire inductance you need to produce significant voltage drops. Calculate how long a wire you need to cause a problem. Calculate how this is all affected by bypass capacitors you may install. Perhaps do some real life measurements to check your numbers. It's not a rocket science, you know. Then perhaps you'll see that you're just making an elephant out of the fly trying to blow the effect out of proportions.

author: 2N3055
author_rank: Super Contributor
timestamp: April 09, 2019, 10:56:41 pm
content: It's not voltage drops that are your problem. That whole thing is a resonant circuit that rings like crazy.. If you take DIP meter close to it will react. You could design RF oscillator with a FET few resistor and protoboard as a resonant tank..

author: tggzzz
author_rank: Super Contributor
timestamp: April 09, 2019, 11:04:07 pm
content: Quote from: NorthGuy on April 09, 2019, 10:44:26 pmGo on then - do it yourself. State the equations and assumptions and plug in the numbers. Prove I'm wrong. Write it up, you will have made your name and people will flock to your door, and you will be able to charge outrageous consulting fees. Seriously.For bonus points, indicate clearly why people with just a little experience like Winfield Hill (one of the authors of The Art Of Electronics that I referred to) have erroneous calculations and measurements. Or Howard Johnson. Or the device manufacturers.Hint1: tell us what do you thinkdoeshappen with an LC circuit?Hint2: inductors don't always "produce significant voltagedrops"Hint3: here's part of the reference I gave and you have ignored. Note that the PCB conditions are farbetterthan you could find on a solderless breadboard.

author: NorthGuy
author_rank: Super Contributor
timestamp: April 10, 2019, 01:23:59 am
content: Quote from: tggzzz on April 09, 2019, 11:04:07 pmI did write a blog about signals and breadboards, but you haven't even read it. I guess if I write about ground bounces you won't read it neitherQuote from: tggzzz on April 09, 2019, 11:04:07 pmIt is quite a bit in my blog on what I think happens in LC circuits on breadboards, with models, diagrams etc. It's not too late. You can click the link and read it.Quote from: tggzzz on April 09, 2019, 11:04:07 pmThat's an interesting graph. It is taken from 1988 TI application note ("Advanced CMOS logicDesigner's Handbook"), where they discuss the pin location DIP packages for their new HC series. They decided to relocate the power pins to the center of the chip. The picture above is the measurements with DIP package having power pins on the sides. When they have put the power pins into the middle, the effect has been alleviated and voltage spike became negligible.TI certainly wanted to exaggerate the effect to show the advantages of their clever innovative pin placement. They drive 7 50 pF loads. The is equivalent of suddenly connecting 350 pF capacitor to the power rail. Voltage sagged 2V. Today, if this happened to me, I would say that it's either a bad power supply or inadequate bulk/bypass capacitors. Cannot relate to what it would mean in 1988, but anyway, the voltage sagged 2V.Sane people don't drive capacitive loads directly. It's a good idea to add a series resistor, which limits current and completely eliminates the inrush effect. Thus, the effect of such magnitude cannot be observed in real circuits. This has nothing to do with breadboards, BTW.Quote from: tggzzz on April 09, 2019, 11:04:07 pmIn this particular case, the extra inductance of the signal wires would help. TI had the capacitive loads very close. If there was a foot of wire between the driver and the 50 pF load, none of this would happen. The inductance of the wire would limit the rate of current rise thus eliminating the magnitude of the inrush current. No way you can achieve super fast rise times when driving through long wires. Thus, there wouldn't be any inrush current in the first place.Not only that. You should expect all the problems caused by too sharp driving to be alleviated by wire inductance in the breadboards. It simply doesn't have enough bandwidth to pass through very sharp pulses. When I was writing my blog, I wanted to find reasonable values of inductance and capacitance which would cause high frequency (500 MHz or so) oscillations, and I failed. I still published the picture of what I wanted to achieve, but the capacitance and inductance I used to model it were out of the range of what can be found in breadboards.

author: tggzzz
author_rank: Super Contributor
timestamp: April 10, 2019, 07:40:41 am
content: Quote from: NorthGuy on April 10, 2019, 01:23:59 amDampedinductance in the right place can help, e.g. ferrite beads.Undamped oscillation rarely helps in digital circuits. In signal wires it causes excess current in clamp diodes, which can upset circuits.Inductance in the ground leadneverhelps.I fail to see what is diffiicult about getting VHF/UHF oscillation. A 6" wire (i.e. 150nH) and 15pF (i.e. 3 gate loads) oscillates at ~100MHz. That'seasyto demonstrate and is a problem even with well constructed circuits: all you have to do is use a typical *10 probe, and the probe itself resonates! Hence the benefit of short/zero length ground leads and (expensive) low capacitance probes. Alternatively you could just look at some of the simulations in your blog!Modelling can only be as useful as the accuracy of the model and the type of the analysis. Your blog, fig 10, isunrepresentativeof a solderless breadboard circuit constructed by abeginner:a typical R1 "drive" resistance can be as low as 7ohms, not 100ohmsyour R2 is unreasonably low; 10kohms would be less unrepresentativethere's no ground lead inductanceNo beginner would insert extra resistors to increase R1 and decrease R2. Nobody with experience would bother either; they would just construct it properly in the first place.If you want to model an unrealistically good beginner's circuit, then you should also model the parasitics associated with the extra resistors and their wires required merely because solderless breadboard is being used.Your blog only indicates indirect measurements at disrete frequencies. Real digital signals have a spectrum that is more complex than that. Such complexity is best modelled anaytically in the frequency domain. That's easy to do with, say, LTSpice. If you can't do frequency domain measurements, then eye-diagrams are an excellent direct measurement technique.I suggest you re-analyse your model in the frequency domain with a source resistance of 7ohms or so, a receiver resistance of 10kohms, and a ground lead inductance of say 50nH.

author: NorthGuy
author_rank: Super Contributor
timestamp: April 10, 2019, 03:10:11 pm
content: Quote from: tggzzz on April 10, 2019, 07:40:41 amI can assure you, the same laws of physics exist on every breadboard in the world, whether it's used by a beginner or by anybody else. It is these laws we're interested in. It is immaterial what someone would or wouldn't do.Quote from: tggzzz on April 10, 2019, 07:40:41 amIt wasn't the goal to build an exhaustive model of the breadboard. The goal was merely to test if you can use high speed digital signals on a breadboard.If someone approaches an engineer and says - look I want to prototype a 100 MHz digital circuit on breadboard, and I need a 2 GSa/s logic analyzer for that - in 90% of the cases the engineer would say that this is a crazy idea, 100 MHz is too fast and 2 GSa/s is a huge overkill. So, I decided to check by myself and the result is quite decisive:- Yes you can test 100 MHz on breadboards. 200 MHz might be Ok too.- 2 GSa/s logic analyzer is quite adequate in this situation.Quote from: tggzzz on April 10, 2019, 07:40:41 amDigital sampling. That's the whole point. You're not really interested in details of frequency content of your digital signals. The only thing that matters is how it's sampled. Be it a perfect square wave or something which more resembles sine wave, or something with huge harmonic distortions, none of this matters if you get the digital sampling correctly.Quote from: tggzzz on April 10, 2019, 07:40:41 amMy model, albeit simple, gave me the answers I was looking for, and they matched the real experiments well enough. I don't think there's a need for further modeling.However, if would be interesting to look at real-world eye diagrams, perhaps some frequency domain analyses with a network analyzer might be interesting. It would be especially interesting to analyze failure modes. But, like I said, I don't have adequate scope/probes. If you do, make the experiments. If you do it reasonably well, I'll be happy to publish it.As to the resistor values - you use what works (which is something not too far from critical damping or slightly over-damped), not what's popular.

author: tggzzz
author_rank: Super Contributor
timestamp: April 10, 2019, 04:24:38 pm
content: I've reinserted therelevant contextthat you snipped for some reason or other, since it is beneficial in understanding why I made that statement.Quote from: NorthGuy on April 10, 2019, 03:10:11 pmI don't think you are adding to the sum of human knowledge by stating "the same laws of physics exist on every breadboard".This thread is largely about what beginners would and would't do, if you go back and read the thread.QuoteUnfortunately that isn't correct: the modelling result isn't as decisive as you might like to believe, for the reasons I gave. Basicallyyou have only done a test at a few frequencies, not at all the frequencies present in a digital signalthe tests are't representative of the majority of problems found in these situationsQuoteFirstly, they aren't digital signals, they are analogue signals that are being interpreted by the receiver as digital signals.Secondly, referring to "harmonic distortions" leads me to doubt you understand the spectrum of digital signals. That is congruent with your not using frequency domain modeling.More importantly, if the eye is closed due to distortions in the channel, then there is no correct sampling instant!QuoteIt is easy to create models to give you the answers you seek. Boring.It is important to use models to give you insight into phenomena that you might need to understand but don't realise are an issue in the first place. In this case, inductance in the ground lead is important.QuoteNot having the experimental equipment is one reason why modelling is important - provided your model is up to the task (which isn't easy and requires experience).If an implementation is functioning as designed but doesn't cope with the real world, I don't think "failure modes" is the right term. "Inadequate design" would be closer to the mark.QuoteYou are avoiding the point that people don't put source and termination resistors in solderless breadboard circuits.Beginners don't realise they are necessary.Those that understand why they are necessary wouldn't use solderless breadboards in the first place!

author: NorthGuy
author_rank: Super Contributor
timestamp: April 10, 2019, 05:23:20 pm
content: Quote from: tggzzz on April 10, 2019, 04:24:38 pmThis is, how do you call it, "strawman argument". I made no claims on how people use breadboards, I am not interested in the usage patterns at all. I'm arguing about the physical things happening in breadboard circuits. Resistors are irrelevant here. 100 MHz signals worked without resistors in all cases. 200 MHz signals may require resistors. If you were using PCB, I'm sure you would terminate your signals as needed. Why is it wrong to use termination on breadboards?My point is very simple. I did some modeling which suggested that high speed signals would work, then I run the tests, and they worked. The bottom line is that if I need to run some tests with 100 MHz digital signals, I may consider doing this on a breadboard, which I would never do before. That's a benefit to me, and perhaps to other people who may decide likewise. End of the story.

author: ebastler
author_rank: Super Contributor
timestamp: April 10, 2019, 05:34:15 pm
content: Quote from: NorthGuy on April 10, 2019, 05:23:20 pmI sure hope so. Alas, I lack the faith...

author: Oak
author_rank: Newbie
timestamp: December 22, 2021, 04:46:01 pm
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