Somebody goofed up - Page 1
Forum section: electronics / general

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: September 05, 2019, 06:31:16 pm
content: Or not? It's in a very popular dev board. Suddenly its magic smoke escaped today...

author: bd139
author_rank: Super Contributor
timestamp: September 05, 2019, 06:35:06 pm
content: That sort of shit is why humans invented QA

author: fourfathom
author_rank: Super Contributor
timestamp: September 05, 2019, 06:47:02 pm
content: What is "LS1"? It looks like the problem is there, and not the upside-down transistor. I've seen people deliberately swap emitter and collector in order to get a slightly smaller saturation voltage (less gain, though). That by itself shouldn't cause any smoke.

author: Gyro
author_rank: Super Contributor
timestamp: September 05, 2019, 06:52:18 pm
content: Quote from: fourfathom on September 05, 2019, 06:47:02 pmIt looks like a magnetic audio sounder (it would have to provide DC continuity for the circuit to 'work'). The GPIO stuck high would probably do it.

author: bd139
author_rank: Super Contributor
timestamp: September 05, 2019, 07:04:10 pm
content: Quote from: fourfathom on September 05, 2019, 06:47:02 pmFair point. Gain is close to unity doing this so I'm not sure what the deal is. Perhaps it was in the linear region too. Pd off the scale.

author: magic
author_rank: Super Contributor
timestamp: September 05, 2019, 07:36:29 pm
content: If LS1 is something inductive it may easily avalanche the BE junction. People say a lot of bad things about avalanching BE junctions, I don't know how true they are

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: September 05, 2019, 07:54:54 pm
content: That NPN has become a short circuit, and as the thing is powered by a LiPo, the LiPo went smoking hot as well. I was trying different "beeps" to find out which one seemed louder/could be heard from farther away, gpio 26 was outputting a square wave @2.8 kHz when it happened...

author: thm_w
author_rank: Super Contributor
timestamp: September 05, 2019, 09:30:50 pm
content: DET402-G-1 attached, seems like the top cover is missing in OPs photo for some reason.And it does appear to be coil based, which would give a voltage spike.

author: rsjsouza
author_rank: Super Contributor
timestamp: September 05, 2019, 09:36:59 pm
content: Quote from: fourfathom on September 05, 2019, 06:47:02 pmA.k.a. common collector configuration.https://en.wikipedia.org/wiki/Common_collector

author: Circlotron
author_rank: Super Contributor
timestamp: September 05, 2019, 09:52:18 pm
content: Quote from: rsjsouza on September 05, 2019, 09:36:59 pmIf that’s the case, the power supply rails are reverse polarity.

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: September 05, 2019, 10:00:18 pm
content: Now that I think about it, I was flipping gpio every 350 µs, but that's not 2.8 kHz, it's 1.4 kHz. Since it's close to the resonance frequency of the DET402-G-1, could that have accelerated the unfortunate events?Code:: invert 0= if 1 else 0 then ;26 output: speaker: beepbeginspeaker speaker digr invert digw350 delay.uskey?untilspeaker 0 digw;

author: fourfathom
author_rank: Super Contributor
timestamp: September 05, 2019, 10:20:37 pm
content: Quote from: rsjsouza on September 05, 2019, 09:36:59 pmNot the same thing at all. Look again.

author: fourfathom
author_rank: Super Contributor
timestamp: September 05, 2019, 10:26:00 pm
content: Quote from: GeorgeOfTheJungle on September 05, 2019, 10:00:18 pm

author: SiliconWizard
author_rank: Super Contributor
timestamp: September 05, 2019, 10:30:43 pm
content: Oh well, do NPNs not have a right to be used inverted? Maybe some of them just feel "right" when used this way.

author: Kjelt
author_rank: Super Contributor
timestamp: September 05, 2019, 10:43:06 pm
content: Found the culprit in a different topic, she is the one that goofed uphttps://www.eevblog.com/forum/chat/gender-politics-has-now-infected-engineering-as-well/msg2667105/#msg2667105

author: SiliconWizard
author_rank: Super Contributor
timestamp: September 05, 2019, 10:47:02 pm
content: Quote from: Kjelt on September 05, 2019, 10:43:06 pmOh, I was not that far away then!

author: Ian.M
author_rank: Super Contributor
timestamp: September 05, 2019, 10:57:33 pm
content: IMHO its just a shitty design. If the transistor can't stand the max. current the sounder will pass @3.3V DC, they should have included a series resistor to limit the continuous current, possibly with a capacitor across it so you can get more drive when you pulse it. Also relying on reverse E-B zenering to turn the transistor on and clamp the back-EMF from the inductive load is just plain nasty.Alternatively they could have used a NPN+ PNP pair as a complimentary emitter follower, and a capacitor in series with the sounder - that's particularly robust because the non-active transistor will turn on enough to clamp the output if the load tries to drags it more than one Vbe outside the rails.

author: Sal Ammoniac
author_rank: Super Contributor
timestamp: September 05, 2019, 11:09:30 pm
content: Quote from: GeorgeOfTheJungle on September 05, 2019, 10:00:18 pmThere's your problem right there... Forth killed it. When the transistor saw it was being controlled by Forth, it did the only thing it could: commit suicide.

author: SiliconWizard
author_rank: Super Contributor
timestamp: September 05, 2019, 11:14:42 pm
content: There's reason in controlling an inverted transistor with an inverted language.

author: bd139
author_rank: Super Contributor
timestamp: September 06, 2019, 07:22:27 am
content: Quote from: Sal Ammoniac on September 05, 2019, 11:09:30 pmI actually just spilled coffee everywhere laughing at that

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: September 06, 2019, 07:30:21 am
content: Where's techman-001 ?

author: techman-001
author_rank: Frequent Contributor
timestamp: October 09, 2019, 09:03:31 am
content: Quote from: GeorgeOfTheJungle on September 06, 2019, 07:30:21 amJust stumbling across this topic right nowI think the inductive load and possibly the on/off frequency killed the transistor being used in "uncommon emitter mode".I think it may have also killed it if it was in common emitter mode.George is that Forth your "ATlast" ?

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: October 09, 2019, 09:12:16 am
content: Quote from: techman-001 on October 09, 2019, 09:03:31 amYes it is. The only other Forth I've ever had (and used) is one for the Apple II that John Drapper (a.k.a. Captain Crunch) in person sold me at the NCC in NYC in 1979.Edit:But that code above won't run in yours because I've added some words to mine: e.g. delay.us (delayMicroseconds), digr (digitalRead) and digw IIANM.

author: techman-001
author_rank: Frequent Contributor
timestamp: October 09, 2019, 10:39:34 am
content: Quote from: GeorgeOfTheJungle on October 09, 2019, 09:12:16 amJust having bought a Apple II from Captain Crunch makes you alegend!Yes I could see your extra Words.Forth people never copy each others code, for one we don't need to, and 2) our systems are all different.Your code is:: invert 0= if 1 else 0 then ;26 output: speaker: beepbeginspeaker speaker digr invert digw350 delay.uskey?untilspeaker 0 digw;Mine would be something like:( not inverts all bits): beepbeginspeaker dup digr not digw350 delay.uskey?untilspeaker 0 digw;

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: October 09, 2019, 10:54:03 am
content: Quote from: techman-001 on October 09, 2019, 10:39:34 amBought him the Forth not the Apple II!Quote"not"? Hahaha. Thanks! I'm a beginner, my Forth-fu betters every day, albeit slowly.

author: techman-001
author_rank: Frequent Contributor
timestamp: October 09, 2019, 11:35:32 am
content: Quote from: GeorgeOfTheJungle on October 09, 2019, 10:54:03 amBuying anything from Captain Crunch makes you a legendI'm a Forth beginner also. Forth is easy to learn, but harder to master."not" is part of my default dictionary, but ": invert 0= if 1 else 0 then ; " works perfectly. I mention it because Atlast has "not" in its default dictionary alsoOddly the Word "words" only lists part of the actual Wordlist, this is unusual however the "Atlast Primitives: Alphabetical Reference" in the 64 bit html has a complete list of Words, and it is extensive! The Word "WORDSUNUSED" does list all unused Words. These methods are foreign to me, but certainly not wrong, just different to what I'm used to.To check if a "not" Word is available: the number returned is the memory location of the Word itself-> ' not .34378764744 -> wordsThis fails because there is no such word as xanadu-> ' xanadu .'XANADU' undefinedAtlast includes these cool packages:The REAL package. Enables floating point operations. Primitives: (FLIT), F+, F-, F*, F/, FMIN, FMAX, FNEGATE, FABS, F=, F<>, F>, F<, F>=, F<=, F., FLOAT, FIX.The SHORTCUTA package. Enables shortcut integer arithmetic operations. Primitives: 1+, 2+, 1-, 2-, 2*, 2/.The SHORTCUTC package. Enables shortcut integer comparison operations. Primitives: 0=, 0<>, 0<, 0>.The STRING package. Enables string operations. Primitives: (STRLIT), STRING, STRCPY, S!, STRCAT, S+, STRLEN, STRCMP, STRCHAR, SUBSTR, COMPARE, STRFORM, STRINT, STRREAL. If the REAL package is also enabled, the FSTRFORM primitive is available, as well.The SYSTEM package. Enables submission of commands in strings to the operating system for execution. This package may be enabled only if the implementation of C used to build Atlast provides the system() function. Primitives: SYSTEM.The TRACE package. Enables runtime word execution trace. Primitives: TRACE.The WALKBACK package. Enables the walkback through nested invocation of words when an error is detected at runtime. Primitives: WALKBACK.The WORDSUSED package. Enables the collection of information on which words are used and not used by a program, and the primitives that list words used and words not used. This facility allows you to determine, in the development phase of an Atlast application, which packages are needed and which can be safely dispensed with. Primitives: WORDSUSED, WORDSUNUSED.I'm very impressed, I may consider using Atlast on this PC for some X86 programs.

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: October 09, 2019, 12:47:26 pm
content: Quote from: techman-001 on October 09, 2019, 11:35:32 amI think I noticed that and fixed it. Not sure if the fix is in the gitlab repo or not, though. It's an easy fix anyway.QuoteLOL. Good! I'm glad to know. This man is (or was?) the owner of AutoDesk. He wrote most of AutoCAD if I'm not mistaken.

author: PCB.Wiz
author_rank: Super Contributor
timestamp: October 09, 2019, 10:18:21 pm
content: Quote from: GeorgeOfTheJungle on September 05, 2019, 06:31:16 pmReverse connect is not common, as already mentioned. It does work : it gives lower HFE, and lower VCE, but can give lower VCEsat(at low currents)Not usually seen when driving a power load.Did you check the actual device pinout, to verify it actually is wired up 'reversed' ?The posted link says 120mA, but does not mention the resistance or inductance.Did you scope the transistor & measure the resistance of DET402 ?With no flyback clamp diodes, the little npn is doing both the drive and the clamping.It's demise is trying to tell you, that's too much, on a continuous basis...

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: October 10, 2019, 08:07:24 am
content: Quote from: PCB.Wiz on October 09, 2019, 10:18:21 pmYes, it was connected as in the schematics.QuoteI haven't checked anything else other than its upside-down-ness.Wonder why they use these tiny fleas that are nowadays all over the place, lol. What's with a good old proven 2n3055 that would still be alive? Or even a bd139?Other than that, the thing is a beauty:Just delete the buzzer, because if you use it the thing catches fire! (LITERALLY)