Activity for Lundinâ€
| Type | On... | Excerpt | Status | Date |
|---|---|---|---|---|
| Comment | Post #287773 |
Any idea why they added R104 and R105? Looks very strange. That they are in parallel is probably just some Bill of Material optimization(?) but why limit the coil current way below the spec? (It's 30mA for this relay.) (more) |
— | over 1 year ago |
| Comment | Post #287689 |
If the accuracy isn't important, why not just pull a number like 1ppm out of a hat and be done with it? And there are numerous valid reasons why the accuracy would be important. For example you could just hook a MCU PWM output to a RC filter and there you go - it's a sine wave. (more) |
— | over 1 year ago |
| Comment | Post #287689 |
@#57886 As with everything-electronics, you need to specify a necessary accuracy (in frequency and amplitude both). There exist no electronic components without error margins and a specified accuracy. Just as in mechanics there are no exact lengths but only lengths with allowed tolerances. (more) |
— | over 1 year ago |
| Comment | Post #287646 |
@#52938 Yikes, you should never use autorouting for... pretty much any purpose, but certainly not for high speed communication lines. Olin's theory of crosstalk being the culprit sounds quite likely. Or in case of 2 layers, maybe ground problems. A picture of the PCB copper layers would be helpful. I... (more) |
— | over 1 year ago |
| Comment | Post #287554 |
On the first picture you trigger on ch1. On the second you also trigger on ch1, but on a different signal. Meaning that you are viewing that signal at different points in time. Since we have no idea what signal this is, it is hard to say anything else. Maybe there are 6 pulses at some point in time b... (more) |
— | over 1 year ago |
| Comment | Post #287480 |
"This is the GND where the shield/metallic enclosure should be connected through a low-impedance connection as well." This seems counter-intuitive. The sole purpose of a shield is to catch and conduct noise down to ground. So in case of external EMI, this would then route that EMI into the "clean gr... (more) |
— | over 1 year ago |
| Comment | Post #287400 |
@#52981 I never claimed that the CRT should be doing all these things for you. But it needs to provide a location where you can place such code. For example by exposing the reset vector in a separate file so that it can be changed by the application program without having to modify the CRT code itsel... (more) |
— | over 1 year ago |
| Comment | Post #287400 |
@#36396 Well in case of .data/.bss initialization, the compiler by default has to perform it because it claimed to be C standard compliant. Regardless if the user asked for it or not. And so they end up with a solution which is standard compliant but unlikely to be of use to any single user. Or in ca... (more) |
— | over 1 year ago |
| Comment | Post #287400 |
On classic microcontrollers you can often just "hack" the CRT by replacing the reset vector with a custom one, execute all critical code, then call the CRT and let it do its thing, and then the CRT eventually calls main(). (more) |
— | over 1 year ago |
| Comment | Post #287400 |
@#36396 Yeah sure but the normal use is: you wish to use the watchdog, you wish to use the clock quartz which you provided, you wish to enable LVD/brownout detect, you wish to set GPIO port directions and pull resistors etc etc. I once wrote a summary on how to do this correctly here: https://stackov... (more) |
— | over 1 year ago |
| Comment | Post #287400 |
In case of mid- to high-end MCUs that provide data cache, the `.data`/`.bss` initialization will get carried out much faster if done by the CRT than if done by individual application modules. This is simply because the MCU can utilize the cache much more efficiently if chewing to through a chunk of c... (more) |
— | over 1 year ago |
| Comment | Post #287400 |
It should be noted that in case of C++, default constructors of objects with static storage duration will also get called by the CRT, adding even more execution time to start-up. C++ has very intricate rules for initialization, especially past C++11, so the standard compliant start-up time in C++ mig... (more) |
— | over 1 year ago |
| Comment | Post #287359 |
Maybe we could do a list which is posted by one user but other trusted users can "sign up" as co-authors and only those approved are allowed to edit it? Then we can protect it from too many exotic additions. With the original author having the final say (and the possibility to carry out edit rollback... (more) |
— | over 1 year ago |
| Comment | Post #286964 |
Well, some hobbyist or school project is naturally a different story than professional electronics development. In general it is always nice to check what multiple vendors can offer. Some even have integrated MCU/RFIC in the same chip. (more) |
— | over 1 year ago |
| Comment | Post #286672 |
Indeed this doesn't really give a proper current loop unless Vdd is a current generator. But I had already delivered the system when the customer changed their mind completely. So we ended up doing a quick & dirty solution just converting voltage to current over a resistor, since the PLC was located ... (more) |
— | almost 2 years ago |
| Comment | Post #286595 |
The main problem that I'm having is that one direction of the semi-duplex transmission works worse than the other, for which there could be many reasons. In case the impedance turns weird, then I'd get standing wave phenomenon which might explain the loss of signal currently experienced. But as you s... (more) |
— | almost 2 years ago |
| Comment | Post #286595 |
Thanks for your reply. A bit more background info: this system was actually delivered some ten years ago and has been working somewhat ok given the tough environment and the questionable installation. Everything electrical is built into a large, proof cabinet with air condition temperature control. H... (more) |
— | almost 2 years ago |
| Comment | Post #286434 |
First of all, this is a simplified schematic of a voltage clamp IC SN47TVC3306, so it doesn't likely contain the whole story. I believe the double lines means these are so-called "pass transistors". https://en.wikipedia.org/wiki/Pass_transistor_logic. Basically for a voltage clamp to make sense there... (more) |
— | about 2 years ago |
| Comment | Post #286314 |
Either PLCs handle the current measurement internally or they require an external resistor. That's a specific and very narrow question. Most of my experience from PLC-like computers come from automotive ECUs in heavy machinery and they typically don't use external resistors, but then 4-20mA isn't nea... (more) |
— | about 2 years ago |
| Comment | Post #286179 |
Picking a MCU which can DMA the ADC reads might be a good idea. Modern ADC can easily sample > 1 MHz, the bottleneck is that without DMA, the CPU has to be fast enough to respond to that sample rate. Building such with old school interrupts is cumbersome, especially when the CPU has a lot of other th... (more) |
— | about 2 years ago |
| Comment | Post #286049 |
Since this is an electrical engineering site, questions regarding the design of a power supply are on-topic, questions regarding where to find/buy one are not. (more) |
— | about 2 years ago |
| Comment | Post #286035 |
PCB inside a metal enclosure, either aluminium or stainless steel. Enclosure grounded to chassis, antenna connector like BNC or TNC also grounded. The enclosure partially serves as ground plane for a 1/2 wave antenna. (more) |
— | about 2 years ago |
| Comment | Post #286035 |
This particular product is for an industrial/automotive application so telling someone to wear ESD protection is simply not going to work. The product isn't allowed to break from ESD or it will piss off the customers, regardless what's written down in terms of warrenty. And regardless, suppose there ... (more) |
— | about 2 years ago |
| Comment | Post #285889 |
@#53110 Or, since this has been discussed multiple times and always without concensus, there's no reason to believe that it will get consensus this time either. (more) |
— | over 2 years ago |
| Comment | Post #285919 |
https://www.onsemi.com/pub/Collateral/AND9093-D.PDF, explains this better than I could. Basically N-channel have two advantages: it has lower Rds(on) and it often has a gate-source voltage that allows it to be driven with positive logic voltages directly from a MCU pin. (more) |
— | over 2 years ago |
| Comment | Post #285913 |
@#36396 Again, we do know from SE because all _close votes_ are public there and it's a drama factory. (more) |
— | over 2 years ago |
| Comment | Post #285913 |
@#36396 Or far more likely because I was the first person who cast a _public_ close vote to a bad question. (more) |
— | over 2 years ago |
| Comment | Post #285889 |
This was discussed several times on the Codidact meta, example: https://meta.codidact.com/posts/278438. The whole network needs to have the same rules, so I think this discussion should be kept there. To have individual sites come up with individual voting rules will lead to anarchy. (more) |
— | over 2 years ago |
| Comment | Post #285878 |
All of this sounds like good ideas, I vote yes on all of your proposals. Based on the current site activity I think votes could easily be capped at 5 per day, perhaps even lower. We roughly get at most one new question per day currently. (more) |
— | over 2 years ago |
| Comment | Post #285858 |
So it seems that this would be like Papers but lower the bar of what's expected? Maybe "Articles" would be a good name? Since that implies something that might get printed in a journal but not necessarily a full scientific study, which is what I think of when I hear "Papers". (more) |
— | over 2 years ago |
| Comment | Post #285855 |
This kind of irregular voting in a short period of time would have set off an automatic protection mechanism on SE. I believe 3 down votes against the same user in a short amount of time would lead to moderators getting notified and a vote rollback kicking in, something like that - I don't know the d... (more) |
— | over 2 years ago |
| Comment | Post #285817 |
Thanks for the feedback. In this case the antenna connector is the standard horrible little U.FL, which is connected with coaxial to a bigger one grounded to chassis. The main ESD risk is when someone is connecting or removing the coax. It's quite easy to touch the center pin with ones fingers on a U... (more) |
— | over 2 years ago |
| Comment | Post #285721 |
@#53110 I have a specific problem which I thought was related to ESD. Turns out it wasn't... This question here is mostly conceptual - how would I go about placing a TVS in a RF path? (more) |
— | over 2 years ago |
| Comment | Post #285721 |
@#52935 Yes and these tests are usually not hard to pass, in my experience, I've done lot of such tests in the past. Basically if every metal part is grounded and every input from connectors is protected, you pass. But in this specific case with an antenna (connector), I'm not sure how to add protect... (more) |
— | over 2 years ago |
| Comment | Post #285782 |
I've done lots of self-answered Q&A here on Codidact, but the problem with that is that then I stand as the author and none would come in and edit the actual contents of the posts. (more) |
— | over 2 years ago |
| Comment | Post #285737 |
Any [human body model](https://en.wikipedia.org/wiki/Human-body_model) will do for now. (The one defined in MIL-STD-883 is for example available for free). Considering conducted susceptibility from other sources like charges to chassis might be the next step, but for now I'm just trying to narrow dow... (more) |
— | over 2 years ago |
| Comment | Post #285725 |
They also break in different ways. Some just are dead, conducting nothing. Others only work in one direction. And this latest one seemed to have shorted tx with rx with antenna. Which perhaps implies varied strengths of a ESD. Had it been some standing wave/impedance matching/reflection problem, I'd ... (more) |
— | over 2 years ago |
| Comment | Post #285725 |
Thanks for the feedback. It sounds as we will need to run this in a simulator or we'd be fumbling around in the dark :) In case of the tx path behind the switch, then this "pi-filter" is actually part of a larger Chebyshev filter which should be split across the switch like this according to the RF e... (more) |
— | over 2 years ago |
| Comment | Post #285693 |
@#52987 I answered that comment. (more) |
— | over 2 years ago |
| Comment | Post #285693 |
I've added some details from the AN regarding PCB layout recommendations for this part, where all of this comes from. (more) |
— | over 2 years ago |
| Comment | Post #285687 |
@#52987 Well I suppose, though then the question turns much too broad and complex - I don't expect anyone to go read a thick datasheet plus a bunch of AN on my behalf. I've updated the question with the expected output power where this filtering would be needed. I understand this as at high output po... (more) |
— | over 2 years ago |
| Comment | Post #285543 |
@#52987 Yeah it makes sense, though why not also compensate for inaccuracy in the local oscillator and the mixer? I just checked what the datasheet of the previous RFIC I worked with and it actually says it's located on the LNA too - the RSSI is fed as input to the AGC. So maybe AGC on the IF amplifi... (more) |
— | over 2 years ago |
| Comment | Post #285346 |
That is, we did pretty much as in your upper left example picture. (more) |
— | over 2 years ago |
| Comment | Post #285346 |
Reason I ask is I've been in several projects where we placed the via more or less directly adjacent to a pad. Tight designs with 144QFP and similar. I don't know if it is actually good practice though, or if some tricks were used with solder masking or stencils. Though I don't recall the PCB vendor ... (more) |
— | over 2 years ago |
| Comment | Post #285346 |
On the actual pad or very close to it? Could you post an example picture of the proposed via layout? (more) |
— | over 2 years ago |
| Comment | Post #285171 |
@#54107 If not on-topic here - as you can see there's no consensus - then such questions should be fine at https://software.codidact.com/. Particularly questions regarding the higher layers and the Internet protocol suite. Questions that are specific and solely about the physical and data link layers... (more) |
— | over 2 years ago |
| Comment | Post #285198 |
@#36396 Ok then I believe you merely have to design the zener barrier after zone 0 rules but you shouldn't need to worry about things like random shorts elsewhere on your PCB. I mean as long as you have a resistor and a fuse living up to the requirements of 60079-11, then it wouldn't matter if for ex... (more) |
— | over 2 years ago |
| Comment | Post #285201 |
@#36396 The general recommendations are something like this: https://www.sensorland.com/HowPics/Zener-001.gif. For higher safety levels, multiple zeners in parallel are used. So regarding my previous note about your zeners on the supply, a similar circuit should be placed towards the hazardous zone i... (more) |
— | over 2 years ago |
| Comment | Post #285198 |
@#36396 Yes temperature limits only apply inside the zones. Since you used 3 zeners I assumed it was for zone 0/20. Generally speaking - take for example a gas station: zone 0 would be inside the fuel containers, zone 1 would be the pumps, zone 2 would be the rest of the gas station, not hazardous zo... (more) |
— | over 2 years ago |
| Comment | Post #285201 |
Actually after reading chapter 7.3 I don't think the fuse is optional either. It seems that a PTC thermistor might be acceptable though. (more) |
— | over 2 years ago |