Hey guys, I'm trying to properly bias the LM34476U chip (datasheet here) for operation in the saturated MODE. However, I want to be able to dynamically change the bias to on mode when my signal source changes. I've sketched out a design using the MAX4640AB 4:1 multiplexer that will switch out bias resistors but I'm getting a split second where both resistors are conducting and the feedback causes ringing in my output that I can't get rid of. Can anyone recommend methods to reduce the bandwidth of the LM3447 to eliminate the ringing? I've checked the app notes but the method they suggest there doesn't apply directly to my circuit topology and I don't know where to connect the feedback capacitor with my setup.
Wow, just wow. It's questions like that that I open up my circuits text book for.
Literally - check out this question here. I was even nice!
But sometimes there are questions asked that... spawn blog posts. That spawn stand up comedy routines ('Hey guys did you hear about the guy that asked a stupid question on the internet?'). Questions asked by people with obviously little knowledge of engineering, analog design, programming, digital logic, etc. Out of respect for the guilty I will not post one of the questions here but instead show you a creation of my own twisted mind that makes me approximately as angry as the real thing:
Hey guys, I've just had a great idea that I'd like to follow up on but I don't know where to start so I was hoping you could give me some pointers.
It seems to me that a lot of disabled people have problems with picking things up, so I want to build a robot that will roll around and pick up the things that they need picked up and you can control it with voice commands.
I've got a lot of software experience with VB6 and I've been reading up on the PIC so I think I can write the code for it when I find an implementation of the .NET framework for the PIC.
What I don't know about is the motors and stuff and the voice control maybe. I need the robot to roll around with wheels and its hand has to be just like a persons hand so it can pick everything up.
It also needs to know what the words for things are and it should probably understand if you point at something too.
My cousin is disabled and he has such a hard time... I really want to help him and think this is a good idea. Do any of you guys know a website or book that can help me figure this stuff out?
Thanks guys, I know together we can work this out!
This just makes me angry. Doesn't it make you angry? The first thing that pops up in my head is that this isn't really a question. If you had to distill it it wouldn't end up as 'Is this possible?' or 'What will be involved in doing this?' but instead 'Tell me how to do this'. It's like saying 'I want to get into Heaven - tell me how to do this.' Man, you'd be in for quite a discussion let me tell you....
But what are the specific ways I hate this question: Oh, let me count them:
Hey guys, I've just had a great idea that I'd like to follow up on but I don't know where to start so I was hoping you could give me some pointers.
First off, I hate it when you use any honorifics ('Dear sirs, I am many problems with this software having! For much to help please!') or really, any form of address. Don't call me 'guys', don't pretend like you know me unless you post regularly. Yes, I do check. Secondly the phrases 'I don't know where to start' and 'give me some pointers' indicate this person has no idea how to do what he wants to do. At all. Not even close. When the last time you had a great idea didn't you at least have some clue how it might be done? You think 'I want to know when I should stop pulling my car into the garage' and then immediately assume that this is a question you shouldn't even consider - that you should go consult a professional? Even if you start thinking about it and conclude you don't have enough specific knowledge to formulate a final solution that at least leaves you with some specific questions to ask. If for some reason you decided it needed to be electronic you'll quickly reach the question 'How can I measure distance electronically?' Then you ask THAT question to the professionals. Saying 'I don't know where to start' means you didn't bother to think through it even a little or you honestly don't understand what you want.
It seems to me that a lot of disabled people have problems with picking things up, so I want to build a robot that will roll around and pick up the things that they need picked up and you can control it with voice commands.
This boggles my mind. Do I want to help disabled people? Yes. Do I understand some of the issues that may be affecting them? Yes - apparently they 'have problems with picking things up'. Could I design an apparatus that might help disabled people pick things up - via voice commands? Perhaps - but it would take years. You see, I'm a simple embedded software engineer (before this I was a controls engineer - before that an electrical engineer and before that? Farmer) and the request you just made involves at least four different fields of study (Mechanical engineering, embedded software development, computer science with a specialty in artificial intelligence, digital signal processing, analog design - all of the top of my head) and would require someone with a college education in each. I'd probably need one PhD as well - just for good measure. It's not as if I could do wonderful things to help the disabled but I just get drunk instead. This is HARD.
I've got a lot of software experience with VB6 and I've been reading up on the PIC so I think I can write the code for it when I find an implementation of the .NET framework for the PIC.
Okay... this means you don't understand any of the potential tools you might be working with. Do you guys know what the PIC is? An 8-bit microcontroller that can't find its ass with both hands. Actually, scratch that - the PIC only implements one hand in hardware and requires you to emulate the other hand in software if you want to access it. This thing is dumb as sin. It most certainly doesn't have an implementation of .NET and even if it did the first thing he'd probably try to do is make 'Hello World' using console.writeline or whatever prissy function they use because they're not man enough to call it printf. You have to work with bits when you use this thing. Software people don't even know what bits are anymore - this guy is way out of his league.
What I don't know about is the motors and stuff and the voice control maybe. I need the robot to roll around with wheels and its hand has to be just like a persons hand so it can pick everything up.
It also needs to know what the words for things are and it should probably understand if you point at something too.
Oh okay, what you'll admit you don't know about is maybe 3/4's of the entire thing? So at the very least it's only ten years of school? Do people seriously think that these matters are trivial? Many legitimate college graduates are simply lost as far as practical skills in their first job and even then a mechanical engineer (for instance) isn't a machinist - he may be able to design the mechanical parts but he can't make them. You need someone who works with his hands and hopefully still has all of his fingers - that means he's good! And I'm not even going to get into how difficult it is to 'make it understand words'. Suffice it to say the most advanced processing hardware in the world takes years to learn a language and usually doesn't learn it correctly anyhow.
My cousin is disabled and he has such a hard time... I really want to help him and think this is a good idea. Do any of you guys know a website or book that can help me figure this stuff out?
Thanks guys, I know together we can work this out!
Oh of course - a book! Or website! All he needs is a website - one that tells him EXACTLY WHAT TO DO. Every step from A to Z to make this magical device that barely exists in his mind because he hasn't thought it through very much. Yes, I wrote that webpage - it's on Geocities. I dare you to find it. Face it - even if such a thing exists someone's selling it and they're not going to tell you how to make it. They're not going to document it completely and put it on the web for you to reproduce so you can not pay them anything. People like their effort to be rewarded - and this is effort
People will try to defend this person. 'But Angry', they'll start, 'he just wants to know if it's possible!' Screw that - everything is possible. Period. It all depends how much you want to pay. And I can't tell you how much it will cost. Do you realize that real companies have people who are paid - full time, real money - to estimate how much jobs will cost? And (call me cynical) when you tell him that the price for development of this miracle is in the millions he'll say 'I don't understand why it needs to cost so much!!! You can't be for real!' You see, he has already demonstrated that he lacks the ability and knowledge necessary to judge the difficulty of the ideas he presents. Remember that as far as he's concerned he simply hasn't found the right website to tell him how to do it. After that it's easy.
'He just wants to know what it will take!'
Seriously? Remember how he can't tell whether he's asking for something reasonable or something insane? When I tell him it's something insane guess what? That's not the answer he's looking for. He has every reason to ignore me and perhaps ridicule me. I can't say for sure whether he has a rigid mindset that won't listen to reason but I am saying for certain he has no facility to judge whether something is reasonable or not. So why even ask? Why not ask 'Am I way off base here?' instead of 'Show me how to do this'.
'You should at least be nice to him'
Well... I could. It's true. I don't have to do anything - so many questions simply remain unanswered, bereft and eventually die in obscurity. It feels so fulfilling to see no answers, no comments, no nothing on a question months after it's been asked. But I have my limits. I am the Angry EE for a reason. And that reason is that some things I just can't let go. On the internet anyhow - where all I have to do is type. Otherwise? Waaaay too lazy. But I will not refrain from essentially answering his question in the only way one paragraph can. I am not on retainer for more than one paragraph - no one on stackexchange sites should be. It will be pithy, it will be a little acerbic, but it will be right. If you choose not to believe it, I will follow up with comments that make fun of you more and more.
The moral of the story is to do work for yourself. Do some, any! Then you can ask more specific questions - questions which I will be less hesitant to answer than blanket questions about topics you obviously don't understand and haven't thought about. I answer lots of questions on this site and there's plenty of good ones which means that plenty of people don't expect me to do their homework for them. I like those people. Yeah, don't expect me to do your homework. Homey don't play dat.
(Does anyone get that reference?)
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