5 ms·

I'm an EE. My first job out of university had a pretty good whiteboard interview (I know - we're not supposed to say good things about whiteboard interviews on

by Sanzig 7y ago

I'm an EE. My first job out of university had a pretty good whiteboard interview (I know - we're not supposed to say good things about whiteboard interviews on HN). I thought the process was pretty straightforward. The first exchange went something like this: Interviewer: "Can you draw me the schematic symbol for an LED?" Me: Draws LED schematic symbol. Interviewer: "What would you say the forward voltage is on that LED?" Me: "That depends - maybe between 1 and 4 volts depending on the color?" Interviewer: "Good, let's call it two volts. What would you say would be a reasonable current if we're just using it as a power indicator?" Me: "I usually set it to around one milliamp on my boards." Interviewer: "That sounds good. Can you show me how you would connect that to a 5 V supply?" Me: Calculates ballast resistor size for 1 mA current from a 5 V supply with a 2 V LED drop, then draws a circuit with an LED, resistor, and 5 V source. --- And on it went. We ramped up through complexity: next we did simple BJT and FET switches, then basic op-amp circuits including single-pole filters. I stumbled on a differential BJT amplifier question, but the interviewer helped me through it. And so on. I didn't nail everything, but I got most things right. I ended up getting the job. When I asked the interviewer later about his experiences using test for hiring, he told me a sizeable chunk of new graduates flunked out on the first question, which I found pretty shocking. A lot of students with excellent resumes didn't even know how to hook up an LED! As to the cause - it's just a guess, but I think many "good students" these days are very good at regurgitating information and memorizing procedures to complete formulaic exam problems, but aren't very good at actually developing the physical understanding of what's really going on. When I was in my senior year, I designed a buck converter as a small part of my capstone project. One of my team members remarked that he didn't realize a buck converter was a power supply, and that he had seen it in his power electronics class but had no idea what it was used for. He could do the duty cycle calculations for one all day long, but he didn't even realize it was a DC/DC power supply! Universities these days do not seem to successfully evaluate deep understanding. Rather, they seem to optimize for the superficial appearance of understanding. Even "lab courses" when I was a student were formulaic: plug this wire in here, put your probe here, read this value here, do this calculation here for your report. There were very few courses that were actually designed to encourage real experimentation and practical learning. A good EE needs to develop a mental model of the underlying physics and be able to relate it to practice, and that is a tricky thing to teach in the classroom. Anyway, all that said - I really like the idea of the "bad schematics" approach for an interview question. If I ever find myself in a hiring role, I am 100% using it.

artemonster 7y ago
"Universities these days do not seem to successfully evaluate deep understanding" If you (as Uni) try and do that, you'd immediately find your quota of those who have finished a degree to plummet. At our university we had basically only TWO courses that required you to "understand" to pass them and not just mindlessly puke out formulas and insert values. These were theoretical electrodynamics and integrated analog circuits. These were exactly the exams that kicked people out of university, since you had only 3 attempts to pass them. So, no, uni's will never try to force understanding, since so few are actually capable of that. Unis teach you to know the basic set of symbols, be a mindless symbol manipulating monkey and hope that industry would pick you up and enlighten you afterwards.
- JadeNB 7y ago
  > If you (as Uni) try and do that, you'd immediately find your quota of those who have finished a degree to plummet. Indeed: as a teacher, I have had the experience that there's pressure to pass underachieving students in the elementary courses (we don't want to scare everyone off by flunking them out of their first courses!) and then there's pressure to pass underachieving students in the advanced courses (it's not fair to pass them to this point, and then suddenly hold them to higher expectations!—or even, directly, "if we don't pass them then they won't be able to graduate").
userbinator 7y ago
The closest standard value for that resistor would be a 3k3, if I'm not mistaken... In the software industry we have a similar problem; alot of people can follow instructions on how to glue together lots of libraries and frameworks, but have no idea how to go beyond that --- or understanding of how computers work in general --- much less debug it when something goes wrong. There's a classic article about this: https://blog.codinghorror.com/why-cant-programmers-program/ https://blog.codinghorror.com/why-cant-programmers-program/
- mlyle 7y ago
  Yah, but IMO 1mA is on the "low end" of lit, so you want to round down the resistor value to get a little more current. Pick 2k7 instead. Most small LEDs will tolerate per datasheet 20mA; 4mA is "well-lit". A little less than 1mA is going to be pretty anemic looking on lots of LEDs. So I'd be more inclined to put down 470 to 1k5.

by Sanzig 7y ago

artemonster 7y ago

"Universities these days do not seem to successfully evaluate deep understanding" If you (as Uni) try and do that, you'd immediately find your quota of those who have finished a degree to plummet. At our university we had basically only TWO courses that required you to "understand" to pass them and not just mindlessly puke out formulas and insert values. These were theoretical electrodynamics and integrated analog circuits. These were exactly the exams that kicked people out of university, since you had only 3 attempts to pass them. So, no, uni's will never try to force understanding, since so few are actually capable of that. Unis teach you to know the basic set of symbols, be a mindless symbol manipulating monkey and hope that industry would pick you up and enlighten you afterwards.

JadeNB 7y ago
> If you (as Uni) try and do that, you'd immediately find your quota of those who have finished a degree to plummet. Indeed: as a teacher, I have had the experience that there's pressure to pass underachieving students in the elementary courses (we don't want to scare everyone off by flunking them out of their first courses!) and then there's pressure to pass underachieving students in the advanced courses (it's not fair to pass them to this point, and then suddenly hold them to higher expectations!—or even, directly, "if we don't pass them then they won't be able to graduate").

userbinator 7y ago

The closest standard value for that resistor would be a 3k3, if I'm not mistaken... In the software industry we have a similar problem; alot of people can follow instructions on how to glue together lots of libraries and frameworks, but have no idea how to go beyond that --- or understanding of how computers work in general --- much less debug it when something goes wrong. There's a classic article about this: https://blog.codinghorror.com/why-cant-programmers-program/ https://blog.codinghorror.com/why-cant-programmers-program/

mlyle 7y ago
Yah, but IMO 1mA is on the "low end" of lit, so you want to round down the resistor value to get a little more current. Pick 2k7 instead. Most small LEDs will tolerate per datasheet 20mA; 4mA is "well-lit". A little less than 1mA is going to be pretty anemic looking on lots of LEDs. So I'd be more inclined to put down 470 to 1k5.