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Posts by Olin Lathrop‭

326 posts
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Q&A Calculating base voltage of NPN transistor

If this is a contrived homework problem where they are looking for an "exact" answer, then you have to solve a bunch of simultaneous equations. However, that would be neither useful nor anything y...

posted 3d ago by Olin Lathrop‭  ·  edited 2d ago by Olin Lathrop‭

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Q&A Understanding inductive ringing

are there more elements contributing to this effect that I have not placed in the circuit? Definitely, but it's hard to say how relevant they would be. The real world is messy. There is parasiti...

posted 6d ago by Olin Lathrop‭

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Q&A Standardized way of measuring AC line frequency

There is no "standard". Do whatever works best for the situation at hand. In a microcontroller, it's usually easier to measure period than frequency, especially for "low" frequencies like the pow...

posted 10d ago by Olin Lathrop‭  ·  edited 10d ago by Olin Lathrop‭

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Q&A Power Line Filter - Loaction of Cy and CMC

For easy reference and to protect against possible edits to the question, here is the circuit you are asking about: In order to attenuate a signal, you need two impedances. Imagine you had a 0 ...

posted 10d ago by Olin Lathrop‭

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Q&A Flash light frequency and rise time calculation

The flashing-light frequency shall be 90+/-30 times per minute. I don't know what could be more clear. This spec says that the light must flash 90 times per minute, ±30 times per minute. In othe...

posted 19d ago by Olin Lathrop‭

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Q&A How do we calculate signal rise time from frequency

Your question is ambiguous. First, you need to define "rise time". That applies to a step, not a periodic signal. Let's say you have a 0 to 5 V digital signal. The rise time is how long it take...

posted 19d ago by Olin Lathrop‭

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Q&A Control logic for mosfet in piezoelectric energy harvesting circuit

I'll take it that you want this circuit to actually work, not just appear to work in some software simulation. In that case, it's about the circuit, not the simulator. A simulator is just one too...

posted 26d ago by Olin Lathrop‭

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Q&A What are these mystery components (one of wire coil, another labeled "100-10L A9")?

The component with the coil of wire is an inductor. Judging from the small size, it is probably only a few µH. There are lots of uses for inductors, like for filters, switching power supplies, tu...

posted 1mo ago by Olin Lathrop‭  ·  edited 1mo ago by Olin Lathrop‭

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Q&A Determining the output swing, output common-mode range and input common-mode range in a differential amplifer

First, common mode is something that only applies to a differential signal. When a signal is encoded in the difference between two voltages, the common mode voltage is the average of the two. The...

posted 2mo ago by Olin Lathrop‭

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Q&A Regulated charge pump design

That circuit is drawn rather obfuscated, but it does seem to make sense: Start by looking only at D1, D2, C1, and C2. Pretend D3, C3, and D6 don't exist. Although not drawn very well, this is ...

posted 2mo ago by Olin Lathrop‭  ·  edited 2mo ago by Olin Lathrop‭

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Q&A Step voltage 750kV lines

It's really not clear what exactly happened in that video. We see someone slinging a hook over the power line, then we see a white picture. We don't know what the cable was made of and where the ...

posted 2mo ago by Olin Lathrop‭  ·  edited 2mo ago by Olin Lathrop‭

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Q&A MAX485 transceivers breaking, Pi filter generating spikes?

At first glance, your design looks reasonable. I assume D1 and D2 are really supposed to be on opposite data lines, and them both being on the A line is a typo? One thing that sticks out to me is...

posted 2mo ago by Olin Lathrop‭

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Q&A 1-wire interface overvoltage protection

It's been a while since I did 1-wire, so I don't remember the current levels. R18 seems rather high for supporting the minimum required voltage at the maximum possible current. Let's say for sake...

posted 2mo ago by Olin Lathrop‭

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Q&A MOSFET drain current ringing in saturation region

Your controller is too fast compared to the plant (the thing being controlled), thereby causing instability. The most obvious culprit is the 50 kΩ resistor between the controller output and the FE...

posted 2mo ago by Olin Lathrop‭  ·  edited 2mo ago by Olin Lathrop‭

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Q&A PCB as a wall of an underwater enclosure

I guess it would work. I have used electrodes on a PCB to detect whether water level got high enough to turn on a sump pump. It worked, although it hasn't been installed very long. In that case ...

posted 3mo ago by Olin Lathrop‭  ·  edited 3mo ago by Olin Lathrop‭

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Papers Phone fix adventure case study

posted 3mo ago by Olin Lathrop‭

Article case-study
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Q&A Why would a standby UPS fail to power devices when there's no power outage?

Now that you've supplied a link to the product, I can provide a different take on this affair. Your "UPS" is an Amazon Basics model described at https://www.amazon.com/gp/product/B073Q3BSPG/?th=1....

posted 3mo ago by Olin Lathrop‭

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Q&A Why would a standby UPS fail to power devices when there's no power outage?

I see that manassehkatz has already given you a good answer and plausible explanation for what you observed, so I'll fill in a few other points. Your battery is 5 years old, so is getting to the p...

posted 3mo ago by Olin Lathrop‭

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Q&A What type of button is this on a remote control

Such a domed button is usually called a "membrane switch", at least here in the US. As you say, the small metal bubble makes contact with something underneath when pressed. Advantages of membrane...

posted 3mo ago by Olin Lathrop‭

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Q&A estimation of pogo pin resistance

Is there a scientific way to estimate the resistance of a pogo pin? Ultimately there must be, but it generally requires knowing things you don't know. Worrying about the resistance of the barrel ...

posted 4mo ago by Olin Lathrop‭  ·  edited 4mo ago by Olin Lathrop‭

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Q&A High voltage transformer design

When should a transformer core be potted? Whenever you need some of Mechanical ruggedness. High dielectric strength. Minimize vibrations (and therefore audible whine) from capacitive, inductive...

posted 4mo ago by Olin Lathrop‭

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Q&A Most reliable galvanic isolation technology for extreme EMI environments?

My first knee-jerk reaction was to use opto-isolators. There are some that have been around for decades and are unlikely to go obsolete any time soon. I wasn't previously aware of these "digital ...

posted 4mo ago by Olin Lathrop‭

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Q&A Weird grounding on a vintage hifi sideboard

It has two female inputs on the backside that are labeled as "Grounding". This is incorrect. Take a closer look at the two connections and you will see that the left is labeled "Antenne" and t...

posted 4mo ago by Olin Lathrop‭  ·  edited 4mo ago by Olin Lathrop‭

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Q&A CAN BUS monitoring with a LED

CAN lines in the most common implementation have 60 Ω impedance between them. Anything that is substantially larger than that won't effect the lines much. I'd use 1 kΩ at least, preferably more. ...

posted 5mo ago by Olin Lathrop‭

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Q&A Converting 5V to ±12V

You say the only thing that will be powered by the ±12 V supplies is a comparator. The first thing I would look at is whether you really need the comparator to run from that voltage range. Presum...

posted 5mo ago by Olin Lathrop‭  ·  edited 5mo ago by Olin Lathrop‭

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