Activity for Olin Lathrop
| Type | On... | Excerpt | Status | Date |
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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 other words, the flashing rate must be from 60 to 120 flashes per minute. It should be obvious t... (more) |
— | 1 day ago |
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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 takes to go from the low state to the high state. However, that is still ambiguous. Let's say the sign... (more) |
— | 1 day ago |
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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 tool in designing or verifying a circuit. A brain and a calculator are usually much better tools. First... (more) |
— | 9 days ago |
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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, tuned oscillators, and others. I would not try to guess the use from this scant information. The... (more) |
— | 24 days ago |
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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 common mode range is the range of common mode voltage over which a small differential signal can stil... (more) |
— | 28 days ago |
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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 a basic charge pump. For simplicity, let's pretend the diodes are ideal. The actual output voltage... (more) |
— | about 1 month ago |
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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 other end really was at the time the hook reached the power line. One possibility is that the cable w... (more) |
— | about 1 month ago |
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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 the value of the clamping diodes. Why so high? What's your expected common mode range? A large com... (more) |
— | about 1 month ago |
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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 of example that your 1-wire device is specified to work down to 2.0 V. You're already going to lose ... (more) |
— | about 2 months ago |
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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 FET gate. The resistor and the gate capacitance low pass filter the control signal, which effecti... (more) |
— | about 2 months ago |
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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 the PCB extends upwards to where it is dry. That's where wires are soldered that go to the detection ... (more) |
— | 2 months ago |
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Phone fix adventure case study I've had a Nexus 5X smart phone since 2016, so now in Feb 2024 it's almost 8 years old. I like the phone and have had no problems with it until three days ago. I had it in the car plugged in and connected as usual when I noticed it rebooting. I thought that was a bit odd, but figured maybe that wa... (more) |
— | 2 months ago |
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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. First, it's clear that unit is optimized for one parameter only, which is minimum possible price whi... (more) |
— | 2 months ago |
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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 point where it could start to fail. I wouldn't expect a 5 year old battery to be bad, but it's to the ... (more) |
— | 2 months ago |
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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 switches over the capacitive or conductive sense switches in the rest of your remote include better e... (more) |
— | 3 months ago |
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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 and spring is missing the point. The limiting factor will be the small contact area between the cir... (more) |
— | 3 months ago |
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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, piezo-electric and magneto-restrictive effects. Can I place the high voltage conductors... (more) |
— | 3 months ago |
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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 isolators". They seem like they go thru a lot of trouble to ultimately do what opto-isolators do. I'... (more) |
— | 4 months ago |
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A: Weird grounding on a vintage hifi sideboard It has two female inputs on the backside that are labeled as "Grounding". This is incorrect. Imagealttext Take a closer look at the two connections and you will see that the left is labeled "Antenne" and the right "Erde". That's German for antenna and ground. Symbols for antenna and groun... (more) |
— | 4 months ago |
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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. The lead from the bus line to the resistor must also be short to minimize the characteristi... (more) |
— | 5 months ago |
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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. Presumably you are asking for ±12 V because that is the range of the signals being compared. ... (more) |
— | 5 months ago |
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A: Noise from oscillator on top layer to clock on bottom layer with VCC & GND layers between It's hard to answer your specific case since you didn't label the layers in your picture, or which traces are doing what. That said, a few traces crossing each other on different layers is not much coupling. In most cases of a typical board with a typical "SPI clock signal", there won't be any pr... (more) |
— | 5 months ago |
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A: What fabrication process is being used for jellybean parts I want to know why the top-of-the-line CPUs and GPUs from Intel, NVIDIA, and AMD are all bragging about the fabrication process (7nm and 5nm) and trying to be consistently smaller. It's marketing hype intended to make them look more high tech than the other guy. There is little reason the end use... (more) |
— | 5 months ago |
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Ceramic capacitor "memory" effect? I have run into an interesting phenomenon related to ceramic capacitors. This question is part of the effort to understand the issue, and eventually work around it. But first, some background of this particular situation is required. Device background I have designed a high-accuracy 32-channe... (more) |
— | 5 months ago |
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A: Can I make an AC inductor (reactor) rated 75mH 40A from a 3-phase induction motor? An induction motor with its shaft held still will mostly look like an inductor with a series resistance electrically. However, there will be some issues: It will be difficult to guess the inductance from the motor datasheet. There will probably be higher effective series resistance than for a ... (more) |
— | 6 months ago |
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A: Will shorting a lithium ion battery cause an explosion? Since you seem to be asking about whole batteries, not individual bare cells, dangerous effects should be limited. Consumer batteries made from lithium cells almost always include integrated protection circuits. These prevent over-charging, too deep discharge, and probably also mitigate shorts some... (more) |
— | 7 months ago |
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A: What are some best practices for library management? I don't know about "best practices", but I make all my own library parts. I use Eagle, and the library parts that come with Eagle are quite inconsistent in things like pad shapes, what is shown on the silkscreen, size of lines and text, what goes into the various layers, etc. It might be tempti... (more) |
— | 7 months ago |
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A: derating MLCC ripple current for transient current spikes how much higher can i go in current ripple RMS None, of course, at least if you want to rely on anything else the datasheet says. The heating is a function of the RMS current. No, you don't get to cheat physics. Calculate the RMS of the pulse waveform, and make sure that doesn't exceed what t... (more) |
— | 7 months ago |
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A: Burned Source Driver - Noise Spikes from Relay Coil At first this sounded like it might be a classic case of forgetting the flyback catch diode across the relay coil. However, now that you've posted a schematic we can see that a diode is built into the driver chip for each output. That leaves two possibilities I can think of, power overload and gr... (more) |
— | 7 months ago |
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A: What residential wiring questions are on-topic here? Thanks for asking. In my view, if it's something you'd first think of asking an electrician, it's probably off topic here. That includes what type of cable to use, whether it should be in a conduit or not, working with breaker panels, what size wire is needed for a particular application, etc. T... (more) |
— | 8 months ago |
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A: Soft-start circuit behaviour First, let's redraw your schematic so that it's not so annoying to look at. High voltages go at top, low voltages at bottom, and logical flow left to right: This is not a great soft-start circuit since it relies on unspecified behavior of the FET. It seems the strategy is to low pass filter ... (more) |
— | 8 months ago |
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A: Can the corner frequency of thermal noise change with change in source impedance? The thermal noise of a resistance depends only on that resistance. However, there is always some parasitic capacitance. That capacitance against the resistance causes a low pass filter. So in a sense, yes, the frequency content of thermal noise does vary with resistance in the real world due to ... (more) |
— | 8 months ago |
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A: Power switches and automotive load dump, unclamped It seems you want to protect a device against power spikes. The power supply is nominally 12 V, but can have spikes up to 79 V with an impedance of 500 mΩ. Two timing values were given, but they are useless without being defined, so we can only ignore them. The device can draw up to 200 mA. ... (more) |
— | 8 months ago |
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A: Professional vs Hobbyist advice and potentially dangerous projects the original question is interesting and deserves a technical answer So go write one. That's your call, just like it's mine not to. We are all volunteers here, and are therefore never obligated to answer anything. I didn't answer with technical details because: I don't know all the specs f... (more) |
— | 8 months ago |
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A: What is Ground Electrode in EMG? When measuring signals at different points on the skin of the body, you don't usually want to connect the victim patient to ground. Usually you use an extra electrode connected some distance away that is driven by the circuitry to the average of the other signals. That reduces the common mode range... (more) |
— | 8 months ago |
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A: Essential safety features of an EMG/medical grade device? Safety of medical devices is not something you should be asking random folks on the internet about. The rules are stringent, for good reason. The clearance and creepage distances to line voltage, insulation voltage, leakage, and other specs are much tighter than for ordinary consumer devices. Be... (more) |
— | 8 months ago |
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A: How to deal with design review questions? I agree with this approach. Categories should only be created when they are expected to have reasonable traffic. A category with only chirping crickets is an anti-advertisement. Take a look at the Photography and Outdoors sites. They have lots of nearly unused categories, which I think makes th... (more) |
— | 8 months ago |
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A: Disabling breakpoints in real-time section of firmware I have a similar problem when debugging firmware on a dsPIC that drives a flyback power supply. The switch isn't designed to be on for very long, as eventually the inductor saturates. Usually the transistor blows out when it is left on too long. In normal operation, the PWM hardware in the micro g... (more) |
— | 8 months ago |
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A: Tag naming guidelines. Adding to what Lundin said (+1): s is seconds, S is siemens (1/Ω). What we write here is inherently HTML. Greek characters like µ and Ω are defined as HTML entities, and can always be written with "µ" and "Ω", respectively. There is therefore no e... (more) |
— | 9 months ago |
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A: Two way circuit breaking capability for ideal diode controllers The two ICs you reference don't do the same thing. The first sentence of the first datasheet says: The MAX16141/MAX16141A ideal diode controllers provide system protection against a variety of system faults, such as reverse current, reverse voltage, overcurrent, input overvoltage/undervoltage, ... (more) |
— | 9 months ago |
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A: Is there an easy way to measure the characteristic impedance of a cable using basic lab instruments? What you basically ask for can be done (I've done it), but not all your specific constraints can be reasonably met. The way to measure transmission line impedance is to drive a step onto the transmission line with a known resistance, while observing the waveform on a scope. During the time the st... (more) |
— | 10 months ago |
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A: Are a JFET's Idss and Vgs(off) values correlated? I'll let someone else answer about the device physics. I'll answer from an electrical engineering standpoint. The answer is: Maybe, but it doesn't matter since you should be considering worst case in your design anyway. You are really asking whether there is any correlation between the gate vo... (more) |
— | 10 months ago |
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A: Floating circuitry and diodes is the "X" point floating when there is no 12V applied ? Perhaps over a limited range, depending on whether the 12V line is left open or connected to something other than 12V. Case 1: The voltage on X is bounded by the Zener diode. X can't be more than one diode drop below ground, or th... (more) |
— | 10 months ago |
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A: Choosing between common-drain JFET amplifier, and common-source The first circuit uses the FET in follower mode. That means it works as an impedance buffer with a gain a little below 1. Such configuration can be useful to turn a high impedance signal into a low impedance signal. The second circuit uses the FET as a common source amplifier. This inverts the ... (more) |
— | 10 months ago |
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A: Ground pour on outer layers on 4-layer PCB I would not do deliberate ground pours on a board like that. It's relatively small, and not exceptionally high frequency. I also wouldn't try to guess what effect or not it might have on the board fab process. I've put similar microcontrollers on larger boards many times and not had any issues l... (more) |
— | 10 months ago |
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A: How to convert dv/dt of noise into frequency for filter capacitor selection? It looks like you've sort of re-discovered a motivation for Fourier analysis. The difference between looking at slope versus frequency content is exactly the difference between time domain and frequency domain analysis. Both are perfectly valid and provide the same ultimate answers. However, one o... (more) |
— | 10 months ago |
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A: Should posting on Meta affect reputation? Yes, votes on meta should not factor into rep. Meta downvotes indicate disagreement, not that you're a terrible person, have the IQ of a garden slug, and cast dispersions on your heritage like they do on the main site ;-) Users should be free to express their opinions, whether popular or not, as ... (more) |
— | 10 months ago |
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A: High power LC circuit with programmable resonant frequency What you are asking for is totally unrealistic, and your numbers don't add up. With 10 mH and 80 µF, the resonant frequency is 178 Hz. Getting down to 1 Hz even with 10 mH would require over 2.5 F. Keep in mind that with the inductance fixed, the capacitance required for resonance is inver... (more) |
— | 10 months ago |
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A: Titanic submarine control considerations I don't have any special knowledge about how submarines get controlled, so this is mostly speculation. I expect that the actual controls are fine. There seem to be the necessary degrees of freedom, and as you say, people are already familiar with the interface. In that sense I don't see anything... (more) |
— | 10 months ago |
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A: Sensing 3 states in a single mcu pin using firmware Starting with your first circuit: It seems a little klunky, but should work. I don't like the D1 and D2 diodes. The reason I placed D1 is to avoid triggering the mosfet with very low voltage like 2V to 4V. Is D2 really necessary? The input voltage threshold for sensing high is the 8.2 V... (more) |
— | 10 months ago |