Activity for Olin Lathrop‭

Type	On...	Excerpt	Status	Date
Answer	—	A: Is this AD8307 fake? I am not familiar with that chip, and only took a very quick look at the datasheet. Here is the block diagram of the part from the top of the first page: A few things pop out from this: This chip has a differential input on pins 8 and 1. You tied the negative input to ground via a cap, bu... (more)	—	about 3 years ago
Answer	—	A: Estimating the input capacitance of an BLDC motor controller What is seems you really want to know is how to size a power supply filter capacitor, not what the input capacitance of something is. The objective is to keep the ripple voltage below some value. To determine ripple voltage, you need to know the characteristics of what charges the capacitor, and ... (more)	—	about 3 years ago
Answer	—	A: Why are antenna PCB traces square instead of rounded? PCB antennas are not designed by electrical engineers, but guys with pointy hats and wands They use trial and error after starting with the result of some mystic ritual including lots of mumbling and waving of the afore-mentioned wand. OK, that's not completely fair, but there is still a high com... (more)	—	about 3 years ago
Answer	—	A: Design considerations for a synchronous DC/DC converter First, let's clarify something: replacing a diode with a MOSFET switch I have never seen the diode actually replaced. The intent is to have the FET on only when the diode would conduct, but no such timing is perfect. Having an actual diode there allows falling back to the classic case when th... (more)	—	about 3 years ago
Answer	—	A: How could you model a 10M/100M Ethernet PHY architecture? I'm not going to get into how to model the PHY interface, but will try to explain why there are differences. The type of Ethernet you are talking about is transformer-coupled. The line itself is a differential pair with 50 Ω impedance. However, since a transformer is supposed to be between... (more)	—	about 3 years ago
Answer	—	A: Why is the resistance of water so high and still so dangerous? Pure water does indeed have very high resistivity (different from "resistance"). Reasons water is dangerous around electricity include: Even small amounts of impurities greatly increase the conductivity of water. The water that you worry about that might contribute to a shock hazard is especia... (more)	—	about 3 years ago
Answer	—	A: Can you call an IC pin 'N.C' if it has hidden functionality? Manufacturers can call their IC pins whatever they like. NC stands for "No connection", as the datasheet even says. There is nothing wrong with that. The only questionable part is "Must be connected to ground" for a pin that is not connected to anything. Without further explanation from the m... (more)	—	about 3 years ago
Answer	—	A: Max V/Hz value for motor Here is a copy of your specs to make them easier to discuss here: None of those specs really tell you what the V/Hz of the generator inside that motor is. We could take a reasonable guess at if we knew that all the "Rated …" specs were at the same operating point, but that's not clear. What ... (more)	—	about 3 years ago
Answer	—	A: Why is it is always power consumption or power delivered more in usage? Power makes sense for steady state conditions. A certain energy will be used over one second. Then the same energy will be used the next second. And the next second. If I told you that such a circuit used 3 J, the first thing you'd ask is "When?", "Over what time?". Only knowing that is used 3 J... (more)	—	about 3 years ago
Answer	—	A: Is there a particular type of lead-free solder that does not degrade soldering tips? A different type of solder, other than using lead-based solder, is probably not going to help. There are two causes to your problem: Crappy tips. Higher temperature required due to lead-free solder. You can fix the first by getting a good soldering tool. Leaded solder will help with ... (more)	—	about 3 years ago
Answer	—	A: How building a follower satisfying rather extreme requirements. I don't have a real answer. This is just a suggestion for how to proceed. Look for amplifiers intended to drive 50 Ω cable. Sometimes the term line driver is used, even though that also means other things. If you only needed a few 100 MHz, a video line driver might work, but finding somet... (more)	—	about 3 years ago
Answer	—	A: Can there be a global EMP disaster, whether totally natural or partially natural and partly artificial? EMPs (electro-magnetic pulses) occur naturally often. Every lightning strike is one example. Larger EMPs have been created artificially with nuclear weapons. The Starfish Prime H-bomb test caused damage a long way away in Hawaii. There were cases of the wires in street lights getting fused by t... (more)	—	about 3 years ago
Answer	—	A: Isolated Digital Input - Overvoltage protection To summarize, it seems you want a circuit that will detect an input voltage high/low with a threshold somewhere between 0 and 3.3 V, must operate correctly with 0-3.3 V input, but must tolerate input up to 32 V. Snap action (hysteresis) is not required. An opto-isolator is to be turned on when the ... (more)	—	about 3 years ago
Answer	—	A: My grid dip: how does this electron tube technology work? The video helped explain a few things, but it's still not clear what the overall purpose of this device is. You showed it clearly producing a signal, but the documentation you quote talks about an incoming signal. The meaning of the current shown on the meter is unclear, and so is the function of t... (more)	—	about 3 years ago
Answer	—	A: What is causing this massive discharge traveling down a power line? It is hard to know from a single static low-res picture, but my guess is that something caused a short across the high voltage lines. That could be a falling tree limb, a squirrel making an unfortunate hop, a bird with outstretched wings in the wrong place, some conductive debris blown across the wi... (more)	—	about 3 years ago
Answer	—	A: Is it always necessary to use the ground terminal of the oscilloscope probe? Yes, you should connect the scope probe ground to the circuit ground near where you are probing. The unit under test (UUT) and the scope may have their grounds connected, but that is via a round-about path. This causes problems: The ground path can have significant impedance at high frequencie... (more)	—	about 3 years ago
Answer	—	A: Name of this current limiting device Your circuit It doesn't make sense that the yellow blob is a current sink: If it were a current sink, then there would be no point to the resistor in series with it. That only wastes power, reduces the compliance range, and doesn't change the current. You need to look at the whole circu... (more)	—	over 3 years ago
Answer	—	A: Is a BJT 3-transistor Wilson mirror faster than a simple mirror? First Circuit Let's start by looking at the conventional current mirror circuit: The base of Q1 (Not sure which one that is? Use component designators next time!) is driven to whatever it takes to pass the current dumped onto the collector. Q2 is assumed to have identical properties, so it... (more)	—	over 3 years ago
Answer	—	A: BLDC motor - initial rotor position This is usually done by driving the motor very slowly open loop at startup. The idea is that the rotor will follow the magnetic field. Once you think the rotor is in sync with the drive, you speed up the drive and look for the back EMF. Since the magnitude of the back EMF is proportional to speed,... (more)	—	over 3 years ago
Answer	—	A: Why are two identical filters required for each signal, if the signals can be multiplexed into a single filter? There are a number of things that are unclear. You talk about the red and IR phases of the light sensor signal being demultiplexed into separate red and IR signals, but there is no evidence of this in what you show. If this is happening at all, the crucial information of what each filter is driven ... (more)	—	over 3 years ago
Answer	—	A: Why does AC frequency affect my microwave's RPM? The turntable is apparently run by a cheap synchronous motor. There is a type of motor that's easy to manufacture, that turns synchronously with the line frequency. You say the table used to rotate at 6 RPM with 60 Hz power, and now rotates at 5 RPM with 50 Hz power. That is exactly what you'd e... (more)	—	over 3 years ago
Answer	—	A: How about a new section for code reviews? Personally I wouldn't want another category (what you seem to mean by "section"). I also don't think this should be a code review site. However, asking for validation and advice on small and specific pieces of code is already on topic, if that code is somehow related to hardware. For example, ... (more)	—	over 3 years ago
Answer	—	A: MOV vs. TVS diode You really have to compare datasheets. There are some general differences, but you shouldn't go by those in specific instances. MOVs usually have softer knees, are available at higher voltages, and are available for dissipating higher powers. Usually. One drawback of MOVs that they get "used up... (more)	—	over 3 years ago
Answer	—	A: Why is the Linear Time-Invariant System (LTI) dominant in Signal processing? Linear systems lend themselves to analysis since they follow certain rules. Because of this, much analysis has been done and theory developed, so there is now lots to keep undergrads busy with. Many simple passive systems are linear systems, or close enough so that they can be approximated as suc... (more)	—	over 3 years ago
Answer	—	A: recommendation for chip programming connection (pogo?) I have also had this problem for production runs of 100s to 1000 where you don't want to spend too much on a full fancy jig. Put plain round pads on the bottom of the board. 50 mils is usually a good diameter. Those work well with simple 90° pogo pins. Don't use holes. In my experience, a ... (more)	—	over 3 years ago
Answer	—	A: What should be considered when picking a flyback diode? Catching a flyback pulse is actually a rather easy application for a diode. Many of the diode parameters don't matter much. The basics are: Reverse voltage. This is simply the maximum voltage the coil will be driven with, which is 24 V in your example. There is nothing magic about the flyback ... (more)	—	over 3 years ago
Answer	—	A: PCT2075 temperature sensor accuracy The text values in the specifications section are always the real specs. Unless otherwise stated (and that's quite rare), graphs are suggested values, typical ranges, variations due to a single variable, and the like. They are NOT specifications. The only accuracy you can count on is what it say... (more)	—	over 3 years ago
Question	—	What should rep gain/loss be on Papers? The Codidact team has recently informed us that it is now possible to have different rep bumps on different post types. See this new answer by Monica to the old meta discussion that created the Papers category in the first place. Papers were always intended to be significantly more substantial wo... (more)	—	over 3 years ago
Question	—	Cable loops between utility poles? Sometimes cables between utility poles make a loop and do a U-turn. What is the purpose of such loops? The loop I'm asking about is in the lower set of wires towards the left of the picture. These must be communication cables. The 3-phase power is clearly evident at the top of the pole. ... (more)	—	over 3 years ago
Answer	—	A: is this too obvious for a post? This sounds like it could be a Paper (https://electrical.codidact.com/categories/35) if written up nicely. It doesn't make sense as a question because you're telling, not asking. I haven't heard of this idea before, and I have definitely not used it. It sounds like rather a cute trick. You shou... (more)	—	over 3 years ago
Answer	—	A: Confused about the amplitude and shape of output voltage pulse Coquelicot's answer explains what is going on, so I won't duplicate that. However, one of the sources of confusion is that you are looking at the two waveforms in isolation. Your scope obviously has at least two channels, since we can see a unused blue line in each picture. Use both channels. ... (more)	—	over 3 years ago
Answer	—	A: CAN Bus - Internal Oscillator You are making this too complicated. The only thing that matters is the percentage mismatch between any two clocks on a CAN bus. You seem to imply that you are willing to guarantee the -10 °C to +85 °C temperature range, so the oscillator will be within -1.9% to +2.3%. Any two devices co... (more)	—	over 3 years ago
Answer	—	A: Transformer - Vsec or Current rating parameter In addition to what Andy said (+1), the 350 mA AC figure is probably limited by power dissipation, and therefore temperature. It applies during normal forward operation where the secondary current "unloads" the core as fast as the primary current tries to load it. The 11 V⋅µs figure is... (more)	—	over 3 years ago
Answer	—	A: Driving ADC with opamp with large rails Is the risk too great? That depends on parameters you haven't told us. How cost-sensitive is this product? What is the reliability expectation of the users? How mission-critical is its usage? For example, if this were a toy, I'd say screw it and look for a way to not even buffer the signal i... (more)	—	over 3 years ago
Answer	—	A: ESD USB Shield Connection & Filtering Your question is impossible to answer without carefully looking at the layout and schematic. However, from gut feel and experience, this smells like poor grounding design. Common mistakes: Not a single board-wide master ground plane. Too many large islands in the ground plane. The metric o... (more)	—	over 3 years ago
Answer	—	A: Flyback Converter - Output Ripple Ripple doesn't need to be that high. I've done flyback supplies to power isolated sections quite a bit, using a pulse on demand scheme like yours. It's not hard to get the ripple down to ±50 mV. Usually the ripple is within ±100 mV even when you don't do anything special to minimize ... (more)	—	over 3 years ago
Answer	—	A: How can I debug, (and eventually fix) this Roomba PCB? The charger is supposed to output 20V-24V when the roomba is plugged in. However it's only showing 1.6V. If this is really true, then there is no point going further. The charger isn't working, the Roomba got discharged, and now wont run because it can't be recharged. However, it's not clear w... (more)	—	over 3 years ago
Answer	—	A: Can I ask about debugging/fixing a broken product? Repair questions can be on topic if it's about the underlying electronic principles. Just "How do I fix this?" is off topic. There is little wiggle room for trying to repair a consumer device that you don't even have the schematic for. That doesn't mean you can't, but that such questions are har... (more)	—	over 3 years ago
Answer	—	A: Digital multimeter display count range Digital voltmeters generally display decimal digits. The resolution implied by that is not necessarily the same as the underlying binary A/D. Since voltmeters for human display don't need to be fast, but high resolution is good, these usually use delta-sigma A/Ds inside. These can have 20 or mor... (more)	—	over 3 years ago
Answer	—	A: Cleaning flux out of USB connectors after soldering Direct answer How to clean off flux depends on what type of flux was used. Most electronic parts can handle being washed in clean water. In fact, boards often go thru what amounts to an industrial dish washer after soldering. If water soluble flux was used, then this will probably work. Chec... (more)	—	over 3 years ago
Answer	—	A: High Power Switch - High Side vs. Low Side Switching It's still unclear what you are really asking, so I'll discuss the tradeoffs between low and high side switching of power to a load. Low side switching The main advantage of low side switching is that controlling the switch is easier. This is because the logic that decides whether the switch s... (more)	—	over 3 years ago
Answer	—	A: What is the role of the differential amplifier in a delta sigma converter? Your question really comes down to how a delta-sigma A/D works. The A/D internally models the input voltage with a stream of bits. Each bit can only indicate the minimum or maximum voltage. The aim is to make a stream of bits that in the aggregate when averaged together accurately represent the ... (more)	—	over 3 years ago
Answer	—	A: What is the difference between differential amplifier and differentiator? A differential amplifier and a differentiator are two completely different circuit blocks. Differential Amplifier A differential amplifier has two inputs and one output. It takes the difference between the two inputs, multiplies that by the gain, and makes it the output.     Out =... (more)	—	over 3 years ago
Answer	—	A: Are questions about proper cable repair on-topic? Lundin's answer notes: I just realized that the on-topic page https://electrical.codidact.com/help/topics doesn't address electronics assembly. It does now. I just added: Physical construction of circuits or electrical products, within limits. This is generally on topic when there is some e... (more)	—	over 3 years ago
Answer	—	A: Bit-rate vs Baud-rate Baud rate is about the speed of bit slots in the channel or symbols. Bit rate is the rate at which actual data is transmitted. Put another way, baud rate is what you see when you look at a scope trace of a communication signal. Bit rate is how fast data gets from one end to the other. The bit... (more)	—	over 3 years ago
Answer	—	A: How to plot the I-V curve of a tunnel diode? Apparently you want to measure the current/voltage relationship of a tunnel diode. The tricky part is that the voltage isn't unique for currents over parts of the range. From your question: Image Note that the current is still unique as a function of voltage. One solution is therefore to swe... (more)	—	over 3 years ago
Answer	—	A: Creating an additional "user" Personally I'd rather have everyone use their real name and affiliation. That basically puts their reputation out there on anything they say. If you really believe in something, have the guts to say so. If you don't, then I don't want to hear it. However, that's not the policy of the site. I w... (more)	—	over 3 years ago
Answer	—	A: Please find other ways to hide inloved questions that prompt close I have boycotted the SE and neither asked or answered any questions so am happy to have a new home here. I'm glad you're here. You might also want to mention this in your SE profile, and point people here. For example, see my profile on SE. Also I believe that my and many others who have call... (more)	—	over 3 years ago
Answer	—	A: Using FET based followers and design rules FET source-followers are generally less predictable than BJT (bipolar junction transistor, like NPN or PNP) emitter-followers. An emitter follower output is one diode drop below the input. The voltage across a diode varies little as a function of the current, so this offset remains fairly constan... (more)	—	over 3 years ago
Answer	—	A: ESD Protection - Differential Amplifier Not a diff amp Something doesn't make sense here. You want A1A to act as a differential amplifier, but that's not how you wired it: Image Here is a real diff amp: Image Note how the right side of R1 is tied to ground, not the opamp output. The diff amp above is really a 3-input cir... (more)	—	over 3 years ago

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