Activity for Olin Lathrop‭

Type	On...	Excerpt	Status	Date
Answer	—	A: Resistance of digital ampmeter What you linked to is more of a user's manual than a datasheet. Particularly for more consumer-oriented meters, this spec may not be explicitly available. However, you can easily measure it. Use an ohmmeter to measure the resistance of the ammeter. You should see the ammeter report a small curr... (more)	—	over 2 years ago
Answer	—	A: What is sacrificed when buying cheaper oscilloscope probes (of same BW/cap/R/gain) Some issues: Physical robustness. Some probes just are built better than others. How well does the clip pop off? How well does it stay on when you don't want it to pop off? How solid is the hook at the end of the clip? Is the hook sized well? When you remove the clip, how sharp but yet s... (more)	—	over 2 years ago
Answer	—	A: Low-frequency PWM-controlled Mosfet heater circuit Your main complaint seems to be that the 24 V power rail sags 800 mV when the heater is on. Three responses pop to mind: So what? It probably isn't anyway. What did you expect? #1: So what? I don't see any harm in the 24 V supply actually being 23.2 V when the heater is on. Unless ... (more)	—	over 2 years ago
Answer	—	A: MOSFET not turning completely off To protect against future changes and to provide something slightly more readable, here is your schematic: There is no immediately obvious reason the FET should blow, but there are a number of issues here: If "VIN17V" is to be believed, and the voltage really is 17 V, then that is way too m... (more)	—	over 2 years ago
Answer	—	A: React feature guidelines? Summary "Outdated" should be used for "this won't work anymore today", not "we would do this differently today". Detail "Outdated" should be reserved for when an answer is wrong or misleading because something has changed since the answer was written, and it's not obvious that the answer app... (more)	—	over 2 years ago
Answer	—	A: React feature guidelines? I think "dangerous" is pretty clear. It's when doing as recommended can cause significant damage to property or health. For example, recommending to a hobbyist to make a direct line-connected capacitor charge pump power supply for powering his breadboard would qualify. Dangerous does not mean ... (more)	—	over 2 years ago
Answer	—	A: Most correct term for radio switching noise? I don't think there is a formal term that means exactly what you describe. Switching transients generally means short term glitches that might cause noise, usually resulting from power being switched on or off. Note that this refers to the transients that cause the noise, not the noise itself. ... (more)	—	over 2 years ago
Answer	—	A: Find feedback of circuit You are asking about feedback in this circuit, and how R3 fits into that: First, note that the circuit is an emitter follower, and has a voltage gain less than 1. Second, R3 bypasses the transistor for most input voltages. The block diagram you show is usually meant to be used when the for... (more)	—	over 2 years ago
Answer	—	A: PTC resettable fuse leakage current That's a marketing blurb. Look at the real datasheet. I just checked a polyfuse datasheet, and see that there is usually only about a 2.5 to 3.0 ratio of trip current to hold current. That should be enough to keep the motor from overheating. Polyfuses work on heat. When cold, they have low r... (more)	—	over 2 years ago
Answer	—	A: CAN "split" pin, bus termination and common mode stabilization Can anyone explain the theory behind this pin You have already done so yourself: used to give a common mode stabilization and thereby reduce radiated emissions As far as I know, that is exactly the reason. Since the CANH/CANL lines are supposed to be a twisted pair, radiation comes from the... (more)	—	over 2 years ago
Answer	—	A: Driving PMSM machine as an AC induction machine A motor with stator winding and permanent magnets on the rotor, is very different from an AC induction motor. As a result, they require very different drive. You can just apply an AC signal to an induction motor, and there will be a net startup torque. The actual torque is a somewhat complicated... (more)	—	over 2 years ago
Answer	—	A: Change of pins in monostable multivibrator The circuit you show doesn't make any sense: Start by examining the steady state condition. In steady state, C1 is effectively an open, so you ignore it. R4 keeps Q1 on. That means the collector of Q1 will be low, which keeps the base of Q2 low, which means Q2 is off. The diode doesn't d... (more)	—	over 2 years ago
Answer	—	A: Quality control of the site There are four things we can do with bad or poorly written questions. In order of seriousness, these are: Leave a comment. Downvote. Close. Delete. The questions you mention have mostly been addressed with #1 and #2. Do you really think more severe measures are appropriate for th... (more)	—	over 2 years ago
Answer	—	A: Capacitance of inductor What is a typical value for capacitance of a real inductor? "Typical" capacitance is a useless to design circuits with. It will also vary considerably by inductor size, geometry, and materials used. The only real answer is in the datasheet of whatever inductor you are considering using. There... (more)	—	over 2 years ago
Answer	—	A: Inductance vs frequency No. An inductance is an inductance. One way to look at an inductance is as an impedance that is a function of frequency:     Zind = ωL = 2πfL Where Zind is the impedance magnitude of an inductance, ω and f the applied frequencies, and L the inductance. When &omega... (more)	—	over 2 years ago
Answer	—	A: Current and voltage of inductor For reference, here is your circuit properly drawn with component designators: The question is what happens when the inductor current starts at 0, then the switch is closed. The first observation should be that the current source and the two resistors can be reduced to the equivalent Norton... (more)	—	over 2 years ago
Answer	—	A: Select resistor for a diode What the "appropriate" value of R1 is depends on what you are trying to achieve, which you haven't told us. Will this device be used in bright light, like outdoors, and the LED therefore needs to be as bright as possible? Is it an illumination source? Is it just an indicator, and it only needs to ... (more)	—	over 2 years ago
Answer	—	A: Diode like a frequency mixer A diode mixer exploits the fact that the voltage across a diode is the log of the current thru it, to a good enough approximation for many uses. Now note that multiplication can be performed by taking the log of two values, adding the logs, then doing the un-log (take the exponential) of the result.... (more)	—	over 2 years ago
Answer	—	A: Thermal relief for through-hole on multi-layer PCB That's a rather strange thermal relief pattern. It's also not clear where the hole is supposed to be. A proper thermal pattern has a plated hole and annular ring around the hole as usual. Then there is a gap with only a few narrow bridges connecting the annular ring with the surrounding plane. ... (more)	—	over 2 years ago
Answer	—	A: What is the difference between emitter and collector of a transistor? I see you already have an answer based on the device physics. I'll answer that this means in a circuit. BJT (bipolar junction transistors) do work in reverse, at least somewhat. Generally, the characteristics aren't as good, particularly the gain. However, in most cases you still get some gain ... (more)	—	over 2 years ago
Answer	—	A: SPI modes difference "Stream" and "memory mapped" should be defined in the documentation for whatever microcontroller you are using. "Memory mapped" can mean different things. It might be just a different way of saying DMA, meaning the peripheral gets and puts data directly to memory buffers without code intervention... (more)	—	over 2 years ago
Answer	—	A: $Q$ and $\overline{Q}$ in bistable multivibrator Whichever you choose. I notice that you deliberately made the gain of one transistor a little higher than the other. That is irrelevant. The positive and negative outputs don't depend on the power-up state. They depend on which way the outputs go in response to inputs, like SET and CLEAR. Yo... (more)	—	over 2 years ago
Answer	—	A: A signal with one mode or with three or more modes with just one mode Others have already explained that "discrete" means a finite set of values, not just two. This is to point out that having just one "mode" (it seems you mean symbol) doesn't make any sense. A signal that can only ever be in one value is no signal at all since it can't carry ... (more)	—	over 2 years ago
Answer	—	A: Motor Controller - What might be the purpose of these resistors? Reasons this is sometimes done: To get higher power dissipation. To get higher voltage capability. To get lower parasitic capacitance. For 1 and 2 the "normal" answer is to use a resistor rated for the required power or voltage in the first place. However, there are some advantages t... (more)	—	over 2 years ago
Answer	—	A: Adding resistance to varactor circuit in my schematic we must add R1 correct? No. Ultimately you are adjusting the varactor with a DC voltage that has a certain impedance. You can think of it as a Thevenin source. In your case, the DC voltage is created by the divider of Rs and Rv, then the impedance increased by R1. However, yo... (more)	—	over 2 years ago
Answer	—	A: Is English translation of technical terms on-topic? I think such questions are OK as long as they are EE-specific. General purpose dictionaries often do a poor job with specialized technical terms, especially when they are the same or similar as regular words in either language. There can also be nuances how EE-specific terms are used in different c... (more)	—	over 2 years ago
Answer	—	A: Division of binary numbers logic circuit I dont understand how to make a logic circuit which does that job:check if the divisors is greater and equal or less than the most left digits of the divident So think about it. Break it down into small chunks. Let's ignore the reason behind your question and try to make a digital block that com... (more)	—	over 2 years ago
Answer	—	A: 2 bit subtractor using full subtractor We don't just give direct answers to homework (or homework-like) questions here, but can help you work thru the problem on your own. You might consider trying to synthesize a subtractor from scratch, just like you would an adder. The fundamental building block of an adder is the half-adder. It t... (more)	—	almost 3 years ago
Question	—	What is this metal panel under power lines? I was hiking around the Berkshires in western Massachusetts yesterday, and came across this metal panel where some power lines were crossing a ridge: Image alt text Image alt text Image alt text The panel is a few meters wide, and appears to have no electrical connection to it. It cost... (more)	—	almost 3 years ago
Answer	—	A: Can a paper be a tutorial or textbook-like? This is a good question. I wasn't originally envisioning introductions to known concepts, but that might work if well written. If so, the Paper should at least be clearly labeled as such. We don't have a lot of Papers, and I wouldn't want to see introductory material drowning out new concepts. I ... (more)	—	almost 3 years ago
Answer	—	A: What are the guidelines for porting one's answers from ElectricalEngineering.SE, if any? Sorry I didn't notice this earlier. We definitely don't just want to import questions and answers directly from SE. This has been discussed several times on various Codidact sites. Some of the first few Codidact sites did mass-import from SE, and that didn't go very well. Those sites are doing ... (more)	—	almost 3 years ago
Answer	—	A: Input offset voltage/bias current noise contribution in operational amplifiers While input offset voltage is technically noise in the sense that it is something unwanted added to the signal, it is not included in opamp noise specs as far as I have seen. Think of the "noise" spec as the AC part of the noise, with the offset voltage and current telling you about the DC part of... (more)	—	almost 3 years ago
Answer	—	A: Electric circuit with antenna Antennas are not lumped-parameter systems. They may be open circuits or shorts at DC, but this changes as the frequency goes up. They aren't just a bunch of wires anymore at the intended operating frequency. Take a simple dipole as example. It's just two disconnected wires at DC, but that doesn... (more)	—	almost 3 years ago
Answer	—	A: Diodes used in mixers Take a look at the circuit and try to see what function it will perform on the input signals to yield the output signal. For simplicity, let's consider the diode ideal, R1 and R2 the same, and R3 much larger. R1 and R2 will average the two input signals onto the anode of the diode. The diode wil... (more)	—	almost 3 years ago
Answer	—	A: Trouble understanding how to use adjustable LDO regulator I just happened to re-read this question, and I now think I see better what Microchip was trying to say here: On closer examination, I think this is actually correct but badly worded. I believe it should be interpreted as: Dropout voltage is defined as the input-to-output differential when... (more)	—	almost 3 years ago
Answer	—	A: MOSFET differential to single ended converter intuition To be clear and protect against possible future edits, here is the circuit being discussed: As you say, this is a differential to single ended converter. In this case, the MOSFETs have likely been optimized so that they act as voltage-controlled current sources over most of their range. They... (more)	—	almost 3 years ago
Answer	—	A: Voltage of tank circuit is invalid You need to be more careful. First, you should have been able to see for yourself that the first equation isn't written right. I'll assume the whole "-0.5t" is the exponent of e. You were too sloppy to notice, or too lazy to fix it. Either way, it's really rude to the volunteers here. That's w... (more)	—	almost 3 years ago
Answer	—	A: Capacitor in 2nd stage of opamp That looks like the internal compenstation capacitor. It creates a single dominant pole over most of the opamp's intended operating range. Opamps with dominant pole compensation can be characterized by a fixed gain bandwidth product from a bit past the dominant pole frequency and higher. This ch... (more)	—	almost 3 years ago
Answer	—	A: Battery voltage: to boost or to connect in series. To summarize the problem, you have 12 V battery packs that you don't want to change due to certifications, but you need to power a 48 V 4 A load. The battery system also needs to be compatible with an existing charger that is meant to charge each of the 12 V packs with the negative ends tied togethe... (more)	—	almost 3 years ago
Answer	—	A: Trouble understanding how to use adjustable LDO regulator Your question is quite long, so it's not clear what exactly you are asking. It seems the main point is what Microchip means by Note 5 on page 7 of the datasheet: You are right, that makes no sense. Fortunately it's so clearly inconsistent with itself that you know it's wrong. Not all datash... (more)	—	almost 3 years ago
Answer	—	A: Help with differential to single ended voltage converter First, let's draw the schematic properly so that it's not so annoying to look at: Yes, it's a differential amplifier. Q1 sinks current as a function of VIN+. Q3 and Q4 are a current mirror that takes the current sunk by Q1 and dumps a current of the same magnitude onto Q2. When VIN- is a li... (more)	—	almost 3 years ago
Answer	—	A: Unexpected phase shift in results I get a phase shift of 90 degrees between voltage of the capacitor and current through the capacitor which doesn't make sense it should be 45 degrees You don't need a whole circuit to see that the phase shift should be 90°. You can see that from a capacitor in isolation. The current thru a... (more)	—	almost 3 years ago
Answer	—	A: Current and voltage in AC circuits without impedance Since this is homework, I'm not just going to give you the answer. When all else fails, go back to first principles. That's what handy shortcuts, like using impedance, were derived from. In this case, you'll end up with a system of differential equations. You have already written the equation... (more)	—	almost 3 years ago
Answer	—	A: Questions about the style of "Papers" say that materials should be small and focused There are many many theories of how to best present information. Any one or two particular opinions aren't really relevant, especially since there is a such a broad range available. The point of what you quote was mostly to set the expectation tha... (more)	—	almost 3 years ago
Answer	—	A: Meaning of some components around voltage reference in SMPS At first glance, R22, C22, and C23 look like a compensation network around the TL431. However, this doesn't make much sense because the TL431 is being run open loop. Rfbt and Rfbb divide down the output voltage. The TL431 is turned on when that reaches 2.5 V. The TL431 is therefore used to compar... (more)	—	almost 3 years ago
Answer	—	A: Contactor control - Higher voltage PWM Your basic idea is fine, but your implementation is not. C1 makes the whole thing not work, as it will block DC. C2 puts a burden on the switch. D1 would preferably be Schottky. I'll write a more detailed answer when I have time, probably tomorrow. I'm back now and have more time to answ... (more)	—	almost 3 years ago
Answer	—	A: Is there a way to reliably measure antenna return loss outside a lab? It sounds like you are doing the measurements right. However, I expect the problem is in the space around the antenna. At 434 MHz, the wavelength is 690 mm or 27 inches. Everything out to about a meter or 1½ m should be considered near field, and can effect the antenna directly. This inc... (more)	—	almost 3 years ago
Answer	—	A: What is the popular 12 V DC jack connector? There is no "standard" 12 V DC jack. Asking end users to buy a separate power supply is asking for trouble. Don't expect users to know about center-positive versus center-negative, and inner and outer barrel diameter. If this is an OEM product, then you can provide binding posts or even just lab... (more)	—	almost 3 years ago
Answer	—	A: What is the purpose of paralleling capacitors on the input/output of a power converter? Lower ESR can sometimes be a reason, as you say. However, most of the time the advantage is a wider frequency range over which the combined capacitor has low impedance or low dissipation. The frequency capability of a capacitor depends on its type, and generally reduces with higher capacitance. ... (more)	—	almost 3 years ago
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

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