Activity for Andy aka
| Type | On... | Excerpt | Status | Date |
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A: LED driver with feedback through light. Which feedback topology is better? > Which topology is preferable? The one below because the LED driver is less likely to produce instability and, if it does, you can always tweak C4 (upwards) in order to kill-off the potentially oscillatory pole produced in the response in your first circuit. How to draw schematics that prov... (more) |
— | about 1 month ago |
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A: MAX485 transceivers breaking, Pi filter generating spikes? What part of the absolute maximum ratings for the A and B data lines do you think would be protected by 33 volt TVS diodes: - Imagealttext If the chip is powered from a 5 volt supply then you use 5.6 volt TVS diodes to ground. Maybe you can raise the TVS to 10 volt if you have a lot of common-m... (more) |
— | about 1 month ago |
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A: MOSFET drain current ringing in saturation region It's got nothing to do with the MOSFET's miller capacitance. Miller capacitance causes problems in common-source circuits but, your circuit is common-drain (or source follower) hence, with a steady DC voltage on the drain (your power supply), there can be no problematic feedback via the miller capaci... (more) |
— | about 2 months ago |
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A: Matched transistors If the data sheet doesn't indicate that the two devices are matched then sorry, they probably are not and, you should use a matched device like the PMP5201Y that you linked. That data sheet mentions "match" 16 times and 3 times on page 1: - Imagealttext There are zero occurrences of the word "m... (more) |
— | about 2 months ago |
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A: High voltage transformer design > When should a transformer core be potted? Should it be potted at all? For this type of job, you would pot the transformer when you can't obtain the necessary creepage and clearance between the secondary (raised externally to 10 kV) and the low-voltage parts of the transformer (including the f... (more) |
— | 3 months ago |
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A: Speed of EM waves from the point of view of an electrical engineer A loss-less coaxial cable has inductance and capacitance and, their associated formulas introduce \$\epsilon\$ and \$\mu\$. But, to home-in on the velocity of propagation, the characteristic impedance must also be determined. We can avoid the complexity of the telegrapher's equations by looking at a ... (more) |
— | 4 months ago |
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Speed of EM waves from the point of view of an electrical engineer An important formula in physics is one that relates the speed of an EM wave (c for instance) with the magnetic permeability and electric permittivity of the medium. In short: - $$c = \dfrac{1}{\sqrt{\epsilon\cdot\mu}}$$ Where \$\epsilon\$ is the absolute value of permittivity of the medium and,... (more) |
— | 4 months ago |
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A: Transformer design for a Series Resonant Converter > The website that I mentioned before mentions the max flux density in ferrites at 400 kHz as being close to 0.04 T. Is this correct? No, you have misinterpreted the graph. The graph shown is flux density (not maximum flux density) and is only telling you one thing; that if you increase the frequ... (more) |
— | 4 months ago |
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A: What are some best practices for library management? There is no definite answer to this but, if you want my advice, you store all symbols and footprints locally with your project. Of course you may begin by using standard parts from a global (comes-with-the-installation) location that isn't under your control but, as soon as you can migrate the ones y... (more) |
— | 7 months ago |
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Apparent loss of reputation in last 24 hours Has anyone else noticed a loss of reputation recently. I thought I checked yesterday and my reputation was a hundred points higher at 1889. Now it is at 1789. My vote summary doesn't indicate a loss. I also reckon that Olin and Lundin have also suffered, particularly Lundin (if suffered is the right ... (more) |
— | 9 months ago |
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A: Role of C2 (bypass capacitor) > Is C2 here to protect the voltage source from thermal noise? There's absolutely no chance that any level of thermal noise produced by a resistor will be sufficient to cause any reasonably designed power supply (voltage source) any problems whatsoever. Even badly designed power supplies will c... (more) |
— | 12 months ago |
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A: DC offset correction loop (DC servo loop). What's its advantage, compared to a high-pass RC filter? > What are the advantages of such DC offset removal loop, compared to an RC high-pass filter? The primary advantage is that it keeps the front-end amplifier output centred in its DC operating region. If you used an external RC filter after the front-end amplifier and, sufficient offsets develop... (more) |
— | 12 months ago |
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A: What does it mean for a signal to have impedance? > What does it mean for signals to have impedance? I expect that what it means is that a particular signal source has an effective series resistance (for a voltage source) or, an effective parallel resistance for a current source. Typically, a signal generator might have an output impedance ... (more) |
— | about 1 year ago |
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Should a fake user's posts be deleted if the fake user has subsequently been deleted by the site The question below was raised by a "new user". The identity of the "new user" was deleted because it was found to be an alias of an already suspended user: - Image alt text So, why is the question still active? It's a fake user created by a suspended user!! Shouldn't the question be "locked"... (more) |
— | over 1 year ago |
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A: How to check realistic specs of small solar panel? All good designs and design testing is based on information contained in the component data sheets. A solar panel is no different so, you need to establish the operating conditions for measuring voltage and current based on the information provided by the supplier of the product. It's quite likely... (more) |
— | over 1 year ago |
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A: How to calculate the voltage of a coil? The magnetic field will always be strongest in the middle of the solenoid. It will be slightly less at the ends of the solenoid and, it will be a lower value on the outside of the coil half way between the ends of the solenoid. In other words, no amount of voltage present on the coil will change ... (more) |
— | over 1 year ago |
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A: Energy harvesting from non-invasive current sense transformer Most of the energy produced by the CT windings is being wasted in the internal burden resistor. See this data sheet to see what I mean. I calculate that it has a 60 Ω burden resistor and, at full primary current (30 amps) it wastes nearly 17 mW of power. At 3 amps, it wastes only 167 μW. ... (more) |
— | over 1 year ago |
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A: Ceramic filter vs ceramic resonator The Murata part you have chosen as a replacement is unsuitable. Its only application is to cheaply replace crystals in oscillators and, as such, it will have a profoundly tight bandwidth (maybe less than 100 Hz or so) whereas the original filter you linked has a 20 dB bandwidth of 750 kHz (as per the... (more) |
— | over 1 year ago |
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Buck-boost converter fed from split input supply I have recently finished designing a buck-boost converter for a job that uses a split (+/-) input power supply. Load power is taken equally from both positive and negative input supplies and, the load is connected to 0 volts (mid-rail of the split input supply). $$$$ For a single rail supply,... (more) |
— | over 1 year ago |
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Deriving resistor values for a taper pad attenuator A taper pad is a resistive attenuator that maintains impedances on both ports and provides a specific amount of gain-loss (\$A{12}\$): - Image alt text I have derived formulas for each resistor (that I know to be correct) and have checked with micro-cap using DC analysis: - Image alt text ... (more) |
— | over 1 year ago |
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A: Technique to reset pulse transformer core quickly > Is there any way to reset a core quickly without having ground / reference terminal pulled towards negative voltage Unfortunately not but, if instead of trying to send the complete pulse through the transformer, you send edge information (i.e. use a series capacitor to perform a kind of diff... (more) |
— | over 1 year ago |
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A: Power amplifier for remote controller The data sheet gives a perfectly good example of using the nRF24L01 without an external PA. It has an internal PA capable of driving an antenna Is there a way to calculate the approximate range of this remote controller? You can use the Friis transmission equation to calculate the free-space li... (more) |
— | over 1 year ago |
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A: Battery protection circuit > What kind of IC can be used to drive the MOSFET, so that when the voltage drops below 6.2 V the battery disconnects from the load? That reverse protection MOSFET works fine for reverse protection but, it cannot be used to turn-off the load when the battery is correctly connected. Look closely... (more) |
— | almost 2 years ago |
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A: Complex frequency of a pole > if we don't apply a sinusoidal signal at the input s may become a complex number $$$$ All real-world signals exist only on the \$j\omega\$ axis. Consider that a complicated signal can be broken down into a fundamental sinewave and its harmonics. The harmonics are still sinusoidal an... (more) |
— | almost 2 years ago |
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A: Unexpected impedance spike when paralleling capacitors I think you can make a pretty good case for the spike being caused by the addition of the 100n and 10n capacitors: - Image alt text > I assume that the solder blobs between capacitors introduced a series > inductance that in turn caused the spike in impedance at 8MHz. It can't be ruled out ... (more) |
— | almost 2 years ago |
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A: Thévenins Theorem for Transistor Circuit > Is the Thevenin's Theorem being applied incorrectly for the circuit ? It's being applied inaccurately. The final Thevenin voltage should be 2.782 volts (rather than your calculated value of 2.61 volts). I calculate the Thevenin resistance to be 759 ohms (near enough to yours so that it doesn'... (more) |
— | almost 2 years ago |
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A: What is this fourth connection in NMOS device? That fourth connection is the bulk/body/substrate connection: - Image alt text Image from here. On a normal 3 terminal MOSFET the "body" is connected to the source. On your device, the 3 n-channel MOSFETs share a common bulk pin that should usually be connected to the most negative voltage of y... (more) |
— | almost 2 years ago |
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A: What reactance actually is? "React" implies a response to an "event". - For an inductor, the "event" is a change in current, \$\frac{di}{dt}\$ - For a capacitor, the "event" is a change in voltage, \$\frac{dv}{dt}\$ $$$$ So, an inductor or capacitor will produce a proportional reaction (or response) to something c... (more) |
— | about 2 years ago |
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A: Why are some PCB design software programs considered to be 'hobbyist' programs? > Why are some PCB design software programs considered to be 'hobbyist' programs? Elitism and, folk with money to burn. I've used Altium, PADs, OrCad, Eagle and my current personal favourite is KiCAD. Yeah it's a bit messy on libraries but it's a small price to pay. I pretty much like Eag... (more) |
— | about 2 years ago |
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A: How can we grow this community? Embedding pictures is a pain in the ass. First you have to find the picture and save it locally then you have to drop it onto a special box before it can be processed. On SE, you just drag it to where you want it to appear and it's job done. There's still the issue of an embedded picture not showing ... (more) |
— | about 2 years ago |
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A: Let's make all downvotes public Very short answer - get rid of downvotes on answers; just don't allow them In fact, wouldn't it be a better policy to award upvotes to people who point out errors. That would encourage folk to want to help people fix crappy answers without the discontent that downvotes bring. OK, it may be a trick... (more) |
— | about 2 years ago |
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Still getting downvotes - what are you guys doing about it? It's still happening: - Image alt text Can someone actually do anything about this? This has happened on stack exchange before but this is ridiculously more far fetched than what has ever happened there. Do you really want to be tarred with the same brush? If this were a criminal offence ... (more) |
— | about 2 years ago |
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A: Flyback transformer for Vout > Vin > How is it possible to generate 500V on a trafo secondary given the 1:1 ratio? In a DCM flyback transformer circuit, the secondary winding is being used as a pure inductor. So, once the primary is disconnected, the rate at which the core magnetic field collapses, dictates the secondary termina... (more) |
— | about 2 years ago |
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Why am I receiving so many downvotes at once? Why am I getting these downvotes? It started last week (or the week before) and now it seems like it's getting contagious: - Screenshot of 9 downvotes on February 6, 2022 Seems like this site has some of the same outrageous inclinations as stack exchange. Downvotes should be registered and view... (more) |
— | about 2 years ago |
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A: How to protect RF switches from ESD? Currently there are $\boxed{\color{red}{\text{three}}}$ downvotes so maybe someone can explain why this has happened. Anyway, on to my downvoted answer: - You have "mentioned" the threat (the ESD level) but, you haven't defined the peak voltage or current limit for the potential victim. Neither ha... (more) |
— | about 2 years ago |
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A: Flyback transformer with Intrinsic Safety > Please let me know if there is anything wrong with this logic. So far so good. The voltage clamp (3 zener diodes for European IS category iA and two for category iB) is the limiter on voltage and, providing you do not generate more then these zeners, it's virtually a rubber stamp job. It's li... (more) |
— | over 2 years ago |
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A: How long does it take for energy to propagate in a circuit? Try this out for size: - Image alt text Hope it's clear. Maybe a little simulation of 10 km 600 Ω line might help paint a better picture: - Image alt text The voltage (V1) that feeds the t-line via the 100 Ω lamp is a 1 volt step. The end of the t-line is shorted: - Image alt t... (more) |
— | over 2 years ago |
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A: 208VAC triple-phase to single-phase conversion > I want to convert the power from the wall from 208V triple-phase to 208V single-phase before feeding that single-phase into the transformer I got. Try this using a 1:1, 208 volts isolation transformer: - Image alt text Or get an isolation transformer that directly delivers 230 V AC on... (more) |
— | over 2 years ago |
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A: Resistance of digital ampmeter Image alt text You might get lucky and be able to measure the input resistance using this method. It should work because the black socket (common) is shared by all measurements. (more) |
— | over 2 years ago |
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A: Inductance vs frequency Inductance is defined by the shape of the coil, the area of the coil, the number of turns in the coil, the distance between turns, the ferromagnetic permeability of material within (and surrounding) the coil and induction to other not-so-obvious conducting parts. Frequency lowering (with a fixed A... (more) |
— | over 2 years ago |
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A: Coupling of inductors > Which will be the total inductance of this circuit? Quite simply, if both the individual 1 henry inductors are perfectly magnetically coupled then, the net inductance will be 4 henries. If both 1 henry inductors are totally uncoupled, then the net inductance is 2 henries. This can be... (more) |
— | over 2 years ago |
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A: Adding resistance to varactor circuit > in my schematic we must add R1 correct? Yes that works except: - Image alt text > One last question if we deliver voltage to a house are there varactors which can handle 120V AC No, they don't exist. (more) |
— | over 2 years ago |
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A: Diodes used in mixers There are plenty of ways a single diode and a couple of resistors can perform multiplication (RF mixing). Consider this circuit that takes two inputs (a 1 MHz sinusoidal carrier wave and a 10 kHz triangle wave used to modulate the carrier): - Image alt text Now look at the signal on the cathode... (more) |
— | almost 3 years ago |
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A: Extract DC component of mixed signal > How can we extract a DC signal from a mixed signal? You use a low-pass filter with a cut-off frequency that is significantly lower than your lowest AC signal frequency. If you need better filtering use a higher order low-pass filter. If you need both fast response to the DC level and high AC ... (more) |
— | almost 3 years ago |
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A: Capacitor ESR vs. Impedance > Which graph on the picture above better represents real-world use-case? They both represent real-world use cases. The impedance graph informs you how much ESL (effective series inductance) the capacitor has and, at the series resonance point you can evaluate the ESL value with a simple formul... (more) |
— | almost 3 years ago |
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A: Filter RF Harmonics With Additional PI Network > Since we are trying to keep the impedance matched to 50 ohms, what is the best strategy to approach this circuit? A low pass \$\pi\$ network seems a good route to go. Basically your \$\pi\$ network is designed to do two important things: - - Impedance match a 50 Ω source to a 50 Ω... (more) |
— | about 3 years ago |
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A: Why is it is always power consumption or power delivered more in usage? > In circuit analysis why always the power has upper hand over energy? One obvious reason: - If we calculate how much power a resistor dissipates we can calculate how hot it will get (knowing it's thermal resistance and ambient temperature and some other factors). We need to know how hot stu... (more) |
— | about 3 years ago |
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A: Is it always necessary to use the ground terminal of the oscilloscope probe? To add to Olin's excellent answer, if you were probing on a digital IO line in order to view a fast changing signal, without the local ground clip (or spring) grounded close to where you make the measurement, you would, in effect, be adding an antenna to that IO line and causing interference to other... (more) |
— | about 3 years ago |
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A: What should be considered when picking a flyback diode? > a coil with plain on/off functionality, for example a 24VDC relay coil with 700mW max coil power. That means a coil current of 0.7 watts / 24 volts = 30 mA. A relay might have a coil inductance of anything from 1 henry upwards but this can be estimated by the relay activation time in the... (more) |
— | over 3 years ago |
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User's reputation score not displaying on top ribbon It appears that a user's reputation score has disappeared from the top ribbon at the side of the user's login avatar/picture. Is this an intentional thing? (more) |
— | over 3 years ago |