texts: SOA analysis for MOSFET-based Electronic Load

texts:
I'm working on a second-generation design for an electronic load. The first generation is described in this prior question if anyone is interested (scroll down to section containing first photo), but this question doesn't bear on it much.

The load has this conceptual schematic. Loop compensation, gate drive, and device choice are neglected here for simplicity.

A comment by Neil_UK on this question got me thinking that the thumbnail-sketch SOA analysis for the MOSFET I did for the first generation might not be quite adequate, so I thought I'd take a more formal approach.

The specs for the load are:

1.5 to 30 V (from connected source)
0 - 5 A (within limits of power dissipation)
30 W maximum power dissipation

One of the devices I've been considering for this second generation is the FQP13N06L (datasheet here). The datasheet contains a nice SOA chart that seems to give me what I need. I've indicated the bounds of my expected operating area with a red line (neglecting effects of \$R_{DS(on)}\$ at low \$V_{DS}\$:

Now, this all seems straightforward to me as I'm reasonably well within the DC boundary. But Neil_UK's comment has been niggling at me and I'm wondering if I'm missing something:

  Don't let a 50 watt FET fool you into thinking you can dissipate 50 watts in it like you can a 50 watt BJT. You can if it's saturated, and blasts from on to off in microseconds, you can't if you try to use it in a linear mode, like the pass element for a linear regulator, controlled load, or audio amplifier output device. The Safe Operating Area has timing constraints, the array of cells in the FET unbalances thermally if dissipating for too long. – Neil_UK

The other uncertainty I have is that the datasheets for the IRFZ24N I used in the first generation (and other devices in that family) don't have a DC line. Based on Spehro's answer to this question on SOA I'm figuring I can just draw that in myself (in red below) based on maximum continuous drain current (12 A) and power dissipation limits (45 W):

So my question is: "Am I understanding this correctly? Or is there a long-term heat-dissipation problem with MOSFETs I'm not seeing?"


texts: What happens with transistor outside max temperature range?

texts: Suppose I have an IGBT transistor rated for 60A, that has junction temperature range of -55 to 175C. What happens if I do not exceed max current, but I do exceed max temperature? The characteristics in the datasheets don't seem to have any changes around max temperature limit, so what is the problem? I would like to see some basic physics behind it in the explanation.


texts: Why this source transformation leads to different result?

texts:
I've been stuck for this source transformation, it seems quite simple, but I just can't tell why the results are different.

As pictures below, I transformed (-3mA par 5Kohm) to (-15V series 5Kohm), but Vab just not the same. I appreciate if anyone can help me, thank you.

I am trying to think the way you simplifed the circuit but got stuck at the final step. I am fluent with solving problems by applying Nodal, Mesh and Thevenin methods(Vth, Isc, Rth), but lacking of schematic sense. So I try to solve this by cogitation instead of calculation only. Below is what I think, I know I am totally wrong, but can you give me some advise to clear the concept? Thank you very much.


texts: PCB Design - Mini Pcie Express to Thunderbolt 1 2/Mini Display

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What I want to achieve is to connect a Mini Pcie Express device to a thunderbolt (1 / 2) port. I have looked around and such connector does not seem to exist, so as a computer engineer I went looking on how I could design my own PCB for that.

From the information I gathered so far, it seems that Pcie should work straight through Thunderbolt. I have seem the specification for mPcie and of the minidisplay port(which should be the same as thunderbolt).

 https://imgur.com/a/Q2fRI5P

 https://imgur.com/KpOJF2I

Through my readings I found out that Pern0 and Perp0 are data receiving pairs and Petn0 and Petp0 are data transmiting pairs.

I was unable to find decent specifications regarding the thunderbolt end point,  my big question then is, in which lane in the display port cable should I put Per and Pet, and if there would be a need to supply information to Pin 2(hot plug), 4(config1), 6(config2), 20(pwr out) in the mini display port cable. Also, is there anything else that would have to be supplied to the Pcie ?

There are a few thunderbolt docks, with PSUs, etc that achieve what I'm trying here, but they are way too expensive and overkill to my problem. I am also trying to this to learn more about PCB design.


texts: Can I use 8pF 200ohm 10MHz crystal with ATMega88 w/o caps?

texts:
I'm trying to save board space. I know crystals typically have 20-30 pF ratings, and need 20-ish pF caps to ground.

I found this crystal: http://www.mouser.com/ProductDetail/AVX-Kyocera/CX3225GB10000D0HEQCC/?qs=sGAEpiMZZMsBj6bBr9Q9aSMajaFx5yeOFWolaA6tkgz4rswCxFq0Sg%3d%3d

It's extra-small (2.5x3.2 mm), has an ESR of 200 ohms (which seems high - is that going to be a problem?) and a load capacitance of 8 pF.

I know that in general, you need caps to ground. But I have also read that there's typically 5-10 pF of parasitic capacitance which should be subtracted from the caps you add. So - does an 8 pF crystal need caps at all?

This is for a real product, so I don't want to cut corners if it will hurt reliability.

EDIT: I found two other people asking the same question; I read the answers they got; I still don't know whether it's correct to leave off the caps.
How do I deal with different XTAL pin capacitance when selecting XTAL and load capacitors and How do I choose the correct capacitors to use with my Crystal?

One of the answers said it would be "easier" to design with a crystal with more capacitance, but didn't say why; other answers say that getting within a factor of 2 is probably sufficient. From this, I deduce that the more capacitance the crystal needs, the less you will be messed up by mis-estimating the stray capacitance. So I should pick a crystal that needs 30 pF, put 25 pF on each leg, and I'll probably be good.


texts: How to choose TVS/ ESD for sensitive application?

texts:
I am using ad8232 ECG with 3 electrode configuration,
Edited
ad8232 used schematic
I need to protect circuit from any voltage more than 5V, since ecg measure only around 300mV with common mode signals. the circuit should protect from even high voltage such as 5V to 150V surge current max 50mA at 50Hz-200Hz range,
I have a doubt,
I hope to use bidirectional TVS/ESD due to all leads are on body. and same GND is on body for another application
How to choose correct TVS that will not affect ECG measuring signal range (0-300mV) at all. or with minimum affect, what parameters of TVS/ESD should I consider?


texts: Bluetooth receiver board into 60's console stereo Tape In

texts:
I'm looking for a bluetooth receiver board to connect to the Tape In of my 60s stereo record player console.  We've used our Android phones with a 1/8" to RCA Y cable into the Tape In, and it works great and plays at a similar volume to the other inputs (radio, phono) when the phone volume is all the way up.  I've been through 3 cheap bluetooth reciever boards (THIS, THIS, and THIS), and they are all much quieter (by about half) than the other inputs, which leads to deafening sound if you flip to radio without remembering to turn it down.
I tried a 5W amplified version of the board (THIS), and even if I turn it way down, the scratchy buzzing noise over top of the music is extremely loud and awful.
I seem to understand that the headphone out of my phone is a higher level than the line level being provided by these boards.  I'm happy to keep trying other devices to see if one is louder, but it looks as if they are all going to provide a line level that is too low.  I'm also happy to buy/build something to solve this problem, but what would it be?  I'm also happy to buy one of those cheap TFT digital oscilloscopes to help diagnose the problem and/or test new hardware options, but I'd need to learn how to use it for that.
Open to all suggestions!


texts: What is this kind of "Multiplexer" called?

texts:
First of all I am new to electronics so i might use wrong terms.

What is this electronic component called or is it even a thing (Can it be bought)?

I have 10 input wires/channels for example. Only one wire is active at a time (5v).

The "multiplexer" output is the number of the active wire/channel.


texts: At what point should I switch between a resistor divider and a LDO?

texts:
My problem is that I have a RF chip which is supplied 3V3 and interfaces with my MCU over 1V8/2V8.

I have an external source of 3V3 which will supply the RF chip. I'm space restrained on my PCB and as such would like to have the least amount of external extra components. This means I prefer not to LLC the UART lines between the MCU and RF chip.

My MCU can run on between 1V8 and 3V3. As such it would be possible to run the MCU at 1V8 and bypass the LLC question.

Would it be possible to run this MCU using a resistor divider circuit wherein the 3V3 is converted into 1V8?

My MCU sinks 142 µA/MHz at 3V and runs at 24MHz making 3,408 mA at 3V. (5,68mA @ 1V8) Which is a relatively small amount of current which makes me think the normal problems with resistor circuits as supply source (e.g. variable and highly subjective voltages) would be possible.

Is this line of thought correct or would I be better of using an 3V3->1V8 LDO?


texts: How is the filter response affected by the sampling rate?

texts:
At this filter, the sampling frequency is changing the output bode plot.
I have never thought this before. What is the explanation of this?
edit: will be updated soon!


texts: Seeking ideas for powering a hot water cylinder directly from solar panels in an off-grid situation

texts:
At our off-grid cabin, I want to power a 240V 3 kW residential hot water cylinder more or less directly from a 5 kW solar array (when the sun is shining). The panels are not required to do anything other than heat the water. If the sun is not shining then we have no hot water - that's OK.

I want to use as few as possible parts, except for the panels themselves and the hot water cylinder.

Looking for design recommendations.

Here are some solutions I have rejected.

Solution 1 (the "chuck the kitchen sink at it" solution):

Connect the panels to a charge controller such as an Outback FM80 (http://www.outbackpower.com/downloads/documents/flexmax_6080/specsheet.pdf)
Connect the charge controller to 4 x series connected 12V car batteries (no real storage effect - just enough to keep the inverter charger working)
To the "battery bank", connect an inverter/charger likethe Outback VFX3648 (http://www.outbackpower.com/downloads/documents/fx_vfx_series/fxvfxeries_specsheet_english.pdf)
Connect the AC out from the inverter to the hot water cylinder

Add to the above some kind of circuitry to turn off the inverter when the sun is not shining (we never want to actually dip into the ultra light-weight battery bank).

I believe this would work, but would be hideously expensive. Also when the power from the sun drops below the 3 kW drawn by the water heater, the inverter needs to be shut down - whatever power is available is wasted.

Solution 2 (the "AC? who needs stinking AC?" solution):

Connect the panels in a series/parallel configuration, with a blocking diode in series with each string, such that the peak voltage from the array is < 240V (the rating of the water heater).
Connect the resulting DC directly into the heater element of the water heater.

I like this solution from the point of simplicity, and virtually zero parts cost. Also it makes best use of the available solar energy, and will work even when the sun is low, by just pumping a lower DC voltage into the heater.

However I am concerned about damage to the heater's element due to electrolysis, from running it on DC instead of the AC that it is designed for.

Solution 3 (the "dunno quite how" solution):

Some kind of DC to AC chopper that can turn the DC from the panels into AC, at <= 240V.

I don't believe the heater will suffer if it is driven from a lower voltage than it is designed for. This solution also makes maximum use of the available solar energy.

However I'm not familiar with building this kind of circuitry, or whether this is in fact a good idea or not.


texts: Using Solid State Relay board for wired low-voltage switch activates AC outlets

texts:
pardon the noob question (though I have a EE degree back in the day, it's been a long time).

Let me ask this simply, then explain my use case below. I am wanting to use several existing CAT5 cables with a simple manual switch on them to activate individual AC outlets. I'm thinking that something like the SainSmart SSR board should do it. However, all examples of using relay boards like that relate to computer controlled applications. I don't really need all that. I just want a remote low-voltage switch to kick on an AC outlet. If it matters, each outlet is only going to pull 20-50 Watts.

I'm thinking this should conceptually be okay for what I want. But... I don't know exactly how to hook it up. Would wiring a separate 5V DV supply to the switch and then to one of the input terminals on the relay board do the job? Would I need a limiting resistor? or is that built in? From the schematic, it looks like that's included and I'd just apply +5V to the channel input.

If this were something I could quickly buy and play with, I'd do that, but it looks like these things take 3 weeks to arrive and I don't see any option to return it. So, I was hoping someone could toss me some advice on this.

Here's the details on the use case. I'm trying to replace a whole-house stereo system with a DIY version. Each room has CAT5 run from the central location to a control panel in each room. however, those control panels are shot. So, rather than replace with a new set of panels which will just wear out and avoiding a more expensive remote-control (or even iphone) based system... I want to leverage the CAT5 in the room to just have a simple switch to turn on an outlet for a small amplifier which will drive that room's audio. Thus, each room can then independently kick on a small amplifier for that room (rather than a big expensive multi-room amplifier). Each zone is just going to have a 20 watt amp (possibly a 50 watt in a large room) so it's not a lot of power. but, I obviously don't want to try running the AC power to the amp's power supply via the CAT5. And, even though the amps have a 12V DC power supply which I could potentially run over CAT5, I think that's going to try to pull too much current. So, that's why I'm thinking a SSR or traditional relay is what I want to be using.

Further clarifications: I have one central hub (basement closet) where all wiring is routed. so, from that closet, CAT5 goes out one line to each room. Also, from that closet, a pair of speaker wires go out to each room. My plan was to use a distribution amplifier from an audio source to feed a series of small amplifiers--one for each zone. and I would use the CAT5 to simply kick on an outlet to activate power to that room's amplifier. The audio source is going to be something I can manage via iphone app (select audio stream, volume, etc.) so I just want something to control which rooms have the sound turned on. I know this is crude and simplistic. but, I don't need an awesome elegant system. I'm looking for cheap.

I hope that makes things more clear. Audio and power isn't really bouncing around the house... it's all centrally located. I just want to find a way to remotely "flick a switch" to kick on the amp for the room I'm in.

Any issues with doing what I want? Any other products I should be considering? I don't want to go spend $400+ for a commercial product and I don't want to go completely DIY (I can solder, but I don't really want to build an 8-channel relay circuit from scratch either).

much appreciated for anyone to help guide me before I order and waste time waiting for something to arrive which might not work.


texts: Why does design_vision compile my carry-lookahead adder into a ripple-carry adder?

texts:
At my school we have Synopsis "design_vision" in the computer labs. I don't know how to use any of the features so to me it's just a schematic-drawing tool.

Out of curiosity, I hand-coded in Verilog an 8-bit carry-lookahead adder, and then asked design_vision to compile it. The result looks a lot like a ripple-carry adder.

Now, the ripple-carry adder uses fewer gates, but it is so much deeper. Why does design_vision prefer the ripple-carry?


texts:
I'm doing some calculations for a system that is going to use a few buck converters. I need to make sure that the battery will be able to feed enough current but I'm not 100% certain how power on the output and power on the input relate.

Using a power resistor in series the battery will see the same current draw as the lower-voltage circuit.

What draw does it see with a buck converter and is it relative to the load?


texts: Xilinx XPS does not shown user IP cores, not even when IP core is generated in XPS; how to make it?

texts:
The Xilinx XPS (part of EDK) should have a list of IP cores present in the directory structure that I searches, but there are none, as seen in the figure below where the red ring indicates where the list of IP cores should be:

Even if I create an IP core template using Hardware => Create or Import Peripheral... feature, as seen in figure below, the create IP core template does not show up for use in XPS.

How can I get access in XPS to the collection of IP cores that I have?


texts: GND connections and ground plane routing?

texts:
When I let Altium do autorouting and then I define a ground plane using a polygon connected to my ground pin, I often get layouts where a GND line is flanked on both sides by the GND polygon, and then at the ends, both connectors are connected to the GND polygon:

Is this actually good layout for a ~10-50 MHz circuit? Would it be between to get rid of the gaps between the two grounds (image center) and have the ground plane be continuous?  That way there is more conductive material, and the left and right GNDs have a shorter path between them.


texts:
Im new to electronics and have problems with calculating the resistors needed for driving an IR LED with an transistor.

My VDD is 3.3V, the LED needs 1.3V and I want to drive it close to 20mA, so I need a 100Ω resistor. But how can I calculate R2?


texts: P Channel mosfet seems to put out the voltage of the MCU input

texts:
Please help me understand this.

I built this circuit, exactly, with the exception of the Zener.

When I test the output of the  Channel mosfet, it shows approx 2V below whatever voltage I used to trigger the gate on the N channel side.

For example, if I place 12V on the N channels gate, the P channel Drain, measured at the drain is 10.5V, and if I put 24V on the N Channel's gate I get 21.3 on the P channel's Drain.

I have searched and read and all seems to point that I should be getting approx 24V (VDD)-IlRDS at the drain.

What on earth am I not understanding here? Surely, irrespective of whether I apply 12 or 24 to the N channels gate, should I not be getting 24V-IlRds on the P channel's drain? Why am I getting 10.5 or 21.3V on the drain?


texts:
I am referring to Xilinx FPGA P/N: XC6SLX45-2FGG484C (Spartan-6)

Link for part: http://www.digikey.com/product-detail/en/xilinx-inc/XC6SLX45-2FGG484C/122-1674-ND/2408284

Link for pinout: https://www.xilinx.com/support/packagefiles/s6packages/6slx45fgg484pkg.txt

My query is, if I want to use SPI interface for ADC,Touch and memory.. Do I need to use any GPIO's or dedicated SPI I/O's only ( SCK,MOSI,MISO,CS)?


texts: How to debug a program using FTDI in STM32CubeIDE?

texts:
I want to debug a test project for my board the STM32F103C minimum systemboard, sometimes called the bluepill, I use linux so i downloaded the original STM32CubeIDE as .sh execute it and downloaded everything needed.

after creating a new project and ready for debugging, when debugging when I choose the debug probe I didn't see anything related to com ports or FTDI which i previuosly used in Arduino IDE, I googled the internet but couldn't find anything related to FTDI, and i am a total beginner when it comes to this STM32CubeIDE and don't know what to do, I will already get an ST-Link v2 for me so that I can debug using ST-Link easly but at the moment i don't have except an ftdi board which i use to upload sketches to the board using the Arduino IDE.

in short i was using the Arduino IDE so i upload all my programs to the board using a FTDI usb to serial converter, now i want to learn how to use the original software for my board The STM32CubeIDE, when debugging I couldn't see anything related to FTDI to upload my code so please help me.

Thanks in advance.


texts:
I've been looking for a simple LED fade in/fade out circuit when power is turned on/off for a 12 V LED. I have tried the following circuits but the problem is that I can't reach the full brightness of the LED that it reaches when simply connected to 12 V power supply.

I think it is due to the resistor which connects the capacitor to VCC. It allows the capacitor to charge slowly and show fade in effect, but also limits the current and thus max output voltage. I have tried altering the component values but if I decrease the value of the resistor the fade in effect gets faster.

Please help me with this.

EDIT :-

(Sorry for not mentioning these points before).

1) Don't worry about the fade in/ fade out time being same. I just need a good fade in effect and don't care about the fade out.

2) WHAT I NEED IS - I just need a circuit at the output of which the voltage goes from 0 to 12v when power is on and from 12 to 0v when power is off. Please suggest me a new circuit if this is not possible with the one below.

Thanks...

simulate this circuit – Schematic created using CircuitLab


texts:
I need to sequence some micropower (low-microamp range) logic at a once-per-several-minute rate, and am falling back on the good ol' 4060 as my timebase (plus a 138 and a 534 for the sequencing).  I need to run the 4060 oscillator in the 1-10 Hz range, which according to the numbers I can do with resistors <100k and X7R chip caps <1 uF or so.  Tolerance, drift, board leakage, etc will be adequate for my application based on specs for the passive parts... my question is are there any gotchas running the 4060 oscillator that slow?  I know the divider chain is fully static but... rise time limits?  Capacitive loading?  Other things not mentioned in the datasheet?  I get nervous once I get off the edge of the datasheet performance curves...

Thanks!


texts: STM32F091 VBat pin sinking a lot of mA's

texts:
I'm trying to set-up a STM32F091 with a battery connected straight into the VBAT pin. For the first couple times I turned on this vbat at 3V, it worked ok (no weird behavior). However, after trying to program the MCU via SWD, this VBat pin became a low impedance path to ground (around 150 Ohms) sinking 20mA.
At first I thought this low impedance path was in my board, but then I removed the MCU and measured the resistance on the chip between pins VBAT and Ground, getting 159 ohms as a result. This problem manifested itself in two different chips and similar resistances were measured (150 and 250 ohms).

I'm inclined to believe this is a problem, since the VBat domain is supposed to power the RTC and back-up register, definitely not sinking 20mA @ 3V. I have not found any information on the device errata sheet and the data sheet says this pin draws uA's when powering the RTC domain.

The circuit is a straight connection between the battery and this pin. All others power pins are connected according to the datasheet. An interesting fact is that the ADC channel 18 (ADC_IN18) measures the voltage on VBat pin correctly.

Have anyone experienced this before? Am I missing something when using Vbat or is this a configuration issue?

Update: Problem found. See photos of PSU voltage wild excursions when turning off:

and turning on:


texts:
I am looking for some advice regarding my control setup for an ROV and how to make it as smooth as possible. Currently, I have two arcade style joysticks with standard micro switches inside. How I envision the system working is like this: Joystick outputs 3.3V or logic 1 equiavalent to a GPIO input on the BBB. I have a script setup to run on boot for the BBB that immediately sets up the input pins, and sets the output pins to low (temporarily) to avoid any floating high. A series of while loops or equivalent designate what input on which pin will correspond to the BBB outputing a HIGH value on another pin, which then goes to a 16-channel relay board, which in turn feeds out to 8 (maximum) 12V bilge pump motors.

Now here is my issue: How do I go about getting the joystick to output a signal that is of the proper voltage/amperage so as to not harm the BBB by damaging the substrate by having a GPIO sink too much current. I have seen some 3.3V regulators out there, and I assume with a proper current limiting resistor the system would function correctly without harming the Beaglebone. However, I am not sure if this would even work and how it would be setup for optimal function. For example, should I have a regulator feed 3.3V to the microswitches and have the joystick switch 3.3V? Seems like this would work in theory, but I would really like to be sure before I do any damage to the board.

If you are still not sure what my question is, let me put it to you this way: What would be the optimal setup utlizing the components above to produce a system that is both safe for the BBB and functional for the purpose intended (controlling 12V bilge pump motors by driving a relay board). To be clear, I'm not asking for anyone to design this for me, more just looking for constructive feedback and criticism to see if there is anything I can improve. Let me know if any clarifications are needed.


texts:
In particular, I was trying to understand the behavior of this precision rectifier given an input wave \$V_{in}=V_{o}sin(\omega t)\$. To my understanding, the circuit reduces to what we have in the left for \$V_{in}>0\$ (first half-wave) and whenever \$V_{in}<0\$ the voltage polarity on the diode becomes positive and we move to what we have in the right.

So now, we're in the second half of the wave \$V_{in}<0\$ and we will remain there so long as the voltage polarity on the diode is positive. I'm confused because given the two equations that I have the polarity on the diode will be positive no matter what; \$V_{out} > V_{Y}\$ always holds true due to the second equation because \$V_{ON}\$ should be constant. Meanwhile, I think that there should be a way for us to transition to what we have in the left again once \$V_{in}>0\$, so what am I missing?
Edit:
In the picture, \$V_{y}-V_{on}\$ should indeed be \$V_{y}+V_{on}\$


texts: My company has some plastic enclosures with circuit boards inside.  The board has been exposed to corrosion, which we will repair and test for continuity and current.  Is there a test that can test for "longevity" or durability of the trace?  For example, we repair a trace, tests good for continuity/current, how long with the trace last (is the test we need).


texts: If you have a DC in of 8.5V will a DC out of 19.5V work without ruining it?

texts:
If you have a DC input of 8.5V will a DC output of 19.5V work without ruining it?
I have a PlayStation 2 that I don’t have a power cord for.
It says above the plug in on the console 8.5V.  I have an adapter with various tips you can put on it that has an output of 19.5V.
I was just going to try and see if it worked. But I’d rather not ruin it.
Will it ruin it if I try and use this?


texts: Derivation of cutoff frequency and phase shift for RC low pass filter

texts:
I've been having some problems with how to find the cutoff frequency and the phase shift for a simple RC low pass filter circuit. I've read this post, but I need a better understanding of what frequency response to fully be able to understand it.

So how is it that the cutoff frequency is \$f_c=\frac{1}{2\pi R C}\$? And how can i derive the phase shift being -\$\arctan(\omega RC)\$ ?


texts: What is the critical temperature when (batch) desoldering?

texts: I have seen videos on youtube with some guys using hot air pistols (or even small propane burner with bunsen flame) to desolder the components from a PCB. The job is done REALLY quick! The components were really hot. They were still handling the components with gloves, many seconds after they fell from the PCB. My question is: can the components survive this kind of treatment.


texts: Looking for a wire mounted pin header connector

texts:
There are connectors on many modern motherboards and peripherals intended to control RGB LEDs. For example, this one has a connector like this:

And it is intended to be connected to the pin headers on the mobo:

I am looking for such a wire mounted connector like these on the fan, both male and female. The only connectors that I've found so far are ugly jst/molex. Are there connectors like these on the picture?

Thank you


texts: Are those some kind of timed-resetting fuses in DMMs?

texts:
Yesterday, I did something dumb, in a hurry. I wanted to check the AC voltage at the terminals of a hair-dryer, to determine the voltage being applied to the terminals of the AC fan behind it. However, in a hurry, I plugged in the positive lead, to the unprotected 10Amp AC socket on the DMM, instead of keeping it in the regular 5Amp protected, 750VAC socket. While I do think the DMM showed me right (or expected) values of AC voltage (between 12-15VAC for fan), and I kept it connected only for about 5-10seconds at max., it apparently drained the 9V battery in DMM, and all other measurements started showing "1" or "Err". There was no smoke or anything, but no correct readings, or even a valid continuity test. I thought that it must be just the exhausted battery, so I replaced it with a brand new one from a pack, and still got same results. Then I tried yet another new battery, and still same. I checked batteries with 2 LEDs, and they were glowing pretty bright, and very feeble on the first battery I'd replaced, indicating that the new batteries were probably fine. I left the DMM there, and went ahead and ordered a new replacement (yet to arrive). Now all this was about 24hours back.

However, just before dumping the DMM, about an hour back, I thought of doing the continuity test one final time. Voila, it worked, as did every other measurement I took. While I am happy to know that my trusted DMM isn't dead after all, I was surprised that this seemed like some safety-fuse which had blown, but auto-reset after some time. Is this really true / possible ? This is a very cheap ($5) small basic DMM, bought from SEA, shipped free kinds.


texts: I am planning on using CAN bus in an industrial automation application, however I'm having a hard time deciding how to implement the network layer. Does anyone here have any recommendations for a higher layer protocol to use over CAN that provides guidelines for how to assign message IDs and how to format data packets? Should I develop my own proprietary network layer or implement an existing standard like CANopen?


texts: Determining the number of turns for a solenoid

texts:
I am trying to determine the number of turns that is required in a solenoid to cause it to move an armature inside. From what I understand the greater the B the more force that it can produce on the armature.

To increase B I know that I can increase the number of turns to do this, but this is where I am finding problems, if I increase the number of turns this will result in an increase in inductance (L) and if the inductance of the coil increases, my PWM will be affected (will it not?) because it will resist changes in current when I apply the PWM, but if I reduce L then my B is affected. So how do I choose the best number of turns?


texts: How do I test a USB drive to be sure it is not a “USB killer”

texts:
I have recently read of a dangerous USB drive containing a circuit instead of storage, that destroys the hardware of a computer by injecting a high voltage, high current pulse into the port it is plugged into. See this article

It should be easy to test an unknown USB drive for this sort of danger by plugging it into a separate test module before taking the risk of inserting it into a computer's USB port. Does such a test module exist? Is there a commercial version, a circuit or kit that can be obtained?

Having read that article I would routinely test every USB device before using it.


texts: 1966 Ford Mustang original 8 track stereo/AM radio that will not change tracks if the voltage is above 12.5 to 13.  The 8 track and AM radio will play as designed without regard to the voltage being put out by the charging system but will not change tracks. My system is putting out 12.5 to 15 volts which is what the car repair manual gives as the proper range.  What can I put in between the car radio and car power wire to get the voltage down to around 12 to 12.5 volts?  I have looked at regulators but confused as to the specifications I need to look for in the regulator.  For example, most regulators I looked at stated the input voltage ranged from 12-40 volts with 12 volts output.  Also, I am confused about what the regulator in regards to amps, volts, etc. What would the regulator do if the voltage dropped to less than 12 volts with the stereo or radio on?  I have taken the radio to a classic car radio repair shop who stated they fixed but it was not fixed.  Any recommendations on what I should buy, to include source if known, would be appreciated.


texts:
We are having issues with a small 12V DC pump which is used in a number of test systems in the field. The pump is powered by a standard DC power supply and integrates a small PCB driving stage, with speed measurement and motor supply circuits.

Some of the pumps from the field reported failure, after circa 1 year of use. Since the system is used for less than 8 hours a day and the MTBF of the pumps is in excess of 30.000 hours, we suspected that the failures could be caused by an external factor.

We verified the supply stage, but it looks like that there are no problems. We then opened one of the pumps and we found out that a part of the driving stage PCB was "corroded", some of the holding screws being totally rusty. The environment in which the pumps are used is exposed to moisture and this moisture can penetrate in the case and reach the PCB driving stage.

Is there a way to make the PCB totally waterproof or moisture proof in a fast and cheap way? Should we take specials regards with contacts and connections? How to properly isolate them?


texts: How to map a C/C++/Python code to an Intel FPGA?

texts:
I have a piece of code that mainly consists of matrix-matrix and matrix-vector multiplications, but has other operations too. I have written my code in both Python and C and would like to map it to an Intel FPGA.

What I currently do is that I write a Verilog code that implements the same Python/C code and instantiates as many multipliers and adders as it is required to perform all operations in parallel. Obviously, this is not a scalable solution because when the size of matrices becomes large, all device resources will be exhausted quickly. As a result, there should be something like high-level synthesis that schedules these operations in different cycles.

Since I have not worked on such large designs before, I'm not sure what the best way is to go from a Python/C code to a code that includes the required datapath and controller for FPGA implementation.

Should I use a high-level synthesis tool that converts my C code to a Verilog code or there are better/easier solutions?


texts: Arduino Uno, weird characters sent to COM (SoftwareSerial)

texts:
I'm trying to send ASCII characters from Arduino UNO to a computer serial port. I'm using a cable with a male COM connector, attached to the computer's serial port, and three wires (TX, RX and Ground) on the Arduino side.
I used pins 12, 13 and Gnd as shown in the picture:

And I am running this piece of code to send a string every second on the serial port:

#include <SoftwareSerial.h>

SoftwareSerial mySerial(13, 12); // RX, TX

void setup()
{
  mySerial.begin(9600);
}

void loop()
{
  mySerial.println("Hello world");
  delay(1000);
}

But, when I read that port (at the right 9600 speed), instead of "Hello world" I get strange characters instead:

I thought I had set the pin erroneusly, so I swapped RX with TX, but I get a different but still wrong output:

What am I doing wrong?


texts: What is a "current load" on a 24 V input used for?

texts:
The MAX14821 (datasheet) is a 24 V IO device that features selectable current loads for use in actuators on the inputs.

What would this be used for? It's not just to load a 24 V "high" signal coming from a PNP-logic output, i.e. pull the input down of there's no signal? If it were, where's the equivalent high side current source for use with NPN signals?


texts: Multiple step-down of DC voltage in one circuit

texts:
I need to read some signals from a machine which outputs the bits in form of 0 and 24 VDC.

I will be using Raspberry Pi 4 (4 GB) or an Arduino Mega to read the same, however since Raspberry Pi/Mega accepts only 5.0 VDC, I will have to decrease the voltage from 24V to 5V.

I understand that this can easily be done using a voltage divider (or a combination of a resistance and a 5V zener), but the real issue is that there are about 30 different outputs that I can get from the host machine.

Is there a way I can step-down the voltage on 30 different pins with common ground ? I am not sure if any similar device is already available, but if it is there would be great.


texts: how to calibrate temperature sensor IC DS1621?

texts:
I have made temperature indicator using microcontroller P89V51. My temperature sensing IC is DS1621. I'm using LCD for the display..n ckt is working very fine,
Do I have to calibrate this IC?
If yes, then how can I?


texts:
Okay, I'm a total noob and don't know if I'm even wording this question correctly, but I'll try.

My understanding is that the power supply (an USB power supply in my case) determines the current. I have a 2.5A 5V supply, and a USB-to-DC cable that connects that power supply to an USB hub (5V as well). Now that hub would get a total input of 900mA from its data USB 3.0 connection to the PC + 2500 mA from the power supply. Does it just always get that current, regardless of whether it actually needs it? In other words, if I just have one little USB drive in the hub, will that USB drive get all the 3400 mA and burst into flames?


texts: How to place two inductors on the pcb? Which is better: example A, B or C?

texts:
I'm making a single phase pwm rectifier as my final year project. General topology consist of an inductor that connects ac voltage source with an inverter, as in the picture below:

But since this is a prototype I decided to add the second inductor, so it will be easier for me to adjust the inductance and do tests. Also have heard the second choke is often used for EMC reasons.

So, my question here is, which placement in the pcb in such circut is correct/better? Note that pictures below are some random pcbs from the Internet, the only thing that matters is the inductors placement on the pcb.

Example A:

Example B:

Example C:


texts: How to find second order transfer function from a graph?

texts:
I have been given this step response graph and asked to determine the second order transfer function of the system. I completed the question, using a lot of help from this post and got the answers below:

steady state gain = 2.5
un-damped natural frequency = 3.18 rad/s
damping factor = 0.16

I then decided to use ServoCad to produce a graph of my transfer function, to compare against the original and check my answers. This is the graph below. The two graphs look very similar, but on my graph each oscillation appears to take double the time it should on the original graph.

I feel like this is a relatively simple mistake but I'm new to this so if anyone can point out where I've gone wrong I'd be grateful! Thanks!


texts: I know that the ideal notch filter passes all frequencies but one, but is there a filter that passes only one frequency and blocks all others? What is do you call such a filter and what is it used for (if anything)?


texts: Measuring power consumption of system with buck converters

texts:
I'm trying to measure the power consumption of a circuit which utilizes a buck converter. If I know the circuit in absence of the converter utilizes 5.125V @ 142ma, then I introduce a 12V battery source with a buck converter to drop the voltage to 5.125V, should I see ~0.061ma going into the converter (assuming 100% efficiency)? In other words, is it right to assume conservation (if 100% efficient)? If the converter is not 100% efficient, does that mean I should see a higher current flowing into the converter, where the difference between that measured and the theoretical conservation is the power loss across the converter?
Overall, I'm trying to understand where I should be measuring the power consumption of my system. I have 2 devices connected to a battery in parallel (i.e. 12V going to each device). Both devices have buck converters, which drop the voltage to ~5V. Currently I measure the battery at ~12V then put my multi-meter inline with the hot lead of the battery and measured ~300ma, which I'm assuming means my system utilizes ~3.6W. The one circuit/device I mentioned above uses ~0.72W, which means the other must use ~2.88W, but the datasheet says that it should be 1W. I'm trying to determine if the datasheet is publishing power consumption values not representative of full load or if I'm testing the system incorrectly. A discrepancy of 1.88W is a lot and I'm not sure how to explain it.


texts: Pullup resistor operation between the ESP32 and a Bus MCU

texts:
I have an ESP32 as my main controller and a Bus.

The bus operates where Pins 55 & 56 needs to be HIGH in order for the bus to be OFF. My ESP will drive the bus by enabling it by pulling those pins Low from the connected pin 14 of the ESP.

Therefore, I would like to use a pullup resistor to pull those pins high during the ESP32's booting / reset sequences.

This is my schema for this so far:

My questions are as follows:

Is this wired correctly to act as a pullup resistor?
Will the ESP be able to pull that pin low, if 5v is connected via the pull up? The linked question below suggests I might need an "open drain output" in order to protect the ESP, but I am unsure how to wire that up in this configuration. If that is correct, can somebody roughly draw how that would wire up?

The question I refer to in point2) above is : How should I drive a chip where I need to pull pins low in order to enable -- one of the answers suggests pull up resistors for startup / reset situations of the ESP which I think is a good idea on further reflection.

Many thanks for all support.


texts: Using "modern" batteries with old devices

texts:
I have a Sony Vaio p-series laptop which is a tiny computer build in 2009. It is a wonderful device but the battery is only 2500 mah and lasts about 1.5 hours.

My phone battery on the other hand is a quarter of the size, 4500 mah, and lasts almost a day and a half with heavy use. My question is, what would it take to make an upgraded battery for the little laptop? Assuming I had access to some big cell phone batteries, let's say. Can I just wire it in somehow? I assume the new battery would have to match some kinds of numbers so that it inputs and outputs energy at the same rate... Or something like that... I am pretty well-versed in how operating systems work but have no experience with actually building anything. Is this idea totally infeasible or do I just need to learn how to do it and obtain the right parts?


texts:
I'm trying to display a 4-bit binary number on a 7 segment LED as a hexadecimal number (0-F). I have an assortment of 7400 series ICs including the 7447. But that one only works for BCD (0-9). The 7400 series doesn't seem to have a hex to 7-segment decoder and I don't have one on hand.

So I figure I'd have to build my own. The datasheet for a 7447 comes with the internal circuitry but I couldn't find a similar circuit for hex to 7-segment. I did K-diagrams for each LED segment by hand but the terms are rather large, much larger than for BCD.

Does anyone have a finished circuit for this that I can check my work against?

Does anyone have an optimized circuit for this that takes advantage of common subterms? There aren't many duplicate terms (like A0 & ~A1 & A2) but maybe using (A0 & A2) & ~A1 would allow sharing the (A0 & A2) subterm and overall reduce the gate count.

Or maybe some tricks to use NAND, NOR or XOR gates for some parts?

I don't care about different path length or races in the circuit as it's only going to drive LEDs and should be far too quick to see any of that.


texts: Differences between LM555CN-R and LM555CN/NOPB

texts: I am trying to buy a LM555CN-R online, however I can only find an LM555CN/NOPB. What are the differences, if any, on these chips?


texts: What is VAR knob used for and why should it be usually in CAL position in analog scopes?

texts:
I'm trying to understand the VAR CAL uses in analog scopes.

Almost all the texts I read mention briefly about these and do not explain well.

Here are some examples:

  CAUTION! There is usually a small knob marked VAR (or VARIABLE) that
  allows adjustment between the “clicks” of the HORIZONTAL control knob.
  When measuring times from the screen, ensure that the VAR knob is in
  the CAL (or CALIBRATE) position!

or

  Turn to the position marked Cal – completely clockwise.

or

  Sensitivity calibration. This knob is used to change the vertical
  scale. If it is not turned all the way clockwise, the scope will be
  uncalibrated and your data will be worthless. Check this knob
  frequently as you take data.

Is there an easy way to explain or illustrate what is VAR knob used for and why should it be in CAL position in analog scopes?


texts: JFET - Ceramic Resonator - Oscillator Phenomonom going in and out of oscillation

texts:
An oscillator using a ceramic resonator is going in and out of oscillation.

I have an oscillator circuit with a peculiar phenomonon. The oscillator does work (mostly).

The “crystal” I am using is a ceramic resonator, #ZTBF455E.  ESR=20, L=8800uhy, C1=14.5pf, Co=256.3pf .   Manufacturer App Note for resonator.

Pathetic Data Sheet that manufacturer gives.

This oscilloscope photograph shows the output voltage (Vout) and gate voltage. Channel 1 (yellow) is Vout.  Channel 2 (blue) is gate voltage (to ground).

After a few seconds (approx 10 seconds), the output slowly fades to zero volts AC (DC level maintained at near 9 volts).  The gate voltage (AC) also goes away (DC level maintained at 0 volts).

The “fade away” takes about 5 seconds,  then stays at “no oscillation” for about 10 seconds.  Then, slowly the oscillation begins and grows back to the original  magnitude in about 6 seconds.

I monitor the the volts across the 100 ohm resistor (R2).  When oscillating properly, the volts across the 100 ohm resistor is about 0.7 volts ( 7 mA).  When the oscilation begins to die out, the volts across the 100 ohm resistor drops slowly down to zero volts (Id=0).  As if the JFET were cutoff, yet I see zero volts on the gate (gate to source) (cutoff voltage is  -2v to -6v) (Idss = 10mA).  So how could drain current be zero with gate volts at zero (not cutoff).

The schematic shows a 2N5486, but I am using a HEP802 ( I know it's an antique ). My purpose here was to make a BFO (Beat Frequency Oscillator) for antique radios that I restore. So Morse code can be heard on old radios.
HEP802 equivelant to 2N5486.

If I touch the case of the ceramic resonator with my finger, I can influence the timing of the fade in and fade out phenomonom. But doesn't effect the frequency of oscillation.

The circuit does stabilize in the oscillating mode.

Given the timing of the fade in and fade out of the oscillator,  it would seem to be a thermal phenomonom.  I recognize that a substantial current is flowing through the resonator (series resonant).

Is there a thermal function of ceramic resonators not specified?  Any thoughts on this phenomonom ?

How does Id go to zero without the gate voltage being at cutoff?

EDIT 1/9/2016 :  per Andy Aka suggestion, R1 was reduced from 1M ohm. At R1=270K, the fading in and out of oscillation stopped, with the oscillator running with same output amplitude.

Remaining puzzle is still How does Id go to zero without the gate voltage being at cutoff? Id=0 Vgs=0 when oscillator previously failed to oscillate. Shown in second photograph above, with both oscilloscope channels on DC coupling.


texts: USB Charger Voltage Specification - Transients

texts:
Is there a specification for a USB charger that discusses whether voltage transients are acceptable, is if so, under what conditions?

Specifically, I know a USB charger needs to have a voltage of 5V +/- 5% in order to be complaint with the USB standard.  However, is it ever possible to have a voltage spike above or below that threshold and still be in compliance?  I am specifically looking at it during a radiated immunity test.


texts: I have an old oscilloscope which doesn't work. I tried swapping the 3.15A/250VAC fuse with a 4A/250VAC fuse. The fuse immediately blew. My questions are: Did the fuse blow because it was the wrong fuse? Or did it blow because there's likely something else wrong with the oscilloscope? Must the fuse be exactly as specified? Thank you.


texts: How to design a pierce oscillator circuit?

texts:
I need to design a crystal resonator that can be used as a clock source for a uC.
The first design is for an ENC28J60 IC, it's an ethernet - spi module and needs a 25MHz frequency.

I tried to follow a lot of tutorials and sites but I still can't wrap my head around it, I'm not sure if the design would work.

I picked a crystal that looked fine to me, the QCS25.0000F18B35. It's 25MHz, Cl is 18pF, Frequency tolerance is +- 30ppm and the stability is +-50ppm.

I used this application note from STM as a reference for calculations. Since the second project is to design a STM32F207 uC that needs another crystal too.

In the document it said
$$
Cl\:=\:\frac{C1\cdot C2}{C1+C2}+Cs
$$
to calculate C1 and C2, since they can be the same value the formula would be
$$
Cl=2\cdot \left(C-Cs\right)
$$
If you use 18pF for Cl and 3pF for Cs it gives you a C1 and C2 value of 30pF.

So far, is this a correct way of doing this?

Next is the drive level, the maximum power the crystal can dissipate is 1mW. If I use
$$
I_{Qmax}=\sqrt{\frac{DL_{max}}{ESR}}=\sqrt{\frac{1mW}{40}}=5mA
$$
When I then calculate the current that will flow in the oscillator using
$$
I_{Q\:RMS}=2\cdot \pi \cdot f\cdot V_{RMS}\cdot C_{tot}=2\pi \cdot 25\cdot 10^6\cdot \frac{3.3}{2\sqrt{2}}\cdot \left(C+\frac{C_s}{2}\right)=5.79mA
$$
Obviously this is more than the maximum current, so with this setup there should be an extra Rs inserted. But how to calculate that one... I have no idea. I've read that you could calculate them using the 'insides' of the XTAL, or to take a value that could work using a potentiometer and work from there to get a workable value. But I can't test the crystal in real life. It has to be possible to calculate it right?

When I tried other values for Cl, for example 12pF, using 3pF for the Cs gives you C1 = C2 = 18pF. This should give a current of 3.58mA, and that should work. Is this a workable value too? and is it possible to use my earlier values using Rs?


texts: How does a wifi antenna work in full-metal laptops?

texts:
As far as I understand, metallic covers of devices like MacBook Air should shield the interior from electromagnetic waves rather effectively.

Even if a wifi antenna is right behind the screen, the other side of the display cover is metallic, so reception would be quite directional.

What do metal-clad consumer devices (laptops, phones) do to pick up radio waves?


texts:
I'm trying to implement two cascaded low pass filters in a software application so that I can smooth out a potentially volatile data set. Based on the incoming data, I want a signal to be turned on/off at a certain threshold (i.e. the filtered data drops below x). But I want this signal to turned on and off smoothly, so that its not affected by big spikes, but is affected by consistent samples below x (or above in the opposite case). From what I remember from my DSP class, low pass filters are what I want. The exact equation I'm using, with two cascaded, is:

Signal at time T = (sample at time T) * gamma + (signal at time T-1) * (1-gamma)

My question is, could anyone demonstrate the exact mathematical calculation to determine the sensitivity of my filter, based on my values for gamma. I.e. a gamma value of x will ensure a single sample does not move the overall signal by more than y%, or a similar calculation so that I can have a numeric value on this.


texts: Compensating Saturation Voltage of a transistor

texts:
simulate this circuit – Schematic created using CircuitLab

I am working on this circuit, which is a voltage controlled oscillator. I am using the transistor as a switch in this circuit. The problem is that it is not an ideal switch. It has a saturation voltage, say, 0.4-0.6V. I have to compensate for this effect by may be.. using a matched transistor or anything. But, I haven't been able to get any idea. Could someone give a hint as to how to proceed?

Thanks!

EDIT-

I did it this way finally. The duty cycle was 50% .


texts:
I have a crowbar circuit which uses an SCR with 100mA gate current shown below.

In order to use this resistor value at 100mA it would need to be rated for 60W. Obviously here the resistor will pop. While testing (with lower-rated resistor) it does work, the fuses blow and the output is protected while also blowing the resistor.

It's not the end of the world as when the fuses are replaced the resistor could be too, however this is not ideal. Is there any way round putting a massive bulky resistor there?


texts: How can I use an Arduino to simulate button presses on this PCB

texts:
I'm trying to simulate a button press on a PCB - potentially with Arduino and some additional components.  I think I'll need to solder wires on either side of the button, connect those to an Arduino setup and toggle power on the wire maybe?

I've connected a multimeter set to 9 volt, and when connecting the leads to either side of the button I get a reading of -0.07.  Does that give me an indication of the amount of power I need to pulse to the switch?

I may be approaching this the wrong way. Any guidance on what I need to be looking for is much appreciated.

Edit:  When the button is depressed, the voltage goes to 0


texts: How to buy electronic components for little projects?

texts:
I have some projects in mind, some of them under development, and I want to design PCBs for them with little SMD components. So I have been choosing some of the ones I need in websites like Digikey or Farnell, but they charge an incredible amount of shipping costs if the total cost is less than 50 euros, and some of my projects just need components with a total of 3-5 euros.

Does anyone know how or where to buy the big variety of components that can be found in those sites? The most of the electronic shops only have common chips and usually not in SMD/SMT version. So I need some specialization as the other ones.

I was wondering if there exists any association of hobbyist in Europe (I am in Spain) or anywhere that accumulates multiple orders till there are no shipping costs, and then resend the individual orders to each one.


texts: How much power is really wasted by a wall wart?

texts: The title pretty much sums it up... Hyperbole aside, how much actual power is consumed by a typical wall wart when the device it's attached to isn't powered on? And are there designs for wall warts that minimize or eliminate this sort of parasitic load?


texts:
I have a large anti-static mat lying on the table of my workdesk, which looks like this.

And it's connected to ground through the wall outlet from one point, meaning it's an open-loop:

Let's say I connect myself to the mat using an anti static wrist strap, how is it supposed to help me discharge my static charge when there is no closed loop between me, the mat, and the ground? And lets say I am using a power supply which I am feeding from the mains, and the positive clip of the supply touches the mat accidentally. Wouldn't it be a dangerous scenario for me to be in contact with the mat? I am quite puzzled with the usage of the anti-static mat and nature of the electron movement when there is no closed path. Have a nice day people :)


texts:
I was reading this page which says:

  What Edison discovered (and it was promptly dubbed the "Edison
  effect") was that electrical current doesn't need a wire to move
  through. It can travel right through a gas or even a vacuum.

Maxwell introduced the term displacement current for explaining how the capacitor is passing an alternating current through its plates.

But what I understand is that the displacement current does not move in the form of electrons, but it moves/passes in the form of circulating magnetic fields up to the other side of the plate.

The paragraph claims that the electrical current can move in vacuum. But it doesn't state the form of the current.

For the Edison effect in vacuum, is the current moving in the form of actual electrons or magnetic fields?


texts: One LED capable of being turned on by two IC's

texts:
simulate this circuit – Schematic created using CircuitLab
I want to be able to turn on a single LED with either one of these two micro-controllers.
Would there be anything wrong with this simple approach? The LED would experience double the current
if both IC pins are grounded, but it wouldn't be enough to damage it; also the LED only blinks for a couple hundred milliseconds in any case, and never stays on constantly. Max sink current is also a non
issue.
Please let me know if I am making a mistake or not.
edit for clarification:
U2 pin is an open drain power good indicator that goes low automatically when usb power is supplied. U1 will turn on LED based on a couple of software events


texts: What's the maximum wattage air conditioner I can run for 8 hours through a 12V-120V inverter from 200Ah batteries?

texts:
I have an RV with two 100Ah batteries that provide 200Ah of 12V power in total. I would like to have a classic air conditioner (I've looked at swamp ones but they won't work for my needs) and I'd like to be able to run it for about a maximum of 8 hours.

How do I work out if this is possible, given that there also needs to be a 12V-120V inverter? I've found AC units as low as 465W (although I don't know what their max pull is).


texts: How is it possible that lower CAS latency and lower timings on RAM memory to result in lower performance?

texts:
I have watched many benchmarks on RAM memories and I was shocked to find out that sometimes lowering the memory timings can result in lower performance in BOTH synthetic benchmarks general use of programs.

In my opinion if everything works correct in the RAM modules, lower timings should always result in better performance. The only case that I can think of where the performance would be impacted negatively is if the memory would actually have transmission errors and the data would have to be re-transmitted. I think this is why ECC memory was invented.

The last video I watched which is a very detailed analisys of the results after changing the memory timings is this one.
https://www.youtube.com/watch?v=zrsuP48qsJE

The results seem mathematically impossible to me.
Are there errors that cause this loss in performance or is it something else?
How can I start to find out more about this subject?


texts: Determining H-Bridge DC-link decoupling capacitors

texts:
I'm trying to determine the optimal DC-link decoupling for a class D full bridge amplifier.

Parameters:

8 ohm speaker load
PWM frequency = 300 kHz, 40 ns rise time.
Max duty cycle = 90%
DC bus voltage = 50V
Ipeak = (50 V / 8 ohm) * 90% = 5.625 A
Desired ripple voltage = 0.5% or 250 mV

The formula I found in order to calculate required bulk capacitance is:

C >= (Ipeak * Tperiod * Max duty cycle) / Vripple = 67.49 µF.

And capacitor ESR should be below Vripple / Ipeak = 44 mOhm.

What capacitor type(s) would be most cost effective? 4x 22 µF SMD ceramic capacitors are expensive at these voltages. Electrolytic capacitors are probably too slow to handle the high harmonic frequencies of the square wave edges. A combination of electrolytic and ceramic perhaps? How to determine how much ceramic capacitance too add?

In case of electrolytics, how do I calculate the ripple current trough the capacitors in order to determine the required ripple current rating?


texts: What are the causes and solutions to battery-powered LCD backlight buzz/hum?

texts:
Many battery powered devices with LCD displays (eg: clocks or thermostats) will illuminate with a turquoise backlight when a button is pressed. Some of them will emit a buzzing/humming sound while the light is activated.

What causes the sound?
What can be done (either in design, or for the consumer) to dampen or eliminate the sound?

I'm guessing that the sound is caused by some sort of inverter/charge-pump. This Link on watch backlights briefly mentions that low battery voltage must be brought up to something around 200V AC.


texts:
Currently I am using the internal BlockRAM from a FPGA to safe the samples I am getting from an ADC with a frequency of 200MHz. In the future, I want to use equivalent time sampling to get a virtual resolution of around 500ps.
The BlockRAM has a size of a few MB. I want to safe around 2GB of ADC samples.
I am considering using a DDR3/DDR4 RAM module that is typically used in PCs.
I never saw someone using a PC RAM module to store data coming from an ADC.
Is it even possible to store the samples in a DDR3/DDR4 RAM module?


texts: How to connect phototransistors in an additive style? The output current should resemble the total power of light received by all of them. Eg. if one gets 0 lux, the other one 10 lux, the result should be "10", likewise if both of them getting 5 lux. Is there a simple solution like a phototransistor - resistor - network?


texts: Ultrasonic sensor 960KHz reading with arduino or any other SBC

texts:
I have an ultrasonic sensor pair which I bought from https://hacktronics.co.in/water-flow-meter-sensor/ultrasonic-flowmeter-sensor.
The sensor is of 960khz... I wish to make water flow measurement inside a pipe from it using any sbc preferably Arduino. the sensor has only two wires VCC and GND, hence I am not able to get as to how to interface it with an SBC or make a sensor pin...


texts: Design advice when daisy-chaining multiple JTAG devices

texts: I know that JTAG was specifically developed to support daisy-chaining of multiple devices, but I am still worried that my board will show up and I won't be able to talk to one of the devices because I did something wrong.  Does anyone have any advice on what the common pitfalls are or what precautions should be taken when implementing more than 1 device on the JTAG bus?


texts:
Hi i am new to the forum and this is my first question so fell free to help me with formatting.

I am working on a project that involves controlling RGB LED strips from a Arduino. I have as my power supply a 18.5V 6.5A power-brick. I need to have a regulator to generate 12V at at least 6A. Any suggestions on components or premade boards? I am open to DIY solutions.

Thanks in advance.


texts: High gain and high modulation frequency photodetectors

texts:
I have been reading more into the gain of a photodetector and how the system works. We are picking up extremely small signals and need to use a detector with a gain of around 1.0 × 10^7 but preferably higher. We are not looking to use PMTs. We are then also looking at a photodetector which can pick up modulation frequencies on the order of 500MHz - 2GHz so the detector needs to be very fast.

There are a few questions within this:

Are there specific types of detectors which are best for this applications, such as Avalanche photodiodes or others?
With detectors that have lower gain, how much is it possible to amplify them, can you take a detector which has a gain of around 1.0 × 10^5 and increase it to around 1.0 × 10^8 within hurting other areas such as Dark Noise?
If you know of detectors which can do this can you point me in the right direction?
Are GE Avalanche photodiodes more sensitive than Si and InGaAs?
Are there other methods which can improve a photodetector which cannot achieve it currently?

Extra notes:
- The wavelength that we are using in between 750-900nm

Thanks for the help!


texts: Chip masking process...what can be changed during the process?

texts:
I'm working with an overseas vendor.

We've tested the electronics and code of the product.  We gave them the green light to start chip masking.  However, a few days later we realized that the working samples of the toys had dB levels (for sound effects only) are too loud for a toy.

The vendor said that we can still change the program.

My understanding is that once chip masking starts we can't change the program anymore.

Can someone explain to me the detailed steps of the Chip Masking process and what can still change during that process?


texts: Calculating resistor and capacitor values for an op amp differentiator circuit design

texts: I need help in designing a differentiator using an op-amp. I know that the equation for an op-amp differentiator circuit is Vo = RCdVin/dt, but I don't know how to calculate the component values to finish the design. All of the web resources that I have viewed so far shows the characteristic equation of the differentiator, but they don't give any guidance as to how to calculate the actual values. Can somebody help me with this please?


texts: DC and AC analysis of a Common Emitter Amplifier Circuit

texts:
What we know about the circuit is that in DC-analysis (when \$V_{in}=0\$), \$V_{out}=10V\$.

We also know that the circuit (even outside of DC analysis) will have \$I_{C}=2mA\$ and \$V_{CE}=5V\$. \$R_{1}\$ and \$R_{2}\$ should be so that \$I_{B(max)}=\frac{1}{10}I_{2}\$ where \$I_{2}\$ is the current over \$R_{2}\$.

I'm assuming

\$V_{out}-V_{B}=0.7V\$

and

\$V_{B}=V_{CC}(\frac{R_2}{R_2+R_1})\$

And in DC-analysis if \$V_{out}-V_{B}=0.7V\$ holds, I can conclude that

\$V_{B}=V_{out}-0.7V\$, so that \$V_{B}=10V-0.7V=9.3V\$

But I'm not 100% certain on what I should do to figure out the formulas to calculate the resistors to match the assumptions and how to proceed overall.

Edit 1

If \$V_B=9.3V\$, \$I_2*R_2=9.3V\$ and \$I_1*R_1=20V-9.3V=10.7V\$

\$I_1=I_2+I_B\$

assuming \$I_B=max\$

\$I_1=I_2+\frac{1}{10}I_2=1.1I_2\$


texts: Constant Current Square Wave through LED

texts:
I am running a somewhat powerful LED, on the order of 3.5V 500mA, off of an ~11V battery using a constant current switched mode power supply from Ebay that uses the LM2596. What I need to do now is turn on and off the LED using an Arduino at a variable frequency of around 10 to 100 hz and 30% duty cycle, and have the current rise and fall times be under 5% of the period, which is 0.5ms at 100Hz. In other words, a square wave, not a sine wave. I have an Arduino Pro Mini in the project already that is outputting the correct pattern, but how do I amplify this?

I've thought of a couple of solutions, but none seem to be feasible.

Switched mode power supply controllers with a PWM input seem to try to smooth out this input and give an even output current, the opposite of what I want.
I could use a simple current limiting resistor with a transistor between it and the LED, but this is too much power dissapation (~5W) for a reasonably sized resistor, not to mention the variation in current with battery charge and LED temperature (and therefore voltage drop).
I could have a switched mode power supply bring it down to maybe 4-5V and use a resistor and transistor after that, which would solve the heat and battery voltage problems but make the accuracy even more dependent on forward voltage.
If I keep the constant current power supply and a transistor is put between the battery and power supply input, the inductor would keep the current from changing quickly enough.
The most feasible solution I've thought of is to put a transistor between the power supply output and the LED, but can switched mode power supplies handle this kind of switching on their output? Would the power supply spike the voltage when the LED is disconnected to try to maintain the constant current? How well does the maximum voltage setting on those power supplies work?

I'm going to spin a custom board in the future, but right now I'm looking for a solution simple enough to implement on a protoboard.


texts:
I have been exploring how LED light bulbs work and the circuit inside of them. One particular question I have is how the lights are actually arranged?

LIFX, for example, has 4 different types of LEDs; red, green, blue and white. I am assuming each string is controlled by its own channel b the microcontroller, but how are the strings arranged?

Assuming there are 10 Green LEDs, (20mA, 3Vf), would the green LED string be arranged in series? Having a voltage of 30V?

If so, what would happen if one LED fails, would the rest of the LEDs in that string also fail?

Would it be better to arrange LED's in series or in parallel for this kind of scenario?

sample LIFX teardown (from google results)


texts: Protocol for WiFi network to connect to a website?

texts:
Ok, I'm trying to wrap my hands around communicating over WiFi using a microcontroller. There seem to be various options such as UART, SPI etc.

If I want an Arduino to get or put content on a website, what protocol does the Arduino use to talk with the WiFi module? I see there are cheap UART WiFi modules available, but I don't think they have the TCP/IP stack built in.

2 Questions:

How do I interface between a microprocessor and the WiFi module? Or what connections do I use? I2C, SPI, UART?
What are the minimum requirements for a WiFi module to be able to talk to a website? I want to read data from a website and write data to a website.

I hope this makes some sense, but to me it is still confusing.


texts: Schematic Question with electronic button

texts:
I have a question about this schematic, the arrows with the lines going thru them.

what I'm trying to do is hook up a push button, either a:

2-wire push button,
or a
4-wire push button  (Push Buttons that look like on this PDF):

http://ardx.org/src/circ/CIRC07-sheet-OOML.pdf

whichever type of button is required. (I don't want to blow the circuit).

Here is the Diagram:

What I'm trying to do is this.. We own a coin operated washing machine in a building & we want to give family free washing, but the other tenents will pay. we want to hide the button being its very small in a discrete location somewhere.. I'm not worried about the hiding part.

I need to know looking at the Diagram, how would I go about that? would I use a 2 wire push button or a 4 wire like in the above PDF (i have those on hand). from videos I have seen & research I have read.. I am guessing wires # 1 & 4 (Blue & White/Blue) ?

But I dont understand what the wires # 2 & 3 do? they have the same arrows with lines going thru them.

And do I need more then just a push button? like a resistor or something too?

I'm sorry, I am not very good at this, any help would be appreciated.

** EDIT:
I am adding in the full Schematic so you can see.. if you tell me to run a wire from point 'A' to point'B'.. I will do whatever it takes to make this work, again please any help would be appreciated.. I don't know what to do.


texts:
I have a stepper connected to a leadscrew, on which is situated a nut somehow connected to a load, along with linear bearings -- so a typical linear-actuation setup. I'm using a commonplace A4988 module (along with an Atmega328 MCU on Arduino) to drive the stepper.

What are the primary things I should do with a stepper motor setup to make the load move as fast as possible?

I'm guessing at least some of the following are useful:

Applying the maximum voltage that the stepper and driver are specified to handle: I am applying pretty close to the maximum already.
Increasing the pulse frequency in my code: I did this up to a point, but beyond a certain point, I start to hear a strange high-pitched sound.
Use a stepper with higher torque specification: I'm assuming this by itself won't make the steppper go faster but, for a given load, it will help in not skipping steps at high speeds.
Some other motor-specifications or driver-specifications that I should take into account when selecting a stepper or driver to purchase?


texts: how to determine the current capability of a transformer

texts:
Hello I have this transformer from ebay its from a north court 50 amplifier.
There is not much information online.
It has 400 0 400 volt ht
i think it ran a pair of KT66 valves with gz34 rectifier

dimensions are about
L x B x h 4" 3" 4"
if anyone can help me out on this one it would be great


texts: While using DC 12V power supply, if I connect only positive line to my electronic board and dont connect negative, what actually happens?

texts: While using dc 12 power supply, If i connect only positive line to my electronic board and do not connect negative ,what actually happens ?


texts: What is the purpose of the hole in the top of an LD1117V33?

texts:
I'm planning on using an LD1117V33 with input from the Raspberry Pi 5V rail (circuit diagram), and (maybe because this is my first electronics project) the hole at the top of the LD1117V33 makes me think that it could be laid flat and fastened.

But given that regulators turn extra voltage into heat, is this ever done? Will the leads even remain sound after bending?


texts: Recommended way to connect the exposed pad to ground pins

texts: Is it okay to connect the exposed pad to the ground pins as in the image below, or is there a recommended way to do it?


texts: measurement errors: add up or cancel out?

texts:
Take an accelerometer, or a hall sensor, or a thermometer, or any sensor. It will have an accuracy, which means the readings will contain some error of this sort.

My guess is that by taking a big number of readings of the measured parameter will cancel out the sensor inaccuracy to some extent. Or am I wrong ?

And if I am not wrong, how do I compute the accuracy of the averaged number of readings that I take over a period of time ?


texts: PCB test patterns to assess etch quality

texts:
Does anyone know of a good test sheet for assessing the quality of home etching?

Rather than create something and reinvent the wheel, I'm looking for a PDF/PS file featuring tracks of different thicknesses at different orientations.

Ideally, it might even be something useful (eg. some fine pitch SMD adapters).


texts: In a p-channel MOSFET, if I connect the bulk to the drain instead of connecting the bulk to the source, I will have my bulk-source pn junction forward biased. Since the source potential is by definition lower than the drain voltage (which is the same as the bulk voltage because bulk and drain will be connected), the voltage of the source will be lower than the voltage of the bulk. Will current flow from the bulk to the source? Is it to prevent this that we connect the bulk to the source?


texts: Writing high bytes in Intel Hex file to PIC 16F886 using MiniPro TL866A

texts:
I'm a newbie trying to write an Intel hex file to a PIC 16F886 using a MiniPro TL866A. When I try, I get the message:

$ minipro -p PIC16F886 -f ihex -w downloaded-file.hex
Found TL866A 03.2.86 (0x256)
Chip ID OK: 0x2062 Rev.0x2060
Found Intel hex file.
Incorrect file size: 3145742 (needed 16384)

Looking at the hex file in the parser at Nordic Semiconductor, I can see that there are two parts that are outside the range of the PIC:

Block starting at 2097152 (0x200000), 8 (0x8) bytes long
Block starting at 3145728 (0x300000), 14 (0xe) bytes long

What are these 8 and 14-byte values, and how do I write them to the PIC?


texts:
I am working to lower the leakage current in an isolated power supply.
The power supply uses an isolation transformer to step down from 120V/240V to 6.5V.  The voltage is then rectified and run through five TO-220 LM2941 regulators to generate individual supplies for the different parts of the final circuit.  The LM2941's are attached to an aluminum heatsink with Thermafilm insulators in between the regulator and heatsink and thermal compound on top and bottom of the mica.  The screws used to attach the LM2941's have shoulder washers.  The heat sink is attached to the enclosure of the power supply which is connected to earth ground.

If I lift all of the regulators off of the heat sink, I see a drop in the leakage current of about 10uA, indicating that the contribution of the regulator-heat sink interface to overall leakage current of the power supply is 10uA.  I would like to reduce or eliminate the 10uA of current if possible.  Is this amount of leakage current normal for this configuration, or should I be able to reduce it by using a different insulator or mounting configuration?

Background:

I am measuring the leakage using a Dale 601 Electrical Safety Analyzer.  The specific test is the mains on applied part test where mains voltage (120/240V) is applied to the isolated side of the power supply and the leakage current to the protective earth ground conductor is measured.


texts: Why do different colored LEDs interfere with each other when connected in parallel?

texts:
My very basic electronics education has taught me that parallel circuits are equivalent to separated circuits. To my surprise, when I was playing around with some electronics I found the following:

Essentially I connected two red and two blue LEDs in parallel. The red ones lit up, but the blue ones didn't. Only when I removed the red LEDs would the blue ones light.

Why is this?


texts:
I wish to put a Bluetooth receiver into an old hi fi amplifier. There are +/- 33V rails available and the Bluetooth device needs 3.9V and about 100mA maximum.

I was going to use an LM317 but I think it's getting close to it's input limit at these voltages or it will need some serious heatsinking.

Any ideas on how to drop the volts reasonably without allowing noise from the Bluetooth device back onto the 33V rails?

I thought of either a resistor divider prior to the LM317 or maybe a suitable (9V) zener?

Any help is appreciated


texts: How build a practical AC over voltage protection circuit for the input of an arduino board

texts:
The input signal to my board is an AC signal.

My board will process this signal. My board can handle 3.1Vpk-pk maximum without any damage occurring.

In the event that my input signal exceeds that I want to build a circuit that can stop (and hold or hold it at 0V if easier) the input to the board at 3.1Vpk-pk.

What I want to do: for signals in the range 0-3.1Vpk-pk they will pass through the circuit unaffected, for signals above this the output can be either a constant value or zero, which ever is easier to design.
We can assume that the maximum voltage that could be supplied can go up to 20-30V while the typical input will be in the range 0-3.1Vpk-pk. The signal's frequency should be unaffected by this circuit.

I have been searching for days for protection circuits but cannot find any for an AC input signal which is unbelievable to me.

How to I go about designing and building this? My initial simulations included a unity gain buffer that would saturate at max input but this failed.

Any guidance to the name of this circuit or guidelines that can help me design one on my own will be great. Thank you.


texts: Given specific equipment wattage, and the capacity of an industrial grade portable battery, how can I determine theoretical run time?

texts:
I am located in North America and all equipment is standard 110-120v.

The 4 appliances are:

2 Pioneer CDJ-800s. According to Pioneer's website, they operate at 21w (I assume this is PEAK consumption)
1 Allen & Heath Xone 62 Professional Mixer. According to the rear of the product, it operates at 30w PEAK.
1 Pioneer RMX-1000 unit. I was unable to find the wattage of this unit, but page 26 of the manual indicates that power consumption is 1.4A - I am not sure what this means. https://www.pioneerelectronics.com/ephox/StaticFiles/Manuals/DJ/RMX-1000_OperatingInstructions070312.pdf

If I were to acquire this portable powerpack, which has a reported 400 watt-hours of capacity, how many hours will I be able to run the above equipment? https://www.amazon.com/Anker-PowerHouse-Generator-Alternative-Rechargeable/dp/B0196GQAKM/ref=sr_1_1?s=automotive&ie=UTF8&qid=1482833614&sr=1-1&keywords=portable+power&refinements=p_36%3A1253497011

Thank you,

D. Jay


texts: what is the relationship between rated voltage and angular speed frequency in an AC generator?

texts:
in Ac generator, the internal voltage is directly proportional to the mechanical speed by the equation:
E = K * magnetic flux * mechanical speed
but does this hold also for the terminal voltage? I personally believe it is not! but, for example, the solution of the following problem is done by assuming :
V2/V1 = 50 /  60

why is it true?


texts: Low latency digital wireless audio transceivers

texts:
I would like to start a project developing diy low latency digital audio transmitters.

Issue is there is not much information online and I'm unsure where to start. I live in England UK, I would like these to be short range transmitters  (maybe up to 30 metres).

I would like to transmit 24 bit 96 kHz audio  at a latency that is less then 5 milliseconds. Could someone please tell me what digital wireless protocols or modulation over what frequency ranges can make this possible? And I can start looking for a wireless transceivers IC to start designing.

I would like to develop something very similar to this:

http://stageclix.eu/stageclix-v5-jack-receiver-transmitter/


texts: Implementation time of Linear Feedback Shift Register (LFSR)

texts:
From implementation point of view, how much time will pseudorandom number generation by Linear Feedback Shift Register (LFSR) take when implemented on, for example, Digital Signal Processor? Seed is supposed to be 4 bit long. How can the implementation time be calculated before actually implementing LFSR?

Any help/hint is appreciated!


texts: Multiplexing signals of two wires of a BNC cable and transmitting over a single wire

texts:
Background: I have a normal CCTV camera (650 TVL) . It requires a BNC cable in order to feed video signal from camera to DVR.

Problem The problem is I have only a single copper wire from CCTV to DVR. The wire which is to be used for the transmission has no shield. It is normal spare copper wire used for household electricity (AC). This is a spare wire and does not have AC current in it.

My Understanding  I think that the two wires used in a BNC cable (one core and other shield) can be multiplexed and feed to a single wire

So my question is can I multiplex the signals of two wires of a BNC cable, transmit over a single copper wire and at DVR side reverse the process (i.e. demultiplex the signals and feed to DVR)

Will this work? If yes then can someone please give a head start on how to proceed in order to make or buy such mux/de-mux.


texts: What is 'valid signal' that router receives to indicate physical status is 'up'?

texts:
If the Ethernet interface has a cable connected and is receiving a valid signal, the physical link shows an “up” status and there are no active alarms or defects. If the interface is not connected or is not receiving a valid signal, the output shows a physical link down status and an active LINK alarm and defect.

Source: http://kb.juniper.net/InfoCenter/index?page=content&id=KB26486

What is that 'valid signal'?


texts:
Why is -Vout equal to the voltage going through Rf?

here is a link to a site which explains the inverting amplifier circuit but I couldn't understand why this is.


texts:
In the datasheet for an overvoltage protector (TI BQ771815) there is a device I don't recognize:

It is used in the datasheet as a fuse which can be opened by an external signal from the overvoltage protector (in this case, by pulling the signal connection to ground).  It is used to protect Lithium battery packs.  This is from Page 10 of the BQ771815 datasheet:

What is this device called?  Who produces them?


texts: Opamp Saturation between different manufacture part numbers

texts:
I am working on an old design which opamp is in saturated mode,  what I would like to know why some manufacture part number keep staying on a saturating mode such as LT2079IS#PBF but some crash (negative rail voltage goes close to zero and the output is no good) such as LT6012CGN#PBF.

Let take a look at below example: This is transimpedance opamp design which saturates when Vin- be greater than 20uA but how do you know how long it will stay in the saturated mode before crashing(output is not valid), (from Datasheet)

simulate this circuit – Schematic created using CircuitLab


texts:
Stability of the closed loop system (with -1 feedback) can be assessed via Bode plot gain/phase margin analysis of its open loop system.
How can one deduce stability of the closed loop system directly its Bode plot?
One approach would be to fit a transfer function to the Bode (Frequency Response) and examine the poles' location of the fitted transfer function. But I'm looking for a rather intuitive approach using directly the Bode (frequency Response) plot of the closed loop system.


texts: Calculating the dropper / series resistor for an LED

texts:
I'm so sorry if this is a stupid question. I have read some of the questions previously asked but in afraid the maths and physics are way over my head.

I have made a wooden template and would like it to have light up eyes. I am hoping to use 1.5 V AA battery to power them. The eyes will be initially yellow LEDs. I don't want to fry them so if I wanted to power two separate 'eyes' which I believe are 2.1 V each, what resistor would I need to add to my circuit please? In the future, I may want to use other colours which are different voltages so if anyone can explain how to work this out in dummy terminology I would be incredibly grateful. Also, does it make any difference to the equation if you change the amount of LEDs being powered?


texts:
I have a floor lamp in which I have installed 2 LIFX Color 1000 A19 Wi-Fi LED Smart Bulbs (http://www.lifx.com/products/color-1000)

The lamp is designed to have 2 bulbs and has a two position dimmer switch for the bulbs wired in parallel so that in position 1, both bulbs light at 50%, and at position 2, both bulbs light at 100%.

The problem is, the smart bulbs do not work with the dimmer switch (they lose the wifi connection intermittently) so I would like to remove the dimmer switch.

The dimmer switch is wired such that it has one wire going into it, and one wire leaving it. The easiest thing I can do is to cut the wires on either side of the dimmer and connect them together, therefore bypassing the switch altogether.

The only thing is that there is a 3A fuse in the switch.  Is this needed?  Or is my solution ok (bypass the switch and fuse altogether).

I live in the United States.


texts:
I am doing some calculations to determine battery life under certain load conditions. As such I have turned to the internet and found this online calculator by DigiKey. The calculator used the following equation:

  Battery Life = Battery Capacity in Milli amps per hour / Load Current in Mill amps * 0.70

My question is:

What is the 0.7 scalar multiple on the equation for?
how can i take into consideration battery internal leakage current into my calculation?


texts: How to control power output from a ZVS driver?

texts:
I am trying to carry out heat treatment of Steel cylinders. I want to set up my own heat treatment apparatus. I am using the popular ZVS (Zero Volt Switching) driver for this. I bought this device.

In my experiment I want to control the heat supply according to temperature. When the temperature reaches a threshold then the device should turn off. When the temperature goes below this threshold then it should switch back on.

At first I thought of doing this with an SSR (Solid State Relay) where I would control the on/off function to the ZVS driver from Arduino. In regards to using SSR I have the following two questions:

I found in a YouTube video that the workpiece should not be inserted in the coil before turning on the driver. I don’t have the link to the video but he said the reason was to avoid cross conduction in MOSFETs. This is not a problem for the initial insertion. However, as I plan on using the relay with the workpiece still inside the coil I may not be able to take out the workpiece (already hot) in and out.
What could be an alternative technique to control the power to the ZVS driver?


texts:
I am trying to build a lithium battery charger (Li-Ion) for charging banks of 6s batteries of varying capacities (2-30Ah) from a varied DC input.

Given that I need to supply CC/CV to charge these batteries I plan on using a buck/boost converter such as this one:
https://www.ebay.com/itm/1500W-30A-Voltage-Step-Up-Converter-Boost-CC-CV-Power-Supply-Module/292853831480?epid=13026837672&hash=item442f72d738:g:EfsAAOSwtYZcCiBH

Connected directly to a BMS (or several in parallel) which offers charge balancing:
https://www.ebay.com/itm/Waterproof-BMS-6S-25A-35A-45A-60A-24V-25-2V-Li-ion-Battery-PCB-PCM-with-Balance/153021323145?hash=item23a0c81789:m:md0CttkjID5Rn60hEU8c1BA

My questions are as follows:

1) Will the above parts safely charge a 6s li-ion battery, assuming current supply is set appropriately for their cells' capacity?

2) Is it necessary to add a separate system for charge termination at low current (the above BMS claims to offer overcharge protection but I am dubious, not to mention 4.25v seems high)?
If this is necessary what would be the easiest way to integrate such a function?

3) Final question - what would I need to adapt about this system for charging LiFePo batteries in series?

Thanks in advance


texts: Why are NPN Darlington transistors used to sink current?

texts:
I notice that NPN Darlington transistors are commonly used to sink current. Wouldn't it make more sense to use PNP for the purpose? This would avoid shunting the load current through both junctions at once. Granted, we might want to share the current between two transistors; but in which case, please note that the second transistor is still carrying the full load (half via the C-E path, and half via the B-E path).

For that matter, why are transistors most commonly used for sinking current anyway; rather than driving it? I've never understood that.

In the above example, it seems more sensible to either (1) place the load below the transistor; (2) use a PNP Darlington; or even better (3) use a complementary PNP pair as shown here:

EDIT:

To clarify, one of the questions I'm asking is: Why can't we place this NPN transistor as-is above the load? Or, for that matter, place a PNP Darlington below the load? And also, why do Darlingtons even exist, when a complementary pair looks to be a cleaner solution?


texts: Anti Aliasing Filter and the bandwidth selection

texts:
I am currently analyzing the raw measurements of a sensor with the sampling frequency of 400[hz]. According to Nyquist theorem,  the bandwidth must be less than a half of the sampling frequency, which means less than 200 [Hz]. What will happen if I select the bandwidth as 50 [Hz] or 100 [Hz]?

(I have already tried to design two low pass FIR filters with the same characteristics, but different bandwidths, one 200 [Hz] and the other one 50 [Hz]; I noticed that for the bandwidth of 50 [hz], the pass band gain is not 1 anymore).

Thank you


texts: Could you double the speed of a GPU by doing half the work?

texts:
Is the thermal impedance from a GPU's wafer to the heatsink low enough that you could get close to doubling the clock speed if you halved the duty-cycle (render 50% of the full-TDP framerate).

An assumptions I've made through research is that the TDP (joules per second of thermal dissipation capacity) is highly related to the amount of work a GPU can do per unit time.

This capability at some degree is made apparent by reference to the "boost" modes and thermal dissipation schemes of today's high-power GPUs.

I do realize that this is probably not a linear relationship, but I'm talking very small bursts of work at the higher frequency:

Say a card can render a specific frame in 16ms continuously at its TDP, that's 60fps. I want to instead render that same frame in 8ms and then skip a frame, repeat (or maybe 6ms if I skip 2 frames?)


texts:
I am currently learning how to design/build a crystal radio receiver, transmitter and have a question for the 180 degrees phase shift for the carrier amplifier/oscillator system.

I commonly see this network setup: C1 to ground in series with the crystal and then another C2 to ground. The other networks have been left out for simplicity. I am not seeing how this works. If the RF signal is AC why doesn't the AC signal just go straight to ground? It's the exact same setup you see when placing an external crystal on a microcontroller. With the crystal in between two (usually 10pF) capacitors that are grounded. How does this work?


texts: How do I make a transistor turn on at a certain voltage?

texts:
I have made the following circuit:

When power is applied, C1 charges up and the LED lights up.  When power is disconnected, the LED gradually dims.  It turns off when C1 reaches around 1.5V.

I'm trying to get another LED to turn on when the first LED turns off.  So basically, I want a circuit to turn on when the capacitor has below 1.5V:

I am using a SS9014 Transistor (it says something else on the diagram).  I'm not too familiar with reading transistor data sheets, so I have no idea of the conditions that make a transistor turn off.  Is it a certain voltage or is it a certain amperage that makes it turn on?

If it's a certain amperage, then I could just adjust R2 to make LED2 turn on when C1 is under 1.5V right?  What is that amperage?

If it's not amperage that makes Q1 turn on, then it must be voltage.  I assume the voltage is less than 1.5V because 1.5V can turn it on.  What are my options in this situation?  Is there a way (or possible a 4000 series IC?) to reduce the 1.5V from C1 to the minimum voltage that makes the base turn on Q1?  If so what is that voltage?

Sorry if my question is confusing.  Feel free to ask questions in a comment.


texts: How much voltage does a 12V led strip need to light up?

texts:
I'm designing a photovoltaic powered installation. In my current design, I'm using a 12V battery, and I intended to power the lighting directly at that voltage without the usage of an inverter.

I understand that at 12V voltage drops quickly with distance unless thick wires are used. I wanted to know how much voltage I can afford to drop in order for the led lighting to still work.

The problem is the technical specifications of lighting only say "12v", and I find it impossible for them to require exactly 12V because it's not possible to have a 0 voltage drop.

So, looking for example at this light, what's the minimum voltage it will need to light up?


texts: Which of these layouts for decoupling capacitors attached to an IC is wrong?

texts:
I've started designing my first PCB and I'm trying to figure out how to layout my decoupling capacitors. I've done a fair bit of reading both on here and elsewhere on the internet and I'm still not sure how my capacitors should be connected.

Case 1

Specifically, these (1 and 2) stack exchange posts seems to say that the GND pin should be connected to the capacitor, which is then connected with a via to the ground plane.

Case 2

Meanwhile, this post says that we should have the GND pin go directly to the ground plane, like this:

Which of these is right? Or am I misunderstanding something and are they both correct? Thanks!


texts: How clock signal is distributed in Microprocessor chip?

texts: How clock signals are distributed in Microprocessor. I have been searching over the internet but nothing found useful. To complete process certain clock periods are needed 4 or 80 cycles.How signal is driven to the particular mosfet gate.


texts: Using a momentary push button as a latching on-off toggle switch

texts:
Please check the schematic here>

Here is the circuit that I have developed. I am not very sure about the design.

Here is what I want it to do. When the user presses the push button S2 the TPS_EN line should toggle.

I am using BSS84 P-ch mosfets.The resistor values are as in the schematic.

Here is an explanation of how the thing should work.The TPS_EN line is low at first. Since it is pulled down by a 10k pull down resistor(not shown in the schematic).When the user presses S2, the mosfet Q2 turns on because ground is applied to its gate. which enables the power regulator connected to the TPS_EN line . The regulator now starts up and starts powering the microcontroller. The microcontroller pulls the LATCH_OP1 and LATCH_OP2 low. The mosfet Q2 and Q6 now 'turns on' due to this.Q6 is turned on and now causes the 1st and 2nd terminals of the push button s2 to go high. And the LATCH_OP1 causes the Q2 to latch thus enabling a constant high signal (VBATT)on the enable line.

Now when the user presses the button Since Q6 was 'on' the VBATT gets applied to gate of Q2 and turns off Q2.The regulator turns off. turning off the microcontroller and the LATCH_OP2 and LATCH_OP1 return to VBATT.

BATT is around 3.7v.The Micrcontroller is running on a 3.3v supply

The circuit does not work as intended. I tried manually changing the latch lines to ground when turning on and it worked. But when i connect the lines to the microcontroller it does not work Please help me out!

Feel Free to point out mistakes if any. This is my First circuit design!(So please excuse my noobness! :p)


texts:
I am learning MIPS data path with piplining and I am a little confused in the following two things?

How do we perform Stall in MIPS data path?

What is the difference between Stall and Flush?

Here is the data path: