texts: What should be the Vout for a CM-driven amplifier?

texts:
I am somewhat confused by what should be the amplifier output voltage after a purely CM signal is fed. Let me it clarify what I'm talking about:

simulate this circuit – Schematic created using CircuitLab
I would say it should be \$0\$ because, assuming large DC CMRR, such 1V CM will be blasted off by the amplifier. Mathematically, since \$v_{out} = A_{diff}(v_{diff}+\frac{v_{CM}}{CMRR})\$.
However, I'm rather told one should expect a midrange output wrt supply rails, from a design standpoint. Thus, if say the amplifier is railed from +3V to 0V then I should expect \$V_{out}=1.5V\$. This criteria actually leads to some design specs at the output stage, where one should size the transistors to have exactly the same current.
This standpoint eventually results in the same conclusion if supply rails are symmetric e.g. from +3V to -3V, but then I wouldn't expect a Vout = 0V for +3V and 0V, as Circuitlab says.
So, which one is correct? Or are we talking about the same thing?

Clarifications are due, I'm sorry. I do know a real amplifier will inevitabily be affected by a statistical offset voltage, likely leading to saturation close to rails depending on polarity. But that's not the point of the question.
My question is: if theoretically \$\mathbf {V_{OS}=0}\$, then, for high CMRR, should one expect Vout to be slightly above 0V (i.e. regardless of the opamp supply rails) or should one expect it to be at mid range i.e. close to \$(Vcc-|Vss|)/2\$? From the previous \$v_{out}\$ equation, I would say the former -- but I wouldn't know whether the output stage may be able to reach it without a negative rail (if for instance the opamp was powered with +3V and ground on the lower side).


texts: Inverse Fourier transform of a shifted cos

texts:
I am preparing for an exam.
I found this signal I want to inverse transform using the Fourier transform:

The problem is that when I try using the general formula for inverse Fourier transform I get stuck by the infinities. I tried using the properties but nothing can be done.
I hope you have a way of tackling this.


texts:
I want to use MOSFET-N (MTM232270LBF) as a power switch for several ICs in my project. It should poweron the devices when logic level is high (3.3V) and poweroff when 0V.

I want to ask you if everything is ok with the design presented below.

Especially am I right if the MOSFET-N will work in saturation zone?

Some of the ICs will be connected to uC through SPI, UART, I2C. Everything will be ok when I shutdown the power?

Do I even need R2 resistor or I can connect uC directly?

I want to power the OPAMP for PT1000 temperature signal and the ground will have 0.003V offset from "real" ground. Should I consider this in error calculation for the PT1000 temperature?

simulate this circuit – Schematic created using CircuitLab


texts: LED Intensity variation with Temperature (At constant Forward Current)?

texts:
I have developed a product in which LEDs spectrum is sensed by CCD (TCD1304) using ADC of pic microcontrollers. It is being observed that LED spectrum changes with time. We concluded that it could be due to change in temperature and change in forward current (consequence of change in temperature).

The datasheet of one of the LED is over here. The LED is being driven using NPN transistors. I am using PWM to control the intensity of LED and the maximum current that flows through LED is 12 mA. The datasheet of LED shows change in intensity with the temperature at constant forward current. The graph which states that in given below and you can find it in the datasheet of the LED.

My question is after starting the system (and starting the LEDs), how to nullify or counter the change in intensity of LED with time. We know there are many products in which LEDs is being used and sensed. I just want to know how industries or experts tackle this type of problems and what are industries best practices to be followed to avoid or counter such effects?

The schematic of my LED circuit is:

Note: NC in the schematics means a zero ohm resistor.

UPDATE:
We have tried few experiment with constant current source (LM334) and results were a bit better but still they were not acceptable. I have designed a new PCB with PWM-Controlled constant current source. I will test it in a week and update my question with the results. I liked the answer given by Misunderstood alot and will try LEDs suggested by him.


texts: Dual voltage output flyback power supply - skip mode vs continuous operation

texts:
I am currently trying to solve an issue with a vintage PC power supply (Schematic here: http://techmattmillman.s3.amazonaws.com/wp-content/uploads/2017/01/5150_PSU.png)

At idle, there is about 5A load on the 5V rail, and pretty much no load on the +12V rail, during this time I can see with my scope that the power supply runs in DCM mode, resulting in it making an annoying hissing noise.

But then if I put a small load (say 200mA) on the 12V rail, it switches to CCM mode and becomes inaudible.

Here's the tricky part: If I instead put that extra dummy load on the 5V rail, but at 500mA, this does not have the same effect. The supply remains in DCM mode and gets even noisier! (I tried a whole range of loads: 100mA to 3A, they all have the same effect)

What on earth is going on here! What is the difference between loading the +12V rail and the +5V rail from a DCM/CCM point of view?

Why does the load have to be on the 12V rail to stabilise the supply?


texts: Porting from iccavr project to Atmel studio problems with Atmega2561 8 bit MCU

texts:
I'm currently in the process of having to port a large project from ICCAVR known as the imagecraft IDE to Atmel Studio 7.0 and have had great difficulty trying to get the Atmel build of the project working on the custom board. I've followed the documentation of the code ports I need to do as shown in the link below with the interrupts and the flash memory but it's still failing. The MCU I'm using is an 8 bit ATMEGA2561.

ICC to Atmel Porting guide: https://www.nongnu.org/avr-libc/user-manual/porting.html

These are the following things I've tried to get the Atmel version of the build working

Used ICCAVR header files in Atmel Studio
Rewritten interrupts from ICCAVR to Atmel Studio as required from the documentation
Used Atmel header files in Atmel Studio (#include , #include ) for the port

I can visually show what is happening with the help of these two videos I have posted on here. The first one is the custom board with the ICCAVR build loaded on the MCU. It just does one beep with the piezo buzzer and goes through the void main() code as proven with the UART debugging printouts.

ICCAVR Build Video: https://www.youtube.com/watch?v=G58d3CC0AB4&feature=youtu.be

The second video is the custom board with the Atmel studio build, where the piezo buzzer just continuously keeps beeping until I pull the battery out of the board. No UART debugging printouts get down.

Atmel Studio Build Video: https://www.youtube.com/watch?v=vPUr4qzoOQI&feature=youtu.be

I have been struggling for 4 days now with multiple attempts to port the project code and am have very little luck.


texts: Making a nail electromagnet with bare copper wire?

texts: When creating a simple electromagnet, all you need is a nail and some copper wire, and a battery.  I did this using non-coated copper wire, and after thinking about it for a bit, I was confused as to why it was working.  Theoretically, the current moving through the coil around the nail should induce a strong magnetic field concentrated in the center of the coil (in the nail).  However, if this wire is not coated, wouldn't the current simply "jump" between coils rather than following the spiral pattern around?  And since it is no longer moving in a coil path, wouldn't it fail to create an electromagnet?  Yet still, the electromagnet was able to pick up several paperclips with only about 20 coils around the wire.


texts: Why do I need two PNP BJTs as a switch rather than only one?

texts:
As far as I know, the circuit into the read circle works as a switch. I would like you to help me to understand how does the circuit works as a switch and why I need something so complicated instead of a simple circuit with one BJT only.
Also, why do I need PNP BJTs while the most of the world uses NPN BJTs?


texts:
I bought some plug ends to hook up to my outlet

I wanted to connect the plug with some wires, I was told that I needed these type of wires
I however wanted to use low voltage wires like these
It will be hooked up to a transformer that will output 6 volts, and then connected to a rectifier if I were to use the low voltage wires instead of the thick ones would that cause any issues? I believe that the amount of power that enters the system is the same as it leaves so I believe that the low voltage wires shouldn't cause issues as long as its under 1 Amp


texts:
This might be a touchy subject, but bear with me. I have a 2.1 speaker set which has typical 3.5 mm AUX input and output. The problem is that sometimes the left and/or right audio channels cut out and I have to jiggle the cables to get them to work again. I've tried duct taping the cables in certain positions, but the problem always reoccurs eventually. I tried buying a better quality aux cable, but the problem seems to be with the female connectors on the subwoofer. It's a massive annoyance.

It is for this reason that I am a shameless supporter of the death of the 3.5 mm connector. I know, I know. Hate me if you must. Call me whatever names come to mind. All I know is that I am currently listening to Zeppelin's 'Ramble On' with one audio channel and it's torture.

I think I may have a solution, but I'm not sure if it's viable. On the inside of the sub is a PCB with a couple of female 3.5 mm jacks soldered on that look like this:

I am wondering if I can remove them and replace them with something similar to this:

Is it just a matter of soldering certain connections together? Or would I need a DAC and/or other components? What gets soldered to what? It's a pretty cheap speaker system so if something breaks I'm not too worried.

I have very little electronics experience, but I would like to make a small project out of this anyway. I appreciate any tolerance of my unpopular views on tech. Go easy on me.


texts: What is the real speed of my system implemented on FPGA? How to check this value?

texts:
I created an FPGA system on ModelSim (a simple algorithm that calculate an equation and save on-chip), synthesized with Quartus Prime, then downloaded to my DE1-SOC.

My intention is to compare my results with an implementation made in a paper. In the paper they make almost the same calculation than me, and they report speeds around 15 "ms" mili-seconds. They don't provide frecuency speed about their system but about the NIOS-II processor itself which is 75 Ghz.

In my system I'm not using NIOS-II, but rather calling altera IP's for Mul,Div etc.

Now, I don't know exactly how to read my own speed values. Here in this forum I was told that I should look at the compilation report of Quartus Prime, exactly what segment of the compilation report should I look at?

Looking at the wave in the modelsim, tracking when it finish the calculation it says it is completed on terms of "PS" Pico-seconds and the conversion to "ms" I'd have less than 1 milisecond. So it means my system is faster than the aforementioned paper?

Exactly which department should I see in the compilation report of modelsim to know the Speed of my system aka calculation time.

This values come from softwares, are these values exactly the same that what is physically happening in the board itself?


texts: I have to admit up front this is a borderline shopping question. But the fact is I'm looking at an application note from Linear Technologies. That application note calls for Coiltronics CTX02-14659 for the isolating DC-DC transformer. What are the salient properties of this transformer I should be considering when looking for substitutes? I don't work with transformers regularly so this is all a bit foreign to me. If possible, I'd rather not get backed into a corner on having a single supplier for this part, so how do I go about finding an acceptable substitute parametrically.


texts: controller for interleaved Flyback converter

texts: I want to use the topology below and I want to know whether there is an IC for controlling it or not.


texts: What is this operator called as "+:" in verilog

texts:
I am going through verilog test case and found a statement

assign XYZ = PQR_AR[44*8 +: 64];

What does "+:" operator be known as. I tried to find this on google but didn't get any relevant answer.


texts: Will a potentiometer let me adjust the volume on an RCA to 3.5mm headphone cable?

texts:
I don't know a lot about EE, and this might not be the best place to ask, but I have a really basic question. I'm thinking about cutting an RCA to 3.5mm cable in half and inserting a pot for volume adjustment (it goes from TV to bluetooth transmitter). If that would work then what kind of pot would be best, and could I add another pot for right-channel adjustment? I was thinking that a concentric pot might be able to simplify things (one is better than two). I'd buy a premade cable that does what I want, but I don't think it exists. Any advice would be appreciated.
I'll draw a diagram and update my picture, if needed.


texts: Power NodeMCU with 12v to 5v 3a - 15w DC-DC Converter?

texts:
I want to power a NodeMCU and a LED Strip with 12v power supply. I don’t want to risk doing anything to the NodeMCU though so I want to convert the 12v to 5v. I have already tried a LM7805 but it gets way too hot to even touch slightly. Would a DC-DC converter like this work okay to convert to 5v? https://www.ebay.com.au/itm/Better-Waterproof-DC-DC-Converter-12V-Step-Down-to-5V-Car-Power-Supply-Module-3A/281296554356?epid=2100111522&hash=item417e94c974:g:3ioAAOxyUI1TGV9B
It’s the cheapest alternative I could find to an LM7805 so I’m curious if it would work just fine.
Thank you.


texts: Voltage levels of Microcontroller Oscillator Pins

texts:
I am using MPC5606S Microcontroller.

I want to clear one concept and have a doubt.

The Microcontroller using 8MHz crystal on the pins 27 (XTAL) and 29 (EXTAL) And a 32.768kHz RTC crystal between pins 71 (XTAL32) and 72 (EXTAL32).

My understanding :

The Crystal is constantly bombarded with some noise composed of many frequencies. But since the Power is not provided to the microcontroller, the amplifier (OP-AMP amplifier) circuitry present inside the Controller is inactive and does not amplify the resonant frequency of the crystal which is 8MHz. Once, the Controller is powered, the amplifier is active and now only the 8MHz resonant frequency is amplified and is provided to the other sub-section blocks inside the microcontroller. Is my understanding correct?

My doubt :

What determines the voltage levels of the RTC 32.768kHz and 8MHz oscillations?

I have captured the below waveforms for both oscillations :


texts:
can i make switched reluctance motor with sinewave input voltage and sinewave current using series LC resonant filter (Inductor L and capacitor C in series resonance (for 50 Hz 0.1H and 100 micro Farad) on the input side of the motor) ?

If i put just like that sinewave voltage, the current will not be sinewave (some kind distorted signal).


texts: Why is this photodiode operated in reverse bias

texts:
Referring to the following document by NXP on figure 9. The cathode of a given photodiode is connected to the transimpedance amplifier in forward bias.

To me, this seems wrong, as almost every source i've read about photodiodes states, that a photodiode needs to be in reverse bias, as that's the only way electrons can flow over the depletion region.

When the photodiode is put in reverse bias, the depletion region expands, and thus, photons that strike the surface of the photodiode generates electron holes, that consequently allows current to flow.

Why is NXP then placing the diode in forward bias?


texts:
I (think I) want to use an ITS4060S-SJ-N (+datasheet) in a circuit that can't handle over 40V (an LM2576T-5), but will normally receive 8-30V with a ≤12W load. Its purpose would be to provide overvoltage protection, short circuit protection, thermal shutdown, and reverse battery protection*. But I'm having trouble making sense of the datasheet to find what voltage it would clamp at. From the datasheet, I see that:

Overvoltage protection \$V_\text{SAZmin} = 41\text{V}\$ (Product Summary, p2)
Max supply voltage \$V_\text{S} = 40\text{V}\$ (Absolute Maximum Ratings, p5)
Overvoltage protection \$V_\text{OUT}=V_\text{S}-V_\text{ONCL}\$, \$V_\text{SAZmin}\$ = 41V (Electrical Characteristics, p8)
Output clamp at \$V_\text{OUT}=V_\text{S}-V_\text{DSCL}\$ (inductive load switch off), \$V_\text{DSCLmin}\$ = 41V (Electrical Characteristics, p8)

Does that mean it would clamp to 41V? \$V_\text{ONCL}\$ is only mentioned once, without further explanation. I've searched for \$V_\text{SAZmin}\$ online and couldn't come up with anything either. The \$V_\text{DSCL}\$ line seems to indicate that the output voltage is at least 41V lower than supply (\$V_\text{S}\$) under inductive load switch off, so perhaps that means that for say \$V_\text{S}<41\text{V}\$ then \$V_\text{OUT}=0\text{V}\$. But what constitutes the maximum output voltage? It could be anything up to 41V in that case. I think there would have to be something more in the logic block on p3...

* Will include a 150Ω ground resistor and a PMOSFET to limit load's reverse current, see note 4 on p8.


texts: How do I implement a DPDT-switch here using NPN/PNP instead?

texts:
I have a small project where I select two states by redirecting Vcc/gnd to the thing that's supposed to be active. See image of how it looks.

This works fine, but now I'm looking into removing the physical switch and implement it in a PIC instead. One output pin of the PIC will be either low or high, and I want this to simulate the physical switch. It does not matter if the switch is done with BJT or FET, but I have BJT at home so this will be the easiest to try with.

However, I'm at a loss figuring it out how it should be coupled. Tying the base of a NPN/PNP together gave me the state of both "things" having Vcc/gnd at the same time (which is supposed to be an illegal state).

Question: is it possible to achieve what I want using only one GPIO-pin and NPN/PNP:s?

EDIT

For clarity, Pin 1 (Vcc) and Pin 4 (Gnd) goes to a small milliamp-load (LED #1), while Pin 3 (Vcc) and Pin 6 (Gnd) goes to another small milliamp-load (LED #2). The DPDT-switch controls both Vcc and Gnd to the loads, I'm looking for a transistor solution that does the same.


texts: Electrical resistence between two different terminals

texts: I have to calculate the resistance R_AB, R_AC and R_CD. But I'm confused because there are two different terminal, one on the left and one on the right. Can someone give me a hint how to solve this?


texts: Ciruit Board with traces on top and bottom?

texts:
I was looking at re-making a Circuit board. The Circuit board I have has the same exact traces on top and bottom. I cant figure out why this would be done. Any one have any idea why you would have the same layout for traces on top and bottom side?

Thanks
GM

EDIT
Pretty much its a back plane that takes a 50 pin ribbon cable from the back side of the board to a 65 pin quick connect to front side of board. with the other 15 pins, they go to other connectors that are connected to DMM , Spec Anlizer , o scope ect..


texts: How was this formula of voltage on capacitor achieved?

texts:
We know that voltage across a capacitor is given by

But there is this other formula

How this second formula was deducted mathematically from the first one? or from another one?


texts: Why is the offset voltage present on the non inverting terminal? What would happen on placing it on inverting terminal?


texts: Mosfet gate driver have no direct connection to ground

texts:
This picture shows some part of a high frequency (about 250kHz) MOSFET gate driver circuit.I searched for various types of gate drivers in google and didn't encounter anything like this. Can someone explain this configuration.

What is the purpose of the diodes?.
why mosfet Source isn't connected directly to the gate driver supply ground?.
what is the purpose of two 2k resisters and C12 capacitor connected between +12V and the ground?.

In here +12V and the GND are the gate driver power supply terminals.


texts: Can not recognise this piece of equipment. It is attached to the mains

texts: It is normally quite noisy, but has gone silent.


texts: STM32 HAL VS dual 595 driven 7 segment display

texts:
I got this arduino shield with four 7 segment display what I'm trying to make work with STM32 nucleo. The displays are driven with two 74HC595 shift registers.
I wrote the following code to control it, but somehow it doesn't work, always shows the same pattern whatever I modify in the array.
int digits[16] = {1,1,1,1,1,0,1,0,1,0,1,1,0,1,1,0};
while (1) {
    HAL_GPIO_WritePin(STCP_GPIO_Port, STCP_Pin, GPIO_PIN_RESET);
    for(int i=0;i>=15;i--) {
        HAL_GPIO_WritePin(SHCP_GPIO_Port, SHCP_Pin, GPIO_PIN_RESET);
        if(digits[i]==1) {
            HAL_GPIO_WritePin(DS_GPIO_Port, DS_Pin, GPIO_PIN_SET);
        }else {
            HAL_GPIO_WritePin(DS_GPIO_Port, DS_Pin, GPIO_PIN_RESET);
        }
        HAL_GPIO_WritePin(SHCP_GPIO_Port, SHCP_Pin, GPIO_PIN_SET);
    }
    HAL_GPIO_WritePin(STCP_GPIO_Port, STCP_Pin, GPIO_PIN_SET);

}

SHCP: Shift register clock
STCP: Storage register Clock
DS: Data
What could be the problem?


texts: Would a standardized graphics chip socket be sensible?

texts:
I am not an EE, and so I'm running this conjecture on breaking out the GPU from the CPU by folks who have better knowledge than me.  Perhaps you can point out something I don't know about modern CPU architecture.

Many modern processors provide integrated graphics, with the exception of some AMD processors which provide additional cores in some models (Ryzen 5 2600) and integrated graphics in others (Ryzen 5 2400G).  Off-chip graphics currently use a PCI-Express bus, while on-chip graphics appear to the OS as some kind of IO device on some kind of bus (details unimportant:  figuring out bus and device is what your OS does).

Per my understanding, a CPU may execute extended instructions such as for FPU; whereas a graphics chipset is a self-contained computing platform performing I/O on a working set on its own.  Software does not intermix GPU instructions with CPU instructions, and the GPU doesn't operate on the same RAM; rather the GPU has its own processing frequency, its own instruction stream, and its own RAM space.

This suggests to me that a GPU off CPU would be sensible.  Just as modern PCI-Express graphics adapters use a generic interface, a GPU chip could use a standardized socket interface.  The CPU could connect it to a bus and provide RAM; while the output pins could route to whatever chipset encodes to HDMI, DVI, or other video output port.

A CPU could assign the GPU's video range to a DMA-mapped area of RAM, or it could allocate a separate RAM channel (e.g. one or two RAM slots) to a second MMU which services the GPU, thus avoiding contention with the CPU.  An MMU capable of shared access can also disable its own access to a RAM slot and enable a secondary MMU, making this configurable.  The CPU would allow the GPU DMA access to system RAM so it could copy data into its own memory space just like a graphics card.

This seems to leave one trade-off:  the VRAM would be regular system RAM, rather than GDDR5 or LPDDR4 or whatever the manufacturer wants to stick on their card.

If the above is correct, then there's no real advantage to integrating the GPU with the CPU on non-embedded systems; whereas providing a GPU socket would allow pairing better CPUs with separate low-cost GPUs.  A desktop PC doesn't make sense as a SoC, while a dedicated socket for a GPU makes sense because every PC needs some kind of graphics and the interface is routinely standardized across PCI-Express.

Integrating the MMU and north/south bridge makes plenty of sense due to the specific hardware interdependence and large amounts of data passed between each continuously:  this saves latency.

Likewise, graphics card DMA would go across the MMU in the CPU, tightly-coupling these.  The MMU would expose a chunk of RAM just like it works with integrated graphics; if the GPU wants to manage virtual memory, it can treat that as physical RAM and integrate its own MMU, thus avoiding the overhead of an off-chip MMU.  This seems no different than on-die GPU.

Does all of this make sense, or is there some enormous advantage I'm missing (besides separate package cost) having the GPU on the same die instead of plugged into a nearby socket?


texts: Confirmation of transfer function of circuit with op amp

texts:
Hey I got an assignment on which I need to calculate the transfer function. It is about the following circuit:

simulate this circuit – Schematic created using CircuitLab

So my approach (note all capicitors values are the same and so referred to as  C):

At node A: i1 = i2 + i3 + i5
Ideal opamp so: i3 = i4
$$\frac{Ua}{Zc}=-\frac{Uo}{R4}$$
$$Ua=-\frac{UoZc}{R4}$$
Filling in 1.:
$$\frac{Ui-Ua}{Zc} = \frac{Ua}{R2}+\frac{Uo}{R4}+\frac{Ua-Uo}{Zc}$$

$$\frac{Ui+\frac{UoZc}{R4}}{Zc}=-\frac{\frac{UoZc}{R4}}{R2}-\frac{Uo}{R4}-\frac{\frac{UoZc}{R4}-Uo}{Zc}$$
$$UiZc+\frac{UoZc^2}{R4}=-\frac{UoZcR2}{R4}-\frac{Uo}{R4}-\frac{UoZc^2-UoZcR4}{R4}$$
$$UiZc=\frac{-UoZcR2-Uo-UoZc^2-UoZc^2-UoZcR4}{R4}$$
$$Ui=\frac{-UoZcR2-Uo-UoZc^2-UoZc^2-UoZcR4}{R4Zc}$$
$$\frac{Uo}{Ui}=\frac{R4Zc}{-2Zc^2-ZcR2-ZcR4-1}$$
$$Zc=\frac{1}{jwC}$$

$$\frac{Uo}{Ui}=\frac{jwCR4}{(jwC)(-jwC-R2-R4)-2}$$

So the question is is this correct? I hope it is however I tried testing my results by simulating the design in LTSpice, taking R4 = R2 = 1K and C = 1uF and then I entered the formula, with the same component values, in matlab however the graphs are not the same.. :(

EDIT Okay now it is confirmed the answer is wrong how would I derive such circuit? I tried it again but I'm yet again not getting the right answer.. I won't post it here since it takes to much time to type it out.


texts: What makes an incandescent light bulb run out?

texts:
What is or are, the most likely and common ways - the weak links in the chain (including I assume poor electricity wiring / configured housing) - that cause a traditional incandescent light bulb to blow?

And how much does manufacturing / materials quality of the bulb make a difference in any of those factors? (In other words, should an expensively, state-of-the-art constructed bulb in terms of materials purity and construction robustness, generally last a lot longer than the average bulb on the market?)

I understand it is a fairly simple lighting technology, so what complications cause them to not last longer than they generally do? Is 'blowing' the only way that an incandescent can ever expire?


texts: N-MOS real-life gate threshold voltage (Vgsth) lower than claimed

texts:
I faced with a paradox that N-MOS transistor real-life Vgsth (gate-to-source threshold voltage) is significantly lower than claimed. It should be about 1.7 V (and the simulation confirming that assumption):

However, real-life test shows that the Vout voltage is about 0.6V (real-life test schematic was similar).

During further investigation I was lucky to find a "Sub-threshold drain current" chart in NXPs datasheet page 7 (usually there is no such data in MOSFET datasheets) for this MOSFET (2N7002):

As you can see, at my given current (0.5 mA) Vgs should be miminum above 1V (I'd say 1.1V).

Is there anything I left outside my sight?

Actually the main reason I am asking this question is that I need this schematic to provide me with Vout as low as possible (0.6V is not a bad result, but the closer Vout to 0 V the better). But this is a bit scary to put in mass production a schematic which not behaved in accordance with data sheet. So I'd like to pick a different MOSFET with as low Vgsth as possible.


texts: What could be the reason to use a current source for potentiometric vane measurement?

texts:
On page number 507 of this document, there is a signal conditioner for a potentiometric wind vane.

It seems like they use a current source but I don't get how the mechanism works.

I guess O/P below means the output of the wind vane.

My questions are:

I didn't get how the O/P terminals above is connected to the wind wave. Doesn't such a potentiometric wind vane have 3 terminals? Which terminals are connected to the O/P in this case?
Why use a current source? Wouldn't a voltage source and a ratiometric measurement work instead?

I used to measure the vane as in the following model:

Vs is a voltage source (Rs can be a protective resistor or the output impedance of the supply). R3 and R8 are data acquisition input channel impedances. R2 and R1 represent the vane potentiometer. So in this case Vref and Vout is measured to calculate direction.

What could be the reason they are using a current source?


texts: Trying to create Finite-State Machine, can't figure out these syntax errors

texts:
So I've been trying to figure out where I went wrong in my VHDL code for my finite state machine however I feel a new, more experienced set of eyes may help. Any help would be welcome.

Here is the code (I've marked the lines where the errors occur):

LIBRARY ieee;
USE ieee.std_logic_1164.all;

ENTITY part2 IS
        PORT(clk : in std_logic;
                        w : in std_logic;
                        res : in std_logic;
                        st : out std_logic_vector(8 downto 0);
                        z  : out std_logic);
END part2;

ARCHITECTURE behavior of part2 is

        TYPE state_type is (A,B,C,D,E,F,G,H,I);
        signal y_Q, y_D : state_type; --y_Q is present state y_D is next state

        BEGIN

        process(w, y_Q)
        BEGIN
        case y_Q is  -- DIFFERENT STATES
                when A => IF(w ='0') then y_D <= B;
                else y_D <= F;
                end if;

                when B => if(w = '0') then y_D <= C;
                else y_D <= F;
                end if;

                when C => if(w ='0') then y_D <= D;
                else y_D <= F;
                end if;

                when D => if(w = '0') then y_D <= E;
                else y_D <= F;
                end if;

                when E => if(w = '0') then y_D <= E;
                else y_D <= F;
                end if;

                when F => if(w = '1') then y_D <= G;
                else y_D <= B;
                end if;

                when G => if(w = '1') then y_D <= H;
                else y_D <= B;
                end if;

                when H => if(w = '1') then y_D <= I;
                else y_D <= B;
                end if;

                when I => if(w = '1') then y_D <= I;
                else y_D <= B;
                end if;

                end case;
                end process;

                --clk and reset
                Process(Clk, reset)
                begin
                if(reset = '1') then y_Q <= A; --resets fsm

                else if(rising_edge(clk)) then
                y_Q <= y_D; --state change;
                end if

                end process; --LINE 70 !!!!! ERROR 1

                Process(st)-- Determines z
                begin --LINE 74 !!!! ERROR 2

                if(y_Q = A)
                then
                st <= "0000000001";
                end if;

                if(y_Q = B)
                then
                st <= "0000000010";
                end if;

                if(y_Q = C)
                then
                st <= "0000000100";
                end if;

                if(y_Q = D)
                then
                st <= "0000001000";
                end if;

                if(y_Q = E)
                then
                st <= "0000010000";
                end if;

                if(y_Q = F)
                then
                st <= "0001000000";
                end if;

                if(y_Q = G)
                then
                st <= "0010000000";
                end if;

                if(y_Q = H)
                then
                st <= "0100000000";
                end if;

                if(y_Q = I)
                then
                st <= "1000000000";
                end if;

                end process;--LINE 122 !!! ERROR 3

        end Behavior;


texts: Approximating dynamics in continuous-time with discrete-time

texts:
I'm not sure if this is the best place to ask this question, so please direct me to the appropriate community if this question seems out of place here.

I am working on a project in which I'm trying to generate chaotic behavior in a system consisting of three RLC circuits interacting with each other nonlinearly with feedback. The system is intended to be a highly simplified model of a real-world phenomenon. Each circuit is driven with two inputs:

a sinusoidal voltage source
measurements made at nodes on one circuit which are amplified and fed into the others

Chaotic behavior in circuits has been demonstrated by Chua et al. in the so-called Chua circuit.

I have two ways of generating the sinusoidal inputs to the circuits. First, I can use standalone function generators, which, according to Wikipedia, generate signals by charging and discharging a capacitor. Second, I can use a data acquisition system (or DAQ), which interfaces with my computer and generates signals by sampling a virtual waveform and outputting the samples. The value that is outputted is held for 1/F_s seconds, where F_s is the sampling rate.

For convenience, I would prefer to use the latter because the input can be easily controlled (switched on or off and the amplitude or frequency adjusted) based on measurements of voltage that I take across different elements in my system. However, because the signal generated by the DAQ is not truly continuous-time (unlike the real world in which time is continuous) in the sense that the outputted value is only updated every 1/F_s seconds, I'm wondering if the interactions and feedback will be able to accurately recreate the same type of chaotic behavior that truly continuous time inputs (such as those generated by a function generator) would produce.

Importantly, my sinusoidal input signals are band-limited to 100 Hz and the sampling rate of the DAQ can be up to 80 kHz. At low sampling rates (less than 1 kHz), I can clearly see jumps in voltage between successive samples when I measure the DAQ-generated signal on an oscilloscope. At higher sampling rates (tens of kHz), these jumps essentially disappear (even though I know they are there and just cannot be seen).


texts: Amplitude Spectrum of FM wave from Bessel First order

texts:
given the values for \$\beta=5\$, for the Bessel of the first order:

\$ J_{0}(5)=-0.26, J_{1}(5)=0.34, J_{2}(5)=0.49...\$

in order to plot the amplitude spectrum of the FM wave, do you treat the negative numbers as absolute?  The \$ J_{0}(5)\$ amplitude should be \$ |J_{0}(5)|\$ ?


texts: Can the top off a coke can serve as a heat-sink?

texts:
Looking around here for a heat-sink for a TO-18 (2n2222) form I don't quite see one around that will serve. The thought in my mind is whether I may cut the top off the Coke Can, and use it as a sink; punch a hole the size of the TO-18, cut tabs along the perimeter of the cap, and stick the transistor in it.

Will the aluminum from a coke/beer can serve as a heat sink?


texts:
I'm having a DRC error for the diameter of a trace. The error:
Diameter: 0.61mm(24mil)
DRC Diameter: 0.61mm(24.016)mil

This has been discussed here and here with only a "we will improve this issue" message from EasyEDA. Other users are still running into this.
How do I resolve the issue? I have it with all my via's. Where do i need to go in the menu and what do i need to do?


texts: Did I calculate this MOSFET circuit correctly?

texts:
Edit: I have updated the question with the marked answer
Follow up question to my question from two days ago:
How to calculate this resistor MOSFET circuit?

These are the tasks:

Choose \$R_D\$ and \$R_2\$ that if a current of \$50mA\$ flows through \$R_D\$, and \$U_{GS}\$ and \$U_{DS}\$ are \$6V\$

Calculate \$I_{D,max}\$ and \$U_{D,max}\$ and chart the characteristic into Figure 6

Mark the operating point in Figure  6 in which region is it ? What has to be done to shift the operating point into the linear region?

Calculate the factor \$\beta\$ if \$U_{th}\$ equals \$1V\$

Calculate the draincurrent with the factor \$\beta\$ and the values: \$U_{GS}= 7V\$ and \$U_{DS}=2V\$ and mark the operating point in the characteristic in Figure 6

This is the circuit:

This is the characteristic (Figure 6):

There are the given values:
\$U_B\$ is \$12V\$
\$R_1\$ is \$100k\Omega\$
Here are my solutions/thoughts
I have calculated that \$R_2\$ has to be \$100k\Omega\$.
But this is already where am not sure what is correct. I have been told (here, full disclosure) that \$U_{GS}\$ and \$U_{DS}\$ will always be equal in this circuit and in the case of \$6V\$ \$R_D\$ has to be \$120\Omega\$. I have mixed feelings about this, since I myself calculated \$240\Omega\$ and in the question earlier have been told that even \$240k\Omega\$ is correct.
Then to mark the characteristic, I would have marked either \$12V\$ or \$6V\$ and \$100mA\$ or \$50mA\$, why \$100mA\$ the task later asks, how to get the operating point into the ohmic region again, almost implying that I is in the saturation region initially. In this instance only \$100mA\$ and \$12V\$ would make sense, because thats the only instance the operating point is in the saturation area. I am confused.
Then in the next task, calculating \$\beta\$ should be no trouble, since I know all the variables, and only have to solve for \$\beta\$, but I need the correct operating point to be able to solve it.
Then in the last task, which I haven't done aswell yet, my solving way should be to simply solve for \$I_D\$ with the factor \$\beta\$ from the task earlier since I have all the variables.
Marked Solution:
If translation is nessecary please comment below


texts: Voltage / amperage / setup for tingling sensation

texts:
There are small pens (powered by a single or double  1.5V battery) or other medical devices that upon touching your skin produce a tingling sensation.
Main question: I wonder to what voltage, amperage (or both) this sensation appear? Is the current suppose to be AC or DC? What frequency? In general what are the conditions for the sensation to appear?
(Optional) On the fun side can I achieve that with my Arduino board or a Raspebbery ?


texts: Determining which voltage is higher in nodal Analysis

texts: Im trying to learn nodal analysis.In the below example  why do you subtract Vb from Va and not the opposite? ///y for Vc and Vb?


texts: Do brand new rechargeable batteries have a charge?

texts:
When a standard Duracell AA battery is manufactured, it contains all the charge it will ever have (right?), and can't be recharged.

But, for a rechargeable battery like a NiCd AA battery, or a lithium laptop battery, does the battery have voltage just from the process of putting all the materials together, or is it an "empty container" that then needs to be charged before ever leaving the factory (or being used)?


texts:
In tuning an antenna, there are multiple possible topologies that will take it to the middle of the smith chart.

Some differences that I can see between them are:

Component ESR (losses).
Effect of component tolerances.
Resulting antenna bandwidth.

For example:

Alternative 1 "LpCs"

Alternative 2 "LpLs"

Alternative 3 "LsCp"

Which one would you choose and why?


texts: Is the dynamic input resistance zero for constant voltages?

texts:
This might sound a stupid question but I'm confused with the following excerpt:

If Vbe is constant 0.7V which means ΔVbe is zero, does that mean the dynamic resistance is zero?

I think I have problem with interpretation of the graph above. If there is no change in the Vbe signal and Vbe is kept always constant at 0.7V, can we still talk about any kind of resistance here?


texts: Using a current mirroring source to power 6 Nixie-Tubes

texts:
I would like to drive 6 Nixie-Tubes from a standard USB-Port (500mA / 2.5W), which is somehow hard to do because \$ 190 \text V \cdot 3 \text{mA} \cdot 6 = 3.5 \text W\$.

If I could reduce the source voltage to 120 V the power consumption would be about 2.2 W, which could probably be doable with a flyback-converter (~90% efficiency). I would then use short 190 V impulses to ignite the Nixies and use 120 V for most of the time.

This schematic shows the idea:

simulate this circuit – Schematic created using CircuitLab

V1 would be the flyback-converter and I1 would be some kind of µC controlled current sink. The Nixies would then be driven with about 5 times I1.

This looks about right in simulation, see figure below, but I'm not sure how well this works with real hardware.

Is this generally a very stupid thing to do?
I would have to use one (non-existent) chip with 7 matched transistors with \$V_{CE} \gt 80 V\$. What kind of transistor could I use instead, so that the currents vary no more than, say, 10%?
Transistor choice is generally not trivial because of the relatively high \$V_{CE}\$ drop vs. small currents. Are there any other parameters to watch out for?
Temperature is obviously a problem (\$ 10 \text{V} \cdot 3 \text{mA} = 30 \text{mW} \$), so I would connect them to the same heat-sink
Is there anything else (i.e. voltage ripple from the flyback) to consider?


texts:
I've been trying to make a butter passing bot, like the one from rick and morty.
https://www.youtube.com/watch?v=X7HmltUWXgs
I can do pretty much everything on there, but I need someone to help with the camera on the front. I need a low cost system that will look for the butter and tell my motors to go to it.


texts: How to design a high pass filter given a stopband and cutoff frequency?

texts:
I have fs = 132 Hz and fc = 770 Hz

I want to design a first order high pass filter that increases gain at a rate of 20dB per decade from 132 Hz until 770 Hz.

Before 132 Hz the filter must stay around -17dB.

How do I select components to design this filter?

I am aware of the equation to select RC values for some cutoff frequency, but am not sure how to account for the stopband frequency.

Edit 1.

Below is a picture of what I have been able to achieve so far.

Next is a picture of what I need the circuit to do.


texts: Is it good to route PCB tracks under a heatsink?

texts:
A heat sink is a piece of metal. If the solder mask on a PCB track is broken, it may be dangerous, right?

Below is a small heatsink for TO220, seen from bottom.


texts: How do I solve this gate with constant voltage at both ends?

texts:
I'm trying to understand the behaviour of the circuit in the work "Polynomial-time solution of prime factorization and NP-hard problems with digital memcomputing machines" for a project.
I'm not strong with circuit analysis so I'm having some problems understanding how to approach the problem.

The M elements are memristors, basically resistors with memory. Before trying to understand the dynamics though, I wanted to get a gist of how the thing works at a specific time t.
Memristors have an internal variable x that varies from 0 to 1. The resistance of the memristors is:

where R_off is equal to R in the circuit scheme and R_on is a value that is lower than that. Other than this they behave exactly like resistors, so V = M I.
L_M are voltage-controlled voltage generators. Their equation is:

Where a_1, a_2, a_0 and d_c are all constant unitary values that comes from a table.
My question is: how do I even approach a circuit like this? If I undestood correctly, if v_1, v_2 and v_0 obey the configuration of an AND gate (such as -1, +1 and -1) there should be no current flowing. But given that both ends of the circuit have a constant voltage applied to them I can't see where should I start applying Kirchhoff's laws etc.
I tried starting from a configuration in which all the x values are 1 so that all memristors are just like normal resistors, but I still think I'm not doing things in the right order.


texts: How can I make a safe Ni-MH charging station?

texts:
I wanted to make a docking station for my robot. My idea was simple - robot drives in, batteries are disconnected, pins that I attach to my Ni-MH charger's electrodes are inserted into battery pack, and start charging. Like on this picture:

But I've read on the internet, that chargers look at batteries temperature, to know when to stop. Is it going to work? Or are there any alternatives to dock my 4 Ni-MH battery pack?

These are 4 batteries, 2400 mAh, connected in series, 1.2V to generate 4.8V.

EDIT: I have also read about super fast charging, something like this: http://www.batteryspace.com/ch-v2880superfastnimhbatterychargerhomecarwithlcdmonitor.aspx. Will this work?


texts:
I am harvesting energy from an NFC device using a tuned antenna on my PCB. Though this method I am able to generate about 3.05V. I would like to charge a super capacitor using the power harvested from the NFC device. To do this I have  used the simple diode circuit provided here (and shown in Figure 1 below).

The problem I am facing is my circuit requires a minimum of 3V to operate within operating conditions, however with the added drop by typical diodes I believe there with be various situations where the generated voltage will drop below the required 3V. Are there any Diodes available which have ultra low voltage drops of less then 0.01V? and is that even possible?

Please note:

my system load will be < 5mA
The 3.05V generated was without a diode in the circuit


texts: Why would a transistor have its base and emitter tied to ground when its collector goes to another base?

texts:
OK, calling me an amateur is being polite.  But I am trying to learn more about how these circuits work.

One example I am learning from is the ZX Spectrum ULA book.  There is a oscillator circuit on page 87 that is really confusing me.  I can post a picture if anyone wants but it's mostly irrelevant for my question.

Anyway, that circuit has a transistor where the base and emitter are tied to ground.  But, the collector is tied to the base of another transistor.

Everywhere I read about transistors, the water analogy is used.  But I then read this reference (https://electronics.stackexchange.com/a/61787/32770) that used a natural gas analogy which really made sense to me.  Basically, the emitter is a pipe that goes deep underground to highly pressurized natural gas.  The base is a valve and the collector is a pipe that just goes into the air.  By turning the valve (base) on, the gas (current) is allowed to flow upwards into the air.  Which is opposite of the conventional current flow.  This was an ah ha! moment for me.

But, looking back at the circuit, it would seem that a transistor's collector tied to the base of another transistor would be useless because the valve (original base) would always be "on".  So why have it?  Why not just tie ground to the base of the SECOND transistor?

I hope my question makes sense.  I can post the actual schematic if people need it.

Thanks

EDIT

Here is the diagram. Hopefully it will explain my question better.

Take a look at Q5 and Q6

EDIT 2

It's embarrassing but it appears that my ancient eyeballs could not see the original connections of the transistors and that the base's are connecting to other items as well.

Thanks to @Ignacio Vazquez-Abrams for pointing that out.  If this is true, would you mind answering it?  I want to give credit where it's deserved.

BTW, thanks for rasterizing that photo!


texts: Error to execute QEMU on Eclipse with STM32F429

texts:
I follow this tutorial: https://gnu-mcu-eclipse.github.io/tutorials/blinky-arm/

And, installed openOCD, QEMU, Packs... all that is need. But when I start the Debug the follow error occurs:

He compiles succesfully, but when the starts this crash happens... And prorgram not execute.

Error:

PRIGROUP unimplemented
assert_param() failed: file "../system/src/stm32f4-hal/stm32f4xx_hal_rcc.c", line 470
abort(), exiting..

Also, I noticed that "Play Button" is not available, but "Pause"
 and "Stop" is.


texts: Micro-controller controlled current source

texts:
I am trying to design a programmable current source that can go up to 5 A. I have a few designs in mind but none of them really seem to be best solution. I would appreciate if any one has any good opinion of a new design or an improvement.

The first design:

For the first design I simply use power amplifier from Burr-Brown - OPA549 [datasheet]. I know the load resistance (R_L), so I simply change the Voltage output of the voltage follower, and since the power amp can handle the current (up to 8A continuous) . The circuit is pretty straight forward.

The problem with this circuit is the power dissipated (wasted) as heat. From the OPA549 datasheet :

It has horrible output voltage swing to supply voltage characteristics. My R_L is about 1 Ohm. So to drive 5 A, I have to produce a 5V output through the voltage follower. Which means, I have to use at least 8V supply ( to compensate for horrible output voltage swing). 8V is not a standard supply, so I use a 9V supply. And the power dissipated becomes: PD = IL (Vs-Vo) = 5 (9-5) = 20 Watts [Page 11 of the datasheet].  I have tried to find other power amplifiers to replace it. But could not find others that could go up to 5A. I have found rail to rail 2A power amplifiers, but I cannot use that.

The second method

Use a BJT with a microcontroller :

I basically control the current through the load (iC) by controlling the base current (iB) of the BJT.

The problem with this approach is the unreliable beta value in the npn transistors. And I don't know how noisy the signal will be.

The third method
I can use a opamp and a BJT like so:

But it too is highly dependent on that Beta value.

The fourth choice

This is probably the best solution, but I am not very sure and need some opinions. It uses a Opamp and mosfet like so:

The full discussion of this circuit can be found here.It seems to only depend on the resistor R3 (R_L in my case), which I know the value of precisely.

Which method should I use? the current through the Load  must be as precise as possible, since I am controlling the current with a PID control. I would appreciate any and all suggestions.


texts: Component recommendation for my PCB (probe)

texts:
I have completed hardware and software (on the Arduino platform) for measuring resistance on custom sensors.
Now it is time to move away from the breadboard and use my own PCB (I plan to make it on top of the Arduino, in the form of a shield.)
The problem is I don't know what components to use as the probe to perform the measurement.
Take a look the the sensor:

As you can see, the probes are soldered on the sensor.
The other end of the probe cable looks something like this:

I need some components that will go out of the board and I can solder to the sensor.
But, since I want to address 8 sensors, this means 16 cables, so the size has to be as small as possible - not like those huge oscilloscope-like connectors in the picture.
Ideally, I want them to be as basic as possible - since I plan to use Fritzing. I want to stay away from Kicad, as I want to prototype it as soon as possible.
Is there any standard and basic solution to use as a probe?


texts: What are the dangers of cutting PCB with Dremel?

texts:
I'm cutting PCB's with a Dremel. Works really fine at high speed and with the finest cutting wheel. Can get really nice and clean results.

There's a lot of project and dust so I place next to my third hand a large PC fan at maximum speed oriented to the opposite of me, wear protection glasses for projection and a 3M dust mask for dusts.

But after the cutting there's still a freaking smell in the room and some dust floating in the air.

Are these dangerous? Should I quit and ventilate the room for 15 minutes before continuing to work? I don't know the composition of PCB and I'm asthmatic so...


texts:
We are looking for a solution to detect small animals (birds and bats) within a 50m radius of the hub of a wind turbine. Ideally this system should be able to differentiate between animals species - for example we are more concerned with bats, and less concerned about birds. We would however be willing to install a system that detected any wildlife and develop the intelligence afterwards.

So far we have been in touch with suppliers of audio equipment to detect animals by their song but practically the frequencies used by these animals is only detectable within a radius of 5-30m.

I would like to hear from any one experienced with infra-red, radar, video or other technologies that may be useful.

Are these technologies suited to proximity monitoring?

How would you deal with the rotation of the blades? (maybe monitor the two hemispheres each side of the rotor?)

Are there any commercial technologies available for proximity detection over long distances?

EDIT :
This has been achieved using video for the exact purpouse that I had intended. However it only works during the day (minimum 50 lux) - dtbird.com


texts:
Could anyone please explain to me the difference between rated power and power output. It says in the instruction book that the power output is 20 mW/ square centimeter but at the back of the machine (fetal doppler) it says: rated power less than 0,7 W). So it operates at 20
mW
Or 0,7 W?

Thank you so
Much for explaining this to me.’yes Inwas referring to the fetal doppler. I am trying to understand the technical
Details of the devices .

Ina different doppler there is a value:
Max. Audio output 500m W rms.

What is this exactly? Can it be a power output?
Or is it the same as rated power?

Do you know how to determine a thermal
Index and mechanical index for a doppler operating at:

Ispta 10.8,
Power output less than 20 mW square cm
( or are other values needed as well)?I can provide them

I am
Wondering if the transducer has to be aligned with a heart to
Detect it? I used a transducer with a beam
Range of
300 square mm. So if The baby measuring 7cm is in the range of that beam even if the beam is not in a straight line to a heart will i be able to hear the heartbeat or
Will i only hear it when transducer is in the straight line to  heart ( aligned with heart). Im trying to find the answers to those questions for two weeks already...


texts: RF splitter resistor placement and 0 ohm resistor RF test port question

texts:
I have 2 questions and any help is appreciated.
The frequency is at 5.5 to 6 GHz range. RF trace impedance is 50 ohms.

I have a resistive splitter to split RF signal into 2 traces with 6 dB attenuation. What is the correct way of placing the Zo/3 ohm resistors on the PCB?  I placed R31, R32, and R33 as below with T like orientation. Would it be any better if I move R31 and R32 to sides and put R33's pad right between them? What is the most correct way of placing these 3 resistors?

I want to add u.fl connectors at some stages of RF signal path next to RF trace for debugging purposes. I learned that 0 ohm resistor or 10-100 pF capacitor can be used. Is there any difference between splitting with 45 degree or 90 degree angle? Right connector's trace is split using 0 ohm jumper resistor with 90 degrees angle to PCB antenna's RF trace. Is that ok or could it be better if the angle between traces have an angle like mitered bend? Because when I solder 0 ohm to select u.fl connector then the RF signal will see a 90 degree corner which is not recommended.


texts: At what resistance can a real inductor act like an ideal inductor?

texts: So it's my understanding that an ideal inductor with a constant voltage applied should have a constant ramp for the current through it (a triangle wave), but an inductor that's not ideal (with resistance) will have an exponential charging curve for it's current (like with an RC circuit's voltage).  But is there a low resistance at which point the current would increase at a constant rate like an ideal inductor?  If the RL time constant is larger or smaller than the time it takes for an ideal current source with constant current I to charge the inductor with energy equal to (1/2)LI^2, will the inductor basically act as an ideal inductor?


texts: Current flow based on voltage difference

texts:
If I have two sources of DC current, one of 28V and the other of 26V - the LOAD will preffer the higher voltage source ?

I'm trying to create a DC-UPS without any kind of "failover" switches, the AC-DC PSU is set for 28V and the SLA-AGM battery at 26V - my load will consume the battery (even a tiny bit) or it will preffer the higher voltage source (AC-DC PSU) ?

The battery current flow is controlled with diodes so in theory they will NOT be charged by the AC-DC PSU and it will only provide current if needed.

Thank you!


texts: Why are stepper motors sometimes rated in AC voltage?

texts:
Now, I think I get why steppers are rated at (for example) 48VDC - as I beleive it's to overcome any back-EMF, and that's why stepper controllers are typically constant(/max) current devices - they'll use the available voltage to get the stepper moving, up to the rated current.

But where it gets confusing for me is when they begin rating it in volts AC... Or sometimes only offering an AC voltage rating... eg.. "9Nm 100VAC". I'm hoping someone can explain exactly what they mean when they specify that AC rating, as there is little point applying an AC voltage to a brushless DC motor.

(Example image below from a Leadshine Stepper datasheet showing performance transitions from expected DC voltages, to an AC voltage)

PS: "They just got it wrong because it's a cheap chinese brand" is an invalid answer, as this DC/AC rating ambiguity is present across a lot of brands - including very expensive German ones.


texts:
I'm working on a project which involves automating the pressing of some buttons on a device. There are five push buttons, which are quite stiff and require fast repetitive presses - around about ~7Hz with 50% duty cycle. I also have one toggle switch that needs to be switched at a rate of ~10Hz.

My first thought was to use servos, but the ones I have seem to be too slow and weak for the push buttons. They don't quite get the speed I need for the toggle switch, either. I don't want to spend a fortune on expensive servos, so I figured there might be an alternate method using cheap motors and a rack-and-pinion setup. The idea would be to have one fast servo for the toggle, and a bunch of cheap motors with a vertical rack to press the buttons.

Are there any alternatives to this approach? Am I missing any obvious methods to automate this?


texts: Electromagnetic Waves (Microwaves)- Does the effect of rain on a wave in point A impact it in point B

texts:
I'm trying to find the answer to this question with no luck. If a wave is traveling across a distance with Points A and B... and there is rain or some other factor of fading/absorption in point A.... will it impact point B where it's not raining? (Assuming distance covered by propagating wave has some rain in A and no rain in B).

Therefore, the Question is essentially asking whether whatever happens in point A of wave1 does or doesn't impact point B of wave1 in free space.

Example: Would I still be able to receive the signal with same strength in point B even though point A in propagation path of wave is fading due to rain or other damping?

Your answers would very much be appreciated.


texts: How to map adc count to voltage when your ADC reference is a battery?

texts:
Normally things would be easier if you have a voltage regulator and you can know that your reference voltage is fixed.

Assuming I have a 10-bit A/D, and counts are in au (arbitrary units), we can map from a count to a voltage (think y = m*x + b).  Take the example of getting a reading of 620au from an ADC register with a reference provided by a 3.3V regulator:

V_sample(counts) = (V_ref - 0)V / (1023 - 0)au * counts au
                 = 3.3V / 1023au * 620au
                 = 2V

Assume a system powered by a single-cell lipo (V_nominal = 3.7V, charges to 4.2V).

Now instead of an external voltage reference, all I have is an internal fixed voltage reference of 2.048V.

How does the math work out to cancel out the negative effect of my battery voltage (and A/D high reference) slowly dropping over time?

This has to be a common thing for low-cost projects, no?


texts:
I'm looking for advice on how I should setup a long range irrigation monitoring system using multiple Arduino boards. I would like advice/options available on what hardware I require to achieve my concept. Particularly the 12km line of site communication between boards.

To give you some context we irrigate a crop every year and the paddock that we irrigate is roughly 12km from the homestead. The drive alone is a 24km round trip which is usually just to check and balance water levels.

On average a workman would do this trip between 3 to 8 times in a day and 3 - 6 times at night
1 watering takes 3 full days around the clock and we water between 12 to 16 times in a season

You don't have to do the math to figure out the fuel cost alone is massive. My goal for the project is to reduce the man hours required to monitor water levels and reduce fuel costs.

My proposed solution to this is setting up 3 x Arduino boards in each of the 3 fields monitoring their respective water levels and the 4th Arduino board at the homestead displaying each water level on a LCD screen. In short:

Arduino 1: Monitors water level and sends this data to Arduino 3 (2km
line of site)
Arduino 2: Monitors water level and sends this data to Arduino 3 (2km
line of site)
Arduino 3: Monitors water level, receives water level from arduino 1
& 2 and sends the 3 water levels to arduino 4 (12km line of
site)
Arduino 4: Recieves 3 x water levels from Arduino 3 and displays this
on LCD

Additionally, each Arduino board will have colored diodes that indicate water level at night so workers in the field can easily see without physically checking that all the water levels are ok when changing fields and starting/stoping siphons or if they need to make adjustments. It's important to note that I know how to achieve this just thought it was important to mention to provide more context.


texts: How can I properly tell if a wall wart is OK to use for old hardware?

texts:
I bought a Sega Genesis model 1 from a local thrift store recently for $10.  It was sold as "broken, for parts only".  It didn't come with any cables.

I've repaired several vintage gaming systems in the past so I took a chance on seeing if I could repair it.

When I got home I realized that I didn't have a proper power supply for it.  I have several Genesis model 1's and 2's but the only power supplies I had for them were for the model 2's.  Which takes a smaller barrel plug.

Anyway, first thing I do is Google the power requirements for a model 1 (couldn't find it listed on the actual unit) and after some investigation, it appears the model 1 needs 1.2A/9V DC.  I'm going from memory but that should be pretty close.

So I dig in my parts bin and I cannot find anything that fits and has those specs (several 1A but no 1.2A).

Next I get on eBay and find a vendor that claims to have sold thousands of power supplies for Sega and claims he has exactly the one I need.  His ratings were good but when I asked him the specs, he said it was 350mA and 10V.  Well, I figured the 10V would probably be OK but the 350mA seemed too weak.  He assured me it would work (and it was cheap) so I bought it.

It arrives and when I plug it in, it worked like a champ.  Total investment $19.95 for a working Sega Genesis.

My question is, how is this possible?  Are the 1.2A specs online just simply too conservative?  I have tons of 500mW supplies so they would probably work too.  How can I "properly" tell what kind of power a unit like that REALLY needs?

EDIT

Sorry, I meant 350mA NOT 350mW.


texts: Step up converter - voltage drop on load

texts:
I decided to build step up regulator to power DHT22 (temperature sensor) from two AA bateries. The DHT22 needs 3V (or 3.3V acording to some datasheets) for operation.

I picked up MCP1625 (from Microchip datasheet here) step up regulator because it can accept low voltage and keeps high efficiency.

I used reference design

According to datasheet I used 10uF for input filtering.
I used little smaller resistor on feedback voltage divider resulting in 3.25 V output. Which should be fine.
I used two alkaline batteries with voltage 2.8 V
For second test I used Nimhd Eneoloop batteries 2.5 V.

Now, my problem is this:

Without load, I get on output 3.25 V
With only small load 3mA I see drop to 2.98V. At this point the
current on input is 4.62mA, voltage is 2.8V (no drop here)
I did test with resistor as load to test whether batteries are able
to provide more current then its taken by converter. They are capable
to deliver more than 10mA.

My question is why my regulator is not taking more current from batteries?

Could it be caused by bad PCB design? (For example to thin lines for Vn, Vout)
Could it be caused by sloppy soldering? (My first SMD soldering project)
Something else?

Any advise would be appreciated.

Than you.

Unfortunately, I cant post my PCB because of restriction for new users and two links in post :-(.

List of components

L Ferrocore DLG-0403-4R7 (4.7uH, 1.15A, 110mOhm)
Cin, Cout Samsung MLCC, 10uF, 6.3V, X7R (CL21B106KQQNNNE)
Rs 1.6MOhm 5%, 1MOhm 1%

EDIT 2016-05-25 I fixed link to datasheet, editet inductor specs, PCB and photo in comments.


texts:
I am trying to find \$R\$ in \$R_5\$ via mesh analysis. I see that loops 1 and 2 are a super mesh, so then applying KVL to them I end up with:

$$
4\cdot(i_1-i_2) + R\cdot(i_2-i_3) + 2\cdot i_1 + 5\cdot i_2 = 0
$$

It is clear that the current in mesh 3 is -1. In the super mesh \$i_1\$ and \$i_2\$, the current is \$i_1 - i_2 = 6\$.

after plugging in my values I am left with the following:

$$
36 + 7\cdot i_2 + R\cdot i_2 + R = 0
$$

How am I supposed to solve for \$R\$ from here? What am I doing wrong?


texts: connecting different capacity batteries in paralell

texts:
I have 12 li-ion batteries but in different capacities. Half of them is 2000 mAh and half of them is 6000 mAh.

What happen if I parallel them?


texts:
When an air-conditioner is switched on, light bulbs in the house flicker a little.  I was told that this is due to the inrush current of the ac. I am assuming that voltage drop is causing the flickering.
Why does this voltage-drop occur? Does it have to do with the long transmission lines?
Does this voltage drop happen even when a normal electrical appliance (like another bulb) is switched on?


texts: What flip-flop should I use to design a logic circuit with minimum number of logic gates?

texts:
How can I know with which flip-flop I can design a complex logic circuit with minimum number of logic gates?

In our homework and exams, we are supposed to use minimum number of logic gates. In one problem, we are asked for designing a register with simple binary counter, serial load, 2 bit rotation, and parallel load options(synchronization is not mentioned in problem). We are free to use whatever flip-flop we want to use. Which flip-flop would you use in this case? And why? Is there a way to know with which flip-flop we could design the logic circuit with minimum number of logic gates?

Thanks in advance.

Edit: In this assignment, we're allowed to use D, T, SR, JK flip-flops. The problem is, when we use different flip-flops, our combinational part of the circuit is different, is there a way to know with which flip-flop this part would be smaller(contains less number of logic gates).

The register we are asked to design is holding 4 bits. We have 2 bit input which specifies the operation will be running on register(counting, rotating, parallel loading, serial loading).

And by "rotation", I mean Circular Shift

Also, nothing mentioned about "synchronization", so I think it's up to us.


texts: Why is this clock signal connected to a capacitor to gnd?

texts:
I am trying to understand the following circuit:

My problem is to understand why the CLK signal is connected to the capacitor (C7). The bottom side of C7 is connected with a resistor to GND. This means that the "plate" will (after some delay) have the same potential as GND. The upper "plate" will oscillate with the CLK signal.
The logic is connected to the bottom side, so I don't understand how the NAND Gate can ever get some other input than LOW on the bottom pin. This means that the NAND gate will never output LOW and thus the RAM never stores anything, which doesn't make sense.

The only effect the capacitor could have in my understanding is to delay and flatten changes in the clock signal, but I don't understand the use of this.

Also I don't understand the meaning of the resistor. It pushes the loading time of the capacitor, but after the bottom side is on GND potential there will be no current after that.

I hope someone can help me understand this.


texts:
I am using the PIC24F to make a simple stop watch and it was all going well.
I am using TIMER1 and various interupts.

The problem I am having is that I cannot seem to get TIMER1 to have a period of 1ms. at the moment I am putting 6250-1 into PR1 and it isn't accurate enough.

Does anyone know the formula or method I should use to work out what to put into PRI? I think the chip is currently running at 8MHz

Any help would be fantastic!


texts: How would you filter the DC input suitable for use to bias/power an LNA?

texts:
We are building a transmit/receive module for the 144MHz and 440MHz bands.  As I understand, a good LNA can provide poor performance if the environment or the bias voltage is too noisy.

What are the best practices for things like filtering and preventing outside noise to get good success with an LNA implementation?
Other considerations?

This is the LNA we are looking at using: Qorvo QPL9547


texts: How does inductor resist the increasing dc current?

texts: I understand the point that inductor will have high resistance for ac current.this is because the magnetic field produced during positive half cycle will oppose the negative half cycle since the energy during positive half cycle will be stored in magnetic field. But how would this happen there is an increase in dc current.please explain how would inductor react.


texts: What is this type of AC power connector called?

texts:
What is the name of this style connection?

It seems to be more popular with electrical powered equipment for the Asian market.


texts: Transmittance of a capacitively coupled shunt resonator

texts:
I have been trying to understand the expression of |s21| for the resonator mentioned in this article. For a circuit similar to the drawn below, in which R1 is used as the temperature sensitive element, the transmittance at resonance is given by $$ |S21| = 2\kappa\frac{G_0}{G_1+G_0} $$ where
$$\kappa = \frac{C_2C_3}{C_2^2 + C_3^2}$$
$$G_0 = 4\pi^2({C_2^2 + C_3^2})Z_0f_0^2$$ I couldn't obtain these expressions on my own. Can somebody explain me the logic behind this derivation ?

simulate this circuit – Schematic created using CircuitLab


texts: Should CAN bus in a vehicle be isolated?

texts:
I'm wondering whether to use an isolated CAN transceiver or not. A few of the nodes in the vehicle use a TI ISO1050 which has an isolated power supply and run GND and 5 V with CAN-Low and CAN-High signals so they have a common ground. I wanted to use a TI SN65HVD232 because of the reduced package size and no need for an isolated power supply.

I'm unsure if I should use an isolated transceiver like the ISO1050 or not.  Will I run into problems if I don't use an isolated transceiver?

This system is non-critical. It's just for data logging.


texts:
In the datasheet it is said that the collector current shall not surpass 20mA.
Then there is

VCC = 5 V, RL = 100 Ω, IL = 5 mA

which should be with a voltage drop from collector to emitter of 0.1V -> 4.9V/100Ohm = 0.049mA. Too much.
I believe I don't understand some fundamentals here, so it would be great if someone could help me out.


texts: 4 6v batteries, with one connected wrong way round?

texts:
Today i was working on a machine with 4 6v batteries connected in series.
It was in a building that was very dark and the batteries were covered in dirt and i briefly accidently fitted one of the batteries the wrong way around.
After i corrected the mistake i couldnt get 24v across the four batteries, only 18v, from wherever that battery was out of the voltmeter circuit.
Yet the same battery measured 6v on the meter, and load tested ok.
Could the polarity have been reversed on that battery after connecting it the wrong way around?
If so, does charging the 4 batteries in series correct this reverse polarity.
Thanks


texts: Microcontroller Interface with Modbus Serial

texts:
I'm a beginner and I'm trying to acquire data from a microcontroller with Modbus serial protocol in order to create an interface with LabVIEW. I'm using a Prolific Technology USB-RS232 converter and Windows 7 as OS.
I can't read data from the micro. I know that read only varibles are in registers from 100hex and 1FFhex and read/write variables are from 200hex and 2FFhex.
How does the memory of micro need to be used? How do I define holding registers and input registers?

Thanks in advance for any advice.

Andrea.


texts: How to calculate output power of a multi-MPPT inverter?

texts:
I would like to know how to calculate the output power of a multi-MPPT solar inverter. As an example, I have chosen the Fronius Primo 8.2-1 inverter.

This inverter has 2 MPP trackers. For what I understand, this means you can have one string of PV modules connected to each of the trackers and have both strings operate at different optimal current+voltage points.

Now, the datasheet shows some operating efficiency curves:

If I have these operating points in each of the MPPTs (completely made up):

710 V and 8 A
270 V and 6 A

Let us assume the temperature does not affect the inverter's efficiency.

How do I calculate the output power?

Do I need to calculate the DC power of the MPPT input (i.e.: 710 * 8 = 5680 VA) and then multiply it by the efficiency given the MPPT voltage? If so, which output power should I use to get the efficiency point from the curve?
Internally, how does the multi-MPPT inverter work and how does it differentiate from 2 separated inverters?


texts: Controlling 120v line with a 12v switch on a different line

texts:
I have 10a 120v power sockets in my garage that currently doesn't have any switch on it and powers some overhead lights that I have plugged in. Separate to that, I have a 12v circuit powering various bits and pieces that is controlled via a 12v remote. I want it set up so that when I turn the remote on, it allows the power to the 120v sockets to pass and, when the remote is off, the power is cut. Effectively, the one 12v remote will be controlling both my 12v lights and my 120v lights.
Its my understanding that this should be quite easy and all that I need is a Relay. My trouble is knowing exactly which one should I use. I looked at a couple of Solid State Relays and they mentioned that they didn't handle sustained use well (headed up too much), even when underutilized. Hence I'm wondering what I should be looking at?


texts: Suppose that you have a typical laptop computer that is turned on, muted, doing pretty much nothing (e.g. no fan, CD drive, or speaker use), has pretty much nothing being done to it (e.g. no presses of the keyboard), and only has RAM and SSDs as its sources of memory. To my surprise, such a computer still makes noises. Why is this? In my time of only using computers with hard drives, I had thought that they were the main sources of noise, but I was recently shocked to discover that my SSD-only laptop isn't silent.


texts: How do European to American outlet change frequency?

texts: So for the transforming of voltage, a transformer could get a european outlet from 240 to 120 volts. How do these switch the frequency though, do they have to convert it into DC and then generate a signal back to AC? Or is there an easier way? Or do they just leave it at 50 hertz assuming everything is going to work properly?


texts:
I'm designing a board that can be powered either by USB or an ATX power supply.  They can both be plugged in at the same time, independently.  I'd like the ATX to provide 5V if its plugged in, but fall back to the USB if possible.  The chips in the circuit will all be running at 5V.

Any ideas?


texts:
An audio tone \$Acos(\omega t + \theta)\$ undergoes uniform quantization by a quantizer that has the average quantization noise power \$q^2/6\$ joules, where \$q\$ is the quantization step size. If the dynamic range of the quantizier is adjusted to 15dB and the signal-to-quantization-noise ratio (SQNR) is targeted to be at least 40dB, how many bits per sample are needed to code each sample?

This is an past-exam exercise from my university. I tried to solve it, but I only got a solution as a function of \$A\$. Anyone can give me a hint? I don't know what I'm missing. Thanks!


texts: Programming a ATmega328P on a breadboard - programmer cannot connect

texts:
What I am trying to do is program the ATmega328P on a breadboard. I have followed the schematic by which the Duemilanove board was wired to no avail.

I have a SparkFun AVR Pocket Programmer that works fine. I am able to successfully program, using ISP, the ATmega328P on the Arduino Duemilanove board. Further, I am able to remove the stock controller, replace it with a new controller (same model and same chip I am attempting to program on the breadboard), and program successfully as well.

I directly connect the following:

MISO to pin 18
SCK to pin 19
RESET to pin 1

RESET also has a pull-up resistor

VCC to pin 7
MOSI to pin 17
GROUND to pin 8

I have tried tying AREF to VCC and both GROUNDs together - still nothing. I also tried programming the board by powering it externally (i.e. removing VCC from the ISP connector). The pins I have described above are the only connections. Is there something I am missing here?

There error I get is:

Where I have read this result indicates that the programmer cannot connect to the target board.

I tried looking over the schematic further to see if there were any extra connections that I was missing(i.e. some other grounded or 5V supplied pin I would otherwise be bypassing by tying VCC directly to pin 7); I could not find anything. Any suggestions?

Here is the verbose output ( -v flag  using avrdude  ). I am not sure what to make of this information.


texts: DC batteries connected to multiple-core transformer

texts:
My understanding of transformers is that they take in and give out AC signals.

However, the UPS system below has its DC batteries connected to a transformer. Is

it possible to know the rational behind this design?

(source: wasp.kz)


texts:
I found this circuit, built a kit and it works perfectly. Here are my question:

Why C2 can control the duration of the switch?
Is D1, a red led, used as a voltage regulator here? and so it's a very important part?
Will C1, a 25V cap, explode if I don't install D1?
Is this circuit only work as a light switch? that it is a DC switch, not AC?


texts:
While designing DDR4 SODDIM schematic for a mini-pc motherboard, I understood that I need to set an address to Serial Presence Detect (SPD) EEPROM so the CPU can identify the memory.
While looking at a previous design at a project in my company, I noticed that 3 pull down resistors are equal to the address A0. and someone wrote (0x50).
(NOP means Not Populated Resistor)
I'm trying to understand how to find these addresses and the conversion between (0x50) to A0 and vice versa.

looking at this article, I found this table:

I'm not sure if this is relevant. personally I didn't get from it any information that I can link to the previous image. but I thought it could help the answer.
regarding the last answers, I still don't understand how these addresses correspond with the outside resistors. actually I want to validate that the addresses are right. here is another example which makes the confusion, this image for the second SODDIMM slot in the design:


texts: Turn on power when voltage higher than set value

texts:
We are trying do design a circuit which works by harvesting energy from a split core current transformer. Most of the electronic works correctly, we use a 1.5F 5.5V SuperCap to provide enough power for an STM32F411 micro-controller and an LoRa transceiver. Most of the time the micro-controller is in deep-sleep, allowing the cupercap to charge enough for sending phases.

What we want now is to turn on power to the micro-controller only when voltage at the supercap is over the desired voltage (say 3.6V). The hard part is the we don't have stable "high" voltage at the beginning, when the supercap is empty, to provide power to active circuits.

My idea is to use a Zener diode to control a Mosfet like this. Do you think it would work? If I use a high resistance value before the Zener, will it be enough to avoid drawing too much current.


texts: Why does autorouter revert to 98% after reaching 100%?

texts:
I managed to route an entire complex board with eagle, or so I thought. At first it worked. Then I began adding large fills (ground planes and VCC planes) in order to minimize impedance.

I now added extra circuitry to my board and manually routed those parts in place.

I now run the autorouter one more time and watched the progress. In all optimize stages, it showed 100% which made me think everything went perfectly. Then after it was done, it reverted back to 98% (1 unrouted wire left).

I turned off the copper layer on the board as well as the grid and I couldn't see where this unrouted wire is and I even zoomed in.

Is this a bug that exists in eagle when I define multiple planes close to each other? or is there some other trick I can use so eagle can stay at 100% instead of reverting to 98%?


texts: Gate drive for IRF540N using Arduino Uno

texts:
I am trying to build a prototype for the WPT system seen in the figure below. The MOSFET I am using is an IRF540N (source connected to ground) at a switching frequency of 1MHz and is being modelled by an ideal switch.

My question is, can I use an Arduino UNO as the gate signal to switch the MOSFET with a 1MHz, 50% duty cycle square wave? My knowledge of timers/interrupts is essentially non-existent so full code/explanation is extremely helpful.

I am currently using a signal generator to generate the square wave. The current supplied by the signal generator is not enough to charge the internal capacitance's of the MOSFET so I am passing the signal through a TC4427M chip.

Please help me. Any input is appreciated.


texts:
I was playing around with a 16V output AC adaptor and I unfortunately shorted the output VCC and GND by mistake. A spark occured at the end of the wires.
Since then, the output voltage is around 0.3 V. I was wondering if there is a common component failure that would explain this regulator failure (which part of a regulator is most likely to fail when the outputs are shorted?). I opened up the device, but there are no signs of component damage anywhere.
Thank you!
Edit:
I should have mentioned it is a wall AC-DC adapter and regulator (for a camera I believe, looks like any laptop regulator though) so inputs 120V AC and outputs 16V DC
Hopefully photos can help determine the functionality of the circuit. I really haven't a lot of experience with AC PSUs yet... Hopefully I can learn a bit from this.
So the spark was seen at the end of the wire, but it seems it as destroyed an onboard component... I find this strange.


texts: How can I regulate the output voltage in this inverter circuit

texts:
Beginner here ! I just modeled this circuit in proteus 8 I saw it from a youtube video. (https://www.youtube.com/watch?v=5QaKiXRa-n0&feature=youtu.be)
I want to make this inverter but I can't understand it well enough
. what are your opinions about the circuit and what do I do to regulate the output voltage ? I want to fix at 220V
help please ! thanks


texts: Advice on choosing components for a flyback arrangement, for switching inductive loads fast

texts:
I have a bank of x6 MOSFETs (SUG90090E) connected in parallel, which I am using to switch a current of maximum 30A through a coil (resistance 1R and inductance 1mH), and am looking for some general advice with regards to the "flyback" section of the circuit. The current will not be switched at high frequency - only once per second or so. My schematic at present looks as below (each MOSFET has its own dedicated driver chip):

My goal is to have the current reduce to zero in several tens of microseconds. Based on pieces of designs I have seen elsewhere, I have tried to create an arrangement of components which I believe may do the job. The idea is that when the MOSFETs are switched off, the large induced voltage that appears at the bottom of the load is allowed to rise until it reaches the clamping voltage of the TVS diode D1. When this happens, the TVS allows a small amount of current to flow to the base of Q7, switching it on, and allowing the large circulating current to dissipate away. As far as I understand, the fact that a large voltage is allowed to build up means that the rate of decrese of current can be greater, due to V = -L*dI/dt, when compared to the case of using a simple single "flyback diode" (which would allow it to build up only to a diode drop or so).

I have tried to choose the components suitably - for example, the clamping voltage of the TVS diode 1.5KE100A is maximum 178V:
 and so this should be enough to protect the SUG90090E MOSFETs, which have a VDS(max) of 200V. I have also chosen the transistor Q7 BUF420AW and diode D2 IDW100E60 such that their forward currents are at least greater than the steady state current through the load when switched on (their max rated values are 30A and 150A, respectively). I have added a small capacitor C1, but am sure if it will make any difference in practice?

My question is whether this is generally a reasonable approach to switching off the current fast in this type of situation, and am looking for reassurance that it's wise to continue down this route? Are the components chosen suitably enough, or is there something that I have not accounted for? Any advice or tips would be helpful.

With thanks.

EDIT

At the suggestion of @Bimpelrekkie , I have tried to make a simplifed LTSpice model of this situation. The simulation also compares the case when the transistor Q7 is removed, leaving only a TVS diode across the coil (as suggested by @Andyaka).

The simulated schematic is the following:

The the resulting currents and voltage spikes just after switch-off:

There is little difference between the two cases - the current is reduced from 35A down to zero in ~250us, and the back EMF spikes are capped below safely below the 200V rating of the SUG90090E MOSFET. The difference is that in the case with the BJT, it is this transistor which absorbs the power of P = I*V = (170V - 35V)*35A ~ 4.7kW (peak value, when current is maximum). With only a single TVS, then it is the TVS which takes the 4.4kW peak.

I feel now that @Andyaka suggestion is reasonable, and as long as I choose a TVS which is able to handle this power then it could be the only snubber element necessary.


texts: Generating C code from a Matlab-Simulink model for DSP C6748

texts:
I'm trying to generate C code from a Matlab-Simulink simple model (eg.: sine wave generator with a DAC at the output). This code must be executed with Code Composer Studio
for TMS320C6748 DSP (Texas Instrument C6748). Specifically, for the development board OMAP-L138 ZOOM ™EVM DEVELOPMENT KIT.

For this, I am using the following versions:
Simulink (Version 7.7 - R2011a)
Embedded Coder (Version 6.0 - R2011a)
Code Composer Studio v3.3

I tried several options (with generic modules in Simulink and programming the C6748 timers, configuring a module "Target Preferences" with "OMAP_L138/C6748 EVM"...) but it isn't working.

Is it possible to implement this idea? Is there an example working?

Thanks


texts:
I recently made a slayer exciter which produces arcs about 1-2 inches long. It also makes any electronic device near it go mad (it froze my iphone 6S when I was recording the arcs). What radiation is being produced? Electric field, electromagnetic waves etc. If it can create high voltage on any metal object that comes near, surely it will do the same to human nerves?

Should I be concerned about using it?


texts: Why do LED/OLED HD and UHD displays have "global refresh rates"?

texts:
What is the benefit to scanning vs. individually addressing and updating lines or pixels or screen areas?

Is there a standard interface to the majority of HD or UHD displays that allows the possibility to implement a compressed protocol that only updates changed pixels or areas - and update some more than others? Is there a possibility of saving energy this way?

Is the "brute force" way really the best, or is it an artifact from CRT days?


texts: Leaving the heater of a vacuum tube on all the time vs cycling it

texts:
I want to build a tube amplifier that will be on for ~7 hours/day. I was wondering whether the life expectancy of the tube would be higher if I left the heater on all the time and just turned the plate supply on and off.

The tube will most likely be a 6N1P or a similar general purpose small tube.

What is your opinion/experience with this?


texts: how can i added macro step in tia protal

texts:
I'm using Tia portal V13 and i need to add a macro step in my graph-7 .
how can i can integrate the macro step in my principal  Graph-7 ?


texts: How can I feed my microstrip patch antenna with phase difference? I managed to get more directed beam but now I want to scan an area by changing directivity.


texts:
I'm 15 and I recently started electronics and just had a question about batteries.
(I'm going to use a 9v battery as an example)
From what I understand and from what I've read, a 9v battery creates a voltage (potential difference) by doing 9 joules of work (9 joules of chemical energy into 9 joules of electrical potential energy) to pull electrons away from their atoms and their normal state to a point of high potential energy, therefore creating a potential difference, or voltage.
Could someone tell me if this is correct please?
Thanks


texts: Secondary voltage, lagging load power factor (transformers)

texts: Theoretically in transformers, will the secondary voltage increase or decrease (with increasing load current and a lagging load power factor) and why?


texts: Servomotor takes too much power so the µController (ATMEGA328P-PU) resets all the time

texts:
I have got the following circuit diagram.

For a little explanation. When the button is pressed the µC is powered for about 10 sec. The µC contains code that moves the servo. When the servo is connected it takes so much power that the µC resets all the time. How can I change the circuit that this does not happen?

It is powered by a 9 volt block.

Now I changed the power supply for the servo with an other 7805 like this circuit diagram:

Now the µC resets a bit later.


texts: Why route signals orthogonally in adjacent layers?

texts:
I am investigating PCB stack-up. Everywhere I have seen it says to route signals on adjacent layers orthogonally to reduce the coupling. I have two questions:

How does orthogonal routing reduces the coupling?

Is the coupling mechanism inductive or capacitive?


texts:
I'm building a capacitive vibration sensor and it has to reject the stray capacitance by locking the LC oscillator at 64 MHz, where I can demodulate relatively small frequency changes. The best way to do it seems to be a PLL and I chose to lock it to an 8 MHz crystal reference (see diagram below).

However, I stumbled upon a variety of PFDs and I don't understand which one I should use; which one is better for my application. I've found these 3 topologies but I don't understand the difference between them, which one will give me better noise, spurious performance etc:

I also found this detector (source), it has higher gain, so I should get lower noise with it but they use it in conjunction with a frequency detector, so I'm not sure about it. However, if they are using the detector only for decreasing lock time, it's fine since the lock time is not a problem in my case.


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Here is an example from a data-sheet of an opamp:

  (At TA = +25°C, RL = 10 k connected to mid-supply, VCM = VOUT =
  mid-supply, unless otherwise noted. Boldface limits apply over the
  specified temperature range, TA = –40°C to 85°C, guaranteed by
  characterization and/or design.)

Does mid-supply mean ground for dual-supplies?
And what does it mean for a single supply opamp?


texts: Raspberry Pi with usb audio interface direct connection with an external device mic in / speaker out

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I want to connect raspberry Pi using usb audio adaptor directly to a device mic-in / speaker out.
RPi spk out -> device mic-in, then
device spk out -> RPi mic-in
I have seen simple circuit and suggestion to match level between mic-in and speaker out. (Connect speaker output to microphone input).
My question, since the RPi has software to control both channel (speaker out and mic-in) level, is the suggested circuit for line matching necessary? If I want to attenuate signal level going to the external device mic input, I will lower the volume on my RPi spk. And, lower Rpi mic-in level to attenuate external device spk out signal?


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I want to use SPI module in loop-back mode. so I wire MOSI to MISO.

but how about the clock??. is it wired somewhere?? and how the clock works  loop-back mode


texts: How closely should I space my thermal vias?

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How closely do you pack your thermal vias?  I know that more vias divides the amount of heat each via can move and that smaller vias allows more vias to be packed together.  Knowing this, it seems like more vias are better for thermal dissipation.

There are diminishing returns for the amount of vias that are placed, but assuming that you can place as many as you want without accruing extra manufacturing costs, how many vias can you place before compromising the structural integrity of your board?  (assuming using the standard fr4 board substrate at a standard 1.6mm thickness)

Should they be placed in a pattern?  What do you do personally?  Does everyone just choose a target amount of watts to dissipate through the board from the junction and make the minimum amount of holes?


texts: In CMOS, can I assume the delay of a multiplexer is negligible compared to the delay of an inverter?

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Let say I have a ring oscillator, and I modify the ring so that the output of an inverter is connected to an input of a 2-to-1 MUX, and the output of the MUX is connected to the input of the next inverter (see picture: http://imgur.com/i0Fafls ). Assuming I have an odd number of inverters, this structure allows me to skip some even number of inverters and still have an oscillating output. For example, let say I have 9 inverters and I decide to skip the first 4 inverters. The remaining 5 inverters forms a regular ring oscillator. My question is: Would the frequency of the output produced by this 5-inverter ring oscillator be significantly differently from the case where the same 5 inverters are connected directly without any MUX between adjacent inverters?

In other words, in CMOS, can I assume the delay of a multiplexer is negligible compared to the delay of an inverter?


texts: Can replacing a capacitor with a different brand cause audio channel imbalance?

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I recently broke a "Nichicon 100µF 10v Fine Gold High-Grade Audio Capacitor" off my motherboard's audio circuity and replaced it with a generic 100µF 50v capacitor I found at a local electronics store that best matched its dimensions. The new capacitor is rated for 115C vs 85C for the old one so I assume the quality is the same if not better.
However, upon testing my front audio connection I am noticing an extreme imbalance in my left and right audio channels. The left channel is nearly imperceptible and the difference is too large to overcome through balancing controls in my audio drivers.
Could this have been caused by not replacing my capacitor with an identical type? From some searching I was given the impression that as long as I kept the capacitance constant I could increase the voltage rating when replacing a capacitor.


texts: Reduce a potentiometer value from 1M to 500K

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I have an AC speed controller board and I would like to replace the 500K potentiometer on it with a potentiometer/switch combo to suit my application. However, the potentiometer I have is valued at 1M. It's a common type of speed controller from amazon.

Is there an easy way to reduce the overall resistance of the pot by half to make it 500K? A resistor in parallel to make some kind of a voltage divider?


texts: How to amplify small voltage from hall effect sensor

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I have an analog hall effect sensor, and the difference I am trying to sense in mT is quite low. The voltage output goes from 1.0V (no magnet) to 1.1V (magnet) on the hall effect sensor. This was the most sensitive hall effect I could find.

I want to amplify this signal such that 1.0V = 0V and 1.1V is 5V. Is there a common Op-Amp configuration that works well for something like this?
I know using a non-inverting amplifier I can change the gain to 50, but this just gives me 1.1x50 = 55V. It seems to me I need to subtract 1v from the output first, then amplify this. Am I on the right track?

EDIT:
Thanks for the suggestions below. I have tried to build the circuit using an LM324 op-amp, and a voltage divider to create the 1v offset. Long story short I am not skilled enough to figure out why it is not working. I am able to sense a strong magnet quite reliably, but not the very small magnetic field I had hoped to sense.
Some of the comments below mentioned that there may be a chip that is already suited to this application. I have looked on digikey but am overwhelmed by the qty of options and specs. Can anyone provide a suggestion?
Thanks so much!