texts: In npn transistor, why doesn't some base current flow in conduction band?

texts:
Free electrons in emitter are in conduction band.
Free holes in base are in valence band.
Since base is thin, most electrons pass the base while staying in the conduction band and enter the collector.

Since the life time of free electron in base region is quite large due to thin doping, is it possible for some free electrons in base region to reach the base terminal staying in the conduction band? That is can some base current happen entirely in conduction band avoiding the recombination?

In other words: Why must every electron that enters the base terminal be from the valence band? Why can't the base terminal attract few conduction band electrons like the collector?

EDIT: Intuitively it feels like the electrons that entered the base from emitter have 3 options:

Go directly into the collector
Recombine - fall into valence band and go out the base lead to the base supply
Go directly out the base lead to the base supply


texts: AoE3: Grounded Emitter Amplifier Distortion

texts:
I'm trying to understand a passage in the 3rd edition of Art of Electronics which explains the distortion of grounded emitter, common collector amplifiers vs. those using an emitter resistor (ch. 2, pg. 95, left column).

It defines distortion as the change in gain between the quiescent point and the peak output voltage, expressed as a fraction of the quiescent gain, which for a grounded emitter amplifier is:

\begin{equation}
distortion=\frac{\Delta G}{G}=\frac{\Delta V_{out}}{V_{drop}}
\end{equation}

where \$V_{drop}\$ is the quiescent voltage drop across the collector resistor. The gain \$G\$ at a given voltage is \$-\frac{R_C}{r_e}\$ when the emitter is grounded, and \$-\frac{R_C}{r_e+R_E}\$ with an emitter resistor.

This all makes sense to me, and I can calculate the distortion for the grounded emitter amplifier. But the book then goes on to say that when an emitter resistor is added, the distortion is multiplied by a factor \$\frac{r_e}{r_e+R_E}\$.

The exact text (referring to \$r_e/(r_e+R_E)\$), is:

  Only the first term in the denominator contributes to distortion, so
  the distortion is reduced by the ratio of \$r_e\$ to the total
  effective emitter resistance...

I have been trying to show mathematically how the distortion of the two amplifiers is related by this factor but have now been going round in circles for hours. Can anyone explain?

Also, since the intrinsic emitter resistance \$r_e\$ is a function of output voltage, what exactly would the \$r_e\$ in that factor refer to - the \$r_e\$ at the quiescent point, or at peak output?

Thanks for any help.


texts:
I'm trying to understand the principles of reverse recovery and read several documents about it, but there are still a few questions I cannot find an answer to or just don't understand.
As reference to my questions I will use the application note AN5028 and the following picture has been derived from this document.

\$( I_F/dt)_{OFF}\$ is said to be "imposed by the circuit". What determines this \$I_F/dt\$?
Is it the speed of the switch that turns off the forward current \$I_0\$, which cannot be instant? Or is it determined by an inductor/transformer which is found in several SMPS topologies? (I doubt the latter because reverse recovery is discussed in general, not as phenomenon specific to circuits with indcutors/transformers.)
Although the meaning of words fall out of the scope of this site, you understand the context of the sentence and therefore I kindly ask to help me understand, page 4 on AN5028:
The recovery charges \$Q_{rr}\$, the recovery current \$I_{RM}\$ and the recovery time \$t_{rr}\$, are intrinsic parameters of the diode during its turn-off phase. They depend on:

\$I_F\$: Forward current flowing through the diode before it turns off
\$dI_F/dt\$ : Slope applied to the diode and imposed by the circuit
\$T_j\$: Operating junction temperature of the diode
\$V_R\$: Reverse voltage applied across the diode

My understanding is that an intrinsic property is an property of something in itself, so independent. Can someone please clarify?
I recall I read somewhere the circuit can limit the reverse current, such it cannot 'reach' \$I_{RM}\$. (I think this is rather the circuit failing to provide the reverse recovery current than some active protection.) If I did recall this correctly, could you please give an example of it?

EDIT:
It was in the document Rectifier Reverse Switching Performance by Microsemi

  In lower current applications, the reverse current overshoot for charge recovery is often limited by the circuit or test method used rather than the diode itself. When test limited in this manner, it is then simply identified as reverse current \$I_{RM}\$ as shown in Figure 2. This is an important distinction from \$I_{RM(REC)}\$ since \$I_{RM}\$ is not a diode dependent feature.


texts: Measuring current drawn on a 12V barrel plug

texts:
I would like to replace my monitor power supply it's 12V 3A and I doubt it's actually necessary -- old LCDs were pulling that current and this is not CCFL but LED. So I would like to measure the current drawn. The supply and the monitor is using a simple 5.5mm / 2.5mm plug, central positive. I would like to not damage anything in the process :)

OK, so presuming I have an extension cord (I do) I am ready to throw away, I guess I need to cut the cable -- does it matter which conductor? Just cut one of the conductors and touch the tips to the cut sections and done? Wrap perhaps the conductor around the tip for better contact.

Edit: so it seems my motivation matters and it got lost in the comments. A 3A adapter means it's an adapter with a separate AC cable. That's not particularly helpful for travel, especially not when even my Lenovo laptop 65W charger is now available in a small wall wart format (FSP Twinkle btw). 12V 1-2A very small wall warts are readily available. I have yet to something in a similar small format for 12 3A. I am not sure why but such a thing is unavailable AFAIK. I don't want to haul around AC cables. And yes, hacking a very small 12V 3A adapter with a fixed IEC C7-Nema 1 plug is a possibility but what about not hacking? :)


texts: How does Nyquist bit rate formula relate Bandwidth, Signal Rate, and Bit Rate?

texts:
I know what each of Bandwidth, Signal rate, and Bit rate mean. But I am having trouble in their mathematical relationship with each other. I will use the notation of the textbook I am reading from (which I think is the cause of this confusion, and I don't know if I can name it here or not). Specifically, I am trying to understand how to derive the BW for a certain line code. The book defines \$r = \frac{number~of~data~elements}{number~of~signal~elements}\$ and relates the bit rate \$(N)\$ with the signal rate \$(S)\$ as follows:

\$S = c \times \frac{N}{r}\$ . . . . .(1)

Where \$c\$ is some constant. When calculating the bandwidth \$(BW)\$ of a line code the book uses formula (1) above and seems to substitute \$c\$ with \$\frac{1}{2}\$. My sources of confusion are:

1) \$S\$ is defined as the signal rate not bandwidth

2) Why always \$c=\frac{1}{2}\$?

3) In the plots the X axis units are \$f/N\$ (is this Hz/bps?)

I searched a lot and I think the answer is in Nyquit's bit rate formula which says:

\$N=2\times BW \times \log_2(L) \$

where \$L\$ is the number of signal levels which is equal to \$2^r\$. This means that:

\$BW = N/2r\$ . . . . . (2)

But this suggests that \$BW = S\$ (from (1) and (2)). This is where I get stuck. How should I understand this?

Edit after Mr. Snrub answer:

So if we go back to Nyquit's formula \$N = 2 \times BW \times log_2L\$ and take a look at the units we see that the units for \$2 \times log_2L\$ or equivalently \$2 \times log_22^r = 2r\$ should be bits/cyc, i.e.:

\$\frac{bits}{sec} = \frac{cyc}{sec} \times \frac{bits}{cyc}\$

We know that \$r\$ units are bits/sym. So for everything to line up correctly the units for the \$2\$ should be sym/cyc, i.e.:

\$N(\frac{bits}{sec}) = 2(\frac{sym}{cyc}) \times BW (\frac{cyc}{sec}) \times r(\frac{bits}{sym})\$

This is easy to see for the case with highest frequency for patterns of 101010... or 0101010... in NRZ line coding where we have 2 symbols (one 1 and one 0) per cycle of a pure sine wave. But what if the line coding was polar RZ? In this case a pure sine will not line up with the transmitted bits. So how can we know the  symbols/cycle factor for any line code?


texts: Programming Multiple STM32F4 Controllers

texts:
I Have designed a board that contain 3 ICs of (STM32F407) as shown in the figure below.
these chips programmed by using (SWDIO AND SWCLK) for each chip.

Can I use JTAG pins to programme these three chips with the same set of pins??


texts: How to measure distance between two moving objects?

texts:
I wanted to ask if anyone knows a way to measure the distance between two moving objects (actually one is fixed and one moving)?
Can I place on one of them a transmitter and on the second one a receptor and know in real time the distance between the two? The range I'm looking in is about 0 - 0.5 meters and resolution of about 0.5 cm.
Can anyone recommend on a way of doing it?


texts: Amplitude drop as frequency increases on function generator

texts: As I increase the frequency on my function generator, the amplitude of the transmitted wave decreases. Is this to be expected? Or is there an issue with my function generator?


texts: How do I increase the voltage gain of a Common Emitter + Common Collector without distortion in Vo?

texts: I started with R1 and R2 half of what they were now, and with R_C = 5k. This had a gain of about 11, I managed to increase that by increasing R_C, but it seems to be plateauing when I start to get close to a gain of 30, and also the Vo waveform is distorted/clipped, which I want to avoid. I need a gain of at least 50.


texts: How do you calculate Vout on a voltage divider with a diode in parallel to R1?

texts:
If you have a simple voltage divider circuit, but with a diode in parallel to R1, how would you calculate Vout? My attempt was a simple voltage divider (.5 * Vin) for Vin < 0.7, then Vout = Vin after 0.7 V. When I attempted this circuit in ltspice, it gave me a continuous function, contrary to my idea. How would this be calculated?

simulate this circuit – Schematic created using CircuitLab


texts:
Suppose I have an unknown system and I would like to know its linearity.

I am confused by the proper measurement of the IIP3. The gain is defined as "total output power" divided by "total input power".

By sweeping a single input tone and obtaining a the power of the single output tone, I know that the gain is about 24.

But to create an IIP3 plot, one uses TWO tones and measures the power of ONE output tone and ONE IM3 (e.g., https://www.maximintegrated.com/en/app-notes/index.mvp/id/5429).

Option 1: Use one output bin and subtract 6dB from the total input power (since it consists of two tones)

The gain is correct
The IIP3 is worse than I would expect
The input power is the DUT is actually wrong ... in reality it is twice as powerful (since I have two tones but only consider one).

Option 2: Add the power of both output signal bins and both output IM3 bins (in linear domain) - use total input power:

The gain is off by 3dB
The IIP3 comes closer to the region I would hope for
I do not like that because the amplifier is frequency dependent and in general, the two tones (as well as the two IM products) can be (slightly) different.

Option 3: Use one output bin and one IM3 output bin and total input power

The gain is off by 6dB (This is expected because I am considering only half the power at the output than I have at the input)
The IIP3 is closer where I could hope it to be

Option 4: Use total input power. For output power, use sum (in linear units) from both signal bins ... for the IM power, only use one bin

The gain is again off by 3dB
The IIP3 is where I would hope :-)
It does not sound right to take the sum of the output fundamentals but only consider one output IM3.

In any case, none of these 4 options looks "correct" to me.


texts: How do i measure Ethernet signals on an oscillocope

texts:
I have a device that works on 100 Mbps using a CAT5E cable.

Any idea of how can I show the data communication (capturing the signal integrity eye pattern) of this device using an oscilloscope (4 GHz/ 40 GS/s)?

I can connect the probes to the inner cables of the CAT5e cable.
I have differential probes.


texts: Unable to simulate a SystemC model in Modelsim

texts:
I've created a systemc-xor gate in eclipse. It works fine with a SystemC testbench.

Eclipse offers the possibility to make a coupling with VHDL, so I can make a testbench in VHDL and then simulate it with modelsim. A .so file is generated in eclipse, which should be loaded by the VHDL file. But when I run

vsim -gui     work.xor_gate_if_tb -do xor_gate_if_tb.do

I get the following error

Error: (vsim-3193) Load of "./xor_gate_if.so" failed: DLL dependent library not found.

Looking for more information about this error I find the following

Dynamic loading of the specified file did not succeed. Verify that the
full path to the file is correct and that the file is marked as readable.

Also verify that the object file was compiled and linked on the same type
of platform as the QuestaSim that is trying to load it.

The file is in the current path, and both the compiling and simulation process are made in windows.

I would appreciate any help to solve this issue. Thank you.


texts: Does a CPU completely freeze when using a DMA?

texts:
I have pretty straightforward question, but I couldn't find an answer to it anywhere.

On a Von-Neumann system where code and data live in the same RAM, the CPU must fetch all its instructions from memory. Now, in order to move large amounts of data between computer components, there is a Direct Memory Access controller that allows peripherals to have access to main system RAM.

My question is this: if the DMA is allowing a (possibly very long) data transfer between, say, the hard disk and RAM, doesn't that mean that the CPU cannot use RAM and therefore can't fetch its next instruction?

In brief, the DMA is meant to replace the processor arbitrating all I/O reads and writes, in order to free up the processor to do other things. However, if it can't fetch its instructions from RAM, then it hasn't been freed up anyway.

Is there some detail that I'm missing here?

Thanks


texts:
I am trying to power 3 led strips (in parallel) and use pwm to make the leds change colors.

https://www.adafruit.com/product/4245?gclid=CjwKCAiAg9rxBRADEiwAxKDTuu_xi9ko-vFyyAg11iDd7-xmcpdqORtwGIjh6pR70E7w2zXKsYGXoRoCFA4QAvD_BwE

My idea for this is to use 4 (possibly 5) I/O ports to be connected to the input of the power relay

( https://www.mouser.com/ProductDetail/Adafruit/3191?qs=A50fv7uxK7UJSQBi%252B9%252BHlA%3D%3D&gclid=CjwKCAiAg9rxBRADEiwAxKDTuqilwitS4hRS94J63TydHgmhdZo8sEMSf6e-uV1QMoTsdh08cvleGhoCJD0QAvD_BwE )

to provide it with 3.3V. The relay also states that when switched off, it draws up to 100mA. That would be the reason for using multiple ports to feed into the input of the relay as each pin can only handle a maximum of 25mA. The board to be used is: http://www.ti.com/tool/EK-TM4C123GXL (I know it's a little overkill but it's what my friend had and he didn't seem to mind to use it). I am also planning on putting some reverse-current limiting diodes on each connection from the pins to the relay.

I was then going to have the output of the relay, which is either 10A,240VAC or 5A,240VAC to this on-board power supply of 12VDC,3.8A https://www.trcelectronics.com/View/Mean-Well/IRM-45-12.shtml in order to provide 12VDC to the led strips in parallel. At maximum use case a single led strip will consume 1.2A, so that's why the 3.8A.

Does anyone see anything I'm overlooking or that doesn't seem right? I've never tried creating a portable higher voltage power supply setup like this before and was wondering if I was approaching a reasonable solution. The only thing that is really concerning me is the current output from the relay to the on-board power supply, because the power supply says the ac current input for itself should be around 1A and 5A output from the relay is far too much. Would there be a way to sink a desired amount of current output from the relay before it gets to the power supply?


texts: This is my first post, and I'm very new to the Hardware side of Making but I'm working on an led project and I need some advice. I want to use individually addressable leds, but my project is pretty large scale (think Christmas light show) and I want this to be done using consumer grade electronics.  My concern is that I cannot find a high voltage low amp solution for my leds (Most I've seen run around 5v).  I'm guessing this is because the micro-controllers require very low voltage before they burn out. I'm not super comfortable using high end high amp low voltage DC power supplies, and I was wondering if anyone knew of an alternative solution, or if I'm just wasting time looking. Thanks again, and please let me know if this is not the right place to pose this question or I'm not providing enough detail. I respect the stack exchange community and want to follow the rules.


texts: find TH1 in AT89s52 micro controller in serial communication

texts:
I want to establish serial communication between an 8-bit microcontroller, AT89S52, and a PC. I am using a crystal oscillator of 8 MHz frequency. For baud rate calculation I have used the following formula:

 Fbaud = (2^SMOD * Fosc)/(12*32*(256-TH1))

In my case

 SMOD = 1;
 Fbaud  =9600; // baud rate
 Fosc = 8MHz   // oscillator frequency

So using formula TH1 = 251.659722222

I have used TH1  = 251 i.e. 0xFB and also 252 i.e. 0xFC. In both cases I am getting garbage values on Hyper terminal.

I have used following code::

#include <REGX52.h>
#include <stdio.h>
void serial_ini();
void serial_ini()
{
    SCON = 0x50; // mode 1 , 8 bit UART, enanle receiver
    TMOD = 0x20; // timer 1 mode 2(auto reload mode)
    TH1 = 0xFB ; // baud rate 9600 // crystal = 8.000 mhz..
    TR1 = 1; // Timer1 run
    TI = 1;
}

void main()
{
    serial_ini();
        while(1)
        {
            SBUF = 0x41;
            while(TI==0);
            TI=0;
        }
}

Please suggest to me how to calculate TH1 for AT89S52 microcontroller.


texts: matching input and output impedance in an audio circuit

texts: I have searched many places but have failed to get a clear and convincing explanation about why we match input and output impedance in audio circuits. For example: lets consider a simple audio circuit where microphone is connected to amplifier and then to a speaker. So here, what are input and output impedances and why is it important or why do we care about matching the input and output impedances? Please enlighten me. Appreciate it!


texts: What type of headphone connector is this?

texts:
I got a pair of Onkyo headphones as a gift a while ago, and now one of the connectors on the cable broke (the red one in the picture).

What type of cable connector is this?  Searching the Onkyo website and amazon didn't get me anywhere.  What do I look for to find a replacement regardless of the manufacturer?


texts: Calculating Necessary Resistance In Current Source Circuit

texts:
I have a problem where I must calculate the resistance required in R3 to have 1A flowing through the two 9.7V sources in the image below (i.e. Charging the batteries at a rate of 1A). I have simplified the initial circuit to what is shown here:

simulate this circuit – Schematic created using CircuitLab

Using Mesh Analysis from left to right I have the values:
I1 = 6.8A
I2 = 5.99637A
I3 = 5.54432A

So the branch of V1, V2 and R3 has a current of 0.45205A (confirmed by circuit simulator). I now need to make the current 1.

Using circuit simulators I have determined that I require the resistance of R3 to be approx.  13.16Ω to achieve 1A through that branch, but I cannot reason the maths to myself (and obviously I need to understand not just give a correct answer).

I've been thinking about it from an Ohms law perspective but I cannot seem to get it to add up. I know that I will = 1 for the branch, but I cannot figure out how to get V to calculate R. Using KVL around the circuit hasn't really helped me either.

I've reasoned for I to equal 1, then I2-I3 = 1 this will however also affect the relationship of I1 to I2. So I'm getting a bit tripped up on reasoning the problem.

Any help in the right direction would be appreciated.


texts: Mapping two characteristic curves of a power amplifier to each other

texts: How van these 2 curves shown below map to each other: So where would point B or point A on the IDD vs VDD curve  be on the power output vs power input curve?


texts:
I have a 3.8V mobile-phone battery that I need to discharge.
However I don't have any electrical components (say led) with me.

What is a crude way to do this using household items?


texts: Analog voltage control via Microcontroller

texts:
I have a BLDC motor driver that's powered at 24v DC. The control for this driver is via a line that modulates speed based on the voltage applied (between 0 and 24v) so a voltage divider using a pot seems like the simplest solution that works flawlessly for testing.

Now to actually implement this, what would be the best way to do this with a microcontroller? Using a DAC or a digital pot seems like a simple solution but options are limited at those voltage levels. Current requirements for the control line are low (10ma or less).


texts: Why does low power factor make my LED bulb and clock radio flicker at 0.2 to 3 Hz?

texts:
[California, USA, regular 110 V power.]

I'm reading the power factor of my "Late 2013" 27-inch iMac using a P3 P4400 Kill-A-Watt. It reads 0.95 when operating normally (60 to 120 W), but when sleeping, even with Power Nap off and power bouncing between 0 & 2 W (to power the USB mouse & keyboard to allow user wakeup) the PF bounces around 0.50.  The K-A-W has a low update rate, so it's hard to read with the computer in this state.

If I "Prevent computer from sleeping when display is off", with screen off it draws about 22 W and the PF sits at 0.50.

In both of these cases (just screen off or computer sleeping), an Ikea LED bulb and my 15+ year old Sony ICF-CD831 CD clock radio's LED display flicker.  Usually a few seconds between flicks, sometimes at about 3 Hz.  The Ikea bulb runs very hot in a non-enclosed fixture.  It might be failing and I'll throw it out when I'm done using it as a diagnostic.  A GE bulb on the same circuit does not flicker.

As soon as I wake up the computer, the flickering stops.

My house has a 40 year old 100 Ampere Zinsco panel that the landlord's going to replace.  There are only 2 20 Amp breakers for all outlets in a 3 bedroom house and some 3 prong outlets don't have the ground connected.

How can poor power factor on the computer cause devices with poor regulation to flicker?  Is oxide on circuit breaker contacts a possible contributing factor?

I checked the line voltage with a DMM & saw it dipping from ~120 to under 110 with a 10 W LED bulb switched on giving an ESR of about 165 ohms, but an 1800 W hair dryer caused the same sag, so there doesn't seem to be a simple non-reactive loose wire.

Diagram added:

Load A is iMac causing interference, B is clock radio or 10 W LED light fixture being sensitive to that interference.  X and Y are the 100 V loads around the house (refrigerator, lights), Z is lumped 220 V loads (stove, clothes dryer).  The only way to eliminate X, Y and Z would be to get a 200+ W inverter and battery and run A & B from that in isolation of other loads in my house & neighbors on the other side of the pole transformer & I only have a little 50 W.


texts: max. switching power of relay in datasheet

texts:
I want to use SPST relay to control resistive load as well as inductive load i.e. ceiling Fan (Load<150W).

I used the 5VDC relay (HF46F-G) which is capable of 7A current, 250VAC.

Datasheet: http://www.hongfa.com/pro/pdf/HF46F-G_en.pdf

As we know, P=VI so that we can control the appliances which power rating is 1000W with this relay (P=230V*4.5A = 1035W; current is less than 7A)

then why datasheet says that its maximum switching power is 300W?
What does it exactly mean?
What would happen if I switch the appliance which is 1000W rated?
Is ceiling fan (Inductive load <150W) control safe (arching, relay
health perspective) with this relay?

My understanding

We can safely control the appliances rated below 300W which means safe rating is 1.3A current if voltage=230V and
7A means that relay can handle the sudden peak up to 7A without any damage if it happen.

And if load is greater than 300W then arching chance increase more and relay life become shorter.


texts:
I'm looking into a LED driver and i'm quite curious about the inrush current.
Where does it originate from? Is it to load up the input/output capacitors?

Can I limit the inrush current? Whats the most simple way to do this, inrush current limiters(ICL), PTC:s or any other way?

Can the inrush current be limited by starting the luminaire in a dimmed mode?

Thanks in advance!


texts: What's the current leak path of the electrostatic discharge during an EMC test?

texts:
When we develop a new product we need to pass the EMC test,I really wonder what's the current path during a  electrostatic discharge test.
Here is the test situation：

Q1:
If the EUT(equipment under test) is metal shell,is there a discharge path? If yes,what's the path going to? the ground?
Q2
Q2:
If the EUT  is not metal shield(for example plastic shell),is there a path exist? and what's the discharge path?

Let's assume the EUT is a battery powered plastic shell device which have a PCB inside. When we do the electrostatic discharge test at a voltage of +-6.6kV , the discharge current do have an influence on the device such as cause it to work abnormal,so what's the discharge current path?

[updated]
I add a new picture to assume the discharge current loop,that is my confusion.

Can I always find the discharging current loop in my test?

Q1 is easy to consider as the discharging current flow through the metal shell
but in the situation of Q2 I cannot find a current path.


texts: Simple way of measuring RPM of motor by How to make Frequency/Pulse counting circuit

texts:
I want to measure RPM of a motor. For this, I am planning to put an assembly where an IR LED facing with IR sensor under line of sight. With every rotation, the line will be cut once - and hence the IR sensor LED.

Where I am stuck at is that once I get pulse of the signal, how do I count these pulses to make the Frequency (i.e. rpm) estimate? Is there a simple way to do it? I can use Oscilloscope - but I don't have easy to access to one. I have seen that most entry level multimeters don't have frequency measurement.

Also, unlike this question, I would also refrain from involving microprocessor based counting on this. [Basically this is a simple hobby project for high school student]

So is there a good and easy way to do it? Is there any completely alternative way to do this?

PS: The motor speed will typically be between 0-500 rpm not beyond.
EDIT2: I want this to use a tool for physics experiments - so I need it as a quick indicator of rpm.


texts: How can human finger pressure be measured?

texts:
I am dealing with a situation where a patient can only very lightly press his fingers / hand to signal what he / she wants. Speaking or eye tracking is not possible.
The person is also not able to lift his hand. The only movement possible is a slight press with the hand / fingers.
I was therefore thinking about using a capacitative device that would be calibrated to detect how much pressure is a willing / intended press and which amount pressure is simply a resting position of the hand on the device.
I guess a capacitative device is what is required here.
I saw a solution of a custom device here on YouTube, but that looked so custom-made and so rigid that I was wondering if what I need actually already exists.
I would therefore like to ask how I could measure the pressure of a human finger / hand on a device in a reliable way.
Thank you.
Edit: Nobody so far suggested to use a precision balance with USB output option. May I ask if that would not work?


texts: Is this microcode control store realistic as a hardware implementation?

texts:
In a simple control unit using microcoded sequencing, I use a ROM to store the sequences of control signals. The instruction forms the top 8 bits of the ROM address, and the bottom eight bits are formed by a counter that is incremented on the falling edge of the clock.

The zero address of the ROM contains the signal to load an instruction into the instruction register, thus pointing the ROM to that address and outputting the data there in order. After the instruction is completed, the ROM will output bits to clear the instruction register and microcode counter, restarting the whole process. When these bits are set high, the ROM address is instantly reset and the bits go low immediately.

My goal is to implement this circuit using 7400 series logic and an EEPROM, but I am suspicious that my method of using the ROM data to asynchronously reset its own address registers will introduce a race condition or otherwise invalid state. Is this method acceptable. If not, what is the appropriate way to do this?


texts: ATtiny85, timer 1B does not work if COM1A1|COM1A0==0

texts:
I read the datasheet, and checked http://www.avrfreaks.net forum, but I cannot understand why on an ATtiny85:

int main()
{
    TCCR1|=_BV(CS10);
    GTCCR|=_BV(PWM1B);
    GTCCR|=_BV(COM1B1)|_BV(COM1B0);
    DDRB|=_BV(PB4);
    OCR1B=0x80;
    while(1){}
}

Does not work until I add:

 TCCR1|=_BV(COM1A0);

Which I guess I should not need if I want to use only timer 1B.


texts:
I need to use a fast decoder to communicate with a SRAM memory, CY7C1041GN. The circuit I need to implement is the circuit suggested in the Example #5 of the document AN2408 .The suggested decoder in this example is obsolete, but I found another, even better, with a smaller Tpd, the model that I found was the SN74LVC1G139, its Tpd is in the range of 0.8ns to 3.6ns using VCC = 5V. The problem with this model is that it does not have active low Enable pin.

I supposed that the work done by the decoders in the example #5 of AN2408, could be done by logic gates, but I didn't find logic gates that are faster than the found decoders.

I searched in many places, I listed many 2x4 decoders at digikey site,  I did parametric seach at Texas, Nexperia and OnSemi websites,  but I didn't found a model that have a Tpd(propagation delay) as low as 3.6 ns. Does someone know, or has a tip, of a model of decoder with Enable-Low  pin that is able to reach these values of Tpd ?


texts:
Can anyone suggest the best way to get a 12V DC electric motor (70RPM) to rotate roughly 360 degrees and then stop?

So the process would be;

Power switched on.
Motor rotates once, then stops.
Power switched off.
Repeat

Thanks in advance


texts: Sensing Mobile Battery full and cutting down power on V_bus line

texts:
I just come across the situation to cutoff the power when mobile battery full is detected (by breaking the +5v line) .I planned to implement this using high side current sensing method.When the battery is full it draws very less current, so when the current goes less than 100mA I would like to cutoff the power on +5v line (as shown in the figure). The problem is once if the current goes less than 100mA the output of second comparator activates the switch to break the connection.
How can I detect the plug in/out of the USB cable when there is no power on +5v line as I have to reset the switch position on every plugin/out action so that if a new phone is connected to charge it.
Also is there any better method to detect battery full and turn off the power on +5v line.
Also I dont want to use any microcontroller as i'm making this project at absolutely minimum BOM.


texts:
I am trying to implement a instruction pipeline but getting one issue. Please help me :

How can we write all zeros in a latch using hardware?

I am not that much into Electrical Engineering so please go easy on me :)


texts:
I have a device that essentially controlled by a potentiometer and a rotary switch. I would like to keep these (although I would replace them with other components if that helped), but I'd like to be able to read the position of the switch and potentiometer with a computer (or Arduino for example).

Is there a simple way to do this? I thought I could measure the value of the potentiometer's resistance but it's integrated into a circuit.

Any hints on how to go about this?


texts: Pintech PT-710 sensor identification problem

texts:
Welcome all. I need some help with identifying a component. Recently I opened my Pintech PT-710 current probe and tried to see what type of sensor is used. Inside the jaw there is a single sensor shown in picture attached. I suspect it is Hall effect or TMR sensor. It has 4 pins in idle state following voltages are present.
PIN1 6.8V
PIN2 5.7V
PIN3 4.6V
PIN4 5.7V
All voltages are measured in respect to 9V battery “-“ terminal. This would suggest that pin 3 is sensor GND and pin 1 being sensor Vcc. Pin 2 and 4 being outputs seating at half of sensor supply. Last clue is a code on sensor itself “A115”. I understand no one has crystal ball to guess it. However, perhaps someone could give me some clues e.g. package type.


texts: pull up or pull down resistor for optocoupler

texts:
I tried to make a PWM AC dimmer circuit which found in instructables.com as below:

but the 100k 1W resistor got hot. Could using a pull up (or maybe pull down) resistor for optocoupler solve the problem?


texts: Is it a safety issue to only bring the hot wire onto a board for mains switching?

texts:
I have a DC board that will be controlling my system. As part of my system, I need to toggle an AC motor on and off. At the moment, I have the hot wire off of my mains connection going into a terminal block, through a relay, out through a terminal block, then out to my motor. The neutral and ground wires are going straight from my input mains connector to my output connector.

simulate this circuit – Schematic created using CircuitLab

Does not bringing the grounding wires onto my board present a safety issue? I feel like it won't, but I haven't worked with mains before and am a little hesitant to say it with certainty.


texts: When will electromagnetic waves reflect? What are the criteria for reflections?

texts:
When an EM Wave comes to a boundary of two different media (i.e different electrical permitivity and magnetic permeability media), the things below could be seen:

Reflections
Refractions (Transmitted wave)
Absorpiton
Scattering (I am not sure)

I want to learn the criteria for the above events. For example, when do reflections occur? When does transmittance occur? Do they depend on the characteristic impedance or electrical permittivity differences of the media?


texts:
I want to construct my own capacitor, primarily as an experiment in different plate configurations and orientations, so I can better understand field theory. (In other words, I'm playing, and not looking for an off-the-shelf solution. The building of it is half the point.) I've built small PCB units on the order of a few nanofarads. I'd like to build something larger, on the order of 5-10 uF, which seems to make PCBs impractical. I also want the cap to be unpolarized, so I can run AC across it.

I'm thinking I need a couple rolls of foil, a roll of some insulator, and some way to attach conductors to the foil. But before I just go to Wal-Mart and buy all their aluminum foil, I wanted to ask: what might I be missing? Are there standard techniques for hand-building capacitors? Are there particular materials I should use (or avoid)?


texts:
I am using the following circuit in my design:

The desired behavior is the following: After #ON is turned low, the GATE output from U5 goes high (VIN voltage + around 6 V) and Q1 goes ON. After the #ON goes high, the GATE goes low (0 V) and Q1 transistor is off.

For some PCB pieces I have noticed the following behavior: De-asserting #ON (high state) doesn't make the Q1 go off (even though GATE voltage is 0 V). Q1 will go off only after sufficient amount of load is applied to VOUT (ie. I short VOUT to ground with a 10R resistor).

What could be the case in here?


texts:
A 5KW, 220V DC Shunt Motor draws 2A at rated voltage when running light. If the
armature and field resistances are 1Ω and 165Ω respectively, determine its efficiency
when running as a motor drawing an input of 5KW.


texts:
I'm helping my brother (8) build a small toy car powered by a tiny 3V motor that we have at home. Most tutorials we've found on the internet suggest using a 9V battery, but never specify the voltage of motor they're using.

As I only have basic and theoretical knowledge in electronics, I'm assuming I should power the motor with equal voltage (3V). Could I use a couple of AAA batteries in series (which, frankly, I have no idea how to do except maybe use electrical tape to hold them together) to do power the motor? Would it be enough? Should we use the 9V battery instead?

I'm just... trying to make sure we don't hurt ourselves or burn the house down.


texts: Controlling a simple RC vehicle at long dinstace from a PC

texts:
I would like to control a simple, ground-based vehicle wirelessly, at ranges up to 5-6 km. The communication would be bi-directional (to get a feedback of "command received") but would only require binary states, just as if I wanted to remotely switch a small number of switches.

I hoped that this day and age there would be plenty of such devices available for USB. I searched for long range USB radio transponders, and got nothing of interest. Most RC toys use high frequency, have a very limited range, and rarely have a USB connection. Wi-fi routers have amazing speeds, but even less range. Normal walky-talkies would have the range, but I just couldn't find readily available devices or ICs which just send a few bits to remotely trigger a few switches.

Does this mean I would need to build the antenna and all the electronics myself, or are there readily available solutions hiding under a (for me at least) unknown term?


texts: solving minimum voltage to turn on a diode

texts: Im having issue with this problem. The question asks for the minimum Vs voltage to cause the diode to be on (current flowing through diode). This same question also asks for the current through the diode ID if Vs was 6 volts. The issue Im having is that the answer they give is 122 mA, where as my answer using either .6 or .7 as the voltage drop across the diode comes up too high (around 140 mA). So far this book uses only the ideal diode model and uses usually .6 for the voltage drop. Even when I used 0 volts for the drop across the diode I still came up with a current much higher than theirs. So I have no idea what value they are using for the voltage drop across that diode in order to use it when solving the minimum value for Vs in the second half of the problem!


texts: Designing a bluetooth audio unit for speaker

texts:
(Cross posting from Sound design stack exchange since it was declared off topic there)

I have a sony speaker from an old Home Theatre System that is broken now leaving the standalone speakers in a good unused condition. I'm trying to design a Bluetooth capable audio unit to convert this into a nice Bluetooth speaker for my room. I need some help selecting the components for this project. Attached is an image of my speaker.

How can I find the rated power of this speaker as I'm unable to find a proper datasheet or document on the internet that gives me this value. Is there a way to experimentally find out the power requirement of a speaker?
The rated impedance is 3 Ω. I've found some amplifier modules (like PAM8430) on the internet but the specifications say that it can support 4 Ω and 8 Ω speakers can I still interface 3 Ω speakers and expect decent performance? Or is there a way I can increase the impedance of this speaker by adding some resistors etc or do I have to search for an amplifier that supports 3-ohm speakers?
This speaker has +ve and =ve pins, can I directly connect these to the different parts of a 35mm TRS headphone jack or is some other kind of interfacing required?


texts: What RF frequency can I freely use without a government's permission legally?

texts:
So I want to create a transmitter that sends digital signals that have 30 kilometres of range but in my country.
Radio transmission without authorisation is only allowed upto 50 metres.
I researched about ISM bands but I don't know if it's allowed to transmit on them for distances up to 5 kilometres.
Please let me know if it's allowed or not, or if there is other internationally free to use limitless frequency that I can use.


texts:
I'm driving a blue 7-segment LED display with a TI CD4026BE on a 3.3V circuit.

I cannot find any data sheet for the display part. It has a common cathode pin layout and it's marked FJ5161AB on the side and D5611 A/B on the bottom.

At first I tried putting some conservative resistor values, but then I noticed that the formula would give a Vf (LED drop) pretty close to Vcc. So I tried connecting the LEDs directly to the chip's outputs (3.28V) and the current consumption is 0.67mA per LED.

I know that blue LEDs can drop up to 3.3V. Is this current value low enough that I can get away with no series resistors?

Here's a couple pictures:


texts:
I used the Using the PLECS Scope to edit the scope but when it comes to the name of the signal I could not change even though I double-click on it and tries many times, is there any way to change the signal name?

best regards,


texts: Buck Converter not increasing the current?

texts:
I am constructing a 20 W buck converter. The voltage is bucking but the current is not, the current that the power supply is producing is going straight through to the load. Please help.

I am suppose to apply a 12 V input (1.66 A maximum) and get a 5 v output with a maximum of 4 A of current.

simulate this circuit – Schematic created using CircuitLab

Also is it necessary to use the ground terminal (green) of the bench power supply when testing?


texts: STM32 HAL Using ADC with DMA affects UART transmission

texts:
I am using STM32 Nucleo F334R8 board. I transmit some data using UART in asynchronous mode to my PC using:

HAL_UART_Transmit_IT(&huart2, &data, sizeof(data));

I noticed that after enabling ADC in DMA mode microcontroller started to send incorrect data over UART.

When I just only commented out:

HAL_ADC_Start_DMA(&hadc1, adc_dma_values, 2);

UART transmission sends correct data.

When I replaced HAL_UART_Transmit_IT() with HAL_UART_Transmit() it also surprisingly works well.

I do not understand how HAL_ADC_Start_DMA() may affect HAL_UART_Transmit_IT().

Here's whole code of main.c, maybe it would be helpful.


texts: Odd results solving this very simple first-order RC circuit

texts:
Here's the circuit:

I'm trying to find the differential equation for the current through the capacitor (i_c(t)).

Using KCL at the top node, I know that 10u(t) = i_r(t) + i_c(t).
Using KVL around the right loop, I know that i_r(t) = v_c(t) seeing as the resistance is 1 Ohm and i_r(t) = v_r(t).

I can now rewrite my KCL equation to incorporate the equalities I've found:

10u(t) = v_c(t) + i_c(t)
because i_r(t) = v_c(t)

However, I need this in first-order differential form. So I take the derivative of both sides of the equation:

10u'(t) = v_c'(t) + i_c'(t)

And using the V-I characteristics of a capacitor, I replace v_c'(t):

10u'(t) = (i_c(t))/C + i_c'(t)

However, the derivative of the step function is the delta function - which is defined as 0 for t < 0 and t > 0. So we can replace it with 0. This makes my final differential equation:

i_c'(t) + i_c(t)/C  = 0

Is this correct? I've tried to illustrated my methodology so that my steps are clear. The reason I'm skeptical this is the actual answer is because when I try to find a value for i_c(0+) (leveraging the continuity condition on the capacitor's voltage), I get zeros all across the board.


texts: Calculate RGB color ratio for a color space given a white point?

texts: I am new to the field of displays and color science. I am trying to calculate RGB color ratio for NTSC color space using D65 white point. Can anyone point me to a good reference on it or how I can do it? I found this article but I don't understand the logic he uses to calculate the color ratio. I understood up till the point he starts calculating blue to red ratio using purple point and green to purple ratio using white point.


texts:
I am working on a complex 8-layer PCB to which I have made a number of changes and improvements.

I now want to sent the board out for production and want to check for any unnecessary cost. One of the things I want to check is for any buried vias. The board has plenty of blind vias. If a buried via is found, I want to design it out.

My question is; How do you find buried vias in Altium Designer?


texts:
Both these terms: controller(forexample PID controller) and compensator(Lead compensator) are often encountered in control systems,but what is difference between these two?

Brain douglas in this following video tells that both these terms controller and compensaator are used interchangeably

https://www.youtube.com/watch?v=xLhvil5sDcU

But in the below link ee SE question with almost same content/query ,controller and compensator are mentioned as different entities

Difference between a controller (e.g PD) and a compensator(e.g Lead)?

I have also attached snapshot of pg5 of qnet vtol workbook where i have highlighted "compensator" term used with PID instead of "controller" term?


texts:
So I'm building a tachometer for my car. It's pretty simple, basically I have a wire wrapped around the spark plug wire about 10 times, and the 30-50k volts travelling through the spark plug wire should be sufficient to induce a small current through the wire wrapped around it. I'm detecting the voltage in an arduino and then doing a simple calculation to figure out the RPM.

So, I set this all up, and I have no idea where to put the ground. Now, if I just have one end of the inductor wire going to the arduino, through a diode and then voltage divider, the whole thing works, which doesn't make any sense to me, the other end of the inductor wire is just floating in the air, not connected to anything.

Here's what it looks like

Thanks for any ideas. Like I said, this works, and it's giving moderately stable results, but I can't figure out why it works or how.


texts: Altium rules help: keepout region around mounting point throws collision errors for the mounting point itself

texts:
I'm working on an Altium footprint for a plated mounting hole with embedded vias arranged around the hole. I have the copper the way I want, but Altium is now throwing DRC errors at me that I'd like to resolve.

I'm getting a collision error between the Multi-Layer pad/vias and the Region Keep-Out Layer.

I would like the Keepout layer around the mounting hole to keep this area clear from any other PCB objects. I don't want it to throw errors due to the internal elements of the mounting hole itself. I'd like to resolve this within the library so the footprint is reusable, rather than manually ignoring this specific DRC or otherwise finding a workaround at the PCB level.

Is there an elegant way to resolve this DRC error at the footprint level?


texts: How can I determine the best trace width for my pcb?

texts:
In my project I use 2 external layers in air. How ever in my circuit the maximal current (Imax) in transient mode is about 70A and in steady sate it gets to 12A.

My question is, how can I know for how long this trace will hold high current above 70A?

Because I used this site
and when I entered the current section 70A then I get the width is: 1.84mm.

What will happen if for a short time (in the transient mode) the current reaches 90A?

Will it destroy the traces of the PCB?


texts: Communication protocol for microcontroller to PC host

texts:
I am looking for a reliable serial protocol that can be used for communication between PC host and a MCU programmer. Currently I've devised a prompt-like protocol, which has been great for testing, but I need reliability and functionality in terms of error checking, ACK/NACKs, parameter parsing, etc. The device I am working on will communicate with the host PC via UART.
I've done some testing with the current protocol, and it turns out the PC sends data too fast for the MCU to react, and a lot of data is lost. In the beginning I though I would be able to get away with a custom protocol, which I've used a lot (prompt-like, no error checking, ASCII-based), however it appears it's not good for the application.
Edit: The programmer I am working on will be used with the BDM protocol of some very old MPC55x processors. The custom serial protocol currently has the following properties:

Data from MCU is encapsulated in STX and ETX\r\n symbols
Data from host (PC) is not encapsulated but must end with \r. That's makes it easier to use a terminal
Each command returns a response
The MCU returns an error response if the command is not recognized
The host software waits for a valid response a number of seconds after each command is sent. If no response is returned, application takes action
The host app provides error checking in terms of reading back data which has been written in the flash

My question is: Is there a serial protocol, which I can employ, and which would have all the features above (and possibly CRC/checksum).
Now when writing it all down, it appears that such a protocol will be a hard thing to find, since I want to be able to use the console for debug - that makes encapsulating messages hard. Therefore I am considering moving away from that concept towards a more machine-friendly interface.


texts: What is the connection between ULN2004 and ULN2804 drivers?

texts:
I have an unipolar stepper motor that im driving with an Arduino. As a driver for the motor i bought a ULN2004 driver chip from Ebay. Or so i thought. I might be missing something, but the chip i received has 9 pins on each side, not 8 as my sketch illustrates, and the number on it is ULN2804, not ULN2004.

The link to the data sheet on the ULN2004 listing i bought from spinatronics says it's a ULN2804 chip. I'm unexperienced in how manufacturers set the numbers on the chips.

Have i bought the wrong chip, or can a ULN2804 driver be used the same way as a ULN2004?

How do i then change my sketch to implement the last two additional pins of the chip?


texts: HCSR04 with PIC18f24k22 stuck in real test

texts:
I have a problem with HCSR04 ultrasonic distance sensor. I wrote a code that works perfectly in Proteus simulator but when I upload it in real microchip it stop working properly. Looks like it sticks at one while loop and never get a echo signal. Btw when I'm uploading the code with PicKit that few seconds while code is uploading looks like system is working because led is blinking, after few seconds after upload the system stops and only one led shines without blinking.
#define _XTAL_FREQ 8000000

#include <xc.h>
#include <stdlib.h>

#pragma config FOSC = INTIO67
#pragma config WDTEN = OFF
#pragma config LVP = OFF

#define RB0 PORTBbits.RB0

#define RA1 PORTAbits.RA1
#define RA2 PORTAbits.RA2
#define RA6 PORTAbits.RA6

void delay (unsigned int ms)
{
    unsigned int i;
    while (ms--) {
        for (i = 0; i < 398; i++);
    }
}

void main(void) {

    float time;
    float distance;

    OSCCONbits.IRCF2 = 1;
    OSCCONbits.IRCF1 = 1;
    OSCCONbits.IRCF0 = 0;

    ANSELA = 0; //RA0,RA1- analoginis iejimas
    ANSELB = 0;
    ANSELC = 0;

    LATA = 0;
    TRISA = 0b00010000;
    LATB = 0;
    TRISB = 0;
    LATC = 0;
    TRISC = 0;

    T0CON = 0x80; // Konfiguruojamas Timer0

    while(1){

        TMR0H = 0;
        TMR0L = 0;

        RB0 = 0; //Trigger 0
        __delay_us(2);
        RB0 = 1; //TRIGGER 1
        __delay_us(10);
        RB0 = 0; //TRIGGER 0

        while(!PORTAbits.RA4); //Waiting for Echo
        TMR0ON = 1;
        TMR0=0;

        while(PORTAbits.RA4); //Waiting for Echo goes LOW
        TMR0ON = 0; //Timer Stops
        time = TMR0;

        distance = ((float)time/58.82);
        distance = distance + 1;

        RA2 = 0;
        RA1 = 1;
        delay(distance);
        RA1 = 0;
        RA2 = 1;
        delay(distance);
    }
}


texts: Thermocouple Simulation Test Circuit and Voltage Comparator Circuit

texts:
I have a challenge that I would like to share with you. (at least a challenge for me)

The resistor R8 (10 turn potentiometer) can be adjusted from ~0 to 1K Ohm to output voltages from 3mv to 30mv. The divider labeled (400F) outputs constant 8.3mv that equals 400ºF for a K Type Thermocouple. All that worked great.

So later I decided to add a fancy LED (D2). The LED should turn ON when the temperature is above 400F and OFF when below. I suspect using a LM741 as a comparator is a poor design because of precision and low voltages. One option would be an AD790 comparator http://www.analog.com/static/imported-files/data_sheets/AD790.pdf
A comparator in the .25mv offest range would be suficient for the precision I need.

Is there a simpler (cheaper) way to achieve this with precision and low voltage in mind?

*UPDATE - HERE IS THE FINAL DESIGN
http://iddevlabs.blogspot.com/2014/09/diy-thermocouple-testing-circuit.html


texts:
I did a pcb mount for a stn1110 "Multiprotocol OBD to UART Interpreter" and followed exactly schematic from datasheet.

The issue I have is that after is starting, there is a sequence of flashing the 4 leds, I can see it on the serial. Sometimes I am able to send ATZ and I get answer, but after few seconds something is happening and LED1 just keep flashing rapidly and I can't get a serial connection.

Can someone tell me what means that flashing? Where I should look for the issue?
I am sure should be something related to my pcb mount probably but have no idea how to debug this.


texts: Is event control iff in systemverilog the same like clock gating?

texts:
I have found like this code.

Always @(posedge clk iff rst==0 or posedge rst)

I think above code like clock gating code.
As I know , when rst is 1 then this block is never triggered.
So in other word, if I make rst 0 then the block is working.

But I'm not sure why this schme is introduced in here?


texts: Simple amplifier circuit, norton, thevenin questions

texts:
I have the above circuits and I have some questions related to them:

I drew above the Norton and Thevenin equivalents where \$R_{no}\$ is the resistance of the whole amplifier circuitry, excluding the load. Are they correct?
Is \$V_{th} = V_1\$? If not what is it equal to and why?
I simulated the circuit and have two sets of values for \$V_{out}\$, \$I_{load}\$ and \$R_{load}\$. How can I go about finding \$R_{no}\$? I tried various approaches but none of them seem to work.

Here is one approach I tried:

$$V_{load} = I_{load} R_{load}$$
$$V_{th} = \frac{V_{th}R_{no}}{R_{no}+R_{load}} + \frac{V_{th}R_{load}}{R_{no}+R_{load}}$$
$$V_{th} = \frac{V_{th}R_{no}}{R_{no}+R_{load}} + V_{load}$$
$$V_{th}R_{load} = V_{load}(R_{no}+R_{load})$$
$$\frac{V_{load_1}(R_{no}+R_{load_1})}{R_{load_1}}=\frac{V_{load_2}(R_{no}+R_{load_2})}{R_{load_2}}$$

However for some reason I do not get the expected value for \$R_{no}\$ from this answer. I cannot see what is wrong with the derivation though?!


texts: Recently I bought this motor and I want to control it with an Arduino. I read that I can drive the motor with a H-Bridge with TIP120 Darlington transistors, but the problem is that voltage in the motor and the arduino should be the same. This is not possible since the motor should operate at 12 VDC and the arduino is 5V. There is anyway I can drive that motor with the arduino. I just want to rotate the motor in both directions clockwise and counterclockwise at the default constant speed of 6 RPM.


texts: Why is it that a TEM mode propagates in a - Two separate conductor wave guide?

texts: Please someone explain to me in Simple English or Basic equations as to why does a Transverse Electric and Magnetic Modes(TEM) propagate on only two surface Wave guide like a coaxial or a parallel plate wave guide?


texts: A transistor AND gate outputs a small current when one of the inputs is HIGH. Why does this happen?

texts:
I built a simple transistor AND gate as specified by the following schematic:

http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/trangate.html#c1

It works very well, however it outputs a small amount of current when input B is HIGH, enough to illuminate a standard 3mm LED. Why does this happen? How can it be prevented? Ultimately I would like this circuit to illuminate the LED only when both inputs are set to HIGH.


texts: Limiting current WITHOUT dropping voltage

texts:
I'm trying to limit a current of a 5V power supply to 100uA. I was first thinking of putting a 50k resistor. That will never allow above the treshold.

However, the load requires at leas 4.5V and varies in the amount of current in needs. So this is obviously a too simple approach for the problem.

How can I extend this circuit to limit the current and keep the load voltage current independent?


texts: Graphic cards/components reliability after crypto minning

texts:
In the near future we will be probably flooded with graphic cards they were used for crypto mining. There are many not very well-founded discussions about their reliability. And similarly many un-founded comparisons between used and used for crypto mining. Hence I would like to dig deeper, educate myself and find more information's regarding this service life topic. Any technically/physically focused comments and sources describing components service life welcomed. I propose to skip electrolytic caps in this discussion as its reliability is already well described. However ICs, ceramic caps, resistors and magnetics is part of my focus.
As a starting point I cite Murata MLCC chart where with X5R they declare that 20C difference in case case temperature (range 60C-80C) is a question of almost 10 years of service life. Woo-ow!


texts: Circuit design questions related to powering laser from Arduino UNO

texts:
I bought an Arduino UNO, a laser, connectors, resistors, transistors.  I'm trying to hook up the laser and perhaps a few other components to eventually measure the light intensity frequency of reflected beam.

My first attempt worked for an hour or so.  I hooked up the 5v power through a transistor controlled by one of the mainboard's digital pins.  Burned out the laser eventually.

Bought a second laser and an assortment of resistors, but I don't know how to design the circuit properly.

Laser: http://www.sparkfun.com/products/9906
UNO reference: http://arduino.cc/en/Main/ArduinoBoardUno

I'm trying http://ledcalc.com/ to determine what resistance I should use according to the laser's specs.  But I'm confused about a few things:

How ought I power the laser properly?  I burned it out (unless I burned out something else instead?) presumably because of too much ... something.  Volts?
The UNO specs seem to say that the 5V pin, when the board is powered by USB is not available as a power supply (when compared to the 3.3V pin).  However, I read about 5V on my multimeter.  I am unable to determine how many AMPs are available to draw as the specs don't say it, and I must not know how to read it correctly on my meter.  Is it possible to measure available current between the 5V and GND without any load?  My meter is an Ideal 61-310 set to DCA 200m with probes in COM and mA.
Even if the 5V is available and offers amps, if it's in the ballpark of the 3.3V pin at 50mA, that's not nearly the 300mA that the laser is capable of.  How did I burn out the laser?
On ledcalc, with 5V input, 4.5V power drop, 300 mA (correct for the laser, I believe), I get a recommendation of 1.8Ohms.  I'm also getting 1250mW power dissipation by the laser, which is not the 5mW listed in the spec.
If I do need a transistor to control the circuit and a resistor to limit the current, does the order of the components in the circuit matter?

That's a lot of stuff, but I'm confused about a lot, and they're all interdependent.

(I have safety goggles for working with the laser)


texts: Read multiple modbus devices information by multiple PLC

texts:
The requirement is to read many different Modbus devices by different masters.
Since this can't be done through RS485, so the following image is the solution coming to me.
My questions are:
1.Is it possible to use a normal switch (like 20$) to support those devices which use Modbus-TCP?
2.Is there any possible risk of this solution?


texts:
I'm trying to find the voltage at the emitter and i use the property they give me of the absolute value VBE where in the book its equal to the small AC signal plus the DC VBE ( in this case that small signal is not applied).

The KVL on PNP BJT is Getting me frustrated.

i want to find the voltage at the emitter so i first set my kvl on Q2 to see if its on.

My loop current is opposite the direction of the arrow on the BJT Q1

-VB-VBE-VE=0 ==> VE=-VB-VBE =-1.2V

My loop current is opposite the direction of the arrow on the BJT Q2

-VB-VBE-VE=0 ==> VE=-VB-VBE =-0.7V

on the book the solution says it should be 0.7V for VE. im not sure why


texts:
Is it possible to detect whether a person is climbing or descending stairs using the data obtained from an accelerometer alone?
EDIT
If you have a accelerometer in your pocket(Mobile phone) then what about the forward acceleration along the z- axis. Won't that help to distinguish walking and climbing as forward acceleration in both cases will be different.


texts: Is it possible to get audio tone from STM32405RG off PB7 pin?

texts:
I have been doing some software work on an open source hardware/software project that produces a video overlay, but also offers an apparent audio out pin that is so far unused. The original developer of the hardware is nowhere to be found, and no questions asked of him have been answered for almost a year.

The board (which has already been produced in quantity, so changing it is not an option currently) offers a hook to an apparent audio out line off PB7:

https://github.com/StewLG/PlayuavOSD/blob/master/hardware/PlayUAVOSD_Schematic.pdf

I would like to get a simple tone of variable pitch on this line. If it could be a smooth sine wave from the DAC, that would be best, but even a rough triangular or even square wave would be useful to the users of this board.

I am not a EE guy by trade, so the 2 hours I've put into researching this might not have been enough. If someone actually has relevant code that would be a lovely miracle, but just general directions for how I might be able to hook the components of the microprocessor together in code would be most welcome. Can I use one of the DACs? Am I limited because this is UART pin?

The alternate functions of PB7 are listed as TIM4_CH2, I2C1_SDA, USART1_RX, FSMC_NL, and DCMI_VSYNC. Are any of those functions useful for making audio?

@ChrisStratton:

TIM4 is apparently being used to count horizontal lines in the video:

// Line counter: Counts number of HSYNCS (from hsync_capture) and triggers output of first visible line

See line 274 here: https://github.com/StewLG/PlayuavOSD/blob/master/src/osdcore.c


texts:
EDIT 1:
I was able to get it to work, but I am not at all sure what happened here... I decided to build this circuit again - exactly the same layout and parts (see original question below).

As soon as I turned it on (with 800mA load), I heard quiet crackling, like something was repeatedly sparking (I heard the same sound when the EN pin burned  in the previous attempt). This time I could see the sparks and the smoke coming from the input capacitor, not the EN pin!

I turned the circuit off, doused the board in isopropyl alcohol and then blew it out with a can of compressed air. I saw quite a few chunks of dried flux (I  am assuming it was flux) fly off the board. Turned the converter on again, and now it's been running cool and quiet for 30 minutes.

So what is that all about? I was sure flux was non-conductive... So what did I remove with compressed air that finally made the circuit work? I am using Acid Paste Flux SP-30.

Original Question:

I've been struggling with making a functional buck converter based on AP3431, and after getting some good suggestions here I was finally able to achieve stable operation for about 6 minutes (that's a huge improvement on my previous result of 30 seconds). Before the problem was wild oscillation of the output voltage. This does not happen now. Yay. The new problem is - fire :)

I've never had this happen before, so I am looking for some ideas on what the cause may be:

If you look at the video of the burning process, you can see the conformal coating boiling around the chip, which suggests a lot of heat:

https://www.youtube.com/watch?v=GttTQ8RhIts&t=0m7s

It is strange that most of this action is going on around the EN pin, which is supposed to have ~2uA going through it.

Here's how the board is designed:

Any idea what might be going on here?


texts: Why does (dis)connecting a stepper motor while powered on damage the driver?

texts:
In many manuals (for example for 3D printers), one can find the warning not to connect or disconnect the stepper motors from the electronics while powered on because that will very likely damage the drivers.

What is the actual process behind the damage occurring?
Is ist just costly to design the driver in a way that it would survive this event or is it actually not possible for some technical reason?


texts:
While investigating analog technologies I discovered these images of a quadraphonic 8-track player. All 8-track players I've seen before use analog voltmeters as displays rather than square graphical ones.

I thought they were vacuum fluorescent as the markings are persistent even when the screen is off but I have never seen dynamic multi-colored ones with a red indicator like that.

What are these displays and how were they meant to work?


texts: What type of schematic to use for a symmetric power supply?

texts: I want to build a phono stage preamp for my vinyl player. I have the components needed but I got a bit confused on which power supply schematic would fit my purpose. I have found several and in each one there are different amount of capacitors with different values in input and output stage. My transformer is 12-0-12v center tap 5W. I have L7808 and L7908 voltage regulators, so to my understanding they would put out 8 volts which should be enough for the NE5532. Here are the circuits I found online. How to know which one would be good for my case and what types of non-polar caps should I use ? I've tried to read about the purpose of these capacitors but it's still not quite clear why different values and combinations can be used and how would it affect the resulting output?


texts:
I'm using LTSPice XVII.
I'm trying to set a resistor to every node, helping convergence.

This is not recognized (spell?)

.options rshunt = 1e12

however, capacitor is working

.options cshunt = 1e-13

Thank you in advance,


texts:
I'm looking for building a power supply circuit that will convert 230VAC to 5VDC in order to power up an Atmega328P. I also want this to be as small as possible.

I know a transformer is one option but since I want to shrink it I was concerned about using a 5.1V zener diode.

Here is a schematic I found:

But how much heat will the the capacitor/diode produce? Is it more efficient to use a transformer instead?


texts:
In my design - rugged computer - I have connected the digital gnd to the isolated CANbus gnd by mistake.

Does the CANbus standard state that it has to be isolated?
Can that connection harm the CANbus?
Can this connection harm the computer?


texts: pic24fj128ga310 uart not working in application, but works with PuTTY

texts:
I'm trying to connect a PIC24FJ128GA310 mounted on an Explorer 16 board with an embedded wireless module. I have been able to set up both to communicate perfectly well with PuTTY (an equivalent to Hyperterminal), but they won't communicate with each other!

I haven't configured UART for a microcontroller before, but here is my set-up code (which works for PuTTY):

   RPOR8bits.RP17R = 5; // RP5 as U2TX mapped for peripheral pin select
   RPINR19bits.U2RXR = 10; // RP10 as U2RX mapped for selectable input source
   U2BRG = 25; // 9600 baud rate
   U2MODEbits.UARTEN = 1; // UART2 is enabled
   U2MODEbits.ABAUD = 0; // Auto-baud disabled
   U2MODEbits.RTSMD = 0; // 0 = Flow Control and 1 = Simplex
   U2MODEbits.BRGH = 0; // Low baud rate
   U2STAbits.UTXEN = 1; // Transmit enabled

Can anyone help? I have tried both straight-through and null modem cables. The microcontroller is able to show reception of a signal on the U2STAbits.URXDA 'Receive Buffer Data Available bit'.

I can send and receive a string of three character maximum, if flow control and echo settings are the same at both ends, and I terminate the string with '\0'. No hardware is connecting the two except for the RS232 cable and null modem adapter. However I need to reset the microcontroller after each attempt in order for it to show a signal received again. Why do I need to reset it, and why is 3 the maximum number of characters?

When I say it works with PuTTY, I mean that using this equivalent to Hyperterminal I am able to send messages to the microcontroller which are displayed on the Explorer 16 LCD display with no problems (if it echoes the characters received back to PuTTY).

*RESOLVED: it was a receive buffer overflow. @Madmanguruman I tried answering but the website won't let me for 8 hours after posting the question, so will do it later...


texts:
Actually, we have 1x30HP, 2x10HP motors working at our workplace. When we start the motors there is a lot of torque generated due to which our grid supply charges us penalty every month.

We need information about the device(s) that are used to control the torque.

While doing some research, I got to know that I can get myself set up control panel that has capacitors either separately on each motor or on my 100kVA transformer. This will control the torque as well as give me saving on electricity bill.

Kindly help in this regards.


texts: Synthesizing this simple analog notch filter?

texts:
I want to synthesize this simple analog audio filter which is a notch:

The inductor with resistor creates a simple one-pole low pass filter with the cutoff frequency at:

fc = 1/(2pi L R)

The capacitor with the resistor creates a one-pole high pass filter with the cutoff freq at:

fc = 1/(2pi C R)

So is synthesizing this circuit as simple as just running the input through both filters and summing it together?

ie.

onePoleHPF.setFreq(1/(2pi*C*R));
onePoleLPF.setFreq(1/(2pi*L*R));

output = onePoleHPF.process(input) + onePoleLPF.process(input);

Or is it not really that simple? Do I need to "weight" their contributions or gain scale them somehow to ensure I'm not adding gain at any overlapping frequency? If so, in what proportion? Like

output = onePoleHPF.process(input * 0.5) + onePoleLPF.process(input * 0.5);

I think one of these two approaches is correct because parallel elements share the same voltage across them so I think the input voltage is just split 50/50 between the two pathways.

Or will this not work and I need to create a completely new filter to get the right output? If so, how would I get a transfer function to make this work?

EDIT this is inserted after I got an answer from user287001:

The answer was what I needed.

The principles I used come from: https://www.dsprelated.com/freebooks/pasp/String_Excitation.html. If I have two resistors in series of identical impedance at that point instead of one resistor (more accurate for my simulation) like this:

(Sim from https://www.falstad.com/afilter/)

Then the equation becomes:

\$V_o(s) = V_i(s) * \frac{2R}{2R+\frac{1}{\frac{1}{sL} + sC}}\$

Substituting \$s = \frac{1-z^{-1}}{T}\$ where T is the sampling period and having Wolfram Alpha simplify:

\$V_o(z) = \frac{2 R V_i(z) (C L z^{-2} - 2 C L z^{-1} + C L + T^{2})}{2 C L R z^{-2} - 4 C L R z^{-1} + 2 C L R - L T z^{-1} + L T + 2 R T^{2}}\$

Multiplying both sides out I get:

\$2CLRV_o[n-2] - 4CLRV_o[n-1]-TLV_o[n-1] + 2CLRV_o[n] + TLV_o[n] + 2RT^{2}V_o[n] = 2R (V_i[n-2]CL-2CLV_i[n-1] + V_i[n]CL + V_i[n]T^{2})\$

Then to isolate for \$V_o[n]\$:

\$V_o[n] = \frac{2R (V_i[n-2]CL - 2CLV_i[n-1] + V_i[n]CL + V_i[n]T^{2}) - 2CLRV_o[n-2] + 4CLRV_o[n-1] + TLV_o[n-1]}{2CLR + TL + 2RT^{2}}\$

Does that look correct? Thanks a bunch.


texts:
I have a simple circuit I built using a 7-segment LCD glass display and an ATTiny (just a simple timer for now). I was hoping to use the setup in a low power, single coin cell device (3.3V - 2.7V), but then I noticed that the recommended voltage on the LCD is 5V. I looked for lower voltage LCD panels (they use them in the little freebie calculators that give away, and those have little coin cells) but either I'm looking in the wrong place or they don't exist.

Never mind, I just tried using lower voltages, and I can almost get it usable at around 3V by putting a large (\$>10M\$) resistor from the signal pins to GND (somewhat legible at 2.9V and 50Hz PWM at 50% duty). I thought this might work because I think the segments are capacitive so the resistor increases RC and causes the segment to stay lit longer.

So my question is, does anyone know if there is a secret to getting these LCD panels to work at lower voltages? Ideally I'd like to get down around 2.5V and still somewhat readable, and I imagine it's possible since I've seen simliar devices that must be working from small 3V batteries. Or am I barking up the wrong tree and there exist LCDs somewhere that already use a lower voltage?

And before I get "there are 3V panels listed on Mouser, Digikey, etc.", I see that some of them come up as such in the product databases, but they are not <3 digits (I only need 2 digits) and the datasheets/technical drawings/whatever all still list 5V anyway, so I'm guessing they are all the same.


texts: Hacking Dell charger to run directly from an external 19.5V power source

texts:
I needed to power my Dell laptop without having 220V (because my inverter is burnt in the middle of nowhere) in my van.
By using a boost converter that can deliver the required power, I simply set the output voltage to 19.5V and used a spare cable to deliver the power to the laptop. Without the middle pin connected I knew that laptop won't be able to communicate with the charger, therefore it will refuse to charge the battery, but that was okay.
However, after a while I discovered that Dell laptop was degrading its performance by around 3/4 if an original adapter is not found. The only solution at this point is establishing the required middle pin communication.
Is it possible to establish the Dell Charger Identification without using special tools and electronic components?


texts: How much shielding does an ungrounded metal box provide? That is, a circuit is in a metal box but the box is not connected to either circuit ground nor externally earthed


texts: how to create electronic switch cut off PV from MPPT charger when no battery connection

texts:
MPPT chargers are sensitive if PV is connected without battery connection. MPPT will be destroyed.
So I want put electronic switch on MPPT PV input in a relation with battery voltage
.
No voltage on battery input no connection to PV input. PV current can be up to 40A,150V. And battery voltage from 10V to 30V. I can put relay but there is no space in MPPT and relay consume more power.
Can somebody advise mosfet solution for such idea. Thanks, and sorry for to big jpg.


texts: Using Dynamo Pull Strings to Charge 9 x 3.6 V li-ion batteries @ 120 mAh in Series

texts:
This question has several parts. I ordered this pull string operated flashlight --- http://bit.ly/t1lZF1 --- which charges this coin cell battery --- 3.6 V lir 2450 lithium ion battery 120 mAh ---

Like these

The battery is charged by the pull string. There is a switch which uses this battery to power three LEDS.

I want to use this battery to power something with a higher amperage rating (ideally a cell phone).

I am wondering first whether it's possible to connect these coin cell batteries in series to get a 3.6 V output @ 1080 mAh.

Next, would I have to charge them all individually in their respective pull string charger circuits and then connect the charged batteries to achieve the higher amperage?

Lastly, I wonder if I could replace the coin cells with another Li-ion battery that outputs 3.7 volts at 1000 mAh.

My guess is that that is a dumb question as both battery types require a different charging circuit, and that my best bet is to connect them after they're charged.

Hopefully someone can shed some light,
thank you so much,
M


texts: How do I replace a CdS sensor in a circuit with an ALS replacement?

texts:
I am wanting to replace a resistor in a 555 circuit with a light sensor, but don't want to use the traditional CdS cell.  I'd like to use an ALS such as the Everlight ALS-PDT144-6C/L451.  This is the example circuit I'm basing it on, trying to replace R1. The supply voltage will also be a 3V coin cell.
I'd like to know how to choose the correct ALS to provide a similar response to a CdS cell in R1 that ranges from ~1k dark to ~10k light.  Is there a simple method to choose the ALS parameters, and will I need to tweak the other resistor in the circuit?


texts: I just need to know who in the USB communication must open the pipes. Endpoints are already configured, descriptors was sent and now there should be a process of pipes opening (between correct endpoints). Who opens these pipes?


texts: Laplace transform - How to determine the initial conditions of the derivative functions

texts:
I m trying to get the transfer function of this circuit. I do it essentially for fun. I clearly a newbie about Laplace's transformation. Nevertheless here is the circuit :

Here is the differential equation :

As you can see, I tried to use the Laplace's transform to get the expression of the transfer function Ic(s)/Vin(s) in the s-plane. But the Laplace transform depends on the initial conditions of the systems which seems clearly logical. Nevertheless I have some troubles to determine the value @ t = 0 of the derivative functions of ic(t) and Vin(t). Actually I would like to simulate a step reponse. If it is a step response I want to say in theory that Vin'(0) is equal to infinite. What about ic''(0) and ic'(0)... Is there a way to know what could be those values ?
Thank you very much and have a nice day.


texts: How to choose between PCIE and USB3 in a CPU pin?

texts: While looking at Validation Reference Platform for 11th Gen Intel CPU (Tiger Lake UP3), I noticed that some pins for the MCP (Multi Chip Package, which is a package that includes PCH+CPU on the same chip), I found out that some pins can be used both as PCIE and USB3. I was wondering how we choose what protocol can be used each time?


texts: Is 1 Hz equal to 1 rotation of a motor shaft?

texts: I'm rather new to the world of electronics but I have been trying to find the frequency of a DC motor. I've found that 1 hz is equal to 1 revolution per second, but does that refer to shaft rotation or something else because it seems almost too easy if thats the case. Thanks for any tips!


texts: Protecting microcontroller from inputs rising faster than Vcc

texts:
I have a microcontroller (ATMEGA328) that I'm using to do analog data acquisition. The problem is that I want my ADC values to be referenced to a regulated external source that is ~3V, but that source rises faster than my power supply. Since the microcontroller has ESD protection diodes like shown, I think it is likely to blow up when the circuit starts. Is that true? If so, how can I create a low impedance path (<32 Ohm) between ARef and the external source, but still protect the circuit?

The external source is part of an irreplaceable system, so I don't want to just put a Schottky to VCC since that might overdraw the external regulator.

I thought perhaps an n-channel MOSFET with the gate attached to VCC between the pin and the reference?

simulate this circuit – Schematic created using CircuitLab


texts: Is it dangerous/harmful to increase the voltage supplied to a 12v electromagnet?

texts:
I have a 12V-rated electromagnet which I bought online. As it isn't strong enough for my needs, I tried applying a higher voltage (~20V) which did make it stronger.
It does get a bit warmer after a while but I wanted to know if apart from the additional heat, such an increase in voltage could harm the magnet, as I know that when building my own electromagnet, I can increase the voltage as far as I want as long as the heat doesn't become a problem.


texts: pass thermocouple K type through d-sub and circuit box - what might be error?

texts:
What might be temp error if I'll pass my TC through simple d-sub (green & pink) and from my circuit box (blue) to destination device (yellow) I want to use copper wire, wire lenght between them will be about 1-1,5m, both of them will be same environment.
I alredy have special TC connector (orange), they are expensive hovever it's in variable environment and 2-3m form my curcuit box (blue).

I want to do it because it will simplify my harness but I'm not sure is it worth. I know there are also special thermocuple pins for d-sub but they are so expensive.


texts: A question about a step-down transformer with its secondary winding shorted

texts:
Above is a transformer with its primary and secondary windings. I just wrote my understanding about a transformer very shorty before my question:

Neglecting losses, we can write the voltage and power unity equations as:

Vs = (Ns/Np) * Vp
Vp * Ip = Vs * Is

It seems like; as long as the Vp and (Ns/Np) ratio are the same, whatever the load R is Vs will be the same. Only the current drawn will change.

And if the above argument is true the power dissipated in secondary part is:

Ps = (Vs^2)/R

And if R goes to zero or should I say the secondary winding is shorted, Ps goes to infinity which means this secondary winding would burn.

I have the following questions:

1-) Since there is power unity i.e. Pp = Ps; would that mean if the secondary winding is shorted, would the primary winding burn as well?(I'm asking because the interaction between the windings is electromagnetic which could be a different phenomenon)

2-) If the conclusion is primary winding would burn as well, is that enough to add a fuse to only before the primary winding but not secondary winding?


texts: How do I use a button to wake up an atmega32?

texts:
Sorry for any noobiness, I'm more of a software engineer.
How do I use button interrupts in general?
As in, if I put my microcontroller to sleep, I'd like a button to wake it up.
How should I go about doing this?
Edit
Adding this to main, thanks to @jippie
DDRD &= ~(1<<PIND2)
PORTD |= 1<<PIND2
GICR  |=   ( 1 << INT0 );   // Enable INT0
MCUCR = (0<<ISC00)|(1<<ISC01);

sei();

And this outside of main
ISR(INT0_vect) {
  sleep_disable(); // If ISR got called while it was sleeping, this would work
  lcd.string("works");
};

ISR does work, but only if the device is not sleeping.
FIXED
Changing from INT0 to INT2 ( and moving from PIND2 to PINB2 ), it works...
According to documentation, INT0 and INT1 use level interrupts but PINB uses edge... so.. that's maybe why?
My voltage meter drops to .2 while in sleep mode, then wakes up from ISR.


texts: Driving 5V powered relay module from 3V3 powered microcontroller

texts:
What I'm trying to do
This question is about the use of any 3V3 supply microcontroller to drive 5V powered relay modules which are available from many suppliers. I have provided details below of the microcontrollers and modules that I am specifically using, but the question is a generic one.
In my application I have a Raspberry Pi Zero and an Arduino that I'd like to use for an automation project. I have two of the SSR modules (HCMODU0115), like the one in the picture below.

I connected them to my GPIO pins, kind of like the picture below, and activated them, but I noticed that both the LEDs were shining regardless of output provided by my controllers. Only that when it was active the LED were like 100% bright, and when inactive they were at half brightness, but still turned on.

Out of curiosity I decided to connect a pair of diodes in the channel inputs, like the picture below, but then the relays wouldn't activate at all.

Then I decided to invert the diodes and suddenly the relay module started working again, but this time the LED1 and LED2 were working as they should, being lid up only when active.

This brings up two questions for me.
First, is it safe to directly connect this relay module to my controllers? Why are the LEDs always turned on?
Second, Why did it only work when I reversed the diodes? It has something to do with the direction of the electron flow?


texts: I have heard the term Node in the Power Grid or Smart Grid, what does this node compose of? Is it a group of houses connected to the same substation?


texts: Would it be possible to charge a Ring video door bell from solar power, but using the doorbells external pins for the wiring of a 8 to 24v ac transformer. Say using a 12v solar panel, would regulation be necessary or can a simple circuit handle the swing in voltage from the panel? Would a simple circuit be economically comparable to a H-bridge as a possible prebuilt solution? What would an example of such a circuit look like?


texts:
I want to pick up atmospheric noise at 7 MHz and multiply that up to 400 some odd MHz. The reason to do this is I have a USB receiver for digital television that I would like to open in windows and grab some random numbers using the noise.

What sort of tools and supplies do I need to achieve this task?


texts: Single key not working on DIY mechanical keyboard (xd75re PCB and Switch both work)

texts:
I have assembled my first mechanical keyboard using the xd75re PCB. I used a plate mount, and all of the switches were installed without issue (this PCB has hotswap). When I used keyboardtester.com to test the keys (after assembly), I found that there was one key that wasn't registering at all (from the factory, it was the letter 'D' in a qwerty layout).

I tried the switch in other locations and it worked. I also shorted the contacts for the key using a paperclip, and it registered the letter ('D'). Yet, when I put the switch (or any other switch) into that location, nothing registers.

I thought that the pcb might not be close enough to the plate for the switch to reach the contacts, but all the keys around it work and the plate is parallel to the PCB. Tightening the closest bolts made no difference holding the two together did not make the switch work either.

I'm at a complete loss for what to check next. Everything else about the PCB and the switches work perfectly. I am able to type on the rest of the keyboard and was able to flash the microcontroller without an issue.

Any help is appreciated.

UPDATE: None of the switches were properly seated (from inexperience generally and with hotswap in particular), which caused the plate to bend away from the PCB. After testing again, with the plate and PCB parallel and all the switches flush, the 'D' key still does not work. I've re-checked the switch and the PCB, both work separately.


texts:
We have designed quite a few FPGA-based boards, and so far, we have used a lot of bypass capacitors. Our rule of thumb was, "as many as we can".

In our next design, we would like to reduce the part count. Since BGA packages are quite dense, the distance between several supply pins (say for the 1.2V VccInt rail) are quite small (<1cm in most cases).

Would it make sense to replace 4 100nf capacitors for 4 supply pins with a single, larger bypass capacitor, located such that it is as equidistant to the 4 pins as possible?

EDIT: Here's the source of my confusion: Xilinx has a PCB design guide for Spartan 6 devices here. For example, if you look at Table 2.1 on page 14, for an LX45 device with FGG484 package, for the VccInt rail, it recommends a total of 1 100uF, 1 4.7uf and 2 0.47uf capacitors. The thing is, this device has 20 VccInt pins!. Is it really recommending using 2 0.47uf capacitors for 20 pins?

To add to the confusion, Xilinx's own evaluation board for the same device has 6 2.2uf, 5 10uf, and 1 470uf capacitors for the same 1.2V VccInt rail!


texts: Single LED connected in parallel to conducting wire does not light up

texts:
LED connected in series to resistor. All is well.

This doesn't work.

Neither does this.

This would be the schematic diagram.

simulate this circuit – Schematic created using CircuitLab

Why doesn't it light up? Is this the absence of a load, even though the breadboard connection has a minimal resistance?

Conclusion

Straightforward answer: Wire without load sucks up all the current because its resistance is approximately 0 (see Ohm's law V = RI). Points which have approx
0 resistance between them are called electrically common.

A bit more elaborate: The voltage on the wire is equal to 0. The LED leads are connected to this wire, hence no current can flow through the LED (analogous to a bird sitting on a high voltage power supply wire).
Why is V = 0 in the wire? Because there is no resistance. If you measure the pressure of a flowing river without any obstacles between two points of
not inmense distance between them, they are practically the same. The water can keep on flowing though, because
the initial pressure from the potential difference between the mountain top and sea level (the power source) produce the current. If there's an
obstacle in the way, say a small dam, water can accumulate (as well as electrons can do) on one side of the obstacle
(the resistor) creating a potential difference on each side of the obstacle. Therefore a voltage builds up. Resistors can be thought of as narrowings
of a pipe, but as such, the water analogy would fail, because Bernoulli's principle would come into consideration. Even though the voltage drops just like the
as pressure drops in the narrowing of a pipe, in a circuit it happens before and after the resistor, not only within it. With Bernoulli, current
(mass/time) is equal everywhere. That is why the water molecules are accelerated in the narrowing in order to get the same amout of mass through.
In circuits it is more like closing of lanes in a road due to an accident. The road gets narrower and technically the drivers would have to
accelerate in order to get the same amount of cars through in the same time interval. In reality, they slow down, producing a traffic jam, and with so
a "car potential difference" is built between before and after the accident site.


texts:
I am testing a board that has external SRAM. Apparently the SRAM is relatively sensitive to the soldering heat from the manufacturing process, and so careful testing must be done to check integrity of SRAM for newly manufactured boards.

What is the best (bare-metal) way to test SRAM? I have a driver that initialises the SRAM for read/write access. My first thought is to run tests such as:

1) Set all bits in SRAM to 1, and check that the SRAM was properly written.
2) Write the digits of Pi in SRAM, and check that the write was done properly.

Are there other kinds of tests I should consider?


texts: Where do these three dc error input voltage comes from?

texts:
The book said that there are three unwanted dc error input in an differential Amplifier:

Wherein:
$$I_{in(bias)} = \frac{I_{b1} +I_{b2}}{2}$$
$$I_{in(off)} =I_{b1} - I_{b2} $$
(V_in(off) is input offset voltage)
I don't understand what each error voltage refers to. For example:

Why would V_1err becomes automatically zero when resistance is the same regardless if current I_b1 and I_b2 is the same or not?

Why would V_2err becomes zero when current is the same regardless if resistance Rb1 and Rb2 is same or not?

What is the difference of V_3err from the two error voltage above?


texts: Electric shock : what risk working with a 6V power supply?

texts:
I am planning to cut the end connector of this power supply to work on it and build a dummy 4 LR6 1.5V pack.

But I wonder : is there a risk to have an electric shock manipulating those wires while the power supply is plugged ? Let's imagine that my pack is done and I touch the metal parts when the power supply is plugged into the wall.

What about using the same power supply with just 1A (item or item) or 2A power (item or item)

I wonder because I've read in many places things like the following (Google traduced) :

  AC, we can retain these values:

  1 A: Stopping the heart
  40 mA to 75 mA: irreversible cardiac fibrillation threshold
  30 mA: Threshold of respiratory paralysis
  10  mA: Threshold not release, muscle contraction
  0.5 mA: Threshold of perception, feeling very low

  DC, we can retain these values:

  130 mA: Threshold of cardiac fibrillation
  ??? : Threshold not let go
  2 mA: Threshold of perception

So... with my 3A or even a 1A power supply... I'm worried.


texts: Can someone help me interpret these diagrams?

texts:
I am extremely new to electrical engineering, and I am using it for a personal project. I tried looking into circuit diagrams for a part(a pushbutton), and I don't recognize any of the symbols. Most of the resources I have found cover general circuit diagram symbols like diodes and switches. Can anyone point me in the right direction?
edit: The part is MPSA-22 E08-O-150
https://www.knitter-switch.com/eng/Series/17


texts: How to determine the model/type of SMD Capacitor and EMI Suppression Filters on a laptop PCB?

texts:
I am a newbie to PCB electronic components and I have the following questions on SMD on a laptop PCB.  The picture below shows the SMDs around a m.2 connector for SATA SSDs.

1) The SMD in the red rectangle are ceramic capacitors (earth colour with golden end connectors) ? And the ones in the green rectangles are EMI suppression filters (black colour with silver end connectors)?

2) How can I determine the type/capacity of these SMD and where can I find the catalogues of manufacturer on the net?

Thank you very much!


texts:
I am trying to understand power transformers practically.

I have an inverter that outputs 12V AC. I want to step this up to 120V AC.

My load will just be a resistive load that takes no more than 200W (like 2 light bulbs).

Does this mean my transformer has to be rated at least for 200VA?


texts: Strange behavior in a non-inverting op amp

texts:
I've designed a simple non-inverting amplifier to interface a 3.3V MCU and a 5V signal to a motor controller. When I first tested with the MCU and the desired values to the low-pass filter, I noted that something was strange. This way, I decided to perform a test using the circuit below, where the PWM is from an Arduino.

The table below shows my results:

I tried swaping the PWM + filter for a 1k pot but the results were similar. I also tried swaping the multimeter and the op amp, nothing changes. Some tip why I'm having this behavior in this circuit?


texts: max. output current of USB port and damage to the USB device

texts: A USB host can generate up to 500mA. Would it mean that the host device is never damaged by a short circuit on a USB guest device? When I play with Arduino, I sometimes see that my PC freezes. The reason was always short circuit over the Arduino board. So often I wonder if I need a tool to limit the current output of my P to protect it from being fried.


texts: How does wiring resistors in series and parallel affect their errors?

texts:
In an experiment I am conducting, I am trying to measure low currents by wiring a radio device in series with a small-resistance resistor setup, composed of 9 of 1 ohm +/- 5% resistors in series and parallel as shown below, resulting in a total of 1 ohm.

By my understanding, resistors are manufactured such that there is a distribution of values centered by the marked value with most of them lying in the +/- 5% range, but in theory, there will always be resistors outside such range.

While in theory (by error analysis formulas) my series-parallel setup would have the same error as each one of the resistors, intuitively, doing so is in essence taking the average of the 9 resistors and thus tightening up that distribution curve, such that the error %age is lowered. This was my intent in doing those 9 resistors as opposed to only 1 resistor.

So my question is: What is the error of the 9 resistor setup? Theoretically, I calculate 5% but by intuition, it is less. If it's the former, I would like to know why, and if it's the latter, I would like to know how to find the final percentage error in this situation. I hope it is the latter so that I can qualify my experimental technique (oh and speaking of which, please assume that the voltage drop of the resistor setup does not drop the current through the circuit).


texts:
This is an article about bilateral feedback analysis.

Could anyone explain the what is meant by this sentence?

  The most important fact about this circuit is the symmetric bilateral transmission through the feedback impedance \$Z_{F}\$ albeit the forward amplifier is still unilateral.

What does "symmetric bilateral transmission" mean here?

Thank you.


texts: What does the term 'lifetime' mean for electrolytic capacitors

texts:
I am making a circuit for a car and a regulator is used to get from 12V to 5V. This regulator is surrounded by two 10 uF electrolytic capacitors rated at at 25V. These capacitors have a 'lifetime' of 2000h. Does this mean that there is a 50% probability that the capacitors will fail after 2000h of usage?

Since the circuit is for a car the longevity and integrity of the circuit is important.

This is the datasheet.


texts: Electrical Part on Connector Board ME302C for Asus Memo Pad

texts:
I have some unusual question: does someone know [![Part1][1]][1]  what kind of electrical part is on that pcb (encircled)? This is a connector board (ME302C) for ASUS MEMO PAD. The part is unfortunately broken, so I cannot see any letters or something else on it. Thank You!
Here is a larger picture:


texts:
The description for T_e is missing on this page.

Source: https://se.mathworks.com/help/physmod/sps/ref/steppermotor.html