texts:
I have a doubt about the working principle of a simple Radar.

Consider a stationary object, which does not move with respect to our transmitter. We send an electromagnetic wave to it, and it will reflect it with the same frequency (since it is not moving). This wave will return to the transmitter with a certain phase shift from which we can evaluate the distance between the object and the transmitter.

But we know that in general the composition of an incident wave and its reflected wave generates a standing wave. Therefore, why at the transmitter we get the incident and reflected waves (from whose phase shift we evaluate the distance), instead of a unique standing wave?


texts:
I have this surface mount switch and noticed that the lead type is slightly different than other similar switch types. I know that it's not a J-Lead or Gull Wing as J-Leads typically protrude from the surface of the package.

Would it simply be called an SMD terminal, tab, pad, etc? Or would there be a proper name to this? Would anyone know if there's specific terminology for this lead?

I'm not designing anything, I'm simply curious about the terminology.

Here's the datasheet of the device in question.

When I compare the joystick leads to that of this JEDEC standard, the pins do not form into a J-shaped configuration with the portion of the lead in contact with the printed wiring board.


texts: how does capacitor work ? how do they conduct electricity ?

texts:
Sorry, i am novice in electronics, trying to understand basic fundamental of electronics.
1. How does capacitor conduct current when two plates aren't physically connected.


texts:
Brief background first; I have data from CAN bus of a steering angle which is obviously in hex. The steering angle covers two bytes of a message. The specification document I have says that those two bytes form a 16-bit signed int which are the steering angle which a prescaler of 1/1024, that's all I have got (I don't have access to the source). What I am trying to do is to convert those hex values into signed int, however I am not sure how to do it correctly.

A small section of the CAN message within short time period (we are focusing on byte 2 and 3):

can0  700   [8]  00 00 99 93 55 0B EF BD
can0  700   [8]  00 00 95 95 10 0C 17 BE
can0  700   [8]  00 00 6F 97 FB 0A 17 BE
can0  700   [8]  00 00 39 99 5C 0A 40 BE
can0  700   [8]  00 00 AD 9A 62 08 EF BD
can0  700   [8]  00 00 EF 9B B5 08 40 BE
can0  700   [8]  00 00 CA 9D 9A 09 17 BE
can0  700   [8]  00 00 3E 9F 55 09 40 BE
can0  700   [8]  00 00 91 A0 ED 09 17 BE

As far as I know, typically, data in CAN messages follow this format: one byte for the actual data, one byte for the number of overflows.

For example, let's take an unsigned int of a value of 2000. Assuming byte #0 is for overflows, byte #1 is for actual data, we get:

CAN message -> [07, D0, x, x, x, x, x, x]

07 indicating that there have been 7 overflows, D0 indicating the remainder is 208, therefore:

7*255 + 208 = 2000

I understand how to do it with unsigned values. But this time in my scenario I am dealing with signed values. I am assuming one byte is for overflows, one byte is for the remainder, however I am not sure.

How are overflows calculated for signed values? Is it overflow += 1 when value > 127 and overflow -= when value < -128? Does it even make sense for overflows to have signedness?
How can I convert these bytes into signed decimal in C/C++? Let's say my byte value in hex is 91. Last time I tried storing it in int and printed it out, it printed out 145 (normal binary) and not -111 (2's complement). How can I enforce 2's complement (if that makes sense) in my code?
Could I be interpreting the byte format wrong? All it says that these two bytes represent the steering angle and that the steering angle is int16_t. I have monitored them change in real time and one of them changes erratically, almost like jumping from 00 to FF, whereas the other one is increasing/decreasing slowly and almost linearly with time. Ideas?

I am really stuck here, I don't even know if I am going in the correct direction.. Any suggestions and help are really appreciated!


texts: Post-Transformer RMS Voltage for This Circuit?

texts:
I am confused here. For the below circuit:

simulate this circuit – Schematic created using CircuitLab

Ripple voltage is given as 1V peak to peak, Vo = 15V DC. I have assumed a 0.7V drop across any given diode. Please note that I was a little hasty in my construction. I do not know the values of the capacitors or resistors yet. The transformer line has 60 Hz frequency.

I'm trying to find the transformer rms voltage to the circuit where the turns of the transformer are not known.

I calculated: 2*16V + 1.4V, since there are two diode drops, the center tap configuration giving two instances of the maximum load voltage, which is 15V + 1V ripple. This gives 33.4V, which, dividing by sqrt(2) for rms gives about 23.6V (rms). However, the given answer is 22.9V (rms)

What am I missing in my calculation? Any clarification would be greatly appreciated!


texts: Process statements and sequential execution in VHDL

texts:
For process statements in VHDL, it is said that the order of execution is sequential. My question is, are the signals a, b, and c assigned to their new values concurrently, or sequentially?

process(clk) is
begin
    if rising_edge(clk) then
        a <= b;
        b <= c;
        c <= a;
        a <= c;
    end if;
end process;

If this is sequential, I must say that after the end of the process, a is equal to b, b is equal to c, and c is equal to b, because we assigned b to a before we assigned a to c.

And finally a must be b, because c is assigned to b before last signal assignment. However, this does seem impossible to implement in hardware.


texts: HV9961 led driver: trying 170V led output

texts:
I face to some issue with my prototype based on the HV9961 (see picture).

I replaced L1 by a 1.8mH power inductor and R1 by a 68k resistor. Those values came from HV9961 datasheet formulas for a 170V led output. Also i added a potentiometer between R2 and the LD pin to adjust the VLD voltage between 0.2V and 1.6V. The output led current depends of the VLD voltage. R6 and R6a have been replaced by a 0.3 Ohm to setup ILED at 920mA max.

After power on, my design works very well. The 170V led string sees a 350mA when VLD is adjusted at 0.6V and brights fine. But after 5-10mn, D1 breaks! I decided to change D1 by the same reference STTH2R06H (fast recovery diode 600V 2A). The problem is the same, D1 is destroyed after 5 min.

Could you help me to find the good recovery diode ? and explain why it breaks ?
|

HV9961 datasheet
STD5NM50 datasheet
STTH2R06 datasheet


texts:
I've tried to make this circuit, a 1.5V audio amplifier.

I've omitted P1 and directly connected C6 to C3 as stated in the page.

I've also omitted the switch SW1 and connected a wire for the path represented by the dashed line(ganging?)
Is this the right thing to do?

Since I can't afford a CRO, what is the next best thing I can do to debug this circuit.
Any help appreciable!


texts: Shift Registers - How does one pronounce QH'

texts:
In the datasheet for the 74HC595 shift register, pin 9 is labeled "QH'" (not to be confused with pin 7, labeled "QH" without the "'").  I understand that this pin outputs the current contents of the register as new data is shifted in for the purpose of daisy-chaining registers, but...

What I'm not sure of is, what would a professional engineer call this pin in verbal conversation with another engineer?  Maybe "Dump pin?", or "Exit strategy?", or maybe "Que Aych Huzzahh!"  Probably none of the above, which is why I'm asking.

Thanks.


texts: Do I need a resistor between my battery and servo?

texts:
I'm trying to better understand Ohm's law as it relates to general microelectronics projects by taking a simple project I'm working on now.

I have a 9V battery powering a small tower pro sg90 servo. The specs on the motor is that it takes 5Volts, and has a running current draw of about 220 milliamps (+-50). So if I use ohm's law to calculate the resistance needed if I'm supplying 9V, that'd be 9V=.220*x or 40 ohms. That seems really small to add a resistor on. The smallest I can find are about 110ohm resistors.

Should I add a resistor before the motor? And if so, how do I calculate what size I need?


texts: Digital to Analog Converter math question

texts: I'm having a hard time understanding how to calculate this. I'm getting an answer of 3.33K which is not listed in the answers. Am I doing something wrong here or is the answer not given?


texts:
I have three questions that have been troubling me for a long while:

We say that, in a Bode plot, there is a drop in gain of 20 dB per decade whenever a pole is encountered. But aren't poles defined as the values of \$s\$ which make the transfer function infinity? So why doesn't the gain go up at this point instead of going down?
Physically what happens when we feed a system with a pole frequency?
Also, consider a transfer function \$1/(s+2)\$. The system has pole at \$s=(-2+j0)\$. That is, for the pole, \$\sigma=-2\$ and \$\omega=0\$. But when we apply a sinusoidal signal to its input and draw the Bode plot, why do we say that there is a pole at 2 rad/sec (even though, for the pole, \$\omega=0\$ and \$\sigma =-2\$)?


texts: Short circuit protection for my voltage source

texts:
Can someone suggest me some short circuit protection schematic? I have 12V DC source (1.2A max. output current) and I will use it in some amateur electronics projects, but I would like to add some short circuit protection (between voltage source on one side and load on other side). I found some schematics on web involving BJTs but I would like to see opinion of professionals here :)
Thanks in advance.


texts: (When) Can I use Cat5e wiring to carry a POTS signal to a DSL modem?

texts:
According to this answer by @asndre,

  It is very bad idea to use Cat5e-based wiring/cabling to establish a
  xDSL connection.

However, my telephone/internet provider technician recommended -- and gave me 100ft of -- Cat5e cable to carry the telephone signal to my DSL modem so that I could move the modem. Others have had the same experience.

Of course phone/internet provider technicians can be wrong. (Mine was wrong in saying that the WiFi modem he installed would reach the other end of the house with no problems.) But they could be right. Hopefully they have tried what they're recommending and found it to work.

Why could Cat5e for a DSL connection be a bad idea?

  Cat5e wiring is not designed for so low frequencies and therefore does
  not feature an appropriate characteristic impedance (i.e. Z(f)) at the
  frequencies employed by xDSL which works in telephone line bandwidth
  (<20 kHz).

  Using Cat5e for xDSL also results in dramatical signal attenuation,
  about 3~5 times worser comparing with an appropriate cable/wire.

  To be short, POTN is about 600-Ohm techniques while Cat5e if for
  100-Ohm ones.

That sounds to me like the answerer knew what he was talking about. (He also said he had done testing that supported his conclusions.) However the original question was not about the suitability of Cat5e cable for carrying a telephone signal to a DSL modem, so that issue didn't get discussed much.

On the other hand, maybe the results of the impedance mismatch are such that it wouldn't affect actual DSL performance in a typical household? I understand that the effect of impedance mismatch could be signal reflection (causing distortion) and reduced power transfer (= signal attenuation?). This Wikipedia article section suggests that impedance matching to telephone lines in modern devices is no longer very important due to active amplification and filtering.

Does anyone have experience or insight into whether using Cat5e wiring to carry a POTS signal to a DSL modem causes noticeable problems?


texts: Piezoelectric Transducer, effect of voltage amplitude vs frequency of pulsing signal?

texts:
I am not an expert in piezoelectric transducers used for ultrasound applications so I am looking for some insight into the matter.

To extract the greatest amount of acoustic energy from the transducer is the frequency of the pulsing signal more important or is the amplitude of the pulsing signal.

For example assume there is transducer that has a resonant frequency of 12MHz is there a graph that would compare say perhaps the effect of 100V square wave centered around 10Mhz vs an 80V square wave centered at 12Mhz.

In general the question is does voltage amplitude play a greater role in a generating a stronger response from the transducer or is the resonant frequency of the applied signal more important?


texts:
I've implemented a driver for the Intel 8042 (keyboard controller in the IBM PC AT). The IBM 5170 (PC AT) Technical Reference served as my, well, reference for that.
The output port and the test input port both contain "test inputs" (pp. 1-44):

I assume the bits contain the current state of each line, i.e., clock and data.

But what are those "test inputs" at all? Why connect "test inputs," as for testing during initialization or something, to clock and data lines?
Also what do "(output)" and "(input)" mean?
Does this have something to do with the internals of the controller, that the clock and data lines exist in "input" and "output" forms, for instance? Or is it related to the command 0xab, "Interface Test":

  This commands the controller to test the keyboard clock and data lines. The test result is placed in the output buffer [...]

Even though that command returns five possible values, thus needing three bits of data for unique representation.


texts: Voltage regulator transistor circuit analysis (question about the emitter current)

texts:
To determine the value of the resistor \$\text{R}_\text{v}\$, we can use the formula that is given in the wiki page:

So, I did a little bit of maniplulation:

For the resistor \$\text{R}_{\text{v}}\$, we have:

$$\color{red}{\text{R}_{\text{v}}=\frac{\text{U}_{\text{R}_\text{v}}}{\text{I}_{\text{D}_\text{z}}+\frac{\text{I}_{\text{R}_\text{L}}}{1+\text{h}_\text{FE}}}\tag1}$$

Now, for \$\text{U}_{\text{R}_{\text{v}}}\$, we have:

$$\text{U}_{\text{in}}=\text{U}_{\text{R}_\text{v}}+\text{U}_{\text{D}_\text{z}}\space\Longleftrightarrow\space\text{U}_{\text{R}_\text{v}}=\text{U}_{\text{in}}-\text{U}_{\text{D}_\text{z}}\tag2$$

And for \$\text{I}_{\text{R}_\text{L}}\$, we have:

$$\text{U}_{\text{R}_\text{L}}=\text{U}_\text{out}=\text{U}_{\text{D}_\text{z}}-\text{U}_\text{BE}=\text{I}_{\text{R}_\text{L}}\cdot\text{R}_\text{L}\space\Longleftrightarrow\space\text{I}_{\text{R}_\text{L}}=\frac{\text{U}_{\text{R}_\text{L}}}{\text{R}_\text{L}}=\frac{\text{U}_\text{out}}{\text{R}_\text{L}}=\frac{\text{U}_{\text{D}_\text{z}}-\text{U}_\text{BE}}{\text{R}_\text{L}}\tag3$$

So, for \$(1)\$ we get (using \$(2)\$ and \$(3)\$):

$$\color{red}{\text{R}_{\text{v}}=\frac{\text{U}_{\text{in}}-\text{U}_{\text{D}_\text{z}}}{\text{I}_{\text{D}_\text{z}}+\frac{\text{U}_{\text{D}_\text{z}}-\text{U}_\text{BE}}{\text{R}_\text{L}}\cdot\frac{1}{1+\text{h}_\text{FE}}}\tag4}$$

Now, for \$\text{h}_\text{FE}\$ of the transistor we have:

$$
\begin{cases}
\text{I}_\text{C}=\text{h}_\text{FE}\cdot\text{I}_\text{B}\\
\\
\text{I}_\text{E}=\text{I}_\text{B}+\text{I}_\text{C}\\
\\
\text{I}_\text{B}=\text{I}_\text{BS}\cdot\left(\exp\left\{\frac{\epsilon\cdot\text{U}_\text{BE}}{\eta\cdot\text{k}\cdot\text{T}}\right\}-1\right)
\end{cases}\space\space\therefore\space\space\space\text{h}_\text{FE}=\frac{\text{I}_\text{E}}{\text{I}_\text{BS}\cdot\left(\exp\left\{\frac{\epsilon\cdot\text{U}_\text{BE}}{\eta\cdot\text{k}\cdot\text{T}}\right\}-1\right)}-1\tag5
$$

So, we get for \$(1)\$ and \$(4)\$ (using \$(5)\$):

$$\color{red}{\text{R}_{\text{v}}=\frac{\text{U}_{\text{in}}-\text{U}_{\text{D}_\text{z}}}{\text{I}_{\text{D}_\text{z}}+\frac{\text{U}_{\text{D}_\text{z}}-\text{U}_\text{BE}}{\text{R}_\text{L}}\cdot\frac{\text{I}_\text{BS}\cdot\left(\exp\left\{\frac{\epsilon\cdot\text{U}_\text{BE}}{\eta\cdot\text{k}\cdot\text{T}}\right\}-1\right)}{\text{I}_\text{E}}}\tag6}$$

Now, for a diode the relation between voltage and current is given by:

$$\text{I}_{\text{D}_\text{z}}=\text{I}_\text{S}\cdot\left(\exp\left\{\frac{\epsilon\cdot\text{U}_{\text{D}_\text{z}}}{\eta\cdot\text{k}\cdot\text{T}}\right\}-1\right)\tag7$$

So for \$(1)\$, \$(4)\$ and \$(6)\$ we get (using \$(7)\$):

$$\color{red}{\text{R}_{\text{v}}=\frac{\text{U}_{\text{in}}-\text{U}_{\text{D}_\text{z}}}{\text{I}_\text{S}\cdot\left(\exp\left\{\frac{\epsilon\cdot\text{U}_{\text{D}_\text{z}}}{\eta\cdot\text{k}\cdot\text{T}}\right\}-1\right)+\frac{\text{U}_{\text{D}_\text{z}}-\text{U}_\text{BE}}{\text{R}_\text{L}}\cdot\frac{\text{I}_\text{BS}\cdot\left(\exp\left\{\frac{\epsilon\cdot\text{U}_\text{BE}}{\eta\cdot\text{k}\cdot\text{T}}\right\}-1\right)}{\text{I}_\text{E}}}\tag8}$$

  Question: How can I find \$\text{I}_\text{E}\$? Can I make the approximation: \$\text{I}_\text{E}\approx\text{I}_\text{C}\$?


texts:
(I am learning the digital circuit design. Excuse me if this is naive question.)

From the Wikipedia, I found the following diagram about SIPO shift register:

As I understand, this shift register is made of DFF (D Flip-Flop). DFF is triggered at the rising edge of the clock period. So for each rising edge of the Clock signal, the data from the Data In will propagate through one stage of DFF.

My question is, since the Clock is shared by all the DFFs, when the rising edge arrives, all the 4 DFFs must be in triggered/transparent state. So what ensures that the data propagate through only 1 stage of DFF rather than 2 or more stages?

Let's say:

Td is the internal delay for 1 DFF stage to load data from D to Q.
Tr is the lasting time of the clock rising edge. See below pic.

I think to limit the propagation to 1 stage, it has to be:

Td < Tr < Td*2

Am I correct?

But in the link above, it says:

  In this configuration, each flip-flop is edge triggered. The initial
  flip-flop operates at the given clock frequency. Each subsequent
  flip-flop
  halves the frequency of its predecessor, which doubles its
  duty cycle. As a result, it takes twice as long for the rising/falling
  edge to trigger each subsequent flip-flop; this staggers the serial
  input in the time domain, leading to parallel output.

It makes me confused about a few things.

What does halves the frequency mean?
How could a DFF be characterized with a frequency?
Doesn't a DFF only work at the rising edge of the clock and in general don't care whatever frequency the clock is at?
And how could frequency be related to duty cycle? Frequency is related to period while duty cycle just means the percentage of one period in which a signal or system is active. I see no relation between frequency and duty cycle.

ADD 1

As Neil_UK said in his reply below, the above wiki quotation is plain wrong. And he has fixed the wiki page.

As EM Fields said in his reply below,

  ...nothing more can happen until the next rising edge of the clock,
  since the clock edge that did the work has already died...

Strictly speaking, there's no ideally vertical rising edge. There should be some Tr as shown in above illustration. I guess to limit the propagation of signal through DFF stages, the rising edge must last long enough for the signal to propagate through one stage and short enough for the signal not to propagate through to the next stage.

I just think this kind of control is too tricky/delicate to be true. But if it is true, how is it achieved?  (I just placed a bounty for this question.)


texts: GPIO Input fluctuating between high and low when no input is received

texts:
I posted this on the Raspberry Pi StackExchange but I feel as though it might be better suited for here, as the SE is pretty inactive anyway.

I've got a fairly simple circuit that I've made where a motion detector is connected to a Raspberry Pi B+ GPIO by way of a fairly long ~30ft stretch of wire. The detector is being powered by a 9V battery and the schematic is as follows:

I'm running a python script to pick up the motion and it is as follows:

import RPi.GPIO as gpio
import time
gpio.setmode(gpio.BCM)
gpio.setup(17, gpio.IN)
while True:
  print ("LOW","HIGH")[gpio.input(17)]
  time.sleep(.5)

I was getting an output that was consistently 9-11 HIGHs, then 9-11 LOWs then repeating, and I was wondering what was up so I disconnected the PIR motion detector, leaving the wire not connected to anything, and I got the same result: a consistent fluctuation between low and high.

From my research, LOW for GPIO is roughly <0.54V while HIGH is >2V. Measuring the difference in voltage between the wire and the Raspberry Pi GND pin (PIN 39) gives me 0.32V consistently, with no fluctuation. Why is this happening, and how can I fix it?


texts:
There is a electric field in the far zone of the rectangular aperture antenna as shown below.

Antenna lies along the xy plane.
$$E_{\theta}=\dfrac{jke^{-jkr}}{4\pi r}\dfrac{sin(0.5\lambda k sin\theta sin\phi)}{ksin\theta sin\phi}$$
$$E_{\phi}=\dfrac{jke^{-jkr}}{4\pi r} cos\theta \dfrac{cosh(\lambda k sin\theta cos\phi)-1}{\lambda k^2 sin^2\theta }$$

How can I find the first side lobe level of this kind of complicated pattern?


texts: How to design Zener diode for a kickback voltage protection of motor?

texts:
Vcc: 34 VDC
Motor load current: 5 A

How to design motor kickback voltage protection of Zener diode?


texts: calculating current draw for opamp circuit

texts:
I am trying to understand how to estimate the current drawn by the following opamp circuit and how much current the regulators for the +14/-14 rails should be able to deliver.

The opamp used is the NE5532. I've drawn the circuit in TINA-TI, and loaded the NE5532 spice model and then ran a transient analysis. The input signals for the circuit are sine waves with amplitude 2.8Vpp around 5V. When I zoom in on the plot I can see a steady current draw of 2.2mA on both the +14V and -14V rails.

Is this correct and realistic, and can I use that as a basis to determine how much current my regulators for the rails should be able to deliver?


texts: LCD Dimmer with Variable Resistance Circuit

texts: essentially I'm trying to make a very basic circuit where a 3.7 volt battery is wired to a liquid crystal display, (or LCD), and the brightness of said display is controlled by a pentiometer to variably resist voltage headed to the LCD display. In theory, twisting the dial should resist voltage going from the battery to the LCD thus darkening or lightening the screen. Unfortunately as of right now the display is either completely dark with the battery in or clear if the battery is out and the pentiometer does nothing one way or another. I have no idea how to fix this so any help would be great. Pictures of the circuit are below. Keep in mind in the pictures that the solder to the two pins on the pentiometer are not actually touching though that is how it appears. Thanks.


texts: Regenerative braking with electric bicycle hub motor

texts:
What kind of circuit would be required to implement a regenerative braking system on a electrical assisted bicycle with a motor like this?

The motor is brushless and the kit comes with a big ESC box. Regenerative braking was not an advertised feature.

As far as 'why do this': you could use it with a small battery for using energy (on the next hill) that would otherwise be waisted in burning up your brakes during long down hill stretches


texts:
I have a little hard time to understand how a CAN bus actually can work. I looks to me like a scenario where everyone is talking at the same time.

The CAN bus is simply two wires that everyone is connected to, CAN-H and CAN-L, right? If we have lets say four nodes on it, with ID's 1, 2, 3, and 4, just to make it simple. The priority of the messages are arranged from highest id to lowest, 4, 3, 2, 1, right? CAN-H is always oposite of CAN-L, when CAN-H is high, CAN-L is low, and oposite, right?

But how do CAN bus avoid collision on the bus? Lets say node 3 is done talking, how do they decide who is next? If node 1 and 4 decides at the same time to transmitt data to the bus, it would result that data that are transmitted to the bus is corrupt, since two nodes are transmitting at the same time?

If node 1 is transmitting binary 00100110 and node 3 is transmitting 11011001 at the same time, it would result that both CAN-H and CAN-L is high at the same time?

Can someone example to me how CAN avoids situations like this?


texts: Is there an easy way to interface a receiving 457kHz ferrite rod antenna with a microcontroller (BeagleBone Black)?

texts: I have a (actually two crisscrossed) 457kHz ferrite rod antenna from the internals of an avalanche beacon where 196uH <= L < 204uH and C = 560pF. I need to be able to evaluate the data from the receiving antenna's signal to determine the distance between the transmitter and receiver with a BeagleBone Black. Originally I thought I'd be able to wire the antenna up to the input of an ADC on the board, but after spending hours playing around with a beacon set to transmit and the receiving antennas wired up to an oscilloscope I realized that the voltage signal (mean, amplitude, and rms) coming from the antenna really doesn't fluctuate much until the transmitting beacon is within very close range. What parameters of the receiver's signal are used to evaluate distance? Is there any easy way to interface these two parts?


texts: How to fill a polygon generated by importing a .dxf file to Altium?

texts:
I am trying to import a .dxf file to Altium. I was able to import the file, but I could not fill it up with copper trace completely. I tried to draw a polygon to cover it and use 'Explode polygon to primitives' option to fill it with copper trace. I tried to change the clearance rules to make sure that the entire area gets filled up.
Is there an easier way to import a .dxf file to Alitum while making sure that it is filled up with copper trace during the import without having to go through all these hassles?


texts: Does decoupling capacitors try to charge the fluctuating source back?

texts:
In common examples of decoupling capacitors, the scenario is like this:
When the voltage fluctuates below or above its ideal value, capacitor either stores or releases energy to compensate the fluctuation in power so that the load gets a nice, flat voltage.

simulate this circuit – Schematic created using CircuitLab
Now, when I read the circuit form left to right (first looking at the source, then the cap parallel to it, then the load parallel to it) this explanation sounds right because it seems like power is delivered from left to right and capacitor behaves like a buffer in between.
But when I think about it, if cap is at 1V and power source suddenly drops to 0.95 volts, there is a short circuit between 1V and 0.95V so a relatively high current must flow from the cap to the voltage source. This not only tries to charge the source back but also wastes most of the power on that little short between 1V and 0.95V.
So, how should I think so that this circuit will make sense to me?


texts: (How) can I save my components after ESD accident?

texts:
In winter time I am often charged with electricity and frequently encounter esd during the days. I know I should have esd protection when working with electric components, but now it is too late:

I have this display and this board. Both where connected with each other and with my Laptop via USB. When I touched the display I heard a "zap" and it immediately went black. The board is still blinking though. I tried powering the display with another controller, but it will not light up anymore. This is why I am pretty sure I damaged it with esd.

My question is, would it be possible to rescue the display? What tools do I need (I guess something like multimeter or oscilloscope)? Does it make sense to try to measure each resistor and capacitor on the board to find the (in my naive thinking one and only) broken one and replace it? Or is it likely that I have to throw it all away? As the display costs nearly 50$ and I had to wait an eternity for it to arrive I really want to save the one I have...


texts: How to use L298N motor driver with battery

texts:
I connected L298N motor driver (https://www.itead.cc/wiki/MotoMama) to 4x AA batteries in series (6V) connecting battery holder's positive terminal to Vsupply and negative terminal to GND which is under Vsupply in datasheet. Mentioned setup is illustrated on image below:

Apparently the result was short circuit. As a result batteries heated up and started to smoke. If I connect it the same way now, nothing happends - probably something broke inside the driver.

Could someone explain me what would be the correct way to setup above mentioned motor driver with 2 DC motors and battery holder for testing without a microcontroller (e.g. Arduino)?


texts:
I'm trying to complete homework with what appears to be a newer version of the software than what the instructions are for. It says in the instructions that I should select "pin" from the category option like this from the instructions

But my view doesn't look like that when I open the assignment editor in my Quartos 2 web edition:

What I'm supposed to do is add my input x1 to the "To" box and select a pin from a "location" option but it is not available. Can you tell me how I can select a pin for my compilation?


texts:
Overlay AC plots using text file

I tried using PWL source and attaching transient simulation text file from other LTSpice schematic run this works good. But when I try AC simulation this is the error.
This is text file content

Keeping two schematic side by side and simulating might be one solution.
Can we overlay AC plots in LTSpice? What are the steps?


texts:
I am trying to find out why my current mosfet is not working by looking over the datasheet. Ultimately I am just trying to buy a mosfet that I know will work, but I want to understand the datasheets fully before purchasing.
I am trying to drive a solenoid with a microcontroller and using the mosfet as a switch. The MC outputs 3.3 volts, and the solenoid is a 12V, 2 amp. Direct current. The mosfet is an RFP30N06LE. The MC goes high for 500ms then off. I have my circuit wired as below (ironically, this random picture even has the same mosfet as me)

I understand that a solenoid will require a flyback diode that is not shown. I do not currently have one, but I dont think that is the problem. In the datasheet here are the values I understand to be important to follow when sizing a mosfet.

Looking at the above data, it appears you need to apply a minimum of 1 volt to get the mosfet to begin opening. By 5 volts, the mosfet is fully open. I am applying 3.3 volts, so the mosfet is not fully open. However, according to the graph, a voltage of 3.3 to the gate allows for about 20 amps (albeit at 15 volts, not 12), which is more than my required 2. When I tried this in real life, I did not get a reaction from the solenoid at 3.3 volts. I then used an arduino 5 volt output to try and trigger the solenoid. Still nothing, but the mosfet got very hot. Finally, I applied 12 volts to the mosfet gate (above the MFG 10 volt maximum) and the solenoid opened.
What am i missing? Since this mosfet doesn't work, I want to get the Nexperia PMV28UNEA instead. It has a VGS of 0.45V - 1V (smaller), and an RDSon of 3.9 amps at 2.5V (I need 2 amps at 3.3V). I want to make sure I understand things before I buy it though.


texts:
I'm getting strange data from my LDR sensor.

Without any significant changes in light is constantly goes from 0 to its max value 1023 and back.

What could be the problem? Is it possible my LDR sensor is broken?

Code:

int ldr = 0;             //analog pin to which LDR is connected
int ldr_value = 0;        //variable to store LDR values

void setup()
{
  Serial.begin(9600);   //start te serial monitor
}

void loop()
{
  ldr_value = analogRead(ldr);          //reads the LDR values
  Serial.println(ldr_value);                 //prints the LDR values to serial monitor
  delay(1000);                  //wait
}

Output:

0
0
0
0
0
26
102
206
349
505
643
813
957
1023
1023
1023
964
821
633
434
249
83
0
0
0
0

and so on


texts: Unknown Ψ variable in JFET's drain current equation

texts:
This question considers unipolar transistor, that is JFET.

I really didn't find any other formula than this one which applies only for linear/ohmic/triode region of JFET U/I characteristic.

What is the variables marked as "Ψ" (psi) in the next equation (underlined with green colour)?

The unknown variable can be also seen here:


texts: What are the differences between a x1 and a x10 osciloscope probe

texts:
I've heard pros of x10 probe a lot.
Now I need to know the cons but I couldn't find a clear explanation.
Some people say x1 probe is for small signal.
How do you decide either x10 or x1.


texts: MAX5033CASA DC-DC converter not providing correct output voltage

texts:
I'm using MAX5033CASA DC-DC converter to generate 12V/500mA from a 48V voltage. My schematic is attached to the message.

The inductor I'm using is DO5022P-334MLD.

The input voltage to the converter is 30V (I will need to figure out why) and the problem is that the converter generated 5V output, when it should be 12V.

My schematic is the same as that provided in the datasheet. Does anybody encountered this problem? Is there a problem with the schematic? If so, can it be resolved?

Thank you!

UPDATE

I tried the following:

followed metacollin's advice, the converter does generate 12V, but the power fails to maintain; after about 400ms it drops; same thing happens with PG;
the above statement is valid when I remove the DC converter input capacitor; I tried a 22uF, 47uF, 22uF, 100uF capacitor, but every time I connect the capacitor, the PSE (LTC4263) does not supply power, instead it indicates low signature resistance.

I will create another thread because I think this problem is related with the PSE-PD circuits, not the converter.


texts:
I am still beginner to design and so I would to confirm that the variable resistor setup is correct?

I have an LED that operates at 2.7V with 100mA so I added a 23 Ohm resistor. Vcc provides 5V and so I calculated by doing (5-2.7)/100mA = R giving R 23 Ohm.

Does that seem correct?


texts:
I am looking at some datasheets for 5-12V DC motors.  The datasheets specify the stall current is ~1.9A at 12V DC.  They do not specify anything with regards to maximum safe operating current.

In my application there is built-in overcurrent protection in the circuit but it made me curious; Is there a rule of thumb for safe maximum current for small DC motors?


texts: Calculating the saturation current of an inductor?

texts:
How can I calculate saturation current of a Toroid inductor, with a core?
What effect does the current have on the inductivity after crossing the saturation current?


texts: Allowing a BJT to turn on and turn off at different set points

texts:
simulate this circuit – Schematic created using CircuitLab

The circuitry I have on my board currently is the schematic above.  It is showing a start up regulator.  D1 is an 18V zener, as is D3.  When the AC line comes up, D1 clamps at ~18V.  Q1 turns on, allowing the 18V rail to charge up.  Once the 18V rail hits about 15.5V, the primary side gate driver starts switching, the 18V rail starts being powered by a coil on the transformer (represented by L1), and D2 becomes reverse biased, turning that circuit off during normal operation.  With D1 clamping at 18V, and counting the drops of Q1 and D2, Q1 will not have current flowing through it unless the 18V rail is below about 16.8V.

My issue is that at corner points of our operational parameters, that can happen.  What I'm looking to do is pull Q1's base low once the 18V rail hits about 16V (or by somehow detecting when switching starts), and then hold it low as long as the 18V rail is above about 13V.  The gate driver can continue to operate down to 10V, so I'm not concerned about that.

What I've seen happen is that the supply will start up, the 18V rail comes up as I want and reverse biases D2.  Then, if I decrease the output voltage to the bottom end, the 18V rail drops to 16.5ish, allowing Q1 to conduct current, and in some cases overheating Q1 and R1, and causing damage.

There are a couple ways I know of to fix this - I can redesign the transformer to bump up the voltage of the 18V winding, or I could add a comparator circuit to detect the the level of the 18V rail, pull the comparator and Q1's base low at some point, and add hysteresis to only release it at another, lower point.  Problem is, this is an inherited design, and we're very close to going to market with it.  I'm trying to find the least intrusive way I can to fix the issue.  I really don't want to go the route of redesigning a magnetic, and the comparator doesn't strike me as the most elegant solution.

So, I would appreciate any insight anyone has.


texts: Will switching a refrigerator on and off regularly shorten its life?

texts:
For our bar, I needed a refrigerator which could operate at 10°C in order to serve ale and dark beer at the ideal temperature. Being of the DIY bent, I bought an under-bench refrigerator second-hand and built a simple system to keep it at 10°C.

There is a one-wire temperature sensor in the refrigerator, and a microcontroller switches the fridge on at 10.375°C and off at 9.625°C (via a relay driven by a transistor and separate 12V supply).

This keeps the refrigerator acceptably close to 10°C, although I may experiment with turning it off sooner to try to reduce how low the temperature drops (although this will result in more on/off cycles). The temperature is graphed below (the red lines are the relay on and off points).

From this fine establishment

My question is: will treating the refrigerator like this shorten its life? Which components, if any, are being stressed by this setup, and how? If it is relevant, the fridge is relatively old and is unlikely to have digital control circuitry.


texts: Can Lipo protection boards be daisy chained?

texts:
I've got several 1S Lipo protection boards.  Would it be possible/safe to daisy chain them to make higher voltage packs?  Example:

        Balance Charger Port 3     Balance Charger Port 2      Balance Charger Port 1
                         |                   |                   |
         ------Brd1----  |   -----Brd2-----  |   ----Brd3------  |   -----Brd4-----
         P+  B+  B-  P-  |   P+  B+  B-  P-  |   P+  B+  B-  P-  |   P+  B+  B-  P-
+14.1V --┙   |    |  └---┴---┙    |    |  └---┴---┙   |    |  └---┴---┙   |    |  └---GND
           +Battery-            +Battery-           +Battery-           +Battery-

Let's assume that the application would not require more current that any one of the protection boards can deliver.

EDIT: As requested below, here is a bit of info on the boards I've got in my drawer:
product details
Maximum charging current :              3A
Maximum discharging current:          3A
Charging cut-off voltage:                  4.2V
Discharging cut-off voltage:             2.75V
Battery protection chip models:        DW01
MOS model:                                     8025
Function:                                          Overcharge, over discharge, short circuit protection

Datasheets: DWO1  8025 MOSFET


texts: MOSFET threshold voltage and body effect

texts:
I'm trying to simulate a common drain amplifier on LTSpice which can be used to shift the input voltage either up or down by the threshold voltage (\$V_{IN}+V_{TH}\$ or \$V_{IN}-V_{TH}\$, depending on PMOS or NMOS configuration). The bulk terminals of PMOS must be connected to the most positive rail while NMOS bulk terminal must be connected to the most negative rail for the transistors to work in the reverse bias hence, allowing control of current flow and \$V_{TH}\$.

My question is, would it be possible to adjust the threshold voltage by varying the connection of the bulk terminals?  Or is this a bad practice?


texts:
For a work school project of mine, I am trying to make a self-balancing robot. I am using these Pololu DC motors and my 4s Lithium Ion battery pack outputs 15.7V at a rated 2Ah. Currently I am using the L298N Motor Driver and a PWM signal from an Arduino Due to control the geared motors. I understand that effective voltage corresponds to RPM and effective current corresponds to motor torque. My teacher would strongly prefer I
switch to a current-controlled driver instead so that I can vary motor torque as apposed to RPM. How do I go around doing this? What motor drivers vary current and keep voltage at a steady 12V?? I also need the driver to be bidirectional. Will this driver sold on Pololu work??


texts: Snubber design for switching an inductive mains load with a relay

texts:
I am envisaging a relay which switches an inductive load consisting of a couple of switched-mode power supplies (standard ATX computer power supplies) in addition to several wall-wart style power supplies powering other equipment.  The total power consumption is about 600 W at 220 VAC. The exact nature of the load may vary over time as different equipment is substituted, but what I have described is the typical size and character of the load.

I've been reading about snubber designs and it seems that some combination of a RC snubber and/or a bidirectional TVS (Transorb/Tranzorb) diode in parallel with the load would be required.  I'm not comfortable with the alternative design of snubbing in parallel with the contacts because I want zero current flow when the relay contacts are open.  Something like the diagram in this
application note for Driving and Relay and Contact Snubbing [PDF] is what I imagine.

First of all, what combination of snubber components is appropriate for my situation - RC network, TVS diode or maybe a MOV?  Secondly how can I conservatively estimate the values and ratings of the required components to ensure that my relay contacts don't erode or weld?


texts: Understanding the relationship of Pulse and Stepper RPM

texts:
I have a pretty simple script that I'm using to control the RPM of my stepper motor:

void loop(){
  digitalWrite(PIN, HIGH);
  delayMicroseconds(wait);
  digitalWrite(PIN, LOW);
}

as you can see it's just producing a pretty standard pulse, I have my Arduino connected to a driver that manages the motor. The wait variable comes from a second order equation I derived from measuring the RPM with a Tachometer and tweaking the value.

// From data RPM = 31729/x + 17.327 thus x = 31729/(RPM-17.527)
wait = M/(RPM-C);

It works pretty well, I get readings consistently within only 1 - 2 rotations off. But the slope and intercept seem completely arbitrary to me. Is there a chance it has to do with the clock speed of the Arduino? I'm using an Uno and from playing around with the numbers I can't seem to find a relationship. From what I can tell, the driver looks hardwired so I don't think it has much to do with the equation.

Any idea what these values, the slope/intercept mean?

Equation: RPM =
 31729/wait + 17.327


texts: If I make a basic 2.4 GHz antenna like from this link (http://www.wikihow.com/Design-a-Simple-Antenna) and connect signal pin and ground pin to oscilloscope what would I see ? I mean will there any AC voltage if so , what will be level of it milli , micro or pico ?


texts: Does it matter to which ground you connect a MOSFET?

texts:
I'm a beginner when it comes to electrical engineering and recently started a project where I build my own portable bluetooth speakers. I already have a rough layout of the whole thing. I basically want to power a 2x50 Watt Amplifier with two batterypacks wired in parallel, that I weld together myself.
Now I also want to be able to drive it with a 100W Powersupply, but in a way where I can plug in the Powersupply and flip a switch to disconnect the batteries from the circuit, so the speakers don't draw power from them. If I were to not flip the switch, the powersupply should work as a charger, independent of if the device is on or not. Instead of using multiple switches for this I wanted to use a MOSFET to close the battery circuit whenever the powersupply is plugged in, by using the 20V it would provide. Does it matter to which groundwire I connect the gate?
I will post a "schematic" or rather sketch of the whole thing below. I am aware that what I drew might be not applicable at all. So please point out all mistakes you find, after all I came here to learn. I would also appreciate any beginner resources for learning more.

Thank you in advance for any replies.


texts:
This is just for me to understand basic household economics.
Let's say my electricity provider charges me 1$ for a kWh and let's say I have a device which claims to consume 100W running in my household.

Does this mean, that it will cost me 0.1 dollars per hour?
Did I understand it correctly?


texts: What ADC requirements for 20 kHz to 10 MHz signal?

texts:
Currently, I am searching for an ADC which can read a sine wave signal with a maximum frequency of 10 MHz. I know that I have to choose an ADC of at least 20 MHz due to Nyquist theorem.
My signal of interest is between 20 kHz - 10 MHz.
Which ADC requirements should I take into consideration and why, for example: can't I use like an ADS4145 with 125 MSPS for reading signal from 20 kHz to 10 MHz?


texts: Driving a large 7 segment display using a micro-controller

texts:
I need to drive a large seven segment display (segment length is a about 2 inches) using a micro-controller (PIC 16F877). I've driven normal seven segments directly from PICs without issues, but I found that 5v is not enough to drive this one. It needed something around 9 volts (is this normal?)

So what came to my mind is this. (Designed using Proteus ISIS 7 Pro)

I've supplied 12v to this circuit and used the RV1 preset to adjust it (to make it 9V or something close). 8 inputs to the transistors come from the micro-controller. So I can drive the large 7 segment (which require 9v) this way...

But it wasn't success. I checked the voltages and found the transistors switch between 0-5v (can't imagine how can this happen???).

Anyway, then I tried putting the resistor to the collectors side. And took the output from collector pin. That was somewhat ok. But the brightness was varying with the number of lighting segments...(When lighting only one segment, there was very little brightness. It's almost not visible. But when lighting all the segments, brightness was too high. Felt like the display will blow.)

I don't feel like to try other means. This was a so simple project. But this large seven segment ruins everything. Can some one help me with this...


texts: Regenerative braking circuit for a BLDC Motor

texts:
I am trying to design a regenerative braking circuit for clamping the voltage when it is increased due to BLDC Motor acting as a generator. Simulation wise I am getting the exact result. But when I implemented the same circuit the resistor is directly dissipating the heat when power supply is switched on. Actually the power resistor has to be activated when the pulse is generated by the control circuit.

Now my question is why the power resistor is dissipating the energy when I switched on the power supply. Will there be any fault due to the n-channel mosfet which closes the circuit when control circuit initiates the pulse?

N-channel mosfet connections -  Gate receives control signal from p-channel mosfet drain, n-mosfet drain is connected in series to the power resistor one end and the n-mosfet source is connected to ground.

One end of power resistor is connected to the diode cathode and diode anode is connected to variable supply voltage (0-60V).


texts: Explanation of 5 Parameter Model for Solar Cells

texts:
I am having a hard time understanding this equation, the 5 Parameter model for photovoltaic cells.

\$I = I_{ph} - I_o[\exp(\frac{V + R_sI}{nV_t})-1] - (\frac{V+R_sI}{R_{sh}})\$

My goal is to apply a regression algorithm on this to extract the 5 parameters

(\$I_{ph}, I_o, R_s, R_{sh}, n\$)

How do we interpret this equation?

If I have all the five parameters defined how will I get the value of current with just voltage. This seems confusing as \$I\$ appears on both sides of the equation.


texts: Decoupling a Stereo Audio CODEC (CS4271-CZZ)

texts:
I have a schematic with decoupling capacitors that I do not know how to connect to the codec. They are not connected to the codec directly in the schematic as I assume that connecting them is a given for anyone who has studied electrical engineering (I am a chemical engineering student, this is my hobby).

Information about decoupling the codec, found in the data sheet:

My question:
How and where should the 3 caps (c53,54,78) be connected in relation to the IC ?
My thoughts:
It seems hat Filt+, AGND, VA, DGND are taken care of in the schematic. This leaves VL and VD. VD and Vl are parallel connected as described in the datasheet [ VD may be run from the systems logic supply (VL) ]. I have x2 0.1 uf and a 10 uf capacitor, the power inputs are parallel connected, so maybe I should arrange them in some special way...(?)
Any thoughts/comments would be greatly appreciated.


texts: Optocupler-Mosfet output for various output

texts:
I'm designing a board equipped with a MCU (atmega4809) that need to control different type of industrial graded equipment at 24VDC. These will be mainly a relay or a solenoid coil for pneumatic valve.
At the moment my circuit design is something like this...

...with just a current limiting resistor that keep current bellow 150mA (it seems from the datasheet of my Optocupler that this is the limit for it's output stage.)

I'm a bit uncomfortable with this solution especially with the current passing thought my Optocupler.

My idea was to use more a solution like this.

Not having lots of experience i would like to have some feedback and some suggestion if this solution will work and how to improve it.
And maybe some part suggestion

Thanks

_________________Edit________________

As mentioned the output can be a 24vdc solenoid coil or a 24 drivable relay.
The solenoid coil usually are rated around 3W, let's consider 6W for caution.
The relay will be a monostable one that can commute a 230VAC 1,5kW load using 24vdc on the coil.
I think this want exceede the 6W we are considering for the solenoid coil.

For the component at the moment i have a bunch of FOD852 as optocoupler.
For the mosfet i have no idea at the moment.


texts:
I am trying to learn how a phototransistor works, and I have made a schematic to show how I understand the photo-diode and NPN transistor to be linked in a phototransistor.
I think that when light intensity reaches a certain level, the photodiode should conduct current and the bulb should light up. Is this correct? I am also wondering whether there would need to be a connection between the photodiode and the emitter, as shown with a question mark in the image below.

simulate this circuit – Schematic created using CircuitLab
The image below is how I image the electron flow should be when the photodiode conducts:

For reference, this is a less detailed depiction of the design I would like to achieve with the above schematic:


texts:
Trying to control a Peltier to cool and to heat.

Does the following code allow me to reverse the current to switch cooling/heating depending on whether I input "a" or "z"?

Source: http://garagelab.com/profiles/blogs/how-to-use-a-peltier-with-arduino

int peltier = 3; //The N-Channel MOSFET is on digital pin 3
int power = 0; //Power level fro 0 to 99%
int peltier_level = map(power, 0, 99, 0, 255); //This is a value from 0 to 255 that actually controls the MOSFET

void setup(){
Serial.begin(9600);

//pinMode(peltier, OUTPUT);
}

void loop(){
char option;

if(Serial.available() > 0)
{
option = Serial.read();
if(option == 'a')
    power += 5;
else if(option == 'z')
    power -= 5;

if(power > 99) power = 99;
if(power < 0) power = 0;

peltier_level = map(power, 0, 99, 0, 255);
}

Serial.print("Power=");
Serial.print(power);
Serial.print(" PLevel=");
Serial.println(peltier_level);

analogWrite(peltier, peltier_level); //Write this new value out to the port

}


texts: Phone replacement parts: original vs copy

texts:
I'm looking to buy a replacement micro USB board for my Xiaomi Redmi 6. As your can note for example on this product page, there exist "original" and "copy" versions for the same component.

The "copy" has a lot less components than the "original" one. So I'm wondering, how could they achieve the same functionality with that much less components?


texts: Circuit simulation shows gain with only passive components. Why?

texts:
This feels like an ignorant question, but here it goes.

I'm trying to understand the antenna circuit from the 430 MHz reference design for TI's CC1125 transceiver IC. The antenna circuit is at the bottom right of this schematic. Here's a link to the datasheet for the device.

I tried to simulate the circuit's behavior in receive mode (TRX floating, in transmit mode it's grounded to protect the receiver). I made the assumption that the PA would be effectively a short to ground in transmit mode. Here's the schematic I'm using in LTSpice. The source has a 50 ohm series resistance and is set to 1 V AC.

The output voltage is the voltage across L5. Here are the results of the AC sweep:

I have a secondary request before my main question. I would appreciate help understanding the function of the circuit. I understand the general operation of the balun in the upper left, but I don't understand the purpose of L5. It shorts the receive pins together at DC, but it seems like it would seriously mess with the tuned balun operation. I assume that the lowpass filter is meant to remove harmonics. What is the purpose of the series LC elements connecting the lowpass filter to the balun? What is the purpose of the parallel LC structure connecting to the Tx pin?
This is my main question:

How is it possible that any voltage in the simulated circuit is larger than the input?

Shouldn't the output voltage have a hard limit at 0 dB (or even -6 dB with a series resistance in the source)?


texts:
Am just messed with the generation of a square wave of specific frequency and a duty cycle using Verilog and dumping to FPGA kit.  Can anyone clarify how the clock frequency is derived?? Which bit is to selected while using the derived clock frequency??
 Here is an example code for generating square wave of 1KHz with 50% duty cycle.What modifications need to be done to generate a square wave of frequency 2KHZ and 40% duty cycle in the present code??

module square_wave(clk,rst,dac_out);
  input clk;
  input rst;
  output reg [0:7] dac_out;
  reg [7:0] temp;
  reg [7:0] counter;

  always @(posedge clk)
  begin
    temp <= temp + 1'b1;
  end

  always @(posedge temp[3])
  begin
    if (rst)
      begin
        counter <=0;
      end
    else
      counter<=counter + 1'b1;
  end

  always @*
  begin
  if (counter<=127)
    dac_out=8'd1;
  else
    dac_out=8'd0;
  end
endmodule


texts: Sending CAN protocol data(1Mbps) via serial port

texts:
I would like to build a tool for viewing CAN protocol data on my computer. The CAN protocol data is captured using a microcontroller (STM32F4 discovery board) and sent to a PC via a serial port. My requirement is to send only CAN ID, DLC, DATA and time stamp (i.e at what time a particular CAN ID was received).

I have a few questions that I couldn't find good results for after searching the Internet:

Is it possible to send CAN data via the serial port using some compression techniques for the data packets since the CAN protocol operates at 1Mbps and I am planning to run the serial port at 115200 baud rate? If yes, could you provide information or links?
Have you seen any similar projects which send 1Mbps CAN data via serial port. If yes, could you provide information or links?


texts: Identifying function of passive components in op amp circuit

texts:
I was reading this report on a digital guitar effects pedal design and I came across the circuit above. "AUDIO_IN" is where the guitar signal enters the pedal. The signal is then filtered through the op amp circuit and ends up at a high res ADC. According to the report, the circuit is a "4th-order unity gain Sallen-Key band-pass filter with cutoff frequencies of 25 Hz and 16.5 kHz".

I set myself to the task of justifying each component and got lost pretty quickly. Here's what I think I know:

R9: Weak pull-down resistor on input to ground

C10, C12: Coupling capacitors (Why are there two?)

R10: Pulls AC signal up into the 0V - 5V range, centered around 2.5V

R11: ???

C14: Decoupling/bypass cap

R14: ???

R17: ???

C18: ???

C19: ???

R18: Resistor in RC filter before ADC input

R19: ???

C21: Capacitor in RC filter before ADC input

I'm really curious about R19. I have a fair amount of experience with DC op amp circuits but I don't have a ton of experience with op amp circuits with AC signals. I want to use this circuit in a project but I want to know what everything does first.

Can anyone help me identify the function of the passives I'm unsure about? Reading suggestions on good AC op amp circuit design are also very welcome.


texts: How does 3-wire RTD or resistance measurement works in bridge of wheatstone?

texts:
I cannot understand how 3-wire measurement will improve the resistance measurement.

They say that IF lead resistance \$ R_L \$ is the same, it will compensate. How can this happen?

If bridge is balanced (without \$ R_L \$):  \$ \frac {R_1}{R_2} = \frac {R_g}{R_3} \$

If \$ R_L \$ is added: \$ \frac {R1}{R2}= \frac {R_g+R_L}{R_3+R_L} \$

\$ \frac {R_g}{R_3} \$ is not same as \$ \frac {R_g+R_L}{R_3+R_L}\$; is this true only if \$ R_G=R_3 \$ in the beginning?
So this means that \$R_L\$ does not get compensated?


texts:
I am  trying  to  build  a  switch  that can  cut  by  control  the sine wave V1
From  the  load  R1.
The  main  problem  is  that  we  have  a  parasitic  capacitor  between  the drain  and  source
So  in  high  frequency  this  parasitic  capacitor  is  act  as  bypass and  I  get  a  signal  also  when
V2 = 0.

I can't use     a  really as  I  need  to  switch  I in  100HZ.
SSR  - solid-state relay  is  also  not  good  for  that from  the  seam parasitic  capacitor  .

Any  idea  will be  helpful

Thanks
Aharon.

simulate this circuit – Schematic created using CircuitLab

simulate this circuit


texts: Altium PCB Layout: The Difference of Through Via, Micro Via, and Burried Via

texts:
This is my very first time doing 4 layers PCB layout.

What is actually the difference between Micro Via and Buried Via?
Say I have Layer 1, Layer 2, Layer 3, Layer 4. What I know I use the Through Via for Layer 1 as start layer and Layer 4 for Stop Layer.

And how do I use the Micro Via and Buried Via?

Last question, what about the Drill Pair Properties, should I connect every layer there?


texts: ESR in Electrolytic capacitor vs Voltage rating

texts:
I would like to know why in an electrolytic capacitor the ESR decreases as voltage rating increases.
And why the current rating increases as voltage rating increases.
Thank you.


texts: Why not detecting zero crossing of the back EMFs in BLDC by software?

texts:
I am reading about the state-of-the-art approaches to detect the zero crossing of the back (trapezoidal) EMFs on a 3-phase BLDC for sensorless control. Even digitally implemented, they use various strategies to detect the zero crossing of the back EMFs (e.g. using Hall sensors to detect the position of the rotor).
Since the EMFs are fed back to the controller, I just wonder why the zero crossing has not been so far detected by software; for example by the following pseudocode:

IF EMF_1 == 0  THEN ...

where EMF_1 could be the variable representative of the EMF read from phase 1.


texts:
I plan to do a 3d scanner with low-grade digital camera.
I opened a coolpix L27 and found this :

Does anybody knows how this kind of button is called (may be it is normalised and finding a datasheet is possible)
Or would someone here have a service manual for the coolpix L27.

Thanks

So here is what I did :

il you look closely you can see in the 4th pictures that I inadvertedly put
some solder below the power button, this caused a short circuit.
However this camera is protected against short circuit and shut down immediatly.
Removing the solder with som "solder absorber" (tresse a dessouder in my language)
solved the problem.


texts: Common mode impedance in operational amplifier

texts:
While looking at this simulation, as they say no current flows at the non inverting terminal of the op-amp, but looking at the differential stage of the operational amplifier shouldn't there be some current from ground to -15V point THROUGH THE NON INVERTING INPUT?
Secondly, they define common mode impedance as the impedance between the input terminal and ground point.

Now the current producing by the action of the AC voltage source has to travel from -VEE to ground. So the impedance should be of this path, then how impedance between ground and terminal is defined as the common mode impedance?


texts: How does a microcontroller development board use USB cable to transmit serial data?

texts:
I'm trying to understand every section of the journey of data from a microphone via a microcontroller to a pc terminal.

I realize now after reading about serial data transfer that real-time audio data transfer through a serial port is not possible, since the maximum data transfer rate is around 115 kb/s, However, I would still like to know about serial data transfer in a microcontroller.

I have an electret microphone connected to an analogue input on a stm32 nucleo-144 development board with a stm32F746ZG microcontroller (https://os.mbed.com/platforms/ST-Nucleo-F746ZG/) and the development board is connected to a pc via a USB cable.

My understanding is that the audio signal is sampled by the adc on the microcontroller chip, this new digital data is then moved to memory via one of the Advanced peripheral buses (APB) and then the Advanced High-performance bus (AHB) it then comes back out of memory and goes via the APB and AHB into a UART within the microcontroller and after into a (RS-232/RS-485) line driver (don't know if this is in the microcontroller on on the development board) where the voltage is increased and then after this I'm lost.

Does the data just progress along the tx line from the line driver to the USB port on the development board? And is it then transmitted as USB data or  as serial data using one of the USB data lines?


texts:
Is there a way to do "jumpers" without actually using a jumper connector on a PCB? Ideally just using holes or pads.

For example, one idea for doing it is to use pads on the edge of a PCB then using crocodile clips to do the bridge.  Should work ok, but requires the "jumper" at the edge of the board.

These jumpers aren't meant to be a permanent part of the final board, but just to use temporarily and easily for things like diagnostics and without adding cost to the final PCB.


texts: Automotive 3.3 volt supply that can survive engine start

texts:
I am powering a PIC32MX microchip using a 3.3V Linear Regulator (LM2937), supplied from an RBO40 which I fitted in an effort to protect against adverse conditions such as load dump. As an aside, I've just ordered a Murata buck converter (RS-Online part 796-2141) to replace the linear regulator.

The PIC32MX is connected exactly as per the datasheet with the recommended capacitors within a few mm of the power supply pins.

The PCB is mounted inside my classic car and controls various systems such as PWM dimmed lights, gauges, switches etc etc. Whilst not safety critical it would be desirable if the PIC would remain running during engine start, which it doesn't (always resets). A breadboard-ed thru hole version of the PIC does continue running during engine start on my regular (modern) car, so I wondered if perhaps the classic has a more aggressive starter motor or alternator, or weaker battery that is contributing to this issue.

I'll try the buck converter instead and see if that's any different.

Otherwise should I consider any particular rating of bulk capacitor perhaps? Before or after the voltage regulator? I've googled the issue but not got anything definitive, just confusing myself. Thanks in advance.


texts: what happen if a high voltage connects to pc-based oscilloscope's ground?

texts:
What happens if a high voltage (for example 500V) is connected to PC-based oscilloscope's ground?

In principle, nothing should happen, but if somehow the PC's ground and high voltage's reference tied together (through home wiring or etc) this looks like
ground loop problem in oscilloscope.

Will the PC be damaged? If the answer is yes, how did PC-based oscilloscopes solve this problem? Can you suggest any circuit to fix this problem? I want to design a channel 200Msa/s 50 MHz bandwidth PC-based oscilloscope.

------------- Update

my circuit is like this:

I'm using LMH6702 instead of AD8021. I'll sample from signal with ADC8200(8 bit 200Mega sample ADC) and ... Finally, the data is transferred to the computer by cy68013 the circuit works fine but as i said i dont know how can i eliminate the problem i said


texts: bi-directional half-duplex communication between two AT89C2051's micros without serial port

texts:
I'm trying to do a direct two-way communication between two AT89C2051 microcontrollers with only two GPIO pins so that I have other GPIO lines free for other tasks.

P3.7 is the data wire, and P3.2 (INT0) is the control wire, and they are externally pulled high to VCC (of 5 volts) through 10K resistors.

One microcontroller has an 18.432Mhz crystal connected to it so I can connect it to my computer at a clean 9600bps baud. The other microcontroller is connected to a 20Mhz crystal (which is the highest speed lowest-priced compact crystal I ordered from the internet) for fast memory and wireless communication.

Initially I was going to reserve 4 GPIO pins for data communication but I wouldn't have any free for other tasks such as memory and LED manipulation.

This is my idea behind the two wires.

The sender loads P3.7 with the one bit and then sends P3.2 low then waits a bit for remote processing. This repeats until the whole byte is sent.

When the receiver receives data, the interrupt is supposed to be executed (from the remote sender making P3.2 low) and the byte received from P3.7 is stored in a temporary location until all bytes are received which a counter tracks. Once all are received, a flag is set.

The sending seems to be ok, but the receiving always stalls.

Do I need to adjust my timings or is there a better approach of doing half-duplex bi-directional communication with only two wires connected to the same pins (with pull-up resistors) on both micros?

Here is my code for reference. I have to remove the first line of code after programming the first chip to ensure the correct code is on each chip.

UNIT equ 1h ;1 = 8051 to interface to PC, 0 = 8051 to interface to radio.
RDATS EQU 40h ;remote data temp
RDAT EQU 42h
RDATCT EQU 41h
RDI EQU 0h ;remote-data-interrupt bit
CT EQU 1h ;carry temp - receive
CTS EQU 2h ;carry temp - send

org 0h
ljmp main
;INT 0 natural address is here (03h)
ljmp intZ
org 002Bh

;called
intZ:
  clr EX0
ifdef UNIT
clr P3.4 ;This is supposed to execute on 8051 connected to PC but does not.
endif
  mov CT,C
  push ACC
  mov C,P3.7
  mov A,RDATS
  RLC A
  mov RDATS,A
  inc RDATCT
  mov A,RDATCT
  cjne A,#8h,no8
setb RDI
mov RDAT,RDATS
mov RDATCT,#0h
  no8:
  jnb P3.2,$
  pop ACC
  mov C,CT
ifdef UNIT
setb P3.4
endif
  setb EX0
reti

sendrdat:
  clr EX0
  mov CTS,C
  mov R7,#8h
  push ACC
  sendrmore:
clr C
rlc A
mov P3.7,C
clr P3.2
nop
nop
setb P3.2
  djnz R7,sendrmore
  pop ACC
  mov C,CTS
  setb EX0
ret

serialin:
  clr RI
  jnb RI,$
  mov A,SBUF
ret

serialout:
  clr TI
  mov SBUF,A
  jnb TI,$
ret

pserial:
  rewr:
clr A
movc A,@A+DPTR
jz exl
acall serialout
inc DPTR
  ajmp rewr
  exl:
ret

main:
mov RDAT,#0h
mov RDATS,#0h
mov RDATCT,#0h
clr RDI
mov P3,#0FFh
mov P1,#0FFh
mov SP,#50h ;skip most ram so SP doesnt be wrecked
mov scon,#50h
mov tmod,#020h
mov 087h,#80h ;pcon.7
mov TH1,#0F6h ;9600 baud on 18.432Mhz
setb EX0
setb EA
setb TR1
IFDEF UNIT
ajmp PCmode
ELSE
ajmp RADmode
ENDIF
;branch

PCmode:
  clr RI
  jnb RI,$
  mov DPTR,#ptest1
  acall pserial
  ;send 0AAh to remote 8051
  mov A,#0AAh
  acall sendrdat
  mov DPTR,#ptest2
  acall pserial
  ; code stalls here forever.
  ; It should only stall until remote 8051 calls this one.
  rwait:
  nop ;no overloading processor
  jnb RDI,rwait
  ;RDAT = remote byte received
  mov A,RDAT
  push ACC
  mov DPTR,#ptestr
  acall pserial
  pop ACC
  acall serialout
  mov A,#0Dh
  acall serialout
  mov A,#0Ah
  acall serialout
  mov DPTR,#ptestdone
  acall pserial
sjmp $

RADmode:
  ;radio mode... only obey commands at this time
  nop
  jnb RDI,RADmode
clr RDI
mov A,RDAT
cjne A,#0AAh,nosig ;AAh=get signature = 41h (A)
  mov A,#041h
  acall sendrdat
nosig:
  ajmp RADmode
sjmp $

ptest1:
db 'Sending data to unit 2...',0Dh,0Ah,00h
ptest2:
db 'Receiving data from unit 2...',0Dh,0Ah,00h
ptestr:
db 'Received: ',00h
ptestdone:
db 'This is a test that worked!',0Dh,0Ah,00h
END


texts: I have found this tutorial but don't have a 0.1uF Capacitor. I am an amateur when it comes to electronics, but I don't know if I can swap 0.1uF for a 1uf or 1.5uf. Any help would be greatly appreciated.


texts: Voltage divider equation tunnel diode - Art of Electronics

texts:
Early on in the book "The Art of Electronics" (p.15, 2nd edition) a voltage divider circuit is described: an input voltage \$V_{in}\$ over a tunnel diode \$D\$ and a resistor \$R\$, and an output voltage \$V_{out}\$ the voltage across the resistor.

It is then written that a change in \$V_{in}\$, denoted \$v_{sig}\$, results in an (amplified) change \$v_{out}\$ in the output:

\$v_{out} = \frac{R}{R + r_{t}} \cdot v_{in}\$

where \$r_{t}\$ is (negative) dynamic resistance of the diode \$D\$.

Unfortunately no derivation is given.

Now I have been trying for the last two hours to derive this form but keep getting stuck. Unfortunately there seem to be no leads on the internet. Could someone derive the formula (in a clean manner)?


texts: How is the positive input of this op-amp calculated

texts:
So suppose the following circuit.  \$ V_{out} \$  needs to be 0V. The negative voltage input is 100mV.

I now want to calculate the positive voltage input. The gain of the amplifier is -(R3/R1) = -9. \$ V_{out} \$  is calculated by

\$ V_{out} = A(v^+ -   v^-) \$

\$ V_{out} \$ is 0, A is -9, \$v^-\$ is 100mV.

So we get

\$0 = -9(v^+ - 100mV)\$

which eventually leads to

\$v^+\$ = 100mV.

But it should be 90mV. I cannot really find my mistake. I am assuming i have a wrong formula for  \$ V_{out} \$  but this should be the formula for how  \$ V_{out} \$  is calculated.

simulate this circuit – Schematic created using CircuitLab


texts: By touching neutral why we do not get shock?

texts:
According to Benjamin Franklin, current flow from +ve to -ve terminal. But after Joseph Thomson's discovery it was conceived that although current flows from +ve to -ve electrons flow from -ve to +ve terminal.

Now w.r.t. Alternating Current neutral provides return path, so why touching metal of neutral doesn't give a shock?


texts: Debugging tool for the FTDI FT2232H in Sync FIFO mode

texts:
Does anyone know of any software available to take data from the FT2232H in 245 FIFO Sync mode and write it to screen or to a log file?

Basically, I am using the FT2232H IC to transfer a large amount of data from an FPGA over USB. I chose the IC because I've had some experience with FTDI chips before using their VCP (virtual com port) driver and because of the USB2 speeds available.

Unfortunately, it needs to use the D2XX driver, which doesn't allow it to show up as a virtual com port on my windows machine so I can no longer use TeraTerm to display data being sent through the IC.

It seems to me that the FT2232H in sync FIFO mode should be a popular enough option that someone has already written software for a windows machine that would let me see data coming off the USB - either on screen or to a text file. A google search didn't turn anything up and I figured this is a valuable enough question that others might be interested in the answer too.


texts: A switch that is only ON if the reference voltage is matched -+ 0.1 volts

texts:
Im a beginnerish will electronic and im looking for a switch that is only ON if the reference voltage is matched -+ 0.25 volts. So if i have a reference of 2.7v to match and i feed the switch a 2.75v the switch would be ON. But if i feed it  2.5v or 2.85v the switch would is OFF.

This might be a simple google search, but i am lacking the correct terminology.


texts: Clocking scheme for LAN8720A - Cortex M4

texts:
This is regarding a design choice involving LAN8720, specific to clocking schemes.

We are interfacing an ARM cortex M4 (with inbuilt MAC) to the 8720 PHY via RMII in the REFCLKO configuration. In the datasheet for the 8720, Fig 3.9/page 36 (sorry but i do not have enough points to upload an image) shows the 8720 receiving its clock from an external source(25 Mhz) and the MAC is fed an output reference clock of 50MHz from the 8720.
 The text in the datasheet prior to this figure reads: *"In some system architectures, a 25MHz clock source is available. The device can be used to generate the REF_CLK to the MAC as shown in Figure 3.9. It is important to note that in this specific example, only a 25MHz clock can be used (clock cannot be 50MHz). Similar to the 25MHz crystal mode, the nINT function is disabled."* Absolutely nothing else on this scheme is mentioned.

Now, the controller itself is clocked by a 25MHz crystal. The controller generates a 25MHz signal on its MCO. From the figure mentioned above, it should be a correct design to clock the 8720 via the MCO output of 25MHz from the controller and providing the REF_CLK output to the controller's MAC. However as mentioned earlier there is hardly any information(read none) regarding this. There are development boards of 8720 which support every other clocking scheme but this. I even checked the schematic review checklist provided by SMSC which describes quite a few clocking schemes but doesnt mention this at all. Are there any issues known with such a clocking scheme?

See the third document in the link below.
http://www.smsc.com/Products/Ethernet_and_Embedded_Networking/Ethernet_Transceivers/LAN8710A_LAN8720A/Download
(As mentioned earlier, I do not have enough points to upload an image)


texts: SIM7000E modem stops sending SEND OK reply

texts:
I am using a SIMCOM SIM7000E modem to send data using MQTT. Usually modem reply correctly to
AT+CIPSEND command and sent ">" to enter the required data and then reply with "SEND OK" after entering the data. But I have noticed when running after around 5 or 6 hours modem stops replying with SEND OK, anyway data is received at server side. Have anyone noticed this? Is there a solution for this?
At the moment I have updated the firmware of the modem to 1351B08SIM7000E results are same.


texts: Let's say a series circuit has two loads and a battery with 12 volts. Do the loads each use 6V? Or do they each use 12V? And then let's say there is a parallel circuit with a battery (12V) and two loads in parallel. Same question, do they each use 6V or do they each use 12V?


texts:
I am attempting to interface with the TLE5012B (datasheet here) using SPI. The master in this case is a Nucleo F411RE, which uses an STM32F4 processor. The sensor communicates in 16-bit words, so I set the chip up in Cube as shown (some other peripherals which won't be used in this question's code are also activated):

All seemed to be going well, but a problem arose when I noticed that for some reason, an extra word was being clocked in by SCLK when there was nothing to be received from the data line, resulting in a rogue 0x0000 being stored in the buffer, which messes up future reads.

Here is my code:

#include "app_main.h"
#include "stm32f4xx_hal.h"
#include <stdint.h>

extern SPI_HandleTypeDef hspi2;

uint16_t command = 0x8088;
uint16_t safety = 0;
uint16_t data1[8];

int app_main()
{
    HAL_Delay(1000);
    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_10, GPIO_PIN_RESET);
    HAL_Delay(1);
    HAL_SPI_Transmit(&hspi2, (uint8_t *)(&command), 1, 0xFF);
    HAL_SPI_Receive(&hspi2, (uint8_t*)data1, 8, 0xFF);
    HAL_SPI_Receive(&hspi2, (uint8_t *)(&safety), 1, 0xFF);
    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_10, GPIO_PIN_SET);
    HAL_Delay(1);

    while (1) {
    }
    return 0;
}

And here is what happens in the SPI, read using a logic analyzer (Lines in descending order are CS, MOSI/DATA, SCLK, CS does drop low/set high outside the zoomed area):

As can be seen from the code, I should expect to send one word and receive 8 plus a safety word; however, 10 words are being clocked in, with the last being 0x0000 due to no data on the line, which then stays low for some time.

To get a better idea of what was going on, I altered my code slightly:

#include "app_main.h"
#include "stm32f4xx_hal.h"
#include <stdint.h>

extern SPI_HandleTypeDef hspi2;

uint16_t command = 0x8088;
uint16_t safety = 0;
uint16_t data1[8];

int app_main()
{
    HAL_Delay(1000);
    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_10, GPIO_PIN_RESET);
    HAL_Delay(105);
    HAL_SPI_Transmit(&hspi2, (uint8_t *)(&command), 1, 0xFF);
    HAL_Delay(75);
    for(int i = 0; i < 8; i++)
    {
        HAL_Delay(15);
        HAL_SPI_Receive(&hspi2, (uint8_t*)&data1[i*2], 1, 0xFF);
    }
    HAL_Delay(50);
    HAL_SPI_Receive(&hspi2, (uint8_t *)(&safety), 1, 0xFF);
    HAL_Delay(10);
    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_10, GPIO_PIN_SET);

    while (1) {
    }
    return 0;
}

This produced the following output:

From a distance, this seems correct; 8 words received back, plus the safety. On zooming in, however, the problem becomes visible; the command transmission is fine:

However, the first received word is not one word but two clocked in at once by SCLK:

While following words are fine:

What this double word appears to be doing is shoving the receive buffer ahead of what's actually being read in, meaning when the safety word is meant to be read, 0x0000 is added into the buffer, as the safety word has already been received and stored.

It could be worth noting that some of the delays are slightly smaller/larger than they're meant to be, but my question is, what could be causing this double-word to be read in? I tried changing the SPI peripheral to 8-bit mode instead of 16; this didn't fix the issue, it merely made the extra word 8 bits instead of 16. Running similar code on an F3 processor gave incorrect results as well. The TLE can't drive the SCLK line so it must be the micro that's doing something wrong, but I can't for the life of me figure out what.

EDIT: I did some fiddling with wires and set the STM into full-duplex with a resistor on the MOSI line. This fixed the problem, but doesn't tell me what caused it in the first place. Does half-duplex have some strange protocol I don't know about?


texts: What is the purpose of an RC branch accros the diode of a rectifer circuit?

texts:
Recently I was going through the data sheet of the TOP264 TOP Switch IC. In a typical application circuit diagram, at the secondary of the transformer they have used a configuration for the diode as follows instead of using a simple diode for a half wave rectifier.

What difference does it actually make in the output?  Can anybody explain the advantages of this configuration?


texts:
I have built the following circuit. I am using a microcontroller via 3 transistors to drive the transformer and applying a 50% duty cycle 15kHz PWM signal.

With 18V applied to the VIN header input, I am not getting the expected (approximately) 9V output, instead I measure 7.2V approximately.  When varying the PWM duty cycle I also do not get a variation that I would expect. This led me to check the waveform on the input to the gate transformer, which can be seen below:

After viewing this on the scope, I made a couple of test:

Removed C4 and placed a 1K resistor from the Emitter of Q3 and Q4 to ground.  then I observed the output waveform on the scope to be a perfect square wave slightly amplified, as expected.
With C4 back in the circuit, I removed R6 and placed a 1k resistor between pin 6 of the transformer and ground.  With this setup the same waveform as in the image above was observed.
I carried out one final test by using the circuit as shown in the schematic, but removed the 18V from the VIN.  Then I scoped the gate of the MOSFET, and observed the following waveform.

I believe this is being caused by the transformer as everything points to this from the tests I have made.  Is there anyway to reduce this effect with discrete components?

Edit  I could not comment on a question (Andy aka thanks for the prompt reply and links) and the criteria for a re-post on this questions was against forum etiquette hence this edit.  Just to clarify something, the MOSFET I am using is a logic level MOSFET.  I have used this successfully with a similar circuit but as a boost converter.

Would this circuit (image below) on the secondary side help reduce the noise I am seeing?


texts: Non-inverting amplifier ; Single supply ; Bipolar input

texts:
I am working on the non-inverting amplifier using a single supply, which can amplify bipolar input signal. Non-inverting amplifier is working fine without any issues, only the negative portion of the input is clipped. The schematic is shown below.

To amplify both positive and negative portion of the circuit, I gave DC bias voltage at non-inverting terminal, but in the output I was not getting any signal. Schematic is shown below. I even simulated the circuit and I got proper waveform amplifying both positive and negative signal, but while making, it is not working. I am getting flat line in the oscilloscope.


texts: Can tricolour LEDs be connected in series?

texts:
I'm constructing a LED matrix using tricolour LEDs. I was wondering - will I be able to wire these in series?

I was told to mount the LEDs in series using stripboard, then wire each stripboard in parallel.

Here's the datasheet for the tricolour LEDs.


texts: Integrator Circuit using Op-Amp Differentiator

texts:
Source: http://www.electronics-tutorials.ws/opamp/opamp35.gif

This is an OpAmp differentiator circuit. Output is the derivative of Vin.

My question is: If I use output as input and Vin as output, would I get the integrated signal of input?


texts: Why do the inputs of this CC circuit op-amp need clamping?

texts:
I'm studying the constant current circuit of the HP E3610A DC Bench Power Supply. I'm building a supply of similar topology using surface mount components and the LF442 isn't available in a SOIC-8 package. So I need to re-spec this op-amp, which is actually welcome since retracing the full design exercise is half the reason I started the project :).

(Click to enlarge. Original is here on 3rd-to-last page and contains component values for those marked with asterisks.)

The current error amplifier is the block on the middle right. Note the two clamping diodes across the op amp (1/2 LF442) inputs.

I'm wondering why this op amp would need input clamping diodes?

The non-inverting input goes to ground (0V wrt +12/-12 supply, S+ in this schematic)
The inverting input goes to a summing point which will be at 0V when the current output equals the constant current (CC) set point.
The summing point is a 20/1 resistive divider formed by R24 (50K) and R23 (2.5K). R24 receives the set point voltage, 0 to -6V on the top and R23 receives 0 to 0.3V from a 0R1 current sense resistor on the bottom. Worst case (max set point, zero actual current) results in -0.3V applied to inverting terminal.
Feedback capacitor C12 is 180pF.
So I'm assuming these voltages are unlikely to get too crazy and I'm not seeing any source for violent transients on startup or shutdown. C12 could get charged up to +/- 12V, though, so maybe that's something.
The LF442 has a Differential Input Voltage rating of +/- 30V, which I would have thought would be plenty for input protection purposes.

So I'm not seeing why the clamping diodes would be needed. I suppose I'm inclined to think it's to improve the response time of going into and out of CC mode somehow rather than to protect the op-amp inputs.

Can anyone help me understand why the designers might have put them there?


texts: For a transmitting Antenna, can the gain be positive in decibel scale?

texts:
Gain in dB scale of the transmitting antenna is:

$$G=10\cdot\log \frac{P_o}{P_i}$$

The input power will always be larger than the output power. However, I see a lot of radiation pattern graphs with positive gains in dB. How is that possible? Shouldn't the gain value ALWAYS be negative as the power ratio P_o\P_i will always be less than zero?


texts:
When we describe a AC signal (voltage is this case) in time domain we use an equation something like this below:

\$v(t) = V_m \mathrm{sin}(\omega  + \phi)\$, where  is the angular frequency of the voltage.

I know  is the symbol for angular frequency which is equal to \$2  \pi f\$ and is measured in rad/s.

So why does the voltage equation above show the angular frequency as  and not just ? Is the \$t\$ there just to show the measurement is with respect to time?

Or is it because  and  not the same?


texts:
As per the datasheet, to use Multidrop system, I have to match for the ROM address of the slave device, and then issue the READ ROM [0x33]command.
But as per my understanding its a static process, i.e. having all the slaves connected on board we cannot obtain the address of a single slave. Each have to be connected separately, obtain the address and so on.
Is there any method to get the sensor value without knowing the address, in multidrop system?


texts: Can a nRF24L01+ chip work alone? (i.e. without Arduino borad)

texts:
I have a prototype based on the ESP8266 wifi tranceiver as a standalone module, without any Arduino borad.

It works fine, but I have heard that the nRF24L01+ chip is less power consuming.

After some online research, I think there is no possibilities to embeed a program on the nRF24L01+, as it has no memory.

I just wanted to check in this forum if I am right or wrong.

(If I am right, there is no point considering the nRF24L01+ as I should also power the Arduino board)


texts: You see them in various stereo systems and such, they are used to simulate a potentiometer. There is no limit to how much you can turn them in either direction and as you turn them they send pulses indicating the direction. What are they called?


texts: Arduino Nano disconnecting from PC on plugging in 3.3v NRF24L01 into PCB

texts:
I've built this PCB which includes two I2C port expanders, an Arduino nano, inputs for buttons and encoders, and headers to plug in an NRF24L01 board.

Currently, I just have code running to read two encoders plugged into J12 and J11 on this schematic, and send how far each of them have turned over the serial port.

This all works perfectly, the problem comes when I plug in the NRF24L01 into the headers on the board. As soon as I do, the arduino disconnects from the PC; I get the little noise from Windows, both the COM port and the device disappear, and it resets the arduino. However, I can still see the TX LED light up, so the code is still running and the data is transmitting over serial, the PC just doesn't see it anymore. As soon as I remove the NRF board, the nano reconnects and works as usual.

I've tried plugging in an external power source and get the exact same behavior, so I don't believe it's an issue of the NRF drawing too much power. I've tried several different NRF boards as well, so it isn't an issue with the specific board I have plugged in.

What could my problem be?


texts:
According to "the art of electronics" (p 651) and other internet sources, the ćuk switch converter has the most desirable properties: continuous input and output current waveforms, boosting and bucking, and "zero-output ripple" current.
There are plenty of switch converters sold in any store like eBay (e.g.:this one), but I found nowhere a ćuk converter at such a low price (and even hardly at high price). Is there a problem with them that makes them unpopular? Why aren't they sold ?


texts: can fourier transform be used in circuit design?

texts: If I formulize the input voltage that I am planning to give to a circuit and if I formulize relative output voltage that I expect to see with respect to input voltage, I can take their fourier transform and divide them to find fourier transform of impulse response of the circuit which is LTI if it involves linear or linearized elements I assume. Then I will find reverse fourier transform of fourier transform of impulse response to find impulse response in time domain. By using it,somehow, I want to relate the input voltage to output voltage in a block diagram. Then I will replace those blocks with relative circuit blocks. Ex: if there is a block that integrates input voltage to it, I will replace it with integrator op amp. Is this possible to do this? I would be happy if you correct flaws in my strategy. I searched web/youtube/my text books but there is no such attempt I came across


texts: What micro-controllers are suitable for a closed-loop DC Motor?

texts:
I am working on a small experiment on a closed loop DC motor for speed control.
The DC motor is separately excited and fed through a DC chopper.

I would like to know what are the best micro-controllers best suitable for this project?


texts: Eliminate/reduce speaker pop when powering off amp

texts:
I'm repairing an old 1970's record player and one of the items on my list is to try and reduce the loud 'pop' noise when switching off the amp. I've done a little research and it seems there are a few different reasons this might be happening, my first challenge has been diagnosing the origin of the problem.

A common fault is arcing across the power switch contacts. I've seen various suggestions for this online, including:

Add an X2 cap across the power switch
Add an X2 cap across the power transformer primary
Add an MOV (in series?) with the transformer primary
Replace the switch

I've ruled out (with some help in the comments) that the problem is not likely to be the power switch contacts. I've now identified the following conditions cause the pop:

Turning the amp off with the power switch
Pulling the plug on the amp while it is switched on
Stopping the turntable (the amp and turntable deck are one unit)

The last condition is particularly interesting, since the amp does not lose power when the turntable stops. My next step is to familiarise myself with the link between the deck and the amp, as this might narrow down the source of the problem.

I'm not sure if I'm on the right track here. Is there a better approach to my problem that I should be taking?


texts: Recognising output impedance of an amplifier though inspection

texts:
The output impedance of FET amplifiers seem to be a hit and miss affair when I try to find it just through inspection. For example, sometimes it's easy to predict, whereas some other times I have to go through very tiring circuit analysis just to get it; and my answer through inspection seems to be way off from the actual value. For example, the common gate amplifier has an output impedance of \$1/g_{m}\$ which wasn't intuitive at all.

So, I wonder if there's a way that one can tell from inspection because its possible that the way I'm inspecting things is wrong.


texts:
Attached simulation of op-amp .

Q1) In Op-amp ckt 1 has power supply of 20V and  In Op-amp ckt 2 has power supply of 15V (rest everything is same). How current consumption is more in 20V rather than 15V supply ( see image opamp ckt 1 and opamp ckt 2 , current consumption is 1.33mA and 1mA respectfully). If everything is same then current consumed should be low or high.

Q2) How to Calculate total power consumption in opamp ckt 3. ( as per simulation result, see image opamp ckt 3)

Q3) In opamp ckt 3 , Input power consumption is 15 V*1m A=15 mW , and output power given is 9.59 V*9.59 mA= 91.9 mW, how output can divilerd more power than input consumed.


texts: What does this bidirectional TVS diode do

texts: This is a schematic for a crude taser design ive been studying. From what i can tell when the switch is on the relay turns on and off continuously, which charges up the LC circuit in which the capacitor and primary of the transformer (inductor) continuously charge each other up. Since the circuit turns on and off due to the oscillating relay, according to the law of voltage across an inductor, large voltages are dropped across the inductor, which when multiplied by the transformer create huge voltages on the secondary, thus the sparks. That all makes sense to me, but i have no idea what the purpose of the bidirectional TVS diode is, apparently it is to clamp the voltage at 350 volts but i have no idea what that means and the google searches i have madebwerent helpful.


texts: Conductive object to raise 6mm height off PCB

texts:
I am designing a PCB where I expect to have a certain part assembled at the edge of each board (blue in the picture below).

However, this part needs to be at connected/soldered at a height of about 6 mm above my PCB. Therefore, I'm considering using some conductive object/part to create the vertical displacement (green in the picture below).

So far I have considered

right-angle header pin; but may be too thin/flimsy.

zero-ohm resistors (0402-sized or 0603-sized); but I'd need to stack too many of them to get the 6 mm height.

I am interested in ideas for some object/part I could use for the 6mm height-creation; anything as long as it would be:

inexpensive
widely available
conductive
preferably NOT through-hole (soldered on PCB top surface)

What would be ideal is if it were just a 6mm cube of conductive material, but no such normally-sold object seems to be readily available!

(Note: This height-creator needs to be strong in its soldering to the board, just as any standard part soldered on a PCB, but it does NOT need to be strong in its soldering to my blue part.)


texts: Why having two resistors (1k and 10k) in my circuit works?

texts:
I've put together a Vellman MK102 kit (Flashing LEDs) to try and get a handle on how circuit work.

I wondered why resistors where placed after the LEDs, and I learned that it's because resistors affect the overall current flow throughout the whole board (electricity being like a chain link rather than flowing like water through a pipe).

My board has both 1K and 10K resistor. How does that work? If electricity is resisted by 1K throughout the whole board how does it go up to 10K? Which has precedence and why are there two types of resistor in the board?

Can somebody explain to me how having 1K and 10K resistors in the same circuit works?


texts: Make my battery level indicator dimmable

texts:
I wired up this battery level indicator using a 9V battery (power supply is for ease of changing voltage.)

It works well with only D1 lit at 6 volts up to all five LEDs at 9 volts.  My problem is that I need to be able to dim the LEDs with the potentiometer at the top of the diagram.

In actual practice the LEDs dim very little when I increase the resistance to the maximum. I need them to go from full brightness to fully off dependent upon the setting of the potentiometer.  I am relatively new to electronics and I have no education in the field.  Any thoughts?


texts: Determining whether a system is LTI given response to a rectangle box input

texts:
Given a system, it is possible to determine whether the system is LTI given the response to input to the system, other than the unit impulse?

Specifically, my input to the system is

$$x(t)=\begin{cases} 0 & t<0, t>0.5 \\ 1 & 0 \le t \le 0.5 \end{cases}$$

The output is given by

$$y(t)=\begin{cases} 0 & t<0, t>2 \\ t & 0 \le t \le 1 \\ 2-t & 1 \le t \le 2 \end{cases}$$

I do know that, if the system is LTI, then the differential of the step response would give the impulse response. However, I'm not exactly sure how to use this information.

While I'd appreciate a specific response to my question, I'd be more interested in a general answer that characterizes the nature of input for which whether or not the system is LTI can be determined, and if it can be determine, and algorithm to do so.


texts: In a transformer, how do you determine where the induced EMFs (E) and voltages (V) are placed in a vector diagram?

texts:
I will be citing pictures from Electrical Technology by Theraja.
So there are different cases with regards to the transformer depending on what losses and loads are considered. Each of them have different vector diagrams. My question is how do you know where to place E1 and E2 as well as V1 and V2? It feels like it's different depending on the case. You will see later in the cases I present that there is no consistent placement of E1, E2, V1 and V2 in all 5 cases.
I want to know how those vectors were made in the vector diagram, and from there I can get how to make the rest since I already have an understanding of the angle relationships between voltage and current.

Case 1 - Ideal Transformer
No losses of any type and no load.
Taken from Page 1121.

As you can see, E1 and E2 are in phase. V2 is not shown because probably it is equal to E2 since there is no load.

Case 2 - Practical No Load Transformer
Has core losses and no load.
Taken from Page 1126.

As you can see, E1 and E2 are in phase. V2 is not shown because probably it is equal to E2 since there is no load.

Case 3 - Practical On Load Transformer
Has core losses and load.
Taken from Page 1129.

What happened to E1 and V2?

Case 4 - Practical On Load Transformer with Resistances
Has core losses and load with winding resistances.
Taken from Page 1132.

This one is clearer since E1, E2, V1 and V2 are all present in the diagram. I just want to ask for an explanation why they are placed that way.

Case 5 - Practical On Load Transformer with Resistances and Reactances
Has core losses and load with winding resistances and reactances.
Taken from Page 1135.

This one is also clearer since E1, E2, V1 and V2 are all present in the diagram. I also just want to ask for an explanation why they are placed that way.

EDIT: I actually noticed that for Case 3 to Case 5, where a Practical Transformer has a load, E1 and E2 have a constant placement in the y-axis. That would probably make things easier to explain to me.
My question is why are those induced EMFs selected as the reference for those cases? Why not the voltages (V)? It might be for convenience or tradition, but I was wondering if there are other reasons besides those if those are one of the reasons.
Then for Cases 1 and 2, why are E1 and E2 in phase with each other and why on the negative y-axis?
Also, (a) (b) and (c) in pictures with 3 diagrams refer to (a) resistive load or 1 pf, (b) inductive load or lagging pf and (c) capacitive load or leading pf.