texts:
I have been attempting to simulate a DC-DC Boost converter in 'CircuitLab', rather than going down the route of using an IC I have decided to go down the 'traditional route' and use a MOSFET, simply because I need to be able to digitally vary the duty cycle of the switching frequency which will be driven from an Arduino Uno. I have used the equations given from Texas Instruments - However, I'm unsure if this is would still work with my circuit seeing as these calculations are eventually used with an IC.
The requirements for my converter are as follows;

Vin = 3v
Vout = 14v
Iout = 500mA
Switching Frequency = 100KHz

Based on the equations given I have been able to form the following calculations;

Duty Cycle = 0.83
Inductor Ripple Current = 0.47A
Inductor = 50uH
Maximum Switch Current = 3.17A
Output Capacitor = 41uF

When selecting a MOSFET, the main characteristic I looked for was to make it a 'Logic Level ' MOSFET - As the PWM will be driven from an Arduino. The chosen MOSFET is the 'STB55NF06L' with an RDS of VGS = 5v, 27.5A.
In order to decide which diode to use I checked to see if the Non-repetitive Peak Surge Current was > than IOut. Also, I chose a diode with a short reverse recovery time. The selected diode is the '1N5819'.
Since deciding on these components I have tried to run a simulation, but am not getting the results I have desired. The output isn't boosting at all, Vout is dropping to 2.5v. Any ideas on how I can fix this?
Here is my circuit diagram;

Update;
I have built the boost converter using the information I have gathered from the answers given and I've run into a slight problem. I have used a 22uH inductor and a 33uH inductor that I had immediately available (FT00765 & FT00766). As these inductors have a fairly low current rating, they were unable to take the current of my circuit - as a result, getting incredibly hot. I understand that I need to purchase an inductor of the same value but a higher current rating. However, what I don't understand is the difference between current rating and current saturation rating. Based on my simulation, the peak current through the inductor is around 16A at the initial boost, and then levelling off at between 2A to 4A in CCM. Therefore, I have been looking at inductors such as; 2300HT-220V-RC with a current rating of 19A, would this be a suitable inductor or do I need to look at an alternative? I have also looked at AIRD-02-220K which also seams like a feasible inductor.


texts: How do I compute the closed-loop gain when using an op-amp with finite open-loop gain?

texts:
my future fellow Electrical engineers.

I can't figure out how one gets -500(b) as the Open-loop gain.

Using node analysis:

\$i_1 = \frac{v_- - v_{in}}{100 Ohms}\$

\$i_2 = \frac{v_- - v_{out}}{100k Ohms}\$

and then substituting in \$v_- = v_+ - \frac{v_{out}}{A}\$. As the open loop gain of an op amp is not infinite. However, using this method, I got a wildly different answer (assuming I solved for \$\frac{v_{out}}{v_{in}}\$ correctly).


texts: Is \$f_{\text{hfe}}\$ independent of BJT capacitances?

texts:
Bipolar junction transistors (BJTs) exhibit a gain rolloff as a function of frequency known as \$f_{\text{hfe}}\$, closely related to the device's transition frequency, \$f_T\$. As I understand it, this phenomenon is related to the transit time of carriers through some parts of the device.

Is this phenomena distinct from the frequency response characteristics of a BJT caused by its various capacitances such as \$C_\text{BC}\$? Or is it just a convenient way of thinking about the frequency dependent behaviors of those capacitances under typical operating conditions?

The reason I'm asking is I want to understand the role of \$f_{\text{hfe}}\$ in characterizing the frequency response of a BJT amplifier. I'm taking from some of the sources I've been studying that \$f_{\text{hfe}}\$ can be considered separately from any poles produced by the interaction of, for example, \$R_{\text{input}}\$ with \$C_{\text{bc}}\$, but other sources seem to neglect \$f_{\text{hfe}}\$ altogether.


texts: Altium: unable to slice a polygon pour on a mechanical layer

texts:
In Altium 18.1, I need to create a layer for a flex stiffener.  I created a mechanical layer
and did a polygon pour for the entire board area.
Now I want to slice the polygon pour to remove the pour from flex bend lines.
It appears that slicing a pour on a mechanical layer doesn't work. The slice line vanishes
on the last click.
I am able slice a pour on a signal layer.  Am I stuck using a signal layer for a stiffener
or is there another solution?


texts: Connection of dusl 12v NiCd battery packs

texts:
I have the 12v battery (it is actually 10 Ni-Cads in series), and, of course, it has a red wire coming from "+" and a black wire coming from "-".

However, on the schematic I am confused about whether the red wire should go to terminal 24, or the black wire. (It's the top line, with terminals 24 and 20.)

I was changing the batteries and didn't take a photo of the connections first, and didn't see this battery was -12v, not +12v. Stupid...

Appreciate any help. This is probably very simple for anyone here, but I don't want to make mistake and bolax this instrument.


texts: What switching speed limitations will this H-bridge circuit have?

texts:
I would like to use an H-bridge to switch higher voltages (between 5v and 48v using an adjustable linear regulator as the input voltage to the circuit VCC below) on a small piezo electric buzzer (reversing polarity on the buzzer). I'm ideally wanting to switch these voltages with really tiny pulses between 1\$\mu\$s and 20\$\mu\$s. I'd like to know if the circuit below would have any limitations to switching small pulses like these on the order of single to tens of microseconds. Is it possible to use this circuit to get close to square output pulses on such tiny width input pulses?

edit
Jonk has suggested simulating this circuit. I can see using a 2N222 transistors that I will not be able to achieve a perfectly square output for such a narrow pulse.The circuit below is using 1K resistor between gate and source and 1k resistors at the base of the transistor.

I'd like to achieve within 10%-20% tolerance on the width of the amplified pulse between the top of the rising edge and falling edge. For example if my input pulse is 1\$\mu\$s then I'd like my output pulse to remain high at 48V for at least 1.2\$\mu\$s even if the edges of the amplified pulse are not perfectly square. What should I take into consideration to achieve this or is this a poor circuit choice to do this?

Plot 3 and 4 below show the voltage of each output on the bridge.


texts: Help identifying this Connector - Looks like a smaller version of mini-DIN

texts:
Does anyone recognise this connector. It is used as power connector on a Targus universal laptop docking station. It is 10mm diameter, 4 pins. Similar to but smaller than the one on the right which is a 4-pin Mini-Din. (The one I bought before I checked the dimensions )

Thanks,


texts:
I am developing a new open source device which consists of several functionalities. My plan is to get it printed from a PCB manufacturing company and get it assembled from the same company. I have discussed with several people and came up with the following options. Please note that the device has 150+ components and 350+ nets.

Develop the PCB as a 4 layer PCB and components on both sides. (Size : Arduino Uno)

I have tried obtaining a quotation from seeedstudio and for 100 boards, total cost was estimated as USD 4994.26

Develop the PCB as 2 layer PCB and components on one side. (Size : Arduino Mega)
Develop the PCE as 2 layer PCB and components on both sides. (Size : Arduino Mega)

For the above two cases, it was quoted as USD 4878.23

So my question is this; In production, if we place components on both sides, does it have a major impact in the cost and the process? (As the boards need to be turned to solder the other side etc.)

Edit!

I am adding more details about the PCB. The PCB is a device with a 16 bit PIC microcontroller (TQFP44) which acts as the main processing unit. All the components are SMD. It has a UART bridge(MCP2200) and a couple of OpAmps (SOIC8) to generate sine waves, square waves and a ADC chip with a few voltage doublers and inverters to provide functionalities such as a 4 channel oscilloscope, 4 channel logic analyzer and expansion slot for an ESP chip. The device can be connected to a computer via a USB cable and with the use of a desktop application users can interact with the device.


texts: A lot of resistors, like This one, are rated both for breakdown voltage and for maximum power. Well, this is probably a stupid question, but if a 10MOhm resistor is rated for 10kV, 1Watt, certainly at 10KV it will dissipate 10W and will be destroyed (which is the most evident breakdown failure). Similarly, considering a usual 1/4 Watt film resistor of 10MOhm, rated at 500V breakdown voltage, if 500V is applied to it, surely it will dissipate less than 1/4 Watt. At least one of these ratings is redundant and even contradictory with the other. What is the logic here ?


texts: Why is the ADDR flag cleared without reading the SR2 register?

texts:
I am doing I2C project with MPU6050 using STM32F4DISCOVERY board. The ADDR bit in SR1 register is clearing in one instruction execution without reading SR2 register. Because of clearing ADDR bit, I can't do acknowledge disable is made during EV6 in single byte receiving case.

The datasheet states:

  ADDR: Address sent (master mode)/matched (slave mode) This bit is cleared by software reading SR1 register followed reading SR2.

In case a single byte has to be received, the Acknowledge disable is made during EV6 (before ADDR flag is cleared) and the STOP condition generation is made after EV6.

If I write any instruction (or declaration) between I2C->DR=address|0 and while(!(I2C2->SR1 & (1<<1))) in below code, then ADDR flag is cleared without reading the SR2 register (I2C2->SR2).

if(direction==i2c_transmitter_mode)
{

    I2C2->DR = address | 0;//SEND ADDRESS WITH ZERO LAST BIT
    while(!(I2C2->SR1 & (1<<1)))
    {
        if(--i2c1_timeout==00)
        {
            return 1;
        }
    }
    I2C2->SR2;
    return 0;

}

How can I fix this problem?


texts: Sine to Square wave converted using only transistors

texts:
I have this circuit:

can someone explain how this circuit works?

I did Ppsice simulation for the circuit and the results:

I don't understand how this circuit works, on the simulations its clear that it takes Sine wave and the output is amplified square wave with the same frequency, But how it does it?

does this circuit better than the circuit suggested on this topic: Sine wave to square wave - Schmitt trigger
??

What is the purpose of Q8 on the Scheme?


texts:
I am looking for a way to recharge some glow in the dark paint in a way that isn't noticeable to others. My idea is to use a very fast pulse of light from a bunch of UV LEDs every few seconds, but where the pulse is below the human perceptibility range.
My first thought was a 555 timer, but that seems to struggle at less than 50% duty cycle as I look at all the online calculators. I dug up a digital PWM that I found in a drawer, but its lowest setting is 1% duty cycle and 1Hz.
I was thinking something more along the range of 0.01% duty cycle at 0.25Hz. What would be an appropriate way to solve this if not with a 555? Since I don't know exactly what the human perceptibility range is for a strobe of light, it would be nice to be adjustable so I can let it be on as long as possible as I test it.


texts:
I'm fairly new to electronics, but I understand the relation between current resistance and voltage. I wanted to make a heating element for a project of mine. I have a spool of 14 awg bare copper wire, but I don't know how many amps I need. I'd like to get the heat output on the wire to 60-70 watts. If anyone could tell me a formula or relation between current and/or resistance and wattage, that would be great.

Thanks for your time


texts: Guidance on programming control registers in a device (DAC)?

texts:
I need to program audio DAC chip registers, I know it is controlled through I2C pins but other than that im clueless.
DAC is Ak4493

First off what options are there of devices to control it? e.g are there USB to I2C interfaces that can allow it to be controlled through a PC software?

Secondly how would I begin to be able to understand how to actually program the registers?
here is one example taken from the datasheet, How would you make use the Address and Bit values? :

If you are wondering the PCM, EXDF, and DSD columns are simply referring to different DAC modes and indicating which of these options are available in those modes


texts: How to control on/off with multiple LEDs without traditional multiplexing

texts:
first post here but I've been doing some research and cant find a definitive answer.

Goal: Use some type of voltage-controlled switches in parallel (similar to schmitt trigger) that will accept PWM DC power from an Arduino Uno that will all actuate at different times (voltages).

Example: Source voltage is 6v, I want an array of 5 LEDs that can be turned on/off individually, each one triggering at a different input (1 Vdd each) from a single Arduino PWM pin.

I would like to use simple components that I already have (good selection of transistors, diodes, resistors, capacitors etc.), and don't mind building a circuit that's already on an IC if it means I don't need to go get parts.

I've looked into Schmitt Triggers and can't find a version that will run off of PWM DC power, AC only (kinda the same thing? couldn't get it to work). I'd like to avoid the 74HC595 because it requires 3 inputs not one. Physical size isn't a problem, only specialized parts. Tried using simple transistors as switches but there's a lead in/out dimming effect, I want as close to all the way off and all the way on as possible. I also looked into a 555 timer option where there's a voltage divider network leading to each timer, and pins 2/6 on the timer were inputs from the Arduino, but couldn't quite get that to work also (with the whole 1/3 and 2/3 being on and off instead of being relatively close).

If I'm missing any crucial info please let me know! I'll be pretty happy if there's a simple fix that I'm overlooking, thanks!


texts:
I need a help from someone who knows DALI standard well and has experience on it and knows DALI control gears' structure.

I make a DALI related application and aim to detect if the connected lamp is broken. To do so, I send following commands to the DALI control gear (slave)

0x92 Check if there is a lamp failure
0x93 Check if the lamp is operating
0x9B Check if the slave is in power failure mode

before it, I disconnect the lamp unit, then send the commands above, however, the slave unit does not report any failure. I use couple different DALI unit of Tridonic. I wonder why removing a lamp source do not generate a failure report?

Could you please explain the logic how the DALI control gears detect the broken lamps (e.g. in what cases the DALI unit generates response to 0x92, 0x93, 0x9B)?

What command is the best to detect the broken lamps?

EDIT:
I send 144 query message, its definition on the standard:

As a reply, I get this signal at the oscilloscope:

means:

start bit(1) |  reply (8)          | stop bits(2)
     1       |  0 0 0 1 0 1 0 0    | 1 1

means:

0: the ballast is working fine
0: no lamp failure is detected (if there is no lamp unit, why it is not a failure? and what is the description of the failure?)
0: arc power is off?
1: limit error -- (I send 0xFEA0 which is an arc power setting, I could not understand why it is 1)
0: no fading is ongoing
1: reset state is present
0: it has short address
0: no power failure ( it received RESET command and arc power control command)

the timing is a little bit bad but I have an ad-hoc method to read it successfully anyway. I get the same reply if the lamp unit exist or if I remove the lamp unit on the run-time.

I wonder why DALI do not generate a failure if the lamp unit does not exist (or removed on the run-time)? What cases are defined as failure? I wanted to test that I can detect the lamp failures (without breaking my lamp unit:), so that I am disconnecting the lamp unit. Is it a wrong thinking? If it is so, how should I have tested it so that I can get the lamp failure report from the DALI slave?

What command (or command sequence) is the most reliable way to detect a broken LED lamp (by querying from DALI LED control gear)?

I feel like I cause to take one's time to get a reply. I would be happily give 100 bounty for a satisfactory answer to show my gratitude.


texts:
So I'm trying to design two mirroring current limiters for a +-15 volt power supplies.

I don't understand why these two circuits don't behave more like each other.

The PNP circuit has +15 on the top and ground on the bottom and

The NPN has ground on top and -15 at the bottom.

The npn limits at around 600mA which is what we expect ,but I'm not sure why the PNP is 450mA.

I don't understand why the Vbe on the PNP is only 0.46 V and not around 0.65.

Any comments are much appreciated.


texts: Passive filter design, transfer functions and loading

texts:
I have been playing around with some basic passive filters (first order), really just to try and get a better understanding of the equations and transfer functions.

I was talking to someone about the transfer function for a band-pass filter - I was thinking that to get the full systems transfer function, I needed to multiply the high pass filters transfer function with that of the low pass filter, but they seemed to think that I would require some sort of buffer between the two stages, so I don't "load" the second stage.

I know this is quite general, so may get closed, but I am hoping someone can explain a bit about loading the second stage, and the problems this might bring up and ways to avoid it (i.e. is a buffer the only way to go).


texts: How to calculate the number of windings of a unknown coil?

texts:
I'm basically trying to determine everything about an unknow coil. I have a DC power supply, function generator, oscilloscope and various small electronics parts (resistors, capacitors and so on). I have zero information about this coil except that it has no core (air core). The diameter of the core is 7mm.

The coil itself is encased in plastic. I only have two wires available.

How can i calculate/measure the inductanse?
How can i calculate/measure the number of coil windings?

Is it possible to calculate/measure the diameter of the wire, without measuring the wire itself?

Regards


texts: Amplifier circuit for different frequency

texts: I have construct the amplifier circuit by using LT1227 for gain=15. suppose for the input waveform should be amplified to 15 xVin for 0 to 5MHz, but why the output amplitude for higher frequency from2-5Mhz,the output amplitude waveform will decrease? as shown in figure below, the amplitude for input waveform of 1 and 5MHz is about 950mV, but the output amplitude for 1 and 5MHz difference much for the same gain,why are the possible causes of its?


texts: Auxiliary circuit to reduce power losses in idle stage of this oscillator (wireless power application)

texts:
I am trying to implement the following resonant oscillator for wireless power transfer application. There will be a secondary coil coupled with Lp. .

Reference - WPT Application Note

One of the pitfalls of this circuit is that the power consumption can be high when the secondary coil is absent.

Is there a way to design an auxiliary circuit to detect when the receiver is not present and to reduce the idle power consumption (possibly, by introducing a high series impedance and decrease resonant current)? However, it should also be able to detect when the receiver is coupled and activate the normal operation.
Can we use something like tickler coil for this purpose?

Edit:

I want to exclude obvious approaches which require the installation of additional sensing layer, for example, proximity sensors to detect receiver or additional communication link.

Next, as some of the answers suggested, using a simple micro to detect the changes in primary phase or define a current threshold to cut off the supply can be implemented. However, such approaches are highly dependent on the circuit parameters (frequency, power, etc) and most importantly, these sensing become challenging if we want coupling to be weak. When coupling is small, reflected impedance may be very small to make significant changes in primary side.


texts: Converting PWM to Constant DC for Power Applications

texts:
Main Question:
What is the best way to convert PWM voltage generated by an external (i.e. 'blackbox') power source to a constant DC voltage while minimally affecting the load it is connected to?

Background:
I built this PWM switch circuit to dim a 12V, 2A LED strip. This would be installed into a boat, and would be connected to the onboard 12 volt battery. Attached to this battery is an inverter and a battery charger, which is powered by the shore power (mains).

Everything worked fine in testing whilst the board was powered by a benchtop power supply, but after being installed into boat it was discovered that when the battery charger is connected, the LED strip begins visibly flickering erratically.

What I believe is happening is that the battery charger converts the shore power into pulsed DC, which it modulates depending on what it decides is required to charge the boat's battery. Because my board is connected to the battery at the same time, this modulated voltage becomes the input voltage to my board, which resets the 555 timer on each cycle of the battery charger modulation, leading to the flickering. I also presume that even if it didn't reset the 555, beat frequencies would be produced and could be visible due to the difference in the power source modulation and my board's PWM switching.

If this is indeed the problem, how can I stop the modulated DC power source from affecting my downstream switching circuit or the load? Thank you in advance.


texts:
I have few questions related to the schematics(BBB_SCH) sheet 2 in link

There is a bulk decoupling capacitor of 10uF,10V connected to the pin 10(AC) of the PMIC tps65217.pdf. Can some one please explain how is this value calculated now I know  C = I * dt/dv but where in the data sheet can I find I , dt , dv.
There is a 100K ohm register R1 on the INT pin number 45. Can some one please let me know how is this value calculated.
Also on sheet 3 there is a SN74AUC1G74 which is connected to the CEC Clock for HDMI Framer. Can some please let me know is this a clock for the HDMI.

Regards

Nick


texts: What's the difference between using SPICE and just putting things on breadboard and testing?

texts: Can SPICE programs do most of the imaginable simulations with any kind of components in the market? Is it important to run SPICE before you do any kind of breadboard work/prototyping?


texts: Significance of \$V_{GS}-V_{th}\$ for MOSFETs

texts: What is this factor's significance? Please, don't give any long mathematical explanation. Seeing the drain characteristics I can easily place all the regions. But where does this  \$V_{GS}-V_{th}\$ lie on the curves? Basically it just dictates how large you have made the voltage at the gate compared to the minimum required to turn it on. Why is it related to \$V_{DS}\$ in bizarre ways in saturation and linear regions?


texts:
I bought pogo pins to use for firmware uploading.

So I have to make a Jig for my PCB,
but this is the first time I use pogo pins.
I have no ideas where I have to solder, I mean I want to know if pogo pins have a direction for soldering.

as far as I know Gold surface is for better current conduction so I think Gold end is for contact point, but in this picture It seems silver end is for contact point; I'm a little confused.

How can I make a Jig for this tiny one? (I use 2.54 mm gap for Test point on PCB)
and
what is the direction of soldering for this Pogo pins?


texts:
Anybody has reference of the what chemicals photoresist for PCB patterning are made of?
I would like something as specific as possible. No brand names please. Peer reviewed papers would be awesome.


texts: system verilog 3d array ,cant insert data , what am I doing wrong?

texts:
Im trying to implement 2d convolution (8 bits each cell int he convolution so in systemV it's 3d) in system verilog,and I have trouble inserting data into the "result" array, and i dont understand what im doing wrong, this is my code:

module conv2d (
                input clk,
                input logic [7:0] img[3:0][3:0],
                input logic [7:0] kernel[2:0][2:0],
                output logic [7:0] result [4:0][4:0]
                );//#(parameter img_size=16,kernel_size=4)()
int i,j;

always_ff @(posedge clk) begin
    for(i=0;i<5;i++) begin
        for(j=0;j<5;j++) begin
            for(int k=0;k<3;k++) begin
                for(int l=0;l<3;l++) begin
                    if ((i-k > -1)&&(j-l>-1)&&(i-k < 3)&&(j-l < 3))begin
                        result[i][j] <= result[i][j] + kernel[i-k][j-l]*img[k][l];
                    end
                end
            end
        end
    end
end

endmodule

my testbench:

module test;
logic clk;
logic [7:0] img[3:0][3:0] ;
logic [7:0] kernel[2:0][2:0];
logic [7:0] result[4:0][4:0];
initial begin
    for(int i=0;i<5;i++) begin
        for(int j=0;j<5;j++) begin
            result[i][j]=8'b0;
        end
    end
clk=1'b0;
img[0][0]=8'd1;
img[0][1]=8'd0;
img[0][2]=8'd2;
img[0][3]=8'd0;
img[1][0]=8'd1;
img[1][1]=8'd2;
img[1][2]=8'd3;
img[1][3]=8'd1;
img[2][0]=8'd0;
img[2][1]=8'd0;
img[2][2]=8'd1;
img[2][3]=8'd0;
img[3][0]=8'd1;
img[3][1]=8'd0;
img[3][2]=8'd3;
img[3][3]=8'd1;
kernel[0][0]=8'd1;
kernel[0][1]=8'd0;
kernel[0][2]=8'd0;
kernel[1][0]=8'd0;
kernel[1][1]=8'd1;
kernel[1][2]=8'd0;
kernel[2][0]=8'd1;
kernel[2][1]=8'd1;
kernel[2][2]=8'd0;
end
//#100;
//$stop;
always #5 clk = ~clk;
conv2d con4test (
                    .clk(clk),
                    .img(img),
                    .kernel(kernel),
                    .result(result)
                    );
endmodule

this is my first time my first time working with system verilog and 3d arrays, couldnt find any helpful info online, dont be harsh with me.

Thanks!

EDIT: fixed the test bench problem.
And my problem is that the result array is not updating meaning it's still 0

EDIT: working!

I did few changed in the code, but the one who did the work (I think) was changing always_ff with always I will tell the truth i have no idea why..
and I'll be super interested if some one knows.

Thanks again.


texts: I changed my turn signals to LED light bars the other day. They are completely legal, but the issue I'm having is I can't use my parking lights and turn signals. The bulb that I took out and replaced with the light bar had two filaments, I want the turn signal to work as follows: When the parking lights are on and I apply the right turn signal, I want the right light bar to flash while the left one stays on. And Vise Versa. Except when I do this now the light bar dims a very small amount while the parking light and the turn signal is applied. My Question would be, what do I need to do to get the light bar instead of dimming a little bit to turn off and on while my parking lights are on. I'm not sure if this little explanation made sense, but you can ask if you need more info. Thanks!


texts: I built a light sabre some time ago Light Sabre using a sledge-hammer on ant approach with a micro-controller. Does anyone have a circuit that would do something similar just with discrete components?


texts: What are the limiting factors of these op-amps?

texts:
I designed a multiple feedback band pass filter

input voltage = 100kHz sine wave, 80mV amplitude
gain = 2 AV,
center frequency = 100kHz
pass-band = 10kHz
output voltage => centered around +2.5V
supply voltage => +5V

Design restrictions are that I must use a single-supply operational amplifier.

Calculations were taken off Op-Amps For Everyone, and I got the desired result with two opamps: OP27 and OP355NA

Points to Note:

Tried multiple JFET op-amps as listed below
Used ideal op-amp to check that calculations are correct

The below circuit was constructed and tested on both Proteus and LTSpice software. Both yielding the same results, which were expected.

Circuit Design:

Analogue Analysis (Gain of 2, centered around 2.5V)

Frequency Response (Center Fre at 100kHz)

The issue is that these parts are either surface mount (OP355NA) or very expensive (OP27). I can't afford to pay more than 20 dollars for an op-amp.

These are the single-rail op amps I have available at my disposal, and none of them work as expected!

Tl 081
Tl 082
Tl 071
Tl 074
LM 358
LM 324

I will be using TL071 and TL074 to simulate from now one.

All op-amps are outputting a very similar result, the following output is from TL071, tested on both Proteus and LTSpice. Here, I present the LTSpice version.

Analogue Analysis

 (Decreased voltage p-p)

Frequency Response

 (Center Frequency shifted to the left)

As can be seen, the gain is incorrect and the central frequency is shifted to the left. This was a recurring theme for ALL op-amps I have available.

I know that the op-amps listed above are all different, but they should all be able to provide an output peak to peak voltage of 1V at 100kHz. The following characteristic graphs are for the TL071 and TL074, both of which give the same incorrect response.

The utility-gain bandwidth is 3MHz.

Surely I am missing some important specification, which I'm not taking into consideration, but I find it very strange that none of the above op-amps work properly for my current task.

Why can I achieve correct results with OP27 (GBW = 8MHz) and not with
Tl074 or Tl 081?

EDIT:

Thanks to the helpful comments and answers it looks like I underestimated my circuit requirements - Mainly the attenuation from the input resistance ratio (40dB)

  Looks like you're trying to get a Q of around 20-40, just eyeballing it, so the GBW is going to have to be that much higher than the center frequency, and preferably 5-10x that, so more like 10-40MHz.

Why do I have a Q of around 20-40? Isn't Q the (center frequency/BW)
or 100k/10k (=10) in my case.
Also, why should my GBW be around 5-10x the center frequency? Are
there any calculations one should refer to or anything of the sort?


texts:
The following circuit is nearly exactly what I need for the output stage of my function generator:

datasheet: https://www.renesas.com/us/en/www/doc/datasheet/ca3140-a.pdf

What I don't understand is how an op-amp with GBP = 4.5 MHz and slew rate = 9 V/us, followed by a unity gain buffer, could possibly have an overall nominal bandwidth of 10 MHz and SR = 28 V/us, especially in a gain of 10 configuration. What am I missing here?


texts:
I'm using my custom circuit in the figure for driving dc motors. I'm providing a PWM (25khz). While trying the activation threshold (minimum duty cycle that activates my motor) experimentally I have noticed (with an oscilloscope) that my circuit I have a problem: if the duty cycle it is 0, the voltage on the motor is 0, but just after I increase my duty cycle, even 1%, I have the VCC voltage on the motor, without any pulse width modulation.
I don't really know what can be the problem, anyone have any idea of the problem? thanks

p.s. The PWMU header (ULN_OUT wires) are connected to the single PWM1, PWM2, PMW3 and PWM4 headers on the mosfets'gates


texts: Calibrating a k type themperature probe for a PID controller

texts:
I just purchased an inkbird PID controller with a k probe to controll a temperature in an oven. I calibrated the k probe at 60F using a trusted digital thermometer with 2 probes.
I installed the probe in the oven and increased the temperature to 120F (measured with the trusted thermometer). My PID was increasing the temperature a lot slower than my thermometer and never went above 100F. So, at 60F both are showing the same temp, but at 120F there is a big discrepancy.
I calibrated at 120F, and now both show close readings in the 120 range, but when decreasing and increasing the temperature, the discrepancy is increaing. The farter from 120, the higher the discrepancy.
So, the question is if I calibrate the k probe at a certain temperature, will the measurement be accurate only in a small range, close to that temperature? Thsi doesn't make sense to me.


texts: What distinguishes an ordinary thyristor from a GTO thyristor?

texts:
A thyristor, I know, is a four-layer PNPN structure, with an anode on the first P section, a gate on the second P section, and a cathode on the second N section. This simple structure suggests that any thyristor ought to be possible to turn off, by routing all of the anode current out through the gate, making the cathode current go to zero, thereby unlatching the thyristor.

In a simulator, a two-transistor model of a thyristor as shown below does indeed turn off when a sufficiently low-resistance path to ground is provided.

simulate this circuit – Schematic created using CircuitLab

And one can purchase thyristors specifically designed to be used like this, called GTO (gate turn-off) thyristors.

So my question is this: What makes a GTO thyristor special? Is it just an ordinary thyristor but with specified characteristics for this mode of operation? Or is there some different silicon structure inside of it that makes it work fundamentally differently?


texts: Creating an Assembly Drawing for Fabrication Houses

texts:
I have a design for a PCB that I have been thinking about producing. One thing that I have found is that I need is something called an assembly drawing. So far, all I have been able to come up with is that they are used to describe which components go where for PCB assembly. But I think they are also used for turnkey supplying as well.

What are the key things that fabrications houses look for in a good assembly drawing?

If I am using turnkey manufacturing, how do I describe what parts I want, and how specific do I need to be for things such as capacitors, resistors, and IC's?

What does a good assembly drawing look like? And is there an easy way to create them with Eagle?

If I order, say 500 PCB's, it is common practice for a supplier to create the first 10, ship them, make sure they work as required, and produce the rest?


texts:
While reading a topic on opamps, I came across this topic. It said, other devices like capacitors amplify signals differently for different frequencies, while opamps amplify signals irrespective of the frequency (sustained gain.)
I haven't heard of amplification using capacitors. I wish to know how does it do and can we find the frequency response of amplification using capacitors?


texts: If I have for example DC signal (voltage and current) and I select on my "scopecorde/datalogger" LPF (low pass filter, not digital! with 5 Hz) what happened on output signals? Is that the same as "mean value" of input signal?


texts:
I want to design a finite state machine that is similar to a 3 bit counter. There are 3 bits of state (i.e. a 3 bit unsigned number) and the counter must count by 3's. More specifically, the sequence it should undergo is 0, 3, 6, 1, 4, 7, 2, 5, 0, 3, 6, 1.

I want to first produce a truth table showing what the next state of the machine should be as a function of the current state. Then I want to produce a combinational circuit using gates and D-flip flops that implements this state machine.

How do I do this?


texts: High speed (>30KHz) 10-bit PWM generator

texts:
I'm looking for a way to generate a high speed PWM signal into a high impedance input gate driver IC. This would be used to replace a lab bench waveform generator. Preferably I would use something like an Arduino so I can use also use the ADC and do my feedback digitally. Unfortunately Arduino does not have that combination of frequency and resolution.

The next best option would be a PWM controller that can be controlled with something like I2C so I could just control it with something like an Arduino.

I've looked high and low, but so far I'm striking out. I need at least 10 bits of resolution because my duty cycle is low (3-5%) and is relatively sensitive to small changes.


texts: How to inteprepret jumper confiuration guide on PCB?

texts:
So I have a M.2 to mPCIe adapter board that unfortunately I don't have any documentation for. The purpose of the board is to allow for a 4g M.2 modem to connect to a PC with a mPCIe slot.
Presumably by changing the configuration of R4/R5/R7 it's possible to set the card to use the USB, PCI, or SATA interfaces. For the life of me I can't tell what they mean by the X's and O's. Should I interpret either X or O as populated?
If it helps, this is the M2BU3S-U3D card from Bplus Tech:
http://www.hwtools.net/Adapter/M2BU3.html


texts:
I'm building an FPGA feed handler and one of the problems is I want to do Monte-Carlo simulations which require a high-quality entropy source, i.e. a pseudo-random LSR implementation won't do. I've read that one can try using metastability as a source of randomness, does anyone do this, is this a viable option?

Also, since FPGAs have external clock inputs, can those be leveraged by some hardware "true RNG" solution? Do such solutions exist on the market?


texts:
The inductor in the middle is the coil of a single-coil latching relay, which requires a H-bridge to drive.

How do I add flyback to the 74HC04's internal MOSFETs? Or should I just rely on body diodes?

simulate this circuit – Schematic created using CircuitLab


texts:
Im confused with this fact. In books I've seen that when DC current is passed in LCR circuit it behaves as purely resistive circuit.And the impedance in LCR is given by $$Z=\sqrt{R^2+(\omega L-1/\omega C)^2}$$ So if ω (frequency) is taken as 0 $$\frac{1}{\omega C}$$ term becomes infinity then the impedance should also be infinite. Then no current should flow through circuit.

Please help me clear this confusion.


texts:
preface
in the AVRs, when I wanted to create a variable frequency waveform (50% duty cycle) within a limited range defined by timer frequency and its prescaler, I used CTC mode:

the OCR registers work both as a TOP value for the timer (or Auto-reload value in ST's nomenclature) and as a compare match with their related IO control (e.g. toggle on match or force HI on match). so I could make a variable frequency with setting just one register (aside from the prescaler).
The problem
the STM32 has 2 different registers for this purpose. while the AVRs had a single OCR register, the STM32 has the TOP value set by ARR (auto-reload register) and the output control with CCR (capture/compare register).
so when we want to variate the frequency, we have to set both registers; ARR for the frequency and the CCR for just keeping the duty cycle of the waveform at 50%. and it seems pretty much the same procedure for activating PWM, despite the different bit settings:

The question
is there an easier way (single register setting) to get a variable frequency on a pin, with the timer in STM32?
STM32F0 ref. manual. the timers with similar numbering are similar on various models so the model number or family doesn't matter.


texts:
I'm developing a device with an Arduino that has to switch off a servomotor that has 3 wires: GND, +12v and pwm signal.
I'm not sure where is the best place to put the relay to switch off the motor.
This is a particular servomotor controlled by a computer, what I need to do is to switch it off using an RF remote.
I don't have a datasheet or detailed informations because it's an OEM part and informations are not public.
My question is, is it correct to stop it functioning by placing the relay on the GND wire? I'm thinking about the GND because if I put it on the PWM or +12v it will be still powered on and maybe it could have some malfunction
What do you think about it?


texts: 1602a LCD - Voltage drops to zero when both VSS and VDD are connected

texts:
I'm currently trying to connect a 1602a LCD screen to an ATMega328P MCU:

As you can see, I use an Arduino Uno for power supply and as ISP. However, when I connect both the first (VSS) and second (VDD) pin of the LCD screen, the voltage in the breadboard drops to zero (Arduino also stops blinking its leds). I was wondering what is causing this voltage drop? Is this possible because of bad soldering or a short circuit? When I connect VSS without VDD and vice versa the screen turns on.
Here is closeup picture of the LCD holes:


texts: Phase Shift Keying: Is it ever actually used?

texts:
during my course in digital communications Phase Shift Keying is talked about where the modulation consisted of altering the phase of the carrier signal. This process takes up a lot of spectrum so I am wondering, is it ever actually used in wireless communications?

Or when PSK is talked about, is bandlimited PSK implied which amounts to QAM with a circular constellation?


texts: Why can't I simulate a current sensing IC (LT6100) using Proteus 8?

texts:
According to this image, I should be able to design a high side current sensing circuit with a gain of 10V/V using an LT6100:

However, if I try to simulate this using Proteus 8 I get an error.
Here is the circuit I'm simulating:

And here is the error:

Any idea why this is happening?

Thank you!


texts: How can I emulate the PS/2 protocol without a microcontroller?

texts:
I am trying to emulate the PS/2 keyboard protocol with a custom piece of hardware, without using a microcontroller. The said piece of hardware will consist of 13 momentary push buttons.

http://pcbheaven.com/wikipages/The_PS2_protocol/

The keys will be hard mapped to specific ASCII values. My idea is (with intricate trace design), on button press, to fill a shift register with the correct ASCII value + PS/2 bits and shift the bits out as the PS/2 data. I was hoping to control the shift register with a decade counter, opening the the latch and inhibiting the clock to the shift register for one cycle, then waiting for 11 cycles to shift the data out of the shift register.

Is there an simpler more obvious solution or should continue to refine my design? I'm testing the concept with 8 stage shift reg + counter, but will expand later to accommodate the necessary 11 bits if the concept works. Also, no formal training in electrical engineering, I apologize if my question is not appropriate.


texts: I'm having difficulty identifying these components. I salvaged them from a diy power supply enclosure from a garage sale. Each of the black leads in the image attached to female connectors on the face of the enclosure. I'm assuming they're transformers of some sort. Any clues would be appreciated.


texts: Solving the time constant in this specific circuit

texts:
I'm having some problems with this circuit from a tutorial website:

When the switch is open, the LED is on.
When the switch is closed, the LED turns off and the timer begins. After a while, the LED will soon turn on. It changes with depending values of the resistor and capacitor (so i think its an RC circuit with a transistor). Im wondering how you would find like an equation that will determine the time constant of this LED turning on when the switch is closed.

Note: the capacitor already has a voltage when the switch is open and it begins to decrease when the switch is closed. When it reaches zero, the voltage goes in the opposite direction (negative), until it hits -0.6V and allows the transistor to turn on and allow the current through. Is the capacitor actually discharging???

Any help appreciated!Thanks! :)


texts: Maximize efficiency and brightness of diff color, cheap, 5m 5630 SMD LED strip lighting

texts:
I'm a science teacher and we are going to explore different design/effects of grow-light setups this year in class. I've gotten some great ideas for this project from reading from this stackexchange site, thanks! I also see problems I hadn't even considered, double-thanks :-)

For cost and brightness and versatility purposes I'll be buying the ~$10/5m strips of 5630 SMD LED's. But, there are issues of efficiency (current-controlling resistors wasting power) and unrealized brightness needing to be address and also here.

First, in the question exploring why there was such a huge loss of energy with LED's that are energy efficient, it was explained that the blue and white LED strips might be up to 80% efficient, but red LED strips be only 45% efficient. Now, it's not the LED's 'fault',  as I understood that discussion, but the circuit design. The strips (regrettably) used a consistent circuit design, regardless of the forward voltage of the LED's being used. The blue and white LED's have a 3-3.6 forward voltage and with 3 in a series meaning they will need anywhere from 9 to 10.8 of those volts, but the red LED's have 2-2.2 Vf so will only need 6 to 6.6 of those Volts. And, if one is using a 12 V power supply, there's a lot of 'pressure' that needs to be reduced with resistance. And as I understand it, the resistors 'waste' that energy. SO... I'm wondering, if I can match my power supply more closely to the demands of what each 3-LED module needs and then adjust the resistance to what it needs to be, I could substantially increase the efficiency of the strips. (I know, it's crazy, but remember, I have many students who would be happy to solder resistors in parallel on these strips!!!--a learning opportunity.)

What do you think about this idea? Lots of these sites where I buy don't give the Vf specs of the individual 5630 LED's so how could I find that out?

Relating to that question, how ought I decide at what current to drive these LED's (so as to be able to calculate the total resistance each module will need)? The discussion about why an LED strip was using less power than expected got me wondering if I should be driving the strips at a higher voltage than they recommend, for example 14.5 Volts to get the hoped-for brightness as given in that discussion. I know heat sinks and LED life relate to this, I'd really like to hear people's thoughts and recommendations on this, too.

For those people interested, from discussions w/plant people I've had at the U of MN about this project, I'm going to suggest to my students to start out with a 3:2:1 ratio of red:warm white:blue LED's in their initial designs of plant-grow systems (though that is the ratio of lumens so depending on the comments on the preceding questions, this may not be the ratio of lights, themselves).

EDIT to include new questions from comments:
Do I need the data sheet to determine what the highest light value I can drive the LED at and still have it last a long life? Or, can I driving it up until it reaches some rule-of-thumb temp.

Also, It seems that the closer one can match the voltage of the power supply to the sum of the Vf of the LED's, the smaller the resistor and therefore the less power wasted. Is that true? What margin of error should one calculate for? (BTW yes, each of the modules has 3 LED's and 1 resistor in parallel.)


texts:
We're building Ben Eater's CPU. We have voltage on the bus of ~1.4V.

We isolated a 74LS273 and wired it like so:

simulate this circuit – Schematic created using CircuitLab

At VM, we're measuring 1.2 V even with a 10k pulldown resistor.

Why is that and how do I get it closer to 0V? I need the voltage below ~0.3V so that other components as the 74LS157 will properly detect it as a digital LOW.

Of course I can replace the pulldown resistor by 0 Ohm (we tried and it worked), but then the input becomes completely unusable.

This is in a less professional environment. We have ESD protection, but I cannot completely ensure it has always been used. Is it an indicator that the 74LS273 is broken?


texts: Why isn't there any 9.5 digit multimeter or higher?

texts:
Why can't you buy a 91⁄2-digit multimeter?

Isn't there any need for it? Is a 81⁄2-digit multimeter the latest high end you can buy? I have tried Keysight, Keithley, and Fluke, but there is nothing higher than 81⁄2 digits.


texts: How can I make/find very small on/off 3x3x3 mm switches?

texts:
I'm looking for very small on/off switch that fit in a 3x3x3 mm bounding box. The application is a tiny figure and all the electronics need to be contained within the body. There is an LED, coin battery, resistor and switch. There isn’t much space left in the body.

The smallest switch I could find is 7.2x2.5x2.5 but it is not small enough.

I considered making my own but I am struggling to come up with ideas to make such a tiny switch. It needs to be easy to make and strong.

Thank you in advance.


texts:
I was communicating two  stm32f4 discovery board and i wanted to create some failure scenario to take precautions. I shorted CANH & CANL and pulled VCC, GND respectively. But now my both of board cant communicate via CANbus.
LOOPBACK mode works well. Communication starts.. (SLAK=0, INAK=0) but later, TEC= 0xF8 , error passive =1 warning=1 and busoff=1 and last error code is = bit dominant error. What will i do now ? My mcu's CAN peripherals are down ?? Please give me a solution.


texts: LTC2852HDD Transceiver defect when the polarity is change

texts:
I have been unsing the above transceiver for our application.  I have discover that when I turn the polarity of this device, the Transceiver does  not work anymore or is defect, because taking back in right polarity, he does not work anymore.

Have been reading many on the topic, I am still wondering, why the transceiver is defect. But I am looking now for solution for the problem.

Will it be possible to just a schottky diode on the line? But I will get a voltage drop and I am afraid that this will lead the Transceiver in an unknown domain.

Here is DATA1+', DATA1-'  and DATA2+', DATA2-' are at the input connector and
DATA1+, DATA1- and DATA2+ and DATA2- at the output connector.

the error occurs when the connector of input is plug to output.

The pin mapping of the connector are as quoted above.

Please of suggestion.

thanks


texts: NMOS bidirectional variable resistor: How to increase body diode barrier potential?

texts:
I want to use an NMOS as a variable input resistor to an inverting amplifier. The source is connected to virtual ground and the drain is connected to the input. I need to accomodate both positive and negative input drain voltages. I know that the NMOS requirement for triode operation is:

Vds< Vgs-Vth

This works for Vds>0....but i want the variable resistor to work even for Vds< 0. The NMOS still works as a voltage controlled resistor for negative drain voltages as long as the body diode isn't forward biased. So I need a large barrier potential to ensure that the diode doesn't conduct.

Right now my solution is to use multiple NMOS in series, but Is there a way to tweak the parameters and geometry of the NMOS to increase the diode barrier potential.


texts: Can we control the data sending by Phasor Measurement Unit (PMU)?

texts: Since PMU send the data after sampling the data to the PDC. Can we design any scheme so that PMU send the data to PDC only when I want? That means to reduced the communication bandwidth can we design any scheme to the PMU so that PMU send the data only where there is any fault?


texts:
I was reading on Capacitive Coupling a bit and become confused when reading the Parasistic section, specifically regarding two claims.

  If a high-gain amplifier's output capacitively couples to its input it often becomes an electronic oscillator.

I imagine this to be similar to the situation when you have input from a microphone and output through an amplifier. The output is then coupled back into the microphone until the output of the amplifer rails, clips, or whatever happens that may cause the loud ringing (what is happening exactly?).

My only problem with the electrical example is regarding how the system may couple its output back into its input. Is this a simple case of simple feedback? How does simple feedback relate to capacitive coupling?

It seems that the output would need some ripple voltage to begin with that would be amplified. Without a clear example, I imagine an unstable amplifier with a small margin of ringing to begin with, but through feedback eventually oscillates much more significantly. Is this correct? As in:

  One rule of thumb says that drivers should be able to drive 25 pF of capacitance which allows for PCB traces up to 0.30 meters.

What does this driving requirement have at all to do with capacitive coupling? To give some context, the article was talking about the parasitic coupling that exists between PCB traces, breadboard metal strips, and PCB traces to ground. I imagine that type of coupling to exist like this between traces:

And this between a trace and ground:

What exactly would "..drivers should be able to drive 25 pF of capacitance.." be defined as in terms of specifications for a driver, and how can one verify compliance?


texts: Physics explanation of charging time by increasing dielectric constant

texts:
I am having a problem understanding in physics of the relationship between charging time and dielectric constant of a parallel plate capacitor.
I'd like about physics aspect not based on time constant.
If dielectric constant increases then capacitance also increases and so the time constant RC.
However, how would you explain it in physics?

With dialectic material between two plates of capacitors, the electric field is reduced. But how that affect the time constant?


texts: ADC not referencing to 4x fixed voltage referenced - PIC16F18854

texts:
I am using a PIC16F18854 with a stable VDD of 5.0V. Tried multiple chips.
Code has been primarily generated using MCC and verified with the datasheet.

Applicable registers:
ADREF: ADNREF = VSS, ADPREF = FVR_buf1
FVRCON: ADFVR = 4x, FVREN = enabled

The ADC range appears to be VSS->VDD; changing VDD affects the ADC output
The ADC acts as if it is being referenced to VDD (between 4.75V-6V)
Changing just one bit of FVRCON to select to 2x or 1x works as expected - a reference 2.048V/1.024V and the ADC performs conversions. The output is stable when varying the supply voltage.

Could anything be leading to such an issue? Or a silicon/datasheet error?


texts: Where can i get the actual implementation of component diagrams?

texts:
is there a place where i can get the actual implementation of a component diagram such as the one below?
Usually the tutorial are high level and dont provide any details of how the connections are actually implemented. SPIxBUF is said to be an interface register which writes and reads to ther FIFO. Exactly how is this implemented? I can only guess that it involves controls signals and mux addressing
Anyone have any resources? Will the implementation details usually be provided from a book in which the diagram is taken from?
Im reading references from Xilinx and it really doesnt provide these details just mainly the functionality, any help is appreciated thank you


texts: What the difference between a phone patch and a Subscribe Line Interface Circuit?

texts: I'd like to construct a device that allows me to use my Western Electric 302 phone with a cellphone, plugged in via the trrs jack, and also have a circuit which allows me to ring the phone, and detect if it is off the hook. I've found this previous question, which suggests I use an Subscriber Line Interface Circuit (SLIC), and I also found this article which details how to construct a 'phone patch'. Is a SLIC just a phone patch with a ringer circuit and off the hook detection? If I were to construct a phone patch, and a ringer circuit, and a circuit for off the hook detection (which I believe can just be done with a micro controller), would I have a SLIC? (Some what off topic, I have a Linksys RT31P2 router and SIP device, could I harvest an SLIC from this?)


texts: How to make servo rotate in a given range no matter how its placed in a chassis

texts:
I'm working on a humanoid robot project everything works but I have one issue. When I disassemble and then reassemble the joints, the servos will more than likely be placed in a different rotational position than which they were last, meaning that they will need to be calibrated again in the program for when the joint is being moved.

What i mean is that if the knee servo's base position is say 0 (knee is straight) and 180 is the max (knee fully bent), if I took apart the knee and fixed it back together chances are the position values for the knee servo will need to be changed cause the servo was placed in at a different angle.

My question is then essentially what sort of calibration system could I make to fix this problem? Could I modify the servos (HS485HB servo) to be 360 degrees and then find a range of 180 degrees for it to rotate through and set it to that, if so how and if not what else can I do?


texts: How do I create ground voltage for my op-amp?

texts:
I am trying to create a practical Wien Bridge Oscillator and I created a simulation for it. Everything works fine in the simulation.
Then I proceed the real part. Since I have only one power supply, I created a very simple voltage divider and used the middle as ground. It didn't work. I tried the same setup at the simulator and it really didn't work.
So how can I simply create a ground voltage for my op-amp?

Edit: I tried this as voltage divider. It works with a DC generator signal and ground but not with a DC source or battery.


texts: What is the advantage of analog subtractor/summer?

texts:
Why we use opamps like in figure 2 instead of just add or subtract signals from each other as shown in the first figure? Is this choice differ if I apply DC signal instead of AC one? Sorry if this is a trivial question.

simulate this circuit – Schematic created using CircuitLab

simulate this circuit


texts: ALE and PSEN example waveforms - are highs and lows "flat enough"?

texts:
Sorry if this is a silly question. All of my waveforms (square, rectangle, pulse) exhibit the kind of behavior in the image where the highs and lows are not super-flat.

Clock is 18MHz and these signals are approximately 1.5Mhz. This is an IDE-host interface to allow "modern" IDE drive to emulate a legacy one. Ground on these traces is with the probe's ground on the PCB ground (which is negative). This is a 5V TTL system.

1) Is this poor measurement or poor signal or both?

2) What practical impact will this have on my circuits? (I.e. will they work?)

Thanks


texts:
I have the following simple circuit:

I thought that the capacitor under R1 can be used to filter off the offset of the DC, but instead I am still measuring (steady) voltage on the output.

Is this the correct way to filter the DC? What am I doing wrong?

P.S. Capsule=Microphone


texts: Potential difference in case only one plate is charged of capacitor?

texts:
A capacitor of capacitance C is charged to a potential difference V
  from a cell and then disconnected from it. A charge +Q is now given to
  its positive plate. The potential difference across the capacitor is
  now?

In case the negative plate was also given a charge -Q then the answer would be simply V+Q/C but in this case I'm confused.Can someone please guide me or give some hints how to find potential difference in case only one plate is charged?


texts: Torroidal transformer design help needed

texts:
I have an idea for a simple circuit that I'd like to use to detect current flow in regular (US) AC household 120V, 60 Hz power.  All my electronics-making friends told me, of course, that there are numerous current sensing ICs on the market now, and that's true, but I'd like to pierce the veil of magnetics a little more myself.
Advice here on Stack Exchange was to go with a Rogowski coil and feed that to an integrator, which I started, then realized 1) Rogowski coils, when purchased, seem expensive, and 2) there isn't as much data about designing with them compared to torroids.
I would like to see if its possible to feed the line I'd like to monitor through the primary of a torroid, and feed the output of the primary to an op amp integrator.  I am at a loggerhead though.  So many engineering textbooks simply mention the very basic formulas for transformers, like ratio of turns in the primary to the secondary.  Few mention a design process using Al of the core, permeability, diameter, etc.  Also, I know an op amp is a very high gain device.  So what is a good level of voltage to shoot for to feed it in order to design around?  Or is that even the proper place to start?
In any datasheet, there is tons of information, and we find usually 2 or three of those parameters are the heavy hitters that frame the entire design, the rest usually are good for fine tuning.  With magnetics, I'm lost.  I need a kind of road map and a list of the parameters that are the important ones to start from.  I could grab a core, make a number of wraps, and see what I get and tweak from there, but I want do be able to eventually do some real engineering here.  Does anyone have any pointers or good books they can recommend?
Thanks for any help.


texts:
I am looking through some old exam problems and I came across one with a solution, I don't quite get.

"In the circuit below what is the voltage drop across R3?"

Their answer is zero, and they come to that conclusion the following way:

$$vb=va\cdot \frac{R5}{R4+R5}=\frac{2}{3}\cdot va$$

$$vc=va\cdot \frac{R6}{R2+R6}=\frac{2}{3}\cdot va$$

$$v_{R3}=vc-vb=0$$

My question is how they can just ignore R3 when making the voltage division equations in the first place. Doesn't voltage get distributed to R3 as well? It almost seems like they know it's gonna be 0 volts and therefore they ignore it immediately.

Can anyone explain to me why this is, and if my intution of how voltage division works is wrong?


texts: Altium - how to select/move the PCB designator when it is "inside" the component outline

texts:
I have some parts where the designator is "inside" the component on the PCB. I want to move them but when I try to select the designator I get the whole part instead.

The only way I've found to do it is:

lock the component location
select the designator
move it outside the component outline
unlock the component location

It works but it is annoyingly time consuming and I have lots of designators to move.

Is there an easier way to select only the designator?


texts: Does ATMEL SAMA5 SPI rely on NSS for byte alignment when configured as slave?

texts:
I am using the Atmel SAMA5D2 SPI interface configured as slave to communicate with an external device that insists on being master. I'm uncertain of the role of the NSS signal in this case.

In a previous project with the same SAMA5D2 but a different external device, I was keeping NSS low for 32 clocks, and then high for 4, to transfer 32 bits of data. This was working fine. However, it doesn't work with the current external device, because that one is keeping NSS low all the time it is transferring data. I only receive garbled data, which makes me suspect that data is not taken from the shift register properly. This then makes me conclude that the SAMA5D2 takes data from the shift register on the rising edge of NSS, but I cannot find any documentation to support this.

There's only one page in the datasheet (section 46.7.4 on page 1703), where it says:

  If NSS rises between two characters, it must be kept high for two MCK clock periods or more and the next SPCK capture edge must not occur less than four MCK periods after NSS rise.

This implies that I was doing it correct before (NSS low for 32 bits and then high for 4 bits), but the "If" implies that it is not a requirement.

What does the SAMA5 expect from NSS in slave mode? Is there any documentation for this case?


texts: Finding AC equivalent circuit of a BJT amplifier

texts:
Given this circuit,

I want to find the AC equivalent circuit. Now, the rules I apply are

Short the DC voltages
Short-circuit the capacitors
Open-circuit the inductors
Simplify
Find amplifier parameters.

The solution given was .

My questions are the following.

Why is C1 still left in the circuit?
I assumed the current would be beta * Ib. But they are using gm * Vpi. I know gm = Ic/Vt, with Vt = 26mV. However, I am confused on which convention to use. Or are they both the same thing?
Why is gm multiplied by Vpi? If it's voltage controlled current source, then shouldn't it be gm * Vo?
Lastly, would Re be calculated by doing Vo/Ie or Vt / Ie?

Different sources are giving me different ways of answering my questions and I want to narrow down to the most accurate method.


texts: SPDT simulation, relay, optocoupler or something else?

texts:
I am currently working on a project where we have to pilot the command of a machine via a remote control based on some input.

Normally, the remote control is a simple push button but we are working on making this push button to be activated based on some logic, hence we need a mcu to send a signal to the machine to simulate a push button which is normally mechanic.

We are currently designing the remote control schematic and PCB but first we have a small doubt on one point:

The machine user manual mention this:

  The remote is a normally open SPDT switch connected to the machine
  with a 1/4 inch stereo phone jack. The sleeve contact of the phone
  jack is at common, the tip contact is the normally open signal PCA*.
  The jack is metal threaded and bulkhead mounted on the rear of the
  device. A harness connects the jack to the MCU PWA with a 4 pin,
  locking, polarized connector.

  Activation of the switch results in signal PCA going low as long as
  the switch is held. The third signal PPP*, is low if the cable is
  connected and the pendant is not pressed. This provides positive
  identification of a correct and functioning remote control

A few questions:

Should we rather use a relay or an octocoupler to simulate this SPDT switch ?
I don't very well understand what they mean by "The sleeve contact of the phone jack is at common, the tip contact is the normally open signal PCA". How do you understand this ?

EDIT: the asterisk lead nowhere.


texts: Is the polarity of a polarized capacitor fixed irrespective of the direction of current?

texts:
If I have a circuit as shown below, does it mean that the polarity of capacitor is fixed(irrespective of the direction of current through it)? I have to write the differential equation for this network and then find other quantities. So, the sign of voltage drop (in the equation) across the capacitor depends on this information.

simulate this circuit – Schematic created using CircuitLab

Thanks!


texts: relay ratings at 120v and 240v...can I use a 20A 240V relay with a 13A 120V pump?

texts:
I have a relay from SparkFun (https://www.sparkfun.com/products/10924), and a pump that draws ~13 amps.  Can I use this relay with the pump?

Also, I don't understand why this relay says NO20A/NC10A, anyone know?  The datasheet seems to suggest it is 20A, but the NC10A worries me.

Is there typically a difference between amperage ratings at 120 and 240V, or are they usually the same? I don't quite understand what it is that determines the relay's rating.


texts: Where does GPS interference such as that from Lightsquared come from?

texts: A recent government test shows LightSquared products affected 75% of GPS receivers on adjacent frequency bands. Is this most likely because (a) the Lightsquared transmitters bleed over onto the wrong frequency, (b) because the GPS receivers receive signals from adjacent bands in addition to their own, or (c) some other reason?


texts: Does the word voltage exist in academic engineering?

texts:
In Portuguese, the word voltage does not exist. Neither academic nor technical.

In engineering, Portuguese speakers refers to volt as electric tension or potential difference.

The word voltage was popularized in the Portuguese language because some places use 220V and others use 110V and people always had to ask if the "voltage" for the equipment is 110 or 220. So, it's kind of a nickname/shortcut for non-technical people to refer to electric tension.

What about in English academic engineering? Does the word voltage exist or is it just a shortcut/nickname for electric tension or potential difference?


texts: NXP LPC1114 UART doesn't work after reset

texts:
I'm building a simple circuit with LPC1114 to make a "hello world" application using UART. Trying to write all the code from scratch, to have a better understanding on what's happening.

My problem is that UART only works only after flashing (i.e. when lpc21isp asks MCU to start running code). The same code doesn't work if MCU is reset.

Here's the code I'm using:

void platform_uart_setup(uint32_t baud_rate) // 9600
{
  // Make sure UART IRQ is disabled
  NVIC_DisableIRQ(UART_IRQn);

  // Setup pin 1_6 as RXD
  LPC_IOCON->PIO1_6 &= ~0x07;
  LPC_IOCON->PIO1_6 |= 0x01;

  // Setup pin 1_7 as TXD
  LPC_IOCON->PIO1_7 &= ~0x07;
  LPC_IOCON->PIO1_7 |= 0x01;

  // Enable & configure UART clock
  LPC_SYSCON->SYSAHBCLKCTRL |= (1<<12);
  LPC_SYSCON->UARTCLKDIV = 0x1;

  // Setup format: 8N1, enable access to divisor latches
  LPC_UART->LCR = 0x83;

  // Setup baud rate, which is based on system clock
  uint32_t Fdiv = platform_clock // take cpu clock (12000000 in this case)
      / LPC_SYSCON->SYSAHBCLKDIV // divide by ABH clock
      / LPC_SYSCON->UARTCLKDIV // divide further by UART clock
      / 16 // divisor latch is 16x the desired baud rate
      / baud_rate;

  LPC_UART->DLM = Fdiv / 256;
  LPC_UART->DLL = Fdiv % 256;

  LPC_UART->FDR = 0x00 | (1 << 4) | 0;

  // Enable and reset FIFOs
  LPC_UART->FCR = 0x07;

  // Disable access to divisor latches
  LPC_UART->LCR = 0x03;

  // Read to reset LSR
  volatile uint32_t unused = LPC_UART->LSR;

  // Make sure there's no data
  while(( LPC_UART->LSR & (0x20|0x40)) != (0x20|0x40) )
    ;
  while( LPC_UART->LSR & 0x01 ) {
    unused = LPC_UART->RBR;
  }

  // Enable UART IRQ
  NVIC_EnableIRQ(UART_IRQn);

  // We don't care about interrupts for now
  LPC_UART->IER = 0;
}

void platform_uart_putc(const char c)
{
  while( !(LPC_UART->LSR & 0x20) )
    ;
  LPC_UART->THR = c;
}

On after the reset there are absolutely no signal changes on TXD pin.


texts: short to ground in custom Arduino shield only when connected - how do I find it?

texts:
I've built a custom Arduino shield using a PCB and surface mount components. The board has a short between power (5V) and ground (GND) when it is connected to an Arduino Due.

When the shield is not connected, the short does not appear to be present. With a continuity checker on my multimeter and the board disconnected from the Arduino, I've tested for continuity between GND and all the shield pins (including 5V). I only get continuity where I am supposed to - on the GND pins. I also tested for continuity between the 5V pins and the other shield pins (including GND), and only get continuity where I am supposed to - on the 5V pins.

How can I debug this problem? Why doesn't the shield show a short to ground when it is not connected, but when it is connected, there is a short? What am I missing?


texts: How can I prevent a non-rechargeable backup battery from inadvertently being charged?

texts:
So, I'm working on a design for a device that is to be powered both from the AC line (using a power supply module, for now at least), and a non-rechargeable battery pack (6 alkaline AA cells).  The device has a rather low (easily submilliamp) standby current, but when fully activated, draws nearly 2A peak, irrespective of whether it is on AC or battery power.  As a result, the typical approach of using a diode in series with the battery practically requires a Schottky to be used, and even then, losses are relatively high, on the order of 400mV for a 1N5821.
This is problematic due to the low battery threshold of the device overall being relatively high, so a 400mV drop atop that means that the low battery detection could be set off falsely.  Furthermore, using a relay for switching between AC and battery is unattractive for reasons that have to do with both the size of the relay and the amount of control logic hackery that would be needed to provide for low battery monitoring in that case.  Finally, the classical P-FET reverse battery protection circuit seems like it would not work correctly with 9V imposed on the source from an external power supply, nor will a switched power jack work due to the AC supply being a hardwired unit in this case.
Is there a better low-cost/low-parts-count solution to this problem out there than burning power in a diode or deal with the infelicities of controlling a relay?  A full power management train is very unattractive for this application due to the simplicity of the rest of the circuitry, and while an individual ideal diode IC could be used, they tend to be relatively expensive and featureful parts that do far more than is needed in this application.  (They're also small and thus relatively difficult to prototype with, but that's neither here nor there at the moment.)


texts: Help identifying SMPS controller IC to change output voltage from 54v to 42v

texts:
I need a 42v DC adapter for charging a battery pack.
I have this 54v DC brick from a broken PoE switch and want to change the output voltage.
I've taken it apart and tried to locate the voltage divider that sets the reference, but can't identify the controller and don't feel safe poking around 220V AC (and 54V DC).
The powerbrick is a FSP Group FSP090-DMBC1.
The two yellow/green spots on the  are connected with piece of PCB shield.
Down in the left corner there's a diode bridge with part number FEP16GT.
The IC looks like it ends with 75ST.


texts: Could anyone suggest the type of pressure sensor I need to measure human breath? When someone blows into the device I want to measure them blowing in and also sucking out. Could this be done with Barometric sensors?


texts: Is a transfer function of a LTI system the same and valid for all operating points of the system?

texts:
Let's say that we have a LTI system (speaking strictly theoretical at the moment) and it has a transfer function H(s). Is this transfer function the same over all the operating points that the system can be in ?

For example a purely theoretical circuit, composed with ideal passive elements, has one input, one output and couple of nodes where we can set DC voltages. Will the output of that circuit be predictable with it's transfer function acquired with a certain set of DC voltages at it's nodes, and will that function be valid if I change the DC voltages on the nodes (implying a different operating point)?


texts:
I have the question "An alternating voltage V has a periodic time of 20ms and a maximum value of 200v. When time t = 0, V = -75 volts.
Deduce a sinusoidal expression for V and sketch one cycle of the voltage showing important point."

So I know that:

time t = 20ms
Max value = 200V
angular value = \$2{\pi}f\$, f = 1/T = 1/20 = 0.05.
Therefore angular value = 0.314

But the solutions say that the expression should be:

V = 200sin(10\$\pi\$t - 0.384) V

I'm not sure how this is achieved. I understand the maximum value which is given as 200 but not how the rest was achieved.


texts: When a buzzer 'rating' is 3v, What does that exactly mean? When my buzzer 'input range' is from 3-10v?What does 'rating of a device tell us? Can someone differentiate between the two parameters above?


texts:
I'm a newbie when it comes to electricity, and this has been bugging me since like 9th grade when I first learned about V/I/R/P combinations, and to this day I still can't wrap my head around the concept.

I understand about the mathematical formulas, but what I'm having trouble with is the meaning of V/I when it comes to wiring things.  I'm thinking of starting a small project wiring up a solar panel to computer fans just to learn about this.

Solar panel is rated at DC 6V/1W
Fans are rated at DC 12V/160mA

What do these rating mean?

Does this mean that the fans can only operate if the source voltage is 12V?
What if the source is under-voltage like 6V? Will the fans not power on at all?
What if the source is over-voltage like 120V? Will the fans start catching fire?
What if the source is just slightly over/under like 13V or 4V?

If my solar panel is rated at 6V/1W (~160mA max), and I connect four fans in parallel, which means each fan will receive ~40mA, does this mean that the fan will not spin? Or will the fans spin at 1/4th of the speed?

Lastly, if my solar panel is only 6V, and fans are operatable at 12V, does this mean that I have to connect two solar panel serially?  Can I put a resistor between the panel and fans to increase it to 12V?


texts: custom made symbol not showing up in schematic

texts:
I was able to define footprints and symbol for a customized part.

I was looking forward to using it in my schematic.

But when I looked for my part (ATF33143), it did not show up. (2nd image)

I have obviously enabled the part given the green light.

I am not sure what I'm doing wrong here.

It does show up in PCB board though.


texts: plot the max slopes of Voltage-Transfer characteristics in ngspice

texts:
I have implemented a basic CMOS inverter in ngspice, performing a DC sweep analysis on the input voltage to obtain the Voltage Transfer Curves (Vout vs Vin) at varying Vdd voltages.
. cmos g (gain) vs vdd

.include tsmc180.txt

vdd source_p 0 0v
vin gate_common 0 0v

m_p out gate_common source_p source_p cmosp w=2u l=0.18u
m_n out gate_common 0 0 cmosn w=2u l=0.18u

.dc vin 0 2.5 0.01 vdd 0.5 2.5 0.5
.control
run
plot v(out) vs v(gate_common)
plot deriv(v(out)) vs v(gate_common)
.endc
.end

On running the above, it gives me two plots as expected, one the VTC and another the slopes of the vtc which represent the inverter gain.

I need to plot the maximum gain points (the negative peaks on the gain curves) as a curve with respect to vdd. I have thought of using the .MEASURE command to do this.
.measure dc g deriv v(out)
.measure dc g_max min g

but this gives me an error
No. of Data Rows : 1255
        measure 'g'  failed
Error: measure  g  :
        function '' currently not supported
 .measure dc g deriv v(out) failed!

I couldn't find any such example in the ngspice pdf manual or their git repository for ngspice simulation examples. Some guidance is very much appreciated.


texts: Digi XCTU 7.0 not recognizing Xbee Pro SX but can recover without issue

texts:
I've assembled a custom PCB that has a Xbee Pro SX on it. After not using it for about a month, I am unable to add it to XCTU, or to communicate with it over UART. However, I am able to use Xbee Recovery to reset the firmware without issue, so I know it's hooked up correctly to my UART/USB converter. What do I need to do to communicate with this module?

As a side note, why are Digi's support forums so shitty? I posted this question three days ago on their forums and it still hasn't been "checked and approved". I'm not even asking for somebody from Digi to reply, just want to post the question.


texts: Do I need to replace the transformer when switching from halogen to LED

texts:
Total noob question.

I have MR16 halogen downlights and want them replaced with LEDs. Someone told me that, if I simply replace the bulbs but not the transformer, then the power draw will still be the same (or perhaps not as improved as if I get new transformers or replace with newer GU10s with an integrated transformer).

Is this correct? Or nonsense? Am I over simplifying it and more information required?

Thanks.


texts: Difference between setting up clocks on Verilog

texts:
These two statements are used quite often, to set up clocks in test benches:

initial
begin
  clock = 1'b0;
  forever #5 clock = ~clock;
end

always
begin
  clock = 1'b0;
  #5 clock = 1'b1;
  #5;
end

Is there any difference between the two or are they 100% equal and interchangeable?


texts: Reverse engineer: How do I remove the black plastic that hides the ics?

texts:
I am hacking a circuit and it has this black plastic thing (see picture below) that hides part of the circuit.

How can I remove them to see what is inside?

What they are for? I think they are for chips that have no packaging, is this right?

What the real name of this?

Thanks for your help.


texts:
I need to stack two PCBs together, but the stacking height is extremely critical. In terms of board-to-board connectors, the best I could come up with was SAMTEC GFZ series.

What other solutions can be recommended to stack two different PCBs? I need to have very low stacking height (less than 2 mm, the lower the better), and about 100 connections.


texts: How far can radio signal be transmitted through a straight steel pipe?

texts:
We are needing to transmit data between a robot that will be traversing a pipe, and a base station located at the end of the pipe. The pipe is about 2 feet in diameter, made of steel, and is relatively straight so we expect to have line of sight to the robot the entire time.
We would like to use radio transmission to be able to maximize the distance of travel without having to worry about a spool of cable, however I have relatively little experience with transmission of radio signals through something like this. Assuming line of sight between the transmitter and receiver, will the signal travel less distance in the pipe than it would outside the pipe? We can assume video at around 900 MHz.
We also have the option to be able to poke holes in the pipe at any interval to setup relay antennas if needed, but we are first trying to determine if this is even a viable method before falling back to a tethered system. Any help is appreciated.


texts: Can I use TXB0104B bidirectional level shifters on the Intel 8085 NMOS CPU buses?

texts:
I want to connect an old Intel 8085 CPU to an FPGA board. The basic issue is that the 8085 works at 5V while the FPGA will not accept any voltage avobe 3.3V so I decided to use the TXB0104 / TXB0108 bidirectional level shifters, however, I am unsure whether the bidirectional buses would work or would cause any trouble with either side of the shifter.

Also, the Intel 8085 is an NMOS circuit, not CMOS, so I am not really sure if that would cause any issues.

Edit: the H variant of 8085 I am using is "enhanced NMOS" HMOS

The circuit I am intending to use is as follows.


texts: Same awg wire but larger diameter on one?

texts: I bought 22 awg wire from the same seller twice at different times. When I bought it the second time, I noticed that one of the wire including the insulation is noticeably larger. Does this 100% mean that the wire gauges are different, or is it possible that both wires have the same number of strands but one has thicker insulation resulting in a larger diameter wire?


texts: UART connection using PL 2303. Weird characters

texts:
I took a while to errors when playing movies from the player (lock screen, reboots).
After updating the firmware, still not working.( Same reboots, lock screen)
I open the media player and I have seen that has a UART port.
Pinout:
1 Ground
2 UART_RX0
3 UART_TX0
4 UART_RX1
5 UART_TX1
6 VDC 3.3v

Image below.
I tried to connect the port UART with  connector Sitecom CN-104 v4002
sitecomlearningcentre.com/es/products/cn-104v4002/usb-to-serial-cable-0-6m/downloads
This mounts a PL2303 chip.
I had problems with windows 7 installing driver. I tried Windows XP and GNU/ Linux. In all cases the same problem (Weird characters) in Putty program.
I connected:
UART             DB9

GND              PIN5 (GND)

UART0_TX0        PIN2 (RXD)

UART0_RX0        PIN3 (TXD)

I connected with putty.
Speed: 115200
Data bits: 8
Parity: None
Flow Control: None

I have turned off the mediaplayer and then I have started and only appear strange characters. Dmesg not the system nor the bootloader appears.
I tried different bauds. But nothing.
I have also tried to use the UART1 has and turn the wires, check the cables but not touching.
I tried to connect it directly to the DB9 port without passing through the converter. But exactly the same problem occurs.
Any help on how I can display the data sent from the port UART correctly.


texts: What is the collector-emitter resistance of NPN Transistor?

texts:
the question may look ridiculous since I'm not sure if the collector-emitter resistance exists or not.
Here is a simple commom emitter circuit

As I learn that when the Vb increase that will make Ib increase so Ic must increase too. When Ic increase as there is Load Resistor but Vcc is constant and Ic = (Vcc-Vc)/RL (Load Resistor) then Vc must decrease and vice versa. That how common emitter work

Now, what I concern is the Voltage Drop between Vcc and Ground is constant as well as Load Resistor value. Suppose that there is not thing between Emitter and Ground that make Ve = 0 and Vb = 0.6-0.7 while Vc is much larger (that depend on load resistor). So, there must be something that wastes the energy to make Ve=0 that cause voltage drop between collector and emitter. Is there something act like varying resistor between collector and emitter to make that.

In other words, to make voltage drop between collector and emitter there must be something act like resistor between them, right? If no, what make the difference in voltage?

In other configuration does collector-emitter have resistance as well?


texts:
We have a voltage source of 5 V and a resistor of 100 Ω is connected to it. The other end of the resistor is connected nowhere. To simplify terminal “A” of resistor is connected to 5 V & Terminal “B” is not connected anywhere. So my questions are

What will be the Voltage value at the Terminal “B” of the resistor? and How?
Will there be a decrease in Voltage from 5 V or it remains 5 V on the both terminals of the resistor?
What is Voltage? Is it Voltage at the Terminal “B”? or it’s 5 V - Voltage at terminal “B” ?


texts: 3.3v Zener Diode Shunt Voltage Regulator giving a 4.3v output

texts:
We are trying to use a zener diode shunt circuit to develop a voltage regulator.

Our input voltage is 5v.
Our desired output voltage is 3.3v.
The average load current is 80mA.
The peak load current is 150mA.

We assumed the load current to be 150mA.

We used a Zener diode of 3.3v and 0.5W. Based on this, we concluded that the current through the Zener diode is 150mA.

Thus, the total current is 300mA.

Based on this, we calculated the current limiting resistor value to be 5.6 ohms and 0.5W.

When we actually connected the circuit, we noticed that the output voltage across the Zener diode was coming out to be 4.3v instead of 3.3v and it starts to heat up gradually. Why is this happening?

We then replaced the 5.6 ohm resistor with a 220 ohm resistor and noted that the output voltage was now 3.3v but the current was insufficient (as expected). We then replaced the 220 ohm resistor with two 5.6 ohm resistors in series and found the output voltage to be around 4v. Similarly, with three 5.6 ohm resistors in series and found the output voltage to be around 3.7v.

Questions:

Are our calculations correct?
Our assumption is that the voltage across the Zener diode is independent of the current limiting resistor. Why is there an apparent dependence?
Are there any fundamental errors that we are making?


texts: Noisy output on active bandpass filter PCB Design

texts:
I'm trying to design a 40dB active bandpass filter with a centre frequency of 130KHz and a passband of 80KHz. I don't really know much about filter design so I used the TI filter design tool to design one. I wanted to power the design using a single 3S lipo battery so I added a rail splitter to the design. And since the output of the filter was going to a  single Ended ADC, I added a summing amplifier at the end to bias the signal by 1.65V. Here's what my final design looks like.

I designed this on a stripboard and the circuit was working so I decided to make a PCB for it. My isue currently is my PCB design is extremely noisy. I grounded the input to record the self-noise of the pre-amp and  I get the following waveform (amplitude is about 600mV).

  I took the FFT of the signal and it seems to be at around 235KHz or so. (centre is 130KHz, 50KHz division).

If I add a sine wave to the input of the board, I get the following output:
(Input is a 130kHz 0.01Vpp signal)

And the FFT of the signal looks like this:

The goal is to eventually design a low-noise preamp and I'll be connecting a hydrophone to it. However, right now, I'm a bit stumped as to what the problem could be. Simulation works fine, stripboard design is fine as well.

I've used 0603 package RC components but used Aluminium SMDs for the electrolytic caps. My plan is to eventually switch to tantalums in the second revision. Could anyone possibly see an issue with this?

For completeness, this is what the PCB looks like:

I'm still waiting on the voltage regulator but I'm currently probing from the output of the filter.


texts: Enabling/disabling a PID loop via FSM in a microcontroller

texts:
I have a PID loop for a small vehicle implemented in a microcontroller. Currently the PID loop is implemented in a timer interrupt. I want to implement an FSM that will have states that enable or disable the function that the PID loop is controlling, so in some states the PID loop should be disabled and in some it's enabled. I want to implement this control in a way that minimally disturbs the PID loop.
I've been told that I shouldn't disable the timer interrupt if possible. Is a good option for this to implement the FSM itself inside of the timer interrupt and then update the PID loop inside the FSM states?
The alternative would be to have just the PID loop inside the timer interrupt and then the FSM implemented inside the microcontroller's main(), which I think would need to temporarily enable or disable the timer loop while updating state.


texts: Can I charge and discharge a NiCd/NiMh battery at the same time?

texts:
I presume there will be opposite movements of the charged particles inside, with collision energy being exhaust as heat.

On the other hand, such a setup would probably introduce an extra noise/voltage fluctuation immunity, would also greatly simplify the circuit layout, would enable short-term high current anytime (i.e. motors, stroboscopes etc.).

Can I simultaneously charge & discharge the battery? Might it cause any harm to it?


texts: Which program can I use to draw schematics?

texts:
I would like to draw this schematic for my report.
It will be used just for drawing and not for technical things.

An example is this I found online.

Which kind of program do you use?


texts: How to do i solve this electrical circuit?

texts:
I've been trying to solve this circuit with two current sources:

Following is given:

ia = 1mA, ib = 2mA

R1 = 1K, R2 = 0.5K, R3 = 2.2K, R = 4.7K

Personally I've been trying to use KCL to determine the current I through R2 but haven't got much further than lining up a few equations. I do suspect that I might have to superposition and current division to get on the right track, but I am still not entirely sure.

My question is: How would I 'exactly' solve this circuit?


texts:
This part of a schematic from the I/O board in the link below shows a 1N4148 diode in parallel with an optocoupler's input circuitry.
What is this diode for?

https://startingelectronics.org/projects/small-open-source-PLC/PLC-components/

I'm thinking of 3 things.

A diode that prevents negative voltages from damaging the optocoupler.
A diode that protects the optocoupler's input from overvoltages.
A flyback diode. (Very unlikely for semicons right?)


texts: Practical ways to associate a known pulse to an adequate oscilloscope bandwidth

texts:
Is there a rule of thumb for a scenario for deciding minimum required scope bandwidth whew we have a known pulse train of 5MHz repetition rate and each pulse has 1ns pulse duration?
I know that these may depend on how much pulse distortion we can live with but at least how can we quantify the needed minimum scope bandwidth to observe the pulse shape in scope. Is thee a quick way to roughly estimate?


texts:
I'm programming a MSP430 in C language as a simulation of real microcontroller. I got stuck in addressing modes (https://en.wikipedia.org/wiki/TI_MSP430#MSP430_CPU), especially:

Addressing modes using R0 (PC)
Addressing modes using R2 (SR) and R3 (CG), special-case decoding

I don't understand what does mean 0(PC), 2(SR) and 3(CG). What they are?
How to check these values?


texts:
after finishing some designs, it is time to manufacture and assemble them.

For making these designs I have to create all padstacks, footprints, etc from scratch, so I took PCB Editor examples as guide for doing mine.
Now, when I send the gerbers (etch layers, soldermask, silkscreen, drill) to our manufacturing house, they requested me the pastemask ones.
Although they can generate them from gerbers, they are enquiring me to generate the pastemask gerbers with our own requirements.
So, I need a little help to get the proper guidelines to avoid any possible error.

Then, I wonder if you can provide some guidelines about how to define and create the proper pastemask layers.

From PCB Editor examples, most of passive components have no pastemask defined (SMT and THR), and from IC pads the relation between pads size and solder paste are 1:1 in most cases.

I have in mind next possible requirements:

THR components: 1:1
SMT components with padstack larger than 1mm: 1:1
SMT components with padstack shorter than 1mm: 1:0.9
IC perimeter pads: 1:1
QFN perimeter pads: 1:0.9
QFN thermpad: <1:0.7
BGA pads: 1:0.9
Any other pads: suggestions accepted

Are these requirements right?

And finally,

Which is the best option, provide pastemask layer to manufacturers? Or should I let him create them?
In the case, I have to create the pastemask layers, which are the best guidelines to follow them?

Kind Regards.


texts:
I would like to make a circuit that allows to detect activity on a RJ45 cable (on which Ethernet would be used).
When the cable is only connected to a single computer, link test pusles are emitted. These signals are about 1 us long and between 0,5 mV and 3 V.
Otherwise, data is Manchester-encoded, with a frequency of 100 MHz. I do not know the amplitude.
I would like to detect, with a diode, activity on the RJ45 cable. As the signal is not continuous, a simple LED would not work. I also would like not to damage the signal.
Do you have an idea on how it would be possible to do it?


texts: Can floating cat6 shield be worse than unshielded?

texts: I'm having an electrician fish an Ethernet cable through a wall. I can put shielded or unshielded cat6. However, the electrician doesn't know how to crimp Ethernet cable so I agreed to do that part myself, and I only have materials on hand and experience for plastic crimps. Thus if I put shielded cable, the shield will be left floating. Can a floating shield potentially have worse characteristics than an unshielded cable?


texts:
I have been trying to figure out how the following circuit works and what it might be good for without any luck so far.

What might the transfer function be?

Is there a way that analysis can be applied generally to many such loops inside each other ?

(for analysis purpose exact op amp type does not matter, and may be considered ideal)

Upon recommendation, i tried the delta-star transformation, and came up with conclusion that n loops can be simplified to the circuit below:

This looks like inverting op amp but there is one resistor left from the last transformation connected to inverting input. Is this correct, or am I missing something ?


texts: Would there be any problem putting reverse-parallel diodes in parallel with the inputs of a microammeter?

texts:
Many multimeters, when used to measure microamps, don't have an overly-high burden voltage when passing less than a milliamp, but the they can drop over a volt (and even blow a fuse) if a device has a momentary current draw of 100mA or more.

If one has a device under test which will usually draw a few microamps, but may occasionally draw half an amp or more, and if one is only interested in measuring the current during those times when it's below 2mA (e.g. if one were testing a lawn-sprinkler controller, which will occasionally need a lot of current to open or close the valve, but should otherwise only be drawing a few microamps most of the time) would there be any problem connecting a couple of reverse-parallel diodes in parallel with the inputs to the meter?  I would expect there must be at least some type of diode that would pass only a very tiny amount of current at voltages below 0.1 volt, but which would nonetheless be able to handle an amp or more with roughly 0.7-volt drop.  Would there be any problem with attaching such a pair of diodes in parallel with the meter?  How much would doing so affect accuracy?  What sort of diodes would be best?

PS--Alternatively, if one wants to get precision real-time current measurements at an adjustable regulated voltage, and supplying a higher input voltage wouldn't be a problem, are there any stock devices that would supply a regulated output voltage while also supplying a ground-referenced signal proportional to current?  Assume as requirements: (1) device must supply 500mA with minimal drop, regardless of measurement scale; (2) current will always be flowing in one direction, (3) 100Khz bandwidth is desired to facilitate measuring the duration of high-current-draw periods; (4) some ripple on the output would be acceptable, to the extent that it does not interact with the input capacitance of the device under test so as to impede measurement accuracy while the current is within range, or within 100ms or so of it coming into range.