texts: Bridge circuit and the error caused by a differential amplifier

texts:
I am currently struggeling with solving the following problem: The circuit below shows a bridge circuit, where the differential voltage between the branches is measured by a differential amplifier. I need to know the relative systematic error caused by using the amplifier circuit.

Given values:
$$
R_0=100\Omega \\
\Delta R=1\Omega \\
R=1k\Omega
$$

Well, my approach to solve this was to first analyze the bridge circuit itself, then together with the differential amplifier and calculate the relative error by:

$$
\frac{\Delta V_a}{V_a}=\frac{V_{a-amp} - V_{a-ideal}}{V_{a-ideal}}
$$

Analyzing the bridge circuit alone:
$$
V_D=V_2-V_1=V_s(\frac{R_0-\Delta R}{R_0+\Delta R +R_0-\Delta R}-\frac{R_0}{2R_0})=V_s(\frac{R_0-\Delta R}{2R_0}-\frac{1}{2})
$$

Alright, now analyzing the complete circuit. Well, V_2 is now also applied on the two resistors R, located at the non-inverting input:

$$
V_2=V_s\frac{(R_0-\Delta R) || 2R}{R_0+\Delta R + (R_0-\Delta R) || 2R}
$$

But now I am stuck. What do I do with V_1? Because there is actually no ground in the upper branch of the differential amplifier (inverting input). Is my approach as it is correct and my calculations up until now?


texts:
i have NI 6229 DAQ and datasheet and i come up across the settling time versus time for different source impedances

i would know how is settling time calculated? i was thinking a simple RC network and the settling time is the time that the capacitor take to fully charge depanding in the source resistance and then i come up across the settling time for multichannel measurements

i would like to know how is the values of settling time calculated and for what source resistance since i can't find it in the graph

thank you


texts: Do I need to reset a DDR's DLL when I change clock frequencies?

texts:
I have a system that boots at one frequency and then the main PLL is reloaded to continue boot at a higher frequency.  When this is done, the DDR is put in to self refresh.  After the main PLL locks, the DDR clock will change from 100Mhz to 133Mhz.

It seem that the DLL inside the DDR is related to the clock frequency.  Should I re-run the MRS sequences to lock again before operating at the higher frequency?

Bonus: What exactly is the function of the DLL with-in the DDR?  I thought everything was run off of CK/CK#.  I know the host DDR controller needs some delays for latching data, but I thought DDR was designed so the RAM could be simpler.

The specific DDR2 I am using is Micron MT47H32M16 and Samsung K4T51163QG-HC.


texts:
I ordered a few STM32F030F4 chips in a TSSOP 20 package, and some dip adapters.

I wired one up using a 8Mhz crystal and connected my st-link device to it via SWD.  st-link detects it correctly as an stm32f030 small device.

My problem is that I'm finding it very hard to figure out how to create a simple program for it that just blinks an LED.  Most GCC examples are for newer chips.  I even went so far as to boot into windows to try some of the IDEs available for it, but Ive had no luck.

Anyone have any suggestions for how I can get a simple GPIO program onto this chip to see if I wired it up correctly?


texts: Dual led and transistor 3906 3904 switching with spdt switch on and off toggle help

texts:
Hi i have 3904 and 3906 transistors, leds and spdt switch.
I tried to use the 3904 so that when voltage is applied to base, it flow from power source into the led and then to ground. But now i have difficulty to use another transistor so that when 0v or ground is applied to the base of the transistor, the led will turn on. How would i do this?
In other words the spdt will toggle 2 leds, one led will show the on status and the other led the off status. Schematic i drawn below is working but i need to add another led that will switch on if voltage is 0 or ground.
Thanks a lot, very noob here.


texts: Relaxation oscilator with only transistor to measure DC voltage

texts: I need to measure voltage from 12 to 100 volts with an MCU but with an isolated solution (so no voltage divider), my idea was to use relaxation oscillator coupled to Optocoupler in order to obtain a kind of voltage to frequency converter. I have no way to use OP amp in this schematic since I have no power supply except the MCU one (3,3 volts) and the DC to measure. My main problem is the range of measurement 12 to 100 Volts DC. Any help appreciated.


texts:
I need to pass a domestic -10dbV audio signal (it should oscillates between -447mV and +447mV) to a microcontroller's ADC which only accepts signals that oscillates between 0V and 5V. I think that the simplest solution is to implement an op-amp summing amplifier circuit.
My final configuration will look like this:

simulate this circuit – Schematic created using CircuitLab

Now the question is: can my old UA741 do the work? My fear is that it cannot accept a potential of 0V as Vcc-. In the case the UA741 is not suitable, can you point me out a valid replacement?


texts: si7060 I2C temperature sensor with STM32 CubeIDE?

texts:
I am trying to read an SI7060. It's my first time using i2c and it doesn't seem to work.
Do I make something wrong here?
SI7060 datasheet
static const uint8_t REG_TEMP = 0xc1;
uint8_t buf[12];
HAL_StatusTypeDef ret;

buf[0] = REG_TEMP;
ret = HAL_I2C_Master_Transmit(&hi2c3, TMP102_ADDR, buf, 1, HAL_MAX_DELAY);
HAL_Delay(100);
if ( ret != HAL_OK ) {
    strcpy((char*)buf, "Error Tx\r\n");
} else {

    ret = HAL_I2C_Master_Receive(&hi2c3, TMP102_ADDR, buf, 2, HAL_MAX_DELAY);
    if ( ret != HAL_OK ) {
    strcpy((char*)buf, "Error Rx\r\n");
    }
}

HAL_UART_Transmit(&huart1, buf, strlen((char*)buf), HAL_MAX_DELAY);


texts:
I'm trying to build an 8bit counter in Verilog. I specifically need to create a module that I instantiate 8 times. I have followed the diagram below (and assumed that I can just build on it to make it 8 instead of 4 bits). It appears what I have built instead is a shift register, it can shift ones and zeros - instead of 0001 -> 0011 I need 0001 -> 0010 (duh!). I feel as though I have misinterpreted the circuit diagram, as my logic seems otherwise sound. Any help much appreciated!

TFlipFlop:

module tflfl(t, clk, clr, q);

input t;
input clk;
input clr;
output reg q;

always@(posedge clk, negedge clr)
    begin
        if(~clr)
            q <= 1'b0;
        else
            q <= t;
    end

endmodule

Modular Implementation:

tflfl t1(.t(enable), .clk(clock), .clr(reset), .q(q0));
tflfl t2(.t(q0), .clk(clock), .clr(reset), .q(q1));
tflfl t3(.t(q1 && q0), .clk(clock), .clr(reset), .q(q2));
tflfl t4(.t(q2 && q1 && q0), .clk(clock), .clr(reset), .q(q3));
tflfl t5(.t(q3 && q2 && q1 && q0), .clk(clock), .clr(reset), .q(q4));
tflfl t6(.t(q4 && q3 && q2 && q1 && q0), .clk(clock), .clr(reset), .q(q5));
tflfl t7(.t(q5 && q4 && q3 && q2 && q1 && q0), .clk(clock), .clr(reset), .q(q6));
tflfl t8(.t(q6 && q5 && q4 && q3 && q2 && q1 && q0), .clk(clock), .clr(reset), .q(q7));


texts: Best approach/practice to design PCB which can handle 50-80A current?

texts:
I'm designing a PCB which needs to handle high currents across various fuses, relays and connectors. The current ratings would be 8A, 20A, 50A, 80A. So I would like to know which is best approach to handle such currents considering the temperature and losses. I'm sure massive traces are needed to do this and which is not possible as I'm using Mentor Graphics PADS 9.5 in which the max trace width I can get is 0.25mil. Also heard of copper pours and planes but not exactly sure how to approach.

If anyone have come across such thing and had practical experience. Please let me know.

Thank you


texts: Frequency dependent behavior of an inverting configuration of an opamp

texts:
I am a third-year chemistry student. I have essentially the understanding of a second-semester physics student when it comes to circuitry and electrical engineering. For reference, I know what gain is but I cannot tell you what it has to do with bandwidth. The course I am taking requires us to build our own simple analytical instruments. We are in the process of trying to understand operational amplifiers.

I cannot find an explanation that I can follow about why inverting configuration operational amplifiers behave like first-order low-pass filters. So far I have found that Dave Tweed's explanation is in the right direction.

https://electronics.stackexchange.com/a/233578/248412

The gain of any active circuit falls with frequency because the speed of the individual active
devices is limited by various effects associated with charge storage at various nodes (modeled as
  parasitic capacitances).

Thank you,

I hope this does not read as whiny as I think it does


texts: Question about powering a small vibration motor

texts:
I have a SparkFun ESP8266 Thing board that is powered by 1 Ah battery. My goal is to toggle a small 10 mm coin motor on and off. The GPIO pins provide very small current (12 mA) which results in a vibration that's quite weak. However, the Vin pin board can supply 500 mA which is adequate for a strong vibration in my testing.
The idea that I currently have is to use a typical MOSFET + diode + resistor circuit with the Vin pin acting as the Source and one of the GPIO pins as the Gate.One wire from the motor would be connected to the GND on the board and the other to Drain on MOSFET. Would this work? Is there a simpler way?


texts: Is it possible to find any information about a proprietary IC with no manufacturer name on it?

texts:
I used a Kenmore/Frigidaire microwave oven controller board to teach a class on VFD driving/multiplexing and few other topics. It was well received, but many students wondered if they could find more information specifically about the micro-controller chip used.

Unfortunately no information whatsoever comes up on Google when searching any of the numbers from the chip. Apparently it is proprietary with no publicly available information about it.

This is not the first proprietary chip I came across, but the first one I am really looking forward to find info on. Are there any other sources of information I could tap into to get a datasheet?


texts: Twisted pair's effect on power supply rise time

texts:
I am having a tough time wrapping my head around this question.

I am well aware of the benefits of using a twisted pair for signal wires: the cancellation of common mode noise coupled onto the wires, and the cancellation of radiated noise from the loops when there are changing currents through the wires.

Now, we have a power supply with a fast rise time and long cables. This is causing concern about generating a voltage spike at the load from the wire's inductance and the load capacitance.

Someone recommended we twist the power supply cables to help with this... does this actually help? Thank you!


texts: Output of diode clamper circuit for a sinusoidal wave input

texts:
I have seen a common explanations of clamper circuit shows in figure and have doubt in that. Here is the two explanation:

As RC >> time period, the capacitor charges immediately within no time to Vm. In positive half cycle the diode is forward biased (short ckt) and so, the output voltage is zero. During negative half-cycle the diode is reverse biased (open ckt) and so, the output is (Vin - Vc), which in this case is (Vin - Vm). Hence, the output voltage appears as shown in figure.

Doubt:
(i) If the capacitor charges immediately then it will supply a constant voltage of –Vm to diode which will keep it in reverse bias always. Which violates the output waveform shown.

(ii) However, if the capacitor charges to peak value of input i.e. at π/2 and then when the input voltage goes below peak value, diode becomes reverse biased and remains like that until input waveform goes above zero at 2π and diode becomes forward biased again. Even in this case the output voltage should remain zero from 0 to 2π.

Where am I getting it wrong? Can someone give a point by point explaining when the diode will be forward biased and reverse biased and what will be the output voltage during that time.


texts: Real device with derivative transfer function

texts: Is there a device that has \$s\$ as its transfer function, that is, a physical system implementing a derivative?


texts: How to identify and remove unintentional PCB antenna?

texts:
It has been pointed out to me, more than once, that I might be making a few too many antennas unintentionally on the PCB with the copper pour, an obvious example is this L shaped pour at the edge of the PCB:

I can easily remove that, with a restrict polygon, so that it looks like this:

I was wondering what to look for exactly, generally speaking, and if placing vias to the ground on the edges of those shapes would stop them from acting like antennas and radiating ?

Note: the red and blue pours are ground planes, 2 layer PCB.


texts:
I'm trying to build the following circuit

Except mine is a 24V ~20A (500W) motor, so I need to swap the components. I'm currently looking into transistors and I've stopped on the 2N6284 (NPN) transistor, which is rated at 100V 20A. This basically means it's good to up to 2000W (right?), but it says the maximum power dissipation is 160W. Now this makes no sense so I'm guessing it's how much of the 2000W going through it will be lost as heat? I've looked all over the data sheet and there are a lot of things I don't understand on top of which is this diagram that suggests that temperature increases as power dissipation decreases? Isn't the relationship supposed to go the other way around, the more power lost as heat the higher the temperature?

If any of my assumptions is correct then how can I calculate how much power will be lost running my 500W motor at 24 volts?


texts: Will products based on different ZigBee stacks (like the "Zigbee" and "Zigbee Pro" profiles) be interoperable?


texts:
I'm doing my first BGA layout with a microcontroller. The bypass capacitors must be on the bottom side and I'd like to have the minimum capacitor size 0402. Now I just have the problem, that the capacitors are too big and I can't place them only between the pads on the bottom side. Therefore I had in mind to use filled+capped vias and place the capacitors directly on top of the vias. Without the use of buried vias it is inevitable to connect the ground pad of the capacitors to another pad of the BGA chip. See this picture:

Pad A10 is currently not used, so I wanted to place the capacitor such that pad A10 is connected to ground.

This just leads to a direct contact of the microcontroller's pin A10 with the ground potential. I'm not very satisfied by this because while programming the microcontroller, one could by accident set a high output potential to the GPIO pin A10 and cause a short circuit. Therefore, I had the idea to use via tenting with solder mask of the pad A10 so the microcontroller's pin won't be connected to the pad.

But: Is this a good idea? Does this cause problems while soldering the chip? Since the solder paste can't fill the pad A10, the chip could be slightly lifted here, I assume. The BGA chip is pre-balled.

What would be your choice to prevent this?

Thanks!


texts:
So, after a bit of searching I can't seem to find an answer to this anywhere, at least not in an easy to understand manner.

Ok, lets set a scenario, if we have an audio input (in my project it would be buffered by a op amp in a 3403 quad op amp IC) and have that go into a passive RC filter (possibly 3 band) and have the output of that go into an overdrive circuit.

Question: Does that RC filter need a ground to filter to, or could I instead wire that to a second "identical" overdrive circuit and have part of my signal filter to od1 and the other part to od2?

Just a curious question, since all I can find are explanations of how RC filters filter to ground, but as I understand it, the filter works by having the "unwanted" frequencies follow a path of least resistance to ground, by that logic I would think that it doesn't matter whether that path is to ground or to some other part of the circuit.

Edit 1: Hypothetical schematic added.

simulate this circuit – Schematic created using CircuitLab


texts: How does this blinking circuit with op-amp work?

texts:
Can somebody explain how this circuit works?

The OP tries to make the same voltage at the input cables.
At first, the LED is on. Therefore we have a low voltage (maybe 1V) on the negative input
The positive input also get this voltage (1V)

and then?
Why the LED turns off?

EDIT:
This example comes from the German Book: Kosmos eletronic X3000 (page 15).
R1 = 15 kOhm
R2 = 100 kOhm
R3 = 470 Ohm
C1 = 100 µF
U_B = 9V


texts:
I was trying to make a circuit using 7 segment and arduino logic state and I am successful in showing binary number on 7 segemnt as take input from logic state but now when I am trying to code for gray code like I wanna show 2 binary into Gray that is 3 not working any idea
As I use arduino pin 12,11,10 for input for binary representation but pin 4,5,7 for gray representation but I'm stuck in gray I'm using xor gate but it's not working


texts: What is the purpose of these PTs installed on the two coupled busbars? And we have whole panels in the HV room for these PTs. Kindly explain. (Photo attached)


texts: Different Altera DE2 boards do not behave the same way

texts:
I have a simple VHDL file which can be simulated correctly and that synthesizes  with Quartus II-11.0 (web edition). I can interact with switches,leds, seven segments and push buttons.

My problem is that among the 9 Altera DE2 boards I have, only 3 of them behave as expected. The FPGA seems the same...

Visually however, there are little differences on the two kind of boards, but I cannot understand why they don't behave the same :

This one works as expected, while this one does not (notice that e.g capacitors are not the same on the top left).

I am using exactly the same bitstream (pof or sof).

What I am missing ? Where can I find the exact info about these differences ?


texts: Probabilistic Analog to Digital Convertion

texts:
I was listening to a talk where the speaker mentioned a couple of ways to represent an analog signal with a digital signal. He mentioned the typical ones like:

Encoding the analog value in terms of the duration of the digital pulse.

Doing something like a sigma-delta modulator, where the average of the pulses is the analog value.

I'm familiar with these techniques. Then he mentioned another technique which I haven't heard of. He said another method is to generate a random digital signal in which the probability of getting a 1 corresponds to the analog value. Can anyone direct me to what exactly he is talking about.


texts: Correct diameter and name for wire for LED cathode connection

texts:
I'm building an 8x8x8 LED cube kit like this:

But I'm not happy with the wire provided for connecting the cathodes to the board as it's red and ugly.

I'm looking to purchase a better substitute for it - something metallic looking (preferably silver to help conceal it) but insulated.  White would work as well.

My problem?  I don't know how to search for it online - I don't know the correct diameter or how to refer to the wire properly to find exactly what I need online.

What diameter is proper, and how should I refer to it when searching?

EDIT TO ADD:  In the packing list from the kit (amazon.com) this was the contents description:

Includes: Blue LED's (512 pcs) PCB board USB power cable 40P round female power pin DIP-40 IC socket x2 STC12C5A60S2 (code pre-loaded) DIP-20 IC socket x9 SN74HC573AN x9 DIP-18 socket ULN2803APG A103J Resistor 10uf electrolytic capacitor x2 crystal oscillator 22pf ceramic capacitor x2 470 ohm resistor x8 4.7k ohm resistor x2 DC005 socket Self-locking push switch Red LED 0.8 Single Conductor

I'm thinking that the bold "Red LED 0.8 Single Conductor" is the description of the wire included - so would that be 0.8mm?


texts: I am planning on using a rechargeable lead acid battery for my tennis ball pitching machine. Is it feasible to hook them up to motors and run the motors until the battery is empty, and then come home and charge it (repeat this process nearly daily)? If so, what type of charger do I need? Any advice or product recommendation would be great. Thanks!


texts: I am trying to find any resources on the LED parameters (i.e. preferred intensity and luminosity ranges) that are used as indicators in various home appliances, such as Networked devices (i.e. routers) or TV sets. The general concern I have is to have indicators that do not pollute light and are not aggressive to the eye, but I am trying to find any numbers that can be used to describe this functionality. I would appreciate all feedback.


texts: Getting a 100k Thermistor to read properly

texts:
I built a 3D printer with a build space of 600mm x 600mm x 900 mm. My heat bed has a 100k Thermistor built into it, initially I could not get it to read properly seeing as how it was only a 2 pin connection and the connection required at least 3 pins.
So I wired in a 4.7 k ohm resistor into the thermistor along with a third wire as seen in the picture below.
Now I ran this with a 12 V 750 W ATX, and the thermistor read properly but the heatbed and the extruders were unable to heat up for they require 24 Volts. The heatbed is wired into the main using a 25 amp DC SSR.
I replaced the ATX with a 24 V 1200 W  50 amp power supply. Now my heat bed heats up as do my dual extruders but the 100k Thermistor built into the heat bed doesn't read properly. The Thermistor keeps fluctuating in every direction about -10°C to +5°C causing my heat bed to heat inconsistently and continue heating after the necessary temperature has been reached.
My question is, what do I need to do to get the thermistor to read properly and steady and why did it read with the 12v 750 w atx but not with the 24 V 1200 w power supply?


texts: SIM800C returns +HTTPACTION: 1,602,0 during HTTP GET

texts:
I have several boards with SIM800C GSM module.
One of them works correctly when I issue HTTP GET request (returns HTTP 200). All other boards returns HTTP 602 all the time. 602 stands for "No memory" according to manual.
HTTP POST works fine on all boards.

[2018-12-29 00:43:30] <DEBUG><GSM >Sending to GSM:AT+HTTPINIT
[2018-12-29 00:43:30] <DEBUG><GSM >GSM returned 0
[2018-12-29 00:43:30] <DEBUG><GSM >Sending to GSM:AT+HTTPPARA="CID",1
[2018-12-29 00:43:30] <DEBUG><GSM >GSM returned 0
[2018-12-29 00:43:30] <DEBUG><GSM >Sending to GSM:AT+HTTPPARA="URL","http://37.19.1.5/firmware/new?serial_number=FF
[2018-12-29 00:43:30] <DEBUG><GSM >GSM returned 0
[2018-12-29 00:43:30] <DEBUG><GSM >Sending to GSM:AT+HTTPACTION=0
[2018-12-29 00:43:30] <DEBUG><GSM >GSM returned 0
[2018-12-29 00:43:33] <DEBUG><GSM >GSM returned +HTTPACTION: 0,602,0
[2018-12-29 00:43:33] <DEBUG><GSM >Sending to GSM:AT+HTTPTERM
[2018-12-29 00:43:33] <DEBUG><GSM >GSM returned 0

GSM module on the board that works fine was purchased via trusted local reseller. Buggy GSMs were bought on aliexpress.
All boards have the same SW revision - 1418B08SIM800C24_BT.

Does anybody have any idea what can cause this issue?


texts: Getting Right parts and building ZVS flyback correctly

texts:
I recently built a 555 timer flyback driver. I used 2 IRFP450 MOSFET's in parallel to drive it and I got pretty good arcs. Something always seemed to fail, and I always was buying another 555 chip or another MOSFET. I powered it at 12 volts with a lead acid battery. I now want to build a ZVS flyback driver but I really want to get every right parts and build this correctly so I don't have to keep ordering new parts. I want to use as much stuff that I have already as I can and I will be using only Digi-Key to buy the parts to keep the shipping low.

My first question is the primary coil of the flyback. According to this schematic, I need to have "5+5" turns. I don't know what this exactly means, but I think it means to wind 5 turns with two separate coils and connect the two middle ones together. I also Don't know the exact gauge of the wire I should be using and if it will be too small of a gauge, but I used fairly thick magnet wire from a radio shack roll of three thicknesses (i used the thickest). (tell me if i need thicker). Here is the image:

*note that the two middle wires in the picture are connected together

Next, I am wondering about the inductor. The schematic calls for a 170μh 10 amp inductor. I am planning on winding one myself due to price, so what size toroid core should I buy, is that same magnet wire reasonable for 10 amps or do I have to buy larger, aprox. how many winds do I need to get close enough for the circuit to work!

Third, I have a bunch (like 30) aerovox capacitors. The schematic calls for 6 1μf 270 volt capacitors to make a large bank but I looked and they can get quite pricy especialy when buying 6 of them so I am wondering if these would work. I have values from .33 μf to 5 μf and I have voltage ratings for 270-600 VAC (600 volts on some of the lower values) Here is a few pictures of them:

Next, is the flyback itself suitable for a ZVS driver? And is it possible I don't even have to wind my own primary? (maybe it has something like 5+5 turns already built in)

The label on the flyback itself says 8014-3 {new line} MSH1AAS92A. I couldn't find the datasheet anywhere and the closest thing I could find was this which was a little singing arc tutorial. Here is a little picture of the label on the flyback.

I'm pretty sure the rest is pretty straight forward: ordering 4 resistors, 2 1n5349b diodes, 2 mur1560 diodes, and 2 IRFP250 MOSFET'S. My main concern is winding the primary of the flyback CORRECTLY and EFFICIENTLY and the capacitor bank and the inductor.


texts: How to count until a number with timer peripheral

texts:
I'm trying to use the TIM peripheral to count external pulses until a number and throw a interruption. I'm using STM32F429 and HAL library. I am initializing the TIM2 with this code:

void InitializeTimer2()
{

    TIM_SlaveConfigTypeDef sSlaveConfig;
    TIM_MasterConfigTypeDef sMasterConfig;

    htim2.Instance = TIM2;
    htim2.Init.Prescaler = 0;
    htim2.Init.CounterMode = TIM_COUNTERMODE_UP;
    htim2.Init.Period = 5;
    htim2.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
    if(HAL_TIM_Base_Init(&htim2) != HAL_OK)
    {
        /* Initialization Error */
        Error_Mensage("TIM2");
    }

    sSlaveConfig.SlaveMode = TIM_SLAVEMODE_EXTERNAL1;
    sSlaveConfig.InputTrigger = TIM_TS_TI1FP1;
    sSlaveConfig.TriggerPolarity = TIM_TRIGGERPOLARITY_RISING;
    sSlaveConfig.TriggerFilter = 15;
    HAL_TIM_SlaveConfigSynchronization(&htim2, &sSlaveConfig);

    sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
    sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
    HAL_TIMEx_MasterConfigSynchronization(&htim2, &sMasterConfig);

    HAL_TIM_Base_Start_IT(&htim2);
}

But I tried many HAL_TIM functions to get the interruption but with no success.

It will be a pleasure to provide any other helpful code...


texts:
I was given a transfer function:

$$H(s)= \frac{5 \cdot 10^8}{s^2+6\cdot10^4\cdot s+5\cdot10^8}$$

The question I was asked was , what was the phase relationship between input and output voltage at high frequencies.

My approach was to find the phase of the transfer function, which I got to be:

$$-\tan^{-1}\Bigg(\frac{6\cdot10^4w}{5\cdot10^8-w^2}\Bigg)$$

I assumed that "very high frequencies" meant w = ∞, plugging it in, I get the answer to be 45°.

However, the answer from my teacher was that it was -180, because the transfer function had 2 poles, each at -90. While I can understand this, I wanted to know why my method was wrong.


texts: Floating inputs and Vref on a voltage subtractor (PWM to Gate converter)

texts:
A little background: I'm trying to extract a gate signal from someone else's circuit (ckt1) so that I can synchronize events in my design (ckt2) to a sequential trigger in theirs. First problem is I have no way of accessing a schematic or firmware for their design, so I'm having to get creative. What I do have is ckt1's status LED's which light up during the gate events I'm interested in extracting. The LED's (and current limiting resistors) are arranged in a 4x4 matrix controlled by darlington transistor pairs (best I can tell anyways). These are the nodes I'm breaking out to ckt2 (left of the black line in picture).

Second problem is the LED's aren't held high for the duration of the gate on signals of interest, rather they are driven by PWM (presumably to save battery and soften the light). So The circuit on the right half is what I've devised to reproduce the longer gate signal from the PWM.

In their off state, the LED/CLR pairs are floating between two transistors (at least one transistor in off state anyways). As a result, their common mode voltage when off is relatively low, but their voltage WRT ground is all over the place. So my first question is, can I get away with having these inputs to ckt2 floating? (ie. no common ground connection between the the two circuits). In my first tests, no common ground produces a cleaner output when viewed on the oscope. But are there any potential long term problems? The only one I foresee is that elsewhere in the circuit I'm extracting some signals which are referenced to ckt1 GND, so I'm thinking I'll have to use a rail splitter to create a virtual GND in ckt2 to connect to this reference (thus preserving the floating inputs in the circuit above).

Also, I realized I could eliminate one schmitt inverter on the output if I instead reference the subtractor to +12, swap the inputs, and change the subtractor/inverter interface as shown below. Is there anything wrong with referencing the subtractor to the positive rail like this?


texts:
I typically use the 2-lead metal can style crystals, but for our frequency stability needs our crystal manufacturer recommended we use the 4-lead flat SMD style crystals (sample picture attached).
I was looking through our reference design, for this product and the symbols for the 2 lead can style crystals are mostly used for the MCU.
In one separate reference design they use a 4-lead SMD symbol for the same MCU. The layout guy only connected one of the GNDs pads in this design.
Is there any conceivable reason NOT to connect both GND pads on this 4-lead crystal? Is there something I am not aware with these 4-lead crystals?
Should I use a separate via for each GND connection?
I've seen layout guys not connect all the GND pads on a mechanical switch, for seemingly just putting less traces on a board.


texts: Android Microchip Accessory Development Starter kit PIC24F

texts:
I have the PIC24F Android Accessory Development Starter Kit from Microchip. I am running Android 4.4.2 on a Samsung Galaxy S4, however I am unable to get the phone to recognize the USB device when plugged in. The Microchip Accessory Support detection app reads as follows:

android.hardware.usb.accessory=true
com.android.future.usb.UsbAccessory=false
android.hardware.usb.host=true
android.hardware.wifi.direct=true
android.hardware.bluetooth=true

From what I can tell the Accessory mode is supported in Android 3+, is there some process to enable the Accessory mode? Any advice on how I would get this working?

EDIT:

I have contacted support at Microchip, there does seem to be an issue installing the compiler and the Application libraries mentioned in Keelan's answer below. However on a windows machine once the MPLAB X is installed, the 16 bit compiler and the Application Libs. Simply build the Demo firmware and install it onto the device, then attach to an Android device with the Demo app and it all works well !


texts: SPICE simulation of voltage multiplier using log and antilog amplifier

texts:
I am trying to simulate a voltage multiplier circuit for positive DC input using logarithmic amplifiers and inverting adder implemented by op-amps(uA-741) and non-ideal diodes. The first stage takes the natural log of two inputs, which is summed by the inverting adder in the second stage, inverted using a unity gain inverting stage, and finally sent to an antilog stage to get the product of two signals. I have no problem with the temperature-dependency of the configuration and so am trying to keep it simple.

The circuit seems fine until the last stage, where the forward biased diode forces a voltage differential(about 433 mV) between the two input terminals of the op-amp thus saturating the output. This is obviously happening because the input to the exponential stage is too high.

I am aware there was a similar problem posed in the following link: Analog multiplier using logarithmic and anti-logarithmic opamp issue

However, the poster could not provide sufficient information about his inputs, component models etc. to get a proper answer. Someone suggested raising the resistances which for me has failed to solve the problem.
Thanks in advance.


texts:
I have problem controlling dynamixel MX28R servo motor.
I've tested two kinds of connection. First one to raspberry Pi B+ and this is a
main use case. Here is my connection scheme.

Servo connects to RS485 communication board. RSE pin connects to GPIO_0 of
raspberry. RSE needs to be set
to zero to receive and set to 1 for data transmission. I have modified C++ SDK
and add turning GPIO_0 on before writing and off after.
from DynamixelSDK/c++/src/dynamixel_sdk_linux/port_handler_linux.cpp

#define RES_PIN 0
...
PortHandlerLinux::PortHandlerLinux(const char *port_name)
  : socket_fd_(-1),
    baudrate_(DEFAULT_BAUDRATE_),
    packet_start_time_(0.0),
    packet_timeout_(0.0),
    tx_time_per_byte(0.0)
{
  is_using_ = false;
  setPortName(port_name);
  wiringPiSetup () ; //           <<<< this is my code
  pinMode (RES_PIN, OUTPUT); //   <<<<
  digitalWrite (RES_PIN, LOW); // <<<<
}
...

int PortHandlerLinux::writePort(uint8_t *packet, int length)
{
  digitalWrite (RES_PIN, HIGH); //<<<<
  // delay1 don't work with or without delays
  int res = write(socket_fd_, packet, length);
  // delay2
  digitalWrite (RES_PIN, LOW); // <<<<
  return res;
}

...

But when I run examples
I see There is no status packet! error. And motor doesn't reacts. I've tried to send
commands through dxl_monitor. For example to turn on LED: w1 1 25 1 or
w1 255 25 1 but nothing happens. Also I've tried to send raw instruction packet from this example.

import serial
import time
import RPi.GPIO as GPIO

GPIO.setmode(GPIO.BCM)
GPIO.setup(0, GPIO.OUT)

port = serial.Serial("/dev/ttyAMA0", baudrate=1000000, timeout=3.0)

while True:
        GPIO.output(0, GPIO.HIGH)
        port.write(bytearray.fromhex("FF FF 01 05 03 1E 32 03 A3"))
        time.sleep(0.1)
        GPIO.output(0, GPIO.LOW)
        time.sleep(3)

        GPIO.output(0,GPIO.HIGH)
        port.write(bytearray.fromhex("FF FF 01 05 03 1E CD 00 0b"))
        time.sleep(0.1)
        GPIO.output(0,GPIO.LOW)
        time.sleep(3)

I've also tried to change baudrate to different values from
this manual with no result.

Here is another connection that I've used.

RSE pin always set to 1 for transmit data from PC.

I sent raw instruction packets with the same python code (without GPIO stuff).
But servo does not react.

Also I've noticed that led on UART turns on for a while, when I turn on dynamixel.
Like it sends some data on power on. I've tried to read data with screen utile:

screen /dev/ttyUSB0 1000000 cs8

Tested with different baud-rates but screen shows no info.


texts: What is the typical range of a nRF24L01+ module with PCB antenna?

texts:
I have seen the nRF24L01+ ( http://iteadstudio.com/store/index.php?main_page=product_info&cPath=7&products_id=53&zenid=qa08tp07o8bn54mjpo155e5o1 ) module linked before as a solution for low cost short range communication between MCUs, but finding a reliable range numbers has been difficult.

Does anyone who has experience using these chips in a real environment give an approximate range at the lowest data rate?


texts: How to debug current consumption with STM32 Nucleo board?

texts:
I'm trying to configure an STM32L011-Nucleo developement board to consume about 600 uA of current or so. It uses an STM32L011K4.

The datasheet states that this should be possible if I drive the MCU at 8 MHz and keep it in sleep mode for most of the time.

So I expect that MCU should consume about 1.3 mA or so in run mode. My exact case isn't listed - there are examples for 16 MHz HSI and 8 MHz HSE. I think that 1.3 mA is a good estimation.

In sleep mode:

So it is the same story:  looking at 16 MHz HSE and 8 MHz HSE I could expect less than than 500 uA of consumption with 8 MHz HSE in sleep.

To test the current I put 100 Ohm through-hole resistor on the power jumper like this:

After all I have the following picture:

As you can see I have 1.7 mA in sleep and 2.2 mA in run modes. Which is WAY more than I expected.

I've already set all unused GPIO's to GPIO_Analog mode as I expect that this will minimize leakage current.

I've checked the schematic to verify that VDD is only feeding the MCU (looks like this is true).

I tried much lower frequencies and I was able to drop current consumption to 400 uA at 625 kHz which is also not match to datasheet...

Well, I have to state that I'm confused. AVR controllers (ATmega48PA) behaved as expected in one of my previous device.

Is there anything I am missing?

My clock configuration:

UPDATE

After I changed the PLL setting to None I reached less consumption: 1.1 mA for sleep and 2 mA for run mode:


texts: How to calculate reactance of a capacitor for a square wave

texts:
Capacitors block DC signals and pass AC signals. Their resistance, ideally, is purely reactive (no real part to its impedance). For a sine wave of frequency f passing through a capacitor, the reactance is given by the equation:

\$X_C\$ =1/( j \$\omega\$C) = -j/(\$\omega\$C)

|\$X_C\$| =1/(2*\$\pi\$*f*c)

\$\omega\$=angular frequency (rad/s)

C=capacitance(Farads)

f=frequency (Hz)

Similarly, how to calculate the reactance for a capacitor when a square wave is passing through it. What is the formula?


texts: How to tap a pin on very small surface mounted IC

texts:
I have very small surface mounted IC (see link https://www.st.com/resource/en/datasheet/stm32l486qg.pdf).
I need to access some pins on the IC in order to perform ETM trace.  My challenge so far has been how to tap into the pin.
Would I need any specialized tool?


texts: How to find a truly bi-directional level shifter?

texts:
I'm trying to create an interface PCB to a 32 channel USB GPIO device which has 3.3v IO, and I want the flexibility to use 1.8, 3.3 or 5v - across all pins, or at most in 2x banks of 16 - I don't need different voltages on a per-pin basis.

Speed-wise I'd be looking for at most 1MHz switching frequency, but as low as 200kHz would probably be fine.

When searching through Farnell (UK version) I've found lots of 16-channel level shifters that are technically bi-directional, but only with a switchable direction using a DIR pin handling an 8 channel bank. I need something that will give true bi-directionality on each pin without having to set the direction.

As an example, what I currently use for level shifting is this SparkFun board: SparkFun Logic Level Converter - Bi-Directional but this requires a 'low' side and a 'high' side. I suppose I could shift everything to 5v and then back down to 3.3v, but I'd prefer a simpler packaged solution.

Is there some terminology I'm missing that would help me narrow down my search to find what I need? If it even exists, that is.


texts: SCART to composite video conversion without IC, is that possible?

texts:
I have assembled this project http://cb2.qrp.gr which was lot of fun, but I have a TV with a composite video input only. Now I know there are ICs out there that can convert from RGB/HSYNC/VSYNC to composite video (PAL/NTSC), like the AD725, but I would like to investigate how such a conversion can be done in discrete components, if this is not too difficult to do.
Is that possible and what parameters should I investigate?
Note that the project has already a black and white composite video output, but I also need the colors to present.


texts: RF transceiver and antenna near LiPo battery?

texts:
Would there be any foreseeable issues with placing a ~300mAh LiPo battery within 10 or so millimeters of an RF transceiver and antenna?

Units are in milimeters.  (Click for larger image.)


texts: If-else decision structure using op amps or any other non-programmable electronic device

texts: The title is pretty clear, I would like to know if there is any circuit or an IC capable of dealing with signals to perform algorithmic sort of decisions, I mean, as you can solve differential equations using op-amps, I can design a circuit which output is the GCD of two input signals, finding them with Euclid's algorithm.


texts: Where does the MOSFET body diode come from?

texts:
Where does the body diode in a MOSFET come from? I understand that its built in and an intrinsic part of the MOSFET. All illustrations of a MOSFET that I've seen depict the structure as two diodes back to back but non hint at where the diode comes from.

simulate this circuit – Schematic created using CircuitLab


texts: What coordinates should an USB HID mouse return?

texts:
I am trying to implement an USB HID mouse for my custom board (to move the mouse pointer on my display). Right now, I am able to read the descriptors.

I found the logical min and max to be -127 and +127. After reading the documentation for HID, I got confused.

What is physical min and max of a device?
What is its role?

If I want to calibrate my mouse to a given display, where to give the coordinates? Also, when the mouse action takes place, I am getting coordinate values (X and Y and buttons) two or three times.

Is it because the values returned by the mouse are continuous and I have to implement some averaging? Or is it like the mouse coordinates returned are relative and I have to initialize my mouse coordinates as (0,0) and from the previous position I have to calculate the current position?

Thanks for the reply. But from which field of the descriptor I can find the unit, means whenever I move a mouse I will get the X and Y, how to find out what is the unit it has moved?(inch or meter). Because the HID descriptor I am getting consists of the following fields:

Usage Page-   05 01
Usage Mouse- 09 02
Collection(App)-a1 01
Usage(Pointer)-09 01
Collection(Physical)-a1 00
Usage Page(Button)-05 09
Usage Min- 19 01
Usage Max-29 05
Logical Min-15 00
Logical Max-25 01
Report Count-95 05
Report Size-75 01
Input(Data,Variable,Absolute)-81 02
Report Count- 95 00
Input-81 03
Usage Page-05 01
Usage X- 09 30
Usage Y- 09 31
Wheel   - 09 38
Logical Min-15 81
Logical Max-25 7f
Report Size -75 08
Report Count-95 03
Input-81 06

05 0c
0a 38
02 95
01 81
06 c0
c0

I dont know what are the values after the input field.

This is what I am getting as hid descriptor from my logitech mouse. I understand it is relatve(from 81 06).And in addition to it, I get coordinates(X and Y) and buttons whenever I move or click. But where to get the unit and unit exponent(for finding the resolution and how much the mouse has moved)?? Thanks again


texts: Short Coax for carrying low frequencies (120kHz) - does it matter if 50 Ohm or 75 Ohm?

texts: I'm using coax to carry signals whose highest frequency component is 120kHz over a distance of 2 or 3 meters. Does it matter whether the characteristic impedance is 50 or 75 Ohms? My feeling is it does not, but would like a second opinion.


texts: Conjugate, non-conjugate and single poles in an RLC circuit system

texts:
In all the texts I encountered so far, I find the following pole-zero diagram example for an RLC series circuit:

The transfer function for the above circuit can be found as:

H(s) = XC/(R + XL + XC) = (1/sC)/[R + sL + (1/sC)]

H(s) = 1/(LCs² + RCs + 1)

But when I plot the pole-zero diagram of the above circuit for different R,L and C values, I don't always obtain the poles as conjugate.

Below are three different pole-zero diagram of the above RLC circuit for different R,L and C values:

1-) Conjugate Poles

R = 10;

C = 0.00001;

L = 0.001;

2-) Non-conjugate poles

R = 10;

C = 0.001;

L = 0.001;

3-) Pole at the origin

R = 100;

C = 0.001;

L = 0.001;

Question:

What can we say about the real response of the circuit for each three case above by considering the locations of the poles? In other words, what does it mean poles being conjugate, being asymmetric/non-conjugate and being at the origin only for an RLC series circuit?
(Especially, in the second case there is two different non-conjugate poles which is the most confusing situation to say something about the system)

Edit:

Following the answer I was able to reveal the higher pole for the third case:


texts: How to design an optocoupler circuit for raspberry pi

texts: I want to give sensor pulse to raspberry pi. The sensor signal comes from a running conveyor . The sensor gives 24v signal hence I used a optocoupler to convert the 24v to 3.3v . How should I design a best optocoupler suitable for PI.


texts: How do capacitors affect Operational Amplifiers?

texts:
When we have an OpAmp as the one below:

This was extracted from an exercise in which V2 was an AC power source. However, I have tried to imagine what would happen if it was DC. It is obviously a non-inverting OpAmp, but according to my book, this is a Buffer Gain = 1 system because C1 blocks any current from flowing through R1. Could someone explain this? I am confused since I do not see how C1 can affect the node at which we apply Kirchhoff's Current Law.

If this is the case, where we have a Buffer, then I know VA = V2. But since we have C2, right after this capacitor, would we have VB = 0 for the same reason?

I am very confused and I could use some help with both questions (in bold above). Thank you!


texts:
Is there any use for parallel RC circuits in DC applications? Look at this now full diagram for example. The IC has 3 pins (mosfet maybe).

It seems that the resistor in parallel would only drain unnecessary current out of the source without changing anything on the output, not limiting current and not changing voltage.

Thanks.


texts: Can my weather station cause interference with my wireless network?

texts:
I know my weather station is on 433 MHz and my home Wi-Fi network is on 2.4 GHz  and 5 GHz. It's ok so far and everything seems to be fine.

But I found many cases on the Internet that cheap stations like mine may cause Wi-Fi interference: can it be harmful for my wireless network?


texts:
Today I saw a USB Wall charger for sale and it claimed it can output 3 amps at 5V and it only had one USB port. USB specs say a dedicated charging port is rated for 1.8A.

So how is this charger USB port able to handle 3A? I have looked online and I can't find a USB port that is rated to handle 3A. Best i could find is a USB port that has gold plated on the USB pins inside the port.

I have tried to draw 3A from a normal USB 2.0 and the USB connector got really hot. How can a USB charger with USB-A connector handle 3 Ampere?


texts: Why the neutral of the UPS or inverter or generator is advised to be earthed/grounded?

texts:
In my company we had few earthing related issues. When an consultant was brought in and apart from solving the issue, a suggestion was made to ground the neutral of the UPS and diesel generators that we have.

The situation prevented me to seek clarification from the consultant, but I could not help myself pondering why?

I Googled and it seems few other results also suggest the same but the pros and cons are not listed anywhere.

I thought this would be the right place to ask and hence this question.


texts: ADC resolution vs Accuracy of signal measurement?

texts:
I want to get accuracy of 0.1% in the following analog signal measurement:
AC voltage in the range of 0-300V (0.1% = 300 mV)
Then what is the minimum no of bits or resolution of ADC that I can use?
My understanding is following:
If I use 16 bit ADC then I get:
300/65536 => 0.0045 => 0.4%
So I need an ADC with better than 16-bit resolution.
Is my understanding correct in this calculation?

Edit: adding more details:
I want to do all calculations based on ideal cases only at this time. I am not worried about the frequency of signal, sampling rate or power supply issues of the design at the moment.
If I also need to use the same ADC for following signal measurements with 0.1% accuracy:
Current (DC and AC) in the range of 0-50 A. (0.1% = 50m A)
Resistance in the range 0f 0-10 MOhm. (0.1% = 10k Ohms)
Then what additional conversion factors I had to include in my calculations?
For example how will it effect my calculation when I convert a current signal or resistance related signal into voltage to feed into my ADC?
Can a 16-bit ADC fulfill the 0.1% accuracy design requirement in all of the above V, A, R measurements?


texts:
I have a TFT display which accepts 24 Bits Per Pixel (BPP) display data, but my connector mechanism supports only 5:6:5 mode.

What is the prefered way of getting the display to drop the extra pixel data and use the 5:6:5 data?

Should I just pull-down the unused data lines?


texts: I just want to confirm my thoughts regarding this op-amp circuit

texts:
I was constructing a circuit which contains an operational amplifier designed to be controlled by a digital signal (5V HIGH, 0V LOW).
My intented design was: upon receiving a 5V signal, the amplifier should function as a non-inverting amplifier with a gain of 1+(Rf/R1); receiving a 0V signal should remove the gain.
A kind user suggested me this circuit design involving an analogue switch in series with resistor R1 (on when receiving 5V, off when 0V):

I need someone to verify my understanding regarding this circuit: The op-amp behaves like a typical non-inverting amplifier with gain 1+(Rf/R1). Upon sending a 0V signal to the switch, the R1 is disconnected from the circuit. This consequently turns the gain to 1, i.e. the op-amp behaves like a voltage follower.
Is my understanding of this circuit correct?


texts: Powering an IR + RED laser with an Arduino

texts:
I am hoping to run a laser diode from an Arduino.
The specific one with included data sheets are here:
 https://industrial.panasonic.com/kr/products/semiconductors/laser/red_infrared/red-and-infrared-ir-laser-diodes/LNCT28PS01WW

It seems the red component operates at 2.4V 128mA and the IR component operates at 2.5V 210mA. I've done some calculations and arrived at 20 ohms for the red and 10 ohms for the IR series connections, but I am wondering if there are any considerations I need to make since they are both integrated. What would my circuit diagram look like?

Is it reasonable/feasible to operate this laser from an Arduino, or do I need to look for another source with a fixed current?

Thanks.


texts: Is it possible, and if so, how difficult would it be, to replace the volatile memory in Gameboy games with non-volatile memory?

texts:
my working knowledge of electrical engineering is quite limited, so please excuse me if my question has been answered under different terminology!

I was looking at old Gameboy games, which require a CR1616 battery to keep their saved games, and then I noticed how cartridges for the N64 variously used the volatile memory in early releaes and EEPROM non-volatile memory in later cartidges, as weel as later era Gameboy Advance cartridges and pretty much any modern solid state memory, thumb drives all that do not require a current to keep the data.

So Is it possible, or plausible, to take an old Gameboy cartridge requiring the CR1616 cell and replace it's memory with something non-volatile in the average hobbyist's home workshop?

I do not intend to do this, I only ask if it is possible to replace only the save memory keeping all the rest of the original hardware intact. I am aware there are many ways to accomplish something similar, such as an adapter for SD cards and then running some sort of emulation, but that is too un-original (hardware wise) for what I am thinking.

Thanks for any input folks!

Edit:
If memory is memory (so long as the capacity is recognized by the system using it), and memory with a compatible number of pins isn't able to be acquired, would some fancy soldering be a way to either bridge or split pins from the IC to the board of the cartridge?

Edit 2:
It appears that what I am talking about is replacing "SRAM" with "nvSRAM". Not much help to me, but at least I understand some terminology better.

Also, here is aq link to the inside of the exact cartridge I had in mind when thinking about this question:
https://en.wikipedia.org/wiki/ROM_cartridge#/media/File:PokemonSilverBoard.jpg


texts: Switching between external power and batteries with varying voltages

texts:
I want to supply some voltage regulators (12V, 5V and 3.3V) with one of two power sources: one wall power-supply and/or a LiPo-pack. The input voltage would be in the range of 10V-24V and a continous power draw of ~50W is expected. It should be always powered by either the external power-supply or the batteries.

If one of those power-sources fails (due to unplugging, etc.) it needs to switch to the other one.

Some problems I can think of are:

Schottky-diodes generate too much heat with my power requirements and I don't want to rely on active cooling.
Are there special requirements for the circuitry (e.g. can I build it on a protoboard w/o problems)?

How would best go about this given these requirements?


texts: Trying to understand push-pull output mode and open-drain output mode in a MCU's GPIO pin

texts:
I have a MCU (STM32H7xx) whose GPIOs, when configured as output, can be configured either as open-drain or push-pull. Before seeing this, I though that open-drain meant hihg-Z, however I don't see how that works just reading the STMicro documents. Let me explain:
This is the GPIO schematics:

And this is the explanation I'm reading (attached as image to not lose the formatting):

Now, with regards to the push-pull output mode, my understanding is that the pull up/down resistors are disabled, the mosfets are used to output VDD or VSS (which is ground). I'm happy with that.
What I don't understand is what is the goal of open-drain mode, let me explain: the doc. says that you need to enable the pull-up resistor to work in this mode. In that case, I understand that when you enable the NMOS, VDD is grounded through the pull-up resistor, therefore the output pin is driving a 0. However, if the NMOS is disabled, it will be driving VDD through the pull-up resistor.
Questions: Is the above correct? If so, what is the point of this mode? It seems to achieve exactly the same behaviour as the push-pull one. How do you get a high-Z output?
Sources:
stm32h7 43/53 reference manual - see 11.3.10
STM32 GPIO configuration - see 3.3.2


texts: What kind of LC circuit can produce this response?

texts:
I am trying to come up with an equivalent circuit for a structure that I'm working on. The response is shown below:

The modelling of the structure hasn't incorporated any loss, therefore the real part of the impedance is 0. I am not a circuit expert, and would like some pointers on what kind of circuits would be capable in producing a response like this.


texts: SAVR. Is it even possible to reduce environmental EM radiation without using Faraday cage?

texts:
Recently I saw a product called SAVR Radiation Reducer in the market by PowerLink claiming the followings:

  SAVR Radiation Reducer basically scans and detects EMR waves and it
  generates reverse signals to neutralize and reduce low, intermediate &
  high-frequency electro-magnetic radiation emitted by computer and
  other surrounding devices. Apart from this action, it also filters EMR
  waves and flushes it through the A/C power

  Significantly reduces EM radiation around your computer and other
  devices on WiFi with a coverage area of 4 square meters*

  Eliminates over 95% low, intermediate and high-frequency EM radiation

  Radiation clearance range up to 1GHz

Basically you just power up the device and place somewhere near you, it will 'reduce' EM radiation around you automatically.

Attached photo is the demo of the product effectiveness

[Updated 4 Aug 16]: Attached photo

My question is,

Reducing EM radiation? is it even possible this can be done without shielding myself inside a Faraday cage?
Is it possible to scan & generates a 'reversed EM wave' to cancel off or reduce the current environmental EM waves?
If EMR really was reduced to 0 (shown in photo), why the mobile phone still have GSM signal?
If working range claimed up to 1GHz, most GSM band and WIFI band is above 1GHz range (e.g: GSM above 1.8GHz, Wifi 2.4GHz & 5GHz), how reduction was able to archive ZERO (shown in photo)?

The product official info,
http://www.savr2u.com
http://www.powerlink.com.my/#sav
https://www.facebook.com/SAVR-Your-Smart-Radiation-Reduces-525916917552326
https://www.facebook.com/powerlink.my/


texts: MATLAB: Pole at 0.1 rad/s contributing to nothing on the Bode Plot - Why?

texts:
Consider the transfer function

$$G(s) = \dfrac{48000}{s(s+100)}$$

The Bode plot is given as

Now observe that the gain at frequency w = 1 Hz is 53.6244 dB. Completely reasonable, because this is exactly $$20\log10(48000/100) = 53.6244 dB$$

Now I change the system to:

$$G(s) = \dfrac{48000}{s(s+0.1)(s+100)}$$

Consider the Bode Plot

MATLAB is telling me that the gain at frequency w = 1 is 53.5812 dB. This is roughly unchanged. Wouldn't the pole at 0.1 = 10^-1 contribute to greater drop in gain than the previous system? I should expect the Bode plot to show full 20 dB lower at w = 1 compared to the the first system, so according to this logic 53.6 - 20 = 33.6 dB, instead of 53.5812 dB.

Can anyone explain this? Why isn't the pole at 0.1 contributing to anything on the magnitude plot?

Code:

  G = zpk([],[0,-0.1,-100],48000)
  bode(G)
  grid on

More craziness:
$$G(s) = \dfrac{48000}{s(s+0.001)(s+0.1)(s+100)}$$

We have two poles before 10^0 = 1 Hz and contributing absolutely nothing to the magnitude plot!


texts: Leakage Current in a AC/DC PSU without earth?

texts:
I'm looking at the data sheet for a Meanwell NPF-40 PSU. This is a class II unit and hence does not have an earth connection (see also mechanical specifications, page 6), yet the data sheet specifies a leakage current of <0.25mA @ 277VAC.

I was wondering how a class II unit without earth can even have leakage current. Where does the current leak from and to? This is a similar question, but the accepted solution states that there is leakage from the DC ports to earth, which I don't think can happen with this PSU.


texts: I am new in BJT. Why is the hFE of a BJT less than 1 in reverse active mode?


texts: Help with identifying a component on a PCB

texts:
I'm trying to troubleshoot a malfunction smart-outlet.
I think the marked component is a fuse. It's not conducting.
Is this a fuse?
Thanks


texts: What is the purpose of this bias resistor?

texts:
I am unsure what the following statement on page 4 of this application note (Over Voltage Protection Circuit for Automotive Load Dump)  means.

  Resistor R4
  provides a small amount of bias to Q2 in order to satisfy Q2
  ’s drain leakage in the off state.

I assume R4 is to satisify Idss in the datasheet of 50uA but I am unsure how the value of R4 was even selected.

Does this mean that all mosfets must have their leakage currents requirements satisfied in order to work ? Why wasn't R5 + R6 not sufficient for this path ?


texts: Possible ways of protecting comparator input from coupling?

texts:
Overview

So as I'm implementing some logic with a comparator, I've run into the problem of the output swing coupling with one of the inputs, and now I'm searching for possible ways to minimize or work around this problem.

From TI datasheet, the expected ways is to a)  layout , b) add hysteresis.
It turns out that the coupled noise (see 2) is of 160mv, being an order of magnitude bigger than the recomended hysteresis (and way more than I hoped for!).

Symptoms

Have v1 = 5.6v, v2=1.2. By making the comparator switch (Ref ~ 'sum' on non inverting), noises appears on V1 (thus on the sum). In 4 you can see this noise.  An output swing of 0-12v makes V1 swing 160mv.

This error of +-80mv has all sort of nasty consequences for my system.

First, I would expect the comparator to swing randomly when ref is close to sum (ie: less than 10mv), but because of the added noise of the output swing, this region of instability is of ~100mv. That is, in place of having a stable output after 10mv, I need 100mv.

Second, if I have a signal on V1, it will be masked by this noise since it rises much faster, switching the comparator by-itself. If the noise was on the non inverting input, it wouldn't be such a problem.

So I'm searching for  2 things. Minimize the noise on V1 (since I'm measuring it!), and if not enough, make the comparator immune from self switching.

Circuit

simulate this circuit – Schematic created using CircuitLab

Top layer

Bottom layer

Description

So as you can see, I'm working on a 2 layer board, and I tried to be cute and had the signal sources(output from lm324 opamp) below the comparator.

Signal u goes to a push pull before driving a mosfet (at this moment the mosfet gate is not connected to the driver)

V1 is an AC signal in the range 5.6V+- 200mV

V2 is a DC signal in range 0.5-3V

Now, I have no need for the input band-witch to go all the way to 700khz (the previous layout that I worked on had a cycle of 10khz), but I don't want to limit the rise time of the comparator output (since it drives a power mosfet).

Possible solutions (and perceived drawbacks):

Get the OPAMP somewhere else.

Away from agressor. Makes routing harder (and longer).

Add a gain to V1 of 10, in place of dividing V2 by 10.

Reduces the impact of noise by 10,  requires reworking the board

Add dynamic hysteresis of 100mv that last the switching time.

Not sure how to calculate C. Doesn't solve the noise source.

Add low pass on output of comparator.

Less agression, but is bad for the mosfet.

add low pass on input of comparator, as close as possible from the pin.

Same problem as 3

So did I miss any possible solution? What would be the first thing to test here?

I expect 2 to give a solid result while not changing too much of the layout, but maybe there's something else to reduce the aggression.

Extras

Noise figure!

Yellow trace is V1,
Blue trace  is u. Both AC coupled.

The frequency of oscillation is ~700Khz, which is also the response frequency of the comparator.

The board.

Please excuse the bad solder skills, second PCB I've ever printed! I've added a 100ohms to the input of V1 that had no effect at all.


texts: Is it possible to exchange the content of two registers in a single clock pulse?

texts: There are two register R1 and R2. How is it possible to exchange the content of R1 and R2 in a single clock pulse using Common bus architecture?


texts: dsPIC system configuration bits in MPLAB X project vs the same config bits in the code

texts:
I can setup system configuration bits (fuses) in the MPLAB X project and/or in the code directly:

I understand that the ones on the Configutaion Bits tab are stored in the project somewhere. Is that right? If yes, my questions is:

How do they relate to each other as they can be easily different?


texts:
I am trying to write a simple code to receive and resend data using USART but the code is not working.

Could someone give suggestions on possible flaws in the code?

I am using USART at baud rate 9600 with clock frequency 4MHz.

#include<pic.h>
void main()
{
    TRISB=0X00;
    TXEN=1;
    SYNC=0;
    BRGH=1;
    SPEN=1;
    CREN=1;
   //RCEN=1;
    SPBRG=0X19;
    INTCON=0X80;
    TRISC7=1;
    TRISC6=0;
    RCIE=1;
    TXIE=1;
    while(1);
}

void interrupt rectrans()
{
    if(RCIF==1)
    {
      TXREG=RCREG;
      while(!TRMT);
      RCIF=0;
    }
    else if(TXIF==1)
    {
      TXIF=0;
    }
}


texts: Analysis of the full bridge bidirectional converter's buck mode operation?

texts:
This is the circuit I was trying to learn.

Here is the equivalent of the buck mode operation:

And following is the waveform in the buck mode of operation:

My intention is to derive the output voltage equation.
Theory used, Voltage across an inductor, averaged over a steady state cycle time, must always be zero

Mode - 1    (When MOSFET is ON)

VL1 = Vin * (1/n) - VCLV            for   0≤t≤DT       ------- (1)

D = Duty Cycle
T = Time Period

There is a dip in the output inductor waveform, hope it is the dead time to avoid the cross conduction.

Now I need to evaluate the second part of the inductor voltage equation when MOSFET is OFF. After solving both the equations using the theory I have mentioned, can evaluate output voltage equation. But I am  stuck with the second part of equation.

Edit

Let me make an effort to do mode-2 (MOSFET is OFF) inductor voltage analysis

VL2 = Vin - VCLV   for DT ≤ t ≤T

Since net voltage over a steady state cycle is zero,

( VL1 + VL2 ) / 2 = Zero,

From this, VCLV = VOUT = Vin * ((D/n) -D + 1 )

Please recheck and confirm the derivation


texts:
I have a project that is powered by a 12v power supply. I need as bright of an LED as possible and decided to use this 9v LED. According to the datasheet, its max current is 1A, which is what I would like to get it to. In order to do this, I am using this 3 Ohms resistor

According to my calculations, (12v-9v)/1A = 3 Ohms. This should get my LED to the correct current.

To test the current, I placed a multimeter in series with the 12v power supply, LED, and resistor. However, I am only reading 0.639A. I tried several power supplies and meters and it's all the same.

What am I doing wrong? Is my test setup providing too much resistance, thus decreasing the current?


texts: this signal is connected to multiple drivers

texts:
library ieee;
    use ieee.std_logic_1164.all;
    use ieee.std_logic_arith.all;
    use ieee.std_logic_unsigned.all;

    entity ctrl_unit is
    port(   clock_cu:   in  std_logic;
        rst_cu:     in  std_logic;
        PCld_cu:    in  std_logic;
        mdata_out:  in  std_logic_vector(15 downto 0);
        dpdata_out: in  std_logic_vector(15 downto 0);
        maddr_in:   out     std_logic_vector(15 downto 0);
        immdata:    out     std_logic_vector(15 downto 0);
        RFs_cu:     out std_logic_vector(1 downto 0);
        RFwa_cu:    out std_logic_vector(3 downto 0);
        RFr1a_cu:   out std_logic_vector(3 downto 0);
        RFr2a_cu:   out std_logic_vector(3 downto 0);
        RFwe_cu:    out std_logic;
        RFr1e_cu:   out std_logic;
        RFr2e_cu:   out std_logic;
        jpen_cu:    out     std_logic;
        ALUs_cu:    out std_logic_vector(1 downto 0);
        Mre_cu:     out     std_logic;
        Mwe_cu:     out     std_logic;
        oe_cu:      out     std_logic
    );
    end ctrl_unit;

    architecture struct of ctrl_unit is

    component controller is
    port(   clock:      in std_logic;
        rst:        in std_logic;
        IR_word:    in std_logic_vector(15 downto 0);
        RFs_ctrl:   out std_logic_vector(1 downto 0);
        RFwa_ctrl:  out std_logic_vector(3 downto 0);
        RFr1a_ctrl: out std_logic_vector(3 downto 0);
        RFr2a_ctrl: out std_logic_vector(3 downto 0);
        RFwe_ctrl:  out std_logic;
        RFr1e_ctrl: out std_logic;
        RFr2e_ctrl: out std_logic;
        ALUs_ctrl:  out std_logic_vector(1 downto 0);
        jmpen_ctrl: out std_logic;
        PCinc_ctrl: out std_logic;
        PCclr_ctrl: out std_logic;
        IRld_ctrl:  out std_logic;
        Ms_ctrl:    out std_logic_vector(1 downto 0);
        Mre_ctrl:   out std_logic;
        Mwe_ctrl:   out std_logic;
        oe_ctrl:    out std_logic
    );
    end component;

    component IR is
    port(   IRin:       in std_logic_vector(15 downto 0);
        IRld:       in std_logic;
        dir_addr:   out std_logic_vector(15 downto 0);
        IRout:      out std_logic_vector(15 downto 0)
    );
    end component;

    component PC is
    port(   PCld:   in std_logic;
        PCinc:  in std_logic;
        PCclr:  in std_logic;
        PCin:   in std_logic_vector(15 downto 0);
        PCout:  out std_logic_vector(15 downto 0)
    );
    end component;

    component bigmux is
    port(   Ia:     in std_logic_vector(15 downto 0);
        Ib:     in std_logic_vector(15 downto 0);
        Ic: in std_logic_vector(15 downto 0);
        Id: in std_logic_vector(15 downto 0);
        Option: in std_logic_vector(1 downto 0);
        Muxout: out std_logic_vector(15 downto 0)
    );
    end component;

    signal IR_sig: std_logic_vector(15 downto 0);
    signal PCinc_sig, PCclr_sig, IRld_sig: std_logic;
    signal Ms_sig: std_logic_vector(1 downto 0);
    signal PC2mux: std_logic_vector(15 downto 0);
    signal IR2mux_a, IR2mux_b: std_logic_vector(15 downto 0);

    begin

      IR2mux_a <= "00000000" & IR_sig(7 downto 0);
      IR2mux_b <= "000000000000" & IR_sig(11 downto 8);
      immdata <= IR2mux_a;

      U0: controller port map(  clock_cu,rst_cu,IR_sig,RFs_cu,RFwa_cu,
                     RFr1a_cu,RFr2a_cu,RFwe_cu,RFr1e_cu,
                     RFr2e_cu,ALUs_cu,jpen_cu,PCinc_sig,
                     PCclr_sig,IRld_sig,Ms_sig,Mre_cu,Mwe_cu,oe_cu);
      U1: PC port map(PCld_cu, PCinc_sig, PCclr_sig, IR2mux_a, PC2mux);
      U2: IR port map(mdata_out, IRld_sig, IR2mux_a, IR_sig);
      U3: bigmux port map(dpdata_out,IR2mux_a,PC2mux,IR2mux_b,Ms_sig,maddr_in);

    end struct;

I have a vhdl code like above but when i try to implement it, it show error like this:

can anyone please tell me what i'm doing wrong here? thanks.


texts: How to make a small spot welder for E-cig mesh coil welding?

texts:
I want to make a DIY spot welder

I am planning to rebuild a non-rebuildable heating coil (Eleaf HW-N) and I need to weld two non-resistive (low resistance) wires. A stainless-steel net to a nickel-chromium alloy to protect the rubber(red on video) at the bottom of the assembly from melting

Coil specs:
I want to use the "net" version of the coil but I didn't find a video for that
The original: Dim:37.5*12.6mm Mat:Kanthal Res:0.2Ω≈ 1.6 Ω/ft

My Found: Dim:∞*13mm Mat:Kanthal Res:0.2Ω≈ 1.2 Ω/ft with this as the legs

I can find a lot of DIY builds for "wire zappers" but they are all for connecting two wires (around 0.5 max) I don't know what is my current/voltage need to connect the wire to the mesh

Click: Video of the coil disassembly

The circuit is quite simple I found one here

R1:  3.3 OHM 10W

R2:  33 KOHM 1/4W

Fuse1  :  3A

D1:  1N5400

C1:  2200 uF 50V

I'd use an LM2596 board(35V output) I know that this works for .5 wires.

What kind of capacitor should I use to make a good weld?

What would be the approximate current that is enough to melt the 13*1mm area?

And what voltage would be needed? I saw others with 60V, 45V, 35V

Also, I'm not sure if I can weld SS-Ni as they have such different melting points.


texts: Keeping SMD parts in place while soldering with paste and heat

texts:
I was very happy to learn that I could solder SMD parts in place, by dabbing dots of solder paste on all the pads, placing my parts, and heating. I've done it using a modified toaster oven, or alternately hot air (from a re-work station). I learned about doing things this way from answers to a similar question I posted years back, when I was still soldering parts one by one with an iron.

But I still must be doing something wrong because much too often, parts sized 805 or lower tend to lift upright on one pad, skew themselves to some unacceptable angle, or in some cases literally jump completely off their place. Sadly, when I wrote to the manufacturer of my paste, all they suggested was that I use a stencil to apply my paste more evenly. In other words, they blew off my question. (By the way, I've been using Chip Quick syringes, SMD291AX.)


texts: Of the millions of transistors in a typical microprocessor, what percentage of them are BJTs and MOFSETS?

texts:
This is broad in the sense of which microprocessor I am referring to. I expect them to be similar, but if not, then how about in an Intel 7th gen CPU and in an A11 iPhone chip?

And what about how many MOFSETS/BJTs in an entire iPhone(let's say 10X)? Are BJTs used at all?

I am curious to know the distribution due to the notion of MOSFETs being much preferred for switching purposes. Thanks


texts:
So I want to use the VNH5019 motor Controller shield for the Arduino Uno for a project. My question regarding this is the voltage of the motors. Since they differ from motor to motor I'm not sure which voltage works with the VNH5019. I haven't found any data in the regarding data sheet. Is there a way to tell the controller the max voltage that the motors could handle or how does this work?
I'm quite new to this topic so any help is appreciated!


texts: Corrupted files generated by Arduino with SD library. How to avoid that?

texts:
I have a sketch that runs on an Arduino Ethernet (that comes with an SD card reader and, of course, an Ethernet interface).

There is a unique place in this sketch where I write to a file on the SD card, which basically looks like this:

char dpath[13]; // File path
char logline[30]; // String to be stored in

/* ... */

File dataFile;
if (dataFile = SD.open(dpath, FILE_WRITE)) {
    dataFile.println(logline);
}
dataFile.close();

I didn't experience any problem for a few months having a couple of Arduinos running this sketch.

Recently, I put to work another one that is behaving weirdly. In particular, I see that on the SD card it generated a somewhat corrupted file.

The file size appears to be 4.0 GB, altough the total size of the SD card is 3.7 GB, and if I try to read it with a hex editor it appears empty:

$ du -h 20130206.DAT_
4,0G    20130206.DAT_

$ df -h
Filesystem   Size  Used  Avail  Use%   Mounted on
/dev/sdb1    3,7G   58M   3,6G    2%   /media/B045-FE58

$ hexdump 20130206.DAT_
0000000 0000 0000 0000 0000 0000 0000 0000 0000
*
fd000000

What could be happening to the microcontroller?

I'm asking this here, because I can't notice any programming problems, and the sketch is running fine on other boards. Should I be aware of some electric known problems? Could for example a not-stabilized power supply or some electromagnetic radiation be leading to this behaviour? I would appreciate any suggestion about electronic issues I should check.


texts: Questions about class-F and Inverse class-F RF power amplifiers

texts:
I have few questions regarding class F/F-1 RF power amplifiers, i've read few textbooks but none satisfied my exact questions

Why class F/F-1 are sometimes classified in the textbooks as a switched mode power amplifier? the way i see it is, it's like a linear amplifier with class B up to -almost- class A but with harmonic network synthesized to square the voltage (class F) to reduce the volt/current overlap and increase the fundamental frequency power, in other words, the amplifier is used as a current source with conduction angle rather than a switch.
in class F , assuming the current wave form is half-rectified sine wave, it contains only even harmonics which are presented with short circuit, so the voltage waveform won't contain any even harmonics but contains only odd harmonics, though ideally the input does not have any odd harmonic content, Prof. Cripps answered this question in his book that the current waveform will contain non-negligible odd harmonics content, so that may answer the question but in the case of class-F inverse I have no idea how the square current will appear if the input driving signal to the gate of the device is sinusoidal? it's said that the voltage waveform affects the current waveform in an iterative complex manner, but i don't quite get it.


texts: How do USB micro-B phones determine the host?

texts: Phones typically use micro-B instead of micro-AB or mini-AB, meaning that micro-A and mini-A cables can't be connected to them. Since these cables use an additional, grounded pin to identify which device is the host on the micro-A / mini-A end, how would a phone with a micro-B receptacle determine the host? Or do phones lose the ability to act as a host by use of the micro-B port?


texts: What is Partial Crossbar Interconnection

texts:
I have difficulties understanding the concept of Partial Crossbar Interconnection and I could not find any reference on internet to read on. I have the photo below from a lecture slide of many years ago and I can not recall what was it about. I remember another alternative was nearest neighbor interconnection but that itself had many problems when it comes to implementation.

So my question is what is Partial Crossbar Interconnection and what can be understood out of the image below?


texts: How can i simulate this circuit to match with the truth table?

texts: How can I simulate this NAND logic circuit to match the truth table?]2


texts: Trying to power 100 Arduinos from single power line

texts:
I'm trying to power up to 100 Arduinos that will be spread across a 25m wall using a single power line.

The idea is each Arduino will have a few a few buttons, leds & an oled screen and will all communicate to a master server using rs485.

====[A0]====[A1]====[A2]====[A3]====[A4]== ... ==[A99]

I've already followed this brilliant post http://www.gammon.com.au/forum/?id=11428 to implement the data connection using an rs485 bus.

However I'm struggling to understand how I could power multiple Arduinos from the one line without affecting the quality of the data bus.

Would I be able to use a 48v power rail with buck converter for each Arduino?

Would I have to isolate each Arduino and rs485 driver (my concern is the length of the wire will create different ground potential and effect the quality of the data bus)?


texts: Extending length of wire where the spark is produced on a mini tesla coil

texts:
How can I extend / increase the length of wire where the spark comes from on my mini musical tesla coil?  See my mini tesla coil below along with the quick connector I'm using to extend the wire with.  When I try and extend the wire using a quick connector the spark goes out (I was only trying to extend the length of the wire about a 1 foot.

PS: I believe the circuit is a Slayer Exciter.


texts: Does boosting voltage using MT3608 from 3.7V to 10V module reduces the Lipo battery capacity?

texts:
Suppose say, Iam trying to boost the voltage of my 3.7 Lipo battery to 10V using MT3608 STEUP UP CONVERTER and I need to run 3 LEDs(connected in series) which takes 9V (3v for each LED)
If my LIPO battery specifications are 3.7v and 750mAh, how long does my LEDs last with that battery if my voltage had been boosted to 10v?
After boosting my voltage to 10v from 3.7v, Do the capacity of battery still be 750mAh or does it reduce? If it reduces how much will be the output capacity at 10V. Explain in brief
P.S : I know that number of hours a LED can light up from my LIPO battery can be calculated by 750mAh/30mA = 25hrs (assuming my LED takes 30mA forward current and 3V forward voltage).
I would like to know the boosting circuit effect on my battery capacity


texts: Does a cable exist that would allow me to power a USB device via 2A while also connecting it to a computer for data transfer?

texts:
I know that when we charge devices via our computer, it is usually at 500ma (.5A). Does a cable exist that would allow the data transfer to happen to a computer via one USB A connector, but then it splits and has another USB A connector that I can connect to a power brick for 2A power?

              USB A
+-----------+ 2A charge
|Wall Outlet+-------+
+-----------+       |
                    |      Micro USB +----------+
                    +----------------+USB Device|
            USB A   |                +----------+
 +--------+ for data|
 |Computer+---------+
 +--------+

Possibly related: Can the power source for a USB device be different from the data source?


texts:
I'm having a problem with simple pulse generator circuit using LTC6993-1 (datasheet).

Circuit is not starting to pulse... This is my schematic and PCB layout:

I have checked the voltage levels and all of them are fine... I'm running it from 3V supply.

I don't know what I managed to get wrong with this simple circuit... Any ideas?


texts:
Is it possible to design a circuit using op-amps such that it's output gives the Laplace transform of the input signal?Is this idea new?

Here it goes:

Our task is to design a black box. Its property is such that it takes on an input signal and then converts the signal to a signal which would have been obtained if we had operated a Laplace transform. Even though in Laplace transform the result obtained is in 's' domain, we are not interested in converting the signal to frequency domain instead only in the magnitude i.e. if we apply \$sin(wt)\$ we should get \$\dfrac{w}{s^2+w^2}\$ [by Laplace transform] -- changing \$s\$ with \$t\$ --> \$\dfrac{w}{t^2+w^2}\$

Here is its graph at FooPlot.


texts: Mosfet Conventional current flow direction in the circuit

texts:
I am working on a project to control heavy loads with Arduino up to 10 Amperes. I found the circuit which is made using p-channel Mosfet and a p-type transistor. I am confused in the flow of current through the circuit. I uploaded the diagram please see if the conventional current flow is right in the diagram? and what about the current through the red box (Gate of Mosfet) what will be IL=?.
If the input current is up to 10 Amperes does it effects my arduino digital pin? Also if you have any recommendations regarding the circuit please share them.


texts: How strongly does patient movement affect the magnetic field in an MRI?

texts:
The magnetic field in an MRI is insanely stable due to a closed current loop in the superconductor. A normal conducting magnet would always have (in addition to a ridiculous power consumption) power line fluctuations in the field strength, which would lower image quality (drift of Larmor frequency and phase encoding).

But when the patient is moved into the MRI there is a change in magnetic flux through his body, so there also is an induced current flowing in the patient (this actually limits the speed with which the patient can be moved without getting dizzy in large field MRIs.)

But this also means that there is dissipation of the energy stored in the magnetic field.

So does the field get weaker and weaker with every patient?

Does this affect the imaging capability, too?

Is the amount of energy dissipated large enough to significantly drift the Larmor frequency?


texts: How does modulation technique affect channel capacity?

texts:
Shannon's channel capacity formula does not consider modulation techniques. How then does LTE achieve high data rate using advanced modulation techniques?

P.S: I am novice in RF and signal processing.


texts:
I have an XOR gate wired (74LS136) and I don't think it is working properly. Here is the table I think it should be outputting:

|X|Y||O|
-------
|0|0||0|
|0|1||1|
|1|0||1|
|1|1||0|

1 is a High
0 is a Low

I think this is the right output for the gate, but this is not what I'm getting.  This is what I am getting out of my XOR gate:

|X|Y||O|
-------
|0|0||0|
|0|1||~|
|1|0||~|
|1|1||0|

1 is a High
0 is a Low
~ is nothing

When I probe the output pin I get neither a high nor a low, it says no current. I have tried a couple different chips from the same manufacturer but they all have the same result. Is this normal for an XOR gate? Is this chip suppose to be doing this? Am I using the wrong chip?


texts: How to detect a plug is connected to socket

texts:
I have a plug and socket. Before I turn on power supply from a contactor, I need to detect if the plug is connected to the socket via a microcontroller. Any ideas on how to do this ?

UPDATE: The Plug I am using is

The Socket i am using is

All the four pins of both socket and plug are connected to neutral, ground and (120v) ac lines.


texts:
Let's assume I have a voltage sources V-A (like Arduino) and V-C (like Computer) and there is a load R-B (like some bidirectional thing) in between. I want to power up the R-B from either voltage source or both.
There is also a load R-C, which must be powered only from V-C.
I suppose a diode in between should do the trick . I there any other dangers in a circuit like this ?

simulate this circuit – Schematic created using CircuitLab

Now let's assume the voltage drop of 0.7V in diode is too high for the load R-B. I have read that MOSFET could be used in diode configuration and would have less voltage drop, but cannot quite get hold of it. Would the following work ?

simulate this circuit

If the above does work, would a NDT451N MOSFET be OK for 5V cicuit ?
I want something that is reasonably cheap and can be soldered with basic skills.


texts: What is the current - voltage relation in a wire?

texts:
This is a question from a TV game show. Fill the blank with appropriate words.

  Current flowing through a wire is ... to the voltage drop across the
  wire.

The answer in the dots is "proportional".

I am wondering if this is really an accurate statement. Should it be "current flowing through a resistor..." instead?


texts: Gate drive circuit for 1500VDC two switch flyback converter

texts:
I am designing two switch flyback converter for 1500VDC input solar application. I am little bit confused while selecting gate driver circuit, specially for high side gate drive. I didn't find any gate drive IC to withstand such high voltage. Most of them are for 650V rail voltage.

Is there any special technique for such high voltage application other than pulse transformer ?


texts:
I am trying to understand the spec of a Datasheet of a thermal fuse.
for example the one below :

https://nl.farnell.com/panasonic-electronic-components/eyp2bn134/fuse-thermal-cut-off-2a/dp/1832031

from the datasheet: http://www.farnell.com/datasheets/2244108.pdf

I see the temperature at which it fuses.
But there is also a rated current.

my initial understanding was that if the current through the fuse is higher than this rated current , the fuse would blow.So basically, my reasoning was that the thermal fuse can then also be used as electrical fuse.

However, I did an experiment with my PSU where I was passing 2.5A through a similar fuse, but it still did not fail.
The fuse in the test was rated 1A.

so my question is :

what is this rated current provided in the datasheet?


texts: Is it possible to step down 240 AC to 5 DC without transformer?

texts:
Microcontroller which is controlling mains voltage circuit requires 5 volts to operate.
Is it realistic to use diode bridge followed by capacitor to straighten the ac wave and then use voltage divider to get 5 volts from 240 without actually burning anything up ?
Or using transformer is the only means ?
Just thought to learn something new, if it is realistic.


texts:
I’ve received a very old pair of mono bakelite headphones that I would like to re-use for demonstration purposes. Just for voice audio and morse code tones.

The writings on the side of each headphone:

SB & CO
C.L.R.
1939

This leads me to believe it’s a C-type unit (whatever that means) with Low Resistance (Impedance) from the year 1939. The DC resistance I measured is around 62 Ohms for each headphone and there are no shorts or open circuits. The two earpieces are connected in series and each earpiece has two coils below a thin metal disc.

Image 1: inside closeup of headphone coils (disc removed)

Image 2: wiring

What would be the ideal or maximum signal levels can I drive these headphones with, and what sort of pre-amplifier would I need to make these headphones produce the best possible (probably still awful) sound when driven from a laptop or radio's headphone socket?

Is this where I need to dig up and replicate an old, valve radio's audio  output stage? I am hoping to do this with slightly more modern components..


texts:
I am currently using a RealDigital Blackboard FPGA and wanted to know if it is possible to connect an FIR motion sensor to it. The link to the website with the FPGA schematics is here: https://www.realdigital.org/hardware/blackboard
Looking at the board, there are only a few pins for servo motor control, however, I'm pretty sure those can't be used to program sensors. There are also 3 PMOD connectors (each 2x6) which I think can be used to achieve my goal, however, I'm not 100% sure. I already have a 3-pin motion sensor at home that I got from Amazon (https://www.amazon.com/gp/product/B07GJDJV63/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1), however, I am unsure if it is possible to connect this specific motion sensor to any PMOD port. If it is not possible would I have to buy a motion sensor specifically for PMOD's? Any help is greatly appreciated. Thanks.


texts: RC snubber across mosfet or diode with ferrite bead

texts:
I already designed a RC snubber across a mosfet and diode successfully .

Reading through some whitepapers , I have seen the addition of a ferrite bead in series with RC snubber.

Do you recommend it or I should stick to RC snubbers only ? (the goal is to reduce noise/emi to lowest possible levels)

Adding link to ferrite bead addition (fig 4) https://www.infineon.com/dgdl/Infineon-ApplicationNote_Optimizing_CoolMOSCE_based_power_supplies_for_EMI-AN-v01_00-EN.pdf?fileId=5546d462584d1d4a01584ee2e19d0376


texts: Connecting the Shield of a strain gage cable connector to PCB with ADC

texts:
I have a half-bridge strain gage sensor (pre-assembled product) with a 30cm cable, which I am trying to interface with my PCB containing a 24-bit ADC.

The connector at the cable end toward the ADC (i.e., the end away from the strain gage) has the following four pins, based on my reading of the resistances:

Pin 1: V_Excitation
Pin 2: Doesn't seem to be connected to anything
Pin 3: V_signal
Pin 4: Ground

All good so far.

However, in addition, there is the metallic shield constituting the body of the connector.

Being new to strain gages and ADC measurements, I am unsure of the shield's significance -- I presume it has something to do with minimizing interference-based offsets. (Also, I don't want to break open the cable to see what's inside but I'm guessing it is a standard twisted-pair cable.)

Question A: What role exactly does the shield play in a strain gage / ADC application?

Question B: And thus which of the following is good practice to follow with the shield? :

Just isolate shield from GND (i.e., leave shield alone) ?
Or connect shield directly to the Ground plane on my ADC pcb ?
Or place 4.7 nF Capacitor and 1M resistor between shield and Ground, as suggested for USB connector shield in this question ?
Or connect shield to metal chassis of my enclosure only, as suggested in this question ?


texts:
I am a newbie in ASIC design process and have a question.
What is difference (or pros and cons) of shorting the voltage supply pins(which have the same voltage requirements) in package level or in die(chip)level?

Thanks
G


texts: Is a pin fin heatsink with 4 fans enough for 2x 80W LEDs

texts:
I need advice: I plan to use a heat-sink for cooling 2x 80W white LEDs over my friend's tank.  The heat-sink is a "pin fin" design, 6 inches by 6 inches which combined with active cooling should dissipate more heat than other fin designs. Here it is:

Ebay Link

Now, I plan to attach 4x 12-volt fans on top for strong active cooling. My question is would such a system cool 2x 80W warm white LED chips effectively? I know LEDs aren't very efficient, and only a percentage will be actual heat produced, a few degrees above operating temp is no bother for us, so bearing all this in mind is this 4 FAN "pin fin" heat-sink idea feasible enough to effectively cool both 80W chips?.


texts: Find equivalent of a destroyed IC (voltage regulator?) - top marking 3P=4G 50Q

texts:
I’m trying to replace a damaged IC due to accidentally short circuit. But it seems like it’s impossible to find original one. How could I find an alternative?

What is 3P=4G 50Q?

Photo showing more of the PCB:


texts: How much FLASH memory is free for a program?

texts:
I'm programming for a STM32F103C8T6 (aka blue pill), with the be datasheet here.

On page 14 it states:

  2.3.2 Embedded Flash memory 64 or 128 Kbytes of embedded Flash is available for storing programs and data.

Now mine has 64 KB, however, does this mean I have 100% available, or is there some part reduced? And if so, how much? Or is there a way to find out when it will not 'fit'  (like an error will show up?).

I use an STM32 ST-LINK V2, and afaik I'm not using any special bootloader, development environment is Workbench 4 STM / Eclipse, and using HAL/STMCube.

Currently I'm using only about 19KB but I'm not finished (and running my unit tests also within this code, although I can switch it off, which saves half).


texts:
I'm reading a paper on a superconducting magnetic energy storage (SMES) power control system. One large superconducting inductor (L1 in the figure below) is charged up by a 10kA power supply. Once charged, L1 is isolated from the power supply (Sw1a & Sw1b are switched off) and connected to the DC chopper circuit with switches Sw2a & Sw2b. The chopper circuit transfers the energy to SMES inductor L2 with a switching frequency of 300Hz. The energy is then stored in L2 or transferred back to L1 again with the chopper circuit. This serves as a demonstration of transferring energy between SMES systems.

I’m confused with how the DC chopper operates specifically. I’ve tried to picture different switching scenarios where one or two IGBTs are off and the others are open. What is the order of how the switches S1, S2, S3, and S4 are operated in the attached figure? Is the purpose of the chopper is to split up the DC output and isolate L1 from L2 so all the energy from L1 can be transferred to L2? For reference the paper is "Energy Transfer Experiments between 3 and 4 MJ Pulsed Superconducting Magnets" by T. Onishi, 1985.


texts: What's the relation between the serial connector RS232-DB9 and 10 pin cable?

texts:
I bought one refurbished TP-LINK switch model TL-SL3452:

and I needed to restore it to factory settings. To do that I tried to connect the serial cable but I accidentally broke one of the pins on the connector RS232-DB9:

so I thought that I could replaced it, to do that I opened the switch to see how things was connected and I saw that the RS232-DB9 connector that connected to the motherboard via a 10-pin cable.

so I removed the cable from the switch to see if was possible to change the RS232-DB9 connector:

and I discovered that the head of the  RS232-DB9 connector is removable (yay) so I removed it and released all the pins connected (stupid):

and with a new  RS232-DB9 connector:

I tried do solder the new connector in the wires as was before. But I think I got this wrong because the serial communication is not working.
so, what's the relation between the serial connector RS232-DB9 and 10 pin cable?
General image of the cable:

Image of the pin relation in the 10 pin cable tested with multimeter (red is 1):


texts:
Every time I try to create a footprint and embed an .stl file of the actual mechanical CAD of the part, the color information seems to get lost.

When I select the footprint in the .PcbLib file, under Display >> 3D Color I do see the color that I want but the model still shows up glaring white.

I can move on, but this seems to be an issue for a while now and at some point it'd be nice to fix, especially as I ship off screenshots of the model.

I'm attaching an example of a voltage regulator.

I'm using Altium 2010 I believe.


texts:
Is there a way to use wrapTo2pi in simulink without getting error 'Function 'wrapTo2Pi' not supported for code generation.'
Thanks.


texts:
From what I have read the Inductosyn has incredible accuracy (~3um) and repeatability (~600nm) yet it seems to be phased out for position sensing applications and nobody talks about it anymore. What was the drawback? Cost, speed, reliability? If anyone knows I would greatly appreciate it, I've spent days looking but it seems like it was already superseded by optical encoders before the internet.
http://www.ruhle.com/rotary%20transducers.htm
https://www.maccon.com/rotary-linear-encoders/magnetic-encoders/inductosyn.html
The link below provides a great comparison for Encoders vs Resolvers which is similar and I understand, but the Inductosyn doesn't have the accuracy drawback.
https://ormec.com/Portals/ormec/files/Services/Applications/ApplicationNotes/EncoderVsResolver.pdf
1999 website that goes over inductosyns
http://what-when-how.com/electric-motors/linear-and-rotary-inductosyns-electric-motors/


texts: Will these optocoupler configuration work to tri-state high voltage GPIOS?

texts:
I am trying to control an array of LEDs that require a very high voltage due to the high impedance of the connections (there is no option to change that).
Since the charlieplex configuration makes use of the tri-state logic, I need to design a system that allows me to obtain the HIGH, LOW and HIGH-Z states through a microcontroller without burning the GPIOS. That is why I have dealt with BJTs, MOSFETS and comparators without having good luck.
Now, what I present below is the last alternative that I have been evaluating, which in the simulations has proven to work perfectly. This consists of an arrangement of three optocouplers, two used to define the HIGH and LOW state through a single GPIO (1, 3 and 5) and a second optocoupler that allows the HIGH-Z state to be defined through a second GPIO (2, 4 and 6).
My question is, is the design right? Should I consider any particular variable in an optocoupler design?

This diagram is basically a low pass filter to increase the activation threshold a bit and avoid activation by ESD or noise (resistance) and attenuate spikes and transient suppression (capacitor). The switches are only to see the changes while the simulation runs. I don't plan on using physical switches in the design.

So far I have not seen a single design on the web that uses optocouplers or even optical SSRs to obtain a tri-state logic. So I do not know if I am doing an electronic aberration or this may be something useful.
thanks for any feedback.
EDIT: The total amount of pins of the Charlieplexed array is around 8, thus 16 GPIO, 50±5 LEDs, and 30 optocouplers.


texts: Wien Bridge Oscillator Resonant Frequency cannot reached!

texts:
I am so bothered by the output frequency of my Wien Bridge oscillator because I cannot reached the resonant frequency which is given by
f=1/2iπRC.

FOR EXAMPLE:

R = R1 = R2 = 1.5kΩ

C = C1 = C2 = 10nF

The resonant frequency is 10.61kHz

but the output frequency that I got (in my oscilloscope) is ~7.40kHz

I used a LM324 and OPA541AP op amps but the results are the same!

**Is there something wrong in my calculations? Or there should be some factors that I need to consider! **