texts:
I am using the OSTT7020150  connector for my board.
This connector has capability to connect wires 10-25AWG which means it can tolerate about 25Amps(from the AWG chart). Now, when designing the board, I have seperate planes for both Vcc and GND. But, my doubt is regarding the drill dia and the solder masking.
Pls see the picture below of the board with the connector(i am showing the bottom view).

It shows the VBAT (VCC) and GND. But can such a small drill be sufficient to pass 25Amps. I am a bit surprised. Can you advice me on this. Also, is it suggested that I keep that area solder mask free so as to let out heat and help in heat dissipation. Kindly advice me please.


texts:
How can I calculate this band-pass filter input impedance?

I know from the datasheet that the Ri and the R0 of the ampop are 2M\$\Omega\$ and 75 \$\Omega\$ and the Gain at the central frequency is 30 dB


texts: Generating AC current from microcontroller

texts:
I have a CT that has a 1000 turns secondary winding, 1000 turns test winding. So the ratio between secondary and test winding is 1:1, and from primary to secondary is 1000:1. The test winding is not always active, compared to the secondary winding which has a burden resistor and is being continuously monitored with an ADC. What I'm trying to do is generate a detectable 50Hz AC current (something between 30 uA to 10 mA) with the microcontroller to perform the test function.

The CT detects current as low as 10 mA in the primary. Let's say we have 20 mA in the primary, we have 20 uA in the secondary. So that's why even 20 uA would be enough as the test signal (I may be wrong).

So I came up with the circuit attached below. The idea is to generate a PWM and make it pass through a low pass filter to get a sine wave. Added the capacitor at the output of the opamp for ac coupling and a resistor to limit the current.

Would this approach work? Any better suggestions?


texts: Can someone explain this op amp "tone control"?

texts: Its supposed to be part of a guitar effect pedal, why is there positive feedback besides the negative feedback? I was reading about op amps and from what i understand positive feedback is very rarely used. How would this affect the signal?


texts:
EL_IN signal varies from 0-12V. The output ADC_EL is going to controllers ADC with 0-3V range.

Can someone please explain this circuit & if this circuit is correct or not?
Should the EL_IN be connected to inverting or non-inverting terminal?


texts: Interconnect between different blocks of SoC from different vendors

texts:
So I am planning to do a learning project of installing embedded linux into to SoC. One from smartphone vendor Spreadtrum SC7731 and the other from generic smart devices vendor Ingenic JZ4725B. Since both SoC have different blocks (GPU, IPU, MMU ..etc). My question is, does the vendor of SoC provide any resources to allow interconnection between each blocks that can be used with generic linux kernel or the vendor provides system specific linux kernel which can be used directly?

P.S I am newbe so i dont have right wording for proper search for the answer I am looking for so will appreciate any help I can get here.


texts: Is it possible to use one DAC to process signals from different channels that are delayed at different times?=

texts: So I have a small project where I need to delay multiple signals that come out from a microcontroller. The signals are around 40kHz, have the same attributes, except that they are delayed by a few milliseconds. Would I need a separate DAC for each channel, or can I use a single DAC to process this? Since the sample rate is at least 80kHz, I believe I would need a DAC which can support 96kHz.


texts:
All opamps are ideal. The question is to find the input impedance Zin(s).
Using KCL:
$$I = (V_i-V_{o2})/R_1 $$
$$V_i/R_4 = I-[(V_i-V_{o2})/R1 + (V_i-V_{o2})/R_2] -[(V_i-V_{o1})/R_3+(V_i-V_{o1})sC]$$
Where Vi is the input voltage, Vo1 and Vo2 are the output voltages of the first and second opamp from the left respectively. But this method wouldn't work since we don't know the output voltages of the opamps since they are ideal.
Please help me with the proper method to find the impedance.


texts:
On https://www.rfsafe.com/product/diy-rf-meter-led-powered-rf-detector-diodes/ , there is a kit which contains:

nine 1SS86 Schottky diodes and
one LED,

which uses to detect mobile phone and microwave radiation.

It states:

  range of application: mobile phone GSM signal. It is useless for PHS, fixed-line telephone,CDMA mobile phone

How can I improve the circuit, in order to detect also cordless phone radiation, like the dect 6.0 cordless phone, which, actually, operates on 1.9GHz?

BTW:when they explains how this circuit works, they using the word germanium diodes, while refering to the 1SS86 diodes. As far as i understand,they are not germanium diodes,they are silicon diodes (silicon Schottky diodes).
Am I right?


texts: Can a large charge controller damage or explode a battery?

texts:
I have a 12V 200Ah/20Hour battery and a 60A MPPT Charge Controller. Currently, I only have 200W of solar power to charge my system (planning to upgrade to larger system soon when my proof of concept is done). However my concern is whether my charge controller could charge my battery too fast, causing it to explode. I haven't found anywhere online describing how to calculate whether this will happen or not.
As I understand it, the MPPT controller will output a maximum of 60A but it could be lower depending on the current of my solar panels. Is that correct? And how do I know how much charge current my battery can handle?


texts:
I have the following circuit, and have asked to be found the potential Vo:

simulate this circuit – Schematic created using CircuitLab

Using nodal analysis and Kirchoff's Current Law, we have:

At Node V0: $$\frac{V_0}{R_5}+\frac{V_0 - V_1}{R_4}=2\times 10^{-3} \\ \therefore \:3V_0 - V_1 = 4$$

At Node V1: $$\frac{V_1 - V_0}{R_4}+\frac{V_1}{R_3}+\frac{V_1-V_2}{R_1}=0 \\ \therefore \: -3V_0 + 5V_1 - V_2 = 0$$

At Node V2: $$\frac{V_2 - V_1}{R_1} + \frac{V_2}{R_2}=6\times 10^{-3} \\ \therefore \: -2V_1 + 3V_2 = 36$$

Hence we have the matrix equation:

$$\begin{bmatrix}3 & -1 & 0 \\ -3 & 5 & -1 \\ 0 & -2 & 3\end{bmatrix}\begin{bmatrix}V_0 \\ V_1 \\ V_2\end{bmatrix} = \begin{bmatrix}4 \\ 0 \\ 36\end{bmatrix}$$

Therefore we can solve to yield:

$$V_0 = \frac{44}{15} \approx 2.9333, V_1 = \frac{24}{5}, V_2 = \frac{76}{5}$$

However, the book that I am working from (Basic Engineering Circuit Analysis, Tenth Edition; Irwin and Nelms) states that: $$V_0 = 2.79 \mathrm{V}$$

What have I done wrong here or is this a typo in the book (I am unsure because there have been previous typos such as 60 seconds in an hour)?


texts:
I have DAC 3.3V generated narrow square pulses that I need to amplify to 50Vdc. For this purpose an OPA551 single supply opamp works fine, but it's quiescent current of ~7mA @ 50V consumes too much power.

I hoped to use a LT1013 at 44V (trade off) and 0.5mA Iq, but it seems to only swing to the negative rail.

Because high voltage single supply opamps are hard to find and expensive,
should I go with a transistor or FET amp circuit to amplify the 3.3V pulses? Any suggestions on how to achieve this? Or any other design ideas?

Update: Some more details on the circuit as requested. It is battery powered, the 50V is generated by a DC-DC converter, is stable and works ok with the OPA551. The pulse frequency is 1kHz and are 50µS wide and the required output current doesn't exceed 10-15mA. The OPA551 was a good fit besides the current consumption. That is to say I want to preserve as much power as possible because of the battery operation.

And indeed the LT1013 as a low power amp also had problems with the slew rate.


texts: Variable capacitors (capacitive microphone)

texts:
Why in this circuit

$$V_{out}=\frac{C_1}{C_1+C_2} V_{cc}$$ and not $$V_{out}=\frac{C_2}{C_1+C_2} V_{cc}$$?

The instructor drew also this picture:

but nothing is reported on x-axis and y-axis. Can you help me to understand its meaning? Many thanks


texts:
What does Transient Protection mean?

I'm looking at a datasheet that explains transformerless PSU's, and there is an example schematic that shows a varistor or MOV that provides transient protection (VR1 below). There is no description in the datasheet that explains what this is or how the VR protects against it.

It's taken from Microchip application note AN954, page 10.


texts: Inductor and noise due to buck regulator (high frequency)

texts:
This is a generic question on the selection of inductors in buck regulators.
The selection of inductors is based on mainly the ripple current and the switching frequency parameters of the buck regulators. As a rule of thumb, all recommend the ripple current to be 30% of the max load current. How did this magic number appear? I can say I want to limit the ripple current to 1% and reduce noise. Why is it not possible?

.

Now, the switching frequency of buck regulators is very important as if it's high it might put noise into my other circuits. How does that happen? I understand that buck regulators have a high and low MOSFET to source power using a PWM mechanism at that frequency.

What is the exact reason for noise creeping into the rest of the circuit?


texts: How to find a DIP component implementing this simple logic?

texts: I need to implement this logic in a very simple circuit. It will be perfect if I can use a single component in a DIP package, implementing the logic. How can I find one?


texts: Can the Ids equation of MOSFETs be applied to real devices?

texts:
In my engineering course, we have studied MOSFETs a lot, and always in the context of integrated circuits. And what we have been teached is that (in the basic approximation), its current is given by (taking the nMOS as example):

$$
I_{DS} = K_{n} \left[ (V_{GS} - V_{Tn})V_{DS} - \frac{{V_{DS}}^2}{2} \right]
$$

in the normal (linear) region and

$$
I_{DS} \simeq K_{n} (V_{GS} - V_{Tn})^2
$$

in saturation.

Now I was answering this question, and looking at a datasheet of a P-channel enhancement MOSFET, I've seen that the threshold voltage can vary in a wide range, and apparently Kn is not given nor obtainable from the values, if not trying to get it from the graphs.

So what I would like to understand is: there are FETs for which this equations are appliable (thus usable as analog devices), or how these equations can be applied to discrete FETs?


texts: Why does the output voltage of my linear gain amplifier depend on the JFET gate voltage?

texts:
I am trying to build a linear gain voltage controlled amplifier using an N-channel JFET as a voltage variable resistor (see circuit below).

As the circuit is set op now, I would expect Vout to be zero since the negative input of the opamp is grounded.

But what I find instead is that Vout depends linearly on the gate voltage Vgate above some threshold (Vgate = 0.6V).

Why does Vout depend on Vgate for this particular circuit?

simulate this circuit – Schematic created using CircuitLab


texts: Recenlty I saw a kind of current mirror circuit used to provide bias current for a differential amplifier. The circuit is posted below and I don't understand its working mechanism, as well as the method to do specific design. Could anybody explain that for me? Thank you very much


texts: I am currently using an arduino coupled to a mosfet to drive a 3v DC motor. What it does, is turn on the motor for a second, wait 10min, turn it on again for a second, and repeat the next day. I would like to go a step further, and replace the arduino by a simpler setup, but I don't know what circuit I'm looking for. I feel like it should be a modification of something that generates square waves, just with a much longer period.


texts: Blink Code ATmega2560 not working in Proteus

texts:
I am running a simple blink program in an ATmega2560 with external 8MHz crystal.
When I run it in Proteus, the LEDs do not blink. Refer to my files below.
This is the simple blink code. I just add prescaler bits to verify its functionality.
    void setup() {
      noInterrupts();
      CLKPR = 0x80;                           /*Enabling the clock prescaler function*/
      CLKPR = 0x00;                           /*Setting the prescaler to div by 1*/
      interrupts();

      pinMode(13, OUTPUT);
    }

    void loop() {
      digitalWrite(13, HIGH);   // turn the LED on (HIGH is the voltage level)
      delay(500);                       // wait for a second
      digitalWrite(13, LOW);    // turn the LED off by making the voltage LOW
      delay(500);                       // wait for a second
    }

I correctly choose the ATmega2560 with external 8MHz.

And this is my circuit in Proteus: (Removing the VDD in reset, AVCC, AREF doesn't help.)

And I set the fuse bits to work with external crystal:

I don't know where I went wrong. Please help.


texts: Difference between drill layer, hole layer, and milling layer in Eagle

texts: What is the difference between the drill layer (44), the hole layer (45), and the milling layer (46) in Eagle PCB?


texts: Solar Panel as power supply for multiple borehole pumps

texts:
I want to use solar panels to power my existing borehole pumps (5 of them). Someone says I'll have to power each pump separately with several solar panels. I am however thinking; I could build a small solar farm and connect the pumps in parallel on the grid i would have created, what do you think. The pumps range from 1.5hp to 3 hp and i am considering a 100W or 200W panel.

My other consideration is replacing all the ac pumps with dc pumps.


texts: Current Transformer Rated primary current vs Max. Primary current

texts:
I've been reading up alot on how to work with a CT. Basicly you have a primary current (eg: 100A) and a turns ratio (eg:1:2500) and a load resistance (eg:5 ohms) so now things are straight forward we can calculate the secondary current (40mA) and let's put a burden resistor 3 ohms to get 120mV while not exceeding the maximum power the CT can deliver. Now I'm currently working on an energy meter design, and while looking for the suppliers i'm getting these specs.

As you can tell the supplier is giving out " Rated primary current " and " Max primary current". I've opened a 80A rated energy meter and found out the CT's have a writing " 5 (80)A / 2.5mA/0.1 " , is it 5A or 80A ?

My questions :

On an absolute maximum load 100A will this CT not saturate ?
How can i work with this thing ? is it supposed to be saturated somehow and still work on both spectrums ?

UPDATE:

Finally got a response from a supplier. The response is as follows,


texts:
I am building an Inductive Power Transfer (IPT) system. As of now I am using a design based on a flyback converter. It works great but I am having issues adding features such as power control feedback from the receiver coil and load detection.

I see this has all be solved using the WPC standard as shown below.

The issues is that these WPC standard IPT systems are only 5W. My flyback design is 20W. Can anyone help me accomplish this for a 20W system?

Thanks!


texts: AC current probe readings connected to an oscilloscope

texts:
I have a Fluke clamp on reading a 11 amps on for an AC load.
I bought two different AC-DC current probes for the scope.
The DC readings are great and match dc loads.
When reading the AC load for the 11amps on the scope, I get 160mv peak or 320 peak to peak.
The probe claims 40amp scale use 1mv=100ma.
This gives me 16,000ma peak or 32,000ma peak to peak.
How does this calculate to 11amps?


texts: Q: Amplifier's Output filter not having the Correct Cut off frequency

texts:
I am trying to design a output filter, a simply one (First order) just to play around with and for some reason when I run the simulation of it its not the correct Cut off frequency which it was designed for.

There's already a High Pass Filter at the input of the Amplifier Fc = 0.320Hz.

simulate this circuit – Schematic created using CircuitLab

This make sense as 560K R and 1uF C has a Fc ~= 0.318Hz

Bode Plot of Node 1:

Bode Plot of Node 2:

But whats happening here? Why isn't the FC ~=0.284Hz but its 581mHz?

And if I change the Fc to something like Fc = 20Hz with RL = 8 it works perfectly

Whats going on?


texts:
Two boards: arduino nano and stmvldiscovery.
Boards are connected by spi interface. Arduino is master device. Stm32vldiscovery is slave device.
In the txBuf (transmit buffer) both board have the same data - uint8_t array (1, 2, 3, 4, 5, 6, 7, 8, 9, 10).

Both board send same data. Logic analyzer captured wrong data from stm32vldiscovery.
I don't know why...

Both board have spi settings:
arduino: msbfirst, freq = 1Mhz, spi_mode_0, 8 bit data;
stm32: msbfirst, cpol = 0, cpha = 0, motorola frame format, same freq;

I tried set hardware/software NSS control for stm32. It haves same result.
Same result I had with two boards - stm32f4-discovery and stm32vldiscovery. stm32vldiscovery was slave device same.

Why? What's wrong?

Yellow is arduino. Green is stm32.

stm32 code:

#include "main.h"
SPI_HandleTypeDef hspi1;

uint8_t txBuff[10];
uint8_t rxBuff[10];

void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_SPI1_Init(void);

int main(void)
{

  HAL_Init();
  SystemClock_Config();
  MX_GPIO_Init();
  MX_SPI1_Init();

  for(int i = 0; i < 10; i++)
  {
    txBuff[i] = i+1;
    rxBuff[i] = 0;
  }

  while (1)
  {
    HAL_SPI_TransmitRecieve(&hspi1, txBuff, rxBuff, 10, 10000);
  }

}
...
static void MX_SPI1_Init(void)
{
  hspi1.Instance = SPI1;
  hspi1.Init.Mode = SPI_MODE_SLAVE;
  hspi1.Init.Direction = SPI_DIRECTION_2LINES;
  hspi1.Init.DataSize = SPI_DATASIZE_8BIT;
  hspi1.Init.CLKPolarity = SPI_POLARITY_LOW;
  hspi1.Init.CLKPhase = SPI_PHASE_1EDGE;
  hspi1.Init.NSS = SPI_NSS_SOFT;
  hspi1.Init.BaudRatePrescaler = SPI_BAUDRATEPRESCALER_4;
  hspi1.Init.FirstBit = SPI_FIRSTBIT_MSB;
  hspi1.Init.TIMode = SPI_TIMODE_DISABLE;
  hspi1.Init.CRCCalculation = SPI_CRCCALCULATION_DISABLE;
  hspi1.Init.CRCPolynomial = 10;
  if (HAL_SPI_Init(&hspi1) != HAL_OK)
  {
    Error_Handler();
  }
}

Arduino code:

#include <SPI.h>

void setup()
{
    SPI.begin();
}

void loop()
{
    delay(5000);
    SPI.beginTransaction(SPISettings(1000000, MSBFIRST, SPI_MODE0));
    byte arr[10];
    for (int i = 0; i < 10; i++)
        arr[i] = i + 1;

    digitalWrite(SS, LOW);

    for (int i = 0; i < 10; i++)
        SPI.transfer(arr[i]);

    digitalWrite(SS, HIGH);
    SPI.endTransaction();
}


texts:
When I connect several vhdl components to create one design, how do I ensure that the fpga's internal (ex. register to register) setup and hold timing is not violated?

Ex. Data bus between components is sampled correctly on rising clk edge.


texts: Drive IR LED with maximal power (for IR barrier with max distance)

texts:
I'm making a light barrier and working on a "sender" part right now.
The main thing I want to achieve is the maximum distance. I'm using Vishay TSSP4038 for receiving signal. In the datasheet it's stated that it can work on distances about 30m. I can't get even close. With 350mA (1W) LED it's about 3m max (outdoors).

Here is my current schematic:

T1 is NPN transistor. Q2 is N-channel mosfet. LED power schematic is taken from this instructable.

ATTINY25 turns the LED on/off 38000 times per second (kHz). So effectively I can double max current through LED (change R3 to 2.5).
I also have some 1W chinese LEDs from ebay, which do work better (distance-wise), but I'm not sure how much more current I can give them without burning.If you think that the transmitter is  good then should I provide receiver details ?

I would be very thankful if someone better than me in electronics would check the schematic and maybe give me some advice or tell if something is really wrong.


texts: What is modern fire alarm cable made of?

texts:
I'm curious about the fire alarm cable that's being installed in a new building next to my office.

In the fairly distant past, I learned that fire alarm cable was "pryo" cable. Under the red jacket it was a copper tube containing two conductors, all mutually insulated by a white mineral powder. Apparently it would stay working unless a fire melted the copper, because there was nothing inside that could burn or decompose.

What they are using today appears to have layers of polymers. Under the red outer layer is a stiff white jacket. Inside is a bare (earth?) wire and two wires insulated with blue and brown polymer.

What are these polymer materials, and what happens to them in a fire? Was the "pyro" cable deemed overkill and used only for lack of alternatives to PVC in past decades?


texts: How exactly does the transition between Software and Hardware occur?

texts:
Well first allow me to explain what I actually meant to ask. Ok, so it is clearly known that without software, a piece of hardware is just a lifeless body, something without a soul. But I clearly cannot understand how this communication/interface between software and hardware is actually happening?

A Software is nothing but lines of code which finally after getting compiled, assembled, linked and is converted to a string of binary digits. But you see the hardware of the processor doesn't understand ones and zeros it understands a high voltage level and a low voltage level. but how is this transition from binary digits to voltage levels actually taking place?
For a really quick analogy, if I wanted to lift a book there is actual physical contact between my hands and the book. But what about the interface between hardware and software?

I hope you people understand the crux of my question. It is really difficult to put it into straight-forward sentences. This may sound like a bizarre question, but trust me it's been bugging me for a really long time. I've taken courses on Computer Organization and basic processor Design, but they clearly failed in providing me an answer.

A similar question exists on StackOverflow and there is not one convincing answer.
https://stackoverflow.com/questions/3043048/how-does-software-code-actually-communicate-with-hardware

EDIT:
You see the standard process for the code to be executed by the processor is such that it passes through
compiler -> assembler -> linker -> loader -> Memory.
Because once the instructions get into the memory it is pretty straight forward as to how the processing takes place.
The only inconsistency which I feel in that flow is about how the transition from loader -> memory. is happening? This is one of the straightforward ways I can put up the question. But if it would be really grateful if you've understood the soul of the question.


texts: How do I find the proper transfer function of this passive filter?

texts:
I've been looking at this circuit for a long time trying to derive the transfer function of it.

My attempt goes like so.

You can separate the circuit into two RC filters, into a system that looks like this:

where each block is like so:

We can then simplify H1(s) by combining impedences:

Where Z = R||C or R in parallel with C
This is the same as $$\frac{1}{\frac{1}{R}+SC} = \frac{R}{RCS+1}$$

This is where I get stuck, there's no voltage divider, so I cannot use a regular transfer function like one would use for an RC circuit.

The answer, however, is known:

Is there something wrong with my approach? would a more formal KVL/KCL approach be required? what would the correct approach look like?


texts: Best way to run 3.3V circuit for long time using 3 AAA batteries?

texts:
I have a circuit that is off almost all the time, when a button is pressed an MCU will be brought outside of sleep mode perform a log and go back to sleep. This device should run on 3 1.5V AAA batteries giving more than 3.3V.

How can I regulate the voltage when I wake up from sleep and have the regulator not waste energy when device is not used?


texts: Can the coaxial cables be connected to a triaxal connector and other way around? I am asking this because I have a instrument that has BNC connectors, but I want to use triax for extra shielding. If not, how about the convertors between triax and coax, are they recommended?


texts: How to explain the difference in modeling small signals for BJT and JFET devices?

texts: I know there is a difference between modeling BJT and JFET devices for small signals, but I would really like to know, in depth, how to explain this difference.


texts: How do I solve using nodal analysis when there is a battery before the resistor?

texts:
I need to use node analysis on the following circuit.

I am confused as to how to solve node 1 as there is a battery of 3V between the node and 4 ohm resistor. Should I solve for it?


texts: Volume reducing resistor in speaker lines

texts:
I recently ordered a small amp from ebay, a LVPIN LP-A6, 4-8ohm, 20w. The speakers available to use with it are from a stereo which says 4 ohms under the wire tabs. Not sure if that means each or both are 4 ohms.
This gets extremely loud for the small apartment I'm in. Not even an eighth of a turn and it's way too loud. Would a resistor in the speaker lines be a good way to handle this, and what value would you recommend given the stats above? Dropping the level to 1/8th would be good. (Not a shared ground).


texts:
I just disassembled an external FM antenna designed for an old Asus laptop.
I expected to find some circuitry and a monopole or some other simple antenna. However, what I found was the antenna shown in the picture (bottom and top view). Honestly, it resembles somewhat a monopole because there is a ground plane and only one side of the wire is connected to the coaxial cable that exited from the case of the antenna. But I can't explain why it has that strange shape.
I should add that the bottom of the pcb was in contact (or maybe just really close) to two magnets.

What kind of antenna is that and how does it work? (or where I can find how it works)
What was the purpose of the two magnets?
Why the is the wire shaped like that? And why is the ground plane shaped too? (see the bottom view)


texts: Replacing Ideal current source in two-stage opamp

texts:
I am now investigating on replacing the ideal current source with the circuit similar to the one attached below.

Why would the mosfet M16 be connected to drain of M12 ?

I am confused about how the additional circuitry works.


texts: Circuit simulates in Falstad but not in LTspice

texts:
I'm having trouble simulating what should be a simple circuit in LTspice. I am designing a simple PWM-regulated power supply, but I'm running into problems when I try to simulate it.

When I simulate it in Falstad circuit simulator I get a result I expect, that is that voltage is regulated proportionally to the PWM of the generator.

However, in LTspice I can't simulate this circuit with same and consistent result.

I tried constructing this circuit without ground connection, but LTspice gives me an error that it needs a ground connection. Then if I try to connect ground somewhere in this circuit, I am running into problems. If I connect it before the diode bridge, the diode bridge itself stops working and only works as a half-wave rectifier. If I try to connect it after the bridge, the simulation stops working correctly at all. It can slow down to simulating only a few us in one minute, I start getting either huge GV or small nV readings on the probe, lots of transients and artifacts.

How can I fix this to get correct simulation results in LTspice?


texts: Harmonic balance Michael Steer derivation?

texts: I was going through harmonic balance method and one of the references I used was Microwave and RF design Systems Approach by Michael Steer . In one of the examples provided , he derives the current harmonics for the non-linear subsystem however I couldn't quite follow how he derived it . Could someone please shed some light? The set of currents on the right side are the ones I couldn't understand. Here's the link to the power point presentation https://people.engr.ncsu.edu/mbs/MicrowaveRFDesign/CS_AmpHB/CS_AmpHB.pdf


texts: Controlling op amp gain with an mcu, would this work?

texts:
I need to be able to control the gain of an op amp with an mcu.
I know the obvious way is to use a digital potentiometer or an op amp which was already designed for this purpose.

I am wondering if this will do the trick:

simulate this circuit – Schematic created using CircuitLab

basically the mcu can use the mosfet to switch another resistor in parallel to R2 which would increase the gain from 2 to about 27 in this example.
So i'm thinking to have an array of mosfets, maybe 3 in total or so.
Would that work ?
I realize this would effect the high pass filter of C2-R2.

Another way of doing the same thing is putting R4 in series under R2 and shorting it out with the mosfet.

Which way is preferable ?

Thanks in advance !


texts: Why is the signal inverted on a VDB transistor?

texts:
I've got a 3904 connected in a voltage divider bias.

Probing the input and output I notice that the output signal is inverted.

Would someone explain the interworkings of how and why the output signal is inverted?


texts: Current limiter circuit is damaging MOSFETs

texts:
I have a circuit where a charged capacitor must be discharged over a load resistance. The trigger switch here is a 10A relay so, to avoid damaging it when the load resistance is too low, I decided to add a current limiter circuit between the capacitor and the load. This is the circuit (everything between the right button and the LOAD):

As you can see, the capacitor is charged with 160V, taken from a previous step-up circuit (not showed here). The RSENSE value of \$0.1 \Omega\$ should limit the output current to 7A (\$0.7V/0.1\Omega = 7A\$). Considering the 160V input, the current limiter circuit kicks in if the load resistance is inferior to: \$160V/7A \simeq 22.8 \Omega\$
I ran the simulation and everything seemed fine. Then I assembled it for real and ran some tests:
Using a \$100\Omega\$ load (maximum output current: \$160V/100\Omega = 0.16A\$, inferior to the limit) I got the following discharge curve:

All fine here. Next test I used a \$10\Omega\$ resistor. With the limiter actuating, the output voltage should be capped to \$10\Omega \times 7A = 70V\$. I got this curve:

The limit was a bit above 50V which implies the current is being limited to 5A but that is something I can fine tune later tweaking with RSENSE. I repeated that test several times with the same outcome and no problems whatsoever.
Next test, I used a \$1.2\Omega\$ load, and this happened:

As you can see everything went fine for a moment, with the output voltage capped to 7V (\$1.2\Omega \times 5A\$), than the MOSFET shorted and the rest of the capacitor charge flowed without any limits. Further tested the MOSFET and confirmed the damage.
So, what caused this to happened? I started to seek for possible culprits and developed some hypothesis:
1 - Overcurrent inside the MOSFET.
That doesn't really make sense because the current would be limited to 7A (5A for real) no matter what and the MOSFETs are rated to 9A of sustained current (32A pulsed). Anyway, I tried to use two MOSFETs in parallel and what I got was that one of the two MOSFETs always ended up damaged (probably the "weakest" one).
2 - Gate to Source overvoltage.
According to the simulations, that never exceeds 10V but I decided to add that 15V zener diode for protection, anyway. Same result as before.
3 - Drain to Source overvoltage.
Those MOSFETs are rated at 200V, so that should not be a problem but as this is a parameter that stretches out when we drop the load resistance, I decided to try the following configuration using two MOSFETs in series, so each one would receive half the voltage:

The result: now I got two MOSFETs damaged at once!
So, those are the questions I'd like to ask you guys. What´s is going on here? Why does it fail only when the resistance is that low? What would solve that problem?
Thanks in advance.


texts: Wireless security for repetitive messages?

texts:
I'm designing myself a custom home automation system. Eventually, I want to expand the system to include security/alarm. The easiest way I know to do this is to include wireless capabilities.

This got me thinking about wireless security. The messages from let's say motion detectors should be encrypted, that's a given. The motion should have a regular keep-alive type message so that when a sensor goes dead or is disable the system would flag it.

This is where I see a weakness. If a sensor is constantly transmitting the same message ("no motion detected" for example), the message can be recorded and spoofed. Even if the message is encrypted because it is constantly transmitted, the same encrypted packet would be seen. Without knowing its content the packet could be captured and spoofed after disabling the sensor. I know it's paranoid but I'm trying to cover all my bases.

Is there a wireless protocol that automatically accounts for transmission of repetitive messages in their encryption? If not, how can the repetitive transmission weakness be patched?


texts: What is the blue film that covers the PCB in my TV's remote?

texts:
As a weekend project I am trying to fix my TV's remote and I noticed that the contacts of the remote's keyboard is covered by a thin blue film:

As you can see, the remote's PCB is covered by a blue layer of some sort of film. I wondered what is this film that the remote is covered with? Also can this film be affected somehow if the remote fails to indicate that a button has been pressed?


texts: Antenna design for radio energy emission into a fresh-water test tank

texts:
I would like to emit as much RF energy in the frequency range of 433.9 to 434.5 MHz into surrounding fresh water with a 100mW transceiver.

The antenna is in the middle of a 4mx8mx2m fresh-water tank connected to a VA by a 4m thin coax cable.

So I took a simple half-wavelength dipole sleeve-antenna design. I calculated the 433 MHz half-wavelength in fresh water as round about 19mm, but when I compare several antennas of the same type with different pole length, the one that has a peak in the reflected power plot at 433 MHz has a pole length of 80mm and for antenna variants with shorter poles the peak moves to the higher frequencies.

So I ask myself now why is my resonance antenna length longer than my calculated value?
Could it be that the RF field will be disturbed by the air around the test tank and if how would this be related to the length?
If I would like to emit as much RF energy as possible into the water, what do I have to respect in my antenna design?


texts: How can I wake up an ATtiny84 microcontroller at specific time of the day?

texts:
I am trying to create an alarm that wakes up at a certain time and does a series of instructions.  To set the times that it wakes up, I am going to use the headphone of an Android device to send serial data to the MCU about what time(s) to wake up.  I will simply plug it in, make the transfer and unplug the jack.  Then the time is set on the MCU.  The transfer will also sync the time to set the timer appropriately.

I can set a timer interrupt with a prescaler to give me 4s on each interrupt.  Then use 2 bytes as secondary counter of some sort.  That would give me 72 hours that I could wait and I only need 24 since I can reset when the day ends.

So my question comes when the device is reset.  I can save the current time in the EEPROM and then read it on load but how much overhead does that have on current use?  I want the battery to last as long as possible.

My question may need to be elaborated on but I was wondering if there was a better way or if I am going about this the correct way.


texts: Resistors - binning and weird distributions

texts:
I read about a little quirk related to binning resistors in a comment on this recent question.

Some manufacturers will sell, for example, 1% and 5% resistors that are really made in the same batch. When the resistors are being sorted by value, the more accurate ones are put into a 1% category and sold for a slightly higher price, and the less accurate ones are sold as 5% resistors.

This method of sorting guarantees that 5% resistors running through this process will never be within 1% of their nominal value. In other words, a 1 k\$\Omega\$ +/- 5% resistor would have a resistance in the range [950, 990] or [1010, 1050] - but never [990, 1010].

Does this actually happen? I guess that the parts are still what you're paying for, but it seems really odd that a 5% resistor would have 0 probability of being within 1% tolerance.


texts: MCP16301 Step Down Voltage Regulator PCB Layout Validation

texts:
I'm looking for some feedback/validation that the layout for this MCP16301 is correct. I'm trying to get 600mA 3.3v Out from 12 input.

I'm using the circuit as described in the datasheet on page 23 and loosly based on the layout on page 21.

Here's my current PCB layout:

Cin - C2/C3 : 4.7uf
Rtop - R8: 31.6k
Rbot - R9: 10k
L1: 15uH
Cb - C6: 100nF
FW Diode - D4: Diode Schottky 40v
Boost Diode - D5: 1N4148
Cout - C7/C8: 10uF
Reg1: MCP16301

The smaller traces are 10mil and the larger ones are 25mil.

REVISED PER COMMENTS(location moved and orientation flipped, but same circuit:

Revised to larger package D4 SOD123 40v 1A Diodes:

Is component placement and routing correct? Anything that I should change? Is the large 3.3Vout pad going to create soldering issues?


texts:
I am using a 74HCT1G125 buffer as an '5 V output driver', but, in some cases it has a 12 V, low impedance source presented at its output pin (but in these cases its enable is false, i.e the output should be high impedance (Hi-Z)). When I do this, the 5 V supply (that the buffer uses also) is pushed up to around 8 V. Surely if its Hi-Z is an open circuit, how is the external 12 V making its way and affecting the 5 V?

I have checked and indeed the device is being 'told' to be in Hi-Z. I then put 12 V onto its output pin, and somehow, the VCC gets pushed up.


texts: USB serial enumeration with different power source

texts:
I am working on an evaluation board that is powered off of a micro-b USB port. This also serves as a serial port (through an FTDI chip). There is a jumper that allows to choose to power the system from a different source than the USB, but doing so causes the USB-serial port to not be recognised on my computer anymore. What changes will I need to make in order to use a different power source and also get access to the serial port?
Added a drawing of the schematic for a better picture of what's happening


texts: What is purpose of the "assignments" in the Qsys custom component editor signals and interfaces tab?

texts:
Here is the image showing what I am talking about,

For Avalon Memory Mapped Slave port I can see that there are 4 options already there and they are already assigned custom values.

I just want to know, what is the usage of this "assignments" when making custom components and what is the usage of the assignments that are already defined and set for the Avalon Memory Mapped Slave port? i.e what is the master supposed to do if any of these options isFlast, isMemoryDevice isNonVolatileStorage, isPrintableDevice where '1' rather than '0'.

Thanks.


texts:
I want to add/charge a lead-acid battery UB1250 with the 12v system in my car. I put a battery quick disconnect directly to the battery so that long term, the main battery does not die. Problem is when you disconnect the battery all the settings on the radio get wiped out. So I want to add this battery to the radio memory wire so that it will keep the settings. Question is, do I need anything thing else like a resistor. I plan to put a diode so the battery does not back  feed the entire system.

Do I need anything else?


texts:
I have been tasked with building a simple alarm device. It just needs to measure a few inputs and the outputs will respond accordingly (to put it very simply!). To me, it seemed that using a few discrete logic gates would get the job done, but a colleague (who was working on it with me) decided that we should use programmable logic instead. His case won, because firstly, he is more senior than me, and secondly, his main argument was that programmable devices are the future and we want to make future proof products.

My question is if you have a design which could be easily implemented by a few discrete logic gates, is it worth designing with discrete logic any more? IS there any advantage to using them over programmable? Or is it slowly going to be phased out completely by programmable logic? To be clear, I don't want answers of 'I believe this is the case' or 'personally I think this but...' I'd like to know if there are any actual advantages to designing with discrete over programmable and is it worth designing with them these days in consumer electronics products?


texts: Decoder Expansion. Constructing a 6-to-64 decoder from 3-to-8 decoder

texts: I just started to study decoders and multiplexers and I saw this task which I'm not sure how it's done. Can you please explain me (solution attached): Using the decoder DEK 3/8, construct the decoder DEK 6/64.


texts:
I am working on a IOT based Project which uses GL868 Modem & minimizing power consumption is very important goal for me now. One way of minimizing the power consumption is to turn off GL868 Modem when it is not used. This can be done by issuing following command:

AT#SYSHALT=1

This successfully shutdowns the Modem. When I need to use the modem again the RESET Pad of GL868 must be tied low for 1Sec & and then released. But after the reboot the Modem fails to Register to the Network. I issued AT+CREG? command to check if modem is register to the network or not. The modem is registered to the network if we get result as +CREG 0,1 when we issue AT+CREG?, but instead I get result as +CREG 0,2 which indicates that Modem is not registered, but it is currently searching a new operator to register to.

Can anyone help me to find the cause of the problem & solution for it?

Here is the link for the datasheets:

Hardware user guide:
 https://jt5.ru/files/pdf/gl868/telit_gl868-dual_hardware_user_guide_r0.pdf

Software user guide:
http://www.adaptivemodules.com/assets/telit/Telit-Modules-Software-User-Guide.pdf


texts: Is there a fieldbus with more than 250 nodes per segment?

texts:
We plan to realize a sensor cable several 1000m long which has ideally every 1-2m a magnetic field sensor on a small 10x30mm platine with microprocessor/FPGA for DSP and I2C on chip communication. Later this will be integrated into an ASIC.

The sensors slaves are thought to do alarm handling/asynchronous messaging to the master/repeater, if a distinct magnetic field value change is too high. Several limitations exist I'm aware of to yield a nearly real-time and cheap and low power consuming cable. It is important that all sensors in the cable check with at least 10Hz the field, the power consumption of the sensors will be in the 50 microA range. All sensors should be powered by the fieldbus cable.

I studied different fieldbus systems

Best for our purpose seem to be CANopen, MODBUS or Profibus (but no sensor voltage supply for this). For a sensor every 1-2 meter with maximum node of 250 we would need every 250-500m a fieldbus repeater (which is not very cheap).

Is there a technical/fieldbus alternative for our purpose if high data rate and is not the most important criterion but keeping the cable cheap?

Would it make sense to create our own fieldbus protocol which maybe can handle 1000 nodes on 1000-2000m without a hardware repeater or even develop a own repeater for our start-up company on our own? We have a engineering team which will do this if it is possible and feasible (price and expense) and funding.


texts: Comparator circuit with hysteresis window adjustment + offset?

texts:
I am looking for a circuit that allows the user to adjust the delta (= hysteresis window) between thresholds using 1 pot. and offset the thresholds using another.

For example - Using one pot. the user sets the window to 0.4V & using the second pot. the user sets the low threshold to 3.2V which means the high threshold is going to be 3.6V (3.2 + 0.4).


texts: Does an isolation transformer make CRTs any safer to work with?

texts:
CRT tubes are often described in training materials as huge capacitors capable of delivering very high voltages, often enough to severely injure or cause death. Before working on them, they should be discharged by shorting the pins on the tube's neck to the chassis or ground.
Unfortunately, the comparison to a capacitor confuses me. The two plates of a regular capacitor are in reference to each other, not ground. Does this mean the CRT tube is not really a capacitor, per se, but the anode; and earth ground is the cathode?
To add to my confusion, assume we were to power the CRT using an isolation transformer and then turn it off. Is the charge in the CRT still in reference to isolated ground, meaning it is safe? I suspect not. My reasoning is the charges are from static electricity. Am I correct?
Finally, many electronics materials strongly the use of an isolation transformer for safety reasons. Does this, however, pose a false sense of security if the CRT charge is in reference to ground?


texts: Figuring out the principal working of constant current source

texts:
I've the following circuit:

simulate this circuit – Schematic created using CircuitLab

I was told that this is a constant current source. I think that the resistors \$\text{R}_1\$ and \$\text{R}_2\$ determine the current in trough the load. Is that true and how is the output current related to those resistor values or other components in the circuit?


texts: Compare white LED radiated optical power: lumens vs milliwatts

texts:
I'm trying to compare the brightness of various white LEDs, some of which are listed in lumens and others in milliWatts (this is milliwatts of optical output, not watts of electrical power consumption).  Is there an easy way to do this that doesn't involve integrating the spectrums?

For example, Mouser 997-L1502270500600S0 is a 2200K white LED with 690mW of radiant flux.  Mouser 997-L15027705060  is a 2700K white LED with 600lm of luminous flux.  Which is brighter?

The lumens to watts conversion always assumes one wavelength, which white LEDs don't have, so I assume that calculation can't apply here.

Some background:
1) Lumens to mW conversion for a single wavelength
2) A few other SE questions on Lumens and Watts.


texts: measuring elapsed time when voltage reaches specific value in RC analysis

texts: I am trying to measure the time a capacitor has reached  63.22% (1 tau) of the total voltage for a basic RC circuit. I can measure it directly from the .TRAN output, but when I try to use .MEAS TRAN MyVal WHEN v(OUT) = (VMAX * 0.6322). In my application, VMAX = 5V, so (VMAX * 0.6322) = 3.161V. Attached below is a copy of my LTSpice schematic.


texts:
I have a 3 lead AC125U Germanium Transistor with a little metal tab next to one of the outer leads, and a small red dot next to the opposite outer lead. I understand the middle lead to be the "base" lead. How do I identify the "collector" lead from the "emiter" lead.

Thanks!


texts: Do I need a diode? How would I put one across my motor?

texts: I've been building a circut to run a motor forwards and backwards for a project I'm working on. I'm not sure if I need diodes to protect the transistors, because I have no idea how to add them as the current alternates direction. I'm not sure if having no diode will damage the transistors.


texts:
I have a question on part A) iii

Here is what I have so far

What I know is to get the overall phase you have to add the phases of the two frequency response H1 and H2, but I don't know how to get the phase of each frequency response. Any help is appreciated thanks.


texts: Potentiometer minimal turning for high resolution

texts:
I have a 1 turn 10k Ohm Potentiometer attached to the analog input of an Arduino. Now, the full range of the pot gives me values from 0 - 1023, nothing new.

The problem: I only want to measure change within a small rotation range of the pot. So the start position is at 30° rotation and the end position is at 40° rotation. I want to achieve a maximal numerical range within those 10°.

Are there any potentiometers that don't turn about 270°? Or can I maybe achieve it by putting more resistance in line?

Appreciate the help!
Thank you,
Marcel


texts: Fighting overshoots/undershoots using ferrite beads does not help?

texts:
I posted relative problem a while ago here but we came to conclusion that the overshoots were just artifacts. Later, when I extended the signal lines, the overshoots increased and were about 2V of magnitude.

First thing I tried were unknown to me before ferrite beads. I tried several different types of bandwidths but only one had shown some positive effects. I connected one and then two FB in series making a total of 940 Ohms (MPZ1608B471A), the overshoots were smoothed out, but the undershoots remained:

Then I found a similar discussion about my problem here and a simple 100 Ohm series resistor fixed the whole deal:

Finally, questions:

why a simple resistor (that kills DC as well) fixed the problem, whereas the ferrite bead that should only attenuate high frequencies was not as effective?
if I run two wires (one is signal the other is GND), should the ferrite beads go on both wires or just the signal wire?
do I need a pull up/pull down resistors if I connect two DI/DO interfaces?
could someone, please, add "overshoot" and "undershoot" tags.

Thank you so much.

simulate this circuit – Schematic created using CircuitLab


texts: What is "formal verification" of hardware?

texts:
I read that testing and verification are different but in what way? I read that somebody writes theory to prove that the hardware is "correct" but how is that done? I tried reading Wikipedia and googling about it but I either end up in too advanced research (HOL4 and theoretical proofs) or brands, standards or outdated deprecated hardware abstraction layer ("HAL") that seems to be not used in general anymore.

I have created a 4-bit ALU (with Quartus) that actually works if I load the FPGA with the ALU. I used the logical primitives and wrote tests for the ALU. Now I want to learn more and understand the difference between testing and verifying in general and how to prove that an actual hardware is working correctly.

I see that ML is used in projects using HOL theorem prover. Is that something within my reach of understanding and handling if I am intermediate programmer and engineer? I know mathematics and programming but I'm not good at physics.

My ALU worked and I could test it in Quartus but I don't know what "formal verification" is. Can I do it and if yes, how and what should I learn?

I tried the proof assistant Isabelle and writing trivial theorems with HOL that I could compile and get the expected output. I don't have much experience with ML but I think I could use it since I have experience writing C, assembly and machine code.

Can you help me find what to read or answer what I should learn and study?


texts: How to deal with long chip lead times in small company

texts:
I am the chief engineer at a small company.  Our product popularity is growing rapidly, and now we are learning about painful lead times for microcontrollers.  The owner is demanding product overhauls to avoid distributor lead times.   My question is:

What is the norm in electronic manufacturing?

should I convince him to get a loan and keep 4-6 months of chips in stock at all times?
or do I just keep switching parts until I find things more readily available.


texts: Can STM32F429IGT6 and STM32F429IIT6 be used interchangeably?

texts:
I bought a STM32F429IIT6 after reading a detailed introduction article about this device.
The problem is after I got this device I found out that I got a STM32F429IGT6 at home already, so are these two can be used interchangeably?


texts: How long will electric car batteries last?

texts: My UPS's batteries have to be replaced every 3 - 4 years even though I use Deep Cycle batteries.   I am wondering how long electric car batteries will last before having to be replaced, and at what cost, and are new buyers aware of this possibly expensive future maintenance problem?


texts: Understanding a common mode signal conditioning module

texts:
As far as I understand, normally an ideal differential amplifier(or an instrumentation amp) can reject common mode(CM) voltages up to around its rail voltages.

Let's say the rails of the diff. amp are +/-10V DC. And let's say the inputs are such that the normal/differential mode voltage is 1V, and the common mode voltage is 20V. As far as I understand, this will saturate or maybe damage the amplifier because 20V>10V. But if the common mode voltage at the input would be 2V this would be rejected well and the amplifier would work fine because 2V<10V.

There is this signal conditioning module and below is some specs from the data-sheet:

I know that after this signal-cond. module, the signal are coupled to data acquisition inAmps whose rails are +-5V.

Normally if there were no conditioning a 20V common mode voltage would saturate the amplifier. But this module says "CMV, Input to Output 1500V max."

Does that mean that the module can get rid of a common mode voltage of 200V or more? I also came across the following:

:

Does that mean the 5V battery above can be read as 5V even though Vcm=1200V?
Is that what this module doing and acting as a common mode filter or choke?


texts: Can car alternator back-emf damage electronics?

texts:
I know on startup a motor or generator produces back-emf and current ( correct me if I'm wrong, been a while since I've worked with electric machinery ). Thus, it'd be reasonable to expect that when you start a car with a device connected to 12 V socket there would be a spike of voltage that could potentially damage the connected device. Is this expectation actually reasonable ? Do there exist protections for such spikes, either built into automotive circuitry already or external ?

Context for the question: in the last 3 weeks I had two cellphones die in very much similar fashion. The only common link I could establish between them ( aside from old age ) is charging from my car's socket, and in both cases phones were plugged in while I would start the car.


texts: Finding time constant in terms of R and C

texts: I got a different expression for the time constant than the actual solution. Can anybody tell me where I went wrong? Why is it that in the solution all three resistors were put in parallel? What do you think is the correct way to go about doing this?


texts:
I'm trying to drive transistors with just a push of a button without using a MCU. The circuit I drawn drives different transistor on every button push and resets back. First part is a debounce circuit and the other is a counter which drives the transistors.

Is this circuit enough?
Do I need to add more passives like pull-downs?
Can you recommend a schmitt trigger with lesser I/O?
Is there a better circuit that does this? without using MCU
ofcourse.

simulate this circuit – Schematic created using CircuitLab


texts: Is it possible to use 2 relays instead of a DC motor controller?

texts:
I have been for motor controllers to control two 12V motors that have a stall current of 130A and at max power (expected operation) will draw 68A.

I am having trouble finding low cost motor controllers for these motors.  I do not need to be able to control speed but only need on/off in both directions.

Can 2 relays per motor be used instead?

Thank you for your help


texts: Manufacturer reference or part number for "3+1 fan connector crimp male wire-to-wire"

texts:
I'm experiencing some unusual difficulty looking for a manufacturer part number for the connector shown here:

http://www.moddiy.com/products/modDIY-Male-4%252dPin-(3%252b1)-PWM-Fan-Connector-(Molex-%232510)-with-Pins.html
http://www.performance-pcs.com/male-4-pin-3-1-pwm-fan-connector-molex-2510.html
http://www.bizrate.com/system-cooling/oid4026851578/merchant/
http://1088992.en.makepolo.com/products/Male-3-Pin-Fan-Extension-Connector-p87525796.html

.. which is found on computer fan cable extensions.
There are 3-pin versions and 4-pin versions that use a polarization rib (power, tachometer, PWM control): http://www.formfactors.org/developer/specs/REV1_2_Public.pdf

It's everywhere on the web in already-assembled cables but I can't find anything regarding the connector itself using the regular search tools (digikey/mouser/farnell/google)...

The best "reference" I could find is MDY-CO052.


texts:
I'm currently working in a circuit which I'm trying to switch on using a button. The main idea is that when button is pressed, the power source gives power to a PIC microcontroller which writes '1' to PWR_CTL, causing the circuit to remain ON.
I can use BTN_IN to detect when the button is pressed again for two seconds, and then, write '0' to PWR_CTL and power off the circuit.

The problem is: When the circuit is off, I have about 1.7 V in V_IN, which means to have 1V in the regulator output. This is causing several problems in the rest of the circuit, since it is not completely powered off (in addition I have an undesiderable consumption).

Can anybody suggest a simple soluition to keep the power source completely off?

Thank you!!


texts: Generating Professional Functional Diagrams

texts:
I have designed a nice breakout board that I would like to share with the community but I would like to make it look super professional.

How does the Functional Diagram below get generated?

I am sure this can be hand crafted but there are so many similar functional diagrams like these that I am convinced there might be a single app/designer/company that generates these.


texts: Can we change op-amp inputs when using virtual ground?

texts: It may be some kind of stupid question and i'm sorry if it is. Let's say that we have ideal non-inverting op-amp and we use virtual ground to solve the Vo value. But what if we change inputs? Does it really matter in ideal case?


texts: Is there a better filter or a modification to the Kalman filter that could take advantage of having all the data during the trajectory at once?

texts:
I am trying to reconstruct the trajectory of an object with an strapped down IMU on board to do dead reckoning. A Kalman filter seems to be in order. But the Kalman filter seems to be oriented toward real time updates of position.  However I have the luxury of not having to figure out the position of the object while it is moving. At the end of the path I will have all the data(gyros and accelerometers and maybe magnetometers) I can use to calculate the path.  Is there something better than Kalman that can be used?

Right now I have a superficial understanding of the Kalman filter so forgive me if this question is a little dumb. I did not want to get involved with the Kalman filter if it is sub optimal.


texts: Doubt in PMDC motor pulsed switching current

texts:
I am controlling a dc motor by switching through the MOSFET. I am able to run the DC MOTOR and I have measured the current through scope by putting a RESISTOR SERIES of the DC MOTOR.

My doubt is, since the motor is an inductive load I was expecting the DC current will be averaged by switching at High frequency(switching frequency 20KHZ), but what I get is a pulsed current which matches with the input PWM.

Why I don’t get an average current?

Why I get that spike?

Control details:

PMDC motor

Motor input Voltage:180VDC

Mosfet:IRFP460

Freewheeling Diode:MUR3060

Switching speed:20KHZ

PWM control.

Series Resistor (for measuring current) Value:0.5E/20W ceramic resistor.

Circuit:


texts: How to decipher hex code for time data on an older serial port device

texts:
I’m using an old Draeger PAC III sensor to measure gas concentrations, with the goal of remotely transmitting the data via Arduino. Accordingly, I cannot use the proprietary software to output the system information/data. Even though the system has been “retired” by the company and is no longer sold/distributed, their technicians will not provide the datasheet for communication on the device.

To circumvent this, I’m attempting to use a serial port monitor to read the com between the device and PC. The PC communicates through a RS-232 port, but uses only ground and a combined Tx/Rx line to get data from the device. To activate communications, all written data starts with a high (01). All read data duplicates the written data, then tacks on device data. The first command is always 'initiate communications by identification' aka the first 4 chunks of data. I can only assume the remaining data communicates time, but I don’t understand how to decipher it. If endian is used/needed, how can I do this? Thank you in advance!

According to the proprietary program’s reported values:

Time (probably 24 hr clock): 1:13
Date (mm/dd/yyyy): 4/9/2008
Serial Number: ERXL-0162
Part Number: 4530011
Software Version: v3.50

[03/08/2019 16:44:22] Written data (COM4)
    01 01 01 02 00 05                                          ......
[03/08/2019 16:44:22] Read data (COM4)
    01 01 01 02 00 05 01 01 01 26 02 34 35 33 30 30     .........&.45300
    31 31 20 20 20 45 52 58 4c 2d 30 31 36 32 20 20     11   ERXL-0162
    20 20 34 35 33 30 32 37 30 76 33 2e 35 30 07 3b         4530270v3.50.;
[03/08/2019 16:44:23] Written data (COM4)
    01 01 01 02 00 05                                             ......
[03/08/2019 16:44:23] Read data (COM4)
    01 01 01 02 00 05 01 01 01 26 02 34 35 33 30 30     .........&.45300
    31 31 20 20 20 45 52 58 4c 2d 30 31 36 32 20 20     11   ERXL-0162
    20 20 34 35 33 30 32 37 30 76 33 2e 35 30 07 3b         4530270v3.50.;
[03/08/2019 16:44:23] Written data (COM4)
    01 01 02 02 00 06                                       ......
[03/08/2019 16:44:23] Read data (COM4)
    01 01 02 02 00 06 01 01 02 07 89 28 01 0d 38 01     ..........‰(..8.
    02                                                  .
[03/08/2019 16:44:23] - Close port COM4

Edit: Two more time stamps as requested

Time: 1:02 4/9/2008
[03/08/2019 20:04:30] Read data (COM4)
    01 01 02 02 00 06 01 01 02 07 89 28 01 02 28 00   ..........‰(..(.
    e7                                                ç
Time: 1:04 4/9/2008
[03/08/2019 20:05:50] Read data (COM4)
    01 01 02 02 00 06 01 01 02 07 89 28 01 04 00 00   ..........‰(....
    c1                                                Á


texts:
I'm going to start a new project and I wonder if the concept makes sense.
(I'm not so familiar with ATA specifications to answer this by myself :))

The concept:

HW design:

"SATA connector on motherboard" <-> "SATA cable" <-> "SATA/IDE HW converter" <-> "ATMEGA168"

"SATA connector on motherboard" <-> "SATA cable" - Device would be connected to SATA port on PC motherboard with typical SATA cable
"SATA/IDE HW converter" - on my PCB I will use one of SATA/IDE controllers, so far I've found:
JMicron - JM20330,
Atmel - AT78C5010,
ACARD - ARC-770
"ATMEGA168" - as programmable unit I'd like to use ATmega168 (or any other cheap 8-bit microcontroller)

Purpose

With this device I'd like to simulate presence of hard drive in a system. As I want SATA/SCSI stack to be used by OS I need to use SATA ports on motherboard.
AFAIK connecting to SATA interface without SATA/IDE converter is impossible with ATMega microcontrollers due to big speed of SATA bus interface.
Nevertheless I've found IDE/ATA implementation for 8-bit uC:
http://www.opend.co.za/hardware/avride/avride.htm

Wonders

My biggest concern is the SATA/IDE converter, I wonder if it can be easly used with micro-controllers as ATMega?


texts: How can I implement this function with JK Flip Flop + NAND Gates

texts:
I have a problem about logic design. I need to design MOD 5 Up/Down Counter with control input x, when x=0 it will count down and when x=1 it will count up. I'm allowed to use only JK flip flop and NAND Gate. Complement of x is not available. I thought a 3-bit number which is ABC. I wrote the table and I created a Karnough map for A which is the first digit. But, I am stuck in here because the function I got for A is (A'.B'.C'.x'+B.C.x) and I couldn't find any way to implement this function with given gates. The final step must be in JK Flip Flop to make it synchronized with the clock. I'm thinking for 2 hours about this. Can you give me a way to implement this function? Thanks in advance...
Note: Complements of A, B, C are available and Logic Levels 1 and 0 are available.


texts:
I am attempting to use a CTEC D250se in a 12v dc vehicle setting.  It is a dual batt/batt solar charge controller.  The max solar input voltage is 23v and I realized i have a 36v solar panel.  The rep said it wont work and has offered no solutions.  My question is how do I regulate the solar input?
I have looked at a few Buck style trans but they say not for use w solar power.  Its a really good product and I would appreciate any solutions.  Space is an issue.


texts:
I am new to this field and need help calculating current I2 through voltage source 2.

U1=1V

U2=3V

R=10 Ohm

Unfortunately I have no clue how to calculate this.
Would be so thankful for help!


texts: How do we test and determine if a USB cable+connector is version 2, 3.0 or 3.1?

texts: How do we test and determine if a USB cable+connector is version 2, 3.0 or 3.1, without using port, PC and/or having data transfer but instead with basic physics tests e.g. using multimeter?


texts: Is there a mandatory pattern for stator windings in 3 phase induction motors?

texts:
Imagine simple 2 pole 3 phase induction motor, is there a mandatory pattern for the stator windings to creat a rotating magnetic field?
Why must the angle between the coils be 120 mechanical degrees to create a rotating magnetic field?
why can't I just put the coils in the stator in the order : aa'bb'cc'  (each coil in 2 adjacent slots) ?
and for 4 poles or more what is the rule?

I understand the math but is there anyway to imagine the whole process in my head?
and the last question : How to consider a set of coils as a pole? like in the picture, why did he put the north pole and the south pole there and not vertical for example?

I am sorry if i'm not clear but these things are very confusing..


texts: what is the problem of grounding a 1 ohm resistor to a power supply?

texts:
(Vcc)-(load)-(1 ohm 5 watt)-(gnd)

I am making a dc-dc boost power supply circuit, and I need a shunt resistor to measure the current. is there a con or problem in this approach of using a 1 ohm resistor?


texts: How to analyze this Diode Circuit by hand?

texts:
I need to analyze this circuit by hand, I'm a Mechanical Engineer, so I really have no idea what I'm doing here. I thought about doing the parallel of the 2 top resistances and same for the bottom ones, but that wouldn't work. How do I analyze this? I need to know whether or not the diode is conducting electricity and the intensity of current that goes through it.

Sorry if any mistakes language-wise are made, I don't know the technical terms for this stuff in English. Cheers.

EDIT:
Assumed it was off, calculated the Voltage on the left and on the right of the diode, it's 0.25V, therefore not conducting.

Thanks for the help guys!


texts:
I have a photodetector device that outputs charge pulses proportional to incident light. From the device's datasheet (here) and some infor provided by the manufacturer (here), I've understood that this particular device, with 900 detectors, outputs about 3.72*10^-13 Coulombs per incident photon, on top of a dark current of about 0.372-0.743 uA.

I'm reverse biasing it with about 64V, and since I only have single supplies at my disposal I've implemented a non inverting charge amplifier/integrator (here, pag.23). However, since the transfer function of this amplifier only relates input and output voltges, how can I estimate the input voltage at my amplifier? The photodetector already includes quenching resistors, but the datasheet does not specify their value. On the other hand, that amound of charge, for just 1 detector, could lead to a current pulse of about 1.24 mA if one uses the FWHM value, which I'm not sure can be used to compute this.


texts: FFT + filtering sound = triggering signal

texts:
I'm trying to FFT the live input sound and filter it to have only 350 to 500 HZ.
So, my goal is to turn the LED light on only when some sound has frequency between 350-500.
I looked at FFT codes, but don't know how to filter it and send the output signal out.

I'm very new to arduino board.
You can assume I know nothing about the arduino board or C programming..
Please be specific as possible..
Thanks.


texts: Is it possible to identify what magnet has crossed over a hall effect sensor?

texts:
We are currently doing a project with DCC locomotives, involving a micro controller LPC1768.

Now the scenario is that we have a railway and under the railway we have hall effect sensors which the locomotives crosses over. Since we will have two different locomotives running on the track, is it possible to identify which one is currently crossing a particular sensor, since the trains do have their specific addresses in an address byte would it be possible to measure how the magnet(one magnet is in the form of a cylinder and one of a cube, and we are assuming they should affect the voltage or current differently) on each train affects the hall sensor. Another solution we have already thought of is to run the trains and measure where they are based on the magnets it has crossed. But for a nicer implementation a solution like the one ask for would be far easier to implement.


texts: Analog-Digital Conversion Clock Prescaling - ATmega328P

texts:
I am trying to use the ADC on an ATmega328P clocked at 16 MHz. The datasheet mentions the typical ADC clock frequency range as being from 50 kHz to 200 kHz.

  By default, the successive approximation circuitry requires an input clock frequency between 50
  kHz and 200 kHz to get maximum resolution. If a lower resolution than 10 bits is needed, the
  input clock frequency to the ADC can be higher than 200 kHz to get a higher sample rate.
  The ADC module contains a prescaler, which generates an acceptable ADC clock frequency
  from any CPU frequency above 100 kHz. The prescaling is set by the ADPS bits in ADCSRA.
  The prescaler starts counting from the moment the ADC is switched on by setting the ADEN bit
  in ADCSRA. The prescaler keeps running for as long as the ADEN bit is set, and is continuously
  reset when ADEN is low.

The prescalers for the ADC clock range from 2 to 128. As I understand it, for remaining 'in the spec' I'd probably require a prescaler of more that 80 i.e. 128.

However, the ADC works for all clock frequencies from CLK/128 up to CLK/4 but not on CLK/2 i.e 8 MHz where it just returns 0x3FF (it is a 10-bit ADC) for all conversions. Is it just because I am running the ADC beyond its recommended maximum or is it something else I need to know about?

ATmega328P Datasheet


texts:
This old, crusty inductor found in an old Iskra (Yugoslavia) TV intrigued me, and I was hoping that someone could tell me what's the story behind it's design.

I don't know if the pictures are descriptive enough, but inductor's "head" is magnetic, and the plastic casing is "hugging" another ferrite cylinder with small square hole in the middle.

It's unlike any inductor I scavenged this far, and while I do understand how inductors work, I can't figure out a useful purpose of this arrangement.


texts: Voltage Divider returns incorrect voltage reading

texts:
I have created a simple voltage divider circuit as shown below:

Using the simulator, I can see that the voltage measures in at 0.838935V, which is expected.
However, when constructing this circuit in real life, I seem to be only reading ~0.513V on my digital multimeter. This project was initially supposed to read the battery voltage on an ADC, but this seems to be the root cause on why it is constantly returning a lower voltage.
Any ideas on why possibly this is happening?


texts:
I am looking for the best way to provide an analog output from an Arduino to control the blend and mode doors in my truck's HVAC system.
They both take a straight "12V" signal from the control unit ("12V" because it is more like 12-14V depending on whether or not the truck is running.)
The control unit uses a simple 10k potentiometer for each of these, as a voltage divider, thus giving a variable voltage between 0 and "12V". The wiper of the blend door potentiometer goes through an 82k resistor, and the wiper of the mode door potentiometer goes through a 3k resistor (I'm not sure if that matters, but if possible, I'd like to match this setup.)
Things I have looked at:

PWM using MOSFETs - These would have to be high side switches, and I admit I am not skilled enough to be able to pick out components for this. If there is a turnkey high side switching solution that will allow me to use PWM through an RC filter, that would be great. I think this would be the simplest answer, and use the cheapest components.

Digital potentiometers - again, there is a wealth of these out there, all with different specs, most of which don't seem to support more than 5V. I think potentially this one might work: MCP41HV31-103E/ST-ND

So my question is:
I have an Arduino Nano, and I need it to output an analog signal between GND and a reference voltage (in this case 12V to 14V), what is the best way of doing that?
Edit: Additional information, I have found schematics for both the actuator, as well as the control interface:
Actuator information
Controls information


texts: Measuring SuperCap current leakage avoiding voltages drops in ADC

texts:
I have a circuit with a SuperCap used as a battery. I want to know the curve of SC voltage in time to finnaly measure its self-discharge.

Is this can be done with a simple arduino or another microcontroller throught the ADC if I programm the ADC with interrupts every hours for example ?

The idea is to avoid to the maximum the leakage current in the ADC, to perform a reliable measure in time.
I found that ADC on the arduino as a Impedance of approximatly 6 MOhms, does this permit the measure I want ?
There will be of course a voltage drop in the arduino.

The other option is to seperate the measure points and the SC with a relay commanded by the arduino when it has to make a measure.

The process will act the act with the followings steps :

Wait for interrupt, Relay = open: no measures
Time interrupt (every hour), closing the relay
Read the SC Voltage,
End of interrupt, opening the relay
Wait for interrupt

What do you think about this second method ?


texts: Conducting plastic for capacitive touchscreens

texts:
As I am disabled I have to use a headstick (see picture below) to do stuff on the computer. I also have a phone with a resistive touchscreen, which works well with my headstick.

But here is the problem: I cannot operate any devices with capacitive touchscreens, since the tip of the headstick is made of plastic. I heard, though, of conducting polymers, and wondered if my problem could be solved using those. So basically I thought of just making a new tip of such a conductive plastic.

What do you think about this approach? How expensive are these materials? What can yu say about their electrical properties vs. human skin? Would this be a good idea?

Would something different work? Like putting a little coil inside the tip of the headstick?


texts: What In-Wall Project Box Should I Use for 110AC PSU+MOSFETs+Controller?

texts:
I have a project where I will be putting a 180W PSU (80+) and a bunch of N-Channel TO-220 MOSFETS, a few PWM PCBs, and an ESP8266-based controller in a wall cavity for a ≤150W LED lighting system.

If I don't want to PCB-mount the MOSFETs (since this is a one-time design and I'd love to get good heatsinking for the FETs), what material/bar/whatever should I mount them to?  Since IIRC I can't mount all to a metal strip since that'd be shorting them all together on their ground side.
This is a new space with decent room in the cavity (≥ 2m^3), so waste heat can go in there, so is there a project box that's OK to receive 110VAC, output lots of 12VDC, and not give an inspector fits?

I'm comfortable with conventional 110V wiring (outlets, switches, fixtures, etc) and I'm comfortable with wiring up ≤10W PCB-based systems (like ESP8266 work), but this combo of house voltage and (marginally) higher wattage is a bit out of my comfort zone and I want to do it safely.

I'm OK with (indeed would prefer) an access panel through the drywall, but would want any fans out the back if possible because of noise.  Preferably fans that are heat-activated.

I have a 3d printer and could print something, but I suspect melty thermoplastics are no bueno in this case.

Thanks in advance!


texts: How to use a ZVS voltage booster to create the Jacob's ladder?

texts:
How to use this ZVS voltage booster to create the Jacob's ladder?

I bought it from the internet (eBay):

  Description:

  This is the design of a flyback foreigner drive circuit
  for driving the ignition coil, as do zero-voltage switching (Zero
  Voltage Switching) and the majority of domestic fans are referred to
  as "ZVS". Because power, low heat, simple and reliable are widely used
  in driving enthusiasts spark gap Tesla coil (SGTC) and Jacobs ladder,
  Marx generators and other devices.

  The ZVS driver circuit are of high quality components, high
  reliability, strong power. Input 12-24V / 10A DC. High voltage DC
  output voltage is about 800 times the input voltage.

  Product parameters: Size: 74mm * 77mm Input voltage: DC 12V-30V Power
  requirements: less than 12V≥5A 15V above ≥15A Operating Frequency:
  30kHz-50kHz adaptive Secondary parameters: 5T + 5T

  Voltage: Input voltage and current output voltage with maximum power
  12V / 5A approximately 10000V 60W 24V / 10A about 20000V 200W

  This element driving circuit used are new and original, never cut
  corners. ... The board is double-sided, using the entire back surface
  of the resonant circuit traces, resistance is small, less heat, good
  heat dissipation, high-performance is not a single panel can compare.

I followed the documentation to use two copper rods. The spark does appear, but it won't go up, but remains on the bottom side.

*   *
|   |
 | |
 |x|
+---+
+---+

The x is the spark. After it appears, if I move one of the rods, it jumps on the top, but I would like to not move the rod and make the spark jump.

How can I do that?


texts: Do Electrical Engineers use microcontrollers?

texts:
I've always loved to program, and I just recently became interested in electronics and programming microcontrollers. It is very fun, but I am wondering if I am learning something useful that can get a job in when I grow older. I am wondering whether Electrical Engineers use microcontrollers.

I know that jobs where you need to bring power to different parts of a house probably would not, but perhaps a job like this:

  Your Responsibilities:

  Design and develop new defibrillator products. Primary focus will be on new product design and current product support in the area of analog and digital design.
  Model analog circuits using various simulation tools, such as PSPICE and MATLAB.
  Build prototypes and prove design feasibility, functionality and performance.
  Document all phases of the design including requirements, specifications, plans, reviews, test procedures, and test reports.
  Support existing products. Investigate and determine root cause of product issues found in manufacturing and the field. Troubleshoot systems, PCBs, cables, and firmware. Use test equipment to analyze and resolve issues.
  Identify, evaluate and recommend key suppliers based on electrical technical abilities, experience, history, and certifications.
  Facilitate and maintain constant communications with key suppliers and internal stakeholders during project development.
  Represent the EE development group as a technical team lead on projects. This would include providing technical solutions as well as project scheduling and project tracking.
  Document the design for manufacturing (i.e. drawings, schematics, experiments, changes, test results, data, PCB layout, etc.).
  Work with cross functional teams that include: Mechanical eng., Software eng, Clinical applications, Learning Products, Marketing, Support Engineering, Quality & Regulatory, and Supply Chain. Teams are experienced, but relatively small and members hold many development roles.

Would people who do this use Microcontrollers or something similar?


texts: I need clarification regarding the rating of the battery shown in the below figure. I know battery ratings are given in Ah(Ampere-hour), but here it is given A/s. The picture is from "Linden's handbook of batteries" section on Thermal Batteries(Page No:21.14). So, what does 3400-A/s tells us?


texts:
Can anybody identify the connectors in the two images below and give me some names or links, or whatever? The connectors are from inside a Microsoft Kinect sensor.

Full size: http://i.imgur.com/fYNWE1r.jpg

Full size: http://i.imgur.com/ogPXnqW.jpg


texts: How to safely insulate the Power PCB of a display computer monitor?

texts:
CONTEXT

The other day I was checking the heat coming off an aluminium heatsink on the power PCB of an eizo EV line led display monitor. It was okay, not too hot, just warm and tad bit hot. When I touched this it was okay. The display for my custom project was on and still works perfectly. Then I touched the aluminium bezel of the monitor and that was okay too.

BUT... when I touched with both handes BOTH the lcd panel's aluminium back (to check if the led backlighting was warm) with one hand AND the aluminium heatsink on the power board of the monitor with my other hand, I got a huuuuge electric continuous  shock for a full second. Boy it hurt! I've had a few times in my life touched live wire accedentally while fixing lightbulbs etc, but this time it was long and Im lucky to still be here telling the tale. This seemed or felt more dangerous / higher voltage! How can that be I thought LED was cute and safe!!

QUESTION

How can I insulate the tiny aluminium heatsink on the power pcb of the monitor?

I am planning on covering these PCBs with an aluminium cover as a ground encasing for protectingmyself and children, so first I must insulate this PCB and make sure no heatsinks touch the aluminium plate covering it. HOW can one insulate a Power PCB?

Can I pot the power PCB and the monitor PCB completey submerge it with hot glue or with epoxy resin for example? Or could I just cover the pcb with a rubber layer? All suggestions will count as answers as not only I appreciate your input, it (your answer) might in some cases even save lives! So, thanks in advance!


texts: Fundamental TTL circuit and its operation

texts:
So i am studying TTL circuits and i started with fundamental configuration as shown in the following picture.

NOTE: Transistor Q1 is actually a two emitter transistor, i just couldn't find proper symbol when i was drawing this circuit, however, thats not too relevant to the question i am asking.

Let's say that Vin is at low state, 0.2V for example, that  would mean that voltage at base of Q1 is about 0.9 volts, which would mean that we have a significant current at the base of transistor, 4mA approximately, that would mean that transistor is either in direct active mode or in saturation, with second option being more likely, since this base current is for most transistors above the saturation current, which means that collector current of Q1 is not very high, yet it exists and goes from collector to emitter.

Now, considering this configuration, that would mean that current flows out of base of Q2, which means that Q2 has a negative base current, and don't know what is going on with transistor when it has negative base current, so my questions are:

How this situation is affecting Q2 transistor?
What would happen when Q1 is in direct active mode, having significant collector current, how it would affect Q2 transistor?

Any help appreciated!


texts: How do I analyze this negative feedback?

texts:
I'm working on understanding the four negative feedback topologies.  My process has been to first analyze the circuit's dc and ac characteristics for quiescent current, gain, impedance, etc.  Then, I like to compare the circuit to the common "block diagrams" that show the internal amplifier and the feedback network.  It was very helpful to me to be able to see that (for instance) the emitter resistor provides the feedback for the common collector and common emitter.  One such example is here.
I'm struggling with the following circuit.

I know a little about it already, but just enough to confuse me.  I know that I must use a current source for the input signal, as the feedback provides a current.  I know that the internal amplifier will see a current and provide an amplified voltage, so that makes this a transimpedance amplifier.
But here's what I can't figure out.  For the transconductance and voltage amplifier topologies, I was able to remove \$R_E\$ in order to view the circuit without feedback for comparison.  With that I was able to verify that the gain of the internal amplifier and the feedback network proved out.  But in this circuit, I can't seem to figure out how to remove the feedback.
How do I analyze the circuit to get values for the gain of the internal amplifier without feedback (open-loop) in ohms and the feedback factor, \$K\$ in seimens?
Here is the block diagram I am referring to (top-right picture).


texts: What is the use for non-inverting input resistance in a negative feedback opamp?

texts:
Here in the Figure R5=50K.
This resistor value is not in the equations to obtain output voltage, and in many tutorials non-inverting input is directly grounded without a resistor. What might be the reason to use it here?


texts: Oscillations in voltage controlled current source

texts:
I'm trying to build a pulsed voltage controlled current source using an op-amp.  It has a tendency to oscillate (although sometimes to works okay, just often enough to give me hope that I might be close).

I'm looking to drive currents from 100 mA - 1A through a load which ranges from 12 Ω - 35 Ω.  I'm using an LM675 (datasheet) because I have it at hand, and it's rated for the voltage and current.  Vin is provided from a Labview-controlled DAQ.  The schematic is below.

simulate this circuit – Schematic created using CircuitLab

The 1 Ω resistor and 0.22 uF cap from the examples on the LM675 data sheet.  I confess I don't understand stability all that well.

I've tried similar circuits with other op-amps and the past, and sometimes been sucessful, and other times encountered the same problem I have now.  I'd appreciate any advice.


texts: Turn-off voltage for SiC modules, does it always have to be negative?

texts: I have been using SiC power modules for my application.Normally we use negative voltages at the gate to turn-off the modules. Would want to know if the power modules can be turned off with the zero voltage at the gate and what are the deviations or effects of it.


texts: How much single-sign (static) charge is storable in a reasonable mass?

texts:
Let's take a high-voltage low-current AC source, and two devices capable of storing single-sign charges, at the ends of long wires.

simulate this circuit – Schematic created using CircuitLab

This device, spinning in a uniform magnetic field (perpendicular to the lines) at frequency equal to the frequency of the source, will have a force acting on it, perpendicular to the lines of the magnetic field, and to the wire connecting.

it's an idea of a spacecraft propulsion in Earth's magnetic field.

This all rests upon the ability to store single-sign charges in the devices at the ends of the wire - this is the limiting factor of how much current can be driven through the wires in each cycle, and as result, the thrust of the propulsion. And I know about all current solutions of storing larger amounts of electric charge involve a gap between opposite-sign charges as small as possible. Still, even the old "rub the rod of a certain material to give it a charge" experiment stores -some- single-sign charge in the rod. So we can store some single-sign charge. The question now is, how much? What's the state of the art?

While size (volume) is something of a factor, especially for devices that can be unfolded it's not that bad. But mass is a significant factor, so multi-ton solutions are right out.

So, what is our state-of-the-art capability of temporarily storing single-sign charge in some reasonable (say, up to a few hundred kg?) device/material?


texts: GSM 3G VSWR and antenna testing question

texts:
I'm a recently converted SW engineer to EE (Graduated less than 3 years ago, BS in Comp Eng, focus on Digital hardware) and I've been made the hardware lead on a project here at work. The project is in the final testing phase, and the module deals with 3G cellular, with a custom designed antenna our in-house RF guy made up. My question is that we're doing some pretty intense testing, and I'm seeing all these graphs with SWR readings, and I have no idea what I'm supposed to be seeing. Typically, the Y-axis is 1 - 15dB, and the X-axis is Freq (usually in GHz).

An issue I know is occurring (from meetings) is that we're having spurious emissions on one of the harmonics, which is "bad." My question is "Why is this bad, and how can I not look like a complete idiot when looking at future graphs?" Should the dB be higher or lower when you're looking to attenuate? When working in the GSM signal band (we're targeting both EU and USA standards), what should the graph look like?

As a followup, instead, should I just smile and nod and let the RF guys handle this?


texts: How to fix/reduce inconsistent IR Receiver Modules performance

texts:
i am trying to copy an IR signal from a remote for a project. I noticed that the data i am recieving from my TSOP38238 is different from the what the remote is transmitting. To show my problem here is a picture of a Oscilloscope.

The blue line is probed from the output pin of the TSOP38238 while the yellow line is probed from the positive LED pin of the remote.

If you noticed the one that i underlined in red, it would seems that TSOP was not able to detect these 4 burst. This does not happen consistently sometimes it would miss 1,2, or 3 times and i am getting a very low chance it getting the correct signal perfectly.

In the picture the circuit used is fairly straight forward. Using an arduino as a power supply:

5v   ->   TSOP Vcc
GND  ->   TSOP GND

I had not connected the TSOP OUT pin to anything yet except for the oscilloscope probe. I have also calculated that the remote's burst is around 38 khz.

I will be doing this to a fair amount of buttons and it would be highly inefficient to keep repeating over and over until it gets it right. I also don't have 24/7 access to this oscilloscope to check.

So what should i do to reduce or completely remove these errors. What is causing it? Is the TSOP38238 just a bad reciever? Are there better IR Reciever module alternatives that are available?

Thank you.


texts: Certification for automotive accessories?

texts:
I have read a number of posts here relating to certification of devices for sale in the US, but the majority of them pertain to emitters such as BLE and Wi-Fi.  To keep it simple, I have 2 microcontroller based automotive devices that I have taken all the way through the custom PCB prototype phase, and I am now realizing the legal hurdles of manufacturing and selling them.

One is a simple LED dome light replacement, and one goes inline with the vehicle speed sensor to adjust the frequency of the signal.  There are no power supplies involved, and no emitters involved.

I see a lot of small electronic devices on web sites, and no certification is quoted (you would think they would advertise it if they had it).  Does anyone have any advice on whether or not devices like that need certification?  If so, what?

Would the best answer be to contact one of the testing labs and see if they say it needs to be tested?  I worry that will be like asking a car salesman if I need a new car though.


texts: What happens when you get silkscreen over a via?

texts:
See image below;

My suspicions would say that part of the silkscreen would disappear over a via, does this happen in production?


texts: Why is the signal amplitude low on the oscilloscope even though the impedance is matched?

texts:
I have a photodetector with differential outputs that are each 50-ohm terminated.
When I connect one output to the oscilloscope to look at the signal, I see a higher signal amplitude with higher channel impedance on the oscilloscope. According to my very basic understanding, maximum power transfer should occur when the impedance is matched. Could you help me understand what is happening here?

The pictures are taken from my scope, and you can see the amplitude of the signal when the termination is 1-Mohm is more than double what I get when the termination is 50-ohm. The cable connection to is as follows:

PD --> 50-ohm SMA --> SMA-BNC adapter --> 50-ohm BNC --> Scope


texts: In which way proportional valves are controlled solely by current?

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Proportional valves are drived by current because we need a steady force and since resistance changes with temperature if they were driven by voltage this force wouldn't be steady.

Ok, this is what I read. What I don't understand is how can a device be driven only by current and not by voltage if voltage is the cause of current?


texts: What happens when there is a simultaneous Read and Write launched to the same address in AXI3/4?

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I have a doubt regarding the AXI3/4 protocol. Assume a hypothetical scenario where a single master issues a valid Read and Write transaction to the same address simultaneously.

From the AXI specification, I understand that there is no interdependence between reads and writes and each has a channel of its own. With this in mind, is the above scenario valid?
In case the above scenario is valid, is there a specific order in which these requests are served? (so that there is determinism in the type of response to expect from the master, since there are two ways this could end)

I am aware that (2) can depend on a lot of factors related to the master (posted writes, wait for response read, instruction execution for read after write etc.) and that AXI offers semaphore mechanisms through Exclusive Accesses. But these aside, what should be the expected behaviour?


texts: Pullup resistor value based on current sinking capabilities

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Actually a lot simpler question than the title would suggest. I'm planning on using a SN74AHCT125 quad buffer as a logic-level converter from 3.3V to 5V. I only need two of the four inputs.

As per the function table, when \$\overline{OE}\$? input is high, the output is disabled. Presumably that just means tie both the \$\overline{OE}\$? pins for the unused inputs to VCC. However, another thing caught my eye in the data sheet:

  To ensure the high-impedance state during power up or power down, \$\overline{OE}\$? should be tied to VCC through a pullup
  resistor; the minimum value of the resistor is determined by the current-sinking capability of the driver.

Does that only refer to if I was using another device to control the \$\overline{OE}\$? For instance, using a microcontroller which can only provide 10mA (for example) per pin? If that was the case, with a supply voltage of 3.3V, what value resistor would I want to use? Am I right in thinking it's just using Ohm's law, which would give a resistor value of 330\$\Omega\$ ?


texts: What does a dashed resistor symbol mean?

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What is the dashed resistor symbol going to the ground shown in the picture?

Thank you.


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I need to drive 80 RGB leds (so 240 individual leds), physically and conceptually aligned as an 8x8 matrix + an additional vertical line and an additional horizontal line.

I'd like to drive the matrix using 595 shift registers, so that I only need 3 microcontroller lines to drive all the leds, multiplexing the leds.
The RGB leds I'm using are common anode. I'd like to have at least 3 levels of brightness for each color (full off, half on, full on).

I found many examples of driving an 8x8 RGB matrix with shift registers, but I'm trying to understand what's the best way (code-wise, mainly) to add the additional 16 RGB leds.

Option 1: a 9x9 matrix. If so, the additional column pin and additional row pin would come directly from the microcontroller and not from and additional shift register, since a shift register for only 2 pins would be wasted.

Option 2: a sub matrix in series with the first, that shares the anodes with the main matrix, but uses only an additional shift register to drive the additional cathodes.
Other options?

thank you and sorry for my bad english.


texts:
Is nrf24l01+ from Nordic Semiconductors FCC certified ? It is hard to find out from their datasheet whether FCC approved ?
Is it FCC approved ?

If it is approved and I use it in my PCB and control it via my ARM cortex processor, do I need to get the entire PCB board FCC approved ?

Also, I am using sierrra wireless HL series modem chip which is FCC approved. This will also be on my PCB. So, do I have to get my PCB FCC approved again although my modem is FCC approved ?


texts: Dual polarity (\$\pm15\$V) from a bench power supply with only one output

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I have a GW Instek bench DC power supply (0V-30V, 0A-3A~5A). The output terminals are labeled as -, GND and +. The GND terminal is physical ground because it has continuity with the power supply's chassis. This ground terminal is isolated from the + and - DC output terminals.

I need to get +15V and -15V in reference with a common, but how can I do this if I only have the former outputs? Maybe I need a rail splitter? If somebody has a simple circuit I would appreciate it.


texts: I am trying to upload a hex file to my ATtiny85 with my AVR ISP MKII programmer. But avrdude says it cannot find my programmer. How can I find where my (USB) programmer is located (I am using Ubuntu 12.04 LTS) and how can I implement this command: avrdude -p t85 -c avrispmkII -e -U flash:w:src.hex to set the path of where my programmer is? MANY THANKS!