texts: STM32L4 Complementary PWM use only the negative Channel

texts:
I have problems using the complementary PWM feature of the STM32-L432KC. The non-complemementary pin ch1 is generating the right signal, but the ch1n pin is always at GND.

I want to use channel 1,2 and 3 on Timer 1, optimally only the inverse channel, as far as i can see this should be possible. For testing is have also enabled the ch1 which is working.

I have configured the HAL using CubeMx, my initialisation code is:

void MX_TIM1_Init(void)
{

  TIM_MasterConfigTypeDef sMasterConfig;
  TIM_OC_InitTypeDef sConfigOC;
  TIM_BreakDeadTimeConfigTypeDef sBreakDeadTimeConfig;

  htim1.Instance = TIM1;
  htim1.Init.Prescaler = 80;
  htim1.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim1.Init.Period = 20000;
  htim1.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
  htim1.Init.RepetitionCounter = 0;
  htim1.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;
  if (HAL_TIM_PWM_Init(&htim1) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

  sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
  sMasterConfig.MasterOutputTrigger2 = TIM_TRGO2_RESET;
  sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
  if (HAL_TIMEx_MasterConfigSynchronization(&htim1, &sMasterConfig) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

  sConfigOC.OCMode = TIM_OCMODE_PWM1;
  sConfigOC.Pulse = 1000;
  sConfigOC.OCPolarity = TIM_OCPOLARITY_HIGH;
  sConfigOC.OCNPolarity = TIM_OCNPOLARITY_HIGH;
  sConfigOC.OCFastMode = TIM_OCFAST_DISABLE;
  sConfigOC.OCIdleState = TIM_OCIDLESTATE_RESET;
  sConfigOC.OCNIdleState = TIM_OCNIDLESTATE_RESET;
  if (HAL_TIM_PWM_ConfigChannel(&htim1, &sConfigOC, TIM_CHANNEL_1) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

  if (HAL_TIM_PWM_ConfigChannel(&htim1, &sConfigOC, TIM_CHANNEL_2) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

  if (HAL_TIM_PWM_ConfigChannel(&htim1, &sConfigOC, TIM_CHANNEL_3) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

  sBreakDeadTimeConfig.OffStateRunMode = TIM_OSSR_DISABLE;
  sBreakDeadTimeConfig.OffStateIDLEMode = TIM_OSSI_DISABLE;
  sBreakDeadTimeConfig.LockLevel = TIM_LOCKLEVEL_OFF;
  sBreakDeadTimeConfig.DeadTime = 0;
  sBreakDeadTimeConfig.BreakState = TIM_BREAK_DISABLE;
  sBreakDeadTimeConfig.BreakPolarity = TIM_BREAKPOLARITY_HIGH;
  sBreakDeadTimeConfig.BreakFilter = 0;
  sBreakDeadTimeConfig.Break2State = TIM_BREAK2_DISABLE;
  sBreakDeadTimeConfig.Break2Polarity = TIM_BREAK2POLARITY_HIGH;
  sBreakDeadTimeConfig.Break2Filter = 0;
  sBreakDeadTimeConfig.AutomaticOutput = TIM_AUTOMATICOUTPUT_DISABLE;
  if (HAL_TIMEx_ConfigBreakDeadTime(&htim1, &sBreakDeadTimeConfig) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

  HAL_TIM_MspPostInit(&htim1);

}

Is there anything configured incorrectly? Is it possible to only use the inverse channel?

I start the timer by calling:

HAL_TIM_Base_Start(&htim1);
HAL_TIM_PWM_Start(&htim1, TIM_CHANNEL_1);
HAL_TIM_PWM_Start(&htim1, TIM_CHANNEL_2);
HAL_TIM_PWM_Start(&htim1, TIM_CHANNEL_3);


texts: high accuracy analog differential signal switching solutions to prevent distortion (relays?)

texts:
first let me define the application and circuit. the application of this is to sence currents ranging from 1nA to around 900mA. to accomplish this two resistors are used, a 10K for the nA range, and a 0.01R for the mA and uA ranges. the differential signals from each are then fed into a (and here is what my problem is) analog switch, mux, relay or some other solution. the single differential output is then fed into a x10 op-amp circuit, a programmable gain amplifyer, and finally a pair of ltc2410 24-bit ADC. the solution would need to switch states fast, but would only do so very rarely, as nA range is used rarely in this case.

if the solution didnt require a good amount of accuracy, a good quality analog switch or mux with low on state resistance and good channel-channel matching would be good. however i have heard that these can have problems, such as added voltages (charge injection) (my voltage + added voltage = bad, what i would want is my voltage + ~0 = good) or distortions and leakage currents.

here are two i had in mind (#1 is an unlikely final choice):

(1) https://www.digikey.com/product-detail/en/maxim-integrated/MAX4685EUB/MAX4685EUB-ND/948014 (1nA leakage)

(2) https://www.digikey.com/product-detail/en/analog-devices-inc/ADG888YRUZ/ADG888YRUZ-ND/997607 (200pA leakage)

another solution i have heard used in high accuracy low distortion applications such as this is the use of reed relays. looking on digikey i only found "one" relay i think would work here. board space for me is limited so only smd components can be used. it is a spdt relay so 2 would need to be used.

-https://www.digikey.com/product-detail/en/coto-technology/8L61-05-001/306-1271-ND/1914965

my ultimate question here is which is better, a silicon solution (mux etc) or an electromechanical one (relay)? i have found information about the application of the silicon solutions, but little about using relays. what would be the ultimate advantages and disadvanteges to each in this situation and is there a clear victor? (also am i overlooking any devices?)


texts:
I need to implement the equivalent of a variable resistor of range 10 - 200 Ohms, to be controlled by a microcontroller or FPGA. It is for a gain setting resistor for an op-amp, so I need be ends of the ‘resistor’ available (ie. not one at ground).

What is a cheap, simple way to implement this?

I’m thinking of using analog switches with various resistors, but I can’t think of a structured way to choose these. Maybe this is another question, but if this is the best way to go, then what is a good way to find the setup and values?

Digital potentiometers have too high wiper resistance to use here.


texts: Right now I'm using HyperLoad to program an LPC2148 through USB. HyperLoad is a windows program and I have a Mac so I have to open up a Windows virtual machine to use it. Is there a way to program it in OSX? I found a program called lps21isp, but I don't know how to use it. Also, don't I need a special driver for OSX so that it can communicate with the ARM7?


texts: What's wrong with my voltage multiplier segment?

texts:
The moment I learned about voltage multipliers I was really excited. What an awesome way to kill yourself!

I found a high voltage multiplier guide and using the image below, I created my first voltage multiplier:

Of course, mine is a little smaller:

Diode 1N5404 datasheet. Philips capacitor datasheet is probably top secret. But it's 100nF and 400V (DC I believe).

I'm connecting what I believe is 30VAC 50Hertz input (that's what I get when I measure the voltage after connecting Graetz bridge to rectify the AC). However, I can't get more than 10VDC anywhere on the "multiplier". So what's wrong? Where are the right places to get the output?


texts: Why won't my hover board battery charge?

texts:
I have a standard hoverboard battery which I bought for my electric skateboard project.
The battery has a 10s2p arrangement. 36V and 4.4 AH.
Now the battery voltage is 20V.
When I plug my charger in it does not charge and the light is still green. The charger light should turn red to indicate charging.
The charger output is 42V 2A which is the recommended for this battery.
What I think is the pack voltage might be below a certain level and that's why the BMS is not allowing the battery to charge.


texts: Why is there heavy oscillation in my capacitor discharge circuit and is there anyway to fix it?

texts:
I have the following capacitor discharge circuit:

simulate this circuit – Schematic created using CircuitLab

When solving for the voltage across the primary and secondary inductors, I get the following:

Where in the current setup C = 160 nF, R_L1 = 200 uOhms, L1 = 1 nH, L2 = 2.5 uH, and V0 = 500 V. When I try to simulate this, I am getting intense oscillations in the voltage across the transformer that can vary quite drastically depending upon the values of omega and tau. I've even noticed a certain type of "beating" behavior depending on the value of omega and tau. Here are two results:

Is there a reason for these oscillations? Or did I somehow do my solutions for VL1 and VL2 incorrectly? If indeed the problem is physical (and not mathematical error), then how can I prevent this from happening? The goal of a capacitor discharge circuit is to generate an initial high voltage (~ 25 kV) on the secondary coils. This voltage should sustain briefly and have some type of fall time. I am not an electrical engineer, so I am not too certain if I can add some kind of element in the circuit to prevent these oscillations - maybe a diode of some kind? Any help is highly appreciated!


texts:
I do not understand a concept about the Nyquist - Shannon sampling theorem.

It says that it is possibile to perfectly get the original analog signal from the signal obtained by sampling if and only if the sampling frequency is higher than twice the maximum frequency of the initial signal.

I can understand it if I think at what happens in the frequency domain, in which the sampling produces replicas of the initial spectrum and therefore a low pass filter reconstructor can delete them and keep the original spectrum.

But in time domain sampling simply means to extract values of the original signal at instants separated by the sampling time T.

Once I have extracted these values, I have lost all the informations about the points between two consecutive instants of sampling. How can the reconstructor device perfectly obtain the original signal? It does not know how to connect the sampled points (they can be connected by infinite mathematical curves and all the information inside T time are lost). For example, it can connect them as in figure 1 (the correct original signal), or as in figure 2.

figure 1

figure 2

This makes me think that a very high sampling frequency is surely a good thing, since the points are very close together, but there is not a frequency that if overcome, allows a 100% perfect reconstruction, since sampling implies losing information.


texts: Pickup Signal from a Wire - without a physical connection

texts:
I am not an RF engineer and I don't even know if what I'm asking is possible.

The idea is that the system will be outputting a 12V 10KHz signal onto the wire with one end connected (Wire Under Test) - and I would like this signal to be detected by another wire that is wrapped onto this wire but not connected electrically.

This is for a quality test system and for quality reasons, I cannot connect the Wire Under Test's other end electrically anywhere.

If I output a 5V 10KHz signal via my function-gen onto this wire (with only 1 connected to the function-gen) and put the tip of my oscilloscope probe onto the PVC insulation, I am able to pick up a 200 mV 10KHz signal very easily.

If I further wrap another wire onto the wire under test and put my oscilloscope on that wire, the signal jumps to 1V 10 KHz.

How can I design a circuit that lets my amplify the signal from the wrapped wire? In my naiveness, I tried and connected a LM324 based Inverting amplifier but I received no input - until I connected the probe of my oscilloscope at the input!


texts:
I know this question has been asked many times before, however this question differs in the use of an uneven set of capacitors.

I'm replacing the crystal on an old computer.

The original symptoms were as follows: If the crystal got hot enough the system would start up, heating up the crystal by aiming my hot air station at 100C for 2-3 seconds would heat the crystal enough for it to work a few minutes.

I replaced the 32.768kHz crystal marked with S3238E with a new one (32.768kHz, 12.5pF) however although the system is less sensitive to the crystal not being warm, it still has the same issues. The only difference is that the crystal now also stops functioning when it gets hot enough... (>65C)

Since the 25 years between this device got manufactured I assume a bunch has changed in the world of crystals and maybe its original crystal has a higher load capacitance.

The circuit being used is as follows:

The MCU in question is an MC68HC05E1 which the datasheet can be found for over here: https://www.nxp.com/docs/en/data-sheet/HC05E1GRS.pdf

What would the Load Capacitance of the crystal be like?
What does it tell about the circuit when a crystal will only work at
a certain temperature?


texts: Could I add a potentiometer to a dremel?

texts: I bought a cord Dremel a while back for some of my personal projects and it seems to speed up after a minute and the rotary bit I like begins to jump and chips pieces away. I haven't sliced the cord but I am assuming it has the standard white,black, and green wires. I would surely have to add a resistor somewhere in the line. Just wanted to check and see if this would be doable?


texts: What is back-emf: counter-electromotive force?

texts:
Could someone knowledgeable on the subject explain what exactly is this back emf?

How is it caused in a motor/generator, which components and which effects determines it?


texts: Using an External interrupt from any pin PIC16F873A

texts: I'm trying to use an interrupt, which will occur on a rising edge of a signal coming from my LSM303DLHC accelerometer. The accelerometer has a Data Ready (DRDY) signal that fires every time new data is added to the registers I've read from and I want to use this signal to fire an interrupt so I can only read from the accelerometer when data is ready. Problem is, I don't have any port B pins available because I'm using them for interfacing to an LCD (not serial). Right now, I'm just polling a status register bit in the accelerometer to see when data is available, but this obviously isn't very efficient since I also want to be reading in GPS data and controlling servos at the same time. If there isn't anyway to get an interrupt from any port A or Port C pins, could someone possibly give me another way of synchronizing with my accelerometer using the PIC16F873A?


texts:
I understand that if you have resistors in series, you can tap into a smaller voltage inbetween them. For example, if you have two resistors of the same value, the voltage inbetween them will be halved. Though I'm still unsure how that works practically in a circuit.

See the attached diagram:

Assuming the resistors are the same value, the voltage at point A will be 9v, and will be 4.5v at point B. The voltage returned to the power source (point E) should also be 9v.

What are the voltages at the remaining points C and D?


texts: How does a PC sound card be able to detect 433 MHz signals?

texts:
I have developed a radio driver that can detect sensor RF packets for a particular protocol, in 433 MHz band using a 433 MHz receiver module like this one and also similar to this one. Before I started with the software implementation, I was given a sound card to which the receiver module was connected. I connected this sound card + receiver module to my PC- USB and was able to capture and visualize the RF packets using an audio editing software known as GoldWave-Link.

My question is: How is it possible for a sound card to detect 433 MHz RF signals, whats the principle behind it?

Another question is, on a PC sound card hardware, how do I figure out which points is the Vcc, GND and data input?. For a sound card like this one here


texts: RFID System with protected serial number

texts:
In RFID Technology, usually there is a reader, and RF tag that contains an unique serial number and optionally storage technology.
In the field of access management there are the the fundamentally different solutions:
1.) UID-Based
In these Systems, usually the RFID Tag only contains an unique number that is linked internally in the system to a data. This is generally used for access management in leisure sector or wherever you don't need hard security because for example a ticket can only be redeemed once, even if you made 5 clones of it.
2.) Data Based
In these Systems, the RFID Tags are encrypted with good encryption (e.g. Mifare DesFire) and contain valuable information, for example access parameters for facility doors.
To protect your solution against tags from different manufacturers, you can encode a customer ID to the UID-Based systems that is checked by the reader if the card is from a "genuine supplier" or not. In Data based systems, different manufacturers cannot supply cards because they don't know the encryption.
In both cases, the problem is, that all major RFID Solution (Mifare, NTag, etc) do not allow protection of the UID itself, so even if you encrypt your tags, someone can read the UID with any reader. This allows "reuse" of tags for another system supplier, if their system is UID based
Are there any RFID Card technologies, that need a password/key to read out the UID? If the password is incorrect, it should act like there is no card present at all


texts: Why is DC sqrt(2) higher than AC after rectifing?

texts:
I've Googled this question (and similar questions) but cannot find an answer that I can understand.

My theory was, mathematically speaking, that it would be 1.41 times higher because you get the peak of the sine wave after rectification.  Is this correct?


texts: Will a large amount of constant-power loads make an electrical grid unstable?

texts:
Over time, a larger proportion of electronics are constant-power loads, while they used to be constant-resistance. Will this lead to an unstable grid? If not, why not?

Constant power loads at home are battery chargers, TVs, many appliances.

In a constant-resistance environment, the grid is self-regulating to a certain extent, as if power generation cannot match power consumption, then a slight drop in voltage would reduce the consumption.

In a constant power environment, this self-regulation would not exist, as a slight drop in generator voltage would just lead to an increased current draw and a constant power consumption. This sounds like it would lead to a run-away process if left unchecked.


texts: Can I use a computer UPS with an oscilloscope?

texts:
I recently bought a basic digital oscilloscope and wanted to power my oscilloscope from 600VA computer UPS.
I have two questions:

Can the UPS give isolation from main supply? (As an alternative to an isolation transformer.)

The output of the computer UPS waveform is "simulated sine wave." Will it affect the performance of the oscilloscope?

UPS datasheet


texts: how to calculate DC resistance of transmission line from telegrapher's equation

texts:
Can someone explain to me how to use the transmission line (TL) formula (from telegrapher's equations) to calculate the DC resistance of the TL?

Here's my work so far:

V(x,s) = A * exp(-gamma*x) + B * exp(gamma*x)

where
A and B = complex amplitudes of forward going and backward going waves, respectively

gamma = sqrt((R+sL)(G+s*C))

Assumptions/model:

Telegrapher's model (L,C,R,G constants)
A DC source (Vs) is attached at one end of the transmission line, and the output of transmission
line is a shorted.
G = 0 (no shunt resistance)

I expect the DC resistance of the transmission line to be equal to R*(length of transmission line).

I should be able to calculate the constants A and B from the boundary conditions (voltage = Vs at one end, 0V at other).

However, when I plug s = 0 (DC) and G = 0 into formula for gamma, I get gamma = 0. When using gamma = 0  in transmission line equation, I get V(x,s) = A + B

This implies that V(x,s) is not a function of x at all, which contradicts the boundary conditions.

Please help me figure out where my reasoning went wrong. Do TL equations not apply at DC, and if so, why not?

Thank you.


texts: I have this schematic here I'm trying to recreate in Kicad. I'm lost on the meaning of part "PH_A, P8".


texts:
I have the body of an old Airsoft M4A1 and I had the idea of making it have simulated recoil through a solenoid.

I realize that I can't make something with the kick of a real gun but at least something i could feel, like the arcade games.

I have had some really successful tests with Li-Po batteries, but they were all too big and had bad connection spots. Then I tried 6 AA batteries in series with a 1000 uF 16 V capacitor (I don't know if I am using the right capacitor and if I wired it correctly), but my attempts have failed.

I am new to circuits and electricity, any thoughts on a power source?

The solenoid is homemade and is made up of 14g wire, and functioned well with a 3.7 V 6000 mAh Li-Po battery.


texts: Creating programmable look up table on STM32

texts:
I am trying to define a look up table that is not a constant on an STM32F103. Basically I want to have a page of flash that acts like a constant lookup table in normal operation, but every once in a while (think days apart) I want to be able to erase that table and write a new one to the page of flash. I believe I understand how to use the HAL to functions to do what I need in my program, but it seems like I would need to declare this block of memory in the linker file and I'm having a lot of trouble finding an example that covers that. The default mem.ld from CubeMX looks like this:

MEMORY
{
  FLASH (rx) : ORIGIN = 0x08000000, LENGTH = 128K
  RAM (xrw) : ORIGIN = 0x20000000, LENGTH = 20K
}

It seems like I need an output sections block after that where I commit a keyword to >FLASH but I don't know what keyword that would be or how I would declare the table in the code to give it the right address.

I have seen the emulated EEPROM application note, but it seems like a lot of extra overhead for memory that will not see enough erase/write cycles to be concerned about the memory's lifetime. Help!


texts: I am doing ac analysis of a simple passive RC low pass filter. The input is a 2 V peak to peak sinusoidal signal. R=1.2k and c=12nF. I want to add a 2.5 V dc offset to the input signal. When I change the dc offset value of the signal generator I always see the same magnitude value. With a 2.5 V offset it must be 13.1 dB at low frequencies but I always see 6 dB. So, how can I see the effect of the offset voltage?


texts: How to quantify the cable impedance for common mode voltages?

texts:
Since a coaxial cable is not twisted, in the case of a common-mode interference the positive and negative lines will pick up different voltages. This unbalanced impedance nature of the cable can be modeled as shown below(source output impedance is taken zero):

Imagine a 10m straight coaxial cable. Above Rc1 and Rc2 are the resistance of the inner and the outer cores. Lc1 and Cc1 represents the impedance of the inner core to a common mode interference. Similarly Rc2 and Lc2 represents the impedance of the outer core to a common mode interference.

But for a 10m coaxial cable how can I roughly estimate this Lc1, Lc2, Cc1 and Cc2 values? I want to model in SPICE simulation and see the affect of BNC coaxial cable's imbalance to the CMRR degradation.


texts: Problem with using Timer Counter interrupt on Atmel ARM

texts:
I'm using an ATSAM4E16C microcontroller and i need to get a 1 millisecond tick.
I want to implement this using the timer counter module to trigger an interrupt.
The clock frequency is 96 MHz, so using a prescaler of 128 and a compare of 750 i should get 1 millisecond.
Problem is if i try to activate the interrupt, when the program reaches the delay_ms function if freezes (i think), and the debugger stops working (still connected)

void timer_init(void)
{
    sysclk_enable_peripheral_clock(ID_TC0);
    //init TC0 channel 0 with a prescaler of 128 and WAVEFORM
    tc_init(TC0, 0, TC_CMR_TCCLKS_TIMER_CLOCK4
                |TC_CMR_WAVE
                |TC_CMR_WAVSEL_UP_RC);
    tc_write_rc(TC0, 0, 750);

    // trigger interrupt on RA compare
    tc_enable_interrupt(TC0, 0, TC_IER_CPCS);

}

int main (void)
{
    wdt_disable(WDT);
    sysclk_init();
    board_init();

    irq_initialize_vectors();
    cpu_irq_enable();

    NVIC_DisableIRQ(TC0_IRQn);
    NVIC_ClearPendingIRQ(TC0_IRQn);
    NVIC_SetPriority(TC0_IRQn, 0);
    NVIC_EnableIRQ(TC0_IRQn);

    timer_init();
    tc_start(TC0, 0);

    delay_ms(10);
    thermocouple_init(&thermocouple);
    delay_ms(300);
    thermocouple_read(&thermocouple);
    set_led(true);
}

I've tried also with different interrupt priorities but still the same result.
Any ideas as to why this doesn't work?
Thanks


texts: Reasonable maximum exciting current 60Hz step up transformer

texts:
What should be a resonable exciting current for a 720VA 60Hz transformer? Primary 12V/60A and secondary 110V. I'm measuring about 2A (around 3% of maximum rated current) in the primary while the transformer is idle (secondary open circuit). This is the step up transformer of my inverter project.

Another question: when the transfomer is fully loaded @ 720VA, suppose for simplification a pure resistive load, does this exciting current still represent a loss? I.e, are these 2A still wasted? I understand part of this current is just reactive and part is effectivelly loss. I'm trying to figure out the maximum theoretical efficiency of a system like this.


texts: Error reading characters over serial on ATmega8 using CVAVR (USART)

texts:
I am trying to program ATmega8 for testing purposes using CVAVR as cross compiler and avrdude GUI as burner. Though I am able to burn the program, I think I am missing something in the coding part. It may be quite silly.

I have 2 questions:

I am using Xbee Pro for wireless communication. It works with 5V and my ATmega8 board, I think provided the required voltage. But there is no communication happening with the other Xbee Pro module attached to my laptop. I am using XCTU and have checked the baud rate and other settings. On the other hand, when I used a MAX 232 circuit and then communicate with my laptop using a Serial to USB converter, I was able to send data to my laptop on XCTU. I used putchar("f"); on the XCTU sometimes "." was getting printed and sometimes "K" (then I realized that it was junk).

So I want to ask: is voltage causing problems with transmission?
In the coding part, when I am using MAX, I am using the following code:

 x = getchar();
 if(x == 97)
 {
     lcd_clear();
     lcd_gotoxy(0,0);
     lcd_putsf("x");
     PORTB = 0b00000001;
     delay_ms(300);
 }
 else
 {
     lcd_clear();
     lcd_gotoxy(0,0);
     lcd_putsf("Shailendra Singh");
     PORTB = 0b00000010;
     delay_ms(300);
 }

The rest of code and registers initialization is done by CVAVR itself but this is the code of main concern. What I want is that when I press "a" on my laptop, if operation must be performed but I am confused by

if(x == 97)

97 is the ASCII value of "a". Am I using it correctly by comparing x with 97 (I assumed that when "a" is pressed).

Along with that with getchar(), I can receive only one character, what if I want to receive a full string?


texts:
Question about: "Circuit Analysis Demystified", David McMahon, 2008, Chapter 6, page 131, Quiz question 7.

How to derive differential equation for current?  Example:

$$L~C~ i'' + \frac{L}{R} i' + i = 0$$

where:

$$\begin{matrix}i(0) = 1 & v(0) = 0\end{matrix}$$

for this circuit:

KCL with all currents leaving node:

$$I_R + I_C + I_L = 0$$

$$\frac{V}{R} +  C\frac{dV}{dt} + \bigg(I_L(0) + \frac{1}{L} \int  \limits_{0}^{t} V(\tau) d\tau \bigg) = 0$$

Then I'm not entirely sure how to get rid of the integral.  I suppose I could differentiate the entire equation with respect to d/dt and hope it act as the inverse of the integral..

maybe another problem, is that if I use KCL i'm getting the differential equation for voltage instead of the differential equation for current...

They didn't really specify which current I'm looking at in the Differential equation... maybe its the i_r, i_c, or i_L?


texts:
Recently I have been studying feedback in switching power converters, and one thing that is still a bit confusing to me is the way the error amplifier is implemented. Here is what the control diagram looks like from what I understand:

The thing that is still confusing me is the error amplifier. From what I understand, that block takes the difference of the + and - terminals, and passes that to the next stage. In terms of things I know, you could use a difference amplifier such as this:

When I look at other designs online though, it seems like this is not typically how this is done, and instead the op-amp is driven open-loop with a reference on the non-inverting terminal, and the inverting terminal connected to the voltage divider, like this:

I guess in a sense, it is doing the same as the other implementation, except the gain here is much greater. Are both of these approaches valid? What are the advantages/disadvantages of each?

Thank you!


texts: ESR meter: Are in-circuit readings accurate?

texts:
I recently bought one of these ESR meters, a 'MESR-100':

http://www.amazon.com/MESR100-AutoRanging-Circuit-Capacitor-Tester/dp/B00G7OPBP2

It claims to be able to test capacitor ESR with the caps left in-circuit.  It appears to work well from my tests so far.  However, how much can I trust the in-circuit readings?  Are they going to be less accurate?  Are there certain circuit configurations where it wouldn't be possible to measure ESR in-circuit accurately?

[EDIT: Added the model as requested] :


texts: I designed a 4 Resistance biased amplifer, I used the Voltage divider MOSFET amplifer circuit for 2N7000

texts:
The blue lines in the simulation are the output and the green lines are the input, So I designed this amplifier while trying to limit Id to 200mA and I wanted to Bias the MOSFET such that I get no clipping with a change of ±20% of Vth. I wanted to know what I could change in this circuit to make it better or simpler. I calculated the capacitance for 20Hz and resistance of 67k. I don't know how to choose Rs, I chose 10 to increase the voltage range of the output (I was playing with the simulation).
I have been learning about MOSFETs on my own, so I wanted to try this out.


texts:
I've come across this diagram, I researched a bit, but I don't get what this contact is supposed to do. The circuit below is an audio effect, and I'm confused because it apparently doesn't mean that it will power the circuit when the Jack is connected?
What are your thoughts? Help is really appreciated :).

I post the complete diagram, because i have another contact at the output.


texts: those who are much cleverer than me please help me with this.. Which sensor would be best suited for measuring the intensity of in and out of a person's breathing at rest when the sensor is to be positioned under his nose?


texts: Trying to program an STM32 device with ST-LINK_CLI.exe

texts:
I have a project developed using STM32IDE, all is well and I want to develop a test script to program the devices in bulk, using the STLINK/V2. To do this I want to invoke ST0LINK_CLI.exe
I can connect to the device and erase it fine like this:
ST-LINK_CLI.exe -ME

When I take the .bin file from my project I can program it onto the device but the chip does not run. In addition if I add the -V option to verify, there is a problem:
C:\my_dir>ST-LINK_CLI.exe -P C:\Temp\my_img.bin -V
STM32 ST-LINK CLI v3.5.0.0
STM32 ST-LINK Command Line Interface

ST-LINK SN: xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
ST-LINK Firmware version: V2J37S7
Connected via SWD.
SWD Frequency = 4000K.
Target voltage = 3.2 V
Connection mode: Normal
Reset mode: Hardware reset
Device ID: 0x413
Device flash Size: 512 Kbytes
Device family: STM32F405xx/F407xx/F415xx/F417xx
Loading file...
Flash Programming:
  File : C:\Temp\my_img.bin
  Address : 0x00000000
Memory programming...
▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ 100%
Memory programming...
No OnChip verification function found. Verify after programming will be performed.
██████████████████████████████████████████████████
Reading and verifying device memory...
▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ 0%
Programming error @: 0x00000188

What's the issue? The bin file should be a memory image, right, it does not need to be loaded at a specific address? I've searched and looked in the docs, I don't find a reason that this would not work.
Many thanks.


texts:
As an electronics engineer, I understand one spends a lot of time understanding datasheets. I discovered the skill of reading datasheets is much more difficult than I expected. If anything, a datasheet is not "self-explanatory": a lot of technical background knowledge is assumed.

I have set myself the challenge of understanding most of the content in this DAC datasheet. I already have asked many specific questions about it (see here, here, here and here), and could ask quite a few more.

How is one meant to learn to read datasheets? Is it through experience? Are there guides?

Also, is it meaningfull to try to understand all the contents of a datasheet? Are there sections which are almost always ignored?


texts: I have a question about parasitic inductances. Let's take the figure below as an example, a DPT circuit is shown here. I have added an inductor (parasitic loop inductance). I would like to have a closer look at the switching characteristics of transistors. Should an inductor also be added before and after the diode as well as between diode and MOSFET in order to consider the parasitic effects of the PCB? Or is it possible to keep the parasitic inductances so low (few nH) that they have hardly any effect on the transient processes when designing such a PCB?


texts: If you have a funky Lilypad clothing and it gets rained on or you spontaneously decide to go for a swim in it  :)   what happen?


texts: How to Use Diode Oring to Switch between Two Power Sources?

texts:
I want to switch Power Between a AC/DC adapter which is supplying power to the circuit when AC power is On and when power loss power the circuit using 12V 7Ah Battery. AC/DC adapter is rated 12V 1Ah.

First I thought switch power with a Relay and Arduino with a sensor to monitor AC power loss. but I Came to know there is a better way using a Diode Oring.

Please explain how to use diodes to switch between power Supplies and what diodes to use for this?

I saw that in a article, to Diode ORing to work main supply should greater than backup. so in my case both the main supply and backup supply is 12V.

so Diode ORing option will not work as expected?


texts: Does current in a circuit change when it passes through a resistor?

texts:
When I power an LED (a small one used as an indicator) with a 5VDC, it blows up, but when I use a resistor in series with the LED, it lights.
My instructor calls this resistor  a current limiting resistor.
It is known that current in a series circuit remains the same.
How does the current limiting resistor work in this case, and why does the LED blow without the resistor, even though the current remains the same in both cases?
Below is the schematic of the circuit

simulate this circuit – Schematic created using CircuitLab


texts: Additional TX and RX pins for FT232RL Microcontroller Interface

texts: I'm designing a board that needs to be programmable via USB and external TX/RX pins. I decided to use FT232RL ( http://www.sparkfun.com/datasheets/DevTools/Arduino/FTDI%20Basic-v21-5V.pdf ) for the USB interfacing. For the external RX-TX pins, do I need any logic or jumpers to disable the FTDI chip, or simply if there's no D-,D+ signals, I can use external RX and TX pins, that are connected to both MCU and FTDI, without FTDI chip interfering. Any help is greately appreciated.


texts: I found this transistor on a board that I have no idea where it came from and I want a datasheet of its current and voltage handling. Has anyone seen something like this? I have looked all,over the web for a datasheet and couldn’t fine one. If you can, that would be greatly appreciated!! Thanks for your time.


texts: Wiring a 3.5mm Audio out jack where Speakers were previously

texts:
I'm stumped on this one. My monitor has these cruddy un-amplified speakers that you can barely hear when there is any other sound in the room you are in. My solution was to wire an audio out jack to replace the speakers. Below is how I changed the wiring:

Before putting the final wiring in place I tested this configuration using my phone as the audio source connecting an aux cable with bare ends to the jack of the original cable, then plugging external speakers into the female port. Worked wonderfully.  So i hook in the jack to the monitor, pack it all up, and play something on it. I get immense static over the speakers, and any volume past a certain point cuts out the audio altogether. My hunch is that twisting the two grounds together is what is causing this issue, but i'm not experienced enough with electronics to know how to resolve this.

Am I stuck with the original cruddy speakers, or is there a way to do this correctly?

EDIT:
Also here is how I wired up the 3.5mm jack for reference:

EDIT 2: I have tried isolating one channel as others have suggested, this yielded the interesting result of preventing the cut-outs from audio peaks, but the intense static remained. I've also tried reversing what I assumed were left channel and ground, and that did not work.

I guess what I'm looking for most is that my logic with this correct? can you replace a stereo speaker output with an aux jack reliably? is this just a fringe result where it typically would be a success?

EDIT 3 (5-5-17):

Finally got a chance to wire it up how Trevor specified, still same issue, heavy static on the line through my amplified speakers, then I tried something that yielded an interesting result. in my frustration I figured I'd test the setup with a different speaker, just to see, but I only had a pair of headphones handy. I plug them in and nothing. Dead air. Through the speakers I get heavy static and distant speaking (no warble now that I've removed the two middle wires) but through the headphones I get dead silence. Maybe this is the clue that breaks the case?


texts: Help Identify Potential BLDC Protection Circuit

texts:
I am trying to determine the function of a small circuit on a separate PCB that feeds a more complex Brushless DC Motor PCB. As far as I can tell (from physically measuring between 9V-24V) the output voltage equals the input voltage.

I'm trying to understand why I couldn't just bypass this circuit and directly connect a voltage source. Is this some kind of protection circuit?

The two unidentified capacitors are ceramic SMDs about 1.5mm x 3mm.


texts: Why is the current wrong after resistors in series with simple LED?

texts:
Setup

source --- 1.5V batteries x2 = 3V
LED --- 2V 35mA http://www.futurlec.com/LED/LED5R.shtml
Resistors --- CR1W 1W 10ohm +-5%  x 4 = 40ohm

Description

I have your average "Light up a LED" experiment. I have a 3V source(worn out to 2.72 now) followed by 4x 10ohm resistors and a 2V 35mA LED.

Problem

3V... need to drop that 1V on the resistors and the current below 35mA... LED lights up but the reading is wrong! I get 2.08V after resistors which is good. But my current reading after resistors reads 58mA. Since current in series is said to be same for all circuit, it was supposed to be 1V/40ohm = 0.025A = 25mA(worn out now, so: 0.66/40 ~= 16mA). Why on earth is it 58mA?

I have tested the resistance between source and before LED(right after resistors), reads 40ohm.

Any ideas? I'm lost :(


texts:
I found this circuit in an old book.  It is a two stage audio amplifier

I wanted to try it but I didn't know how to do the dc analysis.

I couldn't find any current.
Could you help me to find a first one?  After that, I can find the rest.


texts: Buck converter or a linear regulator for a low current 3.3V source

texts:
I'm currently building a power module to power a few raspberry 3 pis and a set of microcontrollers. For the 5V power source, I'm using a buck converter for efficiency to deliver 5 Amps to power the pis.

However, I'm not too sure if using a simple linear regulator to source a 3.3V rail would be better than using another buck converter, as the load would only be within the mA range?

I'm using a set of batteries to power the power module too, so I'm trying to be efficient as possible.


texts:
I'm starting to work with stepper motors and I'm not sure what the conventional way of denoting a current rating is.
I've attached a picture of what looks like a 2 phase bipolar stepper motor and the current rating is specified as 2A. Should I interpret this as 2A per phase or 2A in total?


texts: I am looking for recommendations how to lower the noise in this preamplifier circuit

texts:
I have a circuit using MMBT3904T-7-F parts, operating at 100uA collector current, which is rather noisy.  This is a preamp for the 475kHz ham band.

I need to stick with bipolar NPN.

How can I lower the noise in this circuit?


texts: Using 1 IR receiver for 4 LED controllers

texts:
I've purchased 4 cheap LED controllers from China for controlling 20m LED stripes.
After setting the system up, I encountered the problem that at least 1 of the 4 LED controllers doesn't respond to the signal from the IR remote.

This is a real problem if I want to turn them off, because 1 out of 4 doesn't turn off and if I press the ON/OFF button again, it may turn off - BUT - the other 3 LEDs turn on again.

The controllers look like this:

So I had the idea to remove 3 of the IR antennas and only use 1 IR antenna for all 4 LED controllers.

Here's the schematic for this:

The problem: It doesn't really work (well it did for ~10 minutes). Now the LEDs are not lighting up anymore.

Is my circuit wrong or have my LED controllers gone broken? (The LEDs are fine - i tested it with a different LED controller)


texts: I have a 3 phase power at home, the third line is always at 220V, why is this the case?

texts:
I have a 3 phase 220V power at home and L1, L2, L3 is at 220V.
When I measure the voltage using my electric meter as follows:

L1 & L2 = 220V
L1 & L3 = 220V
L2 & L3 = 220V

Yes my electric power at home is 220V, but I wanted to have a 110V socket at home so what I did was take L2 and take another line from the grounding rod which is earth from the ground, and the output changed to 110V, I did it.
What I'm really curious about is when I take L3 and earth ground it always outputs at 220V.
Why is this the case?
I did a test to make sure:

L1 & earth ground = 110V
L2 & earth ground = 110V
L3 & earth ground = 220V

Can someone explain to me why L3 is always at 220V?


texts:
I have an application where I need to make a ADC input pin (0-1V) float controlled by GPIO (any connect it in other cases to its input obviously).

I was considering a transistor in-line with the ADC input but that does not seem feasible since neither collector nor emitter have a defined voltage.

Does there exist a solution apart from a mechanical relay?


texts: How many periods of an electromagnetic signal are required to be detectable?

texts:
Lets say you want a receiver circuit to light up an LED when it receives a radio wave pulse.

How many periods must the emitted pulse last to generate enough electric current to be detectable and amplified by the receiver? Is one enough or do we need a hundred of them? What would the amplifier schematic look like?

PS: This is related to another question.


texts:
I'm fairly new to micro controllers especially the Pic series. I have a question about the TMR0 of the pic16F877A.

I am aware that TMR0 is an 8 bit timer, which takes a total of 256 ticks until an overflow occurs. My configuration runs on a 4MHZ quartz crystal, therefore each tick is equal to 1us. A total time of 256us will cause an overflow keeping in mind the prescaler is chosen to be 1:1.

After simulating this delay by setting bit RB1 equal to (HIGH), a total delay of 265us was measured using proteus 7. Where is this discrepancy coming from? Thanks in advance.

Code:

#include <xc.h>

#define _XTAL_FREQ 4000000

    #pragma config FOSC = HS
    #pragma config WDTE = OFF
    #pragma config PWRTE = OFF
    #pragma config BOREN = OFF
    #pragma config LVP = ON
    #pragma config CPD = OFF
    #pragma config WRT = OFF
    #pragma config CP = OFF

void main()
{
    TRISBbits.TRISB1=0;
    PORTBbits.RB1=0;

    TMR0IE=0;
    TMR0IF=0;
    T0SE=0;
    T0CS=0;
    PSA=1;
    TMR0=0;

    while(1)
    {
    while(TMR0IF!=1);
    PORTBbits.RB1=1;
    TMR0IF=0; //I assume it takes 1us
    TMR0=0; // Also 1us?

    while(TMR0IF!=1);
    PORTBbits.RB1=0;
    TMR0IF=0;
    TMR0=0;
    }
}


texts:
In the image attached above, the book uses I2 = V2/Z2. However, the question says "primary is excited by 200V". So, V2 should be 100V. Is the solution wrong then.
Question for reference: Question
Book : Basic Electrical Engineering, McGrawhill


texts: STM32F4 HAL - PWM Phase shifting channels on the same timer

texts:
I've configured my STM32F407VG (STM32F4Discovery) TIM4 timer using the following code:

void TIM4_Init(void)
{
    // Configure TIM4 for PWM
    hTim4.Instance = TIM4;
    hTim4.Init.Prescaler= 42000 - 1; // (84MHz / 42000 = 2KHz)
    hTim4.Init.CounterMode = TIM_COUNTERMODE_UP;
    hTim4.Init.Period = 2000 - 1; // Period = 2000 -> 1 second
    hTim4.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
    HAL_TIM_PWM_Init(&hTim4);

    // Configure channels 1-4 for TIM4,
    // each channel is mapped to a GPIO pin
    TIM_OC_InitTypeDef oc_config;
    oc_config.OCMode = TIM_OCMODE_PWM1;
    oc_config.Pulse = 1000;
    oc_config.OCNIdleState = TIM_OCNIDLESTATE_RESET;
    oc_config.OCIdleState = TIM_OCIDLESTATE_RESET;
    oc_config.OCFastMode = TIM_OCFAST_DISABLE;

    HAL_TIM_PWM_ConfigChannel(&hTim4, &oc_config, TIM_CHANNEL_1);
    HAL_TIM_PWM_ConfigChannel(&hTim4, &oc_config, TIM_CHANNEL_3);

    // Flip the OC polarity for channels 2 and 4
    oc_config.OCPolarity = TIM_OCPOLARITY_LOW;
    HAL_TIM_PWM_ConfigChannel(&hTim4, &oc_config, TIM_CHANNEL_2);
    HAL_TIM_PWM_ConfigChannel(&hTim4, &oc_config, TIM_CHANNEL_4);

    // I want to shift channel 1-4 90 degrees apart...
    HAL_TIM_PWM_Start(&hTim4, TIM_CHANNEL_1);
    HAL_TIM_PWM_Start(&hTim4, TIM_CHANNEL_2);
    HAL_TIM_PWM_Start(&hTim4, TIM_CHANNEL_3);
    HAL_TIM_PWM_Start(&hTim4, TIM_CHANNEL_4);
}

Each channel is mapped to a GPIO pin, with the intention of driving a stepper motor.

I would like to generate a signal, with a duty cycle of 25% each, where the phases have been shifted 90 degrees apart.

How do I go about shifting the phases on the 4 channels?

Should I setup another timer, and use it as an interrupt upon which I can call HAL_TIM_PWM_Start() for each channel at the appropriate timing?


texts: Solid-state Electronic switch for low level signals

texts:
I need a very simple circuit to connect a signal to one of two ways like this:

My com signal is actually a microphone input, so very low voltage, <200mV, how can I make a solid state switch that not interfere with the low voltage signal? So com can go to L1 or L2 with no distortion. Im planning to actuate the switch with TTL voltage.


texts: Accessing SWO on STM32H743 hangs the CPU

texts:
I'm trying to initialize the debug trace SWO output pin on STM32H743. I have tried various code snippets for initializing the port, currently this one:

void SWD_Init(void)
{
  *(__IO uint32_t*)(0x5C001004) |= 0x00700000; // DBGMCU_CR D3DBGCKEN D1DBGCKEN TRACECLKEN

  //UNLOCK FUNNEL
  *(__IO uint32_t*)(0x5C004FB0) = 0xC5ACCE55; // SWTF_LAR
  *(__IO uint32_t*)(0x5C003FB0) = 0xC5ACCE55; // SWO_LAR

  //SWO current output divisor register
  //This divisor value (0x000000C7) corresponds to 400Mhz
  //To change it, you can use the following rule
  // value = (CPU Freq/sw speed )-1
   *(__IO uint32_t*)(0x5C003010) = ((SystemCoreClock / 2000000) - 1); // SWO_CODR

  //SWO selected pin protocol register
   *(__IO uint32_t*)(0x5C0030F0) = 0x00000002; // SWO_SPPR

  //Enable ITM input of SWO trace funnel
   *(__IO uint32_t*)(0x5C004000) |= 0x00000001; // SWFT_CTRL

  //RCC_AHB4ENR enable GPIOB clock
   *(__IO uint32_t*)(0x580244E0) |= 0x00000002;

  // Configure GPIOB pin 3 as AF
   *(__IO uint32_t*)(0x58020400) = (*(__IO uint32_t*)(0x58020400) & 0xffffff3f) | 0x00000080;

  // Configure GPIOB pin 3 Speed
   *(__IO uint32_t*)(0x58020408) |= 0x00000080;

  // Force AF0 for GPIOB pin 3
   *(__IO uint32_t*)(0x58020420) &= 0xFFFF0FFF;
}

However whatever I do, the CPU hangs during the SWO register access. This also causes debugger to lose connection. If I comment the SWO register initialization lines, the code runs ok but of course SWO output doesn't work.


texts: How does Instruction Code tell an automated adder what to do? (Charles Petzold Code book, Chapter 17 Automation)

texts:
I'm reading Chapter 17 of Charles Petzold book Code (which is excellent) and in it he's describing an automated adder which he's adding different Operation Codes or Instruction Codes.

In the diagram, he has an output for an 8 bit latch which says "Code", but it doesn't connect to anything else.

I'm just wondering how does the Op code instruct/tell the adder what to do (add/subtract/jump/halt/etc).

I'm guessing that it must change the control signals for different parts of the adder, but how does it recognize each Op Code?

Is it a lot of AND gates and Inverters? that connect to the control signal inputs of the other parts?

Thanks and by the way, I'm a newbie trying to understand and haven't even got to transistors or chips or anything else yet, so may not understand anything above a layman's explanation! And sorry if this question is a bit basic.


texts: Are there cases for Phidgets IO boards such as the 1019 ?


texts: Is there a difference between an NFC and RFID chip?

texts: The other day, my friend said that he wants to write an app that uses the NFC chip on a phone to read pet microchips. I told him I was pretty sure that pet microchips don't use NFC, but he said he was pretty sure they did. So I hopped onto Wikipedia and read the article about pet microchips. Sure enough, Wikipedia told me that pet microchips operate on RFID. My friend said that they were the same thing. Is he right, or just talking through his hat?


texts:
I understand about input impedance and capacitance... My question relates to the cable: What is the characteristic impedance of the cable connecting the probe to the scope? It must be terminated in a matched impedance to avoid reflections but the input impedance is typically 1 M ohm in parallel with a few pF - that can't be the characteristic impedance.
So what gives?

I have noticed that the cable has a centre conductor that is very small in diameter - is that to create the correct Z0?

I've been asking this question of professional EEs for many years and no one knows...


texts: H Bridge runs for few minutes and MOSFETS start smoking

texts:
I have created an H bridge as shown in the schematic below.
PWM signal to the MOSFET driver is given by a microcontroller running on 5V.
The MOSFETS are screwed to heat sinks.

To control the motor direction I set either one of the driver inputs to 0 and another driver input to PWM.

I am using a 10kHz frequency for PWM.

For clockwise rotation, I use a 40% duty cycle PWM signal on IN1 and 0V input on IN2.
For anticlockwise rotation, I use a 20% duty cycle PWM signal on IN2 and 0V input on IN1.

Now, In the code, I turn the motor clockwise for 1 second, Set both IN1 and IN2 0 for 50ms for braking, and turn the motor anticlockwise for 1 second.

The circuit worked fine for 3 minutes, but later Q3 MOSFET was smoking first, and the rest other MOSFETS also followed the same, the motor was stuck at the braking condition.

Mosfets don't get warm during normal operation.

I don't understand what I am missing here.
Even the frequency is not that High.
The rise and fall times of Mosfet are at worst 150ns according to the datasheet.

Am I missing a snubber circuit? I yes how to properly design one.

Motor nominal current is 1.5A and the stall current is 8A.


texts: AC analysis on transient model of Buck converter

texts: I'm unable to understand why can't we run AC analysis on a transient model of Buck converter.


texts:
Is there a way to connect transformers secondarys so that I get only two output wires and not three(It doesent mater if the wires aoutput 3 phases or 1 phase or some wierd signal).

This is step down transformer and it outputs big current.Tranformer now is set to 8 V AC output.

And will the transformer draw equal from all 3 primaries.

This is the schematic of transformer.


texts: How to throttle power consumption of a heating coil?

texts:
Which is an appropriate but simple electrical circuit to reduce the energy (power) consumed by a heating coil which has an AC feeding without generating an asymmetric load (large DC component, e.g. with a diode)?

I know that this would make it cooler.

Some heating coils consume a lot of power (kilowatts), so a simple resistor in series would be a bad idea (difficult to cool). A capacitor in series is also very easy, but way to expensive for the two months application I want it for.

I think what I need is a kind of dimmer, a thyristors or triac. But I want to have a fixed rating, it doesn’t have to be adjustable. Of course I have no problem if it is adjustable if the electrical network is still easy to understand and to build.

E.g. if my power source is 230 V AC, 50 Hz. The heating coil has a power consumption of 2300 Watts at this voltage but I want it to consume only 1400 Watts, which parts are most recommendable and how would the circuit look like (or what is it’s name, I could then search for it).

PS: This is the second attempt to ask this question. The first one was to specific on my dishwasher and inverter, but also got some interesting answers.


texts: How to calculte mosfet capacitors (Cgs Cds Cdg) knowing the charges Q

texts:
I need to use the best model for the MOSFET in my circuit I'm simulation on PSIM, the MOSFET is Si4108-TI-GE3.

But I am not given the parasitic capacitance values (Cgs Cds Cdg), I am only given this:

I think I should use Q=CU, but I don't see how to use Q=CU for Cds since I only have Total gate charge and I don't know if that is the drain-source charge. How do I calculate the necessary parasitic capacitance values?


texts: I am doing this project on Low noise amplifier using 3503M04 HJFET.My instructor insists I use some resistor in series with the drain to make it more stable.It actually gives a K factor of greater than 1 if I add the resistor (I am doing K delta test The Rollet's condition)....My question is why does this decrease S21? Imagine the resistor trapped between drain and port 2.


texts: What does "Current Detection" feature mean in KNX actuators?

texts:
I understand that KNX/EIB actuators are used to switch on/off lights in fancier homes.  Some of these actuators have "current detection" feature, and some do not.

What can that feature do?

Is it for systems where you may want to know much power each circuit is consumes?  Or is it a safety/protection thing?

This question should be tagged KNX/EIB, but these tags don't exist.

Examples:
https://library.e.abb.com/public/cfaa4977bc174ddaa7c6da77c9f46ce0/Technical%20Data%20SAS%20x1661.pdf

http://gvshome.com/product/gvs-kbus-switch-actuator-8-foldwith-current-detector/


texts: Issues with SPI slave select on PIC18F4321

texts:
I'm trying to get 3 PIC18F4321s to communicate using SPI, with one of them in master mode and the other 2 setup as slaves.  We first got it working with just 2 devices and no SS (slave select) signal with no issues.

We then added the second device and enabled SS and physically switched the SS wires between 5V and GND and it worked as expected, but when we had the master alternate two output pins between 5V and GND and hooked each up to one of the slaves SS pins, the communication stopped working.  We hooked the SS lines up to a scope and could see they were switching the way we expected them to and we had significant delays in to make sure they were never enabled at the same time and that there was time between SS going low and SSPBUF getting loaded with the data.

There doesn't seem to be a difference between physically switching the wires and having the uC do it if there are delays, so the only thing we could think of was that the master couldn't drive enough current to the slaves, but I would think that the SS pins are a pretty high impedance, so I am not sure what could be wrong.  Any suggestions would be greatly appreciated.


texts: What are tin whiskers and what causes them?

texts: I can imagine what they might be, but how and where do they form and what causes them?


texts: I was wondering which waveform suits the best for ultrasound sensing. For instance, if I am going to detect distances to the objects, does it matter if I send sawtooth, square wave or pure sine wave? It is really interesting how will it affect the analysis of the received signal, might there be a possibility that some kind of waves would get less resistance in air, or would they reflect better and etc. I would appreciate your help on the topic.


texts: What is the difference between Flash memory and EEPROM?

texts: Flash memory storage and EEPROM both use floating gate transistors for storage of data. What differs between the two and why is Flash so much faster?


texts: Improve this schematic to guarantee 12V and 70 mA in the fan

texts:
I would like to learn how to correctly design a circuit to drive a fan using a mosfet and a battery as a power source. These are the characteristics:

FAN

Model: SPDL8025S
Rated Voltage: 12V
Operating Voltage Range: 6-13.8V
Rated Current: 70mA

MOSFET

In principle, now I only have these two N-Mosfet to test the circuit:

IRF730
IRF540N

BATTERY

Nominal Voltage: 14.8v
Voltage at end of Discharge: 12v
Charging Voltage: 16.8v

The schematic that I have thought to use is this:

simulate this circuit – Schematic created using CircuitLab

QUESTION

Because the range of the battery is between 12-16.8V. What would have to change in the schematic to guarantee (approximately) 12V and 70 mA in the fan?


texts: How does this voltage-reference circuit works

texts: I have been trying to understand how this circuit works for the past few hours, it is supposed to be a voltage reference circuit that uses a zener diode, I am supposed to derive an expression for Vout given a Vz, I dont know if it there is supposed to be a current going through R4. Can somebody help me please.


texts: 60335-1 27.5 Test - Am I doing this right?

texts:
I work at company producing household appliances, and I'm looking into a way to test compliance with part 27.5 of the NEN-EN-IEC 60335-1 standard (which is derived from IEC 60335-1).

It states (emphasis theirs):

  The connection between the earthing terminal or earthing contact and earthed metal parts shall have low resistance.

  If the clearances of basic insulation in a protective extra-low voltage circuit are based on the rated voltage of the appliance, this requirement does not apply to connections providing earthing continuity in the protective extra-low voltage circuit.

  Compliance is checked by the following test.

  A current derived from a source having a no-load voltage not exceeding 12 V (a.c. or d.c.) and equal to 1,5 times rated current of the appliance or 25 A, whichever is higher, is passed between the earthing terminal or earthing contact and each of the accessible metal parts in turn.

  The voltage drop between the earthing terminal of the appliance or the earthing contact of the appliance inlet and the accessible metal part is measured. The resistance calculated from the current and this voltage drop shall not exceed 0,1 Ω.

  NOTE 1 In case of doubt, the test is carried out until steady conditions have been established.
  NOTE 2 The resistance of the supply cord is not included in the measurement.
  NOTE 3 Care is to be taken to ensure that the contact resistance between the tip of the measuring probe and the metal part under test does not influence the test results.

I thought of the following way to do this:

simulate this circuit – Schematic created using CircuitLab

By switching lamps on or off, the current can be chosen, in increments of about 8.3 amps. The diode is there to ensure the voltage doesn't go above 12 volts. Test point B will be connected to the device's earthing contact/terminal, and test point A will be used to test the various earthed metal parts of the device's housing.

My questions are these:

Is this a good way of testing compliance to this part of the standard?
I'm thinking of using a computer PSU (ATX) to supply the 12 volts. Is there a reason I shouldn't?
The lamps are halogen ones. Good idea? (I am aware of their PTC tendencies, the presence of the ampmeter fixes that.)
I figure 15AWG (or 1.5 mm²) will be sufficient for wiring all of this?
Anything else I'm not thinking of?

EDIT

Power resistors will be used in stead of lamps (due to initial resistance being to high, and PTC behavior)
4mm² (or 11-ish AWG) was suggested, to prevent measurement error problems


texts: Wirelessly get the current date and time

texts: I know there is a wireless signal all over the US (at least) sending out the current date and time. Some clocks use it so they don't need set, just not sure what its called. Is there a module or a circuit out there to listen to this to get the time into a MCU?


texts: LM2576-ADJ bipolar power supply troubleshooting

texts:
I'm hoping to find some help here troubleshooting.
The circuit in question is a bipolar power supply that makes use of two LM2576-ADJ. The desired output voltage is +12v and -12v. I've breadboarded this circuit before ordering the PCB, and it seemed to work exactly as intended, where the 20k trimmer sets a positive and negative output voltage between ~1.23 and ~14V.
However, on the PCB, it doesn't function properly. The negative output voltage always reads as -13.4V and doesn't adjust with the trimmer. The feedback pin of the corresponding LM2576 reads instead as -11.5V.
On the positive voltage side, upon powering on, the output voltage slowly rises from about 2.5V to 12.4V. Here, the feedback trimmer also has no effect on the output voltage. The feedback pin on this LM2576 instead reads the same as the output voltage.
Here is a link to the datasheet. On page 22 you can find the schematic from which I based the voltage divider part, and on page 19 is the inverting buck-boost version.
Do you think the problem is related to the feedback resistors? Why does the voltage slowly rise on the positive side?
The input voltage used is 12.68V, from a 12V DC adapter.
Here is an image of the schematic, and also of the PCB layout.


texts: Arduino AC Motor Control and Automation?

texts:
My question is about the automation of single phase AC motors.

I am aware that I can purchase TRIAC controllers with manual knobs or even 0-10V control inputs.

I am new to the world of AC controllers so I would like to know if there are many other kinds of controllers with different control inputs. If so which is the most suitable for automating with an output from an Arduino?

Ideally I would like to obtain a controller without the need for 'hacking'. If that is necessary are most of the 'knobs' to adjust AC speed controllers just a potentiometer?


texts: Can't identify these elements in this schematic

texts: could anyone help me identify these elements I have highlighted in red in this schematic? I'm trying to learn how to read schematics and am making a lot of progress but since this document is from the 70s early 80s it uses some non standard symbols.


texts: Resistor in series with Solenoid Valve (for voltage reduction)

texts:
I have a question regards the use of a resistor in series with a latching solenoid valve.  Specifically, I have a valve that wants to see 14 Volts, but my power supply is 28 Volts.  So if I put a resistance equal to the steady-state valve resistance (which is 9 ohms), then the valve will never see more than 14 Volts.  However the resistor will also limit inrush current, which is not necessarily a good thing, if it is needed to get the valve moving.  So my question is whether valve performance will be degraded by having the resistor in series, versus what these valves normally see, which is essentially an infinite source powering them (i.e., low series resistance)?

Any help would be greatly appreciated.

Thanks, Jim


texts:
The diagram below shows a capacitively coupled parallel RLC resonator. Through simulations I observe that C2 and C3 influence the resonant frequency . I'd like to obtain the analytic expression for the resonance and eventually calculate S parameters. What would be the good approach to analyze this circuit  ?

simulate this circuit – Schematic created using CircuitLab


texts:
I have a 10 years old but slightly used Sanwa YX360TRF analog multimeter I hide in a cabinet I removed batteries. I used it, very rarely and I took extra care to remove batteries when not in used. A month ago, I put fresh new batteries on it, and then I noticed that I am unable to zero-ohm adjust in the usual way that I'm able to do in the past. When I short the probes, the needle only moves very lightly, no amount of ohm-adjuster can zero-ohm it. The DC measure is still fine. The fuse is fine.
I just bought a new Fluke 17B+ DMM and I wanted to diagnose and fix the analog one so that I'll have an extra analog meter. I opened-up the Sanwa YX360TRF and checked the insides, looked shiny and no visible suspect. How do I fix this analog meter?


texts: I am going to blink with LED from MCU I/O port. Where do I need to connect LED: VCC ot GND? I think it might be a difference whether the current goes into the inside MCU (when the port is low level and LED is connected to the VCC) or the current goes out from the MCU's port (when the port pin is high and the LED is pulled down to the GND). Is one of them better than another or they are equal and why?


texts: Can Arduino IR Recievers Detect Signals from IR Flashlights?

texts:
If one has an IR reciever module similar to this and a IR flashlight like this, would the IR signal be able to be detected by the module? If not then, why?

From what I understand, these sensors don't have a particularly long range. They seem to be primarily intended for use with remotes. So, I'm not expecting to be able to do anything too fantastical here, but rather I'm simply interested in the proof of concept and/or any tinkering to make them interface better.


texts: What is \$V_{ADJ}^{+}\$ and \$V_{ADJ}^{-}\$ for this adjustable delay schematic?

texts:
Here is the adjustable delay schematic,and as i know,the \$V_{ADJ}^{+}\$ and \$V_{ADJ}^{-}\$ is off chip for testing ﬂexibility.

But i'm curious that the delay is for the time delay,why should we feed the voltage to it?If we don't feed voltage to \$V_{ADJ}^{+}\$ and \$V_{ADJ}^{-}\$,is this schematic still a delay schematic?but if we don't feed it,where should i connect the gate of \$M_{PGm}\$ and \$M_{NGm}\$ to?

blue wave is \$V_{DLY}\$,output.Red line is \$V_{CP_PK}\$,input.

\$V_{ADJ}^{+}\$ connect ground,and \$V_{ADJ}^{-}\$ connect \$V_{DD}\$


texts: What's the advantage of lead-free solder containing silver?

texts: I'm looking to buy some lead-free solder. There appears to be two different kinds available, tin-copper alloys and tin-copper-silver alloys. What advantage does the latter have, as it is more expensive?


texts:
I recently saw a circuit that implemented a BAV99, which is just two diodes, between +3.3V and GND. How does this work? Based on the spec sheet, the fwd voltage varies based on the current. Am I to interpret it as the first diode connected to ground dictating that the voltage abide by the fwd voltage (that is, pin 3 shows 1V given 50mA), and that the upper diode to +3.3V doesn't come into effect until the pin 3 voltage is at (+3.3V - 1V [upper forward voltage])= +2.3V? But how is +2.3V ever reached if the bottom diode clamps it to its own forward voltage?

Any help is greatly appreciated - thanks!


texts: Digital input to mobile phone headset port?

texts:
This seems to be a common smartphone project, but I haven't seen circuit diagrams with explanations.

What filter network (or resistor network, or other buffering circuitry) should be used to connect a 3.3V digital output (say from an Arduino or similar) producing a square wave at a suitable audio frequency (say around 300 to 3000 Hz) to the microphone input on the headset jack of a typical mobile phone (say an iPhone 4), so as to:

not damage the mic input circuitry of the phone,
provide a reasonably high signal-to-noise ratio, and
not significantly distort the spectral portion of the digital square wave that is within the mic input audio frequency bandwidth?  (to allow experimentation with digital modulation schemes beyond simple FM.)

ADDED: The following text has been moved to a new question:
In the opposite direction: how should a mobile phone headphone audio output be interfaced to a microcontroller digital input?  (assume no audio frequency capable A/D is available.)


texts: Dimming multiple power LEDs with individual constant current PSUs from a single arduino?

texts:
Main question: how to individually dimm (PWM) multiple power LEDs that are each powered from a separate constant current power supply, and do this dimming from a single arduino?

I have 10 LED fixtures already installed in my ceiling and running from 220AC. Each LED is driven from individual constant current power supply giving 320ma and 2-12V:

I want to make a controller board that would enable dimming those LEDs. I am on a tight budget for this project, so my goal is to reuse those PSUs.

I will make a custom PCB with Arduino-loaded Atmega328P as the brains, 74HC595+ShiftPWM for expanding PWM outputs and a bluetooth module to control it from my smartphone.

After browsing this site I found suggestions to use MOSFET in series with LED and PSU to PWM it. However, in my case there are 10 LED-PSU pairs, and in order to PWM them the same way I would need to connect all of theirs GNDs together, and also connect them to GND of the 5V supply that will power controller board. Since those LED PSUs are somehow "smart" devices (they constantly monitor current?) and I am not as smart as they are in this field, could this common GND for everything somehow mess things up? Or am I just being over-paranoid due to my lack of competence? This is what I am talking about:

So I guess this rephrases the question to: "can multiple constant current and constant voltage PSUs share common GND without interfering each other?

I have only included 8 LEDs and no other parts in this schematic for sake of simplicity. While browsing the net I found dedicated ICs for driving multiple power LEDs (e.g. STP04CM05), but I want to stick to what I already have.

And another question: do I have to pull-up or pull-down MOSFETs' gates? I've read it, that MOSFET's are charge-activated and removing voltage from gate does not necessary turn it off if there is no electrical path to lose this charge. On the other hand I can see that original ShiftPWM board does not contain any pull-ups/downs and seems to be working fine. Is it something special about this shift register (74HC595) or am I missing a point somewhere? I am planning to use PMV28UN MOSFETS.

Thanks in advance for Your answers!

P.S. This project is a bit larger in scope - the same board will also be driving 4 RGB LED strips, but I wanted to keep it off-topic as that part does not raise any questions for my so far.

N.B. In my defense, I have no formal electrical education, only some very general knowledge and this will be my first self-designed board.


texts:
As part of my research, I'm doing calculations on a hypothetical high-current (4000 A) medium-voltage (5000 V) DC power transmission system using two parallel busbars. However, I need to decide how the busbars are oriented relative to each other, and I can't find information on what best practices are for this. Are there best practices, or does it really depend on the situation?

The main question I have is this: Should the busbars have their long or short sides facing each other; that is, should they be arranged with cross-section like this?

or like this?

(assume the ground plane is to the right, if that makes a difference.)

Edit: Come to think of it, should the ground plane be to the right? I assumed that would be best because we want symmetric impedance to ground on both the positive and negative busbars, but if there's a compelling reason not to, do let me know.


texts: Capacitors not keeping charge as expected

texts:
I have a voltage doubler charge pump that is used to provide voltage over an IR LED for a short pulse, I also have a driver circuit for the LED to sink the right amount of current that I am requiring. Individually, these two circuits work fine, with no load over the charge pump, there is a nice pulse up to double the input voltage (which could be anywhere from 2-3VDC), and with a constant supply over the LED driver, it sinks the right amount of current as I am expecting. Below is a circuit diagram of what I am talking about to make it more clear:

simulate this circuit – Schematic created using CircuitLab

On the right is the charge pump and on the left is the driver.
Now this circuit does kind of work for a 3V input, ie. gives out the current I am looking for ~150uA, but there is no spike in voltage over the LED that I can see on a scope where there should be. I believe the problem lies within the Charge pump side of things as the driver does give the right current given the proper voltage over the LED. The thing is, I am running out of ideas as to how to get it to work with a voltage as low as 2V ao if anyone has any ideas, that would be great!

It is probably very worth noting that the +2VDC I have put going into the transistor bases, is in fact a pulsed signal rather than a constant 2V supply, sorry for any confusion.


texts: Altium: One resistor, or multiple resistors on your lib?

texts:
How you deal with resistors and capacitors in Altium?

If you have a single resistor/capacitor, it is easy later to change values, etc, but how do you deal with the BoM later?

But, if you have different components, i think it is a nightmare!! there are so many!! with links, etc. And I think, you have the same problem here, because for a resistor, there are many supplier id's...

How do you manage all this?


texts:
I'm currently making a radio controlled fighting robot and have pulled apart some drills which have a brushed RS550S DC motor (0.5Nm 18V 60A so 1080W) and a gearbox attached.
Right now I'm looking at replacing the brushed DC motors on the gearbox with a brushless motor because I can't find any ESC's that would work with a brushed motor at 18V 60A.

So my question is how can I find an equivalent brushless motor to replace the brushed motor. I have seen people say brushless is more powerful etc but I have no proof of that. Can a 14.8V 45A 1400KV brushless motor potentially have the same torque as a 18V 60A brushed DC motor? I can't find much info on torque for brushless motors which is why I'm asking here and I don't want the motor blowing up my gearbox particularly quickly. Is it as simple as if the brushed motor is 1080W I need a 1080W brushless?

Thanks
If you need any further details I'll be happy to provide.


texts: LT Spice incorrect output voltage for boost converter

texts:
I was simulating this simple boost converter circuit in LTSpice and it always gives an incorrect output voltage. (Almost 500V, compared to 444V obtained by calculation).

As the IRF430 model is not available in the software, I tried using the model given in Infineon website, producing the following plot for output voltage.

Then I tried the simulation replacing the model with one given in a book which produced the following result.

Then I simulated the same circuit in Cadence PSpice using same parameters, and surprisingly it produced an output waveform similar to the second result with the final stable output at ~444V. Was I doing something wrong in LTSpice or can this be considered a bug in the software?


texts: Why are reversed geometry (0306, 0204) capacitors not used more often?

texts:
It seems that reversed geometry or low inductance ceramic chip capacitors (MLCCs) are simply better in every spec than regular geometry, and may allow using just one value to bypass instead of two (eg a reversed 1uF instead of a 1uF and 0.1uF).  Despite that, they seem to be a specialty/unusual part (for example, Digikey stocks 6M of the most common 1uF 0402 but only 60k of the most common 0204).

Why is that?  Are there any hidden drawbacks?


texts: What is the difference between a hard module and a softmodule in RTL verilog code?

texts:
I understand a Verilog code is made up of modules there are RTL codes where a lot of submodules can be instantiated in the main module. If I assume the main module(the top one) to be the parent and all the other submodules instantiated inside children.
The child can be hard module or a soft module, I kind of know the difference but want a better explanation if possible


texts: Is it possible to read a 10 by 10 switch matrix with 8 by 8 I/O pins?

texts:
I was asked this question on an interview: given 8 output pins and 8 input pins on a microcontroller, is it possible to read a 10 by 10 switch matrix without using multiplexor and demultiplexor chips?
I'm not sure it's possible...


texts: How  to  simulate Drain current vs Drain source voltage  characteristics  of a NMOS with respect to process variations in LT Spice?


texts: Segment display – Why selecting segment by GND

texts:
I bought display and for my surprise it works same as display i already had. I must chose segment i want to light up by GND and not by output pin on my Arduino.

Is it normal or there is something what have to be done when working with this kind of displays?

For completeness, here is data sheet (SD-36)


texts: Decreasing voltage ripple across current sense resistor

texts:
If you ever checked constant current/constant voltage sources such as LT8613 or LT8611, while reading datasheet you probably encoutered such sentence:

  Care
  must be taken and filters should be used to assure
  the signal applied to the ISN and ISP pins has a peak-to-
  peak ripple of less than 30mV for accurate operation.

It's also said that:

  In
  addition to high crest factor current waveforms such as
  the input current of DC/DC regulators, another cause of
  high ripple voltage across the sense resistor is excessive
  resistor ESL. Typically the problem is solved by using a
  small ceramic capacitor across the sense resistor or using
  a filter network between the ISP and ISN pins.

So, I've tried to simulate such circuit in LTSpice.

I've already put 1uF ceramic capacitor across the sense resistor and added capacitors to feedback (FB) resistors so it wouldn't generate, and it doesn't even on light loads but voltage ripple across current sense resistor is too high so current is set inaccurately. What else would be a good idea?

To put more clarity I add example from typical application. I increased current resistor value to get 100 mA on the output and used diode in series with resistor to simulate load that has 1.3 to 2 V voltage when driven by different current.


texts: Selecting the equipment with the optimal 10 MHz reference

texts:
In a larger testbench I have 5 synchronized instruments (signal generators, ARBs, VSAs etc). I am trying to decide which instrument to take as "master". I rule out the older/cheaper parts (Tektronix AFG3253 and HP 8648C) and select between the following high end devices

Rohde & Schwarz SMW200A ARB (with B22 Enhanced Phase Noise)
Rohde & Schwarz SMF100A Signal Generator (with B22 Enhanced Phase Noise)
Rohde & Schwarz FSW (with B4 OCXO Precision Reference Frequency)

Based on 10 MHz reference distribution (daisy chaining vs. BNC tees vs something else) it does not seem to matter too much. But I would still like to decide for the most optimal way.

I have been told I should use the "FSW" because it has "the best" but without further reasoning this sounds like yet another "gut feeling".

I have two general questions ahead:

What does it mean to have a "clean" 10 MHz reference in the first place? Low phase noise/jitter or super stable 10 Mhz wrt to temperature/aging etc?
If it is the latter case: Why would it matter? Say aging: If my setup is stable in short timespans of measurements (say, hours), why would I care if the reference is 10.00000 Mhz or 10.00001 Mhz? All instruments are synchonized anyway, hence the exact value should not matter too much.

Now I looked at the datasheets of the three devices and found that they only show "static" accuracy, temperature, aging ... but do not state jitter at all. That's counter intuitive because I assumed that jitter would be my most important criteria for the reasons discussed above.

The datasheet specs are shown here.

I assume aging is not an issue since and I do not care the exact value of the 10 MHz. Furthermore I assume temperature is not an issue because all instruments are running. Looking at the "Achievable initial calibration accuracy" of the FSW versus frequency error of the SMW and Aging/temperature for SMF (the only given spec) I would go for the FSW (5e-9), then the SMW as second choice and surprisingly the SMF as last choice. Jitter is not taken into consideration at all.


texts: What is the relationship between feedforward control and bandwidth?

texts:
This is a control theory question, but because there is no control theory stack exchange, I thought this was the closest appropriate location:

I've been studying feedforward control system designs, specifically motion stages that use acceleration feedforward control. In this control system, a control signal is generated based on changes in the command signal (as opposed to relying solely on feedback control).

My question, what does feedforward typically do to the system response bandwidth? If done correctly, I would assume it increases the bandwidth? Say for example the feedforward controller is designed as the inverse of the plant, is there a proof that illustrates that bandwidth is increased?

Furthermore, most feedforward control setups combine feedforward control with feedback control. In this scenario, how does the bandwidth between a feedback system and feedback-feedfoward system compare? Assume feedforward control is used in the sense of creating a command signal that attempts to compensate for changes in the reference command.


texts:
This is a very basic question which I can’t quite wrap my head around. Say you have a wire/coil in a magnetic field in such a way that if you apply a current in the wire it will move. So you charge up a capacitor or some other power source and discharge it through the wire, a force is generated and the wire gets some of that electrical energy converted into kenetic energy via F = BIL.

suppose I have the same charge, same everything but I increase the magnetic field by a factor of 10. The current should remain the same (right?) thus I have increased the force/acceleration by a factor of 10 and thus increased the final speed of the wire also by a factor of 10. Now this doesn’t make any sense, since in theory I could increase the magnetic field strength to some arbitrary number, meaning ”infinite efficiency”, so what am I missing here?

If it’s simply that the magnetic field affects the current, how exactly does it affect the current? (What formulas do I use to calculate the actuall current?)

Thank you in advance for clearing up this confusion in my brain.


texts: What defines a frequency in electronics?

texts:
As Hertz is defined as one cycle per second, what are the requirements of an electric wave to have a certain frequency? What I mean is more lucid in a picture.

The black wave has a frequency of about 3 Htz and the orange 0.6 Htz, but can the blue wave be defined as 1.5 Htz? How far does the line need to fall each cycle to define a period point?


texts:
In DDC112 Analog to Digital converter, its mentioned that its suitable for Low-level current output devices, such as photosensors, and can be directly connected to its inputs.

But to increase analog signal strenght it has inbuilt op amp, but how to adjust gain of this in built op-amp. ( In datasheet its mentioned that it has programmable full scale range.

Link for datasheet:
http://www.ti.com/lit/ds/symlink/ddc112.pdf


texts:
I have a digital output board design which has 32 open collector (sinking) outputs which can be connected in parallel to drive a resistive load. The collector of each output transistor is connected to a cathode of IN4001 diode. The anode of this diode is connected to the FIELD connector (where it is connected to a resistive load and 24V supply.

What is the use of this diode?


texts: How to use a photodiode over a broad range of optical powers

texts:
I am using a GaAs photodiode to pick off a small amount of the light of a high-powered infrared laser, supply this to a PID loop and thus have a way to stabilize the intensity of the laser. The thing is now that the optical power has to be changed continuously over up to three orders of magnitude (40W to ~10mW) by applying a voltage ramp to the setpoint input of the PID controller. Unfortunately, I could not manage to find a set of parameters for the PID loop for which it shows a reasonable response over the whole operating range.

While reading about the issue I came across what are called Programmable/Variable Gain (Transimpedance) Amplifiers. What do you guys think about supplying the voltage ramp to the gain input of the programmable TIA instead and keeping the setpoint at the PID regulator constant? This way, the PID regulator has a signal to work with that has a constant magnitude and - beware my limited EE knowledge - the system should be able to regulate the power better over this broad range?
Or is there anyone that has ever used one of these before, perhaps for a similar application?

Of course, I welcome all other suggestions about ways to get a reasonably high signal out of a photodiode over such a broad range of optical intensities.


texts: How to remove audio balance control from this schema

texts:
The part of the schema I need to understand is this:

simulate this circuit – Schematic created using CircuitLab

It is part of the schematic of a stereo audio amplifier. Being the two channels perfectly the same, the schematic only represents the left channel. I need to understand how the Balance part works. The "To right channel" will be connected to the Right channel circuit exactly like the "Left" part? With 3.5k Ohm Resistor and all?
I have a broken exemplar of this amplifier I would like to repair. The Balance potentiometer is completely destroyed, and I can't buy a replacement, because the amplifier is very old and some spare parts can't be found on the market anymore. So I would like to remove R3 or replace it with two 50K Ohm resistor. Which way would you suggest?


texts: Motor rated 7.6AMPS. How will motor behave if driven with PWM controller with 4A output?

texts:
Firstly, I apologies for having to ask such a basic question.

I'm looking to buy a controller for a permanent magnet motor. The specs of the motor are: 200VDC, 1.5HP, 5700RPM, 7.6A, form factor: 1.0

I am trying to decide between two controllers that I have seen on ebay:

500w, 4A

800W, 8A

The cheaper one has the following specs: DC 0-220V (output), 4A, 500W

The more expensive has these specs: DC 0-220V, 8A, 800W

My question is: what will happen if I tried to run the motor with the first controller?

The motor draws 7.6A but the controller is rated at 4A. Will it run at half torque? Will the motor cause damage to the controller/vice versa?

(...or am I better off getting the 800W controller?)


texts:
I have a component with a land pattern I haven't routed before. Usually thermal pads have the vias in them so the connectivity is obvious. However, in this case the vias are placed between the pads. My understanding is this is a way to stop the solder from sinking into the vias.
I'm routing a 4 layer board so I'm wondering what the best way to connect this is. Is the intention here to just connect all the pads to the vias?
The second image is from the datasheet which contains the land pattern.


texts: Arduino Mega 2560 - Stepping down voltage as input

texts:
Maddy from Little Bird Electronics suggested I go direct to the experts so here goes..

My requirement is:-
20 Rooms temperature to monitor

In Place:-
We currently monitor these rooms back to a patch panel that displays this info. Using TP2000 Probes. These use resistance which from the output of the dislpays creates a output voltage which I wish to use as input.

New Requirement:-
If the Temp gets above or below n degrees C a SMS alert is sent to a tech.
Data to be logged on a pc.
I can code any program for the data logging / sending alerts etc but electronics is not my strong point. Intermediate understanding though. (Plus google).

It has been suggested to use the Arduino Mega 2560 along with a ArduinoGSM Shield (for connectivity / sms).

Issue..
As this Arduino board only accepts max 5v as input (able to have 50 inputs) how can I step the voltage down.
Ie.
If the shed is 30 degrees c then the input will be 5v
If the shed is 15 degrees c then the input will be 2.5 etc etc..

Is the Arduino the answer to use along with sonething to step the voltage down for input.. or is there something better that may meet my needs.

Regards
Mark


texts: Effect of negative voltage at NPN transistor base (interesting example)

texts:
I'm trying to understand the behaviour of an NPN transistor and two diodes connected to the output of an instrumentation amplifier [image below].  The transistor appears to switch on when there is a negative voltage applied to the base, as well as when there is a positive voltage applied.  Can anyone explain what is happening here?

I would also like to know how I could tailor this circuit to work with a different voltage range and different supply voltage, in particular, for +-1.4V input to base with a 3.3V supply.

Thanks.

The supply is dual rail +-5V and the instrumentation amplifier gain is just under 10.

The text and images are from the book "Medical instrument design and development: From requirements to market placements" by Claudio Becchetti and Alessandro Neri.


texts: What is wear leveling in SD cards? How I can check my sd card has wear leveling or not?

texts: I searched on internet. Still I'm not clear about wear leveling can somebody explain this concept?


texts: LTspice simulation doesn't work, what am I doing wrong?

texts:
We were talking about this simple ramp generator: What would be the simplest BJT based *linear* ramp generator?
and talking about simulation. So I downloaded LTspice drew up the circuit and started to measure. But it's not working! Here, the green trace is at the collectors of Q1 and Q2, the blue trace is on the PULSE generator to verify that I have it set up right.

When I only measure at the collectors of Q1, Q2, I get this weird line:

Here is the ramp.asc file. I must be doing something really stupid. Who can spot the error?
Version 4
SHEET 1 1196 680
WIRE -64 -144 -240 -144
WIRE 96 -144 -64 -144
WIRE 96 -32 96 -64
WIRE -240 0 -240 -144
WIRE -64 16 -64 -64
WIRE 32 16 -64 16
WIRE 96 96 96 64
WIRE 352 96 96 96
WIRE -64 128 -64 16
WIRE 96 144 96 96
WIRE 352 144 352 96
WIRE 576 192 496 192
WIRE -240 288 -240 80
WIRE -64 288 -64 208
WIRE -64 288 -240 288
WIRE 96 288 96 208
WIRE 96 288 -64 288
WIRE 352 288 352 240
WIRE 352 288 96 288
WIRE 576 288 576 272
WIRE 576 288 352 288
WIRE -64 304 -64 288
WIRE 800 464 768 464
FLAG -64 304 0
SYMBOL res -80 -160 R0
SYMATTR InstName R1
SYMATTR Value 2k
SYMBOL res -80 112 R0
SYMATTR InstName R2
SYMATTR Value 10k
SYMBOL res 80 -160 R0
SYMATTR InstName R3
SYMATTR Value 10k
SYMBOL res 512 176 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R4
SYMATTR Value 1k
SYMBOL cap 80 144 R0
SYMATTR InstName C1
SYMATTR Value 33 pF
SYMBOL pnp 32 64 M180
SYMATTR InstName Q1
SYMATTR Value BC556B
SYMBOL npn 416 144 M0
WINDOW 3 57 67 Left 2
SYMATTR InstName Q2
SYMATTR Value BC546B
SYMBOL voltage -240 -16 R0
WINDOW 123 0 0 Left 0
WINDOW 39 24 124 Left 2
SYMATTR InstName V1
SYMATTR Value 5
SYMBOL voltage 576 176 R0
WINDOW 3 44 86 Left 2
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V2
SYMATTR Value PULSE(0 5 0 0 0 .005 .01 100)
TEXT -274 328 Left 2 !.tran 0.05


texts: I think they are tvs diodes but i can't find what type they are.


texts: Powering Evaluation Board, Voltage Regulator Fizzles Out

texts:
I'm trying to power a FPGA evaluation board using a 5V linear voltage regulator. I supply the 5V through the USB connector as shown: (this goes to the microUSB on the board)

For a basic test, I power the board up with no attached loads. I have a 12V AC/DC adapter that powers the 5V regulator. I have a 22uF capacitor at the output of the regulator, as the datasheet recommended this for stability.

When I plug this all in, I probe the voltage output of the regulator - it appears to work for a minute or so (holds a constant 5.0 V), then it rapidly drops to below 5V, and starts erratically pulsing. The FPGA stops performing and the LEDs on the board pulse.

My guess is that it's drawing too much current and overheating? The regulator is rated for 5A, which I figured was plenty for this application. The evaluation board doesn't seem to have a datasheet, but the FPGA does have a datasheet (download here).

Any thoughts as to why the regulator stops working? Any suggestions of a better method to provide the 5V to the board? I'd like to use the 12V AC/DC adapter as a power source if I can.


texts:
I don't see any reference in the specification that says so, but then I don't see anything that says otherwise.  Other sections do talk about uniqueness, so I'm guessing they don't need to be unique.

EDIT: 2/18/11: I'm using Mentor's HyperLynx simulation software.


texts: Type-N vs SMA connector (relative merits)

texts:
What are the relative merits of using a Type-N connector vs an SMA connector for an RF application up to \$18\,\text{GHz}\$? From the type-N wikipedia page (linked), it's stated that the type-N connector is favored when ruggedness is required. What does this mean specifically? In comparison with an SMA connector, does this mean that the type-N connector has a higher rated number of mating cycles? Some of my additional guesses are that it's more difficult to bend the inner conductor pin of a type-N and that the dielectric between the inner and outer conductors is less exposed to scratching during mating than the SMA connector. An additional advantage of type-N connectors is that they are meant to be hand-tightened, whereas SMA connectors should be tightened with a torque wrench to achieve the best performance.
The main advantage of the SMA connector seems to be size, since it's quite a bit smaller. This means that it's easier and cheaper to mount to a PCB (requires less board space) and (as far as I can tell) there are a lot more options for SMA PCB connectors than for type-N. Is there an additional performance benefit to SMA connectors? Some manufacturers offer SMA connectors good up to \$26.5\,\text{GHz}\$, whereas I haven't seen the same for type-N connectors. Additionally, the higher performance connectors (3.5mm, 2.92mm, etc.) look a bit like SMA connectors (and indeed some can be mated with SMA). Does this mean that it's easier to achieve better performance (e.g., lower VSWR) with the structure of an SMA connector?
Are there any other advantages/disadvantages to each that I haven't mentioned? Are my guesses correct?


texts:
What does the blue color of  SMD resistors mean?
I saw a board with blue colored body resistors (and another one with green) as part of high voltage measuring circuit, so I am trying to figure if these resistors are special in some sense.


texts:
In order to reduce the size of my board, I would like to connect directly my microcontroller to a current source which sink 9 mA (worst case). The datasheet above shows that it is possible. Nevertheless, I would like to have your opinion about this. I think that it will reduce the life time of the circuit as it heats up the microcontroller. What do you think ?

Thank you very much and have a nice day !


texts:
I'm pretty inexperienced in EE, but I'm adapting the circuit given in this question to amplify microphone inputs to drive an ADC.

I am going to be driving 4 ADC channels (on a Beaglebone Black) from 4 microphones, so I'm planning to use a quad op-amp.

The upper left of the circuit is a voltage divider providing bias voltage, with a 1MΩ resistor R3 isolating it.

My naive question is this: How much of the bias voltage circuit do I have to replicate per-channel? Can I drive all four channels from the node at the right of a single copy of R3?


texts: Could an FPGA be connected via DMI to a processor, if so how would this be done?

texts: Can an FPGA be connected to a processor via Direct Media Interface (DMI), without a dedicated Platform Controller Hub (PCH)? The FPGA would serve as the south bridge/ PCH. Along the lines of processors, I was thinking about the Intel LGA2011-3 ones.


texts: Unusual old resistor symbols identification

texts:
Image from: here.

This image is the schematic of an old Tesla 521A valve amplifier radio.
On the following resistors in the schematic there are weird markings:
R4, R5, R6, R24, R25, R26

I am guessing they signify the wattage of the individual resistors.
As I have this specific circuit heavily damaged and I would like to salvage the parts, it would be great to know what wattage do these signify(or what else they mean)

I know that these symbols are definitely not standard, but I guess maybe someone here has met these.

If the symbols are not good enough I can supply images of the resistors too.


texts: If capacitors are connected in series with a vltg source, then how would each plates get the polarity? For a single capacitor, the electrons from one plate are pumped by the source towards the other side of the plate, but for series connection how would the flow of electrons be in between the capacitors (i.e. for the inner plates of the capacitors). Say, if three capacitors are connected in series, how would the middle capacitor gets charged? Would current exist between each capacitors?


texts: 90 degrees rotated MIFA 2.4GHz Antenna reference design?

texts:
NXP offers a reference design of a MIFA antenna for the 2.4 GHz BT LE frequencies. On page 4 of the PDF the design is shown:

For my application this reference design is too wide; does anyone know of an existing reference design that offers a 90 degree rotated reference design (about as below, and yes, I know the traces are not connected ;). I would assume that I cannot simply add another 90 degree angle right at the beginning of the antenna and not suffer dire RF consequences.