texts: Help with circuit to alternate a light switch with solid state

texts:
I have designed a PCB that allows me to turn a light on with a mechanical relay.  The difference between your average implementation here is that I also wired the board up to a wall light switch which allows me to alternate the state of the light switch.

I managed to alternate the behavior of the light by using an SPDT relay and a 3-way switch (which is wired in U$3 below).  The theory of operation is pretty simple.  The HOT wire is connected on the relay's center pin and the current is either brought out of the NO or NC pin.  The light switch is connected similar to the SPDT relay but in opposite (you can think of the switch as an SPDT relay).  ie: The center pin P$2 is the output and the other 2 states bring the current from NC or NO out to TRIGGER.  Thus flipping the light will alternate the current from NC to NO and the relay essentially can do the same to alternate the current.

The issue with the current design is that I'd like to get away from using a mechanical relay and move to solid state for all of the typical reasons (audibly noisy, low life, sparks, ...).  How can I achieve the same goal using solid states?

SPDT Triacs virtually don't exist.  I found a few designs for SPDT triacs using a few SPST triacs, but I wasn't exactly thrilled to see the large number of components and I'm a bit worried that I may lose any significant power gains I may have gotten from moving to solid state.

Are there any other clever ideas that anyone can think to achieve my high-level goals of XOR'ing the state of the light switch with a relay and a light switch?


texts: Why is voltage output inverted between common-emitter and common-collector amplifiers?

texts:
My resource shows the following common-emitter transistor configuration and claims that the output voltage compared to the input voltage is inverted (higher input voltage means lower output voltage):

This makes sense to me. But then he shows the following common-collector transistor configuration and claims that the output voltage grows directly with the input voltage (higher input voltage means higher output voltage):

The author makes the claim that a key distinction between common-emitter and common-collector configurations is the fact that the output signals are inverse. This doesn't make sense to me because he seems to be measuring the "output voltage" at different points in each circuit. In the common emitter circuit, he uses the voltage across the two leads of the transistor as his output voltage. In the common collector circuit however, he uses the voltage drop across the load.

How can he claim that these circuits differ in the nature of their output voltage when it's really just him measuring the voltage drop across different points in the circuit? If in the common-emitter circuit, he measured the output voltage as the voltage drop across the resistor R, would he not receive an output voltage similar to that of the output voltage in the common collector circuit? Where am I mistaken?


texts: Resistance between two points in/on a large volume/sheet?

texts:
I want to model the resistance between two points on a large mass of uniform resistivity.

There are two cases I am particularly interested in:

a) a cuboid (e.g. a tank of conductive fluid), we could say it is axis-oriented with (0,0,0) and (w,h,d) being diagonally opposite corners, I put two pointlike probes in at known coordinates and measure the voltage between them.

b) a thin sheet whose shape can be decomposed into uniform squares, for example:

For a) it might be acceptable to treat the cuboid as infinitely large. How big would the error be? Or, under what size conditions is the error "small" (within some specified tolerance, i.e. a few percent)?

For b) it would be acceptable to treat the probes as being squares of the same size and alignment as the tiles which comprise the whole shape, if that simplifies things.

How can I calculate the resistance between the probes in these situations?


texts: Is a 250V lamp compatible with both 120VAC and 220VAC?

texts:
Is a 250V and 660W lamp compatible with both:

120VAC at 60Hz, and
220VAC at 50Hz?

And why? Also, does the frequency of the mains have any bearing on the lamp?

In North America I was very surprised to notice a lamp certified for 250V but plugged into an 120VAC mains. My naive intuition is that the lamp should be certified for 120V. And similarly, the same 250V lamp would probably be compatible with a 220VAC mains (as in Europe), but I would have expected that a lamp in Europe should be certified for 220V.

But I'm most likely wrong here, so:
Why is a 250V lamp compatible with both 120VAC and 220VAC mains?

PS To avoid confusion, by "lamp" I mean a light fixture and NOT a light bulb.


texts:
So i was reading a few papers regarding redox transistors and I would like to model one in spice. However, I don't know how exactly to do it. Looking at this, there is a sample schematic in the implementation figure:

I am looking for some pointers on how to possibly model this in spice. Obviously, this would be better to model in TCAD software, but I am not aware of any free solution. Does anybody have any idea? Thanks :)


texts:
I am trying to figure something apparently basic and I hope somebody might give me an advice.
The IC I am working with is XC6SLX25. It has 6 different power regions -- Vccint, Vccaux and Vcc for each of the four banks. Xilinx provides a PCB design guide (UG393) where they specify the number and type of decoupling capacitors per each power region but still I am not sure how to connect them to all the pins.

For example the guide states that one 100 uF, one 4.7 uF and two 0.47uF capacitors should be connected to the power pins of Bank 1.

According to this guide 100 uF capacitor could be placed almost anywhere near the IC, 4.7 uF should be placed within 2 inches of the outer edge and 0.47 uF should be preferably placed on PCB backside. As it can be seen on the attached pictures there are 6 power pins and 6 GND pins located on Bank 1.
My questing is this -- what is the correct way to connect these four capacitors to the six pairs of pins? Should each type of a capacitor be connected to each pair of pins and if so how should the capacitors be interconnected?


texts: Implementing Bellman-Ford algorithm on finite state machine

texts:
I wanted to ask whether it is even possible to implement the Bellman-Ford algorithm on a finite state machine.

How can you determine whether a machine will have a finite number of states or not?

Edit:
The Bellman-Ford algorithm finds the shortest path between 2 nodes in a set of nodes.


texts:
I am designing a device that automatically adjusts it's physical position as temperature changes. If the device it shut off or power is disconnected the device needs to remember it's last temperature and position. I have the ability to store these values in EEPROM but the problem is the position and temperature could be changing very rapidly. If I were to write the temp and pos to EEPROM after every time they changed that would (1) slow down the firmware a bit, and (2) likely kill the EEPROM after a year or two. So as I see it my options are as follows...

1) use a capacitor/battery to keep the device powered for a short time after power is lost so that I can write the values to EEPROM at that time only. I don't like this because the board is kinda power hungry and this would require a big cap. And I don't have a ton of free space. And I don't want the added cost of a battery and battery holder / or a big cap.

2) use F-RAM instead of EEPROM so that I can write to it trillions of times without wearing it out. I don't like this option because FRAM is quite a bit more expensive than EEPROM and this is for a production product (not just one).

3) Only write the position and temperature every 5 minutes or so. That way I always have a fairly recent position/temp recorded but I am not writing every second so my program is not slowed down and the EEPROM won't die as fast. This seems like my best option.

Does anyone else have any suggestions that I'm not thinking of?


texts:
I'm having trouble doing the Sum-or-product of this truth table and then simplifying the logic expression.
For the SOP i got Y= A’.B’.C’.D’+ A.B’.C’.D’+ A’.B.C’.D’+ A’.B’.C.D’+ A’.B’.C’.D+ A.B.C’.D’+ A’.B.C.D’+ A’.B.C.D’+ A’.B.C’.D+ A’.B’.C.D+ A.B.C’.D+ A’.B.C.D+ A’.B’.C.D’+ A.B.C.D’+ A.B’.C.D
but I don't know where to go from here


texts: How to understand connected USB port type from the UFP side?

texts: I am designing a USB 3.X device with a Type-C receptacle. I know that a standard USB 3.X downstream port can supply 900mA current and a USB 2.0 port can supply 500mA current. I am expecting the designed board to draw a current between 500mA-900mA and this would cause a problem if a user connects it to the PC's USB2.0 port. I am looking for a way to understand the type of DFP and warn the user to use an external supply or connect it to a USB3.0 port. I will use the FT601 chip as a USB3.0 bridge and it can only tell whether the connected port is standard(500mA/900mA) or charging(1.5A) port, but doesn't tell if it is 500mA or 900mA. Do you have any design suggestions to understand the port type?


texts:
I have a sensor that requires 9-30 VDC power, 600 mW at 24 VDC nominal voltage. I have a power supply that can source up to 15 VDC and up to 400 mW in power. If 24 VDC is the nominal voltage of the sensor at 600 mW, then I assume that it requires 25 mA as the nominal current. For my power supply, if I were to set 15 VDC, then I could source 400mw/15V = 26.7mA of current. I know that the 15 V is a lower potential, and thus the current would change as well, but would it still be enough to power? My main questions are these:

Does the load require 600 mW or 25 mA for power? What exactly "powers" it?
What is the meaning of the 9-30 VDC power? Does it somehow change the resistance to allow more current if I am using a lower voltage power supply?

I'd greatly appreciate any clarification with these!


texts: Does this circuit have proper isolation?

texts:
I have a development board from Microchip. It works on 12 V DC. The input pins can only work on 3.3 V so what I have done is I have designed a circuit using a PC817 optocoupler. So on the LED side I am supplying 12 V and on the transistor side I am using the 3.3 V from the development board and connecting to the input pins of controller. Circuit below:

Now, looking at the circuit it is isolated. But I am powering the development board and supply the 12 V as input to optocoupler from the same power supply. So I think ground is still common. So this kind of circuit still isolated? If not, how to properly achieve isolation? Do we really need different power supply for isolation? What is the effective way of providing isolation?


texts: I'm trying to design a three-phase PWM inverter connected to the same single-phase DBR and ac source while keeping the same load for each phase. I have the one-phase circuit but can't do the three-phase...Can anyone help pls?  The specification of the base case is that the load is constantly consuming 1.5 kW at Vrms = 100 V, f = 30 Hz and the switching frequency is 15 kH .This single-phase AC source is 220 Vrms, 60 Hz.


texts: Some USB cables work, and some don't - why?

texts:
Connecting a PC to a board with USB i/f. Some (2m) cable work OK and some don't. The obvious reason being that probably signals are marginal.

The board is powered from the USB, and takes around 200mA. Symptoms are typically "USB not recognized".

However, the immediate question is this: Why would two different USB cables have different responses and how can I choose ones that work. What parameters am I looking for?

I have just come across this PDF document:


texts:
Yesterday I asked a similar question and realized I still don't quite get it, so I'm sorry about that.

Here is explicitly what I mean:

This is a part of a full adder. The first row in which carry in equals 1 makes sense to me, because the row before that, carry out equals 1. But why does carry in equal 1 the second time, when on the previous row carry out is equal to 0?

Would really appreciate some simple explanation.

Thanks in advance!


texts: Why telephone dc voltage drops to about 8 volts?

texts:
I found out that the DC voltage supply is about 48 volts in the central office, and the typical line impedance is about 600 ohms. Also the typical current in off-hook state is about 20mA.
So with a simple calculation, I see that the dc voltage in off-hook state must be about 48 - 12 = 36 volts at 20mA current. But in most resources I saw that the typical value for this is less that 9 volts (and I've seen same thing in practice).
Why is this happening?


texts: Going ultra low power with a reflective optical sensor

texts:
I'm using an nrf52 and an OPR5005 reflective optical sensor which takes roughly 20mA. In the design I have only 30mmx30mm space, so only suitable battery is cr2032 or cr2477 so far. The question is how far I can go without switching the sensor on and off? (sensor should be always open)

EDIT : Here is my final schematic file after answers below.
I decide to go with nrf24l01 and for mcu I put a stm8l also I add a load switch to on/off the sensor

Typical power consumptions for IC's:

nrf24l01 : 600nA at powerdown, 0.12mA at TX (it will only transmit from eeprom and it will do it only once when I power up device)

stm8l : 3.7uA at sleep, 0.5mA at run mode (it will wake every 25ms and will enable sensor and record the data to eeprom and will sleep again. It will take almost 5ms estimated, including settling times)

OPR5005 : 15-20mA in run mode, 12nA at sleep (leakage from load switch)


texts: What's this sensor called? Found it in my AC unit

texts:
It's a 2 wire sensor I found in my central home air-conditioning unit. Any ideas what it's called? Wasn't able to find a part number on it.

Is there a test I can do to find out, using a multimeter?


texts: How do ASIC designers approach designing for extremely low supply voltages like 0.3V?

texts:
In ASIC design, there is a tradeoff between performance and energy efficiency.  Since most consumer CPU's are designed for maximum performance, they operate at high voltages and clock frequencies, have large caches, use complex branch predictors, and so on.  The cost is very high energy consumption per operation.
By contrast, Bitcoin mining ASIC's are designed for maximum energy efficiency.  Thus, they tend to make the opposite design choices.  For example, they use lower supply voltages, even if (as a result) their transistors need to switch more slowly and the clock frequency must be reduced.  This often reduces the key energy-per-operation metric because power consumption scales as \$fV^2\$.
As an extreme example, BitFury advertises that their most recent ASIC, "Clarke," can run at just 0.3V.  That seems really low to me, possibly even in the subthreshold regime; Clarke is manufactured using UMC's 14nm process, which ordinarily needs 0.8V.  So my question is: how would an ASIC designer approach designing an ASIC to operate at such a low supply voltage?


texts: Finding practical solutions for discharging and charging a capacitor

texts:
I am wondering can I charge and discharge a supercapacitor at the same time like a battery.
I have 1.3V going into a 10F 2.7V capacitor in series with a 0.5 ohm resistor. I calculated it will take about 30 seconds to charge to "full". And I will have a 2.6A peak current.
The minimum voltage I need is 0.9 when I discharge the capacitor. I have a 500mA current load (1700mW) that I need for startup for 1 second.
I calculated that it takes 8 seconds to discharge to 0.9V (which is more than enough time).
I then need a constant 0.085mAs after the 1 second power surge.

Can I charge and discharge at the same time?
Will I be able to charge the capacitor fast enough to keep the voltage above 0.7V after the power surge?
Will I be able to keep my load running after the power surge when my load only requires 0.085mAs?
I see that every 1 second my voltage from the capacitor drops 0.05V, so when I get to 1 second I have 2500mW of power left. If my load needs 1700mW, do I subtract that and I'm left with 800mW of power to deliver to my system while I charge my cap?

I am trying to figure out if a capcitor can supply a consistent wattage even when not completely full.


texts: Cable based data transmission without common ground

texts:
I have a question with regards to how data is sent using single-wire cables between devices which are otherwise electrically isolated?

edit:

I understand now Coaxial has a common ground, but my question still stands: how is data transmitted without a common ground?


texts: Best way to determine power consumption of a microcontroller

texts: What is the best way to determine the power consumption of a microcontroller? Need to select the right voltage regulator to supply 3.3V for PIC32MX795F512H.


texts: Throttling data from USB serial connection on STM32 microcontroller (flow control)

texts:
I've just integrated the code from ST's STM32 USB Virtual Com Port example (stm32_usb-fs-device_lib.zip from here) with my project in order to get the STM32 to appear as a Virtual Serial Port.

However the code example throttles the data it receives by having the callback function EP3_OUT_Callback block (in an interrupt) until all data is dealt with. The exact comment in the code is "USB data will be immediately processed, this allow next USB traffic being NAKed till the end of the USART Xfer"

In my project, I need to process the data that has been received in the main loop (outside of an interrupt), so I need a way of throttling the data that I get from USB without blocking in EP3_OUT_Callback.

What I would like is a function:

Do_Not_Call_EP3_OUT_Callback_Right_Now(bool yes_or_no);


texts:
I am using msp-exp432p4111 devalopment board and trying to use DAC161S997 with it.The main goal is creating a 4-20mA according to an anolog sensor's value. But firstly i am just trying to control the output of DAC. The communication protocol is SPI. I have found a sample code for my DAC but it is for an msp430 chip so i have changed it for my chip. According to my debugger code works fine, i mean sending data with spi is complated but nothing happens at output(2mA always). Here is my code and connections:
Connections
Datasheet

void main(void)
{
    WDT_A->CTL = WDT_A_CTL_PW | WDT_A_CTL_HOLD;     // Stop watchdog timer

    USCIB0_setupMasterSPI();
    __enable_irq();

    // Configure the DAC161S997
    Setup_DAC161  (DAC161_STD_ERR_CONFIG_MASKED, 3370, 21800);
    DAC_Error_Processing = 0;
    dacValue_mA = 4;
    dacValue = dacValue_mA * 2730;
    DAC161_Set_Out_Value_uA (dacValue);
        while(1)
    {
        // In case we extend the time between samples in the future, we will still need to keep the DAC
        // from timing out by sending a NOP command every time the loop is processed.
        DAC161_Nop();
        // Did the DAC161 indicate an error?
        if (DAC_Error_Processing)
        {
            // Perform DAC ERROR Processing Here
            DAC_Error_Processing = 0;
            dacStatus = DAC161_Read_Status();         // Read Status to clear error
        }
    }
}

const eUSCI_SPI_MasterConfig spiMasterConfig =
{
        EUSCI_B_SPI_CLOCKSOURCE_SMCLK,             // SMCLK Clock Source
        3000000,                                   // SMCLK = DCO = 3MHZ
        500000,                                    // SPICLK = 500khz
        EUSCI_B_SPI_MSB_FIRST,                     // MSB First
        EUSCI_B_SPI_PHASE_DATA_CHANGED_ONFIRST_CAPTURED_ON_NEXT,    // Phase
        EUSCI_B_SPI_CLOCKPOLARITY_INACTIVITY_HIGH, // High polarity
        EUSCI_B_SPI_3PIN                           // 3Wire SPI Mode
};
void USCIB0_setupMasterSPI(void)
{

    GPIO_setAsPeripheralModuleFunctionInputPin(GPIO_PORT_P1, GPIO_PIN5 | GPIO_PIN6 | GPIO_PIN7, GPIO_PRIMARY_MODULE_FUNCTION);
    GPIO_setAsOutputPin(GPIO_PORT_P4, GPIO_PIN0);
        SPI_initMaster(EUSCI_B0_BASE, &spiMasterConfig);
}

    void USCIB0_SPI_write (unsigned char *outData, unsigned char *inData, unsigned char length)
{
    unsigned char i;

    // CS Active Low
    P4->OUT ^= BIT0;
    for(i=0;i<100;i++);                     // Pause a bit

    for (i=0; i<length; i++)
    {
        inData[i] = USCIB0_SPI_writeByte (outData[i]);
    }
    while (!(EUSCI_B0->IFG & EUSCI_B_IFG_TXIFG));               // USCI_B0 TX buffer ready?
    for(i=0;i<100;i++);                      // Pause a bit
    P4->OUT |= BIT0;

}

unsigned char USCIB0_SPI_writeByte (unsigned char data)
{

      while (!(SPI_getInterruptStatus(EUSCI_B0_BASE,EUSCI_B_SPI_TRANSMIT_INTERRUPT)));
      SPI_clearInterruptFlag(EUSCI_B0_BASE, SPI_getEnabledInterruptStatus(EUSCI_B0_BASE));
      SPI_transmitData(EUSCI_B0_BASE, data);
      return SPI_receiveData(EUSCI_B0_BASE);

}

void DAC161_Set_Out_Value (unsigned short value)
{
    DAC161_Write_Regs (&value, DAC161_DACCODE_REG, 2);
}

    void DAC161_Nop (void)
    {
        unsigned short deadCode = 0xdead;

        DAC161_Write_Regs (&deadCode, DAC161_NOP_REG, 2);

    }

    void Setup_DAC161 (unsigned short errConfig, unsigned short errLow_uA, unsigned short errHigh_uA)
{
    unsigned short errValue;

    DAC161_Write_Regs (&errConfig, DAC161_ERR_CONFIG_REG, 2);

    errValue = DAC161_CONVERT_ERR_VALUE(errLow_uA) & 0x7f00;;
    DAC161_Write_Regs (&errValue, DAC161_ERR_LOW_REG, 2);

    errValue = DAC161_CONVERT_ERR_VALUE(errHigh_uA) & 0xff00;;
    if (errValue < 0x80)
        errValue = 0x80;
    DAC161_Write_Regs (&errValue, DAC161_ERR_HIGH_REG, 2);

}


texts:
I have 2 meters, 32wg, 19 ohm per meter. NIchrome wire

I want to calulate what amps and volts i need so 2 meters of nichrome heats to 35 celsius.

How can i calulate this and what formula do i need to use.


texts: What is the reason for high frequency noise when amplifier is powered with battery?

texts:
Hi I made a small headphone amp and powered it using lipo battery.voltage is stepped up to 5v.everything is working with direct supply (ie., while charging battery)but as soon as I unplug the charger ,I am getting high frequency output to amplifier.what could be the reason?
Note:this is happening even when battery is fully charged and there is absolutely no noise when battery is charging.


texts: How to connect LVDS signals to oscilloscope?

texts: I have a bunch of LVDS signals on a PCB I want to look at with a scope (without wanting to tear my hair out). They range in speed from hundreds of Hz to ~200 MHz. How can I do this in a way that will be simple to interface with a scope and can be appropriately terminated such that the signal integrity will not be compromised?


texts: Can MCU memory be subject to bit errors and failures?

texts:
One of my older prototypes for Super OSD always had one little bug. A single pixel in the video, about midway in the frame would always be off. It did not really affect anything as most pixels normally stayed in the off mode, but it was noticeable during test patterns. I could never narrow down what the cause was.

Thinking about it now, could it have been a failed bit in the memory array? Is this at all common with MCU's with SRAM? The prototype was not abused: a fixed +3.38V (within the rated 3.0V - 3.6V), room temperature operation, minimal load on the outputs. It was a dsPIC33FJ128GP802.

I'm designing a new prototype now and I think it's the same chip as I used last time, so I will see if the problem occurs again. Does anyone know if it is prudent to run a "memory test" on a chip?


texts: Floating Source Voltage Difference to Earth

texts:
I was reading about floating voltage on web but there is something that I couldn't understand. I attached photo of circuit. As you see it shows 60v difference between neutral of flating source and earth but how is that possible since there is no physical connection between them ? What is the reason of this voltage difference.

Thanks in advance.


texts:
I found the picture below on the Internet about a double primary winding transformer. I understand how a simple primary double secondary winding transformer works, but I don't see the point in making a transformer like the one found below (output is at the bottom of the picture, input at the top of it).

Is it the same thing when you put two voltage sources in parallel so you can get twice the current at the output (so you get twice the power)?


texts:
so i have a SPICE simulation where i put a 1 volt sawtooth wave through a diode in the following circuit with the following graph

Then i can then plot the V-I graph, and then i've tried to use a curve fitting program in order to find the value of the saturation current, ideality factor and the other terms given by the diode equation,the problem is that the values don't make any sense as i get a value of 7.713E-08 for the saturation current and 0.15 for the ideality factor.

letting S be saturation current, and n being the ideality factor. thermal voltage is assumed to be 0.25
I've also tried the circuit without the resistor so the I-V graph takes into account the whole voltage drop of the circuit, but nothing seems to help. i've also tried using different diodes in SPICE(I'm using Partsim)

Am i doing something fundamentally wrong? and can this method be used in order to get the diode equation or not?

thanks


texts:
I need 4 accurately matched resistors for my circuit, I heard resistor arrays have better matching quality. but I don't know what parameter to look for in the datasheets. all I see is Tolerance. I don't mind if the resistors have 10% tolerance but if one of them(for example 10k nominal) is 10.91k all others be exactly 10.91k. is there any specific parameter in datasheet of resistor arrays that refers to this kind of accuracy?
also, what is the difference between thick film and thin film?


texts: If charges flow along the surface of a conductor, why is resistance a function of cross-sectional area?

texts: The skin effect dictates that charges tend to flow along the surface of a conductor. And yet resistance of a material is equal to resistivity multiplied by the cross-sectional area of the material divided by the length. Shouldn't it be based on the surface area?


texts: Kirchhoff's circuit laws - regular tetrahedron

texts:
I would like to ask for help in following exercise. I have tried to solve it, but I don't know if it is correct.
In every edge of regular tetrahedron is placed resistor R and to two vertices there is connected electromotive force unit U. Write Kirchhoff's circuit laws for this circuit, determine electric current for branches and electrical resistance between two random vertices of tetrahedron.
My first picture:

Then I have modified it to this

And finally I have added direction of current

From the equations I have got this results:

electrical current between Ic and Id is equal to 0
node A: I1 - I3 - I4 = 0
node B: I8 + I9 - I10 = 0
node C: I4 + I7 - I8 = 0
node D: I3 + I7 - I5 - I6 = 0
node X: I - I1 - I2 = 0
node Y: I2 + I10 - I11 = 0

Electrical current in node IA:
I2R = -Ue

Electrical current in node IB:
-I2R + I4R + I8R = 0

Electrical current in node IC:
I3R + I6R - I4R - I7R = 0

For I3R = I4R and I6R = I7R, I have got equation 0 = 0
Electrical current in node ID:
I5R + I7R - I6R - I8R = 0

And for I6R = I7R and I5R=I8R, I have got equation 0 = 0
Is this solution correct, or am I somwehere wrong?


texts: Is RoHS and EMC compliance enough for a 24V industrial sensor to carry CE Mark?

texts:
My company is planning to produce a fork sensor (example). Before starting design, I looked up EU Directives to find if there are any electrical requirements for product safety. First stop was Low Voltage Directive, however it clearly states that products between 75V DC and 1500 V DC are in the scope of the directive.

However, there also is a harmonised standard under LVD which fits for the definition of my product: EN 60947-5-2.

My understanding is that, LVD only cares about product safety, and wants to ensure that nobody gets hurt while device is in operation. The harmonised standard more specifically defines what the product should behave, however not obeying it is not a problem for the product to be in the European Trade Zone.

My questions are:

Does a product operating below 75 Volts mean that it is
intristically safe (per European Standards)?
Is compliance to RoHS and EMC directives enough to mark my product
with CE?


texts: MOSFET voltage is opposite from what I expect

texts:
I have this circuit on LTspice.
The voltage from the 12V seems to rise when the 5V is falling.
What am I doing wrong?


texts: How this for loop could be translated efficiently in vhdl using for generate statements?

texts:
Hi guys i have this pseudo-code nested for loop (very simple to translate in C)

Input : x; //is an unsigned
Output : y;

val = 0;
for i = 0:n-1
  for j = 0:n-1
    if( ((x >> i) & 0x1) && ((x >> j) & 0x1) )
        val = val + x << (i + j);

y = val;

Is there a way to translate this using for-generate statments in VHDL? I'm aware of the fact that i could implement basically the same code using process and sequential for loop, but it is possible to do something similar using the for generate instead?

(my main issue is that there's no variable in concurrent statements).


texts: Conversion of Additive Noise to Phase Noise

texts:
RF Microelectronics by Razavi contains the following snippet in section 8.7.3 concerning the analysis of phase noise in oscillators:

  We write \$x(t)=A\cos(\omega_0t)+n(t)\$ where \$n(t)\$ denotes the narrowband additive noise (voltage or current). It can be proved that narrowband noise in the vicinity of \$\omega_0\$ can be expressed in terms of its quadrature components:
  $$ n(t) = n_I(t)\cos(\omega_0t) - n_Q(t)\sin(\omega_ot)$$
  where \$n_I(t)\$ and \$n_Q(t)\$ have the same spectrum of \$n(t)\$ but translated down by \$\omega_0\$ (Fig. below) and doubled in spectral density.

I don't see how the math adds up though. Taking the Fourier transform of \$n(t)\$,
$$ S_n(\omega) = \frac{1}{2}\left[ S_{nI}(\omega-\omega_0) + S_{nI}(\omega+\omega_0)\right]
+ \frac{j}{2}\left[ S_{nQ}(\omega+\omega_0) - S_{nQ}(\omega-\omega_0)\right]$$
If the quadrature components are the same as mentioned so \$S_{nQ}(\omega) = S_{nI}(\omega)\$,
$$ S_n(\omega) = \frac{1-j}{2} S_{nI}(\omega-\omega_0) + \frac{1+j}{2} S_{nI}(\omega+\omega_0)$$
Doesn't this show that the spectral density of \$S_{nI}\$ and \$S_{nQ}\$ is \$\frac{2}{\sqrt{2}}\$ that of \$S_n\$ rather than double, in order for the magnitude to equal?


texts:
I have to measure \$R_{in}\$, the input resistance seen by the signal.
It was told me, that the quickest way is measuring the voltage gain using oscilloscope, insert a resistor before \$R_B\$, measuring the new voltage gain, make the ratio and find the expression for \$r_e\$ (the input resistance seen between base and emitter looking into the emitter) and then substitute this value in the expression of \$R_{in}\$..

But in the expression of \$r_e \$ appears \$r_o||R_L\$.. and I don't know the value of \$r_o\$ (the output resistance of a BJT)... the only thing that I know is that "usually it is large"... but how much large? what about the range of its values? If \$R_L\$=1k ohm, can I neglect \$r_o\$?


texts: PWM with opamp does not show expected output

texts:
I'm trying to get a PWM modulated signal using the next circuit

It is supposed the oscillator part changes the voltage from 2.5 V to -2.5 when reaching saturation, I was expecting something like this

using the variable resistor to change the duty cycle , but the output done is

What Im missing? Its wrong done the circuit? The variable resistor is placed right?

UPDATE
After updating the circuit

It gets the next output

but Im having trouble with the source since only after these values (0-25V) its behaving like the triangle source and the time on/off (duty cicle) is showing as well, I was trying to use a small source but I dint get how to correct the hysteresis; aside the oscillator part seems to be not working, even when changing the property of the variable resistor

I have never used a variable resistor in pspice so I don't know if this is well connected or the property well adjusted. It was expect to varyate the duty cycle by changing the value of the resistor R12.


texts: How to stream data from embedded system to PC fast?

texts:
I'm working on an embedded system which will generate data at a pretty high rate, 100-300Mbit/s.  This is coming from a bunch of SPI busses. I need to get this into a Linux PC.  What's the best way to do that?
At the moment I have a small portion of this built with a STM32F4 microcontroller as proof of concept. It gets data at around 20Mbit/s.  I'm realizing that (a) there is probably no way for the F4 to read data at 100Mbit+, and that is probably still going to be hard/impossible for faster parts like F7 or H7 since the APB clock is limited to 100MHz; and (b) there is no way to send data to a PC that fast from these microcontrollers either, especially while both reading and sending.  Reading and sending simultaneously at 20Mbit is probably (just barely) possible.
The main options for sending data to the PC would seem to be USB or ethernet.  High speed USB is theoretically fast enough at 480 Mbit, but ST microcontrollers mostly don't have it - although it looks like some parts have ULPI.  100Mbit ethernet is not fast enough; gigabit is again theoretically fast enough, but none of the ST microcontrollers have that (or SGMII).  I don't know what the practical speed ceiling is for streaming data over HS-USB or 100MBit ethernet, but I'm guessing it's a lot less than the theoretical speed.
So, the question is, what is the best way to stream data at the aggregate speeds I need? (either with a fast IO friendly microcontroller, or something else).
A few options:

split the device into several independent devices (maybe 4-8 or so) and send data from each one either over HS-USB with a ULPI USB chip (USB3300 or similar) or 100Mbit ethernet to PC with multiple USB ports/multiple ethernet ports - the PC can reassemble these streams, or
same, but put something in front to aggregate the connections: USB hub or ethernet switch.  could be on board to the device reduce number of physical wires, or a separate device
use a different microcontroller or SOC which can handle the total data rate in one device
use a FPGA (but which one? it seems like most low cost FPGAs like ICE40 don't have SGMII either)

In this case there is literally no processing that happens; the micro sends a few setup commands to the SPI buses and after that it's just passing data through (possibly assembling the data into blocks and adding headers per block on the output).  There are also no special timing/latency requirements, as long as the data can stream continuously with nothing dropped.  I want a setup that is as simple and robust as possible.  I'm very familiar with ARM microcontrollers; less so with FPGAs.  I'd like to avoid high-end/specialty parts (of course a Kintex FPGA could handle this, but...)


texts: Safety of this circuit (involving hand-to-hand current):

texts:
Note1: The voltage source in diagram is 3 lantern cells in series.
Note2: Hands are placed on acrylic/plastic mesh so not directly in contact with metal trays.

The hands would be submerged for 20-30 minutes at a time and process would be repeated (say, every day). Given the hand-to-hand contact and submerged hands, I'd like to know  what level of current would be expected to flow (in particular through the heart) and if there's any (non-negligible) risk associated with this circuit in both the short- and long-term.

I've looked at previous, more general threads about safe levels of current/voltage (How much voltage is "dangerous"?, Safe current limit for human contact?) and realise that there are too many variables to give exact answers to those but I'm hoping the specifics of this setup will allow for a more definitive answer!


texts: Remove the voltage between RTN and NEUT in a power supply unit

texts:
There is an AC/DC power supply based on TOP246 (schematics is similar to this one).

220V GND isn't connected (suppose, a fault occurred).
The voltage between RTN and 220V NEUT is about 60V, but the current flowing is very small (less than 10 microA).

Is it possible (by modifying the power supply unit) to remove the voltage between RTN and 220V NEUT or make it less than 10V?


texts: I have a 12 volt starter motor on a diesel engine that is rated at 2000 W. Typically a fully charged lead acid battery is 12.7 volts. Therefore the current draw would be 157.48 amps  but for only a few seconds. What is the correct way to size a battery to this starter? Do I look at amphours (battery capacity) or CA/CCA?


texts: How do I keep the "detected" state ON in a PIR detector until a human has left the detection area

texts: A PIR detector stops alarming after a while, if a human in the detection area doesn't move. How do I keep the alarming state ON as long as there's a human in the detection area even if he doesn't move?


texts: What is the application of capacitor between Vcc and GND

texts:
This is a schematic of a ATmega328P used circuit.
It has paralleled two 100nF capacitors between Vcc and GND. (C8 and C9)
What is the function of this two capacitors and why they are paralleled?


texts: 3.3V LDO alternative using SOC analog output?

texts:
I want to build a little adapter board to connect an existing PSOC prototyping board (CY8CKIT-059) to QIIC connector (which is just I2C using JST 4-pin connectors).   The QIIC standard calls for 3.3V power, but my board doesn't have that, just the USB VBUS derrived 5 Volts.
Rather than drop an LDO on my adapter, I thought I might take advantage of a spare opamp on the PSOC, but the output pins are limited to about 25 mA, I want to go higher than that.   Dusting off mental cobwebs, I recall building an emitter follower with a 2N2222.  (Does that part date me?)   Here's the idea:

Would a using a MOSFET here instead of a bipolar have any advantage?
I've not done any surface mount before, but with JLCPCB's assembly service, it seems like time to give it a try.   Is there a way for me to look up something similar the old through-hole transistor in a SMD package.


texts: Power a laser from Arduino using a audio cable/ jack plug?

texts:
I want to power a laser from an Arduino, and have a connection between a phototransistor.
A easy connection seems to me a audio cable with a jack plug.
Is this possible? Power consumption of the laser is 10mA@5V.
Setup is a Arduino and 2 long easy to connect/ disconnect cables with laser on 1 and phototransistor on the other.


texts:
Hello I have been working on an analog temperature sensor TMP36 and I am trying to get the temperature and display it on the NEXYS3 SSD.  I am aware the NEXYS3 does not have an analog pin and I built an analog to digital converter using the TI ADC0804 an 8-bit ADC.  The part I need help with is particularly getting the input from the temperature sensor.  I do not understand the data sheet well enough to come up with the formula in verilog. The only example I found was for an arduino in the link below

https://learn.adafruit.com/tmp36-temperature-sensor/using-a-temp-sensor

DATA SHEET

http://www.analog.com/static/imported-files/data_sheets/TMP35_36_37.pdf

I am powering the ADC with 5 volts and need help converting their formula to verilog.

Voltage at pin in milliVolts = (reading from ADC) * (5000/1024)
Centigrade temperature = [(analog voltage in mV) - 500] / 10

Those are the two formulas I need help with. I need an formula equivalent in Verilog.  The output to the SSD is an 8-Bit number in other words am only interested in temperatures 0-99 for my project. Thanks any help would be appreciated.


texts:
I am trying to understand how radio IF transformers are characterized and specified.  In the image above from a Mouser catalog are three different IF transformers with a center frequency of 455 kHz.  The inductance for all is listed as 680 uH, but the impedances for both the primary and secondary windings are all different, for the primaries 20K, 30K and 60 K; for the secondaries 6K, 500 and 600.  All three have a capacitor of the same value (180 pF) across the outer leads of the primary winding.

As I understand it, the IF transformers resonant at their center frequencies.  The calculation for resonance for 680 uH and 180 pF gives 455 kHz.

I am guessing that the listed impedances are actually resistances, i.e., no reactance, at the center frequency of 455 kHz, and are altered from one IF transformer to the next by the number of windings and the nature of the yellow, white or black tuning slug.

I am at the stage where I don’t know what I don’t know.  I have looked for a white paper on IF transformers and so far have come up dry.


texts: Using a LCA110 DIP-6 Solid State Relay to switch 330v DC

texts: Would a LCA110 DIP-6 solid state relay work for switching 330v DC? I cannot find information on the datasheet of whether or not this is suitable for switching 330 volts DC. I am using it to switch 5 80uf 330v capacitors into a coil for a coilgun, using an Arduino.


texts: How to include Rayleigh fading into path loss model?

texts:
I am doing a student project to localize the physical position of a network's nodes in outdoor environments. It will be done by RSSI values.

Background:
To do this I need to get a good model of how the signal strength propagates/attenuates in the environment of choice. I have studied some theories and the most used (as I understand) is the log distance model:
PL(d) = 10n*log(d/d0) + PL(d0), where d is the distance, d0 the reference distance and n is the environment path loss coefficient.

This can be expanded to take shadowing into account with a stochastic variable X ∈ N(0,σ)
PL = PL(d) = 10n*log(d/d0) + PL(d0) + X

Question:
I have read a lot about Rayleigh distributions but I do not see how this shall be implemented in this equation. Can someone help me to understand how it can be included?


texts: Turn on/off led via headphone jack in iPhone

texts:
I have an iPhone project , I need to turn on and off a led powered with a battery using iPhone via 3.5 mm jack.

there is some examples what I need

https://www.youtube.com/watch?v=w0VopnVZQ-w

http://www.ipinlaser.com

I need suggestions. I know some simple basics on circuits but I'm totally noob about this.


texts: I found a motor/generator thing at my school's storage. I was wondering if anyone could identify it

texts: Im not sure what this is because it has both a commutator and a stator. It didnt have anything else with it. Im guessing it has something to do with ac generation.


texts: Audio Grade Capacitors - Marketing Hype or Better Technology

texts:
I have been reading a lot about audio grade capacitors lately, and I cannot find very good information about them. I have read many posts from different sites saying that audio grade capacitors are just a marketing hype, and that there is nothing new inside of them. Is this true? Or is there something special about these audio grade capacitors that I am missing?

If they really are better for audio than traditional capacitors, what then makes them better? Also, what would be a good test circuit to compare the differences between traditional capacitors and audio grade capacitors?

If anyone reading this has experience with audio grade capacitors please share your thoughts and experiences below. I really want to figure out if this is a marketing hype or not.


texts:
In a buck converter, is there any correlation between switching transition time and decoupling capacitor requirement?
As per the TI document attached input decap values are only determined by input ripple current and switching frequency.
In the text book "A to Z Switching power supplies_Sanjay Maniktla", it was mentioned the noise has little to do with the basic switching frequency of the converter itself — it is the transition that is responsible for most of the noise, and all its attendant problems. Is the author referring to voltage spikes (noise) due to stray inductance alone?

TI document on capacitor selection

Thanks in advance


texts: Find v1 and v2 of a summing amplifier when it is in series with another Op-Amp

texts:
There is a summing amplifier with two AC power sources (v1+v2,) each connected to a different Ground. Each of these sources connect to a resistor (R1+R2,) and then to a summing point, which branches off.

One branch leads to the inverting (-) input of an Op-Amp (with the non-inverting (+) input connected to a 3rd Ground.) The other passes through a feedback resistor "Rf1" before connecting, along with the output of the Op-Amp, to point Vx.

The circuit then continues from point Vx (through a resistor Rc) to a second summing point, which also branches off. One of these branches leads to the inverting input of a second Op-Amp (with the non-inverting input connected to a 4th Ground,) and the other passes through a second feedback resistor (Rf2) to meet the output of the second Op-Amp at another point. This point then continues on to V0.

I know that R1 is 1.8kOhms, Rc is 2kOhms, and Rf2 is 6kOhms.

Supposedly the operation of this circuit is v0= 3v1 + 1.5v2, but I don't know what that means.

[![enter image description here][1]][1]


texts: I am looking for a single 12V DC switch which has an on-off-on actuator that will do the following: two 12 volt+ input pins completely separate from each other, each with its own two loads. In other words, when switch is in up position, only ONE power source in with two loads going out. The same would be true for the down position. The two power sources should never share the load together. I am wanting to run two 12V devices from one switch using two separate power sources. I hope this makes sense! :-) Smiles


texts:
I want a board I'm designing to accept either 5V or 3.3V power as input. If 5V power is supplied I want to generate 3.3V regulated power on board. The rest of the board all runs off of the 3.3V power. If I call my input power VDDIO, and VDDIO = 5V, then I know I can stick an LDO in there to get my 3.3V for the board. My question then is how do I allow for the case of regulated 3.3V input power.

One solution I thought of was to put in a normally-open solder jumper between Vin and Vout of the LDO, to let someone manually bypass the LDO. A more accessible direct analogy to this would be to include a bypass switch. But I'm interested in whether there may be a more elegant way to achieve the same effect "automatically", or whether the LDO will "handle" this for me already (i.e. if regulated 3.3V is fed into it, maybe it will just pass through to the output).


texts: What are the advantages of a synchronous switching regulator?

texts: DC-DC switching converters come in synchronous and non-synchronous varieties. What are the advantages of the synchronous regulators? Are there different advantages for a synchronous buck versus boost regulator? Am I likely to need the same number of external components for either topology? Will they produce the same amount of EMI or ripple?


texts: Using the audio input port as a voltmeter

texts:
I'm a physics undergraduate currently studying electromagnetism. I have no experience at all with playing with electronics. I'm trying to see the effect of a changing magnetic field on a closed circuit (the Faraday-Lenz law)

Now, I have collected some old wires, a male-male audio cable, and some magnets taken from a toy for children. I am also using my MacBook Pro (mid-2009). What I built a rudimentary coil, connected the two ends to two of the pins of the audio cable, and connected the cable to the computer via the audio input port. I expected to be able to see some audio input when I would pass the magnet through the coil.

What really happens, in the best case is just nothing, there is no audio input, even when I make the magnet pass inside the coil. However, when I connect just one side of the coil (which in fact is a long wire) to one of the pins of the audio jack (without connecting the other side), the computer records continuously a fuzz. The first question is why does it happen? I can understand that, given that the two pins are not connected, a potential difference between them is detected, but this happens even the two pins were connected before disconnecting one of them. Why does a potential difference instaurate?

Moreover, I suppose that my experiment is a failure because I'm trying to detect potential differences which are orders of magnitude lower that what I can detect. I have really no experience in the field, so I'd like to ask you:

what are the voltages of a typical audio input? For my computer Apple says nothing.. and if they are much larger than those produced with my coil, how can a small microphone produce them? How come that even when I use my headphone as a microphone it works, but my system does not
what is the typical value (in Teslas) of the magnetic field produced by a simple toy magnet?

I'm attaching a picture of the "apparatus", so you can see yourselves what I'm speaking about

Thank you very much for any response


texts: Are the 3.3V and 5V pins on an Arduino input or output?

texts:
I need a 5V supply for a device I want to control with my Arduino, and was wondering if the power pins on the side of the board are solely for powering the board, or if i can take a line from them and power other devices?

I know there are other answers to this question but they seem quite complicated, and I am very new to Arduino.

Also what's with the VIN pin? I saw somewhere it is 9V?


texts:
When I am learning about DMA, I came to know that it can be implemented in UART peripheral operations too. Till now, I have used UART peripheral for simple communication operations. Sometimes I use it for Modbus protocol based projects. Put aside, simple projects, in Modbus protocol projects, I constantly process every byte received via UART receive interrupt to do further process quickly or with very minimal delay.

But DMA explains that it can trigger CPU interrupt after all of its buffer/half of buffers get filled only. Also, there is a situation that I don't know how much data comes via UART reception. If I receive only 4 bytes, then I need to process it. If I am supposed to receive 120 bytes to process, I need to wait for it. So here the length is not constant, at least in my requirements. But using DMA with UART needs constant byte count as far as I know. So, I dropped the idea to use DMA in Modbus based communication projects. Is it correct?

But using DMA free CPU burden more than a regular interrupt method. But in which applications can I use it? In which applications is UART + DMA concept more suitable than normal UART interrupt method? If there is any application link or examples available it will be helpful.


texts:
For our term project we have to design a vehicle which has to have three functions; move forward, turn left and turn right. The vehicle will have two dc motors that will work at the same speed for forward motion and at different speeds for turning movements. And by remote controlled, I mean the controller and the vehicle will have a single wire connecting them.

The components we can use are a DC power supply, any types of resistors, capacitors, inductors, diodes, LEDs, LDRs, op-amps, transistors, push-buttons, and switches.

So we will have three buttons on the controller which will generate sinusoidal waves of 10kHz, 30kHz, and 50kHz; and three bandpass filters at the vehicle with corresponding center frequencies.

Our first problem is about the sine wave generators. We have to be able to control the speed of the forward movement and I think changing the amplitude would be the best way (with a POT for example). Our first idea was to use Wien-Bridge oscillator but honestly I couldn't figure out a way to control the amplitude. So if you happen to know any sine generator that we can control the amplitude with a single POT, it would be great.

Our first problem is about the type of the bandpass filters. We need one with a narrow bandwith and we don't want to use any inductors, but again we could not come up with a good one.

So any suggestions or ideas?


texts:
This circuit looks like an active high pass filter but without a second series resistor.

What is it really?
What is the transfer function Vo/Vi?


texts: How to determine timing delay of SR-Latches?

texts:
I don't understand how to determine how long a delay should be. I understand 1.4 and 2.8 come from the delay of the gates, but how can you determine which delays first?

For example, why does Q' have a 1.4 ns delay while Q has a 2.8 ns delay. Why doesn't Q' have 2.8?
Don't they both go through the same two gates?
How do you determine Q' changes first?


texts: Generation and transmission of electricity

texts:
According to my textbook the three phase power is generated so that the power that is needed to generate electricity by the torque remain constant. Another reason is that the summation of the three signals are zero so only one return wire is needed when the loads are equal. Therefore, the number of wires get decreased from 6 to 4.

I have some questions about the basics of generating and transmitting electricity.

1- I don't see how can we assume that the loads are equal when that depends on the users and the number of appliances that they use.

2- So the electricity is generated and transmitted as three phase, could someone explain to me in one form it enters our home.


texts:
New here + reasonably new to electronics - can solder + hack, but anything finer I need help with!

Building a games rig out of an old console case. I'm looking to have the PSU outside of the unit to keep temps low.

The key component is an Odroid XU4 (http://www.hardkernel.com/main/products/prdt_info.php?g_code=G143452239825)
It's rated at 5V/4A. I've been advised that the voltage/A needs to be super steady:

"5Volt +/-5% tolerance is required.
So the PSU must have well regulated output at 4.75V ~ 5.25V range."

What I'm seeking to do is also power other components in the unit. Thankfully all at the same voltage:

Powered USB2 Hub - 5V 3A
Powered USB3 Hub - 5V 1A
HDMI Audio splitter - 5V 1A

Thus, I'll need a new PSU (I'm guessing rated at 5V 9A??). My questions are:

1) How do I split the 5V supply 'cleanly' in the unit - that is to make sure the Odroid is protected. I've been advised against something like this, due to 'voltage drops' or something:

2) Considerations around buying the 5V 9A PSU? Need anything in particular?

Been re/searching for a couple of days now and still none the wiser. Thanks + hope someone can help!

====================================

EDIT: Worried my potential solution got lost in the comments below. So put here.

So will this work:

I can amend my design to use:
 1x12Vx2.5A USB3 Hub;
 1x5Vx1A HDMI splitter and the
Odroid @ 5Vx4A.

I see a 120W picoPSU with ratings: 5V @ 6A, 5VSB @ 1.5A, 3.3V @ 6A, 12V @ 7A, -12V @ 0.05A. So this should work, right? One question though, I'd have to put the Odroid on the 6A 5V line, but would need the 5VSB line activated to power on the other devices?


texts: How to adjust duty cycle of an existing square-wave, based on light level

texts:
I am making a wall-powered, battery-backed, BCD alarm clock with discrete logic.

I'd like to adjust the brightness of the LEDs based on light level, as this clock will be used on a nightstand. So very low brightness in the dark, and high brightness in daylight.

The LDRs in my junk bin are about 70 ohms in bright light, and 500k in darkness.

As part of the clock oscillator, I already have 128Hz and 256Hz square waves available, which should be an appropriate PWM frequency for LEDs.

Supply voltage is about 4.6V.

For the duty-cycle adjusting, I can use a 555 timer, or general purpose transistors.

Trimpots to adjust the min and max levels would be nice.

The LEDs are wired as such, each with a 150 ohm resistor, so I'd like to switch the common GND.


texts:
I'm designing a IEC Class I device with requirement of grounding the chassis. The device use a AC power supply with V- and V+ outputs.

How should I connect the ground of the internal circuit? Should it float (connect to V- of the power supply) or is it OK to connect V- with the chassis that share AC ground?


texts: Decision Feedback Equalizer, what is the use of it if data are already detected?

texts: Since the decision feedback equalizer relies on correctly estimating the symbols in a detector before the feedback  , what is the use of it if the symbols have already been correctly detected?


texts:
I am working on a setup where  OPT301 is fed with an optically filtered light output yield a very low current which is then Current to Voltage converted by integrated op-amp within the device, but the feedback resistance used here is 100 Mega Ohm to derive output voltage of 0.14 V (min) to 1.2 V (max).

Now, I wish to digitize this voltage for the purpose of monitoring it over a period of time. For this I tried to buffer the output from sensor, amplify (using difference amplifier configuration) it to range of 0V-5V and then feed it to MCP3208 ADC through an op-amp buffer again. Op-amp that I am using is TL084 which is a JFET-Input Op-Amp.

Now at the input of all the devices put in this circuit I am able to measure constant voltage for a particular sensor output, but as soon as I try to retrieve my ADC output through SPI (with as low as 10KHz SPI clock), I see an oscillating voltage on the logger. However, the multimeter gives a static reading all the while.

Following is my circuit:

Please suggest where I am going wrong.

Is the choice of Op-amp is wrong? [Will be trying the same logic with OP07]
Is there a need to filter the sensor first?


texts: 4.5 volts voltage with the 74HC logic family?

texts:
I'm sorry if my question is too specific to the 74HC logic family, but as the answer may vary by family, I place myself on the safe side.

The 74HC family runs from 2 to 6 volts or 4.5 to 5.5 volts as nominal voltage according to Wikipedia.

I will probably be using 4.5 - 5.5 volts chips, as those are the easiest to find.

The problem is, while my project will possibly be powered from a 5 volts power supply, I would like it to also run on batteries.

For my needs, I think I should use 3 AA batteries in series, which output will output 4.5 nominal volts.

But, as the batteries discharge, there will be drops in voltage across the circuit. As 4.5 volts is already on the low edge of the 74HC logic family, my project will definitly go below that.

Is the use of voltages of 4.5 volts or lower still "ok" for the ICs, at the cost of increased propagation delay ? Will it affect the lifespan of the ICs ?


texts: Weird fault in circuit - Charge building up and blocking potentiometer?

texts:
I've made some inline headphone volume attenuators myself for live use, so that we have some volume control on our hip and don't have to wander over to the headphone amp, partly because I didn't want to shell out 60€ for a couple of Behringer Powerplays (also I didn't want the XLR input, I prefer a 3.5mm input) and partly because I like a challenge.
So I've made this circuit (a little voltage divider with 1Kohm stereo potentiomers)

And, I'm experiencing a couple of problems, I'm pretty sure I've isolated it down to the potentiometer. For some reason the potentiometers get 'jammed', I don't know how else to describe it. The channel sometimes goes silent unless I bridge the contacts with a screwdriver, after that it seems to work just fine and I have no idea why this fixes it. It's like a charge builds up in the potentiometer and stops the signal travelling through. Does anyone have any suggestions why or possible solutions?
My potential idea is to bridge the contacts together and to ground with a large resistor (1MOhm or something), is this sensible?
Thanks.


texts:
I am trying to build a circuit with 2 inputs and 1 output using Mosfets.

I will try to explain what I want..

The circuit should accepts 2 input DC voltages , the first input voltage called "MAIN_SUPPLY" which will be the "ALWAYS ON" input that may vary between 22VDC to 25VDC. If the main supply goes OFF then my output LOAD should switch to the secondary input which will be treated as batteries (AS BACKUP) .. Battery Voltage may change from 20V to 30V (Due to the charging).

The circuit image is below , it should work for input voltage below 20V due to the absolute maximum ratings for VGS for each mosfets .. I am unable to make this circuit work with 24V system . Is there a solution for me to use the same circuit 24V system or is there another circuit that would help me .

I chose to use mosfets , because they can switch fast (nano seconds).
I have 3 routers with a total power consumption of about 30 to 40 Watts.

The below ciruit shows a complementary design using N-channel and p-channel .I don't have a problem with the P-CHANNEL mosfet . My problem is IRF2805 as its Max VGS +20VDC and i require +30V. Because I am applying 24VDC to the source pin of IRF2805 that means Gate pin must have higher voltage than its source .

When the 2N7002 or similar control MOSFET ties the gates together and pulls them to ground, the p-channel MOSFET is on. Pulling the gates above the supply rail by turning the 2N7002 off results in turning the n-channel MOSFET on. Pulling the gate of the p-channel MOSFET above the source potential has no effect; the MOSFET remains off with low leakage. The resultant switch is a break-before-make configuration, which is necessary to ensure that the secondary, or always-on, supply never has to power the whole circuit.

the label NET [USING_BATTERY_V] is to charge the gates of nmosfet an pmosfet. N-channel has no effect on that . [USING_BATTERY_V] has to be always ON 28VDC. p-channel is affected and it stops 30V to pass thus allowing MAIN_SUPPLY to pass . When we charge the gate of 2N7002 then it turns off all gates and the load switch to secondary_supply. I have rb260gsp as a router and it accepts voltage from 12 to 30VDC so I don't get hurt if the 2 supplies have different voltages.

I don't want to work with surface mount parts.

I can buy any part online .

Is there any mosfet p-channel and n-channel that accepts VGS up to 30VDC.?

I really appreciate your help.


texts: Simple circuit to protect 2.7V supercapacitor from exploding

texts:
I need advice and help. I am newbie and kind of interested in building things. Please bear with me.

Situation:

I want to power my wireless modem/router using a solar panel so when there is no electricity I can still watch videos and surf internet as there are frequent brownouts in my area.

Buying a lead battery is expensive and not nature friendly, secondly I want to explore things or building things. So I started reading about solar panels, capacitors, diodes and transistors, etc.

I bought soldering (irons,leads) and digital multi-tester. I bought a super-capacitor rated as 100F 2.7V

I read that when the capacitor is charged or exposed to more than the values it is design it will explode.

I tested the solar panel using multi-tester and it shows 7.2V.

QUESTION:

If I connect my solar panel (7V) supply to my super-capacitor which is only 2.7V then my super-capacitor will explode, right? Is there a simple way (circuitry) you can suggest to avoid my capacitor from exploding?

The input is 7V and I read that capacitor explode when they are exposed to a higher voltage source.

I cannot buy resistors in my area so I am salvaging some resistors from older radios and TVs that are still working. I can order online but it will take weeks to come.

How to make sure that the input will never be above 2.7 volts since super-capacitor is rated only 2.7V 100F.

[EDITS]

Sorry I like to correct the capacitor value: 2.7V 10F

I would like to add more about my situation.

My location is always sunny and in-case there is a power cut and it's  daytime I want to power my router/modem using the solar panel that we have.

The solar panel supply is not fixed depends on the sunlight. It sometimes produces 5V up to 9V.

I read that capacitors function like a temporary battery. The goal is to provide a steady flow of 9V for the router.

In case the solar power source drops then the super-capacitor will still have the power to supply the 9V.

Please note I have 6 super-capacitors (2.7V, 10F.) I bought them online. See the image below.

Bear with me. Thank you.


texts: Current Starved inverter with current sources connected to Vout node

texts:
The figure a is the conventional Current Starved inverter with M1 and M2 acting as current sources.
However, I saw somewhere the variant as figure b. The current sources are now connected to the Vout node instead.
What is the advantage of the structure in figure b?
UPADE FIGURE:


texts: How to count the units moved with 2 motor encoders

texts:
I have a 2 wheel device that both has motor encoders, counting the units moved on both motors is simple if the both motors speed is the same. My problem arises when the device is turning to the left or to the right. Turning causes one motor to speed up and the other to slow down. The count now on each motor is different.

Is there some logic or arithmetic i can apply that takes into accounts turnings? and can calculate the true distance moved of the device. The point of refence now of measuring the distance is now not on the wheel since it is not very reliable but now on the center of both wheels.

What I came up with is just to AVERAGE the left and right motor counts, but i do not know if this is the best solution to approach this problem

Any thoughts?


texts: 2 x 60 Watt audio amplifier with 4 Ohm speakers

texts:
I need some help designing a stereo audio circuit for my speakers.

some info about them:
The speakers I want to use and already have are the ones from the Phillips DCM3020/12. They are 4 Ohm speakers with an output power of 60 Watt RMS. Since the amplifier and cd/radio/usb/ipod thing is too big for what I want to build my own amplifier.

The input I use if from my PC or my phone (audio jack cable to RCA).

The problem is that I dont know how to start designing this circuit since I dont have a lot of experience with audio amps.

Im not asking for someone to design the circuit for me, Im just asking how to start (what specifications does the amplifier need to have for these speakers etc. and maybe give me a direction of what audio amp to use).

I see a lot of things about input power, but on the site it only says that output power is 2 x 60 Watt rms. Hopefully it is possible to make this since I dont really want to buy new speakers.

Thanks!


texts: Why 2 zero-crossing detection circuits in heater?

texts:
I reverse engineered the power board of an electric heater. I think, I understand most aspects of this circuit. One thing is not entirely clear to me though: The circuit seems to have two distinct ways to detect the zero-crossing point which is needed to control the Triac:

Via the opto-isolator (U1) that is directly driven by the primary
Via the voltage divider R7/R8 that taps the secondary of the transformer

Both signals feed directly into a microcontroller (PIC16F886). Both pins (RA5/RB0) on the microcontroller can be configured to be inputs to the built-in ADC.

What could be the reason for having those 2 separate circuits?


texts: 75 Ohm trace with error markers in Altium

texts:
I am designing an RF PCB in Altium and I have set rules for 75 ohm as well as 50 ohm impedance traces. The picture attached shows a particular 75 ohm traces with error markers. The trace width is as specified by the rule and the DRC check does not show any errors. When I reset the error markers the markers do not go away. As you can see the traces are not the problem since the markers are also showing up on component pads.

I appreciate any comments.


texts: If the integrated circuit die is very small what is the role of the extra circuit packaging?

texts: I noticed that the actual integrated circuits of processors, GPUs, ROMs, specific integrated circuits and other ICs are very small but they usually come in a package that is much bigger. What is the purpose of the packaging? And what are the materials that IC packages are made of?


texts:
My question may seem a little bit easy but I'm new to these concepts and was hoping if you could help me clarify them by answering my questions.

The received signal at the detector writes:
$$ y = h x + n$$
where \$h\$ is the channel gain, \$x\$ is the transmit intensity being \$0\$ or \$2P\$ and \$n\$ is Gaussian with zero-mean and variance \$\sigma_n^2\$.

I want to compute the BER in BPSK modulation. My problem is how can I compute \$y\$ knowing that \$x\$ can be either \$0\$ or \$2P\$. I know how to sample from \$h\$ and \$n\$ but I don't know how to generate \$x\$.

If \$\mathbb{E}[x^2] = 2 P^2\$, does this mean that \$E_b\$, the energy per bit equal to \$2P^2\$?


texts: What effect does the thickness of metal plates have on capacitance?

texts: Clearly a decrease in thickness of the dielectric increases capacitance, but how about the metal plates on a parallel plate capacitor? If you increase or decrease the thickness too much will you see a increase/decrease in capacitance? Is there an optimal thickness of the metal plates?


texts: What is the point of R3 in this reference design?

texts:
The TPS565201 datasheet (page 5) specifies that EN has a typical resistance of 245k to GND so I know it is safe to connect EN directly to 12V (max 19V rated).
My questions is if there is already an internal 245k pulldown to GND on EN, what is the point of the 10k R3 resistor?
Is it a cue for designers to add an external switch or is there some internal thing I'm missing?


texts: Inverter Circuit using IR2113, TLC555 and signal inverter IC

texts:
Input DC = 30V

operating frequency = 10kHz

problem =
When I am at the no-load condition at the output, only the oscilloscope is connected, I am receiving the proper output. But when I connect a load, which is a 10 Ohm resistor, the output voltage drops down to almost zero.

I really need a bit of professional advice here.


texts: Power supply for a solenoid to open a secret compartment

texts: I'm an avid DIYer, I don't know anything about circuits, meters, mathmatical equations etc. I have created a secret storage compartment so the door has no visible hinges, handles or locks, It's made of wood and weighs around 10 kg, it's held closed with medium strength magnets. I'm looking at using a push solenoid with a spring to return the pin back to starting position connectted to a doorbell type button via the main lighting circuit using 1.5 cable. 2 problems. Firstly can this be done, do I have to add a transformer into the mix,if so how? Secondly how will I know if the power of the solenoid will be able to detach the door from the magnets to open? Only place that sells solenoids in lamens terms is Amazon so this is where I'll be purchasing it from.


texts: I have gone through various sources... But I am not quite sure what it is.I want an and gate and the logical equivalent is two inputs feeding to one gate and for Y=AB' the logical equivalent is feeding to one not gate and one and gate. But it is the same LUT for both AND and Y=AB'. I think we store the values as desired in the LUT. Someone elaborate on this


texts: Determining distance between wireless sensors - sailing project

texts: I'm looking for a solution which will allow me to determine the distance between two points, one of which is static and the other not. It's part of a project I'm working on which will involve the creation of a sailing app for my boat. Based on a wireless network of sensors, I want to be able to determine and display on a tablet, information which shows how far the sails have been hoisted up on the mast. I need to put some sensors on the mast and in the sails themselves. I worked on RFID tags but got poor results due to high power consumption. I tried ZigBee distance measurements and accelerometers but ended up with a lot of noisy data. Any ideas on the matter would be much appreciated. Please remember that there are environmental matters to consider (weather) and the fact that the boat is in constant movement.


texts: How to create a 13.56MHz PCB antenna in Eagle?

texts: How can I create a 13.56MHz PCB antenna in eagle since I can't find any suitable antenna library in Eagle, even failed to download 13.56MHz antenna .lbr in the internet. Kindly help


texts: How to flash error if a macro is not defined in program

texts:
I want my program to flash compile time error like "LCD_PORT not defined" if it is not defined in program itself. For that I modified the header file like this

.
.
.
#if LCD_IO_MODE
#ifndef LCD_PORT
#error LCD_PORT not defined //(e.g. #define LCD_PORT PORTA/B/C/D)
#endif

#define LCD_DATA0_PORT   LCD_PORT     /**< port for 4bit data bit 0 */
#define LCD_DATA1_PORT   LCD_PORT     /**< port for 4bit data bit 1 */
.
.
.
...

But even after defining the LCD_PORT (like in the following program), it flashes the error.

#include <avr/io.h>
#include <lcd.h>

#define LCD_PORT PORTA

int main(void)
{
    lcd_init(LCD_DISP_ON_CURSOR);
    lcd_home();
    lcd_gotoxy(0,4);
    lcd_puts("Hello world!!");
}


texts:
I am working with USB HID in stm32f072. On Get_Report Request I have to send data to Host PC through Control Transfer Endpoint. I am trying to do so. But it is sending always some wrong data. If I want to elaborate the problem, that is

 case HID_REQ_GET_REPORT:

  if(req->wValue==PID_POOL_BLOCK_REPORT){

    buf[0] = 0x07;
    buf[1] = 0xFF;
    buf[2] = 0xFF,
    buf[3] = 0x0A;
    buf[4] = 0x02;

    if(USBD_LL_FlushEP (pdev, 0x00)==USBD_OK){

      USBD_CtlSendData (pdev,
                        buf,
                        5);

    }
  }

But the data send through is actually "0xF6 0x3A 0x82 0x28 0x45". I have no clue what is happening inside. I have benn trying it with flushing the endpoint too. But it seems no working. What to do really? Any clue please. Thank you.


texts:
I am just getting into the plant environment and the first thing I noticed is that virtually all the motors are controlled by VFDs.
I understand that your supply goes into your RST terminals and the motor to the UVW terminals.
My question is, just like how a contactor is normally open and kicks in when the coil (A1 & A2) is energized, is a VFD also normally open and what kicks the VFD in?
Also, the drive also trips and cuts out the power during faults. Exactly where is this power being cut from?


texts: I want to design the following inverter circuit, I know the general working of it, but I need some details. in the gates of the FET transistors used in H Bridge there is a design contain 4 diodes 2 resistors and tow capacitors connected to bjt then to the 4013 ic, I want to understand how this component works to determine the floating point in each transistor drain.


texts:
I'm learning about circuits and came across open collector and drain logic circuits, I wanted to ask...

What are the benefits of open drain/collector circuits?
In which logic circuits are they used?
Are they used for logic gates?


texts:
I have this DC-DC converter:

For reference the model is R12-150B and the manufacturer is RECOM.
Every single pin is doubled, what's the purpose of that? When I connect it to my PCB should I connect every single pin or should I connect only one of each?


texts: Pmos or Nmos? Which has the biggest contribution to flicker noise?

texts:
I would like to ask if this sentence below is correct.I had find it, when I was reading a paper.

"PMOS transistors have lower flicker noise than similarly-sized nMOS transistors in most CMOS processes."

I am a little confused why PMOS transistors have lower flicker noise.I didn't find a good explanation for this.


texts:
Just understanding some syntax. On my Ram (6116) and Rom (27C64) it has a asserted low CE and OE pins. These I believe are control pins.

I'm assuming to use the RAM for example, chip enable (CE) has to be low. Then Output enable has to be low for data to be sent/read to the CPU?

If I'm right so far by looking at the 6116 ram the data bus pins can be either input/output. So CE or OE don't determine whether data is being read or written to that address location. There's another pin called WE which I'm assuming is a control pin for data to be input/output.

What does WE stand for and am I right with what I've assumed?


texts: Noise when amplifier and chromecast share a power supply

texts:
simulate this circuit – Schematic created using CircuitLab

I want to power a chromecast and an amplifier from the same power supply.

When the dc/dc converter is powered by a separate power supply, there is no noise coming from the amplifier.

But when the dc/dc convertor is powered from the same power supply as the amplifier there is noise coming from the amplifier.

The DC/DC converter is isolated, so this shouldn't be a ground loop.

What could be causing the noise?
How can I fix it?

Isolated DC/DC converter


texts: What is the meaning of Change in Output Offset Voltage between complementary output states

texts:
I have MAX9278 deserializer IC which is connected to a 3.1inch TFT display 800 (W) * 480 (H).
Deserializer provides 4 LVDS lanes and 1 clock to the display.
While I checking the electrical voltage compatibility between the Display and the deserializer, both have a differential voltage levels of 1.125V to 1.375V. So, I believe they are compatible. But,
In the table "DC Electrical Characteristics" page 10 :

Does the Output Offset Voltage "Vos" actually mean Common Mode Voltage?

What does the "Change in VOS Between Complementary Output States - del(Vod)" & "Change in VOS Between Complementary Output States - del(Vos)" ? Can someone help me with a diagram on what does this mean?


texts:
I am working on a battery charging circuit based on a solar panel and require a constant voltage supply of, let's say, 5.0 V to the battery. However that's not what one gets from the solar panel. This calls for the use of a voltage regulator.

The constraint here is that I shouldn't be wasting much power from the solar panel through a standard linear regulator like the LM317. Is there any alternative to this?


texts:
I am routing a 16 bit ADC chip, the LTC2217 (datasheet) to FPGA. Each bit is an LVDS pair and I know +/- of the pair should be the same length but what about from pair to pair? I have 2 of these chips, 18 pairs, if you include OF and CLK, 36 pairs of LvDS having to be meandered to the same length becomes somewhat messy.

IE say bit 1 is 35mm and bit 0 is 37mm, how far off, if any are they allowed to be? I assume it has to do with sampling frequency, which for this chip is 105Msps.


texts:
I'm following a bare metal course, I have managed to set up the project within IAR, my project compiles and runs.
I'm attempting to get the user LED (LD2) to flash before I continue the course.
I'm operating on a NUCLEO board with the STM32L053R8 chip. Trying to manipulate the chip registers with this User Manual
the LD2 on the NUCLEO board is connected to PA5.
#include "stm32l053xx.h"

void delayMs( uint32_t delay);

static volatile uint32_t ms_tick = 0 ;

int main()
{

  RCC->IOPENR |= 0x1;

  GPIOA->OTYPER &= ~(1UL << 5);
  GPIOA->MODER = (GPIOA->MODER & 0xEBFFFCFF) | 0x00000400;
  while(1)
   {

      GPIOA->ODR ^= (1UL << 5);
      delayMs(1000);
   }

  return 0;
}

void SysTick_Init(void)
{
    SysTick_Config( SystemCoreClock / 1000 ) ;
}

void SysTick_Handler(void)
{
    ms_tick++;
}

void delayMs( uint32_t delay)
{
    uint32_t start_tick = ms_tick ;
    while( (ms_tick - start_tick) < delay );
}

I'm very sad to admit that this has cost me somewhere around 10 hours of trying different things :)
I was going to take a look at configuring the clock (HSI) but wanted to ask for some pointers before attempting that and possibly digging my hole deeper.
So what in the world am I doing wrong ? I have read the other threads about the subject, but can't get it to work regardsless.


texts: Why is my homemade pulse transformer so inefficient?

texts:
I built this transformer core out of 30 mm mild steel. It is 13 cm by 8 cm. The primary winding is 30 meters of #29 wire, and the secondary is 60 meters of #29 wire. The windings measure 5 ohms and 10 ohms. A 100-ohm resistor is across each winding to absorb voltage spikes.
When I apply a 15 volt pulse to the primary, the secondary only produces 5 volts. The core will have eddy currents, and is not the most efficient design, but 17% efficiency seems overly low. I tried resetting the core magnetic field by applying reverse voltage, but it has no effect on the output.
The 15 volts on the primary seems to produce a very strong magnetic field, the pieces of steel are locked together when it is energized. But this field does not seem to induce any significant voltage in the secondary.
Am I having massive hysteresis loss?
What modifications do you suggest to get the output at least above 80%?


texts:
I'm building an electrolysis unit which will comprise a refractory crucible, containing the electrolyte and the electrodes. The heat will be generated from a furnace to aid the desired reaction.

A direct current will flow in from a programmable power supply to the electrodes.

The problem I imagine I'll have is that heat from inside the crucible will be conducted through the electrodes and cabling and into the power supply.

Firstly, is this definitely an issue? I can't imagine the heat would conveniently stay in the crucible. Secondly, how's best to stop dangerous levels of heat feeding back into the electronics? I thought about galvanically isolating the crucible from the power supply by having a pulsed direct current run through a coil, with that then inducing a pulsed direct current in an adjacent coil connected to the electrodes. I can then smooth the pulses out using (passive components) in an RL circuit.

If a diagram would help, let me know.

Basically, just don't want to fry the power supply! Thanks in advance!


texts: How can I solder a 2nd connection to a mini USB?

texts:
I have a device that utilizes a mini USB port to send and receive data. I am trying to figure out how I can hook a micro controller to that mini USB port so that it can also send and receive data.

When the mini USB is desoldered, there are 5 surface mount spots, 4 of which are for VCC, Ground, Data+, and Data-. I could directly solder 4 wires to those surface mounts, but I have two problems:

Soldering them is difficult because the surface mounts are very tiny, it requires steadily holding the wires in place, and since the area is so small, the solder crosses over to the other surface mount areas.
If there is any way, It would be really helpful if the mini USB was still functional

Is there any good way of achieving this?


texts: If I were to design a multi core processor with a lot of cores, what are the pro cons of having 8 bit, 16 bit or 32 bit cores?

texts:
I was lurking into wikipedia, looking about processors with the highest number of cores, and obviously when you need cores to communicate between each other it can be problematic since it require much more wiring.

I was also curious about how word length affect a core size in general (not considering printing resolution): if a core is square, theoretically, would it mean (I'm making wild assumptions here) a single 32bit core takes as much room as 16 8bit cores or 4 16 bits cores ?

If I would design a processor with as many as hundreds or thousands or cores, would 8 bit cores be more interesting to increase the number of cores at the expense of word length ?

(I'm considering 8 bit cores to see if constraining the programming to its minimum to maximize parallel processing.)


texts:
I'm looking for the pad dimensions and land patterns for the SO8W package. This page has drawings of many SO footprints, but no dimensions.

Where can I find dimensions for the SO8W package's PCB footprint?


texts: so here's the situation, i have a motor and i am controlling it with a bunch of transistors and an arduino, so i think i need a flyback diode to protect the transistor and my arduino, problem is i am printing the circuit on a single layer PCB , and i have to connect the motor connected as shown, transistors are used as switches and they are activated depending on the desired direction of the current, the problem is when i added the 2 parallel diodes, however was the direction of the current one of the branches will short the circuit, so i suggested this change in the second pic, this way current will go back to the battery, problem is i dont have any idea if that's gonna work and i don't even know how to test it


texts:
I studied electronics in a far away past and have sadly forgotten quite a lot. I was wondering what a signal to an 8 bit CPU looked like.

Suppose I want to send one word to the CPU, do I send 8 values encoded in a binary format or 1 value encoded in a 256-value scheme?

As in, does the signal ever only have two levels and the cpu knows that it must read 8 values to form a word? Or does every signal have 256 levels and one value is a word?


texts: STM32 - 2 MegaByte DMA Transfer ADC To SDRAM

texts:
I want to transfer 2 MB of converted ADC data into SDRAM. I'm using STM32F429 Discovery board which is shipped with a 4-bank SDRAM (1 Meg Bits x 16 Bits x 4 Banks (64-MBIT)).

I've configured the ADC and linked the related DMA; I'm using HAL_ADC_Start_DMA(ADC_HandleTypeDef* hadc, uint32_t* pData, uint32_t Length) to start the adc and DMA transfer, but the length is limited to 65535. As I investigated further I saw that the STM32F4xxx DMA's NDTR (Number of data register) is only 16-bit wide so I can transfer at most 65536 bytes of data in each DMA request!

Is there any way to fill all of the Bank2 of FMC (2MB of data) in one DMA request? Or can it be done with double buffering?

And second to that, The SDRAM has 4 banks each capable of storing 2MB of data; but STM32F4xxx FMC has only 2 banks for SDRAM. How can I initialize and use all 4 banks simultaneously to have the SDRAM's full capacity?


texts: Reverse voltage protection for lithium battery charging module with smd component(s)

texts:
I want to add to this famous single cell lithium ion battery charging module a reverse voltage protection:

I ended up with the following circuit (Load draws up to 700mA):

Sorry, updated:

My question(s):

Is this already enough, or should I add a zener-diode/transistor etc (if yes which one - smd preferred)?
Is this one p-channel mosfet able to switch fully on, even when the battery is almost empty (2.9V) or would another fit to this circuit better - smd preferred?

I've found a lot of solutions out there, but either for 12V-stuff or oversized.


texts: Is there more elements beside resistor, capacitor etc

texts:
If relation C = (dQ/dV) defines a capacitor as element,
what woudl raleations like (d2Q/d2V) and so on would represent? New elements or not? How is this related with current and voltage harmonious components?
How does it relates to Taylor series?


texts: Will voltage gain change in non-inverting op amp when load is connected?

texts: Is there any significant change in amplified output voltage when a load is connected to the output compared to a no-load connection in a non-inverting op-amp? Why?


texts:
I have two different UPS of different ratings. Currently I am only using one of them, but lately I have been thinking to add another one so that more load can be added and they can share the load.
Here is the circuit, do you think can work?
b1, b4 & b5 will be directly using mains and no UPS
b2 & b3 will be powered though Inverter 1 (or UPS 1)
b6 & b7 will be powered though Inverter 2 (or UPS 2)

Please note wherever its mentioned Inverter, I mean UPS (which is a more appropriate technical term)


texts: What exactly is the Primary Oscillator in the dsPIC 30F2020? How accurate is it? How does it compare with the Internal Fast RC Oscillator (FRC) on the same device? (I know this is more than 1 question, but are strngly related, so I hope it's no problem... :))


texts: Forming Norton generator from a voltage source and two resistors

texts:
Can I combine the E,R and Xl to form a current generator, with R and Xl in parallel. I need to find the impedance of Z so it develops most power, R-jX, or Z*, if Z is the impedance of the rest of the circuit.

EDIT: That is whether it can be transformed into this:

simulate this circuit – Schematic created using CircuitLab


texts:
This is a 40mW laser. It's about 2 inches long.

What kind of laser is it (diode, etc?)


texts: How to add/sum field strengths given in dBuV/m?

texts:
I'm trying to theoretically analyze the resulting field strength, R, from two devices with given field strengths (say r0 and r1), both represented in dBuV/m.

My first intuition was to use

R = 20*log( 10^(r0/20) + 10^(r1/20) )

But now, I'm starting to think that maybe I should use

R = 10*log(  10^(r0/20)^2 + 10^(r1/20)^2  )

, since if I were to first convert the dBuV/m to V/m I would have to sum them using (v0^2+v1^2) right?

To sum the question.

How to sum two field strengths given in dBuV/m?

EDIT (after answer by @Andy aka ):
Is below then the correct computation for resulting field strenght in dBuV/m?
r, R in [dBuV/m]
v, V in [V/m].

Given (1), (2) and (3)

(1)
\begin{equation}
v = 10^{( (r - 120) / 20)}
\end{equation}
(2)
\begin{equation}
r = 20*log(V) + 120
\end{equation}
(3)
\begin{equation}
V = \sqrt[]{v_0^2 + v_1^2}
\end{equation}
Gives (4).

(4)
\begin{equation}
R = 20*log(V) + 120 = 20*log(\sqrt[]{v_0^2 + v_1^2}) + 120 = \\
10*log((10^{( (r_0 - 120) / 20)})^2 + (10^{( (r_1 - 120) / 20)})^2) + 120 = \\
10*log((10^{(r_0 - 120) / 10)} + 10^{( (r_1 - 120) / 10)}) + 120 = \\
10*log(10^{r_0 / 10} + 10^{ r_1 / 10})
\end{equation}


texts: Choose right transistor for Battery protection IC

texts:
I would like to use the BQ2970 as a protection cuircuit for my litium battery (Varta CP1254 A3). It has a max. continuous discharge current of 120mA and also max. charge current of 120mA.
How do I have to choose the external transistiors? I read that I need to take the overcurrent detection voltage (Uodv = 100mV) and devide it by the maximal current (I):  Ron= 100mV/2*120mA = 0.41 Ohm. This restistance has to be the Ron restistance of the transistor. Is this correct?

I could not find any transistor which has such a high on-resistance. Will I get problem regarding heat, if the transistor has such a high resistance? Usually the resistance is in the mOhm range.

Did I make a mistake?

I think that I am not the only one who is using a battery with such low current limit.
Is there a way to choose a transistor with low On-resistance by for example using a voltage devider?

Added:

Thanks a lot for your answers.
So could I do it like on this picture?

Is it better to choose a high resistance and low Ron or like I did in the picture?

Will I lose a lot of battery capacity for my application when choosing high resistances because of low efficiencies?
Is there a problem regarding heat?

  One easy way to get more on resistance is to select a higher voltage part that has the same package .>

What do you mean by that? Can you give an example?


texts: How to power 12V 1A device with two 6V lantern batteries (1209)?

texts:
I have 2 EverReady 6 volt batteries model number 1209.
I also have a 12 volt 1 amp screen that I need to power.

How can I power the screen with these batteries?


texts: Why cannot circuits like astable multivibrator, RC phase shift oscillator and wien bridge oscillators be used as inverters?

texts:
I have been having this doubt for quite a while. An inverter basically is a power electronic equipment that converts DC voltage in AC voltage for powering loads that work on AC supply.So this means that the inverter switches operate at a frequency of 50Hz (for India).

Astable multivibrators also does the same job of converted a DC voltage into a alternating square wave voltage. Also I've found that research is going on in elimination of harmonics from inverters in order to obtain pure sine wave. Instead of that, why not use a simple RC phase shift oscillator or wien bridge oscillator designed to oscillate at 50 Hertz? Is it difficult to design? What are the complications faced in doing so?


texts: Do official transistor counts include cache?

texts: Title says it all: do official transistor counts, such as here, include the transistors needed to implement L1, L2, and L3 cache? I assume they do.


texts:
I'm looking for a way to transmit a clock signal and data over a single line,
 perhaps using a self-clocking signal such as Manchester coding.

The design I'm working on has a number of chained units, with data fed into the first unit in the chain and passed along to subsequent devices. In order to make connection easy I'm using USB connectors, so I have four lines (VCC, GND, D+, D-) for communications. Ordinarily I'd just use one for clock and the other for data, but I'm concerned about data corruption and cross-talk over the distances involved (1ft or so). As such I'm planning on combining both signal and clock onto one line, then using LVDS for improved noise resistance - after all, USB is differential in the first place!

This would likely be trivial with a microcontroller, but I'm trying to avoid that for both complexity and cost reasons. Is there such a thing as a transceiver IC which translates between discrete clock and data pins and a combined self-clocking signal? What sort of keywords should I look for?


texts:
The excerpt below is from ASDTIC control and standardized interface circuits applied to buck, parallel and buck-boost dc to dc power converters.

On page 2, introduction section:

  The electrical performance of a dc to dc converter depends, to a large
  extent, on the quality of its control system. Unfortunately,
  most single-loop approaches suffer from many inherent limitations:

  ...

  The long time constant associated with the low-pass filter delays the    rate of power-switch-modulation adjustment responding to a
  dynamic    line and/or load disturbance, thus compromising the
  converter dynamic    response.

  ...

What is time constant in LC circuit? I know time constant in RC, RL circuits but the time constant in LC circuit is somewhat strange to me.
 Can anyone explain it?


texts: How can I connect wires to my breadboard?

texts:
I am building a couple of data acquisition fixtures. I'm locating the USB daq hardware and a breadboard inside an enclosure with panel mount sockets for the external connections. Nice and clean, nothing fancy.

I had originally planned on using through hole screw terminal blocks in the breadboard to make the connections between the panel mount connectors and the data acquisition hardware.

There are some voltage dividers and other small circuits that I planned to implement on the breadboard. So the idea is:

I would go from enclosure mounted connectors (e.g. 2mm pin female socket)
Solder wire to the connector and connect the other end to the breadboard
Implement basic circuitry in breadboard
connect wires from breadboard to DAQ (DAQ hardware has screw terminal blocks for connections)

I've run into a snag where the 3.8mm leads on the terminal block aren't long enough to properly seat in the breadboard. Now I'm trying to decide how I can easily workaround this with another design, here is what I've thought of:

Basic headers and plugs (the crimp on type that take a ribbon cable, usually)

Header and solder wires to the header pins
Wire wrap to something (never done it)

I'd like to avoid purchasing special tools to crimp specialized molex tpye connectors. I'm looking for a solution that will let me easily "hook up" my panel connections to my breadboard and disconnect them when I need to make changes or service something.

I'm asking the community here if you have any tricks or other suggestions?


texts:
I'm trying to make a push-pull audio amplifier with a pair of power darlingtons (TIP142 and TIP147), but i'm having problems with the biasing.

Here's the diagram of one of its configurations:

Here i'm using 3 diodes, but I used different things in their place to try to get the correct biasing voltage.

With a biasing voltage lower than 2.2 V (between the bases of the transistors) it has crossover distortion, because there'll be small parts of the signal where none are conducting.

With 2.2 V or more, both are always conducting and there's no more distortion, but there's a problem: The current flowing between them quickly escalates as they heat up until they take on fire (being that the starting current isn't even that great and they're on a very large heatsink, the heatsink doesn't even have time to heat, so fast this happens). They're only stable with biasing voltages lower than 2.1 V, where there's distortion.

The only components heating up here are the output transistors, i've cheked and none of the resistors or diodes are heating up.

I've checked if a negative feedback could help, but it didn't, because the voltage in the output doesn't change as the current flowing through them escalates (both are conducting more and more but equally, just like if someone where increasing the biasing voltage).

Also, if you note on the base of the transistor driving the TIP's, you'll notice a 47k potentiometer I use to make sure both will be conducting equally when there's no signal (so the output will rest at 0 V).

But somewhy, this is exactly the point where there's more distortion. If I make one of them conducting a little bit more than the other (in a way the output will not rest at 0V but in something like 1.2 V) then there'll be no or less distortion.

In the simulations in MultiSim none of this problems occur, it shows no distortion when it's properly biased, but in reality I have either distortion or a very great instability.

I know I could put two resistors between their emmiters to limit current, but the load (my speaker) is 4 ohms, even 1 ohm resistors would create a great loss.

So, can anyone help me?

Thanks!


texts: Could you explain how a quartz crystal works, maybe with a simple schematics with the essential things ? I know it acts like a kind of stabilizer for an oscillator, but nothing more than that.