texts: Starting torque of series vs shunt DC motors

texts:
Recently, I read that starting torque of series motors are much higher than shunt motors.
I try to find out what is reason behind it and I get to know that this is because in DC series motor torque is proportional to square of armature current (and hence we get maximum torque at starting because armature current is maximum at that instant) because field current is same as armature current.
While in DC shunt motor torque is proportional to field and armature current but in this case value of field current is very less (because we take resistance of field winding very high) hence we can say that starting torque is proportional to armature current only.
But there are few points which I still don't understand. Hope someone can help me!

Why we keep high resistance of field winding in shunt DC motor, isn't low resistance of field winding in shunt DC motor can provide same benefits as of series like high starting torque?

Why we don't consider inductances of field winding for starting torque calculation (while I think inductance value must be high as it is wrapped on a ferromagnetic material) for starting torque calculation?

And isn't starting torque should be zero in case of series and shunt motor as Inductances of field winding doesn't allow current and hence starting torque is zero?


texts: I am using an array of WS2812 leds for an application of mine. The length used is around 10 m with 60 leds/m. The current for one led is 40 mA, this makes the total current to be around 25 A. I wanted to know if this is a dangerous current at 5 volts. I want to know this as I have to put my circuit in an insulation class where a single fault would result in electrical shock to the user.


texts:
I am a little confused regarding the order of bytes that are transferred through SPI to a slave device.

The next time diagram depicts the sequence of bytes to be sent when we want to write data to a a flash memory chip

After I send the command byte (first 8 byte to the slave device (Flash Memory) I must send the address bytes and then the data I want to write.

So my question is this: Which byte do I send first, after the command byte? The High Byte or the Low byte of the address? Although it doesn't make sense to me why the High Byte should be sent first it is obvious in the diagram that the High Byte must be sent first and then the Low Byte. So, I wanted to ask in case I am thinking it the wrong way.

Thank you for your time


texts:
If I build a coil A, of 10cm height with iron core and a 4cm diameter, and alimented it with a DC 15v,6amp source, it will produce a magnetic field.
Let’s say A is set vertically.
Will building another vertical coil (solenoid) B of the same dimensions and wiring it to a circuit containing LEDs, and placing it at a 5cm of distance to A, light the circuit of LEDs continuously? If no, what can I change to make this idea function?


texts: Does a LED also emit light when conducting in avalanche mode?

texts:
I wonder this by pure curiousity. If we polarize a LED in avalanche mode by applying a very high reverse voltage (but keep the current low so that the component doesn't fry), is it possible that it also emits light when used this way ?

(The reason I don't "just try it and see" is because of the high voltages involved).


texts: Has anyone hacked an IOS cable and knows what data is going in and out of which wire. Maybe a diagram of an iphone cut cable?


texts: How to test if a discrete system is causal or non-causual?

texts: I know like this might seem like a trivial question but I am a bit confused with it. Take for example the the system y=x(n-10). Initially I thought this system was noncausal because n-10 means that the graph of the signal would be shifting 10 units to the right, meaning that the signal would be delayed by 10 seconds and so the output of the system would rely on a future value. However, apparently this system IS causal because if you take your time n and subtract 10 you arrive at 10 seconds in the past and thus the signal only relies on past values. Obviously, these two conclusions contradict each other. How can I reconcile them and make sense of this?


texts: ESP8266 Flashing Problem-A fatal error occurred: Timed out waiting for packet header

texts:
I have been having some issues with flashing the firmware to my ESP8266 wifi module.I am using Linux OS and using the method illustrated Here to flash the the esp8266. The following are the connections between the esp8266 and FTDI board:

  FTDI (Rx)<--ESP(Tx)
  FTDI(Tx) -->ESP(Rx)
  Common ground between the FTDI, ESP and external 3.3 power supply.
  ESP(GPIO0)-->Ground (While Flashing)
  ESP(CH_PD)-->VCC (3.3V)

I have researched online and have verified all my connections to be fine. But some observations I have made are as follows:

The ESP does not respond to any AT commands or display any garbage data on the serial monitor, when restarted with the GPIO 0 pin connected to ground.
The ESP responds to AT command as OK and works fine while displaying some garbage data followed by "ready" on the serial monitor, when powered up with the GPIO 0 pin floating.

3.Shows ERROR for the command  AT+CIOBAUD?

Have also read that, there are some duplicate FTDI hardwares floating around in the market and online stores, that may be one of the reasons for this flashing problem.

Coming to the problem i.e. whenever I try to flash the esp8266 using the esptool.phy, the flashing begins and at around 8% to 12%, it gets stuck displaying the error

 A fatal error occurred: Timed out waiting for packet header

I have stated my observations above, so that it would be easy for the fellow members to address the issues with the flashing. Looking forward to response from people who have faced, solved, encountered or have any opinions/suggestions regarding this problem.


texts: pH sensor buffering, gain, and offset with one inverting opamp

texts:
I'm working on the above mentioned circuit. I'm a hobbyist with little electronics training so don't laugh if something terribly dumb comes out of my keyboard please.

Anyway, a different question on stackexchange had a comment that opamps don't need a negative rail in order to invert a signal. I'd always thought a negative rail was required to handle a negative signal so this was like a bolt of lightning. instead of messing with voltage inverters etc, this just uses plain old single supply. Circuitlab seems to like it.

Anyway, I'm concerned with pH 4-10 (just enough to sneak in standard pH solutions for calibration). I've add enough gain so that 4-10pH @ 40C almost hits the entire span (which is plenty more resolution that I really need).

What circuitlab can't really help with (or at least I don't know to to do it) is handling noise and instability. How do you think this would hold up in the real world? I figure I'll need an RC filter on the output and I'm just reading up on those. Like the description says, if it takes 2 minutes to go from 0 to 1.8V that's actually Speedy Gonzalas territory in this application.

So, is this simply not going to work the way I think or is there modifications I can do to make it work (better)?

Thanks!

simulate this circuit – Schematic created using CircuitLab

P.S. BBB = BeagleBone Black. 3.3v supply, 1.8v ADC and 1.8v analog supply limited to about 10mV which is why the voltage follower/buffer to power the opamps.

Edit: Spotted a tip about matching input resistances between the two inputs. Reduced R7 and R8 to 1k and 4.3k to get 811 ohms on - and 779 ohms on +. Should I add the extra 30ish ohms to the + input or do you think the 30ish ohms makes no difference?


texts:
i'm in trouble trying to figure it out how to properly control a peltier cell using current control principle .

I'm using a sine wave to figure circuit behavior through 0 to 6V and 0.5HZ .

Take a look

The problem is that the output voltage(BLUE) do not follow its input troughout (YELLOW) .

i wonder if the discharge of mosfet capacitance is taking too much time to happen? how do i fix that? i've tried vary its gate resistor but nothing changes .

Thanks for your help ..


texts: Everything stops working after I enable PWM

texts:
So I implemented a simple PWM on a PIC 12F617. Had to use the Compare peripheral with interrupts since I couldn't generate 50hz with the PWM module (too low frequency). I set a value to the CCPR1 register and when TMR1 reaches that value, an interrupt is firing in which I either set a pin to 1 or 0 to generate the duty cycle I want.

Now I also bitbang I2C in the main loop and here's the weird thing. I tested both PWM and I2C separately and they work fine. Once I enable them both, I2C gets completely messed (can see it on the scope), it looks like it can't pull the line low so it basically is oscillating a few millivolts below VCC when it wants to pull it down, while on other occassions it is just oscillating all over the place.

And now the even weirdest thing. While I2C alone works and stops when I enable PWM, if I disable PWM again, it won't go back to where it was before! At first I thought it was slave device acting up, but power cycling everything wont do anything. After a few hours of fiddling here and there looking for ghosts, breaking the whole circuit and assembling it again it starts to work again. So I enable PWM again and sure enough, everything is screwed again! I disable PWM and back to square 1, everything is messed and just doesn't want to work. I spent all day trying to find out whats going on, I've done this 4 times already and everytime the same story.

Anyone had this happen to them? Any advice on how to prevent PWM making everything go crazy?


texts:
I'm trying to execute the SPI example from STM32Cube using a STM32F429 board and a STM32F4 board. The first has 180MHz of clock and the second one has 168MHz, both with similar Arm cortex-M3 microcontrollers.

I am using the HAL library to access the peripherals and I am configuring it with this:

main.c ==>

  SpiHandle.Instance               = SPI4;
  SpiHandle.Init.BaudRatePrescaler = SPI_BAUDRATEPRESCALER_64;
  SpiHandle.Init.Direction         = SPI_DIRECTION_2LINES;
  SpiHandle.Init.CLKPhase          = SPI_PHASE_1EDGE;
  SpiHandle.Init.CLKPolarity       = SPI_POLARITY_HIGH;
  SpiHandle.Init.CRCCalculation    = SPI_CRCCALCULATION_DISABLE;
  SpiHandle.Init.CRCPolynomial     = 7;
  SpiHandle.Init.DataSize          = SPI_DATASIZE_8BIT;
  SpiHandle.Init.FirstBit          = SPI_FIRSTBIT_MSB;
  SpiHandle.Init.NSS               = SPI_NSS_SOFT;
  SpiHandle.Init.TIMode            = SPI_TIMODE_DISABLE;
  if(HAL_SPI_Init(&SpiHandle) != HAL_OK)
  {
    /* Initialization Error */
    Error_Handler();
  }

stm32f4xx_hal_msp.c ==>

void HAL_SPI_MspInit(SPI_HandleTypeDef *hspi)
{
  GPIO_InitTypeDef  GPIO_InitStruct;

  /*##-1- Enable peripherals and GPIO Clocks #################################*/
  /* Enable GPIO TX/RX clock */
  SPIx_SCK_GPIO_CLK_ENABLE();
  SPIx_MISO_GPIO_CLK_ENABLE();
  SPIx_MOSI_GPIO_CLK_ENABLE();
  /* Enable SPI clock */
  SPIx_CLK_ENABLE();

  /*##-2- Configure peripheral GPIO ##########################################*/
  /* SPI SCK GPIO pin configuration  */
  GPIO_InitStruct.Pin       = SPIx_SCK_PIN;
  GPIO_InitStruct.Mode      = GPIO_MODE_AF_PP;
  GPIO_InitStruct.Pull      = GPIO_PULLUP;
  GPIO_InitStruct.Speed     = GPIO_SPEED_LOW;
  GPIO_InitStruct.Alternate = SPIx_SCK_AF;

  HAL_GPIO_Init(SPIx_SCK_GPIO_PORT, &GPIO_InitStruct);

  /* SPI MISO GPIO pin configuration  */
  GPIO_InitStruct.Pin = SPIx_MISO_PIN;
  GPIO_InitStruct.Alternate = SPIx_MISO_AF;

  HAL_GPIO_Init(SPIx_MISO_GPIO_PORT, &GPIO_InitStruct);

  /* SPI MOSI GPIO pin configuration  */
  GPIO_InitStruct.Pin = SPIx_MOSI_PIN;
  GPIO_InitStruct.Alternate = SPIx_MOSI_AF;

  HAL_GPIO_Init(SPIx_MOSI_GPIO_PORT, &GPIO_InitStruct);

  /*##-3- Configure the NVIC for SPI #########################################*/
  /* NVIC for SPI */
  HAL_NVIC_SetPriority(SPIx_IRQn, 0, 1);
  HAL_NVIC_EnableIRQ(SPIx_IRQn);
}

Both, master and slave have the same configuration. The problem is that the slave receives the data correctly but the master has some time of operation in the last bit of each byte. For example, I sent {0x01, 0x00, 0x00} and master received {0x00, 0x01, 0x00}. It seams to me that it is doing a OR operation with the last bit or simple substituting it by the last bit from the last byte received.

Thanks!


texts:
Which diodes for 12v indicator light circuit?

I have a car whose signal light audio indicator is too soft to hear.  I would like to set-up an visual indicator on the dash for when the signal lights (and selected auxiliary equipment) are on.  How can I feed multiple indicator sources into a single indicator light?  I assume that a one-way "gate" (diode??) will be needed on each indicator source input to prevent electricity from being feed back on all input leads.  What specifically do I need for the "one-way gate"?

More detail:  I have a 2007 Toyota Innova (which is an Asian only model) which I use in one of the developing nations in Asia.  The audio "signal stat" that beeps when the turn signal lights are on is usually too soft to hear.  The "signal stat" itself is not the traditional two or three prong relay type components that were used on older (1960-????) US cars that I am familiar with; the component on the Innova has at least a dozen wires feeding into it.  The car's electrical system is the usual 12v negative ground.

My thoughts are that I can easily tap into the two signal light circuits (left and right signals) to provide input feeds to a 12v LED indicator light that I'll mount in the dash area.  Additionally, I will want to tap into an auxiliary backup flood light circuit (so that I know if I have accidentally left it on.)  I might want to tap into other future auxiliary equipment that I add later.

Since I really don't need individual indicator lights (-- I just need to be aware that something is "on" --), I would like to combine the inputs from the three or more sources to drive a single 12v LED indicator light.  However, for example, to prevent the back-up light from energizing the signal lights, I need "something/diode" that allows the electricity to flow only one way towards the indicator light.  I need help with identifying exactly what that "something/diode" should be.  I assume that I will need a separate diode to protect each input source.

Also, I would like to be able to adjust the brightness of the LED.  I assume that I need some kind of a variable resistor type component installed in series between the indicator light and the combination of all the input leads.  Any specific recommendations of what variable resistor I need would be helpful.

Presently I am Stateside and have easy access to parts via RadioShack mailorder, etc.  Getting/finding parts overseas in a developing nation can be very difficult -- so I'm trying to get the components on this trip.

As you can tell from this post, I'm a total novice at designing even the simplest circuits -- but I can assemble things if I know what is needed and how they relate.  Thanks in advance to those who are willing to help me.

PS: The closest relevant post I found to this topic was Which DIODE for 12V lighting circuit? .  However, that article was focused on voltage drop on a circuit with higher wattage lights as opposed to a very low amperage feed to an LED indicator lamp.


texts: I2C: Is a repeated start between different slave addresses legal?

texts:
I'm writing I²C code for an application where I have only one master, but several slaves. In all the datasheets I've read (not only for this project), the repeated start condition is only used to switch between write and read and write to/from the same slave or vice versa. Of course, those datasheets wouldn't show other slaves (why should they, anyway).

Is it legal to omit the stop condition between transfers to/from different slaves?

Do some slaves misbehave when addressed after a repeated start condition, after different slave had been addressed before?

I know that the second question cannot be safely answered with "no", but if any of you had problems in such a situation before, that's enough for me.


texts:
I want to control an N-channel MOSFET from a 3 V power source.

The thing is, I have difficulties understanding how to know the minimum Vgs value is to be applied for the MOSFET to be saturated. For example, what about the MOSFET CSD19501KCS (80 V N-Channel NexFET)?


texts: Band pass filter unstable and lower gain than simulation

texts:
I’m trying to make an ultrasonic distance sensor and got the 40kHz emitter working but am struggling with getting the receiver circuit working properly. At first I just amplified the output of the receiver without filtering and it picked up a lot of noise (mostly around 25kHz), which was screwing up my distance measurements so now I’m trying to implement a bandpass filter. I used a design for a narrow (single frequency) band pass filter #4 on this page and used this calculator to get part values for a filter with a gain of 10 centered at 40kHz and a Q of 10. I simulated the resulting circuit in Multisim and it worked as expected but when I tried breadboarding it the gain was between 2 and 3 instead of 10 (I used OPA2134 op amps for both simulation and testing). Other than the decreased gain it seemed to be working and I wasn’t sure what the problem was so I just connected four stages back to back to get the gain high enough and got a barebones PCB made of that design. On the PCB the gain of each stage actually increased to between 5 and 6 (still short of the expected 10) and they worked independently but when connected together I started seeing a 36kHz oscillation at the output of the filter chain even when there wasn’t any input signal. I read that if a high gain amplifier’s output couples to its input that can make it act as an oscillator so I’m not sure if this is happening somehow (maybe by the output traces crossing the input traces?).

Basically, what I’m trying to figure out is why the gain of my band pass filter is lower when implemented than simulated and why four stages cascaded together becomes unstable?

Current schematic of one stage:


texts: MC34063 heating & low performance problem

texts:
I designed below circuit to provide 45V/200mA for a LED ceiling lamp.

First, I built it on breadboard. Everything was fine. No voltage drop. MC34063 was warm and transistor TIP31C was hot but can cool down by heatsink.

After some tests, I made a stripboard version with the same components but cannot work normally...
 1. MC34063 became very hot after powering up. (~5sec)
 2. TIP31C became cooler than breadboard version (touchable).
 3. Output dropped to ~39V.

I guess the driver/output transistors inside MC34063 wasted too much energy and generated too much hot. Should I lower the value of input resistor of TIP31C or do something else?

By the way, I tried to replace the inductor with netshop's product during breadboard version test and found the circuit's performance decreased (They have the same rating 470uH/3A). Origin inductor's core is yellow and netshop one looks like:

I can't explain why. Can anyone explain it for me?


texts: Connecting Switches to Hidden Supply Pins in Proteus ISIS

texts:
I am currently working on a simple circuit involving logic gates in Proteus ISIS from Labcenter. By default, the power pins are hidden. You can access them by right-clicking the component, selecting "Edit properties", and going to "Hidden pins". You can then select the power supply you want to use. However, for this particular circuit I am attempting to put a switch between the power supply and the chip's VDD pin, and another switch between the VSS pin and ground (I know this switch is not necessarily needed, and probably should not even be used, but this is just an experiment). Is there a way to do this? Whenever I add in a different netlist name for VDD and VSS when editing the component properties I get errors saying No power supply specified for net <my net name> in Power Rail Configuration.

I am using Proteus 7 Professional. I don't think a schematic would be all that helpful at this point,  but let me know if you need it. Basically I just need switches between VDD and +5V and between VSS and GND.


texts: Path of a signal traveling on a mismatched transmission line

texts:
I have a basic question about the path of a signal traveling on a transmission line with a short circuit as termination.

Suppose that this line is driven by another line (at left) with Zc = 50 Ohm characteristic impedance. The line in my scheme is matched with it but its termination is not, so there will be reflection (in this case total reflection because it is a short circuit load).

I'd say that the signal which comes from left travels along al the line in the scheme, arrives at the short circuit, and then it is reflected back.

But if you evaluate the input impedance of the transmission line and then find the correspondent reflection coefficient, you see that there is total reflection also at the beginning of the line (as shown in the scheme with the equation |Ґ(0)| = 1). From this consideration, it seems that the signal is reflected at the beginning of the line.

It's seems not correct for me since the signal knows the presence of the short circuit only when it arrives at it, but math says that |Ґ(0)| = 1. Which is the solution? And why do people often evaluates the input reflection coefficient, since the reflection will be in other positions (I think so)?


texts: Avalanche Pulse Generator: Common-collector alike setup with no input and fairly high voltage on the Common

texts:
I am wondering what would be purpose of a setup like this?

simulate this circuit – Schematic created using CircuitLab

If you notice there is no input in this setup and the voltage is fairly high on the Common leg which exceeds the tolerance level of 2N3904. The output with the CRO shows a spike of roughly 10v high in approx. 300pS rise.

Would appreciate it if somebody point me into the right direction.


texts: PIC microcontroller: actual behaviour differs from simulator

texts:
I was encountering some quite strange differences in the behaviours of my PIC16F628a microcontroller compared to the MPLAP built-in simulator.

After a long search, it turned out to be different due to the free cells' default values.

In the simulator, when accessing a memory location that has not been initialized, the W register is loaded with 0x00, whereas in the actual device, some other value may be loaded (I don't remember if it was 0xFF or 0x7F).

Is there a way to either make all unused bytes 0x00 on the device or to change the default value of the simulator to the PIC's uninitialized default value?

(It might also be that my question shows that I didn't understand some fundamental principles about PICs... In this case I would be grateful if someone would teach me. ;-) )


texts: Are E and B fields in phase in electromagnetic radiation?

texts:
I recently wrote this answer, in which I said:

Radio waves are electromagnetic radiation. Electromagnetic radiation contains of two components, one electrical and one magnetic. These components create each other, as said above. The red magnetic field creates a blue electric field, which creates the next magnetic field, and so on.

I got this diagram from wikipedia, but my physics book and Jim Hawkins WA2WHV give the same diagram.
In the comments, a discussion followed:

Olin Lathrop: Your first diagram is wrong. The B and E fields are actually 90 degrees out of phase with each other, not in phase as the diagram shows. The energy is constantly sloshing back and forth between the E and B fields.
Keelan: Are you sure? Wikipedia and my physics book show different. The two fields should have a fixed ratio, I believe, which cannot happen when out of phase. One field is horizontal and the other vertical, there's a 90 degrees angle - the diagram is an attempt to show three dimensions.
Olin Lathrop: Hmm. I always understood them to be in quadrature, but I don't have time to look that up right now. This could be a case of one bad diagram blindly copied by lots of others. Where is the energy when both fields hit 0 in your diagram? In quadrature, the sum of the squares of each field's amplitude is a constant, which gives a good explanation of how the energy can persist. It sloshes back and forth between the two fields, but its total is always the same.

I follow Olin's logic and can't say myself why the fields would be in phase. So my question is: are the E and B fields of electromagnetic radiation in phase or not? How can one understand this?


texts:
On the AVR XMEGA, or any AVR, is it safe to do pointer operations, like passing by reference and accessing pointers while interrupts are on? I keep feeling like I need to wrap each pointer operation into an ATOMIC_BLOCK() macro. Is this necessary? Also, I need to copy a structure with like 30 bytes of data, should this be in an ATOMIC_BLOCK()?

The AVR address bus is 16 bits, and takes two cycles to access a pointer, correct?


texts: KiCAD: Footprint etc. for a breakout board on a PCB, which is to be designed

texts:
(I am no native English speaker....)
I am a very beginner to KiCAD (not to electronics, though) and want to design my first PCB with KiCAD (Linux): A Nixie clock.
To make my life a little more easier, I want to create a PCB, which mostly connects breakout boards of different parts of the Nixie clock together (Arduino Pro Mini, Nixie HV drivers, I2C expander etc.).
And here I got stuck: How can I create a "footprint" (?) and other things I need to have beforehand?
One solution I found was to use FreeCAD for this ... but some quirks in my system prevent to install FreeCAD successfully. And honestly...most of the parts of the solution I didn't understand.
Question remains: How can I create "footprints" for breakout boards easily?


texts: What are the primary differences between AHB, APB and AXI?

texts:
As far as I am aware, the AMBA specification has multiple versions and describe different buses which include the AHB, APB and AXI. My questions are:

Are the different specifications of AXI backwards compatible?
Are AHB, APB and AXI just evolution of a single bus specification?
Are AHB, APB and AXI compatible with each other?
What are the primary differences between APB, AHB and AXI?

There is also a variant of AHB called AHB-Lite.
The most important questions:

Why do we need so many different buses in the first place?
How do we know which bus to use at any time?


texts: Using arduino to simulate a pt100 temperature sensor

texts:
I want to simulate a temperature PT100 sensor using arduino. What I did till now is on that draw that I attach here. The components were determined by experiments so I guess if there can be some calculations maybe it will improve.

I have a device that reads a PT 100 sensor and if instead the sensor (2 wires model) I wire my device I am able to simulate different temperatures and also I am able to make some sort of calibrations means for example at pwm 163 I get 100 degrees on the device.

My problem is that at some point in time that temperature varies without touching anything. Also there were cases like from a day to another to measure some different temperatures with same setup.

Any idea or hint will be much appreciated

Thanks


texts: What is the name for the low pass topology in this figure?

texts:
I am a student researching physics and I am currently fixing some old equipment (RF signal attenuators for our acousto-optical modulators), I found the control voltage passing through a low-pass filter box as shown below, but I am not sure what this topology is called and why it has been used. Could someone enlighten me?

EDIT: Apparently this is a type of circuit suggested by Mini Circuits to use mixers as signal attenuators. We are putting signal into IF port, but usually IF port is where you pick your (RF +/-LO) signal. So if a high frequency noise reflects back from the LO port it will show up in the IF port, and the circuit is supposed to filter out whatever high frequency noise is reflecting back into the IF port.


texts: Fast-stabilising skin temperature sensor

texts:
We're currently trying to build a portable temperature sensor for the purposes of estimating human core temperature. This is a bit of an engineering problem (more to do with choice of materials than choice of IC), but it does involve electronics and related issues like heat transfer, so I feel it's relevant enough to this board. Please correct me if I'm wrong in this regard.

There are quite a few articles out there on various attempts to achieve this, but we've been having trouble finding a solution that fits our criteria.

Since the device is portable and must be in contact for extended periods of time, invasive (rectal, esophageal) or cumbersome (axillary, in-ear/tympanic) methods of measurement are infeasible, leaving skin temperature as the next best alternative, since core temperature can normally be fairly well estimated from these values given certain constraints, such as known position on the body, shielding from environmental effects and so on. Contactless detection via infrared is unworkable since the uncertainty is greater than ±0.5°C, which is outside the acceptable range for clinical significance (i.e. the uncertainty needed in order to diagnose issues such as fever). Thus, the sensor needs to be in direct contact with the skin.

However, this creates further issues, the most pressing of which is the immediate cooling of the skin upon contact with the sensor, which will invariably be the temperature of the environment rather than the skin. While the skin will eventually return to its previous temperature, it normally takes around 20-30 minutes for this to happen. This is considered too long for our purposes. While insulation has reduced the difficulties caused by the sensor module's different thermal conductivity "permanently" reducing the skin temperature near the module, the additional thermal mass has not helped with stabilization times. As can be seen in the above articles, this has been approached in different ways - for instance, using a thermocouple and feedback-controlled heater adjusted for skin temperature to detect whenever temperature flux is zero (and thus whenever the sensor has the same temperature as the skin). This has a faster response since less heat will travel out of the skin, creating a lower discrepancy that needs stabilizing - however, the energy and power requirements of the heater are outside the scope of the battery and will quickly drain it, making this unsuitable for portable use.

Would anyone know of any way to get a good response time (<10 minutes at the very least... 2-5 minutes as a rough estimate perhaps) for such a device while keeping within clinical significance parameters of <±0.5°C - either by active (but low power) or passive (perhaps by superior thermal insulation) means?


texts:
I'm trying to configure Timer1 of a pic24h to 1ms per timer tick but don't seem to be able to get the math to match my results.

I have a 20MHz external oscillator (with a 1M resistor in parallel for stability) and think I have it enabled with the following configuration bits set in code:

#pragma config FNOSC = PRIPLL           // Oscillator Mode (Primary Oscillator (XT, HS, EC) w/ PLL)
#pragma config IESO = ON                // Internal External Switch Over Mode (Start-up device with FRC, then automatically switch to user-selected oscillator source when ready)

I'm toggling a pin and watching it on the scope to check my math.  I thought the calculation is as follows:

//  ms_per_tick = ((F_OSC / 2)/prescaler)^-1 * PR1
//                    = ((20MHz / 2) / 8)^-1 * 4200
//          NO= 1ms

bit a value of PR1 = 4200 is about the closest I can get to a tick of 1ms.

What am I missing?  Does the PLL change the value of what I think is F_OSC.  Is there a way to validate F_OSC?

The ISR just increments a variable and clears the interrupt flag.  Here is the initialization code:

T1CONbits.TCKPS = 0b01;   // configure the timer prescaler to divide-by-8
T1CONbits.TCS = 0;        // do NOT use the external clock
PR1 = 4200;               // configure the timer period

// configure the Timer1 interrupt
_T1IF = 0;             // begin with the interrupt flag cleared
_T1IE = 1;             // enable the interrupt
T1CONbits.TON = 1;         // turn on timer1

I'm starting to learn more about the PLL via some SFR's:

CLKDIV is: 0x3040 (PLLPOST = 1, PLLPRE = 0)
PLLFBD is: 0x0030 (PLLDIV = 48)

I also just found this on p.16 of the datasheet:

  "If the PLL of the target device is enabled and configured for the
  device start-up oscillator, the maximum oscillator source frequency
  must be limited to ≤8 MHz for start-up with the PLL enabled to comply
  with device PLL start-up conditions. This means that if the external
  oscillator frequency is outside this range, the application must
  start-up in the FRC mode first. The default PLL settings after a POR
  with an oscillator frequency outside this range will violate the
  device operating speed. Once the device powers up, the application
  firmware can initialize the PLL SFRs, CLKDIV and PLLDBF to a suitable
  value, and then perform a clock switch to the Oscillator + PLL clock
  source. Note that clock switching must be enabled in the device
  Configuration word."

Now, the first thing I run after main is this example code:

void ConfigureOscillator(void) {
  // Disable the Watch Dog Timer
  RCONbits.SWDTEN = 0;

  // When clock switch occurs switch to Prim Osc (HS, XT, EC)with PLL
  __builtin_write_OSCCONH(0x03);  // Set OSCCONH for clock switch
  __builtin_write_OSCCONL(0x01);  // Start clock switching

  // Wait for Clock switch to occur
  while(OSCCONbits.COSC != 0b011);

  // Wait for PLL to lock, if PLL is used
  while (OSCCONbits.LOCK != 1);
}


texts: Connecting BeagleBone Black to an Arduino

texts:
I am a software guy (everyone immediately downvotes...) trying do the following:

(1) On a BeagleBone Black ("BBB") I am driving a GPIO pin high in software.
(2) Then I am sending PCM (audio) out another pin as I2S serial.

I want to measure the time between (1) and (2).  Of course I could use an oscilloscope, but I want to do the measurement 1000 times and take an average.  So I plan to use an Arduino as a timer (I've already written and tested the software using push-buttons as inputs).  My question: how do I connect the BBB to the Arduino?

I realize I must connect the GPIO pin of the BBB to an input pin on the Arduino.
And the I2S serial pin of the BBB to another input pin on the Arduino.

Is that it?  Do I connect the GND of the BBB to the GND of the Arduino as well?  And do I need to worry about the 3.3v output from the BBB (both pins) to the inputs on a 5v Arduino?


texts: How to differ output & input resistance of small-signal model BJT?

texts:
I understand how input and output resistance of small-signal model for bipolar transistor is defined and how draw one.
What I don't understand quite yet is how actually input and output resistance of BJT are separated.

How do you know which resistances should be included for input and which for output resistance?

Because, if you ask me, models like this one could be identified as one whole resistor, whose value would be considered as input and output resistance simultaneously.

*For the record: ru - base-collector resistance, rpi - base-emitter resistance, ro - collector-emitter resistance, rb - base contact resistance, rc - collector contact resistance, rex - emitter contact resistance.


texts: Can I harm my device doing these connections?

texts:
I was using a device (1) to intercept and read the SPI communication between a microcontroller and a LCD of another device (2). So, I did the conections as showed in the figure below. They use the same voltage level and SPI communication have the same voltage levelas well and I read LCD communication everyday without problems.

But, I have some questions:

I think the connections are right, is that correct ? Do you think there is another way, a better way ?
Today, I energized the device 1 before to energize the device 2 (device2 not energized), could this do some harm to device 2 ?
If I energize device 1 before device 2 (device 2 not energized), and somehow the GND line is not connected properly, can I damage device 2 ?

Sorry, about my doubt, but, I made this connection and everything was fine during days, but today, I power on the two and the LCD stayed blank... not responding anymore. I think some connection became falty or, maybe what happened can have something to do with another issue

I'm very sad about it. I don't know what happened . Any help would be great


texts:
I'm trying to make a counter that counts: 0,1,2,3,4,5

I need this for a frequency divider of 6

So I made this table:

From this I get:

J0= 1

K0= 1

J1 = NOT Q0 AND Q1

K1 = Q1

J2 = Q1 AND Q2

K2 = Q1

I made the circuit in the software:

It does compile with 1 warning:

And when simulating only the first jkff is working:

Thank you


texts: Where does the power dissipation go in this Thévenin equivalent?

texts:
The circuit below contains an AC current source and an ideal transformer along with some passive elements. I marked the points A and B, because I'm trying to find the power dissipated in the terminal A-B.

I could rewrite the circuit using Thévenin's theorem to this kind of circuit, where Z are complex impedances and V is a voltage source, because I feel safer calculating the power dissipation from this kind of source.

The part of the transformer on the left-hand side could be written as an impedance related to Z1 through \$(N_1/N_0)^2\$

Now, though, my question is: Which power dissipation in this "equivalent" circuit would be equal to the power dissipation over the A-B terminal above?


texts: xbee doesn't respond to command sequence

texts:
I have two Xbee S6 wifi modules (XB24-WFSIT-001 rev G), DF robot xbee atapter V2 and  sparkfun XBee Explorer USB.

I'm able to upload firmware to any of them (version 102D for example) using sparkfun adapter,(not df robot's one), but X-CTU can't set AT parameters after upload. I use this adapter with other xbees and it works fine.

Also it's not possible to enter command mode using +++ sequence, module just ignores it.

I have tried Xbee Factory -Hardware reset without serial communication and it didn't help.


texts: Converting "MPR121 capacitive keyboard" sensor filter data into capacitance values?

texts:
The project that I'm working on, the MPR121 capacitive touch sensing keyboard connected with a 8051 microcontroller, my first intention when I started implementing the project was to measure the capacitance on the touched electrode, reading the datasheet I learned that I can get the capacitance value from the filter data later on I figured that the value I'm getting from filter data is reverse proportional with the capacitance

Image below shows the relation between capacitance and the voltage

Image below shows the value range 0-1024 that we can get from the filter data and shows that the value is inverse proportional with the capacitance

I've configured 0x5c and 0x5d register so that charge current I is 16 mikroA and the charge time T is 0.5 mikroS, I'm getting values of filter data in range from 0-600 does this mean that the capacitance is calculated as below..

C=(I*T)/V=(16*0.5)/(0-1024) ?

Thank you!


texts:
I've recently started trying to reverse engineer my old car's ECU (2001 Holden Jackaroo/Isuzu Trooper with a 3.0L diesel 4jx1 engine),  purely as a learning experience. I've managed to identify and dump the contents of the EEPROM on the board (AM29F200BT). You may have to bear with me as my knowledge in this department is very basic.

As I understand it, it will make it easier to reverse engineer the program stored on the EEPROM, if I manage to identify the main microprocessor and the code it uses. However I'm having trouble identifying the main microprocessor on the board. I've tried googling the numbers with no success.

Has anyone seen one of these before or can anyone point me in the right direction of working out which family of microprocessors it belongs to?

Thanks in advance.


texts:
I have an inverter that requires to set the batteries type.
The inverter accept 3 kind of batteries : AGM , GEL , FLD.
But i can't find any information on my batteries about these types.
The only thing i can read on my batteries is Calcium Premium.
What type should i select on my inverter ?

Thank you !

Update
Battery is :

Solite Calcium Premium 68022


texts:
The common differential amplifier takes two signals and amplifies the difference between these two signals. I am aware that this difference usually is around a few millivolts or microvolts so, to put it in engineering terms, it is zero.

Everywhere here, in the text books, or internet, the mathematical calculations are based on the fact that the voltages at the inverting and non-inverting terminals are exactly equal to each other, so conceptually we should have a zero output voltage, and that's not the point, because this circuit is going to amplify nothing.

Am I fundamentally wrong here?


texts:
H i, I am new to this, so please excuse my lack of knowledge.
How can I bias this to zero, and is there a way to increase the dynamic range.
I will mbe using this as a sound trigger for an arduino based unit.

edit:
What I meant by Bias to zero was.  The output voltage ranges from 1.7 to 3.3, is it possible to have go from 0 to 3.3.


texts:
I am working on a PCB layout on a very space constrained, 4-layer board. On the board is a MIPI-output image sensor (1 lane) which go to an FPGA.

Layer 1: Image sensor
Layer 2: Full Gnd plane
Layer 3: Some signals, some 1.2v plane
Layer 4: FPGA

Since the board is very small, the differential pairs are only about 10mm (40 mils) long. At this length, do I still need to be very careful about their layout?

Here's what I have now:

The FPGA is at the top of the image, on the blue (bottom) layer. The Image sensor is at the bottom of the image, shown in grey (top layer).

And here we can see Layer 3 under the differential pairs.

As you can see, this plane doesn't fully cover the differential pairs. And when the pairs change layers, and thus change reference planes, the nearest capacitor, to help move the return current between planes, isn't that close (red circles).

One last point, there is clearly a change in impedance as the tracks change from 0.075mm (3 mils) to 0.12mm (5 mils).

The question is, does all of this matter when the pairs are so short?


texts: Frequency divider works only for some divisors (Verilog on Lattice iCEstick FPGA)

texts:
I'm trying to build a frequency divider on a Lattice iCEstick using Verilog (with yosys, arachne-pnr, and icepack/iceprog):

 module demo(input clk, output LED1, LED2, LED3, LED4, LED5);

   assign LED1 = state;

   // Generate impulse at lower frequency:
   wire out_clk;
   reg [31:0] cnt;
   initial cnt <= 0;
   always @(posedge clk) cnt <= cnt >= 6000000 ? 0 : cnt + 1;
   assign out_clk = cnt == 0;

   // On impulse, toggle state:
   reg state;
   initial state <= 0;
   always @(posedge out_clk) state <= ~state;

endmodule

This works as expected, i.e. the LED on the board blinks about once a second (the clock is 12MHz).

However, when 6000000 ('h5B8D80) is replaced with 5000000 ('h4C4B40) the LED simply stays on permanently. Why is that?

Simulating with Icarus shows the expected state changes, no matter what the divisor is.

Here is a table of experiments with more values:

'h5B8D80 blinking
'h5B8D7f permanently on
'h5B8D7e blinking
'h5B8D7d blinking
'h5B8D7c blinking
'h5B8D78 blinking
'h5B8D70 blinking
'h5B8D60 blinking
'h5B8D40 blinking
'h5B8D00 blinking
'h5B8C80 blinking
'h4C4B40 permanently on
'h400000 blinking

Also, for 'h4C4B40 adding the line "assign LED2 = 1;" makes LED1 (!) blink as expected. This is not the case for 'h5B8D7f.

Altogether, the behaviour seems wildly random.

EDIT For the record, when synthesizing the same design with Lattice's iCEcube2 the problem doesn't occur.


texts:
I've been trying to get into electronics after finding an old electronics kit in the back of my closet. It came with an Arduino Uno, a bread board, a bunch of wires, LEDs, resistors, and other things.

I decided to try to see if I could light an LED on a bread board for a few minutes before trying the Arduino.

I built this circuit:

When I try the circuit the LED lights but 30 seconds later it gets hot and burns out.

I'd rather know what I'm doing wrong before I burn more of my LEDs.


texts: Toroidal transformer voltage breaks down

texts:
I am having some trouble understanding the behaviour of my toroidal transformer.
Currently, I am using a 400V to 12V transformer in reverse, meaning I supply 12V and around 1.5 A to the secondary side of the transformator and try to get 400V output voltage.
My problem is, when I connect anything to the primary side, my voltage breaks down, meaning I only get around 2V of input voltage and 60V of output voltage.
I am supplying the secondary side with a OPA548, which should be able to easily supply my 12V 1.5A, but no matter how and if I limit the current, the voltage always breaks down.
Can someone please help me understand what I am missing about my circuit?
EDIT: Could it be that because of the low input impedance of the secondary windings, I nearly short my circuit and therefore the voltage drops?


texts: Name of the Samsung Galaxy end of charger

texts:
This is probably a weird question to ask but I am looking for the end "jack" of the Samsung Galaxy S3, S4 etc charger name. Is not the USB side of the cable, is the actual bit which goes inside the phone. I looked online with various names and I cannot find the name for it. I know the headphones side is called "jack" but not the charger bit apparently.

Anyone willing to help me please?

Thank you.


texts: Why is the linearity of a sensor a desirable feature?

texts:
I mean, a sensor can have a characteristics like Y=X^2 (X = the input, Y=the output).
That is, I can easily find X if I know Y.
Why is the linearity so important?


texts:
I am looking to add a battery to this BLE beacon with as few parts as possible.

In their product's datasheet they include a section on an example schematic for adding a battery (included below). My issue is

The picture is far too blurry to see what is going on
The process of adding a battery seems very complex

Given a 3 V coin battery, what are the steps to powering this BLE beacon?


texts: I need to use a switch for dimming 2500W resistive loads (lighting). Currently I am using SSRs, but looking for other options like MOSFETs. Are there such switches available?


texts: Please help identify this component, marked 222F

texts: I think it's a capacitor marked "222F"  (2,200pF) +/-1%.  However, it seems encased and has 4 pins instead of 2.    Two seem to be for the capacitor and the other two for the plastic looking bracket around it.    First I thought it was a coupled inductor of sort. Peaking inside a small opening it looks like a capacitor based on the color.  It's about 3mm x 3mm x 2mm square.   The arrows point to the mounts, there is one more on the other side not showing in the picture.  Thank you.


texts: Photo diode / light sensor to detect backlight PWM frequency of LED displays?

texts:
Hi and thanks in advance

I'm not from the field so please understand.
I need a mean to detect a PWM frequency of pc/laptop displays externally. Some led displays use PWM mechanism to produce different brightness levels and I need to detect it for multiple machines.
The frequency can get as high as 20Khz

Any clue for such a high frequency sensor?

Thanks


texts: What other microcontrollers use "real" IDEs?

texts:
TI moved Code Composer Studio to an Eclipse-based platform a few years ago, and Microchip recently moved MPLAB to NetBeans.

Which other microcontrollers have "real" IDEs like Eclipse/NetBeans/IntelliJ IDEA for editing/debugging in C++?

("real" in my book = includes code refactoring + code completion, has UI that's been used by large # of users to root out bugs + have high useability -- I haven't used IAR's IDE in 2 years but when I did, I was Not Impressed.)

(I'm especially interested in IDEs of this type for ARM processors.)


texts:
(source: learningaboutelectronics.com)
Design Operating Characteristics
Current Draw: 2 amps
Operating Voltage: 13.5 V
This design will operate in an automotive environment and we would like to implement over voltage and over current protection utilizing a zener diode and fuse to accomplish this, respectively. Is this the proper way to go about doing this? And if so, what kind of voltage characteristics should the zener diode feature?


texts:
Does anyone have any recommendations for an FFC/FPC connector that locks the flex cable contacts directly to pads on the PCB rather than the connector bed?
I am trying to get a VERY low inductance connection system sorted.

Ta


texts: Antenna polarization and antenna directivity are the same?

texts: I'm working on an RFID project, and looking for information about the antennas that I have to use, I have the following doubt: Antenna polarization and antenna directiivity are the same? Thanks!


texts: What MOSFET is used in this waveshare e-paper display?

texts:
I'm trying to create my own circuit around this schematic. Its from a Waveshare 1,54inch E-paper display. I want to create my own board for this display, but I'm confused about what MOSFET this circuit uses.

It clearly lists that a Si1304BDL from Vishay Siliconix is used which is a N-channel enhancement mode MOSFET, but the symbol in the circuit diagram specifies a N-channel depletion mode MOSFET.

Here is an image of the MOSFET and the part number lines up with that of the datasheet.

I'm pretty sure it's a N-channel enhancement mode MOSFET, but I just want to be sure.

Thanks for your time!


texts:
I was trying to solve a problem from SEDRA-SMITH book. I got stuck so I refer to the solution. When Studying how the author solved the problem I got even more confused.

Let's refer first to the given vbe and ic in the question. As per the explation in the earlier chapter of the book these givens are instantaneous values.

Here's the first part of the solution. This is only the part I need to understand.

the part of the solution that I don't quite understand is the equation for vbe1.
I suppose this is a DC value. An uppercase letter is used for the symbol and the subscript. But if that is so, the equation does not agree with the equation for the instantaneous vbe that is

Following the above setup the equation for vbe1 should be something like this

One other thing that confuses me is the use of 4.8ma in the second term of VBE1 equation. Isn't that supposed to be Is? How is ie equal to Is? From what I undestand Is is a very small quantity. Why does ie used in this case?

That's all the things that got me stuck. Thank you.


texts: How can EEG electrodes pick up EMG signals and still function?

texts:
EMG signal is the signal generated by muscle flex. EEG electrodes is the scalp potential generated by neuron firing.

EEG is on the order of micro Volts whereas EMG is on the order of mili Volts, this implies that EMG is 3 order greater than EEG.

The problem is that when doing EEG experiments, some EMG signals are transferred onto the EEG electrodes. The question is that how can the circuit designed to handle signals at the micro Volts capable of withstanding a mili Volt signal. This cannot be done by some sort of power blocker because the EMG signal is still picked up (that's how we know it is 3 order higher).

Imagine if I had a 250 kV power line. Now the voltage on the line swings upward by 3 order in magnitude. Nothing can measure this voltage and survive...but why is the EEG circuit capable of withstanding a surge of 3 order higher?


texts:
I have developed load indicator interfaced with load cell to display the value of load. The device is to be used in on-line weighing of a bag that is moving over the conveyor. Due to the mechanical movements there is a spike in load reading and in order to remove those spikes i need to implement software based filter to stabilize the readings.

Can anybody point me to the right direction, on where to start ? I am using 8051 micro controller and ADS1231 ADC for converting the analog voltage levels to load value.


texts: How bad would it be for a NiMH battery or/compared to a Lithium-ion battery in a device to sit unused for years?

texts:
I have a Sonicare toothbrush which has Lithium-ion battery and a body hair trimmer that has a NiMH battery.

I have charged the Sonicare once or twice without ever using it, just to stop it go to 0% even though I am not completely sure if that is true. The trimmer is unboxed, for over a year now so I have never charged it and/or used it since it left the factory.

I know that the Lithium-ion are better for such conditions, but I don't know the details. Does the type of storage, temperature and such affect the battery? On what way does it really affect it? Does it matter that I have never once used the device, so is it different if I used the toothbrush to check it out a few times (like 4) while the other one just sits in a box. And should I always choose the device that has a Lithium-ion batteries over the NiMH? Should I periodically charge them if I plan on not using them? Lastly can a Lithium or NiMH the battery destroy the device just from sitting in it?


texts:
I'd like to connect two Sparkfun ESP32 dev boards (a 3.3V device) through I2C where one would act as a master and the other as a slave. Each board gets its own LIPO battery, however it is only the master that might be connected through USB; this allows for both wired and wireless operation.

Currently I have 5 common connections bridging the two boards:

GND
SCL
SDA
V-usb (5V)
V-lipo (4.7V)

This is convenient because the 5 wires fit neatly into a 5 pin, micro-usb cable connection (and I'll be building a custom cable to connect both sides).

My question is this: do I need to have a common 3.3V line connection for the I2C communication to function properly between dev boards, or am I ok with just the 5 common lines detailed above?


texts: Techniques for determining the peak of sine wave via ADC

texts: From the book "Digital Protection for Power Systems" the author presents some algorithms to process a sinusoidal waveform. For example, below there's a fragment taken from the index. He also mentions the Walsh Transforms in another chapter. Although the author proposes the mathematical formulations, there's no sample code. In my case, I'm reading a 60 Hz signal from a CT, and added a DC shift for the ADC. I don't need to calculate RMS, rather the peak value is just OK. Has anyone used any of these methods? The simplest method I think is to sample let's say at 1 kHz, and then find the min and max.


texts: Replace Li-Ion battery with buck converter?

texts:
I have a  remote control for a GoPro camera. The remote runs off a 3.7 v li-ion battery. The remote draws about 100 mA.

I want to extend its usability by supplying 12 v power. The camera cable takes 12 v power then has its own converter cable that plugs into its bus port to supply 4.2 v. I  have a separate power line off the 12 v that inputs to an eBay dc dc buck converter set at 4 v. I have removed the battery and the buck converter (LM2596) is soldered in its place. I removed the battery since it is no longer needed and space was an issue.

 It seems to work well, however I'm wondering whether I can expect any reliability issues, or whether this is not good practice.
FYI, i tried running both camera and remote off the camera converter cable but this does not work.

Thanks a lot.


texts:
I'm new here, and I'm new to electronics. I have a keen interest in building a wind powered battery charger and I'm having a crack at the charge controller. I found a circuit that is published free on the 'net and after a few false starts and blind alleys I finally finished my charge controller- or so I thought! My mosfet exploded (well,it went pop and split apart really but it surprised me).

Can anyone tell me what I might have done wrong? Will it have damaged any other components on the board?

If it helps, its an IRF9520 P channel mosfet. I'm not sure whether it should have been an N channel - would this have caused the problem?

Grateful for any help or advice.


texts: What would the units of thermal noise be?

texts:
This came up during an assignment question, but is a tangent.

Thermal Noise is given by;
N=k  T  B where;

k= Boltzmann's Constant (J/K) ir (W-s/K)

T = Temperature (K)

B = Bandwidth (Hz)

That would mean that the units of thermal noise can be expressed as Watt-cycles? That doesn't make sense to me.

Normally noise is expressed in dB or dBm. How does that relate to the units here?


texts:
Using non-linear regression I have worked out the ideality factor to be greater than 2 (2.04987187490894) using spreadsheet software.

Is this realistic for a diode. Is the maximum ideality factor for a diode 2?

The data are as follows:

VOLTAGE := [0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0]:
CURRENT(mA) := [0, 0, 0, 0, 0, 0, 0, 0.07, 0.92, 12.02, 158.29]:


texts: Do I have to initialize Dali lamp somehow if I use broadcast commands?

texts:
I have few Dali lamps. Some of them are new, some of them are used. It is hard to tell which was initialized (addressed?) and which was not.

I have simple DALI circuit with microcontroller and simple application that uses broadcast addressing and it sends STEP_UP_AND_ON, SET_DIRECT_ARC_LEVEL and OFF commands.

The problem is that only few lamps work.

Do I have to address lamps before I send some commands?

Is this possible (normal?) that new lamps are not reacting for broadcast commands at all?


texts:
I have the following buffer schematic set up:

I am trying to understand why the S11 Parameter goes out of the unity gain circle,
which indicates that the buffer schematic reflects more power than is being input.
The op amp has a PNP type input stage and was operated with an offset bias of 1.5V,
powered by at least 5V - so the inputs were operated within range.
This is the S11 Curve, plotted with qucs using the s4p file of the vector network analyzer,
ranging from 300kHz to 200MHz.

This curve was measured with a freshly calibrated Rohde & Schwarz ZVA8.
This VNA has a bias port, providing a DC bias to the output over a bias-tee.
The connections were made with an SMA connector and the board layout has a clear 'direction'
such that input and output lines don't come close to each other.
To me, there are no obvious spots for capacitive coupling of the input and the output line.
Can it be that the high impedance mismatch of the VNA output (50Ohm) and the buffer input caused this?
An experiment showing the contrary is that I have measured an instrumentation amplifier with NPN-type inputs and the curves were fine.
For reference, here is the LTC6226 Datasheet: LTC6226
Any ideas what could cause this behaviour?


texts: I tried powering a XP Power IZ2415S and another similar converter with a power supply from an older laptop and it stopped working. I thought it would work because I assumed the laptop supply was voltage regulated and it was the correct level (19 V) for the input to the 3 W supply. Where was I wrong? what would be a appropriate power source for the 3 W converter?


texts: Confused about battery voltage warning circuit with PNP transistor and Zener diode

texts:
Below is a circuit where an LED will light on when the battery voltage (Vcc) is below approximately 8.8V. However, I'm confused as to how it works. My understanding is that when the battery voltage is less than 8.8V (6.8V Zener + 2.0V LED), the PNP will be in saturation mode, and thus the LED will turn on. However, when the battery voltage is greater than 8.8V, why does the LED turn off? Wouldn't the PNP be in active mode?

Please correct me if anything I've said is wrong. I apologise if this is a trivial question, but I've searched everywhere and asked a few older peers already. It also isn't very helpful when most resources on BJT transistors talk about NPN.

Thanks!


texts: Interfacing cell phone to microcontroller

texts: I have a microcontroller (ARM Cortex M3/4) that can interface with USART/SPI/I2C devices that I need to interface with an Android phone (Lollipop >=v4.2). My idea is to send data through USB from the phone and convert that to USART. The control for these signals could be asynchronous, where messages are picked up by the microcontroller when available, or synchronous, where the microcontroller polls for messages on a regular basis. What is the setup that I will need to do this? Is there a better method for interfacing these two devices? I already have the microcontroller and the phone.


texts: Custom VGA output : what resolutions are expected to work?

texts:
I am thinking of creating a device which displays graphics and animation to generic computer display with 16:9 aspect ratio via analog interface (D-sub).

The question is which resolutions are guaranteed to work on most monitors?

Obviously, standard HD and fullHD likely to work (1280x720 and 1980x1080), but how about more exotic 768×480, 960×540, 1024×576 - can I expect that they would work on most of more-or-less modern HD-capable monitors?

FullHD and HD have too high pixelrate and require too big frame buffer for my hardware hence my interest of smaller resolutions.


texts:
I am trying to get the boot chatter from a UART on IOT device. When powered up TX line goes high as expected (3.3V), but when it starts "talking" - scope shows that hi/lo levels swings are around 200 mV - between 3.26V - 3.18V.
Any helpful clues how to go about to get it sorted up, please?


texts:
Recently I've decided to build a simple RC oscillator circuit using UA741CP IC as an amplifier in my circuit. I think the way I connected the resistors and capacitors to the chip is correct. But the only thing that is not correct is power supply. You see, I've been told to power the chip by two separate power supplies. Even if I did this, the circuit wasn't working and it was drawing 0A. Nothing was working.

Schematic I connected it according to:

UA741CP pinout:

Now the way I have my circuit connected:

My power supply looks like this:

If you know the solutions, please let me know and explain it to me in details so I can continue in my work.
Thanks in advance!


texts:
I've looked at DC-DC converters for 12v to 18v and they usually have low amperage ratings. One for $50 can use 15A with 25A spikes. But cordless tools can pull much more than that, especially the saws (I've read up to 70A). I want to run a cordless reciprocating saw off my car battery (clearing some thick trunk bushes) far from AC outlet, the portable batteries run out of juice fairly quickly (3-5 minutes operating and they are new NiCd).

Yes, can just use the 12v on cables from battery but not the same zip to saw and blades don't seem to get as much bite (not just slower).
I'm unfamiliar with how many amps or current I can put through a resistor over time to split voltage to add additional 6 volts though the ones I see rated at 500w are for brakes and such are 10 inches long and cost $22 each. And I don't know if they are appropriate.

Looking to run the saw for ~2 minutes at a time, brief pause, 30 minutes altogether.

Adding a 6v battery (like golf cart or others) and mount them in my vehicle to tie into regular 12v when needed for tool. Guessing I'd need some rectifiers there but will the car over charge the 6v battery? And how do I go about all that?

Update: Ran it directly from car battery and wasn't good till I replaced wires with heavier gauge. Then acceptable. Power continued to diminish and I questioned whether doing this in 105°F weather affected it. Then I noticed some warm spots within the tool. I opened it and there are some fairly thin wires in there. Not much room to stuff wires (especially around the variable speed switch) but thinking up a plan to beef up the internal wiring and see if I can get much more solid performance at 12v.


texts: hard drive head/seek motor with Arduino?

texts: I can see there are many writings on line for using an Arduino to control a 4 or 6 wire stepper motor, that spins the platter in side an IDE hard drive. I want to control the seek read/write head motor instead, can this be done? I'm struggling to find anything at all on this?


texts: Charging 24V battery from 12V-24V converter

texts:
I have a wind turbine, which generates 12V/400W and two 12V batteries connected in series to have one 24V. I have two questions, is it possible to charge them from the turbine just through the 12/24V converter without using the 24V charger? The second question: Is it possible to charge them just with the 12V from the wind turbine without using the converter at all?
The batteries must be connected in series the whole time.
Thanks in advance.

Edit: The batteries are both Varta Professional DC -LFD140-12V-140AH - lead acid.

Edit2: Is there any way how to charge the batteries from the turbine?


texts: Can FOTA be performed by changing the execution point of the code i.e, changing the program counter in lpc1759

texts:
For FOTA can we divide the memory into two blocks, eg : block A and block B.
And whenever there is a new version of firmware detected, we shall change the execution point of the code.

Is this feasible?


texts: How to measure EMI without special equipment?

texts:
I have bought a cheap dashcam to play with, only to discover that my GPS receiver stops working when it's on. After I ruled out power supply issues (both devices have batteries), I'm left with a hypothesis that the dashcam produces EMI interfering with GPS carries frequencies (1.2-1.5 GHz).

Before I start wrapping my head the dashcam in tinfoil, I want to have an actual measurement of the interference I'm facing. Unfortunately, all I have at home is a multimeter and a toy oscilloscope, in no way capable of GHz measurements. I'm thinking about making some sort of antenna probe for my measurements:

simulate this circuit – Schematic created using CircuitLab

Is this approach realistic? Is there a way to reliably tune it to the frequency range of interest?


texts: DC to AC inverter (full h bridge) with single pwm channel

texts:
I have only one PWM channel.

but I have found PWM and inverted PWM signal is required to run the full H bridge to convert DC to AC.

a square AC signal is more than enough for my application

is it possible to use a CMOS NOT logic ic to invert the PWM and give it to the full h bridge?

PWM frequency range will be 0-300Hz

also, I have found 3ns switching time NOT gates available in market

power supply source will 150-220V DC 50mA


texts:
Receive interrupt flag (RCIF) is not getting cleared even after reading the RCREG (several times!). Because of this I could not receive further data. How to get rid of this problem?

PIC16F877A


texts: Should input power be greater than output power in a buck converter?

texts:
For example,

in order to provide for 10W (5V*2A), the input must be greater than 10W?

I asked this because in datasheets, only input voltage is mentioned. There is no mention of the input current. I assumed, as the voltage decreases, current increases. Of course, the power will be the same. 12V*1A = 12W. 6V*2A = 12W. Else, I am wrong again.


texts: LPV7215 comparator misbehaving in simulation

texts:
I'm simulating the following comparator circuit using TINA-TI (Version 9.3.150.4 SF-TI). The behavior, however, is not as expected:

Hopefully it is clear that V- remains constant, while V+ swings above and below it. The output stays at 5V though, it only slightly nudges in the right direction.

As a reference, here's the comparator LPV7215 datasheet.

Common mode input voltage is within range, inputs are within range, power supply is within range. The output is a push-pull. What gives?


texts: How do I find the equivalent resistance between terminals A and F? The only idea I had was simplifying the parallel 300 and 60 resistors, but where to from there?


texts:
I am wanting to put have a few LED's flash with the intensity of my music. I don't need a color organ, but just want the LED's to flash in sync with the music. I am amplifying the signal with a LM368 chip and playing music from a 4ohm 3W speaker and it's sound quality is great. The problem is my LED's don't turn on at all..

I am using the configuration that many people claim works well but its usually done with a TIP31 transistor and not a 2N3904. I tried inserting an opAmp with a gain of 10 before the base of the transistor with no success.

Does anyone see a problem with my circuit or know of a reason the LED's arn't turning on? Any advice would be appreciated

Thanks


texts: On/off Circuit with an AVR and a push button

texts:
Here is maybe a difficult question I mind asking but here we are, I need to do a Power On/Power Off switch with an attiny 2313 and a push button, the code is ok, but I want this "switch" to power on purpose a HD44780 4x20 LCD, an atmega1284, multiple Leds and 1 RF434 Emitter and a receiver on the other side is the attiny 2313, an FTDI FT232BL and an enc28j60 coupled with an atmega328 so I want or the FT232BL or the enc28J60 via WOL or the push button to power on the LCD and the atmega1284. But my question is how to do it?

I thought of an NPN transistor (like the 2N2222A)  but unfortunately it doesn't drive a lot of current and a relay but I don't pretty like (and my current is pretty limited if USB powered) this option, any other idea ? (here is a basic schema of what I want to do, I remove almost every component related to each chip for better 'reading')


texts: Antoniou gyrator with op-amps, simple explaination?

texts:
I need to demonstrate that this circuit behaves like a gyrator:

circuit

Now, I made this new version of the image:

edit

If I apply KVL to the blue surface I find out that the voltage on the top left resistor and on the bottom right one are the same and equal 1/2*V1 with reversed polarity, when I apply the same rule to the light blue surface on the right I find out that the voltage on the resistor equals V2 with reversed polarity, applying it to the red surface suggests me that the middle resistor has a voltage of 1/2*V1. In the end applying KVL to the perimeter of the circuit makes me believe that V1=2*V2. But how do I close my reasoning to demonstrate that this behaves like a gyrator?


texts: Single inductor buck-boost idea for MPPT (maximum power point tracking)

texts:
Basically my inspiration is this guy's work. A buck converter that provides MPPT as long as the solar voltage is higher than the battery voltage. But I want to extract power to the battery even at low voltage.
I tried building/testing a small 4-switch single-inductor buck/boost but I blew a couple of capacitors on the output. My understanding is - this was because, while switching one side (buck xor boost), I was unable to supply a 100% duty cycle to the opposite side. The interference of the PWMs on both sides caused some serious current/voltage spikes. So I thought of this:

Input: Solar panel or rectified wind turbine output.
V_in, I_in for power throughput tracking, and V_out for battery level checking
H-bridge with NMOS/PMOS setup so there's never a short and (I think) simplifies driving circuitry. The project Tim Nolan did (see link in first paragraph) uses a 50kHz PWM. I would like to use logic-level MOSFETs, but will I be able to switch them at 50kHz from the Arduino?
2-to-1 multiplexer set up so that if one side is receiving a PWM signal, the other side is fully ON and not interfering with the power flow. So just one PWM signal is needed (in this case, Arduino using the Timer1 library). Freeing other pins for SD datalogging, communications, alternator RPM measurement, whatever.
Output: A (lead acid) battery will be connected to the output, which will pretty much prevent the output voltage from actually changing, but the MOSFET switching should be able to match the impedance (is that the correct terminology?) to the input and extract maximum power.

The benefit (I think) is that this should be scalable to a wide range of DC inputs / battery outputs with suitable sensing resistor / MOSFET / minimal code changes. Using lead acid / deep cycle batteries since those are more tolerant to abuse.
Your inputs are welcome! I guess the question is, is this a feasible design?
EDIT: Just found the CircuitLab thingy. Mocked up a slightly more professional-looking picture.

simulate this circuit – Schematic created using CircuitLab


texts: Reverse-polarity protection P-channel MOSFET

texts:
There are many ways one can build a reverse-polarity protection circuit. Using diodes, Shottky diodes, n-MOS in the return path and using a P-channel MOSFET on the positive side of the circuit. My question is about the P-channel MOSFET type of reverse-polarity protection circuit.

In the below schematic there is a P-channel MOSFET, a Zener diode to protect the MOSFET from having an excessive Vgs voltage, a resistor to limit the current through the zener diode and a capacitor.

Main question: I have got no clue whatsoever what the capacitor is doing here. What is it for and how do I choose its value?
How to choose the value of R? Do I only take the max current that the Zener diode can handle?

I've searched the Electronics exchange forum and indeed I found a lot of pmos reverse-polarity protection posts, but none of them addressed the capacitor question.

simulate this circuit – Schematic created using CircuitLab


texts: Differential Equation of RC Low Pass Filter

texts:
I'm trying to analyse the following circuit to find the differential equation describing the relationship between \$V_{in}(t)\$ and \$V(t)\$:

Where \$C_1 = 2uF\$, \$C_2= 1uF\$ and \$R_1=R_2=1k\Omega\$.

I understand that:

\$V=IZ\$

\$I_c = C \dfrac{dv}{dt}\$

and \$X_C = \dfrac{1}{2\pi f C}\$

So from this, I can work out that current through \$R_1\$ and \$C_1\$ is given by:

(1) \$I_{c_1} = 2\dfrac{dv}{dt} \times 10^{-6}A\$

And I get 3 KVL equations:

(2) \$V_{in}(t) - V_{R_1} - V_{C_1} - V_{R_2} = 0\$

(3) \$V_{in}(t) - V_{R_1} - V_{C_1} - V_{C_2} = 0\$

(4) \$V(t) - R_{C_2} + R_{R_2} = 0\$

This shows that: \$V_{C_2} = V_{R_2} = V(t)\$ which is obvious from the diagram.

This can then be substituted into either (2) or (3) to give:

(5) \$V_{in}(t)-V_{R_1}-V_{C_1}=V(t)\$

It's at this juncture I get stuck and I'm not sure how to proceed. I don't need a full solution, just some advice on what to try next.


texts: What is the rating current of zener 1N702

texts:
I'm trying to solve a problem which requires the rating current of this diode 1N702. In the book, the author uses 1N961 zener for the examples and states that the rating current \$I_z = 12.5\$mA. In the exercises, however, the author requires 1N702. The question is

  Design a 7.5-V standard voltage source using a zener diode if the
  supply voltage is 20V. Use a 1N702 diode.

The solution is

$$
R = \frac{V_{dc}-Vz}{I_z}
$$

I can also determine the dissipating power but I need the current first.


texts: Earbud wire color shielding is red/white and yellow/black, which are the grounds?

texts:
All wires are white metal, no copper, and they run side-by side and not one inside the other, ground.

I'm trying to - well, will - hack my laptop via the headphone jack (yuck) into a Yamaha YAS-71 analog inputs because I apparently don't have optical outs on my laptop, an older HP.


texts:
I'm designing a board with a control port. The control port allows an external controller to reboot the system by pulling the BRD_RESET low, effectively restarting both regulators.

However it is possible to use an external DC power supply (5-12V) instead of the USB bus voltage provided by the control port.

In this case I could fry my external controller (5V system) because the BRD_RESET is pulled high to the external supply voltage (5-12V) by R1.

How can I protect my external controller? I need to limit the voltage it's seeing on BRD_RESET to VBUS and at the same time allow it to pull down BRD_RESET to GND


texts: Finding the broken cicuit in an Xor Gate

texts:
I am new to this particular stack site but I feel that this is the most appropriate place to ask my question.

-Background-

I've been following an online web course called Nand2Tetris that takes you through the steps of building basic logical circuits to full ALU and Processor components, that's the first half of their program, the 2nd half then uses that built virtual PC to implement an operating system, a higher level programming language up to using their language to write your own programs in. I thought this course was a great step in bridging the gap between the Physics part of computational logic to the field software development.

I have never wired or soldered a bread board or a circuit before although I do have a background in physics for understanding the Mathematics and Physics portion.

As a side note I have also followed Ben Eater's videos on youtube for in the process of building an 8-bit pc.

I ended up coming across an online virtual simulator by AutoCAD called TinkerCad that allows you to build bread board circuits and to simulate them. So far I have completely made an And, Or and Not gate successfully. and I am currently now working on an Xor gate.

Originally I was trying to make the Xor gate based on the version by Ben Eater which can be found here: Logic Gates by Ben Eater. However I was struggling with the connections of the green wires that were behind some components from within his video.

I then found this web page: NPN Transistor Xor Gate that provides the schematics and the bread board wiring setup. Here is the image for the schematic:

So I followed this design of the Xor gate and was trying to build this within TinkerCad, however I keep running into a problem.

This diagram is using 10k resistors to each of the 6 transistors' B terminals. They are using 1k resistors for all ground or (-) terminal connections.

-My Work in Progress-

Here is an Image of my work in TinkerCad:

-Diagnosis-

However when I try to run the simulator based on the schematics nothing is working in the simulator. Now if I change all of the 10k resistors to say 1k resistors then I get some functionality. With all of the resistors being 1k and I simulate the circuit: If I press the A input button (farthest to the left), the green LED does light up and when I release it goes off, this seems to be correct. Now if I press the A input button the button to the (right). No light comes on. However if I go back to button A and press it to keep it in the down position leaving the light on, then come back to button B the light does shut off.

The Basic Xor truth table is quite simple:

A B Out
0 0 0
0 1 1
1 0 1
1 1 0

However the behavior I'm getting from the simulator is resulting in a truth table of:

A B Out
0 0 0
0 1 0
1 0 1
1 1 0

-The Problem-

I can not seem to find where the fault in the circuit is, and I don't know if this is a bug within TinkerCad or not, but here is another image of my Bread Board circuit with the Transistors pulled up so that you can see where the Resistors are connected.

I don't know where the problem is coming from but maybe someone here can help with the information that I have provided to see if there is anything that I am over looking. I have followed the wire connections dozens of times, I've changed and modified the resistors that are tied into the transitions to many different values ranging from 0.5kOhm up to 10kOhm. For some reason I can not seem to get switch B the one on the right to work the LED light properly. I don't know where the broken connection is or if it is a matter of having the correctly resistors...

Any and all feedback and or help is very much appreciated.


texts: Do I need to protect every single 18650 battery in a parallel block?

texts:
For my project, I will need to connect around twelve 18650 lithium-ion batteries in parallel. Is it necessary to protect every single one of them, or are there any protection circuits that can protect and balance the block as a whole? And, if I use unprotected batteries and connect them in parallel, will the resulting circuit be safe for the usage and charging? In industrial packs of parallel 18650 batteries (like in Tesla cars), is every single battery protected as well?
The batteries used for the project are standard Samsung 25R 18650 2500mAh 20A ones.


texts:
I'm just reading through Texas Instruments' Application Report on Switching Regulator Fundamentals and came across the half-bridge converter and the formula for both the output voltage of the entire converter and the peak voltage across the secondary winding of the main transformer. I have included a diagram of the half-bridge in Figure 1 and have included its associated equations in Figure 2. You'll notice that I have highlighted the Vrect term in equation (5) of Figure 2. Can anyone tell me what this Vrect is and where it comes from? Cheers!

Figure 1:

Figure 2:


texts:
We want to know how exactly do we make the connections of the photodetector since they are so fragile.Can we do a PCB,  and if so is there any IC base for it.How do we work the RF output as we need to connect it to the BNC connector.
https://4donline.ihs.com/images/VipMasterIC/IC/UTAG/UTAGS00060/UTAGS00060-1.pdf


texts: Design circuits with unused inputs or has a constant expression

texts:
I just started to learn about circuits design (without any prior experience), as a result I would like to ask a question.
I was given a truth table for a circuit that has three inputs, and I need to design a circuit based on the truth table. However, after simplifying the expression, I found that one of the input is not used at all (That is to say, the expression only depends on the other two inputs). How can I draw a circuit that involves three entries but not using the first one at all?
What if one of the expression is a constant, no matter what is the value of the circuit. How can I draw it?
I know I surely need to draw something, and surely I can't ignore that input because it is physically there. So I am not sure how to deal with it.


texts: Calculating equivalent resistance using loop analysis with no applied voltage

texts:
I have a bridge circuit that I am supposed to find an equivalent resistance between points K and P for using loop analysis.  I am aware that a delta Y transformation is the much more direct route, however I am required to use loop analysis.

I am having trouble understanding how to do this with no voltage present.  I am familiar with using Kirchhoff's Voltage rule and current rule to do a loop analysis and find the overall current when there is a voltage applied.  However, when there is no voltage applied I am not sure how the voltage rule applies.  I could of course apply a dummy voltage at points K and P which would allow me to calculate the currents and, by Ohm's law, the equivalent resistance.

I've searched the web for loop analysis of resistor circuits but everything I keep finding has a voltage source included.  This suggests to me that the dummy voltage is the way to go.

Basically I'm wondering if there is some type of loop analysis method that I am unaware of that does not require a voltage source, or if the dummy voltage method is what the question is asking me to do.


texts: Do we need to define the delay, power and constraint templates for characterising a library (.lib) file out of post-layout netlists (transistor level)

texts:
I am designing standard cells at the transistor level and I want the characterize these cells into a library file (.lib). Do I need to define the delay, power and constraint templates (sequential) compulsorily?
Can I not just start off with setting the PVT values?
I am using Cadence Liberate for characterization. I used Cadence Virtuoso for transistor level designing and now I have the post layout netlist spice (.sp) files.
thanks in advance!


texts: Why do these USB mobile phone chargers have multiple output ratings?

texts:
PSU that comes with any electronics device usually has a single output voltage rating. This is because they are intended for use with a single device.
These Samsung phone chargers have multiple output ratings!

Why is this necessary?
How is the output switched to different output voltages? There is no switch to do this so I assume the device being charged tells what voltage it needs.


texts:
I am new to XBee and I am using Xbee s2c module with AADD-XBEE Adapter to configure it in XCTU. I am having two XBee s2c module and separate adapters.The problem is that,I could discover one of my xbee moudule(say, module no 1) in xctu and I could configure it perfectly. While I could not discover the another module(say, module no 2) and it shows me no device found.  I tried 'XBee Recovery tool' too but its showing like this,
- Looking for active bootloader... [ERROR]
        There is not an active bootloader in the module.
- Resetting and entering bootloader... [ERROR]
        PutData1: Sent only 0 of 1 bytes
[ERROR]
        There is not an active bootloader in the module.

I also would like to mention here that, the ASSO led in the adapter for the undiscovered xbee module is glowing dimly while for proper working xbee module its adapter's ASSO led is glowing brightly.

Even if I interchange my xbee modules between adapters, the same thing happens, this confirms me that there is no problem with my adapters think so.
Kindly help me resolve this problem, your help could help me save my money.
Thanks in advance.


texts: How can I tell if something's controlled by an analog or digital input?

texts:
Is there a way to tell if something's being control by an analog or digital input without knowing and understanding all the rest of the circuitry involved?

I have a Wowwee robot (Elvis) that I'm trying to interface with an arduino, so I can "parasite" onto it and control its functions (very simply).

I've hooked in my multimeter to the output pins that head toward the motors (and their respective circuit boards). I get a signal of mostly 3.3v, but occasionally it dips down in the 2's and 1's. Now I know this looks like analog, as digital would just be 3.3v or 0v, but I'm wondering if it's still a digital signal just being PWM'd...?

I just got a logic sniffer/analyzer. I've been trying to interface it with the Elvis to see what the output's looking like on the pin(s), but I've been having other issues with the logic analyzer (and noisy, ungrounded pins). But I digress.

So is there a way to tell if this is an analog signal that's actually moving up an down the range between 0v and 3.3v, OR if it's still a digital signal that's just being pulsed fast enough to "effectively" be/look like an analog range?

Thanks!


texts: Art of Electronics 2nd edition p. 67, figure 2.8 -- what causes the clipping?

texts:
I have been rereading this section and realized I always get hung up here.  The idea of clipping happening because the emitter is not able to stay .6 or so volts less positive than the base is familiar, but I find it difficult to be sure how that happens here.
At positive input voltages of .6 volts or higher, it seems that positive current flows through the emitter resistor to the -10v supply and also through the load resistor to ground.  Since the voltage drops are different, the currents through each resistor should be different, too.  When the emitter reaches zero volts, the current through the load resistor crosses over to a negative flow, while the emitter resistor is still a positive flow.  When the emitter reaches -5 volts, the forward drop across RE is exactly the same magnitude as the negative drop of RL, and beyond that point the transistor would need to be drawing current instead of supplying it, leading to cutoff because the emitter voltage will rise compared to the input at the base.  Is this correct?  I feel like I can't quite make the connection here.
I gather from internet searching that the distinction the authors make about large-signal vs. small-signal impedance has to do with the signal getting large enough (-5v in this case) to stop the linearity of the circuit, is that right?  And is it the idea that the change in current direction at the load represents a change in the effective impedance?
When they say that the large-signal impedance is larger than the small-signal (as large as RE), do they mean that the load is somehow out of the circuit at that point, so we no longer enjoy the parallel resistance of both resistors? Edit: I guess that's the case, since up to -5v on the emitter the current is split (parallel) between RE and RL, but below that point all the current would have to go through RE (with the load current, [if there were any below this point] effectively passing through RL and RE in series?), right?
They also mention that the transistor can only source but not sink current.  Is the idea here that if the base tries to draw current it does so without the aid of collector current?  Or just that reversing the current direction immediately backbiases the BE junction?  Any thoughts would be appreciated!
p.s. In the course of writing the question I think I might have figured out a big piece of the solution and the significance of the caption under the figure.  Below the -5v point, RE is limited to (-5-(-10))v/1000= 5ma of current and falling, while the load resistor's current will be increasing above 5ma in the opposite direction.  All the current drawn from the load then passes through RE.  In order to reach -6V at the emitter, RE would have to draw -6ma through RL, but it can't because the voltage drop across RE is too small. So the base keeps getting more negative, but the emitter is stuck and thus the backbiasing. Right?
Sorry this is so wordy!


texts: How to do via fencing of an RF trace with a 5V front copper plane and a GND back copper plane?

texts:
Background

I am a building a board to send RTTY via a Radiometrix NTX2B as part of my final year High Altitude Balloon (HAB) project. I have just created a PCB which I uploaded to JLCPCB for manufacture, but hours later starting to doubt the via fencing I had done with the SMA centre pin to transmitter antenna pin.

Since I have the back copper set as a GND plane and the front copper as 5V plane, as you do, then placed the vias labelled GND either side the very short 0.5mm RF trace.

I cancelled my order upon doubting what I did, in case it was a silly mistake, since it was my first time using via fences (or anything to do with RF on PCB). If both the top copper and bottom copper were set as GND planes I wouldn't have this doubt.

Have I just done something stupid, e.g connecting the 5V plane to the GND plane or....?

I emailed by electronics lecturer, but no reply so I thought I ask here for a faster reply since I am close to a deadline. (Please ignore the fact the email was written for a specific person)

I'm starting to think that it may have been okay due to the zone showing the 5v plane avoiding the vias, but I am not certain.


texts: What is the impedance of audio output of cell phones

texts:
What is the impedance of audio output in cell phone. I mean 3.5 jack for headphones. Is that somehow standardized? Do we know ranges among cellphones? Or mp3 players. I haven't found any information about impedance, when searching manuals for cellphones or mp3 players.

Does anyone have experiences, how non-matching impedance of audio output and headphones impact the quality of sound?

I'm trying to find perfect headphones for Sony Experia L.


texts: I saw a post on raspberry official forum. It's about GPIO remote switching PC on/off, but it is not very detailed. I am pretty interested in it and i have this relay. I am wondering if anyone here has done that before. I want to get tutorials or manuals about it. I haven't posted on their forum yet.


texts:
Update

  Ok, it may be related to the adhesive I'm using to glue the toroids on the 3D prints.. I'll wait till tomorrow for it to cure and test again..

I'm trying to build a portable/battery powered core rope ROM after successfully having built a "desktop" one.

This is the device I built:

I'm having trouble however with the waveforms of the transformers when the
 2 AA batteries start to drain, with just one or two transformers it works fine until 2.5V and even less, but in the case of the following set of transformers at 3V already the one with the blue line does not trigger the latch (ch 4 on the scope).

I've been empirically swapping toroids with more or less windings to see how well I can get it to work at lower voltages but now I'm just plainly confused because the three transformers shown on the scope shot are made from the same toroids(datasheet), with the same amount of windings. I'd understand if there was a bit of variation (i.e. maybe I counted the windings wrong or there is some fabrication tolerance) but this waveform is just way too different. I wound a new one and it had the same lower waveform, however if I swap a "good" toroid with a "bad" one in position, the waveform follows the toroid. So I guess it is something related to the winding or material of the toroid.

Is this something design related or fabrication related? (i.e. the permeability is way lower on this one and I have to test a lot of them?)
Is there something that maybe I'm not taking into consideration? Do the order of the toroids matter? Does the distribution of the windings around the toroids matter? (although they are identically wound as far as I can tell)

These are the 3D prints that the toroids are glued on:

Here follows a block diagram of the system that produced these waveforms:

simulate this circuit – Schematic created using CircuitLab

(Sorry I could not find a better way of drawing transformers with multiple primaries)

p.s.: this just wasn't a problem on the desktop version because I could drive them a lot harder since parts count and power weren't issues


texts: Why does a resistor have this value in a circuit with an operational amplifier?

texts:
I'm analyzing this circuit to condition a PT100.

I clearly understand what the circuit does, but the current flowing through R7 is very small and negligible.
So in theory it could be any value (generally from 1k to 100k), but I don't understand why the value should be 49.9k.
There is no information on why the value of R7 where said circuit is described.
Any suggestion or comment is welcome.
The circuit is described here:  Precision Temperature Sensing with RTD Circuits


texts: I'm completely new to electronics but want to build a blue light led array 8x9 with a 12V input and have no idea how to do this on a protoboard! If someone could help with a schematic it would be great, i think the 12V would light 3 of the leds if I did a paralell circuit but not sure?


texts:
Hey all I have the following question and I am having trouble getting to the correct answer. Here is what I have: (sorry I do not understand how to format the question)

Consider a linear time-invariant system such that

$$H(e^{j\omega}) = \frac{1}{(1-\frac{1}{2}e^{j\omega})^2}$$

If the input x ̃[n] is periodic with period N0 = 8, then determine the output Fourier series coefficient y4 if x4 = 9.

I have this so far:

$$y_4 = x_4 H(e^{jk\frac{2\pi}{N_0}})$$

$$= 9 H(e^{j\pi})$$

Goes back into the given function:

$$= \frac{9}{(1-\frac{1}{2}e^{-j\omega})^2}$$

I am stuck here. How would I get a solid answer from this. I know that in the end the answer is 4.

Thanks.


texts: Measuring Arduino internal voltage reference with respect to Vcc

texts:
How do I read the internal reference voltages of the Arduino (Ardino Mega, ATmega2560, specifically the 2.56v reference) with respect to the input voltage?

I'm trying to measure the remaining battery capacity of a device through a voltage divider. The Vcc going into the Arduino is also hooked up to the battery and thus varies as well. I've measured the internal 2.56v reference so I know approximately what it should be regardless of the varying Vcc voltage but I can't find any simple documentation on exactly how to measure that particular internal reference voltage with respect to the Vcc.


texts: A question about estimating non-filtered data

texts:
We have made data acquisition with 200Hz sampling rate which sampled amplifier analog signals. But unfortunately the amplifier filter was set to 20Hz and it shouldn't have been using the filter. 20Hz active 3rd order bessel filter was used.

Is there a way to recover this data as if it werent filtered?


texts: How to calculate load flow/power flow in a DC grid?

texts:
From my understanding this depends exclusively on the voltage level, but I have not found documentation about how this happens or is done.

Is it purely based on KCL?
Are there any tools or procedures to calculate the load flow or the active power flow in a DC network such as a DC microgrid?


texts:
I'm trying to use a dsPIC33F to generate a data signal which must not be interrupted between words. It must be a continuous train of 240 bits. I am clocking the SPI using DMA with 16-bit words, but I am getting gaps in between the words. Is there anything I can do about this or am I stuck with it?

Now here's the odd thing! If I do it using a looping routine continuously writing to the SPI register, there are no gaps! So the DMA is creating these gaps somehow. It would be nice if I could reduce the CPU usage with DMA, as high CPU usage prevents other background tasks from executing.


texts: How to sketch the spectrum of \$m(t) = \cos(1000)t \times \cos(3000)t\$

texts:
I know how to sketch the spectrum of \$m(t) = \cos(1000)t + \cos (3000)t\$

But I stack with that....when it's multiplied? How to sketch the spectrum \$m(t) = \cos(1000)t \times \cos(3000)t\$?


texts: Which one is correct for this power consumption estimation?

texts:
If a MOSFET gate driver is supplied by a 12V DC power supply and if it is drawing a current I(t) from the power supply, what can we say about the power consumption in terms of voltage and current?

I was thinking the power consumption would be:

P = Vrms x Irms = 12 x Irms

But I saw some calculates as:

P = Vdc x Iavg = 12 x Iavg

Which one is correct? Why?

Which one is convenient here to calculate? The average power consumption or rms power consumption? I'm a bit confused about which one relates what.


texts: Sensors to detect inside liquids temperature and percentage of alcohol

texts:
I would like to measure and study the correlation between temperature and percentage of alcohol inside a bin with fermenting beer, what type of sensor do I need.

I was planning to plug this sensors to a raspberry pi, but in case not compatible I could try to plug them to a pic18 or pic16, which I worked with some time ago. However if compatible with raspberry pi, even better.

Thanks for your feedback.