texts:
On days I read a very interesting article, saying, that there's exist two general architectures in GPU design: IMR and TBDR architecture's.
One of them used in modern PC-based graphics card GPU's, and other in embedded devices, such as mobile phones, et cetra.

  The core design principle behind the TBDR architecture is to reduce the system memory bandwidth
  required by the GPU to a bare minimum. As transfer of data between system memory and the GPU is
  one of the biggest causes of GPU power consumption, any reduction that can be made in this area
  will allow the GPU to operate at a lower power. Additionally, the reduction in system memory
  bandwidth use and the hardware optimizations associated with it (such as using on-chip buffers) can
  boost application performance. Because of this development strategy, POWERVR graphics cores
  have become dominant in the embedded electronic devices market.

I'm just curious: why do they even need to drive vertex data from GPU to CPu and vice versa?
Why not just load all the data (at the begining) in VRAM, so a GPU would have a riect acces to them without any delays? Because, as far as we all know, all operations, connected to operations on vertex or texel data are done in GPU internally, there's like no reason for CPU to even touch these data.
CPU in this chain are only needed to send commands to GPU, like, "Hey, you, GPU, turn on the camera, that I set previously on coordinates 0,0,0, by 25.61415 degress in X plane" or "Hey, GPU, set framebuffer resolution to 1024*768, 32bpp color-depth".
Maybe I missing some part of how GPU and CPU's are operating together todays, but anyway.
Hope you'll enlighten me a little.


texts: People I am having a problem regarding the control of the stepper motor speed, I understand that in order to change the speed of the stepper motor I will need to generate pulses at different frequencies using a micro-controller. My problem is that I can't find an algorithm of how to program a micro-controller so that I will be able to generate pulses with different frequencies. Can Someone plz find time to explain how can I interact with the MCU so that I will be able to accelerate/decelerate the stepper motor. To make my question more clearly, I need someone who can give me an Idea on how to tell the MCU to change the frequency of the output it generate,because the motor speed also depends on the frequency of the pulses, I will then try to code that myself, plz people just an Idea. Thank You


texts: Current sensor and ADC with different ranges

texts:
Is it possible to have this Current sensor, with ranges from 0-7V out, to this ADC, whitch have a voltage range of 0-5V (0 - 2xVref), and just use a voltage divider inbetween to change the voltage out of the Current sensor down to 0-5V

Since the output from the current sensor is analog is it going te be any problems solving this issue this way?


texts: If the neutral wire carries current, why do many people believe that it's safe? I've heard "You can touch the neutral wire/bar in the breaker box and not get shocked. Only the hot can hurt you." If the circuit is complete and current is flowing, can't you receive a shock?


texts:
I work in a typical electronics lab, with resistive earth mats, ESD straps and isolated DC power supplies to test prototype PCBs. I prefer not to use the power supply earth-ground, and to leave the test setup "floating".
Mobile phones and laptops do it just fine, so why can't my PCB, and all its connected equipment? However my colleague is uncomfortable having things floating and says they need a reference (connect Earth to the 0V rail).

1) What are the pros and cons of connecting the power supply to Earth?

2) The oscilloscope ground pin has continuity to Earth. Why?

3) Any relevant referece materials available?

Many thanks!


texts: What causes this resistor to fail - open circuit and no visible damage?

texts:
The resistor in question is R10 (523K 1% 1/4W) in the circuit below:

The resistor is reported to fail as open circuit and there is no visible damage.  We have shipped some boards and got some damaged ones back with R10 damaged.  So this is not a single instance.

The AC input is 220V.  The resistor specification from the manufacturer is:

1/4 W
Max working voltage: 300V
Max overload voltage: 500V
Max dielectric withstanding voltage: 500V

Since R10 withstands an AC signal, the Vrms it sees is less than 300V.  The wattage it withstands is also less than 1/4 W.  But R10 on a few boards just failed and they are now open circuit/huge resistance and there is no burn mark on the outside.

We did a few tests, trying to amplify the problem.  We overload one board with 253V AC (230V*1.1) and let a blower heat up the board.  We also put a more-than-usual load on the board.  The board did not fail after several hours of continuous test.

I have no clue on how R10 would die.  Any pointers are greatly appreciated. Is there any way to examine the dead bodies of R10 to determine the cause?

The excerpt of the resistor (Metal Film type) is shown below (I do not have the full datasheet):

The measurement on R10 and GND (the voltage drop across R12 is less than 3.3V) is shown below (the peak is about 320V):


texts:
I have a question about working with Altium Designer Software. I put some devices in schematic, but I do not want all of them importing to PCB. I mean I want to mask some part of schematic in such way that software does not import those parts into PCB. Would you please tell me how to do it?
Thanks in advance


texts: What does it mean when i2c_smbus_read_byte() returns 0

texts:
i2c_smbus_read_byte() returns a negative value when there is an error in reading data. But what if it returns 0?

Following is the code from adt7316-i2c driver

static int adt7316_i2c_read(void *client, u8 reg, u8 *data)
{
   struct i2c_client *cl = client;
   int ret;

   ret = i2c_smbus_write_byte(cl, reg);
   if (ret < 0) {
     dev_err(&cl->dev, "I2C fail to select reg\n");
     return ret;
   }

   ret = i2c_smbus_read_byte(client);
   if (ret < 0) {
      dev_err(&cl->dev, "I2C read error\n");
      return ret;
   }

   *data = ret;

   return 0;
}

Even if i2c_smbus_read_byte() returns 0 here then the driver will successfully
probe.
So my main concern is to know whether returing of 0 from i2c_smbus_read_byte() is a valid case or not for a driver to probe.

I am not sure but maybe it means that there is no error and also no data has been read.
If this is the case then under what situation does this happen?


texts: Several questions about the ADC LTC2323 function, I'm new in electronics

texts:
http://www.manuallib.com/pdf/2014/0707/linear-ltc2323-16-input-adc-datasheet.pdf

this adc is part of a little project I have to interface and fpga with this adc.

I want to understand how does the source signal input in the ADC and how does it come out from it, not so interested in how it's produced inside. Excuses for my basic understanding of electronics.

Several questions:

1) As I can see, the source signal is an analog wave: This source signal is from -0.3v to 0.3v?
2) which pins are to be connected to the source signal? AIN1+ and AIN1-? what about the AIN2+ and AIN2-?
3) What's the purpose of REFOUT1,2 ??

4)The general function of the ADC, is like this? Please correct me!: the ADC "pick up" an "instant" value of the source signal in an exact time, this value which varies from -0.3v to 0.3v is converted (through successive approximation) and the result is successively latched to the SDO in 12 cycles (who can be also successively be picked up by my ADC interface on my FPGA),

5) Those 12 bits represent the binary fixed point (with fractions) representation of the "instant" value processed for the ADC in that exact time?

6) So this all happens for this small instant before getting the next "instant" value from the wave, so the process start over again?

It would be like:
1) 0.000
2) 0.111
3) 0.112
4) 0.113
...
?) 0.299
?) 0.3
then...
?) 0.299
?) 0.288
...
?) 0.000
?) -0.299
?) -0.3

if it's so, what tells me how many fractions will this value have, -0.299 or -0.2999 or -0.299999? and lastly, how many of this values will adc give me per wave (from 0.0 to 0.3v and 0.0 to -0.3v).


texts:
Sometime back I made a relay board to control my table lamp using bluetooth. It worked perfect and so now I would like to upgrade to a beefier power relay.

The aim is to be able to control any household device. Mainly air conditioner, water heater, room heater.

I am based in India (230V, 50Hz). We use the Type M power plugs for power devices (BS-546 standard) that support 16A max current. I am assuming that none of the devices would consume more than 16A in steady state.

Based on this, Maximum Apparent Power = Vrms * Irms = 230V * 16A = 3.68 KVA

I am looking at the O/E/N 62 Heavy Duty Power Relay Form 1A(data sheet here). In it the relay parameters are:

Max Current = 30A
Maximum Power Rating = 7.5 KVA

So I should be fine using this relay?

What about the life expectancy of the relay?

As per the datasheet, electrical life = 10^5 operations. Assuming I operate the load (close and open relay contacts) 5 times a day and ideal conditions, that gives me 500+ years.

Any way of getting a more 'realistic' estimate on the lifespan of the relay?


texts:
I'm designing a board that implements a USB hub. The upstream port will be connected to an Android tablet (or something like that) and the downstream ports will feed some other devices.
The board itself will be self-powered from a battery and related dc-dc circuit so I don't need to draw current from the upstream port.

The question is can I provide current to the upstream and downstream connected devices to power/recharge such devices?
The answer is true for downstream ports but I never found an application note providing backfeed to upstream port (maybe only as an unwanted side effect).


texts: How to use .step param with more than two parameters in LTSpiceIV

texts:
I need to do three transient simulations with different values of certain resistors (conveniently called R1 and R2) in each. What I mean to do exactly is this:

Sim. 1: R1 = 1 k\$\Omega\$, R2 = 10 k\$\Omega\$
Sim. 2: R1 = 1 M\$\Omega\$, R2 = 10 M\$\Omega\$
Sim. 3: R1 = 1 k\$\Omega\$, R2 = 1 M\$\Omega\$

If there were just one resistor whose resistance to vary, then I would just set its resistance to "{r1}" (I use lower case letters to make it a different variable/parameter than R1) and use a command such as:

.step param r1 list 1k 1meg 1k

However, since I have to change two parameters (together) two times each, I have read here that (at least on LTSpiceIV) that a workaround to my problem could be using something like this:

.step param X list 1 2 3

.param r1 = table(X, 1k, 1meg, 1k)

.param r2 = table(X, 10k, 1meg, 10meg)

Upon doing the simulation, I get the following warnings:

WARNING: Can´t resolve .param r2 = table(X, 10k, 1meg, 10meg)
Select OK to continue the simulation with the default model or Cancel to quit now.

The same applies for r1.

For some reason, the simulation doesn´t "break" if I add one extra element to the table. In that case, the simulation takes too long, advancing more slowly every time, as it would never end. I have tried setting X to 0 1 2 instead of 1 2 3, but that does not work either.

Here are some pictures:

Circuit + commands

Error message

Your help would be much appreciated.


texts: Natural discharging duration of an unpluged capacitor

texts: Can natural discharging period of a charged capacitor be detected by a certain formula? If it is related to initial voltage and the internal parasite resistance, what are the factors affecting this quite high resistance that is measurable through a simple circuit? May it be related to capacitance or something else? If there is, can you give a certain expression in terms of V and C to find the total time needed for a charged capacitor whose initial voltage is V, capacitance is C to completely be discharged or remarkably get closer to zero while not being connected to any circuit?


texts: How to simulate the exponential growth op-amp?

texts:
According to Wikipedia, the following is the exponential output operational amplifier.

I would like to test this out in a simulated environment and see how this functions. For example give a sine wave as the input and observe the resulting output signal.

But I do not have any prior knowledge about simulating electrical circuits. Could somebody help me out here by suggesting a way to get started with this ? Thanks!


texts:
I'm going to control my Canon DSLR with an Arduino board.

How can I get current camera "busy" state before firing then next shot so I will keep waiting until it will finish all its jobs?


texts: A question on Vb Ic characteristics of an NPN transistor

texts:
I wanted to plot a Vb Ic curve of an NPN transistor in LTspice as follows:
Vbe is swept from 0 to 2V.

But all the tutorials I encounter shows this curve as the following:

Why in this characteristics they always omit plotting the settled part(I guess the saturation part) or am I doing something wrong?

Edit:

Here when I set series source resistance to zero:


texts:
I need to generate two open-loop PWM signals with different duty cycles for my converter. The frequency is 20kHz. I did generate one signal.

Should I use another TL494 and connect it to the same supply and ground to generate the second signal?
Will the two signals be synchronized?


texts:
I'm trying to read a LF (low frequency) RFID transponder, it works in the following manner: It uses load modulation, the receiver (the base station) generates the carrier and the transponder modulates it using magnetic coupling (like a electrical transformer), the transponder (or tag) being read switches a load (resistance) and it changes the carrier's amplitude like can be seen schematic ilustrated below (but it is only an illustration, the circuit is a bit more complex).

simulate this circuit – Schematic created using CircuitLab

The generated signal was obtained by an oscilloscope and is presented in the following explicative picture:

The information being modulated, as can be seen, is very weak compared to carrier's amplitude. The carrier frequency is 125kHz and the base band signal has a 20kHz bandwidth.

I assume that amplitude demodulation would be a better approach to solve the problem. At first, I tried to apply the sampling and filtering to obtain the modulating signal from transponder. I tried to sample at different rates, 250kHz, 500kHz and 900kHz, I designed the low pass filter using windowed sinc with window
function being Kaiser-Bessel, -3dB frequency of 30kHz and I tried to use different number of taps (coefficients), 8, 12, 16 and 32.
But, the sample rate and the number of taps almost made no big difference.

I read a suggestion to perform downconversion. So, I tried to perform downconversion by sampling based on fact of replicas, in frequency domain, being generated by sampling. It is illustrated in pictures "a" to "c" below.

The carrier frequency (Fc) is 125kHz, so I used 62.5 kHz sampling frequency, this is Fc/2. But it doesn't work --- when sampling is performed at 62.5 kHz, a kind of bouncing at the signal appears that is not present when I perform sampling at higher sample rates, as can be seen in the figure above.

I do not  know why this bouncing appears, I know what aliasing is, but I thought that the aliasing would only appear in the analysis of the data collected by the A/D converter, but the picture was obtained by an oscilloscope. In other words, I thought that the data collected by oscilloscope would not be affected by the sample rate of the A/D converter of another circuit that has nothing to do with the ocilloscope.

Anyway, this bouncing is affecting the filtered signal and the filter doesn't remove it. So, I gave up to perform downconversion via sampling and tried to perform downconversion by another way. I know that I can achieve this by multiplying the modulated signal by a generated wave with the same frequency and phase. This way, there will be a replica near DC, so I would perform filtering at a lower frequency.

But again I'm having problems, I'm using a dsPIC33EP, it's sampling rate
can reach up to 1MHz and the DSP core can reach up to 70 MIPS. But it doesn't have a mixerfrequency or a PLL, so I can't generate a sine wave with the same frequency and phase of the carrier to multiply by the signal in order to allow to perform downsampling.

I saw some ways to generate a tuned sine wave to perform using Taylor series by using look up tables. But what caught my attention was a trick that I found in another forum, there they use a trick, and instead to generate all the sine wave, they only uses 4 points {1, 0, -1, 0} to perform downsampling to an intermediate frequency. They call this trick of : "DSP Trick: Complex Downconverters for Signals at Fs/4 or 3Fs/4" it is briefly explained at dspguru.com .

Anyway, a question arises, because, to perform downconversion this way I need to multiply the modulated signal by a generated signal or by the 4 values representing the points of the generated signal (as explained in the page referenced by the link above). And, only after that ( the multiplication ), perform sampling. How can I sample after multiplication, since I need to sample the modulated signal before in order to perform multiplication?

I do not know what to do anymore. Any help will be very appreciated.


texts: ACS712ELCTR-30A-T never changes output with changing load

texts:
I am using an ACS712ELCTR-30A-T breakout board to measure the current on a 230V AC appliance. I have connected the hot wire of the AC connection to the two measurement terminals of the breakout board. The breakout board looks like this:

I have added a 5V DC source to VCC and ground and am using a voltmeter to measure the output. I started with the appliance turned off and it more or less correctly showed 2.53V on the OUT pin. This might seem strange as it is not properly centered at 2.5V, however I am using a voltage converter from 12V to 5V that is set up by hand and it supplying 5.06V is very likely. I then turned the appliance to its maximum power. I am not really sure what its consumption is, but based on the components used it should be between 0.5 and 1A. I would expect some kind of change in the voltage of OUT against ground. However it still shows 2.53V. The 30A version of that chip has a resolution of 66mV per ampere, therefore it should jump to at least 2.56V (2.53 + 0.5 * 0.066) on the voltmeter. The voltmeter (0.01V resolution) not changing its value means the current of the appliance would be less than 1 / 6.6 = 0.15A which is impossible.
An obvious issue would be that this chip cannot measure AC current, however the datasheet indicates the opposite.

The  Allegro™  ACS712  provides  economical  and  precise  solutions for AC or DC current sensing


texts:
I am using MAX712CPE(DIP) version for charging 1.2 volts × 8 batteries. Using the datasheet and available information on the Internet, we made the circuit schematic and are about to implement it. But still I had a small confusion in my mind with respect to V+ and Vin of the MAX712 IC. After reading the datasheet, I came to know that wall cube voltage (i.e. input voltage) needs to be at-least 1.5 V more than the series voltage of the batteries that we are charging, which in my case is 9.6 volts.

Now my question is, what is the difference between Vin and V+? For reference, I had taken this schematic information into consideration. I don't understand what V+ is used for. If V+ needs to be +5v, why we are considering wall cube voltage to be 1.5 V more than the net voltage of the batteries we are charging?


texts: How to get the value of a capacitor in series if I have the total value

texts:
I have 2 capacitors in series. 1st capacitor's values is 24.5uF. The total value of both capacitors are 16.5uF. How to calculate the value of the second capacitor?

The formula to calculate the total value of capacitors in series.


texts: Can this be done with the TLP2368 optocoupler (open collector)? (Toshiba)

texts:
I have tried to write to Toshiba technical service, but no one responds.
I have the layout of this optocoupler (TLP2368).

According to the datasheets, the VCC voltage to GND is a maximum of 6V, so I will use a 5V LDO regulator.
But there is no information regarding the maximum voltage with respect to the collector and emitter when the transistor is off. (Vo regarding GND)
I want to connect a resistor to VO and the other terminal of the resistor to connect to 24 V, obviously the resistor will have a value that the current flowing through it is less than the maximum allowed.
Any idea if it is possible or would there be a problem?


texts: Mosfet load control - different design compared

texts:
i've seen in a forum this design (Circuit 1) to drive a load using mosfet, i'm wondering in which differs from the "well-known" MCU mosfet driven loads like the second one in the image below (Circuit 2)?

What are advantages/drawbacks on using the first design over the second?


texts:
In my Arduino Mini (3v) project, I am using DC Motor Driver (BD65496MUV) to run a small 50RPM DC Motor. Motor rotates an independent mechanical knob whose starting and ending points, I do not know.

At some point I expect the knob to get locked/stuck. I need to know when that point reaches and stop the motor from running. I cannot access the mechanical knob so crash sensors etc are not an option.

I understand there may be a way to read the current to the motor and from that deduce when the motor is stuck, however I am drawing blank beyond that. How can I tell when the DC motor is stuck?


texts: Current solar panels being manufactured are not considered efficient. I have also read articles saying there is talk or even ongoing  research about four P-N layers (i.e: PNPN or vice versa) for solar panels. What I mean is, if more junctions equate to more absorption, why are photo-transistors  not used in solar panels instead of photo-diodes?


texts:
why we choose -180 degree as a critical point for bode plot?
i want the explanation for why we choose the factor 180 degree i.e,****above 180 degree represents instability and below 180 degree represents stability of the system****

** corresponding bode plot as a function of grid impedance and inverter
 output impedance**


texts: Why are ARM9 and ARM11 processors still used when the Cortex-A5 is more efficient?

texts:
Many consumer devices that require a low-power processor capable of running for several days to a few weeks on a charge still use ARM9 or ARM11 processors.  However, the ARM Cortex-A5 is more powerful and more efficient, is capable of running modern ARMv7 applications, and is intended to replace ARM9 and ARM11 for these uses.  (I'm seeing this on devices where signal processing is not as important as applications performance, such as high-end graphing calculators; devices such as low-cost MP3 players and portable DVD players are best served with the Cortex-M series.)

Why are device manufacturers still using these old ARM cores when a more efficient processor exists?  If a high clock rate (> 600-800 MHz) isn't required, why aren't they just using a low-clocked Cortex-A5 manufactured on an ultra-low-leakage process for efficiency?  (And yes, there are low-clocked Cortex-A5 processors out there.)


texts:
I am using TMS320F28035 in SPI Master mode. Where I have to transmit 8 Bit data to the slave device and have to read 16-bit data out of the slave device after completion of data transfer from master to slave. So total of 24 SPICLK cycles to carry out complete communication.

Since I have to read 16-bit data from the slave, master device should keep clock running for 24 cycles. But clock stops as soon as the data in SPITXBUF transmitted. To acquire at least some data from the slave I am keeping clock running by placing 16-bit data in the SPITXBUF so that 8 bits of useful data and 8-bits of garbage just to hold the clock total 16 cycles. During this period I am able to read 8 bits of data from the slave.

Problem:

Now the question is how should I hold the clock running for 8 more cycles to read remaining 8-bits from slave?


texts: How to select source termination resistors by looking at signal?

texts:
If I have two devices that some distance apart on a fairly large PCB (could be 1 in, or it could be 20 in). If I arbitrary select a value for R1, lets say 33 ohms in this example and if my digital signal is distorted due to reflection, how can I determine if I should increase or decrease my resistance to get my digital signal correct ? What indicators when I look on a scope, should be key characteristics that my voltage divider ratio is too high or too low (referring to source impedance + R1 and Zo)

Assume that the characteristic impedance (ADD: of the trace) is (ADD: constant but) not controlled (ADD: / known).

simulate this circuit – Schematic created using CircuitLab


texts: Trying to understand how a guitar pickup switch works

texts:
At the risk of being off topic, I need to ask a guitar electrical  question.

I am trying to replace an old guitar's pickups (including the pickup switch). The idea is to put two active humbuckers. All the diagrams (that you will see below) talk about a SPDT Switch, but the (new) one I got, has seven connectors in it. Images are going to better explain my dilemma.

This is the pickups diagram from the manufacturer (Seymour Duncan):

I have encircled in red the SPDT switch. Problem is, I don't have that.

Another diagram (straight from their website):

I'd argue they are very similar, but not 100% the same, however, this one too has a SPDT switch. I'm not sure what the difference means… in the 1st diagram each pickup has a volume and they connect to the tone via another pin and then straight to the switch; the 2nd diagram, however, seem to connect the pickup to the volume and the same pin to the tone. The connection to the switch is made from the other volume pin; i'm not sure what difference does this make (none?)

Now the switch I have, looks like this:

You can see the three positions in the left column and which connectors make contact in each one. E.g. when the switch is like in the picture, connectors 1, 4 and 5 are making contact.

Enough with the images… what I want to understand is how do guitar pickups work (not the theory behind the strings+magnetic field, that part I got), but more the electrical part of how the current gets from the pickups through the volume and tone pots, switch and jack (out).

What would be the best way to understand this?

Bonus: These pickups came with what I think (given my limited knowledge) are capacitors:

Where am I supposed to solder these? I think they are the 1µF things draw in the first diagram (or the green in the 2nd?). I'm confused. I thought those were supposed to let certain frequencies pass, and given the nature of how they are usually soldered, those frequencies are discarded (thus changing the tone).

Irrelevant to this lengthy post, is the fact that the guitar got badly damaged and had a sentimental value, so I'm repairing it, the electronics (my super-weakest part) are the last step in this adventure. And here I am. Stuck. :/

Thanks again for any help, direction, manual, site, book you can point me to; apologies if this is off topic, couldn't find a better place full of "people that know what they are doing".

UPDATE: I finally managed to finish the guitar. It all worked out really well, thanks for the help!

Pics:

 Scalloped Frets 13-24, added Seymour Duncan Dave Mustaine, Routed Battery compartment, made room for 4 knobs (previously there was only one) and other minor wood polishing (the guitar is cheap, made in indonesia, but plays really well).


texts: 8 bit-increment register with load and clear

texts:
I am quite new to design circuits topic and i have one question regarding to my assignment question.

I've a simple assignment to create circuit below :

I've worked on logisim to create this circuit with logism's counter such as like this :

And this is working as requested... The main question is that, what if i  try to make this counter via my implementation using flip-flops, how may i put clear,load,increment inputs to circuit and how should be design ?

I am just trying to learn design things better and any help would be appreciated for me.

Many thanks in advance!


texts:
I am working on a STM32f4 board and I have a problem with passing pointer as input in a function.
I have my main :

    float32_t var;
    function(&var);

And my function :

    void function(float32_t* x){
        *x = 1.;
    }

But, oddly, when I debug this code, the x address doesn't fit the var address (x address is 0x00000000 pointer in function) and the value of var is not 1 after function calling.
Why do I have this problem ? Moreover, this kind of function worked efficiently...

In fact, I found a new bug, once I launched the debugger a error occurs

  No source available for ""

I never had this message...

I use the GCC GNU ARM compiler with these options :

     -mcpu=cortex-m4; -mthumb; -Wall; -ffunction-sections; -g; -O0; -fno-builtin; -DSTM32F407VG; -DSTM32F4XX; -I.;


texts: Looking for the solution for very close board interconnect using pin headers

texts:
Here's how it looks like

The small board with potentiometer is mounted above another board.

I used Connfly 1.27 pitch headers with 1.7 mm body height, cutting its body to  approximately 1 mm.

But unfortunately I made a mistake in this design: 1 mm is too much, and boards must be closer than that. Both boards are having vias and pads, and while I cut all the through-hole pins (of potentiometer) so nothing protrudes, it is still bad idea to couple boards together for risk of shortage and capacitance, thus I need about 0.5 mm clearance. The headers are required for electrical connection, so they serve not only as mounting, but also for conducting.
Unfortunately I can not find any headers less than 1 mm height (and these are only on order). I am not sure I will be able to cut 1.7 mm thick header to 0.5 mm - it will simply broke during processing.
What would be a hack for this situation? What can I put between boards, preferably around the header pins, non-conducting and with least capacitance, to serve as a base for boards?
How would you approach this problem with minimal effort and in minimal time, given all the parts are already on the table?
Update: thank you very much for your answers. The plastic spacer solution would be great, except... my thought is that board will be subject to the physical force stress in its plane (when pressing and rotating the pot), and thus this stress will fully apply to the pins and then copper. Not sure how damaging it will be, but putting and leaving the spacer between boards where pins are located will make some relieve for these boadr-copper tensions. Would you agree to this point of view?
The material on hand from the defective power supply I was mentioning is ITWFormex, 0.45 mm thickness. It does not list the exact type of plastic, but looking to all the datasheets I see dielectric constant of no more than 2.22, therefore small spacer of 3 sq. mm with 0.45 mm thickness on the pins gives about 0.14 pF capacitance, which is tolerable within the design.


texts: Replacing 12 x (internal) CR2032 batteries with one (or more) external batteries

texts:
As Christmas was on a budget this year, one of the presents I came up with consisted of a fishbowl with battery operated (flat CR2032 3V) tea-light candles in the bottom, these were covered in coloured glass beads and then I put air plants in the bowl mounted on driftwood. The effect is really nice (i.e. the flickering light under the beads).

However, it is not practical to keep lifting out the plants/driftwood, emptying all the beads, and swapping the batteries in every candle every few days or so.

Therefore, I thought about sticking the candles to a cardboard base, soldering thin wires to all the negatives and to all the positives of the candles (i.e. leaving the small battery cover off each one), running the cables to the back of the bowl and attaching some form of 'battery' holder that will site above the beads so it will be easy to plug in new batteries when needed.

My initial thought (as there are 12 candles and they all require 3V CR2032 batteries) is to connect them in 3 banks of three batteries and use a square 9V battery for each.

My question is (as I have no experience of this at all) will this work or am I simplifying this too much (i.e. will the 9V battery give the same 'power' output and drive the candles or will it damage them, does the length of wire have an effect at such a short distance, do I need to measure the resistance of each candle and do some calculation based on that?).

Apologies for the long-winded question but I just wanted to give someone as much info as possible.


texts: Voltage supply plus ideal current source connected to capacitor in series

texts: This might be a wierd question but I was asked this in an interview. I know the basic behaviour of an RC network when it is connected to a battery (practical situation) and also the ideal situation when there is an ideal constant current source in series charging a capacitor (when the circuit is like a loop). However, what will happen if there is both an ideal current source along with a voltage supply in series with the capacitor. Edit: Added a picture, need to sketch the capacitor voltage at node A.


texts: Differential impedance calculation: reference plane doubt

texts:
I'm calculating the width and spacing for my differential signals to meet impedance requirements.

I have downloaded Saturn Impedance Calculator for making calculations.

My pcb stackup has embedded layers that I want to use for differential signals, looks like the next table:

...
-------------
GND Layer 35um
-------------
Core 180um
-------------
Layer 35um
-------------
Prepeg 176um
-------------
Layer 35um
-------------
Core 180um
-------------
PWR layer 35um
-------------
...

So I have two layers there to place differential signals. Now I'm doubting how should I calculate the impedances. I'm unsure if the reference plane would be the GND and the PWR layers.

As an example, If I want to meet the 80Ω diff/ 40Ω single impedances, taking the first inner signal layer,and using the Saturn Edge Coupled asymmetric calculator, the input would be:

H2= 180um
H1= 176um
w = 0.225m
s = 2mm

But I'm doubting if the Height 1 entered is right, or if I should put the distance to the next reference plane, that is the PWR layer... That distance would be much bigger: 176um + 35um, and would change the impedance.

Anyone knows how should I proceed?

Thanks in advance!!


texts:
I'm using TI Tiva C TM4C123GH6PM on a Launchpad  combined with an AD 9850 DDS to create frequency modulator.

Currently I have an extremely simple program which basically sets up microcontroller's peripherals and the AD9850 and then goes into a loop in which it samples audio signal coming to the microcontroller's ADC and based on the results adjusts the output frequency of the DDS.

My problem is that the loop's execution time is not constant.

The loop is divided into three basic parts: In the first part, I get a sample from the ADC, in the second part, the required settings for the AD9850 are calculated and in the third part those settings are sent to the AD9850.

After doing some cycle counting, it turns out that the second and third part always last for 2670 clock cycles. This leaves me with the only suspect being the first part.

After measuring the execution time of the first part just by itself, I've noticed that it varies from as low as 100 cycles to as much as 8000 cycles.

Here's a nice graph I got from the debugger showing how the number of cycles changes with time:

I did look into the datasheet of the part and into the Tivaware Peripheral Driver Library User's guide and I couldn't find a reason why the sampling would have such drastic jitter. The ADC sampling plus conversion time is listed as 1 microsecond, which is around 80 processor cycles, since I'm running at 80 MHz clock frequency. This makes the loop duration in the area of around 100 to 200 cycles look OK, but I have absolutely no idea what's happening in the case when the time is in the thousands of cycles.

I have also read the errata for the ADC and as far as I can see, none of the numerous problems apply to my case. Also the part I have is an actual TM4 part, not an experimental XM4 part.

Here's the problematic part of the code:

c_start = HWREG(DWT_BASE + DWT_O_CYCCNT); // starts cycle counting
ROM_ADCIntClear(ADC0_BASE, 3);//clears interrupt flag
ADCProcessorTrigger(ADC0_BASE, 1);//Triggering sequence 1
while(!ROM_ADCIntStatus(ADC0_BASE, 3, false))//Waits for ADC to finish converting
{//Busy wait to be replaced with an ISR at some point
}
ROM_ADCSequenceDataGet(ADC0_BASE, 3, adcData);//adcData pointer to memory location
//used to store results
c_stop = HWREG(DWT_BASE + DWT_O_CYCCNT); // Ends cycle count
c_dur=c_stop-c_start;//Provides number of cycles, refresh breakpoint goes here

Here's the ADC setup code:

ROM_SysCtlPeripheralEnable(SYSCTL_PERIPH_ADC0);//Pin is PD1=>channel AIN6
ROM_ADCHardwareOversampleConfigure(ADC0_BASE, 64);
//Averages 64 samples and stores them in one FIFO slot,
//has apparently no effect on the conversion time, same results when disabled

HWREG(ADC0_BASE+ 0x038) = 0x40;//This enables hardware dithering

ADCSequenceConfigure(ADC0_BASE,3,ADC_TRIGGER_PROCESSOR,0);
//Uses ADC0, sequence 3=>FIFO with length of one, highest prioroty
ADCSequenceStepConfigure(ADC0_BASE,3,0,ADC_CTL_CH6|ADC_CTL_IE|ADC_CTL_END);
//First and last step, selects ADC0, sequence 3, step zero, channel 6,
// enables interrupt and ends sequence
ADCSequenceEnable(ADC0_BASE,3);
//Enables sequence

UPDATE:
I went ahead and did the test with pin wiggling and I got relatively similar results.
On this image, a pin goes high and then immediately low as soon as ADC is done. This is taken with dithering and hardware oversampling disabled, with sample rate of 1 MSa/s and FIFO buffer depth of 1.


texts:
I am tired of BMS that doesn't work the way I want, so I have decided to made my own BMS. Searching on internet I have found the schematic for a 4S BMS and I want to understand how it works before try to create my own 2S, 3S... versions.

As I understand from the schematic:

Top left part is composed of DW01A ICs that protects the battery from OC and OD.
Top right part is composed by HY2213 ICs that balance the charge on the cells.
Botton left part is composed by an array of mosfets and an MMBT3904 transistor that is deactivated when the OD protection is activated.
Bottom right part is composed by another array of mosfets and another MMBT3904 that is deactivated when the OC protection is activated.

My questions are:

Why there is a mosfet in the arrays that is a different configuration than the rest? The first mosfet in P- for example, must resists all the current that pass through the BMS while the rest are in parallel. If OD or OC protection is activated, all mosfet turns off at same time. Maybe to avoid that the MMBT3904 transistor will stay connected to negative when protection is activated?
When OC protection is activated on a cell I suppose that MMBT3904 stay activated to allow the BMS to balance the charge and the HY2213 IC must protect this cell draining some current through the 2x150R resistors. It also happens when the OD protection is activated on a cell, because then this cell will stay discharging until the others also activate the OD protection and can lead to damages.


texts: Under what circumstances would the large internal input resistance of an actual op amp affect circuit operation?

texts: I was able to find a lot about why the input resistance is high and basically infinite. I understand that the input resistance is high so that it doesn't become a load on the signal. I also know that it  makes sense like a voltage divider, the high impedance means that all of the voltage drops on the op amp. But I can't find any research on a case where the high resistance might actually affect the circuit itself (despite how high it is).


texts: i have small rectangular box with blue led strip 450 nm placed on top of the box. what device should i use in order to measure its power density or the irradiance of my blue LED?


texts:
I have been using LT1028 in a lot of my projects to amplify bipolar signals before digitization with a (bipolar) analog-to-digital converter.  Now I need to use a 5 V unipolar ADC and am trying to figure out level shifting.

The following amplification scheme works according to simulations with LT spice
(red = op amp output, blue = sine voltage input):

but unfortunately not in real life, at least in my attempts.  Here is my board layout and some DC voltages that I measured with an oscilloscope.

My question: is the circuit appropriate for the LT1028?  If yes, what else could be going wrong?  If not, then what is a better circuit to use?

DC potential differences:

V+ to AGND = 4.15 V (from Li cell)
output to AGND = 3.29 V.  In theory, should be ~ 2.0 V
VC2 to AGND = 0.128 V

Solution: see accepted answer.  Below is the oscilloscope trace showing amplification of a 50 mV, 10 kHz sine wave with AD8061 op amp.


texts: Low pass Sallen-Key with variable cut-off frequency

texts:
I have a project that I would like to get some help with and would like some things confirmed. I want to construct a 2nd order Low pass Sallen-Key filter with variable cut-off frequency using one or two  potentiometers (variable resistor). The topology can be found here: Sallen-Key topology. Low pass filter - Application one

The filter should be able to take away all frequencies above 5kHz and all frequencies above 20kHz. I.e. it should be able to take away all frequencies above 5kHz when the potentiometer is set for a specific value (ohm) And take away all frequencies above 20kHz when the potentiometer is set for another specific value.

First of all, anyone have any tips or advice in how to begin the design? What components are the most critical and how do I determine them? I´m not really asking for any specific answers, more of guidelines in how to proceed. I have no restrictions in any component values (except the natural of course).

Moreover, I need the phase shift to begin as near the cut-off frequency as possible due to the fact that a phase shift more or less equals a time shift and I don´t want any of the passing frequencies (as few as possible at least) to be affected of this time shift. This mean a want a high Q-value, correct?

Also, one question about the cut-off frequency. The wiki-page states that the "natural frequency" is:  $$ f_0 = \frac{1}{2*pi\sqrt{R_1R_2C_1C_2}} $$

So if I have understood this correctly, to get the cut-off frequency I just go down three dB from this (natural frequency)?


texts: What is causing the erratic sine wave in my Hartley oscillator?

texts:
I have made a Hartley oscillator in multisim in order to convert a DC input into an AC output but my output sine wave is not smooth. I don't know what is causing it.
Hartley oscillator configuration and component values:

Hartley oscillator AC output:


texts: Incorporating Additional Devices in Custom PCB

texts:
I've been tasked with designing a custom PCB based on a prototype I made this past year. This prototype uses ST's NUCLEO-F030R8T6 development board along with some stepper motor drivers (AMIS-30543) and a BLE module (HM-10). As I understand it, I'll have to use the NUCLEO's electrical schematic to incorporate the development board's MCU (STM32F030R8T6) in this custom PCB. I came across this question and it has provided some great information but I still have some questions of my own.
My question is what do I do about the stepper motor drivers and BLE module? Should I be doing the same for them? The BLE module has its own AT firmware, so if I am to 'break it down' for the PCB then how would I flash it with that firmware? I'm not sure if the stepper motor drivers have their own firmware (sorry, I'm extremely new to embedded and learning as I go), so if they do, same question as the BLE module.
I could design the PCB to simply have pinouts/sections to solder the BLE module and drivers to, but I want to do a good job at this.
Thank you all for your time!


texts: Super capacitors in series vs voltage up converter

texts:
If I connect super capacitors in series, I'm able to raise the voltage by the sum of the capacitors' voltages, but I lose 1/2 of each of the Farad capacity for each of them in series. Correct?
If I connect these super capacitors in parallel, I have the sum of the Farad capacity without loss of charge. Correct?
So if I instead use an up-converter to increase the voltage instead of connecting the super capacitors in series, I would have a huge amount more storage available. Is my logic correct here?
Even if the up-converter is only 92% efficient, It beats the 50% loss per capacitor in series. Right?


texts: Why Vds increase slowly even if it decrease fast?

texts:
The schematic is

The wave form is as follows, yellow line is channel 1 which is gate voltage and blue line is channel 2 which is drain voltage.

The 148kHz PWM signal is totem pole output of UC3845, MOSFET is n-type (IRFZ44N) and 12.4V power.

The drain voltage drops fast when gate voltage is on, but it increase very slowly (about 2.5us) when gate voltage is off. If I replace the 1K resistor with lower value, the Vd increase faster. But this means more power consumption.

Why Vd increase slowly?
For the speed up of Vd increase, is there any other way than decreasing Vd resistor(1K)?


texts:
I'm trying to make a kit for my students for online schooling next semester. On one of the modules, I want to teach them how to control a DC motor using a microcontroller and a 6V battery pack.
Normally, people use motor drivers to handle the high draw of current from the motor and to specify a signal to direct the motion of the motor (Clockwise vs Counter Clockwise vs no motion) from the microcontroller.
Since there are a lot of wires involved in powering the motor driver with the ESP32, I was looking for a simpler solution to power the DC motor.
My Goal is to simplify the motor to be similar to a standard MG90S servo motor where the 4 inputs to the motor are power (from the battery), ground, and two signal pins. Some solutions that I have thought of to achieve this with the DC motor have been:

Printing a PCB of the motor driver and soldering it onto the DC motor for my students, This would allow them to only have to connect 4 wires to the output of the PCB (would look similar to the image attached below).
Using a brushless motor which has a motor driver built into it. The problem of this is that it would require manual intervention (clicking a reset button) to get it working again after an overcurrent has been detected.

I would really appreciate it if anyone has any other suggestions on how to simplify this process or if anyone knows of a motor that already exists that is capable of doing this.
Thanks,
Jason Easton


texts: Can I rely on a the simulation of an op-amp based differential amplifier without looking at my op-amps common mode signal

texts:
Can I rely on what a simulator gives me for the output of an op-amp based differential amplifier without verifying that the common mode input to my op-amp is between the voltages of my op amp's power rails (or otherwise appropriate for my op amp?)
Suppose I have an op amp based differential amplifier use to measure the voltage across a load RL such as this:

simulate this circuit – Schematic created using CircuitLab
The transformer is 1:1, and Vac is 168V peak (120V rms). I calculate the current through RL to be 120V/10\$\Omega\$ = 1.2A(rms).
When I run the simulator, it shows a 3.36 peak output (approximately). This makes sense, because my amplifier gain is 100k/2k = 1/50. If I multiply the input by the gain, I get 168V / 50 = 3.36V.

Even though the the voltage across the secondary is 168V peak, and my op amp supply is only +/- 5V, my op amp is fine because the resistor network (R1, R2, R3, and R4) reduces the voltage at the op amp inputs.
Now, however, I add a common mode signal thus.

simulate this circuit
If I run the simulator, I again get a 3.36V peak output sine wave.

Everything looks good. However, if I take a look at the common mode voltage at the op amps input (either should work if I am running negative feedback, and the op amp is running in linear mode) like this:

simulate this circuit
when I run the simulation, I see that the common mode voltage at the op amp's input exceeds its specification. For an LM358 the common mode voltage should be between V- and V+ - 1.5V.

From this I conclude that I cannot rely on the fact that the simulation appears to give the output I hoped for. The simulator does not seem to check for this. It seems I should verify that the common mode voltage on the input pins of the op amp are within the specified limits as well.
Is that a valid conclusion?


texts: Capacitor charging: do electrons migrate from the source to the dielectric?

texts:
Encyclopedia of Electronic Components - Vol1, pg:98 by Charles Platt

  Electrons from the power source will migrate on to the plate attached
  to the negative side of the  source, and will tend to repel electrons
  from the  other plate. This may be thought of as creating  electron
  holes in the other plate or as attracting  positive charges,

Isn't this dead wrong! Electrons don't migrate from the source (battery, power supply). Electrons aren't little rolling balls that leave the battery on a journey to the dielectric where they polarize atoms!

Instead, the battery/PSU provides a Electric field (that travels at c=speed of light approximately) that polarizes the dielectric across a region of space within it; electrons are displaced from their favorite haunts around their home atoms and you won't find them there anymore (or you might - the probability distribution is altered).

This does not create a hole, or ion! A hole is the promotion of a valence band electron into the conduction band where it's free to move about in the material lattice.

What is important is that a capacitor stores an electric field by aligning it's (atoms, molecules - charge carriers) in one way.

Maybe electrons in the wire will move into the battery and cause a chemical reaction that is used to maintain the Electric field.

So that para is wrong -right?

One thing i don't understand though is why, when the cap is disconnected, it still retains the orientation (in the absence of the external E-field).


texts: Discrepancy between simulation and measurement for a voltage doubler/ rectifier design at 5.8 GHz

texts:
I am designing a pretty straight-forward voltage doubler at 5.8 GHz with MACOM's MA4E1317 diode, which I have used before and know from previous experience that matches pretty well with the spice model they provided.

A block diagram of the circuit is shown below:

The RF signal is a pure tone generated by a siggen.

The matching circuit is determined empirically with a PNA at measurement to make sure that the return loss is greater than 10 dB. In simulation ideal elements were used to populate the PI network so that good return loss was obtained.

The two capacitors were basically chosen to be large enough.

Rload equals 40k Ohm and was chosen to obtain peak efficiency when the input power level is around -3 dbm.

The circuit was built on a two-layer FR-4 substrate with a thickness of ~57 mil.

I used circuit models from vendors for all the components, modelled the pads (0201 and diode) with microstrip lines.

In simulation, I was able to obtain around 70% of peak efficiency at around -3 dbm, in which case I expect to see at least around 3V across the load. However, when I measured the circuit, I was only getting about 1.3 V across the load at -3 dbm, despite the circuit was pretty well matched (S11 < -10 dB).

The simulation was done in ADS with harmonic analysis with an order of 8.

Since this is such a straight forward topology, I am absolutely out of ideas of what could have caused the problem - I built a prototype at a much lower frequency (480 MHz), but I am seeing a similar behavior, thus I am ruling out that this is caused by the parasitics by the pads or unexpected losses from the dielectric.

Could the fact that the caps are beyond their self resonant frequency be the cause of problems, even though it should have been captured in the vendor models?

Here are the measurement data:

Would appreciate any help!


texts: Does TI's LiFePO4 CV-free fast charge method reduce cell lifetime?

texts:
TI claim that you can charge LiFePO4 cells by CC (constant current) charging as usual but to a higher than usual voltage (eg 3.7V rather than the usual 3.6V for LiFePO4) and then step transition to a lower float voltage with NO intermediate CV mode.

Their bq25070 IC implements this method as described in the bq25070 datasheet.

This goes against ALL other advice, IC specs and charger circuits that I have seen.

Doing this with Vcv  <= 3.6V is fine enough - with or without a CV stage. It's the extra voltage and no CV mode that is radical. The implication or statement from all other sources is that exceeding the normal Vmax of 3.6V for LiFePO4 by even a small amount is liable to be damaging or fatal.

Have TI gone utterly & irresponsibly mad or is this a fantastic new way to charge Lithium Ferro Phosphate cells?


texts: FPGA floating pins, when place pull-up/down resistor on Input or Output

texts:
I've looked my FPGA datasheet and found that there is no pull-up/down resistors on it's pins(just a pull-up but that need to be enabled). So, when I power up my circuit I've for a "big" amount of time all IO pins of my FPGA floating. Since I've found that floating IO may damage some device or create problems, I want to put some pullup/down resistors.

Can someone advance me if it's better a pullup or pulldown resistor with which value? I've found someone advice pullup but they in some case can slow signal, other advice pull down, same for resistor values.

My main questions is:
Floating pins can create problems only on input pin of a device or also in output pins?(where input or output are always defined in the device)


texts: IEC socket rated for 250V at 10A - can it be used for 13A @230v?

texts:
I'm building a relay board which I'll eventually control using an Arduino. I'm using an IEC socket so that I can use a simple kettle lead for my AC input. The appliance the relay is controlling might be drawing 13Amp. Can I still use this IEC socket?

According to my calculations I can't because at 13amp it's 2.9Kw not 2.5Kw. Is that correct?


texts: Why does a longer fiber optic cable result in lower attenuation?

texts:
I just carried out an experiment in my college to study the attenuation of fibre optic cable versus length and type of cable.

This experiment was carried out with an LED light source and a power meter connected at the other end.

The wavelength is set to 1300nm and the results obtained as follows:

Single Mode (1meter) = -36.14 dBm
Single Mode (10meter) = -36.12dBm

Multimode (1meter) = -35.94dBm
Multimode (10meter) = -18.48dBm

Anyone could explain to me why as the cable gets longer, the received power gets higher and also why multimode fiber optic cable has higher received power than single mode cable?


texts: IGBT-based capacitor charge transfer and thyristor-based capacitor discharge

texts:
simulate this circuit – Schematic created using CircuitLab

I am designing a circuit to provide a couple of strong and fast current pulses (~1000 A, more current is better, ~100 us, half-sine) to a coil in rapid succession. The purpose is to provide a magnetic 'kick' to a cloud of cold atoms. My idea is to use a large capacitor bank to quickly charge/recharge a smaller capacitor bank which stores the energy for the pulse. This idea is outlined in words below and drawn in a block diagram in the attached hand drawn schematic. The sequence for a single pulse would be:

1) charge a large capacitor bank to high voltage (1000V, 940 uF) using an IGBT switch, within a couple ms

2) transfer some of that charge to a smaller capacitor bank (1000 - 2000V depending on capacitor coupling, 80 uF) using an IGBT switch, within 100 us

3) discharge the small capacitor through an inductor (~3 uH, ~0.2 Ohm) using a thyristor ,within ~100 us

For multiple pulses, steps 2) and 3) could be repeated.

I worked out some details of gate driving the thyristor and IGBTs and had a PCB printed with all the switches and screw terminals for connecting up the power supply, capacitor banks, and coil.

Initial tests all worked well up to 1000 V on the large capacitor bank, providing in the neighborhood of 1500 A to the coil in a pulse of about 80 us. In reality, I have to drive four of these circuits, so I next built four of the switch PCBs, four large capacitor banks, four small capacitor banks, and branched the HV supply to each of the switch PCBs. The firing scheme would be to first charge each large capacitor bank in succession, then I could simultaneously transfer the charge to the small capacitor banks and simultaneously discharge them through four independent coils. This test failed, so I went back to single board tests and now, for unknown reasons, even the single board tests are failing above 200 V.

More on the what I mean by "fail." During the capacitor-to-capacitor charge transfer, there is a transient on the thyristor gate line. The transient lasts as long as it takes to transfer the charge. The transient is not noisy or high frequency since the IGBT is toggled at effectively zero current so I don't think adding a snubber could help much (I am also unsure of the design for a high side IGBT snubber). The transient scales with the applied HV, and at about 200 V, it becomes large enough to trigger the thyristor. When the thyristor triggers at the same time as the charge transfer, the large capacitor bank is allowed to discharge completely through coil which burns out my charge transfer IGBT. The only way I have found to affect this transient is by changing the capacitor to capacitor coupling element, labeled as ??? in the hand drawn schematic. The transient can look like a single half sine pulse if I couple the two capacitors with an inductor (18 uH) and looks like a decaying exponential when I couple the capacitors with a resistor (4 ohm).

My question: Given that the circuit worked great before but is now failing due to transients, I suspect either a grounding problem, a problem in the way I'm driving the gates of the IGBTs/thyristor, or a problem with my capacitor-to-capacitor coupling element. The details of my gate driving are also specified in the attached hand drawn schematic. Note that the 12 V supply is floating and powers the DC-DC converter with +12 V and 12Vrtn. I use the same 12 V supply for both IGBT gate drive circuits. The -5 V and +15 V supplies powering the thyristor's optocoupler are referenced to ground. Any advice would be greatly appreciated, especially if there is something obviously wrong with my method of gate driving.

I've tried adjusting grounding and adding a capacitor between the thyristor gate and cathode (0.1 uF and 2 uF) per SCR circuit falsely triggered during capacitor charging

Let me know if you would like any other information (data sheets, scope traces, pictures of my capacitor banks or set up, etc).


texts:
I'm designing a voltage mode PSU for learning purposes. I've noticed that powdered iron toroids are almost exclusively used in the construction of PFC inductors as well as in low voltage boost converter inductors, with the exception of an electronic HID ballast that I took apart which was a gapped EE65.

I'm currently reading "Transformer and Inductor Design Handbook", where it seems that I can use either EE or toroid cores in the construction of an inductor. I already have a bunch of EE cores. Is there a reason why I shouldn't use one of those as opposed to ordering toroids?


texts: How can I increase the number of USB outputs of a powerbank which only has one output?

texts: I'm talking about outputs which we use to charge our devices with. Would using USB male to two USB female cord be a bad idea?


texts: What material can I use to block a capacitive touch from registering?

texts:
I am a self proclaimed tinkering problem solver, but this one has me absolutely stumped!
I have a capacitive touch switch panel with six touch areas that close or open a relay to supply power to various accessories on my motorcycle (fog lights, driving lights accent LEDs...).  The problem is the touch is registering from both the front of the panel and the back of the panel where it is mounted.
How do I block the back from being sensed?  The back is picking up the disrupted grid from the mounting bracket (and other items that get too close) and causing the relay to close and open without me touching it.
I have tried dense rubber sheet, sheet metal of various types, silicone rubber...
Any help would be greatly appreciated!


texts:
I'm designing a circuit using Simulink to VHDL generator to be burned into a FPGA.
Simulink model works fine on Simulink, however, when I try to compile the VHDL code using Quartus II I get the following error:

  Error (10481): VHDL Use Clause error at dsc_escalado.vhd: design
  library  "mylib" does not contain primary unit "sen"

My top level code is dsc_escalado.vhd which uses library "mylib" generated by Simulink, which contains a file named sen.vhd where CORDIC algorithm is used to generate sine waves.

All files where generated by Simulink, I haven't modify any line of code. It works on Simulink, but wont compile on Quartus.

Update
I have included all files in the project, However I get the same error. Here is the log generated by Quartus:

  Warning (20028): Parallel compilation is not licensed and has been    disabled
  Info (12021): Found 0 design units, including 0 entities, in source file sen.vhd
  Info (12021): Found 0 design units, including 0 entities, in source file sen_120_not_ascii.vhd
  Info (12021): Found 0 design units, including 0 entities, in source file sen_240_not_ascii.vhd
  Info (12021): Found 2 design units, including 1 entities, in source file dsc_escalado.vhd
  Info (12022): Found design unit 1: DSC_escalado-rtl
  Info (12023): Found entity 1: DSC_escalado
  Error (10481): VHDL Use Clause error at DSC_escalado.vhd(90): design library "mylib" does not contain primary unit "sen"
  Error: Quartus II 64-Bit Analysis & Synthesis was unsuccessful. 1 error, 1 warning

The VHDL code for sen.vhd retrieved from the comment link

Editor's Note: The source file comment line in question shows

  -- Source Path: DSC_escalado/sen

while in the original the last three characters consisting of a space (x"20), a SUB (x"1A") and a LF (x"0A")in the original file. There isn't a way of demonstrating the illegal character without resorting to another tool due to the originally being iso8859-1 character mapping and the StackExchange network using UTF-8.)

-- -------------------------------------------------------------
--
-- File Name: hdl_prj\hdlsrc\DPWMfinal\sen.vhd
-- Created: 2018-06-27 14:40:51
--
-- Generated by MATLAB 9.0 and HDL Coder 3.8
--
-- -------------------------------------------------------------

-- -------------------------------------------------------------
--
-- Module: sen
-- Source Path: DSC_escalado/sen
-- Hierarchy Level: 1
--
-- -------------------------------------------------------------
LIBRARY IEEE;
USE IEEE.std_logic_1164.ALL;
USE IEEE.numeric_std.ALL;

LIBRARY WORK;
USE WORK.ALL;

ENTITY sen IS
  PORT( clk                               :   IN    std_logic;
        reset                             :   IN    std_logic;
        enb                               :   IN    std_logic;
        angle                             :   IN    std_logic_vector(31 DOWNTO 0);  -- sfix32_En28
        sin                               :   OUT   std_logic_vector(31 DOWNTO 0)  -- sfix32_En30
        );
END sen;

This is how Quartus II shows the illegal character.


texts: Does this sort of connection on a Yagi Antenna make sense?

texts:
Here is an image of a WiFi yagi antenna I bought recently (and opened up for I could see no spectrum out of my SDR)

I see that the coax has been connected to two plates, which I think act as dipoles. But they are insulated from the rest of the frame. Is this normal (shouldn't the dipole be in contact with the rest of the frame), or is it just dismal construction?


texts: is soldering necessary for a robotics and electronics hobbyist?

texts: I know it is VERY common but I am worried about the exposure. I do understand it is minimal if an extraction           device is used to get rid of the gasses and if a lead-free solder is used but I still have worries. I was wondering if it is essential since  I am very interested in robotics and electronics.


texts:
I've heard of On Board Units (OBU) can communicate via RS485. My question is, how?

For example, I would like to ask the state of some runtime variables from the OBU (what doors are open?, etc.) Or another example, I would like to send some data to the OBU (outside temperature).

What protocol must I implement to do these?
Are the any sample implementations available somewhere?


texts: monostable Eccles - Jordan multivibrator, theory

texts:
I’ve a few problems and questions to the principle of monostable multivibrator’s work. Basic schematic is as below:

What is the reason for D1, C1, R3 elements at input? Why I can’t just tie a transistor base to the trigger input, without these elements?
I've read that Vcc voltage can’t be as high as you would and it has some max value, but I can’t determine what it is and where it comes from.


texts: Securing a pcb to be used in a keyboard to its case

texts: I'm looking for a way to secure a pcb I will be making for a cherry mx (homemade) keyboard to a case which I'll also be making. Obviously, I don't want the pcb to move. I could use standoffs/screws, but wouldn't the added height between the pcb and case cause the pcb to flex when keys are pressed? Glue/tape seems mega sketch and may mess with conductivity. How is this done on normal (production) keyboards? Advice is much appreciated.


texts:
My fridge is sending bad clacks to my loudspeakers when it turns on/off, I fear for the tweeters. I'd add a snubber/suppressor to the compressor but my notions about RC filters from school are 15 years old and I have no idea how to dimension it.

It's an old european fridge, so mains are 220V 50Hz, and the compressor mentions two other values In=0.8 and Icc=6.3, which I suppose are nominal and startup current. Do I need to compute the motor inductance? What condensator/resistor values to pick? Is an RC snubber even the correct fix?

How to estimate the RC values for snubbing an A/C motor?

Trying another approach. I've found a some usual R/C values for suppressors. For instance this one is 47ohm / 0.1µF, giving 33kHz of cutoff frequency... but the datasheet says up to 62Hz? Why is there 3 orders of magnitude difference ?

EDIT: in the end I added a capacitor to the fridge and that resolved the problems. That was quite long ago so I don't remember the exact value, but if anyone wants it just bump me…


texts:
I'm trying to construct something like the band reject filter on the bode graph below.

I know that I could make this by using four different filters and adding them up (low pass filter + high frequency amplifier + high frequency amplifier + high frequency "reducer"). By adding them up I mean connecting them with buffers.

I read on many webpages that this could be made by just using a high pass filter and a low pass filter like this:

I don't understand how could I make this frequency shift on the high pass filter shown in red so it doesn't "subtract" frequencies below \$f_L\$. And how to translate this into an actual circuit.

Any help is appreciated!

EDIT:
Sorry I don't have much knowledge on this, but I'm guessing that it could be made with something like this:

\$G_v(s)=\left(1+\dfrac{s}{a}\right)^{-1}\left(1+\dfrac{s}{b}\right)\left(1+\dfrac{s}{c}\right)\left(1+\dfrac{s}{d}\right)^{-1}\$

Where the first and last terms are low pass filters with cutoff frequencies of a and d respectively.

How could I make the second and third terms in a way that all are connected in series with dependent volages?


texts: Is there an advantage to beta-vs-Ic flatness in BJTs?

texts:
Something I've wondered. Some BJTs have flatter beta vs Ic than others in the graph provided in the datasheets. I realize the scales can mislead a bit but there are still differences. Some Toshiba and Sanken products are shown with seemingly perfect flat profiles at lower Ic.
Is there an advantage to such flatness (as opposed to variation part-to-part or vs temp)?


texts: Working of -12V buck-boost supply using LM2576

texts:
I want to make a -12V supply and I came across a circuit using LM2576 that match my requirement but I am not confident enough about its working.
There is a note in the datasheet page no-16, Application and implementation section saying:
Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.

Form the functional block diagram, I understand the connection of the feedback pin, but in the buck-boost configuration in the upper image, the feedback pin is connected to the ground, and I want to know why?
Please help me understand the working of the buck-boost circuit shown in the above figure.

Datasheet: https://www.ti.com/lit/ds/symlink/lm2576.pdf?ts=1609223000480&ref_url=https%253A%252F%252Fwww.google.com%252F


texts: How to protect high-bandwidth low-voltage lines from transients?

texts:
I've been using bidirectional TVS diodes for protecting a 2 Mbit single-ended 5V serial bus.
Unfortunately, the TVS-es I've been using have too high capacitance, and distort the shape of the bus so serial decode doesn't work.
Looking at data sheets, pretty much all of the low-voltage TVS-es have about 3 nF of capacitance at 5V stand-off / 6.5V break-down, or thereabouts. A representative data sheet is here:
http://www.littelfuse.com/~/media/Files/Littelfuse/Technical%20Resources/Documents/Data%20Sheets/Littelfuse_TVS%20Diode_SA.pdf

3 nF is enough to distort the output waveform when the inputs connected to that capacitance are all high impedance, and the output is not super low impedance (an AVR microcontroller with a 70 Ohm current limiting resistor.) Quick calculator check says corner freqency of that RC circuit is about 750 kHz, so it sounds plausible that this is my problem.

So, what can I use to protect this bus?
Sub-questions:
- Is there some particular part/series of TVS that performs substantially better?
- Should I re-buffer the signal? (Unfortunately, I'm out of board space, and it'd be a pain to make more.)
- Would a small-signal Zener be "good enough" or not fast enough for transient protection?
- Or maybe Zeners have high capacitance, too?


texts: 120V AC-to-DC Power Supply High Voltage Regulator

texts:
By using an isolation transformer-variac-full wave bridge rectifier and a capacitor, I have built a AC to DC power supply. Now, I would like to regulate the output. My desire is to get a 150V DC constant output. For that I decided to use this LM317HV and want to apply the configuration given in the link. http://www.ti.com/lit/an/snva583/snva583.pdf

Can I directly connect this to the output of an Isolation Transformer-Variac-Bridge Rectifier-Capacitor group as shown in the image? Or, do I need something connected in between?

Also, should I use the negative output of the rectifier as a ground connections of the regulator? Or, by leaving the negative output unconnected, should I use the earth ground as shown?

Thanks in advance!


texts: OptoCoupler Relay and EMI - How to be sure it is not a "regular relay"

texts:
Motivation: A way to be sure a relays in hand are opto-coupler ones.

Reason: Due to AC power interference ( on the client side of relay - an AC motor ), I'm afraid wrong ones were sold.

Edit 1:

Attach 2 kinds of items both ( and there is some more )

Example #1

Example #2

Edit 2:

Adding pics: tries to overcome EMI on relays ( one try - is sheilding wire only, second try - shield relays box)

**edit 3: add schematic **


texts: Where does the spark come from? (an embedded system circuit)

texts:
We are developing an embedded system product. As an inexperienced engineer, I am really scratching my head to make our product reliable: temperature, ESD and etc..

The following diagram shows my circuit:

Yesterday I connected one pin of MCU with 3.3V(SELECTION port, which is a two pin 2.54mm header) using a jumper, when MCU is on, and sparks appears at the connection. After that, our MCU stopped working normally.

Where are the sparks from?

Could connecting 3.3V with pin pulling down to ground cause sparks?
I heard that sparks can only be generated at high voltage ESD, say over 8kV.
I tend to think the sparks are not caused by ESD, since the same operation has been done multiple times during the same hour before the sparks appear.

For the code part

Library: STM32F4xx_StdPeriph_Driver

GPIO_InitStruct.GPIO_Pin = GPIO_Pin_10 | GPIO_Pin_12; // we are going to use PB6 and PB7
GPIO_InitStruct.GPIO_Mode = GPIO_Mode_IN;           // set pins to alternate function
GPIO_InitStruct.GPIO_Speed = GPIO_Speed_50MHz;      // set GPIO speed
GPIO_InitStruct.GPIO_OType = GPIO_OType_OD;         // set output to open drain --> the line has to be only pulled low, not driven high
GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_NOPULL;           // enable pull up resistors
GPIO_Init(GPIOC, &GPIO_InitStruct);     //Init PC10, PC12

GPIO_InitStruct.GPIO_Pin = GPIO_Pin_2;
GPIO_Init(GPIOD, &GPIO_InitStruct);     //Init PD2


texts: How do you design a power supply for an LED strip if you do not have any specifications?

texts:
I have a monochrome LED strip of six meter length installed in some indoor furniture.
The manufacturer used a very under-dimensioned power supply that "died" after half an hour of use.
Unfortunately I have no documentation of the LED strip.
Below is a picture of the LED strip.
The manufacturer foresaw to connect the LED strip with the power supply from two ends of the LED strip forming a loop - see the second picture (possibly to have enough brightness over the whole length of the strip). I would like to keep this design.
I would like to buy a suitable power supply but am unsure about the power consumption of the LED strip. Additionally I would like to be able to dim the LED strip.
I have the following questions:

How can I design the power supply without knowing the LED strips consumption?

Additionally I want to dim the LED strip. Is this possible with every LED strip?

Background information:
I could imagine that the manufacturer thought to create a very intimate light atmosphere by using an under-dimensioned  power supply. After complaining to the seller, I was informed that the manufacturer stopped equipping this kind of furniture with LED strips.


texts: Is it possible to design a switch circuit with XNOR's truth table value?

texts:
We all know XNOR's truth table right? Is it possible to design a switch circuit (not a gate circuit) using XNOR's truth table value. I had tried for 40 mins and it seems impossible.

Switch Circuit Example:

image


texts: Considerations for solar powered thermoelectric cooler with fan

texts:
I am building a food cooler for camping this summer.  My plan is to build a thermoelectric cooler that is solar powered.  My cooler is looking much like this:

including a CPU fan on the hot side and heat sink on the cool side.

I bought a 5W, 12V solar panel to run it (and make it so I can also plug it into my car).  Both the fan and the TEC will be connected in parallel to the source.

Because the source is driving two things, are there any special considerations I need to think about such as a diode on the TEC so that when it loses power it doesn't dump heat back into the cooler by powering the fan?  Or do I want it do run the fan after it loses power to remove heat from the hot side to reduce the differential faster?


texts: Relation between reflection (coefficient) and bandwidth

texts: I am reading into single stage microwave amplifiers and how to design for a specific gain (source 1, source 2 warning PDFs!). In both sources the claim is made that the highest bandwidth is achieved with the smallest reflection magnitude. But why? What is the relation between the magnitude of the reflection coefficient and the bandwidth? I believe I have seen this claim before for matching networks in general, and not just limited to the context of microwave amplifier.


texts: How do GPS satellites refresh their clocks

texts:
How do GPS satellites keep their on board clocks accurate? I assume that they need to get update from a base station. But how do you make sure that after the update all the satellites are synchronized, i.e. there isn't any phase shift.

You have your base station on earth, and assume that all the satellites you want to update are in line of sight. You send an update command. But, each satellite is a different distance from the base station. There will also be a delay from receiving the command, to updating the internal clock. Some satellites may have newer hardware, which is faster.

If you update the satellites separately, you would need to ensure that your timings of the commands that you send are very accurate. This seems like a difficult thing to get right. Is there a better method that is used in practice?

I guess what I am interested in is say you have a clock at location A. How do you synchronize it with a clock at location B, which is far away from A? You have the message flight time delay, processing delay in B etc.


texts: Why a diode is in parallel with the current source in the equivalent circuit of a solar cell?

texts:
The model of a solar cell has a diode in parallel to the current source:
(source)

Why is the diode in parallel and not in series with the current source?


texts: How to measure power consumption of pulsed DC motor correctly?

texts:
I built a permanent magnet pulsed DC motor, and am trying to accurately measure power input, which proves to be harder than expected.
The motor is pulsed with a 25% duty cycle square wave and powered by a 24V battery.
Normally, Power = Volts * Amps, but that does not take the duty cycle into account.
On top of that, the rotating permanent magnets induce a counter EMF, and the difference between the applied battery voltage and the counter EMF is what determines how much current flows through the windings.
This means the current waveform is no longer a square wave, as I tried to illustrate below:

One research officer from an electric company mentioned the following:

However, it seems to me that the average current Iav already takes both the ON and OFF current into account, so why would you still need to multiply by the duty cycle?
How would you accurately measure the power input into a permanent magnet pulsed DC motor?
Thanks!!


texts: Function run in MCU generate noise to the analog circuit

texts:
As my circuit is a little complicated, I don`t know how to pose the PCB here. So I just want to know the probable causes of the problem and I will test them one by one later and report back.

My problem is that:

The MCU(STM32F4) would run a function with 300Hz frequency. When the function runs, I can observe a set of noise(2100Hz,2400Hz,2700Hz,3000Hz,3300Hz...)in the analog circuit. Amplitude of the noise is about several mVpp. The observation point is the output of a 45dB-gain, 3kHz-center-frequency bandpass filter. I need to get rid of those noise as my desired signal is also 3000Hz.

So does anyone meet the same or similar problem before?

More information:

I once modified the frequency of the function to 600Hz and the set of noise became 2400Hz,3000Hz,3600Hz... and the amplitude became a little larger.
the digital ground and the analog ground are in the same plane.

EDIT

These days I have done some experiments and found that the noise maybe comes from the ground plane.

I measured the voltage difference between the GND terminal of the power supply (connected to the main plug of the device) and the GND on my PCB. The 300Hz noise appeared. So I think the noise is from the noisy ground plane. But I am not sure my measurement is correct. Is it?

One more strange phenomenon: I measured all the MCU pin. Also found that noise. So is this phenomenon due to the noisy ground plane?


texts:
In Altium Designer 18.0.8 I am working on some power supply:

As you can see, there is a wire named GRETZ_OUT using Wire command and if I hover on it with mouse, I get net name GND and NOT GRETZ_OUT, which is wrong:

Why?


texts: What use would a D flip-flop being fed an analog signal have?

texts:
I'm contemplating a non-electronic system that is analogous to a D flip-flop being fed an analog signal and a fixed-frequency clock. The system has an analog input which changes over time. The output of the system is a single bit. The analog input is sampled at fixed intervals. The output goes high if the input exceeds one value, and goes low if the input deceeds a lower value.

I feel like this circuit has a name or common application, but I can't track down what it might be.


texts:
As far as I understood, the WS2812b or SK6812 LEDs use PWM output to drive the diodes. This could cause flickering on camera when the LEDs are dimmed.

Does anyone know the output driver PWM rate?
Is there any known issue with flickering on camera?


texts: Will a tvs diode help my relay with inductive loads?

texts:
I am not an EE, so please be gentle!  I will obviously get a certified EE to review my design before anyone else touches this so please assume that I know enough to at least be safe with 120VAC and am comfortable with frying my own electronics :).

What I'm doing

I'm using one of these ubiquitous Sainsmart 5V relay modules with an onboard SRD-05VDC-SL-C relay.

You can follow that SRD-05VDC link to a datasheet about the relay module itself.  While it's rated for 10A @ 125VAC for resistive loads, it's only rated for 3A @ 120VAC for inductive loads.

Since my application is for controlling a standard (US) AC outlet, I don't know what people might plug in (blenders, vacuums, leaf blowers, etc).

My question

My question is about whether it would provide any additional inductive protection if I placed a TVS diode across the relay terminals?  If so, what would be an appropriate diode to use for general household 120VAC applications?

If my question is dumb

If that's a bad idea in general, what would by an appropriate relay module to switch a general purpose 120VAC outlet using a 3-5V input signal?

Thanks!


texts: What are some ways to power dual supply ICs with a single Supply PSU?

texts:
What is the best way to power a dual supply Op-Amp (CMOS) with a 9v Battery or a 12-Volt wall-wart (Inside +).

I can do it with two .5 Watt 200k Ohm Resistors in a voltage divider configuration. However, I want to use three and get a "low" signal above Earth Potential.

I purchased some ICs on eBay for very cheap, ICL7660, that supposedly will do the DC to AC conversion for you.

Any suggestions on how to power dul supply ICs with a single supply PSU?


texts:
My question is with regard to how attenuators effect noise.  From what I understand
$$
\text{NF} = 10\log \left( \frac{S_{in}/N_{in}}{S_{out}/N_{out}} \right) = 10\log \left( L \frac{N_{out}}{N_{in}} \right) = L_{dB} + 10\log\left(\frac{N_{out}}{N_{in}}\right)
$$
Now since (for an attenuator)
$$
\text{NF} = L_{dB}
$$
that would imply that
$$
\frac{N_{out}}{N_{in}} = 1
$$

From what I can tell, this means that the noise on the input passes through the attenuation unaffected by the attenuator.  In other words, the attenuator minimises the signal but not the noise.  I read that this is only true at 290°K and that the attenuator can not reduce the noise below the noise floor.  I don't really understand this though.  If the temperature were 50°K, would the noise still pass though the attenuator unaffected?  It'd make sense to me that it would, unless there is something special about 290°K.  As a bit of an educated guess, I would've thought that if the room temperature was, say, 50°K and the noise at the input of the attenuator was also 50°K (so \$N_{in} = kB \cdot 50\$) then the attenuator would not reduce the noise; however, I'm not exactly sure why.

I would've actually thought that the attenuator might actually introduce noise to the output because it is made passively.  I can see that perhaps the resistors in the attenuator introduce noise, and the configuration of them reduce noise and the two may cancel and result in no net noise being added, though I'm not sure about this.

If someone could shed some light on this to help me understand this better, that would be great.

Thank you.

Edit: Specifically what I don't get

The scenario above is often a source of confusion for RF engineers, because it is commonly known that the noise figure of any passive component is equal to its loss.  Noise figure (NF) and noise factor (F), are commonly described in terms of the ratio of input SNR to output SNR at the specific temperature of 290 K.  As described in the equations below, noise figure is simply the logarithmic equivalent of the noise factor measurement.

Based on the equations above, it might SEEM that use of an attenuator on the output of a vector signal generator would attenuate the signal strength without attenuating the noise power.  However, it is important to recognize the equation for noise figure ONLY relevant when the noise level is equal to the thermal noise density at -174 dBm/Hz.  In general, terms such as noise figure and noise factor should only be applied to wireless receivers, since the noise power from an antenna at 290K will be approximately -174 dBm/Hz.

For example, suppose a receiver observes a signal with a SNR of 60 dB at a power level of -114 dBm.  In this scenario, applying a 20 dB attenuator would attenuate the signal power by 20 dB to -134 dBm.  However, the noise level would remain unchanged, since the noise power is already at the thermal noise level.  Thus, when Pnoise = -174 dBm/Hz, the noise figure of a passive attenuator is equivalent to its loss.

On the other hand, output noise density from an RF generator is caused by active components and will result at levels that are sometimes significantly above the theoretical noise floor.  In this scenario, noise power can be attenuated to the level of the thermal noise floor.  As a result, high sensitivity receivers can be tested with a stimulus which has a noise power that is well below that of the signal generator.

The above for paragraphs are taken straight from: http://www.ni.com/white-paper/6810/en

I don't understand why 290°K seems special and what the noise power is acting on.  I don't understand why in the third paragraph, it says that it won't attenuate the noise.


texts: How do I accurately measure the B value of an NTC thermistor?

texts: I'm trying to find a part number for an NTC thermistor being used to monitor the temperature of a rechargeable battery. The thermistor I have has no color markings or numbers to indicate any information. I have measured the resistance at multiple temperatures, but I am worried my calculations are not very accurate, as I just used an ice cube and the hot surface of a food warmer. I need to ensure that the resistance - temperature curve matches the one of the thermistor I have, so that the battery charges when it should. Is there any sort of tool made to reliably produce different temperatures for measurement, or a better way I could go about this?


texts: Confusion with unregulated PSUs: RMS current, transformer rating

texts:
I'm trying to understand a paragraph in Horowitz and Hill, "The Art of Electronics", under the sub-section "Transformers":

"Since a rectifier circuit draws current only over a small part of the cycle (during the time the capacitor is actually charging), the RMS current, and therefore the I^2R heating, is likely to exceed specifications for a load current approaching the rated RMS current of the transformer. The situation gets worse as you increase capacitor size to reduce pre-regulator ripple' this simply requires a transformer of larger rating."

What I do understand is that given a resistive load, for example, where ripple is small, current will only flow through the rectifiers for a small proportion of the cycle, therefore the current flowing in that small proportion will be a lot higher than that through the load at any time.

What I don't understand is why this would cause I2R problems with heating. Perhaps my understanding of RMS current is flawed. My contrary reasoning is that If for example 1 amp is drawn 90% of the time, the I2R heating would be the same as if 9 amps are drawn 10% of the time, since the heat dissipation is relatively slow compared to the 50Hz cycles.

I hope I've given enough information for someone to spot what I'm failing to understand.

Thanks


texts: Need a system to isolate an external charge circuit in a vehicle

texts:
I am looking for some assistance with options in isolating 2 parts of a circuit.

I have a 4G hotspot that I am using in the car, powered via the cigarette lighter socket (rated at 12V/10A)  and a 5V USB regulator.  The hotspot is intended to be always available even when the car is off.  Due to the fact that the car is off for far longer than it is running, the device discharges it's internal battery in a few days as it is not charging long enough.

To this end I have a circuit that will charge several (in my case 3) 12V 2.2Ah Sealed Lead Acid batteries in parallel and operate the hotspot device while the vehicle is operational. The batteries alone will power the device while the vehicle is not operating (ie the Ignition switch is off).

However, I am stumped on how to isolate the rest of the car's accessories within the accessory circuit (as isolated by the ignition switch) from the charge circuit when the ignition is off.  Once activated, the charge circuit feeds power back into the vehicle accessory circuit.

One version I have has a relay to enable the circuit when the ignition is on, but the power feeding back from the batteries through the closed relay energises the activation circuit and keeps the relay closed when there is no power from the ignition.  The dashed line is roughly the boundary between the part of the circuit that needs to be permanently powered and the part that should only powered when the ignition is on.

I have another that replaces the relay with parallel diodes in the power path, but the ~1V voltage drop and heat dissipation from regular silicon diodes is undesirable, and I tried several Schottky Diodes in parallel (because they have a smaller/acceptable voltage drop of ~0.13V each (measured)).  However the Schottky diodes leave ~1.8V on the 'dead' side circuit that could put extra drain on the SLAs when the ignition is off.  The LED on the plug interfacing with the 12V car socket indicates power is there when the ignition is off and I measured the voltage with a multi-meter across the terminals of the plug with it disconnected from the car.

Is there a way that I can have a low or no voltage drop, low impedance circuit, fairly high current (but < 10A) that will sense when the ignition is off and isolate the external batteries and charge circuit, without modifying the car's built-in and under warranty wiring?

I have seen mentioned elsewhere use of a MOSFET(s) and a sensing circuit to control it to replace diodes to make an 'ideal diode' but the references are mostly in the context of rectification of AC current not this circumstance and I haven't worked out how to apply the theory to this situation.

The hardest part in anything I have dreamt up is the fact that once the circuit is first powered from the ignition, you cannot tell when the ignition has been switched off as the batteries in the charge circuit maintain the power on both sides.

Any pointers would be appreciated.

EDIT [2018-05-30 - 22:51 AEST [UTC+10]:

Would something like this work to have the battery circuit connect to the car supply if the car supply voltage is over 13V (ie the car is running and alternator is operating at 14.2V).  As the SLAs are only about 12.5V fully charged then no current would flow thru the zener diode and the transistor would be off.  If the voltage was above 13V, current would pass thru the zener, limited by the resistor and switch the transistor on to activate the relay.  My zener theory is rusty and transistor theory even rustier, but would something like this work?  Calculating the resistance values would be the next challenge (for me at least...).


texts: Why is power supply from electrical utility referenced to earth?

texts: In response to the question Basic Training for working with 120V AC zebonaut had replied that "A regular wall outlet is referenced to earth" and this provides the close loop for the circuit to complete. Also it was stated that for safety if an isolation transformer is used the current will have to flow back to the transformer and you won't get shock by touching with only one hand. So why don't the power supply from electrical utility come from an isolation transformer? This way won't there be less risk of electrical shock from electrical appliances ?


texts: Comparing power consumption of different FPGAs

texts:
I want to compare power dissipation of FPGAs from different vendors, the I/O count and the logic resource shall be matched as close as possible when choosing the FPGAs.
I want to create a trivial design that would utilize a big chunk of the logic resource and the I/O pins. This design shall be implemented across the different FPGAs and the power dissipation shall be measured on each power rail.
The problem as it exists is that, there is no simple way to create a design for this. The design being sought does not need to do anything productive but merely needs to implement switching activity, it should just occupy say X% of resource inside an FPGA and this number can be specified as amount of LUTs also.
Is there a standard way to produce such a design that would have huge amount of logic which keeps switching and helps us make the power measurements? I do not think any standard method to create design of such nature exists.


texts:
Do you have to place the input and output capacitors on LOAD basis or the capacitors specified in the datasheet.
I have a linear power supply that supplies 16 Volts with no load.
The maximum load I want to apply to this regulator would be less than 2A and maximum Voltage, 9 Volts.
I just need to know what values of capacitors to use. My supply does have a 4700uF filter capacitor but it is around 2 feet away. I want to make this regulator in separate box.


texts: My circuit simulation basically would last forever, it's a filter circuit but  LTSpice can't run it. any help/insight will be greatly appreciated!


texts: Will a Transformer work from a DC inverter's output?

texts: If so, is it ever more efficient to use an inverter into a transformer to dial down DC Voltage?


texts: Will a 3V3 rated UART be damaged by applying 5V signals?

texts:
If I have a device specified for 3.3V operation and I connect a 5V level TTL signal to it ? Will it's UART ports be damaged or not ?

I have a WiFi module and I want to know if its UART ports will have been damaged by applying 5 Volt signal levels during an experiment or if there is still hope that it has not been damaged ?

This WiFi unit

This may be the manual


texts: Splitting strain gauge signal before amplification

texts:
I have a strain gauge full bridge force sensor with 3mV/V sensitivity and power it with 10 V excitation, giving up to 30 mV output. Normally the output is connected to a 3rd party device's strain gauge input (call it device "X"). That device can't plot the force during measurement, so I want to show the real time data in a different device. That is why I need to get the signal. I have 2 ideas:

Option 1:
Split the strain gauge's raw output signal, for example with a device like this. Splitted signal 1 goes to device X. Splitted signal 2 goes to my own device.

Option 2:
Get an external strain gauge amplifier, scale signal to 10 V, and split 10 V signal afterwards, as in option 1. The device X also has a +-10 V input, so no problem here.

I think option 2 is better. But I really want to understand HOW the strain gauge output is affected by splitting the signal as in option 1. I know that the splitter is pure analog, no A/D conversion is happening.
How does a splitter possibly work? Is it creating a parallel circuit? Then I assume that it would not increase the load on the strain gauge output, hence having no bad effect. But if the splitter would be somehow connected serially only, I think that the total resistance increases and I am going to measure a lower voltage in device X. Is it conceptually much different splitting a strain gauge signal in contrast to a potentiometer signal (for example from a travel sensor)? Could you please explain in detail?


texts:
(I've reworded this question from earlier)

I ground the input of an ADC that has 50 Ohms internal termination, and observe a noise waveform. I measure the RMS voltage of this waveform.

Then I remove the ground at the ADC input and terminate the ADC input to 50 Ohms (just a resistor to ground, that's all). I measure exactly the same value for RMS voltage of the resulting waveform.

Assume this ADC noise is Gaussian (random).

Now I connect my signal to the ADC. Will the ADC noise above (the RMS value) add directly to the "true" signal? So, if I measure 2 mV RMS when grounding the input, will the observed signal be the "true" signal plus 2 mV RMS noise?

Or, is the noise generated internal to the ADC flowing through the internal ADC termination such that when I connect my signal source with 50 Ohms termination, the voltage divider that results cuts the observed signal in half as well as the input referred noise from the ADC? (So, I'd observe the "true" signal plus 1 mV RMS noise.)


texts: Is it possible to use multiple bluetooth profiles for a pair of devices?

texts:
I have a project in mind that uses Bluetooth and I'm currently doing some research. What I have in mind is to build an app that can send audio signal via bluetooth to a raspberry pi 3 and be able to control the GPIO pins of the raspberry pi all in the same app. This means I'll be using some sort of audio profile and a serial profile (for the GPIO portion).

However, I'm not entirely sure if this is possible because I'm essentially running two different profiles between paired devices. Is this possible? Or does it depend on some other factor?