texts:
I just learned about SR Latches, D Latches, and their gated versions and I've got a little burning question.

So of course with the SR Latch, the professor told us that the "11" condition cannot occur because the circuit is unstable

(source: kfupm.edu.sa)

Gated D Latch

Then, we learned about the D latch, which has a single input as opposed to 2, and eliminates the "11" condition from ever occurring.

But I realized at this point that in going from 2 inputs t0 1, the D latch also loses the ability to store a value while the clock signal is high because it will always be either "01" or "10" and setting or resetting.

So I was a little confused by that, what if the clock was connected and cycling over and over, and you wanted it to simply store the value? Why not a safe gated SR latch? So I just added some gates to the front to filter out the "11" condition.

So why isn't this used, or is it? Or how do memory elements that use this then store their value when clock is high? Our professor didn't mention this so I'm just curious.

"Safe" Gated SR Latch

animation

Safe Gated SR Latch


texts: Integrating battery and battery charger with my project - I never want to remove batteries from this device for charging, how do I do that?

texts:
(I used to design and build electronics - HiFi, automation, digital systems up to and including CPU-based controllers - so I have a good understanding of the basics. I just stopped being involved in the field about 15 years ago, so my knowledge of what's currently available in terms of components is quite foggy.)

The device is a controller for a scientific instrument. Removing batteries for charging every once in a while will be cumbersome. Plus, I want seamless transition between batteries and AC (well, not AC per se, but external DC at a higher voltage).

The battery needs to be 12 V or a bit higher. In terms of how much energy it needs to store, something like a small laptop battery should be enough.

So, basically, I need to integrate the battery charging circuit with the device. The battery will not be (easily) removable. The device will provide a port for an external DC supply for charging. Switching between internal battery and external DC must be seamless. It must handle automatically all the chores related to battery charging (regulate the current, stop charging when fully charged, stop the device when fully discharged and there's no external DC, etc). Indicating the current charge level would be nice.

Any suggestions?

I'm pretty sure I could use an actual laptop battery for this purpose, I just don't know how to connect it.

Could I use 4 x LiPo or 4 x 18650 elements in series? I'd have to use some kind of battery charger/controller, I'm pretty sure such a thing already exists, I just don't know where to start looking for it. I know these elements are finicky.

Any help would be appreciated, thanks.


texts:
Good Afternoon

A IC which has Max current rating is 10A , But in my Design i will always use it at 5A current only. Will my component life will be double by doing this or not??


texts: Which layer of PCB is used to identify cut-out of individual boards within a panel?

texts:
Let's say I'm using a software like EagleCAD to create a panel with a few copies of a design (or even different designs).

There is a "Dimension" layer (mapped to an Outline layer, e.g., GKO), but this is for the overall outline of the panel.

Which layer is traditionally used to communicate where the individual cut-outs should happen around each constituent board/piece on the panel?


texts: Lightning Connector Power Output rating/ Apple Policy

texts:
I am currently in the process of developing an external antenna for smartphones, so the answer of the following question(s) pertains to the feasibility of this product.

What is the line level output from a lightning connector, and is there a limit placed by apple?

After doing some research on this forum I found that the Lightning connector outputs a maximum of 100maH at 3.3V....is this correct? Does Apple limit the amount of power output by its phones?

Sincerest Thanks for your time and effort.


texts: PID regulator steady state error problem

texts:
I'm working with a PI controller that regulates temperature through a pwm duty cycle.

It generally controls well.  However, the system requires a certain minimum duty cycle to balance the heat loss.  When the PI finally gets it right, that is, when the Proportional error is Zero and the Integral error is Zero, the output also goes to Zero and throws the system off.  Then the PI starts working hard at minimizing the error and repeats.

Is there a solution to this?

Additional Information

The heater is only allowed to go from 0 to 1 maximum of 3 times per unit time (a strict requirement).  This causes the fixed frequency saw tooth wave you see.

Here is the overview:

Here is the problem area zoomed and marked.  The Integral crosses zero and results in a whimper output which then causes a large error and the pattern repeats:

PID output.  Yellow: Integral, Magenta: Proportional, Cyan: Error, Red: Output.

You can see when the Proportional and Integral near zero, the whimper occurs.

The PI output is passed through a duty limiter and sign filter resulting in only 0 or 1 outputs.  It is then passed to the frequency regulator that does not allow more than one 0->1 transition in the same 1/3 of unit time.  This means that for a portion of the cycle, the output of pi controller is culled.  The integral portion continues to build however and compensated in the next period.


texts: Wrong load capacitance for 20 MHz, 20 pf crystal

texts:
I am new to microcontroller development, and I wanted to try running the MSP430f5529 off of an external crystal of 20 MHz that requires 20 pF of capacitance. I read on the datasheet that the pins can support up to 12 pF of internal capacitance, which is what I planned around when I ordered external 22 pF capacitors. When using the equation described here.

$$\frac{(22+12)\cdot(22+12)}{22+12+22+12} + \sim3 = 20\,\text{pF}$$

Unfortunately, I did not do my research well enough, as it seems that XT2 (the high frequency external register) does not have internal capacitance. The XCAP bit is only for the XT1 register. My question is, will the lower capacitance be a significant problem for running the clock near 20 MHz (±500 kHz)?

$$\frac{22\cdot22}{44} + \sim3 = 14\,\text{pF}$$

That makes it 6 pF less then desired.

edit: Also, I do not know if this is how capacitors work in series, but another option is I could put two of the 22 pF ones inline on one terminal. So I could have $$\frac{(22+22)\cdot22}{22+22+22} + \sim3 \simeq 17\,\text{pF}$$ Does that work?

Thanks


texts: Reading a photodiode in nanosecond intervals

texts:
I need to turn on an LED (NTE 30030) for 100 milliseconds, turn it off and then immediately (< 1ns or as close to zero as possible) take measurements on a nearby (< 10mm away from LED) photodiode at 1 ns intervals for 5 ns. Those measurements can be put in a specialty buffer chip that can be retrieved later with an Arduino device.

Is this possible with specialty chips? Can Arduino do this? What kind of literature do I need to read to understand this problem?

EDIT: For clarity, this is for atomic fluorescence. The biomarker we are using continues to fluoresce for only 2.6 ns after excitation cut off. I can also use a laser if that makes it easier. For cost reasons, we cannot go down the route of photomultiplier tubes or monochromator style of setups. We're trying to make this accessible but it may not be feasible to do this reading some of the comments below. I am not an electronics expert.


texts: Inductance of air core coil with small diameter

texts:
I have some legacy circuits with air core inductors (copper) w/ 19 turns, SWG = 24, dia = 3.20 mm, Length = 12 mm.  The measured inductance on a good instrument was 80nH/13.7 milliohms & 93nH/13.37 milliohms.

However, calculations show that it should be 272nH, using outer dia, and ~185nH using mean dia.

I need to replicate this board. But what value of L (also Q and C) to choose ?? This is a very simple board for an antenna amplifier for MW/SW/FM bands which works very well - gives > +20dB all the way from 500Khz upto 125MHz FLAT (based on simulations), and I don't want to mess it up.

What is the community opinion/ advice ?


texts:
In the datasheet for fuses (for example, I'm looking at the Bel Fuse 0678L9150-02 -- datasheet at https://www.belfuse.com/resources/CircuitProtection/datasheets/0678L%20Jun%202016.pdf), they report the melting I²T integral (in A²·sec), but they say @ 10 In --- not sure whether the first letter is a capital-i, or lowercase-L.

What does In (whatever the right spelling may be) mean in this context?
What does the Time-Current characteristic curve tell me?  For example, in the above fuse model, if I look at the 10A curve (presumably that means the curve for the fuse with 10A rating), then 20A maps to 5 sec.  Does that mean that if a fixed current of 20A runs through it, after 5 sec it will blow? (understanding that this is a "theoretical" / average figure).  What doesn't seem right about this is that the curves get to very high amounts of time --- I mean, it doesn't make sense that the stress would be cumulative at such a slow rate until reaching an amount of accumulated stress that makes it blow.

I guess this brings me to a more fundamental doubt I have:  what does the Amp rating really relate to?  Is it:

the point at which the fuse should blow? (meaning that normal operating current should be, say, half or a tenth of that value?)
the maximum normal operating current? (meaning that the fuse will blow when the current exceeds that value by a factor of, I dunno, 5 or 10 times that?).

I suspect that strictly speaking it is neither, and that one has to do somewhat more involved calculations?


texts: Inverting amplifier to measure shunt voltage?

texts:
I've built a motorhome-type vehicle, and wish to perform coulomb counting for the battery bank. I've placed a 100A/75mV shunt between the battery bank negative, and the negative bus (which is also connected to vehicle chassis to reduce wiring cost for alternator charging etc.)

simulate this circuit – Schematic created using CircuitLab

How can I most accurately measure the mV across the shunt? The value will typically be 1-10 mV, up to 100 mV peak, and will be either positive or negative, depending on the direction of the current.

I understand that I may need an inverting amplifier, since the microcontroller will be grounded at the load level, e.g. unable to measure a negative voltage.
Or is it sufficient just to use offsetting?

I'm new to amplifiers, and worried that I'll spend countless hours trying to get the wrong components to work, particularly having difficulties accurately reading the 1-5mV level.

Typical usage, as measured across the shunt with a multimeter:
 - Charging at 20-30A = (negative) 15-22mV
 - Constant loads, ventilation etc., 1-2A = 0.75-1.5mV
 - Peak charging from alternator 50-80A = (negative) 38-60mV

The multimeter reads the values quite well/stable.


texts: Transient analysis with Laplace and nodal analysis error

texts:
Have the schematic:

Solving using MathCAD:

There is an error in my equations with nodal analysis but I can't find where? May anyone help me?

I also add the solution using approach of series RLC circuit:

But it seems to be A1 and A2 constant sign is incorrect comparing my result with that in textbook.

I also tried to solve with Laplace but using Mesh Current Method, my equations are (I1 - left mesh current, I2 - right):

But same thing - I can't get properly result, may be something wrong but I can't understand what!


texts: USB host-mode on uC, to support small pre-defined set of USB devices

texts:
Apparently, one of the main reasons why most 8-bit/16-bit uC's do not support USB host-mode operation is because of the rather expensive process called "enumeration". From my research, this step seems to be necessary when the host must identify the class of device connected to it, identify specific vendor/device and then load the appropriate driver to handle communication between host processor and device. The other reason being need to provide sufficient current to the devices.

Now if the "sufficient current" is not a big issue, let's say because my uC (which I'd like to act as USB host) is powered (via a well rated, regulated wallwart), and there are only 3 USB devices with which it needs to work, for instance --

Device that uses proprietary Serial over USB
Device (sensor) that uses USB-HID
Specific vendor/model USB2.0 Bluetooth2.1 device

via say a USB hub device ? In fact, if it can be a powered hub, then the question of "sufficient current" is anyway addressed by it.

Is it possible to make do with say something like Atmel ATmega32U2 ? The idea being, instead of enumerating devices from a large list of possible devices, I know in advance which devices are connected, and how they are connected ? What might be the caveats if this were to be possible ? If someone is aware of such attempts (successful or not), would love to hear about them.


texts:
I've been reading Tanenbaum's Structured Computer Organization and he says one of the major bottlenecks for increasing CPU clock speed is heat. So I started thinking: Is it possible to remove the heatsink altogether and use that heat to generate more electricity? I've been searching on this and found these thermoelectric materials and this thermoelectric generator:

I read on that Wikipedia article that "Silicon-germanium alloys are currently the best thermoelectric materials around 1000 °C (...)", and I know CPU normally operate around 30~40°C. So, getting to 1000 °C would require more CPUs.

So I thought: What about putting a lot of CPUs in parallel without their heatsinks to gather more heat? We can also overclock these CPUs a whole lot and see how much heat they can generate.

But I'm stuck. I don't know what to think next. I don't even know if it's a good line of thought.

My question is: why not develop some sort of heatsink that generates electricity from the CPU's heat? I know somebody must already have thought about that and thought about a reason why not to do it, but I can't figure it out.

So, why is it not possible?

EDIT for clarification: I do not want CPUs to work at 1000 °C. I'll list my reasoning steps (not necessarily correct), which were roughly:

CPU clock speed is limited by working temperature (T).
CPUs generate heat. Heat makes T rise.
Heatsinks take care of that heat in order to maintain T=40°C.
Replace heatsink with thermoelectric generator (built from SiGe or similar material)
Put a lot of CPUs side by side to increase heat generation.
Heat comes out the CPUs to TEG, so CPUs stays at T=40°C.
Is this possible?
How to build such a TEG? Which material to use?
Why such device doesn't exist already?
Asked this question.

EDIT2: I see that my idea is fundamentally wrong and bad. Thanks for all the answers and comments. Sorry about any misunderstandings.


texts: Why are the inputs on my analog multiplexer tied to each other in pairs? (0+1,2+3,3+4...)

texts:
I'm currently wiring the signal of 16 potentiometers into a CD74HC4067 16 Channel Analog Multiplexer. The circuit is powered by the 3.3V signal on the Teensy 4. P0 (the first potentiometer) is wired to C0 (channel 0), but its value is read as the output to C0 and C1. P1->C1 has no effect, P2->C2 is read by C2 and C3. P3 has no effect and so on through all 16 pots.
Does this have something to do with the mux not receiving enough power? I didn't see anything on the datasheet about the signal splitting like this. On the Teensy forums I was told to not use the 5V signal as it could damage the T4.
Any help would be much appreciated! Thanks
Also, not an issue with code I don't think because the same channel reading works fine when I use 16 buttons


texts: Reverse engineering target chip to be used with OpenOCD

texts:
I have a board that has JTAG pins and I want to connect OpenOCD to the board. However the CPU chip identification number is not written on the chip and I couldn't find the datasheet of the board.

What do I need to do in order to find the chip identification number?


texts: Using ICs from old computer hardware and such

texts:
Like many other users of this site, I have tons of old computer parts laying around my house.  Often I enjoy looking up the numbers on the ICs on these old parts to see what they do, and every now and then I'll come across one that I find useful for whatever project I'm working on.  But the leads from them are so small!  Is there any reasonable way to use these tiny ICs from old parts in new projects?  These are things I would throw away anyway, so I'm certainly willing to risk damaging/destroying the part.  I've tried cutting the PCB itself around the chip with a Dremel, exposing the copper leads on the board, and then soldering wires to those leads, but it doesn't really work that well.  Has anyone else tried this or any other technique and had success?

(Side note:  I know that for most of these ICs it would be far easier to just buy them off of Digikey or something like that in a reasonably sized casing; it's the principle of the matter and the idea of making something new completely out of old parts.)


texts: What is the relation between noise margin and impedance in a CMOS circuit?

texts:
A well-designed CMOS inverter, therefore, has a low output impedance, which makes it less sensitive to noise and disturbances.

How can we say that a well designed inverter i.e with proper noise margin have low output impedance or vice versa?


texts: Switching Regulator (LED Driver) "Flickers"

texts:
I have a constant current LED Driver (LM3410) that effectively functions as a switching voltage regulator to provide enough voltage for LEDs in series. When I power it with a relatively low voltage it lights up the light strip pretty well, although under the current it should be regulating at. If I increase the input voltage so that the current output is higher, the strip turns on fine for about a half second then starts flickering (slow at first then fast, maybe 5hz to 20hz).

I followed most of the recommendations in the datasheet so I'm pretty sure I'm using good capacitors and resistors (high enough voltage and values) but I'm somewhat unsure about the Inductor. The Inductor is 8.2uH but the SRF is unspecified and I'm worried it may not be compatible with the two available frequencies of the Driver. Current is about 1.5 A and the Inductor is rated for 2 A.

Can someone tell me what the reasons usually are for a switching regulator to flicker it's power supply when input voltage changes like in this scenario?


texts: STM32F4xx barebones SPI (HAL initialisation)

texts:
I am working on a piece of software for an STM32F4xx device which started from a STM32CubeMX generated project.

I am using the SPI peripheral which has been initialized using the HAL library.
This is an example of an SPI write function that works:

void spi_write(uint8_t data) {
    HAL_SPI_Transmit(&hspi2,&data,1,HAL_MAX_DELAY);
}

If I want to send data using the SPI without using the HAL library, but doing it barebones on the registers (because it is faster) it does not work. This is my implementation:

void spi_write(uint8_t data) {
    (&hspi2)->Instance->DR = data;
    while (!((&hspi2)->Instance->SR & ((uint16_t)0x0002))); //Check TXE flag (SPI_I2S_FLAG_TXE)
    while ((&hspi2)->Instance->SR & ((uint16_t)0x0080)); // Check busy flag (SPI_I2S_FLAG_BSY)
}

Any idea why the second implementation does not work? Thank you!


texts: Difference between standard and extended Steinhart-Hart equation

texts:
I looked up the data table for a thermistor I purchased and noticed it uses an 'extended' Steinhart-Hart equation. I'd like to understand the difference between these equations, such as how the D coefficient is acquired, whether more coefficients add accuracy, and so on.

The standard Steinhart-Hart equation I had seen is:

On the thermistor data sheet, page 4 includes the 'extended' Steinhart-Hart equation:

Is the inclusion of a D coefficient here simply an instance of resistance data having been measured for a third temperature? Does the inclusion of an additional coefficient relate in some way to the material properties of the thermistor? Or did the manufacturer simply choose to include it for further accuracy?


texts:
I've created a PCB for my newly built 3D printed Windmill. Now I am not entirely sure about all the components and the way they function, so I'd like to have your opinion on the circuitry before I place my order.

The idea is that the circuitry charges an externaly protected and managed 18650 and stores sudden current spikes inside the a capacitor (C1). The battery management circuitry requires a voltage of 3.7V and specifies 9A max (Aliexpress protector board, so I'm expecting around 4.5A max charging current)
The board should be able to recover from a total black-out using only the the generator's power.

I expect a maximum of 20V@6A to ever come from the BLDC under load, which will probably only occur during a tornado. You can find the BLDC here.

The schematic requires some comments.

The power from the BLDC comes in through connector J2 and goes through a diode rectifier bridge (D3-D8)
In order to have the capability to slow the BLDC down, I've added three 0.22 Ohm power resistors in combination with a N-Channel mosfet (Q2) to control the speed of the motor in a high wind force push event.

To enable/disable charging another N-channel mosfet (Q1) is used, but as I'm writing this down I am wondering if this should be a P-Channel mosfet. This mosfet might be used for MPPT.

To get the voltage of the current spike caps, a voltage divider is used (R4-R6).

A current sensor is integrated onto the PCB to monitor the current.

U3 is the 5V system power supply, which provides power to the MCU and various sensors. The idea is that this power supply is able to wakeup on it's own, without the MCU running. (WeBench)

U4 is the battery power supply, which converts the input voltage to 3.7V. (WeBench)

A temperature sensor is also present to monitor the temperature inside the windmill.

The connectors:

BT1: the battery connection terminals.
J2: the 3 phase BLDC input.
J3: the magnetic sensor header for the BLDC.
J4: the UART header.
J5: the ICSP header.
J6: the 433 MHz radio transmit module.

The screw terminals visible are not the ones that will be used.

There is a cut-out between the current in and current out pins of the ACS712 which also goes underneath the chip it self.
The 3 pin mosfets use the tap for the drain instead of pin 2, the solder mask has been removed underneath the taps.

Those big blocks next to the diode bridge are the power resistors that dump the energy when needed.

I ran the DRC and everything is solved and passes the checks.

My questions;

Have I implemented the mosfets properly (I don't mean the mosfets used around U3 and U4)
What do you think of the schematic and the PCB?
Do you spot any cricital faults?

Block diagram


texts: Zener dynamic resistance Rz: Is this graph or the values for Rz correct?

texts:
The textbook I'm studying from states that the typical dynamic resistance ranges from 1 Ohm to 50 Ohms. Seeing the following graph something doesn't make sense:

Since the slope in the breakdown region is 1/Rz and the graph is almost a vertical line the typical values I'm given are not justified. In the best case scenario and for Rz=1 the slope is 1. Looking at the graph the slope should be a very big number.

Is this graph a supposedly ideal zener diode? Is the slope smaller in reality? Or have I utterly failed my high school math teacher?


texts:
Could someone please explain the reason why the 93C66 EEPROM outputs a dummy 0 during a read operation?

From datasheet:

  5.1          Read Data from Memory The Read Data from Memory (READ) instruction outputs data on Serial Data Output (Q).  When the
  instruction is received, the op-code and address are decoded, and the
  data from  the memory is transferred to an output shift register. A
  dummy 0 bit is output first, followed  by the 8-bit byte or 16-bit
  word, with the most significant bit first. Output data changes are
  triggered by the rising edge of Serial Clock (C). The M93Cx6
  automatically increments the  internal address register and clocks out
  the next byte (or word) as long as the Chip Select  Input (S) is held
  High. In this case, the dummy 0 bit is  not  output between bytes (or
  words)  and a continuous stream of data can be read.

If the input/output is byte oriented, and first bit of a read is a dummy bit 0, all data after that is then shifted (delayed) by one bit to make space for this dummy bit.

For example if the data stored in the EEPROM is:

byte1:[000000001] byte2:[000000001]

it is read from the EEPROM  as:

byte1:[000000000] byte2:[100000000] byte3:[100000000]

I would like to store some data to EEPROM but this shift is the issue, what is the use of this devil thing called dummy 0?

EDIT:

I just want to leave comment on my solution.
Because I was able to change IC in my case I went on using 25LC640A-I/P DIL, it behaves like I wanted, so if anyone needs hint here it is.


texts: When to treat transformers as non-ideal?

texts:
For an experiment I need to sum a DC and AC Potential. My solution to this was to construct the following circuit:

simulate this circuit – Schematic created using CircuitLab

Testing this circuit I found the following:
1. It works. I recover the AC signal with a DC offset.
2. The transformation ratio was inconsistent
3. The inconsistency comes from the DC offset?

The set-up is:
Test 1:
\$ V_{ac} = (0.5\$V\$)\$Sin\$[2\pi 8 t]\$
\$ V_{dc} = (5\$V\$)\$
\$ V_{out} = (20.8\$V\$)\$Sin\$[2\pi 8 t] + (5\$V\$)\$
\$ \frac{V_{out}-V_{dc}}{V_{ac}} = 41.6 \$

Test 2:
\$ V_{ac} = (1\$V\$)\$Sin\$[2\pi 8 t]\$
\$ V_{dc} = (15\$V\$)\$
\$ V_{out} = (48.8\$V\$)\$Sin\$[2\pi 8 t] + (15\$V\$)\$
\$ \frac{V_{out}-V_{dc}}{V_{ac}} = 48.8 \$

Approximately a 17% increase.

I reran these experiment at a later date and, found a transformation ratio of ~50 which is the expected result. The second time these we ran, the ratio did not change. Clearly I am neglecting to account for some practical aspect of using a transformer. I will be re-running the tests a third time with an AC source that has a floating ground so I can connect it to the DC supply.

Finally, I noticed that the transformation ratio nearly doubles at a f\$\approx\$810Hz and then falls off rather quickly. I imagine this must be due to some inductance / resonance effect, but I did not expect resonance anywhere. My AC source has an output impedance of 50Ohms.

I'd love to hear your thoughts on the causes for the inconsistent ratio. If you have any other solutions to adding AC and DC potentials (Max AC swing \$\approx\$ 6kV, Max f\$\approx\$1kHz), I'd love to hear those as well.

Details on experiment
I am applying this AC+DC potential between to concentric spheres to create a minimum potential in free space. This allows a charged particle with a low enough charge to mass ratio to levitate in open air. I am studying the non-linear dynamics of said particle. What this means for the circuit is that I need to produce the potential with no load attached (no current runs from one sphere to the next). More the physics can be found here

Transformer Details
I am running in the forwards direction. That is, I expect ~ \$V_{out} = 50 V_{in}\$ assuming the signals are sinusoidal. The core material is unknown. The turn ratio is unknown. The transformer is rated as a low power 6kV mains transformer. When plugged in directly to the mains, then, it should produce 6kV. I haven't tested this with a wall outlet, but I wouldn't be surprised to find that it actually only produces about 5.5kV. Various experiments show the transformation ratio to hover around 50, thus this was what I am taking as the expected value. Power is regulated through the use of two 10MOhm resistors in the path of the current, in case of a short. The test I describe above used current limited sources rather than the 10MOhms.


texts: C stands for capacitor, R stands for Resistor, Q stands for transistor but what are the rest? All of the time I see PCB boards with Components I don't know, and unfamiliar abbreviations on the board. The only site I found on this was this, which has a few, but didn't have many I saw on the board. Is there an official list of circuit board abbreviations anywhere?


texts: Read AC signal frequency of 2-100Hz at 80mV to 12V with Arduino

texts:
I have a sensor (NRG #40 Anemometer) that produces an AC signal with a frequency between 2 Hz to ~100 Hz with an amplitude of 80 mV to 12 V peak-to-peak. The signal to read is the frequency (zero crossing?), amplitude is not relevant.

The signal gets read by a Arduino Uno. To convert the sine wave (from the sensor) to a square wave (suitable for the MCU input), I was thinking of using a 74HC14N Hex inverting Schmitt trigger. The sensor application note suggests adding Over-Voltage Protection, Low-Pass Filter and a limiter. I am running the Schmitt trigger at 3.3V.

Unfortunately my Schmitt Trigger output is always high, meaning the input signal is low and doesn't register.

How can I bring the input signal to a valid level for the Schmitt trigger?
How can I DC bias the input signal to about 1.65 V and limit it to not pass 3.3 V and 0 V?
I thought I ignore the Over-Voltage Protection and Low-Pass Filter for the test setup, is this ok?


texts:
I'm an artist currently working on an installation piece that requires a little more engineering knowledge than I possess. In short, what I'd like to achieve is a 2 LED blinking circuit with battery efficiency in mind. Preferably fresh batteries should last for a few months to a year or better. I'm guessing the best way would be with two layers of blinking: one blink would be more of a high frequency strobe and just appear "on," the other would cycle the LEDs off and on every second.

I don't know where to start with this, let alone if I'm headed in the right direction. Am I?  What frequency would be best for the strobe? Again efficiency is the priority. I don't mind if there's a slight flicker like a GFI switch indicator. Any advice that will get me moving is appreciated.


texts: On page 376 of Hennesay's book Computer Organization And Design, the following illustration is listed to illustrate branch prediction. But what do "IM" and "DM" mean? Does IM stand for instruction memory and DM stands for data memory or is it something else?


texts: I'm trying to find a three-pin connector like the ones photos below (taken from this page). I have tried asking in the comments but my question is still 'awaiting moderation' after a week so I don't think they're checking them any longer. Can anybody here point me in the right direction?


texts:
I have a requirement for a 24V +- 15% rail to power a laser sensor off of a 24V lead acid battery pack. I implemented the reference design provided by renesas for a 12V buck-boost converter(ISL85403EVAL2Z userguide) with input range of 8V-40V. The only thing that i had to change was the feedback resistors in order to drive higher output voltage. This is the design below. I have also pasted the link for the gerber and kicad files if anyone is interested in the design.

The issue i'm facing now is that the converter never enters boost mode. The condition for the converter to operate in boost mode according to the datasheet is that the EXT_BOOST voltage has to be between 200mV and 800mV. My choice of resistors R10 and R11 ensures that this voltage stays around 500mV. Also the output falls rapidly, almost instantaneously to ~1-2V as soon as i connect the load (laser sensor). I tested it by adding load resistors and with a load of 40 ohms the output falls down to 5V. The LGate pin has no activity at all when monitored on a scope. I use an old lecroy scope and wont be able to paste the output waveform here. I'm not experienced with power converter designing. My background is mostly robotics and mechatronics. If anyone could be kind enough to have a look at my design and point out the errors i'd be deeply grateful.

P.S. I have some extra pcb's for this design available. If anyone is interested in tinkering please let me know, i could have them shipped to you.
https://github.com/Tal-seven/isl85403_referenceDesign

Regards


texts:
Pin configuration of a photo-multiplier tube (PMT) is presented in its manual as can be seen in the attached image. All dynodes have been related to specified pins (numbered circles in the image) except Photo-cathode and Modulator that they are marked with the letters "Phi" and "M" respectively.

This PMT is manufactured by GS-Tube (https://www.gstube.com) and its part number is FEU-49B. The image below shows a view of the PMT. Now, I don't know how these pins can be connect to high voltage power supply when there is no identified pin?


texts: Audio amplifier provides the capability to drive 660Ω loads directly without buffering

texts:
From PGA2311 datasheet we can read this sentence.

Does that mean if I drive a 660ohm load at power P, in order to drive a 100ohm load with same power, PGA2311 won't be able to source enough current? So a buffer is needed?

How can I determine load values range from datasheet? Is it related to output buffer short circuit current?


texts:
I am streaming output on MAX32660 SPI0 at 48Mbaud. Since it is streaming, I can't predict the length when I start sending.
The problem I'm running into is that slave-select assertion and deassertion seems to be based on SPI0_CTRL1.tx_num_char. I can maintain transmission by periodically writing a large number to SPI0_CTRL1.tx_num_char, and writing bytes directly into the 32-byte hardware FIFO as they become available. But then when I get to the end of the stream, how do I tell hardware that I'm done with the transaction? I tried writing SPI0_CTRL1.tx_num_char to 0 (or 1 and then writing a final character), but it didn't work completely. The SPI clock stops after everything is transmitted, so all data is properly handled, but the slave select remains asserted.
It's a bit odd that SPI0_CTRL0 has a start bit, but no corresponding bit to stop. Surely I don't have to know the length in advance?
I suppose I could just use another GPIO as a slave select, which would also enable me to use more than one peripheral. Is that what everyone does? But then why do they bother with all the fancy slave-select timing features in hardware? (Do the manufacturers do this just to make us think we need to buy a more expensive device if we want more than 1 slave select?)
Or is there a more proper way (i.e., more likely compatible across multiple devices) to start and finish streaming SPI output?


texts:
I am examining the st-micro rtd circuit for the STM32373C-EVAL kit. What does this circuit do?

Can I use it to support both pt100 and pt1000 rtd elements? The circled area is the point of confusion.

http://imgur.com/QsWV0hI


texts: Increasing Gain of OpAmp Design - increase or decrease drain current?

texts:
I was reading one of Razavi's op-amp design examples (telescopic fully diff) and he mentions how to increase the gain.

Notice in the highlighted part, he uses an equation for gmro but there is drain current on the numerator and the denominator? So increasing or decreasing drain currrent will change gain?

How does he then simplify that and reduce that reducing the drain current will increase gain?


texts: What does this value mean in a BJT datasheet?

texts:
In the switching characteristics section of a BJT datasheet I often see test conditions like "Ib1=Ib2=1mA". I understand this is base current but what exactly do they mean by Ib1 and Ib2? Example: https://www.mccsemi.com/pdf/Products/MMBT3904(SOT-23).pdf

Thanks in advanced.


texts:
Can you define a bit slice in Verilog?

For example, is this possible:

`define opcode 5:3  // is this possible?

reg [ 7:0 ] a, b;

...

if ( a[ `opcode ] == someValue )  // a[5:3]

    doStuff

if ( b[ `opcode ] == someValue )  // b[5:3]

    doStuff


texts: Power factor down after solar connection

texts: We installed solar plant in factory. After that power factor goes down to 0.16. Normally it never goes below 0.85 in history even if we keep APFC off. We always maintained it to 0.99. Note - Main meter is uni directional and not bidirectional.


texts: Apparently correct D-flipflop implementation breaking my circuit. When using built-in D-flipflop, the circuit operates correctly

texts:
I need to design a simple 4-way traffic controller for an assignment.
Traffic is from Road 1, Road 2 and Road 3 (see diagram below). If there is traffic on road 1 only, road 1's traffic light stays green and the other roads stay red. Similarly for the other roads.
If traffic on more than one road, then the green lights alternate.

The specifications say that I need to use a d-flip flop with asynchronous clear for the sequential circuit part.
I have already designed the circuit. When using the built-in Logisim D flip-flop, the circuit operation is correct.

The assignment however requires us to implement the D flip-flop ourselves.
I made a d flip flop as a subcircuit, and it seems to be working fine (outputs as expected)

However, when using my d flip flop in the main circuit, it works when only one of the inputs is asserted.

If more than one input is 1, instead of alternating red and green lights, I get an "oscillation apparent"

The error definitely seems to be with my d flip flop implementation, and more specifically the asynchronous inputs, but I can't figure out what's wrong.
Let me know if I need to provide more information. Any help much appreciated, thank you!


texts: Is there really a proper way to send private bits even 1 with CANBUS?

texts: I was thinking of making an authentication protocol for canbus. Is there a way to send even 1bit privately to another node ? Have seen many implementations quite a few good ones. In particular ESA Academy states that they have a way to send a private bit within nodes. Do you think its possible ?


texts: I need some help calculating values for a variable 555 oscillator circuit

texts:
For the past few hours i have been strugling with a 555 timer.
What i am trying to do is generate a square wave of variable frequency controlled by a potentiometer. At the time i have a 200KΩ potentiometer, and using this page i calculated that if R1 is 200KΩ, then R2 has to be 10Ω, and the capacitor will be 1μf.
That will allow me to vary the frequency between ~3Hz and ~120Hz which is just what i need.
After i built the circuit and placed an LED between pin 3 and ground (using the apropriate resistor), and connected the circuit to the 9V DC supply, the LED turned on but didn't blink to the slightest, so i thought it was some sort of high frequency, and thats why i couldnt see the oscilation, so i turned the potentiometer fully to the oposite side thus turning R1 to 200KΩ.
Still nothing, no oscilation at all! I even replaced the potentiometer with a fixed 200KΩ resistor just in case it was damaged but yet again, nothing.
The circuit is exactly as seen in the diagram of the page provided above, the only difference is that R2 between pins 6 and 7 is not of fixed value.
What have i done wrong?
Thank you!


texts: LW/MW and FM antenna suggestion for old car radio (25 years old)

texts:
First of all, i want to listen in my house, you can forget a car. It has been in the warehouse for a long time. Yesterday i tried it. Although I haven't connected an antenna yet, it still works. Because of it has 10-12 cm antenna plug cable probably. As it stands, FM is listened almost perfectly, but i want to improve it. And my main goal is listen to LW/MW. Now i can't listen anything. My first question is:

How can i listen LW/MW bands? You can give me a advice about most effective antenna(it can be DIY, i will so happy), because i don't have enough experience about RF, i am young learner :D
Actually this is not a question i think. Can i listen LW/MW and FM with same antenna? It would be very good.


texts:
I am trying to create a program that contains UART using the PIC18f25j50 device. I have attached my creation so far which is a simple program that outputs a single character repeatedly to the console of a PC. The problem is the console displays a different character (þ~) to the selected one. This character stays the same despite the character that is selected changing (e.g "M" -> "þ~",  "g" -> "þ~").

My thinking is that it something to do with the clock or the baud rate but I can't see any error. I have a 8MHz crystal connected and the fuses are set so that there is no PLL. The baud rate equation is correct given that I desire the peripheral to be asynchronous, 8-bit and low speed (P.327 of the linked datasheet).

Would anyone have any idea where the mistake is or have ideas to try to fix this?

#include <xc.h>

#pragma config WDTEN = OFF  // Watchdog Timer (Disabled - Controlled by SWDTEN bit)
#pragma config PLLDIV = 2       // PLL Prescaler Selection bits (Divide by 2 (8 MHz oscillator input))
#pragma config STVREN = ON      // Stack Overflow/Underflow Reset  (Enabled)
#pragma config XINST = OFF      // Extended Instruction Set (Disabled)
#pragma config CPUDIV = OSC1    // CPU System Clock Postscaler (No CPU system clock divide)
#pragma config CP0 = OFF        // Code Protect (Program memory is not code-protected)
#pragma config OSC = HS      // HS
#pragma config T1DIG = ON       // T1OSCEN Enforcement (Secondary Oscillator clock source may be selected)
#pragma config LPT1OSC = OFF    // Low-Power Timer1 Oscillator (High-power operation)
#pragma config FCMEN = OFF      // Fail-Safe Clock Monitor (Disabled)
#pragma config IESO = OFF       // Internal External Oscillator Switch Over Mode (Disabled)
#pragma config WDTPS = 1        // Watchdog Postscaler (1:1)
#pragma config DSWDTOSC = INTOSCREF// DSWDT Clock Select (DSWDT uses INTRC)
#pragma config RTCOSC = T1OSCREF// RTCC Clock Select (RTCC uses T1OSC/T1CKI)
#pragma config DSBOREN = OFF    // Deep Sleep BOR (Disabled)
#pragma config DSWDTEN = OFF    // Deep Sleep Watchdog Timer (Disabled)
#pragma config DSWDTPS = G2     // Deep Sleep Watchdog Postscaler (1:2,147,483,648 (25.7 days))

void tx_data(unsigned char);

#define FREQ 8000000    // Frequency = 8MHz
#define baud 9600
#define spbrg_value (((FREQ/64)/baud)-1)

void main()
{
    TRISCbits.TRISC6 = 0; // TX pin set as output
    TRISCbits.TRISC7 = 1;   // RX pin set as input

    TXSTAbits.TX9=0;
    RCSTAbits.RX9=0;
    TXSTAbits.SYNC=0;
    TXSTAbits.BRGH=0;
    BAUDCONbits.BRG16=0;
    SPBRG=spbrg_value;     // Fill the SPBRG register to set the Baud Rate
    RCSTAbits.SPEN=1;      // To activate Serial port (TX and RX pins)
    TXSTAbits.TXEN=1;      // To enable transmission
    RCSTAbits.CREN=1;      // To enable continuous reception
while(1)
{
    tx_data('m');        // Transmit the same data back to PC
}

}

void tx_data(unsigned char data1)
{
    TXREG=data1;
    while(TXSTAbits.TRMT==0);
}


texts:
I am designing a non-volatile memory cell and foundry does not have model for floating gate . So I used the Voltage controlled current source to mimic floating gate. For output characteristics, I already had the measurement of previous fabricated custom made floating gate and I inserted the CSV file link for the measurements in vccs. Now for simulation I have to test the floating gate (vccs in my case) for process variations (PVT). For voltage it is simply the increment of voltage, for temperature I somehow scale the output based on the temperature value. But for process variation, it is not possible to use this vccs . So can anyone guide me is there any way I could mimic floating gate using simple P-MOS transistor of the technology I am using?.

I have found some papers online on simulation model of floating gate:

Cadence-based simulation of floating-gate circuits using the EKV model
Practical Simulation Model of Floating-Gate MOS
Transistor in Sub 100nm Technologies
A SIMULATION MODEL FOR FLOATING-GATE MOS
SYNAPSE TRANSISTORS
A Comprehensive Simulation Model for Floating Gate Transistors

Am I on the right track or I am missing something ? Anyone has experience in modeling the floating gate using simple p-mos ? or does anyone have better solution?

Thanks


texts: Is it safe to recharge a battery without a specific device?

texts:
I have 9V Li-ion battery. If I apply regulated 9V to it, will it recharge?
What about other kinds of rechargeable batteries?


texts: How can I simulate different realizations of these joint random variables with the given PMF?

texts:
If I have two Discrete Random variables X and Y which have the joint PMF:
\$P_{xy} = c(x^2 + y^2)\$, where \$x\$ belongs to {1,2,4} and \$y\$ belongs to {1,3}
I tried to make two discrete random variables but I am stuck on what is the next step.


texts: What is this foam ribbon cable alternative in an old Norstar set?

texts: I came upon some old Nortel phones and took apart one of the sidecars. The PCB is connected to the buttons and LCD displays using four sets of styrofoam-looking ribbon cables. They look like gross pink and black licorice candies. What is this sort of connector called? Just looking at one, you can't even tell that it's got multiple conductors. But I checked with a multimeter and it does. They adhere rather poorly to the PCB (maybe because the phone is about 18 years old).


texts: Is there a chip similar to the FTDI SPI to USB chips that integrates USB HID client device functionality (with µC interaction via some control protocol over SPI or UART)? FTDI chips cannot be used; see http://www.ftdichip.com/Support/Knowledgebase/index.html?canimakeftdidevicesappear.htm


texts: How do I turn a 4-variable k-map with don't cares into a simplified boolean expression?

texts:
The trouble I'm having here is that I don't know a method (well I do know I could do it the long way i.e w'x'y'z' + w'x'y'z . . .) for turning this into a simplified boolean expression. I've done some searches on the web and looked at some YouTube videos: there was this one method here, https://www.youtube.com/watch?v=dYJNJIkiv80; however, I'm still confused by it.

Update: (I've used the method where variables are not counted if the columns/rows are different.)

A big update to this: my solution even though it was correct was not the best solution: the professor did not like it, so when he went over this problem, he gave what should be the answer which in this case only has 4 literals:


texts: Do USB 3.0 male-to-male A-to-A cables swap SSTX and SSRX?

texts:
There are many USB 3.0 Type A male-to-male cables on the market (example on Amazon), but I can't find any information on whether they would switch the SSTX and SSRX lines, so that the SSTX pins on one side reach the SSRX pins on the other side and vice versa, or if they connect SSTX to SSTX and SSRX to SSRX instead.

I know that A-to-B cables have opposing pinouts for SSTX and SSRX, so I suspect that in that case the SSTX pins on the A site go to the SSRX pins on the B side, but I'm not sure whether this maps to A-to-A cables.

Is there a standard for this? How are they wired?


texts: 20V laptop power supply from four 5V+5A 'baby' supplies

texts:
I've got an old gaming laptop which comes with a  very annoyingly big brick PSU, rated at 100W and 20V. I do not care that the PSU is heavy, but it has a weird form factor, and I always have to drag it around. Looked around, and did not find any slim power units (besides, not including the PSU weight in the laptop weight spec is cheating, imho).

So I wonder if I can get four of these, seemingly high-quality, low profile PSUs, each rated at 5V and 5A (25W each), bolt them onto the laptop on the side, and wire them together to get 20V and 100W. Also, these are modular, so once the laptop dies (this thing just wouldn't die!) I would have many other uses for the PSUs.  I am not quite sure how to route the AC to them -- split the cable into 4 in parallel?

There was a topic on combining DC power supplies, but I wonder if, for a laptop, I need special precautions.

Thanks in advance!

http://www.farnell.com/datasheets/2286955.pdf


texts: Switching back and forth from 12v to 48v

texts:
I need to be able to power a claw (2 wires) with 12V constantly. But sometimes i need to power it with 48V to increase strength for a few seconds then go back to 12 V.

I looked for a few solutions but i'm not sure..

1) i could use 2 relays switch and wiring my claw to the two relays and then disabling the 12V relay and enabling the 48V one when needed ?

2) Using something like a motor driver (similar to L298N? but it can't handle that much voltage) and using the analogWrite / PWMwrite to change the "speed" aka the volatge sent ?

3) linear regulator?

Note: I'm using a raspberry to control everything.


texts: Problem with ADC of Atmega16A in differential mode

texts:
I am having some problem while using ADC interface of Atmega16A. I want to calculate RMS voltage of the power supply coming to my house(usually 250V, 50Hz) and display it on LCD. I am using the following circuit. But I am facing some problem that I don't understand at all.

I haven't shown all the connections here. A 16x2 LCD is connected to PORTB(D0:D7 pins of LCD) and PORTD(RS,RW and En pins to PORTD4,PORTD5,PORTD6). The problem is as soon as I connect the output pin of LM741, the voltage on this pin drops to zero as if the input resistance of the ADC is zero.

The ADMUX reads as ADMUX = 0b01010000.(REFS1:0 is 01, ADLAR is 0, MUX4:0 is 10000)  I am using 24MHz external crystal.


texts:
This was one of the questions for the repetition paper before the test.
"A lit light bulb has a resistance of 1320 Ω. It uses tungsten as a filament, and when hot, has a resistivity of 0.92 µΩm. Assume the filament is 2.0 cm long, how thick is then the filament?"

I work it out as follows:
Using the formula for resistance in conductors:

ρ = Resistivity
l = length
A = cross section area
R = resistance

R = ρl/A
A = ρl/R
A = 0.92 µΩm * 0.02m / 1320 Ω
A = 1.39×10^-11 m^2
A ~= 13.9pm^2

That's just ridiculous. The answer given by my professor is 4.2µm^2.
What am I doing wrong here?


texts: I have a BT137-600E and I want to know how long it takes to activate, the datasheet does not say anything about time rising or time falling


texts: How to measure the input impedance of a summing amplifier?

texts: I have a summing amplifier set up like so, and I need to come up with a test to find the input impedance, I know because its a 741 IC that it will be in the region of 250k - 10 mil ohms, but don't know how to test it and explain the test results


texts:
I found this type of pin in some 3 pin female connector. I want to buy it but I don't know what is name of this pin :)
Any idea?

(I put dimensions approximatively)

Here are dimensions of plastic connector:


texts: Missing top solder mask complaint when trying to order PCB? (PCBWay)

texts:
I'm really new to PCB layout and after creating my PCB layout and ordering it from PCB Way my audit was failed for reason "no top solder mask layer." What does that mean and how would I add that? If it helps here are my schematic and board design. Also in my zip file I had the .cmp file, .drd file, .dri file, .drl file, .gpi file, .plc file, .sol file, and .stc file.

Any help would be greatly appreciated, thanks.


texts: Intuition behind why nodal and mesh analysis work?

texts:
I'm looking for an intuitive explanation (not a proof) of why the equations produced by nodal analysis and mesh analysis are always linearly independent and always have a unique solution, if the circuit has a unique solution.

Again, please note, I'm not looking for a proof, rather an intuitive explanation.


texts:
My question is how to measure the SOC (State Of Charge) of a Li-Ion Battery. Now i know it is a very common question and i can google it. So i did google it and read about all the techniques for e.g Coulomb Counting Method and Open Circuit Voltage Method, also some adaptive methods like Fuzzy Logic Method and Kalman Filter etc. And after going through all the techniques i am planning to do it by Coulomb Counting Method.

Now my main question here is that i can calculate the SOC of my battery while i am charging or discharging it by measuring the current, but how can i get to know the SOC of my battery if i just connect it to my measuring system (i.e before the charging or discharging process is initiated) ? One method that comes to my mind is Voltage Translation (measure the battery's voltage and give a SOC value against that since the battery voltage changes with the SOC). This method could be quite okay when the battery's voltage is on the extreme positions of its charging/discharging cycle's graph, but the problem lies in the flat Voltage curve (which has a considerably long span) which would make it difficult to guess the exact SOC in the flat voltage region.

So can anyone give me suggestions regarding that ? I shall be grateful.

Thankyou.


texts: Charging LiFePO4 with high voltage but low current?

texts:
I'm trying to charge a 230 volt 24 kW bank of LiFePO4 batteries.
It's difficult to generate the right charging voltage because it needs about 250 volts and most inverters don't do that. It's usually 220, 230, 240, 260, 300.
I was wondering if it was possible to use a higher voltage inverter but count on the voltage drop from the current not being sufficient. If the supply current is lower than the demand, then the voltage drops.
The 230V 24kW LiFePO4 bank can absorb 7,500 amps at 1C charging. So if you hook up a 15 ampere 300 volt inverter, the voltage will just fall to the optimal charging voltage and current.
Do you think this is a good idea, or will it just melt the inverter from being run on permanent overload?


texts:
My objective is to program a single ATmega328P sitting on a breadboard. Due to my location and cash at hand I cannot acquire a AVR ICSP programmer so instead (through research) I found I can use a arduino as a AVR programmer and decided to use it.

The ArduinoISP sketch was uploaded to my Arduino Uno R3 successfully and the appropriate pins were hooked up to my breadboard.

I wrote a simple C program in Atmel Studio and compiled it to a intel hex file then proceeded to use avrdude to upload the file to the μCU. Avrdude reported a successful flash (verification successful as well) but the μCU doesn't seem to be responding.

The simple C program as below:

//Define CPU speed to 1 MHz (8 MHz internal with CKDIV8)
#define F_CPU 1000000

#include <avr/io.h>
#include <util/delay.h>

int main(void){
    DDRC = 0xFF; //Set all of port C to outputs

    while(1){
        PORTC = PORTC ^ 0xFF; //Toggle all of port C
        _delay_ms(500); //Delay 500ms
    }

    return 0;
}

Command used to send the flash to the Atmega328P:

$ avrdude -c arduino -p m328p -P COM9 -U flash:w:"compiled_file.hex":i

A single LED (with 220 ohm resistor) was hooked from ground to pin PC5. If my logic is correct this light should toggle on/off every 500ms but the light remains off. The LED has been tested and connection polarity confirmed (positive to pin, negative to ground).

As a side note, I also found that when I told avrdude to read the fuse settings on the μCU, they all registered to be 0x00, which is quite strange.

Any help would be much appreciated.

Update:

Through some experimentation I found that the command listed above was somehow telling avrdude to program the ATmega328P on the arduino uno itself rather than the ATmega328P on the breadboard. I've successfully reflashed the ArduinoISP to the Arduino so I'm back to step one. Does anyone know how to get avrdude to write to the ATmega328P on the breadboard?


texts: ON Semiconductor diode - markings 751 KE

texts: I can't seem to find this on the ON Semiconductor page. It's 4mm in length and about 3.5mm in width. Can you tell me how you figure it out, so I can learn?


texts: What is the best approach for reducing harmonic distortion?

texts:
I have a power system where on some buses, large converter driven machines result in high harmonic distortion. As far as I know, there are mainly two ways to reduce the harmonics.

A filter to remove (reduce) unwanted harmonics within a range of frequencies
Reactors to create a smoother wave form.

I'm wondering what are the pros and cons for the two alternatives, and are there any other (better) alternatives? I cannot change any of the existing equipment, but I can add equipment (criteria: smallest size then lowest cost). The converters are 6-pulse rectifiers without filtering, and cannot be substituted (12-pulse would typically give a smoother wave).

The filter will only reduce some harmonics, and I have problem with the 5th, 7th and odd harmonics between 25-37th. I could design a filter to reduce the higher order harmonics, but then I would be stuck with the high 5th and 7th components. (Or have a filter to remove the 5th and 7th, leaving me with the higher order components).

Reactors seems like the best approach, but almost all similar systems I've seen have filters. The size and weight must be as low as possible (even if that might increase the price of the equipment).

The equipment rating is in the range 800-1500 kVA and I have THD above 10%. There are no resonance frequencies in the network (the lowest is around the 180th harmonic).

Is one of the approaches generally better than the other. Will there be any significant difference in size for the two?

I hope someone has any views on this. Thanks!


texts: Determening some home appliances. Based on their power consumption behavior

texts:
I placed a current sensor on the main power line going into my household  and I m trying to use that data to determine if an appliance is pluged in such as a fridge or heater. It should be easy since a resistor would draw current diffrently then a electric motor. however the fact that all the currents are added up I cannot do it. The only thing I can detect is if a fridge or a heater is on from the huge inrush current they draw at startup.
And unfortunatly they are all at the same frequencies.

Any idea on how this could work would be helpful
Thank you


texts:
How does the current flow through this circuit and thus how do the components work together to cause the flashing LED?

I know the basics in that the current first charges the capacitor which consequently turns on the transistors, however I don't understand the role of the resistors or how the circuit works as a whole. Also, why does the current first reach the 2.2uF capacitor first?

Thank you


texts:
While disassembling a Sega Saturn to clean it, I removed this power switch:

I needed to separate the top grey button (1 in the image) from the rest of the switch.
After verifying with a multimeter that there wasn't any dangerous current on these components, I pulled like an idiot piece 1 with a lot of strength, and I think piece 2 made a sort of clicky noise, only to realized it would have been sufficient to widen the clips underneath the button to remove it easily.
I reassembled the Saturn, all works perfectly except for this switch, which I suppose have been mechanically damaged. When I press the power button 1, the console turns on, but only while I keep the button pressed. As soon as I release it, the Saturn turns off. I tried to tape the button down and it works indefinitely, until I remove the tape.
I would happily buy a replacement, but I can't seem to find it anywhere, and buy a broken console just to replace this seems like a total waste to me.
I have some questions:

what component is the black box (2)? I can solder, so I thought I could replace only that part, but I can't find anything similar. I'm a noob in electronics, is it a relay? I need the keyword to search for this piece. My understanding is that this thing has two states, which are toggled when pressing the button (piece 1), but now the state doesn't toggle and I need to keep it pressed down to have it "on".

Until I find a solution, is keeping the button taped down dangerous for me or the console? Can this cause more damage?

Is there a DIY solution to try to fix this thing given that is broken already? Heating, freezing, shaking, or other arcane methods from forbidden magic?

Bonus question: is the blue round component (piece 3) a capacitor?


texts: Broke my first soldering iron after 5 minutes of using it

texts:
I started getting interested in drones recently and I bought a soldering iron last week on Amazon.co.uk

After using it for 5 minutes to try pre-tin some copper wires, the solder was unable to retain the lead on the tip, it would just fold its self and escape the iron. Also the iron apparently got so hot that it melted itself.

Can someone give me me some tips on what kind of soldering Iron I should use (please not very expensive hopefully up to £100) and how to actually take care of it so this doesn't happen again. I want to believe that this is not just my lack of experience but also a very poor quality soldering product that I bought.


texts: TCL command in Libero SOC [Microsemi] to generate the IP cores

texts:
Does anybody knows the TCL command to generate the IP cores in a design for the Libero Soc tool of Microsemi (v11.4 SP1)?

So the IP core (e.g. a FIFO) is configured and in the design.  However, the output files has still to be generated before the synthesis and implementation can be run.

I'm missing this TCL command because I would like to run everything in batch mode.
Exporting the GUI instructions to a TCL file is  not generating that line of code :-9


texts: 120VAC latching relay controlled by a low voltage momentary switch

texts:
I have low voltage dry contact closure switches rated to handle 32V AC/DC.  I want to use these to control standard 120VAC lighting.  So I need a device that can take 120VAC, supply a low voltage signal to the momentary switch that in turn will control the 120VAC latching relay.

This all has to fit into a single gang switch box behind the wall mounted momentary switch.  Budget is not an issue, just want something that works and is of course safe in that environment.

Any thoughts on simple solutions to this?  Thanks..


texts: Resistors in an instrumentation amplifier

texts:
I'm designing a circuit where I'm using instrumentation amplifier to amplify my input voltage

The formula for the amplifier is $$\frac{V_{\text{out}}}{V_{\text{in}}} = \left(1 +  2\frac{R_1}{R_{\text{gain}}}\right)\frac{R_3}{R_2}$$

In the circuit, there are an overall 7 resistors but only one controls the gain. From what I can find online, to find the gain of the amplifier what they did is they set all 6 resistors equal to each other and hence only one variable is left.

What I don't understand is why did they all equal to each other? What determines the value of the resistors? Why didn't they randomise the resistors and if they did what effect would it have on the amplifier?


texts: Why is Capacitance Effect Modeled as Admittance Branch and Not as Series Impedance in Transmission Line Circuits?

texts:
I am reading the very basics of the transmission lines circuits. I am asking this question to know more about the fundamentals and to reason out the basics.

I have two questions:

(1)

The basic circuit of a transmission line circuit consists of the elements that cause losses of the transmitted voltage and current. I always see: cable resistance, inductance and capacitance. Why do I see the inductance and resistance modeled as just series impedance (which makes things so smooth and easy in circuit analysis... just a voltage drop by an impedance) but the capacitor element is modeled as an admittance and not like them?

What I know is this:

Inductance is modeled as a XL = jωL in the frequency domain.
Capacitance is modeled as Xc= -j/(ωC) in the frequency domain.

Mathematically, I can add up these two as one impedance but why do I see the transmission line circuits "insist" in putting the Xc as an admittance branch and not as series impedance? Why do they confuse us?

Is it:

Conventional thing?
Physical reasoning behind it? See this question what is shunt charging in power systems? I mean just to show off that it is a capacitor between the line and ground?
Mathematical Easiness? Y as an admittance is 1/Z. Okay? Would this cause the series Z to be flipped vertically in the circuit diagram? is this the reason?

Also,
(2)

As I was reading the basics, there is a Line to Line C and there is a Line to Neutral C. Are both of these two modeled in the circuit diagram in the same way..an admittance thing?


texts: What is the criteria of choosing a given pin pattern in ICs?

texts:
For example, why in the Atmega328P or other MCUs, the group of ports are not contiguous? Like PORTC and PORTB in the Atmega example:

Another example is this MC9S12ZV:

In particular, checking the PPn ports, the PP4 is far from the PP5 and PP2, and yet all of them have similar alternative functionalities (KWP and PWM), so is not that I see other functionalities which are spacially grouped. They seems random, yet of course are not, but I miss why.


texts:
Well I'm designing a PCB with SPI comunication between a mastar and slave. My question is about the SCLK trace. Does it Has to be the same length as MOSI and MISO traces? It is clear that the last two have to be the same length but I'm not really sure about SCLK.

I will be very grateful if anybody can help me.


texts: Multiple I²C slaves with different addresses VS. using a multiplexer

texts:
I'd like to interface a lot of identical I²C sensors, let's say 32, with a MCU that has only 2 I²C busses.

I can configure each sensor to have up to 8 different addresses. Hence I can have 8 sensors per bus or 16 sensors in total which is not enough for my application.

I plan to use a multiplexer or some sort of I²C buffer (described in this document, page 8) in order to increase the number of sensor I can interface.

However, I have now to choose in between several options :

Having 4 different sensor busses with 8 sensors each and using two 2-channel multiplexers (or buffers) on each MCU bus to switch between those 4 sensor busses.
Having 8 different sensor busses with 4 sensors each and using two 4-channel multiplexers on each MCU bus to switch between those 8 sensor busses.

Those are just examples, there is plenty of other configurations but the question is the same :

Is there a reason to prefer having more channels with fewer sensors on each over having fewer channels with more sensors on each ?

I tried to figure out if there would be a change in the max. update rate of my sensors in each configuration but I can't see any difference.

If some of you already faced this dilemna and/or has any element of answer, I'd be glad to hear it !

EDIT : the sensor in question is the TLV493D, a 3-axis magnetometer. A descritpion of the bus with up to 8 sensors is available at page 24 of the User Manual linked previously.

I have no precise idea of multiplexers yet but it will probably be something similar to the PCA954* family.


texts: How to trigger several cameras from a microcontroller

texts:
I have 3 Nikon D300 cameras, each with a remote trigger release cable used to externally trigger the camera. Inside these cables are 3 wires, shutter, focus, and ground. The shutter and focus are always connected as I do not need to use the auto focus. When the shutter and ground cable are electrically connected the camera triggers. The cables are very sensitive and only need to lightly and briefly touch to trigger.

I have tested the wires with a volt meter and there is 5V across the shutter and ground.

Therefore I need the microcontroller (a Frdm kl25z (very similar to Arduino uno)) to create a short between the two cables. I do not want to use external components such as a relay or transistor for various reasons, although I'm starting to think it's unavoidable.

What I have done for now is connect the 5V shutter wires to the Vin  (5V to 9V) pin on the kl25z, and the return wires on the camera to separate digital output pins on the kl25z. When this output goes high (5V) I assume the 2 pins become electrically connected, creating the short and triggering the camera.

The problem is that when I trigger one camera, they all trigger at the same time. I have noticed that the trigger is very sensitive, you only have to very slightly and briefly touch the two wires for it to trigger, so I think that when one camera triggers the noise is enough to trigger the others.

I considered opto isolating the 3 cameras, but I'm not sure where to wire them, or if this will even fix the problem.  Is there a better way to trigger the cameras, or will I have to use the opto isolators?


texts: Impedance of an Edge-Coupled Coplanar Waveguide With Ground

texts:
How can I compute the differential impedance of an Edge-Coupled Coplanar Waveguide With Ground?

I couldn't find any free calculator online, so I wrote a small program which computes the the impedances of an Edge-Coupled CPWG and compared the result of an example calculation with values I could find at http://www.edaboard.com/thread216775.html#post919550 (a screenshot of Si6000 PCB Controlled Impedance Field Solver). For some reason my result appears to be wrong.

So I tried the following manual computation with the same solution. Where did I go wrong?

I used the equations from Coplanar Waveguide Circuits, Components, and Systems from Rainee N. Simons (2001). The Edge-Coupled CPWG can be found at pages 190-193.

My Calculation

  Let \$h = 1.6, S=0.35, W = 0.15, d = 0.15, \epsilon_r = 4.6\$.

  $$r=\frac{d}{d+2S} = \frac{3}{17}$$ $$k_1 =\frac{d+2S}{d+2S+2W}=\frac{17}{23}$$ $$\delta =\left\{\frac{(1-r^2)}{(1-k_1^2 r^2)} \right\}^{1/2} \approx 0.992787$$

  $$\phi_4 = \frac{1}{2}\sinh^2\left[ \frac{\pi}{2h}\left(\frac{d}{2} + S +W\right)\right] \approx 0.176993$$ $$\phi_5 = \sinh^2\left[\frac{\pi}{2h}\left(\frac{d}{2} +S \right)\right] - \phi_4 \approx 0.007438$$ $$\phi_6 = \sinh^2\left[ \frac{\pi d}{4h}\right] - \phi_4 \approx -0.171561$$

  $$ k_0 = \phi_4 \frac{-(\phi_4^2-\phi_5^2)^{1/2} + (\phi_4^2 -\phi_6^2)^{1/2}}{\phi_6(\phi_4^2-\phi_5^2)^{1/2} + \phi5(\phi_4^2 -\phi_6^2)^{1/2}}\approx 0.786198$$
  $$\epsilon_{\mathrm{eff, o}} =\frac{\left[2\epsilon_r \frac{K(k_o)}{K'(k_o)} + \frac{K(\delta)}{K'(\delta)} \right]}{\left[2\frac{K(k_o)}{K'(k_o)} + \frac{K(\delta)}{K'(\delta)} \right]}\approx 2.800421$$

  $$z_{0,o}=\frac{120\pi}{\sqrt{\epsilon_{\mathrm{eff, o}}} \left[2\frac{K(k_o)}{K'(k_o)} + \frac{K(\delta)}{K'(\delta)} \right]}\approx 50.4850\qquad(\Omega)$$
  $$z_\mathrm{diff}=2\cdot z_\mathrm{odd}\approx 100,97\neq 89,67\qquad(\Omega)$$

  with \$K(k)\$ the complete elliptic integral of the first kind and
  \$K'(k)=K\left(\sqrt{1-k^2}\right)\$

I wasn't sure about the curly braces in the \$\delta\$ equation and just assumed the author went out of braces ;).

Quick Update:

I just found atlc. A very useful numeric Impedance calculator. I let it run

create_bmp_for_microstrip_coupler -b 8 0.35 0.15 0.15 1.6 0.035 1 4.6 out.bmp
atlc -d 0xac82ac=4.6 out.bmp

and the result is reasonable close to SI6000.

out.bmp 3 Er_odd=   2.511 Er_even=   2.618 Zodd=  46.630 Zeven=  99.399 Zo=  68.081 Zdiff=  93.260 Zcomm=  49.699 Ohms VERSION=4.6.1


texts: How can assign a synthesizable string to a byte array in SystemVerilog?

texts:
I want to initialize a byte array (or any other possible type) to a long string. For example define: string str = "abcdefg". I read these two links (1 & 2) but I couldn't find a simple way. These are two hard code ways which I found:

1_ byte str [0:7]; = '{"a", "b", "c", "d", "e", "f", "g", "h"};
This is not an appropriate way, because the string is very long in my real application and I can't write them letter by letter.

2_ Using string type :string str = "abcdefg". But it can only be simulated and isn't synthesizable. Quartus just allows defining string in function or task. So I use the function getStr() for initializing string :

typedef byte string_t[0:7];

function string_t getStr();
    int i;
    string tmp_str = "abcdefgh";
    string_t str;

    for(i=0; i<8; i=i+1)
        str[i]=tmp_str[i];

    return str;
endfunction

and use it in my code :

byte str [0:7];
always @(posedge clk) begin
     str = getStr(); // str will be "abcdefg" after getStr() return it.
     //The rest of the code...
end

I think there must be a better and simpler way for initialize a string in SystemVerilog. If you know it help me. Thanks.


texts: Error when trying to use Verilog from VHDL in Lattice Radiant

texts:
I'm trying to use an IP generated with the IP Catalog in Radiant, which was only available as Verilog, from my VHDL top level entity. I use it like this:

ebr_inst : ebr port map(....

The Verilog entity starts like this:

module ebr (clk_i, clk_en_i, wr_en_i, wr_data_i, addr_i, rd_data_o);

But when I try to synthesize it, I get this error:

ERROR - w:/projects/ice40serialtest/source/top.vhd(71):
ebr is not a component. VHDL-1235

I can use other VHDL entities in my project without a problem. This is the full project: http://www.frank-buss.de/tmp/ram-test.zip


texts: Detecting length of button-press using a microcontroller

texts:
I'm interested in creating a seek button panel (2 buttons - back and forward) that will connect with my Android's native music player, similar to the CD player in my car.

I'd like for the buttons to have dual-operations:

Seek backwards/forward in the duration of a specific track
Seek backwards/forward between tracks in a playlist

I'm contemplating on how this works in my car, in order to build it on my own - is there:

A different voltage going through the circuit when the button is pressed longer

or

Is there some sort of timer in the micro-controller's code that tells it to send a different order when the button reaches a certain period of time being pressed?

Please pay attention to both parts of my question - how this actually works, and how should I go about building it on my own - preferably using Arduino, as per I've got one lying around.

Feel free to correct me if I'm making terminology errors - I'm more of a web kind of guy, this hardware stuff is new to me.


texts: How can I power a USB cord from a 12v 2a power supply?

texts:
I'm new to the forums and have a problem I cannot find an answer to.

I am making a lamp with LED strips inside powered by a 12v 2a power supply.

I want to also power a USB cord with this power supply so I can charge my phone at night.

Is there an easy way of going about this so the same power supply can both power the lights and charge my phone?


texts: Voltage divider with short circuit part 2

texts:
simulate this circuit – Schematic created using CircuitLab

This question is a slightly modified follow-up to my previous question Voltage divider with a short, what is Vout?

In this voltage divider I was originally wondering what \$V_{out}\$ was when a short was created across points A & B.

With the short, the voltage at A is given by:

$$V_{A} = \frac{R4}{R1 + R4} \times V_{in} = \frac{200\Omega}{200\Omega+200\Omega} \times 5V = 2.5V$$

The CircuitLab simulator shows the voltage at \$V_{out}\$ as 2.5V, and I actually built this on a breadboard to test it out and indeed the voltage at \$V_{out}\$ is 2.5V.

What I don't understand, is why the voltage at \$V_{out}\$ is 2.5V, since it seems like all the current from A to B should be flowing over the short, i.e. the path of least resistance.  My intuitive expectation is that \$V_{out}\$ should read 0, or at least have a floating value, but this isn't the case.

Perhaps this is rightly a Physics question, I don't know.  But why is there a voltage on \$V_{out}\$?


texts: What could be the reason Micro-Cap is showing very different current from LTspice for this circuit?

texts:
I just try Micro-Cap SPICE simulator and trying to check it with LTspice.

I'm simulating this MOSFET in LTspice with 10Hz 12V gate voltage and the gate current due to MOSFET capacitance peak to 200mA as in the following plot:

When I simulate the exact circuit in Micro-Cap the voltages are the same but the gate current is not how it is in LTspice not even close. Here is the setup in Micro-Cap:

As you see the bottom green plot shows the gate current which is like noise:

What could be the reason I'm getting very different gate current wave-forms?


texts: symbol of a potentiometer with a buoy to work as a level sensor

texts: I am designing a circuit and I am going to use a potentiometer with a buoy to work as a level sensor. What symbol do I have to put?


texts:
I'm using an LM358 op-amp for unity gain (feedback to V-).  However, I'm getting some unexpected results.  When Vin is from 0v - 3.75v, op-amp output is as expected 0 - 3.75v.  However, when Vin is greater than 3.75v, op-amp output is capped at 3.75v, even though Vcc is 5v.  Can someone help shed some light to why op-amp unity gain can be less than 1?

LM358 datasheet can be found here:
http://www.onsemi.com/pub/Collateral/LM358-D.PDF


texts:
I am trying to control a custom made LED strip remotely. I already have an RC power pack with an output of 5V, but it only provides power as long as I hold the buttons on the controller.
I was thinking to use it to control a relay and use another power source for the LEDs.
I am, however, having trouble finding the right component (also because I recently moved to France and I am not sure of the names.) I saw some relays on Amazon but according to the comments they need a constant signal to keep it on, which is what I already have.
Can someone tell me if there are relays available to control DC currents and what are they called?


texts:
Okay, here's some background info leading up to the [obvious] question with further elaboration:
I have been using a 28 pin PICAXE for small projects here and there for the last couple of years and am ready to move up.  My current project is the PICAXE as a data acquisition module.  I have simply mounted the board inside an enclosure, and run the inputs and outputs to [a lot] of screw terminals on the outside for quick and painless component swapping.  (And for further visualization, I also built in a 5V regulator and put in a DC jack so i can hook up a universal wall wart for power and wired the USB connection to a mini-usb that can be plugged into from the outside.)  Well, interfacing with the computer is pretty much a pain with the PICAXE, and it can only be programmed with their official program.

So, I am going to upgrade to Arduino.  I was thinking the Arduino Mega Starter Kit because it seems like the most versatile, and I know that whatever board I get will be the board I will be using for a good while.  If I could do it over again, I would have started with the Arduino.

The things I am most interested in is data acquisition and sending data back to my computer, as well automation, which I know will not be an issue.  I have experience with C and BASIC but I prefer C; I am not sure if the there is a difference in language across Arduino's or not.  So, what would you recommend as the most versatile Arduino that will accomplish my current goals and keep me fat and happy on capabilities for whatever strange things I desire doing next?

As a secondary question:  is it possible to interface any (or all) of the Arduino's with LabVIEW?


texts: I am studying bjts and one thing keeps me troubled. Bjts are shown as 2 diodes put together back to back but when I study this (let's say for npn), it is okay for base current flow to emitter as the diode between them is forward biased but I see that no current should flow from collector to emitter as there is diode which is reverse biased in between collector and base, which is on the way to emitter from collector. However, we get a current flow from collector to emitter anyways. Can you explain so that I can better understand Bjt circuits.


texts: Is the reverse biased breakdown of a rectifier diode a reversible process? (that is if the voltage is reverted to a value within the specification range will the diode behave as expected of an ordinary diode? Or will it cease to be functional anymore) If no, then how is the difference of behavior between a rectifier diode and a zener diode implemented?


texts: yesinductane heating stainless steel bolts

texts:
I wish to heat 303 stainless 10 mm bolt to form an eye with 10 mm ID.

My gas torch just doesn't get the bolt hot enough for me to hammer it into the shape I need. So I would like to make an inductance coil running from the mains 220 V. I guess 2 kW power would be more than enough to heat the stainless bolt. I think the internal diameter of a hollow coil could be say 20 to 25 mm. I don't know the wire size or the number of turns of insulated wire I would need to make the coil.

I also don't know where is the most economic place to buy the wire I need.
When in use I would cool the coil by air from my compressor and I think that would not cool the stainless to much to prevent heating to bright red?
Can you assist me in designing/specifying what I would need please?


texts: Identify resistor with faded color bands

texts:
I would like to replace this resistor, but its color bands are faded. Does anyone know what resistor I should get for R31?

Thanks.


texts:
I'm trying to calculate the hysteresis of the comparator using currents but something isn't right. I'd like a little help to find the hysteresis thresholds without the simplified equations.

simulate this circuit – Schematic created using CircuitLab

The voltage at inverting input is:

\$ V_{(-)} = \dfrac{V_{IN}}{2} = 0V ...6V \$

The reference voltage is:

\$ V_{REF} = 8.2V \$

So, when the output of the Op-Amp is low we have a voltage divider as follows:

simulate this circuit

Then the current \$I_{1}\$ will be \$\dfrac{V_{REF}}{R_{4} + R_{5}} = 0.112 mA\$

So the upper threshold is \$ V_{th(H)} = 0.112mA * 72kΩ = 8.064V\$

When the output of the Op-Amp is high we have the following circuit. That I think is analyzed with the Superposition Theorem.

simulate this circuit

And the lower threshold is \$ V_{th(L)} = 8.252V\$. Is this correct?

Would it be different if it was a non-inverting comparator?


texts: How to find Vs in this circuit with current and voltage sources

texts:
The problem is stated as follows: Find the value of Vs in the circuit below such that the power supplied by the current source is 0.

I realize that voltage across the current source has to be zero for the power supplied to be zero. I've tried to solve the problem using nodal analysis by grounding the node in between the 3 and 8-ohm resistors and am getting an answer of -72 V (for Vs) but am not confident in that answer. Would solving the problem using KVL and KCL equations be better? Please help. Thank you.


texts: Compare register value using logical AND (&) and ==

texts:
// Hardware sets a RIS interrupt status bit
if(GPIO_PORTE_RIS_R & 0x10)
{
   // Software acknowledges the flag and clears the read-only RIS bit by setting ICR
   GPIO_PORTE_ICR_R = 0x10;
   // something useful
}

The above code should be self explanatory - the hardware flags a register bit, the software clears it. What I don't understand is why the code uses GPIO_PORTE_RIS_R & 0x10 to compare register value instead of GPIO_PORTE_RIS_R == 0x10.
== operation would probably equivalent to a CMP followed by a BEQ or BNE in assembly, or it can be SUBS with a branch by flagging the Z (Zero) bit.  Either way using == is straightforward and intuitive - I don't have to convert values into binaries to predict an outcome.
But with & and say if GPIO_PORTE_RIS_R = 0x20, the logical bitwise AND operation between 0x20 & 0x10 or 0010.0000 & 0001.0000 in binary will result in 0000.0000 or a false. And imagine if GPIO_PORTE_RIS_R = 0x30 or 0011.0000 in binary, the condition statement would return  true even if the two operands (0x30 & 0x10) don't equate. It seems as if the & operator checks if a register contains a value (or vice versa, a register is subset of a value). It's just confusing to think or use.
In what situation should I use & instead of == and why? And is there a simpler way to think about it?


texts: Art of Electronics - Zener Diode Example

texts:
I'm working through the Art of Electronics and I'm stumped by a zener diode example.

The text presents this circuit:

And then shows that the zener diode behaves like a voltage divider:

\$R_{dyn}\$ is the dynamic resistance of the zener diode.

1.

$$ I = {V_{in} - V_{out} \over R} $$

2.

$$ ΔI = {{ΔV_{in} - ΔV_{out}} \over R} $$

3.

$$ ΔV_{out} = { R_{dyn}ΔI} = { R_{dyn} \over R } (ΔV_{in} - ΔV_{out}) $$

4.

$$ ΔV_{out} = { {R_{dyn} \over { R + R_{dyn} }} ΔV_{in} } $$

Everything makes sense through #3, but I don't understand how we make the leap to #4. I'm probably missing something obvious, but if anyone can explain that last step I'd appreciate it, thanks!


texts: AC / DC adaptor, unexpected voltmeter reading

texts:
I'm planning on using an AC/DC power adaptor to power an Arduino and various devices.

Before actually powering up the Arduino with the adaptor I wanted to play with the AC/DC adaptor, as it has variable voltage setting (1.5, 3.0, 4.5, 6, 7.5,9 and 12 V), by using a voltmeter to check the voltage at different setting. To my surprise, the voltage readings were not 1.5, 3.0 etc..., but instead larger (5, 15, etc ...).

Is this normal behavior for an adaptor, do electrical devices labeled at 1.5 Volts initially require 5 Volts?


texts:
Wikipedia says the following:

  Conventional semiconductors like silicon have a bandgap in the range of 1 - 1.5 electronvolt (eV), whereas wide-bandgap materials have bandgaps in the range of 2 - 4 eV.

According to this table of semiconductor materials, however, there are semiconductors with both higher and lower band gaps, ranging from 0 - 6.36 eV. Where is the line? What is the criteria for determining whether or not something is a semiconductor?


texts:
I write embedded software that runs on a single board computer running Linux and talking to FPGAs. I do not do FPGA design, so I'm at the edge of my knowledge with this question: how do I program an FPGA without JTAG?
Background
At my previous employer, we had what folks called "chain flashable firmware" which meant once we had programmed it via JTAG one time, we could then forever after use software to update the FPGA's code, and next time it booted it would be running the new FPGA version. It took a couple minutes, but worked without issues (unless the power went down while you were running the update... then you were back to JTAG the next time around).
At my current employer, this "sounds crazy" to those who write FPGA code. Every time we have to update the firmware, we have to tear everything apart, connect to the JTAG headers, and burn the firmware. (Yes, I understand if we routed the JTAG headers to the outside we would have a much easier time... that's not what I'm asking here.)
I want to be able to do this via software, but don't know enough, and every time I search the web for "update FPGA without JTAG" or something like it, I get answers about consumer electronics devices and how to update them. Just not what I'm looking for.
To the best of my understanding, the FPGA code is simply loaded into flash or an EPROM or a CPLD of some sort via the JTAG header.

What is the mechanism folks use to update firmware without JTAG?

Is it just a matter of writing to flash?
Do we have to include some IP Core into the firmware that allows it to write back out to the place it reads its program from?

Is it a good idea to allow updating firmware without JTAG headers?

I don't have any issue with it, but some express reluctance. My view is if we can do it in software and save ourselves a ton of time and effort, let's do it.

Is there a MicroSemi version of Xilinx's SelectMAP? I think this might be what I'm looking for.

What am I not asking that I should have?

Note: according to this guys answer, this is totally doable, BUT in my case I must have the firmware up and running well before the software comes up, so I can't be dynamically loading the FPGA code from the software each time the FPGA boots. It needs to be stored in some memory the FPGA uses upon its boot up, not coming from software. The only time I want it to come from software is when I attempt to change what the FPGA sees upon it's next boot up.
Thanks!


texts:
A submarine (for example) uses a VLF communications system to remain in contact with its headquarters while submerged. The submarine drags a resonant dipole wire antenna behind it in the water. The Headquarters uses a resonant wire dipole antenna mounted on poles along the coast. The frequency is 20 kHz.

My first question is: How long (end-to-end) is the antenna at the headquarters?

and

If light propagates more slowly in water than in air, and if the speed of light in water is only ¾ as fast as in air, how long (end-to-end) is the antenna being dragged behind the submarine?


texts:
I was wondering if anyone knew what this type of connector is called.

One of the wires connected to this seems to have a tear, and I'd like to see if I can get a few of these connectors for future use.

The device that this connects to is a third party accessibility Xbox controller, which doesn't seem to be in production anymore. http://lpaccessibletechnologies.com/products/game-controllers/lp-pad
I've reached out to the company to see if they can offer me any support, so far nothing though. Was hoping someone on here might have some idea.

For extra detail, the contacts are more like blades than they are pins, and have a pitch of about 0.8mm/0.0315in


texts: How is the internet able to transmit data so fast?

texts: I'm not sure if I'm in the right place or not, but I figured someone here could maybe provide a good answer. I want to know how electricity is able to flow so fast. For example videos games nowadays, you can shoot someone across the world and they die almost instantly. How is electricity able to do this? I was trying to google this question but found poor results, that's why I am here.


texts: Skin/Proxmity effects near transformer core

texts:
The above picture shows a rectangular wire carrying alternating current wound across a core with permeability much much greater than of free space(and also assumed is the fact that the width of the conductor is much greater than the skin depth at this frequency). The current is flowing into the screen, denoted by a cross. The graph shows the current density distribution along its cross section. Basically, every transformer core and its nearest winding.

Why is the distribution one sided? Shouldn't skin effect be the same on both sides of the current carrying conductor? Why does the core affect the current distribution in this way?

I've been looking this up for a while now, and no one adequately explains this. When the concept of skin effect(due to eddy currents) was explained to me, it was shown as a completely internal phenomena. Current carrying conductors induce a magnetic field that links with the conductor itself and causes current to flow opposing the cause. Because currents flow in loops, the current in the center is diminished and current on the surface is exaggerated. Now, no one said anything about materials outside the wire here. And how these materials may influence fields inside. If someone could shed some light on that, It'd be much appreciated.


texts:
I'd like to design an RFID reader with 4 output antenna ports. My RFID reader's module maximum output power is 30 dBm.

My target is for the maximum output power in the antenna ports to be 30 dBm.

If I use an RF switch to configure the antennas, I will have power losses and the power of ports will be less than 30 dBm.

Can you recommend a way to switch between antennas that won't cause losses?


texts: In Kicad 5.1, how do you access the Net Class Editor

texts:
In Version 5.0, you accessed from the Setup Menu.  However, I cannot seem to find a way to access this at all in version 5.1.  The is no Setup menu.

Perplexed.
-Jim


texts:
I want to connect up a relay module (wired up to control a normal desk lamp) to an mbed LPC1768 board. I have the circuit connected up successfully using an Arduino via the Arduino's 5V pin. From the control perspective, all I am doing is turning on/off the lamp; I have no problem from the code side, just the electronics!

Mains voltage-->relay module-->lamp
                     ^--mbed

From what I have read, the mbed's Vout is 3.3V. Some of the other pins are 5V tolerant, but looking at this datasheet, it seems to say that the pin has the same tolerance as Vdd(3v3), which has a max voltage of 3.6V.

The other option I have seen is using the VU pin. As far as I can tell, it is a 5V Out pin as long as the board is connected up via the USB cable. If so, then that makes life a lot easier. I have read mixed accounts of whether it is Out or In, but most people seem to be using it to power 5V peripherals, so I assume I can do that then. I couldn't find confirmation of this in the documentation, though, so if anyone knows more about this I would be grateful.

Fail this, then I would appreciate any suggestions on the best way to boost the voltage to run the relay. I imagine I will need a MOSFET or similar, but I know very little about how to wire them up. I saw this, but it blew my mind a little...

I am also not sure on the current requirements, but as it runs from the Arduino without a problem then I don't think it is too much to imagine that it would also run from the mbed. Feel free to berate me for assuming anything if incorrect!


texts: What are the specifications of this type of LED strip?

texts:
I have found these strips. They have no part numbers on them, but the metal on the anode is marked with a black + on the top side centered next to the strip (not visible in the pictures).

This is how the strips look.

And in this picture you can find that each strip has 18 LEDs. To give an estimate of the brightness, that picture was taken with ISO 100, a Canon EOS 400D, the kit lens, aperture of 5.6 and an exposure time of 1/4000s.

I made a few tests with those LEDs to get a first good guess at their specifications. First, I started to figure out the voltage range at which the strip starts to light. To do this, I limited the current of my lab supply to 20 mA and gradually increased voltage until an effect was visible.

At 7V, the strip starts to light visibly, but not very bright. At 8V, it already draws the full 20 mA current my lab supply allows it to and is already considerably bright, already enough to make my eyes hurt slightly in a medium-lit interior room.

Looking at the voltage of white LEDs, I guessed that each LED might have about 3V of operating voltage. Judging from the above figures, I assume that the LEDs are arranged in a 3×6 pattern, that is, six sub-strips with three LEDs in series each.

To confirm that theory, I allowed the lab supply to supply up to 120 mA current to a strip and went up to 9V. A single (cold) strip draws 90 mA of current at that point. Letting the strip run for several minutes lets the draw increase up to 115 mA, presumably this would increase further if I gave it more time.

Hopefully, this information is helpful to answer the following questions about this part:

Ideally: What is the part number and the manufacturer, or even better, a link to the datasheet?
Less ideally, but also very appreciated: A good and reasonable guess on the actual specifications, that is: At which operating voltage and current do these strips normally run? I assume that someone more familiar with LED strips than I am might be able to guess some of this from conventions and my measurements.

If more data is needed, let me know.


texts: Interface 5v digital pulses to keyboard contacts?

texts:
I currently have the following bit of kit: Photoplethysmographic sensor for measuring heart rate
It outputs a 5v pulse each time your heart pulses. What I need is to do is interface this pulse output to a keyboard (So each time your heart pulses a key is pressed on the keyboard).
I have stripped an old USB dell keyboard and worked out what contacts on the keyboard PCB need connecting to simulate the key I am after.
I have drawn a circuit on how I think would be the right way to interface the two electronic circuits:

My question(s) are:

Will this circuit work as I intend it to?
Will the relay be able to switch on and off 50-120 times a minute?
Can you offer a better method of interfacing the circuits?


texts: Voltage through resistor connected to positive terminal of op amp

texts:
I have done quite a bit of research on this but I cannot seem to find an example or an answer at all. If I connect a resistor to the positive terminal of an op amp, since no current flows from the negative to the positive terminal, how does this affect the voltage of the two inputs of the op amp?

See the below figure:

Is the input voltage of the op amp just 0 volts, or does the 10 ohm resistor have an effect?


texts:
I am trying to start a new project and the entire library seems to have been deleted or something.  When I select ADD, I get empty page.

It was working fine last week and the only change to my computer since that time was video driver update.

I have tried uninstall and reinstall of Eagle 7.5 64 bits and the library is still showing empty. I think a setting somewhere got corrupted and the setting file was for some reason not deleted when I used uninstall.

I checked, the directory is set correctly, and the lbr directory is still full so I think Eagle program got borked.  Seems uninstalling and reinstalling did not help so there needs to be something else?


texts: I am currently working on a personal project and part of it involves battery charging and discharging. I intend to use Li-ion battery in my project. I've researched on various dedicated ICs especially in the BQ24xxx series. My concern is mainly in controlling battery discharge current from a fully charged battery. Are there any ICs capable of monitoring battery discharge current from batteries? Or is the discharge current from batteries dependent on the load?


texts:
How does one go about picking the limits for a HALT test?  Voltages, temperature, ramp rate, how much vibration and at what frequency?   Is there a science to it or some standards?  I remember one lab asking me if I had to do HALT style vibration or just vibration and I didn't know the difference.

I'm working on a piece of commercial outdoor telecom equipment (smaller than a breadbox).  I've done halt before but always just handed it off to the test lab.

After that how do I take the data I get back and come up with a screen?  That might be too broad of a question though so just the general idea would be OK.


texts: Value of LED current limiting resistor incorrect?

texts:
I am confused as to why the value of R297 is 1.8k in the circuit below:

Shouldn't the value of the current limiting resistor be = (5-2.35)/.025 = 106

Thanks