texts: Electro-Mechanical Connection: from screw straight up to electrical-wire?

texts:
I am developing a system that includes aircraft cables with threaded studs - screw endings that are used for mounting. Here is a picture of the stud connected to a cable:

Now I am searching for an elegant solution to make the electrical connection to the screw. I am looking for connectors that would allow to go straight up from the screw ending
(instead of sideways with ring/spade terminals). Basically I am looking for a nut-wire connector. Ideally something that would help with isolating the whole connection, while still looking pretty as it will be visible.

Anyone aware of such a product? We are calling it the 'magic nut' here and we are still hoping it will pop up from somewhere! :)

Any tips, comments would be very helpful!


texts: Why can't absolute delays be used in ASIC?

texts: Verilog allows the definition of absolute delays when modelling hardware but the ASIC synthesizer will strip these out. Why does it do this?


texts: Any Problem With Two PMOS Sources Tied Together?

texts:
This is my third revision of this supply switching circuit. Do you guys see any problem with this revision?

This is a circuit to switch from disposable lithium battery to USB power when the device is plugged into a computer. Q1 and Q2 are PFETs. When there's no USB power, both FETs Vgs is -3.6v. When USB is plugged in, the USB interface IC sends 3.3v to the FETs gates, sufficiently turning Q1 and Q2 off. VBUS is a regulated voltage from USB. The diode to is keep from back feeding the regulator when there's no USB power.

I can't use an ORing diode circuit, I cant afford the parasitic losses. The losses from the diode on VBUS are fine since it won't be from the battery.

Thanks guys


texts: How can I find the right resistor to make 50% brightness in an led? I know how to find the right resistor to get the brightest but I'm wanting to find the perfect middle.


texts:
In a design I have, I am using a memory arb (receiving mem requests from two masters) What are the pros and cons for each of the follwing:

use a mux for the read data of each master, so that if the memory is sending data to the second master, the bus connection to the master will not toggle

pro - maybe save power consumption on the frozen data bus from the mem to the unused master? or does the addition of the mux spend more power?

con - maybe create latencies for the timing calculations of the data
send the data from the mem to both masters every time it corresponds to one of the masters (along with a valid bit for each master)

pro - better timing?

con - more power consumption?


texts: Why there is not a sqrt(3) factor between rated currents on the delta-wye transformer?

texts:
When calculating the rated current on either side of a delta-wye transformer, we will use the following equation:

$$
I_{LL}= \dfrac{S_{3\Phi}}{\sqrt3*V_{LL}}
$$

Since this same equation is used for either the delta and the wye side, there is no square root of 3 factor between these two currents. For example, if the high side is 66 kV and the low side is 12 kV, then for a 28 MVA transformer, the rated currents on each side will be:

$$
I_{LL}= \dfrac{28\ MVA}{\sqrt3*66\ kV} = 245 A
$$

$$
I_{LL}= \dfrac{28\ MVA}{\sqrt3*12\ kV} = 1347A
$$

So according to this equation, the only factor between the line to line currents of the low and the high side is the transformer ratio, which happens to be 5.5 in this example. My question is, why isn't the square root of 3 also a factor?

For example, if we were to find the rated current of the high side to be 245 A, then shouldn't the rated current on the low side be given by:

$$
I_{LL}= \sqrt3*Tranformer\_ratio*245 = 2334 A
$$

Why do we ignore the square root of 3 factor between the high and the low side of a delta-wye transformer when calculating rated currents?


texts: How to clip a portion of waveform and pull it to zero level?

texts: I've generated a sawtooth waveform of 5v and i want to allow 1.5v to 2.5 v and rest of the voltage should be detected as zero. I tried using clipper but it didnt get desired result. Is there any circuit which works like window clipper? How do i get the above result?


texts: Identify capacitor for really old motor?

texts:
A friend has acquired a really old table saw / jointer combo that was apparently made in the 1940s/1950s. The motor is a dual shaft arrangement where one side runs the table saw and the other runs the jointer. Attached to the motor is a large capacitor that sealed and painted and has no markings. The capacitor is dead and I'm trying to figure out the best size replacement and whether it was a start or run capacitor. Because of the dual shaft arrangement, I can't see an easy way to get into the motor to see if it's got a start switch and I'm at a loss how to size the replacement capacitor.

A photo of the motor plate is attached.

Edit: Included more pics of the motor, wiring and capacitor. I had to destroy the case to get into it (which I was trying to avoid), and once inside the capacitor has no markings at all on any surface.


texts:
Our circuit has three supercaps in series across the Battery+ and GND rails.  The average current draw is very small -- around 250uA -- with peaks of 20 mA.

Short form

Do we need load balancing across the supercaps?

Details

Our battery powered system needs to last for > 2 years, so minimizing current draw is crucial.

We've included the supercaps to soften the peak load on the batteries when the WiFi radio kicks in (about 40 mA), but most of the time, the system is in deep hibernation and draws about 50 uA.

The three supercaps are 3F, 2.7V devices, in series across a (nominal) 7.2V supply rail.  In the units I've measured, the voltage drop across each capacitor is close to 7.2V / 3 = 2.4V, so -- at least for now -- the voltages are balanced.

But I'm concerned about variations due to ageing.  Is it important to provide a load balancing mechanism, or will the capacitors continue to self-balance (as it appears they are doing now)?

If load balancing is important, then what technique do you recommend (keeping in mind that minimal current draw is crucial)?

Putting a 2.5V zener with a sharp knee across each supercap would offer protection in case things got really unbalanced.  Similarly, a 1M resistor across each supercap would offer some balancing and would only increase the current draw by a couple of microamps, so that's also acceptable.


texts:
In my application the 16-bit ADC would have enough resolution, but is there any pros choosing 24 bit ADC over a 16 bit ADC, if they otherwise have the same specs?
Both of these would be suitable for my application.


texts:
Previous to my question on stepping down the voltage from 4.5V to 3.3, this was for the VCC pin of the MPR121 IC. Do I need to step down the voltage for the SDA, SCL and IRQ pins of the chip and if so, how would I go about doing it?

EDIT: I'm connecting the MPR121 keypad to a PIC project board (Genie 20).


texts: Chaining Multiple USB Hub Controllers for Serial Interfacing

texts:
I have a need for a large amount of serial I/O from a desktop computer in a robotics application. I considered using all off the shelf parts with a large set of USB hubs and usb to serial adapters, but off the shelf solutions were too large.

I need about 26ish, maybe more channels running anywhere from 9600 to 115200baud. To fit in the tight space I was considering getting some USB hub controllers, and putting them on a circuit board with the usb to serial ASICs.

The host computer is a mini itx intel based machine.

My current concept involves this 4 channel USB 3 hub controller:
4 Port USB 3 Hub
And several 7 port USB 2 hub chips:
7 Port USB 2 Hub

The 7 port hubs would be connected to the super speed 4 port hub ports, thus giving all the USB endpoints I need. The USB to serial ASICs (FTDI or similar product) would be directly connected to each 7 port hub controller port. I know that FTDI for instance offers multi channel usb to serial devices, but I don't know if each USB channel enumerates as a separate device in linux (as in a seperate /dev/usbttyx device)

My questions is, how difficult is this hardware to implement? I've done some differential signal design before, but never USB speed fast. I was also considering having separate control of the power to each hub controller so they could be separately reset if needed.

Are there any traps I need to watch out for specific to working with these USB chips? This will be my first board design that has USB on it.

Thanks!


texts:
The PIC18F family I guess has high and low priority interrupt-service-routines, not just one ISR.  My first time dealing with this and I can't seem to get the compiler (XC8) to recognize the two difference interrupts from some legacy code.  Basically, I don't know where to look when hoping to figure out what to tell the compiler to mark these two functions as interrupts?

#include <xc8.h>
...
__interrupt(high_priority) void MyHighPriorityIsr(void)
{
// stuff
}

__interrupt(low_priority) void MyLowPriorityIsr(void)
{
// stuff
}

I'm getting:

error: (285) no identifier in declaration
error: (1275) only functions may be qualified "interrupt"

Page 34 of the compiler's user guide make it seem fine, but I'm getting errors and can't compile:
http://ww1.microchip.com/downloads/en/DeviceDoc/MPLAB_XC8_C_Compiler_User_Guide.pdf


texts: Steady State RLC Circuit With Dependent Current source

texts:
I'm trying to figure out the reason why in the following circuit, at steady state, the current ix is zero. My best guess is that because there is a parallel branch which by KCL should equal 100ix and would be zero because of the open circuit provided by the capacitor.

However, this seems counter intuitive because wouldn't the electricity want to go around the outer loop. And in this case, how do you deal with a loop that has a dependent current source dependent on its own current? Is that even possible?

Thank you!

Here is the circuit:


texts: How to determine necessary electrical components for breakout board

texts:
With the fairly recent emergence of the Arduino/Raspberry like boards, I have a new found interest in circuits/electronics. I took some introductory classes back in undergrad and I'll be honest, it was rather difficult. That being said, I feel my question is rather simple for a seasoned electrical engineering, but I'm having a hard time finding a straight answer.

When I buy a breakout board that consists of an integrated circuit (IC), often there are capacitors, resistors, etc. placed inline with the header pins. What purpose do they serve? Why don't they put those components in the IC to begin with? The seller of the breakout board does generally forward datasheets on the IC itself but there isn't much said about the additional capacitors, resistors, etc.

Hypothetically, lets assume I wanted to build my own breakout board for a Arduino/Raspberry based on a select IC. How would I know what additional capacitors, resistors, etc. are needed to make the breakout board functional? What kind of questions do I need to ask myself in order to layout the circuit(s) connecting the IC to the header pins? I know it's dependent upon on the IC and the target board, so I'm not looking for a specific answer, but what if I change the target board? What if I change the IC? How do these influence the design?

Basically I'm trying to get a better understanding of the additional capacitors, resistors, etc. found on breakout boards. I can do more research on my own, but I would at least like to get a general explanation to help guide me with further research.


texts:
I have two signal sources providing the same differential audio signal (VIN1 and VIN2). I want to sum those signals. The result (VOUT) shall also be differential.

The idea is to take a fully-differential op-amp and to sum the inputs just as you would do it in a single ended inverting adder configuration.

Will this work?

A quick LTspice simulation seems to work as expected. However, I could not find any examples on the internet, so maybe I am missing something?


texts: Can electric bulbs be powered by connecting the negative terminal to earth?

texts:
I have a very fundamental question, will an electric bulb glow with one point connected to the positive terminal of the electric line and the other point to earth? In my school some 10 years back I learnt that we are connecting the two points of the bulb to positive and negative to make the connection closed.

As earth is considered as a huge potential of ions it could be considered as the negative side. If my thinking is wrong then why do the LEDs glow in the tester? In the tester we touch the tail which is indirectly connected to earth.

Note I dont know what the tester is called in other countries. The Tester is a small instrument to check if the current flows in a circuit or not and is size of a pen.


texts: Cascading ADC's to get higher resolution

texts:
Suppose I have a pair of 12-bit ADC's, I can imagine that they can be cascaded to get <= 24-bit output.

I can think of simply using one for the positive range and the other for the negative range, though there probably will be some distortion in the cross-over
region. (suppose we can ignore are a few error bits or, perhaps, place a 3rd ADC to measure the value around 0 volts).

Another option I had been thinking of is using a single hi-speed ADC and switching the reference voltages to get a higher resolution at lower speed.
Also there should be a way of getting a real-valued result with using one fixed-ref ADC and then switching the aref's of the secondary converter to get more precise value in between.

Any comments and suggestions are welcome.

I am presuming that a quad 8-bit (or dual 12-bit) chip is less expensive then a single 24-bit chip.


texts: How to set the sampling frequency for this filter+

texts:
I need to make a passive LP anti-aliasing filter(recommended cut off freq.).

Filtered signal from an hotwire-anemometer will be measured by DAQ has 100Meg input impedance.

The thing is that my sampling freq. twelve khz and I'm not sure it is fine enough. At which freq. should the stop band start? How to decide the adequate sampling freq. for this

to be updated...


texts: Estimating Li-Ion (or any other type) battery resistance

texts:
I have a Li-Ion battery cell, with a given datasheet providing the following discharge curve:

I thought to estimate its DC impedance (resistance) by, at a given capacity, making the ratio between the delta between open voltage vs voltage at given load, and its current. So, considering for example the  discharge rate of 1C:

\$ R = \frac{V_{noLoad} - V_{1C}}{I_{1C}} \$;

But considering that from the datasheet I have only the 0.2C as the most light load, I thought to use 0.2C voltages instead of the no load voltage (open voltage):

\$ R = \frac{V_{0.2C} - V_{1C}}{I_{1C} - I_{0.2C}} \$.

I'd like to know if I am completely off-road, and maybe suggestions on the topic.
Moreover, analyzing some points at different state of charge and different loads, seems that higher the current, the higher the resistance, as shown also from the curves. But also that with a higher current, the average resistance is lower, despite the increased drop.

It may be not so precise, but it could be useful since I would like to find just an upper and lower bound on the resistance values.


texts: How is the current adjusted from a power bank with adjustable current?

texts: When using a power bank with adjustable current I'm just wondering how the current is adjusted? it can't be anything to do with resistance of the recieving component because this would be constant, using ohm's law is this done by increasing or decreasing the voltage from the power bank?


texts: Above is an excerpt from a textbook. My question is, why is that when we plot H(w), we need to think of it as a complex exponential???, can't we just plug in values for w and t, evaluate it, and then plot it?? (I thought that if we are going to plot H(w), we simply substitute the value of 'w' and assume t as constant and then plot the corresponding value to the w axis)... If we think of it as a complex exponential, the magnitude is 1. But what if H(w) is not of the form "", but it is in the form of . How can now we plot it? (It has no complex exponential on it so theres no way to regard for magnitude and phase.)


texts:
I made a 1 phase to 3 phase inverter using arduino and IR2104 to control the speed of an induction motor and it is working perfectly.

To complete the protection scheme, I need to monitor voltage of each phase to protect motor if one phase is lost due to malfunction of IGBT or something else.

In addition, I need to monitor current for overcurrent protection.

In case of voltage I know that it is possible to use optocoupler to convert high level voltage to logic level 5 VDC. Is there any better and simpler practical method to monitor voltage and current of each phase for such application?!


texts:
It is possible to design networking systems that only use two wires: one for data and one for a common ground. Examples include 1-wire and Pin&Play. These are called single wire systems because the requirement for an earth wire is implied too. But you can also get systems to extend home networks that use the home earth to connect network points, like Power Line Communication. How is this possible over just one wire?

== EDIT ==

From the answers (thanks!) I think I failed to word this question clearly. Let me try again.

Can you send data usefully over one wire, literally one wire? Radio is zero, 1-wire is two, but is it possible with one? "No, and here's why" or "Yes, here's how it is done in X" are the kind of answers I am hoping for.

(N.B. I'll also change the question title from "Single wire systems need two wires; so how does ethernet over ground work?" to "Can you send data usefully over one wire, literally one wire?")


texts:
Screenshot:

and a link to the live simulation:
http://everycircuit.com/circuit/6287241984868352

I have been told there is a body diode inside however my simulation shows power travelling from drain to source and vice versa. I thought there was a body diode inside that would only allow for current in one direction.


texts: Frequency locked loop for input jitter rejection

texts:
I have an application where I want to multiply from a xtal oscillator
at 32KHz to a system clock of 40MHz. A standard PLL isn't going to do the
job, because the 32KHz jitter is measured in ns. Since the PLL multiplies
up the phase noise, and the output period is much shorter, the output will
get swamped in noise from the reference - even if the PLL adds no noise at all.

I saw a few patents and designs kicking about which are for a frequency locked
loop, and the claim is made several times that these designs are insensitive
to input jitter, presumably because they use input counters rather than
the more traditional PFD of the PLL.

Can anyone explain to me how a FLL would reject input jitter without
having the reference divided down by some big integer? If that is done, then
the feedback also needs a big divide ratio and VCO noise at the FLL
output will rise (due to very low correction frequency). Ideally I would like
the reference divided by unity and the feedback by 125, output frequency
can be a few % off if necessary, its just a micro system clock.


texts: How I can get access to failure data of high-k dielectrics caused by tunneling (trap generation)? I need a dataset for my research. (if someone could help me with the data, his/her name will be mentioned in the acknowledgment part of my paper).


texts: Can I use this h-bridge variation for power inverter application?

texts:
(of course replacing the motor with the load..)

Why most inverter circuits use the classical four switches not any other variation as this one as example? i just want to reduce the number of signals to control the bridge. The classical one needs 4 signals (people refuse to connect the gates of similar states together but i don't know why..)

also, Is there any reason to prefer h bridge over push pull configuration?


texts: How to interface camera sensor to microcontroller

texts:
I want to make robotics vision project. Ideally one would want to go with hi tier expensive sensors, they have no such problem, because they are interfaced directly to x64 CPU, via PCIe bus. Thus, raw pixel data can be easily further pushed, for example, to GPUs array, for really powerful processing schemes. Extremely straightforward thing, but very expensive.

To get started with some prototype, I would choose some cheaper sensor like OV2710. But they have problem, between sensor itself and a cpu there exists some "malware layer" which ruins raw picture to MJPEG or something like this, as well as unwanted usb slave->cable->host.

I would like to do my own encoding/compressing scheme with some ARM cortex MC, for example raspberry PI. It has GPIO interface. I wish to unsolder all unnesesary USB stuff from that sensor, and wire it directly to the raspberry GPIO pins. Then cut central 512x512 pixels area, and have it in Pi RAM updated at 120fps. Can I do like that? Is there some "internal" raw sensor protocol? How is it called? Or should I go another way?


texts: What's the risk of leaving VPP/MCLR floating?

texts:
In the microchip PM3 ICSP design guide, this diagram is shown to demonstrate a typical implementation of ICSP:

Here, the MCLR/VPP pin is pulled to 5V during normal operation, but isolated when the high voltage for programming is supplied.

A similar setup is shown in this document. But I've also seen quite a few circuits taht completely omit this feature and just leave MCLR/VPP floating when no programmer is connected, like this:

Why should I not do it like that? What possible negative effect could this have on the operation of my circuit?


texts: What happens to the electrical grid when I turn on a heavy load?

texts:
I'm trying to understand exactly how an electrical grid works, and I'm having one simple question that is challenging me. What happens when a new load appears on the grid? I know in practice that any single small load doesn't matter, so let's say it is either a small grid or a huge load. I'm assuming whatever is done it is enough to affect the grid in a measurable way.

My thought is that the new load will attract more current on the power lines, going all the way back to the electricity generator. In order to provide the same power out, the voltage will effectively drop slightly. Measuring the current level of the voltage along several lines is a good way to determine the load, which will let the grid know if power plants need to operate at higher levels, or turn on additional power plants. When a new plant comes on, it will come on slowly, which will allow for more current to pass through the devices, and increase the voltage on the system somewhat. If the same load turns off then later, then less current is running through, which will increase the voltage. Is this understanding even remotely close?


texts: Why does the resistance of a brushed Dc motor from an experiment kit vary?

texts:
I am currently performing an experiment in which I measure the Current and Voltage of a motor that experiences changes in load. I am using a 3V (3V battery) supply however the voltmeter's (connected to the terminals of the motor) reading changes from 3V at no load down to 1V at max load. I understand how the current changes since less back-emf is produced at lower speeds. I also understand how using V = IR could result in that change of Volts. But wouldn't that require constant resistance and that is not the case with the values I have. For example, I tried calculating R using the equation and each time I got a different answer, Which itself increased in respect to the load. Is this a case of simple experimental error or am I missing something rudimentary? And if the voltage is changing is calculating power with
P = I*3(V) all through the experiment incorrect?


texts:
As seen in this picture, I have a circuit that has created those desired pulses in the output. There is a last stage in my circuit and that is:
Translating the times that more pulses have happened to "1", and the times that fewer pulses have been received to "0" (for examples as seen in the picture). in other words I need to get the second signal in the picture as my output (Latency is not important, but the width is important).
I tried low pass filtering the output. but it doesn't give me a square wave.
I thought of counting the pulses. (more than 5 pulses in 50 nanoseconds would translate into "1"). But I don't know if it can be done using a Verilog-A cell view in Cadence.

Update:  This is a Super-Regenerative Receiver (SRR) which mostly works with an oscillator that periodically turns on and off. when there is an input signal, the oscillator triggers sooner compared to when there is no input signal. Then there is an envelope detector that tracks the envelope and compares it with a reference voltage. then the output of envelope detector is fed to a comparator which creates these pulses in the first picture.

now I need to demodulate these narrowly spaced pulses as high value and the widely spaced ones as low value.
I don't know how to do that.:(


texts:
I thought I understood the concept but wikipedia has confused me. There are two outputs because one's for a partial sum and one's the carry bits. But why must it be used to "compute the sum of three or more n-bit numbers" why can't it compute 2 n-bit numbers?

Also the example given under the basic concept (where the result is 21122120202022022122111011102212) confuses me more because that is just one output, not two?


texts: Having trouble constructing this sequential circuit

texts:
I am to construct a sequential digital logic Moore circuit for the back lights of a car based on the following information:
We have input: x2, x1, x0, I decided to make x0 simulate the right turn signal, x1 the left turn signal and x2 the brake pedal.
We have ouput: z5, z4, z3 z2, z1, z0
The output is supposed to be connected to 2 groups of LEDS, I decided to make z5,z4,z3 the left group and z2,z1,z0 the right group.
So this is how it's supposed to work:
If x0 = 1 and x2 and x1 = 0 then the z2,z1,z0 should sequentially light up starting with the inner LED first (z2)
If x1 = 1 and x0 and x2 = 0 then z5,z4,z3 should sequentially light up starting with the inner LED first (z3)
if x2 = 1 and x0 and x1 = 0 then the back lights will light up constantly
If either turn signal is high (x1 or x0) and the brakes (x2) is high too then the turn signal should light up sequentially as before but the other 3 LEDS should light up constantly.
I made a picture describing the situation here:

Now I have been trying to figure this one out for a while now but I end up getting a machine with at least 16 states which I feel is way too much. Is there something I'm missing?


texts: LM35 temperature sensor strange behaviour

texts:
I have a set of LM35 temperature sensors hooked up to an Arduino. I find it hard to believe all 3 sensors are broken.

The Arduino code is very simple.

void setup()
{
  analogReference(INTERNAL);
  Serial.begin(57600);
}

void loop()
{
  Serial.println(analogRead(5));
  delay(xxxxx);
}

The LM35 is connected correctly, but the values received by the Arduino are highly inaccurate. As is is ~20°C, the output should read 180-190, as the Arduino has a 10 bit ADC from 0 to 1.1V, and the LM35 outputs 0.1mV/C

I have plotted the output of some scenarios with different circuits and delays for your viewing pleasure. The y-axis is simply the ADC output from 0-1023.

Fig 1.

The 10ms between reads had an average value of 185, which is correct. Looking at the plot though, I believe this to be coincidence.

The fixes suggested on the datasheet and in other stackexchange questions such as
this, it is suggested to put a 1μF capacitor between the ground and data lines, which leads to this plot:

The spikes at the start are due to me touching the circuit I believe.
However notice the steady increase above 200 (room temperature).

Finally I constructed circuits 12 and 13 from the datasheet.

12 gave this result:

Circuit 13 with an RC filter constructed of 5 parallel 330ohm resistors and a 1μF electrolytic capacitor gave a steady reading of 10 or 1°C, which is incorrect.

It looks to me like I am sampling a higher frequency oscillation, but I cannot seem to dampen it with a filter without killing the signal.
Any help is appreciated. Thanks.


texts:
I've got an old stereo that doesn't have a remote control. There was a model that did, and after looking at the service manual it looks like I just need to populate a PCB with an IR receiver to add that functionality. However the part isn't available in quantities smaller than 1000. I think I found one that has pretty similar electrical characteristics. What are the chances this could actually work? And yes, I realize I will end up spending a lot more effort attempting this than just getting off the couch and turning down the volume.

Some details: radio is a Sony CFD-G30. The CFD-G50 is the version with a remote. The service manual is very detailed. Here are some relevant images:

I haven't cracked it open yet, but looking at those images it looks like possibly I just need to add the IR receiver a couple resistors and capacitors and a $.05 transistor (KTC3198GR-AT). The IR receiver called for is NJL63H400A which I can't find stock for but the one I found in stock for single quantity is RPM7140-H8R.

I'm most interested in knowing whether IR receivers are pretty interchangeable or if there's a lot of tuning at the micro-controller level to work with a specific part, which would make this endeavor quite fruitless.


texts:
Some background

I have simplified understanding of inductance which is incorrect yet has been a useful falsehood so far. The idea is that a changing flow of current through a loop creates magnetic flux through the area of the loop and the change in this flux in turn induces a voltage in the loop. The effect is proportional to the area of the loop and thus quadratic in the number of turns of a solenoid. Roughly I would say the inductance of a loop would be naively calculated as so:

$$ L = \frac{\mu_0 r_{loop}}{2} $$

However much more complicated formulae are typically quoted, for example:

$$ L = \mu_0 \left[ \ln \left ( \frac{8r_{loop}}{r_{wire}} \right) - 2 \right] $$

Clearly I'm wrong, as if you consider the inductance of a 1m loop of 1mm wire my formula gives an inductance of 0.1uH and the real formula gives 1.02uH, which is quite a difference. This gross misunderstanding may or may not be relevant to my question.

The actual question

I frequently see talk of partial inductance and this confuses me. I have no problems with a 1uH SMD inductor for example (so long as it is electrically small), as I just imagine that if you connect it in a loop then the inductance of that loop will be 1uH larger than it would otherwise be, or as the length of the loop tends to zero the inductance will tend to 1uH.

However there exist tools such as FastHenry which can take an arbitrary geometry and assign inductance to each individual wire, despite the presence of switches in the circuit. How is this possible, given that surely the inductance should depend on which route the current actually takes through the wires and the resultant loop area? For a realistic motivating example you can imagine an integrated circuit where the switches are MOSFETs that source and sink current to/from the power rails in some unpredictable fashion, and people care deeply about the "inductance" of a particular power or ground wire.

Is this really possible, or is there some horrible simplification that has occurred when people talk about 'partial' inductances? If this really is a self-consistent method what is the right way to think about it and the justification for it? And, if scope allows, what is the right way to think about inductance in general?


texts: My power supply doesn't start: sleeved wires

texts:
electrical engineering community.

I would like to ask for your help in this matter - my computer PSU does not start.
I got an old PSU which I'd like to make something very useful of it:
transforming it in a lab bench power supply like the one in this video. I started by cutting the heads of the wires and sleeve them. Next, I tried to start the PSU by wiring the green cable (power-on) to a black cable (ground), but I had no success... I wonder if it has some protection activated or if I can't have the other wires disconnected.

Thanks in advance.


texts: How does resistive feedback affect noise figure?

texts: I am working on a design with cascode CS amplifier with resistors in the feedback. What are the advantages and disadvantages of such topology? How the resistors in the feedback affects noise figure? It will be great there's a book or paper that I can reference to.


texts: What is the purpose of pre-synthesis simulation?

texts:
I have used Verilog to develop RTL representations of synthesizable digital circuits, and have recently been using Verilator to run simulations of these.  My understanding of Verilog semantics, therefore, is based on how things work under those simulations (Verilator attempts to match a synthesized representation).

However, this question on StackOverflow (see also this linked document) has drawn my attention to the idea that Verilog can legitimately be run in two different modes, these being pre-synthesis and post-synthesis, and that the meaning of the language (and the results of simulation) are not the same between the two modes.  Of particular interest to Q&A sites like this one, discussions about Verilog's behavior might become quite confused by lack of an explicitly specified distinction between the two modes.

I am aware that Verilog can be used to describe algorithms in ways that cannot be readily synthesized by automated tools, but assuming we have a design that is targeted for synthesis, what would be the purpose of running a pre-synthesis simulation?

Note: What actually started me wondering about this was this response to another question that I posted.  I was interested in post-synthesis semantics, but the answer seems to be addressing pre-synthesis semantics, although the distinction is not explicitly indicated in the question or the answer.

I understand that the physics and timing of real hardware is not addressed in pre-synthesis simulations, but this is not what I am asking about.

An example of language semantics differences (as indicated in the linked document):

pre-synthesis: the order of blocking assignments can matter
post-synthesis: the order of blocking assignments does not matter

The point being, pre-synthesis simulation may fail to match hardware due to semantic rules -- even if there are no problems in the timing.  So running a pre-synthesis simulation may give the wrong result (one that doesn't match hardware) unless you have carefully constructed the code such that it will work the same for both modes of the language.  So the question is basically, why run a simulation that is known to have wrong semantics.

Further note: Verilator is completely idealized, and has no notion of any specific hardware, so perhaps it is not accurate to call that post-synthesis.  However, it uses the semantic rules of post-synthesis, and is purportedly very fast, so to me this establishes a baseline of what first-order simulation should probably do.


texts: Circuit Diagram for a D Flip-Flop with a reset switch?

texts:
I have created the following D Flip-Flop, which works as expected. I am now trying to implement an asynchronous reset to it. How can I edit my circuit so that when the button is pressed, Q is set to 0 and Q' is set to 1 immediately, regardless of whether the clock is on the positive or negative edge?

Logism has a D Flip Flop with an asynchronous reset built in, but I would like to create my own.


texts: Problems communicating by SPI from STM32F429 and ADE7878 board

texts:
I'm trying to change the microcontroller that comes with the ADE7878 evaluation board by the STM32F429i. The documentation from Analog Devices shows how to do this using SPI. I'm trying it but I'm getting no response from ADE7878. I put some images to ilustrate the question:

And finally the problem:

As one can see, the MISO is oscillating in phase with clock but seams to be just a noise and everyting it sends is 0xFF.

I am configuring SPI with this parameters:

SpiHandle.Instance               = SPIx;
SpiHandle.Init.BaudRatePrescaler = SPI_BAUDRATEPRESCALER_128;
SpiHandle.Init.Direction         = SPI_DIRECTION_2LINES;
SpiHandle.Init.CLKPhase          = SPI_PHASE_2EDGE;
SpiHandle.Init.CLKPolarity       = SPI_POLARITY_HIGH;
SpiHandle.Init.CRCCalculation    = SPI_CRCCALCULATION_DISABLE;
SpiHandle.Init.CRCPolynomial     = 7;
SpiHandle.Init.DataSize          = SPI_DATASIZE_8BIT;
SpiHandle.Init.FirstBit          = SPI_FIRSTBIT_MSB;
SpiHandle.Init.NSS               = SPI_NSS_SOFT;
SpiHandle.Init.TIMode            = SPI_TIMODE_DISABLE;

The clock of the STM32F429i is 180MHz.

I tested this STM32F429i SPI communication with another STM32F4 board and it was correct, with no problem, using this same configuration.

Please any question, any doubt let me know. It will be a pleasure to help you to help me... :)

Thanks!


texts: Is that possible to know micro controller pin voltage and current without using multimeter?

texts:
So, the condition is there is a Photo Voltic (PV) module connected to a microcontroller (directly to pin 5 and assume that PV module is generating 3V, hypothetically!).

I am wondering if I can some how write a microcontroller firmware or algorithm (may be in c/c++) to know what value of voltage and current I am getting from the small PV module.

Is this possible or I should have to have something in between PV module and controller? I haven't done any physical connection as described but just curious to know.


texts: Calculating Thevenin's open circuit voltage

texts:
I am unsure how to calculate \$V_{Th}\$ with the circuit below.

I have attempted to reduce the circuit below into the following circuit, but I am unsure if this is correct. Can anyone confirm that I am taking the appropriate steps?


texts: 3-wire load cells and wheatstone bridges from a bathroom scale

texts:
I am involved with a 4H project looking to take some weight measurements with bee hives and am trying to figure out some 3-wire load sensors to do just that.

I have four 3-wire sensors (load sensors/strain gauges) from one bathroom scale (each sensor was at a corner). Each sensor has a red, black and white wire. The resistance between the red wire and either the black or white wire is 1k ohms. The resistance between the white and black wires is 2k ohms (the resistance between the leads on my load cells and each came away with R->B=1K, R->W=1K, B->W=2k).

Because of this, I was told each 3-wire load sensor represents 1/2 of a Wheatstone bridge (each sensor containing two 1k resistance legs).

I can get my head around the single wheatstone application but I'm confused how a scale would work when made from two wheatstone bridges. My question is, if this is so, why would a scale require two Wheatstone bridges (remember, all four 3-wire sensors came from one bathroom scale)?


texts: Does a BMS reduce the quality of the output of batteries?

texts:
I plan to build a high quality headphone amplifier. It does not use much power (<1A) so I think about using 18650 batteries as power supply. I am pretty sure these batteries should be a very smooth power supply without any ripple or spikes, etc.
But how about if I add a BMS to the batteries. Does a BMS have a negative influence about the power output? Will the BMS possibly produce ripple, spikes, or other unwanted power problems?
I don't plan to charge the batteries at the same time when the amp is on. When I use the amplifier any external power to charge the batteries will be disconnected.


texts: Is it possible to make an on-off loop circuit with common transistors?

texts: Can I make a circuit that turns something like LED or similar small DC devices turn on for a second then turn off one second then on and loop like this with transistor only? I mean without using any IC or relay. I have common transistors in hand like 2N2222, BC547, BC557 etc. Timing can vary but is it possible? I can provide different power source for the switching circuit.


texts: How much current does the back light of ILI9341 LCD take?

texts:
I'm planning to do a turn-on-back-light construction with transistors like this:

Where the LED is the back light of the LCD ILI9341.
But to select the resistors, I need to find first how much current the back light of ILI9341 take. Do you know how much it want?


texts:
I am planning to create few circuit boards. I am considering getting the PCB printed from a manufacturer and do the SMT via a machine my self. Do you think it is good idea.

The reason i an planning to do is i need 50-100 circuits boards every few weeks and the cost of PCB printing is less but PCBA SMT is huge. As manufacturer charges around $400 for any new design. So i thought of getting a machine like SMT460 Youtube so i can do it my self.

I am not sure if it is a good idea or not. I have no experience in doing that so would like to get some opinions.


texts: Is there a motor which has regular torque, but extremely high holding torque? I mean, the motor probably holds by some mechanical lock rather than by the torque generated by the magnetic field. Is there some such motor, either linear or regular?


texts: What is the circuit's logic diagram of a (2-bit binary to decimal) encoder

texts:
To give a sense of what I am looking for ... this is a the circuit's logic diagram of a 4-bit binary to decimal encoder.

Here is its truthtable

Now, What is the circuit's logic diagram of a 2-bit binary to decimal encoder?


texts: misconception of full wave and half wave filter rectifiers

texts: Can someone please explain to me "The difference" in output voltage between the full wave and half wave rectifiers. Im asking about circuits with a single diode and 2 diodes .. NOT bridge circuit. And when they are functioning as "filter" circuits using a capacitor....


texts:
How does a darlington pair work?
I am curious about how the second transistor sustains the current Ie of the first transistor.

Why is the base not damaged despite this high current?


texts:
I have a weird behaviour of the bath ventilator. The make and model: Rotheigner Air Basic 100.

When I switch it on it is working for 1 second and stops until I disconnect the power and connect it again.
I thought it is a defective device, so I bought a new, but the new one reveals the same behaviour.
I did a lot of home electricity before, but now I am completely confused about what could be the reason.
I have tried to switch the polarity (swap the Line and the Neutral cables), I have tried to remove the Earth protection cable - the same behaviour repeats all the time.

"CZAS TIME" regulation has no effect (tried max/min positions - no difference).

Please, any ideas?

P.S. Line tester shows voltage on the brown cable; the yellow-green is connected to the Earth socket contact in all sockets.


texts: Asynchronous serial bit transmission/reception

texts:
I am asking this stupid question for my general knowledge.
Why in serial protocol often send least significant bit first?
For example, in UART, data byte 10101100b (0xAC) is send as 00110101b (0x35).
What protocol designer may have considered?


texts: Using an LM386 with input and output transformers for isolation from power supply

texts: The LM386 TI applications notes page 11 show an amplifier. Would like to use this chip  with complete isolation of the output speaker and with the addition of an isolated input speaker. Am using impedance matching transformers on input and output for speaker isolation from the power supply. Should the 10 mfd shown be polarized?


texts: LM358 - as analog voltage mapper 3.3V to 5V

texts:
I built a circuit based on ESP8266, MCP41100 digital potentiometer and LM358 op-amp. Its purpose is to use it as 0-5V DAC, but I have the following problem:

I use LM358 as non-invering amplifier. It's connected to 5V from VIN ESP8266 pin, non-inv. input is connected to output of voltage divider made from digital potentiometer, inverting thorough 12k and 22k resistor to output and ground.

For some reason I cannot go above 3.3V on output. Could you tell me how to debug it? Everything except part with amplifier works as it should.


texts:
After a lot of hustle and online search, I understood that an LCD segment cannot be driven like the LED ones and that I need a special driver.
The problem is I cannot find a driver that I can understand how to wire and multiplex, does it make a difference if the LCD I am using have a backplane for each separate digit or 1 backplane for all 8? Can I use CD4543B driver to multiplex all 8? How to use multiplexing with a microcontroller that has LCD driver built in?
Thanks


texts:
Just wondering , If some how the MOSI and MISO tracks which connects the slave get cut. At that time, its disconnected from the slave.

So if the micro controller tries to read data from MISO pin, what will it read?


texts: 7400 series CMOS vs 4000 series logic IC

texts: I understand the traditional difference between the 7400 series and the 4000 series logic ICs, but since there are CMOS versions of the 7400 series, is there an advantage to use the 7400 CMOS version over the 4000 series chips? Please note I'm not talking about TTL vs CMOS, as that has been discussed thoroughly before. If there is no difference (read significant difference), I'm assuming then that they would be able to interface with each other? I would think the voltage levels for high and low for both CMOS versions would be near identical, but please correct me if I'm wrong.


texts: What is difference between EMF given as \$\epsilon=-L\frac{dI}{dt}\$ and voltage on inductor \$V=L\frac{dI}{dt}\$? In circuit analysis is \$V\$ used as the voltage on inductor, and why is it equal to \$-\epsilon\$ ?


texts:
I'm using Digispark Pro with my program successfully.
I bought new  ATtiny167 chip for custom PCB board  (for HID USB device). I use the scheme from: https://electrobattery.ru/product/plata-arduino-digispark-pro-attiny167/
and this is not working. Result is: “Unknown USB Device (Device Descriptor Request Failed)”.

What I tried:

I read fuse from my digispark pro (E:FE H:DD L:DF). I wrote this fuse successful.  I read flash from my Digispark Pro . I wrote this flash successful. Not working.
I tried this variant: How to write a bootloader and drivers for ATtiny167. same result.
i Tried micronucleus 2.04 (https://github.com/micronucleus/micronucleus) with both fuse variants. same result.

Part2:
I solder out chip (old chip) from my working digispark pro, which successful work with USB. And tried  use this chip on my breadboard. Result: “Unknown USB Device (Device Descriptor Request Failed)”

I tried another variant: i took new chip and soldered it in digispark pro. Try 6 combination: 2 variant of fusses and 3 variant of flash (probootloaderr2.zip from http://digistump.com/wiki/digispark/tutorials/proisp; t167_default.hex dвdrom https://github.com/micronucleus/micronucleus/tree/master/firmware/releases and readed flash from my Digispark Pro). Result: “Unknown USB Device (Device Descriptor Request Failed)”

I returned old chip  to digispark pro. everything works good.

WHAT the problem(((
Please help

I only write fuses and flash to chip. May be i have to do anything else?

Please help.


texts: How should I find the base resistance when a common-emitter amplifier is at its Q point?

texts:
Using this circuit diagram and the characteristics below, I've been asked to determine Rb when Ib at the Q point is 30 micro amps.

I've tried solving this problem in two different ways: first, KVL, and by finding the slope of two points on the input characteristics (specifically (0.6 V, 30 micro Amps) and (1.0 V, 0 amps)) and setting that to -1/Rb. I get two different answers when I work these problems out (13.3 k Ohms w/ KVL, 20 K by finding the slope and equaling it -1/Rb). Which is the correct way  to do this?


texts: What is the peak to peak voltage of a Colpitts Oscillator?

texts: I am designing a colpitts oscillator having a frequency of 100MHz. However, I am not sure how to calculate the peak to peak voltage for the sustained oscillations. Attached is my workings. Is the peak to peak voltage equal to the total voltage supplied minus the voltage drop across Rc? Thanks in advance for your help.


texts: Where to place hall sensors (BLDC motor)?

texts:
I have a BLDC hub motor (out runner type; 3 phase wires) for my electric bike. It currently has 1 set of hall sensors (3 pieces) and I would like to install a second set (3 more) for spare (in case one of the original 3 stops working).

Current hall sensor's locations:

NOTE: on the photo the middle hall sensor is not installed since the photo was taken when replacing it with a new hall sensor.

In the following picture I have tried to indicate which wires serve which purpose:
(The wires indicated in red are the motor phase wires)

The hall sensor-wires indicated in green in the picture go from the outside of the motor (top right in the picture) to the PCB (green circle in the picture) and via traces in the PCB the wires go to the 3 hall sensors.
Color coding:

Red, Black = 5V DC
Brown = Temp. sensor
yellow, orange, blue = sensor signal wires

Photo from slightly different angle:

There is also 1 wire for a temperature sensor among the wires inside the green circle but Its currently not connected.

There are hub motors which come with 2 sets of hall sensors from the factory and I would like to upgrade mine to 2 sets.

The current set was installed from the factory.

I was wondering where I should put the new set of hall sensors in order for the motor's timing (of the different coils) to remain unchanged (in other words so that I don't mess up the motor's timing), both sets of hall sensors have to be activated at the same time such that if i were to connect them in parallel (hall sensor A (set 1) to hall sensor A (set 2) they would only give 1 signal (if that explanation makes any sense).

Is my only option to either place the new hall sensors on top of the existing hall sensors (not sure if i have enough room for this) or to place  the new hall sensors on the other side of the motor (current set of hall sensors are placed on top of the windings on the right side of the bicycle (when the motor is inserted), I could perhaps place the new set of hall sensors on top of the windings on the left side of the bicycle. (if you look at the photo I'd want to place them in the same location but on the side of the windings that is currently laying on the table (on the green cloth)).
Any other (better) suggestions for placement of second set of hall sensors are definitely welcome.


texts:
I have a multi layer board and have 2.5V plane as one of the layer. Some how during testing something go shorted on 2.5V. I am using the Toneohm 950 to detect the plane short after removing whatever components possible. I am left with 12 BGA ICs which cannot be reworked at lab.

But the surprising part is the instrument is detecting the short near power entry. Is it possible that my 2.5V somehow sparked to reach the ground via inner plating?

Please refer the picture below. This is an inner layer of 2.5V(yellow) and blue color vias are ground thru-hole vias.

The minimum distance between the 2.5V and ground via is 15mils.


texts: How to vary the supply voltage for Xilinx Virtex-5 FPGA ML501, ML506, and ML510 boards?

texts: I'm trying to do an experiment to see how different supply voltages affect the frequency of ring oscillator and the reliability of SRAM cells. I have access to a couple of Xilinx Virtex-5 boards, namely, ML501, ML506, and ML510. I have tried to search the web, but so far I haven't found anything useful. I have some experiences with FPGA design, but I have never tried to change the supply voltage before. So I'm really clueless on how to start. Can someone (who have done similar projects) please tell me how to vary the supply voltage of those FPGA boards?


texts:
I purchased a 3G dongle from an unknown manufacturer (ZD Incorporated), and I am trying to boost its signal with a 3G antenna. I'm on the assumption that the manufacturer did not put an antenna there, but it's possible to solder one, because I've seen exactly the same model but with an external connector (more expensive). The only known information is that uses a Qualcomm chip.

Here is the antenna:

I have bought an UFL connector in order to solder to the PCB, but I do not find the standard placement (2 ground connectors and 1 signal), so I cannot really decide where to solder it.

Any suggestion or experience with this devices? Is this even possible?

Edited (@PeterJ): Here it is a zoomed image:


texts: How do I separate ground planes on a PCB with two different voltages?

texts:
I am using a four-layer PCB with the following stack up: top signal, ground, 3.3V VCC, and bottom signal.
All of my components require a 3.3V input except for this sensitive optical sensor (MAX30102) that needs both 1.8V and 3.3V inputs. In the MAX30102 datasheet, the 1.8V needs to run to a separate ground from the rest of the system.
How should I go about separating the ground planes? I am using two linear voltage regulators in parallel and have attached an image of my design.
Pad 12 is the ground for the 1.8V input and pad 4 is the ground for the 3.3V input on the MAX30102. How should I connect pad 12 to ground to minimize noise? Furthermore, how do I tie both 1.8V and 3.3V grounds together?
I'm guessing that I make a separate ground plane underneath anything that connects to 1.8V and then connect that to the ground of the 1.8V linear voltage regulator.
Or maybe, I have to connect the 1.8V ground to the main ground source at only a single point with a track? Currently, the second layer ground is tied to all of the other components powered by 3.3V.
Please let me know, I'm a student.


texts: Why does my BLDC motor change behavior at high speed?

texts:
Background

I've recorded torque vs speed performance of a small sub 50 gram hobby BLDC motor, the KDE 2304XF-2350.

I power the motor at different fixed voltages to the ESC (electronic commutator) and at different throttle settings for the ESC. The throttle of the ESC essentially steps down the fixed voltage. I measure the "quasi-multiphase" AC electric power entering the motor using a 3-phase wattmeter. I say quasi-multiphase because only a single phase of current flows through 2 motor windings at any point in time.

I load the motor using an eddy-current brake: an aluminum disk is connected to the rotor, and the motor/disk are suspended above two electromagnets. Increasing power to the electromagnets induces larger eddy-currents into the spinning disk which generates a larger torque. I measure steady-state torque and speed at different load-currents using an in-line torque cell and a hall sensor.

Here is my data at 8V, 50-100% throttle. Each dotted experimental set has a corresponding solid prediction based a simple DC motor model and KDE's specs.

$$ V = dV_{DC} $$
$$ V = IR + E $$
$$ V = \frac{T}{k_t}R + k_t\omega $$
$$ T = \frac{Vk_t - {k_t}^{2}\omega}{R} $$

Where

\$d\$ is the duty ratio of throttle setting
\$V_{DC}\$ is fixed voltage entering the ESC
\$R\$ (182 mΩ) is the winding-to-winding resistance of a motor (KDE provides the per-winding resistance of 91 mΩ) because that is the total resistance seen by a voltage applied instantaneously to the motor terminals
\$k_t\$ (0.0041 Nm/A) is as provided online

Problem

I simply do not understand why the experimental data diverges from my model at high speeds - specially at low throttle.

I initially though this was some sort of "accidental" field-weakening. The divergence stems from a change in slope, and the slope of a DC motor curve is only a function of \$k_t\$ and \$R\$. At high speed/low current, \$R\$ won't change (low current = low temps), but \$k_t\$ might change due to an increase in inductance.

The experimental slope becomes less negative as if the \$k_t\$ has been decreased to achieve more speed, yet the motor still maintains higher torque than if \$k_t\$ had remained the same.

For example, at 70% throttle and 10 kRPM, my model predicts ~ 20 mN-m of torque, but the "field-weakened" motor produces 25 mN-m of torque. What gives??

Is this field-weakening of a BLDC? If so, why doesn't torque suffer?
If this is not field-weakening, what else could cause the torque-speed curve slope to change with speed?

Addendum

What also confuses me about this high-speed divergence is that the experimental motor efficiency improves with FW.

As I understand FW for PMSMs, some of the stator current (Id?) is spent "fighting" the armature field rather than generating torque (Iq), so you actually lose some efficiency.

However, my motor's experimental efficiency does not drop as precipitously as my model since the motor is producing more speed (relative to the model) at the same torque.

As Neil_UK mentioned, the ESC may be playing some sort trick with the phase angle at the armature. How can I measure the phase angle at the armature?

I am already measuring the total phase angle at the motor terminals via my wattmeter (Φ = acos(∑P/∑S) across all 3 phases), but this phase angle includes current lag from speed-increasing inductance and harmonic distortion from noisy switching.

Hypothesis

Torque doesn't suffer at accidental FW region because the BLDC motor continues to draw more power at FW unlike PMSMs that pull "constant" power during FW (ignoring inefficiencies). I will check data now!


texts: What does this diamond, arrow and tail symbol means in schematic diagram

texts: What does these symbols in the electric schematic means?  I believe the arrow head indicates the direction of flow of current from left device to right device.  What is the tail of that arrow symbol is?  Is that source of current?  What does the diamond symbol indicates here?


texts: Effect on output voltage when voltage regulator caps are undersized

texts:
I recently corrected (increased) the sizing on the capacitors around a voltage regulator and then realized I didn't really have good intuition on what it would look like in the wild if they were wrong.

What is the affect or symptoms I would see on the output voltage if the voltage regulator caps are undersized?

My LM78M05 datasheet

From the datasheet, the first input cap is simply 'required' with no explanation as to why.

*Required if regulator input is more than 4 inches from input filter capacitor (or if no input filter capacitor is used).
**Optional for improved transient response.

For the optional second capacitor, I usually choose a nominal value and type as given by the datasheet but don't really have a rule-of-thumb formula to increase that value if, say, the destination is very far away (e.g. microcontroller power pin).


texts:
Many moons ago, as a kid, I was playing around with electronics and proudly demonstrated my latest project to my parents. In my eagerness, I made a mistake in my nest of wires, and the acrid pale grey smoke of shame was released from a small silicon signal diode, perhaps a 1N4148.

My father stated that I probably "shorted out the diode". I bowed to his superior knowledge without question, and sheepishly requested that he replace the diode (I had not yet mastered the soldering iron).

Now I have age and rebellion flowing through my veins, and I demand an explanation! What might cause such an embarrassing failure?


texts: Patient protection in a biopotential amplifier

texts:
My question is in regards to biopotential amplifiers, more specifically an instrumentation amplifier as part of an ECG.

I know that IEC60601 states that a paitent must be limited to 50uA under fault conditions.

What type of methods are used to ensure a paitent does not get a shock and receive current of 50uA and above?


texts: Why the magnitude response of my low-pass passive filter is not flat at some frequencies?

texts:
I design a 7-order linear phase low-pass filter (which is exactly the same anti-aliasing low-pass filter used in Agilent 33220A), which is:

This filter is used as an anti-aliasing filter to filter the current output of AD9744 DAC (digital to analog converter). Plus the passive filter itself, it also include some load resistors such as R1, C1, R3, R2 which are shown in the following picture. I simulate this circuit in LTSpice:

However, the magnitude and phase response is NOT flat, as can be seen in the following picture (V(ap) is the voltage at the ap node, V(bp) is at the bp node):

Where the voltage at the ap node in NOT flat, which seems like to be fluctuated, and the response at bp is also NOT flat. So what is wrong with my circuit?

The followings are my simulations using NuHertz:

And the simulation in NuHertz using the values in Agilent 33220A:


texts: MOSFET Circuit Design and Thermal Considerations

texts:
I'm a newbie at EE, and just I wanted to verify that the design I came up with for a MOSFET circuit that drives a 12V 500mA water pump will work. I'd also like to confirm I can run the N-Channel MOSFET in question (RUR020N02) without a heatsink.

P8 is a two-pole terminal block which the pump will be attached to.
The MOSFET has a 1.5V Logic Level gate, which will be driven by a 3.3V I/O pin from an Atmega328p.

By what research I've done, I've learned that it's good to have a pull-down resistor (R9) in the event the digital I/O pin on the microcontroller (PUMP) is left floating, as well as a limiter resistor (R10) to keep the uC I/O pin within spec (20-40mA). I think this can also act as a voltage divider, but the voltage drop should be negligible in this case and still well over the gate threshold.

I've added a flyback diode just in case, though I'm not sure if one is truly needed. The pump is an impeller so I assume it has the same problems as running a DC motor--I'm not sure if the pump has its own internal protection circuitry.

So, my main question is whether or not this design is adequate for my needs.

However, I'd also like to know if I would need to use a heatsink for this particular SOT-23 MOSFET.

Based on the datasheet (linked above), it has a power dissipation of 0.54W at 25°C. Since the MOSFET has a RDS(on) value of around 105mΩ and my pump draws 500mA, I should be OK without a heatsink since it will only need to dissipate 52.5mW, correct?

0.105Ω x 0.500A = 0.0525W

Assuming the MOSFET turns on fully in an acceptable timeframe.


texts: What is the use of magnets around electrical cables?

texts:
I haven't seen any for a while now, but a couples of year ago I saw some several times: cylindrical magnets around electrical wires. I'm not talking about specialized equipments but items of everyday life which comes with such a magnet. In fact I did not know it was a magnet until I accidentally broke one. Unfortunately I did not manage to find any picture from the web.

Do you know the use of them? Also, are we still using them?


texts: DC-DC converter to regulated +/-30V supply

texts:
I'm having trouble with a circuit that converts a low DC voltage (e.g. from a wall adapter) to a +/- 30V regulated supply. The circuit has a boost regulator (LT8330) followed by a dual supply inverting charge pump (LTC3260).
Here's the circuit:

And the PCB layout:

The spice simulation works as designed, however in reality not so much. The regulator (LT8330) circuit worked on the PCB, however the LTC3260 burnt immediately after connecting the supply. From the simulation there's some pretty large current spike at the Vin of the charge pump during start up which may be the problem. It's not clear to me from the datasheet how much this component can handle though.

Any help would be appreciated. Thanks.


texts: NUCLEO-G031K8 ADC conversion for audio recording -- bit resolution and recording quality

texts:
I am planning to use NUCLEO-G031K8 board as an audio interface for my electric guitar to computer. So I designed a circuit to amplify small signal of guitar. When I check board's datasheet it is written it samples analog signals with 12-bit depth. (Source)  and it
can be extended to 16-bit resolution through hardware oversampling. I did some research online but could not find a solid answer. How to use oversampling? And also when I record my guitar is it a good quality interface to use after design or not? How to evaluate it? Because for example this audio interface samples 24-bit/96 khz resolution I wonder will I have similar to this one or a worse one.


texts: I am looking for a darlington array IC like the ULN2803a that can sink up to 1.5A. It needs to be in a DIP. Any recommendations? Its needed because i am driving a stepper motor and requires 1.2A per coil. I am controlling the stepper motor from a PIC. So if you have another solution let me know.


texts: Solar panels at night without diodes - short circuit or source of power dissipation?

texts:
So the title pretty much sums it up. I have a circuit that has a solar panel and some other power sources and I am to do a circuit analysis when there is no sun and show how it affects the system.

However I have been told that in reality if solar panels are not fitted with blocking diodes then they will drain the battery or consume power from other sources if they are hooked up to it. So would I treat a solar panel as a source of power dissipation at night or would I simply assume it creates a short circuit?


texts: How to view Eagle gerber files in ViewMate?

texts:
I'm trying to view my gerbers generated from eagle (using SparkFun's CAM file) as I and cannot get the drill file to import correctly for some reason.

When I drag the files into ViewMate, I choose 0.1mils as the unit of measure for the .dri file and inches for the .gpi file. This is the result:

As you can see, the scale of the holes is messed up.

Here are the Eagle and gerber files.

What am I doing wrong? How do I get it to display correctly?


texts: Li-Po battery ritual when using first time

texts:
We are using lithium-ion polymer battery in our project. The battery manufacturer recommends that battery needs to be fully charged and discharged for four times before usage as to reach its maximum battery performance.

Is this necessary to do and I am unable to understand the logic behind this ritual. Why not all battery manufacture write it in their user guide.


texts: Is the ESD and overvoltage protection for my ADC circuit sufficient?

texts:
I am currently building a data logging device for monitoring battery packs which contain 8 Lithium cells. The device will periodically log the voltages of all 8 cells, as well as log temperatures collected from 3 thermistors. My device has an STM32L series microcontroller.

As of now I am trying to figure out what the input circuit for the ADC should be. Due to the high power nature of the system, and it containing two large industrial motors which are subject to varying loading, I am assuming the battery pack would be subjected to  high voltage and current spikes. I will be taking taps from each cell and connecting it to my device.

In terms of protection, I have done some research and found I should probably be looking into TVS and clamping diodes as protection means.
The input range that needs to be measured is 0-32V. I have guesstimated the following circuit:

The TVS diode is SMAJ33A (http://www.littelfuse.com/~/media/electronics/datasheets/tvs_diodes/littelfuse_tvs_diode_smaj_datasheet.pdf.pdf) with a standoff voltage of 33V, and maximum clamping voltage of 53.3V @ 7.5A (Ipp). I am not sure how to select the TVS diode (or if I even need one!), so I would really appreciate any advice on this. For the clamping diode part, I am following ADC input protection?. I have selected Bat54S dual Schottky barrier diodes. This is to hopefully provide over voltage protection.

Do you think my choice of circuit protection is sufficient for this application? Any advice would be really appreciated. Thanks!


texts: What is the difference between a hard switched vs soft switched architecture in power converters

texts:
I've seen many examples detailing ZVS/ZCS for boost/buck converters, but I haven't found any evidence that soft switching is a design goal for motor drivers.
Why is it difficult to soft switch a motor drive? What is the fundamental difference between a hard and soft switched converter architecture? My understanding is that a motor drive is a hard switched architecture.


texts:
let's consider this picture in which a cylindrical resonant cavity is excited through a waveguide.

I have some questions:

1) Why is it called "Magnetic Coupling"? I thought this excitation simply was the propagation (through the slot) of the wave already present in the waveguide towards the resonant cavity

2) Why is there a magnetic loop in the last two pictures? what are its terminals connected to? Should be present also in the first two pictures?

Reference: here.


texts: about formula in temperature of resistor

texts:
I have 10 watt resistor.

I am using resistor with ac current. I need mathematical formula for learning temperature of resistor in t time.

temperature of resistor depends P=V^2/R and time. Such as for R=20 ohm.

Formula inputs: V,R,t
Formula Output: temperature.

Is there a formula for this state?


texts:
I'm reading an article which is about wearable smart watches.

To their credit, many of the manufacturers have made charging a
non-micro USB charging affair, though Motorola’s Moto 360 is probably
the most handsome execution of the idea. Sony, for reasons unknown has
chosen the ol' plug-it-in approach with the Smartwatch 3. None of
these methods would matter to me if didn’t have to go through the
exercise on a daily basis though.

As above context says Motorola's Moto 360 smart watch uses non-micro connector, I found following image as Moto 360 connector (which is micro USB connector) :

Now, I'm confusing what is non-micro USB and how it looks like?


texts:
I am working on a project which involves scanning all the BLE devices which are present in the vicinity. I can send scan requests and receive scan response from devices which are in discoverable mode. For this I used following commands on my laptop:
hcitool lescan &
btmon

In scan response I am able to get name, bluetooth address, rssi.
However, I am not able to scan devices which are already connected to some other device. E.g. I have bluetooth earphones which are connected to my mobile and after that if I perform hcitool lescan from my laptop then I am not getting earphones in scanned devices. But while going through videos about BLE I found https://youtu.be/be9ct7OKI7s video (screenshot attached)

and in this video around 05:00, application is able to show nearby devices even when they are connected. So is it possible to sniff ble packets in the air and figure out all devices present in the vicinity?
As per my understanding, advertisements are unencrypted but once the connection is established then all the communication between connected devices is encrypted. So how can we get the list of devices which are in the vicinity and connected to some other devices?


texts: Is there a way to disable automatic brace completion in Atmel Studio 6?

texts:
My apologies for a "barely on topic" question, but if any community knows, it should be this one.

I've been using Atmel Studio 6.1 (6.1.2562) for a few weeks now for AVR and ARM development. I'm very experienced with Visual Studio 2010, so it's not unfamiliar territory.

However, the automatic brace completion in Atmel Studio is driving me crazy and I can't find any option to disable it.

Is there some option to disable automatic brace completion?


texts: I ask this question, just out of curiosity. In this die of 556 IC, what are the wave-like squiggle at the four corners, and two more on the top?


texts:
I am using the Atmel AVR32 UC3C AT32UC3C2512C for a project and the datasheet doesn't say anything about terminating the USB connection, but the AVR32768 Application note, clearly points out a 39 ohm termination resistor (page 13).

Is it a problem if I left the PCB with no termination resistors at all?

I will connect this USB to another and make an extension so I don't know how this will influence the impedance of the traces and deal with this resistor. (I am new to Signal Integrity and High Speed Signals, but I know the basic theory already).


texts: Does a personal computer have just one clock and where is it?

texts:
I want to check my understanding which I have gleaned from several sources, many of which seem to be out of date and many of which are conflicting.

My understanding is that there is just ONE CLOCK inside a modern PC that regulates pretty much everything. It is an oscillator that depends on the vibration of a quartz crystal and it outputs a  frequency of 100 MHz and a frequency of 133 MHz. This clock/oscillator is located in a chip on the motherboard (the 'chipset'), NOT INSIDE THE CPU as some literature seems to suggest. There are however multiplier circuits INSIDE THE CPU which can increase the 100 MHz signal (about 35 times to 3.4 GHz) in order to to control program execution.  The 133 MHz signal is supplied by the same clock to the memory controller and is multiplied up (about 16 times) to regulate the speed of the memory bus.  The memory controller is also inside the CPU.  There is no front side bus any more.

Could you please let me know if this information is correct, in particular, the location the clock and that there is only one clock?


texts:
I'm trying to convert a 0 - -500 mV signal to 0 - 1.1 V. I came up with the following circuit in LT spice. Is there anything wrong with it or can it be improved? Any way to get rid of the negative reference or create it simply, or have I messed it up in some other way? I don't have any knowledge about transistor circuits.
This is for a PSU voltmeter.
edit: I should have clarified: input should draw/supply less than 100 nA
so, requirements are

high impedance input
invert the signal
scale from 0 to 1.1 V
hopefully better load regulation than what I have

I have a few bjt and 1 single opamp (1/4 of a LM324) to spare.

edit: Here's a simplified circuit which uses an opamp for the gain and output. It seems the bjt inverter works just like an opamp inverter except the voltage at emitter, not at the base, gets inverted at collector. Thus, with no extra input bjt,  there is a single pn junction increase in the output which can be lowered by an output bjt with similar current across it (and maybe gluing the two bjt will help minimize temperature difference). [With 2 pn drops this becomes 2 pn junction increase in output which is probably why I needed the darlington output in the schematic above. Also, every increase in gain will require an offset for Re close to Vcc/gain, to keep Vee in range. Thus, for gain of 1, no offset is required. That's my rudimentary understanding of the electronics.]
Input current is less than 37 nA. Output gain can be set at the opamp without disturbing the input.


texts: How do chargers with different output values work?

texts:
I have a few USB-C devices with their own chargers and I'm not sure if I can interchange them. What's confusing me is the different output values listed on the charger. From what I understand too high voltage can damage the device that is being charged and too low current can damage the charger/cable, while current above required is always fine (please correct me if I'm wrong).

For example my laptop charger can output: 20V=3.25A, 15V=3A, 9V=2A and 5V=2A. If I were to charge my power bank with it which accepts 5V=3A, 9V=2A and 15V=1.2A as input, could something go wrong? In this case if I were to plug in the power bank to my laptop charger how do I know that it's charging at the 15V=3A that it should and not at 20V?

On the other hand, if I were to charge my laptop with the same power bank (output: 5V=3A, 9V=2A, 15V=1.2A, same as input) could the power bank be damaged?


texts:
My family and I managed to break the aerial cable of our TV a few days ago.

The cable is of this kind of design:

And I believe its called a coaxial cable.

Fortunately, someone more practical than me has fixed the cable, but it made me wonder: how do these cables work?

The person in question was talking about the signal going from the outer of the inner to the inner of the outer. This made sense at the time, but I was doing a little more reading and that seemed to focus on the current flowing through the inner core, with the outer layer acting as a shield.

So, how does a signal get passed through a coaxial cable?


texts:
I wanted to ask for help in researching appropriate Microcontrollers to create a Wireless Artnet/sACN Node for DMX communications with film and stage lighting Fixtures.
The ultimate goal for the system is to have a mesh network of Nodes that are capable of putting out realtime DMX frames at 44fps.
the main reason for a mesh system is to allow a user to control lighting fixtures from an Ipad and allow them to move freely around the stage without worrying about loosing signal connection.

At the moment I've been experimenting with an ESP32 Devboard from Sparkfun and their DMX shield. I've used their example libraries (here) as well as another Arnet Library for the ESP32 (here). I'm still looking into other libraries but so far the ones I have tried all  "stutter" (only send one frame of DMX every second or so), then crash after a while and I can't find the bug int the code. I run the ESP32 Module as a wireless access point and this appears to be a cause.

My main question is would it be best to use 2 Microcontrollers for the nodes say an ESP32 for the wifi mesh and Artnet  aspects and then an ATmega or Cortex-M4F /ARM Cortex-M7 (teensy 3.0/teensy 4.0) or something else to output the DMX information to the fixutre? Or would it be best to stick with a single microcontroller? Also how does the Serial buffer size affect the ability to output the information of a 512 channel universe, would a 256byte buffer be too small? What other factors, hardware wise would limit its ability to perform constantly for long periods of time?

If it isn't obvious yet I'm fairly new to all of this and exploring out of interest so please be kind. ;)


texts:
I have a IRF530 connected to a 5V micro. The trace is on a PCB and very short, with only a pull down resistor on the gate:

simulate this circuit – Schematic created using CircuitLab

The MOSFET is switching a long length of 24V LED strips, which draws 6A. There is a 5m 2 core cable from the MOSFET to the strip.

When I set the pin to high, the mosfet gets very hot. On shorter lengths of LEDs, it only gets marginally warm. When I PWM the mosfet (f=500Hz), it still gets hot but takes a little longer to warm up.

How come this is happening? I am above the threshold voltage of 4V, so I assume the FET is not in a linear state, and the power dissipation according to Rds(on) is only 0.96W, which the un-heatsinked (un-heatsunk?) package should handle.


texts: DIY charger: solar panels in series or in parallel?

texts:
I am working on a DIY project where I am thinking of using a small solar panel to charge my iPhone.
I know iPhone chargers usually are 5 W, 5V at 1 A.
I can see two small, portable, and easily solderable solar panels:

one at 5V and 100 mA, and
another one at 1.5 V and 400 mA

Questions:

I cannot connect >5V to my phone as I risk damaging the electronics. But would connecting lower voltages still work? Slower charging, sure, but what's the difference between a high current at low voltage, and a low current at higher voltage?

Would it better to use 2x (or more) of the 5V solar panels in parallel, so as to keep the voltage at 5V but increasing the current, or to use 3x of the 1.5 V ones in series, to as to have high current and to reach 5V?


texts: How to run encoder motor with motor driver and raspberry pi

texts:
I am kinda new to the Robotics field and Raspberry Pi and has worked on very basic projects with the hardware so far. My current task is to run the "Encoder Motor" with a motor driver(preferably L293D).
I have already researched a lot on how to run the encoder motor with the raspberry pi but unable to find that.
If you can provide me with a detailed explanation on how to make connections and the code required that would really be helpful for me to understand from the robotics point of view and build projects on top of it.
Any relevant links/resources would be appreciable. Thanks!


texts: Why does a MOSFET threshold Voltage not increase when the channel length and/or oxide layer is increased?

texts:
I am reading through Fundamentals of Microelectronics by Behzad Razavi.
I am okay with the information provided in the images, and understand that if the channel length or oxide layer is increased, the resistance on the gate increases, causing a less steep increase in Ids as Vds increases.

But I would also expect (on graphs a and c) the VTH of a MOSFET with longer channel length to be further to the right (increase) than a MOSFET with shorter channel length. (or oxide thickness), because the voltage required to turn it on would now be more due to the increased resistance. I have sketched what I would expect to happen here:

However on the graph VTH remains constant value despite the increases to resistance, why doesn't the ON threshold also increase?


texts: How can I receive multiple bytes on SPI with CS being held low?

texts:
I have an FPGA which sends out a stream of bits over SPI communicating to 3 AD8403 daisy chained together. The FPGA keeps CS low, until 30 bits (2 address bits, 8 data bits  x 3) have been transmitted, then brings CS high.

The way the AD8403 are setup is that as bits come in, they get shifted out to the next chip if the internal shift register is full. The first 10 bits transmitted becomes the data for the last AD8403 and the next 10 bits becomes the data for the second AD8403 and finally the last 10 bits transmitted become the data for the first AD8403.

I need to be able to read this data as well. I'm thinking of just tapping into the SDI (MOSI) of the first chip. I have not used SPI in slave mode on a microcontroller before so I am a little lost when it comes to how the reception works.

I'm looking at using the AT32UC3C2256C (AVR32) for this task. It can transmit 8/16 bytes and I assume it can receive the same, but can it receive an arbitrary number of bits? The FIFO is 4 layers deep, so I would have to read data and store them some place else.

Question: How can I receive an arbitrary number of bits (multiples of 10) properly?


texts: Watts used by chargers eg laptop, wall warts etc

texts:
This is my first question on here, its quite easy and I am sure I have half the answer, maybe. I was thinking about how much power was being used by these wall chargers etc, you read the label it may say 1A 240V that equates to 240 Watts? Can it be that high or is there another equation to use? Don't be shy to show me math.

Thanks


texts: Since Arduino 1.0 string to upper case conversion does not work

texts:
I try to run this example code on my Arduino, but since Arduino IDE version 1.0 it doesn't work no more. The example is mainly copied and stripped down from this example.

void setup() {
  Serial.begin(9600);
}
void loop() {
  // toUpperCase() changes all letters to upper case:
  String stringOne = "test";
  Serial.println(stringOne);
  stringOne = (stringOne.toUpperCase());
  Serial.println(stringOne);

  // do nothing while true:
  while(true);
}

Error message:

  StringCaseChanges.cpp: In function ‘void loop()’:
  StringCaseChanges.cpp:12:39: error: no match for ‘operator=’ in
  ‘stringOne = stringOne.String::toUpperCase()’
  /usr/share/arduino/hardware/arduino/cores/arduino/WString.h:83:11:
  note: candidates are: String& String::operator=(const String&)
  /usr/share/arduino/hardware/arduino/cores/arduino/WString.h:84:11:
  note:                 String& String::operator=(const char*)

On the help page one can see that:

  As of 1.0, toUpperCase() modifies the string in place rather than
  returning a new one.

However I don't see the reason why the example code doesn't compile.

Can you help me?

Thank you!

//EDIT

OK, this one works:
    void setup() {
      Serial.begin(9600);
    }

void loop() {
  // toUpperCase() changes all letters to upper case:
  String stringOne = "test";
  Serial.println(stringOne);
  stringOne.toUpperCase();
  Serial.println(stringOne);

  // do nothing while true:
  while(true);
}

However, the help page should be changed!


texts: MIMO: How Can Two Antennas So Close Together Receive Different Signals?

texts:
I'm trying to understand how MIMO (as used by 802.11n wi-fi and some upcoming cellular data standards) works in practice.  I understand at least the gist of the theory of spatial multiplexing.  What I don't get is how it works in practice.  Let's say you have two TX antennas ~30 cm apart, two RX antennas ~30 cm apart and the distance between the transmitter and receiver is about 30 meters.  The angular separation of the transmit antennas as seen from the receiver is tiny.  From the perspective of each RX antenna the two TX antennas are about the same distance away.  How is the difference between the signals at the two RX antennas measurable and not buried in noise?  I would think that in such a configuration they would be nearly identical.

EDIT:  Both answers I've received have mentioned phase.  This doesn't make sense to me.  Assume a coordinate system where the two TX antennas are separated only along the X-axis. The Y component of their separation is zero.  As the Y-axis distance between the transmitter and receiver goes to infinity, the difference in distance between the two TX antennas as seen from the receiver goes to zero.  If the distance between the TX antennas is 30 cm and most of the distance between the transmitter and receiver is along the Y-axis, then 30 m is for all practical purposes infinite separation between the transmitter and receiver.


texts: Misunderstanding document about leakage inductance in a flyback converter

texts:
I am currently reading a document about leakage inductance in a flyback converter from ON SEMICONDUCTOR . Here it is : https://pdfs.semanticscholar.org/c061/313303ee8c231b069be4f0d67d9e4cddcbf0.pdf
(the document is really insteresting)

Here are the schematics :

And here is what I do not understand (in yellow):

I do not understand why the current through the diode is null for a certain time. When the switch opens, due to lenz's law the voltage accross Lp reverse and as the leakage inductance was energized, the current across Lp and Ll is the same. So if the current through Lp is not null, as the current to the secondary is proportionnal to the current through Lp, it is not null... So there is something like the voltage across Lp and Ll are opposed in order to iLl(t) = -iLp(t), but why the voltage across Lp and Ll would be opposed ? It would mean that the leakage inductance by "discharging its energy" is still charging the energy of the primary inductance ... Why it would be ? and why it would not be the inverse ? I M LOST ...

Thank you very much,


texts: What is the most widely accepted EMF exposure limit?

texts:
I know that there isn't a specific answer to this and different countries have different guidelines in regard to this. There are a couple cell-phone towers in my vicinity (one of which is some 15-20 meters away). I live in India and I filed a complaint with our Department of Telecommunications and just today, they came to my house and took various readings in and around it. Being new to this subject, most of the terms I found on the internet were alien to me. And I couldn't convincingly convert readings through Google.
My question is as follows: their instrument showed the EMF readings to be around 2.8-3.8 mW/m2 (milliwatts per metre square) at various points around the house. Is this safe?  They told me that the limit imposed by the Indian government is 4.5 mW/m2. It would be great if someone could verify that as well. I know for a fact that Indian regulations for EMF radiation are much more stringent than the EU and the US. I want to stay in the 'extreme' safe side and it would be great to know how this reading compares to the average exposure levels and those in different countries.
I know there isn't one set in stone, but I would like to know the generally accepted limit for EMF exposure.


texts:
I was trying to understand the circuit of  my mechanical keyboards.
There was a point abbrevated as "JA" on the board.
What does JA stand for?


texts: libmodbus modbus_read_bits() returns illegal function

texts:
It is all okay when it comes to read registers with:

modbus_read_registers(ctx,0,32,destination);

It gives me values of 32 different registers. But when it comes to reading bits(coils) in registers i get illegal function error.

modbus_read_bits(ctx,0,1,dest)

After getting this error again and again i made a scanning program like:

for(int i=0; i<100000; i++)
   modbus_read_bits(ctx,i,1,dest)

All gives me the same error. I have altivar 930(ATV 930).
What to do to read CMD register that has 15 bits with logic address 16#2135 = 8501?

ps: I also tried inputting 0x2135 and 2135. I also get invalid address when i try to read

modbus_read_registers(ctx,8501,1,destination);

libmodbus.org/docs/v3.0.6/modbus_read_registers.html
http://libmodbus.org/docs/v3.0.6/modbus_read_bits.html


texts:
simulate this circuit – Schematic created using CircuitLab

β = 100

I am applying KVL Clock Wise on both Loop.So I came up with

5 - 100IB - 0.7 = 0

On the second loop:-

VCE + 50Ic - 8 = 0
or

VCE + 50Ic + 8 = 0

which one is correct please explain.


texts: I need to power 2 brushed dc motors with 2A each and 3 to 6V, one direction(no bidirectional or break). To the enable the rpi 3.3V pwm, and standard pins(breadboard), not those micro pins. I know the l298 is an option. Are there better efficent options ? May be mosfet ? Thanks.


texts:
I would like to know how to filter the pixel clock in order to reduce emitted radiations.

Block diagram

The LCD controller is part of a motherboard. A board, connected at the other side of the FFC cable (15 cm), filters the signals on the TFT LCD side.

The used filters are EMIFIL chip ferrite beads (BLA2ABB121SN4 from Murata).

Investigation

EMC tests have been done on the machine that embeds these cards and the results showed that an unacceptable peak (~5dB greater than the limit) occurs at an harmonic of the pixel clock (~60MHz). This peak is generated when the 15 cm length cable is connected to the motherboard (regardless of the connexion of the other board nor the LCD).

A ferrite bead (Kitagawa SSC-40-12M) has been plugged on the FFC cable (15 cm length) but it didn't reduce this peak drastically.

Limitations

The ground of each board cannot be connected to the chassis.
The pixel clock frequency cannot be reduced (flickering occurs at lower frequencies).
The length of the FFC cables cannot be reduced.

Question

Should I use termination resistors on both sides in order to reduce eventual ringings? Or is there any other good practice to prevent this kind of radiations?

Edited - 2013-04-29

I measured the pixel clock frequency at the following places and it looks really horrible as you can see. Furthermore, its frequency should be 30MHz and it seems that it is only 10MHz. I suspect a bad line impedance matching. What's your feeling about this signal?

Measurement done on the LCD controller pin

Measurement done after the first EMI filter (on the LCD controller side of the FFC cable)

Measurement done on the LCD display side of the long FFC cable (before the second EMI filter)

Measurement done after the second EMI filter (just before the second FFC cable)

Honestly, I do not understand this waveform. It sounds like there are signal reflections or something like that. Any ideas?


texts: Find transfer function \$V_o(V_i)\$ on a figure

texts:
Given this figure:

simulate this circuit – Schematic created using CircuitLab

I want to calculate the transfer function of \$V_o(V_i)\$, but I can't find any good resource on it and I thought someone could explain to me how it's done, also with those NANDs I wanted to create inverters.


texts: What's the advantage of 'electrical tape' over 'regular' adhesive tape?

texts:
For covering copper wire and the like (whether it is carrying current or not), what's the advantage of applying electrical tape as opposed to 'normal' consumer adhesive tape (of similar thickness?

How much of an improvement in insulation or other important factors does it offer?


texts: How can I calculate the amplitudes of this signal's harmonics?

texts:
How can I calculate the amplitude's of the harmonics? This signal is the voltage of a capacitor bank. There is a few amperes of current on the capacitors in form of PWM. On the signal the 200mV Jumps are the voltage drops on the ESR. The jump occurs when the PWM changes from Ton to Toff or vica versa.

On the second picture I approximated the 200mV jumps with an instantaneous jump.
How should I derive the Fourier transformation on this signal?


texts:
Has anyone programmed a PIC using the command line interface with a batch? I have Pickit 4 and I've tried this:

@echo off & setLocal enabledelayedexpansion
echo Flashing with PIC ...
"C:\Program Files (x86)\Microchip\MPLABX\v5.30\mplab_platform\mplab_ipe\ipecmd.exe" /P16F1783 /F"C:\Users\xpp\Desktop\pic.hex" /TPPK4 /E /M /OL /W

I'm getting this error and also it's pretty slow:

EDIT:
To get it working from external power supply, we have to remove the /W command.

@echo off & setLocal enabledelayedexpansion
echo Flashing with PIC ...
"C:\Program Files (x86)\Microchip\MPLABX\v5.30\mplab_platform\mplab_ipe\ipecmd.exe" /P16F1783 /F"C:\Users\xpp\Desktop\pic.hex" /TPPK4 /E /M /OL


texts:
I have a fairly simple circuit with an MCU and few N-mosfets for controlling RGB LED strip.

Available voltage is 24 V. Same will power up the LED strip. I need to use the same line to power up the MCU which works on 3.3 V.

My peak mosfet current requirement might go up to 15 amps and I am constrained by size so I cant use heat sinks. As such I want to go ahead with mosfets with low RDSon (about 3-4 milli-ohms). To achieve such low RDSon, gate drive voltage should be about 10 V. 5 V can also work but the RDSon will be 1-2 milli-ohms higher as compared to 10 V drive.

Architecture-1

I use MC34063 IC to convert 24 V to 5 V line. Use an LDO to convert 5 V to 3.3 V for MCU and further use a voltage level shifter between MCU and mosfet to drive the mosfet with a 5 V signal.

Pros - Relatively simpler power tree architecture. Cheaper.

Cons - I miss out on driving the mosfet with 10 V signal which might cause more heating in the mosfets.

Architecture - 2

Use MC34063 IC to convert 24 V to 10 V. Use linear regulator to convert 10 V to 3.3 V.

Challenge - There are no (in reasonable price range) level shifters which convert a 3.3 V signal to 10 V signal. I might have to implement it using discrete components.

Architecture - 3

24 V -> MC34063 -> 5 V -> LDO -> 3.3 V

Besides this, I use a zener regulator or a voltage divider (2K + 2K) and generate 12 V. I use a transistor to feed this higher voltage to mosfet gates. I am using a resistive voltage divider because mosfets need very low current to turn ON, which can be provided by the voltage divider or the zener regulator.

Which one should I choose? Is there a better approach to this problem at hand?


texts:
We brought the following sensor from Boundary devices.

https://boundarydevices.com/product/nit6x_5mp/

The idea is to add Camera for our i.MX6 Customized board

I connected the following to check whether the board is working or not..

Only connected all the Grounds to Ground and VDDs to 5V and
SDA to SIOD, SCL to SIOC.

We have the following header exposed on the board as like Sabrelite.

i2cdetect on the linux command line did not gave any address. Touching the camera it is very hot.. What I am doing wrong here.


texts: What is the ASBBA-001 battery connector (GoPro Fusion 360 camera)?

texts: I am designing a PCB that will be powered by a battery. The battery model is the one used by the GoPro Fusion 360 camera. Specifically, it is the ASBBA-001 battery. I need to know which is the model of the male connector compatible with the battery. Any ideas? Do you at least know what type of connector it is? Could it be a blade connector?


texts:
I have a stepper motor controller which controls 4 fairly powerful steppers and has input pins for 3 proximity sensors. The controller requires 48v so I have the power supply for that. The 3 NPN proximity sensors I have operate at 10-30v and draw 150mA. I initially connected the out pins of the sensors to the controller and powered the sensors from a 12v psu I had lying around. I then connected ground from both power supplies. I was told this was incorrect because if one power supply failed it might wreck other parts of the circuit.

My problem then was how to get it all working correctly. I thought about a relay for each sensor but my preference was for powering all sensors from the 48v supply. I thought about stepping voltage down from 48v to 30v but it requires knowledge I don't have. I could use resistors to do it but I get the feeling that isn't a good idea. It would only draw a maximum of 450mA-500mA but steeping down from 48v to 30v would generate a lot of heat correct?

My other idea was to wire them in series but that's not working as planned. The voltage across sensor 1 is 22v, across sensor 2 is 15v and sensor 3 is 11v. Sensor 1 is operating correctly, when metal passes it the sensor triggers. Sensors 2 and 3 are always on which is confusing because they're clearly getting power but for some reason think they've been tripped when they haven't. When I read the voltage between the + of each sensor and its out pin I get whacky results. Sensor 1 is reading 0v which is correct. Sensor 2 and 3 read 8.33v and 25v respectively.

Since sensors 2 and 3 are trigger, I would've thought those readings would've been the voltage applied across them (15v and 11v) with slightly lower values due to resistance. But, seeing as they're triggered without anything near the sensor then it's strange they have a voltage across them at all.

Is there a way to get the 3 sensors working in series or should I tackle it another way? I'm wondering if there's something I can do to split the voltage into 3, thus delivering 16v into each sensor without any fancy electronics.

Sensor doco (PL-05N)