texts: Digital Clock --->Bad Accuracy (Help to Troubleshooting)

texts:
INTRODUCTION:

I'm a student in the Electronic Engineering program at my University. I'm building a digital clock as a self initiative to learn more. Some of the requirements and steps that is necessary for this project are topics that are above my level compared to where I'm at in my program. However, I'm really engaged in this project and would like to understand more about how I can improve upon the problems i've been having.

DETAILS/PROJECT:

I'm using a Arduino Micro-Controller (MODEL: UNO). I've built a simple program to send a byte of information to a (TTL) 595 IC shift-register. Each binary digit is then transferred out each of the 8 outputs on the 595 IC to their corresponding pin out of the LED.

PROBLEM:

I've noticed that because I'm using (4) 595 IC's to control a 4 digit LED I'm experiencing a delay. Therefore, my accuracy is gone. I could shortened my code to limit the number of times I use the function "delay()" in my code but I would still have the same problem.

SOLUTION:

I've been told to use a clock (555 IC). I do not know anything about this IC. Is there anyone that has had some experience with the 555 IC that could give me some guidance when I start to implement this into my project? Will I need a Arduino Micro-Controller if I use this or not? Is there any other suggestions to how I can go about fixing my problem I stated?

I'm attaching a picture of my layout if it helps. I had removed 3 of the 595 IC's when this picture was taken but the picture clearly shows my micro-controller, 595 shift registor and 4 Digit LED display. I'm also going to attach my code that I've made. It's very generic as I'm a beginner so if there is something evident in my code that's wrong take it easy on me. However, by all means let me know what I'm doing wrong and could do better.

int clockpin = 11; //595 pin 11
int latchpin = 12; //595 pin 12
int datapin  = 13; //595 pin 14
int binary = 0;

void setup()
{
pinMode(latchpin, OUTPUT);
pinMode(clockpin, OUTPUT);
pinMode(datapin, OUTPUT);
}

void loop()
{
digitalWrite(latchpin, LOW);
shiftOut(datapin, clockpin, MSBFIRST, 63);
digitalWrite(latchpin, HIGH);

delay(1000);

digitalWrite(latchpin, LOW);
shiftOut(datapin, clockpin, MSBFIRST, 6);
digitalWrite(latchpin, HIGH);

delay(1000);

digitalWrite(latchpin, LOW);
shiftOut(datapin, clockpin, MSBFIRST, 91);
digitalWrite(latchpin, HIGH);

delay(1000);

digitalWrite(latchpin, LOW);
shiftOut(datapin, clockpin, MSBFIRST, 79);
digitalWrite(latchpin, HIGH);

delay(1000);

digitalWrite(latchpin, LOW);
shiftOut(datapin, clockpin, MSBFIRST, 102);
digitalWrite(latchpin, HIGH);

delay(1000);

digitalWrite(latchpin, LOW);
shiftOut(datapin, clockpin, MSBFIRST, 109);
digitalWrite(latchpin, HIGH);

delay(1000);

digitalWrite(latchpin, LOW);
shiftOut(datapin, clockpin, MSBFIRST, 125);
digitalWrite(latchpin, HIGH);

delay(1000);

digitalWrite(latchpin, LOW);
shiftOut(datapin, clockpin, MSBFIRST, 7);
digitalWrite(latchpin, HIGH);

delay(1000);

digitalWrite(latchpin, LOW);
shiftOut(datapin, clockpin, MSBFIRST, 127);
digitalWrite(latchpin, HIGH);

delay(1000);

digitalWrite(latchpin, LOW);
shiftOut(datapin, clockpin, MSBFIRST, 111);
digitalWrite(latchpin, HIGH);

delay(1000);
}


texts:
I have 2 MM232R USB-to-Serial converters and both are genuine products ordered from Farnell with FTDI chips. I am using those to reproduce an existing circuitry yet the new ones I ordered cannot be established properly although I can see the COM port. I installed VCP and FTD drivers from FTDI website but still no chance. Attached you can find 2 screenshots displaying the events after I plug working and not working MM232R modules:

Where the first image is from a working chip and the second one is not working.
Any help is much appreciated, thanks!


texts: microstrip patch antenna representation as an array of two slots

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from the article bellow we can see the microstrip antenna as an array of two radiating slots which are separated by half a wavelength
As shown in the photo bellow.these Electric fields cause magnetic current in the same direction at every slot.
Why becase of the same magnetic direction we get a stronger radiation pattern?
i cant see it in the equation bellow.
Why we get constructive sum of both radiations?
Thanks.
https://www.ece.mcmaster.ca/faculty/nikolova/antenna_dload/current_lectures/L21_Mstrip2.pdf


texts: I am unable to understand how does galvanic isolation work either via an optocoupler or a transformer. In an optocoupler, the input side current caused LED to emit infra red light which basically switches on the photo transistor on the output side. In case of any voltage surge on the input side or any noise, the input current will vary henceforth the light output and thus the collector current on the output. So how does isolation works? Or am i missing something really basic. Similarly for the transformer.


texts: Understand an I2C clock line implementation

texts:
I am trying to understand a C function from a legacy project which is supposed to manage the clock line for an I2C interface. It basically does as follow:

Set pin to output: P0_1 |= 0b00000010; and then drives it low: P0_1 = 0;.
Or set as input: P0_1 &= 0b11111101; and wait for the clock line to be high: while (!P0_1) { wait(1); }.

What I don't understand is the second case, code comment says:

Set as input with pull-up to wait for the slave to be ready before driving the clock line to high.

How does this work? Is this how the master slows down its clock rate to let the slave follows it?


texts: Keep out zone of microSD card set footprint

texts:
I'm designing a PCB with Hirose microSD card set DM3AT-SF-PEJM5. In its datasheet, page 3, there are several "no conductive traces" area, which are marked as "keep out" zone in the footprint I found.

My questions are:

Why these areas are marked as "no conductive traces"?
If I design a multilayer PCB, say 4 layers, and place the microSD card set on bottom layer, then I cannot route tracks in any of the 4 layers , or just in the bottom layer?


texts: IC with configurable output : high-side, low-side, push-pull

texts: As the title mentions, I need to implement a design that would require an IC that can be driven in high-side, low-side, or push-pull configuration. The main purpose for this is that I need to drive some I/O with current sensing depending on the configuration. The voltage on those specific I/O goes from 4.5 to 36V. I've done some research and didn't find anything relevant, is there any IC that can accomplish this?


texts: USB communication keeps disconnecting because of power dip/spike

texts:
I've got a question. I've got CNC router that's connected by USB to a desktop computer. We're in an old building, and wiring is not optimal :) I'm not an expert, but I think too many rooms are on the same group.

My CNC machine disconnects every few minutes/hours. This happens when someone else turns on; a light, a water cooker, a vacuum cleaner, coffee machine, heck even the radio. This does not even have to be in the same room.

In a approach to fix this I've:

put one machine (cnc or pc) on a different group
put both machines on a different group
added a powered usb cable (5 or 10m)(the pc is a few meters away)

But no result. So my question is:

Do you know something to fix this?
would adding a UPS to the pc and/or cnc help? (are they quick enough to catch the dip/spike?)
Could or should a I add capacitors to the usb power wires. (if so, which)
Or even better, what is the exact cause for it all to crash. :)

-- edit --

The setup is as following

CNC Router from X-Carve

The machine (execpt the spindel) is powerd by the x-controller
it has an internal 24V 400W power supply

The CNC is connected to the PC with a USB cable

The USB cable has it's own (extra) external power adapter (5V 0.25 amp), a powered usb cable.

The desktop computer sends the commands to the CNC router

The pc has, from the top of my head, a power supply of around 200W

When a power drop occurs the CNC freezes. This is most likely because the connection to the pc is reset and it stops receiving commands.

Note, the power drop is always also noticed on other electronical devices.

Radio/Stereo speakers make a crispy/ticking sound on a power drop
Some people experience the mouse cursor jump a few cm on the screen on a power drop.


texts: Need help determining smoothing capacitor(s) for rectifier

texts: I am making a rectifier for a single N-Scale train building. It takes DC, but the train controller gives out 19VAC. I have 4 1N4001s and some capacitors, but probably not the right size/uf. I only need to make the 19VAC into 19VDC for this one model. I do not know its current draw however.


texts: When using a Primera-Line Wattage and Current Meter, is it showing AC or DC measurements?

texts:
I am new to the electrical engineering stuff and am looking for some guidance.
I'm going to be designing a off-grid power system for some devices. So I will need to get the power measurements from them. The devices are DC but come with invertors. I'm placing the Wattage meter between the UK mains outlet and the plug on the invertor, are these readings in AC or are these DC readings? The meter doesn't specify.
Thanks


texts:
I'm trying to create a circuit that can sense the state of a SPST switch in a series loop (constraints don't allow for the use of a DPST switch).  The idea is to expand this to work with more than just 1 switch in the loop, but for this example, I'm just testing with 1 switch to rule out variables.

I'm using an in-amp to measure the potential difference across a switch-resistor pair.  Circuit and important waveforms are as follows:

The blue waveform (V(n001)) is the node connected to IN+, the red waveform (V(n007)) is the node connected to IN-, and the green waveform (V(n004)) is the node connected to the output of the in-amp.

I'm using a spice model of the AD8422 as the in-amp.  In the simulation, I'm turning on the switch (SW1) after 5ms elapse, shorting the IN+ and IN- terminals.

According to the datasheet, with the 1k resistor connected across RG- and RG+, I currently have the differential gain set to ~500.  With a potential difference of 3V across the inputs of the in-amp, I would expect this to rail the output of the amplifier, but the results show the output is slightly higher than 1V.  I am wondering why this is the case.  Am I missing something?

Thank you in advance.


texts:
I'm looking at high channel multiplexers that can operate at voltages over 10V and for this component it says that the supply voltage is 12V which is okay for my application, but when you read under the section "Theory of Operation" it says "The valid input range for ±12 V supplies is ±5 V".

So what does this mean? Does it mean that when I supply the component with 12V it can only handle inputs of 5V?

Also, this component has specified input and output ports, they can't be both like this one from intersil? Am I correct?


texts:
The magnitude at w=0 comes out to be 0 (=1/infinity) , which is different from previous problems (they didn't have any zero) I've calculated, is this right? I guess it should be right (because G(s)should be zero at w=0, that's what comes to my mind if u ask me meaning of having zero at s = 0) but I'm not sure how to do Polar plot if this is right.. pls help me
PS: Did I calculate magnitude for w = 0 right?


texts:
So I've bought Chinese glue gun at ebay, but it had incompatible power plug and terrible cable.

I decided to replace wire and plug. I disassembled gun, and saw that wire goes straight to tip (which usually melts glue). But when I took metallic clip which was pressing to place where cable ended, I suddenly drop it.

I look what was there: yellow insulator (that plastic wrap which is hard to melt), 2 "golden" plates (connected to wires), and one metallic plate (looks like aluminum, sure it's not nichrome).

So looks like that metallic plate should be between "golden" ones. But here is the problem: It has only 0.07 ohm resistance when assembled back.
I've thought that original cable has resistance, but then wires should heat more then heater, but i checked anyway -- its 0.

Then I heat tip with solder till it started melting glue to check if resistance increases a lot with heat, but resistance still was very close to 0.

Looks like it's unsafe to use it because it'll be short circuit.

Am I right? Maybe I just assembled it wrong? Should I try to test it?

Photo:


texts:
This is a basic block diagram of source synchronous interface I found in altera document.

Here

This is how edge aligned source synchronous output looks like.

They say the reciever will shift the clock to meet setup and hold requirement. So I think it means the clock edge that is sent aligned with the data is latching edge or next clock edge. NOT the edge it used to launch the same data. Ha but the diagram given by altera (at the first), looks like it sends the same launching edge aligned with the data.

Then there is one more statement I found.

"Source synchronous interfaces often exhibits different behavior. Data may be latched by the same edge that launches it".

How is that possible. Is not this a hold violation ? I am Confused on which clock edge is sent edge aligned with data. Is it the same launching edge or next latching edge ?


texts: Can I use my PC SMPS 12V 450 Watt for my Embedded System work

texts:
I am a computer programmer and after a project with Image processing which runs on ARM Embedded system board. Specification says it needs 12V 1 Amp Supply. I have a computer SMPS which gives me 5v and 12v constant supply and rated as 450 watt. Also it is written it can draw upto 24A current so here I cam confused. Can this heavy amount of current burn my board ? Also I recall Ohm Law that if the v is constant then current will vary according to load. Please give me some right direction whether I can use PC PSU for my embedded works.

Thanks


texts:
I read this question and I have the same issue: acquire and protect an input with 5-24V range. I wonder if nowadays I can use a BSS126 as current source transistor.

It's a depletion mode N-channel, I checked the output characteristics and they seem correct.

I'm afraid about the type of transistor: BFR30 is a field-effect transistor (FET) while BSS126 is a MOSFET (SIPMOS). Is it suitable for this application?

UPDATE

Actually I don't need a constant current to detect the input status in the 5-24V range. But I have very limited space on the PCB board so I'm looking for a minimum-components solution.

I tried with the simplest scheme:

simulate this circuit – Schematic created using CircuitLab

Some notes:

I selected a zener with a reverse voltage slightly below the minimum input voltage
R2 can be selected to allow about 5 mA through LED and opto-coupler: (4.3V - 2.1V - 1.1V) / 5mA = 860 ohm
with 5V at input, R1 should let flow 5mA towards the opto-coupler and a couple more for the zener, say (5V - 4.3V) / 7mA = 100 ohm
with 24V, the current flowing in R1 is: (24V - 4.3V) / 100 ohm = 197 mA it's too much (about 4W!)

This is why I was looking for a more efficient way to acquire such a signal with few components.


texts: Measuring low current at very high speed

texts:
I have a circuit with a very-low-power Jennic JN5148 module with microcontroller and 2.4 GHz radio, and some low-power sensors.

I have to measure the supply current of all these components, in an interval of around a second and with a resolution of about 100 uA. These currents may have a maximum value of about 30 mA for the Jennic module, and slightly under 1 mA for the other components.

I should measure these currents simultaneously and at a frequency of about 10 ksample/s, and i need at least 4 channels.

The other requirements are to use as more as possible instruments over building amplifiers and so, and to perturb at least as possible the supply of components. Actually, the requirement is NO COMPONENTS and ONLY INSTRUMENTS.

Does anybody has an idea about the best fitting solution?
(i think that i've explained all but tell me if it lacks something)

EDIT: Found this that could be a solution, but can you help me understanding what is the perturbation that it adds to the circuit?


texts: Identify 3 states at the input - Automotive circuit 24V system

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I have a requirement to build a circuit which can identify 3 states at the input and the output is given to ADC of uC. I have the below circuit for 12 V systems:

The input can be connected to gnd, battery(T87) or left open. I am trying to use the same circuit for 24V system but since the ISO pulses(have to consider ISO pulses since input can be connected to battery) would go up to +- 600V in the 24V system, what are the changes that I will have to make. I have to probably change the resistor values and packages. What about the diode ? what are the parameters that I have to consider for diode selection ? and what would be the worst case for the diode, for example like Jump start, load dump , ISO pulses, reverse polarity ? the switching diode BAW56W was chosen for 12V system because it was already available in the BOM of our product.
Here is the link to my other related question, I was not too clear while asking that question. My main requirement is that my circuit differentiate between 3 states
Automotive electronic circuit design, Voltage divider to uC ADC pin


texts: Why does the difference amplifier formula not work in this case?

texts:
I calculated Vo for this ideal op amp circuit using the formula: \$R_2\$/\$R_1\$(\$V_2\$-\$V_1\$) = \$V_o\$
I believe the correct \$V_o\$ = -14V I did not get this result using the above formula. It seems the formula is not correct for this circuit but I don't understand why. Would someone please enlighten me?

simulate this circuit – Schematic created using CircuitLab


texts: how can a little led indicator work in a power cord - why doesn't it explode from 240v

texts:
my LED goes well when i use my little electronics kit but i have seen one in a power cord. it has 240v in it. why doesn't it burn out in the power cord.  there doesn't seem any room in the plug bit to have a resistor and to get rid of the heat if there is one.
Thanks. Kid friendly answer please.


texts: Transistor count in NAND or NOR implementation of boolean algebra?

texts:
I have a complex output function in boolean algebra ( Where '~' means NOT):

F=~( (a c ~d) + (a ~c ~d) + (~a c) + (~ a c d) + (a c ! d b) )

I know this can be simplified down to:

F = (~a ~c) + (a d)

Now the simplified version can be implemented in CMOS using 8 transistors, using custom gates. (i.e. not NAND and NOR exclusively)

If I was to implement the simplified in CMOS using ONLY NAND or NOR gates, how many transistors would there be? Is there an easy way to count by just looking at the function?

I figured that

1 AND -> 2 NAND
1 NOT -> 1 NAND
1 OR -> 3 NAND
1 NAND -> 4 transistors
1 NOT -> 2 Transistors

Which means the simplified version can be made up of 28 transistors?

EDIT:

So if I use demorgans: F=~( ~(~a ~c) ~(a d) )

~(~a ~c) is 8 transistors (2*2 for the inverters + 4 for NAND)
~(a d) is 4 transistors ( For a single NAND)
The above 2 are then combined in 4 transistors ( 1 more NAND)
Making a total of 8+4+4=16 ?


texts: How to add a multi-emitter BJT to LTSpice?

texts: I want to simulate the standard TTL NAND gate which contains a multi-emitter BJT transistor in LTSpice. I've searched the components available in LTSpice but didn't found this component. How can I add it to LTSpice (if possible)?


texts: Is there a prebuilt PCB that does the equivalent of a wall wart for a similar price?

texts:
I am working on a project, and I need to convert 240V AC power to 5V DC to power a microprocessor. I can't use a wall wart, and I am looking for a PCB that will do the same as one - for near the same price. Everything I have found that even remotely resembles what I am looking for (pretty much just the innards of a wall wart without having to actually take apart a wall wart) is really overpriced.

Any help?


texts: LED's brightness difference in these 2 circuits

texts:
I have past exam's problem as follows. Suppose there are circuit A (left image) and B (right image). The question is why LED in circuit A is brighter than in B. The solution states that the Low-level output current (20 mA) is much higher than High-level output current (1 mA). Hence, the LED in A is supplied with proper current. What I do not understand is how one can arrive at this conclusion using Kirchhoff's law and determine the brightness using voltage drop. I also want to know better about these current parameters by doing so.

simulate this circuit – Schematic created using CircuitLab


texts: How to measure collector current in BJT?

texts:
In the following circuit:

I know the expression for the collector current is $$I_C =\frac{V_{CC}-V_C}{R_L}$$
Say I have a potentiometer for \$R_L\$ and I decide to set it to 0 Ω. What would \$I_C\$ be in this case?


texts: Parallel RAM without large number of pins?

texts:
Back in the 1970s, Texas Instruments had a now-discontinued range of products that they called GRAM (and read only equivalent GROM) which was basically a standard memory chip with address and data all multiplexed onto 8 pins.  You'd start an operation by sending the chip two bytes of address and then every time you pulsed either the read or write pin it would read or write a byte using the bus, then increment the internal address counter.   The result was a memory chip that was almost as fast (at least for sequential access operations) as a standard parallel memory chip, but which only need a 16-pin package, rather than the 28-pin packages other similar memories of the day needed.

Today, for similar applications, you'd probably most often use SPI-accessed serial memory -- but the problem is that such memories are quite slow (most have a maximum throughput of about 20Mbit/s; some run as fast as twice that, but I haven't found any faster than that) whereas a modern equivalent of those TI parts could be much faster than that, easily allowing 100+Mbit/s access.

Does anything exist that's still in production and which behaves similarly to those TI chips?  The closest I can find today are custom-purpose parts, e.g. the VLSI VS23S010D, which combines a memory device that supports the kind of interface I'm looking for along with a display driver, which puts the pin count up to 48 pins... I'm ideally looking for something in a 14 or 16 pin package (I think 14 is the realistic minimum - 2x power, 8x data, clock, address select, read byte, write byte).


texts: SPI chip select --> data + clock delay tolerance

texts:
I know this likely depends on the specific chips and devices being used, but I'm just looking for estimate ballpark numbers.

I'm considering using the spi protocol for a project, and I can't seem to find any good timing diagrams, on the time tolerance from the assertion of the chip select till data must be pushed on the data line.

I'd love to be shown such diagrams for different devices, and what seems to be 'standard values', assuming that's a thing.

This is a learning project, electronics is not my main field.


texts: Serial communication between embedded system and PC with only USB ports available.

texts: I am working on an application where I have part of an embedded linux system transferring some data to a PC utilizing PySerial (a Python module). My question is: is there an alternative to finding a PC with an RS232 connector in order to establish two way communication between the PC and embedded system? Thanks.


texts: Design constraints when dealing with very high resistances in op amp's feedback loop

texts:
I have designed a PCB for a charge amplifier to handle a piezoelectric sensor, the first prototype is working properly. However, now coming down to the specific working frequency range, since the feedback loop is effectively a high-pass filter, with a cutoff frequency of 0.1 Hz, and there is a constraint on the capacitor's magnitude, with it being inversely proportional to the gain, I need to use very large resistance(s), in the range 3-10 Gohm, so I came to this question regarding the PCB design.

I have ordered SMD resistors, 5, 1, 0.5, 0.1 Gohms, all with the dimension of 0805 (inches), and the material of the Board of the PCB is FR4, the data sheet of which can be found here: https://www.farnell.com/datasheets/1644697.pdf, it's gonna be just the plain board with no coating or anything else after etching the copper.

I assume there might be some complications when it comes to such high resistances, stuff that I should be aware of, some design tips, and I just want to make sure there is no fatal flaws in my selection of components, or some properties that render them unusable for my application, like for instance the resistivity of the FR4 material, and the shortness of 5Gohm resistor. I have researched about aspects that seemed relevant to me, but I am still not so sure, I thought of everything.

So, if you see anything fishy or if you care to shed a light on anything related to this design, I'd very much appreciated.

By the way, is there any drawback to installing a number of resistors in series in the feedback loop instead of one gigantic one, maybe noise issues?

Thanks very much!

Albukhari


texts: Help with calculating voltage using watts/ohms (batteries/coils)

texts:
Okay, so I have no experience in EE (I do SE), so I don't know where to start. I apologize in advance this isn't the right place for this kind of question.

I bought a vaporizer with a small battery a while back, and the specs online say 3.7v 190mAh. Recently the battery died, but I have a much larger 3-7.5v 2000mAh Variable-Wattage battery that I want to use with the atomizer from the original battery. The resistance of the coil the current runs through in the atomizer is 2.44ohm, and I'm really trying not to blow out the atomizer or short it out with too much power, but using the interface I can only modify wattage, not voltage directly (if I'm correct in assuming it actually outputs 3.7v, or if that refers to something else I'm not aware of?)

TL;DR:
If I'm not mistaken:

3.7v -> 2.44ohm = 5.6w
3.8v = 2.44ohm <- 6.0w

That 0.1v shouldn't make a huge difference in the lifespan of the atomizer, right?


texts: Solar powered single cell LiFePo4 charger circuit

texts:
As a follow-up to this question I've come up with this schematic for a solar powered battery charger:

Subcircuits, from left to right:

Solar cell (just a voltage source), 12V, 10W.
Buck regulator with current limit set to about 300 mA,
output voltage selection: 3.5V (float) or 4V (fast charging)
LiFePo4 battery with charge enable transistors (M2 and M3)
3V LDO for the application circuit which includes an MCU

M2 and M3 are used to enable charging. If M2 is off, the battery can supply the application through M2's internal body diode. The gate voltage of M2 can rise above 3V, which is the reason why M3 exists.

M1 is used to alter the FB voltage divider. When M1 is off, the buck regulator's output voltage is 3.5V. When it is on, the output voltage is 4V.

I have selected the regulators as shown above mainly because they were available in LTspice, but also because U1 (the buck regulator) has current limiting and because U2 (the LDO) has a low dropout voltage. I don't need a shutdown pin on that one.

The design suggested in the linked question also includes a signal to detect if solar power is available, but I have omitted that in this schematic.

I also omitted the battery protection IC (BQ29706) because I could not simulate it. It will disconnect the battery from the charger when the battery voltage reached 3.85V (in fast charging mode), so that the buck regulator's voltage rises to 4V. With a simple voltage divider this can be detected by the MCU (not shown), which will then let the battery relax to 3.5V.

I chose a LiFePo4 battery because I want the circuit to operate at both low (say -20°C) and high temperatures (60°C). On average it will draw very little current and I want it to work over a full year. Peak current is 300 mA for a few milliseconds every now and then, and less than 1 mA while sleeping.

Specific questions:

Are there alternative parts that you would recommend? Is anything wrong with the parts I chose?
If I wanted to add MPPT to this, how could I get finer control over the solar cell current? The selectable voltage divider I'm using now is a bit coarse.
Apart from the battery protection, what other means of protection should I consider?
is it safe to add another transistor next to M1, below R2, in order to shave away those 20µA through the fixed part (R1 + R2) of the voltage divider?


texts:
I'm trying to poll the value of the ADC and store it in a variable using DMA but the variable store the value of the ADC1->DR only once(when the program start).
In the debug the value of ADC1->DR change but the variable stay the same.
This is my code:

#include "stm32f4xx.h"                  // Device header
volatile uint16_t DMAVALUE =0;
int main()
{
RCC->AHB1ENR |= RCC_AHB1ENR_DMA2EN | RCC_AHB1ENR_GPIOAEN;
RCC->APB2ENR |= RCC_APB2ENR_ADC1EN;

GPIOA->MODER |= GPIO_MODER_MODE0;
GPIOA->PUPDR |= GPIO_PUPDR_PUPD0_1;

DMA2_Stream4->PAR = (uint32_t)( &(ADC1->DR));
DMA2_Stream4->M0AR =(uint32_t)( &(DMAVALUE));
DMA2_Stream4->NDTR = 1;
DMA2_Stream4->CR &=~ DMA_SxCR_CHSEL; //STREAM4 CHANNEL 0
DMA2_Stream4->CR |= DMA_SxCR_PSIZE_0 | DMA_SxCR_MSIZE_0 | DMA_SxCR_TCIE |
DMA_SxCR_CIRC  | DMA_SxCR_EN ;// CIRCULAR MODE IS ENABLED
NVIC_EnableIRQ(DMA2_Stream4_IRQn);
NVIC_SetPriority(DMA2_Stream4_IRQn,0);

ADC1->CR2 |= ADC_CR2_ADON | ADC_CR2_CONT | ADC_CR2_DMA;
ADC1->SMPR2 |= ADC_SMPR2_SMP0;
ADC1->SQR3 &=~ ADC_SQR3_SQ1; //CHANNEL 0 IS FIRST IN SEQUENCE
ADC1->CR2 |= ADC_CR2_SWSTART;

while(1)
{

}
}
void DMA2_Stream4_IRQHandler(void)
{
DMA2->HIFCR &=~ DMA_HIFCR_CTCIF4;
}


texts:
I'm not an Ethernet connector expert.  I was wondering what are the CT pins in RJ-45 connector are used for.
From a search in https://www.edaboard.com/ I found this interesting answer from a user called Brian:

CT = Center Tap, they are the 'half way' point along the windings and used as the zero SIGNAL reference point for the differential data. On the LAN side they usually have an isolated DC supply added to them to alert the other end of the link that it is 'live'.

I wanted to know if this is accurate, and maybe get more information on this topic.
I'm about to implement a Pulse J4-2504HL 2.5GB RJ45 connector in my design of a PC motherboard using an I225 Ethernet Controller with Tiger-Lake UP3 CPU. I was wondering how I can know to what capacitor value and voltage should the CT pins there be connected to. I couldn't find this in the datasheet.
Here is the datasheet.


texts: How can I find the current position of the stack without a stack pointer in micro controller programming?

texts: How can I find stack position without using stack pointer you were given with upper bound of stack and depth of stack using embedded C or assembly language for 8051. Can anybody please help me finding the answer.


texts:
So, in my previous question I asked about using the SPI bus over short distance for board to board communication. I was recommended to try termination resistors. I placed a resistor close to the destination (but not exactly there, there was a distance of 1 cm) and grounded it [as this was a board without termination resistor footprints, I had to improvise. I couldn't solder the resistor onto the device as it's a TQFP and has delicate pins.]

From some basic testing, I found that a 1K resistor barely reduced the overshoot. 470 Ohms and 180 Ohms worked better. The lower I went, the better it worked. With 180 Ohms, the overshoot was about a volt or a little lower. Now, unfortunately, I can't go down much more than that because the current is more than my MCU can handle. I did fix the problem, on the current revision of the board, by using a 330 Ohm resistance in series. This brought the overshoot to 3.7 V and the rise time was 10 or 11 ns. But I would really like a 'proper' solution on the next revision. My frequency requirements stay the same: 2 MHz but would prefer 4 MHz.

So I felt I should ask here: on the next revision of the board, should I place beefy buffers on the lines? Finding a buffer isn't really a problem but the current draw will increase significantly - I have 8 devices on the SPI which need termination and 3 lines that are always active go to each. An example, SCK goes to all 8 devices. Each device will have, say, a 100 Ohm termination resistor. So that is a current draw of 12 * 3.3/100 = 390 mA!

So what is the best recourse here? Should I go for 'active termination' by using Schottky diodes as clamps?

EDIT: Regarding line impedance: As I mentioned previously, the intention is to connect 4 external board. The pad to pad distance is the same for all (12 inches). However, there are also devices on the same board as the MCU - but these don't need terminations - the lengths are about an inch (or less) and there is very little overshoot (300 or mV). The traces that go to external boards are rough the same length and width. The 2nd layer on my board is an unbroken ground plane.


texts: Cheapest reverb to stick in analog audio circuitry?

texts: What are the cheapest (<$5 in large quantities) reverb implementations you can think of for interfacing with analog audio circuitry?  It can be crappy but, of course, better is better.


texts: Is it appropriate to use the TB6621 or DRV8871 motor driver for powering 12V 1 amp motors?

texts:
I'm looking to make an Arduino powered rock crawler with 4 motors (want independent control of each wheel, also need to reverse).

I'm looking into buying 12V DC motors that seem to have about a 1A current draw. I'm looking at the 20 rpm 12V version here. Not sure if the motor will draw more current than 1 Amp based on the limited data sheet.

My original thought was to use 2 L298N motor drivers. I then realized the large voltage drop would be too inefficient so am now looking into MOSFET based drivers.

I'm now looking into using  a set of DRV8871 (datasheet) or TB6621 (datasheet) motor drivers. Each of these appear to be much more efficient MOSFET based drivers. Would the DRV8871 be superior in this scenario?

Which of these drivers, if either would be appropriate for this project? I'm open to using other motor controllers as well.


texts: Why is my instrumentation amplifier's output voltage completely wrong?

texts:
I'm trying to amplify the voltage of my load cell (Wheatstone bridge I believe), but my calculated values are not the same as my experimental values.

The load cell outputs a differential voltage of 0.1mV - 5mV (measured with a voltmeter), and I want to boost it to 0V - 5V (initially, then from 0.3V - 3.3V).

The OP Amps I'm using are MCP6273 "170 μA, 2 MHz Rail-to-Rail Op Amp".

Problems:

First stage is amplifying the voltage - I put a 2.5KG mass on the load cell, and it output a voltage of 2.5mV differential voltage as expected. However, when I measured the differential voltage between the outputs of the first stage op-amp's (all resistors removed, unity gain) I get a differential voltage of 7.8mV. Why?
Output of second stage is complete wrong. R1 and Rgain are 1Kohm each. R2 is 470 ohm, R3 is 100k ohm. This should give me a gain of 638 (i.e. 63.8mv - 3.19V at the output). However, even with no load (i.e. 0mV) the output is 3.3V. At 2.5KG (i.e. 2.5mV) it hits the 5V rail.

I have checked the connections multiple times
I have tried simply buffering the input (i.e without R1/Rgain/R1)
All the op amps are identical

What am I doing wrong?


texts: Over voltage protection IC keeps burning

texts:
I am currently working on a project where over voltage protection is necessary. I made a test circuit using an LP5300 (SOT23-6 type.)
https://datasheet.lcsc.com/szlcsc/1912111437_LOWPOWER-LP5300B6F_C387703.pdf
I supplied it with 5V and I used an LED (140mA-measured) without a resistor for a first test. For a second test I use the same LED with 3K resistor in series with it.
According to the datasheet it should also protect against over-current (2.5A) but I kept burning out the IC in the first test. During the second test it did not burn out. I assume this is because of the lower power dissipation, as a consequence of the 3K resistor. According to the datasheet, tests were conducted by the manufacturer with 5V input, and 2A current (\$R_{DS}\$ On graph.)
Question:
How is it possible that I can't even pull 140mA through without it burning out (0.7W power dissipation) but they achieved 5V 2A results? What am I missing? Can I achieve 5V 2A with this IC at all?
I would really appreciate some help on this.


texts: Does signal ground have to be connected to actual ground?

texts: Does signal ground have to be connected to actual ground, or does it simply need to be a common node? I have a number of "floating grounds" in my schematic (denoted by the upside-down triangle) and also actual grounds (on Arduino; denoted by lines slanted to the left). I assume they are distinct, and I'm guessing I have to connect all of the signal grounds together but I don't know if they need to also be connected to "earth" ground.


texts: Avoiding opamp saturation - working with apd

texts:
i have avalanche photo diode with which i am trying to digitalize the current from TIA through a comparator, the diode biased using a HVDCDC

the source is being a 20ns laser with a PRF of 3Khz

the circuit is as below

simulate this circuit – Schematic created using CircuitLab

the output of opamp for an high intensity light is like above, we can see the opamp fully saturated, but i am clue less about the over shoot and ringing effect, this happened when i have put my bias voltage 300V, i am not able to stop the opamp to enter in to saturation.

even if i see the datasheet of DC-DC CA05N, it can maximum source 2mA of current, and the peak current of didoe is only 0.25mA, so i understood the dcdc current is exceeding 2mA

so to avoid the opamp going in to saturation i tried to use a 300K in series with the source but still the opamp went to saturation,

it evident that in order to make the opamp not to go in to saturation, the only way i can try is to reduce the bias voltage to as less as possible, so i operated it at 70V for which the response is as below.

reasons are unknow for the expansion of 20ns pulse to 100ns even through the APD is having a BW of 70MHz,

so in order to operate the APD properly, i understood i have to bias with higher voltage to see proper response for low light, but at the same time i have to avoid saturation.

i feel limiting the current to the TIA will solve problem, kindly suggest some ways to bypass the excess current which is to the opamp.

Kindly throw some light on behaviour of APD in saturation also

EDIT:

as the answers suggested to go for a unity gain stable equivalent, i went for changing my opamp to LTC6269 which is 400Mhz unity gain stable

below is the result i got with photo diode polarity inversed, so you may see a inverted output, but effect persists

the analog support was suggesting me also on using a subber at the photo diode bias so i used a 20ohm in series with 100p cap thinking this disturbance is due to the power supply i am using, frankly i am clueless how to tweak a snubber

please help me in identifying the problems rootcause

**EDIT2:**i have to tweak my Cf accordingly i feel, to avoid this, i dont think this is ringing, i feel i have solved my problem , will comeback with results shortly

EDIT3 : replacing Cf with 4pF given me a clean pulse with out any ringing
Thanks for the help

EDIT4: But after few experiments i identified that i am not saturating the photodiode/opamp completely, so i have increase the pulse width and pulse power on photo diode with which my response turned like below


texts: How to find out if the input of a logic gate is negative in two's complement?

texts:
I'm trying to create something which will output whether the input of the logic gate is a negative number or not in two's complement. I understand how twos complement works etc, but i'm not entirely sure how I would convert that into logic gates. I was perhaps thinking of using a Not gate at the start since there would only be one input and one output as well.

Thanks.


texts: 50 and 60 Hertz, what is the visible effect?

texts:
I hope this isn't too noob of a question for this community and that the title is worded correctly...

I've got a few devices from Europe I'm using in Canada that are naturally 50Hz. I have to pro level transformers (not Samsonite ones from an airport, LOL) that are doing the job for these devices perfectly and with no real visible or audible difference. So, I'm wondering for example with my hand blender and food processor... the basic science answer is that the motors are going to spin faster. But is there a way to get a quantitative sense of what the extra cycles are doing to the appliances I use the transformer with other than, the manufacturer built it to work for 50 and you're making it spin faster? Should I use them at lower speeds, in shorter bursts?
Apologies if my terminology and descriptions are completely amateur.
Thank you!!


texts:
I am trying to choose my output capacitor for the TPS6107 boost converter. I am using the equation Io x D/ Fs x Delta Vout(Desired Output Voltage Ripple). I have found all the other values for the equation, but I am getting hung up on finding my output voltage ripple. Can someone help me understand this a little better?

Thanks


texts: Interactive Diff Pair Length Tuning Altium Designer

texts:
I am using Altium Designer and sometimes (very often) when I am using the Interactive Diff Pair Length Tuning even when I click properly on the wire I have this error :

As said in the response below I have done all the necessary about PreConditions for Differential Length Tuning and I am clicking on one of the _P or _N nets.


texts: Equivalent impedance seen at input terminals of inverter stage

texts:
I am using a three phase interleaved DC-DC boost converter which is followed by the three phase inverter. I need to model the impedance seen by the DC-DC converter when inverter load is connected to it. I have series R-L load for inverter. Now, intuitively, I the impedance seen by the DC-DC converter should be the impedance of inverter, which I believe is (Cdc_link) || (R+Ls) (where s shows frequency domain, s=jw). But when I take frequency responses, I get this impedance to be (1/sC) || 2*(R+Ls).
Can anyone help me figure out the factor of "2" here? I am attaching images for further clarification? Why is the equivalent impedance seen by DC-DC converter is (1/sC) || 2*(R+Ls) and not (1/sC) || (R+Ls)??


texts: Why is the last carry block's gate in a full adder an OR gate (and not a XOR)?

texts:
It seems that a half adder (there are 2 inside a full adder) can't output both HIGH values for sum and carry, it's either Sum is 1 and Carry is 0 or the inverse. It's never Sum = 1 and Carry = 1.

To make it more explicit, the truth table of a half adder:

 IN               OUT
 A | B (or Cin) | S | C
 0 | 0          | 0 | 0
 0 | 1          | 1 | 0
 1 | 0          | 1 | 0
 1 | 1          | 0 | 1

The carry of the full adder is made with an OR gate, which can never receive 1 in both ins in this context. The difference between an OR and a XOR is that if both ins are HIGH the OR returns 1 and the XOR 0.

So an OR gate seems (at least to me, for now) to be inappropriate for that logic because it would act as if we were supposed to have that possibility, an OR gate outputs 1 if it receives both 1 in, right? Which a XOR gate wouldn't. I suppose it doesn't change anything as it's not supposed to happen so both components would work.

So why use an OR gate instead of a XOR? Is it because it's a less complex component? Is it some kind of convention? Or is it that if in any ("impossible") case both values are HIGH the output should be HIGH? (and possibly cause an error?)

Or did I miss something? I'm new to electronics and it bugged me...

edit: updated with image from @hacktastical and tried to clarify the question.


texts: Running DC motor at higher than spec voltage, but less current than max

texts:
I have a LS-280SF-20508 6V DC motor that I am hoping to re-purpose for a project, but I would like to use a 12V power supply as I have had better luck with MOSFET switching using standard (rather than Logic) FETs.

The motor will be running ~15 sec at a time, and at-most twice per day.
I will be using a 12V, 0.5A power supply (6 Watt max)
The spec sheet says that this motor supply can consume 2.6A (I assume at 6V) under peak efficiency -> meaning max 15.6 Watt.

Given this information, can I assume that I probably won't burn out this motor under these conditions? Am I also safe to assume that I won't burn my house down?


texts:
I have this synchronous buck converter.

Input voltage - 8.7V
Output voltage - 5V
Switching frequency - 350kHz to 450kHz
Output load current is 2A

Schematic:

I have an input capacitor of 68uF and an output capacitor of 200uF.
I am measuring the input and output ripple current through the capacitor (lifting on end of the capacitor component, and connecting a wire loop between the PCB pad and the lifted capacitor component pad and connecting a current probe on the loop) and I get this below waveform:
Yellow waveform (C1) - input ripple current. Peak to peak value is 3.59A and RMS value is 1.26A.
Pink waveform (C2) - Output ripple current. Peak to peak value is 73.32mA and RMS value is 24.48mA. (Even though I am using an electronic load to sink 2A, the RMS and peak values mentioned above is not matching. Is that correct?)

My questions:

Why is my input ripple current value so high and is it correct?

Why is my output ripple current so low even though I am loading the output with 2A? Is there any relation between the load current and the output capacitor ripple current? Are the values correct?

Can someone tell me how the input current waveform (in buck converter or boost converter or any switching converter topology) would look as I am unable to measure and also tried searching, but unable to find. Please help me understand the input current waveform.


texts:
I typically put a TVS diode on all of my power rails as standard practice to protect against ESD events. I'm using an FPGA in a design for the first time and I'm finding that I can't get a TVS with a 1.2V reverse standoff voltage to protect the FPGA core voltage. The only close options I could find were these two:

1.0V holdoff (too low?), 1.5V breakdown: https://www.digikey.com/product-detail/en/VESD01-02V-G-08/VESD01-02V-G-08CT-ND/2658775

1.5V holdoff, 4.8V breakdown (probably useless given the 1.32V absolute max voltage on the FPGA?): https://www.digikey.com/product-detail/en/DF2S5.1ASL,L3F/DF2S5.1ASLL3FCT-ND/5415965

Can I get away with using the 1.0V holdoff part? Is there a better way to protect a power rail at this low of a voltage?


texts:
I am building a hobby oscilloscope on ATmega16. I am testing ADC by generating a square wave at 2kHz with small amplitude and applying it to the ADC pin through a capacitive input with a voltage divider to shift zero-level.

This is how the signal looks after being sampled by ADC:

It looks fine, but after I start shifting zero-level by adjusting the potentiometer I get these strange spikes:

After shifting level a bit higher it looks fine again:

And then the pattern repeats:

Overall, I get 3 ranges where the spikes appear.

Some info

AVR is running at 16MHz
ADC uses internal 2.56 reference voltage
ADC is in free running mode at 125kHz (prescaler=128)
I transfer data via CP210 to an android tablet which is used for real-time plotting. The circuit is also powered from the tablet. I get the same results when the circuit is connected to PC.
USART baudrate is 500000b/s (UBRR=1)
AVcc and AREF are not connected. I also tried connecting AVcc to Vcc and adding a .1uF cap between Gnd and AVcc but this had no effect.

Some more info

this noise does not come from the generator (tested with analog oscilloscope)
this noise does not come from the potentiometer
LFUSE = 0xFF, HFUSE = 0x89.

ADC initialization routine

ADMUX = (1 << REFS0); // AVCC with external capacitor at AREF pin
ADCSRA = (1 << ADEN)
        | (1 << ADIE)
        | (1 << ADATE)
        | (1 << ADPS0)
        | (1 << ADPS1)
        | (1 << ADPS2); // Division factor = 128
MCUCR |= 1 << SM0;
MCUCR |= 1 << SE; // Sleep-mode enabled
ADCSRA |= (1 << ADSC);

ADC data transfer routine

volatile uint8_t adcLow;
volatile uint8_t adcHigh;

int main(void) {
    ....
    while (1) {
        if (ADCSRA != 0x00) {
            USARTSendByte(adcLow);
            USARTSendByte(adcHigh);
        }
    }
}

ISR(ADC_vect) {
    adcLow = ADCL;
    adcHigh = ADCH;
}


texts: CLL(Capacitor long life)capacitor filtering to reduce the current spikes

texts:
if we are using capacitor between the coomutation segments of brush dc moto then it reduces spark generation.
as main function of commutation system is to reverse the current in the coil.
by using capacitor filtering we can reduce the current spikes

but i need some detail understanding about this mechanism how actually it reduces spark generation...?

please give your valuable guidance regarding this

i have basic understanging regarding commutation system its principle and fuction.


texts:
Summary

I have a digitial guitar amplifier that can be controlled via a footswitch. The footswitch is connected to the amplifier via a DIN 5-pin cable. I want to be able to control the amplifier with another device. Therefore, I want to reverse engineer the communication via the DIN 5-pin connector. How would you approach this?

Some more info:

The amplifier is a Yamaha THR100H. I use it live with different effect pedals like overdrives and delays that come after the guitar and before the amplifier in the effect chain to alter the sound. Also, the amplifier has different build in amplifier types I like to switch to get different sounds. The problem is, that sometimes I have to push up to three buttons to get the setting I need for the next part in a song. This really bothers me.

My idea is to use a switching system such as the BOSS ES-8 with which I can switch different pedals on and off simultaneously. The top notch solution would be if I could also switch the amplifier types on the THR100H with this device. Like that, I would have a "One-button"-solution which would be really awesome.

If the protocol between the THR and the footswitch was MIDI then I could very easily integrate it with the a switching system like the BOSS since these often come with a MIDI interface to integrate with more complex devices. Unfortunately, Yamaha states on its website that although they use the standard MIDI connector (the DIN 5-pin) the protocol is not MIDI.

In this forum post a person named spiral opened up the standard footswitch and discovered that it has its own MCU. In the same thread spiral also states that the footswitch requires power over MIDI.

I really like the idea with the BOSS ES-8 and in general controlling the THR via MIDI. But I have never done something like this before although I am not too far away from the topic. I myself am a software engineer. So, if some of you could get me some starting assistance I could maybe build a device that transforms MIDI commands into the THR commands.

The first questions that comes to mind is what hardware do I require to get the footswitch to work with the THR while being able to sniff the communication? In the forum post above spiral says that he got the footswitch to boot but then it did not send anything. Most probably it needs to see the THR. So, the piece of hardware you put in between must really be invisible for the THR as well as the footswitch.

So, what device would you suggest?


texts:
I am working on a DIY Project where i have to control some brushless motors so i went for the vesc and i am using vesc 6. I have already done the configuration on the vesc tool.
I am trying to use the internal IMU and other functionalities of the vesc so i thought about connecting it to a microcontroler and i am using a heltek lora32. i used many libraries but none of them worked with my board then i found this project : https://hadi.timachi.com/project/7/DIY_mountain_e_bike_version_2
i started digging a little on the library used but same i ge nothing from my vesc.
I am willing to know if there is a way to connect my vesc to the microcontroler via UART.
Thanks for your help.


texts: What's the best way to mute summed stereo channels?

texts:
I am building an audio mixer, and most of the instruments produce mono signals (internally split to L/R), but want to make sure it is flexible enough to use true stereo devices, and sum to mono in my design. I was previously using 4.7kΩ resistors to achieve this, but the audio was rather low. I've since seen sub 1kΩ resistors being suggested here on EE.SE, but my concern is the muting of a "live" signal. Here is the circuit I am considering using.

The Question: If I were to use 100Ω resistors for R1 and R2, would there be any danger to my devices while the circuit is open? If so, what's a better way to handle this?

Additional Details (updated 4/24)

Muting (unless advised otherwise) will be performed with CD74HC4316 analog switch ICs controlled by touch-sense, so I want to mute as mono to limit switch count.
All instruments have stereo headphone outputs. I don't know the impedance, and it will likely vary from device to device, but they all function fine with Apple earbuds, as well as my 80Ω studio headphones.
I previously had R3 (A50k) before the switch so that there was always a path to ground, but this doubled the wiring between PCBs. The old design went: input to Control PCB (vol), out to Switch PCB (mute), and back to control PCB (pan/sum). I'd rather go in to switch PCB, and then to all Controls. A schematic of the old build can be found here.
The control PCB is already built, so I'd like to keep changes on the switching board if possible.

Possible Solution

Here is a new schematic depicting the audio path from input to summing bus with modifications based on a combination of the suggestions below.


texts: I'm trying to flash an LED when an AC current is over 4 amps.  To do this, I'm using a current sense resistor of 0.01 ohms.  That gives a threshold of 40mV.  But I can't figure out how to use this voltage to trigger the DC LED flashing circuit.  I thought of an optoisolator, but 40mV isn't enough to run it.  Any other ideas on how I can "connect" the AC to the DC LED circuit?


texts: My PCB manufacturer just informed me that he is facing PCB warpage issue in my simple, single sided, copper poured PCB. He says to avoid this issue he suggests to add a dummy copper patch by keeping 3mm copper clearance from all sides. I am not very experienced with PCB issues. Can somebody tell me what leads to this issue and what are possible solutions to this problem ?


texts: Why does voltage drop in a series circuit but current stays the same?

texts:
my basic understanding of electricity is as follows:
Voltage is the difference between the electric field strength of 2 points and how much work can be done by a charged particle as it is moved by those fields between those 2 points.
Current is the flow of charged particles and the consequence of voltage. There can be no current without voltage although there can be voltage without current.
Resistance is a measure of how much a material inhibits current.
The relationship between these three is expressed in an equation:
V = I x R
The problem I have is that when I apply this understanding to a series circuit, I struggle to wrap my head around how current and resistance can remain constant throughout the circuit but voltage varies? Shouldn't the current drop with the voltage? There are other people who have asked similar question but I could not really understand the answers so please keep it simple for me. Thank you.


texts: Current Sensing with Non-Inverting Amplifier

texts:
Hello, I'm implementing a current sensing circuit as shown in the schematic. The simulation works but the physical circuit does not. On the breadboard if I measure between the shunt and the load to the ground on the power supply I get 67.3mV, however if I measure across the shunt I get 27mV (expected value since current @ 100ohm load is 110mA). As a result the Op-Amp amplifies the 67.3mV and I get the wrong amplified voltage. I've connected all the ground rails together and to the power supply. Can anyone say what's the possible problem ?

EDIT: I changed the shunt resistor to 1ohm and it works as expected, so why doesn't it work with the 0.25 ohm shunt ?


texts: Use both manual switch and WiFi Smarth switches together

texts: I have Sonoff Basic WiFi Smart Switch that I would like to connect to my lamp and control it via phone. However if something will go wrong, or there would not be WiFi or for whatever other reason I want to have possibility to switch the lamp on/off manually also. The manual switch is the simplest one, where you can just on and off it, 2 wires are coming to that switch. In WiFi switch 2 wires are coming in and 2 are coming out (N,L).


texts:
I am having trouble finding the exact spec for the female F connector- what I need exactly is to know what is the connector diameter and the thread width. I found some info on Wikipedia, but its not clear to me.

What I need is the female connector diameter, possibly with and without the thread:

Should I assume, based on the information from Wikipedia that the female F connector diameter (including the thread) is 9.5 mm?


texts:
I am trying to do a simulation on the start up speed to a system powered by an AC motor.

As part of this I am trying to find a mathematical torque/speed curve that I can use.

I expect a curve that looks something like this.

I have used the equations HERE as reference for the below calculations.

My general process is

Determine motor resistance & inductance based on published data for full load conditions
Use this to plot a curve of the motors torque speed relationship

However the curve I am getting looks nothing like the published curve at low speeds. Have I done anything wrong, or is there a more accurate model I can use.

I am using a WEG motor as a reference with the following published data

  Frame: 315H/G
  Output: 185 kW
  Frequency: 50 Hz
  Poles: 6
  Full load speed: 988
  Slip: 1.20 %
  Voltage: 415 V
  Rated current: 328 A
  Locked rotor current: 2000 A
  Locked rotor current (Il/In): 6.1
  No load current: 119 A
  Full load torque: 1789 Nm
  Locked rotor torque: 190 %
  Breakdown torque: 210 %

Update

The best I can fit based on Charles Cowie's Answer

Rth = 0.03424
Xth = 1E-9
R2  = 0.0020499
X   = 1E-8

This still looks nothing like the published curve I am going to give up and go with just taking samples from number of motor curves. But I would still like to get a solution to this.


texts: FreeRTOS - Potential issues with Periodic Tasks

texts:
Suppose Task 1 has the highest priority of all tasks, and is run periodically using vTaskDelayUntil().

Task 2 has a lower priority, but is also required to run periodically in strict time intervals.

Does this mean that there may be cases when Task 2 isn't always able to execute at the right time, whereas Task 1 will always execute in the correct intervals?

What difference would setting both tasks to the same priority have, if any?

It is my understanding that an RTOS is supposed to execute tasks predictably/deterministically. How can this issue be avoided?


texts: Choosing external adapter voltage to power Arduino & Relay

texts:
I am designing a simple Arduino Nano-based circuit that will control a relay. The constraint is that it's going to run unattended, in a sealed box, for many days/weeks/months. So I'm worried about about choosing a power supply and how to power both Arduino Nano and the relay from it, with regards to longevity/heat.

Additionally, I want to use an external power transformer to keep the circuit at a low voltage, and I would like to use a relay module with all the necessary circuitry to be controlled via Arduino.

I can think of the following options:

1) Use 9V adapter, 5V relay, power the Arduino through its unregulated input pin with 9V, power relay through the Arduino 5V output pin.

2) Use 12V adapter, 12V relay, power relay directly from Vin, power Arduino with 12V through its unregulated power supply input pin.

3) Use 12V adapter, 12V relay, power relay directly from Vin, use a step-down converter to get 7V into Arduino's unregulated power supply input pin.

Option 1: I'm not sure though about the relay module's power requirements when powering through Arduino.

Option 2: 12V is at the upper limit of what the on-board linear regulator can handle.

Option 3: Extra components, but potentially more safe/stable?

As a sub-question, how can I source a decent power supply with a nice, regulated output? Do I care about "noise"? Should I get a switching supply or a transformer-based one? I need them to have "plugs" for easier installation and some semblance of electrical code compliance.


texts: Random values of voltage near ADC in current loop

texts:
I have implemented a circuit which allows to isolate a current-loop-based sensors. The schematic is as follows:

Everything seemed to work good in the breadboard. Without a MAX14626 IC, the circuit started from 2 mA. Now, I have this circuit on the PCB board. I get some voltage oscillations on the R13 resistor when the current is in the range between 4 and 5.5 mA. In the range between 5.5 - 20 mA everything works quite good.

What are possible issues with such solution?


texts:
I am under the impression that one reason the high voltage distribution network is earthed is to dissipate electrical environmental effects (say, a lightning strike on the line).

For long distance, high voltage distribution (275kV - 400kV as used in the UK), distribution is delta-connected.  I am unclear how a delta-connected line (which, as it is delta connected has no reference to earth) is earthed in this scenario?

I have heard about zig-zag transformers but know little about them, I am also stuck on the fact that the zig-zag connection is on the secondary, so the primary (delta) would still have no reference to earth.


texts: Component identification: general semi LP 3C

texts:
I have this component salvaged. I think it's very generic, but I cannot find it.

Properties:

Dimensions: SMT 1206 length size, although the width is wider
Logo: General Semi (now Vishay I think)
Texts: Line 1: LP, Line 2: 3C
One connection at each end
PCB: Unknown

I would like to know what this is, as I cannot find any datasheet or identification.


texts:
I have an hobbyist/newcomer pcb project that needs a SD card connector.
I link the datasheet of the part: DM3AT SD connector spec.
At page 2, it says: Voltage rating : 125V AC
SD card spec says it can have a 3.3V(DC) input.
My PCB is powered by a 5V current (micro usb) and a level shifter is present to convert to 3.3V where needed on the circuit.
--Question:
What should I do with that 125V AC? ignore it and put my 3.3 DC voltage to the VCC pin of the connector?
Everyone seems to do the same, even the modules have a level shifter but that is it.
I am a bit lost.
Thanks


texts:
A friend of mine is building a boat. On this boat, he has 12V batteries with a 230V/13A transformer.

Recently somebody suggested he should connect the null with the ground. With DC, this is common practice. But how would somebody suggest doing the same with AC?! Polarity switches continuously on AC.

I suspect he either misunderstood the advice or the advisor didn't understand it himself either.

What might the advisor have wanted to tell? There's no reason to assume malicious intent.


texts: How to select TVS diode for HCSR04 and ESP8266?

texts:
I am working on a home project with esp8266 12f module and ultrasonic module hcsr04. Since the voltage logic is different for both the modules. The esp uses 3.3v and hcsr04 uses 5v logic and hence I purchased microsmps from Easy Power with part no SO3V35400.
The microsmps provides 5v and 3.3v with 200mA each. So the 5v will be connected to the HCSR04 and the 3.3v will be used by ESP8266. The  5v supply will be used by the HCSR04 sensor and a relay. The 3.3v circuit will have esp8266 and 4 leds connected to its gpio pins.
From the datasheet of microsmps, it is recommended to use MOV and TVS as shown in figure.

How to select the TVS for my load.? Can you suggest any TVS and MOV?


texts:
We have two different computers with the same instruction set. There are three classes of instructions (A, B, and C) in the instruction set.
Computer M1 has a clock rate of 80 MHz and Computer M2 has a clock rate of 100 MHz. The average number of cycles for each instruction class and their frequencies (for a typical program) are as follows:

Instruction Class   Machine M1 Cycles/Instruction Class     Machine M2 Cycles/Instruction Class     Frequency

Class    M1 Cycles/Instrctn Class   M2 Cycles/Instrctn Class   Frequency
A               1                               2                   60%
B               2                               3                   30%
C               4                               4                   10%

Calculate the average CPI for each machine, M1 and M2.

My initial hunch would be to just do something like M1: .6*1+.3*2+.1*4 = 1.6/3=.53 average for M1 but that makes no sense.


texts: Generating error condition randomly inside a digital design inside FPGA

texts:
In order to aid in testing of the design, it is required that we put it into a "debug mode" whereby specific type of error conditions will occur at random intervals. We must then monitor the impact of these errors on the rest of the system. The type of error to be generated can be specified when we enter this "debug mode".
I can see that LFSR can be used to generate random numbers which is an interesting subject and that we need a seed to start them. However, I have found that I already have certain sources of noise in the system. There are 3 sensors on the board, one is for temperature, one is for acceleration and orientation of the device while the third basically converts readings from a transduer via ADC conversion. All three sources contain noise of course. The range and "at rest" value of these sources are not similar.
How should I exploit one or more of these sources in order to generate random number within specific range e.g 0 to 100 or -1024 to + 1024? Should I just take some bits from the ADC conversion from the sensors and not use the LFSR at all?


texts: How to calculate run capacitor value for inductive motor?

texts:
Hi.

At the attached circuit diagram you can see the connection of inductive motor (2 coils) with a capacitor and 12VAC source.
I would like to know how should I calculate the right value of the C1 capacitor in order to achieved a 90° shift in the capacitor-coil branch, so the motor will spin well? (according to the spec. that I drew on the diagram).

Thanks.


texts:
I'm using the ISP762T.

I have a 12V power source and all I want to do is switch it on and off (via microcontroller) depending if I want to power my 12V circuit or not.  That datasheet says present a logic high to turn it on.  Easy right?   Well, when I present a logic high to the input it works great - ie. 12V supplied to load.  When I present a logic low to the input (IN) it supplies around 10V to my load.  Why won't it turn off?


texts:
I write a VHDL code for an adder tree, with a parametrized number of vector. It's only for Learning purpouse, so I dind't implemented the carry between the block, I simple created a larger bus so I haven't theme.

I created the internal signal adders_intern, and I created the shown algorithm. To explain it, I attach the immage  with the adder tree (sorry for the quality).

Each number represent a signal in the adders_intern vector. So, in the example of the image, related to the algorithm, in the first stage the number of signal is odd so I do I(6) = I(0)+I(1), I(7)=I(2)+I(3) etc. In the second stage I do I(9) = I(6)+I(7), but in this case the number of signals is odd so the last signal is ported as is, so I(10 = I(8), and then I go to the next stage.

This bheavior is generalized for a number of signals equal to M. I check many times the algorithm, it seems correct, but the RTL add only the first two signals, and I don't know why.
Here is the code (only the process) :

    process (shifter_out)
        variable  x,f,k : integer ;
        begin
        for i in 0 to M-1 loop
            adders_intern(i) <= shifter_out(i);
        end loop;

        x := M;
        k :=0;
        while ( (x-k)/2 > 0) loop
                    if (  (x-k) mod 2 = 0)  then -- even case
                                     for i in x to x+((x-k)/2)-1 loop
                                           adders_intern(i) <=std_logic_vector( to_unsigned( ( to_integer(unsigned( adders_intern(k))) + to_integer(unsigned(adders_intern(k+1))) ), (M+N) )   );
                                           k :=k+2;
                                           f:=i;

                                     end loop;
                    k := k+2;
                    x :=f+1; -- next value of x
                    else             -- odd case
                                     for i in x to x+((x-k)/2)-1 loop
                                           adders_intern(i) <=std_logic_vector( to_unsigned( ( to_integer(unsigned( adders_intern(k))) + to_integer(unsigned(adders_intern(k+1))) ), (M+N) )   );
                                           k :=k+2;
                                           f:=i;
                                     end loop;
                    adders_intern(f+1) <= adders_intern(k); -- finalization, for the odd case.
                    x := f+2;
                    k := k+1;
                    end if;
        end loop;
outp <= adders_intern(f-1); -- the last sum is stored in the output
end process;

I'm wrong something in the algorithm, or VHDL don't permit the description of this type of sctructure trough a process?

EDIT : I understand that it can't be made by a process, because process describe the bheavior, not how the interconnections should be wired. But now I was wondering if it is possible to do it with the "generate" statements. I see some paper on the internet that use "generate", with nested for statements, to do the inverse of the tree that I want to make (from one element to multiple elements, balanced tree. I want to make: from multiple elements to one element).
So I tried to do it with generate and some variable, used in the same way of the code I used in the process. But of course I got errors because I can't use variables outside the processes. I tried also to find out a clever way to manipulate the index and achieve the gol, but nothing seems to work.


texts: Is there a good solution for attaching wires onto a PCB which needs to be plugged into some sockets?

texts:
I need to plug an OpenCM9.04 A-type board into an OpenCM485 expansion board and connect some cables to the gpio sockets. From the manufacturer, the gpio sockets on the OpenCM 9.04 board are through holes and the 485 expansion board has the PCB socket pre-soldered on and I do not intend to remove it unless I have to.
My current solution is shown in the pictures. I soldered some long pin PCB headers with soldering pads on the other end onto the OpenCM 9.04 so that I can plug the board onto the expansion board. Then I solder wires to the soldering pads. However, it is not a pleasure to solder the wires, and the wires may come loose if the board is not carefully handled. What would be the recommended solution to this?


texts: How to indicate breakaway tabs in PCB design?

texts:
I'm designing two boards that'll always be used together. I'd like to place them both on a panel and break them apart after manufacturing.

I found a document on PCB CAD Design Guidelines that explains breakaway tabs and lists guidelines for their design.

  Board assemblies can be de-tabbed using perforated breakaway tabs, v-grooves breakaway tabs, or hand-cutting with a de-tabbing tool.

However, how would I indicate break away tabs in the CAD file? For the perforated tabs, I could add through-holes in a line (although I hope there's a more standardized method), but I'm not sure how to indicate v-grooves.

Also, what concerns should I be aware of with breakaway tabs?


texts:
I'm designing an expansion board for a Gumstix Overo IronStorm COM (Computer on Module). I need to connect three different USB devices to the Gumstix acting as a USB Host - all devices and the Gumstix will be on the same PCB. I'm using the TUSB2036 USB hub IC from Texas Instruments to do the job.

I think I've figured it out, but would appreciate any comments on the design below from any more experienced members who have used the gumstix and/or USB hubs before. All devices (the hub and three downstream USB devices) are self-powered. The downstream USB devices need to see 3V3 on the USB VBUS line to initiate their USB subsystems; that is why the PMIC input is 3V3. So, any comments on the attached schematic?

Secondly, the Gumstix documentation explicitly states that all logic is 1.8V. Does this mean that even the USB signals need to be level shifted before connecting them to the Gumstix? I'm pretty sure I should be able to connect the TUSB2036 upstream port (DM0 and DP0) directly to the Gumstix USB Host lines. Is this correct?

Schematic:


texts: Difference between antenna resistance and impedance

texts: From what I understand about antennas, they have a certain impedance.  At the antenna's resonant frequency, the capacitive and inductive reactances cancel and the reactive part of the antenna impedance is 0 ohms.  However, there is also something called the radiation resistance that still exists at resonance (for a dipole, it is commonly 71 ohms).  How can this be?  At resonance, doesn't the feedpoint of the antenna look like a short circuit due to resonance?  When the antenna is matched to a transmission line, do you use the reactance or the radiation resistance?


texts:
I'm struggling with non-linear control by myself.
By the way, I have a question with limit cycles. So Could you help me?
The problem is that

xdot = y + x(x2 + y2 - 1)sin(1/(x2 + y2 - 1))
ydot = -x + y(x2 + y2 - 1)sin(1/(x2 + y2 - 1))
Using polar coordinate,

show that the system has infinite number of limit cycles.
-> I guess that the "sin" term can have a zero at N*pi, It means it may have infinite number of limit cycles.(rdot=0 at the point)

determine the stability of these limit cycles( stable, unstable, semi-stable)
-> I dont know how can I solve...
(I think the sign of rdot can change around the point which can make rdot=0...)

I'm sorry that I can't attach my problem as photo due to app error.
I really appreciate your help in advance.
Thank you and Take care!


texts: I couldn't find much details about this protocol than an IEEE paper which I couldn't download. Any quick comments on this?


texts:
I need a 560k 2% resistor which has 5 bands, I am not getting it online.
The available resistors online are 560k 1W, 2W.
Which one should I choose?
Will one these resistors work as it should be instead of the existing 560k 2%?


texts: Ubiquiti/UniFi PCB component identification and polarity question

texts:
I stupidly dropped a brand new Ubiquiti UniFi AP-LR wireless access point on the floor. The impact broke off a component (shown in the picture) from the PCB which is preventing the AP from working properly.

I'm a complete novice when it comes to electronics but I feel that with a bit of luck I should be able to solder the component back on.

My question to you is, what is the component? I see there are many on the PCB of various sizes (highlighted in the picture).

And, should I worry about the polarity/which way round I solder it back on? This of course may be a bit difficult to work out, but at least I'd get a 50/50 chance of getting it right :)


texts:
I have struggled to understand this code but I can't understand the little endian for loop. Why is it necessary? And how could I read the page back? One byte at a time as an array? Is it even possible? Code from here

#include <inttypes.h>
#include <avr/interrupt.h>
#include <avr/pgmspace.h>
void boot_program_page(uint32_t page, uint8_t *buf) {
    uint16_t i;
    uint8_t sreg;
    // Disable interrupts.
    sreg = SREG;
    cli();
    eeprom_busy_wait();
    boot_page_erase(page);
    boot_spm_busy_wait(); // Wait until the memory is erased.
    for (i = 0; i < SPM_PAGESIZE; i += 2) {
        // Set up little-endian word.
        uint16_t w = *buf++;
        w += (*buf++) << 8;
        boot_page_fill (page + i, w);
    }
    boot_page_write(page); // Store buffer in flash page.
    boot_spm_busy_wait(); // Wait until the memory is written.
    // Reenable RWW-section again. We need this if we want to jump back
    // to the application after bootloading.
    boot_rww_enable();
    // Re-enable interrupts (if they were ever enabled).
    SREG = sreg;
}


texts:
My usbasp was working fine.I could burn programme to atmega328p.But last night i wanted to cahnge the clockspeed by clock_prescale_set  (   clock_div_t     x   ).
after that it burned successfully and changed the clock speed.But  I couldnot burn any new program.it shows this error massage in avr studio:

avrdude.exe: warning: cannot set sck period. please check for usbasp firmware update.

avrdude.exe: error: programm enable: target doesn't answer. 1

avrdude.exe: initialization failed, rc=-1
             Double check connections and try again, or use -F to override
             this check.

What is the problem and how to solve it?


texts: Beagle Bone Black interrupts for optical encoder

texts:
I'm trying to have my optical encoder work on interrupts. I found some resources online that discuss it but they all seem to be based on an older version of debian since the files and folders in "/sys/class/gpio" are different. The article I was trying to use says to alter "/sys/class/gpio/gpio7/edge" by issuing "echo both > /sys/class/gpio/gpio7/edge" and monitor "/sys/class/gpio/gpio7/value" in the user program the interrupt is implemented in. I was wondering if anyone knows the equivalent files to alter in "Linux beaglebone 3.8.13-bone70"? I plan on using python w/ Adafruit_BBIO.GPIO but I wouldn't mind using C/C++ if needed. Any input or alternate method of implementing interrupts would be much appreciated.

thanks,

Link to article:

https://www.linux.com/learn/tutorials/765810-beaglebone-black-how-to-get-interrupts-through-linux-gpio


texts: Easiest way to find transfer function of a lossless ladder filter after we finish design?

texts: I have completed my Lossless Ladder BPF design, but I don't know how to find the transfer function of the resulting circuit without going through the slow and rigorous process of getting resistances of capacitors, inductors, and resistors in s-domain and working backwards from the end of the circuit until I have an equation relating the output to the input and then solving for Vout/Vin. Is there a faster way?


texts: What does a High Impedance input mean for an ADC

texts:
The ADC ADS131M08 list a feature:

Can someone elaborate what this feature implies? Does this mean i can place a 300 Kohm resistor in series with the inputs? There is even a reference on page 88 with 900Kohm for measuring 220 VAC.

Because if it is it would be great because i can increase the overvoltage the pin can handle just as disscussed in this article. Would i suffer some aliasing using high value resistors??


texts:
From this paragraph, I understand that the reason for putting a notch on a 32 bit PCI card is simply to prevent people that doesn't read the specifications from frying their cards.

In other words, what I understand is, 32 bit PCI cards (and their sockets) could very well be made without any notches whatsoever. But in that case, people would need to read the specification of their motherboard and of the PCI card, in order not to connect a card that has a different voltage requirement than of the motherboard.

I.e, putting notches on PCI cards is not a technical requirement, but a user experience requirement.

For 32 bit double voltage PCI cards, I understand that having two notches is to be able to insert them on both 3.3V and 5V type sockets.

My question is, why do single voltage versions of 64 bit PCI cards have two notches? Is it to create some kind of backward compatibility with 32 bit PCI card slots?

What is the reason for an extra notch in 64 bit PCI?

Edit

I am talking about the rightmost notches in the card and slot of 64 bit PCI. Both images are from Conventional PCI Wikipedia page.


texts:
I have connected a photo-resistors terminal to atmega320'S ADC0 (PC0) PIN, the other to 5V and the third to ground via resistor

I'm powering my atmega with 3.7v. My goal is to output the value of ADC0 on DC6 pin using PWM. I have the following code:

#define F_CPU 8000000UL

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

int main(void)
{
    initPWM();
    initADC();

    while(1)
    {
        startConversion();

        OCR0A = ADCH;

        _delay_ms(20);
    }
}

void initPWM()
{
    DDRD   = 0b01100000;
    TCCR0A = 0b10100011;
    TCCR0B = 0b00000001;
}

void initADC()
{
    // Internal 2.56V voltage reference
    // set ADC0 as the ADC input channel
    ADMUX  = 0b11000000;

    // enable ADC
    // set prescaler to 128
    ADCSRA = 0b10000111;
}

void startConversion()
{
    // enable ADC
    // start conversion
    // set prescaler to 128
    ADCSRA = 0b11000111;
}

I tried to output both ADCH and ADCL via OCR0A, but the light intensity of the PD6 doesn't change, but if I set 0CR0A to 255, it glows super bright so PWM is working. I tested photoresistor with multimeter and I'm getting 0.6v to 1v between the ground and ADC0. Any suggestions?


texts: Do I need PSUs with similar current rating when I connect them in series?

texts:
I need a 48V power supply with 20-25A so I decided to use old ATX power supplies I have lying around.

I know already that the series of ATX PSU can be used to charge lithium packs for RC planes, it works by insulating ground from negative in all but one unit.

However, is it correct that only the unit at the highest potential will supply all the current?

Can I use differently specced PSUs with only the "top" one rated for the current I need? In this case, I could use even a simple step-up converter as the low PSU, powered by an independent DC supply.

simulate this circuit – Schematic created using CircuitLab


texts: Controlling 12V Magnetic Latch Solenoid with RaspberryPi 3b

texts:
As the title says I am trying to control a solenoid with a raspberry pi. I am currently using an npn transistor (will post link with parts at the bottom) however I am having a hard time getting it to work. The collector is at 12V and the gate is controlled by the raspberry pi gpio pin (runs at 3.3V and 16mA (this is the max amount I believe)).

Attached is a picture of a circuit I used to verify my solenoid circuit. It is essentially the same except that it has LEDs and that it runs on 3V instead of the 12V for the solenoid. Unfortunately I do not have any pictures with the solenoid. It would look roughly the same except that the two positive legs on the solenoid replace the LEDs and the single ground wire is hooked up to the negative row on the breadboard.

This verification circuit works perfectly, but the solenoid circuit does not. I have read online that MOSFETs can also be used as a switch, would this be better? In the case that it is, I would like to try to get the NPN transistor to work as I would rather not use more money.

Any help is greatly appreciated.

Thanks.

Solenoid (15mm version): https://www.pneumadyne.com/way-normally-closed-latching-solenoid-valves-p-1448.html#1-YToxOntzOjQ6ImdyaWQiO2k6MDt9

Transistor: https://www.mouser.com/ProductDetail/Diodes-Incorporated/ZTX688B?qs=sGAEpiMZZMshyDBzk1%2fWizF0eVyYE44ZxbGt8e1SnMg%3d

Images: https://imgur.com/a/gOnuPFT

I have included a diagram of what my solenoid circuit looks like.
For reference on the transistor labeling, as I am not sure what is common.
B - base (gate)
C - collector
E - emmitter


texts:
I'd like to use this isolated DC-DC converter:

https://power.murata.com/datasheet?/data/power/ncl/kdc_nmg.pdf

to feed a 7915 linear regulator.
I'm wondering if it is possible to use that DC-DC converter (the variant with +24V output) to feed the 7915 by reversing the polarity of the DC-DC output (so - goes to VIN on the 7915 and + goes to ground).

would that work correctly?

ps. I know it would be better to just get a single DC-DC converter to obtain -15V, but I really need to go into the 7915.


texts: Accuracy Beyond Current Rating of Current Transformer

texts:
We're currently working with a current transformer of the follow specifications:

Link:http://www.eastrongroup.com/productsview/30.html
I'm a bit confused when it says it's still accurate up to 120%. Does that mean it's able to output beyond 333 mV (near 400 mV)?

Also, are these ratings in RMS or Peak?

Edit: Changed "beyond 120%" to "up to 120%"


texts:
Lets say you want to operate at 20uA base current.
To move along that 20uA graph, you need to vary Vce.
But to vary Vce, you either vary Vb (voltage at base) or change the values of the resistors at emitter or collector or the Vc (voltage at collector), is this correct?


texts: Trying to understand why power equation and ohm's law equation aren't agreeing

texts:
Hobbyist EE-in-training here. I've been doing some simple problems to reinforce my knowledge of ohm's law and I've run into a snag -

  A stereo speaker has a resistance of 8.00 Ω. When it is operating at full power (exactly100 watts) it uses 35 volts of electricity. What is the current drawn by the speaker?

If I solve it using ohm's law with $$R = 8.00$$ and $$E = 35V$$

I get

$$\frac{35}{8.00} = 4.38A$$

and if I solve it with the power equation I get

$$\frac{100}{35} = 2.86A$$

Shouldn't these two equations agree?


texts: Differenece between TV Indoor antenna and Satellite Dish

texts:
Satellite Dish for TVs enables you to gain access to paid tv shows through subscription.

I'd like to know if the Indoor antenna specs below can also get paid signals on the air and if it could be an alternative to Satellite Dish. Please do not consider the signal external interference's like the environment.

Antenna Specifications:

Built-in High gain booster
Gain Control Yes
Retractable dipoles   are adjustable for best VHF reception
Large UHF     loop improves image quality
Power-on  indicator
Input Voltage    AC 220~240V
Working Voltage  DC 12V/100mA
Reception Frequency  VHF: 47~230MHz
UHF: 470~860MHz
Blown-Up gain
VHF: 15dB
UHF: 20dB


texts: How to superimpose 2 signals to test op amp circuit noise inmunity

texts:
I have a simple circuit with uses a non-inverting op amp. Just for the shake of my learning, I want to add some noise to the op. amp.'s input and see if I can remove it applying filters.
To do this, I have a oscope which is able to generate a random signal (range -1V to +1V). In addition, I have the data of a a noise signal that has a +14V spike. Since the signal generator can only go to +1V, I will amplify this noise signal with another op. amp. to reach those +14V.
What I don't know is how to safely wire the circuit to superimpose my scope noise signal to the "production" op. amp. input (the op. amp. I want to test, not the one used to amplify the noise signal). I'm specially concerned about keeping safe my oscope.
How can I do this?


texts: I have designed a data collection device which is mounted on a moving vehicle. Is there any recommended connectors that can survive high vibrations for digital sensors?


texts: Instrumentational Amplifier with Summing Amplifier

texts:
As you all know, most Inst. Amp. examples on the Internet have a 'Differential Amplifier' part as shown below.

But, what would happen if a summing amplifier was used instead ?
What kind of disadvantages I would have ?

Noise elimination and gain are very similar like Diff. Amp. does if my calculations are correct.

Any comment will be appreciated.
Thank you for your consideration.


texts: DESFIRE does not reply to REQA from MFRC522

texts:
I'm writing an stm32 driver for the NXP MFRC522 ISO14443A PCD but cannot get it to talk to DESFIRE cards.

My code will correctly identify both Mifare Classic (4-byte) and NTAG203F (7-byte) PICCs and it can correctly read the contents of an NTAG203, so I'm confident that the analogue layer is probably right and that I have the cascading anti-collision protocol close enough to correct to select a single card.  I'm using one of those $5 eBay MFRC522 boards with a PCB antenna that's about 32x35mm square, 4 loops.

However when I present it with a DESFIRE card, there is no reply to REQA or WUPA.  For lack of ATQA, the code doesn't begin the anticollision process, it just thinks there is no PICC present and keeps on REQA-polling at a few Hz.

My android can talk to the DESFIRE cards (MF3ICD81) with no issues, so the problem must be with my system.  Likewise our local bus passes are DESFIRE and can be detected by an android but they do not respond to REQA from my system.

Does anyone know if there is any manner in which DESFIRE cards need to be treated differently, e.g. modulation settings or something (I have set the "Force 100% ASK" bit)?  Any common pitfalls?


texts: Will this circuit function properly? (Toggle Flip Flop)

texts:
I am new to electrical engineering and was trying to design a toggle flip-flop. Will this circuit work?

The D2 (LED) should remain on once T1 is pressed and released. T2 should short the power from the transistor and turn it off until T1 is pressed again.

D1 is supposed to keep the base on TRAN1 positive once activated. Is this correct, or will it not happen?

If it won't work, how could I rewire it to function properly?


texts: How good is the advice to run the car headlights before starting the car in cold weather?

texts:
I'll do my best to formulate this as a purely electrical problem so that it isn't claimed to be belonging to Vehicle Maintenance SE.

We have a lead-acid starter battery (not a deep cycle fashion) that has been sitting in low temperature conditions - something like -20 degrees Celsius (-4 Fahrenheit) and so it's capacity has seriously reduced compared to warmer weather. We have an engine starter that drains about 200 amperes from the battery for several seconds.

Now there's a claim that simply trying the start the engine is not the best practice because the very cold battery will not give much power and the engine might not start. The "better practice" is claimed to be to turn the headlights on for about half a minute so that "the juice starts flowing" and the battery warms up and outputs more current.

So the myth goes. Now a typical headlight bulb power is 55 watts, so for both headlights we get 110 watts which means like 9 amperes current through the battery.

A typical car battery weighs about 17 kilograms (about 40 pounds). So the claim basically means that 9 amperes for half a minute is enough to warm a cooled to -20 Celsius lead acid battery and notably improve its characteristic.

Then shouldn't draining about 200 amperes for several seconds make the battery heat further and perhaps boil and explode?

From the point of how a typical lead acid starter battery works at about -20 Celsius is it possible that running about 9 amperes load for about half a minute would help it warm and output more power and get the engine starter run better?


texts: Calculating high side switching resistor values, Vout, and heat

texts:
I added 3 high side switches, like below schematics. And all needs to turn 5V on and off.

I have few questions about it.

How do I calculate the resistor values ? I have few ideas but I want to know how its done
How do I calculate Vout of Q3 ? I think Vout will not be 5V
How do I calculate the heat of both Q6 and Q3 ? because one switch load will take around 5A, another will take 1.5A and third one around 1A. And they might be ON for hours.


texts:
I am trying to come up with a bit of a derivation for \$ P = \frac{1}{2}V_mI_m\cos(\theta) \$ and \$ Q = \frac{1}{2}V_mI_m\sin(\theta) \$, but using phasors (because I can visualise it better).

I know the following (mostly from another question that I asked):
$$
\text{Let } v(t) = V_m\cos(\omega t) \text{ and } i(t) = I_m\cos(\omega t + \theta)\\
p(t) = v(t)i(t)\\
p(t) = V_m\cos(\omega t)I_m\cos(\omega t + \theta)\\
p(t) = \frac{V_mI_m}{2}(\cos(\theta) + \cos(2\omega t + \theta))
$$
Then from the above it is easy to see that the average value is:
$$
\bar{p}(t) = \frac{V_mI_m}{2}\cos(\theta)
$$

Now this is not at all with phasors, I tried to get a similar thing going with phasors...

Here is my (failed) attempt.

If I assume I have some vector I for the current and some vector V for the voltage such that
$$
\textbf{I} = I_m\angle \theta\\
\textbf{V} = V_m \angle 0 = V_m
$$

Now from my understanding of Real Power, the real power is the component of the current, I, that goes in the direction of the voltage, multiplied by the voltage, V.

So the component of I that goes in the direction of V is
$$
\textbf{I}_v = |\textbf{I}|\cos(\theta) \cdot \frac{\textbf{V}}{|\textbf{V}|}\\
\textbf{I}_v = |\textbf{I}|\cos(\theta)\angle 0
$$

So now we have the component of I that goes in the direction of V.

Now I thought I'd just literally multiply that by V
$$
\textbf{P} = \textbf{V}\textbf{I}_v\\
\textbf{P} = |V_m||I_m| \cos(\theta) \angle 0
$$

Now bringing that back into the time domain
$$
p(t) = \left(V_mI_m\cos(\theta)\right)cos(\omega t)
$$

I'm pretty sure that this is just wrong...  However, I can't work out where it doesn't make sense!


texts: High pass filter (HPF) removing the DC component of the voltage

texts:
The HPF attenuates frequencies which are below the cutoff frequency. But, in many cases a HPF is used to remove the DC level from any voltage.

For example, in this case, the IC AD5933 supplies an output voltage of 2V DC with a frequency sweep from 50 kHz to 50.5 kHz.
In step 3 is used a 10 nF capacitor and 100 kOhm resistor to make the HPF, the cutoff frequency is approximately 160 Hz.

The output at the end of the HPF will be 1Vpp with the same frequency.

In this case, the purpose of attenuating frequencies below the cutoff frequency does not matter. Because the filter is only used to remove the DC component.
It does not matter if the cutoff frequency is 160 Hz, 10K HZ or 20K Hz.

I have two questions.

This change of purpose confuses me. Used this way. Is the circuit a high pass filter?

How exactly does this circuit work for this purpose to remove the DC component?
The value of the resistor does not make much difference, what really matters is the value of the capacitor, which should be 10n F, correct?


texts: What do I need in order to build and test a ferrite rod antenna for a specific frequency?

texts:
I am trying to piece together what I'd need for a small hobby project. I'd like to build something that is basically the equivalent to a home made avalanche beacon finder. Avalanche beacons transmit at 457 kHz and from the bit of research I've done it seems a ferrite rod antenna is the first piece I need. While I am pretty technical, hardware and especially radio are completely new to me.

So specific questions:

If I get a ferrite rod from here -> http://www.stormwise.com/page26.htm do I want the 125u ferrite or the 2000u ferrite? They seem to both cover the frequency I need.
Everything I find on the net involves building an antenna for AM frequency radios. I only need it for one frequency and it is below AM, right?
Given 2) How do I know how much wire to wrap? It seems like it's almost trial and error and I haven't been able to find any good resources for such calculations.
If it is trial and error, once I have my ferrite rod wrapped in wire, how do I quickly test it? Do I need an oscilloscope or some other piece of equipment? I have an avalanche beacon I can set to transmit, but I guess my question is how do I know my antenna designed to pick it up?
Any resources for this sort of stuff will be useful. I'm having a hard time tracking down an info and I think that's because I just don't know what search terms to use.


texts: How many Peltier will be connected to obtain 18V and 1 amps?

texts:
I am trying to generate electricity through a Peltier. I could supply heat of 120-degree Celcius to the hot side and 0-degree Celsius to the cold side.
I am thinking to use TEC1- 12706 Peltier whose configurations are:
Model number: TEC1-12706
Operating Voltage: 12V
Maximum Voltage Umax (V) : 15.4V
Maximum Current Imax (A) : 6A
Maximum Power: 92 W
Maximum Temperature: 138°C
Power Cord: 200mm

Though it has been stated I don't a single module will be able to provide 92W (Please correct me if I am wrong)
I want to generate 18 V and 1 amp. I have two queries:
1.How to determine the number of Peltiers required?
2.Is there any other way than connecting them in series to be able to obtain the required power?


texts:
So in designing a deep underground sensor network, my team wants to use a 1 MHz radio, but we cannot determine a way to model the soil, so as to calculate how deep i can bury a radio for showing proof of concept. The soil we are going to be using will have low humidity.

If there is any advice out there please let me know. thanks