texts: Trailing edge dimmer circuit limitations

texts:
I just came across this circuit meant for trailing edge dimming of LED bulbs but I was wondering what else could it be used for and what its limitations are during general use.
To my understanding by triggering the FET this circuit could either act as trailing edge dimmer / leading edge dimmer / normal switch.
This would be ideal to not only dim some LED bulbs but also to be able to control inductive loads and dim regular incandescent bulbs. Of coures a zero crossing circuit is necessary and a controller for switching the optocoupler (not included here.)
However, this circuit uses a rectified mains voltage compared to designs with two opposing FETs and there is no further protection but the built in diode of the FET.
I have a few questions regarding this circuit:

This was originally taken and modified from here.

Is my understanding correct that the circuit can be used as trailing edge dimmer / leading edge dimmer / normal switch by changing the timing of the FET switching?
Do inductive loads e.g. a heater pose a threat when dimmed due to the induced reverse voltage or is this covered by the bypass diode?
Are there devices known that can not cope with the rectified AC voltage or does this not matter since it reaches U=0v during each half period anyways?
Are there further protections required to switch inductive / capactive loads with leading- or trailing edge dimming or switching at U=0v?

EDIT: Datasheet of used FET


texts:
I'm working on a sensor similar to an oximeter that measures light attenuation through a medium. I have an LED on one side, and an IC photodiode with on-chip transimpedance amplifier (OPT101) on the other. The photodiode measures the LED output. To make the signal as clean and stable as possible, I run the LED through a current regulator (PSSI2021SAY). Here is a simplified schematic:

The problem I'm encountering is that when I switch on and off the LED, I do not get a square wave signal. When I shut the LED off, the falling edge is a square wave as I would expect - which makes me think the issue is not from the OPTI101 . However when I turn the LED on, the output signal is not square as the signal spikes, and then levels off. This happens on the order of 5 seconds which is not intuitive to me. I thought that LEDs have a much faster response time than this, so id be surprised if this is due to an LED warmup period. The OPTI101 also has a very fast response time (~50ns), and as the falling edge is square, I don't suspect it very much. Ive run may tests where I've removed all capacitors from the circuit to see if that was the issue, but still not getting square waves. (I've even run tests where I power the LED independently using a separate battery and a switch to further reduce capacitance). Ive run this experiment with/without the current regulator as well. Here are some plots of the signals I'm getting:
Turning LED on creates spike:

turning LED off produces nice square:

Full view:

Does anyone have any idea why I'm not getting square waves? Do LEDs really require a warmup period on this timescale?
EDIT: some updates on more tests I've performed:

Instead of turning on/off LEDs, I tried dropping the current, then turning it back up. I found that the issue still remains, but what's interesting is that there is a negative dip when it goes down as if the LED output has inertia. I think this too suggests that the issue is warmup related. As the current drops, the temperature drops, and the LED efficiency increases. Thus the initial drop would be from the prior low efficiency state at high current, then as the LED cools down, efficiency increases, and the light output increases. Here is a plot of the data (ignore x axis label):

I also tried mechanically blocking the light. THIS WORKS! This suggests that the OPTI101 is not to blame here (though I did not suspect it anyhow). So this further points at the LED system as being the culprit. And I still think it is temperature related, which if it is in fact the case, I don't see any solution for electronically...

Heres a plot of the result:

I must say that I'm still skeptical that it is impossible to get a square wave from an LED, given the fact that other instruments do operate by flashing LEDs, and they presumably don't have this issue... so question still stands!


texts: Frequency dependent capacitor for AC sweep analysis in LTspice

texts:
I need to model a frequency dependent capacitor for AC sweep analysis in LTpsice. I see that it is possible for inductors with GLAPLACE component, but I don't find anything about capacitors. The value of that capacitor, in LTspice code, is:

Cap = (1/(pow((6.28*Frequency), 2)*InducFilter))

where InducFilter is a constant.

Here is the example of a frequency dependent inductor:

Inductor example


texts: Why is the voltage across a dependent voltage source connected to an open circuit not zero?

texts:
I have the circuit shown below. I need to find the Thevenin voltage for it. If the dependent voltage source was a resistor instead, I think I could have disregarded it when using KVL (since the current equals zero). According to the solutions manual, however, I need to consider the dependent voltage source when using KVL, even though there is no current through it. Can someone explain why this is correct?

simulate this circuit – Schematic created using CircuitLab


texts: How to measure power consumption with a hall effect sensor?

texts:
I am trying to make a project in which power usage of our daily life devices such as refrigerators, television etc will be measured using a Hall effect sensor and a microcontroller (ARM Cortex-M TM4C1233H6PM series).

I know how the Hall voltage is measured using the sensor but I do not understand how should I connect it with my micro-controller and also how can the data from this sensor (Hall Voltage) be used to find out the power?

I know that this might seem like a very basic question but any help is much appreciated. If you know of any good resources then kindly refer them to me as well so I can learn it better.


texts: Difference between Ground and Digital Ground

texts:
While working with circuit simulators, I often come across two separate grounds:

Ground
Digital Ground

What is the difference between these two?


texts: Passive Convention Specifics With Regards to Resistors (Problem linked)

texts:
I was wondering how exactly passive convention works with respect to unlabeled resistors. In the problem attached, I realized you only get the answer if you label the resistor terminals one way, regardless of the direction you choose for the current. I was wondering, then, how you know which way to label these resistors. The initial method I used was wrong, which was to go clockwise and label the unlabelled resistor terminals positive to negative in that direction, but that turned out to be incorrect. Is there a general rule on how to label them, and if so what is it? I know it works the other way, (setting them negative to positive in the clockwise direction starting from the top left corner), but I don't understand why, or what dictates that. I am not concerned about the answer since I know the method to get it after trial and error, just the reasoning behind it, as this was a question of mine throughout other problems as well. I truly appreciate any help!

Problem:


texts: How can z80 uses a 4-bit ALU and return results in a single clock cycle?

texts:
According to Ken Sheriff's blog post Z80 ALU is 4-bits wide. If we take a look at page 8 and 9 of Z80 User Guide we will find the following information:

  Clock states T3 and T4 of a fetch cycle are used to refresh dynamic memories. The CPU uses this time to decode and execute the fetched instruction so that no other concurrent operation can be performed.

We also know that many instructions are performed in 1 machine cycle with 4 T-states, such as ADD r, SUB r, etc.

Considering the following facts:

Z80 data bus is 8-bits wide while its ALU is 4-bits wide
Some instructions that use the ALU are executed in 4 clock cycles (T-states)
We know that T1 and T2 are used for fetching opcode from memory and we need T3 to decode the opcode

How is it possible that a 4-bit ALU produces a 8-bit result in just a single clock cycle?


texts: Converting a 5 Volt controlled current source to 3.3V compatible

texts:
I want to create a relatively simple voltage controlled current source with a 3.3V micro controller. I have found THIS circuit and it seems to be what I need. The problem is it is designed for 0 to 5V.

So here are my questions and my research so far:

Question 1) Do you think a simpler solution exists (fewer parts, updated
    parts, etc.)?

Research 1) I can go with a single chip solution, something like LT3092 But, is that chip can be controlled by a microcontroller?

Question 2) What should I change in the schematic to make it 3.3V?

Research 2) In original circuit, 0V gives 0A and 5V give 100mA, so if I do not change anything in this schematic, 3.3V will give around 66mA. I guess it has to do with the pulldown resistor at the first input which forms a voltage divider?

Question 3) What should be changed if required maximum current is 200mA?

Research 3) It will be probably the internal resistance of the PFET at the output that limits the current, right? then, will I need more voltage at its input or I should change it with another PFET?

I am asking these questions to learn how the original circuit works, e.g.:

What is the role of those 100pF capacitors?
Why are the feedback resistors 10k?


texts: STM32: UART Interrupt is triggering without any flags getting set

texts:
I am using the UART4 module of an STM32F105. I'm using the RXNE ("RX Buffer Not Empty") interrupt to grab data as it comes in. It's working as expected.

When the RXNE interrupt is enabled it also enables the Overrun interrupt (ORE). This also appears to work as expected.

The ORE status flag is mapped as USART_FLAG_ORE. The corresponding interrupt flag is USART_IT_ORE. If the RXNE interrupt is enabled, when the Flag bit gets set it should cause the IT bit to also get set. Copied from the User Manual:

I'm handling the interrupt like so:

void usartISR(void)
{
    // Did we receive data?
    if(USART_GetITStatus(UART4, USART_IT_RXNE) == SET)
    {
        // Add it to the active buffer
    }

    // Did the receiver overrun?
    else if(USART_GetITStatus(UART4, USART_IT_ORE) == SET)
    {
        // Clean up and clear the Overrun condition
    }

    // No other triggers have been enabled
    else
    {
        ErrorHandler(ERR_BAD_INTERRUPT);
    }
}

The problem happens if the ORE flag is already set when I enable the interrupt:

{
    // The USART_FLAG_ORE bit is already set

    // The following command causes an immediate vector to the ISR:
    USART_IT_Config(UART4, USART_IT_RXNE, ENABLE);
}

The code vectors to the ISR, but the USART_IT_ORE flag doesn't seem to get set. The ISR merrily skips to the end and calls the error handler. If I look into the USART_CR registers, none of the other interrupt events are enabled. If I bypass the error handler, the code repeatedly vectors to the ISR even though no IT flags are set.

Why is the ISR getting triggered without the USART_IT_ORE flag getting set? Am I missing something obvious?


texts: How to determine the polarity of a piezoelectric buzzer?

texts:
Inside of a piezo buzzer is a little unimorph/bimorph disk which converts voltage to mechanical movement. To function as a buzzer, you just feed it an ac signal at its resonant frequency. However, John Alexander, the author of this project: STM Project, patented a design that uses the unimorph disk inside of a cheap buzzer as a fine-adjustment mechanism (US5866902).

Basically, if you apply a DC voltage to the across the ceramic part of the disk and the brass part, the disk will flex a very tiny amount (around 100nm/V).

My question is this:
Piezo electric elements are given a polarity by applying a strong electric field that aligns the dipole moments inside of the piezo material. Thus, I cannot a priori know if the piezo disk that I remove from a buzzer will extend or contract when I apply a positive voltage bias. Keeping in mind that an application of 15V would yield a flex of around 1um, what is a clever way to test a disk for its polarity?


texts: How to calculate this resistor MOSFET circuit?

texts:
Here are the given values:

\$U_B = 12V\$
\$R_1 = 100k\Omega\$
The transistor is not "loaded" meaning, the Source-Drain current and the current through \$R_D\$ are the same.

Here is what is needed:

Find \$R_2\$ so that \$U_{GS}\$ is \$6V\$. I have already calculated this and \$R_2\$ should equal \$100k\Omega\$.

Then the assignment asks if the current through \$R_D\$ is \$50mA\$ the voltage across \$U_{DS}\$ should be \$6V\$ aswell.

This is where I don't know any further. If the current should be \$50mA\$ the \$R_D\$ should equal \$240\Omega\$, but then theres no way \$U_{GS}\$ is going to be \$6V\$.


texts: Measuring a smartphone's power consumption

texts:
Scenario: A smartphone (Nexus S) battery is charged via USB connection, connected with a laptop. A measuring device (USB Tester) is running between laptop and smartphone.

Observation: The measured current and voltage while charging battery is - more or less -constant. After the battery is charged, the current drops to zero. This is the expected behavoir, but here it comes: After using the charged phone a few seconds, although the phone shows a "battery charged" status, the measured current rises again. It is not constant, but depends on the screen status, cpu load, apps running etc.

Question: Is this state - variable current, depending on actions taken on the smartphone - a direct measurement of the smartphone power consumption? Or do you have another idea what is causing this phenomenon?


texts: Why is there copper on the side of this package?

texts:
I'm searching around digi-key when I noticed one of the MEMS oscillators has these copper pieces on the edge of the package:

I'm not talking about the pads, I'm just talking about those little copper pieces on the side of the package.  I've seen them before and I've always wondered but I never really thought to question it.
Now I'm curious.

What are those for?  Are they the internal copper connections, and if so, why are they brought out to a visible location other than the pads you solder to?


texts: How to calculate the power dissipation of the snubber RC?

texts:
I have this snubber circuit in the DC-DC Converter.

Can someone tell me how to calculate the power dissipation of the encircled resistor?
And what would be the maximum voltage acorss the capacitor?
Input voltage max is 16V. Output is 3.3V.
Load current is 0.45A (max). Switching frequency is 2.1MHz.


texts: Current through a resistor and diode in series

texts:
Current i is same for every element connected in series in a circuit. Let, there is a diode and a resistor connected in series . Current through the resistor should be same as current through diode . But From the graph of load line and diode current equation it seems that current through the resistor will increase as voltage increases. But it is known that
current  through the diode will not increase that much(a tiny increase will happen). Isn't this a contradiction that elements connected in series shares the same current ?

A sample graph of diode i-v characteristics and load line:

Edit:
voltage through the diode will not increase that much


texts: Do RGB LEDs actually behave like three separate LEDs?

texts:
I am trying to operate a lot of RGB LEDs for a project. I came up with a crazy scheme which only works if the RGBs work exactly as three separate LEDs.

What I want to do is connect the R, G and B lines of all the LEDs with the same source of PWM and connect their grounds to separate pins(which have tri state logic). So when I want to turn on a pin I will give the PWM for the color on the PWM line and drive its ground pin low and ground pins of other RGBs to high impedance (theoretically separating them from the circuit). Will such a circuit work?


texts: Can I use use a set of transistors to 'select' from one or more capacitors

texts: I'm working with a monolithic audio amplifier IC that reads its gain setting from an RC network between two pins. The IC has fixed gain settings and the data sheet has a table specifying which resistor and capacitor values to use for each setting. I'm trying to make the gain setting selectable over I2C with a microcontroller. I think I did a similar configuration in the past with resistors but tbh it's been 20 years.


texts: How to use Counters ONLY to construct a School Bell circuit?

texts:
I am really stuck here, our instructor told us not to use the 555 timer (and to be honest I never used it). So we are supposed to make a circuit by using counters only, I guess.

How can I generate time periods, and set time in seconds or minutes? Is Johnson Counter the best to use here?

I included the project needed and the periods I made, if any one could help me on that.
My project is due to next Monday, and I would be really grateful if someone could give me an idea or a hint to start.

The Project: Design a digital circuit that can be attached to a school bill which can work automatically
from 7:00 AM to 12:45 PM, and it has the following features

1- Rings for 5 seconds.

2- Start ringing 7:00 AM to announce for the field gathering.

3- Rings 7:20 for going to class.

4- Rings for the start of the first class period at 7:35 AM.

5- Rings for end of each period after 40 minutes from its start.

6- Rings for break after 10 minutes from the end of the previous period to announce for
the next class period.

7- After the third period, a break of 30 minutes.

*The Bell rings for 5 seconds.

7:00 AM (Ring for field gathering)

7:20 AM (Ring for going to class)

7:35 AM (Ring for the 1st class START)

8:15 AM (Ring for the 1st class END)

8:15 AM – 8:25 AM   (Break for 10 minutes)

8:25 AM (Ring for the 2nd class START)

9:05 AM (Ring for the 2nd class END)

9:05 AM – 9:15 AM   (Break for 10 minutes)

9:15 AM (Ring for the 3rd class START)

9:55 AM (Ring for the 3rd class END)

9:55 AM – 10:25 AM  (Break for 30 minutes)

10:25 AM    (Ring for the 4th class START)

11:05 AM    (Ring for the 4th class END)

11:05 AM – 11:15 AM (Break for 10 minutes)

11:15 AM    (Ring for the 5th class START)

11:55 AM    (Ring for the 5th class END)

11:55 AM – 12:05 AM (Break for 10 minutes)

12:05 AM    (Ring for the 6th class START)

12:45 AM    (Ring for the 6th class END)


texts: Help Needed to Identify/Source Varistor S14 K140 0023

texts:
Could someone please advise on how I interprate the codes on this Varistor below..
I'm almost there, I can find the S14 / K140 on RS Components, But im unsure about the last 4 digits.
RS Website PN:2508485459
The part I have is numbered 0023  Im unsure what this stands for. I have heard that it may be the manufacturing date, in which case the one I have found will be the correct item. I just want to be sure it isnt another rating variable of some kind.
The Varistor is from a 110v Honeywell DKO 972 Flame Control unit from an EOGB X500 oil Burner.
Could someone just give me the nod as to if I have found the correct part and that I only need the S14 K140 part of the code.  Thanks in advance.  Roy


texts:
I can't seem to find an answer to this on Google.

Take a K-type thermocouple for example. The voltage produced is around 41uV/K. I'm wondering how this changes when a load is put across it. What equation determines the current? Can I assume that the thermocouple is equivalent to voltage source and internal resistance? What current would typically be produced when short-circuited?

Thanks


texts:
Just before I start description my question, I would like to let you know that I am new at this.

I am working on a solar air heater for one of my window. I've been researching and reading up on a lot of things but I am not sure if I understand how this whole thing works.

I have a computer 120mm fan that I want to run on solar power. I recently bought a solar panel thinking it was more than enough to run the fan. As it turns out that it was not putting out enough power. So, here is the specification for my fan.

I would like for someone to point me in the right direction as to what I need to buy in terms of volts and current level or the type of and size of solar panel to run my computer fan with solar panel.

UPDATE:
solar panel I purchased as follows:
Moultrie 12 Volt Solar Panel

UPDATE
I recently purchased a new solar panel 2.5W 12V NOCO BLSOLAR2 Battery Life Black 2.5W Solar Battery Charger and Maintainer. When I connect my CPU fan directly, it fails to run. In fact, there is an indicator light on the Solar panel connector and it came on right away as soon as I opened the solar panel. However, every time I connected my CPU fan to the wire, the indicator light went off. I believe it has built in safety that is preventing the flow of DC power to my CPU fan. I just want your thoughts before I decide to bypass its safety circuits by splicing the wire.


texts: Project Parameters as variable In Altium

texts:
I can't for the life of me figure out how to make the Project parameters show up in my schematic template.

I have a variable string called =Title which I'd like to set in the project parameters, but it doesn't show up. I know I can set it up in Document parameters, but I want it to be in the project since its global to the entire project and not just the specific sheet.

Anyone quickly know how to set it up ?

edit

The question may not have been clear.

In my schematic template, I have a string whose value is "=Title" without the quotations.
I have gone to the Project Paramaters tab {Project-Project Options-Paramters} and have created a new paramter.

For the name property, I have called it Title and for the value I have called Test123.

What I expect to have happened was my special string to convert to Test123. It does not.
I have changed the Name property to =Title and .Title and it still does not change.

If I change the Document parameters, I am able to change my special string into Test123.

Hopefully that's a bit more clear.


texts:
I have a little bit of confusion on how the textbook author is determining the high frequency cutoffs for the parasitic capacitance parameters for a common emitter amplifier. This is Boylestad Electronic Devices and Circuit Theory 11th edition.

For the analysis, he treats \$ C_s\$, \$ C_c\$, and \$C_E\$ as shorts since, at these higher frequencies, these high pass-filter capacitors will be low impedance. This makes sense to me.

He ends up with two high frequency cutoff frequencies (both a low-pass filter effect) as follows:

\$  f_{Hi} = \frac{1}{2 \pi R_{THi}C_i}\$

Where

\$ R_{THi} = R_{sig}//R_1//R_2//\beta r_e\$

with

\$ r_e \approx \frac{26mV}{I_{EQ}} \$

and

\$ C_i = C_{Wi} + C_{be} + C_{Mi} = C_{Wi} + C_{be} + (1-A_{VL})C_{bc} \$

So \$ C_{Wi} \$ is input wiring capacitance, \$C_{be}\$ is the base to emitter junction capacitance, and \$ C_{Mi}\$ is the Miller effect capacitance due to \$ C_{bc}\$ feedback from input to output.

\$ A_{VL} \$ is the loaded pass-band gain (though not accounting for the AC voltage source series resistance)

The other cutoff frequency is determined by:

\$ f_{Ho} = \frac{1}{2\pi R_{THo}C_o} \$

where

\$ R_{THo} = R_L//R_C \$

and

\$ C_i = C_{Wo} + C_{ce} + C_{Mo} = C_{Wo} + C_{ce} + (1-\frac{1}{A_{VL}})C_{bc}\$

Again the miller effect is seen on the output side.

The author goes through a numerical example, and using these formulas I get the same results.

However, when I simulate this circuit in LTSpice (being sure to convert the NPN model to an "ideal" NPN, and manually insert the shown capacitors), I'm seeing that only one of the break frequencies is close (the break frequency closest to the pass-band, aka the -3dB frequency). However, the other break frequency seems to consistently off by almost exactly +1 decade (higher frequency than calculated).

I'm curious if someone can explain why this is, or indicate the correct way to calculate both cutoff frequencies.

Here is my LTSpice simulation:

And here is the plot I'm seeing:

So from the math, I get a cutoff at 689kHz and 18MHz, but checking where the asymptotic lines cross, I am seeing more like 700kHz (good) and 120 MHz (bad).

On the other hand, if I compute the values of Ci and Co using the equations, and reform the simulation to use these values directly:

I am getting a much closer match to the textbook example (700kHz and 18MHz) :

So it's either the textbook isn't calculating the equivalent miller capacitors correctly, or the simulation isn't handling the feedback capacitor (Cbc) quite correctly.


texts: Question about a mosfet driver gate resistor

texts:
I'm considering the ZXGD3003E6 for driving an N-channel MOSFET - PSMN4R5-40PS,127. There is a typical application schematic in the MOSFET driver datasheet (as shown below). My question is how do I calculate the value of R1 and R2?

Edit: Will be driving the gate driver with a TLC272 opamp as a buffer which is connected to a 12V supply. Also the current through the MOSFET will be no more than 10A DC.


texts: Actuating a pneumatic solenoid manifold with Arduino

texts:
I need to programmatically actuate 5 pneumatic solenoids. Would it be feasible to do this by coupling a sufficient number of driver boards like one would use with stepper motors (i.e EasyDriver) to something like an Arduino Mega 2560 R3?

The solenoids I'm considering are 12vdc 3w.


texts: Spec sheet for a pulse generator: Interpreting current output

texts:
I am looking at the specifications of a device that produces a narrow pulse waveform, direct current, pulse  duration < 1 ms, frequency variable from 5 to 500 Hz. The specs for this device say that the output currant is 1 mA. My question concerns the conventions of spec reporting:

Does output of such a waveform at 1 mA mean that the currant is one mA integrated over the period of the wave, including the slack time between pulses, or does it mean that that the currant is one mA during the pulses when the current is flowing? To put the question in simplest terms, suppose the frequency was i Hz. In a second, would the current flowing through the circuit be 1 mA, or 1 μA?


texts: Current Boosting Techniques for Source Side

texts:
I'm trying to use a portable power bank (5V/2.1A) and try to supply power to my DC/DC Converter which will then be used to power something else (probably a laptop or so). However, the issue is that with a load of 70W (in the case of a laptop), my input will need significantly higher current than just 2.1A (70W/5V=14A). Also, it seems like a 10W source from my port battery bank will not be able to supply enough wattage for a 70W load and hence my question.

However, the flexibility is that I do not need to supply a full load charge to the laptop and I just need to verify that this concept works and able to charge up a laptop even if it's a slow charge. On a side note, I need to feed the output of my DC/DC Converter to my laptop AC adapter. I'm using DC only because of SMPS-based adapters since rectification is the first stage.

Hence, I'm thinking if there are any current boosting techniques at the source side where I can use to amplify the 2.1A to a higher rating? I've heard of methods that is able to have a certain pulses of higher current (e.g. 5A) for an interval and a slightly lower current interval (e.g. 1A) and it averages it out to whatever the input can supply (e.g. 2.1A for my case). Not sure what is that called though. Anyone knows?

And what about darlington pair? Heard that transistors are used to obtain a higher current gain but not sure if this is applicable for my case as it seems to be used for small signal applications.

Any advice on this? Thanks!


texts: Current capabilities of P-Channel Mosfet Circuit

texts:
I don't know how to ask the right question it would appear, but the following answer by Dave Tweed Refers:

Floating Voltage to Bias a P-Channel Mosfet without Exceeding Source-Gate Max Voltage

In Dave's answer, he refers to the transistor as being the current sink. Now my question is this:

Imagine, hypothetically speaking, I have a P-Channel mosfet IRF4905. And I drive a resistive load of -20 amps through the Mosfet. I am also driving the base of the transistor with a 10V signal. Would the current through the transistor be the 10V/1000R or would the current seen through the transistor be 20amps as well?


texts: Help identifying capacitor-like symbol with a bracket or "U" shape on one side

texts:
I came across a circuit diagram online which I want to modify for a circuit I am designing but I wasn't sure about one of the components in the diagram.

The component is labeled as CP has a value of Farads so I'm assuming it's just a capacitor but after searching around I couldn't confirm if it was or not

Is it some kind of special component or just an odd circuit symbol for a regular capacitor?

(whole circuit: https://learn.openenergymonitor.org/electricity-monitoring/temperature/files/rtdmodule.png)


texts: Why is Cat5/Cat5e Ethernet cable rated 100MHz?

texts:
As the questions says, is there any specific reason why Ethernet cable is rated 100MHz?

For a 100Mbps Ethernet the data rate is 100Mbps, and the baud rate is 125Mbaud, because of the specific line coding that it uses. What is the relationship between 125Mbaud rating of data transfer and 100MHz rating of cable?

Thank you.


texts: How to use my bits to transmit this photodiode signal in the most efficient way possible?

texts:
Suppose I have photodiode with a Dark Current of 5 pA and that using the NEP of that photodiode at some frequency \$\lambda\$ I determined that the smallest signal I could detect was of 1 pA.

First of all, does it make sense that my signal is smaller than the Dark Current?, my understanding is that they are additive, so when I have no signal I would see Dark Current \$\pm\$ Noise, but that would always be smaller than 6 pA, thus when I get 6 pA I know I had a real signal.

Now, assuming this is the case, what should I do with my ADC in order to have all my bits carrying information from the signal?.

Again, my understanding is that if I have, for example, 16 bits, and the Dark Current uses 8 of those, then there are only 8 for my signal.

Should I set the ADC to ignore signals smaller than 6 pA?, 11 pA?.

Signal theory is really not my area and I am not sure where to start learning it.


texts:
I was given the following data about a transformer

1 \$\phi\$
25 kVA
220/440
60Hz
gave the following test results

Open circuit test (440V side open)

220 V, 9.5 A, 650 W

Short circuit test(220V side shorted)

37.5, 55A, 950 W

While the values of the \$R_{CL}\$ and \$X_{ML}\$ are right (74.46 and 24.36 Ohms, respectively), the values \$R_{eqH}\$ and \$X_{eqH}\$ are not. It was solved in class way different from what I did, (sorry I understand that the nomenclature is changed sometimes) so I don't know which way is the valid one.

simulate this circuit – Schematic created using CircuitLab

What I was told -
To calculate the values of \$R_eqH\$ from to apply
\$P=I^2R\$
and then from the Short circuit test
\$\frac{950}{55^2}=0.31404\Omega\$

then from the \$V=RI\$,
 \$R=\frac{37.5}{55}=0.681\Omega\$
and then, apply the Pythagorean theorem

\$X_eqH=\sqrt{.681^2+.31404^2}=0.605\Omega\$

(fairly easy)

What I did
First I referred the values of the short circuit test to the primary side using the ratio \$\frac{220}{440}\$
giving the  values
18.75 V, 110 A and 950 W

then since the 110A are different to the nominal current   \$I_{1N}=25kVA/220=113.63A\$
I again adjusted the values to calculate if the nominal current was applied.
\$\frac{113.63}{110}=1.033\$
and the square is 1.067089,then the final values of
19.35 V, 113.63 A and 1013.73 W

To calculate the final equivalent values required then,

\$\frac{1013.73}{19.35*113.63}=.4608\$,
the angle is 62.55 degress and the sine is .8874

calculate
 \$Z_{sc}=\frac{19.35}{113.63}=.17035\$

and then the values of \$R/X_eqH\$ are
\$R_eqH=.4608*.17035=.0785\Omega\$
\$X_eqH=..8874*.17035=0.1511\Omega\$

that clearly does not match the other values, what did I miss?


texts: DC floating ground and TVS Diodes for ESD

texts:
I want to provide ESD protection for a low voltage battery powered device and I do not understand what sort of net I should attach to the cathode side of the TVS diodes:

I do not have a strong understanding of grounding, but it seems to me that attaching GND to the cathode end would allow the transient to flow into IC pins (via GND) and thus provide no protection.
Would it be correct to attach a metallic shield to the board at one point and and route the transient there, or something else I am unawares?  I'm quite lost and unsure if I am even in the ballpark.


texts: Is telephone and LAN wiring symmetrical?

texts:
Is telephone and 10/100 MBps LAN wiring electrically symmetrical? I mean is it allowed to swap wires in the pairs, or is one of them like GND so they cannot be swapped? It's important to know when I plan longer wires if I can use just two wires of the same color.

I am unable to find some information on how telephone and 10/100Mbps LAN communication works on this physical layer because I don't know the correct technical terms I should search for.

(I am not talking about symmetrical speed of digital lines.)


texts:
How exactly is JMP XXXXH; executed ?
First the PC(Program counter) will contain the address where this instruction is  present. In first machine cycle opcode will be fetched and PC will be incremented . Now in the second machine cycle we have to read the second byte of this instruction which is nothing but half of the address where we want to jump . So it should be loaded into half of PC.
But then how do we know the address of the 3rd byte of this instruction.
I'm confused


texts:
Hello everyone I realised after burning through 6 L293D's that they were getting old. I hated them mostly due to the fact that they were fragile. I also burned 3 of them because of static electricity. So I decided to try and make a cheap H-Bridge from transistors.

This is just a test circuit, what I need to know is: is the circuit correct, can this type of H-Bridge handle more than 5 Amps depending on the transistors used, and do you guys have any suggested modifications if it is wrong.

EDIT  11/27/2013

Here is the newest version


texts: Using 2N3904 as an amplifer for 3.3 V PWM to 10 V PWM

texts:
I was thinking of a circuit to amplify my 0-3.3 V PWM (500 Hz) signal to a 0-10 V PWM and the following circuit came to my mind:

simulate this circuit – Schematic created using CircuitLab
I tried this circuit on a breadboard and I noticed when I decrease the DC level of the PWM on the input the DC and amplitude of the signal on the probe node both decrease which I can't understand why! Because I expected that changing the DC amount of the input signal doesn't affect the amplitude of the output.
What is the reason?


texts: I have an old printing press that needs to be looked up.  The nameplates on the equipment say 230 V three-phase . The building I am putting it in has 120 - 240 with a Delta high leg. I am worried that the high leg will  Will harm the equipment as it goes to a control panel with lots of relays.   My question is does all 230v three phase power have a high leg .


texts:
I am routing a PCB with MOSFETs in LFPAK (aka SOT-669, Power SO8) packages for the 1st time. They look like D2PAK. The manufacturer, NXP, advises to draw identical polygons on top and bottom sides, connected to the drain tab, and linked together by vias, to transfer the heat from top to bottom side (bottom side cooling). They suggest to put the vias right through the drain pad, and around it.

Vias

They mention vias with 0.8mm (32 mils) hole diameter, but they don't comment on how they came up to this value. Isn't it too big ? I am concerned about the solder paste filling all the vias and the MOSFET not being soldered well. I'll have them soldered in an oven.

My reference : https://assets.nexperia.com/documents/application-note/AN10874.pdf, page 16.

Polygon connect

Should I use thermal relieves to connect the MOSFETs to the polygons ? I've read I shouldn't use them for vias.


texts: Currents and voltages in npn transistor circuit

texts:
I have the following circuit:

simulate this circuit – Schematic created using CircuitLab

And I am trying to calculate Rc and R2. I started by adding the currents but I am not sure for I1 or I2:

Is I1 the same with Ib or Ic?
Is I2 the same with Ib or Ie?
Does it matter? What I mean is even if I add more currents in the circuit will the result be same?

About transistor voltages:

Does Veb equals to 0.7V?
If yes, then Vbc equals to Vec - Veb (4.3V)?

And last question:

Is it true that Ie = Ic + Ib or is it true only when the transistor works on the linear region?


texts: Back feeding when connecting one side of circuit to differential op-amp

texts:
simulate this circuit – Schematic created using CircuitLab

I am building four 30v voltage sensing circuits to measure battery+/battery-, load+/load-, battery+/load- and battery-/load+ voltages to verify contactor open/closing sequence.

V1 is 30v battery
Load will be DC motor switched by 2 contactors, now im just using a open circuit to do testing.
The monitoring circuit can use battery negative as circuit GND, but I prefer not because I dont want connect low voltage side to high voltage side.
The circuit will be powered independently of battery because of above reason.
Schematic above only shows battery+/battery- and load+/load- sensing circuits.

When sw1 and sw2 are both open or closed, I got expected results (1.99v at outputs with 0.066 gain). However, when sw1 is open sw2 is clsoed (or sw2 is open s1 is closed), I see a weird 0.66v at output 1 while output 2 is 2v. What would be the reason?


texts: Can I submit bitmaps to be used for PCB silkscreen?

texts:
I have an image which I would like to silkscreen on my PCB. It's quite detailed and when I import it into my editor (I am using the easyEDA web editor) the software simplifies it before it imports it. I believe this is because it coverts it into a vector.

Is this image vectorisation a requirement of the Gerber standard or is there some way I could submit the original bitmap image to be used to create the silkscreen?

I have contacted the production house (JLPCB) and they said this was a design issue.


texts:
I got a flash for my DSLR camera: A mecablitz 52 AF-1 digital Canon with multi-language manual from here.

In section 15.2 (page 187 for english), it states:

  15.2 Conditioning the flash capacitor
  The flash capacitor built into the flash unit
  undergoes a physical change when the
  device has not been used for a long time.
  For this reason it is necessary to switch the
  device every three months for approx.
  10 mins. The power supplies must deliver
  enough power so that flash standby lights up
  no later than 1 min after switching on.

I'm wondering: What physical change could a capacitor undergo, which can be more or less avoided by charging it every three months?


texts:
I watched this video on YouTube, it covered fake energy saving devices.

I have seen many of these fake devices and they all seem to use a capacitor. My question is why would they bother? The person in the video explains that the capacitor would change the inductive loads, however normal household electric meters do not measure this.

Perhaps there are still countries which do pay for inductive loads where this device could be used? Otherwise, why would the scammers waste money on a capacitor and changing the inductive load...?

P.S I know nothing about electricity so please keep this at an easy level!


texts: wirelessly remote-controlled DC power supply with variable voltage

texts:
I need a remote-controlled (wireless) power supply, outputting between 0 and 10 volts and 0 and 2 amps, preferably DC. It should take 110v/120v AC as input. Its voltage should be controllable with a wireless remote control.

Does anyone know how to find such a device, or implement it simply?

I looked at LED power supplies, but they all appear to be constant voltage power supplies, which is not really what I need; this power supply heats an incandescent filament. Thus it seems I would rather have variable voltage, not variable current. Perhaps I should just add a resistor and convert this current source to a voltage source.

It could also be a DC power supply that uses a fiber-optic for communication/control (but I have not found any). It could also be a DC power supply that is programmable via some interface which can be converted to fiber optic or infrared wireless.

I want this DC power supply remote-controlled because it is going to be held at a local ground of 1000V (inside a metal cage), so this DC power supply cannot be touched by hand (resulting in shock).  It will be fed power from an isolation transformer, and held at 1000 volts local ground by a high-voltage power supply.

Application: The output of the DC power supply (1000 volts, and 1000 volts + Vdc) will heat a filament in vacuum, thereby creating effectively a hot, charged cathode that forcefully radiates positively-charged ions from residual gas in the vacuum.


texts: Does the EM radiation from AC power lines propagate through air or is it fixed around the line?

texts:
Because of the AC current flow, there is a changing magnetic field around the conductor, that in turn induces a changing electric field and vice versa

But does the EM radiation get "loose" from the conductor and propagate through air like with a dipole antenna for example or is it fixed around the conductor getting weaker with distance?


texts: Very Basic Electronics Question regarding current flow

texts:
This would be considered a basic electronics question that I should know (I've been all over the place with questions tonight and I apologize).

But anyways using this circuit (It's a TTL SR latch)

Simulation Link But the picture below shows the current flow in yellow. (This is the circuit linked above)

Anyways I mostly understand the circuit, yellow is current flow. Makes SR latches make more sense......but how come current isn't flowing into "OUTPUT" where I pointed with my Red arrow. I mean the Compliment Output doesn't really have much different, I mean current is flowing right next to both......or is this because this is on conventional current? I guess I just don't understand why both outputs are not High regardless....since we have current flowing right next to them (The dot over wires on them means they are connected correct?)

To Put simply I guess also:
Why does this show High

But this shows Low

When they are practically the same circuit....but one output is literally just lower than the other?


texts:
I'm trying to simulate a 3-phase inverter for BLDC(PMSM) in LTSpice. The problem is that drain current is way too high and also phase voltage isn't right.

**New image

*One leg

If I put one source(48V) I get spikes as drain current(green) instead of rectangle signal, blue signal is drain-source voltage:

Here are phase currents:

If I put two sources then I get rectangle but is way too high(3.5kA):

Here are phase currents:

Here are phase to phase voltage(blue) and voltage on one phase(green):

To get SPWM I compare sine wave and triangle wave, for other two phases I change Phi to 120 and 240. Also I have dead time circuit and that works fine.

It works the same even with or without back-EMF. I tried changing Rm and Lm parameters but nothing changes.Rm=1 Ohm, Lm=0.5 mH. I tried adding ground but it doesnt work either.

UPDATE1: Thanks to everyone.
I realized that I need to bootstrap MOSFETs. Now I'm trying to make driver with bootstrap capacitor and pnp and npn as seen in some datasheets/forums but it doesn't work for 3 phases(uploaded new pictures). I don't know what's wrong.
Tried with/without ground but it doesn't help.
Is it better to just include gate driver model?
I just need it for simulation to measure currents, voltages etc.


texts: How can a speaker have a higher output power than input

texts:
Looking around the internet, there haven't been many answers to this questtion. Here is one which doesn't fully explain it:
Power input smaller than output? How can this be?

So I am confused. I know that a transformer (step-up or step-down) can change the voltage and amperage, but without changing the overall power output. So how is it that a speaker (eg Panasonic SC-CMAX5) have a much higher output than input? How can the energy which is put in be less than watt is put out (get it?). The SC-CMAX 5 has a nominal input ("power consumption") of 92W but an output (RMS) of 1000W.

Is it something to do with the RMS or PMPO listed on the spec sheet?


texts:
Suppose I have a line of N LED's, of which only one is on at a time.  Is there a formula relating N to the minimum speed at which I have to switch between one being on and the next one?

IE: I give the formula my number of LEDs and then out comes the frequency at which I must cycle through them.

NOTE:

This should work in such a way that a human can not distinguish that any of the leds where off


texts: Simplifying this circuit using optotriacs?

texts:
I'm currently trying to create an interface between my Arduino-compatible (NodeMCU) and my OpenTherm boiler. OpenTherm is a protocol used by some boilers (mainly in Europe) which allows for the control of boiler temperature and other things like the boiler state; this is usually done by a stand-alone OpenTherm-compatible thermostat wired into the boiler. The protocol allows you to send and receive information from the boiler. However, the protocol operates on AC, and at a much higher voltage than an Arduino, thus, an OpenTherm to TTL levels adapter is needed

I've found myself upon this tutorial which seems to be the only one available relating exactly to what I am trying to accomplish. The writer of the article has made an Arduino Library which allows for the Arduino to communicate directly with OpenTherm via this circuit:

X1 & X2 are the Opentherm wires (doesn't matter which); the IN and OUT go directly into the Arduino's GPIOs. Finally, the VCC goes to Arduino 3.3 or 5v and the GND to Arduino ground.

Whilst the circuit does function perfectly, I felt that this was slightly overcomplicated as it involved numerous different components like multiple diodes. This would require the purchasing of a wide range of components which is not desired. As a result, I did some more digging and found myself upon this question on the forum. Whilst the question is not the same as mine, the top answer notes that:

  • any of these parts will the same or better job.

What was linked was optotriacs. The answer also states that:

  That circuit provides a DC current shunt to an AC rectified source and series load from a 24Vac furnace transformer. All it has to drive is a logic driver to activate the furnace, the same way a reed relay might work.

Now, whilst it does seem that the original poster of the question asked for more clarity on how exactly the optotriacs could be used in this situation, I feel the person answering does not give a sufficient enough answer for the skill level of the person asking.

Similarly, I am not super skilled with electronics and found the explanation of the proposed solution rather lacking. As a result, I am asking this question.

My question is: How can the above circuit be replaced with a simpler solution? Is all that circuitry required to allow the communication from 5v DC to 24v AC and back? The answer linked above mentions optotriacs, how could they be used in this situation to simplify the circuit?

Best, John

P.S. The NodeMCUs logic voltage is 3.3V


texts: Displaying 6 bit numbers on two 7-segment displays

texts:
I designed 6 bit binary adder which should add two numbers in first complement. The numbers are being input via registers. I have to display the numbers and the result on two 7-segment displays via ROM in decimal, and an output before the displays which will tell if the number is negative or positive. I am having trouble with configuring the ROM. I made the table for all 64 numbers. The first display acts as 'tens' and the second as 'ones'.

The 6 full adders are on the left connected in parallel vertically. The left 6 bit result is not complemented, the right is. How can I configure the ROM and what size should it be? Right now it is Address bit width: 6, Data bit width: 12.
Thank you very much!


texts: How can I make any basic boost converter that actually works?

texts:
I have spent probably around 8 hours working on this today, and I cannot make any progress.

I'm trying to use the TI MC33063A in a boost converter circuit, just to make a proof of concept. Right now I'm using a 9-volt battery and I'd just like to see any voltage boost.

I have followed the sample circuit layout on page 6 as closely as I can, but the voltage coming out is at most 8.75 volts. The only noteworthy differences are that I'm using a 22mH inductor, since it's the closest I have, and that my voltage divider is a 10 to 1 ratio, which is different from theirs. I'm using a 100k ohm and 10k ohm voltage divider. I have spent hours looking for differences and I see none, at all. My circuit does not produce any voltage boost at all, and my calculations show that it should be generating at least 13 volts.

A voltmeter shows that the voltage divider circuit is -- expectedly -- about a tenth of the V_out at all times, which means the comparator should be outputting a constant value. The #2 pin seems to be draining about 85% of the power that is sourced from the 9 volt battery, based on mA measurements I took.

Earlier, I doubled up on 9 volt batteries and pumped about 18 volts through the system. If I left the circuit ungrounded and just connected it to the positive lead on the series batteries, I actually did see 21 to 24 volts come out the output, but grounding the circuit quickly negated any transient voltage spikes.

Does anyone have any suggestions of what I could be doing wrong? After a full day of trying and failing to cause a voltage boost, and I spent some time trying with a Maxim IC as well, it's starting to seem like voltage boost converters can't possibly work at all... very frustrating.


texts: Proper way to perform loops in System Verilog for testing purposes

texts:
I am testing a Find First One module in ModelSim-Altera. The target  code of the test-bench is System-Verilog. For my gold test I am using a loop as the way that show in the followind code:
always @(a)
begin
    for (int i = 31; i >= 0; i--)
    begin
        if (a[i] == 1)
        begin
            result = i;
            break;
        end
    end
end

The test works well, but I wonder if it is the proper way to perform loops in system verilog. Evidently, the test-bench has not purposes of be synthesized, but the testing module yes. So at some point I will perform a gate level simulation with it.
Therefore:

What is the proper way to perform loops in test-benchs?
When a gate level simulation is performed, the way that the test-bench is implemented, in this case, the loops, they could infer in the output results of the gate level simulation? Maybe this question sounds silly, but until now I have never used loops inside a System-Verilog test-bench.


texts: I have a simple question, can you identify what this is on my plug and what it does? I'm kinda curious as to why it is there and I have never seen anything like it before.


texts: What is the name of this connector (on a Fuji GX680)?

texts:
I have a Fuji GX680 (I) camera; it has a remote shutter connector. Buying a remoter shutter control second hand is quite expensive. So I am wanting to fabricate my own. Unfortunately I am unable to work out what the specific connector socket is (so I can buy the correct plug).
The connector has :

8 Pins, evenly spaced in a circle
3 orientation lugs, 1 large 2 small
10mm outer diameter
A stylized logo of the letters HRS


texts:
I normally use an Arduino for my projects because it has 5V inputs and outputs and has 5V Vin so that makes life very easy when interfacing with 5V components. For this project I want to use a Raspberry Pi because I want to hook it up to a display. The Pi is powered by 5V so that's easy enough. It has 3.3V I/O pins however and the devices I want to interface with are 5V.

I have a device with a 5V input pin, which needs to be driven to 5V. The device has a 5V output pin, which the device drives to 5V when it outputs.

I've converted bidirectionally between 5V and 3.3V devices before, but that was with a logic level shifter that was active LOW. The circuit is the typical one with a transistor and a diode and two pull up resistors. This application requires active HIGH. This project thankfully does not require bidirectional I/O.

For the 5V to 3.3V direction, a crude voltage divider will work.

For the 3.3V to 5V direction however, I don't know of an easy solution. I did some searching and there seem to be boost-converters (DC-DC boost converters) but to build them from discrete components I need to build a PWM circuit to drive the switching.

I was just wondering if there was a simplier way to achieve this, with complexity comparable to the active low logic level shifter.


texts:
I am looking for a small form factor capacitor that is capable of 12V at 500 mA for approx 2 seconds.
This is to open a small 12vdc air solenoid that is under about 100PSI of pressure for just 2 seconds.
Then the capacitor could be recharged.

I have not been able to find a formula or calculator.


texts: Stencil Required for Through Hole Components

texts: I was creating a pcb board that is mostly made of header pins that are suppose to connect to adapters. I was wondering if a stencil is required for soldering through hole components on a bare bone pcb.


texts:
I don't know to retrieve the \$r_\pi\$ value of common collector .

re model (or pi model) for common emitter configuration
Ok for \$r_\pi\$ model from common emitter with
,
 and

re model for common collector configuration ?????
But to calculate $$ {v_{bc} \over i_b} = {\beta * r_e} $$ i don't know...
I get
and
$$ {v_{bc} \over i_b} = {{v_{be}-v_{ce}} \over i_b} $$
Ok for \$ v_{be} = i_e \cdot r_e \$, but for \$ v_{ce} \$ ? Which is the voltage between the current source ?

re model for common base configuration
, ,

\$ R_{in} \$ for common collector configuration with hybrid h-parameters
It is easy with this technic but i don't find \$r_{be}\$
,
FALSE :
$$ r_e \neq {1 \over g_m} $$

Putting a short circuit from e to c to get \$ R_{in} = \beta * r_e \$ for \$r_e\$ model for common collector configuration
putting \$r_o = 0\$  i get

but \$r_o\$ is big no ?

Putting \$ R_{L} \$ after the common collector configuration circuit to find \$r_e\$ model

cannot continue because 0 found
But with h-parameters : OK

Putting \$ R_{L} \$ after the common collector configuration circuit to find \$r_e\$ model with \$gm \ne {1 \over r_e}\$

Without \$ R_{L} \$ : \$r_{in}\$ of common collector configuration circuit with \$r_e\$ model (\$gm \ne {1 \over r_e}\$)
I don't understand why I have to add the mass to node e when I remove \$r_o\$, because finally it's like this I put the value of \$r_o\$ to 0.
Note : for the other circuits : Common Base, Common Emitter, i didn't need to do this trick adding a wire to make a circuit.
Why adding mass to calculate \$R_{in}\$ ?...


texts:
I am basically from a background of small microcontrollers(arm7,cortex-m series). As I started working with a cortex a8 board(beagleboard xm), I always wonder how to store applications in flash/ram memory. In small controllers, you will directly give the location(which you know either flash or ram), but whensoever I store an application /home/root which memory is it stored?

Basically where the rootfile system is located in memory?


texts:
Not sure if this is the right stack to ask this question on, but it relates to an engineering project that I and a student electrical engineer are starting.

Can an LCD screen be used as a masking layer between a UV light and a photosensitive material?

I have looked at a lot of other options and this seems the simplest and cheapest. Because LCD screens are inexpensive, have a high resolution, and are easy to control (no spinning mirrors or mechanical parts). This only works if the LCD screen is capable of controlling where the UV back light is admitted on its surface.


texts: How the diode in this circuit achieves AM modulation

texts:
For the last week, I've been looking for a simple circuit to transmit VHF
analogue TV video signals, so that I can transmit my Raspberry Pi output to a TV set. Since I don't have enough experience in RF, I searched google for a design and got this:

To my understanding, it's a common-base oscillator running at almost 60 MHz,
question is: How can 1N4148 diode achieve modulation in this configuration,
and what this type of circuit is really called (RF engineering term)?


texts: Auto-zero chopping op amps & ADC conversion

texts:
In our project, we developed and tested a auto-zero chopping op amps coupling with Sigma-delta ADC for low-frequency voltage signal measurement. Below is the FFT spectrum from the 1-bit data stream of the ADC. Now, I am designing a decimation filter to convert 1-bit to high-precision data word. I noticed that there are several noise peaks around our chopping frequency. I wonder if I have to design a notch filter to take care of those peaks or just a regular sinc3 filter would suppress the noise and do the conversion efficiently.

Thanks in advance.


texts: I just tried desoldering an SMD receptacle off a mass produced main board of an IBM ThinkPad X41 laptop, but that beast stuck to the board like glue, and I destroyed it. Is it possible that the component was indeed glued?


texts:
Trying to have Fast PWM mode when TOP == ORCA.

Works fine with OCA toggle (measuring correct frequency), but doesn't work in non-inverting mode.

cli();

// Fast PWM Mode
TCCR2A = 0;
TCCR2A |= _BV(WGM20) | _BV(WGM21) | _BV(COM2A0) | _BV(COM2A1); // Inverting mode fails
//TCCR2A |= _BV(WGM20) | _BV(WGM21) | _BV(COM2A1); // Non-Inverting mode fails
//TCCR2A |= _BV(WGM20) | _BV(WGM21) | _BV(COM2A0); // Toggle mode OK

// Prescaler set to 1024 (p.162)
TCCR2B = 0;
TCCR2B |= _BV(CS20) | _BV(CS21) | _BV(CS22) | _BV(WGM22);

// Enable interrupt on counter match
TIMSK2 |= _BV(OCIE2A);

OCR2A = 127;

sei();

Update with more information:

MCU=Atmega328. In non-inverting mode I just got steady 1 on output and inverting mode gives logical 0. I was expecting to see the frequency

$$F = 16*10^6 / (1024 * 127) = 123Hz$$


texts:
I am trying to configure a Thorlabs temperature driver (MTD415TE), using a UART-USB connection. For this, I am using a Foca v2.2 with a FT232R USB-UART cable. I am using serial terminals such as Termite, XCTU, and RealTerm. I have obtained a partial connection with the chip: when I turn it on, it automatically sends the configuration information to the terminal, as can be seen here:

The problem begins when I start sending information: either the chip doesnt respond at all, or says "unkown command" some times.

I listed some possible problems:

Termite serial terminal is supposed to work with RS232, not with FT232R USB-
UART cables. I doubt this is the problem since the program receives the data
without problem.
No information about XCTU and FT232R. I suppose it works with FT232R too.
Wrong input of commands. For example, "m?" is supposed to be a command.
Datasheet says: Command /response Terminator: Line Feed ()
I already tried multiple combinations such as: "m?", "m?", "m?". None
seem to work. The datasheet can be read here:
https://www.thorlabs.com/drawings/70589858588c8cf-53F8C637-D3AC-D6EE-30854FA37155D43F/MTD415TE-DataSheet.pdf

Thank you


texts: Parallel resistors circuit analysis question

texts: I started by combining resistors in parallel so instead of 4k and 12k I can get 3k but then as the independent current source exists in the middle confuses me what to do next. Can someone guide me through?


texts:
Phototransistors are a new tool for me, and I'm wondering how to select one that will match a specified source (LED worklight, color temp 5000K, wavelength unspecified). My prototype works but apparently does not match the light source. Of course the data sheet for the transistor (ROHM RPM075PTT86) specifies its spectral response. I can't find out how to correlate a color temp of 5000K to a wavelength. There must be a better way than trial and error. For reference the app is a conveyor package detector, light is overhead strip about 2' above the surface, sensors are in a strip across the conveyor. Any suggestions appreciated!
Harry

Datasheet HERE


texts: Are there disadvantages of heat shrink tubing with higher shrink ratios?

texts: Heat shrink tubing comes in various shrink ratios.  The most common of which is 2:1, but there are also 3:1, 4:1 and higher.  Assuming cost is the same, are there any disadvantages or consideration points when using higher ratios?


texts: How can I tell if a given MOSFET can be fully driven by 5V TTL high signal? (what should I look for on the datasheet?)

texts:
How can I tell (by reading the datasheet) if a specific MOSFET can be turned fully on (with the minimum drop) with simply 5V on the gate? (assuming 5V or 12V potential between the drain and source).

What specs am I looking for (preferably ones that are not on graphs, ew) to determine if a MOSFET is suitable, apart from the fact that it must be N-Channel?


texts: I am currently designing a synth based on various designs online and modifying them(the vco). I am not sure what I'm going to use in between the MIDI and VCO. What parts/circuits would I need to add/replace in order to make this synth polyphonic?


texts: Control servo motor via PID to stabilize a robot wheel using IMU

texts:
I'm trying to stabilize a robot with a servo motor attached to two wheels of a robot. I already built the system as following:

Apply Kalman filter to gyrometer/accelerometer output
Calculate a roll angle (accurate one)

Now I use these results and feed it back to incremental PID controller. My problem is that the PID controller output is very high or some times is negative, I want to scale it to a proper servo angle, for example:

The PID output is 5000, but the servo understands "commands" between 1 & 180 degrees. So how to scale the output via a scientific method to make sure that the motor receives the right commands from PID?

My target is when the robot wheel goes right, the motor should make it in the opposite direction and so on.

Update #1:
The error of PID output depends on the refrence roll angle i want to be at and the cureent roll angle measured from IMU (that depends on the the accelerometer & gyro meter ) ,

the input to the servo is the servo angle position which lies between 1 degree to 180 degree


texts:
I am currently designing a mips microcontroller for a class. I am now working on the control unit for the microprocessor and I am wondering if I should use minimization vs using flow control (if, case).

Is minimization (ex : using karnaugh) really good performance wise when using vhdl or should I just keep it easy to expand, modify with flow control?


texts:
I try to rebuild an electronic board for an old potter's wheel. I try to build a "Phase Angle Control" with BTA16-800BWRG and MOC3043SR2M to control motor speed (the old board seem to use this principle).

Here is the old factory board :

Here is the full schematic of the old board

Here is my homemade new board :

Here is the full schematic of the new board

For instance I use filament light to build the firmware but I got problem, my output stage work only when I do measurement. (I use transformer to check signal with my oscilloscope).

When I plug the transformer to isolate and see signal between pin 4 and 6 of the MOC3043 the signal on oscilloscope almost look like I was expecting and filament light is lighting (depend on pulse characteristics), all is OK while a leave transformer connected.
When I remove the transformer the filament light is completely off, and when I try to see signal at the terminals of the lamp (with my isolation transformer) I got no signal at all.
When I put the transformer at the load, filament light stay off and I got no signal at all.
When I put the MCU pin "motor" at steady high level, the filament light is lighting and I can get signal with transformer at the load. (I got the full 50Hz wave without glitch)

To sum up, I'm be able to steady glow light with steady high level on "motor" pin, on when I put transformer on pin 6/4 of the MOC3043 when I pulse the gate with pulse signal synchronized with a zero crossing detector.

This is the first time I use TRIAC and I don't understand what append.

Here is the interesting schematic part :

 - Only filament light OR motor (with 16uF capacitor) is connected at the same time.
 - The motor, light and transformer characteristics came from measurement with ohmmeter and LC100-A
 - I try with and without R1

Here is the TRIAC gate signal with the /20 isolation transformer :

I could not get both signal (gate and load) because I got only one transformer

Here is the MOC3043 command signal :

In yellow : The zero crossing detector signal entering the MCU
In blue : The "motor" pin signal from the MCU. I know high level of pulse is very long but it's to be sure TRIAC is really fired

Can someone help me to solve the problem and calculate the right value for components for filament lamp and for motor ?
(I'm more comfortable with software than hardware, I need help)

EDIT 2019-11-29 (1)

Thank to I directly replace the MOC3043 by MOC3023 (without zero-crossing trigger) and I replace R3 by 130 ohms resistor to increase current in led to 14mA.

Here is the new schematic :

Now I'm able to control the phase for the filament light. YipHa !

Here is the signal at load with the /20 isolation transformer :

All is not perfect, I got some random glitch. Sometime the light quickly glow strongly. I use my transformer to capture the glitch

Here is the glitch capture at load with the /20 isolation transformer :

We can clearly see the glitch, the phase continue after crossing down to zero.

I don't think glitch came from my firmware, I could not implement the supplier recommended schematic for instance page 7 of MOC3023 datasheet

Here is the recommended schematic :

Do you think glitch can come from the lake of snubbering the MOC023 as it recommended on schematic ?

EDIT 2019-11-29 (2)

My glitch problem came from software problem, I try to "hand" build the pulse from a STM32 timer triggered by zero crossing interrupt. I update the timer period twice for low and high level of pulse with complicated "state machine" automaton. I got jig from flash latency and interrupt preemption.

Now I use a simple "output compare" timer (OC) in "one pulse" mode, and the output signal is very stable now use much less resources. Ready to implement motor control algorithm like PID or other algorithm...

I think I will re-route the board with the recommended MOC3023 schematic


texts: Need help identifying component from my couch

texts:
I am out of my depth with this, I need to identify this part. (to replace it)

This component is on a board that connects to the controls for the reclining motors.

Is there any additional information I can provide to help?


texts:
I suspect the answer to this is going to be "no", however, just in case anyone knows something...

I need to broaden the emission peak of a near IR LED. Is there any generally applicable method of doing this in a reliable manner?


texts: How to extract minimum supply voltage from the datasheets

texts:
I am relatively new to electronics and need to know

  What is the minimum supply voltage (Vcc) for  LM1875 and for LF347 and how do I extract it from the datasheets?

In LM1875 it is written that the supply range is 16V-60V but the graphs in the datasheet show a good activity also for 15V so is 15V OK?

For LMF347 it is written that the recommended conditions are min supply of 3.5. So I guess 5 volts should be OK?

Is it better to use NE5532 in which the supply is specified for a "wide range of 3V to 20V"?


texts:
How do I control a hobbyist DC motor with a TIP122 transistor?

I want to control it with the Arduino PWM pins, the power supply is 4 1.5V AA batteries connected in series giving 6v.

Also, what steps should I take to protect the arduino against and EMI from the motors?


texts: Using forward voltage drop of diodes with linear regulator

texts:
I want to clamp the output of a adjustable three-terminal linear regulator Vout to -1.8V relative to a reference voltage Vref.

My approach is to use the forward voltage drop of three diodes but I am having trouble sizing the resistor to ground R2.

Clearly, it needs to be large enough to limit current through D1...3.

What other boundary conditions are there? I imaginge it must not be too large either to avoid pinching off the regulator's ground connection or create an voltage rise due to Iadj?

Or what are the relevant boundary conditions for sizing?

The LM338 has:

Iadj = 50 µA
Vref = Vout-Vref = 1.25V

simulate this circuit – Schematic created using CircuitLab

In the alternative I thought of something along the lines of:

simulate this circuit


texts: Can I replace a capacitor with one of lower voltage?

texts: I have broken power supply for PC, 400W. A capacitor has failed. I don't have the same capacitor. The one I want to replace is 220μF 25V, and the one that I have to replace it with is 220μF 16V. Would there be any problem with this?


texts: Matlab code to determine and plot impulse response

texts:
I have a signal y[n], represented by the vector y in this form

y[n] =x[n] + ax[n−N]

About this signal:

x[n] is the uncorrupted speech signal which has been delayed by N samples and added back in with its amplitude decreased by a<1
N= 1000, and the echo amplitude,a= 0.5.

I need help with:
Determining and plotting the impulse response of the signal. Also I was hoping to store this impulse response in the vector for 0≤n≤1000

What I have and which does not work:

% Testing the input:
sound(y,8192)

% echotime,N= 1000, and
% the echo amplitude,a= 0.5.
N = 1000;
a = 0.5;

n = [0:1000]; %time vector

for i=0:1000
    y(i)=x(i)+a*x(i+N)
end
stem(n,y) %output plot

This would give me an error lie:

Undefined function or variable 'x'.

Error in (line 15)
    y(i)=x(i)+a*x(i+N)


texts: Is Magnet in pmac motor degrade while they are in use because in tesla model 3 they uses pmac motor so we have to replace magnet frequently ?


texts: I am attempting to repair the amplifier stage of a Harmon kardon 1970's vintage stereo. The right channel is fine but the left exhibits extreme distortion. I fed a sine wave in and can see that the entire negative half of the waveform is being clipped (except for a slight 'ripple' at the beginning). This only happens under load (speaker connected). Any thoughts on where to look?


texts:
I am not an expert in this area and therefore need suggestion regarding what is the best way out for this case.
For my experiment, I am installing a camera that requires a BNC based trigger signal. In the manual, it suggests the properties as given in the picture:

From what I have known so far, there are usually 50 or 75 ohms BNC connectors and cables. Where can I find 1 kOhms available?
Second, what exactly LVTTL means? Previously, I was using 1.7 V rising edge required trigger signal.
Any help would be appreciated.
Thanks!


texts:
I have DE1 Soc development board. I have been following this youtube video in order to start casting some stuff onto the screen.

I am unable to display anything on the screen at the moment unless pitch black counts.
I have initially followed all his instructions in order to see how it is done myself, but unable to get anthen ended up copying his .vhd files from git.

I am able to compile it and program it fine, pins are assigned correctly and use other peripherals.

I have found this thread useful especially that checklist.

  Did you simulate your design?
  Are you sure the timings in your design are correct?
  Did you check the signal levels (with a scope)?
  Are you sure that all the pin assignments are correct?
  Have you tried it with a different screen?

I have simulated the design to see whether HSYNC and VSYNC control signals are present and whether they are driven with the proper ratio
Timings I have created using Altera PLL rather than Avalon PLL, as that was not available for me. Not sure what is the implication if any of usinf Avalon PLL rather than ALtera PLL. Input is 50MHz and output 108MHz still.
I will do that tomorrow as wasn't able to get a oscilloscope today, when rebooting the board the initial terasic promo is displayed on the screen so it seems that the board can communicate via VGA with the TV
Went through all the pin assignments twice
Screen does work and nothing was showing up on a different screen.

I have went through it in detail and I think I have ticked off all the points correctly (besides actually tasting with the scope my build rather than factory one). Yet still I am still unable to get anything displayed at all. No amount of tweaking with timings, RGB selection, or any of the porches seems to change anything. Screen is constantly dark, it doesn't go into power saver mode so something must be happening.

I was wondering whether anyone has any ideas off what else could be the cause of it that I am missing or may have incorrectly assessed current state of affairs. Cheers.


texts:
I began to study One-hot machines, and I want you to check my transition table, because I'm not sure if it is true. Below you will find:

state machine
transition table
Karnaugh map

First of all, I know that I can find next state by simply looking at state diagram, and next states will be:

Q0+ = q0*X' + q2*X

Q1+ = q1*X' + q0*X

Q2+ = q2*X' + q1*X

it is true?

If I do Karnaugh map for Q2+ for example, it won't work. I will have a different next state. But why? Karnaugh Map works fine if I'm working normally (without one-hot).

Karnaugh Map for state Q2+ will be Q2+ = X*Q2'*Q1*Q0' + X'*Q2*Q1'*Q0'

For Karnaugh map values, I did it like that:

check where Q2 has value 1
take code from X Q2 Q1 Q0
Q2 = 1 => X=1, Q2=0, Q1=1, Q0=0 => 1010 = 10
Q2 = 1 => X=0, Q2=1, Q1=0, Q0=0 => 0100 = 4


texts: Can I use the P3020L Mosfet with 5>Vgs>3 without any linear region consequences?

texts:
So I've been searching for a long time, for a power mosfet I can switch safely at a Vgs of 3V. I'd like to know if this is the one, because luckily, I recovered it from a computer power supply, thus I actually have it.
Link to the datasheet
So the minimum Vth is 1V and the maximum is 2.5V, hence 3V is going to switch it fully on right?


texts: Class AB amplifier BJT operating point question

texts:
Lets say we have a diode biased class ab amplifer. As known at the output, npn handles the positive part and pnp handles negative part of a signal. This bjts are operating between +/-12V and output voltage is 18Vpp. VCEs of the output bjts are are around 12V. Is it possible to get same output(18Vpp) if we change operating voltage to 0-12Volts?

I am asking because of confusion. From the Vce there is a swing of 18volts. At +/-12 supply voltage thats ok but since each transistor amplifies half portion of the signal the swing for each part will be 9 volts and at 0-12V operation if I set Vces to 6Volts the swing will 4.5V upper 4.5V lower for each signal?

Best.


texts:
With regard to signal processing, how is frequency modulated continuous wave (FMCW) radar similar/different from stepped frequency continuous wave (SFCW) radar?

Do we actually modulate the RF carrier with a low frequency signal in order to lower the cost of analog to digital conversion? This doubt naturally arises because the property of concern here, is only the phase difference between the Tx and Rx signals, which can be extracted equally nicely from the raw RF signals (Tx and Rx) as well as the demodulated baseband signals.

If anyone could point me toward detailed processing steps used in these radars?

Thanks,


texts: how to calculate resistor value for optocoupler - 230V

texts:
I am trying to implement the following circuit. I am trying to understand how the resistance values are calculated. I followed this - "how do I calculate resistor value"

According to my optocoupler (SFH6202) datasheet, following are the calculations:

VF(typical) = 1.25V

If = 60mA

So

Vres = V - Vf = 230 - 1.25 = 228.75

R = Vres / If = 228.75/.06 = 3812.5

But the circuit shows two 100K resistors. Am I doing something wrong here?

Also the Power dissipation is:

P = Vres * Ifmax = 228.75 * 0.06 = 13.72 W

The power dissipation seems too high for 1/4, 1/8 or 1/10 W resistors. Am I doing something wrong in this calculation also? Or do I need some special kind of resistors?


texts: What is this spice model? Is it a level shifter?

texts:
Does anybody know what is this symbol in spice?

I think this is something like Gate Drive or Level Shifter, but I want to know the exact part name or something like this part.


texts: Can I use 2 Power Supplies in series like this?

texts:
I just started doing electrical engineering as a hobby.

I want to build a circuit where a Micro-controller controls 300 LEDs.
Those LEDs can draw a lot of power, so I use a larger power supply, which is quite inefficient when idling (3Watt Standby). This matters because the LEDs won't be on all the time. I will implement some kind of sensor which fires when I want light (like a button, human detection IR sensor, Bluetooth, ... ) and my idea was to use a second, more efficient power supply, which can power the controller as well as all sensors, but has not enough power for the LEDs. As soon the sensor fires, the micro-controller will activate a relay to activate the large power supply.

I am not quite sure if it is safe to use this layout, however, because I heard that you should not connect 2 power supplies in series. The LEDs get a DATA signal from my Micro-controller (which is on the efficient PS) while the LED is on the large PS.

I made a quick draft. Keep it in mind that I am no expert, so I might have made some errors.

Outlet: 230V 50Hz
PowerSupply1: 5V 2A
PowerSupply2: 5V 30A
Micro-controller: ESP32
LEDs: WS2812B
Data1: 3.3V < 10mA
Data2: 3.3V < 10mA

simulate this circuit – Schematic created using CircuitLab

Edit1: I added a big blue wire connecting both grounds together like many suggested


texts:
The human body seems to be a good antenna to pick up 50Hz, at least touching a scope's probe shows a 50Hz waveform more than a volt in amplitude. Is it possible to construct an electronic antenna that does the same thing? (Wavelength at 50Hz is 6000km)
And if there's so much energy in it (1V in 1M\$\Omega\$ is 1\$\mu\$W), then why don't high-impedance pins pick this up?


texts:
For ultrasound transducers for imaging, high voltage drive pulses need to be generated, typically using a 3-level or 5-level pulser structure which resembles the image below. For a 3-level structure, two are connected together at the output, and for 5-level, three are connected.

Image Source

The problem with this design is that discrete P-Channel MOSFETs are harder to come by with sufficiently high Vds(max) which must be at least 250V for a ±100V supply (when the output is -100V, the Vds of the PMOS is 200V). While they can be found, they generally have much higher Rds(on) and are much slower.

For one of the projects we are looking at, ideally we need to be able to drive a transducer at high frequency - 30-40MHz range - using a relatively arbitrary waveform (5-level PWM). However in order to achieve this the pulser needs to be able to switch somewhere in the region of 200MHz which means a rise time of <5ns which is beyond the range of what any of the available PMOS devices can do.

In order to get to this sort of level, the only thing I can think of is to replace the PMOS device with an NMOS device. However herein lies the challenge. Most of the high-side NMOS drivers are typically designed for applications like BLDC drives and DC-DC converter where the frequencies are in the 100kHz range at most. Additionally they and are not usually designed to cope with the high side gate sitting at negative voltages which would be the case at times in this pulser.

In order to switch from, say 0 to 100V in 5ns, the source of the high-side NMOS has to slew at more than 20kV/us which means whatever is driving the gate must be able to cope with such a high common mode transient. It must also be able to drive the gate fast enough to switch in <5ns which is quite a current spike although that will depend on the gate capacitance of the MOSFET.

I've been looking at ways to translate the signals from the logic circuitry through to the gate of the NMOS but am struggling to find anything fast enough. Optoisolators max out in the 25MHz range, and the only digital isolator I have found is the ADN4650 which can doo 600Mbps but those are not cheap and would require additional LVDS-LVCMOS circuitry which will take up space, especially when the channel count goes up (e.g. 16 element). Passive level shifters would be even more tricky to implement as the source will be going negative as well as positive.

So on to the question. Basically has anyone developed such a high frequency high-side drive? or have any ideas on circuitry that could be used to drive it?


texts: Why does DAC INL follow a pattern, with peaks repeating at certain specific intervals?

texts:
INL curves seem to have relation with "digital" effects from the codes,like a major carry transition. Could someone help me understand an electrical or rather an analog, explanation for this occurance.

Would this be the case with DACs implemented as simple R-Strings, that donot have binary weighted elements in their architecture ?  Here is a crude drawing to explain the INL pattern that I have been trying to explain.


texts: What is the difference between these two half bridge configurations?

texts:
I have seen two different half bridge versions.

One has an extra capacitor attached between the load and the neutral point of the capacitor divider.

What is the difference?


texts:
So I'm completely new to electrical design. I thought I'd try out the most basic experiment I could think of. Here I hooked up two AA batteries to a breadboard along with a 10 K resistor. When I attempt to measure the voltage drop across the resistor by touching the leads to both ends I get an output of .1 V. If I understand correctly the output should be about 3 V. Is there something I'm doing wrong?
Here's a picture of my set up.


texts: Ferrite Beads - Maximum DC current and resistance

texts:
I'm building a PupDAC (http://www.diyforums.org/PupDAC) and am looking into two different Ferrite beads. The plan for the PupDAC calls for this Vishay/Dale model (link 1) while I'm looking into this Bourns model (link 2) which is cheaper. Both are the exact same size and have the same indapendance.

http://ca.mouser.com/ProductDetail/Vishay-Dale/ILB1206ER801V/?qs=sGAEpiMZZMtoiMfofRG0LbeaUJjp%2fOFUt90sRTRBhVI%3d
http://ca.mouser.com/ProductDetail/Bourns/MU3261-801Y/?qs=sGAEpiMZZMukHu%252bjC5l7YeIIR6MXfgmdW77QhVIYZMI%3d

The Vishay/Dale one has a maximum DC current of 200mA and a maximum DC resistance of 0.3 ohms. Meanwhile, the Bourns one has it at 300 mA and 0.6 Ohms respectively.

Basically, does this really matter? The Bourns models seems to just have higher maximum values, so can it replace the Vishay/Dale one without quality issues?


texts: Battery Power Density - Voltage Higher than Load Requires or Not?

texts:
I'm working on a project that is battery powered where run-time is an important consideration.  The project has two distinct required voltage levels, both served from a single battery:

6.4V which powers the main load - draw is anywhere from 500mA to 5A (very rare, short-term load for anything over 2A)
3.3V which powers all the control IC's and the screen, nominal draw is about 1200mA, not much variation

Current design uses a 6.4V (nominal) 6.6Ah (LiFePO4) battery with a switching regulator to get to logic level and gives okay life.  Space is a constraint to add more battery capacity.

It occurred to me that something like a 20V, 5Ah tool battery which are all over might be interesting to consider.  I would have to add another switching regulator to get from battery voltage to load voltage, then keep the same existing switching regulator to get from load voltage to logic level.  I'm not too concerned about being able to dissipate the heat generated from losses.

The crux of my question is this:

From an energy-density perspective, the 20V, 5Ah battery can generate (nominally) 100 Wh of energy where our current battery can only generate about 42 Wh.  So, even with a 15 or 20% loss from the switching regulator, it seems like I could still get almost double the energy from the higher voltage battery - and as far as I can tell - double the life for the same power draw.

This makes sense to me, but it seems if it was true then other things (like phones) where battery longevity is important would utilize this concept.  Maybe they just can't afford to dissipate the heat, or maybe there are products using it and I'm just unaware of them.

EDIT1: Corrected "power" to "energy" when discussing Wh


texts:
Hello so i have a microcontroller that is driving the following circuit:

Both the MCU and the circuit are powered by a 5v power supply, when PAD_PWM and PAD_PWM_return are not shorted ore there is no load between them the circuit its Drawing 6.22 mA which is correct. But when i short PAD_PWM and PAD_PWM_return with a wire i see a voltage drop from 5V to around 0.5V and the total current consumption of 18.88 mA. the duty cycle of the PWM its 50% so in theory the difference in current I'm seeing its correct as 5*.5 its 2.5V/ 200 ohm its 12.5 mA which its almost the current difference that we got from working under no load and working under load.
But i cant know for sure if that increase in 12mA its in fact going through the R10 and the wire. because I'm seeing a voltage drop, it doesn't make sense to me.
The MCU works flawlessly and it doesn't stutter or anything at all.


texts:
The theory says that the current return path at high frequency is on the reference plane right under(or above) the signal trace.

I know it is true and I have always assumed it was, but I would like to understand it properly.

My trouble is about it can be power or gnd plane for the reference plane.

If we use a 6 layer stackup:

Signal

GND Plane

Signal

Signal

PWR plane

Signal

If we take the example of two device U3 and U4 on Bottom layer (referenced to a Vdd power plan), with U3 having a Tx pin connected to a Rx pin on U4:
When U3 output a 1 the current goes:

Power Vdd=>U3 Vdd pin=>U3 Tx pin=> U4 Rx Pin=> U4 Vss Pin=> and then?

How is the current passing from U4 Vss pin to Vdd power plan? Capacitor? Because there is no connection as you can see in the picture/

Also wy is the current not flowing to the GND plan? Is the inductance created by going to the GND Plan that much bigger than the one created by going to the Vdd Plan?

Now if we take the same example but on Top layer( referenced to a ground plane):

When U1 output a 0 am I right to assume the current goes:

Power Gnd=>U1 Vss pin=>U1 Tx pin=> U2 Rx Pin=> U2 VddPin=> again and then?

How is the current passing from U2 Vdd pin to Gnd power plan? Capacitor?

Also why is the current not flowing to the Vdd plan? Is the inductance created by going to the Vdd Plan that much bigger than the one created by going to the Vdd Plan?

Another question related to the answer is, what if the reference power plane is not of the same voltage as U1 and U2 power voltage? Is that still working as a power reference plane?

Edit:
Here is a drawing of the stack up and components I am talking about for clarification:


texts: SPICE issue: keeping subcircuits independent of eachother

texts:
TLDR I want to make circuits that are connected but independent in Spice.

I am using the Xic graphical editor for WRspice, but I think that this issue isn't specific to the type of Spice being used. What I want to do is this: send an input into my subcircuit, and then take the output of said subcircuit and pass it onto other subcircuits.

Basically: input -> subcircuit1 -> output -> subcircuit2 and onto more subcircuits. My trouble is that when I add anything else to the output location of subcircuit1, it affects the behavior of subcircuit1. Does that make sense? Adding a resistor onto the circuit changes how the circuit behaves.

I want to send an input into a circuit, have that circuit generate an output, and send that output onto the next circuit without the components of the second circuit affecting the behavior of the first. I.e making these circuits independent of each other while being connected. Is this possible?

I hope I am clear.  Thanks!


texts: Why do NPN/PNP transistors need to use doped semiconductors for the 'N' region?

texts:
By my understanding, as long as the P layers are properly doped (to have fewer free electrons), the electrons could not flow between collector and emitter until the P is given a satisfactory level of charge, as otherwise the base layer could not pull electrons from the poles. In this case, why can't the N layers be just made of simple conductors, like copper? What is special about the negative doping process that makes it different to just a conductor? Is it to do with polarising the flow of electricity?

E.g. on this diagram, why couldn't we just replace the red bits with copper, provided we keep the blue bit positively doped? More specifically, what is the difference between these regions and your standard conductors?

For reference, I really don't know a lot about this area: all of my knowledge comes from reading (this article)[https://www.explainthatstuff.com/howtransistorswork.html] followed by a skim though the (Wikipedia)[https://en.m.wikipedia.org/wiki/Transistor?wprov=sfla1]


texts: 1200w dc-dc boost converter low voltage protection not working

texts:
I've purchased a 1200w dc-dc converter with the model number SZ-BT07CCCV.
I'm using it to convert 12v from a big battery to 24V.
the converter comes with three potentiometers according to the following image

now the converter works fine except for the most important feature for me which is the low voltage protection, I wanted to set the potentiometer of low battery voltage to around 11 volts to protect the battery from over-discharge and after adjusting it correctly and supplying the converter with less than 11volt then the Undervoltage led(labeled UVO) lights up but instead of the booster shutting down completely and cutting the power to the load it just shuts down the booster circuit and output the same voltage that is being supplied(11v), this is not good for my use case, and it will also not protect the battery.
My understanding of low voltage protection(over-discharge protection) is if the voltage is under a specific limit it cuts of the power to the load, not supply the load with that low voltage.
So is there something in particular wrong with my unit? or is this intended and by design? is it possible to modify the circuit somehow to achieve true over-discharge protection?


texts:
I have this battery operated lawn mower (https://www.mowersdirect.com/Homelite-UT13110-Lawn-Mower/p10883.html) but the battery died and I just want to replace it with a wired power supply.
The battery says 24V, 12Ah Lead Acid.
Is that feasible ? What kind of power supply/change do I need to proceed ? I found something about adding Voltage Regulator Circuit but I am not sure if that is what I need.
Thanks for your help.


texts: Determine torque required to operate manual adjustable height desk

texts:
I have a manually operated adjustable height desk (1) that I'd like to motorize, hook up to a raspberry pi etc.

How can I determine the torque required to rotate the mechanism so that I can buy a powerful enough motor?

1: http://www.amazon.com/gp/product/B00626AFXI/ref=oh_aui_search_detailpage?ie=UTF8&psc=1


texts: Fan speed slows down, the moment a new load is added

texts:
I am using a rectifier, and 4500uF capacitor to reduce the ripple. After connecting to the power source (60Hz, 120V), I was able to turn on the fan. The issue occurs when I turn the switch on to power the other load. Below is the schematic. After turning the switch on to power the processor, the fan would start slowing down. I have noticed that the ripple does increase after adding another load. I have tried adding multiple capacitor on the output of the rectifier, and it would only increase the delay in fan slowing down. I am positive that the rectifier can output more than 20Amps. Both the load added takes in less that 11Amps.

Is there anything I can add to this circuit to help reduce the effect on the fan when the switch has been turned on to power the processor?


texts: Bit-accurate modelling for algorithms (FPGAs)

texts:
What are the software tools used in the industry to build bit-accurate models for algorithms (algorithms which are to be implemented in FPGAs)?

Before using a tool like Quartus, we tried our algorithm in C language. It worked. But the problem is floating point arithmetic is utilized in C. But when we have to implement it in FPGA we only have fixed point arithmetic. So before coding in verilog, are there any tools to convert the earlier mentioned C code to a bit-accurate model which uses fixed point arithmetic instead of floating point arithmetic!!! What are the tools used in industry if such tools exist?


texts: How to lower current consumption in JN5148-J01 Microcontroller?

texts:
I am using JenNet-IP stack and JN5148-J01 MCU for smart home application. As per JenNet-IP stack my MCU will not be in sleep mode because it is working as router in WPAN.

But I have to reduce current consumption using sleep mode. My results are as follows:

Without Sleep Current - 18 mA.
In sleep mode - 1.05 mA.

Problem is, in sleep mode my radio will be turned OFF. So, I will not get any interrupt when any RF packet received.

So how can I reduce current consumption with radio ON?

if anyone has used wake up timers , then please provide me sample code of wake timer for JN5148-J01.


texts: Unstable Lower And Upper Voltage Charger Wall Adapter For Charging Battery

texts:
i have 2 charger adapter and both of them i testing with usb meter tester

Charger A : Showing 4.92V-4.96V (the number keep moving ups and down between 4.92V-4.96V when high load)

Charger B : Showing 5.12V-5.19V (stable at 5.16V sometimes ups and down to 5.12V and 5.19V when high load).

which one are good or safest one to use for charging my smartphone and portable music player walkman (sony nw zx300)? both device required 5V for charging the batteries
and also i do want to know if im using not stable voltage especially lower voltage like charger A or upper voltage like charger B would it damaged batteries if i use it in long term?

thanks in advance


texts: Digital control stability for more than impulse response stability?

texts:
I have a digital control system which is described by the transfer function
$$
Y(z) = \frac{-\beta}{z - 1 + k \beta} X(z)
$$
where \$\beta\$ is a real parameter I can adjust to modify the characteristics of the system, and \$k\$ is a positive real constant.
Using the BIBO stability criteria that the poles must be inside the unit circle, this means that for BIBO stability I need
$$
0 < k \beta < 2
$$
which is exactly what I observe when \$x[n]\$ is an impulse response:
$$
x[n] = \begin{cases}0 & n < 0\\
x_0 & n \ge 0\end{cases}
$$
However, I am trying to design my system to handle "arbitrary" inputs. For example, in the above example suppose I have an input which jumps between two values:
$$x[n] =
\begin{cases}
x_0 & n~\text{is even}\\
-x_0 & n~\text{is odd}
\end{cases}
$$
The z-transform for this particular input is
$$
X(z) = x_0 \frac{1 - \frac{\cos(\pi)}{z}}{1 - \frac{2 \cos(\pi)}{z} + \frac{1}{z^2}} =
x_0 \frac{z (z + 1)}{z^2 + 2 z + 1}
$$
If I try to simulate the system with this input, for \$k \beta > 1\$, \$y[n]\$ actually tends towards \$\pm \infty\$ (oscillating), which I would consider unstable, or at the very least unacceptable.
How would I go about analyzing (and designing) a control system when I have to consider other possible input responses than just the basic impulse response? Are there any useful search terms I could use for solving this type of problem?


texts:
I have been developing a digital controller for water cooling system of power
electronics converter. This system consists of plate heat exchanger, pipe with
demineralized water flow (this fluid is heated by power losses of power
transistors of the converter), pipe with common water flow and a control valve
which is placed in pipe with common water near the input into the heat exchanger. Controlled variable of this system is temperature of demineralized water at the output of power converter and control variable (action) is position of control valve which sets flow of common water into the exchanger. For controller design I need a transfer function of this system. Because of control valve (it introduces a dead time) I have chosen FOPDT model i.e.
$$G(s)=\frac{K_p}{s\cdot T_p+1}\cdot\exp(-T_d\cdot s).$$

Now I would like to identify values of the system gain Kp, system time constant
Tp and dead time Td. So I am thinking about sutaible experiment. I have tried
to warm demineralized water and then suddenly to fully open the control valve.
I have got following response (both values are in per units). Then I have used Matlab command idproc with
argument P1D for identification. The transfer function I have got is following
$$G(s)=\frac{1,341}{s\cdot 571,6+1}\cdot\exp(-0,4\cdot s).$$

It is absolutely different than I expected. I don't understand on one hand the
large value of time constant and on the other hand small value of dead time.
I expected \$K_p = 0,1 (-), T_p = 97,3 (s)\$ and \$T_d = 45,43 (s)\$ from rough estimate
from directly measured data. I am not sure whether the experiment I have
performed is correct. I have heated the demineralized water by hydraulic friction caused by flow of demineralized water through heat exchanger and various folds.The pumps which produces this flow were running also after opening the valve.This hydraulic friction is from control point of view a disturbance signal, but I think that the measurement after opening the valve is relatively quick so I have omitted its influence. Can somebody tell me whether this identification experiment is correct or incorrect? Why there is large difference between Matlab results and expected values? Thanks for any ideas.