texts: Is my illustration of this configuration good enough?

texts:
I do a university project about hardware peripherals. I have little experience with it coming from a computer science background. The project is about connecting a peripheral to the serial UART RS-232 console.

I could easily demo direct root shell if I open the serial UART connection and connect with minicom, then I got a root shell without a password with "the humble shell" hush on busybox/barebox using uClinux.

My illustration is the following.

Do you agree that my illustration is "good enough" ? I'm going to add Linux on top and then I might think it could get approved by my supervisor. ''

UP means "user process", DR means "driver" and K means "cryptographic key" or some other data that should be protected.


texts: calculating total power consumption with LDO vs switching regulator

texts:
I'm just getting somewhat familiar with voltage regulators and am trying to make sure I'm understanding a bunch of parameters correctly.

Scenario:

I have a project that spends 1/3 of its time drawing 20uA, 1/3 drawing 40mA and 1/3 drawing 150mA. The project is powered by a 3 cell LiPo battery, meaning input voltages ranging between 9 and 12.4V. I'm trying to decide whether I should power the whole thing off a single LDO, a single switcher, or try to separate out the parts that push consumption to 150mA, and use an LDO for the low power part and the switcher as necessary for the high power.

I'm looking at an LDO with the following quiescent current (listed as ground current in the datasheet)

  1mA   @ 150mA output current
400uA @ 50mA output current
100uA @ 1mA output current

I'm also looking at a switching regulator with the following efficiency:

90% @ 150mA
90% @ 50mA
85% @ 1mA
60% @ 100uA

If I'm understanding the comparison correctly, then the LDO will pass along (output current + the ground current) * output voltage and waste (output current + the ground current) * voltage difference, which reduces to just input voltage * (output current + ground current), meaning:

11.1V * (100uA + 20uA) = 13.2mW in the first state, and so on (the 11.1 is the nominal voltage of the battery, so it'll spend a fair bit of time there)

For the switcher, the total power consumption as I understand it is Vout * Iout / Eff, so at that first state it would be 3.3V * 20uA / .6 = 1.1mW. My understanding was that for switchers, the quiescent current is factored into the efficiency graph you're given in the data sheet, hence steep fall-off at the start.

Is this right?


texts:
So say I have a 10 W LED, most have a forward voltage of 9-11 V and a maximum current of 700 mA.

If I wanted to connect it up to 13 V (a fully charged SLA battery) couldn't I simply do 11-13=2 (LED drops 11 V and rest is across resistor)then 2/0.7 = 2.85, meaning I would need a 2.8 ohm resistor?

And 2 * 0.7 = 1.4, so that means I would need to use a 1.5 W resistor (or greater).

Is this all correct? I know it wouldn't be the most efficient but I'm checking to see if I'm understanding this correctly.

A more efficient way would be using a current regulated/limited supply, right?


texts: in dsPIC33 assembler, can I use all of the w registers?

texts:
Most of my dsPIC3 application is written in C, but one function is particularly speed sensitive, so I had to write that function in assembler. The function looks roughly like this:

_FunctionName:
lnk #0x0
push w0 .. w15

< code that uses all registers >

pop w15 .. w0

ulnk
return

Is this a bad idea? Or will the use of some registers cause me problems, even if I've pushed them onto the stack?


texts: I am getting the opposite result from simulation from Quartus in two cases, while the others are correct

texts:
I have created a Quartus schematics according to the following K-map;

However, I am getting a wrong result; the output should be 1 when the input is 7 and 0 when 14, but it is going the opposite. The outputs of the rest inputs are correct. The following picture is the simulation waveform.

Thank you in advance, for your help. :)


texts: Can I use an isolated DC-DC module with breaking its isolation?

texts:
I'm in need of a DC-DC module on a project.
The DC-DC module I have is here.
This is an isolated module but in my situation its input and output is going to be on the same ground.
Will it cause a problem if I break the isolation on this module?


texts: What is the best type of solder for strength and creep resistance?

texts:
I am looking for the best solder type to connect a wire to a copper substrate. However, the wire is also a mechanical support as well as an electrical connection. Cost is not an issue.
The wire is Platinum/Iridium alloy.

Seems there is quite a variety of solder types


texts: Using Matlab to draw a step response graph

texts:
I've got the next transfer function:

$$ \frac{\hat{\alpha}}{\hat{\alpha_{ref}}} =\frac{w_n^2}{s^2+2w_n \xi s+ w_n^2} $$

Now I want to draw a step response input at height of \$\alpha_{ref}\$, where \$\xi\$ comes with differing values (i.e different graphs on the same axis for different values of \$\xi\$, and the value of \$w_n\$ depends on \$\xi\$).

How to implement this in Matlab?

Thanks in advance.


texts: DC DC Converters in Parallel for double current

texts:
I am  using a 15V 7A DC DC converter for powering a robot. I am looking for a 15V 20A supply. For this can I put three of those regulators in parallel and expect them to provide about 20A of current? Also can anybody suggest a better method?
(given that my original source is a 5 Cell LiPo Battery(18.5v))
By parallel, I mean shorting the 3 inputs and 3 outputs. I connect the battery to the shorted inputs and attach my device to the shorted output.


texts: Hold time and voltage maximum analysis for D flip-flop?

texts:
Following is the analysis I have done for the circuit:

This circuit is a part of the shift register and I am posting only a section which is required for the analysis
(By the way, D flip-flop (74LVC1G80) is powered to 3.3 V ) and the output D is connected to another D-FF (74LVC1G80) using R(1 K Ohm) - C(20 pF) filter and so on.

Data signal, Din: Frequency = 400 kHz, voltage range = 0 – 3.3 V
Clock signal, CLK = 12 Mhz.
D-FF input capacitance = 3.5 pF

My intention is to analyze the RC filer and find the input voltage V at the pin D.

Figured out that the purpose of the RC filter is to provide sufficient hold time. But I was trying to understand how the hold time will be improved with an RC circuit at the input and how I can I calculate the hold time mathematically. Guessed in this way, the data logic high or low will stored in the capacitance (20 pF) and this will be available to the D-FF, thus enough hold time. Basically I am not convinced with it and unfortunately there is no reference for this case from google as well, kindly share your views about the purpose of RC filter and how to calculate the hold time.
What will be the maximum voltage (V) at pin D.

See the voltage division approach,

$$V_{max} = V_{Din} \frac{ X_{C\text{(20pF)}}}{ X_{C\text{(20pF)}} + R_{\text{(1k)}}}$$

If I take the voltage division rule, how it is going to be wrong, what is the criteria to select the VD rule?

Another approach:

$$ V_{max} = V_{Din} ( 1 – e ^ \frac{-t1}{R_{\text{1k}} C_{\text{20pf}}})$$

When can I use this formula over the VD rule?
How can I select the time t1?


texts: Lack of color displaying composite video

texts:
I'm attempting to output video from a TMS9118 VDP to a television's composite video port.  Right now the result I'm getting is grey scale (whereas the background should be green), and I have no idea why.  I have compared the output from the TMS9118 comvid line to output from a DVD player on my oscilloscope, and the signals are somewhat different in quality.

The yellow signal is the dvd player.  The blue signal is the VDP.

Following is what the VDP produces on the television screen:

The TV displays the DVD player signal perfectly.  In summary, what is wrong with the signal coming out of the TMS9118 comvid line?


texts: Using different compilers in same vhdl project

texts:
I am currently working on a mips microprocessor for one of my class using modelsim's tools.

I want to be able to work on the same projet whether I'm at home on my windows pc or on the go with my Macbook without having to use a windows virtual machine so I installed ghdl which is a gcc based vhdl compiler/simulator.

I just want to make sure that every vhdl compiler are standardized and can be used on the same project without impact. Is this the case?


texts: Voltage fault injection possible on switch output?

texts:
I am required to check that the software in a system correctly handles a fault condition from a high side power switch.  The switch has a current sense pin which sends a voltage back to a microcontroller to let the microcontroller know all is well or not.

I could destructively cut the track and simply add the voltage signal but the same track is required later in the test process, (plus everytime I do that I destroy an expensive PCB).

If I inject the voltage directly to the output of the switch using a PSU, what would happen?


texts: 7-segment gas discharge display - segments are not lit up completely

texts:
I'm currently trying to revive an old (as in 30 years) panel meter (a Weston 1234). I was able to re-calibrate it again, but I'm facing a problem with its display.

The display consists of two parts, and on the right one the segments do not light up completely. It is enough to distinguish the segments though (the display shows a 38). The left one works fine though. Unfortunately there is no part number visible on them.

With the help of the comment from Dave Tweed, I could most likely identify the display as SP351 and SP738.

What I did so far:

re-soldered the connections between the main board and the display board
re-soldered the pins of the right display
driving some segments to ground, via a resistor (between 22k and 4.7k)

I also measured the voltages on the pins. On the right display I measure and average of about 7-8 volt (for on segments), on the left display its about 10 volts (relative to ground). I also looked at the waveforms with a scope - they look the same, just with different voltages.

Each digit is driven by a separate driver IC (these are DS8880), I would rule out problems with them (it would the affect only one digit). These driver are constant current drivers, and all are configured the same way. So the current on all segments. The voltages I measured above are voltages over the DS8880, so the defect segments have a lower voltage on the driver, indicating a higher voltage on them, and therefore a higher resistance.

When driving some segments with a resistor to the DS8880 ground pin, the light up some more. The left display just gets brighter, and on the right one the segments light up completely, though they are still rather dim.

Has anybody an idea where I could look next? What could explain the different voltages I measure on the segments?


texts: Cut-off frequencies for common mode and differential mode filter?

texts:
Attached is the circuit section for the differential signal amplification. The circuit is comprising of common mode and differential mode filter capacitors.So there will be two different cut-off frequencies for different filters.

During my study on the same, i found that normally cut off frequency is considered with only differential filter capacitor(C2) and the expression for  the same as fc=1/(2*pi()*(R2+R3)*C2.

My question here is why don't we consider C3 and C4 for the corner(Cut-off) frequency calculation. Could somebody explain on how we calculate the same here?


texts: Battery powered step-up converter not gives enough amps

texts:
I am creating two part PCB running on Li-ion battery 26650 (3C discharge rating, max capacity 5000mAh) powering few LED strips with controller. PCB 1 (schema 1) has step-up converter MT3608 which steps up battery output to 5V. LED strips requires 5V. Battery is placed on 2nd PCB with battery controller circuit (schema 2).

Issue: PCB 1 more likely MT3608 not provide enough amps to run LED strips (0.7A max in basic mode) & controller (ESP32 ~200mA) however MT3608 should be able to deliver 2A (I need 1.5A top). If I power up PCB 1 directly via ESP32 usb connector then Windows run audio about disconnecting USB but both devices are running well (also tried powerbank 2A delivery, works, input ESP32).

I think there is issue with MT3608. I disconnected PCB 2 and used computer PSU with 3.3V node. Still not working. When devices freeze I can hear loud noise coming from power inductor. Running just ESP32 without LED part is just fine for ESP32. Plugging in LED connector makes ESP32 crash.

Schema PCB 1

VIN => 3.3V (PSU) | 3.7-4.2V (Li-ion 26650)

Some parts are not soldered onboard

Schema PCB 2

I can post up PCB wiring if you need.

I did some measurements.
TYPE  | 5V node | VIN ESP32

26650 | 4.6-4.7 | 4.7

PB    | 4.3-4.4 | 4.3

PSU   | 2.8-2.9 | 2.9

PB => Powerbank
PSU had 3.3V
There is for sure some voltage drop on PCB 1.

Any idea what to improve?

Layout PCB 1 - MT3608 part

(line on the right goes to VIN ESP32)

Datasheets:

Power inductor

Diode

22uF caps


texts: Where am I wrong? I think my calculation should be correct, but my answer is wrong

texts:
The question wants me to calculate the \$V_3\$ value,and the solution is as below.

Solution:

\$V_3=(\frac{10}{2}+5)(2//3)=12V\$

simulate this circuit – Schematic created using CircuitLab

However, here is my thinking. My answer is not the same as solution's, but I don't know where am I wrong. Can anyone tell me where am I wrong?

simulate this circuit

\$V_3=I_3\times R_1\$,and \$I_3=I_1+I_2=5+(\frac{10}{R_1+R_2})=5+(\frac{10}{2+3})=5+2=7\$,

so \$V_3=I_3\times R_1=7 \times 3=21V\$

Where am I wrong?  I think my calculation should be correct, but the my answer is wrong.


texts: Is there a better way to plan a circuit to square a 3 bits binary number?

texts:
I need to plan a circuit that will square a 3 bit binary number:
$$\{Y_2, Y_1, Y_0\} \rightarrow \{S_5,S_4,S_3,S_2,S_1,S_0\} $$

I thought of the common way we multiply numbers and used it to plan the circuit (as you can see in the top left of the attached picture)

What do you think? Is there a better way to do the following using the basic gates, FA, HA and MUX?


texts: What's the difference between these two marking types?

texts:
On the datasheet for LTC3526L, it says the LTC3526L and LTC3526LB have two different part markings, LCSS and LCST, respectively. What does that mean? Below it says For more information on lead free part marking go to: http://www.linear.com/leadfree/

That link leads me to their material declarations page. When I search for the LTC3526L and LTC3526LB the material declaration is exactly the same for the two.


texts: Why this high-pass filter behaves like a low-pass filter for high frequencies, on this ideal LTSpice simulation?

texts:
I am simulating the usual active, first-order high-pass filter on LTSpice, as below:

The Op-Amp I'm using is the following:

This is the simulation result:

What is the explanation for the behavior above 100 kHz?

The gain starts to fall, and the phase also falls...


texts: Different answers when using two different equations to find the same unknown (BJT)

texts:
Problem 43, chapter 6 in sedra and smith microelectronics.

simulate this circuit – Schematic created using CircuitLab

We are asked to find the current flowing in R1 and R2 knowing that VBE = 680 mV and Ic = 1 mA,  β = 100.

if I compute Ie using (β+1)*Ic / β, I get 1.01 mA

if I first compute I(R1) using ohm's law (0.1 mA) and then use kirchoff current law: Ie+I(R1) = 1.1 mA, I get Ie = 1.1mA - 0.1 mA = 1mA

Not the same answer. Why?

Thank you very much.


texts: PI Compensator (for DC-DC Converter Control) transfer function derivation

texts: Here is a PI compensator implemented using a OP-AMP. However, I'm wondering why Gc(s) = - vc/v, instead of vc/v. Not quite sure why there is a negative sign here since Gc(s) is defined as vc/v if I'm not mistaken. .


texts: How to calculate the output amperage of transformer

texts:
I am going to attempt to wind my own transformer, but I need to know the how to simply calculate the output amperage. I know how to calculate the voltage:

Np/Ns = Vp/Vs

Power = Voltage x Current

Vp = 240
Np = 100
Ns = 2

100/2 = 240/X
100/2 = 50
240/X = 50
240 x 50 = X
X = 12000
240/12000 = 0.02

voltageSecondary = 0.02V

But I don't know the amperage calculations. Keep in mind I am very young.
I cannot find it anywhere on the internet. Thanks!


texts: Is there any significant difference between the couple of photointerrupters and a reflective?

texts:
This may sound a little bit silly though.. but I do hope you guys can give me a little bit of tips if u do have any? :)

Which kind of optical encoders you think is the easiest to use if I am to connect to a micro?

The term "use" perhaps can be explained in terms of:

sizing flexibility
mounting method
wiring work

OH! and I do have another question for the reflective sensors!

Do you guys know why some of the small reflective optical sensor recommends ROP of 11mm? especially AEDR family ones..
Maybe in case of space constraint, where a small code wheel is needed,
Can I just shorten the ROP to less than 11mm, but of course still maintaining the recommended LPI?


texts: How to resolve the drift around Z axis in MU6050 Gyroscope?

texts:
For IMU 6050, one could use the accelerometer to calibrate for the drift in x and y rotational axis by applying a complementary filter. However, I haven't found a way to calibrate for the drift in z direction. Because, if it's drifting, eventually there appeared where the axis of x and y switched, and the program started to fail.

How to calibrate the drift around z axis?


texts:
I have learned to us KiCAD and have designed and ordered several PCBs through OSH Park which solder onto the pins of Teensy PLC. I would like to take my skills further and learn how actually design a logic PCB schematic (like a Teensy or Arduino, for example) from scratch, not just drive the schematic software itself. I am having trouble finding sources to give me common practices and approaches to the engineering design process for a circuit like this, because most of my searches pull up only information specifically about how to operate the PCB layout software.

If anyone knows of a really good source of information that could help me along I would greatly appreciate it, be it a textbook, website, Udemy source, etc. I know that obviously a logic circuit is a delicately engineered product so I by no means expect it to be simple--I just would like to find a source that is not purely theory-based that explains more specifically how to apply electronics fundamentals to actual design.

Much appreciated!


texts:
I came across instances where NMOS was used as a capacitor in analog circuits. This is done by shorting the drain and source. The drain/source acts as one terminal of the capacitor while gate acts as the other terminal, as shown below.

Here are some observations about its working:

1) This acts like a capacitor if drain/source terminal is connected to ground. If drain/source is connected to VDD, its as good as open (0 capacitance)
2) To get a good capacitance value when drain/source is grounded, we have to use a large length and small width for the NMOS

Now, I am trying to reason out these observations.

1) I guess that when drain/source is grounded, the gate oxide acts like the capacitor with n-doped regions providing the charges. But what happens when drain/source is set to VDD. Why can't it still act like a capacitor between gate and the body?

2) How to reason out the need for large length and small width? I guess it is to reduce the effect of overlap caps between the gate and drain/source. But I am not able to arrive at a good explanation.


texts:
I couldn't find this question anywhere else.

I have a pump, a 12v battery and a switch and can purchase any relays etc that may be required.

I want it so that when a switch is triggered and kept on for 3 seconds it starts another circuit, or something, which powers the pump for 10 seconds and then stops, during this 10 seconds the switch may be kept triggered or it may break the circuit but I don't want the pump to stop until the 10 seconds is up.

If the switch is disconnected during the 3 seconds I want the 3 second timer to reset to 0 seconds again.

I hope this explains my problem.

In short:
Switch on for 3 seconds > Pump on for 10 seconds > Reset.

If switch breaks during 3 seconds then reset to 0
If switch breaks during pump for 10 seconds then continue pumping until 10 seconds is reached.

ADDITION:
If the switch is held on thru to 13 seconds then I would like it to retrigger the pump again.

If the switch triggers (held for 3 seconds) whilst the pump is active then I just want it to finish the 10 seconds and wait for another 3 second switch stint, not continue or start another 10 seconds.

Thanks Matt


texts: Ensure serial has been written before executing next line

texts:
When executing the following code on my Arduino Micro, only the first line is printed:

void crash(void) {
    abort();
}

void setup(void) {
    Serial.begin(9600);

    while(!Serial.available()) {
        Serial.println("Please input something to begin");
        delay(500);
    }

    Serial.println("First"); // Gets printed
    delay(500); // Make sure Arduino is done writing to the serial connection

    Serial.println("Second"); // Doesn't get printed
    crash(); // Makes the Arduino device crash
}

void loop(void) {

}

I would like to something like this to make the second line get printed, before the device crashes:

void setup(void) {
    Serial.begin(9600);

    while(!Serial.available()) {
        Serial.println("Please input something to begin");
        delay(500);
    }

    Serial.println("First"); // Gets printed
    delay(500); // Make sure Arduino is done writing to the serial connection

    Serial.println("Second"); // Doesn't get printed

    wait_for_serial_write(); // Not really a function

    crash(); // Makes the Arduino device crash
}

void loop(void) {

}

Which function can I use instead of wait_for_serial_write?

The reason I want to do this is because my Arduino crashes "randomly" so I have put some debug Serial.println statements, that I would like to see before the device crashes.

I also cannot use delay in my real code as the crash occurs while in a timer interrupt, where delay doesn't work.


texts: Slow PNP turn-off time, how to optimize it

texts:
I'm multiplexing a pair of Nixie tubes. The high-side control is done with two pairs of transistors, MPSA92 high-voltage PNP to switch the 160V to the tubes, and a BS108 to control the base of the PNP:

simulate this circuit – Schematic created using CircuitLab

(R2 represents the Nixie tube).

The multiplexing is at 1000 Hz. However, I'm having some ghosting issues, and as seen on the 'scope, and in simulation, the problem is the turn off time of the PNP. It is quite slow, around 100-200µs.

I want to optimize this - I read about Baker clamps, but I was confused as there are no circuits with PNP transistors about them. I tried adding two diodes, one from collector to R1, and another from base to R1. However, this didn't improve anything at all! I'm not even sure there is such a thing as a PNP Baker clamp...

So, what are the possible options for fixing the turn-off delay?


texts: Design Counter With Arbitrary Sequence Using Load

texts:
I'm trying to design an asynchronous counter with JK flip- flops, with an arbitrary sequence.

The sequence is: 0, 1, 2, 3, 4, 5, 2 ?

I know how to solve this kind of problems, but in this case how can one solve this problem with the 6 and 7 ? Because a state can only have one next state ?

Edit: This is what I did so far after doing the K maps. I get J2 = 0, K2 = Q1, J1 = 0, K1 = 0, J0 = 0, K0 = Q2Q1. But when I try to simulate it in multisim, it gets stuck to 0. Did I make a mistake in my k map simplifications or is there an issue my circuit ?

N.B.  in this image, Q1 is the LSB, Q2 is the '2' bit, Q3 is '4'


texts: Determining Operational Amplifier Offset Voltage

texts:
I am designing two stage operational amplifier in CMOS technology. After sizing all transistors and preeliminary checks I wanted to determine input offset voltage of my circuit, and browsing many pages with simillar questions, I actually did not find answer that would make thing clear for me.

First of all, most of the answers in that topic assume that by applying only common voltage to both inputs the Op-Amp output would be 0, which is basically not truth, as there will always be some Common Output Voltage. And this Common Output Voltage is already affected by Input Offset Voltage.

And here is where I am unable to handle this problem. I think applying any resistor divider etc could not work as any obtained result will be useless without knowledge about common output voltage. That seems as a vicious circle to me.

Should I just make spice .op to make input pair's VGS to be equal, or there's a better way to simulate the offset value?


texts:
I'm attempting to design a circuit that will determine the frequency ratio between a known reference frequency \$f_\text{ref}\$, and an unknown signal frequency \$f_\text{sig}\$. The signal frequency can vary dynamically between 1 GHz and 2 GHz. The goal is to use a reference frequency of about 100 MHz such that the frequency ratio can be easily represented with an eight bit counter.

My current thinking is to use a T-flip flop to create a gate signal from \$f_\text{ref}\$ such that the positive duration of the gate pulse equals the reference period. At that point there appear to be a couple of approaches that seem viable. The first is to AND the gate pulse derived from \$f_\text{ref}\$ with \$f_\text{sig}\$, then feed the output into a counter. This is a direct measure of the frequency ratio. The second option is to use the gate pulse as the enable signal into a counter. This is the approach I'm leaning towards. After determining the frequency ratio, I'd like to use this frequency ratio count to program the divider in a separate phase locked loop or direct digital synthesizer.

Ultimately I'm looking for help in finding a counter with the following capabilities. The first is the ability to accept a count enable that is driven by the gate pulse produced by the T-flip flop. Once the count is completed when the gate pulse goes low, I want to output the frequency count in the form of a binary output to program a separate divider before the gate pulse goes high again. It seem that a counter such as the 74HC590 with output registers would be a good candidate. But I'm also considering the benefits of using the timers of a microcontroller to compute the frequency ratio instead. It seems as using the microcontroller would make for a more efficient solution, as it could be used to compute the frequency ratio and then send the computed value to a PLL divider.

I hope my description of the problem is clear, and I would appreciate any insight on appropriate counters, or whether the microcontroller route is better.


texts: Programming an FPGA using C Vs using openCL-C

texts:
I came to know about Altera openCL devlopment Kit, for programming FPGA using OpenCL. I know what OpenCL is and how to write programs in this.
This is an extension to C, and it has threading possible. So you can launch thousands of threads, and each work in parallel if sufficient resources are provided.

MY question is from FPGA developer point of view how openCl development is different from C based FPGA development? (I have never programmed an FPGA in C)
If you say OpenCL has parallelism, then I think when implemeneted in C, the final design after compilation and place and route will also have parallel units of hardware on the chip. So how is C and openCl different ?


texts: Finding the total impedance and voltage across open terminals

texts:
The question that I'm trying to solve is the following:

In the circuit shown below, what is the total impedance in ohms across the open terminals? What is \$v_{T}\$ if \$v_{L}\$ is 80 vrms?

This is how I solved the problem.
I let \$Z_{1}\$ be equal to the 10-ohm resistor, \$Z_{2}\$ to the -j60-ohm, and \$Z_{3}\$ to \$30+j40\$.
Solving for the total impedance:
$$z_{t} = z_{1}+z_{2}\left |  \right |z_{3} = 10 + \frac{\left ( -j60 \right )\left ( 30+j40 \right )}{30-j20}=\frac{1210}{13}-\frac{60}{13}j$$
I'm not sure though if looking for the total impedance is similar to looking for the equivalent impedance/input impedance as shown in my textbook.
For the voltage, I used the voltage division principle:
$$v_{L} = \frac{z_{3}}{z_{1}+z_{2}+z_{3}}\left ( v_{T} \right )$$
Then, I solved for \$v_{T}\$ which is equal to \$\frac{64}{5}-j\frac{352}{5}\$.
Now, I have two worries in mind.

Is total impedance the same as input impedance or equivalent impedance?

Is 80 vrms interpreted as 80 V?

Thanks in advanced!


texts: I cannot find information about some chips in 3 stage LNA circuit

texts: Hi, here you can see 3-stage LNA circuit. I want to know information about two chips(6 pins) with R8 mark at the top. Also, 4 chips with D4 mark with 3 pins at right side. Is there anyone who has a good intuition of this?


texts:
I am designing a battery charging circuit for an in circuit NiCd battery (used on a RC car).

From my research I understand that I need to charge using a constant current source, and for fast charging on NiCd batteries this can be a maximum of 1C (provided that the shutoff circuitry is well designed). However, as BJT are likely not able to provide this current I have chosen a 0.1C charging time.

Therefore I have designed the following constant current circuit, with the mathematics shown.

Battery Specs

Capacity = 2100mAh
Voltage = 7.2V

simulate this circuit – Schematic created using CircuitLab

Calculations

Current for the battery
\$0.1C=210mA\$

BJT
\$V_{be}=0.7V\$
Zener
\$V_z=5.1V\$

therefore

\$R1=\frac{(5.1-0.7)}{(210\times10^{-3})}\$

\$R1=21Ω\$

Base current
\$h_{fe}=100\$
\$I_b=\frac{I_c}{100}+2mA\$
(2mA for the Zener)
\$I_b=4mA\$

therefore
\$R2=\frac{(12-5.1)}{(4\times10^{-3})}\$
\$R2=1.7kΩ\$

Which shows the circuit below.

Is there anything here that I have missed or is this correct?

Further questions:

If the motor is suddenly turned on (it will draw approximately
35-50A) during charging will this current be provided by the
battery? I would assume so as the battery acts as a capacitor and
therefore will resist the change of current to keep the voltage the
same?
Is it possible to redesign the circuit so that the full 1C can be
provided (2.1A)
Would it be a better idea to use a regulator somewhere?

EDIT1:
Updated to show location of motor in the schematic.

EDIT2:
New schematic

simulate this circuit


texts: Charge and discharge LiPo batteries with BMS 3S

texts: I am looking for a solution to power a Raspberry Pi connected to a LCD screen 10 inch with three LiPo batteries 3.7V 5000mAh connected to two BMS 3S for charge and discharge. I designed the following circuit but I have doubts on its correctness. In case this is correct what is the expected battery life in hours?


texts:
I plan on driving a heating coil of about 1.4 Ohms from a 3-4V power source; which gives an current draw of 2.14-2.85 A. So Watts from the following info is 6.42-11.4 W of power. The MCU will output a PWM signal at 490Hz at a voltage of 3-4V as well. knowing this I found a few potential mosfet's; and wanted some opinions from the pro's!

Here's the potential candidate list so far:
SiA400EDJ
SQA410EJ
PSMN012-25YLC (this one is interesting as it has a unique package, but is due to be phased out..)

Any opinions or recommendations are appreciated! NOTE: I'm going for smallest size and smallest cost as well!


texts: 3 switches, one lamp with existing wiring

texts:
I have an existing wiring with two switches for 1 lamp.

How to add third independent switch without changing to much wiring inside walls (usual wiring [with the triple switch in the middle of circuit between two two ways switches] is not fit, since it will require replacing three wires inside concrete walls)

Thank you


texts: Can anyone locate specs on this wifi module?

texts:
This little module was liberated from a Canon wifi enabled printer that decided not to work anymore. It appears to bear the label "Product Number: K30306" at the upper left, which naturally was the first target for a thorough googling.. as were all the other numbers that looked remotely like part IDs. Sadly this did not yield the expected results.

Probing the connector on the printer's motherboard did not reveal any obvious power rails; apparently this printer doesn't turn on the wifi unless it's happy, i.e., not generating a terminal error code. If I were to speculate, I'd guess that the two twisted pairs might be USB and the 5th wire a special line for powering the RF sections.

Hopefully someone has run across this module or something like it before and can shed some light on how to make use of it. Fwiw, the printer was a Canon pixma mx860.


texts: Lead-acid battery charger, specific circuit, 3~4.5 Amps, doubts + recommendations

texts:
I want to build a lead-acid battery charger which can reach an average charge current of 3 to 4.5A, and start with a prototype.
The charger needs to be supplied by the mains, up to 250VAC, for example.
I was looking for some circuits on the web and did selected the circuit below.

I want to check your considerations and recommendations about this circuit and the components that I have choose (list below).
My list of components would be:

D1, D2 = B560A, SMC package (60V x 5A schottky)
M1 = AmpMeter or short-circuit
Rx = 1R or 1.5R or 2.2R, 10W, wirewound
R1, R2, R4 = 1K, 1210, 0.5W, 5%
R5 = 10K, 0603, 5%
R3 = 470R, 1210, 0.5W, 5%
P1 = 5K PCB potentiometer, PN CT94EW502 (Digikey)
D3 = SMD 1N4007, SMA package
D4 = BZX84C5V6, SOT23 package
C1 = ceramic 10uF , 0805, 16V
SCR2 = NYC0102BLT1G (Littelfuse Inc.)
https://www.digikey.com/product-detail/en/littelfuse-inc/NYC0102BLT1G/NYC0102BLT1GOSCT-ND/2705214
SCR1 = MCR12DSMT4G (Littelfuse Inc.)
https://www.digikey.com/product-detail/en/littelfuse-inc/MCR12DSMT4G/MCR12DSMT4GOSCT-ND/964541
Both theses SCRs have sensitive gate current (low IGT), lower prices and available in high quantities on Digikey.
Is it suitable to use SCR1 as sensitive gate? Or it will be better to use a standard SCR for this part?
Also, would it be better to select a higher temperature grade for SCR1?
Is it possible to make a low cost protective circuit in case inverted battery connection occurs?
What would happen to the output voltage when the battery is not connected to the circuit? If we considerar that the floating voltage of the battery is 13.8V and we set the potentiometer accordingly, the output voltage would be limited to 13.8V when the battery is not present?
Also, you can suggest other good circuit for the same purpose (3 to 4.5A average current charge), maybe also a switching circuit.

Next month I will buy again on Digikey, so if you have some recommendations, I can buy any component present there for tests, giving preference for price and quantity available.


texts: Induction motor electrical and mechanical angle

texts:
How do we reach the relation between mechanical angle(\$\theta m\$) and electrical angle(\$\theta e\$) as: \$\theta e = (P/2)\theta m\$ ?
; where P is the number of poles.


texts:
EDIT: This is a homework question. What I need to know is how to solve the circuit through the transition table. That is, how do I write the circuits for the state changes (is it a flip-flop circuit, or a combinatorial circuit?) and the outputs?

I have a simple state machine with 3 states to control the automatic doors of a mall: waiting, entering and leaving. Two sensors, one in each side of the door, a timer that counts to 10 seconds.

The door opens when one of the sensors is activated, and remains open until the other sensor is activated or 10 seconds pass without any other input. Every time a person goes in or out, an alarm goes off. One of the suppositions is that only one person goes in or out at any time, so the sensors can't go off at the same time.

I have then 3 inputs to the circuit: S1, S2 and the Timer. And one output, the alarm A.

I was wondering how I'm supposed to write the state transitions table. I'd written something like

S1    S2    10s    Q(n)    Q(n+1)    Alarm

0     0     0      A       A         0

...

1     1     1      A       X         X

0     0     0      B       B         0

...

1     1     1      B       X         X

And so on, with the 0-7 table being repeated for the states Q(n) = A, B and C.

Is this correct?

What's the next step to build the combinatorial circuit? I know I have to make the Karnaugh maps, but how do I factor in the states A, B, C? Are they supposed to be flip-flops? Are those then different "functions" I have to make the Karnaugh maps for?


texts: Charging NiMH batteries with 1W solar panel, charge controller needed?

texts:
I want to know if a charge controller would still be needed despite the solar panel never outputting more than C/10 of current to the battery.

This is a follow-up about my question here.

The solar panel is rated at 1 W with a max load voltage of 6.4 V and the product page is here.

The battery capacity is 2450 mAH with a nominal 1.2 V per cell and the datasheet is here.

I actually tested the panel myself and found that in the best case with 90,000 lux (full sun), the max voltage was 5.2 V, corresponding to a max current of 157 mA. Thus, the maximum power point is 814 W. At a lower voltage (1 V), the current still never exceeded 165 mA, which is much lower than C/10 but higher than C/40. I've read that despite this, it would still be detrimental to the batteries to constantly charge them at this rate. However, since this is the absolute best case of light intensity, and even then the sun would only be up for around 13 hours at the most and not even at full intensity the entire day, is this a problem?


texts: How to convert a TowerPro 18A MAG8 (HH30A_V1.1) Electronic Speed Control (ESC) from PWM to I2C?

texts:
A while ago, I purchased four of these ESCs to use them for the control of brushless motors.

Now I need to know how to convert them from PWM to I2C.

I'm not a electrical engineer, so I don't know how to do this. I already searched the web, but I didn't find anything helpful. I usually get displayed confusing Forums or the versions of the controllers were different.

Any ideas how to modify them?


texts: Rough Battery (9V Alkaline) Level Estimation with Analogue Reading

texts:
I'm building a portable desktop weather station using an Arduino Nano micro-controller. The system is being powered by a consumer 9V alkaline battery, with the voltage being regulated by the Nano's on-board regulator.

I want to have a rough battery level displayed on the LCD screen.

The initial approach I have taken is by using a voltage divider which scales the input 9V to 3.3V. This signal is then input into to the Analogue IN (A6) of the Nano, ( AREF is set to 3.3V due to other analogue input device requirements).

From this I was assuming that ranges of voltage readings could correspond to FULL, HALF and LOW battery indications.

I understand that the battery terminal voltage will change with current draw. I expect a peak current draw of 350mA with a typical draw of about 100-150mA.

What is a good scheme/algorithm/cutoff values I should use to roughly measure battery level?

EDIT:
-My Estimated power draw was wildly inaccurate. After measuring the current draw of the final device, consumption was approximately 30-40mA continuous, with rare peaks of 50mA.

-I ended up using a simple battery percentage using AnalogRead(). I calibrated a fresh battery to display ~90% by adding a fudge factor. It was fairly successful as a rough estimation.


texts: Running cables through drainage, what is the best cable to use?

texts:
I have a project where we have been provided with cable routing through the water drainage and will therefore need to be suitably protected from being submerged in water fairly frequently.
What are the best cables to use for this, I am currently planning on using either H05VV-F or H05RN-F but is this going to give sufficient water protection?
Is it worth upgrading to H07RN-8-F or putting some conduit in?


texts: Observation of negative voltage at the output of the op-amp

texts:
I am using ADA4898 op-amp.
Without connecting any elements to the circuit at the output of the IC, I see a negative voltage.
Is my IC broken?

simulate this circuit – Schematic created using CircuitLab

simulate this circuit


texts: Extremely small electric shock device - could this work?

texts:
My question is this: Is it possible to build a device which could deliver a small electric shock every hour or so, and to fit this into a standard size ring?

I am talking about a small electric shock to the wearer - enough to be noticeable but not painful. An on/off switch could be added to the outside.

I am skeptical that a battery, timing chip aswell as well as the rest of the circuitry could be squeezed into that small a space and still deliver a noticeable shock. Battery life could also be a problem.

Can you think of a plausible way to do this?


texts: Auto disconnect the load while charging the battery

texts: Here is a tentative schematic that would use the battery (3.7V, 3500mAh single 18650 battery) to power the load under normal circumstances. The charger is disconnected at this point. When the AC-DC adapter is connected to power the charger (5V at the charger input), the load will disconnect and the charger will start charging the battery. Would this work?


texts: In an idealized model, the voltage at node1 is the same as the voltage at node2. However, in reality waves take time to travel and the voltage at node1 will not be identical to the voltage at node2. I was wondering how to choose the component values and wire lengths such that I can observe a different voltage at node1 and at node2.


texts: Driving stepper motors with A4988. Problems with current and torque

texts:
I bought a dozen types of stepper motors with rated voltages ranging from 4v to 12v and currents from 2A to 0.3A. I am unable to get anywhere near the rated torque on all motors except those with rated voltages 10v and higher.
My setup:

Power supply: Agilent E3610A set to output 12V (current limited to 2A)

MCU: Teensy 3.1

Stepper Driver: Pololu A4988 (Cant provide link due to low reputation)

Now, for steppers like this one with rated voltage of 4.2v and current 2A - no matter what I do with current limiting pot on the surface of the driver - I simply cant get the motors draw more than a fraction of their rated currents. Its a single turn pot - so I fall off the adjustment space before current (measured at power source AND motor coil) reaches any appreciable amount (usually it maxes out around 0.1-0.2A). Torque too is very low, naturally. I tried voltages 8-17V (the range limited by the driver board and my power supply) - but still, cant get the motors produce more torque.

All 4 wire steppres are in bi-polar config.

Interestingly, it is not a problem with steppers rated 10-12v, for instance CanaKit stepper (cant provide link due to low reputation) rated at 0.33A and 12v - I can get them draw more current, although even in that case - there is a huge mismatch between the current they ought to draw based on VREF pin reading, and what the actually draw. For instance, measuring the VREF (~1v)and applying the formula - I should have gotten 2.5A (or slightly less due to 70% energization) - but I really measure only 0.29A on the coils.

Everywhere I read, it looks like I should not have this problem. I.e. read the threads on SE (cant provide links due to low reputation)
What am I missing? All is wired up together on a breadboard. Wiring is solid, but could this be a problem? Should I consider a different driver?

Appreciate any tips!


texts: Use a wooden frame to avoid dissipation of high-frequency current?

texts:
In reading a description of a 32-kilowatt induction heater of the spark gap type by Frank Curtis (p. 29), I see the following passage describing the enclosure:

  The entire assembly is mounted within a wooden frame so that stray
  high-frequency currents will not be absorbed or otherwise dissipated.

To what effect is he referring? He seems to be suggesting that if the machine had a metal enclosure, it could somehow leach power out of the circuit and therefore it is better to make the frame out of wood.

The book in question is "High-Frequency Induction Heating" (1944).


texts: Why don't over damped and critically damped circuits oscillate?

texts:
The reason underdamped LRC circuits oscillate is because the energy keeps flowing between the inductor and capacitor. The energy is being constantly exchanged between the capacitor  and inductor resulting in the oscillations - the fact that energy is being lost to heat explains the asymptote and why the amplitude of the oscillations keeps decreasing.

I'm having trouble understanding why this doesn't happen for over damped and critically damped circuits though. Sure, I can set up the differential equation and solve for the function. But that's not the part I'm having trouble with - I'm having trouble intuitively understanding what's different about over damped and critically damped circuits.

So can someone please give me an intuitive explanation of why critically damped and over damped circuits don't oscillate? Why isn't the energy being exchanged back and forth between the capacitor and inductor?


texts: Why does a UPS need an isolation transformer?

texts:
Why would we need isolation transformers before and/or after for a UPS system? What are we trying to protect, and from what? I have read that it has to do with grounding and neutral but I didn't understand.

This is 100KVA UPS. The inputs are 3 phase, neutral, and ground, coming from the service panel which has the neutral connected to the ground inside the panel. The output 3 phase, neutral and a ground while only the 3phase and ground are connected to the load (no neutral is connected to the load). When the UPS-company-man saw the installation he said that we must use a isolation transformer before the UPS.

Here is a simple schematic of the this configuration :

simulate this circuit – Schematic created using CircuitLab


texts:
I've looked around on the internet, but there's so much conflicting advice on how to find the value for the necessary resistor between the base of the transistor and the microcontroller. I'm completely at a loss at this point.

The microcontroller I'm using is a the huzzah ESP8266 breakout board from adafruit, and the transistors are TIP41C's.

Here's a schematic:


texts:
(Q1)  Can an active differential probe such as this Agilent N2752A
be used in a single-ended way, i.e., with one of its inputs at the GND of a circuit?    Understanding of course, that we have (a) 1/10th the usual input impedance of single-ended probes and (b) that we are limited in our voltage swing to 10Vp-p?  Any other 'gotchas' about doing this?  The reasons why will be explained in the next question ...

(Q2) I've acquired a scope with a 6GHz bandwidth, and the inputs on the front of this scope have warnings: "All Inputs 50 Ohm, +/- 5V Max  Cat I"    I am wondering if I can use this scope as general purpose instrument.   So in addition to the above-mentioned single-ended measurement, I'd like to extend the voltage range to 50V.    Would this mean a 10:1 differential probe is required  ( 50V --> 5V  for compliance with the warnings on scope )?   Would a 50-ohm active differential probe with a 10:1 attenuation translate my single-ended measurement of 50V --> 5V and match this scopes 50 Ohm input impedance?


texts: How is the sweep type affecting the Bode plots for the same AC analysis in LTspice?

texts:
When I do an AC analysis for the following circuit between 0.1Hz upto 20MHz, and by selecting "decade" in sweep types I obtain the following plots:

But if I do exactly the same thing only this time I set the seep type to "linear" I get some sort of unusual plot:

I couldn't find information about these different sweep types.

Why am I having different plots for the same AC analysis with different sweep types?


texts:
All!
I am trying to figure out characteristics of a second order system
The system is (for example)

And its characteristics for an unit step input are

I want to solve this equation by hand and extract damping ratio and natural frequency, but my knowledge is the transfer function of undamped second order system should be in this formula

How to determine damping ratio and natural frequency?


texts: Running a magnetic buzzer using coin cell battery

texts:
I would like to operate a small magnetic SMD buzzer using a coin cell battery. However, magnetic buzzers require at least approx. 40mA to run, which I think is more than a coin cell battery can output. So, is there any possible way to operate a magnetic buzzer using a coin cell battery? Maybe with the use of other components etc?
If not, is there an alternative? (I considered a Piezo buzzer but they don't come as small as magnetic buzzers, which are 5mm x 5mm).
Thanks.


texts:
I'm currently undertaking a project that uses a thermistor and a voltage divider circuit to calculate the temperature. I'm reading the voltage into my Arduino Uno.
I've set up a room temperature test and my circuit gives credible results against a reference thermometer and I'm satisfied with its performance in that range. However, once I place my thermistor probe into a water basin that is kept at a constant temperature by using a hot plate, my thermistor gives a reading that is 3-6 degrees more than my reference thermometer. Does any one have any ideas why there is such a degradation in performance and how can I rectify this?
Quick Schematic
    +Vref---[Thermistor]---+--[1.8K]---GND
                           |
                       ADC @ thermPin

I'm using a lookup table which contains expected values through my required range of temperature.
Any help is appreciated.
Thanks.


texts: Digital Control Engineering book recommendations

texts: What are good books on digital control engineering specifically? I'm a third year electrical/computer engineering student who will be doing a course on digital control next semester, but would like to get a head start.


texts: Pull down resistor for Arduino input to read LOW when no voltage from switch

texts:
I'm building the Arduino spaceship interface from the project book and everything works fine. It involved connecting 3 Arduino outputs to 3 leds, and 1 Arduino input to the a switch. For a photo of the setup, please see here: http://imm.io/V5oh

(source: i.imm.io)

The switch is set up like this:
5V ---- push button-----10kOhms------0V

The Arduino input is connected between the push button and the 10kOhm resistor.

My question is: Why is the 10kOhm resistor needed? The manual says it is needed so that the Arduino "reads LOW when there is now voltage coming in through the switch".

Could I not simply get rid of the resistor completely (just replace it with a wire), then if the switch is open, it will still be connected to the ground and still read LOW? What is the resistor actually doing, if anything?


texts: I'm trying to use de IC ULN2003 to logically drive the current of different LEDs from a logic input. I have searched for the data sheet but i don't understand how the IC works. I know that there is a Darlington pair for each Input-Output set but I don't understand what should be connected in the COM input of the IC. Can somebody explain me this?


texts: Polyphonic sounds from a microcontroller?

texts:
I can make monophonic sounds by toggling a single pin (at a varying rate) connected to a piezo buzzer.

How can I generate two mixed audio signals in software to create polyphony?

Here's the code I'm using to play a simple tune.

#define F_CPU 8000000UL // 8MHz
#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/delay.h>

// number of timer0 overflows/sec
#define INT_PER_SEC 31250

// Frequencies (in Hz) of notes
#define F_FSH_4 370
#define F_A_4 440
#define F_B_4 494
#define F_E_4 330
#define F_CSH_5 554
#define F_D_5 587
#define F_FSH_5 740
#define F_CSH_4 277
#define F_GSH_4 415

// number of timer0 overflows for notes
#define REST -1 // special case
#define FSH_4 INT_PER_SEC/F_FSH_4
#define A_4 INT_PER_SEC/F_A_4
#define B_4 INT_PER_SEC/F_B_4
#define E_4 INT_PER_SEC/F_E_4
#define CSH_5 INT_PER_SEC/F_CSH_5
#define D_5 INT_PER_SEC/F_D_5
#define FSH_5 INT_PER_SEC/F_FSH_5
#define CSH_4 INT_PER_SEC/F_CSH_4
#define GSH_4 INT_PER_SEC/F_GSH_4

#define SEMIQUAVER_TIME 60  // ms
#define BREATH_TIME 20      // ms

volatile uint32_t intrs = 0;
volatile int32_t curNote = REST;

// TIMER0 overflow
ISR(TIMER0_OVF_vect)
{
    if (curNote == REST)
        intrs = 0;
    else
    {
        intrs++;
        if (intrs >= curNote)
        {
            PORTD ^= _BV(PD4);
            intrs = 0;
        }
    }
}

void play(int32_t note, uint32_t len)
{
    int i;
    curNote = note;
    for (i = 0; i< len; i++)
        _delay_ms(SEMIQUAVER_TIME);
    curNote = REST;
    _delay_ms(BREATH_TIME);
}

int main(void)
{
    /* setup clock divider. Timer0 overflows on counting to 256.
     * 8Mhz / 1 (CS0=1) = 8000000 increments/sec. Overflows every 256, so 31250
     * overflow interrupts/sec */
    TCCR0B |= _BV(CS00);

    // enable overflow interrupts
    TIMSK0 |= _BV(TOIE0);

    // PD4 as output
    DDRD = _BV(PD4);

    TCNT0 = 0;
    intrs = 0;

    curNote = REST;

    // enable interrupts
    sei();

    while (1)
    {
        // Axel F
        play(FSH_4, 2);
        play(REST, 2);
        play(A_4, 3);
        play(FSH_4, 2);
        play(FSH_4, 1);
        play(B_4, 2);
        play(FSH_4, 2);
        play(E_4, 2);
        play(FSH_4, 2);
        play(REST, 2);
        play(CSH_5, 3);
        play(FSH_4, 2);
        play(FSH_4, 1);
        play(D_5, 2);
        play(CSH_5, 2);
        play(A_4, 2);
        play(FSH_4, 2);
        play(CSH_5, 2);
        play(FSH_5, 2);
        play(FSH_4, 1);
        play(E_4, 2);
        play(E_4, 1);
        play(CSH_4, 2);
        play(GSH_4, 2);
        play(FSH_4, 6);
        play(REST, 12);
    }
}


texts: AVR ATtiny1634 - PB3 as Input and Watchdog Timer

texts:
I'm quite a beginner in AVRs and this is my first project soldering the microcontroller and programming it on board. I know the ATtiny1634 QFN might not me the best micro for a beginner, but everything worked as expected when I programmed and tested the board, except for the PB3 as input PIN.

After carefully checking the solder and the code, I decided to search on the internet about the problem. I found this topic https://www.avrfreaks.net/forum/pull-not-pulling, that describes a situation very similar to mine, and also other topics talking about an annoying limitation that t1634 has, that curiously only appears in the datasheet's errata:

Errata Rev A

2. Port Pin Should Not Be Used As Input When ULP Oscillator Is Disabled
Port pin PB3 is not guaranteed to perform as a reliable input when the Ultra Low Power (ULP) oscillator is not
running. In addition, the pin is pulled down internally when ULP oscillator is disabled.

Problem Fix / Workaround: The ULP oscillator is automatically activated when required. To use PB3 as an input, activate the watchdog
timer. The watchdog timer automatically enables the ULP oscillator.

Unfortunately, due to the fact that this information is not notified in any I/O Ports description of the datasheet, I found out about it just now that I have my board soldered and the PB3 input is crucial for project's operation.

But, as said in the errata, it seems like the problem can be solved by activating the watchdog timer. As a beginner, I have never user the Watchdog Timer and I know very few things about it. I tried to set the WDTON-Sets watchdog timer permanently on High Fuse, but when I tested it not only PB3 but all of the other inputs didn't work.

Do I have to set this WDTON bit on Hfuse or do I have to do something in my code for activating the watchdog timer as the errata suggests?

Thanks in advance for any help!


texts: Why use only oversimplified/ideal equivalent circuits?

texts:
Most circuit analysis books use ideal resistor, inductor, capacitor and don't even bother to show practical circuits of these components, let alone any solved examples with practical circuits.

For diodes, all of these books give examples for ideal and practical diodes (to some extent). My question is if it is just because of the complexity involved (although students should be helped to solve at least a few of these to understand it better) or is it because results using ideal components are very close to original/practical in case of R, L, C than in case of diodes?


texts: RF Link with APC220 between two PIC16F877's

texts:
I am attempting to communicate through a RF link between two PIC16F877's using APC220 Radio Transients. When the PIC UART's are connected with wires between TX and RX they communicate just fine, but will not communicate with APC220 module. I have the APC220 modules connected as in this diagram from the user manual.

GND and VCC connected,
EN Disconnected,
TX and RX connected,
SET as High,

The APC220 modules settings are being written and read correctly using RF-Magic.
The baud rate for PIC UART and APC220 are set for 9600.
Air rate 9600,
No Parity,
Same Net ID and Different Node ID's,
434MHZ.

I have read what seems like every document ever written on these RF units but can not for the life of me get them to communicate. Can anyone help?


texts:
I'm trying to (hopefully) reuse a smartphone LCD and touchscreen controller, among some other components.

The first step is to break out the tiny connectors on the board. It appears to be 2 board to FPC connections. See picture here: http://i.stack.imgur.com/jctIv.jpg (bottom right, sorry for the poor quality)

I found this resource but it's almost impossible for me to tell which one specifically is used.

Any suggestions for how I could get to those signals or wire it up to a breadboard?

Much appreciated.


texts:
I have been working on 4-20mA transmitter project and stuck with a problem. My design is based on  CN0319 evaluation board but I changed some of it, to make it works with other part of the design.

Below is my design, I want it to transmit 4-20mA current when the input of op-amp is PWM 0-100% duty cycle. It uses power supply 24V and drop it to 5.7V to supply entired circuit.

My problem is when I try to drive 4-20mA output current with 0-500 ohms load resistor. At around 400-500 ohms load, the circuit sense output current as desired. but when load resistor is 0-400 ohms. the current goes a little bit higher than it should be. For example, if I want to drive 4 mA, my circuit can drive 4 mA at around 420-500 ohms. But at 0 ohms, it senses about 4.2mA and it slowly goes down to 4mA when I increase load resistor to 420 ohms.

To drive 4-20mA, input voltage at V- of op-amp must be 0-0.6V. So I measure V- and V+ compared to DGND, V- voltage is constant at any load resistance but V+ is goes lower when load resistance is 0-400 ohms. What am I missing if I want to make the current consistant at load 0-500 ohms.

I measured voltage across Rload using oscilloscope and start to see ripple on it when I decrease the Rload. the more Rload goes low the more ripple voltage goes high. So, I measured voltage at Pin3 and see the ripple. But did not see that on input voltage at pin2. Input voltage at Pin2 is from PWM and pass through the low pass filter to make it DC.

This is the voltage at Pin3 at Rload = 356 Ohms

This is the voltage at Pin3 at Rload = 445 Ohms


texts:
I'm designing a circuit for my 3D printer's aluminium heating plate (200x200 mm) and I wanted to be sure before buying resistors. Also, I'm using a Sanguinololu 1.3a.
I want it to heat at 120° fast.

So, I think ~150 Watts was enough.

I'll explain everything, people who'll have same problems may find solution here :).

Using 5 x 5ohm in parallel means I have a 1ohm load.

simulate this circuit – Schematic created using CircuitLab

$$
\frac{1}{R_{equivalent}}=\frac{1}{R_1}+\frac{1}{R_2} + \frac{1}{R_3} + \frac{1}{R_4}+ \frac{1}{R_5} \\
\frac{1}{R_{equivalent}}=\frac{1}{5}+\frac{1}{5} + \frac{1}{5} + \frac{1}{5}+ \frac{1}{5} \\
\frac{1}{R_{equivalent}} = 1 \\
R_{equivalent} = 1
$$

I am using 12V to it, I am getting:
$$
U = R_{equivalent}I \\
I = \frac{U}{R_{equivalent}} \\
I = \frac{12}{1} = 12 A
$$

12A of current from the PSU. Which would give 12*12 = 144W, or 144/5 = 29W per resistor.

I wanted to use these: RESISTOR 50W 5R

Are my calculus ok ?
If they are, do you know a way to find the time it'll take (in theory) to heat up it to 120 ° ?


texts:
I wish to use a transistor for switching.
The datasheet says it allows a maximum collector current (continuous) of 200mA.
If my application just requires pulses of current every 1 second, would the transistor be able to pass through an Amp?

Is there a way, I can calculate or figure out the maximum collector current, when its not continuously flowing through it?


texts: H bridge not switching correctly - Induction heater

texts:
I've been working on an induction heater over the last few months and have had varied success. I can drive about 600W through it but as I begin to push past this point it isn't long until one of the FETs explodes. Below is the circuit schematic I based my driver on and the physical setup itself.

One of the issues that seems to plague the circuit is that each arm of the H bridge appears to switch on prematurely; the voltage at either node A or B will rise to the level of the DC bus prior to the high side gate being driven high. I've included a couple of waveform captures to help illustrate this. The first image shows the input to the high side gate (yellow) versus the output of node A (red). The second shows the 'precharge' that occurs between node A and node B.

Currently the circuit is driven with a PWM waveform at 15.34KHz, 48% duty cycle. Q1 & Q4 are switched on simultaneously followed by a short dwell period to prevent shoot through and then Q2 & Q3 are driven simultaneously followed by another dwell period, repeatedly. The dwell period isn't apparent due to the 'precharge' that appears on either node. I'm trying to understand why this precharge is occurring and what I can do to resolve it. I suspect whatever may be causing it is creating other issues such as ringing etc.

I had thought of increasing the duty cycle of the low side drivers to 50% while retaining the original duty cycle of the high side drivers in the hope of draining any residual charge, but this requires four PWM inputs which I don't currently have available and I'm not sure this is the solution to the problem. I've also tried using a 1uF capacitor as a snubber between one of the nodes and ground, I've found it does partially correct the issue but realistically just delays the effect until that arm discharges itself. You can see the effect below. The yellow signal is the logic reference.

Here you can see the effect 'pushed' onto the end of the waveform.

Apologies for the direct image links, SE is quite restrictive. Can anyone help me identify what is causing this 'precharge' effect?


texts: Calculate the input impedance of a passive AC voltage sensor

texts:
I got a AC voltage sensor to measure AC voltage. And I want to know its input impedance. But the sensor's data sheet only tells how to use it, doesn't tell the internal details. It's used as below:

The \$R_{i}\$ is calculated as:

$$R_{i} = U_{i} \times 1K \Omega/V $$

Rated output is 1mA, max load voltage 1.2V, rated input signal frequency 25Hz~5kHz.

That's the main specifications.

That is, if Ui = 1V, Ri = 1KOhms, and a 1KOhm resistor connected between Pin 3 and Pin 4, I can get about 1V output.

I think the internal is basically a current/voltage transformer. But how can we deduce its input impedance with some specific load resistor?


texts:
I've found it useful to have a bunch of 2.54mm headers laying around. They fit nicely into breadboards

Now I'd like to use a connector to connect to them. Something like this:

I'm not sure how to look for these in the catalogs.

I see these in mouser mouser part: 538-47054-1000 for $0.06 each.

Or these mouser part: 571-103688-7 for $0.50 each

My questions:

how do I shop for these in the catalogs?
how do I know if the crimp terminators (what's the proper term) are included?
If they're not included, how do I spec those?
How do I actually connect these to my wires?


texts:
using 21nos 3w led diode.  I am using 24v dc and 3amp supply. Connected 21x 3w led

Can I add another parallel connection to run 5v dc 0.16 Amp fan ?

Now I am using 3 x 4.7 ohm , 2W resistors, which are too hot from 24V.


texts: Trouble with engineering project - 555 timers

texts:
I'm currently finishing my GCSE engineering project and I am attempting to use a dual 555 timer circuit as a timer. I am using a schematic I copied off Kitronik Alarm Project Kit, but when simulating and after creating the physical circuit, it has failed to work. I have gone through everything I can think of to no avail.

I have researched how this circuit works, and understand simply how the capacitor charges and drains, but I still have very little understanding of how the circuit is meant to work, and I am having trouble diagnosing problems.

I have used crocodile clips to simulate the circuit, but no combination of reset/trigger switches results in anything changing in my eyes. I have consulted with teachers, but they have not been able to help. Here is an image of the simulated circuit:

Here is the original diagram I copied off, which can be found in this PDF: alarm_project_essentials_2_0

Sorry if I have misused tags


texts: Three-phase Y and Delta Configurations Polarities

texts:
Please take a moment to look at the three-phase Y and Delta configurations pictures below (The pictures are screenshots taken from the “All About Circuits” online book).

The first picture (Y configuration) shows the neutral node with negative polarities for all phases and the outside nodes with positive polarities for all phases. The second picture (Delta configuration) shows opposing polarities between the consecutive phases (plus, minus, plus, minus, plus minus clockwise rotation).

My questions revolve around the phase polarities as follows:

1) On the Y configuration, you can see that the author of the drawings labeled the neutral node with negative polarities for all phases. Given that AC voltage constantly changes polarities, why is he deliberately labeling the node with a fixed minus sing? The same goes for the outside nodes, why is he labeling them with fixed plus sings when those polarities are also constantly changing?

2) The other reason why all minuses and all plusses don’t make sense in my head has to do with phase shift. If all phases on a three-phase power are spaced 120 degrees apart from each other, there should be no way for all phases to have the same polarity at all times correct? In other words, it should be impossible for all phases to always be positive or always be negative. At one point in time or another, some will be positive and some will be negative correct?

Anyway, I am pretty sure that I am totally missing the point of what the diagrams are trying to convey so I was hoping someone could help me get a clue.

Thank you.


texts:
Below is a circuit schematic of sources and resistors.
  $$I_s=2A, V_s=20V, R_1=10Ω, R_2=6Ω, R_3=80Ω, R_4=15Ω$$

Question 1:  Calculate the current i1 flowing through resistor R1.

Question 2:  For the same circuit, calculate the current i3 flowing through resistor R3.

Question 3:  For the same circuit, calculate the current iVs which is flowing through the voltage source from node c to the ground.

I decided to use mesh analysis in this problem:

I thought the currents for each of the following questions are the following:

Question 1:  The current flowing through R1 is just i1.

Question 2:  Current through R3 is i1+i3.

Question 3:  Current through the voltage source is i2 + i3.

Assembling my equations I get the following matrix:

\begin{pmatrix} R_1 + R_2 + R_3 & -R_2 & -R_3 & 0 \\ 0 & i_s & 0 & 0 \\ -R_3 & 0 & R_3+R_4 & V_s \end{pmatrix}.

When solving the the matrix, however, I do not get the right answers:


texts:
Can anybody kindly tell me what this electronic component in the picture is called?

I've seen this component in:

Mobile phone circuit
WiMax modem circuit
GSM Module circuit

I tried but was unable to find its name. I'll be grateful to know your answers.


texts: What advantages to permeability tuning as against capacitive tuning?

texts:
I learnt recently about the RBZ80 ; a vintage valve receiver which used variable permeability tuning rather than variable capacitor tuning.

In thinking about the possible reasons for permeability tuning in lieu of capacitive tuning the thoughts that come immediately to mind as follows

The receiver was designed for hostile environment. Air dielectric would be bulky. Any other dielectric may be damaged/corrupted by exposure to the elements (e.g. salt water).

What advantages does permeability tuning offer as compared to capacitive tuning?


texts: Tradeoff between low-noise and low-power design

texts:
Can anyone help me to understand why this sentence below (which I had find it in a paper) is correct?

  Designers must address the tradeoff between low-noise and low-power designs of the amplifier.For an ideal thermal-noise-limited amplifier with a constant bandwidth and supply voltage, the power of the amplifier scales as \$1/(vn^2)\$ where \$vn\$ is the input-referred noise of the amplifier.

But I had read in a lot of books that refer that the thermal noise given by this expression \$P = K \cdot T  \cdot \Delta f= \dfrac{vn^2}{4 \cdot R}\$ so power and \$vn\$ are proportional. So which statement is correct?


texts:
I'm planning to make a plant watering system . There is a beeper so it will alert us when the soil is dry.I have got a 12V DC motor . So i'll be removing this beeper and i need to add this DC motor.What all change are needed to made in the circuit so as to make this automatic.I can use my Laptop Adapter as the power source. This circuit was taken from internet . I had actually made this one with the 12v DC motor back in 2012 with the help of a Electronic Engineer.He actually added a small circuit at the end of this circuit  without actually making a big change to the rest of the circuit.I had lost that modified circuit .There were two power sources with that working circuit one from the Batteries and other from the Mains via 12v adapter.

List of  items in the circuit.

R1,R4 : 470K   1/4W Resistors
R2 : 47K   1/2W Trimmer Cermet or Carbon
R3 : 100K   1/4W Resistor
R5 : 3K3  1/4W Resistor
R6 : 15K   1/4W Resistor
R7 : 100R   1/4W Resistor

C1 : 1nF  63V Polyester Capacitor
C2 : 330nF  63V Polyester Capacitor
C3,C4 : 10µF  25V Electrolytic Capacitors

D1 : 1N4148  75V 150mA Diode
Beeper : 3V

IC1 : 4093  Quad 2 input Schmitt NAND Gate IC

Q1 : BC557  45V 100mA PNP Transistor

P1,P2 : Probes  (See Notes)

B1 : 3V  Battery (2xAA, N or AAA 1.5V Cells in series)


texts:
Good Evening,

I am fairly unfamiliar with DSP and want to engage in a project. I wish to perform a FFT on the source current going into a non-linear load and observe its harmonic content on an LCD. I understand the basic circuit setup but I am having a hard time understanding how it interacts with the microcontroller.  Fundamental frequency is 60Hz, voltage is 120, max current is 20A. I know I will need a CT or differential amplifier since the microcontroller cannot sustain those high values.

Do any of you have any resources that can help me out?


texts: Why should we avoid including both blocking and unblocking assignment in same always block?

texts:
Nearly all verilog books and blogs strongly suggest not to include blocking and unblocking assignment in same always block.

But sometimes I also saw some code that has both blocking and unblocking code in same block, it can still work fine in simulator.

So what is the deep reason for why not using them simultaneously ? What potential problem would be caused ?


texts: Is Peltier Cooler Good for Outdoor Application?

texts:
I have a Raspberry Pi 3 w/ an Intel Movidius Neural Network Compute chip attached via USB. It has recently come to my attention that I may be asking the Movidius chip to perform too much work and as a consequence a thermal fail safe is being tripped in it after excessive use at room temperature. I want the whole thing to be contained within an enclosure for an outdoor application. This thermal problem has me worried since if the device is in a metal box for security/safety there won't be any air circulation to cool it down. Adding sunshine into the mix will cause the whole thing to heat up real fast.

Would integrating a Peltier cooler into the mix so that the cooler is in contact with the Movidius chip on one side and the interior, metal wall of the enclosure is on the other be a good usage of the cooler? Should I be using a fan instead? Since the device is outdoors it has me worried that rain/bugs or other problems could crop up if an entrance is present into the core of the enclosure. I have no experience building electronics that are intended to function outdoors and don't want any surprises.

Thank you,


texts: How can I connect mains to a 230V heating band?

texts:
I am planning on using some 230V heating bands for a project of mine. I was wondering what kind of equipment I would need to connect this heating band, which has +,- pins to mains. What kind of equipment would I need to convert the L,N and G cables of a mains power supply to be able to connect to the heating bands?
EDIT#1
The link to my heating band is:https://uk.rs-online.com/web/p/heating-elements/9209956/.It is a 235W heating band. Would I need a 230VAC to 230VDC inverter for this project? If so, what is the cheapest way I could source one?
I do not have much experience working with mains.


texts: Understanding id-Ugs and id-Uds graph of a nMOSFET

texts:
I'm so sorry posting such a horrible-looking picture, but I really cannot found pictures similar to it online and/or in English! If you found one, please let me know and I'll replace it immediately!

The left graph is a iD-uGS profile of a nMOSFET, and the right one is its iD-uDS. As you can see, the cparabola on the left is extremely alike to the dashed curve on the right graph(that is, the curve marked "预夹断轨迹", which indicates the boundary between linear and saturation modes).

I guess there might be some relationship between the two curves. However, I cannot figure out on my own. I've tried to draw a 3D graph showing the relationship between iD, uGS and uDS, but failed, because I don't know any model about MOSFETs.

So is there any relationship between the two curves?


texts: For this antenna, which cites a VSWR of 1.4, can that be improved (decreased) with the use of a matching network? Could the matching network be between the feed cable and the board or must it be between the antenna and the feed cable?


texts: Regular (not Zener) Diode as Voltage Regulator

texts:
I see a lot of information regarding Zener diode voltage regulators but how about a regular diode voltage regulator?

What would be the potential drawbacks of using something like this on the picture below:

simulate this circuit – Schematic created using CircuitLab

Where Rload should get whatever voltage is across the 1N4001 or whatever diode we use?


texts: Single ended to differential driver low-pass filter

texts:
I am taking a single-ended source, using a SN75ALS191 driver to convert it to a differential signal. This differential signal will travel over twisted pair cabling several hundred feet, to a single terminated input. The single-ended source signal will have a maximum frequency of 8MHz. The SN75ALS191 driver has a minimum rise time of 3.5nS, so ~285MHz.

I am not familiar with differential signal transmission, but my initial thought is to use a filter right at the output of the SN75ALS191 to limit the rise time to say 3x 8MHz. I would perhaps just use an LCL filter (Chebyshev) as shown below. Of course, I could change the filter type/order to have a better response, but they would all be referenced to my driver's ground. (The values and type of filter depend on the cable type/impendence/etc, this is not what my question is about - designing the filter w/ values)

This would work I think, since the driver is still referenced with it's common-mode to ground, so it should effectively still slow down the rise time leaving the board. However, I see most app notes that mention filtering, don't reference the filter to the driver ground, but instead, the out+ to out- as shown below. Does my filter above, not work? Or why is the below filter the better choice?

I do see some info on other appnotes, shown below, that seem to show an RC filter drawn like mine.


texts: Is Matlab able to formulate a second order transfer function from just a dataset of 2 inputs and their 2 outputs or I still need to conduct a step response on my MIMO model to calculate the TF parameters?


texts: Can I control a voltage output from a microcontroller?

texts:
I have to generate values between 0 V and 0.8 V for a circuit and take the value of the voltage output from the system and analyze the data. Can I generate voltage values automatically using a microcontroller? (For example: 0.05 V, 0.1 V, 0.15 V ...)

If the answer is yes, which microcontroller should I use and what techniques would you recommend?

If the answer is no, can you suggest any other means?


texts: Reliable 110 & 230V AC line detection on 3.3V GPIO

texts:
A manufacturer provided the following circuit, to detect AC line voltage in a small IoT module (non-isolated power supply).

SW1 is pulled up with an external 10 kOhm resistor and connected to the Input of an ESP32 for pulse detection.

R5, R6: 180 kOhm
R19: 15 kOhm
ZD2: 100 nF Cap
Q3: MMBT2222A Transistor (data sheet)

There is however a problem with induced voltages (similar to this I guess) in the wire connected to S1, due to other cables conducting 230V AC nearby. I can sometimes measure up to 100V AC with a multimeter on the cable I connect to S1 (even if it is not connected to the S1 input of the IoT module yet).
A suggestion of the manufacturer was to switch the circuit to a MOSFET, but this didn't help much either.

R5, R6: 150 kOhm
R19: 7.5 kOhm
ZD2: 100 nF Cap
Q3: HSS2300A MOSFET (data sheet)

I tried playing around a bit with the resistor values (see this simulation), to get the Gate voltage of the MOSFET below the threshold voltage of 0.3V (according to the data sheet), but didn't find a solution that worked reliably in hardware either. I basically need a circuit that detects 110 & 230V AC, but ignores the induced voltages from coupling. I guess another option would be to put a huge capacitor in front of the MOSFET, but to not change the existing PCB too much, as I would like to stick with the existing packages of the parts. If there is however a huge improvement by changing this, I am willing to re-layout the PCB.

R5, R6: 1206 package
R19: 0805 package
ZD2: 1206 package
Q3: SOT-23 package

Thank you!
EDIT: another Image from an alternative circuit added, see reply and comments below.


texts:
I am planning a project very similar to the one seen in the following gallery. (http://imgur.com/a/G7iww) I like the idea of having my phone plugged into the same unit for charging. My only concern is I only want to have one power cable being attached. The power cable needs to power both an Arduino Micro, some LEDs, and charge the phone, so I will likely be using a 5V wall wart or something similar (high enough power rating).

My big concern is making sure the battery is charged properly and is not over charged. I don't want to just plug it into a constant 5V-1A circuit, and ruin the battery. I have seen a few charging circuits online (like this one), but did not know if this was a safe option.

Any suggestions would be greatly appreciated. I am looking for a package that is relatively easy to use/solder and is reliable/safe. There are plenty of charging circuits, but are not exactly user friendly for small-ish hobby projects.

For what its worth, it is an iPhone 6 that needs to be charged, so it is a 3.8V  1800mAh lithium ion battery.


texts: Diode Bridge with differential voltages. Transfer function

texts:
Hi, I've been struggling with this problem for about an hour and I just don't know how to determine the transfer function for this circuit. My first attempt was analysing how the circuit behaves when the input is positive but I couldn't get to any reasonable result. I've also made the analysis when the the input is zero by setting up two loops sharing the test load (the one that is connected to vo).

I don't know if you could point into the right direction.


texts:
I am looking for a level shifter circuit, that can convert 5V to 50V logic. I've been looking through some designs. I see a lot of designs uses a current mirror for this. And was wondering, what is the advantage of using a current mirror type level shifter as opposed to a more "easy way" like double npn inverting logic, or npn-pnp level shifter?

Best regards!


texts: Simulate a battery with an AC wall transformer

texts:
Entry level EE has battery question. I use a heating element (vaporizer) that takes a 1.5V AA rechargeable 2000 mAh battery. It comes with an AC wall adapter that is OUTPUT 12V DC @2000mA so 24 WATTs right? That passes through some circuitry that has a variable knob so you can control the heat (which I assume current) and simulate the battery. It's much more powerful than the actual batteries are though. I'm sick of using rechargeables.

Anyway, the power adapter burnt out (just the circuit side, not the transformer) and I don't want to spend 80 bucks on another one. I'd like to simply plug another wall adapter directly into the device. I don't need the variable setting, whatever power it comes out as (as long as it's comparable to the battery it should be fine).

Can I use a wall transformer with 1.5V at ~16 AMPS and get the same result? Do they make such adapters at like Radio Shack? If I use higher voltage will the device still work as long as we don't exceed the 24 WATTS that the original power adapter was using as input? It is a small incandescent light and a heating element, nothing more.

Opinions?


texts: is the ib current correct i went the KVL through the first transistor


texts: Polarity of Keyestudio W5500 Ethernet Development Board Power

texts:
I've just received a Keyestudio W5500 Ethernet Development Board, I bought this device because Arduino Ethernet Uno r3 was discontinued, and I don't want loads of shields. So anyway it arrived this morning.
The device needs to be powered by 7 - 12 Volts DC power source via a barrel connector. However, the polarity is unclear.

The power polarity is not indicated on the board anywhere
It isn't indicated on the box that the device came in
It's not indicated on the company webpage for this product here: https://www.keyestudio.com/keyestudio-w5500-ethernet-development-board-for-arduino-diy-project-without-poe-p0368.html
It's not on the wikipedia page either: https://wiki.keyestudio.com/Ks0304_Keyestudio_W5500_ETHERNET_DEVELOPMENT_BOARD_(WITHOUT_POE)
The sales team need to consult with engineers to find out... and that could take a while...

So I'm wondering if there is a way to check what the polarity is using a multimeter?
Now I've checked that the outside of the barrel connector goes through to all the ground pins. But I read somewhere that ground can be negative or positive, so actually, I'm not sure that helps me.
I'm an electronics n00b. Are there standard ways to checking these things?


texts:
I'm trying to create a driver for an analog signal. The signal will be an analog signal from the DAC that will be converted from 0-3V3 to 0-1V. I want to switch this signal on and off using a digital port of my microcontroller but when I calculate this schematic there will always be a small voltage leak due to the Rds(on). How can I prevent this leak current? The duration of the pulse form the microcontroller will be about 300 us or smaller with a frequency of 100 Hz or lower. The signal may be less then 0 V when the MOSFET is conducting.

simulate this circuit – Schematic created using CircuitLab


texts:
Here's my working:

$$ V_P = \frac{V_L}{\sqrt{3}}$$
$$ \therefore V_P = \frac{21.651kV}{\sqrt{3}} = 12.5kV$$
$$ S = 3V_PI_P$$
$$ \therefore I_p = \frac{S}{3V_p} = \frac{2400+j1800kVa}{(3)(12500)} = 80\angle36.86^\circ$$

The solution given in the answer sheet is $$80\angle-36.86^\circ$$

Is there a mistake I made? because this messes up the answers for the rest of the tut. Thanks!


texts:
I may be able to get my hands on an old 600MHz LeCroy oscilloscope. However, it doesn't have any probes.

Is it feasible to make an active differential probe for it using a high-speed op-amp, like the THS3201DBVT? It has a 1pF input capacitance, 1.8GHz bandwidth and is for arbitrary waveform measurement applications. I would like to examine a 100Mbps LVDS signal.

The basic idea would be to mount the amp on a little PCB with a couple of parallel gold probe pins, power it off a local +-6v battery, and use a short piece of coax to connect it to the 'scope.


texts:
simulate this circuit – Schematic created using CircuitLab

I am trying to be able to switch off the motor, then energize or de-energize the relay coil for a motor direction change.  I can't get this to work.  I am just a very beginner and am trying to learn.

simulate this circuit

But if I delete the two lines and put a "GND" it works.  Is GND not the negative terminal of the 12V battery?  How can I get this to work?  I would like to understand and also know what kind of diode or protection for my gpio pin would be suitable for this circuit.

Thanks


texts:
I'm looking to find the maximum current rating that a H.FL75 cable can handle. Particularly this cable...
https://www.mouser.com/ProductDetail/798-HFL752LPG084N2A
However, I cannot seem to find any mention of it on any internet search.
Does anyone here happen to know it?
Thank you in advance.


texts:
A short, useless intro to the question, feel free to skip it:

I had a power outage in my home yesterday. Power outages aren't what they used to be - Back in the day, it rendered me completely unable to do anything, but nowadays I have my laptop, which is still connected to the internet via my phone, which is connected to a strong mobile recharger I have (10 Ah) - and I can hardly care less about the rest of the power.

Except for the part about my fan. It gets really hot where I live. And I currently simply have no solution for this. Small USB fans don't do the trick. And I just can't figure out how nobody I know has a solution for such a simple, supposedly common problem. Is mankind simply not advanced enough to take on such problems? Will we be able to operate fans during blackouts? What level on the Kardashev scale must we advance to before we can solve this?

[/end-rant/intro]

Is it possible to operate a normal, standing fan during a power outage? How?

Is connecting it to a UPS a good idea? I've read elsewhere that the waveform generated by UPS devices doesn't behave well with these sort of devices.

And how long is a fan expected to last on a standard UPS?


texts: How do I determine the phase response of a high pass filter?

texts:
I am stuck trying to determine the phase response of a high pass filter. I was able to find the transfer function for the high pass filter and the magnitude but I am stuck finding the phase. I found the transfer function of a high pass filter as $$\frac{V_{out}(j\omega)}{V_{in}(j\omega)}=\frac{j\omega}{j\omega+\frac{1}{RC}}$$

and I calculated the magnitude of the high pass filter as

$$|V_{out}(j\omega)|=\frac{\omega}{\sqrt{\omega^{2}+(\frac{1}{RC})^{2}}}$$

I found online that the phase response of a high pass filter is $$\frac{\pi}{2}-tan^{-1}(\omega RC)$$
But i cannot figure out how the derivation got there. I would really like to understand their logic. Thank you for anyone who can teach me the rest of this derivation


texts: Duplicate MIPI CSI2 camera (one camera, two receivers)

texts:
I would like to feed two processors with the same MIPI CSI2 camera. I cannot afford to have one of the processors to play the role of proxy to the other.

Though I searched hard, I'm not aware of any chip that can really duplicate (not mux) a CSI2 -+ lane.

Therefore, I have tried to do something similar to what is explained in this paper:
http://www.intersil.com/content/dam/Intersil/documents/an17/an1787.pdf

But it's not working.

Is there any way I could manage to duplicate a CSI2 signal?

Edit 1

Not working means that the signal is altered and the receiver(s) can't manage to decode data. Unfortunately, I don't have a good scope so I can't show an eye diagram.

LVDS is close to CSI2 so I tried that option.

There is definitely a problem of "amount of termination", which is supposed to be "fixed" by the resistors. I have tried different values / configurations, but it's the same problem. I have also tried different muxing / configurations in the receivers.


texts:
I am currently working with load cells for weighing small masses. Almost all of them, as far as I have looked, have been made from aluminium. Given that repeatability is critical, why aluminium and not (say) spring steel or a stiffer material?
[I know that this may well be flagged for close as off topic, but would still appreciate any info.]


texts: Health hazard of cadmium plated connectors

texts:
I don't know if this is the right place for my question. Anyways: We work with cadmium plated nickel-base connectors. These are "Amphenol SJRT series" connectors.
See this image:

Catalog
The plating we use: "Olive Drab Cadmium Plate Nickel Base"
I want to know if this metal coating is generally safe to handle on a daily basis.
I've noticed that the green coating is gradually worn out.
I only have some rudimentary chemistry knowledge and the only thing I know is that cadmium is a toxic metal.
Is it in a safe compound when plated on nickel? I read "cadmium plated nickel base" as a cadmium layer on top of nickel. So it is no compound, right?
How does cadmium behave when touched with bare skin? Is it somehow solved by acids / fat / other stuff?


texts: How connect a open collector output to led and to GPIO?

texts:
I want to use this Single Cell Li-Ion Solar Battery Charger (BQ24210). The pins /CHG and /PG are an open collector outputs and it will be connected to two low power LEDs as shown in the schematic. If I would also like to connect /CHG and /PG pins to GPIO pins of the ATMega328p microcontroller.  What would be the best way to do this? The two GPIOs will be configured as digital input. Thanks.

simulate this circuit – Schematic created using CircuitLab


texts: I have read that the thermal design power (TDP) is an important metric while considering energy and power trade off related to microcontrollers. It is said that TDP determines the cooling required and failure to meet that values results in increase of junction temperature of the processor. A possible solution is either reduce the clock frequency or activate a thermal overload trip. I wanted to know what exactly is this thermal overload trip and how is it implemented in the processors?


texts: Why does the voltage induced in the receiver coil of this WPT circuit decrease when a load is added (in parallel)?

texts:
The following is a circuit that wirelessly transfers power via inductive coupling. The circuit is supposed to power a 12 V 0.15 A DC fan and a typical smartphone, which requires 5 V DC across it. The loads are connected in parallel to each other, as seen in the circuit schematic(though there is no capacitor at the output of the voltage regulator). As you can see in the picture below, it powers both just fine, but the phone only charges for a few seconds. And it can only charge both the fan and the smartphone only when the transmitter and receiver coils are very close to each other. The transmitter coil has 9 turns and the receiver coil has 39 turns.

I then used a digital oscilloscope to measure the voltage induced in the receiver coil at two different loading conditions -  at no load and at full load.

The voltage induced in the receiver coil hand an RMS voltage of 28.3 V as shown in its waveform. It also had some ringing, which I assume is because the PCB terminal block acts as a capacitor. Anyways, I assumed that the voltage would remain 28.3 V because the DC fan and the phone are both connected in parallel so the the voltage at the receiver coil shouldn't change, or that's what I thought.

So I then measured the voltage at the receiver coil when both loads were added, and, as you can see in the waveform below, two things changed: the ringing is now gone and the RMS voltage decreases to 13.0 V.

Can someone please explain why the receiver coil voltage decreased even when the loads were added in parallel?

I am sorry for the long post, but I just wanted to make sure every little detail is given.

Edit: Thank you, everyone, for the answer regarding the decrease in receiver coil voltage. I fully understood it.


texts: Combining resistors connected solely at one node, and also a question about parallel/series

texts:
I'm learning how to combine resistors for Thévenin equivalency circuits, but I am really puzzled as to how I would calculate the Thévenin resistance for this circuit. In my mind, none of the resistances are either parallel or in series with one another, does this mean they can't be combined?

Originally, this circuit had a current source connected to the left of \$R_{5\Omega}\$, which I zeroed out.

My second question involves a different circuit.

To find the Thévenin resistance for this circuit, I started out by zeroing the sources. So the \$10\,V\$ source is replaced by a closed circuit, and the \$1\,A\$ source is replaced by a open circuit.

Following this, I see that \$R_{20\Omega}\parallel R_{5\Omega}\$. This yields the combined resistance \$4\,\Omega\$, taking the old \$R_{5\Omega}\$'s place. The second step is to add the new resistance \$R_{4\Omega}\$ to the resistance in series, \$R_{6\Omega}\$. This combined resistance is in parallel with our last resistance \$R_{10\Omega}\$ and together that's a Thévenin resistance of \$5\,\Omega\$.
What makes me wonder though is if we in the second step notice that \$R_{6\Omega}\$ is also in series with \$R_{10\Omega}\$, and add those together, we get the resistance \$R_{16\Omega}\$ in old \$R_{10\Omega}\$'s place. Combining this, with it's parallel resistance \$R_{4\Omega}\$ yields us \$3.2\,\Omega\$, not \$5\,\Omega\$ as the earlier steps.

Why does it only work in one direction? And how am I to know which direction is the right one? Am I not correct in the statement that \$R_{6\Omega}\$ is in series with both \$R_{4\Omega}\$ and \$R_{10\Omega}\$? And if not, why?


texts:
I have the following signal and need to derive its Fourier transform:

I just started learning Fourier transform and don't know how to solve this kind of question. I know though how to derive the Fourier transform for: $$cos(2\pi f_0t)$$

$$\mathcal{F}\{cos(2\pi ft)\}=\int_{-\infty}^{\infty}cos2\pi f_0*e^{-j2\pi ft}dt $$
$$
=\int_{-\infty}^{\infty}\frac{1}{2}(e^{-j2\pi(f-f_0)t}dt
+\int_{-\infty}^{\infty}\frac{1}{2}(e^{-j2\pi(f+f_0)t}dt$$
$$
=\frac{1}{2}(\delta(f-f_0)+\delta(f+f_0))
$$

UPDATE:
I have used the Euler's relation to rewrite the signal like this:
$$g_1(t)=\frac{1}{2}Ae^je^{j2\pi  ft}+\frac{1}{2}Ae^{-j}e^{-j2\pi ft}$$
How do continue from here?


texts:
I have build a latching circuit using both a NPN & PNP BJT to turn on and off an LED, as shown below:

simulate this circuit – Schematic created using CircuitLab

When I built the circuit and tested it, the LED does not light.

When the ON BUTTON is pressed, the voltage across the collector-emitter of Q1 is 9V, meaning the BJT is not conducting to pull the base of Q2 to ground.

I have tried making the value of R3 much smaller (even down to a 2.2k resistor) to where the base current in Q1 was 170uA, but the BJT still won't conduct.

I have left the OFF BUTTON out of the circuit in case it was holding the base low, it is open circuited now.

I have tried a few of the same BJT's which made no difference and I am sure the circuit is wired correctly.

Has anybody got any suggestions ?


texts:
Is there any difference between MOSFETs with a diode in their symbol and the HEXFET?

Also, is there a difference between MOSFETs with a diode in their symbol and other MOSFETs?


texts: How to get started with microcontrollers? (ATTINY2313)

texts: Alright, so I just got an ATTINY2313-2oPI .. But I have no idea how to get started with this thing. Anyone have any tips, or ideas? I just want to get it hooked up, like with a 5V voltage reg. and a USB cable for programming.


texts: Can a transformer be placed next to RF module?

texts:
I'm planning a PIC-based power measuring circuit that will transmit measured data through an RF module to an other PIC. I'd like the circuit to be placed inside one of those casings in which you can plug in an AC device (just like all those digital timers and power measurement devices you can find everywhere). So the whole thing is plugged into the wall, and the AC device is plugged into the casing.

My circuit will include this stepdown encapsulated transformer, a bridge rectifier and a 7805 regulator to power the PIC (I don't want to use an external power supply).

It will also include current sensor and op-amp as described in this project.

My questions are:

Can I place the transformer close to the RF module (as required by the limited space in the casing) without any risk
of distorted signals due to EMI from the transformer?
How do I, if necessary, protect the op-amp from EMI and noise from the transformer?

I don't have a circuit diagram yet as I'd primarily like to learn about the pitfalls and useful tips etc. with this type of circuit.


texts: How do remote access devices work without a cellular connection or internet

texts: This is a sample of one such device i am talking about, i seen a wireless "external hard drive" like electronic at best buy that you can access movies from it without wifi and i have been constantly trying to understand how it works. Please help curb my curiosity.