texts: How to make ONLY a stripline (no parts) on a multi-layer board using Altium

texts:
I'm a beginner at PCB design and Altium. I'm trying to make a 50 ohm stripline using two ground planes, two dielectrics and one signal layer sandwiched between them. There are no other components on the board except this.
My layers look like this: (see image attached) but I cannot get Altium to convert it into a board, even with the correct impedance profile.
I wasn't able to find anything by googling/youtube for this kind of a problem. Would be really grateful if someone could explain how to go about putting down a single stripline trace without any components.


texts: I'm trying to hook up an OLED display using I2C communication to my Arduino Pro Mini clone(with ATmega 168, 16MHz) from WAVGAT but I can't figure out where the I2C pins are on the Arduino.


texts:
I am investigating the relevant standards in USB that allows a USB 2.0 device to obtain increased current from computers.

So far, my understanding is that, when the USB port is not suspended, the original USB 2.0 protocol allows a device to draw 100 mA during device enumeration. After enumeration is completed, the device can either be a low-power device and pull 100 mA (1 unit), or be a high-power device and draw 500 mA (5 units) from the host. Soon it followed that manufacturers started exploiting USB as a charging port, and the USB battery charging specification  (USB BC) is established to accommodate this requirement.

More recently, the USB power delivery protocol is specified and it's possible to use it with USB 2.0, in principle, but it's only a new development and not widely supported.

USB BC standardized three types of ports on a USB host or hub.

Standard downstream port (SDP) - This class is basically same USB 2.0 port as originally specified.
Dedicated charging port (DCP) - This class is identified by a short between D+ and D-. Upon detection, a device can pull up to 1.5 A from this port. It's mainly designed for use by chargers, and can be implemented without any digital electronics. It's still commonly supported by a generic USB charger.
Charging downstream port (CDP) - This class is an extension to the standard USB 2.0 port, allowing a device to obtain up to 1.5 A of current. Upon attachment, a CDP is detected by performing a hardware handshake on D+ and D- lines: If a voltage between 0.4 V and 0.8 V is sensed on D+ of a host or hub device, then D- should respond with 0.5 V to 0.7 V. The device enumeration and digital communication follow after the handshake.

In my experience, every computer's USB 2.0 port is a SDP and power shortage is still a problem today. Charging is extremely slow, optical drives and hard drives drop out all the time. Sometimes, it's possible to obtain higher current, but it's only because the device is cheating by declaring itself as self-powered hub, or because the computer's USB power is not too restrictive and allows more current to be pulled, in this case, it's operating out-of-spec and successful operation is a matter of luck.

The charging downstream port is certainly an interesting port specified by the USB BC standard, and it was supposed to solve the power shortage problem on computer USB ports. But I have never ever seen a USB BC CDP on a computer - it's not useful for USB peripherals if it's not supported by computers.

This is the question: Did the USB 2.0 BC "charging downstream port" never catch on? Has a major computer manufacturer ever implemented it? If yes, which one? If no, are there applications that ever implemented a CDP? For what?


texts: How do I make a micro-controller act as a finger on a touch screen?

texts: I want to make a device that I can place on a capacitive touch screen and it will start tapping the screen repeatedly. Is there any way to do this with the Arduino?


texts: Explanation for circuit with 2-stage op-amp, with diode in between first output and second input

texts:
I am a beginner in op-amp design and would like to get an explanation to a circuit that has a diode wired in between the output of op-amp-1 (stage 1) and the input of op-amp-2 (stage 2).

The inverting input of op-amp-1 takes a voltage from 0V <= x <= 5V, while the non-inverting input is wired to a 1kOhm potentiometer.  The output has a 100kOhm||0.001uF for feedback.

Then, that output is connected to a 10kOhm in series with a 1N4149 diode.  That signal is sent through a 0.1uF||100kOhm pot before being used as an input to the second stage (op-amp-2).

Furthermore, if someone could explain the the inclusion of the 0.1uF in parallel with the pot, that would be very beneficial to my understanding.

Thank you for looking this over.


texts: Circuit analysis using fourier series equations

texts:
I need to find the current and voltage at each of the brach and also power at one of the branch but I am stuck on how to solve this question with the non-sinusoidal voltage source. And how to calculate the power?

this are the formula for power
Here is the calculation that I attempt to calculate. I dont know how to solve for the answer.


texts:
I am trying to understand why GPUs consume so much power. For example, the max power consumption of the P100 GPU is 250W.
As I understand power is measures in watts as current x voltage. Given a fixed power source (i.e. voltage), I would assume that GPUs draw a lot of current. If I understand this correctly, why does a GPU draw so much current?
I think GPUs mostly consist of transistors? So why does the configuration of transistors in a GPU lead to more power being consumed than in a CPU?
Thanks!


texts: How can an electron have 0 electric potential after exiting a resistor but have current?

texts:
Unfortunately, I am not able to respond and ask a question on this specific post so I am going to ask a question based on the answers of the user "Transistor" in this post because I am still confused.

https://electronics.stackexchange.com/a/217000/211088

All my statements are based on the assumption that electrons have 0 electric potential after they go through the last load or is at the end of the circuit. (Statement # 2).

Please tell me if these statements are correct:

Electric Potential is the force created from all the electrons in the negative terminal of the battery. The force is created from the electrons pushing away from each other trying to go to the positive terminal which also pulls the electrons.

So does this create 2 times the force because of an electron's push and the positive terminal's pull? Or does the push and pull just the electric potential? I'm confused about this part of statement 1.

If I have one battery and one resistor only, from what I understand is that after electrons exit the resistor, they have 0 electric potentials.
My understanding based on the first answer of "Transistor":

  It's getting pushed by the potential difference in other parts of the circuit.

This statement is referring to electrons in between resistors.

After the electrons exit the resistor, even though they have an electric potential of 0, they still flow to the positive terminal because of the fact that the electrons currently flowing through the resistor has an electric potential, therefore, it needs to move forward and exit the resistor which pushes the electrons already out of the resistor towards the positive terminal. Doesn't this mean that the electrons out of the resistor already has an electric potential because the electrons in the resistor provide a force for them? Aren't they have 0 electric potentials at the end of the circuit?

In figure 2, in the post that I linked above, when the user "Transistor" replies

  What's driving the current is the potential difference between the top of the tank (battery +) and the open end of the pipe (battery -).

Does this mean that after the electrons exit the resistor, the negative terminal is no longer apply a force or push but now the positive terminal is applying a pull force? So if I place a voltmeter on each side of the resistor, it reads the voltage of the negative electric potential. Is this why electrons are still able to flow to the positive terminal even though it has 0 electric potential? Basically the same question as statement 1. Can someone explain the quote above.

Sorry for bad format, this is my first post.


texts: What is the ammount of current when using no resistors

texts:
Ohm's law states that V=IR, thus if we have a 9V battery and one would use no resistance (R=0) then I= 9/0 which can't be done.
Then what happens to the current? Does this mean there is an infinite amount of current? Or does a battery have a max amount of current it can provide (if so, what is this max amount of current)?
Or do wires have a little resistance for example: R = 1 * 10^-6. This leads to an insane amount of current.


texts: PIC:What is the difference of SPI module of PIC18F4685 and PIC18F66K22?

texts:
I want to configure SPI module in Slave mode for PIC18F66K22.

Can we use common SPI library for both MCU?


texts: Xilinx Place Error 1136 - This design contains a global buffer instance that is driving the following non-clock load pins

texts:
I'm hoping someone can explain in simple terms why I might be getting this error from the Xilinx map tool:

ERROR:Place:1136 - This design contains a global buffer instance,
<reset_IBUF_BUFG>, driving the net, <reset_IBUF_BUFG>, that is driving the
following (first 30) non-clock load pins.
< PIN: clock_core1/pll_base_inst/PLL_ADV.RST; >
This is not a recommended design practice in Spartan-6 due to limitations in
the global routing that may cause excessive delay, skew or unroutable
situations.  It is recommended to only use a BUFG resource to drive clock
loads. If you wish to override this recommendation, you may use the
CLOCK_DEDICATED_ROUTE constraint (given below) in the .ucf file to demote
this message to a WARNING and allow your design to continue.
< PIN "reset_IBUF_BUFG.O" CLOCK_DEDICATED_ROUTE = FALSE; >

First a little background...

The design was building and working fine.
I was in the process of updating the project's SD Card controller to support SDHC cards.
This error suddenly appeared even though I wasn't making any changes relating to the reset signal.
Slowly backing out my changes I narrowed it down to the snippet of code shown below.
Thinking this might be related to the larger project I was working on, extracted the SD Card Controller entity to a separate test project.  I get the same error there.
I don't know where the IBUF_BUFG on the reset line is coming from - it's certainly not something I'm explicitly creating.  I do however have the reset signal driving a coregen'd clock core.

Here's the snippet of code that seems to trigger the error:

when RX_BITS_FINISHED =>
    if do_deselect='1' then
        bit_counter := 2;
        state <= DESELECT;
    else
        state <= return_state;
    end if;

If I comment out the above, the error goes away.  Everything referenced here are either variables or signals private to the module.  The when block is inside a process driven by clock and reset signals.  Nothing special here but the full source of the component can be seen here with the above snippet near the bottom.

Anyway...  I looked up the error and came across this Xilinx answer:

https://www.xilinx.com/support/answers/33025.html

which might explain things for some, but not to me.  I've read the suggested solution and worked through it but I'm concerned I'm just masking a more fundamental problem with my design.

I don't understand what's happening here and need someone to explain it so an amateur/learner can understand it.


texts: What is this AC power connector for a Hughes TWTA?

texts:
I've been picking up some microwave power equipment off of eBay recently and ended up with a Hughes TWTA (1277H04, 20W in the Ku band) on the cheap. Unfortunately it did not come with a power cable and I'm bamboozled about the connector.

I have an 1177 (pretty much the same model with a lower power tube) that has an IEC 320 C14. It doesn't look like that connector is meant to fit over this one. It looks a little bit like a Brazilian IEC N connector but the center pin here is 1/8th of an inch in diameter. The power input instructions say 117 volts @ 3 amps.

Might just be an unfinished amp, who knows. I could probably unsolder this and replace it with a standard connector but I'd rather not fiddle with it if I don't have to. Any help is appreciated.


texts:
Back when I was taking an RFIC design course, I was pretty disappointed by the noise part of the class, specifically calculating the output-referred noise voltage, noise figure of an amplifier, etc. It seems like you should be able to apply basic circuit theory principles, such as Kirchhoff's Laws. However, I'm not really sure that you're allowed to do that, and I don't feel like my class went in-depth enough for me to understand.

Take Kirchhoff's Current Law. It's based on the idea that there can be no sources nor sinks of current in a circuit. The sum of all currents at a node should be zero (an equal amount of current leaves the node as enters it). The problem is that noise sources are random. So, the concept of current flowing "into" a node doesn't really make sense because whether it flows into or out of the node is random, and my impression is that a noise current source wouldn't have a direction/sign unlike a traditional current source.

Either...
A) Is my understanding totally flawed? Do we assign signs to noise sources like everything else and apply regular circuit theory? (I doubt this is the correct answer.)
Or...
B) Does circuit theory need to be reformulated when dealing with noise sources? So, would the rules, like Kirchhoff's Laws, be different? If so, are there any resources that describe exactly how this works in a precise manner? I haven't been able to find anything satisfying, but maybe I'm not as good at Googling as I once thought.


texts: I know that this question is very direct, but I was curious to know why is it that in defense applications, CDMA is preferred over LTE? Is CDMA more secure than LTE and hence more difficult to intercept?


texts: Why isn't the output of the LT1168 equal to its input in this very basic circuit?

texts:
Consider the following circuit (made in LTSpice IV):

And it's simulation:

This is unexpected to me. I thought the output would be equal the input, since I didn't include a gain resistor on purpose:

$$R_{\text{gain}} = \infty$$
$$A_V = \left(V_+ - V_-\right)\left(1 + \dfrac{2R}{R_{\text{gain}}}\right) = \left(V_+ - V_-\right)\left(1 + \dfrac{2R}{\infty}\right) = V_+ - V_- \qquad \text{?}$$

What am I missing here? Is this an issue with LTSpice? If I construct this circuit, can I expect it to have the output equal to the input?


texts: Stability of SMPS designed for a motherboard

texts:
Many books have covered the stability of many configurations of switch mode power supplies and they have given details on how to set the poles and the zeros of the compensator to make the the power supply more stable and robust, but all the books I have undergone, they took the example of the load to be a resistance load.

My question is, if we want to design a more practical SMPS to feed a more complecated and realistic circuit (example of a motherboard of an airconditionar, mobile phone etc.) these circuits are a combination of resistors, inductors, capacitors, actives devices and so on.

How do we study the poles and zeros of the power supply in that case? And how to make it stable?


texts: How will NMOS Vt be effected if the bulk and source is not at GND but at higher positive potential due to isolated pwell leaking to deep nwell

texts: How will NMOS Vt be affected if the Bulk and Source is not at GND but at higher positive potential due to Isolated Pwell (IPwell) leaking Deep Nwell (DNwell). The IPwell is biased at GND and DNWell is biased at VDD. However due to leakage expected the IPwell is at higher potential then GND.


texts: What happened to my second half cycle of my half wave rectifier?

texts:
When I'm doing a simple half-wave rectifier with the set-up as shown above (Note: Diode D2 is not connected) and connected terminal 5 and 4 with positive and negative terminal of oscilloscope, this is what I get:

Instead of getting a horizontal line in the second half cycle as the diode blocks the current flow in the opposite direction, I get a slanted line with a positive gradient.  Can someone give me an explanation on why this happen in my experiment? I have only some basic knowledge about electronics and I'm unable to come up with a plausible explanation.

This is what I get when I connected oscilloscope to terminal 1 and 2, in case it helps:

Edit: I uploaded the wrong picture for the my third one. I have uploaded the new picture.


texts: Is it possible to drive a 2 X 16 LCD display using logic gates? (Without computer)

texts:
I want to make a circuit using logic gates that prints a message on the LCD display (2 X 16). Any  idea? I want to know how to do this "by hand". like the old days.

Can I build a circuit out of logic gates hooked up to a keyboard that when I press a key the character is displayed on the LCD?


texts: Can an electronic device continuously sweep the voltage?

texts:
Modern power supplies can sweep the potential in a given range with a specific rate. I am curious if the electronic devices can continuously sweep the voltage (in a perfect sense) or it is just step-based changes, which seem like sweeping?

For example, consider sweeping with from 0 to 10V in 10,000s. Does the sweep has a resolution of say 1mV, and the data looks like

time/s    voltage/V
1         0.001
2         0.002
3         0.003

Or it is absolutely continuous, as the voltage is 0.0025 at 2.5s, 0.002513 at 2.513s?

Note that my question is not about the voltage resolution, but if the change from 2 and 3s is a step from 0.002 to 0.003V or it is still a gradual change.


texts:
When setting up the gate that is defined as OUTPUT=(AB+C)'
Why is the pull up network equivalent width equal to 4? I know the pull down network is counted in series, so you just add the resistor in series. My professor said the pull up network is counted in parallel, but i don't see how you get 4? I know NOR2 gate is equivalent width ratio 4:1, and that's really the only clue i have, but i still don't know why it's like that?


texts: Quality factor in arbitrary RLC resonance circuits

texts:
I am looking for a way to calculate the quality factor in arbitrary RLC circuits not just standart series or parallel circuits.

It would be great, if anybody could provide a formula and some further readings.

As asked for, here are two examples of my interest:

simulate this circuit – Schematic created using CircuitLab


texts: How to generate .xst file from command line + Xilinx-ISE

texts:
I am trying to learn how to generate bit files from command line. Is there a way to generate the .xst script file from command line tools? I can only find mention of it being something that the GUI auto-generates.

To add some context, I build and generate a bit file for a simple design in the GUI then use the 'View Command Line Log' tool to generate the commands the tool used. Then use "Cleanup Project Files". I am just trying to execute the same commands manually from the command line. The first command is:

xst -ifn "C:/Users/Documents/XilinxProjects/SingleItemTest/item.xst" -ofn "C:/Users/Documents/XilinxProjects/SingleItemTest/item.syr"

Which gives me:

ERROR:Xst:427 - Entry File C:/Users/Documents/XilinxProjects/SingleItemTest/item.xst not found


texts: Isolating an analogue input using ADC/DAC

texts:
I'm looking into isolating an analogue input coming from field equipment and interfacing to a PLC analogue input module. The input will be of the 4-20mA range (1-5V).

There are a few ways to approach this but I am currently pursuing the solution as seen below:

ADC and DAC are being proposed as Microchip MCP3221 and MCP4725 respectively.

A digital isolator would give a smaller footprint than an opto-isolator with its accompanying components and would provide much greater performance. Possible components include TI ISO7420FEDR and Analog Devices ADUM1200ARZ.

Now for the actual question!
Keeping both sides isolated is pretty vital and I'm wondering how this will effect the ADC and DAC linking.

I'm assuming I can send the data line (SDA) through the digital isolator but to synchronise the ADC and DAC they would need a common clock signal. Would sending the clock over the digital isolator be a bad idea? If the digital isolator was many times faster than the clock would it have a negligible effect in terms of delay?

Missing info:

Not tied to I2C, SPI would be appropriate too
Isolation to a minimum of 2.5kV
The ADC will be powered on the 'dirty' side so there is complete isolation, only the data/conversion control signals need to pass through the isolation barrier
Resolution should be between 10 and 16 bit, no specific value is required
Conversion throughput of around 100ksps would be sufficient


texts: Probable issue with 74HC595 not outputting ANY data

texts:
Context: I've been working on a simple PCB design that randomly lights up a cathode of an IN-19V Nixie tube. The driving circuitry is as follows:

PIC16F15313 toggling various lines into the 74HC595;
74HC595 used to select exactly 1 output from 8 based on a byte sent to it that contains exactly 1 bit set in any possible sent byte;
ULN2803 used as the high-voltage interface to the Nixie cathodes (maximum voltage at the output is measured at ~40V, well within spec).

I prototyped the circuit on a breadboard and it worked perfectly throughout numerous tests (in fact, I made the schematic for the PCB by directly copying this breadboard circuit) so this as-good-as rules out a dodgy circuit design.
After flashing the SMD PIC in one of those springy adapters, and before soldering to the PCB, I placed the chip and adapter in place on the breadboard and it worked fine. Having been 'scoped in place on the PCB all signals coming out are correct - I'd say this rules out a problem with the PIC.
The ULN2803 measures the correct diode drops from OUT->COM and GND->OUT on every pin, plus measures the correct resistance from IN->GND on every pin. Indeed, tapping a wire connected to VCC on any input causes the correct cathode of the Nixie to light and all others remain off ruling out the ULN2803 and the Nixie as the faulty component.
The button works, the HV PSU works (~164V), etc.
The problem appears to be the 74HC595, it receives the correct signals on the correct pins but does not output ANY data on ANY output pin. The only exception is the /SRCLR pin which should be connected to VCC but is left floating on the PCB. This has since been rectified with the addition of a wire, both directly to VCC and to VCC via a 10k resistor. Neither case had any effect.
Pin connections from PIC->74HC595 are as follows:

RA1 - Output Enable (active low)
RA2 - RCLK ('latch') (goes high after data is sent and clocked)
RA3 - Set as /MCLR function on the PIC. Currently tied to reset of both the PIC and 74HC595, does not cause the PIC to reset so probably doesn't cause the 74HC595 to reset, right?
RA4 - SCK @ 1MHz
RA5 - SDO with exactly 1 bit set per byte

The full schematic and the relevant section of the PCB are below.

I've replaced all chips now at least once so unless I've got a full-on faulty batch of 74HC595s, I'm running out of ideas on what's not working here... They are 'off-brand' 74HC595s but they were purchased from LCSC.com as opposed to eBay or Aliexpress.
Question: What the heck is wrong/likely not working? Am I missing something super obvious here like a bad PCB trace that I'm blind to?


texts:
I have a circuit which has an input of voltage of the order of micro. I want to convert it into volt order. I am using an instrumentation amplifier AD620 with gain of 1000 to first convert it into milli order. And then I am using TL084cn as a comparator whose one input is the milli order voltage and the other is grounded. The +Vcc and -Vcc is 10 V. Also the frequency of operation is between 8-40 Hz. The question is that theoretically this is possible but before I implement it practically I would want to know whether I could face some issue for such sudden abrupt change in the order of the voltage.
Also, keep in mind please that I don't actually care about the shape of the signal cause in my project the information is in frequency and not in amplitude.


texts:
I'm looking to build myself a passthrough e-cigarette and here is the schematic I came up with :

simulate this circuit – Schematic created using CircuitLab

My question is will this work ? I mean in theory I think it should but is there practical things I'm missing ? I remember in school I saw that switches can do crazy things when pressed, would a step down voltage regulator be able to handle being connected directly to a button ? Is a Cinch cable suitable for such electrical values (less than 5v coming out of the buck converter and 1.8Ohm of resistance for the heating resistance).

Thanks in advance to anyone willing to help.


texts:
On PIC micro controller UART, Baud rate was set to 38400 (No parity,, 8 data bits),

*************UART 1 configuration*********
IFS0bits.U1RXIF = 0;

IFS0bits.U1TXIF = 0;

IEC0bits.U1RXIE = 1;

IEC0bits.U1TXIE = 0;

U1MODEvalue = 0b1000000000001000;

U1STAvalue = 0b0000010000000000;

U1BRG = 103;

U1MODE = U1MODEvalue;

U1STA = U1STAvalue;

Device connected to uC is working fine; they have healthy communication. But I was measuring the baud time of my data, and I observed that the start bit and data bit read 26 us which is ok as per 1000000/Baudrate us, but the stop bit is only about 20us, that looks wrong to me, it should also read the 26us. So I try with different baud rate. But have the same problem ( see below table).

4800Buad rate , Stop bit time =160us ( but it should be 208us)

9600Buad rate , Stop bit time =72us ( but it should be 104us)

38400Buad rate , Stop bit time =20us ( but it should be 26us)

115200Buad rate , Stop bit time =7.2us ( but it should be 8.8us)

I asked the support team, and they say your BRGH value is set to 1, try to change it to 0. So I changed BRGH=0 and this problem is solved.

With BRGH = 0, stop bit error removed and stop bit measures 26uS. We still need to test this with other baud rates too.

Q1) Why BRGH making difference in stop bit baud time only? We are using 8 MHz Crystal.

Q2) Data sheet says BRGH=1 for high speed enable, what does it mean here by high speed, is it baud rate, if so which baud rate is considered to high speed?

Q4) When to use BRGH=0 or when to use BRGH=1, as per test it was observe stop bit baud error in every baud rate as per above given test result table.

Link of uC

http://ww1.microchip.com/downloads/en/DeviceDoc/en026583.pdf
http://ww1.microchip.com/downloads/en/DeviceDoc/39747F.pdf


texts: Transfer data on a 3.3V high speed UART (> 20 MBaud) to a PC terminal application?

texts:
On my PCB I have a ball grid array microcontroller with a 3.3V GPIO pin that I'm generating a UART Tx-only waveform on using bit-banging, as an alternative to trace. The particular pin is not hooked up to any hardware peripheral (UART, USART, SPI, timer, etc). My SystemCoreClock is 216 MHz and the faster I can make the UART run (20 MBaud or faster), the less it will interfere  with the rest of my code.
Can anybody please suggest a way to transfer the data on the UART-pin to a PC terminal application?


texts:
I have to project an AM demodulator using an Envelope Demodulator. To which kinds of AM (DSB, DSB-SC, VSB, SSD) is it applicable to?
Thanks


texts: How do I connect an LED with floating DC voltage?

texts:
I want to connected an LED at the output of 500V DC.  This DC power supply is made by 3phase DC rectifier and is floating.

I would like to have a display on the front panel of the supply which will show the supply is healthy.

I know that it could be done by voltage divider circuit and connecting LED across the one of the resisters. I want to know whether it is safe as per the safety point of view because in this case I need to bring connection to the front panel and if a fault occurs with chassis (grounded,)  it would put high voltage on the chassis.


texts: Ebedded Linux: Recoverable, battery backed-up RAM (/tmp)

texts:
I hope this is an appropriate place for this question as it involves the use of the kernel.

I have an embedded system with a battery backup for the RAM chip. The battery also allows for the MCU to gracefully shutdown.

The data I am writing to RAM goes in the /tmp folder. When Linux shuts down and then eventually boots up again, I lose access to the RAM.

In the graceful shutdown process, is it possible to save the mounting location (memory location) of /tmp to a file in non-volatile memory so that when Linux boots up again it can line up the memory and allow me to access the preserved RAM accurately?

If so, how can this be done?

Thanks!


texts: Why is XNOR gate not referred to as an "Equality" gate?

texts:
I am a programmer and I was thinking about some logic I was just writing and the logical statement started out as a negated exclusive or, but this simplifies to a logical equality check, e.g. var x = a == b. That is to say, we can express this as x <- a XNOR b.

Since I was looking at the XOR page i found that there is an XNOR gate which is just an XOR gate negated. It got me to wondering because XNOR seems like such a convoluted way to refer to the concept of what this gate does.

I wonder if this is just how history played out, or if there is something subtle that I'm missing.


texts:
There is some information on chiphacker about using an arduino to control stepper motors (I'm driving Bipolar, 4 wire, motors), however I'm finding it hard to know how to control a stepper motor using my mbed device.

The fact that I'm using an mbed is really by-the-by, I've rigged up an H-Bridge so that I have 4 pinouts of my microcontroller/microprocessor going to the required pins of the H-Bridge  What pulses should I send to which of the pins when? I can PwmOut if thats more useful. Like this:

Any advice would be very welcome, even if its just a URL to a reasonably detailed tutorial.


texts: When a VHDL code with a rising edge clock is synthesized, what happens at the falling edge?

texts:
I'm a newbie to VHDL and I'd really be grateful if someone could help me solving this question which has been bugging over the last few days. I don't have a code for this. Assuming, if there's a code layout, like below, which does something when it sees rising edge of the clock.

PROCESS(clk)
BEGIN
IF(rising_edge(clk)) THEN
--functionality
END IF;
END PROCESS;

Eventually, at the falling edge of the clock, what would this kind of code do? Will be there any activity? How would the power consumption look like during the falling edge?

Thank you in advance!


texts: Arduino input with CNY17 to sense 12v input

texts:
I have an Arduino Due and i am using a CNY17 optocoupler to sense a 12v brake signal from a car.
The 12v signal is going thru a 1K resistor to the opto on pin 1, pin 2 to the ground.
3.3v is going thru a 1K resistor to opto pin 5 and pin 4 to the ground.
Pin 5 is connected to a digital input of the Arduino Due.

All is working good when the 12v is connected i get a 0 and when not connected a 1 on my digital port.

Now when i touch the wire going from the opto to the digital input is floating between 0 and 1.
The voltage on the pin of the opto stays 3.3v but on the digital input voltage drops around 1.6 volts.
the 1.6v would explain why it floats between 0 and 1.
What i don't understand is why it would drop when i touch the wire could someout explain that to me?

simulate this circuit – Schematic created using CircuitLab


texts: FOC Motor Control Algorithm - ADC sampling

texts:
I'm working on implementing the FOC motor control algorithm on an STM32F411 microcontroller. My question is about when you need to sample the phase currents in relation to your PWM pulses. If you turn on the transistors, you'll get an increasing current ramp over the course of your PWM on time (due to the inductance of the motor coils), so how are you supposed to know what the three different phases are doing if they all take their ADC measurements at (about) the same time? The FOC algorithm requires us to sample ADC's in the center of a PWM pulse to best approximate the current through a phase, but how can I get the ADC measurements to line up with one another if all three PWM signals need to be operating independently? Is this confusion due to using edge aligned PWM vs center aligned? Can anyone point me to a paper on how to pull this off?

Thanks and regards,
Craig


texts:
I am a beginner in digital logic. Please clarify me the following

In case of set condition with Qn=0, i am getting wrong answer
Q_{n+1} and  (Q_{n+1})'  not complement to each other
I am not able to find out where i made mistake. Kindly have a look at the following


texts: Should one terminal of the AC source be grounded?

texts:
Is ground physically 0V or just a reference (like maybe 2.5V) that we use to measure voltages from?

Should i be grounding the VSINE or just take the voltage across it without the reference. Basically i have understood the connected ground is not actually 0V, but only a reference point, because only that would explain the voltage being same in both the circuits across the VSINE component.

Without the ground on the VSINE, i can see that the voltage shown by the probes is same in magnitude but opposite in polarity, for example in the screenshot, -2.8V and +2.8V, which would give a Voltage difference of -5.6V, basically a point on the negative half cycle.

The same can be said of the circuit with the ground, now that i have made one terminal the ground (reference?).

What reference voltage is the probe taking in both the circuits?

Is all this thinking in the right direction?


texts: Is it possible to repair a PCB which has suffered a DRC failure?

texts:
Okay, so I was a bit of an idiot while designing my PCB. The specifications of my PCB fab were 6/6 mil trace/space, and the boards did not meet this. So, below is the design for the PCB:

The trace going to C16 (a ground) is way too close to the pad which is connected through a trace to an inductor (it's a switch mode buck converter.) This basically connects the +3.3V line next to the filter capacitor to GND, shorting it. I verified this with the continuity test on my multimeter.

My PCB:

I have already bought 10 PCBs, so I'd like to know if it's possible to hack these and repair them. I'm okay with having to provide them with an external 3.3V source; in future, I'd like to get the converter working, but it's the rest of the circuit which is important.

Obviously I won't make this mistake in the next version... I might actually run the DRC. This is only for development.


texts: problem with driving the mosfet through optocoupler

texts:
I want to run the mosfet (irf540n) through opto coupler(4n25) for driving the motor. I refered some formula from this website, but my circuit is not working.

I calculated opto coupler current limting resistor by using this formula:

Rf = (vin-Vf)/If = (5v-1.15)/10ma = 385R

then calculated the mosfet gate resistor using

5v/150ma=34R

but this circuit is not working.

I tried this circuit too but not working.

Thanks for your answer, now I attached the image of my schematic. Please check it.


texts:
In something like a regular household, how much energy consumed is transient power vs steady state and what kind of frequency distribution does it have, roughly?
I imagine the vast bulk of the energy being in the lower frequencies but have been unable to find any information backing that up.
Aside from curiosity, the reason I ask is I am currently working on an Amp hour monitoring project for off-grid systems using coulomb counting (measuring voltage drop across a current shunt) and filtering that with a low pass filter before ADC, just wondering if this would cause an inaccuracy worth worrying about.
Thanks.


texts: Does the LT3029 regulator give out 9v 500mA without external circuitry needed for it?... I'm planning to use it for my arduino mega... I really haven't used that regulator before ...My main power source for my whole circuit is 12V 2Amps, that's really big for the microcontroller so ill be using a regulator to power it up. I also need suggestions on what regulator should be fit for arduino mega...please help me ...thanks


texts: Common current limit resistor for multiple LEDs?

texts:
First, I realize the "common resistor for multiple LEDs" question has been asked. However, I have a different case where the LEDS are FET driven and reverse logic.

I have the following circuit. The circuit is actually four more of what is shown, i.e. all 16 outputs are used. The selector chip outputs are sinking type. The current to the LEDs is controlled by an external voltage controlled current source.

Since I never plan to turn on more than one output at a time, I would like to know if I can use a single, common current limiting resistor for all the LEDs? In other words, all the anodes (pin2) of the LEDs would be connected together and R8 would feed them all.

I'm thinking it would be ok if ensure the following: Start with current source=0 and turn on 3.3V.  Set all selector outputs to ON, thus turning off all the FETs.  Apply the desired current using the external current source, then finally turn off the selector output for the FET I would like to turn on. Continuing I would turn off the first LED prior to turning on the next LED. Note that I will not be switching LEDs very fast at all, only once every few seconds.


texts:
This is my first designing an Arduino 'shield', so I wanted to get some input. This board interfaces with sensors using I2C. A Raspberry Pi interfaces with the Arduino, which reads magnetometer data from six to seven different sensors through an I2C expander. The schematic can be shown below:

I'm using KiCAD as my CAD software, and the following are the parts I'm using:

Arduino Uno Rev. 3
TCA9548A I2C Expander (Breakout) from Adafruit
Adafruit HMC5883L Breakout - Triple-Axis Magnetometer from Adafruit

Link to Fabrication Print: https://learn.adafruit.com/adafruit-tca9548a-1-to-8-i2c-multiplexer-breakout?view=all

The magnetometer sensor breakout board consists of six pins, but I'm only using four of the pins. They'll connect to 4-pin headers which I will attach a ribbon cable to, so they will be used from a 1.5 meter distance in a box. The pin layout at the sensor is different but by crossing some wires on the connector at the sensor, I can get the 4-pin configuration shown in the schematic so SDA/SCL will be separated by +5V and GND. I'm designing the Arduino shield which will attach to the Arduino to eliminate the need of a breadboard.

So, for my design, I figured I would add some 10k pull up resistors to make the total pull up resistance be 5k for each sensor SDA/SCL line. The sensors already have a 10k pull up resistor, and by adding another 10k resistor, we can read the sensor from a long distance. I tested all of this on a breadboard with 1.5m wires, and it seems to work out well. I then added some capacitors from the +5V power pin from the Arduino to keep the voltage steady since it has to power a lot of devices.

For the board layout, I have a ground plane on both the top and bottom layer, but I turned it off for the picture to show the routing. For the capacitors and resistors, they're all SMDs using 0805 size standard, so I can easily hand solder them. I placed most of the pull-up resistors on the bottom of the board so as to use as much space as I can. Judging by the size of the Arduino, it shouldn't touch the parts (unless I'm mistaken by the distance from the shield to the board). As a first Arduino shield design, do you see anything wrong with the design that might be a concern? Design-wise, the multiplexer has 0.6 inches (15.24 mm) between the two sides of the pin, so there should be plenty of room for the 0805 resistors. But, would their placement like this have any issues that I don't know about? Similarly, the capacitor values were just picked based off another design that was working off of +5V. I was powering an OpAmp, and the reference design used those values, but now that I'm powering more items, should I go with a larger value?

EDIT: Apologies, but I wanted to clear something up. The part that I used for the TCA9548 I2C expander is a little strange, but I just used a 2x12 part in the schematic and labeled as the TCA9548. I didn't know that it was left to right rather than CCW. Nevertheless, I made sure that the pin placements matched up with the component shown on Adafruit's page, so it is fine.


texts: How can I identify the fault on an Arduino Uno board that's had the smoke let out?

texts:
I recently purchased an Arduino Uno.  I've been having a ton of fun fiddling with it -- that is until I pushed +12V to the Vin without any kind of voltage step-down.  The smoke was violently released from the Atmega chip and the chip socket itself even melted somewhat.

I purchased a replacement ATMega328P-PU for the unit which was pre-loaded with the Arduino firmware, however when I energize the board from the USB port the status LED stays a solid orange rather than the fast-3-blinks that indicates the firmware is ready.  I'm not sure if this is a case of "the chip really wasn't loaded with the Uno bootblock" or if there's another component on my Arduino board that is fried.

I have access to a multimeter and a 10MHz oscilloscope, can anyone give me some ideas on how I can diagnose where the fault may be?


texts:
I have a turntable which rotates cw and ccw. This turntable is rotated by AC synchronous motor of 230V. I want to be able to rotate the turntable with Arduino.  For this reason I need to control the switch (toggle switch) of the turntable. This switch is connected with motor with three wires, one of the wires is for cw rotation the other ccw; the middle one is common or no rotation.

Problem is that I need to make sure that only one direction of the rotation will work on the same time otherwise motor may be damaged. So I need to have some restriction not only in program but also in electrical components.

I am thinking if there is any relay that can be connected with both rotations and also with common. Or any other idea how to realize this would be appreciated.


texts: Changing the receiving frequency of a cheap RC car

texts:
My kids both have a RC car and unfortunately they both work on the 27MhZ frequency range, which means they can't both play at the same time because of interference.

I opened up one of the two cars and fount out the emitter is using a 27.145MhZ crystal while the receiver has no crystal in sight, but an adjustable multi turn inductor in the antenna path.

Naïvely, I tried changing the crystal to a 40.685MhZ one and then turn the inductor until the car reacts. As it may be obvious to some of you, this did not work at all.

So, I went back to the bench and created a schematic of the receiver circuit board. From what I gathered during various searches, it's built around a RX2C / ATS302R IC or a very similar one as the pins connection match what is inside the datasheet for that IC. Note that the IC inside the toy has had its markings scratched to render them unreadable...

What's puzzling me is that the antenna parts values does not respect exactly what is inside that datasheet but rather are like this:

The L1 and L3 inductors are through hole parts with color rings on them like so :

L1: Red, Red, Gold, Silver
L3: Green, Blue, Gold, Silver

I thus believe they are 2.2µH and 5.6µH respectively.

This does not look like the simple RLC circuit I know about from my "initiation to electronics" textbook, but I'm not surprised at all.

That being said, do you think I could modify part(s) of this circuit to shift the frequency to 40MhZ? Like, for instance, add a resistor in parallel to R1 so that it gives an equivalent resistor with lower value, thus decreases the RLC constant and increases the frequency?

A few additional remarks:

VCC is 4.8-6V, from a 4 AA batteries pack
D1 is believed to be a 2.7V Zener diode
C12 is an electrolytic capacitor whose value is printed on its side, rated 10V
All resistor values match their marking and were confirmed with an ohmmeter.

Many thanks in advance for any pointers as to what I should be looking for or trying.


texts: Internal circuitry of integrated circuits

texts: Is it possible to know the internal circuitry of integrated circuits?  I know that some ICs contain billions of components.I mean, do IC manufacturers publish these ?


texts: Using lots of slide potentiometer for computer control

texts:
I want to mount a bunch (say 16+) slide potentiometers in a long project box (or other housing that can sit on a desk) that I can use to interact with software on my computer, specifically lighting software, which I would program.

How could I get the output of these slide potentiometers into my computer so software could read the values? I'm thinking using a USB input.

Keep in mind I'm a beginner at electronics (but I can do software).


texts: Export Modelsim waveform as image from command-line

texts:
Is there a way to export Modelsim/VCS waveforms as images (png, jpeg or SVG)?

Currently the only method I know of is to fire up the simulator, run the simulation and then either do a Print Screen or File->Export Wave in Modelsim.

Is it possible to do this from the command line? I want to be able to script it through TCL or bash.

Note that I'm not limiting myself to these simulators. Is it possible to convert VCD files to images at all?


texts: Active Tone Control Hum and Buzz in Potentiometer

texts:
Here is another problem with my circuits, that I cannot solve.

I am working on analog active tone control - Bass, Volume and Treble with TL081/82 chips.

The reason I put volume control on the output of first TL chip is to reduce hum in the tone control ciruit by seting volume to zero while not playing music.

At first I thought that the hum comming from potentiometers was because of testing it on vero board and not on pcb so I designed a PCB.

Putting the circuit on a PCB was a little better, because the hum was reduced by GND polygon all around potentiometers and circuits. However, by touching the potentiometers with my hand I get a lot of hum and buzz on the output. When I was get close with my hand to the potentiometers, the buzz and hum starts to get stronger, moving the hand away, the hum and buzz reduces to little value and so I believe that the problem is with the potentiometers.

Then I decided to ground potentiometer by soldering the shield to ground and getting plastic covers on potentiometers; the hum and buzz was reduce to a minimal level even when touching it.

The idea was good for a little time, but when I put potentiometers in metal housing, then the all housing will be at ground potential.

So I unsoldered the potentiometers from ground and attached them in metal housing "see picture above" and the problem come back. When I touch the metal housing (not the potentiometers) buzz and hum start going even louder.

How can I solve this problem with potentiometers or hum in circuit? I've also tested and resoldered a lot of identical new potentiometers, but the buzz and hum does not go away.

Using potentiometers in plastic shield is not solution, because a lot of audio amplifiers on the market use the metal shield potentiometer and work perfectly.

Please help, I already spent a tons of hours solving that problem.

UPDATE

Hi everyone, I just resolder some components and test @Andy aka proposal:

The hum does not go away with these solution :/, the most noticeable are potenciometers for bass and treble. When I toch the potencimeters hum start go very loud, but when i tuch myself to the ground with other hand the hum go away.

For faster understanding, I uploaded hum on vocaroo, here is the link:
https://vocaroo.com/i/s1oMDxBu4z3h


texts:
Is it possible to share 32.768kHz crystal for nRF52 and BNO055? The purpose is reducing cost&space.

Preferred crystal this one:
FC-135R
https://support.epson.biz/td/api/doc_check.php?dl=brief_FC-135R&lang=en

Also,how can i handle different load capacitance values?(If sharing possible,surely)
Other question's accepted answer not satisfy me


texts: Circuit for opening/closing sprinkler valve solenoid?

texts: If I wanted to create a circuit (that was plugged into a typical 120VAC outlet) that was able to open/close a 24VAC Sprinkler Valve, where would I start? My ultimate goal is to control it with an Arduino but just a basic circuit to get started is my goal. Even with a simple push button as the controller would be nice. Where should I start for this? I think I would need a transformer to convert the 120vac to 24vac, right? Next think I need to determine the input current requirement for the solenoid/valve. Any help would be appreciated. I'm not a noob to electrical stuff but I can't remember most of it.


texts: Have Cell Phone Display Panel(s) been hacked to accept HDMI?

texts:
Cell Phone Displays are cheap and have high-resolution and touch sense, but use varied specialized inputs via ribbon cable. So, has the DIY community made any controllers to input HDMI? What about the touch sensor?

Recently, I only know of one solution, which is exactly that. It is open source and a great accomplishment, however, it does not support touch, yet still is not cheap, which defeats the purpose.
 https://hackaday.io/project/364-mipi-dsi-display-shieldhdmi-adapter

The single-board PC market has a selection of cheap, low resolution, touch screens. They input HDMI, and output USB.

This is an update to the old question Is it possible to wire up a cellphone screen to work with a different device?

This question isn't necessarily seeking consumer products as much as home-made devices.


texts: Using mesh analysis to get the transfer function of electrical system

texts:
I am studying the book: Control system engineering for Norman S Nise.

I left the college few years ago, and I forgot lots of thing about Kirchhof's laws (Voltage and current).

I tried to solve the following exercise:

PROBLEM: Given the network of Figure 2.6(a), find the transfer function,
h(s)/V(s).

Figure:

The author said in a previous part that:

[Sum of impedances around Mesh 1] I1 - [Sum of impedances common between Meshes] I2 = Sum of applied voltges around mesh 1

But as I remember, the both currents I1 and I2 are in the same directions, so it should + instead of - ?

And at the end he said that the transfer function is G(s) = I2/V(s). And as I remembered the transfer function should be Vc(s)/V(s).

And when we should use the Nodal analysis instead of Mesh analysis ? When there is a lots of calculations ?

Can anyone explain it to me ?

After transforming the components


texts: Design of a switchable dual voltage power supply

texts:
My project would benefit from power supply with two modes selected by a switch. The 'normal' mode is full voltage (±13.5V) at full current (~5A), the 'high' mode is double voltage (±27V) at half current (~1.8A, see note 2). I came up with pretty basic doubler/rectifier circuit with the circuit ground either being connected to a transformer winding or being disconnected from it.

simulate this circuit – Schematic created using CircuitLab

According to my simulations the switch would need to handle quite high peak currents, up to 60A with a 27V 5A transformer. The question is, how should I design the switch? At currents this high relays tend to get rare and expensive. Also, automotive relays for instance are usualy spec'ed for 14VDC so there is a bit of uncertainity there too. The switching would need to occur a few times in an hour at most, but I'm trying to design for longevity anyway.

Is there a better way to design such a supply? Without buying another transformer that is.

Note 1. Ideally I would use a proper transformer with center-tapped or dual windings. However, this is not really an option, transformers get kinda expensive and hard to find where I live. So I have to compensate for that with schematic tricks. I also don't mind extra capacitance in the filter, capacitors are easier to get.

Note 2. I understand that at high mode there will be less than half of maximum current due to increased peak current and thus heating.


texts: Why cant clock be directly used instead of DQS in DDR during read and write

texts: I have been reading about DDR lately and I am not able to understand the exact use of the DQS signal. The timing diagrams show dqs in phase with clock so why cant the clock only be used for the write and read, how does dqs improve performance of ddr.


texts: wiring up laser pointer directly to usb power

texts:
I have a red cheap laser pointer/lantern which I'm using to do some experiments. But I find that the batteries have a very short lifetime for what I'm doing, It uses three LR44 button cell batteries,
from what I saw online, each battery is 1.5V so it needs around 4.5 volts, I'm not sure about the current though.
But I have a USB phone charger adapter that is rated at 5V and 1000mA
So my question is:
Can I wire the USB charger directly to the laser battery contacts without damaging it?
If not, what kind of circuit do I need to adapt the USB power for this?


texts: Forward voltage tolerance on an ordinary diode

texts:
If one examines the datasheet of a diode such as the Vishay US1G, there is a graph of the typical voltage vs current such as Figure 3 below (with multiple lines for different temperatures):

However, there are very few guaranteed specifications for the forward voltage at any given temperature.  Typically, there will be a single value for a single current at 25C:

Since the typical value from the graph is about 0.85-0.90V at 1A, it would imply a tolerance a tolerance of 10-15%.

So my questions are:

Is a 15% variation in voltage (and other parameters) realistic?
Would this tolerance this hold for each V-I temperature curve?
Is 15% also applicable a low currents (e.g. 0.01A in this instance)?
Are there any parameters that are likely to have tighter and/or looser tolerances?
Is 15% a reasonable tolerance value to assume between different part numbers (for ordinary diodes) and manufacturers?

Background: I am attempting to calculate min/max voltage requirements for a circuit. A diode is used for reverse voltage protection and thus will affect the limit.  Of course, I can choose a different reverse blocking scheme with less of a voltage drop, but that's not the purpose of this question.


texts: Why mosfet drain is connected to its case?

texts:
I have a TO-220 package of irfz44n mosfet that have the middle pin (drain) connected to the mosfet sink tap , why is that?. And do I have to insulate the heatsink from the body of the mosfet ?

I've searched for similar stuff about the subject and I found many topics that talk about insulating the mosfet but I don't know if that connection has a purpose as it will reduce the efficiency of cooling (increasing the themal resistance between the mosfet and the heatsink).


texts:
This is a AC 220v 60W 0.2A fan I recently bought to replace my old bathroom vent that gave up some time ago. The problem is that the new one doesn't come with a built in speed controller like the old did, so the fan is running really loud. The people at the store tell me to go to another store to buy a speed controller but I have only found dimmers or expensive industrial speed controllers. I studied electronics some years ago and have been looking for a way to build such a speed controller, the question is how. My first guess is to control the speed by reducing the watt or amp. Any help would be welcome.

Some schematics that came with the unit (The instructions are in German):


texts:
I am using the LM2902 as a voltage follower. I recently discovered one of the wires to the input pin of one of the op amps was crimped In a tight spot and bare wire was touching the ground intermittently.

This was discovered because anytime the sensor was hooked up to op-amp 3 of the IC, its measurements would drop to 0.so I had to troubleshoot and probe everything.

I probed the lm2902 and found that between the input pin of op-amp 3 and the ground pin, the resistance was about 20k ohms and between that same pin and VCC, it was about 30k. All the other input pins on the other op-amps didn't even register anything on the 2000K ohm setting.

My question is this, if the remaining 3 op-amps on the lm2902 IC show infinite resistance WRT to ground and VCC from the input pins, can I guess that the other 3 op-amps have a high chance of being functional?


texts: Interpolating output specs on SN74LVC1T45 transceiver

texts: Section 7.5 of the datasheet for the SN74LVC1T45 shows minimum HIGH and maximum LOW voltages for output lines of the chip.  Values are given for several different Vcc values (e.g. 2.3V, 3V, 4.5V).  What's the most reliable way to interpret values for intermediate Vcc's?  Or do you need to jump down to the next-worst-case value?


texts: Could someone please help me find (page#) where in the IEEE 802.11 standard it directly says that Access Points are responsible for choosing the channel/frequency to be used and not clients. I know it's in there somewhere but I can't find where it says that in plain text and was hoping maybe someone on here is more familiar with the standard may know.


texts: Calculation of base current resistor resistance for a transistor operating in switch mode?

texts:
I have a 9V DC motor and I want to control its speed with an Arduino board with help of a power transistor TIP120. In one of the web-tutorials the writer explains how to calculate the resistor resistance. Here is the link to the page:
http://teachmetomake.wordpress.com/how-to-use-a-transistor-as-a-switch

In Example 1, if you scroll down to read the paragraph starting with:
“Finally let’s take a look at the datasheet for the TIP120. First, we see that Ic(max) = 5 A, and that Vceo(max) is 60, 80, or 100 V, so we are fine so far.
Next we check the base current...” you can read his explanation.

Here the writer of the blog uses a logic to calculate the resistor value for the base.
If I use his logic I obtain a resistor value which is very low comparing to other examples in other websites. Here is my scenario using his logic and by looking at TIP120 data sheet:

1-) The DC motor will be fed by a 9V battery and will be controlled by a pwm pin from the Arduino using a TIP120 transistor.

2-) The DC motor draws 500mA with no load; and 2500mA stall current as Imax_load. I measured these with an ampermeter.

3-) In this case the TIP120 satisfies the condition for Vce and Ice_max.

4-) Since Ic/Ib = 250, Ib_max will be 2500mA/250. So Ib_max = 10mA.

5-) Accoridng to TIP120 data sheet, in saturation zone for 2500mA the base emitter voltage will be Vbe = 1.75V.

6-) Since Arduino pin output is 5V, the voltage drop in resistor should be Vr = 5V – Vbe = 5 – 1.75 which means Vr = 3.25V.

7-) We can then use the base current Ib as 10mA < Ib < 40mA. Below 10mA the current will be too low and above 40mA might damage the Arduino. So I also choose a calue as 20mA. This means a resistor value R = Vr/Ib = 3.25V/20mA so that I obtain the proper resistor as R = 162.5 ohm.

I found many tutorials for Arduino and this transistor they use resistors such as 1k or 2.2k ect. For example here at this webpage they use 1k resistor: http://www.instructables.com/file/F9LKDFGGU7FXUMH There are many other use 1k and 2.2k.

My question is, is his logic and my calculations are right? Can I safely use the resistor I calculate?


texts: what is the maximum load for an instrumentation amplifier, in particular the AD620?

texts:
From the reading of This datasheet, I can't figure out what is the maximum load I can put at the output. To make my question more precise, suppose I need a gain of 10 (for DC measurements), for an input voltage between 0 and 1V (at very high impedance, that is why I want to use this amplifier (in my stock) that has only a few nanoAmp of input bias current), and assume the supply of the amplifier is generously above 10V.

question 1: What is the maximum load I can put at the output ?

question 2: In p. 15 they say the maximum input current is 6mA (or 60mA for few hours). I thought amplifiers are not supposed to draw any input current, except, of course, the input bias and input offset currents. Can someone explain ?


texts: Unused output of LTC6957-4 (or LTC6957-3)

texts:
The LTC6957-4 has two complementary CMOS outputs, and I only need one. What do I do with the unused output? My goal is to minimize noise on the used output signal, REFCLK_OUT.

The datasheet is clear on how to handle unused inputs, but provides no guidance on unused outputs.

As a follow-up question, if I only need a single output, are there any trade-offs between using the LTC6957-3 (in-phase outputs) and LTC6957-4 (complementary outputs)?

Below is what I currently have (currently, the unused output is left open):


texts: ALD1106/1107 transmission gate "off" state behaviour in LTSpice

texts:
I am making a transmission gate using ALD1106 NMOS and ALD1107 PMOS model files. For -5V (to NMOS and +5V to PMOS), with input 5V, the output should come 0 as the transistors would be in off state. But the output is coming 5V.
What is working: When NMOS and PMOS voltages are +5V and -5V respectively, the source voltage is reflected at drain.
What is not working: When NMOS and PMOS voltages are -5V and +5V respectively, the source voltage is reflected at drain. The gate should be in switched off mode.
What I have tried: My target input voltage at source is sine wave of amplitude 1Vpp and frequency 1kHz. Now I know that, condition for switch to be off is Vgs (gate to source)<Vth (threshold). So for my case of sine input and supply voltage(which is + or -5 volts), the condition might not hold true as Vth is state to be around 0.8V in the spice file. So, I changed the sine input to 10Vpp to have a maximum of 5V. But the input is still getting reflected at output even in off condition.
Note about inverter: I have used the default inverter from [digital] in LTSpice component bank. To get +/- 5V, I have added "Vhigh=5 Vlow=-5 Ref=0" to the "value" line in the attributes of the inverter (and by attributes I mean when one right clicks on the inverter and gets a dialog box with some attributes like value, value2, spiceline, spiceline2)
My schematic:

ALD1106/1107 spice file contents:
Model file for ALD1106 and ALD1107
SPICE Level 1

.MODEL ALD1106 NMOS (LEVEL=1 CBD=0.5p CBS=0.5p CGDO=0.1p CGSO=0.1p GAMMA=.85
+ KP=479u L=10E-6 LAMBDA=0.029 PHI=.9 VTO=0.8 W=20E-6)

.MODEL ALD1107 PMOS (LEVEL=1 CBD=0.5p CBS=0.5p CGDO=0.1p CGSO=0.1p GAMMA=.45
+ KP=206u L=10E-6 LAMBDA=0.0304 PHI=.8 VTO=-0.82 W=20E-6)

This is present inside a file named ald.txt that I am including using ".lib ald.txt" statement. Then I am using the default NMOS and PMOS from the LTSpice component bank and I am renaming them to ALD1106 and ALD1107 respectively to behave like the desired transistors.
Output observed (for sine wave of amplitude 10 Vpp):

What I expected: The output voltage to be 0 since switch is off, but output is same as input (as you can see two overlapping traces taken at input and output).
Netlist of my asc file:
* C:\Users\w\Desktop\LTSpice Models\Lab 5\Transmission Gate_Switch\Transmission_Gate.asc
V1 N001 0 -5
A1 N001 0 0 0 0 N004 0 0 BUF Vhigh=5 Vlow=-5 Ref=0
V2 N002 0 SINE(0 5 1000)
M1 N003 N001 N002 N002 ALD1106
M2 N002 N004 N003 N003 ALD1107
.model NMOS NMOS
.model PMOS PMOS
.lib C:\Users\w\Documents\LTspiceXVII\lib\cmp\standard.mos
.tran 0.005
.lib ald.txt
.backanno
.end

Is there something beyond my current knowledge base that I missed or is it something silly that I am overlooking? Why is "off" state not happening.


texts: How to wire up a logic-level MOSFET to a PWM Signal?

texts:
I'm trying to control a 12V Led strip with a logic-level MOSFET transistor (STP36NF06L), but I have no idea how I should wire it up.

This:

 _______
|       |
|       |
|       |
 ───────
 |  |  |
 |  |  |
 ↑ LED strip GND in
    ↑ 3.3V PWM Signal
       ↑ LED strip GND out

Wouldn't work, right?

Sorry if this is a very noobish question, but I have found absolutely no good ressources online explaining how I should set this up.


texts:
I got a simple bell system from elcom. It works with 12V AC.

When I measure the voltage at the switch it is 1V when not pressed.
When I measure the switch sides to the power input of the bell system I get 0V on one side and 16V AC on the other. Now I want to use the switch as input on an Wemos D1 mini.

When I simply wire the switch to gnd and an input it works if the switch is not attached to the bell system.

If it is attached and I also attach the Wemos the bell rings which is a sign that this will not work in combination. At least I did not yet burn my microcontrolller which I get might easily happen :-)

Any ideas how I can have the switch attached to my bell system and to the wemos D1?

I power the D1 from the same 12V AC using a regulator board. The powering of the D1 already works but I can not guarantee the start order.


texts: I have a DC motor with an encoder attached. In the encoder's PCB there's a component I can't recognise labeled IR1. At first I thought it was an IR LED just by it's name and it being transparent. But why would I need an IR LED in an encoder? And, if it's not an LED, what is this component?


texts: Audio to Low-Pass Filter to Comparator to LED = Fading LED based on the Frequency?

texts:
If I were to pass an audio signal through a Low-Pass filter with a cutoff frequency of 200 Hz (bass), and then send that signal to a comparator, then use this signal to drive an LED, would the LED be able to change its brightness based on the frequency? For example, a high frequency would drive the LED brighter than a lower frequency.

edit: The audio signal would be some sort of music from a computer.


texts: Making a portable HTC Hero Android phone charger

texts:
I want to make a little battery-powered portable phone charger (maybe 9V).

I have seen similar USB powered battery chargers such as the Mintyboost.

My phone is the HTC Hero. Would the design be basically be the same? Except instead of USB I'd use a mini-USB perhaps? I believe the charger is a standard mini-USB.


texts:
I'm trying to use my arduino to control my car's simple key fob which is controlled by a 3v battery and probably draws a very small current. I am controlling it with bluetooth from my phone.
As a noob in circuitry, I researched how to use transistors so I can use a transistor to trigger the push button (the rubbery kind, just connecting + and - when you press it) and I believe I wired it up correctly.
My test works when I hook it up to an LED but whenever I try to trigger the 3rd wire on the transistors I soldered onto the remote buttons, they don't complete the circuit and send the signal.
I tried using resistors to limit the voltage/current going to the remote down from 5v to a lower amount but I'm not even sure if that is the issue.

5v is going to + on the key fob.
ground is going to - on key fob and neg wires on the transistors that are on the buttons.
positive on transistors is wired to the + connector on the buttons
third transistor wire is connected to digital outs on the arduino, which are enabled for 1 second when pressed in the app, and tested on the LED to verify they are coded properly.

My question is:
What is the issue with my circuitry?
Does anyone have an idea what I could be doing wrong?


texts: Splitting a big Power Trace to several smaller

texts:
I would ask if i can layout a big trace and split it into many smaller ones (see attachement)

I need to run a trace capable of handling ~5A. But the trace would be too thick to fit between the pins (screw terminals). My idea was to run a big trace and then use smaller traces (2mm)from the screw terminal to the big rail.
Is that OK or wold it burn the board?
Its homemade btw.

~Straw


texts:
Hi
Can someone please help me out. I've been battling this problem for ages and I don't know what I'm doing wrong
My AC input is 50mV and the output is measured as -190mV giving a voltage gain of -3.8. If I were to calculate the voltage gain without the graph I would do -RC/RE = -3900/1000 which gives me -3.9.
Why are the 2 results not equal? am I missing something?
Thanks


texts: Purpose of inverted channel for UART bus communication

texts:
I'd like to understand the purpose of an inverted logic channel on device-to-device communication that is being done via UART.

For some background - I'm trying to reverse engineer this device-to-device communication with a logic analyzer that I have determined uses UART with the following configuration:

Parity: None
Data Bits: 9
Baud Rate: 38400bps
Stop Bits: 1

On the device, i determined three pins that seemed to be transmitting within an expected logic level. After recording for 20 seconds, I noticed the first and second pin seemed to be linked - a perfect inverse logic level of each other at all times, an example is  shown below:

My first instinct, is that one channel is TX and the other is RX, and when data is being transmitted on TX the RX line is being used to confirm the data is being received as a method of validation. Is this something that is commonly done for UART communication?

The transmission medium is through a flat-untwisted RJ-12 cable, with lengths around 1M-3M. Context is for an audio device connecting to its remote.


texts:
this question is regarding standards and/or best practice guidelines for ESD control in a professional lab environment.

We are currently tightening up our (admittedly too lax) ESD control in the labs, in preparation for an audit. We've had a chance to see the audit results from another one of our labs and are working on all the things they failed on.

One of the issues we have is how to manage non-ESD areas in a Lab. The lab itself is marked off as an ESD protected area, and has suitable flooring. The lab in question is our 'construction' lab, which has a few soldering benches and general tools/equipment. The majority of it will be ESD protected and grounded as appropriate, but there is going to be a mechanical rework bench in the corner which will not be ESD protected. The bench will be a metal frame, with a thick piece of ply on top so you can hammer/drill/bash/whatever.

Does anybody have an idea as to what best practice/standards would say about non-ESD working areas in an ESD room? Would it be sufficient to just mark out the area? It has the same dissipative floor tiles underneath, is that an issue? Would you ground the metal frame of the mech. workbench?

It terms of geography, the room is isolated from the rest of the office by walls, has ESD flooring throughout the room and ESD walkway to the other labs. In order to walk to the mech. working area, you would need to walk through the ESD protected area. It is likely that workers will swap between the mech. work bench and the ESD-safe soldering bench.

Any thoughts?


texts: USB datalogger ground read isn't zero volts

texts: Im using NI DAQ USB 6008 datalogger. When I connect A0 (or 1,2 etc..) to ground in single-ended mode it gives 6 mV. Shouldn't it be 0 mV? Is it corrupted or normal?


texts: Dupont jump wire in order to replace 20 pin cable

texts: Hello, I bought a mp5 player for my car and I didn't find the 20 pin cable for this player. My question is if I could replace it by Dupont jumper wires as the picture shows


texts: I need to turn an Arduino on when something triggers an independently powered tilt sensor; the Arduino needs then to stay awake and use an output pin to switch itself off. I couldn't find an example of what I need on the internet, and the only kind of circuit I came up with (but not tested) involves 2 relays, which doesn't sound good to me (although I'm not an expert).


texts: How do I measure impedance of my guitar pickups?

texts: How would I measure impedance of my guitar pickups with a multimeter? Is it similar to measuring resistance?


texts: Laplace Analysis of Step Response of a Parallel RC Circuit

texts:
simulate this circuit – Schematic created using CircuitLab
My KCL Equation:
$$\frac{Cdv}{dt} + iΔ(t) = \frac{Vo}{10k} + iΔ $$
My laplace transform is:
$$\frac{Vo(s)}{s} =  \frac{sVc(s)}{20} - 0.00005 $$
The circuit and my initial solution is shown in the picture. I'm not sure if even my KVL equation is right. But the way I understood the circuit, because m=1, then the dependent source will have the same current magnitude as the current on its right, hence, because of the opposite direction, they will just cancel out.
The part i'm having trouble with is the laplace transform (which I have to convert back to time domain after). Did I do it right? If yes, for my resulting laplace transform of the equation, how would I find Vc(s)? Is not that Vc(s) and Vo(s) is just the same voltage? How would that work out with the equation?
Then the last question was asking for m that will make Vo(t) boundless and i'm unsure where to start.


texts: Finding constant in electrostatic equation given only charge

texts:
So in a region of free space with zero charge, all I'm given is that the electrostatic potential V is given by:
$$V(x,y,z) = kz(x^2) y + 2y - 6y(z^3)$$ [Volts]
To find the constant k, would I have to use the assumption that there is zero electric field and that the corresponding partial derivatives dV/dx, dV/dy, and dV/dz also equal to zero?


texts:
I'm looking for an IC with the following functional diagram. Basically it's an inverting buffer whose output is open-collector, and that has an enable signal. An equivalent logical circuit would be to replace the notional tristate inverting buffer with a "NOR" gate driving the base of the transistor. Essentially I want the output to unconditionally float when the enable pin is "low". When the enable pin is "high" I want the output to be driven low when the input is driven low and float otherwise.

Does anything like that exist? Ideally I'd power it from 1.8V (but I'm flexible on that requirement) and it would come in an SOT-5 package. Suffice it to say this is not for a new design, but rather to put a band-aid on an existing design problem (that I've inherited).


texts:
I have been reading the documentations about KeeLoq Encoder and Decoders for some time. My goal is to build both the Transmitter side and the Receiver side using the KeeLoq system.

I almost completed the basics, but I can not understand how do people clone KeeLoq Remotes or other Rolling Code remotes that easy. There are lots of remotes on Ebay telling they are able to clone a Rolling Code Remote by just pressing some of those buttons. There also some videos showing the same things on Youtube.

Q1: If I build my own transmitter using a KeeLoq Decoder (e.g. HCS301), can they clone my transmitters too? Or, can they just teach another KeeLoq Remote to my receiver and use it in the case they have the access to the learn button on my receiver. As I understood, they have to know the Shared Key in order to teach the Remote to my receiver.

Q2: If they can not clone it or they can not teach new remotes to my receiver; do my costumers have to request a new remote from me every time they need another one?


texts: USB-to-Serial cable based on the Prolific chip - Windows 7 driver problem

texts:
I have a problem getting a USB-to-Serial cable based on the Prolific PL-2303 chip working under Windows 7. This problem has drained me for a few hours and after searching for miles on the Internet I have been unable to find the correct solution. The Prolific PL-2303 chip is used extensively for serial to USB connectivity.

It seems others also have a problem getting cables based on this chip working under Windows 7 after downloading various drivers. How can I get my PL-2303 based device working under Windows 7?


texts:
Are there any high-stability oscilators, which are not crystal based, given that temperature is stable down to 0.01 C and voltage down to 0.001V?

Will LC-based oscillator be able to show performance comparable to crystals in such conditions (probably in wierd variants like LC-opamp-LC-opamp-LC-opamp... so that any energy loss on each stage is recovered and we are getting narrower bandwidth)?

Price is not limited here, to a some degree (so brand new atomic clocks are above the budget, but 100$ for peltier/oven & parts is ok).

From my (naive) point it seems that it should be possible to achieve better short & long-term stability than with crystals...


texts: LIPO Battery: Bare Arduino on LiPO cell charging circuit components

texts:
I am building a bare Arduino project, very basic, and want to make it portable. I need my circuit to run on 5V.

I am new to LiPo batteries and how to manage/use them.

After a lot of online reading and research I found that I need a specific charger to charge a single LiPo cell with USB. I have also found that a LiPo must not be used below a certain voltage. For my application I am not planning on coming near that voltage before recharging, so for the Alpha version of my project I am planning on ignoring a cut-off.

Basically, all I want to know is, would these breakouts work sufficiently for a charger/booster combination circuit? The step-up and the charger. I am buying from a local store so I don't have access to the whole inventory range that e.g. Sparkfun has.

Thanks

PS: I hope this product-specific post does not violate the SE policy.


texts: Is it possible to "intercept" a 20-pin FFC?

texts:
I'm not an electrical engineer but a software developer but I'm trying my hand at a DIY project that will involve connecting a couple of pins on a device in my home to the GPIO pins of a Raspberry Pi, so that I can programmatically press buttons on it. Pictured below is a 20-pin FFC coming from a panel of touch buttons into the device's circuitboard. Long story short: one (or more) of these pins are pins that I'll need to "press" programmatically, though I'm not sure which ones as of yet.

In all, I need to do two things: (1) hold a multimeter up to the pins to test which ones correspond to which button presses on the device, and then once I've determined which are the correct pins, (2) solder or otherwise attach a wire to those pins so I can connect those wires to a Raspberry Pi, and trigger "button presses" remotely.

The trouble is that these twenty pins are very small, and when I hold up my multimeter red and black ends to any one of them, the slightest hand shake results in touching more than one of them at a time. So I'm wondering if there's any kind of "intercept" device that I can plug the FFC through that would pull off (and enlarge) the same wires so I can better touch them? Or if not the cable, then maybe something that would fit the receptacle and expand the touch points? Thanks.

EDIT: There are a total of 34 buttons on the display. And as you can see from the picture above, only 15 of the 20 pins are actually used. One commenter suggested that would imply a "keyboard matrix wiring" with rows and columns, which would make sense since obviously you can't have a 1-to-1 ratio of pins to buttons if there are more buttons. Does this mean I'm completely in over my head? Or are there any standards for how this sort of thing might be done? (e.g. two or three pins lit at the same time to indicate certain buttons, based on some specification)


texts:
I am working on a circuit for a science competition, and one of the tasks is cooling a thing of water to a certain temperature (we are doing about 25C to 18C) and then using that to trigger a circuit. To do this, I am using a PTC thermistor, I have a TTC-103 one. The challenge I am facing is how to set up the circuit, so that when the resistance drops to a specific amount with this thermistor, to trigger another circuit, here a UV light.

One way I thought was just wiring the thermistor in parallel and once the resistance drops, the light can turn on. But with such high resistance still, the light is weak and the circuit is not as cleanly cut off as I would like. Someone suggested a voltage matching circuit, where the resistance drops enough that the voltages are equal. I, however, do not fully understand how I would implement this with a thermistor, so if you could provide me with an example of how to set one up, that would be amazing.

Thank you!


texts: Why am I getting shocked from "hot" line and touching "ground" (Earth)

texts:
So I live in an EU country and don't have Earth grounding for my house. Still I am getting shocked when touching "hot" line (220VAC) and standing on "ground" (Earth). How is this possible?

From my understanding it needs to close a circuit to generate a current flow through my body. I heard of some sort of capacitance that can close the circuit, but didn't fully understand the concept. (It will close the circuit between "ground" and neutral through air ?? So current will flow through me, ground and neutral)

So to extend this idea, if getting a "hot" line somewhere far from civilization will cause a current to flow through me and then "ground", going back to the source.

Neutral line is not touched in any way. Just floating.


texts: How to use chip XL6007E1 to build a boost ciruit?

texts:
My ciruit:

Input: 3.7V
But no matter how I adjust the potentiometer, the voltage did not rise.
How can I solve it?


texts: How to find transfer function for the diagram

texts:
I'm studying Control Systems and the teacher gave homework of writing the Transfer Function for given diagram:

During the class, we solved easier diagrams but with my intuition and experience I came up with a transfer function which looks like this:

Did I calculate a correct formula?


texts: What's the ideal positioning for analog MUX in microcontroller circuit? (in a design with two boards)

texts:
I'm designing a set of PCBS for a midi controller and am wondering what is the best placement for the multiplexers in my design.  Here are the details:
Board 1:  a microcontroller (Teensy 4.0), power in, usb out
Board 2:  A control panel with around 50 pots and switches, all of which will be fed into 74HCT4051 multiplexer chips and then into the Teensy's analog inputs
The boards will be connected with an IDC cable, like this one.
So, is there any advantage placing the multiplexer chips on one board or the other (ie positioning the chips closer to the pots or closer to the microcontroller)?  Or should I assume that either way should work fine?
To be clear, the pots and switches will be biased with the 3.3V coming from the microcontroller.


texts: How do I simulate a physical push button from an AVR

texts:
I've been messing a bit with EL wire that I purchased from amazon, I dissected the control unit and it appears to consist of a transformer, timing circuits(s) and a push button. When you push the button it toggles through the different modes (solid, blink, blink fast).

I want to try and control the wire in a very basic manner from an arduino. I simply want to toggle through the different states. How would I apply voltage or PWM across the contacts of the pushbutton to simulate a push


texts: Purpose of diodes on ADC inputs in DRV8305 example circuit?

texts: All sense pins in this schematic are used with diodes before the ADC input (on the MCU). Anyone can explain? And what diodes will work here? No info in datasheet.


texts: Looking for TCP/IP Ethernet  RS-485, Half Duplex Device

texts:
We are currently using the Wiz108SR device and need to provide this as a consumer ready component with a power supply. We would rather not build and package the powersupply but instead purchase something that is already done and packaged.

Does anybody know of a similar product that we can buy, rather than this DIY component?


texts: Driving dots (periods) next to digits on Terasic DE1

texts: I have a Terasic DE1, and have imported the maker's pinout file, which contains pin assignments for HEX digits. However, I noticed that each HEX digit has a dot next to it and I cannot find any pin assignments for those dots. I'm wondering if they are disabled or I can somehow map them myself. Can you help?


texts: Using a 3 phase step down transformer in reverse

texts:
I have a 30kVA transformer with primary 480V delta to 208V Wye secondary.  I am relocating to a building that has 208 service, and would like to use the above transformer in reverse, so that I can run my 480V equipment without other conversion.
This transformer used in reverse to produce 480V delta output will not have a ground or common terminal on the output side.  My question is: What then are the grounding requirements for the machinery that the transformer would be servicing, and, are there any other wiring requirements for the transformer itself?


texts: Interrupt deduplication with discrete components

texts:
I am playing with interrupt mode 2 on a z80. Once pulled low it will disable interrupts and make a subroutine call to 0x0033. Before returning from the interrupt handler, interrupts should be explicitly activated through an opcode.
http://z80.info/zip/z80-interrupts_rewritten.pdf
Say I have a manual, debounced switch that, once pressed, will cleanly trigger this interrupt. Say the routine takes 80 clock cycles to complete at 8Mhz, ie 10us total before the interrupt will be re-activated.
I assume the manual switch press will last longer than 10us. That means that several interrupts will be processed on a single key press. I would like to avoid that.
Some solutions could be:

don't use interrupts, silly, just do what everyone else does and just poll it.
in the interrupt routine, poll the switch and only return after the swithc is reset.

That's all fine.
It however would be cool if there was a way to use discrete components outside the cpu to ensure that only a single interrupt is issued.
One thing that comes to mind is an RC circuit with a very fast (10us) cutoff.
But are there other solutions?


texts: Biasing circuits are designed to fix the Q – point at the centre of the active region. why it is designed in this way?


texts: Analyzing circuit with two transformers in parallel

texts:
I'm interested in analyzing a circuit with two transformers in it. The tricky thing about it is that the transformers are in "parallel" around the same loop, so I can't just use the usual trick of multiplying the effective impedances by N^2 to simplify the circuit.

Here's the circuit in question:

For the curious, this is a circuit built using the impedance analogy for mechanical systems in which torque is analogous to voltage and velocity (\$ \dot{\theta}\$) is analogous to current. My goal is to be able to write transfer functions for the relationship between \$\tau_{em}/\tau_{op}\$ and \$\tau_{em}/\tau_{od}\$ and \$\tau_{op}/\tau_{od}\$.

How can I write equations for the voltage across the two transformers? I was thinking that I could perhaps create two separate circuits and solve some system of equations but I haven't been able to find any examples of this so far.


texts:
This may look like a homework, but it's not. Actually it is related to Christmas. My Chrismas lights in front of the house are constructed from segments. Each segment consists of 16 incandescent light bulbs connected in series. Each single light bulb is rated 1.5V 0.07A, so they need 24V power supply. I use hundreds of these.

The problem is that I am unable to obtain identical spare bulbs this year. I can only get 2.4V 0.07A. My question here is simple: What happens if I connect these bulbs together in series?

For simplicity, if I connect 2.4V 0.07A and 1.6V 0.07A together in series, what happens? Which one of them will be brighter or darker? Or will they shine the same? Can I consider such a tiny light bulb as a pure resistive load? May I expect a constant resistance on each bulb, and use Ohm's law to compute the rest?


texts: Is there a reason that dryers aren't grounded

texts:
One minute ago I cried out in pain, after being electrocuted again by my clothes dryer; probably the thousandth time in my life that this has happened.

I was taking out clothes after they're dry, made the mistake of touching the metal parts of the dryer, and a jolt of static electricity went through my hand. I've had this happen in different brands of clothes dryers over the years. The one I'm using right now is a Bosch, which is supposed to be a good brand.

I'm guessing that the static electricity is generated by the clothes continually rubbing against each other, robbing each other of electrons. That's understandable, electrons will be electrons. What I'm wondering is, why wouldn't the metal body of the dryer be connected to the mains grounding?


texts:
I am going to built microwave system with following system configuration.

Power Circuit -> Magnetron -> Wave Guide Coupler -> Isolator -> 3 Stub Tuner -> Applicator.

Now, I want to make 3 Stub Tuner Automatic.  I understand that, to do so I need to measure reflected power.

I am thinking of doing it cheaply using isolator.

I am using water circulation for dumping excess power in isolator.

So, If I measure incoming and outgoing water temperature at constant flow, will I have accurate measure of reflective power ?

And if so, will that can be use to change the 3 stubs accordingly to tune the system ?

( thanks. I'm newbie in microwave engineering...)


texts: How safe is to work on an ATX PSU as a bench power supply?

texts:
I'm trying to convert an old ATX PSU into a workbench supply. I saw there are many safety warnings about discharging the internal capacitors before opening the PSU. I'm not really concerned with it as I managed to cut the wires directly outside the box.

What I didn't find is if it's actually safe to work with the external wires (so the 'output' low-voltage side of the PSU). Up to now, the PSU has been disconnected for several years, but what if I want to test it? Will I then risk something by touching/soldering the wires after shutting it down again?


texts: If I turn a AA around will it drain or damage electronics?

texts:
I have an Apple Bluetooth keyboard.  The thing turns on all the time when I put it in my backpack.  This is bad because it blocks the soft keyboard on my phone.  It runs on 2 AA batteries.  Lately, I have been turning one of the batteries around to make sure it can't turn on.  This works as intended, but my questions are:

Can this damage the electronics?
Will this drain the batteries faster?


texts: I am aware of voltage signals being clipped when inserting a diode in series, however, I have been struggling for a few hours to clarify the behaviour obtained by adding a second resistor in series. The clipping seems to be replaced by amplitude reduction. Can some please explain this behaviour and how to calculate this amplitude reduction?


texts:
Are strip(vero) boards good enough for prototyping RF circuits ?

Frequency range is between 100 MHz to 450 MHz.

Previously I've used strip boards for frequency range of around 100 MHz to 150 MHz, they all just worked. But I had no clue if something was wrong.

Now I want to increase the frequency range to 433 MHz with SAW resonators.

I think the capacitance between two tracks is going to make it hard.


texts:
For quite some time I am thinking about making 'passive' usb 'amplifier' - but the main question is how it is possible to detect direction of the transfer by some clever way, so that I can disable one of amplifiers?

Classical approach of using USB-HUB chips to extend cable for another 5 meters is too boring.


texts: real time short distance range finder and visual output

texts:
I'm badly visually impared in one eye and find judging distances while walking downhill hard. My goal is to create a real time range finder than can display the distance of the next step(s) while at normal walking pace. for example: walking down a 4 in 1 hill on an uneven forrest path.

First step is to choose a method of range finding that is lightweight, low power, accurate to within 5cm and returns distances in real time. The range of the device needs to be 50cm to 500cm. The target area for measurement needs to be about 10cm square.

This is my first attempt at this kind of device and know nothing of what types of sensors even exist, so even research suggestions would be useful.

So, what types of sensors exist that could return a realtime distance measurement?


texts: How to avoid gated clock on a flip-flop?

texts:
I've read that it is a bad practice and I should use the enable signal.
Is it also a bad idea to connect a gated, divided clock signal to the enable input?


texts:
A channel has bandwidth 3 KHz, signal to noise ratio is 40 dB find maximum data rate for 16 level encoding schemes.

There are two ways to find channel capacity. First one is with Nyquist theorem and second one is with shanon capacity. For Nyquist theorem I found 24 kbps and for Shanon capacity I found 39.84 kbps. So which one would be preferable? Is there any other method to do?


texts: Why is a capacitor before a voltage regulator more effective than after?

texts:
I have 5 V coming in from a USB power bank to an LDO voltage regulator that drops it down to 3.3 V. On the 3.3 V line I have several ICs and IR sensors. One of the IR sensor consumes quite a bit of current in short bursts (I have a 10 µF cap across it).

Whenever that power hungry IR sensor turns on, it causes some other parts of my circuit to behave oddly for a split second. I figured adding a large capacitor to the 3.3 V rail would help eliminate that, which it did. But I also noticed that I could instead add a significantly smaller capacitor on the 5 V side, and that also solved the problem.

Why is it that the capacitor is more effective on the input side of the regulator rather than the output? I figured the charge would be "more readily available" to the system if it was on the output/3.3 V side, where the sensor is.

(I just tinker with electronics and have no formal knowledge beyond basic physics E&M.)

*Edit: Before the problem/experimentation I already had on either side of the regulator a 0.1uF cap, a 1uF cap, and two 10uF caps (totaling 21.1uF on either side). I began to add extra caps after the problem.


texts: Flash an LED with an extremely low power source

texts:
Let's say I have a very low power solar cell, which is producing a couple of uA of current at 100-200 mV for an output power of a few hundred nW. What I would like to know is what is the best (most efficient) way to flash an LED using this as the only power source? I'm aware that a typical LED consumes maybe 40 mW, so I could at best hope to turn flash the LED for maybe 10 ms every half an hour or so.

I am not an electrical engineer by training, nor very adept with circuit design and analysis, so I'm not sure if there's a relatively simple circuit that could used consisting only of capacitors, resistors, and mosfets and/or zener diodes, or if I would be better off trying to utilize a power management IC with a boost converter, something like the TI BQ25504 or the LTC3108.

My sense is that these ICs are overkill for something that I would imagine is relatively simple, but my Google-fu is failing to come up with an approach for something like this.


texts: Behavior of a pin that, initially is configured as output, but, inevitably is configured as input when it should not be

texts:
Helo, all !!

I have a doubt, I'm using a MC9S12DP512 microcontroller to read another microcontroller, that I will name it as A. But I'm having some problems. Here, I will present you a image of a log made with an oscilloscope. The Blue signal, I will name it X, and the Red I will name it Y.
So, The X pin( the blue signal) needs to be an output, and the Y pin(The red signal) Needs to be an input. However, both pins are at the same port, Port H, on the MC9S12DP512 microcontroller. And, the driver that I'm using, change the direction of all pins of the Port H at the same time.

So, I observed that, after the command below, The X (Blue signal) goes to low-logic.

DDRH = 0x00;   / DDRH is Port H Data Direction Register */

I observed too that,the Y (Red signal) seems to be very attenuated in some instants and others moments don't.

I did the same test, using the same microcontroller MC9S12DP512 to read anothers similar devices on the other side, all others similar devices has the same internal microcontroller, that I called it as A, and the majority were read without problems, and the pulses did not appear. Only one of them showed problems. I know that the problem is not in this particular device, because it can be read by others equipements that I have and it works fine.

So, I have two doubts.

Why signal X(The Blue one) has the behavior showed on the figure ?
Why this behavior does not happen when I do it using a MC9S12DP512 to read a similar device with the same microcontroller A on the other side?

Thank you very much!

Added Later:

Both microcontroller are 5V. By the read line I expect to read the microcontroller A using the MC9S12DP512. By the blue Line I expect to write to microcontroller A using the MC9S12DP512. But, the reading and writting does no happen at the same time.
It is part of a JTAG communication, the red is TDO and Blue is RST


texts:
So I'm fairly confident in my ability to do circuit analysis on closed circuits, that is, circuits where all loops, sources, and elements are given. However I still find myself getting stuck on circuits where only a particular section of the system is given.

For example: In a problem I'm trying to solve, it is asked to use Thevenin's theorem to simplify this circuit:

I'm honestly quite lost, I understand that the voltages given at the terminals are relative to ground, but I have no idea how to translate those into an equivalent source. My first instinct would be to start by reducing the outside parallel resistances, which would reduce the circuit down to a T-shape with equivalent resistances of 5 ohms on each side. From there I'm stuck. Would I add the voltages as sources in series with the resistor?

Any intuition on best practice when considering systems like this would be appreciated. Thanks!

Edit: So I think I understand, flipping around some signs, would the following be an appropriate representation?

Edit2: Diagram with common ground