texts: Advice on upgrading a circuit design for s-video

texts:
I'd need some advice on a circuit, which generates analog video (s-video) from composite and Chroma (a mod inside an old Sinclair Spectrum computer). I haven't designed the circuit myself, but I managed to build one :) The circuit is working, but for some reason the chroma level is apparently too low. I'm a real newbie regarding electronics, so I hope I'm asking something that is actually viable regarding this circuit design.

Would it be possible to raise the chroma output level (easily?) by changing some of the components of the circuit above? The transistors are all BC547B:s. The input level for the chroma part of the circuit measured with a cheap (rms) multimeter without load is ~4v measured directly from the ic (LM1889) that generates the chroma subcarrier (sorry, but that's all managed to measure..). The monitor has 75Ohm termination for the video signal.

All help highly appreciated :)


texts: One large microcontroller, or lots of small microcontrollers?

texts:
I'm used to doing basic and straightforward things with microcontrollers, relatively speaking. Things such as driving LEDs, running motors, basic routines, GUIs on character LCDs, and so on, but always just one key task with at most a few little side tasks. This has relegated me to low end products since that's really all that's needed in those cases.

I'd like to start designing more complex things but the upper side of the microcontroller continuum is not something I've been well exposed to. Thus, I've been having a very challenging time trying to pick a microcontroller where I will do lots of tasks simultaneously — I can't tell just by a MIPS number and a satisfactory pinout if it has enough horsepower to do what I want it to do.

For example, I would like to control 2 BLDC motors with PI routines, alongside some serial and USB comms, a GUI, and a slew of other tasks. I'm tempted to just have a microcontroller for each motor and then one for the miscellaneous tasks so I can guarantee that the overhead from the miscellaneous stuff won't gum up critical motor functioning. But I don't know if that's actually a good idea or a naive way to go about things.

I guess my question is really two-fold:

Is the all-in-one approach a good idea when having to do a lot of multitasking, or is it better to segment and isolate, and
How can I intuitively find out if the microcontroller I'm looking at has enough compute power to do what I need based on my list of tasks?

I'm looking at moderate dsPIC33s all the way up to ARM SoCs that run RTOS. A systematic way to hone down what I need would help me out a lot.


texts: Connecting to HC-05 from iOS based device

texts:
Continuing from Standalone Bluetooth my project is almost complete.

For any of you who haven't seen that, here's a short info:
I'm trying to make an automated list of attendees by using a program that runs on a smartphone that can detect the HC-05.

So far it's all good, good only on Android based smartphones. Unfortunately, it doesn't work with iOS based devices. I've read several posts around that iOS based devices can't see the HC-05 because of the limitation in their bluetooth rules.

But, in every single post that "I've read" there's none of em that talks about the solution. I want to know if there's any workaround for this? Or should I change to another bluetooth module? If anyone need more info I could provide everything.

Thanks in advance!


texts:
Hey guys, I'm trying to understand how to use op amps, right now I just have a battery hooked up to the non-inverting, and a virtual ground, this is a single supply cause I don't have many tools to make split supply.

The all the resistors are 220 Ohm except the left one, which I've just tossed 33,10, and some other values, but I keep getting the same as the Vin, can someone help and possibly explain how to do AC signals also, I've spent weeks trying to figure this out but can't rip YouTube.


texts:
I am working on a project for a watering controller where I would need to turn on or off an solenoid valve (electric valve), my first thought would be to use a relay, but I know relays are good for things like 110V/220V AC, but I feel like it would be too overkill for 9V/12V DC.
Would a transistor work as a switch for 9 to 12 volts? Or is a relay still a better option?


texts: Cell balancing of two batteries connected each at the output of parallel converters

texts:
I am developing a scalable energy storage application where I connect bidirectional dc dc converters in parallel and battery is connected at output of each converter. I am uploading a block diagram to understand the project.
I had a doubt do I need to deploy cell balancing for this?

Two batteries 12V lead acid and 12V lithium polymer


texts: What is the proper configuration for an adjustable voltage divider circuit

texts:
I am making a circuit that need a voltage reference that is adjustable. The the answer that many of us would think of is a voltage divider.

There are 2 configurations that I thought this can be done, and it is only now that I have wondered which is the proper or probably the best.

The configuration on the right seems to be the most optimal since it requires less parts.

Are the two configuration essentially the same? If not what are the pros and cons of the each configuration?


texts: How do you get the data out of a d flip flop?  On wikipedia it says that if the clock is non-rising then it ouputs Q.  Isn't the clock always non-rising if it's not changing the data?  If it is, then the data is constantly being output every second, even when not asked for it...


texts: A simple digital current sink for a fuel gauge?

texts:
I need to simulate a 1200Ω fuel sender with an arduino, so I can control the fuel gauge.

The fuel gauge has one wire which it supplies with an unknown current and voltage, where the voltage is no larger than 12V and the current no larger than 50mA.  The fuel sender is a resistor to ground.  It's this resistance to ground I need to simulate.

I could go to the trouble of finding and fiddling with a digital potentiometer, except for the large voltage and current requirements.

It seems like I should be able to accomplish this with a ULN2803 and a series of resistors.  I can use 6 outputs on the Arduino to control this driver, which then sinks it's outputs. (the other two outputs will drive dashboard indicators)

The simplest method would be to connect 6 different resistors, each representing one fuel level, and activating only one at a time.

A more complex solution would involve an R-2R ladder, but those designs are meant to work with digital I/O that both sources and sinks current, whereas I'm seeking merely to sink current to avoid having to deal with the 12V issue.

Is there a simple solution with the ULN2803 and some resistors that will give me more control than just 6 levels?
Is there a better way to drive a fuel gauge such as this?


texts: Reset pulse generated by UART break condition

texts:
I'm trying to create a reset pulse triggered by external inputs to my circuit. My circuit is connected to an external 5V supply and TTL level UART (actually a half-duplex single line).  I would like to generate a reset pulse for the local CPU when the UART line goes low for a long period.

My analog design experience is quite limited. I suspect I'm looking for a monostable multivibrator but I've no idea how to modify that standard circuit.

I initially created this circuit, but it generates a low level rather than a pulse, and on analysis, it can latch the board into a permanent reset state. A reset once-off pulse is required.

To be clear, here is a waveform of what I'm looking for.  Any comms transmission should transition between 0 and 1 fast enough to prevent false triggering (for baudrates between 9600 and 115200, or more) .  The condition for generating a low-going pulse should be 5V present with the comms line staying low for around 100ms . The low-going reset pulse should be long enough to allow various signals on the board to return to steady state - I say at least 1ms or more.  Only 1 reset pulse should be generated per long low level "pulse" on the comms line.

The circuit is battery powered, so it needs to have low current consumption in while its not active.


texts: What the heck is a "radiator plate" in a CRT based oscilloscope?

texts:
I managed to pickup a used BK Precision 1474 oscilloscope for $10 and figured it would be a good gamble for the price, I powered it up and the CRT had no spot. I did some hunting and managed to find the original service manual as a pdf, and started working down the troubleshooting chart. I have made it as far as a section that wants me to check the voltage across a "radiator plate". So far I have found absolutely nothing that mentions what this part is, and google just wants to show me car radiators for sale. I am 16, and this is my first scope, so any help figuring out what this is would be deeply appreciated.

Schematics are here (Diagrams and schematics start on PDF page 25.)

Here is a screenshot of the chart that wants me to check the radiator plate:

Thanks in advance!

EDIT:
Thanks for digging into this with me guys! :)
The general consensus seams to be that it is some kind of thermal plate on a transistor or something. So I will probe around when I get home, and will update when I do!

I also added a link to schematics for those of you that know more then me to have a look at.


texts:
I've done a lot of googling and the answer just isn't jumping out at me.

I've got a project that has two SD card slots. Access to the two cards is never simultaneous. I'm upgrading this project to an ATSAMS70N19 (mainly to get hi-speed USB), which has an HSMCI interface... but only a single one.

How can I multiplex the two card slots across this interface?

I already know that I can properly multiplex two cards in SPI mode using the !CS line (my current version of the project does that), but I am hoping to increase performance with the HSMCI interface.

I'd like to use a GPIO pin as an A/!B pin. The spec that I'm reading at least seems to suggest that I can simply switch the clock back and forth between the two cards (holding the idle card's clock either high or low) is enough to keep the idle card out of the way. Is this correct?

If this isn't good enough, how can I switch the whole bus back and forth between the two slots given that 5 out of the 6 pins are bidirectional and relatively high speed?


texts: Is there any way a usb device can identify the usb host operating system?

texts:
Is there any way for the USB device to know if it is connected to a Windows or to a Mac without the installation of a third party software?

Maybe there is a way to "ask" a question via USB and figure that out from the USB Host reply?


texts: STM32 - How to trigger a DMA transfer via hardware timer, while CPU is in SLEEP mode?

texts:
I'm trying to set up a simple project that does the following:

Enter sleep mode and in the main loop, it waits for interrupt - __WFI().

Transmits data from a buffer[4] to the PC, via UART.

The second point of the program would ideally be done via DMA, so that the MCU wouldn't wake up from sleep.
To that effect, I was thinking of hooking up a DMA transfer in circular mode. So every time a timer (say timer1) overflows, it automatically triggers a UART transfer. When the DMA transfers the 4th byte of buffer, it would start over from the beginning.
Can I trigger a DMA when the CPU is in sleep mode?


texts:
I'm interested in buying some LCD for my amateur Z80 retrocomputer, and I'm searching for 320x240 dot matrix screen with 8-bit parallel bus.
What is common for them all, they need 3 independent power connections: for logic, LCD itself and backlight... and for LCD the voltage is quite high - 23V (why is it so high?). I would like to ensure how to properly connect it without burning.
Pls see this example and that table:
https://www.aliexpress.com/item/1320170071.html
As I understand:

connection for logic is between VSS and VDD: 5V
connection for backlight is between BLK and BLA: 5V
connection for LCD: it needs 23V, but I'm not sure where exactly. There's written VDD-VO=23V. Does it mean I have to connect independent supply of 23V, where (-) to VO and (+) to VDD? There is also another pin: VEE, which is "output voltage for LCD" - this one is totally confusing.

Or maybe using such LCDs is dead end for amateur project?


texts: Why does the conditional CALL instruction in the 8085 microprocessor take 2 machine cycles, when the condition is not satisfied?

texts: When the condition gets checked in the 6th T-state itself and is found to be not satisfying, why does it need the 2nd machine cycle?


texts: Resistance measurement and standard uncertainty

texts:
In a text there is a section regarding a basic example for uncertainty calculation of a resistor. Here is the related part:

Above the text uses the the accuracy of the current source and the voltmeter.

But if we were able to see the voltmeter's data sample measurements as below:

Is the text talking about B type systematic uncertainties given in device datasheets? And if we have the voltage data samples should we also add the standard uncertainty as well?


texts: Can an integrated circuit package contain more than one die?

texts:
I always see illustrations like the following one:

In the examples I saw always a single die from a wafer is inserted into an IC package. Is this always like this or can an IC include more than one die?


texts:
I'm trying to build the Circuits@Home USB Host Shield (based on the MAX3421E chip) from scratch; since I need to be able to power the Arduino using OTG mode, a premade board will not work for my application. To start, I'm simply trying to recreate the Mini Host Shield, but I'm stuck when it comes to getting the USB data transfer to work. The "board_qc" sketch passes every test when I run it on my homemade shield (connected to an Arduino Pro Mini 3.3V 8MHz) but then fails with "USB State Machine Reached Error State" when I plug in a Pluggable BLE dongle. I purchased a full size host shield for my Arduino MEGA 2560 to gather control data for debugging, and both it and the dongle work perfectly with the board_qc sketch. I've looked at the USB D+/- signals from both boards with an oscilloscope (see attached image link) and they're all but identical except for the tail end of the waveforms. What could be causing this problem, or is my problem somewhere else in the circuit?

My thoughts were:

1) too much capacitance (my 20 pF crystal oscillator + 2x39 pF capacitors vs. the specified 9 pF oscillator and 2x18 pF capacitors)

2) I've incorrectly shielded/grounded my USB Female A plug

3) Since I haven't had time to make a 3.3V->5V boost converter, I've been powering the USB port with 5V from my Arduino MEGA 2560 and grounding the MEGA to my circuit. Maybe the cross-grounding between Arduinos messes with the USB signals or shielding?

At this point, I'm almost entirely lost, so I appreciate any input! Thank you!

IMAGES:


texts: how to find Thevenin equivalent for circuit in black box

texts: if circuit on the left of terminal A-B are in black box and I want to find Thevenin resister by apply voltage source v1 to the terminal A-B measure current i1 then change voltage source to v2 and measure current i2. But R=v1-v2/i1-i2 = infinity because i1=i2. How can I find Thevenin equivalent circuit?


texts:
I am currently working on a hardware design, its function is to realize the Taylor series of cosh. In it, I need to use a multiplier and a divider. They are both 32-bit input and 64-bit output. I connected the multiplier and the divider as shown below, Convert 64-bit output to 32-bit
But in the simulation process, the system runs indefinitely at the division step, there is no valid output, and it can't break out of the loop. Is my divider connected incorrectly? If so, what should I do with the divider?
thank you very much.


texts: How to Shift the DC Level of Positive-going Op Amp Input Signal into the Negative Supply Region

texts:
I have a 1Vpp 1Hz repetitive arbitrary wave signal that resides entirely above the DC line. IOW there is no negative-going excursion. This is output from an LM358 inverting op amp buffer powered between +12VDC and ground (0V) rails.

I would like to feed this into an LM358 op amp with a gain of 10 that is powered in a non-standard way as follows. Its "positive" rail is set at 0V. The "ground" rail is set at -12VDC. There is a reason for this, and I do not want to change it.

When I connect the signal from the positively powered buffer op amp to the negatively powered gain stage op amp there is no output, presumably due to the DC level mismatch.

I have seen circuits that shift signals to a higher positive DC level, but not any that shift a positive signal into a negative region. Some level shift circuits also include a capacitor in the signal path, which I would prefer to avoid due to fidelity issues at such a low frequency.

Can someone please provide a working circuit that will enable the gain amp to output the arb wave signal so that it swings between about -10 and 0V? A trimmer adjustment for the DC shift would also be helpful in case I decide to use reduced gain.

This has been a persistent design issue which, due to my limited knowledge, I have not solved so far, either by inquiring online or hours on the bench. Any assistance to get me over this hurdle would be greatly appreciated.


texts:
I'd like to measure the power draw of my CPU. The way that seems the most straightforward to me is to cut into the ATX12V cable and put a shunt based sensor in the middle of the 12V line. Now in the 4 pin cable there are two of them and I assume they are wired in parallel to divide the current and still keep the overall cabling flexible. Naturally I'd cut both and wire up together and the terminals of my sensor.
Is there any non obvious downside or danger in that that would force me to install a current sensor on the each wire instead?
Apologies in advance for silly question, just making sure I don't miss anything.


texts:
In a BJT in common emitter configuration, what formula can you use to calculate the real \$V_{BE}\$ so that you don't have to approximate it as \$0.7V\$? The problem below asks for the actual value of \$V_{BE}\$ to see the difference it makes in the other parameters when \$V_{BE}\$ is not assumed to be \$0.7V\$. However, I can't find a way to calculate the actual \$V_{BE}\$ because it is usually just assumed to be \$0.7V\$.

1) Find the collector current, \$I_{C}\$ , base current, \$I_{B}\$ , and the output voltage, \$V_{OUT}\$ using \$V_{BE}=0.7V\$. State all necessary assumptions.

2) Solve for the real value of base-emitter voltage, \$V_{BE}\$ @ T = 300K, and the corresponding \$I_{C}\$, and \$V_{OUT}\$. Assume that the transistor parameters given were measured at 300 K. State all other necessary assumptions.


texts:
I'm currently building a theremin from the circuits form here:LINK
This uses Colpitts oscillators. However, when I've tried calculating the frequency, for example of the fixed-pitch oscillator (below), I've failed.

I've always got wrong results. I've read on the wiki that this freq us determined by two capacitor values and the coil. The actual freq is calculated by the well-know formula, and C is the sum-capacitance of the 2 caps in series, eg do repluss.
According to the schematics on the wiki, I'd need to repluss the 680pF and the 33nF caps. But that makes no sense! I've got a wrong freq value, and there's even 2 variable circuit to change the freq! And those are caps that aren't on the wiki schematic! So wiki says that they don't affect the freq, but I know that they does!

Did I understand some(or every)thing wrong? How can I calculate those freq's?


texts:
Normally this kind of thing wouldn't pose the slightest problem for me, but I am just trying to decipher the colours on a resistor.

Orange
Orange
Gold
Gold
Black

All the online tools tell me it's a 4-band 3.3Ω, but that ignores the 5th black band.

Yes, when I measure it it's 3.3Ω.

So how does the colour coding work for that then? Is it a 4-band with some mystery extra band? Or does that 5th band signify something special?


texts: Electrical reactance : physical inertia analogy

texts: Would electrical reactance and physical inertia be appropriate general analogies?  Each is a resistance to change.  I've thought of trying to construct a table of similarities between disciplines to speed and clarify understandings as courses seemed to converge on these evaluations.


texts: Interfacing Atmel Processor with i2s codec

texts:
I would like to interface an ATSAMS70 with a CS42L51 but this is my first time doing so.
The connection would be this:

MCLK - PCK2
SCLK - TK
LRCK - TF
SDIN - TD
SDOUT - RD

The thing is about the frequency I will work with. I will be using USB on the ATSAM, so I chose a 12 MHz crystal.
I would like to have a sample rate of 44.1 KHz but according to the datasheet I would need a MCLK of 11.2896 MHZ using the 256 scaler.

Would that be a problem? I mean, I would not be matching the 44.1 KHz but I think that's not that bad.


texts: This is not my circuit, but anyway, What are they?

texts:
Hello. This is not my circuit, but I found it on Google. I'm just a newbie student, so I have two questions. Please, help me. (I started studying electronic circuit last week)

1) The meaning of letters? I can see "A", "B" and "C". What are they?

2) V- and V+. What components are they? I can't find.

Thanks a lot.


texts: What parts to really keep out of antennas keep-out box, and which not so much?

texts:
I'm in the process of designing a pcb for a very small IoT device and need to get it as compact as possible. I'm currently considering these two smd antennas:

https://www.molex.com/pdm_docs/as/AS-47948-001-001.pdf

http://www.proant.se/files/user/Documents/Datasheets%20and%20appnotes/Upload%202018-06-08/Application%20note%20-%20OnBoard%20SMD%202400%20MHz%20rev%203.2.pdf

The second one is significantly larger, but it elevates the actual antenna away from the board and the documentation states that it might be ok to place smd components inside the block.

The first one is smaller, but the sheet shows that efficiency drops quite significantly when big metal parts are placed closer than 5mm to it.

I wonder, if I do have to place smd parts close to the antenna due to size requirements, which parts should I prefer to place there?


texts: Drive a Latching Relay with AC Coil from ESP8266

texts:
I have a couple of latching relays that uses AC coils (120 VAC, Finder 20.22.8.120) and I would like to control from a logic level DC circuit (GPIO from an ESP8266).
The relay´s datasheet states that in order to control it a 100ms pulse is needed(A1-A2) and that the coil consumes 54mA.
I tried to control it using a MOC3021 in a simple crude test circuit (I did not have the zero cross version at hand) but I destroyed two of them already on the first run (I did not add a snubber circuit in my tests).

Would I really need add a triac here for such a small current and a short pulse to latch the relay? What did I do wrong in my test? Any suggestions on a possible circuit?
Thanks in advance!


texts:
We are using the Spartan-6 FPGA from Xilinx.
VCCO banks of the FPGA are running at 1.8V.
We a have MIPI IC that outputs serial data, but at 2.7V.

Looking at the Specs for the FPGA, it seems to be able to handle up to 4V, at any Input.

Spartan-6 FPGA Data Sheet: DC and Switching Characteristics

I can't see that there is any clamping diode to VCCO for the individual banks. But just to be sure, is it ok to supply a 2.7V signal into a bank supplied with 1.8V ?


texts: Convert area of ASIC into kilo-gate equivalent kGE

texts:
Is there any resource/datasheet where I can find the kilogate (kGE) of the various CMOS technologies? Essentially, I have a bunch of ASIC circuits with their areas given in mm2 that I want to convert to kGE for ease of comparison. Does the kGE/mm2 vary from manufacturer to manufacturer or is it constant?

I did find some kGE/ mm2  equivalents given in some document, but the resource it cited is no longer existent so I can't vouch for the values provided.

Thanks for clarification.


texts: Transformer with opposite polarity in primary and secondary coil

texts:
What is the effect of having opposite polarity in primary and secondary coil?. Would this result in the current in both windings propagating in the same direction? If so, would the cemf from the secondary to the primary result in a negative voltage across the primary (change of polarity) and the primary then be a series assisting voltage source?

If this isn't correct could you please explain what happens.


texts:
I'm trying to simulate a circuit in Simulink but it's starting to get a bit messy due to the size of the circuit. I want to know if there is a way to set labels that I can input a signal into and reuse in other parts of the circuit rather than drawing long lines between them, similar to in LTspice (see image).

I am aware of the Goto and From blocks which seem to do what I want, however, it appears that this answer describes the only way to use the Goto and From blocks in a circuit. This would be fine if I wanted to simulate a purely digital circuit, however, my circuit is analog so there are many times that I am concerned about both the voltage and the current. Basically, I need a way to just move a signal from one part of the circuit to another while keeping all the information about the signal. Is this possible?
Just to clarify what I want, imagine I have this circuit below:

This is just a minimal example, not my actual circuit. Say I want to get rid of those long wires by "wirelessly" connecting the inductor to the rest of the circuit. We would expect the circuit to resonate. This would work in other simulation tools, but the Goto and From labels cannot be used to achieve this because there is no way for the inductor to return any energy to the left side of the circuit (if the labels go from the left side to the right side).


texts: Why we can't use step function to identify system's transfer function

texts:
The following screenshot is from this web page. The goal is to evaluate (or see if we can evaluate) the transfer function of a system by using the step function as an input. -Please refer the screenshot for the line of reasoning used in this example- .

Why we can't substitute s for jw  in the case of a step function (1/s)?
Any general rule(s) to check, if we want to substitute s for jw in a given function?


texts: 2N3904, Power Supply & FuncGen results on strange output on the scope

texts:
I was having trouble with a Collpitts oscillator output, it was distorted, so wanted to check if I am indeed in the linear region of the transistor, so I decided to use the func gen to check that.

However I am getting some strange reading on the scope that I cannot understand.

Attached is the schematic and what I see on the scope.

V1 is the power supply, V2 is the func gen. Func Gen config is 1kHz Frequence, 1V Amplitute, 2V Offset. The BJT is a 2N3904.

Pink is a probe at base, Yellow at emitter.

Any one can understand what am I doing wrong?

Zooming in, I see:


texts: Effective or minimal area of core to calculate losses?

texts: I've got a problem regarding the information given in coil's datasheet (PQ35/35: http://www.ferroxcube.com/FerroxcubeCorporateReception/datasheet/pq3535.pdf). There are two different areas given: minimal and effective. Which one should I choose to calculate losses?


texts: driving 4 RGB LEDs with PWM using MSP430

texts:
I have a project in which I must drive 4 RGB LEDs using PWM directly from the MSP430. They are separated in two groups of 2 LEDs (1 PWM connection controls one color element of two LEDs) which means I have 6 PWM connections to my uC (two for each color R, G or B).
My uC is a MSP430F5438, having a Timer B with 6 CCRs, therefore able to provide 6 PWM hardware signals.

 (sorry for the horrible sketch)

They must light all with the same color, possibly blinking with 1 second frequency or so.
My question is: how could I save as much power as possible managing/multiplexing the PWM signals and the two groups of LEDs? I thought about simple PWMs for all the 6 signals, or also using only 3 PWMs and multiplexing between the two groups.
I'm willing to use software ISR but I only have timer B available for that (to use together with the PWM). Should also be a quick operation due to the rest of the program being relatively heavy. The use of a LED driver is out of question.
Thanks.


texts: Does a transistor/FET dissipate more power with a freewheel diode?

texts:
My question is:
Does the transistor dissipate more power because of the freewheel diode? Ifso, why?

simulate this circuit – Schematic created using CircuitLab


texts: Signal interference in receiving antenna?

texts:
I’ve been scouring the interweebs for some insight into how electrical signals travel in a wire.
More specifically, I cannot wrap my head around how a receiving antenna works with hundreds if not thousands of electromagnetic waves interacting with it.
How is one signal able to be usefully extracted? Surely the movement of electrons back and forth would be influenced by all the electromagnetic frequencies hitting the antenna that their back and forth movement would no longer reflect a single (useful) signal?
My flawed understanding is based on thinking of the electrons in the receiving antenna as being analogous to a single conga line. Should I imagine the wire as many conga lines of electrons instead?


texts:
I laid my hands on a old power supply (Cisco ADP-29DB CC:B1/1, it came with an Cisco ISDN router many moons ago) and it has a connector with the following pinout:

\begin{array}{ccc}
\text{-12V / 100mA}&*&*&\text{-24V / 120mA}\\
\text{+12V / 100mA}&*&*&\text{-71V / 120mA}\\
\text{RTN}&*&*&\text{RTN}\\
\text{ROF}&.&*&\text{+5V / 120mA}\\
\end{array}

Most pins are clear, I guess 'RTN' is simply short for 'return' or GND. Which leaves one pin with an unclear marking:

What does ROF mean? An interesting detail is that the pin for ROF is a bit deeper down into the connector so it makes contact last of all pins, implying that is has something to do with hot-plugging the PSU.


texts:
In my design I have super capacitor (1.5 F) of maximum rated voltage of 5.5 V.
I am charging it to only 3 V. I am using boost converter to convert it to 3.3 V so that I can utilize the super capacitor at lower extent and at the same time it is not charged to higher side (near 5 V) so that stress is less and super capacitor life is more. boost converter can convert from 1-3.2 V to 3.3 V.

Is my designing is correct? Is using super capacitor down up to 1-1.2 V correct idea.


texts: Calculate transfer function of transconductance amplifier circuit

texts:
How can I model/calculate the behavior from Vin to Iout of the following circuit? (Credits of the picture go to Analog Devices):

Essentially, I am interested in the large signal response, such as a step at Vin.

Using the standard scheme for single loop feedback control systems, I could calculate \$\rm V1/V_{IN}\$, getting \$\rm I_{OUT}\$ from \$\rm V1\$ means then just using Ohm´s law.

Two problems here:

The transfer function should take the form
$$T(s) = \frac{\rm{A_0}}{1 + \rm{A_0}B(s)},$$

with \$\rm{A_0}\$ being the open loop gain of the opamp. I wonder, though, how to obtain \$\rm B(s)\$, which is essentially the transfer function form the MOSFET Gate to its source.
Since the MOSFET is clearly non-linear, I also assume that the transfer function is then only a useful information for a given DC bias point at the gate with an overlay of very small AC signal variations.

Yes, I can simulate the behavior very easily using some spice program, but at least I would like to compare simulation results with some analytical solution. So: Any ideas on how to obtain such as "large signal transfer function" that is valid during the input voltage step?


texts: How to create a cycling clock circuit from scratch?

texts:
I'm thinking about doing a project where I have basic components (hex inverter chips, breadboards, jumper wires, transistors, capacitors, etc.) and I create a simple computer. I've been trying to design a circuit that will have a clock (I don't want to use 555 chips for this challenge) and it will cycle through the outputs one by one, restarting once it reaches the end (see the truth table below).
T----IN----OUT1----OUT2----OUT3----OUT4
1----DC----on--------off----------off---------off
2----DC----off-------on-----------off---------off
3----DC----off-------off-----------on--------off
4----DC----off-------off-----------off--------on
5----DC----on------off------------off--------off
T represents time (probably 1T=10ms), the DC under IN means that it's just steady dc voltage, and I think the rest is pretty self-explanatory. I really don't know what something like this would look like, so anything would help. Thanks in advance!
EDIT:
Would the attached schematic work (not gates inserting energy to the circuit)?

simulate this circuit – Schematic created using CircuitLab
Quick input means just a quick burst of power (possibly a capacitor discharge) that sets off the whole circuit


texts:
I am studying this SPH0645 module for use with a STM32.

I started by checking the timing diagram of the I2S and compatibility between this module and the STM32.

The STM32L151 MCU is compatible with Philips mode which is the most used mode according to my research. I found a problem in the change of the pin data, as we see on the time diagram (here), the chagement (for the Philips mode) is done during the falling edge, while for the SPH0645 this change is done at rising edge. This is the SPH0645 datasheet:here

The SPH0645 timing diagram is not compatible with philips mode.
But I find in the adafruit site an arduino code with philips mode configuration,  I'm confused, and don't know how I can configure the STM32 to be compatible with this module.

You can find also the stm32 timing diagram on figure 257 page 775 in the RM0038 document:here

Can you confirm if the sph0645 module will work or not with stm32 (philips mode configuration), and why?

Thank you


texts: How can I fix 3D viewer problem on KiCAD?

texts: I am designing a circuit on KiCAD. I added new components to footprint with 3D models. When I open 3D viewer in footprint editor, everything looks fine however when i use the component and open 3D viewer on pcb wiindow, 3D models cannot be seen. I coudln't solve the problem. It would be nice to get some help. Thanks in advance.


texts:
I want to transfer data (only numeric values) between Arduino Nano and Arduino Mega 2560. I tried with my own code and tried with several libraries also.

Arduino Nano code

    #define RS485Transmit    HIGH
    #define RS485Receive     LOW

    #define DE_RE 12

    void setup() {
      Serial.begin(9600);
      pinMode(DE_RE, OUTPUT);

    }

    void loop() {
      responseToMaster();

    }

    uint8_t setNum = 0;

    void enaRX() {
      digitalWrite(DE_RE, RS485Receive);
    }

    void enaTX() {
      digitalWrite(DE_RE, RS485Transmit);
    }

    void responseToMaster() {
      enaRX();
      delay(10);
      if (Serial.available() != NULL) {
        setNum = Serial.parseInt();
        if (setNum != 0) {
          Serial.print("setNum = ");
          Serial.println(setNum);
          switch (setNum) {
            case 1:
              enaTX();
              Serial.println(1.2);
              //enaRX();
              break;
            case 2:
              enaTX();
              Serial.println(5);
              //enaRX();
              break;
          }
        }
      }
    }

Arduino Mega code

    #define RS485Transmit    HIGH
    #define RS485Receive     LOW

    #define DE_RE 12

    uint8_t setNum = 0;
    int setVal = 0;

    void enaRX() {
      digitalWrite(DE_RE, RS485Receive);
    }

    void enaTX() {
      digitalWrite(DE_RE, RS485Transmit);
    }

    void setup() {
      Serial.begin(9600);
      Serial3.begin(9600);
      pinMode(DE_RE, OUTPUT);
      delay(10);
      enaRX();

    }

    void loop() {
      sendRequest(2);
      delay(10);
      getResponse();

      delay(1000);

    }

    void sendRequest(uint8_t number) {
      enaTX();
      Serial3.println(number);
      //enaRX();

    }

    void getResponse() {
      enaRX();

      if (Serial3.available()) {
        while (Serial3.available()) {
          Serial.println(Serial3.read());
          setVal = Serial3.parseInt();
        }

      }
      //Serial.println(setVal);

    }

In this program Arduino Mega transmit a request to Nano. Then Arduino Nano receive it and transmit a value (response) according to request. Then Mega should receive the response.

Arduino Nano receive the value correctly and it transmit correct value according to request. But, Mega didn't receive the response.

What can I do for solve this?

I also tried with few different libraries. But those libraries are complicated for my application. I just simply need to transfer numeric values.
Is there any simple library for RS485 communication?


texts: Voltage calculation from RF rigid line directional wattmeter

texts:
I have a question about voltage calculation from RF rigid line directional wattmeter.
I have a device like below:

We tested it under 1kW coming from transmitter.
Schema like this:
|| Transmitter(1kW) >> RF rigid line directional wattmeter (picture is in above) >> Bird 43 model wattmeter >> 1kW dummy load ||

We took DC voltages from BNC mounted connectors like image 2.
While testing we took some voltage examples at 500W and 1kW with some elements like in the table.

I found a calculation  from Bird's documents as in the image 4 but I don't understand, still , how to I calculate RF power to DC voltage as to changing elements and its materials.

So my question again, how to calculate manually voltage coming from RF rigid line directional wattmeter?
If you have any questions, I will be here.


texts: AVR: why each Interrupt Vector occupies two instruction words

texts:
During my study of Atmega328 datasheet I found that each interrupt vector occupies two addresses and after searching i can not find why that.

That is a screen shot from atmega328p datasheet page 82


texts: Does Transistor NPN only amplify Positive charge?

texts:
I know my question might be a bit "stupid", as I am now a student.

I created a circuit like this ... But it does not work. (I mean the DC Motor does not turns.)

simulate this circuit – Schematic created using CircuitLab

(The DC Motor I can't find a real part, so I just simply made a box like that, sorry.)

Then, I searched the internet for help, and I found out the circuit shall be like this ... (I don't know weather this is correct or not.)

simulate this circuit

What does it mean and why should "put" the Transistor at Positive side but not at Negative side? Does Transistors only amplify Positive charge? Thank you.


texts: Is MOSFET threshold min and max only limits when it goes on and off?

texts:
From the 2N7002's data sheet, it can be shown than there is a minimum voltage threshold and maximum threshold and also a typical voltage threshold.

https://www.electrokit.com/uploads/productfile/40327/2N7000-2.pdf
Case 1:
When the MOSFET gate gets 1V, the MOSFET begins to turn ON(> 0%). When the MOSFET gets 2.5V, it's 100% turn ON?
Case 2:
When MOSFET get gets 1V, the MOSFET turns on to 100%. When the MOSFET crosses 2.5V, then the MOSFET remains 100% open until Gate is conntected to ground GND.
Case 3:
Between 1V and 2.5V on the gate, then MOSFET is 100% open. Above that, or under, the MOSFET is closed
Case 4:
When gate gets 1V, the MOSFET turns on. But above 2.5V, the MOSFET can be harmed and breaks.
Please, keep it simple and very clear. I have read lots of post about the threshold and every body talking about theory. I just want a clear answer what min and max and typical means.


texts: Application of the Sampling Theorem to a System

texts:
I have the following system:

$$G(s)=\frac{1}{10s^{2}-5s+2}$$

that I want to discretize. How do I apply the sampling theorem to a system so I can choose the correct sampling period?

Furthermore if I use a wrong sampling frequency how can I demonstrate that there is something wrong with the system? I know that we won't be able to recover the right analog data if something like that happens but I don't understand how I can actually "witness" it.


texts: Multiple radio in a small dimensional sensor node PCB

texts:
I'm planning to develop a wireless sensor node that equips dual IEEE 802.15.4 radios.
Although the board will equip homogeneous dual radios, both of them will operate at different channels.
Regarding the design, however, I'm worrying about any possible bad correlations between the radios which will be placed in a relatively small dimensional sensor node such as 4" x 2".

Is is possible to practically use dual radios in such a small dimensional board?
If possible, what special care should I give the board in layout stage?
If possible, I'd like to use a chip antenna in order to save space in a board.
What is the pros and cons of a chip antenna?
Can it be a proper decision? What special care should be taken for antenna selection?


texts: What would an inductor be doing here, and can I replace it with a jumper?

texts:
I have a small board camera to fly first person view on a quadcopter. The camera outputs a PAL/NTSC analog video and is powered off of 12-17 volts (I'm assuming this is regulated)

During a crash, what appears to be a surface mount inductor came off of the board, and the camera doesn't work anymore. The inductor is close to a surface mount SO-23 component marked A7 (a high speed two diode package) and a bunch of discrete resistors/capacitors.

My research turns up surface mount inductors have very, very small values (in the tens of nH). It would be too small for a switching regulator, and there isn't any other reason I can think of for there to be an inductor on an analog camera.

Since the loss of the inductor, the camera does not output anything. Since this inductor is likely of a small value, can I replace it with a short loop of wire? Or is it a serious risk to assume that the exact value of the inductor is unimportant?

Update: jumping the pins did as expected, the camera turns on but is very prone to interference. Since it's right next to a 5.8g receiver, four brushless motors modulated at 24khz and a bunch of other stuff, it picks up a lot.
So that means that it was a ferrite bead. Can I replace this with a loop of wire wrapped around a ferrite ring, or is that long bit of wire still going to pick up garbage?

Update 2: I dismantled a CD-ROM drive and took the ferrite bead. The camera still turns on, but if anything the interference is worse than just with a jumper. I'll try a proper inductor next and see what that does.


texts: I am looking into USB 2.0 Ports in Host PC and LapTop computers. I am designing a device that will need to draw as much current as possible. Does anyone know how common these ports require enumeration and limit the current to 100mA before allowing the full 500mA+ supply ?


texts:
I've been trying to test my Peltier moodule (tec1-12706) with 2 1.3V batteries (2.6 in total in series) connected parallel to the module..

|+ -| ------|Peltier +|
|- +|-------|Module  -|

The batteries are full and show 2.6 volts.
But when I measure the voltage drop on the Peltier it shows only 2 V and it draws only 200 mA max (according to TEC1 12706 datasheet it should draw 1 A.

Am I missing something?


texts: What can happen to a relay at temperature outside of its spec?

texts:
I am building a system for measuring some parameters in a climate chamber. The test runs from -55 to +125°C. I need to switch some signals between multiple devices under test using relays. I want to avoid using exotic or expensive parts.

I can find "generic" relays rated from -40 up to +105°C. I will be switching low voltages (below 12 V) and low currents (below 100 mA) most likely with a relay rated for 230 Vac and 16 A. Switching speed is not important.

I know that the plastic can melt, but I wonder what else can happen to a relay when it is used at a higher and lower temperature than specified?


texts:
Assume the voltages sources(InducedV1/V2/V3) are created by an inductor/or a strong magnetic field changing rapidly(or in anyway) the PS would power the load, however, there are induced-EMF's V1 in support while as  V2/V3 in opposition. Since they are parallel and connected in series, I believe they all cancel out, the remaining voltage is 20V and the load current drawn is 0.2A from the power supply.

I was wondering, is the diode(D1) blocking any current? In the parallel sub-circuit of InducedV1 and the diode and the wire?

simulate this circuit – Schematic created using CircuitLab


texts:
I tried to DIY to make a custom cable like the one in link:

https://www.fiio.co.in/collections/accessories/products/ml06-micro-to-micro-usb-data-cable?variant=12395665326185

I bought 2 normal usb to micro cables, cut them and soldered by matching colors but it does not work.  I also tried swapping white and green.

Am I missing something?


texts:
Description

I have the following diagram in which a switch connected to a 5V source should control two PNP transistors. I've spent a few hours trying to further understand PNP transistors to better understand what I am doing wrong, but I still can't seem the get anywhere. The logic, as I understand it, should be as follows:
SW1 is not conducting = Q1 has emitter connected to GND and is conducting = Q2 cannot connect the emitter to GND and thus is open = Vout is 0V.

Simplified logic:

SW1 not conducting = Q1 conducting = Q2 not conducting= Vout 0V
SW1 conducting = Q1 not conducting = Q2 conducting = Vout 3.7V

simulate this circuit – Schematic created using CircuitLab

The problem:

The problem I'm having is no matter what the state of SW1 is, Q1 seems to be at 3.7V on the collector pin. Curiously, Vout is also at 3.7V.

Thank you in advance for any help!


texts: DC Motor with coil inside a rotating magnet. How does it work?

texts:
I have seen the following patent online.

And I was wandering how that motor works. It seems that the vector
of the cross sectional area of the coil is parallel to the vector of
the rotation of the magnet. From a basic physical understanding that
I have, it seems that the coil cross section cuts through the same
amoung of flux regardless of the rotation of the magnet. If so how
does the magnet keeps rotating and does not just align itself to the
magnetic field of the coil?

On the left side of the picture we can see the rotor that has a magnet embedded in it. On the right side of we can see the coil windings. The rotor pin is inserted in the bore that is created through the coil in a way that the magnet
can be rotated with the coil inside it remaining stationary (imagine that the coil is mounted in a bigger structure). The four plates that sandwitch the coil are iron plates but are not in contact with the coil (since the coil is electrically insulated by its plastic mount) or the magnet.


texts: Is there a specific name for this phenomenon?

texts: In my Slayer Exciter circuit, the current from the battery flows into the primary coil (with four turns) and therefore, a current is induced in the opposite direction in my secondary coil. This current flows into the wire coming from the base of the transistor and opposes the current flowing through the 22k resistor. Is there a specific name for this?


texts: I'm wanting to use an ethernet switch/Phy LAN9303 to output 2, maybe 3 ethernet signals. I know that I need a 25MHz clock, supporting resistors and caps as well as the magnetics, but I want to know if there's a way to get around having to use an FPGA or processor for the MAC - or do I have the concept completely wrong? Is there an IC that has the PHY and MAC (and maybe the switch) all in one? Thanks


texts: Which cells to use in SG13S library with Cadence Virtuoso?

texts:
I am using Cadence Virtuoso with SG13S library and I am confused about which cells I should use from the library for NMOS/PMOS transistors, resistors, capacitors and inductors. There are cells like "nmos" and "rfnmos", "rfnmosHV" and so on. The same is for capacitors. What do all these cells represent i.e. what are the differences. There isn't a tutorial for this library or any explanation in the IHP user's guide.
Also what are the most important simulations I should run in Cadence when designing a RF power amplifier?


texts: Using .lib module in a Verilog source code

texts:
I'm trying to write a Verilog code using a module in a .lib file, and compile the code using Synopsys design compiler. I compiled a memory module using my memory compiler, and it produced a .lib file. I think it contains a compiled memory module, but I cannot find how to use it in my Verilog code.

Using an analogy with C/C++, I think the .lib file is supposed to have something like a header file, so that I can include the header and use the module in my Verilog code. But it seems like that the .lib file don't have such header.  Could anyone explain how to write a Verilog code using library modules?


texts: Is there a way to increase space between connections and ground planes in eagle?

texts:
The below picture is a screen shot from eagle. The red shade means gnd.
Is there a way to increase the space between where the connection goes and the red, gnd, plane?
I'm paranoid I'm going to solder over the small gaps shown and cause a short to gnd.
Is it possible to increase that space?


texts:
I have a board which is something like this:

(available on eBay)

I know I have to buy a socket, but how do I solder the connector onto the board?


texts: Arranging multiple board files in single board file

texts:
I am going for PCB array manufacturing in order to save some costs. I have totally designed 3 different board files and I want to combine each of them side by side.

Can somebody tell me the steps in achieving this?

I am using Allegro 16.6V

Thank you,


texts: IRS2110 IC & high side floating supply voltage - H bridge

texts:
Hi So far what all IC or micocontroller that I have used that use to have VDD = 5V & GND = 0V.
Now I am working on an H-bridge circuit using IC driver IRS2110 for motor control.

What exactly we mean by these terms, and what are there role :

High-side floating supply voltage ?
High-side floating supply offset voltage ?
What exactly the bootstrap capacitor is doing over here ?

Can someone help me to understand above concept.

Edit link :--
http://www.irf.com/product-info/datasheets/data/irs2110.pdf

In my half bridge circuit :---
VCC = 15V
Vdd = 3.3V

How will value of HO & LO will vary with HI & LI ?

HI pin 12 : 3.3
LI pin14  :0
Then I observed 8V at Gate

However when I kept HI:0V.
Then I observed 14V at gate. ( it should show low here ).

How will i have to trigger this IC to drive H-Bridge ?

Please suggest.


texts: design a password using sequential circuit

texts:
Design a sequential digital circuit that detects a 4-BCD digits password. Assume that you are using # as an enter key where the password will be decided, by your circuit, to be right (output =1) or wrong (output = 0). Assign an unused BCD code for #. Assume that the password is 3542

I tried to solve it by converting each one of them to BCD , then I made the state diagram . But the the problem is I don't know how to do this state diagram correctly . Does anyone have any idea ?

By the way I don't need a code , I want to know theoretically what happens


texts:
Given that I'm using the following circuit (adapted from this forum post):

simulate this circuit – Schematic created using CircuitLab

Which takes a 24V (Nominal) input and converts it over to 3.3V for an input on the Raspberry Pi Compute module. I'd like to have an LED present on the board to signify that the input is on.

The issue is that I'm using the LM2676SX-3.3 to power the 3.3V, which provides a maximum of 3A, and I need to have 128 of these LEDs in the system. At the above values, each LED will consume 8.7mA of power which is 1.3A.

I'd like to power the LED from its own 3.3V source (probably another LM2676SX-3.3), but I'm not sure how to modify the above schematic to use a separate supply?

The other option is to power the LED on the 24V side, but it needs to support a voltage range from 12V to 32V as the input. I'm not concerned with a particular brightness as long as the LED is viewable.

So how can I modify this to use a separate source for D3 (considering I need to duplicate this 128 times, so low part count) or how can I run D3 off of the 24V side with a wide input range and not turn the enclosure into a small heater?


texts: Programmer /Debugger for freescale kinetis series

texts: I want to use frescale MK10 Device for my Project, the Cost of Programmer debugger is very high , so i Want to ask is there any low cost P/D ot any hack available with any system so that i can use that as P/D


texts:
Link1: http://ww1.microchip.com/downloads/en/appnotes/00954A.pdf
Link2: http://arduino.cc/playground/Code/ACPhaseControl

Simple version:  I want to use a picMicro 5v microcontroller combined with the figure 10 circuit from Link1 (Shown below) and a circuit similar to Link2 for motor control.  It has to control 2 AC motors at 4 amps each (but the programming will make sure only one motor can turn on at a time).  I can't afford SSR's to handle that (according to digikey) so I'll go with triacs instead.  What parts do I need?

simulate this circuit – Schematic created using CircuitLab

Long version:
I'm building a new control board for a pop-up range hood.  I plan on combining the figure 10 circuit from Link1 (transformerless power supply with safety considerations) with a phase control circuit similar to Link2.  The actual parts from the phase control circuit won't work, as my range hood states a usage of 4 amps.  I don't see how the blower can use that much, so I suspect it is a rating if both the blower and the lift are running at the same time, but I can't say for sure, so each of my triacs have to be rated for 4A and I'll just make sure by programming that they aren't driven at the same time (and it will be fuse protected as well).  One of the triacs (for the lift) will only be driven full-phase, while the blower will be driven at 3 speeds.

I've done a lot of electrical work, so that's not an issue, and the programming won't be an issue, but I haven't done much electronics work, so reading the numbers are actually giving me the most problems.  I'm going to use one of the picMicro chips running at 5v.  That means the output pins will be at 5v, right?  But the max gate voltage for any of the triacs on digikey are 2.5v.  Do I need a voltage dropper to get the output pin voltage to 2.5v?  One of the triacs I'm considering is part L6004L3-ND at digikey.  Digikey's chart says it uses 3ma gate current, but am I reading the data sheet right that it could draw up to 1.2A at the gate?  Also, that triac isn't opto-isolated, but still appears to be isolated to 2500v?  If that's the case, do I need an opto-isolator?  Basically, I need to know which parts will go together, but I'd also like to know how I'm supposed to read these datasheets and such so that I can figure it out for myself next time.


texts: L5973 (step down) used in constant current oscillates

texts:
For a couple of days i'am playing with a L5973 dc - dc converter whith I want to convert to a constant current driver for 5 or 10W LED's. It kind of works but I get some oscillations in audible range. I want the current to be controlled with PWM signal from microcontroller, but now i use a potentiometer to set volatage on PWM flag. I'm using LM358 opamp.

I also find this document, but they don't use opamps, so the current is controlled by resistor value, and i want to control it via PWM. Or maybe is there a way to add this feature there?
https://www.st.com/content/ccc/resource/technical/document/application_note/f3/ee/83/89/e2/53/4a/7a/CD00072891.pdf/files/CD00072891.pdf/jcr:content/translations/en.CD00072891.pdf

Here is the schematic: I can also post screenshot from oscilloscope if it will be helpful.

Thanks for replies and soryy for my english, I'm from Poland. :)


texts: Both UPS and speaker end up having the same electrical hum, how come?

texts:
I have a speaker (Logitech Z623) which was driving me crazy with a low intermittent hum. In order to get to the root of the problem, I attempted multiple solutions. In the process I discovered that my UPS is making the exact same hum when on AC mains.
In order to rule out the UPS (APC SUA1500I), I plugged both of them directly into an extension cord and both of them hum in sync with each other (the speaker is not plugged into the UPS). I tried plugging the speakers in different outlets across the house and they still make that exact same hum (same tone, duration etc.)
Initially I assumed that capacitors in my speaker as well as the UPS are degrading but there's no explanation for the exact same hum (and of the same duration) in both the devices.
So this leaves my electrical wiring as the sole suspect. Is this possible? What should I go looking for next?
What I have tried so far -

monitored the voltage (230 V), frequency (50 Hz) etc and everything seems to check out.
tested my speaker inputs and the hum is still there without any inputs connected.
tried turning off all heavy electronics in my house
tried turning off the lights in the room
turned off pretty much everything in my house
eliminated the building elevator as a probable source. There's no discernible pattern between the two.
flipped all breakers in the house except the one powering the UPS and speakers. The hum is still there.

P.S. Adding some more details -

Plugging speaker into UPS and switching off the mains eliminates the hum.
UPS has a 3-pin plug while the speaker is only 2-pin.
The hum goes away in the middle of the night. This has happened 3 nights in a row. I can't help but feel that is coming from outside the house. Well, I spoke too son but the duration between the noisy events is way longer in the night than during the day. 1-2h compared to 3-5 mins in a day.

PPS. Attaching a recording. This is a very faithful recording to what I'm hearing. Tested it across the speakers, multiple headphones and phone speakers. The recording is made at 96 kHz and 24-bit (the highest possible setting in my Zoom H4n)
Update - Recording #2 - https://www.dropbox.com/s/isquus515alyz3f/Speaker%20noise%202%20-%20STE-000.wav?dl=0
Starts at 24s and ends at 55s.
OLD RECORDING - https://www.dropbox.com/s/1q0v0ajv1f8dq7g/STE-000.wav?dl=0
ocrdu has provided with an analysis of the audio file:

These are two periods of the noise; the periods are repeating at 100Hz with slightly varying DC offsets. From the comments: The spectrum shows a 5kHz signal with its harmonics (10kHz and 15kHz).


texts:
I am trying to send a string from a Huawei MU509 GPRS modem to a Linux server over the internet. I am using an AT command tester to simulate AT commands. After giving the
ipinit (AT^IPINIT="airtelgprs.com") and
ipopen (AT+IPOPEN=1,"TCP","109.165.220.17",7869) commands, the module indicates that the data connection was established successfully. While sending data using the ipsend command (AT^IPSEND=1,"cgfcgcgs,1100.8683,07656.7037"), no data is received server side.

I also checked the server side program, and it reports no errors. When using a piece of software called Packet Sender, I got an empty response. I've searched some hours in net and I haven't got any possible solution. What is the issue with the module and/or server?


texts: what chip does thetileapp BTLE tracker uses

texts:
I am working on some BTLE prototypes,
I saw this tracker http://www.thetileapp.com/

what chip would this "tile" be using?

im going to be playing with the TI SoC CC2540 http://www.ti.com/product/cc2540&DCMP=LowPowerRFICs+Other&HQS=Other+OT+cc2540

but still to big to use as a tile.

What other option would  this gadget use?


texts:
I need to use a clock signal of 50% duty cycle of 2.5MHZ and I should make a circuit which phase shifts it to 90 degrees.

So now I have four signals...( **  PHASE SHIFT WITH RESPECTIVE CLOCK SIGNAL)

→ signal 3 ( 180 DEG  phase shifted) is just the inversion of the signal 1 ( 0 DEG  phase shifted)

→ signal 4 ( 90 DEG  phase shifted) is just the inversion of the signal 2 ( 90 DEG  phase shifted)

I could easily do with D flip flops, processors, but I'm interested in just using basic components (transistors, resistors, gates, etc.)

In the end, I solved it with flipflops. thank you everyone


texts:
We have the diode circuit in the figure. The diodes are real and Vd=0.7 Volt
I have to find the currents in the diodes and in the resistances R1 and R2

So I apply KVL in loop 1 and I have

-20+ 0.7+0.7 +I2*5.6=0

Here I find that I2=3.3 mA.This means that the current through D1 is 3.3 mAmper.

I apply KVL to the second loop. -0.7 +3.3*I1=0  so I1=0.212

The current through D2 is I2=I1+Id2 so Id2= I2-I1 =3.088 mA

So the operating point of D1 is (3.3 ; 0.7) and of D2 is (3.088; 0.7)..Is this correct?


texts: Why my solenoid valves open only if power is turned on at last?

texts:
I have a set of eight 48Vcc solenoid valves that I'm controlling using an Arduino. The open and close signals are sent using the Arduino's SPI lines, which are connected to a circuit composed by a 74HC595 shift register and two ULN2803. I have a 48Vcc switching power supply that I use to power the solenoid valves. The schematic is:

In the ULN2803 each solenoid is connected to a group of two bases and two collectors in order to allow a higher current limit on this component.

If I don't have any solenoid valve connected to this circuit and I send the "open solenoids" signal from the Arduino everything is ok. I get 48Vcc between all the connector's positive and negative pins (e.g.: between pins 1 and 9, 2 and 10, 3 and 11...). But if I have the solenoids connected to this circuit a strange behaviour happens.

If I turn on the 48Vcc power suply, turn on the Arduino and send the "open solenoids" signal, nothing happens. In this scenario when I measured the voltage between the connectors pins I got various values, all of them lower than 48Vcc. Sometimes the voltage was floating, without setting on a specific value.

But if I turn on the Arduino, send the "open solenoids" signal and, at last, turn on the 48Vcc power supply, all the solenoids open. Once the valves are opened if I send a "close solenoids" signal and right after that a "open solenoids" signal nothing happens again.

In short, my solenoids only open if at first I send the open signal and then I turn on the 48Vcc power supply. Does anyone know what could be happening?


texts:
So I'm using EAGLE for the first time, and I have zero experience with any EDA software. I've completed a schematic and would like to proceed to design the board layout, but I am stalled by these warnings which make zero sense to me.

Whenever I add and connect a power supply element I get these warnings. I'm not sure why, and thus far I have seen people saying that this is a stupid side-effect of how EAGLE handles its nets. So the question is; are these warnings something to be taken care of in some way (if so, how?), or should I simply ignore/approve them? Please advise.

Bonus question; I know a bit about electronic circuitry, but I am not an electrical engineer. Do you have any tips and tricks that I just be aware of in large PCB designs? I.e. I have added decoupling capacitors of 0.1uF across any and all IC power supplies. Are there more things like this to take into consideration? Any information is welcome and helpful :)


texts: The classic 1N34A Ge Diode has a Vf of 1V... how could a diode with such a high Vf work in crystal sets they were packaged in?

texts:
Back when I was younger I got a crystal radio set kit which included a 1N34A Ge diode (as far as I can remember, I don't have it anymore). I wanted to build one again recently and all I had a was a Schottky diode with a Vf of around 0.4V at 1A. I heard no sound from it through a piezo buzzer pressed against my ear and figured it was maybe because of the diode, so I looked around for the datasheet for the 1N34A to read its characteristics. It lists Vf as 1V at 5mA.

It is my understanding that Ge diodes were the choice for crystal sets because their low Vf does not load the tuned circuit. Perhaps I am misunderstanding the datasheet? Thank you.


texts: I am using a SN74HC165 Shift Register to read the signal from some switches. With the SN74HC165 Integrated Circuit near to the microcontroller the circuit below works perfectly. But physically I have to put the microcontroller at a distance of 2.5m from the IC. With this distance I'm losing some data, mainly the K8 signal. I am using pull-up resistors with the value of 10K. Would anyone know a way to improve this signal and avoid data loss at this distance?


texts: Possibility of series connected LIPO batteries for running stepper motor

texts: I have project where I am using a motor driver DM860A2 to run NEMA 34 85 kg-cm stepper motor. Currently I have used a transformer to supply 48V AC during testing. I have with me four 2200 mah 11.1V LIPO rechargeable batteries which I plan to use as a power supply for the motor driver by connecting them in series providing 44 V DC. But I have concerns regarding the feasibility of the battery circuit and should I take any safety precautions.


texts: Finding the address of structure knowing the address of one of it's members in C

texts:
This sounds like a little too far fetched, but is there any possibility to find the address of a structure, if the address of one of it's members is known? The struct itself contains different data types, and is 2 bytes aligned. I am working on an embedded target, with DIAB compiler.

Here is the end application. There is an external device with direct R/W access to the RAM memory. If this device modifies a memory location that happens to be within a structure, I need to know which structure was it(or it's starting address) for some processing to be done later.

Update: A direct solution to this problem is difficult. The answer with some relevant discussions regarding the issue has been chosen.

Thanks!


texts: Advice for Switching High Current Motor (Relay vs. SSR vs. Mechanical Switch)

texts:
I'm working on automating an irrigation system which has a large well pump that uses 24-32 volts, directly from a solar array. This was previously switched by a light switch manually, but after my uncle's death, I'm managing it remotely from 4 hours away, so I'm looking for a reliable solution.
I'm hoping to manage it remotely via Raspberry Pi or Sonoff (ESP8266) controller. The pump will pull up to 24 Amps, but typically uses about 12 Amps. The power is nominally 24 volts, but is unregulated and can peak at 32v.
I've previously used a 60-amp rated SSR, but this failed closed, likely due to being in an enclosure, and lacking thermal paste/padding between it and the heatsync. An emergency replacement also fried a Sonoff with 3 10-amp relays in parallel (specifically the PCB traces).
So I'm now weighing three options:

Use a mechanical relay, rated for 40+ amps, which might require a smaller relay to activate from the 3.3v Pi GPIO. My concern is with a high-current inductive load burning it out due to break-arcing. Should I consider Contactors instead of relays for high-current DC?
Use another SSR, but keep it outside. This would need to handle 110°F (43°C) ambient conditions and not burn out like the previous one.
Use a linear actuator to mechanically switch the good old light switch. This is a bit hacky, but could work reliably. The advantage of a switch over relays is that the pump is "on" for 8 hours at a time, typically switching on/off once a day.

Is there a such thing as a digitally controlled discrete switch that doesn't have the waste energy associated with a relay or SSR during high duty cycles?
The pump will run all day except on cloudy/rainy days, in which the battery bank needs full solar power, hence the long duty cycles, to which a switch seems better suited than a relay.
Any advice about the choice between Relay/Contactor, SSR, or actuated switching would be very helpful, including factors I haven't considered. Thanks!
As a reward for your reading this, here are some pictures of my previous attempts, minus missing magic smoke!


texts: What is the function of zener diode in the fig and power dissipated in zener at No load condition?

texts:
If supply is producing max 20mA at 9V what will be the value of Rz?
To improve the current capability, how can we use NPN transistor instead of diode here?

Ans: According to my understanding, it is step down transformer and the output of the circuit should be 9V DC. Zener diode is performing the function of the voltage regulator providing constant 9V at the output side.
Power Dissipated at zener, P=VI=9*20mA=0.18W
To find the value of RZ,
at no load condition all 20mA current will flow through 9V zener diode
12.5V - 9V/Rz = 20mA
therefore Rz=175ohm

Stuck with the second part where ciruit could perform same operation with NPN transistor, need help.
Thank you


texts: Can a multi meter measure a potential static discharge?

texts: Can a multi meter measure a potential static discharge like between hands and laptop before I open cover and replace a battery? Like if I touch laptop and my hands with the each two probes of a multi meter, is it possible to read a DC potential voltage and determine if it is enough to cause a static discharge? Then we know that if we have to touch ground before touching laptop in the scenario of no static bracelet or failure of it.


texts:
I am designing a system that uses RF to probe the nonlinearity of a target. It works as follows.

Transmitter sends out 2 RF frequencies, such as 900 and 910MHz.
The target/reflector has a nonlinearity, this causes the generation of 920MHz (among others).
The reflected signal (900+910+920) is received by an antenna, and mixed with 919.9MHz LO to generate a 100kHz signal that has amplitude proportional to the 920MHz signal. A low pass filter is applied to reject the higher frequencies.

My question is this: the input to the mixer is 900+910+920MHz. I only care about the 920MHz signal from the reflector in part 2. Will the 900+910 MHz that goes into the mixer be mixed and generate a huge 920MHz signal that swamps out the reflected 920MHz? What are your thoughts on this?

A key part of all this, is that I am hoping to avoid bandpass filtering at 920MHz before the mixer. I prefer to do this using the low pass at low frequency.


texts: Embedded C - Most elegant way to insert a delay

texts:
I'm working on a project involving a cortex-m4 mcu (LPC4370).
And I need to insert a delay while turning on compiler's optimization.
So far my workaround was to move up and down a digital output inside a for-loop:

for (int i = 0; i < 50000; i++)
{
     LPC_GPIO_PORT->B[DEBUGPIN_PORT][DEBUG_PIN1] = TRUE;
     LPC_GPIO_PORT->B[DEBUGPIN_PORT][DEBUG_PIN1] = FALSE;
}

But I wonder if there's a better way to fool GCC.


texts:
I've this formula:

y = AB + AB'C + A'C

I've to build a circuit with only a 2:1 mux and a OR port.

I've done the truth table and k.map, but i've not idea how proced.

EDIT:
@jonk Thanks for your time and for an exaustive and complete answer. It's very usefull! Atm i've done this:

Y = AB + AB'C + A'C
Y = AB + C(AB' + A')
Y = AB + C( (A+A')(A'+B') )
Y = AB + C(A'+B')
Y = AB + C(A'B')
Y = AB + CA'B'
Y = (AB+A'B')(AB+C)
Y = AB + C

Then my circuit is:
Mux 2:1 with input A & B
Mux output enters into a OR PORT + C

simulate this circuit – Schematic created using CircuitLab


texts: What happens when you keep increasing frequency of an RF signal?

texts: I know that radio waves occupy the lowest portion of the EM spectrum and gamma rays occupy the highest. I'd like to know if increasing the frequency of a radio wave can produce visible light and maybe eventually, gamma rays. I've searched a bit but couldn't find any definite answers. Are all the separate radiations distinct (can only be gotten from separate sources), or can you obtain them from each other by raising or decreasing the frequency as you need to? Are there limits to how high you can raise RF frequency (in cables, free space, etc)?


texts:
My question is this one, how the firsts ic's were produced.

The first IC was produced by jack kilby: http://en.wikipedia.org/wiki/Jack_Kilby

Now exists advanced machines, that do all the work. From cutting the wafer to make the ic.

I would like to know what type of machines they used to fabricate the IC, what techniques they used, etc.

If someone could explain me i would be very grateful


texts: DC Motor Control with PWM and Polarity Switching

texts:
I want to be able to rotate the motor both clockwise and counter clockwise while also controlling the speed of rotation of said motor. This is a small dc motor and the whole thing is running on 5V the motor draws about 2A when its straining. Less under normal operation (about 1A).

Is the diode labeled motor diode protecting my mosfet from potential damage? If the motor is spun my some force do I need any other protection to prevent this circuit from being damaged?

simulate this circuit – Schematic created using CircuitLab


texts: Active filter - oscillation and incorrect operation

texts:
I have a noisy and low amplitude (0-50mV amplitude) signal from a hall effect sensor (TI DRV5053) that has a ~1V DC offset. The signal will be in the range of 95-105 Hz and is used to determine the amplitude of piston motion using a small magnet.

I needed to get this into something useful for our data system so I went to the AD website and generated a bandpass filter with a gain of 100 and narrow passband around 100 Hz. THis would get rid of the DC offset and give the signal a good amplitude to connect to a data system and remove the unwanted high frequency noise.

I sloppily soldered two of these active filters together on a small proto board and while one works exactly how I expected it to, the second one does not. Whenever I connect the function generator with a 20mV 100Hz sine wave there is a high frequency oscillation the input at about 350 kHz, however the output is oscillation free and at about 1/2 of the amplitude that I expect.

Unfortunately I lack the experience necessary to deduce where the problem may lie. I have inspected everything I could and it looks like it's connected properly. Because the output is not oscillating I feel like that means that the second stage of the filter is working and the first stage is not. There have been brief moments when connecting the input signal where there was no oscillations but it quickly starts oscillating again. I haven't been able to consistently reproduce this.

Does anyone have any idea about what might be causing this oscillation and what I might want to investigate in order to fix this.

Here are images of the working and non-working filters on an oscilloscope.


texts: Create a fake depth encoder signal on a surface system?

texts:
I am trying to create a test box which will do away with the actual depth encoder as it is awkward to have out all the time the encoder is similar to this: http://www.encoderonline.com/UK/Data-Sheets/Incremental/Data-MXE.htm

The unit it is connected to outputs 9V DC on between the encoder + and - for both the A and B signals.

I would like the circuit if possible to be able to change direction


texts: Suitable amperage for charging 12V 12Ah DC lead-acid battery

texts:
If I have a 12V 12Ah DC lead acid battery, how to calculate the suitable amperage for the charger? And volt too?

Do I need 12V 2A charger? Or can I use 12V 4A for less charging time? Or this destroys the battery?

I want to know how to calculate this because I have 12V 18A battery too


texts: Control System how to get rid of Steady-State Error For Ramp Input

texts:
I am supposed to get rid of the steady-state error for ramp input for this closed loop transfer function

Transfer Function of Closed Loop ^ T(s)

Closed Loop ^

Since the closed loop is equivilant to the Open Loop below

Open Loop ^

I found out that the G(s) is ^

From as far as i know to get rid of transfer function i have to turn G(s) to a type 2 system(by adding another pole at the origin) since there is no steady-state error for ramp input for type two system so I tried the method (1) below

method 1 ^

But using MatLab I am unable to get the result that I desired which is zero steady-state error for a ramp input (not sure if code error or what)

    num=[198025];
den=[1 445 0 198025];
t=0:0.005:10;
r=t;
y=lsim(num,den,r,t);plot(t,r,'-',t,y)

Matlab script ^

But the result I got is something like this

Matlab Result ^

Instead of something like this (note ** that is just some example I found online on how a type two system should be with ramp input)

Expecting Pattern ^

I found out there are positive poles but i am not quite sure what to replace the 1/s with to ensure that there isnt any positive poles while removing the steady-state error for ramp input as well

and also is there a way to get rid of the steady-state error for ramp input by cascading another function at the end or the back of the Transfer function( Method 2 ) without altering the original circuit (the original closed loop transfer function)?

something like this ^ (which is the way I am supposed to do)

Any help would be wonderful Thx.


texts:
I have been a hobbyist solderer for about 6 years now, and my skills are very proficient.  I have always used lead solder because my experience with lead free solder is awful.  But I'm going to college in a few months and I just upgraded to a very nice digital soldering gun because I am making and selling aviation cables online.  I am hoping to expand my little cable business in college and if I am going to be soldering often I would like to get away from lead solder.

Are there lead free solders that can be used as easily as lead solder, and if so, if there really any health benefit from lead free solder?  Are the fumes from solder toxic, and does lead free solder solve that problem?


texts: Read Positive and Negative Voltage in Arduino

texts:
It's a long story, but I took apart and RC car and wanted to have the Arduino use analogRead() to get the values of my motors and steering. I have measured with my multimeter that the voltage in my remote controlled car ranges from -6v to 6v.

However, the Arduino only supports reading from 0v to 5v maximum. Is there a way to convert the -6v and +6v to 0v and 5v? I have heard that it could be done using an Op Amp. Some people have also told me to use a voltage divider. In other words, if I was not controlling the RC car, the Arduino should see 2.5 volts.

Anyways, I am not exactly clear about how I would do this. Can someone please recommend me an appropriate Op Amp with a circuit for this specific scenario?

OR, if possible, can someone show me how to read the negative and positive voltage using two Arduino pins? For example, if there is -6v given, then Analog Pin 0 would return 1023. If there is 0v given, then both Analog Pins 0 and 1 would say 0. And if there is +6v given, then Analog Pin 1 would return 1023. How can I make a circuit that will work like this?

I appreciate it if you have a circuit diagram for this. Thanks!


texts:
So I've been looking at this problem for a couple of hours, and I'm pretty sure I need to use finite state machines or at least some kind of memory elements to solve it... it goes as follows:

  "A producer has asked for a system that packs beers , which we want to work the following way: we have a sensor that outputs \$X=1\$ if it detects a bottle and \$X=0 if it doesn't. You are tasked with:

  i. Creating a digital system that activates (by active-high,=1) an output \$Z\$ which will pack the beers for us when it detects that four (4) bottles have arrived, and is =0 for all other cases.

  ii.The producer now has ramped up production and creates two different kinds of beer, which arrive in random order through the production line. The photoelectric sensor now produces two different signals: \$G\$ and \$B\$. \$G\$ is only \$G=1\$ if it detects a Green beer, and \$B\$ is only \$B=1\$ if it detects a Brown beer.

  The system you must design has to activate an output \$Z_g\$ that will only be \$Z_g=1\$ if it detects two green beers have arrived, and  has to activate an output \$Z_b\$ if it detects two brown beers (again, active means 1). The outputs must be 0 for all other cases (\$Z_g\$ when there isn't two green beers and \$Z_b\$ when there isn't two brown beers). This has to be done using D flip flops"

Could anyone give me some help, or does anyone know what the resulting systems will be? I am really lost.


texts: Can I improve the accuracy of LM35 temperature sensors by averaging several sensors?

texts:
Can I create one super-sensor by averaging together the readings from several LM35 sensors? Wouldn't this be more accurate because I'd be averaging out the systematic bias in the individual sensors? Also, wouldn't it be more precise, too, because any noise will be dampened/averaged out?

This seems almost too good to be true. I mean, these things are really cheap as far as sensors go, so what's to stop me from buying like 10 of them and making a super-accurate temperature sensors with this method?


texts:
I will first write the problem followed by the equations I'm given and then explain what troubles me.

A 3-phase transmission line of 50 Hz and nominal voltage 400kV has the following per phase parameters L=1.296 mH/km , C=0,01 μF/km. The line has no real losses meaning active power at the start of the line is equal to the active power delivered to the load. The line's length is 277.8 km and delivers power of 600 MVA to a load with an inductive power factor of 0.8 .

If the voltage at the start of the line is 400 kV find the reactive power along with the capacitance of the capacitors you need to connect to the line in order to achieve a 400 kV voltage on the load.

These are the formulas (_R means at the load, _S means at the start of the line, δ is the angle(phase difference) between Vr and Vs, S is complex power)

β and Xe both depend on L and C

My main problem is which of the following change and what doesn't after the capacitors are added:

1)phase difference between voltages Vr and Vs

2)the current

3)the complex power delivered to the load(active and reactive specifically)

There has to be a reason I'm given the power factor before the capacitors. I can find active and reactive power but does one of them stay the same afterwards? Active power could be the same but if it were and the load still draws 600 MVA and reactive power would be the same as well and this leads to the change of Xe and phase angle δ.

I can find δ and Vr before the capacitors but it didn't help since they both change afterwards I think.

( I know I haven't included everything required to use the formulas because I don't think it's necessary for my queries. I can add them though if someone wants to give a more detailed answer)


texts: Based on this data sheet for the 74HCT173, which section(s) describes the maximum current I can draw per output pin?

texts:
I want to size the LED's with resistor in series properly.

Thanks

https://assets.nexperia.com/documents/data-sheet/74HC_HCT173.pdf


texts: Verilog design to display character using "16x2 Character Display" IP from Quartus IP Library

texts:
I was trying to display a single character on 16x2 display. I created simple Verilog design for "Altera Cyclone V Development Kit". In the project I used "16x2 Character Display" IP from the library available in Quartus IDE. This IP uses Avalon interface, so I created simple state machine which takes care of Avalon interface timing according to "Slave Write Transfer with Variable Wait-States" from the Avalon spec. BDW, this IP implements old version of Avalon spec  because it leverages chipselect signal (it is deprecated in newer specs). Unfortunately the code below does not work. It resets the display, but the character "B" does not appear on LCD.
What am I doing wrong?
module lcd_display(clk50, lcd_data, lcd_en, lcd_rs, lcd_rw);

input clk50;
output [7:0] lcd_data;
output lcd_en, lcd_rs, lcd_rw;

parameter   S_BEGIN         = 3'h0,
                S_RESET             = 3'h1,
                S_WAIT_RESET    = 3'h2,
                S_DEASSERT_CS   = 3'h3,
                S_CLEAN_CS      = 3'h4,
                S_SET_DATA      = 3'h5,
                S_WAIT_WRITE    = 3'h6,
                S_END           = 3'h7;

reg [2:0] state = S_BEGIN, next_state;
reg [7:0] writedata;
reg reset, address, chipselect, write;

wire waitrequest;

lcd lcd1(
    .LCD_DATA(lcd_data),
    .LCD_EN(lcd_en),
    .LCD_RS(lcd_rs),
    .LCD_RW(lcd_rw),

    .address(address),
    .chipselect(chipselect),
    .read(1'b0), // not used
    .clk(clk50),
    .writedata(writedata),
    .write(write),
    .reset(reset),
    .waitrequest(waitrequest)
    );

always @(posedge clk50)
begin
    state <= next_state;
end

always @(*) begin
    case (state)
        S_BEGIN:
            next_state = S_RESET;

        S_RESET:
            next_state = S_WAIT_RESET;

        S_WAIT_RESET:
            if (waitrequest)
                next_state = S_WAIT_RESET;
            else
                next_state = S_DEASSERT_CS;

        S_DEASSERT_CS:
            next_state = S_SET_DATA;

        S_SET_DATA:
            next_state = S_WAIT_WRITE;

        S_WAIT_WRITE:
            if (waitrequest)
                next_state = S_WAIT_WRITE;
            else
                next_state = S_END;

        S_END:
            next_state = S_END;

        default:
        begin
            next_state = S_BEGIN;
        end
    endcase
end

always @(*)
begin
    if (state == S_RESET)
        reset = 1'b1;
    else
        reset = 1'b0;
end

always @(*)
begin
    if (    state == S_RESET | state == S_WAIT_RESET |
            state == S_SET_DATA | state == S_WAIT_WRITE)
        chipselect = 1'b1;
    else
        chipselect = 1'b0;
end

always @(*)
begin
    if (state == S_DEASSERT_CS | state == S_SET_DATA | state == S_WAIT_WRITE)
    begin
        write = 1'b1;
        writedata = "B";
        address = 1'b1;
    end
    else
    begin
        write = 1'b0;
        writedata = 0;
        address = 1'b0;
    end
end

endmodule


texts: AC adapter power supply design/component quality

texts:
I own a number of 240V AC -> 12V DC power supplies, obtained for different projects or to power appliances. Notwithstanding the maximum output amperage, are there any straightforward methods (short of dismantling) of determining the design and/or component quality for each unit? By "quality", I refer to efficiency and reliability of operation.

Below is a photograph of several units that I have, in case there is some relevant information displayed on the casing:


texts: I mistakenly ordered a 220V 30W solder from ebay. In order to use it in USA, how do I design a voltage doubler circuit? I know sometime it is not worthwhile, but still want to do it for learning purposes.


texts: Does using twisted pair wiring make sense only for differential signalling?

texts:
I read that the twisted-cable wiring is used for eliminating the common mode noise. As far as I know, in differential signalling the two wires carry their mirrored images so any common mode noise like EMI will cancel at the differential amplifier and the signal will remain since a-(-a) = 2a.

But does that mean using twisted pair wiring makes sense only for differential signalling? If not why? And I read Alexander Graham Bell invented this type of wiring to for telephone wires. But were telephone wires differential signals that time? I'm confused.


texts: Why do Clock-radios get static in volume slider?

texts: I noticed something on an electronic Clock-radio recently - as on my previous clock-radio, adjusting the volume control introduces static, and jumps up and down in volume. I assume this is some sort of potentiometer knob in the circuit, is this possibly repairable as a single component? What causes this puzzling glitch, dirt? corrosion?


texts: This multi-layer ceramic capacitor indicated in the picture is missing. It's next to an internal memory chip for the Nintendo Switch LITE. I need to replace it but I don't know its specs. Could you help me figure it out? I have a very basic multimeter, how can I identify it?


texts: long leads for batteries, how to minimize negative effects

texts:
I just made a circuit consisting of a number of digital components including two microcontrollers and I will be adding a home-made radio unit to it.

I will make a few other miniature circuits which are mostly lights that connect to the main circuit through cables.

Due to space and my design limitations, I have considered eliminating some parts of my circuit to allow the battery to barely fit, but that is not possible, so now, my only option  is to run two 3 foot wires just for batteries.

But in terms of everything, both analog and digital, I feel I need to add other components to make the circuit function with the battery source connected so far away.

So far, on the main circuit board where the battery connections are, I connected the connections together through a 10uF capacitor and I plan to connect another capacitor right next to the battery (so that I have a 10uF at each end of the 3 foot wire pair).

Is there anything else I should take into consideration when running power (+5VDC and ground) through long wires? These long wires will deliver power to a radio unit and the digital components and I don't want them to suddenly stop working, just because I increased the length of the power wires.

And also, what is the maximum AWG (thinnest wire) I'm allowed to use to make the circuit run efficiently?


texts: Using a LED like a photodiode to measure light

texts:
I was experimenting the other day trying to find some way to get cheap light sensors and read somewhere that LEDs can be driven backwards and let through current backwards more the larger amount of light shining on the LED. Then my solution involved setting pin to high ( 5V ) and switching to input and measuring time (clock cycles) required to leak down to a false state ( close to 0V ).

simulate this circuit – Schematic created using CircuitLab

Any idea how I can modify my circuit to get a faster more predictable maximum time for the time counter for my controller?


texts: How should I think about this feedback circuit?

texts:
simulate this circuit – Schematic created using CircuitLab

I am analyzing the noise gain of this circuit to determine the frequency response of this amplifier. The noise gain is 1 + ZF/Z where ZF is impedance between the inverting input and the output.

One way I think about the noise gain is that it is the inverse of the voltage at the inverting input if the op amp output is 1V e.g.

simulate this circuit

I can't wrap my head around how to think about the noise gain in this circuit. If I think about the current flowing from the output to the inverting input I get a circuit like this:

simulate this circuit

But if I think about the current flowing from the inverting input to the output I get a circuit like this:

simulate this circuit

In one case I get a smaller capacitor, in the other I get a zero in the noise gain. LTSpice simulations show both. How do I think about this? Thanks


texts: Atmega328p voltage connections confusion

texts:
I am designing a board relying on atmega328p.
In order to be able to load the arduino bootloader I added ICSP pins and connected them accordingly. Pin number 2 is VCC pin and I connected it to VCC pin of the atmega. I also have a step-up voltage converter which gets 1.5 volts and increase it to 3.3 steady voltage and this output is also connected to VCC pin of the atmega. Furthermore, there is a mini USB connection and it also contains a Vbus pin which, I reckon, should be connected to atmega's VCC line so that when the USB is connected, it can power the atmega for serial communication (There is also a CH340G serial converter connected to USB port).

Okay so, when the USB connection is present, battery should not be connected I believe. Because there is 3.3V coming from the battery and another 5V coming from the USB and they all are connected to atmega. How can I tackle this problem, or even is this a problem ?

Another concern is the bluetooth module also connected to VCC line from the battery. This BLE module (HM-11) cannot take 5Volts. So, another problem occurs at this point. If I connect the USB, this 5V VCC line from the USB will also try to power the Bluetooth module and probably damage it.

I also have no idea what voltage comes when I connect ICSP pins to an arduino for bootloading. Even this might be a problem for the Bluetooth in the first place.

All in all I am a bit confused about these VCC lines.


texts: Metastable state when S = R = 1 in SR Latch?

texts:
According to wikibooks, under the section SR Latch, S = R = 1 is a metastable state. The following things are mentioned under the heading

  When both inputs are high at once, however, there is a problem: it is
  being told to simultaneously produce a high Q and a low Q. This
  produces a "race condition" within the circuit - whichever flip flop
  succeeds in changing first will feedback to the other and assert
  itself. Ideally, both gates are identical and this is "metastable",
  and the device will be in an undefined state for an indefinite period.
  In real life, due to manufacturing methods, one gate will always win,
  but it's impossible to tell which it will be for a particular device
  from an assembly line. The state of S = R = 1 is therefore "illegal"
  and should never be entered.

This is simply not true. When both inputs are high at once, both the outputs are zero owing to the property of NOR gate wherein if any input is 1, irrespective of the other input, the output will be 0. Since S and R both feed into the NOR gates, irrespective of the output from the NOR gates, the outputs will both be 0.

Since I am fairly new to electronics, I needed to know what is the correct way of thinking when SR flip flop is in forbidden state.

Also, I am not asking why is S = R = 1 a forbidden state (because Q = Q', and it will have problems afterwards when SR is changed), what I am really asking is why it is considered metastable in the link I have mentioned.


texts:
I'm studying an LDO circuit consisting of a PMOS pass element.
I cannot fully understand the meaning of dropout voltage.
I thought this is the minimum V_SD to ensure that the PMOS operates in the saturation region.
I had a hand calculation, with some arbitrary reference values:

I have a situation that the target output voltage is 5V, this means current through the MOS is 1mA.
Neglecting channel length modulation, the overdrive voltage is 3.16V.
If V_in, source voltage drops below 8.16V, V_SD <3.16V.
In this situation, the MOSFET operates in thetriode region.
The loop gain will become smaller, then voltage at the opamp's non-inverting pin will decrease, resulting in smaller V_out and current.
This means regulation doesn't work properly, so 3.16 V will be defined as the dropout voltage.
If I set a larger aspect ratio, the overdrive voltage is set by a smaller valuemeaning that V_SD can be smaller.
Am I right?


texts: Oscilloscope&function generator, opposite slope traced than trigger slope settings

texts:
I am wondering why the signal that was traced on my oscilloscope started on a negative slope when the trigger slope = rising.

I externally triggered the oscilloscope by the TTL/CMOS output of a function generator and connected it to both the EXT INPUT connector and the CH2 signal input connector of the oscilloscope. My settings on the Trigger Menu are Source: Ext, Coupling: DC, Mode: Normal, Slope: Rising. Then I connected the output of the function generator to CH1 on the oscilloscope.

I displayed a 10kHz sine wave and the triggering pulse at the same time, making note that the function generator DUTY control is in the CAL position.

Can someone explain why the displayed sinusoid on channel 1 began at the negative-slope portion of its slope even though the trigger slope was set to rising? It remained the same whenever the setting changed to falling.

Anything will help!

Thanks


texts:
I have an Avocent SwitchViewDVI (4SVDVI10) KVM that looks to be run by an ATmega64 microcontroller.  Every now and then the KVM locks up and I need to reset the unit by pulling all USB power sources to it, a considerable hassle to access.  I know that the ATmega64's pin 20 is a reset and according to the datasheet "a low level on this pin for longer than the minimum pulse length will generate a reset".  I suspect this can be used to provide a more convenient reset than pulling all power.  I know a bit about electronics and am good with an iron, but microcontrollers are new territory for me.  I'm a geek, but without proper EE cred.
There is a 21k Ohm resistor between VCC and the reset pin, I assume "pulling reset high" possibly for power-on reset.  My theory is that if I "pull low" (ground) the reset pin (easiest attach point being the reset side of the resistor) via a momentary switch I can generate that reset signal.  Is this correct?  Do I need to open the circuit between reset and VCC?  Should I include a resistor between the reset pin and ground to be a current limiter?  My suspicion is I need to keep VCC attached via the 21k Ohm resistor and use a resistor between reset and ground to form a divider, as the datasheet specifies a reset pin threshold voltage range of 0.2VCC-0.85VCC.  Since VCC via USB should be somewhere around the 5V USB spec (I measured 4.1V in testing) I'm thinking a 3k Ohm resistor between reset and ground should get me there?
ATmega64 datasheet
I'm sure this is very EE 101 and I welcome responses/critiques of my described problem.