texts: Why is length matching important for high-speed signals?

texts:
Broadly speaking, I understand that PCB trace length matching is important from signal timing and signal integrity point of view, but I want to know some more specifics about these two parameters and if there are any other considerations and parameters that make length matching important for high-speed signals in particular.

Any comments are highly appreciated. Thank you.

EDIT: Sorry if my context was not clear. By high-speed I of course mean high frequency signals, like for example DDR4, HDMI, USB 2.0/3.0, etc.


texts: Why is the current through the PMOS different to the NMOS?

texts:
I'm trying to alternate two LEDs with a shared PWM signal. When the signal is low D1 should conduct. When the signal is high D2 should conduct. I've created an LT Spice simulation of the circuit I came up with.

Why does D2 conduct less current than D1?


texts: Voltage And Current Leak into My Electronics Design Prototype

texts:
I designed & build a circuit/PCB to control a 5V PWM PC fan on Autodesk Eagle. It's based off the Arduino Leonardo platform (ATMega32U4). The PCB is made by JLCPCB and I soldered on the components myself.

Here is the power section of the schematic below:

It uses a LiPo battery recharge & 5V boost circuit copied from Electronoobs' design. I also used this circuit to switch between USB or LiPo battery power. The output of either the USB or LiPo battery goes through the C1 net of the power switch. If the switch is turned on (C1 connects to NO1), that leads to the 5V Boost circuit which leads to the 5V net that powers the Arduino and 5V PWM Fan. With this design, there should be no power to the micro-controller and fan when the power switch is off.
The big problem is when the usb-c is plugged in and the power switch is off, there is some small amount of power still going through to the Arduino and fan as seen here:

When the power switch is off, the 5V net gets a reading of 3V when I expected 0V and the NO1 gets a reading of 1.2V. we'll call this phenomenon "half off"
Another problem is when the LiPo battery is plugged in and the USB-C is not plugged in, when I turn on the switch, nothing happens (completely off). But if I plug in the USB and unplug it, now the electronics can powered by the LiPo battery. It also will be "half off" when I turn off the power switch with the LiPo battery.
Not sure what is causing this. There is no visible shorts anymore in the PCB and there is over 12 mil of clearance in the PCB design. Not sure if the power inductor (L1) might be a factor. Anyone else know of this problem and/or encountered them before?


texts:
I'm building the following circuit in a PCB . The purpose is simple, the first stage is a TIA amplifier that converts current into voltage and its working fine. The second stage, where the problem is at,  is to add dc bias to center the signal in 1.5V.

The problem is that is not working as expected for low currents like in the magnitude of uA. In this magnitude of currents, where the signal voltage is low,  what is happening is that  DC bias stage is not centering at 1.5V but at a lower voltage, like 1.49/1.48V, probably has to do with the impedance from the TIA stage. The resistors have very low tolerance (0.1%), the 3.0V comes from a buffered voltage reference and all opamp's offsets are in the magnitude of uV.

Can i do something to improve this, have the resistors of the voltage divider some effect ?


texts: How to wake up ESP8266 with light change?

texts:
I want to send information to the server when the light changes (turns on or turns off). As for now, I have a photoresistor connected to ESP8266's ADC pin. I'm measuring voltage and sends information to a server when it changes much. ESP stays always on.

Here is my current circuit:

However, I'd like to make it in slightly more energy efficient way.

The sensor will be used in a bathroom, so the light is usually turned off.

Perhaps I could make ESP8266 wake up somehow by photoresistor and then send a request to the server and wait for the light to turn off back again and then send the second request and enter the deep-sleep mode? Or maybe there is a better way?

I'm seeking help in creating a circuit. What should I use? How the circuit should look like?


texts: How to represent a sum of dirac delta function and a linear function in a graph? (convention question)

texts:
I'm working on my final assignment in signal's course that I'm taking. I want to represent the following function in a graph:
\$ f(t)=\delta\left(t+1\right)+(t+1.5) \$
Where \$ -1.5<t<0 \$.
Generally we represent dirac-delta function as the following:

And the other function that I want to sum looks like this:

So how the summation of the graph's should be ? should it be like this:

Or maybe like this: ?

Or maybe a totally different way?
Thanks in advance, this is highly appreciated and extremely important for me.


texts: What is the base current of a class ab amplifier with darlington pair configuration

texts:
I am trying to design a 3 stage amplifier using transistors, 2 pre-amp stages using class A configuration and an output stage class AB. I have built the class ab amplifier with a darlington configuration and 4 diodes for the bias voltage and it has a gain of about 0.8v but now I am trying to calculate the input impeadance of the ac model so that I can design the 2nd stage but I am having some issues with finding the input impedance since I do not know how to calculate the transconductance with a darlington configuration.

Can you guys give me some hints on what to do ?
Thanks

simulate this circuit – Schematic created using CircuitLab


texts: Circut to turn on a battery powered electric fence

texts:
I want to be able to have a battery powered electric fence automatically turn on in the morning when it's day light, and power off when it gets dark. I don't seem to be able to find a product that does this - they all seem to be the exact opposite e.g. security lights turning once it gets dark, so I'm looking to build my own device to achieve this.
I've searched to see if there's a tutorial for this online, but I don't seem to be able to find one. I don't know if I'm not searching for the correct thing, or if I've just missed examples of this.
My thought was to use an Arduino, with photo-resistor cell to detect the light level, and use simple logic and a relay to turn on a the switch which then supplies power to the fence, and once it gets dark, break the switch to power off the fence. Is this the way to go, or is there a better way?
I'd really appreciate it if anyone could help me with this, or point me in the right direction? Thank you in advance!


texts: Surge protector helped me discover bad wiring at home -- neutral and line swapped; should I be concerned?

texts:
I purchased two surge protectors and when I plugged them in at two different receptacles in my apartment, I noticed that the 'grounded' light did not illuminate on any of them.

To shorten the story, I discovered that at every single receptacle in my apartment, line and neutral were swapped! I rewired the two receptacles (just swapping line and neutral) where I am using the surge protector and it lights up all good now.

My question is, given that all the other receptacles are still reversed, should I be concerned? I mean, most devices don't care I would imagine. They just need to see a differential of 120 V. But clearly the surge protector cared, so are there any other devices that do care?

Also, another question. I have a dsl modem with a telephone cable that does not go through the surge protector. My Xbox has its Ethernet cable connected to that dsl modem which also functions as a router. Is it possible that a surge could go through the telephone wire, then through the Ethernet all the way to my Xbox and damage it?


texts: Algebraic Minimizing: why repeating a minterm?

texts:
I'm studying minimizing boolean expressions using adjacent expressions...

However I'm not understanding this example

http://i.imgur.com/7g3R9Bo.png

Why are they repeating minterms? Why is this correct? When can I do this? Shouldn't the function be the sum on the minterms 0,1,3, 5 and 7 only ONE time?

Thanks!


texts: Worst Case Analysis of the LED circuit - Reg

texts:
I need to perform the Worst case analysis of the LED circuit attached. The value of the resistor has already been chosen and I am doing the calculations for min, typ and max current.

Please bear with this thread for the detailed explanation. Need to get some clarity.

I have three voltages 7.5V/13.5V/16.5V.

This is my LED Datasheet

The Operating temperature of my board is -40degC/+25DegC/+80degC

So, I need to perform WCCA with these parameters.

How shall I go about this? I need Min/Typ/Max values.

Please check if my approach is correct :-

I figured out that the total current through the R, LED and Transistor is Typ I = 13.5/1200=11.25mA

Max I  = 16.5/(1200*1.03)=13.35mA (3% tolerance taken for R)

Similarly for Min I = 7.5/(1200*0.97) = 6.4mA

So, once I have these currents, I will now figure out the Vf of the LED with respect to the LED datasheet graph. (Vf vs If). So, I will have the Vf of the diode also. And since I have different temperatures to consider, I need a graph in the LED datasheet with provides a graph of "Change in Voltage" vs "Temp".
So that I can add the change in voltage to the min Vf and subtract the change in voltage to the max vf af the temp of -40 and +80 respectively.
However, in the datasheet mentioned, i donot have such a graph. But I have this graph in This Datasheet but it is a green LED.
What can I do in this situation.

Suppose, I had done this Vf and temp calculation, I can now perform one more correct iteration of current through the LED by this formula,

I = (Vin - Vf - Vce(sat)) / R. // for all the temp and input voltage.

So , I will now have the near accurate value of Worst case analysis current values.
Is my approach correct?

Please help me if I am wrong and tell the correct method. Will be really helpful. And what about the missing temperature vs change in voltage graph of the LED.

Thanks.


texts:
I am trying to understand how current flows in a BJT NPN and how amplification happens at the collector current.

Here is the link I was reading
http://www.learningaboutelectronics.com/Articles/How-to-connect-a-transistor-in-a-circuit-for-amplification

This is the way I understand it: a Vcc supply to NPN Ic flows from Vcc to the collector but they also say amplification happens when minority and majority carries replace and diffuse from base into collector and a current flow comes which is amplified.

I cant understand how the current is amplified as per circuit laws. Vcc which gives the collector current which flows into the NPN collector. How is this current amplified? as it depends on the load resistance.


texts: I need to vary the duty cycle between 50% and 70% of a PWM signal

texts:
So I used a comparator to compare a sawtooth signal and a reference voltage and I obtained the PWM signal at the output of the comparator. My question is what formula can I use to vary the duty cycle of the PWM signal as I like?
This is the part of the circuit which adjust the duty cycle of my PWM signal.

I was thinking to use a potentiometer between 2 resistors and to vary the duty cycle by varying the values of the resistances.
+/- Vps=+/-15V

Thanks in advance!


texts: Choosing regulator for gyro's and accelerometer

texts:
Should I choose a linear regulator that has good transient response? or ultra low Vrms noise? or high accuracy?

I am using digital accelerometers and gyros (BMA180 and ITG3200).


texts: Why is 30MHz Clock signal distorted on oscilloscope?

texts:
I'm trying to probe a 30MHz clock signal, coming from an FPGA and routed to a CCD sensor.

There are no other components, other than connectors, between source/destination.

When I probe this signal with my oscilloscope, I get a distorted waveform which over shoots and undershoots. The probes I am using are the standard tektronics probes that come with the MSO2024B that we have. They have been calibrated to the scopes 5khz test point and show no overshoot.

The clock signal should be 3.3V peak to peak.

The scope probe ground clip is connected to the 0V reference point near the regulator for the 3v3 rail.

I am investiagting why we are seeing noise on our power supplies after the FPGA has powered up and starts providing the 30MHz clock to the external CCD.


texts: Have CRTs ever used a different raking pattern?

texts:
CRTs traditionally scan top-left to bottom-right, in a row-major raking pattern, and appear to have done so since the 1930s. This is a little unusual though, as standard mathematical orientations have Y increasing upward, not downward, and the behavior of these screens has had a lasting, and likely predictable, impact on software modeling and rasters.

My question is of a electronics-history nature. Have we ever tried any CRT raster displays that weren't aligned this way, as a default? Was there ever a CRT device that scanned in a traditional, bottom-left-to-top-right, or even column-major, order? Why did we settle on top-left-to-bottom-right?

Thanks to anyone who can shed a little light on this for me.


texts: I'm relatively new to using PSpice. I'm trying to copy over a circuit from an example I have in order to figure out the values across the resistors. I cannot figure out how to place a voltage point(without ground) on top of the circuit, with the ground on the bottom of the circuit. Which voltage component do I need to place on the top for this to work?


texts: How would a Laplace transform be useful in analyzing this circuit?

texts: I'm expecting a midterm question about the circuit below that involves the equation t=RC and using a Laplace transform. We won't actually be using differential equations. Memorizing a certain equation is all we need, but we're not told what it is. I've found a lot of equations when looking up Laplace transforms. Which equations would be helpful for analyzing this circuit, and where in the circuit could they be applied?


texts: Exporting ODB++ directory from Altium to CST Microwave studio

texts:
I am trying to export a PCB that I created in altium using ODB++ format to CST Microwave studio 2017 , I clicked import and then chose ODB+ and browsed to the zipped file of the ODB++ but it's giving me this error which resulted failure.

Does anybody have an idea on how to import ODB++ properly?
Thank you very much in advance!


texts: What happens to components which stop being manufactured?

texts:
When a component/IC stops being manufactured, due to newer, and maybe more efficient, etc, chips becoming available, what happens to the designs?

Are they released, so that somebody else can manufacture them if they wish?


texts: How to decide when to use flop or RAM based fifo?

texts: Trying to figure out what are the tradeoff like power, size when deciding between using a flop or RAM based fifo ? Any known publications ?


texts: How to resolve floating node error in PSpice?

texts:
I would like to run an AC sweep for this circuit below.

Unfortunately the following errors occurred:

L_L2         N04540 0  .10976mH
R_R3         N04968 N02907  10.7849 TC=0,0
C_C6         N04540 N04968  7.6091u  TC=0,0
C_C5         0 N02907  .64335u  TC=0,0
I_I1         N04863 0 DC 0Adc AC 1Aac
L_L3         N04858 N02907  1.989m
L_L4         N04863 N04858  3.933m
C_C7         0 N04858  1.099u  TC=0,0
**** RESUMING test.cir ****
.END
ERROR(ORPSIM-15142): Node N04968 is floating
ERROR(ORPSIM-15142): Node N02907 is floating
ERROR(ORPSIM-15142): Node N04863 is floating
ERROR(ORPSIM-15142): Node N04858 is floating

Although I have checked the circuit several times in order to resolve the problem, I have not succeeded. Does anyone know how to solve it?


texts:
I humbly ask for assistance with a somewhat simple little project I am trying to finish.  The project I have started is to have several reels of LED lights flash triggered by the RCA type subwoofer output of a receiver. Some specs are as follows:

ATX PSU converted – 12V @ 24 AMP Max output

On-On Rocker Switch – 12V 16 AMP (Normal Mode/ Beat Mode)

LED Strips – 12V 10 AMPS Max

LED Controller – 12V 24 AMP Handling Capacity

Subwoofer Output Line – 2 V @ 50K Ohms Max Output?  Amps Unknown
MOSFET?
12Volt + / 10 AMP Continuous / Gate (trigger on?) Volts Unknown - Fan Cooled No Heatsink

My troubles are that I do not know exactly what the subwoofer output RCA power is only what it would not usually be more than at full power. Specs. I were able to find on other players generally say no more than 2 Volts @ 50K Ohms. So I have no way of knowing for certain how low the voltage or amps. are at normal listening levels.  If someone did know (HINT HINT) that would lead us to the second most difficult problem.

Choosing a proper switching device. I have seen videos of others using an N MOSFET (TIP30) to flash LEDs however none off of an RCA nor at the amps. I intend. Is a MOSFET not what I need? If it can be then I need one which opens at a very very low, unknown voltage. I have seen that many handle the 12V 10 Amps easily.

I have tried to contact manufactures. I have contacted distributers both national and local who are reluctant to discuss the issue and find me a $1.00 - $3.00 part. I have contacted my local shops for advice but have found my knowledge surpasses their own which is just sad. I have also tried filtering through different manufactures MOSFET spec sheets but it is all so confusing for the novice and they even seem to be switching terminology leaving me with a giant hole in my wall where I’ve twice put my head through. I try to learn, I try to figure things out on my own, but I cannot. Can someone please help me with a widely available part number for something like the MOSFET I intended that I can order? Thank you for your time.


texts: charge a 12v battery from a cigar lighter

texts: would I be right in thinking that to charge a 12v 7 ah sealed lead acid battery from a cigarette lighter socket on a canal boat, I would need to wire a bulb into the positive lead of the connecting wire (series) to limit the current?


texts: "shark teeth"-like PCB feature in high voltage section of modern HDTV

texts:
I found this tooth-like non-masked, solder-covered trace pattern on modern single board HDTV.
It's in the 120VAC "HOT" section of the switch-mode PS.
Looks like some sort of spark gap or protection feature. There are two of them, one with 3 "teeth" and the one pictured with 4 "teeth".
Comes right after 4 large rectifier diodes that are connected to the ac line and before the switching transformer.
I'm pretty sure somebody here knows the function of the feature and would be interested to know what it is.  Why 3 teeth?  Is there some formula to determine the number of teeth?  Is it a fuse like component?  There is a fuse in another part of the HOT section.


texts:
I'm designing an MPPT charger with a Synchronous Boost Converter using the LTC4444 gate driver. For prototyping I made a 1 layer pcb where I soldered all the components and added a few cables. The first time I tested the circuit with Vin = 5V and it was working correctly, I tried it the next day and it was no longer working.
I supply the gate driver with 12V using a DC Power Supply which works fine without applying any PWM signal. After I activate the PWM the voltage drops to around 6.5V and the current rises to the limit of current I used 0.04A. If I raise the current the voltage is able to reach the 12V, but the gate driver doesn't work. This led me to conclude the gate driver had burned.
I FORGOT TO REFER BEFORE: If I only apply a PWM signal on the low side, the gate driver works correctly, applying any voltage in the high side input will make the supply voltage drop and the supply current rise. This means that the high side is the one getting damaged, without affecting the load side.
I soldered a new gate driver and tested it again without any load. At first the gate driver signals were okay, but after a few seconds the voltage at Vcc droped and the current rised, just like before. This happended 3 times. I've tried checking all the wires and paths on the PCB and everything seems ok, I don't know why this is happening, but I suspect there must be a mistake on the bootstrapping of the gate driver.
The PWM signal comes directly from the uC, a Teensy 3.2, and it has a frequency of 80kHz. I then invert the signal using a NAND IC, the SN74S00N.

I also send some pictures of the PCB, the Gate driver has already been removed 3 times, so the PCB is already a bit damaged from the heat but the paths and cables are working correctly:

Links of the datasheets for Gate Driver, MOSFETs, bootstrap diode & bootstrap capacitor.
Thanks for the help!


texts: Microcontroller GPIO control relay with eletronic lock cant pull low

texts:
Please help.

I am connecting 12V electric magnetic lock to a SPDT relay which is controlled via a microcontroller (MCU) GPIO output pin. Whenever the output pin is pulled low, then the relay is turned off else it is turned high when the output pin is pulled high.

Initially, I tried without using any electric magnetic load but with just relay and everything works fine with the relay turning on and off as desired.

However, when i connect it together with the electric magnetic load then the GPIO output wont pull low from high state. I checked on the MCU GPIO pin and it seems to pull high which is the previous state instead of the expected low signal. For the relay seems to have slight contact and then it switched back to high in split seconds. It would practically have no switching at all.

My circuit for connecting the relay is using NPN transistor to drive it high and low where the electric lock is supplied via 12V into the common point of relay.
12V is driving through power supply which 5V is regulated via regulator to the microcontroller. All comes from single dc power source.

My question would be why once the magnetic load is connected then the MCU GPIO cannot be pulled low.
I have provided the schematic as follow.

Do provide some advice :)

simulate this circuit – Schematic created using CircuitLab


texts:
I'm looking to track the position of a pin on a shape display. I wanted to see if it's possible to make a PCB trace that could be put on the side of the pin and act as a potentiometer to gauge it's movement. Is this feasible, is there any way to strengthen the traces if i use a brush to make contact?
Here's an example of the sort of shape display/pin display that i'm thinking of. An accuracy of ±2 mm is all that's needed.


texts: audio, LTspice - crossover simulation problems

texts:
I am currently trying to design an x-over. The response of what I have spiced does not correlate to what I though would happen. Have I made any obvious mistakes?

I want a Sallen-key HP/LP. That crosses over at around 120hz with a gap between the Hp & Lp points because of the driver units being mismatched.

Any thing obvious I’ve done wrong?


texts:
I am being asked to find the output resistance of the current mirror below.
the correct answer is supposed to be R_out = 103k ohms.
but when am simulating the circuit, I get R_out = 3.82k ohms.
Can somebody please help me and tell what wrong is going on????
Btw, R_s in the circuit diagram is 3k ohms.
Here is the problem statement along with the simulation results.

Thank you for your help.


texts:
When only one clock is used in PCIe and let's assume the clock is connected to device A.
How does device B transfer data to device A. Device B does not have a clock source.


texts: Eliminating or reducing the red glow from IR LEDs at night

texts:
tl;dr; my question is simply this: is there a way to hide a bunch of IR LEDs (for a night-camera) so they don't get such a red glow at night?

Preferably not at the expense of the light output, but that would be ok too, if that's the only way.

Background (not-tl;did-r): I setup a baby cam for my son when he was born with a Raspberry Pi and a Pi cam with no IR filter so I could watch him at night.  It has worked flawlessly and frankly I couldn't imagine parenting without it.  He's now 1.5 years old, and sometimes wakes in the middle of the night and sits there talking to his stuffed animals.

Just a few days ago he seemed to notice the IR light for the first time, and now he'll be fine until his eye catches the light and he seems to get terrified and start crying once he sees it.  At least, I assume it's what's scaring him (there's also an LED on the Raspberry Pi itself).

The light is more powerful than it needs to be, I believe it's a 48-LED cluster, so if a solution involves dimming the light, it would probably be fine.  I was thinking about putting it in the opposite corner of the room, but keeping the camera above him, but I think the slats from the crib would block much of the light and it would be very shadow'y.  And I'm not so sure that would keep him from seeing it.

I was thinking maybe some sort of plastic (acrylic) plate or filter.  I'm not sure.

Thanks

Edit, here's a pic of the setup.  This is an older pic of an older IR light that I got from Ebay.  Half the LEDs burnt out within about 3 or 4 months.  It's since been replaced by another cheap Ebay one, but same basic setup.  I'm definitely open to moving things around so it's not so... "in yo face!"


texts: Using a heat gun to transfer toner onto DIY PCB?

texts: Is it possible/practical to use a heat gun instead of an iron to transfer toner when making your own PCBs?  Can you get a uniform heat pattern without for a small board?  Is enough heat applied from the heat gun to actually transfer the toner?


texts:
I want to send two different 10MHz clock signals to a device.
My board have tight volume and power constraints and I would rather not use a complicated clock buffer/PLL/MUX IC.

The first source have a low period jitter, below 10ps. The second source jitter is less important.

I came up with a circuit that could eliminate the need for a MUX:

simulate this circuit – Schematic created using CircuitLab

Only one of the source is enabled at any time.

The device with the LVDS input is a TDC-GPX2.
The LVDS input common mode is limited from \$V_{ID}/2\$ to \$2.2V - V_{ID}/2\$ where \$V_{ID}\$ is the differential input voltage. \$V_{ID}\$ must be higher than \$0.2V\$.

Is there a problem with that circuit?
Could it degrade my clock signal significantly, by adding several picoseconds of jitter?


texts:
Xilinx ISE Design Suite gives information about the resources that a particular design uses. One of the parameters that is given to measure the estimated resources is "Average Fanout of Non-Clock Nets" (as you can see on the botton of the below table where this parameter is 2.5).

I would like to know:

Why this parameter is useful
How engineers can use or take advantage of this information to improve designs.


texts:
Here is the datasheet for this device: TI LM337L, at the 3rd page there is an equation for calculating the resistor needed in the voltage divider to set the output.

-Vout = -1.25 * (1 + (R2 / 240))

The 1st thing that I'm wondering about is the value of the lower resistor (240 Ohm), I could not find an explanation for this in the datasheet so I'm assuming that its a minimum value for R1 + R2 to limit the current into the device.

However, solving the equation makes it impossible to reach -1.2V:
-1.2 = -1.25 * (1 + (R2 / R1)) => (R2 / R1) < 0

The value of 1.25V is the typical reference voltage, this value goes from 1.2V to 1.3V. So if I'm understanding this correctly... If I'm lucky to have a device with a low reference voltage of 1.2V and I will short R2 so that R2/240 => 0 I can have the output voltage equal to the reference voltage and still maintain a good working environment for the device?


texts: What is the terminology used for a (few)-bit permanent memory latch?

texts:
I would need a one bit permanent memory. With permanent, I mean able to maintain it value across power reset. Something like EEPROM or Flash. Ideally, something equivalent to a RS-latch.

Searching, I found several I2C EEPROM or PIC, but that would include too much complexity for my purpose. And seem a drop of resources to use a serveral-Kbits chip when only one is required.

Is there some IC for permanent (few bits) latch? If yes, what is it name so I may search for it? Any example of it?

EDITED:
To clarify,I am asking for a very simple Integrated Circuit. The purpose is to include it on a PCB. As an example, 5x5mm SO/TSSOP for 0.1$ would be something acceptable.


texts: Possibility of hybrid forward-flyback topology

texts:
Within the context of isolated converters, the flyback topology is nice in its simplicity as can be the forward topology, in spite of needing a second primary reset winding. However, both make poor use of the transformer core in as much power is not continuously passed through the transformer. Why can't both topologies be combined by taking the reset windings to the secondary side as a flyback output windings?

Consider the following schematic:

The upper secondary windings are as in a typical forward topology while the lower secondary windings are as in a flyback topology and act as reset windings. Ideally, one would remove L1 altogether by designing T1 with a large magnetizing inductance.

My questions are specifically:

1) Wouldn't this topology offer advantages such as lowered value for C1, no output inductors and better use of core materials? If yes, why isn't it more common?

2) Are there major drawbacks I haven't considered? The ones I see concerns stressed Q1 in no-load conditions and the need for a lot of primary windings so that T1 can have a high enough inductance to remove L1 altogether.

3) I'm considering such a design for a constant power PSU for use with loads that exhibit negative resistance. The idea is to have the ON-state duty cycle more proportional to total output power as the energy not used in the forward part of the cycle will be dumped in the load in the flyback part of the cycle. Would that be an acceptable use case?

I have seen similar topologies in some patents and a few papers targeting its use in solar power systems but it does not seem to be common at all and I can't see why.

P.S.: I'm a physicist by training and I suspect the reason might be first and foremost economical.


texts: AC-DC converter (230V - 5V) supply for microcontroller to control outlet

texts:
I have built a circuit using a PBO-3-S5, AC-DC circuit and applied some necessary components. iIn the description and when testing the circuit I get a 4.8V output voltage which should be enough to drive a Rasperry pi zero.

But the problem that have occurred for me is the part which should be able to switch on and off the outlet.

I have tried using transistors by using two in parallel of each other and controlling them with the micro controller but did not get them to turn on. My second idea is to use a solid state relay, but they are rather bulky and expensive. My question is, are there any other switches that can be used for power outlets with control of a micro controller such as a rasberry pi?
The picture shows how my circuit should look like some how.


texts:
I have a general understanding of how a transformer works and the whole magnetic induction process works, and I also understand that there is heat associated with high current electricity flow, so my question is this:

Is it safe to construct a homemade transformer that would function similar to a neon sign transformer by converting 120V AC into ~3000V AC? If so, where would I find the materials to do this?


texts: Turn a positive clock edge into a negative pulse to make a 74LS170/670 register file synchronous

texts:
This is a follow-up o Why did they make the 74x170 (670) register file asychronous, no CLK input?.

I want to use that "register file" for my project, but I need to make it behave properly as a synchronous D-flip-flop with a proper clock input. Here is the pin-out of the 74LS170:

So there is the active-low write enable -Ew (BTW: how do we write formulas here with an over-line and subscript?). This -Ew is active low. As long as -Ew is low the changes on the input D-pins propagate to the output Q-pins. Once -Ew is high, the last state of the D-inputs is latched in the Q-output.

I am not concerned about the -Er output enable, I tie that to low, and the open-collector nature of the 74LS170 and its adaptation to normal TTL is another subject, not relevant here.

What I want is a short negative pulse on -Ew on the rising edge of the clock.

Here is the very straight forward solution I can come up with, but I don't like it. I am looking for something simpler, more nifty.

So what I have here is 2 input lines, -G for the active-low write enable (named G as it is in the 74LS173 D-flip-flop), and the clock CLK; creating the output -Ew to go into the register file chip.

simulate this circuit – Schematic created using CircuitLab

The CLK goes into an edge detector built with a capacitor in-line and the resistor, to give a quick pulse on the rising edge of CLK. The time constant of about 100 ns should perform OK up to about 1 MHz, and definitely for my slow breadboard prototype. But that pulse is positive, so I need to put it through an inverter to become adapted to the active low sense, and then the OR gate makes sure that -Ew is low only when -G is low on the rising edge of the CLK.

What I don't like about this is that now I need 2 additional chips a 6-way inverter and a 4 x 2-input OR gate, a massive overhead!

I happen to have a spare 5-input NOR gate near this register already (from my zero-detection logic using a 2 x 5-input NOR gate), and I wonder if there might be any way I could use that. But I don't think NOR helps me at all. So the best I can do is bite the bullet and swap that 2 x 5-input NOR gate with a 4 x 1-input OR gate and a 6-way inverter. I need 3 of the OR gates and one inverter for what I did with that 5-input NOR gate, and so I have then 1 OR gate and 1 inverter (plus another 4 spare inverters left over, which I might put to some other use.) That way I only need to add one additional chip to what I already have now. Not too bad actually.

Still, I wish there was an easier way.

For example, how would I build a falling edge detector with a capacitor? If I could build a falling edge detector which would give a quick negative pulse only on the falling edge of -CLK, I could actually save myself the inverter, since I have another way to invert the output from the OR gate for the zero detection by using a 74LS73 instead of a '173 for the zero and carry flags.

UPDATE (from the comments and further thinking):

I don't consider setup time an issue for me, as I am not planning to run high clock frequencies (for now).
Hold time might be an issue if it is long as compared to the
propagation time from D to Q. from the data sheet I see '170 setup
time 15 ns while the '173 is only 3 ns, I guess I'll see how that goes.
The minimal -Ew pulse is 25 ns per data sheet so my 100 nf * 1 kOhm should be fine.
Been thinking all night how to adapt the open collector output of the 74LS170 to straight TTL without inverting, and I haven't come up with anything, so I guess that's where the other 4 inverters of the 6 x inverter IC will have to be used for.


texts: How to choose a blocking capacitor for RF power amplifier

texts:
I'm using a power amplifier that requires an external blocking capacitor for the input and output ports and I'm trying to decide the best value to use. My understanding of this is that I choose a capacitance that is sufficiently large such that the 3dB frequency is a good deal lower than my lowest frequency of operation (answered here). I also imagine that it's important to choose a capacitor with the smallest possible ESL. Are there any other considerations that are important here? What about RF currents heating such small caps?

So, I'm thinking of using a 0402 100pF cap which, given my lowest frequency of 5.3GHz and min Rload of 6ohm, should put the corner frequency around 250MHz, well below the 5.3GHz. Does that seem sensible?


texts: USART, UART, RS232, USB, SPI, I2C, TTL, etc. what are all of these and how do they relate to each other?

texts:
As a novice electronics hobbyist, I have heard these terms and more being thrown around everywhere. At its root, I understand that they are all based on communication between devices, computers, peripherals, etc.

I have a basic understanding of how all of them work, but I get confused when I see so many of them and am having difficulty understanding how they relate to each other. For example, is UART a subset of USART? What is the difference between RS232 and Serial? What are the core differences between all of these communication methods: reliability, cost, application, speed, hardware requirements?

If you can imagine, I have all of these terms written on cards, scattered on the coffee table, and I need someone to just help me organize my understanding. Forgive me if this question is a little vague, but I really feel that is the nature of this question all together.


texts:
I am trying to create a constant current source of 100mA to charge a single cell Li-ion battery. I see the LM317 thrown around a lot as a solution, but I'm looking for something that does not require a 1.2V drop (Due to the Vref=1.2V for a LM317). The problem is when I look at more modern LDOs, they tend to have a ground as well as a ADJ pin, and I'm wondering if these can be floated the same way the traditional LM317 regulators could.
Once such device I was looking at was a ADP123AU due to it having a Vref of 0.5V.

So looking at the block diagram they do not mention what the 0.5V is ref to but it would have to be ground as far as I can understand, so if you float ground as shown, would it work? Or does anyone know another small regulator / specialty IC that can do this?

simulate this circuit – Schematic created using CircuitLab

EDIT:
Thanks for the input, it is interesting but I may not have been clear in the initial question. I am looking to do this as simple as possible, something such as the LM317 with a single resistor. Multiple op-amps and transistors is something I would like to avoid.

Does anyone have an opinion on if what I proposed in my question would work?


texts: How to configure an ADC using an STM32 in Rust?

texts:
I want to write values to an external ADC's register through SPI using an STM32 MCU in Rust.
For example, I want to write 0b00000001 to 0x05 register address of ADC3441 to configure it.
The MCU STM32L053 can communicate with ADC3441 through SPI.
How can I accomplish this in Rust that uses the stm32l0x3_hal.
I have found codes here, but I don't understand how I can transfer any values to a register address.


texts: Why does a body submerged in a more conductive fluid still conduct current?

texts: Let's take for example an electric eel applying an electric shock by creating a potential difference across two points in the water.  It would seem, however, that the current would find a "shorter path" across the potential difference by just passing through the water.  Why, then, does some of the current go through the "target" which is further away and likely has higher resistance than sea water?


texts: Help selecting AC power adapter for DC car monitor

texts:
I purchased a Pyle 9" TFT monitor for use in an automobile with back-up camera. The wiring is designed to connect directly into the car's harness. I have no info on the electrical requirements other than, of course, 12V from the car.

I plan to use this monitor inside to make my nephew a headboard with digital photo/video/netflix frame. I've wired some indoor 12V lighting before, but probably just got lucky. I want to know if a similar power supply will work here? I'm looking at a DC 12V 2A Power Supply Adapter for 110V-240V AC 50/60hZ (whatever that means?). Does that sound like that will work? Should I get the 3A version to be sure since I read on this website the whole "amps are like apples" analogy?


texts: Do parabolic reflectors in globes increase the brightness of the filament's light, or just 'spread' the light?

texts: If you compare a traditional 60W incandescent globe with the same filament specification as one with with a parabolic reflector built into the globe, does the (usually) aluminium reflector actually increase the lux/lumens (without drawing extra wattage, and thus an energy efficiency increase from the user's power usage point of view), or does it just help spread the light to a larger angle?


texts: I'm a Trainee electrician and pc hardware enthusiast. I was just wondering why a mixture of inductors and capacitors are used on motherboards? Why not just use capacitor? I thought the inductor stores electrical charge but it uses magnetism. What's so special about storing it as magnetism?


texts:
I'll be using the TLV5606 to produce a sine wave.
Control is via SPI. Ideally, I'd like to "update" the voltage 2000/sec.

Is this too fast for the IC? I'm struggling to understand the datasheet. What is the maximum update frequency?


texts:
I want to make circuit which can working like a Latching Relay which Hold Current using SPDT Relays.

So i can use this circuit to Pules ON/OFF switch.

Using limit switch when pressed a pulse goes and the circuit ON and if re-pressed the same Limit switch the circuit OFF.

Other option
Using Two Limit Switch First for ON and Second For OFF.

Please help me to make this type of circuit.


texts: Photodiode current vs. irradiance and finding upper limit current

texts:
1.) What equation could be used to calculate, or make a decent estimate
of the current produced by a photo-diode from incident irradiance and its operating parameters. For example for this PIN photo-diode BPW 34 FS from Osram

 BPW 34 FS

here is the plot of the photo-current vs. irradiance

2.) How to calculate (or estimate) an upper limit current produced
    by the photo-diode when the incident irradiance rises.


texts: Will a device capable of receiving a 200 Vrms input signal happily accept a 200 VDC signal?

texts:
To the best of my knowledge, Vrms is used to express an AC signal as the equivalent DC signal that would produce the same power dissipated in a resistor R; I believe this is best calculated using a thermistor to measure the heat given off from the resistor.
Now, if an analog input device were to specify that it can accept a 200 Vrms signal, wouldn't it follow that it can happily accept 200 VDC as well since Vpk-pk of the AC signal must be at least as large as 200V to achieve the 200 Vrms rating?
If the above statement is correct, then it follows that the opposite is not true; that is to say a device with an input spec of 200 VDC may not necessarily be happy with a 200 Vrms signal as that AC signal might have peak voltages over 200V which could damage the input circuitry.
Somebody please edify me
Edit
As requested, here is the device in question. It is a National Instruments 9255 C-Series module. Apparently, it actually supports up to 300Vrms but the same question applies.  Also, here is the datasheet.


texts: What is the reasons of water causing electronics or electrical appliances "broken"

texts:
We always told to keep off the electronic devices from water with no explicit reasons. Or remedies to fix the thing when accidents happened.

So, what is the physical reasons behind that submerged electronic or electrial devices get damaged?

For example speaker, motor(high-voltage). Smart phone, headphone(low voltage). Is the effect same?

Generally, is it because extremely low resistivity of water allows abnormal high current flow instead of designed current and eventually "burns" the electronic components or wires. Then there's an open circuit which disable some parts of the circuit or the whole circuit.

Apart from the problems I mentioned ,is there any chance water directly change the physical behavior of some components? If it is the cause how?

Is only my pure guess. Please point out my mistakes if they exist.


texts: what is the best way to charge a capacitor bank from an SLA battery

texts:
I need to charge a capacitor bank of 25 2.5v 55 farrad capacitors from a 2v 200Ah gel cell SLA battery, and modify the discharge time so that it discharges at 150Ah. I was wondering what the most compact solution is that will not damage the battery or capacitor bank, as at around $200 each, I am not too keen on replacing them frequently.

sorry about the mistakes, and yes the battery could easily drive the motor but, the application is a single loop linear motor, which requires a high amp, pulsed input. my thought was that, seeing as a capacitor has a very low startup resistance, charging it directly from the battery may have the same effect as a short circuit. I also found that a resistor of 0.0135ohms with a tolerance of +/-1 percent will drop the current to a manageable 150 A, which is used as both the charging current and the discharge current, and there is an estimated min. voltage of about 2.5v.


texts: How to find the exact number of turns for a power transformer

texts:
The input and output voltages of a power transformer allow us to derive the ratio of turns on the primary and secondary coils.

My question is how to find the exact number of turns of primary and secondary coils if input and output voltages and power in KVA are given?

For example a transformer with the characteristics Vp=11kV, Vs=400V and power=100KVA.  Can we calculate the number of turns from this?


texts: What is the typical RMS noise of a lithium battery?

texts: Take a typical CR2032 battery, if it is not discharging, what is the typical variation in voltage over a short period of time (eg a few seconds or minutes)?


texts: What is the hardware/device that can switch a 5V and 12V (simultaneously) PC power supply lines?

texts:
What I want to do is to switch the power supply lines (5V and 12V) for a hard drive. The 5V line is meant for data transmission, and the 12V is for the spinning disk DC motor.

I would like to control the hard drive power from PC through a means of serial port or USB, which I already have a device for. The difficulty is to switch on/off 5V and 12V simultaneously. I might need a specific hardware component to do this. Any suggestions on what might be helpful? Thanks.


texts: LM324 instrumentation amplifier gain and offset problem

texts:
I want to translate a Pt100 RTD to a 0-10V range, to be read by a PLC.

I designed a circuit (instrumentation amplifier) using the LM324 op-amp. It is powered using a single 12V supply.The resistor R11 is to be referred to as a Pt100 RTD. I am supposed to get 0 volts at RTD resistance 100Ω, but I get either 2.2V or fluctuating mV if I adjust the pot R4.

Also, I am supposed to get 10V at RTD resistance 250Ω, but I get only 6.5V.

As per the gain calculations I took all flexible possibilities. However R4 (the gain pot) doesn't change the gain much.

Where am I going wrong?

simulate this circuit – Schematic created using CircuitLab

Update from the comments: You can think of R11 as a Pt100 heated from 0 to 400 degree C, giving 100 to 250 ohm resistance.


texts: PSpice simulation of phase-shift oscillator doesn't work

texts:
I'm trying to simulate on PSpice a BJT-based phase shift oscillator, like in the following schematic:

but when trying to measure the voltage on the node connecting R3 and R5 I only get DC voltage (around 5 volts). Am I missing something? I've been trying this for the last 3 hours but no dice.

Thanks in advance for any help!


texts: How to select the resistance value for an Arduino capacitance meter

texts:
I'm working through examples for an Arduino capacitance meter and the ones I've seen give the known resistance of the RC circuit as 10 kilohm. It's my understanding that we could use "any" known resistance. Is there a reason that 10 kilohm is commonly selected?
Two examples that both use 10 kilohm:
https://www.circuitbasics.com/how-to-make-an-arduino-capacitance-meter/
Here's a response to a Quora question about finding capacitance that also uses a 10 kilohm resistor with a 9 V battery:
How can I determine the capacitance of an unknown capacitor?
There are others.


texts:
I have a car remote switch and I'm trying to find its frequency band.

I found this part on it :

 What is this ? I can't find it on the internet by searching the numbers on it's top(601-726S)


texts:
I am a newbie when it comes to Cypress cortex M0 and ARM chips in general. The chip I am using supports SWD. I only know the basic of SWD like IO pins required for it.

Does ARM support Interchangeability of SWD programmers? For e.g. can I use this programmer for programming any ARM chip like CY8C4245AXI. If yes, which programming software needs to be used?

Any kind of help would be highly appreciated.


texts: How to calculate Vout in this resistors network?


texts: What are the disadvantages of using a laptop power supply (into an LM317) as a bench power supply?

texts:
I have a Dell laptop charger, which claims to output 19V, 1.58A .

Is there any value in re-purposing this for hobby electronics?

I'm tempted to do something quite crude, such as feed an LM317 from it, and use that as a basic voltage source.

I'm aware that this will have various limitations, but what are they, exactly?

Are there risks involved in driving the laptop charger in this way?


texts: Realizing an flexible, but fault tolerant, infrared communication chain

texts:
The task fell on me to realize a wireless, daisy chained communication system. The communication must be wireless, esp. via infrared diodes. The end of the chain is connected to a PC (wired).
The whole system consists of n members. Each member has two sides with a sending and receiving diode.

The target is:

The PC must be able to send an initialization command and the system containing of n members must figure out how many modules are installed ("find n").
The PC must be able to send a command to all modules
The PC must be able to send a command to a certain module
The modules are close together, but the distance must be able to vary between about 1 and 3 inches.

My approach so far:

The PC sends a command to module 1. Module 1 sends back its presence to the PC, as well as wirelessly to the second module. Until now the PC knows that 1 module is present. When module 2 receives the init command it sends back its acknowledgement to the first module which transfers 2's message to the PC. Also, module 2 sends the init command further to module 3, and so forth. The init phase ends, when the last module (n) gets the init command and its presence message reaches the PC. After that no more message arrives at the PC's side and it knows that n modules are present.
Further commands contain a header byte addressing the "destination" module. Or, if all modules are meant, the command starts with a "zero"-byte (0x00).

The challenge is:

Physically: I don't know how to prevent the fact that module x could "talk" to module x+1 and x+2 simultaneously (cross-talking) by reflections or mirroring. I need to get the system self-learning. Until now, I dim the diodes until they can only reach a very small distance. But this isn't very fault tolerant.
Logically: Day light and other sources of infrared light cause a lot of fuzzy and gibberish messages. Real messages are currently preceded or even disturbed by external influences.


texts: What is a best way to get a 25% duty cycle square wave (5 V, 1 MHz) on a board?

texts:
I am trying to get two off-phase 25% duty cycle square waves(1MHz) to control a full bridge circuit.

Update:Sorry for the confusion here, what I mean was to have 2 square wave signals, and introduce 180 phase difference in between, off-phase is not the correct way to descirbe it. Please see picture below, green and red line represent these 2 signals, respectively:

The idea is to have everything on the board, instead of pluging in the external square wave signals.

I am not very experienced with this type of design so I have done some research on how to get a square wave circuit on board:

Use a function generator IC such as AD9833, and program it to output the square wave
Use a 1Mhz oscillator, a dc voltage source from battery and a comparator to generator the square wave: in my simulation program I did it as followed(not exactly 25% duty cycle but just something near):

Combine op amps to generator the square wave, an example from TI is shown below:

Use Micocontroller + PWM controller.

It seems to me the op amp option is very intuitive but it takes some time to be fully oscillated, thus I haven't seen any example that it is used for above 1MHz application. I need a sharp square wave(I have been simulating it with 10n rise/fall time) with defined duty cycle.

My question is, what is the commonly accepted way to do it?  It will be really appericated if you can provide me with some examples or reference so I can study about it.

Thank you in advance!

Kind regards,
Suns


texts: Do graphical/pixel mapped LCDs need a screensaver?

texts:
Will displaying the same for a very long time on a graphical or pixel mapped LCD harm the display in any way?

If so, what would be a maximum time to display the same, or how could I determine that time? Would it be a good idea to implement some sort of screensaver?


texts: Would any current flow when batteries and resistors are set up like this?

texts: What would the current flow be through the 1 ohm resistor? They are constant voltage sources, not batteries.


texts: Op-amp power supply driver problem (multisim), LM2679 simple switcher

texts:
The simulation works OK when I run with ideal op-amp but the problem comes whenever
I change the op-amp to a real one (LMH6642MF) and that results in a converge error and a warning.
I have tried to find the problem by changing the power supply to ±15 V for the op-amp.

The above figure is the circuit.

Please help me find the problem. I really have to make it work because I have a deadline in my uni in 4 days. :(

Thanks!

edit: Is it normal for the regulator to draw a lot of currents (app.7A) when there is no load at the output?
see image down for the current draw


texts: Filtering variable-frequency-drive noise by an RFI filter

texts:
We are having random noise issues on PC controlled data acquisition where one is related to VFD drive which is controlling the AC motor.

The thing is that, sometimes we observe continous large noise around 0.3V and right now I cannot say the nature of the noise.
But when the VFD is switched OFF the noise disappeared and when turned ON it appeared again for 5 seconds and disappeared in 10 seconds.
This is strange becuase it is somehow VFD realted but also doesnt appear all the time.

About 12 meters far away we have a data-acquisition computer with various DC inputs and the daq board also controls the VFD through an isolation amplifier.
All input signals are floating, so no ground loop. VFD ground is isolated from the daq side but my guess is somehow VFD's switching noise might be injecting noise to power lines.

If this noise is VFD related my question is:

If I daisy chain some electrical power outlets and power all the daq system(PC, transducers. power supplies) thhrough the same outlet.
And if I also use a filter such as this one after the mains outlet, would that be worth to try? This filter says it can filter both common mode and differential mode signals.
Or should I first find the FFT of the noise and then find a filter?


texts: Real schematic vs. ideal schematic, real components (R, L, C) vs. ideal components

texts:
I have come to a realization that throughout what I have been taught about electronic components and circuit schematics, there is a hidden side that is rarely talked about and not ever discussed in detail.

This is the difference between the ideal schematic that shows the intended current flow with ideal components that follow rules like \$V = I \cdot R\$, \$I = C \frac{dv}{dt}\$, \$V = L\frac{di}{dt}\$, a circuit where the connecting wires have no resistance.

The real world is completely different and the hidden aspects manifest themself at high frequencies when the circuit is not "lumped" anymore where we realize that resistors have frequency responses, capacitors have inductances, and inductors have resistances, PCB tracks have inductances and also capacitances. WOW!!!

What I wish from to do is to have a book/website/app note that will cover these real properties and the "parasitic" effects in detail and explain their origins. To be more specific: Where can I learn about the "real" R, L, C and on a separate note the "real" schematics that show what exactly is there on the board with all the parasitic and other usually ignored details. Is there a book or app note that may teach me how to think in terms of real world components and PCB design issues and explain origins on this "realness"?


texts:
In the textbooks and reference material which I have been using during my course on control systems, a common definition of steady-state error is as follows:
$$E(s)=R(s)-C(s)$$
where E(s) is the error (and also the signal carried forward directly from the summing node), R(s) input and C(s) output.

This definition has the slightly unsettling effect of yielding a negative error in the case that the output is above the reference signal, and vice versa. Wouldn't it be more logical to flip the RHS expression?

Is there any particular reasoning behind selecting this convention?


texts: How do I get high-performance guitar microphone going for cheap?

texts:
Main question:
Can I use a lot of cheap microphones off digikey and combine the signals somehow and will this make it sound like a higher-end mic?

How do you shop for a microphone: what specs are important in judging how "good" the mic will be?

Any experiences with microphones?  What did you find out regarding the above?  Thanks.

I will be sampling audio at 44 KHz approx and also transmitting it lossless.  This will probably be important in deciding whether or not I need a more expensive mic.


texts: According to what I read the circuit above is the schema of emitter repeater, it is used between two amplifiers  to connect  them and it's gain   A = 1; it does not amplify the signal. But  I want to get a better understanding of it


texts: Why does Altium say this net is uncoupled?

texts:
I have some differential pairs in Alitum. They require impedance matching to 100R, which is easy enough. Putting the numbers into Saturn PCB Toolkit V7.08, it works out that I want a conductor width of 0.1mm, spacing of 0.4mm to get impedance of around 94 Ohms.

I set the net rule in Altium; min, preferred and max widths all set to 0.1. Min, preferred and max gap set to 0.3, 0.4 and 0.5.

I route the trace using "interactive diff pair route" option in Altium, keeping all the settings to "preferred". I check the nets, and they are 0.1mm wide with a 0.4mm gap between the traces. Yet Altium throws the error "nets are uncoupled for (the full net length)".

I know that gap is quite large (0.4mm) but that is required with the PCB stack up. If that works for the impedance, why would Altium tell me they are uncoupled?


texts: What is the use of both I²C and UART in Bluetooth module BM78SPPS5MC2?

texts: I am interfacing the Bluetooth module BM78SPPS5MC2 with the STM32F417IGH6 microcontroller as a host, but how do I use the two serial communication protocols to communicate?


texts: How to calculate or estimate total power usage by computer to serve a request?

texts:
I want calculate total power usage by my PC to serve a request.

Each Request needs following:

Take 3 second to execute
Take 40 MB RAM
Transfer 1 MB trough network adapter
System has Core 2 Due 2.80 GHz and the request takes 10% of theme for 3 second


texts: Interfacing a 3.3 V pulled up output to 5 V input

texts:
I have a TIC834 stepper motor controller (https://www.pololu.com/product/3133) which works great for my stepper motor. It's however a 5 V based system. And my stepper motor includes a 3.3 V limit switch where the limit switch output requires 10k ohm pull-up.
Now I want to interface this output to one of the TIC inputs. But it's not clear to me how I can do this. Some input pins on this model already have a pull-up to 5 V. See for example the RX and TX pins which can be configured as inputs (https://www.pololu.com/docs/0J71/all#4.5).
What is the easiest way for me to interface this 3.3 V output that requires a pull-up to the TIC board?
Any help is appreciated.


texts: setting USB to UART input/output/VCC levels for general situations

texts:
I want to make a usb-serial adapter using CH340E(datasheet) chip, and use it on 3.3V or 5V microcontrollers alike, without using a switch or jumper. I've read this and this questions but there, the target voltage is known so things are a bit easier.
the CH340 has an internal regulator so any signal above 3V is accepted as HI.
in the datasheet [which is a little unclear] is mentioned :

CH340 chip supports 5V and 3.3V power voltage. When using 5V source
power, the VCC pin input 5V power and the V3 pin should connect with
decoupling 0.1uF capacitor. When using 3.3V power voltage, connects V3
with VCC, both input 3.3V power voltage, and the other circuit voltage
which connected with CH340 cannot exceed 3.3V.

I have to set CH340 VCC to 3V or 5V, so here are some solutions:

Use the 5V supply. in this case, the CH340E would be fine for any range of logic levels between 3 to 5 volts. the downside is, the idle-Hi tx/rx pins of CH340E are 5V (I've measured it) now and the burden, is on the protection diodes of the microcontroller. I can use a series resistor (1K), but it's a little unpleasing to rely on protection diodes.
Use the 3V supply. in this case, the CH340E will use it's own internal regulator as it's VCC. the problem is, that it's mentioned in the datasheet(above quotation) that in this case, we shouldn't connect anything higher than 3.3V to it. (no protection diodes ?)
Use 3.3V zeners with a series resistor. I just came up with the idea. in this case, it is guaranteed the line level on tx/rx pair stays in the range of 3.3 volts. so the burden would be on these zeners. a series 1K resistor would ease it for the zeners.
Using a combination of buffer gates (e.g. 74HC125). it seems a little overkill for the situation.

simulate this circuit – Schematic created using CircuitLab

Am I right about the (1) and (2) ?
Is the method of (3) correct? if yes, would there be unexpected behaviour (e.g. limited baudrate values)?


texts: Does a 24V inverter consume the same amount of wattage as a 12V inverter?

texts:
Let me clarify. I know how series and parallel setups work. I know that in series the voltage adds but the current stays the same. In parallel current adds but voltage doesn't.

But that doesn't really answer my question about the energy consumption of a given setup.

Let's use an inverter setup as an example.

Say we have a light that uses 10 watts (an LED bulb)

And we have two different inverter setups:

an inverter on a 12V battery with 20Ah
an inverter on two 12V batteries with 20Ah (wired in series for 24V)

The second battery setup doesn't have more current, just more voltage.

If the LED bulb is consuming the same amount of power in both setups,
what happens in the second example?

Does the current draw per battery get divided in half?

I think my misunderstanding comes from the fact that I don't know how electricity storage works with batteries. Elsewhere I've read that I shouldn't think of it in terms of watts but in terms of Ah storage. However, that goes against my way of thinking that \$volts \times amps = watts\$.

Say we have the same set up as above,
will the available watts in the second example be more than then first?

$$
2 \times 12V \times 20Ah = 480W
$$

compared to:

$$
1 \times 12V \times 20Ah = 240W
$$


texts: How do I figure out the ohms of an antenna?

texts:
I'm looking at the CZE-05B FM transmitter and in the manual it states the output load is 50 ohm and I need an 50 ohm antenna.

So my questions are is this antenna 50 ohms? https://www.ebay.com.au/itm/2121-Telescopic-Extendable-Antenna-BNC-Connector-for-Portable-Radio-Scanner/392126393923

I also plan to follow the following guide https://vk1nam.wordpress.com/2m-dipole-for-sota/ to make an an dipole antenna.

I have read I might need a Balun can anyone offer some advice please

Thanks


texts: What device/component from the early 1940's can listen to only a specific narrow range of acoustic frequencies?

texts:
This website briefly describes the development of the first active acoustic homing torpedo of the US Navy:

Investigation of the use of echo-ranging equipment or an "active" homing torpedo system was initiated under the auspices of NDRC in 1941 at the G.E. Co. Research Laboratory, Schenectady, N.Y. Active homing differs from passive homing in that, with active homing, the torpedo steers on the basis of the signal returned by the target through reflection of the torpedo's own transmitted signal. In mid-1942, G.E. began development of the first active homing torpedo, Torpedo Mk 32, which was physically similar to Mine Mk 24 (figure 17).
By mid-1944, the program had progressed through the successful prototype stage... About ten units were completed when World War II ended, and the project was deactivated until 1951 when Torpedo Mk 32 Mod 2 was produced in quantity by the Philco Corp. of Philadelphia, Pa.

So basically, an active homing torpedo needs to send out its own ping and listen for that specific echo, rather than other noise on other frequencies. AFAIK, all active homing systems choose a high frequency, sounding like a high ping, because all large ship screws make very low frequency noise.
Anyway, my question is what kind of electronic device can listen to only a narrow set of acoustic frequencies? It has to be a device that existed in the early 1940's.


texts: Does the noisy-channel coding theorem (Shannon's theorem) apply to two-way communication with retransmission requests?

texts:
Does the noisy-channel coding theorem apply to automatic repeat request systems?
Some people seem to imply that, when a system has 2-way communication,
such systems can have far lower error rates at the same data bit rate
compared to one-way communication.
The implication is that transmitting in both directions allows the system to do things that are simply impossible for one-way communication.

The presentations of the noisy-channel coding theorem (also called Shannon's theorem) that I've heard or seen
all seem to assume one transmitter and one receiver (1-way communication),
using some sort of forward error correction code, without any retransmissions.

What books or papers discuss the Shannon–Hartley theorem or Shannon's theorem with two-way communication with retransmission requests?


texts:
how much is the dynamic impedance/resistance seen from a electret microphone?
I am trying to design a microphone preamp and need to know seen resistance in small signal from the signal source (microphone in this case).
This is very important because I should match poles and zeros so they will disable each other.


texts: Using a capacitor to keep circuit powered for 1s after battery disconnected?

texts:
I am planning on using a 3.3V GPS module which draws 22mA. The module has a requirement that a shutdown sequence be initiated 1s before power is removed from the IC. If power is removed without allowing it to go through the shutdown sequence, the program flash memory can become corrupted and the module bricked. This seems like a really poor design to me, but that's the way it is.

The circuit I'm designing is battery powered, so the battery could die or be removed at any time. I considered using a separate battery as a backup, but it seems like capacitor would be cheaper and easier.

So, I need a capacitor to power it for 1s when the power is disconnected. I'm planning on putting a Schottky diode before the capacitor to ensure other ICs in the circuit don't draw power from the capacitor. I need to determine the capacitance to use and am unsure if my calculations are correct.

I know \$Q = I \times t\$. Therefore, the charge needed is \$Q = 22\text{mA} \times 1\text{s} = 22\text{mC}\$.

Since \$C = Q/V\$, the capacitance needed is $$C = \frac{22\text{mC}}{3.3\text{V}} = 6.67\text{mF}$$

Is that correct? Do you think using a capacitor like this is a viable alternative to using a backup battery?


texts: Momentary Switch NAND Latching IC Burning and (Possibly) Faulty Logic

texts:
Problem:

My issue is that the momentary switch with NAND latching logic that I have designed is not functioning consistently.  It does work as intended at first, but then fails to work after repeated testing, never regaining functionality.

Question:

Is there something wrong with the way I have designed my logic that is determining the voltages at the gates of the two different FET's (DISP FET and MAIN FET) in my circuit? Specifically, my choice of R4, R5, and D4? Or is it something else entirely?

Background Info:

The circuit that I am making is a back-up power bank of lithium ion batteries, and when the momentary switch is pressed ("SW" in the schematic", this provides power from this back-up power bank to the main power bank (through the "BOARD-" terminal shown in the schematic).
The "SN74" chip is a latching double NAND, part #: SN74LVC2G00DCTR.
The CHRG IND terminal is NC to ground.
The diode "D4" is rated 10V, 100mA, part #: 1SS367,H3F
I designed the latching logic of my circuit based on Fig. 5 from the example on this site.
The purpose of the DISP FET is to allow the battery capacity display to turn only when there is a charger plugged in, but not turn the rest of the circuit on (the USB ports, switch on the LED, and the power supply from the batteries to "BOARD-")

Testing of the Issue:

I have the lithium ion batteries at 41V, and then my buck converter is outputting a consistent 5V everywhere it is tied to, which I verified with a multimeter.  I also did a continuity test across the board, there are no shorts between any of the power rails or ground, or across any of the components.

My tests

When I first assembled the PCB, it was working exactly as intended.  So, I push the main momentary switch of the circuit that provides the functionality and as a result, The USB ports, the LED on the switch itself, the battery capacity display, and the output to "BOARD-" are all on.  Then, I leave my circuit for 10 minutes.  I come back, push the switch again, and the switch does not turn on.  The way that I verified this is that I tested the voltage at the output of the SN74, and it stays at ground, it does not go to 5V as it did when it worked in the first place.
After this initial failing, I put a scope meter on the gate signal, and sometimes I would see the gate voltage spike to about 560mV, so not enough to turn on.  Other times, it would spike all the way to 5V, but not hold the high state, but just go back down to ground.  Other times, the switch would turn on without me even pressing it, upon me providing power to the board.
I swapped the NAND IC for a fresh one, and the circuit would work.  But, it would then soon fail again as before.  I tried removing the diode "D4", creating an open circuit there, and then the button would work as intended.  However, it would then also soon fail afterwards.
I also tried shorting across the diode, and it seemed that when it was working, the button would turn on, but not turn off.  Then, just as before, it would also just not even turn on anymore.
I tried putting a scope meter on the input of A1, see oscilloscope below for output.  The blue line is the voltage at the output, so pin 1Y , going to the gates of the FETs, and the yellow line is the voltage at the input pin 1A.  The max voltage of 5.8V at the input pin 1A did not exceed the 6.5V maximum rating of the SN74. The ramp up and ramp down of the yellow line is from me pushing the momentary switch.
I took the SN74 off, and connected the CD4011B to the circuit using a breadboard and wires.  Still, the circuit did not function.

Conclusion:

All these testing results are proving to be inconsistent and I can't seem to figure out what the cause of the issue is.  Ultimately, I know that my design did work for 10 minutes, and then the failures started, so that would perhaps be the biggest clue.


texts: I am a beginner in simulation on LTspice. I have this circuit to simulate but each time it displays an 'unknown controling source 100' error. I don't know how I should add it and or.


texts:
My SNR is better with DC Free transmission. Why?

Example:

1.) Datasignal with DC:

Datastream consisting of 0V and 1V.

2.) Datasignal without DC:

Datastream consisting of -0.5V and 0.5V.

The variance is the same at both examples.

So I don't get, why the SNR is better without DC.


texts: Are these (dis)assembly screw symbols standardised?

texts:
Sometimes there are these two half-arrow symbols on PCBs and on enclosures. See the images, for examples.

Those symbols are often placed near the screws, that are to be unscrewed upon disassembly.

Are these symbols standardised? If yes, which standard they are from?


texts: Power ATMEL ATMEGA328P directly from USB

texts:
im wondering if it is Ok to power an ATMEGA328P directly from an USB-Poweroutlet i.e. an Apple-USB-Charger.

And I mean directy:
VCC to Pin 7+20
GND to Pin 8+22
Peripherals should be powered from this source too.

Or is the output from an usb-charger not stable enough to power an ATMEGA328P?


texts: Arduino - Connecting to a remote Bluetooth device asking for a passcode

texts:
I have worked on many Arduino projects but this time I am facing some hurdle that is too strong for me.

I want to use a Bluetooth module as a MASTER. Purpose: Connecting to a camera and sending instructions to take photos.

Problem: When trying to connect, the camera prompts a security key which you can type on a smartphone. Problem: I didn't find ANY way of doing this with an Arduino.

The closest I was is using AT commands to set the same passkey as the other device. Problem: it has to be done before the connection attempt, and in my case, the passkey could not be guessed…

Therefore I'm as stuck as frustrated!

I have various BT chips on hand : HC-05 HC-08 MLT BT05… so various solutions available. Will buy other ones if needed.


texts: Value of blown resistor in this simple lead acid charger, Please help if you can

texts:
I hope someone can help with this very simple circuit, I have traced from the pcb, my electronics theory has really gone out the window, The circuit shown is from a car battery charger and has a 2 transistor circuit to monitor the battery turning the 'Full' LED on when charge is complete, however the resistor in series was blown due to an accidental short, I have no idea of it's value as it was fried! I have replaced it with a 0.5 ohm 1.5watt resistor as a rough guess, the resistor in the circuit was about 0.6 watt.

The charger output is marked up as 12volts 2.7Amps (4A RMS)

Hope you can help me out with the correct resistor value.


texts: Why do 7 segment LED displays break apart when I brush my teeth?

texts:
This question might sound silly, but it is very serious (although geeky, I must admit).
When I use my electric toothbrush in front of my alarm clock (one of those with a big red LED display), the numbers seem to break apart. Why?

With my current alarm clock the first 3 segments (a,b,c) make one group and the other 4 make another one. The striking thing is that both groups seem to slowly oscillate, in anti-phase. I cannot affirm that the grouping is the same for every display of the kind -- and I cannot check now because I only have this one LED display at home -- but I've seen this illusion on many different displays in the past.

I think this illusion is fascinating (told you I'm a geek) and I would like to understand why it is...

I believe that it has something to do with
   1) the vibrations of the toothbrush making my eyes oscillate in their orbits so the image seems to move (a bit like when you touch your eye on the side with your finger and the whole image seems to move),
   2) with the periodic refresh of the segments. I suspect that the two groups I'm seeing actually correspond to two groups of bars blinking in sync, so there really are two groups, (but why do they dislocate like that?)
   3) with our periodic perceptual "refresh rate". Something similar to what makes us see car wheels as stationary when they rotate at a certain speed.

I must say my competence in electronics is close to zero, so my questions might be trivial to you guys. How does the refresh of the line segments in a 7 segments display happen? Is it cycling (a,b,c,d,e,f,g,a,b,c...)? How come I see two groups, then? At what frequency are the LEDs blinking? I understand some of these questions depend on the specifications of my alarm clock, but since I've seen this illusion on basically every type of LED display I passed by with my toothbrush (microwave, VHS video recorder (yes the story started long ago. I bought the toothbrush I'm now using just for understanding this silly illusion, but it was actually as a teenager that I noticed it)...), I guess there is something constant there...


texts: What is the best way to solder these wires to circuit board?

texts:
What is the best way to solder these stranded wires onto a vero board (strip board)?

I am thinking maybe using some kind of connector instead of just soldering on. It will make things more flexible. I also want it to look semi professional.

If using connectors, what connectors would be the best?


texts: current transformer and primary positioning inside window

texts:
I am designing a setup that is a little convoluted. but it's on purpose. The point is to make a toroidal current transformer act as an electromechanical pickup. Just for musical experimentation and as a practical exercise.

So,
I would use a tensioned conductive string as a primary, with one turn (cable going straight at the center of the toroid). The primary would pass an arbitrary DC current, let's say 1A

I wound two windings over the core. one CW the other CCW.
Both windings are 26 turns, Both are wound opposite to each other. Both windings use 1/4 of the winding window.
The theory is, if I pluck the string with parallel motion with respect to both secondaries while a current flows inside the string, When the string gets closer to one winding (lets call it the top winding) the magnetic flux will be stronger with respect to the top winding and weaker with respect to the bottom winding.
It will induce open circuits high voltages on both secondaries, with a slight differential due to the string vibration. so, now if i connect the two secondary windings in parallel; Such as the phase dots are opposed, I should see only the voltage differential due to the string position inside the window. Right ?
Now if the theory is valid, is it practical in terms of currents and voltages ? What preamp setup should I use ?
the core used is 85*50*30 (outside diameterinside diameterheight in mm.) 26 turns gave me a value of 2.65 mH.
Any ideas ?


texts: First checks after oscilloscope unboxing

texts:
You bought your first entry level oscilloscope (e.g. Rigol DS1004Z series, 4 Channels, 50-100MHz, 1Gs/s) and while it is slowly warming up to room temperature you are wondering if the unit you have is really working well and did not suffer any damage from shipping etc.

Since your next complex measurement equipment is a multimeter, you wonder how to test it. Like, for a new computer you run memory test, hdd test, burn in tests (like mprime), so what is kind of an equivalent for oscilloscopes that can make you certain it is functioning mostly correctly?

Besides the built in square wave generator, what can you measure and check if it is properly displayed?

I am thinking of something like

A simple (breadboardable? though probably not at 100MHz) circuit that is almost guaranteed to work and can be used to check most things like bandwidth and accuracy of the scope.
A signal source that is rather easily accessible to most people and has quite known characteristics that when off tell you something is wrong.

Note: I am not asking about how to get familiar with the scope, but rather than some simple checks that assess it is functioning probably correctly.


texts:
I'm thinking of hacking up something simple to check toilet occupancy in an office. Ideally, the system should be unobtrusive and out of the way.

I know you can use a PIR sensor to track moving objects (What sensor to choose to track human presence indoors?) - however, if somebody is sitting still on a cubicle, that will probably not register since they're stationary.

Apparently parking spot sensors use both IR and magnetic fields to detect cars (http://www.nedap.com/business-units/identification-systems/parking-detection-makes-sense/). Obviously the second part of that won't work on people.

I know you can get those IR-based sensors that bounce a beam off a reflector, however, I'm hoping to be able to mount just one sensor on the ceiling, if possible.

Is there another type of IR or ultra-sound sensors that might work here?

Has anybody got any particular parts or approaches they could suggest? Any caveats I should be aware of for this use case?


texts: How to calculate input impedance for this simple circuit?

texts:
I'd like to calculate the input impedance of the following circuit, assuming that Q1 is "active". I know that the impedance of the voltage divider is \$\frac{R_1R_2}{R_1+R_2}\$ and the impedance of the emitter follower is \$\beta R_3\$, where \$\beta\$ is the gain, but it's not clear to me how the impedance of the whole circuit can be calculated. I'm not just looking for a recipe. More importantly, I'd like to know why that recipe leads to correct answer, knowing the definition of impedance, i.e. \$\frac{\Delta V}{\Delta I}\$.

simulate this circuit – Schematic created using CircuitLab


texts: What are your best resources for winding custom transformers?

texts:
What are the best resources that you have found for winding custom transformers?

prose, videos, forums, etc.

I am looking for things more on the practical side rather than resources explaining the basics of transformer winding ratios. Once I get enough responses, I will compile them into a list. I purposely did not differentiate between power and signal transformers, so I am hoping to get some of both.

For instance, here are a few of mine:

https://sound-au.com/xfmr.htm
http://www.ieee.li/pdf/introduction_to_power_electronics/chapter_15.pdf
http://www.coilcraft-cps.com/pdf/doc857_Multiple_Applications.pdf
http://www.jensen-transformers.com/an/Audio%20Transformers%20Chapter.pdf


texts: Weird 240 ohm resistor on zq line to DDR

texts: I've been looking at schematics that interface ddr ram and noticed a weird notation for their zq pull down resistor. What is with the dot at the top as well as the 1%? Haven't seen this before.


texts: Custom-built NAND SR latch not resetting

texts: I'm trying to build SR latch in Logisim using NAND gates, but I seem to be unable to get the latch to truly reset. I can set S to 0 and R to 1, but once I set it back to 0, Q goes back to being 1. How do I get Q to be 0 when S is 0 and R is 0?


texts: Find autocorrelation function of a signal

texts:
Find auto-correlation function of a signal

$$g(t)=e^{-2t}\cdot u(t)$$

where \$u(t)\$ is the unit step function.

I don't know how to start to solve this problem. My book list this equation only:

$$\int_{-\infty}^{\infty} g(t)g(t+T) dt$$

The problem does not tell us what \$T\$ is so that is why I am confused.


texts: Can Micro-controller bear the voltage at its pins more than its rated voltage?

texts:
I have a micro-controller, for which i have a datasheet specifying the ac/dc characteristics of that mcu. But in this datasheet there are no absolute maximum ratings only the operating conditions are available.

According to datasheet, MCU I/O can have voltage signal in range -0.3V to 3.6V.
I have test case in which almost 8V appears at these pins of MCU for 10 milliseconds.

Now i was wondering, if this signal can affect the reliability of device or damage it. Or if this signal persist for longer duration or repeats itself more than one times, can this voltage 8V (higher than rated 3.6V) enough to damage the device??

Thanks in Advance..


texts: Serial programmer not working, what are the possible problem sources?

texts:
I have been trying to make a serial programmer for AVR chips. I have been using this schematic as reference, http://www.elektronika.lt/_sys/storage/2004/05/06/avr_prog.gif.

I made the circuit and have checked that the connections are correct. Here is a picture of it on breadboard

The problem is it doesn't even get detected in linux.

rick2047@Sophiya:~$ setserial -g /dev/ttyS*
/dev/ttyS0, UART: 16550A, Port: 0x03f8, IRQ: 4
/dev/ttyS1, UART: unknown, Port: 0x02f8, IRQ: 3
/dev/ttyS2, UART: unknown, Port: 0x03e8, IRQ: 4
/dev/ttyS3, UART: unknown, Port: 0x02e8, IRQ: 3
rick2047@Sophiya:~$ dmesg |grep ttyS
[    0.220488] serial8250: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
[    0.221036] 00:08: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
rick2047@Sophiya:~$

In window there is a com3 and com1 but cannot connect to com3, it says check your port settings.

I checked the bios and there is only a Serial Port A in the peripherals section. Does that mean I can use only one serial? My monitor is an old CRT which runs on serial cable.

UPDATE
The monitor is on VGA. So why does this not work?

rick2047@Sophiya:~$ avrdude -p atmega8 -P /dev/ttyS0 -c ponyser -V -U flash:w:test1.hex

avrdude: AVR device not responding
avrdude: initialization failed, rc=-1
         Double check connections and try again, or use -F to override
         this check.

avrdude done.  Thank you.


texts: What is the acceptable current draw on pin #9 on a VGA connector?

texts:
I'm trying to appropriate the 5v that comes into an LCD monitor on pin #9 of a VGA connector to power a microcontroller with some sensors, and LEDs.

I've found a discussion on this topic on a cached forum thread from EEEforums.  While there are references to standards it only discusses a monitor on an external power source and not a locally powered monitor.

How much current can I draw from this pin reliably?


texts: multiplexing 256 led with atmega128 not working properly

texts:
Original/First version:

Second Version:

Second Version display, Brightness not the same for all led!!

Originally, I have 8 resistors for each 8x8 dot display, then in this newer version, trying to simplify the circuit, I only use 8 resistors for all 4 dot displays, but the brightness is not very good, ie, they are not the same brightness. Technically, I think it's okay to just use 8 resistors to power these 4 dot displays. That is how I power 7-segment led display anyway. Am I correct? What is the problem here?

GOT IT working now!!:


texts:
In the datasheet of LM2596, 33uH or 47uH inductors are recommended for 5V output. I can't find any high amperage inductors of those values. So that if I use 100uH of 2 inductors in paralell(they will act as 50uH together), will the circuit work in real life like in the theory?

datasheet of LM2596:
http://www.ti.com/lit/ds/symlink/lm2596.pdf


texts: PCIe - SATA bridge/host controller ICs unavailable to the hobbyist/from low volume suppliers?

texts:
I was toying with the idea of a project that would involve adding a SATA device to an existing PCIe lane; probably far too ambitious for me, but before I could confirm that I noticed that there aren't any PCIe-SATA bridges available from suppliers like Digikey, Mouser, Element14.
There are PCIe/SATA redrivers & muxes, and PCIe-USB bridges, and USB-SATA bridges, but not PCIe-SATA bridges. Such chips exist (e.g JMB58x) but are not available anywhere that I'm aware of that an individual/someone ordering low volume might be able to use.
Am I misunderstanding some terminology? My best guess was that it's just too specialised/high speed, unavailable because nobody/org that can't 'call for pricing' etc. would be capable of using it anyway - but then surely that would equally apply to redrivers and muxes, and to PCIe-USB bridges for that matter.


texts:
I have a verilog code that describes a simple RAM. I use Genus synthesis tool to do synthesis, then generate a .sdf file for post-synth simulation. However, The tool generates .sdf file with faulty timingchecks. The setuphold timings are off. Summing setup and hold times yields negative values, which causes failure in sdf backannotation when simulating.

Following is a part of the SDF file,

(CELL
 (CELLTYPE "SDFQD1")
 (INSTANCE memory_bank_reg\[29\]\[1\])
 (DELAY
    (ABSOLUTE
      (PORT CP (::0.0))
      (PORT D (::0.0))
      (PORT SI (::0.0))
      (PORT SE (::0.0))
      (IOPATH CP Q (::-6916) (::-6612))
    )
 )
 (TIMINGCHECK
    (SETUPHOLD (negedge D) (posedge CP) (::11915) (::1925))
    (SETUPHOLD (posedge D) (posedge CP) (::12580) (::-12089))
    (SETUPHOLD (negedge SI) (posedge CP) (::4566) (::6006))
    (SETUPHOLD (posedge SI) (posedge CP) (::15967) (::-18683))
    (SETUPHOLD (negedge SE) (posedge CP) (::12574) (::3588))
    (SETUPHOLD (posedge SE) (posedge CP) (::7001) (::-2850))
 )
)

As you can see, one of the setup hold time is faulty. There are hundreds of errors like this in the file, this is just one of them. I tried different processes (FreePDK, TSMC), but they all yield faulty results.

Following is the verilog code of the RAM,

`timescale 1ns/10ps

module instruction_memory(
clk0, csb0, web0, addr0, din0, dout0);

input clk0, csb0, web0;
input [5:0] addr0;
input [15:0] din0;
output reg [15:0] dout0;

reg [15:0] memory_bank [0:63];

always @(posedge clk0)
begin
    if(!csb0)
    begin
        if(web0)
        begin
            dout0 <= memory_bank[addr0];
        end
        else
        begin
            memory_bank[addr0] <= din0;
        end
    end
end
endmodule

Finally the synthesis script for Genus,

# Reading Verilog Codes and Elaborating
read_hdl -v2001 {instruction_memory_dff.v}
elaborate instruction_memory

# Defining Time Constraints
create_clock -period 80000 -name clkin1 -domain domain_1 clk0
set_clock_transition -min -rise 100 clkin1
set_clock_transition -max -rise 200 clkin1
set_clock_transition -min -fall 100 clkin1
set_clock_transition -max -fall 200 clkin1

set_input_delay -clock clkin1 -clock_rise 500 clk0 web0 din0* csb0 addr0*
set_output_delay -clock clkin1 -clock_rise 500 dout0*

set_driving_cell csb0 web0 addr0* din0* -cell BUFFD6

set_load 5 dout0*

# Synthesizing
set_db operating_conditions NCCOM
set_db syn_generic_effort high
set_db syn_map_effort high
set_db syn_opt_effort high
syn_generic instruction_memory
syn_map instruction_memory
syn_opt instruction_memory

# Writing Report Files
report timing > report_time.txt
report gates > report_gates.txt
report area > report_area.txt

# Writing Design Files
write_hdl instruction_memory -language v2001 > synth_instruction_memory_dff.v
write_sdf -edges check_edge -design instruction_memory >
instruction_memory_dff.sdf

What might be the problem here? Let me know if I missed some information.


texts: Why doesn't function generator documentation ever mention the maximum output current?

texts:
The output impedance mentioned, but how does this translate to maximum current? What happens if you short circuit the output of a function generator?
Let's take the XR-2206 for example.
The datasheet states an output impedance only for triangle wave of 600 ohms and nothing for the other wave forms.
Why is this 'never' important?


texts: Does cassette tape change its velocity while playing?

texts:
Looking at the old cassette tape,

From the POV of the head, let's say that it reads at speed \$v\$ (the magnetic medium scrolls at speed \$v\$).
But looking at the right wheel, which is the one that's pooling the magnetic medium - its radius is growing(!) over time.
Now, \$v=r\omega\$, where \$\omega\$ is the angular velocity, i.e. a constant
Question
I don't think that's true. What is really going on here? Radius is growing over time, for sure. I also assume that \$\omega\$ is constant. so did \$v\$ increase?


texts: Why MIPS uses R0 as "zero" when you could just XOR two registers to produce 0?

texts:
I think that I am looking for an answer to a trivia question.  I am trying to understand why the MIPS architecture uses an explicit "zero" value in a register when you can achieve the same thing by just XOR'ing any register against itself.  One could say that the operation is already done for you; however, I cannot really imagine a situation where you would be using a lot of "zero" values.  I read Hennessey's original papers, and it just assigns a zero as a matter of fact without any real justification.
Does a logical reason to have a hard-coded binary assignment of zero exist?
update:
In 8k of an executable from xc32-gcc for the MIPS core in the PIC32MZ, I have a single instance of "zero".
add     t3,t1,zero

the actual answer:
I awarded the bounty to the person who had the information about MIPS and condition codes.  The answer actually lies in the MIPS architecture for conditions.  Although I was initially not wanting to assign time to this, I reviewed architecture for opensparc, RISC-V, MIPS-IV and OpenPOWER (this document was internal) and here are the summary findings.  The R0 register necessary for comparison on branches due to the architecture of the pipeline.

integer compare against zero and branch (bgez,bgtz,blez,bltz)
integer compare two registers and branch (beq,bne)
integer compare two registers and trap (teq,tge,tlt,tne)
integer compare register and immediate and trap (teqi,tgei,tlti,tnei)

It just simply comes down to how the hardware looks in implementation.  From the RISC-V manual, there is an unreferenced quote on page 68:

The conditional branches were designed to include arithmetic comparison operations between
two registers (as also done in PA-RISC and Xtensa ISA), rather than use condition codes (x86,
ARM, SPARC, PowerPC), or to only compare one register against zero (Alpha, MIPS), or
two registers only for equality (MIPS). This design was motivated by the observation that a
combined compare-and-branch instruction ts into a regular pipeline, avoids additional condition
code state or use of a temporary register, and reduces static code size and dynamic instruction
fetch trac. Another point is that comparisons against zero require non-trivial circuit delay
(especially after the move to static logic in advanced processes) and so are almost as expensive as
arithmetic magnitude compares. Another advantage of a fused compare-and-branch instruction
is that branches are observed earlier in the front-end instruction stream, and so can be predicted
earlier. There is perhaps an advantage to a design with condition codes in the case where multiple
branches can be taken based on the same condition codes, but we believe this case to be relatively
rare.

The RISC-V document does not hit at the author of the quoted section.  I thank everyone for their time and consideration.


texts: How to "debounce" or clean up this logic signal

texts:
I may not have used the correct terminology with "debounce" as I'm aware this word is usually reserved for the noise created as the output of a physical button goes from low to high, so please forgive me but I wasn't sure the best way to describe the signal I have.
I'm making an audio sensing circuit which feeds the signal from an electret microphone (powered by 3.3V) into two op-amps (dual op amp LM358P): the first op amp amplifies the signal and is configured with negative feedback (inverting amp). The output is fed to the non-inverting input of a second op amp, and the inverting input is set using a voltage divider with variable resistor so that it can be calibrated to filter out power supply noise.
Here is my circuit:

If I click my finger, the output of the second op amp looks like this (see blue waveform):

I would like the output to be a single, clean pulse of e.g. 1 or 2 seconds long. Much like a PIR or similar sensor might give. It can reset after that period as long as no more audio is sensed. (The reason is that I'm sending it to the input pin of an ESP32 running Tasmota, with a switch input set, however the switch is not triggering.) The max voltage of the output I currently have is 2V, I believe this is because the LM358 will swing between VCC -1.5V and GND according to its data sheet. I think this should be fine to trigger the digital input of the ESP32, if not I could use a buffer.
What type of circuit would I need to use to achieve this "time trigger" with minimum components?
Ideally I would use a single additional IC, or a couple of passives to achieve this.
Options considered
These are things I have guessed so far might work:

I considered changing the second op amp into a multivibrator or even an integrator, although I don't fully understand if these will do what I want, also the former does add quite a lot of components.
I also considered rectifying the wave before it enters the first amp (which currently cuts the bottom half of the wave off, I think this is because the rails are GND and 3.3V), then smoothing the input out with a capacitor.
I also have 555 timers in my project box, but I don't know how to use them creatively to achieve what I want.

Are these ways viable? Is there a more simple or quick and dirty way?
I would appreciate any additional input if there's a trick I'm missing in the overall design.


texts: Is this address decoding circuit correct?

texts:
The problem is to design an address decoding circuit for two 4Kx8 RAM chips at the 2050H . We have 16 address lines. So, for 4Kx8 RAM we need 12 address lines to address the memory. Remaining can be used for deriving CS' (chip select) signal.

Here, For RAM 1 we have

Starting address 2050H : 0010000001010000

Ending address   304FH : 0011000001001111

For RAM 2 we have

Starting Address 3050H: 0011000001010000

Ending Address   404FH: 0100000001001111

Bold = A12

So, if we use a 1x2 decoder as in the picture, and A12 is the input. The chips will be selected depending on the state of A12. It will work fine until ending address is used. What happens when someone tries to access the ending address?