texts: Earphone wiring and how do I unscrew the housing from a 3.5mm plug?

texts:
The 3.5mm plug on my earphones broke. My earphone is the Xiaomi hybrid pro HD. It has the left and right earbud, a 3-button controller and a mic. It has 5 wires:
-copper twisted around a white-colored wire (this white-colored wire also has straight copper strands inside it)
-red
-green
-blue
-red twisted with copper.

I'm wondering what these color codes could possibly stand for.
I'm also planning on transplanting my old headphone's 3.5mm plug to this, but I'm wondering how to "unscrew" the housing of this headphone plug to expose the wiring and terminals. Is it possible at all to disassemble the plug's assembly or is it a fixed and sealed unit?


texts:
I don't know if this is the right place to ask, but i'm asking anyway.

How does a computer shutdown really work?

I want to know the electronics (or physics) behind it. Like, how does a system signal make the device disconnect?

I am interested only in the last step of the process - when it is disconnected from the power - when the CPU stops receiving current.

My non-researched idea is that it actually never shuts down completely, as long as it is connected to power source.

(And the next question would be how does it really start up :D )


texts:
I have been studying the 8032 microcontroller. It is mentioned that 8032 doesn't have internal ROM. Now there are few questions I have

Do we need an external ROM to execute programs necessarily? Can't we use the 256 byte internal RAM?
Suppose I am using the 8032 microcontroller with an external ROM2732 and also using a latch for storing the address (lower order) of port P0.(which may transfer address/data). Now after enabling EA and connecting the PSEN how does 8032 execute the program? What happens if I turn on the system ?(How does the program counter of 8032 microcontroller executes intructions? From which address of external memory the program should be read ?

I have read these manuals-
Intel 8032H Keil , Atmel 80C32E.


texts: How does a tunneling microscope collect data and construct an image?

texts: Upon reading on the  subject of these complex machines, I wondered how they are able to construct images from the tunneling effect. What types of algorithms are developed? and what kind of signals are received?


texts: Solving a circuit containing a resistor and inductor in parallel

texts:
I am working on a problem involving a resistor and inductor in parallel with eachother - I am trying to work out the voltage across the inductor as a function of time.
It is clear to me that I will need a formula for 0 < t < 1ms and one for t > 1ms (Because the switch is closed then opened again) however I am really struggling to get my head around how I will work this out.
If someone would be kind enough to point out the logical steps for this problem it would be much appreciated - I am wondering if I need to work out a thevenins equivalent circuit then try to solve, however when I attempt this I find the resistance would change with time which wasnt helpful in solving. I have tried my textbooks and google but I couldn't find a worked solution or notes on how to solve such a circuit.
Many thanks!


texts:
Please see the screen shot of the 74LS161 wave form.
the yellow line is the clock input.
the blue line is the QA counter output.
I am surprised to see such a large negative voltage spike of the counter output. The negative spike last about 80ns.

My question is that: is it normal?

btw, nothing is connected to the counter, just one 74LS161 on the breadboard, input clock, enable T,P, disable load, disable clear, and measure the output. I added a 0.1uF despike cap, doesn't help on the output spike.

thanks!


texts: how can I calculate the smallest measurable voltage for a given adc?

texts:
I have a project where I use 4 strain gauges in full bridge configuration with a hx711 module and an Arduino mini pro.

How can I estimate the smallest voltage I can measure with a given adc from its datasheet, in this case the hx711 module?


texts: Sensing Ground Faults on a High Voltage Pulser - Coupled Inductor Issue in LTSpice

texts:
I am building a ground-fault protected High Voltage Pulser. The pulses may be as high as 500V and as narrow as 50us (20kHz).
The question of how to create GFCI protection is proving to be a complicated decision. AC and DC ground faults must be identified. This question will deal with AC faults, but I am also interested in any info on sensing DC faults as well (high-side sense resistors are out of the question at this high voltage range).
Off-the-shelf GFCI modules are out of the question, since they're intended for household wiring. This leaves coupled inductors:

In LTSpice I have modeled a coupled inductor containing three coils. My intuition tells me that L1 and L2 will form a common-mode choke. When differential current is flowing, there is no net flux in the core. However in the event of a ground fault, there will be some common current, and thus some net flux in the core. This net flux will induce a current in L3, which I intended to sense with some sort of TIA.
I'm observing that L3 carries a current, even when there is no GND fault. Can someone help explain what I'm missing? Also, if this is based on an existing topology, I'd love to learn its name.


texts: What is the metal sheath surrounding a USB connector, and is it commonly connected?

texts:
I was tearing apart a mouse for repairs and noticed that the small plug for the USB connection had a fifth connection. This connection had a much thicker wire than the other four.

I assume it is connected to the metal sheath on the male end of the connector, but what does it actually do?


texts: How would one measure the microvolts change in a 50kΩ Bolometer, as a result of the radiation impinging on it?


texts: Can we say that the circuit is a circuit of Nand element

texts: Can we say that this circuit is nand element ?


texts: How to find input impedance of RA30H1317M1 RF power amplifier module?

texts:
I am building an amateur radio VHF transmitter. I want to use off the shelf transmitter module like DRA818V (or similar) as the drive amplifier and RA30H1317M1 as the final amplifier.

This is my idea:

simulate this circuit – Schematic created using CircuitLab
The driver outputs 500mW, while the RA30H1317M1 has absolute maximum input power of 100mW. I have studied datasheet of RA30H1317M1, but I can't find the input impedance. If I knew the input impedance, then I could calculate the divider.

My questions:

Is it okay to drive RA30H1317M1 this way, or what is the proper way to do it?
Should there also be an LPF between the amplifiers?


texts: What's the difference between Laser Diode, LED and Lasers?

texts: I'm struggling a bit with this. I know LEDs are built using semiconductors, but a diode is a also a semiconductor right? So, Laser Diodes are not essentially the same as LEDs?


texts: What are these components in these circuits?

texts:
I have seen a documentary about making BGM-71 TOW (an anti-tank missile - the Iranians make it). You can see it in this link (part 1). I have seen two odd components. In your opinion, what are these components?

The first component is this (at 4:17 minute):

The second component is this (at 4:38 minute):

Here's another picture of the second component (at 4:50 minute):


texts: Where exactly is the USB spec that explains what to do when the cable is first connected?

texts:
So I know about the USB 2.0 spec located at the USB.org site.

I am a little lazy and impatient. Can someone tell me where to go to find out exactly what is expected of my peripheral device when the USB cable is connected?

For example, if my peripheral device is a printer, how do I tell the computer at the other end that a printer (with a specific model description, I suppose) has just been connected? Than, in the computer, how does the printer driver know which USB port was connected to the printer?

My application is actually USB MIDI. I have also gotten this USB-MIDI doc, but I am deficient with the more fundamental USB protocol.

Just for people's information, the USB chip I am using is the FTDI FT220x and it's hooked up to the SPI of an ADSP-21479 SHArC. We now use it simply for text communications using the PC (running TeraTerm) as a "console".  i have access to the code that sets up the SPI port and connects to the FTDI chip, but there is no code that does any initial communications. I do not know what the FT220x does when it's first connected to the PC.

I am not unhappy to read and learn, but i would like to know where to start reading, and a 100 MB USB spec is too big of a target to shoot at. Sincere thanks to anyone for actionable help.


texts: Are hand held AC power testers (the ones that looks like a screwdriver) completely safe? Why/why not?

texts:
What are chances that the carbon resistor gets shorted and we experience lot of current and die?
Cause of doubt arisal:
https://www.youtube.com/watch?v=wLAJ-keFmpk


texts: Control Loop Stability of DC-DC Converters

texts:
I am performing a control loop stability test on my 5V DC-DC Buck Converter with the help of this Keysight App Note

I understand that we are injecting a noise signal on the feedback network of this converter and checking how well our converter is responding.

My questions are :

How much noise voltage should we give while testing? What would be the ideal noise voltage that should be injected at the resistor?
I want to understand intuitively where to give the red and black probes from the injection transformer and where to probe Ch1 and Ch2 in the circuit? Where am I injecting the noise (at the top of the 5ohm resistor or at the bottom of the 5ohm resistor) and where am I taking the output?
On Figure 6, is the 0 degree on the phase plot convey actual -180deg ?

It is not clear from the app note


texts: My raspberry pi produces a 3.3V on it's GPIO. I want to buy a through hole MOSFET so I can simulate touch-events on a smartphone screen like this video. I'm trying to find something on Digi-Key, but I'm not sure how to choose the right component other than VDD needs to include 3.3 or 5V. Suggestions? (Can you explain how you picked the part.)


texts:
I am sorry if this sounds to be a silly question. Maybe I am having trouble interpreting the expression in english since it is not my first language.

I would like to know what the expression "net current" means.

Example of usage: "KCL states that no net current can flow into a node".


texts: Second Order Low Pass Filter Proteus Simulation

texts: I am trying to simulate the following circuit on proteus but on the oscilloscope I see the signal has no change in between input and output. In accordance with the data sheet (LM348) I am supplying 18V from pin 11 and -18V from pin 4. I have also attached pin 4 to ground and tried other possible ways but the oscilloscpoe shows the same result. Input voltage is 100mVp-p, frequency 2kHz. What am I doing wrong or what is missing?


texts: Connecting an 80's style computer cassette to an FPGA

texts:
I'm re-implementing a 1980's Microbee computer on an FPGA (see here) and trying to figure out how to do the cassette port. Here's the schematics for the original Microbee cassette interface:

(source: toptensoftware.com)
I also found this description of it in a technical manual:

The cassette data output consists merely of an RC network which
accepts a signal from  DB1, pin 28 of the PIO. The signal is
attenuated and then decoupled prior to sending it to  the cassette
recorder MIC input. This signal appears on pin 3 of the 5 pin DIN
socket.
The cassette data input circuit is slightly more
complicated. The input from pin 5 of the  DIN socket passes first to
an attentuator -decoupler. Following this is a CA3140 op-amp, to
allow a wide range of input levels to be squared up before the signal
is passed to pin 27 of  the PIO, DBO. The two diodes across the
inverting and non-inverting inputs to the op-amp  clip any input
signals greater than the diodes' forward voltage in either direction.
The  47pF capacitor is required by the CMOS op-amp for
precompensation.

My questions:

What does "de-coupled" in the description mean?
Would the same circuit work if connected to two of the I/O pins on a Xilinx Spartan 6 FPGA (through the PMod connector on a Nexys3) and if not, could it be adapted to make it work?

First attempt, based on comments in answers, but the output resistor shouldn't be in series.
I'm leaving this here for context and instructional reasons, please see the next schematic
MicrobeeSchematic2 http://www.toptensoftware.com/fpgabee/MicrobeeCassettePortSchematic2.png
New questions:

Is the polarity of the comparator correct?
For the MCP6546, does Vss go to ground and Vdd to 3.3V?
I'm not sure what to make of the "dotted out" resistor across the tape inputs in the original circuit.

Incorporating feedback regarding the output of the comparator being open-drain:
MicrobeeSchematic3 http://www.toptensoftware.com/fpgabee/MicrobeeCassettePortSchematic3.png
What alternatives could I use for the MCP6546, which I've not been able to find in retail stores here in Australia.  I can get LM311 or LM393 which, from what I can tell are similar. Will these work just as well?


texts: I came across term "half bandgap voltage reference". I expect it is somehow related to bandgap circuit. Do you know what it is, know its schematic or principle of operation?


texts:
I am using a TIP120 Transistor with pwm from my Arduino to fade an led strip. The RGB led strip requires 12 volts and 1.6 amps of current. I bought a 12 V / 2.5 Amp power supply from Radio Shack and I'm using it to power my TIP120. Here's how I have the set up:

[0-5v] PWM from arduino - > base of tip120

emitter of tip120 - > ground

ground of led strip - > collector

hot of led strip - > +12 v power supply

I have connected the GND from Arduino with the GND from the power supply to keep a common reference for ground. Now here's my problem, the setup works fine in terms of function, but my led strip doesn't light up at all. When I switch it out for a small led with a resistor and change the power supply to 6V, the small led fades in and out as expected but when I switch back to my original setup, the led strip doesn't budge. So I hooked up my multimeter and checked the current, it read 12.8 on the 200mA range. I assume that's 12.8 milli amps, which is weird because it should also show up on the 20mA range on my multimeter but it maxes it out.

So anyway, I figured I wasn't getting enough current out to the led strip. But I know that the TIP120 can handle up to 5 amps. My power supply can supply 2.5 amps, so what am I doing wrong? How can I get the current up to 1.6 amps?


texts:
I'm interested in a hand powered generator similar to the one in this Gakken Helicopter Kit.

Are these easy to come by? Easy to make?


texts: Why ripple counter increments on each 8th pulse

texts:
I have connected the ripple counter CD4020 to an Atmega328, which sends a 50ms (low logic level) pulse to the CD4020's input each second and monitors all of its 12 outputs.
However instead of incrementing the output on each pulse, the CD4020's output gets incremented on each eighth pulse.

Why is this division with the factor 8 happening?

Pin values: 000000000000
Pin values: 000000000001
Pin values: 000000000000
Pin values: 000000000001
Pin values: 000000000000
Pin values: 000000000001
Pin values: 000000000000
Pin values: 000000000001
Pin values: 000000000010
Pin values: 000000000011
Pin values: 000000000010
Pin values: 000000000011
Pin values: 000000000010
Pin values: 000000000011
Pin values: 000000000010
Pin values: 000000000011

The datasheet also states, that the CD4020 is a 14-stage counter, but it only has 12 outputs. Why 14?


texts: Hello can anyone tell me what is the positive on this microphone ?


texts: What is the benefit of using carrier frequency for an amplifier?

texts:
I provide the link here:

http://books.google.dk/books?id=wnPNkbJUBxkC&pg=PA153&lpg=PA153&dq=carrier+frequency+of+an+amplifier&source=bl&ots=mtT6SOFuqJ&sig=1AEAPY4Ke3qHhqqatW2S9kybJes&hl=en&sa=X&ei=YJV9VOqvM4TkaJPQgMAN&ved=0CFcQ6AEwBw#v=onepage&q=carrier%20frequency%20of%20an%20amplifier&f=false

Here at page 153, a carrier frequency amplifier explained.
It is explaining how it is modulating amplifying and then demodulating the signal.
What I didn't get is it what is the advantage to use this method rather than simply amplifying the signal.
What use is the carrier frequency here comparing to usual instrumentation amplifiers?


texts:
I have 3 RGB LEDs with common anode, a shift register and a microcontroller. Currently I have connected a series resistor for each cathode of the RGB LED, so there are 9 resistors in sum. I wondered If I could use only one resistor per RGB LED because there is always only one active RGB LED.

Take a look at this picture and tell me if this is possible and why not if it isn't:

http://www.abload.de/img/schm2yw8.png

Thank you.


texts: I will have a carriage sliding over a round metal shaft and the linear bearings will not necessarily be conductive. I want to calculate the position of the carriage by measuring the resistance from of it to a fixed point on the shaft (with a -0.3 to 0.3V 24Bit ADC and a very high resistance sense resistor). My problem is that I will need an electrical connection between the carriage and the shaft. A brush is an obvious choice but I would like to avoid the friction and wear that would be caused by that and I would therefore need a contactless method of gaining an electrical connection between the two. Induction immediately springs to mind but from what I can see from research is that it won't really help me, is this correct? Any other ideas?


texts: Does (and when how) the lifetime of a LED depend on the PWM frequency

texts:
Let's assume two options for driving a standard LED at its rated current.

PWM set to 50% duty cycle at 10 kHz
PWM set to 50% duty cycle at 50 kHz

Technically both LEDs would produce the same amount of light and the 'blinking' won't be visible to the human eye or a camera (except maybe for a high speed camera...)


texts:
The answer might be obvious, but I am curious, how well are oscilloscopes and probes usually protected against ESD?

I noticed that oscilloscope probes are usually shipped in esd-protected bags. On the one hand it's just easy to always use these bags for all electronics equipment but on the other it could add up to the cost.


texts:
I'm newbie, thus my simple question.
In the schematic below, which side of the capacitors is the positive? Why? Or are they assuming that I have to use ceramic capacitors?
Usually my schematics come with a plus sign or an side that is bended, but this one is symmetric.


texts:
I made one LNK304 converter per schema:

I used all components as described, but I got output voltage pulsing ~1/2s.
Only thing what I am not sure is L1, I did use 'resistor like' 1mH inductor, instead of ferrite base one.

Thanks.


texts: Positive edge detection triggers on negative edge too

texts:
I have 74LS170s and 74LS670 register files which have the trouble that they are not edge triggered but like SRAM accept data for the entire duration of the write gate being low.
So, I have the following circuit:

simulate this circuit – Schematic created using CircuitLab
The idea is the capacitor should pulse quickly high on the positive clock edge, that is then inverted (I actually use a 74LS14 Schmitt-trigger inverter) which gives me a negative pulse on the rising edge of the clock, just what I need to combine it through an OR gate with the active-low !LOAD signal, like the one you'd put on the 74LS173. And I plan to do the single OR gate with just a couple of diodes and a resister, as I don't want to deploy 74LS32 chips everywhere I need this pulse.
However, as you can see here, the circuit produces a second little pulse on the falling edge of the clock. It's quicker, but it's a spike that could badly interfere with the functioning of that register. This is measured right after the inverter, it's not about the OR gate.
What am I doing wrong? How can I get rid of this second pulse?


texts: What is the upper limit for a charge-pump voltage booster?

texts: What is the highest voltage achieved with a voltage pump? Can it boost into the kV range, around 5-10kV?


texts: Is there a way to plot the current to charge a capacitor given that there is a max current in the circuit given by the power supply?

texts: I'm trying to determine the maximum current of a circuit while charging a capacitor but since the power supply has a maximum current of 20mA that is going to extend my charge time longer than the RC time constant suggests. I have a 235uF capacitor I'm charging to 800 VDC given 200kOhms of resistance in series to the capacitor. Does the Max current even come into play since I have so much resistance in the circuit with the capacitor?


texts: VFD? to power aircraft non-motor/inductive load OR power conversion

texts:
QUESTION: Is it plausible to test power, out of aircraft, a mostly solid state device ie Microwave Oven? Can a VFD be programmed to run with inverter circuits. If so, 3 phase + ground output of VFD is  4 wire load compatable? PHOT0 1 vfd

POWER SOURCE, VFD = 1.5kw 1ph to 3ph, Chinese manual only, seller mistake

LOAD,  Aircraft Microwave Oven = 1.5kw 115v 4 wire 3ph 380-600Hz power requirement

BUDGET $1000~  yes you can spend $20,000 for a ground support generator

Load design, aircraft microwaves have a entirely different primary power design.
3 phase 400hz power is fed thru a RFI line filter for each phase. This power then goes thru power conversion mosfet circuits and AC to DC inverters. Anything to avoid using a transformer. Only one conventional transformer is used to power the magnatron filament, not counting the switching xformers on the boards.

UPDATE METHOD to power 115vac @400hz 1500va Oven
Super advice. Yes the maximum power consumption is 1500W, the intent was to power up and check the brains of the unit with the 1500va VFD and not cook. I have now repaired a 1968 Unitron frequency converter. Producing 2000vA 3ph-200ac in /2 ph-115 out @400hz. The QUESTION now is the oven requires 3ph at 115v, I have only produced the 400hz variable. Im already fooling the frequency converter with "fake" 3ph (3phase motor/cap running off 1ph 220v). Based on the schematic attached, how would it be possible to make "fake" 115vac power?

This is the 3ph Power management schematic.


texts:
The problem is that my 1200 watt conventional heating element is creating a mechanical buzzing noise. Shown below is a schematic of my setup:

PD4 is the output from a 5v microcontroller and is triggered high based on an interrupt from a zero-cross over circuit.

AC hot out and AC neutral are connected to the conventional heating element. The triac is ultimately used to control the duty cycle of the heating element.

From what I've read, the mechanical buzzing is due to the high change in current vs change in time (di/dt) caused by varying the phase of the triac. The step in current can be as high as 15 amps.

Based on some research this problem sometimes surfaces as "light bulb ringing" in light dimming applications. Some solutions people have proposed is to use a choke inductor.

I setup a 39uH inductor in series with the hot load line thinking it would reduce the di/dt of the circuit however it made no change to the buzzing.


texts: SPDT using transistors to switch between two seperate voltage sources

texts:
This is probably a stupid question but I have been searching everywhere and cannot find a solution that works.

I am trying to come up with a circuit using transistors that acts as a SPDT switch to toggle from being powered by one supply to another. The switch enable signal is being supplied by a Raspberry Pi which has very limited current capability (16mA max) so FETs are preferred over BJTs. The device being powered draws around 100mA.

Here is what I am going for:

simulate this circuit – Schematic created using CircuitLab

I have pondered using relays, but I am going for as small of a footprint as possible and relays are rather large (and expensive, especially if using SS relays).

My original intent was actually to use a quad bilateral switch (CD4016BE) but the current capacity just isn't there.

EDIT:
I think this is the route I'm going to take.

simulate this circuit

(with BS170 as NMOS device and IPP45P034L11AKSA1 as PMOS device)

Thanks for all of the help.


texts: What connector did this IBM Model M keyboard have?

texts:
I got got hold of an old IBM Model M (Model 1391403, to be precise). Unfortunately, the fixed cable was cut off by an unknown idiot.

Does anyone know what kind of connector (I assume PS/2?) was supposed to be at the other end, and what pins the colors correspond to?


texts: Continuously Measure 3-Phase Motor Current

texts: What methods are there for continuously monitoring the current in a 3-phase servo motor for a CNC machine and giving an alarm when the current is less than some value?


texts:
I'm using gdb, openocd and stlink to debug an application running on STM32H7. When data cache (DCache) is enabled, debugger does not show correct values. For example if I run this:
int foo;
int main()
{
    foo = 1234;
    while(1);
}

debugger shows foo as 0. Apparently it is reading the values really in RAM, instead of the values in data cache like I would expect it to.


texts:
I'm looking into building some large robotics with (ofcourse) a frame, (shielded) data/communication cables - EtherCAT, and power lines.
Now different 'experts', websites and people say all different kinds of things in order to prevent noise on the data lines, to prevent ground loops and to use the frame as ground.
What we have figured out now is to use the frame as 'ground' for the data cable shielding. Connect both ends to the frame and connect the frame to battery ground on one point only as close as possible to the battery.
How does this not create ground-loops in the shielding? Or have we figured it out wrong? Shouldn't the electrical components' ground plate be connected to the frame on multiple points? Or should they best be electrically isolated from the frame? And if the latter is true, how about capacitances between the frame and ground plates of these components? What if we have to thermally cool these components on the frame?
What is true and what is false? Because we can't see the wood for the trees any longer.
Tips & tricks to keep in mind?
I added a diagram as requested with maybe some clarification. The green 'frame' is electrically connected (green lines represent the connection) and the purple boxes are motor controllers creating some noise when powering and moving the motors represented by the yellow circles. The data cables are shielded EtherCAT cables.


texts: How do I light an LED when a revolving disk is in motion?

texts: This is for a fourth grade science project. The only part I need help with is as follows. There is a revolving disk. When the disk is in motion we want power from the battery to light the LED. When the disk stops, the light should go off. Using an Arduino system can we achieve this? I hope it is simple enough for 9 year old to do (of course I will watch any soldering) and I know I can get parts from my local radio shack, but don't know what package or parts to buy. Can anyone help me?


texts: Easiest/most affordable way to boost voltage?

texts:
I'm running a setup with two parallel D-cell LiSOCl2 batteries (3.6V, pulse currents up to 3000mA), to power up a small microcontroller. However, as I deploy my devices in very cold environments (down to -35 to -40C in the winter) the voltage of these batteries drops down all the way to about 2.5V or so, and they can no longer support the microcontroller (which has minimum of 3.3V, and maximum of 4.2V).

What's the easiest way of ensuring that the supplied voltage stays within the operating range of my microcontroller? My batteries right now connect with a JST-connector straight into the microcontroller. Preferably, I want to change as little as possible to my setup. Any guidance?

Battery: http://gebc-energy.com/en-US/Product-60.html

Better battery spec...


texts:
I'm trying to spy on the state of servo communications with a RC receiver and optionally change the output.  Unfortunately my controller is 3.3v while the servo logic is ~5v.  I'm trying to figure out what the easiest way of doing this is.

The circuit I've come up with is as follows:
reciever -> translator -> mux (translator/controller) -> translator -> servo

Does this make sense and will it maintain a reasonable level of signal integrity?

I know the Ardupilot does something similar but as far as I can tell, the whole device operates on 5v so no logic level shifting is needed


texts: NE555 Based Speed Controller circuit - Contradicting Pins in 2 Tutorials

texts:
I am a newbie of Electronics and learning it as a hobby. Over a course of time I realized that Electronic Blogs are not the best place to learn Electronics, unless you have a strong basics and can correct silly mistakes in circuit diagrams posted online. Often I find it difficult to get a circuit working because they have minor typos or errors.

Now, I am stuck with such a situation. I am referring two separate Electronics Blogs which are appearing in Google Search who have posted couple of contradicting circuit diagrams of a NE555 based DC Motor Speed controller. I don't know if either or both of them are correct. The circuits use pin 3 and pin 7 of the IC respectively to drive the MOSFET/Transistor.

Circuit Diagram 1:

http://pcbheaven.com/circuitpages/PWM_Fan_controller_using_a_555/

and

Circuit Diagram 2:

http://www.gadgetronicx.com/dc-motor-speed-control-circuit-ic555/

My questions are:

Are both of them correct? If yes, it's really couple of exciting circuits to understand how both of them work when the pin 3 and pin 7 are used just the opposite way in these two circuit diagrams. Does the use of MOSFET vs Transistor makes the difference?
If one of them is correct - which one is that?

This question might not be new to Stackexchange because these contradicting diagrams are equally published all over the internet. Unfortunately I couldn't find it on SE. Please link the question, if you already have it.

According to my understanding circuit diagram 2 should be working. Because it is similar to astable-multivibrator config of NE555 and pin 3 seems to be generating square wave (i.e. PWM) signals to drive the MOSFET/Transistor. Please let me know if I am wrong and why.

Many many thanks in Advance!!


texts: In LTSpice, for a 3-input logic gate system, the XOR gate isn't outputting what I'm expecting it to

texts: When A, B and C are all 1, XOR is meant to output 1, but in the simulation it only outputs 0, not 1. Is there something wrong with my schematic?


texts: Request for comments on AC mains frequency conversion method - Supply>PSU>AutoInverter>Load

texts:
Purpose:
To supply 110v 60Hz power to a Lionel o-gauge train set from 240v 50Hz mains in New Zealand.

While the train itself will run fine on 110v at 50Hz, the digital electronics for sounds can be ruined by the 50Hz sine. This claim is based on much reading online, not based on my own knowledge. Many people have posted about ruined transformers from running ONLY a step down. Due to the cost of the trains, I wish to have it run on it's designed Hz.

Proposed method:
Use a 240v New Zealand market computer power supply to feed 12v dc to a high-wattage US-market automotive inverter that supplies 110v power.

Relevance to stack exchange posting:
If this is indeed a viable solution to this problem it will be very useful for many many people wishing to use US-market electronics outside that market.

My idea seems to make sense to me - that once converted to DC there isn't any Hz to measure as there's no wave, and the US-market car adapter will put out AC at the American frequency. The computer power supply puts out plenty of Amps, and the higher-wattage car adapters put out plenty for the Amp draw of the train.

Please comment to let me know if this is a sensible approach or not?

Please focus on the idea for getting the 110v at 60Hz, not on other aspects of the issue.
I appreciate the intent, but this question is specifically about whether my proposed method will work.


texts:
It is said that for a common base configuration the base is grounded, i.e. at zero potential.
But at forward biased for a npn transistor, the battery used to forward bias emitter–base junction is connected to base from its positive pole. That means, the base is at some positive potential, contradicting the fact that Base should always be grounded. Where is the error in the concept??


texts:
I have a problem connecting different modules in a top module. I want to do a very simple PWM using a counter and a comparator.

Counter:

module          counter
                #(parameter N = 6)
                (
                input wire clk,
                input wire enable,
                output wire [N-1:0] q
                );
reg             [N-1:0] r_reg=0, r_next=0;

always @(posedge clk) begin
    r_reg <= r_next;
end

always @(*) begin
    if (enable)
        r_next = r_reg +1;
    else
        r_next = r_reg;
end

assign q = r_reg;

endmodule

comparator:

module          pwm
                #(parameter N = 6)
                (
                input wire [N-1:0] cin,
                output wire pwmsig
                );

reg             [N-1:0] threshold;
reg             d = 0;

initial         threshold = 6'b011111;

always @(*) begin
    if (threshold > cin)
        d = 1'b1;
    else
        d = 1'b0;
end

assign pwmsig = ~d;

endmodule

The modules work fine and if I put everything in one module it works as intended. But if I try to connect them in a top module:

    module          top
                    #(parameter N=6)
                    (
                    input wire clk, enable,
                    output wire pwmled
                    );

    wire            [N-1:0] connection;

    counter         cnt1(
                    .clk(clk),
                    .enable(enable),
                    .q(connection)
                    );

    pwm             pwm1(
                    .cin(connection),
                    .pwmsig(pwmled)
                    );
endmodule

I get an error message:

  ERROR -  Port 'clk' is unconnected.
  ERROR -  Port 'enable' is unconnected.

RTL simulation works fine (I am only including the top module in my testbench). It just wont let me connect 'clk' and 'enable' to actual pins.

I am using Lattice Diamond 3.1.

Edit: I get the following Warnings in the Map Report:

WARNING - map: IO buffer missing for top level port ena...logic will be
     discarded.
WARNING - map: IO buffer missing for top level port clk...logic will be
     discarded.

I ran the design through Quartus II and got working results... any Ideas where I am going wrong with Diamond?


texts: Make Si4703 evaluation board Bluetooth capable

texts:
While looking for a Bluetooth RDS-TMC receiver which could be queried with FOSS software, and after realizing there’s probably not too much on the market, I stumbled across Si4703 evaluation boards for use with single-board computers.

I have successfully used a Si4703-based USB dongle to pick up RDS-TMC messages on Linux, thus the evaluation boards looked like a good starting point—Linux has drivers for it (which will probably need some tweaking, but I’m hoping to reuse the bulk of it), and there’s an application (RDS Surveyor) which can query and parse TMC data from the chip. Analog audio isn’t really a concern—I don’t need it for my purposes.

Is there a way to convert the signals from the Si470x board to serial and hook it up to a Bluetooth-to-serial adapter? Or any other way to get the device to “speak” Bluetooth?

Looking around a bit, the chip seems to speak I²C, with the pins exposed directly through the evaluation board. I’m not familiar with the details of I²C but, to my knowledge, generic Bluetooth adapters exist.

Besides the SDIO and SDCLK pins, the board also has a RST_n pin. Initializing the device involves some bit banging:

Set SDIO and RST_n to low
Wait a bit
Set RST_n to high again
Wait a bit
Start using the device

Is this compatible with standard I²C, i.e. would a Bluetooth-to-I²C bridge be capable of initializing this device in the same way described above?


texts: Filtering analog audio signal using TLV320AIC3111-EVM

texts:
I'm working on a project to filter analog microphone data using the audio codec from TI, the TLV320AIC3111. We are using the EVM However, I'm facing problems with implementing the filters on the software PurePath Studio. I've asked the question on e2e but I'm yet to receive a definite answer. I've linked my PFW and config file. I've been stuck with this issue for a pretty long time and I need some assistance immediately. I'll also link the question to e2e here, where I've asked the question already, and am waiting for a reply.

For testing I've connected a function generator to the audio codec analog line in (header J7) and I'm giving the output of the SPL to an oscilloscope to check the output for attenuation or gain. So far, I've created a Biquad lowpass and I've noticed attenuation crossing the cut off frequency on some occasions. Sometimes the filter works, sometimes it doesn't and I'm yet to figure out how to make it work as expected.

Is there anything that I'm missing? If anyone has worked with a board in this family please help out.


texts: 12V volts being reduced through a PN2222

texts:
I'm trying to build a circuit for controlling the speed of a fan from an ESP8266 MCU.  I have a PN2222 transistor with the base connected through a 1K resistor to a digital out of the MCU.  The voltage at the digital out is +3.3V when it's high and I verified that I can successfully set it high and low on the MCU reading it with a DMM.  So that part seems to be working.

The power supply for the fan that is being switched by the transistor reads ~18V unloaded using a DMM.  However when I read the voltage of the emitter of the transistor using a DMM it reads 8V no matter whether the base is high or low.

simulate this circuit – Schematic created using CircuitLab

I was expecting it to read 18V when the base of the transistor was high and 0V when it was low.

Clearly there is something I am misunderstanding here with my first foray into transistors being very new to electronics in general.


texts: Will a incandescent burn out if you leave them on forever?

texts:
We've all had a time or too two that when you really needed light, and I mean need it immediately, and you flip on the switch, and with a pop and a bright flash, your incandescent is toast. However, I am wondering why this happens.

I know all things will break eventually during use and it's impossible for it not to break over millions of years, but really, why does it happen so shortly? I have concluded that the heating and cooling of the filament so fast is damaging to it, and it just gets to a point where the filament becomes fragile and snaps. But will they not burn out if you leave them on constantly? I don't really mean forever, but I'm mostly asking if it will have 5-6 times longer life than before, not if it will last indefinitely. Just for completeness since we're talking about burning out and the filament expanding due to sudden temperature changes: Will dimming it slowly over a few seconds before turning it off/on help too?  (Letting it cool down/warm up slowly and not a sudden reaction.)


texts: Slave I2C timing relative to master clock edges

texts:
I am working with the STM32F4 microcontrollers. The I2C peripheral uses a clock setting.

I have been told that it does not matter when the peripheral is used as the slave device.

If that is true how is the proper hold time, alignment, and spacing before and after master clock edges maintained? i.e. If the clock falling edge of the master is received, and the slave device assumes a very slow clock rate, isn't it possible the slave device will change the data line too late, possibly after the next clock rising edge is received?


texts:
Let the content of register A is 98H. Both Auxiliary Carry flag and Carry flag are set i.e. AC=1 & Cy=1. If now I execute DAA once, both nibbles will get added with (0110) and the result is FEH having AC=0 & Cy=0. Is FEH the final result stored in A or will it again add (0110) to convert result into a valid BCD?
Although I have never found any question like this, just a random doubt about DAA operation.


texts: Can someone recommend a shift register IC with integrated parity or CRC generator? Is there such a thing anyway?


texts: Is there a processor IC inside a microcontroller package?

texts:
I am reading about the TI TM4C12x microcontroller, which is available as an IC:

The datasheet of one of its variants can be found here: http://www.ti.com/lit/ds/symlink/tm4c123gh6pz.pdf

On the block diagram on p. 48, it is shown that the MCU uses a ARM®
Cortex-M4F processor.

Questions:
Is the ARM® Cortex-M4F processor sold as an IC chip (like the common Pentium chips in desktop PCs)? I thought I would be able to find a picture of the ARM processor chip, but I was not successful in a Google search.

If the answer is yes, does TI (and other MCU manufacturers) somehow put the ARM processor chip inside its own TM4C chip, so if I cut open the TM4C chip, I would find another ARM IC inside?

If not, what exactly does TI buy from ARM?

"Appendix A. Package Information" in the datasheet does not seem to say much this.


texts: Why does the Dual Speed Dahlander motor need a bridge in the fast speed configuration?

texts:
On the nameplate of the motor is a Delta/Wye-Wye configuration, meaning you supply the ones (U1, V1, W1) and leave the twos open to achieve the slow speed. And for fast speed you supply the twos and bridge the ones... That's for a constant torque single winding pole changing motor.
Surprisingly, today I connected this motor without bridging anything and it ran on both speeds just fine.

So the question is why do we need to bridge the ones in the fast speed? Does this also have an effect on the output torque in the fast speed?

Any information on this will be appreciated.


texts: Hacking wall wart as a USB charging station

texts:
I would like to modify an old power supply to have a USB A female adapter so that I could use it to charge any device.

I plan to split out the power lines from an adapter that is:
Input: 100-240V - 1.0A 47-63Hz
Output: 5.0V 3.8A max

I know that some devices like the data lines to be high, but for now I'm focusing on the power required and any pitfalls there.

Am I correct in calculating that I could add four USB female jacks to this power supply and there would be enough power to charge most devices with them. I just need to connect each jacks pins to the correct lines.

Would there be any issues with this that I am missing?

EDIT: Upon further reading I've noted that a 600mA fuse on each line would be good protection if a device draws too much.
Also decoupling capacitors for each line would protect lines from each other.


texts:
I'm designing an AC-DC based on the UCC28780 active clamp flyback controller .

I have a question about the primary auxiliary winding that is supposed to power the UCC28780 and the gate driver. My question is, if at instant t0, my controller and my driver are not powered, that means that i have no current flowing across the primary winding. The primary auxiliary winding is nothing but a secondary winding without isolation. So how is my this auxiliary winding is supposed to power my controllers if there is no power flowing through the primary ( because the IC is off, hence the flyback main switch is off).

Thank you in advance for you answers.


texts: What is the role of zener diode in this clipper circuit?

texts: i don't know exactly why we're adding the zener diode. My guess would be that it functions as a voltage regulator but that's as far as i can go.


texts: Verilog: Are there some basic rules for port settings?

texts:
Iam trying to write a SPI master module by myself to learn FPGA-Verilog efficiently. Here is the spi_master module:

module spi_master(

        output [15:0] tx_data,
        input [15:0] rx_data,
        output mosi,
        input miso,
        output cs,
        output sck,
        input start

    );

     reg [15:0] tx_data;

     reg [3:0] tx_counter;
     reg [3:0] rx_counter;

     wire start;
     reg cs;
     reg mosi;
     wire miso;
     wire sck;

     initial begin

     tx_counter [3:0] = 4'b0;
     rx_counter [3:0] = 4'b0;

     end

    always @(negedge sck) begin

        if (cs == 0 && tx_counter != 4'b1111) begin
            #(5) mosi <= tx_data[tx_counter];
            #(6) tx_counter <= tx_counter + 4'b1;

        end
        else if(cs == 0 && tx_counter == 4'b1111) begin
            #(5) cs <= 1'b1;
        end
        else if (cs == 1 && tx_counter == 0) begin
            #(5) cs <= 1'b0;
        end

    end

    always @(posedge sck) begin

        if (cs == 0 && tx_counter <= 4'b1111 && tx_counter >= 4'b0001) begin
            #1 rx_data[rx_counter] <= miso;
            #2 rx_counter <= rx_counter + 4'b1;

        end

    end

endmodule

And here is the test module;

`include "spi_master.v"

module spi_master_tb(
    );

reg clk;
reg start;

reg mosi;
wire miso;

reg cs;
reg sck;

reg [15:0] tx_data;

initial begin

clk = 0;
tx_data = 16'hF0AA;
#20 start = 1'b1;
#1000 $finish;
sck = 0;

end

always begin
    #1 clk = ~clk;
end

always @(start) begin
    #10 sck = ~sck;   // divided clk by CLK_DIVIDER
end

spi_master SPI_block(

        tx_data,
        rx_data,
        mosi,
        miso,
        cs,
        sck,
        start

    );

endmodule

the spi_master module can be compiled without error but when I try testbench I get this error:

ERROR:HDLCompiler:1660 - "C:/Users/aozel/Desktop/FPGA Projects/myModule/../Test2/spi_master.v" Line 74: Procedural assignment to a non-register rx_data is not permitted, left-hand side should be reg/integer/time/genvar

Why is this? Also when I add: reg [15:0] rx_data;  to the spi_master module this time I get this:

ERROR:HDLCompiler:661 - "C:/Users/aozel/Desktop/FPGA Projects/myModule/../Test2/spi_master.v" Line 24: Non-net port rx_data cannot be of mode input

Why is this happening? I ve read somewhere that says never set inputs as regs. But editor throws exact opposite suggestions. So, to sum up, Are there basic rules for port settings in Verilog? How should I start?

And secondly, I really did not understand why we should not use registers as inputs. Why is that? Where will I store inputs? How will I read them? I think I have to use registers for inputs which is not considered as interrupts. Can someone explain it? I d really appreciate.


texts: I have done a few mods to a PCB with 36 gauge mod wire. Obviously this wire is so thin that it only takes a few bends back and forth to break it. What is the best way to secure this in place on the PCB? I have tried super glue but that makes a mess because it flows too easily.


texts: What does Bias Repeatability tell me in an IMU's spec sheet?

texts:
If there is a standard interpretation of bias repeatability as it applies to a gyroscope, what is that interpretation?

This document indicates that it represents the average change in bias between successive turns-on. So if I estimate bias to be 10 deg/hr and the bias repeatability is 1 deg/hr, I could power off the gyroscope, power it on, and expect the next bias estimation to return something between 9 deg/hr and 11 deg/hr (in 68% of trials).

This forum implies that it reflects how bias changes as the gyroscope ages, but it isn't obvious to me why. If initial bias is changing over years of use, but I'm correcting that bias with proper bias estimation each time, this aspect of aging should not affect performance.

Alternatively, this spec sheet (for this tactical grade IMU) describes its bias repeatability with this footnote:

  Bias repeatability provides an estimate for long-term drift in the bias, as observed during 500 hours of high temperature operating life at +105C.

This seems to estimate the change in bias over a single 500-hour run. So if I leave my gyro on for 500 hours after bias correction, I would observe the bias after that time period to be 252 deg/hr (value taken from spec) on average. If I don't set aside moments in that 500 hours for bias re-estimation, this results in severe gyro inaccuracy.

This other IMU shows its "Bias repeatability (1 yr)" as 1800 deg/hr, which could be (1) the average bias change in a continuous 1-year test, (2) the average change in turn-on bias over a year of usage, or (3) something else entirely.

These different interpretations have drastic differences in implied performance. So while I'm analyzing spec sheets to find the right part for my use case, is there a uniform definition of bias repeatability, or does each manufacturer design their own test to reveal different information about their device?


texts: Household inverter/battery array to supplement generator

texts:
I live in an area that's prone to occasional power outages (e.g., ice bringing down trees in the winter, hay landing on and blowing out transformers in the summer). Last summer we had a standby generator installed (22kw with ATS) because I was tired of pulling out my smaller (10kw) portable unit and dealing with significantly reduced capacity when called on. I've tested it a few times since, and it works great (after about a 10 second delay to start up).
I also had a Sense energy monitor installed at the same time so that I could get a sense of what our actual draw is at any given time. I was concerned that our heat pump (5 ton) might pull too much power. In general, it seems fine. But now that colder temperatures have arrived and it's doing its defrost cycle occasionally, I'm seeing large draws that would definitely exceed the capacity of the generator (as much as 30kw total draw for maybe 3 minutes at a time once or so a day).
The quickest solution would be to just turn off the HVAC when the generator fires up and switch to using in-room portable heaters. I could probably run 10 (way more than I need) of those + the rest of the house with no trouble on that 22kw.
Alternatively, I'm pondering the idea of building a large battery array as a way to maintain continuous power. I'm thinking that it could do two things:

Bridge the 10 second gap in coverage for the generator to spin up.
Augment the power supplied by the generator to cover the short time periods of high draw.

I'm looking at something like this: https://www.aimscorp.net/50kw-50-000-watt-dc-to-ac-pure-sine-power-inverter-charger-384-vdc.html + a 36 battery array of relatively low AH (optimized for high current rather than duration of coverage).
That's more money than I want to spend and more capacity than I need, but the next smallest inverter from AIMS is 30kw which wouldn't cover a worst-case scenario of HVAC defrost + water heater + dryer or whatever during that 10 second window + supplementary for a few minutes to cover the insufficient generator capacity to ride out the defrost cycle.
Is this a thing that people do? Or is this a dumb idea? I have an electrician who I work with who's generally willing to pursue my ideas, but this is much more complex than I've asked him to consider in the past and I thought I'd run it by you folks before I take it to him.
I also have a 4kw PV array and grid-tied inverter. But that's pretty automatic and probably not too complicated to deal with (although it does tend to act funny when the generator is running - it resets and takes like 5-10 minutes to come back online as the generator adjusts to load).


texts: Is there a low-cost alternative to RJ45 cables for large number of signals?

texts:
We are designing two interface (printed) boards and need to connect them by cables (0.5-1.5m). So we're thinking about which connectors to use. We'd like to use twisted-pairs like in a RJ45 cable.

The problem is, we are talking about 200 signals (-10V to +10V), which would require 50x RJ45 cables.

Alternatives I know of are RJ21 or DSUB-50 cables, with 50 pins, 2x25 wires each. Buying them is way too expensive (at least in Germany, it would be around 450€ or more for 8 cables) and soldering 800 contacts is considered too much work for now (+120€ material). For comparison, we could get 50x RJ45-cables out of the box for 70€.

So I wonder if there is an alternative? Are there any cable standards which are as reliable and cheap as RJ45, but suitable for a larger number of signals? (If there wouldn't be the twisted pair condition,  flat ribbon cables would be a good choice).

For the maximum frequency of the signals one could assume something around 200-500 kHz, the impedance of the cable should not matter too much, as the entry impedance of the end device is 1 MOhm (but I'm far from an expert in this matter).

Further clarification:
We have about 60 analog signals and about 100 digital ones, just some of them have a high frequency and stiff edges,  a lot others are just rarely changing signals for controlling a state space machine. About 40 of the 200 "signals" are actually ground.

I'm not searching for an improvement of the basic setup as it cannot be changed. Behind the interface boards directly follow the end devices. Apart from some little amplification and filtering of the analog signals, the purpose of the interface boards is to collect the signals of all sensors and actuators and redistribute them, to enable better cabling.

The system basically looks like is:

As the DSUB-50 connectors of the right system do not provide the possibility of twisted pair wiring in most cases, the idea was to directly connect the DSUB-50 with an interface board (without cables) to offer better suited connectors.


texts: Switching Frequency for Flyback Quasi Resonant Converter

texts:
As I know, the major difference between normal flyback converter & flyback quasi resonant converter is for flyback quasi resonant converter, the switching frequency is variable. This means that the switching frequency is based on the output load. When the load decrease, the switching frequency will increase, and when the load is increase, the switching frequency will decrease.

My question as below:
1. Since the switching frequency is always changing, how do I select the switching frequency as my initial value to start the transformer design?
2. Since the switching frequency is always changing, how do I know that my transformer is capable for that switching frequency range. Let say I choose a transformer A with value of 300uH @ 55kHz, and my switching frequency for quasi resonant converter is range from 35kHz to 130kHz. Will this transformer A is capable for that frequency range? As I know, as the frequency increase, the inductance will be smaller & as the frequency decrease, the inductance will be bigger. Is it means that at lower frequency, this transformer A (300uH,55kHz) will change its inductance value at lower frequency(suddenly will increase inductance) & high frequency(suddenly will decrease inductance)? Or this transformer A will have fix inductance value of 300uH at all frequency?

Thanks


texts: Current Sensing with Differential Amplifier

texts:
Hello, I have to use this circuit as part of a school project so I'm limited to this design and these components. The voltage regulator works as anticipated however the differential amplifier does not. Here it amplifies, by a factor of 10, the voltage drop across the shunt resistor R8 which is ~28mV. I'm having two issues with this however circuit however.

The output of the LM324N on the simulation is 303mV but shouldn't it be 280mV since the gain is set to 10 by the 100k and 10k resistors ?
When I physically replicate the circuit the output voltage of the LM324N is 562mV with all the same parameters as the simulation but the voltage across the shunt is 27.2mV.

How can I solve both problems ? I think that it may have something to do with CMRR and the input offset voltage which according to the datasheet is typically 2mV. I'm also new to all of this and I don't completely understand CMRR


texts:
Hi does anybody know what's the purpose of the Q1 and Q2 transistors,
sounds to me like they are constant current sources. Am I wrong?

Could somebody explain me the purpose of those Q1 and Q2 transistor
configuration there?

Note, This is a simple preamp circuit.


texts: Multiple switches to multiple inputs - what kind of diode?

texts:
I have six buttons going into a microcontroller on six IO pins. I have a seventh pin that acts as an interrupt and wakes the microcontroller, which is always asleep until a button is pressed (this is for a remote control). Is this circuit a legitimate way of doing it so that pressing any of the buttons will wake the microcontroller, and what kind of diode (Schottky, Zener, switching, rectifier) should I use?

I thought about doing SPDT switches but those are much more expensive than SMT diodes.


texts: RL Circuit Analysis with 2 sources, how to find current of resistor?

texts:
I've been tackling some problems related to natural and step responses for RL & RC circuits, but I think I've hit a major roadblock for this RL circuit. I'm trying to find the time constant and current i3(t). While I'm certain that this type of circuit is first-order, I'm honestly stumped as to how the inductor, voltage source, and the current source change (or stay the same) for t<0, t=0, and t>0 conditions.

I'm certain that the equivalent resistance, Req, will be required for the time constant, so I attempted to do superposition (removing sources) at t=0 in order to find Req, knowing that it is relative to the way it is viewed from the inductor. Upon redrawing the circuit diagram (for t=0) and using thevenin theorem to solve for Req, I ended up with Req = 1.59 ohms. I'm not 100% certain whether this is correct, but I found that R3 is || to the series combination of (R4 + R5), followed by adding R2 to that result, then making that parallel to R1, leading to 1.59 ohms.

However, what I'm puzzled about is how to solve for the current i3(t) across the R3 resistor. My way of thinking tells me that i3(t) includes the steady states for both i3(t=0) and i3(t= infinity), in which the first one is found by having the voltage source intact (and all of the resistors too),  but the inductor does short circuit at t<0 (right?). i3(t=infinity) should be able to be found for by short circuiting the inductor, replacing the voltage source with a wire, and having the current source remain intact. I have a good feeling that this is one way to find i3(t), as the general equation for it is:

i3(t) = i3(t=infinity) + [i3(t<0) - i3(t=infinity)] e^(-t/tau)*

Are there perhaps potential gaps I have in my approach of solving for i3(t<0) and i3(t)?


texts:
I am using FreePDK45 in Virtuoso, but I faced the following error:
Error found by spectre during circuit read-in.

ERROR (SFE-23): "input.scs" 12: The instance `PM' is referencing an undefined model or subcircuit, `pfet'. Either include the file containing the definition of `pfet', or define `pfet' before running the simulation.

ERROR (SFE-23): "input.scs" 16: The instance `NM' is referencing an undefined model or subcircuit, `nfet'. Either include the file containing the definition of `nfet', or define `nfet' before running the simulation.

Following advices at https://www.edaboard.com/threads/cadence-virtuoso-and-mmsim-installation.305420/page-3 does not really help.
Could anyone advise ?
For more context, please see https://community.cadence.com/cadence_technology_forums/f/custom-ic-design/45361/freepdk45-usage-in-virtuoso/1368259#1368259


texts: How to measure speed without any mechanical or electrical connection?

texts:
I would like to build an as-much-portable device for measuring the speed of a vehicle, to check speedometer accuracy and know the offset if one present. The idea is a cigarette pack sized box one can take with when test driving a car, for example. This is nothing to do with very high accuracy or racing speeds.

My first ideas range from very a very basic, but very tricky to mount, contraption with some sort of switch that revolves on a wheel, and those revolutions per second are factored with the wheel diameter, to get speed. This metric would be communicated via radio or IR to the display unit.

At the other end of the complexity scale is an accelerometer, no mounting, no wireless connection, but the circuitry would be a good deal more complex.

Is there any other way of doing this.


texts:
I am still very new to electronics, but have been using Arduino to build stuff with.  But I require a component for a project that does not contain any Arduino because of space.

So I am looking to see if there is, or the best work-around, a IC that will randomly generate a pulse if a button is pressed.  So once the button is pressed it either allows a pulse to go though to an I/O, or stops it.  But for this to be random.

The space is width 150mm and length 500mm and a 7mm height. it only has a small current as the battery is 3v.

Any ideas/advice to achieve this would be really helpful.

Thanks


texts: Why does an optical drive use laser light?

texts: Nowadays, lasers are cheap, but back in the day when CDs were first introduced, they were expensive. What is the reason for using a laser instead of a normal light source in optical drives?


texts: Photodiode amplifier circuits - why use an op amp instead of just a resistor?

texts:
Beginner question here. I've built a photodiode light sensing circuit in class and internship such as this one:

I don't understand what it is doing over a simple circuit such as this one:

Can anyone help me out?


texts: Trouble with double-buffer structure -- MachXO2 using FIFO_DC from IPExpress

texts:
In reference to this recent question: I'm seeing a problem with that scheme (the second figure, using the FIFOs as "circular buffers", or shift-registers so that old samples are extracted as discarded once it's full):

When I'm writing to one buffer, the RD signal (as in, the read-clock signal) never arrives to that buffer, so even though I feed the (WE & FULL) signal to the RdEnable, the reads never happen, and the incoming values are lost.

Notice that it's not a matter of using the same RdEnable AND trick with the RdClock (which I assume should never be done anyway — the output of a combinational block used to clock FFs).  The point is, the Read is issued externally and asynchronously; when a buffer fills, the external system (an MCU) is notified, and an unknown amount of time will pass before that external system starts to issue any reads.  Even then, the reads will happen at a completely different speed and 100% asynchronously to the writes  (that was the whole point of using the FIFO_DC modules)

Any suggestions?

[EDIT for further explanation]

I have an ADC capturing at fast rate. A CPU needs only certain small chunks of those ADC samples, when some (easy to detect) condition occurs. The FPGA buffers the ADC data in a double-buffer, so that when the condition triggers, I save the snapshot. This is done by switching to the other buffer, and then the CPU will have some time to read the "saved" buffer.  So, the WrClock in my case is the ADC output-clock (it's a pipelined ADC), and the RdClock is the CPU's bus RD/ signal. On the write side, no problem (the pipelined ADC outputs an uninterrupted clock); but on the read side, I don't have an always-present clock that I can feed and control it through the RdEN.

Now, the two key aspects related to the problem I'm facing are:

When the condition to capture the chunk of ADC data has not triggered, I need the writeable buffer to behave as a shift-register, where each new incoming value kicks out the oldest value in the FIFO (that's what Dave Tweed addressed in his answer to the recent question I linked above).  But that part is not working; the simulation revealed the bug: when the buffer is full, the incoming samples are being lost (because there is no RdClock for that FIFO)
The RdClock is the RD/ signal from the CPU parallel bus interface; so, it is not always present;  when the condition to save the chunk is triggered, the FPGA will notify the CPU, and some time later, the CPU will perform the reads, emptying the FIFO that contains the saved snapshot.

[END EDIT]


texts: Making a circuit entirely with 4:1 MUX, 2-input OR gate and NOT gate

texts:
I'm stuck on this question for half of a day. Let's say I have this function

That's everything I know about it. Now I must implement it using only 4:1 MUX, 2-input OR gate and NOT gate. I've tried to look at the truth table and create a circuit, but it uses a constant and AND gate, which is forbidden in my case.

Is there any convenient way to solve this problem, instead of trying to guess it?


texts:
In some circuits such as crystal oscillators, there is a CMOS inverter with a feedback resistor, they all simply say the resistor bias the 'amplifier' and force it to operate in the linear region, such as Fairchild: CMOS Linear Applications:

  Due to the symmetry of the P- and N-channel transistors,
  negative feedback around the complementary pair will
  cause the pair to self bias itself to approximately 1/2 of the
  supply voltage.

But what's the internal working details?

Why the bias point is '1/2' supply voltage?
It seems the '1/2' bias point only work when the input is open, or the source is capacitive coupled with the inverter, right?

The inverter's VTC from Sedra & Smith's book


texts: Why'd we have reflected waves in transmission lines?

texts:
I've learn today that when you applie a potencial V in a transmission line, we get a V in positive way, but we have to a V in negativa way, being reflected. What does it means? Like, I can understand it if we talk about electromagnetics waves, it colides with a superficie and be reflected, but what happens in a electrical circuit? It is a potencial being applied at a extremity and not a real/physical wave, right?
Mathematicaly I saw that a potencial in negative way is a valid answer (as a answer for those differential equation), but it is phisycaly possible?


texts: Why are 'modern' high-efficiency LEDs easier to damage than 'old' LEDs?

texts:
I have a few 'old time' LEDs from the late 80s and early 90s. The red and green 5mm LEDs (amber was a rarity, blue was 'impossible' back then). Not being very smart, I used to test them with a 9V battery without any resistor and, surprisingly enough, they always outlived the experience.

Fast forward to the third millennium: I bought several dozens transparent 'high-efficiency' (or should I call them 'high brightness', hard to tell without a datasheet) LEDs on the Web. They are superbright, but the one time I tried to "Oh, here's a 9V battery: let's see what color this is" one of those, they almost instantly died after a faint flash that told me "I was blue, you #@@#!"

(Like this: https://www.youtube.com/watch?v=7IoyYj6BJlc )

Now, it is clear to me that a resistor is required to limit the current, but my question is about what exactly kills the LED, or put in another way: why do 'old technology' LEDs survive?

Is it related to the fact that 'old' LEDs exploited recombination between conduction and valence band of a sturdy PN junction, while 'new' LEDs are based on more exotic etherostructures that create quantum wells?
Or is it because the 'old' manufacturing process used bigger dies, or thicker bonding wires, or materials that were so lossy that they provided enough series resistance by themselves?

I think I owe an answer to my two dead blue LEDs.

EDIT: just re-did the experience with an 'old' red LED: I can leave it on for seconds without a problem using the same battery that zapped the 'new' LED.

New EDIT : While I can let the LEDs light up for a few seconds, I managed to blow one up when trying to measure the current. So, they are harder to damage, but not immortal after all. Tried three - four more old LEDs and I can confirm that for at least one second they survive (appearently) unscathed. New LEDs die almost instantly.
I will try later to measure the current in a more controlled setup, possibly with short pulses.

I love the smell of burning GaAs in the morning.


texts:
I'm new to electrical engineering, and I still have many stupid questions. Here's one of them.

This is what I'm reading.  https://itp.nyu.edu/physcomp/labs/motors-and-transistors/using-a-transistor-to-control-high-current-loads-with-an-arduino

  Next, add a diode in parallel with the collector and emitter of the transistor, pointing away from ground. The diode to protects the transistor from back voltage generated when the motor shuts off, or if the motor is turned in the reverse direction.

I thought before that polarity could be reversed in transistors, but now I'm confused. Can it not be? Why would it hurt the transistor, and how would it? Would it instantly break it? How does doing this fix it?

Thank you.

-edit to defend not being duplicate-

The proposed duplicate does not answer my question because it does not give how the transistor is affected. From searching online, I couldn't find this either; I'm probably searching the wrong thing. It also does not answer whether it is instant or how it fixes it.


texts:
Regarding the following text:

  Dynamic Range is defined as ratio between the smallest and the largest
  signals that can be measured by the system.

  Smallest signal is usually the RMS Noise which is the root-mean-square
  value of the signal measured with no applied signal. The measured RMS
  Noise level will depend on the bandwidth it is measured over. Each
  time bandwidth is doubled, recorded noise increases by 1.41 or 3dB.

For the part "Each time bandwidth is doubled"; what is meant by bandwidth here? Bandwidth of what? Do they mean the sampling frequency of the ADC?

So if our noise signal's FFT yields the noise signal's max frequency is 1kHz i.e signal bandwidth is 1kHz. And if the ADC samples this signal with 10kHz. Is the bandwidth meant in the paragraph bandwidth of the noise or the ADC sampling frequency?


texts: Do limiting resistors always need to be used when driving logic level ICs from microcontroller?

texts:
I have a circuit that uses a micro-controller and some driver ICs. The driver ICs state they are logic compatible and the data sheet says that the inputs maximum turn-on volate is 2.7v.

Some driver ICs are powered by the same 3.3v that the micro-controller is running at, and other driver ICs are 12v, but they still say they turn on at 2.7v. So I'm thinking I'm good there.

But the data sheet also says that if I am using diodes to protect the circuit against accidental reverse polarity connection, then I should put some limiting resistors in the line from the micro-controller to the logic level inputs of the driver ICs.

I understand why this is done, or I think I do, in that it limits the current and prevents lockup of the ICs due to the implicit SCR formed by the protection diodes. The data sheets go on to recommend at least 10k resistors.

I do not use the diodes in the group to protect against accidental polarity reversal, but I do have an active polarity protection circuit using two back-to-back FETs in the power side of the circuit using an LM-5050-1 IC.

Do I still need to put the 10k resistors in the circuit or can I do without them? Or is it just a good idea to always provide them no matter what?


texts:
I have only one layer for +5V and -5V power lines on pcb. There are about 10 dual supply OPAMPS which get power from Recom RKZ0505D DCDC converter.
As I know, star topology is suitable for this. PCB looks like;

But this time trace lengths are more than 15cm,
1)how can i handle this?
2)What should be thickness of traces?Thicker is better?
3)Does this effect the operation of DCDC converter as negative?
4)What is the best way to share this plane for +5V and -5V?
Thanks..
Because of very close +5V and -5V,it's not easy large planes under ICs.
Maybe between current star point and DCDC outputs can be used for inserting planes.

Power planes poured as suggested


texts: Is there a name for this type of connection?

texts:
I can't think of a time when I've encountered this, but I think that this is a thing: you have two conductive paths that, when connected, become one path. How they become connected is through tension/compression: they press against each other such that the metal of each path is still elastic. Ideally, this would allow something else to be inserted between the two paths that would still allow them to be conductive and the metal still elastic.

Is there a name for this sort of connection?
(Bonus question: would/could this sort of connection be viable as a four-way connection?)


texts:
I have designed this circuit to measure the current on the load and the comparator trips when the current of 1.2 A exceeds for 2ms.This works fine with simulation.When I build this circuit,my circuit trips within 1 ms instead of 2ms.
I am not sure what goes wrong .Is this due to the inrush current?


texts:
Assume there exists a 1 bit data output port and a 1 bit dataValid output port for a module. Is it OK to assign 1'dx to the data output when dataValid is assigned 0? Will this create synthesis issues?

EDIT: X optimizations seem to happen in both Synopsys DC and Cadence RC. Consider this code (a and b are 1-bit inputs and c is a 1-bit output).

always_comb
if ( !a && !b ) c= 0;
else if ( a && !b ) c = 1;
else if ( !a && b ) c = 1;
else c = 1'dx; // Don't care about this value.

gives an OR gate which is an optimized solution as opposed to an XOR which would have been inferred if c were set as 1'd0. This is a simple example but it seems to prove that synthesis tools do perform X optimization. Considering nasty X propagation bugs and verification troubles, are X assignments worth the saved area?


texts: MPU-6050 angle readings under mechanical vibrations

texts:
I'm in process of making a quadcopter. At this point I encountered a problem with MPU-6050 angle calculation.
When quadcopter is stationary with motors in off state and I'm tilting it, angle readings in all 3 axis is good, but when motors are in on state, readings starts to jump all over the place and can even differ from real value by 20 degrees.
I assume this effect is due to mechanical vibrations caused by motors. I include images of MPU-6050 board mounting  and a graphs of angle readings of MPU-6050 in X axis using Kalman filter, complementary filter and MPU-6050 DMP (Kalman and complementary filter implementations as well as processing code for graphs is from Kristian Lauszus GitHub, DMP used with Jeff Rowberg I2Cdev library).

                                   UPDATE

I connected second MPU to different microcontroller, so it would not be connected electrically with a quadcopter and mounted MPU on board with two sponges from both sides of MPU. Results were pretty much the same. So now I really know that noise (at least majority of noise) isn't related with electrical switching noise from motors.


texts: OV7670 camera, how to use external SPI SRAM?

texts:
I'm using OV7670 camera with no FIFO and Arduino Mega2560 and I want to send 76800 bytes to my laptop, because of Arduino RAM limitations, I'm planning to use Serial SRAM 23LC1024 (1Mbit) so I can store the bytes for a grey QVGA image and then read them into the Arduino and then to my laptop via serial link. I have tried OV7670 with FIFO(AL422B), didn't work for me.
I don't want to go into too much details about my project, this is all so new to me, just want to see if what I want to do, does even sound possible:

Read 76800 bytes from the pins of the camera output at a frequency of 12MHz ---> send them as they come to parallel to serial shift register ---> Store the data as they come in Serial SRAM ---> Arduino ---> Laptop

or

Read 76800 bytes from camera 8 output pins at 12MHz clock frequency or slower, send all 8 bits from camera to an Arduino port and then read the port 8 bit value ---> send that value to SPI RAM ---> later on send that to laptop via serial link.

Is there a better(or correct) way to write 76800 bytes from camera to the SPI SRAM ?


texts: Why is frequency spectrum centred at 1 kHz?

texts:
This is the circuit that I have built

I set the Continuous-Time VCO to a frequency of 1 kHz. Since there is no message signal the modulation index is =0 meaning I would expect one peak and I would expect that one peak to centred around fc which is 1 kHz.  However, when I run it I'm getting it centred around 1.1 kHz as shown below:


texts: Pulse Doppler radar system simulation using MATLAB

texts:
How to code this project in MATLAB
I'd tried coding this project (prob. 3-2, third paragraph) in MATLAB through this tutorial :
https://www.mathworks.com/help/phased/ug/doppler-shift-and-pulse-doppler-processing.html

I'd changed PRF to 100 and pulse width to 5e-4
, And made Velocity of target one dimensional:
    waveform = phased.RectangularWaveform('SampleRate',5e6,...
    'PulseWidth',5e-4,'OutputFormat','Pulses',...
    'NumPulses',1,'PRF',100);
    target = phased.RadarTarget('Model','Nonfluctuating',...
    'MeanRCS',1,'OperatingFrequency',1e9);
    targetpos = phased.Platform('InitialPosition',[1000; 0; 0],...
    'Velocity',[-100; 0; 0]);
    antenna = phased.IsotropicAntennaElement(...
    'FrequencyRange',[5e8 5e9]);
    transmitter = phased.Transmitter('PeakPower',5e3,'Gain',20,...
    'InUseOutputPort',true);
    transpos = phased.Platform('InitialPosition',[0;0;0],...
    'Velocity',[0;0;0]);
    radiator = phased.Radiator('OperatingFrequency',1e9,'Sensor',antenna);
    collector = phased.Collector('OperatingFrequency',1e9,'Sensor',antenna);
    channel = phased.FreeSpace('SampleRate',waveform.SampleRate,...
    'OperatingFrequency',1e9,'TwoWayPropagation',false);
    receiver = phased.ReceiverPreamp('Gain',0,'LossFactor',0,...
    'SampleRate',5e6,'NoiseFigure',5,...
    'EnableInputPort',true,'SeedSource','Property','Seed',1e3);

I did not change anything here :
    NumPulses = 10;
    sig = waveform(); % get waveform
    transpos = transpos.InitialPosition; % get transmitter position
    rxsig = zeros(length(sig),NumPulses);
    % transmit and receive ten pulses
    for n = 1:NumPulses
        % update target position
        [tgtpos,tgtvel] = targetpos(1/waveform.PRF);
        [tgtrng,tgtang] = rangeangle(tgtpos,transpos);
        tpos(n) = tgtrng;
        [txsig,txstatus] = transmitter(sig); % transmit waveform
        txsig = radiator(txsig,tgtang); % radiate waveform toward target
        txsig = channel(txsig,transpos,tgtpos,[0;0;0],tgtvel); % propagate waveform to target
        txsig = target(txsig); % reflect the signal
        % propagate waveform from the target to the transmiter
        txsig = channel(txsig,tgtpos,transpos,tgtvel,[0;0;0]);
        txsig = collector(txsig,tgtang); % collect signal
        rxsig(:,n) = receiver(txsig,~txstatus); % receive the signal
    end

    prf = waveform.PRF;
    fs = waveform.SampleRate;
    fasttime = unigrid(0,1/fs,1/prf,'[)');
    rangebins = (physconst('LightSpeed')*fasttime)/2;

    probfa = 1e-9;
    NoiseBandwidth = 5e6/2;
    npower = noisepow(NoiseBandwidth,...
        receiver.NoiseFigure,receiver.ReferenceTemperature);
    thresh = npwgnthresh(probfa,NumPulses,'noncoherent');
    thresh = sqrt(npower*db2pow(thresh));
    [pks,range_detect] = findpeaks(pulsint(rxsig,'noncoherent'),...
        'MinPeakHeight',thresh,'SortStr','descend');
    range_estimate = rangebins(range_detect(1));

    ts = rxsig(range_detect(1),:).';
    [Pxx,F] = periodogram(ts,[],256,prf,'centered');
    plot(F,10*log10(Pxx))
    grid
    xlabel('Frequency (kHz)')
    ylabel('Power (dB)')
    title('Periodogram Spectrum Estimate')

    [Y,I] = max(Pxx);
    lambda = physconst('LightSpeed')/1e9;
    tgtspeed = dop2speed(F(I)/2,lambda);
    fprintf('Estimated range of the target is %4.2f meters.\n',...
        range_estimate)

    fprintf('Estimated target speed is %3.1f m/sec.\n',tgtspeed)

    if F(I)>0
        fprintf('The target is approaching the radar.\n')
    else
        fprintf('The target is moving away from the radar.\n')
    end

I really have no idea why this new pulse give me this output :
Estimated range of the target is 750350.54 meters.
Estimated target speed is -4.9 m/sec.
The target is moving away from the radar.

I would be appreciated if anyone could give me an advice or a solution. thanks.


texts: Altium paste component at a new pattern shape( like circular or ...)

texts:
I need to past the component in PCB part automatically in one new pattern shape,So is there any why to draw pattern and paste component in that pattern automatically by Altium ( similar to align option but in new pattern type)?

thanks a lot.


texts: Minimizing pulled open collector output rise time on 74LS09

texts:
I have a circuit that calls for one open collector buffer for driving a shared line (/WAIT via Zilog Z80) and one typical AND gate. I've consolidated these into a single 74LS09 open collector quad 2-input AND gate IC.
To make the "typical" AND gate behave typically, I assumed something in the range of 10K to 1K would suffice for a pull-up resistance, but my tests are telling me something else. My oscilloscope sees a rise time of 2.4 microseconds at 10K, and 250nS at 1K. If I cut it down to 320 it still takes 92nS of rise time.
Referring to: https://www.ti.com/lit/ds/sdls034/sdls034.pdf
I was surprised to see the rise time TPLH on page 4 with 2K resistance should be around 35nS. The best I have achieved is around 500nS. In comparison, the fall time I've measured is around 17nS and hasn't changed much between tests.
As you've probably detected, I'm not incredibly familiar with this domain. Does anyone know what knowledge I may be missing? If there is more context I can add about the test circuit please let me know.
Additional context:

My unused inputs are all tied low
My LS09 will be used in a circuit that is clocked at 1MHz, so it needs to be a bit snappy
All logic is at 5V
Adding 10pF of capacitance to output against 5V or ground did not impact results
Decreasing input rise time did not impact results
These LS09 chips were bought on Amazon (https://www.amazon.com/gp/product/B08CCD472L), and were shipped in an antistat bag
Multiple LS09 chips respond the same way, although all are from the same seller


texts: Max current in Analog multiplexers with latch

texts:
In case of multiplexers with a latch, how does one calculate the maximum current that the IC can drive?

I am talking specifically about the HC4351 series. How much can the MUX drive, at different stages of the output? Since we are dealing with a latch, at any point, multiple pins MAY BE up, hence drawing current off the IC.

Here is a datasheet of the 74HC4351 from Nexperia. Although the max current for different conditions has been specified on I am not sure whether the clamping specs can be applied to this analysis.

In another app note on Load switches, some methods to arrive at the current at each pin based on the load current and voltage drop have been outlined.

I am not sure how I should proceed to selecting the right Latch. Can someone please help?

Add more information

I was also looking at using the 74HC259 for doing a latch. I later had realized that it is only a digital latch and may not fit my bill.

Thank you in advance
Rahul


texts:
I have two questions on placement of freewheel diode in a H-Bridge circuit:

1)  In reference to the general H-Bridge circuit below, wouldn't it be safer to place the freewheel diodes directly across the inductor? Wouldn't this solve the problem of high voltage spikes getting into the supply rail?

2)  If it is ok to place the diodes (TVS) directly across the inductor, what would the orientation look like? Would the connection in the schematic to the left (with L2 and D6 through D9) works?

D1 to D4, D7 & D9 are TVS.

simulate this circuit – Schematic created using CircuitLab


texts: RC-Circuit With Two Capacitors that are neither in parallel nor in series

texts:
Background
In our course, we have covered everything related to RC-RL-RLC circuit, however, all questions were based on the fact that you either have parallel or series connection.
I've not taken any course related to differential equations yet, however, I learned a little bit about it.
I have not taken Laplace, instead, mech-analysis, nodal analysis, and so on. Regarding what we have covered related to RC, RL, and RLC, we have taken the cases when we have natural or step response for these circuits, but they give us the solutions of the differential equations related to these circuits, and we just use the solutions to find the unknown voltages and current. For instance, the general equation that can describe the behavior of RL/C circuits is as follows
$$\mathrm{x(t)} = \mathrm{x(\infty)} + \mathrm{x(t_0)}-\mathrm{x(\infty)} \cdot e^{\left(\textstyle -\frac{(t-t_0)}{q}\right)} \text{, where } \mathrm{q} \text{ is the time constant} $$
They teach us the cases in which eventually you can simplify your circuits to have one of four known forms, i.e., one resistor and one capacitor/ inductor, or parallel/ series combination between one resistor, one capacitor, and one inductor.

Problem
In the circuit below, my instructor challenged me to come up with a solution.

Given that \$\mathrm{V_1(0)} = 3 \,\mathrm{V}\$ and \$\mathrm{V_2(0)} = 1 \,\mathrm{V}\$.
How to calculate \$\mathrm{V_2(t)}\$ for \$\mathrm{t} \ge 0\$ ?

Approach
I have attempted to write KVL & KCL and then try to find \$\mathrm{V_1}\$ & \$\mathrm{V_2}\$.
The equations that I know are as follows:
\$\mathrm{I_c(t)} = C \frac{d\mathrm{V}}{dt} \implies \mathrm{V} = \frac{1}{C}\int\mathrm{I_c(t)}\,\mathrm{dt} + \mathrm{V(t_0)}\$
The transient response starts when the voltage is applied at \$\mathrm{t} = 0\$.
What I have tried is \$\frac{d\mathrm{V_2}}{dt} + \mathrm{V_2}-\mathrm{V_1} = 0\$ and I am stuck here.
Unfortunately, I have spent more than a day without any noticeable progress in the question.
So, I seek any hints or tips that can put me on the right path.
Thank you in advance.


texts:
Wikipedia reports a simple model for a BJT in active mode (an approximation to the Ebers-Moll model):

\$I_E=-I_{ES}(e^{V_{BE}/V_T}-1)\$

(in the NPN case). Here, \$I_{ES}\$ is the Base-Emitter inverse saturation current. Finding it from a data sheet is difficult. But we have Spice models, and we can read parameters there. Here is a question about this same topic; an answer suggests using Spice parameters. However, three saturation currents exist: \$I_S\$ (transport saturation current), \$I_{SE}\$ (Base-Emitter leakage saturation current) and \$I_{SC}\$ (Base-Collector saturation current). Which one may be identified with the required \$I_{ES}\$ of the Ebers-Moll model?


texts:
I'm sorry, I may be slightly out of topic. I'm just an occasionnal "handyman" and I did not found any helping ressource on the web.

I'm willing to protect a touch screen and none of the usual offers satisfies me. In the screen protection market, there are usually 3 materials. The old basic one -I don't remember exactly the name of it-, the tempered glass and the TPU.

I love TPU and I feel like it really is underrated, maybe because most industries like our screens to break so often. I've always saw semi-hard TPU full shells for Iphone but when I try to find the same kind of product for my phone, I just have the choice between an ultra thin TPU protection or nothing. I would prefer a thick TPU protection to a tempered glass but a thin one is just useless.

So, sorry for the long intro, I decided that I would make my own, probably cutting it out of an Iphone case. The problem is : it will have to stick on the screen by itself, while on the Iphone I think it's fixed just by fitting around the phone. What is the material that makes screen protectors stick to a screen while keeping it removable and letting electrical signals trough ?

Thanks a lot for sharing you knowledge with me


texts: Best approach for designing 40A laser diode driver?

texts:
I need to design 40A 1.8V laser diode driver and need some word of advice as in the past I did from scratch only much smaller DCDCs. As it's a laser diode there will be no fast current changes.

My idea is: do synchronous buck DCDC, use PWM from STM32 microcontroller, then MOSFET driver then MOSFETS. 40A for mosfets does not looks like a problem. Sense current using high-side (on 1.8V rail) 0.001 Ohm shunt with opamp amplifier.

Few questions though:

1) Vin: I am looking more at 12V instead of 24/48V, to avoid too short transistor on times. Reasonable? Input current 8A vs 2A does not looks like a deal breaker.

2) Inductor. 40A inductor looks scary, and I probably won't find anything readily available. I was thinking about taking standard 13x13mm SMD inductors (which usually 3A), and parallel lots of them. But this will reduce their inductance a lot, probably below acceptable level. Any suggestion?

3) Is there a benefit of implementing multiphase DCDC for this application? I have bunch of PC motherboard inductors, they are like 1uH and too low for any paralleling, but might be ok for multiphase.

For the craziest approach I might just cut piece of PC motherboard with transistors, inductors and capacitors and redo gate drivers. Will look weird, but beating 8-layer board design is something out of reach for me at the moment. Does that look too crazy?


texts:
I have been tasked with designing what is to me a strange circuit. I have to wire a 12/24 led navigation light with an 'on' indicator and an 'off/extinct' indicator.

This is what i tried - switched 24 V to the nav light with a 24 V, 8-pin relay after it in series. I ran a 24 V red led through the N/C contacts for the 'off' and 'light extinct' indicator and a 24 V green led through the N/O contacts for the 'on' indicator. Everything works on the bench but the nav light is dim and the relay only gets about 18.5v at the coil. Its enough to pull it, but I feel I am missing something in the black magic world of resistors and diodes.

The navigation light is 9 - 33 volts, power is less than 2.5 watts. The relay measures 398 ohms across the coil.


texts: Resistor to limit maximum voltage of solar panels

texts:
I have two 20W solar panels (each Voc = 22.3, Isc = 1.22) in series connected directly to an axial fan driven by an EC motor (rated voltage 48V). Here the maximum operating voltage when very sunny has been about 43 V.
This configuration has worked well in the past but I need a bit more airflow. I want to add in series another panel, this one is a 10W, same voltage, about half the current.
I have read elsewhere that this not need to be a problem for the panels since the operating current will fall to that of the smallest panel. That is fine to me, at the moment I am not aiming for high efficiency. What worries me is that the EC motor might get too much voltage out of the three panels.
From the panel curves it appears that with full sun (around 1000 W/m2) the motor might get 60-62 V.
The operating voltage range of the fan according to its data sheet is 28-56 V. The rated current is 0.5 A, however when I connected the fan to 56V I measured 0.4 A.
Question
Can I connect a power resistor in series in the circuit so that with full sun the motor "sees" about 56V instead of 60-62V? Is there a way to calculate the required resistance?
Unfortunately for me the fan does not have much information on its properties to help with this.


texts: Driving 50-pin e-ink display with one chip?

texts:
I'm trying to connect this 50-pin e-ink display to an Atmel ATmega328p for a hobby project.

The biggest design challenge I'm facing is connecting all the pins from the display to the MCU in an orderly way.
Originally I was using six 8-bit serial to parallel decoder / shift registers (e.g., 74HC595, chaining them together) then connecting the 2 leftover pins to the MCU directly. But this approach is a mess on the breadboard.

Is there any way to get a wider shift register (e.g., 32-bit or 64-bit) to make things better? Or is there another type of (inexpensive) chip entirely that would work? I've looked at LED drivers, but thought it has too many special features for this application.

Thanks in advance!


texts:
I have a DE1-SoC with some data coming in through an A-D Card.
After digital processing I want to transmit data to a host PC for records.

I'm trying to figure out the easiest way to go about this. I've never used the HSP side of this hardware before, so am treading carefully.
I think the following options are available, but I may be ignorant of more.

USB Blaster

Perhaps using the Nios ii processor to communicate across USB-Blaster. I am not sure how to save data sets through the nios interface though.
Similar transmission to Signal-Tap?

Using the HPS module (Linux) transmit data over the Ethernet module. Setting up a receiver in python would be quite accessible?

How do I implement a communications interface to an Altera FPGA?


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I just obtained a Rigol DS1052E oscilloscope and so far I'm very pleased with it indeed.

For an early test I used my papilo fpga board to generate a signal using the following verilog -

module Demo(input clock, output led);

reg [0:8] counter = 0;

always @(posedge clock)
begin
   counter <= counter + 1;
end

assign led = counter[0];

endmodule

I connected the oscilloscope probe up to the output pin. I called it LED because it had an LED on in a previous test but it's just a diconnected pin right now, and I got this trace -

The frequency etc is all as expected, however I see spikes at each positive and negative transition. My question is, are these real? And if so are they something I would need to worry about in a real circuit if that pin was connected somewhere, or are they an artifact of the way I'm measuring the signal?

Basically am I using the 'scope correctly? As a software guy doing this for a hobby I tend to think of digital signals as purely on or off, but I know its more complicated that that so wanted to ask am I seeing something real here, and is it something I'd ever have to worry about


texts: The relation between light electric field and light power (optical modulation)

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I have been keeping thinking this question for one week. Hope could get some help from you.

Light 1:

Electric field = \$\text{e}^{j\omega t}\$;

Power = \$\frac{1}{2}A^2\$
light 2:
\$ \alpha = \omega_h \cdot t\$

Electric field = \$A \text{e}^{j\omega t}\cos(\alpha)\$;

power = \$\frac{1}{2}A^2 \cdot \dfrac{1+\cos(2\alpha)}{2}\$
light 3:

\$ \alpha = \omega_h \cdot t\$

power= \$\frac{1}{2}A^2 \cdot \dfrac{1+b\cos(2\alpha)}{2}\$ , 0 < b < 1.

electric field??
why do I want to do this?

Electric field = \$ \frac{1}{2}A^2\text{e}^{j\omega_c t}(\frac{1}{2}(\text{e}^{j\omega_h t} +\text{e}^{-j\omega_h t} )) = \frac{1}{4}A^2(\text{e}^{j\omega_c t + j\omega_h t} + \text{e}^{j\omega_c t -j\omega_h t})\$

The the frequency components of the light can be observed from \$ \omega_c - \omega_h\$ and \$ \omega_c + \omega_h\$

My question is, what is the electric field of light 3?
Is it possible to write down a mathematical formula for this?
If not, how to simulate it in Matlab?


texts: Help choosing modern replacement for Hitachi 1SS86 Schottky diode

texts: I’m trying to find a modern Schottky diode to use instead of the 1SS86 Schottky diode (Hitachi version, specifically). I want to use it along with a low current LED to build a lectenna that works for 2 and 5 GHz signal detection. Apparently only the Hitachi version of this diode works for reasons I don’t understand. I do not have experience with Schottky diodes so I’m not sure which specs to focus on when trying to find a modern (I.e., still being manufactured) equivalent. Any help will be greatly appreciated. - Thanks!


texts: Using a line filter transformer for audio?

texts: I've read that line filter transformers (like the one on the image) attenuate EMI between AC mains and an electronic circuit. Will the RF attenuation also work if I used one of these on audio input going through an amplifier circuit?


texts: Discharging MOSFET using Resistance or Diode (Best possible Alternate)

texts:
I have two Questions about MOSFET as sensor device.

1. I had been using resistance to discharge MOSFET. but I can not figure out minimum requirement of the resistance which could work on 12V power supply?

2. Can I use diode to discharge MOSFET? as given in following circuit diagram..


texts:
I'm tapping the ribbon cable interface between a HVAC control board (relays, etc) and display board (membrane panel + led display) to reverse engineer how to change the set point programmatically. I came across these traces using a logic probe / oscilloscope. Small pulses are clearly occuring when keypresses occur, but I can't understand why they occur in reference to what appears to be a 60 hrz signal. My best guess is that somehow the AC line power is getting picked up by the logic probe but I can't see how since I see this pattern regardless if I ground to the chassis or a persistently zero volt pin on the wiring hardness.
Is there a serial communication protocol that looks like this? (Signal appears to be on channel 3 and 4).
Have already googled extensively for specs on a Ranco 7221081 PTAC control board and found nothing hence the need for reverse engineering.


texts: Two LEDs but they are different in brightness

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I have duplicated the circuit below where the TTL side is a XBee Radio.  The LEDs on TTL TX and RX are the same part number, the resistors are the same value and they are being driven by the same VCC level.  The problem I am having is that when they are biased, the TX is much brighter than the RX, which is barely noticeable.  I have searched and have not found an answer...maybe I'm not searching for the right thing?

Can anyone explain why they are different in brightness?


texts: Why do people use (1 << PA0) when setting port?

texts:
In AVR Tutorials I often see:

DDRA |= (1 << PA0);
PORTA |= (1 << PA0);

used instead of:

DDRA |= PA0;
PORTA |= PA0;

What is the purpose of this?


texts: Can decoupling capacitors be doubled up? Xbee + VR both have them

texts:
I'm using an MCP1700 low-dropout voltage regulator to power an XBee separately from my other Arduino circuit, because it can use up to 215mA all on its own.

There are 1uF decoupling caps on both the input & the output of the VR (as necessary according to the datasheet), but I also followed through with advice given by Digi to put 1uF & 8.2pF caps right on the Vin line of the Xbee.

I didn't notice at first since they are separated out a bit, but looking at my schematic, since there is nothing else getting power from the 250mA VR there are actually 3 capacitors between those two, the 8.2pF one and the two 1uF!

Will the 2 caps do a worse job than just the expected 1? They are parallel so combine to 2uF, is this ok?

Just wanted to double check before I consider desoldering one of them...