texts: Can I control the charge of a Cell-Phone with a 555 Timer and a Transistor?

texts:
I want to charge my phone in a controllable manner, using a 555 and a Mosfet transistor.

The 555 is a countdown timer that gives an output (pin 3) of 5V for 1 minute, and then remains at 0V until an event occurs.

This output controls a Mosfet that enable/disable the charging (the charge is provided by a power-bank).

The schematic is this one:

The problem is:

When the the transistor turns off, the DC voltage between the + (plus) and - (minus) of the cell-phone is 0.3/0.4 Volts.

How can I make the output voltage 0V when the transistor is OFF?

I've already checked if the the output of the 555 is effectively 0V, and it turned out that it was like 0.01V HIGH, but I think this has not effect since the Vth of the 2n7000 is 0.8V.

Thanks a lot.


texts: Bulk Capacitor for Full Wave Rectification

texts:
By using notes from C.Basso Bulk Capacitor Calculation, I managed to plot the ripple curve for bulk capacitors for offline converters.
This bulk capacitor location:

Assume that my system is AC/DC flyback converter, below is my curve for 150uF bulk capacitor calculated with the input specification.

From this curve, by choosing 150uF as my input bulk capacitor, I understand that at low input voltage, 85Vrms, the capacitor DC voltage will discharge from 120V to 68V (with bulk voltage of 52V) in order to maintain the peak power requirement, 94W. Please correct me if my understanding/statement is wrong.
Questions:

What is the maximum limit bulk ripple voltage that should we use for calculation? For my example, I'm using 50Vp-p as the ripple. Are this 50Vp-p value is logic for actual application?
What are the impacts of having high ripple at this bulk capacitor during low input?
Example with 150uF bulk capacitor, what will happen to the system if the minimum voltage suddenly goes lower than 68V during 94W peak power operation?


texts: How can use MP45DT02 and CS43L22 DAC with STM32F4?

texts:
I'm doing an application with MP45DT02 MEMS audio sensor omnidirectional digital microphone.

I'd like to use a STM32F4 MCU to control it, but I don't know much about it. Can I take input from the audio sensor and read it with the CS43L22 DAC unit? If so, how?

Also, are there any libraries available that I can use to drive these components?


texts: How many devices can be daisy chained via SPI/I2C?

texts: How can we determine how many devices can be daisy chained from a datasheet


texts: I designed a PCB in Fritzing, but forgot to mirror it. How do I fix it?

texts:
I designed my first PCB in Fritzing, intending to have it milled at the local hackerspace (they want Gerber files) and then assemble it with THT components.

But now all the copper is on the top side (milling two-sided PCBs is apparently way more complicated and unnecessary for such a simple circuit), and the holes are set up so that the components have to go on top, too!
The resistors and linear regulators aren't a problem, they are symmetrical, but the RJ45 connector and the Max485 chip are not!

Is there a way to mirror the copper traces (never mind the silk screen, it's not gonna get milled anyway!)?
Fritzing doesn't seem to have the option, but it can export Gerber files.

Thanks!

This is the PCB, btw:


texts: Step down 9-36V to 5V: Best and cheap way to power a Raspberry Pi

texts:
I've seen a lot of solutions across the web: MP2307, OKI-78SR-5, LM2596 and so on.  I have to power a Raspberry Pi 4 that draws around 1.8/2A in a smart and effective way (low ripple, extended range from 9V to 36V.)
Also, I need to design and integrate this step down circuitry to a custom PCB that has very low area available (2x3cm.)
Does anyone have experience with those step down converters? What do you recommend?


texts: I am trying to calculate the gain Vout/Vin of the circuit below. I'm not really sure where to start, can anybody help?


texts: What item could this PCB board be from? (NOT serious, misc. question)

texts:
This is a fun, light-hearted question and not meant to be taken too seriously.

As a little fun thing between a group of friends, we found this question on a desk at work sometime ago about a PCB that had been removed from a typical household object. The question basically was what household object do you think this could have come from and what could the function of the board be.

We've come up with all sorts of possibilities such as a smoke detector, microwave oven, old TV, etc, however none of us can confirm whether any of us are right as there isn't any answer to the question available. Given the large number of capacitors and resistors, we don't think it's a simple clock. Furthermore, we haven't been able to deduce what the large plastic piece in the middle is - we're hovering towards a transformer (some are thinking it's a speaker), but the shape of it is throwing us off.

Can anyone shed some light as to what they think this board could be from or what they think it is used for so we here can stop debating on this.

Battery is there for size reference.

Different image also of a similar device


texts: Collector Current in Class A Output Stage

texts:
The goal of this question I am having trouble with is finding the minimum output voltage, in which there are two cases: one in which Q1 turns off, and the second in which Q2 turns goes into saturation. I cannot seem to figure out how to find Q2 collector current, I, in this class A output stage. We were told in class that the diode, Q3, keeps the base-emitter junction at 0.7 V, but I cannot help think there is more to it than that. The one solution I could find online said that I is found as such:

I'm not sure how it is possible to find with the given information. How can the base current equal to the collector current with such a high beta? What am I missing here? Is that solution even correct?
first two images are from Sedra/Smith Microelectronics, 7th edition, chapter 12.
last image is a solution from Slader by SSoliman (https://www.slader.com/textbook/9780199339136-microelectronic-circuits-7th-edition/983/problems/1/)


texts: What kind of output is on this PID Controller

texts:
I have a Altec PC410 PID controller with 2 outputs purchased from eBay. However the exact model number is not known.

On top of the controller is a diagram showing how the 2 ouputs are different. Is it possible to identify what kind of outputs this unit has?

This PID controller will be used to drive an SSR.

Possible Outputs

Actual device


texts:
Hi I'm a complete newbie in EE, sorry if my question sounds dumb:

A combinational circuit hoas one input and one output. And it takes 1 second to generate one output.

If we put the first input into the circuit in the beginning, then we put the second  input into the circuit after 0.5 second.

Will the first output's result be affected by the second input?
Or will  there be no interference, we can get the correct first output after 1 second and also get the correct output after 1.5 second?

Because I'm completed new in EE, so I won't be able to understand technical EE analysis of circuit.


texts:
You can view the image in greater detail on the following link:

http://i.imgur.com/z18qD56.jpg

I have been trying to hack a ball mouse (mechancial mouse) with my arduino. The objective
is to cut off the signals being given to the optical rotary sensor, and replace them
with signals sent by the arduino. This in theory would control the "x" and "y" movements
of the mouse.

Currently I de-soldered the optical sensor responsible for the "y" motion (picture 5 shows the detached optical sensor). This sensor would usually get signals from an infrared led on the other side of the rotating wheel and passes signals to the following mouse parts using "Quadrature Encoding", which is explained well in the following site:

http://www.eehomepage.com/report.php?report=20080225

So I figured that If I send the right voltage signals through my Arduino Uno R3 using the
analog pins (A0, A1), I should be able to manipulate the vertical movement of the mouse on the screen.

The results weren't great. The courser of the mouse would sometimes move upwards a bit,
and then stop for a few seconds. The intervals of this happening were very inconsistent
and slow, and I had coded it in the Arduino to preform a smooth straight line.

Here is the Arduino Code:

int ledA = A0;
int ledB = A1;
int highVar = 255;//equivalent to 5 volts in the analogWrite() function
int lowVar = 0;//equivalent to 0 volts in the analogWrite() function
int varDelay = 20;//20 milli seconds
void setup()
{
  pinMode(ledA, OUTPUT);
  pinMode(ledB, OUTPUT);
  analogWrite(ledA, 0);
  analogWrite(ledB, 0);
  delay(1000);
}
void loop()
{
  analogWrite(ledA, highVar);
  delay(varDelay);
  analogWrite(ledB, highVar);
  delay(varDelay);
  analogWrite(ledA, lowVar);
  delay(varDelay);
  analogWrite(ledB, lowVar);
  delay(varDelay);
}

Having a varDelay of 25 milliseconds seemed to produce the best results, since anything over 100 milliseconds would produce almost no movement.

My understanding is that the optical sensor has 3 pins, 1 for the voltage that comes from the device, and 2 pins that send voltage back to the device. The 2 pins that send voltage back would have the voltage lowered when the infrared light hits them. For that reason, I soldered two jumper wires to the respective pins that send voltage back to the mouse.

I am not sure if pins A0 and A1 manipulate there voltage through Pulse Width Modulation, and even if they do I am not sure if this would be the reason I am getting bad results. Would any of you know what I am doing wrong?

Edited: I was told that A0 and A1 were outputs hence would not work, thanks for the correction. However I had previously used the pints 9 and 10 (which have PWM), and when that failed went to try it with pins A0 and A1, so I still don't have a solution to my problem.


texts: I need to find a datasheet or a similar capacitor part. I am reverse engineering this bug zapper circuit and I need to know the pin out on the capacitor in the pic below. I also need help finding the data sheet for this sucker. I have tried looking it up with no luck.


texts: Eliminate standby leakage current of output capacitor in a DC/DC converter charging a battery

texts:
I am using a DC/DC converter to charge a battery. The output current of the converter is about 6 Ampere at 41 Volts.

I'm trying to eliminate the standby leakage current of the output capacitors in order not to drain the battery (even mere milliamps are too much for this specific use case) while the DC/DC converter is not active.

Furthermore, any capacitor inrush current greater than 30 Ampere is too much for the battery. Thus, it is preferable for the capacitors to be charged through the DC/DC converter.

I have thought of the following approaches:

Using a diode to let current flow only into the battery and not back from the battery to the capacitors. (This would solve both leakage current and inrush current considerations) Thing is, that the diode dissipates a lot of power in this configuration.

Using an N-Channel MOSFET as a low side switch between the output capacitors and ground. This would eliminate the standby leakage current, but not the inrush current problem. I have thought of ramping V_GS of the MOSFET in order to "slowly" decrease the RDS during startup to charge the capacitor more slowly.

Is this a feasible approach? Are there better solutions to this problem?


texts:
In the building I live, the hallway lights can be turned on by pressing any button that are scattered around the building, and all the lights will go on for a given time. I'm pretty sure that its totally analog, since it's decades old for sure. What is the working principle of this?

I'm thinking that pressing the switches might charge a capacitor, which slowly discharges through an electromagnet, which keeps the lights on for some time. This would require cables running from all the switches to a capacitor and from there back to all the lamps, which is a lot of cables. Does anyone know how they did these "back in the days" (I'm guessing modern systems would be simply digitalized with some cheap microprocessor).

Thanks!


texts:
I'm trying to make a circuit to interface a DALI driver (Digitally Addressable Lighting Interface) to a SAML21 microcontroller.
Voltages on the DALI side goes from 0 to 22.5V, a digital 0 goes from 0-6.5V and a digital 1 from 9.5-22.5 V.
So my goal is to translate DALI 0s and 1s to 3.3v levels.
DALI- terminal is connected directrly to GND and DALI+ is connected to a pull-up resistor to 12v power supply. So with a simple transistor to GND I get to control DALI+ to go from 12v (aprox) to 0.4v (aprox) by switching the transistor.
The hard part comes when I need to translate from DALI to 3.3v, because of the different possible voltages.
Could you give me some directions as to how to approach this part of the circuit?
Thank you.


texts: What features should/must be present inside a prototype FPGA board to aid in debug?

texts:
When making any prototype PCB it is always a great idea to have features within it that can be used to aid in debug of the design.
A few examples are:

Use the largest FPGA available that has migration path to the one we expect to use in the final product. This means we can have a lot of logic to implement debug modes and internal logic analyzer like signal-tap. This does mean that our power dissipation measurements won't be accurate since a larger FPGA will have higher static power dissipation.

Embed features into the board that makes it possible to connect certain signal paths to a scope. These could be analogue signals or digital signals. I am not talking about the signals that directly connect to the FPGA. There are different ways to do this, and I am not sure about the best way to do this.

Have 8 or 16 pins exposed via header, that connect to the extra general purpose I/O on the FPGA. These can be used to output internal FPGA signals to the pins which can then be connected to a scope or logic analyzer. The question that arises here is, what type of connector to use since high speed signals require signal integrity to be kept in mind. Certainly we must choose a connector that a scope or logic analyzer can easily connect to.

Have 1ohm resistors on the power supply rails that can be used to accurately measure the power dissipation on all the supply rails, especially the ones connected to the FPGA.

Put in an FTDI chip that can be used to implement USB-UART.

Have an easy method for the prototype to be connected to another FPGA or microcontroller board in case the need arises. One way to do this is to have Arduino shield connectors on the board but then we must be sure that what we intend to connect is compatible before we make the PCB.

I am sure that people that have made many prototype PCBs and then gone to production can give their opinion on this list and suggest some improvements. It is true that the features also depend on what the board actually has been designed to do, so the same techniques can be applicable to every project. So now my questions are:

Is there any improvement over what I have recommended above?
Are there some features further to what I have mentioned that should be utilized?
Having lots of capability to aid in debug is a great idea but, it creates an issue when we come to production level tests. The path to go from the prototype board to the production level PCB for alpha testing e.t.c must be simple.

I would be grateful if someone can put in their two cents. This question is VERY specific and not broad or off topic. I think I have covered most things already.
Thanks.


texts: Does Impedance Matching Imply any Practical RF Transmitter Must Waste >=50% of Energy?

texts:
According to the maximum power transfer theorem, when a fixed source impedance is given, the load impedance must be chosen to match to the source impedance to achieve maximum power transfer.

On the other hand, if the source impedance is not out of reach from the designers, instead of matching the load to the source impedance, the source impedance can simply be minimized to achieve maximum efficiency and power transfer, it's a common practice in power supplies and audio-frequency amplifiers.

However, in RF circuits, to avoid signal-integrity issues, reflection loss, and damages to the high-power RF amplifier due to reflection, impedance matching must be used to match all the source impedance, load impedance, and also the characteristic impedance of the transmission line, and finally the antenna.

If my understanding is correct, a matched source and load (for example, a RF amplifier output and an antenna), forms a voltage divider, each receives half of the voltage. Given a fixed total impedance, it means there is always 50% of power wasted in burning and heating the RF transmitter itself.

So, is it correct to say impedance matching implies the efficiency of any practical RF transmitter cannot be greater than 50%? And any practical RF transmitter must waste at least 50% of energy?


texts: UPS power supply for both router (12V, 2A) and up board squared (5V, 6A)

texts:
I was searching for an UPS (uninterruptible power supply) to power my Up Squared Board (5V, 6A) and my router (12V, 2A).

So far I didn't find something suitable but here is my idea:

Take a suitable UPS (e.g.Mean well SCP-75-12) and convert voltage down to my needs (12V and 5V) with two dc-dc converters before feeding into the consumers. Also attach a battery of course to the UPS.

But I am a complete electronics noob so it would be great if you could help me with choosing the parts...

It doesn't necessarily have to be extremely cheap.

I want to put all the components in one small case so the dimensions should be rather small.

Also I would prefer to have components with high efficiency.

Many thanks in advance!


texts: Opamp output voltage spike and swing due to DC heater

texts:
Turning on the heater introduces a voltage spike and voltage swing on my 3.3V regulator and this causes a transimpedance amplifier output to be wrong.
Every time the heater turns on my 3.3V regulator voltage changes by +-5mV. Note: 12V and 5V regulator voltage also change.
Heater MCH2-80W-001 datasheet
I have tried all below methods but did get any improvement. I need be able to avoid the voltage swing as much as possible.

Add MOV or varistor parallel to the heater
Add inrush current limiter in series to the heater
Add MOV and ICL
Add diode in parallel to the heater

Below diagram is just for demonstration, actual circuit will have all bypass and require parts.

The following graph shows when the heater turns on and off (red circles.)

simulate this circuit – Schematic created using CircuitLab


texts: Why is the output of a filter considered 70.7% of input while determining the cutoff frequency?

texts:
I have seen in many books that while finding the cutoff frequency of a filter (from the transfer function) the output is considered 70.7% of the input.

Why 70.7%?

Why not 50% or 20%?


texts: Can we use Litz multi-strand wire as Tesla coil secondary?

texts:
I am making a mini Tesla coil as a proof of concept. I was thinking, can we use multiple enameled copper wires as the secondary? (Edit: Every wire is individually enameled and the ends  sanded to expose the copper, then soldered. The resulting "wire" is not flat, the individual wires are intertwined.)
After soldering the ends, if I use, say 10 wires, then if I wrap it 100 times, I'll end up with "1000 turns". Will this work?
Assuming both scenarios, where wires are parallel and where the wires are jumbled. I need a detailed answer, Thanks in advance.


texts:
Can anyone provide me correct expression of output voltage between node 1 and node 2 when Vin < -5 V ?
I am getting (-Vin/2)-2.5 while the answer is (Vin/2)-2.5, I am not able to detect my mistake here


texts:
Was looking for 555's in my parts box, and while I did find one NE555, I found a dozen of these, in the same pouch. Wondering if the seller pushed me some slugs, because I can't find datasheet for this part. Not even in the Chinese / Russian parts search sites !!

The form-factor is same as NE555 (8 pin DIP), and markings on top say -

ATML U942
2FB 2
9H07258

and the bottom die sealant says that it's manf'd in Thailand.


texts: ultrasonic-sensor to Logic Level Converter to raspberry pi

texts:
Trying to connect Ultrasonic sensor to my raspberry Pi. Im aware of two methods:

connect the trig to a 1k resister before connecting to raspberry pi
Use a 8-Channel Logic level converter

I trying out method 2 but cant find good example of how the logic converter works/wired up.

The example I'm currently looking it is this instructable. I don't understand why this example board 3.3 V is wired up.

The configuration I'm thinking of is:

Raspberry 5v to Ultra Sensor VCC.
Ultra Sensor GND to PiGND.
PI Gpio pin to Echo pin of Ultra Sensor.
Ultra sensor Trig to Level converter to PI Input Pin.

Can someone tell me how to hook this thing up?


texts: I just got a MSGEQ7 equalizer chip. I have everything wired up like http://nuewire.com/info-archive/msgeq7-by-j-skoba/ except for the 33pF cap. I have no idea where to even find those. I think somehow the cap and resistor work together to control the clock and I have no idea how that works. The chip gives expect values when I hold the wire, but when I plug the wire into 200kohms and my series of 3 10pF caps, it does nothing. Where am I going wrong?


texts: Raise of TRIAC A1-Gate potential under load after triggering

texts:
During experiments with a TRIAC I noticed that appart from the triggering signal the A1-Gate voltage remains 0V under no load condition.
Under load conditions the A1-Gate voltage remains elevated after triggering up to the moment the TRIAC stops conducting.

In the information found so far I find only information on the latching  current nothing on the above mentioned effect.

Why is this happend or do I make an error in the measuring procedure?


texts:
I am trying solve the question shown in the picture below

(I am assuming the switch is down in the picture, I can't tell)
The equation that I am using is $$\frac{V_{\text{out}}}{V_{\text{in}}} = - \frac{R_{\text{f}}}{R_{\text{in}}}$$ because there is negative feedback.
For 2a), I ignored \$R_4\$ because there is no current input to the op amp, so I am assuming \$R_4\$ can be neglected. I combined \$R_2\$ and \$R_3\$ so that the total resistance for \$R_{\text{f}}\$ is \$1000\Omega\$. I then substituted \$V_{\text{in}} = 20\text{ mV}\$, \$R_{\text{in}} =1\text{ }\Omega\$ and rearranged to get \$V_{\text{out}} = -20\text{ V}\$. I am unsure if I applied the right logic to this question and I am don't know how to solve 2b).
This circuit is different from other inverting op amp circuits I have seen which is why I am struggling to answer it. How do I approach a question like this?


texts: Run Stepper motor with more torque and smoothly

texts:
I have a stepper motor and its torque curve is below.

I am trying to get more torque from the motor. Therefore, I decided to setup my driver to half step. I am using an Arduino for generate the pulses as below code.

void move() {
  if (micros() - lastStepTime >= stepDelay) {
    lastStepTime = micros();
    digitalWrite(STEP_DOWN, HIGH);
    delayMicroseconds(1000);
    digitalWrite(STEP_DOWN, LOW);
  }

}

I have used delayMicroseconds(1000) for get 1000PPS output.

Unfortunately, when I use this 1000PPS pulse rate, motor cannot run smoothly.

Greatly appreciate someone can give a solution for that.


texts: Is there a means of USB interfacing to an iphone, which does not require an expensive Apple approval process?

texts:
I am developing an external hardware that needs to make USB interface to iPhone. (30pins for now).

I do not think Apple would approve MFi for an individual.

For USB interface, is there no way? Or any kind of breakout board and protocol available?


texts:
I bought an electromagnet online hoping to make it attract and repel metals by changing the polarity of the voltage on it, but I ended up experiencing attraction all the time.

Is there any way to make an electromagnet that attracts in one way and repels in another way?


texts: I have this circuit that has a p-channel MOSFET driving a motor. The motor is supposed to go when I press the button. However when I apply power to my circuit the motor runs without pressing the button.


texts:
When performing a calibration or a diagnosis acquisition from an ECU using a CAN-bus is there a protocol preferred?
I've come across UDS and XCP but I can't quite get why one might be preferred over the other one.


texts: How to power the microcontroller in a BMS of a large battery pack

texts:
Yeah, it's a short and simple question but I couldn't find an answer on google.

Just imagine I got a lots of LiIons in series , about 400 Volt for use in an electric vehicle.

I use some ICs to control 12 or 16cells each (they power from those cells). But everything of course must be isolated from each other and the µc of course.

How will the µc be powered ? 400 Volt DC -> AC -> 5V AC -> 5V DC cant be a solution.
Maybe they use a separate cell just for the µc and stuff? But how would that one get charged then?
And just powering it from the 2 bottom cells would imbalance the stack.. or not?


texts:
How to make the output of a ring oscillator look more like a rectangular wave?
I have designed a differential ring oscillator whose output takes the following form:

The output of a ring oscillator should be in a rectangular shape. But the output of my ring oscillator resembles no rectangular shape. How can I correct this problem?
My design is a three-stage ring oscillator:

Each stage is a differential inverter:

I have tried the following tactics to make the output waveform looks more like a rectangular wave:

Reducing the output capacitor
increasing the source current in the differential inverters
Increase the width of the transistors in the differential inverters

But all the above methods cannot yield the rectangular waveform. What other techniques I can use?
Thanks a lot.


texts:
I'm trying to connect 32 I²C "root of trust" NXP A71CH devices.

I'm thinking about a good way that does that, I mean what kind of communication should I use?
A digital multiplexer that selects a device? but based on what?
switching on the VDD source? but that needs reinitialization of the device and that takes time.


texts: What is the lowest wattage that can be used to charge a USB 3 Cellphone?

texts:
So obviously there are various protocols to increase the charging speed of USB 3.0, but I would like to decrease it.
Basically I'm working a tiny generator which can only put out about 500mW. Is it possible to charge a cellphone directly using such a small amount of power?
Ideally if the power draw is too great for my generator, the voltage will sag and the phone will just accept whatever power it can get at some intermediate voltage like 4v. But of course it might do the opposite, and draw more current in an attempt to get the same power.
If USB 3.0 can't handle small amounts of power gracefully. What's the smallest amount of power that it will handle?
One solution I'm aware of is to store power in some intermediary like a super-cap or lipo, but if I can I would like to use the power directly, as that's more efficient.


texts: Reduce background noise from a .wav file?

texts: I am planning to compare two audio files. I have recorded two voices and compared them using cross correlation. Since the presence on background noise while recording the resulting correlation value is always near 0.5. If i give any recorded waves from internet, i am able to get the correct value. So how can i reduce the background noise from the recorded .wav file. If i come to know how to do it, then i will try to implement technically. Any basic ideas will be helpful for me to learn and apply it. Thanks.


texts: Today with the help of integrated circuit, data encryption is used in transferring all kind of data in wireless communication. But back to some early days when people build telegram transmitter with vacuum tubes. How were data encrypted at that time. I know if someone transmit message in the form of Morse code, he can encrypt the data in various of ways, like the German Enigma machine. But how about the voice, for example, the voice chat between a navy pilot and aircraft carrier in World War II. It is possible to encrypt the voice at that time, or were there other ways to protect the talk from eavesdropping?


texts: Why does the use of Tristate-Buffer prevent exceeding the fan-out?

texts:
Why does the use of a Tristate-Buffer in digital-circuits prevent exceeding the fan-out of logic gates? The number of Logic Gates-inputs, that are connected to a single output is the same, as using no tristate-buffer.

For example: a logic that doesn't work, due to the high fan-out

and the same logic gate with an Buffer, so it works.


texts: Does changing the diameter of a wire affect the TCR of a wire?

texts: I have a wire wound resistor that is changing too much when being heated and cooled. I know changing the chemical composition of the wire is the biggest factor in changing the temperature coefficient of resistance (TCR) of the wire, but I already have wires with a larger diameter of the same material. Although the resistivity of these wires would be lower, would the TCR improve? There would also be more wire on the resistor. I cannot find anything online that relates to this.


texts:
I have downloaded an scr model file from this website and pasted it in the same folder as that of my .asc file.
But ltspice still shows unknown subcircuit called for the scr present.
What am I doing wrong and how can I correct it?


texts: Why do radiation hardened IC packages often have long leads?


texts: Connecting multiple SPI devices to Texas Instruments CC3200 LaunchPad

texts:
I want to connect one of the two (or both) 433 MHz RF receiver modules to the Texas Instruments CC3200 LaunchPad:

RFM83CL-433S1
RFM65CW-433S2

I also want to connect an SD Card connector to the LaunchPad at the same time. Is this possible? Is it possible to connect all three devices to the CC3200 LaunchPad at the same time and get each of these addressed?

I guess it would require two additional chips, one to change binary format to dedicated lines (green below) and one 4-way AND gate (blue below):

Is this assumption correct? Or is there already something similar available on the CC3200 LaunchPad?

Which chips would I require to accomplish the green and blue area?

Your help is appreciated.


texts: How do I structure a slow speed CAN Bus network with 400 nodes?

texts:
I'm looking into the possibility of building a CAN bus network with ~400 nodes in it. The total cabling distance is about 200m but it doesn't have to be fast; each node only needs to transmit a single packet once per minute so a data rate of 25kbits/sec should be fine.

The nodes are going to be custom hardware, probably using an MCP2515 chip. Power consumption is going to be an issue so I need them to be asleep as much as possible, is it a good idea to isolate them electrically from the bus cabling while they're not in use? In my head that would mean there only actually need to be a few of them connected to the bus at any given time.

What I really want to ask is whether this is A) possible and B) a really stupid way of doing it?


texts:
I'm trying to test the GPIO functionality of Altera (DE1, Cyclone II) with this simple program.

If the GPIO_0[0] gets a high (1) signal, LEDG[0] will light up. If it receives a low (0) signal, LEDG[0] will turn off.

For the input signal, I am asserting 5 and 0 VDC.

Here's my code:

module gpio_test (CLOCK_50, GPIO_0, LEDG);
input   CLOCK_50;
input   [35:0]  GPIO_0;
output  [7:0]   LEDG;

reg [7:0] LED;

assign LEDG = LED;

always @ (posedge CLOCK_50)

if (GPIO_0[0] == 1) // if GPIO received a high signal
    LED <= 1; // turn LED on
else if (GPIO_0[0] == 0) // if GPIO received a low signal
    LED <= 0; // turn LED off

endmodule

The problem is, it seems that GPIO_0[0] is always receiving a high signal (even though I assert a high or low signal) because the LED is always on. Assuming that my pin assignments are correct, what went wrong?


texts: selecting a TIA - and using it for 60dB dynamic range

texts:
before entering in to problem:

my application is a laser pulse detection, in this process when a laser pulse falls on photo diode it generates current, for which i need a  Trans Impedance Amplifier (TIA) (i read literature on benefits TIA have like SNR improvement and response time)to convert that current to voltage

my pulse characteristics:

pulse width min:10ns max:150ns rise/fall time:2ns pulse to pulse width:22uS

How i selected the TIA

key parameters: BW - bandwidth and SR - Slew Rate

from this literature i found my BW can be calculated by formula

BW=0.35/(rise time)=0.35/5ns=70MHz

Now slew rate is to be calculated

SR = 2 * 3.14* BW * Vp = 2 * 3.14* 70MHz *5V = 2198V/us

So Matching both these parameters is  TIA OPA659 from TI

EDIT:

with comments from experts about slew rate i have changed my TIA to THS3001 which has high slew rate and a CFA, (a point to note, even though the settling time of above CFA is 40ns i observed it to offer proper gain with out distorting pulse of 10ns in simulation ), when i tried to use very high BW and very high SR opamps like LMH5401 i found the opamp design to be complex due to fluctuation in common mode voltage and to be very prone to noise in simulation itself.

How to design a 60dB range TIA ?

now my  problem statement has become much complex

  my pulse electrical characteristics are expected to be Imin 50nA
  and Imax 50mA

EDIT:

as the specifications are stringent and after realizing the problem of noise gain explained by Andy

  i came to Imin 100nA and Imax 10mA


texts:
As far as i can tell i am following this circuit, although different components. However, when connected to a DC supply, both LEDs light up dimly and there is no oscillation. It appears that the drains of the MOSFETs are connected together via the inductor and the Vgs of both MOSFETs are constant.

Without the LC tank, only one LED lights up, so I assume that means the MOSFETs are indeed working. I also tested each MOSFET individually without the LC tank and they do indeed both work.

The components I am using are as follows:
MOSFETs: IRFP260N
Schottky diodes: UF4001
The resistors are normal 0603 SMD resistor, all values are as shown above
The capacitor is a MLCC, all values, are as shown above
The inductor is a toroid inductor, all values are as shown above
I am using a simple arduino UNO as the 5V power supply.


texts: What type of voltage control should I use for a battery power bank (using old alk. AA, C, D...) to provide low voltage for a light?

texts:
My collection of partially spent batteries has increased, and I would like to use a battery holder to build a power bank/supply which will provide power for a low voltage light (to be attached to my garage bicycle pump), but am confused as to what kind of voltage control I should best use to adjust the voltage.

From what I read on this site, It seems a potentiometer is not what it best, and that instead I need some sort of simple (cheap) voltage divider. The alkaline batteries would range in voltage from 1v. to 12v (23a: doorbell type), and the light would likely be  3v.

I have used a  DC motor speed PWM to control the speed on a 12V DC motor, but I do not know if that is what I should use on this project.

I am  aware that both the battery voltage and  discharge rate would vary, but unless there is a real problem with that then I rather face that then see these batteries go to waste when they still have some some left in them.

So if someone can tell me the name of what I am looking for I would appreciate it. Thanks in advance.


texts:
I want to use four teensy boards connected via the I2C protocol over a short distance (not more than 0.5m or 20 inches) but only the master one powered by the USB cable.

Should that be safe to connect the Vin pins of the slaves to the 3.3V pin of the master? (provided that the total amperage doesn't exceed the maximum).

In that case should I connect all boards to GND instead of AGNG? (no analog conpontment is included).

Thank you in advance.


texts: Connecting a Lithium battery directly to the GSM module

texts: I have a GSM module (M66 from Quectel) and a single cell Lithium battery,Based on Datasheet module operated in the 3.3 ~ 4.6 V and as I know battery deliver 3.7 ~ 4.2 V based on it's sate of charge.Then is this possible to fed the module directly from battery, without using any other chip (like MIC29302 which was recommended by Quectel)?


texts: How to measure charging current for TP4056 module?

texts:
TP4056 module is connected to usb port on my PC resistor is default 1.2k...

When I put multimetar on output of module I get about 120-130 mA...
I am not sure why is that, should I get 1A?

From datasheet it say for resitor 1.2k chargin current is 1A.

Maybe I doing something wrong, anyone know what is problem?


texts:
is there any substance to increase the SMD codes readability when the component is very small or has a poor print on it?
Some years ago I saw a video where they suggest to use alchol, but I tried without success.


texts: The usefulness of some bits in TIMSK register

texts:
There are things in TIMSK Register that confused me. According to the datasheet regarding Atmega32:

  When the TOIE0 bit is written to one, and the I-bit in the Status Register is set (one), the Timer/Counter0 Overflow interrupt is enabled.

And then it says that the corresponding interrupt, namely TOV0, in TIFR register is executed.

What's the need for TOIE0 bit at all? If it's being enabled by hardware and I can't disable it (well, I might by writing a logic 1 to it but for what reason/outcome?) then why was it ever built into the register? The same story holds for other bits such as OCIE0 in TIMSK register and its corresponding flag in TIFR register, OCF0. I haven't studied other bits in TIMSK register but for now the first two bits have confused me.


texts:
I accidentally broke down the charge controller on my new Powerbank.
However I am left with a brand new unused 20.000 mAh Li-ion Battery. Which I was planning to hookup to a new charging module/powerbank circuit.
But then I saw the writing on the battery and Googled it, but couldn't find a lot of useful information.
Writing is: 3.85/4.4V.
I personally never have seen a battery above 4.25 V
So I have a few questions:

What's the safe cutoff low voltage on this battery?

Due to the differences in voltage, can I still hook up this battery to standard powerbank circuit?


texts:
When a guitar string oscillates over a magnetic-coil guitar pickup, the pickup produces an alternating current.

Would it be possible to do the reverse of this, and feed an alternating current into a pickup to manually oscillate the string? If so, would the signal type being fed into the pickup, have to be the same as the signal typically output by the pickup? (except higher amplitude)

My intentions were to create a sort of "e-bow" style pickup fitted into the guitar, that's only purpose was to excite the strings, with a frequency that I could control with a micro controller

(e-bow demonstration)


texts: Induced Voltage calculation in rotating conductor

texts:
I have uploaded the example problem and the solution of it.
A positive charge will face force Q(vXB) in -z direction which will lead to separation of charges.
The separated charges create an electric field which will generate Q(E) force opposing the lorentz force. So, shouldn't the E be in z direction rather than -z ??
The lorentz force and Q(E) will balance each other and generate a potential difference with +ve down and -ve up and a magnitude of vBh.
Am I missing something ?? Please help me with this concept.


texts: Why is the cutoff frequency of this highpass filter with formula different from LTspice?

texts:
I used this online tool to play around and design a Sallen-Key low pass filter with a cutoff frequency of 0.3Hz. When I now put the resulting values for R1, R2, C1 and C2 in the formula I get exactly my desired 0.3Hz.
But when simulating the circuit with LTspice, the cutoff frequency was unexpectedly at 0.46Hz. That is more than 50% off!

Can anybody tell me where the difference is coming from? Am I missing something obvious? The only thing I can think of is that Spice is using numerical solutions, but the error of the calculation should never be that high! And the OpAmp shouldn't make any difference at these low frequencies either...
What frequency would I probably get when acutally building the circuit?


texts: Charge after turning off an electronic device

texts:
Let's say I've just turned off my Raspberry Pi and put a imaginary boundary around it.

Everything not on this picture is outside the boundary.

Is the net charge, inside the boundary, neutral?


texts: How loud is a 0.25W speaker supposed to be?

texts: I know this is a very broad question; I just want to know what I should be expecting from it. At the moment it's hooked up to an LM386-N3 op-amp outputting a 5V single rail square wave and it is whisper quiet. I get distortion if I turn the input pot too far and I've tried it with 20 gain and 200 gain so I don't think it's the input signal. If I stand at the other end of my room I can't hear it at all. It's a basic 5cm diameter 8Ω paper cone hobby speaker.


texts: Why the current entering and leaving the battery in an electric circuit needs to be same?

texts:
When somebody applies Kirchhoff Laws to the circuit consisting more than two batteries, the current leaving the battery is as same as entering the battery.

I have no problem understanding the circuit consisting of only one battery due to charge conservation. But if there are more than one battery, the current entering and leaving the battery doesn't need to be same. Total charge could be divided in a such way that more charge ends up in one, less charge in other. But the total charge could be conserved again.  For example, the image applies Kirchhoff law in which the leaving and  entering  current for each battery is the same.

One example here:

http://www.physicsandmathstutor.com/a-level-physics/finding-current-circuit-using-kirchhoffs-laws/


texts:
I have designed a power delay switch which is intended to cause a short delay while a reservoir capacitor fills up before giving power to my microcontroller due it needing a short burst of high current before settling down to it's operating current of around 5uA.
The power delay circuit (see below) itself works fine and gives me the delay I need and everything powers up as it should, however my issue arises when the circuit loses power.

simulate this circuit – Schematic created using CircuitLab

The circuit gets 2V from a regulator which regulates batteries (3V) down to the 2V I want to power the MCU as this will ensure that the supply voltage is constant which makes ADC readings and calculations easier to calculate.
Now the problem that I am having is that when the batteries are disconnected (circuit loses power) the two capacitors (C1 and C2) take a long long time to discharge (about 3 minutes) - this isn't a problem is power is reestablished quickly (under 2-3 seconds) which is how long it takes the voltage to drop below the MCU's minimum supply voltage, after this point, however, the MCU completely shuts off and won't power back on unless the capacitors fully discharge (<100mV) and then the power can be applied again and it will work as it should. So I feel I need a way of completely draining the capacitors in the event of power being lost. It might be worth noting that the capacitors initially discharge fairly quickly down to about 0.6/0.7V before beginning the painfully slow discharge process - if anyone has any bright ideas as to how to resolve this, that would be great.
Another alternative is to possibly design a slightly better delay switch that will cut the power line from the MCU when power is lost - as you might notice this one will not do that, but again I can't think of any ideas for that as current consumption is  a big thing and this current design draw virtually no current once running properly.


texts: Not sufficient brightness from Constant Current LED drive to 3W mini LED, with Arduino Nano

texts:
Now, after read my 6 thread tip, no solution clearly given, so I go ahead to  my problem.

When I  power on my 4 LEDs gave      fast full flash brightness for 3-4 seconds. That's a   sign that    all LEDs are ok.  After this the pattern starting   it goes to approx. 20 % brightness. In the    product description, this CC DRIVER LED was a dedicated PWM using with Arduino. As diagram view, I'm using 2 parts of Li-Ion battery 18650/3400 mAh as power source, step up converter prevent 12-14 volt. I was also try switch mode power supplies, 12 V 30A. This         changed the brightness to approx. 30 %.

To find out where this current as 40 mA from Arduino output goes Is measured the output pin voltage. My multi meters has 3.9mV as "noise" voltage when not connected      . I can see I measured  peak voltage from Arduino PWM output to 200mV! Normal this pulse as high/ON are 5V max load 400 mA. As I understand this PWM unit dedicated for use together with Arduino, which makes  no sense to me what are wrong to my diagram. It sounds like this PWM give Nano output goes overload?

Go to this URL and find all  device parts eg. other info in the Word-doc.  https://onedrive.live.com/redir?resid=DD2C186E5334F02C!368166&authkey=!AHIQO10jd5sa-xk&ithint=file%2cdocx

Appreciated volunteers with help and tips!


texts: Operating a Switched Mode Power Supply without a Load

texts:
Background

I'm a second year student at university, and wanted a simple power supply to test a couple pet projects without going all the way to the lab. I picked up a Power-One MPU150-4350 on the cheap at a second-hand electronics store. The output specifications section seems to state that, for the 3.3V output (V1), 3A is the minimum load while 30A is the maximum.

I know that running a switched mode power supply without a load can produce inaccurate output voltages and even damage the system, although I don't understand exactly why this is the case. However, having to always pull at least three amps from a 3.3V rail seems excessive to me.

Questions

What is the minimum load I can put on each of the outputs without damaging the power supply?
Will running a switched mode power supply without a load for short periods of time damage it? Or just produce unstable output voltages?
Why don't switching power supplies like low currents?

If you only know the answer to one of these please don't hesitate to post. Anything that helps gets +1.

Edit
This article will be very helpful for beginners (like me), the answer below is an in-depth and very useful explanation of why SMPSs can fail due to over-voltage when not sufficiently loaded.


texts: Calculating amperage in a current source

texts:
How do I determine the amperage at "?" based on the selected resistors in this current source?

Falstad Simulation

I took a bunch of measurements from the simulation and plotted them. I know that that transistor base to emitter voltage drop increases with current but I don't know how it factors in.

Edit: can down-voters please comment why so I can either amend or not repeat the issue in future?


texts:
I am using this circuit (please don't go by the design it is just a circuit block, this is not the whole circuit). I have connected a 12V DC at the center of the transformer and this 12V is also connected to a 555 timer IC.
 Here I am triggering the transistors alternatively and the transistor completes the circuit of the transformer. Thus transformer generates a square wave at the output.

The circuit is working fine but there is one problem i.e my 555 IC gets blow off in minutes when I switched ON my circuit. I thought it might be due to the
Inductor spike at 12V line (as the only 12V line is the common line for both transformer and 555) so I have attached an electrolyte capacitor at the input of the 12V supply and my problem solves out.

But this generates a confusion in my mind that how the inductor can change the 12V line to another voltage.

My Input supply source --- 12V from SMPS. Maybe if I have used the battery for input supply line then I will never get to know this problem. (As battery is self-act as capacitor)

Correct me if I am wrong in any of the concepts.
Please give your thoughts it will be very helpful to me in analyzing the inductor more closely.


texts: I am new to CANopen protocol and could anyone help me with the difference between PDO2 and PDO3.I am receiving CAN data from the sensor and i could see the message type as TXPDO2, TXPDO3 etc. Is there any difference between the 2?


texts: Inverted high impedance / pull down circuit

texts:
I'm devising a circuit to control the shutdown input on an integrated circuit. The IC accepts a high impedance input (can't be pulled to any voltage) to enable operation, or it can be pulled down to disable operation.

I'm trying to control it with a logic signal which is either 0V or 3.3V. This would be relatively simple with a low-side NPN/N-fet. However I want it to operate in an inverted way, where a 0V input will result in the output being pulled down and 3V3 input will give a high impedance output.

What kind of circuit could I use for this? I've thought about adding a transistor inverter before a low-side transistor, but if possible i'd like to reduce the part number.

Here's a diagram of how the circuit should operate:

Edit: datasheet of the IC


texts: STM32 Discovery -- Requires Official ST-Link?

texts:
I have a custom STM32 CM0 board I spun, and have been programming it using a $2 ST-LINK "clone" programmer.

I needed to test a chip with more memory, so I pulled out an unopened brand new STM32F0-Discovery board.

I connected my clone programmer via SWD (connections are correct, I removed the two jumpers).  AND NOTHING.

The Discovery board is working with a USB connection, just not with the SWD. So, the SWD pins are working and didn't get reset.

There's nothing to reset, I just see nothing from this clone programmer connected to this Discovery board.

Does STM have some kind of protection in place in their development boards, that they only work with an official ST-LINK?

I don't care about how the connection is made...  Is their a vendor lock with the official tool.

Sounds like some tinfoil hat theory, but I'm sitting here with a clone tool that works on my custom board but not on this development board.


texts: Need help finding PCB components on DigiKey

texts:
I am looking at the TinyDuino Schmatics (PDF) and Eagle BRD/SCH from Tiny-Circuits (an open source project) to put together Bill Of Materials. I am interested in creating my own version of this awesome board; this will be my first PCB. I am not an EE, however, have been working with Arduino for a long time. I am looking at digikey to find the corresponding part for each component below and I am left with a few questions. I have attached an image of the TinyDuino with rainbow labels I put myself (which could be wrong?).

ANY help is very much appreciated!

After all the awesome comments/answers (special thanks to Shannon Strutz, PeterJ, Connor Wolf and last but not least Bill Heughan), I have updated the list below. You can also access the DigiKey cart here with WebID: 105367708 and Access ID: 5693

R1-1k OHM: 311-1.00KLRCT-ND
R2/R3-100k OHM: 311-100KLRCT-ND
R4-10k OHM: 311-10.0KLRCT-ND
R5-1M OHM: 311-1.00MLRCT-ND
C1/C2-10uF: 445-6853-1-ND
C3/C4-0.1uF: 445-4970-1-ND
Y1-8MHZ Resonator: 490-1195-1-ND
D1-Green LED: P14180CT-ND
D2-CD0603: CD0603-S01575CT-ND
D3-MBR120: MBR120VLSFT3GOSCT-ND
SW1-Reset Switch: 679-2321-1-ND
Q1-NTZD3152P: NTZD3152PT1GOSCT-ND
Q2-2N7002PT: 568-5985-1-ND
J1-Coin Cell Retainer: 3013K-ND
J2-DF12-32-DP: H5222CT-ND
U1-ATMEGA328P: ATMEGA328P-MU-ND


texts:
I would to know if make sense to obtain the current of the BLDC motor, using the BLDC motor torque measurement. In particular, i'm able to measure the torque of a BLDC motor but not the current that flow in a single phase of the BLDC. My idea is to manipulating this equation:

T(t) = Kt*i(t)  -->  i(t) = 1/Kt * T(t)

So I think that I'm able to obtain the total current that flow of all three phase of the BLDC.

The problem is that i'm able too to measure the current between the battery and the ESC, and this current have the maximum value of about 7 [A], but the current that i calculate using the equation above give me a value of about 50[A], using the value of Kt as the inverse of the Kv value of the BLDC.
This is the current for all the three phases, for one phase i obtain a value of about 16[A] (50/3 = ~16)

I have read this question:
question

and the first answer tell me that the current that flow in the BLDC motor can be higher than the input current.

So, the values that i obtain from my experiment are correct or are they wrong?

UPDATE

I'm sorry, i have done a stupid error in the acquisition system firmware. In practice i have used the windows calculator to translate the arm of the torque sensor from cm to m, but digiting the value i have used the "dot" to separe value after the comma and the windows calculator doens't recognize the dot, but recognize only the comma.. so 3.5 cm became 0.35 m and this is the error.
Now i have correct this error and the result are what are expected as you can see in next image.

The yellow signal is the current calculated with the formula above and the purple signal are the current measured.

I think that the mismacth are due to the other factors that i not considered in the formula above like friction and so on..
Moreover the Kt value is from the motor datasheet and I not measured it directly..

the problem now is with the question in the link above...


texts:
I'm going to flat out say I'm a programmer with a soldering iron. So, if I sound like I don't know what I'm talking about; take this into account.

I was browsing stores for an RCA to Aux converter. However, they are all charging 20-30$. My question, does the red and white audio connectors pass things digitally. So, could I just solder Aux wire to Red/White wire?

Thank you,
Nate


texts: need circuit help with headphone amplifier 'thump' and other issues

texts:
This is my first post and I have a million questions. I hope some kind souls out there will not mind my noobness and be able to guide me any way they can.

Firstly, I have a headphone amplifier circuit that runs off 9v using the TDA2822M chip. The amp works fine as a mono amp (yes i know class D no good for headphones) but that is all i need for my purposes. My question is in regards to the nasty 'thump' I get when I switch on the amp. Is there some kind of capacitor/resistor combination that I can use on the input voltage that powers the circuit on slow enough to minimise the thump in the earphones?

Secondly, I have redesigned and enclosed a digital wireless transmitter/receiver, connected it to a headphone amp and built myself a nice little cheap digital earphone beltpack system. My issue is with the digital noise that is part of the circuit. I also have a great deal of noise when nothing is connected to the transmitter input. I know this probably sounds a bit vague but unless I post pictures and describe in great detail the whole setup (which I can do) it may or may not help with the issue. I have powered the transmitter circuit with a linear regulated 5v power supply. I have used a 10k 1:1 transformer on the audio input. I am suspecting its a shielding issue somewhere. Any advice or questions for clarification will be much appreciated. Please let me know any specifics you might require to be able to answer this question. I know there's probably so many variables and I am not experienced enough to know where to start more than what 'google' has suggested. Kind regards..


texts:
Recently I made a thread about parallel supplies, however my helper fried one of them... Wonderful.

So I got myself 4 of the famous DPS-1200FB-1 12v 100A power supplies. So I am an electronics noob, hence my name. I know the issue with parallel supplies is current sharing, but I don’t see anything wrong with putting all 4 12v power supplies in series to get 48v at 100A.

I am still not clear with what galvanic isolation is. I believe it is making power supplies so the ground wires aren’t touching each other or something like that.

So could I put these 4 PSUs in series to get 48v at 100A? Do I need to float them? What if I don’t float them?

I cannot find a datasheet for these, but I bought them from here


texts: Should I remove the solder mask from an isolation-barrier?

texts:
To be able to fully utilize the isolation properties of digital isolator ICs such as the ISO7731, the PCB must have an isolation barrier that is accoding to datasheets Free from planes, traces, pads, and vias.
How wide this barrier has to be typically depends on the IC package.  I typically use the width of two adjacent legs.
They do not however mention if solder mask should be kept on/off the barrier. I would assume the safest answer is to not place solder mask, but I do not know how insignificant/great the difference of having it on/off is. For example if the PCB is placed in a location where it could be seen in plain sight, and having no solder mask (especially on a colored solder mask) would not be aesthetically appealing.


texts:
As I understand it, a photosensitive diode generates a small current with light. I ordered these off Amazon:
https://www.amazon.com/gp/product/B01F3TU2XC/ref=ask_ql_qh_dp_hza
These change resistance but do not generate any current. I'm currently using a regular clear 5mm LED and my circuit is working. Of course, it does not work with the Amazon ones since they change resistance with light.
I am asking here since a google search produces two different descriptions for a photosensitive diode. Some say it changes resistance and others say it generates a current. Trying to understand...


texts:
Does someone know how to connect this wires without using additional hardware?

Thank you in advance for replies!

P.S. Right item is a Logitech's and left one is SVEN's


texts: Solution for solenoid valve with can give flow without power? or any other alternative way of it?

texts:
I want to use a Solenoid valve for my project, the valve will be used for water in which is facing one problem if there is no power, how can we get water from the valve, I don't want to add any kind of batteries in the project. wants to do it mechanically can someone suggest me some solutions for it?
If there is an alternative I can use for the flow purpose, which can give us water with power and without power


texts: FPGA: Choose RAM or FIFO for ADC input to be filtered

texts:
I will connect an ADS4125 12-bit 125-MSPS ADC with 6-bit parallel DDR LVDS output, with an Altera MAX10 FPGA. The sampled data is over a duration of 100 us, and will be filtered in the FPGA. I will use the FPGA LVDS interface to convert the 6-bit DDR to 12-bit synchronous, store it in either a FIFO or a RAM, do signal processing on the data, save the result as a number of flags (not saving the post-DSP data), and output the unprocessed data along with the flags to a radio.

I am leaning towards using a 2-port ADC over a FIFO, because I will need the unprocessed data twice.

I wonder however, would there be advantages to using a FIFO?


texts: Will replacing a 16.6nH inductor with 2 inductors in series total 16.6nH cause issues on RF board at 433MHz?

texts:
I have a circuit based on SYN480R.
It has an inductor 16.6nH(L1). It works well however it is hard to find 16.6nH inductors. I can find other values that I can put in series and sum 16.6nH. Will it cause issues like decreased range etc?


texts: I am researching some embedded applications that will leverage the use of a single-board computer (SBC). I am looking for a SBC that has a very small form factor, supports wireless networking, and can boot from a memory chip or USB memory stick. Does anyone have experience with something like this and can recommend a manufacturer to use?


texts:
I am attempting to fix a DVD read write drive in a Sanyo VCR to DVD recorder.  I believe the problem to be mechanical, the current disk will not eject.  The disk can be played, as much as it can for a scratched disc.
I am unable to remove the DVD unit simply because I cannot unlock and release the ribbon connectors to the PCB on top of the unit so that I could remove the DVD unit from the appliance.
the connector from what I've just learned in the past 2 hours appears to be an FFC, CONNECTOR,  16POS (or 17POS), 1ROW, 0.??MM


texts: Something interesting I've noticed with cheap devices from China (such as iPhone clones and digital cameras and the like) is that the manuals always specify they are "T-flash" (TransFlash) compatible, instead of "microSD" or "SD" compatible. Is this to get around paying the $3k/yr license fee, or is it something else entirely? The devices seem compatible with microSD as well as TransFlash cards.


texts:
Here is a 5W power led datasheet.
I have several questions about it :

What does "Peak Current (1 / 10 Duty Cycle, 0.1ms Pulse Width) -
1000mA" mean?

Does that mean 1000 mA peak current is possible IF maximum ON time is 0.1ms AND duty cycle = 1/10 corresponding to a driving signal F = 1KHz? If F decreases, e.g. 500Hz, limiting condition is "0.1ms Pulse Width" : max duty cycle will be 1/20. If F increases e.g. 2kHz, limiting condition is "1 / 10 Duty Cycle" max pulse width will be 50µs.
After in electrical and optical characteristics, Why are values given
for If = 1050mA > If(Peak)?
What are Rank L1/L2, Rank V1/V2?
During short duration pulses LED power dissipation is 6.5 x 1050 = 6.8W, giving 680mW with 1/10 duty cycle. In continuous mode Vf ~ 5.5V @350mA giving a 1.9W dissipated power. So why is this product named 5W LED?


texts: Simplest circuit for several hundred volts from 5v

texts:
I am trying to make a simple camera flash circuit for a project, but I am really having a hard time. I can't seem to find a simple circuit anywhere. It doesn't need to maintain the high voltage under load, it just needs to charge a capacitor. I'm a journeyman electrician, but kind of a noob when it comes to electronics.
I built one using a 555 chip, but it could only output about 60 volts. I need about 200-300v. I feel like it can be a lot simpler too. I would appreciate some advice on what approach to use. I took apart a few cameras and they looked pretty simple with some tiny transformers and crystal oscillators, but I don't know the specs or what ones to buy. Maybe you could advise me on what a mini transformer or inductor is called and how to spec them for a circuit.
Thanks guys.


texts: Attaching a 3 mm fiber optic cable to a WS2812 LED

texts:
I am wondering how to easily attach a side-glowing fiber optic cable (I have 3 mm here) to a cheap WS2812 LED that is flat and soldered onto a PCB (like these here).

I tried with Sugru, hot glue, super glue but nothing really stuck. In addition, I'm losing too much light at the bottom and not enough is actually going into the fiber.

Any ideas how to accomplish this? Are there some sort of cool contraptions including lenses that I'm unaware off? Anything else?


texts: Raspberry Pi + Microcontroller for commuting audio input and output (audio matrix switch)

texts:
I am new in electronics and I'm working on a personal project with Raspberry Pi that I need help.
I want to make a board that allows to commute 4 audio inputs (TV, MP3, DVD, FM web) in 4 audio outputs (speakers), can be simultaneously. Whereas that 1 audio input can be routed to even all outputs. All managed by the Raspberry Pi.
From what I researched, I have to use microcontrollers and do the DAC to the speakers. Is it?
Searching about microcontrollers and ICs I found the PIC18F4550 microcontroller and  74HC4067 Multiplexer/Demultiplexer. Sounds good to solve my problem.
Can I do the routing between inputs and outputs with one of them or both together? Is possible to control this with RPi?
Some expert could help me and show me any example or circuit, please?

Sorry, but I don't know almost nothing about electronics and components... and my english is bad.


texts: Unwanted buzzing and reduced volume in a basic speaker set

texts:
I have the following device, which basically contains 18 songs. we can play the next song by switching the switch on and off. It also has a volume control.

Recently it started to buzz a lot and the song was suppressed, the volume control was dead (it had a constant low volume)and the switching operation didn't work. So I opened it,

Pic was taken before replacing the Capacitor

After doing some research, I replaced the 1000 MFD capacitor, The buzzing dropped a bit, but all the other problems persisted.
My Questions are,

Please map out the basic working of this device (like the amplifier followed by speaker etc).
The buzzing is because of the unfiltered noise or the transformer. I took the transformer out, but it dint seem to make any noise, the noise was from the speaker.
What's the solution? (why did the volume control and switching operations went out?)

These are all the components,

Surprisingly, when i replaced the capacitor, i heard a random song (which probably wasn't there in the 18 songs), Finally, is there a receiver circuit of some kind?


texts: What is the danger of using interrupt pre-emption in ARM

texts:
I am working on a system which uses about 4 interrupts. I can clearly define a priority from one to the other. For example, I feed SPI transfers with DMA requests and operate a USB interface which drives the SPI data. To this end I have prioritized my interrupts as follows (ordered from highest to lowest priority)

Systick
EXTI for handshaking signals
DMA streams
USB

Everything works great for a while and then I start seeing some odd behavior that I have not been able to determine the cause of yet, but I am wondering/suspecting if its because I am allowing interrupts to pre-empt other ones at inopportune times.

So my question is, what sorts of issues should be considered when deciding if an interrupt should preempt another, or if it should just be given a high enough priority to tail-chain.


texts: Modulation signal getting distored when connecting demodulator

texts:
Good day Guys,

I have a question regarding output signals of a specific stage getting distorted when connecting the next stage.
In my scenario, I am working on an AM modulator and demodulator of a 10kHz square wave with a carrier frequency of 850Khz, currently, my Modulation is working and producing a nice modulated signal.
Before implementing my demodulator I run my modulated signal through a Gain stage ( Operational Amplifier ) to amplify the modulated because of its low peak values that are influencing the accuracy of the Demodulator.
When I send the demodulated signal through the gain stage (without the gain stage output connected to the demodulator) I get a nice amplified signal.
However, my problem comes in when I connect my demodulator to the output of the Amplifier stage, the output from the Amplifier stage changes to a very weird looking signal. The modulated, amplified (without demodulator stage connected) and amplified (with demodulator stage connected) can be seen in the figure below,

So my question is why does this distortion happen, and how can it be fixed?
I am terribly sorry if it is due to noobies mistake!

If have attached a screenshot of my Circuit below,


texts: Using SFP modules from a microcontroller

texts:
I'm interested in having an embedded device send data optically. This is for test and measurement, where having conductive cables is problematic since it will perturb the measurement. The device is built as a prototype now except for the data sending interface.  The data rate requirements are moderate (10-20Mbps one way).  The distance is short, 5-10ft.  This is somewhat power limited, but using 0.2-0.5W for comms is okay.

I looked at IrDA but that seems to be almost completely obsolete, and the data rates are too low (other than the very unavailable UFIR/GigaIR). I also looked at TOSLINK, and that seems to be almost-obsolete, and I can't source fast (125Mbps) transceivers, nor can I figure out how to run the slower 10MBps ones reliably at anything close to their max rated speed.

Now, I could hack some kind of completely proprietary UART-over-fiber protocol, or wait for LiFi, or mod some of the really expensive Corning optical USB cables to not have a power conductor... all of these are problematic in various ways. Then I thought, why not just use SFP transceivers on both ends?

I have only a very basic idea of what is inside a SFP, and essentially no idea how to talk to it.  Could someone explain to me how to drive a SFP from a microcontroller?  Either (a) a UART-over-fiber using SFP and microcontrollers on both ends, or (b) ethernet using SFP from a microcontroller and regular SFP ethernet device on the other end?

P.S. If it matters, the microcontroller is a STM32F446; I would like to stick with STM32 if possible.  The device is battery powered from a 2500mAh lithium ion battery.

P.P.S. I can build devices on both sides of the link; the near side would probably have some kind of optical-to-USB-serial converter, if it is not simply ethernet.


texts: What is the way to implement 8b/10b encoder/decoder in FTDI chip?

texts:
What I want to do is interface a Visible Light Communication link I have made to a computer using USB. I am regenerating the clock from the data at receiver end so I need clock recovery transition edges in the data, hence I want to use 8b/10b encoding. I am looking for bit-rate of 1Mbps.

I have heard about FTDI chips which interface the USB protocol on the hardware and give programmable access to GPIO pins. I have also previously directly used FT232 for USB to UART conversion.

Is it even possible to add an LUT to FTDI chip and program it to encode/decode?
If yes, how would I proceed and primarily what chip do I use?
Is it advisable to encode on the computer and send data? I am not 100% for this option because it would require breaking the encoded 10bit sequences to 8bit chunks for transfer on the computer.


texts:
I'm designing a step-up constant current source to drive LED strips (nominal load voltage is about 54 VDC). Requirements:

Vin: 18..32 VDC
Iout = 0.2 A
Vout = 54 VDC (nominal) - 57 VDC (maximum)

Since the circuit should have an on-off input, I decided to use LM2586SX-ADJ.

Problem

A hand-made fast prototype worked fine at the R&D stage, so we manufactured a hundred of the circuit. The circuit works fine after energizing. However, after some time (I really can't say an exact duration, but it varies between 15 minutes and 1 hour) the inductor starts to buzz, overheats and then finally fails permanently (burns) in a few seconds. I've to say that both the IC and the inductor keep quite cool during normal operation.

What I've tried

At first, I thought that the problem comes from the DC resistance of the inductor. So I replaced the inductor with 7447709681 from Würth. It didn't help.
Increased the switching frequency to nearly 200 kHz. It didn't help.
Placed a 0.1 µ capacitor across the input of the LM2586. It didn't help.
Placed a snubber (47 Ω and 10 nF) across the SW pin. It didn't help.

Schematic:

PCB:

NOTES:

The bottom layer is completely GND with neither cuts nor holes.
There's a pi filter (100 µF elco - 68 µH - 100 µF elco) before the input, VX. But it's in another sheet, so I couldn't show it here.
BL input comes from the microcontroller (5 V or GND).

So I'm stuck at this problem. Any help will be greatly appreciated.


texts:
I am strongly considering upgrading my old Px Vespa to a new electric motor/battery driven. I am unsure I will be able to connect the 2 together
Firstly the motor:

http://www.cnqsmotor.com/en/article_read/Powerful%20V3%20electric%20scooter%20hub%20motor%204000w%2010inch/380.html

Secondly the controller:
http://www.cnqsmotor.com/en/article_read_789.html

This is what I was looking at as a battery supply:
https://m.alibaba.com/product/60746330746/Deep-cycles-2000-times-72V-75Ah.html?__sceneInfo=%7B%22cacheTime%22%3A%221800000%22%2C%22type%22%3A%22appDetailShare%22%7D

This is a link to the kits that they have available but they don't have the 4kW in kit format.

http://www.cnqsmotor.com/en/article_read/QS%20Motor%2010inch%203000W%20Electric%20Motorcycle%20Kit%20/%20E%20Scooter%20kit%20/%20Electric%20Scooter%20Conversion%20Kits/542.html

Also how would I go about connecting the electric lights to this power supply headlamp, indicators & brake lights? Would a step-down transformer be required?

I am a newbie to this thanks in advance for your help

Keith


texts: Ver2.0 SDHC Card long response time after ACMD41 during initialization

texts:
I would like to implement a very low power SD card handling with MSP430 processors. I would like to log measurement data onto SD card without a file system. I want to turn on and off the SD card power to save power. And I would like to reach as fast SD card initialization as I could.

To initialize the SD card I used the @vaxquis suggestion from this issue:

What is the correct command sequence for microSD card initialization in SPI?

It is working great, I can initialize the card, save the data and reload it if necessary.

BUT, after SD card power reset, before the ACMD41 command when I set the chip select signal to LOW, then the SD card will response 0x00 only after approx. ~50-80ms. During that time 0x01 is the response from the SD. So if I keep sending the ACMD41 continuously I got 0x00 response only after 50-80ms. OR, if I set LOW for CS and wait 50-80ms then I immediately got 0x00 response.

After the initialization, everything goes smoothly.

Any suggestion to my problem?

So my init sequence:

Enable SD card VCC
wait ~1ms
start initialization (CS high + send 80 clock)
CS LOW
CMD0 (arg:0, crc:0x95) + wait R1 response
CMD8 (arg:0x000001AA, crc:0x87) + wait R1 + arg echo response
CMD55 (arg:0, crc:0x65) + wait response
CMD41 (arg:0x40000000, crc:0x77) + wait response
repeat ACMD41 (CMD55 + CMD41) until 0x00
CS HIGH
... write, read data ...
wait ~ 1ms
disable SD card VCC
sleep ~800ms
start again

If the SD card power is not switched, this issue does not appear.

And I am using an 8GB SDHC Ver2.0 card.


texts: How to store and step 12V to 5V with capacitor and regulator?

texts:
am a hobbyist with little prior electrical engineering knowledge so please bear this in mind! Trying to safely store and step down voltage from 12V to 5V using capacitors and L7805CV regulator.

Have been advised to follow the circuit for this below, however during testing there is a significant drop in voltage (measuring with multimeter at the points before and after C1 on circuit) and nothing appears to be getting to the 5V battery beyond the regulator.

1. What is the correct schematic? Since the above isn't working (preferable that circuit includes a voltage regulator and a capacitor)

2. Are the capacitors in the right place / correct values?

3. Capacitor C1 discharges very quickly, why is this? (>1 min charge goes down)

Thanks

Edit: noticing a number of comments unrelated to the above three q's, which was why this post was created. To save time I will not be responding to unrelated comments. Cheers


texts:
I'm trying to find the quality factor of this circuit but I'm not sure how to do it. I know how to find it for a series RLC circuit and completely parallel RLC circuit, but I don't know what to do when the resistor is in series as shown here.

Any help is appreciated!


texts: Help me see if I understand this RLC circuit

texts:
The switch closes at t=0

I need to determine the current and the voltage of Capacitor at t=0.25s

at t<0 the switch is open there is no current and no voltage

at t=0 the switch closes the current starts flowing, the current that enters the RC part I called I1 as it is defined by R1

I1=E/R1=100/2500=0.04A

the current will go into the CAPACITOR because less resistance? anyway until the CAPACITOR get boosted to its voltage no current will go thru the R2

when the voltage is reached on the CAPACITOR the current starts flowing thru R2 and we can now get the total current I

Rtotal will be calculated as series resistance because iC=C du/dt and once there is no voltage change in time the current stops flowing thru the CAPACITOR

I=E/Rtotal=100/5000=0.02A

I can now get the voltage that the CAPACITOR needed to reach by using R2 as they are in parallel and therfor share voltage values

V2=I*R2=0.02*2500=50V

V2=VC=50V

now if the CAPACITOR is being "charged" the voltage grows and the current passing thru it(I1) falls with time

vC(0)=50*(1-e^(-0/tau))=50V for t=0

iC(0)=0.04(e^(-0/tau))=0.04A

tau=Rtotalpar*C=1250*100*10^-6=0.125

vC(0.25)=50*(1-e^(-0.25/0.125))=43.23V for t=0.25s

iC(0.25)=0.04(e^(-0.25/0.125))=0.005A


texts:
The motor I am talking about has six wire slots of which two are unused and wires coming from the motor are restricted to four (4 to 4 jumper connecting wires are there to connect the motor ).So why are these two slots left unused? Does this means it's originally a  unipolar six wire motor ? The vendor told me it's a 4 wire Bipolar motor.How do I know why these two slots are left unused?

I have stepper motor from Astrosyn. I couldn't find the data sheet and sorry I cannot provide an image for the motor. So the specs on the motor are as follows :

Astrosyn Stepper
P/n 4K1-4054
TYPE-17PM-J311-P1ST

MIEBEA CO.LTD.


texts: Can I high current charge port transfer data at the same time?

texts:
I was reading about USB charging ports and how a host can tell the device what current it may draw: How do USB charging and "smart" charging ports (e.g. Anker's PowerIQ) work?

Do all these "identifier" techniques occupy the data lines all the time? Is there no data transfer possible while the host is identified as a "charger"? Or is there also a solution to tell the device it can draw a higher current only at the beginning of the connection and then the data lines are freed up to transfer data?


texts: Eagle: supply pin vcc overwritten with more than one signal

texts:
in some words, my circuit is feeded from battery (VBATT). The VBATT is taken with a voltage divider for read voltage by Atmega, and is routed into a voltage regulator (from 0.8/3.2 to 3.3) VREG.

All net for voltage and GND have their names and labels (I need "only" to do the signal routes and voltage divider) as you can see.

Checking for errors, DRC errors complains with

supply pin vcc overwritten with more than one signal

This is the image (if needed I can also give sch and brd)

On board all airwires seems ok, instead.

Thank you for your effort and support.


texts: Can't figure out voltage-controlled current sources

texts: I'm trying to teach myself how to wire circuits, but I don't know if I got the correct answer for this? Where is a good place for me to learn the order of operations for solving circuits? Thanks.


texts:
I've routed a board, and redid my designators in the schematic and updated the changes to the pcb. In doing so, the nets which I have routed, now give me an error. Basically what's happened is that some of the traces netnames haven't been updated.

Yesterday a trace from component A to B had a netname of net_a_to_b. Today after i changed the designators, the trace still holds the net_a_to_b, but the components are now C and D. The trace should have updated to net_c_to_d.

There aren't that many nets, and I can just redo them, but I shouldn't have too.

Does anyone why this happens and how to get it right every time ?


texts: MOSFETs in high voltage low current applications

texts:
I am constructing a circuit designed to release a very brief pulse of current at a voltage of 1000V. A low power DC converter is used to charge a 0.1uf pulse capacitor to 1000V, and then I intend to use an n-channel MOSFET to discharge the stored energy into a very low (~10 ohm) resistance load. According to the manufacturer (KEMET) the capacitor is capable of fully discharging on the scale of multiple nanoseconds. For my application, the discharge duration is quite important, and the faster the better. In my tests, connecting the MOSFET without any pull down or gate resistors, some current leaks across the MOSFET into the load. For my application, it is very important that very little current flows across the load when the transistor is "off." The signal for "switching" (saturating?) the MOSFET is to be supplied by a function generator. As such I have two questions:

Is a high voltage MOSFET appropriate for this application, keeping the requirement of low leakage current and fast switching in mind? Is there a better component? (I have purchased a Vishay IRFPG50 (1000v, 6.1A))

To limit the leakage current, where and of what value resistor should I add to the circuit? Reading other posts, I have heard discussion of adding a resistor to the gate of the MOSFET. What would this achieve and are there other similar common practices I should know about?

Circuit specifications:
MOSFET: Vishay IRFPG50
Capacitor: KEMET C4540H104KUGWCT100


texts: CMRR of op-amp is the ratio of the differential mode gain and common mode gain. What is the difference between these two ? What is the importance of CMRR in the performace of op-amp? How does CMRR in affecting the offset voltage and output voltage ?


texts: Convert i/q data to power measurement (e.g. db)

texts: I have raw i/q data from an rtl-sdr.  I want to do stuff with signals and different frequencies, but only if they exceed a threshold power.  Software like gqrx, sdr#, etc. take the same data from rtl-sdr sticks and express the energy at a given frequency as a dB measurement (dbFS, or whatever.)  How can I do the same thing?


texts: Detect a missing PWM signal in the smallest possible board space

texts:
I have a motor control board that basically has zero space left, and the customer wants to add a fault flag to tell if their 2 kHz PWM input signal is lost.

So basically, I need to detect a lack of edges over a few milliseconds, using a small number of very small components. There is no microcontroller on the board, and I have maybe 10 square millimeters I can scrape together for it.

I had the idea to use a watchdog supervisor IC, but I can't find a small one that is active high and has the right timeout period. Now I'm leaning towards something with a 555 timer or maybe an RC filter that fills from 5v and gets drained whenever there's an edge.


texts: Driving an input with a 12V 4k7 pullup from 3V3 logic

texts: I have a board with 12V CMOS logic whose inputs are pulled up via a resistor. It was designed to interface from a board via open collector opto-coupler. Now I have a request to drive it from 3V3 logic. Any suggestions? (I have the one time option of modifying the board, but it must remain backward compatible)


texts: HID descriptor to use for a Playstation 2 controller

texts:
I'm currently making a Playstaion 2 controller to USB converter using an Arduino Uno, and it's going along very well, but I'm stuck on a specific problem.

I'm trying to support the pressure sensitive buttons, but I don't know what HID descriptor to use for the USB. I currently have the following, but my computer doesn't seem to be registering the button states properly, with jstest showing that the buttons seem to "stick" in an on state. Also, I'm not very sure if using Rx and Ry for the second analogue stick is correct.

What areas of the descriptor should I change to make everything work properly?

Here is my current descriptor:

const PROGMEM USB_Descriptor_HIDReport_Datatype_t hidDescriptor[] =
{
    0x05, 0x01,                    // USAGE_PAGE (Generic Desktop)
    0x09, 0x05,                    // USAGE (Game Pad)
    0xa1, 0x01,                    // COLLECTION (Application)
    0x09, 0x01,                    //   USAGE (Pointer)
    0xa1, 0x00,                    //   COLLECTION (Physical)
                                   //     ; Right stick
    0x09, 0x33,                    //     USAGE (Rx)
    0x09, 0x34,                    //     USAGE (Ry)
    0x15, 0x00,                    //     LOGICAL_MINIMUM (0)
    0x26, 0xff, 0x00,              //     LOGICAL_MAXIMUM (255)
    0x75, 0x08,                    //     REPORT_SIZE (8)
    0x95, 0x02,                    //     REPORT_COUNT (2)
    0x81, 0x02,                    //     INPUT (Data,Var,Abs)

                                   //     ; Left stick
    0x09, 0x30,                    //     USAGE (X)
    0x09, 0x31,                    //     USAGE (Y)
    0x15, 0x00,                    //     LOGICAL_MINIMUM (0)
    0x26, 0xff, 0x00,              //     LOGICAL_MAXIMUM (255)
    0x75, 0x08,                    //     REPORT_SIZE (8)
    0x95, 0x02,                    //     REPORT_COUNT (2)
    0x81, 0x02,                    //     INPUT (Data,Var,Abs)
    0xc0,                          //   END_COLLECTION

    0x05, 0x09,                    //   USAGE_PAGE (Button)
                                   //   ; Pressure sensitive buttons
    0x19, 0x01,                    //   USAGE_MINIMUM (Button 1)
    0x29, 0x0c,                    //   USAGE_MAXIMUM (Button 12)
    0x15, 0x00,                    //   LOGICAL_MINIMUM (0)
    0x26, 0xff, 0x00,              //   LOGICAL_MAXIMUM (255)
    0x75, 0x08,                    //   REPORT_SIZE (8)
    0x95, 0x0c,                    //   REPORT_COUNT (12)
    0x81, 0x02,                    //   INPUT (Data,Var,Abs)

                                   //   ; Other buttons (L3, R3, Select, Start)
    0x19, 0x0d,                    //   USAGE_MINIMUM (Button 13)
    0x29, 0x10,                    //   USAGE_MAXIMUM (Button 16)
    0x15, 0x00,                    //   LOGICAL_MINIMUM (0)
    0x25, 0x01,                    //   LOGICAL_MAXIMUM (1)
    0x75, 0x01,                    //   REPORT_SIZE (1)
    0x95, 0x04,                    //   REPORT_COUNT (4)
    0x81, 0x02,                    //   INPUT (Data,Var,Abs)
    0xc0                           // END_COLLECTION
};

PS. I'm using LUFA and flashing the firmware of the Uno's USB controller


texts: Do I need to use the 'add' function in mips to store into a variable or can I store into a variable with load word?

texts:
The following problems deal with translating from C to MIPS. Assume that the variables f,g,h,i, and j are assigned to registers $s0, $s1, $s2, $s3, and $s4, respectively. Assume that the base address of the arrays A and B are registers $s6 and $s7, respectively. Write the MIPS code for the following C lines of code:
I am trying to mimic the following code snippet from a C program and write it in MIPS.

if(g != h){
      f = A[3];
   } else{
      f = B[4];
   }

Below is the MIPS I have so far

bne $s1, $s2, Tru
lw  $s0, 16($s7)
j Done
Tru: lw  $t0, 12($s6)
     add $s0, $t0, $zero
Done:

If I was unclear please comment below.


texts: Can I use DC to run an AC device in some cases?

texts:
I think there may be devices specified to use  alternating current (AC) which can run supplied with direct current (DC) instead.

There are devices which depend on AC in some fundamental way, like a motor creating alternating magnet fields. These do not work on DC.

But other devices use DC internally, but are specified to run on AC. They convert the supply current to DC as the first step.

I would like to run a device that is specified to require alternating current using DC, because DC is easily available. The device seems to use a full bridge rectifier (consisting of four diodes) as the first step of using the supplied power.

I think for a device like this, DC should work. But if so, it is not clear to me which voltage to use, in relation to the specified AC voltage.

Do you think the case above would work?
How to decide for which devices it works?


texts: How does triple level cell FLASH memory achieve 3 bits per cell?

texts:
Originally each cell of FLASH memory held either a high or low level or state, and reflected one bit of information; 0 or 1.

Mutli-level FLASH was then developed, with often four levels of voltage possible for each cell. These four voltage levels were encoded and decoded to represent two bits of information; 00, 01, 10, or 11.

Now Triple-level FLASH memory can store three bits of information in one cell; 000, 001, 010, 011, 100, 101, or 111.

How does going from four levels to three levels allow the representation of three bits instead of two bits of information? What am I missing here?

Trying to read this article I think I see eight voltage levels shown in this figure. I can easily understand how that could store eight bits - but why would it then be called "triple-level" and not "octa-level"?


texts: Can someone explain what this op amp circuit achieves?

texts: In this schematic a line-level audio signal is passed in to R42 and out of the op amp. Can someone explain the effect of the op amp on the signal in this configuration?


texts: Is there a clever way to use a small variable capacitor where a larger capacitance is required?

texts:
I am designing an activity where students should band pass a song to find a hidden message at 1000Hz.

Problem

I have considered using a notch filter and tank circuit, but using the formula $$f=\frac{1}{2\pi\sqrt{LC}}$$
I cannot reach the range of 1000Hz with my variable capacitor. Is there a clever way to achieve a circuit to filter 1000Hz and use my variable capacitor for tuning?

At my disposal:

A variable capacitor (20-350pF)
Various capacitor values ranging from 100pF to 220uF. (I can find more if need be)
Inductors ranging from 250uH to 3mH
The drive to work on the weekend because I find this project so interesting.


texts: Where do I start to look for an automatic off feature on a circuit? (Guidance)

texts:
My child has a light up toy that turns off after 20 minutes and she likes it all night when she’s sleeping. I’m trying to figure out where to start looking among the circuit for the automatic off feature so I can remove it. Is it typically something as simple as a transistor I can short or is there an rtc for the timer? Does anyone know the common practice for light up toy automatic off timers?

Any help or general suggestions would be great as there’s no version that stays on all night for her.

Thanks


texts: What does NP and NO means in datasheets?

texts:
I will be using a DC-DC Converter from Cincon: EC4BW11
I do not understand what NP and NO means on the pinouts. I am assuming that the input voltage will be connected on pins 1 and 2 (+Input, -Input) and the output voltage on pins 3 and 5 (+Output, -Output) since this is and ISOLATED DC-DC Converter which would mean they don't have a common ground?

Would the pin 4 (Common/NP) mean that this is the common for dual output, am I right?


texts: Schottky diodes or regular ones for input protection circuit

texts:
Which ones would you use for protecting a low voltage signal input (digital)? Schottky or regular? I plan on using it in this configuration:

Or is there a better way?


texts: Node Voltage Analysis with independent and dependent voltage sources

texts:
simulate this circuit – Schematic created using CircuitLab

I'm having trouble solving for the voltage drop across the 80 ohm resistor using the node voltage analysis method. I can get the correct value (120 volts) doing a mesh current analysis on the three loops but can't seem to come up with this same value doing a node voltage analysis. I created a supernode at the V1 node and V3 (drop across the R4 resistor) but not sure if I got the current polarities correct.


texts: Battery and External Power without Diodes Circuit

texts:
I'm designing a power system for my project. My project is powered from standard 18650 li-ion battery (or other 3.7V battery) or from USB 5V power source. Originally, my requirements were broader, I wanted it to support 20V input too, so I have a MP8860 buck-boost in my current design, which is large (not really a problem), but it's also pretty expensive and requires a gang of external components, and considering what it can do it feels like a big overkill for my application.
Currently in my project, battery meets USB DC-IN through two Schottky, all of that is fed into the buck-boost, the output should be 5V. At least that was the design, I haven't ordered any prototypes yet. External power input not only powers the devices, but also initiates battery charging.
Requirements changed, it was decided to simplify the things and abandon 20V power. So now I have just 5V input. The thing is, the system needs 5V, and I would really like to keep my 5V at 5V without a voltage drop from Schottky. Not that I'm too crazy about precision, but if it's not too hard, I would prefer to have 5V. After googling I didn't really find anything suitable, so I tried some pen-and-paper creativity and tried to build different circuits of diodes, mosfets etc., this puzzle solving was fun, but I didn't come up with any solution that I would call elegant and viable enough in terms of component count, reliability and functionality. But my very limited experience also limits what I can come up with.
Anyway, the questions are:
1) How do I combine 3.7V battery output boosted to 5V with USB 5V input, so that my target devices always receive full 5V either directly from USB or battery's boosted 3.7->5. I want to have an ON/OFF switch that will cut power from the device (mechanically), and I would want zero off current. Yet while device is off, I should obviously be able to charge battery. This is the main question, and if you could describe or roughly sketch a circuit that would do just that (always provide 5V output, no shutdowns if charger removed). The only thing I thought of is a boost converter with passthrough, and battery is Schottkied into USB DC-IN line, all of that goes into boost converter. If it's 3.5V, it's boosted, if line is at 5V (which means USB power), it just passes it through. Power off and charging aren't hard to design around it, I believe. Anyway, there have to be better ideas.
2) I'm using Type-C usb port. Is it right that I should include 20V input protection just in case? It's just a pair of components, including dedicated chip, which is no problem to add. I have a lot of space, and I want to make things safe. So protect against 20V or no need?
3) Do I need any charger negotiation? Considering the device will use over 1A at 5V most of the time, I will need a 2A charger to charge it. Do I have to do anything to make sure a compatible charger provides the required current, or can I assume the necessary 2A will always be available as long as the charger is able to provide so much current. I really like Type-C and making it a Micro USB would feel like returning to Stone Age for me, but if it makes my life a lot easier, I will consider it (although I would still want an answer about how to implement it with Type-C).
Also, I have to admit, I'm not entirely sure what performance of my current buck-boost MP8860 would be if its input voltage is 4.8 and output should be 5V, in other words, if I keep my current circuit with both power sources Schottkying together, would I get 4.8V output if USB voltage is just passed through, or would I get boosted to 5V although it's such close voltage, or would I get maybe some weird oscillations because 4.8 and 5 are so close. As I said, it was intended to withstand 20V input, although it looks like it should work with 5V. In other words, I think my circuit should already work, but I'm looking for a smaller solution without price/space/complexity overkill, but safe and reliable enough.


texts: LVDS Displays - Swapped EVEN and ODD Channels?

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A friend of mine gave me 2 LCD display driver boards (VGA/HDMI to LVDS). One has RTD2553V chip (from Realtek) and the other has RTD2660H (I cannot share the datasheets because they are not public). The main difference between them is the latter one accepts HDMI input. He said that he's currently using the first one and wants to use the second one due to that difference, so he asked me to check if it is possible without modifying LVDS display connection.

Anyway, I checked the connections between chip and LVDS output socket (2x15 vertical header /w 2.54mm pitch). And I noticed that EVEN and ODD channels are swapped. For example, pin7 is TXE3- in the 1st board but it is TXO3- in the 2nd board. Likewise, pin29 is TXO1+ in the 1st board but it is TXE1+ in the 2nd board. And it is true for all of channel outputs (i.e. if a pin is EVEN on the 1st board, the same pin is ODD on the 2nd board), only VDD and GND connections are matching.

Without further ado, I'm finalizing this verbiage with the actual question. Can it be used? Will that difference cause any problems?


texts: How does the comparator set the motor speed at a fixed level?

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How does the comparator below sets the motor speed at a fixed level?

I can think that the comparator output will turn ON if the speed proportional generator output voltage is lower than the zener reference voltage; and the comparator output will turn OFF if the generator output voltage is higher than the zener reference voltage.

But how does this makes the motor speed constant? Is there a step by step logical explanation?