texts: How to set up a LiPo battery to be able to charge and discharge from the same circuit

texts:
I am new to using rechargeable batteries in electronics projects. To give some background on the context of the project, I'm trying to build a solar charger/power pack for a cell phone. My problem is that I'm not sure how to connect the battery in the circuit. Is it as easy as this? PV being the solar cells. I feel like there needs to be some sort of additional IC to regulate the Cell to the battery.

Can help me understand the steps I'm missing in this circuit?


texts: KiCad 5.1: New footprint from existing footprint

texts:
Is there a way to duplicate a footprint in one library into another for making changes? Or "create new footprint starting with existing footprint"?

I want to make a footprint for Adafruit's Itsy Bitsy 32u4. It's basically a 28 pin 0.6" DIP with five additional pins along one of the short ends. I could make it from scratch, but the built-in 28 pin DIP footprint has everything I need (except for the additional five pins, which should be easier to add than creating the footprint from scratch).

Adafruit provides Eagle files for their products, so it may be possible to import one of those into KiCad then extract the PCB as a footprint, but if that's my only option, I'll probably create the footprint I want from scratch as practice.


texts:
Two 2's complement numbers having sign bits x and y are added and sign bit of result is z.Then occurence of overflow is indicated by which boolean function?
I believed that overflow occurs when the XOR of the sum and carry is 1 ,there is overflow,else no overflow.Keeping this in mind,I came up with the following truth table:

X                     Y Z Overflow

0 0 0                                   0

0 0 1 1

0 1 0 1

0 1 1 0

1 0 0 1

1 0 1 0

1 1 0 0

1 1 1 1

Is this table correct?


texts: USB charging and powering circuit with MAX1555 and MAX1881

texts:
I'm new to (rechargeable) battery powered devices, but I found the following article about using the MAX1555 and MAX1881 for building a charging (via USB) and powering (µC-circuit, 3.3V, max. ~70mA) circuit. They describe the following diagram:

The MAX1555 seems to fitting very well for my application. It is cheap, compact and easy to use.

But the MAX1881 looks uneconomical for my application. It has a lot of functions, it is rather large and the datasheet describes another usage area for this IC. Its particular advantage seems to be reverse battery protection.

Does anybody has experience with the MAX1881 or does anybody know a good alternative?


texts: Is ARM a microprocessor or microcontroller?

texts: I have been having a hard time trying to know if ARM is a microprocessor or microcontroller or something else?


texts:
Given this bode plot from an OP-Amp Amplifier:

What is the method for determining the voltage gain?


texts: Multiple Voltage Sources using a single Ground

texts:
I'm having a hard time understanding how a circuit can have multiple power sources and have them all tied to the same ground. See the following schematic as an example:

Here's my current thought process, which is probably fundamentally flawed. The large Voltage source pumps current through the curcuit to drive the motors. That same current comes back through the servos and hits the ground wire. As it goes through the ground wire, how does it know to go back to the battery and not the ground on the Arduino chip?


texts: Reducing transistor switching time with a resistor from base to a negative voltage

texts:
Connecting a resistor from the base of a transistor to ground/negative voltage (R in the first scheme below) helps reduce its switching time. I would like to know why and how does it help; what are the benefits of such a connection as opposed to one such as in the second circuit. The transistor's application is of course as a switch.

This question: Reducing transistor switching time does not contain the specific connection mentioned here.


texts: What is the effect of EN_CRC on NRF24L01+

texts:
Throughout the datasheet, CRC is mentioned as mandatory field of all packets, and NRF24L01+ will check it before accepting a packet in FIFO.

But then there's this register that says I could disable CRC. I would like to know:

Will it disable CRC check on Rx if EN_CRC is 0?
Will it also inhibit transmission of CRC bytes on Tx if EN_CRC is 0?

I don't intend to use E-Shockburst and NOT having CRC check in hardware is useful to me. I'd like if Rx will just deliver packets to FIFO without CRC check. Also I could really use 8 us of time per transmitted packet.


texts: SPI communication with DRV8908-Q1 motor driver

texts:
I have designed a board to drive 4 BDC-motors using a DRV8908-Q1 motor driver (datasheet). Here is the schematic of chip with all connections

and here is the microcontroller (Teensy4.0)

The connection for SPI is fairly simple. I am using the hardware SPI pins and pin 10 is the chip select. According to the datasheet (page 19) the SPI signal should look as such:

Which from what I understand is SPI Mode 1 and most significant byte first (MSB). I am running it at 1Mhz to ensure I comply with all the timings. The chip expects a 16 bit word to be sent with the following format (page 59)

where W0 = 0 for write and 1 for read. Ax are the address bits, and Dx are the data bits. Using the register map (page 94) I wrote a script which 'should' set the high side of each H-bridge to continuous mode so that connecting a dummy load between any output and ground produces a high voltage (12V in this case, I am using a 1K resistor for the load so only a few milliamps). I have checked using my scope and the SPI signals are being sent correctly (i.e. the clock and data line up, and I've checked all the timings to make sure they are within spec), however there is never any output from the motor driver.
Here is the test code I wrote:
#include <SPI.h>

#define ss_drv 10 //define slave select for motor driver

void setup() {
  //Initialize serial
  Serial.begin(57600);

  //Initialize SPI (for DRV8908), runs in SPI_mode1
  SPI.begin(); //initialize SPI
  //SPI.setBitOrder(MSBFIRST);
  //SPI.setDataMode(SPI_MODE1);
  //SPI.setClockDivider(SPI_CLOCK_DIV128);

  pinMode(ss_drv, OUTPUT);
  digitalWrite(ss_drv, HIGH); //set the slave select High (default)

  delay(100); //give time for everything to settle

}

void loop() {

  digitalWrite(ss_drv, LOW); //pull low to start the SPI transfer
  SPI.beginTransaction(SPISettings(1000000, MSBFIRST, SPI_MODE1)); //min period 200ns
  delayMicroseconds(1); //must be higher than 100ns
  SPI.transfer(0b00001000); //select OP_CTRL_1
  SPI.transfer(0b10101010); //set all HS enabled
  SPI.endTransaction();
  delayMicroseconds(1); //must be higher than 100ns
  digitalWrite(ss_drv, HIGH); //pull high to indicate end of SPI transfer
  delay(1); //must be larger than 600ns

  digitalWrite(ss_drv, LOW);
  SPI.beginTransaction(SPISettings(1000000, MSBFIRST, SPI_MODE1));
  delayMicroseconds(1);
  SPI.transfer(0b00001001); //select OP_CTRL_2
  SPI.transfer(0b10101010); //set all HS enabled
  SPI.endTransaction();
  delayMicroseconds(1);
  digitalWrite(ss_drv, HIGH);
  delay(1);
}

I'm not sure what to do next since as far as I can tell it's not a hardware problem (the chip and passives were selected and laid out according to the reference design), so the issue is likely with how I am sending the data, but afaik I've followed the datasheet to the t.


texts: Why does this isolation transformer have another transformer in it?

texts:
The isolation transformer I'm looking at: http://www.mouser.com/ds/2/336/HX1188NL-515471.pdf

My question is why is it there? Is it not enough to have just the transformer on the left?


texts: Questions for a personal LED/ATmega328P-PU project

texts:
Ok, so first of all, here's I'm wanting to use in this project

x14 5mm Red LEDs
x14 Resistors (1 per LED due to individual control -
how many ohms each? I don't quite understand Ohms law)
x1 Battery and holder (was thinking a button
cell battery if possible)
x1 Latching button (on/off)
x1 Momentary button (switch modes)
x1 "Joule Theif" for 3.3v/5v (i.e. https://www.youtube.com/watch?v=K53beWYdIpc)
x1 ATmega328p-pu (that I plan on underclocking to conserve
power - there a more efficient chip to use in this situation?)

Each LED would be connected to a separate pin on the chip with a resistor to turn on/off individually to form patterns. I'd like to limit battery use to a single battery (ideally cell for its size, or AA/9v since they're also common). I'd be using 2 proto boards on standoffs, one with just LEDs, the other with everything else and battery/buttons on the back. The positive LED terminals and ground would go into female headers on the other board for easier disassembly.

I'll be completely honest, I have no clue where to start. I'm really fresh into electrical work/arduinos and I spent a good 2/+ hours just trying to figure out if I could get the step up + >3.3v battery method would work, let alone if a button cell battery could do it.

Some things I think I've gathered:

The ATmega328p-pu can work off of 1.8v minimum, but the Red LEDs would require a higher voltage than that (what would the difference be in Voltage needed in series vs a distribution like I mentioned?)
A button cell battery probably won't work because of limited mA
DC/DC Step-ups aren't optimal(?)

I'm willing to go other routes entirely, such as just using an Arduino Nano and just plugging it in for power, but the battery route would be awesome if it could hold 1-2 max batteries and be small enough space-wise. If using a step up, would it be best to aim around 5v instead? I'm open to any and all suggestions. I know there's plenty of questions and all of them are pretty amateur but I find myself in over my head in most relevant posts I've seen so far.

Thank you so much in advance for your help!

Edit: Done some more hours of research and wrapping my head around all this and I have a complete setup designed now, all that's missing are values/power ratings I'd need and some other questions I'd have. I might post those as a new question instead down the road - thanks for your guys' help so far!


texts: Which chip or module could I use to replace MCP23017 I2C expansion chip to avoid using I2C as communications bus as it has interferance issues

texts:
Currently I'm using an Odroid C1 (It's like a Raspberry 3 more or less) and 4 MCP23017 expansion chips to increase the input/output pins. It gives me 64 additional pins that I use for a domotics project using some pins for switchs and some other for relay boards and things like that.
The thing is that the project works.. but sometimes the MCP23017 fails.. and I need to reset the software or the circuit entirely. I think it's due to having everything connected in a small box with 220v wires running near all circuits, so when an interferce is created the bus may get jammed and stop working. It's not something that often.. I'm using the system in my house and it might get jammed after a few days of continuous use.. but it's quite a pain when it happens.
So I'm looking for a more realiable solution to have IO pins expansion without using I2C or a protocol that can get interferences so easily.
I will attach a photo of the "box" where everything is wired up and a photo of the circuit board I created to connect everything.


texts:
I heard many people say that CAN message have ID's and not nodes.
I think this could be due to the fact that, irrespective of assigning a unique ID for each node, all nodes receive the messages. Also, in the event of any retransmission of a message, duplicate messages can be discarded when messages are assigned ID's when sending to each node.

But what if a system has 3 masters talking to many slave and all the 3 masters execute the same code(like in a 2 out of 3 voting system).
In such an architecture, it makes sense of assigning each node a unique ID so that the slave knows which master sent it data and reply back to each master uniquely.
Also, i cant think of a situation where a node may receive a duplicate message because retransmission occurs only in the event of error detection and when an error is signalled by a node, every node that received the data destroys the received data.

I'm confused now because i plan on assigning unique Id's to each node and the masters shall send message to each node based on its node ID(But the vast majority of CAN experts out there disagree with me).
Assigning each message a unique ID would mean that,if Master A sends 500 messages,500 unique Id's out of 2048 possible ID's(11 bit identifier) must be used by Master A. Remaining 500 by Master B,and remaining 500 by Master C.
Any insights on which would be a good approach would be greatly appreciated.

Also, any situation as to when a duplicate message can arrive at a node that already received the message would be of great help as that would be a solid explanation as to why each message must be given a unique ID and not a node.
This will help me understand that if Master A always sends the same identifier,the receiver will have no way of differentiating if its a duplicate message or not.


texts:
I'm trying to design curent steering DAC with binary weighted inputs - I'm using M4, M5, M6, M7 to copy the reference current flowing in M8 with coefficients of 1,2,4,8. The idea is to put either 0 or 1 to the drains of M4, M5, M6, M7 and use them as switches. After that I sum all the currents from the current mirrors at the resistor R1 and It's working as it is. Now, comes the problem.

At the right side I made a simple two stage op amplifier which I'm trying to use as current to voltage converter. I want to convert the sum of Im4, Im5, Im6, Im7 into Vout voltage equal to one of the sixteen possible input states - from 0000 to 1111. Actually, I don't know how to do that. As far as I understand the op amp.. whatever voltage I apply to the gate of M22 that is what is flowing in M18. So, my question is how to bias M22, so that I can be able to get the equal current to input combination of 4 bits. The other question is how to make the feedback. It should be a resistor and Vout = -Iout*R. And how to simulate the op amp to see that everything is properly working.


texts: Limits of my Arduino  Smartphone communication

texts:
I want to transfer signals from my smartphone to my Arduino Uno by using the audio jack.
I have directly connected one channel of the audio to the analog in on the board.
The smartphone is sending ~ +-0.5V. This will be interpreted as either 1 or 0 bit signals.

I got the Arduino to read the voltage within ~10 microseconds (100kHz).
My problem is that I can't send data with this rate, but I want to speed up the transmission as far as possible.

Below you can see the voltage which is read with 100kHz. On the top right side you can see the bit value. The bits were send with 10kHz. With higher sending frequency the bit "blocks" are not blocklike anymore and blur into each other.

Is this a problem of the smartphone? Can't it produce good signals with this high frequencies?

Or is it a problem of the circuit?

What can I do to get a better signal?

Edit:
Here is the Arduino Uno code:

byte data[500];
unsigned long lastRead =micros();
int i;

void setup() {
  bitClear(ADCSRA,ADPS0) ; //boost up analogread
  bitSet(ADCSRA,ADPS1) ;
  bitClear(ADCSRA,ADPS2) ;
  Serial.begin(9600);
}

void loop() {
 while(analogRead(A0)<50) (true); //wait for start of transmission
  for(i = 0; i<500;i++){
   data[i]=analogRead(A0);
  }
  for(int i = 0;i<500;i++){
    Serial.println(data[i]);
  }
  delay(1000);//just prevent starting again to soon
}


texts: Identify the change in switch states using a single wire system

texts:
Say I have 10 switches which will be automatically tripped at any time. The switches are supplied with the constant voltage(Say 5v). So the conventional way for identifying the trip is by connecting each switch to the GPIO's of uC and monitoring their voltage levels.

I want to know is there is any other simple way to identify this problem. Below is the sample circuit diagram (only for understanding)

simulate this circuit – Schematic created using CircuitLab


texts:
I have designed my first custom board in KiCAD using STM32L452RE and I am planning to program using ST-LINK via SWD Pins but I am not familier with the process of bootloading the MCU.
How can I bootload the MCU before programming?
I have only bootloaded custom ATMEGA328 boards.


texts: Toggle Switch to swap the connections of two buttons

texts:
I am trying to mod my arcade stick so I can switch two commonly swapped buttons on the controller.

Essentially they are simple 2 terminal momentary switches connected directly to the controller PCB. I would like to switch their responsibilities, so in my case the Back button and the LB button on the XBox pcb I would like to swap so the Back actuates the LB button on the PCB and the LB actuates the Back button.

My assumption is that I would need a switch with 8 terminals, 4 in 4 out.

What type of switch am I looking for?


texts: i have a coding machine here and on its pcb it has this IC ULN2003AN. it was burnt because of feedback polarity issue and i want to replace it with ULN2003APG. Is this possible, will it result to another problem. pls help.


texts:
I've been making my own simple FM radio. I know it's not quite appropriate to make this stuff on breadboard, but if it works, I'll move in on the board and solder it. I wanted to ask why my radio is not picking up any signals.

At first I thought of having a very small antenna for this purpose. I don't know if it is enough, but I don't think so. Then I realised I also might have connected my circuit wrongly. Or the variable capacitor. I've been thinking a lot how I am supposed to connect it properly. Because I have no idea. Can anyone tell me? And is there a way I could vary my variable capacitor with a metal screwdriver? I don't have any plastic ones..

Here's the schematic of the circuit:

Here is the screen of my variable capacitor:

And the way it's all connected on breadboard could be seen here:

I filtered high-frequency noise using low-pass filter and I only heard some small humming noise there. I wasn't sure if it was talking or not.. After I used my screwdriver, I didn't hear anything, everything was quiet.

Help me out with this project, please.


texts: Kicad - Change add unconnected/unnamed trace to an existing net

texts:
I have a complicated guard ring of sorts that surrounds a network of pads and traces. This guard ring is/was connected to the GND net. I had to make so changed and reload the net list. As a result the guard ring traces were orphaned and no were longer marked with the GND net. As a result, the router will not allow me reconnect the trace ring to GND. There would be considerable work to redraw all these traces.

Is there a way to apply a net to an unconnected net of traces that is not part of an existing net?

The red circle in the image below indicate where I am trying to create a connection between the net with no name around the pads on Col7 and the GND net around Col8.


texts: Running a MOSFET from a transistor for a fan controller

texts:
I have a PC fan controller that is capable of powering 10w per channel. I'd like to put 23w of fans on a single channel, so I am trying to find a way to use the electronics already on the fan controller to activate a MOSFET or other transistor that will be able to handle 23+w.

Basically, the theory I thought would work is to look at the PNP transistor on the fan controller, and take a wire from the gate of that transistor and using it as the gate on the MOSFET to make the MOSFET switch quick enough to step the voltage and vary fan speed.

Unfortunately, doing this did not result in what I wanted to do. The fans spin at a constant rate of approximately 60% top speed. I only have one fan tachometer wire wired to the feedback of the fan controller, so it doesn't get any weird signals from out of phase tach signals.

Is there any good way to accomplish this?

Here is the equipment I am using to test this with.

Fan controller: [BitFenix Recon]

PNP Transistor in fan controller: B772 PNP Medium Power Transistor

MOSFET: ST P14NK50Z N-Channel 500V MOSFET


texts: Can anyone make an analysis for this crystal oscillator circuit?

texts:
Figure 18.34, Crystal-controlled oscillator operating in parallel-resonant mode, from "Electronic Devices and Circuit Theory" by Robert L. Boylestad and Louis Nashelsky

Can anyone make an analysis for this circuit using any assumed values? I don't know how or from where to begin.


texts: is it ok to power a 90v dc motor with 170v dc and pwm?

texts: I need to control a 90v dc motor, the thing is that I dont have a way to get a 90v suply so I just rectified the ac voltage and got 170 volts, without any load and filter caps, as far as I know this voltage will drop once there is a load but it is stil high, is it ok to use pwm at this voltage to power the motor, obviously with about 60% duty cycle.


texts: ST ST25R95 - NFC chip - Impedance of transmission lines

texts:
I will supply the chip with 3.3V, and the datasheet of ST25R95 IC shows it has a ZOUT of 27R at this condition.

There is a circuit between NFC antenna/coil/inductor and the IC, the LC filter and matching circuit:

My doubt is about the black lines shown on picture above, the transmission lines. Should they have 50 ohms? or 27 ohms? I think it should have standard 50 ohms but I would like to have sure about that.

Here is the datasheet if you need: https://www.st.com/resource/en/datasheet/st25r95.pdf

Regards.

EDIT:

There is a distance of around 10mm between the transmitter pads and the antenna:

EDIT 2:

Calculation of microstrip with AppCad of Avago Technologies


texts: Inductor and capacitor for energy storage instead of battery

texts:
I am trying to see if it would make sense to use a LC network to store small amount of electrical energy (500 mWHr or less) as an alternate of a 3.3 V battery. What I understand is that L and C are reactive components and they do not dissipate energy at least in their ideal case.

Specially if I have to recharge by AC mains outlet or by wireless-charging then recharging an LC would be easier compared to a DC battery.

Any expert thoughts about it?

Can someone throw out some mathematics to prove or dis-approve the above idea?


texts: For ESD protection, is it wrong to clamp isolated I/O to chassis ground?

texts:
I am designing a device which drives I/O with circuits powered off an isolated power supply. To protect against ESD shocks, I placed bidirectional TVS diodes with 60 V forward voltage (SMBJ60CA). I connected one end to the I/O net and the other to chassis ground.
Just before sending this design to layout, it struck me that the reference for the I/O (let's call it ISO_GND) and the chassis reference (GND) may be at very far-apart galvanic levels, which could easily cause a potential difference > 60 V. If I'm not mistaking, this could cause arbitrary biasing of the diodes.
Is this something to worry about? What is a better way to implement ESD protection?
Edit: added an image to illustrate


texts: Simple self oscillating flyback converter

texts:
Please am studying about switching power supplies, starting from the simple ones. I've just concluded on joule thief and blocking oscillator, now am progressing to Self oscillating flyback converter(or RCC) and am finding a bit difficulty on how the transistor switches OFF.
It seems the transistor switch off concept is quite complex than the switch ON process. Some say the operating principle is very much the same to that of blocking oscillator, but i think the are some contrast.

Here I only understand that a small current flows through the startup resistor to the base of the transistor, to initiate the turn on process. As the transistor is partially ON(active region), collector current will flow and energize the primary winding, as a result, a same polarity voltage will be induce in the feedback winding which will create a positive regenerative feedback and conduct more current to the base of the transistor, and the transistor turn on fully(saturation).
That's all I know. I don't know how the transistor will switch OFF. I might make some assumptions based on my knowledge of the joule thief circuit, but am not sure.
I don't also know how RC circuit can affect the switching frequency.


texts: How to condition a NTC of very low resistance?

texts:
I want to use a temperature sensor which changes its resistance. For 0 degrees celsius its resistance is 0.5325 ohms and for 40 degrees celsius it is 3.264 ohms.

Obviously putting it in series with another resistance to produce a variable voltage is not logical since the current that would circulate is high. (the variable voltage must be within the range of 0 to 5 volts).

It occurs to me to use a small voltage (reference voltage) for the voltage divider and then variable voltage should be amplified but when working with very small voltages there may be problems with electrical noise.

Can it be done better and economically?

Thanks


texts:
I'm having an intermittent issue with a motor control setup I'm working on. I'm using a Pololu G2 18v17 motor driver controlled simply with an Arduino. I have a current limiting resistor installed on the motor driver which sets the maximum output to 10A per the datasheet. The driver offers a lot more control than I'm using in this case.

My setup is to drive the required pins low/high to engage the controller and then an external pressure switch actually turns the motor on and off. This is really just giving me current limiting. (I'm sure there's a better way to do this and less expensive, but not the focus of my question).

I'm seeing an issue when the motor turns off that my whole system resets. I was thinking it might be a reverse voltage issue, but the driver datasheet lists reverse voltage protection. Am I negating that protection with the way I'm using it? Should I add an additional diode at the power supply?


texts: Is there a simpler solution for highside current sensing here?

texts:
I have an existing automotive circuit simplified in the image. The loads (2 or more solenoids in parallel) share a 12V supply and are individually switched to ground through the car's ECU.

I need to detect when any one of the circuits close (only one closes at any one time), using a single PIC digital in (or comparator if I must), and with the minimum of wiring (the car's wiring is buried and a pain to get to although the common 12V rail is easy to get to). I can't disturb the ground plane(s) and can't add much load.

I have looked at highside current sense ICs but can't find them in DIP and don't want to use SOT if I can help it as I will be hand-soldering to stripboard. Anyway, I don't need to know how much current is flowing, just whether it is or not.

There must be a simpler solution that I'm missing?


texts: How to constrain a clock signal out from a multiplexer

texts:
How would you constrain this design?

ext_clk and clk_in are asynchronous to each other.
clk_div is derived by clk_in with double period.

clk_out may be driven by either clk_in and ext_clk, according to the selector pin of the multiplexer.

This is what I would do:

create_clock -period 42 -waveform {0 21} [get_ports "clk_in"]
create_clock -period 300 -waveform {0 21} [get_ports "ext_clk"]
create_generated_clock -name clk_out -source [get_ports "clk_in"] -divide_by 2 [get_pins "xmux/y"]
create_generated_clock -name clk_out -source [get_ports "ext_clk"] [get_pins "xmux/y"] -add

I am not totally sure this is the proper way to constrain this design.
What do you think will be the impact of these constraints to the CTS generation in terms of balancing for the logic clocked by clk_out if it talks, mutually exclusive, with the logic driven by clk_in and ext_clk?


texts: When there is diffusion of electrons to the metal from the n-type semiconductor, why does Wikipedia says there is no charge carrier depletion region at the junction in a Schottky Diode?


texts: Zener diodes in glass axial package - not inherently shielded from photoelectric effect?

texts:
I discovered today that a glass packaged axial leaded 5V Zener diode will become a source of about 0.450 Volts when the glass package is held in the beam of a low-power purple (405nm) laser pointer.

The test setup:
Scope probe (with ground clip) attached across the zener.  With laser turned off, scope reads zero volts as expected.  Turning laser on and aiming it at the glass package of the diode, the scope reads a fairly stable 450mv (noisy though: 30mv p-p ~100kHz).  (edit: this noise could be a product of the laser-driver step-up circuit)

The laser is a cheap one and purports to be 1mW rated.

Interrupting the beam with opaque materials instantly stops the voltage reading from the diode.  Modulating the laser with a 5kHz square wave causes the diode to exhibit a 5kHz response (in phase with the laser's modulation as far as my scope can tell).

I realise that this is rather unscientific but my question is this:

Is this typical of glass zeners and if so, should a designer avoid using glass zeners in sensitive analog circuits.  Or is this too specific to be a real-world problem?


texts: The role of the series resistors for ESD protection

texts:
When one needs to protect a transistor or I/O pin of a processor, then a TVS diode can be placed between the connector and the transistor. Also a series resistor (R1) can be placed between the connector and the TVS diode in order to protect the diode. However, is it useful to have a resistor(2) between the diode and the transistor? The circuit is shown above.

If so, what's the function of R2? Also, what's the recommended resistance for R2? Often it is not easy to just increase the resistor value, because it can degrade the signal integrity. Is 47 ohms enough, or should it be also 100 ohms or higher?


texts: 3 wire signal to 4 core shielded twisted pair

texts:
So I have some flow sensors, which have a 3 wire interface.

The three wires are 5V, signal, and ground. Signal is pulse output that varies between 5V and ground at a maximum frequency of about 200 Hz.

The wires are a bit short (30cm) and I would like to extend them to 1 to 3 meters.

I've bought some really nice 4 core cabling, with 2 twisted pairs, shielding, and center wire strands.

I'd like to know if there is anything I need to consider when going from the 3 wire signal interface to the 4 wire twisted pairs.

My plan is to make one wire from each pair ground (both the blue and green wires), the one wire from the first pair (red wire) 5V and the other wire from the other pair (yellow wire) the signal. So that each pair has a ground wire, and when the signal is activated the ground return current can follow the path of least resistance.

Is there anything I need to consider with the shielding and center strands? What would be the best way to connect them, considering that the previous interface had no shielding at all.

Can I connect the shielding directly to PCB ground, or should I connect it via  a resistor (~10k), or via a ferrite bead?

Regards,


texts: Supply white/blue led with 3V3 at constant current

texts:
I need to drive a white/blue led at low constant current (about 10mA.)

To do that I usually use the schematic below, but in my case I can only supply the LED with 3V3.

Since the typical forward voltage of white leds @10mA ranges from 2.7V to 3V, the voltage drop across R2 could range from about 0.5V to 0.3V.

For tolerance reasons I'm afraid that with this variability I cannot guaranteed a repeatable luminous flux with different leds.

Can you suggest to me a different way to drive a led that can control the resistance?

simulate this circuit – Schematic created using CircuitLab


texts: Temperature sensor (TMP36) inaccurate readings

texts:
I've got a TMP36 temperature sensor of which I'm trying to read the value of using an Arduino Uno. I know that the sensor has an accuracy of -/+ 2 degrees celsius but my readings are peak far past this range.

I soldered three wires onto the three legs of the sensor. I hadn't exposed the legs (and thus) the sensor to the heat of soldering for that long a time, but could this have damaged the sensor?

Also the three wires I've soldered on are about 50cm in length and are twisted together, could this cause interference of the voltages?


texts:
I bought an E9001 servo on Amazon (which was my first mistake, but it was cheap- see link) to use in a robotics project, but I can't figure out how to use it, and I cannot find any formal documentation for it.
https://www.amazon.com/gp/product/B07F1NZ6GR/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1
I'm trying to control it with an STM32L411 Discovery board by sending it 1-2ms pulses every 20 ms as you typically do to control positional servos. When I first turned it on, the motor torqued clockwise 90 degrees and then the power supply current limited at 2 A and stayed that way no matter the size of the pulse or PWM frequency I applied (I tried 50-200 Hz and 0.1 to 5 ms pulses). I had to change the current limit to reapply the correct voltage. I am certain I am sending the correct control signals because I have been observing it with an oscilloscope. Any suggestions?


texts: Current measurement with a multimeter: how am I doing it wrong?

texts:
I want to measure the current draw of a strip of LEDs. This depends on the intensity of the pattern the strips are running so I need to do it in "real time" to get an accurate idea, rather than just do maths from the spec sheet.

I made this cable that should not be in order to insert my multimeter in series with the circuit:

After I plug this in between the (earthed, double-insulated) 12V power supply and LED controller box and clamp the two red wire ends together, everything works fine.

But when I set my multimeter like this:

... and complete the circuit with the multimeter's probes (the red probe on the wire closest to the power supply, black probe closest to the LED's controller box), I get a reading around 3.5A on the multimeter but the controller does not seem to be receiving power and the LEDs don't light.

Any idea what I could be doing wrong?


texts: What are the two gate leads on a thyristor?

texts:
I have a simple question: what is the second gate lead on a power thyristor (see the figure below) ? What is it physically attached to ?

I understood that the thyristor turns on when you force a small current pulse into the gate.
So I don't understand what is the purpose of the second one.


texts: Leading edge Vs Trailing edge PWM Modulator in SMPS

texts:
How does the leading or trailing edge affects voltage mode PWM modulators in SMPS and how to be aware of that?
If we take the following modeling equation of voltage mode buck-boost converter:

Which techniques suitable for simulation of this equation in Simplis or SPICE?


texts: How very high frequencies (VHF) are propagated during night over large distances?

texts:
I am new in telecomunications and this question just came up today and I coudn't find an explanation.

Here is the most common model for the ionosphere:

The ionosphere layer E is the main resposible for the reflection of the VHF signal which will allow communication over long distances during the day. But, during night, we don't have E layer because of the absence of the sun.

So, how does it happens during night?
Does F2 layer became the main responsible for the reflection of the VHF signals?


texts: Finding a minimal cost function from a Karnaugh Map

texts:
Below is a problem I made up and did. Is my solution wrong?

Problem:
Attached is following map for the function \$f\$. We want a minimal cost expression using only and, or and not gates. The cost of a gate is the number of inputs it has plus 1.

In the above diagram 'd' represents 'don't case' so '0' or '1' would be acceptable.

(original)

Answer:
We can cover the entire area with three selections.
1.) The four squares in the upper left hand corner.
2.) The two squares in the upper right hand corner.
3.) The squares in the upper right hand corner and lower left hand corner.
$$ f = \overline X_1 \overline X_3  + \overline X_0 X_1 \overline X_3 + \overline X_0 X_ 1 \overline X_2 $$

Based upon the comments I got, here is an updated solution.
Another approach is to cover it with the following four selections:
1.) The four squares in the upper left hand corner.
2.) The top row.
3.) The top half of the left most column and the top half of the right most column.
4.) The squares in the upper right hand corner and lower right hand corner.
$$ f = \overline X_1 \overline X_3 + \overline X_2 \overline X_3  + \overline X_0 \overline X_2 + \overline X_0 X_1 \overline X_2 $$

Another approach is to cover it with the following three selections:
1.) The four squares in the upper left hand corner.
2.) The upper two squares in the left most column plus the upper two squares in the right most column.
3.) The bottom square of the right most column and the top square of the right most column.
$$ f = \overline X_1 \overline X_3 + \overline X_0 \overline X_3 + \overline X_2 x_1 \overline X_0 $$
Is this right?


texts:
I am looking to combine a cheap wifi baseband/mac chipset with a STM32 F1 or F2 MCU to run the IP stack.

I have to use the cheap USB wifi dongles or use SDIO/SPI interface and port the drivers.

I am facing a problem in finding the correct chipset which has datasheets / opensource drivers to continue with this work. The problem with Atheros / Broadcomm is they do not give datasheet unless an NDA is signed.

My only requirement is the chipset should be able to act as "Access point" for initial configuration.


texts:
I'm new to electronics so forgive me if this is an obvious question.
I'm making a small circuit to read out a digimatic caliper. There are many designs only and I'm wondering why some components are there. The digimatic uses open collector signaling. There are 2 output lines and 1 input line. One of the schematics can be found here: http://www.imajeenyus.com/electronics/20140109_digimatic_interface/digimatic_circuit.pdf
What I'm wondering is:

Why does the CLOCK signal which goes to the SPC_CLOCK have a resistor and capacitor after the pullup. My MCU has internal pullups. Can I use that instead and save myself 3 components?
Why does the SPC_REG contain a resistor which then connects to the base of the transistor?

Any help is appreciated!


texts: How to increase frequency modulation index?

texts:
I'm thinking of making a low power FM transmitter. Here's a diagram.

It seems an absolute pull range of a VCXO will limit the modulation index. Is there possibly a way to extend it?


texts: Could memristors be used to improve speculative execution?

texts:
I've been reading about different methods of improving processing speed, and speculative processing stands out to me. My question is, could the integration of memristors that are trained by instructions passed through a processor improve speculative execution in a meaningful way, or would the added complexity be too prohibitive to make it useful?

I understand memristors are extremely conceptual, but I feel that talking about them in this context is appropriate.

Edit: I mean utilizing memristors as a physical perceptron, not as just raw memory.


texts: Are ripples and harmonics the same thing?

texts:
I started working on the "Direct Power Control of Grid Connected Voltage Source Converters", everywhere in the literature, authors state that one of the major drawbacks of this control technique is the presence of active and reactive power ripples due to the use of Hysteresis controllers.

In the other hand I've already worked on Power Harmonics, active power filtering and UPQCs, and i know that harmonics must be multiple of the fundamental frequency.

My questions are the following :

Are "power ripples" cause by hysteresis controllers considered "harmonics"?
What are the frequencies of those power ripples?
Do they affect the value of THD?


texts: Dimming LED powered with an AC driver from a MCU

texts:
I want to power an LED (Forward Voltage: 30-35V, Forward Current: 50W:1750mA) with an AC driver (link), the title says "Dimmable", so my first question is regarding drivers, all of them will work with a dim or only the ones that say "Dimmable / TRIAC"?
Next questions are about a proper module that can do the job paired with the driver, i have seen this:
Module 1

and Module 2

Now regarding modules:

Module 1 says 220V, but will also be compatible with 110V? (I'm on 220V, but still like to know if is compatible)
Module 1 have no zero cross pin, does it handle it on hardware?
Both modules will work with the driver above?
Which module is best to go with? or other?
Dimming with a constant PWM rate, eg. 50% will cause any flickering to the LED light?

The PWM signal would come from an Raspberry pi and will not include effects nor smooth increments, most of the time it will be used at 0% or a fixed rate (ON/OFF) but the dimming feature is necessary to have.


texts: what do the nm or µm for a process technology refer to e.g 22nm process technology for device fabrication

texts:
There are many "process technologies" that exist to fabricate circuits on silicon. They are mainly differentiated based on size of some feature. Here is the list of them:

10 µm – 1971
3 µm – 1975
1.5 µm – 1982
1 µm – 1985
800 nm – 1989
600 nm – 1994
350 nm – 1995
250 nm – 1997
180 nm – 1999
130 nm – 2002
90 nm – 2004
65 nm – 2006
45 nm – 2008
32 nm – 2010
22 nm – 2012
14 nm – 2014
10 nm – est. 2015
7 nm  – est. 2017
5 nm – est. 2019

What I wish to know is, what precisely do these numbers refer to e.g the 90nm that was reached in 2004, what does it precisely mean?

I think it has to do with some dimension of the transistor that is fabricated but do not know the details. So what does it mean?


texts: Click-and-pop suppression when circuit is not yet powered

texts:
Problem description:
Power supply, for some reason, false-starts on power on of the device:

the red is system +5 V supply rail, and yellow is my device's 3.3 V buck converter powered from the system's 5 V. You can see the power surge when switch is being turned on, and 3.3 V power supply also false-starts.
Here's more detailed picture of what is going on:

But in general I can not control what is going on with the system's power supply.
Due to this false start, audio subsystem experiences pop-click sound which I want to eliminate.

Research:
Thus I am looking for ways to suppress this false start influence onto the audio outputs. There's system's RESET signal, which is kind of not logical 1 when false start happens:

Red is reset signal (5V TTL), yellow is 3.3 V converter. Thus it seems I can use RESET signal to control circuit suppressing the audio output.
I am simulating the following circuit (which is not my design):

The result of simulation is:

where blue is reset (V3), green +5 V power (V1), and red is an output. Audio input (V2) is always running at 1000 Hz.
The problem is that if power is not yet there, Q2 is off and input audio signal is not pulled down.
I also considered solution based on MAX9892, but its switches are open when power is < 1.7 V, so it must exhibit the same behavior.

Question:
is there any solid-state circuit which would be "normally closed" when power is not in there?
Update, following @bobflux comments:

I connected probes to the input and output capacitors of the 3v3 buck converter:

now connected yellow probe to its alligator clip:

same, closeup

Now things become more interesting. I put my device into another platform, based on ATX power supply, and connect to the same wires. Below is an image when I turn ATX power switch on, but active power is not yet applied to the device (only standby somwhere inside it):

now closeup

and now I press ATX switch to turn main power up:

So the outcome of measurements is that noise comes from main receptacle power wires being connected to the mains, not from device being powered on. The first, non-ATX platform is having virtual ground and only 2 mains power wires, the second, ATX one, is expected to be properly grounded with the scope.
Small addition, it may matter: I use scope and its probes in X1 mode.
Update: agreed it is caused by the common mode transients.
Meanwhile seems I have found the cause of the pops and clicks. It is DAC UDA1334, if powering it down, and then quickly powering it up, the analog and digital parts of it improperly reset and DAC gets arbitrary value. Then, when DAC starts to be driven by writing 0 to it, the output clicks.
I suspect I must do something with Vref input of the DAC ensuring it got as low as 0.75 V during reset so that analog part properly resets. Not sure if it will reset digital part properly though, but hopefully problem is not in digital part, but in analog subsystem power up calibration, then resetting analog part properly will solve the problem.


texts: How can I sum two PWM signals of different frequency with a Op Amp?

texts:
I need a suggestion how to sum two PWM signals, PWM 1 + PWM 2 to an output that have them both included.

Questions:

Is this possible? Other suggestions?
What Op Amp do I need to use if I want the output handle heavy load of 12 volt? I'm going to control a large 12 DC motor and the small frequency PWM 2 is going to be the dither signal to make sure that the 12 DC motor is still in a vibrating movement. It reduces friction and makes the 12 DC motor more linear and proportional to the PWM 1 signal.


texts: Driving a dual axis with one stepper motor

texts:
I'm busy learning a bit of electronics, and trying to create an analog gauge replica of a Cessna 172 aircraft altimeter.

I'm using an Arduino Mega 2560 to fiddle with, and thinking of using a stepper motor to drive the two hands on the gauge.

The tricky part of this is, driving two hands, sitting on the same axle on the gauge using one stepper motor. So I'm trying to figure out a way how I can achieve this.

I have an idea to have two shafts inside of each other, an inner shaft driving the one hand, and another shaft around the inner shaft for the other hand. The inner shaft is driven directly by the servo motor, and a few gears attached to it, should transfer the rotation at a ratio of 1:10 (I think), to the outer shaft.

So with each revolution of the long hand, the shorter hand needs to revolve 1/10th of a full  rotation.

The question is, where can I buy these kind of shafts that fit snuggly into each other, that will allow me to fit gears to them? Are there kits I can buy for this sort of implementation?

I looked around at sites like http://www.servocity.com/ and http://sdp-si.com/web/html/products.htm, but not really sure what to look for, or what this kind of shaft/axle would even be called.


texts: I have been forcing a problem regarding to corruption of the MCU flash memory content during software running. This corruption occurs randomly and I have got an idea whether the flash memory corruption could be result of stack overflow event. Is it ever possible? After all stack is in the RAM. Thanks for any suggestions.


texts:
I have this DC motor that I tried testing with common sense, but doesn't work.
The description classified it as "Female terminals"
I don't have a multimeter on me now so I can't be sure about if there's "contact" being made, though I am sure that the battery works, and there are no dead shorts or broken wires.
With a multimeter what tests do I attempt? Any other information too?


texts: Scheduling: Is is a Physical layer functionality or a Data(MAC) layer functionality or is it both?

texts:
Fellas,

When we use the term SCHEDULING in wired/wireless communication, does it relate to a physical layer functionality or a Data (MAC) layer functionality or to both?


texts: Arduino-based oscilloscope: attenuate the input by varying reference voltage?

texts:
I don't have a proper oscilloscope. I don't have the budget to buy one, even a used one. I have to roll my own. :(

The plan is to use an Arduino Leonardo or Due as a combined A/D and USB interface and write an app on my Mac to display the waveform. Now the problem is how should I give it V/div options without losing resolution?

I am wondering whether this will work:

simulate this circuit – Schematic created using CircuitLab

By changing the AREF voltage I can change the full range voltage of the DAC. Will this produce the effect of giving me lower V/div without losing resulotion?

For higher V/div, would a simple single digital pot work?


texts: Noise on PWM before connecting to buck circuit

texts:
I have built a buck converter in the circuit configuration below in order to charge a supercapacitor. The PWM signal is being applied with an arduino and is in the place of the signal generator in the image. The problem is that the PWM signal from the arduino is highly distorted after it is connected to the circuit. I have attached pictures of the PWM before it is connected and after. Any help would be greatly appreciated.

PWM before connected to circuit

PWM when connected to circuit


texts: How can I test guitar effects box without a guitar?

texts: I want to play around with guitar effects circuits on a breadboard, but I don't have a guitar. How can I test my circuits without a guitar?


texts: Reading from multiple sensors and synchronizing data

texts:
I am working on a project which requires reading from four sensors simultaneously with time stamps down to millisecond.

Right now the best I can come up with is to use four PICs to read from each sensor and output through four RS232 to a laptop. So those sensors don't interfere with each other. For time stamps, I use a mechanical switch to trigger a external pin voltage change interrupt to start timers in all PICs at the same time. Timers increment every one millisecond and I just simply append the value from timers at the end of every measurement and output them through serial ports.

It works but I just want to know if there is a better solution since this project is kind of time critical (1000 measurements per second required). And also internal timer for each PIC varies which defeats the purpose of synchronizing timers.

I also thought about just reading from one additional chip's timer using SPI so all time stamps come from one source. However, I don't know when those PICs will read the time from that source chip. There could be four PICs reading from it at the same time which will mess up time stamps.

Sensor 1: Quadrature encoder (channel A B and Index)

Sensor 2: Laser (sending measurement back through Rs232 interface)

Sensor 3: accelerometer (analogue)

Sensor 4: inclinometer (RS232 interface)

I am using four DSPIC30f4011 chips. They have QIEs enough UARTs and also support four channel simultaneous ADC.

For Quadrature encoder, I use an on chip QIE to read from it and send measurement to a laptop through UART.

For Lazer and inclinometer, I read from them through UART1 and send measurements to a laptop through UART2.(one chip for each of them)

For accelerometer, x y and z information are being collected using four channel simultaneous mode. Measurements are sent to a laptop through UART.


texts: What voltage of Li-ion battery to run 24 volt motor (6 cell or 7 cell)

texts:
I have the option of replacing my aging and almost dead lead acid batteries with Li-ion to run a 24 volt motor.  The data sheet for the Li-ion cells report the cells as having a nominal voltage of 3.8 volts.  If I use 6 of these cells in series, the average voltage will be slightly lower than what the lead acid provided, but if I use 7 cells in series, the average voltage will stay above 24 volts, (starting at 29.4 volts).

The lead acid batteries are rated and 18Ah and the Li-ion are rated at 30Ah and tested at a 100 amp discharge rate to provide 28.3 amps, so they can handle a high current!

I am leaning toward the 6 cell battery because when I look at the datasheet for the battery, the discharge curve shows the voltage to stay at about 3.8 volts or higher (at a 20amp discharge) until the last 15 minutes out of a 1.5 hour discharge, and for my purposes, it wouldn't be discharged that low. So this would keep the voltage at around 22 volts.

So is it better to run a DC motor with more volts than rated or less? - if you have no choice?


texts: What is the difference between Interrupt on Change and External Interrupt on PICs

texts:
What is the difference in function between IOC and EXT Interrupt on a PIC?  I am currently using a PIC12F1822, and apart from the extra layer of checking you have to do with IOC (i.e. which pin caused the interrupt) the two are identical.

What is the practical difference if any? When would you use either one or the other?


texts:
Sometimes, when checking datasheets of Three Phase equipment, specs for "220-240 VAC" and "380-440 VAC" appears, as for these Mitsubishi Contactors Catalog AC-3 Power Ratings.
Normally, I interpret this specs as "voltage between terminals". Hence if mains is 220 VAC, then under a star connection, we will fall in the "380-440 VAC" range, and under a delta connection, we will fall in the "220-240 VAC" range.
But this is only a reasonable assumption. I am not sure if this works in all cases, I have been confused in some opportunities, or if there any IEC paragraph ruling the specs for three phase equipment, in order to be sure.


texts: How to use HC-05 Bluetooth module with STM32?

texts:
I'm an absolute beginner and not very familiar with the terminologies used in the HC-05 manual. After trying everything, I haven't been able to connect to the Bluetooth module yet.
I have an STM32 Nucleo board, a servo and a Bluetooth module and I want to match the servo PWM with angle(as the ones specified in the servo manual weren't very accurate). I connected:
+5V->USB +5V
GND->USB GND
RX->D8
TX->D2

My code (mbed OS 6) is:
#include "mbed.h"
#include <string>

PwmOut servoPwm(D9);
DigitalIn btn(BUTTON1);
BufferedSerial blutooth(D8, D2);//Tx, Rx

float fDutyMin = 0.05f;
float fDutyMax = 0.10f;
float fDutyRange = fDutyMax - fDutyMin;

float angleToDuty(float angle) {
    return fDutyMin + fDutyRange * (angle + 90) / 180.0f;
}

int main() {
    servoPwm.period(0.02);

    float fAngle = 0;

    while (true) {
        if (btn.read() == 0) {
            while (true) {
                if (btn.read() == 1) {
                    break;
                }
            }
            fAngle += 10;
            string message = "Angle: " + to_string(fAngle) + " PWM: " + to_string(angleToDuty(fAngle)) + "\n";
            blutooth.write( message.c_str(), message.size());
        }
        if (fAngle > 90) {
            fAngle = fAngle - 180;
        }
        servoPwm.write(angleToDuty(fAngle));
    }
}

My Problem is I can't connect to the Bluetooth module with my phone. Do I have to set it to pairing mode somehow? I can't find anywhere how to. And I just can't find it in the "new Bluetooth devices" list on my phone. When I power the system up, the LED on the HC-05 module blinks 3 times and then it goes dark.
Please help me out.


texts: Confusion over SMPS controllers/regulators

texts:
I am looking at datasheets for ICs like FAN4800 or NCP1337.  Some of these are PFC boost converters and others are for other types of SMPS topologies.

My confusion is that I can't tell if these ICs are actually supposed to be regulating the output voltage.  There is never any mention of PID or compensation techniques to use with these ICs.  I am hoping that its all included internally, but I see no hints of a PID system when I look at the internal block diagrams of these parts.  Is this correct to assume or do I need to design an external compensation circuit?


texts: I need to switch a load with a 3.3 volts logic level (pic microcontroller) is this design is correct?


texts:
I'm using some QFN devices in a PCB I'm designing using the Eagle PCB software. The QFN packages have a centre pad that is grounded and intended to help with thermal dissipation.

When creating the package, if I have the centre pad as an actual pad then I get DRC errors when I come to place vias on the pad to connect it through to the ground plane on the opposite side of the board.

Another possibility would be to leave the centre pad off the package and draw it in on the board, but this is a pretty unsatisfactory solution.

What's the best way of dealing with this problem?


texts: I am trying to build a pink noise machine to use at work.  See  schematic below.  If I connect the output from the MM5837N (noise generator), directly to the amp circuit.  It works fine, and is nice and loud.  However, when I include the passive LPF as shown from the example, no sound comes out. Using a scope, Fig. 1 shows the output from the MM5837 w/o the LPF.  Voltage is around 4V.  Figure 2 shows the output after the LPF.  The signal is around 2V.  At this point, the output from the LPF is not connected to the amp input.  When I do connect the output to the amp input and probe at the same point, the signal drops to around .2V, and there is no output from the amp.  Scope shows a flat-line on the amp output.  I am not an EE, so don't understand what is going on here. Do I need some kind of a buffer op-amp between the two? Any help is appreciated!  Also the LPF cap is just a ceramic type, if it matters. Link to the amp data sheet.


texts: Precision shunt regulator failure behavior

texts:
I'm working on a project that uses an LM4040 precision shunt in order to obtain a 2.5 V reference voltage (in particular, I'm using the LM4040-N-25). My circuit is similar to the one shown below (from TI's website):

In designing my project, I was basing my design on a prior project that used a 3.3 V input voltage Vs and an appropriately sized shunt resistor Rs. Unfortunately, I hooked Vs to a 5 V input and exceeded the maximum specified current for the device for some minutes (which is 15 mA, according to the datasheet). However, I only exceeded it by 1 mA, so I haven't let out any magic smoke.

What is the expected behavior of a precision shunt like this if it's failed? Currently, I am obtaining 4.3 V across my output and ground, indicating to me that the LM4040 is doing something, though I'm not getting the desired 2.5 V.

Thanks!


texts: STM32L0 Low power UART-receiver reads the wrong data at high baudrate after MCU waking up

texts:
I'm using a STM32L0 MCU for my project. The MCU has a Low-power Timer (LPTIM) for waking the MCU up from Stop-Mode, and a Low-power UART (LPUART) for both waking up the MCU from stop mode and receive/transmit data.

My problem is:
    - When I let the MCU staying in running mode, LPUART working fine at baudrate over 256000.
    - When I set MCU to go to Stop-mode, then when the MCU receives something from LPUART-Rx, it's woken up and keep reading the received sequence data. For this set up, when UART baudrate is lower than 56000 it works fine. However when the baudrate is higher than this (e.g at 115200), LPUART read the wrong data. I'm aware that in this set-up, the first transmitted byte will be lost but the others should be read correctly.

I tried with several different transmitted data with different lengths, however the received data is always wrong. (work fine when baudrate is 56000 though).


texts: Would there be any advantages to having magnet wire with a square or hexagonal cross section? Could this allow stronger or more tightly coupled magnetic fields in electrical motors or transformers?


texts:
i've picked up some 10w rgb leds with the following specs:

DC Forward Voltage (VF):Red 5.4-6.6V;Green 8.7-9.3V; Blue 9.0-9.6V.
DC Forward Current (IF): 300-330mA

i would like to drive several in parallel from one constant current source.

do i need to match the 300-330mA current value in order to safely drive them or is getting a constant current buck converter w/enough amps sufficient?

rephrased: do you have to match the amperage value from a constant current source like you do with the voltage value from a constant voltage source when driving high power leds?

also, will they draw whatever voltage needed when being driven by a constant current source?

thank you in advance

noob edit: the "Customer Label" is DC-LE14221 but i can't find a datasheet on that id.
i have 4 of these leds in parallel...trying to make a spotlight w/a rear projection television lens (aspheric)
noob edit2: the leds are of the high power smd chip variety with a common anode that can be easily cut into 1/3s to access each color channel individually & i am currently trying to drive each channel with it's own current limiting bjt, fet, set resistor circuit.


texts: Why do designers use a series diode and zener for coil suppression rather than just a zener?

texts:
I understand the use of the Zener but what I don't understand is one topology uses two components, but why can't the other topology be used ?

simulate this circuit – Schematic created using CircuitLab

The circuit on the left uses two components (D1 and D2), whereas the circuit on the right only uses one (D3).

I can't really see a difference between the two, other than that the left might decay a bit faster because of of the higher clamp voltage, but aside from that, I would imagine they operate the same.

So why do most schematics I've seen with regards to coil suppression use a series diode zener pair ? There must be something I am not seeing or understanding.


texts: What's the smallest and lightest way to supply 5V to a 1"x1" circuit board?

texts:
I'm creating a payload that will need to be supported by a small structure. This payload contains a 555 timer which needs 5V. So far I've only found coin cell batteries and have been using a LilyPad Coin Cell Battery Holder that holds a 3V coin cell battery. On the underside of this, I've attached a 5V step-up breakout to supply a constant voltage to the chip.

This method is fairly heavy, though, and I'm looking for an easier, lighter way to supply 5V to the circuit. Does anyone have recommendations or ideas?


texts:
I am implementing a system where I need to use 2 switches, 1 NMOS and another PMOS. The switches are controlled by a PWM wave that operates at a frequency of 1MHz.
You can see in the attached figure the current that is needed at each gate. The NMOS transistor is not critical and does not require a drive, but in the case of PMOS there is a need for a gate driver but I am not able to find any that consume little (max 2 / 3mW).
Thank you!


texts: What is the danger of using ground as the return path in normal use?

texts:
I watched a video in which a man showing how to save money by only spanning a single cable as follows.

The ac current passes through the single 30 meter long cable, a breaker, a lamp, and return via the ground.
What is the danger of this mechanism?


texts: STM32F746 Clock not reporting as expected

texts:
I'm using an STM32F746VGT6 microcontroller configured from STM32CubeMX for all the clocks and I'm getting roughly 220% higher clock rates when compiled.

For instance I have an HSE crystal at 11.2896MHz with the following main PLL settings:

PLLM /11
PLLN *234
PLLP /2
PLLQ /5

I have selected HSE for PLL source and PLLCLK as System Clock Source.  Doing that in STM32CubeMX yields 120.080291MHz.

However, after SystemClock_Config(), SystemCoreClock = 265909059.

Due to that discrepancy, the microcontroller thinks it's working 220% faster than it actually is so all my timings are off by that much.

Has anyone else seen this issue and what could be the problem here? Thanks for any insight.


texts:
I am doing a dissertation in Electrical and Computer Engineer which involves supercapacitors.

I read the norm IEC/EN 62391–1 and the 60384-1 but still I don't have a clear answer for what's the electric model to be used to simulate a ultracapacitor.

It seems to be a Series-equivalent circuit. (R_leakage || C ) in series with (R_ESR-L_ESL). But if in case I intend to use this model, I don't seem to find these parameters in the supercapacitor's datasheet, only C and R_ESR.

What should I be looking for?


texts:
I am trying to make a full sine wave from two half waves wire-ORng through triacs

However, as long as the triac output terminals (MT1 for both) are not shorted, the signals seem fine. When I short the MT1 terminals, the waves, instead of combining to form a full sine, become a fully rectified sine instead, sometimes positive, and sometimes negative, randomly. Where am I going wrong? The double fully rectified waveform is seen because the two probes remained in place, so one signal is slightly below the other, but at the same point after shorting the outputs.
My signal was a 50KHz PWm signal in the circuits above, so I filtered it before sending it into the triac, as can be seen.
I could see 2 possible causes for this ocurring, the high frequency and/or a high dv/dt rate.
AFter the above attempts, in order to narrow my possible causes for the ckt not working, I did this: I eliminated the 50KHz signal, and used 230V 50Hz from the AC mains. The supply in this part of the world is horrible, as can be seen by the wave shapes, but there is no choice in the matter.
Anyway, I set it up like so

I isolated the signals by using two 6-0-6 step down xfmrs back to back. No difference in the outcome. The triacs simply pass the AC fully once the load is connected (220K to reference).  There is a half wave rectifier that works correctly before the triacs, but after the triacs are even lightly loaded, its like there is nothing there.

So, I further dropped the input voltage down by using the first 0-6 xfmr output connected to the second xfmr 6-6 end to end, to make the isolated ac about half of the AC mains. No change seen, abd the sine wave passes as though there is no circuit at all.

Finally, I just used a single 6-0-6 as a step down, and the circuit worked as intended. I once again tried the circuit with SCRs this time instead of triacs, and it worked again, at low voltages, but not at high voltages after stepping up again

My questions now are

Why am I not able to make this circuit work at higher voltages, though the devices are supposed to have minimum dv/dt ratings of 40V/uS in case of the BTA16 triac, and 50V/uS in the BT151 SCR
What basic fact am I so blindly missing, if any?


texts: How does voltage output of a solar cell increase/decrease?

texts:
I am confused on how voltage and current work in a solar cell. I know that current is affected by the amount of sunlight the cell receives from the sun, and the voltage of the cell is based on the electric field of the PN junction.

When I learnt about solar cells, I thought that voltage was constant or at least close to constant, but looking at I-V curves, voltage increases for some reason and I am not sure why. I saw a video that compared the voltage output of a solar cell at different resistors, which changed as the resistance changed, so is this why the voltage increases? Also, if this is the case, does this mean voltage is dependent on the current and resistance of a circuit (instead of current being dependent on the voltage and resistance of the circuit?) because I learnt that Ohm's law stated that current is dependent on the voltage and resistance, not the other way around.
Or am I just thinking about this the wrong way? Thanks for helping me!


texts:
In the concept of memory interfacing (cpu<=>memory), it is desirable to have two banks for odd and even addresses. The reason goes back to the history when manufacturers increased data bus width from 8-bit. So, they decided to put odd addresses on one bank and put even addresses in the even bank.

See this for more information.

            ODD                       EVEN
         D15     D8                D7        D0
        +-----------+             +------------+
  00001 |           |       00000 |            |
        +-----------+             +------------+
  00003 |           |       00002 |            |
        +-----------+             +------------+
  00005 |           |       00004 |            |
        +-----------+             +------------+
        |  ....     |             |     ....   |
        +-----------+             +------------+

However, if you buy a ROM, it contains all addresses (00000-00001-...)

With banking we are using half of the capacity for each group (odd/even). Isn't that right? That means, using two physical ROM chips for addressing/accessing the memory is the same as one physical chip which has both even and odd addresses.

So what is the benefits from using multiple banks?


texts: I am using a passive infrared sensor TMP006 to make a burglar alarm. However I notice that the data returned is not accurate enough. Are there any other ways by which I can improve my accuracy. Or should I use an ldr on which I shine a continous beam of IR light which breaks when the burglar steps in?What do commercial burglar alarms use to detect motion?


texts: Differential amplifier for current measurement

texts: I'm studying reference design from TI (pdf).This design shows the solenoid control circuit. I was interested, why a differential amplifier is used to measure the current? Why not use non-inverting circuit op-amp?


texts:
I have the following plot (please see first 2 plots below).
The asynchronous motor is working as a generator. I wonder why the slip is going negative, is it because the torque also goes negative? Like what would be the mechanism behind the behaviour? My take is that the slip is becoming negative as the torque is negative as well.

The following machine has been used to achieve equilibria:

Cheers!


texts: How to Filter Very High Voltage Power Supply Noise

texts:
Any suggestions of how to filter out this noise? Basic filter math is not working out.

I am adapting a cheap commercial HV supply (variable DC voltage up to 40kV at 10mA) for physics experiments.  The supply works adequately, but it has output noise I can’t seem to filter away.

The noise comes as regular high frequency pings at a significant percentage of total voltage.  For example (at 20kV into a 4 MOhm load), there is a ping each 18us with a maximum amplitude both up and down 6kv from the base 20kV.  The frequency of the ping is about 36 MHz and it mostly fades away after 500ns.
An RC filter (10k Ohm / 4nF) cuts this noise in half, but the results are far short of theory, and this still leaves a big spike.   The capacitors are high voltage polyester & foil caps.  LTSpice modeling with ideal components suggests that I should have a clean output, so I assume that real capacitors, resistors & wires are not ideal at this high frequency and high voltage.

Adding ferrite rings between the R and C cut it about 10% more.

Another thought I have not yet tried is to loop the HV wire a few times around a ferrite torroid and then add a separate single short-circuit loop to act as a short circuited transformer secondary. My thinking is that this would pass the DC but waste the AC part into heat.


texts: Is it possible to replace the ref pin of AD620A with a fixed voltage?

texts:
I am trying to implement the below circuit (from) without ADuC842, I will use Arduino mega2560 ADC.

the circuit generates -5V to 5V rail to rail voltages for ad620a
and they control ref voltage via DAC to adjust offset dynamically.

from the link,
To avoid output saturation, the usable gain is limited by the output swing and the maximum input voltage to the IA. With a +-5 V power supply, the output swing of the AD620 is about +-3.8 V; and the maximum input is +-5 mV plus a variable normal-mode dc offset of up to +-300 mV, allowing a maximum gain of 12.45. Here, the gain is conservatively set to 8 (+-1%), using RG = 8.45 kOhm.

I need to change how Ref pin voltage is supplied,

I have the following doubts?

if the voltage at ref pin is 5V the out swing between 0-5?

how can I get the output of ad620 to swing between 0-5V (pin 6 ad620) what voltage should I apply to ref pin

dummy doubts

is it possible to measure the negative voltage from the microcontroller ADC?

can aduc842 generate a negative voltage from DAC?


texts:
I am reading up on Thevenin's Theorem and this has prompted a few questions that I hope somebody will be able to answer.

This is the tutorial I am reading.

The circuit below is then given as an example. (I can't post images yet so the image urls will have to do, I'm also limited in the number of hyperlinks, so I'll have to remove )

The first step involves removing the 40Ω resistor and shorting all the emfs to produce this.

It then says the 10Ω resistor is in parallel with the 20Ω resistor.

If there is no connection between A and B why are the resistors not in series, to me it looks like there is only one path?

Secondly does shorting out the emfs mean removing them? Presumably if they where still connected the resistors would stop a short circuit.

Later the voltages are added back in to produce this circuit:

Is the reason it is shown to go counterclockwise because the 20V battery is more powerful than the 10V battery causing current to flow in that direction?

I'd appreciate help with any of these questions. Thanks very much in advance!


texts:
For some context, see my earlier question:
Ceramic capacitor value for an LM386N project

What I learned is that the 10k potentiometer on pin 3 (Vin) forms a voltage divider. When I carefully dial it, I find a spot where I get clean audio (the 10k pot is then at ~ 500 Ω). This is the same with the ready-made breakout board that I used for comparison.

Now the point of not using the ready made module was that I wanted to add a volume control. Apparently scaling Vin is not how one supposed to do that. If I go up or down from the spot where the audio is good, I get distortions, but never a quieter signal.

I also tried to add a pot between pin 1 and the ceramic capacitor that goes to pin 8. The datasheet has three examples:

gain 20: by default there is a 1.35 kΩ resistor
gain 50: use a 1.2 kΩ resistor
gain 200: use no resistor

I only had a 2k potentiometer and when I dial it from 0 Ω up, the signal gets a bit quieter, but I can't get it down to silence. If I remove the circuit between pin 1 and 8 to operate at gain 20, the output is pretty quiet though.

I searched the Internet quite a bit, and I probably miss something obvious. It would be awesome to get some pointers.


texts: Based on EMI RL circuit.... time constant

texts: How is the time constant for an LR circuit is determined in the case of charging, where one resistor is connected in parallel and another resistor is connected series to an inductor.


texts:
The gain of an ideal opamp is considered infinite and Vout=K(V+ - V-).
where V+ is the non-inverting input and V- is the inverting input.
The output voltage in the case of an inverting opamp amplifier is Vout=(-Rf/Ri)*Vin.
Does this means that (V+ - V-)=Vin??
If yes, then how it is possible as while calculating the Vout in inverting opamp amplifier we consider virtual shorting i'e V+=V-.
Is then Vin is approximately zero??


texts: How to convert high AC voltage generator to DC voltage to charge a capacitor

texts:
I have bought several high voltage generator which outputs AC voltage. I wish to convert this high AC voltage to DC voltage to charge a capacitor. I have tried connecting the output (10kV) to a 20kV rated diode and to a 5kV rated capacitor, all in series.
However, it didn't seem to work because the measured DC voltage across the capacitor is too low (600V). Also when I tried to short the capacitor terminals with a screw driver, I observed a small continuous spark which made me think the voltage across the capacitor terminal is not exactly DC.

Parameter:
PCB size: 5.4x1.8 cm
Voltage and current: DC 3-5V, 5A, 15W. Recommend 3.7V 18650 lithium battery.
Output pulse voltage: 0.5kv-0.8kv
Working frequency: 20khz-25khz
Arc distance: 5-8 mm


texts: How would I be able to measure the current using this setup?

texts:
What ways can I measure the current as test points on a circuit?
Would I need to add a zero ohm resistor and solder the resistor for normal operation and desolder the resistor and then place my ammeter in parallel with the desoldered resistor pads?
Does this look correct from the image?
Thanks


texts:
i wan't to measure the maximum and minimum output swing of a Comparator. I'm using the circuit which you can find attached.

However, since the Output of the Comparator (TI LM2903) is open drain, I need the Pull up. I also  need the Load Resistor to measure the output swing with a load.

To trigger the Comparator, I'm using a +-1V voltage with a given 0V reference voltage.

With the -1V at the non-inverting input I get -9.8V at the output, but with +1V I only get 4.9V because of the voltage divider (Pullup to Load 1:1).

How can i achieve a full positive output swing to nearly 10V?

Best regards


texts: The way the input source is applied to the Class AB amp, it seems that there should be no output that appear. Because when the input is positive half cycle, the diode D1 is reversed biased, there would not be an input to Q1 and Q2 is cutoff. Why is there an output?


texts: Using thermistor vs. soft starter for motor

texts: What is the advantage that complex soft starters give over NTC thermistors if one is only trying to get rid of inrush current spikes?


texts: How can I quickly and safely discharge a charged capacitor (small and low voltage; <= 42V)?

texts:
I am learning how to use capacitors (ceramic and electrolytic from 1pf - 1000uf) and am trying out various experiments using a breadboard. I am constantly adding/removing things to my layout to see what happens... but waiting for a capacitor to discharge sometimes takes a long time! The book I am currently reading (Make: Electronics) suggested to "discharge a capacitor by touching a resistor across it for a second or two". Is this safe/recommended way? Can I just hold the resistor with my fingers and touch it across both terminals?

Note: I have to admit I am a bit paranoid with capacitors after seeing pictures of exploded capacitors and resulting fallout such as melted breadboards, burnt tables and even reading about people losing fingers!

Edit: I am currently working with 1.5 - 12V though I also have some 24V stepper motors which I'd eventually like to get working.


texts: Altera Quartus detects 2 CPLD devices instead of 1

texts:
I try to program a design I made using 5M40ZE64C5N CPLD. The software side was successful and I got a .pof file without any critical warnings or errors. The problem occurs when I try to upload the design to real hardware using USB-blaster by JTAG. It doesn't work completely. I followed this diagram:

The JTAG connections to CPLD are like from this picture and go to CPLD corresponding pins 14-17. I connect GND to board GND and VTref to VCCINT (1.8V). I also connect power pins 3.3V and GND to Arduino UNO clone. There is only 5M40ZE64C5N chip, 3.3V -> 1.8V voltage regulator and 2x 1uF caps on this board at this moment and absolutely nothing else
As I said, the board doesn't work at all. Quartus throws "Can't access JTAG chain" error. However once I try to run JTAG debugger then things get interesting- it detects 2 devices instead of 1. Here are full logs:
Info (209060): Started Programmer operation at Fri Feb 26 14:41:53 2021
Error (209040): Can't access JTAG chain
Error (209012): Operation failed
Info (209061): Ended Programmer operation at Fri Feb 26 14:41:54 2021

!Error: JTAG chain problem detected
!Error: TDI connection to the first detected device UNKNOWN_FE000001 might be shorted to GND
!Error: The TCK and TMS connections to the device before the first detected device UNKNOWN_FE000001 might have a problem
!Info: Detected 2 device(s)
!Info: Device 1: UNKNOWN_FE000001
!Info: Device 2: UNKNOWN_2000001

When I check connections with multimeter, nothing is shorted to GND, VCC, together or anywhere else where it was not supposed to be. The chip was soldered using hot air and looks fine. Everything looks like the cleanest job ever with best connections but it doesn't work. 3 different PCBs show the same exact result. Please give me some advices because it starts to drive me crazy... Many thanks in advance!

UPDATE: here's the diagram of the essential section. There is nothing else on this board anyway at this moment


texts: Why does USB signaling to microcontrollers need resistors

texts:
I'm currently trying to make a USB device with the ATMega16U2.

On page 187 of the datasheet, there are unspecified resistors between the USB port and the pins of the microcontroller

The Arduino Uno (R3) similarly uses these resistors in its design, with a value of 22 Ohms.

What are these for, and why are they needed with such low values?

Bonus question: The wiring between UDP, UDM, D+ and D- in the figure on page 187 is a mistake, right? On the next page, they are reversed.


texts:
I'm working on a Silicon labs MCUs. Few of it's MCU requires JTAG while few requires C2 interface for flash programming and debugging. Below I've uploaded a image for JTAG & C2 Interface. And it's been the same adapter used for both the interface.obviously they are compatible. JTAG interface I understood clearly but for C2 interface I have doubts regarding their pins connections.

I went through adapter's user's guide(page no 2) for better understanding, where it states 2 pins as C2CK & C2D pin share. I didn't understood what you mean by this and how this resistive network are used for C2CK & C2D pin sharing? Because no such circuit diagram(resistive network for C2 interface) is given in user's guide. And when I studied about C2 interface from other sources, it was mentioned only about C2D & C2CK & nothing about such pin sharing.

Another thing, TCLK(CLOCK) & TDO(Data out) of JATG is share by C2D and TMS(mode state) & TDI(Data in) are shared by C2CK. can someone actually explain what is actually happening here?

So my question's are-

How would we understand C2CK & C2D pin sharing means such resistive network?
How C2 & JTAG interface are made compatible with this design? (P.S. I'm not sure about this question as I did not understand it completely or I can just assume both the Interface are compatible with this design)


texts: How in detail does a teleprinter system work? I am aware that many teleprinter used the Baudot code to relate alpha-numeric symbols to a sequence of 5 bits. What is the mechanical means by which a letter inputted in the type-writter machine on the sending end results in a signal being interuptted according in the corresponding Baudot sequence. And what is the means by which such a signal can be recieved by a machine and then converted to the corresponding letter (which is then printed on a tape, I believe). Also can somone please clarify how exactly start and stop bits are used to signal transitions between letters/words?


texts: How do I get VCC and GND pins on a PCB using an Eagle schematic?

texts:
I've just started learning EAGLE and I've been trying to make a PCB to mount some LEDs on. I read through a few online tutorials, and I believe I have (correctly?) made the schematic in EAGLE.

But when I error check, it gives me 2 warnings. There is only one pin on net VCC. One is where the VCC connects to the net and the other where the same net connects to the resistor. I can't seem to find any information on what the issue is or how to fix it.

When I switch to the board layout, I only have the resistor and the two LEDs. How am I supposed to get the VCC and GND pins on the board? Are they even supposed to be there? All the tutorials I've found online include some part with included voltage and ground pins so the entire package shows up on the schematic.


texts:
So this is my first post so please forgive me but inform me if I'm breaking any forum rules.

I'm trying to layout a through hole HDMI connector in Eagle. The issue I'm running into is that the gap between the trace and the pads it passes between is too narrow. If you have any tips or suggestions of things to try that would be so helpful.

Thanks!

Here is a link to the part drawing:
https://www.amphenolcanada.com/ProductSearch/drawings/AC/MHDRA111XX.pdf


texts: How is a NFC "connected tag" different from a full blown NFC reader?

texts:
I have played with NFC in the past, but those were full blown "NFC readers" based on NXP pn53x chips.

I want to know, how is a so called "Connected tag" different from NFC readers?

I found this chip from NXP on mouser, and while reading the specs it looks a lot like a reader. But the reader ICs like pn53x family are much more expensive, so what is the difference?


texts: Altium 18 PCB Filter Select X *except* if Y

texts:
I'm trying to create a PCB filter that will allow me to select everything on the board except for components that have an 0402 or 0603 package size. We have a parameter in our passive parts called "Package" which can be '0402' or '0603', so this would be a perfect way to isolate these components.

I can easily select these using this filter query:

HasParameterValue('Package','0402') And HasParameterValue('Package','0603')

However, if I try to invert this, it selects everything on the board, including the 0402 and 0603 components. I assume this is because the Not operator does not invert the results returned by HasParameterValue()...

Since we have a lot of footprints that are 0603 and 0402, and since these could change in the future, I don't want to specify a long list of Footprint = 'blah0402blah'. So I tried:

Not (Footprint LIKE '*0402*')

The Not has the same effect here. I attempted to do "Not LIKE" but that is not syntactically valid.

Does anyone know of a way to remove or except results of the query based on Parameter values or a similar method?

Edit: @LoganF
I have tried it with various paranthetical combinations. Just tried it like this to no avail:

(Not HasParameterValue('Package','0402')) And (Not HasParameterValue('Package','0603'))


texts: Detect presence of Passive HF/LF RFID TAG with BT 4.0 (NFC not supported)

texts:
Trying to understand if with current capabilities of Bluetooth 4.0 / Smart / BLE, is it possible to detect a passive RFID TAG, within a very short range (less than 5cm).

New phones both Android/iOS are to abandon NFC as far as I know, so does this mean that Passive tags are just no longer supported on these phones?

To be more precise: I am not looking for anything fancy.. In fact I just need to be able to detect the presence of one passive tag. No security or anything more complex.

Also, not to imply that this question regards specifically existing TAG product, also it would be nice if there is. I am willing to develop a new circuit, if that's possible...


texts: Defined LM339 behavior when the (+) input is floating

texts:
I was troubleshooting a charge indicator circuit on a tire inflator/flashlight. The green LED is supposed to light up if the battery voltage is above a certain voltage level. The LED is connected to one of the outputs of an LM339 Quad Comparator. The corresponding (-) input to that output was connected to the circuit tracing back to the battery, but the corresponding (+) input just seemed to be floating. I couldn't see any traces off of that pin going anywhere. According to the 339's datasheet, output will go HIGH (with a pull-up resistor) if the (+) input voltage is higher than the (-) input voltage.

My question: With the LM339, if the (+) input is floating, does the IC have a set percentage of VCC to "make" the (+) input?

I'm not a pro at searching through datasheets, so maybe the answer is staring me in the face and I just missed it. I am as sure as I can be about that pin not being connected to anything on the PCB, though.


texts: what will happen if an optocoupler output is connected to AC?

texts:
What will happens to the output of an 4n25 if the final user by mistake wires an AC current (12 V . AC)?

Will This destroy the transistor?

I can't find this condition in datasheets.


texts: Building NOT gate with transistor -- output remains always high

texts:
I'm following this tutorial to build a NOT-gate using a transistor (using slightly different parts).
The issue I'm seeing is the following: when no voltage is applied to the base of the transistor, then current flows, normally, through the path including the collector (as it should). However, when voltage is applied to the base, then current still flows through the path of the collector (should not). In other words, I always get high output, no matter what.
Question: I would like to find out is what I'm doing wrong, or what is wrong with my (still very limited) understanding of how the circuit should work.
Summary of what the tutorial says (in case the link dies later)
This is the circuit we are trying to build:

simulate this circuit – Schematic created using CircuitLab
This is how it is supposed to work (in my understanding):

If SW is open, then current flows like this: +6V -> R1 -> LED1 -> GND
If SW is closed, then current flows like this: +6V -> SW -> R2 -> B->E -> GND (In other words, no current flows through R1 and LED1).

Circuit I built
My circuit is slightly different, because I have different parts (in particular, I don't have any jumper cables yet), and also because I added some extra leds to try to "debug" the problem. I realize that these extra leds add more resistance (and previously I was using real resistance, where tutorial said to use a jumper cable), but I'm not sure if that matters or not.
This is the circuit (I think) I built:

simulate this circuit
And this is what is happening:

When SW is open then only LED3 is lit up (as expected)
When SW is closed then all three leds are lit up (LED1 and LED2 should be, but LED3 should not). In other words: the base has voltage (because LED1 is lit up), the current is flowing through B->E (because LED2 is lit up). However, the current is still flowing through +9V -> R3 -> R4 -> LED3 (because LED3 is lit up -- it shouldn't be).

(N.B.: I was seeing the same problem even before adding the extra "debugging" LED's, i.e. LED3 was always lit up, independently of the state of the switch.)
Pics of the board
Open switch:

Closed switch:

Research
This answer (to the related question) seems relevant.
In particular:

What you have done is connect the emitter to ground, and the collector
to ground via a resistor. You have then applied a voltage to the base.

Yes, I did the same, with the exception that I connected the emitter to ground through a resistor (either the LED2 or the 220 Ω resistor I was using before due to the lack of jumper cable -- I'm not sure if that matters, though).

However in your case, the collector is not at a higher potential than the base, it is at a lower potential. [...]
You now have current flowing from the base to the cathode, through the resistor to ground, thus the mysterious current flow is identified.

Could this be the reason in my case too?
I don't know how to calculate the potential at the collector, and at the base, but I compared my circuit to the one of the tutorial, and these are my conclusions:

The voltage of the battery is higher in my case (9 V vs 6 V), but I don't think it matters.
The resistances are lower (440 (=220+220) Ω vs 1 kΩ), but they are the same on both branches. (I.e.: tutorial has 1 kΩ both on collector and base, I have 440 Ω both on collector and base).
Also, I tried to increase the resistance for the collector, to 880 Ω (with two extra resistors), still the same result.

One more thing: I'm fairly sure that I connected the transistor the right way, but I tried the other way round too, just in case (same result).


texts: Why is the output voltage of this circuit is changing in simulation?

texts:
Circuit 1:

Circuit 2:

The only difference between Circuit 1 and Circuit 2 is`that in Circuit 2 a parallel 2.2k resistor R8 is added as a load next to R6.

Why adding this R8 is halving the output voltage here?

I tested this in real with a scope, and the voltage remains at 12V pulse when I add R8. So unlike in simulation R8 didn't change the output voltage. In real implementation the grounds of the input side and output side are isolated.

edit:


texts: Very hot mosfet when powering an led strip

texts:
I'm basically following this instructable which is using an arduino to control an rgb led strip.  I have wired it up exactly as shown, although I didn't use a breadboard i just soldered everything.

I'm using an old laptop power supply that's 12v 5.83a, and for the mosfet I'm using irf530n.  I've noticed that when red is full power the mosfet that's connected to the red led gets really hot after a few minutes of being on. It seems to only be affecting the red one, even if i have it on full white only the red one is hot. The other two barely get warm.

Are the mosfets supposed to get that hot?  Why does it only get hot on the red side?  Are there mosfets out there that are better suited for this application?  Are there any ways to reduce the heat?

Thanks for any help!

Edited to add a schematic:


texts: Concurrent central and peripheral mode with BLE

texts:
I'm having an ARM M3 which I would like to connect on one hand to a smart phone for data visualization and to two sensors for data acquisition on the other hand. Both connections should be BLE.
My understanding is that this would require concurrent mode (central to peripheral), where peripheral is required to talk to the smart phone and central to talk to the sensors, correct?

I have a BLUENRG-132 from ST around but could find any information regarding concurrent mode. Is this normally supported by these devices or do I have to implement some kind of switching myself? Or isn't possible at all?


texts:
Hello. I have one question to solve, but I have no idea about calculating bandwidth and converting time domain into frequency domain.
Can you give me a hint?


texts:
I'm working with Eagle 7.7.0 and trying to import SVG files using svg2poly to put a logo on the silkscreen. To aid in the process, I've downloaded the current version of Inkscape, which is 0.92.  I'm working from a combination of the instructions on the GitHub site and this tutorial from SparkFun.

The short version of the problem is that I can import shapes just fine, but any text in the SVG file is either muddled beyond recognition or missing completely. I've tried different fonts, including the default sans-serif, and different sizes.  I followed the instructions for breaking the closed-loop letters into multiple open shapes, and that had no impact. As an ultra-simple case, I tried to import an SVG that was just a lower-case 'l', which is essentially just a rectangle in sans-serif, and even that did not work. (Came out as a triangular shape.)

The only things that I see that are different between what I'm doing and what's published:

I'm using the current Inkscape (0.92) and the instructions are for "Inkscape 0.47 or newer".  Are there any known problems for with the newest version?  Is there perhaps some trick to making text work that's not documented?
I'm drawing / typing my examples directly in Inkscape, whereas some of the online guides talk about importing SVG that was made with a different program.

More detailed description of steps for the simple case with just lower-case 'l':

Open Inkscape.  Make text area and type lower-case 'l'. Change font size to 72, but leave font as sans-serif.
Select all layers (ctrl-alt-a). Click the lock button to lock height/width ratio. Change units to mm and set height to 100.
Under File > Document Properties... select Resize page to content drop-down and click Resize page to drawing or selection.
Convert object to path (shift-ctrl-c). Ungroup (shift-ctrl-g).  Repeat ungroup a few times. (For this simple case, nothing seems to ungroup.  When I had a whole word there in an earlier trial, the individual letters each became their own entity.)
Select all nodes (F2 followed by ctrl-a). Select Extensions > Modify Path > Add Nodes leave defaults and click Apply.  Select Extensions > Modify Path > Flatten Beziers leave defaults and click Apply. (Neither of these steps made any obvious change for the single 'l' or for larger cases with whole words.)
The single 'l' has no closed loops, so I skipped the related steps for that. (When I had whole words, I did follow these steps.)
Export as "Plain SVG" using Save As from the File menu.
In Eagle, type mark and click a location.
Type run svg2poly 0.1 and select the file created above.
Observe result.  In this case a triangular shape instead of an 'l'. (Again, it's sans-serif so the original was basically a rectangle.)

In some cases with more text, I got apparently random polygons.  Maybe a few looked vaguely like letters.

Are their known issues with svg2poly and newer versions of Inkscape?  Are there undocumented tricks that I need to make this work?


texts: Understanding the oscillation action inside this 12V DC-to-AC CKT

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A friend brought this circuit to me and asked me to explain the working.

I decoded the following schematic from the PCB.

simulate this circuit – Schematic created using CircuitLab

In the primary coil of the transformer I measured about 19KHz 14VAC. I am unable to understand how oscillation is being produced in the circuit. C1 and L1 looks like a tank circuit but I don't see how its oscillations are being fed to the PNP transistor and a specific feedback path.

Kindly help me decode the working of this circuit.

EDIT: It seems I mistaken the transformer primary winding taps to be short in my description. So the transistors are not short circuit or parallel.