texts: Why is the MOSFET driver in this circuit dying?

texts:
This circuit kills the driver (an IR2104s) when under normal conditions.
Bat+ goes to a 12V lead acid battery.
In+ goes to a 20V laptop power supply, though it is intended to be a solar panel instead.

The circuit takes Vin, passes it through a SMPS with two MOSFETS (driven by the ir2104 that dies) and into Bat+. The LM321 is just a latch that allow the MCU to control and read the ir2104). The connector in the left comes from the MCU, the right one holds the power lines.
PWM(PWM signal for the 2104) CS (current sense pin, for safety -it can stop the ir2104-) SHDN (a shutdown signal)

Using a purely resistive load instead of the battery works. Then the battery is connected and the driver gives up. The MOSFET doesn't die, though. This using a current-limited (to 30mA) power supply.

There is a power regulation loop (that feeds the PWM that goes into SMPS_PWM) which is not really good or responsive (it is a very simple ramp algo), but even then, why would the driver die?
My guess is that there's a voltage that goes too high in the wrong pin, but how or where?
One running theory is that, if the PWM were to be 100% you'd have an upper MOSFET that's permanently closed, and that'd be a problem, but I don't see why? (and sure a 100% duty cycle won't work in a charge pump driver, but that should affect the MOSFET, not the driver...)

Some misc data:

The driver dies very quickly (before any heat is noticeable) but builds heat until unplugged
The power supply is a laptop-type SMPS.
This same setup supposedly works with a solar panel, could it be some detail on the supplied power makes it break?
The MOSFETs are not broken in any visible way. Could a MOSFET bridge so it would kill something through its gate at a high voltage but look okay when testing?

NOTE: I found a document from Texas Instruments that, in page 9, deals exactly with the issue and provides a number of solutions and trade-offs.


texts:
I have 3 devices on SPI: Atmega328P, ZM5202 and flash with CS.
When I connect Reset of Atmega to GND I cannot talk with other ZM5202. And then I am reading id of avr also.
When avr programming:
AVR Reset -> reset of programmer
ZM5202 Reset -> Gnd
CS -> high
Result: OK

When Memory programming:
AVR Reset -> Gnd
ZM5202 Reset -> Gnd
CS -> low
Result: OK

When ZM5202 programming:
AVR Reset -> gnd
ZM5202 Reset -> programmer reset
CS -> high
Result: NOKbut

When ZM5202 proramming:
AVR Reset -> floating
ZM5202 Reset -> programmer reset
CS -> high
Result: OK
In programming cycle I can set timings:
I switch on the power for 100ms then 100ms off and after that on again for programming routine.
Do You have idea why AVR is not in reset when Reset pin connected to GND?
Fuses are not blocking ResetPin. They are low:FF, high:DA, ext: FD


texts: what is the function of pre-emphasizer and dee-emphasizer in Stereophonic FM Receiver?

texts:
what is the purpose of theses two block ?

I know that pre-emphasizer will  boost the high frequencies before transmission and dee-emphasizer will reducing them by a corresponding amount in the receiver

But is it important in the Stereophonic FM Receiver ?


texts: Wire capacity - Total power or just current?

texts:
So I've gotten myself into a healthy, educational Facebook discussion. Link is here if you're a member of that group.

When I thought about it, everyone defines wire capacity by current only. The voltage only comes in when talking about wire insulation.

However, I've always thought about a wire's capacity by total power transmitted, not just the current.

Assuming arcs and corona discharges aren't a problem, could I transmit say 10 kW via a #40 AWG wire at 10mA, 1MV DC? The ampacity isn't violated, but that doesn't look right for wire that's around the width of a hair.

I'm aware of the math behind it (5th year Electronics engineering student) and I can judge what voltage/current I need for X watts versus safety/other constraints, but wires being rated by current only hasn't bothered me up until this point.


texts: Moving from ICF in-amp to traditional in-amp, removing bridge offset, driving ref pin with shunt regulator

texts:
Right now im using AD8237 with MCP4725 to remove bridge unbalance. I'm using 3x 1k Ohm resistors and one strain gauge arranged in Wheatstone bridge.
My circuit looks like that:

It works perfect for me, but I came across two problems:
-Availability of AD8237,
-Need more samples / sec.
That's why now I'm thinking about moving to traditional in-amp like AD8421.
I came up with such circuit:

I don't have enough PCB space to drive in-amp Ref pin with Op-amp, and there comes first question - can i drive that with shunt reference? I't has low impedance of less than 1 Ohm, so it shouldn't be a problem?
Then I've cut half of bridge and replaced it with Reference voltage + DAC output voltage with two not-yet calculated resistors.
That do You think about it? Will it work or not?


texts:
I Have a 16GB Wi-Fi SD HC Card from Transcend.
I try to initialize the card via SPI using an Arduino Uno, sending

CMD0, arg: 0         , CRC: 0x95
response:0xFF

but the expected response is:

0x01

When i try the same process with an 2 GB SD (no SDHC) card, the response is:

0x01

as expected. So the initialization process itself can't be the problem.
Here you can see the Timings of the 2GB SD card analyzed with a logic analyzer:

Here you can see the Timings of the SDHC card analyzed by a logic analyzer:

The strange thing about it is, the SD card acts as expected using:

Mode 0 (CPHA=0,CPOL=0)

So the MISO value is always stable at the rising edge as i expected it to be: (Using MMC/SDC)
On the other hand, the SDHC card doesn't behave like this, and this might be the reason why the initialization process fails. The SDHC card seems to work in Mode 1 , so the MISO value is always stable at the falling edge.
Why is the SDHC card not running in mode 0, as I expect it too?
Update:
I am using the sdfatlib which is waiting the required 74 clock cycles.

// must supply min of 74 clock cycles with CS high.
for (uint8_t i = 0; i < 10; i++) spiSend(0XFF);

And also the recorded behavior shows that there are more than 74 clock cycles until CS is set to low to send the init command.

Pulses: 79 ( up: 79, down: 80)


texts: Why did my 12v battery charger blow, when connected to a 12v battery in a 48v bank?

texts:
this is a puzzler here. I have a 48V bank of Battleborn lifePO4 batteries connected to a huge 10kva inverter.
When I tried to charge one of the 12v batteries while the pack was still connected to the inverter, the charger went berserk immediately, I don't understand why this happened.
When I had LEAD ACID batteries (same 48V bank), connected to a smaller inverter, I used to be able to charge any of the single 12v batteries while the bank was still active on the inverter. So, lets say the inverter had finished charging and the pack wasn't balanced, I used to be able to just pop on the 12v charger to bring up the lowest in the pack without having to disassemble anything.
Why can't I do that now? It's a simple series connection, but could the fact that it's a huge inverter be playing a role?
The batteries are wired to a start cap before the inverter, I believe it's called a CLS500 and the negative is wired to a grounding rod buried underground.
For those reasons, I just don't feel comfortable having to disconnect the batteries every time i wan't to balance them out.
Please someone explain to me why I can't charge them individually while they are still connected. I can't afford to lose my new charger to the same failure as I am in Nigeria and it will take ages to get a new one if I mess this up.


texts:
I want to solder a wire onto this metal contact, but the solder wont flow into the contact. I have my soldering iron on 300 degrees Celsius using a chisel tip using 60/40 rosin core solder. I sanded the metal contact because it was corroded. I kept the soldering iron on the metal contact for 10 seconds to heat it up, but it still does not work. I have tried using Rosin Core Flux Paste.

What should I do now?

Edit: I increased the temperature to 400 Celsius and now the solder is melting on the metal contact, but it balls up onto the metal instead of flowing.


texts:
I want to power STM32F429 Vbat pin with an existing Lithium Ion battery on board. However, the maximum voltage on the discharging curve of this battery is 4.2v which is above the maximum operating voltage of the Vbat pin(3.6v).

My question is can I directly connect the battery to the Vbat pin, or should I use the voltage divider to divide the battery voltage into a suitable range? If I have to use the voltage divider, is there any problem if I simply use two resistors to divide the voltage?


texts: BJT based mosfet driver, what resistor values to use?

texts:
I designed this MOSFET driver for a 24V motor with parts I have in my junkbox:

The idea is basically Q2 and Q3 make a push-pull driver to drive the MOSFET gate to 0 or 24V. This allows the use of a low value resistor for the gate so it can be charged and discharged very quickly.
Q2 and Q3 bases are held up by R2, or shorted to ground by Q1. This allows the use of a 5V PWM signal to drive the high voltage switch. R4 just keeps the base tied to GND so it's not floating.
Is this a good design for this application?
Are the resistor values reasonable?
I think R3 may be a little larger, maybe up to 100 ohms to prevent destroying the gate, but at the same time, avoid negating the use of a push-pull driver. R2 provides a base current of 2.4mA to the transistors which is within the acceptable (<100mA) base current for BC8x7. The collector current of Q2/Q3 is hard to estimate and depends on the real gate charge of the MOSFET
Finally, R1 provides around 1mA of base current for Q1 which is more than enough for the collector current of 2.4mA


texts: ft24c02a EEPROM Raspberry Pi I2C issues reading

texts:
I have a digital scale that I am trying to take apart and feed the weight into a raspberry Pi.

The digital scale has a FT24C02A EEPROM that is I2C enabled. I am guessing that the weight is calculated / stored in the registers on the EEPROM. For some reason, I am  just not able to get the information out of the registers correctly.

It is the 8 pin version listed on digikey as...
https://media.digikey.com/pdf/Data%20Sheets/Fremont/FT24C02A_Rev_Dec_2010.pdf

I have I2C installed on turned on in the Pi configuration manager.

I am hooking up to the SDA and SCL pins on the FT24 by hooking them directly up to the SDA and SCL pins on the Pi (I do not have the ground on the FT24 and Pi connected).

I am able to run the I2CDetect command on the Pi and see the FT24 on registers 50-57....

But when I try and read those registers, via byte or word, they are just filled with fs (FFFF).

What am I doing wrong? I searched on line and there a few "tweaks" you can make to your Pi configuration but none of them worked for me so I dont want to mention them here.

Am I looking for the weight in the wrong place? It should be stored in the EEPROM right?

P.S. I know there are breakout boards that allow you to just hook the load cell up directly to your Pi, but I want to utilize the scale as is and just pull the digital readout from the scale itself.

Attached is an image of the PCB.


texts:
I'm using an Arduino to drive two hobby servos but they draw too much current when not in use so I'm trying to use a transistor as a switch to cut the power to them when not needed.

simulate this circuit – Schematic created using CircuitLab

I've tried using the transistor both high and low side with no luck. The peak current of a 2n2222 is only 600mA so I tried a TIP 31 that I had lying around as well with no luck either. The circuit has enough power to drive the servos when the transistor isn't used but when inserted into the circuit I can hear them humming when they're supposed to be activated but there's not enough power to turn them. If I put my multimeter probe from the emitter to ground there's only 2V drop, rather than the 5V from the battery.


texts: Piezoelectric component connection circuit

texts:
I have a question about piezoelectric component and microcontroller connection circuit.

I use 7BB-20-6L0 Murata piezo.
Here is the datasheet - Link

Here is my current variant:

Is this schematic correct and safe?
Are all this components necessary? (Is there any need in D1 and R2?)

And one more moment...

I'd like to use two MCU pins to increase the voltage level:

What should be done in this case in order to get maximum safety?

Thank you in advance!!

Update:


texts: Which microcontroller for a program with many floating point operations

texts:
I'm using the STM32 uC for quite a long time, from F1,F2,F3,F4 to F7. In one application I changed from the F4 (100 MHz) to the F7 (200 MHz), but this seems like it was a mistake.
The application run on the F4 with around 15kHz, on the F7 with around 12 kHz, although the F7 runs on double the clock speed. So it seems, that the two processors have different FPU architectures and as I read, the F4 has some parallelism for the FPU while the F7 can only do sequential operation.
So is it true, that for an application with heavy FPU load, an F4 outperforms an F7?
Edit:
So I made some measurements on real hardware to verify my toughts:
Hardware: STM32F722RC vs STM32F412CE
Programm: Just some FPU operations as used in my application
  for(uint16_t i = 0; i < 2000; i++)
  {
      if(x > 6)
      {
          x = 0.1f;
      } else if (x < -6)
      {
          x = -0.1f;
      }
      x = x + 0.05f;
      x = x + sinf(x)*cosf(x);
  }

  cyclic_time[ptr] = htim6.Instance->CNT;
  cyclic_time[ptr] /= 1e6f;
  ptr++;
  if(ptr >= 20)
  {
      ptr = 0;
  }
  htim6.Instance->CNT=0;

Performance F4:

At 100Mhz:

--> So an average cycle time of around 7.365ms
Performance F7:

At 200Mhz:

At 100Mhz:

--> So an average cycle time of around 9.954ms @ 200Mhz best case (I verified, that in both cases the timer runs on the correct clock speed, 100Mhz and 99 Prescaler, such that the measurement is correct)
So that is exactly what I observed in my real application. Somehow the F4 outperformance the F7 when it comes to floating point operations.
Edit2:
Compiler Options F4:

Compiler Options F7:

Edit3:
To ensure, that the optimizer is not a problem, I tested the cycle time with the optimizer enabled on speed:
F4:

--> Around 6.44ms
F7:

--> Around 8.344ms
So this leads to the same problem.
Projects for F4 and F7:
http://www.mediafire.com/file/lljhgsez4xk9vat/Test_Projects.rar/file


texts:
I am getting started in electronics/robotics by making a Raspberry Pi robot. I have a (somewhat) working prototype but realized that I need to have a single rechargeable power source. Currently, I have the Pi, sensors, and two servos working out of a 3.7V battery that is connected into a PowerBoost 1000 DC-DC boost converter. I am aware that powering servos off the Pi is not ideal--I plan to change this layout in the next design.
The robot also has two DC motors that are connected to another source, a 5 AA battery pack that feeds a L298N Motor driver. I made a diagram to illustrate the current setup:

I thought of using the built-in voltage regulator in the L298N to feed the Pi and sensors/servos but from what I understand, this is a linear regulator which is inefficient.
I really need to add into my design something similar to the PowerBoost charger that allows me to supply power to all my components, use a single battery pack, and that is rechargeable (via USB).
Assuming everything is being powered with 5 volts, I roughly estimated the power usage:

Pi Zero W (no display, no bluetooth, Wi-fi, camera connected): ~120mA
2 x TT Motors (155mA no load, 1.2A stalled): ~1.2A
2 x SG90 9g Servos (10mA Idle, 360mA stalled): ~360mA
HC-SR04 ultrasonic sensor: ~15mA
Pi Camera 1.3 (100mA Idle, 240mA recording): ~170mA

That's around 1.865A@5V, so around 9.3W? I need a battery that could handle this load, with some extra headroom just in case, and is easily rechargeable without removing the battery from the robot. I don't expect all components to be powered on at the same time though.
Any suggestions/feedback is appreciated.


texts: Use Xilinx Primitive elements in Verilog inside ISE

texts:
I generated Verilog Post-Route simulation model of my original Verilog module, using Xilinx ISE. It will generate a Verilog module using LUT and fpga level primitives such as IBUF,X_LUT4, ...
 When trying to compile this code directly and synthesis it inside ISE itself, it cannot find Xilinx primtivies and assert compilation error such as ERROR:HDLCompilers:87 - "test.v" line 26 Could not find module/primitive 'X_OPAD'. I want to know how can I include related modules/libraries inside ISE verilog code to avoid compilation errors.
Part of code is brought below:

module tripler (
  TRIPLED_OUTPUT, INPUT_SIGNAL
);
  output TRIPLED_OUTPUT;
  input INPUT_SIGNAL;
  wire INPUT_SIGNAL_IBUF_23;
  wire GATE3_OUT_0;
  wire GATE1_OUT_0;
  wire GATE2_OUT_0;
  wire GATE4_OUT_0;
  wire GATE5_OUT_0;
  wire GATE6_OUT_0;
  wire \TRIPLED_OUTPUT/O ;
  wire \INPUT_SIGNAL/INBUF ;
  wire GATE3_OUT;
  wire GATE1_OUT;
  wire GATE2_OUT;
  wire GATE4_OUT;
  wire GATE5_OUT;
  wire GATE6_OUT;
  wire TRIPLE_OUT;
  wire VCC;

  X_OPAD #(
    .LOC ( "PAD1" ))
  \TRIPLED_OUTPUT/PAD  (
    .PAD(TRIPLED_OUTPUT)
  );
  X_OBUF #(
    .LOC ( "PAD1" ))
  TRIPLED_OUTPUT_OBUF (
    .I(\TRIPLED_OUTPUT/O ),
    .O(TRIPLED_OUTPUT)
  );
  X_IPAD #(
    .LOC ( "PAD2" ))
  \INPUT_SIGNAL/PAD  (
    .PAD(INPUT_SIGNAL)
  );
  INPUT_SIGNAL_IBUF (
    .I(INPUT_SIGNAL),
    .O(\INPUT_SIGNAL/INBUF )
  );
  X_BUF #(
    .LOC ( "PAD2" ))
  \INPUT_SIGNAL/IFF/IMUX  (
    .I(\INPUT_SIGNAL/INBUF ),
    .O(INPUT_SIGNAL_IBUF_23)
  );
  X_BUF #(
    .LOC ( "SLICE_X0Y13" ))
  \GATE3_OUT/XUSED  (
    .I(GATE3_OUT),
    .O(GATE3_OUT_0)
  );
  X_BUF #(
    .LOC ( "SLICE_X0Y13" ))
  \GATE3_OUT/YUSED  (
    .I(GATE1_OUT),
    .O(GATE1_OUT_0)
  );


texts: Difference between RSSI and Received Power

texts: Is Received Power and RSSI same thing? I have been looking into it and think they are the same. But please guide me the difference between them if they are not the same.


texts: Something I don't understand with electricity and my circuit

texts:
My title is strange, but my circuit is acting weird and I hope someone can explain me this strange behavior.

I have made a simple circuit with an ATmega which send output to the TX pin, and my USB to serial is receiving the data. The TX output is only working when I touch some metallic part of my circuit. The rest of the time this is not working.

For example, if I touch any of one of my LED pin, or one of the capacitor pin, a resistor or even my voltage regulator, my circuit is actually working great. If I stop touching it, it doesn't work anymore.

Here you can see the picture of my circuit, and the second image when I touch the voltage regulator, the RX LED of my FT232R is blinking, at the same rate at the TX data. (I send data each 100ms).

I have already checked the source voltage, and it is a nice 5V. My FT232R is sourced from the USB of my laptop and the only connection to the circuit is from TX pin from ATmega to his RX pin.

If I post the question, is that I have actually no mean to explain that. The fact is the circuit should work of course without my body. I have tried to change the source voltage to 3.3V and this is the same behavior.

Can someone can explain me what to do in order to make my circuit working? If I reset my FT232R (unplugging / replugging it), it works as expected few seconds. But after nothing happens at all.

This makes me very perplexed.


texts:
I have a project that I want to power with a single cell lithium ion battery, which is to be charged from a USB plug (but not from a laptop or computer, rather from a wall supply like a phone charger). I have been researching charging circuitry, and found the MCP73833.  I was going to impliment it as follows:

The switch is a double pole double throw (DPDT) switch. That way, with the switch configured as it is in the picture, the battery is being charged and is disconnected from the load, while the load is being powered by the external supply. With the switch flipped, the external supply will be disconnected from everything and the battery will power the load (through the boost converter to reach 5V).

I then discovered the MCP73871 which seems to automatically switch between the battery and external supply. It seems like a better (more simple!) method of implementing this charging circuit, however I am concerned that if the system load draws fluctuating current, I have heard it may affect the life span of the battery. I am also unsure from the datasheet of the MCP73871 whether the system load voltage (on the OUT pins 1,20) varies whether the external supply is plugged in (i.e. when the USB is plugged in is the load voltage 5V and then when the USB is disconnected the load voltage drops to 4.2V down to 3.7V as the battery is discharged). I'm guessing this doesn't matter however, as I can just use a boost converter again to bring the voltage back up to 5V. Using my circuit with the MCP73833 as shown above the system load always receives 5V.

I am also concerned that as per the MCP73833 datasheet the maximum charging current with USB is 450mA. The Li-ion cell I am using is 3450mA so I would like to be able to charge it up to about 1.5A (~0.5C) which is a current I know is possible with USB phone chargers.

Are there any advantages and disadvantages to either the circuit I made or just using the MCP73871? This is my first time dealing with charging circuitry so want to make sure I get everything right. I am leaning towards using the MCP73871 but want to make sure I understand fully the benefits before making a decision.

Thanks in advance.

EDIT: I don't have a circuit decided for it, but if I decide to use the MCP73871, I will probably be using it in a very similar configuration to the Adafruit Powerboost 1000C

EDIT2: Another question about charging circuits, both of these ICs (as well as many other charging ICs) have a pin for a thermistor to limit current if the battery is heating uup too much. I would like to implement this but can't find much about how to go about it, do I just put the thermistor as neer as possible to the battery? Does it need to be touching it? Thanks again


texts: Multiplex Analog pin and digital pin on single pin

texts:
I have to manage one single analog pin with other digital IO.
I am using a PIC micro, where I have utilized all the pins and I want one more pin for analog input. At the current stage, I can not really afford a new controller design for my project.

I have assigned 7 pins for 7 segment and the other pins are assigned to LEDs, which is a must.

I am looking for multiplexing circuit design (using transistor or something) where I can multiplex analog input and digital output in the design.

I will be connecting an LDR to the analog input.


texts:
If I buy a transceiver module with CC2530 like this one and a programmer for it like this one is there any readily available firmware for the chip or will I have to write the firmware myself?
If available is it free or do I have to buy it from TI or a 3rd party?


texts: Determining the resonant angular frequency

texts:
I am facing trouble with finding out the resonant angular frequency of the above circuit.I know that at resonance impedence of the circuit is minimum.I am new to this topic and I tried to find out the impedence of each branch and then to get the minimum,but I failed..

I tried differentiation after this but it is not giving the correct answer.
tAny way to solve such questions will be highly appreciated.Thanks.


texts: Using a lipo charger AND discharger at the same time

texts:
I'm looking to use a li-po in my project, I can find many battery charge modules, and many 5v boost modules, is it possible to use them both at the same time?

I'm not sure how I'd wire that though, power in would go to the charger, then the chargers power out would connect to the battery, would I ten splice the battery to connect to the 5v boost module?


texts: Suggested schematic check DRC settings for Tools>Verify in DxDesigner

texts:
I am using DxDesigner for the first time (9.2).  When running a Design Rules Check (DRC) there are many rules that can be applied.  Many of them make sense to check, e.g. "Property name exceeds maximum length".  Others are giving me trouble, e.g. Un-driven Net is an error if I enable it when a net is driven by a transformer with pin type analog.  Which ones do you use?  Disable?  Check, but often ignore the notes or warnings?

Updated 11/23/2010:  Under Connectivity here are some I had questions on.

drc-101 Output and bidirectional pins connected together
drc-102 Output and tristate pins connected together
drc-103 Un-loaded net
drc-105 Un-driven Net
drc-106 Multiple Output Drivers
drc-116 Output directly connected to Power or Ground

Note that I am not doing circuit simulation.


texts:
I have found an opamp schematic that I don't understand.
As far as I know a transimpedance amplifier "converts" my input current into an output voltage.
But in this case the positive and the negative inputs are driven by an input current.

Does that mean that my current difference will be amplified?

I tried to simulate this schematic in LTspice, but unfortunately I cannot explain this schematic to myself.

It would be very helpful if someone can name this schematic.


texts: Is it possible to toner transfer and hand solder MSOP's?

texts:
The chip is 3mm by 3mm (10 lead)
My printers max DPI is 1200dpi

If etching isn't possible, are the MSOP breakout boards on eBay an option? The breakout boards dimension says 1.25mm between the two sides, but this chip says 1.68mm. There is a metal pad on the bottom - does that mean I can't use this?


texts:
I have a rectified DC Voltage and I will switch in a dump load resistor. I have a 25PV045 Schottky diode connected across it as a flyback to deal with the inductive properties of the load when the switch is turned off.

I also have an LED which goes on when the switch is on and this has a protective 1N4148 diode.

My question is when the Schottky is in flyback mode will any of the current go through the small diode and perhaps damage it or will resistor R68 prevent this?

Thanks.


texts:
I'm trying to understand the circuitry of TV signal splitters and associated boosters/amplifiers, and I have two questions.
My situation is as follows.  I have a TV aerial (antenna) in my loft.  It connects to a non-powered box, which I assume must be a passive splitter.  From there cables run to sockets in a total of 6 rooms.  However, only in two or three of those rooms does a TV connected to the socket show any signal; and even in those rooms, there is no signal unless a booster, located in the room nearest to the aerial, is connected and powered up.
That all sounds sensible, but then I stop being able to understand.

Here's the odd thing, and the first question.  To make any TV on the system work, the booster has to be connected to the aerial socket, but nothing needs to be connected to the booster output; so long as the booster is connected and switched on, the TV in a neighbouring room will work.  It's as though it is somehow sending the amplified signal back up its input cable.  But I've looked at circuit diagrams for boosters, and that doesn't look possible.  Can anyone explain what is going on?
I am trying to find out what is wrong in the rooms where no signal is ever reported.  I read somewhere that if I look across the terminals of the TV socket with an ohmmeter, I should see effectively zero resistance, since there is continuity through the aerial.  However, this is not true for any of my sockets.  With all devices disconnected, if I look at the resistance at the socket the booster normally connects to, I see about 4k.  If I look across any of the other sockets (including those where a signal is successfully received), I see no continuity at all.  So I suppose that the passive splitter must have a capacitor or transformer somewhere in its circuitry, but I can't find a circuit diagram anywhere that would show whether this is true.  Can anyone say whether this is the case, i.e. whether I should be able to see continuity when looking into a socket?

Background information:

Until recently we have never tried to use TVs in the rooms where we now find they don't work, so this is probably not a new problem.
In particular, the non-functioning sockets have not been used since the analogue era.
The wiring is probably at least 30 years old, and certainly pre-digital.
I'm in the UK, and the TV signal is digital terrestrial.
Fitting an outdoor aerial to get a better original signal is not an option in our neighbourhood.
The passive splitter and aerial connections are all screw-downs, and they are not conveniently located, so swapping cables around for test purposes is slow and painful.


texts: Current Conveyor CCII internal circuital realization

texts:
I have read this article about current conveyor CCII, and I have some problems about understanding its circuital realization (page 4):

The article says:

  The feedback of opamp structure [this expression refers to the circuit shown above]
  copies the voltage from input “Y” to the input “X” and at
  the same time guarantees a very low impedance at the input
  “X” node. The current from the input “X” is then conveyed
  by the transistors M5, M6 and corresponding current
  mirrors M7, M8 to the output “Z”. In the shown circuit the
  “push-pull” transistor branches were used.

Can you explain me in a more detailed way? Why the voltage at X is the same of that at Y? And why the current on Z is the same of that on X?


texts: Measuring voltage while maintaining isolation

texts:
I'm building a variable power supply, and want to provide the ability to digitally measure the outputted voltage and current. The digital power supply used to drive the ADC, microcontroller and friends is separate from the unregulated power supply used to derive output voltages.

The power supply for the microcontroller is galvanically isolated from the one for the output voltages — the first is an unregulated transformer, while the second one is an SMPS supply.

Now, measuring the current while maintaining galvanic isolation is easy, since I'm using a Hall Effect sensor for that, but I don't see a similar method for doing that for voltage measurements. My plan was to use a resistor divider and shoving that voltage into the ADC. However, that completely ruins all the effort I put into galvanic isolation of the two rails, since the downscaled voltage output would get into the ADC, causing all kinds of problems.

Is there any kind of solution out there that will let me measure that voltage, while still maintaining galvanic isolation?

I don't think optocouplers will work, seeing as they're either on or off, and I'm not familiar with any other kind of isolation, and I'm not really familiar with any other kind of isolation techniques, but I'm thinking that perhaps transformers could be useful in this situation?


texts: I have build an LED array consisting of 75leds, 5 connected in series with a 39ohm-1/4watt resistor and 15 such series connected in parallel to the rectifier circuit having 2-IN5408 diodes and 1- 25V_4700µF capacitor. The transformer is 12-0-12v_3A. The leds forward voltage is 3.3v-3.4v and forward current is 60mA. As the whole fixture is for an aquarium i have to run it continously for 6 hrs and the transformer gets quite hot (cannot touch it for more than 5 secs)? Is the rectifier circuit and the transformer not adequate for running the leds?


texts:
Suppose that I have a serial signal (example below), which is transmitted without an accompanying clock signal, I would like find a circuit (using discrete components / ICs, possibly an FPGA, but not a microcontroller) to reconstruct the clock for this signal.

The main challenge is that the frequency of this serial signal varies over time. The signal is received from a wireless ASIC. When the ASIC transmitter is on, the receiver produces a signal, like what is shown below.

Additionally, the ASIC may intermittently (and asynchronously) cut out after a few seconds, and a different transmitter will come online. Any given transmitter's nominal frequency can be anywhere from 35 to 65 KHz due to design issues.

Depending on how much power the transmitter has, I have seen a single ASICs clock drift by as much as 2 KHz from a nominal 50 khz during continuous operation. I have never measured a noticeable frequency shift within less than 20 frames of data, but I don't have an actual figure for rate of change in the clock frequency....

There is one start bit per frame, and a parity bit and stop bit at the end. There can be as many as 13 consecutive zeros in the frame. There are always 4 zero cycles between frames coming from a single ASICs transmitter. Consecutive frames come from a single transmitter, but as I mentioned, the transmitter can periodically cut out, and another one can come online at a different clock frequency.

What I am looking for is a circuit to recover the clock, using a combination of digital logic, and discrete analog components (not a microcontroller!) which is very robust, that can adapt to a drifting clock, and can lock on to frequencies in that wide range. Also I would like to find a design which scales well to higher frequencies, because future ASICs will have a transmitter clock which is much faster (I have heard as much as 20 times faster).

An FPGA will be utilized to decode the data stream (and use the recovered clock, in fact this has already been implemented before assuming the availability of the clock), and as such can be used as part of the clock recovery circuit if that helps.

Very sorry for the confusion, I hope everything has been clarified.


texts:
I have not used any BGA packages before, but (lucky for me) my first one is a 0.5mm pitch device.

Since the pitch is so fine, there is no room for vias between the pads, even at the smallest drill size of 0.2mm. For this reason, I have placed the decoupling capacitors on the same side as the BGA, rather than on the opposite side, as is usually recommended. The board thickness is 0.8mm. The passives are all 0201 packages.

I would be grateful if someone experienced with fine pitch BGAs could take a look and see if I have made any obvious mistakes.  I have tried to clearly label all of the tracks with their functions, but please let me know if I can annotate the images better.

Top two layers
Coloured tracks are on the top layer. The grey background is the ground plane on layer 2.

Bottom two layers
The coloured polygons are power planes on layer 4. The yellow track is on layer 3.


texts:
I used this schematic for making a power supply. Output is single instead of double and is 36 V, 20 A.

Core is ETD44.
Freq is 50 kHz.
Primary is 30 turn Litz wire (6 × 0.55). - - - Secondary is 8 turn Litz wire (21 × 0.55) so current density is 4 A/mm2.

There is a problem in transformer secondary winding. After 30 seconds at full load secondary winding becomes very very hot and I can't use power supply more than 1 minute. What is cause of this extreme heat in secondary?


texts: Powering LED Strip with Arduino using Transistor

texts:
I am trying to use the 5v output from an Arduino to control a 12v LED strip. I have an N-Channel MOSFET but I am confused on how to make it work. Here is the MOSFET Datasheet: http://www.st.com/web/en/resource/technical/document/datasheet/CD00002848.pdf

I basically want to use the MOSFET as a switch. When the Arduino outputs 5v I want 12v to output from the MOSFET (using 12v battery), but if the Arduino is not outputting voltage, I want the MOSFET to output 0v. Is this the correct component?

If it is the correct component, how would I set it up? I have never worked with transistors so this is new to me. Are there resistors I need to make this actually work?


texts: How do I convert, lower, or raise voltage?

texts:
I have a project that needs a different voltage (or multiple voltages) than what I have available. Sometimes I need DC instead of AC, or I need a lower or higher voltage. How do I convert from one to another? Should I use resistors or a regulator or something else?

I've heard of converters, transformers, regulators, inverters, step-down, step-up, buck, boost, switching, linear, and other terms. Or acronyms (initialisms) like PMIC and LDO. Can someone shed some light on all this?


texts: Sensor to distinguish between different types of pegs on a pegboard

texts:
I have a project that is essentially a pegboard with 4 different types of pegs. Each peg fits into every hole, but when one is inserted, I'd like to digitally record its type and position. There are a total of 120 pegs, 30 of each type. The board itself is a square grid, with at most 40mm between holes. The size and design of the pegs and holes hasn't been decided yet.
The simplest and cheapest idea I could come up with was a switch at the bottom of every hole and a separate input method to declare the type: eg. 4 buttons somewhere on the side, which you could push afterwards to tell the system that type A was just inserted. This has a large effect on the user interface, one I'd like to avoid.
I could design the hole to be asymmetrical, wire 4 switches to the bottom and have each peg have 4 prongs with one being longer than the others. That would mean soldering a lot of very tiny things together and a more delicate final product, though.
Cost is also an issue, as it's a hobby project.
Is there some sort of sensor I could use for this?
Edited to add: I should have probably said this to start off with, but I tried to slightly generalize the question to maybe make it more useful: the project is a board game. The idea is to have up to 4 players capture territory on a board and have the board itself handle all the necessary bookkeeping in real time.


texts: What could be done with a deactivated SIM card?

texts:
I was reading https://reverseengineering.stackexchange.com/questions/15011/how-does-a-sim-card-work and from that, I can say that, really really simply put, a SIM card is sort of an extra memory that allow the phone to hold data that the carrier can use to communicate with.

Now let say the carrier deactivate a SIM (for instance a SIM that was not used for a REALLY long time). I'm asking myself what could be done with that SIM. Sure IMEI for instance in written inside the SIM. But it is not mapped to any carrier phone number anymore. The carrier only know of the existence of the SIM at this point, not its activity.

So what can be done with the SIM to make it work without having to reactivate it from the carrier for instance ?
Or what other activities (programming wise) can be performed with the SIM at this point that for instance can make it work with a different carrier, sort of making it a stealth SIM on any carrier ?

I'm not asking for implementation details.... I'm just wondering if at all possible.

For instance when you buy a PC, if you Windows licence does not fit you purpose, you can flush the HDD and install a new OS, Windows, Linux, etc...


texts: Is the op-amp supposed to be in negative feedback?

texts:
The above circuit was simulated using Multisim-Live. A rough see through tells me that the op-amp is in positive feedback as the output of op-amp is at base and inverting terminal to the collector, which is inverted wrt the base. But the simulation doesn't show output of op-amp to saturate, i.e., +- 15V (check the probe values). Note that the op-amp is not a particular model. It's just named "5T_VIRTUAL".
A similar question was asked here and my understanding holds as much as I see. I have been scratching my head all morning and I don't understand why the simulation is showing such results.


texts: LC-Circuits and Feedback into power supply

texts:
I am a medical researcher and I found an effect that I think I understand half way, but not completely and I hope someone more skilled in electrical engineering can clear this up for me. I am a novice on the field, so I aplogize in advance if it is a silly question.

I am working with two systems. System A produces an electromagnetic field that constantly and quickly changes it's polarity. System B produces strong electrical pulses (frequency unknown). I have noticed an effect, where activation of System B interferes with system A if (and only if) they are plugged in the same power outlet.
I know from my hobby as a DJ that the power supply can be "bad" or "noisy", and that systems with LC-Circuits can cause this interference. I suspect this to be the case, but since I am pretty ignorant in the field I do not know how to verbalize the problem and where to start looking. I would like to know two things:

Is there a clear concept on how these circuits interfere with the power supply?

What can be done to avoid this problem? I foggily know that one should plug the systems into two different phases (dependent on two different fuses I think?) but this is all a bad case of half-knowledge.

Is there a piece of hardware that guarantees a "clean" power supply?

Thanks in advance. In clearing this up, you are helping me significantly.

Edit:
System A is an electromagnetic field generator used for tracking purposes. System B is an electric scalpel. System A produces a high frequency field that constantly changes polarity and system B produces strong pulses electric pulses that it uses to cut tissue.

The interference is independent of physical proximity. I can disable the effect if I use two different outlets.


texts: How to properly measure voltage of external supply

texts: What is the proper way to measure an external supply like a 9V battery which is not connected to the controlling part (micro-controller) of the system. Take an external 1-Channel SAR ADC with SPI interface like MCP3001 and a micro-controller which has its own supply. I see we must divide the 9V first to 5V so the MCP3001 can properly handle it. But where to connect the VREF pin of MCP3001? Can I connect it to VDD like usually? Also do I need a galvanic isolation?


texts: PSU First stage with IRCL Voltage rails swapped

texts:
The image below shows the first stage of a power supply I am trying to design and build. The transformer is a toroidal type with two 18V coils on the secondary and a 230V winding on the primary.

The resistors and the relays are active inrush current limiting. The relay should short out the resistors 2 seconds after power on to give the capacitor bank enough time to charge up without setting my diodes on fire.

In the drawing below, I am expecting VM2 to read just under 18V and VM1 to read just under 36V. I am however getting a higher voltage on VM2 (about 27V) and a lower voltage on VM1 (only 11V)

simulate this circuit – Schematic created using CircuitLab

Note:

I have not activated the relay so all the current is still flowing through the resistors (which, I think, explains most of the voltage drop) but why the voltage swap.
The resistors are actually a set of 10 470ohm 3W resistors in parallel for each of R1 and R2 in the diagram below.
C1 is 14 470microF 50V Caps in parallel (6.58mF - not micro)
C2 is 6 more 470microF 50V caps in parallel (2.82mF - not micro)
Transformer: (I have connected Red and Orange together to form the centre tap)

PRI: 230V/50-60 (Blue and Brown wires)
SEC: 18V/80VA (Black and Red wires)
SEC: 18V/80VA (Orange and Yellow wires)

What am I doing wrong?

Update based on Neil_UK post:
What I need out of this stage is one +18V rail (the bottom one in the diagram above) and one +36V rail (the top one in the diagram above) or as close as possible.

simulate this circuit

Neil, you've been very helpful and I will redo the circuit, but I'm keen to fully understand this before I continue, if you don't mind.

I've redrawn the diagram so that the individual components can be seen. I understand that D4 and D7 are in parallel on the output of the Rectifier, but I don't see the parallel part of the input signal. Are you referring to D3 and D5? They have separate outputs. I get that the caps AC couple them, but there should be no AC component on that side of the Bridge Rectifiers.

You said: "Consider what happens when the common AC input is negative, and BR1's AC input is positive. Draw it out." Would that be solvable by switching the wires around on one of the secondary winding to bring it back in phase (I get that I would have to be sure that this is the case first).

The first time I turned this thing on, my diodes actually blew quite dramatically. Investigation lead me to install the Inrush Current Limiting circuitry because with the amount of capacitance I have I calculated that I would be sucking roughly 160A-370A through my diodes when I first turn it on. These diodes have a max surge current of 70A each. But now I'm wondering if this was not caused by the fact that they are cross coupling (Still need to understand that as explained above, please ;-) The parallel nature of D4 and D7 should not cause that as they are parallel so should provide slightly higher current (assuming they are thermally locked and all, which they aren't, but for the purposes of this discussion...)

Another update for Neil
Okay, so since I can not spot the difference between the two images I drew, I'll include an actual screen grab of my schematic with the transformer coils drawn in the way I connected them. (I simply turned the image around in the second image showing the common in the middle but I thought the circuit was the same as the first.)

Here is what I have done: (I've also updated the output voltages to compensate for the gain in peak voltage. I.E. (1.4141*36)-1.4=49.5V and (1.4141*18)-1.4=24V)


texts: From the picture, the switch can be considered 'closed'. Could someone explain what effect the 'ground' has on the different currents (I1, I2...)? If I had the exact same diagram, except WITHOUT the ground, what would be different? What about when the switch is opened after a long time?


texts: How to monitor high voltage capacitor bank?

texts:
I am working with a large ring launcher and a capacitor bank that has the potential to charge up to 3000 volts in a bank of capacitors totaling 12,000 μF. I need to provide a sort of tap to measure the current capacitor bank voltage outside the circuit with a meter. First thought was a 10:1 voltage divider but I'm worried that might leak current and drain the caps too fast. A secondary concern, I'm not sure I could limit the current enough to bring that down to a safer level as well.

Is there a more efficient way to monitor the voltage with minimal leakage or would a voltage divider be the more correct solution? Is there way to give a safe voltage/current on a tap in either regard?


texts: Electret microphone amplifier for computer using transistor

texts:
I'm trying to make a electret microphone amplifier using transistor to connect on my computer using a P2 connector, the problem is that using the amplifier the sound actually is lower than connecting the microphone without the amplifier. What I'm doing wrong?

The sound input is the electret microphone connected to 5V through a 10K resistor. The speaker is the P2 connector.

Schematic:


texts: AVR ATmega328 low fuse wrtiten and issue

texts:
I am using an Arduino Uno as the hardware programmer together with avrdude as the software programmer for flashing an Atmega328.

I have noticed PB0 was set to output the system clock with a logic analyzer. The currently running code was setting PB0 as an input. Double checked with avrdude that the CKOUT bit in lfuse was programmed, so I have changed it like such:

avrdude -P COM20 -b 19200 -c avrisp -p m328p -F -U lfuse:w:0xe2:m

-F is there because this old avrdude that I am using does not know about m328. According to the datasheet the fuses are the same between the P and non-P versions of this MCU.

The low fuse has been verified by avrdude to be written fine, no more clock on PB0 logic analyzer trace, all good. Except that I am no longer able to program the ATmega238. I am stuck at the dreaded avrdude.exe: Device signature = 0x000000

According to the datasheet 0xe2(0b11100010) is:

CKDIV8 - unprogrammed
CKOUT - unprogrammed
SUT1 | SUT0 `10` - Slowly rising power (default)
CKSEL3 | CKSEL2 | CKSEL1 | CKSEL0 `0010` - 8 MHz inner oscillator (default)

I wonder how I have managed screwing up this time and whether I can unscrew it somehow. Any clues ?

fixed

In short, no idea on what was wrong, but the previous lfuse changing just happened to coincide with the moment it has stopped working.

I have replaced the MCU. Still not working; observed a finicky MOSI line with the logic analyzer, messed around, eventually took out a 47 ohm resistor from the MOSI line and in the process galvanically separated another chip from the same MOSI line.

LE: I have put the 47 ohm resistor back in and it does not fail...


texts: Reading and understanding electrical specs on laptop AC adapters

texts:
My Dell laptop comes with an AC adapter with the following specs:

65 W
Input AC: 100 - 240 V, ~1.5 A, 50 - 60 Hz
Output DC: 19.5 V,  3.34 A

My HP laptop:

65 W
Input AC: 100 - 240 V, ~1.7 A, 50 - 60 Hz
Output DC: 18.5 V,  3.5 A

I have 3 questions:

On the Input AC, why 1.5 A vs 1.7 A?  I just have one type of power outlet for everything, such as lamp, TV, refrigerator, etc.  So this number is not too significant?
The output DC voltage and current are different.  Would it be safe for me to interchange the adapters, i.e. use the HP laptop with the Dell AC adapter and vice versa.  Which way would be safe and which is not?
If there's another adapter with the same output DC but higher wattage, would I be able to use it as well?


texts: Non-wet open solder fault on the same ball of two different devices of the same part?

texts:
Sophisticated PCBA, with a DM6446 using two 16 bits DDR2 devices to implement a 32 bit memory space. On some boards, we see a stuck bit on either bit 24 or bit 8, which map to the same BGA ball (C8) on the two different devices. Of the known-bad boards, 12/12 have this failure mode (either bit 8 or bit 24 stuck).

Sent one board out for cross-section & SEM. Reliability lab says the solder ball did not wet the pad, so electrically open.

Did a die and pry on a second board with the same failure mode. All balls on the two devices are good, except for ball C8 on both devices. On one device, the joint is half failed; on the other device, full failure.

Anyone ever see anything like this?


texts: Breadboard Dimensions for making DIP PCB

texts:
I'm working on a development board which will mount on a solderless breadboard.  It uses a 100 pin TQFP IC and Ethernet jack, among other things, so it would be a nightmare to get it to fit on a single section of breadboard at only 1.1" wide, and I'd like it to be big enough for users to make some edits.  I'd also like to be able to plug into power distribution rails on the breadboard (like the Sparkfun Breadboard Power Supply).

However, after comparing my breadboard with a few friends and coworkers, I see that there are a number of differences in layout.  I hope that I can accommodate some if not all of these differences by including multiple places to mount the headers for various breadboards.

Here's a dimensioned diagram so we're all on the same page.  Imagine that there are two full strips side by side (one mostly off to the left), with power rails on both sides.

[Whoops!  I forgot the horizontal dimension between B and C. Let's call it E, since I don't have the source for this image anymore.]

1. What are the dimensions of popular, currently manufactured/used breadboards?
In addition to the measurements in the diagram I'd like to know the following:
 2. Is there an electrical discontinuity between the top and of the power rails? (If so, is measurement '3' different at this location?)
 3. What is the configuration of the breadboard?  Using the convention that P is a two-column power strip and M is a middle section (rows of connections with a gap for DIP ICs in the center), my breadboard looks like: PMPPMPPMP
 4. How many rows are in the breadboard middle section and power sections? Mine has 64 pairs of 5-pin rows in the middle and 10 5x2 blocks.
 5. Any other discrepancies I missed which would affect PCB layout?


texts:
I'm trying to replace the old NiMH Roomba battery with a bunch of 18650s recycled from old laptops. Lucky enough Roomba uses 12s NiMH battery, that operates in voltage range 12-18V, and has quite similar characteristics to 4s Li-Ion battery: 12-16.8V. After adding a simple 4s protection board, it seems to work fine and generally does the job. There's one small caveat I'm trying to tackle - Roomba's charging circuit complains about the battery when the protection board cuts the current to prevent a cell from overcharging and the robot reports a "Charging Error 5". I'm guessing that it's just because the battery is unable to reach voltage any higher than 16.8V. I also know that people solve this issue somehow without modifying the Roomba itself - there are third-party Li-Ion batteries available on the market. Is there any simple solution that'd allow preventing the error message?

I thought about connecting a capacitor to the output to allow charging to a higher voltage when the battery gets cut, but it doesn't work - it'd need to have a very high capacity I think to work properly.


texts: Why is the trace on my DSO displaying faintly (too light) at longer sweep rates?

texts:
I am using a Rigol DS2102 (DS2000 series) DSO to monitor clock output on a microcontroller. For whatever reason, the trace intensity becomes very faint at 200ms/division sweep rates and longer.

I've tried increasing the trace/waveform draw intensity to 100%. I've tried turning on/off bandwidth limit, changing voltage per division, different input signals, and a number of other tweaks. It happens on both input channels. Notably, when changing the voltage per division setting, the trace is briefly displayed at the expected intensity. Once the sweep resumes, it returns to the barely-visible faint display.

It is running the latest firmware (03.05.SP4). I looked for errata and changes in the firmware but there's no mention of it.

Why is the trace displaying so faintly at 200ms/division and up?


texts:
I am using an AD590 temperature sensor that is interfaced to an STM32f427 MCU.
It is a 2 pin sensor that must be connected to an ADC pin of the STM32f. But, the ADC590 needs a min of 4V to work and the STM32 is working on a 3.3V rail.

So, the first thing that comes up in my mind is using a voltage divider to step down from 4V to say 2.1V(which is my Vadc ref).

Is using a voltage divider advisable in such cases ? Also, should I then use resistors of high precision (say 0.1%) ?


texts:
I have an Arduino Uno r3 board which has an atmega16u2 chip that normally contains the usb to serial firmware that allows the board to communicate with the IDE.

I have been learning how to flash that chip with different firmwares that let it act as other types of USB devices ( Keyboard / Mouse specifically ).

I have found some hex files that I can use online, but I am trying to learn how to build my own version of the keyboard and mouse hex files.

Here are the variables that I've set in the make file:

MCU = atmega16u2
ARCH = AVR8
BOARD = UNO
F_CPU = 16000000

the LUFA_PATH is set like this (I did not change it):

LUFA_PATH = ../../../..

When I save the makefile like this and try to run make all an error occurs:

../../../../LUFA/Drivers/Board/Joystick.h:119:31: error: Board/Joystick.h: No such file or directory

../../../../Common/Common.h: No such file or directory

../../../../LUFA/Drivers/Board/Buttons.h:135:30: error: Board/Buttons.h: No such file or directory

The weird part is that I can travel to the path that it states and those files do actually exist and are located there.

How do I need to set my LUFA makefile parameters in order to build for the atmega16u2 that is on the Arduino UNO rev3?

EDIT: These are the only steps that I've taken, which led to these errors.

Download LUFA project zip.
Travel to dir: C:\LUFA-111009\Demos\Device\ClassDriver\KeyboardMouse
Open makefile in this directory.
change the MCU, Board, and F_CPU speed to the values located above.
(Arch is already set correctly)
save make file
Open cmd in this dir.
Type "make all"

this process results in the above errors.

EDIT 2: Ok, I made blank Buttons.h, and Joystick.h and put them in the KeyboardMouse/Board/ folder. that got rid of the file not found errors but still gives me this:

KeyboardMouse.c: In function 'SetupHardware':
KeyboardMouse.c:111: warning: implicit declaration of function 'clock_prescale_s
et'
KeyboardMouse.c:111: error: 'clock_div_1' undeclared (first use in this function
)
KeyboardMouse.c:111: error: (Each undeclared identifier is reported only once
KeyboardMouse.c:111: error: for each function it appears in.)
KeyboardMouse.c:114: warning: implicit declaration of function 'Joystick_Init'
KeyboardMouse.c: In function 'CALLBACK_HID_Device_CreateHIDReport':
KeyboardMouse.c:174: warning: implicit declaration of function 'Joystick_GetStat
us'
KeyboardMouse.c:175: warning: implicit declaration of function 'Buttons_GetStatu
s'
KeyboardMouse.c:183: error: 'BUTTONS_BUTTON1' undeclared (first use in this func
tion)
KeyboardMouse.c:188: error: 'JOY_UP' undeclared (first use in this function)
KeyboardMouse.c:190: error: 'JOY_DOWN' undeclared (first use in this function)
KeyboardMouse.c:193: error: 'JOY_LEFT' undeclared (first use in this function)
KeyboardMouse.c:195: error: 'JOY_RIGHT' undeclared (first use in this function)
KeyboardMouse.c:198: error: 'JOY_PRESS' undeclared (first use in this function)
make: *** [KeyboardMouse.o] Error 1


texts:
I'm travelling at the moment and the three-prong plug on my laptop power brick is going through a two-prong adapter and therefore losing the connection to ground.
The laptop stopped charging and I took it to a local repair place. The guy put it down to the power brick and sold me a replacement. This looks like a genuine HP product but could be a copy. The sticker says "connect only to a grounded outlet".
I have had several electric shocks when handling the plug. Does this mean that the power brick is faulty, or is it normal given that it is not grounded?


texts:
SI4463 can  listen before talk (LBT) . I found this function in  29 page of datasheet . I think I can use LBT to make a band scanner like this . But there is not any example to show how to do.

Only arduino I am familiar to , and I think I should use SPI library to send commend to SI4463 and recieve data, for example, SPI.tansfer(commend). But I don't know which commend can do this .  In fact,  I just can use RH_RF24.h to control SI4463. But there is not suitable function to make a scanner. The RSSI of  RH_RF24.h is the RSSI of the last received message. It can't be used to LBT.

Sorry for my poor English. If there is any problem about my question , please tell me.

Thanks.

#include <SPI.h>
#include <RH_RF24.h>

// Singleton instance of the radio driver
RH_RF24 rf24;

uint8_t Recieve_Data[20];

uint8_t receive_buffer[RH_RF24_MAX_MESSAGE_LEN];
uint8_t receive_buffer_length = sizeof(receive_buffer);

uint8_t Rssi;

unsigned long Micro_Time;

uint8_t status[8];
uint8_t buf[RH_RF24_MAX_MESSAGE_LEN];
uint8_t len = sizeof(buf);

void setup()
{
  Serial.begin(115200);
  if (!rf24.init())
    Serial.println("init failed");
  // Defaults after init are 434.0MHz, modulation GFSK_Rb5Fd10, power 0x10
   while(!rf24.setFrequency(443));
  rf24.setModemConfig(rf24.GFSK_Rb50Fd100);  //设置成GFSK_Rb50Fd100
}

void loop()
{
  rf24.setModeRx();
  delay(100);
  rf24.setModeIdle();
  rf24.command(RH_RF24_CMD_GET_INT_STATUS, NULL, 0, status, sizeof(status));
  Serial.print("Id   ");
  for (int i = 0; i <= 8; i++)
  {
    Serial.print((uint8_t)status[i]);
    Serial.print("   ");
  }
  Serial.println();
  /*
    if (status[2])
    {
      uint8_t modem_status[6];
      rf24.command(RH_RF24_CMD_GET_MODEM_STATUS, NULL, 0, modem_status, sizeof(modem_status));
      delay(100);
      for (int i = 0; i <= 6; i++)
      {
        Serial.print(modem_status[i]);
        Serial.print("   ");
      }
      Serial.println();
    }
  */
  delay(400);
}


texts:
I have some cheap potentiometers that I would like to use as variable resistors.

The potentiometers have a power rating lower than the amount of power I would like to be able to dissipate across the setup at a fixed voltage, so I have a plan.

Instead of using a single potentiometer set to resistance X and total voltage drop of V, I will put the two variable resistors in series and set both of them to a resistance 1/2 X. The voltage drop across each will now be 1/2 V.

Because the total current will stay the same thanks to an equal equivalent resistance, each variable resistors will get the same current as the original setup with only one variable resistor.

Because P = IV, each resistor should dissipate half the power with half the voltage drop. The total power will be the same, but because I have two potentiometers in series, given that I adjust them to the same resistance each time, I will be able to dissipate twice the total power ago a given total resistance.

Is there a flaw in my reasoning?


texts: What is the basic difference between Inductive and capacitive touch screen?

texts: I have seen Smartphones mentioning of two terms frequently; naming Inductive touch and Capacitive touch screen. What is their basic difference and what is the advantage of one over another?


texts: Does any thermal fuse with the same cut off temperature work?

texts: Would any thermal fuse cutoff for 216°C work as a replacement for the fuse in the picture below?


texts: How do I use those digital LEDs with an I2C device?

texts:
I want to use the MMA8453Q accelerometer via I2C while at the same time sending data to some WS2812B-2020 digital LEDs. I am thinking of using the PIC16F1789 microcontroller.

Since I can't hook the LEDs up to the I2C bus as well, I first wanted to just send data via a normal digital I/O. I need to be able to send 43200 bits per second to the LEDs but I can't find out how high the maximum frequency of a normal I/O of the microcontroller is. I also don't know if this is the smartest way to do this or if there is an easier way.


texts: What does "minimum etch technique" refer to in PCB layout/design?

texts:
in the application hints for an ADC (AD7927 page 26) it says:

  The printed circuit board that houses the AD7927 should be
  designed such that the analog and digital sections are separated
  and confined to certain areas of the board. This facilitates the
  use of ground planes that can be separated easily. A minimum
  etch technique is generally best for ground planes as it gives the
  best shielding.

What do they mean by ground planes that can be seperated easily?

And what is a "minimum etch technique"?


texts: How do I implement a simple and efficient voltage divider for battery level readings for a ESP32 board?

texts:
I'm trying to design a simple device based on ESP32 board, which will control stepper motors from a battery pack (26650 series).

I'm struggling with the battery level control part (red/blue colour on the diagram) and I'm not sure if I designed it correctly.

The 100uf capacitor marked on the diagram is a Aluminium Organic Polymer Capacitors 25V 100uF 20% ESR=40mOhms

Battery level resistors: Vishay

I'm aware that I should use a capacitor for the stepper drivers, but I'm not sure whether or not to use an additional capacitor for battery level readings?


texts:
We have power traces in inner layer (the yellow traces). We have linked all our nets with traces taking care of track width based on current flowing into the nets.

Now, we are wondering if we should keep this like this or if we should create a polygon for each track (which I suppose might be benefical to spreading flow over a larger surface).

What would you do ? Would you create polygon and if yes how would you draw them to make them adjacent to each other and to delimit their borders ?


texts: Stepper driver - pinout: enable, reset and sleep

texts:
Can anybody tell me (as simple as can) what is actual difference between:
ENABLE, RESET and SLEEP pin on DRV8825 stepper motor driver ?

I'm trying to learn programing by writing simple CNC controller.
And I want to disable stepper driver and motor for time when user will be in configuration menu.

I already have read datasheet, but it's still unclear to me.


texts: Of what use can a logic gate be to a circuit that contains a micro-controller

texts: I am wondering if a logic gate would be of use to a circuit that contains a micro-controller.Are there cases when an analog logic gate is preferred over a micro-controller and what are some of the gadgets that use analog logic gates in the age of micro-processors and controllers.


texts:
I have an odd sized PCB (about 0.8" x 14" x 5" ) that needs to be housed in data centers (rack mount.)  It's a fairly expensive device so even though we won't have too many of them we're considering having a custom case designed, and style will matter. We're also therefore thinking aluminum or some other nice material. Further, the device has a PCIe finger. While we don't plan on using it in the near future, we'd eventually like to link up several to communicate with one another over a PCIe bus.

The optimal design would therefore have a case for the cards that left the fingers exposed, but could be mounted as is in a rack, or be placed in a very spacious computer (it's over-sized for PCIe), but also that in the future would allow us to insert the same card into a case with a PCIe bus (magma has a nice kit, but it seems expensive for what it is and it doesn't allow for too many slots.) That plus the low quantity and need for high quality, plus my general inexperience with enclosures has led me here.

So where do I start? What design firms could pull this off? Could laser sintering give us the quality we want?


texts:
I have one question which I encountered during usage of common mode choke.

Question : "If a common mode choke is used on the main power / ground input, ensure that no I/O circuits effectively bypass the ground side of the common mode choke.   For example, the shield of screened cables or I/O signal grounds may present a better AC ground to the module than the main power ground.
Common mode chokes may be needed on some I/O signals to prevent this."

Answer : "AC ground current may find an easier path to ground in the vehicle through IO circuits etc. rather than through the ground side of the common mode choke.
If this occurs, the function of the common mode choke is effectively neutralised, potentially causing conducted emissions concerns.
Normally signal grounds, cable shields would be connected to the "vehicle side" ground of the common mode choke, unless this causes a functional problem (e.g. accuracy of analog signals), in which case a common mode choke on analog / ground signals may also be needed."

I have the answer to the question also. But I am unable to understand it clearly. Can someone explain the question and answer in simple terms please.
What the question is asking me to check and how will I check in my design?

Thank you.


texts: What do I need to know about oscilloscope probes?

texts:
I've run across a Hitachi V-355 oscilloscope, and a friend who's willing to give me a deal if I want it. Unfortunately, there are no probes that come with it. I was searching for probes, only to learn that they're STUPID expensive (either that or I'm STUPID cheap), and I can't find any to borrow.

So here's my thought: I have a ton of test probes from, say, my multimeter. I have a stable of patch cables in every possible banana plug/alligator clip/springy pin clip configuration possible. I also have a whole mess of BNC connectors and adapters in my video cable repair kit.

So here's my question: Can I just solder an alligator clip cable to a BNC connector and have an oscilloscope probe? Or is there something special going on inside those probes that makes 'em cost $50.00?

If the latter, and I end up biting the bullet and getting real, honest and for true oscilloscope probes, what are some things I need to be aware of when shopping?


texts: What's this on a single line diagram? What's its function?

texts:
The unknown part:

It seems like a regular transformer, but is it? What's its function? Why is it grounded?
The diagram itself:


texts: Why isn't phase modulation commonly used in radio stations?

texts: I've tried searching about this and see answers saying that "frequency modulation can be considered as phase modulation" and I do understand that frequency and phase affect each other but why don't stations use direct phase modulation? As in the stations are actually called PM and phase is the variable directly being modulated. Probably there are ways that phase modulation is integrated but I'm kind of looking for a straight up answer that someone not into electronics who is curious why FM and AM stations are the only common radio stations.


texts: Differential Amplifier Input Line-Level Signaling

texts:
This is the circuit I'm referring to:

This stage is often used as input stage of audio amplifier.

I am wondering, how can the input signal be normally amplified since there is no DC bias across the base of both transistors?

In my book, it says that we have to drive this stage with "line-level" amplitude signal (that is around 1V). But still, if the amplitude swings for 1V from its reference point which is probably 0V, then only a bit of a positive signal wave would be amplified, since transistor starts conducting at Vbe of approx. 0.7V!

Without base bias voltage, the output signal would look like this, right?

Instead of this, right?


texts:
I watched this video where ST itself states that BOOT0 and BOOT1 pins are used to select the memmory that MCU starts reading after the boot :
┌───┬───────┬────────────┬────────────────────────────────────┐
│   │ BOOT0 │   BOOT1    │   After reset MCU starts reading   │
├───┼───────┼────────────┼────────────────────────────────────┤
│ A │     0 │ irrelevant │ FLASH                              │
│ B │     1 │ 0          │ bootloader (inside system memmory) │
│ C │     1 │ 1          │ RAM                                │
└───┴───────┴────────────┴────────────────────────────────────┘

Also the offical ST's bootloader guide (chapter 4.1, table 2, pattern 1) mentions BOOT0 and BOOT1.
I check the documentation for ST's MCU and there is no slightest trace of the BOOT1 pin! WTF?
Where is BOOT1 pin?!


texts: How to calibrate multiple magnetometers for mass production

texts:
How would one go about calibrating several magnetometers in a production environment?  The magnetometer is being used for the purposes of a compass.

Currently I'm calibrating them one-by-one in an open field free from magnetic interference (i.e. no hard or soft iron around) by rotating my magnetometer, and associated electronics, in all three dimensions and then compensating, through software, for the inherent magnetic interference of the on-board electronics.

I'm curious though how large companies scale this process without introducing magnetic interference.


texts: How to control the current/voltage in resistive wires

texts: I'm new to electronics, and I was planning to make a heater to heat up a stainless steel container, and I was wondering if there was a way to control the temperature by controlling the current or voltage? I'm using nichrome wires for the resistive wires. The nichrome wires I'm using are 0.3MM in diameter and 20.10 Ohms/m


texts:
There lots of people claiming that 240VAC is much more dangerous than 110VAC. Some even find it insane to have 240VAC.
I think this claim comes mainly from the fact that 240V will draw twice the current through a same resistor and that's what will kill you.

There is also a claim that electrical body resistance is much lower on 240V when compared with 110V

I find this rather laughable since as we all know it isn't voltage that kills you but the current. In the first split second that you come in contact with electricity 240V will give you twice the current of 110V, but I am convinced that what really does kill you is time because once your skin starts to burn the electrical resistance of your skin drops very low that it doesn't really matter anymore if it's 240 or 110.

Personally I find 110V more dangerous and the main reason is that you need bigger currents for the same appliance which in return considerably highers Joule heating, you get bigger wearing on sockets/switches and it could actually burn down the whole place.

So what is more Dangerous : 110V or 240V?


texts:
I'm trying to find a replacement for a little chip that appears to be melted a little bit. It's an 8-pin, surface-mount device. There are no visible manufacturer logos on it, but there are a few numbers, but Google-ing has rendered no results that I could find. It's the chip in the center of the photo, in case that's not clear. It's a little harder to read in the photo than in person, so these are the markings visible on the chip. Thanks for any assistance.
top: 3410G
middle: 2y
bottom: G1128


texts: What's happening in this circuit? Zero voltage drop across dependent current source?

texts:
My main concern is the short circuit on the right. Since I1 won't be zero the dependent current source will have current equal to 5*I1 Amps flowing through. The short circuit, however, implies no voltage drop across the dependent source. Is this possible?

Of course I could start writing down equations to see what's happening but I like trying to understand the circuit by inspection first.


texts:
I'd like to make a bicolor/RGB LED matrix, for this example I'll use 2x2 in size.

Suppose I have this matrix arrangement, without any wiring yet, only the LEDs:

I want to make each LED programmable. I have this in mind:

I tried to turn 0,0 to red and 1,1 to red too. For only 0,0, I can easily connect the pin 0 and pin 5 to the power source, but when I tried to add 1,1 with connecting pin 2 and pin 6, every LED is on.

Where is my mistake in the circuit? Thank you very much, I'd appreciate any answers given.


texts:
When using Litz wire, the accepted method of stripping the wire is by dipping it in a solder bath, which effectively turns the end of it into solid-core wire, so my question is thus:

How good is the contact between a tightly-screwed-down screw-type terminal block and a solid-core, slightly squishy due to solder, wire? Should I expect significant contact resistance, as the round wire makes only a small amount of contact with the flat screw body? Or am I overthinking things?

This is part of a research project. It will not be exposed to any sort of high-vibration environment (there are no motors or anything nearby) and environmental conditions will be pretty much STP (with the possibility of occasional high humidity, if that matters any). It will be operated indoors, with air conditioning.

I don't have a specific spec for contact resistance because I simply don't know what is reasonable. Contact resistance has never previously been something I need to worry about; this is my first time working on a high-current device.


texts: How do I find the phase of a transfer function in different ways?

texts:
Suppose there is a transfer function

Now try to find the phase of this transfer function.
The phase can be expressed in different forms:

But each of these forms leads to a different result in the phase calculation:

So which one(s) of the above calculations is(are) correct?
Thanks.


texts:
I like to implement a simple module without using any DSPs on the FPGA. In other words, I like the whole design to be implemented using logic. Is there an option in Quartus Prime that allows me to disable mapping multipliers to DSPs?

If not, can you introduce a good implementation for a multiplier that I can use and fool Quartus Prime to implement it using logic?


texts: How to measure extremely high temperatures?

texts:
I'm interested in building or buying an electric (arc or induction) furnace for smelting & heat-treating metals.
Most designs I've seen utilize PID controllers and thermocouples.
How are extreme temperatures accurately reached and measured without damaging (i.e. melting) the precision measuring instruments (e.g. thermocouples, etc.)?


texts: Calculation of output impedance of CE emitter bias configuration( unbypassed) with r_0

texts: Can anyone please help me with finding the output impedance of the circuit.? I tried but can't find the answer


texts: This exercise is about a BJT transistor common emitter circuit, with a biasing resistor between the base and the collector. I am supposed to compute the signal amplification of the circuit \$V_o/V_s\$ (\$V_o\$ being at node1). I am given that the transistor has \$\beta = 50\$ and \$r_{\pi} = 1.1\$ for the \$\pi\$ equivalent model.


texts:
I have a problem seeing SCL and SDA signals on the oscilloscope. I am using PIC18LF in Master mode and the bus is pulled up to Vcc. I beleive i have programmed correctly but all I see 3.3V on the Oscilloscope SDA and SCL lines.

I cannot figure out where I screwed up!

Here's my code:

//i2cdem.c

void init_oscillator(void)
{
    // NOSC HFINTOSC; NDIV 1;
    OSCCON1 = U8_SET_HFINTOSC_NDIV_1;
    // CSWHOLD may proceed; SOSCPWR Low power;
    OSCCON3 = 0x00;
    // TUN 0;
    OSCTUNE = 0x00;

    OSCEN   = 0x00;                   // MFOEN disabled; LFOEN disabled; ADOEN disabled; SOSCEN disabled; EXTOEN disabled; HFOEN disabled;
    OSCFRQ  = U8_NOMINAL_CLK_FRQ_8M;  // Setting OSCFRQ register to 0x03 --> 8MHz

}

void set_I2C_baud_rate(unsigned int freq_KHZ)
{
    volatile unsigned int F=8000;
    volatile unsigned int temp=0;
    temp = 80;
    temp -= 4;
    temp /= 4;
    //temp=( (Fosc/freq_KHZ) - 4)/4 ;
    SSP1ADD = temp;
}
void I2C_Inititalise()
{
    SSP1CON1       = 0x28;  //I2C Mode
    PORTCbits.RC3    = 1; //SCL
    PORTCbits.RC4    = 1; //SDA

    TRISCbits.TRISC3 =0;
    TRISCbits.TRISC4 =0;

    TRISCbits.TRISC3 =1;
    TRISCbits.TRISC4 =1;

    LATCbits.LATC3 = 1;
    LATCbits.LATC4 = 1;

    SSP1CON2       = 0x00;

    SSP1STAT       = 0x80;
//    SSP1BUF =( (U8_LDC_ADD<<1) | 0x00 );
}

void send_start()
{
    SSP1CON2bits.SEN=1;
    while(SSP1CON2bits.SEN);

}

void send_stop(){

    SSP1CON2bits.PEN=1;
    while(SSP1CON2bits.PEN);

}

void I2C_wait(void)
{
    while( (SSP1STAT & 0x04) | (SSP1CON2 & 0x1F) );
    PIR3bits.BCL1IF=0;

}

void write_to_bus(unsigned char data)
{
    SSP1BUF = data;

}

//main.c
    void main(void) {

        init_oscillator();

        I2C_Inititalise();

        set_I2C_baud_rate(100); //set SCL to 100KHz

        while(1){

            send_start();
            I2C_wait();
            write_to_bus(U8_LDC_ADD<<1); //Address
            I2C_wait();
            send_stop();

        }

        return;
    }


texts: Soft fade out circuit for turning off speakers

texts:
I have some loud speakers connected to an amplifier. The problem is when I turn the preamp off, it sends a loud POP noise through the speakers. The turn off of the amp is delayed by 1 or 2 seconds, but that's not enough to kill the amp. So here's what I'm looking to achieve:

I'd like to slowly fade the speakers out as soon as as a remote wire goes LOW (it is 12V when preamp is on, but immediately becomes 0V when preamp turns off). And by slow I mean the whole thing happening is roughly half a second.

The speakers are pretty high powered. They draw 30 - 75 watts. So this circuit should withstand that.

If that's too difficult, I can try to implement this fade out function on the preamp outputs. It would be similar to a relay, except instead of a sudden off, I'd like to bring the voltage down to 0 gradually, so it gives the impression that audio is fading out.

Is this too difficult to achieve? Would a digital potentiometer connected in series to preamp signal, controlled by a Arduino, and then fed to amplifier be enough to achieve this? What are the repercussions? Can this be nicer implemented with capacitors? Is there a good way to switch the audio with a relay or something?


texts: Would either of these BJTs require a heat sink?

texts: I am brand new to heat calculations and trying to determine if I need a heat sink for the BJTs or not.  Below is the circuit with voltages and current with the data sheet of the used BJTs.  The maximum ambient temperature will be 25C.


texts: how to properly integrate kalman filter in a project?

texts:
this can be a little bit complex to understand, so I ll try my best to explain and hopefully someone can answer me or guide me on this.

I'm doing a time series prediction on some data that I have, the project is to predict the vehicle trajectory. my data set consists of 40k data points and I have 5 features which are longitudinal and lateral Acceleration, speed, yaw rate, wheel angle and timestamp so my project is about predicting the position from those features except timestamp of course because it doesn't count as a feature.

so what I first thought about was to use Neural Networks and yes maybe it was a bad decision to start with. I had bad results and the network was not able to converge or rather to generalize, I tried FFNN and RNN/LSTM too since I'm doing a time series predictions but as I said the results was bad maybe because my data are not informative enough or the quality of my data are bad etc.. since I'm sure that there was no problem in the model itself or some hyper parameter choice or something.

I read recently that for this type of problems, peoples or engineers use the Kalman Filter. Now the first what I though about was how can I integrate a kalman filter algorithm in my project? I made some search how the kalman filter work but I didn't know where to start. I mean for Neural Network the process would be to build a model by letting it train on the data and then save it as a .pkl or .pt(pytorch) file or something and after deploy I ll just call prediction on the new data with that model and receive the results. My question is how would this deploying process look like with the Kalman Filter, I don't want to start something if I knew that in the end I ll not be able to use it or rather integrate it in my project.

It seems like I don't have to build a model and deploy it when using kalman filter. so how can I use those 40k data points that I have with kalman filter and then test the results?

I'm using python as a programming language


texts:
My mum's sewing machine released its magic smoke, and while I'm reasonably adept with a soldering iron, I don't have sufficient experience with electronic components to do this all on my own.
I have identified one blown electrolyte(?) cap and two other that I also want to replace now that I'm at it. There are two identical 0.1uF and one 0.01uF (edit: corrected 'milli' to 'micro'.
Here are pictures -- can you help me find an online store where I can buy replacement components? Thank you!

This is one of the 0.1mF -- it says "PME 271 M610". I can get no good reading of the smaller type.


texts:
I am trying to create an electronic trigger system with an airsoft gun.
Requirements:

Fire once (rotate motor for one revolution even while trigger held).
Fire multiple (rotate motor for as long as trigger is pressed).
Safety switch to stop motor if closed.

I am Struggling with req 1 as need to detect a full revolution and then disable motor until trigger released and then repressed.
So far I have one switch for the safety (simple flip switch) which will be put in between power and rest of circuit.
I have another normally open button for the trigger which will be placed between motor and safety switch mentioned above.
I then have a gear (turned by the motor) which has a part extruding which will press another button.
I’m then wondering how I can implement functionality to stop the motor if the above switch is pressed.
My idea is to add a electronic switch of some kind which is opened by the above switch cutting the power to the motor for as long as the trigger button is pressed and then closed when the trigger is fully released.
I will also need to add a method to choose between req 1 and req 2.
Thanks hope that explains better.


texts: How to wire several 78XX series regulators?

texts:
I have a 30V power source and I need to get several different voltages from it using linear regulator. 24V for op amps, 12V for relays and 5V for MCU. They all going to be installed on a heatsink.

If I wire them in parallel 7805 regulator have to drop 25V and that means a lot of heat. if I wire them in series all of the current is going to pass through the 7824 regulator and that is going to generate a lot of heat too.

simulate this circuit – Schematic created using CircuitLab

I know linear regulators basically are not efficient but for this specific project I need a linear output.

Comparing this two configuration, which one is more efficient? series or parallel?


texts: Smoothing and decoupling power source input

texts:
I am transforming an old battery-only radio so I can connect it through a DC input. I found an earlier model diagram that includes the DC input (picture attached). I have connected a 18 V DC source (Switching Power Supply from Maplin). However, even using the 0.01 uF capacitor I still have quite a strong hum. What else could I do to further smooth the input? Would it make sense to connect more capacitors in parallel?

I have tried to find a way to calculate the decoupling capacitance or even simulate it without success.

Here is a sample of the hum I'm hearing (I'm setting the volume up and down so the hum can be identified):

http://jorgepena.net46.net/AudioRecording.mov

UPDATE

As suggested I have implemented the circuit shown below. It reduces the hum to about half of its volume without reducing the music volume. Is there anything else I could do to further reduce the high frequency hum? Would it make sense to decrease the voltage to 15.5 V or to add more capacitors?


texts: Why are ethernet ports always upside-down?

texts:
I have noticed that in almost every board, RJ-45 Ethernet sockets are always soldered upside-down. Why are these sockets made this way? Wouldn't it be easier to make and solder them with the pins laying on the bottom?

(source: picclick.com)


texts: resonant frequency in a series resonant converter circuit

texts:
I am designing a series resonant converter and wanted to convert 700 VDC to 100 VDC by using galvanic isolation. The switching frequency should be about 300 kHz (the output load is R = 1\$\Omega\$).

The question is what should be the resonant frequency? Is it better that the circuit works inductive or capacitive?

Please answer me in two cases. First case is when it is an open circuit, without any controlling circuit. The second case, when it is a closed loop, with controlling loop (for example controlling PWM of the MOSFETs).


texts:
Is there some standard how the RX and TX cable pairs in a device are connected to a RJ45 ethernet jack?

Clearly I cannot just connect the TX pair of device A with the TX pair of device B. That would only work with a cross cable.

If a ordinary network cable is used, there must be some place where the meaning of RX and TX is swapped. Where is that usually done? Inside the network hub or in the device?

In my case, I'm working on a measurement device that I want to give ethernet access. It should connect to an ethernet hub just like any PC would be connected.

So, should I swap RX and TX pairs inside my device or is that done within the hub?


texts: Wire bypass/override switches in a landing gear circuit

texts:
The wiring diagram below is for the Landing gear circuit in a homebuilt airplane using Automation Direct pressure switches. These pressure switches turn the hydraulic pump off when a pre-set pressure is obtained. As pressure bleeds off over time the pump will re-energize when a pre-set lower pressure is reached.

I want to add TWO momentary push-button switches that can override/bypass the pressure switches. Why? Well, for example, if the pressure switch in the gear up part of the circuit should fail, I can still get the gear to retract by activating the override push button.

Another example would be on a lengthy cross country at high altitude where the colder temps cause the pressure that holds the gear up to fall enough to slow me down (because of drooping gear doors), but not enough to activate the pump automatically. In this example activating the gear up override/bypass switch manually will bring the pressure and the drooping doors back up.

Is it even possible to do this? I want the pressure switches to do their thing most of the time, but as I indicated there may be times when I want or need to operate the pump manually. In order to do that, however, the pressure switches will need to be completely bypassed.

In the diagram I posted, the red and green marks represent momentary push button switches. I think wiring those switches in as shown should be all that is needed, but I'd like to have an expert's opinion before I start running wires through the airplane. The alternative spot for the push button switches would be in the signal lines (white wires coming off the two pressure switches).

Thanks in advance for any insight you are able to provide.


texts:
Im looking to drive an LED, but am not sure if i should use an op-amp or bjt configured as a switch. Is it possible for an op-amp to source roughly 10mA; the current needed to drive an LED in series with a resistor?

If this depends on the type of op-amp, then how would I go about figuring out the maximum current an op-amp could source?


texts: Using enameled copper wire as a capacitor for measuring water level in a tank?

texts:
I'm trying to make a capacitive water level sensor using two enameled copper wires used in transformers. I've used sanitary silicone to insulate the bottoms of the wires. (Coating is insulated by default.) The distance between them is 0.5 cm, they are submerged in a water tank made out of acrylic glass. As the fluid level rises, capacitance should change, the "sensor" is connected to a IC555 timer which is used to generate a square wave with frequency inversely proportional to the capacitance.

Then I'm calculating the time which passes between two rising edges of the pulse using an STM32 microcontroller. I've connected the IC555 timer output to an oscilloscope and when the tank is empty it gives a square wave of a certain frequency, but when the water level rises nothing changes. What did I do wrong? What could be the issue? I'd like to hear someone more experienced on the matter since I'm just a student and I lack experience. Any help would be appreciated, thanks in advance.


texts: 3 phase Motor connection, 230V delta or 400V star?

texts:
I have a motor with specifications:

star 400V
delta 230V

and motor is of course 3 phase.
Now the question is, how can I connect the motor to delta connection if I have only 400V line to line voltage? Where can I get 230V line to line? Will I damage the motor in delta connection? Is delta configuration only meant to be using with VFD in that case?


texts: For variable voltage devices, namely SD cards, how much power do you save by using a lower voltage?

texts:
I'm designing a computer vision system and my 3 main components are

microcontroller   (VDD = [1.8V, 3.6V])
microSD card (4 bit mode, VDD = [2.7V, 3.6V] according to SD 2.0 standard)
cheap cell phone camera (using the 8 bit parallel DVP interface, VDD = [1.8V, 3.0V], Vanalog = [2.6V, 3.0V])

I suppose using lower voltages will reduce power, but I'm starting to doubt this because I found all the components have an internal switched capacitor regulator that change the voltage further (1.3V for the microcontroller, 1.5V for the camera, and probably a high voltage for the microSD). So, using a lower voltage will just result in a higher current draw. The only exception is for the camera, whos datasheet says it uses a linear regulator to drop the external DOVDD (I/O voltage) to the 1.5V digital core. In that case, I can save (2.7V - 1.8V) * 0.1A = 90mW by using 1.8V instead of 2.7V. This is about a 15% power saving for the whole system.

Currently, I can get away with using 2.7V for all my components. I'm only working on this as a hobby and only have a 1 layer PCB, so I'm hesitant about using multiple voltages.

So my questions are:

How much core/internal power does using a lower external voltage save? None?
How much I/O power does using a lower voltage save? I'm aware from Bill Dally's presentations that data transfer often consumes more power than computation, but I'm not operating at GHz speeds. According to the camera data sheet, table 8-3, when you don't use the internal regulator for generating the 1.5V core voltage, the I/O current, Idd-do is only 9-12 mA, so using a lower swing wouldn't save much power.
How do you use the 1.8V mode on SD cards? Initially, you need to operate at 2.7 - 3.6V. After sending a CMD5 requesting 1.8V, then you can drop to 1.8V. But this seems hopelessly complicated to me? That means I need to drop the voltage to the micro controller too, right? and do it gradually. Are there any regulators that allow smooth transitioning from 2.7V to 1.8V?


texts: Edit a silkscreen over a gerber file in Altium

texts:
I have some gerber files that are perfect, except the legend. I would like to include some useful information on the top silkscreen.

is it possible to edit a new PCB using a gerber file as background in altium?


texts: Reading and processing 32+ ADC channels at high frequencies

texts:
For a project I need to sample 32 or more photoresistors at a time and return an ID and value of the brightest photoresistor over some communication (i2c, serial, etc doesn't really matter to me).  I am struggling with how to read so many ADCs at the same time while keeping high return rates (>100Hz would be preferable, but that may be unrealistic).

I've heard that FPGAs can be used for this purpose, but I have limited time and no experience with them.  Are there any microcontrollers that have so many ADCs, or do you have any other suggestions?  Thanks.


texts: How to use LiPo to power 3 servos, brushless motor, and an Arduino board

texts:
QUESTIONS

Can the LiPo battery at the top of the list be used to power all the
devices below?
How should I connect the LiPo to each device (what types of
connectors, resistors, etc, are required)?

DEVICE LIST
The devices that need to be powered are listed below with their specs.

LiPo Battery

2200 mAh, 11.1V, 25C, 3SP1
Link: https://www.unmannedtechshop.co.uk/gens-ace-2200mah-11-1v-25c-3s1p-lipo-battery-pack-with-xt60-plug/

Servo Motor (Powering 2 of these)

Operating voltage: 6.0 V ~ 7.4 V
Operating current: 320 mA ~ 420 mA

Brushless Motor (already have an ESC for this, details in google doc, link below)

Max current: 15 A
Max power: 176W @ 11.1V (3S) / 235W @ 15V (4S)
ESC: 20 A ~ 30 A

Micro Servo Motor

Voltage: 4.8 V ~ 6 V

Arduino Uno Board

Operating voltage: 7 V ~ 12 V

More detailed specs for all devices can be found in this google doc:

https://docs.google.com/document/d/196PaVFeP7swqFn_bPVLs1uTsZK0QdLwc4sNMUhzOBs8/edit?usp=sharing


texts: What is "recovery time" on CY74FCT191T datasheet

texts:
Looking through TI's CY74FCT191T datasheet I found this line :

\$t_{rec}\$ recovery time | #PL after CLK↑ | 4.5 ns

I hesitate between two interpretations of this line, #PL loading data during it's falling transition :

#PL shouldn't fall counting 4.5 ns from the CLK rising edge
#PL shouldn't be low counting 4.5 ns the CLK rising edge

How to interpret  this datasheet line ? Or in general, what does recovery time means in IC's datasheet (not diode reverse recovery time)


texts:
Circuit 1
i am quite new to PCB and circuit designs. I am trying to build two PCB consisting of ESP8266-12E and Shift Register (SN74HC595N) as a core of it and a high voltage relay control circuit. I have designed a low power PCB design to control via manual switchs which can be connected on terminal.
I am using SN74HC595N because there is a ready library for arduino to control, which makes things easier to code.
here is how my PCB looks like:

here the RED tracks are for jumpers i guess, that will help to keep things on single layer PCB.
Circuit 2
To control the high voltage (220V) appliances i kept things on the another PCB. This is a PCB design not executed anything yet. Need professionals feedback to understand in case if i need to improve something in this. Because i know i might have made mistakes while designing. So just to educate myself i am trying to build this PCB Design. I try to keep proper distance between the tracks and keep the expose copper area as well, so i it can allow higher current to flow.

Note: I am not going to build this relay control circuit. As it might be dangerous, just trying to understand where to improve it.
Also one more thing, is it a good idea to keep ground plane around 220v AC supply in relay circuit? Because i have seen in ready modules available in market they keep it, but i am not sure how much it will be helpful.
Here is complete schematic diagram for the same.

Any feedback from your end will be helpful to understand and gain more knowledge.
AFTER UPDATES
As per the suggestions here are the new updates, i try to maintain as much gap as possible on the relay (HV - Circuit 2) board circuit. To keep low voltage component as far as possible.
With circuit 1, i just changed the whole layout basically, to bring 2 layers to make things easy and also to bring more flexibility on the platform. Please feel free to keep the reviews posted.

TOP VIEW of Circuit 1

BOTTOM LAYER VIEW of Circuit 1

Thank you so much for your kind support guys!


texts: Presence of Crossover Distortion in Class A Amplifier

texts:
This question is about theory facts of class A audio amplifier.

It is known that class A amplifier is usually biased so that an amplifier's quiescent point is in the middle of the amplifying device's load line. For class B amplifier is known that it is biased in such manner that quiescent point is sitting at the lowest point of load line (in cut-off region). In terms of practical terms, class A will be crossover distortion free, while there will be at least some crossover distortion seen in output signal of class B amplifier.

However, author G. Randy Slone had mentioned in a book named "High power audio amplifier construction manual" under section of distortion mechanisms that crossover distortion cannot be completely eliminated from class A amplifier.

I wonder, whether his statement is really true, since it doesn't seems logical that crossover distortion could be recognized or measured in any way in class A amplifier. It seems reasonable for class A amplifier to completely eliminate crossover distortion since amplifying devices are fully biased and are conduction 360° of overall input signal. Does his statement holds true from any point of view? Because to me it seems pretty unrealistic for class A to generate even negligible amount of crossover distortion.