texts: Reliable way of measuring mains voltage by capacitive coupling with oscilloscope

texts:
The question is not about any precise measurements, just for the lack of a better title.

Trying to model what one of those non-contact voltage detectors would see when brought closer to a live wire.

In my understanding it should see an increase in the amplitude of the capacitively coupled waveform of the mains frequency because the closer the 2 conductors are the greater the capacitance.

Now when touching a metal object (e.g. ruler) with an oscilloscope probe it registers a mains frequency waveform. I would expect that if I get the ruler closer to a mains wire then the amplitude will increase, but it doesn't happen it actually decreases and increases when I move the metal object further away.

What's happening?

I guess there may be other factors at play like the fact that the oscilloscope is powered from the same mains (tried isolating it with a transformer but this didn't change this behavior), the mains has no ground wire etc.


texts: AXI interface of an FFT core expecting more data than it should

texts:
I am working with the FFT v9.0 core from Xilinx.

The FFT is configured to use the Radix-4 Burst I/O architecture.

When I reach the last element of my signal, I set s_axis_data_tlast to 1 (while transmitting the last data point) and set it back to zero. I neither get an event_tlast_unexpected nor event_tlast_missing.

My problem is that the s_axis_data_tready signal from the FFT remains high!

In order to satisfy the FFT I had to give it 15 additional data points after it has already accepted the last datapoint:

In disbelief, I reduced the length of my data stream from 4096 points to 64 points so that I could manually count the data points that were transmitted. This caused the same behaviour - again the FFT requires 15 additional data points in order to proceed.

How can I resolve this issue?

EDIT 1

Maybe I should provide some more information:

The FFT core is clocked at 200 Mhz while my data points arrive at a rate of 50 Mhz, so I am actively slowing down the FFT with s_axis_data_tvalid. Each sample has a length of 81.92 microseconds and I start transmitting a new sample every 300 microseconds.

My plan was to feed in my first sample for 81.92 microseconds, recieve the output within 218.08 microseconds and then feed in the next sample.

If I don't fill the buffer (see Dave Tweed's answer), the FFT simply waits 218.08 micro seconds and fills up it's buffer with 15 points from the next sample. Then s_axis_data_tready goes low and the FFT returns it's output while it should be recieving data from the new sample.


texts: Using Dither to achieve finer PWM resolution

texts:
In practical industrial applications (regardless of any particular industry), is there any use for a dither module that goes along with a PWM module considering HRPWM's are available. With my limited experience I can justify using the former as it's most likely cheaper than the latter. However, this is a rather weak reason, and I was hoping someone can share their experiences/thoughts on the usefulness of dither?

My intention is to keep this question as far as possible from being opinion-based or too broad, but just to make sure - I am looking for an extended 'yes' or 'no' answer to whether a dither module may be useful in practical applications.


texts: Leakage current in in-line mains filters

texts:
I have an two inline (EMI) filters. One with the rating (as given in datasheet):

LEAKAGE CURRENT: EACH LINE TO GROUND

A. @ 115 VAC 60Hz............................0.20 mA MAX

B. @ 250 VAC 50Hz.............................0.40 mA MAX

And another one with the following details:

LEAK CURRENT
 0.8mA MAX 250V,50HZ

Are they same when it comes to leakage current as a parameter ? What I am understanding here is that since in first one EACH LINE TO GROUND LEAKAGE CURRENT IS 0.4 mA it will sum up to 0.8mA for both.
I am an Electronics person and Electrical bounces a little above my head. Kindly help.


texts: Singular error when putting a current source in series with a capacitor (ngspice)

texts:
I am getting singular errors when I simulate a current source in series with a capacitor with the following .cir file:

* Spice netlister for gnetlist
C1 1 0 1
I1 1 0 1
.TRAN 100u 6m

(I understand a farad is huge, just to make the numbers easy. I have tried smaller capacitor values, but they have not helped.)

Based on my analysis,

I = C*(dV/dt)

Integrating, I expect

V = (I*t)/C.

So I would expect increasing voltage in the mV range over time when I plot v(1), but I get the following error at the below of this message. When I change the C1 into an R1, no error is observed at all. What is going on?

Doing analysis at TEMP = 27.000000 and TNOM = 27.000000

Warning: singular matrix:  check nodes 1 and 1

Note: Starting dynamic gmin stepping
Trying gmin =   1.0000E-03 Note: One successful gmin step
Trying gmin =   1.0000E-04 Note: One successful gmin step
Trying gmin =   1.0000E-05 Note: One successful gmin step
Trying gmin =   1.0000E-06 Note: One successful gmin step
Trying gmin =   1.0000E-07 Note: One successful gmin step
Trying gmin =   1.0000E-08 Note: One successful gmin step
Trying gmin =   1.0000E-09 Note: One successful gmin step
Trying gmin =   1.0000E-10 Note: One successful gmin step
Trying gmin =   1.0000E-11 Note: One successful gmin step
Trying gmin =   1.0000E-12 Note: One successful gmin step
Trying gmin =   1.0000E-12 Note: One successful gmin step
Warning: singular matrix:  check nodes 1 and 1

Warning: Dynamic gmin stepping failed
Note: Starting source stepping
Supplies reduced to   0.0000% Warning: singular matrix:  check nodes 1 and 1

Trying gmin =   1.0000E-02 Note: One successful gmin step
Trying gmin =   1.0000E-03 Note: One successful gmin step
Trying gmin =   1.0000E-04 Note: One successful gmin step
Trying gmin =   1.0000E-05 Note: One successful gmin step
Trying gmin =   1.0000E-06 Note: One successful gmin step
Trying gmin =   1.0000E-07 Note: One successful gmin step
Trying gmin =   1.0000E-08 Note: One successful gmin step
Trying gmin =   1.0000E-09 Note: One successful gmin step
Trying gmin =   1.0000E-10 Note: One successful gmin step
Trying gmin =   1.0000E-11 Note: One successful gmin step
Trying gmin =   1.0000E-12 Note: One successful gmin step
Note: One successful source step
Supplies reduced to   0.1000% Warning: singular matrix:  check nodes 1 and 1

Supplies reduced to   0.0000% Warning: singular matrix:  check nodes 1 and 1

Warning: source stepping failed

Transient solution failed -

Last Node Voltages
------------------

Node                                   Last Voltage        Previous Iter
----                                   ------------        -------------
1                                                 0                    0

doAnalyses: iteration limit reached

run simulation(s) aborted


texts: Current limiter with low voltage drop out

texts:
I am looking for way to limit the output current from a LDO (Vout = 5V) to max. 150mA. I found only this circuit

but the problem with this circuit is the voltage drop Vbe of the transistor Q1 and voltage drop across Rsense are too big. Using a Mosfet can solve the problem with Q1 but voltage across Rsense will still be big. Are there other kinds of circuits that I can look for limiting current while keeping load voltage > 4.9V?


texts: Convert digital signal to UART and visa versa

texts:
For a project, I am trying to decode the digital signal (depicted as Example 1 and 2 in the diagram below) into UART and from UART into a similar digital signal. The digital signal is generated from a power line communication protocol/chip.

Diagram is made with http://wavedrom.com/

As you can see data is half the speed of the actual changes, the second half of each UART data-bit the signal always goes to logic 1 if it was not already 1.

If the data is 9600 baud 8 bits even parity and one stop bit, the current digital signal is not decoded well. Is there an easy solution to it? E.g. removing the change in the last half of the data bit.

For encoding, how could the UART data be converted back again? Since we need to add again the 1 for the second half of each bit.

How can this be solved? Since bit banging is not the nicest solution.


texts: How do I convert ldi R17, 129 to machine code

texts:
What I got was 1110 1000 0001 0001 when I converted it to machine language. Is that right? Also what are the CPU activity steps and where am I going to use the address 0xF000?

Is this the right CPU activity steps?

PC is 0xF000
   MAR - PC = 0xF000
   0xC000 placed on address bus by MAR
   CPU issues READ command to memory
   next address is returned on the data bus
   PC is incremented by 2


texts:
The 2009 Hyundai Genesis has a combo CD player / stereo / Navigation / car information system. It has an LCD panel that displays information from this system but I'd like to get it working with a different display.
I found a pinout for the connector (see below - top row), and it has Tx0-/+, Tx1-/+, Tx2-/+, TxCLK-/+.... and then one labeled GND and one labeled Data.

With three TX pairs and a TxClk pair this sure looks like HDMI to me.
And I tested the one labeled GND and it is, in fact, connected to the metal casing for the unit. But what about the one just labeled data?
I watched HDMI 2.1 & TMDS Crash Course and while this is a proprietary connection I think it's possible that the additional wire would be one that is part of the HDMI spec. According to the video, the TX0,1,2 and CLK pins are required but an HDMI cable could have some optional ones including DDC/I2C, HEC (ethernet), ARC (audio return), or CEC/hotplug ( see diagram from video below).
There's no reason for this to have Ethernet or Audio Return. I think I2C needs two wires, not "one wire and a ground". And there isn't a 5V source in the cable so I don't see how it could be the hotplug detect wire. I'm stumped.
What would the Pin #5 "Data" wire be?


texts:
I plan on building this buffer circuit to use my sound card as an oscilloscope, but I’m not sure on the best/acceptable way to get the -12V.

Can I use a 24V DC power supply and then use a voltage divider (maybe with a zenner diode) to create a virtual ground?
Can I use something like an LM7812 to step the voltage down from 24V to 12V and use that as a virtual ground?
Or is there a more preferred way to accomplish this that someone can point me to?


texts: How to route a LVDS clock from FPGA input to output?

texts:
Using VHDL, How is it possible to receive a pair of LVDS signals (say external clock) on the FPGA and route them to another pairs of pins to go out, without any modification?

I have tried IBUFDS and OBUFDS with an intermediate single-ended signal in between but all I get at the output is a rising edge, not a clock. I also tried to put ODDR in between but I got the same.

I am using Xilinx 7 series FPGA (on Zynq) and it has LVDS pins. The VHDL code and the constraint file is like this:

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
library UNISIM;
use UNISIM.VComponents.all;

entity fanout is
  Port ( CLK_IN_P  : in  STD_LOGIC;
         CLK_IN_N  : in  STD_LOGIC;
         CLK_OUT_P : out STD_LOGIC;
         CLK_OUT_N : out STD_LOGIC;
         LD0       : out STD_LOGIC);
end Fanout;

architecture data_flow of fanout is
  signal clk_lvcmos : STD_LOGIC;
begin

  -- LVDS input to internal single
  CLK_IBUFDS : IBUFDS
  generic map(
    IOSTANDARD => "DEFAULT"
  )
  port map(
    I  => CLK_IN_P,
    IB => CLK_IN_N,
    O  => clk_lvcmos
  );

  -- Internal single to LVDS output
  CLK_OBUFDS : OBUFDS
  generic map(
    IOSTANDARD => "DEFAULT"
  )
  port map(
    O  => CLK_OUT_P,
    OB => CLK_OUT_N,
    I  => clk_lvcmos
  );

end data_flow;

and the UCF file is:

# Input clock differential pair
NET CLK_IN_N LOC = C20  | IOSTANDARD=LVDS_25 | DIFF_TERM = TRUE;  # "FMC-LA18_CC_N"
NET CLK_IN_P LOC = D20  | IOSTANDARD=LVDS_25 | DIFF_TERM = TRUE;  # "FMC-LA18_CC_P"

# Output clock differential pair
NET CLK_OUT_N    LOC = G21  | IOSTANDARD=LVDS_25;  # "FMC-LA20_N"
NET CLK_OUT_P    LOC = G20  | IOSTANDARD=LVDS_25;  # "FMC-LA20_P"


texts: What happens when 3 phase AC motor running clockwise is suddenly reversed?

texts:
Considering motor as an iductive load, when current passes through the inductor it stores it as magnetic energy. By changing 2 phases in a running 3 phase motor would reverse the motor.

What happens to the stored magnetic energy in the motor inductance?
Will there be an "inductive kickback"?


texts: \$pV/\sqrt {Hz}\$ in Power Spectral Density

texts:
I am trying to plot a Noise Spectral Density from 10 kHz to 1 MHz. The Graph shows a cure which at 1 MHz the noise is 76 pV/rootHz. I am unable to understand that unit definition here. Becuase the unit Says that it is per root of Hertz it has 76 pV. Is that true? Should I apply a formula to convert it to frequency. Please let me know. I have attached an image.

Thanks in advance.


texts: How can I make my flyback converter discharge immediately?

texts:
I'm using a flyback converter (220-100V to 19vdc) to power an electronics unit. But it doesn't discharge fast enough, this causes some relays to stay energised for a second or two after power supply is cut off which is not ideal.
Any ideas on how to make the flyback converter discharge almost instantly?
Also, what can cause a relay to stay energised after supply is out?


texts: Approximation of the resistance in a solenoid consisting of alternating sheets

texts:
I thought it would be a nice idea if a solenoid would use sheets instead of wire to increase the coil density. In the picture, orange parts are placeholders for copper and blue for an insulator.

The issue is that the inner diameter can be drastically smaller than the outer diameter. This would also drastically increase the average circumference, which I use for resistance estimation. So it seems like ever increasing diameters will not decrease the total resistance anymore.

Unfortunately, I am not sure whether using the average circumference for length estimation of the coil windings is really accurate in such a case...


texts:
I would like to make a wire heater to help a beekeper friend.
My idea was to use a laptop power supply that I got for free. The output is at 19VDC and around 4A maximum. However, when the outputs are short circuited, the supply is beeping (short circuit protection). What would be the best way to use this supply to heat a wire? Is there a way to remove the short circuit protection without the power supply starting a fire? Or is another cheap circuit better ? Thanks.
Edit: It won't actually be in a beehive. The aim is to create a heating system to attach wires to frames in wax, that will melt. The wires are multiple and the system only connects to the wires at each end to heat them. (Sorry English is not my mother language so it's hard to explain, I added an image for illustration).


texts: Switching between several high power DC devices?

texts:
I would like to control several high power DC devices (12V DC LEDs). From a tutorial, I found that I can control these using a 3.3V PWM input and a MOSFET. From what I understand, the MOSFET only allows current to flow through the LED to ground when the PWM input is high.

I have several (lets say 4) of these LEDs and want to be able to select which one I am controlling. If I could activate the LEDs directly using the 3.3V PWM, then I would probably try to do something like this:

Get a 2 to 4 bit decoder.
Connect 2 output pins from the controlling device to the 2 select pins of the decoder.
Get 4 AND gates.
Using the AND gates, AND together each of the 4 outputs of the decoder with the single PWM output from the controlling device.
Connect the outputs of the AND gates to the LEDs.

I think this would work (please correct me if I'm wrong). If I got one MOSFET per LED, then this approach could still work with the higher power devices that I can't directly control. My two questions are:

Does this approach make sense?
Is there a way to accomplish this using only a single MOSFET?


texts: Why some phones need a 5V charger although the battery needs 3.7V only?

texts:
I've many mobile (smart phone) chargers. The output of them is 5 volts but the battery needs 3.7v only.

Why is it better to make a 5v charger then convert the 5v to 3.7v ?

Why don't we just make a 3.7v charger?


texts: Replace a three wire tablet battery with a two wire one

texts:
I want to replace an old 300 mAh battery in my Chinese tablet with a new 3000 mAh one. The old battery has three wires: red, black and white. The white wire connects to a pad on tablet's mainboard labeled "T", which I have been told is used to connect to the temperature measuring thermistor built into the battery. However, the problem is that my new battery has only two wires: black and red. I connected the red and black wires of the new battery to plus and minus pads on the board and left the "T" pad unconnected.
The tablet works just fine with the new battery, but the problem is that I can not charge the new battery. I connected the charger for one hour but the battery charge level does not increase, not even by a percent.
I think this is because the "T" pad is not connected to battery. What can I do?


texts: Combining digital signal (0/24 VDC) with analog signal (0-10VDC)

texts:
I need some hints how to make an interface circuit that would combine two signals into one:

one is a Digital output is used to current sink (manufacturer wording) a load that is from 5V to 24V with a max current of 250 mA. This give a square like signal. Maximum frequency is 5 MHz. I refer to this as the digital signal or pulsed signal.
programmable analog output, from -10V to +10V, at 16 bit resolution. I need only the 0-10V part. I refer to this as the analog signal.

The output of the combined signal are used to control the power settings in a machine and if it is on or not. This is done with one input at the machine accepting 0-10V as a control signal. 0V is zero power and 10V 100% power. The digital on/off signal determines if the voltage level set by the analog output is turned on or off at the machine. At the moment we are using a frequency of approx. 5 kHz on the digital signal.

The interface circuit is not driving the machine.

I have present a 24 VDC supply and 5V DC (500 mA) to drive the interface circuit.

I have been looking at using a operational amplifier, like the AD712, and a switch, like the ADG202A, to switch the operational amplifier on and off, is this a good solution?

As mentioned the analog output can be negative, but the machine should only be controlled with between 0-10V. Would the best place be to set a diode before the operational amplifier, as this mean the amplifier only handles positive voltages, and the interface circuit protect the machine from programs errors that would put negative voltages on the analog output?

I am sorry for my bad english and punctuation!

The analog output can provide 5 mA (2K Ohm) according to the documentation. The control input at the machine does not specify anything else than "control signal 0-10V"

Yes, this is my project on RentACoder.


texts: Does fly-by order of bytes matter in DDR3+ design?

texts:
DDR3 introduces a Fly-by mode, which complicates memory controller, which now needs to account for different round-trip times amongst bytes, in exchange for a greater flexibility in PCB design.
I've looked through one of TI reference designs involving DDR3, which IIRC has a mention in the schematics, that control signals should go through bytes in a successive manner, starting from the lowest. And it was realised in PCB/Gerbers exactly this way.
Recently I've looked through yet another TI reference design with a similar CPU and DDR3. What caught my attention was the fact, that this design had lowest byte the farthest in fly-by chain!
I then tried to find any recommendation or standard excerpt in this regard, but to no avail. Every Appnote mentions that control signals go through every byte in a succession and then terminate to a half DDR power supply, but none stresses the order of bytes it should take.
My understanding is that during start-up each byte lane is examined and then measured delays are saved into memory controller runtime configuration space. After that each byte is treated independently from others taking these delays into consideration. So that during read operation, memory controller issues commands and waits for each byte after the delay previously measured. And vice-versa during write it issues bytes according to delays. Is this understanding correct? Or probably does memory controller need to receive bytes in a specific order?
And ultimately, does the order of fly-by topology going through bytes matter? Why or Why not?


texts: Carry look ahead adder with 2-input gates?

texts: I would like to make a 8 bit adder, with carry look ahead, but i only have 2-input logic gates. All I've heard about use some at least 4-input gates. Or do I need to use a totally different method, maybe like the Kogge–Stone adder? (I'm not completely sure how that one works)


texts: I have been looking on the web but all I found was theory that I couldn't fully understand,nor apply .How can a NPN transistor be switched on in active mode?I would appreciate if you would give a more practical and less theoretical answer.


texts: Multiplex Sigma Delta ADC outputs (AD7401A)

texts:
i'm measuring 30 different voltages without common ground. Each voltage is measured by an AD7401A Sigma-Delta modulator/ADC. The signals go into an FPGA (Xilinx Spartan 6). But the I/O-Pins are limited. So I thought to switch between 2 ADC readings and this 15 times simultaneously. Instead of 30 I/O-Pins I need only 15 + 1 control line for the Muxes (TS3A5018DR). But of course the voltage readings need double the time. First 15 simultaneously readings, then switch to the other 15 and then demodulate their outputs.

Do you think that's implementable? And if so, without much effort in comparison to 30 parallel ADCs?
Thanks for your help :)


texts:
I wanted to use Acoustic Emission for the detection of termites. I was going through some research paper and they suggested that it can be done using an acoustic emission transducer of 60khz frequency.

I want to get the data from the transducer so that further signal processing can be done.

For this it was suggested to use a piezoelectric sensor with arduino and then from arduino transfer data to matlab.

But I have never worked before with piezoelectric sensor and that is why I am not able to find the sensor with 60khz frequency.

Can you please suggest a piezoelectric sensor of desired specification or any other sensor that I can use for the same purpose.


texts: Reading signal from 190v magnetic pickup

texts:
I am using a magnetic pickup to detect the phase and RPM of a rotating assembly. The magnetic pickup produces a pulse once per rotation when a ferrous interrupter passes the pickup.

Dependent on the speed, air gap and material that passes it, the pickup produces a pulse of up +-190v.

I would like use this pulse as an input in to a micro controller to allow calculations on RPM and phase shift against other signals.

However, I obviously cannot feed 190v directly in to a micro controller. Are there any ICs available that would either produce a discrete 5v, 0v dependant on polarity, or something similar?

I am also using a precision 18bit ADC, so would a simple voltage divider to reduce the voltage to <5v work? As a slow moving interrupter will produce a very low voltage anyway.


texts: Is there a preferred placement of termination resistor for a differential clock line?

texts:
Looking at a reference design board from Xilinx, we noticed the placement of the termination resistor for a differential clock line (~300 MHz):

The resistor is placed not at the closest possible location, which would be right under the vias which receive the clock (there appears to be a lot of space), rather, it is placed "far away", to the left of the vias. We are wondering if there is a good reason to place a differential termination resistor that way. Any ideas?


texts: Automotive Relays - What is the actual difference?

texts:
Or maybe my question should be 'do I really need one?'

I have a circuit where I am driving an SPDT relay with a PIC (and transistor). The relay is switching 12V and ~150 mA (it is switching the coil current from another existing relay)

The circuit is to be used in a car/automobile and the external relay is an existing standard automotive relay. However, does my circuit's relay need to be 'Automotive' or can I use a standard power relay of the correct rating? What is the actual difference between the two types (if the rating is the same)?

I see from various datasheets that they all have differing shock and vibration resistance, but there are standard relays with better performance than automotive ones. The obvious thing is that the supply is usually 12V and they have high contact currents for big loads, but I don't need the power in my case as I'm only switching coil currents. Obviously there are standard connectors for automotive relays (H4 and so on) but there are also through-hole types, which is what I would use.

I am clearly missing something obvious?

Edit: Added simplified schematic of what I'm doing. Essentially, I am diverting the current from one existing relay to another by using a new relay and inserting a diode. The MCU has associated circuitry not shown, the existing relays are powering motors not shown. The dashed line shows existing wiring that I am cutting. The existing switch shown is a simplified representation of a complex circuit, but basically either one or the other relay is powered, and I am able to change which it is by logic in the MCU (in one direction only).


texts: Correct way to connect MOSFET's source with the circuit's ground

texts:
While practicing in Tinkercad, I stumbled on a problem that I'm not educated enough to solve so I have to ask here.
The goal here is to have the LED powered by the power supply, and Arduino powered on USB, and the pushbutton acts on Mosfet's gate that flashes the LED. When I run the simulation, it works as intended but to be honest the massive ground wiring on Mosfet source seems messy, and when I run the sim without touching the pushbutton, the power supply displays 319 mV and 1A draw - where? I can't figure the mistake, but I sort of think it might have something to do with the way I grounded it? Any advice welcome :)


texts:
I'm having some problem powering my stepper motor through arduino motor shield with external power supply. I already cut the Vin trace on the motor shield, so the main board and the motor shield is not now powered separately.
The stepper motor is rated at 12v, 1.7A.

Using a variable power supply, I've noticed some very odd things. When I restrict the power supply to 5V, 1A, the overall draw seems to be around 0.7-0.9A. When I upped the limit to 2A, the draw was around 1.6A. Understandably, when the stepper motor is braking, the full current is drawn.

However, when I supply 12V, the current draw seems to be whatever I set the limit to. If it is 1A, it always is 1A. When it's 2A or more, it always draws that too. at 12V 2A, the shield is reaching it's limit and gets very hot.

For now, i'm limiting my source to either 12V 1A, or using 5V (since the load isn't that much). But I want to figure out why is it behaving this way. I'm probably missing something very basic here, so any help is appreciated.

Motor Shield: http://arduino.cc/en/Main/ArduinoMotorShieldR3
Stepper Motor: http://www.phidgets.com/products.php?product_id=3319_1


texts: Implementing a Microcontroller with an Iphone App to Control household lights?

texts: Hello everyone I am new to microcontrollers and electronics in general, and would like to learn how I can control lights within my house via an iOS Application. How would I go about doing this...with the use of an custom arduino board or a pre-built microcontroller. Please understand I really have no idea what to do when it comes to electronics, I know the basics and that is all. I also understand how to program. Any help is appreciated thank you.


texts: Measurement of output impedance (ro) of a modified wilson current mirror

texts:
How do I measure the small signal output impedance (ro) of a modified wilson current mirror?

example Q4:


texts: The effect of grounding a simple circuit?

texts:
Suppose I have a simple DC circuit consisting of a battery of voltage V (no internal resistance assumed), and a resistor (resistance R) connected in series by conducting wires. Because the wires are held at a potential difference of V and because they have a non-zero capacitance \$C_{wires}\$, the wire connected to the positive terminal must be positively charged with a charge Q (such that \$C_{wires}=\frac{Q}{V}\$) and the negative wire must be negatively charged with a charge \$-Q\$.
But now suppose that as the circuit operates and current flows through the resistor, we ground the negative wire by connecting it to the earth (which we can approximate as an infinitely large conductor with an infinitely large capacitance). This connection means that the negative wire and the earth will try to attain a charge configuration such that there is no potential difference between the earth and the negative wire. But surely the fact that the earth has a virtually infinite capacitance means that a virtually infinite amount of charge (and hence current) will have to be drawn from the battery to charge up the earth to the same potential as the wire? Obviously this doesn't happen otherwise the neutral wire in a household plug would not be able to be grounded. But what does actually happen? How does the grounding of the negatively charged wire affect the charge distribution of the circuit/earth system and why doesn't the earths huge capacitance imply that a huge amount of charge must be required to charge it up to the potential of the negative wire?
There is a similar question as well as an answer here https://physics.stackexchange.com/questions/397545/surface-charges-on-grounded-conductors-in-circuits-and-energy-transfer however despite reading through it, I still don't understand how the grounding of the circuit doesn't change the capacitance of the circuit.
Any help on this issue would be most appreciated!


texts: connecting speaker and mic to GSM SIM 900

texts:
I have a gsm module but unfortunately it doesnt have an output for mic and speakers. I need to integrate mic and speaker too. In my GSM module, there are male pins available for mic_P mic_N for microphone and spk_P spk_N but I dont know how to connect these to speakers and microphone. Does anyone have any idea about this?
Please share.

I am attaching a pic of my gsm module:


texts: Limiting the Inrush current of the Boost converter device?

texts:
I have a source of 24V and I cannot draw more than 2.4W from the same. This means I cannot draw a current more than 100mA from this supply. Alongside boost converter, it also has some other circuits to supply to. Therefore I would want to charge the output capacitor slowly. This means I want my input current to be limited to at around 40mA.
From the design, you can see that I have got big output capacitance of 2.5mF. Because of which, I have high inrush current while charging these capacitor.
Could you please help me slow down the charging time so that I can limit input current from the 24V power supply? Please suggest your methods that I can try.
P.S.: I cannot reduce the output capacitance as I would want to store the energy and keep in that for dedicated operation.
LM5001 datasheet


texts: RC circuit: C appears to increase in size with frequency

texts:
I've come up with an RC circuit, which is using the output pins of a NodeMCU board to create an AC current for measuring conductivity of a liquid.

What I'm actually measuring is the discharge time of the capacitor, and that's what this question is about. At low frequencies (1-2 kHz) the measured time is exactly as expected based on the capacitance of 47 nF, knowing that the input pin flips when the voltage reaches 50%. That's the time I'm measuring: from fully charged to 50%.

Now at higher frequencies (by lowering the value of the load resistor) the capacitor appears to go up in size, at 120R I'm getting discharge times of around 7200 nanoseconds, that gives me a capacitance of about 120 nF.

How could this be possible?

Other possibly relevant information: the capacitor appears to be a film type (it's a rectangular block); the whole setup is operating on a solderless breadboard (I know there may be stray capacitance in there but that doesn't matter here - I don't care as much about the actual value of the cap as I care about it being constant).

J1 is three GPIO pins of the NodeMCU. The EC probe I replaced by resistors of various value just to measure the response, which I expect to be linear. C1 is first fully charged by the pins 1 and 2 (it gets 100 microseconds for that, RC is just over 15 microseconds), then discharged over pin 3 while pin 1 measures the voltage, flipping when the voltage drops below 50%. All in all a very basic RC circuit. I expect that lowering the value of the resistor over J2 decreases the time linearly - but it doesn't.

At 33k discharge time about 800 us, R/t/0.5 = 48 nF.

At 10k discharge time about 235 us, R/t/0.5 = 47 nF.

At 330R discharge time about 12 us, R/t/0.5 = 73 nF.

At 120R discharge time about 7 us, R/t/0.5 = 120 nF.

My timing is in the 12.5 ns resolution (80 MHz clock speed) so that's not the problem. Being a few ticks off doesn't explain this.


texts:
I have seen references to that feature here and here (pg 20)
I can't quite get why it is useful. Since the memory controller selects the rank, wouldn't be the same if the address on the rank would have been the same as the bank/row/col selected by the memory controller?


texts: In a BJ-Transistor, why do we need to bias the junctions?

texts:
I'm new to electronics and I'm kinda confused about transistors.
In a bipolar junction transistor, why do we need to forward bias the emitter-base
and reverse bias the collector-base?


texts: How to measure/compensate wire's stray capacitance

texts:
How should one measure and compensate (If necessary) a wire's stray capacitance in low-level measurements?

Is Guarding applicable here? If so, does it mean having a wire with same signal voltage twisted around signal wire?

In the example below, DUT is a capacitor whose leakage current must be measured. The black rectangle represents a metal shield. Metal shield is connected to LO terminal of source. (Sorry for childish drawing - I am not Da Vinci :D)


texts:
I bought a Metcal STSS-PS2V-02 soldering iron from eBay, it was cheap and in need of repair. The previous owner had some problems with the handpiece and tried to fix it himself.

I can't get it to heat up at all.

If I turn the base station on without the handpiece connected, it draws virtually no power. With it connected, about 10W.

It appears that he has sawn the handpiece in two, then attempted to resolder the cable. With no soldering tip attached, I am seeing 0Ω between the inner and wire and sheath of the cable, does this mean that his resoldering has shorted it, or should I expect this?

Next week, I'll be able to test the base station against a known working handpiece and determine if the base is working properly, but is there any other way I can tell?


texts: Why are computer displays Class I devices but TVs Class II?

texts:
I was wondering why all computer displays I know are Class I devices, or at least come with a Schuko plug, while all TVs I know are double insulated Class II devices?
I understand it might have something to do with the user being closer to a computer display (although you should not touch your screen anyways or it will get greasy fingers all over it!)
But the computer display casings I know are just made out of plastic so hooking it up to earth really would not make much difference, or am I wrong?


texts: Given a wire and a piece of foil wired to a bread board, is it possible using capacitors wired in series (or some other method) to significantly reduce the capacitance of the wire/foil?


texts:
This is a simple question and I just want confirmation before I buy the wrong power supply.

I am trying to test some LEDs which need about 2-20mA of current at 3.3v. I am gonna be testing a bunch so I need a variable power supply. The problem is that most power supplies have a current regulation of about 0.3% + 5mA. Looking at it I'm guessing that would cause some fluctuations but then I realized it also has a voltage regulation of about 0.3% + 5mV. If I use the voltage regulation at 3.3v and use a fixed resistor that should mean technically my current should only change at a value of VariableVoltage / FixedResistor and thereby essentially giving me a near constant current supply of around 2-20mA depending on resistors used right?


texts: Current transformers, voltage output vs current output

texts:
I'm designing a energy monitoring system that is using split-core clamp current sensors to measure multiple high power lines(40+ lines at 300A each) in a MCB room of a building. I'm currently sourcing the current transformers and noticed that there are typically two types of outputs, voltage and current. I understand the only difference is that the voltage output has a burden resistor built-in the CT. My question is if there are any pros and cons in using one of it in terms of interference or accuracy?
The standard voltage output option seems to be either 333mV or 1V and the standard current output option seems to range from 30mA to 5A. Since most microcontrollers operate at 5V or 3.3V, is there a downside to increasing the burden the resistor, so that the output voltage increases making it easier to measure?
Lastly, if I were to use a 10 channel single-ended ADC on MCUs, and some resistors and capacitors to increase the voltage swing to be above 0V, will I face any significant inaccuracy or interference issues when connecting many CTs to the same MCU?
Any help or advice will be much appreciated thank you.


texts: Analog current and voltage adjustable power supply design

texts:
I saw this circuit on some recommended YouTube channel and I thought it would be a good start to building a custom PSU, learning some stuff along the way. I would like to keep the circuit analog for now since I'm a newbie in electronics so this seems like a good start. The circuit seemed incorrect so I drew one on circuit lab and now I have a couple of questions from what I have. I used parts that I have on hand since I want to know what I'm doing before getting parts online.

How does the current/voltage adjustment work? I understand the two transistors are a sziklai pair which should provide a huge current gain from what is set by the zener diode VD1.
Can I replace VD1 with say, a TL431 which is adjustable? If I can, do I lose R1 or leave it in?
I did it try the circuit on my own, but used a TL431 instead of VD1, the voltage is adjustable, current is also adjustable but when any load is connected that draws over 50mA, the voltage slumps down to zero and but the current can be increased to ~2A. See the second circuit to see my TL431 addition
Would I be better off using a mosfet instead of VT1 and VT2?
Can I leave out the 1K R5 bleeder resistor?

simulate this circuit – Schematic created using CircuitLab

p.s. My transformer is a brick adapter putting out 12V ac from EU's 220-240V Ac. It's rated for 3A but my circuit is intended to put out 1A.


texts: Isolate a linear signal with a regular optocoupler

texts:
In a circuit that considers two different ground domains which can change dependant on the numbers of batteries in a series array (think smart battery), I'm trying to isolate a current sense diagnostic output from a high side switch.
This high side switch will output a current linearly proportional to the load; say 5ma per 1A on the output for example. Because of the different ground domain, it's desirable to isolate this using an optocoupler. Will a non high linearity isolator (like the TCMD1000) with a CTR of around 100% provide a linear current output such that the current sense can be read as a voltage on an ADC on the phototransistor side?


texts: Buck Converter - Closed Loop - Effect of decreasing inductance and increasing capacitance

texts:
Output voltage as a function of output current is plotted from oscilloscope data for a closed loop buck converter.

Switching frequency is kept the same in both the cases.

CASE 1 : Inductance = 2.2mH/Capacitance = 1uF [Closed Loop]

CASE 2: Inductance in decreased to 1mH and the capacitance is increased to 22uF [Closed Loop]

I have to compare these results. I know that increasing the inductance effectively moves the buck converter into DCM.

However, in closed loop control conditions, the waveforms look almost identical. is there any difference? am I missing something?


texts:
I was reading about the HDMI standard and therefore the CML logic, and some alegations are not clear for me about the advantages of the CML.

One of its advantages is the low output voltage swing, so signals varies just some millivolts (about between Vcc and Vcc-0,4V), and thus creating less EMI...but with signals being so small aren't they MORE vulnerable to EMI?

As far as I can see only having a 0,4V swing between 0 and 1 makes any possible form of interference a major issue, isn't it?

I couldn't find many good explanations about the standard online, so any good explanations about it's features and workings are most welcome.


texts: What is this "reversed" connector called?

texts:
Looking at this power connector, what is its name? It's kind of a "reversed" form of the standard IEC 603 C7/C8 coupler.

Also, what could be the rationale of the manufacturer not to use the standard coupler?

Just to be complete, the device is a TP-link TL-WR710N Wifi Router.

I want to get a cable connecting a type C plug to the device to be able to plug it in farther away from the wall box.


texts: Astable multivibrator: what starts the first cycle

texts:
I think I understand how the astable multivibrator works once the LEDs are blinking (cf. below), but I don't understand how the first cycle begins.

I can see that at first, the 2 LEDs are on (based on this simulation) so it's means that Q1 base and Q2 base are high. Also C1 is charging via R2 and C2 is charging via R3.
Then suddenly, the voltage across one of the capacitor reverses its direction (in the simulation linked it's around 370ms). I don't understand why this is happening. Why the capacitors do not continue to charge or stay fully charged ? Why the current flowing through one of them reverse its direction?
All the articles and questions/answers I read start after this step and miss this crucial explanation (cf. this answer "Assume that transistor Q1 has just switched “OFF”")

If I understood well, this is how the cycles work:
When LED 1 is turned on, it's because of a high voltage on Q1 base (and the left side of C2). While LED1 is on, C1 is charging via R2 until its right side reach a high enough voltage to switch on Q2 (via its base). This switches on LED2 and discharge C2 via Q2 thus lowering the voltage on Q1 base which turn off LED1. Now C2 is charging via R3 until its left side reaches a high enough voltage to switch on Q1 base which switches LED1 on. Then the cycle continues.


texts: Why are Nickel Iron batteries expensive, less manufactured and not researched much?

texts:
I have read about Nickel-Iron batteries and from what I have understood they have very long life and large cycles. They are heavier than lead-acid batteries, but even lead acid cells are used in places where weight doesn't matter much.

So, my question is why don't manufacturers innovate or develop this chemistry much? I guess the cost is due to the limited production. Is it because of the long life manufacturers hesitate to produce it which will reduce profit due to reduced replacement cycles? Also this cell chemistry doesn't have any toxic heavy metals either.


texts:
I wondered if anybody knew recent, opensource jtag software to run jtag test based on netlist files.
I see gojtag but it seems outdated software.
Thanks in advance.


texts:
I have a circuit that you can see on upverter.

I've been using this for some time and have built a few of these, but I'm hooking one up now and it's not working. I troubleshot and narrowed it down to the fact that the MOSFET is simply not coming on with the 3.3V that is on the GPIO pin on my Raspberry Pi 2. If I give it 5V (manually) it activates fine. I switched the MOSFET out for another (same model) I have and it still fails the same way.

The datasheet says that it should have 2-4V for the GS voltage to turn it on, so I'm expecting 3.3V to work (and I've seen it work a few times). Any idea why it would be requiring 5V?

You can see in the upverter circuit diagram that my load is a little toy monkey that is essentially a DC motor with 2 AA batteries. I run wires to that circuit to effectively turn it on with my RP2.


texts: Reset circuit (momentary button toggle as ON/OFF using 555 timer circuit) from an external signal

texts:
I have this "MOMENTARY BUTTON TOGGLE AS ON/OFF USING 555 TIMER CIRCUIT". I want to turn on/turn off the circuit using single momentary button and also being able to turn off the circuit from one of the NodeMCU GPIO pin.
As of now, I can only toggle ON/OFF using the momentary button.
The problem is I didn't know how can I reset the circuit when a GPIO pin from NodeMCU has changed state.
I badly needed help. Thank you very much in advanced. Your help is greatly appreciated.


texts: How do I calculate the K for the dependant source using nodal analysis?

texts:
The question has provided power supplied by the voltage source and Vab = -3.6 V.
I had tried several ways but still can't solve it.
Below is the solving steps I tried:


texts: Circuit using LTC3108, inductor selection

texts:
I want to design a circuit using the LTC3108 low voltage step-up converter. The data sheet (pg.18 -Peltier-Powered Energy Harvester for Remote Sensor Applications-) calls for a LPR6235-752SMLB inductor. Since the supplier that I'm using doesn't have that part in stock, so I have to find another part. Can I use this part: https://www.arrow.com/en/products/b953as-7r5np3/murata-manufacturing ?

Regards,
Aslak


texts:
I am struggling to understand S parameters. As an example, I am considering the S matrix of a capacitor in series with a transmission line. It has two ports, so must be represented by 2x2 matrix. But the form of this matrix eludes me. I thought I could deduce it from the reflection coefficient, giving

$$
S=\left( \begin{array}{cc}
\frac{Z-Z_0}{Z+Z_0} & 1-\frac{Z-Z_0}{Z+Z_0}\\
1-\frac{Z-Z_0}{Z+Z_0} & \frac{Z-Z_0}{Z+Z_0}\\ \end{array} \right)
$$

where \$Z=1/i \omega C\$, but this doesn't seem to give the right answers. Is this correct? Or have I misunderstood the concept?


texts: lm35 output differs while changing my power

texts:
For room temperature 21*C LM35 showing,

23 *C while powered by CPU USB port.
18 *C While powered by a 7amph
12V SLA.

My controller consist of Arduino, adruino wifi shild, and ATMEGA32. ATMEGA32 is attached to the 4 redundant lm35. regulated 5V and GND Power rail are interconnected for all controller.

a. The lm35 are designed as unit gain and double gain by a LM324.
b. AREF of ATMEGA32 are controlled by a LM4040.

I want to share some of my observation:

If I do another Analogue read on ground as the same manner That I do for data,
e.g. For this observation I an using gain=3 for both data and ground, and taking the difference, the result become far better.
When the power is only Battery and no connection with CPU/AC Main line, there is no apparent disturbance on the output.
In the given figure the room temperature are noted for around,

a. 1 Hr for Battery and

b. 45 min for USB USB power. Data are communicated over USB serial cable.


texts: What LED driver IC options do I have to build a two-cell driver for a 3 W LED?

texts:
I need a very small and light 3 W flashlight/headlamp for a kind of specific purpose.

I want to use two AAA Eneloop cells.

In the datasheet there is discharge curve at 1.6 A, so I guess I can discharge them safely with that current.

1.6 A at 1.2 V is 1.92 W per cell, so when I use two, there will be 3.84 W available power. If I can archieve ~80% efficiency, I can use a 3 W LED and batteries will last for 30 minutes (it is enough for the purpose of that flashlight).

What I have found so far:

I found the LT1618 (datasheet link) converter which looks just perfect for me:

Minimum input voltage 1.8 V
1 A current
May work as a constant current and constant voltage source
High efficiency (maybe I could reach 80%, if not - 70% will satisfy me)

My problem:

It is hard to get LT1618 where I live.

My question is:

What other options I have?


texts:
I'm having trouble determining how to route this trace for this USB-C component. I have asked a few sources, but nobody seems to know. (This USB-C is only being used for USB 2.0 D+/D- & charging capability, but to use the physical capabilities of USB-C for a personal/hobby project)

Amphenol UC-31PFFH-QF7001

This may look like a duplicate question from one I posted before, but after getting the board made, I discovered that the dimension was wrong and the USB-C would not fit without grinding away the notch further into the PCB.  The result is what you see in this picture above now.  With the modified dimension, I can no longer route CC2 the way you currently see it.


texts: Noise (capacitance-related?) in serial signal

texts:
The "executive summary" pictures:

I want to decode the serial signal coming out of my tablet's headphone jack. This is a somewhat weird "hack" that exists in a few phones and tablets: basically, if you feed 3.3V in the microphone input of your TRRS plug, the left and right channels become serial TX/RX.

I used a Raspberry PI TRRS-to-TV cable (as you can see in the 2nd picture) to get access to the 4 places I needed: GND, MIC, L, R. The cable is not supposed to do anything other than expose the 3 signals (MIC,L,R - paired with GND) in the three corresponding cables (red, white, yellow).

I used my BitScope's probes to probe between the TX (tip of white cable in 2nd picture) and the common GND (brown probe at the bottom of the 2nd picture). I also used two probes (red and blue one) to "feed" 3.3V from my USB/TTL chip (a PL2303HX plugged in my laptop) to the MIC (red) tip.

Upon rebooting the tablet, I indeed saw what is unmistakably a serial signal at 115200 (peak-to-peak of 8 to 9us), but with lots of capacitance (video).

So, my question - before I go online and order a TRRS plug, cables and a soldering iron - is the capacitance I am seeing due to...

the 1 meter long TRRS-to-TV cable, or the use of probes instead of soldered cables

OR

the probes and cable in fact cannot account for this much capacitance, and the reason I am seeing this is that the tablet's headphone jack simply wasn't designed to emit this signal (i.e. what I am seeing is indeed what comes out of the jack).

As you can probably guess, I am very new to this sort of thing; I am a software guy, bought my BitScope a week ago, and would love to access my tablet's serial for "fun and profit" (hacking bootloader stuff, compiling Cyanogenmod for it, etc).

I'd appreciate an estimated guess on whether this is a lost cause (i.e. the cables can't explain this much capacitance) or not.

Thanks in advance for any help/suggestions.


texts: How to choose Drain current for a JFET Differential Amp

texts: I have to design a JFET differential amplifier with a current mirror. I am unsure where to start and what to set the biasing current to. Any help will be appreciated to point me in the right direction. Many thanks.


texts: Dual Comparators connection that affect the design

texts: If we use a dual in package comparator Example LM2903 and do use only one comparator, what should be done with the other one. It is sure that paralleling the two comparator will cause instability and we cannot leave that comparator unconnected too. Are there any inputs how it can be connected?


texts:
When a function generator is used to power a full wave rectifier an oscilloscope will not show the correct output due to a shared ground. A half wave is displayed because one of the diodes is 'shorted'. All of my research points me to the addition of an isolation transformer to separate the grounds. I am still somewhat new to transformers. We just finished covering mutual inductance and ideal/linear transformers in class so some things are still a little foggy.

I have found two different types of isolation transformers. The 'medical grade' type that have the duplex outlets and the bare 'case type-x'. The type x transformers have the 2 wires in and 3 wires out, depending on the presence of a center tap. So I guess my questions are as follows:

Which method should I use to break up my ground?

Should I invest in a transformer that has duplex outlets?(Tripp-Lite IS250HG or similar) I am not sure how these work, but I am guessing the generator and scope plug into the device and the device separates the two?
Should I buy a cheap TRIAD-N48X bare and terminate my function generator directly into the primary winding and continue my circuit from the secondary coil. Unfortunately, the TRIAD-N48x is the smallest isolation transformer I can easily find. It is rated for 115V/115V.

I wouldn't mind using this method if the isolation transformer will perform with 5-10 volts of potential instead of the listed 115 volts. I assume the 115 is just the max voltage.

I am open to other suggestions. I am on spring break so I finally get a chance to start construction on an organized in-home electronic workshop. So if there is something that I should 'build in' now would be the time! Thanks for reading.


texts:
I am working on creating a simple protection circuit for an I/O pin of an MCU. The input signal will be coming from an array of different devices and I will want to monitor for high/low digital values from the following input types:

Reed Switch (normally open) connecting to GND when closed.
Normally open relay/FET connecting to GND when closed.
12v-24v high frequency input pulse. The signal is typical ~0v, and periodically sends a quick (5ms) pulse of between 12v and 24v (the MCU will be counting these pulses).
0v and 24v signal coming from a thermostat (used to trigger HVAC systems, I will just be monitoring this line, not controlling it).
+5v serial signal (Rx UART) at 9600baud.

The device is 3.3v lithium battery powered, so minimal current consumption (at any input signal state) is important. Vdd is ~3v.

I am comparing two solutions. One uses Schottky diode array, and the other uses pre-biased transistors. I am curious what solution would be recommended, and what the pros/cons would be of each approach.

Diode Array

simulate this circuit – Schematic created using CircuitLab

Pre-Biased Transistors

simulate this circuit

Note: I will actually have two of these input lines, so if I use the Diode Array solution I will need to do two of those identical circuits for each input. For the Pre-Biased Transistor I modeled it using the DS30345 so the one IC would support both inputs.

See Input Protection and Solution for accepting 3-24v as digital high for microcontroller for posts about each design.


texts: Impact on grid if entire country turns off all electrical appliances within few seconds and then turns them on within few seconds

texts:
This is not a hypothetical question but a real one. My country (India) will be turning off all their lights at 9 PM local time on 5th April. They will keep it off for 10 minutes and then turn it back on at 9:10 PM. This has been requested by prime minister amidst coronavirus outbreak in order to challenge the darkness that is looming over the country. Some people have raised concerns that this might cause a grid failure because of sudden disconnect and reconnect of a lot of load.

I understand that there will be a lot of people who won't bother much and will continue with their daily lives. At the same time, there will be a lot of people who will turn off everything and not just lights.

So, assuming that 90 % (it should be far less than 90 % but I wanted to know about worst case scenario) of the load is disconnected across the entire country within a span of 10 seconds and then re-connected again within a span of 10 seconds, what would be the impact on electrical grid and power generation plants? Will it cause any failure in grid or power plants?


texts: VHDL - Why does frequency divider counter max at one less than half period?

texts:
In this tutorial on creating a frequency divider in VHDL, we transform a 50MHz input into a 200Hz output with a process that counts from 1 to 124999.  The guide offers an explanation for why 124999 is chosen and not 250000, but I'm unclear as to why 124999 is chosen instead of 125000.  I'm probably confused by some off-by-one counting issue, but I'd appreciate further explanation here.  For reference, the discussion of the 124999 limit is reproduced below.

  The frequency_divider process, lines 16 to 28, generates the 200Hz
  signal by using a counter from 1 to 124999. Why 124999 and not 250000?
  A clock signal is a square wave with a 50% of duty cycle (same time
  active and inactive); for this case, 125000 cycles active and 125000
  cycles inactive. Since the counter begins at zero, the superior limit
  is 125000 - 1.


texts:
In a board design there's a mistake in the voltage level to control a reset pin (Signal RESETB). It should be 1.8v but it is driven by a 3.3v level.

The datasheet shows the next info:

It looks like the max level is 3.6v for VDDIO but RESETB max. level depends of VDDIO selected, would it be properly detected the RESETB as a logic high at 3.3V?

Thanks in advance.

EDIT

Adding  device maximum ratings table:


texts: Nano capacitors in RAM act as leak bucket and continuously lose charge. For this RAM has to be refreshed periodically in order to charge those nano-capacitors again. "During the refresh cycles memory controller reads the data of each cell and recharge it". This thing puts me in doubt. If memory controller reads data during RAM refresh cycle then that data has to be stored temporarily in somewhere else. Suppose I've 4GB RAM and 80% RAM is being used. "So memory controller requires atleast 2GB space to temporarily store data of RAM during its refresh cycles". Does memory controller also have its own memory? If memory controller reads data then who writes it after refresh? I used to think that "sense amplifiers" are used to read and write data in each column of RAM.


texts: In the real world, what happens if a transistor turning on causes it to turn off?

texts:
So say you have the following circuit:

I apologize if this circuit is super simple, but I have very little electronics knowledge. The program I'm using will be for building circuits out of transistors + wiring to learn the basics of logic gates and circuit design, it's not a full fledged simulator.

In the below diagram, the power source feeds into the base and the collector for transistor A. The base for transistor B is activated by the user. If powered on, and you power the base for Transistor B, that allows a connection between the power source and the ground which grounds out the circuit, which should close transistor A (power source no longer powers it's base) which means the circuit is no longer closed out.

In trying to determine what the behavior for this condition should be, I'd like to know what might happen in real life.


texts:
I need conect two small printed circuit board. I can use any metal cable (what is the correct name for it?) so I buy this. It use the number "NU 30" but I don't find this number in other place and it is the thinner cable in this store.

The red cable "NU 30" is this

The size of plastic is 0.92mm or 0.036inch

The size of the metal is 0.31mm or 0.012 inch:

This cable is not easy to break, so I can turn it 90 or 180 degree without problem, even being thinner. I say this because I an afraid to buy a so thinner cable that can easily break.

So my question is: Where can I find a cable that is thinner than this?


texts:
I'm using RFM69 for wireless communication. I'm new in wireless communication. How can I send data trough RL78 micro controller?

This is the datasheet.


texts:
The display counts range is one of the digital multimeter characteristics, we know that a DMM is based on an analog/digital converter. And we know too that each ADC has a resolution nBits. A 16 bits resolution is 2^16=65535 steps log (65536) =4.8164799306 digits, so something between 50000 and 60000 counts, but we know too that an ADC can't see above its voltage reference (the maximum value that the ADC can convert).
so i have here two questions:

the number of steps isn't the same number of counts?
in our example the number of counts, we calculate is 60000 if the reference voltage is 2.5000v then the number of counts gonna be 25000?


texts: Sampling rate for PID control to balance an inverted pendulum using 8051 - AT89c51rc2

texts:
I want to control a dc motor(to balance an inverted ;endulum)
I want to sample the input from sensors(e.g.: ADXL345) and convert it to digital using a DAC.
The maximum output data rate(ODR) for sensor ADXL is 3200Hz.The input sampling rate and the output control data rate to the motor should be high but not too high as the processor needs time to perform PID control calculations as well.
But how to calculate the sampling rate and the output control data rate to motor  taking these into account?


texts: Could some one explain me technically as to why the bandwidth is severly limited in underwater channel for communications?

texts: I understand that, due to the harsh characteristics of the underwater channel, the effective bandwidth for communication underwater (using acoustics) is severely limited. But i would like to know the technical reason behind this? and what is the impact of the underwater channel on the bandwidth?


texts: Is there an industry term for IC "drop-in" circuits used for malicious or clandestine purposes?

texts:
There is a vocabulary for code used for malicious or clandestine purposes. Terms include malware, virus, trojan-horse...

In a large IC with millions of transistors, it is feasible to produce a version with an additional small drop-in that can be exploited without any special software included in the host machine. These tiny additions are particularly difficult to detect without destructive deconstruction and mapping via electron or X-ray microscopy.

Is there are term for this class of hardware exploit?

I'm looking for something beyond "Fake IC" or "counterfeit IC", those presumably deceive the customer for reasons of profit, but wouldn't necessarily contain extra circuit layout for malicious or clandestine purposes.


texts:
Hello) I need a solution for a board with 8 100/10 ethernet ports (with copper/fiber switching capabilities, PTP and idealy also with PRP, HSR protocol capabilities). I've found KSZ8999I switch, but I think it doesn't support PTP (according to the datasheet it doesn't). I also looked at KSZ8463 switch, it supports PTP but  it has only 2 ports. So, I didn't manage to find an ethernet switch that i need. Do such switches even exist and where can i find them? I also thought about decisions based on FPGA or ethernet controllers... Could somebody give me a clue for a more chip and easy solution? Thanks)

Thank you for the answers) We nearly managed to find a suitable chip for our task (by the way we are pursuing IEEE 61850 standard where PTPv2/HSR/PRP protocols are required) - KSZ9477S. That chip has PTPv2 timestamping, HSR hardware handling, VLAN support and it can be connected through SGMII port to another KSZ9477S (so we can get 10 ports in total). The only disadvantage that this chip has is that its PHYs appear to work only in copper mode (they can't be switched into the fiber mode). So, maybe there are some ICs witch we can connect to KSZ9477S MDI ports and witch can convert copper signal to fiber signal and vise versa. Do somebody know such IC? (like media converter maybe). Or maybe somebody can recommend ethernet switch ICs suitable for our application? Is it even possible to find such IC or we are bound to use FPGA based solution?


texts: What is the difference between SOT143 and SOT143B?

texts: I have a component whose package is defined as SOT143B, and in my layout package a footprint described as SOT143. I am having trouble finding out what the difference might be. At a guess, package height?


texts: AVR USB to Serial Converter; Quick Question

texts:
I have a TI86 calculator that I've had for over 7 years now. Well I'm letting a lady friend on mine borrow it, and I was going to load it up with some apps for her. And the tradeoff is happening this weekend. So I figured, "hey, let's just build a cable really quick". Well I got going down the rabbit hole and since I don't have a serial or parallel port anymore, I'd need a converter.

So I found an AVR USB to Serial converter schematic (which I'm sure ya'll are really familiar with) here:

Couple things:
1. I don't have a straight ATMega8\48\88 around. I only have the 48A-MU\PU, 88A-MU\PU, and the 324P-20PU (which is my favorite) and 328P-PU (Second favorite) immediately available. Without sounding too dumb, am I correct in assuming with the exception of the 324P, the other AVR's I have are compatible? I've used a 328P before for some stuff for the 88 since according to the datasheet it's more or less the same chip, just different grades of it.
2. I only have a 16 Mhz and 20 Mhz crystal. Would it be disastrous if I used those instead, or do I need to modify the code to be safe?

And then last question on this schematic:

If I had 3.6V and 5.1V Zeners, could I make them work? Is there an alternative if not? Zeners aren't something I use, so they're also a mystery to me sometimes too.

So like I said, silly questions. But I'd rather ask before I go wasting my chips and parts, you know?

Gracias, my friends.


texts:
I'm stuck with this doping problem and can't figure out where to go with it.

  The built-in voltage of a GaAs pn junction diode is 1.25 V when the diode's temperature is T = 320K. The cathode region of the diode is doped with phosphorus at a concentration of 1e17 \$cm^{-3}\$. Determine the required doping concentration in the anode region.

Would I go about this by using the equation \$V_{bi} = V_T\cdot ln(N_a\cdot\frac{N_d}{n_i^2})\$?

\$V_T\$ being the thermal voltage
\$N_a\$ being the acceptor concentration on p side
\$N_d\$ being the donor concentration on the n side
\$n_i\$ being the intrinsic carrier concentration

I have completed the following work for the above question.
Can I be checked for accuracy please!


texts:
I am trying to replicate a circuit I found in the Art of Electronics (3rd Ed, page 229) but I am having issues.

My load is a LED (Vf=~2.5V) and using a BC237 as the PNP (measured Vbe=~.675V). Using R=10 Ohms and Vin is an arbitrary waveform generator output (so no R1 or R2, and Vin is stuff like sine waves, but would like to modulate with audio signal in the end). Vcc is 5V, no current limit, and the op amp is LTC1050 (powered off 12V and GND rails).

Here's the problem: Given input Vin, V- net can only track from about 3.8V up to 5V. Why can't the op amp output track an input signal below 3.8V?

I'm thinking it has to do with the diode load, but I can't figure out why it's around 3.8V and not just Vf+Vbe.


texts: How should I use rotary switches and resistor networks to uniquely relate each possible combination of switch settings to an analog voltage?

texts:
I'm designing a switched-mode power supply. I need to give my users the ability to set a voltage setpoint, with a range of approximately 200-800V, and at least 4V of resolution. This needs to be a hardware solution that feeds into my microcontroller. Cheap and simple and hard for the user to screw up are the goals. My predecessors have used potentiometers, which make it impossible to know what you've actually set without running the system. I don't have a display to work with, just a couple blinky lights. Not really the most effective way to identify a voltage like this.

I'm thinking of using rotary switches. Three rotary switches, and an appropriate combination of resistors, should let me translate the setting of the switches to an analog voltage. In my ideal world, 000 translates to no voltage, 999 translates to 3.3V, and every setting in between scales linearly. Alternately, I could use twelve digital inputs to read the same information, but I'll need an I/O expander for that.

I'm sure I'm not the first person to consider something like this. Is there a canonical way of doing this? If I go the analog route, how many resistors am I going to need? How many different values? Or is there an obviously better way to address this problem?


texts: How To use ANDWF in Microchip PIC18fxxxx Assembly Language

texts:
ASSEMBLY LANGUAGE MPLAB PIC18f2550

I am trying to "AND" 2 Variables "If Variable_1 = 0 AND Variable_2 = 1 then"
"DO WHAT IS NEEDED."   "End If"

This below makes no sense used as a "AND" Logic Function.
Will the above STATEMENT work using ANDWF or ANDLW? Do I need to ANDWF each Variable separately, or is it possible to use something else?

ANDWF f , d     Logic AND between the content of W register with the content of a file register 'f'. If d is 0 the result is stored in the W register, if d is 1 the result is stored back to the file register 'f'.
Operation: (W).AND. (f) ® destination
Description: AND the W register with register 'f'. If 'd' is 0 the result is stored in the W register. If 'd' is 1 the result is stored back in register 'f'.

I have read the data-sheet PIC18f2550 and the PIC18 Family
Reference Manual and Looked All over the internet and Stackexchange.
I simply have not found an understandable answer. If the "ANDWF & ANDLW" are truly "AND" Functions

ASSEMBLY LANGUAGE MPLAB PIC18f2550


texts:
According to doc1022, p. 17 (AVR Assembler User Guide):

  User defined labels which are given the value of the location counter at the place they appear.

My question is, what goes into the opcode when a label is used in a jmp and in an rjmp instruction since a label is really the value of the location counter at the place the label appears? Secondly, if there exists an official (or non official) document answering my question, do you know where can I find it?


texts: A stable negative supply for an op-amp (using 555)

texts:
I need a differential amplifier circuit for my design and I am using the LM358 op-amp. The problem is of negative supply. I need to give negative power voltage to my op-amp(-Vcc). and I only have a 9v battery. I found a way to genrerate negative supply voltage using 555.

Negative voltage using 555

However as soon as I cinnect my differential amplifier to the circuit the negative voltage drops from -7.9 to -6 volts. (Some drop was expected but this is too much for my application).

Is there a way I can regulate or stabilize the negative voltage. ?

Here is the comlete schematic.


texts: Help me understand what happens with the circuit when an AC signal is applied

texts:
Consider this circuit.

Transistor is 2N2222A. Ic is chosen to be 10 mA.
Hfe is 225 for that current.
Resistors are calculated to have Vbe = 0.7V and Vc = 4.5V.

I am trying to understand what happens when I inject an AC signal at the base.

Suppose an AC signal that is 1Hz, 0.02V of peak voltage (varies between +0.02V and -0.02V). The capacitor is huge (100F), just to be transparent to 1Hz.

What I think happens is this: as the input increases from 0 to 0.02V, base increases from 0.7 to 0.72V. So the base resistor is now connected between Vcc (9V) and 0.72V. Base current is now less than before, because the difference in potential across base resistor is less than before.

If base current is less, collector current is less, right? If collector current is less, the difference in potential across the collector resistor is less. If so, Vc increases, right?

My simulator says Vc (collector voltage) decreases...

What is wrong with my analysis?

YES, I know this transistor configuration for amplifiers is bad. I am just trying to see what happens to this circuit.


texts: Altium warning: Adding items to hidden net +3.3V

texts:
I am drawing a schematic project in PCB Designer and facing the following warnings when I compile the project:

Adding items to hidden net +3.3V

and

Adding items to hidden net Ground

When I double click one of them, For instance (Adding items to gidden net +3.3V), all +3.3V on the schematic sheet are highligheted!

Any idea what does that mean and how to remove the warning!!


texts: Two deep-cycle batteries connected in parallel by a single terminal

texts:
From what I understand, if two 12v batteries with different charge levels are connected in parallel with both terminals, the charges of the two batteries will even out. The one with the higher voltage will raise the voltage of the lower one and lose voltage in the process.

I'm confused about what would happen if two 12v batteries at different charge levels (or voltages) are connected by just one terminal. I think the confusion stems from the fact that batteries don't just have positive and ground terminals, but they actually have positive and negative terminals. So, if I understand correctly the positive terminal "pushes" positive charge and the negative terminal "pushes" negative charge.

Is the negative terminal of a 12v battery always the same voltage as the positive terminal, regardless of how discharged it is?

Let's say there's two 12v batteries at different voltages. The first battery is discharged to 12.5v. The second battery is discharged to 11.9v. They each have their own loads attached. In my case the load is a power inverter for first battery and lighting for the second battery.

What happens if both positive terminals are shared by each battery at some point? In other words, if the negative is separated but the positive is shared, does the voltage of each battery change? What happens to each of the positive terminal voltages? What happens to each of the negative terminal voltages?

What if both negative terminals are shared by the batteries? Does it have the same effect as sharing the positive terminals? Is it because of the negative charge "push" effect? What happens at each negative terminal in this case? Do they become balanced out at the negative terminal, causing the positive terminals to each have different voltages but the same negative voltage?

Lastly, what if the batteries share their negative terminal by a common ground? Do the negative terminals even out their voltage? Would the ground voltage change in any way? Would the ground voltage change to the negative voltage of the most charged battery? Would the ground voltage change to the negative voltage of the least charged battery?

Sorry for so many questions. Maybe the answer is simple and explains all of them. Thank you so much for your answer.

EDIT: When I refer to sharing only one terminal on each battery, it should be assumed that that each terminal is also still connected in a way that completes the circuit. So when both positives are shared, the positives are also still connected to each load circuit and each load circuit still ends at the corresponding negative terminal. When both negatives are shared, the positive terminals are each connected to their load circuits and the load circuits are still connected to each corresponding negative terminal. I'm not sure if that changes anything.


texts: Wires of Different gauge in primary winding?

texts: Would 2 different wire sizes work in a primary winding (single phase transformer) for example 50 turns of 16awg- 100 turns of 22awg- 50 turns of 16awg? All connected End to end sharing the same ac input. In theory (my theory) is it would leave more space for secondary winding and help with heat losses.


texts: When would I use a 4-20mA differential current input?

texts:
I've recently run into a scenario where I need to pick between a singled ended current input (4-20mA) input device and a differential current input device. Single Ended and Differential. I've never run into (or so I believe) the case where I had a differential current output sensor, thus I've never looked into an I/O card that accepts a differential input current signal.

So my question - when would I know if I needed to use a differential input card? It seems like most 4-20mA transmitter circuits operate in a 2 wire interface. Is the two wire interface always considered to be single ended? Thus the only time I would ever need to think about using a differential input card for a current output, is if there was a non-two-wire interface?

I guess I'm more familiar with the concept of single-ended and differential in the context of voltage I/O, not current I/O.


texts: How can I echo characters from UART0 to UART1

texts:
I am looking for a good tutorial or help in working with two UART's at the same time. I have UART1 connected to a BT modem and UART0 connected to a cell modem. I want to be able to have good two way communications between the two modems.

Here is my example code:

int main()
{
    UART0_Init(19200);  // Cell Modem
    UART1_Init(19200);  // Bluetooth Modem

    while(1)
    {
        UART1_TxString("Please choose a menu option.\n\n");
        UART1_TxString("1. Get Cell Modem Baud Rate\n");

        do
        {
            option = UART1_RxChar();
        }while((option<'1') || (option>'4'));

        UART1_TxChar(option);  // Echo option selected
        UART1_TxString("\n\n");

        switch(option)
        {
            case '1':
            UART1_TxString("Sending AT#TCPATCONSER=?");  // Echo command sent
            UART0_TxString("AT#TCPATCONSER=?");  // Send AT command to Modem
            break;

            // other menu options ...
        }

        while(1)
        {
            UART1_TxString(UART0_RxString());   // Receive response from cell modem and send to BT modem
        }

    }
}

UART TX and RX

char UART_RxChar(uint8_t var_uartChannel_u8)
{
    char ch = 0;

    switch(var_uartChannel_u8)
    {
        case 0:
        while(util_IsBitCleared(UCSR0A,RXC0));
        ch = UDR0;

        break;

        case 1:
        while(util_IsBitCleared(UCSR1A,RXC1));
        ch = UDR1;
        break;

    }
    return ch;
}

void UART_TxChar(uint8_t v_uartChannel_u8, char v_uartData_u8)
{
    if(v_uartChannel_u8 == C_UartZero_U8)
    {
        while(util_IsBitCleared(UCSR0A,UDRE0));
        UDR0 =v_uartData_u8;
    }
    else if(v_uartChannel_u8 == C_UartOne_U8)
    {
        while(util_IsBitCleared(UCSR1A,UDRE1));
        UDR1 =v_uartData_u8;
    }
}


texts: What are IC's RF/IF bypass pins intended for?

texts:
I'm trying to make an AM reciever using a certain IC (Samsung KA22427C). More specifically, I want to understand roles of all bypass pins of this IC (these are 1, 7 and 16).

I looked over schemes of test circuits from datasheet and still destination of those three pins is not clear to me. Help will be appreciated!


texts: PWM controlled MOSFET based DC motor driver, stuck with reverseing direction

texts:
See the circuit diagram below and help me to find the problem:

I can drive the motor in one direction as expected and to reverse the direction I added a relay circuit.
I used two SPDT relays instead of DPDT shown in diagram.

But some times one relay get turned off. Spark see inside the relays too while changing direction. Is there any way to remove the high voltage spike that produce as a result of reversing the direction of motor?


texts: Remote Control Program for ATMEGA168P circuit

texts:
Hello I will make maybe a fool questions. I have this diagram:

This diagram is to turn on/off led lights, make blink via remote control.
Now the questions are:

1.-What kind of remote control I can buy or what characteristics to buy for remote for this circuit? Link maybe?
2.-If depending of the remote control, how this circuit will know what brand I´m using, in other words how can I program the remote buttons to apply for each function on each pin of the ATMEGA like you see. Is this defined in the on the code you prgoramr into the ATMEGA?

Thank you


texts:
I've got a PICKit 2 with a PIC16F690 chip plugged in, and installed MPLAB and made a sample program in C, which compiles fine. However, there's only the option to "Program to target device", "Read from target device", or some other options to erase memory, all of which work fine, but I can't work out how to actually make the program run on the chip. MPLAB says I can't debug the chip:
"PK2Error0028:  Unable to enter debug mode"
"NOTE: This device requires an ICD Header for debug.  See "Header Specification" DS51292."
After some research, apparently I need a different interface board to debug it.
When debugging, the option to run the program comes up, but when set to "Release" mode, it only gives the option to read/write/erase from the board. How can I run it?

The code is as follows:

#include <htc.h>
#include <stdio.h>
#include <stdlib.h>

int main(int argc, char** argv) {
    return (EXIT_SUCCESS);
}

Which doesn't actually do anything yet


texts: Arduino infrared problem with universal remote

texts:
I am playing with Arduino and Ken Shirriff's IR library. I am trying to control Sony audio receiver using codes I found on the net.

Everything works OK, I am able to control the device by sending IR signal from Arduino, using sendSony function. However, I have problems learning that same codes onto a universal remote control device (I have tried two so far). It just doesn't recognize the codes which, I repeat, work perfectly with the actual Sony device.

Anyone got an idea where things could go wrong, and what parameters should I play with. I have tried varying modulation frequency (36-38-40 kHz), and the frequency of sending individual codes (by altering the pause between successive emissions).

Here's the code which I'm using:

#include <IRremote.h>
IRsend irsend;

void setup()
{
  Serial.begin(9600);
  irsend.enableIROut(40);
}

void sonySend(int code) {
    for (int i = 0; i < 50; i++) {
      irsend.sendSony(code, 12); // Sony TV power code
      delay(30);
    }
}

void loop() {
  sonySend(0x841); // tuner
//  sonySend(0xc41); // tape 1
  delay(1000);
}

Edit: I have one original Sony remote (with some common codes which work on my device). The universal remotes have no problem learning from that Sony remote. Just from Arduino.

The universal remotes I'm using are kind-of noname, Chinese ones, however they worked flawlessly learning from other remotes.


texts: how to increase current in this given circuit

texts: I am am a beginner to this not having background from this feild  n i I have a transformer less circuit which gives out 12vdc and 30 mamp  how to increase the current to 2 amp


texts: Approximations for the intrinsic carrier density of silicon at room temperature?

texts:
I'm a computer engineering student preparing for Analog Circuits in the spring. My textbook Jaeger's Microelectronic Circuit Design uses an approximation for the intrinsic carrier density for silicon at room temperature of

$$ 10^{10} \frac{e^{-}}{cm^{3}}$$

Now I'm doing fine solving the problems on my own and taking notes except for this approximation. It never defines room temperature but most websites I've found define room temperature as somewhere on the range of 293 Kelvin to 298 Kelvin.

$$(10^{10})^{2}=1.08*10^{31}T^{3}e^{\frac{-1.12}{8.62*10^{-5}T}}$$

By using their approximation I solved for what temperature they consider room temperature by means of numerical solving in mathematica using the equation above using the numbers they gave for boltzmann constant, material dependency of silicon and the approximation for the intrinsic carrier density.

I obtain 3 solutions, two extraneous and one real:

$$T = 299.707-41.3659j$$
$$T = 299.707+41.3659j$$
$$T = 305.226$$

Now 305 Kelvin does not seem very far from 298 Kelvin but for certain problems the difference can be many order of magnitude off if I don't use their approximation. Is this a bad approximation? The one thing I've gathered from this chapter is that these equations and this process is extremely temperature dependent. For one problem I calculated I had a 9 trillion percent error by not using their approximation. Do many engineers use approximations like this in practice? Is this a good or bad practice to be following. I can't help but think I'm doing something wrong by using an approximation such as this.


texts: Connecting a super capacitor to the solar battery in parallel

texts:
I find some people connect a super capacitor like (16v 88F capacitor bank) in parallel with the 12v 100Ah solar battery to optimize the surge current draws from the battery due to running heavy inductive load by the inverter(to increasing the battery lifespan).

But i'm wondering since charging/discharging curve of battery are different from the super capacitor, can this mismatching in charging/discharging behavior harm the battery or super cap. or both of them?


texts:
I apologize if this has been asked before but the answers I found are all over the top for this simple latching application.

I'm looking for a very compact solution:
1) 4.5 volt dc, 3 stacked hearing-aid like batteries.
2) Single 2.xV LED load
3) Push button actuation; push once & release = on; push once again & release = off
4) Soft latching; no power consumption when off.

I'd think something like this should be no more than 4-5 component, not counting the batteries, switch, and led.

A nice to have would be a single chip based solution with (or w/o) switch de-bounce.

I'm somewhat amazed these are not a dime a dozen solutions out there to be found.

Any suggestions?

Much thanks.

EDIT
4.5V, 3 stacked hearing aid batteries offers meany more LED options @ ~ 20mA.
http://lednique.com/leds-and-colour/

Hoping to stick with a soft latch technology t minimize the switch physical footprint.

A resister and toggle button does not satisfy the requirement.

No programming required preferred.


texts:
I don't have much experience with electronics, but I think what I want to do could be cobbled together from a Radioshack.

I have a Dig 5006-IP automatic sprinkler controller. It controls 24V DC valves. It has two "SENSOR" terminals, that when closed will put the unit in bypass mode. Basically a rain sensor is attatched to this, and is normally open. When it rains, the circuit goes closed and trips the rain mode.

Unfortunately, the Hunter Rain-Clik I bought is normally closed, and goes into open mode when it rains. Its more designed to be used inline with the valve. Something I don't want to do.

So how can I reverse this? How can I swap rainclik's signal, so that when it's closed, the dig sees it as open. And when its open, it sees it as closed? I have a soldering gun and basic knowledge of putting things together.


texts: How can I calculate overall how much power my circuit is using per hour

texts:
I have a circuit that has a variable draw of current based on how many revolutions of a wheel is made per hour.

Every other revolution of the wheel my circuit logs data. Which draws around 50 milliamps of current.

I've made this little table to break it down:

Constants

RPM per one-mph on 27.5 inch wheel = 12.2RPM
Current draw per activation = 50 Milliamps
activation uptime = 10 Milliseconds

Variables

Average speed over 1 hour = 20 mph
RPM @ 20mph = 244 RPM
Revolutions per hour = 14640 RPH
Activations per hour (divide by 2 as im only logging every other)   = 7320 Activations

Values

Total activation uptime per hour    73.2 Seconds (7320*10/1000)

But now im struggling to see how I convert this value into a meaningful value. Given my circuit is running at 5 volts I know that drawing 50 milliamps is going to mean im using 0.25 watts. Do I then multiply this by 73.2? to figure out how many wattseconds im using?

Also from that can I then work out how many milliamp hours this is? The reason im trying to work this out is so that I can spec a battery. I think im close but im getting a bit confused.


texts: How to amplify 3.3v to 12v (PIR and led strip light)

texts:
First off this is very similar to what I need to do How to amplify 3.3 volts to 8-9v?

I have a 12v power source PIR and 12v led strip lights, This is the specs for the PIR. I want to cut the leds into 6 leds per strip and put them in the middle of my stairs, So i was going to run 1 wire the length of the staircase and the just attach every led strip (from each step) to that, I also have LDR that I could add to keep the light off in the day or I could just use a switch

Probe LHI778, high sensitivity.
Technical parameters:
1.Operating voltage: DC5V to 20V
2.Static power consumption: 65 microamps
3.Level output: 3.3V, low 0V

Any help would be great Thanks


texts: Is EMC (FCC and EU) testing performed as sold or as used?

texts:
I have a prototype that inserts a fairly weak ISM band RF signal (HF/VHF) as a way of detecting a connection between two metal objects without there being a DC return path (Ideally I would use TDR but I can't do that on my budget at home).

I don't think it would be classed as test equipment (it's not a toy but it's for sports - the inside is basically a very narrow band Vector Network Analyser combined with an equally limited spectrum analyser/Software defined radio), which - if I understand correctly - grants an exemption.

It would be sold just as the sensor(à la test equipment), would it be tested as sold or would it need to be EMC tested as it is intended to be used (I'm not yet sure whether this particular example would pass or not in the sense that it isn't a radio transceiver but that's's a different a question)?


texts:
This is maybe a silly question, but when a lab bench power supply has 2 output channels that are both adjustable, can each channel be set at a different voltage than the other?
Like this one provided by the link, can channel 1 be set to 24V and channel 2 be set to 5V simultaneously, with both negatives tied together for a reference?
RS PRO Bench Power Supply, 3 Output, 0 → 30V, 0 → 5 (Adjustable) A, 3(Fixed) A.


texts: Trying to wire in LED to show cooker element is on/off

texts:
Hi I'm a mechanical engineer so please bear with me.
 I'm trying to wire in an LED to show whether a cooker element is on or off.
Looking at the diagrams below, the easiest way to do this would be to wire an LED into the Aditec MKA-120 outputs between 06 and 07. Would it be that simple?

The images of the diagrams are below:

Internal switchboard: https://imgur.com/mpMYTDU
External switchboard: https://imgur.com/GmqQpgk
Aditec MKA-120 controller: https://imgur.com/uZ0zAjH
Electric diagram for cooker: https://imgur.com/uOERoYz

Aditec MKA-120 data sheet: https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=2ahUKEwjX14W5o4fgAhWWfn0KHb9JCg0QFjAAegQICRAC&url=https%3A%2F%2Fwww.aditec.net%2FMKA120_data-sheet_en.pdf&usg=AOvVaw2zIYtHVWOq1RH_tan575v1

Thanks in advance!


texts: Searching for an Op Amp which amplifies an input voltage of 3mv to say +-5v

texts: It would be really helpful if someone suggests an Op Amp which takes an input voltage in mV and the output of +-5v. If there's an evaluation board that comes with the Op amp which takes the mv input and gives a +- 5V output, then it would be even more helpful.


texts: Why is my transistor switched on even though the collector is not connected

texts:
Newbie here. I bought a couple BC547B transistors to build some logic gates.
I'm using a breadboard which is connected to the 3.3V and ground from my UNO Elegoo R3 controller.
I connected an LED to the emitter of the transistor. It lit up once I connect the power supply with the base pin, even though the collector was disconnected. I have followed this other thread and connected a high resistor (tried 100K and 1M) between base and emitter, which makes the LED glow really dim. Once I connected the collector it lighted up very bright again.
My question is: How can I fix this issue? Ideally I want to LED to not light up at all unless there is current on the collector. I already made sure that the transistor pins are two lanes apart each, but that did not help.


texts: I’m looking at a PIC SoC with Wifi. Can you route the antenna far away from the chip?

texts: I’m talking about the gold PCB tracks form the centre or a circuit board the the edge where it can be clear of any interference say about 50mm.


texts: Clock Implementation Design Warning on Spartan 3E

texts:
I am working with a SPARTAN 3E-FT256 on Xilinx 14.1, and have to generate a 25 MHz clock from the onboard 50MHz clock.I am accomplishing this with a Digital Clock Manager.

These are my UCF designations :

NET "CLK_50MHZ" LOC = "C8" | IOSTANDARD = LVCMOS33 ;   //GCLK 10
NET "CLK_50MHZ" PERIOD = 20.0ns HIGH 40%;              //DCM_X0Y1

DCM Instantiation :

wire clk_ibufg;
wire clock;
wire CLK0_OUT;

IBUFG clk_ibufg_inst ( .I(CLK_50MHZ) , .O(clk_ibufg) );
BUFG  clk_bufg_inst  ( .I(clock) , .O(clk));

ClockManager1 clock_converter (
.CLKIN_IN(clk_ibufg),
.CLKFX_OUT(clock),
.CLK0_OUT(CLK0_OUT)
);

I am very uncertain about the use of IBUFG and BUFG, but the datasheet seems to prefer the connections ---IBUFG to DCM to BUFG---- for minimum skew.

The warning I get :

"The following Clock signals are not routed on the dedicated
   global clock routing resources. This will usually result in
   longer delays and higher skew for the clock load pins. This could
   be the result of incorrect clock placement, more than 8 clocks
   feeding logic in a single quadrant of the device, or incorrect
   logic partitioning into the quadrant(s). Check the timing report
   to verify the delay and skew for this net
Net Name: clock"

Is there any way to specify which BUFG or IBUFG to use? Why am I getting this warning?


texts:
Our product has a hole on the metal panel for the USB2.0 type B port. However, due to the mechanic size variation, on some panels, the USB connector can't touch the panel at all. As indicated in the image, there is a gap between the USB connector and the panel which causes the USB port isolated from the panel. This brings a problem for ESD testing because the electrostatic on the USB shell was supposed to be discharged through the metal panel to the ground. When the USB connector cannot contact the panel, the electrostatic is accumulated on the USB port which makes trouble to the PCB.
To solve this problem, the idea I have is to put some conductive paddings, like copper foil, between the USB connector and the panel, but this makes the product looks ugly. Does anyone have a similar problem and how do you solve it?


texts:
I wonder a question. Let's say I use a circuit board in a project (the left hand side on image below, not the Verabod), and I want to solder a circuit on it.

For example, I want to use the circuit below, the DC/DC converter using NE555:

How should I do with the GND? I mean in this "portable" circuit board.

Should I just lead those line connecting to GND to an empty circuit board track?

I just have a research online and I find out something. So, does it mean the circuit 1 is equal to circuit 2? Which all Ground is connected back to the negative pole of battery.
(1)

(2)


texts:
A friend asked me for advice regarding a lock system based on iButtons as keys.

There are some doors, and a 1-wire bus along the way, connected to iButton readers and door locks. (let's skip the complexities of turning 1-wire command into physically opening a lock, that's for a different question...)

Users are issued iButtons - one per person - and the system authorizes given iButton to open a given set of doors. Except there's a caveat: if I insert the iButton into a reader, the system will know iButton[id] has been plugged in. No info which of the multiple readers. No info which of the authorized doors to open.

So - given a single 1-wire bus, what would be a practical way to determine, where (into which reader along the bus) the button has been plugged in?


texts:
In the main panel, there are 3 wires for 3 phase power going from 3 pole 40A breaker to a sub panel. the breaker is (CKIPSAL 4CB340/6 C40)
The wires are in 2 cables.

Each of these wires has 7 strands 19 SWG each. Online search reveals that 19 SWG handles 4.13amp. which tells me that the wire is expected to handle 29amp (7 x 4.13)

If the breaker should protect the wire, then why it is 40amp when the wire is 29amp? i.e. I expected to see the breaker amp less than the wire amp rating.


texts: Capacitor vs battery which cost less per capacity?

texts:
I know that batteries have better density ie capacity per volume.

But I want to get the most energy capacity for the money. Which one would would you get?

I'm trying to store energy from solar for 1 day.


texts: Some questions about common emitter NPN transistor when the base is open

texts:
Considering a common-emitter NPN configuration with the base terminal open as:

I encountered a conclusion as such it starts with the following premises:

Base is open
CB reverse biased
EB forward biased
Transistor action takes place

So since transistor action takes place, one can write:

Ic=α•Ie+Ico

Base is open, so base current must be zero so Ib=0.
So according to KCL when Ib=0 for the main equation Ie=Ic+Ib, yields for this case Ic=Ie.

So one can write:

Ic=α•Ic+Ico which yields:

Ic=Ie=Ico/(1-α)

Simulation results also shows some amount of leakage current flows through the collector and the emitter while the base current is zero. And simulation also shows that the Vbe is forward biased when the base terminal is open as follows:

1-) Even though no voltage is applied to the base terminal, the Vbe junction is automatically forward biased and causes some leakage current. How is that happening? Does that come from KVL around the transistor?

2-) Base was open and we found a leakage current as Ico/(1-α). But the definition of Ico or Iceo is already the emitter/collector current when the base is open. But this is a bit confusing because when the base terminal is open we find it as Ico/(1-α) not Ico. I mean either Iceo is not the current when the base is open or something I know is wrong. What is the problem here?


texts: Equivalent resistances with the superposition theorem

texts: I have the following definition and explanation of the superposition theorem. I don't understand how the resistance values are calculated. I understand that \$R=V/I\$, so \$I=V/R\$. But how is the equivalent resistance calculated, and how do we know which resistances are effecting the respective branch currents?


texts: Touch sensor with a CR2032 battery and a transistor

texts:
I'm not an electronics engineer but I have a question that may look strange to a specialist:
Can I make a touch sensor that lights a LED using a CR2032 battery?
I tried to use this circuit without the resistances and with a different power source but the LED is not at full power.
Thank you.