texts: Why does the colllector current decrese with decreasing collector-emitter voltage in this circuit?

texts:
I'm trying to understand how the circuit below works so I ran a simulation with TINA and I got the curves shown on the right (C3 is already charged).

Here is a bigger one

Considering the characteristic curve of that BJT (shown below), I can't understand how it is possible for Vce to decrease with decreasing Ic.

My reasoning is as follows (the lines are not the ones corresponding to the circuit above, but they are close enough to expect a similar behavior):

The red line is the DC load (Vtank = 0) and the green line is the one I would expect after Vtank (EDIT: I made a mistake here, this Vtank is 180° out of phase with respect to the one shown above, but the discussion still stands), increases from 0. The yellow dot is the initial Q point. Since the Q point must be on the green line after a certain time, and since the simulation says that both Vce and Ic decrease, I'm having trouble understanding what's going on.

Of course Ic can't simply increase either because otherwise Vbe would go down (through Re) and Ic would be immediately interrupted.

EDIT:

After trying with a lower frequency and with a higher Re I got this:

Here is a bigger one.

So what seems to be happening is that locally (higher frequency) the transistor is behaving like I expected but non locally (lower frequency) the tank oscillations define the behavior. I would like someone to confirm this.


texts: What is the difference between capacitive fault currents and resistive fault currents?

texts:
http://uk.megger.com/battery-ground-fault-tracer-bgft\

This website claims that it's product can differentiate between these two fault currents. But I don't know what the difference is.


texts:
i'm experimenting with transistors, and wired one to my circuitboard. Though I got the LED to turn on with a NPN transistor, I'm not sure it's setup properly.

I read that current moves against the direction the arrow  is pointing for the transistor symbol (emitter to collector), so I wired the emitter to a higher voltage (7.5V) than the base (4.5V). The problem is, when I remove the voltage source to the base, the LED remains lit. Shouldn't it turn off if the base truly acts like a switch for current flowing from emitter to collector?

I included two schematics below, one a crude, most likely incorrect representation of my circuit, and another from a book I'm learning from. My attempt at making a circuit follows my failure to get the schematic in the book to work - please let me know if you spot any errors in either schematic.

simulate this circuit – Schematic created using CircuitLab


texts: How to remove 1 Clock Cycle Read Latency in single port BRAM

texts:
M using single port BRAM in always enabled mode,  when I want to read the data from BRAM and write into the 2D array , its shows 1 clock cycle read latency means the data is not exact, after adding output register to the BRAM it shows 2 clocks cycle latency.Kindly suggest me ,how to remove this. I am using VHDL.
I cant use flipflops and multiplexers, BRAM is required, I already instantiate the BRAM with coe file and now only wants to read one address at a time then fill into the array then again read the next address of BRAM and write into the array and so on. Is there any way to provide the delay in the logic itself?I am using Xilinx ISE, IP core generator for BRAM.Here is the code
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use ieee.std_logic_unsigned.all;
use IEEE.NUMERIC_STD.ALL;

-- Uncomment the following library declaration if using
-- arithmetic functions with Signed or Unsigned values

-- Uncomment the following library declaration if instantiating
-- any Xilinx primitives in this code.
library UNISIM;
use UNISIM.VComponents.all;

entity dummy_handle is

     Port ( clk : in  STD_LOGIC;
            rst : in  STD_LOGIC);
end dummy_handle;

architecture Behavioral of dummy_handle is

type array2D is array (0 to 7,0 to 9) of  STD_LOGIC;
signal M: array2D;

signal addr_array : STD_LOGIC_VECTOR(2 DOWNTO 0) := "000";

signal we_A: STD_LOGIC_VECTOR(0 DOWNTO 0) := "0";
signal addr : STD_LOGIC_VECTOR(3 DOWNTO 0) := "0000";
signal din : STD_LOGIC_VECTOR(7 DOWNTO 0);
signal test : STD_LOGIC_VECTOR(7 DOWNTO 0);
signal dout : std_logic_vector(7 downto 0);
signal i : integer:= 7;
signal j : integer:= 0;
signal flag: std_logic := '0';

COMPONENT a1_p1
  PORT (
    clka : IN STD_LOGIC;
    wea : IN STD_LOGIC_VECTOR(0 DOWNTO 0);
    addra : IN STD_LOGIC_VECTOR(3 DOWNTO 0);
    dina : IN STD_LOGIC_VECTOR(7 DOWNTO 0);
    douta : OUT STD_LOGIC_VECTOR(7 DOWNTO 0)
  );
END COMPONENT;

begin

    test <= dout;

p1_a1 : a1_p1
  PORT MAP (
    clka => clk,
    wea => we_A,
    addra => addr,
    dina => din,
    douta => dout
  );

dat_process: process(clk)
begin

        if rising_edge(clk) then

            if j = 10 then
                addr <= "0000";

            else

                M(to_integer(unsigned(addr_array)),j) <= test(i);
                i <= i - 1;
                addr_array <= std_logic_vector(unsigned(addr_array) + 1);

                if addr_array = "111" and i = 0 then

                    addr <= std_logic_vector(unsigned(addr) + 1);
                    addr_array <= "000";
                    i <= 7;
                    j <= j + 1;
                end if;

            end if;

        end if;

    end process dat_process;

end Behavioral;

Problem occurred when i increment the address of BRAM to fill into the next column of array. I am writting in transpose form.


texts: Two solenoid coils and ferrite rod, how to calculate mutual inductance or coupling co-eff

texts:
I have two solenoid coils, one is wounded on ferrite rod and other is wounded in larger diameter in proxmity of ferrite rod, see picture. It is used as wireless comm (simplex) between RX and TX where I use resonance on TX to maximise signal gains

After bit of reading and now familar with mutual inductance between two air solenoid, impact of cross section area and so on.

(1) How to calculate or estimate mutual inductance as well as coupling coeff under this diagram.
(2) If possible tip how to calculate/estimate the reluctance for this circuit.

My gut feeling that not all flux path will goes to ferrites as flux concreator and need to estimate out how much fraction of flux goes to ferrite rod.


texts: Closed-loop function. Need help to check if my answer is correct

texts:
My answer:

Closed loop function formula can be found using (forward path / 1 + return path)

so Gr(s) = [(A+D(s))B] / (1 + [(A+D(s))B]) = heading angle / desired angle (correct or wrong?)

As for Gd(s) = B / (1 + (B + desired angle)A) = heading angle / D(s) ( correct or wrong ?)

How do I determine the order of the control system given that A = kp + kd s + ki/s and B = 1 /s^2 - alpha

This diagram can be found http://i.stack.imgur.com/LIa4M.png


texts: Which USB spec actually defines support for Dual Role Device? Type-C or USB 3.1?

texts:
I'm trying to get a concrete answer on what determines DRD support... the port type (USB-C) or the protocol type (USB 3.1).  Besides the poor naming scheme with USB 3.0/3.1/3.2, there's a lot of lacking communication about the DRD device support (being able to act as a device or host).
According to https://blogs.synopsys.com/tousbornottousb/2018/05/03/usb-dual-role-replaces-usb-on-the-go it is any USB spec at or above 3.1, but it also confusingly talks about being Type-C
This Intel page talks about having DRD with USB 3.2 Gen 1x1 (5 Gb/s) with no mention of Type-C.
Wikipedia mentions DRD on their USB Type-C page, but not on their USB 3.1 page.
I'm trying to find some kind of authoritative answer on this question, if possible


texts:
I want to change the connection rules for a few polygons in my board. for experimentation purposes I set the default rule to have direct connects on all polygons. Then created a second rule with higher priority that used thermal relief connect for that named polygon.

In the end I plan on making either a class or just adding an 'OR' clause for the other polygons.

But to get to my question is that the polygon named TOP_GND_LEFT still has direct connects even after a repour.

I though maybe pour order but this poly is not on top of another?
Any suggestions?


texts: About voltaic cells and why 2 batteries won't short together

texts:
Why 2 batteries won't short like that?

If we connect both terminals of the same battery it would short, but not when connecting 2 different ones. How does the battery know when it's connected to itself and when it isn't?
From searching similar question I gathered that it has something to do with the salt gate, but I don't see how it solves the problem.

As I understand it:

Electrons from Zinc flow to the copper side because Cu+ is pulling them.

Is that right? Why that happens? the sulfate-copper solution is electrically neutral, isn't it? And if it still attracts negative charge, why won't it stick to the Sodium from the salt bridge? it's closer.

Without the salt bridge, the anode side will quickly get too positively charged, and the cathode will get too negatively charged as to oppose whatever happens in 1. Because the salt bridge is there, the buildup of positive and negative charges at the corresponding places gets neutralized, and what happens in 1 can continue.

Is that the answer to why 2 batteries don't short? How so?
Battery 1 anode gives electrons and neutralizes its solution with its own salt bridge, and Battery 2 cathode receives electrons and neutralized its negativity with its own salt bridge.
Why don't they short then?

Edit
I think I have a breakthrough. I didn't consider the conservation of charge, I understand the importance of a closed loop now, it explains a lot.
I still got the question about the voltaic cell.
Basically, what exactly starts the electron flow from anode to cathode? Both of them are electrically neutral, so what creates the flow?


texts: How do I assemble the mechanical parts of panel mount switch? (lock ring, lock washer, nut, etc)

texts:
I'm sure this is a very simple question, but I'm not familiar with the different mechanical parts of a simple switch.

For example, I've purchased this switch and it includes:

Switch
"Lockwasher" ("tooth" washer)
"Locking ring"
2x nut

Is this the correct order (from inside box to outside), switch -> nut -> lockwasher -> [panel] -> locking ring -> nut?  If so, which direction does the locking ring face?


texts:
I have a device containing an active mic, an amplifier, and an AD converter. I would like to swap the microphone with another completely different mic. I have no tech specs on the microphone that I'm replacing. Would it be a good idea measure the voltage output of the original mic in response to some sine waves at various frequencies and then wind a simple toroidal transformer to get the output of the new mic to look similar?

...or would this be totally dumb?


texts: STM32F070 - firmware-controlled USB connection and HSE activation

texts:
I'm developing firmware for a low power USB 2.0 Full Speed device (12 Mbps) which uses an STM32F070CB microcontroller. The clock source for the USB module will be the High Speed External (HSE) oscillator. I'm using STM32CubeMX with version 1.7.0 of STM32CubeF0 to generate the codebase.

To conserve our power budget, we need to turn off the HSE when the USB is not connected. I'm thinking we should make the firmware delay USB detection by the host until the device is ready, so that the events in the firmware would go something like this:

Event - Detect physical USB connection

Enable HSE
Initialize USB
Connect Data+ pull-up (DPPU) to trigger USB enumeration by host

Event - Detect physical USB disconnection

Disconnect DPPU (simulate physical disconnection to host)
De-initialize USB
Disable HSE (drive PF0-OSC_IN low)

Questions

Is the above the right way to go about this? Are the actions all required? Are they in the right order?
Do I need to call any functions besides USBD_DeInit() to de-init USB?
How can I make the device appear disconnected on the host while physically connected? (i.e. It should disappear from Windows Device Manager.) Why doesn't calling HAL_PCD_DevDisconnect() cause that to happen?

Details

In the following paragraphs, to "physically connect" means to connect the USB cable to the device and the host PC.

I would expect all calls to MX_USB_DEVICE_Init() and MX_USB_DEVICE_DeInit() to take effect immediately, i.e. that I would see the device appear/disappear in Windows Device Manager if the function was called while the device is physically connected. However, I've observed this only on the first call to MX_USB_DEVICE_Init(). All calls to MX_USB_DEVICE_DeInit() and subsequent calls to MX_USB_DEVICE_Init() don't cause the device to appear/disappear from Windows Device Manager until after physical reconnection. (i.e. If it's connected, when the function is called, no change in Device Manager until after disconnect/reconnect.)

Code

As generated by STM32CubeMX:

/* USB Device Core handle declaration */
USBD_HandleTypeDef hUsbDeviceFS;

/* init function */
void MX_USB_DEVICE_Init(void)
{
  /* Init Device Library,Add Supported Class and Start the library*/
  USBD_Init(&hUsbDeviceFS, &FS_Desc, DEVICE_FS);

  USBD_RegisterClass(&hUsbDeviceFS, &USBD_CDC);

  USBD_CDC_RegisterInterface(&hUsbDeviceFS, &USBD_Interface_fops_FS);

  USBD_Start(&hUsbDeviceFS);
}

I created:

void MX_USB_DEVICE_DeInit(void)
{
   HAL_PCD_DevDisconnect((PCD_HandleTypeDef *)&hUsbDeviceFS.pData);
   USBD_Stop  (&hUsbDeviceFS);
   USBD_DeInit(&hUsbDeviceFS);
}

It makes no difference whether or when I call HAL_PCD_DevDisconnect(). I have never observed the device disappear from Windows Device Manager while physically connected.


texts: How to PWM-drive a N-channel non-logic level power MOSFET with a 3.3V signal?

texts:
Follow-up of Using IR21531 as a simple 1 channel gate driver

After doing the above question (I'm very sorry, beacuse my question seems a XY one), I'll try to explain better what I believe that I want (current circuit below):

I'm doing a space-saving design for a LED driver. On it, I only have a 78V PSU and a 3.3V PSU.

The module drive with PWM a LED strip, but the control signal will be of 3.3V and the MOSFET needs more than 10V to trigger. How can I get let's say 15V for driving the gate?

I've seen some vague words on some electronics forums saying that I could use a zener diode. How could I use the zener diode?

I'm open to suggestions. Also I could use a optoisolated transistor along with the zener.

Update: The below circuit seems to be well done, but with more than 50% of PWM duty cycle, the lamp starts blinking and fading as if it have a capacitor.

simulate this circuit – Schematic created using CircuitLab


texts: Schematic for input protection with NMOS? Does this really work?

texts:
I was reading an old schematic and found this and sketched it up;
(see box in image "Some kind of protection")

The closest thing to this schematic that I've been able to find, that could have briefly explained how it was works used a depletion mode NMOS to act as an over voltage protection circuit.
Over voltage protection with depletion mode NMOS

That could have explained it! Sadly the NMOS used is a IRFBG20 that isn't a depletion mode fet, if I did not now totally misread..

So I wonder, is there something I've missed? This design is in use, so it should work somehow..


texts: Is it possible to change the reference clock in a cpu while it is running

texts:
I understand that PLLs have a settling time but if I were to do a hardware modification that changes Vco of a reference clock to scale based on temperature of my CPU, would I be able to do so while the CPU is running or would the system lock due to PLL variance?
If so a corollary: what is the maximum frequency I can adjust the base clock of the PLL while the output frequency can remain marginally stable? Is it the Nyquist rate or the 1/(settling time)?
My understanding of PLLs is elementary please be gentle thank you.


texts: I'm currently working on an 8-bit adder that instantiates a full adder. I have to assign 17 switches as inputs a , b and Cin. How can I do that?


texts: Communication between microcontroller and separately powered PCB

texts: On one board I have a microcontroller with one power supply and on another I have a Flip Flop with a separate power supply. I want to connect a pin of the microcontroller to the reset pin of the flip flop. Can I just put a wire accross or does it need more than that? I was going to do that but now I'm not sure that would work because it wouldn't be a complete circuit and the two boards may not have quite the same ground levels. The two boards have to have separate power supplies because the board with the DSP is premade and the power comes from the mains. Thanks


texts: Name for circuit with multiple paths with aim of reducing inductance

texts:
Trying to find the best way of describing a circuit that uses multiple separate physical paths to reduce effect of inductance on by HF signals.

Is there a term for such?


texts:
I've got a colour sensor that is semi-functional at the moment. I am fairly new to Assembly, PIC especially, and I am confused as to how to handle a "high" and "low" address for a number. Let me explain.

When I read from my colour sensor, I have to read from a high and low address. This much is not a problem, rather my issue is processing this number after I read it. The tutorial that I followed does something like this:

colour1 = (addrH << 8) | addrL ...

Which makes sense: we have 16 bits, left shift 8 to place the high bits then or to handle the low bits. My question is, what is the best way to do this in assembly?

I've ignorantly tried something like this

SHIFT_8L macro count
   rlncf    addrH
   movlw    b'11111110'
   andwf    addrH,1
   decfsz count
   bra SHIFT_8L

   movff    addrH, WREG
   iorwf    addrL, 0
   movwf    final
endm

But really, all this is doing is just moving addrL into final. Ultimately I am going to have to multiplexing to see which colour dominates and so what's the most efficient way in doing this?

Thanks!

Edit 2017/02/21h47 I am using the PIC18F4620 and am interfacing with a TCS34725 Colour Sensor.


texts: In transient analysis, when at steady state, the inductors behave like a short circuit. Can I apply the voltage divider rule, to find the voltage drop across the inductors in series?


texts: SPI Bus Routing: Signal Integrity Issue?

texts:
I am routing a two-layer PCB with a 10MHz SPI bus. (See picture below.) The device on the left is the 5V master, the device on the right is the 3.3V slave, and the IC in the middle is a 74XX08 quad AND gate to perform level conversion on the MISO line.

The trace labeled SO is the slave's MISO which goes to pins 1 and 2 of the 74XX08. This is converted to 5V and output on the 74XX08's pin 3 which goes to the master on the trace labeled RX1.

The master's MOSI line goes directly to the slave on the trace labeled TX1 (bottom layer).

Finally, the master's SCK line goes directly to the slave on the trace labeled XCK1.

All of the other traces in the vicinity are extremely low speed.

My main concern is that the SCK, MOSI, and MISO lines cross over each other near the bottom right of the picture. Will this, or other aspects of the design be a problem at 10MHz?

RX1 length: 15.275mm

TX1 length: 17.834mm

XCK1 length: 23.700mm

SO length: 6.706mm


texts: How to connect multiple 0402 leds to an Arduino for a 1:87 model

texts:
I want to replicate lighting a 1:87 scale police car with the aid of an Arduino Pro Micro ATmega32U4 powered by a 90mAh 3.7V LiPo which is connected to a TP4056 5V Lipo battery charger which is connected to the Arduino. [Battery -[connected to]-> charger -[connected to]-> Arduino]

I want to power the following

8 blue 0402 leds  (2 leds in parallel/pin - 4 pins) - sirens
4 white 0402 leds (2 leds in parallel/pin - 2 pins) - headlight PWM @ 125
4 red 0402 leds (2 leds in parallel/pin - 2 pins)  - rearlights PWM @ 125
4 amber 0402 leds (2 leds in parallel/pin - 2 pins) - sidemarkers PWM @ 125
4 amber 0402 leds (2 leds in parallel/pin - 2 pins) - blinkers (2 leds for left & 2 for
right)

But if all of the 24 leds are powered on the amount of current drawn from the micro-controller will be 24*20mA = 480mA. Which will burn up the Arduino in an instant.

Question:

How to set up the circuitry to light up 0402 leds as in
the 1:87 car so that the Arduino won't get damaged?
How would they have designed the circuitry for leds on the car like
the one in 1:87 car?


texts: Replacing four 6V flooded lead acid (FLA) batteries with two 12V AGM in a floor scrubber. Will this work?

texts:
How do I design a new battery system using two old but large AGM batteries in series?
I realize a load test must be done to determine capacity differences.
AGM batteries are also sensitive to overcharging, and voltage is temperature sensitive.
What are the key critical design specs to define?
I can follow this to implement a reliable design.

I have a floor scrubber that has four 6V flooded lead acid Trojan T-125 batteries. Problem is after using it to scrub the floor, it takes about 4 hours to recharge using the onboard 21A max charger.  Using a more powerful charger on them is not recommended as the batteries will heat up excessively and likely shorten their life.  I have a candidate solution though and wanted to know if it will work and what problems may arise.  At home I have 2 large (but identical) Odyssey PC2250 12V AGM batteries that are quite old (at least 10 years) but have a rated capacity of 126Ah.  They do not hold identical charges and one has slightly higher actual capacity than the other but they have not been in service for many years but I maintained them.  They usually hold 12.7V OCV (Open Circuit Voltage) which tells me they are still in decent condition.
So here is my plan and I would like to know if this will work or if I am headed down the wrong path.  I will do a load test on each of these batteries using my 12V power inverter and 500 watts of incandescent lights  as the actual load.  I will simply measure the duration of the test.  The inverter will beep when the load voltage drops to about 10.5V.  At that point I will shut off the inverter and put the battery back on the charger for a full charge.  I will do this same test for each battery solo and probably twice for each battery to confirm the results.  So assuming they are both similar Ah capacity (let's say the test lasts 1 hour each which would be about 42Ah each since 500W = about 42A at 12V), would it be ok to put these back into service but with a new task as floor scrubber batteries?  To get a quicker charge, I would use an external charger with 55A charge capability which will far exceed the onboard chargers maximum 21A rate.  I expect the actual charge time to go from about 4 hours on the old system to maybe 1.5 hours on the new system.


texts:
So I realized with the suggestion in the comments that there is a much better solution to driving a higher voltage H bridge than using transistors or secondary mosfets and zener voltage.  I have revamped the question.  I am still pretty green to all of this stuff so maybe if anyone has a moment they can check over the schematic I have drawn for any other suggestions or problems with it.  I'll post data sheet links to the parts below if you want to look at them.  I  realize that some of these parts like the 600v diode rectifiers are way over kill, but I have most of them parts on hand except the drivers.

The question(s) I have now is as follows.

the datasheet schem I started with showed a half bridge without the flyback diodes but has the capacitor 5 in the schematic I have drawn.  I do believe that the datasheet schem was not an inductive load so I am guessing that is why they did not have the flyback diodes.  So do I need this capacitor in my case if I have the flyback diodes, or is it a good idea to have it there anyway for reasons I do not yet understand with my wee bit of knowledge?
As far as operating this bridge, my plan was to pwm the high side with arduino uno, and just put the corresponding low side either high or low.
Example: pin 3 pwm value, pin 2 high, pin 5 & 4 low for reverse.  And then pin 5 pwm value, pin 4 high, pin 3 & 2 low for forward.  In my research since I discovered the high side boost drivers yesterday I found some discussion on the capacitors not recovering quick enough but the circuit was a much higher frequency switching circuit like over 100KHZ.  My question on this is, should I pwm the low side MOSFETS instead, or will the capacitors recover quick enough with a 480HZ or max 980HZ pwm cycle of the arduino pin depending on the pin.
My last question, should I run both channels on the driver at the same time so 3 and 2 would be on driver 1, and 5 and 4 on driver 2?  Or is it fine to run the high on one driver, and the low on the other driver like I have drawn in the schem.?

Driver link: https://www.mouser.com/ds/2/196/ir2101-1226834.pdf

MOSFET link: http://www.mouser.com/ds/2/149/IRL640A-1010638.pdf

25v Capacitor: https://www.mouser.com/ds/2/212/KEM_A4069_A758-1140489.pdf

200V capacitors: https://www.mouser.com/ds/2/293/e-uvz-1219460.pdf

             https://www.mouser.com/ds/2/212/KEM_A4018_ELH-1104321.pdf


texts: Intertrack spacing and decoupling cap package for high voltage buck regulator

texts:
We're routing a PCB for a LM5085 buck controller of 8 pin WSON package with a maximum input of 75V. My questions are for the relatively high input voltage

0603 is the smallest input decoupling cap I can use since the distance between uncoated pads is 0.6 mm as per IPC2221 standard says the distance between uncoated external conductors must be above 0.6 mm, right? I'm asking because 10nF or 1nF 100V 0402 caps are available and are of lower ESL.
In that case what about the Voltage input pin and the exposed thermal pad of the IC being at 0.3 mm from each other, wouldn't this be at a risk?
For tracks covered with solder mask the IPC2221 standard says they can be at a distance more than 0.13mm, right?


texts: Obtaining stability information from Bode plots

texts:
I am trying to understand the theory behind gain and phase margins from Bode Plots for systems with negative feedback, specifically this one:

The transfer function for this system is:
$$
\frac{KG(s)}{1+KG(s)}
$$

The poles of this equation determine the stability, and these poles occur at any s such that KG(s) = -1.

I understand that when all poles are in the left-hand plane (negative real part) the system is stable, when any pole is in the right-hand plane the system is unstable, and when any pole is on the imaginary axis the system is at best marginally stable.

If we let s=jω (i.e. confine ourselves to s along the imaginary axis), we can draw the Bode plot. If there exists ω=φ such that |KG(jφ)| = 1 and ∠(KG(jφ)) = -180°, then we know that s=jφ must be a pole. Since this pole lies on the imaginary axis, we can say that the system is (at best) marginally stable.

I think what I have written above is correct, but if there is anything I am misunderstanding please correct me.

Now what I do not understand is what happens if the Bode plot does not pass through 0dB when the phase is -180°? How can you get any information about the poles in this situation (other than knowing that they're not on the imaginary axis), so how can you assess stability?

I can find a lot of information on how to calculate gain and phase margins from Bode plots, but can't find any proper justification for these rules in terms of the positions of the poles.

I would really appreciate any help.

Thanks!


texts: Why do people create web server on a microcontroller?

texts: I have come across people creating web servers using microcontrollers, why would someone do that? What are its applications? What skill set besides C language does one need in order to create such servers? I am quite curious about these tiny servers having such small RAM.


texts: Controlling the input detection on a 1/4" jack

texts:
So, I have a midi piano that outputs to it's speakers when there's no 1/4" jack in it's line out, and else only outputs to the line out. It's rather annoying having to constantly remove and replug the cable when I want to switch between these, so I'd like to build something to allow say an arduino to do it.

So I'd basically be rigging a 1/4" jack to be able to "pretend" its not plugged in, somehow.

I can't seem to find anything similar online, and after looking at the jack schematic, don't even know where to start.

Would anyone be able to make suggestions/point me in the right direction?

Thanks in advance!

Edit: The device is a Yamaha DGX-660


texts: When the maximum efficiency of a linear amplifier occurs?

texts:
When measuring the efficiency of a linear amplifier (say a class AB above), we say that maximum efficiency occurs when the linear amplifier delivers maximum current to the load (output voltage is also at maximum). However, I do not understand the “maximum current delivered to the load” refers to which of the following cases:
Case 1

As output voltage of a linear amplifier varies in a sinusoidal way, maximum efficiency happens at the peak (or the trough) of the wave.
By the same token minimum efficiency happens when the output voltage is at the DC value.

Case 2

Maximum efficiency happens when the amplitude of the output voltage is closest to the supply voltage.
Efficiency drops when the amplitude of the output voltage decreases.

I should be grateful if anyone can

Indicate whether max efficiency refers to Case 1 or Case 2.
Correct any of the misunderstanding in the above description.

Thanks a lot.


texts: What's happening that my I2C sensor is high on SDA when it might be low, as SCL, when in the time pause between bytes?

texts:
I'm using an HDC1080 clone (original by Texas Ins.) temp/humidity sensor which communicates via I2C with an Arduino. Each measurement is 16 bits long and to save its data, you must read first the 8 MSB and later the 8 LSB of each register (there's one for temp and another one for hum).

The first issue was that randomly, it showed me the less significant byte like a 16-bit-word instead of a 8-bit-word, like this

Taking a look at the scope, it could be watched that the mistake occurs when the SDA is high at the time SCL is low in the lapse between bytes, as the pic shows:

It is happening randomly and sometimes in both registers, sometimes just one, but the interesting thing is that it only happens at the beginning of the second byte got from the same register.

Is it any problem with my sensor? How can I try to solve this situation?

EDIT: This is my Arduino code:

#include <Wire.h>

#define HDC 0x40 //Sensor address

int16_t humrawvalue;  //Raw data value, MS byte = valmsb, LS byte = vallsb
int16_t temrawvalue;  //Raw data value, MS byte = valmsb, LS byte = vallsb
int8_t humvalmsb, humvallsb;  //Raw 8-bit byte of humidity
int8_t temvalmsb, temvallsb;  //Raw 8-bit byte of temperature
int incomingByte = 0; //Action input

void setup() {
  Serial.begin(9600);
  Serial.println("Hello");
  Wire.begin();
}

void loop() {
  if (Serial.available() > 0) {
    // read the action input:
    incomingByte = Serial.read();

    // say what you got:
    Serial.print("I received: ");
    Serial.println(incomingByte, DEC);
  }

  if (incomingByte == 49){    //ASCII code for number 1
    Wire.beginTransmission(HDC);
    Wire.write(0x00); //0x00 is the temperature register, 0x01 is the humidity one
    Wire.endTransmission(true);
    delay(200);

    Wire.requestFrom(HDC,4,true); //It asks for 4 bytes, 2 bytes per register
    if(Wire.available()){
      Serial.println("     ");
      Serial.println("Measuring: ");
      temvalmsb = Wire.read();
      temvallsb = Wire.read();
      humvalmsb = Wire.read();
      humvallsb = Wire.read();

      Serial.println("====TEMPERATURE====");
      Serial.print("MSB: "); Serial.println(temvalmsb, BIN);
      Serial.print("LSB: "); Serial.println(temvallsb, BIN);
      temrawvalue = temvalmsb <<8| temvallsb; //Locates each byte in its proper place
      Serial.print("Temp: "); Serial.println(temrawvalue, BIN);

      Serial.println("====HUMIDITY====");
      Serial.print("MSB: "); Serial.println(humvalmsb, BIN);
      Serial.print("LSB: "); Serial.println(humvallsb, BIN);
      humrawvalue = humvalmsb <<8| humvallsb;
      Serial.print("Hum: "); Serial.println(humrawvalue, BIN);

      Serial.println("     ");
      delay(3000);
    }
  }
}


texts:
I am checking the datasheet of one complex component, and the schematics of one demo board, and I find a difference that I would like to ask here. It is a 100Base-tx switch. The chip uses 3.3v for some pins, and 2.5V for some others. To generate 2.5V, the chip has an internal voltage regulator that will drive a transistor with a 0 ohm resistor as a current sensor (i think).

This is the datasheet :

But when I check the demoboard schematic, i found this:

R73 is a DIP switch (i think like the 106-1206-EV), so, you can cut the 2.5V wire to RVDD, and two ferrite beads connect the 3.3V to the RVDD.

why will you want this? the voltage when the circuit is closed, would be 2.5V? what is, in your opinion, the purpouse of the two beads? what values are good for them? and why you want to cut the wire? in that case, you will have 3.3V, but why would you want that?

This is my first ethernet circuit, and this is new for me...


texts: Inverting OpAmp circuit doesn't work (MCP6004)

texts:
I am trying to get -5V from 5V to use it on another opamp for my flexiforce pressure sensor.

Following circuit outputs something around 0V instead of -2.5V either on a real thing or in simulator, so I'm pretty sure I am doing something wrong here:

Thanks!


texts:
I have solved a very long problem where I had to find \$|H(j\omega)|\$ for a given circuit. In the end

$$ |H(j\omega)|= \frac{90 }{\sqrt {(9-\omega^2)^2+ (10\omega^2)}} $$

In my book it says I also have to find the angular cutoff frequency \$\omega_c\$.

How do I find this?


texts:
I had read that average value of current must be calculated for half time period.
For example  if we apply it for a sine value full time period then its value becomes zero. But for any arbritrary graph which doesn't have shape similar above and below x axis. I mean that they have different kind of shape for half timperiod and for another half,
(Periodic function/graph)
Then by calculating avg. Value for current (calculation for half timeperiod) don't we lose the real meaning of average.
Should we include that negative part of waveform to our average I , by taking modulus?


texts: Remote control of audio equipment over RS-232 with Arduino

texts:
These questions are following on from my previous question Reverse engineering old serial devices and cloning with Arduino about the monitoring of RS-232 traffic.

I had some good success and now have some questions about the general approach to take.

Over the past week I have been mapping out the controls of a rather ancient RS-232 remote control for a piece of audio equipment. Using port monitoring software etc., I now know what each control sends in terms of messages etc.

The device has 6 faders, 24 buttons, and can display 48 ASCII characters split into 1 lcd of 2x12 chars and the other 1x24 chars.

The remote also has a stereo dB level indicator made up of 2 rows of 16 LEDs.

I want to re-create the device using Arduino and so far I have come up with this.

PROBLEM 1

The six faders are easy enough without even needing a multiplexer (I think, at least on the ProMini) these vales can be read in, mapped from 0 to 255 and the output of each would need to be converted to HEX and have the corresponding control byte prepended to it's value before being spat out on the serial bus.

PROBLEM 2

The 24 buttons I think will be somewhat more of a challenge, I'm wondering if there are keypad or scanning options I could try for this as there are not 24 inputs available.

PROBLEM 3

As I mentioned above, there are 2 screens in the device, a 2x12 at the top and a 1x24 at the bottom. I believe these screens are chained in some way because If i send more than 24 characters to the 1st display they will overspill onto the bottom (1x24) display.

The commands come over the RS-232 bus like this:
each message of text begins with <00> and ends in <03>
so a full 24 character message would look as follows:

00 74 68 69 73 20 69 73 20 61 20 74 77 65 6e 74 79 66 6f 75 72 63 68 61 72 03

but if this message were longer, how would I want to think about spilling over onto the next screen?

I guess these are 3 large questions that maybe I should split up. I just wanted to get this all out in context.


texts: Adding large numbers in context of analog computing?

texts:
I have been reading about analog computing yet have not been able to find material about a certain issue; in reference to arithmetic, it is said that op-amps are used to perform these tasks, for example addition with a summing amplifier:

What about when one wants to sum larger numbers? (>10^5) I have though about say using smaller input voltages and then multiplying them with a high gain but that would require the op-amp to have a higher rail voltage to avoid saturation, as well as potentially loosing accuracy if one wanted to keep the voltages bounded between the rails.

In analog computing, is there are formal method of summing (or any form of arithmetic) large numbers (without working with thousands and thousands of volts) whilst not sacrificing accuracy in the process?


texts: at what temperature does it become expeditious to use a lithium battery's charge to heat itself?

texts: battery capacity diminishes the colder the battery gets. Is there a point where it's worth using the battery's energy to warm it up, increasing capacity? If so, where's the break-even point? If not, how wasteful is it to do so?


texts:
Here I have an automotive relay (from a scan of a workshop manual I'm afraid) which is rather more complexly wired up than the relays I'm familiar with. In this diagram:
L/Y - +12V
L - From the relay's switched live (a switch in the car)
L/B - Gets grounded if the car's ECU 'allows' the relay to be on
B/G - holds high if another condition is met (engine temp too high), to prevent the relay energising. (As far as I can tell...this is the correct logic for sure, not sure if it technically works that way!)
B/L - the load (2 loads in parallel)
8(?) - goes direct to ground

I understand how the relay works at the moment. However, what I plan is to cut (L) and insert a device which will prevent the relay energising unless some further conditions are met. This is achieved with some logic gates and an output transistor, which will 'join' L when my device allows it.

So far so simple?

What I can't tell is if I need a protection diode across the relay to protect my transistor? And if I do, would this interfere with the logic provided by the combination of L, L/B and B/G?

If this is a problem, would I be better using a small relay? Are these more immune to the relay closing?


texts: Wire color code on usb to lightning data cable (duracell manufactured by esi)

texts:
Hi so i have two duracell chare cables. One is 6 feet the other 10, the 10 foot broke so I purchased a 6 foot and was going to lengthen it. Since they are both duracell I figured wires would match easily...the 10 foot has red, green, white, and uninsulated wire
The other cable has grey, yellow, pink, and white? What colors goto what?

Cable A
Red (power)
Green (data -)
White (data +)
Uninsulated wire (ground)

Cable B
Grey
Neon Yellow
Pink
White


texts: How accurate is current sensing in home using current transformers

texts:
There a lot of solutions in the market to mesure your house electricity consumption, and the number is raising every day. I realize that plenty of them use current transformer clamps:

In today's homes, current is not sinusoidal thanks to electronics devices, and if I remember correctly from my engineering classes, this currents can be represented as a infinite sum of sine waves of different frequencies (Fourier), the most chaotic the current, higher frequency components you got, and high frequency electromagnetic fields are going to saturate the ferrite in the clamp compromising the accuracy of the measurement.

How good are this systems? Whats the minimum power factor you can have and still consider the measurement good enough?.


texts: Single and Double Click on Arduino Multiplexed Buttons

texts:
On my arduino project i have 8 buttons connected to a 4051 Multiplexer.
I would however like to add single and double click funcionalities to each of these buttons, but i can't find a way to do it.

My code for the buttons at the moment looks like this:

for (int buttonCount = 0; buttonCount < 8; buttonCount++){
b0 = bitRead(buttonCount,0);
b1 = bitRead(buttonCount,1);
b2 = bitRead(buttonCount,2);

digitalWrite(10,b0);
digitalWrite(9,b1);
digitalWrite(8,b2);

buttonValue[buttonCount] = digitalRead(buttonPin);

if (buttonValue[buttonCount] == CLICK_SINGLECLICK && buttonValue[buttonCount] != lastButtonValue[buttonCount]) {
  Serial.println(buttonCount);
}

Any help would be greatly appreciated!


texts: What does the leakage current graph of the LM13700 OTA stand for?

texts: On the datasheet ( http://www.ti.com/lit/ds/symlink/lm13700.pdf ) there is a figure of leakage current- temperature. Is this the output leakage current?


texts: Dissipating 1W on a TO-220 without heatsink?

texts:
Can a TO-220 without a heatsink dissipate 1W in still air?

Or, a different way of asking the question is: Assuming an ambient temperature of 25C, how can I go about calculating the maximum power I can dissipate on a TO-220 packaged MOSFET? The MOSFET is a FDP047N10 if that helps. It will be handling about 12.5A of continuous current (ie, no switching).

I would also like to understand the difference in power dissipation of a MOSFET which is continuously ON, vs a MOSFET that switches at 100KHz (50% duty cycle ON).

One final question: If I parallel two MOSFETs to reduce the power dissipation per FET, is there anything I can do to make sure (or increase the probability) that both will supply equal amounts of power?


texts: Wireless game controller - polling vs events

texts:
I'm creating wireless game controller, but I have problem with sending data - should it be in polling mode or event based?

For analog axes I think that polling is better. 100Hz or more polling rate, because analog data can change very often and I want to get responsive feeling.

For buttons I can use polling or events.

Polling - pros

It's easier to send one same "data package" every 10ms (100Hz
polling). With event based data transfer data will have different size
every time I press button, so I need to parse data on main component.

Polling - cons

There is redundancy in data transfer (If button isn't pressed, i'm still sending this information every 10ms).

It is possible that button click will not be catch at all (but user would have to click down button for less than 10ms, which I tried and I personally can't do it)

Which option is better? How is this done in other game controllers? Which polling rate will be good enough?


texts:
I have 2 problems with diode clampers that I don't understand

First, in this circuit for example:

In the positive half cycle, the voltage across the diode is the diode drop of 0.7 V

Then the voltage across the load resistance must be 0.7 V

Then isn't that a constant dc voltage? Why is it that when it gets clamped it appears as a sinusoidal peak? In which, the resulting shift happens like this:

My second question is specified to this following example:

Analyzing the positive half cycle, the diode is reverse biased, then the voltage across the load resistance should be zero ( Me assuming that the capacitor cannot fully charge instantaneously ) But this isn't the case, the input actually shifts by 14.3 V upwards.

To try to make sense of this, maybe they assume that the capacitor needs no time to charge, so it charges up to the peak of the input voltage V_p(in). But still there's a problem, that would produce a shift of 15 V upwards, not 14.3, then there must have been a voltage drop across the diode, but how did that voltage drop occur in the positive half cycle if it's reverse biased? Thanks.


texts: Compatibility of power packs with different devices

texts:
I have 2 different models of the same device. The old model is not receiving power from its power source which is the following power pack:

I want to test another power pack to see whether the issue is with the power source but I don't have an identical power pack. This is the power pack that came with the new model of the device:

Based on the electronics information on these power packs, would the new model's adapter be compatible with the old model device?


texts: Nth-Light Narrow LED, Linear Potentiometer and 12VDC power supply

texts: Is it possible to connect Nth-Light Narrow LED Flexible Strip Light (https://www.adafruit.com/product/3683) directly to a 12VDC power supply and 10K Ohm Sliding Linear Potentiometer to control the light intensity?


texts: how to get the RGB value of a color using phototransistor or photodiode?

texts:
I'm making a color analyzer which can measure Red, Green, and Blue portions of a color (ex: 128,255,0).I'm not supposed to use pre-made color sensors and need 1% ACCURACY.

I used three LEDs - R,B & B to sequentially measure the values. When green led is on. the reflection is caught by the photo-transistor. The deviation of voltage is converted to current deviation using OPAMP's V to I circuit so that intensity of green reflection can be measured and can be calibrated to show a 0-255 value using a micro-controller.

I was successful in measuring green value of a color only if the color contained green potions. (ex [0,255,0] , [0,128,0], [0,200,0] ). likewise I can get RGB values only if one color is present. If I was given a color which is a combination of R,G,B then the voltage reading is different and wrong. For example I get a higher voltage (higher intensity) when I'm measuring white (255,255,255) than green (0,255,0). Ideally I should have got the same amount of green because those colors had same amount of green - 255.

What is the cause of the problem and how can I use an alternating method to achieve my target? Is there a method to separate the reflection in to R,G,B with high accuracy? Thanks in advance. ( I'm using a Photoshop print on a matte photo print paper as the color)

EDIT: The 3 LED's and the photo-transistor is fully covered making sure that no background light will not interfere.


texts: Keithley 2450 Charge/Discharge adjusting appropiate V and I

texts:
I'm using Keithley 2450 model for charging/discharging battery. My aim is to find charge/discharge characteristics of 100mAH 9V battery. In the following link, they have described discharge characteristics of 2300mAH AA battery.

Rechargeable Battery Charge/Discharge
Cycling Using the Keithley Model 2450
SourceMeter
®
 SMU Instrument

The first question during this process is, how can I adjust the proper values for X Voltage batteries and Y ilimit level (current). The second question is what is (smu.source.range = 2) in the codes, would I also adjust it for different voltages?


texts: balance charging current for batteries connected in series

texts:
I've been using this simple Li-Ion charger for quite a while.
It consists of 4x 18650 Panasonic NCR Li-Ion "unprotected" batteries (3.1Ah), connected in series (2+2).
Charging was going well with cell voltage difference of approx. 0.05V.

After the battery has experienced short-circuit condition for ~1sec, cells got unbalanced.

simulate this circuit – Schematic created using CircuitLab

Questions:

How can I balance the cells back? I've disassembled the battery, I've tried discharging strongest cells by monitoring the voltage and internal resistance to match the week cells, but immediately after load is disconnected these values start deviating due to chemical processes. I've come to conclusion doing this manually is quite a challenge.
How can I improve my circuit to not to terminate the charging after i.e. B2/B3 "cell" gets saturated? What are the standard, most common techniques used?
Appending the 2nd question - can such a "balancing" solution be also energy efficient? I could easily add i.e. a MOSFET in parallel to each cell and control it via uC. That way I could bypass certain amount of current for each cell. Week would be charged faster. However, placing MOSFET into the linear region would be very inefficient solution. Also, i could bypass the charged cell completely (like, i.e., battery protection circuits do). However, that way I would stress a weaker cell by sudden boost of the voltage (thus current), as I have no opportunity to control the voltage of SMPS.


texts: I'm trying to make this sine wave oscillator, but I want the amplitude of the voltage sine wave to be 4.8V and the output current amplitude to be 45A. I am not sure how to go about calculating for the amplitude for either the current or the voltage. Has anyone had some experience with these?


texts: Open Collector to drive PNP without Pull-Up

texts:
I need to generate a current signal between 12V and GND, which has to have galvanic isolation. For this, I want to use an optocoupler.

Maximum permittable rise / fall time: < 1µs
Output side Vcc: 12V-14V
Output current: > 28 mA

Because of the high output current, an external transistor is required, since most optocouplers that are fast enough are limited at around 16 mA.
This allows the use of open collector optocouplers, driving a PNP transistor.

The PNP transistor then pulls a line to ground, which bypasses a resistor, increasing the current signal.

Can I use this open collector output to drive a PNP transistor (with an appropriate base resistor) without using a dedicated pull-up resistor?

There are also biased PNP transistors which include a pullup, but those are mostly (only?) available as SMD parts, while I would like to keep using THT.


texts: What is precharge in terms of Static Ram?

texts: In many six transistor static ram cell diagrams, it mentions a so called "precharge" that holds both bit lines at positive voltage. What is the use of this? wouldn't this constant voltage just screw up all your data? And why does it require transistors if they are always on?


texts: What’s wrong with my resistance calculations?

texts:
I was trying to use ohms law, and there is something I don’t understand.

There is a blender that uses 240v at 0.25 A.
240 / 0.25 = 960 ohms
However, when I tested the appliance with a multimetre, it showed 1014 kiloohms of resistance.

Where is my mistake coming from?


texts: Convert single input to multi output with enable/disable for each output

texts:
I want to connect 8 LEDs to one GPIO. GPIO goes high LEDs turn ON, GPIO goes LOW LEDs turn OFF or opposite logic - both are acceptable. I want to have some sort of IC in between which allows me to select one or more LEDs to turn ON when my GPIO goes HIGH (or LOW). It will be convenient if I can do this selection using i2c. So, if I have LED1 ... LED8 and I have enabled 2, 5, 7 then I can do a PWM on my GPIO and only LED - 2, 5, 7 turn ON based on PWM. Rest (1,3,4,6,8) remain OFF.

I am looking at demultiplexer list on Digikey but haven't found the right IC yet. Can someone help me select a part number? The IC needs to generate a weak logic output only. I will use a mosfet/transistor to drive the LED from this weak logic output.


texts:
I am actually designing a BLDC motor control unit with the A4964 Driver.
I made the design for working on 24V supply.
I did severals test and HW/SW modification but unfortunaly, the motor won't run and I always read VDS fault at start on the demoboard software.

You can find below my schematic.

and the fault register on the software


texts: How can the SparkFun Lipo USB charger power other devices at the same time as charging?

texts:
How is this SparkFun charger capable of charging a LiPo at the same time as powering other devices? The Set up would look like this:

This is what the schematic looks like. Basically, my confusion is that the MCP73831 needs to provide current to the battery to charge it, but if you look at the schematic, the VBAT output of the chip is directly connected to the SYS_OUT and BATT_IN headers. This is confusing because it means that the chip is technically providing current to BOTH the device connected to SYS_OUT and the battery? Isn't this a bad thing? Why would I want to provide current to my output device with a LiPo charging profile? Couldn't this ruin things? Also, doesn't it take away from the battery being charged?


texts: Mechanical Power (Application) and Electrical Power (Stepper Motor) Discrepancy

texts:
For my application I need a torque of \$\tau=0.87 \, Nm \$ and a speed of \$ w=140 \, RPM \approx 14.65 \, rad/s \$. This gives me a mechanical power \$ P_m=12.75 \, W\$.
$$
P_m=\tau w
$$
I have selected this stepper motor, which gives me the desired speed torque characteristics.

Now, I want to double check that the motor will generate enough electrical power to match or exceed the mechanical power requirements (\$P_m<=P_e\$).
$$P_e=UI$$
From the motor spec \$I=6.37\$, \$R=0.3\$. As recommeded here, I obtain \$ U=IR\$; this gives me a value \$U=1.91 \, V\$.

Now this gives me an electrical power of \$P_e \approx 12 \, W\$, which is lower than my \$ P_m\$. Looking at the graph I would expect a \$P_e\$ considerably higher than my \$P_m\$ requirement.  Question: why is \$P_e\$ not higher?


texts: Maintaining LM2596 output voltage with switch

texts:
I'm simulating an LM2596 DC-DC voltage regulator to give me a 5-volt output given a 5 ohm load (1 amp). The circuit is shown below:

simulate this circuit – Schematic created using CircuitLab

In my simulation, after throwing the switch after the LM2596 has reached a stable voltage, the load voltage after the switch spiked to around 6.6 V before stabilizing to around 4.968 volts. I'm trying to mitigate that spike by adding a capacitor and a zener diode before the switch in order to maintain the load voltage at approximately 5 volts. Without D3 and only C5, it spikes to 5.5 V before settling to 4.968 V, and with D3 and C5 together, it gets reduced down to 5.04 V and settles to 4.965 V in a matter of milliseconds. Is this a good method at 'stabilizing' the load voltage when using a regulator and a switch? What are some drawbacks of using a zener diode in this method?

EDIT: The SPICE model I'm using in my simulations is an adjustable regulator which I set to 5 V using a voltage divider, but the IC I plan to use is fixed at a 5 volt output. That's what I'm showcasing in my schematic, a fixed-voltage regulator.

EDIT: I'm basing my circuit off of TI's recommended schematic, a fixed output voltage regulator. The image is below, but I used TI's webbench tool to get the values shown in my schematic above.

EDIT:  Below is a simulation of the output DC waveform at the load. Using a 15 V input, I simulated four different variations of the LM2596. The first plot shows the recommended datasheet's parts while the other three show Webbench's part suggestions with and without a post-ripple filter as well as a small 10 nF capacitor on the load at the last plot.


texts: What EMC considerations need to be made with RF bias-t with 3-4A of current consumption?

texts:
After getting a great answer on how to couple a signal on to a DC line, I wonder what EMC considerations that has to be done with using a bias-T circuit used for communications with a  ~130kHz QPSK signal, modulated on top of a 24V DC line which should draw about 3-4 Amperes.

Please add any suggestions to my current schematic draft:

EDIT: My main concern is external influence from magnetic fields caused by mains which may run close to my circuit and/or noise from higher frequency generators like mobile phones or other RF signal wires running in close proximity. My system should be installed on a lot of different sites (industrial, home, ships), so an approximation of what kind of noise I can expect is fairly difficult. Also, how should I ground my system? I guess signal ground an actual ground should be seperated by a fairly large impedance, but my knowledge on this comes very short.


texts: Bi-directional on/off toggle soft power latch

texts:
I need a one-button on/off toggle power latch to connect/disconnect a 36V battery to two VESC-controlled 500W motors with regenerative braking.
Most of the designs I found for soft latching circuits make use of a high-side P-channel MOSFET which have a too high On-resistance for my use-case. Also, I didn't found a design which blocks the generated power from the motor on off-state, due to the latch feedback and/or body diode.
So I tried to design a circuit with the following features:

N-MOSFETs for low Rds_on because of high currents (around 30A)
Bi-directional switching to account for the load/generator states of a motor
Separate latching feedback
Fully analog, no microcontroller
One-button on/off with default state off

I came up with the design below. It seems to work, but I'm not sure why the current in the generative state is halved during button press when switching off. I'm also not sure about the crappy motor modeling...
Do you think this would work in reality? Any hints or tips for improvements?


texts: Overcurrent protection schematic: is there any off the shelf solutions?

texts:
I need to protect my device from the flowing through currents above let's say 30 Amps.

So I need a black box which will generate a digital signal if the current will be greater than specified (e.g. +/- 30 Amps). Rest things (circuit breaking) will be done elsewhere.

First I think about hall-effect sensor with comparator. Except that this is a branchy scheme with a separate isolated power supply this approach is slow (typically about 5 us).

Isn't there any off the shelf solutions for protection?

SOME MORE DETAILS

I need to protect my own device primarily (load protection is also welcome). Mainly from a short circuit. My estimation is that I need to break the circuit within about 1,5 us: if I wrong with this estimation please let me know your consideration.

ABOUT THE LOAD

The load most likely will be LED drivers. So it will not likely to be inductive. Probably capacitive in some degree. Nominal voltage is 230 VAC, nominal current estimated to 20 Amps.

EDIT 2

If asking about how I'm going to break the circuit that fast - the answer is that I have MOSFETs in series so I can switch them all off pretty fast:


texts:
I've found some interesting electronic projects which I wanna build, but I'll need a frequency meter for at least 1MHz. Sadly, I don't own one, but I found on the web that an Arduino UNO could do it.
My problem is that AVR's and other microcontrollers like 0V-5V logic levels as inputs, so it would be nice to create an 5V rectangular wave from the input wave.
I found that a simple Schmitt-trigger could do it, but sadly, I could not get one, and I'd like to use a wider voltage range than 5V.

That's what I've got so far(as a plan):
An opamp in peak value detector configuration, then use a voltage divider to divide it by 2. (I don't know that I can or can't use a voltage divider with opamp output. If not, use another opamp to divide it by 2)
Then another opamp in comparator config, compare the original signal to (peak value)/2. I think that if I feed 5V to the comparator's Vcc, then I should have a nice 5V rectangular wave as output.

Am I right?


texts: Need help troubleshooting Teensy 3.6 SPI to DAC8568

texts:
running out of things to check with this problem I'm having.

I designed a board around the Teensy 3.6 microprocessor, and I wanted to connect a DAC8568 chip to it for some analog outputs.  It works over SPI, and I have verified that it does "work".

HOWEVER it only works when I have an oscilloscope probe on the SCK line!

Here are two images to my schematic.  I am using SPI1 interface, as SPI0 is being used for communication with a CANFD controller.  I have verified that I get a clock output, I get a chip select, and data "flows".

Here is two pictures of my PCB layout.  The second image shows the two lines.  The top one being the SCK1 net, and the bottom being the MOSI1 net.

Like I said, the device seems to only work when I put an oscilloscope probe on SCK1 (on powerup), and if I take it off, it continues to work.  The probe is 8pF, 10MOhm.

CODE

NOTES: 9.2.1 says MSB first
7.3 shows that I should be getting data on the falling clock edge.
For this reason I chose SPI Mode 1 (CPOL 0, CPHA 1).
Just for kicks I tried with all the other SPI modes (0, 2, 3) and none worked.

Any idea what might be causing this??  I will continue trying to debug, but I would appreciate any help possible!! Thanks :)


texts: Is "weight of a sand bucket" analog or digital in nature?

texts:
I've got Digital Logic Design course this semester, during the introduction of this course my professor emphasized about the difference between digital and analog devices, and then gave us some examples from things around us, two of these examples confused me:

Grains of sand in a bucket is digital
weight of a sand bucket is analog.

What I was thinking is that it's pretty much the opposite!

Can I have some explanation to this?


texts: Op- amp comparators and temperature dependent resistor

texts:
The circuit in Fig 1 consists of a temperature dependent resistor (TDR). Compute the:

temperature at which the comparator will change state.
2)supply voltage required for a 40°C trip point in Figure 1.

I have researched and found the text book page 83the question was taken from but there is no example to go about this problem. Kindly assist.
edit:
I have attached my answer if anyone can help.


texts:
Is this a diode or a thermistor?

Also, if possible, can you tell the component manufacturer?
Thank you.


texts: Output Resistance of this circuit - Cascode

texts: Please see images of question, my working out and the correct solution. I seem to be incorrect for some reason. This is without resorting to the small-signal model.


texts: What is the physical meaning of resistance and power ratings of a loudspeaker?

texts:
What exactly does it mean when it is specified that internal impedance (or resistance?) of a loudspeaker is 16 \$\Omega\$? Is that ohmic resistance of the copper of its internal winding? Or is it absolute value of its impedance value? If it is an impedance value; a loudspeaker can play sounds with a wide variety of frequencies, how can they specify a general impedance for a loudspeaker?

And also for power rating, what is the physical meaning of it? Is it the maximum power of sound (the energy transferred to the molecules in the air as vibration in one second) that a loudspeaker can give out?


texts:
I am studying a SLD (single line drawing) wherein the designer is using a
transformer (1000KVA) with dual primary windings (3-phase both delta
connected) and single secondary winding (3-phase star connected) to step up
voltage to 33KV. Both primaries are fed with 3-phase, 1000V, AC , 50Hz
separately the outputs of two inverters. I shall appreciate if output (33KV)
from this transformer is technically and briefly  explained to me. Nothing
else is mentioned on the SLD about this transformer.


texts:
DESCRIPTION: Hi there, I don't know lot about electricity and I`m having problems with my first solenoid-prototype, I tried to build it watching you tube videos. I have attached the pictures of the wire that I used (diam=1.32mm), and the solenoid that I wired. The core is iron pipe (inner diameter= 1.5cm, outer= 2cm), you could see the size from the picture. There are 500 turns around the core, each turn is about 6.75cm + 50cm additional wire from each side, so the total length of the wire should be 6.75*500+50*2=34.75 meters. I used  1.5v batteries (1st test with 1 battery, 2nd test with 2 of them, so 3v). I also found from the internet that the resistance for this diameter of wire is 12.597 milli-ohms per meter.

PROBLEM: I want it to be a strong electro-magnet. But it doesn't stick any metal at all. Please tell me if the design is wrong, or i wired the circuit wrong, or volts are too little. How much volts do I need to make it work best?


texts: Voltage limitation circuit for analog signal

texts:
I want to design a circuit which takes two analog signals with a DC-offset via koax inputs, and forwards them.

In between the voltages should be capped at a user-defined level (between 200 mV and 500 mV), if the input voltage is higher, then it should be capped at the cutoff level. The reaction time of the circuit should be as fast as possible. The input signals have a frequency up to ~2-3 kHz. What is the best way to achieve that?

Bonus: Amplification of the signals in the circuit is also possible.


texts: How is signal strength (RSS) measurement done on Bluetooth and Zigbee ?

texts:
My question is related to an observation that I made.
I tested BLE (Bluetooth Low Energy [ti2541/nRF51822) and ZigBee (ti cc2531) against each other on jumpiness of the signal strength (RSSI). Both use the same freq. and same antenna design (ANO43).

In my experiment I found out that the BLE modules were much more jumpy, especially when a person was in range (only in range not in line of sight). On the ZigBee module it was much more stable.

Does someone has an explanation for this or can give me more background information about how i can find out how the measurement on the modules is made.

Thanks!


texts: Measuring noise of audio preamp power supply

texts: How does one measures noise/performance of audio preamp power supply?


texts: How to prevent EMI from affecting transistor

texts:
I am working on a simple APRS tracker.

The schematic is here:

It's not on a PCB, but just on a protoboard:

The problem:

Q1 transistor activates the push-to-talk on a handheld VHF transceiver, "analog out" outputs the signal. All of this works fine, except once the signal is transmitted, the push-to-talk remains open - the transistor malfunctions.

It was suggested this might be due to EMI. I lowered the transmit power and wound the cable leading to the HT around a ferrite.

Indeed this solved the problem and everything worked perfectly, but only on the lower power setting (1W). I need to transmit at 7W - the ferrite does no good there.

My question is what can I do to prevent EMI problems with the transistor and the board in general?

I tried putting the board in a thin (and light) aluminium housing, which did little. I do have some weight constraints for this projects and the transmitter has to be in very close proximity to the board as well.

Any ideas or insights would be appreciated


texts: What is this inductor symbol from a video circuit?

texts:
This is from the datasheet for the TDA8217 PAL decoder and video processor. This is the "Applicaton Diagram".
The circled item is unfamiliar to me, I asked at my local electronic components distributor and no-one there recognized it either.  It looks like an inductor, but seems to be connected to ground maybe?


texts: How do proceed with larger electronic projects?

texts:
Recently I have read two books about programming in general:
First one being Code Complete and the other being The Pragmatic Programmer that describe how one should think when dealing with large projects. Wonderful books.

My weak point is electronics. How shall one start with larger projects? How do the "professionals" do?

For example, If we are going to make a vacuum cleaner robot, do they review the requirements first? Start sketching in a computer ECAD software? Or maybe the breadboard? What steps should I follow?


texts: MFRC 522 not working when using with relay module

texts:
I have a circuit which basically have to link up to MFRC 522 module, Arduino Nano and also the relay 2 channel module.

See below for the basic schematic.

simulate this circuit – Schematic created using CircuitLab

Apologize for some of the miss out pins as I wanna use the schematic as illustration only.

AC - DC module is using SMPS power supply which come out as 15V. So i use two voltage regulator 12V and 3.3V. 12V to power on Relay module and VIN to Arduino NANO. Another separate 3.3V to serve power to MFRC522 as it is a 3.3V module.

2 Channel Module is opto-isolated Relay module. However, I only uses power supply with all common ground.

All is working as usual at first, MIFARE card is able to be detected via the MFRC522 module and relay is able to turn on.

However, after few round of trial out, the MFRC522 is not responding. Even hitting reset on Arduino Nano, there is no respond. I need to turn off the SMPS 15V supply then turn back on, then it is able to operate back.

As i suspected on the 12V relay module, i remove the 12V to power the relay module. MFRC 522 is working as expected which dont have the intermittent case anymore.

My operation mode is as follow:
1. Scan a MIFARE card, turn on relay to drive a motor then after 3 seconds, the relay will turn back off.

I did not connect any load to the relay yet with only the relay coil energize which causes the problem.

It seems like only with the power off and then it will work back on. As if the relay coil generate noise to the power supply and then the SPI signal does not work.

I understand that we could use separate power source to power on the relay module with separate grounding.
If i would like to do with one power source, how can i shield the relay coil noises to not impact the MFRC 522.

This is the module I am using.
Change it to 12V relay instead of the 5V.

Take note again that if i remove the 12V to the Relay module that flows from transistor Collector - emitter to turn on the relay coil, it works perfectly as expected.

Any recommendation to help shield the noises from the relay coil ?

I have tried to add capacitor to the AC-DC 15V output and 3.3V output as well but it is not working.
Need more advise here.


texts:
I am restoring a stereo amplifier circa 1985 (specifically the Technics SU-Z55). Part of that is replacing the electrolytic capacitors on the mainboard due to some audio popping and general age. There are 6 capacitors on this board that are electrolytic but have no polarity strip on them or negative marking on the PCB.

These are:

C11: 1uF/50V
C12: 1uF/50V
C331: 3.3uF/25V
C332: 3.3uF/25V
C403: 47uF/16V
C409: 47uF/16V

On the board, they are marked with a special kind of capacitor symbol I am unfamiliar with (caps removed):

And here are the old ones:

And here are where 11/12 and 331/332 are on the schematic for the unit:

If I had to guess, I would say these are some kind of non-polarized electrolytics, but I've never heard of such a thing and don't want to bet my amplifier on a hunch. What are these capacitors, and is it okay to replace them with a non-polarized cap of the same value (like a ceramic)?


texts: Why does Moore Finite State Machine need more states than Mealy Finite State Machine?

texts: I was reading about finite state machines. I read about Moore and Mealy machine and also the state representation. I read that in the Moore machine the output depends on the present state only and in the Mealy machine the output depends on input and present state. But I don't understand how this could vary the number of states?


texts:
I'm looking to design a four channel dimmer using the On Semi FL5150/FL5160 dimmer chip.
This will be controlled by a digital signal sent over an isolated I2C interface, with my initial design using the MCP4728 quad channel I2C DAC.
However the reference designs on the datasheet tie the Source pins of the output MOSFET pair to the GND of the dimmer control chip. As I would have to tie the GND of the DAC to each dimmer chip to correctly reference the analog voltage, all four MOSFET pairs would have their Source pins linked, so the circuit would fail to operate as expected (all four channels would operate as one).
Can somebody explain:

why are the Source pins connected to GND ?
is it possible to omit this connection ?
is this connection required for ZC detection, if so could this be provided via a different method ?

NB: this is a different question to FL5150 (LED dimmer) circuit explanation


texts: Small signal analysis of BJT dynamic microphone preamplifier

texts:
I am trying to do a small signal analysis for the following circuit

I did not have any experience with BJT so I am having a hard time to analyze the circuit. From research, I know Q1 is common base and Q2 and Q3 are common emitter. To draw the small signal model, I would have to short all DC source and capacitors.
Then I ended up with the following circuit

I am not sure what to do next. I tried to break the circuit into 3 parts to analyze but I am not sure what to do with the 47K, 56K,15K resistors that's connected to Q1.
Can anyone help with the small signal analysis?
Now I have this for the first part if I were to divided the circuit to 3 parts.

To find the input impedance, applying KCL then it would be
12/47k + gmVpi + Vpi/rpi + Vin/10K?
I am a bit confused with Vpi and rpi. Do I need to calculate that or it's from the BC547 data sheet?


texts: Reverse Polarity and TVS Diodes Not Working?

texts:
This is a follow up to this issue: Damaged TPL7407LA Transistor Array (*Updated With Scope Testing Images*)

We are experiencing both reverse polarity and transient voltage spikes in our automotive circuit application pictured above where we've added protection for both situations but are still experiencing aforementioned behavior when an adjacent input to our device is being switched off (oscilloscope input 3 - PARK).

The only feasible possibility that we can consider at this point is the fact that the diodes may not be reacting quick enough these conditions.

Here are the reverse polarity and TVS diodes we are using, respectively.

Reverse Polarity Protection Diode

TVS Overvoltage Protection Diode

Curious to hear what you folks have to say on this topic.


texts:
I am looking for a Peltier module/TEG to power wearables and I'm not quite sure what specs I need or should be looking at. To be honest I am not quite sure what some of the specs even me. Essentially body heat should be used to power the device.I am most interested in what the following specs mean:

Qmax @ Th
Delta Tmax @ Th

looking at https://www.digikey.ca/products/en/fans-thermal-management/thermal-thermoelectric-peltier-modules/222

Also, the operating temperature in the specs, does it refer to the temperature that the device will perform optimally, or does it refer to the temperature that is required for the device to operate?


texts: What is the function of voltage divider in the below circuit?

texts:
Hello I am a beginner in electronics and eager to expand my knowledge in it. Earlier I was trying to build an Ultrasonic receiver using a transducer and some op amps. I ran searches in the Internet and found this:

I figured that the signal from the transducer is amplified by the two stages of non inverting amplifiers and fed to comparator for triggering. But why is the voltage divider of resistors \$R_1\$ and \$R_2\$ used here? Why can't we just feed the input signal directly in to the + terminal of the op amp?


texts: What's the best cable to transfer audio signal?

texts:
Sorry if this is the wrong place but I'm interested in a scientific and electrical explanation and not some HiFi voodoo magic.

I guess you all have seen the discussions about expensive audio cables and "improved" sound quality.

My question is, what's the best cable for an audio signal? Loudspeaker cables are usually a pair of ~12 AVG cables terminated with banana connectors.

As far as I understand this must be affected by all sorts of noise. To minimize noise it's normal to use coax cable for "radio" signals (LF, MF, HF, ...). Wouldn't coax with proper connectors like APC-7 or equivalent be the best for audio too?  Or are the frequencies too low for coax somehow?

Internet was a bit vague on this topic.

What I'm really wondering is why don't we use coaxial cables for loudspeakers in average home stereos?

Lets say a signal level of 50 dBm (100W).


texts: LED Strip - Voltage Drop when Wired in Parallel

texts:
please have a look at this chart:

I have a question on the calculation of voltage drop on each of the connection point between the wire and led strip. We are using 1.5mm2 wire and 24V led strip which uses 0.6A per meter.

Do we calculate the voltage drop for the first strip using 0.6A or 8.4A (the total current of all the strips)?

How about the second strip? Do we calculate the voltage drop based on 1.5A, 8.4A or (8.4A - 0.6A = 7.8A)?

Similarly, for the second last strip, do we calculate the voltage drop based on 2.1A or (8.4A - 0.6A - 1.5A - 1.8A = 4.5A)?

Thank you.


texts: How can I simulate an 8 LED (complemented) pattern device?

texts:
How can I simulate an 8 led with timer and ic?
I have tried simulating it like this but still it’s not working, it blinks for less than a second and then it turns off

I want it to work like First all LED ON, then only 7 LEDs ON, then only 6 LEDs ON, then only 5 LEDs will be ON... and so on.


texts: does proportionality always works when analyzing DC motors?

texts:
Let's consider this example:
a Trolley that can reach 36kmph when there is lite traffic with a current of 700A, and when the traffic gets heavy, the speed decrease to 20kmph.
now i want to deduct the current form these information.

so my question is, would proportionality rules always apply for these kinds of analysis.
for example the current would be: I2 = (20/36)*700 = 389A

the problem with this approach, is that it contradicts with how DC motors work, which is when speed decreases, the current increases


texts:
A lot of power mosfets have a really nice and low RDS(on), but their charts never seem to go down near 0A. For example the NTD3005L:

The chart shows the value down to something like 5A. What happens below that? Could I use the to switch a 10mA load, and is the RDS(on) just undefined, or would it not work?


texts: Is it possible to wire up a simple camera module with a separate wifi module to create a live UDP stream without full fledged OS?

texts:
Could be any simple camera module, like for example that: https://www.arducam.com/product/arducam-5mp-plus-spi-cam-arduino-ov5642/

Wifi module could be also any available.

I imagine I would also need some kind of H.264 encoding module, is there even anything like that?

Would I need something else to produce an RTP stream? Is there anything for that?

I fully expect the solution to be very difficult (if it exists) but could it even be wired up at home?

Currently I have setup with RPi, and I just wonder if this can be achieved without Linux or any full fledged OS, just with combining multiple modules, some electronic work and some code (I imagine it would be difficult, but I would willingly accept that challenge).


texts:
To preface I am a software developer, not an electrical engineer so please go easy on me as there are likely gaps in my knowledge here.

I am utilizing an nrf52832 SoC (specs: https://github.com/redbear/nRF5x/tree/master/nRF52832) to send sensor readings over bluetooth.
My sensor is a MaxBotix MB1043 HRLV-MaxSonar-EZ4 (datasheet: https://www.maxbotix.com/documents/HRLV-MaxSonar-EZ_Datasheet.pdf)
I want to set a pin high on the SoC to turn on the sensor.

My initial research shows that a 2N2222 Transistor with a 1kOhm resistor would be appropriate for this task.

Updated from feedback:

simulate this circuit – Schematic created using CircuitLab

My question is: Is 2N2222 appropriate and is a 1kOhm correct (based on rule of thumb from my research) or can a more precise value be calculated here that would be better? Does my circuit look correct?

Thanks!


texts: How to control whether a connection dot appears in the Quartus Prime Block Diagram editor?

texts:
I am using Quartus Prime 16.0.2 to draw a block diagram. I connect different components with the node connector (in red box below):

It is unclear to me why sometimes a connector dot appears and sometimes it doesn't. For example, the connection between input pin D1 and the D-input on the left latch has fat connection dots at each end. The connection from the Q-output on the left latch to the D-input on the right latch has a dot on the left side but not on the right. How do I control whether the dot appears? I don't want it to appear except where a signal splits, such as the clock input on the bottom left.


texts: Design reset about top group of SAR logic

texts:
This is the top group of SAR logic,and as you see,it is composed of lots of D-flip flop with set and CLR(reset),and these D-flip flop are active low.

when both set and CLR(reset) are 1 , Q can only depend on D and clk: when set=1,CLR(reset)=0 , Q=0 , Q'=1;when set=0,CLR(reset)=1,Q=1,Q'=0,the truth table is the same as the website,i suggest to see Figure 1: Timing Diagram of a Positive-Edge-Triggered D Flip-flop from this website. http://macao.communications.museum/eng/Exhibition/secondfloor/moreinfo/FlipFlop.html

Is it possible to let a~e become like

initial reset : 00000;

first clk rising edge : 10000

second clk rising edge : 11000,... and fifth clk rising edge:11111?

Here is my thinking,if it is wrong,please tell me

The input are Reset and CLK,but if i want 11000 in second clk rising edge ,i must send Reset=0 to let first ouput is 1,but if i do that,the second d flip flop's output must be 0,because the second d flip flop has CLR=0.


texts:
Working on a design where power supply (on the PCB) is 12VAC to full wave rectifier to 5VDC linear regulator.

Customer switch box is also power via same 12VAC source and will be switching that 12VAC back to my device (retro fit application, must switch the 12VAC).
I am looking to use least amount of components. Therefore was thinking I’d half wave the switched 12VAC from customer supplied box and use inverter IC (we stock this so it’s ideal) to interface to my microcontroller.

I am looking for feedback regarding my half wave circuit interfacing to the full wave common (10uF and ULN2804). Have bread boarded this and all looks good. I’d just like verification that the only use of the 12VAC common (not including power supply) is to power the customer supplied device and should not be referenced to any of the input circuit. More or less just want opinion from others who may have more experience with this.


texts:
Does anyone know a reference design with bill of materials of less than 30US$ for collecting weather data from the Internet eg. Yahoo's and show it on a LCD?

I found many design and dev kits but most of them are too expensive and mainly target tablet, photo frame, internet radio and the like. I just need a slow CPU 50-200Mhz, wifi, and LCD (up to 5", QVGA) or multi-line characters.

I really appreciated any of your feedback.


texts: Position of the voltage source with parallel resistors

texts:
In the following circuit I want to calculate the current flowing through the voltage source (node A)

simulate this circuit – Schematic created using CircuitLab

If I use the KCL I get \$I_A = I_{R2} - I_{R1}\$ (I assumed that the current flows always from left to right and from top to bottom). This can be expressed as \$V1({1 \over R2} - {1 \over R1}) = V1( {R2 -R1 \over R1R2})\$

However if I assume that the circuit is equivalent to a voltage source with a parallel resistors \$V_p\$ (obtained from the parallel of \$R1\$ and \$R2\$) the current is \$I_A = {V1 \over R_p} = V1 ( {R1+R2 \over R1R2})\$.

The same result can be obtained with KCL if the current \$I_{R2}\$ and  \$I_{R1}\$ are assumed flowing in opposite directions (both entering the node or leaving the node) and also the direction of the current flowing in A makes the difference.

It seem like the voltage source position in the circuit matters. What is the correct answer in this case ? Can I replace the two resistors with an equivalent parallel resistor ?


texts: How to analyze a capacitor connected to a DC voltage directly (no resistor)?

texts:
This may be a very basic question but my misunderstanding is due to the difference between how physics explains the charging of capacitors and how we analyze circuits in circuit analysis.
According to physics, when a battery is connected to an uncharged capacitor, electrons flow from one plate to the other creating an electric field, and hence a potential difference across the capacitor. This potential difference starts at 0 and increases until it reaches the voltage of the battery.
However, this means that for the time the capacitor is charging, the potential difference across it is different from the potential difference of the battery. According to circuit analysis (or at least the lumped-element model) this connection is not valid. The definition of 2 elements being parallel is that they have the same voltage.
The only solution I can think of right now is that it is indeed valid to have this connection however in real-life circuits there is no ideal short circuits so if we connect a battery to a capacitor, the wires have a bit of resistance and so we can model them as resistors in the circuit. So when the battery is connected, the resistance will have all the battery's voltage at first while the capacitor will have 0 volts. The current that flows is due to the capacitor charging (and will be very high because the resistance of the wire is very low). As the capacitor is charging, its voltage increases while the voltage of the resistor decreases until the capacitor takes on all the battery's voltage causing the current to be zero and so the resistor's voltage becomes 0.
And that's why analyzing the step response of a capacitor, there's always a resistor (usually with a high resistance, on the order of 10 kilo Ohms) connected in series with the capacitor.
Is this really the case? Or am I missing something?


texts: I am doing boolean algebra simplification and got the result of (A.B) xor(C xor D) Does (A.B) xor (C xor D) = (A.B) xor C xor D ?


texts: It's on pin 14, which is the master clock input (MCLK) of a WM8761: Low cost stereo DAC.  I'm guessing it's meant to act as a small inductor?  But why would you want that on a clock input?


texts: Is it possible for buck boost converter to output -48V with +12V input?

texts:
I have a school task for creating a Buck Boost converter that takes 12V and outputs -48V. I have done some digging and couldn't find my answer since I could only find converters that give a number lower than the input number (like in my case I can get -6V with my calculations but not lower that -12V).

Is this thing even possible only by creating a conventional converter?


texts:
I am trying to build a simple baud rate changer with a Blue pill stm32f103 using the HAL API.
What I'm hoping to achieve:
One old terminal to that's locked at 9600 baud.
One old thermal printer that has a max of 300 baud.
The project consist of 2 "Blue pills", one that just puts of a character stream at 9600.
The other Blue pill takes the stream in at 9600 and dumps every 4 bytes into a register for UART 3.
Using hardware flow control, the contents are dumped into UART2 which is 300 baud.
It works well as long as its a continuous stream but when I stop the primary transmitter I need the downstream UARTs to stop transmitting. I have tried using  the RXNE, TXE and TC flags but they do not work as expected. When I stop the transmission from primary stream, UART2 ( 300 baud), goes into "TIME OUT" and just continuously prints whatever is left in its buffer.
    while (1) {

    if (__HAL_UART_GET_FLAG(&huart3, UART_FLAG_RXNE) == 0) {    // 0 = Empty
        HAL_GPIO_WritePin(BluePill_LED_GPIO_Port, BluePill_LED_Pin,GPIO_PIN_SET);
        HAL_Delay(100);
    }
    HAL_UART_Receive(&huart3, (uint8_t*) uart1_buf, uart_buf_len, 500);

    strcpy(uart2_buf, uart1_buf); // copy the contents of UART1 buffer to UART2 buffer
    if (__HAL_UART_GET_FLAG(&huart2, UART_FLAG_RXNE) == RESET) {
        HAL_GPIO_WritePin(BluePill_LED_GPIO_Port, BluePill_LED_Pin,GPIO_PIN_SET);
        HAL_Delay(200);
    }

    HAL_UART_Transmit(&huart2, (uint8_t*) uart2_buf, uart_buf_len, 1000);
    if (!(__HAL_UART_GET_FLAG(&huart2, UART_FLAG_TXE))) {
        HAL_GPIO_WritePin(BluePill_LED_GPIO_Port, BluePill_LED_Pin,GPIO_PIN_RESET);
        HAL_Delay(200);
    }
}

This code is modified for testing purposes. As you can see I was thinking I could get the LED to come on when the flag conditions were met but the LED doesn't come on. One other odd thing is the although the LED doesn't come on, the HAL_Delay is for sure being executed.
Maybe someone could shed some light on what I'm doing wrong. Thanks


texts: So I'm currently looking to control a lightbulb for some inefficient lighting to produce heat for a mini-greenhouse I am building. I'm looking at plugging in a wall wart 12V DC adapter and wire that to the bulb. In terms of relays/solid state relays what should I look into buying? 12V - 5V DC relay?


texts: Hey there the first part of the question (finding the new C value) is pretty easy. However I am stuck at the second part, it asks me to find the empadance values and etc. Can you help me with that?


texts: Simple ground connection when controlling with gpio different power supply

texts:
I have a STM32F4 Discovery board and I want to activate a LED connected to an external power supply.
I could connect the LED to the 5V supply of the STM32F4 DISCOVERY but I'm testing this to use it with a load that will consume a lot of current, so I need that external power supply. In addition I'm planning to use a N-Channel MOSFET instead of the NPN transistor, but for the moment I'm just testing a main idea.
In order to correctly control the LED toggling I've had to connect the STM32F4 GND to the LED power supply GND using a simple cable (purple cable in the picture below).

simulate this circuit – Schematic created using CircuitLab
If not, the LED is always turned on with a lower light intensisty (transistor not fully switched). I understand this is because there is a voltage offset between both grounds.
Is this procedure correct? If not, how should I proceed?


texts:
My knowledge of electrical engineering isn't great but faced with a challenge I do have a habit of learning enough to see it through. There is a probably a very simple solution to this.
I've been pondering different routes to achieve a 'chuffing' smoke effect on a model train. I'm looking to use a Hall effect sensor to pick up 4 magnets spinning on the axle of the train. Each detection triggering a puff of smoke up the chimney.
To generate the smoke I'm going to be using a vape heating coil of 1.5ohms. There will also be a small 3V fan in an enclosure with the coil to ensure there is airflow and push the vapour out the chimney. Total load would be a smidge over 2amperes at 3V.
However, I would like the fan and coil to be continuously powered at a base load so there is always a little activity. I would then like the Hall effect sensor to come into play to produce 'chuffs' of more intense blasts when the locomotive moves.
There is 12VDC on the locomotive to utilise, but I've got some miniature variable voltage regulators (MP1584en) left over from another project. I was thinking I could use two of these to have a supply of 3V for the 'chuff/HIGH' and ~1.5V for the idle/LOW.
What I need is a way of switching between them with the Hall effect sensor.
I've got a few A3144 Hall effect sensors and some IRF9540N P channel MOSFETss that I was originally planning to use, but a second opinion wouldn't go amiss.
Thankyou to anyone who can spare me a few moments!
(ps. The more I think about this the more issues I for-see.  If the locomotive were to stop in a position where the Hall effect sensor was activated, it would be good to have a way to default back to the lower voltage state after a few seconds.)


texts: How to shift the phase (185 degrees) of the triangle waveform without a distortion?

texts: I need to phase shift the input waveform exactly 185 degrees. Unfortunately, I can't find a good/simple way to do it. Thanks.


texts:
I'm powering (hoping to power?) two boards from one 12V AC source. One is a preamp requiring 12V AC in (easy so far) and the other is a scavenged audio board requiring +12/-15V DC.

I'm using the circuit below to double + rectify the AC into ±18VDC, then into a 7812 and 7915 which measure the expected +12/-15V at output.

The preamp powers up fine, and the audio board powers up fine, but when I connect them via the audio board's audio output, I get sparks and smoke.

Any ideas? Is it because I'm using the AC leg as ground for the DC circuit, and so the DC voltages are fluctuating with ground but staying the same 'distance' from ground, so they meter correctly?

simulate this circuit – Schematic created using CircuitLab

Possibly-not-100%-correct schematic for the preamp:

Pic of the preamp:


texts:
I actually ran into this question just a few moments ago:

https://serverfault.com/questions/12025/intro-to-laptop-hard-drives

The first answer is the one that caught my attention.

Apparently, there are pins created for data flow (information) and other pins made for power supply. And I am currently not aware of any, but that means there may be pins for other things as well.

Are data pins and power pins identical to each other (meaning are they made of same material, configuration, structure, etc)? I have never taken an EE class before, so I was also wondering how the number of pins are decided upon (for instance, in that jpg image there are 6 data pins and 9 power pins).


texts: What is meant by downstream bandwidth in lte?

texts: In my phone, it says that the downstream bandwidth of LTE is 10Mhz. But if a carrier frequency of 900Mhz has a bandwidth of 20Mhz, i.e., frequency ranges from 900Mhz to 920Mhz, then I have almost half the BW of my base station. It's impossible. Can you approximately tell me how much BW will I get if there are a 1000 users in vicinity of that base station?


texts: Arduino relay module interferece on signal pin (230VAC moror load)

texts:
I'm trying to switch a small 230V AC motor using an Arduino Uno, but I'm having same problems due to interference on the relay (so the Arduino itself is not a problem).
Sometimes the module create voltage/current peak on the wires going to the Arduino, and it reboot or sometimes stops running the sketch until I unplug the power to the board and connect it again.
Looking the signal on the oscilloscope I see something like that

and sometimes the peak are in very short periods

I tried to add capacitors or diods in different configurations, but nothing really solved the problem, in some cases it only appear more rarely.
The relay module I'm using are the standard Arduino-type optoisolated ones, already with back-current diod and optical isolation, so I thought it should work without any extra circuit, but apparently it is not, or maybe the module is broken?
What should I do to fix the problem?


texts:
I'm building an LED driver circuit, CD4504B and TLC5916 controlled by a Raspberry Pi:

simulate this circuit – Schematic created using CircuitLab

I'm finding that sometimes when I move the circuit around, the LEDs flicker. It only happens when I'm not driving the GPIOs.

I've already inspected the circuit for shorts and didn't find anything. Did I miss anything in my design? Do I need pull-downs for the level shifter inputs for when the GPIOs aren't being driven?


texts: How does this overvoltage protection work?

texts:
I was looking around for low cost and effective overvoltage protection, and I found this from this page:

With this part list:

RXE025 - 250 mA PTC resettable fuse
Zener diode – 5V6, 1 watt
Resistor – 1K ohm, 1 watt
Transistor – BD139 (NPN medium power 80V, 1.5A CC rating)

As reported by the author, this circuit seems to be effective and low cost, but I don't understand why the engineer placed a BD193 transistor in this circuit.
Can anyone explain the step-by-step operating method of this circuit?


texts: my problem is that I have laser (green one) 20W, 3.7V and I want to power it by a car battery that is 12V. I need 3.7V and 5.4A to make it switch on. Do I need a circuit to do it or there is already made device? Thank you!


texts: Can I use this garage door circuit to power an ESP8266

texts:
So this circuit is from my garage door opener. Basically it has 24VDC coming into it which runs directly back to the motor unit of the garage door opener. My limited understanding says that there is an IC in the motor unit that senses the short or short running through the caps (ie build up time). My question is: can I put an arduino in parallel to this circuit without screwing up the sensing, and will the arduino still function when one of those circuits is closed?

Thanks


texts: Which opamp to use for differential reading of a shunt resistor?

texts:
I've made the following circuit, but I just can't get it to work. My LTspice simulation suggests that it should work, but it doesn't. I can get it to work in a normal inverted/non-inverted setup, but I need a differential reading.

I understand that some precision opamps have built-in precision resistors at a fixed gain?

I'm using the INA214 which has a gain of 100, but even that is giving me +-5% noise

Do you have any suggestions regarding a good 'through-hole parts only' opamp (e.g. DIP8) which is great for this purpose?

I've found a lot of SMD-type opamps, but they're a pain to work with. I'm looking for about 50-100 gain, with input range 0-80mV.

simulate this circuit – Schematic created using CircuitLab


texts:
I was reading in a book that it is often possible to realize a certain capacitance in Integrated Circuits by exploiting the Gate Capacitance of a MOSFET. I read that the main disadvantage of this technique is the presence of a resistance between drain and source, which determines some losses. The equivalent model of this structure is shown in the following picture:

Now my questions are:

1) The first plate of the capacitor is the Gate metal contact. Under it, there is the oxide. Under the oxide, the substrate. Which is the second plate?

2) Why are in this model S and D shortcircuited?

3) Why does the resistance between S and D become a series resistance?


texts: Help comparator circuit for this PWM signal inverter

texts:
I have 2 signal (signal on the left) and how to combine those 2 signal into the signal on the right, I have try using lm 741 op amp, but unfortunately the output signal is different from the signal(not as expected) on the right picture..

Since i use 4kHz of frequency and 4V of voltage input, What the comparator circuit i should use to generate signal like on the right picture? Should i change the 741 op-amp??thanks

here is my output signal, it look different from the signal i wanted


texts:
I've been looking for a part that I can boost a 10 mV signal to a 10 volt signal
using a single op amp, so far most of the op amps I've found only meet the gain requirements, but cannot output 10 volts.