texts:
I am trying to build a supply-voltage supervision circuit based on the design suggested in 2nd answer here (the one with the CircuitLab schematic): What is the simplest way to turn off some circuit when supply voltage reaches a minimum level?

I do not have much of an electronics background so I cannot say if the suggested solution might already be flawed or if I just picked unsuitable components for the voltage range that I am interested in:

As compared to the original thread, I am trying to build a circuit that shuts down supply voltage at a minimum threshold of around 3V while switching through anything bigger, up to around 5V (the goal is to replace my uP's built-in brown-out detection with something that draws less power).

I am using a DN1509N8-G (see http://cdn-reichelt.de/documents/datenblatt/A200/DN1509_DS.pdf) for M1 (same as in original schematic) and a MAX810-T (see https://datasheets.maximintegrated.com/en/ds/MAX803-MAX810Z.pdf) for U1 (which - as I have verified - outputs any input voltage smaller than 3.08V "directly" on its RESET pin but switches the RESET to 0V as soon as 3.08V is reached/exceeded.. the MAX810-T has a push-pull output and I am therefore not using an R1).

When measuring the OUT voltage (at drain of M1) I do not get the desired switching behaviour, i.e. 0V for any input below 3.08V and original input voltage for anything above 3.08V - instead I always seem to get roughly the same voltage which is input (at least in the range from 2-4V) somewhat lowered by some kind of forward voltage drop. It seems that M1 does not provide the desired functionality - at least with the voltages that I am dealing with.

What would I need to change (and how) in order to make this circuit work within a voltage range of 0-5V with shut-down threshold of ~3V?


texts: Is the '0V' on a non-isolated buck converter the same on the input as it is on the output?

texts:
I'm working on a project where I want to switch a load (utility LED light, +- 20W) using a motion sensor. The PIR can only operate at a maximum of 12 volts, while the load can be operated at a voltage between 12-36 volts. I want to power this circuit using a lead acid battery, with the light on the 'unregulated' output and the PIR regulated (with a buck converter) to something like 5V. The PIR also outputs a 3,3 volt signal, so I made a circuit to boost this to the battery voltage. I was wondering if a circuit like this would work or if the '0V' line would be different between the battery negative and the buck converter negative output.

Signal boost circuit

Whole circuit simplified


texts: Equivalent resistance when there is only one terminal?

texts: How would one go about finding the equivalent resistance when there is only one terminal given? Like the picture below: (Where the squiggly lines are resistors, and the 3 parallel vertical lines represents ground)


texts:
I was trying to resolve a problem from "Understanding Digital Signal Processing". I have some questions about it. Why do we need to redesign the filter if we find out that the sample rate is higher? If we want to remove undesired high-frequency noise, should we keep the same FIR filter? I am looking for any other hints. Thank you!
P.S. I haven't seen in the same chapter any relationship of low-pass FIR filters with the sample rate of the original signal.


texts: What is this small white component across transformer's inputs/outputs?

texts:
I was tearing apart a transformer that was not working (from halogen lamps) and I found this little thing inside:

Eventually I found out it was a bad connection that made the transformer faulty and am trying to reassemble it, but I am not sure how this component was wired. What is this component, what purpose does it serve and how do I properly wire it back?

Thank you!


texts: How does isolation prevent input signals to float/saturate for differential ended inputs?

texts:
A differential ended input data-acquisition board has the following architecture:

Here more information.

Through screw terminals it takes the voltage inputs and each input first goes to a signal-conditioning module which also forms a channel to channel isolation.

Normally for floating sources until now I've encountered differential ended data-acquisition boards which needed around 10k bias resistor between the signal return and the AI GND of the board. It was something like at this link. And I remember without this resistor saturation was happening.

But the manufacturer says for the board above, one does not need bias resistor because channels are "truly isolated".

What does truly isolated mean in this context? How can this Take care of the need for bias resistor for return currents? Can it be explained with a simple opamp or circuit model?


texts:
If we have the connection shown below (star connection of the secondary part of a TX), the load per each phase is equivalent (balanced load), then the vector sum of I1, I2 and I3 is zero. In this case, I would like to ask if we can remove the neutral wire from the connection since no current will flow in it (theoretically at least)?

And if we can remove it, where is the return path (to form a closed circuit) for each phase current?


texts: Multiplexing LEDS and Multiple Output Pins

texts:
Ok.....i've been trying to understand something (and trust me, to most people it's a VERY newbish question)

So I see people all the time "multiplexing" LEDS. using just a few Pins.

Lets say for an Arduino that has..... 5 I/O pins for example, apparently this can control 20 LEDS (or so i've been told) using Multiplexing...but.....what Im confused about is that this is all controlled by 5 pins. Maybe im getting Multiplexing wrong but how exactly does this happen?

Also as iv'e been reading assembly tutorials for the AVR I notice that each Port has 3 registers, PORTB, DDRB and PINB, do these correspond with LOW/HIGH/OFF.....or is this entirely unrelated?

I guess I don't understand the whole idea of Multiplexing, I've read tutorials.....but I don't understand exactly how/why you hook them up, and for that matter where (and how much) to use resistors for, I know using certain combinations of High/Low/Input you can achieve a pretty awesome LED matrix. but How do I determine this. Im sure you would have to use transitors though right?

Sorry for the confusing question, it's even harder to ASk the question when Im not very sure about it.

edit: Also I understand Shift Registers/Multiplexing (at least somewhat) in terms of "Truth tables" but I dont understand actually how to implement it. Maybe anyone could recommend a book on using Transistors and the like with Electronics, since some of the basic books really only go over Capacitors/Resistors


texts:
I recently read a lot about guitar sustainers, for those who don't know what are they - it is basically an electromagnet with an amplifier. It takes an input from pickup, amplifies it and then generates the magnetic field that vibrates the string.

I have the question - if we need magnetic field that changes corresponding to specific frequency in order to vibrate the string - why would we put a permanent magnet underneath the core? Wouldn't it be pointless, or even destructive? What's the point of it hanging around there? How does it help?

I probably missing some basic laws here, but can't find out what it is...

The picture below from one of many patents on this kind of invention(http://www.google.co.in/patents/US5932827).

Other patent I found also mention permanent magnets, but none of them describe in clear language what is the point of it.


texts: why is \$P^{max}_{Z_L}=|\hat I_L|^2\times 4\$,not \$|\hat I_L|^2\times 5\$,when \$\hat Z_L=\hat Z^*_{th}=4-3jΩ\$

texts:
What is the max power of \$\hat Z_L ,P^{max}_{Z_L},\$ when the \$\hat Z_{th}=4+3j Ω\$??

First i know the Imaginary part of impedance will cause Reactive Power,so  the real power can't be the same as the apparent Power,so  we can know if we want to have a \$P^{max}_{Z_L}\$,we have to cancel the Imaginary part of impedance,so obviously we can know the \$\hat Z_L=\hat Z^*_{th}=4-3jΩ\$,and \$\hat I_L=\frac{V_{th}}{\hat Z_L+\hat Z_{th}}=25∠0\$

The answer show me \$P^{max}_{Z_L}=|\hat I_L|^2\times 4\$,however, i think the \$P^{max}_{Z_L}=|\hat I_L|^2\times \sqrt{4^2+(-3)^2}=|\hat I_L|^2\times 5\$

So i want to ask why is \$P^{max}_{Z_L}=|\hat I_L|^2\times 4\$? or the answer is wrong?


texts: Explanation of Operation of Class E Amplifier Circuit

texts:
I am looking for a good explanation for the operation of a Class E amplifier circuit (example below from Wikipedia - picture from Yves-Laurent Allaert)

As will be evident by this description, my understanding is rudimentary. I believe I understand that if you just took an LC tank circuit and injected a pulse of DC, AC would be generated in the tank circuit for a little while until the energy is dissipated through whatever resistance is in the components or load.

In the picture above, with the switch open (or without the switch), it seems like something similar would happen where current would flow into the LC circuit and you would see AC across the load.  When the switch T1 is closed, maybe some current is diverted through the switch but there would still be some current in the tank circuit oscillating.

So is the switch just there to "shape" the waveform across RL?

Is there someone that could just provide a basic explanation of how this works?  I tried to simulate this in the falstad circuit simulator but couldn't quite come up with the correct LC values, etc. to see how the switch impacts the AC across RL.


texts: bootloader jump to application address problem

texts:
I have written a bootloader for my board, but it generates a hard fault when it jumps to the application code.

My error is like this question:

Bootloader jump to main application problem using STM32 with Keil Uvision

microcontroller: stm32f103zet
software: keil
BOOT pins: BOOT1 and BOOT2 are 0 (FLASH boot mode)
FLASH_WRITE_ADDRESS: 0x8030000

I did this steps:
in application code:

I changed ROM address to 0x8030000.
I changed VECT_TAB_OFFSET to 0x30000
I used of fromelf for creating .bin file

then I wrote a simple code (blinky)

in bootloader code:
i receive .bin file with USART and then i write it to address 0x8030000 of FLASH
and The following code:

USART_DeInit(USART1);
RCC_DeInit();

__set_CONTROL(ENABLE_PRIVILEGE_MODE);

NVIC->ICER[ 0 ] = 0xFFFFFFFF ;
NVIC->ICER[ 1 ] = 0xFFFFFFFF ;
NVIC->ICER[ 2 ] = 0xFFFFFFFF ;

NVIC->ICPR[ 0 ] = 0xFFFFFFFF ;
NVIC->ICPR[ 1 ] = 0xFFFFFFFF ;
NVIC->ICPR[ 2 ] = 0xFFFFFFFF ;

SysTick->CTRL = 0 ;
SCB->ICSR |= SCB_ICSR_PENDSTCLR_Msk ;

SCB->SHCSR &= ~( SCB_SHCSR_USGFAULTENA_Msk |
                                SCB_SHCSR_BUSFAULTENA_Msk |
                                SCB_SHCSR_MEMFAULTENA_Msk );

__disable_irq();

if( CONTROL_SPSEL_Msk & __get_CONTROL( ) )
{  /* MSP is not active */
    __set_MSP( __get_PSP( ) ) ;
    __set_CONTROL( __get_CONTROL( ) & ~CONTROL_SPSEL_Msk ) ;
}

JumpAddress=(FLASH_WRITE_ADDRESS+4);
JumpToApplication =(void(*)(void))(*((uint32_t*)JumpAddress));
__set_MSP(*(__IO uint32_t*)FLASH_WRITE_ADDRESS);
JumpToApplication();

But it goes to hardfault.
So now I use this part of the code:

/* Jump to user application */
JumpAddress = *(volatile uint32_t*)(FLASH_WRITE_ADDRESS+4);
JumpToApplication = (pFunction) JumpAddress;
__set_MSP((*(volatile uint32_t*) FLASH_WRITE_ADDRESS));
now_pointer=__get_MSP();
JumpToApplication();

but it is the same as before.
What is problem?

This is one second before jump to application code:

And this is result of jump to application code:

okey.now,i find and solve problem:
i put my writing in FLASH mistake picture:


texts: EMC - conducted emissions - unused wires in cable - puzzling coupling

texts:
I am trying to understand the impact of unconnected wires in a cable for EMC conducted emissions tests.

My product has a shared unshielded cable for supply and communication (I know it's bad practice...). It consists of 9 untwisted wires (see picture below). The 12VDC supply is on the red and black wires. The communication (RS-485) is on the brown, pink and green wires (not optimal I confess). All the rest is unused (white, yellow, grey and blue).

The test setup is classical (see diagram below).

When all unused wires are left unconnected on both sides, the RS-485 coupling on the supply is tremendous (>1Vpp on the LISN side for a 15m cable). I can literally read the frames directly on the supply.

However, when I tie together the blue and white wires together on both ends, the coupling vanishes (>1Vpp to something barely noticeable on the spectrum analyzer). I must insist on the fact that the two wires are connected to nothing else.

I understand the capacitive coupling when the wires are left unconnected. But I just don't get why these two wires stop the coupling when connected like that.

Did you have any similar issue or understand the physics behind?


texts: Pressure of an electric contact and resistance

texts: Ok guys, my question is simple, how does the pressure of an electric contact influence the resistance of the human skin?


texts:
I have an Arduino Mega 2560 which was working just fine a few days ago. I've just been working with it and now it's not being recognised by any computer, not even as an un-recognised device.

The power LED lights up and the L led near the USB port flashes briefly, but apart from that nothing much happens. I think it runs the code that was on it before it stopped working too.

The question is, have I fried something on it (like the USB controller) and can it be repaired, or is there something else I need to try to fix it?


texts: How can we calculate single phase to ground fault current knowing only the three phase fault and line voltage?

texts:
I would like to calculate the single phase-ground fault current, but have limited information from the utility. For example, we have information like the 3 phase fault from the transmission pole as well as from each terminal near the faulted transmission pole. From this can we calculate the single phase to ground fault current? If so how?

Line Voltage: 115kV

At the faulted transmission pole:
3IO Mag At Fault (Amps)
3356
3I0 Ang At Fault (Degrees)
-53.4

From Terminal 1:
3IO Mag At Terminal 1(Amps)
2926
3I0 Ang At Terminal 1(Degrees)
-53.9

From Terminal 2:
3IO Mag At Terminal 2 (Amps)
112
3I0 Ang At Terminal 2 (Degrees)
-49.8


texts: Could someone take a look at this Tinkercad file?

texts:
So basically I'm using a 74HC595 shift-register to control 8 LEDs by manually giving the chip pulses with knobs instead of something like an arduino. On the arduino.stackexchange website this question got denied by users because it seemed to be off-topic. It was actually as a test for me to understand what such a thing really does before hooking it up to an arduino.

Anyhow, could someone tell me what I've done wrong in this circuit? Why is it not working? I connected the DS port to a slide switch so I can close both the DS and the SHCP ports to push a 1 in the code. However, nothing is happening when I latch the (hopefully) created code to the outputs.

Could someone give me an explanation?

Tinkercad File


texts:
I came across this Animation and have no idea why the output is shaped like this. Apperantly the capacitor is charging and discharging but I cannot tell when this happens. All I know is that capacitors do not like the voltage across them to change and resist it.
Can you help me understand and comprehend this animation as I am terrible at guessing capacitor behaviour.


texts: 555 timer bistable circuit problem: default flip-flop state is 'ON' on power reset

texts:
The following circuit is a controller for a water pump. It turns the pump on when the reservoir water level drops below the 'L' probe and turns it off when the level reaches the 'H' probe. This circuit works well except a small problem. We have frequent power outages in my area. Every time the power is restored, the water pump starts. Most of the times water level is between the 'L' and the 'H' probes. Theoretically the pump should remain off if the power is restored during the middle levels. Any thoughts what is causing this behavior? How can it be corrected?

Edit:

I simulated this circuit in multisim using the following schematic.

The left two switches simulate the test probes. Down positions of S1 and S2 simulate the lower and upper probe immersed in water, respectively. The oscilloscope output is obtained by switching on-off the power using X-switch. The 555 gets ON after each power restoration. Have implemented the time delay circuit for reset pin IC1-4 as advised by @EM Fields.


texts:
Hi, guys. Does anyone know what causes the multiple waves at a time when you run the oscilloscope? But when you stop (pause) the oscilloscope, you get one wave a time (picture on the answer column).

This is the screenshot of the signal output when I pressed the stop button on the oscilloscope.


texts:
I am building this wind turbine project and the problem I am facing is the irregular winds that does not keep the inverters running continuously. I initially decided to solve this problem by employing batteries so that the battery can give continuous output to the inverter as the battery charges whenever the generator spins.

Then I came across Maxwell's Supercapacitor (https://www.maxwell.com/products/ultracapacitors/56v-modules) which is designed to   provide power during dips, sags in the main power source. The product description is "Maxwell Technologies’ 56V series of ultracapacitor modules provide power during dips, sags in the main power source. In longer term outages, the modules provide transition/bridge power to a longer term back up source such as a motor-generator or fuel cell. For industrial applications, ultracapacitor modules provide power for graceful shutdown of process equipment." They are designed to fit in standard rack systems with up to 10KW (15 seconds) in 4U height.

I am completely new to these capacitors and I am wondering how to incorporate this into my system. Since it has a very fast discharge time should I use some electronics to control the discharge rate to match he input of the inverter?

Can anyone please explain how this works and how does this go into the wiring diagram?

Thanks in advance!


texts:
I wrote a code

int main(void) {
    uart2();
    NVIC_EnableIRQ(UART2_IRQn);
    while(1);
}

void receive(void) {
    SMR_485RECEIVE;
    receive_byte = LPC_UART2->RBR;
    }

void send(void) {
    SMR_485TRANSMIT;
    LPC_UART2->THR = receive_byte;
    }

void UART2_IRQHandler(void) {

    BYTE maska = LPC_UART2->LSR & 0x01;
    if(maska == 0x01){
        delay_1_ms();
        receive();
        delay_1_ms();
        send();
        }
    }

It works first time I send a character via terminal to CPU, it sends me back the same, but then it starts to send me back \0, does anyone have idea what causes infinite loop, i think while(1), but I'm not sure how and why, and how to solve this?

Here is how it looks in terminal


texts: I have constructed my tesla coil. But i couldn't find the MMC capacitors for the primary capacitor bank. So what is the alternative way of making capacitor bank? Are there any suitable capacitor types to do the job?


texts:
hobbyist and students,

[TL:DR] - Can't send (uart) chars from my PIC through my xport to my telnet connection (and can't receive)?

[Software]

MBLAB X IDE
Lantronix DeviceInstaller
XC8 compiler

[Hardware]

MCU: PIC PIC18F66K22
Lantronix: XPORT XP1001000-05R (Rev. A11)
PICkit 3: Programmer
PC (with Lantronix DeviceInstaller)
Switch

[Succesfull steps]

I can see the XPORT in the device installer and can connect with Telnet...
When connecting with Telnet I will get a setup mode. But I can go to monitor mode by pressing 'M'
I can send 'commands' to check it's version in Monitor mode (telnet)
I've got a button (tested with led's) that executes xportSend('A'); (also tested Write2USART('A') on press.
Both xportEnable() and xportSetup() are called in my main.
XPORT communication lights will blink when sending through telnet

I'm using the second usart port of my PIC with default settings of xport

#include <usart.h>
#include "xport.h"
#include "defines.h"

/* XPORT DEFAULTS:
 Baud:      9600
 Databits:  8
 Parity:    none
 Stop bits: 1*/

void xportSetup(void){
    BAUDCON2 = 1;
    RCSTA2bits.SPEN = 1;
    TRISGbits.TRISG2 = 1;
    TRISGbits.TRISG1 = 0;
    Open2USART(         USART_TX_INT_OFF  &         // Transmit Interrupt OFF
                        USART_RX_INT_OFF  &         // Receive Interrupt ON
                        USART_ASYNCH_MODE &         // Asynchronous Mode
                        USART_EIGHT_BIT   &         // 8-bit Transmit/Receive
                        USART_CONT_RX     &         // Continuous Reception
                        USART_BRGH_HIGH,            // High Baud Rate
                        (64E6 / 9600 / 16 - 1)      // Baud Rate 9600
               );
                        //http://www.microchip.com/forums/FindPost/836738
}

void xportEnable(void){
    LDO_SHDN = true;
    XRESET = true;
}

void xportSend(char data){
    Write2USART(data);
}
char xportReceive(void){
    return Read2USART();
}

[SOLVED, yes xport is compatible with PIC, see link below]Question one: Is the hardware directly compatible?
I've heard that the XPORT uses 3,3V and the PIC RX/TX atleast needs 4V (schmitt trigger stuff) (based on 5V). http://ltxfaq.custhelp.com/app/answers/detail/a_id/995/~/5v-tolerant-xport
Question two: Am I using the right setup to receive uart messages (Telnet in monitor mode (port 9999))?
I've also tried TELNET with port 10001 but it also didn't show anything.
Question three: Anything else might be wrong in this interfacing?

I think those questions are fairly easy/quick to answer, though I haven't found a reliable source on my google search. I'm not that interested in code, should be able to deal with that myself (if you only describe what to make) but I think there might be something wrong with my USART setup (aswell).
(As a lot of things can/might be wrong also). I'd hope that some of you with more experience with the XPORT or electronics can enlighten me.

Kind regards,

FuaZe
Student on the HAN university of applied sciences (The Netherlands)


texts:
In Master Slave JK flip flop

Is the master positive level triggered or positive edge triggered?
2)Is the slave negative edge triggered?

I have searched many websites but different answers in all of them


texts:
Is there a way to connect one speaker to another (I'm building my own ones) using WLAN. The idea was having a host speaker with a WLAN transmitter that could automatically transmit the music playing and this could be picked up by other speakers (the clients) using WLAN receivers.

I have searched the internet for how to get WLAN to do this but to no avail. I would like to know how I can connect and pair two WLAN chips (the host and client) to accomplish this. If coding is needed then I already have an arduino pro micro but if there is a way to do this without coding then that would be preferable.

Many thanks in advance! :)


texts: How does this multiple power supplies switching work?

texts:
Here's what I think the circuit is doing:

From what understood is that the circuit has VIN (voltage from DC plug) and VBUS (voltage from USB).
The SY6280 is a current sensing chip to protect the USB from spikes from DC plug.

My question is, how does the BCM856BS (PNP/PNP matched double transistors) with the AO3415A MOSFET switch (I'm assuming it's for switching) between the two power supplies?


texts: Identifying a input protection diode from a power supply by a photo

texts:
block schematic is

.

And connector photograph is

.

and broken element is

.

It seems to be TVS (Transient Voltage Suppressors) diode. Maybe, %20 unidirectional. Because, there is a mini hole in the right. Approximately diameter 6mm and length 10mm. On the writing is 2082 B.

Anybody used it before? I don't find in Internet. What could be DCL and SA? What may be the abbreviation?


texts: What is reactive Power and how it is generated and what is its source?

texts: Many people, including me are good with dealing with real and reactive power in power flow systems, but still has question at the end of the day: What is reactive power and how it is generated or what is its source? After taking few course in power electronics, I tried to come up with simple explaination of what is reactive power and what is its source.


texts:
I am trying to calculate the total thermal resistance of my FET to see what heat sinks are required, are the following calculations correct?

$$ Power = \frac{T_{jmax} - T_a}{\theta_{JC} + \theta_{CA}} $$

$$\frac{175 - 25}{0.29 + 40} = 3.7W $$

The MOSFET I am using is IRFP4468PBF.


texts:
I am new to cad drawings and eagle cad. My professor wants me to build a pcb which has these nail head pins: https://www.mill-max.com/products/pin/5063/5063-0-00-01-00-00-33-0

I am not able to the part that lets me add individual pins (not pin headers). If there is no such part, how do I create that part and how will the pcb printing guy understand the part (since this part wont be in his set of libraries).


texts: Routing USB under the serial converter - good idea?

texts:
I have a design with a FT230XS USB/Serial converter and a USB B connector.
My current layout looks like this:

Is it a good idea to route the USB lines under the FT232XS converter? Another solution is to spin the IC around 180 degree and connect the USB lines without routing them under the IC. But then I have to cross the USB lines so I have to switch the layer:

My question is the following:
Which of this solutions is the better one? Passing the lines under the IC and avoid a layer switch and crossing or cross the lines to avoid a routing under the IC?


texts: How to get more torque using a Stepper motor

texts:
I am using a stepper motor with a belt. The system has more friction due to the belt. So, I need to increase the torque of the motor at rotating.
I am currently using 57HS09 motor and M542
It has microstepping setting as 1000PPR and full current(4.0A) is given.
Pulse generated by an Arduino. The main coding is given bellow.

This is the function of Arduino code.stepDelay is given by another function after some calculation.

void move() {
  if (micros() - lastStepTime >= stepDelay) {
  lastStepTime = micros();
  digitalWrite(STEP_UP, HIGH);
  delayMicroseconds(100);
  digitalWrite(STEP_UP, LOW);
  delayMicroseconds(100);
}

}

I have no idea how to increase the torque more.
How do I increase the torque of the stepper motor?


texts: Buck/Boost evaluation board buzzing/ringing sound

texts:
I'm currently modifying this buck/boost evaluation board to output a range of voltages between ~1.5 V and 12 V. In order to achieve this, I've replaced R14 in the feedback voltage divider with a 20 kohm resistor (see page 10 in the above user guide), thus "tricking" the board into permanently compensating the output voltage to a stable 1.5 V. I've also soldered a digital potentiometer in parallel with R22 in order to draw current from the feedback node, which causes the output voltage to rise depending on the resistance of the digital pot.

I've already done these things and the system is working... to a point. The load that I'm driving is a ~1.8 ohm heating coil, so high current is inevitable. The buck/boost is rated to output a maximum of 10 A at its original 12 V output so I figured I wouldn't have any issues. However, when I connect 12 V at the input and decrease the digital potentiometer resistance to increase the output voltage, the eval board starts to buzz/ring loudly and persistently. This happens when the output gets up to  7.0 V and the current through the coil is about 3.9 A. The voltage across the coil also begins to grow unstable at around this time, varying in voltage about 500 mV.

Does anyone have any ideas about how to fix this issue or what the origin of the noise is? My guess is it's coming from the switching element in the buck/boost. If that's the case is there any way to get rid of the noise?

Any and all suggestions are welcome!


texts: Select power supply voltage using MOSFETs

texts:
I have a circuit which I wish to power using 5V or 1.8V or power off entirely.

For a simpler version, switching one voltage, I decided to use a P-channel mosfet as a high-side switch (see the left half of the schematic).

Then, I added a second mosfet connected to 1.8V. If I understand correctly, when the left (5V) mosfet is opened, current will flow through the load, but also through the internal body diode of the right mosfet back to the 1.8V supply - regardless of the voltage at the right gate. Am I right?

How can I redesign the circuit to avoid this problem? A simple diode would work but that adds a significant voltage drop which I hoped to avoid.


texts:
I have a clock.  It generates ticks.  I want to know the error in PPM relative to another clock, so I count the ticks.

Let's say the oscillator is 1 MHz (for simplicity).  I should count 1,000,000 ticks per second.  I plot the (expected_tick_count - actual_tick_count) per other-clock-second.  I get a nice line which represents the accumulating error, in microseconds.  Linear regression results in R^2 = 0.9999 (i.e. a perfect line), and a slope of 27.  To me, this implies 27 PPM error in the oscillator.

I assume this means I actually get 999,973 ticks per second instead of 1,000,000.  So I tune the oscillator frequency so that it includes an extra 27 ticks per second.

I re-run my test.  I expect to see negligible error.  Instead, I find another line, with a slope of about 3.  So it appears as if my initial regression analysis was off by 3 PPM, despite an R^2 that is the envy of statisticians everywhere.

Am I missing something?


texts: CMOS IC Dynamic Edge-Triggered Flip Flop setup and hold time calculation

texts:
Before explaining i should point out that i refer to changes of signals in the text as a reference change on which i will calculate these times as 50% change of one signal to 50% change of the other on the time axis. I am simply trying to find that reference change on which that time is calculated.
I'm trying to calculate the setup and hold time of this edge-triggered d flip flip using simulations in Pspice but am having troubles in deciding what those times represent in the graphs of the simulations.
In my class notes (which this is the exercise for) it says that the hold time is calculated from the output of the first inverter to the output of the second inverter, and the setup time from the input D to the output of the first inverter.
For simplicity let's say that the outputs in order are A,B,C,D,Q
When calculating the hold time, when CLK=0, B is kept on VDD until both A and CLK are on VDD. That change when B is discharging from VDD to 0 is what should be the reference change for calculating the hold time. That would be the ammount of time it takes for B to pass the information to the other inverter as it can only change once during CLK=VDD. The only way i found to calculate this is when i make CLK=0 and during that time i change D from VDD to 0 to change A from 0 to VDD and observe the discharge as time when CLK=0.5VDD (starts rising) to time time when B=0.5VDD (starts discharging)
The other way, having CLK=VDD and changing A from 0 to VDD i couldn't make happen because CLK in the first inverter interferes even though my class notes say that it is the change from A to B. So i don't know whether this is ok.

Could the first way be used to calculate the hold time?
For the setup time, it should just be the change in A from 0 to VDD so that would be the change of D from VDD to 0 while CLK=0 right?


texts: Two same capacity/model powerbank. Output connected via Y connector (parallel)

texts: If I have 2 same capacity/model of power bank and combine the output via Y connector (parallel), will there be any issue?


texts: Get_ports vs Get_pins vs Get_nets vs Get_registers

texts:
I am doing a design in vhdl for FPGA. I have a top level design which consists of 3 components: clock divider, Module_1 and Module_2. Top level entity has a clock input port. This clock is divided by the clock divider to get two other clocks: clock_1 and clock_2. They are fed to Module_1 and Module_2 's clock ports respectively.

I want to constraint all these clocks. So, how to decide whether get_ports or get_pins or get_nets or get_registers have to be used? I used get_ports for the main clock. What about the other two? I can see these generated clocks under get_pins and get_nets and get_registers in the timing analyser of Quartus II. Also the clock names look different in there with some suffixes like '_var' , '~clk' etc. Are there any specific rules for get_pins and get_nets and get_registers ?


texts:
I was trying to pass EMC tests for my 48V 5A BLDC driver and failed in 30-50 MHz range. I think I found the problem in my drive circuit, but I have a few questions that got me thinking, maybe someone can help me to answer.

If my PCB is not too large (15cm x 5cm) 30-50 MHz emissions are mainly radiated through power cables? If 30-50 MHz 1/4 wavelength is 2.5-1.5 m then I need to mainly look at cables with length around 2.5-1.5 m?

If I have 48V and GND which radiates and I want to decrease emissions. What is the difference if I place ferrite around 48V and GND together or I place two separate ferrites one for 48V and one for GND? If I place one ferrite it will only filter common mode emissions?

Will inductor chokes will work better then ferrites for 30-50 MHz range? Because there is no ferrite to work in such low frequencies.


texts: Is there a way to build a 2k*12 RAM using only 2 4k*4 Chips

texts:
Okay so I know when I need to build a parallel design I can put them near each other and make a 4k*8 to expand the databus. But on this one I only need to use half of them and the databus length is larger than my total chips can reach. But I thought 2k*12 requires 24k b of data and i have 32k of space to store data. So there has to be a way to do so.

When I use a parallel design I can reach 4k*8 but it is not enough.


texts: Meaning of the "pole" of a transfer function with time delay

texts:
I learned in basic control theory that we can determine the stability of an LTI system by the signs of the real part of the poles of its transfer function \$H(s)=\frac{N(s)}{D(s)}\$. For a rational system, where both \$N(s)\$ and \$D(s)\$ are polynomials is s, it is easily understandable because a positive real part of the pole will cause an exponential increase in time domain, thus being unstable. My question is, if the system has a delay of T seconds somewhere, then \$H(s)\$ will contain a factor \$\exp(-sT)\$, sometimes in the denominator. In this case, why can we still determine the stability by looking at the real part of the "poles" of \$H(s)\$ (points in s plane where \$D(s)=0\$)?

An example:

$$N(s)=s$$

$$D(s)=as^2+bs+c+d \cdot \exp(-sT)$$

where a, b, c, d, and T are constants.

In this case, we can not do partial fraction expansion as we do for rational transfer functions. Then, how to link the time domain behavior to the roots of \$D(s)\$?


texts: Is it possible for a computer to use AC power?

texts:
Could someone please explain why computers are built to run on DC power instead of AC.

Is it possible to make a computer that runs on AC, even theoretically?

(I understand that it wouldn't be possible to use diodes)


texts: Ethernet cable with largest conductor diameter

texts:
For a Power-over-Ethernet type of project, I'd like to use cables with low resistance.

It seems a higher category (CAT5, CAT6, CAT7) does not necessarily mean the conductors used are larger in diameter as well.

Any hints on how to identify the ethernet cables with largest conductor diameter / least resistance?


texts:
Inside_process : process(clk)
begin
    if clk='1' and clk'event then
        signal1 <= signalin;
        signal2 <= signal1;
    end if;
Out_signal <= signal1 and (not signal2);
end process Inside_process;

end rtl;

VS

Outside_process : process(clk)
begin
    if clk='1' and clk'event then
        signal1 <= signalin;
        signal2 <= signal1;
    end if;

end process Outside_process;
Out_signal <= signal1 and (not signal2);
end rtl;

I see in some codes signal assignments are made inside processes and sometimes just a bit before end rtl; in this case rtl is architecture. Sometimes many signals are assigned outside process sometimes many. In above example I get no synthesis error and the my circuit works with both versions. So I don't understand what is the difference between them also some signals can't be assigned in the process they have to be outside and they make difference! Why can some be assigned in process why some not? Why sometimes it doesn't make difference? Also how frequently are the signals assigned outside the process, every rising clock edge? Every 5th rising clock edge? How is it decided? What is the use of assigning a signal outside the processes? If I'm going to assign a signal outside a process I usually do it before end rtl; (the last line). I noticed it doesn't hurt doing this between 2 processes as well, so doesn't have to be just before the last line, can be in the middle as well.

If I should give an example signal assignment in process which gives an error :

d3 <= r4  when (sn(3)='1') else d2;

Full code of error line

Error msg: parse error, unexpected WHEN, expecting SEMICOLON.

There is a semicolon actually. But when this line is taken out of the process, it works. I don't understand how, if someone can enlighten me I would be glad.

Also in VHDL shall I declare processes uppercase letters, signals lowercase letters, or everything uppercase? Is there a common usage and discipline? For example it isn't encouraged in Java for variables to start with uppercase? If there is a common usage like this for VHDL, can I get a link for that?


texts: Why would an AND gate need six transistors?

texts:
I'm taking a digital design course, and I've been told that a NAND gate needs four transistors to implement and an AND gate needs six (four for a NAND gate and two for an inverter). That makes sense until one of my classmates told me he could implement an AND gate with four transistors, much like a NAND gate but with some symmetry. I implement his idea using Logisim (see the image below, the left one is a NAND gate, and the right one is a four-transistor AND gate I think of), and it seems the circuit I conceive works. So could anyone explain to me why an AND gate needs six transistors?

Thanks in advance!


texts:
Are there any perks in keeping a CPU at a low temperature; between 0 and 20 degrees Celsius in particular?

In particular, does it produce less errors in computation and therefore slightly improved performance or response time?


texts:
I am using an ADXL345 triple axis accelerometer via a FEZmini1.3 .Net Micro Framework board in a project I am busy with.

The ADXL345 provides data in 13-bit 2's complement.

How do you decode this into decimal?

I have implemented a BitConverter (As provided by Ravenheart (Toshko)) in the project, but surely this assumes a full 16 bits (or two bytes) worth of data, where the most significant bit will always be the sign bit?

In a 13 bit number the 16th bit will always be 0, won't it?

       ------------Byte 1------------   ------------Byte 2-----------
bit#:  15  14  13  12  11  10   9   8   7   6   5   4   3   2   1   0
16 bit: 1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1 = -32767
13 bit: 0   0   0   1   1   1   1   1   1   1   1   1   1   1   1   1 = -4095

but if the 13 bit number is being converted by an algorithm assuming a full 16 bits the number will equal 8192.

Is my understanding correct? If yes, how do I go about converting a 13 bit 2's complement number into decimal?

Edit (After getting some help from my friends below):
So thanks to the responses I now know that my assumptions of 2's compliment was wrong, so for clarity when anyone reads this thread I wanted to correct my initial statement:

       ------------Byte 1------------   ------------Byte 2-----------
bit#:  15  14  13  12  11  10   9   8   7   6   5   4   3   2   1   0
16 bit: 1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1 = -1
13 bit: 0   0   0   1   1   1   1   1   1   1   1   1   1   1   1   1 = -1

In 2's Compliment the numbers count up to the halfway point and then start counting down, so:

00000000 = 0
00000001 = 2
00000010 = 3
00000011 = 4
.
.
.
01111110 = 126
01111111 = 127
10000000 = -128
10000001 = -127
10000010 = -126
.
.
.
11111100 = -4
11111101 = -3
11111110 = -2
11111111 = -1


texts: Where can I find the definition of SMI, SCI pins on a CPU?

texts:
I am trying to understand the SMI (System Management Interrupt) and SCI (System Control Interrupt) in IA32 architecture.

According to this thread, it seems a CPU should have dedicated pins for SMI and SCI.

I guess some cpu specs should cover this. I tried some cpu datasheets, but no luck. In those specs, I can find pin names like below, but I didn't see SMI or SCI pins.

Anyone knows where I can find the definitions of such pins? If I can see it, I will know it better.


texts: dual input temperature comparison circuit

texts:
I would like to build a comparator circuit that will compare two varying  temperatures and operate a relay to a fan when one is greater than the other, but release the relay if the opposite is true. I would like to build in a small differential in temperatures before the relay will operate, something like 10 degrees.  I would like this to work at low temperatures and at higher temperatures,( example; on at 40 degrees sensor 1 while sensor 2 is at 30 degrees for low, and on at 100 degrees while sensor 2 is at 90 degrees for the high side.)  Of course temperatures would need to be translated to resistances or voltages. Using something like the diodes used in thermostats or thermistors or such.
While looking through the site I could find circuits that compare to a fixed setting  and others that are adjustable, but I would like to compare two varying  temperatures and get and output. These examples seem to use op-amps as a well suited comparator. A single input voltage would make it simpler, some low voltage such as 12v dc or 24v ac would be best.
I haven’t worked much in the electronics side of circuits for about 40 years, but do remember and could relearn much about the components needed. My first electronics class in college used slide rules since simple calculators were just starting to appear! I’m sure there is a lot out there that I haven’t heard of since those times!
thanks for any help.
Rex


texts: MicroSD card won't return any data on read command

texts:
I just want to clarify with everyone that I have exhausted all of my search options looking for an answer, and still cannot find the answer to my problem.

I am trying to interface a micro sd card slot with my pic32 project by bit banging an spi. I've had no problem initializing, and I can read the OCR and CSD register just fine, but when I send the read sector command, I get 512 Bytes of 0's no matter what.

I have tried with multiple cards with the same result with all. I am using SanDisk 2GB standard MicroSD cards. They are formatted as FAT(FAT16) by both Windows and using the SDFormatter provided by sdcard.org. I've used Disk Investigator to confirm that the MBR contains the correct data.

Here is the sequence I am using to initialize:

//Low speed
Send 10 Bytes of data to 'wake up' card w/ CS High
Send CMD0 to reset until response is idle (0x01)
Send CMD8 w/ arg 0x1AA and read correct response to verify SDC V2
Send ACMD41 w/ HCS flag to initialize until no longer idle (0x00)
//High speed
Send CMD58 to read OCR and check CCS flag in response
Send CMD16 to set block length to 512 Bytes
//At this point I should be able to read the MBR but get nothing
Send CMD17 /w arg 0x00 to read very first sector

When I send the read command, I do get a correct R1 response 0x00, then a few Byte transfers later, I get 0xFE indicating the start of data, but the data line just goes low for 512 Bytes, and nothing is read.

I've tried writing to a sector with dummy data, getting the 'data accepted' response, but when I tried to read it back, I got all zeros again. I'm wondering if I'm doing anything wrong with my initialization.

I'm sure it's not a problem with my program sending the wrong command, as I have everything hooked up to a scope, and everything seems to be correct. Here are the screenshots:

Here is the read sequence I am sending

And immediately following, the response I get

Any insight into why this is not working would be appreciated. I've spent much more time on this than I'd like, and like may things, it's probably a simple problem I'm not seeing. I'm hoping extra sets of eyes will spot my problem. Thanks in advance, and I will update with any information needed to help solve this problem.

EDIT, more things I've tried:

I've set the CS low for the entire read sequence, and no change in response.
I've changed the fixed CRC to the actual CRC needed by the read sequence, no change in response.

Using Disk Investigator to read the card on the computer, I can see the expected result from reading the first sector as shown:

0000  EB 00 90 20 20 20 20 20   . . .
0008  20 20 20 00 02 40 01 00         . . @ . .
0010  02 00 02 00 00 F8 EC 00   . . . . . . . .
0018  3F 00 40 00 87 00 00 00   ? . @ . . . . .
0020  79 EF 3A 00 80 00 29 10   y . : . . . ) .
0028  41 2E 17 4E 4F 20 4E 41   A . . N O   N A
0030  4D 45 20 20 20 20 46 41   M E         F A
0038  54 31 36 20 20 20 00 00   T 1 6       . .
0040  00 00 00 00 00 00 00 00   . . . . . . . .
----  All Zeros -------------   ---------------
01F0  00 00 00 00 00 00 00 00   . . . . . . . .
01F8  00 00 00 00 00 00 55 AA   . . . . . . U .

List of Miso and Mosi blocks during init (formatted as o-scope picture):

// wake up with 80 clk pulses w/ cs high not shown here
// First CMD0 send:
00 00 00 00 00 00 3F 01
40 00 00 00 00 95 FF FF

//Second CMD0 send:
FF FF FF FF FF FF FF C1 7F
40 00 00 00 00 95 FF FF FF

//Third CMD0 send:
FF FF FF FF FF FF FF 01 FF
40 00 00 00 00 95 FF FF FF

//CMD8 w/ 0x1AA arg
FF FF FF FF FF FF FF 01 00 00 01 AA FF
48 00 00 01 AA 87 FF FF FF FF FF FF FF

//ACMD41 w/ HCS flag          6 times before 00-vv
FF FF FF FF FF FF FF 01 FF FF FF FF FF FF FF FF 01 FF
77 00 00 00 00 95 FF FF FF 69 40 00 00 00 95 FF FF FF

//CMD58 read OCR
FF FF FF FF FF FF FF 00 80 FF 80 00 FF
7A 00 00 00 00 95 FF FF FF FF FF FF FF

//CMD16 to set block length
FF FF FF FF FF FF FF 00 FF
50 00 00 02 00 95 FF FF FF

After this is the read function shown above


texts:
I just bought a 5-32 volt bench power supply with analog volt and amp displays yesterday.  The device is an Astron VLS-10M. I just blew the supply while trying to charge a 150F capacitor with the current on full. I had a look inside, and I have no clue what could have gone wrong...

It has a 5 amp fuse, but the fuse did not blow. When I turn it on, the voltage reading will vary when I turn the knob, but the current is very limited. When I set the current to the highest setting, it will not even turn on a 24 volt horn which it turned on before. The Amperage meter will stay at zero, not moving on any load, only the voltage will go down, so it seems like the current limit is stuck at a very low value. The filter capacitor made a huge spark when shorting, in case that is relevant.

Does anybody have suggestions on steps to troubleshoot and repair the device?

So to recap, there is a voltage on the output, just the thing doesn't seem to want to supply very much current, dropping the voltage on most loads (except for small things like small bulbs etc.) There are two 2N3772 transistors on the back outside. Could this be a power transistor failure?

I also found an lm723 in it. Could this be broken?

I even called astron, and they just hung up on me!

Here are some images:


texts: What type of power supply is this and how does it work?

texts:
I am evaluating a new controller and see a circuit I do not quite understand. I've built the circuit and I see the following (see image), but not understand why. Can someone please give me the name of this circuit so I can look it up?

Bottom line, I do not understand how the cap and resistor in parallel = DC.


texts:
I have a problem for getting the 4-20mA input via 1769-IF8 I/O module. My field device is in good condition, but my AI card doesn’t respond. When I have been browsing about it, most of them said, the impedance of the field device and AI module are not matched.

I don’t have any idea about how to match the impedance of both,explain to me how should match the impedance successfully?


texts: Hey I have Recently Purchased A Deltron W127G Open-frame Power supply, but I am confused on how the transformer works. And Since I do not want to blow the thing up I figured Id ask first. The Transformer Can be used on 120V and 240V Here is a Picture of the Transformer. I currently have 1 and 2 jumped together and 3 and 4 jumped together. Is this Correct did I understand the diagram correctly? If so Would I connect mains to 1 and 3?


texts: Powering phone using LDO regulator on battery terminals - what reservoir cap to use?

texts:
I have rigged up an old phone that does not run without a battery by attaching an AMS1117 regulator to the battery terminals. The regular is fed from +5V USB, and outputs 3.3V. The regulator comes on a PCB with capacitors on both sides.

This works great. Even though the phone expects 3.7V, 3.3V seems to be sufficient. However, there is no tolerance for even the slightest disruption to the power supply. My plan is to add a capacitor to the input. The regulator works down to 4.5V so I can tolerate a 0.5V drop. I assume the phone only needs about 1W (based on nothing tbh).

So if I put all that into a capacitance formula, I get
$$
I=C\frac{\mathrm{d}V}{\mathrm{d}t}\iff C = I \cdot\left({\frac{\mathrm{d}V}{\mathrm{d}t}}\right)^{-1},
$$
where
$$
I = \frac{1\mathrm{W}}{3.3\mathrm{V}} = 0.3\mathrm{A}.
$$
Let's say it should survive 10ms: then
$$
C = 0.3\mathrm{A}\cdot\frac{ 0.01\mathrm{s} }{ 0.5\mathrm{V}} = 0.006\mathrm{F} \equiv 6,000\mu\mathrm{F}.
$$
That seems a bit high. Am I doing this right?

Additionally, how would I hook this up? Just put the electrolytic cap in series on Vin of the regulator pcb? Does it need a parallel resistor to discharge it when it's without power?


texts: Are bent oscilloscope probe BNC connecter pins usual feature?

texts:
I got a new Testec TT-LF312 probe for my oscilloscope and I noticed that on the probe's BNC connector, the pin in the center is bent sideways a little bit.

The result is that it takes a little bit more force than I'd expect to insert the probe and there's a good connection even when the BNC connector hasn't been twisted in the receptacle.

So is this normal manufacturing practice or a manufacturing defect?

UPDATE: Here's the photo. On the left, I have old probe and on the right I have new probe.


texts: Improving transformer voltage regulation / efficiency through construction

texts: I am wondering what modifications can be done to a transformer during manufacturing to improve its voltage regulation and efficiency?


texts: Recognizing good quality electrolytic capacitors

texts:
Too often we get / give the advice to replace all electrolytic capacitors on a PCB when it starts to malfunction (like in DVD player power supply circuit strange behavior. Need help to understand root cause but here are many more examples). Reason seems to be the huge difference in quality for these capacitors. And more often than not, replacing caps actually solves the problem.

Now it occurred to me that some devices just appear to live forever (knock on wood), where others fail in two or three years. With new brands coming and old brands going, compiling a list of good/bad brands is a hopeless exercise, so the question is:

How do I know a decent/good quality electrolytic capacitors, before I buy them?

Let's assume:

I know the brand (by calling/mailing the shop);
The parts are genuine, non-counterfeits;
Fresh parts; short shelf life (no expired "best before" date)


texts: Equivalent block diagrams, how to infer?

texts:
Assume I have one block diagram and I want to simplify it to an equivalent block diagram, how do I find such block diagram apriori?

For example, Smith Predictor structure

The first pic above is Smith Predictor structure, and I would like to know how apriori I can  infer that the pic below it is equivalent to it?

If I calculate the ratio of both I get C(s)/R(s) = G(s)F(s)H(s)/(1+G(s)F(s)), but that doesn't show that they are equivalent, I mean how do I know how the equivalent diagram looks like by only knowing this ratio?

Thanks in advance.


texts: Why is there such a high amp-draw for hoist motors?

texts:
I'm currently looking at a 1.2 HP hoist motor and I can't figure out (or maybe I can't accept) what difference in the construction of the motor causes it to draw so much more power.
At 1.2 HP and 110 V, assuming 90% power factor and efficiency, I'd make a quick guess that a motor should draw in the ballpark of 8.5 A.
$$ I = \frac{HP * 746}{V * pf * n} = \frac{1.2 * 746}{110 * 0.9 * 0.9} = 10 A$$
Now, when I'm looking at this spec sheet (line 5-7), all the 1.2 HP motors draw 23.9 A.

What is causing this increase in amp draw? If I'm more aggressive with my estimate, the pf is probably 0.8 instead of 0.9 but that only increases amperage to 11.3 A. To get close to the amperage listed in the specs the efficiency would be close to 47%. My knowledge is that even lightly loaded motors operate with an efficiency above 70%, maybe that's where my thought process is flawed?
Are hoist motors really this inefficient? Is there a mechanical reason for the increase? Or, is this just a case of the Mondays and I'm overlooking something really obvious.

Details of the motor from the spec:

Single phase
Totally enclosed fan cooled (TEFC) squirrel cage
Re-connectable Voltage:115/230-1-60
Insulation class B
Hertz: 60
60 minute, H4 rated, fan cooled for demanding applications


texts:
I would like to build a circuit for reading temperature from a thermopile temperature sensor. I found this application reference for the circuit (page 6, Single power supply type with thermistor). However I do not understand how to calculate the resistance value (Ra, Rb, Rc).

At step 2, it requires:

1) Measure the thermopile detector output voltage (Voutmin) at Tmax.

2) Measure the thermopile detector output voltage (Voutmax) at Tmin.

What does that mean? How can I measure the thermopile output voltage before I build the circuit?

Thank you very much


texts: How can I measure the current drawn by a soil hygrometer?

texts:
I have one of these ubiquitous soil moisture sensors:

The only information I can find is that it operates from 3.3V to 5V, uses an LM393 to trigger a digital output and also exposes an analogue reading.

I'm intending to hook it up to a low power PIC (actually a PIC16LF1554 ) and want everything to remain sleeping until I periodically read the sensor from the analogue output. So, I'll power the sensor, take a reading through ADC and the power it off again.

Trying to keep everything as small as possible, with minimum components, I'm considering powering the sensor from a spare PIC pin, which I know will source/sink 25mA maximum. So I'll just drive the pin high to power up, take a reading then drive the pin low again.

How can I find out what current the sensor assembly will draw so I don't risk overloading the PIC pin? If I hook my (cheap) DMM in series with the sensor when powered from 3.3V standalone, the power LED on the sensor doesn't light up and the meter shows zeroes on the lowest range (2000uA). So I can't tell what it draws when it's working normally.

Do I need a better DMM or is there some other way I can see if I need to power this via a transistor (or some other way)?


texts: How to connect GPIO16 and RST of ESP8266?

texts:
I use a ESP-12E, where all the pins are broken out and nothing is connected on the board itself.

Online I found different ways to connect the pins GPIO16 and RST (RESET) to allow automatic wake-up from deep sleep:

direct connection (https://jeelabs.org/book/1526b/ and https://www.losant.com/blog/making-the-esp8266-low-powered-with-deep-sleep)
low-pass filter with capacitor between the pins and resistor between RST and Vcc (https://www.letscontrolit.com/forum/viewtopic.php?t=2320)

I also found someone using CH_PD ("EN") pin instead of RST, but I see it's not the preferred way.

What are the differences between the two alternatives I listed?


texts: Is it possible to inject USB signals (with power) through Ethernet?

texts: I'm just curious whether it is possible to inject USB through Ethernet in a way like POE does but with the additional data lines USB needs. As per my understanding Ethernet (at least the slower standards) use two twisted pairs so there are an additional four unused cables. If I inject USB through those lines what effects will this cause?


texts:
I have been trying to steer unipolar stepper motor (5V, 0.7A) using microcontroller powered only by USB (5V or smthing like that). The motor clicking got louder but the motor doesn't move yet.

I tried to lower resistance of R1, R2, R3 and R4 and motor cliks got louder, but when I completely removed these resistors it again clicked more silently... Does anyone have any idea on how to make this motor turn as it should?

I used ohm meter to measure the internal resistance which was 5Ω and I am affraid to lower R5, R6, R7 and R8 any more as my external power supply isn't very strong plus I might damage transistors...

When I tested the motor all by itself with no microcontroller It did turn if approximately 0.3A current flow through the windings. Maybee my:

transistor isn't fully opened
current through the windings in motor is too low
my external power supply can't handle it (this is not an option for me :S i have to make it work lol)

Schematic:

Closeup of the right part of the schematic:

EDIT: This is the circuit schematic after I consulting with you guys:

I hope this will do the trick.


texts: Verilog: Using a counter module to switch outputs

texts:
So I'm pretty new to Verilog and am working on a 3 bit multiplier project that outputs the decimal solution of the multiplier to the 7 segment display on my fpga board. I'm having a problem with conceptualizing how exactly my counter module that was given to me would allow me to switch in between inputs. The counter looks likes this:

module counter (
input clk,
output [1:0]Y
);

reg [24:0] counter;

always @ (posedge clk)
begin
counter <= counter + 1;
end

assign Y[1] = counter[24];
assign Y[0] = counter[23];

endmodule

I feel like I either need to use a 2:1 mux or a latch. I've started my code and it looks like this:

module cath_mux(
input clk,
input [3:0]ones,
input [3:0]tens,
output [3:0] disp
);

reg [3:0] disp;
wire [1:0] Y;

counter count(.clk(clk), .Y(Y));

always @ (Y)
begin
case (Y)

endmodule

I'm just not sure how to set up my case statements since there would be 4 cases with a 2 bit array for Y. The inputs come from a BCD decoder and the output would go to a module that will change my cathode values based on my BCD digit fed into it from the output of this module. I also need to figure out how to use the counter module to switch between active anodes on my board too.

This question seemed similar but I'm not sure how it applies to my question.

https://electronics.stackexchange.com/questions/165609/verilog-for-4-bit-wide-21-parameterized-mux-output-needs-to-be-decoded-to-7-se

Our logic circuits professor has been gone for two weeks and no one in our class has been able to really figure this out. Any suggestions or help would be really appreciated!


texts:
i seem to be facing a weird issue here. First time working with AVR timers. Basically what I am trying to achieve is to set timer2 (with prescaler val @ 1024) and use CTC mode (with val 78) to get 5ms timer ticks.

Every 5ms i just display the current framebuffer on a row of LEDs and every 1sec (using a counter to keep track of 200 timer ticks) update the frame buffer.

my code is

void setup()
{
  pinMode(dataPin, OUTPUT); pinMode(clockPin, OUTPUT); pinMode(latchPin, OUTPUT);
  pinMode(row1, OUTPUT); pinMode(row2, OUTPUT); pinMode(row3, OUTPUT); pinMode(row4, OUTPUT); pinMode(row5, OUTPUT);

  digitalWrite(row1,LOW); digitalWrite(row2,LOW); digitalWrite(row3,LOW); digitalWrite(row4,LOW); digitalWrite(row5,LOW);
  digitalWrite(latchPin,HIGH);
  digitalWrite(clockPin,LOW);

  Serial.begin(9600);
  Serial.println("Program initialized ...");

  //create string map + display the initial frame buffer
  //create_string_map("hello!");
  //generate the first frame_buffer
  Serial.println("1");
  //create_frame_buffer(0);
  Serial.println("2");
  //update_frame_buffer();
  Serial.println("3");

  //disable global interrupts
  cli();
  //init timer2
  TCCR2A = 0;
  TCCR2B = 0;
  //set ctc mode
  TCCR2B |= (1 << WGM12);
  //set CTC value
  OCR2A = 78;
  //set prescaler @ 1024
  TCCR2B |= (1<<CS10);
  TCCR2B |= (1<<CS12);
  //enable timer
  TIMSK2 |= (1<<TOIE2);
  sei();
}

//install the ISR
ISR(TIMER2_OVF_vect)
{
  timer_counter++;
  //disable timer
  TIMSK2 |= (0<<TOIE2);
  if(timer_counter==200) //200 = 1 sec
  {
    //reset timer_counter
    timer_counter=0;
    //update frame
    /*Serial.println("Frame update event ...");
    string_map_col_counter++;
    if(string_map_col_counter>=30){string_map_col_counter=0;}
    create_frame_buffer(string_map_col_counter);
    update_frame_buffer();
    display_and_hold_frame();*/
    Serial.println("1 second tick");
  }
  else
  {
    //display_and_hold_frame();
    Serial.println("timer tick");
  }
  //enable timer
  TIMSK2 |= (1<<TOIE2);
}

as you see i have commented most of the stuff out because i am trying to debug the issue. when i open the serial port the only output i get is "prog" and just stops there.

the only thing i can think of that  might be going wrong is that the timer is cont configured with ticks too fast so the serial.println never gets the time to finish. but as you can see i start the timer AFTER all these serial print statements.

also when i press the reset button on the board does it clear all the timer configs on board or does it remember them b/w resets ?
any ideas what might be causing this.


texts: Logisim - Counter with clock and Magnitude Comparator not working as expected

texts:
I have the next circuit in logisim: It is a simple 8 bit counter, with a magnitude comparator that outputs 1 when certain value is met.

The problem is that if I simulate with a clock, the counter reaches 1d (just before the target value 1e) and then it resets to 00, so the circuit never outputs 1.
Is it something that I am doing wrong?
Thanks!
Edit:
This is the circuit that I am building:

Context: It is a problem of a college assignment. I have to build a "ventilation system". T will be 1 when certain temperature is reach inside a room. N is an orange led, R is an red led and V turns on the fans in the room.
First I build a Moore's diagram and define the states of my circuit.

E0 : Temperature in the room is normal, N, R and V are off.
E1 : Temperature in the room reached target. N (orange led) turns on. R1 = 1 and C1 starts counting.
E2 : When T is 1 for 30 seconds, then N turns off, R and V turns on. (The fans start to cooldown the room).
E3 : Once when T is 0, the fans (V) will be on for the next 5 mins (assume that they will prevent T from change to 1 again). Also, N is on and R is off. R2 = 1 and C2 starts counting.
Finally C2 reaches 5 mins, S2 fires and everything comes back to E0.

Then I built a Moore's FSM (Ei = AB; E0 = 00; E1 = 01; E2 = 10; E3 = 11):

Then, I built this table who it will help me define the logic equations for the outputs, A(t+1) and B(t+1):

The equations:

With the equations then I built C3:

First flip flop is A, the second is B.

C1 and C2 are modules like the first one, but with different target values. I found out if I feed a constant 1 to R1 it solves the problem. Now, when C3 feeds 1 to R1 the counter resets just before reaching the target value. If I increase or decrease the target value, the counter stills reaches target-1 and resets.
Maximum value is set to ff and 'Action on Overflow' is set to 'wrap around'.
My circuit does not fire S1 even though R1 is always 1 and C1 counts to 30 secs:

But if I put a constant 1, it does (even tough R1 stills at 1 also and never resets until S1 fires):


texts: TS3005 Timer End of life...what should I do for an ultra low power astable?

texts:
I am working on a circuit with a Sharp Memory display that requires a VCOM 50% duty cycle square wave signal at a frequency of approx 1Hz.

It was suggested to use a TS3005 (Datasheet)which looked perfect until I see that Silicon Labs has EOL (End of Life) its timers and I cannot seem to get hold of them anymore.

It looks like the whole family of TS3001->TS3006 are being discontinued.

The TS3005 looked perfect because it had an adjustable duty cycle frequency using just a simple Resistor and its Ultra Low Supply Current: 1.35μA at 49Hz.
This is a nice chip because it runs all on its own without CPU intervention.

I looked at the TI TPL5x00 chips but they all seem to need an outside DONE signal, and I wanted my CPU to be completely asleep, while the timer chip refreshes the Memory Display.

I really need something with very low power consumption as it will be running from a coin-cell battery.

Does anyone know of a suitable replacement circuit that performs the same in both duty cycle of 50%, Frequency (1Hz) and very low supply current?

I looked at the 555 timer and the power consumption is way too large.

I am working on something similar to the Chronio watch project here.

Thanks
Mark


texts: LED Quiz Buzzer Circuit With Logic Gates

texts:
I am very new to electronics. I am programmer and I've never done anything with electronics.
However I started using simulators now.

I want to make a simple quiz buzzer circuit With LED. e.g. I need LED instead of a buzzer. I don't need any reset switch.

I want to maximize the use of logic gates in this circuit.
and obviously no capacitors or microcontroller are allowed.

I am trying to do this for 2 days, but cannot make it out.
I think the basic idea should be this:

I've done a lot of things on top of this but none of them seemed to work.


texts: Should Shielding GND be isolated from circuit GND?

texts:
In my system, I have 3 Grounds:

DGND, AGND and Shielding GND,

What steps should I take to isolate shielding ground from the other grounds that exist? Should I connect them with ferrites or use some of the solutions listed in this question about connecting DGND and AGND?


texts: How to determine the step response given a transfer function?

texts:
I would like to know how to draw the step response given a transfer function.

For example, given \$G(s)=\frac{(1-\frac{s}{3})}{{(\frac{s}{0.1}+1)(\frac{s}{100}+1)^2}}\cdot 10\$ a transfer function, I calculated the initial value with the "Initial Value Theorem": \$g(0^+)=\lim_{s\rightarrow \infty}sG(s)=0\$, but other than that, I would also like to calculate the final value and the settling time.

I've been also given the Bode diagrams (I don't know if it helps):

Update: I figured out there's also a "Final Value Theorem"


texts: Correct implementation of overlapping pads in

texts:
I want to use a 3 terminal capacitor, whose land pattern is described on page 9 of the datasheet

I try to replicate it with overlapping SMD and through-hole pads.

According to PCB manufacturer's DR, the minimum restring is 0.2 mm and drill 0.3mm, that is why I am forced to make through holepads slightly larger (with 0.3mm drill). I disabled stop mask on all middle pads and drew with a polygon.

Is it the right path, or there is a better way?


texts: Finding a current through a short circuit (Thevenin)

texts:
I am working through a question that involves superposition. I have attached a picture of the question I am working through. I am having difficulty doing question e) and f). I was hoping you someone could please give me help me in doing question e).

I initially thought that the answer would simply be the value of the current source, or zero, but both of these answers are wrong.

Any help would be greatly appreciated,
thank you very much for you time,

https://i.stack.imgur.com/0mTrV.png


texts: Do I use this equation for a Friis law question

texts:
I am just puzzled as the question gives two gains.

The question is below

input receiver has a noise figure of 4db and a power gain of 5db. It is followed by a mixer stage of with a noise figure of 3.5db and a gain of 3db. what is the composite noise figure for the two stages


texts: Can't get L293D to work with raspberry pi zero w

texts:
I have the following

When i turn

GPIO 17: high
GPIO 22: high
GPIO 27: low

or

GPIO 17: low
GPIO 22: high
GPIO 27: high

nothing happens, what have i done wrong?

I have verified that all GPIO 17, 22 and 27 work by connecting them to a Diode and a 330 ohm resistor and they light up correctly.

Also if i connect the battery directly to the motor it starts spinning as expected.

(Any idea how i can debug this, i have tried to check all connections with a multimeter without finding anything wrong)

i have tried with both a L293DNE and a chip that just says L293D.

http://fritzing.org/projects/raspberry-pi-zero-l293d


texts:
I'm looking at switching a rough hardware design from using a master-IC generated MCLK signal for I2S to using a standalone MCLK generator circuit. I'm a bit new to this area of electronics, but from what I've read I'd need to create a buffered clock signal to avoid any drops in clock between chips. What's the rationale for this? Are there any good example circuits you could point me in the direction of?

Edit -

I've done a rough design for a 12.228 MHz clock with an inverter. It'd be great to get some critique before trying to lay it!


texts: Why do we use RMS current as the input current for calculating efficiency of half-wave rectifier?

texts:
Vi = Vmsin(ωt)
Im = Vm⁄R = maximum amplitude of dc current
Irms = Im⁄2
Iavg = Im⁄π
η = Pdc⁄Pi = efficiency
Pi = (Iavg)2R
Pdc = (Irms)2R
Since the negative portion of the wave is not involved :

Why use RMS of current for input power?
Where is the power being lost?
Why?

Just to add some context please see this link.


texts: Suggestions for improvement of a water heating control system

texts:
I have improved my heating controls circuit design and would like some feedback on how to prevent the operator from temporarily energizing the circuit when a coil is de-energized because of a loose connection. More details on this in #7.

The system to be heated is a 30,000 gallon water basin. A pump draws water out of the basin, which then flows through an immersion heater bank and back into the basin.

Overview of the circuit:

The system has an overtemperature controller (OT20) and process controller (TIC188). OT20 looks at the heater banks and faults in case there is an overtemperature condition in the heaters. TIC188 monitors the water basin and sends a 4-20mA output to the step controller (SC93) which turns heater banks ON and OFF based on how far the water temperature is from the setpoint. So if the setpoint is 25 and PV is 10, all 4 heaters will be ON; if the PV is 22, only 1 heater will be ON.
CR11 is system enable and is energized if the flow, float switches and ESTOP CR01 are okay, OT20 isn't faulted, Drive isn't faulted (CR75 is closed), and CR40 (system health monitor) relay is energized.
The purpose of CR40 is to ensure that the system only starts up when the operator holds down the (illuminated) pushbutton LT33. If there is ever a fault, the system stays in fault till the fault clears and the operator intentionally starts the system back up.
The NC contact of the OT20 energizes CR35 whose NC contact is a permissive for the "system enable" relay. During normal operation, NO contact of OT20 is made and NC is open. If the controller is faulted, CR35 will be energized and its NC contact will open and drop CR11. CR35 is also used for fault indication. The NO of OT20 is the enable for SC93.
TD15 is a timing relay that waits a few seconds for the flow switch to pick up before changing state to OPEN. If the pump fails and the flow switch doesn't detect any flow after a set time, NC of TD15 opens and drops CR11.
In case of an emergency, the operator can push CR01 which cuts off power to CR11 and SC93. I know I could have just cut off power to CR11 and achieved the same result.
CR17 is energized as long as the drive is in run mode (drive run contact CR72). If the drive is in run mode, then and only then will OT20 have power on its COM pin. Seems to be a decent safety measure, however, there is a glitch here: notice that if there is a loose connection between the Drive and the control panel that cuts power to coil CR17, causing the system to fault out, the operator can temporarily energize the system by holding down LT33 while the fault is still there. The heaters obviously won't run but the Drive and the pump will. I do not want the system to pick up if there is a fault of any kind, in this case a loose or a cut wire that cuts power off to CR17. I cannot find a way around this. We could use an NO contact of CR17 as a permissive for CR11 by having another pushbutton that would bypass that contact during startup. I can see this being tiresome for the operator. I'd like some feedback on this.


texts: How to Change the status voice msg of Bluetooth module

texts:
I just buy a Bluetooth module XY-BT-MINI, when I turn it on, it says "The Bluetooth device is ready to pair". But I don´t like the voice. I just want a connected sound,

Can I replace the voice msg with connected sound ?

Can I change the name of the Bluetooth device.

Link: http://www.ebay.com/itm/351804941744?rmvSB=true.


texts: Why increase in resistance of register used in circuit show lesser average power dissipation

texts:
I am working on 6 transistor full adder circuit.

Red marked resistors (25k) are used to show all pattern of full adder correctly. But it show wired behavior. When I increase resistance from 25k to 50k there is minor change in waveform but average power dissipation of circuit decrease. But theory say more is resistance of circuit more power dissipation.

I am using 5.0 V voltage supply and use Tanner EDA for circuit simulation at 180 nm technology.


texts: Can this receptacle power this power supply?

texts: My car has a wall-style AC receptacle in it. It is merely marked 110V 150W. It is not mentioned in the owner’s manual. I’m curious if it can safely power this laptop power supply:


texts: Is this circuit for driving a piezo buzzer correct?

texts:
I'm designing a board which will feature a small SMD piezo buzzer which will be used for generating tones of varying frequencies from a PWM signal. I'm looking for a simple circuit which will be safe for the MCU and other components while also obtaining good response from the piezo.

I've been considering different options: driving directly from MCU (would like to avoid to protect MCU), driving with a single transistor (I understand this is not as efficient since it only drives the piezo buzzer in one direction) and finally with two transistors. For this last option I have the following circuit:

The resistors are chosen to have around 5mA for the buzzer and assuming an hFE of 100 for the dual transistor IC. BUZZ and ~BUZZ will be driven using PWM channel with complementary output on two MCU pins.

Is this circuit correct? Do I need to add other components for protecting the transistors? I've seen that other circuits place a resistor in parallel to the piezo which I'm not sure is needed in this case. Also, I'm concerned about voltage spikes generated by the piezo being manually displaced (for example, during a fall) or when the tone is cut-off.

The buzzer in question I'm considering is this one: https://www.digikey.com/product-detail/en/cui-devices/CPT-1203-78-SMT-TR/102-CPT-1203-78-SMT-DKR-ND/10326255


texts:
I was using a voltage regulator based on LT3045, everything worked fine but after powering the device after longer time of not using it, it stopped working.

The output voltage that i'm getting after powering the device is -0.6V. It should be +15V.

I think that it's a problem with regulator start-up. I've noticed by accident, that when I short input voltage (+18V) with SET pin for a short moment the regulator starts working and everything is fine until i turn the device off. After turning the device off and powering it up the problem occurs again.

SET pin is a voltage reference pin, it drives a resistor with 100mA current and uses a tantalum capacitor, to keep the reference voltage stable. After powering the device SET pin is at -0.6V. The same as regulator output. When SET pin gets +18V for a while regulator starts working normally and SET pin becomes +15V.

I'm wondering if it's a problem with faulty capacitor or a regulator. It's hard to test it, because the device is fully SMD soldered, regulator is soldered to a thermal pad and replacing the components is a real challenge.

Any ideas?


texts: how to wire together multiple photoresistors to make one big sensor?

texts:
I'm using an esp32 dev board, and a bunch of 5v laser diode emitters pointed an equal number of photocell resistors across a plane. The goal is only to detect when any two or more beams break at the same time.

I could try to wire up one resistor per pin (the 32 has 18 analog pins), which I know enough to do on my own, but that feels stupid. I feel like there is a smarter way to just wire up the photocells so that any simultaneous break of two or more beams will result in a net change that is big enough for me to read on one pin.

To be clear, I don't care when 0 or 1 beam breaks, only 2 or more.

Is there a way for me to wire together the photocells (series? parallel?) so that I can then test what 0 breaks reads at, what 1 reads at, and then act on 'whatever 2 or more breaks' reads at? What would that circuit look like?


texts: I am designing a Scissor lifter and I am operating my hydraulics using solenoid valve but I want my system to be ready for every possibility so what should be the backup system if my solenoid valve stops working


texts: Need some help building a TL072 preamp circuit

texts:
I have an early 70's Magnavox turntable/radio console that I want to be able to plug my smartphone into so that I can use it as an external speaker. I'm plugging into the Tape In input, which is an RCA cable. If I go straight in, the volume is too low--I have to crank the phone and the console to get a decent level. I suspected an impedance mismatch and asked for advice on the VintageAudio subreddit. I got this response:

  "The output of the phone is probably a modern "line out" level of
  150mV. The output of the tuner circuit is more likely around 1-2v. The
  function switch in equipment of this era is almost ubiquitously a
  literal switch with no additional amplification adaptations between
  the various input selections. Also, the output of the phone is likely
  8 ohm for headsets, vs. 47k ohm the input expects. You're correct that
  this would be an impedance mismatch. What I've done in these cases is
  build a small preamp module using a TL072 dual-channel opamp. They're
  less than a buck each and I just use the simple preamp circuit
  provided by the manufacturer in the data sheets for the IC. Hang a
  half dozen capacitors and resistors off that 8-pin chip, feed it 12V
  and it can take care of all the level and impedance mismatches like
  magic."

So I bought a TL072 and figured I'd build the "AC amplifier" circuit that is listed on the datasheet (schematic shown below). I have all the necessary parts but I have a few questions as I am a total noob when it comes to building circuits:

1.) Is this in fact the correct circuit (or a correct circuit) that will do what I want? If not, is there a better or simpler circuit that will accomplish the same goal?
2.) Notice the line that the red arrow is pointing to. What does that connect to? All of the other pins on the IC are labeled (VCC+, N1, OUT, etc.) but I don't understand what that line, which is connected to ground, is supposed to connect to on the IC.
3.) I'm assuming that I would connect IN+ and IN- to the mini jack that I'm going to plug my phone into. And on the output, I would connect the OUT to one of the L/R leads of the RCA cable, and the ground to the other RCA lead. Are those assumptions correct? I guess I'm trying to figure out how a single output connects to a stereo Tape In. Please enlighten me. :)


texts:
I know that I should balance input impedances in opamp circuits to avoid input bias currents from causing unwanted behaviour. I can understand how to do this in simple cases, but not in more complex cases. For example, in the case of a simple inverting amplifier, R3 should be added and made equal to R1//R2 (R1 in parallel with R2) if my understanding is correct:

simulate this circuit – Schematic created using CircuitLab

But what should I do in more complex cases, such as this:

I would think that I should put a resistor to ground on the 'fb' node and it should be 5.1k//10k. But what should I do with the other amplifier? How do I balance those filter impedances without changing the corner frequency of those filters?


texts: Stepping up from 12vdc to 100vdc/-100vdc

texts:
I am looking to power a phone ringer circuit that requires +100 V DC and a -100 V DC. I have found a circuit here but this converts it to 120 V DC with a transformer. Is it possible to get +/-100 V DC from 12 V DC without a transformer? If a transformer is the best option then I will use the circuit here and step the voltage down to around 100 V DC (If this circuit is the  best way of course!).

UPDATE: I did find this instructable, Would this work? (I could use 2 for a +100 and -100 V DC correct?)


texts:
So I have a convolution problem.  I have two signals:

I need to find the output, y(t), through graphical convolution.

So I set the convolution integral up like this:
$$
\int h(\tau)*x(t-\tau)d\tau
$$

I set it up this way because I believed it easier to 'flip and slide' the exponential function than the unit step function. So, then I substituted in \$ h(\tau)\$ and \$x(t-\tau)\$ like so:
$$
\int_{t-\inf}^{0} 1*e^{t-\tau}d\tau
$$
This then gave me:
$$
-e^{t-\tau}|_{t-\inf}^0
$$
Which equals \$-e^t\$. This is fine, and acceptable in my opinion. However, when moving to the next section, where the exponential is partially outside of the unit step function, I get issues. The equation I used here was this:
$$
\int_{-\inf}^0e^{t-\tau}d\tau + \int_{t-\inf}^te^{t-\tau}d\tau
$$
This includes the previous section from infinity to 0, and adds the new section, where the exponential has now moved partially outside of the step function, being bound by \$t-\inf\$, as before, and \$t\$. This then gives me this:
$$
-e^{t-\tau}|_{-\inf}^0 + -e^{-t-\tau}|_{t-\inf}^t
$$
This is where I start to have problems.  \$-e^{t-\tau}|_{-\inf}^0\$ evaluates to:
$$
-e^t + e^{t+\inf}
$$
This is, of course, an issue, as \$e^{t+\inf}\$ is infinite, and cannot be used as it doesn't converge.

Is there a different way I can graphically convolve these two signals without running into issues with infinity?

Now, I have done this problem using \$h(t-\tau)\$ and \$x(\tau)\$. This runs into a similar issue. For the first section, where the step function is partially outside of the exponential, I get this:
$$
\int_{-\inf}^0e^-td\tau
$$
That evaluates to this:
$$
-te^{-t}
$$
Fine. Good. Now, when I do the next section, where the step function has passed \$\tau = 0\$, and now the limit of the step function is going along the curve of the exponential, I have this:
$$
\int_{-\inf}^0e^{-t}d\tau + \int_0^te^{-t}d\tau
$$
This evaluates to \$\tau e^{-t}|_{-\inf}^0+\tau e^{-t}|_0^t\$, or \$\inf +te^{-t}\$.

So I run into a similar issue to what I had had before.

So I decided to do this convolution using Laplace transforms.
Since:
$$
x(t) = e^{-t}
$$
and
$$
h(t) = u(-t)
$$
I found these transformations:
$$
H(s) = \frac1s; X(x) = \frac{1}{s+1}
$$
Multiplying these, I find:
$$
Y(s) = \frac{1}{s^2+1}
$$

Applying an inverse Laplace Transform, I get:
$$
y(t) = 1 - e^{-t}
$$


texts: Instrument(s) for measuring (and recording) temperature, voltage and current

texts:
I'm about to embark on a series of experiments regarding thermoelectricity. I am pretty new to instrumentation etc - though I played with electronics as a hobby, when I was a boy.

I am starting to acquire a set of tools for this exercise.

Which device(s) can I use (multimeter perhaps?) to measures:

Temperature (up to say 700 degrees Celsius)
Voltage (from a few millivolts to a few volts)
Current (from a few milliamps to a few amps)

Last but not the least, I would like to record the generated data (voltage, current and temperature) using an arduino Uno.

Can anyone suggest a circuit I can use to capture and record the data?


texts: Battery powered 4-20mA sensing application

texts:
I have a base system that runs on 3-AA batteries which it regulates to a system voltage of 3.3V. I want to interface that system to measure a 4-20mA sensor. For the sake of argument, lets say that sensor has a minimum voltage requirement of 8 - 30V. To my slight embarrassment, in my many years of working with sensors, this is my first foray into this 4-20mA business, so I have some questions, and I'm hoping the community can help me clear them up and avoid common pitfalls.

simulate this circuit – Schematic created using CircuitLab

I've been reading up on working with 4-20mA, and I drew the above schematic as a representative data acquisition hookup. One of the things I've read is that ground loops are a gotcha with these types of sensors. Given that my system is battery operated, is this something that it's essentially immune to?

Given that I'm going to have to throw a boost converter into the system to get up to something like 14V (somewhat arbitrary, but high enough to make sure the sensor gets a voltage that is in its operating range, after voltage drops across my shunt resistor), for a variety of reasons, I want to supply that boost circuit from my 3.3V output buck/boost switching regulator. So my block diagram starts looking something like this (everything here is battery voltage ground referenced, and there's no earth ground in my system). Does everything seem copacetic here?

simulate this circuit

... and finally, my transducer datasheet shows a picture that looks like this:

I'm not sure what to make of the grounded shield in that picture. Does that imply anything needed to be done electrically with respect to the shield at the connection point to my system?

  Update (Alternative block diagram):

simulate this circuit


texts: I am trying to power a high power LED from a 9V battery.  I have 3 10k 1/2 W resistors in series to throttle the current.  I most likely will run it at 200-300mA.  Is there a better way to do this instead of using resistors?  I am new and tinkering around, but could I use a n mosfet and voltage divider with the same 9v battery to throttle the current that way?  How does would a non-newb approach this to not waste the battery with heat.


texts: if the thin wire is use for protection from lightning strike in high tension tower, then tell me that how a thin wire can withstand a high voltage lightning strike.It must be melt when light strike on it before it protect other cable or tower from lightning strike.


texts:
Recently I measured some voltages with my cheap digital multimeter while it was showing the low battery indicator. Later I purchased a replacement battery and decided to redo my measurements. I found that the previous results were off by about 30%, so I learned that I should not do any measurements when the low battery indicator is shown.

But then a question popped up: what if the multimeter battery is only 50% discharged? Will I get accurate measurements when the battery voltage is above certain threshold, or will I get an error proportional to the multimeter battery voltage without any indication?


texts:
I have set Tow-Thomas filter to get bandpass output. I want center frequency to be precise as much as possible. If there occurse center frequency shift in the lab, what are possible way to compensate this shift?

If we take R2=R3=R=R4 and C1=C2=C,

Q = R1 / R  ,
ω0 = 1/(RC) ,
H = -R1/R

where Q is quality factor, w0 is center angular frequency and H is center frequency gain.

I thought one possible compensation, to target a higher/lower frequency to get desired center frequency. But this is very cumbersome, since it requires to change at least 3 resistors.


texts: What happens if the PCI voltage in input to a GPU is different from external power supply voltage?

texts: In particular if there is a difference of one or two volts between the two inputs? Is it safe?


texts: Using Linearity, how can I find Vo in this circuit? (not homework)

texts:
I am making the assumption that Vo is 1V.  Moving right-to-left through the circuit, I want to use that assumption to find Vs.  Then, the ratio of the real Vs to my found Vs will be the same ratio from the real Vo to my assumed Vo = 1V.  I am having trouble figuring out what to do next though.  Any tips?  My markings are in blue on the attached picture.

Possible next step:  KCL @ the top node between the 2k and 4k resistors (calling this V3).... nodal analysis:

1 - V_3 = 8V, V_3 = -7V (???)


texts: check resistance is bigger then a constant?

texts:
As a part of a bigger project, I want to build an high resistance  detector that will respond with a logical pulse
0- under 50KΩ
1- more then 50KΩ
what would be the most power efficient way of doing it?
I thought about using this one some how, but I'm stuck here.


texts:
I was looking for a circuit to fade an LED on and off using no microcontrollers, and found this nice circuit:

http://www.555-timer-circuits.com/up-down-fading-led.html

it seems like exactly what I was looking for, so I went ahead and used it with a few changes:

I used a 2n2222 as the npn transistor instead of the BC547
I used a 12V source instead of 9 volts because I'm using LEDs with from a 12V led strip (led + resistors all built into the strip).
I used a 556 instead of a 555 because I had them on hand (and

I built the circuit as above (with the pinout changed accordingly for the 556), and it didn't work.  I was a bit surprised, and double-checked all of the connections -- but they were all correct.

Would any of the changes altered how the circuit functions?

I'm a bit concerned that changing the source to 12V might have effects, since that changes the threshold and trigger voltages -- could that be why the circuit isn't working?
Should the leds and resistors be attached to the collector instead of the emitter of the 2n2222?  I remember reading that LED driver circuits should be designed this way (something about V_be, IIRC).
Any other ways that changing the circuit may have prevented it from functioning?

thanks!


texts: Best way to crimping the outer tabs of a Crimp Terminal Contact

texts:
I'm trying to find the best way to crimp the JST VH series crimp terminal contact

I'm using my Knippex tool to perform the crimp

Now I always get good results with the inner tabs, but the outer tabs that need to grip with the insulation is never properly crimped.

I always need to do perform "a final non-standard step" using my tool to crimp the outer tabs.

Only then am I able to insert the contact in the housing. (otherwise the outer tabs are too wide in order for them to fit into the housing.

This "final non-standard step" for me is error-prone, as I'm sometimes not able to crimp the outer tabs properly, and need multiple times before I can get it to fit the housing.

Given that there are many different terminal contacts, with different inner / outer tabs, I assume there is no 1 universal tool to handle them all.

What would be the best way to deal with this ?


texts: Why does my GPS and Wi-Fi work inside a sealed copper clad box?

texts:
I have just finished assembling a Raspberry Pi-based project into a DIY box made from copper clad FR4 PCB, with the edges soldered together and the copper surface connected to ground.

I expected, when I put the lid on the box, the onboard Wi-Fi and the USB GPS receiver would stop functioning - that is, the Pi would drop off Wi-Fi and the GPS fix would be lost.

Instead, there is no discernible effect. Wi-Fi and GPS function as if the metal lid is not present.

Given the entire reason I put this project in a copper clad case was to shield it from RF (it will be operating in the near field of a 5W VHF FM transmitter), I could do with understanding what's going on here.

Here's a pic

and with the temporary lid on...

(note the thin stripped wire is just to ensure the lid is making electrical contact, and the USB power bank on top is just providing some downwards pressure also to ensure contact)


texts: At my workplace we have expensive PCBs that are used for testing. These PCBs have conductive pads which wear out by time since they come in contact with pogo pins. These boards operate at temperatures -45°C and 150°C. What is the best option for repairing these pads? We have already tried conductive ink (don't know the exact specifications since the label has faded), but it did not work as well as we expected (probably because it is not suitable for those temperature ranges). Are there any methods that we can apply to repair these? or any conductive ink that can handle those temperatures?


texts:
With a switching DC wall adapter, when I measure AC rms voltage from either of the output wires to earth ground, what am I actually measuring and is this a controllable spec of a wall adapter?

I am dealing with what must surely be an AC ground loop issue that causes 60 Hz hum on telecom equipment. I have many 9 volt switch DC wall adapters. Some work fine (meaning the 60 Hz is not measurable) while others are quite loud.

I have found that the ones that work I measure less than <10 VACrms from wall adapters output to earth ground.
The ones that do not work measure >50 VACrms from either of the output wires to earth ground.

On a scope the signal is 60 Hz and a very distorted sine wave.

When trying to source a new adapter is this something I can find in the datasheet?  What controls this in an isolated switching power adapter?


texts: SPI master and slave operating frequency

texts:
If a master is operating at 4MHz and the slave is at 16MHz the data should still be sampled at the speed of the SCLK pin, the frequency difference shouldn't matter right?

I used a Mikroe Dev board and tried to communicate to a CAN peripheral using SPI. The board module operated @ 16MHz using a external oscillator while my MCU only used its internal 4MHz clock no commands worked until an external oscillator was used at 16MHz.

Can a master and slave operate at two different frequencies not the SCLK pin frequencies but the actual clock cycles frequency?


texts:
I have 12V peristaltic pump and need to control its flow (lowering down more specifically)

Two options I came across:

POT in series
Voltage divider

Is there any shortcomings in above schemes?

What is best way to reduce flow without involving controller i.e using analog circuitry?


texts: How does this old fan regulator circuit work?

texts:
I was on the lookout for an old fan regulator. I had heard that its power consumption was constant at all speeds.
I could lay my hands on this 1970 regulator. It appears to be a transformer with rotary switch tap selection.
I am curious to know about its function especially with respect to the power consumption at different speeds.


texts: Counting pulse in firmware without interrupt

texts:
How can I count the number of pulses using a microcontroller (any), provided the following conditions:

Can not use any interrupt (no interrupt on pin change allowed)
Can not use any of uC's hardware features (counter, timer etc.)

The width of the pulse is random and can not be predicted in advance. This pulse train is given to one of the general purpose IO pins. The solution should be purely software based ( C/assembly).

The software debouncing method which reads pin status as a series of 0's and 1's is a possible option but you need to hardcode the transition pattern, which means that you need to know the pulse width in advance and hence its can not be accepted.

Any idea?

PS:
This question was asked on a technical interview with one of the major automotive component supplier.


texts: Discrete Schmitt Trigger: make output logic level at 0V, not 3V

texts:
I designed a Schmitt Trigger with discrete components (using an emitter-coupled pair) that operates with a Low Disable Trigger of around 3.5V and a High Enable Trigger of around 4V on circuit simulation. The circuit simulation uses a sine wave function generator to simulate a changing analog waveform.

The desired output of the Schmitt Trigger for high and low are 5V and 0V respectively, but this Schmitt Trigger outputs a logic high of 5V and a logic low of 3V, which is not suitable for the rest of my circuit, as they require 5V-0V logic levels to work.

The question is how can I make the Schmitt Trigger output a logic level of 5V-0V from a logic level of 5V-3V? What circuit can I "bolt on" to this design to make it output that logic level, or even better, an entirely different circuit altogether that achieves similar functionality (a discrete-component comparator that can achieve a 5V-0V logic level is also cool with me).

Keep in mind that I cannot use any ICs due to project requirements, and I also cannot use any other power supply other than 5VDC.


texts: Trying to identify a rechargeable battery

texts:
Good evening.
I have just removed a rechargeable battery pack from a flashlight which is about 10 years old and no longer holds a charge.
There is only a model number printed on the battery:
CY100722 and the input charger operates at 5vDC 200ma
Can anyone please help me with establishing the output and capacity of the battery so that I can locate a compatible replacement ?
Thank you in advance


texts: Have I fried the transistor in this circuit?

texts:
It was a germanium PNP transistor. I might've pressed the button too. I saw transistors used as capacitors that were connected like this, but they weren't germaniums. What current (if any) has flown through the transistor? According to the datasheet, the reverse collector current at VCB=20V is 5μA, reverse emitter current at VEB=2V is 50μA, VEBO=3V, for what it's worth.

simulate this circuit – Schematic created using CircuitLab


texts: Reasons for multiple I2C modules in ARM-based MCUs

texts:
I was looking in the NXP product selection guide for ARM Microcontrollers. There are multiple I2C modules in most of the ARM MCUs.

Since I2C is a multi-master multi-slave protocol, is there any clear advantage to this approach?