texts: What other connections are made in the motor housing related to the Centrifugal switch for single phase inductive motors

texts:
simulate this circuit – Schematic created using CircuitLab

The schematic is what I observed and imagined from measurement of the six terminal connections. This is a 120V 2HP electric motor with two external capacitors.
The only way I can get it to come to speed it disconnect the 400uf cap and wait for it to slowly get to speed and hear the centrifugal switch open. It then works as expected under load conditions.
1) U1,U2 goes open at speed
2) Reconnect 400uf cap when at speed no effect
3) Disconnect 47uf when at speed draws 2 more amps going from 5 to 7 amps
4) Try to start with 400uf draws 50 amps will not go to speed for centrifugal sw to open
5) starting without 400uf draws 40 amps, takes 5 to 10 seconds to come to speed.
6) Lines V2,Z1 and U2,V1 control direction of motor, if connected V2,U2 and Z1 V1 would reverse direction.
Something appears to prevent normal startup of an inductive motor.  It was made in China and expects 50hz but was told this should not be the problem running on 60hz.


texts: (System)Verilog: extracting a smaller bus/vector from a larger bus?

texts:
What is the best practice for creating a bus, which is just extraction of certain bits of a larger bus. I do not want to store the index numbers to make the lookup in the generate-for if it could be avoided....I was hoping for something like following code which is of course not valid. Can we take advantage of the fact somehow that the extracted shorter bus is always consecutive bits from the larger bus?

localparam logic [7:0] VALID = {1'b0, 1'b1, 1'b1, 1'b1, 1'b1, 1'b0, 1'b0, 1'b0};

 genvar m, j;
  generate
    for (m=0; m<8; m++) begin
      if (VALID[m]) begin
        assign short_bus[j] = large_bus[m];
        j++;
      end
  endgenerate


texts:
I have attached a schematic of a buck converter circuit I have designed. It's designed using a LMR16030 IC.
Input voltage: 12-14V
Output voltage: 5V
Switching frequency: 1MHz
Output Current: 2A
I'm carrying out a load regulation test by connecting a electronic load at the output. As I increase load current from 0 to 1.5 A, the output voltage seems to decrease at a steady rate from 5V to 4.55V.
What can I do/change to ensure a steady output voltage? (max 2% deviation)


texts: How to generate time delay when input frequency is high?

texts:
Im trying to generate time delay for my gate drivers for a project im working on. But the issue is at lower frequencies my circuit works fine, as I ramp up the frequency (upto 250Khz) the output goes to zero.

I know the theory of generating time delay but have never worked with generating time delay in high frequency signals. My circuit is shown below, there R(both) = 10kOhm, and C(both)=0.1uF.

What am I doing wrong ?


texts: Unregulated Push pull converter simulation (LTspice) and flux walking

texts:
I am simulating a unregulated push pull converter in LTspice (voltage isolator). There is the effect of growing winding currents during the simulation. Is this a flux walk (seen in the first image) ?

I have the duty cycle shown here (~90%)

And this circuit. (The low input/output capacitances are intentional). Is there a significant error somewhere i am missing, what can i do to fix this ? Explanation of the source of this would be helpful


texts: ADC unresponsive when I use a slow starting power supply

texts:
I have a project using an STM32L412. It works fine on my bench power supply, but I made it to run on a piece of modular equipment which has a different power supply - this supply is slower starting. On this supply the board seems to work fine except the ADC freezes on power up - the PWM for the LEDs still works, the external interrupts still work, however the ADC is completely unresponsive. If I remove the reset capacitor, the circuit then works on the slower starting power supply and not on the faster starting one. Only the ADC is affected, the timers / PWM still work, the I2C is still transmitting to an external DAC.
I was advised to drop the debugger in after the board had frozen -  when I did this I could step through the whole program and anywhere I put a break point, it was reached. The registers are exactly the same using either power supply, with the exception that with the slow power supply, the ADC calibration register is 0 and the ADC always returns 0x800.
Sometimes the program freezes up when I step into the wait loop for the ADC conversion to complete, that's the only functional difference I could find
Does anybody know a reason why this might be happening? According to what I've managed to find online, as the behaviour changes depending on what capacitor I put on the reset, it appears it might be to do with the Programmable Voltage Detection / Brown Out Reset. As this is my first project I have no knowledge or experience of these things, or why they would affect only the ADC
any help much appreciated


texts:
Look at this piece of code (flip image on X)

PROCESS(iCLK)
BEGIN
  IF (rising_edge(iCLK)) THEN
    -- Mise en mémoire du pixel
    ram(640*IdxC + PixX) <=  PIXIN;
    -- Choix traitement
    IF (SWITCH='1') THEN
      PIXOUT <= ram(640*((IdxC + 1) mod 2) + PixX);
    ELSE
      PIXOUT <= ram(640*(2-IdxC) - PixX + 1);
    END IF;
  END IF;
END PROCESS;

When  I compile it, the overall project takes about 15% of the logic elements and 13% of total memory bits (QuartusII on cyclone III).
If I change the code to

PROCESS (iCLK)
BEGIN
  IF(rising_edge(iCLK)) THEN
    -- Mise en mémoire du pixel
    ram(640*IdxC + PixX) <=  PIXIN;
    -- Choix traitement
    IF (SWITCH='1') THEN
      PIXOUT <= ram(640*((IdxC + 1) mod 2) + PixX);
    ELSE
      IF (PixX > 1 AND PixX < 640) THEN
        PIXOUT <= ram(640*(2-IdxC) - PixX + 1);
      ELSE
        PIXOUT <= x"111";
      END IF;
    END IF;
  END IF;
END PROCESS;

I get

Error (276003): Cannot convert all sets of registers into RAM megafunctions when creating nodes. The resulting number of registers remaining in design exceeds the number of registers in the device or the number specified by the assignment max_number_of_registers_from_uninferred_rams. This can cause longer compilation time or result in insufficient memory to complete Analysis and Synthesis

That seems that I cannot fit anymore the design. I don't believe this. Is there a bug on the compiler or I'm doing something wrong?

I have the Quartus II web edition

Just putting some -- comments on the lines like this and it compiles again:

PROCESS (iCLK)
BEGIN
  IF (rising_edge(iCLK)) THEN
    -- Mise en mémoire du pixel
    ram(640*IdxC + PixX) <= PIXIN;
    -- Choix traitement
    IF (SWITCH='1') THEN
      PIXOUT <= ram(640*((IdxC + 1) mod 2) + PixX);
    ELSE
   -- IF (PixX > 1 AND PixX < 640) THEN
        PIXOUT <= ram(640*(2-IdxC) - PixX + 1);
   -- ELSE
   --   PIXOUT <= x"111";
   -- END IF;
    END IF;
  END IF;
END PROCESS;

This code works with megafunction RAM 2 port:

PROCESS (iCLK)
BEGIN
  IF rising_edge(iCLK) THEN
    -- Ecrire linéairement dans la RAM le pixel de la cam
    RAMWRITE <= TO_UNSIGNED(640*IdxC + PixX - 1, 11);
    -- Choix traitement
    IF (SWITCH='1') THEN
      RAMREAD <= TO_UNSIGNED(640*((IdxC + 1) mod 2) + PixX - 1, 11);
      PIXOUT <= PIXMEM;
    ELSE
      RAMREAD <= TO_UNSIGNED(640*(2-IdxC) - PixX, 11);
      IF (PixX > 1 AND PixX < 640) THEN
        PIXOUT <= PIXMEM;
      ELSE
        PIXOUT <= x"FFF";
      END IF;
    END IF;
  END IF;
END PROCESS;


texts: Should there be more clearance on RF vias with microstrip?

texts:
I'm routing an RF board ( above 1 Ghz) with microstrip lines. Our plan is to feed it from the backside, take it through the via onto the top layer and continue routing. as part of our rules we pull back the ground copper pour to ensure microstrip behavior.

Should we do the same for the other layers the via passes through? Or is the patristic capacitance low enough to not worry about? Or would the patristic capacitance cancel out the inductance of the via?


texts: SMD Component Identification 6 pin with diode properties

texts:
I am having a difficult time trying to identify the following 6 pin SMD component:

I have been searching for what it might be, or the company who made it but have had no luck thus far.  It seems to have diode qualities, such as current flow from pins 2 and 5 (GND) of the to any of the other unknown pins (aprox 0.7 v on diode mode)

The PCB is used in a stair lift with 24V and a DC motor. There are a total of 4 of these unknown components on the PCB. Three here near a micro controller:

The fourth of theses unknown components has both GND pins (2,5) connected to the negative side of electrolytic capacitor, which is connected to a 18V linear voltage regulator. (Unknown component desoldered in picture)

Pin 1 and pin 6 of this component are connected to switches that enable the chair to travel up/down the stairs along with safety switches.

When powered on, pin 1 is 1.2V, and pins 3,4,6 are 4.94V and they all should be 3.3V; which lead me to believe this unknown component may be faulty.

If anyone is able to identify this component, that would be a great help.


texts:
I've always been under the impression that overclocking of any sort of CPU (for a PC, or a microcontroller), its a bad thing.  Your'e essentially operating the unit outside of the manufacturer's specifications, which means that the device may/may not work as intended.  It may go faster, but at the risk of erratic behavior.

I understand that the answer to overclock/not is a philosophical one depending upon how much risk you wish to take on with your devices.  But,

What kind of permanent damage can be caused by overclocking a CPU?

(Note:  I ask this because a number of my friends are gamerz and think overclocking roxors soxors... and for some odd reason after they do this their computers break with bluescreens and then I get called, and I want some ammunition to use so that I don't have to troubleshoot potentially flaky hardware so often...)


texts: OK, i am new at all of this and for my first project i desided to try to use the power from a coal (like the ones you sprinkle incense on), use a Peltier to convert the heat to dc, now i know i need 5v and i think 250 mAmps to charge a phone, thing is i dont know how to figure out best to regulate and amplify the current that will be produced. i figure a transformer of some sort because the coal wont produce enough voltage on its own, but the also would it need something else to regulate the current going in to the transformer, the coals out put will very. if i will need something to regulate it then what?


texts: How to elevate a solid state tube heater supply?

texts:
If you haven't heard of the AX84 project, it's a collaborative guitar amplifier blueprint that anyone can build.

So, I'm trying to extend the design to use a solid state ZVS power supply (This module: https://smile.amazon.com/gp/product/B010UGJF1I). Everything is going swimmingly, except I realized I'm going to vastly exceed the cathode-to-heater voltage limit of a 12au7 with my cathode follower.

For the heaters, I was going to use this module: https://smile.amazon.com/gp/product/B00C4QVTNU . I just checked both modules, and they both tie their output ground to their input ground.

I'm currently stumped and a bit discouraged. How can I regulate 6.3v, but have it be referenced against the b+ voltage of the tube, instead of referenced to ground?

Certainly this is done "in the real world." There are isolated solid state DC supplies that can sit on top of power lines and what not.

Also, please be kind. This is my first amp build. I'm not an electrical engineer, but I did take a physics class in college. I'm here because I'm trying to learn and fill in holes in my knowledge.

Thank you for any help!

Refs

Block Diagram of my amp:

simulate this circuit – Schematic created using CircuitLab

PSU block diagram for OP to edit.

Actual Schematic:


texts: Using capacitive touch switch as guitar pick-up selector

texts:
I want to use two Schurter 3-101-401 one for each pick up.

I was able to get them wired up but the signal for the pick-ups comes out no matter what.

Here is the info https://www.mouser.com/ProductDetail/693-3-101-401

I basically want to connect the pick-up output to this switch then the output of this switch to a volume potentiometer. However it looks like there is a positive and negative wire for power and two output wires. What gives? How do I wire this up? I am a noob and need help desperately.

simulate this circuit – Schematic created using CircuitLab


texts: Make FTDI 2232D do SPI mode 1 properly? Data seems 1/2 clock cycle off

texts:
This capture by a Saleae Logic Pro 8 (v 1.2.18) shows the result of transmitting (MOSI data) 0x20 0x11.  Unfortunately it is interpreted and shown as 0x40 0x23.  The dialog shows Saleae's SPI analyzer settings which, I believe, are correctly set for SPI Mode 1.  (Both digital and analog versions of each SPI line are shown for thoroughness.)

If I change the analyzer to Mode 0 (by changing to CPHA=0, the original data shows correctly.  However, the device to be written to only does Mode 1 (see 9.5.1 and 10.1.1).

To confirm the correct data/clock phase relationship, see this.

I am using the FTDI MPSSE output command 0x11 (see 3.3.2 here).  I have tried changing several of the setup parameters (adaptive clocking on/off, three phase clock/two phase clock) with no change in behavior.  This is the first two SPI bytes out after using the bad command strategy shown in all the FTDI examples to ensure command synchronization (which works as expected).


texts:
After taking classes in control theory as an undergraduate, I ended up not using them at all after I graduated. I've started to fix that by starting a hobby project in controls. My textbooks are pretty good references for the theory, but my biggest problem is that I have not found a good reference on determining system parameters in models. For example, say I have a temperature sensor located some distance away from a heating element, and on top of that it has some non-trivial amount of thermal mass. How should I model this non-ideality? And even after I've modeled the error function for the element, how do I determine the actual numerical coefficients from bench experiments?

Does anyone here have any good textbooks or references to recommend?


texts: Slowest transmission speed supported by TOSLINK TX and RX?

texts:
I'm writing an Arduino communication library that uses differential Manchester coding (see: http://forum.arduino.cc/index.php?topic=257985.0). I'm wondering how to communicate between two Arduinos that are far enough apart that connecting their power supply grounds is not practical, but without resorting to a wireless system. In that case, a physical communication system that does not need to pass current is needed. I thought of using Toslink fiber optic modules that are typically used for digital audio signals.

The only concern that I have is that the bit rate that my Arduino library (and the Arduino hardware itself) will be able to support is not more than about 20k bps. Digital signals typically carried by Toslink have a bit rate starting at about 1M bps. Since I am not familiar with fiber optic hardware I am concerned that the typical digital audio implementation (e.g. the TX & RX hardware and associated passive components) would not support a relatively glacial data rate of 20k bps.

I could just purchase some Toslink modules and try it out, but I thought that before I buy any parts I would make an attempt to learn about the hardware and ask if there are any inherent pitfalls in sending data at kHz (or slower) rates over Toslink.

So, is this feasible? Are there any obvious problems that will come up?


texts: safe negative voltage divider to GPIO pins

texts:
this question comes from this other, trying to implement the folloging circuit to measure a -3V battery pack (2xAA) (I've to measure in that way, cannot swap or move GND):

Digital PIN 6 will be set to OUTPUT and HIGH, thus providing +3.3V there.

I'm trying to implement that divider without burning the SAMD21 3.3V MCU and allowing to disconnect it, so I reached to the following 2 problems:

When MCU is power disconnected, power on digital pin is cut, so the negative voltage reach both analog and digital ports. Can this burn the protections?
I want to switch off the circuit by setting digital pin to INPUT (isolates by about 100Mohm internal impedance). This makes the analog pin receive the negative voltage again, so, I'm afraid to also damaging the MCU.

I tried to do some simulations,

trying to mimic the internal impedance of analog and digital port to get the voltage in the lines. When powered (digital pin output and high), voltage values are ranging from 1.2V to 2.4V what is safe. When switched off (digital pin input), both ports get the -3V negative voltage.
I placed the diode (1N4007) there as I supposed it would avoid current in opposite direction, but it seems not to do anything there (and multimeter says the same...)

Could you get me some other hint in how to implement this?
Thanks!


texts: getting infinite output impedance in Ltspice but not by manual analysis

texts:
I am a beginner to LTSpice, I make this simple netlist:

*#destroy all
*#run
*#print all
.TF I(vmeas) vin
vin vin 0 DC 1
R1 vin vout 1k
R2 vout vmeas 2k
vmeas vmeas 0 DC 0
.end

I am using a test voltage source( 0 volts source) to calculate current through R2. When I run this simulation I get output Impedance as infinite. I dont get this, If its calculating the ipedance across vmeas then it should be zero since then it will be 0|| 3k and if its calculating output impadnce across vout then it should be 3k because while calculating impedance we zero out the independent sources so it means vmeas will become 0 volts , a plain wire.


texts: Modelling inductive and capacitive coupling in LTspice

texts:
I'm trying to make a very simplistic model showing the effect of inductive and capacitive coupling to wires in LTspice. I want to use this model to show people who are not so familiar with the topic. I also don't want to involve transmission lines and simplify it to a lumped circuit model. Basically I want to show the importance of balanced transmission to eliminate the noise. For example, in below circuit I tried to add capacitive coupling from AC mains and some radiated noise as inductive coupling(using a transformer model). Vs is the signal source 1V 1Hz sine wave. R_source is the output impedance. R_balance is the series resistor to make the transmission balanced. So far I tweaked the values and by removing R_balanced or putting it back and simulating I can show that both noise can be eliminated by balancing.

(please left-click to enlarge)

But I'm not sure my way of coupling in the model is okay enough and especially the values for the parasitic capacitances and inductances C1, C2, Ls1, Ls2 are realistic enough. How can I make this circuit more realistic? Is there anything fundamentally wrong?


texts:
Can anybody briefly explain about Miller compensation?

What is the need of pole splitting?
How does it improve both the unity gain bandwidth and phase margin?


texts:
In an example in Pozar's Microwave Engineering, a conjugate matching circuit for maximum gain is designed using Smith chart. In the shown Smith chart, the matching circuit for input is designed. We locate \$\Gamma_{source}\$  on the Smith chart, convert it to admittance, then move backwards (towards the load) till we reach 1+jb circle. My question is why do we move backwards ?
Thanks in advance.


texts: Lightning arrester sharing earthing with surge arrester

texts:
Is it ok for lightening arrester and surge arrester to share common earthing - that is, to use a common wire and electrode?
Is it OK for the lightening arrester earthing electrode to be close (1 or 2 feet) to household earthing/ grounding electrode?
Context for the question:
A planned household solar power generation installation (location India) shown below (without the lightning arrester):


texts: Confusion in parrallel and series of Transmission line

texts:
A transmission line terminals in two branches,each of length \$\frac{\lambda}{4}\$,as shown.The branches are terminated by \$50 \Omega\$ loads.The lines are lossless and have the characteristics impedances shown.Determine the impedance \$Z_i\$ as seen by the source.

My only confusion in this question is,the two right branches will be in series but i will not get the correct answer ,if i will do it by assuming them in series if i take that two branches in the parrallel i will get the correct answer.
But i am not getting how that right two branches will becomes parrallel?

because only parrallel line i saw is this.can anyone help?


texts: PIC16f877A: Working in Debug mode not working in Release mode

texts:
I am facing an Issue with my PIC16f877A controller.

Its working in Debug mode with PicKit3 connected. But when I program the device for release mode, It gives no sign of working.

I am using MPLAB X with XC8 compiler

I have also connected 10k resistance between MCLR & VDD.

But still unable to resolve the issue.

Here is my main.c

#include "lib/System/config.h"
#include <xc.h>
#include <pic16f877a.h>
#include <stdio.h>
#include <stddef.h>
#include <stdlib.h>
#include <stdbool.h>
#include "lib/UART/UARTLib.h"
#include "lib/I2C/I2CInterface.h"
#include "lib/I2C/idmodule.h"

// CONFIG
#pragma config FOSC = HS       // Oscillator Selection bits (HS oscillator)
#pragma config WDTE = OFF       // Watchdog Timer Enable bit (WDT disabled)
#pragma config PWRTE = OFF      // Power-up Timer Enable bit (PWRT disabled)
#pragma config BOREN = ON       // Brown-out Reset Enable bit (BOR enabled)
#pragma config LVP = OFF        // Low-Voltage (Single-Supply) In-Circuit Serial Programming Enable bit (RB3 is digital I/O, HV on MCLR must be used for programming)
#pragma config CPD = OFF        // Data EEPROM Memory Code Protection bit (Data EEPROM code protection off)
#pragma config WRT = OFF        // Flash Program Memory Write Enable bits (Write protection off; all program memory may be written to by EECON control)
#pragma config CP = OFF         // Flash Program Memory Code Protection bit (Code protection off)

static unsigned char data_Pkt_1[ MAX_BUF_SIZE ] = { NULL } ;                                // this is the buffer to accept incoming data
static unsigned char data_Pkt_2[ MAX_PKT_SIZE - MAX_BUF_SIZE ] = { NULL } ;             // this is the buffer to accept incoming data

bool isDataPktReceived = false;                         // Flag to check the incoming Data Pkt
bool opStatus = WRITE;

char start_byte_addr[] = { 0x00, 0x10, 0x20, 0x30, 0x40, 0x50, 0x60, 0x70 } ;
int maxBytes;
int Error = 0;

void receiveDataPkt();                                  // Function to receive Data from the PC
void transmitDataPkt();                                 // Function to transmit Data to the PC

void initIDComm();                                      // Function to Initialize ID Module Communication
void initBuffers();                                     // Initialize buffers with 0x00
void write_IDM( void );                                 // Function to Write ID Module
void read_IDM( void );                                  // Function to Read ID Module

bool validateData( void );                              // Function to Validate Data
void createResponsePkt( bool opStatus );                // Function to Create Response Pkt
void createErrorPkt( void );                            // Function to create Error Pkt
void interrupt ISR(void);                               // Interrupt Service Routine

/**********************************************************
 Function : Main Function to Initialize the Operation
 Parameter : None
 Return   : None
***********************************************************/
int main()
{
    UARTInit();
    idmInitI2C();

    while (1)
    {
        while ( idmCheckConnection() ) {
            if ( UART_GetRecvByteStatus() ) {
                UART_SetRecvByteStatus(false);              // Set Received flag False
                receiveDataPkt();                           // Receive Incoming data
            }

            if ( isDataPktReceived ) {
                initIDComm();
                isDataPktReceived = false;
            }
        }
    }
    return 0;
}

Please help me debugging the issue.


texts: Monitoring Lithium Polymer Battery Voltage from Microcontroller

texts:
I am working on a project in which a microcontroller (specifically an RFduino) is powered by a LiPo battery and the microcontroller needs to monitor the voltage of the LiPo.  Five of the RFduino pins are already being used for sensors so I only have two pins available for power management.  If possible I’d like to use one pin to detect when the battery is charging and the other to measure the voltage.

Currently this device is using the MCP73871 chip for LiPo charing/power management and a 3V LDO voltage regulator to regulate the voltage powering the RFduino.  I can run the power good signal from the MCP73871 to one of the two free RFduino pins - as seen in the diagram - to detect when the battery is charging.  I would like to use the remaining free pin on the RFduino to measure the battery voltage.

Unfortunately I can not measure the battery voltage directly on the RFduino because the LiPo goes to 4.2V when fully charged and the maximum voltage the RFduino can handle is 3.6V.  I was hoping to be able to uniformly shift the voltage below 3V using diodes or a voltage divider but from a couple google searches it looks like current fluctuations would make that impossible.  I am not an electrical engineer and I’m way out of my element at this point.  Is there a way I can modify my existing circuit to monitor the LiPo voltage on the remaining free pin?  I’m out of ideas and any help is greatly appreciated!  Thanks!


texts: TLP184 Optocoupler - Something is going wrong

texts:
i'm using this simple schematic (using a TLP184) in order to get the status of a reed/dry contact using an optocoupler

There is no way to get it working, also if the connector pins are opened, from pin 4 and GND i get 2.5V.
I'm missing something?
Maybe it's a silly mistake, but i can't figure out on how to solve this.


texts: How to change the temperature of sub-circuits in LTSPICE

texts: I have subcircuits of a solar cell (resistors and diodes) in LTSPICE. I want to connect the solar cells (sub-circuits) together. However, each solar cell has a different temperature. I can set the temperature of the program with .Temp but how can I change the temperature of each sub-circuit separately.


texts:
I am new to the pwm switching technique. Here I have the output waveform of a 3 level inverter with normal switching and switching using pwm pulses.
(a)Phase-A, (b)Phase-b, (a)LIne-ab

(a)Phase-A, (b)Phase-b, (a)LIne-ab.

But the figure 1 seems to be very noisy than the other. But it says it is more preferable than the second one. Can anybody help me to understand the advantages clearly? And what is the advantage if I increase the switching frequency of the pwm?


texts: Balancing NiMh batteries in series over a long term

texts: I'd like to place two NiMh batteries in series to drive a string of single LEDs. I can charge them simply at C/20 or so and the output will be intermittant so the batteries will never reach half charge. However, this will be in a permanent fixture, soldered to a pcb. I worry that variation between the batteries, including internal leakage, could eventually (over a year or so) cause them to have significantly different charge. Is this a problem? Is there a simple circuit to eliminate this? Could high value resistors (10 meg?) in parallel with each battery help? Any suggestions?


texts:
I am designing a small digital synthesizer. Because of space constrictions, I can only use 3.5mm TRS connectors. RCA is already too big.

If possible, I'd like to include not only an analog output, but also a digital output over S/PDIF (coax).

I know that S/PDIF needs 75 Ohms impedance. Would it be possible to run the signal through a mini TRS jack without problems? The connection on the PCB from the IC would of course be impedance matched, and I would solder the TRS plug directly onto a 75 ohms coaxial cable, with a cinch connector after a few centimeters.

Would a 2.5mm TRS maybe be better? Or does it not work at all?


texts:
I made two LED controllers using an ESP. On the PCB I'm using three 2N2222 transistors + resistor (1k Ohm) at the base to control the 12V circuit powering the LED strips by applying 3.3V from the ESP.
Schematic (Q1, Q2 and Q3 have been replaced by the transistors):

Now I've got a problem: On one of the two controllers the Q2 transistor keeps blowing (Q2 is RED, not GREEN, as I accidentally mixed something up). It seems to be the LED strip, because I put it in place of the other controller and now it's working fine.

Could the problem be that the LED strip is too long? Or is there something faulty and I need to replace the whole strip?
If more info is needed, I'll gladly provide it.

Edit: I still have the original controller, which uses an IR remote. If there's anything I need to measure while the strip is on, I can do that too.

The resistor soldered to the base of the transistor works, I just checked that. The red LEDs start flickering, and at some point the transistor blows


texts: In this circuit, the drain current needs to be calculated when S1 opens and S2 closes and remain in this position for long time. In this position, the transistor is in cutoff region i.e Id=0. But the given answer is -25 microA. Please help me with a solution.


texts: How to prevent current and voltage fluctuations for loads connected in parallel to the same power supply?

texts: I have a 12V dc power supply/battery supplying a class D audio amplifier, 12V dc linear actuator (controlled by raspberry pi through an h-bridge), LCD screen and LED light strip (Lighting intensity controlled by raspberry pi through an L293D). My problem is that when music is played through the amplifier, the led light flickers with the base of the music and I can see the voltage and current fluctuating on the multimeter. Also, when i start to raise the linear actuator the same thing happens with the lights and the screen glitches. How can i solve this problem such that everything is still connected to the same power source?


texts:
I am modeling a line sensor car, I like to find out the transfer function of the car under an unit step input for a steady speed so that the system dynamics stay the same for the constant speed.

From the sampling position of the car when apply unit step input, I find an overshooting of more than 100% in the car, which is overshooting 156%.

From there, when I apply the formula of Mp = exp(- damp * pi / (sqrt(1 - sq(damp))), i get a nice damping ratio which is 0.14.

However, when i plot the graph in the Matlab, the overshoot is shown is only 64% as with that value, the damping ratio is also 0.14.

How do u plot the diagram with the exact 156% overshooting?


texts:
I've designed the following circuit:

This is a "self-reset" circuit, VCC_IN es 12V from source, VCC_OUT powers the entire board, including a PIC microcontroller.

The idea behind this is whenever the PIC output directly connected to label uRST on the right pulls down, the whole board should hard reset through the relay (including the PIC) for an amount of time calculated with R403 and C401 (a couple of seconds, to give time for capacitors to discharge)

So with this circuit I am making sure that the entire board, including the microcontroller, plus some particular IC's gets a REAL reset, plus the resistors to ground to make the discharge faster.

When I built a prototype on a protoboard it worked perfectly (I should have tested it more thoroughly), so I decided the build the board.

I've soldered the first one, it powers up fine, but in these cases:

1 - power-off, power-on very quickly
   2 - the uRST pulls down

the board resets as expected, but when the timer finishes, it instantly resets again, and then again, forever.

I've been changing resistor and capacitor values for some time but the problem persists, what values should I change to make this work?

I've built several of this boards, so I don't have the luxury of a complete redesign, I'm looking for some tweeks here and there to make this work as expected.

Small explanation of the circuit:

uRST is a PIC output, normally set to logical 1 (3v), and pulls to logical 0 (0v) to reset.

R404+C402 are there to hold the timer in power up, so the PIC and rest of the circuit powers up.

C405 is to separate the 12V circuit from the 3V circuit and protect the PIC, plus makes the reset trigger with flanks and not states.

R405+R406 are there so when the flank comming from C405 on pull down sets the trigger low enough to actually trigger the reset.

R401+R402 are there to discharge caps just a little bit more gently than a direct short to GND. (just in case this makes the caps to discharge too slowly, I removed and place jumpers there, with the same result)

NOTE: Diodes VR401, D401,D402 and D403 are for protection.


texts: Multiple Wireless charging coils (Qi) in parallel?

texts:
I am making a device that will be wireleslly charged and I decided to go for a standardized Qi transmitter/receiver. The device is a kind of bulk and I want it to have an option to get charged no matter what side it is lying on. I thought of putting a Qi coil on each side and getting the charging voltage on battery port when the device is lying on any side.

Let's say there will be 3 coils. How do I connect them to the same battery charging circuit? If I connect them in parallel, 2 coils will present huge load to the one coil that is currently active. If I connect them in series, It will present additional impedance to the source and may limit the output current.

I thought of putting them in parallel and adding a diode in series to each branches. This way, the diode is going to be reversly polarized when one coil is active and there will be no overload. But at the same time, it will work as rectifier and kill all negative half-periods when it's conductive.

simulate this circuit – Schematic created using CircuitLab

Is there any reasonable way to do this?


texts: Circuit to remove dc and extract AC signal

texts:
I just started working in the Power Electronics domain and I am learning and understanding the concepts of electrical and electronic circuits.

Attached is the circuit diagram I am trying to understand and design.

At the Point_of_Interest, I want a circuit that extracts the AC signal (Sinusoidal 50V 60Hz in this case).  Is it possible to design such a circuit?  If so, can anyone please suggest me how to extract this signal?

Thanks.


texts: Do we always take the corner frequency of a filter at exactly -3dB?

texts:
I'm doing some work on filters, but all the references I can find use a 'perfect' gain characteristic, with the trace starting at 0dB. Is the measurement for corner/cutoff frequency always taken at exactly -3dB? What if the maximum gain isn’t 0dB?
For example, see the below figure, where the maximum gain is -3dB. Surely taking the corner frequency at -3dB in this case would not be useful- instead would we take it at -6dB, which is -3dB from the actual maximum gain?
Thanks for your help.


texts: I want to command a 12V DC motor with the output of a clock alarm

texts:
I want to command a 12 V DC motor with the output of a clock alarm. The output of the clock alarm is a 1V (pp) square  signal of 100 Hz. I just want my motor supplied when alarm is on and then stop when alarm period is over, meaning when square signal becomes zero.

Edit:

R5,L1 and V3 are the DC motor model.
Q3 reference is TIP31 instead of 2N3904


texts: Interpreting a datasheet of resistor for heat sink

texts:
I will have this 47k 50W wire wound resistor which will be across line and neutral which means 230 VAC rms. So the electrical power in theory will be V^2/R = 1.2 Watt.

How should one interpret this datasheet and the below curve whether a heat sink is needed? (Above which electrical power a heat sink is needed needed).

Similarly a 4.7k 50W resistor will electrically consume 1W. Can we say no heatsink required looking at its datsheet as well?

Im trying to find a method or rule of thumb ect., thats why i gave two examples-


texts: How large should a pad be for a 5mm screw terminal block?

texts:
I am using some standard 5mm screw terminal blocks for a simple design at low voltages (less than 20V).

The datasheet does not have a standard footprint for the device.

The pin itself has a diameter of 1.3mm, so I was thinking a hole size of 1.5mm, with a solder pad surrounding the hole of 1mm.

There's no real science in choosing these dimensions. What considerations should be given to choosing the pad size?  If so, what pad size is best?


texts: Is the three phase voltage output from inverse Park / Clarke a "decimal voltage"? Or is it modulated by PWM

texts:
I'm trying to understand brushless dc motor control via field orientated control,
I'm watching this video here : https://youtu.be/YPD1_rcXBIE?t=588
Here we have the "Inverse Clarke/Park" algorithm, being computed on some microcontroller,
or special hardware (Digital signal processors?). The output is the three phase voltage to
be sent to control the motor stator currents. I believe.
I thought the three phase inverter can only turn on and off the motor coil pairs, but can it output,
say a "decimal voltage", to turn it on and off only slightly?
I'm a beginner at learning electronics and motor control circuits... Please correct me when my understanding is wrong.


texts: How to reduces nonlinearities due to the saturation of one of the BJTs in a differential amplifier

texts:
Reading about the differential amplifier in The Art of Electronics, we are introduced to this circuit.

It is claimed that the common mode input voltage is limited at the upper end by \$Q_2\$'s collector quiescent voltage of  \$2.5V\$. Understanding this limitation was because of \$Q_2\$'s saturation, I pondered the effects of saturation , namely that the collector voltage of one of the transistors could not go much lower than the input applied to it.

I transcribed the circuit in CircuitLab and ran a DC sweep.

simulate this circuit – Schematic created using CircuitLab

With the following parameters :

\$V_{diff}\$ : -1 to 1 V

\$V_{com}\$  :  0 to 2 V

I got (as expected) weird variations or offsets when one of the transistors was pushed in saturation.

Given that the nonlinearities result in outright wrong output slope, and are therefore problematic, how does one prevent this behavior ?


texts:
I've recently purchased 40 kHz transceivers and I tested its frequency response in anechoic chamber using a B&K microphone located 90cm away from the emitter. The response provided in the datasheet is

whereas my finding is

What can be causing this discrepancy? The center frequency is clearly not 40 kHz as it was claimed to be.

Is a standing wave causing the notch that is at ~38 kHz?

I am pretty sure the experiment setup is functioning well.


texts:
I have a admp401 digital microphone when I play 8khz tone I get this:

and when I connect the ADC directly to a signal generator, I get this:

ADC sampling cycles is set to 55.5 cycles with 12MHZ clock speed.
timer triggers ADC and then the result is sent to DMA. I receive 2000 sample and when it is done, I send all 2000 data to the computer.
This is the output of ADMP401 when the room is quiet.
I use USB power and give it to 5v lm2576 and then, there is a lm1117 for 3.3v . I have enough 100nf and 1uf and 10uf capacitor on my power line. I also got the same result with xmega24a4u on some kind of same PCB with same power supply.

I disconnected the stm32f103c8t6 blue pill from my board and connected it directly to computer with programmer 3.3v and the I still have the same noise.
My problem is that the microphone output is not symmetric and the bottom of the signal is distorted and the signal looks to noisy.
this is the link of my module  link
and here is the schematic (I did reverse engineering and I drew it myself. There might be some errors I do not take any responsibility about it.)
I do not know the values of capacitors.


texts: I have D.C motor (36V, 450W) and battery (36V, 15Ah). I dont know much weight can my motor handle given that it already carrying lets say 7kg already. I hope you can help me with this. Thank you. Im going to use it in a wheelchair!


texts: Gain of an experimental first order step response

texts:
I have a pwm driven DC motor control system with magnetic encoder that measures the output shaft speed and outputs the RPM values every 50ms over serial comms to plot a graph of RPM vs Time. The system is stepped from 0 to 10% of the maximum possible duty cycle initially and then after a period of time stepped again from 10% of the maximum to 20% of the maximum. I would now like to determine the parameters of the system from this graph - mainly the time constant, gain and time delay.

\$\tau\$ is measured as 0.63 of the steady state value. So this is obtained by taking 0.63*112 = 70.56 and finding the corresponding time, roughly 400ms.

I'd like to know if I have the correct approach in obtaining the gain. I found this formula:

\$K = \frac{\Delta Y}{\Delta U}(t \to \infty)\$

Does this mean I can calculate the gain as the RPM difference between 10% and 20% duty cycle step divided by the difference between the duty cycle step. i.e

\$ K = \frac{120-112}{20-10} = 10.8\$

edit:

I plotted the theoretical response obtained from the experimental response. The step to 20% duty cycle does not seem to  correspond to the experimental output.

k = 10.8;
tau = 0.4;

num = k;
den = [tau 1];

H =tf(num,den,'InputDelay',0.1)

t = 0:0.01:10;
u = 10*(t>0)+10*(t>6);

lsim(H,u,t)


texts: LTspice: Is it possible to have different plot panes with different x-axes?

texts: Is it possible to have different x-axes for different plot panes in LTspice? For example, In following circuit, can I plot both output characteristics and transfer characteristic curves simultaneously in two plot panes? i.e. one x-axis is V1 and other x-axis is V2


texts:
I have a 555 monostable set up which is triggered when an output from another circuit goes low. This then remains on for 10s. This all works almost perfectly.

My issue is that when the output from the other circuit goes high again and then back down within the initial 10s timing , this 10s timer does not restart, it is locked in its first cycle.

Example:
If i send the trigger pin  low, the 10s timer begins and the diode illuminates. Then if I wait 5s and then send it high and low again, it continues the initial timing cycle and the diode goes off after 5s.

Each time the input circuit goes low, i would like to restart the 10s timer.

Anyone know how this can be achieved? I have tried playing around with the reset pin but with no success.

P.S. i know the time constant for this circuit is actually around 100ms, it's just the limitations of the software I am using , can only simulate 10ms/s

simulate this circuit – Schematic created using CircuitLab


texts: How can a pringles can act as WiFi booster?

texts:
How does a wifi transciever placed inside a Pringles can act as a wifi signal booster. I saw this trick on Mr robot TV series.
Do WiFi routers emit less power than GSM or LTE. I know for :

GSM - 2W (33dbm)

LTE - 200mW (23dbm)


texts: Low power amplifier for 433MHz wake up receiver

texts:
I’m designing a low power wakeup receiver (WuRx) circuit that will be used to wake up an Arduino and its 433 MHz transceiver, both of which pull way too much current (tens of milliamps) to keep running at each remote node. The goal is to develop a low power wake up receiver / detector that will wake up Arduino (or any sleeping MCU) when RF wake up signal is present. The RF wake up signal will be a series of brief OOK pulses from the transmitter.

I need to amplify the UHF signal from its ten microvolt antenna level, to at least 100 millivolt to 1 volt level in order to detect the RF envelope via a simple diode rectifier, which will then trip a comparator indicating “RF present” during OOK (on-off keying). These pulses will then be counted using some flip/flops or a counter within a given time window to detect a valid wake up signal.

I have done extensive research on these wake up receivers and prior art. Traditional conversion of RF to IF results in too much quiescent current due to the LO current.  This has led me to conclude that a low power RF amp fed by a ceramic bandpass filter can solve this problem.

Since this is simply an RF wake up detector, linearity during amplification is much less important than very low quiescent current when no RF is present. These IoT style slave sensors typically sit idle 99.999% of the time, only needing to awaken for a few tens of milliseconds whenever the master polls them.

The flow will look something like this:

Antenna -> Bandpass Filter -> RF Amp -> OOK Envelope Detector -> Wakeup Interrupt to Arduino -> Transceiver Wakeup -> Rx Data -> Process Rx Data -> Back to Sleep

My problem is how to minimize the quiescent amplifier current drain (to nanoamp level ideally) yet sufficiently amplify the microvolt signal once its present and coming out of the bandpass filter. Total amplifier current drain when RF signal is present can be a few milliamps.  I’m thinking several 15 dB to 20 dB amplification stages in series to yield a 10,000 to 100,000 x signal boost should be sufficient; e.g. 10 uV to 100mV - 1V.

I’m looking at LNA transistors like the BFP720, a low noise silicon germanium BJT, but willing to consider all low cost options.  Low cost and small footprint are also factors but low quiescent current consumption on 3V battery power is critical.

I’ve tried Class C amplifiers with resonant circuits but simulations are failing (using SystemVision simulator) due to low (millivolt) level input signals being too tiny to allow the transistor to conduct.  What type of amplifier can I use that has very low quiesce bias current and can amplify this tiny UHF signal?

If I can figure this out, it will help a lot of folks out who are struggling to solve this type of low power wake up problem.

Thanks in advance for guidance.


texts: USB UART Bridge with capability of handling fast charge VBus

texts:
I am trying to design a charging circuit which support QuickCharge but also I want to add USB-UART bridge to communicate with on board MCU.
How can I establish voltage level safe communication through UART bridge while VBus level is controlled by fast charge IC? What I mean, VBus would be get higher as 20V. Generally found USB-UART bridges are just handling 5V max.
Lets look CP2102. This IC has actually self-powered configuration through Vdd but that still needs to be connected to VBus with threshold 5V.
There should be some simple solution I could not think.


texts: Is it possible to add up DC/DC converters in series to create 500V output from 5V input on a PCB?

texts: If I have a 5V input source and I wanted an output voltage of 500V, can I use the output of one DC/DC converter to serve as the input voltage to a second DC/DC converter?


texts: Kicad: How to give nets / wires multiple names

texts:
I'm designing a switching power supply using a BD9G101G step-down regulator. The datasheet is here: http://rohmfs.rohm.com/en/products/databook/datasheet/ic/power/switching_regulator/bd9g101g-e.pdf.

If you look on page 18 there is a simplified board layout (fig. 47).

There are two areas which need special consideration: SGND and POWERGND. Logical they are all on GND level but need some special routing.

It would be very helpfull if I could somehow name the nets in Kicad schematic/pcbnew accordingly.

I tried designing some kind of net-seperator symbol (which works) but I can't find/make a footprint which I can place on the layout without getting trouble.

So what would be a way to do this?

EDIT: Removed screenshot because it was leading to far away from the actual question.

SOLUTION: Francois was first to mention net-ties (and why not to use them). But special thanks to Dennis :)


texts:
What are the main reasons why one would choose one of the following options:

sig
(1") space
gnd
(4") space
pwr
(1") space
sig

comparing with

sig
(1") space
gnd
(1") space
sig/pwr
(1") space
sig

I know the impedance would be better controlled and the loopback would be smaller. But what if I want to use layer 3 for signal and local power planes. Can the GND layer be my reference one? Should I even consider that option?


texts: 18650 battery cells died in the winter weather, can they be restored?

texts:
I have 1.4kwh worth of hoverboard batteries for my E-bike that I stored in the garage over winter. They were fully charged when stored. I did not know this was bad for the batteries, I took it for a ride today after letting them fully charge on the charger and they died within a minute. I recharged again and they died again in under a minute.
We had a particularly cold winter this year, I'm guessing they stayed in an overcharged state for prolonged periods of time.
Is there a way to restore them?


texts: Trying to understand Peltier module specification

texts:
I baught this module

The specifcation says:

 Product Specifications:

    * Operational Voltage : 12 VDC
    * Current Max : 6 Amp
    * Voltage Max : 15.4 VDC
    * Power Max : 92.4 Watts
    * Dimension : 40 x 40 x 3.6mm
    * Power Cable Length : 280mm

I am trying to understand each of these values, and have written what I understood:

Operational Voltage : 12 VDC
 This is the input power supply that should normally be used

Current Max : 6 Amp
This is the maximum current this device will draw from the power supply source. So it means my Power supply ratings should be 12 v Dc , 6 A (or greater than 6 A for safetly)

But under Recommendations it says:

RECOMMENDATION:

     * Use standard Power Supply 12V, 5A to power the TEC1-12706.

Is this 5A rating safe?

Voltage Max : 15.4 VDC
This is the maximum voltage that this module can handle.

Power Max : 92.4 Watts
This is maximum power or energy dissipated per second by this module. This energy will be used in cooling oneside of the module.

Kindly let me know if my understanding is correct.


texts: Modifying the MT3608 DC-DC Boost convertor

texts: I am using the DC-DC boost converter MT3608 for a project where my input ranges around 1 V. Is there a way to modify the circuit so that the boost converter can operate at voltages less than its minimum rated input voltage i.e 2 V? If yes, what exact modifications are required in the boost converter or the circuit around it?


texts: After metastability, does the value eventually settle to the correct value?

texts:
I'm confused about metastability. I know that metastability is the condition wherein the output of a flip flop becomes unpredictable (either high or low) for some "duration of time"... Okay, from this definition, it states that metastability will not go on forever, right? Does this mean that after this period, the output of the flop will eventually go to the correct value? Or does it go into an unpredictable value depending on which value has been generated after the metastable period???

Take note, I'm asking here what happens AFTER the metastable period, NOT during the metastable period.

@Neil_UK,

So in the image below, the 2nd flop will not always samples a high value. Am I right?

If the first flop becomes metastable then after sometime the metastability has decayed, its value may settle randomly at either logic 0 or logic 1. Is this correct?... I'm asking this because the author says that it samples the value as high. I don't know how did it sample a high value. Is it just by chance that the output of the first flop settles at logic 1?

If the first flop did not go out from metastable state within one bclk period, then the second flop will also become metastable... and this could also happen when another stage of flop is connected... Is this what you mean that there is no guarantee that a Synchronizer will 'absolutely' give the correct intended output?

I'm reading some stuffs about metastability and synchronizers. I'm confused on the explanation of some of the authors, like this one. I'm reading this article, http://www.sunburst-design.com/papers/CummingsSNUG2008Boston_CDC.pdf on page 9.


texts: adapting 60 LED battery operated string-light to work with wall wart

texts:
I need to adapt one of these 60 LED string-lights to be powered through a wall plug. These are micro LEDs all wired in parallel; sadly, I couldn't find specs for this kind of LED. The string's power supply holds 6 AA batteries (3 parallel-wired-pairs in series) so I know it requires a 4.5V supply, but I have no idea about the current.

Also, I have a similar LED string light with 100 LEDs (this one powered with a AC/DC power adapter) that no longer works. The adapter outputs 4.5V / 1A. So I want to ask:

-What specs should I look for in the power supply/wall wart?

-Can I use the power adapter from the broken string to power this smaller one?

-Is it a good solution to just hook the LEDs up to a wall wart with the correct specs or does this circuit need more components to work and for the LEDs not to burn out?

Thank you!


texts:
I am trying to use EMAX 20A ESC (Electronic speed control), but it does not work. I am supposed to hear some beeps. It is a 3 phase ESC.

1) I am using 12V from a computer power supply instead of 11.1V 3 cell battery 3S LiPo. Is this a problem?

2) 0 volts must be set on the yellow line before connecting the ESC to the power. I do that, but it does not help.

I am using Raspberry Pi to send the control signal. GPIO 18 is connected to the yellow control line of the ESC.

This is a video: https://www.youtube.com/watch?v=uOQk8SJso6Q that uses Arduino, instead of Raspberry Pi.


texts: Eagle tStop pad colliding with other pads

texts:
As you can see from the image, the tStop layer is colliding/wildly close with other tStop pad layer. Is that a cause of concern?

IC is Linear Technology battery management IC - LTC4155. Package is 28 pin QFN. The center big block is the ground pin(I drew that with a big SMD, is it OK?).
http://cds.linear.com/docs/en/datasheet/4155fc.pdf


texts: What is the problem with my LED panel switching circuit?

texts: I have soldered this circuit on PCB. When I switch Q1 via MCU pin-1, I see LED glowing on Q3 (not too bright though). What could be the reason for this? Even though, MCU pin 2 is pulled down to GND! It works fine on the solderless breadboard but not on the PCB.


texts:
Consider an ideal digital milliammeter (zero resistance, zero uncertainty on AD converter input) with realistic (noisy, hysteresic, etc.) AD converter output and a \$3½\$ -digit display. Often when we measure something and the measured value is near the transition between two readings, e.g. \$0.002\; \mathrm{mA}\$ vs \$0.003\; \mathrm{mA}\$, the display (the far-right (last) digit in this case) starts to blink/alternate between the two numbers.

Most of people presume that if you see the number \$0.003\$ for a longer time than \$0.002\$, it means something like: "absolute distance of the real value of input is closer to \$0.003\$ than to \$0.002\$". In other words it means you can round the result to \$0.003\; \mathrm{mA}\$.

Besides the fact that you should use a more precise apparatus in this case, is this practice recommended? And can we use the blinking itself to get a higher precision past the digit precision?

For example: if \$0.002\$ appears half of the time and \$0.003\$ also, we might assess the real value is close to \$0.0025\$. However this gets questionable anywhere off this point and I suppose the display behaviour is different from device to device. Engineers, what are your thoughts?


texts: What is the difference between modulating with cosine and exponential function?

texts:
Say I have an information signal x(t) with frequency f0 and I want to shift it on the spectrum to a much higher f1.

I would have 1) \$y(t)=x(t) \cos(\omega_1 t)\$ and by looking at the spectrum I'd see it's perfectly shifted.

I read you can also do the same by doing this:
2) \$y(t)=x(t) e^{j\omega_1 t}\$. If we only look at the real part we get almost the same as above with a cosine but it's perfectly symmetrical. What I don't understand is why?

If we take \$e^{j\omega_1 t} = \cos(\omega_1 t)+j \sin(\omega_1 t)\$ and look at the real part we only have a cosine. Isn't that the same as above? How is it that signal 1) and 2) are different?

edit: maybe it gets clearer with a picture, black is the information signal


texts: Transimpedence amplifier output from 0 to 3V

texts: I have this circuit configuration using the Lm324an op amp with a 5V rail (needs to be 5V) an infrared led and a photodiode. At the minute using a using a 1M resistor the output swings to rails when I place the light source closer to the photodiode however I would like the output to vary from 0 to 3V. How can I modify or at to the circuit to achieve this? I am also unsure what values of resistor and capacitance to pick.


texts: Why a 4KB (erase block) flash uses too much RAM

texts:
I'm using an SST26VF (4KB block erase) flash with elm chan's FAT FS. And when I compiled it for my STM32F103 it is using up too much RAM. But Mr. Chan's application notes that memory usage doesn't on the sector size (which I have set as 4096).
Why would I be using this much RAM? My program worked perfectly fine with an SD card (FAT sector size is 512 bytes). But now when I reconfigured it for SST26VF its RAM usage is more than what the uC offers.


texts:
I have a very small stepper 4 pin 2 phase stepper motor, I need to know what's the most convenient way to connect wires to it in order to drive it (as I have about 300 of those I need to drive).
Here's the motor:

I'm hoping your experience can help me.


texts: Can I visually obtain an equation from this curve?

texts:
While I was in the lab I was able to get the correct voltage curves on the oscilloscope, but time was short so I took a picture instead of measuring the voltage incrementally (the ultimate goal being a plot that fits the curve).

I'm specifically referring to the top curve - which is channel 2. Is there a way I can get an equation for this curve from the picture alone? The voltage and time scales are there, so I feel like it could be done, I'm just not sure how.


texts: Code Composer Studio + Energia + CC3200 LAUNCHPAD - Energia Sketch Build Errors

texts:
I have a CC3200 LAUNCHPAD and I saw the Code Composer Studio + Energia integration and thought it was sweet. From the tutorials, it looked like it was super easy to use an Energia Sketch in Code Composer. I can import a sketch just fine and I've imported the simple WifiWebClient sketch to try out my environment. When I import the sketch, it also makes a "lpcc3200_core" folder in the tree. When I go to build, that "lpcc3200_core" has errors which are all header file inclusions. The header files that it says are missing are clearly in the project already. I've posted on the TI E2E forum, the Energia forum, and contacted the Energia people directly with no luck. I figured I'd post this here.

EDIT: I messed around with library locations before so here is clean run of the error.

fatal error: cc_types.h: No such file or directory


texts:
I'm new to both StackExchange and electronics in general.

I want to be able to turn on and off a DC motor using my Raspberry Pi.
I have a breadboard, a 6V DC motor, an NPN Transistor (ST 2N2222), a battery holder that holds 4 AA batteries (and consequently has a P.D. of about 6V), a raspberry pi, and wires. Also, can I use Pulse Width Modulation in this setup, and if so, how? If possible, please include circuit diagrams.

I know that this will be much easier to do using an IC Motor Controller (like L293D), but I want to know if it is possible using a transistor instead.

Thanks in advance.


texts:
I have designed a 4x1 MUX. I want to give the selection from two diferent inputs and not one 2bit input. How can I do that, if possible?
In the image you see the "incompatible widths" error which is expected:

              |\
              | \
   (input):(--|  |O--- ... (output)
              | /
              |/


texts: The distribution of phase angle between identical zero mean Gaussian random signals?

texts:
I am trying to solve the 2013 paper set by ISRO for electrical engineers. I was hoping to get some clues on how to approach this problem - No 22. random signals which have gaussian distributions will not be periodic and I can't understand what they mean by phase difference between the two signals.

Question No 22

If x and y are two random signals with zero mean Gaussian distribution having identical standard deviation, the phase angle between them is

a) Zero mean Gaussian distributed

b) Uniform between \$-\pi\$ and \$\pi\$

c) Uniform between \$\frac{-\pi}{2}\$ and \$\frac{\pi}{2}\$

d) Non zero mean Gaussian distributed

My gut feeling tells me that since both signals are zero mean, it's more likely to spend time at 0 (depending on the standard deviation), so a phase difference of 0 is more likely. So I can rule out Uniform distribution and a non zero gaussian distribution. So I intuit that the answer is (A)

I found a paper which talks on this topic, but it went right above my head. I was hoping for an explanation of what the question is asking and what the answer is and why?


texts:
I'm working on designing a new product, primarily for use in Europe. It is a low cost telemetry system for all intents and purposes.

The question I have is: what size should the sim card be? SIM, mini SIM or nano SIM? I know most US phones that have come out in the last year (smart phones) seem to use the nano SIM. Is this also true in Europe? I can not find any affirmative data on the web. Basically I want the most readily available SIM size.


texts: Isolating motor control signals from microcontroller from high voltage/current lines

texts:
We need to design an integrated DC motor controller/driver, which will be under microprocessor control. Due to space requirements, either the digital and analog circuitry will be on a single PCB (think of PC104 size), or they will be stacked on top of each other (again, similar to how pc104 boards are stacked). The load requirements are about 10A at 30V. Stall current can go up to 25A.

In order to protect the controller from the motor, we want to isolate the control signals. In fact, even the power supply and the grounds for the digital and analog sides are different. (Note that this means the the ground of the analog side can be at an entirely different voltage than the ground of the digital side)

My questions are: What is a good way to isolate these two domains (optocouplers, maybe?). The signaling rate between the two domains need to be around 1Mhz.

Also, I'm a bit worried about the noise from the motor affecting the digital circuitry, even with proper isolation of the control signal lines. Just being physically close to a motor sometimes even causes problems, let alone being physically connected. I would like to hear about your experiences in building motor controllers/drives to we don't make the same mistakes.


texts:
I have a LiPo that is 1800mAh,25C,11.1V. it can supply a current of 1.8*25 = 45A. I need a current of 3.5A to drive a LOAD(a Nichrome wire of length 5-6cm) and 7.4V. How do i proceed with this ?

I have tried looking into voltage regulators and Voltage Dividers
if you have a solution or a different method that is of great help as well.


texts: Is that single triangle a tri-state logic symbol or an AND gate?

texts:
Currently I'm a bit confused about that single triangle from that schematics used by an AVR-Microcontroller.
Currently I've figured out, that the:

DDRx  is on the AVR an configuration-Register (What is IN, what is OUT)
PORTx is on the AVR a register for writing or setting the Pull-Up-Register.
PINx is on the AVR a register for read-only

So the next step for me is to understand that triangle. I've searched for that and found similar symbols. One was an AND-Gate and the otherone a tri-state-logic (buffer). Has somebody an idea what kind of job the triangle implements?


texts:
I am somewhat confused with why someone would want to buffer a CMOS logic gate and what the advantages are to doing so.  Let's say I have a certain CMOS logic gate such as a NAND gate as shown below:

This is fairly simple to understand in terms of logic and input voltage levels.  You would call this CMOS NAND gate "unbuffered".  What I want to understand is if you add two NOT gates to the output of this circuit, you would still have the same CMOS NAND gate but it would be considered "buffered".  Could someone explain me what are the advantages of adding additional NOT gates at the output of a logic block and how do they buffer your output?

The circuit I am asking about would look like this:

simulate this circuit – Schematic created using CircuitLab


texts: STM32F4 Discovery + Mac OS X + GCC + OpenOCD + Eclipse

texts:
I'm interested in buying an STM32F4 Discovery from ST Microelectronics. I'm using Mac OS X, 10.8 and would like to use a toolchain including

GCC
OpenOCD for debugging
Eclipse IDE / IntelliJ IDEA Ultimate

and this must work on my Mac.

Would this setup be possible at all?


texts:
I measured with an oscilloscope the characteristic of three LEDs (green, red and yellow) connected in series with a 1000 Ohm resistor. The result of the measurement was this figure:

Why do I have negative currents?
This has been troublesome because I cannot fit the Shockley diode equation.
Is there any other equation that might be useful to fit the data?
I appreciate your help.
PS. I also measured that day the characteristic of a Zener diode, and also got negative currents.


texts: Why can't desoldering wick be used to desolder SMD?

texts:
I've read and heard (in German, as spoken in Austria) that desoldering SMD components with desoldering wick does not work.

Why?

Side note: I wouldn't care if the PCB is destroyed. I want the component.


texts: STM32 Bootloader: How to ensure only uncorrupted firmware boots

texts:
I have a custom board with an STM32F407 on it. As SWD is not available, I have to program the microcontroller through the UART bootloader.

Imagine that the folllowing sequence of events takes place. I pull the BOOT0 pin high and after reset the microcontroller enters the bootloader. At my request, the bootloader erases the flash of the microcontroller. I assume that now all words in memory are 0xffffffff. Then I send a sequence of write commands to write the flash, starting at the first byte of my fimware image and continuing to the last.

If power fails or communication is lost somewhere in this process, I have a microcontroller that has an invalid program image in flash. When the microcontroller is subsequently powered on again, with BOOT0 so as to run the application, it runs what is essentially a corrupted firmware. Depending on the program behavior and attached hardware, the results could be catastrophic.

I cannot find any kind of support to inhibit firmware startup when a corrupt image is present in the STM32F407. Workable mechanisms could be a CRC check before the CPU jumps to the firmware or an "inhibit firmware startup" bit in flash that is set (erased) first during erase and cleared (written 0) last in the update process. However, I find no such provisions in the hardware.

Write a custom bootloader into Flash that has to be programmed one time. The reset vectors are set to always jump to the custom bootloader. That one checks for the presence and verifies the integrity of the firmware. To that end, the firmware has to include size and checksum information at a place known to the custom bootloader. This solution has the obvious downside of requiring me to get hold of this custom bootloader - writing it myself or adapting something that exists - and that the custom bootloader needs to be loaded first during production.
Assume that an erased flash leads to a lock up of the processor. I am not yet this convinced that booting into an erased flash leads to lockup quickly.  Even if the processor locks up when booting firmware, I can still activate the bootloader by pulling /RST low, BOOT0 high and then releasing /RST. During update, after erase, the firmware is written starting just after the initial SP/initial PC reset vector pair. As the last step of the update, the initial PC/SP are written to the first two 32 bit words of the flash. The critical window is now only the write of these two words, reducing the chance of failure by orders of magnitude.

What are sensible strategies to deal with stated problem? Are the options presented above viable?


texts: How can STATCOM output voltage higher than system voltage?

texts:
I’ve read about the multi-pulse vs. multi-level, etc., but I’m hoping an example will be fine with just a 6 pulse H-Bridge STATCOM with triangular carrier PWM.

In order to inject reactive power, the output voltage of the STATCOM must be higher than the system voltage (and in phase with system voltage). How can the STATCOM ever charge it’s DC capacitor to a voltage higher than the present system voltage (the same voltage it uses to charge its capacitor)?

I keep reading that the STATOM can vary its output angle in order to draw active power to charge the capacitor to maintain its DC charge level, but I keep coming to the same question of how can it get its voltage higher than the system while also charging from the same system? Or is it that if the system voltage drops, then since its already charged at the higher voltage level it can then inject reactive power until the active power losses drain its charge to the level of the voltage dip at which point it’s no longer able to inject anymore reactive power. Does it reach some balance level where it is injecting reactive power which keeps the voltage up while at the same time maintaining its charge at that same level?

PSCAD has an example model of a 6 pulse STATCOM which charges its DC bus to levels higher than the present system voltage, which to me seems impossible.

Below is a picture of the 6 pulse STATCOM I'm visualizing:

6 Pulse VSC


texts:
I use boost converter TPS61089 to generate 6V3A output from 5V power. My schematic is almost the same as TI's Webench's recommended schematic except for more capacitors on the input and output. However, when I measure the output voltage, it is not stable 6V output as shown in the image below.
Is there any error in my design that cause this abnormal?

Solved: During debugging, I noticed the cable connects Vin with power supply had melted a bit, so I realized the cable may not suitable for this high current. Then I changed the cable into a wider one and the problem is solved.


texts: How does the ARM Compiler (Version 5) handle double-precision floats in devices whose floating-point unit hardware only supports single precision?

texts:
After reading ARM Compiler version 5's manual, it says that for devices without a floating point unit, floats are dealt with through software implementations, which is likely going to be slower than having a hardware unit.

However, I couldn't find any information on how the ARM Compiler 5 would deal with double precision floats on devices with single-precision FPUs. My assumption would be that it would also use a software implementation as if the FPU didn't exist, but in my code, I tried looking at the disassembly, and it appears that the FPU-specific instructions are being used!

For example,

   696:         spectral_line[2] = 6869.955;     /* B */
0x0800250A ED9F0B81  VLDR          d0,[pc,#0x204]
0x0800250E ED800B04  VSTR          d0,[r0,#0x10]

this above assembly code segment was generated by the ARM 5 compiler, even though spectral_line is an array of doubles!

How/what is the compiler doing here to handle the double-precision numbers?


texts:
In the LTspice simulation I'm needed  to used a piezo sensor LTD0-028K SO The electric scheme of this  piezo sensor is a series capacitance  with a voltage  generator .Any person can help me to determine    the adequate value of the frequency; the amplitude and the capacitance value to used it in my simulation.
In the datasheet  this pizosensor have about four resonance frequency 40/60/90/180 I Can use one of this resonance frequency   ?
the datasheet(https://cdn.sparkfun.com/datasheets/Sensors/ForceFlex/LDT_Series.pdf)


texts:
I have some difficulties understanding something. There are several discretization methods, such as zero-order-hold (ZOH), forward euler, backward euler, tustin, et cetera.

Forward euler, backward euler, et cetera discretization methods approximate the computation of a integral (see below), but what is the integral approximation when using a ZOH? What does a ZOH do?
Why does Matlab not support forward euler, backward euler, Simpsons rule or even higher order integral approximations as discretization methods? But only ZOH, tustin, zero-pole matching? Is there a reason for it?
Is it even usefull to use for instance Simpsons rule as a discretization method or even use higher order approximations? As far as I read, from http://en.wikibooks.org/wiki/Control_Systems/Z_Transform_Mappings#Simpson.27s_Rule, Simpsons rule has only one disadvantage?

For instance,

Consider the transfer function

$$\frac{F(s)}{E(s)} = \frac{1}{s}$$

This corresponds to the differential equation

$$\frac{\mathrm{d}f(t)}{\mathrm{d}t} = e(t)$$

Integrating both sides gives

$$f(t) = f(t_0) + \int_{t_0}^{t} e(t) \mathrm{d}t$$

Now t is evenly spaced, e.g., t = kT, with k = 0,1,2,... During one sampling t0 = kT and t = kT + T, the solution becomes

$$f(kT + T) = f(kT) + \int_{kT}^{kT + T} e(t) \mathrm{d}t$$

Now using the trapeziodal rule (tustin) http://en.wikipedia.org/wiki/Trapezoidal_rule. The integral is approximated by

$$ \int_{a}^{b} f(x)\, dx \approx (b-a) \left[\frac{f(a) + f(b)}{2} \right]$$

As a result, we obtain

$$f(kT + T) = f(kT) + \frac{kT + T - kT}{2} \left( e(kT) + e(kT + T) \right)$$

Using the z-transform you get

$$(z - 1)F(z) = \frac{T}{2} (z + 1) E(z) \rightarrow \frac{F(z)}{E(z)} = \frac{T}{2} \frac{z + 1}{z - 1}$$

and as such you determine by comparing the result with the very first equation that

$$s = \frac{2}{T} \frac{z - 1}{z + 1}$$

The same you can determine using forward euler, backward euler, et cetera. Now I am wondering what is the replacement for the laplace variable s when you will be using ZOH? And what kind of approximation does the ZOH use? As far as I understand you discretize the system using ZOH by applying

$$G(z) = (1 - z^{-1}) \mathcal{Z}\left\{\frac{G(s)}{s}\right\}$$


texts: PC microphone isn't outputting any signal into a scope

texts:
I have one of those average cheapo computer microphones that connects into the sound card via pink 3.5mm jack.

I wanted to find out how much voltage can I expect from it, to get a ballpark value I could use for my opamp noise detection circuit.

The microphone works fine when connected to the PC.

And so I hooked the microphone to a scope, expecting to see my voice visualized on the screen when I talk, but all I am getting is a flat line.

I looked at how other people do it, and they merely just hooked the scope directly to the jack of the microphone, just like me, and it is working just fine for them.

So, what am I doing wrong here?

Thank you


texts: Measurement of delay between two signals using MSO4104 with PyVisa

texts:
I need to automate the measurement of delay between two signals using the oscilloscope. I am using MSO4104 from Tektronix. I programmed the oscilloscope for delay measurement, but I am not getting the output.
The measurement conditions are given below:
Signal 1
High-90%,Mid,20% Low 10% and EDGE-Falling
Signal-2
Low 10% ,Mid 20%, High 90 EDGE Raising
Please see my code below. After executing this code output is not coming.
Can you please tell me where I went wrong?
import pyvisa
from time import *
rm = pyvisa.ResourceManager()
rm.list_resources()
#print(rm.list_resources())
scope = rm.open_resource('USB0::0x0699::0x0401::C002760::0::INSTR')
IDN = scope.query('*IDN?')
print ('Successfully connected to: ', IDN)
scope.write("*RST")
scope.write('SELECT:CH1 ON')
scope.write('SELECT:CH2 ON')
scope.write("AUTOset EXECute")
sleep(5)
scope.write("MEASUrement:REFLevel:METHod PERCent")
scope.write("MEASUREMENT:IMMED:DELAY:DIRECTION FORWARDS")
#For Channel_1
scope.write("MEASUrement:IMMed:SOURCE CH1")
scope.write("MEASUrement:IMMed:DELay:EDGE1 FALL")
scope.write("MEASUREMENT:REFLEVEL:PERCENT:HIGH 90")
scope.write("MEASUREMENT:REFLEVEL:PERCENT:MID 20")
scope.write("MEASUREMENT:REFLEVEL:PERCENT:LOW 10")
#For Channel_2
scope.write("MEASUrement:IMMed:SOURCE CH2")
scope.write("MEASUrement:IMMed:DELay:EDGE2 RISE")
scope.write("MEASUREMENT:REFLEVEL:PERCENT:LOW 3")
scope.write("MEASUREMENT:REFLEVEL:PERCENT:MID 20")
scope.write("MEASUREMENT:REFLEVEL:PERCENT:HIGH 80")
sleep(10)
scope.write("MEASure:DELay CH1,CH2")
sleep(10)
Delay_1_2 = scope.query('MEASure:DELay? CHANNEL1,CHANNEL2')
print('Delay is:',Delay_1_2)
scope.close()
rm.close()


texts: Is the Q-point f the zener diode in figure equal to its breakdown voltage of 4 V ?


texts:
Several designs I've seen have a load of vias underneath high frequency or analog ICs. For instance, this is a part of a PCB design for a DDS unit:

Design from http://rudius.net/oz2m/ngnb/dds.htm

Note the grid of vias underneath the AD9912. This is not a particularly good example, as the AD9912 has an exposed analog ground pad and the ton of vias is presumably just for a low impedance return path to the ground plane, but I'm sure I've seen this in lots of other places too, some of which don't have exposed pads underneath.

Is this perhaps to effectively move the ground plane closer to the sensitive IC, reducing impedance further?

Apologies if this has been asked before but I couldn't find it.


texts:
The picture below shows a PLA, I have done part (a) and found out that;
$$
F_0 = A_0 \mathbin{\oplus} B_0 \\
F_1 = A_0B_0 + (\overline{A_0} + \overline{B_0})(A_1  \mathbin{\oplus} B_1) \\
F_2 = A_0B_0(A_1 + B_1) + A_1B_1\\
$$

What may this circuit be doing, I can't see a function for it?

I have got the output fro  a program, i would want another opinion of what it may be doing, so that I can edit my guess;

-------------------------------------------------------------> EDIT

I don't get it, may be am not good at realizing patterns, I have interchanged both 1st and 3rd output and don't see a thing


texts: Can I recharge 12V batteries individually while why are attached in series?

texts:
Possible Duplicate:
  Charging two lead-acid batteries connected in series, separately (with two solar panels)

I have 12V Solar Panels and 12V batteries. But my laptop needs 17V to recharge. I could attach 2 12V batteries in series, and I would get a 24V current. And I could use this to recharge the laptop.

But then I need to recharge the battery. So, suppose I use two different solar panels for this:
Can I attach each single 12V battery to a solar panel while they are also attached in series between them?

Thanks,
Pietro


texts: How many NAND flash chips (measured in Gb) are required for a 32GB USB drive? What is the economic relationship between the two?

texts:
NAND Flash Contract Price http://www.insye.com/dp/NANDFlashContractPrice.aspx

Context, I am purchasing about 200k USB drives. I sent it out to competitive bid but I want greater insight into the BOM cost for these manufacturers. 200k units isn't enough to demand they give disaggregated pricing (big OEM orders are 1M+ units). I just did a straight transfer from Gb to GB (divide by 8). Thus, a USB 32 GB TLC-based drive would require 8 32 Gb TLC chips at $2.24 a piece, or ~$18. The problem is that I have quotes for the same USB drive from a major manufacturer for ~$10, and this includes the PCB board, the controller, the case, silkscreened logos, plus their markup. Is the spot price for NAND flash simply incorrect (error on site?) or is my math wrong?


texts: How to write subcircuits netlists in Spice with multiplicity factors?

texts: I am trying to port a behavioral device model from Cadence Spectre to Spice. In Spectre it is very easy to instantiate multiple parallel instances of a subcircuit automatically - one just calls the subcircuit - an it works for any subcircuit - with an M factor. I have seen that Spice has this functionality for some components - e.g. capacitors, but I could not find anywhere any documentation on how to do it for my on subcircuits. Does anyone know if it is is possible in Spice and how to enable multiplicity in subcircuits?


texts: My question is about TTP223 module. It is operated on 3-5 Volt DC. But how can I run it on AC supply? I mean I don't want to use DC source. I want to run MOSFET instead of Relay by this.


texts: Why is synchronous logic design not relevant for combinational logics?

texts: I have started learning about sequential logic after finishing combinational logic. I learnt that clocking/synchronizing is very important in sequential logic design. Why is that so? Why could I build MUXes, adders, ALUs without worrying about clocks/synchronizing?


texts: Obtaining data from parallel port without the "phantom power" problem

texts:
After making failed circuits in the past, I learned that the cause is that the parallel port was producing "phantom power" (aka powering the circuit). This is because I plugged my circuit into the parallel port before adding the external 5VDC to it.

Based on other ideas, My circuit idea is this:

On power-up, the 555 timer makes the output disable a 3-state buffer for a short period of time so that all outputs are high-impedance. (I forgot pull-up resistors on the buffer outputs). Shortly after, the left-most buffers are always enabled and then data from the port can communicate bidirectionally with the micro-controller. (data returns as parallel port statuses).

The micro-controller is on a separate board and the thick lines represent ribbon cable. VCC is 5VDC and both VCC and GND are connected to the separate board through the same ribbon cable as well.

My question is, will this circuit work well for two lines of bi-directional data between the parallel port and the micro-controller without having any phantom power?  (I'll be plugging the circuit into the parallel port first before VCC is connected to any power).


texts:
I'm trying to make a DC to DC boost converter without inductors. Actually, I don't know much about this kind of circuits. I did a research on the net and I found the circuit below. But the problem is I don't understand how it works. Especially that boosting stage makes no sense to me. It's quite complicated to me.

I understand that the TL494 produces PWM, but how about those caps and schottky diodes? And 30 kHz PWM? Isn't it too much for this circuit? Can I make this circuit using PIC microsontroller instead of the TL494? Can anyone please explain that?


texts:
There are some potential uses for round LCDs, for example smart watches. Searching reveals couple news from while ago but I haven't seen any in real use. What is the main reason why these non rectangular displays are not common?

http://www.ubergizmo.com/2008/05/lg-circular-shaped-lcd-display/

http://www.electronics-eetimes.com/en/2.3-round-tft-lcd-emulates-gauges-dials-or-clocks.html?cmp_id=7&news_id=222901229


texts: STM32 HAL_DELAY hangs with HAL_GetTick=0

texts:
Environment: GNU_ARM, STM32F407

Every time I use hal_delay() the program hangs just before the call to hal_delay().

I added:

printf("\n%d==>%d,",tickstart,HAL_GetTick());

in the loop of HAL_DELAY. The result is always: 0==>0

HAL_GetTick() doesn't work as expected even after I added:

HAL_NVIC_SetPriority(SysTick_IRQn,0,0);

How can I solve this?


texts: Why does an opto-isolated SSR specify a maximum number of cycles per second?

texts: The AQZ262 can switch on and off in less than 10ms. It is specified as 60 AC/DC at 6A. Yet it has a specification of 0.5cps maximimum. Why?


texts: Power Consumption of Arduino Nano ( Current Draw Low Power )

texts:
anyone got measurements of Arduino Nanos power consumption ?

It guess it should be less than e.g. of the Uno or Mega as the USB Part only get powered when connected via usb and so does the 3.3 Regulator.

Also I should be able to easily disconnect the 5 V regulator and use a DC-to-DC converter instead with ~87% efficiency 34V -> 5V . More or less there should be not much more left than the LEDs (can be disabled by software to only blink every some seconds ?) and the Atmel 328P itself?

It will be able to sleep alot and beeing woken up by watchdog timer every 8s for some measurements and communicaton


texts: Why are readings from multimeter leads are too high?

texts:
One of the multimeters I have is a cheap Craftsman 82140 65EA.  Today I was using it and it was giving wildly high readings for everything.  A battery that measured around 9V on a working multimeter read over 13V on this one and fluctuated.  I also tried measuring a few other things. A batter reading 1.2V on other multimeters read over 1.5V. A 82ohm carbon film resistor registered around 94ohm and measured 81.2ohm on another multimeter.

I was wondering what might be wrong. I changed the battery and that didn't fix it. I tried swapping out the leads with another brand multimeter that was working and then the Craftsman started giving the correct readings. This doesn't make any sense. I know wires break, but why would it read higher values for voltage     ? I would only expect higher readings on Ohms.


texts: How can we neglect copper losses in open circuit test then neglect core losses in short circuit test of transformer?

texts:
When we perform open circuit test, we measure the core losses and we neglect the copper loss resistance (and also the leakage flux inductance?). But when we perform the short circuit test we measure the copper losses neglecting the core losses.
What are the things that make that possible?
And also why only apply rated vlota7 only?


texts: What are the RAM-only microcontrollers intended for?

texts:
While looking for some detailing on part number construction for Texas Instruments's MSP430 series, I came across this wiki page: TI MSP430

There is a statement,

  "L" as in the MSP430L09x series, which indicates a RAM-only part; it must remain continuously powered to retain its programming

While I haven't able to validate the above after going through the datasheet on the official website, the question that bumps me is, if at all there is one such part, what could be the appropriate application to use it?


texts: Designing Common Source Amplifier with NMOS transistors

texts:
I am currently working on designing a Common Source amplifier with NMOS transistors. Unfortunately, I've had a few problems and don't seem to be making any progress. The requirements for the circuit are:

Driving a load of 500 Ohms
Maximum drain current of 100mA
Maximum (W/L) of 1000
Gain of 20dB (10V/V) at 10kHz
Input is a 0.1V sine wave at 10kHz with a series resistance of 25kOhms
Only source available is Vdd@5V (pictured) and GND

Furthermore, my given information is as follows: k = 10^-5 A/V^2, Vt (threshold voltage) = 1V, Lambda = 0.02

Now for what I've tried:

Here, I've substituted many different values for R5 and R4, but my general approach is as follows.

Obtain the Q-Point values of Vgs and Id
Anaylze the circuit via small signal equivalent - doing so, I arrived at the equation Req = 1/((1/R6)+(1/R5)), where Av = (-ₘ)(Req), ₘ being the transconductance value (which itself is equivalent to sqrt(2*k*Id_q)).
I calculated the input resistance as R2||R3 to obtain Rg = R2||R3 = 50kOhms.
For the output resistance, I disconnected the load and assumed the drain resistance to be arbitrarily large so that the output resistance, Ro = R5.

None of my solutions have yielded proper results and I was wondering what I'm doing wrong (any help is appreciated). Thanks.


texts: What does 48k mean when pertaining to a PIC?

texts:
While observing the memory map of a PIC controller, I observed that for RAM memory it specified the starting address and the ending address, and the difference gave the correct size of the memory mentioned in the data sheet. But in the case of program memory it was specified as 48K instructions.

What does it mean when this notation is followed? It is a 16 bit controller.


texts: Why does a DRAM cell necessarily contain a capacitor?

texts:
From some other dynamic logic structures I know that the parasitic capacitances at the nodes(gate to drain/source, drain/source to bulk capacitors) can be used to keep charge on them. Why is there an additional capacitor needed in DRAM cell then?

Wouldn't be drain/source to bulk capacitance providing the same functionality if there was no capacitor?

And maybe it isn't necessarily there but it provides better functionality. If it is the case, is the capacitor connected to the node for specifically larger capacitance?


texts: Control 12v DC motor with arduino and two relays in both directions

texts:
I am using an Arduino and two relays to control 12V DC motor in both directions.
For the first trials it worked fine. Finally, my Arduino was fried on another direction swtich.
I think there is something wrong in the schematic.
I believe that Arduino was killed by reverse voltage spike produced by motor.
Probably I need a diode across the motor. However, I have two directions here.
So, what is the proper schematic for my task would be?
Here is my schematic.


texts: VDDCORE & ENVREG connection when it is not used

texts:
I have 2 PIC18 chips the first one :
1- PIC18F46K80 working with 5V supplied from external regulator, it has a VDDCORE pin.
2- PIC18F65J90 working with 3.3V supplied from external regulator, it has VDDCORE & ENVREG pins.
I read the datasheet more than once and I didn't come to a clear point.
The question is what should I do with those pins? because i am not using the internal regulator feature. Should I tide them to ground or just let them float, Or what should I do?


texts: Design for an analogue oscillator that doesn't drift in frequency?

texts: VCOs (Voltage Controlled Oscillators) in analogue music synthesizers are notorious for drifting with temperature. What design solutions are there for an analogue audio VCO that keeps close (as in human hearing) to the frequency to which it's been tuned?


texts: Why do some PCBs have exposed plated perimeters?

texts:
I've seen a number of PCBs, largely high speed and RF boards, that have exposed copper, either at the perimeter of the entire board, or in various sections, often with stitching vias.

I've never fully understood the purpose of these. Some explanations I've heard called them "ESD Rings" used for handling the board, but that makes less sense to me when there are a lot of individual perimeters, specifically ones more inboard like in the image below. Are these just the top ground plane exposed? If so, what's the point of exposing it? I don't see how it would make a difference from an EMI perspective whether said ground pours are exposed or not.

I've also heard, and more or less accept that for an outer perimeter plated ring of this kind, it's often connected to GND and then used to connect via mounting hardware to an enclosure.

Thanks!


texts: I've found a CDA 10/10N-TE Drop Ampilifier on the street. What is it?

texts:
Newbie question: I've found a CDA 10/10N-TE Drop Ampilifier on the street. I googled it up and found out that it's a "low-noise linear distribution amplifiers, providing various
gain and output options all with extremely low distortion."

But what's a Drop Amplifier? And what's it good for? Can I use it to improve my cable TV picture?

Alternatively, what parts of it can I recycle as a newbie electronics hobbyist? :)


texts: What is the symbol on Ardunio Uno schematic?

texts:
I found the symbol:

It is available on:

https://www.arduino.cc/en/uploads/Main/arduino-uno-schematic.pdf

What is it?


texts: d Solid state relay minimum load current?

texts:
I am looking at using a solid state relay to drive a tiny pneumatic valve.  The SSR spec has a load current range of 0.02 to 3.5A. Most SSRs specify a maximum load current, which is obvious as to why. Can someone explain why there would be a need to specify the minimum load current? Here is the SSR spec:

My valve is 0.45W at 24VDC = 0.01875A, so the SSR leakage current should not be a problem. Should I be concerned about the current draw of the valve being lower that the 0.02A spec?  Could I just throw a resistor across (or in series?) with the valve coil to increase the load current?


texts: Estimating power from a voltage waveform

texts:
I'm working on a project in which I'm using a photodetector module. I'm transmitting a sine wave.
From the output of the photodetector (C12702-12) I can visualize the transmitted sine wave on the oscilloscope. Below, an image with some of these waves, just for reference.

However, in order to achieve what I'm aiming to calculate, I need the power value.
So, my question is if there's a way that I can obtain the power (in watts) from this voltage data (e.g., using the peak values).
Maybe could I somehow estimate the current or the resistance?
If that's not feasible, how could I measure the current (or resistance?) in the lab?
Thanks!


texts: Designing a constant current pulse circuit

texts:
I'm looking for help designing a constant current pulse through a variable load impedance of 10-100k (R4). The ideal response is shown below. This waveform was measured from an off the shelf instrument without access to the design files.

The attractive component is the square wave that it generates. It spends a solid couple of milliseconds at my intended current.

My current design results in a circuit response as shown below with a sharp rise then fall (not ideal).

I'm hoping for my circuit response to more closely match that of the response shown above. What modifications could be made in order to square out the waveform?


texts:
I am trying to interface a RaspberryPi (2B) GPIO-UART to the this serial servo (Hiwonder LX-224HV), as a first step before to switch the Raspberry by an ARM MCU (STM32F407ZE on custom circuit).
The servo is supposed to follow a simple protocol, however, I am unable to manage any response from the servo (neither movement or UART response).
The documentation I found about the servo is limited (Note that this is another servo model, but according to vendor, their controller is compatible with both, consequently, I assume some compatibility):
https://www.dropbox.com/sh/b3v81sb9nwir16q/AADXOwhdw7KLq5t5UM8ND3kwa/LX-15D%20Bus%20Servo?dl=0&subfolder_nav_tracking=1
Testing signal:
For testing purpose, I am sending the following message through command line:
#Some ports initialization here
echo "0" > /sys/class/gpio/gpio24/value # disable rx
echo "1" > /sys/class/gpio/gpio23/value # enable dx
echo -n -e "\x55\x55\xfe\x04\x0e\x01\xee" > /dev/ttyAMA0; sleep 0.001;
echo "0" > /sys/class/gpio/gpio23/value # enable dx
echo "1" > /sys/class/gpio/gpio24/value # disable rx

The message is made of:

0x55 0x55: transmission start tag.
0xFE: Id of the target servo, 254 means broadcast
0x04: Length of the block, including this length to
ending checksum
0x0E: 14 is Read_ID, asking the servo for it ID.
0x01: default Id (not used?)
0xEE: Checksum ~(254+4+14+1) =  ~(17) = 238

The circuit is set as follow:

simulate this circuit – Schematic created using CircuitLab
Note, I added a resistor to avoid burning any component in case of short-cut, It also allows to see variations in the signal if the servo tries to send any data.
The connection to the servo is done as follow:

0-5V to signal, high impedance most of the time.
12V to the VDD
0V to the GND

The breadboard look like this:

The result signal:
The resulting signal at the signal pin of the servo-motor is as follow:

There is no significant signal after this, which I interpret as the servo not responding for any reason.
The question:
Is there any obvious missing element in this approach? or ultimately, how to interface with this servo?
I found many others servos with similar interface, so I believe this could help further users..


texts:
I am restoring a 1930 Stutz, the headlamps originally used a resistor to dim the single filament bulbs from high to low beam.
The vehicle is now 12 volts, to dim the lamps the correct amount I have determined a 3 volt drop will be fine.

Question- what resistor is required to reduce the bulbs (two 48 watt).

Peter H.


texts: How to convert a low voltage (1 - 100 mV) AC signal in the range 1 - 10 Hz to DC for measurement using a DC voltmeter

texts: How to convert an AC signal in the range 1 - 10 Hz so that it can be measured using a calibrated DC voltmeter. In Australia it is not possible to calibrate a multimeter with a 1 - 10 Hz AC range (eg, 3458A) to the ISO 17025 standard. As an alternative, we would like to be able to use a calibrated 34661A voltmeter (or similar) in DC mode for traceable measurement of 1 - 10 Hz AC. Local ISO 17025 calibration of the DC voltmeter is possible. Our application is measurement of a low frequency A/C signal from an accelerometer.


texts: Increase capacitor voltage rating by using multiple capacitors?

texts:
I'm trying to find a small 1000µf capacitor for my Arduino shield. The shield is a digital synthesizer that is powered by the Arduino's 5v regulated power.
After discovering that the 5v supply from the Arduino is incredibly noisy when using it to generate sound whilst plugged into my computers USB port, I popped on a 1000µf cap and all was good.

Now I'm trying to find a more compact solution, as the massive 1000µf cap hanging off the shield is just too huge, plus it gets in the way of the header connections and other components on my board - making it hard to stack the shield with other Arduino shields.

I've found some nice and compact 1000µf caps, they're niobium oxide based and so they have a pretty low voltage rating.

Link to part on Farnell

My question is this: Can I use more than one niobium oxide capacitor in order to increase the maximum voltage handling?

The capacitors I'm interested in have a maximum voltage rating of 4v, I would like to double that, the voltage they will nominally have to handle will be 5v, however I'd like to have a fair bit of head room.

Thanks.


texts: Fourier Transform involving frequency differentiation property

texts:
Going through some past exams, I've came across this question;

To get started, I've noticed that it resembles to the frequency differentiation property;

Now, the differentiation was extremely messy, and as a result, the second derivative was worse than the first

Is there another property that I can use to simplify this problem or the only is using this derivative? The formula sheet we used for this paper is here and here