texts: More advice desired on my Model Railroad Building light controller circuit

texts:
Building is built in O Scale (1/48) and has 40 rooms that are lighted independently (masked out from each other with walls) Rooms are lighted with White LEDs. The rooms will light one at a time (but in different areas of the building to make it appear random)until all 40 rooms are lighted. Than they will turn off in reverse order until all off and than the cycle repeats. A 555 is used as the clock with about a 5 second pulse rate so the complete cycle will be a little over 3 minutes. This is a large model building for my train club that has open houses for the public. Purpose of circuit is to make the building have a different look every time it catches your eye. The LEDs will be powered from 12 volts, the logic will be accomplished by the 555 as mentioned, along with recently purchased TLC5916 8 Channel LED Sink Drivers (5 of them cascaded to get 40 channels, 1 per building room)

I have had some success on a dual chip (16 bit) circuit on a breadboard but know it is not right as it requires a zener diode to make it work and when I tried to expand the circuit out to 5 cascaded chips on a production wire wrapped board it failed miserably.

I am pretty sure Pin 2 (SD1) and Pin 3 (CLK) need to be tied together on all five chips to Pin 3 of the 555 Timer. The question is than, what do I do with Pins 4 (LE(ED1), Pin 13 OE(ED2), PIN 14 (SDO) and I presume Pin 12 (OUT7) of the 5th Chip needs to get tied somewhere else besides the final 40th LED it drives to reset the circuit, but where and how? I am at a loss, have spent many hours and tried every combination of connections possible. Any ideas or schematics would be greatly appreciated!

TY in advance


texts:
I've got a servo setup with an Arduino, and I'm looking for a good way to switch the power to the servo on and off. I've come up with the below circuit:

My intention behind the circuit is to set the MCU Pwr Signal to HIGH when I want the servo to receive power. Then, I'll send the signal through the MCU PWM to the Servo signal connection to control the servo. When I want to disable the power to the servo, I'll set the MCU Pwr Signal to LOW.

My question is, will this work? Have I got my circuit correct?

Thanks in advance!


texts: Improving dynamic range of an ADC by stitching waveforms together

texts:
I am trying to improve the dynamic range of an ADC, by using a second ADC which is the original signal attenuated by a known amount (\$x\$ dB).

So the two signals could be approximated (ignoring any phase differences):
\$y_1(t) = A\sin(\omega t)\$
\$y_2(t) = y_1(t)\$ attenuated by \$x\$ dB

I originally thought about solving this problem by using a 'stacked ADC' approach, which would be to have both signals be analysed and to choose the output of the adc which has not saturated.

However given that the frequency and attenuation of the waves would be a known quantity, would it be possible to combine or 'stitch' these waveforms together into one waveform mathematically by post-processing, and improve the dynamic range that way?

The problem was put to me by my professor but I'm at a loss as to how I would go about it.


texts: How do you make a digital counter circuit which counts to 10 minutes and 15 minutes, it will give a signs buzzer?

texts: I asked in this site before, but apperantly I don't quite understand. I want to make a digital counter circuit which it counts to 15 minutes for my big project in my campus . When the circuit counts to 10 minutes, it will give a signs a buzzer. Same when it continues to 15 minutes, it will give a signs a buzzer again. (the circuit is for public speaking, so the speaker knows that he or she already went speak for 10 minutes and 15 minutes). We weren't allowed to use an Arduino, Microcontroller, PLCs, and IC NE555. The requirements of this project is to use breadboard or PCB, LED (this LED acts as a sign buzzer), each IC Decoder and each IC counter (not a built-in IC Counter and Decoder, so it's a seperate Counter and Decoder), any type of flip-flop (SR/D/JK) wether it's counter UP or DOWN, 7 segments display and 12 V battery. I'm kinda stuck here and I'm thinking it's impossible to make such a thing. Do you have any idea guys? I had an idea to use crystal oscillator, but I still don't understand


texts: The Op-Amps don't work correctly for this circuit [Thermocouple]

texts:
I'm trying to connect a thermocouple to an Op-Amp to amplify the output of a thermocouple. this is the circuit:

Also for R17 I put a 5k09 resistor instead of 6k8 and for R18, 1k032 and for R19, 366k and my circuit doesn't has the P1.

The Op-Amp is LM358N. when I use a potentiometer for the input(HEATER+) to test and check the circuit, everything work correctly but when I connect the circuit to the heater(or thermocouple because it's a soldering iron), the Op-Amp get freezed! :) I mean it just show a little and constant amount in the output (while the input is changing). why? something must be wrong.

Please consider that this circuit should work and when I measure the positive of the Op-Amp, there is the voltage as I expected.

For supply I use this(24V 5A Switching Power Supply) and this Buck Converter to make 5v for circuit and before the buck converter put a 470uf electrolytic capacitor and after it put a 10uf electrolytic capacitor and 100nf ceramic capacitor.

I get the circuit from this project. here is the schematic:

What have I done so far?

I have changed my Op-Amp to some other but I had the same problem. even with a perfect Op-Amp like AD8572ARZ-REEL7. it's an auto-zero drift rail to rail I/O Op-Amp and a good choice for such a job. I have changed 4 Op-Amp to amplify the output of thermo for this job but still the same problem!

I have changed the supply to a 5v battery(because I thought there is noise in the supply) and I saw that the output of the Op-Amp start to changing but the changes was a small amount between 32mv and 13mv.

A bit information from this post about this type of soldering iron and its tips:

  T12 have thermocouple in series with the heater with a voltage of
  around 9mV at 450 degrees celsius, so the voltage to the heater must
  be turned off to measure the voltage of the thermocouple. Don't
  measure the resistance of T12. It is pointless to use it when a
  thermocouple is already available, and is far more precise than
  resistance.

  I have made a controller for T12 myself. Here's how it works:
  - the 24V AC from transfomer is rectified but not filtered
  - this rectified 24V AC is the power to the T12, and is switched on and off for a millisecond on every half period of the AC, using P
  channel MOSFET.
  - when the voltage is turned off, the voltage of the thermocouple is available at t12 terminals, so it can be measured by an ADC in MCU
  - the MCU controls the heating using slightly modified PID algothitm, regulating how many mains periods the heater is turned on, and how
  many mains periods it is turned off.

Edit: I changed the supply to this:

Breadboard Power Supply with 3.3v & 5v Outputs

And applied the heat and I got the output as I expected!! then the problem is the switching supply! any idea to solve this problem?


texts: Will 74HC595 as LED sink damage LED when pin goes high?

texts:
If used as a LED sink, what happens if a 74HC595 pin goes high?  Might the LED blow?

I expect that when a pin is low, current will sink and the LED will light.

What about the opposite condition?  When a the pin goes high, might there be risk of blowing LED's due to reverse flow?  Why or why not?

simulate this circuit – Schematic created using CircuitLab


texts:
I'm testing my first ever OP amp circuit and I ran into a problem.

I have done the following circuit (see picture). The 0 - 3.3V called uC is coming from a Nordic nRF24LE1 PWM and RC filtered output.
I'm using a LM741CN op amp and try to follow the circuit on allaboutcircuits (http://www.allaboutcircuits.com/textbook/semiconductors/chpt-8/voltage-to-current-signal-conversion/).

I assumed that if the uC outputted 3.3V i would get around 20mA through the 85Ohm resistor and if it output 0V I would get 0mA and everything between for the other values.

But for some reason it will never go over 3.37mA. When I output around 520mV the difference between OP amp inputs are almost zero. But when I step up to the next level, 573mV I start to get some voltage between the Op amp inputs (47mV for that level) and it increases the more I raise the input voltage. Why is this happening. Is the op amp not suitable for this type of operations. If so what OP amp should I look for and what is the key specifications?

Best regards RS


texts: Using ADuM3150 for SPI Interface with Arduino

texts:
I am trying to use an isolator for SPI communication with the Arduino. I am presently using the ADum3150. You can find the datasheet here. There are some delays associated with this arrangement and the ADum3150 provides a 'delayed clock' as mentioned in page 17 of the datasheet to read the output in sync.

The arduino has only clock, miso,mosi and ss. How can I use this delayed clock function on the arduino ?


texts:
I am looking at an analog synthesizer circuit the design of which incorporates several "ringing oscillators", which look like this:

I understand that this is a resonant system that enters oscillation whenever the input transitions from low to high or vice versa, which fades in amplitude over time to zero, until another impulse is received. I'd like to understand what exactly is happening in the op-amp circuit to accomplish this, so if anyone could provide a scientific analysis I would greatly appreciate it.

In case it is helpful, this is the larger circuit I am looking at: https://www.cgs.synth.net/modules/v8.html


texts:
I bought some time ago a 2nd hand Philips PM 3253 including probes which shows on the oscilloscope probe inputs:

1 MOhm, 20 pF

While the probes I got with it show:

1:1 1.5m 10:1
130pF +oscCap    10 MOhm/14pF
max 42 Vpk

They seem to work fine though.

However, I would like to use them on the Philips PM3110 which shows on the probe inputs:

1 MOhm, 30 pF

Also here it seems to work.

However, I would like to ask  if I can expect problems/safety/malfunction issues when using the probes on the PM3110 oscilloscope.


texts:
I am looking for a way to convert two TTL pulses from two MCU outputs, to one wire (referenced to common ground on both ends), over a long length of cable. I would like to do this with as little latency as possible, so a digital format may not be ideal, I was hoping to find a way to do this using just analog components.

My initial thought was to boost Output 1 to +15V, and to invert and boost Output 2 to -15V, sending both over the same wire, then find a way to strip them at the other end of the cable and level shift back to TTL. Output 1 and Output 2 will never occur at the same time.


texts: High voltage indicator circuit and short/open circuit protection best implementation

texts:
I am going to designing a PCB for a high voltage, 6kV and 3kV @ 10mA/200mA (660W) power supply for my Ph.D. As you will know, the equipment needed to work at this level is very expensive and as a student, the money available in my account is limited yearly.
With this in mind, what are the quintessential safety precautions that will be needed for my lab work, and possibly within the DC/DC supply itself? For example, is a short circuit or open circuit protection best, or should I have both? At the moment, all I have in my design is my isolated feedback circuit which will isolate the control board from the converter output. But I am worried that faults will destroy my equipment and they will be costly to replace.
If anyone has any recommended techniques for open/short circuit protection at such high voltages, it would be recommended. I plan on having a pulse-to-pulse current limit of the primary transformer current, but I would like to add some more features to address my concerns of faults such as short circuit protection on the secondary current level. I am thinking of having a comparator circuit driving some LEDs as a voltage level indicator also, for example. This will show me how much voltage is on the secondary side and indicate when safe working voltage is reached. I have also come across a circuit which is for overvoltage and overcurrent protection which looks like it might do what I want: https://www.qsl.net/yo8tot/overvoltage.html

But I would also like a level indicator of sorts where maybe an LED lights when a low/safe working voltage has been detected and I am able to modify my circuit safely if that makes sense.
I would rather design in now for the most likely faults rather than worrying about it once I come to the bridge. The load is purely resistive for the purposes of my project.
Any recommendations are appreciated.
J
I will be using digital controller, but am not against using some analog components to interface between my controller and the output voltage in case they are faster and more reliable for example.


texts: How to force Keil to compile with software float for STM32?

texts:
When I am trying to create a float variable in Keil to program STM32 it just crashes.

I had a look online and as far as I read it tries to use hardware floating point unit (which is not enabled and I don't want to use it).

If I want to use software based floatin point then I have to specify that in my compiler.

How do I do that?


texts:
I'm currently designing a circuit to convert an infrared signal (e.g. from an IR transmitter or a TV etc. remote control) and turning it into an audio signal. The first stage of the preamplifier is shown below.

I've worked out the resistor values for R1, R4, R5, R6, and R7. What I don't understand is what the peak voltage will be at VOUT.

According to the SFH213's datasheet, the photocurrent is 135 microamperes. How do I use this to calculate the peak output voltage?


texts:
I am currently in the process of designing a high-voltage bias supply for use with an ionization chamber. The voltage source itself is taken care of however I need a unity buffer to drive the guard of the chamber, also raising it to 500V. A simple diagram is shown below.

In this design they mention it has to be a low-input impedance amplifier serving as the buffer because we are interested in current signals from the chamber. How would I go about picking the correct amplifier to use in this circuit? I've used op-amps to amplify very small voltage signals before, but never current signals and especially never at these voltages.


texts: Stepping over a library (in-built) function in CodeWarrior

texts:
I am using CodeWarrior Development Studio to program and debug the NXP FXTH870911.
To understand the functionalities, I downloaded an example project from their website. It is called FXTH_FW_BLE_Beacon_by_GenFSK.
So NXP has some built in functions in a section of the flash. These functions are factory loaded and their source code cannot be viewed. One such function is TPMS_LF_ENABLE() as shown below.

Since the code of these functions are not accessible, we can't step into the function (or you will be shown a "no source available" error). However, the problem is, that even if I try to step over this function, it still steps inside and gets stuck there. I see the "no source available" message and the disassembly as shown below.

My question is - How do I exit out of this function or not enter it in the first place?
UPDATE:
Upon expansion of the line TPMS_LF_ENABLE(CLEAR); the following macro is visible:
((void(*)(UINT8))(((UINT16)0xE072)))
When I look at the disassembly during debugging, this is what is showing at the location 0xE072:
FF STX ,X
Does this new piece of information help in understanding what the problem might be?


texts: Electric field and potential plots across a pn junction diode

texts:
Below shows how the charge density, electric field and potential is varying along the horizontal axis of a pn junction diode under equilibrium:

I can understand the the charge density plot easily because the left part of the depletion region is negatively charged and right part is positively charged after diffusion of electrons and the holes end, and the rest part of the diode(besides the depletion region) is neutral hence zero charge density there.

How are rest of the plots i.e electrical field and potential plots are derived/obtained from this charge density plot? Some mathematical or physical interpretation would help.


texts:
I know that a circuit is second-order circuit if there are two storage elements.
I used pspice to simulate

and I got this graph

I feel like it is not correct.
Please tell me my mistake.

when there is only L present, the graph would look like this:

when there is only C present, the graph would look like this:


texts: H Bridge Control using Raspberry PI / Micro controller

texts:
I am looking for input on this circuit that I have designed. I am currently working on a project called the Net-EEL RC Car. It is an RC car that will be controllable using Network Socket Servers / Clients. Therefor, you will be able to control an RC car sitting at the network server with a gaming steering wheel.
I am trying to design my H Bridge circuit to control the speed and direction of the motor I will be using. I am using the Raspberry PI as my Data Receiver and will be using the PI to control the H Bridge.
Here is a schematic I have designed.

So far I have the following

Raspberry PI will generate PWM signals to control a BJT. This BJT is used to control a Mosfet. I have chosen a BJT due to the VGS requirements of a Mosfet. It requires me to supply a gate voltage that is equal to the source I am controlling, therefor I am using a BJT to apply the source voltage to the gate of the Mosfet.
I have looked into to using Logic Level Mosfets, which will remove the need to use   BJT's in order to provide a proper gate voltage to the Mosfets.

I also have a Micro controller that will be used to monitor the voltage level of the battery, I am running the battery voltage through a voltage divider so I can properly read the voltage level using a 0-5V ADC.

I believe that my circuitry will work, however I am looking for some input from the community.
Thanks in advance.
** EDIT **
I have added the resistors between the Gate of the Mosfets to ground in order to turn off the transistors if there is no signal present at the BJTs base.
** EDIT 2 **
I have also considered using logic levels mosfets instead of needing a BJT.


texts: Solar powered iPhone for remote monitoring

texts: I want to find a way to use a solar panel to power an old iPhone running a single app to continuously collect temperature and humidity data in remotely located beehives. The iPhone must be continuously charged in order to run the app. I have tried a small solar panel with the iPhone plugged directly into it, but it doesn't keep the iPhone charged if there are a few days of clouds/rain. Once the phone runs out of power the app shuts off and does not restart once power is supplied again by the solar panel. I have also tried a 7500mAh battery pack plugged into the output USP port of the solar panel (to bank electrons from the panel). The battery pack is also simultaneously plugged into the iPhone to keep it charged. This arrangement seemed to work but only for a day. Finally, I've tried various solar powered battery packs but they shut off once the battery is full and don't provide a continuous charge to the iPhone which then runs down and the app shuts off. I'm not sure if I need a bigger solar panel, a bigger battery pack or if this arrangement is not compatible and there is another solution. This is proving to be a harder problem to solve than I thought, but I keep wondering if I am missing something. Thoughts much appreciated from this community of experts!


texts: Are there any such things as real and reactive energies just like real and reactive power? if so, how is reactive energy dissipated?


texts: Sorry for the crappy schematic, but how do I wire up a potentiometer to have variabile resistance (like the symbol an the bottom). I'm using it in a 317T voltage regulator circut.


texts: I am trying to make a circuit for controlling a spark plug using 555 IC.I found two circuits on the forum which are very similar to each other but from what I have observed, they are using different diodes and I want to know the difference they would make on my circuit. As it can be seen in circuit 2, they are using two IN4148 diodes while the other just uses BYQ28E-200 diode array which I am unsure what it does to the circuit. It is to be noted that circuit-2 works for 1 minute and the  MOSFET is heating (slowly), it uses a snubber circuit to protect against voltage spikes but it doesn't really seem conventional to be using the two IN4148 diodes because they might not allow the current to flow. My question is, does the BYQ28E-200 diode array would work the same way as two IN4148 diodes in this circuit configuration? What really is the purpose for a diode array in this? I am trying to see if I even need it after all for what I am trying to achieve. Thanks.


texts: Solving for y parameters using a system of equations

texts:
simulate this circuit – Schematic created using CircuitLab

Question: Find the y parameters for the circuit shown below.

My attempt:

KCL

\$I_1 = I_3 + I_6 \$

\$I_4 = I_3 + I_5\$

\$I_5 = I_2 + I_6\$

EFC:

\$I_3 = \frac{V_1 - V_a}{20}\$

\$I_4 = \frac{V_a-0}{10}\$

\$I_5 = \frac{V_2 - V_a}{4}\$

\$I_6 = \frac{V_1 - V_2}{8}\$

Solving this systems for \$ V_1 \$ and \$ V_2\$ yields:

\$ V_1 = \frac{35}{2} + \frac{25}{2} \$

\$ V_2 = \frac{25 }{2} + \frac{27}{2} \$

Therefore our Z parameters are as follows:

\begin{bmatrix}
\frac{35}{2} & \frac{25}{2} \\
\frac{25}{2} & \frac{27}{2}
  \end{bmatrix}

I know how to find the y parameters using delta Z, but I thought there was a way to solve for these items directly in the system of equations. Can I solve for the y parameters directly?


texts: IEC connector with both Line and Neutral Fused

texts:
I require an IEC connector mains entry with both the Line and Neutral fused. The double fuse is required in order to be compatible with reverse polarity of the mains connector on the other side of the cable.

I tried googling or using a "farnell" (distributor) list:
http://www.farnell.com/datasheets/2328240.pdf
But to no avail. I may be blind to the exact data I am trying to find.

Maybe you can help out or have something else in mind that does the job.


texts: Why should I bother with Frequency Response calculations in a Spilt-rail buck regulator design?

texts:
I'm looking at an existing implementation a split rail step-down power supply  (application report). I would like to know what's the big deal with frequency response in the reference design?

I think the point of these calculations is to determine the value of a compensation resistor & Czero & Cpole capacitors but my question is what are the risks of using a completely wrong value of these components?

Please keep in mind I'm not advocating not performing calculations or not using the right parts. I simply want to know what could happen if wrong values were used.


texts: Low power serial bluetooth module with Arduino

texts:
I plan to use the HC-06 serial bluetooth module with an Arduino Leonardo. To my knowledge, the Arduino's serial pins output at 5V with 40mA of current. The HC-06's datasheet says it will accept input at 3V - 4.2V with 20mA - 40mA of current. I'm more of a programmer than an electrical engineer, but this tells me I will need a resistor between the Arduino's TX pin and the HC-06's RX pin. From my calculations I will need a resistor with 82.5 Ohms of resistance:

$$r = \frac{V}{I} = \frac{3.3V}{0.04A} = 82.5 \Omega$$

Is this the correct way to solve the problem? Online I've seen people solve the exact same issue using a voltage divider with a 10kOhm resistor leading from the Arduino's TX pin to the HC-06's RX pin and a 20kOhm resistor leading from the HC-06's RX pin to ground. So, what's the correct way to solve this problem? If a voltage divider is the solution, why and how does it work? Or why does simply putting in a 82.5 Ohm resistor not work?

EDIT: For simplicity sake, let me reiterate my question from a more general perspective. The HC-06 module requires a power supply voltage of 3.3V (which can come from the Arduino's 3.3V pin) and will also only accept logic inputs at 3.3V. So, what is an easy way to achieve this voltage reduction for the serial wire?


texts:
This is an image from a book showing us how to solve BJT circuits via AC analysis:

So I understand that when doing AC analysis to ground all the DC voltage sources but I don't understand why. Can anyone explain this concept, the book just says to ground it as if it is some simple EE concept that needs no explaining.


texts: Using USB-6210, relay, to control a 12V double solenoid valve

texts:
I am kinda new for the wiring of the relay. I have read some posts in forum regarding connecting the solenoid valve to the DAQ. But I am still not too sure how it all should be done. My objective is to use USB-6210, a crydom SSR (DC60 Series), to control a 12 V 5/2 way double solenoid valve for the extension and retraction of an actuator. I am just wondering how the schematic should be. Based on some googling, I come up with similar idea. Can someone give me some advice?

Since I have a double solenoid valve, I am wondering can I just wire one of the valve ( treating it as just a single valve?) or do I need to wire both valves (which I am not too sure how) to achieve my goal?

Thank you so much in advance!!!!

The valve I have:

https://trimantec.com/products/airtac-4v200-solenoid-valve-4v22008ft

The SSR I have:
http://www.crydom.com/en/products/catalog/dc60-series-dc-panel-mount.pdf


texts:
I want to use the above flash memory to store some data with my MCU, but the flash isn´t answering on the 0x9F instruction:

I use SPI mode 0 and a 125 kHz clock frequency. The Reset signal of the chip is high.
Is there anything that I must do first (i. e. to initialize the flash)?


texts: STM32L0 GPIO EXTI interrupt not triggering

texts:
I'm working with an STM32L073RZ on a custom board. The board is in STOP mode and I have a pin (PB_5) configured as a rising edge interrupt. I'm using ARM Mbed OS 5.12.0 but primarily working with the HAL API.

Here's the code I have so far; main.h is just a bunch of pin definitions. I'm expecting pin PB_4 to toggle every time there is a rising edge on PB_5.

#include "main.h"

void SystemClock_Config() {
    __HAL_RCC_PLL_DISABLE();

    __HAL_RCC_MSI_ENABLE();

    __HAL_RCC_MSI_RANGE_CONFIG(RCC_MSIRANGE_5);
    __HAL_RCC_MSI_CALIBRATIONVALUE_ADJUST(0x00);

    RCC_ClkInitTypeDef RCC_ClkInitStruct;
    RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_SYSCLK;
    RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_MSI;
    RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
    RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
    RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;

    HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_1);

    __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE3);
}

void Pwr_Config() {
    __HAL_RCC_PWR_CLK_ENABLE();

    __HAL_RCC_WAKEUPSTOP_CLK_CONFIG(RCC_STOP_WAKEUPCLOCK_MSI);
}

void GPIO_Config() {
    GPIO_InitTypeDef GPIO_InitStruct;
    GPIO_InitStruct.Pin = GPIO_PIN_All;
    GPIO_InitStruct.Mode = GPIO_MODE_ANALOG;
    GPIO_InitStruct.Pull = GPIO_NOPULL;

    __HAL_RCC_GPIOA_CLK_ENABLE();
    __HAL_RCC_GPIOB_CLK_ENABLE();
    __HAL_RCC_GPIOC_CLK_ENABLE();
    __HAL_RCC_GPIOD_CLK_ENABLE();
    __HAL_RCC_GPIOH_CLK_ENABLE();
    __HAL_RCC_GPIOE_CLK_ENABLE();

    HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
    HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);
    HAL_GPIO_Init(GPIOC, &GPIO_InitStruct);
    HAL_GPIO_Init(GPIOD, &GPIO_InitStruct);
    HAL_GPIO_Init(GPIOH, &GPIO_InitStruct);
    HAL_GPIO_Init(GPIOE, &GPIO_InitStruct);

    __HAL_RCC_GPIOA_CLK_DISABLE();
    __HAL_RCC_GPIOC_CLK_DISABLE();
    __HAL_RCC_GPIOD_CLK_DISABLE();
    __HAL_RCC_GPIOH_CLK_DISABLE();
    __HAL_RCC_GPIOE_CLK_DISABLE();

    GPIO_InitStruct.Pin = GPIO_PIN_5;
    GPIO_InitStruct.Mode = GPIO_MODE_IT_RISING;
    GPIO_InitStruct.Pull = GPIO_PULLDOWN;

    HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);
    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_5, GPIO_PIN_RESET);

    __HAL_GPIO_EXTI_CLEAR_IT(GPIO_PIN_5);
    HAL_NVIC_SetPriority(EXTI4_15_IRQn, 0, 1);
    HAL_NVIC_ClearPendingIRQ(EXTI4_15_IRQn);
    HAL_NVIC_EnableIRQ(EXTI4_15_IRQn);

    GPIO_InitStruct.Pin = GPIO_PIN_4;
    GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
    GPIO_InitStruct.Pull = GPIO_NOPULL;

    HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);
    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_4, GPIO_PIN_RESET);
}

void StopMode_Enter() {
    HAL_PWREx_EnableUltraLowPower();

    __HAL_PWR_CLEAR_FLAG(PWR_FLAG_WU);

    HAL_PWR_EnterSTOPMode(PWR_LOWPOWERREGULATOR_ON, PWR_STOPENTRY_WFI);
}

void HAL_GPIO_EXTI_Callback(uint16_t GPIO_Pin) {
    HAL_GPIO_TogglePin(GPIOB, GPIO_PIN_4);
}

int main()
{
    while(true) {
        load_cell_en = 0;
        modem_reg_en = 0;

        SystemClock_Config();
        Pwr_Config();
        GPIO_Config();

        StopMode_Enter();
    }
}

As far as I'm aware, simply overriding the HAL_GPIO_EXTI_Callback function is the way to handle an interrupt, but the pin never toggles. What am I missing here?

In STOP mode I believe I should simply place the CPU into STOP mode once and do any processing in an ISR as opposed to, for example, a state machine?

Thanks.


texts: Convert DC 0 to +1V signal to -1 to +1 signal

texts:
I need to convert a 0V to 1V measurement signal to -1 to +1 volt. What is the best way of achieving this? I've tried searching but can't seem to find anything relevant, as I'm not entirely sure what to search for.

Thanks.


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I am very new to FPGA and sorry for this elementary question. I just made a very simple XOR code like this with Webpack ISE to download to XC2S100 ( just for test!) but it does not work.
EDITION1: According to comments, I checked DONE situation after programming and it is in High state. Also added pull down resistors to a and b. Also added a 1KΩ pull down resistor to TMS. Now it works fine but after I restart the device, it does not work any more.It seems the configuration memory is erased after shut down.

1- Obviously this code sythesizes well, and simulation is OK. Then Implemented -> Assigned pins -> re-implemented -> and finally Generated  .bit file ( this sequence: )

2- I also used the pins that don't require  Vref. ( a:P3 , b:P4, out:P7). Here is a screenshot of pin assignment. At the end clicked Save:

3- Then I re-implemented and checked the pins in design summary. All OK:
4- I have one of these Alkamar download cables. I connected the pins as recommended and ran iMPACT . It finds the device well and reads its config also well. I was happy when I saw "Program Succeeded " message! but when I connect VCCO voltage (3.3v) to P3(a)  or P4(b), nothing happens in P7(out).I double checked everything but of no avail!
What is going wrong there?

Here is the schematic I use:
1- Test board:

2- Power Supply:

3- Crystal Oscillator part ( Not used in this test ):

This is the programming cable:


texts: Is an opto-coupler fast enough for this application?

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I am counting the pulse edges from a quadrature encoder with an FPGA and using opto-couplers as the encoder is powered with 12V and the FPGA inputs are 3.3V. The encoder is 1000ppr with 2 channels and I count both the rising and falling edges.
The opto-couplers are ILD74 (Link to ILD74 datasheet) and the inputs to the FPGA are pulled up with 10K resistors, like in the image at the bottom of the question. The FPGA inputs go through inverters to match up with the encoder outputs, as an encoder pulse pulls the FPGA input to ground.
So I am unsure if these opto-couplers switch fast enough. The encoder will run at max 4500rpm, so per channel this is an output frequency of roughly 75kHz (1000ppr * 4500rpm) / 60 = 75,000.
The ILD datasheet has a ton-toff switching times of typically 3us which is over 300kHz, so I think these opto-couplers should be ok?
Also I'm interested to hear if anyone has any recommendations to this circuit or any advice as to how encoder outputs are connected to microcontrollers / FPGAs in general.
Thanks everyone.

EDIT 1
I have added the output of my encoder at approx 5000rpm. The output frequency is around 85kHz.

EDIT 2
I am waiting for parts to arrive and I will get back if I have anymore questions. I will close the post when I get the problem working. Thanks everyone!


texts: Possible to have a lamp controlled by both a simple switch AND a relay

texts: There's a lamp in my son's room that we use for reading and the bedtime process. I'd also like to link it to a relay connected to a Particle Photon that we could signal him down for dinner with. But I'd like both methods of turning the lamp on and off to work independently of each other. Is this possible?!


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Does the definition of duty cycle indicate only the percentage of time that the level is asserted?
For example, if a 10 Hz square wave is de-asserted for 5 of those 10Hz cycles and asserted for 5 of the 10Hz cycles, would that represent a 50% duty cycle? If I represent each of the de-asserted 10 Hz cycles in a single second as a 0 and each of the asserted 10 Hz cycles in that same second as a 1, I could represent a 50% duty cycle as 0000011111. But if it is only the percentage that matters, I could also get 50% by the sequence 0101010101. In the definition of duty cycle, is it necessarily the case that the asserted periods be consecutive and that the de-asserted periods also be consecutive?


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I have such a reverse polarity protection circuit for the power supply:

The MOSFET used has a maximum VGS of 10 V, so that's why there's a Zener diode of 7.5 V.

But what happens if I connect, let's say, 12 V? I don't fully understand how this Zener diode is working.

It will start to conduct from 7.5 V.
So from 12 V it will "conduct 4.5 V" to the gate.
So the voltage on the gate relatively to the ground will be +4.5 V.
But the voltage on the gate relatively to the source (VGS) will be -7.5 V (4.5 V - 12 V).
This MOSFET needs around -2 V to start to conduct. It gets -7.5 V, so is that why it's working?

Am I correct with this? Do I understand this properly?


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We are using a MAX9926 in Adaptive mode to detect zero crossing of a crank signal. Its mode cannot be changed (PCBs made) however we have a particular use case where the signal presented is as pictured. The issue is the adaptive threshold goes to 2/3ds of last peak, so after the big peak, 85mS (the timeout of the chip) of the smaller peaks are missed until it resets on the next cycle.

How can we attenuate the larger pulse only (as the average voltages will all increase as RPM of the engine increases.? Note that average frequency will bvary with engine RPM from say 6000 - 60Khz, so it cannot be a simply filter.


texts: How to determine the angular velocity of a DC motor correctly

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I am given a small robot track vehicle, which uses a DC motor to power the left tracked wheel and another DC motor to power the right tracked wheel. I am using an optical wheel encoder to measure the angular velocity of the motor. Now I want to determine the precision of the optical wheel encoder. To do so, I need to know the EXACT angular velocity of the DC motor. Can somebody tell me how to determine the exact angular velocity?

The datasheet of the motor does not contain any electrical or torque constant. I am only given the no load speed, no load current. I get to choose what voltage I apply to the DC motor myself (in the code). Can I calculate the angular velocity the motor should have based on the voltage that I apply? Or do you know an easier or better way?

I am using this motor: TFK280SC-21138-45


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I've been studying inductors and wanted to understand the behavior as a circuit is switched off just like the one below, when the transistor is normally conducting and suddenly is turned off by, say, a microcontroller signal. I know it's weird but please, do not consider the Protection Diode across it, I could neither find a better image nor design one circuit here since I'm asking it via cell phone.

Thus, I know that V=L*di/dt and it's the induced voltage formula across an inductor. I know it's going to yield a large voltage as it's quickly turned off, because di/dt is going to be a huge factor. Also, the current which is supposed to flow through the inductor as t-> (infinite) is I=(V+) /R where R is the coil resistance.
In addition to that, I know that as the transistor is turned off, the current in an inductor cannot instantly change, so it's going to be (V+) /R  in the very first moment the transistor is off, and assuming it'll have a really high resistance when off, the voltage across the inductor should be large in order to try to maintain the current flowing just like before.

My point is I get confused on how to think correctly about it.
What is actually the correct way to think? The way by which di/dt is large and so will be the voltage across the inductor or the way by which the current will try to be kept constant and as the transistor is going to be a huge resistance when turned off, the voltage across the inductor will then be large?

Thank you for any help.


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I have this boolean expression: F1 = a1'a2' + a1a2'.

Could it be reduced even more?


texts: Relation of sweep time and number of measurement points in Spectrum Analyzer

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My configuration is as follows:

RBW: 100 kHz
Detector: MAXPEAK
Frequency span: 1.1 GHz - 1.8 GHz
Spectrum Analyzer: R&S FSV 30

I do not fully understand how the sweep time and number of points are related. If I increase the sweep time and keep the number of measurement points constant, does that mean that the time per measurement point increases (i.e. dwells), or that there are just more measurements being taken at the same point and then being averaged? My mission is to detect peaks of spurious signals with an unknown delta_t of ~ 30 ms with a fixed stepped scan.
And how does the number of points relate with the formula SWT = k * (span / RBW^2)?
Thank you very much.


texts: Confusing peltier efficiency COP/Volts and COP/Amps graphs question

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Is peltier efficiency (COP) based on current and not voltage and could I have any voltage I want and get a high COP if I limit current?

Whats confusing is that one graph shows efficiency based on Voltage and the other graph based on current. These graphs are from 2 different peltier manufacturers and these graphs are just examples of what I saw,  I got to the possible conclusion that COP is based on current.

This is what I am thinking in my head when I came to it:

I remember that Voltage and current is directly proportional to each other so if I would put 10V through the peltier and with that it would draw .5 amps (only an example , don't know the exact current draw with 10v). If I would limit the current to .5 amps with a power supply since and I picked a much higher voltage , (the current draw would be much more than .5A if I didn't limit the current) the COP value stay exactly the same or close to each other , or even rise ?  I also know the efficiency is based on heat , and less current
means less heat , more efficient.

I don't think the power (watts) would affect the COP even though the 1st graph says the higher the voltage less efficiency (COP). With the higher voltage and same current that is higher watts which could make the COP go up since the peltier might remove heat much faster from the side. What doesn't make exact sense is the first graph basically saying the COP drops with voltage. I am thinking what that graph is possibly saying is that as the voltage goes up the current increases as well.


texts: How can I isolate voltage reference from ICSPCLK programmer output

texts: In my application I use PIC16F676 microcontroler with the LM282 (https://www.onsemi.com/pub/Collateral/LM285-D.PDF) external voltage reference (for A/D converter) connected to the RA1 pin. This pin is also used during ICSP (Internal Circuit Serial Programming) as a ICSPCLK clock signal. How can I isolate this voltage reference from ICSPCLK programmer output and succesfully programing the chip?


texts: Designing a common base amplifier to meet given specifications

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I designed the circuit as below and I know that common base amplifier should have a unity current gain(usually <1)  but I'm getting a very high gain. What might be the reason for this, is something wrong with the topology?

DC op simulation:


texts: What causes the background hissing in car speakers?

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My knowledge of electronics is very limited, but I think I should be able to understand the answer to this.
In a car, if I turn the volume up as high as it goes with the auxiliary cable plugged in, I can get a constant, quiet, hissing noise to come out of the speakers. What causes that "static"? Rogue current flows, the air touching the male end that's sticking out, or other things I just am not thinking of?


texts: What is the reasoning for the arithmetic functions on the 74181?

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I don't understand why the 74181 operates the way it does. It does provide the full set of logic functionality (AND, NAND, OR, NOR, XOR, shift),but its arithmetic functionalities are not so clear. For example, it does not contain A - B and A + B in the same mode.

Could you provide some history background about how it was designed?


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I am looking to switch a water solenoid valve using two water level switches, one will be placed at the top of a tank and will be NO (when water level is between full and empty) so that it will send a signal to the relay when the water reaches the top to stop the solenoid. The other switch will be at the bottom of the tank and will be NC so that it will send a signal to the relay when the water reaches the bottom of the tank to open the solenoid.

The switching will be done with a latching relay. The diagram of its pins is here:

I simply do not understand this enough to figure out how to wire this. The switches are SPST. The switches, solenoid valve, and relay are good for 120V.

What I am asking for is this: on that diagram, where do the switches connect? Where does the solenoid valve connect? Where does mains power connect? Lastly, do I need any resistors on the control side of the circuit?

Thank you so much in advance for your time.


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I am working in RF and if i go through articles it is seen that in every point where the RF signal flows it is said we need  LC matching networks or Pi filters, but i cant get the sole reason why they are used.
If it was for impedance match only for matching 50 ohm , we can do it by a trace only ryt because we can get 50 ohm through  that trace only by adjusting the trace width,length etc?
Are those filters or matching networks used to for tuning  or harmonic imbalance,if it is how do we design that?


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I'm connecting 8 switches on a breadboard, with a common ground (the already-connected line of the breadboard):

Problem: these switches are always on,  like if the 2 pins on the common line make them pressed.

I thought that a solution could be to rotate 90° the switches, but then they don't fit on the breadboard anymore (one cannot use the common horizontal line for ground anymore).

I can't believe there isn't a natural solution to connect 8 such switches on a breadboard.

Is there a solution for this?


texts: Inductor equivalent of capacitor's charge

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Because inductors share similar equations in their charging/discharging cycles, I am wondering if inductors have something like charge.

Capacitors have capacitance and charge while an inductor has inductance and _?
Is there a V = Q/C function for inductors?


texts: Difference between same value ceramic capacitors from different manufacturers

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I want to know the impact of the Ceramic capacitor parameters. I have a 4.7uF,25V,0805 capacitor from 2 suppliers Murata and TDK. on comparing the parameters i see that the highlighted parameters are different. When are these differences important? What sort of application should consider these differences?

I am using them as connector end capacitors for ESD protection.


texts: PCB design consideration for a SMA antenna

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I am designing a PCB with the transceiver SX1231 (868MHz) with a SMA connector for the antenna. I don't know much about antennas. I would like to know if there is some parameters I need to be careful to keep the circuit adapted (to reduce reflections of the signal's power).

In another PCB that a friend developed, I see a lot of Vias (a bunch of them, one after the other) around the pads of the SMA connector, what is the reason of this?

Do I need to consider the width of the traces that connect the capacitors and inductors between the transceiver and the SMA connector? How can I calculate this? Do I need to take in consideration the material of the PCB?

Is there something I need to take in consideration about the ground planes?

Thanks for your help.


texts: Bidirectional protection or isolation for generic digital communications

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I am redesigning a company product, it is a product for automotive maintenance and diagnostics. Currently in the product there is a FET BUS switch to perform the interface between the microcontroller and the product connector, to this connector can be connected several other devices that communicate with the microcontroller present in the product. Often it is necessary to perform external assembly to the  to use the product, the assembly depends on the needs of the custumer and needs to be done by him. There is no single protocol and the communication used is diverse, so the lines need to be bidirectional, the only need is that the logical voltage levels for communication are digital of 0 and 5V.

The question I need to deal with then is the following: for reasons of incorrect assembly or carelessness with connectors on the part of the customer, there may be overvoltage in the communication lines and this is burning the bus switch. The bus switch we are using today, the SN74CBT3244DW, is powered by 5V, but it is very common, for the reasons described above, that customers accidentally put 12V on the communication lines. So,I need to reduce the amount of products that return for maintenance because of this issue.

To solve this issue,  I imagined some solutions:

1) The product would no longer present the Switch bus internally, the idea would be to use an adapter that would be connected to the product and would make the interface between the product and the customer's assembly. In this adapter, there would be a protection circuit and, if happens some problem to the adapter, there would be needed only an exchange of the adapter and the customer would not need to send the product for maintenance, so, the customer would not be unable to perform other services offered by the product.

2) For the adapter circuit, the idea was to use some type of protection or insulation. However, as the lines of communication need to be bidirectional, I am facing difficulties in finding circuits that offer protection, or isolation and that have relatively low cost.

Would anyone have any circuit suggestions?


texts: Combining multiple 5v outputs to one output

texts: I have this board https://www.amazon.com/gp/product/B00UUROWWK/ref=ppx_yo_dt_b_asin_title_o06_s00?ie=UTF8&psc=1 It has 3 5V outputs on it and I was wondering if there was a way to combine them to make 1 15v output? If so how can I do it? Any help is appreciated.


texts: High pass filter attenuating frequencies equal to cutoff frequency

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I'm developing a HPF to attenuate frequencies below 30KHz.

My input voltage is a sinusoidal voltage from 0V to + 5V with a frequency of 30KHz.

My objective is to attenuate frequencies below 30KHz including the DC component.

In the end I want to have a sinusoidal voltage from -2.5V to +2.5V and with a frequency of 30KHz.

My HPF is a passive RC circuit. C is equal to 10nF and R is 510 Ohms. The cutoff frequency therefore equals 30KHz. I used this site to help me with component values: sim.okawa-denshi.jp/en/CRhikeisan.htm

But in some simulations that I'm doing with Proteus my signal comes out with attenuations:

What happened? What is the correct cutoff frequency and why? Tks!


texts: Troubleshooting Circuit (Make: Electronics Experiment 11)

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Would someone be so kind as to help me figure out why my circuit is not working?

I am having difficulties with Experiment 11, Steps 2 & 3 in Charles Platt's book. The experiment is designed to teach me how I can use transistors to amplify a signal, and to audibly hear that amplified signal through a 8 ohm speaker.

Here's the schematic:

Here's a picture of the circuit I built:

I am able to build the oscillator with the LED on the top, no problem, but I'm not getting any sound to come out of the speaker. My multimeter tells me that current is going through the transistor. When I scratch the leads of the multimeter against the emitter and collector leads of the transistor, I do get some noise from the speaker, so I know the speaker is not broken.

Any ideas?


texts: Where can I get a display screen with 30 Hz or less refresh rate?

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I am experimenting with a camera recording a display screen.
Based on what I have read - camera recording a screen will have flicker if the refresh rate and frame rates are not synced.

My mobile camera records at 30fps. I wish to check the amount of flicker if the refresh rate is 30 Hz or less.

For this purpose where could I get a display with 30 Hz refresh rate ?

In case finding such equipment is not possible, how can I create one ?

Can I transform a video in such a way that it comes across as a lower refresh rate display to the amera to check for flicker?


texts: What is the difference between pulling up multiple digital IC pins to Vdd with a single resistor vs. one resister per pin?

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I am not very good at understanding current, so I was hoping someone could help calrify the difference between pulling up multiple digital IC pins to Vdd with either a single resistor OR one resistor per pin?

if you are connecting multiple pins to the same resistor, would you just use a higher value resistor? Ie. instead of 4 10k resistors connected to Vdd, pull-up everything with one 40k resistor? Or perhaps the other way around?

Example:

VERSUS


texts: What are the purposes of {L5, R5} , {C10, C11} , {R2, R4} in this HF upconverter circuit ?


texts: Need help with Laser Driver Voltage with Specific 3-PIN Diode

texts: Thanks for reading. I was hoping someone could help me with the electronics of my project. So I am trying to drive a L980P200 - 980 nm, 200 mW, Ø5.6 mm, A Pin Code, Laser Diode. Link to spec sheet from Thorlabs. I have been browsing forever for a laser diode driver and I ended up ordering the LD3000R - Laser Diode Driver, 2.5 A Constant Current. Use this link here from Thorlabs. I don't know if this will work. I need this laser driver to be able to modulate current at 10khz to compliment my photodetector which I will be using a lock-in amplifier with. I ended up buying Thorlab's T1G - Laser Diode Bias-T modulator (I can't post more than 2 links). Could anyone tell me if this will work? In addition could someone tell me if I am able to drive this laser diode? The driver is rated higher than the laser diode laser= 1.5V, 200mW output power and 300-400mA driving current, while the driver=2.5 A, 7.7 V.


texts: why voltage follower can't reach target voltage

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I want to use OP amplifier AD822 to build a voltage follower which generate exactly the same output voltage with the input voltage. The power to OP is 5v.  The input signal is 3.3v, the period is 20ms.

However, the amplitude of output voltage(green) is not 3.3v but only 2.8v. Can someone tell me why there is the gap between the input and output voltage? How can I get the output voltage with the exactly the same value as input?

Edit:
Thanks to Dwayne Reid's comment. I changed the resistor from 100 to 1k and the output voltage is almost the same as the input voltage.


texts: Putting an ESP8266 to sleep via either of two signals

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I've got a circuit which I'm hoping to use to shut down my ESP, except where an interrupt happens from an external chip (MCP23008 GPIO expander), or I have chosen to manually keep myself enabled.

Being a bit cheap, I wanted to do this using diodes - D1 is being fed from the interrupt line on the MCP23008, and D2 is being fed from another GPIO pin on the ESP.  It seems that this works for keeping the pin held high (the ESP boots just fine on power up, when the INT pin is high by default, then I bring the GPIO pin high to keep it up), however when the interrupt pin goes low (I set it to Active-High mode), and I turn off the GPIO, the pin remains at 3.3V - even though the two sources on the other side of the diode are now at 0V.  Clearly the capacitance on the input is retaining the charge and there's nowhere for it to go.
So I've put a 1K2 pull-down resistor in - however this doesn't seem to have quite the desired effect, and the pin sits at about 2.5V (3.3 - diode drop, more or less) and the CPU does not appear to run.  I'm not sure if it's just because the pull-down is too strong.
What is the correct solution here, and can it be done with just diodes and/or MOSFETs (and passives)?
EDIT: this is a followup to ESP8266 Wake from deep sleep with an interrupt (not a duplicate as the question is different)


texts: Connecting PLC with sinking output to PWM analog converter

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I am using this pwm converter with this PLC. The PLC digital out is sinking transistor type.

I changed the pwm converter jumper switch to 24V and connected +24VDc from PSU to PWM terminal and one of the PLC's digital out to GND of the PWM port. Then I measured the analog out when the pwm input is 0% and it keep showing 10V while it is supposed to be 0V. Does anybody know where did I do wrong and how to correct it?

My current wiring:


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There is a lot of helpful information on the internet about getting the OV7670 camera up and running but the following problem has me a bit stumped.

I am using a Maple r5 Board (STM32F103RBT6) to grab an image from this model of OV7670 with AL422 buffer on a PCB.

I've uploaded the circuit schematic for this device from ebay and my code here.

My code grabs one frame from the OV7670, stores to AL422 and then relays it back to the PC with UART over USB connection (very slowly!). As you can see below, the image is initially unaligned, then I only get 640 by about 300 pixels, then the image repeats. I am just reading the grayscale Y channel. From the angle of the camera, it looks like the right hand of the image is repeated to the left.

I have the camera focused on my oscilloscope because that image is rapidly changing to test if the repeats are subsequent frames or the same image. The pixels are identical which I think means the read pointer is wrapping around the buffer outputting the same data. I tried reading out further rows from the buffer and I get the same shortened frame repeated over and over.

UPDATE:
I checked the product sheet for the AL422B. This buffer can hold 393,216 bytes. With two bytes for a pixel (one for color, one for grayscale) this means only 393,216/2 = 640x307 pixels can be stored! I think this explains what is happening here! Now my question is, are there any settings for the OV7670 to output only the grayscale channel so I can store one whole frame!

PS: I am new here so please let me know how to ask questions more effectively.


texts: Can electrical wires be ruined by overheating?

texts:
I have a friend that works with automotive mechanical sorts of things, and he told me that he had a pair of jumper cables that was ruined by too much current; it wasn't that the insulation melted: he said that the wire didn't carry hardly any charge after that.

I can't think of any reason why this would be. If a wire carried too much current it would obviously get hot, and that heat would eventually melt insulation, but even then, the copper (or whatever it is) should be able to carry charge just as well as before, shouldn't it? When it actively was hotter, the resistance would increase and this would impede the flow of charge, but once it cooled down, it should work like before, as I understand things. Does something occur when copper gets to a certain temperature that could permanently impair the electrical conductivity?

I'm not an electrical engineer or even an electrician. I just do some mechanical and automotive work and I have a little bit of experience with physics.


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Let's suppose that \$E \gt V\$. Now, the voltage \$V_b\$ at point \$b\$ will always be \$V\$ and will not depend on \$E\$.

Similarly the voltage \$V_A\$ at point \$A\$ is \$V_E\$ which will be negative in order to make potential difference across the galvanometer wire equal to \$V\$.

My question is that why, at point \$b\$, \$E\$ has no effect on \$V_b\$?

Also, is it true that if \$E>V\$ then the current will be supplied by \$E\$ and not \$V\$?

The potential at c =0


texts:
I am developing a mechanical arm that can be pitched remotely at a certain angle using a high-torque servo motor. The servo needs to keep the arm at a precise position for any give amount of time and, when needed, "uncouple" so the arm can move freely on its hinge. I am new to servos, so this question may seem naive:
Can servos have a true neutral gear, as in a car's gearbox, where wheels spin freely?


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After searching for a about 10 hours, this is my last hope.
I've made my own development board, with Atmega8. The program is also ready.
I bought Atmel USB ISP 10pin from a local shop to transfer program, but when I have downloaded burner softwares non of them can recognize usb to transfer the program.
I have connected the pins and the LED lights on the usb ISP and on the board are on.

In device manager the USB (it is divided into two components) is showed under
Human Interface Devices

HID-complaint vendor-defined device
USB input device.

Errors:

AVRdudess: could not find USB device with vid=0x16c0 pid=0x5dc vendor='www.fischl.de' product='USBasp'

ExtremeBurner: connect USBasp on USB board.

I am using Windows8.1 64bit.


texts: How to prevent common ground circuits messing with each other

texts:
I made an Arduino based 18650 battery tester that has 4 identical circuits that charge and drain.

Testing one battery at a time gives one set of results which I deem to be correct but testing more than one can give skewed result sets all around.

I assumed this was because each battery can be on different charge/drain cycles at any given time and is interfering.

I rewired all the common grounds to one exact point on the Arduino and used the exact same length cables. This helped a little bit but there is still a difference.

How would you go about resolving this in a way simple folk like me can understand?
Like a basic component I could put in between the negative of each battery to isolate them?

Edit:
Added diagram (there are 4 identical circuits all connected to the same GND). I failed to mention that the batteries are not powering anything. The 5v 4A PSU powers the arduino & four chargers. The charger boards should be fully powered off while draining & vice versa


texts: If there are more capacitors, are there more amperes?

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I'm really new to electronics, and I'm wondering if adding a capacitor increases the output current. I have the following questions:

Say for example, I have a 5V 1.0A Source, does the output current capacity increases if there's capacitor in parallel?

Say for example, I have a 5V 1.0A Source, and 2 x 3300uF Capacitors in parallel, and the output is drawing 5V 3.0A, can it accommodate the 3.0A requirement of the output?


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Trying to solve this problem where direct cache would outperform associative:

Propose you have a cache with a line size of L 32-bit words, S number of sets, W ways, and addresses are made up of A bits. Assume that the cache is word addressed, i.e., the low two bits of the address are always 0.

Come up with a sequence of addresses for a MIPS processor for which a direct-mapped cache of size 16 words, line size 4 words, outperforms a fully-associative cache with the same line size, using LRU replacement.

What I've gathered:

Direct Mapped Cache means that a block of memory is mapped directly to line of cache
MIPS uses Fetch, Decode, Execute, Encode, Memory (this might be irrelevant here)
LRU replacement - Oldest Used is replaced
Word are least significant bits which represent the address from main memory

Cache structure:
Tag   |   Line   |   Word

Word represents least significant bits
Tag represents the unique identifier for that
Size 16 words would be 2^4 bytes

number of lines would be cache capacity / line size =     ? / 2^4

I'm not sure how to draft this cache. If we have 16 words, 4 per line it would that would mean 4 total rows. I don't expect a full answer but an indication on how to draft the direct mapped cache and come up with a sequence would be greatly appreciated.

UPDATE:

I attached a picture with a cache that has 8 memory addresses mapped to 4 lines. . With this, a sequence of

  1234567824136857
  direct mapped:  MMMMMMMMHHMMHHMM (4 Hits)
  f. associative: MMMMMMMMMMMMMMMM (0 Hits)

However, I can't figure out how many lines there should be (16 words, line size 4 words). How many memory addresses will be mapped to how many lines in the cache? My image has 8 to 4. Do I need 16 addresses mapped to 4 lines in the cache?


texts:
I have a SoC connects to a DSP with SPI. They are all powered by 1.8V, so I didn't even compare SoC's Voh and DSP's Vih at the first time, they should working fine. However, yesterday my colleague told me that the SoC's Voh cannot satisfy DSP's Vih, so I have a detail look:

You can see the SoC's Voh is at least 0.75*VDD, which is standard 1.8V CMOS Voh (Vcc-0.45).

For the DSP's Vih, it is 0.8Vdd, which is higher than standard 1.8V CMOS Vih (0.65Vcc).

So from the datasheet view, I cannot connect these SoC and DSP together?
Or the minimum Voh is based on highest source current, I need to consider the output impedance of SoC, and input impedance of DSP or maybe also capacitance?


texts:
I'm using a D2PACK triac model ACST830-8G datasheet

According to datasheet (over 1cm2 cooper) it supports 2A, considering Tamb = 43°

TABLE

GRAPHICS

I want to use this triac inside a case and without heat sink.

Inside a small case, can I assume this triac will handle 2A at 43 °?

I worried about this point because, as I understand, it will not be in "free air convection" as the second image says.


texts: A question about using active filter to mitigate both differential and common mode noise

texts:
There is a single ended floating source connected to a data-acquisition device. The system is categorized as single ended earth grounded. Here is the recommended wiring as I use:

Now imagine the source is unbalanced and causing common mode noise and also imagine there is differential noise from the source as well. Would an active filter take care of both in this case?

Below is the details of wiring in my mind so far:

(please left click to view the diagram)

By using the active filter as above would the common mode noise due to unbalanced source be cancelled along with the differential noise?


texts: CAM 5 LASER CUTTER : needing to change the laser tube

texts:
My boss and I discovered that one of the laser tube needs to be changed, and when we figured which one needed it, I told him not to touch the red wire, that there may still be power in it. Well he did, needless to say he's not going to do that again.
 I need to know how to safely discharge the power supply, and or, tube. So we can change the tube.

Off the top of my head it's a 20,000 volt power supply with a 100 watt laser tube. I can tell you more on Monday when I get to work


texts: Adding High Byte and Low Byte of LSM303DLHC Accelerometer Output

texts:
Interpreting LSM303DLHC Accelerometer Output

Hi all,
     This is my first StackExchange question ever, so I will do my best to be specific and offer as much reference as possible. I'm currently working on a navigation module which uses a PIC16F873A microcontroller to read data from a GPS via the USART module and from a LSM303DLHC Magnetometer/Accelerometer using I2C. At this stage of the project, I'm only trying to use accelerometer data, which I currently do by running the PIC in master mode and reading from the appropriate registers. The way the accelerometer works is the X,Y and Z acceleration data are stored in six different consecutive registers inside of the linear accelerometer register area (i.e. OUT_X_L_A (28h), OUT_X_H_A (29h) ... OUT_Y_L_A (2Ah), OUT_Y_H_A (2Bh) ... OUT_Z_L_A (2Ch), OUT_Z_H_A (2Dh)). My I2C_Accelrometer_Data(unsigned char reg_address, unsigned char ack) function reads in one byte of data at a time so my code will read the low byte and then the high byte from the next register, store them in an array of unsigned chars and add them together. According to the datasheet: LSM303DLHC these bytes are expressed in two's complement form.

A section of my C code (XC8 compiler), which I've partly adapted from here on page #6 handles it as follows:

    unsigned char ACC_Data[6];

                                            ACC_Data[0] = I2C_Accelerometer_Data(0x28, 0);//X_Low Byte
                                            ACC_Data[1] = I2C_Accelerometer_Data(0x29, 0);//X_High_Byte

                                            ACC_Data[2] = I2C_Accelerometer_Data(0x2A, 0);//Y_Low_Byte
                                            ACC_Data[3] = I2C_Accelerometer_Data(0x2B, 0);//Y_High_Byte

                                            ACC_Data[4] = I2C_Accelerometer_Data(0x2C, 0);//Z_Low_Byte
                                            ACC_Data[5] = I2C_Accelerometer_Data(0x2D, 1);//Z_High_Byte

                                            int Ax = (int) (ACC_Data[1] << 8) + ACC_Data[0];
                                            int Ay = (int) (ACC_Data[3] << 8) + ACC_Data[2];
                                            int Az = (int) (ACC_Data[5] << 8) + ACC_Data[4];

                                            char Ax_str[];
                                            char Ay_str[];
                                            char Az_str[];
                                            itoa(Ax_str, Ax, 10);
                                            lcdcmd(0x94);//third row, first column position
                                            send_string(Ax_str);

                                            itoa(Ay_str, Ay, 10);
                                            lcdcmd(0x9E);//third row, 10th column position
                                            send_string(Ay_str);

                                            itoa(Az_str, Az, 10);
                                            lcdcmd(0xD4);//4th row, first column position
                                            send_string(Az_str);

My question is: because the numbers are in two's complement binary, won't that mess up the way they are added especially since the bytes are being stored as unsigned chars? Or can I do simply what I have done above to convert these two bytes to an int? Basically, the goal to get these numbers onto an LCD screen by then converting this integer into the appropriate string, I'm just not sure if I'm using the data correctly here. Thanks in advance for any insight.


texts:
I am looking for a good method to clean used solder paste needles immediately after usage. I know they are for one time use, but at this moment I have to clean the needles.

Currently, I clean them in diluent using a thin wire to get all the paste out. Is there a better way to clean used solder paste needles?


texts:
How can I select generically re-usable parts for the unique things I build?
What are good approaches for building unique devices, so that when I no longer need them,
it's relatively easy to disassemble them into parts I can re-use on the next project?

This question focuses on when I build one or a few physical objects.
The "design for disassembly" techniques used in some sustainable designs may also be related, although that focuses more on physical objects built in larger quantities -- is there another question that focuses on that?
Reusing abstract designs for hardware is already covered in another question.

There are lots of items I build exactly one of:
the first (or the 17th) breadboarded prototype of the electronics of a product;
various unique templates and jigs used in production;
test jigs, etc.

When they reach the end of their useful life, they get tossed in the scrap box.

I build them out of
(a) random scrap still hanging around from previous projects, and
(b) new stuff we got with (perhaps shortsighted) focus on this particular project.

I can't help but notice that the shiny new stuff ends up in 3 categories:

a Some things -- solderless breadboards, soldering iron, 1/2 inch (12 mm) socket wrench, pin headers on 1/10 inch centers, alligator clips, velcro cable-ties, etc. -- get re-used over and over again.
b Some things that at first glance appear very similar -- 15/16 inch socket wrench, etc. -- only get used for one job, and are never used again. While those things were necessary for that one job, and so perhaps I should think of them as a "sunk cost" that I've already made back the return on their investment. Since they are still functional, it seems wasteful to simply throw them away. So they end up taking up space and collecting dust indefinitely.
c Some things can only be used once -- zip ties, solder, etc. Sometimes it seems a little wasteful, but (if I maintain a short-sighted focus on this particular project) these disposable items are the cheapest way to get things done, and at least they don't tend to accumulate and take up space.

Category (b) is the worst.
If I knew at the time I was buying that part what I know now after watching that part collect dust for years, I would have either saved a little money and bought some disposable category (c) part instead, or else spend a little more money and bought some more generally useful category (a) part instead.
(Or perhaps not. Sometimes I absolutely need some super-specialized part for some project).

Do you have any tips for recognizing ahead of time that a part I am about to buy is highly likely to end up gathering dust as type (b), so that I can try to substitute something that is more likely to be type (a) or type (c)?
Any other tips for making it more likely that parts and tools I hope to re-use actually are re-used later?

Rather than make one all-singing, all-dancing do-everything hyper-specialized PCB that I'll only use this one time and then toss the whole thing, are there good ways to partition the design so that at least part of it is re-usable later?

What are good ways to improve physical hardware reuse?


texts: Measuring current with ammeter. Circuit doesn't works anymore

texts:
I have a very basic ammeter (UNI-T UT33D). It has 3 connector: the COM and 200mA/V/Res and finally a probe for 10A Max.

I know that current need to be measured in series.

If I interrupt my circuit (9V battery + blue led) positioning the ammeter in series and with probe on 200mA/V port, the LED doesn't lite and I read 000 on screen, whatever scale I'm using.

If I put the probe on 10A, the LED lights and I read 0.01 on screen.

Too little current? The fuse and the battery of ammeter is ok.

Is it normal that the circuit doesn't work? I don't think... Thank you

EDIT

I did buy a set of 10 fuse fast blown. All ok. Now I can measure the current and the led is lite with ammeter in serie.

I did check old fusible with continuity test with the ammeter... dead.

Thank you


texts:
I was trying to repair a blender whose speed buttons were not working. I thought of removing the speed regulating circuit altogether and directly connect power to the motor. Now, when I run the motor I see sparks in it. I understand some initial sparking may be normal, but is a continued sparking also normal? I am not sure if there were sparks before removing the circuit, I never ran the blender with its bottom removed earlier. Is it safe to use this blender now?

I have a small clip here: https://vid.me/VI2n


texts:
I am designing a PCB and I just want to make sure nothing is wrong before I send it off to the fab house. If one of you knowledgeable stack exchangers could give me some feedback, I would really appreciate it.

Here is the schematic :

and here is the board :

I don't have enough reputation to post a link to the eagle files, so if anyone wants them,
just let me know.


texts: can SPDT relays replace SPST switch? Or does it depend on the particular implementation of the relay?

texts: I am working on SKU consolidation and my concern right now is if I have a cheaper option of SPDT switch with all the ratings same as SPST switch which is currently used. Can I replace it? Or does it depend on the particular application of the relay.


texts: What type of ADC input filter for extremely noisy DC signal

texts:
I normally get by with lots of Googling and reading but I've been at this one for days and I'm starting to wonder where to look.

I'm trying to design something called a torch height control for a cnc plasma cutting table. For those that don't know, a plasma cutter slices through metal with a high velocity jet of "plasmerized" gas (air in my case). A torch height control monitors the arc voltage, which represents the torch height from the metal surface. If the voltage is too high, a signal is sent to lower the torch, and visa versa. The plasma "arc" is DC voltage, but as you can imagine there's one heck of a lot of noise on the DC lines. You'll have the switching noise (frequency ????) from the inverter, plus whatever nasty spikes get added by the plasma arc itself.

So I need to be able to read this voltage about 30 times per second. My thinking was to use an active low pass filter to filter out everything above this relatively low sampling frequency. Using filter design software I could get a fairly good Butterworth filter BUT the phase delay through this filter was around 40 milliseconds, much more than I'm happy with. I want my closed loop control to be as tight as possible so 40 mS is quite a bit of lag.

Does anyone have any alternative suggestions for how I can extract a "clean" DC voltage measurement 30 times per second without the phase lag. Am I going to have to do something like high speed ADC sampling with averaging.

The plasma voltage will be attenuated with a resistor network so I have a full scale voltage about 2v.

Thanks,

Keith.


texts: Why will i calculate the wrong power ,but right loading resistance in this circuit?

texts:
The question wants me to calculate that what is the \$R_L\$ value when we                                                                                have the maximum \$P_{R_L}\$ from this circuit

simulate this circuit – Schematic created using CircuitLab

My thinking

When we are calculating the equivalent resistance,we can see the original circuit as the  circuit in the left hand below ,and the left hand circuit is equal to the right hand circuit,by the way,\$R_{10}=R_1//R_3,\$ and \$R_{12}=R_2//R_4,\$

simulate this circuit

So according to \$P_{R_L}=I^2 R_L=(\frac{60}{2.1+R_L+0.9})^2R_L=\frac{60^2}{(3+R_L)^2}R_L\$,and use the Maximum Power Transfer Theorem,we can know \$R_L=3Ω\$, we can have the maximum \$P_{R_L}\$ from this circuit.

So now we can know the voltage of \$a\$ point,\$V_a\$, and the voltage of \$b\$ point,\$V_b\$ is as below

\$V_a=60\frac{3+0.9}{2.1+3+0.9}=39V\$

\$V_b=60\frac{0.9}{2.1+3+0.9}=9V\$

So the voltage of the loading resistor is \$39-9=30\$,so the \$P_{R_L}=\frac{V^2}{R_L}=\frac{30^2}{3}=300W \$

However,the answer shows me

Answer:

simulate this circuit

The \$V_{th}=60\frac{3}{7+3}-60\frac{1}{9+1}=12\$,and \$R_{th}=(7//3)+(9//1)=3 \$ ,so \$P_{R_L}=\frac{V^2}{4R_{th}}=12\$

I found that the main difference between solution and my thinking is that our \$V_{th}\$ are not the same ,my \$V_{th}\$ is the voltage of the loading resistor=30V,but solution's is \$12V\$ ,Why can't the voltage of loading resistor  be calculated as i think??where am i wrong?


texts: In solving an op amp problem with two voltage sources, why can't we combine it?

texts:
Say we have a circuit like

Why can't we solve by doing $$V_{out} = -(V_{in} - V_{offset}) * (R_f / R)$$

We know that \$V_{out}\$ for a typical inverting amp (that doesn't have \$V_{offset}\$) is just \$-(V_{in}) * (R_f / R)\$, so why is \$-(V_{in} - V_{offset}) * (R_f / R)\$ for this diagram not correct?

My reasoning for \$-(V_{in} - V_{offset}) * (R_f / R)\$ is because we know \$V_{offset}\$ is the constant voltage for the positive side of the op-amp.

\$V_{in}\$ decreases until it reaches \$V_{offset}\$.

Thus, can't we just think of it equivalently as \$-(V_{in} - V_{offset}) * (R_f / R)\$?


texts:
I am working on a PSU that converts 230 VAC to 12Vdc (0.1 A). The board has the necessary clearance and creepage distances. Would it cause any safety issue (IEC60950) if the 0.8 mm (or 1.2 mm) thick PCB is used instead of 1.6 mm?

EDIT: There is only one trace under the HV side (highlighted one), the rest is the ground


texts: What size of the fuses does fluke multimeters use?

texts: So I burnt my fuses today using my AstroAi multimeter. I went to several hardware stores in Seattle and they only have fuses with 5mm x 20mm and 1/4 x 1-1/4 inch. I bought the 1/4 x 1-1/4 ones and they don't fit in my multimeter. I measure my multimeter fuse and it has a very weird size which is 6mm*29mm and the closest on Amazon cost 25 USD in total for the two types of fuses I use. Since my multimeter only cost 35 I think it's a bad idea to buy those fuses on Amazon. Is there another brand of the multimeter that uses a more common fuse? Should I get a fluke multimeter? And could I find the replacement fuses easily in the hardware store?


texts:
I haven't done and studies in Op-Amp category yet but I watched a (trusted) video on Youtube and one thing is not quite logical as the next sentence: "No current flows in or out of the inputs of operational amplifier", as says Dave Jones from EEVblog on Youtube (this video: https://www.youtube.com/watch?v=7FYHt5XviKc).

So, I am wondering if he meant like there is a really small amount of current flowing in op-amp on the inputs, or there isn't any of current on inputs at all?

I am sure there must be at least some current on inputs (for base if BJT or for gate if FET/MOSFET for sure).


texts: How to create a photogate that can span tens of feet with multiple sensors to capture items of various sizes passing through it?

texts:
I'd like to create a photogate can create a plane of detection approximately 3' tall by 8-10' wide, with the ability to detect items as small as 6" tall pass through it.
I am envisioning two vertical poles, with photodetectors placed every 4-5" along the length of the pole.  On one side would be IR LEDs and on the other would be IR photodetectors.
So my specific questions:

I imagine I will need some kind of lens to focus/collimate the IR light so that it will not spread out over the 8-10' between the poles - ideally so that each LED is paired with a detector on the other pole.  Is that correct?  If so, any suggestions on what to use?

I don't need to know which photodetector(s) are triggered - just that at least one of them is.  With that in mind, any pointers on designing the circuit as simply as possible (i.e. not going crazy with comparators).

Ideally these can be used outside in direct sunlight - so what is the best way to overcome the IR spit out by the sun?  I was thinking that each LED should emit a particular high-frequency pattern, which it's paired detector would look for.  That way we're not just looking for that spectrum of light being present or not, but that it is coming from that specific emitter.  This would seem to greatly increase the complexity, however.

Here is an example of what I am referring to:


texts: I have an elderly but much loved Kenwood cd/radio/tape stack that has blown a fuse. The fuse rating is T800mAL 250volt. For reasons beyond me these don't seem to be available in the UK and the Amazon US supplier does not ship to UK either. Could someone tell me, please, if there is a compatible fuse that I can install.


texts:
I have couple of lead acid battery reserved power supplies with output voltage from 9.5 (battery discharge cutoff) up to 13.9 (while charging the battery), intended for use with CCTV cameras, but current cameras and DVR allow only 12V+-10% and can't tolerate 13.9V.

What type of DC-DC converter can work with input both lower and higher than output?

Each camera draws up to 0.7A and, there are 8 of them connected to first PSU + DVR drawing 4A on second PSU.


texts: Will brushless controller of Current: 17±1A work on a 13A battery?

texts:
So I recently bought a
'Motor Brushless Controller for 36V/48V 350W' from Ebay for my e-bike
and then when I contacted the seller about the 'Current' because I didn't know what it meant, and he told me:

"That means the current data is not a fixed value, but fluctuating. It will up to 18A or down to 16A."
(still waiting for his response)

This is the item details:

Specification:

Rated Voltage: 36V/48V
Rated power: 350 watts
Current: 17±1A

Item on Ebay:
 - http://www.ebay.com/itm/361462855827?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

So I just wanna ask a simple question, will it work on my e-bike?
I have:

48V 13A Battery
250W Motor Controller (wanted to switch to 350W)
250W 8Fun rear wheel hub motor


texts: I designed a dev board for the STM8L151F2, and even using an external programmer and external power the STM8 has only been able to be programmed twice. Here's the schematic, everything done in eagle.  I've gone over every pin with a multimeter, nothing is bridged and everything is connected to the correct pin. The STM8 is in the right orientation. With the CP2102 it was recognized as a USB device, though never has allowed me to interact with the STM8. Am I making some rookie mistake? All the pins are connected as per the TAC and datasheets descriptions AFAIK


texts: Why is total harmonic distortion defined in the following manner?

texts:
So the total harmonic distortion is defined as

$$THD = \sqrt{\frac{V_{2}^2 + V_{3}^2 + V_{4}^2...+V_{n}^2}{V_{1}^2}}$$

which means Total harmonic distortion is defined as the square root of the ratio of the average power delivered by harmonic components divide power delivered by non-harmonic component. So why include the square root when it would make more intuitive sense not to include it in the first place?


texts: What is exactly modeled by 'transit time' in SPICE diode model?

texts:
I'm trying to find a precise definition for the transit time parameter in SPICE diode model. What I think is the official documentation for standrad Berkeley SPICE diode model says the following

Diode Model (D)
The dc characteristics of the diode are determined by the parameters
IS and N. An ohmic resistance, RS, is included. Charge storage effects
are modeled by a transit time, TT, and a nonlinear depletion layer
capacitance which is determined by the parameters CJO, VJ, and M. The
temperature dependence of the saturation current is defined by the
parameters EG, the energy and XTI, the saturation current temperature
exponent. The nominal temperature at which these parameters were
measured is TNOM, which defaults to the circuit-wide value specified
on the .OPTIONS control line. Reverse breakdown is modeled by an
exponential increase in the reverse diode current and is determined by
the parameters BV and IBV (both of which are positive numbers).

It only says that Charge storage effects are modeled by a transit time. But how are this charge storage effects exactly modeled?
I believe this parameter models the time it takes for the diode to switch from the on to the off state. Simulations seem to agree with these. However, I would like to have a more precise definition, linking this parameter to some physical value of the diode, or at least have a reference of what it is modeling.
I couldn't link it to terms used in literature. For example, in basic diode physics book, when talking about on-off transients, there is a storage time and a recovery time. Following image is taken from Semiconductor Physics And Devices

Storage time ts is defined as "time required for the minority carrier concentrations to reach equilibrium state". During this time diode voltage is constant, and recovery time t2 would be the time it takes for the diode to reach its reverse-biased current.
Then, total turn off time would be ts+t2. This time clearly depends on the forward and reverse currents imposed by the external circuit, apart from physical diode parameters like minority carrier lifetime. If transit time models this total turn off time, is it just an order 0 approximation to the real turn off time?


texts: Would this work? Using a computer SMPS as a DC-DC converter

texts:
I have this crazy idea of using a computer SMPS with active PFC boost to take high voltage DC battery banks (144V+) and drop it down to 3.3V, 5V and 12V.

Here's my thinking: the power supply internally rectifies the AC to DC, and the PFC boost should then boost the 144V to an acceptable 350V-400V for the power supply. The 144V input is okay for it because it falls in the 100VAC range, and most are rated down to 85VAC if not lower.

I'm not looking for a guaranteed solution - it's a one-off problem I'm trying to solve, but I think it could be a cheap and viable solution.


texts: I am new to PWM control. Is it advisable to operate a motor at higher than rated voltage with the "PWM average voltage" more than the nominal voltage specified in the datasheets? After some researching, the majority of the information that I kept seeing is that it should be OK (with a recommendation to operate at high PWM frequency). Secondly, if the "average PWM voltage" is kept less than the nominal voltage (with the supply voltage much higher) is it correct to refer to it as over-voltage operation? Or is it only when the average voltage is higher than nominal voltage?


texts: Why is it slow charging from USB compared to charging from the power plug?

texts: It's almost twice as fast charging my phone directly from the power plug compared to if I charge my phone from the computer's USB port. Why? Isn't the charge the same or is it that USB has much lower voltage, and therefore it is much less energy per time unit?


texts: How does headphone volume correspond to driver excursion?

texts:
I was curious about how driver excursion in a headphone corresponds to the volume that music is playing at.

For this question, let's use my current headphone as an example. It's the Audio Technica MSR7NC, a noise cancelling variant of the popular MSR7's.

Here are its measurements and specifications when the noise cancelling is off...

and here are its measurements and specifications when the noise cancelling is on.

So when I plug my headphones in to recharge them, I typically leave on the noise cancelling. According to the first chart I provided, the noise cancelling provides up to 15 decibels of noise cancellation in some frequencies, and a bit less in others.

Given this, for simplification, let's say that this results in the headphones "playing" some frequencies at 15 decibels for the 18+ hours that I'm not using them.

Then, let's say that I listen to the headphones for a few hours at normal listening levels, say 65-70 decibels.

I understand that decibels are logarithmic, so 65 decibels should be 10,000 times louder than 15 decibels, but I find it hard to believe that the drivers in the headphones are doing 10,000 times more work.

Does anyone have a way to estimate the excursion made by headphone drivers based on their diameter (45mm) and their volume of 15 decibels, at least relative to their excursion at 50 decibels louder? Finally, I want to be able to measure the total excursion of my headphone drivers after a given amount of time (like hours) at a given decibel. How many hours of active noise cancelling is equal to a few hours of normal volume listening in terms of driver excursion?

I want to know this because I don't want to switch my headphone's noise cancelling on and off all the time as the switch seems a little flimsy, but I also want to know what I'd be putting the drivers through this way (I charge them right next to my pc which is computing 24/7).

Thanks!


texts:
I have a blackbody emitter, for which I have to regulate the temperature (to get a constant spectrum out of it) - the only way to do this in our system is to regulate its power (we can't measure its temperature, we can assume that the ambient temperature is constant).

Additional info: the emitter is switched periodically on and off.

The current design only sets the voltage across the emitter with a DAC, and this is ok as long as its resistance does not change. It looks like this:

We would like to compensate for changes in \$R_L\$. It would be possible to measure the current digitally and adjust the voltage, but I would prefer an analog solution. E.g. we set a voltage on the DAC and it sets \$P_L\$ of the load.

I know of the voltage controlled current sinks (like in AN-31), but in this form it is not suited for the task. I don't know whether it can be modified to regulate the power of a load by adding some additional inputs. Any google search gets me to power supplies, which is also not what I need.

Can anybody point me to a reference circuit or a simple IC would be even better. How is this task called - so that I can make a google search for it?


texts: add different current loads to test noise on DC-DC converter

texts: I want to test the LTM8021 DC-DC converter (using an eval board I bought - schematic for it is below) for noise output at varying current loads (10mA, 100mA, 200mA, 450mA) and still fairly new to this. My power supply can limit current but I can't tell it directly to just supply 10/100/200/450 mA. I figured I could add a series resistor using good 'ole Ohms law V=IR. I added it between the supply and VIN and GND and the supply GND and the supply and my multimeter never see it go above using 1mA. I know this is super simple but I can't seem to figure this out. what am I doing wrong? How would I go about injecting current loads?


texts:
I am currently attempting to measure the parameters of a "vintage" germanium BJT in the hope of creating an Ebers-Moll model from the data. So far I have been unable to find a comprehensive source on the topic as it is slightly out of the region of my expertise.

So far my primary source of advice has come from "and yet another Definitive Handbook of Transistor Modeling" which is fantastic, but has no author, no date, and some of the pages are shuffled.

In search of a more up to date source I have been using the doctoral thesis of Martin Linder, "DC Parameter Extraction and Modeling of Bipolar Transistors". This goes too in depth in some areas and does not cover the basics as they are probably not worthy of writing in a thesis.

This did however lead me to the original paper by Gummel and Poon, "An integral charge control model of bipolar transistors" (ran out of links). This has lots of relevant information but is written like a research paper so not very useful when trying to practically apply it.

Has this information been covered in a text book anywhere? A rigorous method of extracting \$I_S,\; \beta_F,\; \beta_R,\; N_F,\; N_R\$?


texts: How to latch a signal high at the first rising edge of a pulse train?

texts:
I have a question about digital circuit design. This is the situation. I have a pulse train. The length of the pulse train is not fixed. So the use of a counter is out of the question. I need to drive a signal high at the first rising edge of the pulse train and need to keep it high as long as I wish. And also I must be able to drive it low when I wish. How can I design a digital circuit to do this?
Thanks in advance!


texts: Boosting 5V/2A to +70/-70V for op-amp rails?

texts:
I am trying to drive an ultrasonic "tweeter" for a wearable research project. Compared to a normal speaker, the tweeter has a very high impedance, upwards of 4kohm. As a result, it requires a very high voltage to produce appreciable power, but the RMS current draw is a few mA per tweeter at most. I've been using the LTC6090 op-amp, which accepts up to +/-70V at the rails and works very well with the frequencies I'm interested.

Until now I've been using a janky combination of an off-the-shelf 12V voltage regulator and an LT1054 voltage doubler to produce +/-22V at the rails, but I'd like to do better if possible. There seem to be a world of options out there, but here are a few I'm considering:

Use the LT8331 to produce a voltage around 135V using the application note on page 22 of its datasheet, then use something like this unipolar to bipolar DC converter with some heavy-duty BJTs to turn this into +/-65V. Or I could just put 0/135V at the rails and bias the 5V signal using a voltage divider?
Use the LM2587 flyback regulator in a configuration similar to the one shown to produce +/-70V. This one seems viable, as the advertised max output voltage is 60V, but I'm not sure if I could simply change up the component values here to produce a higher output voltage.

Use an LT1054 to turn +5V into +/-10V and then turn those into +/-70V with two separate boost ICs.

For some of these, I might need to boost in several stages; I have a 5->35V regulator that I can use as the input to another stage. This may be inefficient but my application is not power intensive, requires very little current, and is mostly a proof-of-concept, so this is not a problem for me at this point.

Essentially, I would like to know the best way to go about doing this. It's unlikely that I'm the first person to be faced with this problem and I'd like to try to avoid tunnel vision or reinventing the wheel in ways that are likely to be inefficient, unreliable, or dangerous. I would appreciate any insight, from high-level design advice to specific components or topologies that could be helpful.

I am new to this stackexchange so please forgive the lack of links to component datasheets, I don't have enough rep to post them.


texts: Changing control values for PIC remotely?

texts: I'm using a PIC to take information from a sensor and transmit it via xbee to control a relay, as well as through a gateway to an online program. Forgive the noobie question here (I've searched and can't find it, maybe because I dont really know how to word this)...How would I go about changing the 'control' parameter for the relay. Say for instance I want a relay to turn on my a/c when it gets too hot, and I want to change what "too hot" is via the custom web program. It seems to me that it would require re-programming the PIC, however I've seen these types of devices before and that's not necessary, so I don't know what I'd need to do instead. TIA!!


texts: How do I find internal resistance of multimeter, in both voltmeter and ammeter capabilities?

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I was wondering how can I find internal resistance of multimeter, in both voltmeter and ammeter capabilities?

I thought it was termed as input impedance but when I looked up the specs of multimeter, in example, Agilent 34410A Digital Multimeter, it said load impedance was 1 MΩ ± 2%, in parallel with <150 pF in True RMS AC Voltage, which did not make any sense to me at all.

I experimentally measured internal resistances for both voltmeter and ammeter capabilities of multimeter but I wanted to compare this experimental value to true value of internal resistances and make percent errors. Help please


texts: Meaning of evolution in LTE (long-term evolution)

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The term evolution/evolved (E) is everywhere in communications, and simply put I don't understand why. The answer I am looking for is one that will help me know what meaning I should associate with the term evolution, why was it chosen? Does it describe a physical property? When I see "E" or "evolved/evolution" I should know it means.
Currently my understanding has been shaped and formed from this resource:
http://www.3gpp.org/technologies/keywords-acronyms/100-the-evolved-packet-core
This has shaped my understanding to be: evolution/evolved is its literal definition, one where something has grown or changed over time. In the context of communications it represents that the technology is no longer based on CS (circuit switching) and packet switching (PS) but now based on IP (internet protocol)
My goal is to gain further insights into the core workings of mobile/IoT networks and I am looking for a more detailed definition of the term "evolution/evolved" and why it is used in a lot of acronyms and what does it mean or what should I know when I see it.


texts: What's the usage of a "Cavity resonator" in a power supply circuit of a CD player?

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To diagnose a CD player I'm currently learning its schematics, yet I don't understand this part.
In the schematic, what could be the usage of PS401?
Thank you!


texts: What is the difference between root locus and routh hurwitz criteria? As according to layman knowledge, both techniques are used somehow to determine


texts: How do I realize this problem with a digital circuit?

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I'm trying to design an indicating system for a vehicle if it crosses its speed limit. Of course I'd be using a potentiometer to realize the action of increasing speed. The input is given to the base of a transistor through a zener diode so that I can get a digital output(OFF below the set value and ON if input exceeds the set value).

I need to have another indicator if the vehicle maintains that speed for more than say 2 seconds. I can feed the output of this transistor to a 555 timer set to produce pulses every two seconds and this clock output will be given to a counter.

The problem is that, I am supposed to have a digital equivalent of the first part of this system(As mentioned in the guidelines for the project). Is there any way to realize the switching action of transistor with the help of digital component.

I don't think it's possible to use a digital component as there is no particular level of voltage above/below which we can consider the output as high/low. This problem can be solved by using a transistor and a zener diode as mentioned above.

Since the input is continuous, I don't think any digital circuit can serve this purpose. Please correct me if this is possible.

Is the remaining part of my design(using a timer to produce pulse when the transistor switches on and feeding the clock pulse to a counter) right?