texts:
I made an H-bridge using this schematic:

Although the circuit mostly works fine, there is noticeable shoot-through.Even with no load at 150-200hz the input voltage drops by a lot.I added dead time of 30us which seems to help, but does not solve the issue,even though the datasheets claim switching speeds of less than a micro-second.Are there any changes to be made to solve this without increasing the dead-time any more?


texts: HC-SR04 with STM32 gives unexpected values

texts:
On an Arduino it is easy to get an HC-SR04 ultrasonic sensor getting to work.
However, on my STM32(F103C8T6) I get strange values.

I assumed I connect it correctly, since I get values on the trigger pin.
I checked the voltage on the 5V pin going to VCC of the HC-SR04 is 4.87 V.

The following program I used (only most important parts and with generated comments removed):

// PA10 US1 Trigger
#define US1_Trigger_Port GPIOA
#define US1_Trigger_Pin  GPIO_PIN_10
// PA9 US1 Echo
#define US1_Echo_Port GPIOA
#define US1_Echo_Pin  GPIO_PIN_9

uint32_t us1_duration;
uint32_t us1_distance;

uint32_t raw_values[1024];
uint32_t n = 0;

And for the loop (default part, auto generated by CubeMX):

int main(void)
{
  HAL_Init();
  SystemClock_Config();
  MX_GPIO_Init();
  MX_SPI1_Init();
  MX_USART1_UART_Init();
  MX_NVIC_Init();

  while (1)
  {
    HAL_GPIO_WritePin(US1_Trigger_Port, US1_Trigger_Pin, SET);
    HAL_Delay(10);
    HAL_GPIO_WritePin(US1_Trigger_Port, US1_Trigger_Pin, RESET);

    uint8_t state;
    do
    {
      state = HAL_GPIO_ReadPin(US1_Echo_Port, US1_Echo_Pin);
    } while (state == RESET);
    uint32_t us1_start = HAL_GetTick();

    do
    {
      state = HAL_GPIO_ReadPin(US1_Echo_Port, US1_Echo_Pin);
    } while (state == SET);

    uint32_t us1_end = HAL_GetTick();
    us1_duration = us1_end - us1_start;

    us1_distance = (us1_duration / 2) / 29.1; // cm (?)
    raw_values[n] = us1_duration;

    n++;
    if (n == 1024)
    {
      break;
    }

    HAL_Delay(1000);
  }
}

I put a breakpoint in the break statement to stop the program to check values. I moved my hand between 10 and 20 cm (4-8 inches) away from the sensor but the raw values I get are:

Name : raw_values
Details:{195, 196, 1, 1, 196, 1, 4, 1, 1, 1, 197, 0 <repeats 1013 times>}
Default:0x20001070 <raw_values>
Decimal:536875120
Hex:0x20001070
Binary:100000000000000001000001110000
Octal:04000010160

The raw values I expect would be in 10-20cm range (at least most of them), which would result according to the datasheet in raw values of 10 * 58 to 20 * 58 which is 580 to 1060. Especially not around 0's and not all same values around a certain value (this time 200).

The data sheet info I used can be found here: datasheet

Update
I checked it with a logic analyzer, and noticed the high parts of the echo durations are less than 1 ms. I don't know why I still get values of 200 sometimes, maybe when there is no echo.


texts: Is there such a thing as an automatic variable resistor

texts:
I have a skid steer loader that in ISO eg driving straight forward with one joystick supplies on average 50 milliamps more power to the right forward solenoid coil than to the left coil causing the machine to steer to the left dramatically, the dealer has swapped out the computer and joystick control pods with no effect, I have hot wired the wiring loom to eliminate that as a problem and no luck, the dealer has abandoned the job, I have taken the machine to a rexroth specialist who tells me there is nothing wrong with the hydraulics and the problem is the electronics, so back to my original question is there such a thing that can be installed between the computer and the coil that can take input of say 500 milliamps and output 550 all the way up to 1.100 milliamps and output 1.140 or can the power to the other coil be reduced by 50 milliamps to achieve the same outcome? Bobcat Skid Steers have software to eliminate this problem however Case skid steers dont I would be grateful for any help or suggestions

The wheel motors start to turn at 560mA and as you push the joystick forward it increases the current gradually through to full speed at 1160mA.
The reason i have put this question up is that i am a skid steer operator who can wire up a light but i have no idea about electronics, so if I were to fit a resistor in series with the solenoid coil would that work through the range from 560-1160 so instead of 560mA it would be 510mA and at 850mA it would be 800mA?
Skid steer machines have one drive motor on each side of the machine, one drive motor is connected by chain to both wheels on the left of the machine and the other drive motor drives the wheels on the right side of the machine.
There are two operating standards

ISO uses one joystick to drive both wheel motors and

H Pattern uses the left Joystick to operate the left side wheels and the right joystick to operate the right side wheels,

the machine works perfectly in reverse and I have swapped the coils around to assess if the coil could be an issue but it does not appear to be,
A youtube video of what is happening is here


texts:
I was trying to find output resistance of a circuit.

The book shows how to obtain Ro step by step. It says Vπ is equal to -Vx. I didn't get that point. My question is what is the relationship between Vx and Vπ in the below picture? Why?


texts: I built this circuit on a breadboard, connected a house plant and 12 volt DC. Not many seconds later magic smoke appeared from all ic's except the in128. I cannot see the error. Can anyone give me a hint?


texts: Barkhausen criteria: which is the overall effect if only the magnitude criterion is met?

texts:
I am going to try to explain better my question.
Considering a simple control scheme made up of a forward-path amplification\$A\$ and a feedback-path frequency dependent attenuation \$\beta(j\omega)\$, assuming a "positive" feedback, such that the loop gain is \$T(j\omega)=A\beta(j\omega)\$ then an oscillation can be kept constant in time if certain conditions are met for a precise frequency value \$\omega_0\$, namely the Barkhausen criteria:
\$T(j\omega_0)=1\$ or equivalently \$|T(j\omega_0)|=1\$ and \$\angle T(j\omega_0)=0\$.
In this way, a sinusoidal signal follows the full loop path and comes back unchanged, without any amplitude or phase modifications.

Now, my questions is related to the phase condition: I have understood that the magnitude condition has to be satisfied in order not to have divergent or damped oscillations (no overall amplification or attenuation per each revolution of the loop),whereas why must the phase be \$0\$? I mean, if it is so, the signal is not delayed after each cycle but what happens if it is not so? Is the signal being shifted every cycle? What is then the resulting output waveform, something like a sliding sinusoid?

Since there are no signals being summed, like it happens in a classical feedback-system with an input, one cannot refer to constructive/destructive interference that would occur due to the phase shift between the two signals added; thus the phase shift of the loop gain \$\angle T(j\omega_0)\$ cannot bring the oscillation to grow up or drop if the magnitude is still \$1\$. Am I right?
In other words, if the phase condition is not met, then no steady state oscillation can be produced, but anyway it is not possible to have oscillations that tend to increase or decrease.

EDITED SECTION:
As additional doubt linked to the previous question, if the Barkhausen criteria are exactly met for a certain frequency, shouldn't one say something more also about the other frequencies, so that all of them are damped (band-pass behaviour)? In other words, how can one be sure that no other frequencies get amplified and enlarged? (even though, saying this I am not taking into account that at such frequencies the phase would not be 0 too, so I cannot figure out which is the effect of loop gain greater or equal than 1 but phase whatever so, the problem is degenerating again into the phase criterion).


texts: Microcontroller freezes (or doesn't) when plugged into different outlets in my home

texts:
I have an ARM development board (Marvell ARMADA XP CPU) and depending on which plug outlet I plug the system into, the system will freeze up after a few minutes or not.

I found that plug outlets in my finished basement, regardless of circuit will cause the unit to freeze, while plug outlets in bedrooms will not. Anyone know why that might be?

edit: In case it helps, the power adapter hooked into the system is a:
Channel Well Technology AC Adapter. Model CAD065121. Input: 100-240V 50/60Hz 1.8A MAX. Output: +12V 5.4A


texts: How to save variables inside microcontrollers memory

texts:
I am designing an application which include GSM SIM900 with PIC18F2520. The application includes basic calling and sms services. A user will press a button a call will be made to a defined number. This number can be changed via sms. So whenever the button is pressed again, the call will be made to the newly defined number. Currently I am using these variables for number:

char callNumber1[10];
char callNumber2[10];
*
*
char callNumber5[10];

The problem I am facing is these variables works as expected. But when I turn off the power of MCU, the data stored in them are lost. I want the data to be remained as it is after the power off and can be used again after power on.
How to save them in MCU's memory. Please provide any link where I can read about memory in MCU. Please help.


texts: Routing the circuit for a snubber diode on a PCB?

texts:
I understand that the "ideal" place for a snubber diode is across the terminals of the inductive device that generates the flyback. But in the interest of making my PCB design for an Arduino shield as "bulletproof" as possible, I would like to have a suitable diode across the terminal block pins that will be connected to the device on my PCB. My question is, how do I route this?

This is my schematic in Eagle. When when I go to the PCB layout, pin 2 of the terminal block (at the right side of the diagram above) gets connected to the ground pours. I think it would be better if it connected to an insulated trace that went first to the anode of the diode, and then joined into the ground plane. Is that correct? Or does it not really make a difference?

[My idea is that this would discourage current coming from the strike magnetics from flowing into the ground plane; it should instead flow through the diode and be dissipated by the diode's (minimal) internal resistance.]

EDIT: I have attempted a few approaches, but the only thing that has done the trick of breaking up the net from J1 pin 2 to the GND plane is putting a 0Ω resistor in the circuit (between the net with the diode and the GND). But this puts a resistor component to be lain out on the PCB, which is not exactly what I want here.


texts: Voltage rating for capacitor in capacitive power supply

texts:
I am trying to replicate this circuit:

Taken from AN679 [PDF link here]

I have a question regarding C17 - 0.47 uF. This is the capacitor which drops most of the voltage in the power supply part.

In application note, they have mentioned the voltage to be 630 V. I want to know the minimum safe voltage for the capacitor that I can choose for 220 VAC line (which can go up to 250 V in some cases). The objective is to reduce the size of the components and I feel that I might be able to find smaller capacitors if I go for a lower voltage.

Also, they have taken phase as the reference (GND?) while making the circuit. I know that we are dealing with ac circuit and this doesn't matter but is it a preferred way to do things? Should I invert the connections (phase and neutral entering at points K3 and K4) or leave it like that?


texts:
The figure below is a diagram of a voltage-mode controlled boost converter.
I am wondering how experts solve the start-up problem for this converter.

Problem:

Assume the output voltage is zero at the beginning. Then from the control loop the output of the comparator will be high. This means the inductor is charged. However, there is no energy transferred to the output so the output will remain at zero forever and the inductor is charged forever.

So how do you solve this problem?


texts: Common cathode laser diode pin connections

texts:
I have a question relating to the operation of a laser diode within an optical pickup head that includes both a laser diode and photodiode.

The Optical pickup head is the HOP-1200W and I am attempting to utilise the CD laser in the head, namely the RLD78MRA1. The laser diode's pin layout can be found in the datasheet of the HOP-1200W, http://dalincom.ru/datasheet/HOP-1200W.pdf , on pg 23. In this datasheet it can be seen that the laser is 'Type A' and shares a common cathode (according to Thorlabs).

My main area of confusion is coming from the current flow and the required reverse biasing of the photodiode for the feedback to be obtained. I currently think the current is supplied (from a driver circuit) into pin 15, the parallel cap removes any unwanted AC component and then powers the laser diode. However will the following not have happened/happen?

1) Will current not then flow directly into ground removing any current that can flow across the photodiode?

2) The photodiode needs to be reverse biased and by my interpretation of events there will be no potential difference at the photodiode left for this biasing after the laser diode?

Any help would be greatly appreciated!


texts: How can Ohms law be used to calculate the resistor value for an LED when multiple voltage/current pairings give the same resistance?

texts:
Say I have a 9V supply, and I want to power an LED that requires 3V and 0.02A. From what I understand, I need to add a resistor that will drop 6V, and reduce the current to 0.02A, and I can calculate the resistance needed using ohms law. So, 6/0.02 = 300Ω - simple enough.

But how can this be the correct resistor when there's plenty of other equivalent fractions that would produce the same result? 3/0.01 also gives 300, so surely you could calculate that this resistor will only drop 3V and reduce the current to 0.01A? What am I missing here?


texts: Why does this 555 timer not work correctly when I plug in the Z80 CPU ground?

texts:
I am trying to build this circuit here: https://www.youtube.com/watch?v=AZb4NLXx1aM

But instead of using the same timer setup I am using this:

When I connect the ground pin of the CPU, the LED starts blinking very fast and the CPU begins to overheat.

Note: I do have the correct pins connected (ground, power, clk), and the 555 timer works perfect without the ground plugged in.


texts: Which is better after rewriting the ROM on a PIC16F? A software reset instruction or a watchdog reset

texts:
I am working on a project where the uP can be calibrate at any time. The new calibrated values are stored in the uPs ROM. After the calibration is complete, I have to reset the uP such that the initialization function can read the new calibrated values.

However, I am not sure what might be a better implementation... resetting the uP with the a software reset (included in the library) or using a watchdog timer to get the job done. While both can provide the same function; I am unsure on what will be a better implementation.

I also thought that it would be a good discussion to find out peoples views :)

Thanks!

PS - I'm using a PIC16f1936 and developing my code in C using MPLAB X IDE v2.15.


texts:
I am switching a refrigeration compressor with an AC control voltage and AC load solid state relay.
I need to choose between zero crossing and instant on / random switching. What is the pros and cons of each and is there any potential issues what are they as they pertain to each switching type.


texts: Why is register file latency, during write-back stage, not included in computing for minimum clock cycle time

texts:
I was looking at the solution for a homework posted here:

https://cseweb.ucsd.edu/classes/sp13/cse141-a/solutions/assignment4_solutions.pdf

and noticed that for 1.1, it didn't include the Register file latency for the write-back part. I know that after the last Mux, the processor should write the result from this Mux back to the Register file as specified by the destination register Rd.

I checked some more sources online and they're all doing the same thing, not just for ADD, but also for the LW instruction. Why is it not included in the clock cycle time computation?


texts:
I know any SOP and POS can be minimised directly with the help of KMAP and there is no difficulty in mapping each Boolean product or sum term into KMAP. However what if the boolean expression is in the form of XOR
Can someone help me map
[(A + B) XOR (BC) XOR (C) ] into a 3 variable K Map which is a function of A,B and C.
I know how to minimise  it using basic Boolean algebra , but K Map minimisation help is required for above expression .


texts: Deciding on lithium battery chemistry, lithium ion (protected) or Lithium Iron Phosphate (no protection) Safety is critical

texts:
I am designing a product requiring high power and energy storage capability. I have narrowed down the selection to two (most cost effective) systems: a 3s system of protected 18650 lithium ion cells (11.1V), or a 4s system of unprotected 26650 lithium iron phosphate cells (12.8V)

Both systems would be charged with a stand alone battery charging IC, with a thermister safety mechanism. I am also planning on including a fuse that will disable the system with excessive current draw (10A) in the case of the unprotected LiFePO4 cells.

Which system would offer a better safety profile for the use with a consumer product?


texts: Detecting a high-resistance fault location (like corrosion)

texts:
I recently encountered a problem where i had a 2 wire cable, one wire with corrosion somewhere and the other wire is perfectly fine. I didn't have a replacement so I wanted to try and find out where the corrosion was (it was giving around 1 megaohm resistance not completely cut.)
I connected it to the live terminal of a wall outlet and used my non contact voltage tester.
Silly me it kept beeping across the whole length.  I couldn't find the fault. J thought that the resistance might impede it and the signal would start to fade.
Anyhow, I eventually figured it out using my multimeter and kept bending small segments until I found an area where the resistance varied greatly and to my surprise it was the area of corrosion.
Is there any other "easy" way of finding out where the high resistance fault is without wasting much time? (I didn't have a cable toner so couldn't test with it.)


texts: When do you need to desolder a rectifier to check if its bad?

texts:
So i have five high amp rectifiers on the board which i suspect are fried, because  when i test them with the multimeter, it shows that all of them are shorted. No matter on what legs i'm putting probes, in both directions, it shows shorting.

But i've read that sometimes you need to desolder them to check if they are bad, so maybe i'm measuring them wrong and that's why i'm getting shorts everywhere?
Do i need to desolder them to check them?

Pictures of schematics:

1 - Primary circuit:

2 - Secondary circuit:

3 -Layout:

I'm getting shorts on all 5 secondary rectifiers and 2 transformer outputs, shown with arrows.


texts:
I've got a Sansa Clip that recharges via USB. Problem is that it "connects" to the PC whenever I plug it in. I learned a trick where you pull the cable out of the PC partially such that the data leads are no longer connected but the power leads are.

However I am looking for a more permanent solution. How can I modify the cable itself such that only the power leads remain and it never transfers data?

(I have an extra cable, so it's OK.)


texts: Is it possible to use a NPN BJT as switch, from single power source?

texts:
I'm attempting to build the following circuit to better understand how to use a NPN BJT as a switch.

What I've Tried

I'm calculating the current across the LED (in order to light it up) as:

5.2V* - 1.7V (LED drop) = 3.5V
3.5V / 17mA = 200Ohms

*NOTE - The  power source is 5.2V because I'm using 4 AA rechargeables in series (at 1.3V each).

The Problem

The problem I see when I push the button to turn the circuit on is that the transistor becomes very hot. I noticed this the first time because I could smell something. Then I touched it. Ouch! :)  I'm assuming I'm providing too much current on the be (base to emitter) circuit.

Things I've Tried / Additional Problem

However, when I attempt to add resistance into the be circuit then the LED doesn't light up, even when my resistor gets down to a value as low as 47Ohms.

Questions

Is it possible (due to ratios of current needed) to even power both sides of the circuit from the same power source?  Or is it ridiculously difficult or something and not done?
Can you help me understand the additional calculation(s) I should be using to power the circuit so my LED will light when I push the button?

simulate this circuit – Schematic created using CircuitLab


texts:
If I have an omnidirectional antenna and put a perfect reflector plane near it (in the near field), it will obviously change its radiation pattern in the direction opposite the reflector.

If I put a perfect absorber plane near it, I understand that it will change the pattern in the opposite direction, but I am having a hard time understanding why and how. I have looked online for a good image/video/explanation. Can someone direct me or explain?

Visualization:

            Area of Interest

                   + (Antenna)

         Perfectly absorbing plane


texts: SPI and I2C connections by using mosfet (high side, low side)

texts: I need to design sensors card in altium for sensors connected I2C and SPI. When I searched modules on internet, while some used mosfet to handle high and low side others did not use mosfets. I could not understand clearly for which purpose they used mosfet. Could you help me, should I use mosfet connections for my card? To explain my question well, I added two diffirent photos for the same sensor type.


texts:
Do there exist materials that:
 - React to electrical pulses having frequency in the band 2-10Hz with a very low frequency response (near to DC),
 - Have a measurable reaction, where measurable means that I can directly transduce the signal into an electrical one by connecting in some way the material to an electronic circuit,
 - The reaction is easy to measure, easy means that the measurement circuit is very elementary,
 - Dissipates very low power (microWatts (or orders about 10^2 microWatt ) if possible).

I actually don't care about the way these materials react, they can also emit some light whose spectrum varies with the pulses frequency.


texts: Is there any product with a combination of both Zigbee and Bluetooth 4.0 protocols? If not is it possible to design a module with such combination?


texts: Operating an inductor beyond its rated current

texts:
Let's assume the following situation: there is a power supply which VCC line has an inductor between some capacitors, for additional filtering capabilities:

simulate this circuit – Schematic created using CircuitLab

It is RLB0712-101KL which rated DC current is 320 mA.

My question is - what will happen if I try to put a load of 1.5A at 15V through it? My vague vision of it - it is going to heat, maybe even blow, also the inductance value will drop at such current. I'd be grateful for a more detailed explanation of what will happen.


texts:
I tried to build a circuit that would allow me to push a washing machine's start button remotely using a solenoid as an actuator.

The solenoid is wired to a 9v battery which also powers an ESP8266 through LM7805 voltage regulator.

Unfortunately, after soldering all the components, I discovered that the soleniod does not produce enough force to actually push the button.

The solenoid I used has the following parameters (sellers ebay page):

Rated Voltage & Current DC 6V 0.15A
Power   3.4W
Action Form Push Pull Type
Force
Stroke: 2mm 35g/0.08lb
Stroke: 1mm 80g/0.18lb
Power On Type   Intermittent 25%
Max Power On Time   1 Second
Body Size   20 x 12 x 11mm/0.8" x 0.5" x 0.4"(L*W*H)
Cable Length    5cm/2"
Material    Metal, Electronic Parts
Weight  14g
Package Content 1 x DC Solenoid Electromagnet

simulate this circuit – Schematic created using CircuitLab

I don't want to desolder anything. The solenoid and battery are connected with plugs into the board so I can replace them easily.

My question is: having these constraints, is there anything I can do to increase the force of the push?

Maybe I can replace the solenoid with a different one? Or plug something else instead of it? Can plugging different power source help?


texts: Is there an equivalent standard in IEC such as UL 467 or IEEE 837 which talks about the various test procedure for bonding clamps? Is IEC 61914:2015 similar to UL 467?


texts: Does the resistor value on D+ and D- line matter on Arduinos?

texts:
I noticed from looking at the different Arduino boards schematic, there are 22 ohm resistors in series between the D+/D- pins from the USB port to the ATMega IC.
A snippet of the schematic of the Leonardo below:

However, the Sparkfun Qwiic Pro Micro USB-C schematic has 5.1K resistors instead (picture below).  This made me think; does the value of the resistors on the D+ and D- line have to be within the 22 ohm range? What happens if there is no resistor or the resistor value is really high (over 10k)?


texts:
I have a circuit with an RTC (DS1307) and an LCD display, both connected to an I2C bus. Because the RTC requires a 5V level (the RTC breakout I use has built-in pullups) I also use a level shifter.

The cable that connects the RTC with the breadboard is an 8-wire flatbed cable (the other wires are currently unused), about 20cm long. With this setup, nothing works. Neither device is recognized on the I2C bus.
Now if I disconnect the SDA wire to the RTC (the orange one) and replace it with a separate wire all of a sudden, everything works as expected and both the display and the RTC work just fine. There's nothing obviously wrong with the wire (such as a shortcut).
I have tried to compare the signals I get with a scope, but don't really understand the difference.

The first picture shows the scope output of the signal, measured at the RTC end, when the communication does not work, the second shows the same signal (maybe not exactly with the same data) with the separate wire. The only difference I see are those tiny peaks. But whether that's ok or not I do not know.
Is the I2C bus so sensitive to cross talk that the parallel wires cause the problem? In another project, I have a 10m I2C bus connection in a single cable, and it works fine.
Edit
The flatbed cable I use has the following wires (in this order): white (5V), grey (NC), purple (NC), blue (NC), green (NC), yellow (SCL), orange (SDA), red (3.3V) and brown (GND). The RTC breadboard is actually this a bit more complex type, but I only use the RTC of it (It's not possible to stack that to the Arduino Due).
Edit2
I also added the scheme. the problem is in the wiring on the far right, between the level shifter and the RTC. The level shifter is this type from Joy-It


texts:
I am complete electronics newbie, so please bear with me :)

I would like to connect an LCD directly to a 433 MHz RFID tag. So whenever I swipe the RFID tag near the RFID writer, the values that are written to the RFID tag would be displayed on the LCD.

Is this possible, if so, can someone please point me in the right direction?

EDIT: To clarify, the RFID tag needs to be on the same PCB as the display.

EDIT - 14/05/2012: Looks like there are a lot of questions on what I am trying to do, so here is what I am trying to achieve:

I want to create a pocket device (more or less the size of an iPhone) that is able to receive a numeric password from a server within the office
The device needs to have a battery life of 3-6 months at least
The range that the device should be able to get the password should be up to 50 meters
The numeric password on the device will be updated every 1-2 minutes

Since battery life is a constraint, and updates are only every 1-2 minutes, I thought medium range RFIDs would be the best option.  Let me know if you can think of a better solution.


texts: How to obtain the in-phase carrier for synchronous detection of an AM signal?

texts:
I am designing an AM receiver that has a carrier frequency of 2MHz with a bandwidth of 20kHz; i.e., the information signal has 10kHz bandwidth.
What I've designed is basically like this:

So I need a carrier signal in-phase with the carrier at the modulator. I have problems with obtaining this carrier signal from the received AM signal. I've designed some passive filters, but non of them had the enough quality factor/selectivity.
I'm looking for a circuit that can separate the carrier signal from the received AM signal, i.e., a heterodyned, Crystalline or Active (etc.) filter. I've tried to design (each) one of the above filters, but I couldn't come up with a working circuit. So I want a more detailed circuit of one of the above solutions. (one of them that can do the job suffices)


texts: Can I replace multiple NPN transistors with some kind of IC?

texts: I am currently using BC 547 transistor and an Arduino Uno to turn a low power switch on and off. I have successfully achieved this with one of the Arduino output pins, but would like to replicate this over 13 of the pins. This would require 13 transistors and resistors, one for each pin, which seems like overkill. I want to know if there is a neater way of doing this with an IC?


texts: Selecting PCB Shape from DFX file with VIAs included

texts:
I have a shape for my PCB as follows in the picture below which includes four holes.

However, when I select the whole shape on Altium Designer and then select PCB from selected shape, it will only leave me the PCB as small round as you can see in this picture:

I wonder how can I make the PCB shape keeping the outer shape as the boarders of the PCB where the 4 circles are holes/vias.


texts:
I'm actually working with a darlington pair of BJTs.

My question is if I need to put a 1kohm resistor between my MCU pin and the BASE to use it as a switch. Since the Hfe ratio for my transistor is quite large, and the collector current will be limited to a reasonable level, does that mean that the base current is dependent on the collector current at all times and thus I can eliminate the usage of this current limiting resistor?


texts:
So I wanted to play around with relays and clearly got it wrong even before I got started. I wanted to control a 12 Volt fan - thinking that it would have a capacity of 12 V to control.. But now I know that it takes 12 V input and can control upto 250VAC...

I have ordered some new 5 Volt relays, but want to know how I can use the 12V relay with an arduino _____________? (bear in mind that I'm a newbie)

This is the relay module I bought:

UPDATE

Thank you all so much for finding your time to help me out, I really appreciate it!
First now I found the time to try out your suggestion.

@jippie comment:

  ..(or Vin on Arduino if you are feeding it from a 12V supply)

got me think about what I really wanted. I wanted to use the 12V power supply to also feed the arduino (hehe..)
- but posting the question I needed to know the anwser to whether an "under"-powered arduino could control a 12V relay.

But first validate that the relay is actually working! So found a 12 V adapter and connected it to a breadboard.

Then connected it to the relay by NC and COM

Compiled the Blink code example and hooked it up using Vin, GND and D13

I then hooked my Arduino to a 9V battery and tried the 5V output

Unfortunately this did not work..

@Madmanguruman and @Kurt thank you both for your answers - I'm just too newbie to figure out all the things you were talking about.

UPDATE 2

Forgot one more possible combination

This kinda brings me down to these options with my relay:

Control something that requires more than 12 Volts, but power the arduino with 12 Volts
Use it to control DC gear motors without using and H-bridge and diode (kinda expensive)
Use the NC (Normally Closed) and NO (Normally Open) logic to do something neat

All this got me thinking.. If I need to power my Arduino with 12 Volts to control a 12 Volts device - why don't I just connect my device directly to my Arduino ____?

As mentioned many times: I'm a newbie and just want to learn electronics mostly by Learning-by-doing - but without putting myself at risk and breaking things (like my Arduino)

But why would this not work:

simulate this circuit – Schematic created using CircuitLab

EDIT:

Controlling 12v DC motorfan with arduino

  Firstly, even if a motor or pump or fan (anything with coils inside) is 3V or 5V, do NOT power it directly from the Arduino pins as the Arduino pins can only supply a maximum of 40mA. As per my previous article on Arduino pins, they are not designed to drive a DC motor or coils.

UPDATE 3

Using 9V and Vin also worked :)

So guess the answer is:

Yes, but I have to use >= 9V (perhaps lower, but not 5V) and the Vin.


texts: LTspice Transient Analysis Simulation error

texts: I am simulating a boost converter, however LTspice is telling me the transient analysis is only 13.8 % done, as seen below. Why is this?


texts: Is is OK to drive AD620 with +-5V and expecting the output range up to 3.3V?

texts:
I'm using AD620 with STM32. So I want AD620 output up to be 3.3V. As 5V is easy to obtain, I want to drive AD620 with +-5V. Is that OK? Could a 5.5V driven AD620 generate 3.3V output? What about AD8221?

Thanks.


texts: Can I drive a led light with help of a CT clamp

texts:
If I have a 230V wire with alternating current and a load in the far end, drawing current. Could you "steal" energy with a CT illustrated in the image, to for example drive a led light?

BR
Chris


texts: Using solar with a 3 phase motor to generate stable 3 phase current

texts:
I have a 220 V 100 hp electrical motor.

I initially had a plan to use the grid 110 V through a step up transformer to get to 220 V along with a 480 kVA capacitors to kick start the 3 phase 100 hp motor. This would power all the smaller equipment but mostly a 50 hp motor for pumping.

I no longer have access to the 110 V grid system. Let's say that I have a suitably large battery bank with 480 kVA capacitors in parallel.

Would I be able to use an inverter from the battery/capacitor bank to still kick start the motor and generate stable 3 phase power?

solar -> mppt -> [_x battery bank] + [13 480 kVA capacitors] plus  inverter to run the 100 hp motor?


texts: What is the standard way to halt a VHDL testbench after a certain time period?

texts:
In Verilog I can use the $finish function to halt the simulation, but my search for the similar option in VHDL has failed so far.

The closest solution that I found online is to use this code in my VHDL testbench:

stop_simulation :process
begin
   wait for 1000 ns; --run the simulation for this duration
   assert false
       report "simulation ended"
       severity failure;
end process ;

How do you set the time for your simulation in VHDL? For example if I want my clock to run for 10 us, then what is the STANDARD option to achieve this?


texts:
Here's the link to the circuit:

http://rustamaji.net/resource/images/flip-flop2.swf

From the simulation, when the 22k resistors are removed the LEDs stop blinking because the current flowing only around capacitor. When either the other resistors are removed or all resistors are removed, the components on the circuit burn out.

What is the function of resistors in this flip-flop circuit?


texts: What might be the reason for improper turn on of IGBT

texts: Here I am applying 3-phase rectified dc to the non-isolated boost converter, the magnitude of applied voltage is 450V and desired o/p voltage is 475V. Switching frequency of PWM is 28k. I am using TC4420 driver IC to drive the IGBT (IKW40N123H3). But when I am starting PWM circuit IGBT's temperature is increasing at a very high rate and this causing igbt failure. I have captured gate to emitter waveform and collector to emitter waveform and I found that collector to emitter waveform is not right. Its voltage is not approaching to zero when GATE PULSE is high. What might be the reason for such a collector-emitter waveform?


texts: X86_64 Architecture, how does it handle instructions larger than 64 bits?

texts:
I have been looking more into how CPU's work, and have a question.
If I have a instruction that e.g. takes a 64bit address and a register, and copies the value from that address into the register. And that instruction has a 2 byte opcode. Then let's say the entire instruction is 80 bits in size.(8 bytes)
Then how would it execute that instruction? Since I presume it doesn't fit in the instruction register(because the register is 64 bits).
Does it just take the opcode and fetch the address(and later it's value) and register later? Or does it have multiple registers? Or does it have one mega big instruction register to fit it all?

Thanks!


texts: I am attempting to drive a stepper motor where each phase draws 1 A at 3.5 V using a sine wave oscillator that outputs two signals 90 degrees out of phase with one another. At the outputs of this oscillator are op-amps, which put out the required 3.5Vpp signals but don't provide much current. What is the best way to boost these signals up to the required 1A, and should I be worried about trying to implement any kind of current limiting? Thanks for any help you could provide.


texts: Powering 12V / 5W device at minimum cost and steady life duration

texts:
I want to power one particular device that feeds of 12V (5W) electricity.

However this device is intended to be highly portable and as such, I am quite tight on space, which means 12V accumulators are too big for this purpose. Also they are in fact, way too durable (and quite costly).

The power source must be rechargeable, so that I can take advantage of my charger.
It is enough if it lats at least 1 hour and I cannot afford more than 10$ for it.

What would be the most cost-effective, small, disposable 12VDC power source that lasts at least 1 hour on a 5W power consumption?

As a side note, I already have x4 LG HG2, they are hi-drain (20A) and quite durable (3000mAh). Maybe I can use some boost converter to make 12V out of it. It may last 4 times less (decrease to about 6A), but that would still be very long-lasting I think.


texts:
I have a problem: We use some Raspberry Pi to manage some contactor with a simple relay. This relay can manage one or more three-phase switches, so basically it is linked at least to three contactors. The relay sends an impulse both to put up or down the contactors.

The problem is that our software needs an input to understand if the contactors are up or down because we cannot demand everything to the software. There can always happen something that will cause the system to go out of sync.

How can I read the status of the contactors? My knowledge tells me that I should put a transformer 230 > 5 under the contactors, then a resistance to bring the 5 V to 3.3 V which is the maximum voltage bearable for a Raspberry Pi's GPIO, but I don't know if this solution is enough, also because the contactors have different negatives... Is there another possible solution, even electronically, to read this information?


texts: 555 delay timer not working, it does not delay at all

texts:
My 555 timer is not working like normal. I don't really know what happened.
I did this on a breadboard and it worked perfectly with a 5s delay at the deck. But now I am building a full circuit were I will need it a lot, I have practically done everything on the diagram but it is not working out, the RC network is correct and properly biase but it is not working well; pin 6 and 2 goes along with the rc network.
How can I fix this?
I am using the following circuit,


texts: 4 AAA 1,5 volt vs 5v 300mah dc power supply

texts:
I have an LED-Lamp which has 4 x AAA 1.5 in it. IIII is the layout of series of the batteries.

I would like to attach a dc power supply of 5V 300mah 1.5VA.

Would this be to much for the LED and eventually (days/weeks I mean) burn it out?

Or would it not be enough (if I do 4 x 1.5 = 6v?) to power it?


texts: How does current flow between two out of phase voltages?

texts: Whether two out of phase voltages can be considered as positive and negative terminals between current flows when load is connected.?


texts: Why does an 802.3 (Ethernet) frame have 2 MAC address fields while a 802.11 Frame has 4?

texts:
I'm trying to understand the IEEE frames. 802.11 frames have four MAC address fields: The source (original creator of the frame), destination (ultimate destination of the frame), transmitter (the last station to transmit it) and receiver (the next immediate receiver of the frame on its way to the destination).

But 802.3 frames only have two MAC address fields: source and destination. Why is that? Why don't stations connected via Ethernet need to know the previous station that sent a frame?

Thanks for any help.


texts:
My task is to design Moore sequence detector. As my teacher said, my graph is okay.

I wrote down next states, and outputs, then decided which flip-flops I'll use. With Karnaugh tables, I miminalized functions for them. My problem is, it's not working correctly. When I'm simulating it in Xilinx, after my desired sequence "01010" on the input, I don't get logical 1 on the output. My question is: are my K-tables and way of thinking correct? I can also include my schematic in Xilinx and outcome if needed.

edit: my scheme:

and the outcome:

VHDL code:

clock <= '1', '0' after 20 ns, '1' after 40 ns, '0' after 60 ns, '1' after 80 ns, '0' after 100 ns, '1' after 120 ns, '0' after 140 ns, '1' after 160 ns, '0' after 180 ns, '1' after 200 ns,'0' after 220 ns, '1' after 240 ns, '0' after 260 ns, '1' after 280 ns, '0' after 300 ns, '1' after 320 ns, '0' after 340 ns, '1' after 360 ns, '0' after 380 ns, '1' after 400 ns, '0' after 420 ns, '1' after 440 ns, '0' after 460 ns, '1' after 480 ns, '0' after 500 ns, '1' after 520 ns, '0' after 540 ns, '1' after 560 ns, '0' after 580 ns, '1' after 600 ns;
xinput <= '0', '1' after 100 ns, '0' after 200 ns, '1' after 300 ns, '0' after 400 ns, '1' after 500 ns;

Updated simulation:


texts:
Consider schematic below.

simulate this circuit – Schematic created using CircuitLab

With a DC source we can use this arrangement to find the force between the plates of the capacitor. We can do this by finding the  mechanical work done pulling the plates apart, the change in the energy stored in the battery and the change in energy stored on the capacitor. I have been told (by more then one professor) that the energy stored in the battery is of the form \$QV\$, where \$Q\$ is the charge on the capacitor (the sign may be negative). But I think this is wrong, this formula says that when \$Q\$ is \$0\$ (i.e. when the capacitor is first connected) the energy stored in the battery is \$0\$. This to me is nonsense. I think the energy on the battery would be better expressed as \$E_0-QV\$ where \$E_0\$. Is my formula better? And in the general case what is the energy stored in the battery?


texts:
I'm trying to understand this mechanical drawing. (Another one. I asked a question about mechanical drawings a while back.)

I can work out most of the dimensions, but the mount pads are confusing me. They have two numbers (0.7 and 1.2) beside them. They could be any size for what I know...!

The drawing is for an SH type connector.

Many thanks.


texts:
I'm working with an ATmega168 with a Linux based board (TI DM365). The ATmgea168 communicates with the TI over UART.

The Atmel is programmed using AVRMKII and is running fine. I was wondering if there was way to utilize the UART lines and program the Atmel from a Linux environment?

Right now the UART is set up to receive basic (single char) commands from the TI in interrupt routines and echo out the results. I suppose I need to modify this to make the programming over UART work.

EDIT: (should have noticed this earlier)
The atmel is actually controlling the power to all the devices, including the TI. So if I try to reprogram the atmel while the system is up and running, the TI will definitely lose power. So, with a set up like this, it will be very difficult to reprogram the atmel. But any ideas or suggestions would be great.


texts: LTSpice power supply simulation: what is wrong with it?

texts:
I have simulated the LM723 based regulator circuit in LTSpice

And after running it I got 16A currents (blue/green) on diodes in rectifier. The max current I supposed to get here was 3.3A. Please tell me what is wrong? I have tried to use different MUR860 models and it did not helped.


texts: Is a low load resistor a big problem in low pass filter and amplifier circuit

texts: I am going to use AVR's PWM output signal to pass through a low pass filter (maybe plus an amplifier). I found the speaker has a quite low resistance (8 ohms). I tried to simulate my schematic on Orcad, obtaining very a low voltage signal on speaker in (mV).  I think that is the problem of this load resistance (I simply put the load resistance across output terminals). But I am not sure how to deal with that. Hope someone can help. Thanks in advance. The same problem occurs when I tried using single simple pole low pass filter. Looking forward to hear your suggestions.


texts: VHDL: when is process sensitivity list triggered?

texts:
In VHDL simulation, there is a concept of "delta time," which is loosely interpreted as "group of events triggered by the previous delta time." After a change, once all cascading changes have settled, and no more delta time events are generated, the simulation time advances. (Also, simulation time may advance after N delta time events, as there is some upper limit to the length of a cascade.)

In a given process, when is a change to the process sensitivity list triggered? Is it only triggered when the state of a signal is different at one simulation time as compared to the previous simulation time, or can it be triggered as a result of any delta time event? If it is triggered at any delta time, a process may be triggered more than once if there are ephemeral combinatoric logic?

Consider this example:

simulate this circuit – Schematic created using CircuitLab

Let's say we start with steady state A=1, B=0, C=1.
Also, let's assume there is no external entity inspecting signal B -- it is purely internal.

Now, introduce a simulation event: A=0.

This will generate an output event for B=1, and an output event for C=0, for the next delta time.
At the next delta time, a new output event for C=1 will be generated, and no more events will be generated, so simulation time can advance.

Now, let's say I have a process with C in the sensitivity list. Let's say this process increments a counter each time it is invoked.

Will that counter be incremented twice as a result of A change? That would be the case if delta-time changes provoke/trigger/invoke processes.

Or will that counter be incremented zero times? That would be the case if only simulation-time changes provoke/trigger/invoke processes.

Or is the relation between change-in-A and process-counter undefined? For example, if the simulator (or synthesizer, for hardware,) optimizes the NOT-and-XOR truth table, it will say that C is always 1, but if it doesn't optimize it, it may generate two changes for C and thus trigger the process twice?

Second question: What's the correct word to use for "provoking/triggering/invoking" a process by changing some signal in its sensitivity list?


texts: Buck converter with current and voltage regulators

texts:
I need to find scheme for Buck converter with adjustable output voltage from 0 up to 12V. Also it may have an adjustable current limit. Max current output is 10A or at least 5A. Actually I will need it to make a bench power suply for my future projects.
I just have started with electronics and I want to make it myself, not to buy. I found many schemes but all of them have higher minimum output voltage, sth around 5V. Or they have maximum current around 3A.
I have one idea how to make that but not sure whether that works. Maybe I can reach specs that i need (max current output 5-10A, voltage 0-12V) if i will connect 2 schemes (at image below ) for 3A in parralel. Will it work?
Also it can be a buck boost converter.

Thank you for the help :)


texts: I am going to buy a fuse, but I am confused about what the purpose of I^2t is can someone please explain to me what it means.


texts: Does this circuit adequately represent the thermal considerations for a boost converter?

texts:
I'm new to electronics, and I'm trying to use a boost converter to get 5V at 1.2A from a lithium ion battery.  I've selected the TPS61232 step up converter for this solution.

The datasheet has a recommended layout:

It's all well and good unless you have a giant inductor (which I have).  I tried to capture the concepts of the example layout, but I don't know if I'm missing anything fundamental.  Does this look like a rational layout?

I added the vias under the IC which I think are probably dual purpose: heat dissipation and potentially also to wick out some solder so the IC doesn't sit on a solder bubble.

I used a lot of pours which I assumed were to provide additional surface area to dissipate heat.

Finally, I added the vias on the Vout pour, but I'm not sure what those vias are for really.

Additional Details

Here is my current planned BOM:

Inductor Options

Here are some inductors I think I could use and give myself some more space:

This one seems better in about every way.
Lower tolerance, higher DC current, lower DCR, higher SRF (this is good, right?), etc.  It's just way more expensive.
https://www.mouser.com/ProductDetail/Wurth-Electronics/744316100?qs=sGAEpiMZZMsg%252by3WlYCkUy4%252bqPuxOV5JxsS7NSlX2UA%3d
My IC has a 2 MHz switching frequency so I feel like I could stand to have a lower SRF.  Is that true?  Like maybe this one at 50 MHz? https://www.mouser.com/ProductDetail/Bourns/SRP6050CA-1R0M?qs=sGAEpiMZZMsg%252by3WlYCkUwWVs%252bZAfRN3be00zVNyvZQ%3d
I'm looking to provide 1.2A (my actual output current is quite a bit less really, but I'm looking at 1.2A for the sake of the exercise) at 5V supplying a minimum of 2.8V (from a nearly dead Lithium Ion battery).  It looks like my efficiency is going to be somewhere near about 80%.  If I call it 70%, then I think it calculates like this . . . my output power is 5V * 1.2A = 6W.  With a 70% efficiency I need 8.6W from the supply at 2.8V.  So, 8.6W / 2.8V = 3.1A?  Well, nevermind . . . after all of that, I don't see any smaller inductors with a lower current rating so it's moot.  Still, am I making sense on any of these assumptions?

Implemented changes

Here's what I've done based on (my understanding of) current answers:

I changed all of the pours (and moved caps) to try to keep pours as straight as possible to avoid bottlenecks.
I flipped the J2 jumpers around so that the Vout and GND pins will be as close to the output caps as possible.  I think that's to reduce the inductance as the current traveled through vias to the other side of the board to get to the ground pin?
I extended the top side of the board and used .6mm vias with .3mm drill holes to connect Vout to pin 7 so that the ground pour will wrap all the way around the top of the board and provide more direct routes for current to flow to various components.
I added vias near the ground pin so current to the ground pad can get to the pin more directly (I made this one up myself . . . it might be a bad idea).
I gave the top ground pour 3mm clearance to increase the surface area slightly.
I put the ref symbols back because it was dumb to hide them in the first place.

Here's what it looks like at the moment:


texts:
I am in the process of designing and prototyping up a circuit using the ATMega328P in a MLF package. It's the first time I've worked with the '328P on my own circuit, and the first time I've worked with MLF (though QFN is an every day experience for me, and I work daily with plenty of other microcontrollers...)

The ICSP portion of the circuit is pretty standard. I lifted it directly from the Arduino UNO schematic, but it's really just directly pins to header.

Trying to program it with a USB-ASP (cheap one from China) and it can't find the chip.  I have confirmed the programmer works by connecting it to an Arduino, so that's fine. I have tried powering externally and powering from the USB-ASP. Nothing has any effect.

I have triple and quadruple checked the schematic and the PCB layout, and all seems perfectly fine to me - however I have probably gone PCB-Blind and am missing something absolutely obvious.  I have checked continuity, probed for shorts, reflowed the chip, replaced the chip with one from a completely different batch, built a new circuit with just the AVR and decoupling capacitors - everything. I have even tried injecting a 1MHz clock signal into XTAL1... And all to no avail.

Reflowing is done using low-temperature paste at 250C.

AVRDude output with "force" enabled:

$ avrdude -p atmega328p -c usbasp -F

avrdude: error: program enable: target doesn't answer. 1
avrdude: initialization failed, rc=-1
avrdude: AVR device initialized and ready to accept instructions
avrdude: Device signature = 0xd037cf
avrdude: Expected signature for ATmega328P is 1E 95 0F

avrdude done.  Thank you.

The device signature is a random number. I get the same result with the programmer completely disconnected.

Schematic:

PCB layout:

MLF Soldering:


texts: How do you set amperage in a simple circuit?

texts:
Volts = Amps * Ohms

Theoretically I wanted this (rounded):
3 V = 0.002 A * 1440 Ohms

Realistically I got this because a limit of resistors I had (rounded):
3.206 Volts = 0.002 Amps * 1421 Ohms

From this combination:
3.206 Volts (1.5V AA battery + another 1.5V in series) and
1424 Resistance (1k resistor + 220 resistor + 220 resistor)

But this resulted in 8mA when I measure the first wire to the
last with a multi meter and 4mA directly on the LED instead
of the mathematical 2.2561mA that I thought we should see.
Why does this happen?

simulate this circuit – Schematic created using CircuitLab


texts: What is the diode for in this 555 circuit?

texts: Here is a schematic of a 555 setup to create a single shot voltage sawtooth pulse across the capacitor C2. It also outputs a square wave pulse on pin 3. A (reversed biased) Zener diode is used together with a another forward biased diode and a resistor to set the bias voltage for the external transistor, Q. My question is why is D1 needed? You can argue the added voltage drop is just enough to be added to the Zener voltage to create the required bias voltage, however a different Zener would achieve the same thing. I'm guessing it is compensating for something, but not sure what. Will be glad to hear suggestions.


texts: Finding the cut-off frequency of a filter

texts:
For a general filter, what is the way to find the cut-off frequency? In this link Okawa Electronic Design shows a formula for the cut-off frequency of a Sallen-key filter that looks like:
$$\text{f}_\text{c}=\frac{1}{2\pi\sqrt{\text{R}_1\text{R}_2\text{C}_1\text{C}_2}}\tag1$$
But how did he find that?

My thoughts. I was in the understanding that the cut-off frequency of any filter can be found by solving:
$$\left|\underline{\mathscr{H}}\left(\text{j}\omega\right)\right|=\frac{1}{\sqrt{2}}\cdot\left|\underline{\hat{\mathscr{H}}}\left(\text{j}\omega\right)\right|\space\Longleftrightarrow\space\omega=\dots\tag2$$
Where \$\left|\underline{\hat{\mathscr{H}}}\left(\text{j}\omega\right)\right|\$ is the the absolute value of the transfer function such that \$\left|\underline{\mathscr{H}}\left(\text{j}\omega\right)\right|\$ is at it's maximum.
If I use that on the Sallen-key filter I will get the following formula:
$$\omega_\text{c}=$$
-(1/(Sqrt[2]
   C1 C2 R1 R2 R3))(\[Sqrt](C1^2 R1^2 R3^2 + C2^2 (R1 R3 - R2 R4)^2 +
     2 C1 C2 R1 R3 (R1 R3 -
        R2 (R3 +
           R4)) - \[Sqrt](4 C1^2 C2^2 R1^2 R2^2 R3^4 + (C1^2 R1^2 \
R3^2 + C2^2 (R1 R3 - R2 R4)^2 +
          2 C1 C2 R1 R3 (R1 R3 - R2 (R3 + R4)))^2)))

I found that using Mathematica, but it shows a very different formula than \$(1)\$. What am I doing wrong?


texts: AD620 instrumentation amplifier for shunt resistor

texts:
I would like to measure the voltage drop over a shunt resistor (60mV@60A) and I want to send this voltage signal to ADC with a resolution of 16bit. I want to amplify the signal to obtain better accuracy.
I'm going to use the in amp AD620.
How do you think I have to connect the shunt with my in amp?


texts: How to connect a large number of multi-throw switches efficiently?

texts:
I have a number of 7 pole single throw switches that I need to connect together in some sort of grid configuration to a microcontroller, while minimizing the number of pins on the micro and the number of diodes/other elements I need.

The controller needs to be able to uniquely distinguish each switch regardless of how many of them are open or closed at a given time; presently there are 17 different switches.

I also do want to have some degree of redundancy on the mechanism - it is possible that one or two of the switch's poles might fail to make contact and remain open. (The other failure, accidental closure, is not an issue.) Ideally I would like to allow for up to two failures per switch without compromising the ability to register each input.

I have considered a few conventional methods:
With a conventional switch matrix, \$n\$ pins gets you \$(\frac{n}{2})^2\$ switches and needs \$(\frac{n}{2})^2\$ diodes.
Charlieplexing the switches would increase this to \$n^2 - n\$ switches while reducing the number of diodes to just \$n\$.

Both these have the advantage that I can just combine all the poles together and get my redundancy there. However, I would guess there might be a clever way to connect them taking advantage of the multiple poles to reduce or possibly eliminate the need for extra diodes.

How can I take advantage of the multiple poles to reduce the number of needed diodes while still maintaining some level of redundancy in the switch network?


texts:
I am trying to build a voltage divider with an offset. I have an input signal of 10 Vpk and I want it to have a DC offset of +1.65 V. The problem is that I don't have a DC source of 1.65 V, but I do have 3.3 V (2x 1.65). I tried to solve this with a resistor, but then I realized there was no current flowing from the source.

simulate this circuit – Schematic created using CircuitLab

Thanks


texts:
The example below is for a perfect lossless circuit with no resistance for the sake of illustration only. In reality this does not exist, but again the purpose is for simplicity.

If there is 1 Joule of energy stored in a capacitor and then that capacitor is connected to a coil to transfer and then store the 1 Joule of energy into the coil's magnetic field, is this work done and if so how much work was done?

Taking it one step further, once the 1 Joule of energy is fully stored in the coil's magnetic field it then has to go somewhere. It then collapses and a diode is used to redirect the 1 Joule of energy to charge another capacitor.

What is the total amount of work that has been done in storing energy starting from the 1 Joule of energy stored in the first discharging capacitor, which is then stored in the coil's magnetic field, and then lastly ending up as stored energy in the second charged capacitor?


texts: How does computer chip know what a 0 and a 1 is at base level?

texts:
I know there are some questions answered like this, and I have read them. I still have the same question though.

So from my understanding is that machine code is basically 0's and 1's. There are many switches that basically get turned on and off by when electricity is running through, its on (or is 1) and when no electricity it is off (or is 0).

We upload machine code so that the metal or what ever the chip on the board is comprised off, understands this and 0's and 1's. My question is how does this chip once it is built know to even recognize that we're saying 0's and 1's? How does the chip even know what a 0 or 1 is? How does it know that when switch is on to be assigning 1 to it and vise versa?

I know I cant just take a piece of metal(or what ever the chip is made of) and upload machine code it thinking that it will understand that I am trying to tell it that when switch is on to be assigned 1. How does this work?

This is one site I looked at:

How does a computer recognize 0s and 1s?

The problem is when the explanation gets to "The transistor can be turned on to enable access to the capacitor, either to charge it up and store a 1". So basically electricity goes through and the transistor is on and is charged and then stores a 1. But how does it know what a 1 is? How does it know how to interpret that 1 is associated with electricity charging the capacitor up?

As you can see, these are the questions I have. Any help would be great.


texts: How does the DW01A prevent overcharging and discharging?

texts:
I am not that familiar with electronics, it's just a hobby.
I am reviewing the TP4056 and DW01A ICs that are used for battery charging.
Actually there is nothing special about these ICs but I was wondering how the red marked area works.
I know the two DW01A pins prevent overcharging and discharging, but how does it work? I searched for an explanation but nothing found.


texts: Why are hard drives not limited to sizes of a power of 2?

texts: For example, hard drives can be 320GB (between 2^8=256 and 2^9=512) in size, whereas memory appears to be limited to sizes of power of 2.


texts: What are the types of damage can a voltage sag cause?

texts:
According to this site, a voltage sag happens when the rms voltage decreases between 10 and 90 percent of nominal voltage for one-half cycle to one minute.

What types of damage can a voltage sag done to any electronic devices?


texts: I keep PCBA's in an ESD bag.  When I want to use them, I put them on the bag to avoid crushing any components on the bottom side.  Is this any better or worse than a table?


texts: How to protect NTC thermistors for embedding in cement?

texts:
My kitchen at ground floor already has a floor (with floor heating) but it needs to be lifted by 3-5 mm with a very fine cement, on top of which tiles will be installed.

I would like to embed a couple of NTC thermistors in it (likely both at the center) to eventually make measurements of the temperature and to estimate losses to the ground, and so on. I'd put more than one to compare values, but all next to each other.

I thought about NTC because they are thinner and because I'll need quite some of them for the other parts of the ground floor.

How should I protect the NTC? I thought about heat shrink and some silicone sealant, nothing more, since no humidity is expected (after drying) and because the expected temperature rage will never be wider than 0°C - 55°C.

Am I correct? How should I protect the thermistor(s) before embedding in the fine cement?


texts: Is it possible to find an inverse system for this difference equation?

texts:
y[n] = x[2n + 1] + x[2n − 1]

I know that a system is invertible if none of two inputs results in the same output. In my opinion two such inputs exist so this system is not invertible since any number of x[n] can be a found which satisfy x[n]+x[n-2]=y[(n-1)/2] . But I am not sure whether I am right or not.


texts: Input Rerouting using IC or Transistor Application

texts:
I'm quite new to Electronics and I have this assignment I have to do - I need to "reroute" the input according to his type.

I have these two inputs, which can be both analog (1 channel, same value on both inputs) or digital (2 channels, different value in every input). I also have this Control input which is given to me, and I can detect whether the input is Analog or Digital (5v - analog. 0v - digital).

I added two schemes that shows how it should reroute the inputs:

if the input is Analog, it should reroute it to the Analog input A0
(of the Arduino in my case).
If the input is Digital, it should reroute it to Digital Input D0 and D1 (of the Arduino in my case).

Case Analog:

Case Digital:

I know I can do it using an Arduino, but I'm looking for something cheaper and smaller to do this, and I don't want my main Arduino to handle this. Is there any IC that does this kind of jobs? If not - how can I do it using transistors?


texts:
As you can see in the below figure no1, I have used two 9V dc batteries. Here BC548 transistor works in the active region and LED glows.

Whereas in figure 2 , connection is made using single 9 V dc battery but circuit is not working and LED doesn't glow.

What  wrong is happening . Is it possible to operate BC548 npn transistor in Active region using single 9Vdc battery?


texts:
I see that some wireless devices like Bluetooth speakers don't use shields like this one

but some do. My understanding of FCC Part 15 is that only modules need shields. So how come some devices use shields whilst others don't?

Thanks


texts: Paralleling of 2 power supplies with different voltages

texts:
I have 2 full bridge dc-dc converter from 12 to nearly 170 volts. each one are designed to 250 watts...

I am designing the transformers and is very complicated to make exactly equals by homemade and without machines... probably one voltage will be different to the other one, what if I parallel them?

I know that if I put 2 equal voltage batteries in parallel, the voltage will be the same and the current capability will be the double, and if I put them in series the voltages will be the double and the current capability will be the same. but what if the voltages are different in parallel? or what if the currents are different in series?


texts:
I try to design a circuit that adds two 4-bit binary numbers, but I get confused about the carry thingy.

Above I add 0100 + 0101. The result should be 1001, but it shows 1100. buzzer

Later I did the 0110 + 1001 and it got it right (1111).

Then I tried 0111 + 0010 and I got 11010. buzzer

Is it the Half Adder fault?

Did I falsely connect each carry to the "CIN"s?

What's wrong?


texts: Is it ok for Vgs be higher than Vds on a n-channel mosfet?

texts:
Is is OK to drive the gate voltage of an n-channel MOSFET higher than the drain voltage?

The scenario is turning on a circuit with a sensor that outputs higher voltage than the circuit runs on. Specifically, a 5V sensor and a 3.0V circuit.

The MOSFET I have available is a 2n7000.


texts: Interpreting some functions of an optoisolator from its datasheet

texts:
I cannot interpret couple of things from the datasheet of this optoisolator.

1-) Is there and hint in the datasheet regarding the maximum CM voltage interference it can handle at its inputs?

2-) The input capacitance is given as 18 pF. Is this the capacitance between the input and the output of the optoisolator? Is it possible to say what frequency of CM interference would this optoisolator pass through regarding this capacitance?


texts: error when trying to build using eclipse. Target is STM32 Nucleo-64 board

texts:
I have also installed zadig 2.5 driver. Please find attached screen shot of my device manager

Error: jtag status contains invalid mode value - communication failure
Polling target STM32F446RETx.cpu failed, trying to reexamine
Examination failed, GDB will be halted. Polling again in 6300ms
Info : Previous state query failed, trying to reconnect
Error: jtag status contains invalid mode value - communication failure
Polling target STM32F446RETx.cpu failed, trying to reexamine
Examination failed, GDB will be halted. Polling again in 6300ms
Info : Previous state query failed, trying to reconnect
Error: jtag status contains invalid mode value - communication failure
Polling target STM32F446RETx.cpu failed, trying to reexamine
Examination failed, GDB will be halted. Polling again in 6300ms
Info : Previous state query failed, trying to reconnect
Error: jtag status contains invalid mode value - communication failure
Polling target STM32F446RETx.cpu failed, trying to reexamine
Examination failed, GDB will be halted. Polling again in 6300ms


texts: Why won't this charge pump supply more than a couple of milliamps?

texts:
I am trying to generate 12V from a 5V source, capable of supplying around 15mA with less than 0.5V of ripple. The circuit must use all through-hole components, and cost is an issue.

Having encountered issues with designing a boost circuit, I decided to try a charge pump instead:

It works perfectly in simulation, but when assembled on matrix board, the 12V drops to around 6V if I try to draw more than about 2mA. I have no idea why.

I am using schottky signal diodes and standard electrolytic capacitors. I don't have any datasheets because they came from Aliexpress. The inverters are a single SN74HC14N.

I have tried varying the frequency and the size of the capacitors. I also added an extra stage (the original design had one less stage than you see here, and worked in simulation).

What am I doing wrong?

(NOTE: I know charge pump ICs exist, and I plan to try one; but I'd still like to know why my home-grown solution is so bad.)


texts: Can a Li-ion battery be discharged in CV mode?

texts:
I have a load which can also be set to "Battery test". I can easily discharge a Li-ion battery using the CC (contant-current) mode, which is also a condition recommended by the manufacturers. For example, a typical recommendation would be:

  Discharge CC (18A) to 2.0V @ 20degC

I have worked with CC before and it works as expected. But what about CV (contant-voltage)? One can never see that on the specs/recommendations. If I set one knob to CV and use the "Battery Test" setting, it says that I can't use it. So I assumed that the load doesn't really like the idea of CV and I was wondering why?

I could switch to another type of load (not "Battery Testing"), where I can actually set the CV, but I'm afraid that this would destroy the battery. Can anyone help me to figure out whether or not I could force CV into the battery and why is there no CV into the battery-testing option? Thank you


texts: Is there a standardized foot print for attaching coax cable directly to a board?

texts:
I'm looking to attach 50 ohms coaxial cable to a circuit board. The signal is only 1kHz. The thought I had is below. Have a pad to solder the braid. Have some space between the braid and center electrode of some insulation and then the center electrode. Maybe for kicks have some drills to run a zip tie through for strain relief. Possibly via stitch the braid pad to the GND layer underneath for added strength.
Are pads like this standardized or am I on my own for this?

simulate this circuit – Schematic created using CircuitLab


texts: Why is speech malformed when listening to a USB signal with an LSB receiver?

texts: When you listen to an LSB (Lower Side Band) signal with your radio set to USB (Upper Side Band) or vice versa, the speech you hear is malformed. What causes this behaviour?


texts:
I have liPo battery with TAMIYA/TRAXXAS/DEANS/EC3
male adapters. Look at the picture:

But there is no luck to find some compatible pcb surface mount female
connector to power up my board from liPo battery.
Any TAMIYA or TRAXXAS or DEANS or EC3 compatible female pcb connector?
Link me please!
I'm sorry if this subject matter is inappropriate for the site.


texts: MC34262 PFC not reaching desired output voltage

texts:
I'm building a 450W PFC with a MC34262. It's the first time I build a PFC. I based my circuit on the reference design of page 12 of the datasheet.

I'm testing with two 100W incandescent lamps in series (the output voltage of the PFC should be 400V). The problem is I'm only getting a 300V output voltage instead of 400V. Here is my schematic:

The inductor is made using two 33x19x11mm stacked yellow/white toroids (bought them here). The primary has a 1 mH inductance and the secondary has 12 turns which gives me about 30V to power the MC34262.

This is the MOSFET gate waveform while powering the PFC with 220V RMS and the two 100W incandescent lamps in series as load:

Zoomed out waveform:

This is the waveform in the drain:

In both cases, with gate and drain waveforms I have to stop the scope in order to get a clear waveform, I can't trigger the signal properly (I can take a picture if needed). I don't know if that means the output from the MC34262 is not stable and therefore I'm not getting the full output power.

Just in case here is the line AC rectifier output:

As you can see the Vpk seems to be the same as the PFC output voltage.

And this is the pin 8 (Vcc) from the MC34262:

I found that the voltage on the compensation pin 2 is nearly 0V and according to the datasheet the voltage should be at least 1.33V, could that be the cause of the output not reaching 400V and not delivering the full output power?


texts: How to measure the quality of a USB charging cable?

texts:
I have a set of USB cables (data and charge) and I noticed that, for a given charger, the charge time differs by cable.

What would be a good way to measure the charging fitness of a USB cable? Possibly with equipment which is not NASA-grade?

I know that I could measure the charge current for a set of charger and cable but I would prefer to assess the cable alone.

Would this measure be dependent on the charger characteristics? In other words,  are some cables more or less efficient depending on the charger (not taking into account the current the charger can sustain)?


texts:
I am working on a simple 2 layer PCB in Eagle. I have my schematic done and I have laid out the board where I think everything is most efficient.

I have created a polygon the size of the board and named it GND for a ground plane on the bottom layer.

When I click on the autorouter it detects the ground plane and has all of the thermals connected to it correctly...

As soon as I do the autorouter (settings from https://electronics.stackexchange.com/a/132346/20610) it ignores the thermals connected in the middle of the board.

I have tried to add the ground plane after the routing of traces only and it looks better but I know I am doing something wrong since I can't get the ground plane throughout the board.

How do I fix this so it auto-routes correctly and I get a ground plane with all of the thermals connected to it?


texts: Shift register SPI control: cascading but individual latch

texts:
I would like to connect several boards to the microcontroller and  send data to shift registers placed on the boards. I'm cascading all the shift registers for the data sending from the SPI. But I would like to latch the values individually as the output of the shift register to the board is time controlled and asynchronous to the other registers.

I found this schematic to connect the SPI to the shift register :

(Schematic source)

With this connection I'm latching the signal directly after the transmission.

Is it possible to just use the clock and the data out of the SPI to connect to the register and choose my own latch signal ?  the CS will "exist" in the software but will not be connected to the shift register.

thanks


texts: How to receive INDUCTION communication at field strength of 3 dΒμΑ/m at 10 metres at 1MHz?

texts:
Is ferrite rod antenna (about 2 to 4 inches) a good choice, or best choice, to receive induction communication (both transmitter and receiver use coil antenna), given that the H (magnetic) field strength is 3 dΒμΑ/m at 10 meters at 1MHz? Directionality is no problem as antenna rod will be fixed and rotated for peak signal level.

Ferrite rod antenna (top left of photo) with LC parallel resonance tuning, has been used in medium wave radio (0.5 to 1.6MHz) since many years ago. Is that still the best choice nowadays, for radio and in my 1MHz application?

As receiver (small current), at 1 to 4MHz, what is the difference, in term of power derived from 3 dΒμΑ/m H field strength, between proper Litz wire and solid wire coil?


texts: How does "mechanical stop" and "electrical angle" differ for this potentiometer?

texts:
I want to use this potentiometer which is continuous turn. In the datasheet it says:

Effective Electrical Angle ...............340 ° +3 °

and there is also:

Mechanical Angle ................ Continuous, Stops (340 ° +8 °, -0 °) available

What are meant by these? It seems mechanical stops can vary but electrical angle is the same. Between which angles will the the potentiometer wiper be floating? Which parameter indicates that?


texts: What is the difference between ARM Cortex M7 and Cortex A53, and their possible applications?

texts: What is the difference between ARM Cortex M7 Cortex A53 (or A17)? Why one will choose one over the other? To what kind of applications does each of those is targeted for? Which one will be more suited (and why?) for wireless communications and video?


texts: Bluegiga BGScript Accelerator sample. I want to understand the example code

texts:
I started BGScript few days ago. I have many questions about BGScript. Any help will be appreciated. Thanks!

*My goal is advertising with accelerator data via BluetoothLE.  I am going to use ADXL345 as an accelerator.

I could advertise with temperature data.  The source code is here (Almost same as reference code) http://qiita.com/zono/items/2e6290e91f5b3728daa9

*My questions are

1 How to read port data?

According to "hardware_io_port_config_direction", the direction is the setting of I/O.
For example, hardware_io_port_config_direction(1,$7) means Port1_7pin is used as Input, isn't it?

2 I want to understand the meaning of the accelerator sample below.

Dim temp (10)
Dim spiresult
dim channel
dim tlen

event system_boot(major ,minor ,patch ,build ,ll_version ,protocol_version ,hw )
    call gap_set_mode(gap_general_discoverable,gap_undirected_connectable)

    call hardware_io_port_write(1,$7,$3)            # Why port 1? The Datasheet shows P1_7 is "DCDC on/bypass control". Why $7?  Just "7" with out "$" is not correct? What $3 means?
    call hardware_io_port_config_direction(1,$7)    # It means Port1 7pin is used as Input?
    call hardware_io_port_write(1,$7,$7)            # What $7 means?
    call hardware_spi_transfer(0,2,"\x0a\x06")      # The Datasheet shows P0_2 is "UART CTS".  What is "\x0a\x06"? What this lien meaning !?
    call hardware_io_port_write(1,$7,$3)            # This line already called. Why is it nessasary?

    call hardware_set_soft_timer(32768,0,0)
end

event hardware_soft_timer(handle)
    call hardware_io_port_write(1,$7,$7)
    call hardware_spi_transfer(0,2,"\x18\x00")(spiresult,channel,tlen,tmp(0)) # What is \x18\x00?
    call hardware_io_port_write(1,$7,$3)
    call attributes_write(x_data,0,2,tmp(0:2))

    call hardware_io_port_write(1,$7,$7)
    call hardware_spi_transfer(0,2,"\x1c\x00")(spiresult,channel,tlen,tmp(0)) # What is \x1c\x00?
    call hardware_io_port_write(1,$7,$3)
    call attributes_write(y_data,0,2,tmp(0:2))

    call hardware_io_port_write(1,$7,$7)
    call hardware_spi_transfer(0,2,"\x20\x00")(spiresult,channel,tlen,tmp(0)) # What is \x20\x00?
    call hardware_io_port_write(1,$7,$3)
    call attributes_write(z_data,0,2,tmp(0:2))

end

event connection_disconnected(handle,result)
    call gap_set_mode(gap_general_discoverable,gap_undirected_connectable)
end

3 What is cdc.xml. Is it necessary?

4 Can I debug using display? I want to display x,y,z_data on screen.


texts: What is conductor to conductor to shield capacitance?

texts:
I am using 6.5 ft (2 meters)  BELDEN 9154 shielded twisted pair cable for a sub 1 MHz application and I wanted to make a model of the cable for some simulations. The datasheet of the cable lists two capacitance as shown below:

How to interpret these capacitance? For a 1 ft segment what values of capacitance is observed across the conductors and across shield and one of the conductors?


texts: How to identify my transistor's pins or leads?

texts:
I searched on YouTube and Google about an easy way for finding the base, collector and emitter  of transistor's pins, and I found this link: http://www.youtube.com/watch?v=DJ9mg7b_SiA

Is this method right? and if not, can anyone provide for me a better way?


texts:
I am working on coding a Regsiter a1 with input signals b1,rst and wra1
the register a1 is initialized to a specific value at reset.
a1 only changes its value to b1 when wra1 is 1 else it keeps the old value

process(clk,regrst)
begin
    if(regrst='1')then
        a1 <= (others =>'0');
    elsif(clk'event and clk='1') then
        if(wra1='1')then
            a1 <= b1;
        end if;
    end if;
end process;

In this statement I have written the register process to update on the needed wra1 signal but I am confused on how to make it keep the old value of the output in case this write signal is 0
does this concept generate unintended latches to store the previous value? if so what can I add as a default register assignment in the begning of the process ? and should I include the else statement with

a1<=a1;

Thank you


texts: BJT Current Source and Current Doubler - Identification and Analysis

texts:
Identification: Is there a name for the following NPN BJT Current Source with three identical BJTs, which doubles the reference input current?

Analysis: If \$R_L = \frac{1}{2} R_1\$ as shown in the schematic, then the following is valid:
$$I_{out} = 2 ( I_{in} - 3 I_B ) = 2 \frac{\beta}{\beta + 3} I_{in} \approx 2 I_{in} \ \text{for} \ \beta \gg 1$$

Can one easily see that \$I_{out} = 2 ( I_{in} - 3 I_B )\$ is true?
What are the values for \$I_{C,2}\$ and \$I_{C,3}\$ based on the above assumptions?

Are the following answers correct?

Due to the identical BJTs and identical base currents, \$I_{C,2}\$ = \$I_{C,3}\$
Hence, \$I_{out} = I_{C,2} + I_{C,3} = 2 I_{C,2} = 2 I_{C,3}\$
Because of the mirroring characteristics, \$I_{C,1} = I_{C,2} = I_{C,3} = I_{in} - 3 I_B\$
Result: \$I_{out} = 2 ( I_{in} - 3 I_B ) = 2 I_C\$
Further transformations:
$$ I_B = \frac{1}{\beta} I_C \rightarrow 2 I_C = 2 ( I_{in} - 3 I_B ) =  2 ( I_{in} - \frac{3}{\beta} I_C )$$
$$ I_C = I_{in} - \frac{3}{\beta} I_C \rightarrow I_C (1 + \frac{3}{\beta} ) = I_{in} \rightarrow I_C ( \frac{3 + \beta}{\beta} ) = I_{in} $$
$$ \hookrightarrow I_{out} = 2 I_C = \frac{2 \beta}{\beta + 3} I_{in} $$


texts: What happens when a multi-fuel generator reaches capacity on LPG or NG?

texts:
I have a multi-fuel generator rated for 7.5KW on gasoline, 5.5KW on natural gas.
It has a 30A circuit breaker that will trip if demand exceeds capacity on gasoline
I would like to understand in some detail what happens if demand exceeds capacity on natural gas.  The manufacturer says the breaker will trip.  Is that right?   How will a 30A breaker trip at what should be around 22A at max power on NG?
Common advice on some other forums is that the generator will overheat.  Will it?  Neither the engine nor alternator are running at the actual full power capacity designed for gasoline.
Will voltage drop?  Presumably this could harm anything powered by it ... not just sensitive electronics but anything.
Any insights much appreciated.


texts: This circuit is two parallel resistances of 10Ω. Convince me otherwise

texts:
I'm trying to find the Thévenin equivalent resistance of a circuit - one that resembles a Wheatstone bridge, but is not at balance. The load in question is where the galvanometer would appear.

Anyway, I have disconnected the load, removed the (ideal) sources, and redrawn the circuit as below.

To me, the resistance seen by the load on AB is two series combinations, both of which evaluate to 10, in parallel - an equivalent resistance of 5Ω.

This is apparently incorrect. My textbook calculates the Thévenin resistances as:

$$ R_L = \frac{3 \times 7}{3+7} + \frac{4 \times 6}{4+6} = 2.1 + 2.4 = 4.5Ω $$

Can someone please explain?

simulate this circuit – Schematic created using CircuitLab

TIA


texts: How to find currents of all nodes using superposition theorem

texts:
Given this circuit:

simulate this circuit – Schematic created using CircuitLab

Using the superposition theorem, I need to find the current of all the 3 nodes of the circuit.
Using superposition I've found that the current from the source:

V1 is 6.32A = i_1
V2 is 1.05A = i_2
V3 is 1.89A = i_3

So is it correct to say that at the node of V1 the current is i_1 - i_3 ?
I am really not sure how to proceed.


texts: How do you find the transconductance of an external crystal oscillator?

texts:
I am trying to connect an external crystal to my STM32F446RC MCU.
I am following this guide to check for the compatibility: https://www.st.com/resource/en/application_note/cd00221665-oscillator-design-guide-for-stm8afals-stm32-mcus-and-mpus-stmicroelectronics.pdf
The only part of the equation I can't find in the datasheet of the crystals I have seen is the transconductance value, where can I find this?
Example of crystal oscillators' datasheets I have seen:
https://ecsxtal.com/index.php?plg=sslfixer&url=http%3A%2F%2Fecsxtal.com%2Fstore%2Fpdf%2Fecx-3sx.pdf


texts: What is this 0.35mm mezzanine/FFC (?) connector?

texts: This connector is used in Retina LCD controller boards to connect the LED strings. Pin pitch measures at 0.35mm, height 0.7mm, overall dimensions (with leads) about 4x2.5mm. Couldn't find it at the usual distributors or at Hirose, I-PEX, JAE and Molex, but of course it could be something else or I could be mistaken.


texts: Decoding power supply regulation (42V from 5V)

texts:
I am referring below schematic where 42V is generated from LM78L05 regulator IC. But I am not able to get how LM78L05 can generate 42V? Which concept is used to get such high voltage from 5V regulator IC.

P48TA and P48TB are points taken from step down transformer.


texts: How to find the short circuit element on electronic board easily

texts: I have two Uster Tester ( this machine used at textile) cards. one is corrupted and the other is the same one that works. Trying to repair the corrupted card by performing comparison test. When I try to make continuity test with the multimeter to the Vcc and GND terminals of the integrated cards on the robust card, only a short beep sounds heared and stops. however, when I test the continuity between Vcc and GND of any integrated circuit on the corrupted card, the beep sounds continuously. as far as I think it has been shorted somewhere in a capacitor. I wonder how quickly I can find this short-circuit element on the circuit


texts: Ways to estimate the rated current of an induction motor without nameplate

texts: I am looking at ways to find the rated current of the motor without the nameplate data. Methods for rated voltage has been found. Assuming that we have the rated voltage, what would be some ways or directions to find the rated current? I have looked into slip but different HP motors have different slip. Unless the motor HP is known, this method cannot be used. Are there any other methods?


texts: Looking for extremely high power dc motor controller solution, 120 VAC to 90-180 VDC, 5-10hp range

texts:
Could use some help with a DC motor application.
Note: A number of factors here are determined by the available hardware. I'm sure this might work better with a more specific AC drive, but this is a budget, fun, experimental project, just trying to make best use of what I have without spending much to build it.
The setup: An experimental electric kayak. Very tiny boat, (8 ft one person)
with a 1/2 hp Baldor 90VDC motor I acquired as scrap, nailed to the back.

Last season's system was a single marine battery, a 2kw Harbor Freight inverter, the 1/2 hp motor and a KB DC motor drive, 90 VDC, 16A max.

I also have a 3/4 hp DC motor, just a bigger copy of the 1/2 hp model.

The observation was that the motors were very, very heavily underrated, and the motors might be able to take more than they say... a lot more.

This was fine, and a lot of fun, but topped out at 2kw when the inverter would cry uncle, alarm out and shut down, right when the kayak was hitting some serious speed. Even using the smaller 1/2 HP motor it was obvious that this was nowhere near the motor's limits... and I was itching to try the 3/4 HP in its place, but lacked any means to supply enough current to drive it properly.

I just acquired a much bigger 12VDC to 120VAC inverter good to a whopping 10,000 watts, for cheap. So now I can drive just about any level of current I want once I put together enough batteries in parallel to feed it. Problem is, my available DC motor controller tops out at 90V, 16A. With a little forced cooling I might manage to pull 20A out of it, but that's as far as it can go. Trying to find a DC motor controller that can handle in the 4-10 HP range, the only ones that even come close are 180VDC and run on 220VAC.

I understand why, (under normal industrial circumstances, no sense trying to toss around that kind of power and run it on 120VAC when most 120V hardware tops out at 15-20 amps, most serious power apps you'd run on 220, half the current, lot more power available...)

But the bottom line is, I'm trying to do this taking advantage of the cheap inverter and free motors, so I have to work around what I have.

I'm considering building a monster rectifier, which, if I remember my high school audio amp builds right, would give me about 180VDC coming off the diodes, give or take a bit, which would be awesome, and allow me to drive those motors harder on less current, but I'd have no means of modulating or applying it.

So I'm looking for, either: A truly massive 120VAC to 90VDC controller similar to the KB line but 2-3x the current, able to apply 20-40A or more at 90VDC, which doesn't seem to exist,
Or,
A relatively crude way to slap a rectifier and a couple of caps onto the output of the inverter, giving me 180VDC with as much as 55A backing it, and then a means to dial it down, PWM or some form of chopper.

I'm considering maybe an intermediate stage, something like a very, very heavy triac lamp dimmer, followed by the rectifier feeding directly into the motor... use the triac to turn it down before it even reaches the DC stage. But I'm not all that sure how a rectifier would handle being fed the chopped-up output of a triac. I've never tried such a combo before and I have no idea if that would even work.

Not sure which way to go with this. There is probably a much better way to do this than I know about, but so far, no luck finding it. Anybody got any suggestions?


texts: Should NC-Pins of IC connected to ground through a resistor to prevent noise?

texts:
I wonder if unused pins of an IC, lets say an NE555 f.e., should be connected to ground via a resistor to prevent noise or not. I have an AVR with analog inputs and just realized there's huge noise, if not connected. So I'm not sure if it is OK to leave unused Pins of other IC's like the 555 Timer unconnected, or better pull them to ground via 10kΩ or 100kΩ resistor?

In other words: could it get trouble, if unused pins of a ne555 left open?


texts: Could A28A transistor work for controlling Rx/Tx pin?

texts:
I want to control a robot with my arduino via RX/TX.
Here is the wiring:

They recommend transistor pnp 2N4403.

Another guy said that a small signal, low power PNP transistor such as 2N2907A could be used.

Howerver, the only pnp transitor that I have is A928A.
http://www.mouser.com/ds/2/149/KSA928A-59269.pdf

Do you think this PNP transistor could work ? I am a beginner so I don't really understand the difference between all those different transistor...


texts: I want to use a resettable fuse for overcurrent protection. I am a bit confused about their features. The hold current is the maximum current for not tripping and the trip current is the mimimum current for tripping, right? Then, what is the current rating? Also, regarding the ambient temperature, I am going to use the fuse inside an enclosure. Should I consider a higher than ~25 C degrees temperature for selecting the right hold current?


texts:
I was having a look at some guitar effect circuits and came across with a company that offers PCBs for some well known circuits. I have noticed that most of ther circuits have a 1N4001 (D1) placed between VCC and GND, without any kind of resistor in series.

This one, for example:

At first I thought it was meant to avoid reverse biasing the transistors, but risking the power supply by placing it in parallel doesn't make much sense to me.

I think it would be better to place it in series to the source or, if needing to keep that parallel setup, at least put a resistor in series to the diode to avoid a direct short circuit.

I just would like to know if the circuit is wrong or I am missing something.

Thank you very much.


texts: What is the physical meaning of an LC circuit having a negative transfer function?

texts:
Say you have an ideal LC circuit:

simulate this circuit – Schematic created using CircuitLab

The transfer function of this circuit is a complex voltage divider: $$ \frac{\frac{1}{sC}}{sL + \frac{1}{sC}} $$ $$ \frac{1}{s^2LC + 1} $$ $$ \frac{1}{1-\omega^2LC} $$

That means that for large values of C, L, and/or \$\omega\$, the transfer function becomes negative. What physical meaning does this have? Does the signal go 180 degrees out of phase with the input? Am I perhaps missing a magnitude sign somewhere?


texts: Safety when creating electronics enclosure

texts: I'm designing an electronics enclosure to be placed in series with the power cord for a device for control purposes and would like to know safest methods to do power breakouts within the plastic box. I'm planning on putting a power entry module on one end or possibly two to make the power breakout easier. I've seen terminal blocks but mostly used for DIN rails/control panels, not small enclosures. I only need 2 separate sets of hot/neutral/earth, one of which will be fed to a 5v power supply. I'd also like to know how to test wiring in something like this since I want to be sure the 120v lines are very secure and there's no potential for loose connections/soldering. There will be a relay switching 120v that goes out through another plug also, so don't know if that changes any protocol. Thanks


texts:
At 210 nm, the shortest wavelength/highest frequency LED seems to be composed of a Aluminum Nitride junction (according to this article).

I was wondering, what would the Vf (forward voltage) be of such a diode. I can't seem find any information on deep UV diodes and their respective Vfs (this source claims 7.5V max for a 250nm diode).

Aside from just stating a number (or an approximate number) is there any way (or approximate way) or calculate a diode's Vf vs peak wavelength (perhaps via some form of interpolation of existing diode Vfs)?


texts: MOSFET as inrush current limiter (passthrough parasitic C?)

texts:
I have a circuit based on a P-FET which shall limit inrush current (20 mA).
However, when turning on the power supply there is always a current peak (30 mA, 5 ms) through the M1. Even if I tie its gate to the source.

My question is: What effect is causing that current peak?

Is the P-FET initially conducting?
Is there a capacitance in series with the P-FET which could be large enough to let that current pass?

Appreciate any hints.
If there are details missing in my description, my apology in advance.

simulate this circuit – Schematic created using CircuitLab

@WhatRoughBeast I have updated the FET type.

In order to detail my last comment about counteracting the condition which leads to initial FET conduction (capacitive voltage divider) I'd like to draw what I have in mind. Maybe that helps to understand and discuss about.

simulate this circuit

So theoretically one would need a charge pump in order to cancel the inrush current through Cgs so no significant (less than Vgs_th) Vgs would develop.
The charge pump would need to be very fast.

What do you/others think?


texts: Why Current draw in DC variable power supply is not sizable?

texts:
I have done a DC variable power supply, and checked it using multimeter the output voltage ranges from 1.3v to 19v, but the problem is when I added a DC load(small DC motor) it was not working, why?

At No load, the output voltage ranges from 1.3v to 19v but, with load, voltage becomes zero.

DC motor specifications
Operating voltage - 3-6v
Current- 300 mA


texts: How much larger should a bga pad be than the ball itself?

texts:
I've never had to do the layout for a board involving a BGA part until now.  I'm curious what the rule of thumb is on oversizing the pad for the ball.  What size pad should I use if a part has balls that are .35 mm diameter with .65mm spacing between centers?  Is there a general rule of thumb for how much to oversize the pad on a bga part?

Edit:

Here's a screen shot of the part from the datasheet


texts:
I have few doubts regarding TL431.

Please correct if i am wrong..

TL431 can be used to generate voltages from Vref to 36V. Output voltage is taken across diode in reverse biassed condition. reverse characterstics says Reverse breakdown voltage is 2.5V, then how TL431 can generate different output voltages. Diode breakdown region allows more current(Ika) to be taken but reverse breakdown voltage(Vka) will be almost const.
I didn't understand physically how it will generate different voltages.
Please explain the operation of the other elements, like When Vref> 2.5V Opamp output will be high, then transistor will be ON and conducts current, but it will not effect diode behavior.

When Ref<2.5 Op-amp output is Low -->Transistor OFF, but it will not affect diode behavior. When the diode will be going to breakdown region?.

Constant Current source using TL431

How to explain this circuit.?

One explanation says, REF always maintained at VREF->2.5V, so, constant current source Vref/Rs ----> How REF always maintained at 2.5V


texts: Current amplification for Raspberry PI4 powering

texts: I need to power the Raspberry PI4 from my embedded system so i used a DC/DC regulator(https://www.sparkfun.com/datasheets/Components/LM7805.pdf) from a bipolar power supply composed of two 9v batteries the DC/DC regulator gives as output 5V and 1A but for the raspberry PI4 I need 5V 3A.Can anyone propose for me a solution to amplify the current or its ok to give the raspberry PI 1A as input current.I am new in this field.Thank you for the help.