texts: Stepping down 12V to 5V without amperage loss

texts:
I'm building a LED wall but I'm having trouble finding a suitable PSU. I need a 5V one but all I can find are 12V 30A which if converted to 5V would be perfect.

My question is, is there a way to buck down the 12V to 5V without any loss of amperage? If so, how?


texts:
I am following up on my earlier question. I am trying to build a very clean 5V and 3.3V supplies. I have asked this question and got several very good answers, we designed it and it will come back soon, I will let you know.

The new question came from a colleague who suggested using two switchers one for 3.3V and other for 5V. He indicated this way, the efficiency would be much better. I wasn't sure since this would also introduce a second noise source to the board. What do you guys think? If cost and space is not an issue, where the only thing you care is noise, would you go for 2 switchers?


texts:
I have a doubt while selecting the inductor for a buck converter.

  TI App Note

In This app note, in the abstract itself, they mention that this :

  This application report gives the formulas to calculate the power stage of a buck converter built with an
  integrated circuit having a integrated switch and operating in continuous conduction mode.

This not mention anything about the DCM mode. So, does it mean that, if I follow the mentioned steps in the app note, for my Vin, Vout and Iout, I will not enter the DCM mode?

I understand about the DCM mode. But in this case, what care should I take while designing such that my selected inductor does not enter DCM.

Vin = 3.3V

Vout = 1.8V

Iout = 0.4A

Selected Inductor = 22uH


texts: Parallel access to memory with multiple DDR4 chips

texts:
Some development boards have multiple DDR4 chips. Does it imply that such boards have multiple DDR controllers and memory can be accessed in parallel.

For example this boards: https://www.xilinx.com/products/boards-and-kits/kcu105.html#hardware has 4 DDR4 chips.

Thanks


texts: High side MOSFET driver with transformer

texts:
I am reading the application note " Fundamentals of MOSFET and IGBT Gate Driver Circuits" written by Texas Instrument.

In order to control High Side MOSFET, the application note suggests to use this kind of circuit :

Why I just cannot use this kind of circuit ?

It seems simpler from my point … But this is probably not the case ?

Thank you very much !


texts: 8x8 LED Matrix with MAX7219 - Control with software SPI

texts:
i am currently trying to get a 8x8 LED Matrix, which is controlled by a MAX7219 IC, working. The chip supports SPI with DIN, CS and CLK pins. I tried to control the chip via software SPI with a STM32F103. This is my code:

#include "stm32f10x_gpio.h"

#define CS 4
#define SCK 5
#define MOSI 7

void delay(long cycles){
    while(cycles > 0)
        cycles--;
}

void initSPI(){
    RCC->APB2ENR |= (1<<2); //Enable Port A clock
    GPIOA->CRL |= (0x3<<(4*CS)); //General PP & 50MHz speed for PA4 (CS)
    GPIOA->CRL |= (0x3<<(4*SCK)); //General PP & 50MHz speed for PA5 (SCK)
    GPIOA->CRL |= (0x3<<(4*MOSI)); //General PP & 50MHz speed for PA7 (MOSI)
}

void transmitData(uint16_t reg, uint16_t data){
    uint16_t serialData = (reg << 8) | (data & 0x00FF); //Last Bit First
    GPIOA->ODR &=~(1<<SCK); //Turn SCK low
    GPIOA->ODR &=~(1<<MOSI); //Turn MOSI low
    GPIOA->ODR &=~(1<<CS); //Turn CS low
    delay(10);
    for(int i = 0; i < 16; i++){
        if((serialData >> (15-i)) & 0x0001){ //Bit is '1'
            GPIOA->ODR |= (1<<MOSI); //Turn MOSI high
        } else{
            GPIOA->ODR &=~(1<<MOSI); //Turn MOSI low
        }
        delay(10);
        GPIOA->ODR |= (1<<SCK); //Turn SCK high
        delay(10);
        GPIOA->ODR &=~(1<<MOSI); //Turn MOSI Low
        if(i == 15){
            GPIOA->ODR |= (1<<CS); //Turn CS high
        }
        GPIOA->ODR &=~(1<<SCK); //Turn SCK low
    }

    delay(10);
    GPIOA->ODR |= (1<<SCK); //Turn SCK high
    GPIOA->ODR &=~(1<<CS); //Turn CS low
    delay(10);
    GPIOA->ODR |= (1<<CS); //Turn CS high
    delay(50);
}

void initMAX7219(){
    transmitData(0x0B,0x07); //Scan Limit
    delay(50000);
    transmitData(0x09,0x00); //Decode Mode
    delay(50000);
    transmitData(0x0C,0x01); //Shutdown Mode
    delay(50000);
    transmitData(0x0F,0x00); //Display Test
    delay(50000);
    transmitData(0x01,0x01); //Display '1'
    delay(50000);
}

int main(void)
{
    initSPI();
    initMAX7219();
    while(1){
        ;
    }
}

And this is how the pin states look like, captured with a logic analyzer:

Even though i think i did everything correctly (bit state of the DIN pin is transfered on rising edge of CLK, full 16 bits are shifted on CS rising edge, which should appear at or after the 16th rising edge of CLK) it doesn't work. The longest timing is 100ns which should be fulfilled. Any help is very much appreciated.

Edit: This is how the PCB looks:


texts:
Let's say there is a USB stick that is specifically for storing dates or days or some kind of arbitrary data. In order to access the data you must have the software.

Is there any way to analyze the USB signals and make your own hardware to read the values on the flash drive? What methods exist for doing so?


texts:
I am testing a simple circuit in which an electret mic is hooked up to two transistor preamps, then to an 8ohm speaker. I am using a 9v battery, and the circuit looks like this. This circuit is meant to be simple enough to teach to kids at school.

I have followed it exactly, and it works... somewhat. As soon as I plug in power, a low noise comes from the speaker. When I try to speak into the mic, the sound changes, but you can't actually hear works. Just change in volumes/sound change. I really want a "megaphone" like circuit, without the excess noise and clear amplification.

please note I prefer this transistor amp over a lm386 chip for this particular project as it is for use in a school

What issues could be causing the excess noise?

Edit

Made purpose clearer.


texts: What are the important values of GNSS antennas

texts:
I want to compare different GNSS antennas, but I don't really know what values to compare.
How can I compare them with datasheets looking like this?
Edit:
The antenne will be used on a rover that will move off-road.
I need maximum precision at all times (I do use RTK.)


texts: Adding Peltier module to an evaporative cooler

texts:
I'm planning to add a two Peltier module (TEC 12706 with heatsink on both sides) on a evaporative cooler but I cannot decide where should I put them.

Here's the idea:

Idea B would be good but I'm planning to use this fan in an small room. Humidity will rise and affect the evaporation process or ditch it and move the cooling element close to the air inlet of the centrifugal fan.


texts:
I'm venturing into JTAG flashing, and thought OpenOCD would be a good place to start. I had a quick look through the documentation and found it hideously complicated. Likewise, the very few "tutorials" I found on other websites were either incomplete, hard to follow, or relating to other hardware.

From start to finish, how would I go about flashing a basic LED blinky program onto the LPC1768 via JTAG, using OpenOCD?


texts: What's needed to get 100 mA from a USB port?

texts:
I'm trying to build a stereo speaker system for use on a laptop. I want to keep it as simple as possible, so I'm thinking of using laptop's audio output to for the audio signal and a USB port for power.

As far as I know, each port should be able to provide 100 mA for devices. Is there any need to signal to the computer that I'm going to try to draw 100 mA, or is it acceptable to just connect the device?

Also, how stabilized and filtered is USB power? I'm thinking of using TDA7053A to drive the speakers and its minimum voltage is 4.5 V. If that doesn't work, I'd use two TDA7052 amplifiers, but I'd like to keep number of parts as low as possible.

As for power consumption, I already have a small radio which uses one 50 Ω speaker and a TDA7052 and it uses at most 25 mA, so even with two of those speakers, I should have lots of power to spare with a maximum supply current of 100 mA.


texts: What does "5k1" in the given schematic mean?

texts:
What does the "5k1" stands for it is a normal 5k Ohm resistor?

(Marked with "A" in the picture)

The chip is an MAX13020 LIN-transceiver.


texts: driving a control pin to ground with different voltages

texts:
I'm using a 3.3V atmega2560 to disable a switching regulator that's operating on a ~12V battery. The EN pin on the switcher is pulled up to the battery voltage, and needs to be driven to ground to disable it. Clearly this is outside what the uC can do. My (very rudimentary) understanding is that I can achieve this with an N-MOSFET, by tying it to the enable pin like this:

Will this work? It looks a bit like I'm creating a short (V_BATT -> R1 -> Q1 -> GND), but I assume that's not an issue given the size of R1.

EDIT

I've got two such regulators:
http://www.ti.com/lit/ds/symlink/lm2734.pdf
http://www.ti.com/lit/ds/symlink/tps62125.pdf

One thing I'm not sure of is whether as asked in the comments, the EN voltage has to be tied to VIN, or if it just needs to be above some absolute value. There's discussion in the datasheets about EN thresholds, but they make no mention of whether these are thresholds relative to VIN or absolute values:

That said, TPS62125 does need to be tied to VIN to avoid a catch 22 - it powers the MCU, and a supercap that the MCU uses for power when it puts the system, and the regulator to sleep. So - until that supercap is charged for the first time, there is nothing to activate the regulator except the battery.


texts: Effects of frequently turning on and off power in the grid

texts:
What would happen to the infrastructure (transformer, transmission line etc) If I would turn on and off power frequently? Will it cause wear and tear? If so how? And how much?
Also the effects of lowering/increasing the power grid?


texts: How to test a CT Sensor (Alternating Current Clamp)?

texts:
I recently purchased a CT clamp. I am left wondering what the best way is to test this in a laboratory environment, specifically with an AC current generator. I just want to know whether the device works properly.

Could I just generate a fixed amount of AC current from the generator and short my negative and positive wires to create a current loop? From this, could I then just clamp my CT sensor around this loop?

If not, I am open to more suggestions! Any help is greatly appreciated!

Kind regards,

Hashim Shamsi


texts: Non invasive Method to measure if there is any current in a line

texts:
We have a project where we have to measure if there is any current through the a cable, but having not common ground and knowing that the current could come direct or reverse direction. We thought about the chance of set a differential opamp, but if the current came reverse that would be a problem .
We also thought about optocupler but we cannot limit the current so much.

Any idea is welcome,

Thanks in advance,

Carlos


texts: Buck converter ringing on rising and falling edges before failure

texts:
I have recently designed a PCB with a buck converter based on the LM3671 buck converter IC from TI to step down 5V to 3.3V. However, there is ringing on the rising and falling edges, and after a short amount of time the buck converter failed. It melted the solder on its solder pads and the internal MOSFET seems to have failed short. The oscilloscope trace that I was able to get before it failed looked like this:

(Sorry for the poor image quality)
I used the reference design from the datasheet for my schematic:

I tried to follow the best practice guidelines from several documents, including the datasheet for the LM3671 for the PCB layout:

I'm assuming I screwed up the PCB layout and added in some parasitic components somewhere which are causing the ringing on the rising and falling edges, but I'm not sure. It might also just be thermal design or something else. I'm just wondering why the buck converter failed, and what changes I can make to correct the issues that caused the IC to fail. Sorry if this is a dumb question. This is my first buck converter design and I'm just trying to figure stuff out.

Edit for some more details:
The maximum load current that I have is about 500ma with the average load current being well below 200ma.  I am using this(MAMK2520T2R2M
) inductor.


texts:
I need to calculate the number of parity bits required for a given word (set of bits).

I know a way, but is not always working, below my current approach:

word length: 8
so 2^3
then parity bits = 3 + 1

I am doing this to any given word (2^n bits), but it is not working for 2^1 or 2^2

Any idea?

Thank you!!!


texts: The output of a boost converter doesn't stay at 5 V

texts:
Let me start by apologizing for my english in advance :)

I'm trying to build an UPS for my raspberry Pi (even though I have basically zero experience in electronics). When the power cuts out, I want the Pi to stay ON for another 10-15 seconds. After doing a little research on google, I've decided to buy some supercapacitors and one of these neat boost converters - https://www.amazon.de/dp/B00HV59922. I set the output of the converter to 5 V, then Ive added two supercaps(5.5 V 4 F) to the input of the converter and finally powered the whole circuit with a 5 V powerbank. Then I measured both the input and the output of the converter to see if it works as expected.. and it didn't.

When the input voltage was between 3,6 ~ 5 V, the output was steady at 5 V. At 3.5 V, the output jumped to 12 V(?).. then it kept falling, at 3 V on the input the output was 7 V.. the output got back to 5 V when the input was approx. 2.75 V.

I was hoping to get either 5 V, or nothing. Can someone please explain what could be wrong here?


texts: Understanding Thermal Stability and Drift in Linear Regulators

texts:
I'm considering 3-terminal  linear regulators (LM317, LM350, TL783, etc.) for a power supply that regulates a 150V wobbly DC voltage down to 145V or 140V. My load is like 30-65mA. So, depending on parameters power dissipation might be 150mW or 650mW. I'd like the same circuit to handle either scenario.

A general phenomenon I've seen with the LM317: with a static load, the output voltage starts at 145.00V and quickly (~10s) drifts down to 144.93V, then over ~60s down to 144.91V, then over many more minutes drifts by some 10mV-order voltage.

I assume this is a negative temperature coefficient effect -- the regulator heating up. I can make Vout rise by absorbing some heat with my fingertip. I've been exclusively using DPAKs without a heatsink. Previously I've seen the opposite phenomenon: a slow rising voltage -- this was caused by high tempco carbon-composition resistors.

I've observed this effect under various loads, output voltages, and circuit layouts. The ultimate goal is to have a power supply which becomes quickly (seconds) stable to within 1mV. I don't want to come back an hour later and find it has dropped by 10mV.

A. How might one build the circuit to negate voltage drift due to temperature?

B. What is the difference between these? Some datasheets list many of them.

Output Voltage Change (%) vs Temperature. Mentioned in LM317, LM350, TL783.

Temperature Stability. Mentioned in LM317, LM350.

Thermal Regulation (%/W). Mentioned in LM350

Output voltage change with temperature. Mentioned in TL783.

Long-term Stability (% or %/time). Mentioned in LM317, LM350, TL783.


texts: Multiple Voltages Needed - Can I Simply Cascade Power Supplies?

texts:
Electronics novice here... I hope this is a reasonable thing to ask here.  I haven't "tried" anything because I'm not really having a problem.  I'm just looking for guidance before I start.

I am cobbling together a device that will need 5, 3.3, 2.5 and 1.8 Volt power sources.  The heart of this thing is going to be a Raspberry Pi Compute Module.

In the documentation for the Pi Compute, they give a fairly strong warning that the power supplies must come up (in time) from highest voltage to lowest to avoid forward-biasing internal diodes between sources to avoid latch-up.

I am planning to use devices like the LM2576 because they seem simple enough to use and have lots of online examples and application notes.

I have two multi-part questions...

First, is it reasonable to simply build discrete power supplies for each required voltage and cascade them?  (12V input -> 5V -> 3.3 -> 2.5 -> 1.8).   Or is there a better practice to follow when you need multiple voltages?

Second, does merely cascading the supplies ensure that they come up in order?  Or is there something I should do (perhaps with larger in-parallel capacitors between them?) to create a short delay between power-ups?

Thanks!


texts:
I have been doing some work with an energy harvesting IC from Linear Technology. It is the LTC3588-1.

In the application information section of the datasheet, there's the following setup for the IC (which I am not using/implementing, it just made me wonder...):

The 150K resistors are there to keep the maximum current within the limits of the IC. The PZ1 and PZ2 are the input pins for an ac source and there is a bridge rectifier inside the IC—hooked up to those pins.

My question, would it make any difference if instead of having two 150K resistors in series with each lead of the voltage source, you had all four resistors in series with a single lead?

Something like this:

simulate this circuit – Schematic created using CircuitLab

I'd just like to have someone's input on what the differences are between the two configurations. Thanks in advance.

ADD: An isolation transformer is actually added in the real circuit for obvious safety reasons. And the actual implementation I am working one DOES NOT use mains power like this. I was just curious about the resistors and thought about asking.


texts: Star configuration using CAN Bus, I2C or RS485

texts:
I need to create a sensor network, with a central node receiving data from +10 different nodes, each one +20meters from the central node. So basically I need to create a star configuration, with a central node in the middle (a pcb with an raspberry pi) and than a big stub(around +20m) for each sensor node. I really don't know what protocol use: CAN, I2C or RS485.
Can I use CAN? Can I use I2C (with P82B96 boost voltage transceiver or PCA9615 differential buffer transceiver) or maybe an RS85 with MAX485 IC?
My biggest problem is how to implement this kind of solution, cause for big stubs, there is a huge mismatch in the bus, so the signal is bad.
This article is amazing, show a lot of different configurations and the importance of terminator resistors for impedance matching. But I really need to implement a solution like Figure 12 or Figure 13, with stubs w/ +20meters.
This article explore the I2C solutions with P82B96 and PCA9615 transceivers, however, I still have the problem about star configuration and big stubs.
Best regards and sorry for my english.


texts: Design a T flip flop in VHDL using Modelsim, signal values not changing as expected

texts:
I was trying to design a TFF in VHDL.
I wrote the code below

library ieee;
use ieee.std_logic_1164.all;

entity TFF is
  port(
    T: in std_logic;
    clk: in std_logic;
    Q, Qn: out std_logic
  );
end entity;

architecture behavior of TFF is
signal q_state: std_logic := '0';
begin
  process(clk)
  begin
    if clk'event and clk = '1' then
      if T = '1' then
        Qn <= q_state;
        q_state <= not q_state;
        Q <= q_state;
      end if;
    end if;
  end process;
end behavior;

Then I used Modelsim to simulate the code.
While testing I noticed that Q and Qn are the same.
I wonder why this happend.


texts: How to find the critical gain K from the root locus

texts:
I am going through Ogata's Discrete-Time Control Systems and working out the following problem found on Page 262.

The problem states:

  Draw root locus diagrams in the \$z\$ plane for the system shown in Figure 4-45 for the
  following three sampling periods: \$T = 2\$ sec

I first obtain the Z-transform of G(s):

and I worked all the way till the very end and calculated break-away and break-in points to arrive at:

and root locus:

However I am unable to calculate the critical value \$K\$ for stability (Answer is 1.4557).

I know I need to use the magnitude condition but I am not sure which value of \$z\$ I should substitute in the formula to obtain the critical value of \$K\$.

Any suggestions would be appreciated.


texts: Bringing P type and N type semiconductors together in vacuum

texts:
Consider the case where a P-type semiconductor and an N-type semiconductor are placed in perfect vacuum.  Now, the two junctions are brought together.

In the time immediately after they are brought in contact (say the first 1 micro seconds after they are brought in contact), will I detect a current through the device if the P and N sides are connected with a piece of conducting wire?
If the answer to the above question is yes, what happens if I do not have any sort of external circuit? Is the depletion region not formed?


texts: Measurement of the retention period of a memory cell

texts:
Manufactures of Non Volatile memory devices give a quote for the Memory retention period of their device.

To the best of my understanding, this period refers to the maximum period up to which the information stored on the device is guaranteed to be retained without once powering up the device.

This retention period is usually in the range of a few years. How are these long confidence periods running into decades calculated?

I am aware of the effects in memory cells like capacitor leakage, transistor degradation and change in threshold voltage of transistors that could contribute to the corruption of memory. But I don't think the interaction of these effects can be modelled accurately enough to come up with these retention period numbers.


texts: Difference between Max Interface Clock and Max Timer Clock?

texts:
I am trying to use a timer from STM32F4 with ARM Cortex-M4 chip. I need to get the maximum frequency out of that timer for my application.
The datasheet has two columns for that Max Interface Clock and Max Timer Clock.

What is the difference between those two?


texts: How can a toroidal transformer be sited within a wire nest?

texts:
I have an application for 2 no. 50VA toroidal transformers that will be used as a power supply running off 240V mains.  This will be a linear supply in the traditional sense.

But.  I am considering mounting the transformers externally to any physical enclosure.  It will kinda be glued onto the side of a metal support lattice.  It will then be surrounded by conductive wire mesh of various types.  Imagine a toroidal transformer sat snugly in the middle of a bird's nest.  The nest will be coiled aluminium and steel wires of random lengths and thicknesses.  Some might be the thickness /texture of wire wool.  Some like coat hangers, maybe some 6mm diameter steel and a few 25mm * 25mm * 1.6mm aluminium angles.  Some may be 50mm long and some 500mm long.  This can all be explained by the term "Functional Art."

My concern is secondary inductance, heating, fire and possibly death.  How can this be made to work satisfactorily?    I'm fully prepared to accept that this might not be possible within a domestic budget, but I'm not looking for comments stating that this is a bad idea.  I'm looking for a good engineering effort to enable this, but will abandon in extremis.

My sense of it is that this is very possible as long as none of the nest metal work forms a full loop though the middle of the torroid.  So loops around the perimeter might be okay?  I know about not shorting the top and bottom of the fixing bolts.

A side question is: if the torroids cannot be mounted within the wire nest, how far away might they have to be?


texts: I have been wondering for sometime now why Hard Disk Drives define storage space in thousands (1000) instead of the real (1024). So, for example, 1GB = 1000MB; 1MB = 1000KB. Is there any significance for this convention? Why is it still being used?


texts:
I'm sitting here with a pencil and paper trying to arrange a charlieplexed 5x8 LED matrix. I'm trying to arrange this in such a manner that no two lines cross each other. Without a guiding theorem of some sort, I keep isolating lines, that is, the line ends up completely surrounded in a box composed of it's neighbor lines.

I'm looking at this problem and thinking "Some mathematician must have already solved this". Nodes, matrices, edges...it just feels like a topology problem. Anyhow, I don't have the maths to solve it, at least not conclusively.

Anybody have any thoughts on this?

To head this off - yes, this would be simple with multiplexing. I need to charlieplex this.


texts:
I  have LT Spice the latest version XVII and I have tried to add some models from component supplies. I did it following instruction:

I created 2 subfolders in library folder lib placed in My user name/documents/LTSpiceXVII and either sym subfolder or sub subfolder with name MyLib for schematic symbols and model lib/sub files.
Copied some standard schematic library file with sym extension, for example, bipolar transistor and I changed standard name to component name.
Opened it in LT Spice and from menu Edit/Atributes
In Symbol Attribute Editor window I have changed: prefix to X, in SpiceModel I typed the component model location with file name, in Value and Value1 I typed name of component and model.
I saved it
When I created schematic and found that component in library list and I placed it in schematic.
When I wanted to edit it I got error message:

Could anyone tell me what is going on and why I can not edit it.

Thank you for your help. Indeed,your advice "Try adding your subcircuit name in the SpiceModel line, and the path and name of the library in the ModelFile line, and it should work as you probably intended" helped and it works as I wanted.

At the moment I have another issue. I added model with type model, this time and when I edited schematic attributes and as prefix I typed M instead of X, because it is not sub-circuit model, in SpiceModel line I put name of model, in ModelFile line I put path and file containing thes spice model.
When I run simulation I get an error message like this:

I don't know really what prefix I should use in schematic attribute editor when I want to add the model with model type, not sub-circuit model?
Maybe to solve this problem I could edit in model file and I could add some lines like those

.SUBCRK model_name 123
Q1 123 MAIN parameter
.model MAIN NPN
{body of model}

What do you think about it? But I don't still know what parameter I should use?
I think it is easier way to do it.

Thank you in advance,


texts:
My setup is E6B2 incremental encoder(1000pr),Stm32 nucleo-l452re-p.I'm trying to measure speed for system identification and my graphs are looking kinda odd.

I tried to increase the gab "Te" but the result is not good ...

I have an acquisition period of 0.0005 seconds;
I'm using the included encoder mode to interface the encoder .
If any of you have a suggestion let me know , it would help me a lot


texts: im well tired of the leds on this sensor and im wondering if i can remove it. I know very little about schematics but i know how to go wild with a solder iron! I found this schematic online and my question is: are they safe to just remove?


texts: Using a suitable Compensator problem - Control Theory

texts:
Problem:
\$\,\,\,\$ A system is described by the open loop transfer function $$\frac{k(s+2)(s+7)}{(s+5)(s^2+2s+5)}$$
Design a suitable compensator in order to have \$w_n =\sqrt{10}\,rad/s\$ and \$\eta=0.3162\$
where \$w_{n}\$ is the undamped natural frequency and \$\eta\$ is the damping coefficient.
My solution:
From the givens I calculated the required closed loop pole to be $$s = -\eta w_{n} + jw_{n}\sqrt{1-\eta^2} = -1 + j3$$ \$\,\,\$  For this pole, the phase of the open loop transfer function is \$-118.74^\circ\$, so it's not in the root locus. To force the root locus to pass over our pole we need to subtract \$61.26^\circ\$ such that the total phase is \$-180^\circ\$. For that, I used a lag compensator. \$\theta_z  - \theta_p = -61.26^\circ\$ . I let \$\theta_p = 70^\circ\$ and  \$\theta_z = 8.74^\circ\$   (\$\theta_p\$ chosen randomly). I solved for the positions on the real axis and I got $$G_{compensator} = \frac{0.1922(s+20.5)}{(s+2.1)}$$
TA's solution:
This solution used a Lead compensator. It calculated the phase to be added by the compensator to be \$-62.26 + 360 = 298.7^\circ\$ ,"but the maximum phase that a compensator can add is \$55^\circ\$" (where did that come from by the way?) so it uses 6 cascaded lead compensators, each of which adds a phase of \$49.78^\circ\$. Then it got $$G_{compensator} = (\frac{1.787(s+1.5713)}{(s+5.5)})^6$$
Question:
Is my choice of compensator correct? I read somewhere that lag compensators are for adjusting the steady state error but I tried my compensator on matlab and it worked.


texts: FPGA Synthesis = 0 LE (Altera Quartus II)

texts:
Just starting with FPGAs and stuck with a synthesis issue.

Basically, the circuit I am designing is coming out with 0 logic units and 0 for all resources except for the pins assignment. The code compiles (with a few warnings) and it seems fine, but when it comes to fitting/placement, nothing shows up.

The circuit is purely combination, asynchronous and has no clock.

I've tried some example simple circuits such as flipflops and they work fine.

So anyone know why/scenarios/cases where FPGA synthesis on Quartus gives 0 LEs ?

Thanks.


texts: What sort of electric "motor" would I need to launch a puck?

texts:
As the title suggests I am looking at making a hockey puck launcher so I can do some off ice technique training as a goal tender. I have no one to train with so I wanted to create a puck launcher similar to the tennis trainers they have that fire balls at you.

My idea was to run an electric motor that was attached to two spindles (via belt or chain drive) with spinning wheels. When the puck is inserted between them it will grab and take off. My problem is I'm unsure as to how to determine what size motor I would need as I don't know much about torque / force.

I want to be able to do the following:

Fire a 100 gram (3.5 oz) inline puck.
Speed should be able to be varied between 0 - 60 mph.
Must be able to be plugged into 240v mains power (I live in Australia) via step down transformer or similar. (Note: I have qualified electricians who can do this for me).

I was looking at hobby RC motors as those cars likely weigh more than 100 grams and many of those can go extremely fast, they also have variable speed control to mimic a real car. My concern is though would they have enough power to grip the puck and throw it? Is there any math I can use to determine this at all?

If you need any more information or would like a design or something to help with the question to prevent it from being closed let me know.


texts:
As many videos are telling about the future when batteries would be exchanged by supercapacitors, which would charge fast and with larger power density.
How much amount of these capacitors with what specifics would be needed for this?


texts: What is the exact timing for testing(continuity, electrical parameter, optical parameter, thermal parameter) of LED lamp after manufacturing?


texts: What are the Smallest Actual 5G NR Transmit Burst Elements?

texts:
What is the smallest single entity that is actually transmitted over the air as an isolated burst in 5G NR?:

One 2-OFDM-symbol Mini-Slot at 125 μs, (one slot has a 62.5 μs minimum duration)
One 14-OFDM-symbol Slot at 875 μs
One 1ms Sub-frame
One 10ms Frame
Something else?

Please also answer if it differs for 5G Frequency Range 1 (<6GHZ) and Frequency Range 2 (>24 GHz).  Thanks.


texts: Bad 100Hz ripple in linear regulator circuit

texts:
Background

I'm a beginner trying to make a linear regulator and made some decent progress on a breadboard powering from a 20V laptop charger. After battling off the typical opamp instability issues I seemed to get a pretty acceptable adjustable CC/CV output with no ripple so I decided try it out with a more realistic input source, a mains transformer.

The transformer has dual isolated 12VAC windings and the circuit above shows the setup I'm using. The maximum output voltage of the supply should be ~20V at 2A and so C1 and C2 are sized appropriately to give enough headroom for the output pass transistor. The diode and C3 into the linear regulator is for powering the control loop circuitry, which draws < 50mA and must stay at 28V. I can provide a diagram for the control circuit if necessary, It looks something like the circuit in another question I asked here

Problem

When the mains transformer is used all of my circuit is plagued with 100Hz ripple -- it seems to be everywhere. The output ripple is at least 50mV and increases with load up to 300mV and beyond. The ripple is not being introduced by the voltage references since they are being powered off a stable DC supply to make sure.
Here's a scope trace of the AC coupled output: https://i.imgur.com/DvnZAIW.jpg

The ripple at the LM317's input is just 50mV yet the ripple at the output is 20mV, completely unexpected based on the PSRR of a chip like this. Dropout is not the issue here either. I don't think it's ripple on the supply of the op amps either which are decoupled and see a pretty smooth DC voltage. I thought that it might have something to do with bad grounding, since I saw the ripple even between different grounds which were physically far from one another. After making more of an effort to ground properly this ripple between grounds is almost gone, but not at all from the output of my circuit.

I'm not sure where to go from here as I don't know enough, I definitely don't understand where the problem lies. I'm almost certain that if powered from a smooth DC source the problems would go but that's not really the point in a regulator. I would have thought that a couple of volts of input ripple would be no problem for a circuit like this to regulate, especially with such a headroom. The problem must be from the input supply, is a better input filter (like a Pi filter) needed? Is it because I'm putting two rectified outputs in series but only smoothing the 0-36V rail? Worth noting that the 18V rail looks like a completely unfiltered rectifier output.

Any help would be greatly appreciated.


texts:
I have the Mitsubishi DA-R45P receiver, but I don not have a remote for this device. And without remote this device can not work.
I see that there are universal remotes with learn function, but for that you need to have original remote... which i dont have :(

Is it possible to learn codes from device or somehow similar?
I have schematics or receiver, can this help? What are my options?


texts:
I need to know which technologies should I be familiar with
to program for Arduino?
Or knowledge of native Java will be enough?


texts: Programming of ICs in general (MCU / FPGA / Serdes IC)

texts:
I have a general basic question. Most of the Integrated circuits (apart from power IC) that are used in applications (Data transmission/communication IC) require some sort of programming or configuration.

In MCU, I see that we are programming the IC through JTAG lines provided. Where as, in one Deserializer IC, there are no lines/pins provided in the IC for programming. Upon researching, I found out that Deserializer or some other ICs do not require programming but they require configuration. Configuration, in the sense of configuring of registers. Can someone help me understand the difference between the programming and configuration methods? Why do we program an MCU but not a deserializer? What is the benefit/purpose of those register settings? Why don't we program the deserializer itself instead of configuring its registers?

It would be great if someone could break the answer in easier terms for clarity.


texts: How to connect a 3 phase 240V machine on a 415V supply

texts:
I have a challenge in connecting a 240 V 3 phase 9kw machine to a three phase 415V supply in Uganda. The machine is from South Korea. The phase monitor trips.

Below is the brief precaution information for the installation of the machine

This equipment requires a lot of power consumption, so it must be installed in a dedicated line power source.

(AC 240V three-phase 50Hz) Install in 9kw or higher power line.
Equipment must be connected directly to the equipment through a dedicated switchboard.
Do not put a plug into the outlet.
Connect directly to a dedicated switchboard or distribution board.
Connect directly to the switchboard using the power cord attached to the equipment.
If the 3-phase power connection is not properly connected, the equipment will not work.
If the power line change message is displayed on the screen and the buzzer sounds, the power line connection is wrong.
The supply is 415V


texts: Should I worry about an initial negative voltage?

texts:
I'm building a circuit that I found online for measuring spark-plug pulses and it seems to give a clean enough slope for my micro-controller interrupt, but it has an initial negative voltage.

Is this something I need to worry about?

simulate this circuit – Schematic created using CircuitLab


texts:
I have a simple question about neutral and ground wire.

Since the neutral is connected to the ground, I have problems understanding the difference. Assuming it is connected to the ground, it should be just a ground?

I believe the only way it could be different is if the current can only go from the Neutral -> Ground and not the opposite?

If not, what is then the difference between both?


texts: Two different voltage input to be monitored by microcontroller

texts:
I just wanted to make a detailed circuit design that I can use in my project.
a design that can supplement on the OR gate

Given the two different voltage input, I need an output of a voltage around microcontroller readable values with protection circuit on it.Maybe I need level shifting and protection?
Please help.

Thanks


texts:
Edit: Sorry, had messed up the capacitor values as I didn't take into account the values halve per leg. This should be fixed now...

I'm needing to attach a crystal to a microcontroller (a PIC16F84A), but the crystals I'm looking at are the 32.768Khz crystals which have either a 6pF, 12pF or as 12.5pF load capacitance. The thing is, I cannot get any capacitors with those values, the closest I can get is a 10pF (5pF per leg), a 15pF (7.5pF per leg) and a 22pF (11pF per leg). Also, the datasheet for the microcontroller says that when running at 32kHz it recommends I use 68-100pF for each capacitor. So:

1) Is the datasheet for the microcontroller really specifying a 32Khz crystal, or is it standard to refer to 32.768 crystal as a 32kHz crystal?

2) Would the capacitors I can actually buy (10, 15 and 22 pF) be suitable, when considering the crystal is specifying slightly different values?

3) Why are the capacitor values specified on the microcontroller datasheet so wildly different from those specified by the crystal? Surely only one of them can be correct, and what effect would this have if one of them is ignored?

Thank you!


texts: Confirmation on how to check microcontroller memory capacity with Atmel Studio

texts:
When compiling code in Atmel Studio, I get the following output showing the percentage of usage for the program and data memory:

Does this output represent the total data usage in the microcontroller?


texts: What happens after a diode is used in breakdown region?

texts: If a diode is operated in breakdown region and if it is used again will it lose its characteristics or work normally?


texts:
So I've got a Sabertooth 2x5 motor driver. I uses standard servo connections, and a micro controller can use standard servo arguments to make the motors go in forward or reverse (much like a continous rotation servo). In any case, it connects to a board in the bottom of my robot, gets grounded to the common ground, and through traces the signal lines go to a JST connector to the next stage of the robot (which is designed to be modular for easy teardown). The problem I have is that sometimes the motors move slightly; this usually happens if the motors are not receving any signals if the robot is in idle. Further if I remove the connector and touch the data line pins with my hand the motors will move.

I was wondering if an optocoupler/isolator for the data lines before the JST connector would fix this issue? If not, what would be the suggested way of dealing with this?


texts: I have no experience creating PCBS, and I was wondering what design considerations should be made concerning having line voltage (sometimes in the single digit amps) running through one. I'm talking wire sizes, trace widths, etc. I want it to be safe after all! =)


texts: Why small LED or CFL lamps usually has better PF than bigger one?

texts:
Some peoples recommend using small LED or CFL lamps in home rather than using big lamps, because they has better Power factor than big lamps,

For example if you need 80 W Lamp in your room, it is better to using 10 lamps (each 8w) rather than using one 80 W.

Already i test a small 9 W CFL and the power factor was 0.8, then i test 50W CFL and its PF was only 0.57,

So can we say always small LED or CFL lamps has better PF? If yes, Why?


texts: Transformers operating at certain frequency

texts:
In one of my previous questions some people commented that transformers are made to operate at certain AC frequencies.
But why is that?
I cannot understand the intuition behind it.
Shouldn't more power be transmitted with an increase in frequency?


texts: AD620 In-Amp, single 5v supply, reference pin affecting gain

texts:
Given the datasheet here, I can't explain my observations with my AD620AN test circuit.

The circuit:

Supply: +5v / 0v (Well regulated)
1k potentiometer across the supply, with the wiper going to both the reference pin and the negative input
+ve/-ve inputs: K-type thermocouple. (41uV/K)
Gain resistor: 100 Ohm (Gain of 500).

It seems that the gain is strongly dependent on the voltage of the reference pin. If I set the pot at precisely 2.5v, I get roughly the expected gain. But even slighly higher or lower and the gain reduces significantly. (For example, just +/- 0.05V change in reference reduces gain by about 10% for output signals of +/- 100mV). I've been taking measurements with a standard multimeter.

I haven't done meticulous testing with this, but none the less have lost a fair bit of hair. Is there something obviously wrong with what I'm doing? I must have run through the figures in the datasheet two dozen times. Is it the circuit at fault? Or my measurements? Or both?


texts:
I'm trying to communicate with a serial barcode scanner. This is how i've linked it to my computer (the circles represent the color of the wires already soldered in the serial plug) :

http://img441.imageshack.us/img441/6126/0079.png

When I scan a barcode (a special one telling the scanner to send an ASCII debug) or just a normal random barcode, all I can see in my serial terminal are accentuated letters and I don't understand why I can't see the barcode. I think the baud rate is fine, and I don't know if it's encoded or something...

Could you help me figure it out ? This is what I get :

ÍøÌÔÃøÃÇøÇËøËÊøÊÎøÏËøÊÎøÎÏøÏÓøÓÑøÑÖøÖøÔÐøÐ×ø×ÔøÔ


texts: Can I substitute a signal PNP transistor for a TIP120 NPN Darlington?

texts:
I attempting to follow this guide on building a motor controller for an arduino:
http://www.instructables.com/id/Use-Arduino-with-TIP120-transistor-to-control-moto/

I have some of these transistors:
http://www.amazon.com/pieces-2N3906-General-Purpose-Transistor/dp/B007JY6W6Q/ref=cm_cr_pr_product_top
Will these work? Will these allow varying voltage levels to be regulated or is that a characteristic unique to Darlington transistors?

How are MOSFETS different?


texts: How deleterious is topping-off my Li-ion batteries (phone/laptop) every time they drop to 90%?

texts:
I have read recently that frequent top-off charging of my personal electronics is hard on the batteries. Specifically, Li-ion batteries in recent model smart phones and laptops will show significant loss of capacity after (very roughly) 300 cycles between the remaining charge levels of 90% and 100%.

Below is a 'cartoon' of a plot to help clarify my question. Is cycling between the 90% and 100% points 'harder' on these types of batteries than an equal number of cycles between the 40% and 90% levels?

By 'harder' I mean a significant loss in battery capacity after (very roughly) 300 cycles, versus maybe 3,000 cycles.

Also, is cycling through the lower end (say 5% to 40%) also 'harder' than in the mid-range?

I'm not looking for opinions or best guess - I need a fairly clear answer with a link to further reading, and ideally an actual plot of this phenomenon - model or data.

edit: assume the charging is managed by the built-in electronics according to manufacturer's specifications.

NOTE: This question requires an engineering answer, but let's assume I am not so much of an engineer (anymore) that I have actually taken my phone and laptop apart and I'm hooking up volt meters to the individual cells!!!

Please assume I am simply either plugging into a power source, or not plugging into a power source, the way most people do, based on the 0-100% scale that my personal consumer electronic device displays.

Thanks!


texts: Burning a microcontroller's peripheral. is it possible?

texts:
Have you came across with a microcontroller by chance which a/two/... peripheral(s) of the microcontroller didn't work? or at first a peripheral of your MCU was working but now it doesn't? I mean could it be possible that a/two/... peripheral(s) of a microcontroller burn out(while other parts of the MCU work)?

Sometimes we hear from some users that when a part/peripheral of an MCU doesn't work, they say "you have damaged that peripheral/part of the MCU". is this remark correct? I'm not a beginner but after several years I'm curious to know it.


texts: Why time period of GPS PPS signal is not accurately equal to 1 second. (7 to 10 mirco sec less)

texts:
I've multiple nxp K60 controller running at different ppm crystals. All have a GPS modules, i want to adjust their clocks using pps signal from gps.
Whenever K60 controller will start it will adjust their clock by taking reference from pps signal.

But the pps signal time period is not equal to 1 sec. First pps time period is 0.99999270 (7.3 usec less) and after first pulse it goes more less for some time.All positive edge of pps signal on different module is alligned within 1 usec. The time period for raising edge of pps is 0.8usec.


texts:
I am planing to design a controller for a universal washing machine motor based on the TDA1085c. While designing the schematic, i have some problems to understand the sizing of some resistors.

Here you can find the datasheet of the TDA1085C.

The resistors to which I refer, are R10 for Pin10 and R15 for Pin15. In my opinion it is not very good described how to size these resistors.

Does anyone has a clue?


texts: Ultrasound transducer excitation - frequency, transistor type

texts:
I currently work on my ultrasound project. I need to excite my Olympus V305-SU-F tranducer with -100 V spike pulses. Unfortunately Olympus does not provide any kind of datasheet. I know only value of impedance - 50 ohms for resonance frequency (2,25 MHz). My circuit will be powered by DC/DC converter MAX5025.

I want to use following circuit for excitation:

At first the C1 is beeing charged to Vcc value through R2,R1 and T1 is closed. T1 will conduct after short positive impuls to its base and C1 is discharged into transducer X.

BUT, how can I determine the pulse frequency? Is it given by C1 capacity? So if I want 2,25 MHz pulse I need pulse with duration about 0,44 ns?

In the description of the circuit above, its said, that I need avalanche transistor. Why? I still don´t understand how will the transistor type affect the speed of discharging of C1.


texts: Can onboard AC plug pins/socket damage the whole PCB if there's a short circuit?

texts:
I am working on a project based on a smart switchboard, so I'm trying to put an AC socket pin onboard PCB.
In the case of short circuits, is there a possiblity to damage my whole PCB?
If it's a possibility, I'll use an external socket and connect them with wires to the PCB.


texts: How are alphabetic characters programmed into a computer?

texts:
I'm no cs student, I'm a programmer. I have a couple of questions and a few assumptions that I will make here (correct me if I'm wrong please).

From my understanding is that all the sequences of 1 and 0's that computers execute are just representations of actual data or instructions that tell other hardware on a system what to do like telling a graphic card to change a pixels color on the monitor.

01100001 being the representation of the letter "a" and that this sequence of bits has been chosen by the fathers of computing/ascii or what have you to represent that letter, it could just as well have been some other sequence right?

All computer systems have agreed that those bits mean the letter "a" for all of the computers around the globe to be interoperable, if there were no standards in place for this the internet would be a mess.

What I want to know is: where is the information stored on a computer that tells it that these sequences of bits here mean/represent the character "a"? Is it in the OS or directly on the motherboard or am I just completely wrong?


texts: Those who work in industries will understand this question better. A pH electrode has pH vs mV table will be somewhat similar to this image. Our company has a digital pH indicator showing input as -1500mV to 1500mV. why this large range of volts, when i/p from electrode can be vary from may be around -500mV to 500mV.


texts:
In geological instrumentation, it is frequent to find the "integration of the acceleration" measurement, as the "empirical estimate" of the velocity, namely, the Particle Point Velocity (PPV).

Assuming:

An real physical acceleration and velocity magnitudes -\$a_0(t)\$ and \$v_0(t)\$- for a steadily oscillating system, unknown. This is standard on sensors placed on ground. This is not the case of aeronautics and navigation necessarily,
An electrical additive noise \$e(t)\$~\$N(0,\sigma)\$, unknown,
An acceleration measurement, \$a(t)\$, known,
A sampling time \$\tau\$ over time, functions and integrals (just for treating the process discretely, not required though).

An accelerometer register can be simply modeled as:

$$a(t)=a_0(t)+e(t)$$

Thus the velocity estimate would be:

$$v(t)=\int_0^ta_0(\tau)d\tau+\int_0^te(\tau)d\tau=v_0(t)+\int_0^te(\tau)d\tau$$

For cancelling the "noisy" tendency in \$v(t)\$, a "baseline correction" procedure is often stated as the "correct" solution. Which is nothing more than fitting a customary function to the wiener process.

This is a "Dead Reckoning" process.

Which should be the optimal way for estimating \$v_0(t)\$? from a mathematical point of view.

PS: The estimate at the instant \$t\$, of a Wiener Process with conditional deviation \$\sigma\$ is:

\$w(t)\$~\$N(0,\sigma \sqrt t)\$

Hence, if the estimated resolution -from DAQ resolution- of the velocity measurement is \$\nu\$, after the time  \$(\frac{\nu}{\sigma})^2\$ the integrated noise will surpass the sensor resolution with "1-sigma" confidence, invalidating the procedure.
Actually, after the time \$t\$ the wiener process itself will be anywhere in 1-sigma confidence interval \$(-\sigma\sqrt t,\sigma\sqrt t)\$.

IS there an standard method, taking in place the inherent gaussian integrated error into account, available?.
I am trying to solve -still just trying- this problem by imposing:

The velocity has no real "baseline" - i.e. a "real" velocity measurement will behave like an accelerometer measure, centered at zero.
The velocity at every smaller interval should have no "baseline". This is incorrect at very small intervals, but a potential solution.
An easy solution is to take any smoother filter, with a look&feel filtering power. This way a trend is estimated, removing the random walk noise and leaving a gaussian noise. This is the solution i have at this moment.
Standard solutions like butterworth lowpass filters as baseline correction, though proper, are not correct, because the butterworth are meant for removing specific low frequencies, and the Wiener process is a ramp in PSD.
A potential solution could be mimic the Wiener PSD, and apply that filtering.

Thanks in advance,

PS: This question will be downvoted for closing (XD??!). If you have something to add, please use the comments or message me through any other question.

A new version of this question, can be found here.

I've been requiring this answer from a lot of time, and some huge project implications are involved. Thank you for your time.


texts: Was given the task of creating the simplest constant current source that can supply up to 50 mA with an ~700 ohm load. I can use any IC's out there. I stumbled across the chip here from linear tech: Which seems to fulfill all of my needs, however the problem I am facing is that I need to create 16 of these DAC controlled current sources and all of the loads on the chip are common grounded, while the image suggests that any load attached would need to be connected to the negative supply. Is there any simple fix that would allow the loads to be grounded? My first instinct was making the ground on the diagram the positive rail, but I am not sure if this would alter the input I need from the DAC.


texts: Constant voltage control via op amp and transistor

texts:
I am trying to design and build a regulated power supply for my "lab" using transistors and op-amps.  I have found many circuits on various websites that all appear similar.  I thought I would try to build one piece of the power supply at a time, starting with the constant voltage supply (easier than the current portion, I think).  The schematic is below [\$V_1\$ comes from a 4:1 transformer at 120V primary across a 3A diode bridge, giving approximately 28V]:

simulate this circuit – Schematic created using CircuitLab

I know I am missing a filter capacitor on the output of the bridge.

If I was to set the pot to 1 volt at the non-inverting input, the op-amp will adjust its output to obtain 1 volt on the inverting input, which is the same as the emitter.  Assuming a base-emitter drop of 0.6 volts, this will cause a current to flow through the collector of approximately 1.1A.  But what happens if I put a 1kohm resistor in for the load?  I can't push 1A through 1kohm at 1volt.  My collector current would have to fall to 1 mA, so does that mean the collector voltage falls with it to get 1mA across the 25 ohm collector resistor? What happens when I short the emitter directly to the negative of the supply, with 1 volt on the non-inverting input?  I can't have 1 volt and 0 volt at the same point.  This is where I am most confused I think.

Assuming \$\beta = 200\$, a base current of 0.1 mA would flow, meaning I do not need a base resistor and the op-amp should source 0.1 mA okay.


texts: How to find the gain of Motorola operational amplifier?

texts: How to find the Gain in dB for Motorola operational amplifier MC33282P (for T=25°C). The manual has only abstract figures.


texts: How to short a push button switch to be always on

texts:
I have a little bluetooth FM transmitter that uses a single button that you press and hold to turn the device on, press and hold to turn the device off, and press once to change the FM station it broadcasts to. Is there any simple way to alter a circuit like this to be "always on" and essentially short circuit the switch?

If it were some sort of toggle push button switch this would be simple, but seeing as it's a simple momentary push button used for other things, I have no idea where to even begin.


texts: Why doesn't the output of the rectifier come out?

texts:
Hello, I made a rectifier circuit. I also include a comparator.
I referred to this paper --> An ultra-low-voltage self-powered energy harvesting rectifier with digital switch control.

The circuit consists of two stage.
first stage, Va signal is working(green color).
In the next step, however, the voltage drops rapidly.

The output of the vc is not generate. A point connected with a load

Please help me.

Have a nice day. thk.


texts: Are most home circuits able to handle 12V 50 amps on a 10/20/50 Amps?

texts: My dad is saying that most home outlets can't handle 12V 50 Amps, is this true, or false? What I'm doing it for is to charge my car battery.


texts: Random wire antenna - why only one wire?

texts: If my understanding of AC and the generation of electromagnetic radiation is correct, then a complete circuit encapsulating power source and resonator is required (a closed circuit). How then can a "random wire" antenna function, as it is an open circuit with infinite resistance - no current should flow when induced by EM radiation.


texts: How can I detect when the air flow in a room stops and report it?

texts:
I have a server room with an air conditioning unit.  The unit is supposed to run 24x7, but ND tends to get 100 °F in the summer and -40 °F in the winter.  This is a little harsh on the equipment and we have had failures.  I have a temperature sensor, but I want a little more warning.

I am trying to cook up some solution that monitors the air flow and sends an e-mail when the air stops.  I have looked at various anemometer (wind speed indicators), but they all seem to log data and not provide updates, plus they all seem to be rather large and not a good thing to have spinning in a server room.  I want to hang the sensor from the ceiling in front of the air conditioner.


texts: Controlling a power strip with a toggle switch. Flight sim design

texts:
I am building a cockpit. It will function basically as a flight simulator but for a different game. Mechwarrior online. a Mechpit. Here is my problem.

Toggle switch 1 when flipped on turns on the power to the cockpit.
toggle switch 2 when flipped turns on the power to the monitors. Separate power strip possibly chained off the toggle 1 strip?
Toggle switch 3 i have yet to assign. Probably activates a 3rd power strip or a power cord that i have a usb hub plugged into to power internal lights.

So house power comes into the cockpit and if i want it totally shut down flip toggle 1.

Here is the catch. each toggle switch is assigned an audio clip to say.
When the 3 switches are all in the one position a 4th audio clip will play after.
Here is the audio.
http://www.youtube.com/watch?v=NCmrp38KjYg

Here is a fellow Mechpit builder. I know how he has his toggle making the audio happen. I've already done something similar. What i don't have is the power control.
http://www.youtube.com/user/Fousticle shows a potential panel/toggle.

I've researched what relays are and what they do. But seeing as its 02:49 am sleep deprivation and making electrical decisions is probably a bad idea.
Anyone have any thoughts?
Thanks.


texts: How to have a seperate power supply of same value to power microcontroller and motor?

texts: I was creating a project which include the micro controller(ATmega328) and the 5VDC motor pump. so i made the circuit shown. motor is actuated by relay. the moment motor is 'ON' the micro controller gets reset(brownout). How do i modify the circuit to have a better performance. and is there any way that i can isolate the power supplies to controller and motor for same DC jack.


texts: Why is the output signal of my amplifier heavily distorted?

texts:
I checked the circuit 1 million times. I got it from a website. Everything is correctly connected. The sound is loud, but it is very distorted. I use a 9 V battery.
Where is the problem? :(
EDIT:I used an LM386M-86 CHIP and not the LM386N-4 CHIP that is used on this schematic.This may have caused he problem??


texts: How to get 1-button-press to output 1-"active"-tick according to a clock

texts:
Background: I'm a software engineer with only a little knowledge of circuits--all informal--trying to build an 8-bit sum-carry binary calculator from basic logic gates.

Question: Are there well-known circuits for making a button press (after debouncing) only trigger a signal for exactly one clock cycle while it's being pressed? What are they called so I can learn more about them?

Context: I've got "1", "0", "+", and "clear" buttons on my calculator, but when I press them, I only want the output of this circuit to stay active for a single, but complete, clock cycle (I can't just let it stay high since the clock may oscillate thousands of times while I'm holding the button down, and each tick would be treated as another button press). Basically 1-press = 1 "active" tick. Note that this is after debouncing the button.

So far I've got this circuit, which seems to be working in Logisim:

simulate this circuit – Schematic created using CircuitLab

Treat the switch as already debounced and the LED on the right as "output". Is this the right way to approach this problem? Or am I completely reinventing the wheel? This sounds like a monostable multivibrator problem, but all of the examples that I've seen of those use RC circuits, and send pulses rather than high signals in-time with a clock...


texts: How to plot an impedance vs frequency graph in Proteus?

texts:
I'm designing a circuit that simulates the impedance behavior of a real world speaker, which is not purely resistive and looks something like this:

I already got the basic circuit but need to tweak the resonant peaks and valleys and what not, so I need to plot an impedance vs frequency graph but I haven't been able to find how, I put a voltage probe as seen in the image below and the db vs freq. graph seems about right although inverted so I guess the probe should go there, however when I tried to put a current probe in different places I got different errors running the graph, where should I put it?

For the impedance part I searched online and found hints to the Add Trace command, but I've never used it before nor could I find tutorials or info about it, how does it work? I assume I should input the voltage probe as P1 and the current probe as P2 and then for the expression P1/P2 to get ohms??

Thanks in advance for your help :)

Here's my basic circuit:


texts: Trying to find find or design 2x20 GPIO header in altium

texts:
For my project i am using DE1 Soc development board.

I am trying to connect a camera to it using the ribbon

Camera has the output of Semtec Connector, and I need to connect the 40pins from semtec to the pins of a female 2x20 header. The Semtec connector specifications I have already as I am only modifying an altium project file which has been made prior by someone else to connect the same camera but to a different FPGA.

I can not find within altium any header which resembles the one I need. I can fin headers for any multiple of 2 besides the 40/2x20 one, let alone having the same pin spacing.

I can not find anywhere within the DE1 Soc datasheets any info about the headers, such as the width of the pins, total length or the manufacturer's number.

If someone could suggest to me how to find the 2x20 female header as I am sure it exists somewhere already or how can I find the exact measurements of the connector that is on the FPGA so that I can design the holes myself.

Thank you.


texts: I read in some books that pollution degree can influence the creepage distance in electronic  circuits, is there any relation (mathematical) between the pollution degree and the creepage distance.


texts: Using battery and USB power at the same time

texts:
I'm trying to make a  Li-ion battery control circuit. I would like to be able to charge the battery via USB and power the load (at 5V) at the same time.

I know how to make a circuit that disconnects the battery from the load using a MOSFET and powers it only from USB (something like http://ww1.microchip.com/downloads/en/AppNotes/01149c.pdf).

However, with this approach (if I understand correctly), plugging a USB cable connected to something that can't supply enough current (eg. 500 mA when 1 A is needed) would still switch off battery power completely.

How can this be avoided? The ideal scenario for me is that in this situation the load is powered from both USB and the battery. If such a circuit is very complicated, simply ignoring the USB power and supplying the requiered current solely from the battery would still be OK. I will be powering a Raspberry Pi, so I would like to avoid a sudden current (or voltage) drop.

I found some load sharing ICs on the Internet, but they are designed to drain equal current from two loads, which might not be the case here.

I hope my question isn't stupid, I'm an electronics newbie :)


texts: Use the RESET PIN on Attiny85 as Input with voltage divider

texts:
Voltage divider & pull-up with analogRead

The Attiny has 6 pins that you can use as I/O.

While 5 of them are really easy to use the Pin 1, the Reset PIN , obviously Resets the Microcontroller if the voltage is lower than around 2.5v.

By reprogramming the fuses to use the reset pin as an I/O pin i'm not able anymore to use the arduino ISP Programmer.

  So the only way to use it as input, without resetting the MC, is to stay over 3v
  and use analogRead?

After i finally got that, i played around a little with my multimeter (only measuring tool aviable) and experimented with resistors.

simulate this circuit – Schematic created using CircuitLab

The powersupply(battery) outputs around 5.11v.

not pressed i get 5.11v on the "reset pin".
pressed i get 3.41v on the "reset pin".

not pressed the resistace is 39K Ω.
pressed the resistace is 19K Ω.

Now, as i don't want to reprogramm the fuses or burn the  Attiny85 my question is:

Can i harm somehow the attiny using this circuit with analogRead(); ?

Readings would be around 680 when pressed or 1000 when not pressed.

Should i use other resistors to consume less current/send to much current continuously ? ... if this works...

Any other suggestions?

Notes.:

I use pins 2(PB3),3(PB4),5(PB0),6(PB1) as PWM channels (with npn transistors);
Red,Green,Blue,white.

Used pin 7(PB2) as button.but i need also a Potentiometer...

SO:

pin 7(PB2)  becomes Potentiometer (analogRead).

and , i hope

pin 1(PB5) becomes a button using analogRead or whatever.

EDIT

this site explains more about the problem, although i need a simple button.

http://www.technoblogy.com/show?LSE

EDIT

I did not test the circuit above.
I'm asking you if it could work , if there is something wrong. I have fear to damage the pin.

All i know is that:

it resets with low voltage using normal potentiometer setup or normal button setup
if i set the fuses i'm not able to reprogramm the chip
pin1 = pb5 = adc0 = analogread(A0) = Arduino pin5 = RESET


texts: Pull Up Resistor on signal too low (Tx from HC-06), why it get fixed?

texts: I had problems with a bluetooth module HC-06 because it didnt transmit the data by UART, but someone told me to add a pullup resistor between the VCC and the TX of the module, it works, we tested with oscilloscope and we saw that when the resistor wasnt there the signal was like 200mV. Can someone explain why it works? and what happend when you have 2 voltage together like that?, the 5 Vcc from the source and the 200mv from the HC-06 TX, didnt the 5V affect the pin Tx from the HC - 06?


texts:
My question is about how to turn on a led before the GPIO pin has been initiated. When the IC has just been powered on and has not yet been initiated the GPIO pins remains in state HI-Z.

In Circuit-1 GPIO-P1 is pulled via a pull up resistor R7 HIGH and the led turns on before initiating the IC. once the IC has been initiated, GPIO -P1 is set to LOW to turn off the led. The problem with this circuit is that if GPIO-P1 is accidentally set to HIGH, it will short the led. (not current limiting resistor)

I believe I can solve this problem via circuit 2 and 3.
In circuit 2 I limmit the current through R2 in case of P1 is accedentially set to HIGH.
In circuit 3 The P mosfet is driven on via R5, lighting up the led, only when GPIO-P1 is set to high does the led turn off.

Out of interest would there be ANY reason at all to choose for circuit 3 over circuit 2? I see none.

simulate this circuit – Schematic created using CircuitLab


texts: Why are MOSFETs used for VLSI IC fabrication instead of JFETs? What are some reasons the use of JFETs is not common?


texts:
http://www.dx.com/fr/p/ssr-25da-25a-solid-state-relay-white-134494#.VDmPWPl_uap

It says AC output but how can this transform DC to AC ? Shouldn't this act like a switch ? If my circuit is DC and I close the switch it will transform to AC or will it stay DC ?


texts: Can anybody help me understand the monitoring function in this safety relay?

texts:
Here is a SIL3 Relay: SCS 24 V DC P2SIL3ES(made by Weidmuller). In its manual, It's written that S11,S12 and S21,S22 connections will provide a monitoring circuit for this relay. But I can't understand how? can any body help me understand Its operation?

Here is the link to the it's manual:
https://www.dropbox.com/s/x3k37ad6lalw1tp/1438130000_00_03.13_MAN_SCS_24VDC_P2SIL3ES_EN.pdf?dl=0


texts:
Suppose I have two current sources as depicted. One current source nominally delivers a current of frequency 1000 Hz and the other nominally delivers a current of frequency 1010 Hz. The nominal current amplitudes are equal. Also R1 = R2 and L1 = L2.

If the current sources were ideal then the coupling between inductors L1 and L2 would be irrelevant to the circuit behavior. But if the current sources are real (not ideal) then I assume that the coupling between the inductors would matter with respect to the circuit behavior.

What sort of departures from the ideal case would one expect to see for real current sources? I realize that this question depends upon the type of current source (ie. the circuitry that tries as best it can to maintain ideal behavior) so anything you can tell me about the expected behavior for the different types would be gratefully received.


texts: The most efficient way to generate -5V out of 5V3 at 30mA

texts: In my design, I need to power up a few op-amps with positive and negative rail. Taking into account amplitude in the signal path, headroom for input common-mode voltage, output voltage swing and voltage drop for LDOs on each rail I need at least 5V and -5V. Generating 5V out of 5V3 is the easy part. Generating -5V proves more difficult. Considering load current, I cannot use voltage multiplier or switch cap approach. The only possible solution I have at the moment is to use isolated DCDC converter (“dual-rail” schematic in the picture attached). Is there any other approach I could use?


texts: Dielectric Withstand Voltage of resistor

texts: I saw many data sheet of resistor give a specification says "Dielectric Withstand Voltage" or similar. But the resistor is designed to be used as a "path" for current. So, how they get this voltage? If they mean the max voltage between the terminals, apparently, for some low power rating ones, they will be burned down at lower voltage level.


texts: Two way switch, original was 16 AMP, can I use a new 10 AMP?

texts:
I have a two way switch (for an outlet), and it was for 16 AMP.

I went to a store and asked for a new one, and when I got home and was starting to assemble it, I noticed the new one was 10 AMP...

Is it ok to use a lower AMP model, or should I get a 16 (or more) AMP?

I am almost positive the charge on each outlet won't be more than 10 AMP, but I don't really know what happens if it goes over it (I'm almost sure the switch doesn't have a fuse).

By the way, the circuit is 15 AMP.

(As you may notice by the type of question, I'm a novice).


texts:
What can I try to fix this display?

I assumed water vapor got into it from opening and closing the fridge door so I tried these things:

I disconected it and left it in the sun for 4 hours.
I resoldered the
display pins.
I heated it with a heat gun.

After all this nothing changed. You can notice that on the right it says 7; that 7 is probably a 3. Also, in the top right corner, next to min, there are two ticks half lit.
On the left it shows -18. I know this because only on -18 the e letter (economic) is lit. The e letter, quick freeze, quick fridge and ! signs work properly.

This is the second display. The original one laster for 1.5 years. This one lasted for 5 months. I could just call the company to change it again but I'm sure it will do the same.

What can I try to fix this display? How does the display look on the inside?


texts: How do I feed a digital value to the PIC CLC system?

texts:
I'm playing with a nice new PIC16F15356, and investigating the Configurable Logic Cell (CLC) capabilities - basically a 4-cell mini-PLD on the chip that can take inputs from any of a list of 40 modules, including certain configurations of I/O pins.

But there seems to be no simple programmatic digital input capability. I was hoping to be able to set a "motor direction" bit from the code, which would be worked into the logic to generate my outputs. I could probably hack it by setting something like a PWM to "100%" or "0%" and feeding that in, but I was expecting there to be 4 bits of a register I could write to, and there isn't!

One way might be to dynamically reconfigure the CLC logic, on the fly, but my mind fills with the horrors of glitches, weird intermediate states, etc. Another is to write to a I/O pin, and then assign that as an input into the logic - that might be the best way.

Am I missing something, please?


texts: Simple Audio amplifier Using Transistors

texts:
I would like to build a simple audio amplifier using transistors. I know there are IC designs specifically for the task. But i want to use transistors so i can learn how to use them for amplification.

How would I go about designing an audio amplifier from just discrete components.


texts:
The impedance measurement handbook (available in more or less identical form from multiple companies / brands) recommends an auto-balancing bridge method for low-frequency (10Hz - 200 kHz) impedance measurements, however a direct I-V method would also work, however the low-end applicability might be limited by the use of a transformer, that would be used to "prevent the effects caused by placing a low value resistor in the circuit". There's also the RF I-V method using impedance matched ports, which is recommended for frequency ranges starting in the MHz regime.
My questions are (related to the characterization of a piezoelectric resonator)

What are the effects introduced by having a low value resistor in the I-V bridge?
Why is the RV I-V method not suitable for low frequency ranges (assuming that no transformer is used)
I used a vector signal analyzer (HP89441A) to supply a sweep to a measurement bridge that matches the principle of the RF I-V method. (I.e. attaching the source directly to CH1 and via the DUT to CH2, all inputs / outputs set to 50Ohm). Is there a fundamental flaw to this measurement setup for a frequency range of interest between 10Hz - 200kHz?
There don't seem to be many devices in the market suited for a full-range impedance measurement which are also suited to the low-frequency range (probably due to the aforementioned effects of the transformer). Is it valid practice to use dedicated signal generators and spectrum analyzers (or somewhat also rare VSAs) to recreate the described measurement setups?


texts: Advice a humidity sensor with I²C interface

texts:
I like to interface a humidity sensor over the I²C bus.

It should come in a small package, and consume little power. Accuracy isn't that important. I'm using the DS1621 as temperature sensor, I'd like something similar, but for a humidity sensor.

After looking for modules with my criteria, I came across the HYT271, but that thing is ridiculously expensive. The low-cost version HYT371 has about the characteristics I'd need, but it's currently not available from my dealer of choice...

I need something reasonable accurate for ambient temperature measuring, and at the same time not too expensive. Should be in the range of a few euros.
(Bonus points if those chips can be sampled).


texts: power supply noise causing resets of MAX7219 LED driver

texts:
I have wired up an ESP8266 wifi uC to a MAX7219 7-segment driver. The setup works well, except that the circuit seems susceptible to external noise. The main issue I have noticed is that activating a light fixture on the same circuit will mess with the device (the display gets scrambled, or even goes blank).

The circuit is currently setup on a bread board with wires everywhere, as shown in photos below. So I thought the issue was just that all these loose wires were acting as antennas (and maybe that is the answer). But the problem seems much reduced if I plug my device into another outlet ("B" on my sketch), which makes me think it is actually a power supply spike and that my circuit is not adequately filtered.

I am powering the whole thing off an old ATX power supply, which I thought would be pretty resilient to mains noise.

I have 10uF and 0.1uF capacitors on the circuit, as recommended on the Arduino site. I think I have the caps fairly close to the leads, especially for the MAX7219. I have tried several combinations of capacitors, but the behaviour seems to be the same.

I am just wondering if I am on the right track with power line issues? Or if I am wasting my time and this circuit will never work properly until I get rid of the "antenna" wires and use a proper circuit board?


texts:
I use Eagle Cad 6.4.0. I do manual  routing to connect SPI signal at 2 MHz.

I need to equalize the trace lengths (I check length of a trace via Meander as Scott Seidman suggested), and bend a trace (e.g., the left trace on the below picture) at some points to be able to equalize the length. However, it causes sharp edges on the traces. I wonder if the sharp edges would be something I should care of at that frequency (e.g., a 60 mm straight line and 60 mm with zigzags)? If it is the case, how would you suggest to extend a trace length?


texts: Charging Lithium ion battery with a modified charger

texts:
I've a defective charger for a small LED torch light, its output is 4.2V / 500mA.

I may not find an alternative one, so I'm considering modifying a mobile phone charger as following:

The mobile phone charger has output of 5V / 1 or 2 Amps.
I put at the output three diodes: 1N4007, and two schottky diodes of about 0.1V voltage drop each: 0.65 + 0.2 = 0.85 V
So the output becomes: 5-.85 = 4.15V (edited )

Is this voltage adequate and suitable to charge the battery? Is it safe to use?
Let me know your thoughts.

Thanks in advance


texts: Does Longley–Rice model model takes into consideration Fresnel zone?

texts: To an extent I understand Fresnel zone.But do know how Longley–Rice model takes Fresnel zone? In other words, how Fresnel zone concepts takes into account by the Longley–Rice model? Any comment would be highly appreciated.


texts: Lightest possible USB solar charger with 5V 2A to 3A output?

texts:
I'm doing a lot of wilderness expeditions an needs the lightest gear possible. I want to make a solar charger (for my nitecore nb10000) that is as light as possible and has a USB output 5V and between 2 & 3A.
I'm considering buying 2 of these USB solar panels 2 x 70grams:
https://www.aliexpress.com/item/33047177046.html?spm=a2g0o.productlist.0.0.41d05a05d70gAr&algo_pvid=87608020-b1de-4a4b-b0bd-554d96f6ba2b&algo_expid=87608020-b1de-4a4b-b0bd-554d96f6ba2b-14&btsid=0b0a556f16108034779727362e6c52&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_
and 1 of these USB y cables 30grams:
https://www.ebay.co.uk/itm/USB-2-0-A-Female-to-2-Dual-USB-Male-Hub-Power-Adapter-Y-Splitter-Cable-Cord/284145962396?hash=item42286b4d9c:g:xUgAAOSwiJRf~ejA
and connect them to get an USB 5V 2.4A output at a total of 170grams.
Some say it works, some say it only works if the 2 panels has the exact same output, some say it wont work, some say you can burn the weakest panel, some say you wont get the double amp output, some say you need to install a 2 or 3A voltage controler regulator module like this one :
https://www.ebay.co.uk/itm/3PCS-5V-2A-Solar-Panel-Power-Bank-USB-Charge-Voltage-Controller-Regulator-Module/202064833235?hash=item2f0c00aad3:g:JDAAAOSw3GtZxMIe
Can anyone help me what to do? Its very important that it works and doesnt break and is as light as possible, because my life depends on my gear and I have to carry everything.
Or if you know an even better way, that works better and is lighter, then I will be very grateful if you will share :-)
Thanx
Thomas


texts:
I’m working on a design incorporating a Gumstix Overo AirSTORM-Y COM, and I note that it can accommodate a backup battery.  I understand that this is handled by the on-board TPS65950 PMIC, which includes a real-time clock module.

However, the Overo documents don’t mention an RTC, so I’m writing to find out if the RTC in the PMIC is functional on the AirSTORM-Y.  Is it?


texts: How can I measure a sensor's load resistance which is adjusted by a potentiometer?

texts:
I have this MQ136 sensor that comes with a shield.  Like most of the MQ series of gas sensors, you can get them with or without a shield.  Unfortunately, I've been unable to find a datasheet that actually displays the shield, much less even mentions it.  However, this datasheet does say that the load resistance (RL) is adjustable, and since the potentiometer is the only adjustable component on the sensor I'm guessing that must be what it's for.  Since the datasheet is also pretty short on what RL actually does, I did some poking around and found this blog on gas sensors which states:

  [gas sensors have] a built in variable resistor that changes its value according to the concentration of gas. If the concentration is high, the resistance decreases. If the concentration is low, the resistance increases. Besides the built in resistor, it is necessary to include a load resistor. This resistor serves to adjust the sensor’s sensitivity and accuracy. The value can range anywhere from 2k Ohms to 47k Ohms. The higher the value, the more sensitive the sensor becomes.  The value depends on whether you want to measure high concentrations of gas or not. If you choose to measure high concentrations of gas, but choose a high value for the load resistor, then the readings won't be very accurate.

First of all, I correct in my understanding this potentiometer is responsible for adjusting RL which controls the sensitivity of measuring gas concentrations?

Second, how can I measure the RL with a meter?  I played around with the potentiometer, and when spinning clockwise I saw a (previously unnoticed) LED light up and it stayed on for a small arc and then it turned off and stayed off when I turned even further until I hit the stop point.  Going counterclockwise the LED came back on during the same arc.  Any idea on what this means?


texts:
I've got a small 12VDC pump that I used on an old project. I now want to use the pump on a different project and make use of a 24VDC transformer I have (because the project also makes use of a 24VDC solenoid valve).

The description on the side of the pump says:

Power 15W
6-24V DC (rated at 12V DC)

I originally bought this as a 12VDC pump so my rather obvious question is can I run this on 24VDC safely without damaging it? Secondarily, will it make the pump run faster or more powerfully?


texts:
I have a simple question, I want for a school project read NFC tags from a large range, can I use a RFID antenna to read the NFC tag ?
I want to know if the RFID antenna is going to work and read the NFC tag.

The scope will be under 50cm to 1m, it's enough (if I could get more scope, tell me).

If the RFID antenna isn't possible, could you tell me if it's possible to build a reliable NFC antenna to read NFC tags with a scope of 50cm to 1m without to need a big antenna on a truck :D, I want a small thing, that I can by example put in a bag.

Thanks for reading


texts: How to connect USB led strip via battery

texts:
I got a USB led strip from Ebay. Unfortunately there is no indication what type of led it is. Looking at power converter it says "5V Output 3x2A"

One strip has 15 leds. I want to connect it via standard battery (9V but if 3xAA are better they I am open to that.)

Also I wanted to add 3 potentiometers to be able to control each color separately.
I did this on my Arduino - connected 3 10k Potentiometers and it kinda works but the knobs are not linear so I get full power when "open" and if I just "close" is a bit it loses like 50% power.

Not sure what's the best circuit I should build to make this work.

Any advice would be helpful.

Pictures attached for reference.


texts: detect rising edge and falling edge to assing signal to Enable

texts:
I'm trying to create a process that detect the first rising edge of PGOOD signal and turn on ENABLE.
Then I need to detect the first falling edge of PGOOD and turn off ENABLE for good.
Here is what I tried but it doesn't work - the ENABLE is always '0'.
 what am I missing?

process(PGOOD,CPLD_RESETn)
begin
if (CPLD_RESETn = '0')  then
             off <= '0';
elsif (falling_edge(PGOOD)) then
             off <=  '1';
end if;
end process;

process(PGOOD,CPLD_RESETn)
begin
if (CPLD_RESETn = '0')  then
             firstOn <=  '0';
elsif (rising_edge(PGOOD)) then
             firstOn <=  '1';
end if;
end process;

ENABLE <= firstOn and not(off);


texts:
I am driving a blue led with a pnp transistor as schematic1.I am trying to bypass the transistor without removing it as schematic2.Is it OK?

Schematic1

Schematic2


texts: Building primitive FGMOSFET for educational purposes

texts:
To illustrate how flash memory works, I thought to build a primitive FGMOSFET and show that it stores a single bit of information (charged, uncharged).
It would require a high voltage to charge, it could be unreliable and leak current, but it would show the basic idea, and I could disconnect and reconnect it, and show with a multimeter that it remains charged or uncharged.
Is that viable?
How would I do it?


texts: Complementary transistor pair with a bipolar transistor and a MOSFET

texts:
I own a set of Soviet IN-14 Nixie tubes and I would like to use them to make a vintage clock. I found this example schematic of a "Nixie clock":

I don't understand what is the purpose of using a MOSFET in the second stage of this quasi-"Darlington pair" (as opposed to a second bipolar transistor in a normal Darlington pair) here:

Is there a particular name for this configuration?

As a secondary question, I also would like to know why a diode was used in place of a resistor in this configuration?


texts: What is the exact definition of a ground loop? Does a ground loop always have planet Earth in series?

texts:
I'm confused as to the exact definition of ground loops. It seems to me that there will ALWAYS be a ground loop if you have:

2 devices (both grounded).
a data cable between them.

You now have a loop in the safety ground wires and the ground of the data cable. Is this a ground loop?
Or is something only a 'ground loop' when the two devices are connected to two separate ground rods and noise/EMI currents passes THROUGH the ground-rod, through the earth and out the other ground-rod?
In more exact terms: does a ground loop always have planet Earth in series?


texts:
For my Circuits II final design project I am given an old transformer that needs to have its power factor corrected to 1 but I am a bit unclear what needs to be done. I'm using this post Power Factor Correction as a reference for power factor information, but I don't really understand it.

Here are the transformer specs:

240V to 120 V at 60 Hz
Single-phase
Isolated
Low coupling
Single primary, dual secondaries

Using a Z-Y Bridge, it was found that Z = (0 + 300j) \$\Omega\$ and Y = (79 + 0j) \$\mu Mhos\$ which are the two measurements I was told were needed. I was also told that an LRC circuit might be the way to go (not sure why exactly).
It is noted that the transformer purely inductive to the 60 Hz and therefore (correct me if wrong please) requires a capacitor be placed across transformer to cancel out the inductive reactance. Does this cancellation result in the power factor being 1?

\$ Z_C = \frac{1}{j\omega C} = Z_L = j\omega L = 300j\$ then solve for C? If so, where does the conductance come into play?

My expected layout is one of these three:

simulate this circuit – Schematic created using CircuitLab


texts: is it possible to design a complex analog circuit through a predetermined laplace equation?

texts:
Let's say we need to design an op-amp with very high open-loop gain (200dB) and with a phase margin above 90 degrees.

We simply calculate the \$s\$-transform of the gain equation as needed. Someting like: $$ A \frac{as^4 + s^3 + bs^2 + cs +d}{es^5 + fs^4 + gs^3 + hs^2 + js + k} $$

Say this equation gives 200 dB DC gain and very high GBW and stability. Can one design the whole circuit (transistors, capacitors, inductances etc.) just from this equation? Does such a method exist?


texts: I am calculating an average voltage of a sine wave for the first half cycle ( which is 10 milliseconds) , and period is 20 milliseconds).


texts: Breakdown Voltage of relay contacts in series

texts:
I am working on a module that allows a small internal-combustion engine to be shut down remotely.  These small gasoline-powered motors are of various makes and models and all have magneto ignition systems.

The ignition systems can have either electronic or Kettering (points and condensor) ignition.

The most-common method of stopping these motors is to ground a node within the ignition system.  For Kettering systems, one simply grounds the points.  For electronic ignition systems, a node is provided that has the same functionality.

My customer wants me to provide SPDT relay contacts.  I prefer to use Telecom-grade relays for this application because there is the possibility that the relays may need to switch low-current / low voltage-level signals.

Problem is that the maximum voltage present at the "kill engine" node is a spike that approaches 400V peak.  All of the Telecom relays that are readily available to me have maximum voltage rating of 250V.

However, these relays are all DPDT.  Theoretically, I should be able to connect the relay poles in series and get double the maximum voltage rating.  Theoretically.

My question is: is connecting relay poles in series to get higher maximum voltage a reliable solution?

[Edit]

It's been pointed out that "All the pain is taken by the last to close and first to open."  I agree completely.  But please follow my logic here and see if the following makes any sense at all.

First: the relay operates only to either allow the engine to run or force it to stop.

When the relay operates, the poles do NOT operate simultaneously.  There is a lag of some hundreds of microseconds between when each contact changes state.

But: does that matter?  The only time this is a consideration is when the relay is changing state.  When the engine is supposed to be running, you have two sets of contacts in series with, theoretically, double the rating of each individual contact.

When the relay goes to the state that will allow the engine to start, the engine is currently stopped.  There is currently NO ignition present, and therefore no voltage on the contacts.

When the relay goes to the state that shuts the engine down, one contact closes first, then the other.  It is possible that the contact that closes last has a single spike that could breakdown the gap.  Before the next spike can occur, the other contact has closed and there are no more spikes.

The total energy contained in a single spike is really quite tiny.  I don't have hard numbers right now but I will get them when I start testing with real engines.   But I don't believe there is enough energy in the spike to damage the contact.

And, I do suppose that I can monitor the voltage across the open contacts (both open) and allow the relay to change state only immediately after the spike has decayed to a low value.  That completely gets rid of the voltage across a single contact.

But my original question stands: can I count on the breakdown voltage to be double that of a single contact if two contacts are wired in series and not changing state?


texts: How can I design a circuit that characterizes photodiodes and phototransistors (as output/input)? That circuit should communicate electronically over an isolated link where one side runs a low voltage system and runs a high voltage on the other


texts:
In this diagram:

What does the S[2:0] mean? I think it is the state but why is the state in 3 bits? What does the 2 and 0 mean?

Cheers!


texts: Why is S11 measurement changing on Agilent E5071B Network Analyzer?

texts:
Just a note: This is the second time I've ever used a VNA.
I am trying to measure S11 of the 1.88GHz RF Input of this Powercast RF Energy Harvesting board. Link to the datasheet.
Powercast Board Datasheet
Powercast Board Schematic
The basic block diagram for this device is RF Input> Rectifier> Capacitor >Boost converter>Load
The capacitor is charged by the rectified output of the rectifier chips and charges to a set "turn on" voltage. When this "turn on" voltage is reached, the boost converter turns on and uses the energy stored in the capacitor to power a load. The load in this case was a simple LED and series resistor.
Now, for the VNA. I have calibrated the VNA port, I have set up a 1GHz sweep with 401 points with 1.88GHz being the center frequency. I set the output power to -5dbm and turned off the "Power Slope" feature. When I turn the VNA trigger to continuous, I see that S11 steadily gets better and better (i.e. lower magnitude at 1.88GHz) and then S11 will get worse (i.e. higher magnitude at 1.88GHz).
The catch is that S11 gets worse right after the boost converter turns on and powers the LED. It repeats this cycle of S11 getting better and then LED turns on and S11 gets worse again. I'm not sure why the capacitor building charge would decrease reflection back to the input.
I've linked a video that I took of the phenomenon happening, you'll see that S11 gets better and then it jumps back up. At the moment it jumped back up the LED turned on, I just wasn't able to record both at once.
YouTube video of the phenomenon.


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I need to measure small distances (from 0-5mm) with precision upto 3 decimal places (like a micrometer). What sort of sensor can I use for this?

This is for measuring terminal heights. I understand that there are dedicated micrometers for this purpose but I'm wondering if there is a better way to do it electronically.


texts: Connecting two different microcontroller outputs together to drive a single device?

texts:
I am interfacing with an existing product. This product uses a PIC16F54 uC and is ultimately driving a solenoid. This device is a black box to me and I have no input into the software running on the device or the design of it. I have identified the pins on the UC which receive the input and control the output of the solenoid.

Without going into all the specifics, my device is going to "piggy back" onto the existing device and give an alternative method of control to the device while reading its output and input.

my uC will need to be able read the same inputs and also control the output. I don't imagine connecting the inputs together so both uCs can see the input will be a problem. However, the outputs will be a problem. One might be driving the pin low, while another is driving the pin high.

What are my options to overcome this? Ideally, I'd like to tap just two or three points and not get into cutting traces to add additional circuitry.

I am thinking my best bet might just be a "man-in-the-middle" type scenario where I cut the output trace from the device uC and wire that as an input into my uC and then make my uC control the output itself.

My uC will be a rasberry PI w/ TE291 3V/5V shifters to get me to the 5V the PIC is using.


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I know that a 9V battery can only power so many LEDs. I need a 9V battery to power 10 of them maybe less or a few more and keep brightness and im not sure where to go to make it happen.

Or if i need a capacitor or an amplifier in the circuit to make all of them work and be bright or what size of either i need or if i should then add a resistor to it or so on.

The LEDs im using are
Ultra Bright LED's
Emitted Colour : White. Size (mm) : 5mm.
Lens Colour : Water Clear.
Forward Voltage (V) : 3.2 ~ 3.5.
Reverse Current (uA) : <=10.
Max Continuous Forward Current : 20mA.
Luminous Intensity Type Iv (mcd) : 15000mcd.
Wave Length: 460 - 470 nm. Viewing Angle : 20 ~ 25 Degree.

So far i have a 9v battery connected to a switch then LEDs (x10), i think i need 32V to power the whole circuit but not sure how to achieve this.

UPDATE
circuit wireup

  --[9v]---[/switch\]---[LED]---[LED]---(x8 LEDs in series)-->[back to battery]


texts:
i made this BLDC motor controller, here is schematic

But TC426 Mosfet drivers keeps blowing out when i connect a load, after drivers fail, mosfets are still working, only drivers blows out, I checked all voltages, they are fine. I am using 33kHz pwm modulation for each phase and mosfets are IRF44N. I can't find a problem, but i was thinking that i need to put resistor between mosfet gate and driver? Could that be a problem?

Thanks for everybody who answered. While you were answering, i tried to do some more testing and i have started to see some pattern, last three times first mosfet driver failed, in schematic it is left driver. I will double check all connections, but I think i will redraw PCB taking all your advice because i am tired going to electronics shop every day and spending money there for drivers! Thanks everybody

UPDATE
I added capacitors to each driver and change mosfets to more powerfull ones, now everything works, thanks to everybody!