texts: How to calculate "effective source impedance" in this audio mixing circuit?

texts:
I am new to electronics and have recently been trying to get my head around audio mixing. I stumbled across a helpful introduction by Rod Elliot on passive and active mixers, but I am stuck on a small part of one diagram.

The annotation describes it as a "Passive Mixer With Channel Level Controls", in this case using variable resistors (faders) to control the levels of the input channels. It is used to explain the issues with passive mixing, but my question only concerns the following statement:

  In Figure 3 you can see that the faders change the impedance seen by the mixing resistors.  The effective source impedance is maximum when the fader is (electrically) centred, and will have a value of one quarter of the fader's total resistance.

Only one quarter of the the fader's total resistance? I would have thought that to maximize impedance, one would maximize the resistance on the variable resistor, resulting in 20k ohms of impedance.

I think it would be helpful if the terms "source impedance" and "electrically centered" were explained? I couldn't find any helpful search results for these.

How did he arrive at the conclusion that the "effective source impedance... will have a value of one quarter of the fader's total resistance"?


texts:
I'm designing a product where we have an ethernet cable from a Raspberry Pi inside the machine going to a PCB with two RJ45 connectors on it placed at the back of the machine. This "routing" PCB today has no other components on it apart from the two RJ45 connectors, and two USB connectors for a similar routing function out of the machine.
When performing EMC tests we have noticed large emissions from the ethernet cable coming out from the machine, from this PCB. This has lead me to believe that we have noise from inside the machine coupling onto the ethernet cable between the RPi and the routing PCB, which is why I'm looking into adding some filtering components to this PCB, and also just improve the design overall.
Here's the schematic of the design:
Here is what the PCB looks like today.

For your info, the RJ45 connector that goes to the outside of the machine is shielded and the shield is connected to the PCB ground. The RJ45 connector that connects to the RPi is not shielded.
My questions are:

For filtering I'm thinking of adding a CM choke, since I believe most noise should be CM noise. Does this make sense?
Reading up on how ethernet is constructed, it seems like I should add a CM choke on line 1 & 2 for TX and one on line 3 & 6 for RX. Is this correct, or should I add chokes on additional/different lines?
At the moment the ground plane of this PCB is not connected to chassi ground, nor any other ground in the machine. I suspect that this is not very good from an EMC perspective, and that I should add a connection to chassis ground, probably through something like a 100nF Y-capacitor. Am I correct in this assumption?

EDIT: Added schematic of the design


texts: What's the deal with this beamed mains transformer design?

texts: Take a look at the image. I always understood that transformers have as little air gaps in them as possible, but you can easily look through this mains transformers that I found in China. Not just for the EM-field, but also for dissipation purposes I'd expect the transformer to be one huge brick of metal. Where is my thought wrong?


texts:
I am reparing a mirror which has IR triggered LED strips in it. I have no data on the LEDs - I can only work from what is written on the components themselves. I know the IR sensor/switch is working.

I am sure the LED driver has stopped working too - 230Vac is going in but no voltage is measured across the o/p (even with no load).

I want to test the LED strips.

The driver primary 230vac and the secondary says 12V 416mA Max 5W.

I figured that I could test the strip of LEDs  by connnecting a 12 dc supply across it (th +/- are clearly labelled). I want to be sure though before I try since I don't want to destroy the LEDs and have to fork out for another set of strips.

So is that ok to do?

Many thanks

E


texts: Determining the correct polarity of a supposedly wrong polarized capacitor

texts:
I'm fixing an audio interface (Scarlett) that was behaving poorly and found a likely culprit - a bulging capacitor. However, it appears to be soldered on the board backwards (based on the `screen on the board!) Given this is a production device it's possible it was screened wrong and assembled right.. this thing was working for many years.

Given that it should have actually exploded, is there a way I can test the board with a multimeter for the actual intended polarity?


texts: Application of buffer chip in serial communication

texts:
On a microcontroller board that I am working on, there is a buffer chip between the microcontroller TI msp430 F1611 and USB interface FTDI FT232BL. The chip is named NC7WZ126.

My question is, why they have used that buffer? what benefits it has and what would happen if that chip was not there at all?

I am asking this because I want to wire up directly to TX/RX pins of the msp430 for some debugging purpose. So should I directly wire to the msp430 pins (Pins #34 and #35)? Or I should wire to the inputs of the buffer (pin 2 and 3 of NC7WZ126)

UPDATE

AFAIK msp430 is using 0-3.3V for low-high (Since  its get its Vcc after a 3.3 regulator) bits and that FTDI is 5 Volts (powered by USB) so can be that a reason for that buffer? Considering That I want to feed in 5V CMOS to RX/TX of msp 430, then I should wire to the buffer and not to the 430?


texts:
I'm trying to find out what the device is called that is found on a car radio.
The dial that you turn to change stations.  I want to track one down to see how it works, but I have no idea what it's called.

Does anyone know?


texts: Op-amp input impedance datasheet specification

texts:
Some op-amp datasheets specify both the differential and common-mode input impedance:

while others just specify "input resistance":

I've always assumed that if the datasheet only shows one value, it's the same as the differential input impedance, but I want to make sure.

Especially because TI's "Understanding Operational Amplifier Specifications" distinguishes between the two terms:

  ri Input resistance: The resistance between the input terminals with either input grounded.
  rid Differential input resistance: The small-signal resistance between two ungrounded input terminals.


texts:
Assume a CMOS-cell, which is an inverter(?) here and hence, the input is connected to both transistors, but please let's treat the transistors independent from each other.
V_0 = 5 V, when upper transistor is conducting and lower not.
V_0 = 0 V, when lower transistor is conducting and upper not.

What is V_0 in case both are conducting?


texts: How to use an normally closed hall effect switch as normally open?

texts: How do you use a normally closed hall effect switch as a normally open. I cant find them easily on shopping sites or they are just too expensive.


texts: My DIY RGB LED panel powered by 9V battery works but certain colors like blue, white, and purple don't work

texts:
I am able to power on my LED unit here with a 9V battery. I'm using a recharble lithium 9V as well.
I can't figure out why I can't get blue, purple, and white. The only colors I get are red, orange, yellow, and green.
The LED panel is normally used for some lights in a car, 12V DC, but I know that 9V can power everything at a lower brightness.
Any ideas what is going on? I can't change power sources because the mod goes into a collectible figure that only has room for a 9V sized battery.
The LED panel is this.


texts: Function of the various capacitors in the schematic below

texts:
I'm trying to analyze the circuit below and I understand that the transistor T201 is acting like an inverter . Am I wrong ?
And also why are the two capacitors in parallel at the beginning of the circuit ?
I know that there are many parameters to be considered to select a capacitor such as working temp, temp coeff,working voltage ,leakage current etc., but how do they matter for the circuit below?
what does "3A" at the input pin mean ? and also what does "10E"
 and "11G" at the output pins mean ?
Thank you


texts: Cable management with magnetic hooks - no good deed goes unpunished?

texts:
The setup
I've got a metal desk (actually a workbench) on which I have my computer, monitor, cable modem, a WiFi router, and some other devices.  Rather than drill holes for hooks, I was thinking of getting some magnetic hooks to use along the back of the desk for cable management. Something like this: https://www.amazon.com/Magnetic-%EF%BC%ADaximum-Neodymium-Corrosion-Protection/dp/B0787Q54M1/ref=sr_1_4?dchild=1&keywords=magnetic+hooks&sr=8-4  One set of hooks for power cables, the other for USB and Ethernet so data is separated from power. Right now all the cables are on the floor behind the desk.
Concerns
I am not at all familiar with electronics.  The Ethernet and USB cables I have do not have any special shielding (the Ethernet cables are UTP). At the moment they are all on the floor, so they could potentially interfere with each other but I haven't noticed anything so far.  The concern I have now is if I have them grouped together and then potentially running through magnetic fields from the hooks. Same thing for the power cables (I'm using surge suppressors for all power).
Am I being overly cautious/paranoid, or are there precautions I actually should take?  Is using magnetic hooks for cable management okay?
Research
I saw Running network cable near X-Ray equipment and this gives me hope, however magnetic fields and X-rays are not quite the same thing so I want to confirm my setup would be okay. Internet searching hasn't turned up anything that really applies to my situation, so I don't want to make false assumptions.


texts: dsPIC33: Bootloader is flashing but resets when GOTO firmware

texts:
So I'm working on a bootloader for a dsPIC33EP32MC504 with a CAN-Bus and the Bootloader flashes the firmware correctly. I verified that by reading out the program memory at the location I flashed it to and compared it with how the firmware looks like when its flashed via a programming tool.

The problem now is that the microcontoller wont let me jump to the address of the firmware. When the command is executed, the microcontroller simply resets itself and starts at 0x000000 again, which jumps to 0x000200 where the bootloader is.

I tried two different types of goto-jumps:

1.: Inline asm code

asm("goto 0x1C00");

2.: function pointer

//first defining the pointer
firmware_ptr = (void (*)(void))0x1C00;
//...
//later using the function
firmware_ptr();

Unfortunately both ways lead to the same result as described above

Another thing I tried is giving the code base of the firmware an offset by manipulating the linker-script and only program the firmware to the microcontroller via the PICkit3 and without the bootloader. I manipulated the two lines mentioning the start of the program in the linker script:

/*
** Memory Regions
*/
MEMORY
{
  data  (a!xr)   : ORIGIN = 0x1000,        LENGTH = 0x1000
  reset          : ORIGIN = 0x0,           LENGTH = 0x4
  ivt            : ORIGIN = 0x4,           LENGTH = 0x1FC
  program (xr)   : ORIGIN = 0x1C00,         LENGTH = 0x55EC  /*here*/
  FICD           : ORIGIN = 0x57F0,        LENGTH = 0x2
  FPOR           : ORIGIN = 0x57F2,        LENGTH = 0x2
  FWDT           : ORIGIN = 0x57F4,        LENGTH = 0x2
  FOSC           : ORIGIN = 0x57F6,        LENGTH = 0x2
  FOSCSEL        : ORIGIN = 0x57F8,        LENGTH = 0x2
  FGS            : ORIGIN = 0x57FA,        LENGTH = 0x2
  FUID0          : ORIGIN = 0x800FF8,      LENGTH = 0x2
  FUID1          : ORIGIN = 0x800FFA,      LENGTH = 0x2
  FUID2          : ORIGIN = 0x800FFC,      LENGTH = 0x2
  FUID3          : ORIGIN = 0x800FFE,      LENGTH = 0x2
}

__FICD = 0x57F0;
__FPOR = 0x57F2;
__FWDT = 0x57F4;
__FOSC = 0x57F6;
__FOSCSEL = 0x57F8;
__FGS = 0x57FA;
__FUID0 = 0x800FF8;
__FUID1 = 0x800FFA;
__FUID2 = 0x800FFC;
__FUID3 = 0x800FFE;
__NO_HANDLES = 1;
__CODE_BASE = 0x1C00;      /*And here*/
__CODE_LENGTH = 0x55EC;
__IVT_BASE  = 0x4;

__DATA_BASE = 0x1000;
__DATA_LENGTH = 0x1000;
__YDATA_BASE = 0x1800;

Unfortunately the same thing occurs: it always resets and never runs

Some more information on the bootloader and the firmware: Neither bootloader nor firmware uses interrupts, therefore the IVT is empty. The bootloader is programmed via a PICkit3 at the beginning of the programm memory (at 0x0200) and the firmware should start at 0x1C00. The firmware is only a small testing firmware consisting of 203 words, and is working fine when programmed normally via the PICkit3 at 0x0200. In the python script which I use to calculate the addresses and words from the .hex file, I only transmit the firmware related words and addresses to the bootloader, not the IVT or the reset vector. The configuration bits of firmware and bootloader are the same. I use the XC16 version 1.35 compiler for firmware and bootloader

Since I am running out of ideas what could be the problem, I think I missed something regarding the organisation of the programm memory in the dsPIC33E series or regarding the inner connection between program pointer, program memory and IVT


texts: Strange result ADC(Arduino Micro) Thermistor KTY 10-6

texts:
Where's the error in the following circuit/code ?

Some time ago i got various sensors . One of those was the kty 10-6 (3 pieces). At the beginning i could not find any datasheet or examples about this temperature sensor. So i got an LM35 which was very simple to setup as it is linear. Now after various months i finally found the proper datasheet and the Mathematical equation to get the proper resistor values.

KTY 10-6 (this is the datasheet link)

Circuit

I found out that it is similar to the kty81-210

 (Vcc 5+)--+-->2.7k--+-->kty81-110-->(GND)
           |         |
           +->100nF--+-----> ADC0 (Analog Port 0)

As i have no 2.7k Ω resistor i used a 2200 ohm resistor.

the capacitor is 100nf i think: IJ63 is on top of the enclosure.correct?

simulate this circuit – Schematic created using CircuitLab

Code

As this thermistor is not linear and i always wanted to use the proper mathematical formula to calculate the temperature, this is the best solution. Based on what i read in the kty10-6 datasheet i changed some values like the resistor and the beta(a) value. the alpha(b) .00788 seems to be the same in both sensors.

float resistor = 2200; // changed
float temp = analogRead(A5);
float ukty = 5*temp/1023.0;
float a = 0.00001937*1000; // changed
float b = 0.00788*1000;
float c = 1000-resistor*ukty/(5-ukty);
float delta = b * b - 4 * a * c;
float delta1 = sqrt (delta);
float x2 =(-b + delta1)/(2 * a);
float temp1 = x2 + 25 ;

Is the calculation correct?

I ask beacuse even if its really hot these days .. i don't think there are 132-135°Celsius.The formula is for celsius.

Even if i don't use this formula but use other simpler calculations (linear) i always get over 130-140°Celsius

source1   source2  source3

Notes

If i touch the sensor the reading increases... as expected.

I tested on all analog pins.

I use the arduino micro.

I use it with a i2cLCD.

It's usb powered.

Nothing else is connected.

If i measure the resistor on the proto board when everything is turned off i read it as 1200ohm... the cap?

Why do i get 120 to 140 as a temperature value?

Optional

I just closed a post on electronics stack wich describes how to increase the thermistors resolution with resistors.
found it

If someone knows how to change my circuit to read temperatures from -10/-20 to +40/+50 i would be very happy. this would duplicate the resolution. i think in my zone the temperatures will never go lower than -20 or higher than +50 ° Celsius.

I buyed 3 of those, i know they are cheap. I know about the nice DS##### Temp sensor which is perfect for the microcontrollers. But i want to get this one to work also.


texts: coplanar transmission line on both sides of a four layer board

texts:
I am designing a four layer board in which i have to run two 50 ohm traces one at the top and other at the bottom side of the board. I have decided to use Coplanar wave guide for both the traces. I am skeptical in calculating the impedance of the trace at bottom since the adjacent plane is a power plane. I have attached  the stack up image of the board.

Calculated impedance using APPCAD.


texts: Does slew rate depend on frequency of input signal?

texts:
I am just beginning to study analog integrated design.

Say I've designed a two stage operational amplifier with compensation. The slew rate would is given by:

$$\text{SR} = I_{\text{sat}}/C$$

For a sinusoidal waveform not to be subject to slew rate limitation, the slew rate must be

$$\text{SR} \geq 2\pi \times f \times V_m$$

Doesn't this mean that at different signal frequencies, slew rate is different?
Why do larger signals place a limit on bandwidth of opamp? If the signal amplitude is high, slew rate is also more. Am I correct?

I would also like to know why slew rate is called the large signal bandwidth.


texts: Most efficient way to step down 48V to 12V high amperage

texts:
What is the most efficient way to step down 48V to 12V? I have a power supply that can output 48V at 40 amps. Assuming the power supply is perfect, that gives me 1920 watts. However, I'm powering some RC equipment such as ESCs and brushless DC motors that need 12V. The perfect step down would be able to push 12V at 160 amps. Is there anything more efficient than the regulators I have found which at most can push 12V at 12 amps?

The ones I have found:

http://www.amazon.com/Converter-Regulator-48V-12V-120W/dp/B00965W4TU
http://www.powerstream.com/dc48-12.htm


texts: How can we sure about common mode voltage for RS422/RS485 without ground connection?

texts: RS422 and RS485 standards specify different common mode voltage limits. In some application notes, I see that ground connection between two node is somehow optional. Suppose that two nodes are isolated. How can we sure about common mode voltages? In optional case, is it assumed that scenario is known and potential of local grounds of two nodes are close enough to each other?


texts: Function Generator - Signal without Neg or Gnd reference

texts:
I have a new PC based function generator (very cheap), and an old BK Precision function generator. The old BK Precision can output a signal without the ground or negative reference lead from the BNC cable, but the new PC based function generator can only output a signal when the ground or negative is connected. Why is this? How can I get the new PC based function generator to put out the same signal?
I need thins on sided input because the device I'm trying to feed seems to only respond well with the input from the BK Precision unit connected with the "red" lead of the BNC cable connected, and the "black" lead floating.


texts:
I am trying to use the wheel encoder mentioned in the circuit but somehow i can't manage to understand why there is a full voltage drop in the IR led and why the resistors are not limiting that voltage drop, considering that in "ohmic" terms my circuit should work.

I would like somebody to help me pin what i am doing wrong

The datasheet is
http://sensing.honeywell.com/index.php?ci_id=50399

In the electric characteristics the datasheet says that the forward voltage should be 1.6 V@20mA and the supply of detector should be between 4.5 and 5.5V@7mA

So to use the resistors i have at hand the circuit is in the following attachment. For the IR led i connected it to a 5V source with a 220hm resistor and to the receiver 47 + 47 Ohm resistors.

Also i am connecting the A and B channel outputs to an atmega328 directly as the datasheet says the HOA0901 has internal pullups. I also set the atmga328p in input mode.

Thanks


texts: Is there a way to prevent code being read from an MSP430 without blowing the fuse?

texts: I was recently involved at a project in a small company where we had fears of someone taking the code from the master chip, an MSP430F2419, and using it for a competing product. We ended up blowing the JTAG fuses for the first few beta releases, but because of the blown fuses we could not reprogram them. Is there a middle ground between blowing the JTAG fuse that will prevent someone from reusing the code on the chip, but let us reprogram the chip?


texts: Fastest way to find R value for RLC under/over/critically damped?

texts: If I have a known square wave source, known capacitor value and known inductor value, what is the fastest way to figure out what the resistor value has to be to make the circuit overdamped, underdamped, and critically damped?


texts: Does a step-down voltage converter draw its maximum wattage

texts:
I purchased a step-up/step-down voltage converter to use my 110-120V electronics in countries with 220-240V wall sockets. It's similar to the one pictured below.

These transformers are sold in a variety of Wattage ratings. What is the power consumption of the transformer? Does it always consume its maximum wattage capacity regardless of what devices are attached to it? If I just turn on my 1000W transformer with no devices attached will it be drawing 1000W, or some lower amount? If I have devices attached that add up to 1000W, is it transformer drawing 1000W or a different amount?


texts:
I am building a 5V DC charger for an offroad motorbike. The main goal is to use this to charge/power a mobile device/phone/tablet whilst travelling/camping.
If space allows maybe also a GPS tracker but that's another subject for another day...

The circuit will be powered by the lead acid motorbike battery.
With the engine off the battery measures 12.8v.
Engine on between 13-14v

The Regulator I have chosen is a SKM10A-05 for a number of reasons (temperature range, heat dissipation, size etc...) but mostly due to the input range due to engine cranking. This also simplifies the design and as a one off i'm not too concerned about price.

To prevent accidental drain of the motorbike battery I want to implement a low voltage cutoff. At around 11v I want to turn off the SKM10A-05 using the R.C. pin:

FUNCTION REMOTE CONTROL;

Power OFF: R.C. ~ -Vin <1.2Vdc or short
Power ON: R.C. ~ -Vin >5.5~75Vdc or open circuit

I find plenty of topics for lower voltage applications or charging a battery but so far nothing for this voltage range. Preferably this circuit also needs to not consume much power and be quite robust as the bike gets thrown around alot.

Would really appreciate any help!


texts: Why is load resistance neglected for an ideal op-amp?

texts:
In the image below, for an ideal op-amp, the output resistance is zero.
But when, we add the load, how does it not affect op-amp output resistance? I can't understand intuitively. I guess I am confusing ideal and real op-amp concepts, as I understand output load affects the gain.


texts: I am having difficulty understanding what "infinite" in IIR means in practice..In theory the impulse response is used for feedback..If this feedback never ends how output is generated?


texts: Is there a way to electronically protect a device from bad chargers?

texts:
In a discussion with a colleage, he claimed that with simple electronics you can protect a device from fake, bad or even malicious chargers.

I do not have a deep understanding in electronics, but I’m interested in whether this is true, and the cynical claim that the only reason Apple puts recognition chips in their cables and chargers is just to make more money - is true.

I’m sure if it was so simple then every device manufacturer would have done it, and Note devices wouldn’t have exploded...

Any insight will be appreciated!

—
Clarification: I have nothing against the Note 7 (except, well, it exploded), it was just an example and indeed I did not look up the exact source of the problem. This is also not an “Apple vs. The World” issue, but just simple curiosity!


texts: Long range sensor readings in a star network with Arduino

texts:
I'm planning a project that requires me to have around a dozen temperature and humidity sensors placed around the house and the yard. These would connect to a central Arduino in the house that would log the data and send it to a database elsewhere.

I have browsed the internet for solutions that work for long cable runs. For temperature sensors I found 1-Wire, especially DS18B20 sensors. However, there doesn't seem to exist humidity and pressure sensors that utilize 1-Wire.

What is the easiest way to accomplish such network of sensors? RS485 seems to do great even with long cables (my longest run will be less than 50 meters, most in the 5-10 m range) but as far as I know it would require a microcontroller in each end, which would add complexity.


texts:
Can somebodu explain why cuttoff frequency of voltage divider should be much lower than other parts? I didnt get how impedance will be less. It according to me be a Low pass network if low cutoff freqnecy. How impedance will be low. I'm using this config here :
Bascically how is the 2nd cap of value 100nf helping me in this circuit?


texts: Safety considerations designing a mains powered device

texts:
I am building a device for hobby purposes- a 3D printer specifically.
It already uses mains (240V AC) powered heater elements to heat the build chamber (4 ceramic cartridge elements at 100W each).

The heater elements are switched on by opto-coupled relay board (something like this: http://www.ebay.com/itm/5V-8-Channel-Relay-Module-Board-Shield-for-Arduino-ARM-PIC-AVR-DSP-MCU-Uno-1280-/200807736090?pt=AU_B_I_Electrical_Test_Equipment&hash=item2ec112e31a one).

I would also like to heat the build platform the same way- using a mains-powered silicone heater mat at 1000W (I have a larger and heavier build platform than most of the other 3D printers- that's why I need so much power to heat it up in a reasonable amount of time).

The build chamber heater elements are not moving, so I'm less concerned about those.

But the build platform is moving, and I am worried that a broken live wire can basically put the build platform at 240V potential, which can be very hazardous to user, if mains connection is not earthed and protected by RCD.

I have come up with the following ways, which I think should protect against such failure:

Use an isolation transformer, and power all heaters from that.
Include a RCD in my device. This should limit the possibility of electrocution.
Power heaters from a DC power supply. I don't like this option because of the price of DC power supply at required power levels.

What is the recommended way of designing such a device?


texts: What does a resistor value of "NOM" mean?

texts:
On this schematic of part of the Apollo Guidance Computer (found here), some resistors have a value of "NOM."

According to this question, "NOM" stands for "nominal" when it's found in a datasheet, but this isn't a datasheet and I don't see how "nominal" would make sense here.


texts: Antiresonance of multiple parallel decoupling capacitors: use same value or multiple values?

texts:
My quesiton:
Is it better practice to put same-valued capacitors in parallel of capacitors of different values to decouple the high-frequency noise caused by digital ICs?
Background
Digital IC need a decoupling capacitor close to their supply pins to ensure a stable voltage during power transients and to deal with noise (mostly to prevent noise generated by the IC to affect neighboring circuitry). It seems sensible to place a bulk capacitor (say 10-100uF), to act as an energy reservoir, and several smaller capacitors to deal with higher frequencies. The reason to place several small capacitors instead of just one is to deal with their Equivalent Series Inductance (ESL), which in practice, causes them to behave like an LC circuit.
The effect of anti-resonance
Yet, here is where best design practices and electronic myth seem to get mixed up and confusing to me. Most electronic engineers I have met like placing several decoupling capacitors of different values in parallel (with the smaller capacitors closer to the IC). The logic behind it is that the each capacitor takes care of a different noise frequency as depicted in Figure 1.

Figure 1: Impedance over frequency of three different value capacitors in parallel (cyan) vs their individual contribution (brown, blue, red). Image taken from All About Circuits.
Note the small anti-resonance peak. It seams no major trouble , and the overall behavior of the three different capacitors in parallel is vastly superior to their individual decoupling capabilities.
However, I have read in Electromagnetic Compatibility Engineering by [Henry W. Ott] that placing capacitors of different values may cause a much greater antiresonance-peak which can be very harmful for our designs (see Figure 2). In fact, it amplifies any noise that falls into the anti-resoance frequency range, which is corroborated by this paper.

Figure 2: from Electromagnetic Compatibility Engineering, by Henry W. Ott, section 11.4.4. The 15nH inductance makes reference to the capacitors ESL.


texts: Is there any way to control volume on ISD1600B?

texts:
I'm using the ISD1610B chip and I would like add some volume control on the Speaker/Buzzer or on the optional speaker.

Can I add a potentiometer at the SP+ or SP- line? But wouldn't that only let me go down to 1/2 volume since it is a differential output? Any other suggestions?

EDIT:
I'm looking to adjust the volume of the speaker used for playback, not the input volume from the microphone (this can be adjusted using the AGC pin as Leon pointed out below).


texts: Change slope of Magnitude plot in 2nd order system

texts:
For the second order PLL with equation:

$$1-\dfrac{2\zeta\omega s + \omega^{2}}{s^{2}+2\zeta\omega s + \omega^{2}}$$

I used Matlab and obtained a Bode Magnitude (with zeta = 0.3, 0.5) like:

In the book "Phase Lock Loops and Frequency Synthesis" by V. F. Kroupa, the author has a plot that looks like this (for a 2nd order system found on page 14 of the book):

How can I get my slope, that is 40dB/decade, to match his 20dB/decade?  Thanks.


texts:
I know how a 3 Transistor CMOS camera pixel works. As I understand, 4T CMOS pixels have one additional transistor that connects the photodiode to a so-called floating node.
What is that floating node and what is it good for? Seems like a storage for photo-generated electrons, but I thought CMOS pixels give you voltage, not charges (light CCD's...).
Maybe it's good for multi-integration to reduce readout noise (think I was reading that somewhere)?
Any help is welcome, including good hints for further reading on the principle of camera pixels.


texts: Wireless power transmission calculations

texts:
I have been able to calculate and fix components for the transmitter circuit of wireless power transmission system but I am still having some challenges. They are:
1. How can I calculate theoretically the gain of the mosfets?
2. How can I calculate the voltage induced at the receiver circuit?
3. How can I calculate the values of the components I can use to rectify the received voltage? I am working with 14MHz frequency.

Note: I tried to use the formular, coupling coefficient (K)* magnetic field (B) to calculate the induced voltage but I got a rediculously little number.
So, I really need answers to help me move forward. I would also appreciate a better circuit diagram that can transfer up to 24 volts.


texts: How are bits put on a bus, the i2c for example?

texts:
I have been to school and through these topics, understand that "bits on a bus" is a behaviour emerging from the very way a CPU works. But still, I suppose this requires some interaction... it doesn't just happen at a clock cycle,  when I press a button, something is taking these bits and putting them on a circuit, as if a switch was "manually" activated.

I tried to look into the Linux source regarding i2c, but still in my mind I can't get around this thing, what is "putting" these bits on-demand on the i2c bus?


texts: Digitally Switching a Single Source into 128 Channels

texts:
I have a device I'm building that uses a single high-precision current source (driven by a DAC for various arbitrary waveforms) to drive one of 128 channels. The current level will be on the order of 20uA

Building 128 redundant current sources is expensive and unnecessary, and a typical 74595/596 shift register won't work because I need to "pass through" the current source to the channel.

Current idea is to use 128 triacs switched by either an fpga (with many pins) or daisy chained 595's and a micro, connected to the common current source. Only one will be open at a time. As the current source and the controlling device are all off the same reference I don't believe I will need to use optoisolators although that will be determined when prototyping

I have 3 questions.

Is there a standard way to do this that I'm unaware of
Will using triacs with such a low current source cause issues with noise or switching
Are there low power triacs in small form factors (preferably smd)


texts: Why/How alternating currents through coaxial cable do not interfere with each other?

texts:
I know that cable TV use coaxial cable with alternating current frequencies varying from 5 MHz to 750 MHz.

Why/How a alternating current of, for example, 5 MHz , 10 MHz, 20 MHz, 100 MHz, 300 MHz, 500 MHz, 650 MHz, etc, do not adds ups or cancel each other, since all those current frequencies are passing through the wire at the same time?

I learnt from high school that all waves interfere with each other, and that is the principle of noise cancelling used in headphones.


texts: Can I rotate the components and the board at once? I try hold click + Space bar but it just rotates the component only. Say I already have a 20mm x 10mm board size and I want to make it 10mm x 20mm. I tried Design >> Board Shape. But I don't know what to do next.


texts: I am uncertain what to use as a light source to expose the photoresis for PCB making

texts:
I want to graduate from toner transfer method of PCB making to using photoresist.
I may be making a bigger deal of this than needed, but I am unclear on what I need to use to efficiently and effectively expose photoresist film when making DIY PCB's.  Someone said that I need high UV, but not sure how to find that. A lot of the grow lights I see say "no UV".  Any help?


texts:
So I am designing a cheap and simple sound device using the Atmega32U4 uC and stumbled across one problem.

I am using the 10-bit PWM output of the uC to output audio and I want the user to be able to control the output volume using buttons, not a discrete potentiometer. A typical solution would be to just decrease the PWM output duty; but that way I am losing the already low resolution - by decreasing the output volume only by 10dB I already get 60% lower output voltage, and, therefore, I am entering the 8-bit resolution territory already.

That's why I started looking for a cheap hardware volume decreasing solution and I don't want to use a digital potentiometer, since they are relatively pricey. In the end, I came up with the solution shown below; basically, it uses two uC PWM outputs, one to control the volume (VOLPWM) and one to output the audio (OUTPWM); the VOLPWM gets heavily integrated and then the Q1 switches according to the OUTPWM between ground and the VOLPWM output voltage. Notice that the output integration happens after the Q1+R2 pair, pure PWM signal enters the Q1 base.

I've also considered using a push-pull pair instead of Q1+R2, however, I wasn't able to get a decent low level output.

My questions are:

Are there any better solutions to my problem?
Won't the similar value of R2 and R5 be problematic?
What could be the other cons of my solution?


texts: Why do most NEMA 5-15P (North America 125V 15A) line and neutral blades have holes in them? I've been wondering this for quite some time and haven't yet found a satisfactory answer.


texts: Communicating between 2 different microcontrollers

texts:
My Arduino runs at 16MHz clock speed; another microcontroller runs at clock speed of 13MHz. If I send digital output directly from an output pin of the former to input pin of the latter, there will be a loss of data and the transmission will be corrupted.

Question 1: How do I get the MCUs to properly transmit the data without any corruption? Do I need to sync them somehow, or I should use another device in middle as some kind of a buffer (or maybe to send data at a lower rate)?

Question 2: If I can send data at a lower rate from MCU#1 to MCU#2 will there be a phasing difference which would result in data corruption?


texts: Building AC to DC circuit that can not be run on a breadboard

texts:
First I have an AC power source.

Can I solder the power source directly to a rectifier to make it DC?

I plan on using a protoboard using the DC power but I need the board to be able to handle 2Amps and from what I found regular breadboards can't be used so I've been looking at veroboards.

What are trace lines on veroboards?

I found this online calculator for max amps of a board.

Lastly would it be safe if I solder circuit together directly instead of using a protoboard?

The circuit would require 12 volts at 2 amps.


texts: is soldering mobile processors something that i could do at home?

texts: I want to connect a mobile processor such as a Samsung Exynos or Qualcomm Snapdragon, which both have their connectors on the bottom to a PCB but im not sure if this is something i can do on my own or needs a pick and place machine, to be honest im not entirely sure what the method of soldering used is called. Can you please inform me if a socket is available for these also? Sorry if this came across as a dumb question, thanks for the help :)


texts: I have a MOSFET (IRF840) hooked up as a DC motor switch. Source is connected to ground, drain is connected to the motor. When I set the Vgs to 5V, the Id is about 1,5A, but the Vds jumps to over 3V. Can someone tell me why the Vds gets so big?


texts: Speakerphones...no feedback...how do they do it?

texts:
I'm working with a factory on a speakerphone type of product but am getting feedback. We are using full-duplex.

This is what we are seeing/hearing:

User A talks into unit A
Unit B's speaker plays User A's voice...HOWEVER Unit B's mic picks up the audio and sends User A's voice BACK to unit A!
Unit A starts to hear the feedback!
Unit B starts to get it too!

How do speakerphones do it?  Do they somehow turn off the speaker (for a really short amount of time) when they detect that the mic is being used?
What happens if the speaker phones are right next to each other?


texts: What is the significance of sensitivity list?

texts:
I implemented BCD counter using JK Flip_Flop. While implementing I missed to add "reset" to the sensitivity list of JK-FlipFlop. Because of that my simulation result appeared like this.

Later I rectified the problem by adding "reset" to the sensitivity list and I got

I got output but I am not getting why there was such an error in previous case. If reset is not included also we should get output at very next clock right? In my case it is not happening. Can someone tell me why is it so?


texts: Ferrite bead for use for filtering a microSD card's Vcc

texts:
I am hoping to use a microSD card in an AVR project and am just trying to find values for all my components.

However, I am not sure what value of ferrite to use here. The few microSD schematics that I've seen with a bead just said "FERRITE" and didn't specify an inductance, or an impedance at a given frequency.

I have an Olimex development board with a full-size SD card using a 470 nH inductor here (PX128A1).

simulate this circuit – Schematic created using CircuitLab

Is this an appropriate inductor for a microSD card's supply voltage as well?

Edit: the accepted answer is a good general answer, but I also have specific example of another Olimex board using a microSD. The OLiniXino board (schematics) uses a microSD with a 470 nH/1.76 R/250 mA inductor for Vcc filtering. They use the same inductors for SD/MCC and microSD. I suspect this is due to being able to reuse an inventory part, but at least it shows a known-working value.


texts: Design considerations for unattended product in public place

texts:
When designing a product that is to be installed and left unattended in a potentially publicly accessible place, what considerations are taken in order to minimise the risk of vandalism and theft? Some example problems:

The risk of the device being opened and peripherals (such as SIM cards, SD cards etc) being stolen.
General vandalism to the enclosure and any external connections (e.g. antennas, service ports etc).

It would be great to hear others challenges and experiences in this part of the electronic product design process.


texts: LTC3106 solar harvester example - different resistance values but same ratio

texts:
I've highlighted the voltage divider on the LTC3106 solar harvester example:

The datasheet explains that the RUN pin is connected to a comparator which enables a certain function of the IC for 0.4 or 0.6V:

Questions:

How did they get the relations between \$V_{in}\$ and \$V_{RUN}\$? Are there some assumptions made on the current going into the IC?
The ratio R1/R2 can be achieved by different resistor values. 3MOhm/3Mohm = 3KOhm/3Kohm. What should one take into account when choosing the values?


texts:
Can someone please help me with code? I have a 24 teeth trigger wheel. Every tooth is registered by hall sensor and I need that Arduino simulate 36 pulse output of that corresponding 24 pulse input.

Here is my code with delayMicroseconds, but I can`t use delayMicroseconds, because Arduino doesn't understand bigger than 16k micros delay.

const int  hall = 2;    // hall sensor
const int ledPin = 13;       // the pin that the LED is attached to

// Variables will change:
int teethCounter = 0;
int hallState = 0;
int lasthallState = 0;
long cycles=0;
boolean cycle = false;
unsigned long microsStart = 0;
unsigned long microsStop = 0;
unsigned long usElapsed = 0;
unsigned long usElapsedUp = 0;
unsigned long usInterval;

void setup() {
// initialize the button pin as a input:
pinMode(hall, INPUT);
// initialize the LED as an output:
pinMode(ledPin, OUTPUT);
// initialize serial communication:
Serial.begin(9600);
}

void loop() {
hallState = digitalRead(hall);
if(cycle==true){
microsStart=micros();
}
if(cycle==true){
usInterval = usElapsedUp/72;
for (int i=0; i <= 36; i++){
digitalWrite(13,HIGH);
delayMicroseconds(usInterval);
digitalWrite(13,LOW);
delayMicroseconds(usInterval);
cycle = false;
}
}

 // compare the hallState to its previous state
 if (hallState != lasthallState) {
 // if the state has changed, increment the counter
 if (hallState == HIGH) {
 teethCounter++;
 if(teethCounter==24){
 cycle = true;
 cycles++;
 teethCounter=0;
 usElapsedUp = usElapsed;

 }

 Serial.print("Tooth count: ");
Serial.print(teethCounter);
Serial.print(" Cycles: ");
Serial.print(cycles);
Serial.print(" Time: ");
Serial.print(usElapsedUp);
Serial.print(" Interval: ");
Serial.println(usInterval);
}
microsStop=micros();
usElapsed=microsStop-microsStart;
}
// save the current state as the last state,
//for next time through the loop

lasthallState = hallState;
}

How can I calculate and from where can I take trigger points?

  If(event happens==true){
  digitalWrite(13,HIGH);
   }
  If(event happens==false){
  digitalWrite(13,LOW);
  }


texts: What is essential to make a super capacitor?

texts: Assume I have two 5x5 cm aluminum foil sheets and activated carbon powder and a normal A4 paper. If I dissolve the activated carbon powder in water to get something like a paint and painted the aluminum foils with it and let it to dry then placed the paper between the two aluminum foils will I get a super capacitor? is there anything else required? is the electrolyte essential? I saw youtube videos all using graphene electrodes and chemical electrolyte that I can't get. So what's the simplest form of super capacitor that I can make?


texts:
I made my own PCB using ADUCM30299 as microcontroller;
in this card I also have a power management, BLE, Flash memory,USB Type C
when I tried to calculate the voltage in SWD_CLK, SWD_DATA, ....
I find that SWD_DATA always equal to 3V on the other hand SWD clock equal to 0.9v and when I click on reset button in my PCB it becomes 3V
This is the Schematic of the microcontroller ,

an someone explain to me and can I download my code in This board,
with Thanks


texts: I2C - Can I control the SCL line with a output only pin if I am not expecting clock stretching?

texts:
I'm short on pins and am working with extremely low budget and small sized circuit board. So, if the I2C slave does not clock stretch, can I safely delegate the SCL pin to some output expander (Shift register or Binary Decoder)?

The circuit contains the following:
ATtiny13a
DS1307
74hc138 (binary decoder) or 74hc595 (shift register)

In short, is it absolutely necessary for the SCL line to be pulled up and kept in open drain condition? (Both in general and in context of DS1307 chip)


texts:
Consider this circuit.

The question asks for write an algebraic expression for the second derivative of the inductor current in terms of the source current \$I\$, the inductor current \$iL\$, the inductance \$L\$, and the capacitance \$ C\$.

\$\frac{d^2i_L}{dt^2}=?\$

So far so good. But let's look answer.

How should capacitor current be equal to inductor voltage?


texts: What glue is it? Is it safe for attaching?


texts: What are the cables for the BK Precision 9123A power supply connections called?

texts:
I bought a BK Precision 9123A power supply on ebay for about $200, but it didn't come with cables.

If you look on the product page here or the image below you can see the type of connectors is has on the front of it.

I've tried searching on ebay using various key words, but can't find the right kind of cables. So, I've concluded that there must be a special name for them, which is... ??


texts: Difficulty stabilizing a system using sisotool on Matlab

texts:
I am trying to design a controller for a synchronous buck converter by using the siso tool on Matlab.
The inductance value is 1.28mH, the filter capacitance is at 4.8uF and the load is a 240Ohm resistor. The maximum input voltage is 800 V and the switching frequency is 75Khz.

I am targeting a 7.5Khz bandwidth for my controller and a reasonable rise time with an overshoot of less than 20%. I am only changing the reference values and am trying to look at how the voltage tracks it. So, I am making a controller for my reference to output.

Vinmax = 800;
fsw = 75e+3;
L = 1.288e-03;
C = 4.831e-06;
R = 240;
H = tf(1,[L*C,L/R,1]);
plant = H*Vinmax;

%launch the sisotool for tuning the controller
sisotool(plant)

I have been trying for a very long time to stabilize the plant for the required specs and have been very unsuccessful. I would be grateful if anyone could comment on how to proceed further and design a controller.

Thank you.


texts: Sensing signal on a power line from high side

texts:
I have a circuit design as above. I'm trying to sense the voltage difference accross the \$ 0.1 \Omega \$ resistor. I physically connected the sensory circuit to the low side of the AC line, and saw that it is working alright.

I'm going to make a boxed circuit of this, and I'm going to connect it to the wall outlet with a standard plug, seen as below:

The plug is symmetric. I can accidentally connect it reversed (on the other hand, i don't want to check the polarity every time I'm connecting it to wall outlet). In that case, the sensory circuit is connected to the high side as seen below:

My question is,
What happens if the sensory circuit is connected to the high side? Would a terrible thing happen? Do I need to do any modification on the overall circuit for making it connectable to the high side?

Supose that,
RMS of the AC is 230V.
VCC is 5V, and it is electrically isolated from the AC by a transformer.
All circuit elements are rated to work between -5V to +10V.
The electrical device drains small current (below 10A RMS).

This question is not about personal usage risks. Please focus your answers on the circuit level, about the risk on the circuit elements.


texts: Calculate battery life when using boost converter

texts:
How should I calculate the time taken to drain the battery to below 5 V when using a boost converter to convert DC 18 V to 28 V for a load on 20 mA.

Battery used is 2 x 9 V, 210 mAh.
The converter used is XL6009 DC-DC adjustable step-up boost power converter.


texts: Front-End Selection for digital FM Demodulator

texts:
Assume that I want to determine the specifications of an analog front-end to build a digital FM demodulator to listen to radio broadcast stations, how would I start?

The broadcast frequencies of interest are im the range of let's say 80 to 110 MHz.How would I start to derive the needed sampling frequency and the number of ADC bits if I would go with an Direct Downconversion Concept?

(I think, additional specifications or assumptions have to be made such as target SNR and the topology of the used digital FM Demodulator but i don't know where to start)


texts: Switch that resets to 'on' after power loss

texts:
amateur Jack of all trades looking for something I'm not sure exists.

I have a mains lighting ring which means I can plug in lamps in my bedroom and turn them on at the door switch (if the lamps themselves are on).

What I would like is to be able to switch the lamps on from the doorway, off from the lamp itself, then on from the wall again (without turning the lamp back on).

I.e. go to bedroom turn the lamps on on entering the room, go to bed and turn the lamps off from bed and then the next night turn the lamps on on entering the room without having to go to the lamps themselves.

I was thinking about some sort of switch that would turn itself on when the power was lost from the wall switch so that I could flick the wall switch off and then on an again and the lamps should come back on.

The lamps should also be able to be turned off and on again overnight as needed from the lamp switches.

I don't want (nor have the skills) to run wires through the walls etc and so was hoping to do it all through a switch I could wire into the lamp wire

Thanks for any suggestions.


texts:
Could anyone explain why I may see cross-over distortion in my output signal of this op-amp circuit?

The input is a 1Vpp sine wave at a frequency of 10kHz, with no DC offset. I am definitely seeing that it is happening, but I'm unsure how I could have predicted it.


texts: Can't seem to write to the status register of nRFL2401+

texts:
So I've been playing around with nRF2401+ radio module lately but been having a few issues. One of them (which could be the cause of the second one) is not being able to properly set the Status register.
So the default value of the status register reads 0xE as shown below. Now In the initialization, I need to clear the IRQ bits by writing 1 so it reads 0x7E but it doesn't seem to change at all.

Below is the attached capture from the logic analyzer. Note that 0x07 refers to the address of Status register.  0x0 refers to read operation while 0x2 refers to write. You can see the last line is where i'm reading the status register and it reads 0x0E instead of 0x7E which I wrote.


texts: How does a "standard" ripple carry adder behave?

texts:
I came across the following problem:

  A half adder is implemented with XOR and AND gates. A full adder is implemented with  two half adders and one OR gate. The propagation delay of an XOR gate is twice that of an AND/OR gate. The propagation delay of an AND/OR gate is 1.2 microseconds. A 4-bit-ripple-carry binary adder is implemented by using four full adders. The total propagation time of this 4-bit binary adder in microseconds is ______.

How does the ripple adder work? I can guess two approaches / interpretations of the internal workings of "standard" ripple adder as explained below:

Interpretation or approach 1: First Half Adders of each full adders compute immediately without requiring to wait for carry from previous full adder becomes available

Delay for first full adder:

For sum: 4.8 μs
For carry: 4.8 μs

As can be seen in below diagram:

The carry of first full adder adder becomes input carry Cin for 2nd full adder. This carry is input for 2nd half adder of the 2nd full adder. Hence 1st half adder of full adder does not need to wait for anything.
This is the case with 1st half adder of all full adders. They all can generate their respective output at the end of time t=2.4μs.
2nd Half adders of each full adders needs to wait till carry from previous full adder become available.
Hence total delay = 4.8 + 2.4 + 2.4 + 2.4 = 12 μs

Interpretation or approach 2: Full adders (even 1st Half adder in the full adder) remains deactivated until carry from previous Full adder becomes available

In this case the delay will be simply 4 * 4.8 = 19.2 μs

Question

My question is "how does a standard ripple carry adder behave?" Does each full adder remains deactivated until carry from previous full adder becomes available or only 2nd half adders of each full adder needs to wait until carry from previous full adder becomes available?
Wikipedia gives following animation which suggests approach 2:


texts: High Side Switching Inductive Load with MOSFET

texts:
I am attempting to make a PCB that high-side switches an inductive load (water pump) that draws 4.6A peak. The switching scheme will not include any PWM, just basic on/off functionality.

My concern is clamping the voltage spikes from the load during turn-off. I want to avoid going into avalanche mode on the MOSFET to ensure maximum reliability as the board will be operating in temperatures of 80-90 C ambient.

The MOSFET I am considering is here and I am looking at this gate driver.

My current circuit idea is shown below:

simulate this circuit – Schematic created using CircuitLab

D2 will conduct below the maximum Vds of the MOSFET, during switch off of the load where the source voltage will go negative.

I am less confident in the behavior of D1. My intention with D1 is to conduct during shut off of the load, so that Vgs does not exceed the maximum allowable. My uncertainty stems from the gate driver - how will it behave in this scenario?


texts: Whose power reduction is better. Clock gating or Data enable?

texts:
I am comparing Clock Gating (ECG) and Data enable methods in term of power reduction. Both can save power.
But which one is better?
I tried these 2 methods in a small design ( a d flipflop ) to a larger one (8-bit data register) and measured their power dissipation. The results always show that Data enable consumes less power than Clock Gating.
Then why is Clock Gating used so often for power reduction? Is there any cases when Clock Gating consumes more power than Data enable ?


texts:
I'm working on building a seismometer using this geophone.  I found a filtering and amplifying circuit as shown below:

More readable schematic here

Currently, I'm failing pretty hard at analyzing the circuit (really, really embarrassing considering I went to school for EE).  There are some parts of the circuit where I am absolutely stumped.

The first thing I'm curious about is the "feed forward" circuit with C9 connected to R11.  Why would there be a connection like this?  Actually, I'm really confused as to why the feedback network in opamp 2 is the way it is (with that line of resistors and capacitor)
I'm not sure why the 2.2M resistor, R7 is there.  I took this out of the circuit and found that there wasn't any effect to the circuit operation.  I'm thinking that resistor is there for stability but stability for what?
Normally I would assume that the other lead for the geophone would be connected to ground but it instead connected to the 2.5 V line.  I'm confused to why this is and I feel like it's a really obvious thing.
I want to confirm that because the op amps have a single supply, 2.5 V is applied to the noninverting input of opamp 1 (and inverting input of opamp 2) to provide a bias.

That's all the questions I have.  The analysis seems really trivial and admittedly, I'm really just starting out in electronics.  I've got to start reading the Horowitz-Hill book pronto!

Thanks for your help.


texts: Is it possible to take a picture from a paper with infrared image sensor without lighting?

texts:
I'm going to make a device which will take a picture from a paper which contains a line of English characters and then process the picture with OCR to get some information in micro-controller. My idea is to make a dark enclosure consist of a  an image sensor inside it and a glass on top like a scanner but very simple. I have done it before with a generic camera (genius facecam x1000) and lighting with some led arrays and then connected to PC.

Now i need to make it an industrial product for special uses. I need my device to be as simple and compact as possible and I need to omit extra costs from this design. as i don't have any experience in optic i have some questions:

Is a B/W IR CMOS suitable to do such a design?
If i use some of these image sensor modules like this link, are the infrared LEDs on the board enough to make a qualified picture to be processed by OCR?
If I am totally going in wrong way, what is the best choice that will do my job with lowest price and is industrial? what kind of lighting is needed?
If I use an image CMOS sensor, is any lens or special prism needed?

I just need a normal quality image of the paper and the ease of communicating with the sensor is an important factor to me.


texts: What to check for hissing noise in a LCD monitor and how to reduce it?

texts:
I have a Dell LCD (LED backlight) without speakers which produces an audible "hiss" when connected the HDMI input. DisplayPort much less.
I have recorded the following spectra:

monitor off (this is about the minimum the phone can record, so it's not very stable)

monitor on HDMI UHD @30 Hz

The noise starts at about 9 kHz and goes up to 20 kHz.

I tried changing brightness 10% and it didn't help.

I am ready to check the monitor myself (while turned on, I'll be careful with the PSU), but I need to know in advance how to treat whatever component may be producing it.

Which components should I check? I guess that only capacitors, transformers, coils and ferrites can produce such noise.

Can I simply abundantly hot-glue any suspicious component to keep it in place and reduce vibrations?

Edit

I opened it. It sounds like the noise comes from the PSU, but I cannot open it further to check inside it. See photos.

PSU

Or LED driver board

Opening the PSU would destroy it.

However, I measured the voltage at no load or when the monitor was turned on, but only the electronics was powered (no LCD, no inputs, ...). The voltage was 19.8 V. It matches a text on the silkscreen of the main mainboard which refers to "19 V USB 3".

The PSU has only that single output, no feedback or anything. I think I could replace it with an external one providing stable 20 V (my tester in AC mode and 20 V scale gave 0.01 V "true RMS"). I'm not sure about the current rating I would need. If Dell states 120 W maximum, I need a 6 A PSU or better. I guess I can replace the AC socket with a DC barrel socket, which are rated up to 10 A. Laptop power supplies already provide 19.5 V and sometime 7.6 A, however I have no idea whether the output voltage is stable enough for the purpose. There is also a Mean Well 20 V 6A, 180 mV p-p with DC barrel plug.

In any case, I hot glued the inductors I could see, but the effect is limited.

It looks like it's a design fault, people had the issue since the beginning.

Result

I replaced it with an external Mean Well power supply and I replaced the US-style power connector with a socket matching the external power supply.
The hissing completely disappeared. Now I only need to find some velcro to stick the power supply to the vertical column of the monitor stand.


texts: Why does this guide recommend a 500MHz oscilloscope for power supply testing?

texts:
EDN have an interesting (for novices like myself!) guide on testing a power supply's design, in which they suggest a 500MHz oscilloscope as one piece of equipment necessary for "proper" testing:

  The test equipment needed for proper power supply testing varies with
  the type of power system being tested, as well as the financial budget
  for the equipment.  Here is an example list of equipment:

  ...
  Oscilloscope 500 MHz BW or greater with probe for noise measurements.
  ...

It seems a random choice, except that it is among the very highest spec'd oscilloscope I've seen on the market.

Are they trying to say you should go for the best your budget can stretch to, or is there some technical reason why 500MHz is the magic number?

I'm guessing it might be related to typical SMPS frequencies, PCB and other parasitics, and other characteristics of current technologies, or some artifact of the nature of EMC?

Firstly it bothers me it's seemingly been plucked out if thin air. And it's weird that the article seems to be written for informing readers of sub-professional level, yet recommending top-end equipment (totalling a near 6 figure sum).

Can someone make sense of this? If that's too vague a question, then simply, why 500MHz? Maybe it's just the one sitting in front of him.


texts: Understanding relay isolation specifications

texts:
I'm building a board with some relays to switch a bank of HF filters. I want to be sure I'm understanding the isolation I can expect from a given relay so as to not degrade a filter's performance by allowing unselected relays to couple into the output.

Let's say I have this circuit, built of relays with a specified isolation: [full datasheet]

simulate this circuit – Schematic created using CircuitLab

Does the fact that the unselected input sees a short to ground change the isolation I can expect to something more than the 37dB in the datasheet, since the unselected input will be able to deliver very little power into the short? Or does it not matter since there can still be current through the short which can couple the signal inductively across the relay?


texts: why is ground needed to be common in i2c communication?

texts: I'm using i2c  for communication between arduino and SBT-150 thrusters , but the problem is that thrusters use 24V and arduino use 5V. So, i want to somehow isolate the two grounds for protection of my arduino.


texts: Coax cable shielding understanding at AC

texts: I know that AC changes its polarity once a cycle. We use coaxial cable for protecting the signal from magnetic interference. But if the cycle is negative then it it will flow in the shielding, won't it? So unprotected.


texts:
Background

I am trying to estimate the speed of a quadrature encoder with the following equation

v = Δx/Δt

Δx is a 16 bit signed integer and Δt is a 16 bit unsigned integer. |Δx| is guarenteed to be <= Δt so that |v| <= 1.0. Both of these are sampled at a rate of 16MHz.

I desire the output to be in a signed Q8.9 (18 bit) fixed point format in units that differ from those that naturally occur. To achieve this I plan on implementing some form of the following arithmetic.

final_v = ((current_x - old_x) / (current_t - old_t)) * (2^9 * 160)

where the 2^9 promotes the fractional part of the division to Q8.9 format and 160 is the factor I need to get the desired units.

I am implementing this with verilog and Vivado 2016.2 on an Artix-35T FPGA and plan on using Xilinx's Divider Gererator and Multiplier IPs to do the multiplication and division for me and I would like to minimize latency as much as possible (throughput is not as important).

The Question

Would it be prefered to multiply by the constant (2^9 * 160) first and then divide or the other way around or is there a better algorithm I should be using? Are there common pitfalls that I should be aware of?


texts: Is it okay to connect directly power supply to usb 5v? ++ & - - to maintain power?

texts:
I am working on an extention cable for my PC usb hub. It goes about 5m using UTP 5e cable, it sometimes can read the data from usb, sometimes it can't. I figured, it is because of voltage drop. So I am intending to make external power supply for the hub to maintain the 5 V voltage.

Is that okay?
I am afraid about the difference voltage reference 5V ground (-) and (+) between PC and power supply. Can this mess up my PC?


texts: Random number generators using a GPIO pin?

texts:
I just read through question AVR Random Number Generator and encountered a number of ways to generate random seeds in an AVR:

Use a special-purpose "Secure AVR"
Use an internal temperature sensor
Read unwritten EEPROM
Measure time intervals between user input
Use a floating ADC pin.

Why not just a single digital pin, configured as input without pull-up and floating? In theory that should generate a stream of random bits. Why not use this? Is the state too slowly changing? Does it tend to stuck at 1 or 0? Any other problems?


texts: How Broadband Radio Frequency Meters work? Broadband Radio Frequency Meters measure cumulative energy density over a wide range of radio frequency. See this page, this or this.


texts: Connect 8086 cpu to memory chips and io devices in proteus

texts:
I have a project based on simulating operation of 8086 processor with memory and I/O devices using Proteus simulator.

Memory is eight 2K 6116 chips and I/O contains 2 seven-segment displays and a 4x3 keypad beside the address flip flops, logic gates for even and odd addresses and transceivers.

Also, I am interfacing memory using 74138 decoder and interfacing I/O with 8255.

The problem is that, during simulation, no value comes on address/data bus of processor, Meaning that control ports of 8086 have the values required as told in assembly code but every 20 bit address (16 bit address/data and 4 bit address A16..A19) take high Z value.

Is there anything wrong with internal memory start address (which is set to 0x00000) or assembly code?

.MODEL SMALL
.STACK 64
.DATA
    PORT_A EQU 60H;
    PORT_B EQU 62H;
    PORT_C EQU 64H;
    PORT_CON EQU 66H;

.CODE

MAIN    PROC
        MOV AX, @DATA;
        MOV DS, AX;

        ;Write arbitary values to memory
        ;RAM1
        MOV AL, 8H;
        MOV BX, 14000H;
        MOV [BX], AL;

        ;RAM2
        MOV AL, 7H;
        MOV BX, 14800H;
        MOV [BX], AL;

        ;RAM3
        MOV AL, 6H;
        MOV BX, 15000H;
        MOV [BX], AL;

        ;RAM4
        MOV AL, 5H;
        MOV BX, 15800H;
        MOV [BX], AL;

        ;RAM5
        MOV AL, 4H;
        MOV BX, 16000H;
        MOV [BX], AL;

        ;RAM6
        MOV AL, 3H;
        MOV BX, 16800H;
        MOV [BX], AL;

        ;RAM7
        MOV AL, 2H;
        MOV BX, 17000H;
        MOV [BX], AL;

        ;RAM8
        MOV AL, 1H;
        MOV BX, 17800H;
        MOV [BX], AL;

        ;Load control word
        MOV AL, 92H; (selection)(mode 0)(port A input)(port B input)(port C output);
        OUT PORT_CON, AL;

PROG:
        ;Interpret keypad
        IN AL, [PORT_A];
COL:    CMP AL, 2H;
        JNZ C1;
        MOV BX, 2H;
        JMP ROW;
C1:     JG C2;
        MOV BX, 3H;
        JMP ROW;
C2:     MOV BX, 1H;

ROW:    IN AL, [PORT_B];
        CMP AL, 2H;
        JNZ R1;
        MOV CX, 1H;
        JMP CALC;
R1:     JG R2;
        MOV CX, 2H;
        JMP CALC;
R2:     MOV CX, 0H;

CALC:   CMP CX, 0H;
        JZ ENDKEY;
        ADD BX, 3H;
        SUB CX, 1H;
        JMP CALC;

        ;Calculate multiply
ENDKEY: MOV DX, [BX];
        MOV AL, BL;
        MUL DL;

        ;Display output
        OUT PORT_C, AL;
        JMP PROG;

        MOV AH, 4CH;
        INT 21H;
MAIN    ENDP
        END MAIN
```


texts: Electronic sensor of some kind but what?

texts:
I purchased a house and I found two sensors which I have no idea what they are for.  It is simply a tube that fits into another tube.  The inner tube has batteries and you can slide it out.  Anyone know what this sensor is what is it for?  Thanks in advance to solve his puzzle.

After digging it out, it appears that it is indeed a mole wacker.


texts: Tools for simulating software-driven PWM

texts:
I want to simulate a software driven PWM. So, I need to program the controller output based on the transient/instantaneous feedback from some part of the circuit in the simulation (i.e. the software logic must run as part of the simulation).

In other words, I basically want to have as simulation input an arbitrary function of the circuit properties itself.

For instance, imagine a PIC controlling a MOSFET, and the output from PIC depends on its analog input from some other part of the circuit. What tools can I use to simulate such circuit? I don't want to simulate the PIC itself, I just want some way to control some digital input signal depending on the instantaneous properties of the simulated circuit.


texts:
I am trying to make a simple CMOS NOT gate using Tanner. I have made schematic using S-Edit. On simulation, A error is being thrown.

Fatal Error : Missing MOSFET model definition for "NMOS"
Fatal Error : Missing MOSFET model definition for "PMOS"

After some research I found that some model is required. I tried generic_025.lib. But on simulation a new error is being thrown.

Fatal Error : "Generic_025.lib" line 27 Misplaced .ENDL

So, first of all I doubt about .lib file. I think it should be .md file. If it is like that than from where can I download this .md file?

If .lib file is correct than what is error in that file?

Thank you for your help.

This is code of my NOT Gate.

.include "C:/Tanner EDA/Libraries/Generic_025.lib"

*-------- Devices: SPICE.ORDER > 0 --------
MNMOS_1 N_1 N_2 Gnd Gnd NMOS W=2.5u L=250n AS=2.25p PS=6.8u AD=2.25p PD=6.8u
MPMOS_1 N_1 N_2 Vdd Vdd PMOS W=2.5u L=250n AS=2.25p PS=6.8u AD=2.25p PD=6.8u
VVoltageSource_1 N_2 Gnd DC 5

********* Simulation Settings - Analysis section *********
.dc lin VVoltageSource_1 0 5 100m

********* Simulation Settings - Additional SPICE commands *********

.end

And this is the link for Generic_025.lib I used.


texts: Is it possible to get an exponential capacitance curve from coded dip switch

texts:
I have a capacitor that controls frequency for a specialty IC with the relationship

\$F \propto 1/C\$

I want to be able to get a number of frequencies in evenly spaced intervals. Currently I have a string of series capacitors some of which I short out with regular dip switches in a binary code to give 16 steps.

simulate this circuit – Schematic created using CircuitLab

This works as adding capacitors in series follows the relationship below giving linear steps.

\$ F \propto \frac{1}{C} = \frac{1}{C} + \frac{1}{2C} + \frac{1}{4C} +\frac{1}{8C} \$

To make it more intuitive to set the frequency for people who are not used to binary code I would like to use a coded rotary dip switch such as this

This means the switches are not all separate and have a common pin.

simulate this circuit

Because of this the relationship is exponential and it is not possible to get even steps based on this circuit

\$ F \propto \frac{1}{C} = \frac{1}{C + 2C + 3C+ 4C}\$

TLDR

Is there a simple way to get evenly spaced frequency steps using a coded rotary dip switch, without needing too many more components.


texts: How to connect dual 5-pin GS232 to a single 8-pin G-5500 Rotator

texts:
I have a Yaesu GS232 computer interface which has two 5-pin slots, one for elevation and one for azimuth. This is supposed to be connected to a Yaesu G5500 Rotator which has a 8 pin DIN slot. Supplied with the G5500 was one 5-pin --> MinDIN which controls azimuth.
It's not clear to me why a secondary cable to control elevation is not supplied as standard with this rotator.
Images of the connectors and the pin outs are shown below:

I am not entirely sure how I would go about making a cable that would connect these two parts and there is not one readily available to buy, please correct me if I am mistaken, does anyone have any ideas on how to go from the 2 x 5-pins to a single 8-pin, so does anyone have any suggestions?


texts: Calculating correct resistor for an optocoupler

texts:
I need to convert 12v inputs to a 3.3v electric imp005, i have a bunch of TLP521 optocouplers i bought to repair something (i've never used one in a circuit before).

From the data sheet it looks like the recommended forward current for the LED is 16ma at 1.15v so i think i need a 680 ohm resistor to power it from 12v

as for the detector resistor, is this just a pull up to stop the output floating?

does this seem right?

Thanks guys and sorry for the noob question.

Dean.


texts: Why does an ISFET need a reference electrode?

texts:
I'm trying to understand why an ISFET needs a reference electrode. I have looked up several answers online but still dont understand.
I have drawn out the doping, a MOSFET and the ISFET:

In my mind, a change in pH changed the H concentration around the sensing pad which changed the properties of the channel?


texts:
A satellite dish with LNB connected to a satellite detector when powered by a 18v source could detect radio waves from satellites. I made one using the ppt here.
The detector, (when it was not connected to the LNB) detected the radio frequencies from my mobile, but as soon as the LNB was connected the detector did not respond to the mobile phone even in proximity.why?

To convert the analog output to digital should i use a bias tee injector near the 18 v source? Would a 1000 micro henry RF choke suffice?


texts:
I'm a developer of control devices for switch mode power supplies which need to generate a PWM signal(s) with a frequencies about 100 kHz, measure analog signals, communicate vie USART, make relatively simple calculations and so on. It is also important to start up fast and react very fast on some events like external interrupts (often within a fraction of microsecond).

Now I'm using Atmel Studio with GNU C compiler.

I'd like to go from 8 bit AVRs to ARMs. The main reasons are (hopefully): faster, more flexible, more powerful calculations, better community support.

I'd really want a short learning curve and fast development cycle.

I decided to use ARM Cortex-M0 and M3 processors.

Will I be able to use operation system on ARM?

The reasons why I think it could be useful in my case - faster learning curve and development time. But I have some doubts that I will be able to run application within several milliseconds after supply voltage will be applied and that I will be able to interact with ARM peripherals (like timers).

So do I need an OS in my case?


texts: Should mounting holes have solder bumps?

texts:
There are many discussions on if mounting holes should be plated or if they should include vias. This is not asking about those issues.

I've seen suggestions to add solder to the annular ring on the mounting holes. This, possibly in conjunction with serrated screw heads, was suggested as a way to lock the screws. I've also seen such solder bumps on some computer motherboards.

Is this actually known to help? What does it help with specifically? Can it hurt? Should it only be on the screw head side?

I can imagine a couple places where this is not wanted; like if you care about accurate dimensions of the holes for mounting heatsinks.

Assuming it is desired, what is the optimal solder pattern? A bunch of bumps around the hole? Or a thin flat solder layer like you'd get with HASL finish?

Also, do different PCB copper finishes/platings change this at all?


texts:
I've just bought 10m of 220VAC LED Strip yesterday just to found out that it flicker so bad on mains. My country is using the 220V 50Hz as their mains.
Anyone can help me on a way to reduce the flicker? What I'm thinking is adding a 0.47uF 400V caps before the LED.. Is it a good idea? Or are there any way to lessen the effect of flicker? I don't need it to be completely gone (as it is pretty much impossible)

I don't want to throw this strip and buy 12v or 24v ones because I've already bought 10m of em and the store doesn't have a return policy.

EDIT: Since many people asked for a schematics.. I don't have any, but I forgot to say that it is indeed an SMD 5050 LED, will try to find any schematics for that. And here's a pic to it http://imgur.com/16Yg96a
For anyone who's wondering what is written on the R, it is 391. Sorry for my camera.


texts:
Basic and stupid question, however it bugs people and creates misunderstanding.

I frequently see the following labeling of 3 wires in the cable

wire 1: "+24 V"
wire 2: "-24 V"
wire 3: "ground" or ground electrical symbol (without circle around it).

When I ask people what is the supply voltage, they say: 24V. When I tell them that according to their labeling it must be 48V with central ground. None still have shown me wire 3 being marked "PE" (then it will be clear that it is not a signal ground, and things are not that they appear to be).

Thus what is the correct way to label 3-wire cable so that everyone understands immediately that power voltage is 24VDC?

I think it must be GND, +24V and PE. Is it correct or there're any other ways? What if power supply must be isolated? If power is AC?


texts:
First of all, let me preface this with the fact that I'm not an EE -- I'm a hobbyist with some experience and a background in software development.

I'm trying to use a TI PCM5102A Audio DAC with a Sierra Wireless BC127 Bluetooth module to output line level audio into an in-car amplifier. Anyways, the I2S link is operational and I'm getting audio from the DSP in the BT module to the DAC, but the gain is through the roof -- so much so that I had to add a pair of 10k resistors just to be able to listen to it via a pair of earbuds. I also tried it directly on the amp, and it was heavily distorted. I have issued the appropriate commands to the BC127 to set the gain as low as it can go (VOLUME <A2DP Link ID> 1) and there was no change.

My questions are:

It feels like I'm missing something about how DSPs and DACs operate -- am I? Is there just an IC I need to add to tone down the audio?
Is there a more suitable DAC for what I'm trying to accomplish?
The BC127 has differential outputs that are suitable to drive a small speaker. Is there an IC I can use to convert the differential output to single ended line level?

Thanks!


texts: I can compile digital components and download them to the boards DE2 and DE2-115 I got. I do it from Windows 7 but I want to enable this on ubuntu while the files from Altera are for Red Hat Linux. I've seen in the Altera forum that there're success installing it on 64-bit Ubuntu which I want to try. Should I try or wait for an official version? Will there be an official version for Ubuntu and not only Red Hat?


texts: Three capacitors in a loop and dependence?

texts:
I was watching a lecture on State Variables on YouTube here

The professor mentioned that "if three capacitors form a loop, the three cannot be independently specified. Only two can be done as the third becomes dependent on the other two". I was wondering how the two capacitors and can independent and the third dependent?

Thanks!


texts:
This is what I read from a text:

  The T1 system is used for wireline long-distance service in North America and is an excellent example of TDM. Speech from a telephone conversation is sampled once every 125 msec and each sample is converted into eight bits of digital data. Using this technique, a transmission speed of 64,000 bits/sec is required to transmit the speech.

If a signal is sampled every 125 msecs and it is converted to 8 bits of data, isn't it equal to total of 64 bits of sampled data per sec? Where does factor of 1000 come from?


texts: Modifying a chip on a bought voltage measurer

texts:
I have bought a battery checker for my RC LiPo battery packs. The battery checker can measure and alarm at low voltages between 2.7 and 3.8 volts, however with LiPo batteries, the interesting range is between 3.7 and 3.8 volts and I was wondering if it was possible to accommodate this range instead?

In the circuitry there is an Atmel 1206 24C02N chip. I found the datasheet for the chip here and it seems like the chip is the one that holds the voltage levels in it's memory (am I right?). I was wondering if it was possible to read and alter the chips memory through Arduino or something similar. I have an FTDI connector like this one that I normally connect with my Arduino nano. Can I use this one to communicate with the chip?

Here is an image of the back of the voltage checker. On the front there are two buzzers, a 3 segment LED display and in the top you can see the button that changes the voltage level at which the alarm should trigger.


texts: Powering Multiple loads from a single 12v battery

texts:
I have built a 12v rover - designed to be fully autonomous with a 12v deep cell marine battery as its only power source.

It uses the following components:

1. [Raspberry Pi3 through a power converter][1]
2. [Sainsmart 16 Channel Relay Board connected to the PI to control motors.][1]
3. [LED Monitor (Draws 2A at 12V)][1]
4. Four 60 Watt Hobby Motors

It works great. I can write the code and drive it around the yard.

However - when the motors are engaged, the LED Monitor shuts off and comes back on again - as if it lost power. The PI seems to be unaffected and everything works fine - except for the momentary rebooting of the monitor.

A voltage meter shows 12.5 at the battery - drops to 11.9 when the motors are engaged, and stays at 11.9 until the motors stop and then goes back to 12.5.

My guess is that when the motors are engaged, it draws a large amount of current, more than the battery can provide, and causes the monitor to reboot. My guess is that this is not good for the components long term.

My question is - can I somehow isolate the motors from the circuit, even though they use the same power supply - so that the momentary start-up draw does not affect the rest of the components? What is the proper way to wire such a circuit?


texts: Calculating the distance between 2 stations in a transfer

texts:
Station A sends \$1024 \times 10^{6}\$ bits of data to station B over a 1Gbps wired link. Station A sends the data in packets of \$8 \times 10^6\$ bits. The whole transfer took 100 seconds to complete. If the signal speed is \$2 \times 10^8 m/s\$, how can I find the distance between the two stations? I'm also assuming all waiting, queueing and processing time are negligible.

Since each packet is \$8 \times 10^6\$ bits, total number of packets sent is \$ \frac{1024} {8}=128\$ packets.

As the wired link has a capacity of 1Gbps, it feels like I could just send the whole file of \$1024 \times 10^{6}\$ bits of data from station A to station B in less than 1 second, wouldn't it?

How does the transfer take 100 seconds and how can I calculate the distance between the 2 stations based on the signal speed?

Update:

The other information provided to this problem were the server and client are directly connected with no processing and queueing delay. Although Station A waits for an acknowledgement packet from station B after sending a packet of data and before sending the next packet of data, the acknowledgement packet sizes are small and so its transmission times are negligible. The packet headers' overhead bits are small and also negligible.

It seems that everything is negligible and I have no other numbers to use to consider.


texts:
We are using a Nema 34 stepper motor driving it using Leadshine M542 driver and arduino UNO.
24 V voltage and 4.2 A peak current being given.
Our motor lifts a metal frame for about a minute (it has to rotate about 1minute) and needs to hold it the 4-5 hours at fixed position.
Now it draws the same current when its running( lifting) and while its holding which makes it a continuously current drawing motor and becomes heated extremely as time goes.
Kindly suggest me a solution.


texts: Finding equivalent capacitance and resistance from DC circuit with combinations of R and C

texts:
In order to get the simplest RC circuit and get equivalent circuit tau:

How can be its transient studied if before t = 0 there only exists one resistive part of circuit? I's obvious that before t = 0 we got 12V at S node. Because it 's open circuit. When switch is on, it connects the followed switch impedance to RL.

Provider gives me this schem:

Reading this, I deduced that circuit adds the capacitance as seen at pict. But, when off, S will be an open circuit. No current. No impedance effects at S node.

Here is more information and wave forms:

"BorneX" are connector input pins driven to switch Sx or Dx. There almost 64 input pins to be connected on CH_A signal and CH_B.
You can see how “Borne X” goes until CH_A signal switch and it also goes until CH_B switch. But when CH_A switch is on, their CH_B switch must be OFF.Antoher important data to be known is that CH_B is M node signal, and CH_A is GND signal.

So, I think it will be the effects of switch off added to the switch on equivalent circuit. But despite this situation, we can tolerate the resulting transient at M node when starting executing our process 1, again and again.

The process consists in (we call process 1):

switching on the “a” group of input pins “BorneX” to CH_A signal
switching on the “b” group of input pins (the rest of input pins)
“BorneX” to CH_B signal.
wait a delay for stablization
get/look at M node voltage level
“a” inputs group – CH_A -> switch off
“b” inputs group – CH_B -> switch off

A larger RC becomes if we just do process 2 sequence after process sequence shown before:

switching on the “b” input pins group “BorneX” to CH_A signal.
switching on the “a” input pins group (the rest of input pins) “BorneX” to CH_B signal.
wait a delay for stablization
get/look at M node voltage level
“b” – CH_A -> switch off
“a” – CH_B -> switch off

Wave forms: blue one is the voltage from b node to GND; yellow one is the voltage from M node to GND.

First process 2 execution after a previous channels inverting (process 1 followed by process 2):

Second process 2 execution (so, no previous channels inverting: process 2 followed by process 2):

Third or more process 2 execution (so, no previous channels inverting: idem):

After three times running process 2 or 3 times running process 1, I’ts possible to apreciate that RCs are decreased, even disappear, so equivalent C has been completely discharged. But after this, if channels will be inverted again, 1, 2 and 3 pattern will also appear.

It can also be noticed that during commutation blue signal and yellow have no differences. This makes me think that Ron and CDS are mostly trivials. Maybe I’m wrong.

So, despite RON and CSDon, seeing the waveforms I think it could be reduced to:

Between process 1 and process 2, 4 involved switches will be off:

It can be seen a short discharge RC transient, followed by a large RC charging transient Vout on my screen up to almost 12V, when measuring VB - GND and VM - GND.
After a previous channels inverting: process 1 seems to let a charged capacitance that discharge and charge when execute process 2.
The transient only appears the first time you switch. The second time, RC decreases, third time RC almost disappears. So, which Capacitor is keeping its charge after switch off the first time? Any suggestions about where this capacitance could be, what is the cause or how to find it?

I'm not looking for detailed calculations, neither explicit expressions. I Only looks for spected VB0 voltage evolution wave form. But if values are needed to get perspective of degrees of influences of elements, I let some details: Ron is little comparing with RL (12000 vs 50 Ohm). CD about 16pF and CDS = 3pF.


texts: Select bootstrap capacitor value too high

texts: What happen if we choose bootstrap capacitor value too high in high side gate driver applications? Can it be harmful for MOSFET/IGBT or it is just not important?


texts:
I have built a micro fridge to store a breadmaking sourdough starter at 9-10C. The cold compartment is 10x10x10cm, so size is 1 litre with removable lid. Insulation is 50mm polyiso foam all round. Cold side heatsink is a 10x10cm plate of 3mm anodised aluminium. There is a small 12v turbo fan in the cold chamber to assist with temperature uniformity.

The hot side heatsink is an aluminium finned extrusion with a 3.5" 12v fan bolted to it. The 12706 peltier is mounted behind the hot heatsink and then I have a piece of square aluminium bar 1.5 inch square and length 47mm that connects to the cold heatsink. I had to think long and hard about this spacer as most designs don't really explain how to maintain a good insulation thickness between the cold and hot sides.

Temperature control is via a thermistor probe in the cold compartment feeding an LAE on/off fridge controller.

Currently the peltier and both fans are all running off a 5 volt supply.

Everything is working OK but I am rather disappointed with the projected power consumption of the set up. I have just measured the electrical energy used over a 24hr period and I reckon this will equate to 60kWh per annum. Not a lot, I know, but if I compare my micro fridge to a Russel Hobbs 17l mini fridge, it only uses 82kWh pa for 17l and a more challenging temperature differential - presumably 25C/4C vs my current 18C/10C.

So (finally!) my question: why is the performance of my micro fridge so much worse? And what can I do to improve it?

The area I am looking at is what I will call "back conduction": when the cooler is not running, cold must be leaking back  from the cold compartment via my ali block to the peltier and then through the peltier which is only a few mm thick to the hotside heatsink.

Surely this must be a major problem with all peltier systems; what can be done to minimise it? I am thinking that perhaps both heatsinks should be small so there isn't a lot of heat transfer without the fans running. And perhaps the hot side heatsink should be inside a totally enclosed insulated housing with the fan blowing in via a duct?

Any thoughts?

Lance


texts: Voltage between collector and emitter (in transistor circuit) [2N3904]

texts:
Let's say we have the following circuit with silicon transistor 2N3904 (the transistor has \$\beta = 125\$):

I am trying to calculate the DC voltage between the collector and the emitter.
One of the solutions I found is the following:

$$Ι_b = \frac{V_{bb} - V_{be}}{R_b} = \frac{10\text{V} - 0.7\text{V}}{1.5\text{M}\Omega} = 6.2\mu \text{Α}$$
$$I_c  = \beta \times I_b = 125 \times 6.2\mu \text{Α} = 0.775\text{mA}$$
$$V_{ce} = V_{cc} - I_c \times R_c = 20\text{V} - 0.775\text{mA} \times 5\text{k}\Omega = 16.1\text{V}$$

This solution is not mine and I am not sure that it's correct. I have two questions:

\$Ι_b = \dfrac{V_{bb} - V_{be}}{R_b}\$. Is this true? Shouldn't it be \$Ι_b = \dfrac{V_{bb} - V_b}{R_b}\$?
\$V_{ce} = V_{cc} - I_c \times R_c\$. Is this true? Shouldn't it be \$V_c = V_{cc} - I_c \times R_c\$?


texts: Improving L297 based Unipolar stepper driver

texts:
There 7408 is used to drive Mosfets (I have IRFZ44n instead of TIP122). Its input is limited to 5.25V (not so much high volt to drive mosfets).

I want to provide higher volt pulse to Mosfet-Gate to make Mosfets turn-on fully. Is it really better idea to do this?

So I want to use L293 instead of 7408. Is it suitable to use.

Is it better to use co-amplifier (single-741, Dual-LM833, Quad-LM3900) instead of 7408?

OR is there any other better option.


texts: using an electret microphone to trigger an LED

texts:
I would simply like to trigger (on or off) an LED based on the pressure level at an electret microphone, much like a stroboscope. The circuit should be

as simple as possible (in terms of number of components) and
work also at low sound levels

After some research, I found a neat circuit scheme from a youtube video. I built it and it worked fine, however it is not sensitive enough.

Now I simulated this circuit in LTSpice and tried to vary a few resistors to see whether I can tune the sensitivity. While increasing the Megaohm resistor makes the thing more sensitive, it also reduces the dynamic range for the diodes.

Since I am a beginner: what would be a nice way to improve said design, such that it works at low noise levels? At best, it would feature a potentiometer to tune the sensitivity...


texts: Is it OK to route a trace through a pad?

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Will I have any trouble routing the traces in this way? (VCC and GND)

Is it OK considering that the entire circuit current is under 50mA?


texts: I require a more comprehensive explanation of the function of zener diodes

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I would first like to establish that I am simply the most basic of beginners in the realm of electrical engineering, and that complex terminology will only cause me to ask more questions.

A circuit diagram was shown in the electrical engineering workbook I acquired to teach myself electronic theory, showing a circuit similar to this one.

The workbook very briefly explained (in an uncomprehensible manner) that the zener diode caused the output voltage to be constant assuming the input voltage is within a certain range. Could an answer please provide some sort of either a literal explanation of what is happening to the electrons that make up the current or an analogy that will help me to understand? To me it seems that the zener diode will simpy deplete the voltage by a constant level if the input voltage exceeds the breakdown voltage instead of maintaining Vout at a constant level.


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I've been looking around for a good CCS schematic, and decided to try making a simpler one even if it means it'll behave worse. I need a 12V (would come from an ATX power supply, more than enough current from the 12V rail) circuit that can handle at least up to 1A on the load (2/3A would be ideal). Would be for general purpose, electronics testing/etc, nothing too serious or in need of high precision. Made this in a simulator, and it seems to work:

The load is represented as a pot to make things easier.

The NPN transistor is a TIP35A, power NPN. Will have a decent heatsink and a cooler pointing in its general direction.

The PNP would be a general purpose transistor, and the adjustment pot would have calculated resistors in each side to limit its throw, of course. (depending on the resulting hFE of the "darlington pair")

My question is: Am I missing something important here? I would add an LM317 as a current limit (or a high-watt resistor on the circuit at least). Would this supply vary too much with resistance changes? (It had no change on the sim, but again this app is no LTspice). I have all the components so I plan on breadboarding it to test it with low currents, but I want to be sure this can work...

One more thing: I have a (totally overkill) ST P40NF0 3L MOSFET which I guess I could use (by replacing the driver NPN with a PNP and the power PNP with this MOSFET, and connecting the PNP differently of course). This FET has a very low on resistance which I guess would make my supply more efficient. Would this be correct?


texts: correct wiring of a preamplifier and a lock-in amplifier

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I've got a question regarding the correct wiring.

I'm operating a vibrating sample magnetometer. It uses two coils to detect the magnetisation via induction. The two signals are amplified and mixed together in a preamplifier. Finally, a lockin is used to detect the signal.

The preamplifier output uses uses a 6 pin socket with the following pin allocation.

Pin Name
1   0/P
2   0/P GND
3   GND
4   -20V
5   +20V

The SR830 lock-in amplifier has two BNC sockets which can be used as a differential input. Also it has the option to float or ground the BNC shield. Additionally it has a D-sub preamp connector.

Pin Name
1   +20V
6   -20V
7   S GND
8   GND

Since everything has different connections, I was thinking of making a box with a 6 pin input connector two bnc outputs and a D Sub output.

Since I'm not an electric engineer, the ground connections confuse me and were the shields should be connected.


texts: How do I calculate how long it will take for a capacitor to discharge when shorted?

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If I know the capacitance, series resistance, and the voltage it is charged to. I tried using a graph y=x/0.003
Where y is current and x is voltage, but now i'm lost, because I don't know where to put the capacitance. And then I wouldn't know how to get time.


texts: How do I find the firing angle of SCR practically?

texts: Our teacher told us to find out the time period and then multiply it by 18.Then 180-(∆t*18) gives firing angle.Why 18 as a multiplier?


texts: Cannot establish communication through RS232 to a digital scale

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I am an electrical engineering senior student and I think I tried everything. Here is the case: (no i am not using the USB to RS232 convertors)

I bought a digital scale that can send the weight serially to a machine. When you request the data by sending W (57 in hex) the scale sends back the weight. As I always do, I try to narrow down the culprits so I tried the following:

1) I created an RS232 connector using MAX232 and a raspberry pi and was able to send through Minicom (like putty) a W and receive a weight value.

2) I used the same circuit to connect the Raspberry Pi to my Windows machine and successfully communicated back and forth with Putty.

Simple right? I mean UART, it should be.

So the cable is fine, the scale works as advertised, putty on windows works, the the ports on the windows machine work; however, the Windows machine and the scale refuse to communicate. Which means that the W is not reaching the scale because I am not getting back anything, not even junk.

3) I also tried steps 1 and 2 with a virtual machine running win 7 instead of Win 10, and even tried a usb to rs232 cable that I know is functional...works with rpi but not with the scale.

I have only one last explanation. In my building we do not have Grounding in the plugs. All appliances work fine, but they will give you a neat zap if you touch them bare foot. What this has to do with the problem is that I think the (rpi+max232+DC power supply) system is well grounded while the PC (not grounded) to scale (not grounded) system is suffering from a noise issue. Can this be the case? Do you have any other suggestions that I could try? (I called my grandma asking for some holy water) Thank you in advance.


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I have a requirement in which I want to track 10+ robots in a field (or hanger), the robots are small.

My first thought would be to use a drone to act as a collector, monitoring the position of each robot, but what should I use to track and measure positions. I need to know where each robot is down to a 1 inch accuracy.

Alternatively could I use some kind of 10 DOF device on each robot to calculate it's actual position from a starting point?

I could also have some kind of post system to act as beacons - but no more than 6-8 in a 80m x 20m area.

Be grateful for any pointers.

thanks