texts: Using two bluetooth profiles at the same time to make a wireless keyboard

texts:
I'm trying to build a wireless, two part keyboard using bluetooth and arduino. Imagine a normal wireless keyboard but split it in two with the numeric keys on the right placed on a separate unit. Then connect it like a normal bluetooth keyboard to a computer, tablet, phone et.c.

Is it possible to do this with only one bluetooth module in each part? Here is my idea:

The right (numeric) unit has a bluetooth module set to SPP profile that sends custom data (when a numeric key is pressed) to the left unit. The left units bluetooth module somehow switches between a SPP and HDI profile and looks like a bluetooth keyboard from the view of the computer/tablet/phone. Is this possible?

If no then I guess I will need 3 bluetooth modules; two in the left side with one using SPP and the other using HDI. However according to one answer here on stackexchange that is also impossible: How can I create a serial bridge using two Bluetooth dongles?

"It is not possible for two Bluetooth devices, with the serial port profile (SPP), to pair with each other. They can only pair to a host."

Is this true? In that case I guess I will have to use 1 bluetooth module (probably this one: https://www.sparkfun.com/products/11601) and 2 Xbee modules?

Are there any other ways to solve my problem?


texts: matching impedance and maximize the speaker’s output

texts:
If I have a signal generator with 600 ohm output resistance and a 8 ohm speaker.
The number of turns in primary coil is 50, so the turn ratio should be
$$\frac{600}{8}=(\frac{N_2}{50})^2 \\N_2=433\\N_1:N_2=50:433$$
Furthermore, will there be any difference on maximizing the power output with applying different frequency output in the signal generator!? such as 1khz vs 5khz.


texts: How to power a GSM Modem from a Li-Po battery?

texts:
I want to integrate an AirPrime SL6087 GSM modem into a design, this is my first try at working with a GSM module. The datasheet states that the modem draws 2A for 1mS every 4mS (max) at 3.6V, the problem is that I intend to run this project from a single Li-Po battery and want to use a buck-boost regulator so I can keep the unit alive for as long as possible (running it down all the way to 3V). The only regulator I can find capable of this is the LTC3113 but there doesn't seem to be stock anywhere. The LTC3112 is also a possibility but it's 2.5A output current is rated at 5V input not down to 3V.

My question is this, there's a lot of small GSM products on the market, how do these go about keeping the power supply stable while running on a single Li-Po battery? I have this nagging feeling that I'm over complicating this...

The complete datasheet for the module is only available after logging in, registration is free however. Here's a quick recap (page 20):

  In connected mode, the RF Power Amplifier current (2.0A peak in GSM/GPRS mode) flows with a ratio of 2/8 of the time (around 1154uS every 4.615mS)


texts:
My major is not electronic, but I really really need the answer of this question:

Compare the MOSFET and LDMOSFET.

Since my major is not electronic, I have searched what is MOSFET and what is LDMOSFET but I didn't know which aspect of them to compare. Could you give me some answer? The answer shouldn't be too long (less than 15 lines). I'm not lazy but they don't require a very detail answer.


texts:
I am a beginner on Eagle. I want make a plated hole on PCB but no any pad on top or bottom layers. Or, a plated hole on PCB but bottom and top layers are electrically isolated. Another
variation is plated hole with a circle only on bottom or top layer.
In all cases plated hole connected with isolated copper wire (trace).
How can I do this with Eagle?


texts: Why on shutdown the SCR can be compared to a power diode?

texts: I have this as a homework question and can't seem to find the answer in my notes, book or internet. I know they will behave similarly when there is a reverse polarity on both, but the way my professor phrased it seems like he is talking about the process of turning off the SCR, in which I can't think of any resemblance.


texts:
In SBAA181 - Respiration Rate Measurement Based on Impedance Pneumography (page 8/11), what is the purpose of having potential divider of 10ME (R1=R2)?

the reference of these resistors are R84,R85,R86,R87.

Kindly explain its significance in the circuit..


texts:
The FM signal (see image 1) is applied to a 50 Ohms antenna, and I am seeking the required bandwith with the Bessel table (image 2). From the FM signal, I deduced that the information frequency is equal to 5 kHz and that the modulation index is equal to 2. So I also know that I have to look in the row of the table where mf = 2.0 and that j0, j1, j2, j3 and j4 exist in this case (significant sidebands).

The solution first says 4 x 5 kHz = 20 kHz, this I still understand (4 because components up to j4 exist and 5 kHz because that is the information frequency). Finally it says that BW = 2 x 20 kHz = 40 kHz. Why do we have to multiply the found bandwith by two? Is this always the case or does the found bandwith have to be multiplied by the modulation index?

Image 1: FM signal

Image 2: Bessel table


texts: Zener Diode identification - Ultimate Speed Battery Charger

texts:
Friend of mine came with this: https://www.amazon.co.uk/Ultimate-Speed-Battery-Charger-Motorcycles/dp/B00JKOA7H8
The charger powered up. Display showed battery voltage, but it didn't switched to charge. After some digging, I found one trace to be burned down. I fixed that path. But the charger is now giving 16 Volts instead of like 14V and the display shows Error. I found out that one of the SMD Zener diodes is shorted. This one probably serves as part of the sensing circuit, and thats why the display shows error.
So right now I am trying to replace it. As I couldn't find any datasheet, my options are limited. I could recreate the schema, if its needed.

Purple line from the left was burned. Yellow SMD Zener diode is dead - Only one letter "D" as a description. Next to it (red) is Opto-isolator. And two (blue) ceramic discs capacitors.
I assume that this pattern (schema) is similar in almost all battery chargers. So what voltage range are we talking about here so I can narrow the search for the replacement?
And how would you advice I proceed?
Thank you.


texts: How do I pick a part that goes into a breadboard when I order it?

texts: I have just bought some 555 timers and they are timers for microelectronic circuits...could anyone tell me what I need to search for in order to get larger ones which will fit a breadboard? Thanks


texts: What percent increase in electricity consumption would a ~30% overclock yield (assuming it works safely)?

texts:
I have a piece of hardware that I want to make run at the same speed as a newer hardware. I know that this increases the energy, and I'm not sure if it is a linear relationship. I want to know how much energy the newer overclock would use. I have a feeling that the energy usage increase will be >30%, but I think it would be OK.

Note: this could possibly cause HW problems, but I read that 30% overclock is OK at least in the short term (I did it on the RPi and it didn't cause any problems).


texts: Circuit to use sound output as a signal generator - design check & choosing values for C and R

texts:
I am a beginner in electronics. I got myself a second-hand analog oscilloscope but I don't have a function generator. So, as a first project, I am trying to design a circuit to use any device's sound output (PC, mobile phone, etc.) to generate simple sine waves. This will allow me to start learning about designing and how to use an analog oscilloscope.

I have been reading about op-amps in the Art of Electronics and on various websites, so I have based my design around op-amps. I would like to have some input about my design, if it has any glaring shortcomings and things that I have missed as a beginner. Also, I am not sure how to choose values for R and C. Here is my design, please keep in mind it is my first ever experience in electronics & circuit design.

First, I have done some research about the signals that a typical sound card outputs, and it seems like it has no DC offset and is centered about 0V. Since I will be powering my circuit with the USB port's +5V referenced to ground, I will need to provide a DC offset to the signal.

The first part of my circuit is meant to supply this DC offset. I will be using an op-amp in the voltage follower configuration driven by a voltage divider.

Questions:

I could have used the output of the voltage divider R1 // R2 as my DC bias out, without using the first op-amp OA1. However, according to my understanding, due to the op-amp's huge input impedance, it serves as a buffer between my computer's sound card and the circuitry I will be driving with the signal, which is a desirable feature. On the other hand, I could've connected the output of the voltage divider R1 // R2 directly to the DC offset input of the second circuit which is also using an op-amp. If I do that, I still retain that huge input impedance and the buffering protection. Therefore I am thinking that the first op-amp OA1 is not really needed, and that I could have done the same thing with only one op-amp.
In the first circuit, how do I determine R1 and R2? Let's say I want +2.5V at the output of the divider, then I have to choose R1 equal to R2. If I choose values too low, lots of current will be wasted through the resistors, but if I choose too high, loading effects will start to be noticeable. I have chosen R1 = R2 = 100K.
C1 is a bypassing capacitor that shorts AC noise to ground, am I correct? How would I choose its value? I have seen on the internet that a bypass capacitor is also inserted at the output of op-amps that provide DC bias (C2). Is it really needed? Why would it be needed if the AC noise has already been shorted to ground at the input? What capacitance value should I set it to?
Could I use a potentiometer as my voltage divider? This would allow me to vary the DC offset with a knob. However, it could short out my USB rail to ground when I turn the knob all the way.
C3 is a capacitor that is used to block any DC in the incoming signal. How do I choose its value?
How can I be sure that R3 won't load my input signal?
R4 and R5 determine the gain of the amplifier (gain = 1+R2/R1). For a given gain, how do I determine R2 and R1? What is the tradeoff between bigger resistances and lower resistances? For example, if I want a gain of 2, R2 must be equal to R1, but what are the constraints and considerations to chose the values of these resistances?
Can I use a potentiometer instead of R4 and R5 to make the gain adjustable with a knob? If I do so, is there anything I should take into account?
C4 is there to make the gain at DC = 1 (roll off the gain at DC). How do I set its value?
Am I missing anything?

Thank you very much for your help. Any comments and feedback will be welcomed.


texts:
Can you explain what for is resistance R101 on next schematic:

I understand why we need R105 (open collector) and R102 (positive feedback). But R101? and C11? Thank you.


texts:
This is a generic concept question that I encountered during the first day of an EE course. Our lecturer told us that electric circuits are essentially electric networks with closed loops.

I would like to know how an electric network with an open loop works. Is it referring to an open circuit where nothing really works or are there actually functioning networks without closed loops? And if such networks exist, how is energy transferred and how does KVL work in that case?


texts: Why triac output goes higher than line 230-240 voltage in AC dimmer circuit?

texts:
I am using AC dimmer circuit using arduino. circuit is working normally but the only problem is about voltage. as the dimmer circuit varies dimming,the output voltage also increases and decrease. Line voltage is 240 volt and output voltage goes till 328 volt. Is this normal working of triac BT139 or I am doing something wrong?

the circuit is which I am using for dimmer on arduino


texts: Modulating frequency of a crystal oscillator circuit

texts:
I have built this simple Crystal Oscillator circuit operating at 30Mhz and it's working fine. Please ignore the values of the equivalent circuit of the Crystal i.e ESR, EPC, ESC, ESI.
I am using this circuit with an antenna at node 4 (emitter) to produce em waves which I hear as silence when I tune to 90MHz (3rd Harmonic of 30MHz)

What simple design should I use to modulate the frequency of the Oscillations? For example using a varactor diode.
How to boost the third harmonic of the oscillations? The various circuits that I saw on the internet to do so use Inductors. Is it possible without an Inductor and a variable capacitor? I have also read this. Since inductors in 0.1uH (to get the 30Mhz resonant frequency) or less range are difficult to get if I build one on my own will it work because it's not possible to get the exact value of the inductor, So will it work even if there is a slight deviation in the inductor?
Please suggest any other modifications to improve the circuit.


texts: How to set registers of accelerometer BMA220?

texts:
I first wrote my problem in Arduino Stack exchange (https://arduino.stackexchange.com/questions/68438/how-to-manage-interrupt-from-accelerometer-bma220) but I was told that I might get a better help here.

I would like to use the interrupt register from the BMA220 accelerometer in order to detect high-g shock. I am using an Arduino Mega2560 as microcontroller. The memory map concerning the registers is shown below
In the datasheet the section concerning high-g registers is as followed :

It is written that whenever a condition is met for the interrupt controller "an interrupt (logic '1') is issued through the INT pin of the sensor."

However after initializing the necessary registers (in I2C):

0xC for high_th
0xA for high_hy and high_dur
0x1C for en_high_x/y/z

I managed to get my interrupt working by latching it during 0.5s but I have problem to understand the threshold level parameter.

Here is the code I am using :

#include <BMA220.h>
#include "SEN0168.h"

BMA220 bma;
byte interruptPin = 2;
byte count = 0;
const uint8_t HIGH_SET = 0xA;
const uint8_t HIGH_LOW_TH = 0xC;
const uint8_t INTERRUPT_REG = 0x18; // to get the bit indicating an interrupt was detected, not used because of the INT pin
const uint8_t ENABLE = 0x1C;

void setup() {
   Serial.begin(74880);
   pinMode(interruptPin, INPUT);
   init_SEN0168(R4); // set sensitivity to 4G
   bma.setRegister(ENABLE, 0b10110111); // enable high-g-detection, reset interrupt bit control and latch permanently
   bma.setRegister(HIGH_LOW_TH, 0x4); // Threshold of 2G
   bma.setRegister(HIGH_SET, 0x1); // No hysteresis and 2 signals needed to trigger
   attachInterrupt(digitalPinToInterrupt(interruptPin),counter, HIGH);
}

void loop() {
    if (count==1){
    Serial.print("x-axis: ");
    Serial.println(accel_range_SEN0168(X,R4));
    Serial.print("y-axis: ");
    Serial.println(accel_range_SEN0168(Y,R4));
    Serial.print("z-axis: ");
    Serial.println(accel_range_SEN0168(Z,R4));
    count =0;
    bma.setRegister(INTRP_RES_REG, 0b10110111); // enable high-g-detection, reset interrupt bit control and latch permanently
    }
    else{
      Serial.println("No shock");
      count =0;
    }
}

void counter(){
  count +=1;
}

As you can see from the table about high-g, writing a certain number of g in the threshold register is equivalent to the double measured by the sensor so in my code it should be 2G of threshold with 0x4 written. However it gets waking up abnormally just by moving it around... Writing 0x8 is much better but I still don't think I give it 4g when it wakes up.

Do you know how to set the threshold properly and use the hysteresis wisely ?

Thank you for your help !


texts:
Mechanical Engineer here, not an EE.

I have some environmental sensors that need to be a part of a flow path.
It occurred to me that it might be possible to have a metal "can" that sealed to the board around the sensors by sodler, providing a gas-tight connection. The current solution uses a plastic part with an oring and through the board screws, and it doesn't work well, as a bonus.

How would I communicate this to the EE's doing the board layout?

Ideally, there would be a lid like rf shields that could be snapped on and off and be gas-tight when on.


texts: Battery voltage not reaching the expected 12.8V

texts:
For a few weeks now I have been charing a deep cycle battery using a 80W solar panel on the roof and a charge controller.

The frist few days the battery voltage would settle at 12.8V once the sun went down. Now days it only has a rest charge of 12.6V and I am no longer able to have it settle at 12.8V. Is this common?

I have tried charging the battery on a long and sunny day. The voltage goes above 12.8V easily but at night it settles down to 12.6V and not 12.8V again.

I am worried I am not charging the battery properly. It is often cloudy were I live and the battery is mostly charged quite slowly. I do not have any charging equipement for condition charging the battery using electricity from the wall.


texts:
I'm following this guide [1] to made a Z-Wave compatible doorbell and it requires a SRU-12VDC-SD-C relay.  I know nothing really of electronics and have found a SRD-12VDC-SL-C relay on Amazon [2] which looks to be similar, but because I've little knowledge I don't know for sure.  Will the SRD-12VDC-SL-C work for the use I intend?

EDIT
I've looked up the datasheets [3], [4] and they don't really mean anything to me.

Links

1, http://www.robbshop.nl/about-z-wave/z-wave-projects/z-wave-doorbel - this link is half in english, it's enough to understand what's going on.  You will have to select the UK language selection drop down in the top left of the page for this link to work

2, http://www.amazon.co.uk/2pcs-Power-Relay-SRD-12VDC-SL-C-Type/dp/B00MO75O30/

3, https://www.ghielectronics.com/downloads/man/20084141716341001RelayX1.pdf

4, http://www.te.com/commerce/DocumentDelivery/DDEController?Action=srchrtrv&DocNm=SRU_series_relay_data_sheet_E&DocType=DS&DocLang=EN


texts: Should nominal or stall current be used for power supply selection for BLDC?

texts:
I'm working with a custom 24V BLDC and I'm trying to find the right power supply to use for it.
The motor is rated for 2A continuous and in normal operation we will be operating under that, however there will be times when it needs high torque instantaneously and will draw 5A very briefly.
When selecting a power supply, I've heard you are supposed to use the nominal current (so we would need a power supply of 24V, >2A output) and to rely on capacitors to provide the high current at short bursts (stall current). Is this true and if so why ? I'm  assuming it's a money issue (if you can get away with a cheaper power supply then you should do that), but is there an engineering reason ?
Using a power supply rated for the nominal current is also mentioned in this question here but I'm looking for a more in depth explanation of why: Proper power supply for BLDC motor


texts: Transmission Line (shielded dual stripline )

texts:
Evaluate and illustrate:
equipotential contours and a vector electric field distribution for .
I got this result: and .
I want to ask that, is the direction of the Electric field lines are correct?


texts: Electrolytic capacitors connected with one terminal only?

texts:
I've got an ordinary PC motherboard. So, out of curiosity, I started looking at the power circuits on it and found several large 1000–1500 μF electrolytic caps:

It's easy to see that their cathodes are not connected to any wires on the back side of the board. However, they aren't connected on the front side as well:

At first I thought that these might be soldered in as reserved components, uhhm... but now I'm inclined to reject that hypothesis. It makes little sense; and what's convincing the most is that other similar caps are wired in the same anode-only fashion.

I guess that this might work, because of electrostatic induction happening inside the caps, which would still allow to store energy in there over 1 wire only (and thereby absorb unwanted ripple current) – but wouldn't that effectively reduce the caps' capacitance?

Also, can the cathodes be wired back to ground, theoretically? Will this enhance power regulation stability?

Finally, I have a suspect that this could be related to the obvious difficulty of routing the ground wire to nearly every component on the board. If I'm correct, is connecting of EL caps by 1 wire only a common practice in the industry? Or did I just notice an extremely dirty awful hack, which I shouldn't ever repeat in my designs?


texts: Integrating an Arduino to a commercial product

texts:
We are developing a product which we hope to introduce to the market soon. It has an Atmel microcontroller and some other circuitry. Recently we thought of directly using an Arduino BLE33 on the PCB without building the microcontroller on our PCB. This gives us the advantage of a easily swappable micro controller in case one fries. This costs a bit more.
But other than that what will be the pros and cons of this approach.
Thank you very much.


texts:
I have this circuit :

I'm trying to write down the logic of every output (W,X,Y,Z), to get a truth table out of it :

W = NOT (A OR B)
X = NOT A AND B
Y = A AND NOT B
Z = A AND B

But when compares to the source, my truth table is wrong, so I know that my logics are all wrong.

I always start from the right to left everytime I want to understand a logic circuit, for example, in this case, output W is the output of an AND gate between two NOT parameters W = NOT X AND NOT Y, but where do "X" and "Y" in this case come from, obviously not A and B? Look at the logic circuit, I felt like I was lost in a maze! Any suggestions, or hints to help me to understand this kind of logic circuits easier is greatly appreciated!


texts: Where should I put the fuse in this circuit ? Critic the design

texts:
I've the following circuit , that used to measure the current through shunt resistance ,

The circuit have analog & digital ground ,
the terminals 1 ,2 ,3 are for AC source .

I need to protect this circuit from shorts .

So where's the right place to put the fuse ? & how to know that this is the right place ?

Will be a fuse on the digital side and the analog side ?

any other recommendation for this circuit ? I found out that 7805 voltage regulator is getting hot fast .

Edit #1 :-

R3 is shunt resistor with 200 u ohm resistance


texts:
I need to design a small board that will go into a large piece of public infrastructure intended to last many decades.  I am looking for papers and the like that give guidance on such design based on real research.

This board will be much bigger for mechanical reasons that it needs to be for even a spacious circuit to achieve the function with discrete parts.  Things like wide traces is a no-brainer.

The customer wants to minimize total parts, and wants them to be thru hole.  I see the point about minimizing parts, but which parts also matters a lot, and being able to get replacements in the future is important.  This function can be implemented with a handful of discrete transistors and resistors, but the customer would rather use a single logic IC in DIP package.  He thinks thru hole is more reliable, but I think I remember seeing a study that says the opposite.  Also, I'm worried about availability of a 16 or 20 pin DIP logic chip in 20-50 years.  But, are SOT-23 transistors and 0805 resistors a better bet?  There will be some opto-isolators.  It seems to me those will swamp everything else in terms of reliability and future availability.  Yes, I'll run the LEDs at a small fraction of the rating to increase life.

So, I'm looking for real definitive research-based information on designing for long-term reliability.  This is an area where it's easy to think about the 10% problem but miss the 90% problem that makes the 10% issue irrelevant.

Added:

I'm looking for evidence-based answers.  I like to think I know electronics pretty well, and can come up with various plausible-sounding reasons why one approach may be better than another, and I'm sure others can too.  However, I don't trust those because what sounds plausible and is based on sound physics may be correct but missing some other more dominant affect.  I'm worried that this is where educated guessing could lead to significantly wrong conclusions.  That's why I'm asking for evidence-based answers, papers from actual studies, rules NASA might insist on, etc.

Added 2:

Consider the environment "industrial".  I'm not sure how well the environment is controlled if at all.  The boards will be protected from the elements, but possibly no air conditioning or heating.  I don't know about vibration, probably not much.

These boards will be installed in a cabinet that houses other parts of the electrical system.  Service technicians can walk up to the cabinet when necessary.  Difficulty of servicing isn't the issue, but downtime is.  This is not what's going on, but imagine if a interstate highway was shut down until the system is up and running again.  Of course there is redundancy already, but failure is something you really want to avoid.


texts:
i prototype a small board with ENC28j60.

Instead of 49.9 resistors I have ordered by mistake 47R ones,

What do you think? will it work? It is only 10M ethernet


texts: How is a common emitter different from an emitter follower?

texts: They seem like two words for the same thing, but I also see some sources have different configurations for them.


texts: Proving something is true in Boolean Algebra given two equations and two variables without using a Truth Table

texts:
Problem:

Given that $$ AB = 0$$ and $$A + B = 1$$ and using only algebraic manipulation is it possible to prove that: $$ \overline A = B$$

Answer:

I believe it is, but I have failed in my attempt to do so. I can verify it using a truth table. Here is my attempt.

\begin{align*}\
AB &= \overline { A + B } \\
AB &= \overline A \, \overline B \\
AAB &= A \overline A \, \overline B \\
AB &= 0 \\
\end{align*}

Thanks,
Bob


texts: I have calculated the transfer function for a given RC circuit, and determined that it was high pass. I was wondering if you could cancel its affect with an inverse circuit, and how this circuit would look?


texts: FET transistor for output channel for arduino not working

texts:
I'm trying to work with IRF640 FET transistor (picture attached).

The problem is when I put 11V on the G-S voltage. The D-S voltage is 4-6 volts or more.

Why the transistor doesn't open fully?

In the simulator, the voltage falls to 120.18mV.(as expected)

Thank you.


texts: How do I control multiple 4 pin LEDs with minimum GPIO pins?

texts:
I am using 42 four pin LEDs (common cathode) for my project, and I have to control them individually.
I know we can use "WS2812b" for more effective usage, but 4 pin is a requirement in my case.
I am using 74HC595 shift register to control 8 pins, but for controlling 42 LEDs I need 16 shift register, and not a good solution. Any idea/suggestions?


texts:
This might sound a bit weird, but does anybody here know of a exercise bicycle that is hackable? What I would like to do is to connect it to a PC (don't care how, usb, parallel port, serial...) to transfer the current speed in real time. My ultimate goal would be to modify an open source racing game in such a way that the speed on the bike determines the speed of a bike/car in the racing game.

EDIT: By "bicycle ergometer" I mean something that you would find in a fitness center. It is not a real bicycle at all and it usually already comes with an integrated computer. The problem is getting the information out of that computer. Sorry if I caused any confusion, but English is not my native language and "bicycle ergometer" is what my dictionary told me.


texts: Alternate programming software to program Altera CPLD

texts:
I am using a Altera MAX V CPLD. When I try to program the CPLD using QUARTUS II, it is reading the device ID and silicon ID correctly, but it failing during verification.
I tried to isolate the signals around TDO and TCk to see if noise was affecting the signals with no change.

Is there anyway, I Could reduce the TCK frequency for programming CPLD in Quartus II?
Are there any other 3rd party programming tools which I could use to program  the .pof file generated from QuartusII?

Thanks,
Vijay


texts:
See images below :

I obtained this component from an old radio set ( possibly 90s made). It was attached to the tuning dial, so most likely it is variable capacitor I believe. It has absolutely nothing written on it except on image 1, which is
C1, C2, C3, and C4 as seen. The text in image 3 (wp0710) returns no result.

Also in image 3, the 2nd leg on left is internally attached to the capacitor.

Since this is my first hands on experience, I am absolutely clueless what are its various legs, and how to use this capacitor. I don't know how to wire this. If it would have been a simple 2 leg capacitor, it was no problem. But what to do in this case ?More important!y, how do I find out over what range does it vary. I have a digital multimeter at my disposal.  Any help and additional information is welcome.

Additional information : The radio from which it was obtained was a 5 band radio : Mw(540 to 1600 khz) SW ( 60 to 19 m) FM( 88 to 108 mhz) Tv1(65 to 75 mhz) and TV2 (175 to 230 mhz). Also there was a single piece of it in radio.


texts: How is the intensity of sensor noise determined experimentally?

texts:
Consider a sensor for which we are designing a Kalman filter for improved accuracy or sensor fusion. Let us restrict this discussion to the goal using the filter to improve the accuracy of the aposteriori state estimate and avoid addressing sensor fusion. Further, let us assume the state and output to be identical and one-dimensional for simplicity.
The designer of the Kalman filter assumes the knowledge of the system dynamics and output channels including apriori knowledge of the variance (or squared standard deviation or squared intensity) of the Gaussian white noise appearing in the process dynamics and observations. While the well known methods to determine the noise variances are as follows,

the standard industry approach to determine the noise intensity is by tuning the value in the Kalman gain computation to improve closed-loop performance,
the auto-correlation least squares method which uses closed-loop data,

it is not clear in the literature if there are any algorithms which use open-loop data for determining the noise covariance.

How is the intensity of the Gaussian white noise model of a sensor determined experimentally using open-loop data?


texts: Nonlinear increase in logic utilization for FPGA design

texts:
I am creating a design using the Altera Stratix V GX-series FPGA. For host device communication we are using the PCIe x8 interface.

The interface itself takes up 3,058 ALMs (out of available 234,720).

With 1 copy of a custom design unit, the number of ALMs jumps to 3,077, just 19 more. Therefore we should expect every other copy to take up 19 units right?

But when we compile with 4,096 copies of the same design unit, 6,282 ALMs are used up, which is much less than anticipated. Why does it seem like logic utilization increases nonlinearly?


texts: FT4232H: Configuring RI# as TXDEN Using FTProg

texts:
I am developing a device based around two FTDI FT4232H quad USB-to-Serial converters plugged into a Texas Instruments TUSB2046 USB hub controller. The serial outputs of each FT4232H channel goes to a Texas Instruments SN65HVD72 RS-485 transceiver, thus creating a dual-quad USB-to-RS485 converter. See Section 4.3.3 (page 20) of the FT4232H datasheet for a diagram of what I am doing for each FT4232H (though using all four channels rather than just two). The FT4232H multiplexes the functions of Ring Indicator and Transmit Data Enable on a single pin, called RI#/TXDEN, and the default is RI#. If I am reading the datasheet correctly, in order to use this pin as TXDEN to drive the DE pin of the RS-485 transceivers, I need to configure it to use this function in the FT4232H's EEPROM. For this I use the FT_PROG utility from FTDI.

When I first plug in my board containing the hub, USB-to-serial converters, and the RS-485 transceivers to my USB port, all 8 COM ports enumerate as they should. The next thing I do is open up FT_PROG and run the "Scan & Parse" command. Once completed, both FT4232H USB-to-serial converters appear, and they show up as "Blank Devices":

My next step is to go into each channel and check the box next to "RI as RS485 Enable", as shown in the following image:

I repeat this process for all ports, A-D, on both devices. Next I click the "Program" icon on the top menu bar, and on the confirmation window I check that both devices are checked and I click "Program". Once done, I see "Finished Programming" appear at the bottom of the window.

Everything appears to work, and after clicking "Cycle Ports" I confirm that data does appear to have been written to the internal memory. After that I click "Scan & Parse" once more:

After running the "Scan & Parse" command, however, the devices appear blank once again and none of my changes "stuck". The "RI as RS485 Enable" setting is unchecked again.

I thought perhaps that "Scan & Parse" might delete some settings of the chips (Think I found this in the datasheet or an app note somewhere, that this setting was cleared on reset), and even though that doesn't make any sense to me I decided to give it a try without re-scanning. Unfortunately I was not able to communicate with my RS-485 device - my terminal program was unable to even detect the presence of any devices on the RS-485 bus.
This is my first time ever using FT_PROG, as well as these particular FTDI chips, so perhaps I am missing a step in the process? I am hoping someone might be able to determine the reason why my changes don't "stick" and why I am unable to communicate with my RS-485 device after connecting to the respective COM port.

For the record, I tried all COM ports which were enumerated when I plugged in my USB cable, so unfortunately it's not as simple as me just not looking at the right bus.


texts:
I have a controller that uses 0.2V voltage as logical zero and 0.4V as a logical one and want to turn a LED on/off depending on these two levels.

I've built a cicrcuit like one below and tried to choose R1 value to turn the transistor off when control voltage is low, but it was eather always open and control voltage was only affecting LED's brightless, or (with big R1) it was always off.

Maybe I'm missing something or some other circuit should be used?

How to solve my problem and turn the LED on/off using 0.2/0.4V control voltage levels?


texts: PCB Design: Through hole components on both sides?

texts: I am making a device, but the PCB is getting quite big in size. I have never made a double sided PCB before, but I am considering it now. I have soldered one at school, where SMD components were on top, and through hole components on bottom. Is it a bad practice to put through hole components on both sides? I cannot think of any downsides to this, but I want to be sure. It would save me a lot of space


texts: Are chopper amplifiers same as chopper stabilized Amplifiers?

texts: I was wondering if the chopper amplifiers are same as chopper stabilized amplifiers. If no, can you explain what is the difference?


texts:
I'm very new to VHDL, please excuse my question.
My output values are always U. I cannot figure out why.

This is my code:

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;

entity first is
    Port ( R : in STD_LOGIC;
           F : in STD_LOGIC;
           W : in STD_LOGIC;
           WI : out STD_LOGIC;
           CF : out STD_LOGIC);
end first;

architecture Behavioral of first is

begin

WI <= not (R and W);
CF <= F and F;
end Behavioral;

And this is my test bench:

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
entity testBench1 is
end testBench1;

architecture Behavioral of testBench1 is
COMPONENT test1
 PORT( F : IN STD_LOGIC;
 R : IN STD_LOGIC;
 W : IN STD_LOGIC;
 CF : OUT STD_LOGIC;
 WI : OUT STD_LOGIC);

 END COMPONENT;
 SIGNAL F : STD_LOGIC;
 SIGNAL R : STD_LOGIC;
 SIGNAL W : STD_LOGIC;
 SIGNAL CF : STD_LOGIC;
 SIGNAL WI : STD_LOGIC;
BEGIN
 UUT: test1 PORT MAP(
    F => F,
    R => R,
    W => W,
    CF => CF,
    WI => WI
 );
 testBench1 : PROCESS
 BEGIN
 wait for 100 ns;
 R<='0';
 W<='0';
 F<='0';

 wait for 100 ns;
 R<='0';
 W<='0';
 F<='1';

 wait for 100 ns;
 R<='0';
 W<='1';
 F<='0';

 wait for 100 ns;
 R<='0';
 W<='1';
 F<='1';

 wait for 100 ns;
 R<='1';
 W<='0';
 F<='0';

 wait for 100 ns;
 R<='1';
 W<='0';
 F<='1';

 wait for 100 ns;
 R<='1';
 W<='1';
 F<='0';

 wait for 100 ns;
 R<='1';
 W<='1';
 F<='1';

 END PROCESS;
end Behavioral;

I appreciate any help, I just cannot find a solution. Thank you all.


texts:
I have a simple radar module (k-band) that is capable of fm modulation and it provides both I and Q as baseband outputs. I like to extend the measurement range of this module by just signal processing options. (I.e. Without changing any hardware)

Would modulation help in terms of range? I can generate any signal such as triangle, sinus etc at the FM input of the module. (I know some range info could be obtained but I am after SNR, range knowledge is not material to my objective)
Currently I only use I to do my calculations. Could I also use Q together with I to reduce noise or improve SNR ? (I couldn't find any literature to that effect but I think there could be some gain in SNR if I use this additional signal)


texts: Finding voltages in a circuit with no power supply

texts:
I´m trying to solve the following circuit

However I cannot understand how is possible that E2 and E1 have voltage if there is no visible power supply on the circuit. What´s the approach to solve this circuit?


texts: RF coil impedance matching inconsistant result

texts:
I'm trying to do impedance matching from a signal generator (60MHz with 50ohms impedance) to a copper wire coil (6 rounds). The coil is connected by a wire (~6 meters long) with resistance 0.9 ohms.

Here is the steps I am planning:

Step 1: calculate the load impedance, both Load Resistance & Load Reactance.

Step 2: insert these values into:
http://home.sandiego.edu/~ekim/e194rfs01/jwmatcher/matcher2.html

In Step 1, I connect the coil + transmission wire in series with resistor. I'm obverving both coil voltage & resistor voltage. And because:

U(resistor) / U(coil) = R(resistor) / Impedance(coil),

I can solve the coil reactance by: Reactance(coil) = Impedance(coil), because it is a 6 rounds coil, with almost 0 resistance.

Here is my problem, I'm using different non-inductive resistors (1 ohms, 3 ohms, 5 ohms). They all give me different results of Reactance(coil).

So how can I determine the reactance of this?


texts:
What causes the rpm difference between peak brushed motor torque and peak brushed motor efficiency?
 source: http://members.toast.net/joerger/AskAaron/motors.html
page 15 of this brushed & brushless motor performance summary talks about efficiency but doesn't mention a connection between torque and efficiency.
http://www.dtic.mil/dtic/tr/fulltext/u2/a577582.pdf


texts:
I have been developing code for this open source flight controller, and the one thing that I would like to improve with my workflow is to be able to flash the firmware wirelessly.

I am able to perform all debug and I/O interfacing with the device wirelessly via WiFi-networked Raspberry Pi's, however the one missing link is that I must plug the board in physically via USB in order to flash the firmware that I build.

Option 1: Push code from laptop to desktop computer through the network. This computer is plugged in to the controller and can do the flashing. Indeed I could probably use a third Raspberry Pi to perform this task as well, but the performance cost of running the firmware build toolchain on such a slow device is unappealing.

Option 2: Wireless USB hardware

I will be using Option 1 because there is clearly not enough support for Option 2, and it also happens to be the case that I need a reliable and robust data link.

However I would like to explore the possibilities of Option 2 because I think there is some potential in it. It seems to me that this should be possible to make USB wireless in a transparent way at the hardware level, by e.g. using RF. What would be some of the challenges in realizing this?

Terribly practical this will not be, and neither will USB 3 (or maybe even 2) rates be likely attainable practically, but considering just the sheer volume of USB devices out there, such a gadget would come in handy.

I'm not very familiar with USB protocol, but maybe some aspect of it will become difficult when the physical layer introduces latency. My hope is that this can be done transparently with hardware so that the wireless USB cable will appear to the host devices as nothing more than a somewhat long cable. Now it does appear that USB is limited in this regard as USB 2.0 has a limit of 5 meters of cable so the latency requirement alone may rule out the ability to do this. Surprisingly to me, USB 1.0, 1.1 and 3.0 also limit cable length at 5 meters or even shorter.


texts: Practical estimate for a capacitor discharge through a resistor and an LED in series

texts:
This question was asked before, but I am struggling with the same question and I can't figure out "how to deal with it in the real world" as someone put it at the time.

Olin's approximation is the first idea I came up with: assume the LED is a voltage source, assume the capacitor initially charges up to 5V - Vled_drop, and assume a simple RC discharge. However simulating the circuit seems to show that the approximation is nowhere close to being valid. With this circuit:

If I assume a simple RC discharge model the simulator gives

RC = - 3s / Ln(V(3s) / (5V - Vs)) = 4.5

after 3s, when the calculated value would be

RC = 1.8mF * 1k = 1.8

(the simulator uses Vs = 1.64V for a red LED).

In other terms the capacitor discharges much slower than the RC=1.8 would indicate.
Is there any better way to predict what will roughly happen without a simulator, or without solving the actual differential equations?

Franck


texts: RC pulldown on the MDI lines between the ethernet PHY and RJ45 Connector

texts:
I came across this circuit as part of the Xilinx Spartan 6 601 evaluation kit board diagram:

Left hand IC is an 88E1111 (incidentally, the datasheet of which is incredibly difficult to obtain), the lines require 100 Ohm differential impedance, which explains the 47 Ohm resistors (why not 49.9 1% tolerance resistors that I've seen in the same scenario on other boards?).

I think I understand what is happening: the voltage divider centre is supposed to sit at zero, but if the diff lines aren't 100% inverted relative to each other, say during a transition from low to high, then the centre of the divider will be non zero and the cap will smooth that change. Is this right? And if so, doesn't the RC filtering have an affect on the transmission lines and rates themselves?

Also, what kinds of voltages are on these lines? 47 ohm isn't very big, so won't there be some current flow through the resistors, in the order of mA? On second thought, the current probably isn't too significant.


texts: In the following portion of circuit, my teacher said that R7 and R8 are attack resistors (I don't know if this is the right word to describe this). Why those resistors are called like that, and what they do?


texts: Why does the Pinch-off Point in the MOSFET move towards the source as we increase \$V_{ds}\$?

texts: Basically, I understand how the pinch-off region forms and I understand how conduction takes place even after the pinch-off voltage is reached. However, why does the distance between pinch-off point and drain start increasing when \$V_{ds}\$ increases?


texts: I am new to Xbee and XCTU software and I wanted know if it is possible to use XCTU to send a "programmed sequence". By that I mean, send something, wait 10 seconds, if receive this thing send this etc. I know that XCTU is not an IDE and that it is not really intended for this but I would like to be able to do this kind of things. If anyone has an idea I would be really happy :)


texts: A question about a circuit simulation using LM331 in LTspice

texts:
I'm trying to convert 0..10V analog voltage to frequency by using an LM331.
Since LM331 works at 5V supply, I can scale 0..10V to 0..5V and feed it as the voltage input to the LM331.

I came across this circuit and this forum.
I followed the instructions to use LM331 in LTspice and simulated the circuit below:

But I'm getting 5V constant output when I use 5V supply. LM331 should work with 5V supply. But in simulation with 5V it doesn't work. It works when I use 10V supply.

Can someone explain me how this circuit works? I mean C1 and R1 sets the frequency but thats all I know. What else sets what here? How can I set the duty cycle to around 50%? How can I modify this circuit so I can run the simulation for 5V supply?


texts:
How can I implement this 2-bit adder circuit:

(source)

Onto http://www.neuroproductions.be/logic-lab/ or logic.ly?
After several attempts (and in spite of the half adder and full adder working) I cannot seem to get this adder working.

Here is the half adder & full adder:


texts:
I'm trying to size a backup generator for a water pump system.

The pump is rated 3HP / 230V / 13.5 A

So it seems that I would need a ~ 3KW generator on a steady state.

However, I'm aware of the need to design for inrush start current. The pump code is H, which from table gives about 6.7 mid range value.

Is the start power required then 3 * 6.7 = 20KW?

Seems that it would lead a grossly oversized the generator. Any guidance of what's acceptable?


texts: Does living near a cell tower decrease your overall exposure to RF?

texts:
I understand that my mobile phone will increase its RF levels when it struggles to connect with a cell tower/base station due to distance. Also being nearer a cell tower will increase my exposure to RF from the tower.

If I was near a cell tower my phone's RF output may decrease and therefore my overall exposure to RF may decrease despite the gain in RF exposure from the tower.

I guess the results would depend on many variables. Maybe their are some rules-of-thumb so... does living near a cell tower decrease your overall exposure to RF?

BTW I'm not asking whether RF is dangerous to humans.


texts: I'm doing a project on stm32f407. I want to configure one of the GPIOs to the timer6 of stm32f407. Which output mode (push-pull mode or open drain mode) of GPIO is most suitable to configure the timer6? It would be really helpful to know why that mode is most suitable for the same too.


texts:
I have purchased a pair of APC220 modules.
I also purchased a USB TTL module to program these.
I down loaded the drivers from Silabs and the RF-magic 4.2 software which is supposed to be able to program thee modules.
The RF-Magic program is proving less than magical as it does not see the device.
Tried 3 different computers
While trolling the web for suggestions option I came across the APC220 software which finds my device but does not allow me to change the settings that I need to change as it is for a different type of device using the same chip.
I tried a FTDI cable but this does not help.
Any suggestions?
Warren


texts:
I have a couple of appliances that already have their power specified on them. However A few of them do not. The device is powered from an external power brick adapter.
One adapter for instance has the following specifications on it:
Input: 100-240V ~ 1.5A (I use 230Vac)
Output: 12V – 3.33A
My question is therefore which power value calculation do I use, the input (264.5W) of output (39.96W)? In order to know how to size my inverter.
I am sure this may be a duplicate question but I cannot search through every post to find that answer and the search field is not narrowing down the options alot.


texts: Strange VIH and VIL specification of MIC4451

texts:
In MIC4451's datasheet, it shows:

The \$V_{IH}\$ min. is 2.4V, then where the smaller typical value 1.3V come from? The same is \$V_{IL}\$, why it has a typical value larger than the max. value?


texts: Effect of frequency division on a signal's spectrum?

texts:
I am constantly on the lookout for effective yet inexpensive means to generate SSB signals. Analog Devices' LTC5598 Direct Quadrature Modulator turns baseband analog I/Q signals into RF from 5MHz to 1.6GHz. Sadly, for my purposes, the performance falls off dramatically below 5MHz.

What would happen, theoretically, if the output of the LTC5598 could be processed through some frequency-dividing means to cover lower frequencies? Would the spectrum of the modulation be preserved, distorted or destroyed? I would appreciate a reference outlining the Fourier analysis of this question.


texts: Why have a small neon lamp in power supply input circuitry?

texts:
A couple of times when taking apart older bits of electronics, I've seen a small neon lamp about the size of a fuse (but its definitely not a fuse) positioned near the power supply circuitry. What is its purpose?

Is it used as some kind of input protection? Does it illuminate under fault conditions? Why not use a MOV or some other purpose designed component?


texts: Combine two L78L05 voltage regulator to double voltage output

texts:
Is it possible to use two 5V linear regulator to get 10V output like this (I already have a bunch of 5V regulators):

simulate this circuit – Schematic created using CircuitLab
Are there any problems with circuit ?
Thanks


texts: Correct formulas for Thevenizing a Single-Source Network

texts:
My textbook has it that the circuit in Figure 1 is thevenized to Figure 2.

However, I got confused with the formulas as the text presented formulas for obtaining the Thervenin equivalents.
1)

2)

My questions are the following:

Is RTh the parallel resistance between R2 and R3 or R1 and R2?
Is VTh at the output terminals for this case (no load) really $$V_{Th} = \frac{V_{S}}{R1+R2}\times R2$$
Is the load current equal to the first picture's $$I_{RL} = \frac{V_{R2L}}{R_{2L}}$$ or the second picture's $$I_{RL} = \frac{V_{RL}}{R_{L}}$$
In this picture, are R2 and R3 the only components that are thevenized? Is VTH positive at point A because it has a positive polarity?

Using each of these formulas gives a different answer. Please kindly assist me. Thanks.


texts:
In the literature, I often see the notion of square law devices. Why are these devices important, to the extent that they have their own characterization as square law device?

In what context does this square law property become relevant, except the fact that it characterizes the relationship between an input and an output parameter for that device.


texts:
I have a series LC resonant circuit L = 44.4mH C = 36.5pF fr = 125kHz.
It is LF RFID antenna.
The LC circuit is powered by an H-bridge with MOSFET transistors.
125kHz carrier frequency, 1kHz modulation frequency (OOK).
The problem is when the key signal goes low. The LC system oscillates for a very long time.
How to extinguish these oscillations very quickly.

The carrier signal and keying is generated from the processor's PWM module.

Could this be the right direction:

regards


texts: Why does this ramp generator drop level outwith 60Hz / 10kHz range?

texts:
I found the following circuit in an old Elektor article:

It is a [edit: ramp generator] that repeatedly (a) charges C3 through R4 to build a ramp, and (b) briefly shorts C3 across T1 to reset the cycle.  (Ramp reset is triggered by the rising front of the square wave input, differentiated by C2 and R2.)  The fundamental frequency of the output signal matches near-exactly that of the control signal.  The circuit maintains a constant output level by increasing the capacitor-charging voltage (U2), hence the current through R4, as the input frequency increases.
However the article states that the circuit can only maintain the constant amplitude for frequencies between 60Hz and 10kHz, without explaining why.
QUESTION: Could someone please clarify what are the limiting factors here, and why?


texts: Are all these C type casts really necessary for bitwise register operations?

texts:
I find the coding style in the STM32F0 (ARM Cortex-M0 microcontroller) SPL (standard peripheral library) unnecessarily verbose. As an example, here is a snippet of code for configuring the phase locked loop for SYSCLK:

/* Select PLL as system clock source */
RCC->CFGR &= (uint32_t)((uint32_t)~(RCC_CFGR_SW));
RCC->CFGR |= (uint32_t)RCC_CFGR_SW_PLL;

Where RCC_CFGR_SW and RCC_CFGR_SW_PLL are macros for integer literals already cast to uint32_t.

#define RCC_CFGR_SW     ((uint32_t)0x00000003)
#define RCC_CFGR_SW_PLL ((uint32_t)0x00000002)

And RCC->CFGR is a (memory mapped) instance of a struct of the type

typedef struct
{
    ...
    __IO uint32_t CFGR; /*!< RCC clock configuration register, Address offset: 0x04 */
    ...
} RCC_TypeDef;

So the result would be implicitly cast to uint32_t anyway, even giving a warning if something funny happens (unlike what would happen with an explicit cast).

Can these explicit casts be eliminated, especially given that C99 guarantees (6.3.1.3) that

When a value with integer type is converted to another integer type other than _Bool, if the value can be represented by the new type, it is unchanged.

Allowing the simplification of the code to the significantly clearer

//Select the PLL as system clock source
RCC->CFGR &= ~(RCC_CFGR_SW);
RCC->CFGR |= RCC_CFGR_SW_PLL;

Or could that cause some unforeseen side effects?
I'm not really sure, and I presume that the people who wrote that code are more experienced writing embedded C than I am...

I'm asking this question on electronics.stackexchange instead stackoverflow since it's quite specific to low level embedded programming.


texts:
Regarding the next problem

why is asumed that there was a power loss of 928 W>?


texts: How much difference do peltier units have

texts: I recently bought a 6 can fridge cooled with a tec1-12705 unit, meaning the current rating is 5 amps. It gets about 7 degrees C inside the fridge and I want to upgrade it. I've been searching for a better cooling unit. Would a tec1-12708 for example, give better cooling results, if the voltage and amps are the same as my power supply?


texts: Inrush current limiter - design questions/review

texts:
I am considering to use the inrush current limiting circuit that was suggested in this answer.

I have a pretty big capacitive load of about 40000uF to charge. Its a buffer for a GSM modem that needs to continue running for several seconds after a power failure. The power supply will probably be an integrated AC/DC converter 9V/350mA. So I figure, I should probably limit the inrush to something near those 350mA.

This is the adapted circuit I came up with so far:

I expect a continuous load of about 200mA and chose the value of R7 accordingly. I also adjusted C2 and C3 empirically.
I am not fully understanding how the circuit works, which is why I require some feedback.

The LTSpice simulation looks promising:

The current -Id is the Drain current from the MOSFET. Charging the capacitor takes about 2 seconds, but that is something I can live with.

Questions:

How exactly does the feedback capacitor C2 work? There are similar circuits without feedback, but from what the simulations tell me it seems to be pretty indispensable to get reasonable results.
C3 only seems to have a very minor effect on the current limiting part compared to C2. Actually it just seems to introduce a delay what makes sense looking at the schematic. What are the considerations selecting a value for C3?
I don't have much experience with MOSFETs and I am unsure how to select an adequate part. Despite from sufficient drain-source current capacity, what should I look for? The first comment here points out that there might be some pit falls.


texts: Where did the base get the current from?

texts:
Still learning on my own so I am really not an expert.
I built a small circuit and can’t get the expected behavior.
Here is the schematic:

This is pretty simple. The PNP on top is connected to 5V on the emitter and the collector is connected to a current limiting resistor and an LED (so I can see when there is current.)
The base of the PNP is connected to the collector of a NPN and the emitter goes to ground.
The collector of the PNP provides currrent to the base of the NPN so when the PNP is on, it keeps the NPN on and the LED stays on.
I also connected the base of the NPN to a switch button that is connected to ground.
When I press it, the NPN base is grounded so it turns off and the PNP base gets 5V (from a resistor connected to 5V and the PNP base) and the LED turns off as expected.
Where I don’t get it is that as soon as I release the button, the LED goes back on.
Like if the NPN base was getting 0.7V from the PNP collector (that is supposed to be off.)
Here's a picture of my breadboard circuit:

I was looking at building something like this and wanted to test if it was working prior to adding the second npn (and using a pnp instead of a mosfet)


texts:
I am using an eeprom M24C32-W from ST.
Here is my schematic with VCC=3.3V. The write protection Write Control pin is connected to VSS and thus should be disabled. The address of the device is 0xA0 (or 0x50<<1) because the pins E1, E2, E3 are connected to VSS.

And here is my write and read command: I want to write value 0xAA to address 0xF0 but I cannot manage to read back this value. This is what my logic analyzer measures at the pull-up resistors.

Here is what I have tried so far:

writing to and reading from different memory addresses: 0x0000, 0x00F0, 0x00FF, 0x0FFF, 0xFFFF,
different delays between write and read: 0ms (it failed), 10ms, 1000ms.
write to device, power down board, power up board, read from device.

None of those worked so far, I am running out of ideas.
EDIT: I have tried various clock speeds with no success: 100kHz, 10kHz, 1kHz.
The EEPROM is the only device on the I2C bus.

Solved:
It was simply a faulty hardware problem. I switched the eeprom for a new one and now it works. Thank you all.


texts: Can we also use conjugate of Voltage (V*) for measurement of Complex Power?

texts:
Why is S = V I* is used a lot? I have never heard a mention of S = V* I. (It does the same job as I*). We get the phase differences in both the cases due to conjugation. So I'm assuming it is right to do V*, correct me if I'm missing any point here.
Also If I'm using V* for Complex Power calculation, will it give the same information regarding Lead/Lag Load or the Reactive power?


texts:
This is the oscillator for an ultrasonic misting circuit (ye olde patent US4996502). I think that something like 99% of the cinese HF misters (the 1.5-2.5MHz ones, not the micronozzle ones) use this topology, with slightly different values and bias schemes.
The idea would be to resonate the TD piezoceramic at its own frequency with a moderate power (10-30W, depending on the design). In my interpretation it should work in this way (correct me if I'm wrong): the whole thing is substantially a common collector Colpitts.
R1, R2, R3, R4 (often there are trimmers or pots there) gives static current for the operating point.
L3, C4 form an RF trap/DC smoothing do avoid losing power thru the supply lines.
TD and C2 are the resonant tank proper, C1 and C3 are the Colpitts capacitor divider. Nominally C1 is 1.8nF and C3 47nF but it varies in the wild. Also I think that they are different to adjust the gain, is that correct? C2 officially is only for protection against a short in TD but I reckon it partecipates in the oscillation. It's drawn horribly but that's the topology. The 'output' of the oscillator would be the C1-C3-L1 node.
L1 is a quite big choke (22µH to more than 220µH).
C5 and R6 gives some noise filtering and decoupling (but a lot escapes, anyway). R5 limits base current and helps stabilizing the gain (I think).
Now, for the things I have absolutely no idea: L2 is 4-5 air spire for about 100nH. Best thing I can think of is avoid spurious autooscillations. C6 (100pF) gives collector feedback but I have no idea of what would be its design function (in fact, it is not strictly needed, it seems to work even without it).
Now, for the question proper: this thing is different from the textbook Colpitts since the tank is anchored to the positive supply. Usually you see the 'external' terminals of TD, C4 and C1 to ground.
I interpreted this in this way: the goal of this circuit is to maximize the power on TD. So they made it the primary branch for current to flow (+ve, TD,C2,R5,Q1,L2,L1), and in fact there is a huge base current flowing (with the whole circuit at 700mA about 600mA are thru the base). Q1 is huge, too, so it works :D
The problem is that the TD transducers have many resonance pairs (they are piezoceramic discs so probably they move in many directions). And on some of them, instead of picking the nominal 1.7MHz, the oscillator locks on a 300-400kHz mode (not good, of course). The usual solution for the Colpitts would be a suitable inductor across C1 to bypass the lower modes (like for overtone crystals), but it can't be done (that would be a DC short).
I was thinking of working on C2 and C3 to steer the response, would that be a good solution? any other ideas or enlightenment about this circuit?
Thanks in advance


texts: The coaxial cable is claimed to show the highest common inductance (M) relative to any other cable configuration?

texts: The coaxial cable is claimed to show the highest common inductance (M) relative to any other cable configuration [Henry W. Ott, (1988), Noise Reduction Techniques in Electronic Systems, 2 Ed., AT&T Bell Laboratories]. When I searched, I could not find many arguments that support / do not support this claim. do you agree, what can you say?


texts: Is it possible for all circuit breakers in a panel to trip in the same time (for one fault)?

texts:
Today, I was in a hospital. Someone told me that there is a falt in a large washing machine. This fault caused all the CB's in the panel to trip.

The panel has many circuit breakers of different capacities/rated current (10A, 16A, 20A, 25A, and 32A). There is also main CB about 80A as much as I recall.

I checked the panel by myself and all CB were closed. It was just a small issue and he just thought that they are all open. Now, I wonder why did he think of this. Can something like that happen?

What I think is that only the CB of the washing machine will trip in case of a falt. If it did not trip, only the main CB (80A) will trip. Am I right? Are there any situations in which all the circuit breakers trip as a response to that single fault?


texts: Importing LT SPICE schematic design into Altium Designer 18

texts: I'm working on designing a front-end data acquisition board for signal analysis, and have completed the schematic in LT SPICE. Now I want to import the schematic design into Altium Designer 18 in order to create the layout and gerber files for manufacturing, but I'm having trouble doing so. From that I've figured out so far, such things are normally done inside of the import wizard, but there's no option for LT SPICE files, and certainly none for .asc anyway, which is the file type LT SPICE outputs. This is especially confusing as Altium owns SPICE. Can anyone help me?


texts: (Another) Tech Isolation Transformer grounding question

texts: I recently bought a hospital grade toroid isolation transformer and removed the secondary grounding wires from the chassis and outlets. However, the outlet grounds are still tied to primary ground through the chassis. No big deal. I can just use a 3 > 2 prong connector on the outlet side for my DUT. My question is should I go ahead and reconnect all of the grounding wires back to their original state?  Thanks.


texts:
I would like to know how to calculate cut off frequency of this summing integrator circuit. I fail to find anywhere on the internet how to calculate cut off frequency in this configuration.

Then how do I calculate unity-gain frequency this circuit?


texts:
I've been working on a simple project involving a Raspberry pi and some switches.
I would never thought I would have any problem for something as simple as a switch, but here I am.

The 2 wires from my switch are connected to the raspberry pi.
One is connected to ground, the other is connected to a GPIO. The internal pull-up resistor of the raspberry pi is used.

The length of the cable is around 7m.

The program is just a matter of reading the GPIO and sending commands according to state changes.

My problem is simple: everything works fine for some time, but eventually the switch ends up not "working" anymore (reading low state whether or not the switch is pushed).

I checked the switch, and of course it still opens and closes as expected, so the problem comes from somewhere else. What I did is I disconnected the switch, and measured the voltage between the two wires: I get 0V.

This is my first clue for thinking something bad happened to the raspberry pi. Because the internal pullup is used, I should have measured around 3.3V. And this is indeed what I measure if I replace the raspberry pi with a new one.

I thought this might be caused by EMI, causing voltage spikes? I really have no experience dealing with this. So what I did is I replaced the raspberry pi, and I added an external pull-up resistor with a lower value (the internal resistor is 30k, I used 1k as external resistor), guessing that this would reduce the noise. But the same thing happened after one day.

This time, when I measure the voltage at the GPIO, I have around 1.2V. According to the reading, using a simple voltage divider, this is equivalent to a resistor value of 600Ohms pulling down the signal inside the raspberry. Definitely not normal.

Then I tried to replace the wires with shielded audio cable, connecting the the shielding to ground. And half a day later, yet another raspberry pi was good for retirement.

I have now placed a ceramic capacitor between gnd and the GPIO (100nF), and for now it seems to be OK (it's only been 12h) but I have to say I have no confidence because I'm not sure what is the reason for this problem.

On the same system, I have another switch with a much shorter wire (1m) and I never had any issue with this one. This is why I guess my wires are acting as antennas, but I don't know for sure (especially since shielded wires did not help).

Any idea about what could happen would be appreciated.


texts: Are the Front- and Back-Porches Required to be Black for VGA?

texts:
My first question for this project was how to process a fast analog signal in the first place:
Digitally-Controlled Analog Processing for VGA Video Signal?

This one is about a specific detail of that processing.  I've copied the latest schematic here for reference:

As I said in the original description, the color-inversion step "provides (an attempt at) the proper signal blanking during the HSYNC interval by switching back to +1 during that time."  (referring to a switchable gain of either +1 or -1)

What I'm concerned about, is that the inverted setting ONLY blanks during the HSYNC pulse itself.  The porches are white instead of black, and it doesn't consider VSYNC at all.  Is that a problem for an older LCD?  (not CRT)

Everything I've found so far either:

Presents its description as a blanket matter-of-fact, with nothing to say what happens if certain things are not quite as described, or:
Suggests that the porches are not actually necessary, like the comments and answer to this question and the accepted answer to this question.

That last link basically says to look in the manual for the monitor to see what it needs, but I've never seen that kind of manual for ANY monitor!  Not new out of the box, and not by googling either.

As I understand, the only reason to have this extra logic at all, compared to just a plain-and-simple analog inverter, is to keep the monitor's DC reference at the same level for either setting.  The porches' original purpose was to "paint black" (nothing) during the "backstroke" of a CRT's beam deflectors or else that would be seen too, and that specific problem doesn't exist for an LCD.

Do I have it right?


texts: Practical question on high resolution to composite/S-video

texts:
I read many resources on the internet talking about NTSC, PAL, timing and voltage levels. But I have specific practical question, and I can not find definite answer to it. There're very helpful posts on Ataris, but they also more theoretical than practical.

The situation: the video display processor (VDP) outputs 1368 color clocks per line in NTSC mode, with 1024 in the visible "active screen" area. It has dot clock of 3.579545*6=21.477270 MHz, and thus display of whole line takes 21477270/1368 ~ 63.669 us (15700 Hz).

VDP has graphics modes of 256 pixels per line, and another of 512 pixels per line - displayed within 1024 clock dot periods. I assume that in former mode each pixel is clocked 4 times, and in latter 2 times.

In RGB mode receiver is free to choose its dot clock, performing oversampling or detection of the underlying a dot clock, or just use clock in accordance to its screen resolution.

But for me it is not clear what happens in NTSC mode - in both composite and S-video (with luma and chroma separated).

As I understand, NTSC's "transmission speed" is 3.579545 MHz, thus it will be performing undersampling of the color (and luma) data generated by the VDP.

Simple calculation gives the following:

Dot clock = 3579545 Hz
Line display time = 63695.24618 us
Dots displayed on the line = 228.

Using the similar calculations for 1024 displayable area I get 170.6666667 dots.

Even for 256 pixels per line, with 3.579545 MHz clock, the media will be able to sample first dot of first group of 4, then third dot of the second group, and will miss third group completely. And so on, with each third dot missed completely.

From this I conclude that composite can not achieve 256 dots/pixels, and image will be displayed with color data loss?

Then how old good CRT monitors were able to display very decent 256 horizontal dot picture over composite?


texts: How to test Pulse Code Modulated sound signal?

texts:
I'm trying to perform a PDM to PCM conversion. The PDM signal is coming from MEMS microphone.
There are different decimation approaches like FIR, CIC, cascade Half Band(HB) filters and so on. How successful is the PCM signal I got and how accurate is the conversion? How can I measure this?
What comes to my mind is to excite the microphone with a sinus tone and time-domain graph, recording the PCM signal and playing it as sound (this may be relative) or examine the frequency response.


texts: X2 capacitor alternative component or circuit?

texts:
My computer monitor (Samsung Syncmaster 732N) started to fail and it seems some capacitors have gone bad. They are all electrolitic but one is a CARLI MPX40 .47K275V-X2 capacitor, which where I live (Argentina) turns out is very hard to find.

I didn't know what an X2 capacitor was so I researched a little bit and it seems they are capacitors designed to be used as filters in the power line, and because of that, they have to meet higher standards of endurance regarding temperature, voltage surges, etc. Is that correct?

My question is, suppose I cannot get one of these where I live. Is there a suitable replacement component or circuit that would meet the same security standards? What could happen if I just put a common .47 electrolytic capacitor? Could it blow up or catch fire or something?

Thanks!


texts: Sending serial data over analog TV coaxial cable (RF-band)

texts:
TL;DR:
I would like to transfer digital serial data over an existing analog TV cable. How do I do that?

Full Question:
In order to transfer some data to a device's control lines remotely, I'm looking into inexpensive, but reliable methods that would use existing in-place system.
Suppose there is a cable running in the client's home that transfers analog RF-band TV signals (e.g. from an RF modulator into an old TV).  I'm looking for a DIY solution, or a prebuilt consumer-level product that would be able to send (and receive) some serial data over the standard analog TV coaxial cables.
I would like this system to coexist with the audio/video signals (VHF or UHF) on the line, and don't interfere with the current devices.  Additionally, power will be delivered to the devices at each end.  I'd also like the transmitters to be able to transmit at different channels, and decode the data back by selecting the channel.
I require both sending and receiving (either full-duplex or half-duplex) serial data (UART, TTL, etc) at a simple baud-rate (e.g. 9600, or if possible 115200 bps), reliably.
Question: Would I be able to build a DIY solution, or design an inexpensive board to handle my request?  Are there any solutions that would make this possible?
I was not able to find such a device or any schematics by searching the web.
Since I'm not familiar with the analog RF-band TV, I do not know how I would design something, if anything.  I would prefer either an existing schematics, or an existing product that would do this.  What route should I go?

Concept schematics:

simulate this circuit – Schematic created using CircuitLab
(n.b. If possible, I would like to have multiple transmitters and decoders.)


texts:
As far as I understand, two resistors are connected in parallel if the node at both ends of both resistors are the same. And in series if only one node is the same.

But what if between two resistors there is/are some component(s) like Voltage Source, Current Source, Ammeter, etc?

For example in this circuit:

The R2 is parallel to the R3. $$=> R_{23} = R_{2} || R_{3}$$

But after that, the R1 is parallel or in series to R23? And why?

And if there was no current source, would it change the relationship between R1 and R23?

Thanks.


texts: I'm trying to solder a few capacitor grounds to a small motor body. I'm using 60/40 flux core solder and I cannot get the solder to stick to the body of the motor! Is there some secret way of doing this?


texts:
We are given this schematic diagram, that our teacher called a high voltage power supply, then test the voltage of each capacitor.

Why is the voltage at C1 half of the voltage at C2 and is the wave at C1 still a sine wave?


texts: What kind of IC is "ATMLU324" "16B 1" "Z8J0534B"?

texts:
I recently bought what I thought it would be an ATtiny85. After a few unsuccessful tests, I discovered (guess what?) true ATtiny85 had "ATtiny85" printed on it, like this one:

Mine is this one:

The printing says:

ATMLU324
16B 1
Z8J0534B

I searched for a datasheet, but all I found was datasheet sites searching for it too. What is this chip?


texts: Recommendation ITU-R BT.1729 test image for 5:4 display

texts:
For radiated emissions testing according to EN 55032 CISPR 32 with displays of category 4, there is a Recommendation ITU-R BT.1729 which specifies a reference test pattern. The pattern is designed for use in either 16:9 aspect ratio or 4:3 aspect ratio.

I'm using a display, that will be used with highest resolution 1280 x 1024, which mean a 5:4 aspect ratio. The recommendation doesn't specify what to with this lower aspect ratio.

Is there a 5:4 test pattern available or how would one define and design this pattern?
Or can someone show me how to use the 4:3 pattern in a way that still respects the purpose of  reference test pattern?

  The reference test pattern has several purposes:
  – quality control of chrominance and luminance through the production chain;
  – checking and adjusting the chrominance and luminance alignment of broadcast equipment, particularly video monitors;
  – general testing of equipment for video production, emission and presentation;
  – establish that a video circuit is active and that associated audio is available;
  – check for audio-video synchronization;
  – check for correct connection of audio channels and correct audio levels.


texts: How to solve overflow stack problem problem in proteus?

texts:
I'm currently working on a countdown timer project.I used PIC18F452 microcontroller for my project. I compiled the code in mplab and it has succesfully been builtHowever in proteus, the countdown timer seems to be working until a certain point and then it will reset. In the simulation, it said that the stack overflow is forcing the device to reset.

The diagram of the circuit:

And here is the code:`

#include<p18f452.inc>
radix dec
bin     set 0x00
bcdH    set 0x01
MINUTE  set 0x03
SECOND  set 0x04
FXMin   set 0x06
FXSec   set 0x07
START   set 0x08

org 0x00
    goto init
org 0x08
    goto interrupt
org 0x18
    goto interrupt

init    movlw   0x07
        movwf   ADCON1
        setf    TRISB
        clrf    TRISC
        clrf    TRISD

;setting interrupt
    bcf INTCON, INT0IF
    bsf INTCON, INT0IE
    bcf INTCON3, INT1IF
    bsf INTCON3, INT1IE
    bcf INTCON3, INT2IF
    bsf INTCON3, INT2IE
    bsf INTCON3, INT2IP

;filling TMR0 value
    movlw   0x06
    movwf   T0CON
    movlw   0x67
    movwf   TMR0H
    movlw   0x68
    movwf   TMR0L
    bcf INTCON, TMR0IF
    bsf INTCON, TMR0IE
    bsf INTCON2, TMR0IP
    bsf RCON,   IPEN
    clrf    PORTB
    clrf    PORTC
    clrf    PORTD
    clrf    CCP1CON
    bsf T0CON, TMR0ON

loop    bsf INTCON, GIE
        bsf INTCON, GIEL
        bsf INTCON, GIEH

show    movff   FXMin, PORTD
        movff   FXSec, PORTC
        bra loop

interrupt   btfsc   INTCON, INT0IF
            bra int00
            btfsc   INTCON3, INT1IF
            bra int01
            btfsc   INTCON3, INT2IF
            bra int02

checkstart  btfsc   INTCON, TMR0IF
            bra inttmr0

exit    retfie

int00   bcf    INTCON, INT0IF
        incf       MINUTE
        movlw    60
        cpfseq     MINUTE
        bra    calcBCD
        clrf       MINUTE
        bra    calcBCD

int01   bcf     INTCON,INT1IF
        setf          START
        bra           checkstart

int02   bcf     INTCON3,INT2IF
        clrf          MINUTE
        clrf          SECOND
        clrf          FXMin
        clrf          FXSec
        clrf          START
        bra           calcBCD

inttmr0 bcf INTCON, TMR0IF
        movlw   0x06    ;0x47
        movwf   T0CON
        movlw   0x90    ;0x00
        movwf   TMR0H
        movlw   0x00
        movwf   TMR0L
        bsf     T0CON, TMR0ON
        movlw   0xFF
        cpfseq  START
        bra     calcBCD
        bra     COUNTDOWNLOOP

COUNTDOWNLOOP nop

CHECK   movlw   0x00
        cpfseq  SECOND
        bra DECSEC
        bra CHECKMIN

DECSEC  decf    SECOND
        bra     calcBCD

CHECKMIN movlw  0x00
        cpfseq  MINUTE
        bra DECMIN
        bra calcBCD;

DECMIN  decf    MINUTE
        movlw   60
        movwf   SECOND
        bra     DECSEC

calcBCD movff   MINUTE, bin
        call    bin2bcd
        movwf   FXMin
        movff   SECOND, bin
        call    bin2bcd
        movwf   FXSec
        bra     show
        retfie

bin2bcd clrf    WREG
        clrf    bcdH
        bsf     bcdH,0

bcd_lp  rlcf    bin
        addwfc  WREG
        daw
        rlcf    bcdH
        bnc     bcd_lp
        return

return

end

`


texts: Square wave oscillator on PSpice simulation

texts:
I'm new to PSpice and here I was trying to simulate a square wave oscillator using a LM193 on PSpice. Here is the circuit that I've created there:

Edit: The capacitor C1 has an IC set to 0
However, when I plot the waveform of Vout, this is the obtained result:

Even though this form "resembles" a square wave, it's not even close to what I wanted. I'd be really thankful if someone could explain a couple of things to me:

Why is the signal oscillating only between 0 and -5V? Shouldn't it be between -Vsat and + Vsat, where Vsat is used to designate the saturation voltage of the Op Amp? What have I done wrong in this circuit?

Moreover, isn't the output voltage supposed to be more symmetrical (therefore resembling more a square wave)? If someone could give me some advice on how to make it more like it I'd appreciate it.

Thanks a lot for your attention!


texts: does hot and neutral wire produce less heat in a single conduit than in two separate conduits?

texts:
an electrician is telling me that having the 2 conductors (hot and neutral) for a branch circuit from my home Electrical Panel in the same buried conduit will produce less heat because the 2 magnetic fields cancel out.
i think the magnetic fields cancel (ie a current loop probe will show 0 net current) but the heat in each conductor is produced by electron flow and not affected by the other conductor.


texts: wireless I2C/SPI communication over XBEE with multiple slaves

texts:
Designing a device for vibration condition monitoring, using multiple wireless accelerometers. Intending to have an arduino as the main controller and peripheral accelerometers sending the vibration data to this for analysis and storage.

Having difficulty with the wireless part of the design. Digital accelerometers use either a I2C or an SPI protocol, and I can't really find a wireless device that will natively interact with it.
I found a BLE module that could, but it lacked the required data rate (https://www.bluegiga.com/en-US/products/ble121lr-bluetooth-smart-long/).
Currently looking into using a XBee module, but I am not familiar with the technology. I understand that I will need to convert the accelerometer data to UART, but am not 100% sure how.

I'm not sure if XBee is the best path to look into, or if it is capable of handling multiple accelerometers. Bit of a novice with this sort of stuff, so I would appreciate someone letting me know if i'm heading in the right direction with the wireless side of things, and to also recommend resources for me to look into.


texts: How to Choose a Lead Acid Battery Charger?

texts:
It has been suggested that you can charge sealed lead acid batteries with a normal power supply.

On the other hand, chargers are available for purchase, but cost almost $100.

Is there a reason to go with the store bought battery charger?

If so, I have six 6V lead acid batteries that I need to charge.  The maximum allowed charge current is 1.5A.  Many chargers (unlike the one I linked above) only put 2A or more.  Is there a way to make that sort of charger easily work?

And do I really need to spend almost $600 on chargers if I want to be able to charge all of my batteries at once?  Or can I hook them up in parallel.  I have been reading pretty extensively on this over the last couple of days, but am finding conflicting information everywhere.  The Battery University source seems good, but it also isn't immediately clear to me what to purchase. I don't want to screw up and end up buying an expensive charger that doesn't work, but I also don't want to spend days figuring out how these work, when this is just a small component of an experiment that I need to have working ASAP.  (Therefore, I will go with whatever is easiest!)


texts: Zigbee network setup for transmission from E(End module) to C(Coordinator) via R(non polling router)

texts:
I am trying to setup a cluster-tree with 3-4 xbee 865 (S8), with nodes configured as
1 - Coordinator (API mode)
1 - Standard Router (API mode)
1 - Non Routing Module

I want network to setup such that, Communication between the coordinator and the non-routing module always takes via standard router (even if the devices are kept in range.)

What steps must be carried out to setup such a network??
Should i configure the DH/DL of coordinator to SH/SL of router and DH/DL of router to SH/SL of module  (point-to-point communication) and have a micro-controller at Standard router to process the data received from Coordinator and modify the API frames to route data to non-routing module?? in such a case, the reverse transmission (data from module to coordinator) will not be done without modifying DH/DL of both router and module.
Can such a network be setup without micro-controller, using xctu software
only?? what steps??
Should i use zigbee api frames or digimesh api frames??
How do i ensure that the data transfer between the coordinator (to and fro) is done via router only??? (as all 3 are in the range, my attempts have resulted to transmission of data between the coordinator and the module directly, bypassing the router).

Note: xbee 865 (S8) doesnt have MYID


texts: Using 74HC154 with LEDS current resistor

texts:
I am using a 74HC154 to control 10 LEDs in a design.
Since only one LED will be on at a time I wanted to use one resistor rather than a resistor per LED. Is there any difference between the two designs? Is one better than the other? Or both will work correctly?

Here is an examples of what I mean. Resistor values are not accurate.


texts: Liquid / water level detection safely using AC voltage - Industrial circuit explanation

texts:
I am planning on working on a project to build a controller which will be used to detect the levels of water treatment chemical tanks and display them on a bar graph. then switch off the dosing pumps once the chemical tank level reaches completely low.

There are plenty of circuit diagrams on the internet to simply achieve that using DC voltages and op-amps. But applying DC voltages are not reliable and may cause electro-metal plating and the electrodes to dissolve. Then I came to know that LM1830 is designed to overcome that issue. Well, I'm curious about that and wanted to know really how this is done in industrial circuits. So I removed a Chinese industrial level control relay and grabbed their design as follows. (Please note that I have erased the brand name and model as it may go against the manufacturer's design rules.)

Now my questions are,

Why is the AC output directly after the transformer, is shorted with a capacitor, without that capacitor wouldn't the E3 probe deliver the AC voltage?
Here probe E3 supplies the voltage to the liquid and E1 & E2 receives it back. But the M7 capacitor in the receiving circuitry limits the current in one direction only. So the current through the liquid still remains DC. Is it correct?
The transformer appears to be 230/24 step down. So this amount of voltage applied to the liquid, isn't it potentially dangerous. As the higher the voltage is, its easier to dissolve the electrodes.
Is this mechanism technically safe to use in drinking water tanks?


texts: Thermoelectric couple heating on both sides

texts: In college my physics professor showed us a thermoelectric couple powering a fan.  He also explained how if you apply a current it cools one side and heats the other side.  I have been working on a cooler that uses a TEC to cool the inside (see my posts Considerations for solar powered thermoelectric cooler with fan and 12V fan does not work when in parallel but does in series) but something is wrong.  When I give power to the TEC in the correct direction, one side gets so hot I burned myself, but the other side was getting warm.  Why is this side not getting cool?


texts: How do i go about getting my own chip made?

texts:
I need a chip like the esp32 with an output  channel thats at least 48kHz. Also, it needs to be able to pair and connect to another esp32 over bluetooth, kind of like Airpods.

Basically, if I want to get a custom IC made, what so i do? What kind of company do I contact or who do i talk to, assuming I have the money (I dont but there's a reasonable chance I convince someone it's a worthy investment)? Any clue?


texts: Altium Designer: How to handle these type of Nets?

texts:
I have such complicated Bus [0..4], which go out from Page 2 to Page 1, and then from Page 1 to Page 3 as shown in the figure below which is a Top Sheet:

I receive the following error when I compile the project:

Net (xxx) contains multiple output sheet entrys

I still receive the same error even if I change port names and/or net names..

How to solve it ?!


texts: Synchonous finite state machine from output sequence

texts:
I'm reviewing for my exam and this questing popped from questions that were previously asked in the exam. Problem is below.

Question: I'm totally confused about this, how do I get started?

Trial: My first intuition is that I should make 4 D flip flop sequence and put the RUN input to the enable input of the last 2 Dff's, and take the A and B from the first two. But I'm pretty sure that this isn't what is wanted here because there should be excitation function from the Dff.

Thanks!


texts: Hot air rework temperature to avoid solder melt on opposite end

texts:
When removing/replacing chips. Is it safer to use little to no air flow but higher temp heat or lower heat with more airflow?

My hot air station is a model 852d+ with a max temp setting of 500c and max airflow temp of 8.

I was testing melting a ball of lead free solder  with a 4mm tip and at 365c 1 air flow speed it melts in 20 seconds. At 340c 4 air speed it melts same amount of time but not sure if more air speed is dangerous for near by components or components on the underside of the board.

Is the goal to remove chip as quickly as possible or at a slower time? I'm working on small mobile device boards that don't require a preheater.

I've ran into issues before while practicing where components underneath on opposite end of the board suffered from the heat causing shorts under the bgas.


texts: Having trouble understanding circuit diagram (paper touchpad)

texts:
A few years ago someone posted a demo on youtube for a "paper trackpad" which is basically an alternative for your laptop mouse (see here). This particular project uses Arduino as a microcontroller. Unfortunately, I was unable to get any schematics from the creator because the post was so old however, I did find a diagram of the circuit.

I had a few questions (I am a completely new to electronics sorry).
The capacitors being used in the diagram, are they for stabilizing the signal?
The wires A0, A1, A2, A3 are they being connected to the Arduino?

Can someone please offer their guidance?

This is the link to the original project.


texts: Possible to have pulses with constant voltage?

texts:
tl;dr: I'm asserting that you cannot have constant voltage pulses in a dc circuit. The pulses will be variations in potential or current that some appropriate device picks up. I think I found misinformation on a car forum.

I'm wondering how a car tachometer works. On this LS1 engine forum there is a discussion. "Mr_Dude1" says that :

  the LS1 tach signal looks like . . .just shy of 5v square wave, 4 pulses per every TWO revs. that is, 2 pulses per rev. like a 4 cyl car.

  it is not a varying voltage... the frequency (how close the little
  bumps in the pic are to each other) is what changes.

He attaches a picture of a square wave pattern with no axis labels, so I'm not sure what is pulsing. I think there must be electrical pulses, which are either voltage or current, but I think these types of pulses are inextricably linked due to ohm's law. I have to do some surgery on the wirebundle from the ECU of my car to get at the tach wire, so I though I'd ask you guys first what's going on here.

I don't think I can use a multimeter to test this. If the tach wire is 12V on the car, I suspect that the multimeter will read either 0, 6, or 12V (or some other whacky value) depending on the algorithm used for computing voltage. I think an oscilloscope would be the proper tool here.


texts: Current limiting for constant current source

texts:
I have 6 LED strips, each of them requires 1080mA & 36V DC.

I've found a Constant Current driver which can supply up to 8.9A & 36VDC. As there is no resistor on the strip so I think it should be current driven for high efficiency.

The driver is: Meanwell HLG-320H-36B

LED Specs:
- Forward voltage: 33.6V - 36V
- Forward current: 0.9A - 2.7A

I planned to wire all 6 LED strips in parallel and use a current limiter circuit to protect each strip. So if one the strips is down, the others won't sink more current.

I want to ask is this a good approach ? And how to build that current limiter ? Any suggestion or instruction ?

As the driver is being shipped to me, I have to use it anyway. So is there any other solution that can help me light up my LED with the driver ?

Thanks.

p/s: I don't want to use separated driver for each strip because of the price & shipping fee.


texts:
I want to calculate the lifetime of a battery operated device. Without self discharge of the battery, it is easy to calculate the lifetime, it's just the battery capacity \$Q\$ (given in mAh) divided by the average current \$I\$ (given in mA).

In my case I have for example 300 mAh and average current of 3 uA. I get a lifetime of 100,000 h or 11.41 years. The self discharge of the battery is given as % per year, e.g. 5% per year. The battery capacity is then:

$$Q = Q_0 * D^T$$

Where:
\$Q_0\$ = capacity at the beginning
\$D\$ = the discharge rate (in my example 0.95)
\$T\$ = the time expressed in years

The lifetime in hours is:

$$t = \dfrac{Q}{I}$$

I replace \$Q\$ by the above equation:

$$t = \dfrac{Q_0 * D^{\genfrac (){1pt}{1}{t}{8760}}}{I}$$

My first question: Is my equation for \$t\$ OK or is there a failure?

My second question: If the equation is OK, how to solve it to get \$t\$?

I asked that question on MathOverflow as well.


texts: How to choose an ARM Cortex M3 microcontroller?

texts:
Based on my rough requirements of being in the 36 to 72 MHz range, having 16kb+ SRAM, 128kb+ flash, being programmable in C, I have decided that for my application I want to use an ARM Cortex M3 MCU.

The question is, what criteria do people use to pick which M3 version to use? There are many possible vendors such as TI, ST, NXP, Freescale, etc, etc.

A main differentiator from my standpoint would be ease of programming. Ideally I test it out on a breakout/development board, followed by implementation in my own PCB.


texts: Altium Camtastic Auto-Rout PCB Border is routing over edge of board

texts:
I typically draw rout tool paths by hand, but I though I would give Altium's built-in router a try.  The command I am talking about is Rout->Auto-Rout PCB Border within the CAM document mode.

The tool properly finds the board outline, but the resulting rout path (when I export Gerbers) is right on top of the board outline - not butting up to the board edge like I am used to seeing when I rout it manually.

Am I missing a setting or maybe just interpreting the rout path Gerber wrong?

I tried some different settings for the rout tool in Tables->NC Tools->Tool Compensation but it isn't changing what I get.

Does anyone who has used this feature have some advice about what is happening?


texts: What contributes gate charge in a MOSFET besides gate-source capacitance and gate-drain capacitance?

texts:
I'm confused by the datasheet for the FQB55N10:

75nC typical total gate charge = 13nC typical gate-source charge + 36nC typical gate-drain charge + 26nC typical gate charge from some other mystery source, namely... what? This is a three terminal device.


texts: I'm looking for a extender/increase in my bluetooth range on my phone, can it really be we don't have any thing like that, or can I just take my phone apart and solder a 2,4ghz antenna to it?


texts:
The basic operators of the boolean algebra are AND, OR, NOT. The modern digital circuits are based on this mathematical concept (Shannon's thesis, 1938).
I am wondering whether the Tri-State Buffer can be build (represented logically) with only these three operators (gates)?


texts:
I don't know that much about electronics, but I was able to put together this PIR module:

(original)

and a LED strip and everything works just fine, when the PIR detects motion, it turns the strip on. Then after set time (you can configure that with the buttons on the module, as well as brightness and other things) it turns off..

I would however like to have some sort of manual control over the thing - I just want to turn on the strip manually If I want to, I don't care about manually turning it off - I can do that at the side of power supply/socket. I thought I could just take my multimeter, probe a few points for continuity and finally end up soldering a simple on/off switch between the input and output of +12 rail on the sensor board (the two gold plates).

Would that work? Is there any possibility of damaging the board that way? If I am not mistaken, this should basically simulate two switches in parallel in a circuit right?

I understand that I would lose brightness control I programmed onto the board. Right now when the PIR tells the board to turn on, it only gives about 80% of input voltage on the output and that controls the brightness (I didn't see any flickering on camera, so it should't be PWM, but I could be wrong). Would there be another simple way of soldering a switch that would keep the board programming? Bypassing just the PIR and not the whole board maybe?

Sadly I don't have any schematic for the board.

Thank you very much, sorry for my english, not a native language.


texts: Op-amp circuit works correctly only when the oscilloscope's probe is connected to it

texts:
I'm using a piezoelectric speaker as an shock sensor. I made a simple non-inverting amplifier using the MCP6021 op-amp as shown in the circuit below. I'm only interesting in the positive output of the speaker so I put a diode to protect the op-amp's input from the negative spikes.

The circuit works as expected when the the oscilloscope's probe is connected to the input (either before or after the diode). When I disconnect the probe from the input, the output of the op-amp seems the become unstable. Sometimes it oscillates at different voltage levels and sometimes it saturates at the positive rail.

What could cause this behavior?