texts: How to pass a DBWx-value 2 block-calls deep on Siemens S7-400/Simatic

texts:
I'm working on code that was transported from a Siemens S5 PLC to S7. The code works with an old FC(FC2 in the example) that uses a WORD-input called "BNR" to load/save data. When block FC2 is called, the BNR-input is simply given a value such as "DBW0", but without an open DB-connection. There's no value in DBW0, so it seems to act as a pointer in the block FC2 where it is used as such:
// Read data from DB to MW250
OPN DB10
L #BNR
T MW250

// Execute program and change corresponding bits in MW250

// Write data back to DB
OPN DB10
L MW250
T #BNR

In reality more DB's and MW's are used but you get the point. However, I would like to "mask" the FC by creating a new FC(FC300 in the example) that simulates all the unneccesary I/O and simply passes on all the parameters we still need to the old FC2. The BNR-input is renamed to "data" in FC300 for clarity.
The problem is that we cannot pass our "DBW0" 2 levels deep. It works in the first block call for FC300, but when sending #data to the BNR-input, it is interpreted as the value in the opened DB. So BNR loads the value in "DB10.DBW0", wich is a useless value. BNR needs to point to "DBW0" I have tried thinking of a way to turn the whole thing into a pointer but BNR in FC2 is a word which is only 2 bytes.
Even if I could remove the DB-call in FC300 it doesn't solve the problem because this throws a "Area length error when reading" in the diagnostic buffer because the PLC is trying to access #data(in this case DBW0) without a DB open. It's confusing because it does work in OB1 even though no DB is opened.
Simulation of the problem:
OB1 calls FC300(mask) wich calls FC2(old/original FC).
FC300 => data is used as pointer to adress in DB => read/write to DB
FC2 => BNR(data) is used as integer value => no read/write to DB

I understand "masking" the old FC is probably strange and bad practice, it is also not my desired solution. But some people are so afraid to change code that works(despite it being from 1982) in our company that I'm trying to offer an alternative solution.


texts: Vibrating bracelet controlled from cell phone

texts:
I was inspired by this project: How do I build a bracelet that vibrates once every n minutes? but I want to take it a step further.

The main idea is creating a vibrating bracelet that is controlled by an application from your phone, which could be used as an alarm.

To be more specific, I've thought of creating an app, where the user enters the time that must pass, until the bracelet starts vibrating for a specific amount of time.

I have almost no experience on projects like this so I would appreciate it a lot if you could give me some instructions on how to deal with this one.

I am thinking of using an arduino gemma due to its really small size. Also I don't know if I am right, but should the app and the arduino be connected via bluetooth?

Finally, to get it a little more fancy I would also like to add this idea:
The user of the app records himself telling the tasks he must accomplish the next morning. So, when the bracelet starts vibrating to wake him up he can use it( the bracelet) to hear the message. Could I add something like that: https://www.adafruit.com/product/1890 to my cirquit? Is this something that can be easily implemented?

Thanks in advance for any response!!!

EDIT

Ok, I've done some research and my questions now are more specific. I decided to keep only the vibration and put aside the audio transportation. I want to use arduino gemma or arduino flora. I also read that gemma is most suitable for simple led projects, so would it be able to perform my idea? Also as far as the bluetooth is considered, can hc-06 be used with arduino gemma or flora...I failed to find any projects on the internet where they are combined.


texts: Electric current injected to ionized gas around laser beam or electron beam to make miles high ham radio antenna

texts:
I found there was a technology which uses air plasma around electron beam or laser beam and it is about injecting current in to this plasma to make far away bombs explode  or damage car electronic, or destroy nuclear missiles.

This technology can be scaled up but I am interested in miles high laser or electron beam which used as ham radio antenna.

I found 5 dollars worth of green lasers can beam 10-20 miles far away and I want to use a beam which was extremely cheap to obtain.

Can you tell me which technology hardware is the most suitable for ham radio operators?


texts: Repurpose an old lamp with LEDs. Where to start

texts:
I have an old lamp which I would like to repurpose to use LEDs.  I'm not really sure where to start so I'm looking for some pointers if this isn't the place. I also don't know how much of this is practical or sensible.  Here's my ideal.

I'd like to replace the existing incandescent bulb with LEDs.
I'd like (if possible) to have the lamp battery powered.
I was wondering if it would be possible to have a "charging" plug to charge batteries.
For charging or power I was considering using something plug-able, like a micro-usb charger.

I've done basic electrical stuff (replacing ceiling light fittings is about as advanced as I get), I have a very basic knowledge of electronics, but I'm quite a geek so I'm hoping I can make it work.

I realise I may be biting off more than I can chew but I wanted to get some feedback, if possible.


texts: What does a half-digit means in case of accuracy?

texts: I am just wondering what does it mean when somone says something like"3 and 1/2 digit" in case of accuracy of test equipments (or maybe A/D converters). Can somone explain this a bit with some numbers as example?


texts: MCP2551 to monitor CAN activity without processor

texts: If I was to connect an MCP2551 to a CAN network and link the TX and RX processor connections would this allow monitoring of any activity on the network as just a 5v pulse train without disturbing the network?


texts: PCB Connector for Sensitive ADC Component

texts:
I am evaluating this expensive BGA ADC component, which has 16 analog inputs, by placing it on a custom dev board.

The analog input signals to this chip dev board will be 20 MHz current-based signals in the 100pA to 1uA RMS range. These signals originate from an arrayed APD detector which is being kept separate during development.

What type of board-to-board connector should be used to apply these currents to the ADC while maintaining signal integrity. Presumably I need a very short connector with extremely low parasitic capacitance, and probably EMI shielding.

The ADC's integrating capacitor is around 3pF, so I think the parasitic capacitance must be significantly less.


texts: Applying kirchoffs law in a simple circuit

texts: Can we apply Kirchhoff's volatge law in this simple circuit and say V1=-r1I1 and V2=r2I2 or is there an other connection between voltages and currents?


texts: How could I read a digital input (an open/closed switch) from a smartphone without a digitizing board?

texts:
I have to read a single digital input signal (a trivial open/closed-circuit push button) and use this signal in an Android application on a smartphone.

Of course, I could connect a tiny Arduino-like board to the USB port of the smartphone, use the digital input pins of this board to read the electrical signal and pass a message to the Android app but this task is so simple that I would like to avoid the use of any addictional board.

So, I wonder if it would be possible to (ab)use a regular headset wire for this task.

I would like to connect a regular 3.5mm headset to the smartphone, cut away the actual speakers and microphone, connect two of the resulting free wires to my push button and read the open/closed-status change of the switch from my app.

As long as I can see, Android has a ACTION_HEADSET_PLUG intent and a AudioManager.isWiredHeadsetOn() function so this is probably possible.

Does anybody have any idea about the correct wiring I should use? In particular, should I insert a resistor/capacitor to protect the inner circuitry of the audio board?

Any suggestion about the software side?

Please note that I'm only interested in reading the change of the switch status from open to closed or viceversa. I do not need to know the current status of the switch.

PS: No, I'm not willing to destroy the smartphone and connect the external push button to the existing keyboard.


texts: How MDIO , SGMII is connected with phy chip and ethernet controller?

texts:
I am trying to get a picture like how all these are connected.

My understanding is that

EthernetController ->connects to PhyChip using MDIO

Since, while writing linux drivers I have seen I have used MDIO to talk to phychip. My question is
where is Mac chip? Also, where is SGMMI in the picture? How are they connected? I am looking for a big picture.


texts:
I have a couple of questions regarding the PID controllers; maybe it is that I have not understood the concept very well.

I will formulate my question with a case:

I have a system which consists of a warp beam in which a thread is wound and a motor to rotate the warp beam (“Process” according to the picture below). This thread should be fed at a constant tension to another machine.
The motor is connected to a control motion in which we have just to specify the speed at which the motor should rotate, so we have a PID controller to calculate the speed at which the motor should run. To measure the tension of the thread we have a tension sensor.

Now the input of the PID controller is the error, which has units of tension (Newtons converted to mA), but we are feeding the output of the PID controller to the process as the rpm for the motors. How is that possible? I mean if I have at the input of the PID units of Newton and the value for the process should be rpm. Does the conversion of these units is done “through” the units of the Ki, Kp and Kd parameters?

And my second question: Let´s say for a moment that the tension in the thread matches with the set point value, which means error is zero (or at least in an acceptable range, to consider it zero), and thus the controller output will be zero. But if the PID output is zero, the input to the process is zero, which I do not understand because the motor should keep running at least at the same speed. So how is that possible? Or what is wrong with my analysis?

Thanks,


texts: PCB conformal coating / potting / resin in an IP65 case

texts:
I'm designing a PCB that will be installed in an IP65 plastic case.
The device will be installed in multiple scenarios and regions (indoors, outdoors, high/lo temperatures, high/lo humidity etc).
The device is a BLE SoC with a relay and is is directly connected to the mains (the device has a 3W power supply on the PCB).
The device will be installed in a fixed place and should last for at leat 10 years without maintenance.
I would like to know if it is necessary to apply conformal coating, potting or any type of resin to protect the device from possible condensation or, as the PCB is inside a plastic IP65 case, it is not necessary.
In case it is necessary, which conformal coating, potting or resin would be suitable for this application?


texts: Unidentified Integrated Circuit - NEC 24 Prong

texts:
Today I was taking apart an old typewriter and I have this IC that was in a socket. I took it out and started searching online to see what this IC does. I spent 20 minutes and nothing showed up about it. It is a

 NEC 833IE9
 D2364EC 071.

Any Help?


texts: How do I keep my inventory items well-organized and tidy?

texts:
My personal lab at home is a total mess!

I was keeping my inventory items in small storage cabinets like below:

But as my inventory expanded in time, they became inadequate to hold all of my items neatly. My work space at home is limited, so I don't want to fill up my room with more cabinets.

I filled 100, 1k, 10k, 100k,... resistors to a cabinet. 47, 470, 4.7k,... resistors to another. This way, all similar resistors to one separate cabinet. All capacitors to another. Transistors, voltage regulators, inductors, ICs, connectors, etc to separate cabinets. For example, when I need a specific BJT in TO-92 package, I have to search among all those TO-92 transistors for minutes with a magnifier in my hand.

The ones in the cabinet are the most frequently used ones. There are much more items stuffed in packs, waiting to be organized someday...

Is this mess normal for someone working at small space like me?

Also, how do I keep stock control of my equipment? Should I prefer a computer software for this?


texts: Lithium polymer battery charger with LDO and AVR

texts:
I am planning to use this in my project.
The AVR microcontroller is asleep most of the time (less than 500 µA), and the current draw raises every minute up to 100 mA, but it lasts 500 ms maximum. So I think connecting the charger directly is not a problem.

In the original LDO circuit there are two Schottky diodes connected. I was told that the first one is to prevent reverse-voltage and the second to protect the LDO when Vout > Vin. I was also told that the first diode's voltage drop will prevent me from using the full capacity of the battery...

So I guess the best way is to remove the first diode. But is this circuit going to work at all?

The AVR battery voltage measurment is a voltage divider controlled by a MOSFET. The voltage divider ratio is 1:2, so the input voltage is always lower than the AVR's VCC.


texts: Twisted pair for long distance voltage measurement

texts:
I want to measure the voltage drop across a shunt, but the ADC performing the measurement will be far from the actual shunt - perhaps five meters.

I'll need to measure voltage drops across the shunt to about 0.1 mV, so stray signals of that magnitude could be a problem.

Can I just run two pieces of 22 AWG wire from the shunt to the ADC, or would something like twisted lair help cancel out noise, and ensure the wire runs are the same length (the latter may not matter since the current flow is minimal - only enough to satisfy the ADC cap).

The environment is a camper van - so it is fairly noisy as it has various DC and AC wiring running all over the place.


texts: Can't make Wiegand RFID-reader and Odroid C2 work properly

texts:
I've got one pretty interesting task. The task is the following:
Odroid C2 (Single board computer) running on Android 5.1 has to recieve card id from RFID-reader over Wiegand interface.
To accomplish this my app listens to UART port (/dev/ttyS1) with SU permission:

public SerialPort(...){
    Process su = Runtime.getRuntime().exec("/system/bin/su");
    String cmd = "chmod 666 " + "path/to/the/device" + "\n"
                    + "exit\n";
    su.getOutputStream().write(cmd.getBytes());
    ...
}

and tty configuration in JNI as follows:

JNIEXPORT jobject JNICALL Java_android_1serialport_1api_SerialPort_open(...) {
    int fd;
    speed_t speed;
    jobject mFileDescriptor;

        /* Opening device */
    {
        fd = open("path/to/the/device", O_RDWR | O_NOCTTY | O_NDELAY);
    }
        //all check blocks are omitted for the sake of simplicity

        /* Configure device */
    {
        struct termios cfg;

        cfsetospeed(&cfg, speed);
        cfsetispeed(&cfg, speed);

        cfg.c_cflag |= (CLOCAL | CREAD);     //ignore modem controls
        cfg.c_cflag &= ~CSIZE;
        cfg.c_cflag |= CS8;          //8-bit characters
        cfg.c_cflag &= ~PARENB;      //no parity bit
        cfg.c_cflag &= ~CSTOPB;      //only need 1 stop bit
        cfg.c_cflag &= ~CRTSCTS;     //no hardware flowcontrol

        //setup for non-canonical mode
        cfg.c_iflag &= ~(IGNBRK | BRKINT | PARMRK | ISTRIP | INLCR | IGNCR
        | ICRNL | IXON);
        cfg.c_lflag &= ~(ECHO | ECHONL | ICANON | ISIG | IEXTEN);
        cfg.c_oflag &= ~OPOST;

        //fetch bytes as they become available
        cfg.c_cc[VMIN] = 1;
        cfg.c_cc[VTIME] = 0;

        //creating FileDescriptor...

        return mFileDescriptor;
    }

Lets move on to the Java side...Here we simply pass corresponding FileDescriptor as argument to the FileInputStream object to read from it later

public SerialPort(...){
    ...
    FileInputStream mFileInputStream;
    FileDescriptor mFd;

    mFd = open(...); //recieve newly created FileDescriptor

    mFileInputStream = new FileInputStream(mFd); //pass it as argument to FileInputStream
    ...
}

I read data from FileInputStream in another class with separate thread. And here is where my problem comes out.
Whenever I place rfid card in front of the reader read() function gets triggered 15 times with hex_val equal to FC (Dec = 252).

public FooClass(...){
    ...
    byte[] buffer = new byte[64];

    int size = mInputStream.read(buffer);
    if (size > 0) {

        for (int j = 0; j < buffer.length; j++) {
            String val = String.format("%02X ", buffer[j]);
            Log.v("hex_val", val);
        }
    }
    ...
}

Searching through the internet I stumbled across one page

https://www.pololu.com/docs/0J9/3.c.07

mentioning this value as an error byte.

I will be infinitely grateful for any suggestion or concreate answers to the questions below:

Is my UART configuration appropriate, or not? Should it be specific for a Wiegand protocol?
Why do I recieve 15 bytes as opposed to 3Bytes (W26) or 4Bytes (W34)?

P.S. If you have working Java or C sketch, please leave it here, thank you.


texts: Issue on reset on RingCounter in Verilog

texts:
Well I keep having this problem on many modules and it never bothered me as I was just experimenting. However now I am trying to be 100% correct so... I have this ring counter for example and I feed the ouput on 8 leds out of an FPGA. Alright, it works as a charm but reset condition is faulty. When I feed the binary on the FPGA it starts correct from MSB=1 and the rest of bits are 0. However when I press reset the led pattern just freezes and continues operation when I release button. The problem in some modules was that I foolishly had the same reset for counter and clock so it was obvious why this was heppening. However now I just drive it from another pulldown resistor button and keep having this issue.

module Ringcounter # ( parameter LENGTH = 8) (
input clk, rst,
output [LENGTH-1:0]q
    );
reg [LENGTH-1:0] f;
genvar i;
for (i = 0; i < LENGTH; i = i+1)
assign q[i]=f[i];

always @ (posedge clk)begin
if (rst) begin f[LENGTH-1]=1'b1; f[LENGTH-2:0]=0; end
else
f={f[0],f[LENGTH-1:1]};
end
endmodule


texts:
I know that the inverter switches when it crosses switching threshold,but I have doubt that  inverter switching should be considered when it is in Vil region or vih region.

for example ,
suppose Vm=0.45
Vil=0.35
vih=0.55

so when v input changes above vih or below vil then only switching should be considered  and not when it crosses Vm...Is this thought process right?if yes then what is true meaning of Vm.


texts: op amplifier with both negative and positive feedback

texts:
For must of the circuits, I know how to analyze them but I am having difficulty with this one, and with the understanding of its purpose.

the switch changes his state every 0.5 msec.
VZ is 5.6V

the problem I am having with this circuit, which is where I think I am doing my mistakes, is that I can't decide if this is a negative feedback or positive feedback.
Also because of my fail to analyze the circuit correctly, I can't understand what is it for? I think it supposed to be astable multivibrator but I can't confirm it.

edit :
the output of the circuit is the output of the opamp.
image link : img

edit2 :
assume general ideal op-amp, I used the TL because it was the 1st op-amp I saw.

edit 3:
I am trying to draw the timing diagram and this is what I get and I can't understand why I am wrong here.
sorry for the poor handwriting, no ruler was around.
Vs = Vswitch. Vx= Voltage point between R1 and R2.

link


texts: Non-stop ADC for full quantization of arbitrary time period signal average. Do ADCs work like this?

texts:
Lets say I have a light intensity sensor and I want to measure the exact average light intensity for one hour using an ADC sampling time that is much less than the input signal frequency.  Lets also say I could setup as many ADC's as needed so that the moment one is converting, one is sampling... no overlaps or gaps between any sampling period.

Will this allow me to obtain the exact average light intensity for as long as this sampling happens?

From my understanding an ADC uses an RC circuit, charging up to the voltage of the source.  Does it also deplete if the voltage drops during the sampling?

A simplified example:

The ADC has a sample time of 1ms.  The sensor gives out a voltage equivalent to 20 units for 0.5ms.  The next 0.5ms of sampling the sensor is at 0 units.  Do I get an ADC value of 10 units for that sample period?

I am not after any particular signal frequency, just the average intensity.  Is it possible to do this or do I have to focus on ensuring the sample rate is >= the Nyquist frequency to obtain this data.


texts: Why is eMMC in a BGA package, despite only using a small number of pins?

texts:
eMMC comes in BGA packages with many pins (100-200), yet it only uses a few of them (10-30).  Why doesn't it come in a package with fewer pins instead, as wouldn't this be cheaper and easier to fit/inspect?

The BGA 153 pinout (designed by committee) can be found in this blog post.


texts: What would it take for me to build something similar to the mockup below?


texts:
I'm trying to solve this problem, and i seem to be unable to solve it, part of the reason being that the there is a dependent current source in here, so I can't find the Thevenin equivalent resistance and voltage, I did find out the Ix current value of 5 Amps tho.

simulate this circuit – Schematic created using CircuitLab

So I would like to ask, if anyone knows the steps to simplifying a circuit with dependent current sources, independent voltage sources and resistors, into a Thevenin equivalent circuit.

I tried to use Kirchoff's current law, to find voltage at nodes and then using that I calculated the value of the current flow, but I am not able to find out how to find the Thevenin equivalent resistance of the circuit, which is the very last step I need to take to get the Thevenin equivalent of the circuit I'm trying to simplify.

Got the circuit now! The Question was: Find the Thevenin equivalent of the circuit to the left of terminals A and B (do not include the load resistor RL)


texts: How much maximum electricity bill (units) can be generated on 2 KW connection?

texts:
I have got a bill of approx 14000 Units (50000 INR) for a month on 2kW connection.
As per my analysis and understanding, it can't be more than 2 * 24 HRs * 30 Days = 1440. I think electricity meter is faulty and it has jumped 14000 Units in a month.

Demand shown in electricity meter is 0. As per my understanding If these much of units gets produced then demand will be near 10.

I have also asked the concerned department they were saying it is possible (but didn't make it clear) and electricity meter is working fine.

Am I missing something ? Plz help me understanding this .

Demand : The maximum demand value is the average from the instantaneous power (in kW or kVA) during a defined time interval, usually every 15 minutes (this time interval will depend on each country).


texts: Design a high accuracy ADC circuit (example of differential ADC LTC2348 for PSD signals)

texts:
Context: I am about to send a board to manufacturing which includes the LTC2348 for high-precision acquisition of the 3 analog outputs (single-ended) of a PSD frontend. The 3 signals are Xdiff (proportional to X displacement, +/-10V), Ydiff (same for Y), Sum (0-10V, the scaled-down norm of the [Xdiff,Ydiff] vector) (100Hz bandwidth), therefore they have to be acquired at the same time. I'm aiming at an accuracy of 300uV peak on each channel, so I need to be careful right?
Could you review the design description below and tell me what should be improved? I have doubts on grounding in particular.
Signal conditioning: My PCB has 3 SMA connectors, each with a passive first order RC filter (R is the PSD frontend output impedance) sized for 1.5kHz cutoff referenced to the local analog ground, and the outputs of the filters are buffered by a low offset voltage precision opamp in unity-gain non-inverting configuration with bias current compensation - the OP1177. I did not find many with these specs able to handle the 600Ohm at 10V from a +/-15V supply (not entirely sure this will work either in fact since 16mA is out of the Vdropout graph, but the extrapolation seems to say it can?). Not sure whether I should add another 220nF cap across the feedback resistor.
Acquisition: Then the outputs of the buffer go to the inputs of a differential truly bipolar ADC - here the LTC2348-16 -, with respect to the analog ground again.

Grounding scheme: Both the buffers and the ADC are supplied with +/-15V with respect to Analog ground. I've checked and normally all PSUs of the system are isolated, so Analog ground should be at the centre of several interconnected grounds without loops:

Layout: I have routed all the signals (including grounds) to make sure I had the shortest, least parallel paths between signals, returns close to signals, and then added 2 analog ground planes on both top/bottom sides. Here is a summary with an overview with planes, and some key signals highlighted in blue without planes:

For the actual control from the uC, I'll start a conversion (at 600Hz frequency) by sending a 1us pulse on the CNV line, then I'll wait for BUSY to be low, and finally I'll initiate a standard SPI transfer until I collect the 3 first packets. This device is the only one on the SPI lines.
Questions:

Is there anything wrong I should change, be it in the schematic or the layout? This is to ensure the board meets the requirements.
What other good practices did not I think about? This is to improve my understanding of analog circuits.

I have tried implementing the ADC datasheet's true bipolar input architecture ; alternatively it also suggests to use a LTC1469 as a way to convert from single ended to differential if you think that's much better, but I don't see why that would increase accuracy here (and the filtering as described would not do well with the 600Ohm Rin).
Otherwise, for the same architecture, the LT1468 may handle the load better in spite of worse perf overall though?


texts: What type of connector is this? Looks like two pins but is only one

texts: Aside from looking like an upside-down Wall-E, what is this connector called?  It may look like there are two pins, but they are the same contact.


texts: RC filter design for ADS1115 (ADC) input

texts:
I am using an ADS1115 for measuring analog DC voltage with range of 0-5V.
The ADS1115 datasheet mentions that an anti-aliasing filter is connected at the input to limit the effect of aliasing during sampling and also reduce external noise from being part of the measurement. It says that the RC cutoff frequency should be set at the output data rate or 10X higher (output data rate of ADS1115 ranges from 8sps to 860sps.) I am configuring the IC for 860 sps, so I am considering the cutoff frequency to be 1kHz.  By my calculations, I am getting R=1.5K and C=0.1uF.
Is that right?
If I change the output data rate to minimum i.e 8sps will this cutoff frequency cause error in the voltage measurement?
Datasheet:


texts: Is there a modern discrete component alternative to the JFET as preamplifier?

texts:
Please consider this schematic of an electret microphone capsule:
    (Source: Wikipedia)

While considering something similar for signal conditioning of a 20 mVpp, 3k impedance output from a piezo bender, I found that discrete JFETs seem to have declined in availability and popularity, and increased in price.

This leads to a suspicion that some other discrete component that works with low signal voltage, high impedance, bipolar signals has replaced the JFET for such purposes, where anything more than a single discrete component would be overkill. A MOSFET would require biasing beyond Vgs(th), that is my fall-back.

Question:

What is the modern discrete alternative to the cheap-and-ubiquitous JFET?

I have considered the ALD110900 N-channel zero threshold MOSFET, but it is not cheap, not ubiquitous, and doesn't support gate voltage dropping below source.

Addendum:

The attraction of the JFET in applications such as the electret mic above is that it is a 3-terminal device, no regulated Vcc is required, zero-bias input signal is fed in, input modulates resistance regulates current, and it all works!

With integrated circuits like op-amps, that simplicity of implementation is lost.

Context:

Please note that the context below is not the question, it only indicates where the thought process started.

A high impedance (3 kOhm) bare piezoelectric sensor (piezo bender) is located in an underwater, hermetically sealed hydrophone at the remote end of a 5 to 15 to  meter long single-core shielded cable. The 20mV to 70 mV peak-to-peak signal is getting swamped along the line due to the location being extremely EMI-rich (industrial environment). At the operator end is a hand-held, battery operated readout device that is attached to the sensor cable when required. The signal needs reinforcement in some way, for getting it back to the hand-held unit.

Some minimal circuitry can be added at the sensor end if needed, and the handheld end circuitry can be modified as required. Modification of enclosures or cabling is not an option. Volumes are 10-20 units, so a 1ku order on parts is not an option.

Constraints:

No option for adding power supply wire to sensor enclosure.
Limited power: 4xAA battery operated readout device.
Sensor enclosure too small for AA cell or much circuitry.
Sensor enclosure cannot be retrieved more than once a year or so for battery replacement etc.


texts: AC Adaptor broke when powering PC case fan

texts:
Backstory: I had some arctic cooling F12 PC case fans laying around and wanted to use one to provide additional cooling to my notebook.

I took an "AC Adaptor" I had laying around and hooked it to the fan, it worked fine until the adapter broke while feeling pretty hot.

Fan product page: https://www.arctic.ac/de_en/f12-pwm-pst.html
Works from 5 to 12V, and should draw about 180mA at 9V from what I understand from the page.

The ac adapter says: 230V~50Hz to 9V~200mA 1.8VA (germany)

What was my mistake? Shouldn't the specs be compatible?

Adapter:


texts:
We are using this audio jack in our design. I am having trouble understand the schematic of this audio jack. My understanding is that

Pin 5 and Pin 4 : Audio left and right
Pin 2 or Pin 3 : Ground or
Mic
Pin 1: detect

Can anyone confirm my understanding? I think that the switch is normally open and pin 3 will short with pin 1 when the jack is inserted.


texts: Ultrasonic Piezo passive component matching

texts:
I am attempting to drive a 640kHz piezo electric transducer with an FPGA. For some reason, I cannot get a matched signal, and do not know why. I've captured a scope readout where CH1 is IN, CH2 is A, and CH3 is B. Any ideas what might be going on?

I've also captured a readout when the transducer is NOT attached. Here it is:


texts: Why would an input pin have both a pull-up and pull-down resistor?

texts:
In his answer detailing the various types of input pins, Russell McMahon leaves the following note [referring to input pins]:

  there are special cases where a resistor to high and low at once is useful

What are the special cases where both a pull-up and pull-down resistor are required? Isn't there a current waste?


texts:
I'm connecting CdS photoresitor and ADC (MCP3204) to the RPi. And MCP has DGND and AGND.

I am about to connect both GNDs to the GND on RPi's GPIO, naively.

Is that problematic if I want to read the value from ADC at maximum rate? Say... 100kSps.

MUST I use separate GND for each of them? If it can't be, putting capacitor, or diode can mitigate some potential risks?


texts: Using LEDs to indicate if a toilet is occupied or not?

texts: We have two toilets in our office. I want to setup two LEDs in rooms that show which toilet is occupied and which not. How can I do that?


texts: Replicate thermistor behavior for second sensor

texts:
I'm working with an R/C electric motor that has a 10K thermistor sensor built into it, which is connected to a speed control that has basic thermal protection. I would like to build a secondary sensor board that displays the temperature on a segment display, but I still want to pass it through to the speed control so that it still has thermal protection.

The issue I'm having is that the thermistor is only connected to ground on one end, no other reference potential, so I plan to read it with a voltage divider. This means I can't just pass the end of the thermistor back through to the speed control, which may have its own voltage divider. Is there a way I can replicate the resistance of the thermistor to two different read circuits expecting a variable resistance?


texts:
i have a relayset for Arduino  where i find these numbers on each relay:
10A-30VDC 10-28VDC

Now, id like to connect that relayset with external devices that run 12V and all the way up to 35A.

I was reading about the logic behind relays and some say that its okay to push in 20A into 10A relay, is just the relay output will not exceed 10A.
I also read that the Watts should never exceed, and that's the most important thing.

So taking my relayset
10A x 30VDC = 300 WDC

and my external devices, lets say one of the connectors run on 35A
35A x 12VDC = 420WDC

To my questions:

Is that okay to work with 420W ?
If not, what can happen ?
Is there a way to limit the input to relays so it stays below 300W ?
If i use a transistor (NPN) in the circuit, after the relays, does the relay still take damage from the incoming power ?

I tried to google but is kind of hard to get specific answer to these questions, also id like you to fills out other points (that I'm not mentioning) that i should concern.


texts: Sealed, long, thin glass tube with two wires and tiny filament - what is this?

texts:
I found this thing, and have no idea what it is.

The tube is 30 mm long, about 5 mm in diameter. Both terminals are connected with two drops of glass. There seems to be a tiny wire or filament connecting both wires inside the tube.

Any suggestions?


texts: About discrete time model for wireless channel

texts:
I am trying to understand Section 2.2.3 of the book "Fundementals of wireless communication" by Tse and Viswanath.
In this section the authors explain how to go from the continuous time baseband model to the discrete time baseband model.
I am going to use equation numbers from the book.
My question is the following:
If one looks at equation 2.29 it shows the sampling theorem.
If I understand correctly that summation is the Whittaker–Shannon interpolation formula and it is from \$-\infty\$ to \$\infty\$.
This means in equation (2.33) the variable \$\ell\$ is from  \$-\infty\$ to \$\infty\$.
And this will imply the same in equation (2.35).
Does this not make the system non causal? Because if the variable \$\ell\$ is allowed to be negative, now the output sample at zero can depend on any future input samples.
May be I am missing something on why the variable \$\ell\$ is not allowed to go negative, can someone clarify?


texts: Professional technique used for logging power consumption of a DC circuit

texts:
I wonder how do the electronics device manufacturing companies log and plot the power consumption plot by time. I would think they sample both voltage and current simultaneously and multiply these two.

But if the data loggers are measuring voltages one needs to add a low value series resistor across the main Vcc line from the supply. But is special way of current to voltage conversion used to measure the current?

This is how I would do it:

Imagine DUT above is a low power device and it consumes power not constant way. And we want to leave it for a day connected to a power supply Vs and log voltage and current data it draws to plot the daily power consumption plot.

So the data acquisition can be done by sampling two channels simultaneously where (Vch1-Vch2)/Rs would give us the current data and Vch2 would give us the voltage data. So the power would be:

P =  |(Vch1-Vch2)/Rs| * Vch2

Is that how companies make such a test during prototyping and verification procedure?


texts: What happened in a LC circuit when I connect two ends of the Inductor by a wire with very small resistance, at the time the current in the Inductor is  $$0 < I < I_{max}$$


texts: Following a Person In Real Time Using RFID

texts:
I am carrying out a project in which a trolley or carrier follows a person and follows him continuously wherever he moves inside a shopping complex or at airport.

I am confused whether to use RFID or some other technology which provides me identification of person and measuring of distance as I have mentioned. If I am able to get all requirements using RFID alone or by alternative method welcome. I am a completely newbie to RF area.


texts: Microcontrollers: Can I perform floating point operations in a Microblaze controller?

texts:
I wonder if I could perform floating point operations in a Microblaze controller?
Thank you to all posible answers with direct references to documentation or articles.


texts: Can my DIY Arduino be powered with 12V battery via lm2576 switching regulator?

texts: I have lm2576 switching regulator circuit with output constant 5v/3A. Can I use it with a 12V battery and connect it to power my Arduino?


texts:
I'm looking at the 4-20mA circuit below and trying to understand it. For some reason I can't get this to click in my mind.

Pressure sensor is a Metallux ME751 with a supply voltage of 9..35 VDC and it outputs 4-20mA.

From my point of view (please correct me where I'm wrong!):

LM317 together with the R1 creates a current limiter at 1.25V / 56Ohm = 22.3mA. This current then goes through Pres sensor which change it based on the pressure. 4mA for its lowest point and 20mA for its highest point. The R2 resistor I don't understand the purpose of, but R3 will give a voltage to the ADC of 0.88V @ 4mA and 4.4V @ 20mA.

My questions:

The pressure sensor needs a supply voltage of 9-35VDC, how do I know what voltage the pressure sensor gets? i.e. what is the voltage on the lowside of R1??
What is the purpose of R2?
If I removed the LM317 and just supplied 24V to the Pressure sensor I would know it got the voltage needed. Would it still produce a 4-20mA current based on the pressure or does it need a constant current to work?


texts: Building a Shunt active power filter in the synchronous reference frame

texts:
This schema representing a shunt active power filter in the synchronous reference frame, I'm focusing on the Area in the red box !

Schema

I want to learn how to build my own shunt active power filter in the synchronous reference frame from scratch, i understood pretty much the method behind it, but i am stack within Simulink, i followed the steps of the Algorithm one by one :

Get the load's current (scope : I_Load)
Clark Tranforation (scope : ab_Frame)
PLL Gives the SinW/CosW (scope : PLL)
Park transformation (scope : dq_Frame)
Extraction of the Harmonics currents (i* d & i* q)
Back from dq_Frame to ab_Frame (Park Inv)
Back from ab_Frame to abc_Frame (Clark Inv)

Simulink Model :

I'm stack at step 5 (The blue box)
Now that i have I_load in the dq frame,

How can i extract the compensation current i* d and i* q from iq_Load and id_Load ?

what is the simplest way to do that ? (in the schema up, they use an FTJ (the Orange box), what is that ? some also put LPF ( at 2*pi*50) why ?)

Scopes :

I_Load Scope

ab_Frame Scope

PLL Scope

dq_Frame Scope


texts: how to put Atmega328 to sleep mode and wake it up without button,without WDT

texts: iam building a IR based faucet i need to include battery backup here iam using only ATmega328 with crystal and capacitor, iam not using regulator or LED ...i need to increase the battey life iam using 4AA in series of capacity 2000mah and device is currently consuming 15ma when hand is not detected ,when their in nod hand infront of the ir receiver it should be in sleep mode and when hand comes near to sensor it should wake up and energise solenoid...insted of waking arduino at every 2sec is their any way that it should wake up only when hand is near ?


texts: Verilog and XST - large LUT long to synthesize

texts:
I have a large Verilog lookup table holding 16bits values that I generate using a case..endcase statement. The synthesizer recognize it and infer a RAM block, all is working fine.

My only problem is the time required to synthesize with XST. We are talking above 10 minutes just for the LUT. How can this be improved? Should I change my design or should I look at the synthesizer options? Right now, optimization level is set to Normal.

Thanks

EDIT:
Here's a snippet of code

module cos_lut_16_16 (
    input[15:0] iPhase,
    output reg [15:0] oCos
) ;

    always @(iPhase)
    case (iPhase)
        0: oCos=16'h7FFF;  //0 -> 1
        1: oCos=16'h7FFF;  //9.5873799242853E-5 -> 0.99999999540411
        2: oCos=16'h7FFF;  //0.00019174759848571 -> 0.99999998161643
        3: oCos=16'h7FFF;  //0.00028762139772856 -> 0.99999995863697
        4: oCos=16'h7FFF;  //0.00038349519697141 -> 0.99999992646572
        5: oCos=16'h7FFF;  //0.00047936899621426 -> 0.99999988510268
        6: oCos=16'h7FFF;  //0.00057524279545712 -> 0.99999983454787
        .....
        65535: oCos=16'h7FFF;  //6.2830894333803 -> 0.99999999540411
    endcase
    endmodule


texts: Buck Vs. Buck-Boost for Portable Variable SMPSU

texts:
I'm looking to design a variable output power supply that can do 0-30V and up to 10A. I am going to build a custom battery pack for it out of 18650 cells so I have control over the capacity and voltage. The idea was to build a battery pack and then using an adjustable Buck converter or Buck-Boost converter set the output voltage. I've never designed a power supply before but I have a good understanding of how the two topologies work, but I have one question that I can't find the answer too and that is which one would be more efficient?

Since the system is going to run on battery power in the field, extending battery life is my goal so is one better then the other or are they pretty much the same? Would I be better off building a pack with 30+ VDC and stepping it down or building a pack of the same physical size with more capacity at a lower voltage, say 12 VDC, and stepping it up when needed?


texts: Will Stressing a Lamp Filament with AC, DC and/or Relay chatter change its lifespan?

texts:
I am building a device that shortens the lifespan of an old style "edison" bulb with an extra long filament as a kind of arbitrary timer.

I am planning to "stress" it (not immediately explode it or anything) by rectifying the current using an unsmoothed Full Wave rectifier assuming that the filament is designed for 230VAC with 60hz duty cycle therefore will do worse under noisy higher voltage DC.

I can also add in a relay turning on and off at 60hz which is very alarming to hear (cool!), would this cause it to cool and heat more times causing metal fatigue?
Is there a way to push more current through a bulb and make it shine brighter?

I have a vague understanding that the current pull is the same, as is the RMS.

To Summarise: What causes more wear on a Filament and how can I increase it :D


texts: Driving relay directly from optocoupler, what is best?

texts:
I'm designing a smart socket using an ESP-32 and a mechanical relay that can drive 5A at 240VAC. Following typical relay driving circuits, I would like to use an optocoupler between the MCU and relay. The relay that I'm using is a Panasonic APAN3105 that operate at a low coil power of 110mW(5V@22mA) based on the datasheet.

Typical relay current driver circuit use an optocoupler connected to a transistor which then drives the relay. Since I'm using low coil power relay, can I drive the relay directly from the optocoupler that is within the max collector current? Are there any downsides to this method?

simulate this circuit – Schematic created using CircuitLab

I have not selected the optocoupler yet but have narrowed down to a few which have generally the same properties (If = 20mA, Ic = 50mA)(EL817S(B)(TU)-F, PC817X2CSP9F, TLP785(GB-TP6,F(C)

What is the best way to drive a relay?


texts: What's the component name/part number of a motherboard audio jack?

texts: I've de-soldered a triple 3.5mm audio connector thing from a dead motherboard and would like to use it for a small project. However, I have no idea what it's called, there's no part number on it, and google reveals nothing (english is not my first language, so maybe I'm not using the right words on the search). Since my college is closed right now I don't have easy access to a caliper to accurately measure pin distances and recreate it on EAGLE, but I'm sure it must be a common enough part to have a datasheet somewhere, right? Here's a picture:


texts:
I've been delving into analog a bit more and am a little confused by a configuration I saw of two PNP BJTs.

I saw two emitters tied together and then their collectors tied together through a resistor. Their bases had different drives. What does this configuration accomplish.

simulate this circuit – Schematic created using CircuitLab

EDIT: I'm not 100%, but I believe in the circuit that I have found the inputs. Apologies if it looks vague. I'm attempting to keep the question simple.

simulate this circuit


texts: Does current get divided into four equal parts for four resistors?

texts: I have a button that has one pin connected directly to 5v. The other pin has four 4000 ohm resistors connecting to it that then each go into a separate base pin of 4 different transistors. I only want the current to be .001 amps. In theory each base pin should receive .001 amps because 5v going into each resistor of 4000ohms will output .001amps at 1v. I know this because R = voltage drop / current needed. I have 5v I want 1v. 5-1 = 4v. And I need .001amps for my base pin. 4000 = 4/.001  Here is what I want to know. I have 4 base pins. Does my voltage/current from my power source get split into 4 equal parts that go down the 4 resistors or does 5v and the same current go down all resistors. If its the first option, do I just divide my power source current by four?


texts: What happens when the DC supply of this common gate amplifier is switched off?

texts: The Vin in this case is a 200mV peak to peak sine wave signal. what happens to the gain of the amplifier when the DC supply of 10V is switched off?


texts: Identification of 2-pin connector on 1999 Pump Machine

texts:
During my master thesis, I need to install an old vacuum pump to an machine (1999).

However I encountered this type of connector, which I am not familiar with. I have searched around the web with no results. Due to the weight and placement of the pump in a cleanroom, replacing this connector with another is a last resort.

I would be really glad if you could help me identify this type of connector.
The diameter of these pins is approximately 1.5mm while I measured a length of 7.5mm.

The width of the inside is 11mm while the height is 6mm.

Thank you for your help!


texts:
I am trying to bit banging an UART Port using PIC32MX with timer5 (the only available at this time) but I am struggling how to configure the timer for a Baud Rate of 115200bps. I don't want a flow control not even to deal with parity bit.
If possible can someone explain me on a Step-by-step procedure?

My Definitions are:

    #define GetSystemClock()            48000000UL              // System clock frequency (Hz)
    #define GetPeripheralClock()        48000000UL              // Peripheral clock frequency
    #define GetInstructionClock()       (GetSystemClock())      // Instruction clock frequency

    #define MILLISECONDS_PER_TICK       10                  // Definition for use with a tick timer
    #define TIMER_PRESCALER             TIMER_PRESCALER_8   // Definition for use with a tick timer
    #define TIMER_PERIOD                37500               // Definition for use with a tick timer

    #define SYS_FREQ                    40000000UL

    #pragma config FPLLMUL = MUL_20    // PLL Multiplier
    #pragma config FPLLIDIV = DIV_1 // PLL Input Divider
    #pragma config FNOSC = FRC // Oscillator Selection
    #pragma config POSCMOD = EC // Primary Oscillator
    #pragma config FPLLODIV = DIV_2 // PLL Output Divider
    #pragma config FPBDIV = DIV_1 // Peripheral Clock divisor
    #pragma config FWDTEN = OFF // Watchdog Timer (controlled by software)
    #pragma config WDTPS = PS65536 // Watchdog Timer Postscale 1048s
    #pragma config FCKSM = CSECMD // Clock Switching Enable & Fail Safe Clock Monitor Disable
    #pragma config OSCIOFNC = OFF // CLKO Disable
    #pragma config IESO = ON // Internal/External Switch-over
    #pragma config FSOSCEN = ON // Secondary Oscillator (KLO was off)

    void initTIMER5( void ){ // Initialize Timer 5

    T5CON = 0x0;
    TMR5 = 0;

    T5CONbits.TCKPS = 0b111;//1:256 prescale value

    IFS0bits.T5IF = 0;
    IPC2bits.T2IS = 0;
    IPC2bits.T5IP = 2;
    IEC0bits.T5IE = 1;

    T5CONSET = 0x8000;
    }

By now I think I just need to configure the T5CONbits.TCKPS and the PR5 register in order to synchronize with the baud rate, right?

I really need your help on this guys.


texts: How to use a pressure sensor (transducer)?

texts:
I have this pair of pressure sensors that are addressable transducers. I want to use them for a project but I don´t really get how to get them to work. I´m used to the type of sensor that has 3 cables( Vcc, GND, and DATA) and these ones only have two cables so I´m kinda lost. These sensors are supposed to give a certain frequency depending on the pressure applied to the sensor.

I found some data on how it's supposed to work but I don´t get what kind of circuit should I use to be able to use this data.

https://www.lancier-monitoring.de/fileadmin/media/pdf/Produkte/englisch/Tech_Info_Tx_Funktion_engl.pdf

"During the transmission, the sensor modulates the currency at a frequency that corresponds to the measured value at 3.7 mApp (= 0 dBm/600 Ω) onto the DC supply current. Therefore the used pair is power supply (direct current) and transmission media (alternate current) at the same time."

This is how the signal looks when transmitting data.

And this is the actual sensor. Any help on how to use it would be appreciated .


texts: What is a good resistance value for voltage divider to measure LiPo voltage with Arduino

texts:
(Full disclosure: I'm a newbie.)

I'm trying to measure my 4S lipo's cell voltages using an Arduino Mega. I know that I should use a voltage divider (actually, several of them) and I think I understand how it works. I also know about the voltage difference relative to GND would increase by up to 4.2V for each cell, and at 4th cell, it can be over 16V so I should be safely dividing it down to max 5V. However, I'm confused with what resistance values should I use for the divider(s). Wouldn't a low resistance value mean effectively shorting the lipo? Would a too high resistance value cause incorrect readings? In this context, what is a "low" resistance value and what is a "high" resistance value? Or are all resistors already way above that limit and I can use them safely? I've got all types of resistors from 47R to 1M, but I don't know what to use.


texts:
I would like to power a white LED from batteries.
The LED I'd like to use has a forward voltage of 3.3V, the datasheet specifies the voltage range from minimum 2.8V to maximum 3.8V.
My idea is to use 1.5V AA or AAA batteries to power the LED, I don't want to use Lithium batteries for this project. I'm open to alternative suggestions though, if they would fit the project better. I'm aiming for a long battery life though, so no button cells.
If I use 2 batteries, I get 3V - this would be in the allowed range, but very close to the lower limit of 2.8V. As soon as both batteries drop to 1.4V, I'm out.
If I use 3 batteries, I get 4.5V and therefore a much greater voltage range that I can work with, but I have to get rid of something between 3 * 1.5 - 3.3 = 1.2V and 3 * 1.3 - 3.3 = 0.6 V.
I see several options here:

Just go with a fixed resistor and drop 1.2V. Works fine when the batteries are fully charged, LED will become dimmer over time until the batteries reach (2.8 + 1.2) /  3 = 1.33V

Use a buck converter to convert 4.5V to 3.3V. I'm not very experienced with buck converters and all items that my local electronics supplier has stocked that have a output voltage of 3.3V need at least 6V input voltage. I don't mind cramming more batteries in there, but does that give me any advantage?
I guess that using a buck converter should give me a steady supply of 3.3V as long as the converter has any input voltage above a certain treshold, so I'd not experience any LED dimming. Is that correct?

Use a linear regulator. Researching my question I found some answers that said something like "a linear regulator is fine, because you don't have much voltage to drop". Usually those questions where about micro controllers though and had a power consumption of some hundred µA. Would using a linear regulator work with a LED that has a power consumption of 20 or 30 mA?

Can you give me some advice which solution I should follow or am I going in the totally wrong direction? Would those solutions still work if I would want to power two or three LEDs with identical specifications?


texts: why capacitor connect serially with resistor on the earth pin

texts: I have this grounding mat, inside the electrical socket as shown in the picture, there are a capacitor and 100k ohm resistor connected serially  to the earth point, the grounding mat is supposed to get negative electrons from the earth to our body, to neutralise our body free radicals, I can understand the 100k resistor is the same as resistance as our dry human body, to limit the current, but I don't understand why they place the capacitor, as it is open circuit, it will not be able to get an electron from the earth. Any reason why there is a capacitor?


texts: voltage across low resistance and short circuit

texts:
simulate this circuit – Schematic created using CircuitLab

The voltage across R ohm should be always V volts for every single value of R except R=0 and at that resistance the current through R needs to be infinite to get rid of all energy and reduce the potential energy to become same with the negative terminal (or 0 joule).

So, at R=0, voltmeter reading will be, V = IR = infinity x 0 = 0.
But isn't it true that if all the resistance are connected in parallel with a voltage source the voltages across all resistors should be same? Then why at R=0, voltmeter will read 0 volts and not v volts? I mean for as small value of R as you can think, voltmeter will read V volts then why not for R=0?


texts:
Functional languages like Haskell, LISP, or Scheme allow a programmer to work quickly using the functional programming paradigm.  They do have their inefficiencies, but my application places greater emphasis on programmer efficiency than efficiency of the program itself.

I'd like to use functional programming on a microcontroller to do machine control, etc.

What limitations are there, such as minimum system resources?
What example implementations of these languages are available?


texts: What's the name of smd buttons build of a simple thin metal sheet which flex when pressed?

texts:
As the topic title, I tried to find them but cannot get any informations about.
They are a sort of SMD tact switch made only by a very thin curved metal sheet. When you press they flex and make contact with the pcb or similar. I would like to post an image but I cannot find anything.


texts:
I am playing with SVCall function in ARMv6 using GNU gcc compiler
see below code with 2 defined SVCall functions ment to be compiled the same way:
void blinkFast(){
    while(1){
        gpio_toggle(LED);
        useless_delay_ms(50);
    }
}
#define SVC(code) asm volatile ("SVC %0" : : "I" (code))
//void SVCall_Handler(void){
    //__asm__ __volatile__("B %0\t\n"
                         //: /* outputs */
                         //:"rm" (blinkFast)/* inputs */
                         //);
//}

void SVCall_Handler(void){
    __asm__ __volatile__("B  blinkFast\t\n");
}

int main(void)
{
  mcu_init_stuff();
  SVC(0);
  while(1);
}

in the disassembly the first one gets assembled to:
b   #-76

while the second one is
b   #0

according to my simple knowledge about gnu GCC this was original thought to use "I" constraint:
void SVCall_Handler(void){
    __asm__ __volatile__("B %0\t\n"
                         : /* outputs */
                         :"I" (blinkFast)/* inputs */
                         );
}

but i got the following compile error :

asm operand 0 probably doesn't match constraints
asm volatile("B %0\t\n"

and hence the only compiled one was "rm" constraint which gets translated to #0 in assembly.
what is the problem and how to fix it?


texts: Circuit to know when two batteries are connected to each other

texts:
I'm using a Victron Cyrix (12V 120A) Smart battery combiner to connect the starter and the leisure battery in my RV. I wanted to know when the two batteries are connected to each other, but unfortunately the device does not have any output signal with this information. What kind of circuit can I use to know this? Some kind of continuity test between the two (+) poles of the batteries?

Below there's a diagram with the connections. Thanks in advance for any feedback.

Edit:
Based on the suggestion from @joribama I think that measuring the voltage of the two Cyrix poles, can be a good indicator if the two batteries are connected or not. I'm thinking about using the ADC pins of a Attiny85 to measure the voltage using a voltage divider as shown below. Since the Attiny can read up to 5.5V we can calculate that for that limit to be reached the batteries needed to have 22V, so there's a good safe margin. The 100k resistance between the positive batteries' poles and the GND result in a max current of 0.14 mA (~2mW using 14V for the calculations), which I can live with...

simulate this circuit – Schematic created using CircuitLab

With this circuit, using the 10-bit converter, I have a resolution of around 21.5 mV (22V/1024), which seems enough to detect when the cyrix is closed. The Attiny would then turn on a LED inside the vehicle whenever the voltage difference between the two poles fall bellow a certain threshold (to be defined).

What do you think? Will this work?


texts:
What the different between WiFi antenna and WIMAX 4G antenna?,
I want to boost the signal for my router to 4 km, I found this antenna in local store, but it seems weird there is only 1 leg, not like the normal WiFi antenna, leg for TX and the other to the ground, how can i connect this one to the router?


texts: BJH H-bridge going in reverse but not forward, LL transistor overheating

texts:
I've built one of this BJT H-bridge to control a DC motor in an old R/C car of mine, but I'm having problems with it and wanted a few tips to help me debug the board.
The motor is a 2-wire DC with about 1.2A stall current.
Below is my schematics.

Note that I've used TIP102 and TIP107 in the actual board, as presented in the original design. I've replaced them for TIP122 and TIP125 in schematics because those were the closest parts I could find in Eagle CAD libraries. All other components I used match exactly the schematics.
Below is my board.

The truth table for the inputs FWA, REV and ENA is shown in the link I provided above, a bit down in the page. In summary, assuming ENA (ENAble, which is active low) is always low (active) we have the following situations:

FWA=HIGH, REV=LOW - The motor gets positive voltage and current, thus going forward.
FWA=LOW, REV=HIGH - The motor gets negative voltage and current, thus going in reverse.

I omitted the other 2 cases (braking and coasting) for brevity.
The board works fine in reverse (situation in the list 2 above). It runs at full speed as it should. The upper-left (UL) and lower-right (LL) transistors heat up a little while the lower-left (LL) and upper-right (UR) transistors remain cold, just as expected.
The problem I'm having is that it doesn't run forward. In that configuration of inputs (situation 1 in the list above), the motor doesn't run at all and the LL transistor alone heats up quickly.
Here's what I know and measured:

Vin = 12V, HIGH logic leve is 5V, while LOW is 0V.

With the motor terminals disconnected, I get +Vin at the terminals with the inputs configured to move the motor forward. With the inputs in reverse, I get -Vin at the terminals, which is expected.

What could be wrong with my board? What other measurements should I make to determine if there are faulty components, short circuits or bad solders or contacts somewhere?
Edit: I found the problem, thanks to Dave Tweed's comment about double-checking the resistor values. The answer was that I switched a pair of the 1K and 10K resistors when routing the board and assembled them incorrectly, thinking they all followed two lines of resistors of equal values. The 1K resistor is highlighted in the image above.


texts: How do simple low power devices store setup when switched off?

texts:
I often come across battery powered items that store their state when switched off, particularly 'simple' items like LED bicycle lights (e.g. flash or solid light, changing each time it is switched on).

How is this usually done?  Do they charge a capacitor or capacitors when on to store a few bits of 'memory', or use a small amount of battery power to remember the state in a flip-flop, or store charge on the gate of a FET?

I'm very familiar with more complex items storing data in EEPROM, FLASH etc, but guess there is a common alternative for simple/cheap battery powered products.

This is a little bit like another question, but it is asking about shorter term storage, my bicycle light 'remembers' its state for at least a couple of weeks (after that, it's me who can't remember!) and battery life when off is much more than a year.


texts: Power distribution boards - hierarchical numbering system

texts:
I wish to renumber the circuit breakers (and possibly the cables) in an industrial plant.

Numbering should give a unique identifier for each breaker.
Numbering should give a path back to the incoming supply.

Figure 1. Part of a power-distribution tree.

I've had a look at various systems such as KKP and its replacement RDS-PP (Reference Designation System for Power Plants) but I'm not sure that either could be used to give the "at-a-glance" hierarchical naming that I want.

Can anyone suggest an expandable numbering system that would identify each circuit breaker in Figure 1? How would the incoming breakers be numbered? How would the panels be numbered?


texts:
I am working with SIMCom's SIM808 2G+GPS modem and trying to connect it to an SD card.  I am following SIMCom hardware design docs, to save some data in SD memory.

The problem is: when I send command "AT+SD2PCM=1" to the module, it returns ERROR message. Can you help me to solve this problem? Thanks.


texts:
In the 7447 BCD to 7-segment decoder chip, pin 4 is BI'/RBO'. That pin acts both as input and output. I would like to understand how exactly the internal circuitry works to make this possible. On page 7 of this datasheet, there is a schematic showing the internal circuitry for the BI'/RBO' connection. Can somebody please explain how exactly this works?

Does the dashed line on the right carry the pin signal fed to the rest of the chip circuitry? If so, how can the signal there ever attain the logical "high" state? The two diodes in series will always clamp down the voltage there to be the sum of two diode forward voltages (i.e., max ~1.4V total).


texts: What would a voltage between 0 & 1 do to a AND-gate IC?

texts: If I have a 7400 chip with an AND-gate (0 = 0V & 1 = 5V) would it be seen as 0 or 1 if the input is at 2V and also 4V?


texts: Stepper Motor Control - Full Step not working

texts:
Good day,

I am using an ULN2003 to control a unipolar stepper motor from my PIC18F45K20. When I only connect the one 12V power cable (Red) the stepper motor works in full step. However, when I connect the other 12V cable the motor stops and has a high pitch noise and the outputs on all the PIC ports go low. So in conclusion when I connect this one specific red cable, nothing works. I tried another stepper motor (same model) the same happens. Any suggestions what it could be?

My motor is similar to this one I found on the web.


texts:
I’m building a simple SBC based on Allwinner A33 for my undergraduate final project, includes two x8 DDR3 chips. I’m going with 6 layers JLC2313 Stackup 1.2mm thickness (cost reasons). It’s my first DDR3 design and I have a lot of questions.

Their website/field solver suggests 14 mil track on stripline and 5.7 mils on microstrip for SE50 ohms impedance. That’s super thick.

I was wondering if I can use SE60 ohms and 120 ohms for differential pairs on DDR3 (That’ll be 9.4/3.8 mils).

I’ve included the stack up. L1=> Signal, L2=> GND plane, L3=> Signal, L4=> Signal, L5=> Split Power, L6=> Signal.  The prepreg (Dk=4.25) between L3 and L4 is just 5 mil (0.127mm) in thickness. Would that cause a lot of crosstalk? Was planning route ACC on L3  and data banks on L4.  Would keeping almost minimum intersection help me out here? I will reference it to the adjacent layers (GND,VDDQ) , separated by cores with a thickness of 14.37 mil (0.365mm).

Any suggestion on ddr3 layout and layer utilization, especially with JLCPCB’s 6L stack up?  (Included a preliminary component placement).

About DDR3 termination, BBB, most of the boards from Bpi, Olimex, OrangePi and even Rpi seems to be termination only the DRAM clock. What about ACC group?

DRAM reset signal, Is it a pull-up or down? Is it SoC specific? DRAM_RESET is active low, but I've seen a couple other designs utilizing a pull down. I’m using H5TC4G83AFR-PBA/PBC DRAM chips.

I understand differential pair’s impedance can be seen as two single ended TL’s impedance coupled with a gap. I’ve tried iCD stackup planner and can’t quite get the bang-on 120 ohms differential geometry right on JLC’s stackup (aware of the 10% tolerance), same story with their website (they seem to be using Si8000). So, is it weird to maintain 60Ohm SE and 100Ohm Differential for DDR3 signals?

I highly appreciate any inputs and suggestions.
Thanks a lot


texts: Datasheet / footprint for this weird USB-C connector?

texts:
I've got this SMD USB-C type connector I want to use:

It has a single row of 12 pins along the back, presumably meaning the other 12 USB C pins are pre-connected internally. Neat. This also suggests it would be easier to solder, having only half the pins to deal with.

However, I can't find a datasheet or land pattern for this anywhere. I can find the two other (conventional) styles - the one where the second set of 12 pins is available, either as a secondary row underneath the body of the connector or as a set of mini through-hole pins (they call that one the "hybrid" pattern).

I have no details about this at all - no manufacturer name, and the store I bought it from has no idea (presumably they bought it in bulk from Asia). There are no identifying markings that could lead me in the right direction either.

Anyone have any clues?


texts: What could cause a relay not to release immediately?

texts: I have got a relay that doesn't release immediately after power is cut off. What could be the possible causes of this?


texts: Power supply filter choke failure - how and why?

texts:
Trying to repair a non-working Fiber to Ethernet Converter.  When connected to power, the unit made a hissing/sizzling/scratching sound and the all LEDs glowed dimly. I isolated a small surface-mount choke on the input power side, filtering 12VDC input from wall-wart to input of main 3.3V voltage regulator.  (Schematic below.) Removed this choke and replaced with a straight wire shunt. The unit powers up and works perfectly.

I don't have an inductance meter, but the choke measures about 0.1 Ohms, so it's not burnt out.

The voltage regulator is a LM2591HVT-3.3 (a 150kHz Buck switching regulator).  I see a clear 150kHz signal at the input after replacing the choke with shunt. Before replacing, there was a very noisy signal at this point, almost impossible to see with my scope.

Three questions:
1) What actually failed inside this choke? Why does it "sizzle" when powered?
2) What possibly caused this failure?
3) Is it OK to replace this choke with a shunt? What problems may arise from this modification?

Output of power circuitry is now stable at ~3.4VDC and unit powers up normally.

Thanks!

Schematic:

simulate this circuit – Schematic created using CircuitLab


texts:
Is it true that GSM signal's field strength in the atmosphere is dependent on the current number of users whereas for TV and FM broadcating the field strength is usually constant, independent of the number of current subscriber.
I am quite sure of this fact, but could not find some written evidence. Can anyone tell me if I am correct and help me with some written evidence of the same?
Thank you!


texts:
I was going to add a bit of information to my post on a previous day using schematics and some instructions. What programs are being employed for this purpose?

I mostly want to see what others are using and that I can easily use to give descriptive schematics.

In a perfect world, and I know this is a case of me wishing, it would be:

Free.
Extremely easy to draw schematics
in.
Allows simple production of
waveforms for the inputs/outputs.


texts: How can I cope with small internal pull-up resistors on an I2C bus?

texts:
I have an I2C sensor that has a some 89kΩ pull-up resistors on the SDA and SCL lines. The controller I'm using has 2.2kΩ internal resistors on these lines as well. I'm worried that the sensor won't be able to handle the vastly decreased pull-up resistance induced by joining up the sensor to the controller.

Is there some way that I can couple the two together so that the resistance of the bus is the intended 89K?


texts: Altium keypad footprints custom pad DRC errors

texts:
I've created a rubber keypad switch footprints which is a simple contact pad design. First I used arcs and tracks to get a outline and then converted them to top copper region(two seperate regions). And then placed a pad on the end of each contact.

Overall the design looks flawless while editing in libraries but when I used it in the schematics then I have come across DRC errors saying there is a short circuit within Top Copper Region and Pads. This is visually true but on the practical side only the Pad will be used to connect the traces.

Could anyone please let me know what's wrong with it and how to overcome such violations especially in keypad contacts design.

Thanks


texts:
I've made a 16 cell battery with Li-ion 18650's salvaged from laptops in a 4s4p configuration at around 16.4V. I'm using it in a Bluetooth speaker I made with a TDA7492 Bluetooth audio board, and am using this 18650 protection circuit.
I was wondering if I needed a 16V power supply and connect the charge port straight to the protection board, or if I need something like a TP4056 micro usb, but made for 16V.

I'm still new to all this and am taking every chance I can get to learn more about DC voltage. So any help would be appreciated, thank you.


texts: Are ratings (volts and amps) inter-changable on components?

texts:
Assume I have a component, it is a flip switch (like so), on the switch it states, 120V at 3A or 240V at 1.5A.

Following this pattern, is it safe to assume the switch is capable of servicing in an environment with 5V at 72A?

Also, when does 5V become unsafe to bare contact?


texts:
I think I've found a solution for my previous question and I'm now going to order some FCI "Clincher" connectors from a local supplier to try them out.

My question is, should I terminate the ends of the flexible LED strips with sockets or pins? And why?

(In practice I'm going to be using sockets for this prototype because that's what Element14 have in stock, but if there's a strong reason to do it the other way 'round its worth me waiting for the stock to come in for the "real" (much bigger, more expensive) project.)


texts: May I use a smaller wattage resistor as mosfet's gate driver for a very short time?

texts:
In a H-Bridge circuit, i am using gate resistors on all the mosfets.
My calculations for one of them, Gate voltage 4.5 V and Resistor 100 ohm gives me 45 mA, means 203 mW.

In a pulse of 16 us i need these numbers to charge/discharge the gate for total 310 ns, 1.94% of the cycle. I am safe using 250 mW SMD resistor.

If i will use a smaller resistor for example 82 ohm it will give me 54.88 mA and 247 mW for total charge/discharge time of 254 ns, 1.59% of the cycle.

May I continue to use a SMD resistor of 250 mW based on the short duration of use?


texts: Bypassing solar charge controller using trickle charge voltage?

texts:
In an effort to simplify a small solar system and to keep the cost down, I am wondering what (if any) drawbacks there are to having the Vmp (voltage at maximum power) in a solar panel setup, at 12.5% over the nominal battery bank voltage and not using any solar charge controller.  For example, for a 48V battery bank, 12.5% over is 6V over which is 54V of charge voltage.  This is in line with (the same ratio as) the 13.5V trickle charge voltage often used on a 12V battery.

So the idea is to select and combination of panels such that the series Vmp voltage is close to 54V (for a 48V battery bank), and NOT use a charge controller, with the assumption that the batteries will never get overcharged.  However what I am wondering is as the batteries become close to fully charged and draw less current, will that "unload" the panels and allow the charge voltage to go higher, closer to the Voc (open circuit voltage) of 70V or so, and thus cause a "chain reaction" of increasing voltage at decreased load, thus possibly overcharging the batteries.

I guess one easy way to check this would be to just take a fully charged 48V bank of batteries and directly apply solar panels with a series Vmp of close to 54V and check on an ammeter how much current is flowing.  If it is something small like 1A, then that will not overcharge the batteries as it will just "fight" self discharge (I have four healthy identical 12V 100Ah AGM batteries in series).  However if it is something more substantial like 4A, then that may have the possibility for overcharging the battery bank if it is already fully charged.  The maximum current the very small solar system can output is about 5A so no matter how strong the sun is, it wont exceed that.  The panels are rated slightly under 5A (Imax).


texts: Calculate rotor slip without knowing synchronous speed

texts:
I am given the rated values of a squirrel cage induction motor:

  A 300hp, 2300V, 3‐phase, 60Hz squirrel‐cage induction motor turns at a
  full‐load speed of 590r/min. What is the approximate value of the
  rotor I2R losses?

However, the synchronous speed is not given, nor are the amount of poles in the motor. How would one solve this problem without knowing these values?


texts: Why superposition theorem has not been executed here?

texts:
Here is the given circuit
In this problem while finding V1 we didn’t took the voltage contribution at that point by Vo(Superposition theorem)Only current source Is has been used to find the voltage at V1.
Why we didn’t consider the effect of Vo on V1?What am I missing?


texts:
How does a wire wrap joint compare to a soldered joint in high humidity conditions?

Corrosion? Electrolysis? Joint resistance creeping up?


texts: How do we get the complex frequency of an exponentially damped sinusoidal function?

texts:
In my textbook, Engineering Circuit Analysis 8.Ed by William H. Hayt (Chapter 14, Section 14.1 page 536) I stumbled across a section explaining the complex frequency. The goal is to cover the concept of complex frequency when it comes to exponentially damped sinusoidal functions.

HOW DID THIS HAPPEN?

How did \$e^{\sigma t}\$ become \$e^{j\sigma t}\$ out of the blue?
And why did \$e^{j(\omega t)}\$ become \$e^{j(j\omega t)}\$ ?
Any help would be much appreciated.


texts: Calculating R and C for schmitt trigger debouncer

texts:
I've been looking all over the internet to try to figure out the optimal values for R1, R2, and C but couldn't find info.

I'm trying to ideally make a debouncer that will work with any button on the first white keypad listed from http://www.futurlec.com/Keypads.shtml.

I used 47nF for the capacitor and 2.2K resistors for each resistor but I'm not quite sure if that combo is right. I want the button to respond as fast as possible without debouncing. (like maybe 500uS waiting time between presses)

I then searched for RC calculators online and found two that gave two different results based on the same values I used:

According to http://referencedesigner.com/rfcal/cal_05.php, their answer is 206.800 uS

According to http://sim.okawa-denshi.jp/en/CRtool.php, their answer is 769.60804203044Hz and converting that to time gives me 1.3mS.

Which answer is right? and how do I determine lowest RC delay I should use?
The datasheet that comes with the above mentioned keypad does not specify the debounce rate of any of its buttons.


texts: Disabled one cpu on dual cpu board. Cant connect anymore

texts:
so I wanted to disable one of the two cpus I got on my board (H745ZI-Q). I have both a CM4 and CM7 core. When I was playing around I disabled the CM7 boot with cube programmer - user configuration. However after that I could not connect to the board anymore. BOOT0 -> high did not resolve this and neither did the stm32-utility link. None of the tools can get a connecting to the board.
Any idea how to fix this?


texts: Integrating multiple sensors onto one board, how many decoupling capacitors do I need?

texts: I am designing a board that will have three MAG3110 sensors on it.  In the data sheet, the "Application Circuit" shows 5 capacitors.  My question is, if I have three of these sensors on one board, all pulling from the same power line, is it safe to assume that the example circuit should be replicated for each sensor, or will I be introducing unwanted effects by adding 10 capacitors between the power and ground lines?


texts: I found a circuit for this metal detector and would like to make PCB. I can not find anything about this circuit. Maybe someone would know what this circuit is. What are the best component housings to choose for a metal detector?


texts: For what reasons is a MOSFET with a square wave at its gate outputting an irregular signal?

texts:
I am switching an IRFP250M with a square wave. Its output should be a sqquare wave too, but this is what i'm getting:

Measurements at 255kHz:

Measurements at 200kHz:

The first waveform is the gate signal and the second one the drain signal with a dummy 1k resistor.

simulate this circuit – Schematic created using CircuitLab

Thank you,

Riccardo


texts: Can anyone help to identify this blown MOSFET? Top markings seem to include F50, "ON" in a circle, 3N and "RE4T" in a circle

texts: I am trying to repair a PCB out of the welder. One of the problems I have found is a blown MOSFET. I have tried searching for a replacement with no luck, as I don't have a complete code. I have posted a picture of the MOSFET and if anyone can identify help it, that would be great.


texts: Frequency Response Function Estimate via FFT Question

texts:
I want to estimate the FRF of a dynamic LTI system given experimental input and output data. I know generally the approach is to use a chirp as an input to make sure enough frequency content is available. Then you take the fft of the output and divide it by the fft of the input. This intuitively makes sense to based on what I know about FRF and transfer functions. However, I am getting a little confused between the nuanced differences between a Laplace transform and  Fourier transform.

The resulting output signal of this system will have some transient solution. My understanding is that FRF is really only about the steady state solution of a sinusoidal input (i.e., the FRF is the transfer function when s = j*omega, which I believe implies there is no transient solution and only steady state). So my question is: does the transient response that is built into the output data corrupt the FRF approximation via FFT? Or is there something in the FFT approach that would mitigate the impact of the transient solution? Or am I completely wrong and the transient part of the output is needed to give an accurate FRF approximation?

I believe there will be some transient solution at the natural frequency(ies) of the system that I would imagine give a different fft of the output than if the output only had the steady state solution.

Any help would be most appreciated!


texts: Safe and stable discharge rate for Li-Ion battery packs

texts:
I have found a battery pack with 74Wh capacity and it supports Qualcomm Quick Charge 3.0 on its output (up to 18W). I wonder is there anything like a safety limit of battery discharge? Is it even possible to increase the discharge rate above 18W and ensure that the wattage remains stable as the battery packs drains down to zero? I tried to google it quickly without much success but I must admit I have a very limited understanding of this field.

PS: if there is any info or variable missing from my description please let me know, I will be most happy to specify to make this case more useful to everyone


texts: IR sensor for line follower not working in day light

texts:
I m using IR sensor ir tx and photodiode for rx for my line follower bot it's working in normal light and night time but when put in sun light it's not working all sensor showing high ouyput. Also I find out that sun light have high wavelength so that photo diode shows always high signal.
Is that any other way to work line follower in day light time?


texts:
My question is simple for humans but hard to search for in Google or somewhere else, so forgive me if this isn't the best place to ask.

I was looking up the power consumption of an electronic device on several sites and all of them stated "this device takes 100ma" or something like this.

My question: If a device uses "100mA" how much mA per hour does it use?

So if I have a battery of 10.000mAh, how long will it last if the device uses "100ma" as they say?


texts: Current sensor with instrumentation amplifier (LT1167)

texts:
Objective
I'm trying to make a current sensor that can accurately measure current up to 5A. In order to do this I'm using an instrumentation amplifier (LT1167) to measure the voltage difference between a current shunt of 0.01Ω.

simulate this circuit – Schematic created using CircuitLab

Description of the schematic
SW1, SW2 and SW3 are used to adjusted the gain of the instrumentation amplifier. A voltage divider is implemented for each of the inputs because the current sensor needs to be able to measure current when the load is on the high side as well as on the low side.

Without the voltage divider, +IN gets pulled to 14V and a voltage greater than 14V gets produced internally in the LT1167. Since the supply voltage is 14V, the instrumentation amplifier can't generated a voltage greater than 14V. This will cause an error on the output.

The voltage divider is used to drop the input voltages by a factor of 4. This will reduce the overall gain by a factor of 4. The reduction of gain is accounted for by carefully choosing values for the gain adjustment resistors.

Problem with the circuit
The output voltage does not behave as expected.
  ie. The output does not follow this formula:
  OUTPUT = G · I_shunt,
  where G = (0.01/4) · (49400/Rg + 1)

Here are some data:

Why is this happening and how do I fix this problem?


texts: Short circuit calculation for KNAF transformer

texts:
I am using a 2MVA transformer (KNAF rating will be 30% more at 2.6MVA)

The question i have is whether we calculate the short circuit rating based on 2MVA or 2.6MVA?

I'm using pu method to calculate, Isc.pu = V.pu/Z.pu

So Isc = Isc.pu * Ibase

Should Ibase be 2886A or 3752A? Assuming base voltage of 400V

Would appreciate any advice on this. Thanks!


texts:
Is it a good idea to replace wires that get bent a lot (e.g., around a hinge) with conductive threads? It's a 5V device using up to 1A.

Thanks


texts: Hi) I want to calculate the width of my 100Mb Fast Ethernet MDI diff pairs. I've got some software (TXLINE 2003 Microstrip). I have 4 layers. The second layer is GND, the third is power, top and bottom are signal layers. I have one diff pair on the top and one on the bottom. For the top everything is clear, I took the height parameter as distance between top layer and GND. But what should I do for the bottom layer? What layer should I choose to calculate the distance (Power layer or GND)? I have also heard that if one chooses Power layer as reference layer for calculation of width then one need to place 10nF capacitors between power and GND on boths sides of MDI diffpairs. Is this correct?


texts: What causes voltage to increase from 12V to 36V as specified?

texts:
Reference article and paragraph:
Relays, Selection & Usage (Part 1) - 8 - Latching Relays

Below are two simplified circuits of dual-coil (A) and single coil (B) latching relay drivers.  As is readily apparent, the dual coil version is far simpler, and just uses a transistor to connect one side of the coil or the other to ground to set or reset the relay.  The two transistors should never be turned on at the same time because the relay state will be indeterminate when power is removed.  Otherwise, no harm is done.  Note the way the diodes are connected - this only works if the coil and drive transistors are connected as shown, and the peak voltage across the transistor that remains off is three times the supply voltage (3 x 12V or 36V in this case).

My question is: how in circuit A the voltage reaches 36V across Q2? from the diagram I thought recognize that the voltage potential on each end of the transformer will create a 24V potential difference, but I don't recognize where the other 12V potential comes from.


texts:
simulate this circuit – Schematic created using CircuitLab
I'm a programmer and self taught digital designer, and I thought I could deal with an Op Amp even though I haven't for >20 years.
Quick version, I'm taking an analog 0-3.3volt signal and turning it into a 0-5Volt signal using a single supply opamp, in non-inverting mode with a voltage follower after that, powered at 10V.  All worked fine, and then suddenly the voltage follower output died.
More detail, I have an analog signal (not PWM, true ADC) coming out of an ARM processor at max 3.3v.  I'm using a 14pin, 4 op amp chip, in this case a TLC2274 which I bought to replace the 30 year old MC3403 I had laying around, which would not go down to the negative supply as my memory and the spec said it would.  I'm going into one of the OpAmps on the chip and using a 4.7K from the output to the neg input and a 5.6K and a 5K trim pot to GND to convert to 5V. I then go into two other Op Amps on the chip as voltage followers, one to each of two outputs.  One is just going to an Analog meter for "visualization", the other is right now doing the same but is intended to go over a long line to a motor controller.
Still in testing, I have the "main" output going to an analog milliamp meter with an appropriate resistor, and a scope.  All was fine and then suddenly the "main" opamp output died.  The input looks good, the output is 0V, as is of course the neg input.  No noticeable overheating, or "Magic Smoke".
I don't know the impedance of the motor controller, and the 100 ft. cable will add it's own problems, but I'm sitting testing on a bench and it failed, how can I prevent that?  Does one normally use a resistor, resistor zener, or something else to protect an opamp output? I'm not seeing that in "Art of Electronics" or any of my (old) op amp circuit books. If it dies on the bench, what do I do in the real world?  The spec says the chip is short circuit protected, could this have been static?
So, questions:
Is there a way to improve this circuit?
I am assuming the problem is from static, but not sure if it could be something else, so what could be the reason for the failure since I have no voltages available beyond the supply and GND, which the part is protected from shorts to.
Is there a way to protect the opamp I'm using?  One comment already suggested 100ohm resistor, but that's to compensate for the cable that has not yet been connected.


texts: Gain equation of cascode common emitter amplifier with an LC tank

texts:
I'm trying to find the gain equation of the circuit presented below.

I know that for a cascode common emitter amplifier without resistor RE and with a current source instead of the LC tank, the gain is equal to:

$$A_V = \frac {V_{out}}{V_{in}} = -g_{m1} g_{m2} r_{o2} \cdot (r_{o1} || r_{\pi 2})$$

How does resistor RE and the LC tank modify this equation? And what is the purpose of resistor RE?


texts: Why is Floating point non-synthesizable in verilog

texts:
I know now a days FPGAs have very good floating point performance as reported here for example  . But then why it is said that  Floating point is non-synthesizable  in verilog?
How FPGA handles float then?


texts:
Lets have 2 electrons travelling with some speed relative to a static observer.

The force between those 2 electrons will be the Coulomb force and the magnetic force.

Is it forbidden from the laws of nature the magnetic force to have the same magnitude with the Coulomb force?

I tried to find a case where it is true and it came out that the charged things must travel at speed c which is impossible for every frame of reference.

Lets take 2 electrons moving at the same speed relative to a static observer.

From the frame of reference where the electrons are immobile , space is moving to the opposite direction.Due to length contraction of space , less electrons now fit the contracted space and the coulomb force is different.The difference of the coulomb force between the 2 frame of references is the magnetic force.

Now for the magnetic force to be equal to electric force the length of the space in the frame of reference where the electrons are immobile must be 0 meaning velocity c.


texts: is one "bigger" psu more efficient than two small?

texts: I'm going to replace my router and network switch, and question is if both devices comes for example with 5v 1a power supply, is it good idea to buy one 5v 2a power supply and connect both devices? I know that power supply not used but plugged to wall uses energy. So in both cases used and in idle (plugged to wall but not in sue) which is more energy efficient two small or one big PSU?


texts: Does forcing a data line to a higher power make it more resistant to interference?

texts: A device I'm working on as a hobby project requires me to transmit a HDMI signal over cat5. The TMDS lines in HDMI are balanced but in order for me to continue transmitting the DDC signal with the TMDS lines (which are needed for the EDID and HDCP) I would need to remove the out of phase line on the four TMDS signals in order to fit all the lines in the 8 wire cat 5. I can simply reconstruct the balanced pair on the other end using a redriver or inverter or something of the sort. My question is, without that balanced line, how high of an error rate can I expect on a 1.65 ghz TMDS signal and if I force the signal into a wider power range can I mitigate the loss?


texts: Speakers humming when used with Raspberry PI 3 and Adafruit MAX 9744 Amp

texts:
I've built a little soundmachine using a Raspberry Pi 3, the Adafruit MAX 9744 Amp and two recycled Car-Stereo-Speakers. Since this installation is ment to be used on a boat, I have an incoming 12v current. To reduce the voltage down to 5v for the Pi3 I use a DCDC stepper. The wiring can be seen in the poor diagram attached ;)

The Amp runs on 12 volts, so it is directly connected to the power source. For if it matters, here at home I'm using an AC/DC stepper (to simulate the boat battery) which turns the local 230 volts AC into 12 volts DC.

On to the problem. When I connect this setup I hear a very audible humming in the speakers. When I disconnect the audio jack from the PI and I use my phone as an audio source, the humming disappears.

I should mention that the picture doesn't show the entire setup. The 12 volt power source feeds another DC/DC stepper which in turn sends 7.5 volts into an arduino. Also a I have used the same power curcuit to feed 12 volts via Power over Ethernet into a device. Since I believe (or rather hope) that these do not have anything to do with the problem at hand, I didn't include them.

I'm a beginner when it comes to electronics, please take this into account when providing a solution ;)


texts: LED DRIVER: Buck Converters output current ripple

texts:
I need to design a led driver of up to 1A, to drive some infrared and near infrared LEDs.

Due to the nature of my application, the intensity of the light should be as stable as possible, as fluctuations in the radiation intensity cannot be allowed.

So far I have considered using Buck Converters as the LM3405 or the TPS92515 from Texas Instruments, however on any DC / DC switching converter, there is always a ripple at the output.

1.- Does this mean, that there will be variations in the intensity of the light ?

2.- If so, Is it better to go for a Linear Regulator solution? (using a MOSFET, Op amp etc)


texts: Confusion over Norton equivalent problem

texts:
So I have two questions regarding this Norton equivalent circuit problem.

My first question is regarding io. io is equal to the 1 volt divided by the 5 ohm resistor. Why does that current not split at the intersection where the resistor and the dependent source meet. How is the io current able to travel directly through the resistor?

Me second question is regarding the isc current. By shorting the circuit, everything is put into parallel. Yet, KCL at node a yields

isc = 10/5 + 2(ix).

What about the ix current flowing through the 4 ohm resistor? In figure 2, node a and b are the same node correct, otherwise everything wouldn't be in parallel. So I'm struggling to understand why the ix current isn't included in the KCL equation.


texts:
Can somebody explain to me, how the following voltage comparator works?

I believe to recognise U4A as an inverting Schmitt trigger, but how everything fits together escapes me...

Should the inverting input of U4A not always see Vtest? Given that Vtest is always greater than Vref, should the output not be constant irrespective of Vtest?

I would have expected the inverting input ot U4A to be connected to the centre tap of a voltage divider to bring Vtest into the range of Vref.


texts: Can a "mini" electromagnet propel a magnet 20 cm or so in the air

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I have an idea to DIY a little thing that would require to throw a piece about 20 cm into the air (straight up).
My idea is the following: To have a mini electromagnet (such as this one  ) and to have a permanent magnet attached to the bottom of my piece. I'd first have the electromagnet pulling the piece, and then instantly switch the polarity in order to repel the said magnet and hopefully propel it upward.
And my question is: could this even work? Assuming the piece to propel is only the magnet, how big of an electromagnet and of a permanent magnet would it require?
Thanks.


texts: Isolated Dc Dc comverter OCP triggers Output OVP on another converter with their inputs connected in parallel and common output ground

texts:
In a system we have a bank of isolated dc dc converters that feed a bank of bldc motors with their respective ESCs. These converters have their input connected in parallel to another identical one's input, that's dedicated to control electronics which only consume 1.6% of its output capacity, the control electronics share a ground with the power electronics for signal reference. When the bldc motors draw a large enough trandient to trigger the OCP of their converters, the separate converter for the control electronics has its OVP trigger on the output/secondary side. I'm looking for a decent explanination as to what is happening and possible solutions.

I don't mind the OCP triggering, transients can be limited in software but the OVP reboots the control electronics which takes a long time to recover.