texts: BNC Male to Cable Connector Proper Method

texts:
I've recently bought some cheap RG58/59/6 BNC male-to-cable connectors for DIY work. The connector qnd its guts look like this:

I couldn't find a proper name for this connector type, even worse, I couldn't find any assembly procedure either (there are videos for crimp and twist on etc. types). Can anyone explain (supporting visuals will be appreciated :) ) how should a RG6 coaxial cable be mounted to this connector? (the part with 4 teeth ruined the shielding foil)


texts:
I have a bunch of 74LS383 (TTL octal transparent latch with three-state outputs) and MM74C83N (CMOS 4-bit binary full adder) that I would like to connect together. I need to connect the output of the 74383 to the input of the 7483 as well as vice versa. The problem is the voltage level.

If I understand correctly, there is no problem connecting CMOS outputs to TTL inputs if the fan-out is OK, but connecting TTL outputs to CMOS inputs may give issues with the voltage levels.

Could I use a pull-up to workaround this issue? What would be a good value?

simulate this circuit – Schematic created using CircuitLab


texts: Does the coil's winding material matter?

texts:
Imagine you've got two coils with exactly the same cores, but one winding is made of material with its density different from the density of winding material of the other coil.

Would that configuration make differences in these two coils properties?
Or maybe only the amperage matters?

What other things describe coils' windings?


texts: Bleed resistor with a load that can be turned off

texts:
I have simple AC to DC 40 W, 18 VDC power supply with a bleeder resistor to drain the caps. However, the load can be turned off of independently of the power supply. This means the bleed resistor heats up while in normal operation rather than only on power-down. I don't know much about this and not sure if,

a. I should care - let it heat up and take the load.
b. Remove the bleed resistor so the circuit is open when the load is turned off - I'd prefer to keep it.
c. Some other solution - switch of the power with an SSR when there's no load or some such?


texts: CAN bus communication between RPi and Arduino

texts:
I am trying to communicate between Raspberry Pi and Arduino. In arduino I am using this program to transmit
#include <SPI.h>
#include <mcp_can.h>

const int spiCSPin = 10;

MCP_CAN CAN(spiCSPin);

void setup()
{
    Serial.begin(115200);

    while (CAN_OK != CAN.begin(CAN_125KBPS))
    {
        Serial.println("CAN BUS init Failed");
        delay(100);
    }
    Serial.println("CAN BUS Shield Init OK!");
}

unsigned char stmp[8] = {1, 2, 3, 4, 5, 6, 7, 8};

void loop()
{
  Serial.println("In loop");
  CAN.sendMsgBuf(0x43, 0, 8, stmp);
  delay(1000);
}

In Raspberry pi I am using this program to recieve
import can
import time

can_interface = 'can0'
bus = can.interface.Bus(can_interface,bustype='socketcan'
while True:
 message = bus.recv()
 print(message)
 time.sleep(1)

All I get is
Timestamp: 1607187085.129426        ID: 0020    S                DLC:  8    00 19 00 01 03 01 04 01     Channel: can0

everytime
What should I do to recieve values I sent from arduino to Raspberry pi
Thank you


texts:
Some very common parts have standard acronyms on schematics: resistors are usually named R#, capacitors C#, and integrated circuits U#.

Is there a typical standard for these names? If I want my BOM to look "normal" at the end of my design (ie: without any symbols that are weird + unfamiliar to other people looking at it), what should I do?


texts: What Makes a Radio Transmitter Powerful?

texts: I've been doing research on radio transmitters, and though I understand how the signal is generated and how data is transmitted, I still can't understand what defines a radio's transmitting power. How is a certain transmitter more powerful than the other?


texts: Low voltage control of 75V piezo actuator

texts:
I am looking to perform position control on a 75V piezo linear actuator with a Raspberry pi.

To do so I intend to use a 5V output DAC and some kind of power amplifier to amplify the range between 0V and 75V. For precise positioning the output voltage of the amplifier has to be stable. I have been looking at op amps for power applications but I am not sure that the previous statement will be met.

Am I not aware of some chip that would be useful in my project? Or an op amp will do the job?


texts:
This question is related to the DMX splitter I'm building and shown in Prototyping a DMX splitter.

However, for testing a different question is appropriate.

I never really tested a hardware device, so be gentle please.

The intended use for the DMX splitter is to use on a music stage with my band(s). The device will be reasonably safe under my keyboard stand.

For completeness: for safety it has 5 optically and power-isolated input and four output channels, TVS's for each DMX output, a varistor and normal and temperature fuse for the main 220/240 AC, but no double enclosure, just one plastic enclosure.

I wanted to perform the following tests which might be typical for the intended usage:

Normal behavior: power DMX splitter on (and check functionality).
Hot-plugging input device: while DMX splitter is powered on, switch off and on DMX input device.
Hot-plugging output devices: while DMX splitter is powered on, switch off and on DMX output device (per output).
Removing the DMX input cable/plug and reinsert it, repeatedly.
Removing the DMX output cable/plug and reinsert it, repeatedly.
Power on a heavy power device on the same 220/240 V group (like a drill), repeatedly.
Power on a 380V 3 phase device in the neighbourhood.
Using 20 meters of cable per output (will be more than we ever need).
Connecting 8 devices per output.
Laying heavy power cables next/on the DMX cables (like the 380V phase cable).

Are these reasonable tests to perform or should I add more?


texts:
I have a H-bridge based on FAN7392 drivers. This bridge works at 350VDC to output a approximately 240V 50Hz waveform. This circuit is isolated from rest of the board and I would like to maintain the isolation. The bridge is fed by two complementary PWM signals from a microcontroller. The signals can be isolated easily with opto-couplers - however I'm worried that the timing difference between the opto-isolators might cause one side of the bridge to turn on both it's transistors simultaneously, for a short time. For instance, if one opto-coupler takes 2us to go high while the other takes 3us to go low there will be a 1us interval where one half of the bridge will be short-circuiting the power supply.

So my main question is, what is the best way to isolated timing critical signals?


texts:
I have been trying for quite some time to program a factory-new ATtiny20. After unsuccesfully trying with a USBASP and with ArduinoISP, I decided to take a look with my scope. Turns out the device is responding, but the voltage on the MISO pin only reaches about 1 V peak. This is not enough to communicate succesfully. Any ideas of what could be causing this?

Things I've tried:

Use a USBASP programmer
Use Arduino UNO as ISP with ArduinoISP (this is supposed to set the clock speed slow enough for a ATtiny85 @ 1 MHz, so should also be slow enough for this ATtiny20)
Add pull-up resistor of values 10 kOhm and 100 kOhm to MISO, this causes the MISO line to always stay high
Add pull-up to SS pin
Add pull-down to SS pin
Try another ATtiny20, exact same behaviour
Check the wiring, many times
Disconnect MISO to make sure there's not something else pulling it low
Measured at the ATtiny MISO pin directly, to ensure it's not a connection problem

Other observations:

I measured the SPI clock frequency to be about 130 kHz. The frequency of the signal on the MISO line has the same frequency so it looks like the device is responding correctly (although I did not check that the data is exactly what it should be), just with a much lower voltage.

edit:
I had the RESET pin connected to the RESET pin of the Arduino ISP header, whereas it should have been connected to pin 10. Changing this did, however, not fix my issue. The wiring is as shown below.


texts: Powering thermoelectric cooler and fans with 12V input

texts:
I was considering a project with a thermoelectric cooling module rated 60w and so obtained an AC power supply of output DC 12V and 4.16A. I'm very new to electronics so excuse me for the basic questions but would I have to place some sort of resistors in the circuit even though the power supply is below the 60w rating so it shouldn't exceed what the module can handle.

Also I needed to connect two 12v 0.2A fans to the circuit, but how would I wire these with the other module and what resistors would I need? Thank you in advance.


texts:
First post, please forgive any errors.

Our dear father passed away leaving us his boat. The owner before had made some changes to the wiring (not for the better) leaving a tangle of loose ends and disconnected components.
One puzzle is the navigation lights. These 5 x 12v bulbs are turned on by 2 switches (1 anchor light, 4 steaming lights). The control panel features 5 LEDs to act as indicators (of some sort).
Currently everything is disconnected and I wish to restore function. I can see how to make the switches turn on the nav lights. But what of the LEDs (which appear to have resistors in series with them so they may be driven by 12v)? And what role is played by the 2 x 1N5408 diodes soldered in series?
Should the LEDs be wired so as to simply indicate that the lights are powered or is there a design such that a LED will go off if the nav light bulb fails?
Any help will be much appreciated.
The elements in the scheme:

The photos of the panel and backplate (featuring, oddly, 2 diodes wired in series with the anchor nav light) give some clues, suggesting the same scheme is repeated 5 times for the 5 nav lights and corresponding LEDs. Note the "neutrals" of the Nav Lights are not obviously available being some feet away in the boat.

Thankyou


texts: Resistive braking of series wound DC motor

texts:
I am looking at braking a series wound DC motor by putting a resistor across the motor feed terminals.

All of the sources that I have looked at state that the polarity of the field winding needs to be switched as you start braking. I understand how this works and how it applies braking.

What I do not understand is what happens if you do not change the field coil polarity. My instinct is that this will apply a reverse current to the field coil reversing the polarity of the output which will reverse the field.... ad infinitum. The result will probably be the field collapsing to 0 as an under-damped second order response totally failing to brake the motor.

If there is anyone out there with any experience of what actually happens I would be happy to hear it.


texts: light a lit when I get an interrupt and keep it lit long enough to let me see it

texts:
I think that I am missing an interrupt from my radiochip but I'm not sure. I'm thinking about troubleshooting it by lighting up a led every time that the interruptline goes high. The problem is that the interrupt is handled so fast so that there is no chance that I can see if the LED gets lit, therefore I added a capacitor to the circuit but it does load fast enough to light the LED.

Do anyone have any suggestions on how I could build my troubleshoot circuit that lights upp the LED for enough time that I will have time to see it every time I get an interrupt?

Thank you all for the responces! it seems like a pulse stretcher is the way to go! I'll see if use the IC or build it myself. I found some easy sketch with 2 op-amps, resistors and capacitors.

Using a scope would of course be easier, but this has dual purpose for me, as much as I want to troubleshoot I also want to learn more about developing circuits.


texts:
I have FIIO E3 headphones amplifier which is powered by 1.5V AAA battery. Am I using it just with my PC, so I got an idea: why don't I power it using USB port and stop buying new batteries ?

Anyway, I have few questions regarding that:

1) I know that USB port can give 500mA, but somewhere I've read that you can get only 100mA without enumeration. Is that true ?

2) Will 100mA be enough for replacing 1.5V AAA battery ? What is the maximum current that 1.5V AAA battery can give ?

3) Let's say that 100mA is enough. Now I need to build something :) I've thought about using LM317T. In it's datasheet, there's a foruma like this: Vout = 1.25V*(1+R2/R1)+Iajd(R2).
If I'm reading the datasheet correctly, Iadj will be really small, so I don't have to worry about that. R1 is fixed at 240 ohms. So I only need to worry about R2. After calculating, it should be around 50 ohms. Or did I do something wrong ?

4) If I get 100mA @ 5V, is it true that I can get about 300mA @ 1.5V ? I don't know why this could be right or not, so I'm sorry if I've said something really stupid :)

Thanks for your help !!!!


texts:
Greeting,

I'm using This Schematic as a reference to create a customized BLE PCB board.
I need some help to identify the below parts (with LCSC part No. if possible) as this is my first time to see those schematic symbols:-

L1 and L2 120 Ohm Coils (may be current a coil for filtering)
C5 and C6 Capacitors  (I guess it is a Polaroid capacitors where the +ve is the solid dot)

PS: The real component are showing in the following picture


texts: Is a ceramic heater good to use in an etching process?

texts:
I use Sodium Persulfate as an enchant at a maximum temperature of 50 C.

My experience with glass heaters is that they break if they are not fully submerged or if they are removed while it is warm which makes me feel that glass is fragile and has tendency to break easily.

I see that ceramic heaters are cheaper compared to titanium ones. I wonder if the enchant corrodes the ceramic material? Does a ceramic heater break if it is not fully submerged or removed while it is warm? and are they resistant to mechanical shock from a drop or hit?


texts: "lithium for buffered usage in UPS", or floating-charge lithium accumulator

texts:
For lead acid there are typically two paradigms of charging (or use-scenarios).

First one is deep cycles, when you exaust 40-60% of capacity (not less than 12.4V), then charge it to 14.4 with impulse-charger, and start to discharge and use it again. Lifetime is measured in "cycles with x% DoD, before capacity fells more than twice"
Another one is buffered use (for example in UPS backup) - you set 13.8V on rail, and keep that voltage forever, performing "floating charge". And battery will take just the current needed to keep itself in tip top condition. In case of power failure battery could stay long, release most of its energy, ready to deploy like 80% or more, waiting before power will be restored. Lifetime is measured in "Years under 13.6V without discharging, before capacity fells more than twice".

That is well known, and I even found very good and detailed report with graphs on lead acids. Later on I will provide a link here on that material (if I could remember it).

Now I am trying to find some information for li-ion. And only what I typically could find is a CC-CV, for a Li-ion specific subtype. Typical algorithm advices (that are typically met) are as follows:

Charge it for 4.2V with current=1C (they mean "battery capacity in AH, divided by 1 hour"), that charges to 80% within hour.
Keep it under 4.2V until current falls under 0.1C, that charges to 99.9% within 2-3 hours

And I learned that by heart to the day :)

What I am trying to find - is an information about "float charging" lithium accumulator of any type - LiIon/LiFePO/LiAnything. Different types have different cell voltage: for example LiFePO CC-CV ranges fot 3.2-3.6V; But Li-ion are higher - 3.6-4.2V; Maybe there's others..

What voltage should I choose to keep battery under voltage source safely for years, without disconnecting?

And for an expert a good answer is a graph series - "How does chosen voltage and ambient temperature affects capacity over time, for various lithium battery types". Cant really find that on the net, it feels like no one ever used lithium for ups needs.


texts:
Currently I'm designing a GPS basestation which will have a radiomodem (broadcasting at 407-480MHz), a ARM7 microcontroller running at 60MHz and a FTDI USB chip. The FTDI USB chip even runs at 480MHz internally, which is in the working zone of the radio. Due to all the harmonics and these high frequencies from the PLL (which ultimately will flow out of the device's power pins), I'm extra cautious with this PCB design.

We've had some discussions among colleagues what practices are best for EMI-proof design. Especially making the microcontroller 'quiet' is important.

Currently my own approach was based on this question, which was more about decoupling. From the recommendations I've changed my PCB design to have a local ground plane  under the microcontroller, which is seperated from the global ground plane. I connected this local plane to the global plane using 4 via's under the chip. Same practice goes for the FTDI USB UART bridge. All caps are routed as close as possible and orientated in a way that the VCC and GND pins have a short connection.

I feed the power in with a via from the supply layer. The GND is a local plane, so that doesn't require a via. I don't have a local supply layer, neither using ferrites to precisely separate the planes.

However, my collogue thinks that having an extra via straight to ground is better. His designs didn't involve local ground planes. All 4 layers are filled with ground, VCC is manually routed. The caps are placed closely, but sometimes the GND connection doesn't have an immediate connection to the GND pin of the controller. The ground plane under the controller isn't continuous , because it's completely broken up because of signals.

His thoughts was that the ground of the caps and pins are very secure to due the global ground plane and each via. He didn't have as much faith in my design because the ground planes are separated.  His designs passed the EMCs tests, so it kind of makes me wonder whether all this trouble even makes a significant difference.  I'm quite confused by that, because some appnotes tell you it's an absolute must to do local ground planes and good decoupling layouts.

My question simply put is: which design practice is better for EMI practice?

A GND are connected to a local plane first, which is separated from the system. This is connected to the global plane at 1 spot.
Each GND pin is routed manually to the global plane. Thus it means that all GND connections will get their own via. Not necessarily importance to a continuous ground plane under the controller.


texts: Data Rate, Bandwidth and Data transfer Rate - PCIe

texts:
I was talking with my senior regarding PCIe speeds.
I am not sure if what I was saying was right. Please correct me and help me understand.

He asked what is PCIe gen3 data rate. I said 8GT/s.

He asked me what is the bandwidth then? for x1 and x16.

How to understand this question and answer. Please help me understand the difference between bandwidth and data rate and data transfer rate

I looked at this link but couldn't understand

Can someone provide an explanation like deriving one after another.

And is bandwidth always told in MB/s?

This link seems to helpful but I am not understanding

Thanks


texts: FCC Certification of same electronics in a different size enclosure

texts: FCC Certification: I already obtained FCC Certification and Labels for a product. My question is: Do I need to apply for certification for a product which has the same electronics inside but the plastic case is slightly bigger? I wouldn't mind spending the money but the process was time consuming. Who should I contact in FCC for an approval if needed?


texts:
I am working with UART and I want to do something but could not achieve myself.

I want to enter an interrupt when the data receive stops, i.e when I unplug the cable, do something only once and then just continue. When I plug the cable again, it should will continue receiving values.

I am using UART in DMA mode.

I looked some about IDLE interrupt but I cannot use it as i want, where should its interrupt be placed exactly? When i use USART2_IRQHandler() func. it both enters when I un-plug Rx cable and also re-plug the rx.

So i am confused about how an IDLE interrupt can/should be used?

Thanks in advance.

The board is : STM32F4-DISC


texts: If we put a led light into a oscillating current, will it blink?

texts:
Sorry for the misleading title cause I have no electronic knowledge.
It is a simple question.

This is the circuit diagram.
In case you don't see clearly, it is XOR GATE.
My question is what will happen with the LED light, will it turn on/off or blink ?


texts:
I've seen and written programs in which the internal watchdog just resets in a super loop and trigers only when something goes wrong and forces the whole system to crash.

I've also seen it can be used as a "system reset" when the program intentionally goes into an infinite loop and waits for the watchdog timer to expire triggering a reset.

But, apart from reseting it over and over again in a super loop, is there any more effective way to make use of that peripheral in case you need something robust?


texts:
In this answer, I made a function to convert an integer to an ASCII string:

void writeInteger(unsigned int input) {
    unsigned int start = 1;
    unsigned int counter;
    while (start <= input)
        start *= 10;
    for (counter = start / 10; counter >= 1; counter /= 10)
        serialWrite(((input / counter) % 10) + 0x30);
}

I tested this function with a loop:

unsigned int counter;
for (counter = 0; counter< 1000000; counter++) {
    writeInteger(counter);
    serialWrite('\r');
    serialWrite('\n');
}

This works, for \$1\le{}n\le9999\$. However, for 10,000 and above, I'm getting weird strings on the terminal:

10000 => 2943
10001 => 2943
10002 => 2944
10003 => 2944
10004 => 2944
10005 => 2945
...

Why is that? How can I fix it?


texts:
I've got the following problem:

We've got a RLC circuit in serie and I would like to find the function:$$\text{V}_{C}(t)$$ the voltage across the capacitor.

Given are the following things:

$$\text{V}_{\text{in}}(t)=20\space\text{V}$$
$$\text{C}=4\space\text{F}$$
$$\text{L}=1\space\text{H}$$
$$\text{R}=5\space\Omega$$
$$\text{I}_{C}(0)=-2\space\text{A}$$
$$\text{V}_{C}(0)=10\space\text{V}$$
$$\text{I}_{T}(t)=\text{I}_{R}(t)\space\text{is the total current}$$

My work:

$$\text{V}_{\text{in}}(t)=\text{V}_{R}(t)+\text{V}_{C}(t)+\text{V}_{L}(t)\Longleftrightarrow$$

Knowing that:

$$\text{V}_{L}(t)=\text{LI}'_{L}(t)=\text{LI}'_{T}(t)$$
$$\text{I}_{C}(t)=\text{I}_{T}(t)=\text{CV}'_{C}(t)\to\text{I}'_{C}(t)=\text{I}'_{T}(t)=\text{CV}''_{C}(t)$$

$$\text{V}_{\text{in}}(t)=\text{RI}_{T}(t)+\text{V}_{C}(t)+\text{LI}'_{T}(t)\Longleftrightarrow$$
$$\text{V}_{\text{in}}(t)=\text{R}\cdot\text{CV}'_{C}(t)+\text{V}_{C}(t)+\text{L}\cdot\text{CV}''_{C}(t)\Longleftrightarrow$$
$$\text{V}_{\text{in}}(t)=\text{CRV}'_{C}(t)+\text{V}_{C}(t)+\text{CLV}''_{C}(t)$$

So the problem becomes:

$$
\begin{cases}
20\text{V}'_{C}(t)+\text{V}_{C}(t)+4\text{V}''_{C}(t)=20\\
\text{V}_{C}(0)=10\\
4\text{V}'_{C}(0)=-2
\end{cases}
$$


texts: Disabling isolation to reduce noise from EMI

texts:
A technician was suggesting we try connecting an isolated ground (described below) to a non-isolated ground suggesting it could reduce EMI noise and possibly fix an issue we're seeing (which we don't know the root cause of yet). This confused me so I thought I would bring it up to discuss here.

Is this a valid theory?

What we have is two isolated potentiometer amplifiers (Turck IM36-11EX-I/24VDC). Originally their isolated grounds were not connected but we've ending up connecting them as a side effect of another isolated circuit we introduced. The two grounds are still isolated from both output's ground, but not from each other.

We've been having some unexplained issues, which may very well be completely unrelated to the new circuitry, but one theory is noise on the inputs of the amplifiers is causing the issue. We can try removing our circuitry to see if that resolves the issue we're seeing (thus once again isolating the two amplfiers from each other), but while discussing a technician suggested our issues might be resolved by connecting the ground from the output side of the amplifiers to the input's ground (thus removing the isolation). Besides ignoring the reason the isolation is there in the first place, would that actually have any merit in solving a noise problem?

As far as I understand, disabling the isolation could just introduce more noise, but I'm looking for more insight.


texts: Can I charge a Lead Acid Battery with a Lithium Ion Battery Charger

texts:
Can I use a charger meant for lithium ion batteries (eg a charger for a drill) to charge a lead acid car battery.  It charges at 14.4V which is what I'm looking for (and will limit to 2Ah with resistor if needed).

I'm starting to lose hope in finding a transformer to build a charger and wondering if the above is an option.

Thanks!


texts: What exactly is the intuition behind physical circuits being linear?

texts:
After learning mesh-current method for solving circuits, I started reading the wikipedia article on linearity to understand more on  the "why?"
Reference.
In this article, I sort of get why resistors are linear - because they obey both properties of a linear object which is
$$ f(x +y ) = f(x) + f(y)$$
$$ f(ax) = af(x)$$
as in,
$$i = \frac{v}{R}$$
$$ i(v_1 + v_2) = \frac{ v_1 + v_2}{R}$$
$$i(a v_1 ) = a \frac{v_1}{r}$$
But, I don't understand why this would be true for inductors and capacitors. Why do these physical systems obey this mathematical structure? I mean I was shocked that the mesh current method was actually a legitimate technique.
Note: The kind of answer that I'm looking for one is one which uses both physical intuition and mathematics to explain but not entirely explain the thing based on both.


texts: So I have a gizDuino ATMEGA 644(an arduino clone), yesterday it is working very well and even uploaded some codes into it. But today my computer suddenly don't recognize the port where my microcontroller is connected, I'm sure that i installed the driver and even tried to use several USB ports and cable but it doesn't recognize it. I'm really confused because it does power-up when it is connected to my computer but it really don't recognize the port.Does someone experienced my situation?What seems to be my problem? How did you solve the problem? pls help


texts: Non-inverting amplifier with negative supply rail

texts:
simulate this circuit – Schematic created using CircuitLab
The formula Vout = Vin * (1 + R2 / R1) is not valid for this case? because for example I'm feeding 2.567V to non-inverting input and getting 2.976V at the output! I'm certainly doing something wrong somewhere...
How to calculate the output of non-inverting amplifier with negative supply rail?

Edit:
What I want from this configuration is to provide -1.25V to LM338 linear regulator to get 0V at its output, James mentioned in his answer to remove R3 from the first schematic and I did that with minor gain modification:

simulate this circuit
At 1V the output is 0V and when non-inverting input is 0V the output of opamp is at 1/4 of Vref 1.250V.

What's this configuration name? is it an inverting configuration?

What's the equation to calculate output?


texts:
I have a problem with my MAX232 chip and can't find the solution. The schematic of the chip is in the attachment. The chip is soldered on to a PCB.

I've checked all the connections, the supply voltage and the grounding. The supply voltage is a steady 5V signal and the ground pins of the caps and chip are correctly connected so I'm guessing that isn't the problem.

The strange thing that I found out is that the VS+ pin is 4,5V and the VS- pin is 0V instead of the 8.5V and -8.5V according to the datasheet.

How can this be possible or is the chip burned?

Thanks in advance.


texts: How to apply Ohm's Law correctly to a circuit?

texts: Ohm's law continually confuses me in my attempts to use it. Right now I'm trying to supply a maximum of 800 mA by 1.5 V from a 5V source. Does that mean that I need a 1.875 Ohm resistor V=IR, 1.5=.8R, R=1.875, or am I misusing it like I think I am? How do you think conceptually of Ohm's law?


texts: Do I need a current limiting resistor for MAX383 digital logic?

texts:
I'm trying to control a MAX383 analog switch using a Raspberry Pi, through an optocoupler (Sharp PC817), to separate digital logic from the analog section.

On the analog side, I will have a bipolar supply (+6, -6V) from a TLE2426 rail splitter.

I want to connect the positive rail to the logic pin on the MAX383, through the optocoupler which would source current to the pin. If my logic is correct, I will also need a pull-down resistor (I assume somewhere in the 100k range would be ok), from the pin to ground.

Question is: do I need to add a current limiting resistor somewhere in there? From the datasheet I see it needs min 2.4V to register a logic high, but there's not max specified, so I assume 6V from the power rail is OK. However, it does state max current to be 1uA.

simulate this circuit – Schematic created using CircuitLab


texts:
This is a follow on question from a previous one about a blown fluorescent UV ballast.

I have discovered that the in-rush current thermistor is blown.  Question 1 is whether it is worth changing it, or is the rest of the circuit likely to be damaged?  Question 2 is about how close the spec of the original and the replacement have to match.  The original is an SG38 and after searching for a while I found the first spec below.  The closest match I can find on the internet is the SL22 30005, which is the 5th line of the table.  Do you think these are interchangeable?


texts: Power output only when mains power cut and only bu ups

texts: I have a ups in my home.I want to install a fan in my room which run only when the mains power supply is cut and ups is supplying the power.How can I do this.


texts: Radiation pattern and propagation direction

texts:
I have a basic doubt about how to read a radiation pattern.

Let's consider precisely the power pattern: it represents how the power is distributed along all directions in space.

For instance, this is the radiation pattern of a dipole antenna:

What I am able to understand about it is only the fact that it is omnidirectional, that means it radiates equal radio power in all directions perpendicular to the vertical axis, for each fixed point of that axis.

But what I was asking is: is there a link between this diagram and the propagation direction of the radiated wave (I mean the direction of the Poynting vector), the directions of E and H fields, or anyway the wavefront? Is it possible to understand something about them by looking at that diagram?


texts: Start / Stop Power when more power is added

texts:
I have Blue LEDs wires to the interior of my car, My plan is to guy a Tachometer Shift light and wire it to red LEDs in my car so when I hit a certain rpm .... The red lights will turn on in the interior telling me to shift ( under dash )

PROBLEM :

At Night I have the Blue LEDs Running, what do I need to do so when I get to a certain RPM ( set on tachometer ) the blue lights will shut off and turn on the red LEDs instantly ..... then back to blue after I shift

( whole car Shift Light is what I'm trying to achieve )


texts:
I am trying to make a square wave generator using 555. I need a 16kHz 0-5V square wave. I have referenced this site (%50 duty cycle). When the frequency increases, the square wave have distorted gradually. This is my circuit for 16 kHz, 741 is used for buffer.

My output voltage is;

When i set R3 to 450Ω to decrease frequency to 1.6 kHz, the response is better;

Do you have a idea to get a better square wave for 16 kHz in this circuit? Thank you so much.


texts:
Let us say you have two networks, A and B, that depend on each other. The voltages in circuit A influences the resistances in circuit B, and vice versa. The goal is to find a steady-state solution of the two networks. Assume that there is some equilibrium condition that can be used to check whether you have reached the final state.

The procedure is as follows
1) Solve circuit A with some initial conditions.
2) Insert the results from 1) into circuit B and solve.
3) Check equilibrium condition. If equilibrium has been reached you stop here, if not; go  back to point 1) but insert the results from 2).

I am using OrCAD PSpice now, and I don't see any straightforward way to implement this procedure. One solution would be to use voltage-controlled resistors and connect the networks in a huge complex network, but this seems very cumbersome and I run into convergence problems.

My question is: Is there a simple way to do this? Perhaps by programming it in Python/Spice. Or is there an easy way to do this in OrCAD? Any suggestions or advice would be much appreciated.


texts: Why DDR4 Specs recommend that Address, Control and Clock buses be referenced to VDD?

texts:
Micron's Technical Note TN-40-40: DDR4 Point-to-Point Design Guide, page 19, says (emphasis mine):

Timing Budget
Suggested practice is to look at the design from a timing budget
standpoint to provide flexibility in the routing portion of the
design, if there is suitable margin. This starts with simulation. By
referencing the eye diagrams in this document, a setup and hold time
can be established. From here, the parameters not included in the
simulation must be added. Typical routing for DDR4 components requires
two internal signal layers, two surface signal layers, and four other
layers ( 2 VDD and 2 VSS) as solid reference planes. DDR4 memories
have VDD and VDDQ pins, which are both typically tied to the PCB VDD
plane. Likewise, component VSS and VSSQ pins are tied to the PCB VSS
plane. Each plane provides a low-impedance path to the memory devices
to deliver VSSQ. Sharing a single plane for both power and ground does
not provide strong signal referencing. With careful design, it is
possible for a split-plane design to work adequately:

Designs should reference data bus signals to VSS.
CA bus and clock should reference VDD.
Signals should never reference VPP.

Why Command, Address bus and clock should reference VDD?
I think the language on the paragraph is a bit ambiguous, some people understand that we SHOULD, but I think its saying what to do IF you have to split a plane...but still looking into DDR4 RAM modules PCBs I can see it's splitted:


texts: Is there a Microcontroller with 16MB of Ram?

texts:
Here's my situation:

As a personal project, I am looking to write a emulator for the Sega Megadrive (Sega Genesis) that runs on AVR. So I have been searching for a Micro-controller that has similar characteristics to the Motorola 68k that shipped with the MegaDrive. However, I have noticed that the specs for the 68k compared to most hobbyist micros. I'm choosing AVR as opposed to ARM because I like the architecture, and thought it would be a good challenge.

M68K:
32-bit CPU
16-bit data bus
Up to 20 MHz
16 MB RAM
No I/O ports

Here is the specs for an Arduino Leonardo:

Input Voltage (recommended) 7-12V
Input Voltage (limits)  6-20V
Digital I/O Pins    20
PWM Channels    7
Analog Input Channels   12
DC Current per I/O Pin  40 mA
DC Current for 3.3V Pin 50 mA
Flash Memory    32 KB (ATmega32u4) of which 4 KB used by bootloader
SRAM    2.5 KB (ATmega32u4)
EEPROM  1 KB (ATmega32u4)
Clock Speed 16 MHz
Length  68.6 mm
Width   53.3 mm
Weight  20g

This seems fairly typical for lower end modern micros. I never see the ram get much into the mbs.

Now, I'm sure modern SRAM is not nearly the same as whatever the 68k had, but is it possible for me to get an AVR micro that matches the power of a 68k, am I looking at this problem wrong? Do I need to change my design to accommodate modern micros?

I don't know if some external source of memory will be fast enough.


texts:
Is there a max voltage drop across a capacitor?
Or does it always charge up to the same voltage as the supply?
If there is a max voltage, then what would happen if the supply voltage far exceeds the max voltage of the capacitor, would the dielectric material break?


texts: RTOS for Cortex M4 with 802.15.4/6LoWPAN stack

texts:
I'm evaluating operating systems to use in an Internet of Things Project and I don't know what's the best way to proceed.

I'm using a TM4C123GH6PM MCU with 32k RAM and a CC2520 802.15.4 transceiver, it would be great if the system already provided drivers for those.

The system will run one (interactive) task that draws a dotmatrix screen and reacts to user input. It will store configuration and application data on spi flash. There will be a mesh of multiple modules (based on 802.15.4) to sync data between the modules, extract sensor data from the modules and forward them to a gateway (rpl comes to mind) and also distribute OtA firmware updates in a gossip-like fashion. All while running a rather memory hungry application as well.

So far I've looked into these systems:

RIOT:

pros

good hardware abstraction
small footprint
very active and helpful community
full 802.15.4/6LoWPAN stack

cons

unstable, still undergoing fundamental changes
still contains race conditions/crashes
no filesystem support
few network protocols

Contiki:

pros

mature system, used in commercial products
full 802.15.4/6LoWPAN stack with many useful protocols
file system support
cc2520 support

cons

development has become stale
'grown' codebase, lots of bit rot
bad quality tiva c port
little support for modern platforms
non-preemptive scheduling might cause problems with the application

FreeRTOS:

pros

little additional complexity
easy to use, reliable scheduler
mature project, used in many products
lots of ports

cons

no file system
no hardware abstraction for drivers/no hardware drivers
no network stack
somewhat high use of dynamic memory

NuttX:

pros

very feature rich, almost feels like Linux, yet still small
file system support
good hardware abstraction
Tiva C port, many other ports

cons

somewhat complex
no support for 802.15.4/6LoWPAN, just 'classic' netstack

My conclusion would be to take the good parts of Contiki (the netstack, file system) and port them to FreeRTOS. But I'm not entirely comfortable with a fork like that. I'd probably be adding errors and wouldn't be able to backport upstream fixes, also I still have to invent my own hardware abstraction to be able to switch the MCU in the future. So I'd end up with my own OS for something that seems like a problem that many other people should have too - hasn't someone done that before? (I mean I did find something, but the idea of running the entire contiki-os as a FreeRTOS task makes me uncomfortable)

Is there something I'm missing? Maybe the pain would be worth it and I should try to get Contiki to a functional state on my hardware instead? Or is there another system I've missed that would solve my problems?

Also I'm not sure whether I need 6lowPan at all, but when that means being able to build onto existing protocols/being compatible with other systems (e.g. Linux), I'd be willing to take the additional overhead.


texts: How to measure small current waveforms using a uCurrent Gold and a mains grounded oscilloscope

texts:
I am attempting to use a uCurrent Gold as referenced by several SE posts such as measuring microampere current without noise with a mains-grounded oscilloscope, to observe the small current into an inverting opamp input, for the first stage of a close reproduction of David Ashton's Pulsing Led for Competition.

My setup is diagrammed below, and I reason this is not the correct setup. The oscilloscope I'm using is a mains-grounded scope, so the connection to the V- jack on the uCurrent is shorted to the I- jack, and that represents a path to mains ground.

Referring to the diagram below, the points I marked as P1 and P2 (purple color) are normally shorted, but to insert the uCurrent, I've opened them up and inserted in the current inputs to the uCurrent.  The ground wires for CH1 and CH2 of the scope, along with the connection between V- and I- on the uCurrent, result in shorting points P2 and P3 to ground, thus shorting the capacitor to ground, which is not intended.

Basically, I've concluded that the dashed green lines in my diagram below are all at equipotential, which is an incorrect test setup.

And, I reason that, had this circuit used a large separate mains-grounded (not isolated) power supply, versus what it uses which is a CR2032 battery, I would run the risk of damaging my scope (reference EEVblog #279 - How NOT To Blow Up Your Oscilloscope!).

Is my assessment correct?  If so, are all of the following approaches viable? :

Buy a differential probe (EEVblog #279 offset 1214s), or
Use two different scope channels, one for the uCurrent V+ and a different one for the uCurrent V-, leaving all grounds at the same equipotential, and avoid hooking any of the scope's grounds at point P2, and using the scopes math function to subtract the two signals, effectively resulting in a voltage differential being plotted (only viable if I have a > 2 channel scope), or,
Just stop using CH2 on the scope to view the voltage on top of capacitor, as that takes out the short at point P3 (but I don't want to do do that as I want to see how the small current going into the inverting op-amp input changes (or doesn't change much at all) along with the voltage on the capacitor).

See also uCurrent with an oscilloscope for a video of someone else struggling with what seems to be a similar issue.

Here is the diagram showing the circuit under test, the latest uCurrent Gold schematic, and the front diagram of the Rigol scope I'm using with connections (high resolution image at imgur):


texts:
I am using the LT3652 charger chip,datasheet. Now, there is a status pin /CHRG. The pin is -

CHRG (Pin 4): Open-Collector Charger Status Output;
typically pulled up through a resistor to a reference voltage.
This status pin can be pulled up to voltages as high
as VIN when disabled, and can sink currents up to 10mA
when enabled. During a battery charging cycle, if required
charge current is greater than 1/10 of the programmed
maximum current (C/10), CHRG is pulled low. A temperature
fault also causes this pin to be pulled low. After
C/10 charge termination or, if the internal timer is used
for termination and charge current is less than C/10, the
CHRG pin remains high-impedance.

Now, an application circuit is as shown below -

Now, it says that the /CHRG pin can sink in a max of 10mAmps and it shows an LED connected to show status. Most SMD LEDs need approx 10mAmps at least to make it turn on. I cannot supply 10mAmps as thats the maximum. So, what practical use could it serve ?


texts: What practical advantages could there be in using a logic NOT gate IC (e. g. schmit trigger hex inverters) when compared to a simple NMOS + pull-up resistor inverter? I want to invert the PWM output of an arduino, and I suspect using a dedicated inverter IC might be a bit overkill for that application.


texts: Collecting values for certain time and store it once

texts:
I am trying to save some values to memory, I have an array with 6 values like as shown below

  Data[6] = {5045.567,4567.987,4.5,190.5, 70.5,500};

I have to save this kind of data into flash memory. I have memory which can store only 16 bit at each address and i am  able to write 16 bit.I need to write two times to write a float value. I am multiplying 5045.567 with 1000 to make long integer 5047567 so that i can save float value(two address to write float value). My data will look like this.

  long int Data[6]= {5047567, 4567987, 4500 190500,700500,500}

Is there any best method to save float value instead of multiplying with 1000 to make it as long integer?

To save this kind of data i need two address sometime and one address is enough some time.I will have this kind of data every 10 secs, I can't write to memory every 10 secs because of power saving features.

  I am trying to collect values every mint and trying write to memory at once every mint.

For this I have initialized an array with size[36] and saving all values after one mint. Is there any best way other than this to collect values for certain time and save once?

I am collecting all 36 values in an array.
for example first two values needs two address in memory then next four values need only one address in memory.
How do i increment address in memory for certain values? or is it best to divide long values into two integers before storing into array?


texts: How does low impedance measurement reveals ghost voltage?

texts:
First, I'm not sure about the terminology and whether it is correct to call this "ghost voltage".

When I was seaching info related to my previous question, I just came across the following video about ghost voltage: https://www.youtube.com/watch?v=mRwsxmn2P-s

I guess large 50Hz AC floating voltages between the SMPS output terminals and earth(as in my previous question) goes into this category "ghost voltage"(?)

The person in the tutorial video uses low impedance setting in a multi-meter and reveals whether the voltage is ghost or not.

What is the logic behind using low impedance and voltage being disappeared?


texts: reading voltage using TI's MSP430 FF22x4

texts:
I am trying to measure a power device's voltage using TI's MSP430. The voltage source is connected to A1 (i.e. P4) and ground (i.e. P1) on the target board.

Here is the relevant code:

ADC10CTL1 = INCH_1 + CONSEQ_0; //A1, single measurement
ADC10CTL0 = SREF_1 + ADC10SHT_3 + REFON + ADC10ON + ADC10IE + ADC10SR; //same as sample temperature sensor code
ADC10CTL1 &= ~ADC10DF; //setting binary format for ADC10MEM
ADC10CTL0 |= ENC + ADC10SC; //Sampling and conversion start
 __bis_SR_register(CPUOFF + GIE);        // LPM0 with interrupts enabled
//read result in a uint8_t[2]
incomingVoltage[0] = ((uint8_t *)&ADC10MEM)[0]; //this is Least-significant-byte
incomingVoltage[1] = ((uint8_t *)&ADC10MEM)[1]; //this is most-significant-byte

I am having following problems:

I am printing the ADC10MEM contents on the AP, and I see that the leading 6 bits of ADC10MEM are all 1, instead of 0. I am unable to get the reason for the same.
If I consider only the last 10 bits of ADC10MEM, I can see that the value increases and decreases with rise and fall in voltage, but if I obtain Vin using the formula:

N = 1023 * ((Vin - VR- ) / (VR+ - VR-)), I do not get the correct value. (VR+ = 1.5V, VR- = 0V, as batteries power the target board)
N: the value in ADC10MEM, in decimal

I am unable to find where I am going wrong. Do I have to enable the pin for analog input (ADC10AE0 |= 0x02), and set direction (P4DIR &= 0x00) as well?

Thanks!

EDIT 1: Vin Values:
These are the ADC10MEM values I am getting, considering last 10 bits.
Following calculations use Vr+ = 1.5, Vr- = 0.
For input voltage 0.38V, N=1100000010 i.e. 770, and Vin=1.12.
For input voltage 0.5V, N=1101010110 i.e. 854, and Vin=1.25.
For input voltage 1V, N=1110101001 i.e. 937, and Vin = 1.37.
For input voltage 1.45V, N=1111011000 i.e. 984, and Vin = 1.44.
As I said, the value is increasing/decreasing with increase/decrease in input, but it isn't correct.

EDIT 2: Interrupts:
I am modifying the sample temperature sensor code. I see

__bis_SR_register(LPM3_bits+GIE);  // LPM3 with interrupts enabled

at the start of while(1) loop in linkTo()/main_ED.c, and there's

 __bis_SR_register(CPUOFF + GIE);        // LPM0 with interrupts enabled

after 'sampling and conversion start' and before 'read results'

EDIT 3: Code based on msp430x22x4_adc_10_02.c from TI's code samples

ADC10CTL1 = INCH_1 + CONSEQ_0;
ADC10CTL0 = SREF_1 + ADC10SHT_2 + REFON + ADC10ON + ADC10IE;
ADC10AE0 |= 0x02;
P4DIR |= 0x00;
ADC10CTL0 |= ENC + ADC10SC; //Sampling and conversion start

I am getting similar values even with this code.


texts:
OK here is the spec:

Solar Panel

4"x6"
200mA
7.2v

Fan

small : 20x10mm, 12vdc, 60mA, 2.17cfm
medium : 40x20mm 12vdc, 140ma, 8.28cfm

What I'd like to do, is to be able to run the fan hook to the solar panel on regular inside incandescent light. Now the fan hooks to the solar panel, and needs direct bright sunlight to run. I think I need a voltage regulator and a capacitor (in micro farad) I'd like to have the fan running only when light on (no need to run at night), running at 1/2 of the 12V speed is fine to me.

So the question is: What capacitor and voltage regulator do I need? I heard that a dc to dc is needed, too.

I know electronics, but I cannot do the maths. I can solder, do breadboard, etc. but know nothing in technical match term.

I know that many capacitors exist, but I like to keep the whole thing under $10, solar panel included. Now the solar panel in retail cost 19.00 but Alibaba can sell it for $5 or maybe you know a US/Canada place to get cheep solar panels. Whole electronic thing excluding fan and solar panel: $3-5.

as told, MAYBE simple incandescent light will NOT be enough, so let think about putting it beside a windows, is it more realistic ?


texts: Temperature Controlled Heat Generating Device (40-80 deg C)

texts:
I'm a physician doing benchtop experimentation. Background: Tissue is known to coagulate at 43 degrees celsius (CEM 43 thermal tissue damage index).

I'm seeking to find/build a temperature controlled heating device to induce various thermal injuries in explanted (ex vivo) tissue. I'll be measuring those changes at the surface level of the tissue using a fiberoptic temperature probe.

Specifically, I need the device to accurately generate heat (40-80 deg Celsius w/ increments of 1 degree celsius). Any ideas? I've explored modifying a soldering iron and heating up metal in water bath to specific temps.

Thanks in advance!


texts: how to make a variable light dimmer circuit without potentiometer?

texts:
I was looking at the Wemo Dimmer and thought to make one at home myself because the price of it is very much if I buy(including import duty). I searched for the knowledge which helps me create a capacitive touch slider switch and I found this video:

1] https://www.youtube.com/watch?v=_r_8z0pAQ-o

I have also watched this video:

2] https://www.youtube.com/watch?v=lqg_Ze_OiiY&t=723s

and this one:

3] https://www.youtube.com/watch?v=mWR9Q_pTagw

which shows how can I create a capacitive touch switch using anything or Arduino nano. I am thinking to use the ATMEGA328 microcontroller to create this capacitive touch circuit and will insert the code of the first video in the ATMEGA328 to run the capacitive slider touch switch.

My main problem is that I am not able to find a light dimmer circuit without the potentiometer. I need some guidance and help regarding how can I create one without a potentiometer and how can I join this dimmer circuit with the capacitive slider switch.

I am still researching this.


texts: ARM Cortex-R for motion control application

texts:
I need to control about 50-motors(brush DC/Stepper) with each of them having an encoder for feedback.Precise motion control is needed for each motor axis.I have been looking at ARM cortex-M4 microcontrollers for this purpose.The ARM website mentions that Cortex-R series would be more suitable as it is designed for hard-real time applications like these.

However, i couldn't find any resources for getting started with Cortex-R series, particularly Cortes-R7 or R8.There don't seem to be any development boards either.Could some one point me in the right direction or give any suggestions about which controller to use here.


texts: LDO Output Capacitor Selection and ESR Consideration

texts:
For a simple application of a voltage regulator with 5V in and 3.3V out, I am looking at these three regulators.

1)AP2127K-3.3TRG1

2)MIC5504-3.3YM5-TR

3)TLV73333PDBVR

They all have different output capacitor requirements.

Regulator #1 (AP2127K-3.3TRG1) Says the following in the datasheet:

"Compatible with Low ESR Ceramic Capacitor: 1μF for CIN and COUT"

And also has this graph of stability range for an output cap of 4.7uF

To me, "Low ESR Ceramic Capacitors" means ceramic capacitors with much lower ESR than 100mOhms. What frequency is this part referring too for it's ESR ratings?

Regulator number 2 (MIC5504-3.3YM5-TR) says this in the datasheet.

"The regulator requires an output capacitor of 1uF or greater to maintain stability. The design is optimized for use with low-ESR ceramic chip capacitors. High ESR capacitors are not recommended because they may cause high-frequency oscillation."

"Stable with 1uF ceramic output capacitors"

I did not see any exact ESR ranges specified. What does this mean? "Low ESR". Regulator number 1 seems to think it's above 100mOhms.

Regulator number 3 (TLV73333PDBVR) says this in the datasheet.

"The TLV733 series is designed with a modern
capacitor-free architecture to ensure stability without
an input or output capacitor."

This means the regulator control loop is stable with 0 ESR caps and I can put any ceramic cap I want on there.

"However,
the TLV733 series is also stable with ceramic output
capacitors if an output capacitor is necessary."

Since these are all the same PCB package, I would like to provide alternate part numbers for the one I choose, but the output cap has to work with all of them.

Questions:

1) What frequencies are the datasheets referring to when they rate the ESR value? Regulator 1 and 2 seem to have different opinions. AVX Corp datasheet lists all tantalum caps ESR at 100kHz. Is this the industry standard frequency for LDO ESR ratings too?

2) I have read app notes that say not to use 0.1uF bypass caps on the output because you can end up with the pole and zero cancelling each other out and the regulator could end up unstable. But most schematics I see have one. Is this because the designer calculates what the zero and pole is or is this normally done in error?

3) Since Regulator #2 says not to use high ESR caps, does that mean regulator #1 and #2 can't use the same output cap? Since #1 would require a minimum ESR greater than the maximum ESR of #2? Even though #2 doesn't specify ESR range.


texts: Test Transmit Signal for nRF24L01 transreceiver

texts:
I have set up a circuit using my joysticks and nRF24L01 transmitter. While I am waiting for another nRF24L01 to use as a receiver, in the meantime I wanted to check whether the nRF24L01 in the transmitter circuit is working well and sending the signal out for receiver to receive.

Question: is there a way for me to test the nRF24L01 transmitter, without having a receiver circuit in place?
I want to see some confirmation on serial monitor on the data being transmitted or in other words, test the radio.write function to ensure the transmitter is working.


texts: Develop an OpAmp circuit to measure average voltages

texts:
With four different sensors, V1, V2 V3, and V4 I need to develope an operational amplifier circuit to measure average temperature with following specifications:

The output voltage range of each sensor is limited to 0-5 V
The output voltage range of average temperature measurement circuit is 0-5V
The span adjustment range is +/- 1V
Total system accuracywith +/- 0.1% of FSO

Please help me to design the above circuit.


texts: Power a 12 volt water pump from a 110 watt solar PV panel

texts:
I have a 12 volt DC 9 amp water pump that I would like to power from a 110 watt 12 volt (17.2 volt at peak) 6.4 amp solar PV panel. I only want to run the pump when the sun is out, it's circulating water through water heating solar panels.

I'm not an electrical engineer so I'm hoping to find a easy and inexpensive way to connect these two in a way that won't burn out the pump.

I've read online about using a battery and charge controller, I'm not opposed to this idea but I really only want it to run when the sun is shining bright and heating the panels.

I've also read about using a "linear current booster", this seems like it would work, but the ones I found cost over $200.

I've tried connecting the solar panel direct to the pump, but that of course did not work.

So... does any one have any ideas? Photos of the labels of pump and panel below:


texts: What Else do I Need to Make a Speaker Work in These Conditions?

texts:
Recently, I was faced with a slight challenge.

My computer stopped wanting to power on, and I needed it to work fast. As a computer technician (in-home), I had all of the tools necessary to fix the problem. Though, I somehow lost my extra motherboard speaker over time. So I got to work on constructing one.

I grabbed some of my microcontroller jumper cables for making the speaker and a female to female 4 wire cable to put on the motherboard header.

So far, I have an old speaker with the ground wires twisted together, and the left and right speaker wires twisted together.

Along with that, I have two jumper wires with one end on each stripped off (to connect with speaker and plug into female cable).

Going back to my question, what will I need to make this work?

I'm not very familiar with how to make electrical circuits, so I cannot go on without some help. I have some labeled resistors around, so if necessary, I have those.


texts: Calculate power consumption that varies every second

texts:
We know that power consumption or Energy is

E = Power x Time

for utility billing, we used

E = kWatt x Hour

But I am not sure how to get the total Energy if we will based it per second having different power over a period of time.

0.5 Watt (time check 5:00:00 AM)
1.0 Watt  (time check 5:00:04 AM)
0.7 Watt  (time check 5:00:07 AM)
and so on.

Let say I wanted to calculate the energy from 5:00:00 AM - 5:00:07 AM

Is this the right calculation?

E1 =  0.5 x 4 = 2.0 Watt-sec
E2 =  1.0 x 3 = 3.0 Watt-sec
E3 =  0.7 x 1 = 0.7 Watt-sec

E1 + E2 + E3
2 + 3 + .7 = 5.7 Watt-sec
           = .00158 Watt-Hr

I just want to know if my calculation is right.
Thanks


texts: MP1584 5v regulator voltage drop problem

texts:
I was debugging the MP1584 module, 5v regulator circuit in the PCB.
I have attached my debug circuit below.

I have completed my circuit in breadboard and PCB also, but I was connected to any load below 2A. It will produce the voltage drop and alternative output voltage.

Mp1584 specs : max 3A , i/p volt = 4.5v to 28v , my i/p volt = 12v

I need 5 V output and less than 2 A current. How can I achieve this?


texts:
2 part question here.

Are there ways to directly test the input and output capacitance of a MOSFET, Ciss and Coss? On that note, due to internal inductance and capacitance, is it possible for a standalone MOSFET to resonate at certain frequencies?

Thank you in advanced.


texts:
I would like to ask you about a problem that I have been experiencing recently. I am using a contactor to safely disconnect a hybrid motor starter. The starter is designed to, when tripped with its signal, disconnect the motor during the zero-crossing of the current waveform, reducing this way the overvoltage produced by switching off an inductive load.

Obviously, when you open the electric circuit acting on the contactor, the current waveform likely won't be zero-crossing, thus resulting in an overvoltage that may affect the TRIACs in the hybrid motor starter.

In order to reduce this effect as much as possible, the starter manufacturer suggests to install a RC snubber. All right up to this point. However, they say you can install this RC element motor interference suppression device in the terminal box of the motor or in the contactor itself.

This would make a difference because I could have a contactor to safely disconnect 3 or 4 hybrid motor starter at once, only needing one RC element instead of one per starter.

But I fail to see how this would be the same thing from an electrical point of view. That is to say, I don't see how the RC placement won't affect the overvoltage that the starter will suffer.

Thank you in advance for your help regarding this matter.

EDIT: I add an image of the problem.


texts: Observing kickback voltage in LC circuit

texts:
I'm driving an LC load using ULN2003AN IC.  The input pulses are 5V at 25 KHz with 50% duty cycle.

I connected an oscilloscope (VM1) to the coil. I was hoping to see some kickback a voltage levels, but there wasn't any. All I got was an alternating square signal between 0 and 11V.

How do I see the kickback voltage? Should I be changing the frequency/duty cycle or is it the ULN2003 not suitable for this task?

simulate this circuit – Schematic created using CircuitLab


texts: Device to switch a 220VAC/40A resistive load

texts:
I need to switch a 220VAC/40A resistive load. I only need on/off switching, no phase control. I would like to avoid mechanical (moving parts) components if at all possible because of reliability issues.

Digi-Key doesn't stock any TRIACs capable of switching 40A. I've thought about paralleling 2 or more TRIACs rated at a lower current, but if I understand this correctly, it may not be a wise thing to do.

I understand that two of these SCRs connected in anti-parallel should do the job. Although they are only capable of 40 A RMS, which appears to imply a safety margin is not included, that's not the case: according to this application note, when two SCRs are connected in anti-parallel they can handle \$\sqrt{2}\$ times as many current as each individual SCR.

I'm looking for either:

a lower cost solution, or
a solution of similar cost, but which dissipates less power (I estimate the SCRs would dissipate on the neighborhood of 30 W each, thus 60 W combined).

Any suggestions?


texts: How to attach wires on a keyboard controller PCB

texts:
I want to make a module with 3 momentary buttons that will be record the numbers of pushes on a pc.
For this first i though about using an arduino but also I am trying to use a keyboard motherboard/ controller to give a key signal, f12 on first button, f10 on second and f10+f12 on third, that will act as a keyboard input to the program on the pc.
As I couldn't solder directly on the pcb because it has a really thin sheet of coper covered in carbon powder, I had to mechanically attach the wires with 2 parts of metal on both sides and wrench them also using a conductive adhesive of 1Mohm rezistance.
After that only 2 keys worked and i have to use f10+f12 for the third button.
They all have a common wire in color white, and 2 wires separately one for f10 and one for f12. my problem is at the third button where i need to connect f10+f12 wires on one side and the common wire on the other side, i will permanently connect them also for all other contact and get the same output on all buttons.
So I used 2 diodes on the 2 wires and now all work except the third button where i get only f10 output and f12 oscillate on and off, sometimes it doesn't even show, if I keep the button pressed f12 turn off after a time but it work on the first button alone,
if i bypass that diode it works but then i get 2 identical outputs on 2 buttons that use f12, i heard of WIRE OR method to attach a resistor connected to ground at the end but it doesn't work at all
yellow wire is for f12
blue is for f10 and white is common wire
Button pressed
http://imgur.com/a/zRzCEdy
This is the button

This is the image of the instalation

This is the schematic, i atached the wires on the keyboard controller pcb at the coresponding pins for f10, 12 keys, using conductive adhesive

I didn t want to use a key combination but my conection of the wores with the board was not good and only 2 of the 3 wires i conected worked and i was thinking of getting a combinatios for the third button. Also i wires the wire on f9 key and i get f10 output , maybe if i ise that adhesive paste that has a big 1mohm resistance can influence the reading ?
If there is anothe way of ataching those wires on the keyboard mdboard, i tried soldering but they are just to thin and come lose from the pcb
I wanted to use an arduino but i am making the mechanical part of the project for my brother who wants to use this on his software, and he wouldn't want to use arduino for some reason also to not complicate the code , like this it is easier to get input but doesn t work when the program is in background on the pc..
Is there any boar that would simulate a keyboard input as f10 or any other key instead of serial comunication ? Because also i saw that arduino pro micro can be used to send keyboard inputs trought serial wich i brlive would be better because it will not intefere other stuff on pc and will be conected to the program directly
I believe the keyboard pcb deal with debouncing of the buttons itself, if i use another board i will have to deal with that in the program


texts: Identifying Source of Periodic Artifact at Op-Amp Output

texts:
My MAX44251 dual op-amp has a very small unwanted 131KHz periodic artifact at the output, seemingly regardless of how it's configured.

My assumption was EMI, but I can't see this 131KHz signal on any other part of the circuit. I've also tested this in multiple buildings, with multiple probes, with all other electronics turned off, and surrounded by foil shielding.

What should I try to remove it? I would like to at least achieve a voltage follower with noise under 1mV.

The chip was originally used in a more complex circuit when I first noticed the problem. BUT, to isolate this issue I made a whole new test PCB with fresh components. I left extra pads to reconfigure the chip in different ways while testing.

Right now it is configured very simply:

simulate this circuit – Schematic created using CircuitLab

The bypass caps are on the bottom ground plane layer. Vias are hand soldered.

I have observed the effect through both the Agilent 10X passive probe (It's hard to see), and through a probe like the following, with which I can zoom all the way to 2mv/div. Originally, it was observed because the output is fed to a comparator, and the comparator output indicated the input signal amplitude was > the desired 2mV.

The waveform is periodic but kind of strange. Here's a few pics from different angles:

200 ns Stopped

50 ns Free Running

20 ns Free running

10 ns Stopped


texts: What's the difference between AT89S52 and AT89C52?

texts:
I am working on a fingerprint security project, based on what I've read so far, I decided to go for AT89S52 as my microcontroller, but I got stuck when I decided to simulate my circuit on Proteus 7.8.

The software offers me AT89C52, but i didn't see AT89S52. So, I am stuck between using AT89C52 but am scared if is going to affect my work, since I don't know if they are the same.

I thought about using another electronics schematic software, I am willing to change but don't know what else to use besides Proteus and the Keil compiler I'm using now. What to do?


texts: Isolated circuits: can their reference voltages (GNDs) be at the same potential?

texts:
Suppose there are two independent circuits isolated from each other. If they are isolated, the impedance is very high between them (ideally infinite) and there is no current flowing from one to the other.

But if there is no current between them, because impedance is so high, shouldn't they be at the same voltage?

My first answer would be, if the circuits are isolated, one floating from the other, voltage is not predictable between both circuits.

Let's say we use a 100 gigaohm resistor to connect both grounds, so there is still plenty isolation but now they are galvanically related. There's a big impedance between both circuits and current is not flowing from one to the other, so now they must be almost at the same voltage... Right?

Connected through a big resistor or coupled through air, if there is a big impedance between circuits, shouldn't they be at the same voltage? Isn't it somehow contradictory?


texts:
I have this circuit, where i wish to turn lower one to ON after a delay, so that at one time only one of them is ON.
The input wave is a PWM Square Wave. Can anyone suggest how i can do so?


texts: Design and simulation of cross coupled oscillator in ADS

texts: I am currently designing a low power consumption and low phase noise VCO in ADS. But while performing the transient response I'm not getting the oscillating waveform in the output. I have attached the image of my circuit. Any help can be greatly appreciated.


texts: Building a micro generator, I need to account for the pulsing DC after my 3 phase diode bridge

texts:
I wound my own motor, and tested it to be about 300 RPM per volt, and if my noob math is right, it should be able to handle about 1600 watts with a ~40 volt supply without burning my nice but thinly insulated wire.

My idea now is to drive this motor with an engine of some kind to get it to turn a little more than 12000 RPM, run the 3 phases through a powerful 1600v 150a rated diode bridge, and hook a capacitor on the other end.

The problem is, I borrowed a friend's oscilloscope and found that when I turn it at about 1,000RPM with a drill, I am getting HUGE voltage spikes. There's obviously little to no load, but i'm getting 4-500v spikes, maybe even up to 1kv. They're very very short spikes.

I get the picture that these will disappear with a load on the motor, but I want to ensure the several thousand hertz DC pulses I am getting at the other end are being somewhat dampened by a capacitor. Is there some math I can do to determine what voltage rating and how many farads/microfarads I need to balance the pulses out? I'm worried about getting a cap rated for 500v and it being too much, but I'm also worried about it blowing the eff up when I actually start putting power through it. I've intentionally blown up tiny electrolytic caps and they are basically bullets. Don't really want to find out what a hand grenade sized one will do.

If there's no way to bridge the super high frequency pulses in a small form factor, I suppose I can just wind the motor to a lower v/rpm, but either way, I want to do it safely.

My end goal is to get 1,000 watts out of it, although 1600 would be outstanding. I doubt the system is going to be more than 10% efficient, but we'll see.

As a side note, I plan on shielding the whole thing with brass mesh to keep EMI down, as I imagine it will produce quite a lot.


texts: What is the purpose of a disconnectable wire in this power supply?

texts:
In this circuit, there is a wire between M5-1 and M5-3 (at the bottom). It's a little plastic connector with a wire in it that you can pull out.

I've been trying to debug a power issue after recapping this 1980's power supply. At first, I forgot to put that connector back. Some of the reading looked correct, but others were too low. When I added it back, the formerly-correct readings jumped to ~1.5x.

What purpose does this connector have in this circuit? Why would you want it connected? Why disconnected? Why isn't it just permanently there?


texts: Why does increasing the sampling rate make implementing an anti-aliasing filter easier?

texts:
From an answer to a question regarding sampling rate and anti-aliasing filter I read the following:

  The closer you get to the theoretical minimum sample rate, the more
  difficult the analog filter become to realize practically.

If I'm not mistaken it says if our sampling rate is close to our required theoretical minimum sample rate, then designing the analog anti-aliasing filter will be more difficult.

I'm sure it makes sense for many but I couldn't figure out what is meant here and why is that so. Could this be explained with an example in a simpler way?


texts: Why isn't a transformer a short circuit?

texts:
I'm a newbie with electronic components and I never fully understood why transformers, while essentially being a short-circuit from a wire perspective, don't act like short circuits (i.e. they don't just blindly behave like a waterfall of electrons).

Why is that and how is it related to the "load" attached to the transformer itself?
I'd prefer a 'layman's terms' explanation but I don't mind some math if necessary.


texts:
A camera will be mounted outside and powered via POE to Aruba 2540 network switch. I don't want indirect lightning surge to travel into the network switch. I don't care if the camera gets destroyed.

The ethernet line to line voltage is 54V, and the requirement that I have is that the TVS should clamp lighting surge upto 2000V or 400Amps.

What kind of circuit would I need for lightning protection with a TVS?


texts: Why ACS712 is abruptly dropping its voltage output?

texts:
I have built a board as shown in the images and the schematic below. I know that according to the datasheet when no current is flowing through the ACS712 it should output something around 2.5V always. However, the sensor is presenting a weird behaviour: When I power the whole board and measure the voltage across the ACS712 output and ground I can see the voltage of 2.5V for a few moments, but then its voltage output drops to something around to 0.3V and keeps oscillating until the maximum of 0.8V.

What could it be? I have already tested with other brand new parts of ACS712 and the same behaviour is occurring.

Things I think it's important to know:

The logic voltage (Vcc) is always stable. 4.99V ~ 5V
The whole board is an H-bridge with a current sensor on it.
When the board is powered (with no load), I can note that the voltage regulator heats, not too much, but the enough to create discomfort after some time.
The L293DD also heats, but less than the voltage regulator

May it be a hardware fault? Maybe the temperature? Maybe some external interference?

Can anyone help me?


texts: Controlling a Wi-Fi relay switch using a "no-neutral" touch wall switch

texts:
I'm planning to install touch wall switches in my apartment. They appear to be powered by leaking current through the switched receiver (e.g. a lightbulb) – no neutral connections.

I also wanted to be able to control them over Wi-Fi and the Shelly switches seemed to be a perfect match. However, due to the way the touch wall switches are powered, I cannot simply connect the wall switch's live output to the SW terminal on the Shelly as that would be recognized as a constant powered on state (I actually verified this physically).

Additionally, some kind of load has to be connected to the wall switches in order to power them – I'm thinking a resistor of some sort, perhaps a so-called LED adapter provided by most touch switch vendors.

What would be the best way of solving this? I'm considering an AC-AC SSR as in the diagram below:

Let me add that limited junction box space is also an important factor. I did put additional boxes in place in order to make room for additional circuitry, but it's still pretty tight.


texts:
what is meant by  LX9 ?
I know XC is xilinx corporation and 6S stands for spartan 6.


texts: Sawtooth waveform used for wireless battery charging

texts: Why don't we use sawtooth AC waveforms instead of the sinusoidal ones? Since the rate of change of voltage is steady for a purely resistive circuit the rate of change of current is costant-> linear change of the magnetic field around so we could use it as a  battery charger or a rectangular waveform generator(from Faraday's law of induction if V = -ΔΦ/Δt , ΔΦ changes linearly over time so the induced voltage is costant).


texts: Need help identifying replacement Magic Smoke Container

texts:
Was doing some electrical work, plugged in a charger for an LED work light, the thing goes foof, charging is not happening so much right now.

I took the charger apart, and the only thing that looks even remotely in a post-foof state is the one pictured (the board itself appears undamaged, albeit scorched). I'm assuming it's a resistor, but I don't claim to be certain, and I don't know which size/rating. There is a black band at the bottom and a brown band at the top, and I don't think there are any bands gone missing since "the incident".

Can you identify it, so that I can replace it and see if that revives the charger? I would like that very much.

The charger is marked as "110-230V, 0.3A" with output rating of "5V 1500mA".

Photos:

Top side 1

top side 2

bottom side (component is between indicated holes)


texts: How to use separate power source for raspberry pi + Arduino and motors as shown in the image below

texts:
Is it possible to make this circuit or will this work?
I want to power the raspberry pi and Arduino with a powerbank and motors with a separate battery through the driver module as the diagram shows. I used The same components as labeled in the diagram.


texts: Measuring Voltage from Photodiode with OpAmp

texts:
I am trying to measure the voltage coming out from my OpAmp after connecting it to my Photodiode. As a Photodiode I am using the BPW34S from Vishay and the Op Amp is the AD822ANZ from Analog Devices. According to the Analog Devices Photodiode Circuit Wizard the following image should be my connection:

The Cathode of my Photodiode is connected towards the Op Amp, while the Anode is connected to the Ground.
I am using a 9V Battery to power my Op Amp as a single supply. The '-IN1' is connected as shown in the above image, '+IN1' is connected to the ground, as is 'V-' and 'V+' is connected to the positive side of the 9V Battery. As ground I am using the negative side of the battery. (I have also tried using the 5V and GND output of a RaspberryPi 4 but I thought that maybe I was not getting enough Voltage).
I have measure the voltage between the Vout and the Ground of the battery with a Voltmeter, but I always get a value of 0V as output from my OpAmp and there is no change when I put more light on my Photodiode.
My Photodiode is working when I connect it simply with a resistor and measure the Voltage passing through the resistor. But I need it to work with an OpAmp as I want to connect it to an ADC afterwards.
I am doing something wrong with the wiring or is there a problem with my Op Amp?


texts: Substituting a matrix keyboard push button with transistor

texts:
I have a remote like this

I removed the plastic sticker and below, we have a series of push buttons. Two pieces of copper in SSS form. When you push and the plastic bends, a little metal piece touches the SSS and you close the circuit.

The device seams to be performing some kind of scan over the rows and the columns since the buttons clearly share "pins" of the "chip".

I tried short-cutting with a piece of wire the two sides of one button and I can easily fake a finger press.

I tried substituting my finger by a transistor powered from the RasPi and .. there is no way to get it to work :(

I removed the battery of the remote and powered straight from the 3V3 of the Pi. The device works (short cutting still works).

I connected emitter and collector to the proper places. (To discover the polarity I short cut it with a diode. It only works in one direction as expected.)

I then connected a 200 omh resistor to the base and connected to the 3V3 and ... nothing happens ...

What can be happening? I tested the transistor in a protoboard with an LED and it works as expected.


texts: How do I find the second order transfer function from this response graph?

texts:
I am trying to find the second order transfer function from this response graph, however since I can't find the correct overshoot value I'm stuck. The graph runs from 0 to 10 seconds and starts at 1 second. The acceleration starts at 0 and ends at 0.
The zero's are [0 -1.5+10i and -1.5-10i ] and the poles are [-1.5 -1-9i -1+9i].


texts: I want to measure lead acid battery self-discharge but I not sure when to trigger the self-discharge measurement algorithm. Is it constantly self-discharge or only in standby mode (no load)? If a battery does always self-discharge then what is the self-discharge rates for load-discharging and charging conditions?


texts: What does the X symbol mean at wire junctions?

texts:
I am a hobbyist and recently acquired a dead Gameboy that I am going to attempt to repair. My first thought is to clean up the damage from leaking caps and batteries and replace the caps. I was trying to understand it a little better and happened upon the following schematic, however I am not sure what the X means at certain wire junctions. I am thinking it means it is not connected?

Further, the power switch has a strange wire symbol that curves up to a white rectangle. Not entirely sure if this is supposed to be a thermistor or something else?

Gameboy DMG-1 power schematic


texts: i touch the PSU|(power supply) bare wires 12v with my hands but nothing happens when power supply is on its harmless or not? please someone reply me i want to know,thanks in advance,i use the power supply in a socket and for beacons 12v


texts: How do electrons carry thermal energy in Peltier coolers?

texts:
I've read that when electrons enter from metal to semiconductor type N, they gain thermal energy and make that side cooler and the reverse happens when they leave semiconductor to the conductor.
Why does this happen?  How do electrons gain, hold, transfer and lose this thermal energy in this process?


texts: ADC / DMA only triggers once before setting OVR high STM32F446

texts:
I am trying to poll a block of sensors and load the data into an array via the DMA but the ADC polls only the first pin and then stops polling and sets the overrun flag high. I have implemented all the solutions I have seen for others having similar problems but can't figure it out. Any help would be appreciated

Code:

#include "main.h"
#include "stm32f4xx.h"
#include <stdio.h>
#include <stdarg.h>

void SystemClock_Config(void);
void printfToSerial(char buf[], ...);
void printToSerial(char buf[], int length);
void DMA2_Stream4_IRQHandler(void);

uint16_t sensorReadings[2];

int main(void)
{

    SystemClock_Config();

    //DMA Setup
    RCC->AHB1ENR |= RCC_AHB1ENR_DMA2EN;
    DMA2_Stream4->CR |= DMA_SxCR_MSIZE_0 |
                    DMA_SxCR_PSIZE_0 |
                    DMA_SxCR_MINC |
                    DMA_SxCR_CIRC |
                    DMA_SxCR_EN |
                    DMA_SxCR_TCIE;

    NVIC_EnableIRQ(DMA2_Stream4_IRQn);

    DMA2_Stream4->NDTR = 2;
    DMA2_Stream4->PAR = (uint32_t) (&(ADC1->DR));
    DMA2_Stream4->M0AR = (uint32_t) (&sensorReadings);
    DMA2_Stream4->CR = DMA_SxCR_EN;

     //ADC Setup
    RCC->AHB1ENR |= RCC_AHB1ENR_GPIOAEN;
    GPIOA->MODER |= 0xF;

    RCC->APB2ENR |= RCC_APB2ENR_ADC1EN;
    ADC->CCR |= ADC_CCR_ADCPRE_0;
    ADC1->CR2 |= ADC_CR2_ADON | ADC_CR2_CONT;
    ADC1->CR1 |= ADC_CR1_SCAN;
    ADC1->CR2 |= ADC_CR2_DMA | ADC_CR2_DDS;
    ADC1->SMPR2 |= ADC_SMPR2_SMP1_1 | ADC_SMPR2_SMP0_1;
    ADC1->SQR1 |= 1 << ADC_SQR1_L_Pos;
    ADC1->SQR3 |= 1 << 5;

    //USART Setup
    RCC->AHB1ENR |= RCC_AHB1ENR_GPIODEN;
    GPIOD->MODER |= 0xA << GPIO_MODER_MODER8_Pos;
    GPIOD->AFR[1] |= 0x77;

    RCC->APB1ENR |= RCC_APB1ENR_USART3EN;
    USART3->CR1 |= USART_CR1_UE;
    USART3->BRR |= 22 << USART_BRR_DIV_Mantissa_Pos | 13; //5 + 12/16 = 5.75

   HAL_Delay(1);

   ADC1->CR2 |= ADC_CR2_SWSTART;

   while (1)
   {
    printfToSerial("%d, %d\n", sensorReadings[0], sensorReadings[1]);
   }

}

void DMA2_Stream4_IRQHandler(void)
{
    DMA2->HIFCR &= ~DMA_HIFCR_CTCIF4;
}


texts:
I have a little confusion about sensitivity list rule: all signals that are read in the always block must be included in the list. When including the posedge CLK and EN in my sensitivity list, I get value of x changed when either of signals in the sensitivity list changes. Thus, if EN changes in the middle of the clock cycle, x changes accordingly, which is expected. However, this is not the outcome I wish to get:

always @(posedge CLK, EN)
if(EN)
    x <= 1;
else
    x <= 0;

I need the value of x to change only at the rising edge. Therefore, I remove the EN from the list to achieve desired outcome. But then, this violates the rule.

This is, probably, a very trivial question, but could someone clarify what's the proper way to implement it?


texts: Does the number of resistors make a difference?

texts:
I have got a simple circuit, where a relay is used to decide which LED lightens up (and I did a small mistake in the image: The power source is actually 12V, not 1V):

simulate this circuit – Schematic created using CircuitLab

Now, my question is: Would it be feasible to have two resistors instead of one, if you would link the wires behind the resistors instead of before them? Does this make any difference?

simulate this circuit

(Of course it does not make sense to use two resistors if it also works with one, but I'm curious ;-))


texts: Running a 12v fridge and protecting the battery from low voltage

texts: I want to run a 12V (65W) fridge from a battery circuit on a boat. However, I want to protect the battery from being drained and potentially damaged by the fridge if the voltage drops too low so I need a switch that will open the circuit if the voltage drops below ~11.5V and close it again once it reaches 12V. What is this sort of switch called so I can search for one?


texts: Do I need isolation for op-amp stages in a current pump circuit like this?

texts:
U3A (OPA703) is used to shift a unipolar DAC signal down to a bipolar signal and feed it to U1 (OPA544). The OPA544 takes this bipolar signal and produce a pretty high current of about 3 Amps at the OUT pin.

In my opinion, U3A is the control stage and U1 is the power stage. I think these two kind of op-amp stages should be isolated, so I created isolated power supplies for them with different GROUND (DGND and AGND).

Does this affect the circuit's operation as a whole?

I used the current source design in LM675 datasheet: www.ti.com/lit/ds/symlink/lm675.pdf


texts: How to turn a PLC smart meter into 3G or Wifi

texts:
My utility has deployed bout 300,000 ZX E221 Three Phase Prepayment Smart Meters and they consist of a Meter control unit (MCU) which the consumer cannot access and a User Interface Unit (UIU), which displays data and has other controls. The MCU communicates with the UIU via PLC, but not communication exists between the meter and the utility.

Since the utility now wants to have access to consumption data they want to know if it's possible to access the data transmitted via PLC between the modules and relay that data via cellular, wifi or another technology.

Is this possible?
Is there a device that can already do this or does it need to be developed? (that's an option).

Thanks!


texts: how to offseting voltage for ph electrode?

texts: is it necessary to use circuit below for offseting? and what is the difference if I connect directly 512mv Voltage to my ph electrode?


texts: Which transistor should I use to PWM switch my car's 12V power with my Arduino's 5V?

texts: I am very confused about these transistors and don't really know what I'm looking for. I am looking for a transistor I can use right now, but I would also like to learn what to look for so in the future I can solve this myself.


texts:
As I read the Nordic datasheet for the nRF51822, the GPIO pins on the chip are able to source or sink 0.5mA, or 5mA for up to three pins configured in high-current mode.  As the schematic shows, the 25 LEDs on the micro:bit are connected electrically in three rows of nine (with two gaps), with common anodes in each row, and a series resistor of 220R for each column, and both columns and rows directly connected to GPIO pins.  This gives a current in each LED of about (3.3V - 2V)/220R = 5mA, making more like 50mA sourced from the pin driving a row of nine LEDs through their common anode.

Have I missed something, or is the chip being used far outside its specification?


texts: Confusion about DC current through conductors

texts:
From electrostatics, we know that all the charges reside on the surface of a conductor. We also know that there is no skin effect for DC flow, which implies uniform flow of current throughout the conductor.

Now my confusion is: since charges accumulate on the surface of the conductor,
shouldn't current flow only along the surface of conductor (for both AC and DC currents)?

Could you please clarify?


texts: How to add a n-mosfet subckt model in gschem ngspice?

texts:
I want to add a N-Mosfet subckt Model.

.SUBCKT ZVN0124A 3 4 5
*                D G S
M1 3 2 5 5 MN0124
RG 4 2 225
RL 3 5 2.4E7
C1 2 5 60E-12
C2 3 2 2E-12
D1 5 3 DN0124
*
.MODEL MN0124 NMOS VTO=1.5512 RS=1.436 RD=9.254 IS=1E-15 KP=1.077
+CBD=36E-12 PB=1 LAMBDA=0
.MODEL DN0124 D IS=3.071E-12 N=1.026 RS=0.511
.ENDS ZVN0124A

What have I do:

This are the attributes of spice-model-1.sym

This are the attributes of Mosfet

If I start the simulation I get a error:

**gnetlist -g spice-sdb -o buck1.net buck1.sch**
**ngspice**
*ngspice 2 ->* **source buck1.net**

Error on line 44 : mq1 ub us2 um zvn0540a
  Unable to find definition of model  - default assumed


texts: TIM 2 PWM Input on different pin STM32F072B Discovery

texts:
I'm trying to change the pin, that is connected to TIM2 in PWM Input mode for frequency measurement.

I just compiled the example, tested it and it works on pin PB03, however, when I try to change the pin to anything else, e.g. PB4, or PA10 the pin doesn't connect to the Timer at all. (Tried through debug.)

I

The setup code:    //The only changes are in the GPIOConf

static void TIM_Config(void)
{
  GPIO_InitTypeDef GPIO_InitStructure;
  NVIC_InitTypeDef NVIC_InitStructure;
  TIM_ICInitTypeDef  TIM_ICInitStructure;
  /* TIM2 clock enable */
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);

  /* GPIOB clock enable */
  RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA, ENABLE); //Change here, to GPIOA

  /* TIM2 chennel2 configuration : PB.03 */
  GPIO_InitStructure.GPIO_Pin   = GPIO_Pin_10;  //Change here, to pin 10
  GPIO_InitStructure.GPIO_Mode  = GPIO_Mode_AF;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
  GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
  GPIO_InitStructure.GPIO_PuPd  = GPIO_PuPd_UP ;
  GPIO_Init(GPIOA, &GPIO_InitStructure);   //Change to GPIOA

  /* Connect TIM pin to AF2 */
  GPIO_PinAFConfig(GPIOA, GPIO_PinSource10, GPIO_AF_2); //And change to pin 10

  /* Enable the TIM2 global Interrupt */
  NVIC_InitStructure.NVIC_IRQChannel = TIM2_IRQn;
  NVIC_InitStructure.NVIC_IRQChannelPriority = 0;
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
  NVIC_Init(&NVIC_InitStructure);

   /* ---------------------------------------------------------------------------
    TIM2 configuration: PWM Input mode
     The external signal is connected to TIM2 CH2 pin (PB.03)
     TIM2 CCR2 is used to compute the frequency value
     TIM2 CCR1 is used to compute the duty cycle value

    In this example TIM2 input clock (TIM2CLK) is set to APB1 clock (PCLK1), since
    APB1 prescaler is set to 1.
      TIM2CLK = PCLK1 = HCLK = SystemCoreClock

    External Signal Frequency = SystemCoreClock / TIM2_CCR2 in Hz.
    External Signal DutyCycle = (TIM2_CCR1*100)/(TIM2_CCR2) in %.
  Note:
  SystemCoreClock variable holds HCLK frequency and is defined in system_stm32f0xx.c file.
  Each time the core clock (HCLK) changes, user had to call SystemCoreClockUpdate()
  function to update SystemCoreClock variable value. Otherwise, any configuration
  based on this variable will be incorrect.
  --------------------------------------------------------------------------- */

  TIM_ICInitStructure.TIM_Channel = TIM_Channel_2;
  TIM_ICInitStructure.TIM_ICPolarity = TIM_ICPolarity_Rising;
  TIM_ICInitStructure.TIM_ICSelection = TIM_ICSelection_DirectTI;
  TIM_ICInitStructure.TIM_ICPrescaler = TIM_ICPSC_DIV1;
  TIM_ICInitStructure.TIM_ICFilter = 0x0;

  TIM_PWMIConfig(TIM2, &TIM_ICInitStructure);

  /* Select the TIM2 Input Trigger: TI2FP2 */
  TIM_SelectInputTrigger(TIM2, TIM_TS_TI2FP2);

  /* Select the slave Mode: Reset Mode */
  TIM_SelectSlaveMode(TIM2, TIM_SlaveMode_Reset);
  TIM_SelectMasterSlaveMode(TIM2,TIM_MasterSlaveMode_Enable);

  /* TIM enable counter */
  TIM_Cmd(TIM2, ENABLE);

  /* Enable the CC2 Interrupt Request */
   TIM_ITConfig(TIM2, TIM_IT_CC2, ENABLE);
}

And the Interrupt code: //I have changed nothing in it

void TIM2_IRQHandler(void)
{
  /* Clear TIM2 Capture compare interrupt pending bit */
  TIM_ClearITPendingBit(TIM2, TIM_IT_CC2);

  /* Get the Input Capture value */
  IC2Value = TIM_GetCapture2(TIM2);

  if (IC2Value != 0)
  {
    /* Duty cycle computation */
    DutyCycle = (TIM_GetCapture1(TIM2) * 100) / IC2Value;

    /* Frequency computation */
    Frequency = SystemCoreClock / IC2Value;
  }
  else
  {
    DutyCycle = 0;
    Frequency = 0;
  }
}

From my understanding, everything regarding the connection to the pin should be done by the pin AF mode 2 - which should connect it to TIM2, but this apparently doesn't happen.

I'm using the STM32F072B-DISCO, and KEIL v5

It is all from the default STM32CubeFW examples, and the project can be found under STM32F072B-Discovery_FW_V1.0.1\Projects\Peripheral_Examples\TIM|PWMInput\

Thank you for any help.


texts: Efficient methods of Chaining Uninterruptible Power Supplies

texts:
Let's assume I have 2 identical UPS and deep cycles are not preferred for battery lifetime.

I can think of 3 different methods to combine. Which one of these methods should I be using under which circumstance? Or should I even use these methods?

Daisy Chaining. I plug them in series. Straight forward but the first one closer to the grid will die very quickly.
Taking out the batteries from the first UPS and Connecting them up to the other battery pack in parallel. Current limit in total will be reduced but at least will I have twice the Ah storage?
Paralleling UPS outputs. Can this be achieved ?


texts: Design practice crossing clock domains and async signals

texts:
I have been designing a few projects on different FPGA's in VHDL, and it seems my most common source of "hard to find errors" is when I forget to synchronize an async signal, or forgets to resync a signal crossing clock domains.

My best weapon so far, has been to draw block schematic of the components.

So my questions is, what is the best design practice to prevent these errors?


texts: What is the meaning of carrier out for an IR receiver?

texts:
I was looking to buy an IR receiver to decode my remote control and was looking at a catalogue at http://www.vishay.com/docs/49845/_sg2145.pdf.

On page two the carrier frequency is mentioned as carrier out for the last two modules while for every other module it lists a specific frequency like 38 kHz,etc.
Can someone help me understand what it is and if these are different than a regular IR receiver module?


texts: Does a program exist to draw logic signal waveform from csv data?

texts:
Assuming that I want to collect several seconds of activity of digital signal on multiple pins of a device, one way is to create a simple FPGA design that buffers all that information and then transmits it to the PC or stores it into a file (csv format e.g) on some form of removeable media (by using a softcore with code that can read/write file access system for example).

Once I have this sequence of 1s and 0s on my PC, I would like to visualize all the activity by making waveforms that can be zoomed in, zoomed out and panned and perhaps do some processing on the results e.g collect sequence of serial bits into a single byte during post processing and then do maths with it.

Does a method to do such post processing of data collected via a custom solution (involving FPGA in this case), exist?

I do not have a logic analyzer and do not think that a logic analyzer can capture a lot of data like this as it has a very limited buffer space and sample rate anyway for such a situation.


texts: How to convert following Karnaugh map to a simplified Boolean expression?

texts:
This is the Karnaugh map which I draw for F = A'B'C'+AB'C+A'BC+ABC'
But  I am not sure how to simplify the Boolean expression for this as there are no groups here


texts: Low frequency Antenna(128khz, 80khz) interference

texts:
Using the antenna, the antenna is used to identify the individual parts of the animal individually.
As livestock passes by, the antenna recognizes the individual animal tag.

The antenna frequency uses transmit(128 khz) and receive(80 khz).

But I suspect that there is a situation where we are not receiving interference from anywhere. because we do not perceive about 10 to 20 %. Only this farm has this problem.

Is there any interference in that frequency band?


texts: Thermal generation of electron-hole couples and reverse biasing

texts:
I'm studying the PN junction and I have some problems figuring out thermal generation of couples electron-hole in reverse biasing.
The analysis is the standard one (for example, one can find it in the Sedra-Smith book, PN junction chapter) and it assumes the two-region approximation with an abrupt change, as in the following figure (from Wikipedia):

Intuitively, how the following relation is explained (always in a condition of thermodynamical equilibrium)?

$$p_n(x_n)=p_{n_0}e^{\frac{V}{V_T}}$$

Notation: \$p_n(x_n)\$ holes in n-zone at the edge between depletion region and neutral region, \$p_{n_0}\$ thermally generated holes in the n-zone at equilibrium without biasing, \$V\$ voltage applied between p and n terminals, \$V_T\$ thermal voltage.

What bothers me is the fact that for heavy reverse polarization (\$V\$ very negative) the thermally generated holes at that edge are practically 0, which for me is very strange, because this is a thermal phenomenon that in principle, I think, has not to be influentiated from the presence of an electric field.

Thank you.


texts: How to calculate the input impedance of a transistor in saturation

texts:
I have a simple circuit where a single transistor is used as an inverter.
The transistor is in saturation when the Base of the transistor is high enough and the output, through the collector is driven low.
But my question is how do I calculate the input impedance, when the transistor is saturated?

Here is my circuit


texts: Does anybody know which pin is cathode at PowerDI-123 socket? Diodes Inc. datasheets are rather confusing and I have no real diode in hands to measure it. (I suppose larger pad is cathode because there is mark and suggested pad layout is reversed.)


texts: How to turn a Latch circuit from Press-ON/Press-OFF to Press-ON/Hold-OFF circuit and how to make it auto-off when power is first connected?

texts:
I'm building a Latching circuit using 555 IC. The schematic is as follows:

The Input voltage is 12V and is used to operate the 555 IC that switches a relay coil through a transistor.
When the circuit is  implemented on a breadboard, it turns on when the power is first connected. How can I change it to be off when power is first connected? Also, it turns on when button is pressed and then off when pressed again. How to make it turn off by long press?