texts: Active highpass filter for microphone, how to choose cutoff frequency?

texts:
I am currently taking a class on filter design, and I am learning by doing.
I want to make a small project by building a microphone circuit.
I found online a tutorial by Great Scott. He made a circuit like this. His results were pretty good so I will probably leave it as it is. His design already has a low and high pass filter implemented in the design building a bandpass filter.

I am thinking also about implementing an active high pass filter on the end of the circuit to cancel out low frequency noise and get better signal quality and also practice the real world application of what we do in the lecture. I used the  Texas Instruments filter design tool to create a  3rd order Bessel filter, with 3dB gain because its voltage peaks were around 3V. I think it would be better if they were closer to 5V, I was thinking a little less than 4.5V.
Now my problem is that I have no idea how to choose the cutoff frequency. I was thinking 60Hz would be induced from AC wires around the house etc. So triple that at 180Hz should be good - I guess. I would appreciate any input and help on the matter.


texts: I am using Mplab X IDE. My question is what does the colours Red, yellow and green dots during selection of programmer indicate ?


texts: Magnitude of transfer functions of two filters

texts:
I need to find the magnitude of transfer function of the follwing two filters. I tried to do the calculation but I get two functions that seems to be incorrect. Here is what I found

1)

simulate this circuit – Schematic created using CircuitLab

$$G(f)=V_{out}/V_{in}=\frac{2 \pi  f L R_p}{\sqrt{\left(R R_p-4 \pi ^2 c f^2 L R R_p\right)^2+4 \pi ^2 f^2 L^2 (R+R_p)^2}}$$

2)

simulate this circuit

$$G(f)=V_{out}/V_{in}=\frac{R_p \sqrt{4 \pi ^2 c^2 f^2 R_s^2+\left(1-4 \pi ^2 c f^2 L\right)^2}}{\sqrt{4 \pi ^2 c^2 f^2 (R (R_p+R_s)+R_p R_s)^2+(R+R_p)^2 \left(1-4 \pi ^2 c f^2 L\right)^2}}$$

Are those the correct transfer functions of the two filters?

Edit : For circuit 2)

I found total impedance
$$Z=R+\frac{1}{\frac{1}{\text{Rp}}+\frac{1}{-\frac{j}{2 \pi  c f}+2 j \pi  f L+\text{Rs}}}$$

I wrote the ratio

$$1/Z \cdot \frac{1}{\frac{1}{\text{Rp}}+\frac{1}{-\frac{j}{2 \pi  c f}+2 j \pi  f L+\text{Rs}}}=\frac{(Rp (-1 + 2 c f \pi (2 f L \pi - j Rs)))}{(
Rp (-1 + 2 c f \pi (2 f L \pi - j Rs)) +
 R (-1 + 2 c f \pi (2 f L \pi - j (Rp + Rs))))}$$

Taking magnitude

$$\frac{\text{Rp} \sqrt{4 \pi ^2 c^2 f^2 \text{Rs}^2+\left(4 \pi ^2 c f^2 L-1\right)^2}}{\sqrt{\left(R \left(4 \pi ^2 c f^2 L-1\right)+\text{Rp} \left(4 \pi ^2 c f^2 L-1\right)\right)^2+(2 \pi  c f R (-\text{Rp}-\text{Rs})-2 \pi  c f \text{Rp} \text{Rs})^2}}$$

Which should be the same as above.

Nevertheless this does not seem right since, for resonance frequency the ratio is zero, while it should not be zero if \$R_s\neq 0\$.

Is there a simpler way to get the correct result?


texts: How to install Arduino Driver, if it is not discovered by pc(Win10)?

texts: I bought an Arduino Uno on amazon, and when I connect it to my pc it is not discovered by the pc. Even if I use hdwwiz and install the driver, it says that the device can't start. Even if I install dpinst-amd64 , it doesn't help. Is there anyother way this can be solved?


texts: Understanding opamp feedback loop with parallel paths

texts:
I am trying to understand this feedback topology. C1 is probably there to form some kind of filter however I am not sure how to go about analyzing this network. The 500 ohms resistor is just a dummy load. I think the DC feedback factor is (100+2.5)/2.5, we can just ignore R8 at DC because it would be inside the FB loop. However, I am not sure.
Thank you.


texts: Capacitor voltage in buck converter and how it steps down voltage

texts:
I am having an issue understanding how the a buck converter circuit actually steps down the input voltage. Specifically, my issue is regarding the capacitor charging and discharging. Let's consider the basic buck converter diagram with an ideal switch:

When the switch is closed an increasing current flows through the inductor, going to the capacitor and the capacitor is charging, right? Now, when the switch is opened, a negative spike appears at the node prior to the inductor such that the diode is forward biased and the polarity of the inductor voltage is reversed. Now, I really haven't figured out what happens with the voltage of the capacitor. Is there a negative current now going to the capacitor which means that the capacitor voltage is decreasing?


texts:
This is my first attempt at learning Verilog HDL testbench for an AND gate:

   '
   '
initial
   begin
  //case 0
  A_t <= 0; B_t <= 0;
  #1 $display("F_t = %b", F_t);

  //case 1
  A_t <= 0; B_t <= 1;
  #1 $display("F_t = %b", F_t);

  //case 2
  A_t <= 1; B_t <= 0;
  #1 $display("F_t = %b", F_t);

  // case 3
  A_t <= 1; B_t <= 1;
  #1 $display("F_t = %b", F_t);

  end
endmodule

My question is  since this is for a two input we had only four test cases, lets say we have 2000 cases, then can we use a for loop as shown below:

   '
   '
initial
  begin
 for (i=0;i<2000;i++)
{
 for (j=0;j<2000;j++)
 {
A_t <= i; B_t <= j;
  #1 $display("F_t = %b", F_t);
 }
}
  end
 endmodule

Is this legally correct to use loops like this? If not then please suggest me the correct method for automating the inputs.


texts:
The following circuit is part of an electronic drum kit, and is repeated several times on the board to connect piezo elements to a micro-controller that samples the various inputs. I've represented the piezo sensor as an AC voltage source in the diagram.

I'd appreciate your help in understanding what's happening in this circuit, and what the responsibilities of the different components are. Below is few guesses as to what I think is going on, but I'd really appreciate some clarification on the intended functionality and how it's achieved.

C1

This seems to do AC coupling of the input to the rest of the circuit. For this application, only changes in pressure are relevant, so I guess that makes sense if that's what its sole purpose is. Maybe it's serving another function, too?
D1

I believe this is to keep the signal towards the MCU from going too far below 0V for the negative part of the input waveform, while leaving the positive half unaffected. Presumably that's to avoid damage to the MCU.
R1

I'm unsure what this does. Is it just limiting current? Is it there to match impedance with something? Is it perhaps forming a filter with some of the other components?
R2

I think this is a pull-down resistor, but maybe it's also part of some filter in combination with other components?
C2

This looked to me like it's supposed to smooth the output, but I'm not sure about it. It seems like in an application like this you'd want crisp edges to detect on the micro-controller. I guess it's part of some kind of filter?

That's my wild guesses on this circuit so far. Your corrections would be much appreciated, as would links to sources that'd help me figure questions like these out on my own in the future.

Thanks!

Extra information as per previous responses:

Here's pictures of the 4 instances of this circuit on the board I'm working with. The pin headers shown go off to the piezo sensors, and the vias after the zero ohm resistors are connected to micro-controller input pins.

Also please note that the capacitor values were quite off in my original question with 1mF for C1 and 100 pF for C2, which many of you pointed out as wrong. I've since removed both capacitors from the circuit for measuring, and have updated the capacitor values accordingly.


texts: How to distinguish different identical sensors in a CAN bus network?

texts:
Knowing about CAN bus protocol, there are parts I couldn't understand entirely. Consider a car, with lots of sensors, say throttle sensor, parking sensor, temperature sensors located at different parts of the car. I know how arbitration works between them but here is the thing: how does the relevant ecu that will process the temperature distinguish the two different sensors? Is it that the two sensors -though their job is the same, to measure the temperature- have different IDs compared to each other? (btw yes I know one node can send different messages with different IDs)

So, let's say there are two exact temperature sensors, one inside the car for the air conditioner(not so important) and one located near the engine(very important) and it is broken. Can't I replace the broken one with the other one?


texts: I have 2 of theses converters. I am trying to get 48v. Can I connect the outputs in series to achieve this?


texts: Fast but affordable way to crimp dupont connectors

texts:
I'm currently doing a small production run of a board I designed. It features a few pin header type dupont connectors which are used to attach cables to the board.

Now, I can surely crimp this using a handheld crimp tool, but I could really use a faster and easier way to do this. I've seen a few of these super-expensive crimper/stripper machines, but as I said, they're super expensive. It's important to note, that I'm not going to open a factory which needs to do 100 000 crimps per day. Instead I need something that can help me crimp around 400 connectors in a single run without spending something like 5 hours doing crimps and pulling my hair out out of frustration.

If it were also possible to strip the wires during the same process, that'd be really amazing.

If anyone could suggest a method of crimping these connectors ideally priced under $1000, it would be really life saving. I don't really care whether it's a fully automatic machine or manually operated tool, as long as it can help me work faster, than if I'd used a hand tool.


texts: Long range communication for a wearable device

texts: We are building a wearable device for low resource settings and are trying to figure out a way to be able to send the data collected over a long range say 5-6 miles at a base station/hospital. What would be the best protocol to use in this case? Also, since this is a wearable device we will have to take into account any possible effects on the body on using a particular kind of communication protocol. Apologies if this is vague. We are still fleshing out the final details and data transmission is a very critical piece which we are grappling with.


texts:
To some this might be a weird question, But I am really confused about the definition of reactive power(of what I know, I think it is used to create magnetic flux)..
If am correct, then how is the power factor of a DC machine unity,when it also requires some current to maintain flux across electromagnets.

(A beginner in field of machines)..


texts:
I have used pi filters in the past with the USB powers and it worked great. This time I need the pi filters to smooth out the 24V supply from a regular SMPS power adapter.
There is a load switch/fuse for safety and some current limiting, but I'm not sure if I need to place the pi filters before or after the load switch. Below is my thoughts on the placements, but I really can't decide which one is better. It's assumed that the adapter has large switching noises.
Supply -> Pi Filter -> Load Switch
This placement can filter out noises from the supply and pass it to the load switch, but I think in case of a high transient current drain, currents can be limited by the load switch. Maybe a simple capacitor after the load switch can handle this issue?

Supply -> Load Switch -> Pi Filter
This placement might be better in transient loads, but I was told that the filters need to be close to the noise source.


texts: A question on specifying RC combinations in analog timer circuits

texts:
When making analog op-amp or 555 timers, many times RC time constant is employed.
Lets say we want 1 sec time constant:
We could chose for instance the combination R=100k and C=10uF.
Or we could choose R=100Meg and C=10nF.
We have zillions of possibilities here.

If possible I was always choosing the combination such that I can avoid using
electrolytic capacitor type.
For example in my last circuit, to obtain a 10 sec RC time constant I used R=1Meg C=10uF. I would like to use nF level capacitors to avoid using electrolytic capacitor. But in this case then I have to increase R to very high resistances.

Here my question is:

1-) Is keeping the cap value low in nF level and increasing the R to hundreds of mega-ohms problematic?
    I thought we might be avoiding the use of electrolytic capacitor but then the very high resistor value could introduce more error?

2-) If I keep the resistor in kOhm level I should use then uF level cap. In this case what is the best alternative to electrolytic caps in uF level to obtain better accuracy and repeatability.

edit: Capacitors I use should not be surface mount.


texts: Laser driver current and temperature management

texts:
For a project I need to make a custom laser driver for a dot green laser module.

Below and here 1 you can find my design, the laser I've using now is a PLT5 510 OSRAM, the VSYS is 3,7 V DC from a Li-Ion battery.

The optical power output measured with this set-up are around 1.5 mW, I need to increase the optical power output around 10 times more. I can adjust the feedback current changing the value of the resistors.

If I increase the optical power output, the temperature of the module increase a lot, 90 degrees instead 35 degrees in the normal use.

How can I make a good regulation of the current of the laser module, and get almost 10 mW of optical power output, with a less temperature in the module?

I've no idea if I can use PWM to drive the laser and how to make this regulation, because the laser has a Feeback PIN and I'm thinking about the PWM can affect to the normal and properly running of the laser module.

Please can anybody help me?

Thanks in advance!


texts: Is WD40 good for restoring corroded electrical contacts?

texts: One of the pins inside my iPhone has corroded my dad said to put a little bit of WD40 on the contacts his an engineer but to me oil on electrical contacts sounds wrong my friend said use alcohol too, who should I listen to?


texts: How to actuate 24V solenoids from 3.6V batteries

texts:
I want to build a battery-powered device that actuates a 24 V solenoid when a button is pressed. How could I power it from a 18650-sized lithium-ion cell? It should work down to about 3 V, when it's nearly flat. Or I could put two cells in series, if necessary.

In my case, the the solenoid seems to be rated at 900 mA, since its coil resistance is 26.6 Ω measured with a multimeter. Only a short pulse is required; there's no need for a hold current.

I'd like to keep the device small, cheap, and robust. If I got a little boost regulator module rated for 30 V / 1 A output, is there any chance it would work from 3 V (or 6 V)? An input current of at least 7.2 A (or 3.6 A) seems like a lot, for both the regulator and the battery.

I could slowly charge capacitors to 24 V (or even 30 V). But I've already experimented with it using a 20 V supply (which IS enough for the solenoid). At that voltage, 6000 µF wasn't enough to actuate the solenoid, but 7500 µF worked. The capacitor bank was annoyingly large though.

My favorite idea is this: build up a current of 900 mA (or more) in a coil and let that discharge into the solenoid. Could this work? It would have to be a big enough coil to power the solenoid long enough for it to actuate. Or would there be sparks or something because the current in the solenoid coil needs time to ramp up from 0? I have included a schematic below (ignore the coil values). A logic circuit would close both switches first, and very soon after that, open SW2.


texts: Should I solder multiple wires together, or is there a better way?

texts:
I need to connect 10 thin single-core wires to each other permanently. They will carry at most 1A at 5V in total (100mA each). Can I just solder them together in a lump with shrink wrap tubing around? Is there a better or more normal/professional way? The wago clips is useful for testing, but looks "temporary" and work-in-progress, so I'd like to remove them.

Sorry I don't know the wire gauges, but you'll get an idea from this picture.


texts: Why does this diagram reject self-resonance behavior for RF chokes?

texts:
Based on this tutorial, after self-resonance the impedance decreases and the inductor behavior becomes a capacitor. But for a real inductor (Murata RF choke):

What is the minimum self-resonance frequency? (In the Specifications table)
Why does the impedance increase after self-resonance frequency? (Characteristic Data)

New Question:

How can I these inductors for high frequency such as 10GHz while their SRF is less than 1GHz? (for example in this application the device works up to 1GHz but the choke SFR is less than 100MHz page 4)


texts: How do I configure a external RTC that uses 3-wire SPI for the LPC 2387?

texts:
Here is the link to the datasheet of the RTC PT7C4302.

I can do it with MISO, MOSI, but SISO I have no idea how to do. Some similar code examples would be great.


texts:
I have been looking at potential microcontrollers for an upcoming project and I have found that the MSP430FR697x microcontrollers fulfill my requirements. At least, I think they do.
I require at least 3 ADC pins, as well as an external analog + and - reference, and looking through the DATASHEET I can look at the pinout. The one I am evaluating at the moment is the MSP430FR6927, which is one of the 64 pin micros. Looking at page 11 of the datasheet (Figure 4-3) there is a general overview of the pins. On the right hand side, pins 41-48 seem to fulfil this AtoD requirement, it has the analog channels required, plus the external reference inputs.
However, when going down to the pin descriptions in more detail (64 pin "PM" package starts on page 21), when you get to those pins (page 25), the pin descriptions miss out pins 45-48. It jumps from 44 straight to 49.
Has anyone seen anything like this before? I know the datasheet covers a variety of microcontrollers in the same family, but usually they just have some notes if some pins are device specific. I've looked through the datasheet and the USER GUIDE too and can't find any reference to why these pins are excluded.
I am wanting to buy the evaluation board, but don't want to spend that kind of money if the device doesn't do what I need it to.
Can anyone point me in the right direction, or does anyone know if this is a common thing and if I can go ahead with evaluating this microcontroller?


texts:
In my digital electronics project I need to calculate dot product of two vectors a and b (256 length of each). Following the basic concept, I need to calculate \$ \sum_{k=1}^{256} a_kb_k \$. Each element of vectors is 4-bit binary number. This doesn't seems to a difficult task in verilog where I can implement this as in XILINX ISE.

sum=0;

for(i=0,i<256,i=i+1)

sum=sum+ \$a_ib_i \$

Furthur I need to implement this on FPGA. But here I got confused in two concept:

Do I need to write the module for 'full adder' and added the inputs previous sum and \$a_i b_i\$ bit by bit and store output in sum. Or simply xilinx will automatically implement the full adder during synthsize.
Is it valid to use for loop insted of writing always@(condition) beacause on FPGA we have clock as a control signal. Or in this case also xilinx itself will implement/control the for loop by clock signal.


texts:
I am trying to interface an ENC28J60 ethernet controller IC with an ATmega16 µC. In order to debug my my code, I have built an UART circuit and wrote the appropriate code and I can display any string or character through it on my PC.

But I'm not able to display the register contents of ENC28J60 through UART since the contents are in binary format. I Googled a lot but did not find a way to display binary data through UART. Any help,guidance or comments is welcome.

My SPI code to access the ENC28J60 registers.

uint8_t ENC_readControlRegister()
{
 //pull PC5(chip select) pin low.
 PORTC = (0<<5);
 //put the command corresponding to ECON1 register into SPDR register.
 SPDR = 0x1F;
 //wait until transmission is complete.
 while(!(SPSR)&(1<<SPIF)) {};
 //make PC5(chip select) pin high to signify completion of sending command.
 PORTC = (1<<5);

 //read the received data.
 return(SPDR);
}

now how to print the uint8_t data received from this function in binary format?


texts: What is the name of this single-row connector?

texts:
Could you help me find the name of the connector below?

EDIT:


texts:
I was looking for a synchronous motor for my rotary spark gap. On this page I found what I need. http://www.tb3.com/tesla/sparkgaps/1800srsg/1800srsg.html
But the motor model is not 100% same on the web page the motor is a (SHINANO TOKKI X7807-202V) and I have (SHINANO TOKKI X7807-015V) the guy is explaining how to determine if a motor is synchronous or not, with a fluorescent light and white plastic tube on the motor shaft (please visit the website so you understand what I mean) I don't have a fluorescent light lying around, so I can't determine if my motor is synchronous.

May question.
Is there other methods for determining if a motor is running synchronous.


texts: Background noise on a amplifier even when no audio is playing

texts:
In order to try to use a high quality headphones-amp TI TPA6111A2, I'm connecting the input to 0V (i.e. no audio input) to first see if I get a clean very-low-noise silence sound in the case no audio is flowing.

According to the datasheet linked before, it gives something like this:

simulate this circuit – Schematic created using CircuitLab

I payed attention to "Typical Application Circuit" (page 1) and page 14, 15, 16 for the choices of the resistors / capacitors.

Still, I get an audio buzz. It is clearly too much, as the TPA6111 is said to be really better than I have according to its specs.

How to debug such a buzz, even when no audio is flowing?


texts:
In many Television shows (such as NCIS (all of them), Criminal Minds, MacGyver, etc.) there is a bomb consisting of electronics and C4 explosive.

Mythbusters have determined that a blasting cap is required to detonate the C4 explosive; no other techniques work (such as applying heat or compression).

The people who disarm the bomb always mess with the electronics.  They don't mess with the C4 blasting cap (like removing it from the C4 or cutting the cords to the blasting cap).

Questions:
1) Can electronics detect the removal of the blasting cap from C4?

2) Is resistance futile (of the C4) for detecting that the blasting cap is inside C4 explosive?

I'm having an issue with these bomb sleuths as to why they don't pull the blasting caps out from the C4 before disarming the electronics (if necessary).

(I'm a software engineer with a fundamental understanding of electronics.)


texts: How to use a low current signal to activate my circuit

texts:
I'm building a small circuit that needs to be powered by another device.
I will power my own circuit from the already existing devices battery.
I need to be able to shutdown/power-up my circuit through a trigger signal from the already existing device.
My circuit needs ~200mA and at least 3.3V.

The only "trigger" signal available is a 3.3V signal, capable of providing something like 5mA.

When the existing device is powered off, the "trigger" signal will still have a small voltage, around 0.8V, so my idea is to use an opamp as a comparator, so when the "trigger" signal is higher than ~1.5V it will activate the power to my circuit, and when it´s lower than 1.5V it will shutdown my circuit.

I´ve attached a simulation of my idea and it seems to work, but i don´t know if this is the best approach to solve this.

Do you guys have any suggestions/changes, or maybe I should scrap my whole idea and do something else?

I´ve used transistors in this schematic, maybe it´s better to use mosfets?
Any suggestions?

The switch in the image is there so simulate the trigger signal, I have no control over it, it´s controlled by the device.
I use a 20ohm resistor to simulate my load.


texts: BCD to 7 Segment is producing too little voltage

texts:
I am trying to use a BCD to 7 segment decoder to power my 7 segment display. This is the decoder I'm using (http://www.mouser.com/ProductDetail/Texas-Instruments/SN74LS47N/?qs=sGAEpiMZZMtYFXwiBRPs05jHvQJpC1NM).

Right now, I just have it hard wired to feed ground into it's binary inputs. I believe this should result in a zero being displayed. However, nothing is being displayed. I used a multimeter to check the outputs and found that only around .14 volts were being supplied out of the chip. I have verified that the supply voltage supplied to the chip is 5 volts and the chip ground is correct. I tried swapping the chip, and that didn't help. If I directly wire the 7 segment display, it operates normally.

When I change the inputs, I find that the correct outputs are high and low, but the high only goes to .14 volts.

Did I wire something wrong? Or maybe I misunderstood the operation of the chip? I admit I'm a novice when it comes to this stuff.


texts:
For a project, I need a means of switching a high-current circuit between two inductors. The purpose is, each inductor serves as an electromagnet, and they are switched every 15s or so in order for one of the two to cool before starting again. The system I've designed uses arduino as a controller and a couple of MOSFETs wired inline in order to electronically switch the circuit. The current delivered to each inductor should be around 75A at 12VDC. In this specific example, I used three 35A rated MOSFETS in each 'bank' which would function similar to a single relay. Here is the schematic:

Bank B of MOSFETs is a splice from green line to Bank C. The idea is that Bank A will act as a supply switch (Open = NO Power), Bank B (Closed = IND1 ON, IND2 OFF), Bank C (Closed = IND1 OFF, IND2 ON). The supply switch acts to isolate IND2 from IND1. To the contrary, with not having the supply switch and splice, the only way I could supply power to the second inductor is if I were also supplying it to the first. That is why I have included the leftmost third bank instead of a simple 2, since I need to bypass power past the first inductor.

I am asking for a few aspects:

1) I feel I need more diodes in the circuit to protect against kickback. Have the diodes been added in the right places?

2) Are all the connections correct for the switches and the circuit to function? (Specifically the MOSFET banks and Source/Drain)

Here is an image i've found of an example NCH circuit:

It would appear from this image, that I do in fact have the connections of source and drain for each MOSFET wired correctly, with source on the positive end and drain on negative end. Please clarify if it is wrong.

3) Is there a solution to the VGS issue described, of the MOSFETS not switching simultaneously?


texts: I'm trying to solve AC equivalent circuits of small signal BJT circuits. I'm confused whether to use the hybrid-pi or T-model.


texts: How Significant is VGA Impedance Matching?

texts:
I've seen a multitude of different resistor DAC solutions for a VGA signal, however they almost always have an impedance of >200 ohms per color, e.g.

when I've been lead to believe that we want to match the 75 ohm input impedance of the VGA destination. How significant is this large difference in impedance? Will the signal reflection effects be more visible on a CRT vs. LCD monitor, or even at all?

For an implementation where number of resistors and obscurity of their values isn't an issue, this can be solved with an R2R ladder DAC:

where each color output has an effective impedance of 75 ohms.

However for a project where the expectation is that people should be easily able to acquire and construct the circuit, this isn't ideal whatsoever.

Thank you!


texts: Multiple differential tranceivers on single bus

texts:
Im using a few moduls of rs422 tranceivers connected on single bus
Easy module has transciver with TX input, RX output power end differential pair output and input - but no EN pin to hold the transmission in high Z mode
What simple solutions can i do in my design to get multiple transcivers share the same bus and not disturb each other ?
Edit : the operation is master slave mode (one master that addresses single device , and only the master "care" for the device responce)
So electricly the slaves TX connected to masters RX
And same the other way around
Edit2 : i need a solution for implementing the high z in my design
Changing the transceiver is not an option


texts: Hacking an existing soil moisture sensor to use lower power supply

texts:
Found a cheap soil moisture sensor that works well. It's powered by a 9V battery which would allow the output range to be outside my microcontroller's A-D input range.

I had two options in mind:

Use a voltage divider to lower the range
Change the power supply

I'd rather remove parts than add new ones, so I'm leaning toward the second option.

Would the new schematic I made be the way to go about it, and would it work well with this transistor Q1 (c1815)? Also Would I want to keep LED D1 or can I remove it like I have in the new schematic?

Original Schematic

The # of LEDs lighting up is proportional to the water level

simulate this circuit – Schematic created using CircuitLab

New schematic

simulate this circuit


texts: Why Direct Broadcast satellite is interrupted by climatic conditions?

texts: Television signals received through direct satellite service are mostly interrupted by the climatic conditions. But other communication systems that uses satellites are not that much affected. Why is this so ? Or is it just because television signals are hard real time?


texts: Need help understanding notation in mathematical optimization equation?

texts:
I have been reading the research paper ["Distributed Joint Power, Association and Flight Control for Massive-MIMO self-Organizing Flying Drones"][1](Paper is from IEEE so it might be stuck behind a pay wall) and I got stuck on the notation they use in there problem 2 (penal) statement. This problem seems to fall under electrical engineering and mathematics, so hopefully this fits here. The problem 2 (penal) is written as:
\begin{equation}
\\Given:\hspace{90mm} x,y,z,\alpha, \mathbf{\widetilde{p}^{\mathit{(v)}}}
\\\\\begin{matrix}
Maximize: & \\ \mathbf{\widetilde{p}}_{\mathit{g}}
\end{matrix}
\mathit{U_g(\mathbf{\widetilde{p}}_{\mathit{g}};\mathbf{\widetilde{p}}_{-g}^{\mathit{(v)}})}+\sum_{g'\in \mathit{G}\backslash g}
\bigtriangledown _{\mathbf{\widetilde{p}}_{g}} \mathit{U_{g'}(\mathbf{\widetilde{p}}^{\mathit{(v)}})(\mathbf{\widetilde{p}}_{g}-\mathbf{\widetilde{p}}_{g}^{\mathit{(v)}}) - \frac{\psi}{2}\left \| \mathbf{\widetilde{p}}_{g}-\mathbf{\widetilde{p}}_{g}^{\mathit{(v)}} \right \|}^{2}
\\Subject \ to: \hspace{60mm} Constraints(24),(25)
\end{equation}
p_gw which is part of the equation blow represents the transmit power that ground user g allocates to a specific pilot sequence. The reason a ground user can use multiple pilot sequences in this case is because the authors are converting an MINLP problem into a convex problem. To do this, they relax there pilot constraint and allow each user to allocate power to each pilot sequence.
\begin{equation}
\mathbf{\widetilde{p}}_{g}^{\mathit{(v)}} = (log(\widetilde{p}_{gw}^{\mathit{(v)}}))^{w\in W}\hspace{60mm}(22)
\\\mathbf{\widetilde{p}}_{-g}^{\mathit{(v)}} = (log(\widetilde{p}_{g'w'}^{\mathit{(v)}}))_{g'\in G \backslash g}^{w\in W} \hspace{60mm}(23)
\end{equation}
The constraints are not important, I just need help understanding the notation in the middle equation. The authors called this equation the pricing-based solution algorithm where the main idea is to let each ground user iteratively determine its own pilot sequence.
The Utility equation is given below:
\begin{equation}
U_g(\mathbf{\widetilde{p}}_{g};\mathbf{\widetilde{p}}_{-g}^{\mathit{(v)}}) = \sum_{w\in \mathit{W}}C_{gw}(\mathbf{\widetilde{p}}_{g},\mathbf{\widetilde{p}}_{-g}^{\mathit{(v)}})
\end{equation}
Where the capacity equation is given below:
\begin{equation}
C_{gw}(\mathbf{\widetilde{p}}) = Blog_2(1+\gamma_gw(\mathbf{\widetilde{p}}) )
\end{equation}
My thinking is that since each user can use multiple pilot sequences, p_g is a 1 x w vector where w is the total number of available orthogonal pilot sequences. I am also thinking that the utility equation in the center returns either a vector or a number. I mainly need help in understanding what the nabla does in the middle equation. I am relatively new to mathematical optimization, so I am not familiar with all the notation that is used. My first thought was that it is a gradient, but if p_g is a vector, does that mean the equation is taking the gradient of a vector? If anyone could help point me in the right direction, I would be very happy! I hope what I have written is clear and I can give more information if needed.


texts: Stabilize voltage input for Arduino nano on a drone

texts:
I am doing a small drone project, and the 8V battery provides power to both the motors and the Arduino Nano. I expect a lot of noise from the motors, however I assume that the Arduino Nano power supply should be quite stable. Is it recommanded to use a RC circuit to low pass filter the input voltage? Or is it possible to directly connect the Arduino Nano to the battery?

EDIT: Given all the comments, it seems that the circuit should look like the one below. No resistor, smaller common wires between motors and Arduino power supply, and at least 2 capacitors in parallel


texts:
I am currently trying to build a low power server with a Raspberry Pi I don't use any more (3B) but I am struggling to find a way to cut down it's power usage in it's off hours. Since the Pi uses ~100mA even when completely shut down, I am looking for a way to terminate the power going to it until such time as it needs to be booted back up for use. The server itself is intended to be outside my control for long (a month or more preferably) periods of time so anything that requires I be there isn't applicable.

Basically, I am looking for some kind of device or module that uses a very low amount of power, 5mA or less (preferably MUCH less), with micro-usb slots that either has a timer or can be programmed with a timer that will power off one of the slots after a certain time period and then turn it back on at another.

Below is a crude representation of what I am looking for.

The only thing I have found that even comes close is the Sleepy Pi (One example of where it's sold). However I really don't want to shell out $50+ for something that should be much easier to accomplish if I can avoid it.


texts: Effect of the Load on a Class AB Amplifier

texts:
I am getting into the world of analog electronics, although it is much more challenging it is much more interesting. Im dabbling into audio and would like to build an op-amp amplifier followed with a class ab amplifier. But while toying around with the circuit the output voltage dropped significantly when the load went from 1k ohm to 8ohm and the phase shifts more. From my knowledge of AB amps there is only supposed to be a slight drop on each peak due to the diodes and shouldn't shift too much.

Can someone explain to me the effect of the load on the output? (Also if someone could point me to helpful resources that involve the mathematics and theory regarding analog electronics that would be greatly appreciated.


texts:
Before adding an capacitor in the input of opamp, the gain is equal to 10.  However, after adding a 100uF capacitor to block the DC components, the gain becomes 9.5. That means there have a relation between capacitor and gain?

This is the schematic before adding the 100uF coupling capacitor in series with R2, input is 1V:

This is the difference value of resistance of R3, have one question why the R3 = 7.76k, the gain equal to 8V not 9V?

As I found there have DC offset in the input, then I modify the schematic by adding 100uF series with R2, and measure the amplitude of the output, at 9.80k, for 100kHz, amplitude equal to 9.6V whereas for 1Mhz, equal to 9.0V. Any explanation?


texts:
I can't understand the wierd pricing of IEEE MAC address:

A 12bit IAB is $645, getting you 4096 addresses.

While a 24bit OUI is only $1,885.

I notice alot of companies buy multiple 12bit IAB's, which greatly surpass the cost of a single 24bit OUI. Why? What am I missing here? Can OUI's only be used on internal lans?


texts:
Does the capacitor in this circuit serve as a low-pass filter?

The premise of the circuit is to be a small SD card based music player. The write
up, Simple SD Audio Player with an 8-pin IC, says that it is necessary to filter the PWM output with a low-pass filter. I believe this is usually done with a capacitor. Unfortunately, I'm not overly familiar with the mechanism that a capacitor uses to act as a low-pass filter. Is the capacitor in this circuit acting as a low-pass filter? If yes, then what value capacitor would be good as a low-pass filter for the PWM output?


texts: Calculate the battery life of a sensor node

texts:
I need a way to calculate the battery life of a sensor node given that the current consumption varies. I have a method but need clarification that it is correct.

Sensor uses 3.3v

Sensor consumes:
80mA for 6s per day,
4mA for 30s per day and
18uA for 86364s per day.

Power consumption per day is calculated:

0.08A*3.3V*6s + 0.004A*3.3V*30s + 0.000018A*3.3V*86364s = 7.110 Ws/day

Battery is 4*1.5V alkaline AAs in series = 4*1.5V*2.5Ah*0.8(converter efficiency) = 12Wh = 43200Ws

43200Ws / 7.110 Ws/day = 6075.949 days = 16.65 years

Can anyone confirm whether this method is correct? Any advice is appreciated.

Cheers


texts:
I'm developing a module and the control switch may be at long distances.

Considering I have the 127 or 220Vac input, I want to use that for switch signal. I believe is better, instead of making a pull up and send 5V through a long wire where can have a lot of interference.

My idea is to make as the schematic bellow:

For the optocoupler, I'm considering use TCMT1109 - CTR > 200%

R1 - to discharge the capacitor when the device gets unplugged.

R2 - to protect against inrush current.

D1 - to ensure C1 can (dis)charge every half cycle and to protect LED D2 against being reverse biased.

Can anybody help me to dimension R1, R2, C1 and D1? Or perhaps indicates a good reference?


texts: Repetitive Problems With DIY Arduino EEG

texts:
I'm a hobbyist with only minor electronics experience trying to construct an EEG machine as part of a basic brain-computer interface. I'm following this tutorial for a DIY EEG using an arduino, but I've been struggling for a few weeks to resolve a problem in the preamp circuit. I'm using this circuit diagram:

I think I've isolated the problem to the 3130 (and surrounding components) between the 15k resistor and the analog input because when I place the analog input directly after the 15K resistor next to the 10uF capacitor, I get very noisy, but seemingly valid, input. Here's a short video of the graph when I connect the electrodes under these conditions. However, when I wire up the high amplification/filtering section containing the top right 3130 I either get an issue where output holds the maximum value (1023 or 5v) regardless of electrode connections or I get a nearly flat line with only tiny, random variations independent of electrode connections.
Oddly, unplugging the .68uF capacitor to ground enables output when I have the latter problem, but the output is heavy in noise and very erratic. When I have the former issue (maxed out input), doing so zeroes output completely.
I'm unsure of how to proceed as, at this point, I've built the circuit six times with little change. I was hoping for suggestions I could use to continue troubleshooting the issue.


texts: Inducitve Proximity Sensor - Safety Gate Latch Codes?

texts:
If I am using an inductive proximity sensors as a safety gate latch, what codes and standards do I need to abide by?

Some safety sensors I research have:
 - Category 3 (EN ISO 13849)
 - Safety integrity level (SIL2, SILCL2)
 - EN ISO 14119

How do I figure out for a given application, what safety integrity level, category, performance level..etc I require for my application?

Edit: We are trying to follow NFPA70, 33, and CSA


texts: Can a lightning detector's transistors be substituted with BC547 or 2N3904?

texts:
I want to build this circuit, but I don't have the proper transistors. Can general purpose transistors like 2N3904, 2N4401, BC547, 2N2222, etc. be used instead of the BC109 in this circuit?

The circuit is a lightning detector.


texts: Automatic RTS control for RS-232 to RS-485 converters

texts:
I got my prototype RS-485 circuit working. Now, I've connected it to my PC through RS-232 as I want to make the PC as the master. However, when I connect to the circuit using Hyperterminal, the RTS line, connected to RE and DE, always goes high. The PC can send data to the circuit but not receive, since the RTS never goes low. Changing the handshaking from none to hardware didn't help.

I later made mods to the circuit, so that, on the PIC side, the pin that drives the SN75176's RE and DE high when transmitting data will also drive the SN75176's RE and DE on the PC side low to enable receiving. This in effect turns the line from two to three. It's wrong, but I'm just doing it to see how it'll really work if the RTS pin is working properly.

How do I go on making the RTS pin working correctly? I know I can just create an app using Visual Studio to connect to the line and have RTS toggled manually, but doing so is too troublesome and I'd rather have a hardware solution if possible.


texts: Measure or detect high current pulse 600A+/15V without osciloscope

texts:
How to measure or detect high current(600-800A) pulse (50-100ms)
without osciloscope?

I don't have any osciloscope now, but i need troubleshoot
one spotwelding machine.
I need to know how much current is going to electrodes.
I don't need exact value of current only to know,
if is current over 500-600A or bellow.

It will be enought turn on LED with some latch circuit
when is current pulse over some threshold (for example 500A).
or hold/freeze voltage on shunt resistor and read value with slow multimeter.

I don't have multimeter with peek function and cheap multimeter is slow for this.

Any idea how to make workaroud "poorman solution" ?

As shunt resistor i want to use a copper wire with defined length
and know resistivity.(cable from powerbank to electrodes)

Thank you for any ideas.


texts:
Lots of electronic hardware gets problems its psu and more specificly: with the electrolytic capacitors.
How do old capacitors usually affect the capacitance of that electrolytic capacitor?
What effect does a bad electrolytic capacitor have on the input of the PSU?
What effect will have if the bad capacitor is on the output?
Note: I have measured the voltage several times and it is usualy correct but the electronic equipment only starts after replacing the capacitors.


texts: How should I read the voltage ratings on this terminal strip?

texts:
http://www.farnell.com/datasheets/63479.pdf

I don't understand the voltage ratings given. On the far left, it looks like four different voltage ratings. Is there some way to tell which ones are applicable under what circumstances?


texts: Proteus 8 component package error message

texts:
i built an H-Bridge circuit using proteus 8 professional and

am having this error below and i don't know how to fix it please help me out and i don't know if those are the right connectors.


texts:
This has probably been asked before but I don't know how to search for it.

In a circuit where there are a battery and a variable power supply, what conditions have to be met in order for the battery to turn into a load rather than a current/voltage source and start receiving charge from the power supply?


texts: What will be the output voltage of the following circuit?

texts:
Can someone help me with this circuit i tried to find similar circuits with diagrams on google but i can't find anything. What will be the output voltage? Is there some good free software's i can test electronic circuits?

My solution for this circuit: https://imgur.com/a/YNlP3ls


texts:
Hello I am confused about how EM shielding works, especially after checking out my VGA cable.

The end of the VGA cable has a metal chassis around the 15 pins, covered by a plastic coat, and 2 screws on the 2 sides. The 15 pins connect to the 15 wires inside the cable. The core wires are insulated by a layer of plastic coat and twisted together, and then shielded by a layer of aluminium foil, and then by a layer of braided aluminium, and then covered by the outside rubber coat. This is how it's made.

Now my assumption is that the shield (the foil+ braided aluminium) has to be insulated from the core of the signal wire otherwise it short circuit's it, or perhaps cause interference and act as a receiver antenna that would absorb the noise to destroy the signal inside the cable.

But that is not true, there is electric connection between the 15 pins, the end-chassis, and even the screws, therefore I assume that the shield itself is also connected to the signal wire. How is this even possible?

Can somebody explain how the electromagnetic shielding works for a VGA cable, because it sounds illogical to me how the inside signal is connected to the shield, I thought they have to be insulated from one another.

Especially how does this shield the inside of the cable from outside noise, doesn't this make the cable an ever bigger antenna if the metal surface is bigger?

And note that this is not a defect cable, I have checked it on 2 different cables, they are all the same and they all work perfectly fine with my monitor.


texts:
I have been designing a circuit that involves a 5V DC Fan. When I was creating the schematic on EagleCAD, I couldn't find something that resembles a Fan other than a Motor. Should I stick with using a motor, or should I opt to find a library that contains a much more intended symbol for a fan elsewhere?
TIA


texts: How should I current limit a LED matrix?

texts:
I have an LED matrix which has a maximum peak forward current of 90mA and average forward current of 13mA per LED (dot). If I power only one LED at a time, this one LED will have a very large current consumption compared to if I power several at once. What values should I choose and where should I put them when I have VCC at 3V on each anode?

Added a simple schematic for clarity.

simulate this circuit – Schematic created using CircuitLab


texts:
first post here so be kind :)
disclaimer : I am not a professional and nor I have any engineering background, all this is part of a hobby.
After fiddling for months with SonOff / Tasmota / MQTT / Home Assistant I decided to move on to something more reliable for my garden light automation system. I got too many issues with the devices disconnecting from WiFi because my garden is to large for this technology and I can't add more access points.
So I figured out some electrical contraption without any connection to anything "intelligent".
What I want :

Turn on my garden lights when the sun sets.
Turn of them at midnight.
Being able to manually turn on lights after midnight if needed.

My hardware :

average 7 pays programmable Digital time switch relay like this one https://www.aliexpress.com/item/1005002492359270.html?spm=a2g0s.8937460.0.0.285c2e0eaGoGl6
NK-301F Light Control Switch https://www.aliexpress.com/item/4000026598297.html?spm=a2g0s.9042311.0.0.27424c4d3xdH2m
3 way switch
light bulb

My design :

My question :
Do I have (and if yes how to) to protect the light control switch load output, because while in "manual" mode, it will be directly connected to line and may be fried.
Thanks for reading me !


texts:
PSIM (an electronic circuit simulation software package) classifies GTO, IGBT, MOSFET as self-commutated switches. However, I couldn't find a clear definition of this.

This is from PSIM manual:

  Switches

  There are four basic types of switches in PSIM:

  Diodes (DIODE)
  Thyristors (THY)
  Self-commutated switches (GTO, IGBT, MOSFET)

  Bi-directional switches (SSWI) Switch models are ideal. That is, both
  turn-on and turn-off transients are neglected. A switch has an
  on-resistance of 10µΩ and an off-resistance of 1MΩ. Snubber circuits
  are not required for switches.

Here is the only definition that I found:

Self-Commutated Switches

  The devices of the third category are denoted as self-commutated
  semiconductor switches. The general properties of devices in this
  class are the capability of being turned-on or turned-off at will by
  use of some form of low power (either voltage or current controlled)
  signal into a third (gate or base) terminal, and normally they have a
  capability of controlling current only in forward direction. Examples
  are BJTs, MOSFETs, IGBTs (insulated-gate-bipolar transistors), and
  many others.

So is "arbitrary turn-on/turn-off time" the only condition to be a self-commutated switch?

Can anybody give a definition for this or explain it in detail?


texts: Is my jk flip flop missing two NAND gates to be complete?

texts:
I created this circuit in an app I have on my phone that runs the circuit and lets you see the output.
I noticed from my research that a jk flip flop was an NAND based SR LATCH with additional  NAND gates attached to S AND R.

So, I went about trying to design create a NAND based SR latch first, which would serve as the core of my JK circuit, in making the SR latch I believe I accomplished by adding a second NPN transistor in series to a NOR Gated SR design. but looking at the JK flip flop diagram, it looks like I need to add two more NAND gates. I believe the gates will output to the emitters of S and R of my latch, and for each of the new NANDS they will  be tied into the SR by the transistor base.   I hope that is correct. However, I'm not clear on how to physically create a NAND gate with 3 inputs. I am going to create a circuit lab diagram of what I think I need to add. And I'll attach it shortly, but I wanted to see if I truly understand this.

update
So, I've learned A LOT today. I spent several hours online pouring over diagrams and articles I barely understood.  And looking at my above circuit I realize I made a lot of mistakes. One fundamental thing I learned was that gates are binary, and so a single gate represents 1 bit and can only be 0 or 1, so...the total number of gates will be equal to the number of bits needed to express the number of inputs. Since I wanted a 3 input NAND for my J and K, I needed to cascade 3 NAND gates since 3 is 001 in binary. So, I just finished creating that in circuit lab. Also, I think I now understand that the symbol used for all logic gates do not try to display Vdd or V0, they are assumed.  Now, all I have to do is duplicate the NAND gate four more times, cross couple two of them and I should have my own JK flip flop!
Additionally, I went through the tedious task after making my 3 input NAND and verified every row in the truth table using a spice simulator.
The circuit is below.  I haven't tested it to verify, and due to not being able to mirror the parts I'm not sure if I have all the inputs tied together correctly.
Any input would be appreciated.

simulate this circuit – Schematic created using CircuitLab


texts: I'm not sure how to change the rules to satisfy the component constraints


texts: So, I have an atmega328p and I need to communicate with a computer from it, so I need an FTDI. However, all I have is a USBTinyISP. Is there some way I could hack something together so that I can use the FTDI in the USBTinyISP as a general FTDI without having to mess with the firmware of the USBTinyISP?


texts:
So im looking at buying this:
http://www.amazon.com/SUPERNIGHT-Waterproof-Flexible-Changing-Controller/dp/B00MN6WTQC/ref=pd_cp_MI_1

Wont the 24v 5a powersupply fry these?
The reviews are misleading.
Is there a voltage regulator somewhere in the IR reciever im missing?
Thanks


texts: How to make/duplicate a NEC Infrared Transmission Protocol

texts:
what i am trying to achieve to be able to duplicate/recreate the infrared signal of my remote control using my arduino.

The arduino has a already a library for this, unfortunately it doesn't seem to support the board that i am going to use the arduino mkr1000. The library has a recieve that makes me able to see the data, but the function for transmitting it back is not working.

So this makes me resort to creating a function for sending myself. I know that the remote i am using uses and NEC infrared transmission protocol. So i looked at its specs.

according to it:

a 9ms leading pulse burst (16 times the pulse burst length used for a logical data bit)
a 4.5ms space
the 8-bit address for the receiving device
the 8-bit logical inverse of the address
the 8-bit command
the 8-bit logical inverse of the command
a final 562.5µs pulse burst to signify the end of message transmission.

What i dont understand is, what is this address and command.

unfortunaly i do not have an oscilloscope inorder to probe my remote to confirm some hypothesis. What i have though is the output of the serial monitor the arduino upon recieving the signal.

Encoding  : NEC
Code      : 2FD807F (32 bits)
Timing[67]:
    +9200, -4500     + 600, - 550     + 600, - 550     + 600, - 550
    + 600, - 550     + 550, - 600     + 550, - 550     + 600, -1700
    + 600, - 550     + 600, -1700     + 550, -1700     + 600, -1700
    + 600, -1700     + 550, -1700     + 600, -1700     + 550, - 600
    + 550, -1700     + 600, -1700     + 550, - 550     + 600, - 550
    + 600, - 550     + 600, - 550     + 600, - 550     + 550, - 600
    + 550, - 550     + 600, - 550     + 600, -1700     + 600, -1700
    + 550, -1700     + 600, -1700     + 600, -1700     + 550, -1700
    + 600, -1700     + 600

unsigned int  rawData[67] = {9200,4500, 600,550, 600,550, 600,550, 600,550, 550,600, 550,550, 600,1700, 600,550, 600,1700, 550,1700, 600,1700, 600,1700, 550,1700, 600,1700, 550,600, 550,1700, 600,1700, 550,550, 600,550, 600,550, 600,550, 600,550, 550,600, 550,550, 600,550, 600,1700, 600,1700, 550,1700, 600,1700, 600,1700, 550,1700, 600,1700, 600};  // NEC 2FD807F
unsigned int  data = 0x2FD807F;

From the output can we point out which is the address and which is the command? so that i will be able to create a code for it


texts:
I am trying to use LPC1769's ADC. The ADC is operating at 12 MHz. In the LPC1769, for one conversion, 65 clock cycles are required. It means that for one conversion, 5.41 us are required. I toggle one pin in ADC IRQ handler. This pin's freq is 57 kHz. It means that one conversion is completed in 17.54 us. First question is why this is happening?

Second question, when I am trying to sample 10 Hz sine wave, it works well. I am reading the ADC value and sending this value to DAC for testing. When the frequency is increased, the peak to peak value is decreased. So what is the problem?

Do you have any advice for these problems?


texts: How can I use Thévenin's method in this kind of question?

texts:
Here is the question:

That wire made me confused. Should I just ignore the wire that independent current source caused?

And then R Thevenin will be equal to 2.25 Ohm I guess.

Edit: I solved. Thanks everyone.

Chu's comments helped me to understand and solve.


texts: Understanding MOSFET gate characteristics

texts:
I am just starting to use MOSFETs more frequently. Rather than use suggested parts in circuits that others design, I want to understand them better so I can design my own circuits. I typically use them to drive inductive loads from microcontroller pins.

I'd like to see if my understanding is correct with the following:

The \$V_{GSS}\$ (Gate-Source Voltage) listed under Absolute Maximum Ratings is the maximum voltage that can be applied to the gate with respect to the source. (And thus should be avoided.)
\$V_{GS}\$ (Gate Threshold Voltage) is the voltage at which the gate starts to turn on, but does not mean that the MOSFET (as a switch) is fully conducting. It is given with min and max values, which means that the starting point may vary from part to part.
To determine the gate voltage at which the MOSFET is fully "on" the \$R_{DS(on)}\$ (Drain-Source On-Resistance) value can be examined: the "test conditions" show voltage values at which the FET is fully on.

I don't think my understanding of #3 is quite right. Olin provided a great answer which is where I derived that point from.

Consider a Fairchild FQP30N06L; the datasheet shows two test voltages (10 and 5V) for the \$R_{DS(on)}\$ at different resistances (varying only by <10 mΩ).

Based on this, I'm confused about how to determine what voltage I should supply at the gate for the FET to be considered fully on. Can you explain what I need to look at on the datasheet to calculate this properly?


texts:
I'm getting somewhat strange behavior from the ADC on my arduino, I will try my best to explain. I made a microphone amplifier circuit that gives a peak-to-peak of 0 to 5 V with a DC offset of 2.5 V. This signal is fed into the Arduino ADC. I'm building a VU meter, so based on the ADC reading, some number of lights is turned on.

The circuit in the following condition with the LED ground connections open, as seen here, works fine. The Arduino reads in values like its supposed to picking up any sound into the mic. I verified this by doing a serial print of the values to my computer and also probing the output of the the opamp into an oscilloscope.

Simplified circuit. (See my first comment to see the full amp circuit).

The problem arises when I close the LED ground connections as seen in the following picture. Oddly enough, the ADC seems to be giving a square pulse at the instant it samples the signal. I verified this by probing the output of the opamp into an oscilloscope: the graph below the circuit shows what I saw on the oscilloscope. The ADC is reading a value of 1016 (almost 5 V) which turns on all the lights perpetually.

Simplified circuit. (See my first comment to see the full amp circuit).

To further complicate things, when I reduce the voltage supply to the entire circuit (including the microcontroller) down to about 3 V, the odd behavior described above does not happen and the VU meter functions perfectly! But at this voltage the lights are too dim and barely visible :(

I have been stuck at this for a long time and have no idea why this is happening.
Any insight or help is appreciated!


texts:
The energy stored in a capacitor is
$$ U= \dfrac{1}{2} CV^2 $$

So when I have a 1F supercap charged to 1V the energy is 0.5 J. When I connect a second supercap, also 1F in parallel the charge will distribute and the voltage will halve. Then

$$ U = \dfrac{1}{2} 2F (0.5V)^2 = 0.25 J $$

What happened to the other 0.25 J?


texts: Why does timing change in dataframe using Manchester encoding

texts:
I have successfully received a couple data frames from an RF transmitter. I compared couple consecutive frames and the timing deviation between them is marginal, so I am convinced it is reasonably accurate to a 50µs resolution.

I think it is using Manchester encoding and one of the properties of Manchester encoding is the ability to retrieve the clock signal from it. Thus I would expect that the signal's preamble obeys the clock of the data.

(click to enlarge image)

Apart from the front porch (-5.5 ~ 0 ms) I would expect preamble (-38 ~ -5.5 ms) obeys the same clock as the data (starting from 0), but it doesn't. The preamble clock is approximately 10% faster than the data clock.

What is the reasoning behind the change in clocks? Isn't that in contradiction to the Manchester clock retrieval properties?

The receiver end is a TDA-5200 combined with a protected ATmega32L, the internals of the transmitter are probably similar but currently unknown.


texts: Can the /OE pin of a buffer be left floating?

texts: Here is a buffer from OnSemi which has an /OE pin that should be tied high for high impedance mode. For all active modes the pin value is stated as low. Would my buffer still work if I were to leave this pin unconnected or do I explicitly need to ground it?


texts:
I recently bought a nice looking regular light bulb, commonly refered to as "Edison bulb".
http://edisonlightglobes.com/Shop/wp-content/uploads/2013/03/Full-set-Bulbs.jpg

I was hoping to find a way to dim the light, so you could just see the filament glowing.
Having zero knowledge of electronics, I started looking for a dimmer to put in a simple electronic circuit.

However, if I try to find answers to how to achieve this, I only find LED-related questions.
Furthermore someone told me about a difference between a dimmer that dims the light, but eats up the same amount of power as when the light is not dimmed?

I guess these are really basic things for someone with knowledge of electronics, but any help would be a huge step forward for me.


texts: Calculate current/voltage: Diode in parallel with resistor

texts:
Without using Kirchoff, I want to understand how to calculate a circuit like this:

simulate this circuit – Schematic created using CircuitLab

Perhaps the values I used will not provide the 0.7V needed for the diode. But this is the general diagram.
I tried this:

I1=I2+I3
I2=(5-I1*47)/22
I3=(5-0.7-I1*47)/2

Is there another way except for using Kirchoff?


texts:
I recently made a voltage divider that uses a 10 ohm (top) and ~90 ohm (bottom) to divide a source voltage of 5v to 4.5v. The resistor values I used was somewhat arbitrary, in that I just picked a random top resistor value based on the resistors I had and calculated the bottom one.

My question: is there any advantage to use higher value resistor pairs over lower value resistors? Would a 100 top and 900 bottom have been better, for example? Or will the circuit work the same regardless of the resistance as long as the ratio remains constant?


texts: Transistor Oscillator Simulation Convergence

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For the circuit in the figure (both in Altium Designer 16, and Proteus 8), by using the standard NPN Spice model, I had a really hard time trying to make the simulation converge.

I tried Trapezoidal, and Gear from order 2 to 6, trying to increase GMIN parameter, changing tolerances, minimum timestep, etc. I was unable to make this oscillator run with the standard NPN Spice model.

When changing the NPN into a 2N3904 model, the solution converged with no problems in both softwares.

My question is why this happen?, which model components are in the 2N3904 which are not in the NPN model?...
I though both models were the same (the same Gummel and Poon), just changing the values of the parameters. Or the parameter values in the 2N3904 are more "gentle" for allowing the oscillator to run?

Thanks in advance.


texts:
I wanted to make sure that my solution would work before wiring it physically and I felt that all the great minds here would be able to do that.
So I have two WS2812B 5 m LED strips, each containing 60 LED/m, or 300 LED per strip. The manufacturer states 0.3 W per LED, and these are 5 V LEDs. That would mean each strip is 300 × 0.3 = 90 W, and requires 90/5 = 18 A at a full white bright.
If I were to just solder one of the 5 m to the end of the other 5 m, I would now have 600 LEDs in parallel correct? Which would mean a current of 36 A would be going through the top line before the respective currents go to the ground after the LEDs. I don't believe the LED strips could handle that much current.
After some testing it turns out that the voltage loss is significant enough that I can't even power one LED from one side, so I'd have to power it from both ends. In order to have two strips powered, I'd think I can power it then from three places, the beginning, the connection of the two strips, and the end of the second strip.
I drew up this quick wiring diagram, would something like this work? I would have three power sources with two grounds, and the LED strips would be fully connected.


texts:
We have a pair of IrDA and its encoder/decoder. After reading the datasheet, we still dont know how to interface IrDA with En/Decoder.
Here is our current connection:

When using BAUD rate 9600, we are not getting any readable data from UART on arduino. The buffer is alway full or 0. We don't know whether it's the en/decoder or IrDA transceiver that is causing the problem.
Is this the right way to interface? Any advice on how to go about debugging this?

Related datasheet and info
IrDA Vishay TFDT4500 : http://www.freeweb.hu/bat21/irda/tfd_4.pdf
En/Decoder MCP2120 : http://ww1.microchip.com/downloads/en/DeviceDoc/21618b.pdf


texts: How does one approach designing an amplifier using BJTs to drive an 8 ohm speaker?

texts:
For a lab class we were assigned a final project where we have to design an amplifier using BJTs, diodes, and capacitors (MOSFETs are not allowed) in order to drive an 8-ohm speaker. The requirements given are as follows:

that we were to be able to have gain adjust control for a certain
range
use 9 volts VCC and must not use voltage dividers, instead use current mirrors
we must attain at least a certain voltage for a certain peak to peak sine
wave input for a certain frequency range when gain adjust control is
set to maximum, therefore there must be a minimum gain for the range of
frequencies that our amplifier will support
we are not allowed to use any op-amps, except to invert signals should we choose to use differential amplifiers
there must be no clipping for a certain peak-to-peak sine wave input when gain adjust control is set to maximumm

I didn't include the exact specs for our final project in this question, since I think that isn't allowed isn't it? But our group's problem is how to approach this from a design perspective.

Our idea is to use a CE-CC configuration, but obviously this is a too basic thought.

I think it just so happened that all three of us always just thought of it from an analysis perspective. Or we all need to study more haha, which is actually true too.

We don't even know about A-B power supply configurations (is my terminology right)? Since it hasn't been discussed yet. Maybe in another class. I'm not sure if we were supposed to come up with a similar thing on our own using diode connected transistors or something, since we didn't cover using diodes in this class. This class is mainly about analyzing BJT and MOS configurations by the way, and their frequency responses.

So a guide on how to approach doing this would be great! So that we would at least know how to start doing this. Maybe we're also lacking insight on how does one actually drive an 8 ohm speaker... I mean we've already done this in lab, but how does it actually manage to emit sound? Is it because of the varying voltage due to the small-signal voltage introduced to the circuit? What would happen if a DC voltage is what's passing through the speaker? (We tried simulating a configuration in SIMetrix, and we made a mistake somewhere where the output voltage (the one across the speaker), is a constant DC level, so obviously we made a mistake somewhere). A clarification on how this actually works would be nice too :D Thanks to anyone who'll help!

[EDIT: Since people are commenting that I should include the requirements from the specs, I'll do so. I was hesitant to include these because it's classwork. But I suppose I really am being vague, and you guys are good judges on how to help me since you know what to do about this. Sorry for the oversight :(]

Requirements:

must drive an 8 ohm speaker
BJTs allowed: 2n3904, 2n3906, 2n4401, 2n4403
gain adjust control must be 50 to 250
9V VCC and don't use voltage dividers
peak to peak voltage across the speaker must be at least 1v for a 20mV peak-to-peak sine wave input, for frequencies ranging 500Hz to 20kHz when gain adjust control is set to maximum. So the amp must have a gain of at least 50 for frequencies ranging from 500Hz to 20kHz
the amplified signal must be free of clipping for a 20mV peak-to-peak sine wave input when gain adjust control is set to maximum]


texts: Is a resistor needed between logical pin and base/gate transistor?

texts:
I'm using a logical pin output (3.3V) to drive a NPN darlington transitor with the max current possible to minimize the fall and rise times. My microcontroler has a 20mA max output current per logical pin and the max transistor base current is 120mA.

My question is: without a resistor, what would happen? The micro would burn it up giving a (3.3-0.7)/0 current or it would simply stick with 20mA?

I have exaclty same doubt about driving a N-channel MOSFET. What would happen at the gate? With the gate capacitance discharged, it would be a short to the ground leading to big current? Is a resistor needed in this case?


texts:
Recently on a book i came across a problem-

Here when calculating the current flow through the diode they didn't consider the voltage drop across the diode.If it is correct then what am i missing?


texts: Bidirectional Digital Communication over Audio Signal?

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I am trying to figure out a way to achieve low speed digital communication over an audio line. I have two devices that are connected with a two wire audio cable. Audio and Ground. From my research, I can't find any current solution to achieve bidirectional digital communication over a single audio signal.

Does anyone know of any IC's or designs that can accomplish this task? I only need something very basic and low speed.


texts:
I'm studying Intel 8086 processor.

I can't understand why the "Fan-out" column is like that in the table below

I understand that only one "74 family" chips or five "74LS family" gates can be connected to 8086 output pin.

8086 can sink up to 2.0mA. So it can handle up to five(=2.0mA/0.4mA) 74LS family chips or one(=2.0mA/1.6mA) 74 family chip.

But why does 8086 handle up to ten 74ALS family chips? I thought that it can sink up to 20(=2.0mA/0.1mA) gates and source up to 20(=400uA/20uA) gates. So it should drive up to 20 74ALS chips.

And why 10 74AS family chips? It should be four because 0.5mA current would flow from one 74AS chip to 8086 output pin and 8086 can sink up to 2.0mA.

It is very tricky to me, so please help me understand it.


texts: Why is the voltage more in case of same polarity during a polarity test of induction motor?

texts:
I was performing experiment in the lab of my university. The experiment was supposed to be performed on a squirrel cage induction motor. But I performed it on a three phase slip ring I.M with its rotor short circuited. All the voltages used were AC voltages. I applied 100 V across one terminal of phase(A1) and neutral(N) of a star connected stator winding.
When the polarity was same (i.e. the star point was at A2,B2,C2), the voltage across A1 and B1 came out to be 84 V, which is less than 100 V. My question is: Shouldn't it be more than 100 V because the voltages induced in both the windings are additive in nature or am I interpreting anything wrong?
When we change the star point to A2,B1,C2, then the voltage across A1 and B2 comes out to be more than 100 V. In this case, shouldn't it be less than 100 V?


texts: How do I transform a unipolar signal to bipolar signal?

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I am trying to design a circuit that will convert a unipolar 0 - 12V square wave signal of about 1kHz to a bipolar +/- 12V signal.
I have tried using a differential amplifier design approach similar to this (using classic diff. amp equations): https://masteringelectronicsdesign.com/design-a-unipolar-to-bipolar-converter-for-a-unipolar-voltage-output-dac/
The circuit I created is below with a TL074 op amp; however at the output of the op amp there is no signal (it just remains at about -12V). Can someone please explain why, or please direct me to a better way to convert a unipolar signal to a bipolar one?
I have also tried putting a .1u capacitor in series with the signal to the non-inv. input to create a bipolar signal input, but this did not work. I have also tried several other op amps (LM741, 4558, and 1458), all of which do the same thing.

simulate this circuit – Schematic created using CircuitLab


texts: Instantaneous Peak Current Delivered by a Battery

texts:
I am working on a project involving battery drills and would like to know the peak current an 18v 3A/Hr (54 W/Hr) battery could deliver, even if for an instant.

I can't find detailed battery datasheets, other than the generic info and one on the chemical composition of the battery.

The peak current would be caused not by a short circuit, but when the motor is stationary (and is generating stall torque), so there would be a completed circuit of a few milli-ohms.

Is it as simple as Voltage / (Winding Resistance + Internal Battery Resistance)?

What ballpark figures could I expect?  <50A, 100 - 150A, 150 - 200A, >200A... etc?

Any help greatly appreciated.


texts: Differential Op-Amp rising and falling error at zero

texts:
So I have a differential OP-AMP I've designed is essentially a cut and paste of the circuit seen below.

simulate this circuit – Schematic created using CircuitLab

I'm using it to track the difference between the output of two Trans-impedance amplifiers.   the circuit works well as long as there is a difference between signals, but as the signal difference approaches zero I have an error I cant fix. it occurs on the rising and falling edges of the signals and I believe it may be due to slight differences in response times from the photo-diodes because when I recreate the signals using a function generator the error goes away.  How would you compensate for something like this or am I incorrect in thinking its due to differences in response times in each photo-diode?

for reference here is the error that I'm seeing on a scope the first two signals represent the output of my trans-impedance amplifier, the third is the error I see as the difference approaches zero.


texts: I do not want to use any adc or dac. I want to see if this is possible by pure analog circuit. Any google links or book names are welcome. From 0 to 1000mV output should be 0 to 100mV. Then from 1001mV to 2000mV output should be 10mV to 20mV from the same terminal.


texts: Impedance between BJT base and ground of a common emitter amplifier circuit

texts:
What is the impedance between the base of the BJT and ground of the common emitter amplifier circuit? The answer should be in terms of RE and hfe (the small current gain of the transistor). Is this a high or a low
impedance (relative to the output impedance)?

Hint, this isn’t that bad remember the rules and the definition of hfe. Write down ΔIE in terms of ΔVB and RE then write down ΔIE in terms of
ΔIB and hfe. Now the impedance looking into the base can be calculated from Ohms Law and by answering the questions what is ΔIB for a
change ΔVB.


texts: Rotate stepper motor in low RPM and minimum vibration

texts:
I want to control a stepper motor about 3RPM and at very low vibration.

I have a ROLLON SRL-M542H stepper controller.If I change it to high step per revolution it works smoothly without more vibration.

Is it a suitable method for reduce vibration?

And how to calculate pulse time for pecific RPM?
Im trying to use an Arduino UNO for pulse genaration.


texts: building a minimalistic rf circuit (as simple as possible just for OOK)

texts: I have been recently interrested in rf transmission. I would like to create a small circuit to generate à 125kHz signal at about 10-15 meters. I am very newbie for these kind of things. When I look on the internet for some schematics they all seem very complicated. I would need to have a minimalistic circuitry to to just OOK (On Off Keying) in this frequency. What would be the minimalistic circuit (you could just point to some schematics) that I could use in practice, that would be operationnal?


texts:
I have implemented C++ queue in my codes, those I run on my PC.

Now I'm programming an ATmega128 micro-controller to implement a .c code. Can I use that queue.

Will it work?

If not please suggest me a queue to implement.


texts:
I have been playing around with some 1-Wire components and got these questions

simulate this circuit – Schematic created using CircuitLab

Can I break anything if I forget the 4.7 k resistor ________?
Does it have to be 4.7k _________?

Came across an Adafruit lib that used 10 k but changing between the two resistors (4.7k and 10k) didn't seem to influence the readout. But is it the lib that defines what resistor size I should use or should it just be between an interval..?

I'm a newbie when it comes to electronics and right now I'm just learning-by-doing. Reading the theory behind thing doesn't help me that much since I don't understand half of the terms used..


texts: How do I observe a PLL's frequency tracking once the lock has been acquired?

texts:
I am trying to design a basic PLL (second order-type 1) to understand its dynamics. I am using Cadence Virtuoso for simulations. I have designed a voltage controlled oscillator that has a center frequency (at Vcontrol = VDD/2) of 16MHz, an XOR phase detector and a passive RC low pass filter.

As I've observed, for an input signal of 15-20MHz, the loop acquires the lock.

I want to observe how the PLL tracks any change in the input frequency, once the lock has been acquired. Is there any way I could simulate this?

Parametric analysis provides different set of curves for different input frequencies. This does not tell you much about the response of loop. If I could observe, once the loop is locked, how the output frequency tracks the input say for a step change in input frequency.


texts: I am new to using eagle. I want to put some exposed copper pads that I can solder to on my board. The catch is that they cannot have through holes. I tried just making polygons in the top layer, but I am unsure if I will be able to solder to that. Any advice?


texts: Charging phone battery with a high current source

texts:
I am working on a project which the goal is using some android tablets to show pieces of video file to form a multiscreen. One electronic problem that I have faced is:

The tablets should be always on. Currently I am using their own wall adapter which is rated at 5V 2A but when the tablets screen is at 100% brightness their battery eventually depletes. I guess they are not designed for this kind of usage (Google nexus 7). The only solution I could find so far is to reduce the brightness to 30% but this kills the whole idea.

So do you suggest me to try another power source for example I have some LED drivers rated at 5V 4A. Is using this rating with the tablet is safe(considering USB cable and port, charging circuitry and battery itself)? Or the battery charging circuitry of the tablet is limited at specified 2A. I really need your opinion before I try to do something stupid!


texts: Completely new to electronics, I've just begun to play with an Arduino. I was wondering, if I wanted to make an LED sculpture, what is the correct way to extend the legs of each LED so that they stand about 3 inchs long and are bendable? Is there a particular type of shielded wire that has enough strength to support an LED's weight?


texts: Design a circuit with range of -10 to +10V

texts:
I'm using a PLC for a project, the output from the PLC DAC is 0-10V but I need to scale it to -10 to +10 V (similar to the graph). Obviously I need to build a circuit with an opamp, I'm thinking of something like this.
Could anyone help with the values of the resisters I should use? Would this work? Is there a better way?


texts:
I know how to calculate voltage noise density for a JFET when I know the noise figure (NF) and source resistance (Rs). But, I have also seen many transistors where the NF is given without any reference to a source resistance. For example in the following datasheet:

CPH3910

What am I supposed to do with this? What is the NF being referenced to?


texts: From DTFT to DFT, why do we take N samples in frequency domain

texts:
In this post:
Why does frequency equal k/K where k=0,…, K-1 in Discrete Fourier Transform?

And I have read several books, the authors take N samples with DTFT to get DFT. Why N?

I think N is simply the sampling rate in time domain, right.

In frequency domain, can we choose other sampling rate to get DFT?

Thank you very much indeed.


texts:
I'm working on a project where my iPhone locates a specific item and triggers a sound alarm when needed.

I did my research and found out that this can be done using Smart Bluetooth technology. However, I'm not sure if there's an integrated chip to do the sound alarm function.


texts: Alternator Synchronization in Smart Grid

texts: Recently I was studying on the web that in the smart grid we need to synchronise the alternators. My beginner question is: Why do we need to synchronise alternators in a power system grid?


texts:
I am using two inductors on both sides of an ac carrying straight wire and want to detect their proximity from the wire. The coils are a set distance apart and move together laterally via mechanical means. As one coil moves closer to the conductor, the other moves further. See @Neil_UK illustration:

The chart below, shows the current induced in the coils as they move about the center of the conductor. Also in orange, I plotted the difference of the two signals. My problem is that the slope of the Diff A-B is to shallow between 4 and 6, where I am most interested in detecting the crossover.

To emphasis the crossover, I plotted the 1/Diff A-B in the following chart. This should give me a very sharp detection signal.

Is this a viable strategy to sense the point where the coils cross-over? If so what would a simple circuit consist of?


texts: Maximum current draw from a step-up regulated output

texts:
I have a LiPo battery pack with 5V, 2.1A output. Now, let's say I boosted that with a step-up regulator like this Pololu module.

At 12V output from the regulator, what is the maximum current I can draw?

By conservation of energy, I'm assuming it cannot be more than 5 V * 2.1 A / 12 V = 0.875 A, but I'm wondering if there are any other factors at play.


texts: How much physics is necessary for learning Electronics?

texts:
i am a CS student i wanted to enter the field of "Internet Of Things", got a recommended book "Art of electronics" now my physics base is school level but my Calculus 1 is pretty rock solid so i have two options right now:

1> Read Feynman vol 1 & 2 and then start Art of electronics?

2> Just start Art of electronics along with Multi-variable calculus?

which option might help me get the core of electronics subject and most out of Art of electronics book? Since i do not know what electronics heavily rely on help from professionals is appreciated, thank you.


texts: Turn very old ductless AC wall unit into smart AC

texts: I have a very old Burnham ductless AC wall unit that I would like to be able to control via a sonoff (esp8266).  I have modified the sonoff to isolate the relay, separating it from the main line so that it will act as a switch to complete a circuit.  I'm really only concerned with turning on cool mode, not fan mode.  I'm wondering if it would be as simple as shorting out the two solder joints (see red line in second photo to which I believe is cool mode).  I have been too afraid to short it out on my own to test my theory, so I've come here as a newbie for expert advice.  I'm hoping to just tap into those joints and connect to my sonoff relay to turn the unit on/off.  I'm a little concerned though trying to introduce another means of turning the unit on.  I'm worried about the "off" mode which appears to be completing some sort of circuit (I follow it up to something labeled 'DV'?).  Can I interject (short out) the cool mode joints while the switch is still in off mode?  Attached are some photos of the wired remote and the back of the circuit board (back of the remote once screws are removed).


texts: Analog inputs with Intel Edison mini breakout board?

texts:
Looking at the schematics of the Intel Edison mini breakout board, there are no pins for analog inputs, e.g. for reading state of a potentiometer.

For a hardware workshop based on the mini breakout board, I am thinking to discuss analog inputs. What circuit or breakout board would provide analog-to-digital conversion in a "cheap" way? What about power rails for the ADC? I2C on the Edison has 1.8V while system voltage can be higher but is not stable/accurate enough for ADC maybe?


texts:
If I want to program a new AT90USB1286 series chip via the standard 6 pin ISP header, do I need any additional components wired up at all?  I'm wondering specifically about the need for a quartz crystal and associated capacitors.

The background is that I have a couple of chips that I believe may be faulty and/or counterfeit (the latter because the Atmel markings on these chips sourced from China are exceptionally faint compared to others I've bought in the UK).  I want to be able to talk to the chips with the absolute bare minimum of other circuitry involved in case it's something else at fault.


texts: Switching 60V with 3.3V microcontroller at 50kHz - 1MHz

texts:
I'm playing around with some switching mode power supply things. For this reason, I'd like to switch the input voltage with a microcontroller, from the PWM output or other output pins.

The specifics:

Input voltage: 4V - 60V
Switching input signal: 3.3V (LVTTL)
Maximum switching speed: 50kHz - 1MHz (as high as I can easily get it)
Required current tolerance: 1.5A or 15W

There is no supply voltage besides the 3.3V signal.

I am looking for suitable components to do this as simply as possible. For me, simple means as few components as possible, and as few requirements on both the inputs and outputs of the components - I do not wish to impose any driving requirements to the microcontroller, or restrictions on how the switch can be used, or similar things. But I'd want the components to be suitable for a high efficiency switching mode power supply.

I know it can be done with a combination of n-MOSFET and a p-MOSFET and a couple resistors. I know it can also be done with a gate driver IC and a n-MOSFET, although I have been unable to locate one that would only require 3.3V supply voltage (and a boost pin?). I know I do not want a solution that would force some minimum off-time rate on the MOSFET to charge a capacitor, but I might be convinced otherwise. In theory, the most direct solution would be a 3.3V compatible solid state relay or analog switch, but the actual solid state relays available do not seem very suitable.

But, primarily I am just interested in learning more about the problem space here and the possible solutions.

Clarifying schematic stolen from another question:

Vin = 4V - 60V
Controller = 3.3V signal, toggling at, for example, 250 kHz
Q1 = the component, or the set of components I wish to find

So, strictly, the question is simply: what do I need in place of Q1?

(Note that this is just an example schematic, not exactly the sort of circuit that I wish to build.)


texts: Regulated DC supply - need help with calculations

texts:
I am in the process of making a regulated power supply to convert AC(220V, 60Hz) to DC(9V, 500ma). I have worked out all the calculations and would appreciate if someone could double check just to make sure they are alright.

My setup is as follows

AC(220,60Hz)  -> Transformer(12V,500ma) -> Bridge Rectifier -> Voltage Regulator(7809)

the 78xx series requires at least 2V to work => i need at least 11 as rectifier output

2.the ac input might vary by 10% ..

peak transformer voltage = 12 \$\cdot\$ \$\sqrt{2}\$ = 16.97V

min transformer voltage = 16.97 \$\cdot\$ 0.9 = 15.27V

vout-bridge = vmin-transformer - (2 \$\cdot\$ 0.7) - Vripple
vripple = 15.27 - 1.4 - 11 = 2.87V
dt * load current / C = 2.87V
C = 8ms * 500mA / 2.87V
C = 1393 μf

can someone confirm this is correct ??

thank you for the help !


texts: why is the feedback or gate resistance RG necessary?

texts:
Here the large feedback resistance RG interposed between gate and drain of the NMOS (usually in the megohm range) forces the dc voltage at the gate to be equal to that at the drain (because IG = 0). Also, it says that RG works just like the RS which is to stabilize the bias current ID in the event of changing VGS.
my question is why is the RG necessary, isn't "the dc voltage at the gate = the dc voltage at the drain" regardless of the RG?

thank you folks


texts: Why is there a resistor in this reverse-polarity-protection circuit?

texts:
I was looking at the recommended reference implementation for a particular integrated circuit (the TI SN65HVS880, data sheet here). It runs off of a 24 volt power supply. The circuit diagram looks like this (taken from page 17 of the data sheet, red added, with V24 being the IC's 24-volt power input):

I am assuming everything between the 24 V power supply and the IC itself is protection circuitry and the BYM10-1000 diode is for reverse polarity protection. But I do not understand the purpose of the 56 ohm resistor (highlighted in red).

Why is the resistor there? Is it necessary?

A few further notes: The resistor must be rated to 1 amp or less (looking up the data sheets for "MELF" resistors, that's as high as they go) and the diode there is only rated to 1 amp. There was no further explanation of this circuit provided.


texts: How to reverse-engineer a remote control?

texts:
I purchased a few bulbs which are manged via a wireless remote control. I would like to use them with my RPi (to which I would add the relevant transmitter-receiver module).

Is there a way for a layman who may have access to reasonable measuring devices (and is an ex-physicist) to determine

the frequency of the transmitter (hopefully 433 or 315 MHz)
the protocol (when I press the "on" button such and such signal is transmitted, ...)


texts: Total Weight for load cell when connected in a wheat stone pattern?

texts:
I have 4 load cells from AnyLoad, Model 563YH-SE5Klb. Each Load cell is 5Klb and i want to connect them in a wheat stone bridge format. My surface area for the load is 3 feet by 5 feet, and thats why i have to use a wheat stone design.
How much is the total pound capacity while using these load cell in the wheat stone pattern? How does one do its calculation?

Please refer the picture below for the specification of the quadro set that i have.


texts: Is there a relationship between thickness of the oxide gate and the length of the channel in a MOSFET?

texts: Is the channel length mathematically/physically related to the thickness of the oxide gate used in a MOSFET?


texts:
I am having a serious issue here. I've bought a Maxbotix XL ultrasonic sensor but I didn't know that it is the AE version, that does not come with pulse width, it comes with Analog Envelope. I have a 8051 board and I need to read these Analog envelope data and measure the distance. I don't know what analog envelope is, but I also have a common analog output, how can I read this data from 8051?

I am very grateful


texts: The meaning of constant current source in BJT

texts:
Taking a sample from TAOE Ch.2 Figure 2.9 for example. The book suggests that BJT constructs a constant current source for the LED and \$\beta\$ is subject to change from multiple parameters thus should be not used to calculate collector current in practical design.

Supposed \$\beta\$ is ~25, \$I_{b}\$ is (3.3-0.6)/10k = 0.27mA and hence \$I_{c}\$ is preliminarily "guessed" to be 6.75mA. Voltage drop across 330\$\Omega\$ resistor is "guessed" to be 330\$\Omega\$ * 6.75mA = 2.2275V, and if I assume voltage drop across LED is 1.65V, total voltage drop on collector side is 2.2275V + 1.65V = 3.8775V, which makes no sense since >3.3V suggests collector is pulled below ground. Now I know it's saturated. But to start the calculation, I cannot avoid using \$\beta\$ to estimate it. So I have the imagine \$\beta\$ is less than 25 and plug in each \$\beta\$ value until the voltage drop in the collector is 0.2V less than the supplied 3.3V, hence the beginning of my saturation current.

If we take a different approach, assuming LED drop voltage by 1.65V, then we calculate current across 330\$\Omega\$ resistor to be (3.3-1.65)/330 = 3.295mA (here I neglect \$V_{ce}\$ ~ 0.2). To drive a 3.295mA collector current, my base current should be at least \$\beta\$ * \$I_{b}\$. Again, I have to use \$\beta\$ which I am not supposed to.

How is this a constant current source if either perspective requires me to use \$\beta\$ which is subject to much variation?  Then I have to go about imagine \$\beta\$ to be a different value to find the "point" between saturation and forward active.
If I change \$V_{cc}\$ from 3.3V to 10V, collector current increases more than 5%, which is not a constant current source.


texts: Voltage Rating of Differential Amplifier

texts: If I hook up a 25v-rated operational amplifier in a differential configuration, with a +/- 2.5v (5v) supply, can I measure signals 100 volts above the negative supply, so long as the difference between the two inputs is within it's rating?


texts:
I am working on making my own "mod" for an e-cigaret (A mod is the device that controls when and how much the coil is heated up to)

I have read a lot about it during the last couple of days, so i have a few different ways to drive it, each with their own ups and downs. Here is what i have learned so far.

First is the mechanical mod, basically a switch to allow and deny current to flow through the coil:

Ups:

Simple to build
No power wasted

Downs:

No safety features (No current limit, other than the coil)
No power regulation

Next is the PWM approach:

Ups:

No wasted power
Able to regulate current, but not fully

Downs:

Coil will get full current, no matter what the mod is set to, just not all the time while firing

Last is the DAC approach:

Ups:

Able to fully regulate current

Downs:

Potentially lots of wasted power
Lots of heat generated in the wrong place (MOSFET)

I want to note the schematics are very simplified, of course additional components are needed in order to have a functional design.

I am most inclined to use the PWM apprach, but the fact that i cant measure current directly with a shunt puts me a little off.

Anyhow, here is my questions:

Is there a way to smooth the current running through the MOSFET so i can measure current with a shunt?
I have two 18650 batteries in series in order to achieve high enough voltage to drive my coil at the wanted power level (110W in this case), but one cell is limited at 25A in its datasheet, that means i can pull 25A at 7,4V nominal voltage, right?
Is there another way to drive the coil that i dont know about, where there is smooth current to the coil and minimal power loss in the switch component?


texts: Combating voltage drop on low voltage distance sensor

texts:
I have a distance measuring sensor unit that I am having some issues with, its a Sharp GP2Y0D815Z0F Digital Distance Sensor (Datasheet) that takes a 2.7-6.2v DC input. When plugged directly into my 3.3v power source (a NodeMCU esp8266) via a 10cm jumper cable the sensor functions perfectly, its LED (& out signal) turning on when there is a part in the way.

However when I use a longer cable (For example a 5m multicore cable or a just two  10cm jumpers) I get a lot of false detection signals (easily seen as the LED flickering). It is worse with the longer cable.

I have tried powering the sensor on the short jumpers and the just sending the signal through the long cable which works fine so I belive it isnt a noise issue. I have tried using a lab-pack to power the source through the long cable and with any voltage of less that 6v i get the noise so I'm led to the conclusion that the voltage just isn't great enough from the esp8266. Unfortunately 5v from a USB port doesn't seem to be enough to prevent errors.

Does my conclusion make sense? Can anyone suggest a easy way to power the sensor? I have a usb port and a 12v power supply next to the esp8266 - this is part of a Home Automation project but I don't easily have any more 240vAC sockets. I'm considering using a voltage divider to convert my 12v to 6v but as the 12v is used elsewhere to power LEDs i'd rather not need to.

Failing all that if anyone can suggest a good short range presence sensor that will work with a esp8266 that would be great.

Thanks for reading


texts:
I'm currently designing a digital mixing console. We have a somewhat large number of ADCs and DACs (more than the multi channel audio serial port on the processor can handle). We decided the solution for this was to use an FPGA to interface with the data converters and let the processor access the data through the RAM in the FPGA. We have not yet picked out a FPGA.

From what I have read we can configure the FPGA RAM as being a NOR non-multiplexed 16-bit device through the GPMC. Is this correct?
And my other question is it would probably be too slow to keep the data in RAM of the FPGA so would it be possible to set up a DMA transfer from the FPGA RAM to other memory in the processor that is easier and faster to access? Or would we need to use a PRU to copy the data?


texts: Is using a TVS diode better than using a parallel reverse-polarity protection silicon diode?

texts:
I want to add a reverse-polarity diode to my design.
It has an input of 24 V (230 Vac to 24 V power supply) which is fed to a 24 to 12 V converter. I plan to draw up to 4 A from the 24 V power supply. The PCB works in a generally room temperature environment and has an SBC, mini pcie port and an RS-485 comm line.
I was planning on adding a diode with a serial fuse too, in parallel to the 24 V in order to prevent reverse-polarity connection damage.
I also want to add a surge protection to the same power terminal.

Can I just use a TVS (bidirectional or unidirectional) instead of the diode?
Do I need to have both?
I know that a TVS adds a substantial amount of input capacitance. Should I be worried about it?
Do I need to have other things in mind, when designing the circuit?


texts: Is my device incorrectly sending ACKs on the canBus?

texts:
I have a prototype device that is listening to the canBus for certain messages (there are only two nodes on the bus, my device, and the sending device). I'm having a problem where the sender constantly sends the same message, I think because the ACKs that I'm sending aren't being 'recognised', so the sender keeps retrying. I think it's because of this that my microcontroller is not picking up the messages (firing the can receive interrupt).

I also have another device which seems to work correctly and ACKs the message and it is not retried.

I have included a screenshot of the scope trace. The yellow trace is what the microcontroller is transmitting, and the red trace is what is being received from the CAN IC on the PCB. v8 is the broken version (note that directly after the ACK, the message is resent). v7 is the correct working version. There's a slight difference in the waveform between the two but I don't know what it means.

Thanks for your help.