texts:
I am still new to the stm32f4 discovery board. I was looking at the board's schematic to see how the user button is implemented on the board:

Since C38 is not fitted, does that mean I have to resort to software methods for deboucing? Just curious, if the answer is yes, what would I have to do to perform hardware debouncing?


texts: Loudspeaker crossover network using Sallen key filters (MATLAB transfer functions)

texts:
I am currently trying to model an active Linkwitz-Riley crossover network using cascaded Sallen-Key lowpass (LP) and highpass (HP) filters.

I can get plots simulated in MATLAB of both transfer functions, however using the same RC values for the HP and LP I thought would cause both to have the same cutoff frequency so that when put together they would cause no gain loss across the system.

However, this is not the case seen. I have used the transfer functions explained in Texas Instruments paper, however they are adapted to not include resistors 3 and 4:
http://www.ti.com/lit/an/sloa024b/sloa024b.pdf

I am currently just using the transfer function for a singular Sallen-Key filter in the hopes of once this is sorted I can then simply cascade them.

The MATLAB code for the transfer functions is as follows :

function H = transferLP(R,C,f)
    s = 1j.*2.*pi.*f;
    RC = R.*C;
    H = 1./((s.^2).*(RC.^2) + (s.*(RC + RC + RC)) + 1);
end

function H = transferHP(R,C,f)
    s = 1j.*2.*pi.*f;
    RC = R.*C;
    H = ((s.^2).*(RC.^2))./((s.^2).*(RC.^2) + (s.*(RC + RC + RC)) + 1);
end

Taking the real part (real(h)) of the result of these functions should obtain the magnitude information while the imaginary part (imag(h)) should contain the phase information.

f = frequency vector
R = resistor values
C = capacitor values (Keep R & C the same i know you can change them individually)

The plot I get out for the magnitude is as follows.

As a side note I was also wondering why the gain dips below 0; is this a ripple in the stop band because I'm using a second order filter?

Thanks for the help in advance.


texts: Voltage, Current, Angular Velocity, and the effect they have on Torque

texts:
I've come across the equation VI = Tw (voltage times current is equal to torque times angular velocity); because power in (voltage and current) is equal to power out (torque and angular velocity). This equation can be changed to T = (V*I)/w. This shows me that an increase in current AND voltage would create an increase in torque; and that a decrease in angular velocity would create an increase in torque. Am I right? Or do I just not understand this stuff at all?

I'm trying to figure out how to create the greatest torque possible WITHOUT changing the other physical properties of the electric motor.


texts: There is no 'latch pin' on MC74HC164A shift register

texts:
Unlike a 74HC595, this shift register (http://www.onsemi.com/pub_link/Collateral/MC74HC164A-D.PDF) doesn't have a latch pin. How then do I output the data stored in the registers (to something like an LED array)?

Thanks.


texts: Transformer Question - Two Output of Different Voltage

texts:
I'm fairly new to electronics, but still have a basic understanding (1st year Electrical Engineering Student).
I've started a project of repurposing a used treadmill I found online for $20 as a variable speed pottery wheel for my girlfriend. When the treadmill arrived it had a blown fuse and after replacing the fuse it continues to trip the RCD. I began debugging the circuit and think that I have isolated the problem to the transformer (I disconnected all of the components with terminals off the main PCB and started reconnecting them from AC forward until the RCD began to trip. The transformer was the connection that caused this to occur).
Attached are some photos of the transformer unit. I don't have too much experience with transformers so my question is - is this a single transformer with 3 windings (1 in and 2 out) or is it two separate transformers packaged as a single unit.

Bonus Question - if theres any advice or other methods I could use to bestconfirm that the transformer is the circuit issue?


texts: Looking for a PCB flag/indicator component

texts:
I am designing a test jig (within a 6U rack) that mates with 6 removable trays. Each tray can hold 16 sensors which can also be removed. The system will be intended to function in the following way:

Technician will populate all trays with sensors,
Trays are entered into rack and all sensors are tested,
Trays are removed from rack and sensors that failed are removed first and binned. The rest are passed and bagged.

My issue is production have requested for indicators next to each of the sensors on every tray that indicate a pass or fail.

When the boards are disconnected from the rack they lose power and although LEDs and external battery would be the first solution....they have asked for alternative solutions.
Is there such a component as an indicator relay or something along those lines? If anyone has a good solution for this issue then please let me know.

Software GUI is currently ruled out also as they believe looking at a screen and then at a PCB could lead to human error...


texts: LED array at high current or high voltage?

texts:
Is it more efficient to drive LEDs at a high current and low voltage, than a lower current and high voltage?

I'm in a situation where I have to design an LED driver for a custom CoB emitter, so can choose the voltage and current as long as it's 22W overall. My input voltage is likely to range from 7-24V. I'll also need the LEDs to be dimmable in some way or another, likely PWM.

I'm not sure whether I should ask for the emitter panel to be made a lower voltage with higher current, or the other way around. It seems after a lot of looking that a reasonably priced simple boost LED driver is hard to come by, but I'm worried that using high current will cause power losses to be greater in the PCB traces and other components with significant ESRs.

So which way is best and why? And while I'm at it, any part recommendations for a cheap-ish driver?


texts:
USB On-The-Go (OTG) has an "attach detection protocol" (ADP) which allows the host device to know if a peripheral is connected.

ADP periodically measures the capacitance on the USB port to determine whether there is another device attached, but the implementation gets cloudy.

There's a short description of ADP on the Wikipedia Page and here is the official documentation. I've read both but maybe I'm not getting something.

In my application, a DPDT relay will be used to switch the VCC and GND of a USB cable between a charger and an OTG cable. However, the signal wires will remain connected to the OTG side all the time. Will this trigger the Attach Detection Protocol and cause the host to supply power at the wrong time?

EDIT:
I found this on the official documentation page 22 and it seems to be answering my question.

  ADP operates by detecting the change in VBUS capacitance that occurs when two devices are attached
  or detached. The capacitance is detected by first discharging the VBUS line, and then measuring the
  time it takes VBUS to charge to a known voltage with a known current source. A change in capacitance
  is detected by looking for a change in the charge time.

Since only the VBUS (5V) is used, is it safe to say that ADP won't be triggered by the signal wires by themselves?


texts:
If an engineer needs to limit how many amps come out of a wall's circuit, how is this accomplished? I know that there is nothing preventing more than 15 amps from coming through my wall other than the breaker that trips if more is passed.

From my understanding of Ohm's law, you can limit the amps on a fixed voltage by increasing resistance. In order to get a 15 amp current, for example, out of a wall, instead of a huge current (which would obviously trip the breaker), what is used?

I am a bit confused on the whole way wattage and everything works, and I appreciate any responses!


texts: I bought Johnson motors for making bot and its max load current is 9A.My batterys are 12V 1.3AH. I gotta problem with my motor driver circuit.It has L293D(2A peak). If load increases on motor current may increase damaging the IC so I am thinking to limit current drawn by motor to 1.8A. Will it work even if load increases and only 2A current is provided? Will Any of the component get damaged?What should i do? Thanks..


texts: Hardware Implementation of Discrete time Systems

texts: Discrete systems work on sampled signal values. Suppose if we want to implement such a system like a discrete amplifier (i.e., \$y[n] = A\cdot x[n]\$), how do we make sure that the input to this system is available only at discrete time intervals? Even if we use sample and hold circuits, the data on the sampling capacitor may change during the sampling time interval.How do we ensure that data input to the system doesn't change between successive sampling times?


texts: Creating hardware acceleration card with PCIe implemented in an FPGA

texts:
PCIe offers a very high speed interface between a peripheral card and PC. Sending and receiving data from the FPGA side which contains the PCIe IP seems to make sense. However, I am confused how it would work on the computer side. On the PC side we have different operating systems and they usually do not allow direct access to I/O ports.
How would one write a program on the PC side (lets say windows) to communicate with the PCIe peripheral card? I think most likely we would use C or C++ but don't know anything more than that.


texts: What are the differences one should consider between designing an RC snubber across a switch and across an inductor? Is there any preference for putting it across the switch?


texts: I am trying to solve for Vo in the circuit above. The input voltage is a simple sinusoidal with Vp = 100V. And all R=2.2k . What I am confused about is how to deal with the two grounds. How do grounds work in an AC circuit in the first place? The -ve side will not always be at 0V. I'm not sure how to go at this problem.


texts:
I looked into this and found only vague indications that it should be no problem, but nothing specific enough to feel safe.
Based on reading this question and its answers and comments it seems like it would be fine, Can an iphone/android cell phone communicate with RFID?
But for my actual question.
I am wondering if it is safe to keep a RFID card in the back of a cellphone case (pressed right against the phones back) and to keep it in the case while using both the phone and the card.
I keep my iPhone 6S in a drop-case and want to put my door's RFID proximity card in the back of the case so I don't have to carry an additional card when my phone is typically in my hand.
I have read that RFID chips are passive so it won't hurt anything carrying it around, my worry is since it will stay in the back of the phone case when I scan it will that transmission cause any issues? I can't see any reason why I would, but I would rather not fry a multi-hundred dollar IPhone on my understanding without asking someone more knowledgeable.
My specific use case is a home-made Arduino RFID automatic door lock, easier to buy something else, certainly, but not nearly as much fun as building one and learning along the way.


texts: SMPS : Average Current Control Vs Peak Current Control

texts:
Please correct my understanding.

I understand that in peak current control mode, the slow outer voltage control loop generates a current command to the faster inner current loop. This current command places a limit on how much current can flow through the inductor. The switch is turned off as soon as the sensed inductor current hits the ceiling. Any swing in line voltage is thus accounted for in real quick time rather than detecting it via changes in Vout which can take time to manifest.

What exactly is average current control? Is this as simple as generating a current command which is representative of the desired average inductor current rather than the peak current? And as in the above case, as soon as the inductor current hits the average current reference, the switch is turned off. Is this correct?

Why would one choose average current control over peak current control? Kindly explain without without algebra. I regret to say that all literature available on this topic is simply not for the layman.

As am interested in doing this the digital way, I would like to utilize the available ADC, DAC and Analog comparators on my microcontroller. What can be a good algorithm here?

Please advise.


texts:
I am new to Altium. I am trying convert gerber files in to PCB. I am getting following error while trying to extract net-list.
It is asking me to compress or redefine layers. I dont know how to do that.
Error I am getting while extracting Netlist.

Layer stack


texts:
The following diagram shows fuses off each of the PT connections (standard IEC fuse symbol) but it also shows a fuse symbol with inverted colouring on the neutral connection.

This second fuse also looks like the IEC fuse but what is the reasoning for the colour inversion? Is there a special neutral fuse that no one has told me about?

More info:

GE 869 Motor Protection Relay
Schematic is from this manual. PDF page 42, manual page 2-8.
PTs connected in wye configuration (shown above)
PTs and fuses are external (i.e. not included) to the motor protection relay.


texts: Life expectancy of a CXY-B1 Li-ion battery

texts:
Last year I got a National Geographic Explorer 4 camera with two CXY-B1 Li-ion batteries (3.7V, 1000 mAh 3.7Wh). In one year, I used them both for about 7 hours in total over the course of the year (calculated from the size of saved footage and average bit-rate).
After charging them both overnight, one of them now turns on for a second before turning off, the other shows the warning sign of low battery.
Is this normal? What is the life expectancy of such batteries?
Update: Following the comments, the first battery has a voltage of 3.7V and
the second has 2.5V. After 5 hours in the charger, they have 3.7V and 4.2V
(yes, 4.2V, and yet this battery fails to turn on the camera). I have often brought these batteries to well below 60%, as my filming sessions lasted longer than 2 battery lives.


texts: Why is the voltage between 2 phases in the wye connection sqrt(3)*E in a delta-wye system

texts:
We've got a delta-wye combination of inductors.

So the delta part is connected to the/a 3-phase voltage source which delivers the voltage E across any combination of 2 phases.

So across the delta connection the voltage drop across each inductor is E.

Now it is claimed that the voltage drop across 2 of the inductors in the wye-connection is E * sqrt(3), in other words between any 2 phases in the wye connection.

Now I can't see the reasoning behind the last claim, how does one find that? And how exactly are the delta and wye connected togheter?


texts: How many WiFi networks can operate concurrently?

texts:
Very hard information to find since Google always falls down in how many devices can be connected simultaneously to a single one network.

Is there a limit to how many different WiFi networks can work properly in the same place?


texts: How do I program an AVR Raven with Linux or a Mac?

texts:
This tutorial starts with programming the Ravens and Jackdaw with a Windows box.  Can I do those initial steps with a Linux or OS X machine instead?  If so, how?  Is there any risk of bricking the hardware if I just try?

I have a USB JTAG ICE MKii clone, which is supposed to work for this.

I'm totally new to AVR, but very experienced with C/C++ programming on Linux or OS X, up to and including kernel programming.


texts:
I'm using this Microcontroller S32K142 64 pin.
I want to understand to whether the RESET pin is Input or Output from the Microcontroller.
I checked the Microcontroller Reference Manual, it is given as I/O.
Can someone tell me whether it is Input or Output ?


texts: Driving two 7-segment displays with a single shift register and BJT transistors

texts:
I'm building a circuit containing 8 switches representing 8 bits in a byte. I have two single digit 7 segment displays to display the two hexadecimal characters that represent the byte value.
I'm quite familiar with using 74HC595 shift registers to drive a segment display, having one register to control the segments and one to control the common cathodes.

I figured that since there is no need for a decimal point in hexadecimal values, I can leave out the second shift register and use the 8th output pin that would otherwise control the Dp segment, to toggle between the two displays.

I've come up with this circuit (left out irrelevant parts)

I know it's more of a hypothetical problem, but I know there is a delay between the moment Q1 switches on and Q2 switches off, since Q3 needs to switch too.
I tried the following:

Connect the Dp output pin of the shift register to Q3's base. Q1 was connected with Q3's emitter and Q2 to Q3's collector. This made both displays either on or off (which I could not figure out why)
Leave out Q3 and connect segment1's cathode with Q2's base. This lights up segment2 very dim when segment1 is on, while segment1 is off when segment2 is on (that must have something to do with segment2 not providing base current to Q1 I suppose?)

Is there a way to switch only one of the displays on at the same time with the same number of transistors for both cathodes? (I can take "no" for an answer)


texts: Photodiodes: the "generation" mechanism behind photocurrent

texts:
Assume I use a photodiode under zero-bias (that is in photovoltaic mode). How/why can a current flow in this bias condition?

As far as I have understood the working principle of photodiodes, when photons hit the depletion region of the P/N junction, the energy absorbed causes the creation of electron/hole pairs. Due to the electric field in the PN junction those charge carriers are separated and "flow out" at the terminals of the diode.

This somehow makes sense to me when a diode is used in photoconductive mode, where an external voltage source provides an electromotive force (and therefore an E field in the diode), but under zero-bias, there is no E field inside the diode that could "pull-apart" the created electron/hole pairs?


texts: Propagation delay of a digital logic circuit

texts:
I'm trying to answer a question on propagation delay. The question is:

Assuming the propagation delays for different circuits are as follow:

4 ns for XOR gate,
3 ns for OR gate,
5 ns for NAND gate and
12 ns for a 4-by-1 multiplexer,

calculate the propagation delay for a change at input A to reach the output F, when all other inputs are constant.

The circuit is below

I have calculated the propagation delay to be 14ns. Is this correct?


texts:
I'm trying to ID diodes on a board - the markings on the diodes are "BK 9EJ3D". I understand this is a TVS diode and it's being used to clamp RS485 differential pair to ground with a termination circuit into a MAX 485 driver (485 to ttl). They measure around 730 ohm in both directions when I use a multimeter. Signal is something similar to DMX.

Any help appreciated.


texts: Level Conversion RGB LED Strip Noise Resistor (3.3 to 5)

texts:
I recently prototyped my circuit on a breadboard that controls a WS2812b RGB LED Strip.

The PDIP (breadboard friendly) ATMEGA644 uses 5V logic while TQFP uses 3.3V logic.

The LED strip specifies a resistance of 680 ohms to the data line of the strip to reduce noise.

The LED Strip does not operate correctly with 3.3V logic so I created a level converter.

My question: Should I include the 680 ohm resistance at the output of a level conversion circuit on the TQFP shown in the one below or should I neglect it or do something else?


texts:
I don't understand most of the antenna balancing instructions I read; for one thing they virtually all seem to assume the antenna is being used to transmit. In my case I am only interested in receiving. I do not want to transmit with the antenna. Basically my goal is to be as sensitive as possible and make the received signal as pure as possible.

For example, one setup I have uses a wideband antenna that looks like the following and can supposedly receive signals anywhere from 3 MHz to 800 MHz:

The antenna is on a mast off the porch. I connect a coax cable to it and it goes about 20 feet to my receiver. Sometimes I connect it to an antenna switcher. It seems to work ok, but I have no idea how to optimize it to make it more sensitive.

I presume that some optimizations would be frequency-specific and others would help increase sensitivity at all frequencies, but I have no idea how to make these adjustments. I have an SWR meter, but the instructions for it assume that I am transmitting, which I am not.

To quote from one of the answers below:

  When your antenna impedance matches the cable and receiver impedance
  the signal power is optimally transfered... Some antennas have an
  impedance matching adjustment on them. This should be adjusted to
  match the cable and receiver impedance. Matching impedances for a
  receiver only system can be difficult as there is not enough power to
  drive an SWR meter. Sometimes the manufacturer will mark approximate
  locations on the adjustment component that will indicate the impedance
  settings. Without any guidance it would be necessary to tune your
  receiver to a very week signal then make small adjustments to the
  antenna, then recheck the signal for any improvement.

So, if it is good for the "antenna impedance" to match the "receiver impedance" how do I do that? How do I measure the impedance of either one? The poster just says it is "difficult".

One web site I read said antennas should be "DC grounded".


texts:
what is the simplest way to regulate the min DC voltage in a circuit?

Desired performance:

Input > 5 VDC     Output = Switch power lane
Input = 5 VDC     Output = Input
Input < 5 VDC     Output = 0.

Current may be around 3A

The input voltage may be from 5v to 22v through USB type C connector. I decided to use module based on MP1584EN to step down voltage from >7V to 5V. But this module works unstable if an input voltage equals to output. And I can't imagine how to ignore this module if the input voltage equals 5V.

Thanks

Update
Ok, in case I will use default DC jack 5.5*2.1, and power adapter may be 5V, 9V, 12V, 24V. How to pass 5V directly, and input > 5V through MP1584EN module

New schematic


texts: How can we find the signal power of \$x_{out}(t)=\frac{1}{2}Am(t)cos \theta\$?

texts:
I am trying to solve the following question:

I have partially worked out the problem and we have:

\$x_{out}(t)=\frac{1}{2}Am(t)cos \theta\$, which is the output of the LPF.

and

\$x(t)=Am(t)cos (2\pi f_c t)\$

My problem is that how can I find out the power of \$x_{out}(t)\$ and \$x(t)\$ because I don't know the amplitude of \$m(t)\$. Moreover, if \$m(t)\$ is not a singletone frequency signal, how can we find out the power of \$x_{out}(t)\$ and \$x(t)\$ ?

  In short my question is:

  How can we find the power of

  \$x_{out}(t)=\frac{1}{2}Am(t)cos \theta\$

  and

  \$x(t)=Am(t)cos (2\pi f_c t)\$?


texts:
This is related to this question.

I'm trying to get started with a DIY reflow soldering station intended for my personal use. I'm planning on starting small and improving the system as time goes on (basically just the unit to begin with and better temperature control as time goes on).

I'm thinking of getting this 1000W hot plate. It has decent reviews and at $20 is pretty cheap, too. I would like the setup to be able to handle lead free solder paste, though I'm not sure if I'll go that route to begin with.

I have 2 questions:
What pros/cons should I consider when choosing between a hot plate/skillet or a toaster oven?

The two I've identified so far are:

for the same rated wattage hot plates/skillets are cheaper (~$20 range vs. ~$30 or higher)
According to Sparkfun toaster ovens might melt plastic parts, though I wonder if this may be due to user error/flawed designs.

My second question is related to temperature and power. The devices I've seen are rated in Watts, not maximum temperature. From what I've read a decent reflow system should be able to reach at least 230-260C if it's intended for lead-free work. However, I'm not sure how this translates into what wattage to be looking for.

Anyone with experience have recommendations on what power ratings I should look into and any other factors I should consider?


texts: Does it Matter Where I Place Resistors on Circuit for Lightsaber RBG LED

texts: I'm trying to figure out the circuit of a Lightsaber I wish to assemble myself using an RBG LED (Tri-Cree RGB EP-X2) and am unsure where I can put the required resistors and also how many I need. I will be running the set up with 4 AAA alkaline batteries at 6V, and I would like to be able to customise the colour blending of the LEDs by changing the resistors that go to each individual diode. Do I need to place the resistor I wish to change the diode intensity with before or after the LED in my circuit? I'm sorry if this doesn't really make much sense, I'm still pretty new to this stuff so any help I can get would be fantastic. Thank you in advance.


texts:
But back in school, I had learned that the "bandwidth" of a communication channel is the frequency of the highest-frequency signal minus that of the lowest-frequency signal that it can carry.

Yet in practice, I see people use the word "bandwidth" when they are referring to the throughput of some digital communication link.

For example, SpeedTest.net boasts that it can test your "internet connection bandwidth", and NVIDIA graphics cards report "memory bandwidth" in GB/s:

I always found it confusing how the term "bandwidth" is used for something that is measured in bytes per second.
Are there any differences between throughput and bandwidth?  Is this a correct use of the term, or is it a misuse that has gotten "stuck" over the years? Why/why not?


texts: How to Use Addresses with Single Port RAM on FPGA

texts:
I am trying to understand this example of single port memory where an 8 by 64 bit RAM is created. If I am understanding correctly, the section of code that says "reg [7:0] ram [63:0]" means that there is 64 memory units that can contain 8 bits each.
My question is why is the address only 6 bits wide? If the address is used to assign values to each memory unit doesn't that mean there is only 6 addresses and 64 memory units?
Thanks for the help!
Here is the HDL code:
module sp_memory( data, addr, we, clk, out );
input [7:0] data;
input [5:0] addr;
input we;           // Write enable, 1 is write 0 is read;
input clk;

output [7:0] out;

reg [7:0] ram [63:0];       //8 by 64 bit RAM
reg [7:0] addr_reg;

//<statements>

 always @ (posedge clk)
 begin
  if(we)
   ram[addr]<=data;
  else
   addr_reg<=addr;

 end
 assign out = ram[addr_reg];

endmodule

Here is the testbench code:
`timescale 1ns/100ps

module sp_memory_tb;

parameter SYSCLK_PERIOD = 20;// 50MHZ

reg [7:0] data_1;
reg [5:0] addr_1;
reg we_1;
reg clk_1;

wire [7:0] out_1;

initial
begin
    clk_1 = 1'b0;
// start write

    data_1 = 8'd04;
    addr_1 = 6'd0;  //address 0
    we_1 = 1'b1;    // write mode initialized
    # 20;

    data_1 = 8'd02;
    addr_1 = 6'd1;  //address 1
    # 20;

    data_1 = 8'd03;
    addr_1 = 6'd2;  //address 2
    # 20;

    data_1 = 8'd11;
    addr_1 = 6'd3;  //address 3
    # 20;

    data_1 = 8'd12;
    addr_1 = 6'd4;  //address 4
    # 20;

    data_1 = 8'd13;
    addr_1 = 6'd5;  //address 5
    # 20;

// start read

    addr_1 = 6'd0;  //address 0
    we_1 = 1'b0;    // read mode initialized
    # 20;

    addr_1 = 6'd1;  //address 1
    # 20;

    addr_1 = 6'd2;  //address 2
    # 20;

    addr_1 = 6'd3;  //address 3
    # 20;

    addr_1 = 6'd4;  //address 4
    # 20;

    addr_1 = 6'd5;  //address 5
    # 20;
    $stop;
end

//////////////////////////////////////////////////////////////////////
// Clock Driver
//////////////////////////////////////////////////////////////////////
always
    #5 clk_1 = ~clk_1;

//////////////////////////////////////////////////////////////////////
// Instantiate Unit Under Test:  sp_memory
//////////////////////////////////////////////////////////////////////
sp_memory sp_memory_0 (
    // Inputs
    .data(data_1),
    .addr(addr_1),
    .we(we_1),
    .clk(clk_1),

    // Outputs
    .out(out_1)

);

endmodule


texts:
I just finished task 1 on my project but my teacher has not provided any good guidelines so I was just hoping if you guys could check my work before I move on to step 2 and let me know if I'm correct or wrong as i don't want to dive into step 2 without knowing if my step 1 is correct. Below i will attach my task sheet.

Below I will attach the motor circuit that i have built

Below i will upload my result. The first result is the voltage vs time of V1

Below i will upload my set of results for my current vs time for D2, V3, R1

Finally i will upload my error log.


texts:
I've got an m1000 tape dispenser which is already an automated tape dispenser for industrial usage. The problem is that I can't get enough grip between my shaft en and tape to get the precise length I've asked of the device. So, I want to modify it using a sensor which can measure the length of the tape that rolled out to get the right length of tape I need. And reprogram the tape dispenser and equip it with an arduino so it would interact exactly how I want him to interact.

My question is what kind of sensor do I need? Would a photodiode or phototransistor work?

Can someone help me out with this please?

The arduino will control the stepper motor etc. So the whole pcb will be replaced


texts:
Imagine I have an op-amp in a standard non-inverting configuration with the gain formula \$G=V_{in}(1+R2/R1)\$. I would like to dynamically adjust this gain by using an FPGA controlled switch to switch in and out a resistor in parallel with R2, therefore lowering and raising the gain.

My question is to how to estimate the transients that the op-amp would create? What datasheet parameters would be useful in estimating those? From what I understand, the op-amp equations (V+=V-, feedback formula, etc) are steady state equations and don't apply to transient analysis.


texts: Altium Interactive Routing - Auto-completing

texts:
i'm having a small problem when going to route my PCB in Altium version 9.4 - When I use the interactive routing tool and click it, it automatically completes the second part of the track, which i've found in tutorials and other documentation to only complete the initial perpendicular section and keep the second bit as a preview?

Any help would be greatly appreciated!


texts:
I'm trying to find the theveinin equivalent of this RC circuit but am a little confused. Since R2 and C are in parrallel, how does this factor into finding the thevenin equivalent resistance?

Is it still \$R_{th} = \frac{R_2}{R_1+R_2}\$ or is there something more subtle here I'm missing?

Does the capacitance remain the same here too?


texts: Parallel wires needing to cross - best practices in a schematic?

texts:
I'm sure we've all run in to the following situation:

Here, I need to connect pin 1 and 2 on the left to pin 1 and 2 on the right, and vice versa with pin 2.
I've considered a few options, however all seem to have some downsides:
Connecting using labels:

The problem with this approach is that there's isn't always a clear name for every pin, and that it does not immediately tell that the pins don't connect anywhere else on the schematic.
Connecting by crossing the wires:

I really dislike this approach, since it both is very unsymmetrical and also looks very reminiscent of a swastika.
Crossing diagonally:

This approach works, but it does look slightly ugly in my opinion as schematics usually only consists of vertical and horizontal lines. Also, not all CADs support diagonal wires by default - in KiCAD you need to enable an option for it, and I'm not even sure you can do it in Eagle.
My question is, which of these approaches would be the "best practice" to create professional looking schematics? Are there any other approaches that would work better than those I've listed?


texts: Synchronised Buck converter - Soft-Switching

texts:
I have a question regarding the synchronised buck converter. This topology is using two transistors instead of a transistor and a rectifier diode. The bottom switch is used to reduce conduction losses in high power applications. My question: Can this technology be defined as soft switching? The reason why I am asking is that a paper from Microchip states on page 4 (see below) that this is indeed soft switching. However, I cannot find any other references approving this. In my opinion, Microchip is correct.
*

Since the source of the low-side device is tied to ground, the phase
node must go below ground by a voltage equal to the forward drop of
the body diode, in order to conduct. Therefore, when the low-side
switch is turned on, there is only a voltage equal to the forward drop
of the body diode across it. This leads to a “soft” switching event,
with losses that are considered negligible in this application note.


texts: Simple low voltage disconnect circuit for Arduino

texts:
Preface:

Under impression to need a low voltage cut out, to prevent 2x AA NIMH rechargeable battery from being drained too now, and damaging them. (right??)
In deployment this circuit will commonly be exposed to complete discharge event if allowed.

Concept:

S1 momentary switch is held down, activating Q1 to power up 328p
Sketch begins and Setup() calls digitalWrite(A5, LOW)
S1 can now be released as Q1 is held LOW by A5
Battery gets low, triggering brown out detect (BOD), 328p resets, and disconnects Q1

Notes:

R1 is resistor wheel and i experimented with different values to get it to work. (as i have not done the math)
I have this assembled on breadboard, radio and lcd module are not pictured
With A5 disconnected it works well (while S1 held down), When off 0ma at Ammeter.
With A5 connected it can work with higher value of R1 (47k) to prevent it booting up itself, but when off Ammeter reads about 2ma.

This 2ma is still enough to drain the battery significantly if left flat for some time.
Im guessing the 2ma and need for 47k resistor are related to what appears as A5 'leaking' while arduino off.

I have been able to reduce 2ma current consumption while off by putting pullup resistor between A5 and +V

I have limited space so need to keep things simple.

Feedback:

Any improvements / suggestions, to get around the leaky A5 issue ?
Or generally meet my design needs better ?


texts:
So my local dollar store doesn't sell rubbing alcohol, but does sell acetone.

Can I use acetone instead of rubbing alcohol on electronics?

I know acetone does attack some plastics but rubbing alcohol doesn't.


texts: Wiring 800kHz signal together with RS485 on Cat5

texts:
I'm planning to have short (~1m) RS485 runs @<500k baud to transmit some data between PCBs. These PCBs also have a few addressable LEDs (WS2812B) that send data at 800kHz.

Would it be problematic to run the 800kHz signal in the same Cat5 cable as the RS485? (Using an unused twisted pair as Olin mentioned)

What precautions do I have to take? I could convert the 800kHz signal to differential with another RS485 driver as well but I'm not sure if this is overkill.

p.s.: The reason I'm using RS485 is that one of these boards will have a long cable and I'm using the same hardware for all of them.


texts:
my earphones broke down and I acted stupid and cut the wire, I put on a new jack and my right earphone works like a charm, but the left one has a significant lower volume... when i press the button, the volume goes up to normal.. I think I wired something wrong. Please help me.

I have no measuring equipment like a multimeter.

the wires are as followed:

Jack:

thick copper wire
one wire with a blue plastic tube in the middle and green/red wires around it
one wire with a green plastic tube in the middle and copper/green wires around it.

earphones: two separate wires:

wire 1:

one green wire
one copper wire

wire 2:

one blue wire
one red wire
one copper wire

I connected the thick copper wire with the two other wires(I am pretty sure that's ground)
I connected the red wires with each other,
the blue plastic wire to the blue earphone wire
the green plastic wire to the green earphone wire...

I did not connect the green wire surrounding the blue plastic wire and the green/copper wire surrounding the green plastic wire.

I found that connecting two of the three wires in form the earphones (the left) doesn't work and for the right one I have no problem.

I no one knows how to fix it, i think i will have to tape down the pause button on the left earphone.

thanks in advance


texts:
I'm running into some issues powering a test board using a LoRa chip (RFM95W) with a CR2032 battery. I'm well aware of the peak current limitation of such battery and I can see a major voltage drop across the battery when too much current is asked during LoRa TX (around 80mA), even using a 100uF capacitor in parallel; the voltage drops down below 1.5v which make my MCU brown-out and reset. Thus entering an infinite loop as my MCU is setup to send a measurement on start-up. I'm using a power gating timer (TPL5110) in order to minimise the current consumption between measurements, 1 mesure every two hours.

The question is: how do people manage to use CR2032 coin cell battery alongside LoRa RFM95W as I assume the peak TX current would be fairly similar in all these other IOT boards I can see around internet. I'm using default firmware mode of communication under LoRa-WAN standard of The Things Network and my support hardware around the RFM95W does not account for more than 5mA of current.

I'm not sure my question if well formulated, but mainly I'm looking for any advices on how to use a CR battery and still manage to power my device. In the meanwhile I'm also looking at replacing by 2x AAA battery, but space is precious.

Thank you for your time you might take to answer.


texts: Preparing custom / arbitrary sequence counter

texts:
I know following types of counters:

Asynchronous counter

  Clock input of each flip flop is output of earlier flip flop.[ref]

Synchronous counter variant 1: with ANDing for flip flop inputs

  Note that in this variant of synchronous counter, we have ANDed outputs of earlier flip flops to form input of next flip flop. [ref]

Synchronous counter variant 2: with ANDing for flip flop clocks

  Note that in this variant of synchronous counter, we have ANDed outputs of earlier flip flops to form clock of next flip flop. [ref]

I know how we can prepare custom / arbitrary sequence counter with synchronous counter variant 1. These two pages give examples: 1, 2

Consider the diagram from second page:

So it seems that to obtain arbitrary sequence, we need to form inputs of flip flop by some combinations of outputs. Does that mean, we cant construct arbitrary sequence counter following other two approaches, asynchronous counter and synchronous counter variant 2, as in both of them inputs of all flip flops are tied to HIGH logic?


texts:
This looks little odd to ask here, but I have stuck in situation where I have my hardware ready and unfortunately the footprint used is of some other part no. Due to time constraint, I cant rework with PCB development and I don't want to add floating connections anywhere in hardware.

To be more specific, I have used SN74HCT245, 3 state buffer with 3rd state as isolation. It's pinning diagram is as shows:

But, I need Latch IC (3rd state as latch, instead isolation) for my application. Is there any part no. with same pinning diagram and matching footprint as shown in the image above to fulfill my requirement.

Thank you.


texts: 12v Input LM2596 Step Down Module to USB 5.2V is Slow Charging

texts:
I am trying to use this regulator module (LM2596) to regulate my car's 12V power (constant from fuse port), and use the LM2596 output set to 5.2V to charge my phone (LG G6) but get the slow charging warning (6hs xx mins to full).

I presume the output Amperage can meet whats specified ~2-3A, but obviously something is wrong.  I gutted a USB extension cable to solder to the output of the regulator.

What Am I missing?  Is this module capable of doing what I want?


texts: Is it possible for a bulb to behave like an inductor?

texts: I have learned that the bulb has made from a coil of tungsten, not only bulbs many other components like electromagnet and electric motors also have coils in it. Is there a multiple behavior for this components i.e. does these components behave like an inductor at the same time? Does these components have inductance?


texts: How to find value of beta = (mu*Cox)(W/L)/2 of MOSFET in ngspice

texts: How to find value of \$\beta = \frac 1 2 \mu \cdot Cox \cdot \frac W L\$ of MOSFET in ngspice? Is there any command that displays that? The 'show' command displays many parameters but it doesn't display value of beta's value. Is there any other way by which we can find its accurate value?


texts: Swapping buttons on a GameCube controller

texts:
I have an old GameCube controller that I want to swap the buttons in.  By this I mean that I want to press the x button and have the signal for the r button sent.  I opened up the controller and found the locations of the buttons on the circuit board:

What I am wondering is how I repurpose the buttons.  Would it be as easy as scratching off the wire that runs to the r button and soldering it to a wire that comes from the x button?


texts: Using iSim to simulate 16-bit CLA schematic on Xilinx, all inputs and outputs on the waveform are 'X'. How can I debug?

texts:
I'm building a sixteen bit Carry Lookahead Adder for my EE class. I'm definitely a noob to all this so bear with me, however I've been googling for a WHILE and haven't found any answers.

Here is the code for the test bench. I KNOW this part is correct because it was given to us by the professor.

Here it is:

// Verilog test fixture created from schematic /home/alexx/Documents/ee101_xilinx/ee101_lab5_xilinx/ee101_lab5_cla/cla16.sch - Mon Mar 16 17:00:11 2015

`timescale 1ns / 1ps

module cla16_tb();

// Inputs
   reg C0;
   reg [15:0] A;
   reg [15:0] B;

// Output
   wire C16;
   wire [15:0] S;

// Bidirs

// Instantiate the UUT
   cla16 UUT (
        .C16(C16),
        .C0(C0),
        .A(A),
        .B(B),
        .S(S)
   );
// Initialize Inputs
   `ifdef auto_init
         initial begin
            A = 16’h0000; B = 16’h0000; C0 = 0;
            #200;
            A = 16’h0000; B = 16’h0000; C0 = 1;
            #100;
         end
   `endif
endmodule

Here is the console output in iSim:

restart

run 2000 ns

Simulator is doing circuit initialization process.

Finished circuit initialization process.

So not much help there.

I ran the "check schematic" tool on EVERY schematic associated and they all returned no warnings and no errors. The only thing different about this than the schematics I've made in the past is the use of user-created symbols. We're given a completed PG and we have to make our own CLL, use that to make a 4-bit adder, and combine those to make a 16-bit adder.

I am very, very frustrated by this.

I've attached a screenshot of the waveform, and I can attach screenshots of the schematics if necessary.

Please help me debug this.

Thanks!!

iSim waveform


texts: What's the rationale behind these warnings about extension cords?

texts:
(Disclaimer: I've read the help center and I do understand that this is bordering on off-topic since it's about consumer devices. However I hope that I've managed to make enough on-topic by asking about why it is the way it is, and what is the explanation from an electromagnetic point of view - in other words, what laws of electricity and what practical considerations have gone into these decisions).

I recently bought a power tool and in its manual I found a few peculiar safety rules. I cannot see why they would be there, although reading up more it seems that they are commonplace. My understanding of electricity is limited (just about enough to be dangerous), so I'm hoping to expand it. :)

The rules are:

Don't use an extension cord longer than 25m. Considering this is an outdoors tool, this limitation is severely restrictive. The best explanation I've seen is that longer cables would simply have too high of a resistance and the tool wouldn't be able to operate at full power. But this argument doesn't convince me. The tool is rated at 2.4kW, and it's meant to be used with 220V AC power source, which means it uses about 11 amps of current. All the extension cords I've ever come across have at least 16A limitation, so there is quite a reserve still. In addition, the power has to travel much, much further to get to my house, and even after the meter it still takes probably close to those same 25m to get to the power outlet. Why only 25m after the outlet? The resistance of the cables isn't that big, is it?
Don't daisy-chain extension cords. I suspect this is a variation of the above - don't exceed 25m; every connection adds additional contact resistance; water in the outdoors connections can be a problem - in general, it just adds risk. However, apart from the water in the contacts, the rest seems to me to be practically negligible. Is there really a significant contact resistance? Assuming that the extension cords are in a good shape.
Make sure that the power cord is entirely unrolled. This is another odd one. My suspicion is that it has to do with inductive resistance. But is it really that strong? Wherever I've seen people actually wanting to create an electromagnet, it's pretty much hard work. You need a lot of neat, tightly-wound loops of wire. An extension cord has a lot of insulator around it, spacing the wires pretty far apart, and the loops are very chaotic. In addition, if that was a problem, why do extension cord rollers exist? They're used especially when you need a very long extension cord, and you don't need to unroll them completely every time you want to use them. Solved: OK, I was off the mark. The correct answer (also a separate question) has to do with the wire heating up from being used close to its limits. When coiled together, the temperature can go pretty high and melt the cables. Not fun.


texts: Electronically verify whether cable is connected to RJ45 connector

texts:
Background:
I have a device that interfaces with a motor controller over RS-485 via an RJ45 socket. Currently, the port is a standard 4x2 RJ45 connector with the RS-485 using pins 2 and 7

Currently my startup procedure tries to connect to the controller 3 times before notifying the user Device Cannot be found. Check cable.
Problem:
I would like a way to electronically check if the cable is plugged in. By any chance are there 10 pin RJ45 sockets sold, where two pins short if a cable is plugged in? If so, what is this feature called? If not, what is a solution used to detect if a cable is present in the system?


texts:
I would like to know how it is possible to remove (external) offsets like temperature and unwanted magnetic fields when using a hall sensor.
As far as I know this should basically be possible by using several hall sensors and rearrange them in a certain way.
I think it is even possible to swap the current and hall connectors but I'm not sure about that.
Note: In my documents (which are in a different language) this principle is under the term

spinning current principle

but when I google that it looks way more like a special solid physics effect or so.


texts: Opamp + NPN and MOSFET in the feedback network, how to prevent oscillations

texts:
Background

The task is to add an electronic means to limit the power applied to an electric motor in an industrial setting. The operator normally controls the motor power through a lever that is mated to a 5KΩ pot:

simulate this circuit – Schematic created using CircuitLab

The electronic device I want to add should be able to cap the signal to a limit, so that the signal fed to the ESC follows the relation

$$V_{\text{out}} = \text{min}(V_{\text{in}}, V_{\text{limit}})$$

or (thanks to @GlennW9IQ for suggesting it!)

$$V_{\text{out}} = V_{\text{in}} * V_{\text{limit}}$$

(in the second case, assume Vlimit is 0..1, i.e. just a normalized multiplier).

One very important detail is that whatever I add should not be able to generate a phantom signal, i.e. Vout MUST be always less or equal to Vin, even in the event of software bugs and reasonable hardware failures. To this end, I initially drafted something like this:

Draft 1

simulate this circuit

There are also other details, e.g. a relay to bypass the whole circuit if my device is unpowered. The purpose of OA1 is to buffer the input signal so it can be read through a MCU ADC pin.
With this schematic, I can be reasonably sure I cannot inject a positive voltage on ESC's input, since I can only pull the pot's signal down.
The problem is that OA2 cannot bring the signal to 0V if the limit signal says so, because the output will always be at least the Vf of the diode. In theory that can be fixed if I add a negative rail to V- of OA2. But in practice this is unfeasible.

Draft 2

So I have this new draft, shown here just the part to the right of OA2:

simulate this circuit

Problem

The schematic in Draft 2 is capable of pulling the pot readout hard to 0V, but I fear the feedback loop is too complicated, too high gain, and the output is going to oscillate a lot.

I've intentionally left the ?? box, because I think that's where some oscillation/stabilization components should be added (e.g. 220k||1µF to ground). The good news is that the input is fairly low-bandwidth, say 10 Hz (how fast can you turn a pot?) and it's okay if the output has some defects/overshoots, since the motor has a lot of inertia. I just don't want it to oscillate all the time.

Problem

So: how to stabilize this feedback loop and prevent any oscillations?

EDIT

Based on suggestions in comments, I've updated Draft 2 to include an integrator around OA2:

simulate this circuit

If I'm understanding the theory correctly, OA2's feedback loop is now bandwidth-limited to around 50 Hz, with -3dB corner frequency around 5Hz. Will these additions suffice?

EDIT #2

As suggested by @GlennW9IQ, I presented the option that the limit value modulates the input, i.e. you can still use the full range of the pot, however your output range is rescaled according to the limit. See the updated formulas for Vout.

EDIT #3

Additional circuit/system details:

My device has a 3.3V power rail, hence the need for resistive dividers, opamp buffers, etc.
I don't have a 5V rail handy (I don't want to use the one from the ESC-to-pot cable).
The Vlimit signal is generated by a 8-bit DAC and its Vref can be either 3.3V or 2.048V.


texts:
I am using MCP3202 which does not have Vref as independent input.  The datasheet states that the current consumption is:

550 μA max. active current at 5V

Can I use a voltage reference (Series) like LT1460 to power it?

LT1460 can provide upto 20mA as stated in the datasheet.

The reference will supply up to 20mA with excellent line regulation characteristics

Datasheets:

LT1460

MCP3202 ADC


texts: How to regulate PWM to control a boost converter

texts:
I am creating a simple boost converter following the classic circuit diagram just for learning purpose.

The switch is a power transistor controlled by PWM  output of an Arduino (with additional necessary components). I want to implement a feedback mechanism to control or regulate the output voltage. I am a novice, but I know how to use a voltage divider to read the output voltage as an analog input to Arduino. What I am not very sure is - what to increase or decrease based on the input. For example if I need to increase the output voltage to maintain desired output voltage level, should I

Just increase the duty cycle and keep the frequency constant?
Increase duty cycle, and decrease frequency?

I want to achieve higher 'On' time on the switch, but what is the right way to do it?

If only toggling duty cycle is the answer, how does the frequency impact the output parameters? Does it also allow controlling the output voltage (but not the right way)? Or does it determine how much current I allow the output load to draw? Or something else? Please help.


texts: Current flowing in a short circuit with a voltage source

texts:
I want to calculate the current flowing in the node A of the following circuit:

simulate this circuit – Schematic created using CircuitLab

This can be approached in several ways.

The tension in a short circuit is 0 but what about the current ? By Ohm's law \$I = {V \over R} \$ if R approach 0 and \$V > 0\$ then I approach infinity. If \$V = 0\$ as in a short circuit then this lead to \${0\over 0}\$. Both forms has no meaning in mathematics and are undefined.
From the parallel resistors formuala, a resistor in parallel with a short circuit is equivalent to a short circuit. So if the entire circuit is equivalent to a shorted voltage source. The voltage provided by the source is \$V > 0\$ but in a short circuit \$V = 0\$. So again an undefined rational number.
By KCL the sum of the currents in node B must be 0. Maybe we can consider V1 and R1 in series if the short circuit is ignored. If that's the case the sum of the currents is something like \$I - I + I_s = 0 \Rightarrow I_s = 0 \$. Is it a valid reasoning ?

How can I solve this problem ?


texts: Simple Circuit: 2 LEDs in Parallel with solar cell

texts:
I am planning on making a circuit similar to this:

simulate this circuit – Schematic created using CircuitLab

Do I need a current limiting resistor to drive the LEDs if the solar cell is only providing 3v? Thank you so much for your help!


texts: State machines and control signals in a simple CPU

texts:
Having built the CPU specified in "The Elements of Computing Systems", I thought I'd try to design a simple 8-bit CPU myself as a fun challenge, with a view to implementing it on an FPGA. However, the book above makes several concessions, and left me with a few questions regarding "real" CPU design.

Say I have twelve different state machines (each for a different instruction) that, in some state, need to manipulate a 2-bit register select line on my CPU to get data into the correct register. How should each of those FSMs physically connect to those control lines? I thought of simply using a multiplexer, but then the question becomes, how do I properly feed the output selection lines on that MUX to control which input becomes the output? I understand well how a MUX works in a simple scenario, but the interconnections become difficult to understand once you throw in a bunch of state machines.

I've read Finite State Machines for Simple CPUs  - which does a good job of discussing the role of state machines and their basic operation in a CPU, but doesn't touch on the physical implementation.

In summary, I can construct FSMs, an ALU and so on, but I'm confused as to how the FSMs needed to affect the instructions physically connect to the control lines that actually instruct the ALU/registers/etc.


texts:
I have the task of designing a ring counter in verilog using shift operator. Here is the code so far along with test bench :

module ring (

input wire [3:0] data,
input wire clk,
input wire rst,
input wire load,
output reg [3:0] q
) ;

/*When the load pin is High, the data is loaded in the counter on clock transition.
* Otherwise the data is shifted  upon each clock.
* Last output is fed back to the first input.
*/

initial     q = 4'b1010 ;

reg tmp = 1'b0 ;

always @ (posedge clk, posedge rst)
begin
if(rst)
    begin
    q <= 4'b0000 ;
    end
else if(load)
    begin
    q[3] <= data[3] ;
    q[2] <= data[2] ;
    q[1] <= data[1] ;
    q[0] <= data[0] ;
    end

else
    begin
    tmp = q[0] ;
    q = q >> 1 ;
    q[3] = tmp ;
    end
end
endmodule

Test bench

`timescale 1 ns / 1 ns

module ringTest ;

//Signals
reg [3:0] data = 4'b1010 ;
wire [3:0] q = 4'b0000 ;
reg clk = 1'b0 ;
reg rst = 1'b0 ;
reg load = 1'b0 ;

//Instantiate uut
ring uut (  .data(data),
    .q(q),
    .clk(clk),
    .rst(rst),
    .load(load)
);

always  #10 clk = ~clk ;

/*Load data every 100 s
always
begin
#95 load = 1'b1 ;
#5 load = 1'b0 ;
end
*/
//Data to be loaded
always
begin
if ( data == 4'b1111) data <= 4'b0000 ;
else    begin
    # 50 data <= data + 4'b0001 ;
    end
end
endmodule

Note : I have temporarily disabled load functionality bcoz the Counter wasnt working. So instead I chose to shift the data with an initial value, which also did not work. The output is always X.

Where am I going wrong ?

Thank you.


texts: How to slow 12 VDC motor for power windows in a car?

texts: I installed power window motors in a classic car and they run way too fast I cannot change the gearing is it possible to reduce the power to slow down the motors?


texts: Bad idea? Powering uC from two separate supplies?

texts:
Okay, a little background: I am designing a micro controller daughter board (uCDB) that is nominally powered at 3.3V by a voltage regulator on a mother board (MB). Also I will have a programmer board (PB) that I can plug directly into the uCDB. As an alternative to powering the uCDB from the MB, I could instead draw power from the PB at 3.5V. This would be very convenient for instances where I wanted to power and program the uCDM even when it was not plugged into the MB. What happens if I try to do this and the uCDB is already powered by the MB? Is it a problem?

An obvious fix would be to put in a jumper that selects what voltage source to use, but requires more thought from the user each time he/she hooks it up; "Okay, what state am I in so I don't burn things up?" Any thoughts on how to allow both voltage sources to be on without burning things up and without mechanical switches/jumpers. Perhaps it is okay to just connect the two lines together either directly or through a resistor or something? Maybe the jumper is the best solution? I attached an image that hopefully summarizes my problem.


texts: Is the frequency cut-off the same for these two AC coupled circuit?

texts:
I have drawn two circuits that I believe behave similar. Do they both have the same cut-off frequency? Is there any pro/cons of the two circuits, except the one is inverting and the other is not?

Schematic 1 (R = Rf):

simulate this circuit – Schematic created using CircuitLab

Schematic 2:

simulate this circuit


texts: Ability of a 100km power transmission line to radiate 50Hz EM waves?

texts:
This is about confusion of relating antenna radiation theory to power lines. Assuming a straight 100km or even longer possible power transmisson line with 50Hz frequency. What can be said about the ability of 50Hz electromagnetic wave propagation to the space?
I found this similar question but didnt find an answer.

I have read part of an answer to a previous question that it wont act as a dipole antenna but rather a transmission line, and the fields will cancel eachother. But I didnt really get what is meant and what is the limitation here. Is that because for radiation to occur the ends of the transmssion lines must be open? An illustrative answer appreciated.

Having asked that I also sometimes read that power lines acting like an antenna when it comes to EMC and radiated noise. So the topic of the power lines radiating “waves” is blur to me. Or when people talk about radiated interference do they also include the fields?


texts:
My project is to extract a gate level netlist from layout, I am going write a parser for GDSII file format.

However, I have trouble in relating the record information represented in the GDSII format specification to the topology of the whole design or even a single gate.

Here is a very useful SPEC of GDSII file format:
http://www.rulabinsky.com/cavd/text/chapc.html

I can get the position of polygon, wire, and cell, however I have no idea how to detect a MOSFET, which can be used to determine a corresponding logic gate.


texts: What is DAP IDCODE for the CPU Motorola 68hc11?

texts:
Does anyone know any of the following info for the CPU Motorola 68hc11?

DAP IDCODE
BYPASS COMMAND
DAP ABORT Command


texts:
Will ignition coil internal carbon tracking/damage be evident through conventional ignition coil tests?

eg multimeter, 12v battery arcing


texts: Detecting if one voltage is bigger than another without an operation amplifier (OP-AMP)

texts: I can't get my hands on an OP-AMP chip right now so I'm wondering if there's any way to detect if one voltage is greater than another voltage without the use of an OP-AMP.  I've heard differential amplifiers are a route to go but it seems impossible to effectively get a digital output out of those.


texts: Can you lower 12v supply voltage only through series resistor to power an Arduino of 5V?

texts:
The more i learn about electronics the more questions i get XD
Today i learned that i could use a 3v led(20mA) in a 12V power supply by just adding 10k resistor... Which if i understand correctly makes the led power at 3V somehow, cool!
So if we just put aside all voltage regulators(don't have any, but do have alot of resistors :D)... What if i want to power an Arduino board(esp32 specifically) that normally demands 5V and can draw up to 150mA.
So if my calculations are correct(R=V/I -> 80=12/0.150) then this would mean that if i had an 80 ohm resistor in series with the Esp32, it would convert 12V power supply into 5V into the board and nothing would get fried??
The main question for asking this is simply because it sounds a little bit too good to be true XD. But if it is true which would be awesome! The board has a max current draw of 150mA when doing heavy tasks, so when it goes into normal tasks it drops to 40mA current draw. Is this a concern with my supplied 150mA? Does the voltage then maybe starts dropping/rising?
Thanks before hand!


texts:
I know this might sound stupid but it has me stumped. I am trying to calculate the average AC power input required for a few electrical devices which will be connected to a generator.

The issue I'm having is:

AC Input - 100 ~ 240V @ 2.5A - So the maximum power draw is: 240 x 2.5 = 600W
DC output - 19.5V @ 6.7A - So the maximum power draw is: 19.5 x 6.7 = 130W

Even if you take into account the power loss (standard is 80% efficiency) - What am I missing here?

The power input does not come close to the power output?


texts: I know it has small phase margin.. but why is it oscillating not at rails?

texts:
I came across an issue at my workplace with the following circuit. I did a OL response and saw that the gain margin is 21 db and the phase margin is 14 deg. Clearly not so good. Note that the 680nF cap is a populated capacitor on a board!!

I measured the test point (TP) with a scope and saw a small oscillation of 50mV @ 42khz. I thought this was interesting because the last few times I saw an unstable circuit they oscillated rail to rail. The oscillation I'm seeing doesn't appear to be from instability - I think it is from a power up charge on the cap and the feedback of the amp is trying to drive it to the correct voltage, causing a small oscillation when it overshoots. When the network is disturbed (a colleague touches the 1.3k resistor lead) it stops oscillating. A power cycle will sometimes cause it to oscillate again. Anyone have a better explanation or reading material I can bush up on?

My inclination is to depopulate the cap from the BOM. But I would like to try to understand the original designer's intent. I tried searching online for circumstances why you would try to put extra capacitance on an output of an op-amp circuit. I find a lot of information about remedies and negation techniques. Does anyone have any interesting stories or reasons where they added a load cap to an op-amp output?

UPDATE

On power up this is kicked into an oscillation that settles around 400 mV pk-pk. Clearly acts unstable-no surprise with the given phase margin. I'm just not clear on the mechanics that dictate how it settles at 400 mV.


texts: Mono jack output to stereo headphones : how to send the mono signal to both sides?

texts:
I have a 3.5mm jack mono output. I'm plugging standard stereo headphones into this jack, and it plays only on one side. I want the sound to come out on both sides in the headphones (same signal, but in both ears).

How can I cut and wire so that the mono signal goes into both speakers ?

I know there are some adapters on Internet that should do the job, but it's not an option anymore since I have to only 1½ day to finish this…


texts:
I am trying to implement the SPI communication on TM4C123.
I have 1 board and try to send data from SSI1(master) to SSI0(slave), but I observe that the received value is always shifted to the left by 1 bit!!
for example, I send 0x01 on the master and receive 0x02 on the slave, and so on.
the SPI settings I used are:

clocking of 8 MHz
CPOL and CPH are zeros on both SPI modules
8 bit for the data field

Can anyone suggest a solution ??
EDIT: Here is the code
void SSI0_Init(void) ;

void SSI1_Init(void) ;

int main(){
    SSI1_Init();
    SSI0_Init();
    InitConsole() ;

    while(1){
    // set ss low
    GPIO_PORTD_DATA_R &= ~0x40 ;            // ss low
    while ((SSI1_SR_R & 0x02) == 0 ){}      //wait till fifo not full
    SSI1_DR_R = 0x01 ;                      // send char a
    while (SSI1_SR_R & 0x10){}              // wait for TX complete
    GPIO_PORTD_DATA_R |= 0x40 ;             // ss high

    uint8_t data ;
    while ((SSI0_SR_R & 0x04) == 0){}       // wait for not empty fifo flag
    data = SSI0_DR_R ;                      // data reading

    // set ss low
    GPIO_PORTD_DATA_R &= ~0x40 ;            // ss low
    while ((SSI1_SR_R & 0x02) == 0 ){}      //wait till fifo not full
    SSI1_DR_R = 0x02 ;                      // send char a
    while (SSI1_SR_R & 0x10){}              // wait for TX complete
    GPIO_PORTD_DATA_R |= 0x40 ;             // ss high

    while ((SSI0_SR_R & 0x04) == 0){}       // wait for not empty fifo flag
    data = SSI0_DR_R ;                      // data reading

    // set ss low
    GPIO_PORTD_DATA_R &= ~0x40 ;            // ss low
    while ((SSI1_SR_R & 0x02) == 0 ){}      //wait till fifo not full
    SSI1_DR_R = 0x04 ;                      // send char a
    while (SSI1_SR_R & 0x10){}              // wait for TX complete
    GPIO_PORTD_DATA_R |= 0x40 ;             // ss high

    while ((SSI0_SR_R & 0x04) == 0){}       // wait for not empty fifo flag
    data = SSI0_DR_R ;                      // data reading

    int dummy = data ;

    }
}

void SSI0_Init(void){

    // settings for TX, RX, SS, CLK in GPIO PORTA
    SYSCTL_RCGCGPIO_R |= 0x01 ;     // clock on PORTA
    SYSCTL_RCGCSSI_R |= 0x01 ;      // clock on SSI0 module
    GPIO_PORTA_AFSEL_R |= 0x1c ;    // alt. function for PORTA 2, 3, 4, 5
    GPIO_PORTA_PCTL_R &= ~0x000fff00 ;
    GPIO_PORTA_PCTL_R |= 0x00022200;
    GPIO_PORTA_DEN_R |= 0x1c ;      // digital enable

    // settings of SSI0 module
    SSI0_CR1_R = 0 ;                // disable during configuration
    SSI0_CC_R = 0 ;                 // system clock
    //SSI0_CPSR_R = 2 ;               // prescaler div by 2
    SSI0_CR0_R = 0x07 ;             // 8MHZ, SPI mode, 8 bit frame, 2nd edge capture
    SSI0_CR1_R |= 0x04 ;            // set as a slave
    SSI0_CR1_R |= 0x02 ;            // enable
}

void SSI1_Init(void){

    // settings for TX, RX, SS, CLK in GPIO PORTA

    SYSCTL_RCGCGPIO_R |= 0x08 ;     // clock on PORTD
    SYSCTL_RCGCSSI_R |= 0x02 ;      // clock on SSI1 module
    GPIO_PORTD_AFSEL_R |= 0x09 ;    // alt. function for PORTD 0,3
    GPIO_PORTD_PCTL_R &= ~0x0f00f ;
    GPIO_PORTD_PCTL_R |= 0x02002;
    GPIO_PORTD_DEN_R |= 0x09 ;      // digital enable

    // settings for PD6 as SS signal
    GPIO_PORTD_DIR_R |= 0x40 ;      // PD6 output
    GPIO_PORTD_DEN_R |= 0x40 ;      // digital enable PD6
    GPIO_PORTD_DATA_R |= 0x40 ;     // keep SS idle high

    // settings of SSI1 module
    SSI1_CR1_R = 0 ;                // disable during configuration
    SSI1_CC_R = 0 ;                 // system clock
    SSI1_CPSR_R = 2 ;               // prescaler div by 2
    SSI1_CR0_R |= 0x07 ;            // 8MHZ, SPI mode, 8 bit frame
    SSI1_CR1_R = 0x00 ;             // set as a master
    SSI1_CR1_R |= 0x02 ;            // enable
}


texts: What are the max. overmold dimensions for USB-C plugs?

texts:
In contrast to earlier USB specs, the USB-C specification doesn't seem to define a maximum width and height of the overmold part of the plug (according to figure 3.3, there is just a length defined).

1) What is the idea behind not even giving a recommendation for this?

2) If I am to design a device with several USB-C receptables, what spacing should I use (horizontally and vertically) to make sure, that 95% of common plugs will fit in next to each other?

And yes, I did notice, that there are dimensions given for screwable USB-C plugs in this sepc, but those are obviously not relevant for normal plugs.


texts: I understand that for MIPS-32, the first 4 bits of the address to jump to are taken from the first 4 bits of the address of j instruction, which means that we have a boundary of 2^28 bits around the address of the j instruction that we can jump to. Online it says this boundary is 256MB but 2^28 bits is 32MB and not 256MB. Can anyone explain why it is 256MB?


texts: Are switched jacks ever used for in-system-programming connections? (If not, why not?)

texts:
It seems like a switched jack would be a straightforward way to make pins do "double duty" in a uC-based application. That is, the "normally closed" connections of the jack could connect the programming-related pins to the application circuit, but when the "programming cable" was connected, you wouldn't have to worry about interference from or damage to the application.

Is this done? If not, is it b/c switched jacks are just way too expensive for this use? Is the wiring just too long and noise-sensitive? Other reasons?


texts: Find transfer function and conditions to stability

texts:
I have this circuit

in which I need to find the transfer funcion and the stability conditions. I first got confused because I only say the transfer function as Vo/Vi, not as Il/Vi as asked in the question, but I tried to do anyway following the same steps to find the transfer function of a simple non-inverter op amp, but I didn't find anything that made much sense, nor with Vo/Vi or Il/Vi.
How can I find the transfer function for this circuit and the stability conditions that can be represented by which equations must be satisfied to the circuit be stable.
It is also said, as a tip, that to find the stability conditions, the denominator from the transfer function must have all the real parts of its roots negative. And it gives as a tip "look the function poles". But I can't do any of this analysis to the stability as I'm having problems fiding the transfer function.

wb is the cut-off frequency in open mesh.


texts:
I'm new to electronics I have need some help with a power supply design I am designing.

I currently have a 0-30 volt, 2 amp multi tap transformer that I am using for the above mentioned power supply but what I am wanting to know whether is I can set it up so that I can tap more than one voltage at a time ( not simultaneously but to be able to flick between one and another )  and if so would I have to set a separate rectifier for each circuit for a given voltage.

Thank you in Advance.


texts: Toggle circuit with 1 x NAND, OR, and NOT gates?

texts:
I am sure there is a more specific name than "toggle circuit".

I am simplifying a schematic. To do so I have replaced a larger circuit with one much smaller, but in doing so, I have lost the 74*74 flip-flop used in a "toggle circuit" as seen below:

I have three spare gates I can use to attempt to re-implement something similar.

3-input NAND
2-input OR
inverter

Diodes, NPN transistors, and passives are allowed too.

Any idea on a circuit that would operate similarly? (Toggle an output whenever 'A' goes high).

As I understand the existing circuit correctly, it acts as a 1/2 clock divider.

I imagine I could simply use two inverters to perform the same function as the flip-flop circuit, except it would switch twice as fast, as it won't be divided by two anymore.


texts: What transistor should I use? And how do I determine that?

texts:
Im new to designing a circuits. I've got my basic design done. I'm now trying to get to specific parts but I don't know which ones to buy. mainly because I don't know how to determine what I need. I'm hoping to use an NPN transistor as a switch.

simulate this circuit – Schematic created using CircuitLab

What part should I buy and why. Could you take me through the process of determining the part?


texts:
Apologies if this is the wrong Stack. I suspect this is a bit of a lowest-common-denominator question. I've got a cheap little Christmas tree covered in blue festive lights that takes 3 size-C batteries. I only had 2 size-C batteries.

Knowing literally nothing of electronics (asides "don't stick a fork into a power socket, it'll probably hurt"), I decided to ram an AA in the third slot. I observed two outcomes:

The tree lit up
I didn't die (probably)

So, is it ok to mix batteries like this? And if not, why not?


texts: Arduino Sketch Compile Error: Trying to Concatenate Float with String

texts:
I am not sure if I should be posting this here or on Stackoverflow, but since this audience likely has the most experience with Arduino, I figured this would be the best place.

I just bought an Ethernet shield, and as a first project with it, I'm trying to publish a TMP36 temperature reading to Pachube. While Pachube accepts multiple formats for your data, I'm trying to post this stuff in JSON, because I like JSON. However, I'm running into trouble getting my temperature value, which is a float, into the JSON string. I'm a Python/PHP developer, and relatively new to C, so I've googled a lot but haven't discovered the right way to do this yet. Here is my code:

float temperature = 85.4; // Or whatever
String jsonData = sprintf("{'version':'1.0.0', 'datastreams':[{'id':'%s', 'current_value':'%f'}]}\n", datastream1, temperature);

I keep getting the following error from the Arduino IDE (version 1.0): "Cannot convert 'String' to 'const char' for argument '2' to 'int sprintf(char, const char*, ...)'"

I found out I am calling sprintf() with the wrong number of arguments/arguments in the wrong order, since it does not return the formatted string. However, I'm not even sure sprintf() is the best function to use to accomplish the goal of getting the sensor's floating point value into a string. Is there a better way to do this


texts:
I am trying to understand FM transmitter circuit working basically on how a signal is imposed on to the carrier signal.
I would like to get an acknowledgement on whether my understanding is correct or not. Next, I have got a few questions.

Here is my circuit -

My understanding -

1) The L1 VC1 is basically a tank circuit which is creating a high frequency signal because of storing and releasing of the energy stored inside L1 or VC1 and this process is repeating and changes the polarity each type. Thus, we get a high frequency sinusoidal signal.

2) This L1C1 is connected to a battery voltage - 9V. Thus, it will not have any losses.

3) The amount of potential difference on the antenna point depends on how much transistor is conducting. So, basically, transistor will conduct less if the input signal on the base is less. It will be like a short circuit when the input signal on the base is maximum. Thus, the output collector voltage is changing based on the input signal. This is happening because transistor is conducting differently based on the input signal magnitude.

Here is my diagram on this understanding.

Question -
 Since Antenna is nothing but a wire with some resistance. But this wire isn't connected to anything. Thus, it is like an open circuit. If it is an open circuit then why does the signal passes to the antenna?


texts: Simple ESP32 driver for solenoid valve rated 24V/2A?

texts:
( As an extension to the question asked here ESP32 driving Solenoid requiring 2A/24V DC with IRF520? , I am adding this question with the idea to help more peoples with the results, since seems like it's widely interesting question with variety of wrong answers on the google )
So - I have ESP32, which must drive solenoid valve rated on 24V/2A ( 1" 1/4' (Ф32) pipe valve ).
The issues is that it turned on that the most showing on google transistor - IRF520 can NOT drive it directly, and there is a need of complex circuit, which is some cases is not suitable for beginners or peoples which does not complicate their circuits too much.
The whole idea is the driver to work in ON/OFF mode (not PWM).

What could be a reliable, simple and widely accessible components circuit which could drive such solenoid valves?


texts: Confusion in max drain current and on-state drain current of 2N7000 E-MOSFET

texts:
Below is the datasheet of 2n7000 series of N-channel E-MOSFET. As you can see on the marked box:

Max-Drain Current(continuous) :200mA

On-state Drain Current: 600mA (typical)

Why is the max rating less than the On-state Drain Current?


texts:
A car uses a car battery and an alternator powered by the engine.  But where does the electrical energy for fighter aircraft comes from to maintain the onboard systems?
And which voltage and frequency do they use?

EDIT:
and how does a fighter aircraft alternator works on a jet engine, what causes the spin at the alternator?


texts:
I was building a bootstrap based gate driver for BLDC motor control application.From this application note (https://www.infineon.com/dgdl/Infineon-HV_Floating_MOS_Gate_Drivers-ApplicationNotes-v01_00-EN.pdf?fileId=5546d4626c1f3dc3016c47de609d140a) I came to know that charge pump is required for continuous turning on of high side mosfet.They have demonstrated using a circuit also.But I need some clarity in this regard.
Here it is stated the timer will output a 7.5kHz square wave with 15V amplitude.How is this 7.5kHz designed.?Does this value have any significance.I need to switch my device at 100kHz.Also my Mosfet require a gate voltage of 6V only.So should i use 6V zener to achieve the required amplitude.


texts: I am trying to figure out how to read the nominal value of this capacitor.  When I use a meter it reads 3.4nF.  I have several caps that have the format of .00X where X is an integer.  Not sure how that decimal point works in there.


texts: Amplify µC output from 5V to 12V for external IC that needs 12V to control without inverting

texts:
Does the following circuit boost the power of an arduino output (Arduino Mega 2560) from the 5V of the Pin to the 12V that I need to control a Wireless Transmitter Module without Inverting it?

Can I use 1kOhm for R3? I have no 2k2 laying around.

TX_DATA_5V is the Output of the µC, TX_DATA_12V will be connected with TX Module.


texts: Reversing Motor with 2 push button switches

texts: i wanted to make a schematic to reverse the motor direction with 2 push buttons, and i failed every time to make a schematic like this, when someone can help me would it be helpful thanks.


texts: Accessing all the data and to store in wire using BLOCK RAM GENERATOR in Vivado using verilog

texts:
I've created a block ram generator(single port ROM) in vivado using a coe file in verilog. I'm able to read the values one at time using continuous statement(able to instantiate rom block once a clock pulse). Here is my snippet:

module coedata(clk,rst,a);
input clk,rst;
output  [31:0]a;
wire[12:0]addra,out;
wire [31:0]douta ;
count c1(clk,rst,out); // just gives count in 'out' to access address(addra)
assign addra=out;
blk_mem_gen_0 your_instance_name (
  .clka(clk),    // input wire clka
  .addra(addra),  // input wire [12 : 0] addra
  .douta(douta)  // output wire [31 : 0] douta
);
assign a=douta;
endmodule

This is ok. I can read value through instantiating once a clock. But I want to store all these values into 2D wire such as [31:0] a[0:100].I want all the values to be available in one clock pulse.(Just assume we have created a sufficient ROM block)

module coedata(clk,rst);
input clk,rst;
reg  [31:0]a[0:99];
wire[12:0]addra,out;
wire [31:0]douta ;
count c1(clk,rst,out,i); // just gives count in 'out-binary' to access,'i-integer' address(addra)
assign addra=out;
blk_mem_gen_0 your_instance_name (
  .clka(clk),    // input wire clka
  .addra(addra),  // input wire [12 : 0] addra
  .douta(douta)  // output wire [31 : 0] douta
);
assign a[i]=douta;
endmodule

It is saying that 'i' is not a constant.

Thanks in advance.


texts: Eagle 'length' of thermals to ground plane

texts: I'm using Eagle pcb editor (Ver 4.15) The 'spokes' in the thermal pads to the ground plane have gotten too short.  I'm not sure how this happened.  The Eagle manual says something about changing the thermal isolate parameter in the DRC supply tab.  I've futzed with this but nothing changes.  Do I need to redraw the entire polygon with the new parameter?  (I can change the width of the 'spoke' with the polygon width command.)


texts: Power supply with three pins on the output, why?

texts:
I opened up the power supply to a HP printer and I see that the output has three pins. I measured voltage on one pin to ground and it shows 8.3V.
The adapter says: Output 24V @ 1A. Is this a dual rail power supply?
Why don't I don't see 24V on the output?
The power supply is fine as it powers the printer.
Here is the photo:


texts: Passive (or very low power sensor) sensor to wirelessly receive wake signal

texts:
Context. I am using an ESP32 and a small circuit to control an electronic lock on my one of my exterior doors. It is powered by batteries. It has a door magnet sensor to detect when the door is open or closed and this launches an interrupt which wakes the ESP32 and allows it to transmit information (have tried both push and pull, e.g. server / client, both can be made to work). I want to have another interrupt that I can send wirelessly from something which is plugged into power.

False positives (waking the device when it doesn't need to be) are acceptable. False negatives are not so hot but tolerable if something like repeating the signal a few times results in it working.

Things I have considered. Buying an ultra low power bluetooth solution and using that microcontroller to wake the esp32. I dislike this one the most because it adds the most cost and complexity. I have to program something like the QN908x.

Finding out if there is a way to do this with RF without all the overhead of bluetooth and complicated protocols.

Use something like an IR emitter and receiver.

Provide power directly to the IC and control the battery powered circuit which controls the motor using something like Resonant Inductive Coupling or even LEDs (I can place these things withen 2-3cm of each other). This latter option being the most interesting and relevant to this forum but also might be the least feasible. The circuit would need to communicate state back and forth. I could use something like a very simple FPGA or some low power IC that can store 4 different possible states. Opening, Closing, Straining and doing nothing.

Before I start designing I wonder if anyone has solved this problem. Namely trying to make something that can communicate wirelessly and consumes less than 5ma. It would not have to check for transmissions more than once every 2-3 seconds. Some latency is ok.


texts: Why is an oscilloscope's Attenuation switch placed on the probe?

texts: I'm wondering why an oscilloscope's Attenuation switch is placed on the probe not on the oscilloscope's body (like the AC/DC Coupling switch that's placed on the scope body not on the probe)?


texts: How do I perform division of two numbers in PIC16F877A in assembly language?

texts:
I'm currently using MPLABX IDE to develop for a PIC16F877A microcontroller. I want to divide two numbers and find out the quotient (let the two numbers be 10 and 4) and store in a register.
I was thinking of a loop which increments the value of register by 1 every time 4 goes in 10 until it becomes zero or indivisible (as in integer).
I'm not able to figure out a way to make the controller recognize the end of division when either reminder is zero, negative or less than divisor.
I would appreciate any suggestions for accomplishing this using Assembly language.


texts: Is it necessary to provide surge suppressor to every control relay?

texts:
We have a motor control centre installed in garage for a commercial outlet.

The MCC has a SMC-Flex ( Low voltage soft starter).

The control relays (700 HA33) are connected to the SMC control terminals. Most of the time the control relays connected to the SMC control terminals are provided with the surge suppressors.

Is it necessary to provide the suppressors to all control relays within the circuit?

Is it essential to provide them to the timer relays?  Please note that I am referring to the control circuit. All the components connected are in the control circuit.


texts: Understanding optocoupler performance with collecor or emitter resistors

texts:
When using an optocoupler, is there a difference performance'wise whether using a collector or an emitter resistor?

When using a normal transistor the base to emitter voltage gain is approximately 1, whereas base to collector gain is much larger. With an optocoupler however, base is not (necessarily) at a definded absolute voltage. For this question I am disregarding optocouplers that have the base available on one of the pins, or at least having an external bias.

So apart from inverting properties, are these identical (R1, Q1 vs. R2, Q2) or is there a difference (eg. in frequency response [parasitic capacity], different rise/fall times, gain, ...). And when using both collector and emitter resistors (R3C, R3E, Q3), will the signal be symmetric or should I account for base current like in a regular BJT circuit (as in \$\frac{\beta}{\beta+1} = \frac{I_C}{I_E}\$). In other words, where does the base current go in this closed circuit?

simulate this circuit – Schematic created using CircuitLab


texts: Which is better - components on both sides or components on one side of the PCB?

texts:
I am working on a PCB design. 50k PCBs will be produced.

SMD components: 100

Through-hole components: 25

I need to minimize PCB size. There are no high-speed signals or sensitive signals in the design.

I have two options:

Components on single-side PCB with multilayer (4 or higher) layout
Components on both (double side) sides of PCB with 2 layer layout

I need to clarify which costs less in production.


texts:
I used to install a lot of in-car UHF radios & hands-free cell phone kits. I mostly worked on trucks & commercial utility vehicles fitted with bull bars, upon which I would mount a big, bulky, high-gain antenna. Alternatively, a bracket could be mounted directly to the chassis under the bonnet (which often meant cutting/drilling). The coaxial cable would run from the new device inside the cab, through the engine-bay, and out to the base of the antenna.

But every now and then I'd get some fancy executive with a shiny new luxury sedan, and I'd use a relatively discrete glass-mount antenna. The cable runs under the dash and up the pillar (under the upholstery or plastic trim) on the passenger side, and pops out near the top of the windscreen. The cable screws into a little black box/panel, one side of which adheres directly to the inside surface of the glass. At the base of the actual antenna mast is a similar adhesive panel that mounts on the exterior surface of the glass, directly on top of the first.

I never fully understood how or why it worked, but essentially the signal was able to flow right through the glass.
My question is: Can this same technique be adopted for 2.4GHz and/or 5GHz WiFi antennas?


texts:
I want to builf a small electrical panel to control the navigation lights on my sailboat.  Depending on if you are at anchor, sailing or motoring, different light configurations have to be used.
A sailboat is normally equipped with the following navigation lights:

One 360 degree - All around white light (usually at the top of the mast)
One stern white light (120 degree angle)
One bi-color RED/GREEN on the mast or at the bow (red post side 120 degrees, green 120 degrees starboard.)

I need to be able to switch between 3 different lights configurations:

At anchor: all around white light
Sailing: white stern light + red/gree
Motoring: white all around + red/green

I will have a dedicated switch on the electrical panel for each lighting configuration.  In order to avoid current conflicts between the various lights and switches, I was told I can use diodes to prevent flowbacks.  So, here is the circuit I have in mind. I am handy and have worked quite a bit on boats and general electric stuff but I have very limited knowledge of electronics circuits.
Typically on sailboats, we tried to waste the least power possible so, I hope diodes are not using much power or generate too much heat. I would appreciate any guidance and advice on whereas this makes sense and what type/model of diode I should use for this.


texts: Display Design - would combining OLED with a white source be more efficient?

texts:
To be clear, I'm not an electrical engineer, nor do I claim complete knowledge of how displays work.

However, I have done research into displays (televisions, computer monitors, AMOLED phone screens) out of curiosity, and wonder why OLED technology and a white source aren't used in complement.

A quick (and over-simplified) rundown: LCD displays use a backlight (commonly LED these days) and Red/Green/Blue color sources to display color. However, this approach is inefficient at displaying dark or black colors because the backlight has to be bright enough for the brightest color, and then cover up the parts that are darker, which is why even a black screen seems to glow. OLEDs self-illuminate, so they don't need a backlight and are generally much more efficient (and more color-correct), and better at displaying black. However, OLEDs can use significantly more power than their LCD counterparts when it comes to light and/or white backgrounds.

Would it be possible to add a white source (like an LED) to OLEDs to essentially combine the energy efficiency of both types? If so, why is (as far as I can tell) it not being done?


texts: What is the industrial equivalent of a dimmer switch for resistive heaters?

texts:
Question: What is the industrial, solid-state equivalent of a dimmer switch?

Background: I am building a PID box, and I want to limit the current draw on a 1.5 kW resistive heating element to simplify the controls. In the past, I have used a PWM controlled SSR, but this still requires the controls to be able to handle the full 12 A draw. Is there a component that does what I am describing? I don't need to be able to adjust it after it is set.

Goal: limit peak current draw.


texts:
So, now that I have a bench power supply (0-+/-25V at 0-1A, 0-6V at 0-5A) on my bench, I need a set of test leads for it.  Considering that I have had variable experiences with power supply test leads in the past, and that bench clutter is a major issue for me, I was planning on making my own up vs. buying premade leads.

Wire

For the wire, instead of using test lead/prod wire (whether PVC or silicone insulated), I was thinking of using UL AWM 2468 or equivalent "zip lead" that is more typically used for the output leads of DC wall adapters.  This has the advantages of keeping the number of leads and the amount of bench clutter down, while having reasonable properties (80°C temperature rating) and availability.  It's also available with pre-molded barrel plug ends, which is useful as it's difficult to homebrew proper strain relief for a barrel plug.

However, despite these upsides, I still have doubts as to whether this type of wire would be suitable under workbench-test-lead conditions; furthermore, the thickest I can get it in is 18AWG -- is this thick enough for a set of bench supply test leads, or should I be using thicker wire yet?

Connectors

Other than the barrel plug ends, I am going to be terminating these with header pins (for direct connection to breadboards) and stackable banana plugs (both on the other end of leads that connect to breadboards or PCBs, and in the banana-to-banana case).  This leads me to my other main line of inquiry: what is the best way to attach stackable banana plugs to test leads? I have my choices between:

Solder-attach (where the wire is put through a hole in the contact piece, soldered, and then folded back into the housing when the housing is fitted)
Setscrew-attach (where a clamping setscrew is used to "pin" the lead wire to the contact assembly in a back-wired arrangement), and
Spring-clamp-attached (where a pushbutton-operated spring-clamp replaces the setscrew for holding the wire to the contact assembly).

Which one of these would yield the best reliability under bench conditions?


texts: making battery charger for lead acid battery 6v

texts:
Hello so I was just given a 6v 4.5 Ah (4500mAh) sealed lead acid battery. I have never made a battery charger before but would like to make one now for this battery as it is for a robot I'm building. How would I go about charging one of these batteries, as I have never done this before. Please correct me on this if I'm wrong but to me it seems that you can charge a lead acid battery by just connecting it to a voltage supply equivalent to what its voltage would be if it was fully charged and wait till the amperage pulled approaches 0. also as a side question I have another lead acid battery with the same specs but I have not used it and when i checked its voltage it was 2.8v. is this battery dead or can it be recharged and brought back to its previous state?

edit: how would I find the maximum current they battery can take?

edit 2: in the batteries spec sheet it said: "“Float” or “Stand-By” Service: Hold battery across constant voltage source of
6.75 to 6.90 volts continuously. When held at this voltage, the battery will seek its own current level and maintain itself in a fully charged condition". does this need current limitation? If so what would the name of that variable be or how could I find it?

Edit 3: So the quote in edit 2 is taken from the specsheet, so following there instruction can I give the battery 6.90V and it will seek its current and it does NOT have to be limited or is there still a current limitation requirement?


texts: What is the purpose of the square vias with no solder mask on this board?

texts:
This board from an electronic combination lock contains a curious mix of two types of vias:

Small round ones with green solder mask over the top.
Larger square ones without green solder mask over the top.

What is the purpose of the square vias?

(full size image)


texts: Circuit interpretation with a short circuit

texts: In the following circuit, which has a short circuit between terminals a and b, I do not understand why the resistors are not all in series. For them to be in series the same current must flow through them and since no current flows between terminals a and b Kirchoff's current law implies that the current flowing through all three resistors is equal and is represented by i. Could someone explain why despite having the same current the three resistors are not in series?


texts: A decent library of component simulation, schematic and PCB layout?

texts:
I am truly a novice in PCB design, so I am new to all aspects of it. What I am having the most trouble with is actually picking suitable components. The trouble I am having is that I am not really able to use most of the components I find from Google or elsewhere.

To use a component on a board, I want to be able to stick it in some PCB design software and be able to use it in a schematic, place it on the PCB and simulate its behavior. However, this seems to be endlessly difficult. The problems I run in to are:

I can't find the part in any component library anywhere
I can't find a simulation (SPICE/IBIS) model for the part
I find a SPICE model, but it is for some different version of SPICE and doesn't work
I find the component in a library, and a simulation model, but it is an outdated component and not recommended for new designs
Everything else is fine, but I can't find the SMD version of the component

The end result is that when going over Farnell component listings, I am forced to pick components based on what I can simulate and find in some library, instead of picking the component that is most suitable for the design. This seems like it should not be so.

Is there any way to actually have a large library of components for which all of these things exist? The best I have come across so far Eagle with component libraries for every manufacturer separately from Farnell community site. But even that is severely lacking as I don't usually find the components I want from the manufacturer in the library - and obviously there are no simulation models for these. Eagle also has the nice DesignLink feature, but that doesn't seem to help me any in this case.

As an example: I am looking for a generic opto-coupler with transistor output, 4 pin SMD package and 100% or more CTR. I'd like to be able to compare a few options and not pick the one option that might be available for both my simulation software and my PCB design software.

Commercial solutions are okay.


texts: Stepper Motors : KG.CM Torque : Does it maintain the torque when connected to a rod?

texts:
I am currently building a machine for a school project.I have a pivot point and wish to use a stepper motor to turn the base at an angle. The base is carrying a load of approximately 10kg.

I was wondering whether a stepper motors rated torque (10kgf-cm) is still maintained if you were to use a 1cm in diameter threaded rod that is 30 cm long.

I have viewed other questions on this topic, and I understand that increasing the radius results in decrease of kilograms able to be moved . But there is no explanation of the effects a rod has on torque.

TLRD: Does a threaded screw, 1cm in diameter and 30cm long vertically, cause a reduction in the stepper motors max torque --> 10kgf-cm.