texts: Modelling Circuit from FSM using Verilog

texts:
I am trying to understand the concept of modeling a circuit from a FSM in Verilog.

I have tried to write down the procedure that I have used in the image below just to make sure that I did it right:

Based on the solution the circuit is as below:

The Verilog code I have developed is:-

//----------------------------------------
//module bit stream generator
//-----------------------------------------

module generator(
clk,
stream  //generated stream
);
output stream;
input clk;
reg c;
wire stream;
assign stream=c;

initial
begin
c=1'd0;
end

always@(posedge clk)
begin
    //c=!c;
    c = {$random} %2;
    //$display("a= %b",c);
end
endmodule

//----------------------------------------
//module D flip flip
//-----------------------------------------

module d(q_w,q0_w,d,c);
output q_w,q0_w;
input c,d;

//wire c;
reg q,q0;
wire q_w,q0_w;
assign q_w=q;
assign q0_w=q0;

    initial
       begin
           q=1'b0; q0=1'b1;
      end
    always @ (posedge c)
       begin
         q=d;
         q0= ~d;
       end
endmodule

//----------------------------------------
//module sequencedetector
//-----------------------------------------

module sequencedetector(
clk,
x,  //input bit stream
out //output from sequence detector
);

input x,clk;
output out;

wire x,y0,y_0,y1,y_1,g12,g32,g2d1,out;

d dff1(.q_w(y1),.q0_w(y_1),.d(g2d1),.c(clk));   //flip flop D1
d dff0(.q_w(y0),.q0_w(y_0),.d(x),.c(clk));  //Flip Flop D2

and gate1(g12,x,y0);
or gate2(g2d1,g12,g32);
and gate3(g32,y1,y0);
and gate4(out,x,y_0,y1);

endmodule

//----------------------------------------
//module sequencedetector testbench
//-----------------------------------------

module sequencedetector_tb;

reg clk;
wire out,x;

sequencedetector UUT(
.clk(clk),
.x(x),
.out(out));

generator UUTgen(
.clk(clk),
.stream(x));

initial begin
clk=1'b0;
//stream=1'b0;
//=1'b0;
end

initial
begin
    $dumpfile ("counter.vcd");
    $dumpvars(0);
end

always
    begin
    #20 clk=!clk;
    end

initial
    begin
    #20000 $finish;
    end
endmodule

But sadly the I the output is not as expected The circuit does not detect any seqience as the output is always LOW.
Am not able to upload the GTKwave snapshot in want of sufficient reputation.

Any help is highly appreciated

EDIT

Just figured out that in the code for the flip Flop the output(q) was not following the input(d) whenever the input bit changed for one cycle only, probably because the sampling was being done at same instance as shifts were happening(in the bit stream). This code was requiring the changed bits to sustain atleast 2 cycles to be followed by the flip flop output. Introduced a delay of 2 cycles in the flip flop code and the output is as expected.

always @ (posedge c)
           begin
            #2 q=d;
             q0= ~d;
           end

The problem now is what should I do if I need to implement the Verilog code on a an actual hardware. I mean what is the alternate of delay (#2) if i need to make a synthesizeble code (definitely not multitude of gates) but some standard hardware friendly verilog function, maybe.


texts: 1/4 wavelength case in transmission lines

texts:
I have studied that in transmission lines, if λ is the wavelength of the signal and L is the length of the conductor, then at L=λ/4 the transmission line act as an open circuit.

So if we are transmitting 1 GHz signal ( λ = 30cm ) through a conductor of length 7.5 cm, will there not be any output at the end?

Is this the reason why we use waveguides at microwave frequencies?


texts: connecting pam8403 and bluethooth module in series

texts:
I am new to this so I apologize in advance for any rookie mistakes.

I decided to make a portable Bluetooth speaker.

I have a pam8403 and a Bluetooth module:

Both of them require 5 V input.

Can I connect both of them in series and connect a 12 V battery to power them?

Is this possible?


texts:
I need to understand how 3-bit multipliers work and then I must design one. I've read through Wikipedia's binary multiplier but I just can't wrap my head around it. I don't understand where to start. Could you please explain to me what happens when two 3-bit numbers are run through a 3-bit multiplier? Maybe then I can reconstruct each step in a circuit on paper. Alternatively, could you outline the relevant sub-concepts I need to grasp?

In general, I'm thankful for any help in understanding 3-bit multipliers.

EDIT: Thank you to everyone who contributed to this Question. You all helped me understand the relevant concepts, and so I wish I could accept all answers as solutions.


texts: 12V LED dimmer burning out after several weeks of usage

texts:
We have changed the lighting in our room, but after several weeks the dimmer just puffs in smoke and stops working. This already happened twice.

Basic setup is like this -> 2 way switch goes to 220->12V transformer (meanwell 12V 5A) -> to dimmer that burns out (similar to https://www.amazon.co.uk/LED-Dimmer-12V-Controller-Brightness/dp/B01B0UP1SE/ref=sr_1_67?ie=UTF8&qid=1479382252&sr=8-67&keywords=dimmer+12v ) -> 6x Philips Lighting 6.5MR16 connected in parallel.

As total power of circuit is under 50W, and dimmer supports up to 96W when operating in 12V, this should not be the cause of burning out.

We are not using dimmers power off feature, as we are killing power with 2 way switch. Odd thing is that after we turn them back on, sometimes bright flash happens (if this might cause anything)

What would you suggest? Use a better dimmer or there are some parts of the lighting system missing that causes this behaviour?


texts: Shift registers - what happens at single clock pulse?

texts:
I think I just don't fully understand shift registers made from D-flip-flops as in http://en.wikipedia.org/wiki/Shift_register

Why does it shift only one bit per pulse? As I look at it it just seems to me that it should shift everything and rewrite with SI at the single pulse.

I think my problem of understanding this origins at D-flip-flop, somewhere I've read that it stores the value only on rising-edge, but the way it's implemented doesn't seem like it to me. It seems like it can store value at any time the clock is at 1 (even change multiple times during single clock pulse).


texts: Node Voltage Analysis with dependent voltage and current sources

texts:
simulate this circuit – Schematic created using CircuitLab

The question for the above circuit asks for the power developed by the 60 Volt power supply. The equations I've written to solve for this value are as follows:

At the super node consisting of V1/V3:
(V1-60)/100 + (V1-60)/10 + (V3-V2)/20 + V3/400 -0.625Va = 0
At node V2:
(V2-60)/5 - V2/200 + (V2-V3)/20 = 0
KVL around the loop consisting of V1, 175Iq and V3
V1 + 175Iq = V3

Conditional equations:
 Va = V2-60, Iq = V2/200

The correct answer is given as 1084 watts but so far no matter how I manipulate the above equations the best I can come up with is 1057 watts and that's by making some assumptions that don't agree at all with the polarities given in the schematic. Note: when I see an arrow pointing in the direction of current through a resistor, in this case Iq through R2, I treat it as a voltage drop with the arrow pointing in the direction of the drop...it that correct? (I'm basing all my calc's on conventional current flow.)

As a final note, this is a circuit question out of the 5th edition of 'Electric Circuits' by Nilsson and Riedel. I took a course some years ago (in 1998) that used this text book so I decided I'd see how much I've forgotten since then. Apparently it's quite a bit.


texts: So there are many topics on using a mosfet to generate a PWM signal, but what I am trying to do is to use a mosfet to act as a switch to open and close a channel that my PWM signal is travelling on. I attempted this and when i apply my PWM signal to S and open the gate, my output on D is an analog high signal. Insight on how to get a PWM signal to flow across SD would be greatly appreciated.


texts: USB connection new car stereo 5 wires to 4 (schematics included)

texts:
I am replacing the stock stereo in my 2015 Nissan Leaf S.  In the center console is a USB port which was connected to the head unit.  I'd like that port to continue to work with my new stereo.  The schematics for the existing unit has the following:

The bottom line represents the back of the stereo.  Here is the legend for those numbers where the letter under the number represents color of the wire (I don't know what shield means)

The new stereo doesn't have a schematic because the USB port is built into cable that plugs into the unit.  It has 4 wires, black, green, white, and red (ignore the yellow, it's for a mic).  Here it is:

My first guess is that I would ignore 57 and connect 53 to red, 54 to black, 55 to white, and 56 to green.  Is that right?  If not what do I do and in either case what is the signal shield?


texts: Buck converter efficiency Vs load current:

texts: Can somebody explain how does the efficiency of a buck converter increases with the increasing load current?


texts:
I am trying to tune this circuit, dimensioning the values of resistors Ra,Rb and the capacitor C... The circuit work in this way: a voltage Vin regulates the current flowing in the inductor, via the VCO block. The operational give a Vctrl to NE555 configured as astable oscillator that (adjusting the duty cycle) will impose the right current. This current could be red from the OP Amp through the feedback 2 ohm resistor.
 I ask you what is the quickest and fastest method to get this circuit work. I followed this procedure:
First i calculated the time constant of the inductor on the drain, with L/R formula. Then i chose a frequency far away the frequency of the pole, to get a "low pass effect" of the current in the inductor, about 100kHz. So, I supposed that the op amp is not rail to rail, and then I did a calculation to impose that with Vin = 1V the charge of the capacitor (from Vdd/3 to about 11V, the rail of the OP Amp) would last about 90% of the discharge time, then getting a current of 90% of the maximum current that can flow in the drain (a kind of 12V/22Ω). Then I tried with a different value of Vin (0.1V), and verified if the duty cycle would be reduced.

I know that it looks so confusing, so please i ask you how do you dimension this circuit.


texts: Regulate low quality battery charger output through solar charge controller

texts:
I have a remote P2P internet relay station that has had just had it's solar panel stolen. In order for me to go service it requires 400L of fuel in a speed boat; so I would like to put off going there until I have another reason to go towards town.
I got a friend to buy a battery charger in town and charge up the battery for me for, but the only battery charger that was available is constant voltage that is too high for the AGM batteries I'm using if it was left unattended to float.
I would like to hook up the charger to the PV input side of the solar charge controller so that it can regulate the charge profile.
However I have done a test with spare equipment I have here at the camp, and although the low quality generic charge controller is happy with 14.5 volts the charger outputs, the better quality MPPT unit I have at the remote site in question does seam not work the same way.  That is, it does not light up the "PV connected"  lamp, no amps flow, and there for no charging happens.
Any insight in to this and possible short term solutions would be much appreciated, I believe it is something to do with the low voltage and power point tracking?
I have considered a 19v laptop charger, or a 24v battery charge, but buying stuff that won't work, and the satellite phone calls it will take to do it is not Ideal......
For now my friend can charge it up for a few hours every now and a gain, but it is not an ideal solution.


texts: 24 bit adc to read +/-10V analog input signal

texts:
I need to read a sensor data which gives analog output(range is +10V to -10V) and convert it to digital form using 24 bit ADC and then store it to a memory card. I have some experience with PIC microcontroller and Arduino. Is it good enough to chose one of these or go to some other platforms  to minimise noise? please guide me what are the factors to be noted in chosing ADC, controller in the design for my application. I just doubt whether it is  possible or not to read at least 18 bit resolution with external ADC and arduino combo.

Specifications of sensor:

Frequency range DC ..... 3 kHz DC – 30 sec
Sensor noise < 0.006 nT √Hz @ 1Hz
Output sensitivity  0.143   mV/nT
Orthogonality error < 0.5°
Output voltage range ± 10V
Measuring range  ± 70,000 nT
Offset temperature coefficient ± 0.1 nT / °C
Offset error ± 5 nT
Supply voltage ±  12V to ±  15V stabilized and filtered
Supply current +26mA, -6mA (+1.4mA per 100μT)


texts: what are tuning dots and how to effectively use them

texts:
I've come across some template designs that have tuning dots included for RF matching. Unfortunately they are using a different dielectric than I am.

What are the basic principles of tuning dots (theoretical to purely mathematical would be great), and how do I then change their design to fit my own boards specifications?

NOTE- tuning dots are filled in the end design, this is merely how my importer displays them


texts: Absolute values of fourier transform of noise-charged RLC circuit

texts:
I am doing time-domain simulations of currents in a parallel RLC circuit charged by thermal noise. In detail in pseudo-code:
dt = 1e-9
T = 20 // temperature
R = 230e6
L = 3e-3
C = 20e-12
df = 1/2 f_Nyq = 1/(2 dt) // df is Nyquist frequency

for(int i=0; i<number_of_steps; i++){
 Inoise = sqrt(4 kb T R df) * G(µ=0, sigma=1) // Gauss with zero mean and stddev of 1 to
                                              // make subsequent values uncorrelated
 // Solve differential equation with U = L * IL, IR = L/R IL', IC = L*C * IL''
 Solve[IL + IC + IR = Inoise]
 Save(t=i*dt, IL, IC, IR)
}

Based on these values I calculate the FFT of the voltage $$ U = L \cdot \dot I_L$$ (which is the same for all components). I use the normalized discrete FFT function.
For certain values of L, C and R I am getting a beautiful resonance curve as depicted here:
Now the maximum value should in theory be equal to $$ U_{max} = \sqrt{4 k_B T R \Delta f}$$. However, the value I get out for U_max is a factor of ~1.6 to small (with df taken into account). I happen to notice that
$$1.6^2 = \sqrt{2\pi} $$
but I don't see why this factor should be there. This factor is invariant under change of any of the variables.
Does anyone have an idea where something goes wrong?


texts:
I have a circuit that used to drive a lighter load.

I need to increase the current it manages to drive (and mainly the turn off time).

In the following schematic I show what I want to do: the old circuit had everything but D1, D2, Q3, R5, that I'm planning to add.

simulate this circuit – Schematic created using CircuitLab

I feel this solution is still far from the best.

Hope someone can tell me a better solution that I can implement just by adding few components to the initial circuit.

Thank you for your time!


texts:
Why does the differential amplifier not need capacitors at the input?
I've seen other amps with BJT as a common emitter, common base, etc; and these do have a capacitor at their input.


texts: generating potentiometer adjustable, non-inverted voltage square pulses from microcontroller gpio output

texts:
I would like to generate a square signal with SW adjustable duty cycle, phase etc using the output pin of a microcontroller (3.3V). Frequency <100Hz.  However, I also want

the amplitude of the high state to be in ~ 2-7V range adjustable with a trim potentiometer from a 12V supply rail,
When the signal is low it should be close to zero.
no spikes or disconnected states between transitions to high/low
signal to be zero when the microcontroller output is zero (non-inverted).

The signal will be fed into high impedance op-amp inputs which will driveflash/strobe circuits, so it is like a common analog input signal to multiple strobe circuits.
What is the simplest way to do this? A mosfet, analog switch IC or ?
Thank you!


texts: Finding equation of curve for NTC type thermistor

texts:
I have an NTC thermistor from the KTM 390 engine which I am trying to interface with the Arduino MEGA. The problem is the sensor has no datasheet. I have got the relation between the temperature vs resistance for the thermistor form another person working on the same project.

I did plot a curve for the points in MS excel and tried getting a function using trendline feature but the equation couldn't map the curve entirely. I have also tried using different websites for curve fitting but the result was the same as earlier.
I need help to form an equation for the above set of points and establish a relation between temperature and resistance. I will use this equation in my Arduino program to get the temperature for the corresponding resistance.


texts: Ground Plane on Top and Bottom layers in 4-layer PCBs

texts:
Is it a good idea to fill free space on Top and Bottom layers in a multilayer (4-layer or more) PCB?

I usually use external layers for signal routing and internal layers for power supplies and ground.

* Top - Signals, High speed signals (if there are any)
* Ground Plane
* Power layer
* Bottom - signals

In the stackup above there's a whole layer dedicated to ground with no traces on it. So, that means there's no need to fill the free space of external layers with copper stitched to ground (using polygon pours) but it's something I tend to do.
I also see many manuacturers follow that design (e.g. Raspberry Pi 3 b+). What is the main reason of that? Is it harmfull for the design?


texts:
I bought 2 solenoid valves. I'm looking to turn them on/off using my relay. However, I'm not sure what the best way to power them would be. Do I plug them directly into the wall (after attaching a wall connector to the wires)?

I know wall outlets are 120V. So does that mean I need to get a converter?

EDIT:
http://www.amazon.com/gp/product/B00827FP26
http://www.amazon.com/gp/product/B00004S1V2

Those are the solenoid valves I'm using.


texts: Programmable Unijunction Transistor Circuit

texts:
I am currently teaching my self electronics and have a question about PUTs.
I am wondering why there has to a resistor on both sides of the PUT in this circuit:

Please note that I have already read the question regarding the Make Electronics Experiment 11 and I didn't find the answer that I'm looking for.

Thanks


texts:
I've been working on a Wifi gardening project that allows me to water plants from anywhere I want. Of course, this means I need to use a water valve and a MOSFET to control it. The MOSFET feeds power from a 9V battery to the solenoid, and a Huzzah ESP8266 (on a separate 9V battery) controls the MOSFET gate.

I found that the ESP8266 would not open or close the valve, so I started testing the valve and I realized that I could not open the valve at all. The valve is a plastic 12V solenoid valve (https://www.adafruit.com/product/997), but the information on that page indicates that it can be run using 9V. As far as the 3 PSI minimum pressure requirement goes, the valve is connected to a resevoir that is 3-4 feet above the valve, so I figure that I have a decent amount of pressure from gravity.

I have almost no idea what could be going wrong - I connected the 9V battery directly to the solenoid through a breadboard and nothing happened. The only thing that seems off to me is the diode I use for reverse current protection - see the picture below. Is that diode set up correctly?

Thank you very much for your help.

https://drive.google.com/file/d/0BwEoZ1ajLf1uWUhrS2JIU2NnZDQ/view?usp=sharing
https://drive.google.com/file/d/0BwEoZ1ajLf1uVlJHUm5YS0VVNlE/view?usp=sharing


texts: Is there a simple way to quantize an input waveform in LTspice?

texts:
How can a 1V sine-wave input be converted to a staircase sine-wave with an 8-bit resolution for instance in LTspice? Or is this even possible?

Can this be achieved without a complicated ADC circuitry? Does anybody have experience with that in LTspice?

Edit:

I found the following example so far:

Version 4
SHEET 1 920 680
WIRE -112 -16 -160 -16
WIRE 176 0 144 0
WIRE -160 32 -160 -16
WIRE 448 48 352 48
WIRE 592 48 544 48
WIRE 176 64 144 64
WIRE 544 80 544 48
WIRE -160 144 -160 112
WIRE -112 208 -160 208
WIRE 544 208 544 160
WIRE -160 256 -160 208
WIRE -160 368 -160 336
FLAG 544 208 0
FLAG 592 48 sq
IOPIN 592 48 Out
FLAG -160 144 0
FLAG -112 -16 s0
FLAG 144 0 s0
FLAG -160 368 0
FLAG -112 208 fs
FLAG 144 64 fs
FLAG 448 48 vs0
SYMBOL bv 544 64 R0
SYMATTR InstName B1
SYMATTR Value V=int(V(vs0))
SYMBOL voltage -160 16 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value SINE(0 7.5 {f0})
SYMBOL SpecialFunctions\\sample 256 32 R0
WINDOW 3 0 0 Invisible 0
SYMATTR InstName A1
SYMATTR Value2 vhigh=1e6 vlow=-1e6
SYMATTR Value vt=0.5
SYMBOL voltage -160 240 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V2
SYMATTR Value PULSE(0 1 0 1n 1n 10u {1/fs})
TEXT -176 -160 Left 0 !.tran 0 3m 0 1u
TEXT -176 -128 Left 0 !.options plotwinsize=0
TEXT -176 -96 Left 0 !.param f0=1k fs=20k

Copy and save the above code in notepad with .asc extension and run in LTspice.

I get the following result for 1V sine input amplitude:

It seems like a sample and hold. But I couldn't figure out the formula to set the quantization resolution for a given amplitude. For example for 10Vpp input the resolution increases.


texts: Non-inverting MOSFET switch circuit and alternatives?

texts:
I am starting a new hobby project in which I need to control both solenoids, DC-pumps or peltier elemtns. I have couple of questions.

To explain the picture below. V1_IN is an input from an 3.3V (max 20-50mA) controller and the V1 is the connector to an solenoid or DC-pump.

I have some questions around this:

Is it a suitable design?
Is there a better one for a load that will be switched quite seldom. Every
20-30minutes in total 2 hour runs or so? (e.g. the solenoids)
Is there a better one for a load using PWM? (e.g the pumps or the peltier)
Except choice of components should I change the design if having a 0.5A solenoid or a 5A peltier?
I also have a +5V available can I do something smarter with it?
I would like to have a LED indicating that the output is on. Can I incorporate it into the circuit or is it best to operate it on a seperate transistor.
Any other considerations/optimizations?


texts: How to drive a high side mosfet with the L6388E driver?

texts:
I've been trying to assemble a circuit to drive an n channel mosfet on a high side mode with this ST L6388E chip click here for the datasheet
with this circuit:

using 12V of a power supply and 5V from an arduino and when I connect the HIN between GND of 5V the mosfet doesn't seem to do anything.

Any clue to why that happens?

Thanks for helping!


texts: PCI obsolescence - IEEE1284 (EPP,ECP,LPT) printer port ASIC

texts:
I have a product in volume manufacture where the embedded CPU is now obsolete.
I have to replace that CPU with a lower cost alternative.  For political (and practical) reasons I don't have a choice which CPU to use.
The original CPU had a companion chip which provided a printer port. The replacement does not have that feature.

The printer port is/was used for debug purposes by a legacy (and very a old/obsolete) RTOS.  I would love to change that OS, but due to the complexity, that is not going to happen before we stop prodution of the current design due to shortages.

The replacement CPU does not have a IEEE1284 port (otherwise known as EPP, ECP, LPT, SPP,printer etc)

I have hunted high and low and can't find an ASIC which implements IEEE1284 on a 3.3V PCI bus.   The only parts I can find that ever were are also obsolete.

I can find VHDL soft IP, but the powers that be don't want an FPGA in the design, and in any case the cost of the IP is far too high.

So, (at the risk of being accused of 'shopping') is there manufacturer that still makes a 3.3V PCI IEEE1284 (sometimes called a SuperIO) ASIC device that can be bought at a low cost in relatively low production volumes for sale in (or import to) Europe?

TIA,


texts: Produce and amplify analog signal with microcontroller (For PLC)

texts:
Overview

I need to create an analog voltage of 0V-10V for the PLC with a microcontroller with operating voltage 5V.

Approach

I've been doing this research since last week. I'll share the results of my research. I need your feedbacks.

First of all, my microconotroller dont have any DAC module. So I'm going to produce an analog signal through the I2C with the mcp4725.
(https://www.sparkfun.com/products/12918)

I will then raise this signal to 10V with an opamp.I think I will use this LMV358 module.
(https://www.sparkfun.com/products/9816)

There's a problem here. I need a lot of these analog outputs. But the mcp4725 addresses are restricted. So I will multiply I2C addresses with TCA3548A.
(https://www.adafruit.com/product/2717)

The modules I use are ready products. I think I don't need to draw a schematic. Anybody have a better idea? Do you think this works?  If it works, will it make any problems?

Yes, I need your comments and suggestions.

Best regards


texts:
simulate this circuit – Schematic created using CircuitLab
The circuit reverse-engineered above is a LED dimmer which is driven by 555 timer in astable mode which then drives an op-amp to provide current for the gate of the MOSFET. The circuit dims quite well but it has an issue, when you power it up for a brief moment the LED strip receives non-PWM voltage what results in full brightness and dimming according to the 10K pot position after a while. I was thinking in order to fix this I could remove the 7805 regulator and just replace it with buck converter which powers the PWM circuitry constantly, but I'm asking if there's maybe more elegant solution here.


texts:
I have set up the following scenario in gprmax. From the results obtained using the software, I realized that when I increased the wood thickness the power received at the receiver increases instead of decreasing. Because if you had more wood in front of the transmitter it will impede the propagation. But from the simulations it kind of shows that the wood 'amplifies' the E and H field. Can someone explain why this is happening, the frequency is 915MHz?

The dielectric constant of wood is 5 and 2.4 for the plastic mount. Conductivity is 0 for both materials.

Or are the simulations wrong in terms of in reality the power should decrease has the thickness increases


texts:
(Note: I am aware that crystal and oscillators are two different things but a lot of people use them interchangeably so I am using it in the title.)
My question is about oscillators, all oscillator datasheets mention the output in terms of XXpF. I presume using that pF at the output provides the stability in output, am I correct?
If I want to process the oscillator output stages, what care should be taken in order to acquire a sine wave with as low THD (total harmonic distortion) as possible?
When I say post-processing, I want to convert the unipolar output of oscillator into bipolar levels. I am afraid this can cause a lot of distortion.
Is there an alternate solution?


texts: What is the meaning of "longer electrical length = more wavelengths"?

texts:
Reading a Keysight-note, not sure what is the following selected line means?
I read and understood the meaning of electrical length, how it is related to bit in flight and wavelength is not clear.


texts: Why might a multimeter ask for "wrong" fuse sizes?

texts:
Why might a multimeter ask for the "wrong" sizes of fuses?

On the front of my Fluke 87 multimeter, the two probe ports for amperage are labeled as fused at 10A (max) and 400mA (max). When opening the multimeter to check the fuses (both are burned out), however, the fuses are different -- 15A and 1A, respectively. Their places on the PCB are even labeled as 15A and 1A fuses.

Wh-wh-what?

Further, while looking up replacement fuses on Amazon's site, I see a number of reviews of people with Fluke 87's recommending an 11A fuse.

...?

Is there some latitude with fuse selection, where the size of fuse you pick correlates with your favorite number of the day... or something?


texts: is it electronegativity or a difference in charge which produces current

texts:
In a battery are electrons generated at the negative electrode due to chemical reactions and do they flow to the positive electrode due to a difference in electronegativity of the electrodes? Is an electric field generated as a result?

I always thought it was due to a difference in charge between terminals which created an electric field from positive to negative, is this wrong?

Thanks


texts: How to calculate the ratings when a mains-rated transformer is used in a SMPS?

texts:
I have a mains-rated transformer that is a leftover part from my previous project. Now since I am experimenting with the idea of SMPS, I am wondering how it would behave when handling the higher frequency of a SMPS. Does this spells a higher capacity?

The transformer in question is rated for input of 220V 50Hz, outputs 12V and have a rated capacity of 3VA. What happens if I try to put it in a SMPS with an operating frequency of 150kHz? Will it catch fire?


texts: What does "strap" mean in low-level hardware programming?

texts:
I see the word "strap" in some low-level hardware programming document from time to time. For example:

...to check if these straps are consistently programmed... if not then firmware re-programs the straps...
...currently this IP doesn’t have this mapping register but have a
strap to program the target ID...
...each sub-ip will have a set of integration straps and it is SoC team’s
responsibility to provide proper strap value per sub-ip...

AFAIK, the interface between hardware and software are registers. So software should interact with hardware through registers.
I looks up the word "strap" in dictionary and it says something like "a strip to bind things together", which seems not quite fit in such context.
So what does "strap" mean?
Thanks!
ADD 1 - 8:54 PM 2/24/2021
Below are some of my thought.
Software/firmware runs in some processor (probably but not necessarily CPU). Software can only use the ways supported by the processor architecture to interact with the platform/board. For example, for X86 processor, software can leverage memory access or IO access, which use memory address space and IO address space respectively. From above quotations, a strap seems different from a register.
If it is not a register, what is it?
And how is it accessed by software/firmware? Is it also accessed through memory or IO addresses in the context of X86 architecture?
(BTW, I will keep collecting more snippet to show more context.)
ADD 2 - 4:33 PM 2/25/2021
I had some discussion with some of my colleagues, they say straps are some non-volatile storage, and ultimately CPLD or fuse. They can be accessed indirectly through some IP's interface. We communicate with some delegate IP, and this IP's firmware will access the strap/CPLD for us.
From here, I see this:
HDD Status : 0A30
MEFW Version : 6.0.50.1244
System Straps : 00000F00 BE036FF1 B2EB6E8F <--------------------Straps!
Hardware Anchor : F01001R06.0116f365a2012-07-17
Certificate : 946944F17906C95E

It seems straps are just another name of some system stored value.
But why call it strap rather than some more explicit name?


texts: Slightly Translated Parallel Electrical Circuit Analysis

texts:
My apologies for the vague title, but I simply do not not how else I could express it. As I was studying for my physics electrical exam, I found nodal analysis quite useful; however, I do not know how to apply nodal analysis to further simplify the following example:

Any help would be greatly appreciated.


texts: State Machine with D Flip Flops; how to deal with race conditions

texts:
Consider a state machine whose entire state is kept in a collection of edge-triggered D flip-flops. The outputs of these are fed into a combinatorial network which fully determines the next state, and is fed back into the flip-flops' inputs. On every pulse of the clock, the FSM transition states.

However, I am unsure about how to deal with races: on the positive edge of the clock, the flip-flops will propagate their inputs to their internal states (and outputs). Immediately, the outputs (through the combinatorial network) will change the flip-flops' inputs again. How is it guaranteed that the inputs are stable for long enough after the clock edge for the flip-flops to switch effectively?

I can think of two possible workarounds:

Cascade two sets of flip-flops; this keeps the inputs stable, but would take two clock cycles to transition states.
Use master-slave flip-flops. I am not sure whether this completely fixes the race, though: if the clock inverter (gating the "slave" flip flop) switches quickly (before the "master" flip flop" turns off), it could still result in unstable inputs.

How is this usually solved?


texts: Can't read an entire page at once (NAND flash)

texts:
I am working for quite a while now with a GD5F1GQ4UCYIG from GigaDevice. The goal is to dump the content of the flash.

To do so I use a BusPirate. The NAND flash itself is still attached to the board, I simply connected its output pins with the BusPirate via short wires. Unfortunately I can't desolder it from the board.

The problem that I have is the following, when I execute a page read I can't read the entired page. (1 page=2048 Bytes + 128 Bytes OOB).
When I try to read 2048 Bytes it starts well but after a few Bytes (the exact number is not consistent but it is around 530 Bytes +-) I only get 0x00 Bytes. I found out the number of Bytes that I can read directly depends on the SPI speed that I can configure in the BusPirate Settings. I tried all 8 SPI speeds and I got the best result with 2MHz. All the other speeds start generating 0x00 Bytes way before 500 Bytes.

Why is that so? I mean I should be able to read an entired page at once, shouldn't I?
And why can I read less Bytes at once with diferent SPI speed values?


texts: How much does it cost to charge a laptop battery (1 cycle)?

texts:
I'm looking for a way to determine the cost of a laptop charging cycle.

Letting the laptop drain its energy and then plugging the charger and charging it up to 100%.

The question may sound dumb but that's something I'm interested in.


texts: Why does a real world capacitor behave like an inductor at frequencies above its self-resonant frequency?

texts:
I've come across some graphs comparing the impedance of a capacitor over frequency and it understandably declines as frequency increases -- up until a certain point. Afterwhich, the impedance begins to increase, like an inductor.

What exactly is going on here? Why do larger capacitors have a more gradual shift from decreasing to increasing impedance while smaller caps have a sharper change?

I'm sure this is something basic but I'm having a hard time finding anything about it.


texts: Can I estimate a cell capacity (mAh) with the amperage and the time of work?

texts:
I'm trying to know the capacity of each cell of a bank power, the finality is to replace them:

6x3.7V cells, 12.35V fully charged. (tested with multimeter)
step-up circuit 12v -> 19v (efficiency: let's say 85%)
3S2P configuration

The battery can work 30 min @ 0.7A and the 19V output.

Is the capacity of each cell can be estimate, or must I know the amperage at 12V ?


texts:
Are there any IR receivers/transmitters with speed higher then 4Mbps?
As I found most parts are limited to 4Mbps, like LT1328 (photodiode receiver) and TFBS6711 (infrared transceiver)


texts: ADC with parallel DDR LVDS interface and also a parallel CMOS interface

texts:
The ADS4126 is a 12-Bit, 160-MSPS Analog-to-Digital Converter (ADC). Its data rate is too high for it to be read out using something like SPI or I2C. It does use SPI for control purpose though.

The output of this ADC is parallel but can be configured to be either DDR LVDS or basic parallel CMOS. My questions are as follows:

Do ultra low power DSPs exist that can interface with an ADC that has a parallel DDR LVDS output?
Is the CMOS output intended for DSPs and the DDR LVDS for interface with ASIC or FPGAs?
Is the ADC not capable of same maximum data rate when used with CMOS output? It does seem like it from the datasheet but it is not mentioned in the front page that this is so.
What is the purpose of giving the Standard Swing, Low Swing, Default Strength and 2x Strength of the DDR LVDS interface on the front page?
Why is it important that we may able to control the default strength and output strength of the DDR LVDS output?


texts: How to test what power a raspberry pi is using per day

texts:
I am using a raspberry pi 3 as part of a system that takes time-lapse photos. I have a camera, router and the pi plugged into a 12v battery, attached to a charge controller and a solar panel. With a bit of trail and error, it works. But I need to make the whole thing more portable and run more efficiently.

I need to know exactly how much power the whole thing needs and work out energy saving things I can do to the pi and program it uses.

I have never tested the energy usage before and looked online but get confused with all the calculations and testing methods, as there are so many. Please could someone explain, in basic terms how to work out what energy it all needs and uses and how long it should work without charging it via the panel (just thinking about smaller battery, less voltage).

Thanks


texts: What happens if two N-wells touch each other?

texts:
When designing the layout of a CMOS inverter, we need to use an NWELL to build the PMOS.

Following scalable rules, when desining the masks I have to be sure that if I want to build two NWELLS using the same mask, they have to be separated by, at least, 6 lambda (while two N+ implantation only 3 lambda.)

Why do they have to be separated?
Can't I build two PMOS in the same NWELL?
What happens if they touch each other?


texts: AVRISP mk2 clone can program Arduino Uno, but not stand-alone ATMega328P

texts:
I have an AVRISP mk2 knock-off that I can't get to work.
Scenario 1: AVRISP mk2 clone vs. Arduino Uno: works
If I take an Arduino Uno, and plug the 6-pin ICSP cable of the AVRISP onto it, one of two things happen, both as expected:

The cable is plugged in in the correct orientation, and I can use avrdude to query fuse status and upload .hex files

The cable is plugged in reversed, and an orange light in the AVRISP starts flashing

Scenario 2: AVRminiProg vs. ATMega328P on breadboard: works
Moving on, I have put an ATMega328P on a breadboard, connecting power/ground, and using jumper wires to connect the Reset and MOSI/MISO/SCLK pins to a 6-pin ISCP cable. I then take an  AVRminiProg, plug in the other end of the ISCP cable, and hook up power/ground (unlike the AVRISP, the AVRminiProg supplies 5V on its own to the system under programming). I can measure the 5V on the breadboard, the ATMega328P works as expected, and I can use avrdude to query fuses / upload programs.
Scenario 3: AVRISP mk2 clone vs same breadboard: doesn't work
The above two steps were just diagnostic; my actual goal is to use the AVRISP to program the ATMega328P on a breadboard, so I can supply my own voltage (my aim is to use 3.3V). So I take the same ISCP cable as in scenario 2, but plug it into the AVRISP instead of the AVRminiProg. I also attach 3.3V (from an Arduino Uno since that's already on the desk) to the breadboard.
However, the orange LED in the AVRISP immediately starts flashing, as if the cable orientation was wrong; even though the same orientation worked just fine for the AVRminiProg. If I try to swap just power and ground, it still doesn't work, but I get the voltage between them to drop to almost nothing.
In my desperation, I've actually ended up downloading the PCB design of the Uno to track the ICSP pins to make sure I am wiring stuff correctly. However, it seems if I just connect power and ground, and nothing else, and both the same way as they are in the Arduino Uno, to the AVRisp mk2, I already get the orange blinking. Yet connecting the same AVRisp mk2 to the ICSP pins on the Uno itself, it works as expected.
What am I doing wrong?


texts: Why is the calculated current with P=VI and R=V/I not equal?

texts:
I'm just starting to learn electronics. I thought I'd start with a simple project of attaching a speaker to a Raspberry Pi (it supplies 3.3V). The speaker I've picked is an 8Ω 0.5W speaker. Now as I understand it, I need an amplifier in order to use this speaker. So I've picked a 3W amplifier.

I have to make sure that I don't use more than 0.5W so I don't blow up my speaker. The amplifier gives the following information:

  3.3V into 8Ω @ 10% THD - 0.8W max
  3.3V into 8Ω @ 1% THD - 0.6W max

As I understand it, THD (Total Harmonic Distortion) is the amount of false data being added to the output so not only would we want that to be lower for quality, but it seems that the lower it is, the less power consumed as well. (Bonus question: How can I make my THD be 1%?)

However, even if I can ensure a THD value of 1%, I still need to shave off .1W to save my speaker. I thought about adding a resistor in series with the speaker and it seems that a 1Ω or 2Ω resistor would do the trick but I can't figure it out mathematically.

While trying to figure this out, I calculated the current using P=IV (I = .6W / 3.3V = .182A) and using R=V/I (I = 3.3V / 8Ω = .413A). Why aren't the current values the same? (Side note: this happened to me when I was trying to solve Exercise 1.6 in The Art of Electronics as well.)

The main question I want answered is why aren't the current values the same, but if you could help me figure out how to save my poor little speaker, that would be great as well. =]


texts:
I have a project to work as follow:
this is a PIC based (PIC16C62B) porudct which measures value coming from mechanical gyro sensor. analog data from gyro amplified and sent to AD7707 to convert into serial. PIC reads this serial of AD7707 and shows gyro values/data on 16x2 LCD after internal processing. I dont know about the internal program/code of PIC being used into it. the PIC is code protected and I cannot read its hex. now I am required to show LCD vlues/data same on computer in any case.

I dont understand how to do it. if anyone have any idea to do this or had worked on please help me in this situation. I will  be thankful for all positive response.

char a,b,c,d,e,f,g,h,var;
char i=0;
char con=0;
char low=0;

//byte sBuffer[256];
//unsigned int nLen;

//nLen = HexToASCII(sBuffer, "65 66 67");

void setup() {
 Serial.begin(1200);
 //pinMode(13, INPUT);
pinMode(12,INPUT);    //Define RS
pinMode(11,INPUT);    //Define EN
pinMode(5,INPUT);
pinMode(4,INPUT);
pinMode(3,INPUT);
pinMode(2,INPUT);
pinMode(9,INPUT);
pinMode(8,INPUT);
pinMode(7,INPUT);
pinMode(6,INPUT);
  a=0;
   b=0;
   c=0;
   d=0;
   e=0;
   f=0;
   g=0;
   h=0;
   con=0;
   low=0;
}

void loop() {

  if(digitalRead(11)==HIGH && low==0)                //EN hight
  {
    low=1;
  }
  if(digitalRead(11)==LOW && low==1){
     if (digitalRead(12)==HIGH){                     //RS high
   a=digitalRead(9);
   b=digitalRead(8);
   c=digitalRead(7);
   d=digitalRead(6);
   e=digitalRead(5);
   f=digitalRead(4);
   g=digitalRead(3);
   h=digitalRead(2);
//   var = (h*128)+(g*64)+(f*32)+(e*16)+(d*8)+(c*4)+(b*2)+(a*1);
   var = (h<<7)+(g<<6)+(f<<5)+(e<<4)+(d<<3)+(c<<2)+(b<<1)+(a);

   con=1;
   low=0;
   }
  }
  if(con==1){
  //  String str(var);
    Serial.print(var);
    //Serial.print("\n");
     a=0;
     b=0;
     c=0;
     d=0;
     e=0;
     f=0;
     g=0;
     h=0;
     con=0;
     var=0;
  }

}


texts: What is the dependence of current through inductor in parallel RLC CIRCUIT with a AC source at resonance frequency

texts:
Consider the parallel RLC circuit:

simulate this circuit – Schematic created using CircuitLab

Assuming $$ C,L> 0$$
$$ I(t) = U(t)*cos(t/(LC)^{0.5}) $$
So, we have a source that starts working at t=0 at the resonant frequency.  I'm being asked about 2 possible conditions:

The initial current through the inductor is 0 and the initial voltage across the capacitor is zero.
The initial current through the inductor is GREATER than zero and the voltage across the capacitor is equal to 1/R.

In which condition the current through the inductor approaches infinity and how can you explain that physically?

I have found the general solutions to both of these problems:

For the first option I get a blocked sin function, so in this case the current does not approach infinity as times goes by.
For the second option I get an exponent with a positive power so the current does approach infinity as time goes by.

But how can I explain that physically?  I mean, in both cases the source works at the resonant frequency and all that is changing are the initial conditions.

Can anyone please clarify for me what does the initial values of the capacitor and the inductor have to do with the current?


texts: OLED ssd1306, "Set the Oscillator Frequency"?

texts:
I am working with a OLED SSD1306 and in the datasheet there is a parameter named "Set the Oscillator Frequency."  It is a four bit value to adjust.

I can't understand the purpose of this.

Can anyone help?

Also I am having artifacts/garbage display randomly, so is it related to speed of this frequency or I2C speed?


texts: ESD capacitor simulation for human body model

texts:
I have designed an ESD suppression circuit with the help of ESD capacitor using LTspice. In the circuit, 15kV input pulse is given to ESD human body model and the resistor, capacitor used near the source are as per the standards.Capacitor C2 value is calculated as per the theory. Now my question is,
1. i have used a switch before C1. Is this switch needed?
2. Output at C2 is same as C1. C2 does not influence the circuit.
What should i do to get the correct output?
Plz refer the image for details.
Thanks in advance.


texts: What is the maximum/minimum possible sampling rate for the signal to be full recovered for a passband signal?


texts: How do I change battery voltage output and make it constant?

texts:
I'm trying to make a battery powered arduino, so I bought a pro mini, that can be powered by 3.3V. I'll be using rechargeable batteries and found that AA Ni-MH are the most efficient / cost-effective / easy-to-use. All of my research made me realize that a voltage upscale is not that easy (if you prove me wrong on this, I'll thank you eternally), so I'll be using 3 of them. That makes a theoretical 3.6V with a range of 3.24V when depleted and 3.96V when fully charged.

I want the voltage output to be constant at about 3.3V, so my best results lead me to this voltage regulator. I understand that it will reduce the voltage to 3.3V and the rest of the input will be wasted as heat, so my 3 battery plan had the least energy waste.

The problem became obvious when the batteries dropped to just 3.8V: the voltage regulator dropped its output to 3.0V.

Now, keeping in mind that the power requirements will differ by the time, since there will be two tiny motors that won't be running constantly, is there any way for me to provide a constant 3.3V from the least amount of batteries and without spending a fortune on the regulator (that is up to 3€, else I just add one more battery)?


texts: Preventing long-press button function on DFPlayer board

texts:
I'm using DFPlayer in stand-alone mode (no Arduino) for a music project. The buttons all have short-press and long-press commands. I want to trigger a short-press command by releasing a depressed normally-closed switch (ie. lifting an object containing a pressure switch.) Since the switch stays closed upon release, it would register as a long-press, but I want the short-press behavior.

Based on my research, it seems like a capacitor-based debounce circuit might allow me to accomplish this, but I can't make the jump from those examples and my application. I don't want to involve a microcontroller.

DFPlayer manual:
https://github.com/Arduinolibrary/DFPlayer_Mini_mp3/raw/master/DFPlayer%20Mini%20Manual.pdf

UPDATE 6/19: To clarify the application, here is what we built previously.
Musical Invitation: https://www.youtube.com/watch?v=r6qroO5coos

This used a different music player that doesn't have as good a sound quality, and required prying it out of a plastic enclosure (150 times) so we could modify it to control the lights, but it did have a push button to activate the music. We wired the switch normally-closed, so while it's in the box, it holds the switch open. As soon as the box opens, it releases the switch and begins playing. But in the new music player, it interprets normally closed as a long press, and depending on which pin I connect to, that will either play a track on infinite repeat, or increase the volume, neither of which are what I want, which is to play the track once and stop. We're working on a similar project and wish to use a better quality music player that requires less manual labor to assemble.


texts: How to correctly use a set of pogo pins?

texts:
Following the excellent recommendation to a previous question of mine (on what to use when I want to connect to a board without soldering), I got hold of pogo pins.

How to use them correctly, when in a set?

Specifically - how should they be "put together" in order to be at the right distance between each other for a typical board?

I built the abomination below to have a straight series of them at the right distance (it works but this is really artisanal):

Are there "holders" (for a lack for a better word) for them? I was hoping that I could squeeze them into a breadboard but they are too big for that.


texts: VHDL: a+b+carry_in creates two adders instead of using carry in in the existing adder

texts:
I want to add A, B and the carry in. This should be done using only one big adder. But when I look at the circuit generated, there is an extra adder for the carry in. How can I solve this problem?

Picture:

Code:

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
entity adder is
    port(
        a, b : in unsigned(3 downto 0);
        result : out unsigned(3 downto 0);
        clk : in STD_LOGIC;
        cin : in integer
    );
end entity;
architecture behavioral of adder is
    signal a_r, b_r, result_r : unsigned(3 downto 0);
    signal cin_r : integer;
begin
    process(clk)
    begin
        if rising_edge(clk) then
            a_r <= a;
            b_r <= b;
            cin_r <= cin;
            result_r <= a_r + b_r + to_unsigned(cin_r, 4);
        end if;
        result <= result_r;
    end process;
end behavioral;


texts: LTSpice noise simulation with custom noise voltage source

texts:
I'm trying to simulate noise of a circuit in LTSpice.
I need to add custom white-noise voltage sources to the circuit, but when I do a noise simulation using the ".noise" command I don't see the contribution of these sources in the output.
I can't share my actual circuit but I created this example which shows my problem;

However when I simulate transient response I see the noise:

So the question is; How do I include custom noise voltage sources in the noise simulation?
Or am I forced to use transient simulation and then calculate the RMS voltage of the output?


texts: Interface USB and SPI flash (Boot PC from SPI)

texts:
Basically I am looking for a way to boot a PC from SPI flash. I'm talking about average AMD/Intel desktop mainboards. BIOS is already on SPI, but I need a way to also put the kernel and maybe initrd there.

It needs to be SPI flash and I probably can't use the one with the BIOS on it.
You can boot from USB and I was wondering if there is some way to make the storage "backend" of an USB device SPI instead of NAND flash.


texts:
Currently I am working with two MSP430G2553 Microcontrollers for a school project and I have to use UART to have them communicate with each other. The transmit MSP430 is to send a character whenever a user inputs a password correctly to open an entryway. The door is being simulated by a servo motor on the receiving MSP430. My current code was functioning very well but the servo kept opening and closing; the only way to stop this was to disconnected or power off the MSP430. When I checked the 'UCA0RXBUF' register, we noticed the character would remain in the register and not clear. We attempted to push a zero to clear the register to no avail. My code has a series of .c files to make initialization of the UART easier to use. attached is my current code and maybe you might be able to point out a mistake, or syntax error, that I may have missed.

#include <msp430g2553.h>
#include <string.h>
#include "uartMsp.h"
#include "adcMsp.h"

void door(void);
void delay(void);
void buzzer(void);
void door2(void);
void door3(void);

volatile int i, x;
char received = 0;
unsigned int mode = 1;

void main(void){
//Setup
WDTCTL = WDTPW + WDTHOLD;// Stop Watchdog Timer

//Setup Timer A0.1 and Port 1.6
P1DIR |= BIT6;//Output for SERVO PWM
P2DIR |= BIT7;//Button to shut off buzzer
P1SEL |= BIT1 + BIT6;
P1SEL2 &= ~(BIT6);//??
TA0CTL = TASSEL_2;//Setup Timer
TA0CCTL1 = OUTMOD_6;
TA0CCR0 = 20000;

//Setup DCO
DCOCTL  = CALDCO_1MHZ;    //DCO at 1MHz
BCSCTL1 = CALBC1_1MHZ;    //DCO at 1MHz

//Setup ADC
ADC10CTL0    = ADC10ON + ADC10IE;             //Turn on ADC and Enable interrupts.
ADC10CTL1    = INCH_5;              //Pick an input to sample from (Any Port 1 Pin EXCEPT P1.0 or P1.6; those belong to the LEDs)
ADC10AE0     = BIT5;                //Set your pin to analog. Hint: BITx = P1.x

__delay_cycles(500000);

clock_init();                // Set clock frequency to 1 MHz
serial_init_inter();     // Initialize UART module
_enable_interrupts(); //Enable General Interrupts. Best to do this last.

while(1) {
    received = UCA0RXBUF;
    UCA0RXBUF = 0;
    if(received == 'o'){
        received = 0;
        door();

    }
    else if(received == 'b'){
        received = 0;
        buzzer();
    }
    else if(received == 'u'){
        received = 0;
        door2();

    }
    else if(received == 'e'){
        received = 0;
        door3();

    }
    ADC10CTL0 |= ENC + ADC10SC;
}//create an infinite loop that does nothing (or goes into low power mode)
}//End of main

// ADC10 Interrupt Service Routine
#pragma vector = ADC10_VECTOR
__interrupt void ADC10_ISR( void ) {
x = ADC10MEM;
if((x > 700) || (x < 300)){
    P1OUT |= BIT7;
    while((P1IN & BIT4) != BIT4){}
    delay();
    delay();
    P1OUT &= ~BIT7;
}
}//End of ADC10_ISR

//Door function
void door(void){
TA0CCR1 = 1500;
TA0CTL |= MC_1;//Setup Timer
delay();
TA0CCR1 = 750;
delay();
TA0CTL |= MC_0;//
}//End of door

void delay(void){
volatile unsigned j, k;
for(j=4;j>0;j--){
    for(k=20000;k>0;k--);
}
}

void buzzer(void){
P2OUT |= BIT5;
delay();
P2OUT &= ~BIT5;
}

void door2(void){
TA0CCR1 = 1500;
TA0CTL |= MC_1;//Setup Timer
}

void door3(void){
delay();
TA0CCR1 = 750;
delay();
TA0CTL |= MC_0;//

}


texts: How to calculate resistor needed between generator and bridge rectifier?

texts: I am almost done with constructing my railgun however, I am stuck with this last problem. To charge my 110 V 35 mF capacitors, I am converting 120 V 30 amp AC current from a generator to a 120 V 10 amp bridge rectifier. Thus, the problem I have is figuring out what size capacitor to uses to lower the amperage from 30 to 10 so I don't blow my bridge rectifier.


texts: How to stop a motor when car approaches wall - phototransistor?

texts:
In a school competition for my son, he wants to make a toy car that will stop before it hits a wall (before, not making an impact).  It can go as slow as it likes and cannot be remote controlled.  I was thinking maybe a phototransistor on the front, shrouded so when the wall becomes close the light level would become low enough to switch and turn off the motor.

Do you think that could work?  I have a feeling it is too imprecise.  Can you think of a better way?  It may not be approaching the wall exactly perpendicularly if the car veers off slightly.

Extra thanks for circuit diagrams - it is a very long time since I did anything like this...


texts:
We are building a low-power data logger based upon the ATmega328P, in order to make use of the Arduino boot loader and IDE, etc. Ideally power consumption should be less than 0.3mA @ 3.3V to get around 4 months life on a single AA battery. Sensor data will stored at a maximum of 76 bytes/sec for the 4 months, giving around 750 MiB of data. Therefore we have the need for a large memory device, that is still low-power.

From what I can tell, the only practical solution to store this much data is to use an SD card. However SD cards seem to use a little more power than we can afford, 0.2mA idle current for the cards we have now, and more when they are writing.

So some questions:

Is a high-side switch the only practical way of controlling power consumption of the SD card?
Are the any caveats we should be aware of when switching power to the card? For example, is wear-levelling a process that will be performed after a block write, or can it happen at any time.
Are there any other alternatives we should consider?


texts:
What's the point below which electrical current is generally considered safe for "casual" human contact?

Is either voltage or amperage more "dangerous" (e.g. high voltage / low amperage vs. low voltage / high amperage), or is the only consideration the total current?


texts:
Does anyone know of a tool that can make jumper wires to fit standard spacings for breadboards?

What I have in mind is a jig where you dial in the number of rows you want the jumper to span, insert your chosen single-core wire, and the tool cuts a piece of wire to length, strips the ends and maybe even bends them.

I've bought jumper lead kits before, but I'm not a fan of them because they always seem to have one colour per length. I'd prefer to keep my 'traces' the same colour, which is hard to do with such a kit.


texts: Practical limits on Raspberry Pi GPIO pin voltages

texts:
I know the Raspberry Pi GPIO uses 3.3V, and you should never connect voltages higher than that to the pins. However, when connecting an I2C device I accidentally put 3k pull-up resistors to 5V (because that's what the sensor used) on the I2C lines and it worked fine.

What are probable maximum voltages where a Raspberry Pi GPIO a) works correctly, and what are limits where it b) doesn't do permanent damage to the board? Does it depend on things like resistance and/or capacitance?


texts: Some questions about current and reading electrical characteristics from a datasheet

texts:
I'm trying to understand the concept of drawing current.

I read in a site(method 10) that Arduino (ATmega328P) can be damaged if i set ten I/O pins to be high and draw 20mA from each one at the same time.

Currently i have made a circuit that uses three L293D (page 5 at the datasheet for the electrical characteristics) to drive three stepper motors and it works fine.

To drive the L293D i use (3x4) twelve pins and in this configuration these are not high at the same time but when stopped (the motors) all the twelve I/O pins are set to low. (these pins control the logic of the L293D, i use a separate power supply for the motors)

Now i read the L293D datasheet and it has the following ratings

I-IH High-level input current 0.2 μA
I-IL  Low-level input current 0.2 μA
                                                           TYP   MAX
I-CC1 Logic supply current -> All outputs at high level   13mA   22mA
                              All outputs at low          35mA   60mA
                              All outputs high impedance   8mA   24mA

Can someone explain me a bit these ratings.
Do i overload the pins by drawing 35mA when all outputs are low
and if i do so why there is no damage?

What is "all outputs high impedance"?

Now i don't really care about this specific personal project, but the general logic about current ratings.


texts: Why is this charge-pump regulator less efficient when operating with a lower supply voltage?

texts:
I'm currently doing some power analysis for an electronics project and am attempting to make my design more efficient. My design uses a 3V coin cell as it's primary power source. Out of good practice (and because my design operates at 3.3V nominal), I've decided to add a voltage regulator. I've selected this Microchip MCP1252 (http://ww1.microchip.com/downloads/en/DeviceDoc/20001752C.pdf).

This chip is able to be configured as either a 5V regulator or 3.3V regulator. Looking at Figure 2-5, it shows the power efficiency when the regulator is configured to output 3.3V. Looking at my application using a 3V coin cell supply, the regulator is only 55% efficient. This is not that good... However, looking at Figure 2-4, the regulator appears to be much more efficient when configured to be a 5V regulator.

So my question - why is this regulator much less efficient when configured for 3.3V output? Does it have something to do with I^2 R losses? Furthermore, why does the efficiency trend from Figure 2-5 look the way it does? It seems to be much more efficient as soon as you change your input supply to 4V. Why is this?


texts: I wanted to use MOSFET as a switch so my teacher asked me to hook it up like this. But I'm not sure how it works. Since I don't know what my source voltage is , how do I know if Vgs>Vt and even if we assume that Vgs>Vt, the MOSFET turns on and now, source voltage is 5 volts. But my gate voltage is 3.3 volts and hence Vgs <0. Hence, it will turn off automatically. Am I right?


texts:
Hi, I am trying to drive a motor using a MOSFET(N-Channel). In my circuit I have connected an indicator for me to know if my mosfet is working. And it really does, but whenever I connect my dc motor, my indicator turns off. I've
tried connecting my motor directly to a battery alone, and it works fine. My battery is 1.2V; 1900 mA. Therefore, it is safe to assume that my motor works within that condition.

Resistor values:
--- 270 ohms (indicator / LED)
--- 1M ohms

Question:
Why won't the motor run? Is it because it lacks current?

PS: The overall circuit uses a 5V as a source.

Can anyone help me. I really don't know what's wrong.


texts:
I have to generate current values between 0mA to 110mA.
Can I generate current automatically using a micro-controller? (For example: 20mA , 30mA...)
I need to keep the current stable for ms in frequency between 1Hz-100Hz.

If so, how?


texts: Differences between OFDM, OFDMA and SC-FDMA?

texts:
I understand that -

multiple user scenarios lead to OFDMA
in SD-FDMA at any point of time, all subcarriers carry the same symbol.

What I want is to understand on what exactly differentiates them.


texts: I'm working on a synthesizer project and I'm confused on what the final audio output voltage should be. The idea is that I would send the audio to a speaker or headphone amplifier, so I don't have to drive a small load or anything. I've seen +-1.4V places, but when I tested that with my headphones it was really loud. Is that just the maximum volume? Also, would the voltage range be different if it were a keyboard amp instead? Any clarifications on this would be greatly appreciated.


texts:
I've been trying to design an omnidirectional PCB inverted-F antenna for a bluetooth project. The aim with the design is to ensure the best range possible with the space I have; Ideally an average gain of >1dBi.  I've come up with a design that I think may work, but I really am struggling to verify if it will perform as required.

Here is the design layout (the tail connects to ground, just doesn't look like it here)

I know antenna design is not a trivial task, but will this antenna work? if not, what might need modifying to make it perform?

Are there any alternative antennas out there that may fit my performance and spatial requirements? I looked at a TI IFA design but it's just slightly too large for the ~34mm x 5.5mm I have available.


texts:
In the office I hear these terms thrown around as if they are the same. My understanding is that USARTs can deliver the clock signal along with the data.

Are there any other differences? What are the advantages and disadvantages of each?


texts:
Undefined exception in ARM processors is described as being taken when the processor encounters an instruction that is undefined or not supported by implementation.

I am not able to understand that processor is in this mode is either due to program portability or due to the wrong instruction of some program which is not part of instruction sets of processor?


texts: Multi-bit tri state buffer in verilog not working

texts:
I'm trying to write a tri-state buffer that buffers more than one bit, this is what I currently use:

assign _memIn[7:0] = (_memRW == 0) ? memOut[7:0] : 1'bzzzzzzzz;

But it doesn't work. It is supposed to assign memOut, which is a [7:0] register to _memIn which is a [7:0] wire connected to inout, when _memRW is 0 (which it is always supposed to be, I checked using the logic viewer thing). But it only partially works. Whenever memOut is either 0 or 1, everything works fine, but if I set it to 2, _memIn becomes x.

I have absolutely no idea why, and am hoping someone can help.

I should note that I assign _memIn twice.

Above assign is in my testbed, and this assign is in my actual module:

assign _memIn[7:0] = (_memRW == 1) ? memOutC[7:0] : 1'bzzzzzzzz;

Don't know if that is the issue, if it is, how do I fix it?

The idea is that the second assign snippet is in my "CPU", so if _memRW is 0, it means read from memory, if it's one, do nothing.

Then in my testbed, I "emulate" a RAM chip by checking if _memRW is 0, if it is, then assign a register containing the correct mem value to _memIn. If it's 1, write to memory.


texts: Sourcing for low power stepper motor driver assembly. Which is best cost and host software wise?

texts:
For small batch production I am looking for small low cost product. Need it to be network controlled (Ethernet TCP/IP) with open documentation. The current is about 1..2..3 Ampere, voltage 24..48V. Also nice to have just 1..4 axes and DIN rail mount.

Problem is, that everything I can find is serial port controlled or modular blocks with 2-3 accessories with proprietary software and lot of unnecessary features, making software part complicated and requiring for host PC to be equipped with extra $100 I/O ports.


texts:
Why do we need a load resistor connected between the output pin and ground?
reference to a detailed description of the sensor


texts: Can I swap an electrolytic capacitor with one with a higher voltage?

texts:
I wish I knew more about this stuff, but alas I do not.  I have a radial lead aluminum electrolytic capacitor (rated 470mF and 25v) that died on me.  Can I swap it out with one rated at 35V, or do I need to get one matching it completely?  It is for a plasma, so if there is chance that 35V could cause more damage, then I would like to know!

Thanks


texts:
First off, I just want to say that I'm still pretty new to PCB and schematics design, and electronics in general, so any suggestions on improvement are much appreciated!

I'm creating a basic circuit to control a string of addressable RGB LEDs. The circuit is powered by a 12v DC wallwart, and then the power is stepped down to 5v to run the heart of the circuit, an ATTiny45. There is also a switch to choose between 5v and 12v for the power output to the RGB string. The micro USB is used for serial communication so I can send commands to a sketch running on the ATTiny to tell it what to display on the RGB string.

As I'm still learning electronics, and as the main parts of the schematic is different schematics I've found from Google searches pieced together, I wanted to get you guys to look over my schematic before I get it printed.

The URLs below some parts of the schematic point to the sources where I found the schematic needed to put together that part.

Any suggestions on improvements, better ways to do things, or critique is appreciated!

EDIT: Changed the barrel jack component to a proper one


texts: Do I need any special equipment to make my circuit run off power from a phone/laptop charger?

texts: Is it safe for one to replace a 5v battery source with a phone charger without installing any other components to prevent power surges or injury to any people in contact with the device? Also, is it safe to use a phone charger to run components like LEDs as if the charger were a battery?


texts: What is the difference between LT, LTC, and LTM prefixes for Linear Technologies' parts?

texts:
I know there are other questions about standard naming, such as this one, but so far I have not found any answers to this particular question: "What do Linear Technology's components' prefixes (e.g. LT, LTC, or LTM) indicate, other than that they are produced by Linear Technology?"

I asked my local sales representative, he did not know, and I felt too sheepish to pester him with arguably unimportant questions. However, I do not think it is random. It doesn't seem to correlate with device type (e.g. usually there are at least two different prefixes within a category like opamps, ADCs, etc.) Perhaps it has to do with the fabrication process? If anyone knows or has conjectures to offer I would appreciate hearing them.


texts:
I am trying to calibrate the internal clock to turn on a output once for 3 seconds every 7 days within a few minutes accuracy. I was able to accomplish this using the OSCCAL register in the chip. The problem this on works if I set this per chip. I am trying to find a way to program it by have it check and calibrate its internal while programming. Maybe there is a feature in the compiler that will auto calibrate?

I am using:

MCU: PIC10F200

Programmer: PICkit3

Software: MPLAB X IDE v3.26

Compiler: XC8 v1.37


texts: Is it good practice to use diodes in a stereo to mono conversion?

texts:
Some background: I am making a VU meter with LED strips using the Alexa Gen 4 Echo as the sound source. I'm planning to modify the Alexa so that I solder external wires to the left tweeter, right tweeter, and subwoofer speaker, along with adding a ground wire, of course.
For the VU meter, I want to use the ESP32 to have it sample two audio signals coming from the Alexa device: One signal from the subwoofer, and one mixed signal from the tweeters.
I know you can convert a stereo to mono signal by adding two resistors in series of the left and right channel speakers (or left and right tweeters in my case), and connecting the end terminals.
I'm worried that I could damage the speaker since I don't know if the left tweeter will backfeed into the right tweeter and vice versa.
I'm being cautious since I'm assuming the Echo wasn't designed with the intent to have it's speakers backfeed audio from one to another.
I was wondering if I could do something like this:

simulate this circuit – Schematic created using CircuitLab
The idea is to use a voltage divider to take the maximum 18V on the speaker (I haven't confirmed if it's RMS or Pk-Pk) and lower it to 3.3V. A filter capacitor is added along with the diode that will keep the speakers from backfeeding. The audio signal is then biased to 1.6V using the 3.3V from the ESP32.
Would something like this work for a VU meter, or is what I'm doing unnecessary?


texts:
Today I learned about the concept of memory training for DDR2, 3, and 4 (I'm not sure if DDR1 has it). The purpose of memory training is to correct for skew in data, address, and command bits being sent between controller and memory (presumably using a programmable analog delay?).

Also important for DDR is the concept of length matching, to ensure that each bit in a given word in DDR arrives to the DRAM/to the controller within a clock period. This is to ensure the data receiver "sees" the correct bit pattern when it's time to latch.

These seem to be accomplishing the same task. Clearly, I can look at any board with DDR memory and see length-matched traces, but it leaves me wondering: What physical, technical, or business decisions make it impractical for a DDR(2-4) controller itself to compensate for skew due to mismatched lengths, as long as the incoming clock is skewed as well to after what the controller determines is the latest-arriving bit?


texts:
Let me ask  you few questions for those who know how to design PCB in PADS.

In case of PCB design in PADS layout, manually routing is  bit time consuming, cant I depend on auto routing ?
When you connect PADS logic with layout, what things you keep in mind in component placing? Do you follow the schematic array? I mean from left to right cascaded circuits?
What benefit you get from "via mode", "layer toggle", "Angle Mode" when you do routing? For design circumstances what you keep on mind? Always control "option"?
When do you feel to add "Flip side" components ?
After significant setting in "Option", take a look this view and leave comment on what we could do for routing,(its a reference design I am trying to re-design )


texts:
I have a question that troubles me a little( Maybe it is quite simple to answer though). Its about the noise bandwidth of a multichannel receiver.

Let's assume we have a multichannel receiver with e.g. 4 channels. Each channel has a BW of e.g. 20 MHz and the channels are next to each other.

Quesetion 1: If I design now the system such that I first have preselection filter that selects the 80 MHz Bw of interest (with subsequent power amplifier and, image rejection filter, etc...) and subsequentially a channel selection filter that selects e.g. one of the channels with 20 MHz that I want to receive/decode/process what will be the bandwidth to calculate the thermal noise power of the system before quantization?(aka: -174dBm/Hz + 10*log10(?Hz)) Would this then be 80 MHz or 20 MHz. It should be 20 MHz right, because the system works at 20 MHz after all. I know there are other possibilities to design such a receiver(direct conversion), but that question troubles me a little.

Question 2: Also, if I would digitize the signals with an ADC firstly (with a high enough resolution and sampling frequency double the BW of all channels => 160MHz) and do the channilization in digital domain (by an e.g. FIR filter) , what would be the bandwidth here? I.e, I quantize the 80 MHz signal and then I use channelization for 20MHz. Will the noise then also be calculated with 20MHz BW?

Maybe this question is rather easy to answer, but unfortunatelly I didn't find a discussion of this problem so far.
Thanks so much
steve

thank you very much for your answer! I still have a question though.

It is more concerning the sensitivity of the receiver now. So if I now think of a system with an overall noise figure of e.g. 10dB and i consider one 20 MHz channel of the 80 MHz, then the noise power can be calulated by -174dBm/Hz + 73(=10*log10(20000000))dBHz + 10dB = -91dBm; So if I want to decode a modulation scheme that requires e.g. 10 dB Eb/N0 for a certain (wanted) BER i would need an input power of at least -81dBm. So far so good.

And now I am still a little bit confused. What if now I would ADC all four channels (=> 80 MHz) and do then signal processing of a 20 MHz channel in digital domain after quantization, what is the sensitivity of the system then? Input noise power of the ADC would -174dBm/Hz + 79dBHz(80MHz) + 10dB = -79dBm. So this is the noise the ADC sees. If I assume, that the ADC does not add any quantization noise would this mean that in this case I would need an input power of at least -69dBm to be able to decode the 20 MHz channel with the same BER, or does it mean that, because i use a 20MHz filter in the digital domain, the noise bandwidth is reduced again to 20MHz and the sensitivity is still -81dBm?

I hope the question is clear so far.


texts: How to calculate resistors for a 555 sawtooth with an opamp sink controlling it's frequency

texts:
I modified this sawtooth-wave 555 osc and removed the ground at the 4k resistor, replaced it with an inverting opamp. The opamp produces a negative voltage and sinks the current, that previously went into ground after the 4k resistor. Applying 0-5V to the inverting input causes the 555 oscillate in different frequencies, where 5V gives the highest frequency and 0V the lowest.

The resistors on the inverting input and the feedback seem not to influence the sink but varying R1-R3 does. Via trial and error I set the values to somewhat "reasonable", that 0-5V produce a good range of frquencies although I have no clue how to calculate the values.
So, if I am using 0-5V at the inv. input, what formular could I use for the resistors to calculate the frequencies the 555 is doing at each voltage?
Link to Falstad sim


texts: Component specifications needed for a high voltage front-end

texts:
I have an ADC here that in the datasheet has this example application circuit for a 100 - 240 VAC front end voltage measurement.

If I was going to build this circuit, what ratings should my parts have in order to survive the high voltages?
Here is the list of the valuse and links to parts that I have chosen I think would work:
Rv
Rhi = 300k Ohms
Rlo = 750 Ohms
Rfilt = 49.9 Ohms
Cfilt = 1000pF Ohms
Putting aside the value and tolerances, what package should I choose for the resistor? This I think can be answered by calculating the maximum power (as higher power requires a bigger package), assuming the highest voltage we normally expect is 350V and a 900k-750 ohm voltage divider would only have 0.3mA of current going through it so its power rating can be as low as 0.1W (0.0003mAx350v =0.105W).
Can my resistor really just be a 603 package 0.1W like the one I linked?
Are those tiny packages really up to the task of high voltage mains?


texts: Modifying an existing 3-cell BMS circuit to disconnect the pack at high temperature

texts:
There are a number of 3-cell protection boards available online for 18650 cells. None of which appear to disconnect the pack at high temperature.

A schematic of one such board is shown below, along with my attempt (circled in red) to add a temperature sense feature.

The idea is that normally JP1 (a NC thermal switch placed close to the pack) keeps Q8 turned off. When the temperature of the pack rises above 40 degrees the base of Q8 is pulled low relative to its emitter. This in turn will turn on Q1 which will turn off Q10 by pulling its gate to ground and disconnect the pack.

My question is do I need a capacitor in parallel with R8 to avoid false triggering i.e. any noise picked up by the cable from the thermal switch to the board?


texts:
I used to make interruptions on a STM32 the next way

#include "stm32f407xx.h"

#define USART3_IRQ_NUM 39

void USART3_IRQHandler(void)
{
    while(1);
}

int main (void)
{
    NVIC_Type *pNVIC= NVIC //Enable the USART3 interrupt
    pNVIC->ISER[1] = pNVIC->ISER[1] | (1<<(39-32));

    //Pending the interruption
    pNVIC->ISPR[1] = pNVIC->ISPR[1] | (1<<(39-32));

    while(1);
    return 0;
}

Im trying to do with a tm4c1294nctpd, I understand that both cards make use of the same ARM M4, so all it would take is to update the USART3_IRQ_NUM?.
Looking for the ISER and ISPR but I cant find it in the documentation of the tm4c.

Besides the include directive fails to locate the tm4c1294nctpd.h, it is supposed to be instaled alongside the code composer studio.


texts:
I'm looking at a brand new foot pedal for a Tungsten Inert Gas (TIG) welder.  This foot pedal uses cascading potentiometers to send a signal to the welder control system.  I'm getting unusual results when I verify the pedal using a Volt Ohm Meter. I'm measuring resistance between the wiper terminal and 'ground' terminal on the pot. Pedal off = 0 ohms, slight push 5K ohms ,push more... 10k up to 12.5k ohms at 3/4 full push.  If I go beyond that however, the resistance reduces from 12.5k down to 1.6k

This is a brand new pedal (yup, off of ebay.) Its obviously never been used. The pot has a smooth shaft with a spur gear attached.  The foot pedal has a 2" gear rack attached.. when you push the pedal down the rack moves and rotates the gear.  The movement feels extremely smooth. I can't find the spec for the pot for that manufacturer but I can find other manufacturers with virtually the same part #.  It looks to be a liner pot, 300deg of motion.  I don't have a lot of practical experience with potentiometers.

Here are my questions.
1) Does the 'hard' stop on a typical single turn potentiometer control full range of travel (i.e. zero ohms at one end of stop, max resistance at the other end of the stop)
2) How robust is the hard stop internal to the potentiometer?  (Clearly with a foot pedal input the functional foot pedal stop should be something mechanical external to the fragile potentiometer. )  If the external mechanical stop was not set, and you pushed the pedal hard, would the stop just break off or would there be other issues?
--3) Do they build rheostats with 300 degrees of function but withOUT an internal stop in them??  (That would make sense for exactly this type of application.. Manufacturer to provide range of motion control external to the pot. Mfgr to ensure alignment of zero and max set points.  If manufacturer allowed the pot to spin too far, the function is off, but there would be no permanent damage to the potentiometer.)

Part number: RV24YN20S B503 Mfgr: Hungyun.com

No, I've not taken this pedal apart to isolate the pot.. I don't want any 'warranty' hassles from the seller.

Yes, I can reduce pedal travel to lock at the max observed resistance.  I'll do that if I'm sure this isn't a different type of 'quality' problem which will cause issues later.

So hey, is the answer to #3 = yes, and I should just adjust the hard stop and move on?

Many thanks. Zip.

Update to add schematic and address some of the questions below:

This type of pedal is found on some 'low end' welding machines.. The side of the pedal has a dial with which you set the max. amperage. The foot pedal potentiometer allows you to easily change output amperage from zero to max amperage.  Obviously its a simple signal back to the welder's output control system.   For troubleshooting this new pedal, I removed an inspection panel allowing me to see inside the pedal.  I can see clearly every wire connection.  Nothing is grounded to the pedal steel chassis.  I was very careful to ensure that both pots are actuated CW (when viewed from end of shaft).  I was also very careful to ensure I have the wire and their attachments EXACTLY per the schematic I just now drew on digikey (scheme it)

For troubleshooting I have a nice fluke V-O-M reading between the red wire and the yellow wire with the "dial at back of pedal" set to zero.  The 'back of pedal' pot is a RV28P B103 (10K ohms).

I think I'm doing this right.. do you agree?  The other thing that is baffling me... I can understand a variable resistance going from 0 to big.  What I don't understand is 0 to big back down to a lot less than big.  I've never taken a potentiometer apart.  I can understand 0 --> max ohms --> max ohms -->max ohms --> zero but never 0 --> max ohms --> some middle value. Can anyone explain?


texts: Let's say you have -120Db noise floor on an amplifier circuit. You feed this noise into an ideal noiseless amplifier with an Av=25. What is the new noise floor? Proper equation?


texts: Can I use a low dropout voltage regulator to drop a 5V 100 nSec pulse to 3.3V?

texts:
I am using an analog switch IC with 3.6V as a maximum operating voltage. The input to the analog switch is the output pulse from a multi-vibrator which is 5V and 100nSec width.

I need to drop the vibrator output to less than 3.6V without affecting the pulse width. In this case, can I use an LDO to drop the voltage?


texts: Using diodes to wire a battery pack in series and parallel for different voltages

texts:
This is my first post on this site.
I have an EV design were I want 900V for a traction motor, but I need 450V for auxiliary equipment.

The first thing that came to mind is DC-DC converter, but it is expensive, and possibly has a notable power loss.

I thought about alternatives and about splitting up battery packs:

For example, lets say I need 36V for a BLDC motor, and 12V for a Arduino.
I use 3 12V batteries wired in series for 36V, and use diodes to wire them in parallel for the 12V.
The diodes stopping the batteries from shorting.

I know diodes have a considerable voltage drop, and for the EV application I would use ideal diodes.
By using the diodes, all batteries should drain equally, avoiding the battery pack unbalancing.
In the EV, the 12V batteries would be separate modules with their own monitoring.

Is this a crazy idea?
Would the battery explode for some reason?
And should I just use a DC-DC converter instead?


texts:
I have this anemometer (wind speed meter).

They provide some specs. But not the circuitry. It basically outputs pulses via a reed switch.

So I opened this instrument to see its circuitry. Here is what I saw inside.

First of all there is no indicator on the components. I mean I am guessing one is a diode an the other is the series resistor. The components are totally black and I read ..V on it, but its not clear, that's all.

On their website it says 330 ohm series resistance. So I'm more sure about which one is the the resistor.

When the switch is on, there is pot. diff. on R2 and when the switch is off there is no pot. diff.

The resistor looks like a chip resistor IEE written on it.

Anyway, my question if one of the component is a diode why can be the reason it is used for.

Since there is no inductive load it is not used for flyback purpose. Can it be a regulator?

Here is how it looks like (the circuitry is in the red window, rest is for measurement):


texts: Inverting OpAmp with voltage divider in feedback loop

texts:
Last week I was looking for a programmable gain amplifier (PGA) with high gains (> 100V/V) and low noise. As far as I know most of the PGA integrated circuits out there are just (inverting) amplifier stages with the option to digitally switch feedback resistors. Please take a look at the block diagram of the LTC6912 for example:

In my opinion one of the problems you'll face when trying to minimize noise in a high gain standard (inverting) amplifier configuration, is the size of the feedback resitor. The high gain forces the resistor to get big, which results into a lot of noise.

So I started looking for other configurations where the feedback resistor doesn't have to be this big.

I found a very interesting article: https://www.electronicdesign.com/analog/digitally-programmable-amplifier-meets-sensor-gain-ranging-needs

In this article a PGA is built upon a sort of inverting amplifier configuration with a voltage divider in the feedback loop. Because I can't find anymore information about his type of circuit I started analyzing it myself and found the gain formula as follows:

The simulation result below shows the circuit with a large gain of 65.7dB with feedback resistors of only 39k. This seems very useful to me, however I've never seen it before...

When I started reading further, I found that the author used the same opamp configuration as a band pass filter, shown in the picture below.

Because I'm very excited about this topology I'm trying to find formulas for the cut-off frequencies of this circuit. However I really don't know how to do it. Is there anyone who can help me out? More information about these circuits is welcome as well! Thanks


texts: What is the function of this transistor?

texts:
There is a tutorial on multi-stage amplifiers. It doesn't explain every details. The first stage is the typical amplifier with stable bias, and the last stage is the push-pull amplifier. But there is also Q2 which is direct coupled in between.  But what is the function of Q2 PNP transistor in the amplifier circuit below? Is that there just to invert the signal?:

UPDATE!: A better version is below. Any one can explain Q2?


texts: What if everyone uses voltage stabilizers?

texts:
A hypothetical question to improve my understanding of stabilizers and power supply.

Consider a rural village where frequent low voltage issue happens.

Now, if everyone there uses stabilizers to overcome the low voltage issue -

Does it give more load on the transformer which supplies electricity?
Why should it have more load? V * I will be almost same,
as less Voltage is compensated by more Current by stabilizer, so summation of
all Voltage * Current of each house will give same load on the transformer.
But possibility of main transformer burning up because of high current(from all house) caused by low voltage.
Most of the stabilizers go to cut off because of extreme low voltage?
What happens to a home which doesn't have stabilizer?


texts: Common Source JFET amplifier input voltage

texts:
I want to compare to different formulas which stand for same parameter/value.

Here is common source JFET amplifier circuit schematic:

Here is the first formula which should apply in general to all BJT and unipolar transistors:

, where Rin - input resistance (usually considered as voltage divider), Vsig - signal/generator voltage and Rsig - signal/generator internal resistance.

And here is another formula that applies for only for common source jfet source degeneration configuration:

, where Vgs - gate-source voltage, gm - channels transconductance and Rs - source resistor

Which one is correct for common source JFET?

To me it seems to be more correct the fist formula since the input signal is attenuated a bit if I'm not wrong, so in every case input voltage is a bit smaller that gate-source voltage, right?


texts: How close to a stepper motor do I need to shield the wires?

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I am trying to shield the cabling on my CNC mill. The motors, unfortunately, do not have connectors but instead have wire leads coming out from the motor housing. I can cut those wires about an inch from the motor and directly solder to the shielded wire, but will this 1" or so of exposed wiring defeat the purpose of shielding the cable? Unfortunately with the length of the cable I can't really slide the shielded housing up over the exposed wires without damaging the cable.

The primary goal is to reduce electrical noise which is causing false reports by limit switches (which is being addressed with an optoisolator / capacitor combo).


texts: Car battery voltage readings different with no load - normal?

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Typical car battery, 12V. While connected to the car, It read 12.38V on my multimeter. Using the absolutely same multimeter, I measured it once I disconnected it from the car - voltage went to 12.56V. This is in the span of 5 minutes. First measure was taken outside at 1C, second at home at 18C.

Car sat for 1 week straight before disconnecting it. I charged it and reconnected, after sitting for one day voltage was back to 12.4V, thus I eliminate some sort of crazy parasitic draw as else after 1 week it would be dead, not same as after one day.

Is that type of drop to be considered normal?


texts: Why isn't there a ground on a 7-Segment display?

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I was working with a 7-Segment display and saw that there is no 'ground', only COM 1 and COM 2 which I do not understand their meanings, either.

Currently, I have the positive rail connected to COM 1 and it seems to be working fine. It seems to work also when I have the positive rail connected to COM 2.

I am using the display to display binary digits, with each digit being a segment of the display. I am using a 4-Bit Binary Counter 74HC93 to make the binary digits, from descending order (15...0).

The weird part is that the wires from the Binary Counter go to the display, but never go to ground from what I see, which breaks the laws of electricity and physics. The display lights up.

Now I use a XOR Gate 74HC86 (because circuits.io does not have a working NOT gate, so I keep value A at 1 constantly, and then use it as a NOT gate), and when I hook up the output of A and B, it does NOT light up one of the segments of the 7-Segment display (I tried all of them), but DOES light up a standard LED. It seems to follow the laws of electricity and physics.

Please explain how I can use the XOR gate to light up one of the segments of the display, what COM 1 and COM 2 means, and how lighting up one of the segments WORKS from the 4-Bit Binary Counter 74HC93.

Here's a diagram on a breadboard with power on and off (Made on circuits.io):

Notice how the DP pin is connected, although isn't lighting up.

To verify that it isn't the XOR gate:

(If you couldn't tell, the LED is lit)

Lastly, it seems to "work" if you have some of the output going to ground. I set up an LED WITH the display, and it fried both; very strange.

If I can have any explination, how to make it work, what COM 1 and COM 2 is, that would be greatly appreciated. Thanks!


texts: With regard to GPS signals, what is the significance of I-parts and Q-parts of Complex signal?

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What is the significance of I-part & Q-part magnitudes and imbalances in the screenshot?
They are listed next to the red Complex signal diagram.

Imbalance of I-part: 4.7%

Imbalance of Q-part: 25.8%

Magnitude of I-part: 56.5%

Magnitude of Q-part: 55.7%

I am running uBlox uCenter and looking at the Extended Hardware Status message.

Is there an ideal percentage of I and Q parts?


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I have a few questions about the LM358.  The first is regard to the schematic below.  I'd like to know why RB is there?  (What purpose does it serve and how do you know?)

The second is with regard to the figure below showing open-loop response.  I don't quite understand why there is feedback (the cap and the 10M resistor).  Could someone please explain why?

My last is, how does one know what the maximum frequency that one can put into an op-amp is?  For example, I think I read somewhere that tying a terminal to a square pulse generator is bad because the square pulse has an infinite bandwidth and putting something with infinite bandwidth into an op-amp is not good.  How does one know how high a frequency an op-amp is rated for (without breaking it)?


texts: Is there a circuit that 'blocks' or 'opens' another circuit as long as there is current running?

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I want to make a light source that runs by main power and only uses batteries when there is a power outage.

Note: Please explain in simple terms, since I'm just a middle school student.


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I recently bought these LED strips. They are supposed to run on 12V/72W and have 300 x the SMD 5050 LEDs on it.
Schematic:

simulate this circuit – Schematic created using CircuitLab
The voltage values on the schematic have been measured with a multimeter. "560" is written on the resistors.

As you can see, the resistors account for 5.6V - that makes 46% of the voltage (or power) consumed by the strip!! Is that normal?


texts: Understanding a simple crystal oscillator transmitter

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I try to understand the AM transmitter on the figure below, but I cannot figure out two essential things. The carrier frequency is created by the crystal oscillator chip.

Why does it suffice to put the audio input in parallel to the battery, in order to add this signal (baseband signal) to the carrier frequency?
Why do we need the capacitor?


texts: I have been strolling towards being a circuit designer, using eagle and ltspice and i am trying to learn about new ic's and stuff. recently the thought about how does an LTXXX module and LVXXX(or LMXX) module differ to each other if they are both based on op-amps.


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In below Design , working ok with Vcc was 5V, but due to some modification I have only 15V power supply available to use this circuit. So i change as per 15V requirement ( see below image),
Pin 1 is open Drain so did not removed R34
Removed R43
WDI_IO is drive form micro controller
Reset of Pin 1 goes to Trigger input of 555 IC  ( which has max working voltage of 18V , not shown in SCH)

Since U3 max voltage range is 5.5V , So I am thinking to change FB28 with 1K resistor and C40 with 5.0V Zener Diode.

Zener Spec:- 5.0Vz, Test Current 5mA
Max PD 500mW
So Max current = 500mW/5V = 100mA
Min Rs = (15V-5V)/100mA = 100oHM

I choose 1K as Series Resistor so Current will be

I= (15-5)/1K= 10mA, This can supply both zener and load whch is my IC I as per data sheet IC Current suppy need in approx 200nA).

Does this look ok ,to use zener in this case as my load current in not much.


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I cannot solve the convolution based on \$h= e^{-t}\$  for \$ t\ge0 \$ and \$u(t) = 1-t \$ when \$ 0 \le t \le1 \$.
Every time I try I keep getting a factor with \$ te^{-t} \$ whilst the answer shows:
\$ y(t) = 0 \$ if \$t<0\$
\$ y(t) = 2-t-2e^{-t} \$ if \$0\le t\le 1\$

\$ y(t) = e^{1-t}-2e^{-t} \$ if \$t>1\$

And I get:

\$ (1-e^{-t})+te^{-t}+(e^{-t}-1) \$
After solving the integration by parts with boundaries of 0>t


texts: Are there different meanings behind digital to analog in digital audio and PWM?

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I'm getting into producing sound waves with various controllers and the two ways DACs are referenced is confusing me.

The first kind of DAC conversion would be from PWM. If a an audio signal is built up of extremely fast changing voltages, PWM isn't doing that. It's just pulsating extremely quickly at different rates so that a speaker will effectively output a wave built up of those simulated voltages. Presumably, to get better output quality, you would convert that to an analog voltage for each small step in the wave.

The other kind of DAC I can only differentiate by calling it a "signal" DAC. If I have a wave made of all of these steps in voltage, a DAC might be used to smooth the transitions to a true analog wave without a sampling rate.

It seems to me like a DAC can be used to convert PWM to analog voltages while still being a digital audio output, then a DAC can also be used to convert that digital signal to an analog wave.

If I want to buy a very fast DAC to just convert a PWM signal to true analog voltages with a sampling rate, what would you call that device when not referring to a DAC that changes a digital audio signal to a completely smooth wave. Being a beginner, I just don't know what to google. There's all sorts of answers about DACs and solutions involving op amps, and the term DAC is everywhere. I'd just like some clarification on what the term refers to in audio and if the definition is somehow changing based on the context.


texts: How should I find the DC bias values for this circuit?

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I would like to build this circuit, but I have to find the DC bias points first. Based on current requirements of total 11mA, I decided to set current through the differential amplifier stage to be 3mA, and 8mA through the gain and push-pull stage combined. I have chosen diodes with forward voltage of 0.7, and transistors with Vbe of 0.7 as well.
However, my understanding is that beta changes with temperature so I cannot have a fixed value for it. I'm not sure if I can assume Vout and Vin+ and Vin- to be 0 at the quiescent point also. How then should I proceed in the calculation?