texts: register with enable signal, problem of understanding simulation results

texts:
I simulated a 32-bit register with an enable input in Vivado.

The following things are unclear to me:

I don't understand why 0xFFFFFFFF is latched at 5 ns and not the previous value 0x0abcdeff.
Because the change of the input signal from 0x0abcdeff to 0xFFFFFFFF is initiated by the rising clock edge at 5 ns.
Until this signal change propagates to the register input in my opinion the old value 0x0abcdeff should have been latched.
Doesn't the input signal need to be stable before the clock edge for at least the setup time to be latched correctly?
Would a real circuit with the same signal changes as shown in the simulation latch 0xFFFFFFFF or 0x0abcdeff?
In other words does the simulation describe the waveforms that occur in the hardware?
Am I using the enable signal correctly to make it work in hardware?
For example if I want to latch a value at the rising edge at 25 ns, do I have to set the enable signal already at the rising edge at 15 ns and reset it at 35 ns?
Because if I set enable at 25 ns the propagation time until it reaches the flip-flops would perhaps prevent them from latching the value correctly.

Here's the verilog code:

module Nbit_register(
// inputs
clk, enable, d, reset,
// outputs
q
);

parameter N = 32;

input clk;
input enable;
input reset;
input [N-1:0] d;
output reg [N-1:0] q;

always @ (posedge clk or posedge reset)
begin
    if (reset == 1) begin
        q <= 0;
    end else if (enable == 1) begin
        q <= d;
    end
end
endmodule

And here's the testbench code:

module tb_register;

reg clk;
reg reset;
reg enable;
reg[31:0] d;

wire[31:0] q;

Nbit_register register (
    .clk(clk),
    .reset(reset),
    .enable(enable),
    .d(d),
    .q(q)
    );

initial
begin
    clk = 0;
    reset = 0;
    enable = 0;
    d = 32'h11111111;
end

always
    #5 clk =  !clk;

initial
begin
    d = 32'hABCDEFF;
#5  enable = 1;
    d = 32'hFFFFFFFF;
#10 enable = 0;
    d = 32'hAAAAAAAA;
end
endmodule

Ok, I connected two 32-bit registers in series now as suggested by Sean Houlihane
and this is the simulation result:

These results make sense to me, but I have one question left. Is it ok to reset the enable already at 25 ns or do I have to wait until the next rising clock edge at 35 ns for it to work in hardware?


texts: Ground Plane, Bypass Capacitors and Differential Pairs

texts:
I've placed a KSZ9031MNX Ethernet PHY on my board, and am now trying to get power routed to it. The digital side will merely be annoying to do, I think, but I'm at a complete loss on the analog side.

The analog supply pins are placed between the inner and outer signal pairs and I have no real good idea where to place those capacitors (except for the backside, which I'd like to avoid as these would be the only components there).

I've highlighted the positive supply pins and the corresponding pads on the capacitors I plan to use. The differential pairs going to the magnetics should be fairly obvious; I think these will have to be moved around a bit still.

My first attempt looks like this:

The traces on the bottom layer routing the power to the vias are still missing, but I think that might work.

Is it a good idea to have the capacitors bridge the differential traces to save space, or will that have negative effects on signal quality?

Should I try to keep the ground plane between the differential pairs, should I connect that area to analog ground to give the analog ground connection in the middle more copper, or is that irrelevant?


texts:
I am trying to use Transistor model as in the NGSpice manual 8.2 BJT Models (NPN/PNP):

.model QMOD1 BJT level=2

however, I got this error:

  q1 n15 n16 n17 qmod1
could not find a valid modelname
Warning: Model issue on line 61 :
  .model qmod1 bjt level=2.end ...
Unknown model type bjt - ignored

So, why I got Unknown model type bjt ?


texts: AC blower with run capacitor sometimes does not start up

texts:
I installed an AC blower motor into a cabinet to act as a ventilator for some electronics. Thankfully it has a wiring label. Based on the label, it must be a run capacitor induction motor. It specifies a tiny 0.6 uF capacitor. I bought a cheap one off eBay.

This is the fan and a picture of the wiring label:

This motor has two blowers on the same shaft. They are a typical centrifugal style. I connected the run capacitor across the yellow and red wires. I connected the mains hot to the black wire. The neutral is connected to the blue wire. You can see the little capacitor in the picture as well.

Here is what happens when I power it up

It turns on and spins up very slowly. I think the slow spinup is normal. When the motor is running the RPM alternates very slightly between two distinct RPMs. Its noticeable because the pitch of the noise changes.
It doesn't start on its own, but if I bump the motor it will spinup and start running like case 1.

Do I have this motor wired correctly? Is the RPM "hunting" normal? Is it possible the motor is bad?


texts:
I have attempted to make this board below at home. Applied negative photoresist paint, left to dry for about 4 hours each side over a radiator, applied a double layer tracing paper with the artwork on each side (4 sheets of tracing paper total), exposed it outside for 25 minutes for each side (cloudy winter day in Europe), developed with washing soda + water, etched with an unknown ratio solution of HCl + H2O2.

At first the solution was 2 : 1 of HCl 37% : H2O2 3%. I have etched a PCB in it fine, loosely put a lid on its opaque container and let it sit for a week. Then I have attempted to reuse the same solution about one week later but it would not etch. Poured some H2O2, nothing, poured some HCl, still would not etch, then poured a bit more H2O2 and it did its thing, but slower than the original solution.

In the picture below the is missing copper and some of the copper is a bit stained.

In this second photo the far side looks OK, but the near side has lots of missing traces (towards the middle of the board).

Any clues on what might need changing ?


texts: I'm going to use this circuit to control some lamps. As I know a short circuit would cause the Triac to burn very fast and I need a way to protect it. Using fast fuse is cool but I need to know If any other way that doesn't need Fuse change or something like


texts:
I'm thinking of buying a DC Motor to play with. I'm wondering is there any way to pass a wire up to electronics spinning on the shaft?

I'd love to pass 4 wires (vcc, dcc, clk an data) lines from electronics sitting next to the motor up to some electronics being rotated by the motor.

I'm wondering if there is a connector of some kind that would let me do such a thing.


texts:
I'm having a problem with odd noises in my guitar amp and I'm really struggling to find anything online.
Here's a sample of the noise:
https://www.dropbox.com/s/z7ggll3q6219l0o/Noise.mp3?dl=0
I've checked and the frequency is 1350hz with harmonics at 4050Hz and I guess at 2700Hz too. This appears to be something I've found to be a "ripple control signal" (German: Rundsteuersignal) which is normally quite a bit lower in other regions but in Cologne it's 1350Hz.
I did try one of these: https://www.conrad.de/de/p/ehmann-0463x0000-zwischensteckdose-weiss-431858.html
However the filtering starts too high and does nothing to help my situation.
Does anyone know of a way to filter out this modulation? Is there some kind of adaptor I can stick in the socket that will get rid of this?


texts:
This is a wideband differential LNA. I am trying to calculate the input resistance of this circuit but the result is not anything similar to the result shown in the picture below.
Could you explain how can I get this input resistance?
Thank you.

Link to the source:
http://www.filedropper.com/2015awidebanddifferentiallow-noise-amplifier2


texts: Deciphering Portable Appliance Test results

texts:
All UK companies are required to perform yearly tests of all portable appliances used in the office, redundantly called "PAT tests". I've recently received my first test result sheet, and while all the equipment passed, there are a couple of columns which puzzled me as to what they might mean. Search engine perusal did not turn up anything relevant.

Here are the column headings and values for some of my appliances:

Item    INSRIS      Earth Bond  VIS     Overall

1       >299        0.03        PASS    PASS
2       DI          DI          PASS    PASS
3       L VOLTAGE   L VOLTAGE   PASS    PASS
4       >299        0.1         PASS    PASS
5       DI          DI          PASS    PASS

I think "VIS" might stand for visual inspection, but I'm lost as to what "INSRIS" and "DI" stand for, and what the values in those columns mean. Any thoughts?


texts: How much power am I consuming from using an AC-DC converter?

texts:
I am duped on how power supplies work as I am not an electrical engineer but rather a hobbyist or a DIYer.

I am looking for cooling solutions and discovered the inverter technology.

If I understood it correctly, the compressor is run by DC, running at variable speed for whatever the system needs. If I want to assemble a phase-change system, using a DC compressor, and I have an AC power source (residential) and convert it using an AC-DC converter, I do not know how much electricity I am consuming.

This is what I am thinking, and these are just examples for simplification: suppose that I use a switched-mode power supply, rated at 10 A, and connect it to 220 V AC - the power consumed is 2,200 W. If I connect it to a load, DC, for example it outputs 12 V, and the load uses 5 A, so that is equal to 60W...

My question is, how much electricity am I consuming, and consequently have to pay for? Is it 2,200W or 60W?


texts: Making Device to Send Data to Smartphones: 100m range, 1kb/s bandwidth, low power

texts:
What I want to make: A device that immediately sends a notification if the device incurs a moment of high acceleration. The notification needs to denote the acceleration. There is no guarantee that there will be a The device needs to be very small, about the size of a penny, and not much thicker. The device should last for a year using a standard watch battery (about 80% of the time, the device will not be moving at all, the device wouldn't send more than 100 times a day).

Bonus qualities:
 - This notification would be sent to a smartphone for convenience and possible future visualization purposes.
 - The notification would be visible from up to 100m away from the device (this could be achieved via wireless signal).

What I'm asking for: Advice on through what medium this notification could be sent (Bluetooth, Zigbee, Wifi), and if it can't be sent to a smartphone, what it could be sent to to achieve the goals of the device (most notably, immediately notifying that the device was accelerated, and how much it was accelerated).


texts: How do you attach an oscilloscope ground spring?

texts:
Sometimes you need to ensure that your oscilloscope probe ground lead is not creating measurement error such as ringing and overshoot. In various forms, I have seen (and successfully used) a ground spring for measuring a circuit. I have shamelessly borrowed AndrejaKo's image to make sure we're all on the same page:

I have determined that this lead length is essential in some of my test configurations, but it requires constant attention to make sure I'm not shorting something out, loosing a connection, or probing the wrong thing. This limits my ability to do other tasks in the test setup, and makes it impractical for other setups that do not allow that sort of access safely (blind or hazardous conditions).

How do I attach a scope probe to the circuit under test with a 1/2" (1cm) ground lead, or otherwise get a hands-free high bandwidth setup?


texts: how to understand a positiveresist PCB developed enough

texts:
I have a positiveresist PCB that I exposed the board to UV to transfer a layout for 5 min. I use UV box that I bought from Mega UK.

After that I put the board onto positive developer. As I did not have a measuring cup, I used a small cup to obtain NaOH to water ratio 1:10 (the datasheet says 20 gr onto 2 liter). Then I put the PCB onto the solution (temp. around 30 C as datasheet says) and waited some time, then it solved all photoresist film including the layout, then I thought maybe the solution was too strong and added more water (the ratio should be 1:20) then put a new board onto the solution, I saw the layout of the board in 15-20 sec then I removed the board and put it under a cold tap water, then the all layout washed away and I had a blank board.

Can you tell what I am doing wrong and how can I understand when to remove the board from the solvent?


texts: MAX31865 RTD converter will it acccept only floating inputs?

texts: We intend to use MAX31865 for measuring resistance values. Since MAX31865 is RTD to digital converter, kindly clarify whether the MAX31865 will accept only floating inputs or it can be used with electrically grounded reference, i.e. can RTD -ve input of MAX31865 be grounded?.


texts: i'm designing a varable-frequency drive with 2 H-bridges based on IR2108 half-bridge drivers. I want it to drive a 220v single-phase motor. Reading the datasheet i got a little confused on choosing the right bootstrap diode (see the datasheet, this is the only diode on Typical connection chart): a lot of people on various forums wrote that they used Schottky diodes for their design. As the wiki says, the maximum reverse voltage of Schottky diodes is less than 200 V. So, assuming that the working voltage of my circuit will be notably higher, should i just use regular diode with appropriate voltage? What problems may come up with this solution?


texts: How does torque control work in three phase motors?

texts:
For a project I am working with a three-phase AC brushless motor, connected to a motor driver. The driver allows digital control over the motor in position, velocity or torque modes.

Below are a few points leading up the final question

My understanding of three-phase motors in one sentence: the three phases over a number of coils produce a rotating magnetic field, that rotates the motor shaft with the same speed (synchronous).

So the speed of the motor is completely determined by the frequency of the three-phase input. Correct?
So the motor driver varies the frequency of the three-phase power going into the motor. Correct?
So when the motor is stalling but not off, the frequency in the three phases simply drops to zero, resulting in three different fixed voltages. Correct?

Then how does the motor driver make the motor exert a target torque, independent of the rotational speed?


texts: Why is the gain of feedback amplifier Vo/Vs?

texts:
Amplification = Output/Input

Then the amplification of the feedback amplifier should be Vo/(Vs +- Vf)

Here,

Vf = feedback signal

Vo = Output signal

Vi = Input Signal and Vi = Vs +- Vf

Vs = Source signal

I have used V instead of phi


texts: Symbols: Double-arrow circle enclosed "10" on electronic appliances

texts: What does the symbol that says 10 inside the double arrowed circle mean? I have seen a similar symbol on another appliance that had the number 25


texts: What ultrasonic sensor+emitter should I use for my medical ultrasound project?

texts:
I'm building a medical ultrasound scanner as an educational DSP project. I'm not expecting to produce something medical grade, but I do want to be able to detect the location of a high-density ball bearing inside a low-density balloon of ballistic gel. I'm putting together my prototype with a Saxo/FlashyD FPGA sensor acquisition device and a batch of SPM0404UD5 ultrasonic sensors, because they're cheap SMDs and I don't know why they'd be inappropriate.

I'd like to use ultrasound transducers similar to those used in medical ultrasound equipment, but unfortunately the manufacturers of those devices don't seem to publish data sheets. Also, I'm not sure who would sell such components, but it ain't digikey.

Any idea what sort of sensors they use?


texts:
I am not able to get the concept of how to calculate the output voltage.
What I did was- I assumed the network N as such-

simulate this circuit – Schematic created using CircuitLab

Now added two networks-

So if I assume R2/(R1+R2)=x. Then Vo=x*(V1+V2)/2.
Accordingly from the question the value of x is 3.Thus the answer of Ques 1 is 0 and the answer of ques 2 is 3.
Is my analysis right?
If possible can you point out to me any reading material for these kind of problems.


texts: I need help identifying this potentiometer

texts:
It is off of a Hifonics mono channel car audio amplifier.
This is the back.  It has 6 prongs and was removed from the gain spot on the amplifier:


texts:
I wrote the code for radix 4 booth's multiplier and also its testbench. No errors are coming, but, the output is not coming correctly. For example, -89 multiplied by 10, it is showing 10032. I am uploading the code and testbench. Please help.
module booth_mul #(parameter N=8,M=8,logN=4)(clk,start,rst,A,B,y,done);
input clk,rst,start;
input [N-1:0]A;
input [M-1:0]B;
reg [M:0]B1;
output reg done;
output reg [N+M:0]y;
reg [logN-1:0]count;
reg [N+M+2:0]acc;

always@(posedge clk)

begin
B1={B,1'b0};
if(rst==1'b1)
begin

    acc = {N+M+3{1'b0}};
    count = {logN{1'b0}};
    done=1'b0;
end
else
begin
    if(start==1'b0)
    begin
        acc[M:0] = B1;
        acc[N+M+2:M+1] = {N+2{1'b0}};
        count = {logN{1'b0}};
        done=1'b0;
    end
    else
    begin
        if(count<M)
        begin
            case(acc[2:0])
            3'b000 : acc = acc;
            3'b001 : acc[N+M+2:M+1]<=acc[N+M+2:M+1] + {A[N-1],A[N-1],A};
            3'b010 : acc[N+M+2:M+1]<=acc[N+M+2:M+1] + {A[N-1],A[N-1],A};
            3'b011 : acc[N+M+2:M+1]<=acc[N+M+2:M+1] + {A[N-1],A,1'b0};
            3'b100 : acc[N+M+2:M+1]<=acc[N+M+2:M+1] + ~{A[N-1],A,1'b0} + 1'b1;
            3'b101 : acc[N+M+2:M+1]<=acc[N+M+2:M+1] + ~{A[N-1],A[N-1],A} + 1'b1;
            3'b110 : acc[N+M+2:M+1]<=acc[N+M+2:M+1] + ~{A[N-1],A[N-1],A} + 1'b1;
            3'b111 : acc = acc;
            endcase

            acc = {acc[N+M],acc[N+M:1],acc[N+M:2]};
            count = count + 2;
            done = 1'b0;
        end

    else
    begin
        count = count;
        y=acc[N+M:0];
        done = 1'b1;

    end
    end
end
end
endmodule

TESTBENCH
module TB_booth_mul;
parameter N=8,M=8,logN = 3+1;
reg clk,rst,start;
reg [N-1:0] A;
reg [M-1:0] B;
wire [N+M:0] y;
wire done;
booth_mul #(.N(N),.M(M), .logN(logN))UUT(.clk(clk),.start(start),.rst(rst),.A(A),.B(B),.y(y),.done(done));
initial
begin
clk = 1'b1;
rst = 1'b1;
start = 1'b0;
A = 8'd89;
B = 8'd10;

#100 rst = 1'b0;

#20 start = 1'b1;

#200 start = 1'b0;

A = -8'd89;
B = 8'd10;

#20 start = 1'b1;

#200
repeat(50)
begin
if(done == 1'b1)
begin
#10 $display("A = %d, B = %d, AxB=%d",$signed(A),$signed(B),$signed(y));

#10 start = 1'b0;
A = $random; B = $random;
#20 start = 1'b1;
#200;
end
end

$stop;
end
always
#5 clk = ~clk;

endmodule


texts: I wanted to know what are the techniques employed in heavy vehicles to avoid short circuit or protect if short circuit happens? Since the batteries in heavy vehicles are highly powerful and short circuit will be very dangerous I think. please advise.I can think of fuses apart from that any other techniques.


texts: Potential causes of Atmel "system" failure after reflash with same binary

texts:
I'm working on a small "cartridge"-like subsystem which attaches to the main device via a 20-pin connector.

On the cartridge, there is an ATmega16a microcontroller and an AT45DB081D flash. I needed to modify a couple of bytes in the flash (external to MCU), so I did the following:

Used a SOIC-8 test clip to connect the flash chip to an SPI interface on a Raspberry Pi.
Used flashrom to read the binary contents 3 separate times.
Used sha512sum to ensure the binaries were identical - they were.
Modified the binary and flashed it back to the device - it verified.

I then noticed that the host device identified the cartridge as invalid/faulty, so I reflashed the original binary.

The device still recognises the "cartridge" as faulty even after reflashing the original binary, so my  question is:

Are there any mechanisms in this flash device which would allow the MCU to identify it as errant, even after reflashing the original binary as seen by flashrom?


texts: For a stack of thyristors, is the "critical rate of rise of off-state voltage" scalable with the number of thyristors?

texts:
For example, in a datasheet I am looking at, the critical rate of rise of off-state voltage is given as $$2000V/{\mu s}.$$

If I have, say, five of these thyristors in series, would the total critical rate of rise of off-state voltage then be $$5\cdot 2000 V/{\mu s}?$$

Thanks!


texts: connecting wifi module to proxy based wifi

texts: I have a wifi module with micro-controller , but my college wifi uses proxy, SO how can I program proxy credentials in my C program so that my wifi module connected to micro-controller can connect to wifi. My wifi connection requires only proxy (like 10.x.abs.pqr) and no username or password authentication.


texts:
I found a schematic online of a 433mhz receiver which I am trying to replicate.
1 component is an inductor 16.6nh smd. However because I cannot find that exact value I was thinking to use an inductor with similar value 16nh.
Would it work or not?


texts: Using 2 laptop power supplies to make plus and minus supply

texts:
I have set of M audio AV30 speakers that had a failed power supply (the transformer).  I replaced the transformer with the closest thing  I could find.  The original transformer had a metal shroud that reduced mains noise, but the replacement transformer was not the same shape. The end result is that the speakers work but I have some mains hum.  The speakers require a plus and minus 19 volt DC supply.
I read that one can create a plus/minus  supply by joining two floating (laptop) supplies.  So plus 19v of one supply joined to '0v' of other supply.
Hence                19v  0v-19v  0v   =   +19v    0v    -19v
I ordered two DELL 19V (ADP-50SB) laptop power supplies,  but long story short, I found that the earth pin from mains plug  was connected to the  0V of the DC side of the power supply.   So the power supplies are not floating.
My questions  are .....

Can I simply disconnect the earth in one power supply and so it becomes a floating supply?

In the same power supply, can I connect the earth to the 19V ,  as this will happen anyway when I connect this 19V to the 0V of the other supply.

Or should I disconnect  both earths?   ( the mains earth is connected to a copper sleeve around the power supply.  The same copper sleeve is connected to the 0v DC pin.)

I do not know enough about side effects of floating power supplies.
Thanks


texts: Is sending a signal over 433.92 MHz blocked by plastic?

texts:
to be honoust: I never understood radiowaves; how I can receive radio in my house? Transferring a complete video through air from laptop to router? Never a clue.

So with that (lack of) knowledge my question: I am sending data with a little sending device which runs at 433,92 MHz (something like this http://nl.aliexpress.com/item/wholesale-Free-Shipping-1pcs-lot-315MHz-433-92MHz-Wireless-Remote-Control-Transmitter-Board-Module-TDL-9912/359001088.html).
(it's attached to my raspberry pi)

Now I want to finalize the project, so I thought to wrap it up in a nice plastic box (the led lights will be popping out of the plastic box, but as I don't think the sending device is pretty, it will be INside the box). And now the question: will the signal be influenced?

I guess it probably is in some way, but are we speaking in the terms of 1 or 2 percent, or does plastic (like a drink cup plastic) always take 50% of the signal or....


texts: Single balanced mixer, multi-tone analysis

texts:
I realized the circuit shown below on ADS.

Schematic of the mixer can be shown below.

As can be clearly seen from the figure below, to perform a multi-tone analysis RF signal is feeded with two tones having equal amplitudes. Also, if you compare the figures of the schematics, there are additional low-pass and high-pass filters on the mixer.
Components of the low pass filter is calculated by using AADE Filter Design software, filter which is a Butterworth LPF is shown below.

The problem arises when the two tone harmonic balance simulation gives the results which can be shown below.

I feed input with two equal amplitudes, but at the output I get two non-equal amplitudes. Marker 2 and marker 4 should be equal.
Why do I get such a "distorted" output?


texts: What role does the capacitor play in an AM demodulating circuit?

texts:
The goal of this question.  Demodulate the AM signal.

(Please assume a diode demodulating AM radio of the most imaginable simplicity.)

I am assuming an alternating current sine wave is coming into a wire from the antenna?
In order for an envelope to coexist with  the sine wave the amplitude is varying I assume?

If the antenna is the correct length then resonance of some fundamental frequency of the EM wave allows the signal to increase in strength in the antenna before it enters the diode? An assumption on my part.

The signal is then converted to DC but since the strength of the signal determines the fluctuations in the "envelope" the voice information is in "duplicate" so the bottom half is cut out of the rectifier , no?  From this point I am lost.

The sketch shows a capacitor in parallel. I know what a capacitor does in principle.  Is it attempting to maintain the voltage as the current changes since capacitors don't like to have their voltage changed and resist it, no?  Please complete my picture to demodulate the AM signal.


texts: Can I break a radio tranceiving device by operating it with no antenna connected?

texts: People tell me I shall not use my CB-radio station without an antenna connected or it will result in damage of the device. Is this true and why is this?


texts: Could the terminal length of components like resistors be reduced?

texts:
When breadboarding the length of the wires on resistors (through-hole) is quite comfortable. The same holds for other components like diodes or capacitors. I presume the terminal length was made to fit this application, because it essentially is similar to how, 60 years ago, valves were wired up with resistors "in the air" (without a pcb).

However, as virtually all through-hole resistors go into a pcb, terminals could be half the length. Or, if they were angled, they could have the correct length for pcb insertion. I have actually seen those, but I can't find them on digikey, for example, so I presume they are not common.

Copper is relatively costly and getting scarcer. The cutting of long terminals only seems to cause additional waste, therefore unnecessary recycling and/or environmental costs.

The question is: is there something holding back a transition to shorter terminals lengths, or would most machinery be able to accept it without problem? Restated: why haven't terminal wires been shortened a long time ago.

I get expect to get answers referring to cultural aspects, as standards reduce costs for everybody, but I am more interested in the underlying technical obstacles (to reducing waste). Would we be able to move on, or not? Why not?


texts:
I have large amounts of inductors and transformers from power supplies or other undocumented sources. They are of course completely unmarked and I have no idea what kind of ferrite material they are made of but sometimes I would like to use them in one-off power supplies or other experiments since ferrite cores are quite expensive to buy in low quantities.

Do you know of any good methods to determine the important characteristics of the cores?
\$A_L\$ is quite easy (I just wind \$N = 10\$ turns and measure the inductance using \$L = N² \cdot A_L\$) but what about \$B_\rm{max}\$ or maximum useful frequency? Are there other parameters I should have in mind?

Basically I like to know all the good tricks you know for determining suitability of cores of unknown origin. :)


texts:
So I have been having trouble understanding the difference of  Rc filters that have the capacitor in series with the resistance and Rc filters that have the capacitor parallel to the resistance .
To make this more specific , why are both low pass filters? Can all filters be made in parallel and in series?


texts:
Im looking at some spring probes, such as are used in test fixtures (NOT on multimeters or scopes).

All the catalogues (Ingun, Coda-Pin, etc) seem to organise by a dimension they call "centers" but never seem to show a matching dimension on diagrams... what is a "center" in this context?

Ta


texts: Where is the oscillator in the 555 chip provided here?

texts:
I have tried a while to understand how the 555 chip is built. I opened the datasheet of TI available  here :
http://www.ti.com/lit/ds/symlink/lm555.pdf

Anyway this is the schematic from the datasheet

how do i understand it :

Q1 - Q6 : a current source ? why to use 6 BJTs and not 4? ("current mirror" ?)

Q7 - Q13 : current source as well?!

Q15 - Q16 : what are they for?

Q17 - Q22 : is it a kind of inverter???

Q23 - Q24 : what is this part role?

Q27 - Q28 : what is this part role?

Q25 and Q14 : the only one that understood (closing Q_23 and set output to HIGH Z)


texts: How to determine op-amp gain with active feedback?

texts:
The Howland current pump uses an op-amp in the configuration below with a resistive feedback network which gives me the gain show below:

But if I decide to swap the feedback resistor for an instrumentation amplifier for less noise and better resolution, what will the new gain be? I've tried searching but can't seem to find anything on this.

simulate this circuit – Schematic created using CircuitLab


texts: Controlling a brushless DC motor with an Arduino--*without ESC*

texts:
I want to build an ESC using an ATmega328 (used in Arduino Uno).  This is the Brushless DC Motor I've chosen and this is the MOSFET I've chosen to gate the power supply.  It will be used to drive a variable speed propeller in one direction.

I understand the concept of "rotating" the power but I can't seem to complete the puzzle.

At what frequency do I have to gate the MOSFET for maximum speed?  The motor is a 700kv at maximum 14.4 volts.  Does that mean I have to gate the MOSFET at 10.08MHz (700KHz * 14.4)?
Do I have have to sense the rotor position? (Using Hall Effect or sensor)  If so, why?
Is a square wave (PWM) or sinusoidal wave better for this application?

Edit:

I mistook 1kV for 1000rpm-per-volt instead of the correct 1rpm-per-volt.  I also was thinking revolutions-per-second instead of the correct revolutions-per-minute.  It is much more plausable now.


texts: I have this question of banked and non banked memory specifically for freescale s12x  controllers. They have both banked and non banked ram and flash memory. I know it will start putting first data in non banked ram, now suppose I exceed the limit will it automatically start putting in banked ram? If I have to take care then I feel I will loose the advantage of banked memory. Similarly for flash memory.


texts:
I have a very simple design that I'm now working on the PCB layout for. And at the moment I'm thinking about the issue of decoupling capacitors. The board is very simple and only consists of this:

 1 x ATtiny85
 3 x resistors
 1 x 32.768 kHz crystal
 2 x 22 pF caps for crystal
 3 x LED

The board is powered by 2xAAA batteries. The MCU is clocked at 32.768 kHz by the crystal.

So as you can imagine it's just a real-time clock with some additional logging functions. Now, the question is this: Do I need decoupling capacitors for this circuit? If so, do I place them:

1. Between the Vcc and GND pins of the ATtiny, close to the ATtiny

2. Between the Vcc and GND traces, close to the battery

3. BOTH of those, i.e. use two capacitors, one close to the MCU and one close to the battery

...or can I simply ignore decoupling caps for a circuit as simple as this? And do you have any advice on which capacitance to use for the decoupling caps?

Also, if I do need decoupling caps, it would be great if someone could explain the advantage of them. I.e. do they help improve the stability of the real-time clock? Do batteries normally have voltage dips in certain circumstances?


texts: Implementing 3 variable boolean function using mux 4 to 1 and inverter

texts:
I'm trying to understand if it's possible to Implement boolean function with 3 inputs using only mux 4 to 1 and inverter.
As far as I understand I can put in the selectors the first 2 variables to select between the 4 options.
then I have another variable which I can connect to the 4 options (00,01,10,11) but I can't solve it to make sure it will suffice any 3 variables function.

I would like to know how to approach this kind of questions, how to "prove" such things?

Thanks.


texts:
I'm using this chip to drive DMX as is common. With no differential load/receiver load it gets hotter than is comfortable to touch, and with a receiver, still warm but not so hot.

The circuit is very similar to DMX on Arduino with RS485 with no isolation and both enables pulled high to transmit.

The circuit is working as expected, but should the supply to the chip be current limited?
Why so hot?

Schematic:
a extract http://www.robocow.net/extract.png


texts:
The cheap ESP8266 boards are offered on ebay with two built-in antenna options:

with a PCB trace antenna
with a ceramic(?) antenna

(PCB photographs see below.)

Has somebody bought both and compared their signal quality?
Or can somebody from looking a the desing hazard a guess how signal qualities will compare?


texts: radio Link works with laptop but not with PC

texts:
I have a complicated issue.

I set my HM-TRP radio modules to use:
117Khz receive bandwidth,
39Khz deviation frequency and
38Kbps air and data rate.

The attached picture is my basic room setup for the module operation. Details follow...

The "Test zone" is a wooden table and at the bottom right shown as a red circle is where one of my radio modules sit (attached to my circuit)

The box marked "Desktop" is my IBM think-center Desktop computer case.
Box next to it is a table and the flat panel monitor (shown as a vertical line) sits on top of it.
A little to the right of the monitor is the second radio module (see red circle) on the adjacent table.
To the left is the laptop.

Back to the issue...

With all my custom hardware setup being exactly the same, I ran tests as follows:

First test:

Desktop PC and monitor are turned off and unplugged. Laptop is running.
I plug my hardware into the laptop, ran tests, and got no problems with any device.

Second test:

All computers powered on. I remove my hardware from laptop and plug it into Desktop PC.
Communication to connected hardware via wire is fine, but the wireless connection seems to be non-existant ant when it should be.

For clarity, I used custom-made hardware between the PC and the wireless world and the custom hardware directly connects to the PC through the PC serial port. For all tests, the wired connections work.

I don't know if the power supply of the PC could be spreading noise over several centimeters? but is there anything else I can do to rectify this problem?


texts: LED frequency indicator for multiturn knob

texts: I’m designing a simple SW receiver for the 20m band and need a rudimentary frequency indicator activated by the multiturn rotary knob. The knob is part of a recuperated Pritt gluestick mechanism pushed into service as a PTO-drive for the VFO. The idea is to use reed switches to power the indicator LEDs on the frontpanel. On the glueholder a stick is glued which holds a magnet at the end. As the knob is turned, the magnet advances over 6 reed contacts, each in turn activating a corresponding LED on the frontpanel. Of course, as soon as  the magnet is advanced, the active LED is switched off and there is no indication for the duration of the next cycle until the next LED is turned on. Is there a way to make it so that the last LED remains lightened until the next is switched on? Of course this also need to work in reverse. Thanks beforehand for your help!


texts: Differences between Colpitts oscillator circuit designs

texts:
What are the differences between this colpitts oscillator design?

I need to build one for the transmitter of my wireless energy circuit for my project in our school, but I don't know what to use.


texts: How can I change temperature range of TMP36 from (-40 °C - 125 °C) to (10 °C - 40 °C)

texts:
I am designing a temperature controller system using TMP36 as a sensor and Arduino UNO as a microcontroller. I am using 3.3V with AREF pin. I am working in the range of 10-40 °C.

How can I change the original temperature range (-40 °C to 125 °C) to (10 °C - 40 °C)? How does it help the resolution?


texts: How do I express a Boolean function with don't cares (X) inputs?

texts:
I know how to minimize a Boolean function with X as outputs (using K-map).

I have encountered an exercise in which I am asked to write the Normal Disjunctive Canonical Form (NDCF)/ Sum of Products (SoP) but i have X as inputs.

Does it mean I will not take them into consideration when writing the minterms for where the functions has output high (1)?

For example:

A B C | Y
0 X 0 | 1
0 X 1 | 0
1 0 0 | 1
1 0 1 | 0
1 1 0 | 0
1 1 1 | 1

Will Y = A'C' + AB'C' + ABC ?

Also can this be done directly from the truth table, no need for a K-map unless we have to minimize?


texts: Problems using ADS1115 to measure battery voltage of Raspberry PI UPS Battery Pack

texts:
Here's my setup:

Raspberry Pi 3A+
52Pi EP-0118 Raspberry Pi UPS
ADS1115 ADC

I'm trying to measure 18650 battery voltage of the UPS. UPS in question does provide voltage reading, but on the output of the regulator. Strange choice, given that the whole point of the regulator is to output stable 5V. Anyways, since RPi does not have an ADC, I thought I would hook one up to it. My wiring is:

ADC V - 5V Rpi
ADC G - Rpi G
ADC SCL - Rpi GPIO 3
ADC SDA - Rpi GPIO 2
ADC ADDR - Rpi GND (not sure if this is strictly needed)
ADC A0 - Battery + terminal

Without hooking up A0 to the battery terminal, UPS and Raspberry Pi turns on just fine. As soon as I hook up A0 to Battery+ two things happen:

RPi Power LED turns on along with UPS RPi Power LED
UPS refuses to turn on, acting like there's a short in the system

I must admit I'm pretty new to using ADCs. I was under the impression that the wiring here makes sense - ADC, RPi and UPS all share common ground, and hooking up Batt+ to A0 would allow it to measure potential. Apologies in advance if I'm doing something obviously stupid here. Any advice is appreciated.


texts: redundancy checks and protection on monolithic and MMICs

texts:
I am using the ISL8026A chip for voltage regulation from 5 to 3.3V. The datasheet is - datasheet.

Now, this is merely an example circuit. Now, I would like to design a power supply for a  hi reliablity application. As part of this I presented a schematic as shown in the datasheet. This is as shown below -

.

Now, as part of this design I presented the schematic above. As shown I am having 2 22uF capacitors for filtering out ripples from the power cable. Now, one of the questions I was asked is ,since this is a high reliability application, I must add redundancy management in this circuit. For eg - the input capacitors. If they are shorted due to some discrepancies the whole system can be destroyed thereby causing critical failure.

This is just an example. There could be many such redundancy scenarios. How can I be aware of all such points where I will be needing redundancy checks ? Is there a checklist for such things ?

This is just an example of a redundancy check on an SMPS. What are the mechanisms deployed on other monolithic and MMIC ?
any pointers would be appreciated.

I agree it could be quite broad. But even pointers on the smps will be deeply appreciated.


texts: Relay Switching On and Off Rapidly During High Current Draw

texts:
I am building a solar pool heater using a solar panel to power bilge pumps that push water through irrigation pipes. When there's enough sun to get the panels to its typical voltage (~21.6V 6.16A) but not enough to provide enough current for the pump, then the relay cuts on and off rapidly until I turn down the potentiometer to a trickle. I'm just learning about electronics and have a basic understanding of the components, of which I assume I'm missing something important here.
I've currently wired this as:

simulate this circuit – Schematic created using CircuitLab
Solar Panel -> Relay with cutoff at 10V -> Buck Converter to 12V -> Potentiometer -> 12V 2.5Amp Bilge Pump

Do I need to add a battery or a capacitor somewhere to ensure the relay has enough power to stay on or remain off when there isn't enough power overall? Is there a way to reserve enough current to power the relay and buck converter?
Thank you!
Actual components in use are:

Solar Panel - https://www.amazon.com/gp/product/B00LXG4AXS/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1
Relay - https://www.amazon.com/gp/product/B07929Y5SZ/ref=ppx_yo_dt_b_asin_title_o06_s02?ie=UTF8&psc=1
Buck Converter - https://www.amazon.com/gp/product/B07JZ2GQJF/ref=ppx_yo_dt_b_asin_title_o06_s01?ie=UTF8&psc=1
Bilge Pump - https://www.amazon.com/gp/product/B01CPKB7BI/ref=ppx_yo_dt_b_asin_title_o06_s04?ie=UTF8&psc=1


texts:
I'm trying to build an LED matrix (32x16) that lights up in certain areas in response to movement, as detected by another matrix (8x16) of infrared phototransistors.

Here's where I'm at:

Main controller: I chose the Raspberry Pi. It would give me the ability to control the LED matrix using other, more complex methods (ex/ drive from music, over the internet, etc) as compared to a simpler controller (Atmega, PIC, etc).
LEDs: single color LEDs in a matrix configuration, each column controlled by a transistor that allows the power to that column to be controlled by the Raspberry Pi. The matrix will use 74hc595 shift registers so it can be controlled using only 3 pins from the RPi.
Detectors: Will consist of 2 arrays; one of infrared phototransistors, and one of infrared LEDs. The IR emitters will be connected to power through a single transistor, giving the controller all on/all off options for the IR emitters. The detectors will consist of a matrix (8x16) of IR phototransistors. An object near the detectors will reflect IR light from the emitters onto the detectors, thus changing the resistance of the phototransistors, triggering action from the RPi.

So that seems great, but here's where I'm stuck: I don't know how to get the RPi to read that many values. For the outputs (digital) it was as simple as using shift registers. Does anyone have any ideas of how to get that many analog inputs into the RPi?

*An important piece to note is that the RPi lacks an ADC, so I would need to add my own IC for that.


texts: Driving a 600W Piezo transducer for sonar application

texts:
I am looking to build a circuit capable of driving a 600W piezoceramic transducer with an impedance of 200Ω at a frequency of 50kHz. Since it is being used in a sonar application only short pulses(around 400uS) will be output around 2-3 times a second.

I am looking to drive it from a 12V source which will need to be stepped up to around 300V. Initially I was thinking on building an amplifier circuit, inputting a sine wave and using the amplifier to drive a transformer.

However I was wondering. Would it be possible to drive step-up transformer with a square wave, simplifying the circuit greatly, and use a band pass filter on the output in order to convert it into a sine to be fed into the transducer?

Any help would be much appreciated. Thanks.


texts:
I have the task of building a sequence detector

Here's the code :

/*This design models a sequence detector using Mealy FSM.
* Whenever the sequence 1101 occurs, output goes high.
* Overlapping sequences are allowed.
*/

module firstFSM (
input wire clk,
input wire rst,
input wire sequence ,
output reg tick
) ;

//State declarations
localparam a = 2'b00 ;
localparam b = 2'b01 ;
localparam c = 2'b10 ;
localparam d = 2'b11 ;

//Signals
reg presentState ;
reg nextState ;

//State assignments
always @ (posedge clk , posedge rst )
begin
if(rst)     presentState <= a ;
else if (clk)   presentState <= nextState ;
end

//Next state logic
always @ *
begin
//Default or unassigned states remain same
nextState = presentState ;
tick = 1'b0 ;

case(presentState)
    a : if (sequence)   nextState = b ;
    b :
        begin
        if (sequence)   nextState = c ;
        else        nextState = a ;
        end
    c : if (~sequence)  nextState = d ;
    d :
        begin
        if(sequence)
            begin
            tick = 1'b1 ;
            nextState = b ;
            end
        else    nextState = a ;
        end
    default :
            begin
            tick = 1'b0 ;
            nextState = a ;
            end
endcase
end
endmodule

Heres the testbench

`timescale 1 ns / 1 ns
module firstFSMTest ;

//Signals
reg clk, rst ;
reg sequence ;
wire tick ;

//Initialise reg ports
initial
begin
clk = 1'b0 ;
sequence = 1'b0;
end

//Set initial reset
initial
begin
rst = 1'b1 ;
#30 rst = 1'b0 ;
end

//Set occurance of sequence
initial
begin
#30     sequence = 1'b1 ;
#20     sequence = 1'b0 ;
#20     sequence = 1'b0 ;
#20     sequence = 1'b1 ;
#20     sequence = 1'b1 ;
#20     sequence = 1'b0 ;
#20     sequence = 1'b1 ;
#20     sequence = 1'b0 ;
#20     sequence = 1'b1 ;

end

//Initialise uut
firstFSM uut (  .clk(clk),
    .rst(rst),
    .sequence(sequence),
    .tick(tick)
);

always #10 clk = ~clk ;

endmodule

Heres the output

As you can see the sequence 1101 does occur after the yellow line.

But no matter what I do output doesnt go high. I am pretty sure the design and tb are correct. So wheres the error ?

(Are these and other verilog Q better fit for stack overflow or EE ? Please migrate it if you feel this doesnt belong here)

Thank you.


texts: Switch Mode Alternative to LM7805/LM7905

texts:
I am attempting to design a dual rail power supply PCB for a university project. There are a number of restrictions - namely that it maintains > 80% efficiency regardless of the current draw. I was originally just going to use a single battery (Maybe LiPo) with a voltage divider to provide a virtual ground connected to the common pins of both a 7805 and a 7905 to provide +-5V (For a microcontroller + numerous op amps), however, they have a relatively horrible efficiency.

I should also note that I need to supply enough current for 4 x 10 DIL BAR LED's, up to 10 op amps, an Arduino Mini. I've roughly estimated this at 0.5A to be on the safe side.

My current solution involves a TL2575-05 switch mode regulator for the +5V @ 1A, hooked up as per the example in the datasheet. My -5V is currently problematic. I've looked at the LT1074HV, but I can't find its efficiency, and it's ~$22 a unit.

Surely there must be a simple way to produce a +-5V power supply from a single battery, that is both efficient and cost effective?

EDIT: Current schematic


texts: Its really bothering me that the diode is shown in the opposite direction here and i don't understand why its been put like that? the input voltage will come from the left side of the circuit then why is the diode's cathode connected to the output of the op amp? does the polarity even matter here?


texts: Help me understand electrical fields better

texts:
I have a hypothetical scenario that would help me better understand (I hope) electrical fields and propagation of electrical fields better.

So let's have a super simple circuit with one voltage source and one resistor:

simulate this circuit – Schematic created using CircuitLab

I understand that Ohms law says that I=U/R so using that we would see 50mA flowing through the whole circuit.

Now I have the hypothetical scenario: lets make this circuit veeeeery large.

Large so that the wires would be 10 times the length that speed of light can travel in one second.

If we presume that the wires are made from perfect superconducting material and have no losses in themselves, how fast will electrical field establish itself at location where our resistor R1 is (be at 5V).

Would current flow unobstructed the whole length with the same current strength until it reaches the R1 resistor and would it only at that time "reduce" itself to 50mA when it is impeded by R1 resistance?


texts: 24VAC vs 220VAC inductive voltage transient

texts:
I'm designing a PCB with a PIC micro-controller that has to switch some contactors. This PIC drives some NPN BJT transistors and these transistors drive some Relays that switch the contactors.

I'm trying to minimize EMI interference and sparks in my circuit and for thus i have to decide what coils to use on the contactors (and snubbers but thats not related to the question).

Seaching for contactors I've got two models (for the coil):

1) 7VA, cos(phi)=0.3 (50Hz), 24VAC.

2) 7VA, cos(phi)=0.3 (50Hz), 220VAC.

What's the comparison between both voltage spikes when the coil is suddenly opened ? (How much higher, how much longer, frequency, etc)


texts: Does MEMS accelerometer stability deteriorate over time?

texts: I am wondering if over time MEMS accelerometer produces any worse output than when it is new? I found this research paper which acknowledges that temperature affect sensor output but there are no conclusions about reading stability over time.


texts: When would AXI4Lite be a better choice than the APB bus?

texts:
I'm working on improving and cleaning up an already functional large FPGA design that has a 64 bit data bus. One of the questions that came up is,

  "should we transition all of our busses to AXI4Lite/APB, or should we leave them as they are?"

Some are AXI4Lite and some are APB.

Those on team AXI4Lite argue that many third party FPGA IP blocks use the AXI bus; on the opposing side colleagues suggest that the APB bus may use less resources (FFs and LUTs)--though I have not been able to confirm that.

I am on the side of pick one and stick with it.

What reasons are there to pick one over the other? Are there scenarios when one bus might require more resources than the other? Is there a strong reason to migrate to one over the other?


texts: How to determine the electrolytic capacitor polarity from PCB printings?

texts:
I have this PCB board that I need to solder a capacitor to it.
This is the board:

And I'm not sure where should I solder the negative and where the positive.
Can someone please explain what this circle represents on the board?


texts:
I have a problem to understand the minimum switching voltage of the relay, especially, what impact it has.  I found these topics that briefly mention, but still unsure what to make of it

Relay datasheet question

Can I drastically undervolt/underpower a relay?

Parameters when choosing a relay

The voltage across the relay is ideally 0, right?
So I it is perhaps the voltage drop on the relay. But what confuses me, since the resistance of the relay is very low relatively high currents would be required to produce ot.

May be I better understand with an example.

Edit3: more details about usage of the relay
I consider this relay that would be used on a custom  board  for testing and measurement of batteries (lithium and otherwise). It would connect/disconnect charging/discharging currents 1 µA to 25 mA. Battery voltages in range 1V-4.5V. The relay isto be controlled from Rapsberry PI 2. Since GPIO pins don't have current capability to drive the coil, the control signal would be shifted to the main analogue voltage level of 5.5 V.

EDIT2 : a rough presentation of how the relay would be used

Edit: example from the datasheet I linked. It is in contact, not coil section

If not it would be very unfortunate because it is only compact DPST relay availible.

For this case additional question:
can be a DPDT relay be used in place of DPST?


texts: Is this transistor switch circuit designed correctly?

texts:
I am making a little home made electronics project.

The plan is to turn on a Red LED when a SCART input is sending an RGB signal. Pin 16 on a SCART cable is 1-3V when the input is carrying an RGB signal (according to wikipedia - in my case it actually sends 4.5V so I figure this is quite a flexible spec).

The circuit I have designed works....but I don't know if it is safe, or done correctly! Please see the schematic below:

simulate this circuit – Schematic created using CircuitLab

I have 2 main questions:

I don't seem to need the 1k Ohm resistor leading to the base of the transistor. I assume any voltage applied to the 2N3904 base will switch the circuit on...so this is just keeping a low current to prolong the life of the transistor?
The circuit doesn't work unless I cannot Pin 21 of the SCART input up to the ground of the main circuit. I don't know if this is safe, or the correct way to make this circuit work, can you validate my decision here.


texts: charging a lead acid battery bank with a 19v laptop charger

texts:
I am new to the forum and I notice that you have decent positive discussion and tips which also includes noobs on any given electrics related topic,

I was requested to post it as a new question here:
Lead Acid Battery charging from laptop psu
 so here goes the copy paste with an added video link I just uploaded:

I am new to lead acid charging and have been using a 19v 5A vaio laptop charger to directly charge the batteries, 2x used 12v 75Ah in parallel (=12v 150Ah) for a few months which in turn power some low watt led lights and a 12v table fan when main grid load-shedding occurs in this part of the world. I've noticed that the batteries can initially draw around 8amps from the 19v 5A psu without overheating the psu. The batteries no longer boil as they used to when charged four in series with the huge 48v controller which was required to overnight recharge an electric autorickshaw (their first hand use) and now remain cool whilst charging, I haven't needed to top up the water in over six months either despite the driver having had to top them up 2-3 times a week previously.

I am wondering if it's OK or whether I need to reduce the voltage output from the psu to ensure longevity of the batteries since the charger is usually left on until I switch the connector between the two sets of batteries which i charge and use alternately as the lights from one set begin to dim after 2-3 days. Any suggestions and links to diagrams if voltage reduction is helpful would be appreciated.

BTW, I also charge another set of four in parallel with another 19v Toshiba laptop charger (trickle charges a few points of a volt every day), i've noticed that smaller laptop chargers (I've got a small pile of them sitting around) tend to immediately begin to heat up upon plugging in (possibly due to lack of intelligence or inability to regulate amp draw?) So there appears to be some sort of intelligent co-ordination between the branded high amp chargers and the batteries - just added that in case it helps in drawing a clearer picture of how things are.

Here's a video with the pulsating voltage multimeter readings:

Charging lead acid batteries with laptop psu

Update: I found this circuit for reducing the voltage, does anyone know if it is efficient enough to charge my larger batteries through?
Or maybe if I added a few more LM317 's in parallel in order to increase the load bearing capacity (datasheet shows max 1.5A each) - and would the transistor cope despite this?
Any other workarounds?

http://renewablekinabalu.blogspot.com/2013/07/homemade-12v-sealed-lead-acid-battery.html?m=1


texts:
Im a very beginner with electronics and started with Arduino. So I tried to make a little device which is a separate board which is being work based on digital out and few output port from Arduino. But rather than separate board system , I would like to make Arduino and my custom board together. Is that possible or from where I could get the good circuit for Arduino nano with its all mandatory components including the bootloader.

Important point is the device Im trying to build is something which is intended to run 365x24x7 (No worries about power failure, its running on perfect backup system)

Also another concern is I dont need all the IO pins I just need 3-4 pins from Arduino. So is that requires any serious changes on the Arduino circuitry. Sorry because of my poor knowledge in electronics Im sharing that stupid question.

Please share your kind thoughts.


texts: Determining amplitude of a 2 MHz sine wave

texts:
I'm designing a class E resonant inverter at a switching frequency of approx. 2 MHz. I need to control the inverter so as to maintain a constant current at the load. My strategy would be to put a current sense resistor in series with the load to convert current to voltage, rectify and low-pass filter it, then read the essentially-DC value with an ADC -- I can take it from there.

Just to get a sense of the values involved, my nominal current is 0.17 A RMS, and I have determined that a 1 Ω current sense resistor is about the maximum value I can use. Hence the voltage drop on the current sense resistor is 170 mV RMS. I can tolerate at most 1% error on the amplitude of the sine wave at the output of my circuit. The circuit must work with a single power supply (say 3.3 V); no bipolar supplies.

Obviously this voltage is too low to rectify with a diode directly. My first thought was to use a precision rectifier; the following circuit, taken from a TI application note, might do the job, and it works for a single supply:

Yet, certain performance demands are made of the op amps in this circuit, so as to meet my requirements above, that narrow down choices considerably:

The GBW product must be significantly higher than 4 MHz (twice the sine wave's 2 MHz frequency since this is a full wave rectifier); otherwise, the signal will be attenuated. I have determined that, if the 3 dB cutoff is one decade above the signal frequency, the amplitude will be attenuated by 0.5%, so a 40 MHz GBW amplifier is the bare minimum I'm looking for.
Since the amplitude of the sine wave is 240 mV, if I impose a maximum of 0.1% error due to the op amp's input offset voltage, I need a part with at a maximum of 240 µV offset.
Assuming a value of 10 kΩ for \$R_1\$ and \$R_3\$, the circuit should have an input impedance of 5 kΩ. Given the source impedance is 1 Ω, this by itself is not a problem, but op amp bias current is. Again imposing a maximum of 0.1% error due to the input bias current of the op amp, the maximum input bias current must be 240 µV/5 kΩ = 48 nA.

The cheapest (Digi-key qty. 1) op amp from a reputable manufacturer that meets these specs is the OPA2365 at $2.73. This would easily account for more than 10% and closer to 20% of the cost of my inverter, so I keep thinking there must be a better way. If it helps, this can be viewed as a peak detection or AM demodulation problem.

So the question is: can anyone suggest a cheaper circuit capable of measuring the amplitude of a ~240 mV, 2 MHz sine wave?

Edit: this circuit will be employed in a portable device, so power consumption must be kept in check.

Edit 2: As per @SpehroPefhany's answer, I'm trying to design a BJT circuit now. It goes something like this:

simulate this circuit – Schematic created using CircuitLab

Yes, I know I cheated there by using a 10 V supply -- I have batteries on my system that can provide this voltage if necessary, which is something I forgot to mention above. Also, I've omitted the filtering part of the circuit; that should be easy after rectification takes place correctly. I can add back the diode drop voltage digitally after A/D conversion of the signal, and since it's amplified (I'm shooting for say 4.5 V amplitude now), I can easily tolerate 50 to 100 mV variations on diode voltage drop in manufacturing without violating my revised accuracy target (5% now, again as per @SpehroPefhany's suggestion).

The problem with this circuit is that, with no load (assuming R6 were taken out of the circuit) the DC voltage on the diode's cathode drifts up until rectification no longer takes place. If R6 is sufficiently low, the rectification effect is maintained, but at the cost of unduly loading the circuit, with a corresponding effect on the DC level seen on the load resistor.

This seems to be the most promising avenue of investigation until now. I welcome any suggestions to improve it.


texts: Detect incidence angle with an antenna array

texts: Having an antenna array, how can we determine incidence angle of an incoming signal. I know it is related to the phase of the signal in each antenna but I only found information about how to send a signal in a specific direction or how to perform a spatial filter. My aim is to determine the incidence angle if it is possible.


texts: Demodulation/filtering of a binary signal

texts:
I'm simulating an amplitude modulation system on Matlab and have got to filtering the demodulated system.

The original data to be sent was a 1x100 set of binary data. Which was then applied to a carrier signal, additive white Gaussian noise (AWGN) was then added to the modulated signal.

Im at the filtering stage, after demodulating the signal, and the low pass filter I'm using attenuates by half the overall amplitude of the received signal. Therefore the decision threshold between 0 or 1 has to be attenuated accordingly. How would I could about figuring this out?

I originally thought this would be 0.5, however as the added noise is completely random so this is not the case.


texts:
I have some questions regarding Cree XHP 70 LED Drivers.

I have 2 LED drivers Cree Model XHP70 from kaidomain. I want to run a LED at 12v.

xhp 70 spec

Maximum Drive Current: 4.8 A (6 V) / 2.4 A (12 V)
Typical Forward Voltage 5.8 V @ 2100 mA (6 V) / 11.6 V @ 1050 mA (12 V)

Cree First Driver Specs (ref.)

Operating voltage: 4-18V, maximum 20V
LED current: 4.5-5A

Cree Second Driver Specs (ref.)

Operating voltage: 4-12V
LED current: 3A

I was thinking using a 4S3P of 18650 (3200 mA) battery that could give: 14.4v, 9600 mAh. Not sure but theses drivers seem to be Constant current drivers. So the first one could be used in 6v mode but current seem any way too high.

The second could be used in 12v mode but the current seem also high.

I would like to have your confirmation about running these drivers at 12v.


texts: PIC32 sleep mode with watchdog wakeup failing

texts:
I am in the process of trying to get a PIC32MX795F512L to run with lower power consumption.  I'm trying to get it to enter sleep mode and then be woken by the watchdog timer.  All pretty standard stuff.

My code works on the first triggering of the watchdog timer, but the second triggering isn't triggered as if it were in sleep mode, but in normal running mode.  As a result it doesn't continue execution but instead resets the whole chip.

On the PIC32 the watchdog timer, when in sleep or idle mode, causes an NMI with the same vector as reset.  You then check some flags in a register to see if it was caused by the watchdog in sleep mode, etc.

My startup code looks like this:

_reset:
    la      k0, RCON        # Load address of RCON register

    lw      k1, 0(k0)       # Get contents of the register
    and     k1, k1, 0x18    # We are only interested in 0x18
    sub     k1, 0x18        # Subtract 0x18
    beqz    k1, _ret_nmi    # and if the result is 0 (i.e., equal to 0x18) then branch.

    lw      k1, 0(k0)       # Same again but looking for 0x14.
    and     k1, k1, 0x14
    sub     k1, 0x14
    beqz    k1, _ret_nmi
    nop

    la      k0, _startup
    jr      k0                      # Jump to startup code
    nop

_ret_nmi:
    lw      k1, 0(k0)
    and     k1, 0xFFE3
    sw      zero, 0(k0)
    eret

Basically it looks for 0x18 or 0x14 being set in the RCON register, then clearing those bits and returning from an interrupt if they are set.

Sleep mode is entered by setting the SLEEP bit in OSCCON (which needs unlocking first), and according to the power saving manual for PIC32 is done like this:

// Standard unlock sequence
SYSKEY = 0x0;
SYSKEY = 0xAA996655;
SYSKEY = 0x556699AA;
OSCCONSET = 0x10; // Enable sleep mode
SYSKEY = 0x0;

You then enable the watchdog timer, "kick the dog" as it's known, and stop the CPU with a wait instruction:

WDTCONSET = 1<<15; // Turn on
WDTCONSET = 0x01; // Kick the dog!
uint32_t i = disableInterrupts(); // We don't want any old interrupt waking us up
asm volatile("wait");
restoreInterrupts(i);

So that causes the CPU to stop and then the NMI triggers after 1.024 seconds.  The CPU restarts from the reset vector, the startup code checks the flags, finds it's an NMI, and returns from interrupt continuing with the next line of code.

The first time.

The second time the RCON register contains 0x10 instead of 0x18, so it acts like a timeout from not kicking the dog.

Inspecting OSCCON after the failed timeout the SLEEP bit seems to have been reset.  Setting the SLEEP bit every time through the main loop just before sleeping has no effect.

However

If I do the exact same thing but using idle mode instead of sleep mode, everything works perfectly.  The wait instruction continues after 1.024 seconds every time without failure.

So why does this not work as it should do in sleep mode?

Is there something obvious I am missing?

Update

I have tried forcing the CPU priority level to be the lowest possible before sleeping, but it has had no effect.  This is the code I am using for it:

asm volatile("mfc0 $8, $12");
asm volatile("ins $8, $0, 10, 3");
asm volatile("mtc0 $8, $12");
asm volatile("wait");


texts: Assign to a wide vector copies of a narrow vector

texts:
X is n bits long.
Y is n*k bits long.
I want to assign copies of X to fill Y. As follows:
assign Y = { X , X , ... , X } ;
I know how to do it with a loop - but is there a quicker alternative ?


texts: How do I get rid of vehicle voltage spikes maybe a choke and capacitor filter?

texts:
My Question is:

Is this a effecient way of filtering high voltage spikes?

If so is the way I drawn the circuit even correct...

How to size the components to work so that any vehicle high voltage spikes get filtered.

Context

I have a pump controller circuit that will be powered by a 12v battery that is charged with a stator.

I need to protect from voltage spikes...

For more info look here:
Circuit Board Design...Getting Rid Of A Relay and Adding a Choke and Capacitor Filter?

@Transistor mentioned possibly a choke and capacitor filter...

I've been reading up on this and the more I read the more confused I get.

Here is what I've come up with so far...

I don't know how to size the componets correctly and running a simulation didn't help me...

simulate this circuit – Schematic created using CircuitLab

Figure 1. Clumsy Voltage Filter

simulate this circuit

Figure 2. Pump Controller Circuit


texts:
I am using an MCP23017 (which shouldn't matter tho) to extend the number of GPIO pins of an arm based linux computer using i2c-dev bitbanging. It all works fine with wires of a few centimetres.

The problem is that i would need 2*~3m wire in between clusters of 3 such MCP23017 based modules. Now, if i use a 3m wire (0.75mm diameter) for SCL and SDA i do get an ack for setting the address but polling the IC for the pin states results in confusing replies.

Sidenote: The MCP23017 has 2 banks of 8 pins each, with the 3 metre wire only 1 bank seems to work and B turns into A... Not sure what happens to the signal there, i guess the address in the request is being corrupted on a regular basis.

So i figured to increase the signal strength i would add an external pullup (the gpio pins used for bitbanging already have an internal one), which again works nice for some 10cm wires but kills even the address ACK for the 3m wire.

I tried 2k2, 4k7 and 10k ohms, all with the (exact) same result from my low resolution perspective.

Unforunately i don't have an oscilloscope to look at the whole thing and i'm not too knowledgeable about all the details to figure this out by just staring at it, therefore trying this route.

I hope someone has an idea what is happening here, what i could try or where i could learn enough to understand this on a level that helps me fix this. Let me know if you need any more info.

UPDATE: 3m wire now works with 850 ohms external pullups. going down to 150 ohms it also works with 6m but isn't a great thing to do since one easily uses more power (to pull the line low) than most gpio pins are rated for.


texts: H bridge Inverting Wave issue sound from gate driver

texts:
[![enter image description here][1]][1]
I am trying to drive H bridge using the following configuration
I am producing an inverting.
4 * N channel mosfets Fdd8447
gate driver ic TC4428 (used alternatively IX4428 and IXDF604 but no avail)
Frequency stays <15Hz
Power rating remains within half a watt
At the Output I have
2.2K Ohm resistor
1Uf capacitor
I am not using IR2110 since I cannot produce the required +10V on high side gate as my  max output amplitude stays within 20V.
I am able to produce the required wave but I get wave this after applying the capacitor... otherwise worst...after adding the capacitor there is unusual sound in the gate driver as well...in fact I have even burnt one. Whats the problem?
New picture
Furthermore my load is not motor but a small and a capacitive one like the human skin


texts: I want to give SMD soldering a try and therefore I was looking for some useful circuit (no LED-blink-crap) I could build more or less easily. So I found a nice DIY function generator here. It uses originally an LM348 OpAmp, which is not in stock at my local electronics store and in general not as SO-8. I wondered if I could simply use two LM358, that are easy to get. Unfortunately I have no clue about OpAmps and so I hope somebody can tell me if this is a compatible replacement.


texts:
I need Ribbon Cable with IDC female header 8pins (2x4) on one side and separate female sockets (2.54mm pitch) on the other side. Like this cables:

But I can't find appropriate cable, the available item have two 2x4 8-Pin IDC headers on both ends.

Therefore, does it possible a DIY solution, what I mean is crack IDC header on one side and pull out a separate crimp sockets.

Then insert these crimp sockets into standard separate 2.54mm female plastic sockets. I don't know how the wires are mounted inside these IDC headers, does they use same crimp sockets as in regular 2.54mm female sockets, or other type of crimp sockets?


texts: Less noise when not following LED Driver datasheet

texts:
I designed a board which uses a LED driver (datasheet).

It clearly states, DO NOT connect DIM- to Vin-:

However, these are the waveforms I get on Analog DIM pin when they are disconnected, and connected:

(I'm using a DAC to drive Analog DIM, the DAC is fed from a linear regulator that is conected to Vin- and Vin+.)

Clearly cleaner with the pins connected:

I measured the pins of the LED driver for continuity and Vin-/DIM- ARE connected to each other inside the driver.

Why would the datasheet recommend not connecting them then? I really dont understand this. I'm considering leaving the pins connected on the PCB aswell for way less noise.

UPDATE

So experimenting I arrived at a solution which gives the least amount of noise in the DAC.

I added ferrites between DAC ground and Driver ground and DAC PSU V+ and Driver V+.

After this I grounded the DIM- pin to DAC ground.

This leads me to speculate that inside the driver DIM- and VIn- are also connected through ferrites (otherwise after connecting DIM- to DAC ground noise would also be present, but it wasnt)


texts: On my PCB, do I need to keep UART lines away from my 1/4 wave monopole antenna?

texts:
I am working on a PCB design with a 1/4 wave monopole helical antenna. Currently, I have the UART TX and RX lines running the length of the board, and about 1.8mm away from my antenna feed line and through-hole pad.
Can this potentially cause cross-talk / interference issues? The datasheet for my antenna doesn't give any information other than how far to place the pads from the ground plane.


texts: Why are 5 Volt 7-8 Amps chargers not available for charging phones quickly?

texts:
Available phone s chargers have either 0.5, 1, 2 Amps rating depending on the batteries (varied capacity) used. Why is it that 7, 8 Amps chargers are not available ?
if the limitation is in the Lithium Ion batteries we use... then what's the maximum possible current to charge them without damaging.... to design a portable charger for phones.


texts: Integrating two I2C sensors into a single circuit

texts:
I have two I2C sensors that I want to combine into a single circuit. Here are the schematics for each sensor side-by-side (i.e. not combined into single circuit).

The BME280 datasheet states the sensor needs two decoupling capacitors: one across GND and VDD and another across GND and VDDIO. I know that supplying power to VDD and VDDIO via a single 3.3V line and using two capacitors works well for this chip.

My other sensor needs a single decoupling capacitor.

Both sensors run off 3.3V and require pull-up resistors for the clock and data lines.

My question is, how do I arrange the resistors and capacitors on a breakout pcb that has both sensors on it? I am assuming the breakout will only need two 4.7K pull-ups, one for SDA and another for SCL. Is this correct? How do I manage the capacitors? Do I need to combine them and use three decoupling capacitors? Thanks in advance for any feedback/help.


texts: I have two ac souces one being the electrical wall outlet and the othee being an inverter that will go to zero volts, and  both at 60hz.  How do I sync the inverter to the wall outlet?


texts: Operational amplifier when the non-inverting terminal is open

texts:
What will be the output voltage from the opamp when one end (non-inverting terminal) is open? (For circuit see the attached figure.)

The way I was trying this question was like this:
For any arbitrary value of \$R\$ (resistance between point B and D) in given circuit voltage at point B is zero and due to virtual ground voltage at pt. A is also 0. Now we can apply KCL to get output voltage, and in this way can I conclude that output voltage will remain same even if circuit is open (as shown in figure?)


texts:
I have a simple adjustable power supply (1.8V - 16V / <1A) that I put together with an LM350, works great for the various small bench-top things I use it for. Typically on a load being applied, I see the typical small voltage drop as current spikes, all expected.

Last night I hooked it up to a hacked together transistor-as-audio-amp circuit I threw together on a breadboard to test the DAC on a new MCU. Eveything went as expected, sound played fine, but I noticed that my voltage went from 8.4V to 9.75V, around a 16% increase! I'm not completely new to building low-ish power circuits, but I'm trying to get better at the theory, and I'm not seeing why this increase occurs. It is constant, not a spike, and a jump of 1.35V seems like a lot.

Of course using a BC547 as an audio is non-optimal, and the transistor only does an ok job handling the current, but I only turn the circuit on for a few seconds at a time. I was thinking that there is some transistor-related phenomenon that I am unaware of that would account for the voltage, but it does occur in circuit simulators, which leads me to believe that it's a real parts vs ideal parts phenomenon. Can anyone point me to a source for understanding why this happens?

simulate this circuit – Schematic created using CircuitLab


texts:
Are there any components/devices out there (available via RadioShack, or some other vendor) that behave as follows (or similarly):

When a signal/voltage is detected, a random (and preferably configurable) timer begins. My desired "random" time range is between 1 and 4 seconds; then
After this random 1 - 4 second timer/window elapses, this device places a signal/voltage on an outbound wire

Any components like this exist, or do you have to build up "random timers" from lots of smaller "subsystem"/constituent circuits/components?


texts:
I'm working with an Arduino, and one of the stripped portions of the wire broke off at some point and managed to get pretty wedged into the 5V pin slot. Obviously, this wouldn't matter as much for a GPIO pin, but I sort of need to use the +5V port.

Tweezers are out of the question; I've tried both non  and slanted-tip. Currently a needle is the only thing that will really fit in, but i just end up pushing the wire around more. Tried using a very small magnet, but it isn't neodymium so likely isn't powerful enough.

Here is a picture of the microcontroller with the wire stuck. The wire is not above the header itself, it's entirely pushed into the header:

Update:

Got the wire out by using a combination of techniques. I did not have access to tweezers that were small enough to get in, but I do have a nice soldering station in the lab. Since the piece of wire was so small (see picture), with one of my instructors, chipped at the header a bit with a pair of cutters and then used a wire and some tin to carefully attach the wires together. If I needed the header to be intact, the best bet would have been tweezers or just putting a new header on, but I don't care if there is a very slight cosmetic flaw on the 1 port on the Arduino.

Picture of the stuck wire segment still soldered to the extraction wire:


texts: How does an addressable LED in a strip work?

texts:
Take an addressable LED strip (e.g. with chipset WS2801) that you might control with an Arduino. I understand that there are clock and data lines, and the data propagates through shift registers on each LED, extracting the information for that pixel (RGB).

I'd like to know more detail. How do the RGB values passed through the data line influence the intensity of the diodes? What logic is involved in doing this? Is it based on PWM or continuously changing the voltage of the diodes? I can't find a schematic.


texts: How to default logic high after a voltage divider?

texts:
I have a 5V logic pin coming in that I want to cut down to 3.3V.  When the 5V pin is detached, however, I want the pin to default logic high (3.3V).  How can I choose R_pu appropriately?

V_in = 5V
VCC 3.3V
R1 = 20k
R2 = 33k
Rpu = ?


texts: Reverse polarity protection on 5-12V input and output

texts:
Can someone help me with reverse polarity protection on 5-12V input and output using a using a P-Channel MOSFET?

How can I calculate which MOSFET, resistor, zener diode I have to use?

I use a 5V 10A power supply.


texts: Position of leds in the RX/TX portion of an arduino compatible

texts:
Given the following circuit , electrically speaking makes any difference the position of leds?

I know R8 and R9 are used to allow the override of the RX/TX pins if any other device is connected, does placing R7,R8 and the Leds after or before these resistors affect this behaviour?


texts: How do I get the output of this circuit?

texts:
I am trying to solve the truth table of the following circuit:

A, B, and C are the inputs. I tried getting the truth table by drawing the circuit in an online circuit simulator such as falstad.com/circuit but it's not working, check it out:

What is the wrong in the circuit? Why isn't the output changing to H?

Is the truth table for the following circuit correct:


texts:
I recently bought an Ender 3 3d Printer that comes with a cheap Chinese 24V 15A PSU. Unfortunately, the PSU went dead and by inspecting the board, I found out that two resistors were fried (both the same value). By looking at the resistor’s code bars, I see that the first band is colored black.
The bands read: BLACK, YELLOW, VIOLET, SILVER and BROWN. (Please see the picture below).
It appears that the last band is brown as it looks like is the one most separated from the others. I would appreciate if anyone can give me any hints on where or what resistors to get.
I already replaced the cheap PSU for a Mean Well. However just for the fun of it, I want to repair the dead one.


texts: How does a computer chip read code, interpret it, and convert it into action?

texts:
I understand that binary is effectively functioning as a “virtual representation” of low voltage and high voltage. However, I do not understand how the instruction set to MAKE the voltage high or low is being executed. Within a computer, what is physically happening to change a circuit to a “high voltage state” or a “low voltage state”?

This is presumably the lowest level instruction set that exists within computers...and I’m not quite sure I understand how it is being implemented. What is making the circuit change between high and low voltage states...and, moreover, how are these instructions designed to ENACT such a change in voltage state actually being carried out?

This is like the “instruction set that proceeds all other instruction sets”...or the “instruction set that exists BEFORE binary instruction sets can even be formed”. How does one program a circuit to do something before a programming language even exists?

In other words: How does a computer chip convert the "text" or bits that make up the program into action? How does it read the code, decide what the code is saying, and then act on what the code is saying?


texts: How can a powersupply have a large input volt range

texts:
I see that computer power supplies that can take a voltage input of anything between 90V and 260V at a frequency between 47Hz and 63Hz.

Meanwhile it can output power at a very precise voltage.

How does that work?


texts:
We all know the Faraday cage effect: light waves get through the screen on the front of your microwave oven, because their wavelength is much less than the size of the holes, whereas
the microwaves don't get out, because their wavelength is much greater.  Yet despite many hours of looking around and dozens of discussions with individuals, I've been unable to
find an analysis of the mathematics of this effect.

Presumably there's a simple argument that shows some kind of exponential attenuation depending on the ratio of wavelength of hole size.  Can anyone point me to the literature on this subject?


texts:
I am using resize function as below to convert 32bit vector(temp2_32) to 16 bit vector(temp2).
 temp2<=std_logic_vector(resize(to_sfixed(temp2_32,3,-28),1,-14));
When temp2_32 value is x"0002ad50", temp2 value is getting updated as x"000b".
In my understanding, while resizing first 16bits will be assigned to temp2 which is x"0002". But here the value updated for temp2 is x"000b". How is this value obtained? how does resize work?


texts:
I saw a PCB with something like this. A trace that connects the four holes on the corners. I assume that they do it to prevent some kind of noise. I am not sure if the connect that trace to GND

Also, for the shield of an USB, I saw some schematics that connect the shield to the GND using a ferrite.

So, this layout, a trace on the border, connected to the shield of the USB cable, and connected to GND through a ferrite.. it is a good or a bad idea?


texts: How to sink more current than specified?

texts:
I am using the TLC5940 (datasheet) in an upcoming project to control the cathode side of an LED matrix, but each of my LEDs needs 70mA of current. If more than one led in a given column are on at a time then that will end up being 70mA*n where n is the number of LEDs in the column that is on. The problem is that the TLC5940 has a maximum current sink of 120mA. Is there a way to sink the current somewhere else while also using the TLC5940?

I was thinking about using a PNP transistor of some sorts but I have no idea about how that would work.

The essentials of my circuit (sorry it is so crude but it includes everything necessary):

Note: This is just two rows and one column of the led matrix.

The problem is not an issue if either A, B, or C send 70mA of current, but if any two or three of those are on then there is too much current.


texts:
I have some ARM processor that have 72-bit width (8 for ECC) RAM controller.

Can I buy eg. two 32bit chips and combine them? If yes then how?
Can I buy just one 32bit and pull down rest of data pins on processor?

Processor brief if needed: https://docs.broadcom.com/docs/1211168571391


texts: 3S Lithium-Ion power solution for a project

texts:
I have a PCB that runs on 12V throughout the day and consumes 2.3A. The power is supplied for 12 hours using a power supply. The other 12 hours it must run on batteries that have charged during the first half of the day an so on and so forth.
So maybe we can use a pack of 3s9p Lithium-Ion batteries with individual cell capacity of 3000mAH as the required capacity is now 27AH(2.3A x12 Hours) to supply the circuit for 12 hours.
Now the first question related to charging.
1-Will a 3A Lithium-Ion charger provide the necessary 27 Ah capacity during charging in 12 hours?
Output current, 3A, constant current charging, the indicator light is red
Conversion current, 300mA, after full conversion, the indicator light is green
2- Using a 3S BMS with balance function and balance current of 45mA.
Can I achieve proper balancing and charging using this BMS and the previous charger?
Thanks in Advance
A charger like this one:

BMS:


texts: Why does voltage always lead current by 90 degrees in an inductor?

texts:
I have learnt that in an inductor voltage leads current by 90 degrees. However, I do not fully understand why it is 90 degrees.

I have been looking everywhere for more information on why this is so. However, all the sources I found just state the rule.


texts: Current rise time. How fast is too fast?

texts: I'm trying to create a suitable response to Pumping a few Amps for a 100usec. The OP wants to create a 5A current pulse for 100us. They want to have a current rise time of 1us at the start of the pulse. This is obviously 5MA/s. Is this likely to cause problems (EMI, ground bounce, etc.) ?


texts:
Is it possible for a single-die QSPI NOR flash module be simultaneously used for both XiP and a file system?  By simultaneous I mean that a function running from XiP accesses data elsewhere on XiP.

The MCU, in this case, is an NXP Kinetis K8x (ARM Cortex M4), which has an onboard QSPI peripheral.  The symptom is:

Code executing from internal flash can access the file system on QSPI flash without any problem.
Code executing from external flash that does not access the file system runs without a problem.
Code executing from external flash that accesses the file system hangs the system.  In the debugger I see that the QSPI peripheral's busy-bit remains set forever.

Can anyone explain what's going on?
Will a dual-die flash module solve this?
Should I be looking at the QSPI peripheral settings?

===

More Info:

How to use Quad SPI on KL8x Series: https://www.nxp.com/docs/en/application-note/AN5244.pdf

A dual-die flash module won't solve anything, as both dies share one QSPI controller on the MCU, with one set of buffers, etc.

If I use memory-mapped reads for the file system, then, of course, the same internal mechanism is used to fetch and buffer both instructions and data. And the system does not hang.

So, all I need to do is isolate the file system write functions, and make sure that these run from internal flash, or as RAM functions.


texts: Identify the manufacturer's logo on the connector used in IKEA OMLOPP LED lights

texts:
Can someone identify the logo on this 2-pin connector used in IKEA UTRUSTA/OMLOPP kitchen countertop lights?

The marking on the connector is 58A and some logo, which I can't decipher but it looks like NSSD or NESD or something like that.

The pitch seems to be 100 mil.

Hello,

I am also looking for this plug to replace plug from my very out of date ikea light. At the end i find this type of plug is called "mini-AMP", and it is very commonly used. So use keyword "LED mini amp 12v" or 24v, 30w, any param u need, you will find a lot options on amazon.

BR, Jingjing.


texts: Help with my design: How can I add these voltages?

texts:
I have to design a circuit that simulates a voltage spike on a dc supply rail. The circuit has a button that, when pressed, generates a short pulse of controllable height (controlled by pot). The internal circuitry essentially has to sit a pulse train on top of a constant dc voltage.

The voltage values are somewhat strict; they are shown in the diagram. The pulse height is controlled anywhere from 0v to 4v and the dc offset is 5.28v. From the diagram, you can see that the output from the 555 and the dc offset voltage are buffered for isolation.

My problem is that with a single rail power supply, the op amps cannot do the summing because the output will be inverted.


texts: How can I determine if my oscilloscope is operating correctly?

texts:
I purchased a used 20/100 MHz oscilloscope many years ago. It has always served me well to look at very simple sine and square waves for my hobby projects.

However, I have wanted to know if I got a 100% functional o-scope. Is there a way I can test or calibrate it to see if it is operating up to spec? I do not own a function generator.


texts:
I have two IC chips.  On one chip I have one 10K ohm pull-up resistor and on another chip I have three 10K ohm pull-up resistors.

At first I was using four through hole pull-up resistors.  Then I moved to an array of SMD resistor.

Could I simplify the design by attaching all four pins of the ICs to the same pull up resistor?  Should this be a 40K ohm resistor? Is this OK or is it better to attach each pin to a different resistor?


texts: Op-Amp High Pass Filter - Cutoff Frequency derivation

texts:
I am trying to derive an equation describing the cutoff frequency of a high pass filter op amp, as seen below:

I have tried deriving the cut off frequency from it's transfer function:

But I can't get the intended result as indicated at the bottom of working? Is anyone able to spot where I am going wrong in my working or method of attack please?


texts:
I currently have this setup in my van:
Alternator -> Car Battery -> Voltage Sensitive Relay -> Leisure Battery (AGM)
I'm thinking of changing out my AGM battery with a LiFePO4 battery instead, which I know has a very different charging profile to an AGM and also has a low internal resistance compared to an AGM. Can this be problematic?
Thanks.


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Many of the newer bike lights use LEDs. Although I understand basic electronics it has been some years since I learned electronic theory. Although I understand the basics of buck and boost drivers I have some questions about how they operate.

Question one: Is it possible that a driver can supply more current to a load than the current that is delivered to the driver from the battery ( or voltage source )? This has been something that I have wondered about for some time. I always thought that the max. current supplied by the voltage source was the same as the max. current supplied and delivered through the load powered by the driver. I've heard that this is not so and that a driver can deliver more current ( depending on the design and components used to build the driver ). Is this possible?

Put another way; Is there such a thing as a boost driver that not only regulates current but boosts current as well?


texts: Altium error: "net contains multiple output pins" on LT3045 chip

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I have two concerns:

Is it okay to have "contains multiple output pins error" in Altium?
Is anyone familiar with LT3045 chip? Its datasheet applications only have 1 "IN" pin and 1 "OUT" pin, and never mentioned why the chip itself has 3 "IN" and 2 "OUT". Its internal schematic doesn't show multiple "IN"s and "OUT"s either, am I safe to tie them together?


texts: YFS201 Flow sensor frequency to voltage converter circuit reg

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I am using YFS201 flow sensors to detect the flow of water in a pipe .
 The response from the flow sensor is frequency and I want to convert output of flow sensor in to voltage.
I have searched in Google I have got some circuit.

http://www.circuitstoday.com/frequency-to-voltage-converter-using-lm331

when I am using that I am getting only 0.2v /0.3v max.

I have used exact components for these circuits which is mentioned on above link

If you one have experienced in this frequency to voltage converter circuit please share your knowledge to me


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This is a follow-up question to How high is "high impedance" on this chip (CD74HC125E)

I finally decided to use a pn2222 transistor to act as a switch that activates the transmitter. The circuit is as follow:

simulate this circuit – Schematic created using CircuitLab

In order to activate the transmitter TX, T1 and T2 must be (dis)connected. The goal of this circuit is to activate TX through the transistor Q1, depending on whether SW1 is open or closed.

Web URL for the transmitter (available in French an Dutch only): http://www.chacon.be/index.php/domotique/my-fox-domotique-a-distance/kit-va-et-vient-micro-modules-rec-em.html

Currently, the switch is actually a custom RJ45 plug, but will eventually be replaced by an arduino output. Feel free to ignore this part if not relevant.

I have three questions about this:

Does it look correct to you?
I calculated the voltage at the base of Q1 to be 1.1v, due to the voltage divider. Is this correct / does Q1 change something in this ? Is it enough/relevant? Provided that the goal is to make TX think that T1 and T2 are shorted.
I could not reduce the average current consumption of the whole circuit, even with more resistors. How can I reduce it?


texts: I created a sinusoid signal(red) using the 555 timer in LTSpice. My goal is to flip this signal about the time axis (i.e. 180 degree phase shift)s so I thought I could use an Op Amp inverting amplifier to do. The resulting waveform (yellow-green) is somewhat like an inverted sinusoid but not exactly. What circuit should I build to successfully invert this sinusoid signal?


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i'm reading a book that it says :

  If a current of 1A flows through a copper wire, the number of electrons flowing by a cross section of the wire in 1s is equal to :

  1A=(1C/1s)(electron/-1.602*10^-19C)=-6.24*10^18 electrons/s

I really don't understand how he can have this result, what's the mean of electron into the division here ?
Thanks for the help!


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I was watching the video on Forever Flasher circuit in Advent Calendar of Circuits 2011 series by vk2zay. Below is the circuit I am talking about. However, there are some things I understand and most things I do not understand about the working of the circuit.

Things I understand and do not understand:

When the circuit is powered up, Q2 is turned on a little through R1 and R2 which turns on Q3. When Q3 is turned on, Q2 is turned on more with the current coming from the collector of Q3, through C2 and R5. So they are complimentary pair as vk2zay said in the video. When Q3 is on, it turns Q1 on through R4. When Q1 is turned on, base current that were supplied to Q2 through R1 and R2 is no longer supplied because bottom end of R1 is in the ground potential.

In this position, where Q1, Q2 & Q3 are on, currents flowing are: from Q3:C to R7 to GND, from Q3:C to C2 to R5 to (Q2:B & (R2 to Q1:C to GND) ), Q3:C to R4 to Q1:B to GND. These are the ones I understand but I do not not how C1's current flows and comes from where and goes to where. But here, I think the voltage at "out" and Q3:C which is supply voltage, adds up.

After some point Vc2 goes up to about 0.9 volts which turns Q2 off. So it turns Q3 off. What happens to the charge and voltage at C2? How and to where it discharges? At this point, how and from where to where will Ic1 go?

I just added QTLP690C as a high forward voltage LED. Assume the forward voltage of the LED is 2 to 2.5 volts.

Sorry if I sounded complicated. I would appreciate any detailed information on this. Also, any tips on how to understand how these kind of circuits work?


texts: Why does this work for biasing an AC signal for A/D conversion

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I have a working circuit for biasing the AC signal going into my ADC, but I cant quite wrap my head around why it works. I can see that it resembles a high pass filter but how/why does it add the two voltages together? For example if the AC signal is at 1.5V, the ADC input is at 4V (1.5V + 2.5V).

The 2.5V comes from a simple voltage divider circuit. The AC signal is coming from a voltage follower op amp.


texts: How the effect of the output inductor is minimized and filter offers only single pole by current mode control?

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In this application note "Switching Power Supply Topology Voltage Mode vs. Current Mode", page 2, Current Mode Control section the author claimed as follows:

  Since the Error Amplifier is now used to command an output current rather than voltage, the effect of the output inductor is minimized
  and the filter now offers only a single pole to the feedback loop (at
  least in the normal region of interest). This allows both simpler
  compensation and a higher gain bandwidth over a comparable
  voltage-mode circuit.

Could anyone explain it in more detail? How "the effect of the output inductor is minimized and the filter offers only a single pole to the feedback loop" as
Error Amplifier is used to command an output current rather than voltage?


texts: How to specify a state when the system does not change in an ASM chart

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This may be simple or obvious but I have not found any definite solution by googling.

I want to include a state in my Algorithmic State Machine chart were nothing changes (no operations on registers) until an input signal changes. One way I have thought of doing this is to include an empty state, where an infinite loop constantly polls until the input changes.
Can state boxes be empty in an ASM chart? In other words, is this allowed?


texts:
I opened up a really tiny mobile phone charger I have, to see how it is designed. The entire "charger" is integrated into a small 2-pin mains plug, 1 x 1.25 x 0.5 inch, that has an USB socket for the phone's USB charging cable.

I could not find anything that seems to be a transformer anywhere in the circuit, and yet I have tested that it is an isolated 5 volt well-regulated output. The tiny flexible PCB has merely a dozen or so SMD parts, ranging from 0402 to 4516 (metric), plus the connectors at the two ends, for mains and for USB. The SMD parts all have part numbers sanded off.

How do they manage the isolation in these chargers?

Responses to comments: This is a no-name "Hi-Standard USB phone charger, Extra Powerful!" I have just bought in Korea, that is supposed to work with any USB-charged cellphone. They have pictures of a half dozen different cellphones on the box, and a hydra USB cable inside that has mini-USB, micro-USB and some other types of connectors.

I bought it just to see whether it is safe or not. That is why I tested for isolation first.