texts:
The following electret microphone preamp circuit seems to work pretty well. My electret model is a little off because on the bread board R6 needs to be ~33k to get the output at 1/2 supply.

Just a little explaination: The current mirrors provide a current source for the electret yielding high gain / linearity and a current sink for the output makes a buffer with high input impedance (for interfacing with the high output impedance of the input stage) and yields good low output impedance. Surprisingly the circuit appears to be very stable. I did not have to add any capacitors anywhere. The noise floor appears to be quite good but I don't want to post a number because my tool chain is very crude. But as you can see there are no resistors at all in series with the signal.

But there is one little problem (at least for my use-case) that I was hoping someone might have insight into. The response of this circuit is totally flat. In fact, you can see there are no capacitors at all (other than the membrane of the electret) so the output is actually DC coupled to the microphone membrane. This would probably make a good measurement microphone but for actually recording an instrument it's not ideal because a gentle breeze would probably cause the output to swing.

So my question is, is there a way to attenuate low frequencies somewhere? I cannot just add a capacitor in front of Q5 because it needs to be biased. I was wondering if there is some kind of clever frequency dependent current mirror that could be used on the input so that at low frequencies it degenerates to a resistive load and thus reduces the gain. Or perhaps a transformer or inductor could be employed somewhere? This seems like a pretty clever circuit so I'm hoping someone could come up with a clever way to remove DC and / or gently roll off frequencies below 100 Hz to make this nice for actually recording an instrument.

UPDATE:

This circuit is not ideal for several reasons. First, both current mirrors are programmed from the same reference so the output current is limited to the current required by the electret which is too low (260uA). So the whole current mirror idea is not that clever. Another problem is that the circuit has too much gain. Even without the current source to increase gain, the output is basically line-level.

However, one thing that is clear is that electret microphones (at least the pc pin one from Radio Shack) is an awesome device. After some careful fiddling, I was able to get a very smooth noise floor of more than 90 dB down @ 1k. I could see the spectrum display change in response to a distant barely audible noise. And that is with the mic carefully enclosed in vinyl tubing and black tape. So a simple bias resistor style circuit, buffer and careful supply filtering could make for a very quiet microphone with a totally flat response and cost next to nothing.


texts:
Intel's 8086 manual shows the following diagram for the CPU's architecture (in page 2-5):

If I understand correctly, the ALU's two operands and result are retrieved from / sent to the same 16-bit bus.

If I understand correctly, this causes every calculation to take a minimum of three cycles:
Cycle #1: put the first operand on the bus, and copy it to a temporary register.
Cycle #2: put the second operand on the bus, and copy it to a temporary register.
Cycle #3: allow the ALU result on the bus.

This seems consistent with the timing tables (e.g. a register-register ADD is said to take exactly three clock cycles). (or not? I EDITed below)

However, this doesn't seem very efficient, and also, I saw other diagrams, like this one:

http://www.cosc.brocku.ca/~bockusd/3p92/Local_Pages/8086_achitecture.htm

that also show the Flags as being sent to the same bus, which doesn't really make sense to me.

So - is this the actual physical implementation, or an abstraction, and actually the "ALU bus" consists of multiple 16-bit lines?

EDIT: I wrote: "This seems consistent with the timing tables (e.g. a register-register ADD is said to take exactly three clock cycles).". In second thought, I'm not sure that it's consistent, because the IP register also needs to be incremented, so with 3 cycles per ALU add, the entire ADD instruction should take 6 cycles...


texts:
I'm currently working my way through a beginner's electronics book(electronics for dummies) where i am introduced to RC circuits as shown in the schematic below.

simulate this circuit – Schematic created using CircuitLab

From the book,I am told that initially, the voltage across the capacitor is 0(assuming it's discharged), and that the voltage drop = the voltage rise(kirchoff's law).

When the capacitor is charging

Initially: Because capacitor voltage is initially 0, the resistor voltage is equal to the supply voltage.

Charging: As the capacitor begins to charge, it develops a voltage, so the resistor voltage begins to fall, which in turns reduces the charging current, which in turn causes the capacitor to charge at a slower rate. This continues until the capacitor is fully charged.

Fully Charged:When the capacitor is fully charged, the current stops flowing, the voltage drop across the resistor is zero, and the voltage drop across the capacitor is equal to the supply voltage.

When the capacitor is discharging

(Battery is removed and resistor is connected in parallel with the capacitor). Voltage across resistor is equal to voltage across the capacitor (V[r] = V[c]), therefore the current is given by the equation V[c] / R (resistor value).

Initially: Because the capacitor is fully charged, the voltage is equal to V[s] (Voltage supply), so the current is given by V[s] / R. (Basically the same as V[c] / R )

Charging: As the charges begin to flow from one capacitor plate to the other, the capacitor voltage( and so V[r] ) starts to drop, resulting in a lower current .The capacitor continues to discharge, but at a slower rate. As V[c] ( and so V[r]) continues to decrease, so does the current.

Fully discharged: When the capacitor is fully discharged, current stops flowing and no voltage is dropped across either the resistor or the capacitor.

What i understand

Voltage drop = Amount of volts/voltage used up.
Ohm's law (V = IR) etc
Kirchoff's law ( voltage used up = voltage in circuit / voltage drop = voltage rise)

Questions(Charging):

Why is the resistor voltage initially equal to supply voltage? Is it because there is no voltage going across the capacitor yet? Therefore, as there is no voltage drop across the capacitor, all the voltage from the battery is across the resistor?

  As the capacitor begins to charge, it develops a voltage........

2.What exactly does the voltage developed as the capacitor charges refer to? Is it the amount of electrons that begin to accumulate on
    it's negatively charged plate?
    What exactly is voltage?
    seems to suggest that it is NOT the amount of electrons. However,
    assuming that the voltage developed by the capacitor refers to the
    voltage rise across the capacitor, WHERE and/or WHAT does
    the voltage risen actually do? Assuming that voltage is the
    electromotive force that pushes electrons around, how then does it
    build up in the capacitor when all that's happening in the capacitor
    is that electrons are building up in it??

3.Am i correct in assuming that the resistor voltage drops because the capacitor's voltage is increasing? (kirchoff's law where volt rise = volt drop).

Question(Discharging)

  As the charges begin to flow from one capacitor plate to the other, the capacitor voltage( and so V[r] ) starts to drop, resulting in a lower current....

1.If the capacitor's voltage is dropping(due to it being discharged), shouldn't the resistor's voltage be increasing due to kirchoff's law? Also,this should therefore INCREASE the current instead of decreasing it, which would then cause the capacitor to discharge even faster?

I apologise in advance for the wall of text above, but i've been scratching my head over this for quite some time now, and it's really eating away at me.

I would appreciate any clarifications i can get.

Thanks!


texts:
I am considering placing a typical PCB in a high-pressure oil environment. Right now it is just a "crazy idea", but I am wondering what would prevent this from theoretically working. Notionally, consider a motor controller consisting of some passives, a microcontroller and servo driver. All COTS.

The oil in use is non-conductive. I believe the core of my worry is about pressure on components. I am looking at about 300psi. Specifically, I would imagine some components on the PCB would not be tolerant to pressure (electrolytic capacitors). Some would be (SMD resistors, IC packages, etc.)

To be clear, the motivation for this idea is not related to cooling. It is simply convenient for my end application to be embedded in oil. (I tagged it with "cooling" because the setup is similar.)

Lastly, I have thought about possible references I can pursue for this. I know that some high-performance systems use phase change cooling within pressure vessels. I couldn't find any references on this, but I'm an EE and not physics. Perhaps there is some information out there on design of these systems?


texts: How is debugging build implemented in VHDL?

texts:
I come from C background and am being introduced to VHDL. I read about the syntax and the concurrency/consecutiveness of actions.

Now I am getting to wonder how are development-only features implemented. Things like assert() and #ifndef NDEBUG LOG_MSG_UART("99 bottles of beer").

The scenario, that I am thinking of, is this. Let us have a development board with an FPGA and several debugging headers. Various signals are output to those debug headers for measurement with an oscilloscope or logic analyzer. In the release version, there will be no such headers. How does one write the code so that they can easily switch between the Release and Debug builds?

An idiomatic example would help a lot.


texts: Ideal Transformer equations when the secondary winding is short-circuit?

texts:
This is my problem

Now I know that ideally $$V_1/V_2 = 1:α$$ and $$(J_1-J_3) = α  (J_2-J_3)$$

where J1 is the current of the left mesh, J2 is the current of the right mesh and J3 is the current of the mesh in the middle(the one that passes through Zx)

If V0 = 0 then that means that ZL is short-circuited thus $$V_2 = 0$$ as well. Can I use equation of currents for the ideal transformer if V1/V2 can't be used?


texts:
I have a few questions regarding the use of the BlueNRG-2 device

I am building a system where I have to send small data packets (10 bytes) from 1 unit to 10+ units. I am aware that you can only have 7 simultaneous connections, but I am wondering if there is a way to broadcast this information, and have anything that is within range receive and interpret the data.

-if so, does anyone happen to have a code sample they would be willing to share?

Do you need an antenna for BLE to function? The range only needs to be about 5-10ft.

Other than the BlueNRG-2 module, is there any supporting circuitry that is necessary for functionality? I need this to fit on a PCB that is 12mm x 12mm so space is very limited

Thanks in advance


texts:
I am new to all this so forgive the dumb rating.

I need to monitor the speed of a few conveyor belts, the belts are around 10ft to 50ft long and 3ft wide and has anything from heavy boxes to thin light boxes placed onto it all day long so whatever I do it needs to be able to take a bit of a shake when the heavy boxes land, if its mounted to the machine somewhere.

Note the boxes are variable in height, width, weight and distance apart on the belts. So I need to work with the belt rather than what's on the belt.

I am thinking of using Arduino (someone has suggested as the best way to interface with a computer). I know C# and PHP and some basic electronics from the 90s (collage), so if you have any other recommendations on interfacing with a computer I would welcome the input.

Ok to my question:

How or what is the best way to monitor the belts speed without anything actually touching it? Speed range 0 to 15kph.

I was thinking:

Light detection? Draw or stick something to the belt which is of a light colour and when it passes a sensor of some kind it registers as on and then off when its not under the sensor. Then I can make the necessary calculations? But I can see the tape peeling off or marker wearing off quickly.
A mouse like laser sensor?

?? Any ideas ??

My primary factors are:

It must be robust and run all day long, 5 days a week
It must update speed fairly frequently
Cheaper the better
Can be boxed and mounted or something

Here is what I am thinking of, but I don't know anything about what sensors does what and where to buy these sensors from (RS Electronics website seems to be down).

Any advice you can give me is much appreciated.

Thanks


texts: How to share ground connection between to microcontrollers connected to a PC

texts:
I have 2 microcontroller evaluation boards and I am trying to make a I2C communication between them.

Both of the boards are connected to the same PC using USB cables. SDA and SCL pins are also connected. Now I want to know how to connect the ground? I mean do I need to connect grounds of the two boards, or since they are powered by same PC which means they have the same ground reference point, an extra ground connection between them makes a loop or something?

I have checked both with and without GND between two boards, and it works, but I do not have access to Scope or something that I can confirm which is the right thing to do:


texts: Creation of Trap Levels in Band Gap Energy

texts:
When I started reading about basics of semiconductors, I read that no electron is present in the band gap energy and it is a sort of forbidden area for them.

But just now I read that some trap levels are present in the band energy in between the conduction band and valence band. How is this possible?


texts:
I would like to ask, which one is the best way to lay underground low voltage (400V) AC cables, flat or triangular formation. The application that i am interested in is a photovoltaic plant.

The Neutral and the protective earth (PE) conductor affect the configuration?
Also in case of more than one AC circuits, how much is the optimal distance between the two circuits.
I know that this topic is complicated. Thus, I would be grateful in case that you have a book or article to propose.


texts:
I'm doing a LED matrix design and it's a cathode row design. Attached is a picture of my matrix design.

The design works ok and I can show any pattern in the matrix.

The problem is when a leak LED is there, the OFF LEDs also lights up dimly. Even a small leak is there in a LED the remaining row LEDs lits slightly.

How can this happen? How to overcome this situation?

Mostly this situation happens in Green, Blue, White LEDS (3V Ones).


texts:
I am working on a simple protection circuit for an I/O pin on an MCU. The device will be 3v battery powered. The MCU's I/O pin has a voltage tolerance of (GND - .6V) to (Vdd + .6V).

Pull-to-ground Digital Input (Pulse Signals)
Digital 24Vdc Input (from a thermostat)
High-Frequency 24V Counter
Pull-to-ground Serial Input (1200 baud - 9600 baud rates)

On the MCU will be an internal setting that will be used to decide what type of signal to look for and process, so this input circuit will just need to make sure that the MCU's I/O pin is protected no matter the input type (listed above).

Here is another one of my posts explaining my first attempts. The below circuit is a modification of the one recommended by @Jeroen3.

simulate this circuit – Schematic created using CircuitLab

So far the simulations look pretty good. Here is a voltage sweep of 0V-24V:

Frequency responses also look pretty good.

Does anyone have any experience with a similar circuit, suggestions, or can spot possible issues?


texts: battery protection circuit - identify discharge current rate that will trigger protection

texts:
We are considering to add a battery protection circuit to our system in addition to the protection circuit that already exists on the 4.2V Li battery pack itself.
I know that the batteries have maximum allowed discharge current rate specified. Let's say it is 1000mA current. Hence I need to make sure that the battery protection circuit will disconnect the battery once the load draws more than 1000mA. Now, in the all datasheets of battery protection circuits, this kind of protection is called "discharge over current", and its range is not given in Amps, but rather in Volts. For this device to be compatible, it should trigger at 1000mA, but I cannot figure out the current value from the voltage values provided in the datasheet. For example, this is the device that I am currently considering to use - AP9221: https://www.diodes.com/assets/Datasheets/AP9221.pdf

Discharge Over-current Detection Voltage: 0.025V to 0.2V (10mV Steps)
Accuracy ±12mV

I can order this device with specified voltage.
Let's say I choose 0.025V. What is corresponding discharge current?
In the datasheet there is also following information:

RSS(ON) 120 mΩ

So, my understanding is following:
I = V/R = 0.025/0.12 = 0.2A -> current rate after which the protection circuit will fire.
But in this post, there is different formula(with factor of 2): Over current protection for a 1-cell battery
What is proper way to calculate it?
I would appreciate any help.


texts: Reading current memory image from a micro controller

texts:
I have the MPLAB XPress Evaluation Board, which has the PIC16F18855 microcontroller on it. The way to program it is just to copy a .hex file through the serial connection, which makes the bootloader update its memory image.

Is there a way to directly read the current memory image of the microcontroller? In other words, how is it possible to dump the memory image of a microcontroller?


texts: Draw the graph of differential of the following graph

texts: Is is like this? I think there should be impulse signal also in the graph am i doing wrong?


texts: What is the small barrel type connector called?

texts: I just ordered a barrel connector but it's bigger then the one i need, What is the small barrel type connector called. My original one has a yellow ring around it, Is that an indicator of what type it is?


texts: Why does the output of a register bank( designed by me in verilog) change after two clock cycles, even if input changes every clock cycle?

texts:
I have designed a register bank (pipeline register) to be used in a pipeline-architecture. The code of the register is:

module if_id(   input clk,
                input [31:0] newPC,
                input [31:0] instr,

                output reg [31:0] newPCout,
                output reg [31:0] instrOut);

    reg [63:0] temp;
    always @ (posedge clk) begin
        temp <= {newPC,instr};
    end
    always @ (negedge clk) begin
        newPCout <=  temp[63:32];
        instrOut <= temp[31:0];
    end
endmodule

Now in this waveform, instrOut changes every 2nd clock cycle. Why?
I cannot seem to find the fault in the code, according to me the output should change at every negedge of the clock.

This is the image of the test bench, pipe1 is the instance of if_id module.

module tb(); // tb for fetch
    //fetch
    reg [31:0] baddress;
    reg clk;
    reg pcsource;

    //fetch
    wire [31:0]newpc;
    wire [31:0]instr;

    //if_id
    wire [31:0]newpcpipe1;
    wire [31:0]instrpipe1;

    //decode
    wire [31:0]rd1,rd2;
    wire [31:0]imm;
    wire [4:0]rs,rt,rd;
    wire [5:0]opcode;

    //main Control
    wire [3:0]ex;
    wire [2:0]mem;
    wire [1:0]wb;

    //id_ex
    wire [3:0] exo;
    wire [1:0]wbo;
    wire [2:0]memo;
    wire [31:0] rd1o;
    wire [31:0] rd2o;
    wire [31:0] immo;
    wire [4:0]  rso;
    wire [4:0]  rto;
    wire [4:0]  rdo;
    wire [31:0] newPCo;

    //ex
    wire [31:0]tPc;
    wire[31:0] AluRes;
    wire [4:0] regDstAdd;
    wire zero;

    //ex_mem
    wire [1:0]wb_m;
    wire [2:0]mem_m;
    wire zero_m;
    wire [31:0] AluOut_m;
    wire [4:0] regdst_m;
    wire [31:0] newPC_m;

    //mem
    wire PCSrc;
    wire [31:0] aluouto;

    //mem_wb
    wire regWrite;
    wire [31:0] AluOut_w;
    wire [4:0] regdst_w;

    fetch fetch1(clk,pcsource,baddress,newpc,instr);
    if_id pipe1(clk,newpc,instr,newpcpipe1,instrpipe1);

    decode decode1(clk,instrpipe1,AluOut_w,regdst_w,regWrite,rd1,rd2,imm,rs,rt,rd,opcode);
    MainControl mc1(opcode,ex,mem,wb);
    id_ex pipe2(clk,wb,mem,ex,newpcpipe1,rd1,rd2,imm,rs,rt,rd,exo,wbo,memo,rd1o,rd2o,immo,rso,rto,rdo,newPCo );

    ex ex1(newPCo,rd1o,rd2o,immo,rto,rdo,exo,tPc,AluRes,regDstAdd,zero);
    ex_mem pipe3(clk,wbo,memo,tPc,AluRes,zero,regDstAdd,wb_m,mem_m,zero_m,AluOut_m,regdst_m,newPC_m);

    mem mem1(mem_m,AluOut_m,zero_m,PCSrc,aluouto);
    mem_wb pipe4(clk,wb_m,AluOut_m,regdst_m,regWrite,AluOut_w,regdst_w);

    initial begin
        $dumpfile("fetch.vcd");
        $dumpvars(0,tb);
    end

    initial begin
        clk = 1'b0;
        forever #5 clk = ~clk;
    end
    initial begin
        //$monitor($time," clk = %b \n ,instr=%b, newPC = %b,",clk,instrpipe1,newpcpipe1);
        #10 baddress = 32'b0; pcsource = 0;
        #200 $finish;
    end
endmodule
```


texts: Can I use a capacitor to power an Arduino for 5 minutes after the power has been cut?

texts:
I'm working on a simple setup using an Arduino Nano to automate the switching of my car headlights when it gets dark. I am happy with how to program the Arduino & LDR use and coding, it will be powered using a DC-DC buck converter to convert the 12.9V(ish) to around 7V. I intend to power the Arduino from the switched live circuit in the car, so that it will not draw power when the car is not in use, and as it will control a normally open relay, there is no risk of the Arduino accidentally turning on the lights when it's parked up. (relay will be on the low current switch side of the OEM factory wiring, before the main headlight relays, there will also be a switch to isolate the Arduino and operate the lights as normal)

However I would like to have it so the lights stay on for 5 minutes or so after the car is switched off, would this be possible using a capacitor or similar that charges when the Arduino is powered, and continues to power it after the power is cut? I assume I would need some circuitry to ensure the cap provides stable current/voltage during discharge, although the Arduino is helpful in being able to run on anything from 5-12V. This would give me automatic lights when the car is on(or the key is turned in the ignition at least), but ensure there is no way for the lights to come on accidentally.

Any help is much appreciated. I asked this question on an Arduino forum but most answers just advised to power the Arduino constantly and do the delay with code, which is something I really want avoid as the car is not used everyday, and I don't want to have to jump it because the Nano has drained the battery.


texts: Is it safe to use a voltage divider for Arduino and DC motor controller?

texts:
I have ordered a Dual H-Bridge 12A continuous (30A peak) Polulu motor driver shield for my upcoming (first time ever, a 1.2m long tank made of wood) robot project.

I was thinking about how to supply the power to all the components in the circuit without wasting much power, but the only thing I can come up with is this simple voltage divider connected in parallel to the motor drive:

Knowing the Arduino can handle max 5V I did make sure to make it a bit lower.

But my wonders go to the fact that I am suspicious that connecting the motor driver and Arduino to the same power source isn't a great idea? Or am I paranoid?

And what about power waste by the voltage divider, how can I reduce/minimize it? Make the resistors smaller? (15/10 ohm - but more error and higher current)

Is there a formula to find the most effective R1 and R2?

Do I have to worry about current spikes?

Any other things I could miss in this simple-yet-suspicious circuit?

Also, if I wanted to simulate any possible scenario, which components should I choose in the circuit to keep it as simple as possible (for simulating in Multisim 13)?


texts: Looking for a motherboard CPU Power MOSFET replacement - is this OK to put not exact the same?

texts:
I have a motherboard with broken PDC3094X (Potens Semiconductor) in VRM circuit. I cannot find the replacement with exact same parameters and the original part is impossible to get. I don't have a lot of experience in finding a replacement parts, so I have a big request for some help.

PDC3094X parameters are:

Id= 90A
Vds= 30V
Rdson= 4mOhm (@Vgs= 10V)
Pd= 115W
Qg= 24nC (@Id= 20A)
Ci= 2200pF
Co= 475pF

PDC3094X PDF datasheet: http://potens-semi.com/pdf/PDC3094X.pdf

Would that be OK to replace it with TEXAS INSTRUMENTS CSD17576Q5BT?

CSD17576Q5BT parameters are:

Id= 100A
Vds= 30V
Rdson= 1,7mOhm (@Vgs= 10V)
Pd= 125W
Qg= 25nC (@Id= 25A)
Ci= 3410pF
Co= 389pF

CSD17576Q5BT PDF datasheet: http://www.ti.com/lit/ds/symlink/csd17576q5b.pdf

Which other MOSFET in such package would fit? What are terms of finding a good replacement for motherboard power-line MOSFET? What parameters are the most important?


texts: How to convert from 2s complement values to binary?

texts: I am trying to build a calculator that can perform addition and subtraction and works like a real calculator(ie, you press the first number, than the operation, then the second number, and press = to get the answer). My problem is that when I subtract, it gives me the 2s complement of the answer. How can I convert from 2s complement to binary, using a machine?


texts: How can I get/build a current controller/amplifier?

texts:
Background:
I have a Lorenz-actuator (coil+magnet) that I need to control precisely using a computer. The computer signal is output from a dSpace microLab box as an analog ±10V signal. This signal needs to be scaled to a current of ±5A at roughly 24V. Given the phase shifting properties of coils as well as the underlying physics of Lorenz-actuators, the output current needs to follow the input signal. The system being controlled is highly dynamic and therefore requires a very accurate step response from the current controller. (Perfect tracking up to 200Hz) Four of these actuators need to be controlled so price and size are a factor to consider.

Attempted solutions:
Using a shaker current amplifier: Shakers cant handle any DC, therefore the amplifier has irremovable high-pass filters. My application requires some DC-component in the signal. The ones available to me are also very large and expensive.

Using a voltage amplifier and hoping for the best: Not getting the desired force trajectory from the actuator because current is not being controlled directly. Also can't tune the PID parameters of the control loop.

Using a current controller: I haven't been able to find any online that can drive a current of 5A dynamically. A constant current source is not useful for this application.

Using elmo servo drivers: The output current follows the input signal perfectly, however the drives are completely overkill. They are meant to take a digital signal and control the velocity, position and current of an actuator. Using them as an analog current amplifier is a waste of money.

Question:
Does anyone know of an off-the-shelf solution to control the current to the actuator? Or possibly a paper describing how to build a circuit that could amplify an analog current signal?


texts: Can a series resistor be used to limit the power consumption of a phototransistor?

texts:
I’m hoping to use several QRD1113 IR proximity sensors in a device, and they work well but have higher power consumption than I would like. I’ve tested many other ones, but I haven’t found another with a combination of features that will work for me. I’m using a circuit similar to the one in the attached image from Learn.parallax.com.

My question is, would it be possible to use a series resistor between Vcc and the collector to reduce the power consumption of the sensor, assuming I don’t mind using a larger load resistor and sacrificing some speed? Would this have undesirable effects on the performance? In a quick test, it seemed like the voltage I was reading would no longer drop to zero when the transistor was dark, which I don’t completely understand.

My reason for not using a larger load resistor value is that the sensitivity then becomes too high (I need to have analog output with a high overhead so I can also sense and correct for ambient light with the LED off).

I have eight of these sensors (it’s a musical instrument where the sensors each sense a finger) and I’m already switching the LEDs at around 1 kHz with a 50% duty cycle, and only one LED on at a time. I also have the LED resistor value as high as I can comfortably make them, because I want a strong signal relative to the influence of ambient light. So, while the LEDs are a significant current sink, I don’t think I can reduce that much more. The transistors, on the other hand, pass a lot of current when not covered by a finger and are exposed to sunlight, which is my main concern. I could switch the transistors too, but I would need a lot more GPIO for that.

I have eight of these sensors (it’s a musical instrument where the sensors each sense a finger) and I’m already switching the LEDs at around 1 kHz with a 50% duty cycle, and only one LED on at a time. I also have the LED resistor value as high as I can comfortably make them, because I want a strong signal relative to the influence of ambient light. So, while the LEDs are a significant current sink, I don’t think I can reduce that much more. The transistors, on the other hand, pass a lot of current when not covered by a finger and are exposed to sunlight, which is my main concern. I could switch the transistors too, but I would need a lot more GPIO for that.


texts: Effective highpass filter with one opamp

texts:
I have a phototransistor giving me some noise at about 100Hz and I am transmitting an IR signal at it of 10khz. I would like to completely eliminate the noise since it would be amplified at later stages and turned into discrete on, off signals using a comparator. I know about first order and second order high pass filters.

I currently have basic knowledge of analog electronics.

Is there any way to completely eliminate the 100 Hz signal?


texts: Are all linear regulators bad at filtering input ripple? (or really as bad as Dave suggests)?

texts:
Background

In EEVBlog #1116, Dave discusses a method to remove power supply ripple, and goes on to show (see 5:17 to 6:15) that you cannot count on linear regulators to remove your input ripple. He gave a concrete example in the lab: at 10 kHz input ripple and MCP1700 (a CMOS LDO), as demonstrated on the 'scope, the ripple largely passes through.

While the rest of the video is meticulously explained, I feel that he present this example in a bit of a cherry-picked manner and omitted relevant details. I remember doing exactly the thing he warns against: I had a class-A headphone amplifier, which, when powered via a specific el-cheapo wall-wart at 12V, had a whistling sound on the output, caused by the switching noise of the power supply. In that occasion I lowered and cleaned the input voltage with a LM317, which completely removed the noise.

Note I'm not saying Dave is wrong - his warning is that a linear regulator, and a LDO in particular, may not solve your problems.

I have enough intuition to guess that what he talks about likely applies mostly to LDOs, since I've heard they can have stability issues and I guess the internal compensation against oscillation makes their pass element somewhat inert, so at frequencies like the 10 kHz he tests with, things can be quite bad. I don't see how they would fail the same test at 50-120 Hz, since this is a very common usage scenario which the IC designers likely thought about.

Question

Do all linear regulators perform poorly — say, have ripple rejection less than 15dB — at some combination of frequency and load current? Assuming other conditions aren't super-bad, i.e. not talking about 125°C and/or input voltage touching the dropout zone?
On a related note, is there a linear IC design, which is particularly good at rejecting input ripple all the way up to 500 kHz?


texts: Buck converter controlled by a BJT based astable multi-vibrator with zener-based feedback?

texts:
simulate this circuit – Schematic created using CircuitLab

This is my rough sketch for a buck converter controlled by a BJT based astable multi-vibrator with zener-based feedback. Before I go through getting the values of each component, I wanted to make sure that I understand how these components would work in my circuit, and if I've done anything dangerous here.

Theory of Operation:

1) The mains go through a transformer which brings it down to 20-25V AC. This also has the effect of isolating the circuit from earth-ground.
2) The bridge rectifier BR1 converts the AC into full-wave DC.
3) C1 is a giant electrolytic which smoothes the DC wave into "constant" DC.

Oscillator:
1) R1 and R2 form a voltage divider which provides 5V to the oscillator. It is acceptable to use a voltage divider because the load of the oscillator will be known, and the current it draws will be relatively low. Our efficiency is not completely compromised due to this, and we don't get an unmanageable production of heat.
2) The 5V is fed into a standard BJT astable oscillator, with one exception. The low-value resistor which dictates the RC time constant of C3 is replaced by a P-Type Mosfet which acts as a variable resistor. Variation in the current on the gate of the Mosfet will change the RC time constant of C3, effectively modulating out pulse width if we apply feedback.
3) The collector of Q2 is used as the input to our buck converter.
4) D2 is a reverse bias zener diode. If the voltage goes above 12V then the zener will allow current through. This current will be sent to the gate of M1, the "variable resistor" Mosfet from step 2.  D2 is placed in reverse bias directly to the load. This channel is used as feedback.

Buck Converter:
1) An NPN BJT (Q3) is being used as a switch. Since we're dealing with 5V logic, saturation shouldn't be an issue.
2) L1 evens out changes in current, while C4 evens out changes in voltage. This averages the input.
3) D1 prevents a massive negative voltage surge from destroying the BJT switch Q3 when Q3 goes from on to off.

Question:
Is there anything wrong with the theoretical version of the circuit, barring that it needs to have values applied to the components?


texts: Explanation for Differing Stator Winding Orientations

texts:
As a layperson, I'm trying to understand the basic configuration for an induction motor or generator. I've looked at many diagrams and photos/cutaways of stator wiring and I've noticed two different orientations for the windings:

All the diagrams/photos I've seen show an individual winding in the shape of a rectangle with rounded corners.

Type One - The axis of the winding points toward the shaft of the rotor.
Type Two - The axis of the winding points 90deg away from the the shaft of the rotor.

The difference between these two orientations is making it difficult for me to conceptualize the "rotating electromagnetic field" that exists in motors/generators. I am looking for an explanation of the pusposes behind these two winding orientations.

[EDIT]

45deg orientation:

0deg orientation:

90deg orientation: I can't find one right now.


texts: Problems running a triac dimmer off a UPS

texts:
I built a circuit (like the one below) to control an incandescent light bulb from an Arduino controller for the digital input.

I did not use the zero crossing part of the circuit and mine is running on 120V and a 220 ohm resistor for the triac. My program turns the triac on and off making it dim but also flickers which is an effect I am looking for cause this will be used to simulate a fire. Works great!

My problem happens when I have it plugged into a computer UPS. When I unplug it, and it switches to battery use, the light bulb switches on and stays on. (I swear I had tested this and it didn't do that before.) The circuit works perfectly if I put the UPS back online. The output of the UPS isn't the nice sine wave I expected it to have for a computer back up and, instead, looks like the output of an inverter I tried before; very spiky. I also measure the voltage dropping to around 90V with a meter.

The whole purpose of this is to make this circuit be portable inside a bucket with a UPS powering it and now I'm stuck and running out of time. Does someone have a fix and possibly a lesson in the process? (I've been out of electronics for a while and not a power electronics guy in the first place.)

EDIT: It is not necessary for me to use this circuit exactly. I once thought of using a FET and driving the bulbs directly from an inverter but my UPS idea solved the problem of charging the battery. But I have the same problem in that I have not done any circuit design in over 10 years.


texts: Dependence of the PWM amplitude of the amplifier on the battery voltage

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I'm going to use speaker connected to internal Class D amplifier in WM8998 in my PCB.
Power source of my PCB is Li-Pol battery with 3.2-4.1V range or external 4V adapter.
Audio codec speaker power pins(SPKVDD) should be connected to battery according WM8998 datasheet.
Do I understand correctly that WM8998 doesn't consider battery voltage to stabilize PWM amplitude and output volume will be depends not only on value in register OUT4R_VOL/OUT4L_VOL but also on current battery voltage?
Is it possible to avoid this dependence on battery voltage without using an additional DC/DC converter for SPKVDD?
WM8998datasheet


texts: Real current output limit of linear regulators vs. heat dissipation

texts: It seems to me that the maximum current output of a linear regulator should be determined primarily by power / heat dissipation, not the actual current. For instance, a 3.3V regulator that has an output current of 100mA with a 40V input could not easily dissipate the voltage drop (3.67 W), whereas it would have no problem providing 1A if it only had to drop the input voltage by .5V (0.5 W). I'm guessing the input and output capacitors would have to be changed to keep the regulator stable, but is there any other reason for these listed current output limits other than a general guideline?


texts: How can you wire a 555 timer to gradually decrease sound volume?

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Say you are taking in an audio input from a headphone speaker and you would like the audio to gradually decrease until inaudible.

Are there better, also very common chips that can do this more reliably?

Let's say you wanted the volume to decrease over 1 minute?


texts: Connect IPOD audio output to old rotary telephone

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I hope you could help me. I want to connect the audio output of an IPOD to an old rotary telephone. The telephone is not connected to the telephone line, it's just a fancy design thing I would like to do. I tried to connect it directly to the telephone speaker but the sound was barely audible. I'm thinking the impedance and the voltage/current supplied by the IPOD output is not appropriated.

So I was thinking maybe, instead of connecting the IPOD directly to the speaker I could make it more practical and connect it to the phone jack. But I don't know much about the phone circuitry, but I assume it's standard.

Could you guide me through this? What kind of circuit I would need to make the sound audible on the telephone speaker?

Thank you.


texts: Determine if two outlets are on the same circuit without breaker access

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I live in an apartment and do not have access to the circuit breaker panel. In the summer I run two AC units, and have inadvertently tripped the breaker before while running my vacuum cleaner. This caused a big hassle, as I had to wait for the super to get home so he could go down and flip the breaker back. I'd like to avoid this ever happening again, as 1/3 of my apartment was without power for about 6 hours that day.

When it happened, I made note of which outlets went out, so I now know all the outlets on that circuit. I'd like to be able to differentiate between the outlets on the remaining two circuits, so that I can space my high-draw appliances out evenly and avoid future issues.

What I'm looking for is a device (or pair of devices) I can purchase that will allow me to check two outlets and see if they are on the same circuit. I've seen circuit breaker testers that come with one device which you plug into an outlet, but the other end requires that you have breaker access and wand the device over the breaker or something similar to check. As I mentioned, I do not have access to the breaker, so this is not an option. Ideally there would be a pair that I can plug into two separate outlets, and have one of them tell me whether they are connected or not. My searches online haven't yielded any results on a device like this, so I'm curious if there's any way to do it from within the apartment, without breaker access and definitely without tripping any breakers.

Not accepting answers that say "turn off your AC before running the vacuum" or any such thing. Obviously in the future I will make sure that I turn them off, but this is more a question of load-balancing my devices which do have to run simultaneously.


texts: I was using my 74173 (d-type register) today and accidentally attached the vcc pin to ground and the ground pin to 5v.  I didn't realize this and turned on the power.  A couple seconds after turning it on smoke started to come out of the IC so I turned it off.  I touched the IC a couple seconds after turning off the power and it was so hot it burned my finger a little.  What I am wondering is what is the best way to check if this IC is fried?  I could plug it in and see if it seems like it is behaving normal, but I am afraid that even if it works in my tests it may still have an edge case that it is broken for.  Basically I want to know if there is any way to check if the IC is 100% functional still instead of just making sure it still works with the cases you test it.


texts: Ohm's law is \$V=IR\$, but what is the equation \$P=IV\$ called? I've never heard anyone refer to it with a name, and my text books and wikipedia don't refer to it by any name.


texts: When setting pin as input it getts pulled high, why?

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I've hooked up a push button to GP1 and a LED to GP2 on my PIC12F683 and this is my code:

unsigned char i = 0;

void main() {
     TRISIO = 0b00000010;
     CMCON0 = 0x07;

     ANSEL = 0b00000000;

     while(1){
              i = GPIO.B1;
              if(i == 0){ GPIO.B2 = 0; }
              if(i == 1){ GPIO.B2 = 1; }
     }
}

But when I plug in the power my LED is turned on, even when I remove the switch from the breadboard.

I'm using MikroC.  When I set GP1 to output the LED was turned off.

What is the problem likely to be?

My config:

Scematics:


texts: Reset Winding in Single Switch Forward Converter - How To Dissipate Leakage Inductance?

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In a single switched forward converter, the core reset is done by a third winding with opposite dot polarity to the primary and secondary windings. This dissipates the magnetizing inductance but how is the leakage inductance dissipated?

If it's left unaccounted for doesn't the remaining energy in the leakage inductance cause huge back EMF? If you use an RCD snubber/clamp the magnetizing energy as well as the leakage energy goes through this clamp which would cause huge power dissipation and inefficiency.

How does a high power (>100 watt) forward converter deal with this leakage inductance without going to a two switch half bridge design?

Thank you


texts: Seemingly having trouble setting an ISR interrupt greater than configMAX_SYSCALL_INTERRUPT_PRIORITY

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How does one set the priority of an ISR when free RTOS is ebing used?
So I have an ISR for push button that I'm setting to a higher value than configMAX_SYSCALL_INTERRUPT_PRIORITY, but it keeps complaining on the following line:
configASSERT( ucCurrentPriority >= ucMaxSysCallPriority );
Turns out ucCurrentPriority has 0 stored while I'm setting a priority of 100.
NVIC_SetPriority(EXTI15_10_IRQn, 100);

Also, ucCurrentPriority is of 8 bits while priority is of 32 bits but it's being cast to 8 bits apparently
 */
__STATIC_INLINE void __NVIC_SetPriority(IRQn_Type IRQn, uint32_t priority)
{
  if ((int32_t)(IRQn) >= 0)
  {
    NVIC->IP[((uint32_t)IRQn)]               = (uint8_t)((priority << (8U - __NVIC_PRIO_BITS)) & (uint32_t)0xFFUL);
  }```


texts: Autotransformer design -- how many turns?

texts:
Let's say I have a 25 ohm resistor, a 28MHz oscillator, and some wire with which I can make an autotransformer. The goal: make the oscillator see a 50 ohm resistance (or something reasonably close to it):

simulate this circuit – Schematic created using CircuitLab

Now here's the question: The turns ratio will obviously be dictated by the transformation required, but in total I can make T1 with few turns or with many turns. How do I decide? What are the tradeoffs involved?


texts: Current flowing inside voltage source or battery

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Current is the flow of charges (many say electrons).

Do these charges flow just between the terminals of the source/battery (terminal to terminal) ?

Or

These charges flow through/inside the source/battery as well?

What i know is that the positive terminal is the lack of electrons as compared to the negative terminal which is the excess of electron.

Current flows when electrons flow from the negative terminal of the battery to the positive terminal of the battery/source?

My question is what happens when the electrons reach from the negative terminal to the positive terminal? Are electrons then "absorbed" by the positive charges or they continue to flow through the source/battery to move in cycles?


texts: Why does unaligned memory read require extra clock cycles?

texts:
I believe I understand how memory reads work with the 8086 processor.

The 8086 has a 20-bit address bus and 16-bit data bus (multiplexed).

The memory module consists of two memory banks, and the LSB of the address bus is used to select which bank to access when reading a single byte. The remaining 19 bits provide the address within the memory bank.

When reading two bytes from a two-byte-aligned address, each memory bank contributes a single byte onto the 16-bit data bus.

As I understand, when reading two bytes from an unaligned address, the read is done in two clock cycles - first, the odd-address byte, and then the even-address byte, from the modified address (i.e. the original 19 bit address plus one).

My question is: why are two clock cycles required to accomplish this?

Can't it be done in a single clock cycle, using a simple adder and multiplexer, to put the two bytes in the correct order on the data bus?

Something like this:


texts: AC coil sensing circuit with A1120EUA-T Hall effect sensor

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I've seen many questions on here asking about hall effect sensors, and their capabilities, and although many seem to say that they can sense an AC magnetic field, I seem to be having a problem.

What I got:

I've successfully made a simple circuit that lights an LED and pulls low on a microcontroller GPIO when it senses a magnetic field. The circuit looks like this:

simulate this circuit – Schematic created using CircuitLab

*NOTE: The switch is not an accurate representation of how the sensor functions, but was the closest approximation
In this circuit, the pi's 3.3V supply and GND are to power the sensor, and the the resistor to Vout of the sensor pulls it high (LED is on, data shows 1) until a magnetic field is sensed, at which point the sensor pulls it low (LED is off, data shows 0).

Problem:

This circuit works perfectly to indicate the presence of a DC magnetic field, for example, it can sense a small neodymium magnet from almost 2cm away.   However, I need this sensor to be able to detect the magnetic field from a DPDT AC relay (datasheet provided) when ac power is running through it. One would think a coil of it's size with 120V AC 50/60HZ would be enough for it to read, but when the AC coil of the relay is less than a few millimeters away, nothing. The sensor nor the LED shows any detectable reaction.

Why is this? Does the field oscillate too quickly for the microcontroller or my eye to pick up? Is this sensor simply not capable of detecting AC? Or is my circuit simply not right for the job? Any pointers are appreciated.

Hall effect sensor datasheet: http://www.digikey.com/product-detail/en/A1120EUA-T/A1120EUA-T-ND/2138527?WT.srch=1

AC relay datasheet: http://www.mouser.com/ProductDetail/Magnecraft-Schneider-Electric/782XBXC-120A/?qs=h3Xc2LqAealUHVBqYsNmcw%3D%3D


texts: How to provide stable power to RF receiver when operating on small batteries with blinking LEDs

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I have a very simple circuit design (simple to keep cost low) consiting of a super-regenerative (or super-heterodyne) RF receiver, a Microchip PIC and 3 LEDs. These are powered on 3 or 4 AG13 batteries (4.5V or 6V voltage). Everything works fine when using a power supply to power the circuit, but when on battery power and flashing the LEDs with the PIC a power drop occurs and the receiver needs a while (~50ms-100ms) to stabilize and output a correct signal. When flashing the LED on and off every 20ms the constant voltage fluctuation causes the receiver to never be in a stable state and interrupts transmission.

Is there some simple way to stabilise the voltage to the RF receiver? I am hoping to find a solution with a capacitor. Adding separate batteries for the receiver would probably be cheaper than adding more complicated power regulation circuitry.


texts:
I referred this YouTube video for buck converter loop stability.

In the image we can see that the gain of the control loop we are talking about is Vout / Vin. Vout and Vin are both measured across the small value Rt resistor.
When we say that the gain of the op-amp decreases at the cross-over frequency, can someone please explain two things:

What will happen when the gain is decreased at the output of the op-amp with respect to the internal diagram mentioned in the above image?

What are we actually trying to simulate by increasing the frequency of the Vin at the input (bottom side of the Rt resistor)? In an actual buck converter working scenario, during very low load at the output of the converter the output voltage will decrease by some value. During light load, output voltage will not decrease.  There will be no scenario in which there will be a load which will draw current at the frequency we are checking using a network analyzer. So, what real time converter scenario are we trying to simulate using this loop stability test using a network analyzer?

What factors determine the Vin input voltage from the network analyzer and the frequency of the input signal? I read that the frequency can be swept till some MHz and the amplitude of the signal show be in the 100-500mV range. Please explain why that is?


texts: Exceeded absolute maximum voltage of FPGA

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I am using cyclone V FPGA. During my testing process, somehow I gave 12V to the IO bank instead of 3.3V. The board is shorted and I found FPGA has gone bad.

Now to prevent such accidents in the future I am configuring my power sequencer such that it will turn off the rail immediately as it sees a higher voltage.

The question is: if the power sequencer shuts down the voltage rail after 500ms after finding the fault, will this damage my device. How much time can an FPGA bear voltages above absolute maximum?

I am attaching a screen shot of fault settings which is not final.


texts:
Sorry if this is a simple question, but I‘m quite new to Arduino. What I‘m looking for is a way to connect 100+ strain gauges to one Arduino board.

Now, those each need a separate ADC (HX711) to convert the input from snalog to digital (best would be if only 1 was needed)(Also, I use 3 resistors to make it a quarter-bridge, so only 1 strain gauge per HX711 is needed.)

What I thought would be a good way, is to connect the HX711 to the Arduino like normal, but also connect the Arduino and the HX711 to something like a switchboard, in which the Arduino tells it to which setup to connect to, and the switchboard then changes the connections (pretty much like a transitor.)

Not sure if I‘m clear here, so something like this:

(This - means connected to)

Arduino - HX711
Arduino - Switch
HX711 - Switch
Switchboard - StrainGaugeQB [1,2,3,4...100] (All 100+ quarter bridges = 400 wires.)

Something like this:

Basically, the Arduino switches between which strain gauge is to be read currently. Although they should at the end still each be read at least 4-5 times a second.

I read something about multiplexers, but they don‘t seem to be exactly what I‘m looking for. They seem to be only serial, or did I get that wrong? They only have one in/out connected, but if it‘s not serial, could I maybe use 4 or those each getting one of the wires of the HX711? Something like multiplexer 1 being connected to wire e+ of multiple quarterbridges, 2 being e- of those, 3/4 being connected to their a+/a-?


texts: 1-2 second home power loss: some circuits stay powered - computer doesn't turn off. How is this possible?

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We've been having some local power outages which last for about 1-2 seconds and maybe at times are only 500ms.
I've noticed that we have two computers which stay powered and I'm trying to figure out why.
The first computer is a tower with a Gigabyte m/b, AMD chip, etc. which I have plugged into a power strip with a few other items.
I noticed that when the power loss occurred our wifi router and cable modem (on another circuit also plugged into their own surge protector strips) would both get rebooted.  Other things (lamps, etc.) flicker off and back on.
I was guessing that it was because this computer happened to be on a home circuit that had nothing else on it and that was why it stayed powered.
This computer is plugged into a power protector strip but that's it.
Today I remembered my headless MacMini is also plugged into that same power strip (and obviously on the same home circuit) however, the 1-2 second power loss does indeed cause the Mac Mini to turn off.
There's another desktop computer in the house that is on a different circuit that also does not experience power loss during these outages.
Is this related to something about the power supply in my desktop?
Is it related to the home circuit I happen to be on?
Maybe you can't tell with this information, but I'm wondering if this is a common thing or if it just so happens that the two computers' power supplies / surge strip are helping in some way.


texts: Why can't a feedback network use a capacitor?

texts:
Possible Duplicate:
  Basic Frequency Control Circuit

In the following schematic, why can't R4 be taken away and the feedback network pass output feedback through C2 and R2?


texts: How do I wire two barrel jacks together in parallel?

texts:
I am quite new to electronics, and especially PCB Design. I want to have two barrel jacks for DC input to my circuit, wired in parallel, but want clarification on my circuit design. The idea is that the amps will increase, to power an ATMEGA64, as well as motors, sensors, etc. more effectively.
Here is a drawing of what I think the circuit should look like. Please provide feedback.

Thank you for the help in advance!


texts:
I bought the P36NFO6L MOSFET n-channel .

Where is the pin connected to the p-type substrate. Is this thing over here?


texts: What is the difference between a Regenerative and a Superregenerative receiver?

texts: I have been reading about radio receivers and found about the regenerative and the superregenerative designs, both from Edwin Armstrong. But I can't find anywhere a good explanation about the difference between  how they work.


texts: Problem with mesuring value from current sensig pin on VNH2SP30

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I connected the Monster Motor Shield (based on the VNH2SP30) to the Arduino Uno and successfully drive the engine, but I can not measure the value from the CS pin on this board (the voltage at this pin is proportional to the current flowing through the motor).
    I measured the voltage value of this pin using a multimeter and it turned out that 1 ampere of load is equivalent 40 mV, 2A - 80 mV, etc.
   But Arduino always shows a voltage of 0 V. I changed the AnalogReference to the Internal (the base value is 1.1V), but the result did not change (although at 40 mV the analogread should be about 37). With Arduino all okay, I checked with the help of voltage divider. The scheme on shilde is this:

I suggested that the problem in the filter and replaced the 10K resistor with a 3.2K resistor, but that did not help. What is the problem with Arduino's strange behavior?


texts: Soldered test point on production board?

texts:
I understand having test points on a production board, but what would be the point of selectively soldering some of them? It doesn't modify any resistance, right?
I assume that the large numbers of potentiometers ("Voltage Regulators") are for ensuring precise final voltages more cheaply than precision resistors? Curious if I'm wrong though.
Taken from the faceplate LCD driver for a car stereo system.


texts:
I just encountered this circuit and I'm a bit confused by it

I see that it's an NMOS current mirror. At first I thought it's a cascode current mirror due to M3 on the right but it isn't. I have two questions

What is the point of M3 in this circuit? I mean it's going to have some factor times Iref through it?
What is the point of R1? I mean surely I_REF will push that much current through it no matter what so?

If somebody could just give me an insight on how it works, that would be great.


texts:
I need to measure the RMS power in a DC-10KHz range of a signal that contains RF frequencies (up to 1GHz).

My idea was to design a low-pass filter with 10KHz cut-off frequency, and then measure the RMS power by sampling with a MCU or using some trueRMS chip.

But if I just design a low-pass filter with capacitors and coils, that will give me 10KHz cutoff frequency, I fear that the RF frequencies will just cripple through the coils and capacitors. Since these components is gonna have relative large values.

How do I measure the LF signal RMS power?

EDIT: I'm an electronics engineer, but I have only worked with digital and analog design, never with RF design. But finding the field interesting, I wanted to do a project mainly to get better RF design skills. So I decided to build a simple spectrum analyzer, using a PLL with integrated VCO, a mixer and some matching circuits. The PLL(VCO) generates the LO signal for the mixer, and by filtering the IF output signal and measuring the power from DC to some frequency, I should be able to get the frequency content at the LO frequency.

So this is why I need to filter the IF signal, since I want to know for which bandwidth the power is measured.

Hope that makes any sense...


texts: Is it always good to have positive slack in STA?

texts: You may find this question easy. But it has been confusing me for a while now I really wanted to make it clear out of my mind. The problem is: Is it always good to have a positive slack along a timing path? Since slack is calculated as Required_Time - Actual_Arrival_Time, through which implies, in case of a positive slack, the Actual signal always comes earlier than expected. Then problems: I know it's good for setup time, but, isn't it a problem to hold time? Why people are only complaining about -ve slack but not +ve slack? Really thanks if you guys can help me out!


texts: Detecting and identifying different light sources in arduino?

texts:
I want to detect different light sources in arduino. The first Idea about solving this problem came into my mind was to add three light detection sensors (LDR, IR receiver Diode and Photo transistor) to combine them and put the outputs of these sensors to analog inputs of Arduino. And after that analyse data according to different light sources (for example Bulb, Tube light, Lighter flame and Sun light) and finally make check according to these data.

My question is, am I approaching problem correctly? Or is there any better but cheap approach toward this problem? because I cannot arrange spectrometer or any sensor to measure spectrogram of the lights.

What is the correct way to detect and differentiate between different light sources?


texts: What can I use to make n (4) analogue values selectable by a digital pin?

texts:
Using an arudino nano as the micro controller, I would like to read a few voltages around my project board.
These values are being read by way of a simple voltage divider circuit for values up to 25v, using 30KΩ and 7.5KΩ resistors on each point I want to read.
My micro-controller only has 1 analogue port free but has many digital ports free. I was wondering what IC would I use to make the voltage to read from any specific sensor selectable via a digital pin and software?
I am very new to this work, so your kindness and patience is greatly appreciated :)


texts:
I am trying to set up a servo controller that will automatically make the servo switch direction when it nears the end of its travel range.

I designed a solution that uses a quad comparator and a peak detector to produce a useful control signal. The circuit has one signal input and two outputs that control a signal to an H-bridge driver. As the voltage across the potentiometer approaches 5V, the first output is high and the second is low. As the voltage approaches 0V the first output is low and the second output is high. The signal flips when the voltage gets close to 5V and again near 0V. It works, but there are some drawbacks.

Is there a standard analog approach or IC that performs the same operation while using a potentiometer for the signal source?


texts: Do I need a voltage regulator to power LEDs?

texts: I am designing a PCB for some LEDs based off of the arduino nano. The LEDs I am using are 24 WS2812, and the microcontroller I am using is the ATmega328P-AU. I have the AMS1117-5.0 voltage regulator feeding power to the microcontroller. The whole circuit is meant to be powered by your computer via USB. Should the voltage regulator also power the LEDs, or can I bypass it? The AMS117 can supply up to 1.5 amps, which should be enough to power the whole circuit, but I want to be safe. Would a better idea be using a dedicated voltage regulator solely for the LEDs?


texts: Multiple inputs into the base of a single FET

texts:
I've been wondering if the below configuration would work: essentially using a single FET (instead of a 3 input OR gate) to determine if a clock signal can be read by a sequence of binary counters:

simulate this circuit – Schematic created using CircuitLab

Am I taking anything for granted here? Any help would be appreciated, thanks!


texts: Eagle board editor not allowing me to place components outside area which is permitted

texts: I am using this https://github.com/nabilt/nRF8001-Breakout-Board here. When I try to modify the schematic I can easily do it. But when I try to place a component in the board it keeps telling me the light version of eagle cannot perform this operation,. The board size is less than the size permitted by eagle.Can anyone give me some pointers as to why this is happening? I have also tried increasing the board size. This doesn't help either


texts:
I am reading though a datasheet of TL064 and I am unable to find supply voltage range of this component. I've experienced this couple of times with datasheets...

Farnell states its supply voltage range being: 7V to 36V, ± 18V. Where from the datasheet did they get that info?


texts: Vertically oriented beams using antenna arrays

texts:
Referring to the above picture, can an antenna array mounted on Node A direct beams towards Node B and Node E, without the need for an antenna rotator (or manually orienting the antenna array towards the respective nodes)? In other words, can the antenna array orient its beam along the vertical direction (along the line joining Node B and Node E)?

The motive for this question is related to the upcoming IEEE 802.11ad standard. By operating at 60 GHz, users communicate with one another through directional beams pointing at each other. Without the use of mechanical rotators for the antennas, how could these users possibly orient their beams in a changing/moving environment?


texts:
Please help-me in this question, first I calculate the I(s) and I get

$$
I(s) = \dfrac{ \dfrac{1}{s+1} }{ s^2+\frac{R}{L}s+\frac{1}{LC} }
$$

How I proceed to find Vo(t)?


texts: Need help explaining this circuit and how it is dimensioned and designed

texts:
I'm working on a project to school where I'm designing a battery charger with battery status indicator, and I found this circuit online:

but to include it in the project, I must explain how it works and how I got the values for the components. Well, I could just say I found it online, but I really want to understand how it works and how I could have designed it if I hadn't found it in the internet.

I know it works based on using the op-amps as comparators, when the tension is higher on the - input of the comparator, it will connect the output to GND, but how do I calculate the formulas for the tension divisor net that connects to the op-amps? Also, I don't understand the Zener, I never knew much about zener diodes... I understand that the pot gives a calibration functionality for lets say, deciding whats the battery full charge status, although I will probably experiment and change it for a fixed value resistor.

Also, the resistors connected to the LED's were too high, whats an acceptable value for connecting it to 24V ? I want the current to be low as this is supposed to measure the battery charge status, not drain it... also, I don't need the LED's to be too bright.

Other than this, I would like for the last level LED to blink when it reaches the <21V status, how can I achieve this? I was thinking 555 timer with reset connected to the 2nd level, can this work?

About the charging part, I was thinking about using this circuit:

Who can help me with the circuit connected to the lm317 adj pin?

Thanks guys

EDIT:

I have made some changes to the circuit after your awesome answers. I've got to a point where i understand how the circuit works, but i still have a few doubts about this.

It has been said that D1 is a shunt regulator and not a shunt reference, what are the implications of this statement, and what will happen when building the circuit? Because It works when simulating, as you can see.


texts: Altium Leaves Board Border Outline on Assembly Notes Layer

texts:
No matter what, Altium leaves a border of the board on my cover page when I try to generate an assembly document. I only have two layers: Assembly cover notes and Assembly notes tops. Neither of which have a board outline on them. How do I remove this outline?

Any help is much appreciated.


texts: Torque relationship to speed in a DC motor

texts:
I have a conceptual doubt about torque-speed relation in a DC motors. It's probably a gap in my thinking but I'm posting this question anyway.

Torque and speed in a DC motor are said to be inversely proportional. But doesn't an increase in torque result in increase in Angular Acceleration and consequently, angular speed?

I know that back EMF/counter-EMF is responsible for the inverse relation but it seems counter intuitive to me. What happens to the angular acceleration, angular speed when the torque is increased and where does all that work go?


texts: Delaying rising edge of input signal - 3.3v logic

texts:
I'm new here and I need help with my project. I working on my DIY home automation and I need to delay rising edge of the input signal. Trigger is faling edge. I need to delay it 100 - 500ms and I use 3.3V logic. Any idea how to do it? Circuit example would be welcome. Thanks a lot for any tip/proposal. More details of the purpose for such delayed signal:
The source of the signal is RESET from Wemos D1 Mini generated by micro switch or CH340C and load/target is OE pin of TXS0108 - logic level shifter. I need to delay enabling of TXS010E, OE pin, otherwise Wemos didn't start/boot. So I need some kind of circuit/IC which will do it.


texts: How to connect a 3 phase motor to class-d audio amplifiers

texts:
How can I wire this motor to these amplifiers?

I am using 1 1/2 of these stereo amplifiers (3 mono amplifiers) to drive a 3 phase motor. The problem I have is that the amplifier has H-bridge outputs. The usual 3 phase motor drivers are simple push pull, 2 MOSFETs/phase.

There reason that I am not using a standard 3 phase motor driver board, is because I am generating my own 3 phase sine wave pattern.

It is for a musical tone wheel project. I already have a PCB that coverts MIDI note to 3 phase. I just need to amplify the sine waves to drive the motor.


texts:
I have a multi stage OA amplifier (pulse applications) and I am not clear if better use AC or DC couple stages (C8 in this example). I removed caps for better response, charging and discharging through high resistors.

The REFH is VDD/2 and simulation looks nice but I question there would be a real (life) benefit by keeping caps or not.

Thanks for suggestions,


texts: Controlling a ceiling fan and lamp with dual triacs and an Arduino

texts:
This question is a follow-up to my previous question about controlling a ceiling fan with a Raspberry Pi. I have decided to use an Arduino Nano instead of a Raspberry Pi.
After some closer investigation, I have realized that my fan controller uses triacs for both the lamp and the motor. I created a schematic that uses the same basic system as the original controller. My questions are is this triac configuration correct and will my power supply supply the 9-20 volts that the Arduino Nano needs?

Edit 1:
After some searching I have lowered C1 from 1000uF to 100uF as it is just a smoothing capacitor.
Edit 2:
I have updated the transformer to have two taps. Here is the fully-updated schematic:


texts:
I have a cirtuit which consists of Resistor, Photoresistor, PNP Transistor, Voltage supply from raspberry pi like on the schema below:

Purpose of this circut is to detect light as a dawn detection sensor. As I know voltage on the base of transistor is expressed by voltage divider:

If the voltage on the base of transistor is 0.7V smaller than voltage on the emitter, then transistor conducts(change from darkness to light).

I would like to connect this circut to Raspbery pi GPIO port configured as INPUT with Pull up resistor and detect the light.

But I don't know how should I do it exaclty. Should I connection below collector directly to GPIO configured as input?

I would be grateful for some advices.

Maybe connection like below could work properly?

Best regards.


texts:
I have a 12V, 200AH AGM battery. The maximum charging current recommended by the manufacturer is 50 amps. Now, I need to connect two AGM 12v batteries in series to connect to the input of my 24 volt inverter with battery charger.

Is it possible to charge these AGM batteries in 5-6 hours?

What is the current and voltage required from battery charger in the inverter to charge the AGM batteries in 5 hours?

Is it safe to charge the battery in 5-6 hours? If not, what is the recommended charging time?

Any special precautions to be taken with this kind of battery charger?


texts: Differences between these FETs as switches

texts:
I've a conceptual question about the difference of the two following circuits in terms of functioning as switches.

The first of is the regular common source circuit, if you choose R1 wisely (?) it it possible to trigger the LED or any load at the position of LED1 both in an analog or digital way, right?

The second is the simple switch with fet transistor with the load as drain resistor, this one can only be used as a digital switch, right ?

My question is : Is there a reason to use one or the other depending on the application?

Thx :)


texts:
I'm trying to assign a 12bit parallel bus to a 12bit register.  I've reduced the problem to this literal assignment but as with the previous case, only the first bit is being written to anything when I check the output.  I've isolated the problem to this section, I can change the first bit data[0] but nothing else regardless of order.

Obligatory sketchy verilog:

input [11:0] ADC_bus;
...
always @(posedge SPIClock)
begin
    count = count + 1;
    if (count == 32)
    begin
        ADC_data[0] <= 1'b1;
        ADC_data[1] <= 1'b1;
        ADC_data[2] <= 1'b1;
        ADC_data[3] <= 1'b1;
        ADC_data[4] <= 1'b1;
        ADC_data[5] <= 1'b1;
        ADC_data[6] <= 1'b1;
        ADC_data[7] <= 1'b1;
        ADC_data[8] <= 1'b1;
        ADC_data[9] <= 1'b1;
        ADC_data[10] <= 1'b1;
        ADC_data[11] <= 1'b1;
    end
    else if (count == 16)
        ADCss = 1;
    else if (count == 64)
    begin
        count = 0;
        ADCss = 0;
    end
end

Result: ADC_data[11:0] is always 1


texts: Distribution of electrons in a capacitor charge circuit?

texts:
Consider the circuit below:

Let us say that the red dot's represent negative charges (electrons) and the blue dots positive charges/holes. Can we say that the distribution of electrons (red dots) in the left side of the diagram is even. If so do why do we only consider the charge on the capacitor and not the charge in the wire?

Further more consider the situation where a capacitor is connected directly to ground like in the circuit below:
When I say connected to ground I mean literally connected to the earth so electrons can flow from and to the capacitor (and battery) from the earth.
What would the charge distribution for this circuit look like?

I can see that the left hand side plate will be positively charged but am totally confused about the right hand plate. So please can you explain how the charge is distributed in the circuit in general and in this specific example?


texts: Powering GSM Module from 2 x AA NiMH or 3 x AA alkaline batteries

texts:
I'm trying to power a GSM modem from 2 AA NiMH batteries in series, and wonder what my options are. Main consideration is that it needs to be USB rechargeable, so I only have 2 batteries to work with. The modem can work from 3.3V to 4.6V and draw 2A of current bursts. Can anyone recommend a boost converter that will suffice here?

So I have 2.4V input, need 3.6V out @ 2A, max ripple is 400mV

Will a TPS61230 do the trick? Its Vin(min) is 2.3V though, so once the batteries loose a little charge will their voltage be just too low?

Another option is 3 x AA alkaline, but their internal resistance is a bit high (approx 80mOhm). However 3 alkalines is 4.5V, very close to the upper limit. If the batts were even at 1.6V, this would run the risk of a fried module. Maybe I could drop the voltage across a diode MBRS340 or similar (4A, VF 500mV).


texts: What is the simplest hot swappable bus protocol?

texts:
After I figured that I2C bus is hard to be hot swapped unless use other hardware solution such as PCA9511A(very expensive industrial solution), I am planning to use another bus to replace I2C.

The requirement of the ideal bus should be:

require as less as the data lines (\$\le\$ 2 is the best)
MUST capable with hot swap
low manufacture cost (as low as possible)
stable
no specific transmit speed/bandwidth (< 2 kb should be fine)
no specific maximum networked devices (around 5 will be fine)
pure protocol hot swap(I know some USB are using the combination of long&short physical pins on the connector to control the priority of which module is detached first, but unfortunately it is not feasible in our design.. therefore we need a pure protocol contained hot-swap solution)

I hope there exist some protocol that matches my requirements but I am quite hard to find them and don't know hidden issues behind them. I know there are some modules designed products such as blocks can make that, so for any suggestions I am deeply appreciated, thanks...

Kind Regards


texts: Current output of a solar panel when connected to battery and load

texts:
I am trying to build a microgrid (final year project) where a 100-250 W 48V solar array will charge a 24V battery bank and a couple of 24V loads (40W lights, 60W fan).

Batteries used (7 of this in series) :
http://industrial.panasonic.com/www-cgi/jvcr13pz.cgi?E+BA+3+ACA4001+NCR18650+7+WW

I will be using a buck converter to step down the voltage of the array to that of the battery.

Assuming the power of the solar array is 200W, 200/48 = 4A~
After step up by the buck converter, it should be around 8A?

Now I am trying to figure out what will happen if only the battery is connected across it. Will it only draw as required (what happens to the solar panel's excess current?) or will the 8A of the solar panel's output be forced into the battery? (and maybe spoiling it).

Also, if the battery is near fully charged, how do I know that? Is it by checking the voltage level? Do I have to turn off the mosfet switch then (cut the connection between the array and battery)?
I will be using a microcontroller to regulate PV supply using the buck converter.


texts: Why do we need sync pulses in digital (LCD driving) context?

texts:
I am studying how to drive LCD TFT display with the microcontroller (STM32F746).

The manual mentions that I have to set up timings for HSYNC, VSYNC, VBP (Vertical Back Porch), VFP (Vertical Front Porch), HBP (Horizontal Back Porch) and HFP (Horizontal Front Porch).

Why do we need theese in digital (LCD-TFT) display context? How do they work?

To understand things better I tried googling "Digital Video Signals" and "LCD driving" and "HSYNC" but all the tutorials are talking about TV and ANALOG signals. Can someone point me to some reading about how DIGITAL graphics/display driving work?

Why can't I just feed linear stream of pixel data to the display controller? Can't the controller automatically detect which "pixel-byte" in incoming data stream is mapped to which physical pixel?
If I understand things right: in the analog world, the CRT beam needed certain amount of time to return back to the beginning of the line/frame, that's why we have the "invisible" parts of picture- but what's with that in digital displays and signals?


texts: Converting a toy from battery to DC power adapter

texts:
My kid's bubble blowing machine runs on 8 AA batteries which it chews through in less than an hour. Also, only the first 15 minutes seem to make a satisfying amount of bubbles and after that, it fades to only a few bubbles every now and then.

I have carefully wired it to a 12V DC adapter and have housed all connections so they're water-tight.

When I initially tested this setup by holding the AC wires to the motor, all seemed to work well and fine. However, now that it's all soldered up, it pulses with intermittent bursts of power.

How do I fix this? Do I require a voltage regulator? If so, can it be applied anywhere down the power line?

Please know I am completely novice when it comes to the nuances of electrical engineering, so if possible, keep it layman. Thanks!

Thank you all for your replies. I am still trying to learn the ropes here at SE but I'd like to upvote all of your replies. Apparently I cannot yet.

From what I collect from my answers, I need a DC power supply that exceeds 1 Amp. I thought that anything that plugged into a wall was AC.

Here is a photo of the info from the adapter I have connected:

It says that it's 1.5A. Is this not sufficient? It does not indicate 12VDC. Is this my problem?

If I need a 12VDC adapter that outputs 2A and I was to purchase one, can I simply splice it in at an earlier stage than having to take the whole toy apart again and rewire throughout? Will the wires from this adapter, in other words, handle the throughput of the new adapter?

Thanks so much again everyone.


texts: Need help troubleshooting after short-circuit, with heaters and thermocouples

texts:
There was a short circuit in one of the furnace that I designed.

Description of the furnace and its components:
The furnace is a copper tube, with 1/2 inch thickness, and 10 equally spaced 1/4 inch bores for inserting the heaters and thermocouples.

Heaters
Thermocouples

I'm controlling the heating of the furnace with the following controllers:

AC solid state relay
16 output Relay
VINT hub

The working of the heaters are controlled by the solid state relays and they are in turn controlled by the 16-output relay. The VINT hub is used to connect the 16-output relay to the computer so I can control them with LabVIEW. There are 10 heaters in total and each heater current consumption is 3A. I used two separate outlets to power 5 heaters each as the power outlet rating is only 20A in total.

Circuit diagram: I apologize for the clumsy circuit diagram, it has been quite some time since I did circuit diagrams and as of now my diagrams quite clumsy.

Description: The DC source is for controlling the solid state relays and goes through the 16-output relay. The AC source is for the heaters,not shown in diagram, the connector HTC2F is the connector which connects to all the heaters. All HTXL's are the solid state relays.

I have made a LabVIEW program where I monitor the reading from the thermocouples and control the 16-output relay for switching the heaters on and off through the solid state relays.

The incident: I was running the LabVIEW program to heat the furnace, but I accidentally ran a previous version I wrote which does not switch off the heaters when the desired temperature is reached. I initially plugged in one outlet and 5 heaters started heating up, and when I switched on the other outlet after a few seconds I heard a pop sound from the furnace and there was short circuit. The phidgets (VINT and the 16-ouput relay) burned. It also burned my computer mother board.

Need help with: Now I'm not sure how to test the system to check which heaters and thermocouples failed and replace them. Quite honestly I'm afraid to control them with LabVIEW as I'm afraid of the short circuit ruining my computer and the phidgets again. Any troubleshooting tips are appreciated. If there are any design flaws please let me know and I'll work on them.

Please let me know if any additional information is needed, I'll update the post with additional information.


texts: Bluetooth module resets because of LC filter

texts:
I added MH-M18 Bluetooth audio module to my Z906 speakers. Speaker's console has only 3.3V, so I have to use boost converter.
For some reason, module outputs 200+Hz noise, no matter what connection status is.
After I added LC filter with cutoff 150Hz, module is in reset loop. LED on module blinks, but I can't find module with phone. Module consumes 20mA(by datasheet).
Scheme and component list are below. Sorry for sketch scheme, I don't have PC near right now. Thanks!
https://hr.mouser.com/ProductDetail/Taiyo-Yuden/EMK325ABJ476KMHP?qs=B6kkDfuK7%2FDcZxNrKjzaQw%3D%3D https://hr.mouser.com/ProductDetail/TDK/TPLC553030-592H?qs=lYGu3FyN48fhxsPwIV5J6g%3D%3D


texts: I am writing CMSIS based code for STM32L476RGT6(on a Nucleo board) to use the ADC. I have gone through the datasheet but I couldn't find a register to specify the channel for the ADC conversion. How do I do that on this microcontroller?


texts: Few basic questions on combinational logic

texts:
I'm little confused in the topic of Decoders.
For example when a question asks:
Build 4-to-16 decoder, using 2-to-4 decoder.

Does that mean the first decoder has 4 inputs and 16 outputs ? If so why the answer to this question has for the first decoder a 2 inputs and only 4 outputs ( that connected later to 4 decoders and each has 2 inputs and 4 outputs)

Lastly, how can I build 8-to-16 decoder (Active low)?


texts: RC circuit How does the current vary after the switch is closed?

texts:
in the image below : a quiz from the book "physics for scientists and engineers" in chapter 28 dicussing direct current circuts and RC circuits

i need an explanation for the answers for this quiz which i don't  understand how it goes , the answers are c,d


texts: I am trying to simulate a buffer with an op-amp using CMOS, I am using Cadence. The phase margin I am getting is negative (not stable) about -272 deg, I am trying to reach 50 deg for a gain of 86 and BW 0f 73MHz. how can I fix this?


texts: Feedback in combinational digital circuits

texts:
It is recommended that one should not use feedback in a combinational circuit and the reason is pretty clear because, the delay of the output that feeds to the input causes malfunction.

However, the ACT-1 cell from ACTEL (see Fig. 2 from datasheet) is a basic cell consists of some multiplexers (which is combinational) which is capable to implement even flip-flops! See this example which uses feedback to implement an RS latch. So, the question is, should we use feedback or not?


texts: Understanding ETSI EN 300 frequency hopping transmit time limit

texts:
In ETSI EN 300 328 V2.1.1 (2016-11), section 4.3.1.4.3.1 Non-adaptive frequency hopping equipment (under Requirements for Frequency Hopping equipment limitations), it is stated:

The Accumulated Transmit Time on any hopping frequency shall not be greater
than 15 ms within any observation period of 15 ms multiplied by the minimum
number of hopping frequencies (N) that have to be used.

What is the meaning of on any hopping frequency?

Accumulated over all hopping frequencies, which means that the device must not transmit at all for an accumulated period of ((15 * (N-1)) / N) within the observation period.
For each hopping frequency individually, which is a lot more permissive. This one seems less likely as it seems to be covered by other FH requirements (e.g. occupancy).

Or maybe another interpretation which I didn't think of?

We use a 2.4GHz frequency range, if that's relevant.


texts: Value of R in reverse voltage protection circuit based on PMOS

texts:
How do I choose the value of R2 in this circuit? (V = 12V, I = 2A)
For the PMOS I am using SI2323DDS-T1-GE3 (Datasheet), is it to ok to use this PMOS (Maximum Power Dissipation=1.7W)?
For the Zener diode I will use MMSZ5236B-7-F Datasheet.


texts: How feasible is it to wire into common household measuring instruments with a solid grasp of electrical engineering?

texts: I'm studying up on EE and I have a budding grasp of circuits and ohms law so far. As I continue I wonder how feasible would it be for me to read data from existing electronic devices such as this  temperature/humidity gauge. My end goal would be to wire this into my arduino. I realize there are existing plug ins for the arduino for this purpose but having the knowledge to do this with my existing devices seems very exciting. So are manufactured electronics like this hard to wire into? What would that involve?


texts: SPI flash bit-banging access over memory-mapped IO

texts:
I'm faced with a problem where we have an SPI NOR flash attached to an Intel I210 PCIe-ethernet adapter on a custom Cortex A9 based board. The SPI flash is normally used by the ethernet adapter to hold configuration data and firmware binary, but at the moment it's empty, in which case the ARM tools that Intel provided cannot touch the external SPI flash, and our ethernet chip now sits there unable to do anything helpful.

After digging around in the Intel chip's datasheet, I realised that there is a register with address offset 0x1201C called "FLA", and some bits in this register correspond with the sclk, miso, mosi and slave-select pins of the SPI flash. The datasheet recommends that, with an empty flash chip, the host should bit-bang commands to the SPI flash to enable writing to it through some other channels. I thought this would be a more promising approach than trying to port Intel's x86 drivers and tools to our board.

My problem is that, since the SPI flash operates at a much slower clock rate than the PCIe bus, how do I make sure that the slave-select and mosi signals arrive with sufficient setup and hold times relative to sclk?

Say, if I drive slave-select low in one memory-write operation and pulse the clock high in the next, does the PCIe infrastructure give any guarantee about the time between the packets arriving? Will it guarantee that the packet containing slave-select will arrive before the one containing the rising edge of sclk at all? Is using nanosleep() to try and add a delay between them a reasonable approach, for example?

I feel as if I've misunderstood some things and am going about it in a wrong way. How is this sort of bit-banging access usually done to ensure that the timing constraints are met?


texts: How much does the power of a magnet increase voltage on electromagnetic induction?

texts:
Searching through the site i found some useful info saying that a powerful magnet means more voltage, but i'd like to know how much does the voltage increase in relation with the magnet power (Given a constant rate of change and windings).

I've done this experiment at home using a coil of about 250-350 turns, and two magnets that are bearly three times powerful than a fridge-magnet (those to decorate) which is, as i've seen, quite low even for a homemade experiment. So i ended up using an electric hand drill at almost full speed to make these magnets to spin, and reached my target which was to lit a LED, although I didn't even get 2 Volts (1.4). I've googled around and saw two magnets of 12000 GAUSS (much stronger) at sale, but I'm not sure if it's worth the money. I'd like to know exactly how much does the voltage increase in relation to the magnet power. If the magnet power duplicates, does the voltage duplicate? does it increase but not as much?

Thank you in advance.


texts: current limiting filament bulb, revisited

texts:
I'm trying to size a bulb to limit DC booster pack current (harbor freight viking lithium) from overloading the 12V aux port (cigarette lighter) wiring which is fused at 15A. I'm ideally looking to achieve 6-10A range; either slightly below 6A so that the small charge port can handle it, or as high as 10A and use the booster clamp port rated for ~400A (hence needing a limiter).

I'm currently using a 12.8VDC 100W bulb in series via the positive lead from the booster pack to the 12V aux port. If I connect directly (no bulb in series) using the 6A charge port, its overload alarm activates when turning the vehicle ignition to run (glow plugs active, diesel during winter scenario). Adding 100W bulb does not trigger the alarm, so it's obviously pulling less than 6A. I am connecting two DC sources in parallel.

When it's cold, the car battery measures ~12.25V and that drops to 11.4V or less when glow plugs are active. When cranking the starter, it sags to 8-9V, even though it's a relatively fresh/new battery (~80AH). The boost pack is typically 13.5V no load, bulb is slightly lit when glow plugs active due to increased voltage potential from booster pack to car battery. The potential obviously increases when starter is engaged (i.e. brighter bulb response).

Until I snag a decent clamp meter or accurate DMM, there are only estimates as to the boost current allowed with the bulb in circuit. I noticed the other Q&A showing a nice chart with 10 Ohm resistor vs bulb cold/hot resistance.

Is there a formula to help size the optimal bulb, or perhaps electrically violating an AC bulb for better performance? Let the Coulomb crunching commence...


texts: PCB has strange looking pads, how do I solder them without impacting nearby surface mount components?

texts:
I've recently brought the px4fmu and px4ui boards. The px4io requires me to solder a power socket and headers onto it.

However there are surface mount components very close to the holes/pads. Also the pads are not silver (see below, points marked in red are of primary concern).

So my question is, how do I go about soldering these without affecting the nearby components. Do I need to tin the pads first? Is 370 Celsius okay for the iron? Do I use the rather thickish chisel tip or go to a fine point?

I'm not the most experienced at soldering but I've done a bit of reading and experimenting on soldering, so I understand the basics (solder applied op the tip of the soldering iron, heat up the wire/pad first, etc). I just cannot find any info on how to handle the situation I find myself in. The closeness of the pins on the header also seem like trouble to me :(


texts: Trying to do a circuit to variate voltage from GND to VCC using MOSFET and transistor

texts: The circuit I am doing is this one in the post, but it only variates the voltage just like a key it goes direct from 0 to 12V. What I want is that it variates the voltage from 0 to VCC in little intervals, just like a dimmer.


texts: This may be a naive questions but is the parasitic capacitance of TVS Diodes a useful capacitance for decoupling a chip? Imagine I had an IC that asked for a 10pF decoupling capacitor and I used a TVS diode with a parasitic capacitance of 10pF, would that parasitic capacitance be an effective substitute for the 10pF decoupling capacitance or is there other phenomena at play here that would prevent that?


texts: Does this device which claims to reduce reactive energy from a house work?

texts:
I've opened a device that states that it can reduce the reactive energy from a house, by plugin it directly to the power outlet/wall socket. I think it is a con, so I've opened it and I saw this black box. Inside this box that I've opened bare handed is this very wierd brown glued sand or silicon, I dont know.

Can someone tell me what this box is and what kind of brown stuff is that?


texts: what will happen if i don't use amplifier before my differential ADC

texts:
i have ADS1672Datasheet from TI. in it's datasheet circuit that is recommended for differential interface is:

but i want to remove amplifier(THS4520 datasheet-it's a Fully differential amplifier) and connect analog input directly to my ADC(ADS1672) ,to simplify circuits.

but i don't know what will happen if i remove it.
thanks all.


texts:
I came across this circuit as part of a larger circuit in a guitar effect pedal:

simulate this circuit – Schematic created using CircuitLab

I was wondering about the function of the resistor \$R_1\$. My calculations show that the same transfer function can be achieved with or without \$R_1\$ (leaving out \$R_1\$ just means that we need to change the other resistor values). The only difference that I can see is the change in input impedance of the circuit. Is this the only function of \$R_1\$ (i.e., reduce/define the input impedance), or is there anything else I'm missing?


texts: Where can I find VHDL libraries? Is there a library for a PLL?

texts:
I heard in the following link that a V4 library about this topic exists, but I'm not able to find it anywere and to understand how to use it:

Look at the last reply at this link


texts:
Why is the bandwidth of pentode amplifier larger than the bandwidth of triode amplifier?

I have searched the following books but can't find the answer:

Electronics devices and circuits by Rajiv Tiwary
Electronics devices circuit and  theory by Robert L Boylestead
Allen Mottershead


texts: Switching/multiplexing RS232 signal lines

texts:
I need to construct a simple RS232 multiplexer. I would prefer a compact SMD solution.

What is the most suitable switch implementation?

Is there anything preventing me from using MOSFETs for this purpose? I am a bit concerned about the threshold voltage.

Are there any other semiconductor alternatives to mechanical smd relays?


texts: Why am I calculating different sampling rate than the scope shows for a given memory depth?

texts:
I have this scope with the following real-time sampling rate and memory depth:

I know the relation between the memory depth, sampling rate and time duration as:

LM = SR x TD

Where LM is the long memory depth, SR is the sampling rate and TD is the total time on the scope screen(time per division x total number of horizontal divisions).

I also know/learned that the scope adjusts its sampling rate when we change the times per division setting.

So I first set the memory depth of the scope as LongMem which is given as 2Mpts:

Then I set the times per division as 1ms.

This means that the total duration for the plot is 18x1ms = 18ms. It is because in this scope the total number of horizontal divisons is 18.

So from the equation I should get the follwing sampling rate:

SR = LM/TD

SR = 2 x 10^6 / (18 x 10^-3 sec)

SR = 111MSa

But here is what the scope shows as its sampling rate which is 25MSa:

What can be the reason I am getting different result for the sampling rate?


texts: How to rename the layer name in PCB Editor?

texts:
How can I can edit or change the following layer name?

I am a self learner of PCB editor. I was trying to design the copy of a file I already have (A reference board file). The below picture is the top layer name of the PCB reference board file. The default layer name for the board I have been working on is simply "TOP". How can I change the class name from "TOP" to "L01_TOP". I know the layer name does not matter much, but I would like to know how to edit it.


texts: what if one solar panel is getting more power than another panel connected in parallel? say if you have two 500w solar panels and one is getting 100% solar radiation and the other due to a angle is getting 70%, would you get a total power output of 500w + 500 x 0.7w?


texts:
After making a prototype circuit board, I usually glue four rubber pads/bumpers to the bottom, to keep it stable on my desk:

Unfortunately, my boards are usually too light. When connected to a few cables, they float around to wherever they're pulled by the cables. Add to that some oscilloscope probes, and I'm even more in trouble.

What I'm looking for
I'm looking for dead weight components that I can glue or solder to the bottom side of my circuit boards. Something I can buy in relatively large quantities (like a pack of 100) and low price.

Extra benefit
A nice extra benefit is the psychological aspect. A heavier product "feels" like it's better quality ^_^.
Nice comment from @JRE:
Some manufacturers agree with you about things needing a certain weightiness to feel right. The Motorola HMN1081 hand microphone (know colloquially as "the potato") had a block of metal screwed to the inside of the housing for just this reason. The housing is plastic, and the parts inside don't weigh much, so the Motorola engineers added a weight to make it "sit" properly in the hand. I looked, but couldn't find a service manual or parts list, but I've disassembled many Motorola radio microphones.