texts: Two different 3-AND gates: correct implementation?

texts:
One of the questions in my textbook (Introduction to Computing Systems) asks to design a 3-input AND gate. The given solution is as follows:

simulate this circuit – Schematic created using CircuitLab

If I am reading this correctly, this is a 3-NAND–NOT combination.
I don't understand why you need the NAND–NOT instead of just creating an AND by itself.
My proposed schematic is the following:

simulate this circuit

This seems simpler, and uses fewer transistors, so I'm guessing that there's some reason that it won't work (otherwise it would be the example solution!).
I don't see any possibilities for short-circuiting: if NAND(A,B,C), then NOT OUT, so there will be no path from power to ground (because it would have to go through OUT).
On the other hand, I do think that everything is properly grounded: if NAND(A,B,C), then OUT should have a path to ground through whichever of (A,B,C) is logically false.

What am I missing?


texts: How to plot voltage vs current graph on Proteus Software?

texts:
I have designed a basic Series Regulator which implements fold back current limiting. I wish to simulate this on Proteus software.

I am expecting the following graph which shows how the output voltage varies with load current:

I have searched online but found no tutorial or documentation which helps me achieve this kind of plot in Proteus software.

How do I plot a voltage vs current graph on Proteus? I am selecting Analogue Graphs and then dragging a current probe to the bottom right hand side and a voltage probe to the top right hand side of the graph as I usually do to plot other kinds of graphs.

I am trying to plot using DC Sweep Analysis and the expanded properties for this type of graph are the following:

Is there some setting which I am missing, or am I using the wrong type of graph altogether? Can this actually be done on Proteus software? Any tips and/or suggestions would be appreciated.


texts: Heatsink calculation for a MOSFET in active mode

texts:
Actually I am working on a project to create an electronic load for power supplies, batteries... testing. The circuit is already designed but I am working now in the heat disipation of the mosfet in such conditions.
I want to make it able to simulate loads up to 100W, so the mosfet will have to disipate almost all the power (wich is a lot). Searching on internet I was able to calculate the requied max Rsa for the heatsink thanks to this formula:
Rsa = (Tj - Ta) / Pd - (Rjc + Rcs)
Now I know that I need a heatsink with an Rsa of less than 1ºC/W but the most of heatsinks I see doesn't provide that info, just the materials and sizes.
Someone can help me with info about how to calculate the Thermal Resistance of a HeatSink?.
Thanks!


texts:
I was wondering if my circuit will work.

The 5V signal is coming from a microcontroller, based on a condition. If its 1(5V) I want the PWM signal to be received by the motor. If its 0, the motor shouldn't get any signal and thus not rotate.

What specs of the mosfet should I look into?

Thanks!

EDIT: I think I am using the wrong term for "motor", I am sorry, I don't know what else to call it. I will be using it to either drive an ESC or a servo motor.

The signal comes from the PWM output of Erle Brain 2, which has a 25 mA current sink capability at 5V.

P.S. Thanks everyone for your inputs! Really appreciate it! :)


texts: Tuning LED circuit so LED turns on at specific voltage

texts:
I am attempting to add a signal activity LED to my dummy load box. I have constructed the following circuit and so far it does what it is supposed to (lights an LED with signal applied and does not interfere with overall load impedance). I am now trying to tune the circuit to turn on at appropriate level and not over-current the LED at higher signals. I am using a 3mm red LED with max current of 30mA, which is what I get when the load box sees a 100V peak to peak signal, about the largest signal the load box will see. The LED currently does not turn on until load box sees ~12.6V peak to peak signal, I would like the LED to turn on at ~5V peak to peak. Is there a way to accomplish this while still allowing 100V peak to peak signals without toasting the LED?

This is my current circuit:

simulate this circuit – Schematic created using CircuitLab

If possible the LED would need to come on at ~5V peak to peak and then increase in light intensity up until 100V peak to peak. My main issue as noted is that I'm already nearing the LEDs maximum current (30mA) at 100V peak to peak and the LED does not turn on until ~12.6V peak to peak.


texts: Mounting a sensor against the inside of an enclosure

texts:
I have a plastic ABS project enclosure which I'm trying to figure out how to mount a sensor to the inside of, against a window that will be placed into the enclosure wall so that it looks through the window and is as close to and stable against the window as possible. I'd like to avoid gluing the sensor -- if that's even possible -- for maintenance reasons.

The sensor is a LWIR sensor in a TO-39 can.

I'm trying to avoid soldering wires to its leads so I plan to use a socket with wires soldered to the socket's leads.

The link is a TO-100 socket, but with the appropriate diameter and spacing (though an extra 4 sockets).

My  plan is that I'll have the TO-39 can on top of the pictured socket.

How do I "attach" those up against the inside of the window in the plastic enclosure? The enclosure will be outside and waterproof, so I'm trying to avoid putting holes in it which I'd need to seal. Also, the window will be quite small. Thus I prefer to glue something to the inside of the enclosure which surrounds the window.

I'm thinking of something like a z bracket:

But that doesn't seem ideal because:

the bracket needs to hold the socket somehow.
bracket needs to be attachable (gluable?) to the enclosure wall
be somewhat adjustable because it's unlikely that I'll find a bracket the precise number of millimeters to keep the sensor against the window.
Ideally serviceable in a way that the sensor can be removed

Maybe some sort of bracket glued to the inside of the enclosure but with a rubberband which pulls the sensor toward the window. If I could use 2 or 3 rubberbands then they'd fit through the socket's leads and keep the socket stable?


texts: switching between two similar power sources - solar battery and cr2032

texts:
I'm trying to create a circuit powered by two alternative power sources. The first one is a Li-Po battery charged by a solar panel and the second one - standard 3v battery, ie. CR2032.

The circuit contains a uC typically powered by the CR2032. Every 10 minutes if the voltage of solar battery is enough, the uC should switch to it, do some work and switch back to the CR2032.

I trying to figure out if the solution from the post below will work.
https://electronics.stackexchange.com/a/271500

If the solar battery takes place of the USB source, would the circuit be powered only from this source?

The working sketch below. Please forgive me some gaps - gnd's, resistor near mosfet, additional 3v voltage regulator, etc.

edit:

I think LTC4412 is the thing I need. The circuit and the description below is from the datasheet.

I can even remove the comparator and read the stat pin.

The STAT pin is used to turn on the MOSFET once the SENSE pin voltage exceeds the battery voltage by 20mV. When the wall adapter input (solar battery in my circuit) is applied, the drain-source diode of the auxiliary MOSFET will turn on first to pull up the SENSE pin and turn off the primary MOSFET followed by turning on of the auxiliary MOSFET.


texts: How does things work between MODEM and PC on the RJ45 ethernet cable?

texts:
I am a newbie in electronic and i would like to ask why there is Transmitter and Receiver in the RJ45 cable connecting the MODEM and Computer? Which one goes first

From Modem --> Receiver Receive signal ---> Transmit to the PC? OR

From PC computer --> Transmit signal to Modem to fetch signal ---> Then receive back into the PC computer

Please enlighten me


texts: Windows limitation in PCB window in Altium

texts: Is there any window limitation in PCB window in Altium? because I can't move my mouse cursor -180.086 on the x-axis.


texts: Should a fuse blow if both neutral/live pin in a three-point socket test live in a continuity tester?

texts:
A possible electrical/wiring problem rather than a core electronics problem; please feel free to vote to close.

I just noticed that the neutral pin, and live pin in all the 3-pin sockets in this building test live. This was not the case a few months ago. To test the status of the pins I used a continuity tester

Attaching a load (1kw well pump) to the socket did not cause damage to the motor, but the motor did not power-on either.

Does this indicate a possible short between the live/neutral wires?
If this does indicate a short, how could supply possibly continue? I know from painful first-hand experience that shorting neutral+live is a sure way to blow a fuse and disrupt supply.

Edit/Update:
OK ... this is weird. Following Russell's recommendation I applied a test-probe

Below are the results from applying the probe

Pins connected  Probe Lighted

PN              No

PE              No

NE              No

I then applied a lead to an iron angle support for a tin-sheet; that worked. Does this mean there is an Earth fault someplace, and I have to ouch rip out the wiring?


texts: Automate sequence of different remote control presses

texts:
I've got the following setup I would like to automate:

Press button A on a remote to turn the alarm system off
Press button A on a remote to open the garage door
Press button A on a remote to close the garage door
Press button B on a remote to turn the alarm system on

In between those steps, I could include a step to press a button on a third remote to turn on/off the car alarm.

I'm a newbie in both RF and electrical engineering, so any bits of advice would be very greatly appreciated.

I see three possible solutions for my problem, unfortunately, one of them I cannot apply:

I - (most preferable, as I can keep the remotes out of the garage) - simulate the presses by sending a signal from a Hack RF place inside the garage. The signals will be chained and depending on one another.
II - (not preferable, as the remotes have to physically be in the garage) - by using solenoids controlled by a Raspberry Pi and placed next to the remotes, those solenoids to actually press the remotes but the whole process to be started externally.
III - (this would void the warranty so it's not applicable) - open the plastic cases of the remotes, and through soldering / desoldering simulate button press through a Raspberry Pi.

I've watched some tutorials, made my research so decided to proceed with the option I. Bought me a Hack RF and started my struggle to reproduce the signal, unfortunately, I'm still failing but this could be due to lack of knowledge or experience on my side.
An issue to add on top of the situation - I'm pretty sure some of the remotes are using a rolling code, so simulating the signal won't be that easy...

Coming to my question - do you think option I is doable at all?
Should I keep trying to replicate the signal, then the second one and so on until I eventually reach the point where I can replicate and chain the successful sequence?

Should I go for a different option or there is something I'm missing and you would advise me to do?   Thanks! :)


texts: Does this PRCD have any differential current transformer inside?

texts: Its very important to have portable residual current devices (PRCD) to plug in our electrical equipments in the field, or use anywhere or even in our workplace. I got this china made PRCD from a package. Do you think it has any differential current transformer or in short, sense coil inside? Have you encountered them or similar form factor made in other countries?


texts: ENC28j60 ethernet interfacing with PIC18F4520 help needed

texts:
I am a newbie to ethernet controller. I need to use ethernet controller to send sensor data to our server using http get method. I went through ENC28j60 documentation and microchip's TCP/IP stack as well. But I couldn't find a proper example similar to my project.

briefing my application below.

PIC18F4520 will read some sensor data and send it to server every 3 minutes.
for example sensor data are voltage,current,temperature etc. It should push these data using http GET method to an URL like
abc.com/index.php/add/add_data?volt=dc_volt&current=dc_cur&temp=temp. Where dc_volt,dc_cur and temp are the measured values in microcontroller.
How can I do this using ethernet interfacing? Atleast what are the things I should learn to do this? Can I do this with the Microchip TCP /IP stack?

any help is appreciated.

Thanks


texts: If ground is a reference point and it is not physically connected how can it protect someone touching the wire from electric shock (I probably misunderstand what that symbol really means)


texts: What HDD‘s to look out for to source strongest voice coils?

texts:
This question is pretty niche, but maybe someone investigated this topic before me and can give advice.

I want to source voice coils from HDDs (new or second hand ones). The more torque/force the better. What HDD properties do I need to look out for to have higher chance of finding stronger voice coils inside them?


texts: How variable sizes are related to processors arhitecture?

texts:
I often come into the situation where I am not sure how big is my variable, for instance: integer, short, long?

I know that I can find size of variable with sizeof(); function in C.

But now I'm in situation where I'm trying to parse some data from file and I have that file structure, when I realize that all that is written for an 8bit microcontroller, I am not sure how can I know how much data INT represents in that documentation? Is it 8 bit - 1B ?
How size of variables depends on processor arhitecture? If I am correct max variable size in an 8bit processor is 1B, so char - int and all other variables are 1B maximum size?


texts: How much resistance will I need to drop the voltage?

texts: 9 Volts is applied to circuit. There is a LED which runs on 3 Volts. I want to drop 6 Volts. how much resistance (\$R_1\$) would I need for that?


texts: Transitioning between 90 and 100 ohm diff pairs using coupling caps?

texts: I'm building a PCB carrier for an FPGA SoM. The SoM has 100 ohm diff pairs routed for all the high speed IO. I'm implementing USB 3 on the carrier so should be routing 90 ohm diff pairs. What is the best method for guaranteeing signal integrity? Normally coupling caps are only used on TX pair for USB3 but this FPGA required coupling caps on both RX and TX pairs... can I route one side of the caps 90 ohm and the other side 100 ohm?


texts: Why does different antenna inductivity influence LF-RFID performance?

texts:
I'm experimenting with LF (125kHz) RFID reader antenna design. And trying two different antennas yields very different results in terms of read sensitivity. Even though one antenna is driven with considerably more current it performs worse. And I'd like to know why :-)

For all test setups:
45mm Antenna inner diameter, same carrier for coil, same RFID tag.
Resonance capacitor adjusted to within 1kHz target frequency. Voltage divider on Antenna demodulation unchanged (same sensitivity of ~37mV).

Antenna test setup 1:

0.75 mH, 0.22mm wire diameter
9.7 Ohm @ 100kHz
Added series resistance of 33 Ohm to get a Q-factor of ~15
resulting drive current: ~130mA
resulting drive voltage: ~83V
magnetic field strength: ~1.86mT
read range: ~2cm

Antenna test setup 2:

2.66 mH @ 100kHz , 0.1mm wire diameter
77.2 Ohm @ 100kHz
Added series resistance of 82 Ohm to get a Q-factor of ~15
resulting drive current: ~38mA
resulting drive voltage: ~91V
magnetic field strength: ~1.23mT
read range: ~5cm


texts: Neon Power Supply Voltage AC Measurement

texts: So I was provided with a circuit which consists of a variable transformer connected to the main (essentially allows the input of the power supply to be controlled) and a Neon Power Supply (Has An Input Of: 120VAC 50/60Hz 0.9A, Output Of: 10kv 30mA). I have realized that once a set "minimum" voltage is set on the transformer (About 30VAC) high voltage pulses can be seen to appear on the oscilloscope display. These pulses however do not allow me to take measurements within the oscilloscope (such as frequency, pk-to-pk voltage and rms) due to the pulsing wave. I have been provided with a 100X:1000V CAT II probe manufactured by Tektronix but have been unsuccessful in obtaining any measurements of this power supply. I would like to know if there is something I'm missing (such as a setting on the oscope) or not doing correctly in order to measure the voltage of the power supply. Appreciate the help!


texts: Good RS232-based Protocols for Embedded to Computer Communication

texts:
I'm working on a project that involves a good bit of data communication between a remote Arduino and a computer. The wireless connection is through a pair of XBees, so we have a RS232 link between the Arduino and the computer. For small amounts of data, it's easy enough to throw together some simple communication protocol. For larger projects, though, what are some good simple communication protocols?

I've looked at MODBUS, which seems like a viable option, but I wanted to see if there were other better options.


texts:
I am hoping for a suggestion; some back story:

My ultimate goal is to learn the intricacies of the Bluetooth connection shared between a PS3 and a Sixaxis controller. I am fairly versed in Bluetooth, and I have the proper SW to sniff out the Bluetooth connection between the two devices. However to do so I require a "Link-access key" and the BT-addr/MAC of the Master device (PS3).

The pairing process between a Sixaxis and a PS3 happens when the USB cable is plugged into the PS3 directly. At the pairing stage, the Link-Key is exchanged between the two devices. My theory is that I could observe the exchange with a USB sniffing tool.

I am stuck with what the proper tool for this may be. Most of the USB sniffing tools I come across appear to only reveal information shared between the usb device and a computer host. I would like a tool that could help me form a "middle-man attack" on the USB exchange and act as a proxy between the PS3 and the Sixaxis.

What SW/inexpensive HW could someone recommend to me to carry this out?

Thank you all.


texts: recommended wattage for soldering station

texts:
I'm looking at buying a new soldering station and trying to figure out what would be the right wattage. I'm going to soldering everything from electronic components (not much SMD, if any) to 16mm2+ cables.

Everywhere I look for recommendations everyone keeps warning about getting an iron thats too powerful. What I don't get though is why it should matter, given that you have a soldering station that maintains a set temperature. It's not like a 120W iron will spin out of control compared to a 15W iron, if anything it'll just keep the temperature from dropping when utilised.

Can you get a high quality soldering iron with set temperature that's too powerful? Is the only downside that the iron tends to get more bulky with higher wattage? Or am I just plain wrong?


texts: how to change pitch value of a LQFP footprint in Altium 20.0

texts: LQFP footprint-I want to change pitch value


texts: ADC in Digital Temperature Sensor DS18B20

texts:
According to the datasheet of DS18B20 temperature sensor, it is clear that the sensor is digital so the output is in digital form.

The resolution of the temperature sensor is 9, 10, 11, or 12 bits, corresponding to increments of 0.5°C, 0.25°C, 0.125°C, and 0.0625°C, respectively, and by default it is 12-bits. Which means, for 12-bits, a change of 0.0625°C in temperature causes an increment of 1-bit.

But there is no information given on how much change in voltage will result from a change in Temperature (i.e. scale factor).
For example, there is an analog temperature sensor in which a change of 10mV in the output voltage is equal to a change of 1°C of temperature.

Is there any way to calculate the scale factor of the digital temperature sensor like the way we do for analog?


texts: What property of USB battery packs allows them to simultaneously output power while receiving power?

texts:
Why do some USB battery packs, usually cheaper ones* allow for charging and discharging but some do not? Is there any problem with doing this?

Context: I want to power a phone by USB battery pack, and at the same time charge the battery pack with a small solar panel unit, thus creating a poor-mans USP setup.

* as I've observed myself and elsewhere

For clarity: I do not want to charge and discharge a battery, I want to charge (or at least leave plugged in) and charge another device from a battery pack. Different thing!


texts:
sorry this is my first post on this forum. I've spent a fair while combing the internet looking for advice and have not been able to find any information.

The problem:
So I've converted the engine in my bmw e30 to a 6 cylinder engine from a 4 cylinder engine and the tacho for the instrument cluster is reading incorrectly. It is to my knowledge that the signal needs to be multiplied by 3/2 to achieve an accurate result. Originally my plan was to implement some kind of frequency divider to achieve this. However, I found out that the coding plugs for 6 cylinder cars were identical in construction to the 4 cylinder cars and when plugged into a 4 cylinder cluster would provide the desired result.

Unfortunately, these coding plugs are out of production and are very difficult to source. The chip itself consists of one 8 pin IC chip. I've tried searching the model number printed on the top but it returns no results. The chip can be seen below:

My goal is to clone the chip by having a board printed and finding an appropriate IC chip to build the circuit upon. I am looking for advice on how I can identify this IC chip and if someone can identify it whether they can point me in the direction of an off the shelf solution.

Thanks, appreciate it

^^ Here are two images, however, these images show the 4cyl chip and not the 6cyl.

Yeah, I know there's thousands upon thousands of IC's. I was just hoping that someone had come across a similar situation. I've worked on black box circuits in the past and have been able to identify various filters from generating bode plots of the circuits at different frequencies but I'm not sure how to go about this for an IC chip. I was going to start by probing the connections on my car to figure out the inputs and outputs of the chip as well as constant power and ground. I could also look up the original wiring diagrams from BMW in some hope  can figure out what each pin does by tracing back its connection. Any other advice on how to go about identifying this IC would be greatly appreciated.

UPDATE

So I managed to get in contact with the seller of the clone chip and he was kind enough to point me in the right direction, really awesome guy. Here's what he said:

The 8 pin IC I used is a microcontroller that acts as a coder - a device that uses a data set for scaling instrument cluster gauges. It is not an analogue signal converter.

Does anyone have any experience with coders for use with analogue guages?


texts:
I am trying to implement a SRAM controller module. It's structured as follows

External connections:

extA[18:0] -- address
extIO[7:0] -- bidirectional input/output
OE,WE,CE  -- control signals

Internal connections:

intA[17:0] -- address
intIO[15:0] -- bidirectional input/output
EN,RDY,RW -- control singals

Basically I am trying to implement a module that splits intIO into two sequential extIOs.
Here is a code I've come up with so far:

module SRAM_Controller(clk,intA,intIOin,intIOout,extA,extIO,OE,WE,CE,rw,en,reset,rdy);
  input  clk, en, rw,reset,rdy;
  input [17:0] intA;
  input [15:0] intIOin;
  output reg [15:0] intIOout;
  output reg [18:0] extA;
  inout [7:0] extIO;
  output reg OE,WE,CE;

  reg [7:0] Dout;
  reg [15:0] Din;
  reg counter = 1'b0;
  assign extIO = (rdy && OE) ? Dout: 8'bz;

  always @(posedge clk)
  begin
      if (reset) begin
      //RESET?
      end
      else begin
          if (en) begin
             CE<=1'b0;
             if(rdy) begin
                extA[17:0]<=intA;
                extA[18] <= counter;
                case(rw)
                1'b0: // WRITE
                     begin
                        case(counter)
                        1'b0: begin
                                WE<=1'b0;
                                OE<=1'b1;
                                Dout<=intIOin[7:0];
                                counter<=1'b1;
                              end
                        1'b1: begin
                                Dout<=intIOin[15:8];
                                counter<=1'b0;
                              end
                        endcase

                     end
                1'b1: // READ
                     begin
                        case(counter)
                            1'b0:
                                begin
                                    WE<=1'b1;
                                    OE<=1'b0;
                                    intIOout[7:0]=extIO;
                                    counter<=1'b1;
                                end
                            1'b1:
                                begin
                                    extA[18]<=1'b1;
                                    intIOout[15:8]<=extIO;
                                    counter<=1'b0;
                                end
                        endcase
                    end
              endcase
          end
       end
       else begin
           CE<=1'b1;
       end
   end
end
endmodule

And here is a testbench for it:

module SRAM_Controller_tb();
reg clk;
reg [17:0] intA;
wire [15:0] intIOin;
wire [15:0] intIOout;
wire [18:0] extA;
wire [7:0]  extIO;
reg  rw, en, reset,rdy;
wire OE, WE, CE;
reg [15:0] datout;
wire [15:0] datin;
SRAM_Controller DUT(.clk(clk),.intA(intA),.intIO(intIO),.extA(extA),
.extIO(extIO),.OE(OE),.WE(WE),.CE(CE),.rw(rw),.en(en),.reset(reset),.rdy(rdy));

assign datin = intIO;
assign intIOin = !rw ? datout: 16'bz;

initial begin
   #1
   clk = 0;
   en = 1;
   rdy = 1;
   rw = 0;
   intA = 18'b010010001100111001;
   datout<= 16'hCA7E;
   #4
   intA = 18'b100001001000001111;
   datout<= 16'h23F6;
   #6
   rdy = 0;
   rw = 1;
   intA = 18'b0;
   #4
   rdy =1;
   #4
   rdy = 0;
end
always begin
   #1 clk = !clk;
end
endmodule

This is simulation from ModelSim for it:

I would like to know how to fix these issues:

extIO signal lags behind extA for one clock cycle ( I am not sure which part of my code causes delay)
extIO and intIOout signals retain "F6" bits from previous write transaction.

Please forgive me for any obvious mistakes in the code, it's my fist time using Verilog.


texts: RGB LED common cathode with 3.3V GPIO +single transistor

texts:
You can control a RGB common anode like this with only one transistor and 3.3V GPIO sources:

How can you do this with a common cathode LED array using only one transistor per LED and 3.3V GPIOs?

The forward voltage of the LEDs are 3.6V


texts: How to analyze Bluetooth Low Energy traffic in Wireshark

texts:
I am trying to analyze the traffic captured for a blue Bluetooth Low Energy device in wireshark.

I have figured out that data is transferred using the ATT protocol, but I do not see anywhere that explains how the ATT protocol works and hence how to interpret the data that I see. Anyone understands ATT and how it is used to transmit data and hence how I can read the data transmitted via Wireshark?


texts: Analog to Digital converter module of MCU - Conceptual question

texts:
Please consider the following codes:

//Code Sample 1
void func_val(void)
{
  unsigned int val;
  ADCSC1 = 0x00; // sets the required channel.
  while(!ADCSC1_COCO); //check for conversion complete flag.
  val= ADCRL;
}

//Code sample 2
void EvalProx()
{
  unsigned int proxval;
  ADCSC1 = 0x02; // sets the required channel.
  while(!ADCSC1_COCO); //check for conversion complete flag.
  proxval = ADCRL;
}

Now both the samples are snippets from a bigger code, which compiles and works.
My question is about the concept of Analog to Digital Converters in MCU.
ADCRL and ADCRH are the registers in which the converted values are stored.
ADCSC is the status control register in which I have specified two different channels to be used.

Question: The ADCRL/ADCRH are same for the two different setting of the ADCSC i.e. same for both the channels. So does the value of proxval influence the value of val when accessed? i.e. If func_val() is executed and then
EvalProx(), is the value of proxval influenced by the val? (when both the values depend on ADCRH and ADCRL)

I hope I am clear. Before down voting this question, I request, please take some time to tell me why you have down voted, so I can improve my question.

Datasheet of the used MCU: MC9S08DZ60

Specific Page Numbers: Chapter 10 :- Page 181,182- for ADCRH and ADCRL.


texts: Can we draw analogy between em power flow through free space and ac power flow through a transmission line?

texts:
Knowing that the free space has a characteristic impedance (which is purely resistive, measured in ohms) I was wondering if I can model the free space as an infinitely long transmission line- comprised of distributed inductors and capacitors.

We know, a lossless transmission line model of infinite length supplied by an AC source at one terminal looks:

If we consider the direction of changing electric field across the capacitance (say X axis) and that of changing magnetic field inside the inductance (say Y axis), we find the poynting vector directing outward of the plane of transmission line (Z axis)-- which seems weird, since power flow direction is certainly along Y axis.

However, if I adjust the orientation of the inductors in following way:

It seems that the problem regarding to power flow direction is solved apparently.
However, I am not still convinced with this depiction. Firstly, I have considered only the magnetic field inside the inductors. But H has a non zero curl, it ends upon itself. So if I take the total H field (around the inductor) into account, I end up with a zero power flow -- which is definitely not what is happening.
Moreover, the power flow, irrespective of the orientation of inductors, must be along transmission line (not outward of the plane containing TX line).

At this point, I wonder where I am making mistakes. (i.e.- is it because I am ignoring current through the capacitor and electric field across the inductor? )Or is it a crap idea to model the free space as transmission line ?


texts:
I am relatively new to thermocouples. We are wanting to get the temperature of fire ball blast. We are using a Type-K thermocouple and a Phoenix Contact mini signal conditioner to amplify the signal. I am using a thermocouple DAQ to record the amplified voltage out from the signal conditioner (a 0-5V analog output) with a 150ms sampling period.

Questions I have:

Do I require cold junction compensation? If so, is it best to just set it to 0°C? If not, how do I find out what it needs to be?
What is the best way to calibrate it and how do I convert the amplified signal (V) back into a relative temperature (°C)?


texts: Calculating low-pass filter prototype specifications

texts:
So I'm just wondering what I need to figure out before I can actually calculate anything here, (only considering the a-part now)? I understand that 2.5 GHz should be 3dB and 3.75 GHz should have 25 dB of gain, and if it's overshooting the specifications, but I'm not at all sure how I can calculate this.

I'm guessing that I'll need to figure out an actual equation for the filter, but I'm also clueless on what principles I should try to use here. Any pointers on what direction I should be headed would be cool.

Should I apply normalized low-pass prototype element values even though I've already been given the component values, or do I want to use that to compare if the components are overkill (assuming they work)?


texts: Hall effect device for circa 1 tesla gaussmeter

texts:
I'm thinking about building an unsophisticated bench instrument for measuring magnetic field density, just to support my learning about electromagnetism and building magnetics for power electronics applications.

I'm thinking I'll want something that can measure up to about 1 tesla (T) and was generally thinking that using a linear Hall effect sensor of some description was the way to go.

There are a number of such projects out there on the web, but they all seem to have a substantially lower operating range, which I understand is perfectly useful for a variety of other applications.

The linear Hall effect sensor devices I've been able to find all seem to top out at much lower flux densities, like 600 gauss (G), which is 0.06 T.

So I'm wondering, are there any Hall effect sensors that can operate at the flux densities I'm designing for? Or is it perhaps silly to be looking for something in that range? I figured line transformer iron can operate at between 1 and 2 T before saturation, so I'd be in the right ballpark.


texts: How does this synchronizing/edge detector logical diagram work?

texts:
This is the logic diagram for a MCU that allows for an external clock option via Tn. This clock can be used as the source for clocking an internal timer register.

According to the datasheet this diagram was extracted from, "Registers are positive edge triggered. The latch is transparent in the high period of the internal clock. The edge detector generates 1 pulse for each positive/negative (depending on the setting of a register) edge detected."

How does this diagram work? I have tried to search around the net to see what the trapezoid logic symbol represents (in the edge portion) but could only find its meaning with respect to program flow (it represents a mechanical/physical step).

That being said, I am not sure at all how the edge detector works. As for the synchronizer, it appears that the latch (the first flipflop) is only enabled (LE) when clk is high and the timer value will be passed, but what is the purpose of 2 flipflops?. I understand that the edge detector must enable the output AND gate only when a LOW/HIGH transition is seen at Tn (and only once period), but I am not sure how exactly this works.

Tn may be equal to or slower than clk.

What if clk = Tn and they are 180 degrees out of phase? That is, their transitions are at the exact same time. It would seem me that the clocking of the internal timing register would be undefined.


texts: Test patterns for testing high speed trans receivers of fpga

texts:
I know that we can generate all possible patterns using LFSR sequences but this will waste memory as we will have to store pattern to do error checking and storing all from 0 to 2^(n-1) will require huge memory.
So instead of that I want some specific test patterns on which my trans receiver will be faulty. So are there any specific test patterns on which they will give error.


texts: Insulation on resistance wire, what's the use?

texts:
I am currently experimenting with resistance wire to generate heat. I have 2 types here. One is insulated, the other isn't. The one that isn't insulated works just fine, but the insulated one gives a huge amount of smoke the first time I heat it and then the outside becomes completely black. After that the smoking stops.

What is the use of that insulation if as soon as I put some current on the wire it smokes and turns black?

I measured the temperatures and I did not exceed 80 degrees Celcius. Voltage applied is around 10V and it draws a current of 2.5A.

Some info about the wire:
Resistance: 10 Ohm / metre
Diameter: 0.25mm
Material: CuNi44


texts: How to combine two resistors in a circuit reduction

texts:
I'm new to electrical engineering so I've been watching MIT's Open Course Ware videos on Circuits and Electronics. In one of the lectures, the professor discusses the different methods to use in order to reduce a circuit to a simpler form. One of the methods he describes as the "intuitive" method, where you consolidate components within the circuit intuitively.

Here is an example he gave:

simulate this circuit – Schematic created using CircuitLab

The problem I'm having is, he states he takes the sum of the two conductances (R2 and R3) and that equals ((R2 * R3) / (R2 + R3)), how does he get ((R2 * R3) / (R2 + R3))?

Shouldn't the sum of the two conductances just be R2 + R3?

Link to course video where he describes the problem at 31:00: MIT 6.002 Circuits and Electronics | Lec 2


texts: Strain Gauge with Instrumentation Amplifier question

texts:
I have a problem making a circuit like this working

I got it from this TI application note. For testing purposes I have set:

\$R4=R2=R3=R1=47 \Omega\$

\$ Rf = 10 k\Omega\$

\$Rg= 26.70\Omega\$

The op amp \$V_S=+5V\$. This should give a gain of 750 having \$V_{SIG}\$ as 0.8E-4V/kg.

I agreed that 80kg would be enough for full scale. The problem is that this setup doesn't show any variations when i load the strain gauge. It just stays at 2.40V which doesn't make much sense since it doesn't reach near \$V_S\$. I am using the TL064. I have tried a lot and think my wiring is correct. Do you have any suggestions?

Update:
I came up with the 750 of gain by assuming that:

\$R4=R2 <=> \dfrac{R4}{R2}=1\$
\$Gain=\dfrac{2Rf}{Rg}+1\$
\$(Sig_+)-(Sig_-) = V_{IN} => V_O=V_{IN} \times 1 \times Gain <=>\$
\$Gain = \dfrac{V_O}{V_{IN}} <=> \dfrac{2Rf}{Rg}+1 = \dfrac{V_O}{V_{IN}}.\$
\$V_{IN}/kg = 0.8E-4V/kg\$

I also i assumed that my absolute maximum load would be 80kg. So
\$V_{IN(MAX)} = 0.8E-4 \times 80 = 6.4E-3\$ V

So we can determine the needed gain for

\$V_{OUT}=5V. G=\dfrac{V_{OUT}}{V_{IN}}=\dfrac{4.8}{6.4E-3}=750\$

Taking the previous equations:
\$ \dfrac{2Rf}{Rg}+1 = 750 <=> 2Rf = 749 Rg <=>  Rg = \dfrac{Rf}{374.5}\$

Knowing this and the resistors I had available I chose to set Rg as a function of Rf because i have to arrange the resistors(series or parallels to approximately get the desired gain) I chose:

Edit:
Corrected Equation mistake but still no results
\$Rf=10 k\Omega => Rg = 10E3/374.5 = 26.70 \Omega\$
Considering I don't have this precise value I came up with
\$Rg = 47 || 47 = 23.5\$ which is close to \$26.70 \Omega\$

Hope everything is clear for everybody, otherwise please ask for clarifications
Thank you


texts:
I have a hobby project where I would like to use micro stepper motors as shown in the picture below.  However, as you might be able to see, the spacing between the pins is incredibly tiny and each pin is much narrower than the 24 AWG wire I was planning on using.  In addition, each pin seems to have a single strand of copper wire attached to it presumably attached to the stepper windings.

So my question to us all ... what technique might one use to attach wires to these pins?  Assume poor/average soldering skills and "normal" mans hands with normal steadyness (and by that I mean (what I hope are) the normal amount of shakes).

Here is a photo I took myself which shows the scale against a rule.


texts: LED forward voltage is a range, so how do you calculate resistor value?

texts:
In all LED examples that I find, they have the forward voltage set to a specific number (i.e. 2.1v) and calculate the resistor needed based on that number. But when I look up datasheets, the forward voltage comes in ranges (2.0v - 2.5v). This makes sense to me since not all LEDs are created equal. But it's making it hard for me to figure out what resistor to use.

So I decided to design a circuit. I have a 3v voltage source (2 AA batteries) that connects to a resistor that connects to an LED that connects back to the voltage source. The LED's max sustainable current is 20mA.

I decided to use Ohm's Law on the low and high end of the forward voltage range to calculate resistances.

$$(3.0v - 2.0v)/20mA = 50\Omega$$
$$(3.0v - 2.5v)/20mA = 25\Omega$$

The problem comes when I pick a resistor. Let's say I pick the 50 Ohm resistor but the LED that I get actually has a forward voltage of 2.5v. The actual amount of current that would go through the LED would be 10mA. That's not using the LED to it's full potential.

If I use the 25 Ohm resistor and the LED has a forward voltage of 2.0v, then the amount of current going through the LED would be 40mA. My LED would explode.

Using the "set value" of 2.1v to calculate resistance gives us 45 Ohms.

$$(3.0v - 2.1v)/20mA = 45\Omega$$

If my LED had a forward voltage of 2.0v, the current would be 22mA. That's over the rating for the LED. If the LED had a forward voltage of 2.5v, the current would be 11mA which isn't using the LED to it's full potential.

Note: I'm not too concerned about getting the full potential out of an LED. (If I understand correctly, 10mA should work fine to light up an LED.) I just want to know how real engineers handle this problem. Is having a 10mA current acceptable? Can you actually get away with 22mA even though the specs say 20mA? What do you do when you need your LEDs to operate at peak brightness?


texts: Using a single power source for both the gate and source of my transistor?

texts:
I am using an IRFZ44N MOSFET (n-type) transistor to regulate the current of a Lithium-ion battery, and I'm trying to use the battery to supply power to both the drain and gate of the transistor. My goal is to allow current to flow from drain to source when I apply voltage to the gate (when I attach the (+) wire to the gate), and stop the current flow when I connect the transistor gate to ground (when I attach the (-) wire to the gate). In my schematic I left the circuit open, but depending on what I want my gate voltage to be I connect either the (+) or the (-) wire momentarily.

My problem is that I don't understand why I'm reading certain values on my ammeter. When I connect the (+) wire to supply voltage, I should see a current of 3.7V/10ohms=370mA, but I'm only reading a value of around 30mA. However, if I use a separate power supply for the gate of the MOSFET with everything else unchanged, I get an ammeter reading of 370mA as expected.

I know the gate-source voltage is the same in both scenarios because I measured it with a voltmeter (measured about 3.5V), and when I use a separate power supply I'm also using a 3.7V battery.

Why does using the same power source to supply the gate voltage only let 30mA through?

simulate this circuit – Schematic created using CircuitLab


texts: Could the OCTC(open circuit time constant) method estimate the current gain bandwidth?

texts: I have already know the OCTC and SCTC method could estimate the cut-off frequency of the voltage gain. Are there any method to estimate the cut-off frequency of the current gain?


texts: Mount a detachable LED strip to spokes of bike

texts: I have an LED strip and Arduino I have mounted onto the spokes of a bike using twist ties (like this: https://learn.adafruit.com/bike-wheel-pov-display/install-on-bike).  I want to make it detachable though and was wondering how to go about doing that?  I was thinking of attaching the LED strip and Arduino to a pvc pipe and using a clip to attach the pvc pipe to the spokes of the wheels.


texts: Noise on probe while measuring Switching Frequency of Buck Converter

texts:
I have a buck converter and I am measuring the voltage ripple at the output capacitor along with that I am measuring the switching frequency at the cathode of the diode. Please refer the below image. I am using 500MHz keysight scope.

Probe 1: Output Voltage across output capacitor (AC coupling mode is used with short ground tip)
Probe 2: Switching frequency measured at cathode of diode (DC coupling with ground of the probe connected to scope ground)
While measuring these two simultaneously, my output ripple voltage is picking up high noise. If I don't measure the switching frequency along with the output voltage ripple, I have no problem. While measuring together, my output ripple voltage probe, picks up noise.
What might be the problem?


texts: Setting Up Long Distance Unidirectional Wifi Antenna

texts:
A neighbor has graciously offered us temporary access to their wireless for basic internet access, but we are about 100 meters apart. I have a wireless NIC, but I wanted suggestions as to the setup.

I found on a popular website where they had made a unidirectional antenna out of an old satellite dish. I found some cheap LRM-200 cable for about 0.60/ft.

But a popular online encyclopedia says that LRM-200 has a whopping .554 dB/meter loss @ 2.4GHz!!!

I have to get to my roof and part way across it to get line of sight. I'm looking at 30-40ft. So, am I looking at 20 dB loss just from the cable alone?

Do you think this setup will work? Have any better suggestions for a wireless setup?

I don't mind spending a little money, but it is temporary after all.

edit

I already have a wideband directional cell phone booster antenna on the roof any chance that would work? I think the antenna model is zBoost CANT-0042, it came bundled when I bought a zboost ZB575V


texts:
What is the exact definition of cascode stage?

And can we regard this circuit as cascode?


texts: Difference between ARM7 and intel i3, i5 & i7 processors

texts:
I am just starting out on a journey to understand microcontroller and microprocessor design. Have read briefly on their differences (ARM7 and Intel i3, i5 & i7).
Couldn't find any information on their differences in architecture.
for example, ARM7 has 21 external interrupt pins. but couldnt find definite information about intel's external interrupt pins.
or how On-chip static ram is 8 kb-40 kb, on-chip flash memory is 32 kb-512 kb, the wide interface is 128 bit, or accelerator allows 60 MHz high-speed operation for ARM7. couldn't find any corresponding information on intel's processors.


texts:
I am new and noob in digital logical design. My teacher give me a scenario and asked for circuit. I made a ciruit here.
Restrictions:
Use only AND NOT and OR gates wih two inputs.

Scenario
UIT is announcing a scholarship program for the students of engineering and computer science. For this purpose three different modular exams would be taken.
If any student wants to get this scholarship he/she should pass all three exams. In the first exam there are three questions and each question has two parts. If any one part is correct that question would be considered correct. If all three questions are correct then that exam would be considered PASSED.
Now after the passing of first exam, he/she would be allowed for the second exam. There are two questions in the second exam. If both the answers are correct then only the exam would be considered PASSED.
Now after passing of second exam, he/she would be allowed for the third exam.  There are three questions in this exam. All correct answers are required to pass that exam, and then he/she can get the scholarship.
Design a logical circuit for the above scenario
Is my circuit correct or not?


texts: I was wondering what the best way to run a solenoid would be from an Arduino board. I was thinking about using a MOSFET that runs into a relay to turn on the solenoid but am not sure how to go about it.


texts: Shifting -5 V to +5 V signal to 0 to +5 V for ADC

texts:
I want to convert the  output voltage of an ECG (-5 to +5) to 0 - +5 volt for ADC.
Should i use Op amp ?
What is my problem in this picture?
I simulated it in Proteus ... but when input voltage is higher than 4 V or lower than -4 V Vout gives an unexpected value.

Below is another simulink that have same problem ...

My idea to make this level of voltage is (Vin +10)/2 that give the range 0-5 V.


texts: How does a Philips Hue Tap transmit a radio signal without a battery?

texts:
The Philips Hue Tap is a remote control for a Philips Hue lighting system. The buttons can be configured to trigger some action on the Hue bridge, such as turning lights on in a particular room.
The interesting thing about the product is that seems that the energy from pressing the button is enough to transmit a radio message to the Hue bridge.

The Philips Hue tap is powered by kinetic energy, which means that when you press the light switch you generate sufficient energy to control your smart lights. A truly wireless, batteryless, solution.

How does this work? About how much electrical power is generated by pressing the button? What components would be needed to make something similar?


texts: Cascade s2p file to measure self-receiving antenna

texts:
If say I wish to measure a radar's 2 port characteristics (it sends to itself via a distance D air link)

Can I make an experiment that I use Network Analyzer to measure it transmitting signal to another antenna B spacing distance D LOS, then cascade the resulted s2p file in the configuration such that

[port 1, port 2] --- [port 2 , port 1] , and divided the dB(s21) and dB(s12) by two respectively and subtract by 3 dB to get the 2 port metrics?

I am not quite familiar with the operations/tricks on scattering parameters, could anyone recommend resources that I can refer to?

Thank you very much!


texts: Identify cable connector for fingerprint sensor

texts:
I want to create a custom PCB to which this fingerprint sensor will connect. The problem is that I cannot identify which connector it uses. The sellers on Amazon and other sites don't know about it.
Any help on how I can identify the name/footprint for the female connector which is compatible with this wire?


texts: Is it safe to breadboard esd sensitive components?

texts:
I would like to first prototype a circuit on a solderless breadboard, then later solder those same components to a prototype pcb board in order to make the circuit more permanent.

Some of the components I plan to use are esd sensitive (mostly mosfets and ICs containing mosfets- all with through hole leads).  I know that precautions must be taken to prevent electrostatic discharge from my body, tools, and the work surface from damaging the esd sensitive components.

Is there any risk of electrostatic discharge from the sockets of the solderless breadboard damaging the esd sensitive components?


texts: How do you solve this circuit with the node voltage method?

texts: This question requires you to find the node voltage between nodes 1 & 2 as well as condense the circuit into its Thevenin Equivalent with R2 as the load. The correct answers are 4 V between nodes 1 & 2 and 36.5 V & 7.8 for Thevenin Voltage & Resistance respectively. Could someone please explain this to me? I'm especially confused as to why the Thevenin Voltage is higher than the source voltage. Thanks in advance.


texts: Does having negative PID gains effects stability and realization of system?

texts:
Can we have a PID controller which has positive I gain and negative P gain?
or will our system and controller will be not be realizable and will be unstable in this case due to a negative value of PID gain?


texts:
Good day to all.

I'm working with the PIC16F1782 family of enhanced 14-bit PICs.  These include: 1782, 1783, 1784, 1786, 1787.

The instruction set in the datasheet shows that the TRIS instruction is supported, unlike some older members of the 14-bit family.  However, it's not working for me.

The 16F178x family has moved some of the registers around compared to earlier PICs.  Specifically, there are two INDF and FSR registers instead of only one.  As a result, ports RA through RC have been moved from 0x05..0x07 to 0x0C..0x0E.

When I run MPASMWIN version 8.92, I get errors anytime a TRIS instruction is encountered.  The error message says that the allowable address range of TRIS is 0x05..0x07.

Is this a problem with MPASMWIN or is the datasheet not correct?

I can always go back to switching RAM banks to load the TRIS registers but it would sure be convenient (and faster/shorter) if I could go back to using the TRIS instruction.

Guidance gratefully accepted.

Many thanks!


texts: XC8 - constant ROM allocation for PIC12F1501

texts:
I have troubles with const memory allocation with XC8. I try to do this:

const unsigned char patterns[12] = {
    0, 0, 0, 0,
    0, 0, 0, 0,
    0, 0, 0, 0,
};

but I get this error: "can't find 0xC words (0xc withtotal) for psect "stringtext" in class "STRCODE" (largest unused contiguous range 0x57)". That's strange because space needed is less than space available (contiguous). In the user guide:

http://ww1.microchip.com/downloads/en/DeviceDoc/MPLAB_XC8_C_Compiler_User_Guide.pdf

I read that

  stringtext psect must be linked within the first half of each program memory page

I'm not quite sure why. I guess the compiler fills all the first halves before trying to find space for constants. Can anyway advice me how to give a hint to the compiler where to locate the constants section? Or Is there any other way to workaround this problem.

I'm using MPLAB because I find it difficult to use MPLAB X.

P.S. Keep in mind that the ROM is almost full - only 0x57 bytes left. It's well fragmented in small sections in order to fit better.


texts: Programming cortex m0+ soic for coustom pcb

texts:
I need a little help. I have designed a small HAVC system, controlled with different sensors which  each is connected to cortex m0+ mcu-s. I have tested my program on development board. Now I have to put every thing together.
My problem is that I don't have any idea how to load program on four Atmel SAM D10C cortex m0+ mcu-s?
I have search on google for a while and didn't get any answer, so please help me ;(.


texts: Controlling a motor with arduino and H bridge and external power supply

texts:
I was reading this tutorial and I was confused on how I would control a motor with a 9v battery while powering my arduino with just the USB cable plugged in.

http://itp.nyu.edu/physcomp/Labs/DCMotorControl


texts: How can I tell if a complex relay is intermittently failing?

texts:
I have some starting issues with my car which sometimes starts fitfully.

It could be the fuel pump relay which looks like this:

Or, it could be the fuel pump itself. For the purpose of this question I would like to know how to eliminate the relay as the source of the problem. Unfortunately, as I understand it, the inside of the relay is full of complex solder joints which age over time and it can be hard to tell whether the joints are good or not.

What is the right strategy here to determine if the relay is sound? Can I put it in some kind of test harness, or is it feasible to just take apart the relay piece by piece and manually check each solder joint?


texts:
I got the following code from the video. However, I encountered an issue that, the motor tended to stop working at maximum value.

#include <Servo.h>

Servo ESC;     // create servo object to control the ESC
int potValue;  // value from the analog pin

void setup() {
  ESC.attach(9,100,2000); // (pin, min pulse width, max pulse width in microseconds)
  ESC.writeMicroseconds(1000);

}

void loop() {

potValue = analogRead(A0);
potValue = map(potValue, 0, 1023, 1000, 2000);
ESC.writeMicroseconds(potValue);
}

The ESC I used was BL Heli ESC. This issue appear to be some what general. Is there any particular reason to stop ESC and motor operating at 100%?

Question part 2: The webpage and online resource usually said "The ESC accept pulse from 1 ms and 2 ms." and "... operated at 50 Hz"(every 20ms), which represented the operation from 0% to 100%.

2a. Can we send 5V constant signal to ESC? Does it represent 100% operation?

2b. What if we send 1.5/2 ms for every 10ms signal to ESC? Does that represent 50%, or some value between 25% to 50%?


texts: Why is DC component ignored and AC analysis is used when obtaining input output impedance of a BJT transistor amplifier?

texts:
What I understand is: in discrete amplifier circuits, the aim of the DC analysis is to find the DC operating point. (I get this part)

And the texts I read so far mentions that AC analysis is done to obtain the Voltage gain, input and output impedance, and frequency response.

My confusion is that: why do we need AC analysis but not DC analysis to find the input and output impedance?
Why do we ignore the DC part of an input signal when finding input or output impedance?

Is there a way to clarify/understand this in a simple fashion? Would be nice to consider a BJT common emitter amplifier with a resistor at its emitter such as:


texts: Is this Moore Diagram designed to identify a sequence Correct?

texts:
I have to make a Moore Diagram in order to identify the following sequence: BABBAA
Two conditions: It shouldn't stop and it should be able to detect overlapped sequences. I don't really know if it is correct and as you can see by the question mark between the state E3 and the state E2 with input A, I don't really know if that is fine. Could anyone point the mistakes I made on this diagram or if its correct?

Thanks for your help!


texts: transistor replacement with parameters -ft/power dissipation difference?

texts:
i am trying to fix a 400w power supply, 16v is going through a 1.5k/0.5w resistor,to h945p npn transistors then to driving transformer, reading of h945 p is short. i want to replace it,the shops here dont have it even after i say the values from data sheet ,they are so dumb. i am getting this ST2SC1815 for a cheaper price ,almost similar parameters except these 2 - ft is 250 for h495p ,80 for ST2SC1815 power dissipation is 250mW for h495p , 400mW for ST2SC1815

can i replace h495p with ST2SC1815 ? thanks


texts: Inductor current ripple ratio of buck boost converters

texts:
I have a question about this paper: https://ieeexplore.ieee.org/document/1210630

I have always thought that the maximum current ripple of a buck converter occurs with a duty cycle of 0.5. The paper on page 1373 shows in figure 3(a) that the maximum current ripple occurs at a duty cycle of about 0.6. Does this mean that the current ripple does not always reach its maximum value at a duty cycle of 0.5 or did the author make a mistake or did I misunderstand the diagram?


texts: What can cause the output voltage of a buck converter to drop (apart from high current)?

texts:
I am using the LTC3388-1 buck converter to provide a microcontroller with a regulated 1.8V voltage. I use pretty much the reference circuit as seen in the image.

When I disconnect the microcontroller (remove the wire CORE as seen in the image), I measure 1.8V in the output of the converter.

When I apply a resistor as load, the output voltage is again stable at 1.8V. As I decrease the resistance of the load resistor, the current increases, until it reaches 50mA (the maximum supported by LTC3388-1). Then, the voltage starts to drop.

So far so good.

When I connect the microcontroller (as seen in the image), I measure 0.6V at Vout. The current is also low at approximately 10uA; nowhere close the maximum limits of the converter.

Figure below shows the behaviour of the system when I connect the MCU.

What can possibly cause this voltage drop?


texts: Battery Switching Circuit using Transistor and PMOS

texts:
I am designing a circuit for charging Lipo battery with control and using the same circuit for switching to Lipo battery supply when there is no power source. I am using the following circuit:

(You can also see the simulation at http://tinyurl.com/htwynv2)

Control Input is from micro-controller (3.3V or GND). 4.18V Power Supply is used which is converted from 12V using SMPS.

Working:

3.3V/GND Control Input is given to transistor (NPN) for turning charging ON/OFF.

When Power Source is available,

At 3.3V control input, the transistor is ON and voltage at point P is low, so PMOS is ON and battery is On charging.
At 0V (GND) control input, the transistor is OFF and voltage at point P is 4.18V (High) and PMOS is OFF and battery is isolated.

When Power Source is not available,

Due to the intrinsic diode of PMOS (which is in the forward direction from drain to source), Battery voltage will be reflected to the power source and current will flow through this diode.

4.18V supply is used for driving GSM module, which operated between 3.4V to 4.4V and while posting to server, the module takes 2A burst current (~1ms).

I have some basic doubts:

Is this circuit is suitable for switching to Lipo battery supply?
Is working of this circuit is same as I described above?
When there is no power source, circuit switches to battery supply with a drop of around 0.4V between drain and source of the PMOS. Can I reduce it by using any other PMOS?
When power is from the battery, then GSM module is facing power reset while posting to the server. I believe this is because of surge current of 2A. Maybe due to the current limitation of a diode or anything else? Should I switch to other PMOS with the low dropout of diode?

Also, it will be great if you people can suggest any better circuit for this purpose.


texts: Current limiter of negative/positive pulse

texts: I have pulse with both negative and positive sides, say -4v to +4v. I want to limit the current for both sides to 1mA. I know how to limit the current of a 0 to 5v pulse using two transistors but I am not sure how to apply it to a -4- to 4v pulse. Any suggestion?


texts: High speed counter for digital oscilloscope

texts:
I'm designing a simple digital oscilloscope, as a learning exercise. It will do the trivial: to sample the analog signal and store it in high speed SRAM and them plot the data to an LCD.

The part that I need help with, is the block that will trigger the ADC and control the SRAM to grab each sample and store it in a given address. I'm still choosing parts and sketching the design, and I would like to hear about the possible approaches.

I have been looking at various open source and commercial projects, and all of them use an FPGA to do this task.

Wouldn't be possible to use some high speed 74XX devices to do that? Are there any reasons to avoid this approach? The oscillator that will trigger the ADC (and also increment de SRAM address) will be about 40MHz. In addition to that, there will be some control signals to start / stop the oscillator, reset the counter and to command the SRAM to read / write data.

Is there any complication I didn't foresee, that will make an FPGA the only practical option?

I would like to hear from more experienced engineers before choosing an approach.

Thanks in advance!


texts: The short circuit test on a single phase transformer

texts: In the short circuit test of a single phase transformer, we connect a wattmeter to on the high voltage side and we increase the voltage till rated currents are set up. The text book says that the wattmeter measures the copper losses of transformer at full load. This means that it includes the copper losses of both the winding in which the wattmeter is connected and the winding which is kept shorted. However the wattmeter is connected only to one side like we know. How is it that it accounts for losses on both sides. Im confused and could surely do with some help.


texts: Timing and clock skew problems in digital designs

texts:
I am reading "Rapid Prototyping of Digital Systems: SOPC Edition", and on p.113 it contains the following statement:

  In VHDL, as in any digital logic designs, it is not good design practice to AND or gate other signals with the clock. Use a flip-flop with a clock enable instead to avoid timing and clock skew problems.

Could you explain what exactly are those "timing and clock skew problems", and give some contrasting examples of good and bad designs?


texts: Why was 4mA and 20mA picked? Was it an arbitrary choice? I don't see this signalling method used much in hobbyist projects, why's that? What are these current signalling loops best for?


texts:
For my product's blurb, it would be really great if I could find out how many transistors average MCU's have, as a comparison to something bigger, like a computer, or even a low-end x86 processor. The blurb is about the virtual challenges part of it which offloads rendering of 3D games to the Real World™ (augmented reality), so I'm comparing GPUs to Super OSD. It sounds a bit obtuse but it's fun and I think it's a cool metaphor.

I'm thinking of asking the manufacturers, but I suspect I'll just get "that's proprietary information" back. Some chips, especially those from Analog Devices and ONsemi, have "chip complexity" or "number of transistors" in the datasheet, but others don't. I'm wondering why they don't include this information, because you could hardly build another chip just by knowing the number of fets, and if you were really dedicated (and paid a lot), you could probably count them yourself with a microscope or an image of the die, or at the very least estimate them by knowing the die area and average feature size.

I'm interested in the AT32UC3B0512, dsPIC33FJ128GP802, dsPIC33FJ256GP506A, PIC24F64GA002 and PIC16F689, as well as some non-MCU's, like LMH1980, LM1881 and 24AA1025 (EEPROM.) But even if someone can hint towards a general number of transistors in their respective classes (AT32, dsPIC33F, PIC24F, PIC16F) it would be great!


texts: Polarization of Radio-Frequency Low-Noise Amplifier

texts:
I was reading the chapter about Low Noise Amplifiers from the book "The design of cmos radio-frequency integrated circuits" by Lee, and I have seen this example:

I do not understand the part inside the red circle. It is used to set the correct bias point for M1. The book says that:

  Transistor M3 essentially forms a current mirror with M1, and its width is some small fraction of M1's width to minimize the power overhead of the bias circuit. The current through M3 is set by the supply voltage and Rref in conjunction with the Vgs of M3. The resistor RBIAS is chosen large eniugh that its equivalent noise current is small enough to be ignored. In a 50 Ohm system, values of several hundred ohms to a kilohm or so are adequate.

Precisely, I have the following questions:

1) Why do we need a current mirror? The current that flows on M3 is not given to any other circuit, what is its aim? I'd say that M1 needs a biasing voltage (and not current) and that may be achieved through for instance a simple voltage divider with two resistances.

2) I do not understand its considerations about RBIAS and noise: higher resistance means higher thermal noise, so I do not understand that statement.


texts: How can I connect two mutually exclusive output on one pin of a MCU?

texts:
I couldn't be sure how to make a proper headline, correct me if I am wrong with it.

I have a reasonably working push button solution including hardware de-bouncing. There is no question on that.

So, now, I was asked if i can also feed that MCU pin directly from a PLC.
There is no secret with that. I choose an optocoupler (LTV-844). It has NPN open collector output.

My question is; should I expect any complication when I connect open collector output of the optocoupler and Schmidt Trigger output to the very same MCU pin? if so, what would be the solution?

A hint; that two outputs won't be available at the same time (mutually exclusive by design).


texts: The difference between dual loop DC analysis and normal DC analysis

texts:
What is the difference between dual loop DC analysis and normal DC analysis ?

Is their difference dual loop DC analysis have two source,maybe DC and DC, AC and AC ,or DC and current source ;and normal DC analysis have just one source,DC voltage source?


texts: Generally we work in terms of either 5V or 3.3V for the micro controllers. Why cannot we work in millivolt range? Just I wanted to know the limitations of working in millivolts.


texts: BLDC won't start up by itself but with some initial help

texts:
As stated in the heading, I'm currently having a problem with driving a BLDC motor with VCC being 30 V. I'm using the DRV8320S motor driver IC from Texas Instruments. It is configured in 1x PWM mode, i.e. it only needs PWM, the desired direction of rotation as well as the hall sensor values. It will then drive the three external NMOS half bridges accordingly.

Given below is a simplified schematics of the board. For simplicity, I removed the two current sensor ICs and their shunts as well as the MCU, which actually gets the hall sensor values and delegates them to the motor controller. It also generates the remaining signals for INHx / INLx. The PWM frequency is 24 kHz. Attached motor is a maxon 402685.

Most of the time, the motor behaves just as expected. Hall sensor mapping is also correct, as other mappings will result in high pitch and frequency noises or rapid vibration of the motor. But if the motor is in standstill, most of the time it won't start up by itself. More precisely, I got this behavior in the following situations:

After powering up the board (firmware is configured to drive motor instantly after initialization)
If motor PWM is a sawtooth (after reaching zero, the direction of rotation will alternate), the motor sometimes won't turn on after PWM passed zero
If you stop motor by applying a high enough external torque

In these situations, the motor driver still generates opposite PWM signals at two of its outputs as expected (active freewheeling). If it helps, current differs slightly if the motor turns clockwise or counterclockwise. Besides that, I didn't measure anything unexpected at all.

A guess from my side is, that the motor reaches a steady state acc. to the hall sensors, i.e. the rotor is perfectly aligned with the stators so that there is no effective torque. Maybe I have to adjust the hall sensor values in the MCU before I delegate them to the motor drivers, not by permuting them but by choosing the next / last state in the commutation table. But doesn't that presumption imply that the motor driver drives the motor always so that it reaches steady state, which IMHO is a contradiction to the fact that it can drive the motor clockwise / counterclockwise?

I searched a lot on the Internet, but only found some solved the problem but won't tell you how posts. Hope you can help me with this issue. If you need any further information, just ask me.


texts: How do I check the stability of a discrete transfer function?

texts: I calculated the transfer function and let n = 1 , but how do I check the stability of the discrete time system when n = 1?


texts:
For instance, let's take this delta-sigma ADC:
http://ww1.microchip.com/downloads/en/DeviceDoc/22088c.pdf

To calculate the average current and other important values for various sampling scenarios I need the true sampling frequency of an ADC.
Most notes deal with SAR ADCs where this is obvious, but what about delta-sigma ADCs?

Let's take the mentioned ADC and consider its 18-bit mode.

In 18-bit mode, it will output 3.75 SPS (samples per second).

Now to prevent aliasing or calculate various stuff like e.g. requirements on time constants etc. I do not care about the data output rate, but about how many times the ADC really physically samples, right? So how do I know how many times the ADC samples, before it outputs an 18-bit sample at the end?

Let's say I want to measure a sensor output once every second (= 1Hz).

A delta-sigma ADC uses oversampling to generate a high bit output with a 1-bit ADC. So wouldn't the ADC need to physically sample about 4^(17-bit) * 1Hz = ~17GHz theoretically to achieve 18-bit output codes?

I'm confused, hope you can help me out, thank you.


texts:
You can see the symbol on the upper right hand side of the board, what appears to be a pictogram of a woman wearing a dress, similar to a bathroom sign (?)

Wondering what this is.


texts: How can I draw layout for 2 NMOS having different body potential?

texts:
I am trying to understand how I can draw the layout of the following circuit where the 2 NMOSs have different body potential. Any suggestion will be highly appreciated.
Thanks!


texts: Controller design for sinuisoidal reference signal

texts:
I just wanted to know what people thoughts were on a controller designed for varying the height of a magnetically levitated ball with a sinusoidal reference signal.
I have completely modelled the system, linearized it about a single operating height and designed an LQR controller that works, but what would I need to implement or do differently to be able to achieve this?


texts: What is the difference between the Seeduino Electronic Brick shield vs the chassis?

texts:
As far as i can tell they are both Arduino shields. Is that correct?

The electronic brick shield
The electronic brick chassis

If they are indeed both shields, what's the difference between them and why would someone buy one over the other? Their wiki is incomplete.


texts:
I'm trying to get an input from an intercom and apparently there is GND and another wire for the call. I'd like to know when there's voltage between the call wire and the ground.

I'm thinking of using the arduino's ground to pull current from the call. Is that possible? What is the best way to do this?

Maybe all I need is a transistor?

Thanks.


texts: Designing an RC Snubber for TRIAC motor control

texts:
I am designing a snubber to reduce voltage transients for a TRIAC load phase angle control circuit.
The snubber is composed by an RC network in parallel with the load. The load is a 230V 5A electric pump (no more information about it unfortunately) and the TRIAC will be controlled by an MCU which is driving an opto-triac to generate the required turn-on impulse. There is also a MOV in parallel to the snubber/TRIAC to protect from the peak voltage of the transient.
I have looked through different Application Notes regarding RC snubbers in power applications and I tried to follow the calculations used in AN1048/D.
Specifically, I used the TRIAC DESIGN PROCEDURE at page 12 with these data:
\$V_{RMS} = 230\,V\$(mains voltage to the load)
\$I_{RMS} = 5\,A\;\$(and I assumed a pure inductive load)
\$\phi = 50\,Hz\;\$(mains frequency to the load)
\${\frac{dV}{dt}}_{max}=5\cdot10^6\,V/s\;\$(for the chosen TRIAC)
\$\rho=0.6\;\$(Figure 6.18 at page 9, this value seems to me a good compromise between \$V_{pk}\approx 406\,V\$ and the chosen \$\frac{dV}{dt}\$).
The results I have applying the equations in the AN give me a capacitor of \$23\,nF\$ and a resistor of \$3\,k\Omega\$. My problem is that these values seem far from those I normally see in similar circuits or datasheets (eg. \$C=0.1\,\mu F\$ and \$R=33\,\Omega\$) and I believe I am not sizing the components properly.
I have tested this circuit with these values for a couple of minutes while changing the phase angle and it does seem to work, however I did not have the chance to verify the peak voltage of the transients as I miss the proper equipment to do so.
I also believe I can reduce \$R3\$ to a \$1/4\,W\$ power rating but I am not sure about the rating of \$R6\$.

Any suggestion is really appreciated. Thank you.


texts: How do I find a shutter-style (off-half-full press) momentary button?

texts:
I'm looking for a momentary button that has three positions, like a camera, so you can momentary-press halfway or momentary-press the full depth.

I don't even know what to call it, so searching 41,000 switches on Mouser doesn't help. If I can't find it I can mimic it in software, but I'd prefer to have the camera-style tactile response


texts: Implementing differentiation and integration in a digital control system?

texts:
In a computer control system (microcontroller-based), the sampling time of the inputs to the system determine whether to treat the system as a discrete system or continuous. From what I have learnt, when \$t_s \rightarrow 0\$, you can treat the discrete control system as a continuous time system.

My question is, how do I implement what an op-amp integrator and differentiator would do on a microcontroller.

Differentiation - Can I simply calculate the gradient between adjacent sampled values, or is it more complicated?

Integration - Similarly, can I add up all the previous values which have been sampled?


texts:
I am learning CAN bus with LPC1769 and the LPCXpresso base board. I am in badly need of some demo code on CAN communication on the LPC1769 to know how it can be configured and works, but I can not find any.

Is there some website that can be recommended where I can find some (I have tried www.lpcware.com, but I did not find anything)?


texts: Should I daisy chain start connect or wire separately?

texts:
This is related to field wiring schemes and interference. Sometimes tens of transducers are needed to be coupled to a single-ended data acquisition board's analog input channels where the transducers are powered from a single power supply. For instance the two modules(it could be transducers) below are powered from one 5V power supply. And in this case as you see(upper left screw terminals) each modules are wired separately at their power terminals from the power supply.

Here below is a closer view where power terminals and the signal outputs to a DAQ is shown(Upper left two screw terminals on the modules are for power and upper right two screw terminals are for signal output coupled to the DAQ channels):

To make the question question more clear I draw the following different schemes:

(left-click to enlarge)

Tr0, Tr1, Tr2 are transducers, PSU is the power supply.

Currently the uploaded photos I guess show the Figure3 wiring configuration. In Figure1, +power terminals and the power grounds is daisy chained. In Figure2, only the +power terminals are daisy chained and the grounds are star connected.

(The signal ground and the power ground is connected on the back panel even though inside the module they are isolated.)

Which scheme would be more immune to interference and noise?


texts: Serial baud calculation without using serial interrupt - 8051

texts:
Here's the situation.

I have a project which utilizes multiple sensors and connects to another unit through standard UART (8N1).

Because no data needs to be missed from any device, I made the multiple sensors function as wireless UART channels which I managed to do successfully, but the standard UART isn't quite working correctly (as some characters are missed on the receiving end of the other unit). I believe it is a math issue.

I cannot use the serial interrupt because if I do then the data will be missed from the sensors, so I am limited to one timer interrupt.

Currently I set the standard UART speed to 38400bps and the individual sensor rates are about 680bps.

Am I configuring the timer correctly?

So my question is this. Is the following math correct when I want to reliably detect when a byte of serial data is processed at 38400bps?

TMOD = 22h ;Timers to mode 2 auto-reload
TH0 = 10h  ;Timer executes every 240 clocks. If I'm not mistaken,
TL0 = 10h  ;   this means Timer executes 2x before serial character
           ;   is processed? or do I need to subtract a number too?
set timer 0 run
set timer 0 overflow  ;to start timer immediately

Also the crystal speed to my micro is 22.1184Mhz with 33pF ceramic caps between each crystal pin and ground.

The reason why I'm asking is because I'm adapting my ideas from Ricky's software uart tutorial at https://www.8051projects.net/wiki/8051_Software_UART_Tutorial but he has added some extra math to detect when bits come in but his program stalls while waiting for a bit. These stalls are what I don't want which is why I'm going with a timer, but I'm looking for that perfect equation.

Can anyone tell me if I'm in the right direction?


texts:
This is likely a noob question, apologies if the answer is obvious.

I'm trying to control a furnace using a 3.3V microcontroller. The furnace operates by connecting a common 21V AC "hot" line to one of two AC "neutral" output lines: Fan and Heat. When connected they have relatively low current flow, ~100mA.

I've had some success using a TRIAC to do the switching - but I'm directly mixing the power sources by connecting the DC battery negative to the common AC "hot" line. Battery negative/hot then becomes the reference at the TRIAC's MT1, and I can switch the furnace on and off by sending +3V or 0V to the TRIAC base.

A simplified schematic is below - SW1 would be in reality a microcontroller output pin with a current limiting resistor.

simulate this circuit – Schematic created using CircuitLab

Question is, is it kosher to mix power sources like this? Do I risk an exploding battery, excessive battery drain, weird circuit behavior or anything like that? If so, what would be the proper way to do this, to isolate the circuits?

Thanks!


texts: Is there a device that converts any AC frequency to 60 hz?

texts: If I have something like a windmill generator that generates AC current, but at variable frequency, what device(s) would I need to convert that variable frequency into a constant 60hz frequency, so that the power can be used for net-metering?


texts:
I was seeing some circuits for a Cockroft-Walton multiplier.Most of them seem to be using an AC input voltage.My specific query is ,would this multiplier work with a uni-polar (pulsed DC) input. For example a square wave from 0~100V for example.
TIA


texts: Naming (C1, C2, R1, R2...) components on PCB

texts:
I want to label all the components on my board C1, C2, R1, R2, IC1, IC2, etc.

I am trying to think about the best naming convention for everything.  On one hand, I want to group together all the components by the IC or function that they are attached to.  So in this way, I would group all the resistor and capacitors attached to IC1 together such that IC1 has C1, C2, R1, R2, R3 and then IC2 would have C2, C3, R4, R5, R6.

On the other hand, I want to group together components by value so that when building the board it will be easier to just drop in R2, R3, and R4, which are all 270 ohm but are spread across different ICs and functional modules.

Is there a standard convention on how to go about naming components on a board?


texts: What is the purpose of a resistor to self bias a MOSFET?

texts: If there is no voltage drop across \$R_G\$ as I have been taught. What is the purpose of it?


texts: Power multiplexing with low leakage current for low power applications

texts:
I have a scenario in which one of two power sources is selected by a power multiplexing:

One solution is to use already existing mux ICs like TPS2115A. The problem is that the leakage of these ICs are relatively high for my application. For example, the leakage current when the input 1 is inactive is around 50uA which is quite high for an indoor solar power harvesting (unless if I'm missing a power mux IC with extremely low leakage).
I'm considering two possible solutions (which I'm not sure about):
1- Use a low leakage switch between the power source and the mux input 1 to limit the inactive leakage current:

The leakage of the switch could be far less than the leakage in mux IC. So when the switch is disabled it would limit the leakage current of the inactive input. To test if this solution is feasible, I manually added a reverse diode between power source 1 and input 1 in the inactive mode; it substantially reduced the leakage current without affecting the output (from source 2).
2- Getting rid of the power mux IC and have one switch for each power source:

I'm not sure if connecting two switches in this configuration is a good idea or not.
But I'd appreciate if anyone has had similar problem or has suggestions.


texts: I'm not experienced at electronics, so please forgive the simplicity of my question. But what is this diode in the picture below doing? The circuit is made of 3 in-series leds wired in parallel (3x3). Each path has a 150 ohm resistor. There is also a path from power source to ground with a diode (I think) which I can't figure out the purpose of. When I apply 12 volts to the circuit, the diode burns up, and if I bypass it, the circuit lights up fine. If it maters, these lights used to be powered by AC to 12V adapter, and I'm now trying to power directly with 12 V.


texts: LM2940CT-12 output measuring 9.6V when relay used

texts:
So I've got a 12V pump, and a car battery, and I'm trying to regulate the 12-14V from the car battery to 12V output.

When using just the LM2940CT-12, it outputs 12V on the dot.
But when I use an Arduino to switch a relay, which then closes the circuit from the LM2940 to the pump to GND, it measures 9.6V across the pump terminals.

What is going on?

Fan Specification is "DC 12V 3.6W",
so I suppose
I = P/V = 3.333A ?
R = P/I^2 = 3.6/11.11 = 0.32 ohms?
This looks wrong.  It's been a while.

Pump Specification is "DC 12V 1.5A"

hmm ah.  So the LM2940 isn't meant to handle > 1  amps... i see...


texts:
In my current project, I need to communicate and supply current to 4 sensor PCBs ("S1", "S2", "S3" and "S4") from a master PCB ("M1"). I will use RS-485 to communicate between PCBs, meaning I can chain the sensors. The distance is relatively short between them (each cable is < 25 cm). M1 also provides the 5 V to all sensors, and current is relatively small (some 10s of mA at max for all sensors).

Let's suppose I have this configuration :

I am concerned about M1 providing power supply to all sensors at the same time. Is the configuration OK, or should I take specific precautions (more ground wires, seperate 5V-GND pair, etc.) ?


texts: One USB device with multiple device types?

texts:
I am just wondering if this is possible with USB.

I am used to programming a device with USB to be a specific device type, say, a HID, or a CDC etc.

Is it possible to combine multiple device types into one USB device, so a single chip (say a PIC32) could be seen as both a HID and a CDC device at the same time, providing the functionality of both?  Ideally with the two device functionalities tied to different parts of the firmware.

Is this even possible with USB, or would I need to have a small 2-port hub chip and 2 USB devices connected to that?

Or could I emulate it by having the chip seen as a hub, then connect "virtual" devices into it in software?

Has anyone tried anything like this before?


texts: Why is microphone + opAmp + Arduino circuit not working?

texts:
I followed the mic + op-Amp part of this schematic exactly using an Lm386 chip:
https://randomskk.net/projects/lightstrip/schematic.pdf

and sent the output from the op-amp into a pin on an Arduino Pro Mini.
BUT, when do an analogRead(pin) and print the value in the serial monitor, the value seems to level out to some constant, no matter how much noise I make into the mic!

Can someone tell me what I could be doing wrong?

As extra information:
I left out the capacitor on pin 7 of the IC that is shown in the schematic.
And the power supply I'm using is my old phone charger that plugs into the wall and outputs 5.9V DC.
I am trying to make this:  http://www.youtube.com/watch?v=Km6ObG_xKm4
Also, how do you tell the anode and cathode on an electret microphone?

Thanks!


texts:
In DDR3 memory there is a signal called DQS that I have several question about.

What is DQS abbreviated for? specially Q
What is the purpose of data strobe in DRAM and why not use simple clock.
Is DQS on DRAM chip an output or an input coming from memory controller?
What is relation of DQS to CLK, Address and control signals? In length matching of DDR signals, I found that flight time of  "CLK+Address+Ctrl signals" are not related to flight time of Data Lane. how this is possible. Is it means that they are completely unrelated?

Explanation
Micron TN4605 explain the need for Data Strobe:

In a purely synchronous system, data output and capture are referenced to a common, free-running system clock. However, the maximum data rate for such a
system is reached when the sum of output access time and flight time approaches the bit time (the reciprocal of the data rate). Although generating delayed clocks for early data launch and/or late data capture will allow for increased data rate, these techniques do not account for the fact that the data valid window (or data eye) moves relative to any fixed clock signal, due to changes in temperature, voltage, or loading. So, to allow
for even higher data rates, data strobe signals were added to DDR devices.

But I don't understand the explanation for maximum data rate for purely synchronous system


texts: How To Calculate the β with limit to infinity?

texts: I am a student. Our teacher gave us a problem that can be done by Kirchhoff's laws. The problem is that in the second case we have to calculate β → ∞, the teachers told us to calculate β using a limit, but I don't know how to do this if there is no function to take the limit to ∞. This is the only information the problem gives. The (O1) and (O2) squares are loops from second Kirchhoff's law.


texts: What is behavior of this virtual ground circuit when sourcing/sinking current?

texts:
simulate this circuit – Schematic created using CircuitLab

This is the virtual ground circuit from a battery-powered headphone amplifier(direct link to schematic PDF). What is the behavior of the pseudo-ground as the opamp attempts to sink/source current to/from it?

A suggestion for improving performance of the amplifier is to switch from this passive circuit to an active one (using opamps, rail splitter ICs, etc.) to provide a "lower-impedance" virtual ground. Before going down that road I'm curious what my starting point so I can know what sort of improvements I might see.

EDIT TO ADD: Another way of asking the question is: does this circuit have any benefits over grounding the load to V- (or V+) and decoupling it from the opamp with a 470uF capacitor?


texts: Does current lead voltage during discharge in capacitors?

texts:
I can see that how current leads voltage while capacitor is charging. Looking at any capacitor charging diagram will explain this: (e.g figures in http://en.wikipedia.org/wiki/RC_circuit)

However, I don't see how the current leads voltage while discharging? Because for discharging, both current and voltage look alike in the same descending format. And, it doesn't seem that there is a phase difference between current and voltage curves during the discharge! Can someone please explain what is happening?


texts: Run multiple charging circuits on the same battery

texts:
I've recently purchased a set of 3.7V 1A Li-Ion charging circuits available HERE and was wondering if i could charge the same battery using multiples of these to get a quicker charge. Is there any safe way to do it?

UPDATE

Heres another idea, Is there a way to use multiple batteries and multiple charging circuits to the charge would take less time yet still have the same capacity?


texts: Is there available differential impedance calculation for this stripline configuration?

texts:
I am trying to calculate the differential impedance of a differential pair in a 4-layer PCB as follows:

Layer: Low speed signal
Layer: Power plane
Layer: Differential pair
Layer: Ground plane

I am currently using Saturn PCB Toolkit, may I know which settings should I consider:

Edge Cpld Ext (Microstrip)
Edge Cpld Int Sym (Edge-Coupled Symmetrical Stripline)
Edge Cpld Int Asym (Edge-Coupled Asymmetrical Stripline)
Edge Cpld Embed
Broad Cpld Shld
Broad Cpld NShld

Thank you.

SF


texts: Trifilar Transformer Common-Mode Rejection Circuit (Signal Recovery, Hybrid Combiner, RF)

texts:
I'm trying to develop a circuit that allows me to effectively subtract two different sources of RF noise from a single signal at the same time.  I am planning to use something called a "trifilar" transformer, which is effectively a transformer with 3 separate windings.  My thinking is that, if I input my original noisy RF signal on one of the windings, one type of RF noise on the second winding, and the other type of RF noise on the third, that the signal can be recovered.

I've heard of this configuration called a "hybrid combiner" which allows you to get the sum and difference of two different signals using this three-winding transformer, using common-mode rejection, like a choke.

In effect, what I would like to do, is subtract two different separate signals from a third signal.  I realize this is a poor way of describing what I want to do, so I've included a diagram below with equal turns for each of the three windings (note the dot convention):

Of course, the DC signals won't be transmitted from winding to another, so that isn't relevant, but I add them for generality.

My question is, when you input signals (or noise) to each of the windings of a transformer, how do they react?  In my typical experience, a transformer has two windings, one of which is the "input" (or primary) and the other is the "output" (or secondary).  What happens when all three windings (primary, secondary, tertiary[?]), have currents applied to them?

Is it possible to recover the original signal?

Thanks!


texts: USB cables combining shield and power ground conductor

texts:
I see a lot of USB "charging" cables on the market with cutaways showing two small data conductors, one large power conductor, and shield.

The implication is that power is conducted in the shield.

Is that really appropriate for USB cables?

Specifically USB, with its wide variety of devices. I realise that there are plenty of application-specific phantom power configurations where the devices are designed appropriately for that situation.


texts: U(S)ART/SPI/I2C - any common/prevalent/recommended connectors?

texts:
Good morning everyone!

I'm currently building the board with the STM32F417 microcontroller, and I want to have separate (out-of-GPIO) I2C, SPI, UART and USART outputs on the board.

But I'm lost on what physical connector should I use for each of the interfaces.
Any recommendations? Are there any commonly accepted variants?

Thank you in advance.


texts: How could I determine if 2 antennas could communicate knowing the distance between them, the power/gain of transmitting/receiving, and the sensitivity level of the receiver?


texts:
I was trying to hack a 3-D system starting from the monitor: VG248QE.
I teared it down to LCD matrix and driver. This is a 1080p(1920 x 1080) monitor so I was expecting that at least 1080(row) + 1920(columnn) = 2000 pins wired from the LCD driver to the LCD Matrix(I am not counting RGB's also!). However, I see 6 x 90 = 540 pins going to the LCD Matrix and I did not see any component(deMUX, MUX etc) on LCD matrix.

I looked up for the Driver chip online but found nothing(no datasheet!).

The question is, how does the driver drives so many pixels with so less pins? Am I not seeing MUX's embedded in LCD matrix? Or is there something else I am missing?

And just to share: VG248QE uses LCD overdrive method to achieve 1ms LCD rise/fall time and uses this chip for several levels of supply(+/-40V, 30V, 15V ...) for overdriving:


texts: Pinout on a USB 3.0 connection to down-rate to USB 2.0

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Simple question about backwards comparability with USB 3.0 from the header pinout side.  If I have a USB 3.0 header and I wish to connect a USB 2.0 device, is the following wiring correct according to the diagram below?

USB 2.0   USB 3.0
USB+5V    Vbus
LP-       IntA_P1_D-
LP+       IntA_P1_D+
GND       GND


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Intro

I am currently working on an e-board.
my esc is a vesc, which has the following ratings:

Voltage: 8V – 60V (Safe for 3S to 12S LiPo).
Current: Up to 240A for a couple of seconds or about 50A continuous depending on the temperature and air circulation around the PCB.

I will be using a DPDT switch to switch from charging mode to esc mode.
(I'm using a DPDT switch so I can cut the current in half)

Question

Now, I would like to set a fuse as an extra safety to my esc. The problem is when I search online for fuses of 50A, I

A)Can't find the fuse itself
B)Can't find a fuse holder for 50A

Is there a way to split this in half like I did with the switch ?
Or can you direct me to a good site that does have these items?

Also would it be better to put the fuse after or before the switch ?

Schema

simulate this circuit – Schematic created using CircuitLab


texts: Rounding up or down with Motor Overcurrent Protection

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When sizing motor over-current protection, CSA 22.1 28-200 3a states that a circuit breaker can be sized up to 250% of the rated full load amperage (FLA) of the motor.

  E.g. 100hp, 575VAC motor draws 99A (CSA 22.1 Table 44): 99A * 250% = 247.5A

Usually I would've rounded up and selected a 250A circuit breaker. I just noticed today that in the over-current example on page 662 that they always size the the next lowest standard size and specified a 225A circuit breaker. This makes sense since a 250A circuit breaker is past 250% of FLA. However, Rule 28-200 4c goes on to state that if the circuit breaker above isn't large enough for the motor to start that you can go up to 300% of the motor FLA (297A). Therefore, 250A isn't in violation.

My question:

As a rule of thumb, when sizing motor branch over-current protection, should you round up or down to the next standard breaker size? If rounding up, do you need to prove that the motor couldn't start with the smaller sized breaker?
Does the answer to #1 change when considering feeder over-current protection?


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I am prototyping a simple board with several (3 or 2) USB-to-Serial convertors (CP2102), a microcontroller (ATMega32U4), and one USB "output" port to connect using USB cable (in case of only 2 CP2102's). I want to use TI's TUSB2046B USB Hub controller to connect all this devices through a single microUSB input. I don't want to use an external hub to save space and to simplify the final assembly.

The question is about interconnection between USB Hub and on-board devices. The official TI's datasheet is proposed to connect several external components on the each output data lines:

Series resistor (27 Ohm).
Capacitor between the TUSB2046B pin and the series resistor (22 pF).
Pull-down resistor (15 kOhm) after the series resistor
and a USB ESD protection unit SN75240…

Also datasheet proposes to use a

Power Management unit (TPS2044).

And also, on the ATMega32U4 side, there should be a

22 Ohm series resistor on each data line.

So, what components should I use to connection on-board devices using like a 10 centimetre length data lines?

Of course, I don't need and ESD protection module, but I'm not sure about other components.

There is a particular question about a power management unit. As I understand it tells the USB hub that something is connected to a certain port, and it does not draws too much current. So, I do not need it for on-board devices? Only for my output port, if any?

Thank you!


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I just learned about voltage dividers and how to calculate the relative values for the resistors to use. For instance, to go from 5v to 3.3v I could use a 1 kohm and a 2 kohm resistor. However I could also use a 100 ohm and 200 ohm, or 15 and 30 ohm or as far as I can tell just any two values with the correct relative values. I think however there are up and downsides of different absolute resistor values.

So my question is, how do I decide which specific values to use?