texts: Large number of termination resistors and bi-directional signals

texts:
I am designing PCB which has an FT601 for USB communication. No matter how hard I tried, I could not keep the traces short enough in order to avoid reflections and simulation was revealing significant overshoot and undershoot (>300 mV) so I decided to use termination resistors. The impedance of the traces is 50Ω so I am going to use this value or a value close to it. So far so good.

What I realized, then, is that this means a great number of resistors. The FT has 36 data lines, which means 72 resistors since they are bidirectional (according to what I have read I must terminate in both directions) as well as 5 other control lines resulting in a total number of around 80 resistors. And here come my questions, since I am a rookie in the high-speed design business:

What type of resistor? Should I use regular SMD resistors or an array in a chip? FTDI in their breakout board UMFT601 use those 33Ω chip arrays which I cannot identify. I did some research over component distributors and found some solutions but I did not notice any significant advantage (space, total price) of using a chip over normal SMD, apart from easier placement during design. Is there a standard approach to this situation?
Max distance between pin and resistor? How far the pin is OK to place the the resistors? I know they should be as close as possible but since the FT package is QFN the array (whether is chip or normal SMD) has to have some distance in order to achieve the connections properly.
Terminate both sides? Do I have to terminate both sides on the bidirectional pins? Most literature is focused and discuss one direction when analyzing signal integrity and I have not found many resources on the subject of bidirectional.


texts: What is fabric in relation to a processor?

texts:
I have heard the term fabric used when talking about a processor in some recent documents I have looked at.

For example, "..and that will erase data within the processors fabric."

Upon researching fabric, I came across this Fabric Computing definition which didn't quite seem to make sense for the definition of a processors fabric.

So my question would be, in regards to computer processors, what is fabric?


texts: How to specify a value for each bit of the reg in Verilog?

texts:
I want to declare a reg of 8 bits and set the value for each one of the bits separately (based on another "counter" reg) inside an always block using Verilog.

Here is what I thought:

module readvalue (
    button_1,
    button_2,
    value,
    counter);

    input button_1;
    input button_2;
    output value;
    output counter;
    reg [7:0] value;
    reg [7:0] counter = 8'd0;
    always@(posedge button_1 or posedge button_2)
    begin
        if(button_1)
        begin
            [counter]value <= 1'b0;
            counter <= counter + 8'd1;
        end
        else if(button_2)
        begin
            [counter]value <= 1'b1;
            counter <= counter + 8'd1;
        end
    end
endmodule

The idea behind the code is that when button_1 is pressed, 1 is stored in a particular bit of value and when button_2 is pressed, 0 is stored. I have a higher module in the hierarchy to make readvalue stop when counter is equal to 8 in decimal.

The code, as expected, gives me the following errors:

Error (10170): Verilog HDL syntax error at calculator.v(17) near text: "[";  expecting "end". Check for and fix any syntax errors that appear immediately before or at the specified keyword. The Intel FPGA Knowledge Database contains many articles with specific details on how to resolve this error. Visit the Knowledge Database at https://www.altera.com/support/support-resources/knowledge-base/search.html and search for this specific error message number.

Error (10170): Verilog HDL syntax error at calculator.v(22) near text: "[";  expecting "end". Check for and fix any syntax errors that appear immediately before or at the specified keyword. The Intel FPGA Knowledge Database contains many articles with specific details on how to resolve this error. Visit the Knowledge Database at https://www.altera.com/support/support-resources/knowledge-base/search.html and search for this specific error message number.

How can we put it to work?

I am using Intel's Quartus Premium Lite Edition 18.1 (with the latest update pack) on Ubuntu 18.04 with the default configuration. If I have not been clear or you need more information, just comment and I will provide.

I am a beginner on Verilog so, sorry for such a simple doubt.

EDIT 1: button_1 and button_2 are never going to have a posedge at the same time (or even in the same second) in my implementation.


texts: Why don't my programs stay in the FPGA MAX 10 after a power cycle?

texts:
I program my FPGA (MAX 10) with a .sof file and works, but when I turn off my device everything erases from my FPGA. After exploration on the internet I found the EPCS IC, and I find out my board needs EPCS. But EPCS is not supported by the MAX 10, so I explored more deeply and I found out that MAX 10 has internal flash.

But I can't figure that how I can use internal flash for persistent programming?


texts: Is my Inverse z-transform solution method accurate?

texts:
The question is as follows:

The book answer is as follows:

However, my approach is as shown below I even cross checked my partial fraction and it was correct.

Please tell me where is my mistake?

Ok. Below is my revised trial after Mr. Any pointed where was my mistake. Kindly review my answer and advise me where is my mistake.

I used the z transform property of shifting:


texts: Hardware/software needed to decode Differential Manchester?

texts:
I have a differential manchester encoded 0 to 5v data stream at 62500bps. What hardware do I need to get this into something I can work with, ie arduino, pi, etc?

I have searched for chips/eval boards on digikey and can't find anything that can decode differential manchester.

I have hooked it up to an arduino uart, but it is doing 8-N-1 on something that I need to see all the bits. It's is also decoding it improperly (of course). I have thought of sampling at double the baud rate and trying to do something with a lookup table, but this seems awfully hackish.

Below shows my thought process and the logic analyzer is giving me enough information to analyze the protocol, but now I need to turn it into something I can process in real-time.

Requirements:
Error free to five 9's, some errors will be known because packets have a checksum.  One off solution.

Other Possible Relevant Information:

A continuation of this question regarding an unknown serial bitstream.

 This picture shows a typical packet of the DeLaval Alcom bus.

We are grabbing 13 bits at time and ignoring the first and last nibble.

Thus the packet is: FF 04 9F 03 00 5B.

This packet we cannot read correctly with 13 bits. We have a bit skew because the number of start bits are different as compared to the previous packet. This can be fixed in software.

  Packet #1 - This packet checks if MPC (or any node) is alive
  FF 54 9F 03 00 43
  FF Start  54 To node 84, this node is an Alpro MPC.
  9F Packet type
  03 From node Alpro master
  00 Data
  43 calculated checksum (not sure how yet, 2 Byte CRC 16?)

  These are "are your alive" packets. They are sent and don't wait for
  response. Response comes later if node is alive.

Sample of packets
FF 55 9F 03 00 F6
FF 56 9F 03 00 B2 <- saw this same packet twice with the same checksum
FF 5C 9F 03 00 B1
FF 5D 9F 03 00 04
FF 04 9F 03 00 5B
FF 0F 9F 03 00 ED <- node 15 does not exist. maybe checking that it is there or not?
FF 58 9F 03 00 C8
FF 59 9F 03 00 7D
FF 5A 9F 03 00 39

  Packet #2 - This packet is from the alpro master saying what to show on the screen of the sort gate MPC: 1463.
  FF 3D 0D 03 1B 17 B7 05 01 00 00 00 00 00 00 00 00 D5
  FF Start
  3D to node 61, sort gate controller
  0D Packet type
  03 From node, alpro master
  1B 17 Data of 6935 means nothing to me.
  B7 05  Data 1463 16 bit little endian, which matches the cow we used.
  01 00 00 00 00  00 00 00 00 Data, no idea
  D5 calculated checksum.

FF start is not really FF. It's a string of 1's of somewhat variable length.


texts: Could a 24 pin motherboard connector be used for a 24v sprinkler system quick connect? If not do similar multi terminal connectors exist?

texts: I'm doing a project where I need to be able to connect/disconnect multiple 24v wires. Instead of connecting each one individually, I'd like to just hook them all up to a molex connector and be able to quickly connect/disconnect them. I was thinking I could cannibalize a motherboard power connector, because it meets the requirements I need (robust, can't be connected backwards, lots of connections), but am not sure if it would accept 24v. Would it work with 24v, and if not, is there a type of connector I could use?


texts: I'm designing a power supply for a smart switch project which requires a 5v dc/2A supply for usb charger and 12V dc for relay operation. is there any way i could do that? my input is 220ac, which will be rectified to 310(approx) dc. any suggestion will be much appreciated. Thanks


texts:
I read a lot of stuff regarding CAN bus arbitration, but it didn't answer my questions.

If one node is already transmitting the data on the bus and in between another node wants to initiate the data transfer, how will that "another node" get to know that the bus is busy?

All the documents (which I read) take condition that both nodes are starting transmission simultaneously and then one with first dominant bit will get the bus but nobody explained the condition which I want to know.


texts: Light activated switch - avoid flicker when turning on

texts:
I have a small light bulb (3W LED, E27/110V) that I am controlling using based on ambient brightness (it comes on when it is dark, and goes off when it is light). The circuit uses a BT136 triac, a MOC3041 optoisolator, and an IR phototransistor (I don't have a part number for it - 2 pins, black cap, looks like an LED).

simulate this circuit – Schematic created using CircuitLab

As built, it mostly works - it comes on when it is supposed to, and goes off when it is supposed to. D2 is included just as an indicator LED, SW1 is included so that the light can be turned on manually (bypassing the light activated circuit) if needed.

However, I have one issue with it:

The circuit is currently located fairly close to the light (around 1.5m under it - but the light faces upwards). When it gets dark enough, the light turns on and the light it produces turns off the phototransistor causing the light to flash. The light continues flashing for around 5 minutes (at varying frequencies), before it remains on. This implies that it doesn't take much additional darkness to offset the added light from the LED bulb. I chose the value for R1 that would let the light turn on at the appropriate time, and R2 is currently set around 50kohm (altering R2, changes the on time, but doesn't appear to help the flicker).

My indicator LED (D1), transitions to on when current through Q1 drops below 1.6uA to 1.3uA. (I am not confident enough in my meters to fully trust that number, but hopefully it provides an idea of the magnitude). In full direct sunlight the current through Q1 is up to 40mA.

Ideally, I would like to resolve this as simply as possible (e.g. with a minimum of ICs), however, my knowledge of electronic circuit design isn't yet where I want it to be in order to know the best course of action from here.

I could resolve this with a microcontroller fairly easily, but this seems like an inelegant solution.
I have considered implementing a circuit similar to one used to debounce a switch, but the time scale on those is normally on the order of milliseconds - whereas I need something over several minutes.
I have seen some designs which use two phototransistors pointed in different directions but would like to have a design where positioning isn't critical.
I have considered a soft-latching design, but am unsure how exactly to implement this.
I was hoping for something which slightly changes the required input current once the light turns on - so that the added current flowing through the phototransistor when the light comes on, isn't enough to turn it off. I believe this would entail a feedback resistor, but unfortunately, am not sure how to implement this.

What would be the best way to resolve the flicker that occurs at dusk when the light turns on?


texts:
I'm using a gate drive transformer to drive w45nm60 mosfet.
And this circuit for increase gate turn off:

But it seem to turning off the gate by throwing excess current from gate to source.
So I want to use negative source taken from gdt (which it wasted every half cycle) to turning  gate off. Here is the schematic:

Will it work?
How to limit negative voltage output to about 5v or less (to reduce gate discharge when returning on at next cycle) by adding zener diode?where the best place to add it?
Is anybody have a circuit which can  turning gate off when Vgs supply start to fall (or before dead time)?


texts: How to utilize three-phase electrical in residential garage for antique shop equipment

texts: I hope this message finds you well.  Please explain how to utilize three-phase electrical in residential garage for antique shop equipment.  The power company will NOT dig new lines for true 3-phase.  What would be the most cost efficient method for hooking up these older machines?  They run on 220V and max 5HP. Thank you kindly


texts: How is the fact that the resistor used to limit the LED current dissipates some of energy addressed in lighting applications?

texts:
LEDs can't be connected directly to a source of power - only in series with a current limiting resistor. Which means that when the LED is powered some power is dissipated by that LED and some power is dissipated by the resistor. Which means that some energy is wasted.

Now suppose I need to construct a powerful light source - a house lighting fixture or a car headlight - that uses LEDs as a light source. I will have to connect all LEDs through resistors.

I guess those resistors will waste quite a lot of energy.

How is this problem addressed when using LEDs for lighting?


texts: How to add an UPS beeper volume controller so that I can make it sound quieter when it beeps?

texts:
I've an EATON 5E850iUSBDIN 850VA/480W UPS.

This UPS makes a very loud beep sound both when it's first plugged into the mains(short beep) and when it's first turned on from the button(3x longer beep) (I'm not including the case when it beeps because the mains power is cut off).

I would very much like to somehow attach a volume controller so that I can make this beep quieter for two reasons:
1. thin walls - I worry about disturbing the neighbors with the loud beeping sound (mainly during the night).
2. this UPS constantly uses 7.5W even when nothing is plugged into it (this is after the battery is already well charged) - and due to 1. I'm keeping it plugged in full time. (as a side note: if I turn the UPS off from the button it consumes 7.0W constantly, even though the battery is already charged)

A volume controller would allow me to unplug it whenever I want thus saving power (and noise).

What kind of volume controller should I attach and where/how to wire it ?
and Would adding it possibly affect the UPS functionality ?

EDIT: picture of the beeper/buzzer inside:


texts: Single Mosfet driver to drive two N channel mosfet

texts:
I am new to the concept of electronic design and require help with my project.
I want to use two N-channel Mosfets to control two 12V DC motors with Arduino's PWM. The PWM frequency will be atleast 10KHz and motors will be running in single direction.

I did some research on how to use a single mosfet driver to run two motors and this is best I have come up with and please tell me if the following circuit is correct,

As my circuit is low side driver, I decided to use Microchip's TC4427A to drive the mosfets IPP45N06S4L-08. TC4427A is a dual non-inverting driver with peak output current of 1.5A and input supply voltage operating range 4.5V to 18V. The non inverting characteristic of the driver will switch on the mosfet when Arduino's PWM signal is high. Am I thinking correctly? (P.S. Since I could not add more than two links, I gave brief description of the driver)

With this arrangement can I control the motors simultaneously? Can this driver provide the same voltage and current required to switch on both the mosfets?

What is gate voltage provided by the driver? Is it same as VDD (in this case 12V)? If yes, what are the changes I have to make to restrict the supply to the gate to 10V?

I have provided 10Ω resistors between gate and driver output? Is this necessary as I read that it reduces the EMI or Oscillations (I am not sure as I do not understand this concept clearly) and improves PWM?

I have provided capacitors between GND and VDD of the driver? Is the arrangement correct? What is the method to calculate its capacitance?

Are there any drawbacks with this circuit? Do i need to be aware of any underlying issues that may blow up the mosfet or driver?


texts: ST-LINK is serial communication possible?

texts:
I am using STM32F4 discovery board and Atollic TrueStudio for ARM Lite 3

I would like to pass some debugging data to PC using printf and I can't find a way to do it through STLink. Is it even possible? It seems essential feature for any debugging process.

Edit:
I need to use Serial Wire Viewer, but still no luck making it work.


texts:
If i input 5V on a regulator's output (the regulator is also 5V output rated), while the regulator has no voltage on its input, will it be damaged? The regulator i am using is L78. I could not find the answer/similar references on its datasheet, this means there is no issue if i input up to 5V on its output, right?

I made an example diagram above. I guess this wont destroy my regulator, right?


texts:
I want to understand the concept of current regulation in the circuit, In my research I came across the following link Boosting Regulator Current for IC 78xx by MJ2955

where in the circuit schematic in link above, the author claims he has obtained 12V,5A as output with 20V input voltage.

I tried to simulate the same circuit but with input of 12V, 0.1A and 7805 regulator as shown in this schematic:

I see that when input current is 0.1A the output is 94mA approx. which agrees with ohms law V = I*R  = 94.086mA * 53.33 ohm = 5.01V

But when I have my input current as 0.06A the output voltage is 3V (why not 5V? )and current is 57mA, as shown in this schematic

This also agrees with ohms law V = I*R = 57.267 mA*53.33 ohm = 3.05V

The results are same as the circuit without the PNP transistor.
schematic:

So what is the impact of the PNP transistor in the circuit?
How can I boost the current in my circuit?
If I want to see 5W output across my load(53.33ohm in the schematic) what are the changes I should make in the circuit?

Note: I assume capacitors are only for smoothing the input and output and does not have much effect in simulation (correct me if wrong). I tried with 470uF in all three cases the results were same. (sorry was bit lazy to copy new screenshots and  I didnt have enough reputation to embed schematics in my question)


texts: What does the dashed line between diodes in a CMOS protection network mean?

texts:
On the datasheet for CD4007 there are schematics for the input protection network:

and the output protection network:

On both, there are 2 diodes connected by a dashed line (D2 on the input and D1 on the output).

What does the dashed line mean?


texts:
I have been trying to understand slew rate and so I set up a circuit with an op amp (LM741) that would allow me to measure it. The claimed slew rate of the package is about 0.50V/us, but my slew rate turned out to be about 0.3V/us.

For such a small number, this discrepancy seems a little too great. I am positive that I set up the circuit right because my circuit's DC gain is very close to what I expected. So how come the slew rate is so much smaller? Are there any specific external factors that might influence the op amp's measured slew rate (like the particular oscilloscope or the power supply I am using)?


texts:
Is there any way to detect skin touching or no-touching between two people? Maybe using capacitive sensing or any other methods? It doesn't need recognizing gesture, only yes-or-no-touching.

The constraints are:

Two people in the classroom. (Each person may bring the sensor. If it only need one person, it's better).
Their gesture is in free way. (both standing, both sitting, one-standing one-sitting, or any gesture).
The size of sensor must not bigger than lunchbox.
The total price of the sensor components must below $100.
The sensor must be powered with battery.
The sensor output may only LED light. The light is on if touching detected.

I've read Touche for Arduino: Advanced touch sensing. Can this method be customized to detect person-to-person?


texts: Why does the placement of the resistor in a filter circuit matter? I've heard if you switch an inductor and a resistor in a series circuit it could change the type of filter you get. Ex: From a low pass filter to a high pass filter.


texts:
Am trying to code a top level module that would connect different modules to make an up/down counter that would display a hexadecimal character on a 7 segment LED on posedges; but every time I try to run the following top level module I get an error that says

'Line 25: Syntax error near "<=".'

There is no one else to ask this and am following the same outline of the example in my reference book. What am I doing wrong?

module Main_Module(a, b, c, d, e, f, g, U, R, P, Clk);
   input U, R, P, Clk;
   output a, b, c, d, e, f, g;
   reg [3:0] Data;
   wire In3 <= Data[3], In2 <= Data[2], In1 <= Data[1], In0 <= Data[0];  //This is Line 25

  Counter Counter_1(Clk_1Hz, R, P, U, Data);
  Segment_Display Segment_Display_1(a, b, c, d, e, f, g, In3, In2, In1, In0);
  ClkDiv1Hz ClkDiv1Hz_1(Clk, R, Clk_1Hz);

endmodule

Thank you Eugene Sh.and Greg  for your time!


texts: Schottky diode part of a laser power supply enable circuit

texts: In this circuit from Jim Williams' AN90 the enable line pulls down the base of Q1 through Q2, through a Schottky diode (1n5712). Why is this Schottky diode there? I imagine it's a Schottky diode so it has a diode drop smaller than Q1's, so it's possible to turn off Q1... but why does it need to be there at all? It seems as if you could short over it and prevent Q1 from conducting just fine. It must be there for a reason! He even seems to omit it in an earlier figure (http://cds.linear.com/docs/en/application-note/an90f.pdf Fig. 2)


texts: Can I power and use 1 small voltmeter for 3 12v batteries in series?

texts: I asked this question for 4 voltmeters before, and received some great feedback. Unfortunately, it generated too much heat. This is the design I'm thinking of implementing now, but I want to make sure I'm not going to cause a short. Will this work?


texts: Delay/Disable Output Pin On Power On Using Electronics

texts:
I have a module that outputs 3V, has a 'Common' terminal (GND), and a switch terminal. The latter two can accept a toggle input OR a pulse input, and internally it switches on a light.

I have a touch switch that sends a pulse on two different pins. Normally, it drives a dual coil relay - so a SET pulse will turn the relay on, and a RESET pulse will turn the relay off. I have removed all this, and want to use the pulse signals to connect directly to the Aeon Labs Module.

simulate this circuit – Schematic created using CircuitLab

The circuit above works great. The diodes create the OR, and the transistor connects the internal switch of the Aeon Labs Module. Perfect.

However, when the device first powers up, the PIC controller sends a pulse to the RESET pin - presumably to set itself to a known state on startup. However for me - it means it will tell the Aeon Labs Module to turn the light on!

What I need is a way to use a capacitor/resistor/etc to delay the transistor being usable. So any pulses to the transistor in the first 5 seconds after power on do not actually operate the transistor. After 5 seconds (enough time for the first unwanted pulse to occur), then the transistor should operate as normal.

Edit:
The RESET pin is just a name - it is not the RESET pin of the uC. Both SET and RESET are output pins on the uC. They were (not anymore) connected to a dual coil relay. One coil was to SET/latch the relay. One coil was the RESET/unlatch the relay. When the uC detects a touch, it sends a pulse on either of those pins (it alternates between the two) to what it THINKS will be a relay. But the relay is gone now. I now want to take those pulse and feed it to something else. Grand.

I can't edit the uC code. It's preprogrammed by the manufacturer.

On startup the uC is programmed to send a pulse down the output pin labelled RESET. I want to use electronics to disable/snub/block that pulse going to the Aeon Labs module. So for about 2 seconds after power is applied - disable the transistor base. After that, have everything behave as it should.

Any thoughts?

Thanks.


texts: Help with my PCB connection. Seems reversed

texts:
Done this in Proteus. I printed this out in the copper board and soldered components.
But turns out my relay did not work.

I used a 9V battery in the the supposed to be 5 volts for the Arduino because I still don't have one. I have two separate batteries.

Put the power wire in the transistor base, connected transistor emitter to the GND did not switch my relay, doing it reverse switched my relay though and I don't understand why?

I'm not good in electronics that's why I'm trying out things. But why did my relay switch with the battery GND in transistor base and power in the emitter?

And my 470ohms resistor is not working I'm directly putting connection in the transistor base where it worked. I used a 2N2222 instead of a 2N3903, and a DEC DI1U relay. I used a tester to check if connection is good. My soldering is clean and I don't know what to do now.

My problem is that my resistor is not working, connection seems reversed and I'm a noob so big problem.


texts: Why is an HDMI signal causing interference with Over-The-Air digital television?

texts:
I do not have cable or satellite television so I rely on Over-The-Air digital programming (free) and Internet streaming services to provide entertainment.

A couple years ago, I purchased a video card for my desktop PC which provides simultaneous HDMI and DVI outputs -- the HDMI cable is connected to my television and the DVI connection is for my computer monitor. The outputs mirror each other so that whatever I see on the Desktop monitor is available on my 65" Panasonic TV whenever I have the TV's input set to the HDMI port that the computer's HDMI cable is connected to. This setup has worked amazingly well, but just his weekend I noticed an issue:

A few years back, one of the regional over-the-air broadcasting stations had their 2000 foot transmitter antenna tower collapse.  Prior to the collapse, I never had any issues receiving their signal. Unfortunately, after the collapse, the broadcasting company decided to retain the same output transmission power, but built the replacement tower significantly shorter. Consequently, I thought I had lost those channels forever.

This weekend, I performed a re-scan of channels on my TV and to my surprise (and joy!) found that these lost channels were again available! The signal is not the strongest, but since the broadcast is digital, everything looks great.

So while I was watching the programming on these rediscovered channels, all of the sudden I heard my Desktop PC wake-up (the fans start buzzing, the speakers crackle for a brief moment.. very common since the computer is always running Skype in the background). Well as soon as the computer wakes up, I notice my television signal is no longer available. I thought that peculiar timing so I tried unplugging the HDMI cable from the TV...and voila the content returned immediately, crystal clear.

Any ideas why the HDMI signal is causing interference like this?  I've done some googling and found similar complaints for Chromecast device used with over-the-air TV, but have not found the explanation as to why it happens?

Additional info:

The TV is connected to an external outdoor antenna on top of the house. The antenna can be rotated, but the direction of the antenna does not make a difference for this channel.

Other TV channels (stronger signal) are received just fine when the HDMI signal is connected to the TV

The Desktop computer and television are on different circuits, but wired to the same ground (no ground loops)


texts: Is Kirchoff's Voltage law valid to derive current for LC circuits?

texts:
In this source it employs KVL: http://physics.info/circuits-rlc/

BUT in this source at page 6 it says "Apply Faraday’s Law in order to find I(t). (Can’t use KVL since magnetic flux is changing)": http://aplusphysics.com/courses/ap-c/tutorials/APC-Electromagnetism.pdf

Many texts use KVL.What's going on?


texts: Powering a Line Laser 5V 200mA using USB port

texts:
I have a IR Line Laser with following Specs

Output Power    : 60mw

Wavelength      : 780nm

Working Voltage : 5.0VDC

Working Current : <200mA

Laser Shape Line

for details please visit the link http://www.aliexpress.com/item/60mw-780nm-Infrared-Laser-Line-Module-120-degrees/1517656084.html

i would like to power this device using a USB port via a cable. iknow USB has an output voltage 5V but isnt it 500mA ?? Some say Device draws only required current from USB port

My question is can i directly connect laser to USB port by cutting a USB cable? Or should i convert 500mA to 200mA? If so how can i do it ? Can someone specify a solution?

Thanks in Advance


texts: Can you attach 2 coaxial leads to a single TV antenna

texts: I would like to hookup 6 TV's to one antenna. The largest splitters only have 4 outputs. Can I run 2 leads from the same antenna each to a 3 way splitter?


texts: ESD protection for device with isolated PSU

texts:
This is my first time posting here.
I want my device to pass the Low voltage directive testing and that includes ESD stuff.

So as you can see below, my device is Li-ion charger with isolated PSU.

The question: Where should I put the ESD diodes(like ESD9B3.3ST5g or  PGB01 series)? At the moment I think they should be connected as in the image.
Data or power supply pins - TVS - mains ground.

I have read several topics regarding connection of grounds and it seems kinda messy, everyone has their own opinion and I can't really decide what is the best solution.


texts: High Drain Current MOSFET vs Low Drain Current MOSFET for Synchronous Buck Converter

texts:
For a battery charging application, i have to build a synchronous buck converter (i/p voltage = 12V , o/p Voltage = 4.5V) which would be driven by a PWM signal from the micro-controller. This Buck converter's operating frequency would be around 62kHz. I am planning to use both the NMOS for high and low transistors, which would be driven by a suitable gate driver.

My question is regarding the selection of NMOS device w.r.t their Drain current rating. For e.g lets say my maximum current to charge the battery would be 4A. So i have to select a MOS device whose Id >= 4A . And here are two power MOSFET devices who have a quite high current rating :  IRLB8748 (comparatively high Drain current capability) and IRL2703 (comparatively low Drain current capability).

Now both of these devices fulfill my requirement w.r.t drain current (and they dont differ much in pricing). Lets say if i use IRLB8748 (having RdsonMAX = 4.8 mOhms), for 4A (maximum current) the power being dissipated will be IxIxR = 0.0768 Watts. And if i use IRL2703 (having RdsonMAX = 40 mOhms) the dissipated power for 4A current = 0.64 Watts. As it can be seen that for 4A, IRLB8748 dissipates almost 10 times less power than IRL2703 does.

So if i want my transistors to dissipate lesser power (less power dissipation = lesser heat produced = better), should i go for IRLB8748 ? Or can I ? I mean i might be wrong here, but can we use high current rating power transistors in our low current applications to dissipate lesser power (in some cases that can may be also let us avoid using heat sinks) ? Also is it true for my case (i mean can i use IRLB8748 so that my circuit may dissipate less power) ?

Your helpful comments and suggestions would be appreciated.

Thankyou!


texts:
I am trying to inject a 1 mA current pulse (10% duty cycle) at a frequency of 10 Hz, across a ball of gel(20 cm in diameter) through rubber electrode pads, using a constant current source (built in house at another university) that is triggered every 100 ms (with a TTL) to generate the desired stimulation waveform. I am monitoring the amount of current I am injecting into the circuit through a series resistance by monitoring the voltage drop across the resistor using an oscilloscope (Va-Vb)method). Please see the below circuit.

On starting the stimulation, I observe there is a DC offset to my pulsed stimulation waveform which I can control using a parameter on the current source labeled "Offset control". I can adjust this control to ensure that the baseline of the stimulation waveform coincides with the "zero marker" on my oscilloscope.

I was wondering if someone can explain what might be causing this DC offset and how we can correct for this offset? I do not have access to the specifics of the stimulator and if I want to implement some sort of my own correction (instead of using the "offset control" function), is there a way to do it?

Also, does this DC offset have anything to do with the capacitive effect caused by the ball of gel (since its not entirely resistive)?
Any detailed explanation will be greatly appreciated.

Thank you.


texts: uni directional logic level conversion with active drive current

texts:
I'm trying to connect an EM4095 to a cortex m0. The EM4095 requires an active high drive voltage of min 4V and has an internal pull down of 50K. Additionally it must be low during boot, otherwise it won't boot or something. yey.

How do you drive such a thing from 3V logic. All logic converter circuits i found rely on the sense pin to be floating or pull-up. Let's look at a couple.

I will call the 3.3V MCU pin LV and the 5.0V EM pin HV.

the diode

all float: 3.3V on LV and ~3.0(minus drop) on HV
LV pushes: same thing
HV pushes: same thing, diode will protect from 5V on LV
LV pulls:  0V on HV
HV pulls:  0V on HV

sounds good, except it won't work because i need 4V high. Let's look at some other circuits:

FET

This one is from a sparkfun i2c converter. The circuit is recommended for I2C and other open drain stuff, which i don't have.

all float: both sides get voltage from their pullups.
LV pushes: FET doesn't do anything, HV will get 5V from the pullup
HV pushes: same thing
LV pulls:  FET closes and starves the pullup, so we get 9 on HV
HV pulls:  right through that diode so HV starves all the pullups.

since my HV thing is actually a pull-down, it will draw current when the fet isnt closed. And it will also draw current when it closes. So it will always waste current. But the worst part is, it'll be high before the mcu finishes booting to pull it, so the EM thing won't boot.

Ok so since everything i find on the internet for 'voltage translation/conversion/etc' is about open-drain pull-up, i am trying to come up with something else. I know its not allowed to ask for ICs on EE Stack so i'd like to ask what the correct discrete circuit is, so i can look up an IC later.

Fortunately i know the direction of all of the pins. They're uni-directional. So i thought this circuit might work:

simulate this circuit – Schematic created using CircuitLab

The idea is that the transistor won't close when LV is high, so no current will flow and the internal pull up will pull HV high. I need to reverse the logic in software then. When LV pulls, +5V will be shoved into HV. This behaves acording to the spec of the IC i'm trying to use.

In the reverse direction, i can simply use a voltage divider to drop the voltage from 5V to something my MCU can deal with.

Will this work properly? Are there better ways to do it? And if this is a good way, whats a name of this circuit that i can google for to find an IC? (not enough space for discrete btw)


texts: ORCAD PSpice 16.6 cannot simulate diode circuit properly

texts:
I am currently panicking slightly because I need PSpice to work properly so I can simulate some diode circuits for my upcoming lab. However, what is happening is that when I try to run the circuit below, PSpice will simulate it once correctly (and show the output graph) with the simulation settings, and then if I change the simulation settings and try to re-run it, PSpice won't open the simulation. Sometimes the simulation fails with an argument error and a can't find error right after. Any help would be greatly appreciated!

This is what I'm trying to simulate:

Where Vin is VSIN with 3V amplitude and 1000Hz, no offset. The diode we are using is the D914 (starts with a D, has the number 914 in it). The capacitor is 22uF, and R_L is 5k ohms. When I run simulate this without the capacitor PSpice seems to work correctly, but if I add the capacitor, it seems to only simulate once, and then not work correctly after that, or the simulation will just crash.

This is what I have in PSpice itself for this circuit with the above values:


texts: Converting 0 to 24V analog signal to 0 to 5V for ADC input?

texts:
I'm using ATMEGA16U4 microcontroller and want to Convert the 0 to 24V analog signal to 0 to 5V for ADC input.

I read this

How to read high voltages on microcontroller?

How to Convert 0 to 10V analog signal to 0 to 2.5V for ADC input?

ADC input impedance on MCUs

and I'm using R1 =4.7K ohm and R2=1.2 Kohm which makes my output impedance R1||R2= 0.95Kohm which satisfies my ADC  output impedance of approximately 10 kΩ or less( as mentioned in the datasheet of ATMEGA16U4 datasheet).

Am I right or do I need to change them?


texts: Measure time between two GPIO events in STM32

texts:
I want to measure the RPM of a motor that I am controlling using a STM32 and some driver chip.. My understanding is that I have to measure the time between 2 hall signal and calculate the speed (RPM).

The question is, how can I start a timer and restart it on each hall signal interrupt. I tried to study the timers but the amount of things to learn are huge...

I mean for my case, what mode should I run a timer? I think there are input direct capture, output captures, etc...

Here is my interrupt code:

void HAL_GPIO_EXTI_Callback(uint16_t GPIO_Pin) {
    if(GPIO_Pin == GPIO_PIN_4 || GPIO_Pin == GPIO_PIN_5 || GPIO_Pin == GPIO_PIN_6) {
        commutate();
    }
}


texts: How to perform conducted emissions testing for electric generator?

texts:
I am doing pre-compliance EMC testing on an electric generator. The standard I am reading explains how to test devices that get power from mains, but it doesn't explain the testing procedure for a power supply/generator. My idea is to put a constant load on the generator and use a current probe hooked up to a spectrum analyzer to see if there are any noteworthy peaks in frequency.

Specific questions:

Would using a constant load/current probe be sufficient for testing all frequencies?
Is there a need for a LISN when testing a generator for conducted emissions?
Are there any online sources for procedural EMC testing of generators/power supplies? (I have googled many iterations to no avail.)


texts: Input interrupt pin associated with TIMER1 on ATmega168

texts:
A few days ago I came across the source-code for this ATmega168 based Inductance Meter from Dan's Workshop Blog. Below is the code that I believe sets up an ATmega168 interrupt to measure an external frequency:

// set up the 16 bit timer as an external frequency counter:
TCCR1B |= (1 << CS10)|(1 << CS11)|(1 << CS12); // External clock, rising edge
TIMSK1 |= (1 << TOIE1); // Enable overflow interrupt,
                        // it will overflow a few times in counting frequency

I'm still studying how to set ATmegas interrupts, so I don't quite understand what that code does.

My questions are:

Does the code above determine which pin will provide the frequency to be measured? How?
Would that same code define the same input interrupt pin on an ATmega328?

From the schematic posted on the site (copied below) I can see that the pin whose frequency is counted/measured is PD5 (pin 11 on the IC). Is that correct?

(source: dansworkshop.com)


texts: is the system with memory or memoryless?

texts:
y(t-1)=0.5(x(t)-x(t-1)
This system is noncausal because depend on future value.But is this system with memory or memoryless.According to me it is with memory as it depends on future value.But the book says its memoryless


texts: Unable to control 24 VDC brushed motor with dev boards

texts:
I'm designing a board that has to control several DC brushed motors. The motors are SY54E-DC24V-2PCE. I didn't find a datasheet but some references like this and this.
I measured the DC resistance of the windings and it is 3.9 ohm.
Powering up the motor with 24VDC, without any load, it draws about 350 mA.
I bought some dev boards to test the drivers before selecting them for my custom board.
On my desk I have:

DRV8256PEVM
DRV8871 breakout board
L293D Arduino shield

DRV8256 is rated for 2.5A and after playing with all the settings the motor barely spins but with a very rough and irregular motion.
DRV8871 is rated for 3.6A (I disabled the current control) but the motor never spins.
L293D is rated for 1.2A only (even the datasheet describe it as "high-current" driver) but it is the only one driver that can run the motor, though with a very loud noise (right now I'm using a 500 Hz PWM).
I really cannot use a large PDIP ICs on my board so I want to understand why the other drivers are not able to control the motor. And anyway the L293(D) has a current too low to drive the motor under load.
I understand you don't have the crystal ball, but do you have any idea about these behaviors? And if I should go deeper and try to get the other drivers to work, or it would be better to select another kind of driver...
UPDATE
Here the current profile at power up, with the following settings:

calibrated power supply 24.0 V (capable of more than 6A)
shunt resistor of 10.1 ohm (measured)
motor connected using 20 cm thick wires

As you can see from the cursors, the steady-state current is about
218 mA, while the initial peak is about 1.44 A well below the current rating of the tested drivers.


texts: Two-stage opamp offset voltage constraint

texts:
I have a question regarding the systematic offset voltage constraint for designing two-stage opamp.

My question is : Why must Id6 equal Id7 for offset voltage constraint ?

Please find below the circuit and its offset voltage constraint:


texts: Can I fix 6 pin volume potentiometer by connecting the Right & Left outputs?

texts:
I have a Logitech Z533 speaker system with a 'scratchy' volume control on left channel.  Upon examination of the volume control board in the volume puck that sits on your desk, it is a 6 pin pot with single shaft.  From research I did, this is called a 6 pin dual gang rotary pot.
It is similar to this
Can I just connect (via a soldered wire) the middle pin output of Left and Right channels together to eliminate the 'scratchy' noise when adjusting the volume?  I think that would be easier than replacing it.
I tried to blow out the pot with compressed air but that had no effect.
Thanks for helping with my first question!


texts: What is the role of bleeder resistor and how to choose the right value?

texts: I'm curious to know the role of bleeder resistance of 1k ohm at non-inverting terminal used in this circuit attached below. Is there any calculations to set the right value for this bleeder resistance and will this reduce any offset in the circuit? Kindly help me to understand this.


texts:
I want to drive a mosfet using a mosfet-driver (TC4428). The frequency of turning on-off of mosfet is 5-10 Hz (yes Hz) and duty cycle is 10-20%. I use PC817 as below to make isolation:

As you see, if FLASH1 STROBE be 4.8 volts, voltage of collector will be 0.18 volt. FLASH1 STROBE comes from a ATMEGA16 port. Is there any problem with this design? I mean 0.18 volt on collector and 4.8 volt on FLASH1 STROBE.


texts: Common mode input voltage range and comparators on an MCU

texts: The comparators on my MCU, a dsPIC33FJ128GP802, give the common-mode input range as AVdd-1.15V. AVdd is 3.3V, so does this mean the comparators can't compare voltages in the range of 2.15V to 3.3V?


texts: Does wiring 18650 batteries in parallel and/or series increase the discharge rate of the whole pack?

texts:
I cannot seem to find a solid conclusive answer anywhere on this, but if I build a pack of 6 18650 batteries in parallel which are 3500 mAh each, that would make the pack 21 Ah in total. Then I take those 6 and make 13 more packs and wire those in series so I have a total of 78 batteries making 48v (3.7v * 13). This would make a 48v 21Ah battery.

If each battery has a maximum discharge of 10A. Does that mean the pack has a higher discharge rate? Or does the maximum discharge of the pack stay at 10A?


texts: Where should the leads go to this kind of DC motor?

texts:
I've recently bought a couple of small DC motors (Motraxx XDrive 2025-02). However, I'm not sure where to solder the leads to, since the motor doesn't have the usual connectors. Here's how the motor looks like:

I'm guessing they should go to the same place where the capacitor (?) is connected, but like I said, I'm not sure. Is my thinking correct?


texts: What's a good estimate on how low an alkaline battery voltage can be to still make the battery useful?

texts:
Here's a YT video by Duracell about how many batteries declared dead and sent to recycling still have some usable energy. In the beginning of the video there's a sequence where they have a row of batteries and a person quickly touches each with a pair of probes to decide whether a battery is worth anything.

The measurement procedure is not documented, but I'd guess they just measure voltage on the terminals. Batteries have likely been idle for days or weeks before the measurement.

Suppose I want to do a similar project and have a pile of batteries and a voltmeter.

What's a reasonable voltage threshold to decide usable alkaline batteries from useless ones?


texts: What capacitor and resistor to use in my simple circuit?

texts:
I’m quite new to electronics but I’m making progress learning about it. I would like to make a circuit to control the speed of two electromotors. (Or two circuits to control separately, whatever is most practical). I got the electromotors from a blender and a drilling machine both labels say: 230V 50 Hz.

I looked at the blender as an example. It seems to be a condenser (6nF, X2 275V?), a resistor 1Mohm and the motor (400w) all in parallel. I know that a condenser is often used for a motor to start turning. How do you know/can I calculate what the value of the condenser should be? And for the resistor, why would they put a 1Mohm one in parallel with the motor and condenser?

Eventually I would like to control the speed in some way. Stepwise or more smooth. Do you have any ideas for this?

Thanks!


texts: Fast voltage regulator for output of an function generator

texts:
First, I am not an expert in the electrical field:)
In a real-time control system (in LabVIEW), for actuating a piezoelectric, I use the generated signal (sine signal 20khz and 10<V<100 Vpp) from a function generator.
Since I need a fast response of sending the signal to piezoelectric, I usually set the function generator with the specific frequency and amplitude and then I trigger it by LabVIEW (on-off by sending digital signals from LabVIEW, I can send digital and analog signals by National Instruments USB-6002  DAQmx.)
Now I need to change the voltage in real-time.
Is there any way that I can change the amplitude electrically? I've seen it is possible for DC by using PNP or NPN, but what about AC? Is there any solution?


texts: What files/directories are needed to recreate a Actel/Microsemi Igloo2 project?

texts:
This question is along the lines of What files/directories are needed to recreate a Xilinx PlanAhead project? but for an Actel/Microsemi FPGA design. I'm looking for a fairly standard design with Verilog and/or VHDL, project files, and a few cores. Their support said "You need .v/.vhd RTL file, .pdc files, and .sdc files." which doesn't even mention any needed for IP cores. These are cores that come with Libero software, but they are configured.

To limit the scope of the question, I'm not asking about simulation files since those may depend on tool used.


texts: Intentionally mis-use the USB port on an Arduino?

texts:
I want to take an Arduino and after programming it on the PC like normal via USB, push a button or something and change its mode so that the behaves differently. Is this possible? I'd like to interface with this:

Pins are +1.5V, clock, data, ground. Blue box on top is what I'd like to replace with the arduino. They're using a mini USB connector for the serial connection. Looks like a mutant form of SPI as the clock is from the box (with readout) to the slide and the MISO data comes in reply with clock pulses from the slide. (update: it uses a 21 bit protocol with 9kHz clock and the code from Yuriystoys is almost plug and play)

I'm working on reading the info while in parallel to the connection via wires I soldered to the board's pads.

Update: I ended up soldering a through-hole USB A socket onto a Prototyping board and using that. I routed +3.3V to pin 1, set up a voltage divider for the clock (D6) 330/470Ω on pin 2, routed pin 3 to MISO (D7), and connected ground to pin 4. I'm sure this is physically/electrically impossible to implement using the existing USB port on the board.

While I did get the results I was looking for, the capacitance based scale's reading technology would slowly drift, rendering results inaccurate over time. I need repeatability and drifting .002" in 10 minutes won't cut it. I am reworking this using a 1 micron glass slider scale from DroPros.com and will maintain fixed position in EEPROM between calibrations.

TFT display is Adafruit 1.8" TFT with SD card and 5-way joystick input. An indispensable i/o shield in my opinion; easy to program, easy for user input, and quite versatile.


texts: Why do op amps need input protection when the input impedance is very high?

texts:
From what I understand, the input impedance of an op amp is very high (ideally infinite) and almost no current flows into the op amp. If that is the case why do we put a resistor in series with the input to protect it like below?

If the input voltage is too high (like from an ESD event or over input voltage,) won't the output just get clamped to the supply voltage anyway? By putting a resistor in series with the input, doesn't that change the input voltage seen by the op amp and introduce an error since there will be a voltage drop on the resistor? There seems to be no explanation anywhere on the Internet.


texts: I have a set top box remote that I can use to control set top box as well as TV by using the set button on my stb remote.That remote can copy any remote IR pattern but when I tried it on a car remote it didn't worked.Do car remote uses different type of radiation?


texts: My board works intermittently... when I short some pins

texts:
I'm trying to get an I2C bus working. I'm using a PIC24FJ32GA002 micro. At the moment it's not connected to any other devices. It doesn't work. I then run a screwdriver along the pins of the MCU and it starts working. Power cycle and it's not working, same trick with the screwdriver and it starts working. The most confusing thing is I do not need to hold the screwdriver there - simply running it across the pins once or twice is enough to get it working.

The software is basic, just an infinite loop sending out I2C data. What could be wrong? It's on a breadboard. I'm beginning to suspect a faulty connection, but what about a breadboard would cause it to stop working after power is reset?


texts: Measuring the inter-winding capacitance of a multi-coil transformer

texts:
I want to measure the inter-winding capacitances of a multi coil/winding transformer. (To use them in a simulation)

For a two winding transformer I would measure it by shorting out the individual windings and measure across the transformer with an LCR Meter.

However, for transformers with multiple windings, I think you would always measure capacitances to other windings as well.

What is the correct/best way to measure the capacitances between all windings?


texts: Should I use both a MOV & a flyback diode for a very high power DC motor (7560W)?

texts: I couldn't find a circuit online that uses both so I figured I better ask those who know more than I do if this would be a mistake or not. Thanks for your help


texts: Can digital clocks and other electronic devices "ride through" a momentary power interruption?

texts:
I recently attended an electric utility training course discussing relay protection practices.  One topic that came up was a fuse saving scheme where a protective reclosing device would momentarily interrupt power to save a fuse from blowing.

My question is how standard electronic devices would react to a very momentary interruption.  The instructor said that if power was interrupted for 18 cycles or less on a 60 Hz system that the digital clocks would not reset and blink.  I was unable to find any reference to back up this assertion.  Are any of you aware of any design standard that would substantiate this claim?

Our practice has always been to push the outage out to the furthest point with a sustained outage rather than "blink" more people than necessary.


texts: Buck boost converter - High current 15A@12VDC +

texts:
I don't have much experiences from designing and understanding more complex circuits. I only have basic knowledge how different components work and how to create and calculate simple transistor circuits with 4 resistors and a transistor. So I need some help from more experienced people.

I'm working on a 12VDC home automated system, and there is components in the system that needs stabile voltage ~(12V - 12.8V), as long as the generator is active, it delivers 13.8V. But the battery voltage can drop down to 10.5V when I'm not on the site.I have also limited battery capacity, and it can go a week between I'm on place and charge the battery. So I need a effective power supply that can deliver stable voltage. So I have done some search and found that Buck boost converter is what I'm looking for.

Not all equitment is powered on 24/7, but I will install such powersupply for every fuse, so every equitment has same stable voltage. And I have calculated that I need least 15A for the equitment that needs most power. So I'm looking for a buck boost converter that can least deliver 15A@12VDC.

I have done some searches for such curcuit, but the best I have found can deliver 5A@12VDC and 10A@24VDC, is it possible to change these curcuit to deliver 15A+@12VDC? Or does any body has a cicuit that can deliver such current.

The reason why I want to solder the PCB by my self is because I want to have PSU and Control unit for the home automation in the same case. The cases are going to be designed as mini-rack (10 inch).

Here is the circuits that I have found:


texts:
I'm working on a controller for ac induction motor and it's spec is given below. I could control the speed without any trouble at higher speeds like 2000 rpm and above. I'm using TRIAC  phase angle control topology in the controller. But at lower RPM like below 1000 RPM but motor takes so much time to reach the set rpm which is not desired as it will add error to the set time period (a timer is there to run the motor @ set RPM for a set period). Also is there any problem if I don't increase the speed gradually.

Motor Spec

1/8hp ,230v/50Hz ,6000 RPM @ No load, I'm using a load of around 1KG


texts:
I have a bunch of network packets and I am trying to specify fields in them, something like

constant UPPER_BOUND : natural := 15;
constant LOWER_BOUND : natural := 7;

I know that this syntax is CORRECT

The range does not change throughout the application and I was thinking if it is possible in the VHDL syntax to declare a constant range if you will. Something to the effect of:

constant FIELD_RANG : natural range := (15 downto 7);

I know that this syntax is WRONG

But, I was trying to understand, if specifying a generic range is possible ? Is the 1st mentioned syntax the only way to do this ?


texts: If I am not using a stencil for my PCB, do I need to use the solder paste (.gtp) tCream layer?

texts: Or is the paste layer always needed? I do have SMD components.


texts:
The following schematic is a class C AM modulator without use of any transformers I've just changed the parameters in spice to get a correct modulation. however I want to find the theoretical value for modulation index.

In class C modulators using transformers modulation index is proportional to the ratio of Vm to Vcc.

simulate this circuit – Schematic created using CircuitLab

My Try:

To find this I tried to think of the transistor as a resistor Rout in the saturation region. Therefore, the Vcc(mod) is

$$\text{Vcc(mod)}=\frac{\text{Vcc}\text{Rout}}{\text{Rout}+\text{Ra}}+ \frac{\text{Vm}\text{Rout}}{\text{Rout}+\text{Rb}}$$

  If this analysis is correct, how should the value of Rout be found?

simulate this circuit

Here is the result of the simulation with Vm=Vcc=9v, Vosc=3.5v:

Edit:

From "Solid state radio engineering", Krauss 1980. page:223


texts: How to find bridge current in this circuit?

texts:
I have this circuit shown below:

simulate this circuit – Schematic created using CircuitLab
Basically this circuit has two inputs and two outputs. The voltage and current at the inputs are defined as: $$V_{1}^{in},I_{1}^{in},V_{3}^{in},I_{3}^{in}$$
and at the output:
$$V_{2}^{out},I_{2}^{out},V_{4}^{out},I_{4}^{out}$$
I know, I can represent these four elements (if you combine RLC together) by using transfer matrix as:
$$\begin{bmatrix}
V_{1}^{out}\\
I_{1}^{out}
\end{bmatrix} = T_{1}\begin{bmatrix}
V_{1}^{in}\\
I_{1}^{in}
\end{bmatrix}$$
$$\begin{bmatrix}
V_{2}^{out}\\
I_{2}^{out}
\end{bmatrix} = T_{2}\begin{bmatrix}
V_{2}^{in}\\
I_{2}^{in}
\end{bmatrix}$$
$$\begin{bmatrix}
V_{3}^{out}\\
I_{3}^{out}
\end{bmatrix} = T_{3}\begin{bmatrix}
V_{3}^{in}\\
I_{3}^{in}
\end{bmatrix}$$
$$\begin{bmatrix}
V_{4}^{out}\\
I_{4}^{out}
\end{bmatrix} = T_{4}\begin{bmatrix}
V_{4}^{in}\\
I_{4}^{in}
\end{bmatrix}$$
On the other hand we know that: $$I_{1}^{out} - I_{2}^{in} = I_{b}$$ and $$I_{3}^{out} - I_{4}^{in} = -I_{b}$$ where $$I_{b}$$ is defined as:
$$I_{b} = \frac{V_{1}^{out}-V_{3}^{out}}{R} = \frac{V_{2}^{in}-V_{4}^{in}}{R}$$
Also we know:
$$V_{1}^{out} = V_{2}^{in}$$
$$V_{3}^{out} = V_{4}^{in}$$
As a result finally we have this matrix equation for this circuit:
$$\begin{bmatrix}
V_{2}^{out}\\
I_{2}^{out}\\
V_{4}^{out}\\
I_{4}^{out}
\end{bmatrix} = \begin{bmatrix}
T_{2}T_{1} & 0 \\
0 & T_{4}T_{3}
\end{bmatrix} \begin{bmatrix}
V_{1}^{in}\\
I_{1}^{in}\\
V_{3}^{in}\\
I_{3}^{in}
\end{bmatrix} + \begin{bmatrix}
-T_{2}\begin{bmatrix}
0\\
I_{b}
\end{bmatrix}\\
T_{4}\begin{bmatrix}
0\\
I_{b}
\end{bmatrix}
\end{bmatrix}$$
The above matrix equation gives me 4 equations but, I have 5 unknowns. My known parameters are:
$$I_{1}^{in},I_{3}^{in},V_{2}^{out},V_{4}^{out}$$
and my unknown parameters are:
$$V_{1}^{in},V_{3}^{in},I_{2}^{out},I_{4}^{out},I_{b}$$
Is there any way to find $I_{b}$ here without further assumption?


texts: How to use blue press and peel transfer foil for PCB etching?

texts: I decided to try etching my own PCBs and I got some blue press and peel transfer foil. It has shiny and matte side. I'm supposed to print on one side and iron the other, but the procedure of transferring isn't too clear to me and the only site which Google provides appears to be infested with malware, so I'm asking here for advice.


texts: Is this thyristor model or circuit wrong?

texts:
As far as I understand when the thyristor is triggered it should turn on and remain on unless negative voltage applied to its gate. I found the model from littelfuse website.

But I tried the following circuit with the model where I plot gate trigger voltage supply voltage and load current as follows:

And when the gate voltage is off the load current also goes off instead of remaining on, aka latching.
What could be the reason the thyristor is not latching as expected here?


texts:
I am having issues with interrupt setup on MCP23S17. Not able to set up the INTB line properly. I have an external 10K pull up resistor connected to the line and 3 input buttons connected to GPB0 - GPB2.

I tried setting the INT line as Open Drain. Still I read 0 on INTB. Also tried setting up the line as Push Pull with Active Low interrupt polarity. Still get a 0.

I am able to control GPA as an output port just fine.

Below is my code

#define MCP23S17_OPCODE_WRITE   0x40
#define MCP23S17_OPCODE_READ    0x41

#define MCP23S17_IOCONA     0x0A
#define MCP23S17_IOCONB     0x0B

#define MCP23S17_IODIRA     0x00
#define MCP23S17_IODIRB     0x01

#define MCP23S17_GPIOA      0x12
#define MCP23S17_GPIOB      0x13

#define MCP23S17_OLATA      0x14
#define MCP23S17_OLATB      0x15

#define MCP23S17_GPINTENB   0x05
#define MCP23S17_DEFVALB    0x07
#define MCP23S17_INTCONB    0x09
#define MCP23S17_INTFB      0x0f

void EXTERNAL_MCP23S17_Init(void)
{
//IOCONA (DEFAULT)
//SET MIRROR = 0
s_external_mcp23s17_write_reg(MCP23S17_IOCONA, 0x00);

//IOCONB
//SET MIRROR = 0
//SET ODR = 1 (INTB PIN IN AS OPEN DRAIN MODE)
s_external_mcp23s17_write_reg(MCP23S17_IOCONB, 0x04);

//SET GPA AS OUTPUT
s_external_mcp23s17_write_reg(MCP23S17_IODIRA, 0x00);

//SET GPB AS INPUT (DEFAULT)
s_external_mcp23s17_write_reg(MCP23S17_IODIRB, 0x07);

//SET GPOA INITIAL VALUES
s_external_mcp23s17_write_reg(MCP23S17_GPIOA, 0x27);
s_external_mcp23s17_write_reg(MCP23S17_OLATA, 0x27);

//ENABLE INTERRUPT ON CHANGE FOR GPB0 - GPB2
s_external_mcp23s17_write_reg(MCP23S17_GPINTENB, 0x07);
//SET GPB DEFAULT COMPARE REGISTER FOR INTERRUPTS
s_external_mcp23s17_write_reg(MCP23S17_DEFVALB, 0xFF);
//SET GPB INTERRUPT CONTROL REGISTER
//COMPARE PIN VALUE AGAINST DEFAULT VALUE
s_external_mcp23s17_write_reg(MCP23S17_INTCONB, 0xFF);
SEGGER_RTT_printf(0, MODULE_NAME_EXTERNAL_MCP23S17"%s OK\n", __FUNCTION__);
}

Not sure what I am missing here. Have checked the datasheet and I don't think I've missed anything


texts: Can I safely use a 6 A, 600 V diode in place of a 6 A, 400 V diode?

texts:
Inexperienced electrical person here, but trying to save significant cost to repair an oven.  The oven I have has a MR754 diode off the main convection heating element, that has failed.  Unfortunately, since it is part of the wiring, the manufacturer only offers up the entire wiring harness as a replacement part at $500+.

Pending all other things checking out with a multimeter, I would like to simply splice in a replacement diode (~$2 part).  However I cannot locate an MR754 in my area and it's multiple business days to get one delivered via online order.  Local vendors do have an MR756 available.  Both are 6 amp current, but the available replacement would be 600 V vs 400 V.  Is this safe to use in this application?  What is the risk, should I try this?  Do I put the other components in the oven (i.e. element or control board) at risk?


texts:
I would like to flip my entire layout from bottom to top side. The flip action should be through the board. Which means that the connectors should not change position (X-Y wise).

I hope you can give some ideas without me routing everything again.

Thanks in advance

Addition: I was hoping to do this without routing anything (or a big part) again.

Edit: I am an Altium beginner, all tips are welcome


texts: RTC (real-time clock) in STM32L4 series - date and time is not updating on the debugger variable

texts:
While using the RTC (real-time clock) in the STM32L4 series, but date and time is not updating on the variable in debugger mode. But when I stop the debugging, the variable gets updated instantly and with the correct value.

What is the explanation?


texts: STM32F411 Nucleo board - what the ferrite bead is used for?

texts:
I'm trying to design my own pcb for the stm32f411 and when i saw the datasheet of the stm32f411 ( http://www.st.com/st-web-ui/static/active/en/resource/technical/document/datasheet/DM00115249.pdf ) and then the schematics for the stm32f411 nucleo board i was a little confused.

In pin 13 (Vref+), in the schematics there is an ferrite bead.I can't understand why it used in the Vref+ pin (since there isn't any mention to it in the datasheet not even the explanation of the Vref+ pin function.

Image is from ST schematics

So, my question is, for what the inductor is used in this application and is it really necessary?

Grateful

Edited


texts: How much does voltage affect the light frequency output of an LED?

texts:
I have a large array of LEDs that I need to be true to their datasheet light frequency emission (ex 635 nm.) The LEDs require Vtyp @ 20 mA ranging from 2.2 V to 1.2 V. Some are within 0.1 V of each other.

In the interest of minimizing the number of Zener power circuits I need to add, could I put both a 1.8 V and 1.9 V on a 1.8 V power source without much light frequency deviation? Any way to know how much or guess the direction of the deviation?

I just remember from past experience that over-volting orange LEDs color-shifted them to yellow. I never knew if this was a bandgap/voltage thing or just overheating LED caused it.


texts:
I'm interfacing a product that operates on a kind of CAN bus. Specifically, it uses the CANL line only.

I'd like to use a transceiver I've used before, the MCP2562, and I suspect there's not likely to be any problem transmitting, but will it receive with nothing connected to the CANH line?

How should I manage termination in this instance?

The bus operates at 1Mbit and my logic analyzer measures levels of 0.9V dominant and 1.8V recessive. I realise these are not standard CAN levels. The frame format is CAN, but I'm happy to use an alternative transceiver type if I can achieve the same levels and it manages the line correctly.

Any help much appreciated !


texts: Designing a FET switching circuit that fails open

texts:
I'm trying to design a drive circuit for a car engine throttle valve. The valve is spring-loaded to close, and has a small DC motor for opening. (I'll also note that this only for my own vehicle.)

Below is my current shot at the thing. Motor stall current is roughly 3A at 12V. Microcontroller is a 3.3V device. The motor is to be controlled by PWM, but I have not yet experimented with it much. The circuit works otherwise fine, but as I burned the FET, it failed closed, forcing the valve fully open. From a quick internet search, failing closed is quite common for FETs. Needless to say, I'd like to avoid this "jammed fully open" -situation.

So, is there a circuit design or a specific FET that would fail open for certain?

(I'm not worrying too much about this particular failure, as the FET was not heatsinked and still had to dissipate ~1.5W of power)

simulate this circuit – Schematic created using CircuitLab


texts:
I'm trying to drive this JBtek 4 Channel DC 5V Relay with a signal originating from a teensy 3.6. This means I somehow need to turn 3.3V @ 10 mA to 5V @ 60mA. I have a high wattage 5VDC PSU I would use, I just need a simple IC or circuit that can take my dinky signal and turn it into a less dinky signal that can drive the optocoupler on this relay board.

So far, I looked into these things which did not seem to help:

A simple BJT circuit

simulate this circuit – Schematic created using CircuitLab

The 83.3 Ohms is my over-approximation of the impedance of the relay input. I figure if I put the relay input at the collector of the BJT, it will always see 5V. Well since I'm here, this doesn't work because the CE voltage is always like 2.3V so inputs never see 5V.

Logic Converters (can't supply enough current)
a buffer (also can't supply enough current, but maybe there's one out there that can?)
a shift register (also can't supply enough current)
recent epiphany on the simple BJT circuit: Any reason why I can't just be a smart and put the relay input & "ground" in series with 5V supply and BJT collector like so:

simulate this circuit

By looking at an Amazon listing, I have found a possible solution to help me with my project:

Is there a better way to drive these relays?


texts: How to implement the circuitry for a reversible connector

texts:
My sports watch has a 4-pin connector on the back used for charging and data exchange. The male connector can be plugged in 2 ways. This means that internally the power and ground are swapped. Same for the data lines ( either RX, TX or USB+, USB-)
I want to implement similar functionality for a project that i am doing. I have been doing research but cant seem to find a solution for this.
Besides dealing with the reverse order of the pins, the solution should also provide short protection (the watch can be submersed in water which shorts the pins)
Are there IC solutions for this?
Does someone know of a reference design for this?
Can someone share schematics of a solution?
This is the type of connector that i want to use for my project:


texts: Replace potentiometer in Dart Controls 90vdc motor controller with raspberry pi

texts:
My existing setup:

Rae Corporation gear motor (90vdc, 4.5amps, 120rpm, 150 in/lb torque, Part number 6040042).  I can't find a datasheet, but it looks a lot like this
Dart Controls motor controller 15DV1A, (datasheet) which takes in AC main power and runs the motor.  Pots on the board control max and min rpm as well as implementing IR compensation.
the main speedpot shown attached to the 15DV1A relocated to the end of a long cable with connecting it back to the board.  I've measured the voltage across this speedpot - it's about 6.5V from Pot-Low to Pot-High, with the Pot-wiper being somewhere in between depending on the pot position.  The site says it's a 5k ohm pot.

Here's the question:  I would like to control the motor with a raspberry pi - how?

I see a couple of approaches:

#1 Replace the pot:

there are variable resistor ICs, but reading around it seems like they would not handle the current that passes through when the resistance is low.
I've also read that mosfets can be used to create variable voltages, but they are very sensitive and only operate this way over narrow range.  Also, it seems like hooking this up is complicated.
digital potentiometer, like this or this.  Would this be able to handle the current as a replacement for the pot?  If so, this seems like the best approach but how can I wire it so the 6.5v motor control signal is isolated from the RPi?

#2 Control the existing pot:

I've seen folks use a stepper motor to control a knob, sort of like this.    While I appreciate that approach wouldn't modify the existing arrangement at all, I want something smaller and more direct ideally.

#3 Replace the entire Dart Board

I really don't want to do this, since the board provides some nice features.  But if this would be cheaper than either of the above two, I'm listening.


texts:
Hi everyone one more time, I have a silly question about trace length measurement on Altium. I was using the PCB tab to measure the length of the traces (on mm). Measuring PCIE_REFCLK_P on the tab de value is 14.072.

But I realized that If I use Reports>Measure selected objects I see this:

The measurement is almost 4 mm less, which is the good measurement or the measurement I should to use? Thank you so much!


texts: Calculate voltage in circuit with capacitor

texts:
I have a circuit where I have a capacitor (2F) in series with a resistor (1 Ohm) and a voltage source (v(0) = 10V). Now I am supposed to calculate v(t) for different t, like t=1s, t=2s and so on.

How do I do that? Is there a formula available for this? I need some ratio between the Farad of the Capacitor and the time it takes for it to load i guess...


texts: Can one instantiate RAM with 2 read ports and 1 write port as IP in Quartus?

texts: As part of MIPS design we have something called as register file. It only has 32 registers each 32 bit which only makes 1024 bits or 128 bytes. I am not sure how to tell Quartus to instantiate this as a memory block with 2 read ports and 1 write port. The Dual Port RAM in Quartus seems to be having 2 read/write ports. It is not possible to have 2 read and 1 write port. How do I create a 2 read port + 1 write port memory using the memory blocks in Altera Quartus II?


texts: Looking for circuit diagrams of current mobile phone chargers

texts:
I am writing an investigation into how a mobile phone charger works and I'm required to break down the internals with a block diagram with component explanations. To help get me on track I'm looking for a circuit diagram of any recent mobile phone chargers in use and/or if anyone knows of any good in-depth sources for this kind of information that could be useful, would be greatly appreciated.

I welcome all feedback, looking forward to hearing your answers.


texts: How do I select the Correct Diodes and Resistors for my LEDs?

texts:
I've got a 2009 Harley-Davidson XR1200 (that can be seen at the bottom of my bio in my profile).

I've replaced the stock incandescent bulbs with nice looking LEDs; however, the stock bulbs were 2-way and had 3 wires (one for ground and one to each filament).

The new LEDs are simply ON/OFF and have 2 wires. Since LEDs do not draw as much power as the stock filament bulbs, load resistors (that come with the LEDs) are included. These resistors get very hot because they pass a lot of current so the electronics on the motorcycle will not think there is a burnt bulb.

I got to thinking that I could wire a Normally Closed relay just past the Turn Signal Module (TSM) so that the LEDs were ON until the TSM sent the "ON" signal - which would cause the LEDs to blink OFF.

The more I thought about how simple this would be to do, the more I thought that this has to have been done by someone before, so I did some research and found several posts where people have done this.

Different posts use different resistors, then I started discovering where some people were clever enough to place a diode and a resistor in parallel so that the LEDs would dim or get brighter with the blink signals, making them appear to be a 3 wire setup.

So far, the best "How To" I've found is a thread called Converting 2-wire to 3 wire Signals on the R6 Forum. This post talks about using electrical components from Radio Shack, but there is not one very close to me. It would be easier for me to buy the components online, if I knew what to ask for.

So, how would I go about getting diodes and resistors that are the right ratings for my application?

I've found a nice Blue Ox 6 Amp diode pack that is sealed to keep out moisture, which would be very nice on a motorcycle, but I don't know if 6 Amps is over kill or about right. eBay has 17,000+ diodes under $3, but I don't know how to pick what I need.

Would the resistor in this diode/resistor setup get as hot as the load resistor in the setup I have now?

EDIT:

To answer the comments: The LEDs I have now only turn on when the turn signals are activated.

Q) What type of LEDs are you using?

A) Rizoma "Zero-11" (link)

Their website shows 12V - 13W on this drawing:


texts:
This question seems trivial and i think i am overlooking something but for whatever reason i cant figure it out.

A city requires 1010W of power at 110V. Assuming 1 foot diameter transmission
cables which has .05 micro ohms per foot resistivity, calculate
power lost per foot.

I've tried taking the derivative of \$P=\frac{V^2}{R}\$ where \$R=0.05\cdot10^{⁻6} × l\$.

I get \$\frac{\text{d}P}{\text{d}l} = \frac{-V^2}{0.05\cdot10^{⁻6} × l^2}\$  which seems like it would be correct but I dont think that give the lost per foot.


texts: At what cable length does matching the impedance at the ends of the cable become important?

texts:
I'm building a base for a PMT that outputs pulses of width <=1 µs. In Hamamatsu's PMT handbook it states on pg. 112 (emphasis mine):

  When using a photomultiplier tube which is not a fast response type or using a coaxial cable with a short length, an impedance matching resistor is not necessarily required on the photomultiplier tube side.

Why does cable length effect the need for termination resistors, and at what length does the having an impedance matching resistor on the photomultiplier tube side begin to matter (for RG-174)?


texts:
I want to use the IPOS3602 datasheet iPOS3602  this is a small motion controller. I have another datasheet which is protected so I can't share it. This datasheet states: The inputs are compatible with NPN type outputs (input must be pulled to GND to change it's default state).
The picture below shows the input circuit for the driver.

My question is I guess the same as This question I'm using 24V PNP sensors, could I use a similar NPN circuit to make this workd? I want to use two end switches (24V PNP)


texts: Do SDIO bus speeds need to match between two devices?

texts:
I have two devices that I'd like to use together, connected via their SDIO pins. The MCU can transfer data up to 200 MB/s with a 200 MHz clock speed (HS-200). The wireless module that I want to use with the MCU can only work up to 104 MB/s with a 208 MHz clock speed (SDR104). In order to use these two devices, do I need to use a bus speed that both devices can handle, i.e. SDR104? Or could I run the MCU at 200 MHz for HS-200 even though the other module can only transfer at SDR104 rates?
For reference, this would be using the NXP RT600 MCU and 88W8987 wireless module.


texts: How can I increase the torque, but not the speed of this DC motor to gear with a potentiometer setup?

texts:
Short video of the machine running.

It's made of three AAA batteries in series giving a total of 4.5V to the DC motor, these are connected through a potentiometer to control the speed. The DC motor is connected to a gear that runs a music box playing Fur Elise, but its too fast, and when speed is reduced, it can't make the gears go around. Off my head it seems there are several methods to get this fixed, I am asking here to get some tips on the best.

Possible solutions:

Change gearing (what gear setup should I use?)
More powerful DC motor
Change batteries


texts: Using oblong / rounded surface mounted pads for chip resistors, capacitors and inductors

texts:
I'm learning to layout PCBs and lately I came across practice that made me curious. The chip passives' pads are etched with oblong / rounded shape, instead of rectangular shape that is used in all example libraries and even the IPC-7351B standard (you can download LP Viewer for free registration and see for yourself). Here are the examples (I marked the interesting pads with yellow):

Beagle Board:

Arduino Mega:

The question is: what are these rounded pads good for? Should I use them instead of rectangular ones to make my board look more "pro"?

My first thought was that it might be because it might be better for reflow soldering, but I'm bit puzzled about that reasoning. The one advantage I see with these is more routing space around such rounded pad (no "sharp" edges).


texts:
I am simulating an op-amp circuit of which a small section is shown in the image. As  per power consumption formula,

P = Icc * (V+ - V-) + Iout * (V+ - Vout)

I tried to calculate the power. I have put the values shown in the image.

P = 1.17mA (I have confusion in this value) * (5V-(-5v)) + 0.36 mA (5V-2.16V)

P = 11.7 mW +   1.0224 mW = 12.72mW. But the Watt meter probe in simulation shows 4.89mW .

I got a confusion that whether I am missing any point or doing wrong in the calculation?

Clarify this!


texts: Balanced delta source to Wye source by considering magnitude only is ok?

texts: I read and derived formulas for balanced delta source to Wye source; it is given by Vy = Vd / sqrt(3)<30 but in some places I see people only dividing by sqrt(3) for conversions are keeping angle 0, is it the correct way for conversion ?


texts: How does the Yamaha DX7 digital analog converter work?

texts:
The Yamaha DX7 keyboard seems to have a quite sophisticated DAC and I wonder how it works. It is mostly specified as 12-bit DAC running at a sampling rate of 50kHz, but this doesn't tell the whole picture it seems.

The broad bus is the main system data bus, the small busses coming in from the left source in the waveform generating digital IC. The analog audio signal exits by the bottom left and are mixed together later.

There is in fact an BA9221 12-bit DAC IC. But it does not run at 50kHz, but actually 16 times as fast, as the 16 voices the DX7 can play simultanously are time-multiplexed on this IC. This can be easily seen by scope.

However, the BA9221 reference voltage is not fixed but can be controlled by a resistor network wired to an multiplexer (IC46) by the system's digital data bus lines D0 - D2 . No clue on what this depends. The smaller sister model keyboard DX9 seems to lack this multiplexer.

The BA9221 output is fed into another resistor network whose outputs are connected by a digitally controlled switch (IC41), controlled by the digital oscillator IC via the signals SF0-SF3. These signals are individually switched by the voice multiplex frequency and seem to depend on the actual waveform played, each line exhibiting a different pattern. So we can expect this to modify the original signal in a multiplicative way I guess.

The is finally switched again by another digitally controlled switch (IC52). There are two outputs generated, these will mix down to a single signal later (not pictured), there is only one mono output. After analog volume control and amplification the signal is feed to the output jack.

So I would like to know how this exactly works and how to describe its characteristics in nowadays terms. It is obvious that a single channel 12bit signal won't reproduce the signal faithfully. And I wonder why this is so complicated and what is achieved by the all those additional parts.


texts: PNP Open Collector output series resistor

texts:
I have the following circuit to drive a logical output (the input is driven by an MCU):

The issue I have is that because of R4, when I want to draw a few mA from the output, the voltage drops. Right now I am trying to drive a 24V DC relay that requires 7 mA, but this is too much current and the voltage drops to ~10V and the relay does not open.
I need help with 2 things:

First, what is the purpose of R4 and why was it designed to be 3.6k?
My understanding is that it is meant to protect Q1 from a short to ground, but Q1 (BC857CLT1G) is rated for a maximum collector current of 0.1 A. So we could have used a 240 Ohm/2.4 W resistor.

Second, would it be acceptable to reduce the resistance to 680 Ohms/1 W?
This would allow a current of 7 mA while maintaining an output voltage of ~19.2V, which should be enough to activate the relay. In case of short to ground, the current would be 35 mA and the power dissipated 0.85 W.

For information, here is the circuit diagram of the relay:

A1+ is connected to the output of the previous circuit and A2- is connected to ground.


texts: How critical is it for SN65HVD1780DR A/B Differential signal lines to have matched trace length?

texts: How critical is it for the A/B differential signal lines of SN65HVD1780DR to have matched trace lengths on PCB?


texts:
I have a 3-phase transformer with primary and secondary windings both star(neutral connected). When connected to 3-phase source whose line volts is 415V, I got the following readings at secondary winding:

    phase A to neutral :  105V
    phase B to neutral :  110V
    phase C to neutral :  220V

Please I want to know the cause of lower phase voltages on lines A and B.
Thank you. i will appreciate your answers.


texts: References for MOSFET as a switch for LED/Laser Diode

texts: I do not have a schematic to show yet. However for a school assignment the task is to create a circuit that switches power for an LED or Laser diode, this seems really is and probably is. But I have never worked with MOSFETS, I know the basics. But can't find any good resources on these, if anybody could provide a good reference for me to read up about these I would be very grateful, thank you!


texts: PICKIT 2 verification failed at memory address 0x0000

texts:
I have been using a DSPIC30f4011 for two days but suddenly I am no longer able to program the chip again.

The message I am getting:

Failed to verify at programming address 0x0000  (when I click the Verify button).

Failed to program at programming address 0x0000 (when I click the Write button).

Successful (when I click Read button).

Successful (when I click erase button).

I clicked on the erase button and tried to get rid of the error. But when I clicked read after erasing it, the first byte is still 0000 0000. Everything else is FFFF.

I am pretty sure the wiring and power supply is correct because when I put a new chip into the spot where the old chip was at, PICKIT 2 is able to program/verify it.

The pickit shows All protect for both old chip and new chip so it's not a problem.


texts: Why Bootstrap switch removes Vgs non linearity

texts:
in the theory they say that by connecting the voltage source inthat manner the non linear dipendancy on Vin is removed.
Buy we are not connecting gate and source with this voltage
we are connecting gate and drain.
Why its removing Vgs Vin dependancy?the connection should be the opposite.
Thanks.


texts:
What does "Vf" mean? I have searched every facet of the internet and I cannot find an answer.
I just want to know what Vf means.


texts: RMS Value of a voltage waveform consisting of a superimposition of 2V DC and a 4 V peak to peak square wave is?

texts: RMS value should be sqrt(2^2 + (4/sqrt(2))^2) which is equal to sqrt(12), but the answer is sqrt(2^2 + (4/sqrt(2))^2) which is equal to sqrt(8).


texts:
I completely new to this field, although I used to do programming in C++/Python and use Ubuntu/Fedora. I am student of experimental particle physics, more precisely Detector Physics. I have just started learning VHDL, but don't know how to start. I have few question,

I am modifying my question completely...

1 - Editor: The one specifically made for VHDL which can recognize VHDL syntax, beautify, indent and highlight VHDL reserved keywords etc.

2 - Compiler: After writing my code I need to compile/run my code to debug, so I need a compiler for VHDL. I don't know if VHDL needs compiler or not.

3 - Simulator: After successful compilation, I want to see its simulation representing as real world phenomenon.

We physicist do most of our work based on simulations. We jump in real world after doing hundreds of simulations. Sometime we need to simulate hardware for our detector before actually start building it, as people do in industry normally.

I guess its pretty precise now.


texts: Is there an appropriate "potting" compound for a DC power barrel connector?

texts:
I need to modify the DC connector on about 100 AC/DC power supplies and will be installing a barrel connector like this:

I would like to make the connector more permanent and prevent a user from opening the connector as well as increase the physical bond between the wire and the connector. I'm thinking I would like to squirt a blob of some compound (potting compound?) before threading the connector back together to lock it all up.

Is there an appropriate compound for this application?


texts: How to offset input voltage of any op amp

texts:
There are some op amps that allow nulling of input offset voltage by provding decidcated inputs where, typically, a potentiometer is connected for the offset correction.
My question is that if a op amp, does not provide such inputs, then can the offset voltage still be corrected? How can this be done?

For example, How would one offset input voltage in Current-to-voltage configuration?


texts: Why did CATV standarize in 75 ohms and everyone else in 50?

texts:
All of the CATV industry runs on 75 ohm systems, while most of the rest of the radio world uses 50 ohms.

Why was this standard chosen?

I was wondering this because good quality RG6 cable can be obtained everywhere for very little, compared to decent quality 50 ohm cabling.


texts:
I would like to find a good way to interface many UART devices (sensors) to a single PC for data collection and processing. For my use, there may be as many as 100 UART devices each operating at 115200 baud. Currently I am using FTDI UART-to-USB bridges - a separate FTDI for each UART device. This, combined with a USB hub works fine for small numbers of devices, but beyond about 5 or 6 devices, there are problems with data drops over the virtual serial coms. And there seems to be a number limit associated with the computer (12 for one of my computers, 17 for my laptop) beyond which the computer fails to recognize more. In general this does not seem like a workable solution and even if you could hook up 100 UARTs+FTDIs+USB hubs etc., this seems like it would be a very clunky solution.

BTW, I also thought about this netburner module that supports 8 UARTs and could send the data over ethernet for a network interface: http://www.netburner.com/products/core-modules/mod5441x . It's an option, but still only 8 channels.

So certainly I'm not the first person to want to hookup and record data from many UART sensors. What is the best way to do it?


texts:
After a successful first design of my AC triac dimmer, I decided to improve it. I did this by adding a snubber circuit, so I could control inductive loads as well. I also added a EMI filter to reduce the noise it is outputting.
The MOC3052 is controlled by a MCU with a dedicated zero cross circuit.

However, after assembling the circuit and testing it for a minute or so at 20% dimming, R4 started arcing. After that, the resistor seems to be broken because I couldn't measure any resistance over it.

After measuring it with the scope, I figured out the voltage drop over the resistor is around 5.5v. However, this are small peaks and not a continues load. Could this be the reason the resistor is killed and started arcing? Right before failure, I can see the resistor degrading because the voltage over the resistor is rising in a quick tempo.
I also tried searching online for answers, however, none of the snubber circuit examples are mentioning a high wattage resistor. After simulating it in falstad (with a diac trigger circuit just for making the simulation more easy), I could see the peak is around 0.01ms long.
I'm unsure what else could lead to those issues. I'm also unsure how to solve this, or how to make a better design.


texts:
I'm in the process of learning about how SFP+ modules work under the hood. I chose a 10GBASE-T transceiver module as my case study. The module I chose is said to be complaint with SFF-8431 spec, so when I look this up on Wikipedia:

It looks like the interface would be XGMII. This interface is
the "MDI" interface, correct?  Does the transceiver implements the entire PHY (LDPC PCS, PMA, AN) or is it just a glorified ADC/DAC?
How would I figure out what the interface should be for ones that don't list anything under "MAC block to a PHY chip?"


texts: Use a photoresistor to read an IR LED from an Itron energy meter

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I want to read my meter at home with an Arduino board. My meter, an Itron C1S, has an IR emitter that pulses once (10ms width) every Wh.

I want to know if it is theoretically possible to use a normal photoresistor to read this values. If yes, how can I specify the photoresistor? If not, what would be the alternative?


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In a design of mine, I need to place two plates on top of each other as close as possible. With a 400v potential difference possible between the plates, what is the best material that can be placed in a very thin layer between the plates to keep them electrically isolated? I understand that there will be a degree of capacitance induced by such a setup, but it will be negligible for me.

I have thought about KAPTON tape. All of this is very small (< 5mm plates).

I found the following quote on DuPont’s website about their KAPTON polyimide tape:

  Excellent dielectric strength makes Kapton® polyimide film a perfect material for thin electrical insulation applications. With a dielectric strength rating of 7700 V/mil for a .001”-thick film, no other material can provide such protection in such a small space.


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Hello I need to communicate with a device using SMBus. However, I could not choose correct value for pull up resistors. Vdd is 4.9V and I use SMBus. In same conditions for I2C communications I used 2k ohm resistors and it worked, but I am not sure the proper value for SMBus. Any ideas?

In its datasheet it says this one, but I could not understand it totally. I think it says for 5 V I need 15 k resistors. However, if I use 20 k resistors with 4.9V Vdd, would it also work?

This quote is from "Application Note: Implementing The SMBus Interface For Use With Bren-Tronics Batteries":

  PULL-UP REQUIREMENTS

  One of the features of SMBus is its ability to interface systems with different supply voltages, through its implementation of an open-drain interface with absolute (as opposed to ratiometric, relative to the supply voltage, like I2C) high/low voltage thresholds.   Vih of the SMBus interface is 2.1V; the upper bound of logic-high voltage is 5.5V – facilitating operation with 3.V/3.3V/5V logic.  The pull-up devices for the open drain interface (one for each line – clock and data) are simply connected to the supply voltage in the host system.

  The “letter of the law” in SMBus is that the “steady-state” output-low current (Iol) must be limited to 350 microamperes or less.  This translates into pull-up resistors of 15K ohms in a 5V system, for the simplest of SMBus interfaces.  However, the stray capacitances present in wiring and/or ESD/EMI-suppression devices of bus-connected devices can sometimes extend rise times beyond the 1.0 microsecond specification limit if resistive pull-ups that comply with the Iol limit are used.

  There are a number of options that can be used to address these limitations.

  Active pull-up devices, that provide higher dynamic current during the low-to-high transition while maintaining the steady-state limit elsewhere, can be implemented as shown in Figure 2.3 of the specification.

  A simpler approach is to use lower-value resistive pull-ups, if currents higher than the Iol limit can be tolerated by ALL bus-connected devices (present and future) without violating the 0.8Vdc Vil specification limit.  This is often the case, as this is a technique frequently used in commercial system designs.  In this regard, Bren-Tronics batteries go beyond the specification, with the ability to sink SMBus current at levels up to 700 microamperes or more.


texts: Power Gain in a Small Signal Mosfet Circuit

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let's consider this circuit, which is the equivalent of a small signal Mosfet amplifier.

where RG is a gate series resistance which takes into account of the oxide leakage, and CGS and CGD are the well - known Mosfet Parasitic Capacitances.

Now, the book The Design of CMOS Radiofrequency Integrated Circuits (Lee) makes the computation of its power gain, i.e. the ratio between the power delivered to the load (by supposing matching) and the input power of the source. Regarding the last one, it is written that:

My question is: is the factor 1/2 due to the fact that in AC we consider rms values, or is it due to something related to the maximum power transfer theorem? I thought it was due to the rms, but if it is true, the formula should use the phasor of the input current (and moreover, the book does not do any assumption about a single - frequency behaviour of the input current source). Moreover, how can I compute the power delivered to the load?
I do not know if I have to use the factor 1/2 due to rms or not.


texts: Wrong inductance at flyback transformer?

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I want to design a 12V-to-48V@0,3A isolated DC-DC converter using LT8302 and I was following the design example given in the datasheet.

Using the values for "8V to 36VIN/48VOUT Isolated Flyback Converter" at p. 22:

Vin_min = 8V, Vin_nom = 12V, Vin_max = 32V, Vout = 48V, I_out = 0,2A

it results that the primary inductance needs to be greater than 58uH, but as you can see at p. 22, they chose a transformer with primary inductance of 9uH. Why? Is it a design mistake?

I have uploaded (at the links below) an Excel file with the design example where you can enter the input values and see the results. In red are the values for the converter I want to design.

OneDrive

File


texts: Avnet IO Carrier: SCL Resistor Function in PMBus?

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I'm studying the Schematic of the AvNet IO Carrier for the Ultrascale+ based SoM.
In particular, I have a doubt about the function of the  R130 resistor on page 14.

Can someone help me to understand its function?


texts: How a modchip overrides specific signals?

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I read an article on the original PSX copy-protection scheme lately, and how the modchips of that era were implemented using PIC MCUs. Then this question popped up, and I haven't been able to find a satisfying answer on the net or between colleagues.

As far as I know and saw on YouTube videos, a modchip is installed in parallel with the IC lines that wants to override. The specific lines that the modchip is attached to are, of course, already in use by another component and are not cut-off. Consequently, you end up in a situation where two different ICs trying to drive the same lines.

In CMOS logic, the signal will be either high (VDD) or low (GND). Which means that if the modchip tries to inject something or the original IC tries to talk to the targeted component then it may end lead to a short circuit or situation where both components try to drive that line high.

So, how a modchip overrides specific signals, essentially telling the target component "use my signals and not the originals"?