texts: How to ensure signals from multiple different clocks are in phase?

texts:
I am designing a pcb where I have a signal of 10 MHz logic signal with 50% duty cycle that might be coming from different clocks. I will be using a pll frequency synthesizer to turn this into a 50% duty cycle 1 Hz signal. Is there any way I can ensure that the 1 Hz signal is initiated by the same rising edge from the 10 MHz signal in multiple setups? E.g. If I have two of these setups, each stemming from the same clock/clocks of significant precision and accuracy, how do I ensure that the two 1 Hz signals will always be in phase?
P.S. if anyone also has any suggestions or sources they can refer me to on how to build PLL circuits, it would be very appreciated.
I am a student with not much experience in electronics, therefore I apologize for any mistakes/poor communication of the problem.


texts:
I'm in the process of assembling an embedded (Raspberry Pi-based) machine that has a lot of sensors wired together via I2C. I find myself adding headers for the I2C lines to all the little tiny breakout boards on which the sensors are mounted, and I have an I2C "bus board" that I've assembled using a prototyping board to simplify connecting all the sensors in parallel, but I'm wondering if there's any advantage to soldering the connecting wires instead of using 0.1" headers and jumper wires. The boards are not very rigorous timing-wise (the bus is set to a low bandwidth.)

For the record, what I have now -- everything assembled via headers -- works just fine. I'm concerned about reliability, noise, capacitance, etc.

What's best practices when it comes to assembling systems like this?


texts:
I am working on Motor speed and position control. The requirements of the project are:
1. Set a speed to run the motor at a particular frequency.
2. Use a potentiometer to set the speed displayed on the LCD (POT and LCD on development board)
3. Create PWM signals to run the motor. Keep PWM independent of the microcontroller.
4. Use encoder to detect motor speed.

I have all the electronics sorted out and tested but my supervisor wants me to use the POT and the LCD on the development board to set a motor speed and then use that to power up a 555 Timer that I'm using to generate PWM signals as the PWM is supposed to be generated externally and not through the microcontroller. ADC converts the POT to a certain value (0 - 255).

My question is if I need the motor to rotate at 500Hz, how do I get the associated ADC value from the development board to run the 555 Timer. I need to set a value of motor speed and start the program to run the timer to oscillate at a particular frequency?


texts: Differential amplifier and large signal analysis

texts:
Let's consider this circuit:

Razavi makes the large signal analysis in the ideal case, that is with an ideal current generator. He shows that Ic1, Ic2, Vout1, Vout2 and (Vout1 - Vout2) are function of only the difference (Vin1 - Vin2), as shown in the following image:

Question: in a more realistic circuit (that is, with a real current source with a resistor in parallel), how would large signal analysis modify? How would the previous graphs change?

Thanks


texts: Building a small D cell battery charger?

texts:
I am looking to buy/build my own D cell Nimh battery charger with the following requirements:
-dual prong AC wall input
-charges Nimh D Cell
-is safe
-contained within 1" x 1.7" x 2.2" enclosure

As far as I can tell there is nothing like this to buy at the moment. I have also searched the web for a schematic and found almost nothing of use.

I have played with bridge rectifiers and basic power supplies in the past and was wandering if building something with these specs would be a possibility? Also are there any ICs that could be safely used instead of actually building the entire bridge (anything to make it smaller)?

What would be "desirable" design traits of this supply?
Would I need to make it a smart charger? Is a smart charger really all that beneficial for Nimh D cells?
Can I get away with a the most basic design of 4 diodes, a cap, a regulator and 2 resistors (similar to this:http://upload.wikimedia.org/wikipedia/commons/1/1d/Diode_bridge_smoothing.svg)?
How much current should I want to design at the load?

I realize this is kind of vague, but I have been searching the web for hours and was hoping maybe someone could provide some insight. Possibly just a starting point and then I could start designing my supply.


texts: How to get a PIC32 SPI port working for transmitting data?

texts:
I am looking to get a SPI serial port running on a PIC32 (PIC32MX360F). can anyone point me to some good resources on how to do this so that a newbie can figure it out? I am using the PIC32 starter kit and have a PIC32 breakout board from Digi-Key.

This is the code that I have been using... I found it in the PIC32 family manual.

#include <p32xxxx.h>
   int main(void){
        int rData;
        IEC0CLR=0x03800000; // disable all interrupts
        SPI1CON = 0; // Stops and resets the SPI1.
        rData=SPI1BUF; // clears the receive buffer
        IFS0CLR=0x03800000; // clear any existing event
        IPC5CLR=0x1f000000; // clear the priority
        IPC5SET=0x0d000000; // Set IPL=3, Subpriority 1
        IEC0SET=0x03800000; // Enable RX, TX and Error interrupts
        SPI1BRG=207; // use FPB/4 clock frequency
        SPI1STATCLR=0x40; // clear the Overflow
        SPI1CON=0x8220; // SPI ON, 8 bits transfer, SMP=1, Master mode
        // from now on, the device is ready to transmit and receive data
        SPI1BUF='A'; // transmit an A character

        while(1){
            SPI1BUF= 'A'; // transmit an A character
            while(i < 10000){i++;}
            i = 0;
        }
}

How do I set the baudrate? I am guessing it got something to do with SPI1BRG

EDIT:

Thanks to tcrosley I feel that I am getting closer to being able to communicate with my pic32. I changed SPI1BRG to 207. By my calculations this will set the baudrate to around 9600.

Fsck = Fpb/(2(SPIxBRG +1)) = 4MHZ/(2*(207+1))= 9615

I am trying to view the output on the picchip with HyperTerminal. The settings I am using are:

Baud: 9600
Data bits: 8
Parity: None
Stop bits: 1
Flow Control: None

The pins I am using are:

93 - connected to db9 3
95 - connected to db9 2

and db9 5 is connected to the boards ground...

I am now getting an output, which is nice, but unfortunately it is garbage. my output on HyperTerminal comes out as a bunch of hearts :S now I just feel like my pic32 is mocking me


texts: How do modern displays output data to pixels?

texts: Do new displays still write pixels one at a time? I thought this was the case until I saw a video showing slo-mo footage of a display, in which it was clear that all of the pixels are on at the same time. If data is updated one pixel at a time, how are the voltage signals saved in order to maintain the correct color in each pixel? My initial thought was that the color data is stored in binary for each pixel, and digital-to-analog converters are used to convert the data into analog voltage to regulate the colors. However, this seems like a very costly method considering the massive number of pixels in modern displays.


texts:
Im prepparing my 1st pcb for manufacturing, and before i generate the gerbers i wanted to ask some things here fist,

What happens when i put a silk screen like this? a logo big enough to cover the solder joints will it actually cover them or it will the clads survive?


texts:
i was studying SSB demodulation and learned that a local carrier is added to the SSB signal to make sure that envelope detection is possible. I came across a problem to find the percentage of power saved in this type of modulation if the modulation index is .5.

I tried to derive the expression, % saving = (Useful power ) / Total power

However i am not able to reach the final expression given in the answer. Please help !


texts: What makes an active probe so expensive?

texts:
This question probably has a similar answer to Why are digital oscilloscopes still so expensive?. But why are active oscilloscope probes so expensive? I mean, they're hundreds, if not thousands of dollars. Even used ones on eBay. I even saw a used broken one on eBay for $139.

I guess the answer must be something to do with low volume and calibration process, but still ... so expensive.


texts: Program LPC1343 thru USB bootloader with the right FILE format

texts:
I'm having a real hardtime programming my LPC1343 with the method mentioned in this question (Can an LPC1343 accept its initial program over USB?).

I am using a Linux machine and arm-none-eabi-gcc. I sucessfully compiled my code to blink a led, and then I get my .elf file and use arm-none-eabi-objcopy to convert it to the final format. Then I get that file in a USB stick and into a windows machine, and there I copy it to my LPC1343 thru the USB interface.

My problem is that after I turn off the chip and go into run mode it automatically goes again back into USB bootloader mode, meaning it didn't recognise the file. I have tried the following formats:

elf32-littlearm
elf32-bigarm
elf32-little
elf32-big
plugin
srec
symbolsrec
verilog
tekhex
binary
ihex.

Has anyone successfuly preogramed this chip thru USB? If so, what file format was used?


texts: Battery Monitoring using voltage divider on ADC pin with STM32F030

texts:
Here i am new to  battery voltage monitoring using ADC for STM32F030.

i have some query related to battery monitoring  with ADC pin.

1) as mention in datasheet external input impedance(Rain) is 50k, how can i achieve matching impedance using voltage divider with minimum current drain.

2) how to calculate ADC Clock frequency for this STM32F030.

3) how capacitor help in matching impedance.

4) what value of resistor in divider should i have to select for matching impedance.

any document related to calculation of impedance matching than please share.


texts: Can I use SSR to replace the contactor for a water pump? So that one hour works and one hour is off. Does this work damages SSR?(for example pool purification pump)


texts: How could a rechargeable battery charge itself without an external source?

texts:
While I was working on my graduation project I had  to charge a rechargeable battery then discharge it and so on.I was shocked when the battery charged itself without any other external sources for many times immediately when it died!
Any explanations please ?


texts: How to connect a load to an amplifier without a loss in gain?

texts:
I have this circuit below, that represents a common emitter amplifier:

When connecting a load of 10 ohms to the collector node and a signal to the base node there is a huge loss in the gain of the circuit. My question is how can i design a way to make the gain at least 3 with a load of 10 ohms.


texts: Multi-Cell Lithium battery balancing circuit explanation

texts:
I found a great application note on building a multi-cell lithium battery charger with cell balancing.

http://www.cypress.com/file/70891/download

The great thing about this one is that you implement the charging algorithms yourself on an on-board MCU. If you already have an MCU and knowledge of the charging sequences of lithium batteries, this can be a cheaper option than buying a  standalone chip that does the algorithms for you.

I understand the functionality of the circuit and what it's doing. But I had a question about a part of the circuit. Specifically the balancing MOSFETs and how they are driven.

Given the below schematic:

See that Q4-Q7 are the balancing FETs that turn on to discharge a cell that is out of balance.

These FETS are driven by a GPIO pin on the MCU with a PWM signal. The app note says the following:

"The cell-balancing MOSFETS Q4-Q7 should be controlled
at appropriate levels. One possible way to do this is to
create a count level translator using a PWM signal
coupled with AC. The rectification of the translator forms
the DC level to turn on the corresponding transistor. This
design uses one pulse width modulator, PWM_BAL.
PWM_BAL has been placed in DCB12 and output to the
demultiplexer, which is built around software-configurable
global output buffers. PWM_BAL is configured in the
software as a 4-bit PWM with a switching frequency near
115 kHz. When a MOSFET is turned on, the internal
output buffer is enabled, passing the PWM signal to the
rectifier. The diode networks D7-D8 are used for PWM
signal rectification with amplitude doubling. The rectifiers’
low-pass filters consist of resistors R10, R14, R18, and
R24 along with the MOSFET gate-channel capacitance. "

I don't quite understand this part of the circuit. The PWM signal is rectified and filtered via the 1Meg resistor and the MOSFETs gate capacitance. I would love to simulate this in TINA spice.

The FET they have is the BS170FTA and has the following gate threshold:

You need 3V just to get 1mA of drain current. We want closer to 35mA to load the cell to drop it's voltage for balancing. So if the GPIO outputs a 3.3V PWM signal, it has to drive the gate much higher to get the 35mA of drain current. Unfortunately the datasheet does not have a VGS ID curve in it.

Would someone be able to explain how this little circuit works? I need this understanding to design my own and choose the proper components. Since it seems like the parasitics of the components are playing a key role here.

Below is a zoomed in picture of the circuit of interest.

Thanks for the help.


texts:
I have implemented a simple adder component with two inputs and one output.

port ( A,B :  in std_logic_vector(31 downto 0);
       R   : out std_logic_vector(31 downto 0)
     );

I created a test bench in order to test this component. Then I modified this test bench in order to read the inputs from a text file and in order to write the results to a text file. Currently inputs must be binary strings; similarly, the output is written as a binary string.

Now I would improve this test bench in order to read inputs as integer value from text file. I was able to make this change successfully. But I would also like the output to be written as an integer: in this case, the compiler reports an error on a line of the following source code.

architecture tb4 of tb4_AdderBehav is
  component AdderBehav is
    port ( A,B :  in std_logic_vector(31 downto 0);
           R   : out std_logic_vector(31 downto 0)
       );
  end component;

  signal A,B : std_logic_vector(31 downto 0);
  signal R   : std_logic_vector(31 downto 0);

begin
  dut: AdderBehav port map (A,B,R);

  process
    variable tbInputs, tbOutput : line;
    variable va, vb, vr : integer;
    file data_file : text;
    file result_file : text;

  begin
    file_open(data_file,"dati_int.txt",READ_MODE);
    file_open(result_file,"risultati_int.txt",WRITE_MODE);

    while not endfile(data_file) loop
      readline(data_file,tbInputs); read(tbInputs,va); read(tbInputs,vb);
      A <= conv_std_logic_vector(va, A'length);
      B <= conv_std_logic_vector(vb, B'length);
      wait for 10 ns;
      --vr := conv_integer(R);   -- ERROR: No feasible entries for subprogram "CONV_INTEGER"
      --write(tbOutput,vr);
      write(tbOutput,R);
      writeline(result_file,tbOutput);
    end loop;

    file_close(data_file);
    file_close(result_file);
    wait;
  end process;

end tb4;

Why does the error occur in the source code shown above?
In the source code I have included the following libraries:

ieee.std_logic_1164.all;
ieee.std_logic_textio.all;
ieee.std_logic_arith.all;
ieee.numeric_std.all;
std.textio.all;


texts:
I need to design a component and choose on which FPGA i will implement it.

One module of the FPGA will be synchronous of a signal TXCLK that is generated by an external component the LM98640 and the frequency of TXCLK is about 640 MHz.

I've read the datasheets but i'm not sure which parameter i should check to be sure that the FPGA can work with signals as fast a 640 Mhz

I'm aware that the way i design it will affect the maximum operating frequency, but i'm looking for the values for each FPGA in case the design is really simple of maximum frequency.

I'm confused between Digital Frequency Synthesizer (DFS) or Delay-Locked Loop (DLL) or GTP transceiver clock ?

Thank you


texts:
I'm fairly new to embedded developping and I'm trying to read and write to a 1-wire device (DS18B20) using USART.
After digging around I found two alternatives:

Connecting USART RX and TX pins with MOSFETS and resistors (which to me is a bit complicated)

Using USART's single wire half duplex mode.

My Question is:
I wanted to know if single wire mode does this internally or do I still have to do it.


texts:
I am trying to develop an ARM development board using ATSAM3U4C with a 96 MHz clock, a few LEDs and a button for external interrupt. Shown below is a little circuit that I have put in place. Using Atmel SAM-ICE 20 pin JTAG connector as the debugger and using Atmel Studio 6.0 for programming. For JTAG connection, pin 3 on 20 pin socket connects to NRST and pin 15 connects to NRSTB.

So far I got the LEDs to blink but I have a few questions:

The debugger does not seem to erase the chip when loading the program. I can run the program once but then to run the program again, I have to use one of the buttons to drive the Erase Pin high (using U5 for now).
I noticed that my 96 MHz crystal oscillator is not actually being used by the ARM processor. Have I wired it incorrectly?

These are the only two issues I am facing right now. I have been using 8-bit microcontrollers and thought this would be a good learning to design my own board and learn to program on it.


texts: What is the connector for bare wires that locks the wire with an orange button?

texts:
I've seen this type of connector on garage door openers and other consumer equipment. It has holes for the stripped wire end, and an orange button that can be pressed with a screwdriver to open the contacts in the hole. The wire is inserted, and when the pressure on the orange tab is released, the contacts in the hole close to hold the wire securely.
What is the name / manufacturer / brand of this type of connector?


texts: Possible to read voltages with a DMM that's coming from an unpowered microphone?

texts: I have an Aneng 8008 auto-ranging "true RMS" DMM with an AC mode that can measure mV. I have an unpowered lavalier microphone but when I put the probes on the ground and right or left contacts of the TRS plug, I have a voltage reading of 0.000 mV when I speak into the mic. Any idea what's going on? Or is it just impossible to directly test a microphone with a simple DMM?


texts:
Would there be any potential problems with the below implementation of a rudimentary li-ion balancing/(overcharge protection) circuit?
Would a resistor need to be in series with the zeners?

simulate this circuit – Schematic created using CircuitLab


texts:
As far as I know there are two major buses - AMBA/AXI and Wishbone. While AMBA/AXI has proven itself in almost every ARM chip, I didn't find some numbers for Wishbone. Are there any benchmarks or real (ASIC) implementations of Wishbone?

Bus requirements:
- patent/license free;
- can connect endpoints with arbitrary bit sizes (e.g. 64 bit to 32 bit);
- fast (can be used to interface ddr3 controller)


texts: In my research I have found that 3 phase AC motor torque ratings are for continuous torque, but that the torque rating can be exceeded for brief periods of time.  Does anyone know how to calculate the amount of time a motor can run above its max torque rating? Thanks!


texts: Want to make Boss RC-505 mobile with batteries, do I need a choke?

texts:
My Boss RC-505 Loopstation is a greaat bit of kit, but I'd like to make it more mobile (already done the 12v battery -> inverter -> 240 boss adapter -> loopstation) but it seems a little OTT when the input on the boss is only 9v @0.5A, never mind the form factor!

On the stock Boss power adapter they've fitted (near the connector to the boss) a dual coil choke - I assume to cut out interference from AC -> DC conversion from messing with the audio mixed with the loopstation - but do I need the choke if I'm planning to power with battery?

Also, any tips on battery or issues I might face would be appreciated :)


texts: Latching power circuit with short-to-ground switch

texts:
I'm trying to build a circuit around an existing switch that allows another component to override the switch state. (Our component is a computer and the feature we're trying to build is remote-activation).

I want the "ON/OFF" state to reflect the last thing to toggle the state. (i.e. If the switch is "on", our component can logically turn it off. If the switch is toggled off, nothing happens, then if the switch is toggled back on it turns on).

I control both sides of the switch and I have two "short to ground" switches (controlled by our component).

I don't want to depend on either of the two switches being held closed for ON mode (i.e. The short to ground switches should work like push button switches). This is so that software failures/resets on our component won't accidentally set the mode to OFF.

I'm pretty sure I can do this with some mosfet latching circuits but I'm quite novice at electronic design. Any suggestions are appreciated!

Edit: here's some more clarifying info:

Here's a state diagram of what I want.  Both B.1 and B.2 should only even be pulsed closed, so they can't be counted on to be held closed to achieve a desired state.  Notably, the desired behavior is edge-triggered by the switch state.


texts: Power transmission/AC or DC/Cable cross section/Converters

texts:
I have unusual project. I want to optimize mass.
Here are strict questions (topics) I would like to get answers to. Any help would be appreciated (direct answer or link).

I would like to deliver about 1300W in about 100m distance.
All I care is to deliver this power and have smallest possible mass of cable and converter.
I would like my system (converter at the end and whole cable) to weight about 2kg at most.

At the end I would like to use 24V DC.
I wonder about:

What cable should I use? What can be the smallest cross section?
At which Voltage should I transmit this power?
Should it be AC or DC transmission?
What will be estimated size of the final converter (I need 24V DC at the end).

Any help would be appreciated.


texts:
Variable capacitors are used in tuning many circuits of radios. I read the theory of basic tuning and resonance frequency. What I understand by changing the capacitor we change the resonance frequency of the radio tuner and select a particular frequency. My question is:

1) What is selected here? Carrier frequency or signal e.g audio frequency? They have totally different frequency bands. If carrier wave is selected, why the modulated lower freq. audio also pass through the circuit. Isn't it contradicting to the theory?

2) If one tunes a receiver circuit to a frequency how can a band of frequencies like audio signals pass through. I mean tuning seems to let pass only 1 particular frequency not a band.

I'm afraid I lost the route at points when trying to understand and confused.


texts: Is it possible to find through-hole, edge connector fingers?

texts:
I would like to do a bit of prototyping and have been wanting to leverage edge connectors as it would make my layout a whole lot easier.  When using these, are you forced to get some kind of prototyping board that has built in fingers like this:

Do they sell stand-alone, through-hole fingers that can be added to a pre-existing prototyping board?  Maybe the connector and plug as a bundle?  I'm looking for something very specific... ~60pin, through-hole, ideally wire-wrap.

On a side note, if anyone knows where to even get the boards with built-in edge connectors that would be great too.  I can't really find any but that's probably because I don't know the proper search terms.


texts: Design a 3-to-8 Decoder Using Only Three 2-to-4 Decoders

texts:
Using only three 2-to-4 decoders with enable and no other additional gates, implement a 3-to-8 decoder with enable. The inputs of the resulting 3-to-8 decoder should be labeled X[2..0] for the code input and E for the enable input. the outputs should be labeled Y[7..0].

Here's my current solution. My question is, is there a better/cleaner way to do this?


texts:
I want to build a NiMH battery charger using an LTC4010. The datasheet doesn't give any hints on how to choose the two FETs.
Here is what I think is important - please correct me if wrong:

R_DS(on) should be low to limit losses while the FET is conducting.
Q_g should be low to allow for faster switching, to limit switching losses.
V_GS must be lower than the drive voltage of the controller
V_DS must be higher than the input/output voltage
I guess Input Capacitance should also be low?
The Continuous Drain Current should be high enough

Any other parameters to watch out for?
To provide an example: My charger will have a 18V power supply and charge 8 cells in series with about 2A. I did a search on DigiKey and looked out for FETs that I thought fit the above criteria and found that the TSM8568CS stood out because Qg and R_DS(on) both were low. Would this FET-pair be a good fit for my application?
Low power/heat dissipation is higher on my priority list than saving a few cents on the FETs.


texts: Why does the frequency increase once the Gunn oscillator is disconnected from the power supply? Is it because more and more electrons move to the lower valley, where their mobility decreases?


texts: How to choose which function to use depending on the parameter value? (MUX and Gates implementation)

texts:
Let's say we have A,B,C , which are all representation of decimal numbers. A and C are 4bit, B is 2bit.

if A is any of those numbers (eg: 0,5,6,11 ), the function is

  F(A,B,C) = AB+C

If A is the rest of the numbers , the function is :

  F(A,B,C) = B+C

We can use 2x1 MUX, 2input logic gates (both as much as needed), and of course FA .

I tried to treat the numbers as minterms, and use K-map for A3A2A1A0. Where is the 2to1 MUX involved? How exactly should I choose how to operate based on the value of the numbers?

I don't have issues as to how to implement/use the adder (for additions and/or multiplications).I don't need any answer there/  I have troubles understanding :

How to treat the actual numbers (as minterms?)
Because in the second function, basically the A is missing, and it is an actual multiplication, is it wise to treat it as 1? . B+C is still 1B+C in mathematics. Right?
Should I  represent every number with gates from scratch, no K-Map needed? What about the MUX?
Since I will need each bit separately ,as an input to the adder, then, should I , somehow, implement the 2to1 MUX to each specific bit?


texts: Why conductivity increases in semiconductor when doped?

texts: I know it depends upon the concentration of electrons and holes . So if we add donor atoms, even though electron concentration in conduction band increases , hole concentration decreases due to more recombination such that np=ni^2. Why do we say that conductivity increases?


texts: Do engineers still design for volume using discrete through-hole bipolar transistors?

texts:
As a hobbyist who likes plugging BJTs and discrete components into solderless breadboard for entertainment and education, I recognise that people like me are an insufficient market to make it worthwhile for manufacturers to continue production.

I've noticed that on this website a lot of questions about BJTs are answered with recommendations to use a purpose specific IC or a PIC instead.

I also enjoyed reading
555 best IC ever or obsolete anachronism

I note 555s and through-hole BJTs are available and pushed by hobbyist shops online.

I have some cheap solar powered LED lamps to mark the edge of a path, recently one was broken so I opened it up and found this board with three through-hole BJTs and a bunch of other discrete through-hole components on a single-layer board.

So why do some large-volume manufacturers still use this sort of technology?

The only reasons I can come up with are

Its a really old design and not worth redesigning?
The educational market is bigger than I imagine?
Maybe old BJT production machinery can be shipped to low-wage economies and kept
running for years at minimal cost?
Wages are still low enough in China to sustain this kind of technology?
There are a lot of old engineers around leveraging accumulated wisdom with 555s & BJTs?
Discrete through-hole BJTs are still the best solution for something (what?)

Do engineers still design for volume production using through-hole BJTs?


texts: Soft start circuit design for audio amplifier

texts:
I have a 100W D class amplifier that runs on 24V. It uses 2 x TPA3116D2 IC for amplification. I also have a 24V 16A power supply. I need to provide a soft start circuit for this, because the amplifier is not protected from pops and clicks. I came up with the circuit below. It uses parts that I already have at hand. I ran a simulation and it seems to be right, but I have doubts.
I was not working with electronics in the last 6 months, and I'm not too familiar with analog circuits. I wanted to get an opinion before I built this circuit. I don't need a complete analysis, just a quick look. Does it have some obvious design flow? Is there anything that must be changed in order to work?
Thanks
ADD: One answer suggested modifying the amp instead of the power supply circuit. The amp is commercial product. I do not want to make any modifications to it."

simulate this circuit – Schematic created using CircuitLab


texts: Arduino logging vertical acceleration data

texts:
I'm doing a project where I want to start and stop recording of accelerometer data set up to measure the vertical acceleration Z axis of a car's suspension movement when it hits a pothole. I want to be able to do FFT on the accelerometer data and try to find a "pattern" that represents a pothole event so I can detect potholes from other events just as car door slamming shut, etc...

My question is I'm not sure what sampling rate I would need to be sampling to get the SHM of the suspension when it hits the pothole. Right now I just have my accelerometer a KXPS5-3157 in analog mode connected to my Arduino and I have a button that you hold in to have it log data, when you let go of the button it will stop logging and start a new session. I do this so I can press and hold the button right before I drive over a pothole to get the data.

Should I use Timer1 for example? I think I would need accurate timing with the acceleration data to make it meaingful?  Since Acceleration is with time, I'm not sure what sampling rate or how to make the Arduino do like 1 sample/sec or 10 samples/sec. It seems like the frequency of the pothole with the suspension operations in the 5 to 10HZ range of mechanical motion. Rarely anything after 13HZ dies out fast below 3dB so it can be ignored.

Any idea on how to detect pothole events? Not even sure FFT would be the right direction. I want to plot the data from the serial port, but plotting it right now I just have acceleration with no time reference???? I think I need a time reference with the data


texts:
I'm pretty new to this SMT stuff, and I'm looking at resistor arrays.

From what I can see on my main supplier's website (RS) most of the SMT arrays are of a package type '1206'.

Now, my PCB layout package (gEDA PCB, yes, I use Linux) has a footprint for 1206, but it seems to only be a single pair of pads and not the 8 pads that the arrays would need.

Do you think this is an error in the PCB package, or is the 1206 'package' just \$\frac{1}{4}\$ of the actual package and I'd need to place 4 footprints at the right spacing?

Specifically this is the product I am looking at: http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=4351807


texts:
I need to generate 500Hz from 50MHz clock frequency. I already got it. My problem here is how should the code to be adjusted if I want to change the duty cycle to 10%?

Thank you.

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;

entity FreqDivider500Hz is
port(
    clock   : in STD_LOGIC; -- 50 Mhz
    clear   : in STD_LOGIC;
      freq1 : out STD_LOGIC
);
end FreqDivider500Hz;

architecture Behavioral of FreqDivider500Hz is
signal adjfreq: STD_LOGIC_VECTOR(15 downto 0) := "0000000000000000";
signal adjclock : std_logic := '0';

begin

freq1 <= adjclock;

countClock: process(clock,clear)
begin
    if (clear = '1') then
        adjfreq <= "0000000000000000";
    elsif(clock'event and clock = '1') then
        -- Flip a the output once every 50,000 cycles (1kHz)
        -- to give a 500Hz output with 50% duty cycle
        if (adjfreq = "1100001101010000") then
            adjfreq <= "0000000000000000";
                if adjclock <= '0' then
                adjclock <= '1';
                else adjclock <= '0';
                end if;
            else
            adjfreq <= adjfreq+1;
        end if;
    end if;
end process;
end Behavioral;


texts:
I'm building a project where I use an ESP8266 module to control a LED with my smartphone. For my project I want to battery power the ESP8266 and the LED so I'm using two Lithium Ion batteries. I've designed a circuit which works but I was wondering if there are more efficient ways of powering this circuit because I'm currently using a step down module in my circuit to power the ESP8266. Everything works perfectly but I don't think I've come up with the best circuit for this project

I know the driving circuit part for the LED is not the most efficient but I've already asked a question about that on this forum to help me fix that. The problem I have now is that I'm wondering if there's a need for a step down module to power both the LED ( LED is a 3 watt power LED) and the ESP8266. Are there any alternatives to this circuit that are more efficient? Is the step down module necessary?

P.S. I apologize for my drawing skills I'm not an electrical engineer so I'm not used to using the right symbols for everything


texts:
I'm new to electronics in general so please don't assume any prior knowledge. I'm developing a control board and I've already had the first revision manufactured. Everything worked as expected with the exception that I had crosstalk from my SCK line to my MISO line on 5 boards out of 5 which was severe enough to ruin the SPI communication. Just for the record, I've successfully set up various configurations of these units on a breadboard, but with fewer components.
The setup is the following (only including SPI-relevant components):

4 layer board (mixed, GND, power (3.3V), mixed)
8 MAX31865 RTD amplifiers (https://datasheets.maximintegrated.com/en/ds/MAX31865.pdf)
4 (Pololu break-out) AMIS-30543 Step motor drivers (https://www.pololu.com/file/0J869/AMIS-30543-D.pdf)
1 piezo driver (https://www.cedrat-technologies.com/fileadmin/user_upload/CTEC/Mechatronic_products/User_s_manual/user_manual_cau10.pdf)
Teensy 4.1
Target clock rate is 1 MHz
There's no other digital communication on the PCB

The first design had terrible routing where I had done the following:

Star topology
All SPI traces very close in parallel at the limit of the manufacturing house specifications
Excess of vias since I routed the SPI last, instead of in the beginning
Although catastrophic layout, the rise time for the SCK was <2 ns.

In this second revision I'm starting fresh and I've done the following:

Routing the SPI first
Serial topology (that's what it's called, right?)
Track width: 5 mils
Min SPI track spacing: 10 mils (ca. 15 mils most of the board)
Going for a higher-end manufacturing house than last time
No vias for SCK line, attempting to minimize vias for MOSI and MISO (this is my issue)
The tracks are ca. 15 inch (380 mm) each

Now for my questions:

I still feel that my routing looks very beginner-like and with more vias than necessary. Do you have any suggestions?
I'm only putting traces on layer 1 and 4, should I consider routing some SPI traces on for example the power layer by clearing out some area? By using long traces in parallel on both L1 and L4, it'll be difficult to cross the path with all the other remaining traces.
Should I worry about any termination in this case?
I've got plenty of Tee-crossings, how does one avoid those 90 degree angles?
Any other tips that could be useful for this project or future ones?

Due to other design considerations, I cannot move the components closer together unfortunately.

This is my first post, so I hope I've included everything that's relevant.
Thanks.
EDIT:
Thanks for the questions so far.
There are 10k pull-up resistors on the CS close to the ICs; on the PCB or on the the break-out boards. No other pull-up, pull-down or series resistors.
I just went to get some additional measurements for this thread, but now I'm more confused than before. I'm not able to catch any measurements using the Arduino SPI functions as it instantly freezes when connected to any of the PCBs. I made these measurements with no SPI-related components soldered/connected to the board. Below are two sets of measurements using DigitalWrite() on the SCK pin, or AnalogWrite(). I notice that AnalogWrite has good signal integrity while the DigitalWrite looks horrible.
Here's a few photos of the scope...
SCK pin with AnalogWrite(SCK_Pin, 1)

MISO pin with AnalogWrite(SCK_Pin, 1)

SCK pin with DigitalWrite, high for 1 us, low for 10 us.

Now, what I find really weird is that even when the Teensy is unplugged from the PCB, the signal integrity is really poor using DigitalWrite as compared to AnalogWrite. The PWM frequency for that particular pin on the Teensy is 3.611 kHz by the way.
DigitalWrite() with Teensy off-board


texts: Extracting images from a camera in real-time

texts:
Me and a group of students are building a UAV and we want to put a high quality camera in it (i.e. a decent ~100mm zoom lens) and interface the imagery with on board processing. I have looked around for a camera that can interface over USB, or any other connection that is compatible with either a Pandaboard or a DE0, but I have not been able to find any that meet the specifications (without being much too expensive).

We have a Casio Exilim EX-Z1050 that has a crack in the screen, and thus perfect for integrating with the UAV. The question is, what is the best way to get either video or at least 2 stills per second out of it in real-time?

I was thinking of using something like this to grab either video or stills as they are being recorded onto an SD card. What is the feasibility of using perhaps an FPGA to perform this? If someone knows where I can find a spec for the SD protocol (the 1/4 bit one, not the slow SPI one), or perhaps a useful enough reverse-engineered spec, a link would be very useful.

Any other ideas?

Many thanks!


texts: For the network shown in the figure, draw the corresponding Thévenin equivalent circuit and establish its parameters VT and RT

texts:
I can't find any examples online similar to this format, please help!
Attempt: RT = (2*5)/(2+5) = 10/7 = 1.429 k-ohms
VT = 8V + 8V = 16 V
Do you ignore the center resistor and just add the voltages together?


texts: Voltage Regulator drawing 0.5A with no load connected

texts:
I recently bought an AUK S1117-33PI 3.3V voltage regulator. Unfortunately, I don't have a proper bench top power supply, so i used a basic travel adapter ,whose output is 5V - 1A, just to test the voltage regulator out. The voltage regulator gave a perfect 3.3V out but it got really hot after keeping it on for about 20 - 25 seconds. I later checked the current draw from the travel adapter and found that the voltage regulator was consuming a constant 0.5A with no load attached.

It might as well obviously occur to most of you guys that the chip is probably a bad one but i want to take my chances and find out any other wild guesses.

Thanks in advance...


texts:
I am currently struggeling with the following problem. I need to find an amplifier circuit which implements the following equation:

$$
U_a=U_1+2U_2-2U_3
$$

I decided to go with the circuit shown below. I calculated the following equation for the output:

$$
U_a=-\frac{R_F}{R_3}U_3+\frac{R_1 || R_4}{R_2+R_1||R_4}\frac{R_F+R_3}{R_3}U_2+\frac{R_2 || R_4}{R_1+R_2||R_4}\frac{R_F+R_3}{R_3}U_1
$$

Now I can formulate all the conditions necessary in order for the equations to fit.

$$
I: \frac{R_F}{R_3}=2 \\
II: \frac{R_1 || R_4}{R_2+R_1||R_4}\frac{R_F+R_3}{R_3}=3\frac{R_1 || R_4}{R_2+R_1||R_4}=2\\
III: 3\frac{R_2 || R_4}{R_1+R_2||R_4}=1
$$
From the conditions I tried to calculate specific values for the resistors, starting with the 2nd condition.

$$
II: R_2=\frac{R_1||R_4}{2}\\
R_2R_1+R_2R_4=\frac{R_1R_4}{2}\\
R_1=\frac{R_2R_4}{\frac{R_4}{2}-R_2}
$$

This result I plugged into a condition following from III.

$$
III: R_1=2(R_2||R_4)\\
\frac{R_2R_4}{\frac{R_4}{2}-R_2}=\frac{2R_2R_4}{R_2+R_4} \\
\frac{1}{\frac{R_4}{2}-R_2}=\frac{2}{R_2+R_4}\\
R_2+R_4=R_4-2R_2 \\
3R_2=0
$$

Well ... crap, R2 is supposed to be 0, so would be R1. And the value for R4 does not matter? I guess I did something wrong but I cannot figure out what. What is wrong with my calculation? Is it possible to implement the given equation with the circuit I drew?

EDIT: I forgot to mention that it is only allowed to use one op-amp.


texts: I am trying to wire a 2 bit adder and a Multiplier on my breadboard. I have the 2 bit adder somewhat done, but dont know where to start on the multiplier. I need help reading circuits and translating them to the breadboard. My main issue is figuring out where the outputs and inputs go. I know the in and outs are at pin 3, 6, 8, and 11 on the 7408 chip, but i just feel im doing it wrong. Help!


texts: How to remove an unused net class that eagle thinks is in use

texts:
I'm currently doing a very complex circuit board in eagle.

Currently I defined 7 classes of which 6 I am using. the seventh I want to delete since I no longer need it.

First I tried the command "class -n" to delete the class where n is the class number I want removed, and I got the error "Net class n is in use"

Then I did some research at: https://www.element14.com/community/thread/47449/l/highlighting-nets-and-colours-for-net-class-es?displayFullThread=true

So I am in my board, executed the cmd-change-class.ulp script, then I put in the correct values for the options:

I specified for current class in board the one I want to remove

I specified "default" for the "change class to" field

I specified mm for grid since that's what I am working with

Then when I clicked OK, the box simply disappeared and I got no indication as to whether the operation was successful or not.

So then I tried again to remove the same net class again as before and I still get the same error: "Net class n is in use"

Rather than highlighting the entire circuit and changing the class to one class (and wrecking my class settings for other nets), what is a simple solution to this problem?


texts:
I have an issue with my binary up-counter using a 74LS74AN D-Flip Flop
The issue is the following:
I am trying to toggle the flipflop state by sending it a 1Hz Square wave (5V Peak) to make it toggle every clock cycle (Rising Edge triggered)
This is the schematic I came up:

And this is the datasheet:
https://pdf1.alldatasheet.com/datasheet-pdf/view/12660/ONSEMI/SN74LS74AN.html

For some reason the flipFlop will not toggle when the LED is connected. I have measured at the D-Pin with the LED connected and it reads 3.3V roughly. Which is expected when the 74LS74AN Outputs at 3.5V. According to the datasheet High Level is 2V.
I already tried out another chip. I got the same issue there.

My idea is:
!Q Starts out HIGH, so when the CLK goes HIGH the FlipFlop will latch HIGH, so !Q will go LOW. On the next clock cycle the FlipFlop will latch LOW so !Q goes HIGH again.


texts: Why does a permanent, non-moving magnet, stuck to a long piece of metal generate a voltage?

texts:
I was just messing around with a very small permanent magnet (round) stuck to a piece of metal.

The magnet is round, ~6 mm in diameter. I guess 1 mm thick. (I lack precision tools where I am at the moment)
The metal is about 5.5 cm long, 0.5 cm wide and almost exactly half as thick as the magnet.

I detected a bit of a sting from it (don't ask me how), so I went to check it with a voltage meter.

There's a very noticeable jump to ~0.6 V, declining very slowly. After I take the voltage meter off, wait a few seconds, and then re-attach it, it has jumped up to 0.6 V again.

What makes this happen? Am I just very stupid and missing some obvious thing here?

This is my setup (sorry for blurriness, seriously bad lighting):

The "metal strip" is a tool from an old lock-picking set. The black plastic is the handle.

After making these pictures, it's now counting up. Over 0.54 V now.
(Update after 3 minutes: It's going down again, no sign of stopping)

(Update)
I now notice that when I pour water over the part where the probe, the magnet and the metal strip collide, the voltage climbs up again, and after reaching a peak, slowly starts falling again.

(Update on setup with multimeter)
As a user in the answers pointed out, my multimeter setup is incorrect. The plugs are plugged in wrong, causing one of the leads to float.
I now plugged them in correctly, and it shows the same, if not higher voltage.


texts: Switch in parallel to a hvdc load. Fail or success?

texts:
Suppose I have 600v dc as my power source to a motor. And I have a isolation relay in parallel with the motor. The motor runs when the switch is open. What happens when the switch is closed?

Would something burnout?
Or would this switching operation work just fine?


texts: How to choose trace width for very high current PCB?

texts:
I am currently designing a PCB layout for my team's high current, high voltage project and am having trouble with choosing my trace width.

The circuit is composed of 12 inductors placed in series with short traces connecting them together (about 5mm max length).
We are feeding 10μs pulses at ~300A/1000V at a maximum rate of 10 pulses per second by discharching capacitor banks into the coils. The capacitors are recharged by an external source.

I have looked for resources on the subject, but nothing I could find applies to the level of current and voltage we are applying.

Is there a rule for determining trace width for very high current pulses?


texts:
I have tried to search through existing questions to find an answer to my question, but so far have had no luck. I apologize (and feel free to flag) if this is a dupe.

I am working on repairing an arcade monitor, and I think that one of the transistors on the neck board is bad. I have removed the transistor, and am trying to test it with my multimeter. The transistor is a C3229, and the datasheet is here: http://www.datasheetcafe.com/c3229-datasheet-transistor/

According to the datasheet, it is an NPN transistor and the pins are (1)Base, (2)Collector, (3)Emitter. I am trying to determine if this transistor is bad, but I'm getting confused. Here are the readings I get in diode mode:

(+)->(-)
B->C: 0.647V
B->E: 0.666V

and in ohms mode (20M):

(+)->(-)
B->C: 13.05M
B->E: ----

ohms mode (200M):

(+)->(-)
B->C: 1.1M
B->E: 1.2M

And I do not get any readings if I reverse the probes. I had assumed that this transistor was bad, but it is possible that it was just a loose solder joint. Is it possible to tell from my readings whether the transistor is bad, or is there something else I can test to find out if it is bad? Also, is there a good place to find new transistors? My searching thus far has turned up a few sites that look promising, but none that carry this particular transistor so far.

EDIT

I tested a couple other of the same transistor which I am pretty sure are not bad, and got very similar readings. I will assume that the problem was not the transistor.


texts: How can I make this Component Tester more accurate?

texts:
EDIT:
In the answer by Reroute (thank you, Reroute!), he references a very active 253 page EEVblog topic -- $20 LCR ESR Transistor checker project that probably includes exactly what I am seeking.  I googled upgrade accuracy precision in the blog, and it looks like this information exists.  If any of you electrical engineers have found out an answer to this quesion because you've worked on this actual open source project, I sure would like to hear it.  Examples of found text that looks like this is a real question and answerable are below:

...the more accurate the resistor, the more accurate the calibration.

upgrade to a 0.1% voltage regulator if you want accuracy

I will accept any answer where you have specifically been active on this referenced blog, or this open source project, and tried out something and it improved the precision of any readings.
Lacking someone with actual experience with this actual (or derivative) project, I will eventually accept an answer done by research alone.

Awhile ago I purchased one of these kits and then fried it by adding one too many AA's in an attempt to replace the 9-volt so the battery would last longer:

I just bought another one because I liked it so much, and was hoping to change a voltage reference / regulator and/or change out some resistors or other components for more accurate ones.  A friend of mine told me this is an open source project, but no documentation came with this product, and I couldn't find it.  I think this is some kind of Arduino, and there is a seemingly infinite body of knowledge to search as soon as you type in "Arduino".  Does anybody know how to modify this to improve it?  In particular, I am interested in a relatively inexpensive inductance + ESR tester for my students for some classes I am planning.  I want something they can use, and I would like to give them decent quality.  (If you know something better and affordable by hobbyists/kids/students, please also let me know).  Thanks ahead of time.  Below is the circuit board itself (again, from the link given earlier):


texts: ATmega168: UART 8 data bits, no parity, 1 stop bit

texts:
According to the datasheet I'm setting the UCSR0C register as following:

UCSR0C = 0b00000110

Description:

Bit   0:   0: TX rising, RX falling
Bit 2-1:  11: character size 8 bit
Bit   3:   0: 1 stop bit
Bit 5-4:  00: no parity
Bit 7-6:  00: asynchronous USART

(http://www.atmel.com/images/doc2545.pdf page 193)

Although I configured the UART to use 8 bit data mode I have to set my communicating terminal (picocom) to use 7 bit data mode. Otherwise I don't get correct data from my ATmega168. I also tried to use minicom and miniterm.py.

My target device I want to communicate with is a Raspberry Pi. I'm using Peter Fleury's UART library (http://homepage.hispeed.ch/peterfleury/group__pfleury__uart.html).

Any ideas what I'm be doing wrong? Did I forget something?


texts:
I have noticed in many papers, publications and in general application the use of LC filter for impedance matching. I wonder why this is the case? How is it that by using an LC filter, it can be used for impedance matching? How is it that an LC filter is both a filter and an impedance match? I know these may be trivial questions, but I'm trying to explain it to myself and I can't (I also know that for example "pi filters" can be also used for impedance matching).
Example of an impedance matching configuration using an LC filter:


texts: MSP432 with temperature sensor TMP102 using I2C not working

texts:
I am trying to using MSP432 to read temperature from digital sensor TMP102 using I2C communication. The problem is, when I run debug, the first loop return correct value

but the second loop it stucks in this function:
I2C_masterSendSingleByte(EUSCI_I2C_MODULE, REG_TEMP);

Go inside this function, it stucks right in this while loop

And this is my source code.
#include <ti/devices/msp432p4xx/driverlib/driverlib.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>

#define EUSCI_I2C_MODULE                EUSCI_B1_BASE
#define EUSCI_I2C_STATUS_SLAVE_NACK     1

static const uint8_t TMP102_ADDR = 0x48;
static const uint8_t REG_TEMP = 0x00;

static void print_uart(char *msg);
static void reverse(char *str, int len);
static int intToStr(int x, char str[], int d);
static void ftoa(float n, char *res, int afterpoint);

const eUSCI_I2C_MasterConfig i2cConfig = {
EUSCI_B_I2C_CLOCKSOURCE_SMCLK,          // SMCLK Clock Source
        3000000,                                // SMCLK = 3MHz
        EUSCI_B_I2C_SET_DATA_RATE_100KBPS,    // Desired I2C Clock of 100khz
        0,                                      // No byte counter threshold
        EUSCI_B_I2C_NO_AUTO_STOP                // No Autostop
        };

const eUSCI_UART_ConfigV1 uartConfig = {
        EUSCI_A_UART_CLOCKSOURCE_SMCLK, 78, 2, 0,
        EUSCI_A_UART_NO_PARITY,
        EUSCI_A_UART_LSB_FIRST,
        EUSCI_A_UART_ONE_STOP_BIT,
        EUSCI_A_UART_MODE,
        EUSCI_A_UART_OVERSAMPLING_BAUDRATE_GENERATION,
        EUSCI_A_UART_8_BIT_LEN };

int main(void)
{
WDT_A_hold(WDT_A_BASE);

/* Selecting P1.2 and P1.3 in UART mode */
GPIO_setAsPeripheralModuleFunctionInputPin(
GPIO_PORT_P1,
                                           GPIO_PIN2 | GPIO_PIN3,
                                           GPIO_PRIMARY_MODULE_FUNCTION);

/* Setting DCO to 12MHz */
CS_setDCOCenteredFrequency(CS_DCO_FREQUENCY_12);

UART_initModule(EUSCI_A0_BASE, &uartConfig);

/* Enable UART module */
UART_enableModule(EUSCI_A0_BASE);

/* Set function i2c for port */
GPIO_setAsPeripheralModuleFunctionInputPin(GPIO_PORT_P6,
GPIO_PIN4 | GPIO_PIN5,
                                           GPIO_PRIMARY_MODULE_FUNCTION);

I2C_initMaster(EUSCI_I2C_MODULE, &i2cConfig);
I2C_setSlaveAddress(EUSCI_I2C_MODULE, TMP102_ADDR);
I2C_enableModule(EUSCI_I2C_MODULE);

print_uart("Start...\r\n");

uint8_t buf[12];
int16_t val;
float temp_c;
char str_temp[7];

while (1)
{
    if(I2C_isBusBusy(EUSCI_I2C_MODULE) == EUSCI_B_I2C_BUS_BUSY){
        print_uart("Bus busy\r\n");
    }

    I2C_masterSendSingleByte(EUSCI_I2C_MODULE, REG_TEMP);

    while (I2C_masterIsStopSent(EUSCI_I2C_MODULE)
            == EUSCI_B_I2C_SENDING_STOP)
        ;

    I2C_masterReceiveStart(EUSCI_I2C_MODULE);
    buf[0] = I2C_masterReceiveMultiByteNext(EUSCI_I2C_MODULE);
    buf[1] = I2C_masterReceiveMultiByteNext(EUSCI_I2C_MODULE);
    I2C_masterReceiveMultiByteStop(EUSCI_I2C_MODULE);

    val = ((int16_t) buf[0] << 4 | (buf[1] >> 4));
    //Convert to two complement, temp could be negative
    if (val > 0x7FF)
    {
        val |= 0xF000;
    }
    //Convert to float temperature value (C)
    temp_c = val * 0.0625;
    //Convert float to string
    ftoa(temp_c, str_temp, 5);

    print_uart(str_temp);
}
}

And this is the result in logic analyzer:

One more thing, I used 1 kOhm pull up resistor and also tried with 10 kOhm but didn't work.


texts: Using a voltage supervisor IC to protect a Li-Ion battery from undervoltage >2.8V?

texts:
Sorry if this has already been asked, I tried searching but might not have the right vocabulary.

I'm starting to use lithium-ion batteries to power projects, and I've wound up with some 18650 cells. Not wanting to use unprotected cells, I hooked them up to some common and cheap TP4056 charge/protection boards. This lets the batteries charge up to 4.2V easily, but I've read that the undervoltage protection on these boards is really more of a failsafe than a way to keep the battery healthy; it doesn't cut off until 2.5V, which I'm worried might damage the cells pretty quickly.

It looks like there are affordable over/undervoltage protection ICs for li-ion batteries, but the highest undervoltage cutoff I can find is still only 2.8V on something like TI's BQ29700.

So here's my question - if I want to err on the side of caution when draining the batteries, can I use a 'low voltage supervisor' IC hooked up to an N-ch MOSFET as a cheap/simple extra layer of protection to cutoff at something like 3-3.5V? Would I be better off just using an opamp? Is the voltage supervisor's 3uA enough to continue draining the battery appreciably?

Here's what I'm thinking of specifically - it's just a high-side N-ch switch with its gate attached to the voltage supervisor's "reset" pin, which is pulled low during undervoltage in the MIC2776L model:

And here are the non-discrete parts; I tried to pick a MOSFET with low on-resistance:

Adjustable low-voltage supervisor - MIC2776L: http://ww1.microchip.com/downloads/en/DeviceDoc/mic2776.pdf

N-Ch MOSFET - PMV20EN: https://assets.nexperia.com/documents/data-sheet/PMV20EN.pdf

Thanks! And sorry if I'm missing something, I'm pretty new to this.


texts: I took apart this old, white alarm clock and there's a small, DIP-8 IC in there with "HWCAT 714C6A CSC2822" written on it. I've tried searching for a datasheet, but I can't find one. I can find some references to the part itself (on some Chinese parts sources), but nothing about what it is or how it can be used.


texts:
I am looking for some way using discrete logic (TTL) to decrement an 8-bit value by one.

Basically I want to present it with an 8 bit bus with a binary number on it, and have it give an output of the input minus one on its output:

eg:

...I3 I2 I1 I0 | ...Q3 Q2 Q1 Q0
   0  0  0  0  |    1  1  1  1
   0  0  0  1  |    0  0  0  0
   0  0  1  0  |    0  0  0  1
   0  0  1  1  |    0  0  1  0
....
   1  1  1  1  |    1  1  1  0

I have been googling and drawn a blank for a chip that can do it, and I have been racking my brains of the best way to do it using just normal gates.

Does anyone either know of a chip for this, or have some ideas on how I could construct it from discrete gates?


texts:
I know that in single ended free running mode the following equation holds:

f_ADC = f_clk/N = 13f_s

where f_ADC is the ADC frequency, f_clk is the avr's clock frequency and f_s is the sampling rate.

The above equation means that if I want to convert an analog signal with a max frequency of 4KHz then I should choose f_s=8Khz (Nyquist theorem), and then choose N such that f_ADC >= 13fs=13*8KHz.

Now, I've read in the ATMega128 datasheet that in case of differential channels gain (eg to convert the difference of two analog signals), an internal f_ADC2 frequency is produced which is f_ADC2 = f_ADC/2 (or is it f_ADC2 = 2*f_ADC ????) but can't really figure out what happens with timings.

So the actual question is: what equation holds (like the one above) if I use differential gain channels at free running mode?


texts: How to study temperature influence on Li-Ion Batteries?

texts:
I would like to study and simulate the influence of the ambient temperature on a given Lithium Ion  Cell. Behavior while charging or discharging for both internal Resistance and capacity.
My Battery-Model is based on this paper (see also here).

The information from the Battery i want to simulate are data sheets with

Power curves (Power-SoC) for 5[s] and 30[s] for different Temperatures.

And I-V Plots for different (SoC's) for 5[s] and 30[s]. (See below)

One thing that confuses me are these measurements of 5 and 30 [s], does it refer to the time difference between each measurement?

As it's my first encounter with Batteries i'm a bit confused, so how could I use these data sheets with my model?


texts: Using a relay to turn on and off really low voltage circuit

texts:
I want to build a thermostat for my fireplace. I want to use my Arduino to turn it ON and OFF.
The fireplace has got a switcher on the wall and I have measured it and the voltage different from one side of the switch to the other side is 0,238V. It seems pretty low but that is what it is.

I bought this relay that I am going to be able to use with my Arduino.

I know relays are usually used to turn ON/OFF circuits that are running at a higher voltage. In this case, my relay will have to run a circuit that is running in a much less voltage. Will the relay do what I need it to do? or it will actually create a higher voltage in the fireplace circuit?


texts: What test points to do for a switching system measurements?

texts:
I am working on a high-performance switching system. I the old ones there was no big issue in just touching a gate with an oscilloscope probe, but this time I have high voltage and very short (5nsec) rise/fall time, so I have to think through test points.

I would go for SMA and then connect it with a coax to the scope, but I have no room for that.

So the question is, what are the recommendations for the smallest possible test points to measure fast switching power transistors behavior. Maybe some special probes can be used. What did you fellas do in the past?

Upd: due to the relatively high voltage and small size of the product, i really don't want to touch it while it is working. It has to be something that the probe is nicely attached to it. Additionally the ground of the probe should be very short, ideally it would even be a nice differential probe (although at this point i am most interested in preparing everything in layout).


texts: how to implement Atxmega256 Port external interrupt

texts:
i have Xmega25, i have to use port interrupt for eight ultrasonic echo signals, i am using ISR to start and stop the timer0 and read the timer value to determine the echo pulse width, i have to do this approach for eight echos by sequentially
my questions are :
what is the difference between interrupt0 and interrupt1 on each port?
how can i know which pin has fired the interrupt in ISR?


texts: What is needed to store readable/writable data to flash/eeprom

texts:
I am wanting to add some readable/writeable memory to my ATmega8/attiny project where I can store data, recall the stored data, then overwrite the stored data. The stored data must be able to be retrieved even after a power loss. The data types I am wanting to store are character arrays (strings) that are stored inside of a type of lookup table (kind of like a hash in which key:value pairs are used).

I know that flash memory is used (or EEPROM), but I am not exactly sure of a part number to be looking for that is compatible with a ATmega8/attiny nor which protocols/pins it uses on the IC.

Likewise how does one normally interact with an external storage IC? Are there specific protocols that are used to do the task? And how about specific libraries to interact with these pieces of hardware.

Over all I am wanting to know:

What are some part numbers for flash/eeprom storage devices compatible with an ATmega8/attiny
How does these external storage ICs normally hook up/interact with eachother
What protocols do they use for communication
If there are libraries to simplify communications between ICs

Thanks!


texts:
I have a circuit where a typical 3.7V LiPo battery supplies power through a bq24074 Charger IC, which should in theory short that voltage straight to the output of the charge-protect circuit, which then can be attached to a load. For a load, I'm having an electronic load drain constant current of 200mA. The flow is as I described:

[LiPo] ---(Vbatt)---> [Charge IC] ---(Vload)---> [Electronic load]

When the load is turned on (draws 200mA), the battery voltage remains relatively unphased, but the voltage between the Charger IC and the Electronic load drops to 1.7V from 4.0V. I followed the application schematic from the datasheet almost exactly, only changing resistors that control charge current rates.

The application I have for this only draws around 15-25mA, and at those draws the voltage collapse is much smaller so there's no urgency in solving this. That said, in the future I want to implement applications that have infrequent large spikes in current consumption, so it begs the questions:

In the situation I described, why might the load be causing the
voltage to collapse?
(and bonus question for curiosity's sake, since google wasn't
helpful:) In general, why might a load cause voltages to collapse?


texts: How to define working voltage class net to calculte the creepage?

texts:
I work of a project of single phase PFC converter and I need to define the working voltage to each each NET of Schematic to calculate creepage distance.

I have a question about the low voltage of NET including the driver of MOSFET( +15V) the sensing (+3.3V ) and also the low voltage of control board; it will be some class of high voltage of PFC (+380V)?


texts: Would you help me understand the design of this induction motor?

texts:
I need to understand the design of a single phase induction motor (I think it is a permanent split capacitor motor).

The motor works on three different speeds. It has 8 poles as shown in figure.

Let's assume that coils 5 & 7 are the main (Running) coils. So, Coils 6 & 8 are the starting (auxiliary) coils that are connected to a capacitor.

There are 4 more coils:

1.What are they used for?

2.Which one is north? and Which one is south?

3.Which one is a main coil and Which one is auxiliary?

4.Can I differentiate between main coils and auxiliary coils visually?

More information about my Motor:

1It is a motor of a small table fan (220V - 40 watts). A picture of a fan that is similar to mine is here: http://konwin.gmc.globalmarket.com/products/details/small-standing-fan-1547568.html

The motor has 16 solts.


texts:
The two questions I am confused about are:

(a)Determine the value of REE to give emitter currents IE of 350 μA in each transistor and the smallest value of RC to enable a 1 volt peak-peak maximum output signal voltage

(b) Determine equations for Adm and Acm and calculate the theoretical values of differential-mode gain and common-mode gain for your designed circuit.


texts:
I am looking for an open-source circuit layout routing tool (with scripting option) for custom layout design. For example: I design a NAND schematic and convert it into layout and place components (NMOS and PMOS) by myself and then auto-route it.
If found Qrouter from OCD but it requires standard cells for routing. I don't want to use standard cells I just want to place individual components and then auto-route the design. I have checked KiCAD and gEDA but they are used for PCB designing and I couldn't find to control or program then with scripting.
Could anyone recommend some other options for me? Can't I use VLSI routing tools without standard cells ?.

Thanks


texts: Does an ISP clock interfere with the on-board clock when programming via ISP?

texts: I am planning to use ISP programmer to program my new AVR board. I use an 8 MHz crystal on my PCB to clock the micro (atmega328p-au). Now, as I understand the ISP programmer will provide its own clock to my board when programming. It occurs to me that this might pose an issue. I've read that using an SPI clock much slower than the system clock is the way to go, but haven't found any specific documentation. Any suggestions? Thanks!


texts:
I'm considering replacing a 300W / 500W R7 halogen fitting with one of those 12v HID car fittings, (and obviously customising the halogen lamp housing) I'm also trying to do it on a budget. I'm looking to change five video lights.

I COULD buy a large lead acid battery of about 28AH, (bulb has inrush of 10A, but working current of around 3.5A @ 12v, so batt could last 7 - 8hrs) but ideally, I would prefer to work with 240V.

So my next idea - and the one that I'm a little concerned about - would be to use a 240V to 12V power supply, such as a PC PSU or similar. Since most items are SMPSU these days, I'm wondering if the output would 'collapse', (ie not even start up) if it's suddenly asked to provide 12v @ 10A to ignite the bulb at the onset. (If it was asked to provide 12v@ (say) 1A at startup, it could possibly build up a reserve in the output cap/inductor to supply more current at a later stage, but to jump straight to 10A ....)

It also seems to be a lot of 'work' electronically, converting 240v to 12v, and then 12v through ballast to control lamp. I've found a few 240v to HID ballasts ... but then read that the "ballast must be matched to a particular bulb"

Anyone worked with these lamps? I'm doing this to a) reduce heat of lamp as I've read that HID run cooler than 500W halogen, and b) get more light output for less current.


texts: How to estimate characteristic impedance for a random cable and tolerance of the termination resistor?

texts:
When we have a source with 50 Ohm output impedance we use a coaxial cable with a 50 Ohm characteristic impedance. And if we don’t know the output impedance then we use a 50 Ohm termination resistor at the receiver end. These are the remedy for reflection issue for the high frequency component of the transmitted signal.

But in practice we don’t always use 50 Ohm coax but a randomly picked cable or pair of twisted wires. Imagine we need to send a differential signal such as with a RS422/485 interface. Now what I read is that the termination resistor at the receiver end must be equal to the cable’s characteristic impedance.

Now the issue is what if we don’t know the characteristic impedance of the cable or the twisted pair we run how can we estimate it? Is there an estimate if we know the AWG and length for instance?

And secondly, let us now assume we figured out the cable’s characteristic impedance as 120 Ohm, does the termination resistor need to be exactly 120 Ohm in practice or a 150 Ohm would suffice?(Assuming knowing at this step the characteristic impedance and the pulse transmission frequency)

(I know theres a huge theory behind the topic but I was wondering whether there are some methods when it comes to practice)


texts: Techniques for placing components on PCB's

texts:
I know that placing components is quite an art rather than following some set of rules to get the job done, but I am looking for some references about the topic.

I already saw this tutorial and it is pretty much useful, but one resource is never enough. So any suggestions please?


texts: PLL loop bandwidth, lock time and jitter

texts:
For a PLL in short,

1) What controls loop bandwidth?

2) What impact does it have on output phase noise/jitter?

3) What impact does loop bandwidth have on PLL lock time?

I am trying to find answers to these questions, could you help?


texts: Is it possible using two 3.3v LDOs from one SMPS AC-DC 5V to power 2 MCUs?

texts:
I'm planning to use two 3.3V LDOs to supply power for two MCUs, one is STM32, one is ESP-12. Input power of these two LDOs come from one SMPS module 5V, 3W (HLK-PM01). The reason for two seperate LDOs: I'm using STM32's ADC and I think separate power supply with ESP will make ADC more accurate. Another reason is there is a distance between HLK-PM01 and ESP, trace length almost 25mm. STM and ESP communicate through UART and both using same I2C F-Ram Memory IC, STM reads ADC, calculates something and save to Memory IC. Then ESP reads data from Memory IC and post to server. All same ground. LDO is RT9013 Datasheet.

So is it possible and working? Or it is a overkill?

Thanks very much


texts:
What is the microcontroller (I assume) at the top of this picture, marked 26384533TVO?

This picture is from the inside of a wireless sensor, where an accelerometer and radio are also present. The device appears to be a 16 lead QFN, likely 3 mm x 3 mm.

(source: staticflickr.com)


texts: Which capacitors to use with voltage regulator IC such as 7805?

texts:
Many of the tutorials suggest to use a large smoothing capacitor (tens and even hundreds of uF) with a full wave rectifier but the datasheets of the voltage regulators and some tutorials suggest only a 0.33uF capacitor to be used for smoothing the input voltage. I am puzzled as there is really a big difference.
Moreover, what if we use a large capacitor such as 10uF instead of 0.1uF after the voltage regulator?


texts: What is the best way to measure current and voltage through a diode

texts:
I am reading the book Learning the art of electronics and on a part about diodes, the author pointed out that in characterizing a diode(I, V relation ) there is an unavoidable error due to the ammeter and voltmeter.
Two arrangements are given:

A voltmeter in parallel to series arrangement of a diode and ammeter.
An ammeter in series to a parallel arrangement of a diode and voltmeter.

Further, the author hints that the value of the voltmeter impedance relative to that of the diode makes one of the arrangements have a lesser error effect than the other.

I understand that in case 2, a voltmeter with an impedance comparable to the load will lead to a significant amount of current going through the voltmeter than the diode(load). Thus the second arrangement is better with a voltmeter of high impedance.

My questions:

In what case will the first arrangement be preferred over the other?
What would be the best arrangement in a case that you do not know the values of instrument impedance's and diode( load ) impedance?
Based on the impedances of commonly available cheap multimeters, which way should i use to characterize a diode?

Thank you in advance for your answers.


texts: Simplest/cheapest way to measure furnace gas usage?

texts:
I want to use an Arduino to datalog the gas usage of my furnace. This isn't really an arduino question though, its more related to finding the best sensor/electronics to interface with the furnace.

I have an IBC DC 33-160 boiler that burns propane. The boiler can ramp up or down between 33k and 160k BTUs depending on heating requirements of the house.

Because of this ramp up/down I can't simply monitor the thermostat contact closure to determine gas usage.

A gas meter is a potential solution, but that's quite expensive and would be quite cumbersome to install.

What I would like to try and do is monitor the air flow on the boiler's fresh air intake, which is a 1.5" PVC pipe. If I know the airflow, it should be relatively easy to calculate the gas consumption.

The question is what kind of sensor would be best for this application? There are three options that I've found while searching:

Mass Air Flow - a powered wire element is put into the air flow and depending on the resistance of the wire, you can determine the airflow. MAFs are commonly used by car ECUs to meter the air and spray the appropriate amount of fuel. The problem with this one is that most MAFs are 12v for auto applications and I'm not sure how I would calibrate it to a known value.
Pitot Tube - these are used to measure air speed and I found that they are also commonly used in HVAC applications to measure air flow - I just don't know if its sensitive/accurate enough to calculate gas consumption.
Ultra Sonic - apparently you can determine air flow using ultrasonic sensors aimed at an angle at each other in a tube - I've found some articles about it, but this option seems like the most complicated of the three


texts: Is audio signal passing through headphone differential?

texts:
I'm confused about how small audio signals are immune to interference.
Headphone wires seems twisted but are they also differential signals?

As far as I know differential/balanced signals are carried by two wires and they are mirrored as shown here: https://upload.wikimedia.org/wikipedia/commons/thumb/e/e7/DiffSignaling.png/1200px-DiffSignaling.png

So the common mode noise is rejected.

But in headphone case the little headphone which goes to our ear is not a differential amplifier hence it is just an impedance. It DOES NOT subtract two incoming signals.

I accept my ignorance on the issue but couldn't find a clear explanation about this.

Lets say you have a smartphone or laptop and you plug your headphone to the device, what kind of signal is that audio signal passes through the vibrating earphones? And how come the wires reject the noise? Can this be shown with a simplistic circuit model?

EDIT:

I would be extremely glad if someone can reply these two point confuses me:

Premise: In below diagrams grounds are meant as analog signal grounds there is no earth involved. Imagine the circuits are in space to neglect confusion.

Sorry for the above quick hand drawn diagrams.

Question 1-)

I. represents the original question. As you see the phone's headphone driver circuit has a GND which is connected to the one terminal of the headphone coil. So some say "no way to tell which, if any, of the lines is grounded". But there is ground. All phone circuit's analog ground is tied to the one terminal of the headphone. (?)

Question 2-)

This is regarding diagram II above.

in A and B why B cannot reject the common mode noise? Isn't B similar to the headphone scenario in I ?


texts: PB7, PD7 (on ATMega32) won't work when pull ups enabled. Also PC6 and PC7 don't show output

texts:
I am making 16*16 keypad(on PORTB and PORTD) with ATMega32 using proteus 6.9 and AVRstudio5.

My problem is PB7 and PD7 won't work when pull ups on those pins are enabled. Here PD7 is output, so no problem here. But PB7 must be pull up enabled for matrix. so this part of code wont work as expected:

if (!(keyportpin1&(1<<col8)))
{
    while (!(keyportpin1&(1<<col8))){}
    key+=7;
    return key;
}

Next problem:PC6 and PC7 also don't give output in any case. I tried changing SFR and too got no solution.

The full code I am using is:

/*
 * keyboard.c
 *
 * Created: 10/15/2011 10:54:24 AM
 *  Author: CMANI
 */
#define F_CPU 8000000
#include <avr/io.h>
#include <util/delay.h>

#define keyportpin1 PINB
#define keyportpin2 PIND
#define keyport1 PORTB
#define keyport2 PORTD
#define keyportdirection1 DDRB
#define keyportdirection2 DDRD

//#define bit_clear(bit) (!(keyportpin&(1<<bit)))
#define col1 PB0
#define col2 PB1
#define col3 PB2
#define col4 PB3
#define col5 PB4
#define col6 PB5
#define col7 PB6
#define col8 PB7

int keyboard(void)
{
    keyportdirection1=0x00;
    keyportdirection2=0xFF;
    keyport1=0xFF;
    int key=1;
    for(int i=0;i<8;i++)
    {

        keyport2=0xFF;
        keyport2&=~(0x01<<i);

        if (!(keyportpin1&(1<<col1)))
        {

            while (!(keyportpin1&(1<<col1)))
            {}
            return key;

        }

        if (!(keyportpin1&(1<<col2)))
        {

            while (!(keyportpin1&(1<<col2)))
            {}
            key+=1;
            return key;
        }
        if (!(keyportpin1&(1<<col3)))
        {

            while (!(keyportpin1&(1<<col3)))
            {}
            key+=2;
            return key;
        }
        if (!(keyportpin1&(1<<col4)))
        {

            while (!(keyportpin1&(1<<col4)))
            {}
            key+=3;
            return key;
        }
        if (!(keyportpin1&(1<<col5)))
        {

            while (!(keyportpin1&(1<<col5)))
            {}
            key+=4;
        return key;
        }
        if (!(keyportpin1&(1<<col6)))
        {

            while (!(keyportpin1&(1<<col6)))
            {}
            key+=5;
            return key;
        }
        if (!(keyportpin1&(1<<col7)))
        {

            while (!(keyportpin1&(1<<col7)))
            {}
            key+=6;
            return key;
        }

        if (!(keyportpin1&(1<<col8)))
        {

            while (!(keyportpin1&(1<<col8)))
            {}
            key+=7;
            return key;
        }

        key+=8;
        }
        return 0;
}


texts:
I was trying to visualize a beginner circuit problem on my breadboard and I plugged in my circuit, touched a resistor and got a nasty shock. I am a cs student playing with circuits to build some logic gates so I really am a complete beginner.
The power supply is 5V 2 Amps
Why did this happen? How can I prevent this from happening in the future?


texts: DALI Click Board: Not clear about the board operation, usage and circuit design

texts:
I am developing a DALI Control Device using STM32 board. I have already programmed the board to send DALI Slave commands according to DALI Protocol. But I am facing problem interfacing my board with DALI PHY Board called DALI Click.

DALI Click circuit design is given its datasheet as follows:

There are two problems for me regarding this board;

I could not understand exactly what is happening in the Red marked zones 1 & 2 design wise. I can see the green marked zone is the current limiting circuit but to what value exactly? What is the PHY_SEL pin? How to use this?

I am rather getting a perfect signal according to the protocol from stm32 transmitter pin (Tx Pin). I have tried connecting the two boards as given below left the pin PHY_SEL(CS) open!

I am not getting any signal from the DALI+ and DALI- pins

Is my pin configuration correct? Why is there no signal coming out of DALI bus pins?

PS: Default jumper positions are as per circuit diagram given above.

EDIT:
I have essentially followed this complete setup, I am not getting any signal out of DALI Click board. I have two of these boards and have tried with both of them. I have tested the DALI RGBW LED with WAGO module as well, it is working fine. The problem is no decent signal from Click!

I did not extend this setup to my STM32 board but I have connected STM32 board to DALI Click as per the described pin configuration


texts: Current sensing, low pass filter and ADC frequency

texts:
I am designing the circuit that will read the current in a DC motor. The PWM on the H bridge will be running at 10/15 KHz with an ADC sampling frequency and a control loop running at ~ 5KHz. I will have to check the R/L constants of the motors to make sure the control frequency is suitable. For now the proposed the circuit is showed below.

Initially I was planning on using a low pass filter before the ADC pin of the PIC. However I have read a few contradicting threads on whether i should or should not use a low pass before the ADC of the PIC. I read a few Application notes all promoting the use of the filters. Should I use an anti aliasing filter here?

If the filter is needed would you able able to comment on the cut-off frequency to use? The cut off frequency of the Sallen Key below is around 2.5 KHz. (1/2 the intended sampling rate of the ADC).

I would also be curious to see if someone could comment on C9 below. I saw a few schematics using a small ceramic capacitor placed there so i decided to use one too. Not sure about its real purpose to be honest.


texts:
In a transistor, we know that current amplification factor alpha (DC) for CB Configuration is given by :

Alpha = Ic / Ie

Where, Ic = collector current;
              Ie = Emitter current

This implies that :

        Ic = alpha × Ie ....................(1)

Also, the total current is given by :

  Ic = alpha × Ie + Icbo ................(2)

Where, Icbo = collector base current with open Emitter (leakage current)

From 1 and 2,

Ic = Ic + Icbo
Icbo = 0 ...................................(3)

This means for any numerical values of alpha, Ic and Ie, the leakage current is always going to be 0. But practically, this is not the case. A small current of the order of micro/nano amps flows as Leakage current. This contradicts the above equation. Does this mean to say that the above equation is faulty?
Please explain.

check out this image from my textbook... This is where i got the second equation which I have highlighted in yellow. Also have a look at the image at the top right.


texts:
I need a single mosfet driver but only have half bridge drivers (IRF2004) in my parts box.

Is there a risk I destroy them if I only connect one mosfet to them? Any other risks which I should be aware of?


texts: Is it safe to self-reset a flip-flop based on its output state

texts:
I'd like to create a logic function that toggles with the (inverted) clock when enabled and stays low when disabled, like so:

clk ena out
 0   0   0
 1   0   0
 0   1   1
 1   1   0

I could do that with simple AND/NOT gates, like in the following schematic:

The output should be glitch-free though, so I thought of the following circuit instead:

To avoid out glitches, ena (which changes triggered on the rising clk edge) is sampled at the falling clk edge.

My question is about the DFF's reset input while ena is high: This will only be a very short pulse (almost like a glitch itself), from the time clk rises until the DFF is reset. Will this cause any problems or is it safe to use this circuit?


texts:
I need to use a L-R-C tank in my design and I'm having trouble with the calculations. And I think it is because of the phase shift I didn't take into account.

Here you can see there is a differential equation introduced to extract the current-wave-charge equation. To my calculations the frequency is correct but I also need to know the phase shift \$ \theta \$ as well.

This is supposed to be the voltage wave of my LRC circuit:

ww = 660.764; vc = 30; slip = 0.99; result =
 Cos[ww*t]*
  vc*(Exp[-t*((0.461 + (ww*slip)*
          ww*1715.38/(66564 +
             6648.72*(ww*
                 slip)^2))/(2*(134*10^-5 + (5420 + (ww*
                  slip)^2*5.385)/(66564 +
              6648.72*(ww*slip)^2))))]); Plot[result, {t, 0, Pi/ww}]

However, as you can see, the cosine wave is slightly shifted and it messes with my further calculations. So, what is the equation for the phase shift \$ \theta \$ ?

simulate this circuit – Schematic created using CircuitLab

I added the example schematic. In the initial condition, VC is 30V. Then I showed the graph of VC. VC is charged up to 30V in initial state and then slowly dies.

This above graph is taken from circuit lab simulation of the circuit above. This is the correct waveform with no phase shift because the simulator included the phase shift into equation. How can I so?


texts: In a 3 phase inverter what is the maximum voltage across each switch

texts: What is Vds value for switches used in the network


texts: DC High Voltage Line Splitting Problem (Electrode "Tuning" Application)

texts:
I am having trouble coming up with a solution to a problem engineering a DC circuit that can take a single line input (Vin) and split into two outputs (Vout1 & Vout2).

The goal of the circuit is to take a high voltage line and supply two parallel electrodes connected to Vout1 and Vout2. By changing the potentiometer setting (R1) one should be able to adjust |Vout1-Vout2| between 0-9V or 0-18V depending on the switch (SW1) settings. The circuit should be able to handle high voltage inputs (Vin: 0-4000 VDC, 1000 VDC typically). The electrodes are floating in ultrahigh vacuum.

The current circuit setup is shown below; however, this circuit does not perform as desired.

simulate this circuit – Schematic created using CircuitLab

The current configuration allows one to change electrode voltages (Vout1 & Vout2) 0-9V or 0-18V by adjusting the potentiometer; however the potential difference between the two electrodes (|Vout1-Vout2|) is always constant (either 9V or 18V depending on SW1 settings). I would like to be able to use the potentiometer to "tune" one electrode relatively. For example, I might wish to use a 1000 VDC input voltage (Vin) and get output voltages of: Vout1= 1000 VDC, Vout2= 1005 VDC.

Does anyone know of a way to modify this circuit or adapt a simple design to implement this idea?


texts: Using Multiple MLX90614 Sensors on Arduino Board

texts:
I've been trying to get something working for a project, getting 4 (just trying to get at least 2 working for the moment) MLX90614 IR sensors connected up to an Arduino UNO board.

I've followed the datasheet instructions and managed to get one working using the schematic provided (using the library here) and got a reading. However, as soon as I attach another one, again using the schematics on the datasheet, I get no response.

I am fairly certain the issue is with the library but I can't be sure. The schematic I followed for multiple sensors is:

(I have crossed out the parts of the schematic I removed, as the datasheet said they weren't necessary)

The pull up resistors are of a value of 4.7Kohms, and the caps are 0.1 micro.

Any assistance with getting this serial connection would be appropriated.


texts:
I have designed an AB Audio Amplifier, but even though the gain is acceptable, the frequency response is terrible.As seen in the schematic, there is a feedback/preamplifer stage and an output stage, I have used MULTISIM to perform AC Sweep of the only the preamplifier stage, and the frequency response there is acceptable, but the response at the output isn't.

What can I do to improve the frequency response while allowing only a reasonable fall in gain?

Below are the input and output stages respectively.


texts: Problem to update firmware using bootloader to PIC18F4550

texts:
I followed the documentation on the Diolan's web site . I changed the project to be programmed to an PIC18F4550 and not a PIC18F4455 as it was originally written.

The compilation succeed and I was able to program the bootloader into the PIC18F4550's flash. I used PIckit3 and MPLABV8 to do it.

I did not encrypt my application using the encoder, I just tried to write it to memory without encrypt it. So, I copied and paste my .hex file application to the bin folder where the fw_update is. I opened the console and typed:

fw_update -e -w -v -vid 0x04D8 -pid 0xFF04 -ix example.hex

The followed message appears:

  U2IO flash erasing: FAILED.

  Device is not found.

  Operation aborted.

Does someone have some advice or tip of what it is happening ?

OBSERVATION:
My Windows 10 is not recognizing my USB device, neither before nor after the bootloader programming. It always inform: "USB device not recognized".

Below is picture of the schematic of my device:

[Edited]

Good observation, I saw at the datasheet that minimum value of CUSB is 220nF and there is no maximum and typical values.The hardware was not made by me, but I put the capacitor of 470nF, based on the PICDEM™ FS USB DEMONSTRATION BOARD of microchip. The Windowa 10 stopped to inform that the device was not connected, but at the device manager it is still with a yellow exclamation(But this time in HID USB). The error mentioned before still happens.

So, I did the following changes on the bootloder code:

In source files where was originally #include "P18F4455.INC" I changed to #include "P18F4550.INC"

On the Header files, I remove "P18F4455.INC" and put "P18F4550.INC instead that I downloaded from here.

My application code is edited on the project by its configuration bits this way:

CPU System Clock Postscaler was:
[OSC1/OSC2 Src:/4][96 MHz PLL Src: /6]

Power Up Timer: Enabled

The others I left default. And this configuration works when I run my  application without the bootloader.

But, when I will compiled the bootloader, I did not configure the configuration bits, the checkbox "Configuration Bits set in code" is selected as is said in the documents.

I found on the bootloader's file usb_desc.inc that :

#ifndef BOOTLOADER_VID
#define BOOTLOADER_VID  0x0000      ; MUST BE VALID Vendor ID
#endif
#ifndef BOOTLOADER_PID
#define BOOTLOADER_PID  0x0000      ; MUST BE VALID Product ID
#endif

So I changed my command line in the prompt to:

fw_update -e -w -v -vid 0x0000 -pid 0x0000 -ix principal.hex

But it still not working.


texts: PCB data trace lengths tolerable difference for high frequency

texts:
I have to interface a camera to a controller using the DCMI protocol for my project. I have around 17 (data+control) lines which are used with the camera. The frequency of operation is about 10 MHz.

I use EAGLE for my designs. However, while designing the PCB, I am not able to match all the lines from the connector to the controller.

It would be helpful to know the tolerance in length difference that is allowed while designing this PCB. Would a 2-3 cm difference in lines beget problems?


texts: I was taking apart this thing that I bought from the dollar store, its this glass block with an encased sculpture that sits on a revolving deck. (see photo below) The deck powers 4 LEDS with batteries, however it must be plugged in to turn. I found that the motor that was used was a AC 6V Synchronous Motor (see photo below). I have no idea why a simple DC motor could not have been used, eliminating the expense of using this motor and allowing the deck to turn on battery power. The block is not heavy, only around 480 grams. Can anyone shed some light on why this motor was used? I'm curious. Thanks!


texts: Can I use a 22 microfarad capacitor in place of a 10 microfarad capacitor?

texts:
I have a bad 10 microfarad capacitor 400V but can not get a replacement.

Can I use 22 microfarads 400V instead?


texts: How do two DC motors of the same power but for different voltages differ in size?

texts:
Suppose I have two brushed DC motors, each rated 3000 RPM and 50 watts. One is rated for 18 volts and the other for 36 volts. How will their sizes differ?

I assume that because of higher voltage the 36 volts one will require two times smaller current in the windings and so four times less cross-section for the winding wires and so the windings will take notably less space.

What other size differences in these motors and their parts (windings and cores) sizes should I expect?


texts: Is it possible to use the load line analysis technique on two diodes?

texts:
I understand the load line analysis is a way of solving two equations. In the two diodes case, I also have two equations.

In number 5 for example, I will try to get the VD1 using the load line method.

1) 5 = - VD1 - VD2

Id2 = Is2 * ( exp( VD2 / (2*VT) ) - 1)

VD2 = 2 * VT * ln(Id2 / Is2 + 1)

Id1 = Id2 because the diodes are in series

So Equation 1 is 5 = -VD1 - 2 * VT * ln (Id1 / Is2 + 1)

2) Eqaution 2 is Id1 = Is1 * ( exp(VD1 / (2 * VT)) - 1)

So now I have two equations in VD1 and Id1, But my calculator can not solve them.


texts: What type of sensor connection would be the most suitable?

texts:
I have a pressure transducer with a 6 pin bayonet MIL-C-26482 male connector. I need to wire this connector with a 9 pin female D sub analog input connector and I am not sure how to do so.

Schematic of the 9 pin connector:

The 6 pin bayonet male connector has the following schematic:
For pins A to F-

        A: +ve supply
        B: +ve output
        C: -ve output
        D: -ve supply
        E&F: Shunt calibration

This is the manual for the DAQ system which contains the D- Sub connector as an analog input pin: https://d36j349d8rqm96.cloudfront.net/3/6/DEWE-43_user%20manual.pdf

This is the link to the pressure transducer with 6 pin bayonet male connector: http://www.southeastern-automation.com/PDF/GESensing/Pressure/5000%20Series.pdf
Here's the link to the pressure sensor with the 6 pin bayonet connector:http://www.southeastern-automation.com/PDF/GESensing/Pressure/5000%20Series.pdf

I'm thinking that the 6 wire full-bridge sensor connection would be the most suitable, but I am not sure.

Types of sensor connections available:


texts: Can I short circuit the SSR load terminals?

texts:
I'm using an SSR but I would also like to be able to turn on the circuit using a switch. Can I use a switch in parallel with the SSR load outputs? This would cause a short between the terminals.

The following diagram illustrates the idea. If the SSR actually works as switch this would be ok, but I want to make sure, considering its true behavior.

simulate this circuit – Schematic created using CircuitLab


texts:
How can I use CAN bus in an elevator (BrE: lift)?
I work at an elevator manufacturer and I want to know more about the use of CAN bus. What is CAN bus, and how can I apply it in elevators? What is needed? Can you show me any block diagrams to help me?


texts: Multisim Multimeter showing blank reading (--------)

texts: I am trying to build a simple circuit to back up some hand calculations that I am completing for a project. However I am unable to get a reading on the Multisim multimeter. I have changed the simulation type to interactive as that is what I have found in another thread.


texts: What is the difference between TO-220F and TO-220FP cases?

texts:
Google search results imply TO-220FP to be full-pack case.
Wikipedia says that TO-220F is full-pack case.
Farnell categorizes TO-220F and TO-22FP differently.

I'm confused. What is the difference between these two TO-220 case versions?


texts:
When we look at the PN junction diode, there is always a depletion region, for which one side in negative and one side positive. The reason behind this is that the N side depletion region is positively charged because its free electrons have recombined with the p side.

My question is that if free electrons are not attached to any particular atom, then how come they leave a hole behind when they go to the P side ? aren't holes formed when the covalent bonds can accept an electron to make covalent bond with two electrons? Since these electrons were already free, they shouldn't leave a hole behind.


texts:
So I've recently been playing with my first Arduino, until it, for some weird reason,  stopped working.

What I did:

I had it attached to a breadboard. When I say attached, I mean it was supplying power to the breadboard. I was messing around with a motor, which wasn't performing very well when using the standard 5v output the Arduino supplies. So, I decided to buy some batteries - 10 AA batteries, to be precise. As I connected my battery back to the other side of my breadboard (there are two power input rows on my breadboard - one on the left and one on the right. (I thought) the Arduino was supplying power to the left input), I had completely forgotten that I had the two power input rows linked together with jumper wires. So I had the Arduino powering both the left and the right side rows of the breadboard. So all of a sudden, when I linked the battery pack to the right side row of my breadboard, my Arduino turned on. I was puzzled. When I finally realized the two power input rows were linked, I slapped myself.

Now, my Arduino turns on, but the code I had on it is no longer executed. And usually, when I turn the Arduino on, the "L" LED blinks twice. Now, it just turns on and stays on. The power outputs still work, as I still have power flowing through my breadboard. The reset button does nothing.

The Arduino IDE also no longer detects my board. Infact, my whole computer doesn't even detect it.

I know it was really stupid of me to supply 14+ volts to it, but I didn't do it intentionally. And, the only reason I used 10 AA batteries was because that's the amount my (only) battery pack required.

Bad news?

What do you guys think? Am I screwed? Is it fried?


texts: what does the "UL" means when specifying the clock speed for AVR MCUs

texts:
So I am using the ATTiny10 for the first time, and I noticed that even after setting the clock pre-scaler register correctly (0x00 in my case) I had to define a value called F_CPU for the _delay() function to work correctly. but when going over the code example I have there was #define F_CPU 8000000UL. What does the UL mean?

Also if someone can recommend a good book to start with microcontrollers that would be appreciated, too many registers and setup conditions it's overwhelming!.