texts:
Basically, I am using a lookup table to output in bcd the square of a single digit bcd.

The problem that I have is that it is not outputting the correct answer.

For example: the result I get for the square of these number are:

1 = 1

2 = 4

4 = 10

5 = 19

10 = 64

as you can see I have to separate MBCD and LBCD and then concatenate them.

Here is my code:

module bcdsquarer(input[3:0]bcdin, output[7:4]Mbcd, output[3:0]Lbcd);
parameter msb = 16;
parameter lsb = 8;
reg [lsb-1:0]ROM[0:msb-1];
integer i;
initial
    begin
    for(i=0; i<16; i = i+1)
        begin
            ROM[i] = i**2;
        end
    end
    assign {Mbcd,Lbcd} = ROM[bcdin];
endmodule

do anyone see where I made a mistake at?

edit:
Okay, So know I have to convert from binary to bcd. I have a code that converts, but how do I implement it with my bcdsquarer?

here is my code

module B2BCD(B,hundreds,tens,ones);
    input [7:0] B;
    output [3:0] hundreds;
    output [3:0] tens;
    output [3:0] ones;
    integer x;
    reg [3:0] hundreds, tens, ones;
    always @(B)
    begin
        x=B;
       hundreds=0; tens=0; ones = 0;
       if(x>99)begin hundreds =hundreds +1; x =x-100; end
       if(x>99)begin hundreds =hundreds +1; x =x-100; end
       repeat(9)
       begin
       if(x>9)begin tens = tens +1; x =x-10; end
       end

       ones =x;
    end
endmodule

I tried implementing it like this: (I just get x for my results now)

module bcdsquarer(bcdin,Mbcd,Lbcd,tens,ones);
parameter msb = 16;
parameter lsb = 8;

input[3:0]bcdin;

output[7:4]Mbcd;
output[3:0]Lbcd;

output [3:0] tens;
output [3:0] ones;

integer x;
reg[3:0] tens;
reg[3:0] ones;
    always @(bcdin)
    begin
        x=bcdin;
       tens=0; ones = 0;
       begin
       if(x>9)begin tens = tens +1; x =x-10; end
       end

       ones =x;
    end

assign Mbcd = tens;
assign Lbcd = ones;

reg [lsb-1:0]ROM[0:msb-1];
integer i;
initial
    begin
    for(i=0; i<16; i = i+1)
        begin
            ROM[i] = i**2;
        end
    end
    assign {Mbcd,Lbcd} = ROM[bcdin];
endmodule


texts: What material can I use to insulate NFC tags so they can be placed almost back to back?

texts:
I have posters with "Tap me to check in/out of this meeting room" drawn on them. I have NFC Stickers behind each poster to send the user to a specific URL in the application.

They are being placed on a glass door so the customer wants them to be placed back to back so you can't see the back of any of the posters. Each poster does different things so I don't want the tags conflicts.

If I put foil/copper mesh between two posters it blocks/absorbs the NFC signals so I can't read the one behind, but that also blocks the one "in front" of the mesh that I want to be able to read.

I'm looking for a sandwich of materials that would work, something like:

Acrylic Poster
NFC tag (stuck to the back of the poster)
Rubber/Silicone(?)
Ferrite(?)
Glass of the door
Ferrite(?)
Rubber(?)
NFC tag
Acrylic Poster

Apologies if I explained that badly, I'm an applications developer out of my depth on materials/engineering!

Thanks


texts: Using a DS3231 RTC alarm + MOSFETS to turn on a MCU

texts:
I'm using a DS3231 in conjunction with two IRLZ44N MOSFETs to switch power to a MCU when the alarm on the DS3231 triggers. The alarm on the DS3231 pulls the SQW/INT pin to ground and turns on the MCU using the IRLZ44N FETs. When the MCU resets the alarm on the DS3231, the power is killed to the MCU.

I'm using this to turn on an arduino or an ESP32 at a precise time, schedule the next wakeup time, and then shut down. I don't anticipate pulling more than 1A with my projects that would use this circuit (probably less than 1A).

I want to be able to use this circuit with 3.3v and 5v MCUs. I've tested with both 3.3v and 5v and it seems to function fine. The datasheet for the IRLZ44N looks like it supports both voltages for controlling the gates on the FETs.

I'm a beginner and I would really appreciate feedback on this circuit. Hopefully I'm not way off!

Here are my questions:

Is this design reasonable? Or are there better solutions? Any glaring issues?
Are the IRLZ44N MOSFETs a good choice for this application?
Are my 100k pullup resistors reasonable values?
Is this is a common pattern to convert something being pulled to ground into switching something else on. Does this sort of thing have a name?

Here is my schematic:


texts: Quartz Crystal with or without metal lid for EMI suppression?

texts:
Is there any reason for choosing a quartz crystal with or without metal lid?
Some datasheets (this one for instance: link) claim better EMI performance and other do not write at all about it.
So is there a reason I should choose quartz crystals with metal lid over crystals in a wholly plastic package?
Here is what I have found on that topic: link
I am aware, that the second link is about a quartz crystal oszillator but I have not found anything else.
Considering the answers so far, especially the second one, I understand that shielding of the quartz itself is not needed. But then I am wondering why the quartz's manufacturer states the following (see first link and there note 2):

Terminations #2, #4 and the metal lid are connected internally. End user may connect these pins to circuit
ground for EMI suppression.


texts: Why opamp output doesn't match with the calculation?

texts:
The actual current passing the load is 44mA, in below schematic the voltage across Rsense is 454mV and the opamp output is 4.52V. which is correct.

But when I replace the Rsense with a 0.1 ohm resistor the voltage across Rsense changes to 1.9mV and opamp output to 8.5mV!

Why current reading become way off when I change the resistor to a lower value? Is it because of the 5% resistors?

simulate this circuit – Schematic created using CircuitLab


texts: Why is the capacitor considered lossless, even if it can store/give out energy?

texts: They say capacitor is lossless because average power is 0.But contradicting this is the fact that the energy stored/disipated by a capacitor is (1/2)CV^2.How and why is this?


texts: I am trying to figure out a simple application/ circuit that would allow me to shift the voltage a little bit. Lets say we have an input voltage of range from 0 to 1 V. I need an output voltage of 0.2 to 1.2 V. This is just an example but I am looking for a generic solution. There is no negative voltage available in the circuit.


texts: Can a 40Khz ultrasonic microphone record normal voice speach?

texts:
I have an occupancy sensor connected to a lighting control system. It uses a 40Khz ultrasonic mic to detect sound to determine if people are still occupying a room.

I'm wondering whether the mic could be used to record normal conversation?


texts: Does a switch need to be debounced when opened?

texts: Suppose that an input on a microcontroller has a pullup resistor to 5V and a switch to ground (normally open) connected to it. I know that a switch should be debounced (in my case, in software) when closed, but is debouncing when a switch is opened necessary?


texts: 4 pin connector is melting even with 5 volt and 0.1 amp power supply, Why?

texts:
I am using a connector as shown:

.

I am using this to connect to my camera, which works at 5 volts and 0.1 Amp. But this connector works only for few days and then the plastic portion of the connector melts as shown in figure.

This connector as per the data sheet can work with 240 volt and 2 amp. Here are the 4 four wire configurations for 4 pins in connector

5V power supply
GND
Video input signal
Earthing of the shield covering all the wires.

One thing which I know for sure is the Impedance mismatch. I am supposed to use a 75 ohm wire but because of many other reasons I am using 100 ohm wire.

Can this cause the issue?
What are the ways to find out the reason of breaking ?

(I can clearly make out that the plastic portion is melting because of heat, I tried different connectors as well but the result is same )

This has ruined my sleep for many weeks. Kindly suggest me a solution.
Thank you all in advance.


texts: What's the point of putting two NOT gates sequentially?

texts:
I found the following diagram in data sheet for M74HC595 8 bit shift register

I have three questions.

Do I understand correctly that all blocks inside red ellipses are NOT gates?
What is the difference between (circle-triangle) and (triangle-circle) symbols?
Why did they put two NOT gates sequentially? These two gates will just pass through unchanged input signal according to NOT truth table. Will the circuit without these two NOTs operate the same way?


texts: Need help with reading mosfet datasheet (safe operating area graph)

texts:
What does indicated time in below graph means?
datasheet


texts: Oscilloscope ground clip : short circuit

texts:
I'm measuring voltage on an audio amplifier mono output. Amplifier is powered using a stabilized power supply. I connect oscilloscope ground probe to one of the two output wire and a probe to another.
Before I had no issues when measuring voltage.

Now, when I first connect ground clip, I get a spark, short circuit indication on power supply, so I disconnect it.

Why do I get this spark?


texts: Diode and capacitor at the Wien Bridge Oscillator

texts:
The circuit below represents the JFET stabilized Wien-bridge oscillator.

we add another diode in the circuit. Shown in the picture below:

The questions are:

Before adding the second the diode the voltage at the input and output where smaller, why was that?
Why positive side of the capacitor C3 was connected to ground?

For the first question the answer I thought was that the negative excursion of the output signal forward bias the diode causing the capacitor to increase the drain-source resistance if the JFET and reduce the gain.

For the second question the answer I thought was that the output signal forward-bias D1 causing C3 to charge to a negative voltage, thats why the negative side of the capacitor should be connected to the circuit and the positive side to the ground.

I am not sure if these answers are correct. Can someone help me with this?


texts:
I accidentally bent one plug on one side of an HDMI cable and, after taking the
plug apart and straightening everything out as much as possible (after which the
only apparent structural oddity is that pin #18 is shorter than the others, but
I think this pin is not used and the plug has always been like this), the display
no longer shows colors.
Audio is fine.  Video is black and white, but otherwise fine.
I must have some connectivity problem with some of the pins (or even with the outer
ground shield around all pins), but can't find it by wiggling things...it's always
black and white.  What is the most likely problem?


texts: Can we place silkscreen inside the footprint?

texts: Can we place silkscreen inside the footprint for through hole PCB? I guess it eliminates "visual congestion". What are the problems associated with it??


texts:
We recently purchased the estate of a 94-year-old gentleman who was an electronic genius.

He started building radios when he was 14 and was a ham operator and repairman of all types of electronics until the day he died.

We purchased the estate mostly for the ham radio equipment, he built some pretty impressive linear amps and customized his radios in a very high tech manner.

He was also a hoarder and since he also had lots of useful old stock electrical parts we purchased these as well. We are sure there are folks who could use these and we would hate to see them get thrown in the dump by the family.

This gentleman was very well organized and had most everything marked as to what it was, how it tested, and what it was for etc.

The piece I have in question is a large Sprague Vitamin Q Capacitor. I have tried to find anything like it, to compare it to but have found nothing. It is 15" tall and weighs around 20 pounds.

We want to resell this, but do not know what it is for or any of the specs. I have found a few sites that explain the numbering of these, but none that have the information on these particular numbers. We would like to get this in to the hands of either a collector or someone who could use it, so any information on the specs, and what it would be used in would be most appreciated.

Pictures are:


texts:
Coming from the world of MCUs, I create bootloaders so that customers can update the firmware. Specifically, i'm talking about a USB bootloader to narrow down the many different mediums.

How is this done with FPGAs and CPLD. I would prefer a solution that is secure. So the image sent is encrypted or obfuscated some how. But I would like to here solutions that are not as well.

For FPGA:

Since the firmware is stored in external flash memory, does the FPGA image just write to it's external flash and then restart? But what happens if the new file is corrupt or the connection is removed while updating? Is there a way to make a default backup? In MCUs, the bootloader is never overwritten so the application can mess up anytime and the bootloader will still work.

Is there a separate dedicated non-volatile memory portion that is not re-configured on power up that you can load a bootloader in?

For CPLD:

Since the image is stored internally, do they have a way to configure themselves? How would one make a bootloader for a CPLD?

Other thoughts:

Maybe you can put an FTDI chip of some sort with GPIO that you can control from a PC app via USB. This way you can bitbang an SPI to load in a new image on the external flash? Anybody do that? That way the FPGA image can be corrupt or missing and still will be able to load a new image.

Note that i'm assuming that the FPGA or CPLD is alone on a board. Meaning there is not an MCU on the board to do all this.

Any insight as to how the industry achieves this task would be great.


texts: Decoupling a Microcontroller/Development Board Design

texts:
Im trying to design a broad purpose microcontroller board (developement board?) to send off to a fab house to then use in future projects. The micro being used is an ATtiny861A.

Referring to the datasheet:

Indicates I should wire the AVCC pin to VCC through a low pass filter. Using an RLC filter with R=10R, L=10uH, C=0.1uF gives a cutoff freq of ~159kHz. Its hard to know what frequencies to expect as this is a general purpose board however the clock will always be 1-16MHz

Are there any other frequencies I need to take into account for AVCC?
If not, the bode plot gives a gain of roughly -30dB at 1MHz, is this considered decent reduction or should I aim for better? I feel like the answer to this question will be "it depends on you application" and if this is the case, what kind of applications would this setup limit me to?

The resistor is also rated to 3W so in the absolute worst case where every pin on Port A sources/sinks its max of 40mA (not that i would deliberately drive a pin anywhere near its max!) The resistor should be able to handle it;
$$
P_r=I^2R = (8*0.04)^2(10) = 1.024W
$$

After reading many posts regarding decoupling capacitors my current understanding is this:

Place a ceramic capacitor as close to the the GND and VCC pins of the micro as possible. Use wide traces/planes (and avoid vias if possible?) to connect the cap to the micro and supply. this capacitor should be placed between the supply and micro and is to deal with high frequency noise, value of 100nF. Is it worth including another capacitor near the micro of a value other than 100nF and 10uF?
Place a 22uF tantalum cap across VCC and GND, does not need to be close to the micro because it is used to deal with lower frequencies which are not effected by the inductance of the traces. The voltage regulator states using at least a 10uF tantalum between OUTPUT and GND (larger values will improve stability further) so only one will be included for both regulator and micro and be placed near the regulator.
The regulator datasheet also suggests a 10uF tantalum cap between INPUT and GND, "suitable for almost all applications". I've read about tantalum capacitors being very vulnerable to even brief voltage spikes above their rated max. The input voltage will be either 4xAA batteries giving ~6V or the external ISP programmer giving 5V, what are likely sources of voltage spikes? initial powerup? The 10uF tantalum caps are rated to 16V, is this likely to be enough of a buffer?
Included on the board are 2x dual n-channel mosfets driving 4 LEDs, the mosfets are there just to serve as a high impedance buffer (i think thats the correct term) incase any of the 4 I/O pins are also used to transmit data. Reading this post: Does my circuit need decoupling caps? The suggestion was made to also decouple the transistor and LED. Can and should the same principle be applied to a mosfet? The LED's are fairly low current, being driven at 2mA each so would a 22nF over the LED, series Resistor and mosfet D-S be sufficient?

Voltage Regulator:

Microcontroller (C16 value not determined):

Dual n-channel mosfet:

This will be my second time using a fab house and first time with something more complex than an NE555 so I would be happy for any feedback that goes along with my many questions!
Thanks


texts: Identification Part Number electronic component

texts:
What is the Part number of this component?
Top mark : B2
Do you have any idea?

Thank you.


texts: How to connect a light dimmer for my lamp

texts:
I have a light dimmer i want to connect to a a floor lamp. I have tried to look for some diagrams but haven't been able to find some.

There is a diagram on the dimmer but I don't understand it.

I have made an illustration to show how the small diagram looks (it's the diagram in the middle, the lamp and the 4 wires and the power plug are my additions.

http://000fff.org/uploads/LightDimmer.pdf

Can anyone tell me how to connect this. I have 1 wire from the lamp to the dimmer with a blue and a brown wire and 1 wire from the dimmer to the power with a blue and a brown wire.


texts: Can the LM324 be used as an audio bandpass filter?

texts:
im currently building an audio visualizer , my intentions were to use the LM741 but i saw that the LM324 operates using a single power supply , i would like to know if the LM324 can be used as Bandpass filters.

thank you.


texts: 1-wire verses CAN-bus for home sensing network?

texts:
I'm trying to put together a home automation solution for my newly built house. I'm very new to this, specifically for hardware matters and asking this question to verify if my understanding of what I've learnt from internet is more of less correct and an advice on how to move on.

I have decided that I will separate the whole thing into three "layers" - sensing, alarming and control. The question is regarding the first one. I put sensors on my floor plan and it counts 60 environmental sensors (temp, humidity, light, movement, moisture) and 40 security ones (smoke, movement, gas, distance, vibration, magnetic contact).

There are two general options I have figured - 1-wire and CAN-bus. 1-wire is relatively simple and there is lots of information on this on the internet and many projects to learn from. But since all the sensors are passive it looks like 1-wire is good for collecting data from temperature, humidity and alike sensors. But doesn't quite well work for light and movement sensors for instance - if you want to know if there is movement right at the time, you'd have to "question" those sensors pretty much as frequent as you can generating a lot of garbage traffic. 1-wire is relatively cheap, too, and requires very little soldering - just making sure 3 wires are wired correctly, even a kid can do this.

CAN-bus seems to contain more possibilities but is as well harder to understand and it's not easy to find sample home automation projects that will explain everything in enough detail. But if I understand it right, since you are able to have a main device and child boards connected to it, the sensors on the child board can be active and trigger signals to other members of the network without involving the main controller device.

If CAN-bus is a good way to go, can someone point me to affordable devices in the field? Like boards that you can connect sensors to and so on?

Here are two pics of topology layout for CAN/1wire - am I getting it right?


texts: How can anyone use a microcontroller which has only 384 bytes of program memory?

texts:
For instance a PIC10F200T

Virtually any code you write will be larger than that, unless it is a single purpose chip. Is there any way to load more program memory from external storage or something? I'm just curious, I don't see how this could be very useful... but it must be.


texts: Charlieplexing 7-segment display segments vs segment

texts:
I understand the principle of charlieplex and the use of tri-state. What I don't understand is, can I light all segments on a display at once or do I have to light one segment at a time?

Say I have 8 displays in a charlieplex configuration with 8 transistors to select which display I want to use (displays are common-anode).

I turn D0 high to saturate Q1 and turn D1-D7 low to ground all segments, D8->input to 'disconnect' it from circuit. No other transistors should be saturated and LEDs connected to D0 should block the reverse voltage. Display 1 is lit and all others are off? I feel like I'm not understanding something.


texts: Problem in going to definition in visual studio codes

texts:
I wanted to defined the Chip select pin of my spi,in the SPI master example.
I am using the recommended visual studio codes.
but when i tried to right click and going to definition it said that its not defined.
I have shown the directory and visual studio code window photos bellow.
Where did i go wrong?
Why i cant see the definition of the SPI variable? i need it to define the API
Thanks.
C:\Users\Asus\Desktop\esp-idf-4\esp\esp-idf


texts:
I have an IRFB7430 which I want to use to switch 12V. There will be minimal load on the MOSFET, since it is only used to switch a signal. I know it is not its intended use, but it's what I have lying around.

The signal on the Gate is only 5V, which should leave the MOSFET with a higher-than-intended R_DSon, but since I only want to switch a voltage, not a current, I thought it might not be a problem.

However, the output is only around 3.6V, and even if I switch with a 12V signal (which should get the R_DSon to single digit mOhm), I only get 10.5V on the Drain.

I have a 26kOhm pull down resistor on the Gate, and a current limiting resistor of 220 Ohm. Removing either of these did not bring significant changes. +12V is connected to Drain and I am measuring between ground and Source.

I guess there is something in the design of the MOSFET which I don't understand and it is its regular behavior. What am I missing?


texts:
I was recently told that it could be a good approach to use different voltage regulators to different IC's on the board. So if I have the MCU and then a different IC somewhere, even though they require same voltage I should use 2 different voltage regulators so one wouldn't send back some noise to the other through the same line.

Is that really considerable or I could just eliminate that with some decoupling capacitors next to each IC (as usually datasheets suggest)?


texts: Compare two voltages and output the lower of the two

texts:
I am working on a circuit that is connected to a 10V supply (can supply about 1-2mA).

We have two signals, let's call them S1 and S2.
We also have an input to the circuit called IN1.

My goal here is to compare the two signals, S1 and S2 (They may range from 0 to 10V) and output the LOWER of the two into the circuit's IN1 pin.

What makes this challenging is the fact that the LOWER voltage needs to be output.

I can easily make a microcontroller compare two voltages on the A/D pins and output the lower on the D/A pin, but i'm afraid 2mA of power will not be enough to run the microcontroller properly - plus i'm sure there must be a much easier way.

EDIT: According to the simulation, accepted solution works like a charm! OpAmp source current is important in order to make sure it doesn't go past the current limit. Proper selection of OpAmp also allows OUT to be very close to V- (0V in this case).

I simulated this in LTSpice with a LT1490A OpAmp and a 22K resistor instead of a 1K.

To simulate i simply chose IN1 as 5V and varied IN2 from 0 to 10V. The results should be quite clear and self-explanatory. V1 (not shown below) and V2 are my V+ and V-. These are 10V and 0V.


texts: Fundamental period of a discrete-time signal

texts:
This question comes right out of the problems section of Oppenheim's Signals & Systems 2ed textbook. I don't understand the solution to the problem.

(problem #1.35)
If a discrete-time complex sinusoid is expressed by \$x[n] = \exp(jmn2\pi/N)\$ (m is any integer), prove that the fundamental frequency is N0 = N/gcd(N,m).

Solution: for a discrete-time signal to be periodic \$x[n]=  x[n+N_0]\$.
Substituting n+N0 into n and expanding that expression means that \$m(2\pi/N)N_0 = 2\pi{}k\$,
where k is some (not any) integer. Rearranging we get the expression N0=N/(m/k).
somehow (m/k) = gcd(N,m).

I don't see it.


texts: Is unshielded untwisted pair cabling fine for audio?

texts: Noob here just trying to work out if there's much difference between the various types of cabling for use in connecting amps to speakers. I have unshielded untwisted pair cabling here at the moment.


texts: How to programm a standalone MSP430g2553 via a com port?

texts: The MSP430 is a dirt cheap MCU and i thought that if i could make a barebone launchpad out of that which can be programed directly via the PC COM port or a virtual one. So is it possible to program it with the energia IDE on the com port?


texts: Why is ngspice showing current as negative?

texts:
I have an extremely simple comparator circuit:

The voltage at pin 7 goes into positive saturation when a positive input voltage is presented at pin 5.

I'm simulating this using SPICE in KiCad. Here's the output:

As expected when +5V is presented at pin 5, pin 7 goes high. But why, oh why, is the current through R3 (shown with the red I(R3) line) listed as negative, and similarly positive when the input is -5V?

I feel like I might have misunderstood some fundamental concept of opamps.


texts:
I am a student doing my Master's Degree having a background in Electrical Engineering. I have studied on my own millers indices, crystallographic planes and directions so to be able to understand the process of silicon etching, which is required in my studies. The problem is that I am unable to understand the following text that is written in my textbook (I quote from it):

"When Silicon is etched anisotropically, i.e. depending on crystal direction, and a {1 0 0} surface direction is used, cavities will result which have the same {1 0 0} orientation at the bottom and are determined laterally by {1 1 1} surfaces. The reason is that {1 1 1} surfaces are etched off using a minimal etch rate and this way becomes the most resistant"

Could someone please help me understand this concept?


texts:
I have small box (10cm x 10cm ) and I need to measure speed of ball (r=2cm) getting inside.

I assume there are at least two possible ways.

Put a sensor inside the box in point A and second one deeper in point B
then measure at what time ball was in point A and what time in point B and calculate the speed.
Use some sensor on the back of the box and use Doppler effect which will measure speed of reflected wave, but I assume that this method doesn't fit here simply because the ball could destroy this sensor.

And advice? Like what sensors I could use, some gates?


texts: Change in gain and cutoff frequency of 2nd order passive filters due to amplifier circuit

texts:
I'm designing an simple equalizer for a first course in Electric Circuits and having some problems. Circuit diagram and AC Sweep Simulation (Multisim 14):

Circuit Diagram

AC Sweep Simulation

The Low-Pass filter was designed to have a cutoff frequency of ~900Hz. Before I put an amplifier in the circuit, the simulation shows a cutoff frequency as projected. But after, it gone to ~1272Hz (see AC Sweep Simulation) and gain at lower frequencies is no longer 0dB (went to -3.3dB). For the High-Pass circuit, gain remains unitary (0dB) at higher frequencies, but cutoff frequency was altered too. So:

Why is this happening? (Change in gain and frequency)
How to avoid it?


texts: Nature of noise gotten from digital oscilloscope

texts:
I've got strange noise while using digital oscilloscope (Auris B-424). Spectrogram of this signal presented on this image: (X time in seconds, Y frequency in Hertz, in this image case from 0 to 50 MHz)

Zoomed versions: 1, 2 On oscillogram noise looks like impulse interference with amplitude approximately 10 millivolts.

Simple scheme (fiber semiconductor detector) is connected to the input of oscilloscope with short 50 Om coaxial cable. Without anything on input channel noise is significantly lower (10-15 times), although still presented. Surge protector and ground used for powering oscilloscope and notebook. (outer conductor of coaxial cable is grounded too) My main guess is impulse interference from notebook and oscilloscope itself, but I can't find way to deal with it.

What do you think? What nature has this noise and is there any way to reduce it?


texts: Adding a callback for processing the UART data seems to cause issues with I2C interrupts

texts:
So I wrote peripheral drivers on STM32 and wrote a simple application to read the user input via terminal and respond accordingly. I am using interrupts for both UART and I2C but the way I previously did was more towards "polling" than just interrupts, as shown in the example below.

// uart.c
void UART_session(USART_Handle *usart, I2C_Handle *i2c) {
    char tempBuffer[usart->rxSize];
    memset(tempBuffer, 0, rxBufferSize);
    while(true)
    {
        ReceiveSerialData(usart);
        ParseSerialData(usart, tempBuffer);
        bool status = ReadTemp(usart, tempBuffer, I2C_Handle);
        WriteUart(usart, tempBuffer);
    }
}
// main.c
int main(void) {

    HAL_init();
    I2C_init();
    UART_init();

    UART_session();  // loop
    while (true);
}

But I modified the code to call a callback function after i'm done receiving the data (using \r as an indication) for processing the data, executing it accordingly, and continue what it was doing before... but when I do so, I don't receive I2C interrupts anymore. I also made sure the static i2cHandle does have the same address as the original i2c from main.

// uart_hal.c
void USART2_IRQHandler(void)
{
   // ....
    if (ptrUSARTx->pUSARTx->SR & USART_SR_TC) // transmission complete
    {
        if (ptrUSARTx->USART_State == USART_TX_BUSY)
        {
            if (!ptrUSARTx->txLength)        // no more bytes to send
            {
                USART_DisableTransmission();
            }
        }
        else if (ptrUSARTx->USART_State == USART_RX_BUSY)
        {
            if (!ptrUSARTx->rxLength || endLine)        // no more bytes to receive OR user pressed enter
            {
                USART_DisableTransmission();
                USART_AppCallback(pUSART); // ** ADDED THIS CALLBACK **
            }
        }
    }
}

// uart.c
void USART_AppCallback(USART_Handle_t *usart) {
        ParseSerialData(usart, tempBuffer);
        bool status = ReadTemp(usart, tempBuffer, i2cHandle); // ** NO I2C INTERRUPTS **
}

static I2C_Handle_t *i2cHandle;
void USART_receive(USART_Handle_t *usart, I2C_Handle_t *i2c)
{
    i2cHandle = i2c;
    USART_EnableInterrupts(USART_RX_BUSY);
}

// main.c
int main(void) {

    HAL_init();
    I2C_init();
    USART_init();

    USART_receive(&usart, &i2c);
    while (true);
}```


texts: FPGA ethernet pass through works one way but not the other

texts:
I am using 2 triple speed IP cores at 1Gig and using them as a pass through between 2 PHYs, one being strapped RGMII to copper and the other being strapped RGMII to 1000-BaseX.  I am using scapy to send UPD packets to test the pass through, and when I send from the fiber and out the copper I am able to view the UDP packets correctly on another system using wireshark.  When I try to send in reverse from copper to fiber, I do not get anything.
Using the signal debugger tool on my IDE, I am able to see the internal data signals for each direction.  The fiber to copper one looks as expected, and I am able to match the packet on wireshark to the packet that I read in the debugger.  When I do the same for the copper to fiber pass through, the signal debugger sees either nothing, or a jumbled mess of seemingly random data.  Obviously it is getting corrupted somewhere between where I read it and the source, but I am a little stuck.  I have tried reading the RGMII signals directly, but I don't really understand the encoding scheme, but they did not match, if that means anything.
I think I can safely say that both of the PHYs and MACs are configured correctly, as I don't think I would see any pass through from one side.  I am thinking this is more of a PCB/timing issue but I'm not sure.  I am sending UDP with the same script on the same machine for both.


texts: Altium: How can i add thermal releif to the GND footprint of one component?

texts: I want to have the pad that is connected to ground on one component to 'relief connect' on altium but have all other components whos pad is connect to ground to 'direct connect'. Is this possible?


texts:
I have a serial to parallel chip ( 74HC595-N ) which work well when I run the arduino script made for it. ( the current wiring work perfectly when I send data through the data pin )

But then I started to play around with other pin, leaving the 74HC595 circuit simply not initialized: I don't use the PIN in the 2nd script ( I use other pins ).

And I realized that when I play around with my 2nd circuit, for no apparent reason, the lights from the first circuit change state.

I though : hum, must be that weird concept of "floating voltage" I heard about... Not sure how to address that, but fair enought.

So I decide to fix the problem the lazy way and unplug the 3 cable ( latch, clock and data), great the light stopped flashing... Oh wait now ALL the lights are permanently ON. Since I'm not sending anything through the data cable, I'd like the LED to be OFF by default. I've tried to put some resistence in a attempt to create a pull up and/or pull down resistance, but it changed nothing ( possibly because I don't know what I'm doing as I don't fully understand what's going on and the details of how that chip work)... I'm just impressed I didn't blew anything.

I know you'll say it's probably a useless question and bla bla bla, but I'm still learning and most of the "project" I'm doing right now are useless anyway, so I'd like to understand why all the light are on, and how to fix this problem. Kind of a side quest in my electronic adventure.

I drew a diagram from CircuitLab. ( Ps.: I know I kind of wired the 7segments display a weird way, I just figured out how to count the PIN order recently ... did I told you I was beginning ? )


texts: Is it possible to power an Arduino Nano and a 6 Volt DC motor from the same power supply?

texts:
I am building a motorized, speed controlled turntable using an Arduino Nano and a 6V DC motor. I have read that the motor and the micro-controller should have separate power supplies because noise from the motor can damage the micro-controller. I was wondering, would it be possible to eliminate the need for a separate power supply by inlining a diode at the power input to the Arduino? I am guessing that this might be possible because the diode would eliminate damaging fly-back voltage from the motor coil.
My question is, would this work? I don't really want to try it without advice first because I don't want to damage my Arduino nano board.


texts: Measuring temperature of microcontroller and other large ICs

texts:
I'm going to be using a microcontroller and SDRAM IC in an enclosure that could, given some environmental variables that I have no control or knowledge of, get too hot for the devices to work properly.  Redesigning the enclosure is not an option.  However, I could notify the operator, if my microcontroller had a means of reading the temperature.

How can I monitor the temperature of a large IC?  I'm using 54-pin TSOPs and 100-pin TQFPs.  I've considered using a SMD thermistor and an ADC on the microcontroller, or using a prepackaged solution like this SOT-23-3 'active thermistor'.   However, with either of these methods, I'm not sure how to thermally couple the devices.  I'd like to avoid having components on the back-side of the board if possible.

Other possibilities include adhering a device on some long leads to the center of the IC, or monitoring the current used by the device, and extrapolate the power consumed to get an estimate of the temperature.  Both of these seem like hack jobs, while a thermistor or temp sensor seems much cleaner.

What single-sided layout will simultaneously give be the best thermal properties to cool my devices, and allow the sensor to be thermally coupled with the die of the IC?  Or, are there other methods that I'm not considering that would be better?


texts:
let's consider this circuit:

Consider the node A: it is at GND (0 V) because of the voltage buffer at right.

So my question is: is it possible to remove it and to consider the following simplified circuit, or we can only put VA = 0 but solving the circuit without removing the buffer?

Does the current I affect the circuit?

Are R1 and R2 in parallel?


texts: For same size and weight, are alkaline batteries more amp hours than rechargeable?

texts:
For same size and weight, will alkaline batteries last longer or shorter than lithium ion recharageable batteries?

I am not just talking about new batteries here. When I use lithium rechargeables I notice that they seem to quickly degrade and last for a lot less time than they did when they were new, so I am asking about typical time, in other words, after the device has been used for at least 3 months and been recharged at least 20 times.

For example, let's say I have a walkie-talkie with a rechargeable lithium ion battery. I use it for 3 months and recharge it 20 times. Will the device last longer, as long, or less long, than if it had the same weight of alkaline disposable batteries?


texts: Confusion of number of times and number of cycles

texts:
I know the question is kind of simple, but I'm a newbie and just bought a 8051 kit to learn MCU myself. I'm working on an example that use djnz instruction to create blinking frequency below.

Assume that djnz takes 3 cycles to execute every time.
MCU clock frequency: 2 MHz.

Number of times djnz instruction executed = 1000  # ln 1
Number of cycles = 3 * 1000 = 3000 cycles         # ln 2
Blinking Frequency = 2 MHz/3000 = 666.67 blinks/s # ln 3

The parts I am confused:
(1) Does "number of times" mean frequency?
(2) Why does # ln 2 use djnz's execution time multiplied by djnz's frequency?
p.s. I know that frequency = 1/cycle, and the duration of a cycle depends on an instruction.


texts: How can a higher power circuit share the ground with a lower powered circuit?

texts:
Just when you think you understand electricity, it throws another curve ball at you.

The following circuit confuses me.  The Arduino has it's own power circuit supplied by either batteries or a transformer at +3V.  The light bulb is powered somewhere between 0 and 60V by a separate circuit. Its ground, however, is connected to the Arduino's ground pin. To further confuse me, the gate is being driven by the Arduino, but its pulled down resistor is also tied to that ground.

I was under the impression that high powered circuits should be electrically isolated from the lower powered digital circuits. How can this work without destroying the Arduino? Why would you want to do this and where does the current sink to?  The Arduino circuit or the external circuit?


texts: Electric potential on different points of a simple circuit

texts:
I had a quick question on the electric potential between two points on a short circuit. I apologize if this question does not make sense or if I am using terms like, "electric potential" incorrectly. Let me know where I am incorrect in my thinking. I am trying to learn this material and it is becoming a challenge.

From what I understand, there exists a potential of sorts between the anode and the cathode terminal of a battery and that I am able to measure this potential with a Voltmeter. I have not been able to test this scenario in real life, since it involves a short circuit, but from what I understand, when the leads of the voltmeter are placed close to the battery terminals, there should be a reading indicating a presence of voltage. This example is shown in the first picture, and I am assuming that there would be a potential of 12 V present.

simulate this circuit – Schematic created using CircuitLab

My question is, as we move the voltmeter test leads closer to one another, would there be an observable change in the potential?

simulate this circuit

I am making the assumption that as the test leads get closer together, the potential between these two points in space is getting lower and I should be able to measure this change in my voltmeter. Perhaps I do not fully understand what exactly a Voltmeter is measuring and how it relates to potential. Any help in understanding this scenario would be appreciated. Cheers.


texts:
Consider the following wiring from a microcontroller to a sram chip:

uC        SRAM
A0    --> A3
A1    --> A0
A2    --> A1
A3    --> A2
A4    --> A4
..    --> ..
A15   --> A15

As you can see, some of the address bits are swapped.

So when it comes to reading / writing the memory, will there be no errors? For example:

Address Microcontroller    Address Chip        Contents
0000                       0000                H
0001                       1000                e
0010                       0001                l
0011                       1001                l
0100                       0010                o
0101                       1010
0110                       0011                !
0111                       1011                \0

So... from the microcontroller's side the addresses are all ascending, but as you can see in reality, the uC addresses various memory places in the sram.

Is this a problem? I think with ONE microcontroller using the memory: no, since the microcontroller can nevertheless fetch the data in proper order (even if its not doing this from outside observation). But I think, with two or more microcontrollers this could become a problem IF the address bits are not connected in the same manner.

Conclusion:

As long as each address is distinct from another, there will be no reading / writing problem. (Considering ONE microcontroller using the memory!)

And:
As long as each data bit is distinct from the other data bits, there will be no reading / writing problem. (Considiering ONE microcontroller using the memory!).

So my final question is: is my understanding for this problem correct or am I missing something? I could not find something on the internet concerning this problem!


texts: Using SPST Switch as Button using Capacitor, which type?

texts:
Before I start, know that I'm still very much a beginner at electrical engineering. I'm building a switch box to be used for PC simulators using mainly (non-momentary) SPST switches and a USB encoder.

However, most games/sims can't use these kind of switches as pulses, as they are on-off rather than pulse-pulse.

I could use one of the dual pulse encoders sold by "Desktop Aviator," but According to this article, you can also use a capacitor to create the same pulse effect whenever the switch is toggled. But, it only says "47uF." Which voltage though? Would any work? The pulse should be under one second. A̶g̶a̶i̶n Obviously, I'm very new to this. Thanks!


texts: Audio Amplifier op amp without feedback?

texts:
i have a question about this circuit

the inverting input is connected to ground , so any voltage different than 0 in  the non inverting input will saturate the op amp ( correct me if i'm wrong).
how can this circuit work without feedback ?


texts:
I'm designing a buck converter based on TL494. And I have to drive high side mosfet, i want to use a gate drive transformer, switched by totem pole driver.

The problem is that slopes of signal coming out at collector are (i think) very bad. (>100ns) I want to drive mosfet with slopes <50ns, and signal will get only worse in transformer etc. Problem is really visible with low duty cycle (signal has almost triangle shape). Also tried with TL494 on high side, and R3 on low side.
I can post scope images.
I am thinking right? Could i get better slopes from TL494?


texts: EMIF interface between FPGA (virtex5) and TI - DDUC GC6016

texts:
I am trying to interface the FPGA and Texas DDUC GC6016 with EMIF interface.
I am a little bit confused in the part of interface: can you help me out?

Problem: the data(16bit), address (8bit), write enable, chip select, data read enable is coming to FPGA from PCI. I have to receive these data and send as per the enable signals and respected addresses to external DDUC chip which is having the same signals as a inputs to communicate.

Does any one know the logic to implement?


texts:
I want to add a 3-bit and a 5-bit number preferably using 4-bit full adder. The 5 bit number only has these 5 possibilities (multiples of 7):
00000
00111
01110
10101
11100
and 3-bits (1-5):
001
010
011
100
101

What is the most hardware efficient solution (minimum no. of ICs)?


texts: Help identifying a component in glass housing (looking like a resistor) and markings "PH 41 48"

texts:
I have found an electric component and am asking what its name is.

The orange thing is smaller than the a resistor, if that helps...
Thanks all.

New Info

The characters written are:
PH
41
48


texts: How to make/describe an element with negative resistance of minus 1 Ohm?

texts:
How do I make/describe an element with negative resistance of minus 1 Ohm?
It's I–V characteristic should then be
\$I = -U\$
Is this possible?

I need exactly what I wrote. No compromises. The negative resistance should not be used differentially.
I need to build such the device. It should not only work grounded, but at any potential.
Of course it should be kind of "active".
If a power source is required for such a device -- then that is ok. Power sources are allowed :)


texts: Tapping power from series of solar panels

texts:
I'm developing a device that runs off 24V DC. I'll be installing it at a client's site who has arrays of solar panel, with 24 panels in series, making it a 1000V system. Can I tap one panel from the series to get around 40 volts, so that i can give it to the charge controller and then to the load?

Would that affect the complete series? A sample series is shown in the figure.

simulate this circuit – Schematic created using CircuitLab


texts:
what is the difference between ATMEGA328 TQFP32-08 and Atmega48 TQFP ?
does he share the same pins ?

I'm a bit confused,  :
https://eu.mouser.com/datasheet/2/268/Atmel-8271-8-bit-AVR-Microcontroller-ATmega48A-48P-1315288.pdf


texts: New to Electronics: How to connect these sparkfun sensors to this radio?

texts: I'm really new to this electronics thing, but I was curious how to connect this High Altitude Balloon sensor board to this modem. I want to think that it will connect easily and that the hardest part will be connecting the battery to both?


texts:
So this question is a bit related to my other question on using Pspice to get the required transfer function of the buck converter.
Here in this circuit I'm trying to get the open loop transfer function bode plot of the converter. As suggested by VerbalKint in the other question, I am using the dB(voltage) probe as shown (not using x,y points):-

And this is what I get :-

The Pspice bode plot is wrong, since there should be an overshoot of nearly 32 dB at the resonant frequency 7.587 kHz, but here its all wrong. : An error I realized pretty late, I should be using the DCM buck transfer function.
Here is the circuit with bias voltage display.

This is what I got on MATLAB using the DCM Transfer function:-

So it is still quite different, as from Pspice I get PM = 48.73 degrees at 89.03 kHz, very different from MATLAB.
EDIT 1:-
Here is the model definition for U3 used here:-


texts: What is the function of this cable surrounding the CRT of old televisions

texts:
I have opened old televisions, and each time, I'm wondering what is the function of this cable, roughly insulated with some tape.

Note: I know what are the risks of opening televisions.


texts:
When is it actually practical to use a fuse?
Like lets say your building a robot using an Arduino.....what area would you want to protect the most with a fuse?

I mean do they even make fuses that small (5v's and such) and how do you go about "connecting" them to wires, since the smaller ones seem to be a solid cylinder


texts: Is there a command or an option in the "plot" command that can generate png/jpg images of the plots?


texts: A4988 Allegro's driver limit current calculation

texts:
I'm not sure if my calculations for limiting current on Allegro's 4988 are correct.
I have a 12v stepper motor with a current draw of 2A per fase.

I want just a 1.6A draw so my calculations for Vref are
Vref= 1.6*8*0.1=1.28v
The RS of the driver is R100 =0.1ohm.

Are my calculations correct?


texts: What happens when I connect an LC circuit to only the positive terminal of a voltage source?

texts:
I have the following circuit:

simulate this circuit – Schematic created using CircuitLab

The switches flip at the same time. In the position shown, SW1 is causing a loop that only connects to V1+ and never to ground, because SW2 is off. What will happen there? Will there be any current flow in the whole L1/C1 branch?


texts: How are oscillator circuits characterized in a lab after their manufacture?

texts:
I know that ADCs are characterized by their INL, DNL ect parameters, but how about the oscillator circuits?

If we need to test/characterize an oscillator circuit block of a circuit on a test board what parameters and methods are mostly investigated?


texts: Can I replace an AND gate with two diodes?

texts:
I am creating a homebrew CPU. My current design has a TTL 'AND' gate that takes two inputs. The CLK (running at 1Mhz) and another that determines if the CLK should propagate onwards to update a register.

This all seems reasonable but I would like to remove the TTL chip from the design as I only need it for this one 'AND' gate. I found that two diodes can be used to create an AND gate in the following way...

Is this a safe thing to do with a 1Mhz CLK input? Will it provide as reliable an output as a traditional TTL 'AND' gate?

EDIT:

The CPU is made up of 74HC series TTL chips. With 5v being a logical 1 and 0v being a logic 0. With a clock speed of 1Mhz and. Input 'A' is the clock line and input 'B' is a control line coming from the instruction decode logic. It will have been stable for several 100ns before the next clock tick.


texts: Why do baud rates need to be same in asynchronous communication?

texts:
As far as I know, TX and RX pins operate independently. On the other hand, experimentally I get garbage reading if the baud rates of a lets say MCU and a PC are different.

Is there a way to explain this for a non-expert?


texts: Using reference PCB trace antennas without tuning them

texts:
I would like to integrate the following reference design of an inverted F antenna into my design http://www.ti.com/lit/an/swru120b/swru120b.pdf
but I am concerned with its performance with the rest of my system. I don't have access to a network analyzer to look at the performance of the antenna and tune it. Does anyone have any experience with using reference designs of trace antennas and running into issues with performance? If I do run into performance issues, is it possible to resolve them without using a network analyzer (i.e. is tuning without a network analyzer possible)?


texts:
What is the meaning of the following warning (raised by Quartus)?

Warning (10445): VHDL Subtype or Type Declaration warning at someFile.vhd(32): subtype or type has null range

The offending line of code is:

-- Drive unused low
q( N - 1 downto X ) <= ( others => '0' );  -- drive unused low

N and X are integer constants used successfully elsewhere in the code (without raising warnings). q is declared as q : out std_logic_vector( N - 1 downto 0 )

The same error is also raised for this line of code (in another file):

-- Upper nibble
q <= zero( N - 1 downto 8 ) & q0( 7 downto 4 ) & zero( 3 downto 0 );

N is an integer constant used successfully elsewhere in the code. q is declared as q : out std_logic_vector( N - 1 downto 0 ). q0 is declared as signal q0 : std_logic_vector( N - 1 downto 0 ). zero is declared as constant zero : std_logic_vector( N - 1 downto 0 ) := ( others => '0' )

It seems ( others => '0' ) is the common point for both, but I don't know how this relates to the null range warning.


texts: LM2664 can I use the ceramic capacitors instead of the electrolytic ones?

texts: I need the negative voltage for my OPAMP and I use the LM2664 inverter. I have a very limited space available on my PCB. Is it OK to replace the electrolytic capacitors with the ceramic ones?


texts: LED switching: Circuit reacts unexpected

texts:
I have my current circuit in LTspice and am trying to simulate it.

The idea is the following: I have a UV LED (360 nm) which I want to switch off  in at most 6ns.

For this I have my LED in parallel with an inductor. As a switch I utilize an NPN transistor. To switch the transistor faster, my intention was to use a Schmitt trigger. But for an unknown reason the diode and the NPN are acting unexpected.

Why does the transistor (V(n003)) not fully reach ground potential?
Why does the diode acting so weirdly?
Why does the Schmitt drigger not work properly? (second image Vn006)


texts: How does ESD protection work with TVS diodes?

texts:
I have two questions regarding TVS diodes.

This paper describes very well what happens when you want to protect a circuit with a unidirectional and bidirectional TVS diode and a positive and negative ESD happen:

http://www.protekdevices.com/xyz/documents/kb/tech/ta1003.pdf

Now let's consider this situation:

If an +8 kV ESD happens, then D2 will be forward biased and conduct, and D1 will be reversed biased and conducting as well. Where will the current due to the ESD go through? Is there a predominant diode? For an instant there is a connection between VCC and GND, isn't it a problem?

Second question: let's say I need to protect a pin so that its voltage range stays between 2 and 4 V. Will this below circuit, where the diodes have a reverse voltage of 4 V, work?


texts: Supply an analog circuit with digital control

texts:
Tell me please how best to power the circuit which has an analog part and the part which, with the aid of arduino and digital potentiometers, controls the analog part. The supply voltage V(in) of the analog part is 9 volts (this is a guitar effect). Is it enough to put the voltage regulator after the same power source to get 5 volts (for example 78L05) or is it necessary to put a stabilizer and 9 volts too? I do not know how to do this most correctly. Please advise how to properly supply this scheme.
Update: It turned out that the analog circuit works fine from 5v, I tried to draw three possible options for powering the analog and digital parts, tell me which one is better, or suggest improvements or your own version.


texts:
I am trying to use ICP (Input Capture Pin) functionality of ATMEGA328p (Arduino Uno board) and somehow it does not seem to work. I have connected a switch to ICP pin PB0 in this case, and want to toggle a LED at PC0 every time the switch is pressed. Somehow i am not landing in the ISR. ICRL seems to show zero too. Here's my code:

void init_input_capture()
{
    TIMSK0 = ( (1<<ICIE1) );                     /*Enable ICP Interrupt */
    TCCR1B = ( (1<<ICES1) | (1<<ICNC1) | (1<<CS11));  /*Enable rising edge detection, noise cancellaton*/

}
void Transmit_string(char *str )
{
    for(i=0; i<strlen(str)+1;i++)
        Transmit(&str[i]);

        Transmit("\n");
        Transmit("\r");

        for(i=0; i<strlen(str)+1;i++)
          str[i]=0;

}

void capture_function()
{
    if(capture_occured==1)
    {
     LED_PIN(SET);

    }
    else
      LED_PIN(CLEAR);
}

void main()
{

   DDRC  = 1<<PC0;  /*Pin PC0 os output LED */
   PORTC = 1<<PC0;  /*Enable PC0 internal pullup */

   DDRB  = 0x00;   /*PB0 as INPUT*/
   PORTB= 1<<PB0;

   usart_init(baud);

   init_input_capture();
   sei();

   while(1)
   {
        capture_function();
        sprintf(value_buf,"%1u", temp);
        Transmit_string(value_buf);
        _delay_ms(300);
    }
}

ISR(TIMER1_CAPT_vect)
{
    capture_occured ^= 0x01;
    PORTC ^= 1<<PC0;  //not working
    temp=ICR1L;

}


texts:
How is profiled Litz wire manufactured?

Is it winded in the shape, or a round one passes thought conforming process?


texts: I'm looking to get started with Arduino and I wanted to know any good books out there. Any help would be appreciated


texts: What benefits are there to programming an MSP430 in C/C++ over Energia?

texts:
I'll start by saying I'm new to micro-controller programming. I've had some (ca. 30 years) experience programming, and some of that was writing C/C++ but those days are long behind me now.

Since I'm just starting, I want to know what benefits there are to coding my logic in C/C++ over the much simpler Energia language. I'm looking for specific features or instructions of the MSP430 that one can only program in C/C++ rather than code organisation (classes, enums, type safety, etc.)


texts: Measuring parasitic capacitance of coil using an LCR meter

texts:
Would it possible to use an LCR meter (DE 5000) to measure the parasitic capacitance of an multi-tapped torid inductor?
If this is possible how should i do this, to get the best results?

Help is much appreciated!


texts: Is it safe to wire an AC-DC adapter directly to a DC motor? (with this setup...)

texts:
I just wanted to check that this setup is safe as I am not an electrical engineer, nor am I experienced...

I am using an AC adapter which outputs 12 volts DC. It has a max current rating of 6 amps. I have wired it directly to a DC motor (rated for 12 volts) using wire rated for 21 amps. The AC adapter has a pin output like on a laptop charger, so I used an adapter which allows me to screw in the positive and negative wires. (Looks like this: https://uge-one.com/image/cache/catalog/catalog/0%20UGE%20JACK%20ADAPTOR%201-550x550.jpg)
I intend on using some insulation tape around this to make it safer.

The motor drives a system of pulleys to lower/raise a shelf in a linear motion, so it has some load. I tested the current drawn with this load with some batteries. With 5.9v across the motor, it drew 1.8 amps (with a load).

The eBay listing for the motor (I couldn't find a decent datasheet) states that its locked-rotor current is 3.25 amperes. I assume that this is the maximum current it can draw, although could the starting current exceed this or exceed the max current rating of the AC adapter (6 amps max)?
I ask this because the load could increase as it is driving a shelf with items on. I am not sure if this is something to worry about as the item description for the AC adapter says that it does have over current protection, so what's the worse that could happen?

So, my question is, does this circuit sound safe with my current, tested load, and would it be safe if the load were to increase? Is the safety gap between the amps the motor is drawing and the AC adapter rating large enough?

Many thanks in advance!

The AC adapter that I am using: https://www.amazon.co.uk/gp/product/B074HX4GJ3/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

The motor that I am using: https://www.ebay.co.uk/itm/775-DC12V-4500RPM-Motor-D-Style-Axle-Mini-Generator-DIY-High-Torque-Bearing/312542643980


texts:
I am using a 26AWG wire for an application. As per specifications a 26 AWG wire can carry, 2Amps max. Supposing I connect a load of 3Amps. For how long will tis be sustained by the said wire ?

The current is applied in pulses in this application, of 25 mSec max.

I mean is there any way I can calculate the time taken before the wire burns out ?


texts: AWR PA Output Power Simulation - Credible?

texts:
I'm working with the SKY65111-348LF power amplifier from Skyworks and wanted to obtain some idea of its performance using AWR Microwave Office. I'm not sure if my process is correct and wanted to have it verified by someone with more design experience.

Starting out, I created a system block diagram that consists of the amplifier with its corresponding parameters and a low-pass filter (LPF) to mitigate harmonics. It is worth noting the LPF block references an S2P file.

Based on the datasheet parameters given, I entered what was available in the amplifier "Basic Settings":

Tuning the model, I found that -0.5 dBm input power yielded +30 dBm output, which is my desired value. The following graphs were obtained:

I am wondering if the PA parameters - on page 3 of the datasheet - were entered correctly and if the resulting output plots can be trusted?


texts: 4-pin PC Fan PWM control and speed monitoring

texts:
I want to control and monitor the speed of a 4-pin PC fan using an esp8266.

When there is no PWM control signal sent to the fan from the esp this code reports the fan speed correctly.  However, when the esp PWM control signal is connected to the fan things go wrong with the speed reporting, but the fan speed actually responds as expected to the PWM signal.

The setup:

The fan is driven from a 12V supply and the NodeMCU v2 esp8266 is
powered by USB from a PC.  The 12V supply and the esp8266 have a
common ground through the esp’s GND pin; and
The tach signal from the fan is pulled up the 3.3V pin of the esp and
is connected to pin D3 of the esp.

When the system is connected in this state (no PWM signal) the fan speed is at maximum and its speed is correctly reported in the serial monitor at approximately 1410 RPM.  I have used the debugging tools in VisualMicro to watch the vaue of the interruptCounter variable in the computFanSpeed() function during operation and its value gets to 49 before it is reset to zero after exiting loop().

The PWM signal originates from esp pin D1 and is measured to be 2.0V using a multimeter.  When this PWM signal is connected to the PWM input of the fan it responds as expected, however the speed reported in the serial monitor climbs to a non-sensible number (123300 RPM).  The value of interruptCounter variable in the computFanSpeed() function gets to 4180 before it is reset to zero after exiting loop().

I don’t understand where things are going wrong – specifically why is the handleIinterrupt() function being triggered when the fan is operating under PWM control by the esp?

Another note:  For some reason if any value other than 0 is provided to the pin argument in the attachInterrupt('pin', 'ISR', 'mode') function the fan speed recorded in the serial monitor is 0 RPM.  I have tried a several combinations of different pins and values for 'pin' and have not been able to have the speed reported in the serial monitor - it always shows 0 RPM.

volatile int interruptCounter; //counter use to detect hall sensor in fan
int RPM;                      //variable used to store computed value of fan RPM
unsigned long previousmills;

//NODEMCU ESP8266
#define tachInputPIN  4
#define pwmOutputPin 5
#define sensorInterrupt 0
#define pwmDuty 630

#define calculationPeriod 1000 //Number of milliseconds over which to interrupts

void setup()
{
    Serial.begin(115200);

    previousmills = 0;
    interruptCounter = 0;
    RPM = 0;

    //NODEMCU esp8266
    analogWriteFreq(8000);
    pinMode(pwmOutputPin, OUTPUT);

    attachInterrupt(sensorInterrupt, handleInterrupt, RISING);
    pinMode(tachInputPIN, INPUT);
}

void loop()
{

    // NODEMCU esp8266
    analogWrite(pwmOutputPin, pwmDuty);

   if((millis() - previousmills) > calculationPeriod) {// Process counters once every second
    detachInterrupt(sensorInterrupt);
    computeFanSpeed();
    displayFanSpeed();
    previousmills = millis();
    interruptCounter = 0;
    attachInterrupt(sensorInterrupt, handleInterrupt, RISING);
   }

}

void ICACHE_RAM_ATTR handleInterrupt() { //This is the function called by the interrupt
    interruptCounter++;
}

void computeFanSpeed() {
    //interruptCounter counts 2 pulses per revolution of the fan over a one second period
    RPM = (0.5) * (interruptCounter / (calculationPeriod/1000)) * 60;
}

void displayFanSpeed() {
    Serial.print(RPM, DEC);        //Prints the computed fan speed to the serial monitor
    Serial.print(" RPM\r\n");      //Prints " RPM" and a new line to the serial monitor
}


texts: How can the following equation which represents two series resistors (a & c) in parallel with a third resistor (b) be written in terms of conductance?


texts:
I've stripped out an old IDE (40 Pin) HDD from 1998 for use in a POV display project (Gr. 12 Computer Engineering), and I've been trying to spin it up.

The problem is that the HDD motor is brushless DC, so it requires more than just a ground and source connection. Our electronics has a max output current of about 200mA (555, transistors, other ICs), so I can't work with those.

Connecting the HDD with the PCB to the PSU will only turn the motor on for about 15s before it shuts off.

The HDD is completely stripped with only the motor and the PCB screwed into the base. The motor has 4 pins. From the time I spent playing with it, there's 1 pin for ground, and 3 other pins that I think is for the 3 pairs of coils.

HDD information:

Fujitsu MPB3043AT
12V DC 0.32A
5V DC 0.5A

Materials:

Arduino Uno
Old HDD
PSU
Breadboard
9V battery
1.5V batteries
74HC164 8 bit sihft registers
555 Timer IC
3904/3906 Transistors
Capacitors, resistors, potentiometers

What options do I have to get the motor to spin (Preferably without the PSU, but I'm open to options with the PSU)? Is there a pin on the IDE that will allow me to turn it on/off?

UPDATE 1: I fiddled around with the IDE cable. When I connect pin 27 (IO Ready) to pin 2 (Ground), the motor started spinning as if I just plugged it into the PSU, but only for about 10s. And I had to wait a few minutes before I can get it to spin again using this method

UPDATE 2: Turns out the motor is only 5V and not 12V, that should ease things up a bit


texts: Wireless Power Transfer at 6.78 MHz Using Magnetic Resonance

texts:
In our situation we are using the GaN 300W kit which drives a coil with 100V @ 6.78MHz. We have two coils, each with an Req = 0.5 ohm and L1 = 480uH and L2 = 432uH. The user guide mentions impedance matching networks in the block level design on page 4.

I reviewed impedance matching on AllAbout Circuits which led me to their L-Matching Network Calculator.

I've been simulating using LTSpice and doing an AC Sweep to plot power vs frequency, expecting a properly tuned circuit to have the best response at 6.78MHz.

Simulating with a 50 Ohm load I get this:

Expected...

I tried a tank circuit which at first did not make much sense to me since to my understanding a properly tuned tank circuit would not draw any power from an AC source that drives at the tank circuit's resonant frequency. But after reading the first response on this page it actually makes sense as why this might work.

Same results. No improvement.

I did some variations of the L-Matching networks but had no luck... so I asked one of our engineers and he said that currently I am treating this problem as a transmission line problem (hence the L-Matching Networks) but I should actually be treating this as a lumped circuit problem, where in the simplest term I just want to make it so that the supply only sees a purely resistive load.

My first thought was putting a cap and inductor in series so that their reactive parts cancel out (im thinking a cap and inductor where in their complex number form their imaginary parts are equal but opposite) so I tried this:

Again, not what im looking for. Havent really looked into why this is the response but that's for another time I guess.

Looking on Stack Exchange I found the second answer to this post (same post as before) and he shows the equivalent circuit of a transformer which looks like the lumped circuit idea I was told to look into.

How does a transformer turn into this lumped circuit? It looks like the two coils are consolidated into one but how exactly is that done? And how do you tune this circuit to resonate at a desired frequency?

And sorry about this one being a little out of place but while writing this I had a thought and tried this:

Unfortunately I dont have screenshots so I cant be sure but I think before I was putting L4 before C2 and that was giving me a circuit with an improper response to the AC Sweep. I used the L-Matching network calculator for 6.78MHz but this circuit looks a MHz off so still would need to be tuned, but is this actually a valid way to implement wireless power transfer for magnetic resonance?

When using the calculator I do two separate calculations, the first L matching network is calculated using the AC source as the source (0 reactance) and the TX coil as the load (0.5 ohm resistance). The second matching network is calculated using the RX coil as the source (0.5 ohm resistance) and 50 ohm resistor as the load (0 reactance).

If neither this nor the lumped circuit equivalent are the routes to go, how is magnetic resonance wireless power transfer implemented?


texts: Can a house battery share common ground with the starter battery without interference?

texts:
I am quite new at this so bear with my questions. I have purchased two 12 volt batteries which I will connect in series for 24 volt and to be used as house batteries. I drive a truck which has a 24 volt system. The truck's electrical system is grounded to the chassis on the negative terminal.

If I ground my house batteries to the chassis on the negative terminal, does it have any effect on the vehicle's electrical system? The starter on my car is 4 kW so I prefer to keep the systems isolated. I don't understand if grounding to the chassis can cause the house batteries to be pulled on when cranking.

The second question is, if I have grounded the house batteries to the chassis, can I drag one cable from the positive terminal on the house
battery to a different location in the truck, and for negative simply use the chassis at that location?


texts: Sodium metasilicate pentahydrate and Photoresist Universal Developer Crystals same chemical?

texts:
I'm thinking about using the photo method for etching PCBs so I need a developer for the positive photo resist.

There is this sodium metasilicate based universal developer that people online seem to praise (e.g. this ebay item) it sometimes goes by the name of SENO 4007, RS components has its own label on what appears to the same thing because the safety datasheets between the RS components one and the ebay one are very similar and both mention "sodium metasilicate" as the sole ingredient.

On the Mike's electric stuff blog he writes that this developer's formula is Na2SiO3*5H2O and the substance's name is sodium metasilicate pentahydrate but then he gives a recipe of mixing liquid glass with sodium hydroxide to produce this developer, I'm not strong in chemistry so I'm not sure this would produce Na2SiO3*5H2O and I don't wont to make things complicated for myself if I can get the same thing as a crystals and just dissolve it in water.

So I wounder would dissolving sodium metasilicate pentahydrate crystals (which is a more generic checmical that I can get locally and don't have to order by mail from abroad which I'm not sure my customs will allow through) in water give me the same results as this "universal developer" thing?

My crude understanding of this development process is that you need an alkaline (base) solution to wash off the exposed photoresist so things like caustic soda (NaOH) are used because of their base qualities.
This sodium metasilicate pentahydate description says

  Sodium Metasilicate forms highly alkaline solutions when dissolved in
  water.

So it looks like this will produce a base when dissolved in whater and this should make it into a positive photoresist developer.

I've searched online but it looks like most of the people there are no better chemists than me so I've not found a clear answer if this sodium metasilicate pentahydrate would work.

Edit: I can confirm that sodium metasillicate pentahydarate crystals work.

I've tried ordering universal developer crystals and sodium metasilicate pentahydrate crystals, both work for developing positive photoresist. The metasillicate pentahydrate I've used was labeled 57%. In both cases I've used a teaspoon of the powder per 200ml of warm tap water. The solution doesn't last as a developer so developing should be done right after dissolving the crystals. My exposure time was about 3.5 minutes, but this will vary depending on the exposure box.


texts: Capacitor specification for computer logic board replacement

texts:
I'm planning on replacing some of the electrolytic capacitors on a non-working computer logic board. I know the µf value, voltage and optimum operating temperature of the replacements, but I'm not sure what the other specifications for these should be. Specifically -

• Equivalent series resistance
• Leakage current
• Ripple current

Or are those values not important in this application?

Thanks in advance


texts: LED Display: Understanding Led pitch, resolution, viewing angle and distance

texts:
i'm working on project in which we need to design a Led Display. I google some information and get a little confused about some key topics.
Some of them are:

Led Pitch
Viewing Angle
Resolution
Distance
Display Size

I understand each topic alone but in order to build an appropriate Led Display I got a little confused with the relationship between these variables.

For example, if I want to design a Led display that will be placed on distance of 200m with dimension of 5.2m width x 1.2m height, how do I design the led pitch, resolution, viewing angle so that we have a smooth image on the display ?


texts: Setting the prescaler on timing circuit for LC meter?

texts:
I am trying to build an LC meter using the Arduino platform. It's based on this tutorial here.

Specification:  10nH to 1000nH, 1uH to 1000uH, 1mH to 100mH and capacitance from 0.1pF up to 900nF.

However, I am unsure which prescaler to use for the timer. If I'm not mistaken the timer affects how accurately the frequency is measured, thereby affecting the measured inductance /capacitance. How can I choose a suitable one?


texts: Trouble with Schimtt trigger settings for varying sinusoidal inputs

texts:
To make my problem easier to describe, I drew the above figures (abbreviated as Fig.).

The sinusoidal input comes from a rotating device, from a small alternator(a permanent magnet AC generator).

My aim is to convert these incoming sinusoidal inputs to pulses with nice sharp edges as in Fig. B. A DAQ hardware will read these pulses to obtain the frequencies...

As you see above, Fig. A is the input to the Schmitt trigger circuit(Fig. D). The input has some noise and its frequency varies between 4Hz up to 20Hz and its amplitude varies from 1V up to 12V. So the input will vary in this range and I want the circuit to work in any scenarios in this range.

My problem is my circuit works perfectly in simulation but fails in real life sometimes. Some outputs results as in Fig. C randomly. I do not remember if this was happening under particular inputs. But the frequency and the amplitude both increase with rotation speed of this alternator.

How can I fix this issue here? I asked a related question before but since I were not able to provide enough data I couldn't find a solution. The only suggestion was to choose C2 as 10uF and connect the negative end of this cap to the input signal, since according to the suggester the input was coming from an alternator.

If I use another Schimtt trigger as cascade at the output of this one the pulses becomes less noisy. But a pulse like in Fig. C looks very problematic. Is that because this circuit's upper and lower trigger limits are not arranged for the input range. I really need help at the moment and would be very glad for any adjustment suggestion in this circuit.


texts:
I am new to electronics and am tyring to figure out something that is a bit disturbing to me. I am trying to figure out the amount of resistance I need to put in series before an LED, and the equation I keep coming across is:

$$R = \frac{V_S - V_{\text{LED}}}{I_{\text{LED}}}$$

Where \$V_S\$ is the source voltage, \$V_{\text{LED}}\$ is the forward voltage for the LED, and where \$I_{\text{LED}}\$ is the forward current for the LED.

If my \$V_S = 5\$V, \$V_{\text{LED}} = 2\$V and \$I_{\text{LED}} = 15\$mA, then I calculate \$R\$ as follows:

\begin{align}
R &= \frac{V_S - V_{\text{LED}}}{I_{\text{LED}}}\\
&= \frac{5\text{V} - 2\text{V}}{15\text{mA}}\\
&= 3\text{V} / .015\text{A}\\
&= 200\Omega
\end{align}

However, double checking my math at the LED center, if you punch in 5, 2 and 15 in those fields, it will tell you that you need a \$220\Omega\$ resistor, and this worries me that either:

I've been away from arithmetic for too long, or
there's something else that I'm not considering here.

Is this web tool broken, or am I missing some important info/understanding here? Where did these extra \$20\Omega\$ come from?!?


texts: Thinking about LED light bulbs..as full wave rectifiers

texts:
Tw questions on LED bulbs.
First Qt:
Just something I was wondering. Since LED's bulbs are, by definition rectifiers ( I believe they are full wave) would it be possible to use them as such by putting a standard light bulb socket in a circuit?

Edit

Second question was cut and reposted elsewhere


texts: how to Design Rule Check an Eagle file in a git hook?

texts:
I can't find how to launch the ERC and DRC from the command line in Eagle. My hope is putting the command in a git pre-commit hook.

I'm perfectly ok with using a third party program or library if need be, but my google fu is not strong enough to find a useful tool.


texts: Looking for the category of IC that would send a signal to all selected output pins simultaneously?

texts: What would a multiplexer like device that allowed multiple outputs to be addressed simultaneously be called? - am looking to address multiple outputs in an array (many as possible - probably ganged) and then send a control signal (digital and or analogue) that appears on all selected pins at same time.


texts: IC to use for multiplexing SPI chip select

texts:
I have a number of SPI ICs but limited GPIOs on my microcontroller, so want to multiplex the CS pins to something that requires only a couple of GPIOs.  I use the predetermined clock, MISO and MOSI on the microcontroller.
My initial thought was a ring counter, but all the ones I have found set a single pin to high and the rest low.  I need a single low and the rest high.  I could use a shift register, but seems like overkill.
What is the best IC to use for this application?


texts: Why Tesla Electric Cars Use Induction Motor?

texts: Most Electric cars these days      use  Brushless        DC Motors. However recently someone told  me that Tesla cars use Induction motor (AC) instead? Why is it so?  Are        DC Brushless      Motors feasible compared to Induction motor?


texts: Does RF chip antennas require top/bottom ground plane to operate?

texts:
I've found a lot of RF chip antennas that in their datasheet provide a reference/test PCB layout with RF results. This PCBs have antenna mounting position and a RF line surrounded by GND plane.

Are this GND planes necessary to antenna to operate or they just report test board layout?

I ask this becouse my board is smaller than 30mm and top ground is splitted becouse components mounting, most reference board have 50mm lenght and solid ground plane.

Here's some examples of what I say:

Datasheet link: http://www.johansontechnology.com/datasheets/antennas/2450AT42A100_v2.pdf


texts:
My dad had just bought a solar array of 4kW together with an inverter, a kaco powador 4400.

The array is now running and generating electricity. I am trying to understand how it all works, but several questions pop into my mind. Does the value of 'total yield' in the display reference the amount of kW generated during the day? is the solar array producing power or energy? how much power or energy is the array generating per second?

I asked these same questions to my dad, and he said that the value in the display is the total amount of kW produced during the day, but as far as I remember, you cannot produce power, for power is the rate at which energy is converted into actual work, right?

Could someone clarify the above?


texts: electrical switch controlled remotely via mobile bluetooth arduino

texts: Without arduino what other ways? If I use arduino should I use ardunioBT and write a mobile software for communicating with arduinoBT. Or using Amarino with a arduino board is better (as amarino has a software portion already). Also there are many arduino board version, which one is good to start with. Thanks for your help


texts: Reduce trace width increase thickness with solder

texts:
Im designing a led driver for a friend of mine. The total consumption would be 0.5A (per Meter of led Strip) * 9 Meter = 4.5A, or around 5A. The strips are connected via screw terminals.
The problem is, that if I use a online width calculator, which says that the thickness should be ~7mm. If I would connect the Voltage Source with a Screw Terminal, the trace would interfere with the other pins of it. Could I just use 3mm (which fits) and then thicker the traces with solder or even solder wires to the points?
Thanks :)

Notes:
-PCB thickness is 35um
-aiming for single sided, to reduce amount of work.

~Straw

Pictures:


texts: I can't use digital ports with my raspberry pi?

texts:
I have a raspberry pi that I really want to be able to control some motors and was thinking of this one at sparkfun: http://www.sparkfun.com/products/9670

The problem is that the Pi does not have digital ports? And the motor require it for control (low/high signal). Is the GPIO on the Pi just plain analog? If thats the case, is there a addon that could transform signal from the Pi to the motor digitally?


texts: How are high-speed circuits tested if test equipment doesnt exist?

texts: How was testing done for Ghz to THz range circuits and devices before fast enough scopes and frequency counters existed?


texts: For a PLL Clock multiplier, where does the new clock come from?

texts:
If I understand it correctly, you use a PLL in an FPGA to get a higher clock from, say, a 50 MHz oscillator by synchronizing the faster clock to the slower reference one. Like if I had a 50MHz crystal and wanted to run my FPGA at 200 MHz, I'd use the PLL to lock the phase so every 4th pulse of the board clock matches the rising edge with the 50 MHz reference rising edge. So it sounds like the PLL here is correcting for error in the multiplied clock signal.

My question is, if I wanted to try this with MY FPGA, and make one of these PLL multipliers myself, where does the new faster clock come from? My first guess would be just using a bunch of buffers and an inverter and letting the propogation delay act as the timing in between pulses, but I'm not sure if this is the correct way to do this.

Also, how would I figure out the practical limits for how fast a clock I can run? Do I just run a simulation of my end circuit, look at the delay it takes for the outputs to stabilize, and use that as my maximum clock speed, or are there other considerations I need to make?

Thanks for any help you can give.


texts: What's the value of the supply voltage in this circuit?

texts:
I've been trying to find out the answer to this question. I know that the final answer is 3V but I can't seem to prove that.

I always get confused when there's two or more supplies on the circuit.

I've already tried the kirchhoff laws but I've never reached to the same result.
Can someone give me a hand and let me know if I at least pointed the directions of the current properly? And tell me the best approach that I should try next?

Thank you!

EDIT: Here are my tries in the meshes and nodes equations. Ignoring Is I am not sure what the I2 equation would be.


texts: Standard way for novice to prevent small round plug from rolling away while soldering wires to it

texts:
This very trivial task is to solder wires to the terminals of a small round 3.5 mm audio plug.

I can do this myself, but I need to show to others and this is one of the first times they're trying any kind of soldering.

The problem is the connector rolling away during the process of soldering. Students use one hand to hold the wire and another hand to hold the soldering iron. The plug itself lies on the table and rolls away after being touched.

Is there a standard, widely accepted way to do this kind of soldering easily? Do I need to provide some kind of vise for them, or there is some simpler approach?

The problem does not require soldering with one hand, using both hands is ok and preferred.


texts:
I know that opamps can be unstable when driving capacitive loads. The input to the opamp is more complicated than the schematic shows, but an unfiltered full wave bridge rectifier is the proper waveform. The waveform varies between 0Vpp to 15Vpp. Other circuits need the rectifier waveform. My Voltage to Current chip needs a smoother signal, so the current is more consistent. The opamp is an LM358 built as a buffer so the rectifier waveform doesn't get filtered. The LM358 is powered by 24Vdc.

The issue I am having is the rectified waveform increases its voltage linearly at its own slope. while the smoothed opamp output increases its voltage linearly on another slope. The two slopes intersect at some value determined by the resister and capacitor. How can I get the slopes to be parallel or the same slope?

Is there another circuit that will smooth out a rectified waveform into a DC voltage?

schematic


texts:
Can I use a 5V 1A usb adapter to power a 5V 500mA lamp?

The lamp describes 5V 500mA as max. rated power input


texts: Powering an AC induction motor with a function generator and an audio amp

texts:
I have 6 AC shaded pole induction motors that I'd like to power and control the speed of using a function generator on my smart phone or laptop for the input signal and using an amplifier to power the fans. The motors are 120v 60hz and approx. 40w each. I plan on controlling the speed by reducing the hz and v down to maybe 35hz 90v or so. I have an older component stereo receiver/amplifier I have been playing around with. I have a few questions, mainly:

-Am I better off using a component amplifier like I have been playing around with or a car audio type?
-If I go with a car audio type, am I better off with a two channel amp, or a bass style amp which would be more in the hz range of what I'm trying to do?
-Is there a better/cheaper amp available to do what I'm trying to do?
-Most amps are rated at 4 or 8 ohm (speaker rating) for the output watts. I do not know how to convert this to what I'd need to power motors.
-Will an amp accurately produce a sine wave generated from a function generator? If not, will it be accurate enough to power motors?

This is a 4 channel (bridgeable to 2 channel) amp I have considered. I'd probably try to power 3 motors each with each channel.

https://www.ebay.com/itm/Crunch-PX-...ash=item4649ce901b:g:DTYAAOSwyjBW6Wyd&vxp=mtr

This is a project my son and I have been playing around with and as you may or may net have been able to tell we're both learning as we go. I'll come up with a few more questions if anyone can chime in here. TIA!


texts: Help identifying an encryption accelerator

texts:
I believe this was released around 2010.  Pin configuration appears to be 8x8

I was able to get it hooked up.  Hardware ID:

  PCI\VEN_104A&DEV_7007&SUBSYS_00000000&REV_21

Vendor 104A is indeed STMicroelectronics.  Thank you!


texts:
Is there an electric circuit which flips voltage? For instance if the input is Vi>0V then the output will be 0V and if the input is 0V then the output is >0V.
And i am not reffering to the NOT gate , I want voltage not current.
I have searched but couldn't find anything.Can we do this with Op-Amps somehow?


texts:
I have a 24c02 eeprom and I want to program it. But I don't have Arduino or any microcontroler. I saw a video about program eeprom by hand, but they are parallel eeprom. This is the link of that video:
https://www.youtube.com/watch?v=BA12Z7gQ4P0
I am very sorry that english isn't my mother language. Sorry about any mistake
Thank you very much


texts: Is it possible to influence the working behaviour of a simple dc motor with an outside electromagnet?

texts:
I am using a simple DC-Motor 9V like this one. Now, I am curious about what influence an outside magnet / magnetic field would have on the working behavior of this motor?

I would like to use the following electromagnet. Is this appropriate to influence the motor or do I probably need a stronger one?

What would probably happen if I turn on the electromagnet near to the motor?

Could I influence the behavior of the motor by randomly turning on and off this electromagnet in a fashion such as a very short period of time (e.g., 10ms on every second)? What would probably happen?

Thanks for your help in advance!


texts:
I'm planning on building a mute button that would physically cut the audio signal from or to my computer. This could be used for both input and output. I would like to be able to disconnect my microphone or my speakers by the press of a button.
I was thinking about using an arduino or simply an attiny85 chip for the logic part (using a button as an input and triggering the pass/block part).
The reason I want to use a MCU is to be able to report the state with a LED, pass HID events via USB to the OS and trigger with things other than a button.
The only thing that I don't know how to do is how to disconnect both stereo channels.
My guess was that I would need a mechanical relay or an opto-isolator but there might be a better way to do this.
The ideal solution would physically break the connection and wouldn't induce distortion when the signal is allowed to pass.
Do you have any idea about the optimal way to proceede?


texts: Scanalogic DIY Logic Analyzer, Extending Sample Time

texts:
I just completed my build of the Scanalogic DIY logic analyzer. It's working great, but I am noticing something odd about it. This question will likely only make sense to someone who has used or built on of these devices.

So when I connect my device and retrieve a sample, it seems like the total sample time is limited to 0.5 ms. Unless I am using the software wrong and there is some way to extend this time, it seems oddly short. A few of the things I plan on analyzing with this device require a lengthier sample.

Does anyone know how this can be adjusted?


texts: How to make a non-linear potmeter more linear

texts:
I have an "Expression pedal" that worked fine on my old keyboard (Gem WX2+) but works almost like a digital switch on my new keyboard (Roland VR-09).

The recommended expression pedal is a Roland EV-5 which has the schema at the bottom right of this page:

I measured the pins of my old pedal and the schema is probably like this (have not opened it yet):

simulate this circuit – Schematic created using CircuitLab

An important difference is that the Roland pot is Lineair, while mine seems to be logarithmic. When close to the heel position I can easily navigate close to a wanted resistance. That becomes increasingly difficult moving closer to the toe (fully pressed) position.

I think it should be possible to tweak it to a more linear like curve by making an adapter, adding a resistor between the tip and the ring to pull the curve up somewhat. And while doing so I can just as well add the minimum volume feature as well. This is what I have in mind so far:

simulate this circuit

I'm not an expert at electronics, so I would really appreciate a peer review of this idea before I order the parts. I'm not sure if the value of the curve correction pot is ideal? At the maximum setting, the total resistance would be 9.6K which is a little lower than the 10K of the Roland pedal...

In fact I'm not sure if this idea would work at all, but since a new pedal is quite expensive and has a smaller "throw/range/angle" than my old one, I'd really like to keep my trusty old pedal with a hack if possible. Any other suggestions are welcome off course!


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I'm a student in Computer Science but, unfortunately, I don't have much experience with the electrical part.
I need to detect the carbon monoxide level for a prevention system using an Arduino board; I saw that a MQ-7 sensor is very useful for this purpose.
MQ-7 datasheet provides a heating circuit having time control function and so far so good.
I don't understand if the MQ-7 board allows me to implement the heating cycles (using, for example, a PWM pin of an Arduino).
Is there the possibility to generate the heating cycles? In the previous MQ-7 board, pin VCC is always connected to +5V of Arduino (all the circuits found so far don't provide this aspect, I don't know why; maybe due to the LM393 already integrated with the board?).
If yes, is it guaranteed that this approach doesn't compromise the detection?


texts: Measuring voltage on an Arduino pin, while powered from USB, with separate grounds

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I have Arduino Uno connected to a computer with a USB cable.
Then I have a DC circuit, powered by a wall adapter.

In this circuit, I have a shunt resistor (connected in series after the load) and I would like to measure the voltage across it with the Arduino analog pin.

But I am unsure if, or how this will work. Since the computer and the circuit have separate power sources, then their grounds aren't common.
Does that mean it won't work?
I am too afraid to connect the grounds because I am scared of frying my PC.


texts: How do you calculate the total power developed in a circuit?

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The figure below shows a circuit with 6 elements

This table show the values for the currents and voltages in the circuit.

While it's clear that you need to sum the power dissipated for a subset of the elements, it is unclear to me which elements are dissipating power.

Could someone please tell me how to calculate the total power developed in the circuit?


texts: IC identification - Analog Devices with top marking S BB

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Please help me to identify this IC. I guess it is an Analog Devices chip.
The top marking says "S BB".  I think it's an op-amp and it's used in a current probe.
Thank you!


texts: Looking for a microcontroller for Audio DSP applications

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I'm currently researching a system that has the ability to playback multiple sound files from an SD-card, add them together then output the signal to a DAC.
I'm basically looking for specifications on how fast the SPI port of any given DSP microcontroller would need be to playback 16 tracks (or alternatively 1 track * 16) simultaneously, the sampling frequency is 44.1kHz standard CD quality for each track. And if anybody knows a good microcontroller (with strong development documentation) for this application..

This feat is the only bottle neck I can currently see in the overall system design, if I can overcome this 16 track playback hurdle, it's all downhill from here.

EDIT:

The equipment will have preset audio tracks on the SD card stored as .wav on FAT32. The equipment also has the capacity to record using an ADC and store .wav on the SD card.
There will also be a looping feature, but I dont think that requires extra onboard memory as it can stream directly from the SD-Card


texts: Is a voltage signal we observe on scope made up of only cosines?

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Pardon me for the dumb looking question but I'm trying to comprehend a "signals and systems" subject and relate it to voltage or current signal.

A periodic signal is made up of sinusoids which is a conclusion of Fourier series. This series has the complex exponential form which means to me that a signal can be represented as sum of exponential functions.

And for a complex exponential which can also be written as cos(ὦt)+jsin(ὦt), the "Cosine" part is called the real part of a complex exponential.

So when we see any voltage waveform on a scope screen or when we view a sampled voltage data, does that actually mean the voltage signal we are dealing is made up of only cosines but no sines?

I might be confusing real part aka cosine part of the signal representation and a voltage signal which is also called a real signal. But totally confused what is meant by these..


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I was thinking of ac signals recently and I am trying to visualize wavelength of an AC signal. If I take a 30KHz signal, the wavelength of this is 10Km which is a super long distance. Can someone tell me how this wave will travel in a standard wire or a trace (of say 10cm)?

I can understand that the signal cycles 30,000 times in a second but I am not able to visualize how it would travel say 10cm. I am sure I am thinking this all wrong and would like some inputs on it.

Thanks


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I need generate special signal PPM for my rc toys, for example:

I'll use stm32F107 and I would use a timer which will be a resolution of 0.1us. The web is a lot of examples to generate the PWM signal but I can not find anything on the PPM.

Present someone an example?