texts: In this parallel RLC circuit, why is there no current flowing through the ideal RLC elements until after the switch is open?

texts:
I have a question about the following parallel RLC circuit:

The text accompanying the diagram says: "We want to find i due to a sudden application of a dc current." This confused me, since I thought that there would already be current flowing through the inductor.

According to the current division formula (applied loosely, since I don't know exactly how it would be applied in this circuit), the resistor R would have no current flowing through it. The capacitor would also set up a little voltage it seems like according to

since there would likely be some initial current that would enter it.

All elements are considered to be ideal, and ideal inductors have no resistance.

By t = 0-, it seems like the inductor would be acting like a short circuit, so current should at least be flowing through the branch with the switch and the branch with the inductor. If that's the case, then there already is an application of dc current to the parallel RLC circuit elements. So my question is why mathematically is there no current flowing through the inductor at time t = 0-?

Let's go back to the initial moment the circuit was turned on, t = - infinity. Right when the current source is activated, from the equation v = L di/dt.

might there be some effective resistance in the form of voltage (since di/dt is not equal to 0) that forces all of the current to go through the short circuit instead? Thus, the ideal inductor never gets to the point where it behaves like a short circuit.


texts: Instantiate sub module according to input value

texts:
I want to instantiate a sub module according to input value but this seems impossible.

I tried these methods:

method 1: always @ -> cannot instantiate sub modules there.

method 2: generate -> gives input is not constant error.

here is the code

module traffic_lights_top(Clk,
                          SN_CI, WE_CI,
                          SN_PI, WE_PI,
                          SN_CL, WE_CL,
                          SN_PL, WE_PL,
                          SN_TJ, WE_TJ,
                          Count);

     input Clk;
     input SN_CI, WE_CI;
     input SN_PI, WE_PI;
     input[3:0] SN_TJ, WE_TJ;
     output[2:0] SN_CL, WE_CL;
     output[2:0] SN_PL, WE_PL;
     output[6:0] Count;

                                // 15                   // 19                       // 34                       // 38
     parameter SEC1_nt = 7'b0001111, SEC2_nt = 7'b0010011, SEC3_nt = 7'b0100010, SEC4_nt = 7'b0100110; // time for each light in non traffic times
                                // 30              // 38                    // 68                   // 76
     parameter SEC1_t = 7'b0011110, SEC2_t = 7'b0100110, SEC3_t = 7'b1000100, SEC4_t = 7'b1001100; // time for each light in traffic times

     //traffic t1(Clk,SN_CI,WE_CI,SN_PI,WE_PI,SN_CL,WE_CL,SN_PL,WE_PL,Count);

     generate
        case({SN_TJ, WE_TJ})
            {4'b1111,4'b0000}:
                begin
                    traffic SN_t(Clk,SN_CI,WE_CI,SN_PI,WE_PI,SN_CL,WE_CL,SN_PL,WE_PL,Count);
                    defparam SN_t.SEC1 = 7'b0000000;
                    defparam SN_t.SEC2 = SEC2_t;
                    defparam SN_t.SEC3 = SEC3_nt;
                    defparam SN_t.SEC4 = SEC4_nt;
                end

            {4'b0000,4'b1111}:
                begin
                    traffic WE_t(Clk,SN_CI,WE_CI,SN_PI,WE_PI,SN_CL,WE_CL,SN_PL,WE_PL,Count);
                    defparam WE_t.SEC1=SEC1_nt;
                    defparam WE_t.SEC2=SEC2_nt;
                    defparam WE_t.SEC3=SEC3_t;
                    defparam WE_t.SEC4=SEC4_t;
                end

            default:
                begin
                    traffic same_t(Clk,SN_CI,WE_CI,SN_PI,WE_PI,SN_CL,WE_CL,SN_PL,WE_PL,Count);
                    defparam same_t.SEC1=SEC1_nt;
                    defparam same_t.SEC2=SEC2_nt;
                    defparam same_t.SEC3=SEC3_nt;
                    defparam same_t.SEC4=SEC4_nt;
                end
        endcase
    endgenerate

endmodule

SEC1_t, ... representing there is traffic

Sec1_nt, ... representing there is no traffic

Is there any way to fix this or I must change my approach?


texts:
Hello I have benen trying to find what this connector is called for a few days. But I can't find it at all. Have been looking at almost all the JST connectors their is. I'm starting to think it's not a connector by JST by now. The connector is used for a scooter motors hall sensors.

Picutre:
female connector:

male connector:


texts: Need help calculating current and understanding Vos in an op amp

texts:
I'm trying to solve a circuit that uses an op amp with a +-4mV offset but I've run into two problems trying to find output offset voltage.

When looking at the solution to the problem, I noticed that the solution had i1 current equal to (VA-Vos)/1Mohm. I don't understand why they made a separate node labeled VA because I had it originally as Vo-Vos/1Mohm. Is it because Vo value changes after going through the resistor so you label the new value VA? Also wanted to know how they label both currents through the resistors i1 because the first one on the left should be I=Vos/1 and the second should be I=VA-Vos/1
why is a voltage source included on the positive terminal when in the original the positive terminal was grounded.

First picture is original and second is the redrawn one .


texts:
What kind of circuit might be required to to play a particular piece of music without an SD card.

For example, a toy car playing a Christmas song the moment it is switched-on. It doesn't require an SD card.

How complex will it be?


texts: When oscillating a piezo, should I use AC or DC square wave?

texts:
I have several piezoelectric stacks that I am trying to get to shake/oscillate.  An example of what I mean by piezoelectric stack is something like Thorlabs PA3CEW.

The drive voltage is specified as 0 - 100 V.  I am wondering, in order to create the best-designed "shaker", should one drive the piezo with either:

Square wave moving between 0 Vdc and 100 Vdc
Square wave moving between -100 Vdc and 100 Vdc
AC sine wave of 100 Vrms

Thank you in advance for your guidance!  I am new to working with piezoelectric devices.


texts: Soldering 18650; is an FX-888D good enough?

texts:
So, I want to make a 18650 battery pack but don't have access to a spot welder. I'm wondering whether a FX-888D would be good enough to do the job quickly and so minimize  risk of damaging the cells.

If yes, any other tips to avoid overheating?

And finally, although I can probably get pure nickel strips; they'll be be hard to come by most likely. Could I do the job with copper wires or copper strips? If so, what would you recommend?


texts: Having trouble with OTA CA3080 making a VCA

texts:
I'm having trouble getting this CA3080 OTA to work properly. :-(

I watched this video ( https://www.youtube.com/watch?v=BbaJ6TOmyVo ) which is quite helpful, but I'm missing a few cues here...

In the enclosed picture you find the circuit as I think he uses, on the right my adaptation (basically changing a potmeter for an input coming from an 0-5v CV)

I built everything on a breadboard. The only difference with my built is I changed the transistor for a BC327 (for now, tommorow I'll receive the 2n3906).

On my scope the sine shows up nice and clean but when lowering the volume with the R6-pot it shifts upwards and distorts the wave (or is that supposed to happen?). In the included video it doesn't seem to do that (but it's only audible).

I did leave out the resistor at the output of the ca3080 cause its directly connected to a tl072. Should I put in a resistor of 100k between the output of ca3080 and the input of the tl072 orso?

I could do with some extra eyes helping me out. Would someone mind checking my circuit?


texts: how a phase delay occurs in capacitors/inductors with visual images

texts:
Capacitors provide a phase delay between the current and voltage. Current leads the voltage by 90 degree. I was taught these only with the equations. But I want visual intuition, what happens in the capacitor that causes phase delay.

The same applies to inductor. Please help me with visuals.


texts: What is the equivalent circuit of a capacitor with two different dielectrics?

texts:
As we know a capacitor with one dielectric has an equivalent circuit like the following image. Having a capacitance and a resistor in parallel.

In the case of having two different dielectrics in the capacitor, then the capacitances are in series. As a result, the equivalent circuit is represented as the image on the left side or the right side ?

I used to know the answer, but it has been a while since I studied the basic circuit courses.
Thanks for your help in advance.


texts: Current transformer as Sensor, can it sense rectified DC current?

texts:
I have been using an inductor around a 230V AC wire ground-side of the switch to check for current in a wire, it is part of control mechanism.

I have to add a rectifier now, so occasionally the current will be ~400V DC when rectified, and it has to be before the switch.

Will DC current induce voltage in my coil?
I think it has to be a varying field, but I cannot check for a few days and its driving me mad!

I cannot put the inductor before the rectifier due to the design of the circuit, and also because it will couple it with the positive mains pin and I get false readings.

Can anyone put my mind at ease?

edit: I have a home made toroidal coil with a ferrite core and a 100ohm resistor across the outputs, that feeds into into a Peak Amplifier,

I am asking if this will work at all/nominally when the current changes from AC to Higher voltage DC.


texts:
Below is a simplified version of a system I'm working on. There's over 10 devices and they all come through the ammeter and split off into each device (only using 2 devices here for simplicity).

The current circuit has been wired where it's red wire all the way until the last device and then black wire to the negative side of the power supply.

What exactly would the correct wiring color be according to conventions? My temptation is to do Red -> Black -> Red -> Black -> Red ....


texts:
I'm trying to make an onboard system for my bike using an Arduino or maybe the Lilypad boards.

I think I should use a Hall effect sensor, but any alternative is good as well.

I want to output my speed to an LCD display and I'm wondering the best way to go about this.


texts: Strange IEC C5 cable with 2-pin wall connector

texts:
I have this cable pictured below. It's an IEC C5 "mickey mouse" cable. What's very strange is that the wall connector should be 3-pin, with an earth, whereas this cable has a 2-pin wall connector.

Some context: this cable is from the power supply of a second-hand Dell laptop I bought on eBay. Just to give you an idea, it was sold as an AZERTY laptop, while it's actually an UK QWERTY keyboard, and the vendor switched some keys without saying… So, we know the laptop is from the UK.

FWIW, the cable is 120 cm long.

So, I can't find such a cable anywhere on the web. I'm searching for info about it. Is it a legit Dell cable? (they often do proprietary cables/connectors, so you are forced to buy from them) Has it been manually made?

Bonus question: is it fine/safe to use this earthless cable for my laptop power supply? I'm already using it for more than a year without noticeable issue, and the 2-pin wall connector is more convenient (more compact, broader compatibility).


texts: Problem using 5V LDO (AP7381) as power source for Arduino

texts:
Goal
I'm trying to build a portable speaker. I want to use an arduino to handle several tasks. The speaker uses a 6s Lipo ~24v as power source.
An LDO the AP7381 has been selected as power source for the arduino.

The AP7381 provides the required 5V on a wide input range while having a low quiescent current which is important for the battery life. The idea is to have a very low power consumption when the speaker is off and the arduino sleeping drawing less than 10uA.

I want to test the power source with the arduino before I blow up multiple components.

The datasheet of the AP7381 recommends to use a 1uF input and a 2.2uF output capacitor. I use ceramic capacitors.

Problem
The isolated test for the power source of the arduino has failed several times now with a destroyed LDO but I cannot see the problem in my schematic.

(I suspected reverse current on the LDO to be a problem which is why I added the diode but it didn't help.)

I have tried the following:
- Using a step down converter -> works
- Using the AP7381 without capacitors -> works (not a good idea I guess)
- Using a diode to prevent reverse current (as seen on the schematic) -> fails
- Using no diode -> fails

What could cause the LDO to blow in this small setup?

AP7381 datasheet: link
Diode datasheet: link


texts: MATLAB's impz is used to get the impulse response of a discrete time filter. freqz is used for the frequency response of a discrete time filter. freqs is used for the frequency response of a continuous time filter. But, there is no imps - how can I plot the impulse response of a continuous time filter without this?


texts:
I was disassembling an old CRT monitor and I came across this component, but I've been unable to identify it. Can somebody help me with it?
It was found in the horizontal deflection circuit, next to the flyback converter.a


texts:
When connecting a thru hole, via or otherwise, to an internal GND or PWR plane, the default Altium configuration uses a thermal relief connection.

Although I've seen a number of posts saying to abandon thermal reliefs in favor of direct connects, I'd like to try reducing the size of the thermal relief first.  The default configuration uses an expansion of 0.508 mm and 0.254mm air gap - leading to overlapping copper pours for vias that are close to each other.

What are the design considerations or reference standards I can use to make sure I don't size them too small?


texts: Digital predistortion of bipolar power amplifiers

texts: What is the peak power limit of a signal beyond which a digital baseband  pre-distorter will not be able to correct for nonlinearities: P1 dB of an amplifier? P3 dB? and why is there a limit?


texts: Can I connect two MCUs directly to one micro SD card without additional components?

texts:
I am new to this community so I am sorry if I'm asking in a wrong place or something out of topic. I think I have considered everything. :)

So, now the basic info: I am working on a project which involves two MCUs, STM32(STM32L496VGT6) and ESP32(ESP32-PICO-D4). STM32 is the main MCU in my project, it controls wireless power receiver, battery charger, captures video, records audio and so on. ESP32 is used for data transfer(video, audio...). By default ESP32 is disabled and is only activated by the main MCU(Pulling CHIP_PU(EN) pin of ESP32 to high) when wireless functionality is needed.

The micro SD card is connected to STM32 via the SDIO interface so the video and audio data can be written on it. But when I want to send data over WiFi I want to connect the same micro SD card directly to ESP32's SDIO with the same traces to maintain max transfer speed between ESP32 and micro SD card. Because I was not confident of the reliability and safety of such connection, because now ESP32 and STM32 share the same pins, I have added SDIO demultiplexer from Texas Instruments(TS3A27518ERTWR) to my project.

I tought about one solution. I really want to remove this demux IC from my project to save cost and space. What if I put every SDIO pin of STM32(which are conneted to micro SD card) in GPIO_Output open drain high impedance mode when ESP32 is ready to use the micro SD card(ESP32 will be able to communicate to micro SD card only when STM32 will give it a signal over USART line)? After that when ESP32 will finish it's tasks the STM32 will disable ESP32 and will reinitialize SDIO pins as needed for normal operation.

So, my question is exactly that. If I put STM32's SDIO pins in GPIO_Output open drain high impedance mode will I be safe to use the micro SD card from ESP32?

I think I was pretty specific and I hope you will understand everything. Big thanks for your help! :)

EDIT:

Okay, after some replies and additional research I got some updates.

Firstly it is true that SDIO(MTMS, MTDO, GPIO2, GPIO4, MTDI, MTCK) pin states of ESP32 when it is in shutdown mode must be considered. I think they can't be tied directly to STM32's SDIO pins because they are also strapping pins according to ESP32's datasheet and in shutdown mode they are configured as GPIO_Inputs with internal weak pull-up/pull-downs enabled, so maybe they will interfere with STM32<->micro SD communication.

Secondly, if we assume that ESP32 will "not present at all" when it's in shutdown mode STM32 will normally, without any problems, talk with the micro SD card. But what about the second scenario, when ESP32 is talking with the micro SD card? I still don't know if setting SDIO pins of STM32 as GPIO_Outputs with open drain high impedance mode will "remove" STM32 from that line. Can someone answer me on that? :)

So, if first statement is true about interference caused by internal pull-up/pull-down resistors inside ESP32 I need to use SDIO demultiplexer. And if it's not a problem but STM32 can't be "removed" from SDIO line by configuring it's pins as GPIO_Outputs with open drain high impedance mode I still need the demultiplexer.

Thanks to everyone. :)


texts: How can I let 2 devices take turns accessing a SIM card?

texts: I need to store data in a sim card using one device, then another device needs to access that data. They do not ever need to use it at the same time. A question was asked about this a few years ago but it was misunderstood and closed without a full answer. One person said it was complicated, but that was it. I was thinking to just break the lines from the SIM card and stick in some kind of MUX/switch that will select whether it gets connected to one or the other. But I'm worried there might be more to consider that I'm not anticipating. Has anyone done this?


texts: PCB header and microcontroller schematics for JTAG connection

texts:
I am using f28017f device from Texas Instruments and for my application I have to implement it on PCB. for debugging this device, I need JTAG connection. I will be using xds110 device for debugging. For JTAG connections, I have copied the schematic from device manual. Does this connection seems fine for on-board programming? Which can be seen from below diagram.

I have also connected pull down resistor with TRST' pin as suggested by TI. But it means that ground is connected to TRST' pin and TRST will have 1 logic. Will it keep the device to reset mode and device will perform no operation? Is that true? How this situation could be avoided? This scenerio can be seen from below mentioned picture


texts: designing a pcb breakout board with micro dsubs

texts:
I am a beginner in the world of pcbs and I'd like to make a breakout board. The board will be breaking out signals from micro dsubs. There are no other components on the board.

What is the simplest software for me to use? I looked at multisim and orcad(I have working licenses for both) but I couldnt find the micro dsub connector available.

Is there some connector database I am not aware of for those two software suites?
Otherwise, what free alternative should I look at? Should I be making the connectors myself?


texts: What are these exposed copper rectangles for on the mbed NXP LPC1768?

texts:
Today I noticed some exposed copper rectangles on the bottom of an mbed NXP LPC1768 dev board. They don't look like they're meant for components. I think they may just be test points, but I'm curious if there's another answer.

Here's an image of the board with the copper rectangles circled in red:

I'm not sure what the mbed interface chip is. Googling it suggests that it's proprietary. I can't tell where the traces are going.


texts: Solid angle measurement conditions for radiant intensity specification in IR-LED's data-sheets

texts:
For some IR-LED's their data-sheets state Radiant Intensity and the conditions under which
that number was obtained, indicating also which solid angle was used for the measurement.

For example, this 15 Deg LED was measured with a solid angle of 0.01 sr
http://www.osram-os.com/Graphics/XPic4/00239136_0.pdf/SFH%204258.pdf

and this 3 Deg with a solid angle of 0.001 sr

http://www.osram-os.com/Graphics/XPic0/00239538_0.pdf/SFH%204550.pdf

This corresponds to CIE standard B (0.01 sr) and A (0.001 sr) conditions.

But for example data-sheets for this two don't give at which solid angle the radiant intensity was measured. I can only guess that the measurement was probably done with 0.01 sr, that is CIE condition A was used.

https://www.vishay.com/docs/83398/vsmy2850.pdf

http://www.everlight.com/file/ProductFile/201407061539021388.pdf

How can one know at which solid angle radiant intensity measurement is performed, is there some standard or rule the manufacturers follow that defines which solid angle is used for radiant intensity measurments depending in the LED half angle ?

Eg. LED' with >=10Deg half angle are measured with 0.001 sr (CIE A) and
LED's with half angle greater than 10Deg are measured with 0.01 sr (CIE B) ?


texts: Cockroach or insects triggering conductive ink sensor

texts:
I want to modify a cockroach to get it to trigger a conductive ink sensor or Arduino with foil capacitive touch setup.

At the moment there is no reaction as far as I can see (in the serial monitor)

I was wondering about spraying it with water to make it wetter?
Or modifying its feet somehow?
Maybe some little shoes? :)

Alternatively, suggestions of better insects?


texts: How can you tell how many layers a PCB has?

texts:
This is a question purely out of curiosity.

I have several various PCBs, and I'm curious as to how many layers they use, which helps me decide how many layers to use in my project (for example a cheap competing product using 4 layers suggests to me it is possible to do my product with a 4 layer design).

From looking at the vias (and where they connect to), I can usually determine if they have 2 layers or more, and I can tell apart single layer boards too because they don't have a top or a bottom side, however, I've never been able to actually count the number of layers a more complex board like a motherboard or graphics card uses.

Any clues?


texts: Creating a Circuit with Resistors Given the Total Resistance

texts:
How can I create a circuit with a total resistance of 144.7 ohm which is composed of 10-ohm resistors? How many parallel and/or series resistors should it contain?

I've tried solving this but the nearest total resistance to 144.7 ohm that I get is 144 ohm exactly. Actually, this isn't for real-life usage rather just a circuit analysis problem. Please help.


texts: With multiplexed displays, what is the correct term for a single "frame"?

texts:
Let's take a look at the following animation demonstrating time division multiplexing.

Source

As you can see and probably know, the image is shown by displaying one line after another in rapid succession.

The whole image is made up of separate entities. Taking an analogy from video, you could call these entities "frames". But, when using a multiplexed display, you may want to display videos/animations, so an ambiguity issue arises. So, when writing (and later on reading) code regarding this, it is hard to distinguish between "video-frames" and "multiplexing-frames", using the same term causes a lot of confusion.

What is the correct term for the entity that an image on a multiplexed display is made up of?

In other words, which word would correctly complete the following sentence?

  An image on a multiplexed display is made up of multiple _____ that are displayed in rapid succession.


texts:
I own a Canon EOS 550d - reading through the manual and from looking at the external power supply ACK-E8 I learned that the camera needs a maximum of 14,8W (7.4V @ 2A).
The Anker PowerCore 20100 USB power bank can deliver 20W (2 ports, 5V @ 2A each), so theoretically it should provide enough energy.

My question is how can I best transform the 5V USB voltage to the required 7.4V for the camera?

Can I use a step-up converter like the TI LM3224 to do the trick? (I took a look at the manual and feel "yes-ish" about it)

Are there better ways?


texts: Can't get PIC 16F876 working.What am I doing wrong?

texts:
I have been playing around with the PIC16F628 for a while, and now I want to transfer to something that has more pins. Specifically the PIC16F876, but I can't get it working. I just want to turn an LED on/off and nothing ever happens. This is my circuit:

I program my PICs in the mikroC editor and these are the settings:

OSCILLATOR: HS
WATCHDOG: Disabled
POWER-UP TIMER: Disabled
FLASH code protection: Disabled
Brown-out reset: Enabled
Low voltage programming: Disabled
Flash program memory write: Enabled
In-circuit debug: Disabled

And this is my code:

void main(){
    TRISB = 0x00;
    while(1){
        PORTB = 0b11111111;
        delay_ms(500);
        PORTB = 0b00000000;
        delay_ms(500);
    }
}

And nothing works. I tried with 4.10 and 11 MHz oscillator values
and nothing. What did I do wrong?


texts: Ground separation between ADC and high current capacitor discharge circuit

texts:
I recently designed a capacitor discharge welder for my welding applications, and I come through a problem about separating grounds between AGND of the controller and (-) terminal of the big 1.3 farads 20 volts cap. after some hanging around on the web, several questions have been confusing me.

placing a separation gap between grounds on PCB and connect them through a zero-ohm resistor.
Connect the grounds as normal but in this situation, due to my lack of knowledge, in the discharging period, the capacitor might cause fluctuating the ground thus damaging the micro-controller.

Any help would be appreciated


texts: Output Resistance Voltage Controlled current source

texts:
I am having problems evaluating the output impedance (\$R_{out}\$) of a voltage controlled volage source, the notes I am using say the output impedance is

$$ R_{out} = \frac{r_o}{1 +AK} $$

but I can't figure out how it was derived, can anyone help me with this?

Solving by Applying Test Voltage/Current:

$$ I_{test} = -\frac{V_{test} - Av_\epsilon}{r_o} $$
$$ r_o \cdot I_{test} = -V_{test} + Av_\epsilon $$

There seems no way of getting the expression \$\frac{V}{I}\$ because \$Av_\epsilon\$ does not depend on \$V_{test}\$.


texts: Should I build my own parts for making PCB with eagle or is there a database somewhere?

texts:
I'm trying to build a custom PCB for a project I'm working on. I'm building a small robot that navigates using a color sensor and moves using two motors. For logic I'm using an Arduino Nano.
My problem is that I can't find the following parts:

28BYJ-48 5V Stepper Motor.
TCS3200 color sensor.

I've found this site, but cant find them there. I also tried to search github, but with out any luck.

It seems strange to my, if nobody else have made a stepper motor and then shared it?! So I'm wondering if I'm looking in the wrong places?

Another question is of its worth the trouble to learn to make my own parts with Eagle?


texts: Should AC voltage supplied to an external device through a relay be electrically isolated from the main power source of the enclosure?

texts:
Given a power supply in an electrical enclosure powered by 120 VAC. An I/O device will trigger a relay with a 24 VDC control. The signal from the I/O device will enable the relay for a set duration. The user wants the relay to switch 120 VAC to power an eject device.

What would be the considerations given to determine if the 120 VAC connected to the relay output need to be isolated from the primary input power?


texts: How can I reduce voltage from 40VDC to 5VDC?

texts:
I'm working to power a micro controller that requires something like a USB power supply - 5VDC  with a normal draw of .75 - 1 amp but could possibly draw as much as 1.5 amps.

I know that with smaller voltages such as a 9V battery it would be possible to use something like a 7805 Voltage Regulator but sacman has mentioned:

  I just found out that these Regulators will stop regulating somewhere between 7v and 7.5v

Since I'm not going from AC->DC I don't need a (bridge) rectifier, right? But do I still need a (step down?) transformer or for a relatively low power draw like this are there other methods? If so,

Which method would be the smallest?
Which would be the least expensive?
Would it be the same answer if I had a 50VDC input voltage instead of 40VDC?

I did search this site for related questions but mostly found things that were AC->DC or low->high.


texts:
How can I determine the collector voltage of Q1 in this circuit?

I suppose it is very simple but it really puzzled me.

Thanks all.


texts: How to perform FFT for I(real) & Q(imaginary) arrays?

texts:
I have two arrays namely I & Q, each array contains 1024 points. Now I'm trying to perform FFT using Cooley Tukey algorithm.

According to the picture above, the number of input points are 8, in my case, I have two sets of 1024 points(I & Q arrays), so what would be the size of input of a Butterfly diagram ?


texts: DC current injected into DR (Distributed Resources)

texts:
I was reading the IEEE 1547 standard, and under power quality topic there was Limitation of DC injection which stated "The DR and its interconnection system shall not inject dc current greater than 0.5% of the full rated output
current at the point of DR connection"

Why and how this dc current is injected into DR (Distributed Resources) connection and how does this affect the Electrical Power System?


texts:
Why are powerful speakers like above 20w or 80w not small? I have never seen enough in the market which are under 3 inch but of 80W.  The opposite is also true, some big speakers are of low wattage. Compare 5 inch 10W and 5 inch 100W (same dimension but different power).

So clearly its not only about the dimensions. To move more air does not mean to have a bigger speaker? Something else is also in play. What is it?

So for my analog 20W stereo amp, what is the smallest possible full range speaker I can get? Aiming to make it small like beats pill, is it possible with this analog power or do I have to shift to digital processing?

And as a side-note, if separating freq with crossovers is suggested, how would I do it? For each channel a tweeter and subwoofer?

And how do companies, like Libratone and Bose, create small speakers with high power(70W, 100W), though they do separate it with crossovers? So is this the way to make it really small and portable? Or is it because of using DSP chips instead of analog?


texts:
So i was asked to design a function generator that eventually produces a sine wave at the output of the circuit and this is what i have come up with so far. A Schmitt trigger and then an integrator and the triangular wave to sine wave converter. But at the moment, i have done a lot of research to understand whats going on completely, and i sort of understand.I'm just very unsure what to do next?

i want to produce a square wave and a triangular wave that give me 5v as well as symmetrical. I should also be able to vary the frequency from 0.5kHz to 10 Khz i also must use an LM741 op amp and 1N4148 diode

i tried calculating R1 and R2 but i did not get the output i wanted so they are probably incorrect.

and this is what i got. Also i know i should use diode to reduce the voltage but im not sure where i should place them


texts:
I can't find any info on this in google. Basically I am trying to find a servo arm (called servo horns) BUT for a potentiometer. They are probably named differently as the axle shaft is different.
All the servo arms I've found have teeth inside so won't work for the pot I have. My pot has a 6mm (0.25inch) D-shaped axle ("flatted shaft"). It is hall sensor but from the outside it is mechanically like a pot.
Basically I'd be just happy to know what is the name of those parts?
Here is a link to the actual pot I have:
https://uk.farnell.com/bi-technologies-tt-electronics/6127v1a50l-5/sensor-hall-0-2v-20v-to-10v-pin/dp/2319669
From there you can download technical pdf which shows exact measurements of the shaft.
Pictures:
So here are various servo arms:
https://hitecrcd.com/products/servos/servo-parts-and-accessories/servo-horns-and-hardware/product
Here it is mounted to a servo:
https://upload.wikimedia.org/wikipedia/commons/thumb/d/d3/Micro_servo.jpg/1200px-Micro_servo.jpg
Here is how the axle of servo looks like:
https://cdn.shopify.com/s/files/1/0672/9409/products/servo_75_f48aef4b-d299-49c8-9151-3b8f363ff796_1024x1024.jpg?v=1430578496
How do I mount a servo arm (or just any kind of arm) to a potentiometer with d-shaped axle like this:
https://www.build-electronic-circuits.com/wp-content/uploads/2015/11/potentiometer.jpg


texts: Raspberry PI power supply switched with FET

texts:
In my circuit there is a microcontroller, that can turn on and off the Raspberry PI power soruce. The schematic is following:

A microcontroller GPIO is connected to RP_SW and 5v_Raspberry is the power supply of the Raspberry. The Q9 FET and DT_1 transistors with R65 and R66 are making an ideal diode, I took the idea from here
(The aim of this diode is to avoid back powering).

The problem is, that the 5V_Raspberry will be only ~2.3V, the rest of the voltage is falling on the drain-source of the Q8 FET.
I tried to pull up the gate of the Q8 FET to 5V, but there is no change. I tried an other FET instead of Q8, but the same effect is shown.
Why is this circiut not working, as excepted?


texts: What is this "paper-substrate pcb" technology called?

texts:
I took apart a broken calculator to show my daughter how it functions. It had a small "traditional" FR-4 PCB mounted underneath the LCD glass, but the pushbutton area was printed on a paper-like substrate:

The paper is plasticized and shiny, but there are fibers present if it is torn.  It has the equivalent of plated-through-holes.  The conductors are thin, matte-back material that look similar to toner.

Where the paper meets the FR-4, the traces connect together with some sort of adhesive (thin glue or tape).  In other words, the copper traces are covered by matching "toner" traces, and affixed somehow...

The calculator was purchased at a Dollar Store for, you guessed it, one dollar :)


texts: Burning a transformer and replacing it from 110V to 220V

texts:
Today I received a preheat bed AOYUE-AO853A. I was really eager to plug it in an test it, ignoring the voltage input rating. It worked for a second making a strange noise, but then some smoke started coming out.
I turned it off, unplugged, I left the capacitors to drain and finally I attempted opening it after it cooled. It turned out the transformer was rated for 110V 60Hz.

I have two questions:

Is there any chance that the components beyond the transformer have fried? From a visual inspection, everything looked ok on the single PCB this device has.

What transformer should I use to replace this one to be able to power the device with standard European 220V?

Update:
I noticed that the board is not only hooked to DC (from the transformer), but also to AC.
Here's a picture:

1 is the heating element
2 is the AC in
3 is the DC in

Note that the capacitor at the right of the DC in is rated at 25V and all the other capacitors are rated 16V

As required by a top user, I posted a picture of the wiring for the heating element. It seems it's wired in series already.


texts:
An amplifier normally has a huge gain which outputs the input voltage Vin to an output Vout.
If gain is G then Vout = G*Vin.

But what about in case of a data-acquisition board's amplifier?

Imagine we apply lets say a 5V DC signal to a single-ended data-acquisition board's channel. So in this case Vin is 5V and we expect Vout to be 5V as well. So what is the gain of this amplifier here?

And if the gain is 1 for a data-acquisition amplifier why an amplifier is always needed before sampling the voltage by ADC?


texts: What is a good project for amatuer PCB designers?

texts:
I'm new to PCB designing, and I was wondering what are good first design challenges? I've done a few circuits thus far, and I want to expand my knowledge by making my own etched circuit boards. I already know basic design principle and circuit theory.
What project, that focuses on PCB design, would be of the most educational value for me as a beginner?


texts: Raspberry Pico and DHT11 not working C/C++

texts:
This is my Wiring here
+ is connected to 3v3, - to GND and OUT to pin28
I'm using this example found on raspberry-pico official examples
#include <stdio.h>
#include <math.h>
#include "pico/stdlib.h"
#include "hardware/gpio.h"

#ifdef PICO_DEFAULT_LED_PIN
#define LED_PIN PICO_DEFAULT_LED_PIN
#endif

const uint DHT_PIN = 28;
const uint MAX_TIMINGS = 85;

typedef struct {
    float humidity;
    float temp_celsius;
} dht_reading;

void read_from_dht(dht_reading *result);

int main() {
    stdio_init_all();
    gpio_init(DHT_PIN);
#ifdef LED_PIN
    gpio_init(LED_PIN);
    gpio_set_dir(LED_PIN, GPIO_OUT);
#endif
    while (1) {
        dht_reading reading;
        read_from_dht(&reading);
        float fahrenheit = (reading.temp_celsius * 9 / 5) + 32;
        printf("Humidity = %.1f%%, Temperature = %.1fC (%.1fF)\n",
               reading.humidity, reading.temp_celsius, fahrenheit);

        sleep_ms(2000);
    }
}

void read_from_dht(dht_reading *result) {
    int data[5] = {0, 0, 0, 0, 0};
    uint last = 1;
    uint j = 0;

    gpio_set_dir(DHT_PIN, GPIO_OUT);
    gpio_put(DHT_PIN, 0);
    sleep_ms(20);
    gpio_set_dir(DHT_PIN, GPIO_IN);

#ifdef LED_PIN
    gpio_put(LED_PIN, 1);
#endif
    for (uint i = 0; i < MAX_TIMINGS; i++) {
        uint count = 0;
        while (gpio_get(DHT_PIN) == last) {
            count++;
            sleep_us(1);
            if (count == 255) break;
        }
        last = gpio_get(DHT_PIN);
        if (count == 255) break;

        if ((i >= 4) && (i % 2 == 0)) {
            data[j / 8] <<= 1;
            if (count > 16) data[j / 8] |= 1;
            j++;
        }
    }
#ifdef LED_PIN
    gpio_put(LED_PIN, 0);
#endif

    if ((j >= 40) && (data[4] == ((data[0] + data[1] + data[2] + data[3]) & 0xFF))) {
        result->humidity = (float) ((data[0] << 8) + data[1]) / 10;
        if (result->humidity > 100) {
            result->humidity = data[0];
        }
        result->temp_celsius = (float) (((data[2] & 0x7F) << 8) + data[3]) / 10;
        if (result->temp_celsius > 125) {
            result->temp_celsius = data[2];
        }
        if (data[2] & 0x80) {
            result->temp_celsius = -result->temp_celsius;
        }
    } else {
        printf("Bad data\n");
    }
}

When I use serial debug I should get something like Humidity = 50%, Temperature = 10C but the only thing im getting is Bad data and Humidity = 0%, Temperature = 0C
What am i doing wrong here
EDIT
The sensor is working on my Arduino UNO
I've now tried UART connection since someone told me that the USB Serial could be interrupting.
This is my wiring 1 2 3
I've activated Serial Port and Serial Console on my raspberry pi and did minicom -b 115200 -o -D /dev/ttyS0 but no ouput is set


texts: What is the difference between digital input with low bias and digital input with high bias?

texts:
I have 3 inputs. Input #1 is low bias. I can hook up a 12V positive to input 1 and it will change it's state to 1 (or input is ON).

Inputs #2 and #3 are high bias. Connecting a 12VDC to either of these inputs causes no change in state.

The description for these two inputs describes +12v via 100kΩ res, with a 2V threshold. I can't change the "high" state on these two inputs.

What kind of input is expected on inputs 2 and 3?


texts:
I have to calculate the value of a resistor so that my circuit has a certain equivalent resistance. This is the circuit, and here are the values:

Ig = 5 mA, R1 = 2 kΩ and R2 = 1 kΩ. R3 is unknown.

So I want to know the value of R3 for a equivalent resistance  of 5kΩ.
Well, what I do first, is calculate the resistance of R1+R3, and then add R2, which its R13+R2 :

So, I replace this for the values :

But if I resolve this, I always get a value of -4kΩ. So whats happening?
Am I doing anything wrong? or can a resistance be negative like this?


texts:
1) What is the decay of the magnetic field of a magnetic dipole?

It can be modelled as a ciruclar current with infinitesimal small radius. The decay of a current carrying wire can be easily calculated with Amperes law to be
$$\vec{H}_\varphi=\frac{I}{2\pi R}\vec{e}_\varphi$$
with the radius \$R\$ and the current \$I\$ (cylinder coordinates). For a magnetic dipole, the field distribution can be calculated via Biot-Savarts law, and in my calculations it results in a \$\propto\frac{1}{r^2}\$ decay of the field. Measurements show a decay of \$\propto\frac{1}{r^2}\$ and \$\propto\frac{1}{r^3}\$ further away from the source.
I should also mention the theoretical formulas for a magnetic dipole
$$\vec{H}(\vec{r})=m\frac{1}{4\pi\mu_0}\bigg\{\vec{e}_r2\bigg(\frac{jk}{r}+\frac{1}{r^2}\bigg)\frac{e^{.jkr}}{r}\cos\vartheta+\vec{e}_\vartheta\bigg(-k^2+\frac{jk}{r}+\frac{1}{r^2}\bigg)\frac{e^{-jkr}}{r}\sin\vartheta\bigg\}.$$
From this formula (spheric coordinates: \$r\$, \$\vartheta\$, \$\varphi\$ ), I conclude that there are three different regions such as farfield etc. However, I do not know the boundaries of the regions and neither how this formula can coexist with Biot-Savarts law which yields (in my calculations) only one region. So:

2) What are the boundaries for farfield, nearfield?

3) How can I merge the analytic results from Biot-Savart and the magnetic dipole Formula above?


texts:
More images are here:

Numbers are:

500B - On the back

6800
+5%
80 - on the front


texts: What will be the behaviour of superconductors if they are used as core or coil?

texts:
Superconductors are strong diamagnetic in nature so if they are used as core of any coil do magnetic lines of forces pass through them – I mean inside them just as with a soft iron core?

Secondly if they are used as the coil wound on core then change in magnetic field induces current inside them. Does mutual inductance occur in them or not – because the magnetic lines of forces don't pass through them, or because they bend towards them?


texts: Automotive Logic Signal Switching and ESD/transient susceptibility

texts:
Sorry...can't think of a succinct question for the subject line!

I am working on a project on my car. The car's existing ECU is connected to a pressure switch, which opens when the A/C refrigerant pressure is low. This causes the ECU to switch off the A/C (via a different circuit). By opening this circuit myself, I will be able to switch off the A/C using a logic output from an MCU. The attached picture shown an NPN transistor in the place that I intend to insert...something. My testing shows that opening the circuit works as intended, and that a simple NPN does the job.

I want to ensure the component is immune to or protected from the dreaded load dumps and other transients/events I know to expect in the environment. However, I don't want to use a relay, as inside the cabin the clicking will be annoying. My MCU is running off an automotive LDO voltage regulator (LM2937), which is protected from overvoltage, reverse polarity, load dumps, etc.

I have two questions:

1) In this specific case...do I have anything to worry about anyway? I pretty much assume the ECU's circuitry should be insulating this line from these events. Maybe the NPN I'm using for testing will be good enough - perhaps with a big diode in reverse?

2) If I DO need to worry...what would be the best solution?


texts: How does early voltage affect collector current?

texts:
The transistor in the following circuit is said to feature \$I_{C} = 1.0mA\$ at \$V_{BE} = 0.7V\$ and \$V_{CE} = 10V\$. If \$V_{A} = 50V\$ and \$\beta = 50\$, find \$V_{B}\$ and \$V_{C}\$.

simulate this circuit – Schematic created using CircuitLab

Attempt:

\$V_{B}\$ Calculation:

\$V_{B} = 10 - 0.7 - 196.5I_{B}\$

\$I_{B} = \frac {I_{C}} {\beta} \$

\$V_{B} = 10 - 0.7 - 196.5 *\frac {1mA} {50}\ = 5.3V\$

\$V_{C}\$ Calculation:

\$V_{C} = 10 - 1 = 9 V\$

How do I incorporate the early voltage
\$V_{A}\$ into the calculations?


texts:
I'm trying to build what amounts to a single-axis CNC machine running off a 12v automotive type electrical system. Here's a basic description of the build:

Arduino Uno
Just for testing, I'm using a 12v dc 30A regulated switching power supply connected to 110v ac.
Also just for testing, I'm using a 426 oz-in Nema 24 stepper. Actual stepper will be larger. This one is 2.8A wired in parallel.
600w boost converter to increase 12v to 36v for input into motor driver.
9v power supply module between 12v supply and Arduino.
Geckodrive G201x motor driver set at 3A.

The machine works fine when powering my Arduino with a separate source from the stepper motor. But it appears to brownout when all connected to the same power supply. Unfortunately, I only have a single source of power.

I originally thought I was getting some kind of voltage spike. The automotive system could produce this (and I was testing on that system at the time). So that's why I thought to put the 9v module there. I think I need it regardless, but it doesn't seem to have fixed this problem.

Then I was given a suggestion to opto-isolate the motor. As best I could tell, I needed to put the opto-isolator between the Arduino and the driver. I put one between the step/dir and the appropriate pins on the Arduino and powered the isolator with a 5v power supply. That's not working either.

If I disconnect the motor, but leave the 600w supply and motor driver hooked up, I don't see the brownouts. My gut is telling me that the stepper motor is pulling too much power and causing a brownout. As I understand it, I could put a diode and capacitor between the Arduino and the power supply. But isn't my power supply powerful enough to not need this? It should be using roughly 100w of power correct? As I understand it, the motor may use more than this when starting up, but would it really use that much more?

Edit:

I attempted to use the 47uF and .1uF capacitor schematic here between my 9v supply and the Arduino. Didn't seem to help. I put my multimeter on the inputs into the Arduino and played around with the system until it did some crazy stuff (It will usually garble the output to an lcd screen I have connected). I did not notice any changes in voltage, although I suppose it could be just a short spike that the meter didn't catch.

I think it would help if I drew a schematic of the system. Maybe then someone can point out something?

Edit:
Here's a schematic. Sorry for the poor quality. Hopefully it's readable. I tried to include everything in my project, but I assume the buttons, toggle switch, rotary encoder, and lcd are not the cause.


texts:
I'm currently working on a small project, an STM32F070F6 uC connected to an oled display via i2C. I also added a LED for debugging purposes. The whole thing is powered by a 3V cr2032 battery and a switch can open/close the power rail. Everything is working fine while the st-link debugger is connected (oled and led toggles). Once powered down and st-link removed, I switch the power back on, the device is working fine but switching off and on again the device won't boot anymore. BOOT pin is well set to 0 via a 10K resistor, reset is high. Im trying to figure out what could cause this and how st-link is related to this issue since it doesnt provide any power. I was thinking about decoupling caps...

Edit : adding 10µF electrolytic decoupling cap in parallel with the batterry doesn't change the behavior. Further information : when reset button is pushed the device doesn't boot after reset button released.
Edit :
I monitored power supply voltage at power up, with or without debbuger the following figure is what I have :


texts: How do I correctly estimate heat output for heater wire

texts:
This is based on a problem that came up today. During the course of this problem I realized that I wasn't so sure I understood the relationship between wattage and heat produced.

In the past we did a test in the lab using .305 Ω /ft wire. The jacket is rated for 150C. We were able to get about 6.5A (at 3.66V)  out of it at 24C ambient, with out exceeding the jacket rating. I want to estimate what the ampacity of 0.027  Ω/ft wire is. So I am wondering if I did it correctly, because this amperage seems a little high for the wire to handle, then again most copper wire is only rated at 90C.

So the math I did on it was this

So you do
.305 * 2 = .61 Ω /ft
6A^2 * .61 Ω = 21.62W   (I^2*r = W)
21.96W * / 2ft = 10.98 W/ ft

So would it be safe to assume that if I did the same with a 0.027w/ft wire with the same jacked I would arrive at this amperage?

If you start with
11W/ft * 2ft = 22W
0.027 Ω * 2ft = .054 Ω
Sqrt(22W/(0.054 Ω)) = 20.18A

ETA: we are planning on testing this tomorrow when we get some wire in. So we shall find out.


texts: Are the results for Proteus simulation and hardware testing for same purpose using different controllers comparable?

texts:
I have used Proteus design suite for simulating sensors (such as temperature sensor) interfaced to LPC2138. The sensors which were not available in the software, for them I have modelled them as voltage divider circuit with potentiometer. If I were to
show mapping/compare the voltage divider results in software simulation and in hardware design, will the results have any dependency on the type of controller as all I am doing is simulating a controlled environment (by changing the R values)? For example if I use Arduino for hardware testing and LPC2138 in Proteus. Would this be correct? Please confirm.


texts: How is clock bus different than peripheral clock in STM32?

texts:
Been looking to clarify this confusion: how is the clock that a specific peripheral is on (APB1, APB2 etc) different than the peripheral clock itself?

Say, I2C1 peripheral hangs on APB1 bus which has a frequency of 42MHz, whereas there's a CCR register for I2C peripheral that needs to be programmed to specify SCLK.

Is it that the clock bus frequency defines the maximum frequency the peripheral can use up to (which I think kind of makes sense)?


texts: Measure voltage of motorcycle battery which varying voltage

texts:
I want to measure the voltage of my motorcycle battery using an microcontroller (ST32F401CE). The voltage from the battery is not a static value, since when riding, it'll be (according to the service manual) between 13.5 and max 15.5.
The microcontroller I use has an embedded 12-bit ADC converter and the ref+ is 3.3 volt. I know I have to use a voltage divider circuit. And I calculated R1 and R2 with the formula: V1 = Vm * (R2/(R1+R2)), where V1 = 3.3, vm = 15.5, R1 = 56K and R2 = 15.148k. Of course 15.148 isn't a valid resistor value, so I'll use 15k which'll give me a v1 of 3.275, which is a bit under the 3.3 ref+ voltage.
My question: Will this voltage divider circuit still work when the battery voltage changes to 13.5 volt or lower? Is the voltage divider circuit never going above the v1 value?
Programming it is no problem, since I got enough experience in that. But this is my first time making the circuit from scratch. My knowledge on voltage divider circuits is also very little. Any explanation is highly appreciated.


texts:
Modern flash memory uses multiple voltage levels to cram two or more bits into each cell, in order to increase density.

This technique is not used in DRAM (perhaps because it would compromise speed?) but it turns out to be workable for ROM, indeed to have been used for microcode ROM several decades ago: http://www.righto.com/2018/09/two-bits-per-transistor-high-density.html?m=1

I get the impression from that article that after the 8087, the technique was not subsequently used. Has it been used in more recent times? If not, why not? Double density would seem to be a big win.


texts: What are the buses known as A, B, C in the following architecture of 8086? I cannot find any information about these.


texts:
In the User’s Guide and Reference of SPICE I see this definition of .SUBCKT command

.SUBCKT SubcircuitName N1 [N2 N3 ... NN ]

As I can understand SubcircuitName and the first node of the subcircuit are mandatory.

I have a spice file which is valid (it is from working program).

.SUBCKT intrpsr_inv8 GND! IIN1 IIN2 IIN3 IN IOUT1 IOUT2 IOUT3 IVDD OUT SLL_IN1
+ SLL_IN2 SLL_IN3 SLL_OUT1 SLL_OUT2 SLL_OUT3 VDD
.ENDS intrpsr_inv8

.SUBCKT inv7 GND! IN OUT
.ENDS inv7

.SUBCKT top_inv8
XI3  GND! NET33 NET18 inv7
XI4  GND! NET12 NET39 inv7
XI5  GND! NET22 NET23 inv7
XI2  GND! NET33 NET12 NET22 IN NET18 NET39 NET23 NET24 OUT NET34 NET10 NET26
+ NET34 NET38 NET41 NET24 intrpsr_inv8
.ENDS top_inv8

The third .SUBCKT command has only SubcircuitName but not the first node of the subcircuit.
How can it be explained?


texts:
If due to some problem in slave, The slave is not able to leave the SDA line free , so that master can gain control over it. Its gets low by the slave in between data transfer , but not able to release it.

In this kind of situation how the controller can gain access of SDA line to again start some  communication?


texts:
Need help deriving a boost converter transfer function

Design Specs:

Input Voltage = 3.3V
Output Voltage = 5V
Output Current = 2.5A
Voltage Ripple = 0.1V
Load = 2 ohms
Switching Frequency = 31250hz

The simulation resulted in

Output voltage of around 4V
and an output current around 2A

Here is the schematic in which I used

Here is the ODE:

\$d(C\dot V_c-C\ddot V_c)+C\ddot
   V_c+\frac{V_c}{L}(1-d)-\frac{V_{IN}}{L}+\frac{V_C}{L}d+\frac{\dot
   V_C}{R}(1-d)=0\$

I get stuck on getting the above ODE into laplace domain, if anyone can shed some light that would be great

The Output is: \$V_C\$
and the input is: d

in terms of \$H(s)=\frac{V_C}{d}\$


texts: Lightning protection for underground loudspeaker wires

texts:
I am tasked with running a loudspeaker to a remote building. The total run length is around 275 feet, with the outdoor portion being around 165 feet.  The cable is Cat5e 24awg unshielded, silicone filled cable installed in a 2-inch PVC conduit buried 6-12 inches underground.
The loudspeaker amp documentation (Viking PA-2A, page 6) shows that the run length is suitable for the wire gauge, and also states that multiple pairs can be ganged to increase current capacity if necessary.  I can use up to all 4 pairs if needed.  They also state that step-up/step-down transformers can be used for very long runs (see this), which I will do if the volume is not acceptable.

I said all this to hopefully avoid unrelated replies such as "it won't work/cable size is wrong/etc".

My question is regarding lightning protection.  Since the cable is outside/underground for 165 feet, do I need any type of lightning arrester to protect my amp and other electronics?

If so, I'm not sure what type of arrester to use.  Most such protection devices are for coax cable, and I've only seen a few screw terminal devices, such as this one, which is only rated for 12VDC.  It's my understanding that the amp outputs ~70V to the loudspeaker speaker horns, so I assume this type of arrester would not work.

I would appreciate your advice on how to proceed.

Thanks!

EDIT: I should have known L-Com would have something like this. Is this overkill?  I'm only running one pair, not stereo.


texts:
Do fuse box connected circuits turn on and off with the vehicle?

I’m trying to connect my Arduino to my motorbike using a fuse tap to the fuse box. I want my circuit to turn on and off with the bike. I’m wondering if the power is cut off on the fuse box by the kill switch (or the key) or if I have to connect the negative pole to my kill switch negative or if there are other solutions.

Ps. I’m a computer scientist, I’m not going to weld anything, cut wires etc.


texts: Eagle: the holes don't come with the component

texts:
Well, I am completely baffled! I created some components with holes, and when I move the component while laying out the board, the holes do not move with the component. Rather the holes just stay outside the board, in the parts default position. Please see the image below

I moved the chip, and the holes (14 little white circles in the bottom right) did not come along for the ride. How can I make them move with the component?


texts: Best way to get 5v or 12v or 0v from arduino pin

texts:
Concerning the answer to this question explained in the link "Best way to get +5V or +12V or 0V from arduino pin"
I am at very basic level of electronics because I am in first semester of Electronics Engineering. I am learning Arduino in my vacations. Please explain me deeply this procedure of  getting 12V output from Arduino pins using transistors; keeping in view my level of understanding.


texts: 4s2p lithium ion battery charging from USB

texts:
I am newby in electronics. I planning to design a 4s2p (3.7 V, 3000mAh) li-ion battery pack and a charger. I want to use TI  BQ series (BQ24618) ICs for charging. I know we can charge battery pack with 14.8V+ DC.

Can we charge the battery pack also from a USB (5V) input. I would like to know how is it possible to charge a large battery pack like 4s2p from USB.

Thank You.
Edit: thanks for your answers.
Lets say we made a similar design with this, Do we need boost input voltage to 4*3.7V? DEsign looks like accept 5v for charging.

Multicell BM Unit


texts: Use of desiccant for storage and delivery of electronics

texts:
I have several questions regarding desiccant and electronic components:

Is there a rule of thumb on how much desiccant, let's say silica gel, to use per volume unit or per package area unit?

Must a package be very well isolated for the desiccant to do any good?

What is the lifetime of some desiccants at room temperature with a humidity of 50-55%?

Naturally, different electronic devices have different sensitivity to moisture. The type of devices I'm talking about here are ICs like operational amplifiers, microcontrollers and memories.


texts: How base and collector has nearly the same majority charge carrier concentration

texts:
Size: Collector > Emitter > Base

Doping: Emitter > Base > Collector

In the Function section of this Wikipedia page, they have said that Collector & Base have the same concentration of majority charge carriers.

Doubt: If the base is less in size and more doped then the majority carriers have less place in base. If the collector is more in size but less doped then majority carriers have more space in collector.

Question: If majority carriers have more space in collector & less space in the base, then how they've nearly the same concentration?


texts: How to power a 10-watt electric circuit without grid connection in cold countries?

texts:
What options do we have for powering electric circuits without access to electric grid? For instance, to power a 10 watt LED lighting at night? The motivation to the project is to add some lighting in places where it is expensive to connect to mains.

In warm countries like Spain, southern USA, Italy etc this is a no-brainer: you just need a cheap solar panel, one cheap lead-acid battery and controller. Costs like couple of hundreds of euros/dollars at maximum, and is economically feasible if compared to mains connection (which might cost thousands of euros/dollars with excavation work etc).

But in cold countries (like here in Finland) there are plenty of problems in winter:

The solar panel gets covered with snow

And even if you place it so that it does not, the power output is negligble

So, a feasible solution would be to use large amount of lead acid battery capacity to get over the winter (basically December, January and February).

But there is a but: lead acid batteries lose their capacity in cold and in addition, you can not use even this reduced capacity because the battery will freeze and break down if it is too cold. For instance, a fully charged lead-acid battery will freeze at -70 °C (which is not a problem), but a battery with 50 % SOC will freeze in about -26 °C, which can happen here in Finland (this cold it is not very common in souther Finland but it is possible, for couple of days).

Is there any feasible alternative ways to solve the problem? The best option I've found so far is methanol fuel cell, the lowest power systems cost 3000-4000 euros/dollars so it is still cheaper than a mains connection.


texts: What do we Gain by Packing Various Components into SoC

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I have been trying to understand that what is the added benefit in shrinking components such as DSP slice, IPU, LCD controller etc into SoC instead of keeping them separate.

Is this done only to decrease the area footprint of the device?
Is there  an added benefit in terms of latency?
Is cpu more optimized to talk to components within the SoC?
If cpu is optimized what kind of optimization is used?


texts: Why is my PAC1934 voltage/current sensor showing lower voltage?

texts:
I'm testing out a PAC1934 click voltage/current meter and am getting weird results.
The PAC1934 board is connected to an ESP32 development board, from which it gets 3V3 power and I2C control.
There are two supplies hooked up to the sense inputs (+) and outputs. One is 9.10V (Channel 4) and the other is 5.15V (Channel 1). Both voltages are confirmed by other measuring devices. All grounds are common.
U | 5V  ----|         |--- 3V3 ---|           |
S | TX  ----|  ESP32  |--- GND ---|           |
B | RX  ----|         |--- SDA ---|  PAC1934  |-- GND
  | GND ----|_________|--- SCL ---|___________|
                                    |5V| |9V|

Unfortunately, my readings are approx. 0.5V off and Channels 2, 3 should be zero.
Here's an example of the readings:
Read start:
 Voltage1    (mV) = 4610.35
 Voltage2    (mV) = 293.95
 Voltage3    (mV) = 268.07
 Voltage4    (mV) = 8481.93
 Vsense1     (mV) = 0.845337
 Vsense2     (mV) = 0.000000
 Vsense3     (mV) = 0.000000
 Vsense4     (mV) = 0.509644

Read start:
 Voltage1    (mV) = 4610.84
 Voltage2    (mV) = 292.48
 Voltage3    (mV) = 266.11
 Voltage4    (mV) = 8490.23
 Vsense1     (mV) = 0.770569
 Vsense2     (mV) = 0.000000
 Vsense3     (mV) = 0.000000
 Vsense4     (mV) = 0.624084

Why are the voltages lower on the 5V/9V channels, and non-zero on the unconnected channels? What could be causing the discrepencies?
Edit:
These are the raw readings:
Read start:
 VoltageRaw1    (mV) = 9435
 VoltageRaw2    (mV) = 579
 VoltageRaw3    (mV) = 523
 VoltageRaw4    (mV) = 17594
 VsenseRaw1     (mV) = 502
 VsenseRaw2     (mV) = 1501
 VsenseRaw3     (mV) = 1501
 VsenseRaw4     (mV) = 440

Read start:
 VoltageRaw1    (mV) = 9440
 VoltageRaw2    (mV) = 583
 VoltageRaw3    (mV) = 519
 VoltageRaw4    (mV) = 17481
 VsenseRaw1     (mV) = 1014
 VsenseRaw2     (mV) = 1523
 VsenseRaw3     (mV) = 1454
 VsenseRaw4     (mV) = 340

And this is the calculation done by the library to show Voltage(ch):
VbusLsb = 32000 / 65536.0;
VbusReal = (float)VoltageRaw1;
VbusReal = VbusReal * VbusLsb;
Voltage1 = VbusReal;

There is a setting for the resistance of the resistor used, but that does not have effect on voltage, rather current calculation. I think VbusLsb should be 32000 / 6553**5**.0, but that makes little difference.


texts: Stability of a two poles negative feedback amplifier

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let's consider this analysis of a two-pole amplifier with negative feedback (Microelectronic Circuits by Sedra Smith 7th edition):

Before showing you my doubts, let's consider this introduction made at the beginning of the chapter about negative feedback:

So, with the term "unstable", this book means "oscillating".

Now, my questions are:

1) Is that definition of stability general? When I studied control theory, I saw a different definition of stability, that is: stable system = system in which bounded input implies bounded output. I do not see any link between this definition and an oscillating behaviour.

2) Now consider again the analysis of the two poles amplifier shown above. The book says that the amplifier is always stable because all the poles of the closed loop system have negative real part. It is true, but they may have also an immaginary part, which means oscillation. It is in contrast with its definition of stability.


texts: Arduino remove power if battery voltage is too low

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I want to power my Arduino using a Lithium-Ion battery. When the battery is below 3.0V, the power to the Arduino should be disconnected, and when it rises high enough again is should be reconnected again. The problem is I don't know how to do that.
I thought about using a transistor that connects in series with one of the battery power lines, and let the Arduino check the voltage and if needed disconnect the transistor. The problem is, how to power it up again?
Also if the Arduino provides power to enable the transistor, how should it get power to do that in the first place? Is there any better way to do this?
The batteries get charged by a solar panel btw


texts:
Looking for the part identification for this voltage regulator on the Zotac GTX 1080 Mini. Hoping that you all will have more luck reading the text on the chip than I do. Trying to read it so I can figure out what surrounding components are missing with a schematic of the regulator. From what I can tell I see the following: Line 1: [Illegible] 3J, Line 2: 638. I already looked up what I could read on google and got negligible results so I must be missing something. Additionally I have researched the PCB and made several calls to the manufacturer, all futile.
Appreciate your help. Thank you.


texts: USB hub inside modular keyboard for comunication

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I'm working on a personal project which consists on a keyboard that also serves as a hub in order to connect more keyboards. For example, I could have the main keyboard with the letters and symbols and attach to this one another one that has the numbers. Another example could be a keyboard that is split into two pieces: left and right. The left piece will be connected to the computer and the right piece to the left piece. I know that most of the people do split keyboards using the I2C bus but I would prefer to use USB for better flexibility. The first challenge I have to solve is how to pass the signal from right to left. I have thought to use a USB HUB controller so each piece will have an Arduino micro which output will be connected to one input of the USB HUB controller and then the output of the HUB controller will be the output of the keyboard. The rest of the ports will be used to connect other pieces of keyboard or others peripherals.

simulate this circuit – Schematic created using CircuitLab

Of course, all the keyboard modules will be built the same way so I can connect 3 of them in series and just the last one to the computer. I would like to have one input and one output in each side of the keyboard in order to get less messy with the cables:

simulate this circuit

The problem with this solution is that I would need a lot of USB type C ports and someone who is not used to this keyboard could connect output to output for example. The ideal solution would be to have just one USB on each side that can be used as input or output. So my question is: Is there a way to make a USB port IN or OUT depending on if it is giving power or receiving it? I was thinking to use the FE2.1 USB HUB controller and some kind of USB switch but I'm not sure if this is possible. Any suggestion will be appreciated.

PS: My experience in electronics is pretty low so sorry for all the stupid things I have said.If something is wrong or is difficult to understand just let me know and I will edit it.

EDIT 1

I have chosen the USB C because it's very thin (the keyboard needs to be portable), it does not care in which direction you try to connect the cable and, as far as I know, it's supposed to be more durable than the micro USB port.

The keyboard will be made by me, it's not an adapted keyboard so the Arduino will be used to handle the button matrix. All the keyboard modules will be made by me in the same way so all of them will have an Arduino and a USB HUB.

It's a personal project and I think that is more elegant to use just one USB per side (I will be spending some money and a lot of time in this project so I want it to be as good as I'm capable of). Using two different types of USB ports in each side is a solution but, if I can, I would like to have just one in each side.

EDIT 2

I think the best solution would be this one:

  I would recommend looking a development kit for a usb type-c hub chip or chipset which is able to automatically switch ports from upstream or downstream, then you can leave all the gory details of usb-c to them and get on with building your usb peripheral.

And if I'm not able to find a usb controller like that or is too expensive this one:

  just provide connectors on all sides and have them switch type host/device depending on where the power is coming from.
  (use USB switch chips)

I just want the connector to be USB C, I don't care which protocol is running under it. It's thought just to connect keyboards so anything should be fine.


texts: Is it necessary to place a capacitor near VCC even if there isn't one in the datasheet? The one I am talking about is QRE1113. On the one hand if it isn't advised in the datasheet that it will feel like a redundant action, on the other hand it won't hurt you if you do it.


texts:
I keep having issues with creating a unity gain buffer amplifier to isolate a voltage source. My voltage source is very limited in current ~1-2 mA and I need that signal to drive a transformer at 10 VAC. I thought it would be as simple as using an op-amp, but I am finding out that op-amps do not like to source more than a few milliamps. My transformer draws about 20 mA at 10 V.

I thought I could use a BJT or two to help source this current, but I'm finding out they do like my 15V rails because all they do is get hot and output nothing. I have them in a push pull configuration. They are darlingtons rated for much more current than what I'm drawing. I am going to be using an NI cRIO module to create a 10 VAC sinewave and all I need is to find a way to buffer the current output, so that I can drive this unloaded transformer.

Someone mentioned the LT1210 but I seem to be missing something since I lose half of my input voltage. ignore the .01 Resistors. I have them there to measure current through that trace.


texts:
Recently i am using a LED as a photo detector . Follow by this instruction :
http://makezine.com/projects/make-36-boards/how-to-use-leds-to-detect-light/

An opamp is used to convert the photocurrent from an LED into a proportional voltage (Vo)
The author stated that "The Linear Technology LT1006 single-supply op-amp (IC1) provides a voltage output (Vo) that’s almost perfectly linear with respect to the intensity of the incoming light"

So is that true that Vo is linear proportional to light intensity ?


texts: What will happen if a MOSFET switch circuit is run without the source?

texts:
I have a situation where I have to supply the power to the MOSFET gate drive circuit permanently even when the main switch for source battery is turned off. It is because of the fact that the drive circuit is connected to the alarm unit and therefore, requires to be ON indefinitely. However, since battery has master switch, which can be turned off thus resulting in a circuit break for the MOSFET switch. So, I wonder if MOSFET would be fine hanging without the source present while Vgs being provided constantly?

simulate this circuit – Schematic created using CircuitLab


texts: Half adder with soft latching input buttons

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I'm trying to build a half adder with soft-latching buttons as input, using only transistors. I looked up online for some ideas and managed to build a soft-latching input circuit and a half adder circuit on a breadboard. Separately they worked, but the output LED was dimmer than I expected. However, once I assembled the whole thing together, it seemed not to be working at all. I'm guessing that the current levels are too low to drive the components properly. With the breadboard I used a 3.2V battery.

Below is the design that I came up with. I'm not sure if it just missing some details or if I got the design fundamentally wrong. I would appreciate any hints or maybe recommendation for some reading that could help me understand this better.

Edit

I applogize about the earlier schematic, here is one that I created earlier with Eagle, hopefully that will be better.


texts:
Is it easy to layout a PCB with this kind of connectors?

And what's the name of the female part of this type of connection?

Honestly, Im just lost in the interconnections world. What are the most common names for SMD and/or trough-hole connectors?

Thanks!


texts:
OFDM is a multi carrier signal divided in frequency domain into orthogonal subcarriers, where each subcarriers carries an information symbol.So the EVM per  subcarrier expresses the quality of the signal within that subcarrier bandwidth

If an OFDM signal at RF goes through a band pass filter that has some amplitude ripples, what is the effect of these ripples on the EVM of the subcarriers? Would the effect be the same like in a single carrier signal?


texts: i have a 1000 volt dc power source with milliamp current. How do i downsize my voltage to 12/18 volts without downsizing current?

texts: I have a 1000 volt DC power source with milliamp current.   How do I downsize my voltage to 12/18 DC volts without downsizing current?


texts:
How would one go about creating a library component for a through-hole fuse that sits in a holder? The part in question is this:

Fuse: http://www.digikey.com/product-detail/en/37202000411/WK4234BK-ND/245312
Fuse Holder: http://www.digikey.com/product-detail/en/56000001009/WK6235-ND/808503

I was thinking of going about it the way I go about DIP ICs that I need to be socketed, which is by adding the IC to the schematic, and simply putting "Socketed" in the comments/notes in the Bill of Materials. However, the above fuse/fuse holder is not standard (as far as I can tell), so I am wondering how others would go about this? Would it be acceptable to use the fuse in the schematic and in a comments/notes section of the BOM say "Socketed, Littlefuse P/N 56000001009" or something similar?

Just wondering if there is a standard way of doing this.


texts: Solid State Relay for Large Inductive Load

texts:
I have an old, transformer-based welding machine, which is rated to draw about 70A at 240V, at full output.  It uses an electro-mechanical relay (contactor) to energize the main power transformer, and depending on the point in the AC cycle that the contacts close, it may have a high inrush current, well in excess of the rating of the circuit breaker that feeds it.  When it was built, in 1960, fuses were the norm, and one would simply use a time-delay fuse, to tolerate the spike.  Since it's in my garage at home, and not in a commercial environment, I don't have the ability to use a breaker with a D trip curve, without replacing my entire breaker panel, at the cost of hundreds of dollars US.  I'm looking for a more elegant solution.
Ideally, I'd like to find an off-the-shelf solid-state relay, which is designed specifically to power inductive (single-phase) loads, by switching on and off only at peak voltage, where the current is at a minimum.  Does such a device exist, or would it be realistic to design an analog circuit that would accomplish this?
A resistive (NTC) inrush current limiter isn't really suitable for this application, because sufficiently high current devices would cost as much as replacing the circuit breaker panel, or more, and I need the ability to rapidly turn off and on the main power transformer primary as many as 20-30 times per minute, and NTC resistors at that power level tend to have cool-down times in the range of minutes.


texts:
I am selecting an MCU (EFM8BB10F2G-A-QFN20 Datasheet here) for one of my projects and I found a strange thing. This MCU has only pin for external clock source:

Till now, I have never encountered this case. In every other MCU I have used, there were two pins for connecting an external crystal. How can I use a crystal in this case?


texts: High bitrate IR receiver (TSOP7000 replacement)

texts:
After a many days of research I turned to stack overflow once again to help me.

I'm looking for High speed IR receiver circuit for laser-tag weapon. Requirements are High noise cancelation, high distance, high speed and low latency.

For obvious reason I can't use IrDA because of complicated protocols which are big overhead to latency. The only suitable solution for me is TSOP7000, but Vishay discontinued it's production.

Is there any way to build a receiver circuit, that replaces TSOP7000 or is there any replacement of this great receiver ?

Thank you very much.

EDIT: High level expectations: 16bits of data@<2ms.

For obvious reasons there is a problem with data collision. In ideal case, there will be one transmitter (gun) and one receiver (sensor) transferring data at once. But the main problem of laser tag guns is the collision. If multiple guns shoot at one sensor in the same time a data collision can occur. That's whole transfer should be executed in shortest time possible. IrDA cause massive overhead.

Most of the classical lasertag equipment is used in dark rooms completely restricted from son or lighting. That's the reason I need to think of the filters, to make game playable at classic hall.

Obviously, the data loss caused by technical background should be as small as possible. (I don't want some raging kid to smash my weapon on the ground)


texts: How to create a variable delay using 8051 assembly code

texts:
I'm just learning assembly and can now set a delay either by checking TF0 or waiting for an interrupt. How can I write a routine that will accept a variable time? Everything I google is not variable. For now I don't need to reload the timer. I have a 1us cycle time so anything between 1 and 65 ms would be great.

I'm a freshman high school student and I want to thank you in advance.


texts: Can we supply 2A DC current at 5V in the pair of ethernet CAT 5e cable?


texts: PHY to PHY connection (KSZ9477S and DP83849IF)

texts:
I want to connect two phys on pcb through AC coupling (max path 150 mm), one PHY is KSZ9477S embedded PHY, other is DP83849IF PHY. The schematic is attached

At first the I made a direct connection and it was 100 Frames per second loss. Now I added 49.9 Ohms and It became 100 times better (1 Frames per second loss, on some channels It 1 packet per our loss. The pcb traces are diff pairs with right impedance and matched length. I only have 200 MHz bandwidth oscilloscope and can't completely evaluate signal integrity, but generally it looks normal (like MLT-3), DC offcets are also fine (at least on DP83849IF side), does DC offsets even metter? KSZ9477S has internal biasing and termination... My question is how to acheave reliable communication in my case? Maybe I should play with capasitors and resistors values? What is the methology? Does it even possible to acheive relaible communication through AC coupling?
I just found out that I have pretty bad ripples on 3.3V power supply rails (+- 200 mV, picture is attached) Can it make a difference?


texts: I have an assignment to create basic digital circuits in HSPICE using various manufacturing processes. I've written a couple of HSPICE decks, but it was just copying off a paper, and it was just gibberish to me. I'm wondering if anyone can recommend a good introductory book on Synopsys HSPICE? If the book you recommend was a textbook for a class, please indicate this.


texts:
I've got a project I'm working that is using an STM32F030K6T6. I've followed STM's example of emulated eeprom for the STM32F0xx microcontrollers, but am hitting a Hard Fault when the EEPROM_Init function calls this line:

/* Get Page0 status */
pagestatus0 = (*(__IO uint16_t*)PAGE0_BASE_ADDRESS);

Here's the PDF document for the STM32 help code: https://www.st.com/content/ccc/resource/technical/document/application_note/2e/d4/65/6b/87/dd/40/25/DM00049914.pdf/files/DM00049914.pdf/jcr:content/translations/en.DM00049914.pdf

and here is a link to the eeprom code itself: https://www.st.com/en/embedded-software/stsw-stm32117.html

I left the example as it was in the STM32 code exmaple, so I assume that the addresses should be okay for a medium density STM32.

Here are the definitions related to the emulated EEPROM

#define ADDR_FLASH_PAGE_16    ((uint32_t)0x08008000) /* Base @ of Page 16, 2 Kbytes */

#define ADDR_FLASH_PAGE_48    ((uint32_t)0x08018000) /* Base @ of Page 48, 2 Kbytes */

/* Define the size of the sectors to be used */
#define PAGE_SIZE               (uint32_t)FLASH_PAGE_SIZE  /* Page size */

/* EEPROM start address in Flash */
#define EEPROM_START_ADDRESS  ((uint32_t)ADDR_FLASH_PAGE_16) /* EEPROM emulation start address */

/* Pages 0 and 1 base and end addresses */
#define PAGE0_BASE_ADDRESS    ((uint32_t)(EEPROM_START_ADDRESS + 0x0000))
#define PAGE0_END_ADDRESS     ((uint32_t)(EEPROM_START_ADDRESS + (PAGE_SIZE - 1)))

#define PAGE1_BASE_ADDRESS    ((uint32_t)(ADDR_FLASH_PAGE_48))
#define PAGE1_END_ADDRESS     ((uint32_t)(ADDR_FLASH_PAGE_48 + PAGE_SIZE - 1))

I usually use Microchip parts, but we are switching over to STM32's for a lot of our future products. In other words, I'm a little out of my natural environment.

I am using Atollic and the STM32CubeMX plugin.


texts: Clamping negative voltage on comparator input (LM393)

texts:
I need to compare a AC voltage against a reference voltage. I'm only interested in the positive part of the cycle so I need to clamp the negative part of the cycle to protect the comparator input. I need some degree of precision so I'd prefer not putting a diode in series with the AC signal. The first thing that comes to mind is a simple diode clamp:

This will clamp the input to approximately -0.65V. However, the LM393 datasheet says -0.3V is lowest voltage allowed on a input, stating in the notes that going any lower may cause the output to behave erratically due to parasitic action:

1) Is there a simple, common way to solve this problem?

2) I've seen the above solution with a simple clamp diode used in commercial devices. Does this mean the problem is not as bad in reality and the datasheet is just overly protective or the commercial product was just poor design ?


texts:
In this circuit, when I switch off the transistor opening the switch SW1, a negative Voltage of circa -6.5V appears at its base.
I would like to understand why, my first hypotesis is because of the base capacitance of the BJT. Is it true?

simulate this circuit – Schematic created using CircuitLab


texts: How do you control an Arduino using Applescript?


texts: Circuit builder for beginner showing the light of LEDs and electical flow

texts: I'm looking for a virtual circuit designer application (for Windows). I assume the application has a design mode and "debug" mode to see electrical flow and lights of the LEDs (for example, if an LED turns on and off every second the application shows that action). I would want to know your suggestions of which application can do this better.


texts: Confused about I2C addressing in PCA8574/74A

texts:
The datasheet for the NXP PCA8574/74A contains the following line on addressing (p.6):

  When AD2, AD1 and AD0 are held to VDD or VSS, the same address as the PCF8574 or
  PCF8574A is applied.

I'm afraid I don't understand what is meant here. Can someone clarify please?
Also, while address ranges are given as (depending on inputs AD0..AD2)

  PCF8574: 0x20 - 0x27
  PCF8574A: 0x38 - 0x3F

both the text and fig.7 suggest that the device address can freely be chosen between 0x01 and 0x7F (though I don't see how this would be done).

Or am I reading this wrong?


texts: Why are chips used in electronic identity cards?

texts:
Why did Germany choose NXP's SmartMX chip in the new Electronic ID Card (see here) instead of having a more conventional solution, like an old credit-card-like approach?

In fact, the question is more general: Why is the chip solution considered the best approach for identity cards vs. magnetic bands, MRZ et al.?

FTR, I think that a much more cost-effective solution would be by having the cryptographic engine in the reader/writer and the card should be a rather dumb storage media which will store the encrypted data.

(Also, we all know that there are also solution to 'workaround' the chip's security features. See here)

What do you think?


texts: I have built a BJT amplifier and I have a function generator connected to the input of my circuit. I have also connected both channels of an oscilloscope to the input and output of my circuit. I need to find the maximum input I can provide to my circuit. I have done this by increasing the output voltage on the function generator until I just see clipping on my output waveform and then I read off the value of the input voltage i.e. from the function generator. I have also see where persons have increases the output of the function generator until they see clipping and then they find the swing and divide it by the max gain of the circuit to determine the max input value. Which approach is the correct approach.


texts: Setting measurement points of the 74HC86 delay time

texts:
simulate this circuit – Schematic created using CircuitLab

I'm measuring a propagation delay and transition delay of a 74HC86 chip.
I setted somewhat high frequency square-wave signal(100kHz) for Input 1. Input 2 was connected to VCC.
I tried to measure delays, but oscilloscope confused me because of attenuation.

As you see in the picture, when the falling edge occurs(Yellow plot is the input of the 74HC86, and green plot is the output of the 74HC86), something like damping is shown and I'm frustrated because I don't know how to set the interval of measurement.

I searched some questions and I acknowledged that main cause is the L or C components in my probe, the breadboard, or my wire. However, I think this cannot be entirely disappeared, and I want to get the transition delay.

Is it okay to get the 0.1Vcc and 0.9Vcc as interval for transition delay? If it isn't, have to I modify the measurement points?

The link of datasheet of the chip is at below:

https://assets.nexperia.com/documents/data-sheet/74HC_HCT86.pdf

You can refer about the delays at page 7.

I don't have a USB flash, please understand about this.


texts: How to connect the emitter of a transistor to the base of another transistor? (PNP)

texts:
I'm a bit new to circuitry, and recently I have been experimenting with transistors, attempting to create some logic gates. I realized however, that basically all of my logic gates output a positive voltage (the emitter receives current from a 5V battery), and if I were to connect two gates, I needed the outputs of the first gate to be used as inputs for the second gate (meaning that the positive current would have to flow into the base of the second gate). My question is, how can you do that? I have spent a lot of time looking into transistors, and it seems to me that only current coming from ground can go through the base of a PNP transistor.

I'm sorry if the problem is due to a major misunderstanding on my part, like I said, I am pretty new to circuitry.


texts: How do I measure startup/inrush current?

texts:
I have some small devices that draw 20mA. I'd like to add a resettable (PPTC) fuse to them but I am not sure what value to select.

My thought is I need to find a value that will tolerate the startup or inrush current when the circuit first turned on, but I don't know how to measure that. (My meter isn't that fast, but I do have an analog 100MHz oscilloscope.)

The devices have a capacitance of about 122μF.


texts:
I have a general question which im not sure how to implement.

Suppose that a car is driving on a straight road and it starts doing some maneuver.

Due to this maneuver the driver moves the wheel left and right in some not uniform "wave" like this:

For Example at the beginning he moves the wheel to the right for about maximum 2 degrees then left for about 1 degree and so on.

Once he finished his drive, I take the information from the car and I have a dataset of the movments of the wheel (Basically a matrix that its first column is time and the second column is the angle of the wheel).

Now, I had like to take this data and to make an equivalent PWM that will eventually move the wheel at the same manner as it did before once I inject this data to the actuator.

Is there a way to implement a PWM signal that will represent the "wave"?

Im asking because from what I know the reference signal here is not in constant frequency and im not sure how it is possible to recreate a PWM signal in that way.

Thank you.


texts: How to calculate address range of memory chips

texts: Hi I am not an Electrical Engineer but need to know something about Memory address ranges. I need to calculate address range of each memory chip(62256) from let suppose bank 1 in below diagram. How can I do this ?


texts: Do I need a power supply unit or just a voltage header?

texts:
I have a 3d printer that I am building which has a heated bed, as most FDM printers. The bed is about 25"x24" and will have (4) 12"x12" silicone heating pads anywhere from 500-700W each.  Each heating zone will control to a temperature setpoint using a solid state relay and PID control.
The printer will be on 240V circuit with high amp capacity, so power is not an issue here.  My question is because each of the heating zones are wired independently should I buy a big PSU and run 240V from the outlet to it and then to each heater?  Could I get by with just wiring each heater in parallel to the 240V outlet.
As a side note, the motherboard, stepper motors, and all other devices associated with the printer are being powered by a small PSU that steps voltage down to 24V.


texts:
Why is this MOSFET (BS170) not turning the LED completely OFF and then ON?
PIN2 of Arduino is set to HIGH for 100ms then LOW for 100ms. The LED does blink by getting brighter and then dimmer, but not ON and then OFF.
Green wire is connected to PIN2.


texts: Cyclone V FPGA SocKit - trying to use LCD from FPGA

texts:
I'm trying to use the LCD screen on a SocKit board with a Cyclone V FPGA.

However, in the documentation I see that the chip is divided into an HPS and the FPGA and the LCD seems to be connected only to the HPS part.

Is it possible to use the LCD on this board directly from VHDL / FPGA without using the Arm processor? If yes, can anyone point me to some documentation on how I can interface into the LCD from VHDL? (I did search but couldn't find anything relevant yet, I'm just starting to learn VHDL.


texts: 12v Latching on/off switch with momentary function

texts:
I'm looking to control a flashing light unit in my car that has several selectable patterns. It uses basic 12v+ to power and a basic +12v momentary to switch to the next pattern in a logical list. These are the only two functions in the unit.

I have a switch in mind that would latch on/off and also provide a momentary 12v+ output in order to pulse the pattern select.

Does such a switch exist as a self contained unit or can I make some other switch switch to suit the purpose?

I found teh Joyluxy QN16C2 on amazon and it's the ideal package. It would be great to see a push down latch on, and still have a reserve throw for momentary function that would not unlatch.

Can such a thing exist? Can I easily convert something else to get similar functions? I'm trying to avoid two distinct switches.


texts: Ethernet pass through connector on bottom of IP phone. What do you reckon is inside?

texts:
I was hooking up some 10/100BaseT Ethernet cables at a customer site and I noticed that the Voice Over IP phone on a desk had an Ethernet input and an additional RJ45 that serves as a pass-through connection. This was handy when there was just 1 CAT5 cable coming into the cubicle. The incoming cable goes to the phone, and then the pass through jack was connected to their PC via another CAT5 cable.

Do you know what circuit is behind these 2 RJ45 jacks?

I would love to have taken a screwdriver to the phone, but that was beyond the scope of my work plan :)

Do you think it is a transformer? Just a couple RJ45s in parallel (yuk!)? Certainly there are not 2 MAC/PHYS, that seems cost prohibitive for a cheap VoIP phone.

How would one design such a pass though to allow several devices to share a single incoming CAT5 cable?

I've seen this question: Ethernet Without a Switch?

that has a link to this circuit: http://www.zen22142.zen.co.uk/Circuits/Interface/pethhub.htm

Perhaps this is what is inside the VoIP phone?

Cheers,
David


texts: 4-20mA to voltage breakout: part identification

texts:
I am trying to recreate the SEN0262 current to voltage circuit and embed it into my own board.
As you can see, the schematics looks pretty good, but I'm unable to identify the D1, D2, and D3 diodes.
Can anyone identify those parts numbers?


texts: Need Help understanding electron flow for this circuit!

texts: So I'm taking my intro to electromagnetism course and we are learning about currents and resistance right now and I'm running into a little confusion when it comes to the conventional flow and electron flow of this voltage division circuit. So the issue is when I try to calculate the voltages between each resistor using conventional current I get the same values like the one in the diagram below. However when I try to do this considering electron flow I'm getting different values, specifically the voltage in the wire from R3 to R2 is 3 volts but the voltage in the wire from R2 to R1 is only 1 volt. I don't know how I'm not getting the same values as with conventional current. Shouldn't I get the same values??


texts:
i have a tv that works on 12v dc and also 220v Ac. i can attach both power cables. I run it on the 12v battery almost of the time but some times the 220v electricity is back so i have to make it work on it by remove the 12v dc blug and re-switch it on again so it can work on 220v blug. if i don't remove it the screen will still work on 12v blug even the 220v is excited. i need a simple circuit that can switch of the 12v blug once the220v ac is back.

note: i used a charger for my battery so once the 220v Ac is back the volt of the battery blug incrase from 12v to almost more than 13v.

any help please.

great thancks


texts: RLC equivalent model and Impedance Smith Chart

texts:
I have done some impedance measurements on an unknown 1 port device. I have measured its impedance at different frequencies (from 10 MHz to 600 MHz) and I have seen it on the normalized (on 50 Ohm) Impedance Smith Chart:

At Low frequencies we are at the short circuit point (left). Then, the device offers an inductive impedance, until, at about f0 = 470 MHz, we arrive at the real axis (right). It seems it arrives at the open point but it is not: if you see the following graph you see that the impedance is, obviously, purely real, but not infinite. It is equal to about 471 Ohm (absolute value).

You may see these results also in the following graphs (the first one contains real and imaginary parts of the impedance, while the second one its absolute value).

So, at f0 the devices resonates and offers a purely real impedance. Now my question is: which is the equivalent RLC circuit of this device according to this analysis?

Precisely:

from the Smith Chart I may get the value of L: I should take the Imaginary Part of Zin at low frequencies (in which the device is almost purely inductive) and divide by 2*pi*f.
from the Smith Chart I may get the value of R (it is 471 Ohm, as told before)
from the Smith Chart I may get the value of C (at high frequencies, where the device is almost purely capacitive)

So, which is the equivalent model? A parallel RLC, a series RLC?
Moreover, at f0, does the device offer a parallel resonance, or a series Resonance? I have been told that if I measure R,L,C through the Impedance Smith Chart, they are the values of the RLC series model, but I am not sure about it because I can also do my measurements on the Impedance Smith Chart for a device which is not a RLC series circuit. For instance, something like that:

Moreover, I'd say it cannot be an RLC series circuit, because at low frequency we are at short circuit point, and not open circuit point.


texts: bulbs connected to a three phase system - what is the current in neutral conductor?

texts:
I wonder about the three phase system.
A three-phase power in the lab have symmetrical three-phase voltages 400 / 230V and terminals marked L1, L2, L3 and N. A 60W bulb is connected between phase L1 and N. Another 60W lamp is connected in the same way, but the phase L2 and N then two bulbs (60W each) between L3 and N .. What is current in the neutral conductor N?

my answer : if we had just one bulb between L3 and N then we get N=0
Now if the two bulbs between L3 and N , if the two bulbs are connected in series then the current through N = 0,26 A * 3 = 0,78 A
Is my solution correct?

thanks


texts: How to generate PWM with duty cycle varying in sinusoidal fashion?

texts:
I have to regulate a sinusoidal current in an inductor.
I have only a DC supply.
There are many ways to do it like using stepper motor driver to regulate step wise sinusoidal in 1/256th step mode.
For a specific application, I want to regulate the current by changing the duty cycle of the input PWM to a half-bridge.
If I can generate PWM pulses with a changing duty cycle in sinusoidal way then I'll be able to regulate the current.
I tried using a BeagleBone and an Arduino to generate PWM with a sinusoidal duty cycle, but wasn't able to do that. Mistakenly I had uploaded wrong drawing, now corrected.

I don't have waveform now to upload. But I can paste the beaglebone code I tried.
import Adafruit_BBIO.PWM as PWM
import time
import math

Ain1 = "P9_14"
duty=50 # initial value

sin_frequency=100
pwm_frequency=10000
pwm_period = 1.0/pwm_frequency
print("pwm period : ", pwm_period )

PWM.start(Ain1,0)
PWM.set_frequency(Ain1, pwm_frequency)
PWM.set_duty_cycle(Ain1, 0)

count=0
no_pulses=(0.5*pwm_frequency)/(sin_frequency)
print("number of pulses : ", no_pulses)
a=1

while True:
    duty= abs(10.0*math.sin((3.14*count)/(no_pulses)))
    PWM.set_duty_cycle(pin, duty)
    time.sleep(0.1*pwm_period)
    count=count+1
    print(duty)

    if count>=no_pulses:
        count = 0
        duty=0

PWM.stop(Ain1)
pwm.stop(Ain2)
PWM.cleanup()
print("Closed the pwm")