texts: Is it possible to jam wireless home alarm systems?

texts:
Sorry if this is the wrong community for this question but in my mind, it's the best fit. Please close or move to a more appropriate community if it's off topic.

The other day, several home alarm companies came to look at my home to quote an alarm system. They all gave me a wireless option since the wired option they said would be super expensive.

I asked if it was possible for someone to jam the wireless sensors and break in.  One representative said no but didn't elaborate why. The other said no because the communication between the sensor and the main panel is encrypted so people can't jam it.

I don't believe this is true but I don't have an EE degree. I think it's not true because I've heard on the news people have built cell phone jammers so it probably isn't hard to jam these sensors too. I think these sensors operated in the 200Mhz range (if I remember correctly), if that matters, although he said there's some encryption going on between the panel and sensor. That confuses me because the encryption is digital but the communication is analog?


texts: Powering a 4-Pin stock CPU heatsink fan with an external power supply

texts:
I have scoured this website and the rest of the internet looking for a solution to my particular issue, but as of yet I have not found an answer. If this is a duplicate question I am sincerely sorry, and I would appreciate being pointed in the correct direction.

I have an only Intel CPU heatsink with the stock Nidec fan that was discarded during a previous computer building project. I now have a new project where I require additional airflow so I decided to try and "re-purpose" the unused CPU heat sink fan for a cheap fix to my solution.

Everything I have read on the internet says to buy a 12V power supply, connect positive to positive and ground to ground and you should be good to go, but this has so far not worked for me.

I currently am using this Nidec CPU Fan and have wired it up to this Power Supply. Following this 4-Wire Fan Description (link 1 in comments) I have connected the yellow fan power wire to the red wire on the power supply and the black fan ground to the black power supply wire. The green tach and blue PWM wires have been left unconnected to anything and are simply hanging free.

When I connect the power supply to an outlet the fan "stutters" forward a single pulse like it is overcoming a single pole on the motor. I would estimate the turn is something like 30 degrees of a full revolution, but I have not measured this accurately. After the initial "stutter" or "pulse" in the right direction the fan stops moving. After waiting a few seconds the fan again "stutters" forward another 30 or so degrees before stopping again.

This behavior and the "simplicity" with which everyone else seems to be making these fans work leads me to believe that either my power supply is insufficient, or I need to feed a signal to the PWM wire. I found this YouTube video (link 2 in comments) where a guy just throws a big cap across what appears to be the positive and ground terminals of his power source and the fan runs. However, I am very unfamiliar with circuitry and his set up so I am not sure exactly what his solution is and if it will work for me problem.

This YouTube video (link 3 in comments) shows a pretty decent break down of how PWM and 4 pin fans work but I don't have a lot of fancy gear to hook up and generate the power signals he is using in the video.

My goal in the end is to keep my solution cheap! I really want to avoid building 555 timer circuit to control fan speed or anything crazy. I have access to a few capacitors from my father so I may be able to build a very basic circuit if a cap is all I need. However, if running this fan requires something more expensive/complex I will likely go buy a cheap 2 or 3 pin fan to replace the one I am trying to use, but again, looking for a near zero cost solution here.

Thank you for reading! Any help is very much appreciated!


texts:
Is it safe to use the exposed heatsink pad of a QFN to also connect the ground pins of the IC? (Like this question, but in my case the pad has many vias connecting it to ground plane.)

Additionally, is it ok to use the very same vias in order to connect components with the ground plane or the heatsink pad and its vias should be dedicated only to heat dissipation?

Edit: According to the datasheet the pad is connected to ground and should be connected to the ground plane:

"The centre pad on the base of the FT601Q is internally connected to GND, the PCB should connect to ground and not have signal tracking on the same layer as chip in this area."

In the image below it's the quarter of the QFN demonstrating my question (the blue component is a cap on the opposite side:)


texts: What does a Bode plot represent and what is a pole and zero of a Bode plot?

texts: I studied Bode plots and the author of my book is somehow relating zeros of transfer functions to Bode plots. What is the relation between zeros or poles of a Bode plot and transfer function? We usually take zeros at \$s=-a\$ (let's say) but how will we show it in a Bode plot since the log of negative values doesn't exist?


texts: How to do a DIY LCD output from a busted android tablet?

texts: I have a cheap android tablet with a busted screen.  Replacement screens cost more than a new tablet and I hate to waste it since it's only a few weeks old.  I took it apart and it runs on a Allwinner A13 ARM chip.  The LCD section of the data sheet doesn't seem all that helpful.  Is there any way to get a VGA output from the chip?  I see the chip has LCD pins for vsync and hsync but I'm lost after that.  Is this a reasonable project to take up or should I just throw it out?


texts:
In school I have learned in both systems and communication about multiplication blocks. I have been taught that these blocks create a sum and difference frequency and can be filtered to get just the sum or the difference.

What I am wondering is how to actually implement a block like this in hardware. I first thought about an OPAMP multiplier setup, but I didn't think something like this worked well for high frequencies like 900MHz or 2.4GHz. How do I go about finding a device that will do this block for me?


texts: Why do most ship alternators generate 440V even though onboard appliance use 220V?

texts:
The main switchboard of a typical ship is as follows:

I was expecting a system where the phase voltage is 220V and line voltage is 380V.
But cannot find an explanation and the link between generating 440V in a ship.
Is there a particular reason to use 440V generators in ships?


texts:
I am interested in what are the fundamental limits for communication, theoretically of course, practically there many be many other limits.

So I have tried to formulate a minimum noise floor for a communication scenario depending on the amount of data and the total time available. The minimum noise floor means, the least amount of noise present in that scenario, so that any amount of power received by an antenna if it's smaller or equivalent to it, it makes communication of the desired scenario impossible (since noise can only be higher than this, that would completely mask the signal). It would perhaps be more accurate to look at the average noise level instead, but to make things certain the minimum noise level represents physical fundamental limits.

We have the Shannon-Hartley formula, which I have rearranged to factor in the maximum time available and the amount of data sent (in bits).

$$SignaltoNoise_{Min} = 2^{(DataSize/(Bandwidth*MaxTime))}-1$$

DataSize is in Bits.
Bandwidth in Hertz.
MaxTime in Seconds.

This gives us the exact minimum S/N ratio below which it's impossible to send through a piece of data in a desired amount of time. Encoding schemes are ignored, so the S/N in reality has to be higher since many bits are wasted on checksum. Also this doesn't mean partial communication is not possible, like if we want to send 64 bits, and only 30 make it, it might still be possible to make use of that information.

For example if we want to send 64 bits through, and we have maximum 1 hour to do this, then at a 1 Hz frequency the min S/N is 1.09458825, at 106204 Hz the min S/N 0.0000069617, again the checksums are ignored.

Then we have the noise floor formula where it can be inserted:

$$NoiseFloor_{Min} (dBW)= 10 * log_{10}(SignaltoNoise_{Min} * k_0 * T_0 * Bandwidth)$$

k0 is the Boltzmann constant
T0 is the temperature of the medium the signal is travelling through
Bandwidth is in Hz

So basically this gives us the minimum noise floor in dB

Going with the examples above, sending 64 bits of information in maximum 1 hour at 1 Hz or 106.204 kHz , at room temperature (290K) , would give us:

-203.582681 dBW noise floor @ 1 Hz
-205.286632 dBW noise floor @ 106.204 kHz

So any signal level that is higher than this, received by the receiving antenna in dBW, can be a successful communication of the data in the given amount of time, while if it's equal or below this, then it's fundamentally impossible to send through the entire amount of information in the given time.

I am looking for opinions, criticism whether my logic and the presented calculations are correct here.


texts:
My goal is to take a typical white clock and make it light up green at 3pm, yellow and 6pm and red at 9pm

I'm guessing I'm going to need 6 red led lights, 6 yellow led lights and 6 green led lights

What I'm not sure about is how something on a timer switch would be wired up, would I use transistors, diodes or something else

The clock is run off of 2 AA batteries


texts: Connect IR Emitter (+) to IR Receiver (+)?

texts:
I have a vehicle stereo deck that has an IR receiver input (+) and a steering wheel control module that has an IR emitter LED (+/-). The steering wheel control module, "translates" (using a mapping created during programming) the button presses on the steering wheel to an IR output -- the idea being that you can still control aftermarket stereos equipped with IR receiver LEDs with the steering wheel controls (which are normally proprietary to the vehicle make).

Unfortunately the aftermarket stereo I purchased does not have an IR receiver LED built into it, so it cannot be controlled purely by IR. However, the aftermarket stereo does have an IR-in (+) wire, just no IR receiver LED attached to it. At this stage of the explanation, the setup looks like this:

Of course I'd like to actually have steering wheel controls for my aftermarket stereo, so I'm wondering how to connect this all together without having to buy and hookup an IR receiver LED (which honestly I don't even know if it's that easy to do given the lack of documentation for this stereo). Can I just cut off the IR Emitter LED from the steering wheel control module, isolate the IR Out (-), and hook the IR Out (+) directly to the aftermarket stereo's IR In (+)? Like so:

(Yellow and orange illustrate the changes I'm proposing.)

My instincts tell me it seems too simple...


texts:
I need light up about 960 square feet of translucent flooring from below. It's an outdoor installation, so it needs to be waterproof.

Further, it has to be done in a matter of just a few weeks, and, as usual, at a very low cost.

I'm planning on using LED rope lighting, as it can be waterproof and is easy to install.

But due to the modular nature of the floor I can't just run a lot of sealed cable from the rope lights to the power source(s), I have to have connectors under there that are waterproof as well.

It looks like I'm stuck with expensive twist circular power connectors, and a whole lot of crimping and wiring.

Are there other options? Cheap prewired waterproof extension cords I can cut in half so I only have to perform one connection per line would be nice, but I'm not seeing them.

I need about 10A at 120V through the most heavily loaded connector.

Worst case I was considering silicone heat shrink connections with IEC computer style cables, but that's not much less work and time than real waterproof connector crimping.

What other options might I be missing?


texts: Accurate localization of a remote vehicle

texts:
I've been working on a project where I'm supposed to design a vehicle that carries antennas to perform SAR (Synthetic-aperture radar) imaging. This vehicle has 3 wheels which 2 of them steered by a DC motor. In order to accurately perform SAR imaging algorithm, I need to know how much my car moved from its last location. There are several methods I've looked up so far, However there are problems with each of that:

GPS: Using GPS, I can do some calculations to see how much my car moved. However, since GPS locations are off about 4-5 meters, calculations that I'll make won't be accurate at all.
Ultrasonic Sensor: The problem about this way is limited distance range. (As I know 5-10 meters)
Accelerometer: Even though it seems mathematically possible to calculate distance traveled using instant acceleration, the errors occurring over time makes this calculation meaningless. There are some proposed ways like Kalman filtering to increase accuracy of these calculations.
Computer Vision: Using CV, I can track something on the vehicle and calculate its distance from the camera. I don't have much experience about this, therefore I can't estimate its accuracy.
Encoder: This way consists an encoder to track how much the wheels have turned. This seems to be a good way however I don't know if I can be accurate with this method.

I'm aiming for at least ±5cm accuracy. The total distance may reach dozens of meters.

In above ways or others, what would be a good possible solution to overcome this?


texts: Why Lm317 burnout and the potentiometer sparks?

texts:
so I tried to make a power supply using Lm317
and it works fine when i used a 12 v transformer but when I used a 9-0-9 transformer like in the picture,when i turn potentiometer, it sparks and then
the output become 23v and burnout .

here is the circuit that i used .

I don't know where the probem and I hope you can help me


texts: Connecting only emitter to collector-BJT

texts: I started studying the BJT Configurations and how they operate in active mode, saturation mode, and cutoff. And that every two neighboring junctions have either forward or reverse bias, But I wonder what happens when I only connect one battery between only collector and emitter (N.Terminal to the emitter and P.Terminal to the collector). what happens to the holes in the middle base. Does current flow? why? or why not?


texts: HDMI Simulate unplugging with Microcontroller

texts:
I want to interrupt an HDMI Connection with an ESP in a project of mine. I have read in some posts (eg. Can an AND gate be used to toggle an HDMI connection?), that you can simulate an unplugging event by just cutting the HPD pin. But in my experience this does not work (tested 1 monitor with a GTX970).
Are my devices just not complient with the HDMI standard, or am I missing something?


texts:
I've a DAC for headphones (GeekOut 720) which has two output jacks with different impedances: 47 Ohm (with a large headphone icon next to it) and 0.47 Ohm (with a small headphone icon next to it).

I'm currently using Sony MDREX110AP headphones, with 16 ohm impedance according to its specs. When I connect them to the 0.47 Ohm output I get much louder output than with the 47 Ohm jack, which makes me wonder, shouldn't the smaller impedance output drive my headphones with less power than the larger one? If such is the case, why is the response louder for the larger impedance output? It seems to me that I'm not quite grasping the output impedance concept.

Bonus question: what output should I use to get better sound quality and protect my headphones?


texts:
I've got to control a tunable filter on a MEMS-FPI C14273 IR sensor. It works by inputing a voltage on a range from 25 to 48 V, wich makes the lens move. It needs to be precise because if i go over 48V by only 0.5V it can break. My professor talked about a switching capacitor converter but I can't find enough information on this. So basically I'm searching for something that can take a PWM or analog signal 0-5V and convert it to 25-48V.
https://www.hamamatsu.com/resources/pdf/ssd/c14273_kacc1265e.pdf
https://www.hamamatsu.com/resources/pdf/ssd/mems-fpi_kacc9008e.pdf


texts: Simple RFID reader - AM demodulator not working

texts:
I'm currently working on building my own simple RFID reader.
I've already build a small circuit in which my coil is fed from 5V current source or is connected to ground dewpending on the 125kHz square wave signal from the microcontroller.

I've measured the frequency of the signal between the coil and capacitor C1 - it's exactly 125kHz. D1, C2, R3 are a kind of AM demodulator.

What I wanted to achieve after bringing the transponder closer to the coil was a change in amplitude, but not of the whole signal, just in some of the peaks. What I got is the whole signal amplitude decrease by about 2V.

Can anyone tell me what is wrong with my setup? I'm attaching my schema and an oscilloscope measurements between L1 and C1 (yellow) and after D1 (blue).

Thank you!

UPDATE (20140323):

The same signal, but I've zoomed out in time domain (without transponder):

The same signal, but I've zoomed out in time domain (with transponder):

If we zoom in the signal after the diode, with transponder near the coil, we can see something like this (with and without software low pass filter):

The same signal without a transponder near the coil:


texts:
Although both are domains of EE, but what are differences between them?
I am able to draw following conclusions from wikipedia article of dip and also from some other web reources

1) DIP(Digital image processing) is a subset of DSP(digital signal processing)

2)Because of above concept in (1), DIP only deals with 2 dimensional images/signals or in some case 3 dimensional images/signals(forexample RGB images) while in DSP there isn't any restriction on number of dimensions?

Please kindly guide me and correct me if i am wrong in my concepts/assumptions


texts: Safety: Can I harm myself using an AC, 9V 500mA power supply for experiments?

texts:
I'm about to embark on my first electronics project and would like to check off a safety question:

I want to build a bicycle hub dynamo -> USB charger based on these instructions.

It is basically a rectifier circuit to convert 6V, 3W AC produced by the hub dynamo to 5V DC needed for USB.

In order to conveniently test and experiment with the circuit, I'm thinking about buying a wall power adapter (this one) that converts 230V AC (Europe) to AC, 9V 500mA, since this is very close to the 6V AC, 500mA that the hub dynamo provides.

I did some research and it looks like AC is up to 4 times more dangerous than DC. My question: would it be dangerous if I accidentally came into contact with the 9V, 500mA AC provided by the wall power supply?

Thanks a lot!

EDIT:

To clarify, by "safe" I mean, "Can I harm myself?".


texts: Pressure sensing controller using Stress Ball

texts: I am thinking of a project proposal for my robotics course and we are required to make one that has a potential application on physical therapy or medical fields. One thing that came across my mind is a motorized wheelchair that moves when a stress ball control is squeezed by the user. As an electronics novice, I wonder if I could integrate a sensor circuit with a rubber ball so that when it is pressed, perhaps by a stroke patient, it triggers some driver circuit. is this possible? if so, how?


texts: Why doesn't commercial LCR meters' band start from very low frequencies?

texts:
I'm wondering why I can't find an LCR meter with frequency band that starts for example from 1 Hz. Is there some specific reason?

EDIT:
My question comes from the need to measure the impedance of a generic "component". I create a meter with an wave generator and an oscilloscope based on this configuration:

The circuit inside the yellow rectangle is the impedance to measure. The source is my wave generator and the Vout is where I read the output voltage with oscilloscope. Then I compared the SPICE simulation with my measure:

The continue lines are the simulated impedance and the circles are my measures on a similar circuit made by discrete component with same values (resistors and capacitors through-hole). The values of the components are reported in legend.

With this example I want to focus your attention on the fact that this kind of impedance varies at very low frequencies, 0.1-10 Hz. This is the reason why I'm wondering there aren't LCR meter at that band.


texts: Why there is continuous variation in output frequency of a Hitachi Inverter (L100 Series)?

texts:
I am using a Hitachi L100 Series inverter and its frequency source is Keypad Potentiometer. During run it is continuously changing the output frequency which is displayed on the Operator Display Screen. I want to have the fixed speed after i set it from the keypad Potentiometer. Please tell me why it is varying and how can i reduce it or make it to run at constant speed.
Note: The variation is small (maximum of +- 0.7 )


texts: When should I use negedge on a clock signal?

texts:
I was reading about block ram and I came across the following post.  I notice here that whoever wrote the code is using negedge on the clock signal.  Thus far almost all the examples I have seen of verilog use posedge on clock signals.  In fact I have not really seen any always blocks with negedge specified.  I am just wondering when you would want to use that and why might the code bellow contain negedge?

module RAM_param(clk, addr, read_write, clear, data_in, data_out);
    parameter n = 4;
    parameter w = 8;

    input clk, read_write, clear;
    input [n-1:0] addr;
    input [w-1:0] data_in;
    output reg [w-1:0] data_out;

    reg [w-1:0] reg_array [2**n-1:0];

    integer i;
    initial begin
        for( i = 0; i < 2**n; i = i + 1 ) begin
            reg_array[i] <= 0;
        end
    end

    always @(negedge(clk)) begin
        if( read_write == 1 )
            reg_array[addr] <= data_in;
        if( clear == 1 ) begin
            for( i = 0; i < 2**n; i = i + 1 ) begin
                reg_array[i] <= 0;
            end
        end
        data_out = reg_array[addr];
    end
endmodule


texts: Identification of hardware interrupts in microprocessor 8085

texts: I am familiar with the RIM and SIM instructions that are available in the instruction set of microprocessor 8085. And thus I can enable RST 7.5 and RST 6.5 interrupts using SIM instruction and EI instruction. But how do I identify the interrupts? Suppose, if interrupt is likely to come on either of the RST 7.5 or RST 6.5, then how do I identify it?


texts: Can you explain the operation of this RC network for a crystal oscillator?

texts: I am trying to work out what the RC network in the circuit below does and how it works. The circuit output is fed as input to a CD4060 binary counter. According to what I have read, the signal from the crystal into the CD4060 must be bounce-less and noise free. Is that what the RC network is doing? How does it work?


texts:
The datasheet of the ST VNH5050A-E H-bridge motor driver says it can take PWM up to 20kHz. Then, on page 10 of the datasheet, it says PWM = 20 kHz in the supply current parameter. Does this mean that the PWM frequency has to be 20kHz or, as it says in the description, it can be up to 20kHz?

Arduino Mega runs default PWM at 490Hz if I am not mistaken.  I am trying to find a driver chip that can handle at least 30 amps with a load voltage of up to 12-18V for a motor.

I'm trying to figure out if this chip will work with the PWM on the Arduino Mega.


texts:
This is the design of a Pierce oscillator that has to cancel the resistive part of the quartz.

Could someone explain what is the purpose of M5?
What does biasing means for this design?

At the points Q1 and Q2 a quartz crystal is connected.
Also, the drain of M1 is connected to a current mirror.


texts: Optocoupler - Emitter follower for driving an optocoupler

texts:
I have some troubles to understand the above circuit :

simulate this circuit – Schematic created using CircuitLab

The goal is to discharge the capacitor which was previously charged to 20V the most rapidly. (At least I think). The collector emitter voltage drop of the phototransitor and the forward diode voltage have to share the voltage of the discharging capacitor. At the beginning of the discharge, ie when the voltage of the capacitor is equal to 20V, the diode forward voltage is equal to Vf (lower than 1V), so VCE has to be equal to at least 19V ! So  if VCE is high, the collector current Ic of the phototransitor is limited by the gain of the phototransitor and the forward current of the emitter diode $$If*CTR = Ic$$ where CTR is the current transfer ratio. So for discharging the most rapidly the capacitor, we have to have a high collector current, ie a high forward current flowing through the emmitter diode. What do you think ? Wouldn't be better if a resistor would be added in series with the phototransitor ? It will allow to saturate the photransitor without necessary diminishing the collector current if the forward current is high.

By the way I did not get why there is a shunt resistor R2. It will reduce If.  Nevertheless it could help to reduce noise problem. (leakage current will not be a problem, isn't it ?) Wouldn't be better if the shunt resistor would be placed as a pull down resistor. Same thing for the capacitor next to the shunt resistor? This capacitor will slow down the discharge of the capacitor charged to 20V. What do you think ?

Thank you very much and have a nice day :)


texts: Dual batteries changeover circuit to avoid power loss

texts:
I have a similar question to the one here How to create automatic dual battery changeover/switching circuit for uninterruptible power?, but would prefer to use a mechanical switch (eg a rocker switch).
The setup is this: I have two 12V batteries that are hooked up with a SPDT switch to a circuit that provides power to a bunch of devices that cannot lose power (combined, they draw up to 10A). In order to prevent them from losing power, I am wondering if anyone knows the rough time delay for a mechanical switch to change states? Should I add a capacitor in here somewhere, somehow?
Here is a rough circuit diagram of the situation. Your help is appreciated!


texts: I'm looking for an extremely sensitive photosensor. I have a setup where a beam of light of some sort (weak laser, or something else) will be shining into the photosensor. Every now and then, a molecule with a diameter of about 1.0 - 1.3 nanometers will pass between the light source and the photosensor, and the photosensor must be able to detect the difference. Does such a photosensor exist, and if so, where could I get one? (The cheaper, the better.)


texts: What's the schematic to share one crystal with two micros?

texts: How do I share a single crystal (not a complete oscillator module) between two micros? Is it OK to just connect everything as normal for the first micro and also directly connect its XO to the XI of the second microcontroller? I expect to place the micros very close together on the board.


texts: Voltage Drop on ATMEGA328 when enabling multiple pins

texts:
I am doing a hobby project working with a ATMega328, however, I am struggling with a with a small issue when I am trying to drive the output high on multiple pins at once. Somewhat new to this field, I am not 100% sure where to start debug.

The problem so far is. I have set up my arduino to program an ATMega using the internal clock. I have then uploaded my program using the arduino IDE to the uC. So far, everything looks good. The program itself is basically just setting some pins to output, and then high.

After this I move the uC to my breadboard, and measure the voltage on the output pins, and everything is dandy. All the output pins shows roughly 4.7V.

Now, I move the uC to my PCB ( I can upload the board and schematics somewhere if it helps ), but now when I measure the voltage on the pins, I see 0.120 or so volts on the same output pins.

Measuring the voltage coming in on the Vcc pins, I can see that it's well within the acceptable range. Somewhere around 4.9V.

Also, after some debugging, I have found that if I only enable ~2 pins, I can get the expected ~4V. However, if I enable 3+ output pins, I see the voltage drop.

I am somewhat confused, and new to this topic, so all suggestion would be useful. There seems to be something different between my PCB and breadboard configuration, and I am struggling a bit to debug where it goes wrong.

Edit:

The code for this is simple:

 void setup() {
  // put your setup code here, to run once:
  //pinMode(10, OUTPUT);
  //pinMode(8, OUTPUT);
  pinMode(3, OUTPUT);
  pinMode(5, OUTPUT);
  pinMode(6, OUTPUT);
  pinMode(10, OUTPUT);
  pinMode(11, OUTPUT);

  //digitalWrite(8,HIGH);
  //digitalWrite(10,HIGH);
  digitalWrite(3, HIGH);
  digitalWrite(5, HIGH);
  digitalWrite(6, HIGH);
  digitalWrite(10, HIGH);
  digitalWrite(11, HIGH);

}

void loop() {
  // put your main code here, to run repeatedly:

}

For the schematics

The toplevel view; For now ignore the leds and the clocks. Not connected in the current version

The board you can find below.


texts:
I have a unique situation where I may want to place a Micro-USB connector on a PCB, but not on the board edge. Mechanically, it would make sense if I could place it towards the middle of the board.

The concern is that the male end of the Micro-USB cable requires additional clearance on the top and bottom, which seems to prohibit this kind of connection as the PCB would be in the way of the bottom clearance:

I can't use a Right Angle (R/A) connector due to other mechanical constraints.
I looked on Digikey and couldn't find anything that seems to fit.. Basically I want to take a regular Micro-USB SMT connector, and elevate it ~0.25" off the board.

One option I thought of is a breakout board like this:

Placed into a 0.100" female header on the board, like this (shown for representation, not the actual board):

I think this could get the job done, but I'd much rather do something integrated to keep things streamlined, clean, and not require an additional assembly step. Open to any suggestions or recommendations.


texts:
In many places I have seen that an AC termination scheme is recommended for high speed clock termination. What is the reason for choosing this scheme?
For AC termination, can a capacitor be connected to a voltage source or should it always be grounded?


texts: Optical sensor for picking up 15 mm² area at a distance of 1 cm and return RGB value (or similar estimate)

texts:
I need an optical sensor for picking up 15mm² area at a distance of 1 cm and return the RGB value or any similar estimate.

I am going to use a custom lens for this focus.

This is basically to read a strip on which a chemical reaction happened on a small surface area and get an estimate of color.

I am thinking of using TCS230 or TCS3200.

Please suggest any better sensor and anything about how I can get such a lens.

This whole thing is going to be packaged in a small cellphone sized device so I also have area constraints .


texts:
I have returned to school at 50 for HVAC/R and am currently in the first portions of the course, Basic Electricity.

The question given in the text is: How much power is consumed by a parallel 120V circuit that contains a 1000 ohm load and an 80 ohm load and draws 2.7A. The answer is not really what I am most interested in, it is the explanation of the process so I am able to arrive at the answer on my own. The text book is not explaining the task sufficiently for me.


texts: What is the effect of doubling the airgap in a flyback converter?

texts: If I understand correctly it would flatten the hysteresis curve. So it would allow to store more energy and it would also decrease the permeability of the core. Would it have another effect or will some type of compensation be needed in the system?


texts:
I'm trying to connect 36 analog voltage sensors to the 6 analog pins of an Arduino Uno and cannot figure out the simplest way to go about it, given that I need to be able to accurately read a voltage that stays within 2.6 and 3.6 volts.

This is the sensor, 10Pcs Voltage Tester Sensor Detection Module DC 0-25V for Arduino Robot Car USA

and they are measuriing 36 of these CALB 100 Ah CA Series Lithium Iron Phosphate Battery


texts:
I'm trying to design a load bank with a power source of 12V. I want to get a range of Amps in the output (from 1 Amp to 120 Amps, so that is 1 amp, 2 amps, 3 amps,…120amps) and I want it to be controlled by Arduino.

I already came up with the design, which is basically a combination of 8 MOSFETs and the resistors to get the needed current. By combining them, I can get up to 120 Amps.

My problem starts now. Since the power is coming from a battery, the voltage will fluctuate. Therefore, I won’t get the current I was looking for, thus the current will be lower or higher depending on the value of voltage.
These are the solutions I came up with:

Apply sort of voltage regulator. (I am not really sure about this, because I’ve been looking around and there are available in the market but they are not allow more than 1 amps).
Design a PID current controller. (I think this should be the best option, but a tricky one though).
I have been trying to do it with a PID, but I’ve spent two days trying to design it and to be honest, I’m quite lost. Could you shed some light if any of you think that the PID is the solution?

I’m looking for a maximum error of 0.5 amps.


texts: In pic18f45k80, the datasheet says one can read and write a byte (8bit) data in EEPROM. I need to write 3 bytes data at once and read it back at once because that 3 bytes data consists of two parameters of the lead acid battery which I have to measure. Are there any ways to do this, reading and writing a bulk of data in Pic Microcontroller? An example snippet will be more helpful.


texts: Is there a way to power a GPU only by external supply?

texts: Actually I don't think so, because I think different components of the GPU are powered by only one of the two sources.


texts: Sustained over-voltage protection for a 1 MHz digital logic line

texts:
I am working on a board which is user-insertable into a DIP socket. Incorrect insertion is always a concern, and in this specific case insertion "shifted-by-one-pin" is especially worrying.

What then happens is that a 3V3 digital logic output line, which normally goes from an FPGA to a TTL input in the socket, instead gets connected to 12V power supply. Once the power is on, this immediately fries the FPGA and renders the board useless.

Given the geometry of the situation, purely mechanical misalignment prevention is going to be difficult to say the least, making it even more important to have a protection circuit in place. Now, I looked into Zeners, TVS diodes, signal diodes in series with the signal line, etc, but couldn't really find a solution that would combine these three items:

Pass ~1 MHz digital signal reliably from the FPGA to the TTL input.
Have the reaction time short enough to prevent FPGA from getting damaged (EPM1270, so basically anything above 4V is unacceptable).
Be able to withstand sustained over-voltage for at least several seconds.

Any suggestions where to look next?

Update: I am choosing my answer, because it works for my case, but since it has its caveats, other responses may be better depending on circumstances.


texts:
I need to supply 10-15A at variable voltage without anything getting too hot. Is it good practice to use several MOSFETs to handle larger currents?

I am currently using an IRF9630 P-FET with an Rds_ON of 0.5-0.8 ohms, but will likely use something better for my finished device.

I am aware that FETs aren’t 100% identical, but I’ll check to make sure they output the same voltage down to two decimal points. A quartet handling 15A would each have a W_dissipate of 3, assuming a terrible Rds_ON of 0.8 ohms.

Cluebats?

Edit: Olin has schooled me, but I need more schooling. My FET absolutely must not fail closed, or some things will be destroyed. How do you guys protect hardware from this kind of malady?

Cluebats... my skull is thick.


texts:
I built a boost converter and I can't see on the oscilloscope the 12V in the output and the real frequency that I defined (70kHz.)

What should I do?

This is my circuit, and below that is what I see in the oscilloscope:


texts:
I recently downloaded a component's footprint and it comes with a peculiar solder paste pattern (see picture attached - solder paste is in gray). Until now I have just defined the solder paste to be the same size as the pad, but know I am wondering if this kind of pattern has a purpose, maybe for better thermal relief?

Should I use a full pad solder paste pattern, or there is any benefit in using something like this one?

Also, I have seen that some people put vias in the pad for thermal relief, but what kind of vias? Through hole vias to a bottom ground plane... blind vias to a inner ground plane? Is it really necessary?


texts: Cheap, reliable, low resolution, linear position sensor

texts:
The question

I am looking for an absolute linear position sensor that can span a distance of 40 cm with ~5 mm accuracy.  My primary concerns are reliability and cost at a production scale of ~10,000 units.  Ideally I can find a vendor that provides an off the shelf sensor but modifying an existing design and printing up circuit boards is not out of the question.  I need recommendations on which technology to be looking at (LVDT's, optical encoders, magnetic encoders, etc).

The search so far

I have heard that potentiometers and mechanical solutions in general are less reliable than contactless solutions like LVRTs and encoders.  Mostly I have focused the search on encoders because I am a bit more familiar with them.  Most encoders I find are accurate to within a micron and cost more than I am hoping to pay for them (example).  It seems to me like what I need is the insides of a cheap digital caliper just blown up a little (to 40 cm long) but I can't seem to find a vendor that builds and sells all the digital caliper innards.

Things I have already read:

Questions like this one and this one are similar to mine but both have different accuracy requirements and neither were asking about production at scale.  Answers like "buy an optical mouse and take it apart" worked for them but they don't for me.  I have also looked at comparisons of position sensing technology (example) but they always seem to focus on solutions with significantly higher resolution than I need.

Gory details in case they matter or your are curious

Mechanical constraints: hardware can't extend more than ~5 centimeters past the stroke length of the sensor.
Definition of reliability: At least 20-30k cycles before failure.
Sample Rate: shouldn't be an issue, as low as 10sps would be fine
Enviromental factors: A sheltered open air environment so temperature can swing ~0-100 degrees C and condensation can exist


texts: Why does my switch need to be wired in this fashion?

texts:
Today was my first foray into electronics since high school, in the form of some simple Raspberry Pi experiments. I managed to get a circuit working where a switch controlled an LED with a potentiometer to control the brightness of the LED.

However, I am confused by the wiring of the switch. Firstly, here's a photo of my amazing work:

NOTE: the black lead on the potentiometer is not connected to anything (hard to tell in the photo). Also, I realised afterwards that I could have just inserted the potentiometer into the breadboard rather than soldering wires to it. Noob mistake (one of many).

Here's an attempt at a schematic (also probably wrong because I don't know what I'm doing):

simulate this circuit – Schematic created using CircuitLab

As you can see, I used a PiFace, which comes with the four switches located at the left and towards the bottom of the photo. It is the wiring of this switch that befuddles me. Since each switch has two terminals, I was expecting one terminal to act as an input and the other as an output. That is, I just feed my circuit through those two terminals and job done. But that didn't work.

I managed to find this image online:

This is what prompted me to guess the configuration below, which works. However, I don't understand why it works. Nor do I understand why there are two terminals for each switch if only one seems to be used. I suspect the clue is embedded within the text in the above image:

  The four switches, numbered S1 to S4 are connected in parallel to the
  first four (0-3) inputs

However, I do not understand what this means. Perhaps a practical example of how I would use each terminal and an explanation of why the grounding is necessary would help my understanding.


texts: Current sensing relay that momentarily closes contact each time state changes

texts:
I have a 240V dust collector that I manually switch on and off using a one-button wireless remote. The dust collector is connected to several machines.
I'd like to use a current sensing relay to automatically turn on the dust collector when one of the machines starts and then off when it stops.
I see many inexpensive current sensor relays, including ones with variable trigger points and delay timers, but they all have the same basic output: NO or NC and Closed or Open when current flows. What I think I need is a momentary closed circuit whenever the state changes. With that I can hack the wireless transmitter to replace the switch that the button closes with my new circuit.
I know I can do this with an Arduino or Raspberry Pi, or I could skip the wireless altogether, but I'd like to know if there is an existing relay that does this or something simple I can add after a current sensing relay to translate each state change into a momentary pulse.


texts: how can I make a large transformer less loud?

texts:
I have a large 2600W 230V -> 28V transformer, and it makes a constant quite loud bzzzzzz sound while it works. Is there any way to make it more silent (other then buying an equivalent SMPS which I don't have money for now)?

I am looking for some quick and cheap ways to make it less loud. Wrapping the whole thing in a large towel might not be the best idea as it will probably prevent the transformer from cooling properly.

Why does it make that annoying sound anyway?


texts: What happens to copper pours that are 'too narrow'?

texts:
What happens to copper pours that are narrower than PCB manufacturer spec?

Let's say spec is 10/10 mils (trace/space) and the copper pour in between soic-08 is only 5mils because it can't be wider (soic-08 pad pitch - 2x 10mil space).

Should I 'take out' that copper pour or leave it there?

Does it get processed? Result?


texts: Why am I not able to simulate a circuit as it is given in a problem?

texts:
I'm currently in the process of working through some circuit analysis books on my own. Though it's easy enough to compare my answers to those given in the appendices, I figured that it would be worthwhile to learn how to simulate the problems in MultiSim as well.
However, I ran into trouble when trying to simulate the circuit shown below.

Utilizing the node-voltage method, I determined that the voltages at the nodes will be the following, with respect to the ground node:
Node A = 40 [V]
Node B = 172 [V]
Node C = -64 [V]

I'm sure that these answers are correct. The problem is that if I run the simulation as shown in the schematic, I don't get the voltages I expect with respect to ground at the three nodes. I figured out that V1 is the reason for this.
I can fix this problem by changing the voltage of V1 from 40 [V] to -40 [V], but I don't understand why this works.
In short, why do I need to change the value of V1 in order to get the expected results from the simulation (rather than just simulating the circuit as it is given in the problem)?
I'm sure that I'm overlooking something important here. Help would be greatly appreciated!


texts: Is this the full-bridge DC-DC converter topology? What's the benefits of iso/non-iso topology?

texts:
I found a power circuit in an schematics, which looks like a full-bridge topology.
Anyone familiar with such design?
I check the websites, but didn't see the same implementation.
The pink blocks are controllers and drivers, but I can't find its datasheet also...

BTW, I have another question.
What the benefit of isolation topology over non-isolated one?
Suppose I just want to provide core for CPU on motherboard, the input is rather 12V, or 48V (server), which topology will be more suitable for my design?
I've seen that for 12V, non-isolated design will be implemented, while isolated solution be used for 48V case. Is the input power which matters?

Thannks


texts: How do I avoid a high DC current flowing through mosfet in my SRSSTC tesla coil?

texts:
There are 6.48 amps flowing through the mosfet but only 12 mA through the capacitor, L2 would be my tesla coil primary.
How can I reduce the amount of components in my circuit and improve its performance? I need a high AC high frequency current flow through the tesla coil's primary.


texts: How much current is drawn by an 18,600 BTU A/C compressor during free run?

texts:
I recently got an old hermetic A/C compressor. I plan to use this as a vacuum pump mostly for some of my hobby projects. The specs on the label on the A/C said that it power draw is 2450 Watts, 11.5Amps.

Does it mean that the current draw is 11.5 Amps always or is it only while there is some load on the compressor like while it is compressing some refrigerant or gas? Also I noticed that the compressor isn't very loud while its outside compared to when it was inside the A/C it was quite loud.

Also I heard that the compressor oil gets acidic while exposed to air. Is it true?


texts: Best way to add PID to thermoform machine?

texts:
I'm inexperienced at electrical engineering. I'm attempting to add a PID controller to an inexpensive, small thermoforming machine. Here's a link to the machine.
https://www.amazon.com/Excellent-Quality-Forming-Machine-Equipmemt/dp/B0067FFW6E
I made a schematic of the internal circuitry of the machine. It's not a complex machine, there is no temperature control, there are 2 rocker switches (ON /OFF only)- one for the heater and one for the vacuum pump. The machine is rated at 600W, I'm running it on 120 V. The heater and the vacuum can operate independently or simultaneously.

The PID controller I am hoping to use is fairly common, the Inkbird ITC-106VH:
https://www.amazon.com/gp/product/B01N1ZUGUZ/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1
My hope is to wire the PID so the machine operates the same way it does now. I'll turn on the heater rocker switch, which will power the PID and the SRR. My hope is that I wire it so that this doesn't interfere with the vacuum switch / pump. I need the heater and vacuum to be able to operate independently with the PID inline.
Here is a schematic of the wiring I think will work.

Does this seem like the best way to approach this circuit? Is it even rational? Thanks very much for any insight or help.


texts:
In this question, I apply the current cycle law,
I find the current i1 to 25uA. I find the voltage on the dependent current source -2 volts. When I go through the formulas, there is no problem here.
but the voltage on the dependent current source is negative (-) obviously confused. I assume that the arrow of the current source is positive and the starting part is negative.
so is this dependent current source supplying current in the opposite direction of the picture because -2 volts are formed on the current source?


texts: How to find phase sequence in 3 phase system using micro controller without zero cross over?

texts:
I have 3 ADCs which are connected to 3 phases respectively. I have to find the phase sequence when it comes in picture...
I'm getting an ADC value for particular phase, but how can I find the sequence using microcontroller? The phases are directly connected with a resistor drop to micro controller.


texts:
In the circuit below the complex voltage \$u\$ should be calculated using Kirchoff's law. I know this law implies that sum of voltage should be zero. I'm trying to solve it like this but I am not sure if I aam doing correct steps:

UPDATE


texts: Controlling 12V 70A Motor(s) with Arduino MEGA (or NANO) and a 4-terminal automotive relay

texts:
Components I have:

Relay (rated at 12V, 70A, cannot find how much current is needed to saturate its coils) Schematic

Arduino MEGA and NANO

12V Powerwheels battery + AA battery packs

Motor: 00968-9015

Transistor:  Pn2222

Diode:  1N4007

Appropriate wire, terminals, crimper, etc

I need help wiring the setup in the title. I am trying to control a DC motor taken from a Powerwheels Jeep Wrangler through the pins of an Arduino. The motor draws 70A under normal load, and is brushed. I've been doing a lot of research online trying to understand how this would work, but I haven't found anything exactly like mine and do not quite understand how it should work. Namely, how do I connect the arduino, transistor, diode, and battery to the relay that I have? I should be fine with the code, like setting the pins to be HIGH, it's just the wiring that is troubling me. I also am not sure if I will be able to reverse the motors rotation with this (without an H-Bridge or expensive motor controller). Any help would be much appreciated, thanks for reading!

Here are some resources I have been looking at:

http://henrysbench.capnfatz.com/henrys-bench/arduino-output-devices/tip122-arduino-relay-tutorial/

https://www.element14.com/community/thread/38334/l/car-relays-to-use-in-projects?displayFullThread=true

http://www.bcae1.com/relays.htm

https://itp.nyu.edu/physcomp/labs/motors-and-transistors/using-a-transistor-to-control-high-current-loads-with-an-arduino/

Here is where I got the figure for the motor's current draw.

Here is the Jeep Wrangler toy


texts: DMA completion interrupt not working for slave STM32 SPI

texts:
I am using stm32f103 to transmit some data over SPI while stm32 acts as slave. I need to use DMA for sending data to the SPI but the corresponding interrupt handler is never called.

The initialization code comes in the following:

DMA_InitTypeDef DMA_InitStructure;
/* DMA configuration */
DMA_DeInit(SPI_SLAVE_DMA);
DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t) SPI_SLAVE_DR_Adress;
DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t) SPI_Buffer;
DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;
DMA_InitStructure.DMA_BufferSize = SPI_BufferSize;
DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord;
DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord;
DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;
DMA_InitStructure.DMA_Priority = DMA_Priority_VeryHigh;
DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
DMA_Init(SPI_SLAVE_DMA, &DMA_InitStructure);
/* Enable DMA Transfer Complete interrupt */
DMA_ITConfig(SPI_SLAVE_DMA, DMA_IT_TC, ENABLE);
/* Enable DMA */
DMA_Cmd(SPI_SLAVE_DMA, ENABLE);

/* SPI_SLAVE configuration */
SPI_InitTypeDef SPI_InitStructure;
SPI_InitStructure.SPI_Direction = SPI_Direction_1Line_Tx;
SPI_InitStructure.SPI_Mode = SPI_Mode_Slave;
SPI_InitStructure.SPI_DataSize = SPI_DataSize_16b;
SPI_InitStructure.SPI_CPOL = SPI_CPOL_Low;
SPI_InitStructure.SPI_CPHA = SPI_CPHA_2Edge;
SPI_InitStructure.SPI_NSS = SPI_NSS_Hard;
SPI_InitStructure.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_2;
SPI_InitStructure.SPI_FirstBit = SPI_FirstBit_MSB;
SPI_InitStructure.SPI_CRCPolynomial = 7;
SPI_Init(SPI_SLAVE, &SPI_InitStructure);

/* Enable SPI_SLAVE Tx request */
SPI_I2S_DMACmd(SPI_SLAVE, SPI_I2S_DMAReq_Tx, ENABLE);
/* Enable SPI_SLAVE */
SPI_Cmd(SPI_SLAVE, ENABLE);

When I use SPI interrupt handler, my system works. But using the code written above, interrupt handler of SPI_SLAVE_DMA channel is never called.


texts: Is the author wrong about this RC low pass filter circuit?

texts:
When reducing an RC low pass filter, the author of a text book makes the following statement: “Let us assume the application is such that, so that the voltage across RL is negligible.”

Is the book wrong when saying RL must be such that RL is much smaller than R ? Normally the filter is inserted before load but here RC filter is after RL. And why the value of RL being small relative to R matters? Im very confused, is the author wrong?

Here is the original book page:


texts:
Usually I recognize the first pin of an IC by observing the small circle and then comparing it with the layout in the datasheet, but in the OPA2365 there is no circle.

In the image, is the red arrow pointing to pin 1?


texts:
I need to design a device that can transmit an RF signal about 200 meters.  The data transferred is very simple.  One device simply has a button, that when pressed transmits a two-digit ID to the other unit.  There is no other data or voice transmission.

Because the product will be sold globally I'm leaning toward doing 2.4GHz, but I'm concerned about getting the 200 meter range.  This range is way outside of most 2.4GHz products.  I'm planning on using TI's CC2541 2.4GHz transceiver SoC along with their CC2592 range extender.  The CC2592 is supposed to extend the range by up to 7x.  BlueGiga sells a Bluetooth Low Energy "Long range" module with a claimed range of 450 meters.  So I think reaching 200 meters should be possible.

The other choice is a 868/915/920 MHz system, but that has its own complications, and I would prefer to use a single frequency 2.4 GHz system.  Also I'm not sure if 868/915/920 MHz will cover all countries.

So my question is what frequency would you suggest for an international product transmitting a simple ID up to 200 meters?

Thanks!


texts: Can CML differential signal lines be flipped to act as a NOT gate?

texts: If I want to invert a CML differential D-Flip Flop (Ex: hmc747lc3c) output before entering into a CML Counter(Ex: MC10EP016), is it as simple as flipping the signal lines before entering the counter? Or do I need to find an actual NOT gate? The reason I ask is because in LVDS logic flipping the signal lines acts as a NOT gate, but unlike LVDS CML is DC Biased.


texts: Why am I getting different flux densities?

texts:
I am trying to find the flux density at the top of the core. The current is known to be 2.5 A, the relative permeability of the core is known to be 800 H/m, and the flux is known to be 0.005 Wb.

When using the following equation: Btop = φ/Atop = 0.005/0.0075, I get Btop = 0.67 T.

However, when using the following equation: Btop = μNi/l = 800(4π)(10-7)(500)(2.5)/0.275, I get Btop = 4.57 T.

Is there a reason why I'm getting two different answers from the two equations?


texts: Which is the costliest step while designing BJT which makes it costlier against designing MOS?

texts: Steps like oxidation, doping, epitaxy, photo-lithography, and metallization etc. are used in the designing process.


texts: Proving that the transistor in this simple schematic is off

texts:
I'm trying to find the collector, base and emitter currents of the transistor in the following simple topology:

In order for the transistor to be on, the emitter needs to be at a higher potential than the base. Therefore, since Ue=0, Ub=-0.7. This implies that there is a higher voltage drop across the top 100Κ resistor(10.7 Volts vs 9.3) meaning that the current through the top 100K resistor is greater than that of the lower 100K resistor. Therefore, the math demands that the base current goes towards the base.

However, in pnp transistors the base current should flow away from the base, towards the left in this case. The equations here demand that it goes to the right. Is it possible? Or does this mean that the base current is zero?

Update: It is implied that |Vbe|=0.7 volts if the transistor is on. I'm trying to prove that the base current is zero. I assumed that the transistor is on and Vbe=0.7 as given. However, as mentioned above, this led to a base current flowing towards the base. Is this enough proof that Ib=0 and the transistor is off?


texts: Creating a coupled inductor with 2 discrete inductors?

texts:
I am working on a EL driver board using Maxim Integrated MAX14521 [1]. The application circuit of the evaluation board [2] uses GA3250 [3], which is designed specifically for the MAX14521. Now, this part is not available via Digikey. I can get them directly from the manufacturer, but I wonder if I can create an equivalent circuit using 2 inductors. I doubt I can, but I am asking here because I don't see why a chip would require a special discrete component!

[1] https://www.maximintegrated.com/en/products/power/MAX14521E.html

[2] https://datasheets.maximintegrated.com/en/ds/MAX14521EEVKIT.pdf

[3] http://www.coilcraft.com/pdfs/ga3250.pdf


texts: What do multiple emitters/collectors imply in a BJT schematics symbol?

texts: I sometimes come across with BJT symbols from which multiple lines come out of emitter or collector. Are such BJTs different kind of devices? What does it mean in solid-state level?


texts:
Recently, I have bought an oscilloscope with model Panasonic VP-5512A

Panasonic   VP-5512A    100 MHz 2CH+1/2+1/2 Dual Timebase

It is an analog oscilloscope.

Unfortunately, it does not come with cable and probes. Therefore, I should prepare probe by myself. and I have some doubts and it would be great if letting me know:

1- Is there difference between probes of analog one or digital one in sense of connection port to the oscilloscope (I mean their size for fitting into each other)?

2- Are probes of different oscilloscopes interchangeable?

3- Does calibration of scope to match any random probe solves mismatch between probe and oscilloscope capacity?

4- If the answer of using random probe is no, then how should I find probe for this specific oscilloscope?


texts:
edit2:  After calling customer service, the impedance is 350k.  Does this change anything?

I am totally clueless when it comes to circuitry,  but am trying to build a grid charger for my old hybrid car, using an online DIY write-up. This charges the battery at a constant current (350-600ma selected )  and the voltage is monitored as it rises from a low of ~120v absolute min to ~ 195 volt absolute max.  I want to add to the setup by monitoring this with a voltmeter display that measures 0-33v, so a logical way to do this would be to divide the voltage by 10.  It seems to be unsafe to just use resistors to achieve this, as I understand this will be dissipating some 30-40w of heat. What is a safe (and preferably efficient) way to do this?

I need to use this particular display because of its accuracy precision, as I only know to stop charging when the voltage stops rising, and the voltage change will be extremely slight (0.1v/hr) at the end of an extended charge.

edit: the intended display is a self powered Drok 5 digit DC.  I did not see any info on impedance. Am I correct in assuming a self powered voltmeter has no or negligible impedance?


texts:
This 0Ω resistor has a tolerance of ±1%.

Well it would only be +1% at best because you can't have a negative resistance* but still 1% of zero is still zero?

Shouldn't it be something like 0\$\Omega\$ + 0.001R?

*except in very special cases with certain devices but never over the full operating range.


texts: How to determine the gain of this op amp

texts:
I want to know how to determine the gain of the op amp signaled by an arrow, or get an ecuation described in terms of V1 that explains what’s going on in there. For the general problem, what I need to get is Vo expressed in V1 and V2.

Can somebody explain me what should I do?


texts:
I've designed a PCB which contains FT2232H for UART and SWD debugging for a microcontroller in the PCB (STM32L0). The FT2232H circuit looks like this:

and the power schematic that contains the USB micro connector looks like this:

When I connecting the board to the USB port in my PC all the 3 LEDs (D3, D4, D5) are light up, it means that the power rails are OK (VBUS - 5V, 3.3, 3V) but,
then I don't see any message from windows about new USB device detection. nothing happens. the system doesn't detect device insertion or removal. I have designed the FT2232H circuit above according to the datasheet(page 69 Bus-Powered Configuration), and this reference design

Do you have any suggestions on how to debug or to solve my problem?

Thank you very much!


texts: Converting appliance LEDs from constant current to constant voltage to allow for dimming

texts:
I'm trying to implement dimming control for the lights in my kitchen hob extractor. The lights are 4x LED spotlights which are each 3v 700mA (2.1W). They are currently wired in series to a 700mA 10W constant current LED driver.

The LED dimmer module I'm trying to use is taken from an Ikea TRÅDFRI LED driver. The PWM dimming module can easily be removed and powered with an external 12v source instead of the 24v supplied by the Ikea power supply. (see here).

The 700mA 10W CC power supply puts out about 12v with the LEDs connected in series. I tried wiring the dimmer module directly into the output of the CC power supply and connecting the LEDs to the output of the dimmer, however this did not work. I think constant voltage is the only way to go with this dimmer.

I was thinking about finding a 12v constant voltage LED driver to power the dimmer and the LEDs in series, however I'd need to use a 6+ watt resistor to limit current to the LEDs, which seems a little inefficient.

Could anyone suggest a better arrangement for achieving this LED dimming setup?


texts:
I have an old MasterView CS104 KVM switch sitting around, still in working condition but without support for USB peripherals. The ports it offers are:

VGA
PS/2 or DIN keyboard (the switch acts as a passive adapter on each port, thus connections can be mixed)
PS/2 mouse
Serial mouse

Switching is done electronically: press a button on the switch to cycle through the connected computers. This can also be done via certain key combinations on the connected keyboard, which means the keyboard signal definitely gets intercepted in the switch.

No translation is done between the two mouse port types; the manual states that if the computers use a mix of PS/2 and serial mice, a mouse of each type must be connected to the switch.

Now I am wondering if there is a way to “bolt on” USB support by adding passive homebrew adapters to the mouse ports (either the PS/2 or the serial ones). Will this particular type of KVM switch pass the data lines as well as the supply voltage in the intended manner? Would I need to use specific pins for specific signals?

Note: I am aware of active adapters that allow a PS/2 keyboard and mouse to be plugged into a USB port (with protocol conversion), as well as the inverse for at least some mice, but this is not my question.


texts: Conversion from 0V ~ 3.3V to -10V ~ + 10V

texts:
I need to do a voltage conversion to control a servomotor.

I need to convert a pwm signal that ranges from 0V to + 3.3V into an amplified signal that ranges from -10V to + 10V.

I thought about doing this with the use of an operational amplifier (as in the circuit below).

However, I can't get the correct Vout signal, just a voltage ranging from 0V to + 10V.

Is there another way to do this conversion?

simulate this circuit – Schematic created using CircuitLab


texts: Why would a circuit designer use parallel resistors?

texts:
I've been reviewing this reverse engineered schematic of a bmax6 style lipo charger.
To my understanding this circuit is used to dissipate excess charge in a cell when balance charging. The circuit uses a parallel resistor network as the current sink (R146, R152, R158, R164, R174, R180). It appears that all 6 resistors are 120Ω, and thus the network has a total resistance of 20Ω (if I did the math right).

Why would circuit/pcb designer chose this configuration over a single 20Ω resistor? What are the pros and cons to consider when doing this?


texts: How to reverse-engineer/find datasheet for an IC

texts:
I have an integrated circuit in the form as a DIN chip, and I have no clue what it is. I have tried searching for the markings on the chip, which are as follows:

Top:
HDJ2100-393
937GA1925463B2WW

Bottom:
TAIWAN
937GA1925463B2WW

It is a 40-pin chip.
I found two of these inside of an old CD mixer.
It is a Numark CD-MIX 1, and it was on what appeared to be the display system, as there were two near where the LCDs were. All I could find for a manual is the quickstart guide here, but I don't have the manual because it was basically in a giant bin of audio equipment.

Could someone tell me what this is or direct me on how to figure it out?


texts: Difference b/w Symmetric and Reciprocal Networks

texts:
A circuit exhibits symmetry when interchanging ports across a plane of symmetry results in no change in the impedance, admittance or scattering parameters of the circuit.

Reciprocity also means reversing the ports. Is this not an operation belonging to the group of symmetry operations?

I also read somewhere that the property of reciprocity is independent of symmetry. How so?

Thank you.


texts: Operative Definitions of Memory in Circuits

texts:
I've been studying Memristors (non-ideal) and some related circuits depending on pinched hysteresis of the IV for use in memory. I'm still puzzled by the lack of general framework for what constitutes memory and what features one needs to use a circuit as a memory volatile or non volatile.
It seems you certainly need some nonlinearity that is preserves history of input as in hysteresis (effectively non-locality of physical quantities such as Current or Voltage). For example recently I found out one of the criterion set by a well cited article is merely a mathematical constraint and has nothing to do with practical purposes or use for memory or engineering purposes of the circuit.
What is an operative definition of memory in circuits and what framework is used in defining such memory and protocols for reading and writing information at the circuit level?
Thanks in advance!


texts: How to find relationship between switching energy loss, temperature and current in an IGBT

texts:
I am calculating the losses of an inverter in Simulink. I used 'IGW25N120H3' IGBT for the inverter.

In the datasheet, they have mentioned switching energy losses for 2 different temperatures and from other graphs in datasheet, I got the information on collector current.

But now I need to find the relationship between switching energy loss, temperature and collector current, as my loss calculations are dependent on current and temperature.

How can I estimate the switching loss in an IGBT?


texts:
I have an AC indicator lamp which I have to add to a design and and here is the only information.

As you see the two terminals are tied on one side and the other two pins has no continuity with any other pins. I cannot verify the correct phase and neutral pins.

Is the upper two(silver like) neutral and the bottom gold like color is for line? What can be the reason there are four pins?

I measure the resistance infinity but shouldn't it be 230/3mA = 76kOhm? I measure between the golden and the silver pins.


texts: Why do laptops need larger transformers than mobile phones?

texts: I was wondering why a laptop power adapter is so huge. Most laptops that I have seen use a ~19V power supply. Using transformer equation, and considering 100 turns in the primary(just an assumption), and a 220V power supply, I calculated that there should be about 8 turns in the secondary. Using the same equation for a mobile phone charger(5V) and considering 100 turns in the primary, there should be about 3 turns in the secondary. So there shouldn't be much size difference between the transformer used in a cell phone charger and a laptop charger. So why are laptop charger adapters so big while a cell phone charger adapter is small?


texts:
I have a stereo amp (LA4597) and is currently wired in a standard stereo circuit. Recently, I read an updated answer from one of my questions stating that wiring the amp in bridged mode doubles the voltage swing on the speaker compared to the other. I have three questions:

What are voltage swings?
What are the benefits of a higher voltage swing on the speaker?
When should I switch to a bridged setup? When shouldn't I?


texts: Communication Theory - Determine efficiency of this protocol

texts:
My solution:

I have no idea if what I did is correct. I'm getting a bit confused differentiating between 500 frames/minute and the 4.8Gb/s, they both seem like transmission rates to me.
I'm assuming 4.8Gb/s is what the channel is capable of and 500 frames/minute is what the nodes can push out.

I should add that in my lecture notes, we have that "Efficiency = Throughput(in packets/sec)*Packet Transmission Time"

Anyways, does my answer seem correct?


texts: Measuring the change of angle on any plane

texts:
I've been trying to come up with a system to measure the change in angle on any plane. So basically I hold up my electronics board in some kind of angle, click on a button to reset the measurement, and then rotate the board over either it's local x, y or z axis, and then measure the rotated angle.

I've tried to do this with gyros, and use their angular velocity to calculate the angle which has moved. However due to the heavy noise in the gyros, the 'angle random walk' of the measurement is so intense that the measurement is almost unusable.

Given that the system is not attached to anything, what could I use best to accomplish this? (Or is there a way to make the gyros work for this application?)


texts: Why can't I have a PWM signal with 5V in the PCA9685 PWM driver?

texts:
I've got a BLDC motor which I can control with a PWM signal ranging from 0V to 5V. So I use the PCA9685 PWM driver to create a signal. The PCA9685 product page at Adafruit says this about the output voltages:

It is 5V compliant, which means you can control it from a 3.3V microcontroller and still safely drive up to 6V outputs

I provide 5V as input to the PCA9685. However, when I set the pulse length to the max of 4096 it outputs 3.3V on the signal line (as measured with a multimeter), instead of the 5V which I expect (and need).
The simple code I use with the Adafruit Python library:
import Adafruit_PCA9685
pwm = Adafruit_PCA9685.PCA9685()
pwm.set_pwm_freq(60)
pwm.set_pwm(0, 0, 4090)

I tried setting the pulsewidth to higher than 4096, but then the voltage I measure returns to 0V.
Is this a software thing or am I misinterpreting the quoted information on the product page? What am I missing here?


texts: How can I create a circuit to poer up pc each 24 hours?

texts:
I can't find idea or schematic for this in google, maybe certainly I search with the wrong terms, but I need plug on the pc to turn pc two times each 24 hours.

I found the circuit with 555 timer, but I can't found how use this 555 to  power up the rest of the circuit, in this case the pc!

I imagine will I need the battery, with the relay, maybe a some resistors, but I don't know how build this schematic/circuit to create this solution!

Thanks


texts:
I have bought 220V Wireless 433Mhz Relay  (AK-RK01S-220-A AC 220V)

I'm newbie in electronics and don't know how to wire it. I think L is line and N is Neutral. That I can find in electrical socket, but
1.What is in the middle 220V then?
2.And How should I wire my, like example, Lamp  on the right side with ON, NC and COM correctly


texts: Compensate potentiometer wiper resistance with negative resistance

texts: Is it possible to compensate a digital potentiometer's 75 ohm wiper resistance with a negative resistance amplifier?


texts: Why nMOS transistors use 'Head' current source and pMOS transistors use 'Tail' current source as their load?

texts:
Here I am taking an example of common source configuration(refer figure). Generally head current source is used as load with nMOS and tail cuurent source with pMOS. Why can't be this other way around? I wanted to know the reason behind this.

Thank you


texts: Are LQFP100 and PQFP100 the same footprint?

texts: Currently laying out a board. The data sheet footprint of the device is LQFP100 but the nearest I have in the layout package is PQFP100. Looking on the Net, they appear to be the same, but are they?


texts: Averaging matrix is not invertible in state space averaging

texts:
I am having a problem with state averaging method. The circuit is a SIDO converter as in the figure below. This circuit is just an example to show the problem.  So please don't care much about the structure and its efficiency.

The problem is that the averaing matrix is not invertible (singular or degenerate matrix).  For the detailed description of the problem and my calculation, please refer to the PDF file showing my work in detail.

Question:

1.What state variable is redundant in this case?    2.How to solve this problem  so I can get conversion gains?


texts: How to create a part in eagle for a TO220-7 with bent leads

texts: I can't seem to find such a reference within the library. How could I make  my own footprint? I'm using the latest version of eagle 6.4


texts:
I am performing a linear frequency sweep from 80 MHz to 120 MHz in 26.84 ms with the AD9910 direct digital synthesiser. I experience that the output amplitude is not constant (see Figure 1).

With my basic understanding about digital signal synthesis I though this has to do with the zeroth order hold of the DAC. However the system clock runs at 1 GHz and therewith 100 MHz is far away from half the sampling frequency. Further the enabled inverse-sinc filter of the AD9910 does not compensate for the response.

So my next idea was that there may be some problem with the digital ramp used to perform the linear chirp. To check this hypothesis I configured the DDS registers to output a constant output signal and incremented the frequency of the output signal manually using the main registers and no digital ramp. The results are presented in Figure 2. There is indeed a slight difference in shape, however the global characteristics stay in place.

So far I cannot explain the origins of the observed amplitude response. I would be interested if this corresponds to known DAC characteristics or if there may be other reasons?

On the measurement details:
The presented amplitude response was obtained by delaying the external trigger signal through a square wave signal generator. By adjusting the square wave width and having the oscilloscope trigger on the falling edge of the trigger signal I was able to capture multiple time windows and still resolve a fine enough signal to perform FFT. For every time window I extracted the frequency with the maximum power spectrum and the maximum amplitude of the signal (this is what you see in the plot).


texts: Identification of IC - Top marking number 3SDM

texts:
I could not find the part number from the IC top marking. The top marking shows 3SDM. I am looking for the manufacturing part number of this top marking.
Added circuit diagram for better understanding


texts: With what stage of the branch instruction does the IF stage executes if the branch is taken?

texts:
I am learning computer architecture and organization. I have the following doubt. Given below is a question along with its solution but I think that the solution is wrong.
Consider an instruction pipeline with five stages without any branch
prediction: Instruction Fetch (IF), Instruction Decode (ID), Operand Fetch
(OF), Execute (EX) and Operand Write (OW). The stage delays for IF, ID,
OF, EX and OW are 5 nsec, 7 nsec, 10 nsec, 8 nsec and 6 nsec, respectively.
There are intermediate storage buffers after each stage and the delay of
each buffer is 1 nsec. A program consisting of 12 instructions I1, I2, …, I12
is executed in the pipelined processor. Instruction I4 is the only branch
instruction and its branch target is I9. If the branch is taken during the
execution of this program, the time needed to complete the program is:
a. 132 nsec
b. 154 nsec
c. 176 nsec
d. 328 nsec
Correct answer is (b).
Minimum clock period = max{5,7,10,8,6} + 1 = 11
I1: IF ID EX ME WB
I2:    IF ID EX ME WB
I3:       IF ID EX ME WB
I4:          IF ID EX ME WB
I5:           .  .  .  .  .
I6:           .  .  .  .  .
I7:           .  .  .  .  .
I8:           .  .  .  .  .
I9:                   IF ID EX ME WB
I10:                     IF ID EX ME WB
I11:                        IF ID EX ME WB
I12:                           IF ID EX ME WB
Total 14 clock cycles are needed, i.e. 14 x 11 = 154 nsec

The solution was provided along with the question but I think it is wrong. In the solution the IF stage of I9 was executed at ME stage of I4 but I think it should execute with WB stage of I4.

Can someone please help me?
References:
Week 11: Assignment Solutions Question number 2.
Please refer here if the solution is not clear.


texts:
I have a Turnigy Rotomax 50cc engine and I am trying to rectify it. I don't know whether it has delta or a wye winding style but I suspect that it is delta(Left Picture).

This is what I have so far:

In my spice simulation I set the schematic up like this:

OUTPUT:

In my spice schematic I have 3 separate voltage sources set as sine waves with there negative terminals connected together. So I am trying to figure out how to hook up my rectifiers to an actual motor. My question is have I set it up right in my schematic? Do each of the motor phases attach to every other rectifier input?

Thanks for the help!

EDIT: Also the load is 50A nominal


texts:
I came across this device recently: The Loupedeck. Now, most reviews say that it's built very poorly and a simple Midi controller paired with Midi2LR will get the job done better and cheaper.

But, I've now got it in my head that it would be a fun project build my own Midi board. So, I'm looking at the right Arduino for the project. (This is my first foray into this type of thing, hence the very basic question...)

The Uno seems to be exactly what I need, except for the limitation of 6 analogue inputs. The Loupedeck has 57 buttons - and with possible expand-ability in mind...it seems like having the ability to support ~75 input devices would be good.

So, here's my conundrum - do I need to find an Arduino that can support that many analogue devices, or will using the digital inputs be okay? Is there a best practice for whether or not to use analogue vs. digital inputs?

Thanks,


texts:
Following this Linear Technology (Analog.com) Application Note AN47FA (1991), I found these kind of RF PCBs, among many others, very similar (fig.32 p.18 and Fig.F10 p.107).

(The images are in B&W because of some aestetics for the document.)

Putting aside that these are actually single copper plates, i.e. not PCBs strictly speaking, some of the criteria inferred from the document explanations are:

Shorten the output lead lengths,
Use a global ground plane,
Use a plate behind a connector as reflection plane.

But are these techniques actually standardized in more modern RF PCBs?

Which should be a more formal guideline for these techniques?

Are them somehow superseed by better components of PCB printing technology?

Or are these circuits build that way because in that time the PCBs were more expensive? I really doubt this last point, lab techniques for making PCBs were well known at that time, and the same document pointed the soldering made carelessly.

Thanks in advance,


texts: What does SWITCH pin do on a microSD connector?

texts:
I'm trying to connect a microSD card connector to my project (Molex 502774) and am slightly confused by the extra pins (nails?) provided. One of them is marked DETECT NAIL and the other one is SWITCH NAIL. As I understand the DETECT NAIL is for detecting when the card is inside - it is shorted to ground when card is inserted and should be connected to an input with a pull-up resistor.

But what is the SWITCH NAIL for? Does it have anything to do with card hot-swapping?


texts: What's destroying the MOSFET in my buck-boost converter?

texts:
I have currently wired up this inverting buck-boost converter circuit:

However, when driving the input of the TC4420 with a 62.5kHz square wave with a 40% duty cycle, the power supply overcurrent triggers and shuts off. After a few attempts, the MOSFET fails with the gate shorted to source and drain.

2 MOSFETS have already died this way. What is wrong with my circuit?


texts: What does the ripple frequency of a buck converter indicate and how does it affect the DC device connected to its output?

texts:
What is the desired ripple frequency for buck converters connected to computers, networking device as power supplies?

Can we judge the quality of power supply from ripple frequency? (buck converter or SMPS adapters)
What does the ripple frequency number mean?

Also can we measure ripple  using multimeter?


texts: Using ptr-10401 LiPo Charger on a 24.8 Whr battery

texts:
I just got in a LiPo charger (ptr-10401) and I want to use it to (yes I know slowly) charge a 24.8 Whr Lithium Polymer battery.
My question is pretty simple. Does this device contain the required logic to safely charge this battery? Meaning, if I were to plug it in and leave it would it be safe (I am not going to do this)
I was looking for laymen documentation or a tutorial but the only thing I could find was the VERY detailed documentation for the LiPo charger.
It's still to far beyond me (but I am trying, I just got Circuit Analysis for dummies)
Below are the parts and the links
I haven't hooked anything up. I want to make 100% sure this is a safe method for charging before I do this.
https://www.sparkfun.com/products/10401

http://www.ebay.com/itm/New-Internal-Battery-replacement-dajn-fit-for-iPad-1st-gen-/231044587897


texts: Control 5V relay board with Raspberry PI GPIO

texts:
I would like to control one of these 8-relay boards with my RPI GPIOs.
Please check the below schematic - it shows the parts involved for one of the 8 relays.
JD-VCC is connected to 5V of the RPI, because the board uses 5V relays, thats fine.

I'm unsure if I should use 3.3V or 5V for VCC (e.g. driving the optocoupler).
I found several tutorials in the internet, some of them tell 5V, some 3.3V.

Since some of the tutorials recommend using 5V for VCC I was asking myself, if that hurts the RPI  GPIO, because as far as I know, they are not 5V tolerant. However, measuring the voltage on the IN1 using my multimeter results in 3V. I guess this is due to the optocoupler diode forward voltage and also the forward voltage of the IN3 LED?

I'm not a professional EE, only a tinkerer and I would just like to have the above mentioned assumptions confirmed. Is it safe to use 5V for VCC?

Thanks!


texts: Can I charge a Li-ion cell with high voltage until reaching the nominal one?

texts: I have one 18650 cell which has a nominal voltage of 3.1 V in the specs. Right now, it is discharged and reads 2.8V. I was wondering if I can charge it directly with a panel solar (18V) until it reaches 3.2V and then disconnect it. A higher voltage difference means a higher current, right? My solar panel can deliver max 0.5 A in theory and the cell can be charged with 1C (2.6 A) so I am not worried that the current is too high, but what about the voltage difference? What can happen if I charge it with higher voltage?


texts: How come distilled water hasn't replaced transformer oil as a high voltage insulator?

texts:
I've noticed that distilled water has an extremely high dielectric straight (65-70 MV/m).

With that considered, how come it isn't used in the place of transformer oil for 10-20 kV applications where the structure might not need to last multiple decades?


texts: Cole-cole plot curve collapses when trying to alter the valule of horisontal axis

texts:
I am a beginner and trying to simulate a cole-cole plot of a simple parallel circuit having two R, one coil and a capacitor. Image attaced, LTspice version is XVII, pc is windows7.

I've read this Q-A;[Bode plot graph: Frequency vs. Angular frequency]
Bode plot graph: Frequency vs. Angular frequency
but things does not seem to be the same.

When I checked out the current for R1, the graph goes well. So altered this curve from R2 to 1V/I(R2) as shown in this image in the upper left.

Then altered the vertical values; 85dB to -85dB, with the tick 5db, and clicked Nyquist. This seems works goo.

But when I alter the horizontal value; o.oohms - 1Mohms, the curve collapses.

Any tips will be very much appreciated, thanks!

p.s.; Incidentally I tried turned off [Autoranging], but the results was the same...


texts:
I am using an MCP3561 ADC (Datasheet) to convert analog readings from a load cell to digital signals to be processed by an ATSAMD20G16 Microcontroller (Datasheet). I have configured the ADC to exhibit the following properties:
Prescaler: 2
Oversampling Rate: 98304
Gain:1
Continuous Conversion
This corresponds to a sampling interval of approximately 100ms given Equation 4.3 on page 27 of the ADC datasheet and an 8 MHz master clock from the MCU. My application continuously polls the IRQ register on the ADC to check the !DR_STATUS bit. When this bit indicates data is ready, the program reads the contents of the ADC's data register and transfers it to the MCU over SPI.
I have configured my main loop to print the value of the ADC read and the time interval between reads over the serial port. I observe a consistent 98-99ms interval between samples. Occasionally, however, the inter-sample interval is doubled. The occurrence of this doubling is unpredictable; sometimes there is a cluster of double intervals in rapid succession, other times it takes 20 or 30 seconds before a double interval occurs.
I edited my ADC read function to toggle a GPIO pin on the MCU every time it reads a sample so I could correlate the serial output to a signal on the oscilloscope. Then I stripped every piece of extraneous code from my main loop, including the serial print statements, with the hopes of isolating the cause of this anomoly. Unfortunately, the behavior persisted, and I am no closer to an answer.
Has anyone experienced this behavior (or anything similar) when using this IC? If so, were you able to determine the cause/develop a solution? Any insight would be appreciated!
Thanks in advance!


texts: Step down transformer voltage between neutral and ground

texts:
I just decided to test the voltages in my old tube guitar amp against the schematic. I live in Australia and it's a US amp, so I use a separate 240-110v step down transformer to run the amp. Upon testing the amp, I realised there was around 240v between the chassis of the amp (grounded) and the neutral line. I went back to the step down transformer and got the following readings

~110v between hot and neutral
~130v between hot and earth
~244v between neutral and earth

My wall plug is fine, with ~244v between hot and neutral, ~244v between hot and ground, and 0v between neutral and ground.

Does anyone know what's going on here? I've left the amp in bits and I'm not playing it until I've worked this out, as it seems I might end up playing with 240v on the guitar strings!
Thanks in advance


texts: LTspice - Measuring the resonant frequency

texts:
I would like to measure the resonant frequency automatically in LTspice, i.e. with the command ".meas" of the following waveform. Is it possible to do it by using the FFT plot? I have tried something, but it seems to me to be relatively complicated and I think there is a better way :)

Here is the schematic if it can help you.

Thank you very much and have a nice,


texts:
Please excuse me if my terminology is not accurate, or if I'm not asking the right question. I will explain my goal first.

I am building a circuit/device to drain a battery to a specific voltage. I am monitoring the voltage with an arduino and that is opening/closing a relay depending on the voltage.

I need to select a resistor to drain a 3.2v cell and draw 500 milliamps.

EDIT:

I am aware that my cells are 3.2v NOMINAL (LifePo4 26650 cells)

Also aware of safety concerns, etc. I'm draining very slowly and under supervision, and in a safe environment.


texts:
I start by saying that I'm not an electrical engineer, I've got a basic understanding of things from school and from work (I'm a long time computer programmer), but this is not much my field of competence.

I'm in the process of evaluating the feasibility of a device that I'd like to try to get designed and produced. But, even before paying a specialist for a feasibility study, I'd like to understand how much I'm far from reality.

The focus of the device (90% of its functionality) will be on writing data on an SSD disks connected via a SATA port, so I'll need some kind of chip capable to do that (or, in extrema ratio, to get one designed for it). Is this a realistic thing, can a SATA controller be just bought and used easily on a board, or even designed from scratch? (so to have just one chip that do everything)?


texts: Altium Designer - How to copy the parameters from one component in the SCH Library to another component

texts:
For context, I am using a component from Altium's Vault Explorer and I want to make a few edits to it. Thus I downloaded the component SCH, but the parameters did not copy over.

Is there an easy method to copy the parameters from a Vault Explorer component and paste them into a component in the SCH Library?


texts: precision current sink for battery discharge

texts:
I'm trying to build a precision computer-controlled current sink to discharge a battery. The maximum discharge current is to be 2mA (at the moment; I might go to larger currents later) and the battery voltage starts at around 1.5V.

I have built this circuit, in which the voltage source is provided by a DAC attached to a microcontroller. The op-amp kindly adjusts its output to control the current through the JFET so that the voltage from the DAC is matched by the voltage drop across the 500Ω sense resistor and everything works very well down to µA ranges. I'm logging the battery voltage and current through an ADC (not shown).

The problem is that if the battery is detached before the output of the DAC is set to zero then the op-amp forward biases the JFET junction and provides the current rather than the battery doing it. I could detect the battery being removed with the microcontroller then set the DAC output to zero but it doesn't seem to be a very elegant solution; can anyone suggest a more "circuitous" way of solving the problem?


texts:
I'm trying to design an EMI filter for a buck converter and I'm following steps on: AN-2162
Here is the question:
At page:6, for the Cf capacitor; two different capacitor values are calculated and highest value is taken(Cfa, Cfb). In my situation, calculations for Cfa results a negative cap. value.
Since there is no negative capacitance, should I neglect this result or take it as a positive value?
Here is the calculation:
Cin=2uF(0.000002F)
L=1mH(0.001H)
fs=30kHz
for Cfa:
0.000002 / ((0.000002) x (0.001) x (((2 x 3.14 x 30000)/10)^2)-1)
0.000002 / ((0.000002) x (0.001) x (355000000))-1
0.000002 / (0.71-1)
0.000002 / -0.29
= -6.89uF


texts: Protecting NPN transistor from negative base-emitter voltage?

texts:
I have a circuit that converts 5V RS-232 polarity signals (logical 0 = +5V, logical 1 = -5V) to 3.3V TTL polarity (logical 1 = 3.3V, logical 0 = 0V) using a BC548 transistor.

It forms a NOT gate so that when the RS-232 output is high, it pulls the output low and vice-versa.

For reference, the RS-232 device (a GPS receiver) is transmitting at 9600bps and is connected to a Raspberry Pi's UART.

My circuit looks like this:

However, this configuration results in the transistor seeing a voltage of -5V across the base-emitter junction due to the negative voltage of the RS-232 input. The BC548 has a maximum Vbe of -6V, but I'd like to protect the transistor by minimizing any negative voltages across the base-emitter junction.

After some searching I came across a post on the Raspberry Pi forums that suggests the following circuit to protect the transistor from negative voltage:

I've constructed the circuit and it seems to be successful: the lowest Vbe voltage is around -0.5V. My digital multimeter only updates about 5 times per second and I don't have an oscilloscope to see things more clearly, but it previously showed the lowest Vbe voltage at around -5V.

My questions are this:

Why is the diode placed where it is? If I interpret things correctly, it means that the lowest Vbe would be the same as the diode's forward drop and that there would be a current flow from ground through the resistor R1 into the negative voltage RS-232 pin. Would it not make more sense to place the diode between the RS-232 input and R1, or between R1 and the transistor Q1, so as to block any current flow into the pin?
The schematic says to use a 1N4148 high-speed diode, which I have used. Is there any disadvantage to using a 1N4001 instead of a 1N4148? 9600bps means each bit is about 100us long and the 1N4001 has a typical reverse recovery time of 2us. The 1N4148 has a typical reverse recovery time of 4ns -- clearly the 1N4148 is faster at switching but does it really make a difference in this context?


texts: Replacing 10uF tantalum capacitors with X7R in ADM2587E circuit

texts:
I'm working on some device with isolated RS485 based on ADM2587E transceiver with integrated high frequency isolated DC/DC converter.
This IC is a bit tricky if you need low EMI, because DC/DC converter makes high frequency noise.
My previous design was based of this evaluation board:
UG-916: 2-Layer EN55022 Class A Radiated Emissions Compliant Evaluation Board for the
ADM2582E/ADM2587E 2.5 kV rms Signal and Power Isolated RS-485 Transceivers
with ±15 kV ESD Protection
I have used same components and device passed EMC tests.
Since tantalum capacitors are "very bad" (conflict material), like many others I want to get rid of them.
Can I just replace tantalum caps (C2, C10) with good quality X7R and expect similar (maybe even better) results in EMI emission?
I know that X7R MLCC has waaay lower ESR and I guess that these tantalum caps on eval board are tank capacitors (not important at high frequency range).


texts: Solving the second-order differential equation for an RLC circuit using Laplace Transform

texts:
I'm trying to solve this second order differential equation for a RLC series circuit using Laplace Transform. The Laplace transform of the equation is as follows:

$$I(s) = \frac{E}{s^2+ \frac{R}{L}s + \frac{1}{LC}}$$

I'm having trouble trying to bring it back to the time domain. Should I be using partial fractions with quadratic factors or there a easier method to go abut this? And is the damping factor to be considered? If it is, how do I go about dealing with it?


texts:
I'm trying to understand how to talk to ESP8266, but I'm very confused. I don't understand how to connect ESP8266 to serial, so I can send it commands from terminal, as far as I understood I need special hardware to do this which I don't have.

I have raspberry Pi and want to use it's GPIO pins to send the 'AT+GMR' command and read the response from the ESP8266.

I want to do this at low level, but I don't know what to look for, because I don't understand the process.

If I set one GPIO as output and connect it to ESP8266 RX and other GPIO as input and connect it to ESP8266 TX, what's next? I would simply write my command byte by byte and new line at the end and ESP8266 should give out singnal from TX to GPIO input? There is no 'protocol' in between or some kind of timing? Thanks


texts: Importance of removing ripples in output of dc-dc converter

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I heard from somewhere that for some power supplies, it is important that there be no ripple and 'dips' in the output of a constant voltage output dc-dc converter. The specific cases are:

1.) When dynamic loading or hot swap testing, basically transient conditions it is not desirable for the output to have small negative dips or some oscillations even though they will eventually regulate at a fix value at steady-state.

2.) When the power supply is turned on, the output voltage must be monotonically increasing, if there is an upward spike which is small that is okay as long as there is no downward spike.

I heard that it depends on the load but is this really that important? Are there examples of load you could give which are really sensitive to these kinds of specs?

Also, I was wondering what if, if you apply a step increase in load, the output voltage of 5V dropped a little bit let's say 0.05V, becoming 4.95V and stayed there but it did not oscillate and it regulated there. Would that be better than if the step increase in load caused a downward dip of 0.05 and possible oscillation but in the end after some time to reduce the oscillation it regulated to 5V and not 4.95V. Which is better?


texts: What is the sensor name and use and circuit diagram for Current TV will be used based on Body parts movement?

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I want to know more about the Sensor which are used nowadays in the TV and Laptops we can access the functionality by moving our body parts. also used in Game play in Playstations, Laptops to change volume, play music etc...

How can I play with Camera and Digital Image.
Can I create my own sensor technology like when I Up my hand automatic change the song from my music player?

Is it possible?

any SDK is available?


texts: Rising edge detector negative pulse emitter - how to prevent firing at power up?

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The point of this circuit is to allow rising edges to send a negative pulse to a 555 timer. C1's purpose is to allow rising edges to trigger a positive pulse which in turn connects output to ground.

I ran a time domain simulation from 0 - 1.2 seconds with .001 interval. I sweep R1 from 1k to 100k in 33k increments. The bottom blue line is the signal from the square wave generator. The circuit passes rising edges as negative pulses as I would expect to "out" but at the startup  a negative pulse is initially sent out as C1 charges. Is there a circuit that can prevent the initial firing to the timer?

simulate this circuit – Schematic created using CircuitLab