texts:
I have a circuit in which there is a mcu lpc1768 and a gsm module sim800l.

For power I use DC/DC converter and made a 4.2v using lm2576 for sim800l. Used that voltage, I made a 3.3v using ams1117 and powered mcu.

My problem is,sometimes not always,mcu keeps resetting for seconds. The time is when sim800l wants to find a network or send data.

I tried to capture signal on reset pin and 3.3 using osciloscope when reset happens.

Here is what I could capture

And here is one of the pulses with t/d on 2.5 ms

Here is some information may help

3.3 node doesn't have this noise
3.3 node is actually 3v becuase of drop out caused by linear ams regulator
reset circuit has 100nf cap connected to ground and 10k ohm res connected to 3.3 node
there is a 2200uf cap on 4.2 v beside sim800l
sim800l doesn't reset and find its network

Does anyone have any idea what may the problem be?
Let me know if you need more info about my circuit

More Info

Here is my board power scheme

and here is reset and 3.3 node together !

In fact I was wrong that those pulse are only on reset pin . They are on 3.3 node too. but they drop more on reset pins

More Info After More experiment

The problem is completely related to antenna! when I close it to my micro it starts to reset and when I close it to my battery wires, my protection circuit shut down the power!!it all started when we wanted to place the board into the case!

Do you have any suggestion how I can clean my circuit from this problem?

here is my reset layout as @Sunnyskyguy EE75 told that it may happen because reset loop is too large and itself is antenna


texts: Controller of BLDC internal vs external rotor

texts:
The 3-phase permanent magnet BLDC motors come in two types, internal rotor and external rotor. Mostly the external rotor types are called Hub motors as they are used in electric bikes. Both types of motors use Hall sensors inside them for position sensing and commutation of currents.
I wonder if the controller of these two types of motors are same or not? Let us say I have a controller for BLDC internal rotor type motor. Will it be possible to use the same controller with a BLDC external rotor type motor? Let us say all other specs of both motors are matching.


texts: TI Photodiode Trans impedance amplifier Circuit?

texts:
I am designing a Photodiode(Vishay/ current of 15uA) circuit amplifier (TI ) in SIMetrix.
frequency of Photodiode is 1MHz. I choose an Amplifier from TI as OPA355_Q1(spice model imported from TI) and I used exactly their application circuit with the model of photodiode as you can see on the pic below;

the response I get is as following:

I should have gotten an amplification and no negative value as well. but I can`t see why. I have tried with another OP (OPA380) even with less GBP and it show better result. I doubt the model spice of OPA355 failed but not certain. how can I check that my spice model is working and tthen do you think my circuit is correct?


texts: SMPS load frequency to switching frequency

texts: If the frequency of the load exceeds the SMPS switching frequency, what are the results?


texts: What is the physical significance of beta and alpha in BJT?

texts:
I have read in the book that beta is the ratio of collector current to the base current in common emitter configuration and alpha is the ratio of collector current to emitter current to common base configuration.
Also, I know that alpha and beta are the current gains in common emitter and common base configurations.
My questions are:
What does both the terms signify actually?
Why are we calculating these current gains?
And Why is there a range of beta for a particular transistor? What does minimum and maximum values of beta mean?
How much does these alpha and beta affects our Early Effect?


texts: How to Prevent continuous switching fluctuation?

texts:
I am designing a digital stabilizer ,I am using ADC feature of Micro controller to sense incoming  voltage and processing output through an AUTO Transformer .The code is like

if(63<Voltage_INT && Voltage_INT<78 )
  {
  Relay1=0;
  Relay2=0;
  Relay3=0;
  Relay4=1;
  }
  else if (78<Voltage_INT && Voltage_INT<96)
  {
  Relay1=1;
  Relay2=0;
  Relay3=0;
  Relay4=0;
  }
  else if (96<Voltage_INT && Voltage_INT<120)
  {
  Relay1=1;
  Relay3=0;
  Relay2=0;
  Relay4=1;
  }
  else if (120<Voltage_INT && Voltage_INT<150)
  {
  Relay1=1;
  Relay3=0;
  Relay2=1;
  Relay4=0;
  }
  else if (150<Voltage_INT && Voltage_INT<188)
  {
  Relay1=1;
  Relay3=0;
  Relay2=1;
  Relay4=1;
  }
  else if (188<Voltage_INT && Voltage_INT<224)
  {
  Relay1=1;
  Relay3=1;
  Relay2=1;
  Relay4=0;
  }
  else if (224<Voltage_INT && Voltage_INT<300)
  {
  Relay1=1;
  Relay3=1;
  Relay2=1;
  Relay4=1;
  }
  else if (Voltage_INT && Voltage_INT<63)
  {
  Relay1=0;
  Relay3=0;
  Relay2=0;
  Relay4=0;
  }

However if the voltage continuously fluctuate between some value say 95 & 97 ,The relays will switch continuously resulting in decreased life. How to tackle this situation if i wish to switch only if a difference of 5 volt is detected   ?


texts:
I want to buy a LM4558N ,which is unavailable in the local store.

I found  similar ones online but not sure if they are the same ones i need.

1)Manufacturer:     TEXAS INSTRUMENTS

Man. Part No.:  RC4558P

2)Part No: MC4558CN

FOC Code: 1467662

Manufacturer: STMICROELECTRONICS

3)Manufacturer:  TEXAS INSTRUMENTS

Man. Part No.:  RC4558IP

Are this the same ones with different names or completely different?


texts:
Capacitive touchscreens are designed to react to the capacitance of a human body. To my understanding the touchscreen is measuring local distortions of the electric field.

Is there a way to influence the electric field of the touchscreen from a greater distance such as a centimeter above the screen?

What I am thinking is that creating an electrostatic charge might perhaps help, for example similar to the way an ionizer works. Unfortunately I lack the electrical knowledge to understand the implications of 'the other half of the capacitor' which is needed to excite the touchscreen.

The goal is to create a 'hover stylus' similar to the wacom digitizer (which of course works differently based on electromagnetic resonance). The stylus does not need to be practical yet, just trying to understand whether any device would excite the touchscreen from a small distance, it could contain a battery, Tesla coil, anyone?


texts: How to choose heatsink for power devices (transistor, LED, regulator)?

texts:
In many projects I need to choose small, but big enough heatsink for transistor or other power devices (LED, amplifiers, voltage regulators).

I know that thermal resistance of many devices is known (from datasheet), but almost all heatsinks available on the market where I live have no datasheets.

My primitive (?) method for choosing heatsinks is:

Put device on "probably big enough heatsink" (use thermally conductive paste, insulation etc. if needed)
Put device with heatsink in conditions where it's supposed to work (casing, ambient temperature etc)
Turn on device (transistor, LED) with 20% power
Wait some time (30s or more for bigger heatsinks or casings with big thermal capacity)
Measure heatsink temperature
Increase power by 20% or more if temperature is low and repeat step 3

I'm observing maximum heatsink temperature, I'm changing heatsinks and when I think some heatsink is probably good enough - I'm estimating junction temperature from power applied to device and heatsink temperature (close to device).

This method was good enough for me until now - I need to build something really small and I need smallest possible heatsink.

I can protect device (measure heatsink temperature and turn device off when temperature is too high).

Is there any better method to choose heatsink?

Edit:

Im using thermocouple and multimeter or homemade thermometer with LM35 sensor glued to small flat copper heatsink, insulated thermally from air on "air side" and covered with some thermal grease on measured radiator side.


texts: How to explain the peak frequency and resistance relationship in this op amp circuit?

texts:
I was studying thid tutorial by Simon Bramble.
I changed the original circuit a little bit and this is the subject of our discussion:

As you see, R1, R2 and R3 are all 1kOhm.
When I run an AC analysis, this is db/Hz curve:

The peak of the solid green line is exactly at 1KHz.
I will name this frequency where the solid green line peaks as "peak frequency."
Now, when I change R (R=R1=R2=R3) from 1k to some other value, this relationship emerges:

To be more verbose:

When R = 1k: same curve but shifted horizontally to peak frequency = 1k
When R = 10k: same curve but shifted horizontally to peak frequency = 100
When R = 100: same curve but shifted horizontally to peak frequency = 10k

So we observe this formula $$R \cdot f = 10^6$$
This holds for arbitrary R and f values as well: like R = 500, peak frequency = 2k
I do not know how this formula emerges. Could you explain me (preferable ELI5, but any clue/tip is appreciated too) the reason behind this observation?
Extra for Andy aka:
When I remove R3 from the circuit, behavior changes radically:

Extra related to Bimpelrekkie's comment:
He was apparently right about RC product affecting the frequency. What I have observed when changing C1 and C2 is in line with his comment. Here it is for record: (in the circuit with R3)

When C1=112nF & C2 = 224nF: same curve but peak frequency = 1kHz
When C1=224nF & C2 = 448nF: same curve but peak frequency = 500Hz
When C1=56n & C2 = 112n: same curve but peak frequency = 2kHz

These observations and Bimpelrekkie's comment may be restated here:
$$f \propto \frac{1}{RC}$$
(This only holds when C2 = 2*C1, if I change their ratio, the curve changes both amplitude and frequency so it becomes weirder.)


texts: Voltage hold up time in power supply design for desktop form factor

texts: While reading this document on power supply design for desktop platform ,I came across the specific hold-up time of minimum of 16ms in page 25 (See section 3.2.9 and table 20). Why is this adherance to 16ms important? Is it because that is the maximum time that UPS takes to power on in case of a power failure?I assumed that it takes exactly one cycle(60Hz frequency operation in case of 16ms) for UPS to power-on.Is my assumption correct?


texts: Changing out driver on sequential switchback DRL LED strip

texts:
I recently purchased this sequential DRL LED kit and tested it on the turn signal in my car. Unfortunately the frequencies don't line up so I was going to try to replace the driver so that I can still use the kit.

The chip on the LED boards is an INK1003 IC Driver

I see the front of the controller says "Output: CV10.4v". Does that mean the existing driver is a constant voltage driver? And I don't need to worry about constant current?

Unfortunately the controller has been filled with some sort of rubber so I can't actually see the components that are in there. Here are some photos of the existing controller:

And my second question is: do I have enough information to know how to trigger the amber sequential lights? Or would I need to see the inside of the driver to know how to do that?

Closeup of the lights here:

Thanks for any help!


texts: Do smaller transistors improve computational efficiency because they decrease the duration of signal transfer?

texts:
There has been a massive improvement of computational power of computers per $ over time. As far as I understand, this has been driven almost completely by the massive  increase in transistors per unit area.

What drives the fact that cost/compute goes down because transistors/millimeter goes up?

By compute I mean "operations per second", e.g. flops.

Note: I am ignoring the fact that smaller computers are intrinisically desirable, e.g. because it means you can have a computer in your phone. I am just asking about the cost per compute, so think e.g. in the context of a cloud computer, where size doesn't intrinsically matter to a consumer.

Here are some of the possible channels I can think of:

less surface area per transistor means less raw material cost per transistor.
less surface area per transistor means less signal travel time between transistors, so more compute per transistor.
smaller transistor size means less heat production per operation, so less energy cost in $.

What is the relative importance of these factors? Are there other important factors?


texts:
I was going through some of the questions in my textbook and I got stucked up here. Kindly help me with this

The Binary number 11 represents __

   1) -3 in sign magnitude and -1 in 2's complement
   2) 7 in sign magnitude and -1 in 2's complement
   3) -3 in sign magnitude and -3 in 2's complement
   4) 7 in sign magnitude and -3 in 2's complement

The answer was 'c'. But I am unable to figure out the reason why and I cant even trust it because I am unable to judge the answer. Please help me with these. Thanks


texts: How to get frequency response from LTSpice?

texts:
I am simulating the Common source amplifier circuit with current mirror.
I wanted to see the frequency reponse of this circuit.
And I got the constant value as you see the upper graph.

I have finally noitced if I change the value the parastic properties at Input Voltage Source, It shows the curve similar as I expected.
I want to ask you I'm on a right way to do AC simulation, And How should I set the parasitic properties.
Thank you.


texts: Differential amplifier inaccuracy resistors exercise to calculate CMRR

texts:
The common mode gain for a differential amplifier in the general case is:
$${V_o \over V_c }={ R_1R_4-R_2R_3 \over R_1(R_3 + R_4) }\tag{1}$$

simulate this circuit – Schematic created using CircuitLab
Suppose the resistances have relative inaccuracy of \$\,\varepsilon_i(i=1\,\text{to 4})\$ so  \$R_i=R_i^*(\varepsilon+1)\$ where \$R_i^*\$ is the nominal value of \$R_i\$.
Also suppose that \$\varepsilon_i\lt\lt1\$ and,
$$\tag{2}R_1^* = R_3^*\,\text{and}\,R_2^*=R_4^*\qquad\text{(condition for differential amplifier)}$$
Then,
$$\tag{3}A_c={ R_1R_4-R_2R_3 \over R_1(R_3 + R_4) }\approx{R_2^* \over R_1^*+R_2^*}(\varepsilon_1+\varepsilon_4-\varepsilon_2-\varepsilon_3)$$
But I can't find this value algebraically.
This is important because the worst case CMRR is:
$$\tag{4}CMRR={A_d \over A_c}={1+R_2/R_1\over\mid\varepsilon_1\mid+\mid\varepsilon_2\mid+\mid\varepsilon_3\mid+\mid\varepsilon_4\mid}.$$


texts: AVR-GCC: Ports Undeclared when compiling

texts:
My Setup

I'm running Ubuntu 12.10, and I want to be able to use gcc and avrdude to compile and program my ATmega328.

I followed this Ladyada tutorial: Ladyada AVR Tutorial

Everything installed perfectly, no errors or warnings. I have not installed avrdude yet, but that is beside the point.

I use the command:

  avr-gcc -O0 -c blink_1MHz.c -o main.o

However, I get one warning, and many errors:

warning "device type not defined"

error: 'PORTC' undeclared (first use in this function)

The error above repeats itself for each Port and each Data Direction Register used in the code.

blink_1MHz.c is just some simple code I'm using to test my setup. It has worked on my Windows setup through AVR Studio 6.

I've tried Google, but the only real suggestion I got was to import the libraries:

#include <avr/io.h>
#include <stdlib.h>
#include <stdint.h>

Unfortunately, still nothing. I've been playing around with this for a while and I'm simply stumped. I saw suggestions that avr-libc isn't installed, but I have installed avr-libc. I would think that if I didn't have it installed, I would be seeing complaints about the libraries not existing.

Question

Could an enlightened individual suggest what may be the cause of these errors? Thanks.

EDIT

Amoch pointed out that I needed to check out avr/io.h; there you will see that you need to define the processor with the -mmcu flag. In my case, I have an ATmega328, so my command looked like:

  avr-gcc -O0 -c blink_1MHz.c -mmcu=atmega328 -o main.o


texts:
I am currently working on a project that uses a 9.8V 1000mAh battery to power a solenoid, and as I understand it (please correct me if I got this wrong.) a battery capable of delivering 1000mAh is also capable of delivering 1Ah, or 2A for 1/2 hour, 4A for 1/4 hour, etc.

So, assuming I got the above correct, I need to know how to limit the battery output current to 1.0A (My circuit would get really hot otherwise.)


texts:
I need to power my Sure JAB 3 250 amplifier from two 12V lead batteries in series, but the recommended maximum of the  amplifier is 26V and the charging voltage of the batteries will be 28.8V.

What is a simple and effective way to make this voltage drop, to ensure not exceeding the max voltage of the amplifier?

I thought about using diodes in series or a step-down circuit for the voltage drop, but what is best practice?

The amplifier component is a TPS3116, with an onboard ADAU1701 DSP.
TPa3116

The specific board model is Sure JAB3-250.
Its absolute maximum rating is of a TPA3116 is 30V, but recommended at 26V.

Tpa3116 datasheet

Sure JAB 3 product page


texts: Building an electrically controlled spring based catapult

texts:
A spring based catapult is at rest vertically. It gets pulled back to a horizontal position to arm, which activates a self-ball loader. On firing, it springs forward and launches ball.

The arming mechanism will be motor based but the issue I can't get past is the motor on the launch portion. My ideas include:

Bike chain and gearing.
Some sort of clutch on motor that releases on launch.
Some sort of indexed cog off the motor that pushes the catapult to the horizontal but at that point the catapult releases back forward and the cog spins around again to pick up.

I've considered stepper motors but I'd like to keep it as simple as possible.

Further Details -

The spring in question is actually a car engine belt tensioner. So we are talking roughly maybe 30 foot lbs to compress. It is bolted to a 3 ton jack stand which is bolted to a frame.

The frame right now is roughly 30 in long, the catapult arm length is still in question due to distance requirements of projectile.

I am considering making the arm length adjustable.

The ball feed mechanism is basically PVC with spring gate that gets compressed when arm is pulled down.

Projectiles are baseballs, softballs. snowballs etc....

I am currently stuck on finding the right motor. So far I've ripped apart a belt sander and an Oreck vacuum looking for answers, with no luck. I am also considering winch methodology or possibly chain hoist theory. Thanks for the responses.


texts: Architectures for High Throughput Data acquisition with embedded systems

texts:
Goal: to acquire a high-throughput ADC-generated data flow (1 Msample/s @ 16bits)  into a System-on-Chip processor. Purpose: real-time data visualization and some (minor) processing in real-time

What are the pros and cons of the various architectures to achieve the goal.

Architecture 1

A Dual Port RAM, taking data from an FPGA which glues the SPI output of the ADCs and the port 1 of the RAM. The SoC IC is connected to this RAM on port 2 using an external memory bus and sees the sampled data in its own memory space. The processor is 100% free from managing the ADC. The sample data is visible in a double buffering scheme from Soc end with interrupts informing the SoC when the buffers are full.

Architecture 2

As in Architecture 1, making the dual port RAM visible on a PCIe bus as an endpoint device (as opposed to using the External Memory Bus which we have seen in several SoCs).

Architecture 3

Use an Soc with embedded SPI controllers and DMA. Program the DMA to be triggered by the End-of-Conversion signal of the ADCs and to move data from the SPI FIFO to memory.

Architecture 4

Use a dual or quad-core processor and devote one core to control the SPI interface with the ADC and poll a GPIO port to detect end-of-conversion.In fact, this solutions implements by software DMA-like functionality.

Architecture 5
Your solution?


texts: Why do cables typically have copper center core when current flows around the edge?

texts:
Given this post, showing a huge 4.4" wide cable:  Original reddit post

Also a Electric Engineering StackExchange question: Electrical StackExchange question

And somewhat knowing that current mostly flows on the outside rim of the inner copper core surrounded by the white XLPE, I'm assuming is due to magnetic forces.

Question is, why is it still necessary to have the very center core be copper as well, instead of filling with the cheap plastic material similar to the surround, like XLPE or something similar, and saving the cost of copper, or does that create its own problems?  (Let's assume the center core material would be 100% EM free)


texts:
Is it safe to bring a arduino digital input pin to high on a 3.3v input..from the 3.3v output of the arduino pin?

Because, I need to reset a 3.3v device on one end..and get the arduino to know about the reset too..but I am too lazy to involve transistors in my design..can i just feed that 3.3v to the arduino digital input too?

It will be just under a second..not persistant..a button tap


texts: How do I buffer a high Frequency clock on a Spartan 6?

texts:
I am trying to create a high speed clock on my Spartan 6 Atlys Board. The onboard clonck is 100MHz. I am trying to use an on chip PLL to get a faster clock. I am using a the clocking wizard IP to generate a higher speed clock.

Things work fine as long as my clock frequencies are below 400MHz. If I try to run the output clocks any faster, I see the warning -

  "CLK_OUT1 frequency requires that this output clock must drive a BUFFPLL"

The datasheet of the clocking wizard states that

  If a clock output requires special buffers like BUFPLL which the wizard does
  not generate in the design, alert messages are flagged to the user. Feedback for the
  primitive can be user-controlled or left to the wizard to automatically connect. If automatic
  feedback is selected, the feedback path is matched to timing for CLK_OUT1.

The Spartan 6 clocking guide mentions BUFPLL as a primitive. I have never done any such designs. How do I proceed. How do I create a BUFPLL in my design? Is this simply beyond the capability of a Spartan 6 or my board?


texts:
I'm kind of confused above the stability of feedback amplifiers.
Here's what I know

\$A_f=\frac{A}{I+A\cdot\beta}\$
\$T(j\omega)=A(j\omega)\beta(j\omega)\$
\$A_f(j\omega)=\frac{A(j\omega)}{I+T(j\omega)}\$

In the notes, it says that

If \$|T(j\omega)| < 1\$, then \$|A_f(j\omega)| > |A(j\omega)|\$

I don't understand how that's true. I tried deriving it but didn't get anywhere

\$|A_f(j\omega)| = |A(j\omega)| - |I+T(j\omega)|\$


texts:
I have a DC motor with a torque constant of 1.05 mNm/A. How do I calculate back emf constant from torque constant (mNm/A)?

I have information that is in the maxon catalog.(DCX 10 S metal brush motors)


texts: Problems with a passive network setup used with a microcontroller

texts:
Here is the circuit in my mind before I ask my question:

The microcontroller outputs 0..5v pulse train at 3kHz.
First of all, the setup between the points A and X needs to be fed by a 3kHz alternating square-wave(this is a must) for some reason about chemistry, reactions ect. which I don't need to know the reason why.

The aim is to figure out the R_unkonwn roughly(R_unknown can change slowly and it should be monitored and measured roughly by a microcontroller).

The idea is to employ a voltage-divider and send the data to AnalogInput_1 and AnalofInput_2. Since we know and can set R_known, and if we are able to send the voltage at point A and point B to the microcontroller's analog input the microcontroller can be coded to derive the R_unknown.

C1 and R1 is to obtain square wave from the 0..5V pulse output of the microcontroller. I put D1 and D2 to only pass the positive side of the square wave since the microcontroller's analog inputs can only be fed by 0 to 5V. As for as I know the input impedance of the uC inputs are 100Meg.

But as you see in the spice simulation I don't get nice pulses as inputs. However my aim was to read the amplitudes at A and B and derive the R_unknown from these(by knowing R_known). But the outputs at AnalogIn_1 and AnalogIn_2 are neither sharp pulses nor I could get rid of the negative voltages.

How can I fix or optimize this circuit so that I can have better pulses(with flat ON part) as inputs by clamping negative voltages?


texts: I understand that in an n channel MOSFET as Vgs increases, electrons are attracted towards the gate forming an n channel. These electrons are responsible for the conduction of the MOSFET. As Vds crosses saturation voltage a pinch-off occurs. This pinch-off results in channel tapering and the n channel effectively reduces. My question is if tapering occurs, shouldn't the available charge carriers in the channel reduces thus reducing current flow?


texts: Reducing the start-up voltage of a low voltage cut-off circuit

texts:
I just built this circuit, with the intent to use it as a low-voltage cut-off switch for a single li-ion cell. It works great, but once it's triggered it needs about 7 volts to turn back on, so I guess it was intended for a 2s pack at least. Source: https://www.rcgroups.com/forums/showthread.php?725572-voltage-cut-off-switch

I was wondering whether using a Mosfet with a lower gate threshold voltage would be sufficient to reduce those 7 volts to just under 4 volts? The Mosfet I'm using is STP75NF75.


texts: How to deal with devices connected via a connectors in schematics?

texts:
I have a few sensors (potoresistor, temp sensor...) that connect to the board indirectly. The PCB will have a connector such as the molex 4pin fan connector that will in turn connect to the sensor/device via a short cable.

How do I show this in the schematic and the PCB layout? If I select sensor schematic I would have to manually add the pcb footprint to the component. If I select schematic for the connector then adding a resistor to a random pin of a connector doesn't seem right either.


texts: Batteries Spike in Watts and Amps Pulled with less than 50% Life

texts:
To give a background on this, I have been running tests to determine the actual lifespan of a 3 cell pack of some Samsung 18650s and Tesla 2170s at just above freezing. The Samsungs are INR18650-35E and the Teslas were pulled from a 2018 Model 3. Voltage was checked on all cells before being wired together with a BMS connected to them. This one.

These cells were placed in a cold environment, around 35F and then connected to the LED strip and left to run in front of a timelapse.

In between the cells and the LED strip was a watt meter/power analyzer, I bought it from Amazon here.

The Voltage dropped from a full charge to 9.0V as expected and then cut out. However after harvesting the data, I noticed something odd. The life of the Samsung 18650s in my test lasted about 7.5 hrs. The amp and watt pull slow decreased over the course of the first 4.5 until they hit 0 (although the LEDs didn't turn off), and then rebounded back up to to their initial pulls at the start of the test and then slowly receded until the BMS cut them off.

Any ideas why this would happen? The same thing happened with the Tesla 2170s too, just after over half their capacity was used.


texts: Are I/O buffers of ICs design to have 50ohm impedance?

texts: Is it true that 50ohm characteristic impedance is a convention followed for signal carrying PCB tracks? Also, are the IC I/O buffers also designed to have a close to 50ohm impedance to match this?


texts: Help me understand NPN transistors, circuit does not work

texts:
I'm working on a project where I need a transistor. I want a Attiny85 mcu to turn of and on a relay. But the current in that chip is to low so I figured out I have to use a 2N2222 NPN transistor as a switch so the relay could draw current from the source and not thru the mcu.

I'm using the tool over at http://www.falstad.com/circuit to help me set up the circuit, but I'm having some problems.

To understand NPN transistors I've tried to take the example at falstad and update it to my settings, using 5V for power, adding a switch. But it does not work. I really want to test it before I get to solder it together so the tool was really nice.


texts: Calculating power needed for a mercury-vapor bulb

texts:
I'm really trying to learn this stuff on my own, but I need some help...
First I'm going to be trying to charge a battery with a 15W solar panel, whose output is DC 5V/2.1 A - how would I calculate the length of time it would take to get it fully-charged? The battery is 98 Wh, 8800 mAh, 11V.
Then, would it be possible to run a 160W mercury-vapor bulb (1.63 Arms) from it? I have a 110V inverter for the battery; 0.9A/100W max.
Thank you very much - I would like to see the workflow for this type of calculation so I can be off and running on my own!!
best,
Eric


texts: STM32F405RGT6 for AD7768 ADC fast enough?

texts:
I want to operate 2 simultaneous channels of an AD7768 A/D converter @ 256 kS/s. Its resolution is 24 bit which yields a data rate of 2 x 24 bit x 256 kS/s = 12.288 Mbit/s.
Using a microcontroller, I want to transmit the raw data of both channels via USB 2.0 and in realtime to a PC.
From an earlier project, I still have an STM32F405RGT6 microcontroller running at 168 MHz. Can anybody estimate if this microcontroller can handle this fast data transmission via USB? (I know, an FPGA would probably be the better choice but would also be more complicated to implement.)
Thanks for your help!


texts: Are there any special considerations for extending a UHF-carrying coax wire in a small device?

texts:
In the process of doing a repair on a mobile phone, I've tracked down a "no service" issue to an antenna lead inside the case. Specifically, it has detached from the U.FL/MMCX (I'm not sure which this is) connector soldered to the mainboard.

You can see on the bottom half of the image the white wire is broken off and sitting to the down and to the right of the connector (marked "1") it's intended to be part of. Note that this wire isn't an antenna itself; it carries the signal from the GSM radio on the mainboard to the actual antenna module on the other side of the device. It is intended to be terminated on both sides.
The problem is that the antenna wire has become so frayed, that I don't think there's enough of it left to cleanly resolder to the connector.
So, some new wire is in order. Problem is, I can't find any direct replacements for this device.
What I need to know is, if there are any special considerations for the right gauge and material of wire to use for this embedded UHF antenna use case. Can I grab an arbitrary bit of copper coax of a similar size and splice it in, or does the 1900MHz signal this line will carry demand more precision in the materials or techniques used?


texts: Capacitor Units For Power Factor Correction

texts: I have got the assignment to improve power factor of an industry. I have worked it out and found capacitance in K Vars and Micro Farads but need to know about the capacitor representation in volts?


texts: Why would credit card reader over audio jack not work on some devices?

texts:
This isn't a troubleshooting question, it's purely to satisfy my curiosity...

MagTek makes a product called the uDynamo credit card reader that uses the audio channel on android devices as a communication bus to interface with the mobile devices. This makes perfect sense; you have a TRRS audio jack, supporting three channels (audio L, R, and mic) and a ground. Everything the uDynamo needs and more to facilitate full duplex communication.

However, one of my phones, the Android-sporting ZTE ZMAX PRO, with a functional TRRS headset jack, doesn't appear to ever succeed in synchronizing or handshaking with the device (there's a tester app that tries for a long time to get to step 2, then says 'test failed'). The app my company developed has the same problem. The PCM sync tone emitted from the android is excessively audible if I plug in headsets when running the test, and the microphone wire on the TRRS jack is functional. Interestingly, the card reader works on my other android phones. It appears that this particular phone simply is not supported.

So, my question is, why would some android phones be able to communicate over a TRRS headset jack while others can't? I mean, it's a PCM signal over standardized audio cables, it doesn't seem like much could be different from phone to phone.

Anyway, thank you in advance.


texts: I've been looking at theremins recently.  I've built a simple one using heterodyne oscillators, but I was wondering how to make a capacitance detector similar to the theremin's antennas.  Basically, a circuit that detects the capacitance between a antenna plate, and your hand (ground), and outputs an analog voltage depending on the capacitance.  I've thought about using a 555 timer as a variable pitch, and then feeding that into a pitch-to-voltage circuit.  But there must be a simpler way to do it.


texts: How to prevent OMAP from running software after poweron reset?

texts:
I have a faulty forgein system using an OMAP5912 whith external SDRAM and NOR-Flash connected. I have JTAG access to the unit with an Segger J-Flash. Now i want to debug why it does not startup anymore. From the powerdraw it looks like it gets stuck somewhere after poweron. I can connect to it by JTAG and also i can HALT the CPU abd MMU, but i can do this only after poweron, where the system is already hung up and maybe some initialized watchdog timers do strange things...

Is there a way to poweron the OMAP in a way that it does not execute any code? So i had a chance to setup the JTAG connection and step through the microcode from bootaddress 0x0 on?


texts: Interesting property of Op-Amp. It Inverts Transfer Function of the system in it's feedback

texts:
This is a theoretical question. I saw this circuit somewhere:

System (a) has transfer function: \$H(s)= V_{out}(s) / V_{in}(s)\$

And it stated that when system (a) is put into system (b) in the exact way that is shown, then circuit (b) has transfer function: \$ H_{o}(s) = 1 / H(s) = V_{in}(s) / V_{out}(s) \$
I tried to prove that but unfortunately i can't figure it out. I want to rigorously prove that this is true. Can someone help me? Thanks in advance!

EDIT
I found the answer. It's trivial but i guess i'll post it here.

In circuit \$(β)\$ the voltage of the inverting input of the ideal opamp is the same as in the non inverting input, because of virtual ground, therefore it's \$V_-(s)=V_+(s)=V_{in}(s)\$. But the voltage on the inverting input also equals to \$H(s)V_{out}(s)\$ (the transfer function of system \$(α)\$ times whatever it has in it's input, which in system \$(β)\$ that is \$V_{out}(s)\$. The two previous equations give us that\$:H_{o}(s)=\$ voltage on it's output/voltage on it's input =\$V_{out}(s)/(H(s)V_{out}(s))=1/H(s) \$ which is what i wanted to prove.


texts: Bypassing a voltage regulator if input voltage is too low

texts:
For my project I want to allow the user to either use a 12 or 24VDC power adapter if needed but I dont want to make 2 seperate DC inputs. Neither do I want to use a buck-boost because I dont want to regulate the 12V voltage but most bucks only work with Vin>Vout by ~1V.
Right now I am using the setup in the picture to get the 24V to 12V, the load side needs min. 5A so thats why I dont want to use any linear regulator aswell.
A user told me I could make a relay or a circuit to bypass the regulator when the voltage is at a specific level.
But that's where I am stuck and would like to know a good and easy way check the Vin or the regulated Voltage < 12V and if so bypass it and just use the 12V directly. I read a bit about comparator ICs that could do that but my knowledge is really limited here. If you could provide me with some guidance I would really appreciate that.
Thanks!
I tried to think of something myself but can't really say if that would work.

simulate this circuit – Schematic created using CircuitLab


texts: TRIAC driver circuit behavior when switching low current loads

texts:
I'm doing a project that involves switching different kinds of loads (edit: by that I mean loads that go from just a couple mA, up to 5A or so) using the usual TRIAC + opto-isolator combo (in my case, a BTA24A paired with a MOC3063).
I designed it following a couple of application notes from ON Semiconductors that I found online (https://www.onsemi.com/pub/Collateral/AN-3003.pdf.pdf and https://www.onsemi.com/pub/Collateral/AN-3004.pdf.pdf) and ended up with 100R resistor + 10nF cap for the snubber circuit, plus a 330R resistor for the peak current limiting in the opto.
My question is related to how this circuit will behave if I used it for switching a particularly low load (say, for example, a LED bulb of some sort).

Let's suppose I1 = IL =~ 30 mArms (i.e 43 mA peak).
I3 should be pretty small, but let's assume it's 1mA peak. All in all, this will make I2, which is the trigger current, to be around 42mA at the peak.
The datasheet for the TRIAC I plan on using states that the gate trigger current may be as high as 50mA, so given the values mentioned earlier, it could happen that the TRIAC itself will end up not switching at all, and thus all the load current will pass through the driver circuit (and back through the gate terminal) during nominal operation, or at least that's what I'm assuming it will do.
So, the issues I'm seeing are:

Too much power is being dissipated in the 330R resistor (~ 0.5W).
Load is losing some good 13V or so to the driver circuit.

Incidentally, thyristors (and TRIACS, for that matter) being semiconductor devices, can be modeled using transistors, right? I couldn't find any curve on the TRIAC datasheet, but I was wondering if in these kinds of cases where you don't have sufficient current for actually triggering the device, it still ends up conducting maybe a little? (i.e does it have some kind of "active region," to draw a parallel with the transistor) Because if so, I would feel more at ease with regards to the whole low-load case.


texts: How to regulate a resonant converter at no load?

texts:
I am designign a high voltage power supply using the half bridge LCC topology (NOT LLC), but I suppose it relates to both.

When operating at full load, the high voltage output settles at the desired value before 1ms. However, when I replace the load resistors with current sources with DC value = 0mA to simulate no load conditions, I am unable to get the output voltage to settle. I have attached a screen grab showing this - it reaches the final voltage but then fluctuates/drops.

Nominally I switch at 500kHz. At the moment, I am sweeping the switching frequency DOWN and observing the output voltage (blue traces). It is to my understanding as the load current decreases, the switching frequency reduces.

Are there any ways to calculate the switching frequency for the no load condition? I know it is a function of the load resistance, but in my case this would have to be in the high MegOhm range since my feedback resistor is 100MEG.

Any advice appreciated. Also see attached resonant current waveform and schematic. Input voltage shown as AC but it's actually 270VDC.


texts:
I have a fairly simple question regarding power transformers.

I currently have 7x Phantom power supply for balanced XLR microphones. This power supply works on 18VAC 600mA input via a 2.1mm barrel jack. Now my question is : if I get a single 220VAC to 18VAC 5A transformer, can I connect all these power supply to it in parallel?

For the moment I have a single power supply for each of them and it's quite annoying to carry and move around.

Thanks you!


texts: Any chance of identifying how this GTX1070 blew a mosfet/VIA on the PCB?

texts:
I've been in the process of trying to repair a faulty GTX 1070. In my previous question I asked about a blown MOSFET which was answered and I replaced it and amazingly the card now has a full compliment of voltages in the board.
However, when testing for the first time after fitting the new MOSFET this trace at the far end of the board blew, next to the DVI connector.
Funnily enough, I had the DVI plugged in to a display of which worked with the previously removed card. You can see the tiny crater left behind next to the DVI port of which the trace was attached to ground (until I cleaned it out)

Looking on the forum's elsewhere, it looks like this part of the circuit is tied into the switching circuit that switches from the PCIE 12V supply to the 8 pin PCIE supply. So like, if you didn't thave the PCIE 8 pin plugged in, it would use the slots 12V supply to display something along the lines of 'plug in PCIe cable'
EDIT:
So I've found a boardview diagram of a GTX1080 which use the same reference circuit, likewise a schematic of a GTX1080 which when compared against matches exactly but still can't figure out why this would have blown.
So the circuit in question is NV12V which takes a 12V feed (12V_F) from the PCIE slot. This comes to Q521 PNP mosfet which was originally blown and since replaced with the same model of mosfet but perhaps slightly higher current ability. Once the mosfet was replaced, I had a full compliment of voltages on the board i.e. the GPU was powered as was RAM.
It was then following this new mosfet fit that the Via then popped. The boardview below shows which components are attached to this circuit.
I can tell you now that:
C545 is not short but connected to the rail
Q521 is not short but connected to the rail
R618 is not short but connected to the rail
R931 is not short but not connected directly to the rail - reads ~732ohm to NV12V
R937 Does not exist on board (DP/Quadro only)
R938 is not short but not connected to the rail
R975 is not short but is connected to the rail to Q564
Looking over the board, there's nothing shorted out, probing resistors, transistors, mosfets, nothing has shorted out.
I'm thinking mechanical failure perhaps? The board looks ok but the ports and bracket are corroded


texts: How can the Model S have a three-phase motor? I thought it was DC?

texts:
Supposedly the Tesla Model S has a three-phase AC induction motor.

I thought it ran on batteries. Aren't batteries DC?


texts:
I wanted to make a power supply providing roughly 8V (+-2V) for small currents, given a whole range of different DC voltages (let's say about 12-30V).
For that I wanted to use an LM317L (link to pdf).
Setup: I hooked a adjustable benchtop PSU to INPUT of the regulator and GND, put a 100 ohm resistor between ADJ and OUTPUT and a 510 ohm resistor between ADJ and GND.
I choose these resistors to have an output voltage of Vout = 7.6V = 1.25(1 + 510 / 100), while loading the regulator with 7.6 / (510 + 100) = 12.4 mA (the specs say the load needs to be at least 5mA).
I omitted the capacitors for this experiment.
Issue: As I slowly increased the input voltage, the output voltage also increased up to about 8V. When increasing the input to about 25V, the output still had a stead 8V. Increasing the input to about 30V made the output increase to about 18V.
When I replaced the regulator with another (LM317L) one, I got a similar erratic behaviour again when the input exceeded 25V. Replacing it with same type regulator in the larger package (LM317 pdf) everything worked fine and I got around 8V for any input of 8-30V. Apart from the amount of output current they can provide, both of them should behave identically as far as I understand.
Can anyone point out what I'm doing wrong or what I possibly misunderstood?


texts:
FPGA are, I reckon, (relatively) expensive because they can be reconfigured many times. If I were to make a design work on an FPGA, and decide to build several (though not many) of them on a custom board using the same code; is there another type of chip that would be cheaper, which I assume I would configure serially once and for all?

In a nutshell, I am looking for the equivalent of EPROM compared to EEPROM for configurable gate array chips.


texts:
Let me say first that i'm a noob in electricity.
I measured the voltage from my diy microwave-transformer-welder and it was 8.
I have no idea how much amps run through it but the fact that it creates lots of sparks and can create welds on metal may suggest that it is a high amount of amps.
Is it safe to touch this or do I stick to my gloves?

Edit: I added an image of my setup, that 230V AC is 16A.


texts:
I have made RC car using using ht12e and ht12d, two geared DC motors, RF module. Now my problem is that when motor starts rotating, it is generating some kind of RF signals which are interfering with my RF receiver signals and it cannot receiver further signals from the transmitter unless I reset power to it. I read about low pass filter over net but couldn't understand well.

I tried shielding motors using aluminium foil which helped to some extent but not completely. How can I eliminate this problem using simple components?

This is my circuit:

I have used 433 MHz ASK module.


texts:
TL;DR: I want to know if there is anything, That on which when a radio frequency falls, and it turns on an LED. Basically an on off switch but controlled when radio waves hit it.

What I hope to achieve is that, I want to have a remote of sorts, And when I press a button, the LED turns on. Without having line of sight.

Why? Because my dog and I play fetch at night, (Don't ask why I have many reasons to. If I could at day I would've but can't.) and I almost always lose the ball every night into the bushes and it's too scary to look for it. I have lost many balls and it's become annoying and expensive to lose balls every night. (I'm a student).

What I have in mind is the idea that I could press a button and it transmits radio frequency and when it hits the ball the LED turns on so I can see it.

I know an Arduino could be used to do it - I found blinking codes for it too but I can't fit it into a ball and even if I did my dog would crush it in his mouth. (And also I don't know much about coding so I'd best avoid it.) So ideally I am looking for something really small and simple that would be inside the ball so if even he bites it there's a good chance he won't crush it.

What I want to know is, is there anything that is available like what I described? A switch that, when RF falls on it, lets current pass through it like a switch allowing the LED to turn on bright so I can find it? Does anything like that even exist? I can find voice activated clap/sound/light/heat/temperature/IR everything activated switches but not this.
Enlighten me.


texts:
I need to convert the following PIC assembly code (below) to an 8051 assembly. It is an inline assembly code. Actually, I intend to convert it to C. I am not familiar with the PIC MCU so I do not understand much of what happens. If I can an understanding of each instruction, I will try and input the equivalent assembly. Or better still, I will appreciate if I can get an equivalent 8051 assembly code of it. "toRotate" is a 32 bit variable. Thanks

    _asm
    movlb toRotate
    bcf STATUS,0,0
    btfsc toRotate+3,7,1
    bsf STATUS,0,0
    rlcf toRotate+0,1,1
    rlcf toRotate+1,1,1
    rlcf toRotate+2,1,1
    rlcf toRotate+3,1,1
    _endasm

This is the entire code below.....I really want to know what is done here. My intention is to convert it to C language.

DWORD leftRotateDWORD(DWORD val, BYTE bits)
{
    BYTE i, t;
    DWORD_VAL toRotate;
    toRotate.Val = val;

    for(i = bits; i >= 8u; i -= 8)
    {
        t = toRotate.v[3];
        toRotate.v[3] = toRotate.v[2];
        toRotate.v[2] = toRotate.v[1];
        toRotate.v[1] = toRotate.v[0];
        toRotate.v[0] = t;
    }

    for(; i != 0u; i--)
    {
        _asm
        movlb toRotate
        bcf STATUS,0,0
        btfsc toRotate+3,7,1
        bsf STATUS,0,0
        rlcf toRotate+0,1,1
        rlcf toRotate+1,1,1
        rlcf toRotate+2,1,1
        rlcf toRotate+3,1,1
        _endasm

    }
    return toRotate.Val;
}


texts: Redesigning TV Remote for a different User Interface

texts:
The buttons of a standard TV remote are simply conductors covered by insulators (for user protection) to be pressed in order to short circuit a node in a grid of wires.

What if we want to replace this mechanical solution (of pressing down) with an electrical solution which depends on wireless commands?

Do we short circuit remotely, and if so what's a safe way to do so?


texts: Use expensive or inexpensive capacitor for decoupling

texts:
I'm in the middle of a project to create a small development board using a 100Mhz Cortex M4 MCU and have to buy some decoupling SMT capacitors.

I've found the following options:

Cheap 10 cent from Mouser
Expensive 50 cent from Digikey

Both appear to have the same properties but the more expensive one is listed as being for "decoupling".

I did find this link about the expensive Johanson capacitor. It appears to be a special purpose built low ESR capacitor that is said to "replace" the need for multiple capacitors.

Will the cheap capacitor be fine or should I spend the extra money on the more expensive capacitors and why?


texts:
I'm very new at all this and hope you will have patients with me, I'm trying to use this circuit diagram to turn a momentary switch into a latching switch, I though it would be straightforward but alas,

I'm building it in tinkercad.com but cannot figure out where the power source (9V) connects and where the load connects. I'm thinking V+ goes to the Battery pack Positive and Vout to the Negative, but I have no idea where the ground connection should go. The circuit turns on, but there is no switching

Thank you for your time.

I have now tried to build this on a virtual breadboard, I have lowered the voltage form 9V to 4.5V as the 74HC00 is only rated for 5V. When the button is pushed the chip fails with the following error "Voltage at pin 1A is 1.84 V while max is Vcc=30.mV I'm sure I'm missing something obvious but I really have no idea, hope some one can help me out.


texts: Is there an online "table" or something for choosing MOSFET's?

texts:
I am planning to buy some MOSFETs for testing and playing around, to decide if I would use one instead of a BC338 transistor (see my intended application below).

My "filtering algorithm" would be:

Small package (TO-92 preferrably);
Small power dissipation (less heat = more light!);
Saturated below 5V at the gate;
Small price!;
P channel (allows for common ground between Arduino and Led module);
Not overengineered (my max current is not expected to go above 1A);
Containing the proverbial "L suffix", meaning Logic-friendly;

I have been looking for a good candidate using "arduino led mosfet" search words, and tried some big-supplier sites (Mouser, Futurlec, DigiKey), but couldn't find a comparative table of Mosfet families, or even a "one place" to search for candidates to a given application, based on "layman readable" numeric parameters.

Also, if you could give me two or three part numbers that would be suitable for my application (see below), I would be glad!

Intended Application:

Use an Arduino GPIO (5V) to switch a module of 18 red leds running at 6V. The leds are wired in nine parallel groups, where each group has two leds and one 330 ohm resistor in series. The led brightness is quite sensitive to voltage drop, so a low "ON" resistance is welcome (preferrably below 10 ohm).


texts:
I've got a power supply unit from a defunct/decommissioned Satellite Internet setup, and I'm hoping to get clarification on some of the markings on the label.

In the following picture, there's four pin numbers, followed underneath of pins 1 and 2 both volts and max amps, and pins 3 and 4 simply "RETURN".

My question is whether I'm reading the label correctly. (Technically, I've got a few questions here).

Does max(A) under pin 1 mean that at 12v I've got 2.99A available, and at the 48v pin, I've got a max of 0.82A?

Also, when pins 3 and 4 are reflected as return, I'm assuming that means ground, yes?

I'll summarize my questions here to consolidate:

Is pin 1 +12v @ 2.99A?
Is pin 2 +48v @ 0.82A?
Are pins 3 and 4 ground pins, that could (and potentially should) be wired together if both pin 1 and 2 are in use simultaneously?

Here's the pic of the label of the power supply in question:


texts:
I have a high voltage power supply for an electron beam system. The voltage regulator is an old analog system that works via a simple comparator and reference signal from a POT. My problem is the feedback voltage from the high voltage tank (tank meaning large steel oil filled tank with all HV components inside) is upward of 124 volts DC and is floating in respect to ground. The feedback signal comes from a 50k resistor which is part of a large resistance network inside the tank. Part of that network also runs to an analog 0-1mA meter that is a kV meter so I don't want to mess with the resistance.

I am trying to replace the analog controller with a microcontroller (ATmega) to replace the closed loop analog control with digital control. I don't want to mess with the resistance network inside the tank so this has to piggyback existing system and not unbalance the resistance.

Below is an overly simplified schematic of the power supply. As you can see R1 is the feedback resistor, two wires are taken from each of its terminals and run to the voltage regulator. R3 represents beam current measurement and overload protection (different circuit). The ground is chassis/earth ground. R2 represents the numerous resistors inside the tank from the negative side of the power supply. R4 and R5 is my planned divider to a difference amp (ignore the TL801 part number). My idea is to use a high impedance divider using 11 megs of resistance and then feeding that scaled down signal into a unity gain difference amplifier or high impedance instrumentation amplifier. The amplifier would be powered from an isolating DC-DC power supply and the signal isolated via an isolation amplifier (TI ISO124). From there I can scale it further using a POT to the uC ADC. Any thoughts?

simulate this circuit – Schematic created using CircuitLab

Notes:
If anyone is wondering, since the feedback signal is within a few volts of ground, there is no need to worry about high voltage isolation, only ground isolation.
The high voltage power supply normal operating range is 0-150kV and at 150kV, will produce a feedback voltage of 100V. however, there is a setting to allow to power supply to output its maximum of ~183kV for what is knows as corona clearing of the gun. That gives you a little over 123V.


texts: What's the difference between all of the Atmega328p clocking options?

texts:
Reading through the data sheet of Atmel's Atmega328p microcontroller, I had heard reference of an internal 127kHz RC oscillator. This being the default oscillator if no external crystal/resonator was configured.

However, after reading through the data sheet some more, it states that device comes shipped with a 8Mhz internal oscillator... Which confused me, does it feature both?

I then started reading into all of the possible clocking options, and there were some terms that I was unfamiliar with. Referring to page 28 of the Atemga328p manual (http://www.atmel.com/images/Atmel-8271-8-bit-AVR-Microcontroller-ATmega48A-48PA-88A-88PA-168A-168PA-328-328P_datasheet_Complete.pdf), it lists all of the clocking option.

Of those clocking modes, what are the differences between low power crystal oscillator, full swing crstal oscillator, low frequency crystal oscillator, and calibrated internal RC oscillator?

I appreciate any help!


texts: In an energy band diagram why is the valance band in the p-type have more energy then n-type?

texts:
I am having trouble understanding energy band diagrams. In an energy band diagram of a semi-conductor during equilibrium the valence band of the p-type is higher then n-type meaning electrons in the valence band of p-type semi-conductors have greater energy but how is this possible when p-type semi-conductor have holes which attract electrons and should therefore, not need much energy?
Please correct me if I am wrong.


texts: Automotive relay contact rating, Can it handle 120vac?

texts:
I have this automotive relay, I would like to use it to switch a 120vac stereo that pulls around 9 amps. If the relay contact ratings are for 12vdc 30amps, how many amps can it handle at 120vac?

Will using this type of relay be safe?


texts:
I am trying to create an SD card from a PCB. My problem is that I cannot find the SD card specification that would give the:

Dimensions of each Pin
Placement of each Pin

All specifications I could find dont consist of those informations:

Does anyone know where I could find this data? I would appreciate all help.


texts: Describing step response in terms of poles and zeros of transfer function?

texts:
me and a friend are stuck describing something, we're both coming to terms with using matlab and we're trying to understand the design of a simple control system for controlling the steady-state error of an open loop system.
We have a block diagram for such a control system here:

simulate this circuit – Schematic created using CircuitLab

As an example, we take the transfer function of the open loop system (G(s)) to be G(s) = 10/(s^2 + 11s + 10)

Then in matlab, we have the following expression used to get the closed-loop transfer function of the system:

[numc,denc] = feedback([0 0 10], [1 11 10], [k2 k1], [0 1]);

We take k2=0 and k1=10 (first order proportional control)
This system yields use the following pole-zero map and step response in matlab:

How can I describe the step in response in terms of the poles and zeros of this system?
I don't know how to relate the two.
Any guidance is greatly appreciated

Thanks


texts: Options for permanently joining two flexible printed circuits (FPC) together?

texts:
Robust, simple and cheap method to join a pair of flex pcbs / flex printed circuits (fpc) together?

One option could be making both circuits rigid-flex then joining as one would two pcbs, which would then be standard.

How is this best done?

edit: this is for permanently joining, not via a connector


texts:
I am understanding loop compensation to DC-DC voltage mode buck converter from this case study   Compensation Case study

For example: I am simulating in PSpice Dominant Pole Compensation (Pg No 8 to 13) by using average model which I am assuming that is correct for ac analysis.

I am assuming error amplifier gain as 10k here (Since this information was not provided)

Phase Margin of 90 Degree and Gain crossover frequency of 74Hz which almost matches with the document plot in Pg12.

Query: How to proceed with line transient using this above average mode in PSpice ?

Since I wanted to understand the transient responses w.r.t compensation.


texts: Given a battery with a certain capacity C (in Ah) and given a certain charging current Ich (in A), how I can calculate the charging time?


texts: Creating a switch between USB and USB OTG for phones

texts:
I'm trying to create a charger that knows how to switch between OTG and charging mode. The OTG side is working, and my Samsung S4 goes into charging mode. However, charging is really slow. It even loses charge, even with the charging indicator on.

There are two things that do concern me about the schematic I came up with:

A diode is used on the Vbus line, causing my 5V supply to become a 4.3V supply
I did not follow the S4 charging specification

Some things I looked up due to the current situation:

Samsung S4 charging schematic: http://www.obddiag.net/usb-power.html
Maxim's "Charging Batteries Using USB Power": http://www.maximintegrated.com/en/app-notes/index.mvp/id/3241

I modified my circuit a little bit, so that my attachment does not need to worry with the charging specifications of different devices.

Would it work if I:

Used a switching regulator to raise the voltage up from 4.3v to 5.0v rated for 1.5A, and
Used a USB multiplexer so that my circuit can support different charging specifications, while still fully functional for USB-OTG devices?

I have attached a schematic for reference:

The chips I used were:

USB Multiplexer: http://www.ti.com/lit/ds/symlink/ts3usb221e.pdf
Switching Regulator 5V1.5A: http://www.ti.com/lit/ds/symlink/tps61020.pdf
Solid State Relay: http://www.ixysic.com/home/pdfs.nsf/www/CPC1017N.pdf/$file/CPC1017N.pdf

Also, what's the advantage of using a voltage divider instead of just limiting voltage with a single resistor?


texts: PWM - signal modulation (sawtooth vs triangle signal)

texts:
In order to get the PWM signal out of a sawtooth (ramp up/down) I usualy use an operational amplifier and set the reference value with a potentiometer. This is how I can then modify the PWM by turning the potentiometer.

Is it possible to get a PWM signal out of a triangle signal using operational amplifier in a similar way?


texts:
I want to design buck converter Vin 12V V out 9V I out 400mA.
any suitable part /
switching frequency I want to use very low like 65KHz


texts:
Whats a good circuit/design that will generate a very stable 4Hz signal  (to feed into a counter) that won't drift with temp / time.

It's not so important that its exactly any particular frequency, just around 4Hz, it's just important for it to stay at that frequency ( it's to be used as a test signal )


texts: A quetion about how an electric shock game works

texts:
can someone explain to me why does the current pass through his hands? why doesn't it pass only through the aluminum since electricity always chooses the easiest path?
https://www.youtube.com/watch?v=7QIcdQPwLmg&t=331s


texts: My node mcu isnt turning on when connecting 3.3V to VIN

texts:
So I'm trying to wire my node MCU using in with 3.3V and in the multimeter, it's reading the 3.3V being delivered properly by the converter, I also tested for amperage and its consuming 37mA and I don't know why it's not turning on when connected.
I'm using a 5V to 3.3V converter with up to 1A of current delivery so I suppose that's not the problem.
In case you're wondering when to connect using the USB to my PC it turns on properly.
What can be the problem with this? Should I buy a new one?


texts:
I am having a hard time understanding why A'+B' is not equal to the following expression:

I understand that when I apply the 4 different combinations: 00,01,10,11 to A and B I get different results for reach expression when we have either the combination 01 or 10.

Is that the only explanation? For some reason I always figured the two expressions would yield the same results.


texts:
How is the maximum current that a certain circuit can provide found experimentally? Say, that of a power supply circuit?
Can it be done without destroying the circuit?

I'm looking at designing some circuits on my own and learning through experimentation. Current limits are clearly stated for ICs in their datasheet, but when it comes to discrete components, it's not so obvious. I can look at the maximum current provided by each component, but it would also help to have that confirmed through experimentation to make sure I actually understand what I'm doing.


texts:
I'm trying to create completely DIY EMG. As many of you may know, I will be dealing with microvolt inputs. I know that op amps amplify voltage, but I am wondering if I can somehow get a 1,000,000x amplification. Do I need to create my own op amp by soldering a few components or are there already op amps available that can do this?

Note: I am amplifying voltage in order to have the signal be read by an Arduino Uno.


texts:
I would like to buy a small external speaker (mono) to use for my laptop and mobile phone, both of which have very poor-quality and low-volume built-in speakers.

However, all that I can find in shops are powered (battery or AC) speakers, and no passive speakers at all. I would be using the speaker at home most of the time, and thus it would not make sense to keep charging the battery every few hours. I don't need the new speaker to have massive volume, thus I'd have thought that a passive solution should be doable.

Also, for convenience, I would prefer the speaker to not require mains plugging, but only a wired connection to the device's audio jack.

Is such a solution at all possible, or will I have to settle for powered speakers?


texts:
I am currently in my final year of University and am completing my final year project. I have a circuit that I am analyzing as part of it and could really use some help.

I am trying to determine the transfer function for the following circuit (within the dashed box):

I have searched around on the internet and have only managed to find a hand full of examples where the R and L are in parallel with a resistance in series with L, none of which have helped so far. I have been trying to derive the transfer function for the circuit for some time with no success.

I would really appreciate if someone could walk me through how to derive the TF or point me in the right direction.

Thanks in advance
Ben


texts: What is the difference between a negative linear regulator and a positive one?

texts:
I am looking for a voltage regulator Vin = 5 V, Vout = 3.3 V, Iout = 400 mA.

In my search I found negative linear regulators as well as positive ones. What is the difference and why can I find more negative ones for higher current than positive ones?


texts: Ethernet Transmission with one MAC and Multiple PHYs

texts: I have been recently learning about ethernet subsystem. I see that the MDIO interface is shared across multiple (upto 32) PHYs from a single MAC and each PHY's state can be accessed using the 5-bit PHY address. But can I route the MII/RMII signals to individual PHY or a subset of PHYs connected to the MAC and transmit the data only through those PHYs? Or Can the MII interface only be shared with all the PHYs and all PHYs simultaneously transmit the same data received from the MAC?


texts:
First of all, I'm a newbie in electronics, please be patient with me.

My problem is that I want to use a pump for a project, a ulka model e type ep5. I salvaged it from an old coffee machine.

It had no power supply, was directly plugged to the wall, and I don't want to put myself in danger.

How could I use it with a lower voltage/without plugging it directly into the wall?


texts:
I'm trying to spec out an output capacitor for a TPS7201 voltage regulator (http://www.ti.com/lit/ds/symlink/tps7201.pdf). It needs to be selected carefully as it is used to stabilize the internal feedback loop. The datasheet suggests using a 10-15uF tantalum (with a max ESR of 1.3 ohms) and an external 0.5 ohm resistor in series with the cap.

First question: Is it be correct to say that the CSR = ESR + external resistor = 1.3 + 0.5 = 1.8 ohms? (EDIT: CSR in datasheet is "Compensated Series Resistance")

Now I would much rather use a ceramic cap, which from what I've read, has an ESR in the milliohms. In the TPS7201 datasheet, figure 30 illustrates the region of stability for a range of CSRs. It looks like a CSR of 0.1 to 2 ohms would be sufficient. So to get proper operation I would need add some additional external resistance to get to the necessary CSR.

Second question: If I use a ceramic cap instead of the tantalum, and if I add an external resistance of say 1 ohm (CSR then is 0.1 ohm for cap, and 1 ohm for external resistance, thus 1.1 ohms total, which is in stable region of operation according to figure 30), would this yield proper operation?

Does this make sense, or am I missing something fundamental?

Thanks


texts:
I'm getting to grips with designing coupled line filters and wanted to implement the band-pass filter described in Example 8.7, p. 435 in David Pozar's excellent "Microwave Engineering" just as a first toe-dip into the discipline. However, the outcome for the insertion loss is very much unlike the one stated in the example. I am missing something very basic, probably.

The filter itself is N=3 (four coupled lines) with a 0.5 dB equal ripple response and a center frequency of 2 GHz. \$ Z_0=50\Omega \$ and the bandwidth is 10%.

The stated odd and even mode impedances are:

+---+------------+------------+
| n | Z_0e (ohm) | Z_0o (ohm) |
+---+------------+------------+
| 1 | 70.61      | 39.24      |
| 2 | 56.64      | 44.77      |
| 3 | 56.64      | 44.77      |
| 4 | 70.61      | 39.24      |
+---+------------+------------+

Using Qucs 0.0.18 and its line calculation tool I make the following schematic, assuming I have a 254 um thick ceramic substrate of sorts and that the couplers are \$\lambda/4\$ long at 2 GHz:

I now get the following results:

which is significantly worse than I expected. There is no ripple in the passband, as seen in Pozar's results, and I only ever achieve a -3 to -4 dB insertion loss.

If I add some transmission lines for impedance matching, I might gain 1 dB in S21 at the expense of bandwidth.

Obviously it is possible to design a much better functioning filter, like this one in the qucs example folder for 10 GHz: http://sourceforge.net/p/qucs/git/ci/master/tree/examples/bpf_10Ghz.sch

Could this be the microstrip models in qucs adding too much reality to the results? ;-)
Any comments are greatly appreciated.


texts:
ETSI standards EN 301 489-1 and EN 300 330 use the term "channelized" (system or equipment).
But I could not find any definition for "channelized" in one of the standards or any other sources.
What is the official definition for "channelized" in this context?
I would assume wireless lan or mobile/cell phone communication to be "channelized" because of the distinct communication channels and defined frequency bands, but e.g. NFC/RFID to be non-channelized. Is this correct? Is there any official source for this interpretation?


texts: USB data serial termination resistors. Need them for STM32F2 micro? If so, what wattage?

texts:
I'm a little confused.

The STM32F2 datasheet says only this, vaguely stated in the features:

  HNP/SNP/IP inside (no need for any external resistor)

Is that referring to the D+/D- termination resistors??  Ie. I don't use external termination resistors?  That'd be a first for me.

While I'm on the subject, stupid question time... how do I figure power dissipation for these resistors?  I attempted to search for that answer and found nothing, which suggests people likely aren't putting 1W (expensive, big) on every cheap-o USB device and they certainly aren't blowing up or I'd find a million hits.  So it must not simply be 5^2V / 27 Ohm = 1W.  What is it?


texts: What power supply current rating can replace 6 1.5 V C batteries?

texts:
I have a more specific question than this one.
As I understand it, different 1.5 V batteries are distinguished by "capacity" (AAA < AA < C < D), measured in mAh (milliamp-hours(?), which is actually what I think I would call charge, 1 mAh = 3.6 C). But what current can be supplied by these batteries (i.e. at what rate can the "capacity" be drawn?)

I would like to replace 6 C batteries with a 9v DC power supply but need to know what maximum current rating is appropriate.


texts:
Sorry for my english and long post again.

After reading this article, I realized that my understanding seemed to be wrong.

I thought that to create conduction current in some wire first we need a "charging" current - a current that will create voltage by build up charges on surface of the wire. These surface charges then create weak electric field inside the wire that drive conduction current (i.e. conduction current will appear only after "charging" process).

In other words, I considered these "charging" currents (e.g. if voltage is changed) to be completely independent of the conduction current.

But in above mentioned article W. G. V. Rosser describes what will happen with wires connected to generator if voltage of the generator will increase:

  ...Transient currents again flow in the connecting wire in the
  direction of extra field ΔE. There is again some current flow towards
  the surface of connecting wire until more charge builds up on the
  surface of the wire and "guides" the extra current along the
  connecting wire...

  ...However, the changes in electric field field intensity (and the
  associated changes in potential and conduction current) are generally
  propagates with a velocity comparable to, but less than the velocity
  of light.

Besides that, after first glance on transmission line theory it turned out that pulse on it consist of both voltage and current. And it seems that the exact value of current already takes into account current required to charge wires to some voltage:

  When increasing the capacitance of a double line, some additional
  electrons are necessary to keep up at given voltage. Therefore the
  current I is increased in relation to V, corresponding to a decrease
  of Z = V/I.

So, now I can't understand how all this related.

Question:

It seems that I should not separate a currents and it is not necessary to wait for the completion of the transients to get changes in conduction current.

Instead, some change in voltage (assume it increased) propagate down a wires simultaneously with corresponding change in conduction current. And some part of this conduction current is "spent" on charging the wires to given voltage. Additionally, as these surface charges accumulates during propagation process, they amplify electric field inside the wires to maintain the increased conduction current at this new level.

Is this new description correсt ?


texts: What is the correct symbol for an ammeter that measures 0..200 mA and generates 0..2 V proportional output?


texts: Arduino based triac dimmer bulb flicker fix on touching Arduino ground

texts:
I've designed a triac based dimmer circuit. It is working just fine except the bulb is flickering on dimming (working fine with full brightness). Bulb I am using is filament based and dims perfectly from other dimmers. I am attaching schematic of my circuit and code. The strange thing that I am noticing is that the flickering stops as soon as I put my finger on atmega's ground or Vcc pin. On touching these anywhere on the circuit, flickering stops immediately. Circuit contains standalone Atmega 328p au circuit along with dimming circuit. I've placed 0.1uf ceramic caps between both Vcc and ground. Also a 100uf electrolytic cap between Vcc and Ground from incoming supply.
Code that I've used is this, and I am pretty sure that code is okay because it is working fine with the dimmer circuit that I've bought from market.
#include  <TimerOne.h>
volatile int i=0;
volatile boolean zero_cross=0;
int AC_pin = 3;
int dim = 064; // half brightness
int inc=1;

int freqStep = 75;

void setup() {
  pinMode(AC_pin, OUTPUT);
  attachInterrupt(0, zero_cross_detect, RISING);
  Timer1.initialize(freqStep);
  Timer1.attachInterrupt(dim_check, freqStep);
}

void zero_cross_detect() {
  zero_cross = true;
  i=0;
  digitalWrite(AC_pin, LOW);
}
void dim_check() {
  if(zero_cross == true) {
    if(i>=dim) {
      digitalWrite(AC_pin, HIGH);
      i=0;
      zero_cross = false;
    }
    else {
      i++;
    }
  }
}

void loop() {

}

This is the schematic:-

Please let me know the solution for same.


texts: 4N35 opto-isolator for MIDI input does not work?

texts:
I have the following circuit which I would like to use to connect a MIDI enabled device. I am not getting any signal on pin 5, could it be because the resistor from the base to ground in too small? I am not sure how to calculate it from the datasheet.

Update #1

I have replaced the opto-isolator, tested the input using an LED and could see the LED light up indicating current flows in the MIDI loop. I have placed a scope probe on the output of pin 5 of the device. pin 6 is now not connected to anything. Normally (idle) the signal is pulled high, when a signal comes in the signal goes low but only down to ~2.8V which is not enough to register as a logic low.

Update #2

I have replaced R17 with 360 Ohm. Now the signal goes as low as 1.6V.

Update #3 - Final one

I've swapped the 360 Ohm resistor for 1K. Now the signal looks much better and it reaches almost 0V when low. It is worth mentioning the scope claims rise time of 7us and fall time of 3us (probably on the low side). Considering the MIDI freq. with about 32us per bit this is short enough not to have false readings. The MIDI signal goes to an Atmel AVR and from testing I did right now it seems the messages are going through clearly. I agree that this is not the optimal device for this task though, and the circuit one would make for it (if he desires) looks very similar to what is contained by the PC900 optocoupler from Sharp.


texts: Memory dump size does not match size of MTD partition

texts:
Device with Linux embedded system on NAND flash memory. I did memory dump of some MTD devices partitions use serial console, from U-boot bootloader use available commands.
First I read MTD partition to address in the memory, then dumped memory from that address to the terminal window.
For example, MTD partition   0x01d60000-0x01e60000 : "FPAR" MTD partition size is 0x00100000 = 1048576 bytes

nand read 0x20000000 0x01d60000 0x00100000
NAND read: device 0 offset 0x1d60000, size 0x100000
1048576 bytes read: OK
md.b 0x20000000 0x00100000

Then saved log file with dump as text file, cut out extra stuff before and after the dump and coverted it to binary use

xxd -r -p dump.txt dump.bin

Resulting bin file size 1,310,860 bytes is mismatching MTD partion size (1,048,576 bytes), its much larger. Is the problem related to hex data conversion or the dump process have errors? I understand that MTD partion size of 1048576 bytes is size assigned to the whole MTD partition, the actual data on partition takes much smaller space, the large space filled with hex 'ff' values. Additionally, can anyone advice good utility for hex to bin data conversion?

Edit: I tried the same steps with 64 bytes data size, and used Raw log session mode, after trimming extra stuff, the resulting ascii file is 318 bytes. After dump conversion, the bin size is 87 bytes.

20000000: a0 7c 4f fa 62 61 75 64 72 61 74 65 3d 31 31 35    .|O.baudrate=115
20000010: 32 30 30 00 65 74 68 61 64 64 72 3d 46 46 3a 46    200.ethaddr=FF:F
20000020: 46 3a 46 46 3a 46 46 3a 46 46 3a 46 46 00 6e 65    F:FF:FF:FF:FF.ne
20000030: 74 6d 61 73 6b 3d 32 35 35 2e 32 35 35 2e 32 35    tmask=255.255.25


texts: "Buffering" spikes between switch positions

texts:
I'm using a 6 position 2 pole rotational switch to change the resistance of two input voltages. Each position adds a resistor on each input, thus increasing the overall resistance and lowering the voltages on the outputs, except positions 1/7 which are direct without resistance. This works fine. My problem is that although I'm using high quality Grayhill switches, there's a sweet-spot between positions that causes the voltage to skip to 0R if the knob is turned slowly. If turned fast, its unnoticeable.
Is there a simple way to get rid of the spikes between positions? Capacitors in series with each resistor?


texts: I have been researching the electron flow which goes from negative to positive in a battery. Since ground the returning point in a circuit, shouldn't ground be the positive terminal?


texts: Why sometimes for Aluminum Electrolytic Capacitors Impendence is mentioned not ESR?

texts:
while searching for Aluminum Electrolytic Capacitors in Didikey or Mouser, they mentioned ESR for some capacitors and Impedance for some capacitors, as both ESR and Impedance are different then why don't they show.
same happened when searching in vendor website/datasheet.


texts:
My Doubt is in voltage swing of a differential signal. Here is the scenario :-

The voltage swing of LVPECL is 800 mV.

Assume it as my driver. So, in case I want to drive an LVDS input, I would go for a translation circuit somewhat like this :-

I understand that I am AC coupling the driver to remove DC level & than biasing it to match LVDS 1.2V level of reciever.

What I dont understand is - How the Swing will be affected before & after the termination. Can someone explain?


texts:
I'm looking to design a power supply that, given 24V input, can deliver +/- 0-12V output at 3A. It will be used to drive a Peltier module in either heating or cooling mode, which is why it must be bipolar. Here's an example of a commercial device that does this (but I don't know what circuit they used).

Is there a specific circuit that is known to be good for this application? Can/should I just feed the output of a standard buck converter into an H-bridge to allow inverting the voltage?


texts: How do I decide which which oscillation frequency and capacitors to use with a boost converter?

texts:
I'm working on a few projects where I'll be driving about 8 WS2812B LEDs on a 5V rail with an ATTiny85 (I think the whole circuit is going to draw about .5A; I'm using .75A for my calculations).  I'm planning to power this with a lithium ion battery with a nominal voltage of 3.6 volts.

I need to boost the voltage to 5V.  I'm considering using the XC9142B50DMR-G step-up converter to do this.

On page 11 of the datasheet (an image is included below), they have a reference implementation and specs for the other components.  There seem to be two options for the oscillation frequency: 1.2MHz and 3.0MHz.  I can't figure out why I'd prefer one frequency over the other.

One difference appears to be a lower supply current.  What does that mean (and if it's an advantage or a disadvantage)?  Are there other reasons I'd prefer one frequency to the other?

They also have 2 recommended capacitors but mouser doesn't have them in stock.  Can I use any ceramic capacitors that are 10uF and at 10V and an X7T dialectric?

Here's the reference circuit and BOM specs:


texts:
I am making a battery charger for a speaker using 4 18650 3.7V batteries.
Now I know that I would need to get a 4S Lipo or Li-ion PCB, the only thing I don't understand is the current rating that I should get.
Like, for example, would getting a 30A 14.8V PCB board cause an issue somewhere?
Also since the voltage of the battery board is 14.8V, would I have to go a little beyond for the DC charging port and its charger?


texts: Bluetooth vs Bluetooth Smart (Low Energy)

texts:
Im trying to decide between Bluetooth and Bluetooth LE. My device needs to transfer 375 bytes per second. Bluetooth LE can send packets of 20 bytes max, so this boils down to about 20 packets per second.

  A Bluetooth low energy device used for continuous data transfer would
  not have a lower power consumption than a comparable Bluetooth device
  transmitting the same amount of data. It would likely use more power,
  since the protocol is optimised for small bursts.

Will Bluetooth LE will still be more power-efficient than Classic Bluetooth at this datarate (375 bytes per second)? And if so, at how many bytes/second will it be better to switch to Classic?


texts:
I use a MOSFET in my project, and I don't know what model of MOSFET I need. I do have a list of specs, but I don't know what they would be called on the datasheet.

I need some help translating my list of required specs into something I can put into an interactive search on an electronics store website.

Switching voltage (The voltage at which the MOSFET lets current flow)
Maximum current it can pass from the source to the drain. (How many Amps can I run through it)
Maximum voltage it can hold back when the gate has no current.(How much voltage can it hold back when not switched 'on')
Gate capacitance (No idea)

Or, would I be able to just use a switching transistor? I feel like it would simplify things if I could. I am using this circuit:

Edit:
Would this MOSFET(datasheet) work? I would be supplying the circuit with 11.4V, the current after R2 would be about 10mA, and L1 gets supplied with about 1A.


texts: What happens when microcontrollers run out of RAM?

texts:
It may just be a coincidence but I've noticed the microcontrollers I've used rebooted when they ran out of RAM (Atmega 328 if hardware specific). Is that what microcontrollers do when they run out of memory? If not, what happens then?

Why/How? The stack pointer is certainly blindly increased to a non-allocated memory range (or rolled over), but what happens then: is there some kind of protection that makes it reboot or is it (among other effects) the result of the overwriting of critical data (which I assume different from the code which I think is run directly from flash)?

I am not sure this should be here or on Stack Overflow, please let me know if this should be moved although I'm pretty sure hardware has a role in that.

Update

I should point out I am particularly interested in the actual mechanism behind memory corruption (is it the result of the SP rolling over -> does that depend on the uC's memory mapping etc.)?


texts: Questions and confusions on transmission line theory and lumped element model

texts:
I want to model a simple signal transmission system by considering it as travelling through a transmission line.
Here is the system:

The original signal generated by the transducer is 0 to 10V step function like signal with very low 3Hz fundamental frequency.
So the signal has high harmonics which matters since it is squarewave-like step function signal.
This is a general question which is related to my previous question: Passive low-pass filtering question for a transducer output

Basically I have confusion when to use which model. Transmission line theory or lumped model...
So I want to model this in LTspice as a Lumped LC Model or something in that sort to see phenomena like ringing.
To achieve an approximate model I will write about each sections from left to the right of the circuit:

Questions when trying to use lumped model:

1-) Rload in the above illustration represents a scope or very high input impedance of a measurng instrument which is known.
    Rout in the above figure is the output of a transducer which is unknown. How to measure that if it is not a function generator with a known output impedance?
    I will use the following method to find the output resistance:
    http://www.qsl.net/w/w2aew//youtube/How_to_measure_output_impedance.pdf
    Do I really need the output impedance or can I take it roughly some hundreds of ohms?

2-) Coaxial-cable in the above illustration is a standard 50 Ohm intrinsic impedance BNC cable. I know its length and lets say it is 20 meters long.
    Since we use lumped element model we will not use 50 Ohm right? And capacitance and the inductance will vary with length?
    In other words, how can I model this cable in LTspice?

A question when trying to use impedance matching in transmission line theory:

Secondly let's forget about the LTspice and lumped model and just assume we only want to achieve impedance matching.
Here is the model considering impedances:

So now we have a transducer output impedance which is Rout=Zout, coaxial cable impedance which is 50 Ohm, and we have a load Rload=Zload which is lets say 100M.
So in this case to achieve impedance matching throughout the line I need a 50 Ohm resistor in parallel with Rload just before Rload to make the Rload 50 Ohm.
And I also need to know the Rout and I need to add a series or parallel resistor to it such that its equivalent or Thevenin would be 50 Ohm.
Is this method/model right? If it is than I will have the following issue:

The 50 Ohm parallel resistor will load the transducer and I will have more error right?
It seems to me for sending data this might not be problem but in this case the signal's voltage level is important.
What would you suggest in this case?


texts: Retrieving data recorded by an IoT sensor

texts:
If an IoT object records data (accelerometer, gyroscope, ...) in memory, what would be the smartest way to retrieve these data after, let's say, 2-3 days?

Store in JSON format on an SD Card?
Store in Memory then wire: USB?
Wireless: with BLE? XBee?

The idea is to retrieve the JSON data very easily from a computer without yet another hub, bridge, etc...


texts:
I'm not sure if I'm on the right exchange here but if not then let me know! Worth trying anyway.

I'm in the process of making a logic circuit to display a number, for example, 15711862 - it has to be that length anyway. I've had to make my own decoder and I'm stuck with the outputs and which gates to use, would I use an AND gate, OR gate, etc. as well as the wiring, how do I determine which letters would connect to which gate, to then connect to the pin of the 7-segment display (I'll add a picture below).

Like I said, I'm not sure if this is the right exchange to ask on and if it's not then let me know and I'll delete the question, but I'm quite confused right now! Any questions please ask below!


texts: How to go about finding the transfer function of a non-linear circuit?

texts:
Note: The concept of Transfer Function is only defined for linear time invariant systems. Nonlinear system models rather stick to time domain descriptions as nonlinear differential equations rather than frequency domain descriptions.

I have the following comparator circuit, which is a single-supply non-inverting Schmitt trigger with VTC offsetting.

\$V_{CC}\$ = 5V
\$V_{TH}\$ = 2.55V
\$V_{TH}\$ = 2.45V

\$R1\$ and \$R2\$ are used to provide a suitable bias for \$Vn\$.

\$V_{TH}\$ and \$_{VTL}\$ are determined according to the following equation, but I doubt if these are relevant when it comes to finding the transfer function.

The lower half of the circuit looks like a non-inverting amplifier where \$Vo\$ and \$Vi\$ are related by:

\$\frac {V_{o}}{V_{i}}\$ = \$1 + \frac {R4}{R3}\$

I don't quite understand what role R5 plays, and how it affects the above transfer function.

As @G36 states:

  R5 is a pull-up resistor because your comparator has an open collector
  type output. So it can only sink current ("output low") and this is
  why the open collector outputs require a pull-up resistor for the
  output to be able to properly “output high”

Original Question: ...provide a bode plot of the filter’s response, the transfer function of the comparator circuit and confirmation that the system is working.

EDIT:

As @LvW sates:

  By definition, a transfer function (as a output-to-input ratio) is
  defined for a linear circuit only (in fact for a circuit that can be
  linearized around a certain bias point ). The comparator is a strong
  non-linear circuit and has no quiescent point within a linear transfer
  region)

However, I am literally asked to provide the transfer function of the comparator circuit. Maybe I am missing something.


texts: How to calculate the cell constant for a flow-through conductivity cell?

texts: I need to design a flow-through cell but I don't know how to calculate the cell constant for such a cell. It needs to have 2 ring electrodes within an insulating tube (see pic below). One of the electrodes will have a voltage applied while the other will measure the current. I know that the cell constant for a parallel plate cell is L/A while the cell constant for a concentric cylinder cell is ln(r2/r1)/2(pi)L as explained in another forum post: How to calculate resistivity from this cell design?. I think it's difficult to calculate the cell constant for the flow-through case as all parts of the surfaces of the electrodes will not be the same distance apart. I would appreciate any help.


texts: Effect of base doping on early voltage,base transport factor and emitter injection efficiency?

texts:
According to me as base doping increases recombination will be less at base region so base transport factor and emitter injection efficiency will increase and as effective base width will decrease due to less doping at the base region so early voltage will decrease.
am I thinking right? No options is matching.


texts:
What does that "OVEN" sign mean?

This is from an audio compressor NTP 179-130 schematic.


texts: On which core on a multi core CPU is the ISR called?

texts:
When a multi core CPU is interrupted, the PC will be changed to point to the corresponding entry in the interrupt vector at the next instruction fetch.
On a CPU having more than one core (e.g. modern x86_64 or ARM). I do not understand, which core is used to serve the interrupt. Is it always one core, such as core 0, or is it configurable? Could someone give an example for a common architecture or possibly more examples for architectures where it is handled different?


texts: Alarm system built with Raspberry Pi + Sonoff RF bridge

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I am developing a personal project at the end of which I should be able to build a sort of homemade alarm system.
All this should be proof against voltage drops / failures, the whole circuit will be inside a "box" that I will print with a 3D printer. To be precise, the project foresees these components:

Raspberry Pi 0 with Domoticz (80 mA / 0.4 W)
Sonoff RF Bridge with Tasmota (30 ~ 200mA / 3.0 ~ 3.6V)
Buzzer
Step up circuit (optional)

I'm looking for a circuit that works as an "UPS / backup battery", which allows me to keep the system running for as long as possible (1h would be the top.)
A PC UPS (just to be clear) must be excluded as a solution, power banks apparently are not good as manufacturers advise against charging them and powering devices at the same time. I have tried circuits like this but they are very poor, the battery does not hold up and unfortunately the charge readings through the GPII are not realistic.


texts: Understanding digital filters, specifically their effects on time domain information, how to preserve the waveform of a signal being filtered?

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According to Steven W. Smith, in his book: The Scientist and Engineer's Guide to Digital Signal Processing, when designing a digital filter, "Good performance in the time domain results in poor performance in the frequency domain, and vice versa", and one needs to find a good trade-off for one's needs; and from what I understood, bad performance in the time domain means that the signal's waveform will be altered, meaning it will be somehow distorted after going through the filter. Additionally, the filter's step response is of the most importance when it comes to achieving good performance in the time domain. http://www.dspguide.com/CH14.PDF

So, after I designed two filters with matlab that aim to rid a signal from the electromagnetic interference (lowpass), and the DC component (highpass), and thinking that linear phase filters preserve the shape of the signal because all frequency components are shifted equally, so I went with the FIR filter option, and by using the function fircls1 that allows for defining the ripple levels in the passband and stopband, with the former being the concern for preserving the amplitude levels of the different frequency components, I thought I am getting the best possible "time domain" response, and the shape of the waveform in the time domain is as intact as could possibly be, moreover, I used an adequate number of points in the filter kernal to get the roll-off I desired, and after all that I came across that phrase in the first paragraph, this time I paid more attention and said let's have a look at the step response of the filter. Before I was solely concerned about the frequency response, ripple and stopband attenuation, etc.

I am attaching the step responses of my lowpass filter (left) and highpass (filter) right, and I would like to understand, what did I do wrong? I have looked at the filtered signal and it looks good, it is delayed considerably, and I know FIR filters requires longer execution time, but I am working on it offline, as in not in real-time, and I think I optimized the frequency response, as I mentioned, pretty much, so if that phrase means what I think it means, then the signal is not preserved and its waveform is some how distorted, and I cannot have that for the intended application, so could some one please help me make sense of these seemingly contradictory understandings.

Thank you very much!


texts: Connecting two transformers of equal rating to recharge a battery

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I have two transformers having capacity 6-0-6(volt) & 0.5amp each.
However, my battery requires 6v & 1amp. How can I connect two transformers to get my battery charged?


texts: How do surge protectors interact with existing circuit protection?

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I recently bought a power strip with a surge protector and it came with this warning.

  Do not install this product if there is not at least 10 meters (30
  feet) or more of wire between the electrical outlet and the electrical
  service panel.

This question mentions that protection devices in series can interfere with each other, such as the breaker/fuse in the service panel and the surge protection (MOV or otherwise).  How would a surge protector interact with the service panel protection?  Does it change based on the types of protection in each?  How would the length of wiring between the two affect it?


texts: Simulate modems and leased line over ethernet

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I am using a leased line with two modems on the edges. Those modems receive x.21 protocol from db25 connector on their back and transmit to each other over the leased line.
For some pairs of leased lines technology made easier to have a wireless point to point connection over wifi. So I am wondering if there is any kind of equipment that can emulate the modems over the Ethernet protocol.
I made a research online and there are many "serial server devices" as they call them...
Do you thing this kind of equipment is what I need?


texts: using ICL8038 waveform generator IC with arduino uno

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How do I use the ICL8038 waveform generator IC with arduino uno ? I have been trying to find apt resources but I find either the IC being used without the arduino uno or resources explaining how to use ad9850 IC ( a DDS module) with arduino. Now since I am not actually aware of how to interface the various IC's with arduino ( only used L293d motor driver before), it would be great if someone can explain me how to go about it.

Or is the interfacing with ICL8038 exactly same to that with ad9850 so I can just substitute my IC in place of it without making any changes ? (I would highly prefer using libraries, if any for the same).

Thank you.


texts: Why do smaller loads require larger inductors in buck regulators?

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The MC34063 Application Note lists the equation for calculating minimum inductor size as follows:

$$L_{min} = \frac{V_{in} - V_{sat} - V_{out}}{I_{pk}(switch)} t_{on}$$

But this implies that as Ipk(switch) (eg, the maximum switch current) decreases, the minimum inductor size increases. This is backed up by interactive calculators such as this one, which show the same effect.

Why is this the case, and does it imply that the regulator will only work as designed if running at peak load, and I thus need to increase the inductor size if I want to handle smaller loads?


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I'm trying to optimize a Wheatstone bridge with a strain gauge sensor and I'm considering all possible wire resistances. The circuit is shown in the following figure:

I don't understand the comment below the figure. I did not realize why we ignored Rwire1.