texts: Analyzing a rail design circuit that must have constant current?

texts:
I'm designing a circuit for the diagram below:

Where a mechanical source will move the rod. During the rod's change in position the direct current must be constant (\$ I_c \$) from \$ t_i \$ to \$ t_f \$. When I analyze the change, I observe that the current's path will increase, due to the two horizontal wires increasing in length, and if we considered the resistances of the R + R(rod) + R(wires), \$ R_t \$ will increase(the magnitude will depend on the length). In order to maintain constant current, the applied voltage must change, therefore, a constant current source(CCS) would be an ideal solution.

I also think that the inductance of the circuit) will increase(not sure).

At the start of the process, current is at it's maximum value and the circuit is in a steady state, as the rod begins to move and \$ R \$ & \$ L \$ increase,  will a constant current source(CCS) maintain \$ I_c \$ throughout the process? Also, how will the increased inductance affect the CCS/or the circuit( self inductance)?

I'm confused as how current can stay constant using a CCS while \$ R \$ & \$ L \$ increase, aside from the input power increasing for the higher voltage, what else would I need to consider?


texts: Rules for choosing power rating of a resistor

texts:
Let's say we're designing a system, and within it we have some resistor \$R\$ with a voltage difference \$V\$ across its terminals. Then it dissipates power \$P = V^2 / R \$.

Of course the resistor has a certain tolerance, so its value lies between \$R - \Delta R\$ and \$R + \Delta R\$.

The voltage has also a certain "tolerance" (maximum ripple over a regulated nominal voltage), so its value lies between \$V - \Delta V\$ and \$V + \Delta V\$.

When deciding what power rating to pick for the resistor, I believe it makes sense to put ourselves in the worst possible situation, so the highest possible dissipated power would be \$ P_{max} = (V + \Delta V)^2 / (R - \Delta R) \$.

If we assume we precisely know the values for \$ \Delta R\$ and \$ \Delta V\$, how much bigger than \$ P_{max}\$ should the resistor rating be? We already are in the worst possible scenario, should we give ourselves some more error-space anyway?

Also, is there a more robust method to compute power rating than the one I mentioned?


texts:
TLTR: My Deliyannis-type narrowband filter is oscillating when I apply GND to the input Vin. I was expecting to get almost zero volts, but I am actually getting a sine wave at almost 20KHz. I´m trying to figure out how to debug. I pretty sure something is wrong here.

I am currently working in an acoustic application for which I built an active filter with a unique opamp: narrow band type centered around 40KHz. I based my design on a cookbook called “Filter design in 30 seconds” from Texas Instruments, which can be found here. The basic scheme is this:

According to recipe, to get the filter centered on 40KHz, I need: R1=4K, R3=77K, R4=4K, R2=50, C1=C2=1nF. EDIT: The recipe is here:

EDIT: the teorical value of R2 is 210omhs, but in AC small signal simulation I saw that only achieved the peak at 30KHz, so I played with it until I got the current value of 50. I am unsure if this modification is recommended.

I soldered the circuit in one of those perfboard (I have yet to get a CNC machine to build PCBs).

Used non polarity capacitors and precision resistors (except for R3 where I soldered two 38K resistors in series).

I bought a few 741 ICs from different brand. I am feeding the circuit with bipolar +-5V, using rechargeable batteries.

I added two 100nF decoupling capacitors between -+VCC and GND.

I added potentiometer fed with -Vcc to cancel the offset. I am using a Hantek 6022 USB oscilloscope to graph the output and voltmeter to check continuity.

I haven’t used the waveform generator to test it with different frequency inputs, because I am on weekend and have to wait until Tuesday to go to laboratory to get access to generator.

Meanwhile I am testing the circuit by applying GND to the input Vin, and I get SINE noise at the output.

WHY IS THIS HAPPENING?

I checked different new ICs and all of them showed similar response.

I simulated the circuit with the theoretical values.

This is LTSPICE freq response for frequency sweep (gain) can be seen:

So I think in theory this should work.

Am I missing something?

EDIT: I simulated the circuit with a TL072 instead of 741 and found that the peak is reached at much higher freqnecy now (58KHz). So R2 needs to be adjusted to 150ohms now, to make it work.

EDIT: I simulated transitory response of the circuit, feeding the input with a 3 series combination of sine signals: 1KHz + 60Hz + 40KHz (amplitude=0.01). I see that 60Hz/1KHz noise is gone, so its actually filtering.

The purpose of this circuit is filter out any frequency other than 40Khz that comes from an ultrasonic microphone. When measured the microphone by itself with a stimulus signal of 40KHz, I can see noise at different frequencies: 60Hz, 4KHz, etc. I need something simple that allows me this. Have tried a lot of differents schemes in breadboard but none of them ever worked (I guess because of parasitic capacitances).

I am open to test a new filter if I figure out that this is an unappropiate selection. I think that I need a passing frequency of 40KHz with a 5KHz maximum bandwidth. About the Q factor, Im unsure and listen to suggestions.


texts: Does the ESP32's Long Range capability work with most smartphones?

texts:
Recently discovered an ESP32 can be its own access point (controlling or displaying data wirelessly through a web browser not connected to Internet). It also has long-range capability:
Long Range (LR)

Long Range (LR) mode is an Espressif-patented Wi-Fi mode which can achieve a one-kilometer line of sight range. It has better reception sensitivity, stronger anti-interference ability and longer transmission distance than the traditional 802.11B mode.

LR Compatibility

Since LR is Espressif unique Wi-Fi mode, only ESP32 devices can transmit and receive the LR data. In other words, the ESP32 device should NOT transmit the data in LR data rate if the connected device doesn’t support LR. The application can achieve this by configuring suitable Wi-Fi mode. If the negotiated mode supports LR, the ESP32 may transmit data in LR rate, otherwise, ESP32 will transmit all data in traditional Wi-Fi data rate.

https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-guides/wifi.html
Or what smartphones cannot receive LR data? Further on that page, "For LR enabled in ESP32 station and the mode is NOT LR only mode, it’s compatible with traditional 802.11 mode." So it appears like it will work...
I will probably test to see how slow the data sends for a 1/2 mile with line of sight and perhaps 1/4 mile or as far as possible in a woodland.
Side question, is this LR the same as LoRa?


texts: Can I only use a crystal earpiece for my crystal radio?

texts: I am building a crystal radio for my science fair project, and I am having some issues. For my earpiece, I am using a telephone receiver which may be the issue. For my ground, I am using a water spigot in my backyard which is completely metal. My diode is a germanium diode, which works. My coil is a bottle wrapped in enamel coated magnet wire that is between 18 and 22 gauge. Instead of sanding a section of the wire and using a wiper blade, I have taps with the enamel sanded off. I have tested all of my parts with a voltmeter, so the circuit isn't the issue. Any advice? What might I be doing wrong?


texts: Can SPI slave work with wrong clockphase setting?

texts:
In our prototype board, we have one 16-bit SPI based ADC [ad 7798] and an SPI based switch [adg1414].

Though some other guy has written the driver for it, and its also working. However when I analysed, I think the Clock and Phase settings are wrong.

I am attaching the timing diagrams for both slaves.
Please can anyone tell me, if the settings that I am assuming is right?

ckpl = HIGH

ckph = High

But In our driver code its written as

ckpl = HIGH

CKPH = LOW

Still it works.. Does any one have idea, how it's working?


texts: How do I find the voltage range for an unknown DC motor?

texts:
I have a small unmarked motor with a burned out speed controller board. I'm able to figure out that the motor is a DC motor because it has two wires coming out of it and there's a rectifier on the speed controller.

I want to find out what is the maximum voltage range for the motor, but it is proving difficult. The board appears to have a triac and perhaps a diac or some diode. There's no transformer so I guess it's probably operating at full 120V.  There's also a bunch of resistors and capacitors which is probably uses for PWM.

I chucked the motor on my drill press and spun the shaft at 570RPM or 59.69 radians/sec and got 16V output. The motor resistance is 39 ohms (was reading 50 before).

Is there a chart or formula for the voltage vs speed and or voltage vs torque for a DC motor?

FYI, the motor diameter is about 2 inches wide and the height of the motor is about 4 inches. The motor has a plastic worm gear attached to it and was used as a neck massager. My guess is that it needs to operate at high torque.

Here's a photo of the motor and a snap shot of the circuit:


texts: Which regulator to use from 12v to 4.2/2.5A and to 3.3V

texts:
I need help for my project: I am using an adapter operating from 12V and I need 2.5A at 4.2V for my SIM808. In the datasheet it says it has a 2A peak. I used an LM2596S and WEBENCH® Designer LM2596(online calculator) and I designed this circuit:

And now I need from the 4.2V an output of 3.3V for my ATmega328/P so I chose the LD1117 regulator and this is the circuit:

Can someone tell me if this is OK: do I need to change anything or choose another regulator? I don't have the parts to test the circuit.


texts: Should stereo speaker cables be elevated to avoid static electricity

texts: I am contemplating a new design for speaker cable stand-offs.  I am unable to find support, only opinions, about static electricity produced by carpet affecting AC current between amplifiers and speakers. Does it affect sound quality or does it endanger electronics used in speaker crossovers?


texts: Current in LED strip different when measured separately vs individually.

texts:
I've come across an interesting irregularity while designing a arduino LED controller. I wanted to measure the current draw of my LED strip to determine power requirements. I was curious as to which color was drawing the most power, and I noticed that when measuring the colors individually the current did not add up to the current measured when combined.

Here is the data I recorded, all measurements are in Amps.

12V Supply 1A    4A

G       0.88    0.97

R       0.53    0.56

B       0.68    0.76

GR      1.2     1.35

GB      1.24    1.44

RB      1.03    1.16

RGB     1.48    1.75

G+R+B   2.09    2.29

The single characters R G B are the individual colors measured, the double characters are the combination of two colors measured together, and the RGB is the measurement of all three colors at the same time.

There is a substantial difference between the individual measurement for R+G+B and RGB. Is this some characteristic of RGB LED?

Also, I tested the current with two power supplies, one is rated for 1A, but is showing a draw of 1.48A. Is is more likely that the supply is underrated, or is it more likely that it is broken?


texts:
I have a 12F683 micro and this is my first program using the new MPLAB with XC8 compiler.

I have configured Timer1 to trigger about every ms. For now I would need an LED to flash on and off but need to do this with an IF statement because later I will add other actions in there. Here is the interrupt code:

#define PWM GPIObits.GP5

void interrupt High_Priority_Interrupt(void) {
  if (CCP1IF) {
      if (PWM) {
          PWM = 0; //NEVER excuted
      }
      else {
          PWM = 1; //ALWAYS executed
      }
      CCP1IF = 0;
  }
}

For some reason the output is never set to 1. If I replace the whole code with PWM^=1; it works like a charm. But I need to do it with the if statement. What am I doing wrong?


texts: How to Sycnhronize STM32F4 Clock with PC Clock

texts:
I'm using  3 STM32F401RE to synchronize their clocks. My desired accuracy is of 1ms and even lesser like 0.1ms. This device is connected to PC via USB port.

Question 1 :

So I would like to know if I can synchronize each one of them with the PC Clock then they would be synchronized?

Question 2 :

Right now I am using RTC and the clock start counting since power up.
Can I for example configure it to start counting with a command (for example with a python script activate it?)


texts: Why opamps honor fourier series but not other series, for exmaple, power series?

texts:
A periodic function can be represented as an infinite sum in many bases. I know at least one other series apart from fourier:

Power series:
\$\sin(t) = \sum\limits_{k=0}^{\infty} \frac{(-1)^kt^{2k}}{(2k)!}\$

Why do linear circuits respond like fourier series and not like a power series?

Is it possible to have circuits like opamps that respond to polynomial functions in an useful manner? For example:
input: \$t^2 + 5t^3+t^{10}+t^{150}\$
low pass filter output:  \$t^2+5t^3\$
high pass filter output:  \$t^{150}\$


texts:
I'm working on a waveform generator for which I'm using the DDS AD9833 chip to generate sine signals and triangular signals. I'm trying to amplify these waves since the AD9833 output is 600mVpp and I need waves up to 10 Vpp. The problem is to amplify these waves without the insertion of harmonics; to do this, I wanted to use the INA129 instrumentation amplifier but, by using a common potentiometer, everything went well, but the gain has to be controlled by a microcontroller, so I wanted to use the TPL0102 digital potentiometer.

The potentiometer works well on its own, but when I connect it as the resistance gain of the INA129, the output is always saturated, even when I set the minimum gain, which is 1.

Details:

INA129 powered with +/- 11V
INA 129 V- input connected to AGND
AD9833's output connected to high pass filter to remoce DC voltage, then, it is connected to the V+ pin of the INA129
TPL0102 Vss pin connected to DGND
AGND and DGND connected through a 1MΩ resistor
TPL0102 controlled through I2C with Atmega 328 microcontroller

How can I correct this problem?


texts:
I'm trying to design a product that have the following features for mass production, and I'm asking from your experience, how to get the lowest price for the components, quality of the chips in terms of stability due to temperature (it must work in temps over 40°C)

I would like to control a 34-digit 7-segment display. Which way should I go? Just connect lots of switch transistors, and give them one data line each? Or are there easier ways, such as dedicated chips with low price?

There are 6 groups of 4 digits
8 digits for the date
2 digits for a counter

I have been away from the Electronics industry since 2008, and I mostly need help to refresh my memory.

I'm keeping in the design that I also need to play mp3 files, read RF remote control, RTC,..etc. So I may run out of the pins because of controlling 34 digits using TDM.


texts:
I am looking at doing some phase-shift lidar experimentation.
To get good accuracy, all the papers suggest that I need to be modulating the laser diode sinusoidally at ~200MHZ.
I am finding virtually no laser diodes that have this sort of speed listed as a modulation capability.
Does anyone know what the main drawbacks of driving a standard (cheap/plentiful) laser diode at that sort of speed would be?
I think from memory that a DVD-R laser is modulated in the realm of 10MHZ, so I was thinking of starting with a laser like that, provided I can find a new one not sourced from a DVD Drive.

Thanks.


texts: Calculating current in the inverting op-amp

texts:
Okay, so I know the "correct" way to calculate current.

Let's first analyze the circuit:

KVL left side:

\$ -V_{in} + i_1 \cdot R_{in} + 0 = 0 \$

\$ V_{in} = i_1 \cdot R_{in} \$

KVL right side:

\$V_{out} = -R_f \cdot i_f \$

\$ i_1 = i_f = i \$

Gain is:

\$ \frac{V_{out}}{V_{in}} = \frac{-R_f \cdot i}{i \cdot R_1}  = \frac{-R_f}{R_{in}}  \$

\$ V_{out} = -18.6 V \$

\$ i = \frac{V_{out}}{-16k} =  1.1625 mA \$

How come, applying reasoning that since there's only one voltage supply, the current through \$R_{in}\$ and \$R_f\$ is just voltage divided by equivalent resistance?

\$R_{in}\$ and \$R_f\$ are in series

\$ i = \frac{V_{in}}{R_{in} + R_f} = \frac{7}{6k + 16k} = 0.318 mA\$

What's wrong with this reasoning? Why is the current not correct?


texts: I'm using an lm3900 quad op amp to run a smart phone audio signal to a bs170 MOSFET. When I use the inverting configuration it works well, but when I use the same resistor values (1k and 10k) with the non inverting configuration it either doesn't work or the output is too low. Is there an impedance issue that I'm not aware of between these 2 configurations or does it seem like a faulty chip? Any help would be appreciated.


texts: "Antenna matching networks for dummies"?

texts:
I'm working on a project where I'm building a custom NFC antenna that will be connected to a PN532 NFC controller. The antenna has already been designed (for 13.56 MHz) and built, the PN532 is also here, what's missing is the matching network between transceiver and antenna.

Problem now is, the ham operator that built the antenna for me can't continue with the project and I'm left with an antenna but no matching network. I don't have access to a network analyzer, and only quite basic knowledge about RF and antennas. However, I do have sufficient electronics knowledge to build a given circuit, and I know how to operate an oscilloscope and a signal generator.

The question now is: with these tools at hand, can I somehow fudge together a working matching network? Or should I rather find another ham operator? ;-)

Best, Florian


texts: Using motor circuit breaker buttons to start/stop motor

texts:
I want to add some protection to an ac 3/4 hp motor. I did some research and found that I could use one of these motor circuit breakers:

My question is, if I use one of these, can I use the on/off buttons it has to start/stop the motor?

A few guys told me I could, but others tell me I should add a contactor with a couple of no/nc push buttons. But if I need to add a contactor, shouldn't I be using a thermal relay instead of the motor circuit breaker?


texts: High Side switching Raspberry PI with 3904 and 3906 transistors

texts:
I'm using an example from this post which indicates that I should be able to use a pair of NPN 3904 and PNP 3906 transistors to provide high side voltage to a load.  The specific schematic I followed from that example is:

The load, in fact, is a low power regulator (LM317) driving a couple of amplifiers downstream.

Instead of an Arduino, I'm using a Raspberry PI GIPO (3.3V) for switching.  The resistor values I have are as follows:

R1: 2.2K
R2: 2.2K
R3: 1K

Source voltage (indicated on Diagram) is actually 19 volts and the downstream LOAD draws just under 100 mA.  The regulator outputs 11 volts and drives a zener diode rail splitter to provide about +/- 7.5 volts with a virtual ground (for the amplifier circuit).

The problem I have is that when the GPIO pin is turned OFF, I still get about 7.5 volts output from the 3906 emitter so I'm not truly shutting off the voltage to the regulator.

Can anybody tell me if my resistor values look reasonable and maybe why it would still be emitting that voltage from the 3906 when the GPIO is OFF?

EDIT:

Updated image with transistor pin labels and resistor values:


texts: What’s the correct way to disconnect this circuit board connector?

texts: Electronics noob here. What’s the correct way to unplug this cable from the circuit board? Don’t want to break it! Thanks.


texts: Are we close to a pure DC (or hybrid) household?

texts:
This is a philosophical question. Over the last few years, many of the household devices, particularly those that are more mobile and etc are DC devices. Are we at some point where a DC household may become a possibility and Edisons dream might come true??

The array of DC devices

Internet stuff - routers, modems
Most complex computer electronics - Desktops, laptops, NAS, phones, tablets, gaming consoles, etc
Lighting - LED
More that I cant think of or perhaps know which also convert AC -> DC

Problems with AC

Each device needs its own power supply ( AC-> DC power brick). This is
a) Unpleasant to look at and deal with, and
b) a costly point of failure.
Each power brick may or may not be optimized, as far as power conversion goes.

Alternative - A central (or a few ) high capacity power adapter which converts the AC into a DC power grid for the house which can then be tapped directly by the various devices. This eliminates the need for the power brick, and hopefully the central power adapter is of state of the art, and can be upgraded seperately from the devices, as needed.

Need standardization of:

Device voltage. Currently devices use 5/ 9 / 12 or others I may not be aware of, for this idea to work they need to work with one particular one, unless switching between voltages is cheap enough, or multiple DC lines are provided.
Power socket input. Each device appears to have its own input socket type, this should standardize if the power supply cable should be comoditized, perhaps USB - C will play a part here.


texts: On the Murata OKR-T/10, the data sheet specifies a 49kohm pulldown resistor but I've seen people using a 1k. Is there a more correct value or does anything 1k or above work just as well?


texts: LED Circuit design (4 switches, 1 potentiometer)

texts:
I need to design an LED circuit that acts as a switching system. It must meet these specifications.

Case 1(Press Button 1): LED 1 ON, LED 2 ON, LED 3 OFF
Case 2(Press Button 2): LED 1 ON, LED 2 OFF, LED 3 OFF
Case 3(Press Button 3): LED 1 OFF, LED 2 OFF, LED 3 ON (and controlled by a Potentiometer)
Case 4(Press Button 4): LED 1 OFF, LED 2 OFF, LED 3 OFF

Each time a switch is pressed (or changes state), the circuit should behave according to one of the four cases. In case 3, LED 3 is controlled by both the switch and the potentiometer. LED 3 is turned ON when a switch is pressed and the Potentiometer is used to adjust the brightness. We can use no more than 4 switches in total and the circuit may be designed with only resistors, LEDs and switches. I've been stuck for some time on this and any help would be appreciated.

Edit 1: These are momentary tactile switches (or buttons). Of the 4 buttons that can be used, each time a button is depressed it exhibits 1 of the 4 cases.

Edit 2: The voltage is being supplied by a function generator but this can be changed to an alternative method if needed.
The type of diodes are pictured below:

Here is a truth table that describes the switching system:

Ultimately, this is what I created. Case 4 did not have to be included as this state exists with no action by the user.


texts: Switching DC with MOSFET: p-Channel or n-Channel; Low Side Load or High Side Load?

texts:
I think, it is time I understand working principle of MOSFET transistors...

Suppose that;

I want to switch voltage on a resistive load by a MOSFET transistor.
Any control signal between -500V and +500V can be easily generated.
The transistor models in the picture are not important, they can be of any other appropriate model as well.

Question #1
Which of the driving techniques are feasible? I mean, which of these four circuits would work with correctly applied control signals?

Question #2
What is the range of the voltage level of the control signals (CS1, CS2, CS3, CS4) that loads and unloads the resistor? (I understand that exact boundaries of on and off states must be calculated individually. But I'm asking for approximate values to understand the working principle. Please give statements like "In circuit (2), the transistor turns on when CS2 is below 397V and turns off when above 397V.".)


texts:
Let's say we have vanilla BC846 (80V), BC847 (50V), BC848 (30V) transistors from the same company, each with 3 bins A, B, C where C supposed to have to highest hfe.

Is that correct, that BC846C should be the fastest, and for example BC847C or BC846B are slower (i.e. have higher capacitances and slower switch-on/off speed)?


texts: bootstrap vs dual power supply in MOSFET gate driver

texts:
I want to ask if my following understanding is correct or not regarding the switching circuits of power mosfet gate drivers in H-bridge where both high and low side mosfets are N-channel.
If we have single power supply then we will need to use some type of bootstrapping technique or bootstrap capacitor to drive the high-side mosfet.
If we have dual isolated power supply then we can drive both high and low sides mosfets using dual isolated power supply without using any bootstrapping technique.


texts: Any simple power supply designs for a 24VAC transforrmer?

texts: I'm a beginner in Electronics Engineering. Any suggestions on simple power supplies with PCB designs which are run by a 24VAC transformer? Thanks!


texts: So I am new to electronics, but I'm trying to figure out if I can boost current from 10mA to 100mA. I researched and found a current booster called the lmc6001 that boosts from 10mA to 30, which is not what I need. Would I need a booster for this or is it possible with some components? It is also worth noting that I boosted my voltage with a step up voltage booster to 2.35v. So, I need something that is able to boost only current, is this possible?


texts: Does the NOT gate count towards the depth of a circuit?

texts:
So I was going through some problems for a course that I am taking this semester and I came upon a problem that seemed to imply something. Let me first say that I am not looking for the solution to this problem, but rather it spawned a question that has me in the need for some clarification.

The problem was to write a two-level logic version of the following equation using AND, OR, and NOT gates only.

F = A + (B*\$\bar C\$)

As far as I can tell - that's not possible unless the NOT gate does not count towards the depth. So this raised the question - does a NOT gate not count towards the depth of a circuit?

The definition I typically see is that the depth of a Boolean circuit is the largest number of gates between a given input and output. The textbook for my course also uses this definition. So is this the impossible task? Or am I just not thinking cleverly enough?

Thanks for any insight!


texts: Develop a system to differentiate laser pointers from the ambient light based on the information collected by two arrays of digital FPA detectors

texts:
I would like to develop a system to differentiate laser pointers from
the ambient light  based on the information collected by two arrays of digital FPA detectors embedded inside the cavity of a commercial airliner windows including the cockpit.
   The principles of operation of the digital FPAs are described in this article,   Kelly, M. W. and Blackwell, M. H., “Digital-pixel FPAs enhance infrared imaging capabilities,” Laser Focus World 49(1), 90 (2013).

The first array of FPA detectors measures the HSV color saturation by converting 24 bit RGB color depths.  The second array of FPA detectors measures the spectral bandwidth after the incoming light wavefront is projected onto a diffraction grating.

Saturation is how pure the color is from spectral point of view.
For example, a laser has a very narrow spectrum, which implies high saturation.

If a laser has high saturation, is the converse true?
In other words , If I measure RGB and convert to HSV,
Does high saturation imply that it must originate from a coherent laser source?
the answer to the previous question is not necessarily a laser.
But it's hard to have a saturated color with a wide spectrum,
since the wider it is, the harder it is to have a high response in only one component.

Is it feasible to develop such a system for differentiating laser pointers from
the ambient light? If so, what might be the design parameters be for it?


texts: Check if electrical current exists in high voltage

texts:
I'm thinking about a simple home automation project, containing a Rasberry Pi, a Sainsmart SPDT Relay, I would like to switch the state of a ordinary bulb (ON , OFF) using both the relay and the old switch, so here if I'm in a remote area away from the bulb, I cannot get the bulb state exactly, is there any low cost way to get if the current exist or not?

I have found this current sensor but it is not the solution, it is not cheap, compared to the relays.


texts:
I have a grid tie inverter powered by a 24V battery connected to a circuit that is on a Generator. The grid tie inverter syncs well and outputs 655 – 800W according to the Load. As the load changes the Generator  supply rises or falls accordingly.
There is a 30A charger in the design to top up the battery. The charger can be switched in or out.
An anomaly has me confused as follows:
When the charger is On (and the gauge shows 30A), the Load on the Generator should rise by 700W but does not.
What am I missing please?


texts:
I am starting in embedded software programming using a RTOS and, since I am already a developer for desktop applications, I kept wondering what is it like to model embedded software using UML diagrams, like Activity Diagrams, Sequence Diagrams, Use Cases, etc.

Is embedded software designed using UML, the same way desktop applications do?
Is it the best option or is there a better one?
Can I have some examples?

Is there a specific tool that does this?


texts: How do safely discharge Li-Ion batteries to check full capacity

texts: I regularly have to test old phone batteries in my mobile phone refurbishment business. I need a safe solution to discharge 3.6V batteries. When I buy batteries they come from old stock so I need to discharge them them check how many mAh it still takes. This is difficult and time consuming. In the past I've used a 3.6V light bulb but the process takes forever. I was considering a 3.6V motor but that would probably get warm and break pretty fast. Any suggestion? I know I'm not supposed to completely discharge Li-Ion batteries but these are phone batteries with built-in protection so it should be fine.


texts: How can i replace a electret mic input with headphone output as input

texts:
I'm using a SIM800L GSM module for my project. In this module there is a electret mic input pin but I want to give audio to this module from headphone output from a mobile (There is no line in pin available). If I directly input from headphone out the module make too much noise.
Now what is the best idea to implement this?

Here is module instruction diagram:


texts: Measuring Power to Load Using Oscilloscope

texts:
I have a small three-phase motor being mechanically driven to act as a generator. My goal is to measure power delivered to a load, which in my case would simply be a 4 ohm resistor, using an oscilloscope. I've seen others with the same goal have measured the voltage drop over a shunt resistor to measure the current and then measured voltage across their load in order to use P=VI.

Why is that extra resistor used to measure current? If I have a known resistance and I then measure voltage across it, can I not use P=V^2/R to get power delivered to load? I know it is probably a simple question but any help would be appreciated.


texts: Omp Amp Design for shifting a voltage range

texts: My DAC can only output voltages between 0-5 V and I want to linearly shift the range to -2.5 to 2.5 V. For example, a 2.5 input would (ideally) lead to a zero volt output. Likewise, a 5 V input would lead to a 2.5 V output. What circuit would be ideal for this? Thanks in advance!


texts: How does a PCIe device know that its 4K configuration space is mapped to memory address?

texts:
PCIe spec defines 3 address spaces:

Memory
IO
Configuration

I can configure the BAR register to specify the memory address range that a PCIe device will claim.
How does a PCIe device know that its configuration space can be accessed through the memory address as well, i.e. MMCFG?
Or in other words, how to enable MMCFG for a PCIe device and tell the device where its configuration space is mapped to?


texts: Can a 6 volt relay coil bear more than 6 volt?

texts: I am using a 6 volt relay in H-bridge and controlling it with a 9 volt battery linked with a 2n2222 transistor (which is used as a switch and getting 5 volts via a low value  base resistor to get into the saturation region (fully on mode)). Once transistor turns on then a little voltage drop is appears at CE of transistor. Around 8 volt is fed into 6 volt relay coil. I am feeding 8V into the relay coil, why it is not burning or getting coil damage? Would low duty cycle operation be allowable? Could coil heating soften plastic parts of the relay? Should I employ a series resistor to be safe?


texts: Techniques for probing circuits that would normaly be covered by a heatsink

texts:
I have a circuit board I have to probe and measure to first debug and then later on verify performance. The circuit board contains a power amplifier that requires a heatsink in order to keep the temperature in check. This heatsink is incorporated in the shield of this power amplifier. However, I now need to probe around this system (checking bias currents and voltages, etc.). For obvious reasons this is not possible when the shield is fitted.

On larger packages I would get small stick-on heatsinks on the package to keep them cool while measuring. In this case I am dealing with a 4x4 mm QFN, and I cannot find any heatsinks quite that small. When measuring other parts of the circuit I can just put a bigger heatsink on, but the smallest heatsink I have is 6x6 mm, and that already covers a lot of bias resistors around the package.

What are good techniques to cool this component? Right now I am thinking of just sticking down copper blocks that I saw to size, but I wonder if there are more elegant tricks to this.

Ofcourse, I could try connecting tiny wires to the points I want to measure and then install the heatsink, but I would prefer a solution that does not require me to dissasemble, solder on a wire, and reassemble every time I want to measure something.


texts: SMPS Buck Converter Output Current Problem

texts:
I'm trying to build a 12V-to-5V DC-DC Buck converter using the LM2576 IC.

This is the circuit recommended in the datasheet:

I've built it (without the optional ouput ripple filter) in a perfboard.

Now I'm doing some tests in it, and it works well when I draw little current from the output. For example, with a 40 Ohm test load, y get an output of 5V and 0.125 Amps, as expected.

But as I test the converter with smaller resistors as loads (20 ohm, 10 ohm, 5 ohm, etc) the output voltage drops from 5V to 4V, 3V, etc., till eventually I get an output voltage of 0V and no current! And also, as the output voltage drops, I start noticing a high frequency sound coming from the converter (from the inductor, I believe).

I don't really have a clue about what might causing this problem. The datasheet of the LM2576 IC says the IC can put up with up to 3 Amps.

Could it be a inductor problem? I've read that the inductor might saturate with high current. But I think that in case of saturation, I would have a ripple problem, not a current problem, am I right?

So, what could be the problem?


texts: Using a DC-DC boost converter to run a stepper motror through a chopper drive

texts:
I am attempting to use a DC-DC boost converter to step up a 7.2V battery to 24V to run a stepper motor, however, I am unsuccessful in doing so.

I have tested my stepper using a DC power supply set at 24V, and it runs beautifully. Yet the moment that I hook up the converter, my motor begins to skip steps left and right,even at very low speeds. I am watching the voltage output from my converter the whole time, and the needle never budges from 24V. I have the recommended electrolytic caps on both of them.

I did notice that the motor ran better (skipped less steps) when I put small ceramic decoupling caps across the motor driver. I suspect that interfering frequencies from the boost converter output and the chopper drive are causing my problems.

The components are an A4988 stepper driver on the breakout board from Pololu set at its max current of 2A and a LM2588 boost converter from TI, using a schematic designed by TI's Webbench software.


texts:
The circuit consists of an NRF52840 MCU controlling the power to a CO2 sensor. The output from the sensor goes to a buffer which then feeds it back to an analog input.
The MCU operates at 3.3V while all the other elements are connected directly to a battery at 3.6V.
In terms of functionality, the system is working. When the MCU's pin is set to low (sensor ON state), the FET conducts, powering the sensor and the buffer and the the analog input has the CO2 measurement signal. When the pin is set to high (OFF state), the sensor is off and there is nothing at the analog output.
The problem is that at the OFF state, there is about 1V at the transistor's drain, when it should be completely off.I can't measure right now since I don't have the parts yet, but any help will be appreciated.


texts:
I designed a constant current buck DC-DC super-cap charger with the NCP3420 as a dual MOSFET driver. The current is hysteresis controlled and the disable and PWM lines are pulled low on power-up.

The circuit is working, but sometimes the driver fails during power-up with the controls pulled low, shorting out the 12V supply. What would cause this?

Link to NCP3420 Datasheet: https://www.onsemi.com/pub/Collateral/NCP3420-D.PDF

X1-1 and X1-2 are 12V inputs from my lab supply

X2-1 and X2-2 are connected to a super-capacitor

The 100n cap is a ceramic 50V

The input is also decoupled by 4 parallel 100n ceramics + 6800µ electrolytic

The diode is a schottky rated 80V, 500mA


texts: STM32F4 Nucleo - how to set pins low while uploading firmware?

texts:
I am busy trying to write some firmware for a system with a whole lot of digitally controlled hydraulic components, and it's a complex system so there is a lot of tweaking of the algorithm and debugging.

I having a problem in that whenever I compile code and upload it to the board via ST-Link, all the pins float/go high, which causes the whole system to go haywire (pumps turning on and valves opening - erratically), and I am also wasting a lot of water/other fluids.

I am using the System Workbenh IDE. Is there any setting I can flick to set all pins low during firmware upload?

I'm sick of forgetting to flick the power switch to all of the hydraulics before uploading.


texts: In this picture write all their equivalent Body in mechanical system and electrical circuit for a piezoelectric. What is equivalent of C0 in mechanical system?


texts: Why is CMRR infinite for coupled differential amplifiers when Re increases ?? I cant seem to understand what happens on making Re infinite.


texts:
I want to interface with two I2C slaves operating in different voltages. By searching around for possible solutions, I stumbled upon this AN by NXP. Although I understood everything and makes perfect sense, I am still a little skeptic about it for possible pitfalls since I don't want to ruin the entire design due to I2C interface failure.
The slaves operate in 1.8V and 3.3V respectively, the I2C clock line should operate in 400 kHz (both devices support that) and the master has configurable I/O levels, so I can connect it on either side. I am thinking of using either a single SSM6N7002KFU or two 2N7002NXAKR for the job.
As far as I can see, it should work fine. Am I missing anything?
There is, also, the option to connect the ICs separately, so each one has its own dedicated bus and voltage levels, but I would like to avoid that for obvious reasons (layout + firmware complexity).


texts:
I have a memory like this:

reg [7:0] memory [1023:0]

How should I use a for-loop to reset the memory in verilog? Please give me the code. For example if reset==0 then how can I reset it?


texts: Calculate the differential common-mode gain of instrumentation amplifier

texts:
I am trying to design an instrumentation amplifier with a CMRR of 50 dB.

I have to target a differential gain of 60 dB.

$$ CMRR(dB) = 50 dB = 20log(\frac{A_{vd1}}{A_{cm1}})+ 20log(\frac{A_{vd2}}{A_{cm2}})$$

Where $$A_{cm1} = 1$$

$$ CMRR(dB) = 50 dB = 20log(1+2\frac{R_1}{R_g})+ 20log(\frac{R_3}{R_2}) - 20log(A_{cm2})$$.

$$ A_{v} = 60 dB =  20log(1+2\frac{R_1}{R_g})+ 20log(\frac{R_3}{R_2})$$

I arbitrarily assigned the gain for each stage, e.g., Av1 and Av2 are 40 and 20 dB respectively. This gave resistors of the following

$$R_1 = 100 k\Omega$$
$$R_g = 2.5 k\Omega$$
$$R_2 = 1 k\Omega$$
$$R_3 = 10 k\Omega$$

Resulting in a $$Acm2 = 0.316$$

If I assume a 5% tolerance for the resistor values, what would be the differential and common-mode gain? And what would be the worst cast CMRR? I am very confused on how to approach this. Thank you for any tips/suggestions.


texts: Trace clearance for 500V insulation test

texts:
Part of my job is to measure insulation resistance of cables using a tester, such as a Fluke 1587. We measure insulation resistance at 500 VDC. We have to measure insulation resistance pin to pin and some of the cables have 56 pins, which gives us 1540 combinations! We currently use a breakout box and have to move the probes manually one by one through all the combinations. We have a couple boxes we made where we use switches to tie the pins to one of two channels which allows us to hold the meter at 500V in two test points while we switch through each pin, checking one channel against the other. This significantly reduces the amount of time to check cables, but producing them is a pain. Currently they are made by hand soldering wires and daisy chaining the switches together. I would like to replace this with a PCB with switches mounted on the board.
My question is in regards to the trace clearance I would need to not effect the insulation resistance reading. Most of the information I could gather from online searches for high voltage trace clearance reference to IPC standards which are needed for safety. Since my application is not safety related nor will cause damage to any equipment (cable is disconnected on both ends when testing), I don't need to worry about injury or component failure. I am assuming the solder mask can provide a decent amount of insulation resistance for this purpose, but I want to make sure before I send out a design that would cause false low insulation resistance reading because of the traces being to close. What would be the minimum clearance I could use and not have an effect on our readings? I am trying to keep size down since we need to ship these things around to different sites on top of all our other tools and equipment.
Thanks.
Edit:
Added pictures of project. The schematic shows enough detail of what I am building as well as a theory of operation for the test kit. The portion not shown is just a repetition of switches and test points.
The PCB has a minimum trace clearance rule set to 11 mils. It is the largest I can make it and still be able to route between the pins of the connector. Layout it nowhere near complete, but I figured I better find out the answer to my question before I go too far.
Snapshot of the 3d model provides a clearer picture of what it is I am working towards.


texts: Can someone help me design an expandeable led strip system

texts:
I want to make an open source expandable system to control WS2812B 5m 60 ip30 (or higher pixel density) led strips. Im going to be using about 40 meters which is about 2400 leds in total but all the controllers I can find have a max pixel count of 2048. Is their a way I could have two controllers take 2 strips each and somehow link them together so its controlled as one strip? Could I reliably use and API to do this or is their some better hardware i could use? Any help would be greatly appreciated.
LED strips
LED controllers


texts: In Gauss's law integral form, when to use Q_free, when to use Q_enclosed

texts:
The question was due to my frustration of text books using Permittivity of free air in Maxwell's Equations while explaining situations in all mediums. Yet they don't even bother mentioning why that's the case. This question is to confirm my understanding of Gauss's law in a dielectric material.

For example, an imaginary enclosed surface within a dielectric material, and we put some free charges into the space within the imaginary enclosed surface. If we take surface integral of D or E,
I believe the following two equations are equivalent:

[1] surface integral of D (calculated using free charges only) = all of the free charges you put in the enclosed surface.

The dielectric material doesn't really matter in this case. My understanding is that, D is almost a geometrical distribution of the free charges "projected" onto the imaginary surface, so this equation is almost about geometry, not physics. That's why permittivity isn't even involved.

[2] surface integral of E (measured right at the imaginary surface) = ALL of the charges in the enclosed surface, the free ones you put in there, and the dipoles induced in the material. Divided by vacuum permittivity.

Most dipoles are fully enclosed, they don't contribute to total charges. The dipoles that are cut in half at the imaginary surface contribute to the total charges. And those half dipoles carries the opposite charges of your free charges, so the half dipoles weakens the E. E is the result of free charges and the material's resistance of the free charges' field.

P.S. I haven't think it thru yet, but I believe the permittivity and permeability in Maxwell's last equation should all be relative, not free air.


texts: Waveform at the negative terminal of an OPAMP

texts:
I am trying to sketch the negative waveform of an OPAMP over here.

I am not sure how to proceed with this as I have usually seen OPAMP with dual power supply. But this one have +9V and ground.

My thinking to go about this problem :

The voltage level at the positive terminal of OPAMP is +4.5V
So, the voltage at Vout would also be +4.5V due to the 100k between between +ve and Vout
As +4.5V is present at Vout, the 10nF capacitor which is connected to ground gets charged.
As it gets charged to 4.5V, the output will will become 0V?
So, the output will go to 0V?

Please tell me how to proceed from this?


texts:
I apologize but I know jack about this stuff and this is probably a simple question I can’t seem to figure out.  I have 12 volt power supply, a 3 wire unipolar Honeywell SRC3-A1 4.5-24 volt hall sensor but only puts out 380-400mv on the supply line and I need it to power a crydom DC60S3 solid state relay that requires min of 3.5-32 volt.  How do I bring up the voltage from .4v to say 5v?  Simplest option preferred for a electricical dummy.

Hall Sensor: https://sensing.honeywell.com/SR3C-A1-value-added-magnetic-sensors

Relay:  http://www.crydom.com/en/products/catalog/dc60-series-dc-panel-mount.pdf


texts:
I struggle to remove the FPC from this connector. I could not find anything like that in this digi list, and I am afraid to damage it.

The connector is 15mm wide and I have found it in an Olympus PEN camera.
 Most of the connectors in this camera are quite regular and can be easily opened by pushing a plastic part. A few are like this. This one connects the back LCD, which I am attempting to replace.

EDIT: I tried the likely solutions (trying to flap the top or the bottom half), pulling (gently) on the FPC, but without success. I don't want to risk breaking or damaging the connector by applying too much force; I hope someone will recognize this particular model / type of the connector.


texts: Signal Change When Oscilloscope is Added

texts:
Thinking this should be obvious, but having trouble identifying a fix: I use multiple channels on an NI PXI DAQ card for RSE voltage measurements. I need to verify the voltage readings returned by the DAQ card with an oscilloscope. Without the DAQ card input running, the Scope shows similar data. If I run the DAQ acquisition at the same time as the Scope, i see periodic blips that happen at the same rate as the card multiplexes between its input channels.

A) Why would I see these blips on the scope?
B) What can I do to eliminate them?

Details:
The AI connections and Scope probe connections are made at the same location.
A higher DC Coupling impedence results in a higher amplitude of the blips.
Switching to AC coupling has no effect.
The blips are seen even if the circuit is not being driven by a signal.

Thank you!


texts: When I write data to a BLE Characteristic (FFE1) to send data over bluetooth, is the data encrypted?

texts:
I have a very simple circuit which includes a HM-10 that exposes a CC2541 Bluetooth device.

simulate this circuit – Schematic created using CircuitLab

It's basically just hooked up to power it off the Arduino Nano and then I have a voltage divider on the HM-10 Rx since it is 3.3V.
There are no problems there. It works and I can send data and receive data.

I'm running some iOS code that does not bond itself to the device, but instead lets the user tap a button and send data via the FFE1 characteristic.

The data is sent using the CoreBluetooth writeValue function of the CBPeriperhal class. It is sent as a stream of bytes.

Questions

is the data (sent from iOS device to Arduino via Bluetooth) automatically encrypted via BLE?
Can you offer any way to prove one way or another if the data is
encrypted?  Some kind of sniffing software to test with?
Is there some property I need to set on the CBPeripheral to encrypt
the data?
Is data only automatically encrypted after bonding the
devices?

Extras

Here's the very basic Arduino code that works great and displays the bytes sent over Bluetooth (from my iPad running my iOS code).

#include <SoftwareSerial.h>

SoftwareSerial BT_Serial(8,9); // RX, TX

bool bytesWereRead = false;
char c = ' ';
boolean NL = true;

void setup() {
  Serial.begin(9600);
  Serial.println("Enter AT commands:");
  BT_Serial.begin(9600);

}

void loop()
{
  if (BT_Serial.available()) {
    bytesWereRead = true;
    int bytesRead = Serial.write(BT_Serial.read());
  }

  if (Serial.available()) {
    c = Serial.read();
    if (c!=10 & c!=13){
      BT_Serial.write(c);
    }
    if (NL) {Serial.print("\r\n"); NL = false;}
    Serial.write(c);
    if (c==10){NL = true;}
  }
}


texts: Using a Laplace transform to figure something out in a DC circuit

texts: When would you use a Laplace transform to figure something out about a circuit? Does the circuit have to have capacitors?


texts: S8050 BJT is rated for 700 mA but gets extremely hot when powering a 12 volt 700 mA PC fan

texts:
I'm working on a project that requires a DC motor, so I salvaged a PC fan from an old computer. The model is AVC DS08025R12U. It needs 12 volts for maximum speed and is rated to draw 700 milliamps. I'm planning to power the motor with a 12 volt 3 amp power brick, which will also help power an Arduino microcontroller and a breadboard power supply module. I'm planning on changing the speed of the motor with a PWM signal from the Arduino, but just to test, I set up the simple circuit that can be found on the sparkFun website. Instead of making a simple code, I am just plugging a wire into ground or 5V manually. I also have the Arduino removed from the circuit. Here's a schematic -

simulate this circuit – Schematic created using CircuitLab

Instead of powering the breadboard with the Arduino, I used an Elegoo breadboard power supply module.

I have a wire going straight from the DC jack (12 volts, 3 amps) to the Collector of an S8050 NPN Bipolar Junction Transistor, which, from the datasheet, is able to handle 12 volts and 700 milliamps. Although the power brick does supply 3 amps, the fan is only rated to draw 700 milliamps, which is the maximum amount of amps the BJT can take, after checking with a multimeter, it only draws a little over 500 milliamps, which should be nowhere near too much for that transistor. The datasheet for the S8050 NPN BJT is right here - http://electronics.se-ed.com/magic/s8050.pdf

Is the potential problem in the physical circuit? Am I incorrectly reading the datasheet? Is this normal?

Also, for some reason, when I use 5 volts to turn the transistor on and off, the fan doesn't spin very fast. Only when I plug the jumper cable connected to the base of the BJT to 12 volts does it reach maximum speed, in which case the BJT gets much hotter much faster.

Thanks so much!


texts:
Pre: I'd understand if this isn't strictly related to electronics but I believe that this is something that would interest electronics enthusiasts.

I have a cell tower 2 buildings down from mine. I wish to know it's operator (so that I can switch) . I have a dual SIM phone. Short of buying SIM of every carrier and putting it in slot 1 and opening OpenSignal, what are my options to find out who operates the cell tower? Ive searched on opencellid.com but they don't list the tower at all.

PS: sorry for the bad tag but on phone I don't get the suggestion list


texts: Power line surge on the Active and Neutral line

texts:
Since a while, I've been having massive powerline spikes on both the Active and Neutral line.

It happens when I turn on a light (with a trafo attached to it), or have an ESD with my floormat, or when the hair dryer is turned on.
The power lines that where used to take this snapshot of the surge, have a surge protector in front of them.
My A/V receiver turns off for a second or two regularly, to protect itself from the spikes (I guess)
The only thing that recently changed was our Energy Meter. The wires have been there for around 20 years and we've never had problems with it. On every socket Earthing is available, and used.
What is the cause of this problem and most importantly, where do I get started to solve it?
EDIT:
The energy meter was checked by a electrician and it was properly installed in the first place.
2nd edit:
I noticed something strange, and I'm not really sure if this is supposed to happen.

The pink line is the neutral line and the yellow line is the active line. Is it normal for the neutral to 'follow' the active line a bit?


texts: I want to make a PCB on which PowerBOost 1000 Basic will be installed. The PowerBoost is a breakout board for a voltage regulator and has four GND pins. In this case is it better to connector the four GND pins to my PCB, or just connect one of the pins to the PCB? I wonder if the former would cause a ground loop.


texts:
I am a new logic hobbyist. This is a USB switch I am trying to build. I want to share my keyboard between two computers and be able to switch between them by clicking on SW1. The keyboard will be connected to the USB connector on the bottom, and the two USB's on the RHS to each computer. It will be great to hear the expert's opinion on this before I go ahead and order parts.

Update: Uploaded a new Fig. Please find the links to the devices blow:

NAND: http://www.mouser.com/ds/2/405/cd4011b-404423.pdf
TS3: http://www.ti.com/lit/ds/symlink/ts3usb30e.pdf
GF1: http://www.mouser.com/ds/2/149/GF1A-188833.pdf


texts:
I drove through a Wyoming thunderstorm today.   Just for fun, I set my AM car radio to the top end of the AM broadcast band where there was no station audible.  Sure enough, I heard the lightning crashes, some of which were visible.

However, occasionally there would be a deep growling sound that would last a full second or more, not correlated with anything I could see in the sky.  I have never heard such a thing before, and I strongly suspect that it is an electrical effect of the storm.  The effect happened mid-afternoon, before AM radio propagation goes DX, so I know it was local.  I found the same noise at the low end of the AM broadcast band.

What are the possible sources of this radio noise?  Can it be duplicated in a laboratory?


texts: preventing Rx/Tx data clashing on a xmega USART

texts:
I am using the USART module on an atxmega128a1 to communicate with a PC, and I've noticed that receiving and transmitting a byte uses the same data register address:

My question is then, if I am in the middle of transmitting a byte OUT of this data register, how do I prevent an interrupt triggered by a byte coming IN from causing me to lose data?

My current code uses Rx and Tx software FIFO buffers, an interrupt to trigger a byte received and a timer interrupt to output a byte periodically from my TxFIFO:

//interrupt to receive a byte (RS232)
ISR(USARTD0_RXC_vect){                          //ISR for when receive flag is set
    if(FIFO_Put(&RxFIFO, USARTD0_DATA)){        //put data into receive FIFO
        USARTD0_STATUS |= USART_RXCIF_bm;       //write 1 to clear bit
    }
    while(!(USARTD1_STATUS & USART_DREIF_bm));  //wait until data register is empty
}

ISR(TCC1_OVF_vect){
    unsigned char data;
    if(FIFO_Get(&TxFIFO, &data)){                   //place a byte from FIFO into &data
        while(!(USARTD1_STATUS & USART_DREIF_bm));  //if Tx FIFO has data, wait until data register is empty
        USARTD0_DATA = data;                        //put it in the data buffer
        while(!(USARTD0_STATUS & USART_TXCIF_bm));  //wait until transfer complete
        USARTD0_STATUS |= USART_TXCIF_bm;           //write 1 to clear bit
    }
}

BOTH of these interrupts are "low" priority and round robin servicing of interrupts are enabled. I want to increase the period of the timer interrupt but anything faster than 5ms interrupts causes data to be lost. I would use RTS/CTS but I want to know what my options are first as I believe the xmega is capable of doing what I want without data loss.


texts:
On the picture above, you'll see a circuit. The exercise is to make a transfer function and draw a bode plot. I've tried to do that, but because there's no solution, I don't know if I'm right.

Specifications: C1 and C2 are infinity, there's no value given for the two resistors (R), R1=180 ohm, R2=180k ohm, C3=22 microF

My attempt

This is an non-inverting opamp-circuit, so the attenuation is:
$$\frac{V_{out}}{V_{in}}=1+\frac{R_1+Z_{C_3}}{R_1+R_2+Z_{C_3}}$$

Converting this to a transfer function:
$$H(s)=\frac{R_1*C_3s+1}{C_3s(R_1+R_2)+1}$$
The zero and pole point is:
$$z_1=-\frac{1}{R_1*C_3}\quad and \quad p_1=-\frac{1}{(R_1+R_2)*C_3}$$
The magnetude and break-frequencies are:
$$|H(j \omega)|=\frac{\sqrt{(R_1 C_3 \omega)^2+1}}{\sqrt{(C_3 \omega (R_1+R_2))^2+1}}\\
f_{break1}=\frac{1}{2 \pi R_1 C_3}=40Hz\\
f_{break2}=\frac{1}{2 \pi (R_1+R_2) C_3}=0,04Hz$$

Can someone check if this is correct, or improve me if I'm wrong, please?

EDIT by the correction from the answers

This is an non-inverting opamp-circuit, so the attenuation is:
$$\frac{V_{out}}{V_{in}}=\frac{R_1+R_2+Z_{C_3}}{R_1+Z_{C_3}}$$

Converting this to a transfer function:
$$H(s)=\frac{C_3s(R_1+R_2)+1}{R_1*C_3s+1}$$
The pole and zero point is:
$$p_1=-\frac{1}{R_1*C_3}\quad and \quad z_1=-\frac{1}{(R_1+R_2)*C_3}$$
The magnetude and break-frequencies are:
$$|H(j \omega)|=\frac{\sqrt{(C_3 \omega (R_1+R_2))^2+1}}{\sqrt{(R_1 C_3 \omega)^2+1}}\\
f_{break1}=\frac{1}{2 \pi R_1 C_3}=40Hz\\
f_{break2}=\frac{1}{2 \pi (R_1+R_2) C_3}=0,04Hz$$


texts: How do I configure system clock while using MBED IDE?

texts:
Just starting to use STM32 boards with web-based MBED IDE.

This IDE don't have anything like Project configuration menu like other IDEs do. So I can not understand how do I configure system clock.

My board is STM32F429I-DISC1


texts: Thermocouple array for generating free electrical energy?

texts:
Thermocouple is a material (junction between two different metals) which generates potential difference in terms of millivolts, isn't it?

Why don't we create a matrix of thermocouples (many thermocouples which are connected in series and parallel) to generate voltage in terms of volts or even kilovolts, and can supply current in terms of amperes?

Today's scientist are able to put billions of transistors inside a tiny chip. Why don't they put billions of thermocouples on a one meter-square plate? Isn't that feasible; if so, why? If it is feasible, just why don't they do it?


texts: Develop Snap-On Board For Easy Connections - Rabbit SBC

texts: At my Company, we are using the BL2600 (Seen here) to create a new automation controller to replace our older controller. Rather than have electricians have to terminate wires into a Molex connector and snap on the side, we'd rather have boards snap into the sockets seen in the picture and then allow simple green screw-in connectors. How can we create this ourselves or purchase from somewhere?


texts:
I see there are a number of questions regarding this but none made it clear to me, so I'll risk being virtually stoned and go ahead and ask it again.

I have a 12V battery which powers some 12V components, however I also have a bunch of other components that require 5V, so I will get a buck converter. On it there is a Vin+, Vin- as well as Vout+ and Vout-. My 12V circuit has only a + wire, the - is connected to ground (which happens to be the metal case of my work), so I have 12V + wire going into Vin+ on the converter and Vin- is connected to ground. On the other side I would like also to have Vout- connected to ground so that it's easier to connect my 5V components without having to deal with wires but it's bugging me because I'm essentially connecting Vin- and Vout- on the converter and if that was okay then why would they even have put Vout- on there?


texts:
I am designing (simulating in LTSpice and building on a breadboard) a charge pump to power my numitron tube. I need to get ~15-20 V out of 3.3 V. The circuit is as follows:

simulate this circuit – Schematic created using CircuitLab

All diodes are 1N4148, the V1 source comes from a voltage regulator, while CLK1 from an Atmega OSC1 pin (Atmega powered by the same voltage regulator). The NOT gate is made from a NAND gate on a separate IC.

The circuit gives me about 18-20 V on the output without load, but when loaded, it lowers drastically. I measured the effective output resistance of this charge pump to be about 11 kOhm which is way too much for me. I tried simulating the circuit with smaller/bigger capacitances or frequencies, but it didn't change much.

The question is: how can I lower the output impedance of my charge pump?


texts:
First time poster here, please excuse holes in the plot.

I have a simple wireless design made of an MCU (atmega328p) and an NRF24L01 module, powered through a 3.3V regulator, talking to a similar board on the other side. This has been working well so far as a through-hole design, so I made a surface-mount version.

Through-hole version above, SMD version below.

As you can tell, the RF module sits above some of the components of the board, although I took care to not put any copper under the antenna. In the through-hole version, there is no copper or components at all under the whole module. There are also a few other differences that I believe don't matter here (the SMD version does not using any crystal, adds some fuses, uses different I/O pins).

With the through-hole version, I could easily get over 10m range. With the SMD version, most messages do not get received even when the boards are cm apart (the receiving end is the same in all tests, in this case an Arduino Nano hooked to a similar RF module).

What I have noticed, though, is:

When I power the board via the ICSP port (bypassing the regulator), transmission works fine (I thought this might indicate not enough capacitance, but adding a 470uF cap in parallel doesn't fix anything, so I don't thing it's that)
When powered through the regulator (target use case), transmission fails unless I do one of these:

Putting my finger on the VCC or MISO pin of the ICSP port (putting my finger on any other ICSP pin doesn't change anything. Touching the same VCC and MISO signals anywhere else on the board doesn't make transmission work).
Touching the antenna with a finger or a few cm of wire
Reducing PA level to MIN or LOW (but that reduces range to just a couple meters). I originally had it set to MAX or HIGH.

My impression is that my design is somehow screwing up the RF module's antenna, and touching some specific parts of the board with a wire or a hand somehow corrects for that and allows the signal to be sent correctly. But as I know close to nothing of RF transmission, I don't know exactly what I am doing wrong.

I am happy to change my design, but I would like to understand what is wrong with it and in which direction I must take it.

Is it being disturbed by the chips under the module, or does this not matter? Is the clearance I gave the antenna not wide enough, or on the contrary, should I have not put any clearance under the antenna in the first place? Should I just solder some extra wire to the antenna (if so, how much? and why?)

I just don't really know which way to go and I'd rather avoid building 100 versions to find out. I'm also not sure of what I can do to find out more (right now the most sophisticated tool I have at my disposal is a multimeter - could a scope tell me more?).

Edit, answering the comments:

Yes, connecting the RF module through jumper wires also makes transmission work.
I cannot find any evidence of the RF module getting its power through the IO pins instead of the power rail. I am seeing 3.3V all the way through to the module.
The regulator is pretty much the same. They're both 1117V33 types. The  SOT23 is a AZ1117IH, the TO220 is a LD1117V33.


texts: Controlling two LEDs with one digital output

texts:
I have a bicolour RG LED, which looks like this:

.

I don't have a datasheet for it. There are three cables on it: one is cathode of each colour (common cathode type) and the other two are the anodes of each colour. The forward voltage of each LED is 24V, and forward current is 10 mA.

I want to change its colour by changing ONE digital output of an arduino. I mean that when the digital output is low, green LED is on, and red LED is off. And then when the output is high, green LED should be off, while the red LED is on. Digital output level is 3V DC when it's "high" state, and "0" V DC when it is "low" state.

So, how can I control which LED is on, while changing one digital output?


texts: How to reflow a part in an infared IR rework station?

texts:
I bought a cheap chinese infrared rework station, mainly to unsolder large QFN's or QFP's from a board. The main problem with hot air is the inability to heat large areas evenly.

I can easily remove QFN's from a board with the station. Resoldering can be difficult because the board needs to be removed from the station to position the part.

A BGA already has solder balls to connect it back to the board, a QFN does not.

My question is, can IC's other than BGA's be resoldered to the board? What is the process that is used?


texts: Need some help to design power supply for custom Arduino PCB

texts:
I am building a custom Atmel Mega 2560 PCB that will run off the 9V 600mAh rechargeable li-ion batteries in a bus. I need to supply - 5V for MCU and other components in PCB, the overall current consumption being 2000mA. I use Arduino Mega 2560 before with XBEE wireless and some sensors, the board fail to deliver the require power so that’s why I want to design my own custom board with some change in components.

The is more than one type of Voltage Regulators, I use Digi key website as an electronics wiki to discover electronic elements and components and I see these type of voltage regulators:-

PMIC - Voltage Regulators - DC DC Switching Controllers
PMIC - Voltage Regulators - DC DC Switching Regulators
PMIC - Voltage Regulators - Linear
PMIC - Voltage Regulators - Linear + Switching
PMIC - Voltage Regulators - Linear Transistor Driver
PMIC - Voltage Regulators - Special Purpose

Mega 2560 use NCP1117ST50T3G to drive 9v to 5v with 800mA output current
There is another AVR board based on Arduino Mega 2560 call Freaduino Mega2560 and its use
MP2307 as a voltage regulator this chip is not linear voltage regulator like NCP1117ST50T3G which used it original Mega 2560 its DC DC Switching Regulators and its provide 5v with 2000mA output current but it’s use many pins not like linear regulators and I read in Digi Key it has frequency can someone explain the difference between DC DC Switching Regulators and not linear voltage regulator.

I continue my search in Digi key and custom my search for 5v, 3A output current in Voltage Regulators and find these items

http://www.digikey.com/product-search/en/integrated-circuits-ics/pmic-voltage-regulators-linear/2556290?k=&pv129=13&FV=c00001%2C1fc11fd%2C2040001%2C2040006%2C2040007%2C204000d%2C2040068%2C204008f%2C20400a0%2C20403ab%2Cfff40027%2Cfff80182%2C1140003&mnonly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25

My questions are as follows:

If I use any one of these 3A regulator in my circuit will it heat up or not.
Is it safe if I use Two 9V battery 600mA and connect it in parallel mode to increase the ampere to 1200mA will this work fine with regulator or these batteries with their output current will not enough to provide 5v with 3A output current.
Do I need to use heat sink or not?
last not least can someone explain the purpose and usage or these type of voltage regulator which I've listed it above and which type is the perfect for MCU board.

Thank you very much for your help.


texts: Computer power supply outputs 5.20 volts at 3.3 volts rail

texts: I got an old 420 watt Tagan power supply. It seems pretty good quality. I wanted to convert it into a bench power supply. It worked fine until I THINK I messed things up. I’m not sure if i actually damaged it or it was just too old and broke down. All I did was desolder a bunch of useless wires from the 3.3, 5, 12 volts and ground rails. After I connected it to a power source and measured the voltage at each rail, I found out that the 3.3 rails output was 5.20 volts!!! Why? Is there any way to fix it? Like replace any broken component. Also I did a continuity check between the 5 and 3.3 volt rail. There wasn't any short circuit.


texts: Charging and Using a Li-Po battery simultaneously

texts:
My system requires a power which is supplied by a Li-Po. however, I need to keep this Li-Po charging at all time so it won't die. Is it possible to connect the Li-Po to my system and also have it connected to the MAX1555  which is charging it? (think of it as using a cell phone while it's always plugged in to the wall, but I am not sure if they use a more complicated charging circuit or not)

if no, could you give me a simple recommendation ?


texts: Voltage rating of capacitor for SSR controlling motor (blinds) 275AC (630DC) V rating? or 600V(ac)?

texts:
I need an RC snubber to protect my SSRs that control my blinds (reversible motor).
I've read a lot about which capacitor I should use (my SSR spec sheet even states to use a voltage between 400 and 600 V).
However, I'm confused do the the lack of ac/dc specification.
Online suggestions for similar systems suggest, e.g. an MKP61R X2 or simular.
These have ratings of 275Vac, and permissible DC voltages of 630V.
Are these sufficient, or should I find capacitor off 400Vac to 600Vac?


texts: Powering a max 360 W Ender 3 Pro with a 300 W inverter

texts:
I’m planning on powering the Ender 3 with a 200 W solar panel with a 300 W inverter. I saw on some posts that the Ender 3 draws 500-ish watts whilst starting up but then drops to an average of 150 - 200 W.

Would the max limit of the inverter being 300 W lead to any problems whilst starting up the Ender 3 Pro?


texts: Why doesn't KVL work for the bottom loop?

texts:
I was doing a practice problem. I calculated the correct value for i_a = -2.4 A. But I used KVL on the bottom loop to get R, and got the inverse of the answer that I actually needed. My equation was -5*ia - 6V + 18*-6R = 0. There is no current flow from the current source above to the loop below.

According to the solutions, I needed to use voltage division to get the correct answer, but I was wondering why is this the case? I could get the correct solution with current division but I don't get why KVL doesn't work for this loop.


texts: How to calculate self-discharge time of capacitors given the leakage current?

texts:
Say I have a Maxwell BCAP0005 supercap (2.7V, 5F), which has a leakage current of 0.015mA. I'd like to estimate the time it takes to discharge to a certain voltage.

I've tried applying a formula for constant current discharge,

$$
t = \frac{C}{V_\text{initial}-V_\text{discharge}}I
$$

So, for $$V_\text{initial}=2.7V, V_\text{discharge} = 0V, C = 5F, I = 0.000015A$$
$$t = 900,000\text{ sec (10.4 days)}$$

And if $$V_\text{initial}=2.7V, V_\text{discharge} = 2.0V, C = 5F, I = 0.000015A$$
$$t = 233,333\text{ sec (9.7 days)}$$

But this seems like an oversimplification. For example, is leakage current constant? Does the ESR affect the discharge time? What other assumptions need to be clarified?


texts: Single LED powered directly from AC mains

texts: Today I disassembled a power strip (power extension) and found a LED connected directly to AC with a normal resistor (not a power resistor). How is it working as I thought it would be burned in no time? The resistor value is 220k.


texts: 1A load with 3 1,5V@2950mAh AA Alcaline batteries

texts:
I have a system that is powered with 3 AA Alcaline batteries Varta Industrial Pro (1,5V@2950mAh).

The batteries are connected to a this 3V3 LDO that supplies power to a MCU. I have taken a minimum dropout of 150mV (so LDO would work down to 3V45).
The MCU system will activate (using a FET) a electronic lock of this type, which consumes a maximum of 1000mA during 1 second and admits a voltage from 3V to 5V.
As my LDO only supports up to 250mA I would like to know.

I would like to know if there would any problem connecting the lock directly to the three batteries power supply, as they are a not fixed voltage power supply.

In case there's no problem, would these three batteries in series be capable of maintaining the required voltage level when the lock is activated?


texts: What does the suffix on the NCV8402ADDR2G mean?

texts:
This On Semiconductor part:

https://www.onsemi.com/pub/Collateral/NCV8402D-D.PDF

is described in the literature as the NCV8402D/AD. It doesn't describe the difference between the D/AD so far as I can tell. Also, it shows the orderable part number to be NCV8402DDR2G but does not describe what the DR2G means - SOIC package? Lead free? Tape?

I've only inferred two things:

The first D after the 8402 means dual, because it's a dual driver - this is made obvious when comparing to other drivers in the series such as the single 8402A
Only the AD version is in production, because the D version is listed as obsolete on DigiKey

I'd like to nail this down so that I can properly enter it in my CAD land pattern.


texts:
I want to use BLDC motor for charging the E-rickshaw for that I need to find the parameters of the motor. I have measured the Resistance and self-inductance of the motor but I am facing difficulties regarding finding the mutual inductance of the motor.
So I want to know What technique can be used to find the mutual inductance of motor for all three phases?


texts:
Whenever I come across this situation:

I feel a strong urge to make a T - joint like this:

However 90 degrees are usually frowned upon. As such what's a better alternative to this T-joint?

If I follow Tyler's suggestion, I'll get this:

However this contains an acute angle which is even worse.


texts: Why is my multimeter reading such a high/erratic current?

texts:
Newbie to electronics here.
I have a simple circuit consisting of just a 9V battery and an 820 ohm resistor.  I was trying to measure the current with a multimeter (by opening the circuit between the positive battery terminal and the resistor and placing the leads in there.) According to my calculations, the current should be 0.011A = 9.2v / 820ohms.
My ammeter is reading values anywhere between 0.030A and 0.200A. I'm assuming my multimeter is faulty, but could it be something I have done wrong or is there a way to fix it?

When I set the range to 20m the meter reads 1.

I'm making the connection just by touching the clips onto the wires, making sure to not touch any wires with my fingers. And the resistor is reading 810ohms. I've tried two different batteries in the multimeter, both fully charged. The voltage across the battery terminals measures 8.64v while the circuit is closed and the current is flowing.


texts: In Xilinx Vivado, simulation mismatch between behavioral and post-synthesis implementations

texts:
While designing PISO (parallel in serial out) in Xilinx Vivado using Verilog, the output waveform of the behavioral simulation (RTL-level, pre-synthesis) shows correct (desired output) value but post-synthesis or post-implementation functional or timing simulation is showing some unexpected results. There is a high frequency noise present at the new clock(slow)at near both edges in the simulation which is the main problem. How to eliminate this noise now? Is there any way to debug post synthesis level netlist? I have included my source code as:

module PISOleft(
input clk,
input rst,
input [3:0]din,

output reg dout,

);

reg [3:0]temp;
reg [25:0]temp1;
reg slow1;
reg slow;

         initial
               begin
                   temp1=26'd0;
                   slow1=1'b0;
               end
           always@(posedge clk)
                    temp1<=temp1+1;
           always @(temp1)
                  begin
            if(temp1==26'b10111110101111000010000000)//clock divided by 50Mhz
                        begin
                         slow1<=slow1+1;
                         end
                     else
                         begin
                          slow1<=slow1;
                         end
               slow<=slow1;
                  end

  always @(posedge slow)       // speed
      begin
         if(rst==1'b1)         // condition
            begin
                 dout<=0;
                 temp<=din;
             end
         else
            begin
                dout<= temp[3];
                temp<={temp[2:0],1'b0};
             end
      end
  endmodule

The warning I am getting at synthesis is:

 [Synth 8-327] inferring latch for variable 'slow_reg'

The noise present at my new clock(slow) is shown:


texts: How do i build a battery charge circuit that doesnt require the battery to be disconnected

texts:
I am needing some advise on how to build a circuit that can charge a 9v rechargable whilst it is still connected to my small robot.  The battery will power an arduino, meastro, 4 std servos and 2 dc motors.

Input to the battery should have something basic that will convert ac to dc just in case.

Secondary to direct dc / ac input, i require another input source but that acts as a harvester.  It will take power from solar panels and a piezoelectric source ( so again an a/c to d/c converter could be needed ).  Maybe this could put the power into a capacitor of some kind, and when it reaches a required amount, release the power to the battery.

Hope you guys can advise


texts: Is BLE 4.1 backwards compatible to BLE 4.0 ? Can a phone with bluetooth 4.0 talk with a mote with BLE4.1?

texts: BLE 4.1 is out and it could be considered the biggest news for internet of thing developers. I want to know if my mote with BLE 4.1 can interact with iPhone 6 which has Bluetooth 4.0.


texts: Eliminate PWM noise in PWM-driven bidirectional motor

texts:
I need to drive a DC motor with PWM, through a H-bridge.

The controller can't generate PWM at ultrasonic frequencies with resolution I desire, and the low-end of the spectrum (~100Hz) may be too slow for my needs (plus still create a 'hum').

There's a question about driving a fan and the answers suggest 1-4.7uF ceramic + some 100-1000uF electrolytic caps at the output as solution (plus a fast diode to clear reverse current). This works well for a fan, which only turns in one direction. In my case, the motor will operate in both directions, so I can't depend on fixed polarity of the output - the moment I reverse polarity the cap will be fried.

How do I go about silencing the motor in this case?


texts: What is a modern 2sd669 transistor replacement

texts:
I have an old Nad 302 integrated amp where one of the 2sd669 transistors is blown. I Cannot find any suggestion on modern replacements. To be honest I am a software engineer and analogue circuits is a bit out of my comfort zone.
To be precise it is the Q411 according to the service manual.
What would be a currently (2021) available equivalent, or better replacement?


texts: How much current can an Android phone's USB port supply?

texts:
I know that a USB 2.0 port can deliver 500 mA and USB 3.0 can deliver 900 mA.

Is this any different on a phone, because it is a smaller device? I was thinking maybe it would be a smaller amperage, like 100 or 200 mA?


texts: How to set up an experiement to measure SNR for an EEG amplifier?

texts:
I have built an EEG amplifier with gain of 2000 and bandwith at 1~40Hz.

I use an Instrument Amplifier for pre-Amp and a non-inverting opamp as post-amp and finally bandlimit at 40Hz using a 4th-order LPF.

I would like to measure the SNR for my EEG amplifier but I do not know the proper set up and therefore I come out with the following experiment steps and please verify for me am I doing the right thing.

How I record the measurement:
I connect the analog output to the SADC pin of ARM MCU. The ADC sampling rate is 7000 samples per second

My input:
A differential Sine wave from function generator @ 10Hz

My output: An amplified Sine wave @ 10Hz @ gain = 2000

1. Measure the Vrms for noise

1.1 Let input of INA to open and then power on the amplifier.

1.2 Measure the output and record the ADC data

1.3 I record the output for ~5 seconds which give me ~50,000 data

1.4 I select a portion of 10,000 continuous data sample, which is 1-10001 data samples

1.5 Calculate the Vrsm using similar equation provided here

1.5.1 Calculate the power of 2 for each of the 10, 000 data
1.5.2 Calculate the average result of the total data (which is divided by 10000)
1.5.3 Vrms = Square root the result of average of 10, 000 data

2. Measure the Vrms for signal

2.1 Let the input connect to a differential Sine wave generator

Repeat 1.2, 1.3, 1.4. 1.5 to calculate the Vrms of signal.

3. Calculate the SNR (db)

SNR(db) = 20 log (Vrms, signal / Vrms, noise);

My question: Am I doing the right thing for the SNR measurement?

Edit: Update question

Now I am confused. The MCU is powered at 5V from an eval board whereas my system is a 3.3V powered. The MCU SADC is taking the voltage measurement at pin SADC with reference to 0V (GND).

However, my system AGND is at 1.65V.

Therefore, how should I connect the output of my system to the eval board?

I try the following scenarios:

1. Connect the SADC pin to my EEG amplifier output and connect the MCU GND to my EEG AVGND

It will measure the noise like this, which is a sharp peaks:

2. Connect the SADC pin to my EEG amplifier output and connect the MCU GND to my EEG 0V ground

It will measure the noise like this, which is looks like a power noise:

Which is the correct one? or both wrong?


texts: What is this circuits output and how can I simplify it?

texts:
I am doing a short module in Boolean Algebra we have covered gates and truth tables, I am doing a sample exam paper as practice but cannot understand how to do this logic gate question.

I need to do the following:

Find out what each gate is outputting
Use Boolean algebra to simplify the gate structure

If I understand this example I think I should be able to do another question. Can anyone help me?


texts:
In the attached image below, I don't understand the text and phasor diagram that I have highlighted in yellow.

Why does the induced emf on the armature winding lag the magnetic flux of the corresponding rotor pole by 90 degrees? I thought they would have been in phase.

Also how does the power factor affect this?


texts: What is the effect of no-current periods in commutation on output power of a PM DC motor?

texts:
I have made a PM DC motor. This motor works on a unique magnetic circuit.  This motor can work very well at different input levels. When it uses an input of 5.915 volts*3.5 Amperes=20.7025 Watts, its output is 8.85 watts.

In this motor, 30% part of each commutator segment area is no-current area. It means that when the armature rotates no current is applied to it during 30% part of the rotation. No-current periods are unavoidable in the present commutation of my motor because the magnetic circuit does not allow the same current to pass through more than one coils.

The armature has 12 teeth and each of the teeth has been winded independently. So, the total coils of the armature are 12. The commutator comprises 24 segments. As a whole, the current passes through 12 segments while 12 segments are empty and are used to disconnect the current. The current passes through a segment then the next segment stops the current to flows, the third segment again allows the current to pass. This process remains going on.

The use of the smaller surface of carbon-brushes is compulsory so that two current-transferring segments should never be connected through the brush surface.
Figure:

My point about the effect of the no-current periods:
The armature needs a specific amount of current during 70% part of the armature-rotation to do a specific work.  30% of armature-rotation occurs only because of momentum. No current is supplied to the armature during the 30% part of the rotation.

This motor uses 8 field poles. It is apparent that during the no-current periods the field poles attract the rotating armature very forcefully. It produces a heavy braking effect. Moreover, when the true current is disconnected because of the no-current areas of the commutation, back EMF might create reverse magnetization in the armature teeth. It should strengthen the braking effect. Practically, whenever I put off the line current (during the work of the motor), the motor halts all of a sudden. So, I assume that the braking effect is too heavy.

It is also apparent that the amount of the input current (3.5 amperes) is strong enough to perform the work as well as to overcome the loss of momentum caused by the heavy braking effect.

A higher than usual current is needed to perform the double task (to do the work and to overcome the braking effect). If the no-current periods are eliminated, the current will not have to overcome any loss of momentum. Moreover, the same current will find 30% more time to work. A lesser but even amount of current will be needed to do the same work.
The even amount of the current should be 30% lesser than the present amount of the current:
Present input is: 5.915 volts*3.5 Amperes=20.7025 Watts. The even amount of the current will be 30% lesser than the present amount of the current. Voltage would also reduce. So, only 10.144watts input would be needed instead of 20.7025 Watts.
(The reduction in the current will be= 3.5 amperes/100*30=1.05 ampere. The Input after the removal of the no current periods should be=2.45 amperes* 4.1405 volts=10.144watts.)

I think that if the commutator is replaced with electronic sensors, there would be no need to maintain the no-current period. At this time, I am trying to guess the possible loss of power that is caused by the no-current periods.


texts: 16x2 LCD connected to msp430g2553 launchpad by i2c: contrast issue

texts:
I am testing a 16x2 LCD screen specifically the 'MCCOG21605B6W-FPTLWI' from 'MIDAS'. It is connected to the with the 'msp430g2553 launchpad'. The connections are described in the commented code fragment that I have attached in this message. The backlight adjusts it through the working cycle of the PWN which connects it to the anode (this works correctly). The character are written correctly on the LCD but the problem is the contrast, it is very very low. To see the characters I have to turn the LCD and at some angle you can see that there is written text. As is an LCD by i2c, the contrast adjustment is done by commands, not by any potentiometer.
As you can see in the code, I initialize the LCD as indicated by the datasheet for a 3V power supply:

/*

MSP4302553|         |LCDDriver
|Pin 1 Boost Capacitor 1
|Pin 2 Capacitor 2 N
|Pin 3 Capacitor 2 P
Vcc (3.5V) |---------|Pin 4 Vdd (Boost Capacitor 1)
Gnd |---------|Pin 5 Gnd
P1.7|---------|Pin 6 (SDA)
P1.6|---------|Pin 7 (SCL)
P2.5|---------|Pin 8 (RST)
P2.4|---------| A (Backlight Anode)
Gnd |---------| K (Backlight Cathode)

*/
.
.
.

char TxData[] =     // Table of LCD display initialization commands
{ 0x00,
    0x38,
    0x00,
    0x39,
    0x14,
    0x74, //Contrast set
    0x54,
    0x6F, //Follower control
    0x0C, //Display On, Cursor On, Cursor Blink On
    0x01
};

.
.
.

The initialization of the LCD is the one proposed by the manufacturer for 3V power supply:

INITIALIZE: (3V)
 MOV I2C_CONTROL,#00H ;WRITE COMMAND
 MOV I2C_DATA,#38H ;Function Set
 LCALL WRITE_CODE
 MOV I2C_CONTROL,#00H ;WRITE COMMAND
 MOV I2C_DATA,#39H ;Function Set
 LCALL WRITE_CODE

 MOV I2C_DATA,#14H ;Internal OSC frequency
 LCALL WRITE_CODE
 MOV I2C_DATA,#74H ;Contrast set
 LCALL WRITE_CODE
 MOV I2C_DATA,#54H ;Power/ICON control/Contrast set
 LCALL WRITE_CODE
 MOV I2C_DATA,#6FH ;Follower control
 LCALL WRITE_CODE
 MOV I2C_DATA,#0CH ;Display ON/OFF
 LCALL WRITE_CODE
 MOV I2C_DATA,#01H ;Clear Display
 LCALL WRITE_CODE

I have tested with various values of the commands that can cause the characters not to be seen: 'Display ON / OFF', 'Follow Control' and 'contrast set' but without any result. It always looks with contrast practically 0. Do you know why the initial configuration proposed by the manufacturer does not work?

This is the datasheet: MIDAS LCD 16X2 Datasheet


texts: Length-matching microwave differential traces

texts:
I'm driving an RF mixer that takes differential input signals. My max signal frequency is \$6\,\text{GHz}\$. I understand that the differential input signals need to be length-matched, but what sort of tolerance does this give me? In other words, how different can the lengths be? I'm asking because the mixer pin configuration makes it really tough to exactly match the lengths without doing some more funky stuff like adding serpentine traces. Moreover, based on my PCB stackup, each differential trace needs to be \$0.85\,\text{mm}\$ wide (\$0.1524\,\text{mm}\$ gap), which makes adding curves tricky without adding substantial length.

Here are my thoughts on the problem. The length matching in this context is important to minimize phase delay between the signals. Basically, we'd like the mixer to take the difference of the signal and its inverse, not the signal and a time-delayed copy of its inverse. The signal frequency components are sinusoidal and the value of \$\sin(x)\$ changes most quickly at \$x=0\$, where \$\frac{d}{dx}\sin(x=0)=1\$. So, if I wanted to keep the delayed amplitude within \$1\%\$ of the value it should be (for arbitrary phase), I should keep the length difference less than \$1\%\$ of the signal wavelength in the transmission line. In my case the electrical length is \$30\,\text{mm}\$ which means I should keep the length difference less than \$0.3\,\text{mm}\$. Is my logic sound? Is \$1\%\$ a sufficiently conservative value? Can I get away with more? Is there a rule of thumb for this? If the answer depends on information I haven't provided, please let me know and I'd be happy to include it.


texts:
I am using this switching circuit to switch a lamp. I am controlling a rising slew rate at Vout (from 0-Vcc) that is adjustable by setting R2 with a poteniometer. It's not necessary for my project, but I would like to control the switch-off time for the MOSFET.  Here is a my output at R6 with a 3.3v input.

As far as I understand it, Vout is staying high after Vin has gone low because the FET will stay on until Vgs is below the threshold voltage, so it makes sense that Vout stays high until Vgs goes below the threshold, but why is the slope after that point so much shallower than the rising Vout slow?

How could I reduce the fall-time of the voltage at Vout? This post has shed some light on the issue, but I haven't been able to figure out a good solution yet. I'm somewhat of a beginner to electronics, so any help is really appreciated.

EDIT:

Simulation with Vg


texts:
I am trying to simulate a circuit which is composed of an oscillator which oscillates and reaches a maximum oscillation amplitude, then there's a peak detector that is following the peak of oscillation in one output (Venv+ in the picture) and Venv- is the reference. the outputs of the peak detector circuit, (Venv+ and Venv-) are then applied to a comparator. and the output of comparator is applied to some inverting stages to produce some delay. then the output of a comparator stage is applied to the horizontal NMOS to quench the oscillations. an ook signal is injected to the oscillator. when the input signal exists, the oscillations start and decay faster and more quench signals are produced compared to when there is no injected signal.

so far everything's fine! but i want to have this quenching mechanism by applying this quench pulses to the gate of the tail transistor. the problem is the amplitude of the oscillations don't reach the maximum, and actually the width of the pulse generated in the gate of the tail transistor is not much (about 2 nanoseconds). can anyone give me an idea about what i am doing wrong?? i could give more explanations .


texts: Beagle Bone Black - Error when finding update packages: sudo apt-get update

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I am very new to using any micro controller and I wanted to use an MPU-9250 sensor with the Beagle Bone to give me serial data either through I2C or SPI.
Whenever I type sudo apt-get update  in my terminal shell I get this error:

Err http://security.debian.org jessie/updates InRelease

Err http://repos.rcn-ee.com jessie InRelease

Err http://security.debian.org jessie/updates Release.gpg
  Could not resolve 'security.debian.org'
Err http://repos.rcn-ee.com jessie Release.gpg
  Could not resolve 'repos.rcn-ee.com'
Err http://ftp.us.debian.org jessie InRelease

Err http://ftp.us.debian.org jessie-updates InRelease

Err http://ftp.us.debian.org jessie Release.gpg
  Could not resolve 'ftp.us.debian.org'
Err http://ftp.us.debian.org jessie-updates Release.gpg
  Could not resolve 'ftp.us.debian.org'
Reading package lists... Done
W: Failed to fetch http://ftp.us.debian.org/debian/dists/jessie/InRelease

W: Failed to fetch http://ftp.us.debian.org/debian/dists/jessie-updates/InRelease

W: Failed to fetch http://security.debian.org/dists/jessie/updates/InRelease

W: Failed to fetch http://repos.rcn-ee.com/debian/dists/jessie/InRelease

W: Failed to fetch http://security.debian.org/dists/jessie/updates/Release.gpg  Could not resolve 'security.debian.org'

W: Failed to fetch http://repos.rcn-ee.com/debian/dists/jessie/Release.gpg  Could not resolve 'repos.rcn-ee.com'

W: Failed to fetch http://ftp.us.debian.org/debian/dists/jessie/Release.gpg  Could not resolve 'ftp.us.debian.org'

W: Failed to fetch http://ftp.us.debian.org/debian/dists/jessie-updates/Release.gpg  Could not resolve 'ftp.us.debian.org'

W: Some index files failed to download. They have been ignored, or old ones used instead.
root@beaglebone:~#

I really don't know what to do from here.


texts:
i want to use example design of GTP transceiver for my ARTIX 7, everything is fine but in the constraint xdc file, i could not find the TX and RX constraint, this is my constraint file, i want to know what is the set_property LOC GTPE2_Channel_X0Y4 is this constraint for TX and RX???do i have to right somthing like Set_property LOC E12 [get_ports RX_P_IN] for RXP???or this constraint is ok?

create_clock -period 8.333 [get_ports Q0_CLK1_GTREFCLK_PAD_P_IN]
create_clock -name drpclk_in_i -period 10.0 [get_ports DRP_CLK_IN_P]
set_false_path -to [get_pins -hierarchical -filter {NAME =~
*_txfsmresetdone_r*/CLR}]
set_false_path -to [get_pins -hierarchical -filter {NAME =~
*_txfsmresetdone_r*/D}]
set_false_path -to [get_pins -hierarchical -filter {NAME =~
*reset_on_error_in_r*/D}]
set_property LOC E10 [get_ports  Q0_CLK1_GTREFCLK_PAD_N_IN ]
set_property LOC F10 [get_ports  Q0_CLK1_GTREFCLK_PAD_P_IN ]
set_property LOC C25 [get_ports  DRP_CLK_IN_P]
set_property LOC B25 [get_ports  DRP_CLK_IN_N]
set_property LOC GTPE2_CHANNEL_X0Y4 [get_cells gtwizard_0_support_i/gtwizard_0_init_i/inst/gtwizard_0_i/gt0_gtwizard_0_i/gtpe2_i]
set_property LOC GTPE2_CHANNEL_X0Y5 [get_cells gtwizard_0_support_i/gtwizard_0_init_i/inst/gtwizard_0_i/gt1_gtwizard_0_i/gtpe2_i]
set_property LOC GTPE2_CHANNEL_X0Y6 [get_cells gtwizard_0_support_i/gtwizard_0_init_i/inst/gtwizard_0_i/gt2_gtwizard_0_i/gtpe2_i]
set_property LOC GTPE2_CHANNEL_X0Y7 [get_cells gtwizard_0_support_i/gtwizard_0_init_i/inst/gtwizard_0_i/gt3_gtwizard_0_i/gtpe2_i]
connect_debug_port dbg_hub/clk [get_pins -hier -filter {name=~*DRP_CLK_BUFG*O}]


texts: Need to Amplify 13mv to 5volts using a LM324 op Amp

texts:
I am using a 13mv input on a LM324 op amplifier. I am trying to get a gain of about 384 to 5 volts. I am not getting any voltage on the output?? Can anyone offer any suggestions why this circuit doesn't work or point me in the right direction. I have attached a schematic which I hope you can follow.
Any advice would be appreciated.

Many Thanks

simulate this circuit – Schematic created using CircuitLab


texts: What is the importance of resistance at emitter and collector of BJT amplifier? What will be effect on output if they are removed?