texts: High Common mode op amp shunt compensation

texts:
The High Common mode Voltage difference op amp AD629 Datasheet on page 12 says that the use of a large sense resistor skews the output.  Why is this so?  I can't wrap my mind around any other reason than that one side or the other would typically tie to either the source or sink of the power supply.

Is there any advantage of using one of these IC's versus using an instrument amp with input resistor dividers?  Would the instrument amp with dividers suffer from the same error?

I am researching an isoamp replacement for an input stage for a galvanic oxygen sensor, which in this case is a small current source converted to voltage by a 2.2k resistor(0-200mv dc).  This is a floating voltage other than water contact through the membrane, and I have doubts about whether this would require a 2.2k rComp as explained in the datasheet Figure 36.


texts: Wy are speakers rated by impedance instead of inductance?

texts: Audio speakers contain coils which product sound by vibrating a cone.  Why are speakers rated by impedance instead of inductance?


texts:
My 240 VAC relay can be either on or off. I'd like to transform that to 1/0 signal for an input pin on my Arduino. I may be able to build something with a rectifier, a step-down and a couple of transistors, but probably not.

Surely there must be an easier way?


texts: Is it safe to use a 120V 300W 60Hz UPS in a country with 240V 50HZ after step down with regular 1000W transformer?

texts:
I'm planning to move to a different place and the voltage there is 240V 50Hz. Currently, most of my appliances are 115V except for few 220V devices. Sold most of the high power 115V devices. I do have a few small office devices and a UPS which I would like to take it with me. I know by using an auto stabiliser it can be solved. But if I were to use a regular 1000W step-down transformer, the frequency would be different right? I'm not planning to use any inductive devices just the UPS. Will it heat up the device? or damage it?
Thanks in advance everyone.
Edit: I've read people specifically mention about inductive loads heating and electronic clocks running slower but didn't come across anyone mentioning about UPS or power electronic devices much.
In the figure, I've used only the transformer not the stabiliser like my original setup I'm planning to use.


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I am trying to measure voltage across a 0.1R shunt resistor. When i measure voltage between input1 and input2 with multimeter i can see 10 mili volts. When i connect input1 to a voltage follower in the picture, op-amp starts to oscillate.

input1 and input2 are connected to voltage follower and  after voltage follower i measure voltage across two outputs with differential amplifier.

I thought that this happens because of noise in input and added ~1hz lowpass filter to reduce noise but op-amp still oscillates.

I also added 1k resistor to output but no success. Op-amp i am using is TLC271CP which supports single supply operations.

Can you please help me how can i solve oscillation problem in voltage follower?


texts:
I graduated in Physics, then fell in love with electronics, so, in the past few months I have been trying to make heads and tails from it on my own.

Today, as I was reading about amplifiers I got stuck with a resistor in the schematics therein.

Here goes it:

As you can see, it's a simple amplifier, not a big deal, but the resistor R2 is bugging me and I cannot make sense of it!

Now, I don't mean to be rude or boastfull at all friends, but I have already passed the entire Ohm's law and basic functionality of a resistor, both in my physics degree, and now while studying specifically electronics. But here, in this case it does not seem to be a mere case of a voltage being recalculated/modified ( pardon my English ), such as the basic examples of a resistor between to wires, it seems to me that it can have totally different broader roles other than just changing voltage values, am I correct?

If you take a look at it, it seems to be just there, hanging onto the circuit, like a bad suit, one ending just there, hanging, and the other one fixed to ground.

Now, the developed voltage at R2 is supposed to be of such order that it enables a small amount of direct polarization to both transistors. And that's the part I cannot understand, for it's just hanging there, with one end straight to ground!!

How could the voltage that is passing just to one end of the transistor be altered/manipulated in a ways to make the resistor such an important piece in the amplifier?

What did I miss?


texts: Best linear position sensor for piston feedback

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I have been looking at measuring the extension/retraction of a piston to record and predict the life of the device.  What would be the best way to measure the piston strokes?

So far, I have come up with following guesses/ideas:

LVDT in parallel.  This is cost prohibitive.
Linear Pot.  I like this idea, but I have not found a decent source for COTS solutions.  No idea what price is.
Optical sensor on piston, stripe piston (encoder-like feedback and the environment is very clean).  I imagine I would need to add limit switches and possibly calibrate this configuration.  This seems overly complicated.

I figure there are other solutions out there, but I am currently ignorant to them.

Info for the piston/interface:
- 8 inch stroke
- Clean environment with some dust intrusion (think home office, not industrial)
- Accuracy is acceptable to within 10% of stroke
- Maximum actuation time of 1 stroke per second
- Ambient temperature is 20C-25C without much variation
- Time is not an issue, this is an experiment
- The cheaper the solution the better.  Ideal price point is $5-$10 though likely unrealistic
- My goal is to test to 10,000 strokes
- An absolute output is ideal, but not completely necessary


texts: Why can't I assign value to this std_logic_vector?

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I am trying to initialize an std_logic_vector but it gives me an error, here is the line of code:

signal a_in: std_logic_vector(7 downto 0) := (7 downto 4 => "1111", others=>'0');

error is

String literal found where non-array type ieee.std_logic_1164.STD_LOGIC was expected.

I am aware that I can just write "11110000" and solve the problem. However, as a learning experience, I want to know what is wrong with this code and how to fix it. How do I assign value to std_logic_vector in "chunks" in a single line?
Thank you for your time.


texts:
I'm attempting to fix my desktop motherboard which is damaged by power surge, and I noticed that the +3.3VSB is giving 1.6 volts. There are few voltage regulators around the board, I checked them either and they're working correctly (Convert from 5v to 3.3v). I tried replacing the faulty one but it didn't solve the problem. Also there is 2 resistors and 1 capacitor connected to the regulator.
The 2 resistors must be 316 and 182ohms, but they seems to be 118 and 113ohms. Can that be the problem?
Why is there even 2 resistors connected to adjust pin when the voltage regulator is FIXED and doesn't need to be adjusted? :/

Btw I'm working with boardviewer app and I don't have a schematic. Thank you!

EDIT: The regulator is AMS1117-3.3v


texts: 60A current drain on supercapacitors in series?

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We have a project to build an RC car from scratch and are only allowed to use NiMH batteries, no LiPo. We're hoping to power the car with an EDF (https://hobbyking.com/en_us/durafly-vampire-v2-rcaf-edf-and-motor.html or similar) which runs at 4s or ~14.8V, 60A. Instead of using two heavy (1kg) 8.4V batteries in series, we would like to try and power the EDF with 6 x 2.7V 60F supercapacitors, charged before the race with the aforementioned heavy battery packs.

So my questions are:

Do capacitors in series need some sort of balance charging like LiPo's?
Do they all discharge at the same time or one at a time, i.e. will we be constrained by the rated 20A discharge rate or the low voltage cutoffs of the ESC?
Is this safe and doable?


texts: On injecting PCIE AER LCRC TX error on device does not report the error from endpoint to root port

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Trying to inject LCRC TX CORR (ERR_CORR) error on PCIe device, the error does inject but
on injecting PCIe AER LCRC TX error on the device does not report/propagate the error from the endpoint to root port and hence not appearing in dmesg in ubuntu.
Tried below experiment below registers:

SERR# forwarding is enabled in the BRIFGE_CNTL register which allows propagating error on EP(endpoint) to RP(root port).
Make sure no CORR error mask is enabled.
Confirmed that CORR error is received on endpoint device through lspci -vv.

Any hint will be appreciated.
Device is multi function device and enabled error reporting on all functional device. could this be an issue while reporting error to RP?


texts: Advantages/Disadvantages of ground fill on both layers (of a 2-layers-board)

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There are many similar questions but I didn't really find the answer I want.

I have many 2-layer boards for analogue-audio-stuff. I use both layers for routing and I have ground fills on just one layer. (mostly on bottom layer). Well it works this way but..

Why shouldn't I fill also the other layer with ground copper and connect them using multiple small stitches/vias? That would reduce the impedance between some grounding components which were connected through narrow ground paths on one layer.

(Image source: forum.kicad.info)

Do you see any reasons not to fill the both layers with ground?


texts: Maximum Power Point Tracker (MPPT) charge controller - what drives the weight?

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I'm having trouble finding any literature paper that studies this problem. What drives the weight of an MPPT charge controller? How would I go about reducing that weight if I had to design a custom design? The only thing that even alludes to the power-to-weight of an MPPT is this paper, behind a firewall so I can't read it: https://ieeexplore.ieee.org/document/7990724
The clue here is that it's the power transistors that are massive? If I had to design an MPPT with an expected range of input/output voltages and currents, how could I go about determining the heavier objects? Maybe this schematic was potentially the most helpful thing I found, which details the inside of an MPPT: https://www.ti.com/lit/ug/tiduej8a/tiduej8a.pdf?ts=1593845160703&ref_url=https%253A%252F%252Fwww.google.com%252F
But there's no mention of weight of anything. Of course, I could buy an OTS MPPT and strip off the housing, etc. to reduce mass, but I'm trying to go for a more sophisticated design approach. I guess weight has never mattered to MPPTs, being installed near large solar panels on houses, etc., but it is an interesting problem (I think?). What are the components by weight? How can they be reduced (e.g. GaN power transistors apparently?)? And what's the driving factors (e.g. is it current that pushes the need for heavier everything?)
Apologies if this is basic electronics - I am new to the electronics world.


texts: Adding 3g wireless capability to an embedded project

texts: How would I go about adding 3g wireless capability to an embedded project? Initially I thought about just using a USB host controller and purchasing a USB 3G card. This idea however seems "hackish" and not permanent. What would be the best way to do this?


texts: Can unwanted coupling drive signal lower than intended?

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Let's consider the following schematics- a switch connected to microcontroller's input with internal 50kOhm pullup resistor.

simulate this circuit – Schematic created using CircuitLab
Now, the following oscilloscope trace shows voltage at TP (CH1) and VCC (CH2, AC coupled) at the time, when CCFL lights are switched off in the room.

I do understand that two conductors can become inductively coupled, and that current change in one conductor induces voltage in other conductor. By looking at the oscilloscope trace, I see that signal voltage drops- my assumption was, that only more positive voltage can be induced.
Is my assumption wrong, and negative voltage (i.e. signal voltage drop) can be induced in a conductor which is close to other conductor?
Or this oscilloscope trace does not show inductive coupling, but something else I'm not aware of?
After I added an external pullup of 3.3kOhm, flicking light switch does not result in LOW level input signal seen by microcontroller anymore- I just wanted to understand what exactly caused it.


texts: Approach to an unknown orthogonal Beta Signal with a known alfa in single phase dq transformation

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I am trying to implement a PLL controller to the MCU for tracking single phase line voltage . I get samples via an opamp circuit with a DC offset and the samples' raw values vary between |-244 , +244| when removed the DC offset  . The key problem I'm trying to overcome is that the DQ transformation needed in the design requires a made up second orthogonal signal (Beta) other than the alpha . As far as I read the papers written for single phase PLL implementation , we need a 90 degrees time delay of the original signal , so it is our alpha .. Let's say an instant adc value is 128 and that is the alpha , so how to create an imaginary orthogonal Beta signal using that ADC value ? What I need for a park transformation is the alpha and beta , I got the alpha but what is the beta ?
D = Alpha*cosTETA  + Beta*sinTETA
Q = Beta*cosTETA - Alpha*sinTETA

Alpha= Instant ADC value
Beta = ?


texts:
I was just thinking about diodes recently and I came across this video

https://youtu.be/bXEyCf1P0UU?t=35
Minute 0:32

He says the power disspitated by the diode will be the forward voltage drop Vf (0.7V usually) times the current through it.
Now, that's my confusion. Why would the power drop only be 0.7V times the current. I mean if I applied 2V across it, it should be 2V*current not 0.7V right?

I thought the 0.7V=Vf is the minimum voltage across it we need (with correct polarity) for it to start conducting,


texts: Rectify 220v ac to 220v dc using mechanical system

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I want to have 220v dc using a mechanical system (without using diodes ,or with using homemade diodes) so I came up with this idea :
when the wave is positive the electromagnet atract the bendable plastic up ,so it will tuch the blue and red , and when the wave is negative the electromagnet atract the bendable plastic down , so it will tuch the red and blue wires (so the polarity switches).

but the problem is the output form is not a line (output is not dc).

where to add capacitor and what value to shift the output ?
is there another way to get 220v dc using an ac motor (or any way) ?


texts: What kind of load do US thermostat control signals drive?

texts:
This page has some really good information on heating system wiring in America. One thing I can't tell from it though, is what exactly the 24VAC call-for-heat and call-for-cool signals drive.

Presumably they don't supply the actual power for heating or cooling (24VAC wouldn't get you far), so I guess it is some kind of control signal, but what is the load? Does it drive a relay? If so what is the coil resistance, etc.?

In other words, what exactly is in the question marks here?


texts: Where to store non-volitile variables on ARM microcontroller

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Noob question here. I have only a little experience with microcontrollers and all that experience was limited to the 8051. I am working on a project and would like to use the ARM cortex M4 microcontroller. Programming the microcontroller and setting up the registers and IO is easy enough. The project calls for a person to be able to input certain variables like time, weight, etc. Those values need to be stored in some non-volatile memory so that if the embedded system loses power the values will be retained.

Do any of the Cortex M4 microcontrollers have on-chip flash memory (or another form of non-volitile memory) that can be used for data? If yes, then how does the program specify this on-chip memory as the location to store the data?

If there is no on-chip memory as described above I assume a flash memory IC can be connected to the GPIO pins of the microcontroller to store the data externally. Are there any resources that would walk me through this process?

I do not need to store much data so using on-chip resources would be preferable compared with purchasing another IC just to store a few bytes of information.


texts: How can I decide whether I can use a Raspberry Pi for my application?

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How do I calculate whether some specific hardware can run my code with a given speed?

It's an image recognition software, and a simplified version of the algorithm is:

Grab a frame (in RGB, 640x480).
Crop it to a given ROI (Region of interest). In my case this would be a 60x60 window, so all the following processing doesn't have to go through all of the pixels, just the ones inside the ROI.
Create a binary image (each pixel has either a '1' or a '0' value), by going through each pixel and applying a simple rule (involving only the intensities of the color of that specific pixel) to decide if that position will have a '1' or a '0' value. This is actually just a color threshold, here's an example of the input and output of this step. In the example the rule is "does the color of the pixel is orange?".
Calculate the geometric center of the binary image created in the last step. This is done simply:

scan the image for valued-1 pixels;
save the coordinates of those pixels in two vectors, one named 'ind_x' and another 'ind_y';
GCx = mean(indices_x);
Gcy = mean(indices_y);

Output the Gcx and Gcy through serial communication.

I'm trying to figure out wheter a Raspberry Pi could process this code 120-times a second (or more specifically, at what rate this could be done in it).

I believe the answer to this question could benefit electronics.stackexchange as well, since it could be abstracted to answer the more general question: given a rough description of an algorithm (clear enough so that one could estimate the complexity of the code) how can I predict whether some specified hardware can process it with a given time constraint?

If more details are needed please say so in the comments.


texts: Why are bitfields in register not sequential?

texts:
Why are the bit-fields in the register not sequential? For example, consider an 8 bit register X . X will have bits 0-2 with flags and 3-6 may be reserved and bit 7 may again represent some flag. Why not use bits 0-3 and leave 4-7 as reserved?

For a practical example, look at the LSM303DLHC datasheet. Register CTRL_REG6_A has the following mapping:

CTRL_REG6_A register:

7: I2_CLICKen
6: I2_INT1
5: I2_INT2
4: BOOT_I1
3: P2_ACT
2: --
1: H_LACTIVE
0: --

Bits 0 and 2 are unused.


texts: How to identify remote keyless entry (RKE) frequency?

texts:
I need to design a system able to identify which frequency is being used by  remote keyless entry (RKE). I found that the wireless carrier frequency can be 315MHz in the US/Japan and 433.92MHz (ISM band) in Europe and can be ASK or FSK. A reference to this can be found at:

https://www.maximintegrated.com/en/design/technical-documents/app-notes/3/3395.html

This was the most reliable document that I found, but this document is old, from 2005,  and I dont't know exactly if there are newer frequencies now. I know there are receivers and transmitters operating in these frequency bands , but for now, I need only to identify in which frequency the RKE is. So I have two questions.

There are another frequencies that are not 315MHz and 433.92 MHz to remote keyless entry?
Someone know a circuit or an IC able to identify these frequencies ?

Any advice would be helpful.


texts: How does a Microcontroller Start and What would be the state of GPIO pins during Initialization

texts:
I am using S32K142 Microcontroller 64-pin.
I am finding some difficulty in reading the reference manual of the controller. I want to know how does the microcontroller initially starts and are there only two basic power modes in the microcontroller?
For power modes, I read in page 1141 of the reference manual. I can see only RUN and STOP (Sleep) as the basic power modes, however there are VLPR and VLPS and other modes. But the basic modes I could find was RUN and SLEEP.
The power mode transition state diagram is given on page 1147.
My question :

How does the microcontroller start?
I am asking in the sense like, what would be the state of GPIO pins during the initial start ? Like, once we provide input voltage to the MCU, there would be some delay till the microcontroller starts its normal operation right? In this delay time, what would be the state be? I read that, the pins would be in High-Z during this short time. But I could not find this High-Z information in the reference manual. Have I missed it?

My main objective is to mention the state of the pin in the working modes of the microcontroller. From what I have read, the modes are -

DURING RESET
NORMAL RUN
STOP (SLEEP MODE)

Just stating the below for an example so that with an example, I can understand better,
Suppose, I have an IC and an I2C device connected to this microcontroller. This Microcontroller provides the Enable to the IC and also establishes I2C Communication with the other I2C Device during normal operation. So, can someone tell me how should I give the information for the pins during the above 3 mentioned states?


texts:
I have a electrical problem that I hope to get some help with. Let me first start of by saying that I'm quite a noob in this field (I'm a IT guy), but I hope to learn something.

The problem I have is this: I have a sensor to monitor the humidity of soil.
When I power it with 3.3v I get a output of 1.9v when it is fully submerged in water and a output of 3.1 v when it's dry.
For my project I actually need a output value between 0.2v and 1.2v

To achieve that, I've created a voltage divider (my first ever) using a 1k and a 2k resistor. When I power it with 3.3v I get a output of 1.04v, which is pretty close to what I want (Close enough I thought).
My schema looks like this:

I measure at points A and B

I powered the sensor with the 1.04v (so at point B), so the connections look like this:

I was hoping to get a well scaled value out of it. Unfortunately the results are not quite what I wanted. When it's fully submerged, I now get 0.71v, and when it's fry I get 0.86. It seems I'm now losing a lot of resultion, so I'm guessing there must be a better way to do this.

This is by the way the sensor I'm using: Link

The reason I need a value between 0.2v and 1.2v is that I want to hook it up to a ESP8266 Wifi module / microcontroller.

Any ideas?


texts:
I'm studying this circuit below which in fact uses a N-channel MOSFET in a power line, with source at the supply voltage and drain at the load.

Why the source is the input supply voltage and not the drain?

LTC4040 datasheet


texts: Schottky diodes in series to reduce maximum voltage at supercapacitor solar charging circuit

texts:
I use the following circuit to store solar energy harvested by photodiodes into a supercapacitor. The cap is rated at maximum 2.8V. The zener diode is rated at 3V, but depending on the harvested solar current it goes up to 3.15V. The schottky diode shall prevent the supercapacitor from discharging into the photodiodes.

Problem is: the voltage drop of the schottky diode is simply too low, which means in direct sunlight the capacitor gets overcharged up to 2.9V -> bad! I do not want to take a lower rated zener diode, as the current one drives the photodiodes nicely at the MPPT in sunny conditions.

Now the question: Are there any disadvantages of using a second Schottky in series, just to get another small voltage drop of around 200mV? That would be sufficient to not overcharge the supercap. But I'm unsure about other side effects. The whole circuit is extremely low power, so I want so save every possible uA.

I have seen schottkys in series, but rather for backup reasons (in case one fails).


texts:
I am trying to simulate a simple inverter in verilog using modelsim 10.7 version. While compiling the code I am getting the -novopt error (error code 12110). As per user manual page 80; the -novopt argument is to be removed from vlog, vcom and vsim commands and from voptflow variable in the modelsim.ini file.

To remove the error, I set the voptflow variable to '0!' but could no find this argument for vlog, vcom and vsim commands. Pls. tell me how to go about solving the issue so that I dont get the error. I am attaching a snapshot of the error popup and my modelsim.ini file here.

Modelsim.ini file doenload link:

http://s000.tinyupload.com/?file_id=88953175349637767605

Thanks in advance.


texts: Phase Margin and Damping Ratio Approximation

texts:
I have read in many texts that the closed loop system damping factor can be approximated as:

\$\Phi_m= 100 * \zeta\$

With \$\Phi_m\$ as the phase margin and \$\zeta\$ as the damping ratio.
The actual relation between the two is more complicated and I think requires numerical method to solve.

How is the approximation made in a second order control system, and when is it valid to consider the approximation (what's the range of the phase margin)?


texts:
I'm looking to make small coils. Or if possible buy a bunch.

But first I started looking into coils. An today I found one that has multiple wires at on side and on the other.

At their end (the connections) they were turned together to make one end on both sides?

so a singlecore multiwired coil.

Question is: Are these better at giving an magnetic field or why do they do this?

This could change my design for my project because they are more studier by the multiple wires that are twisted at the ends.


texts: When do I need a resistor during LED flashing?

texts:
My goal is to flash a few white LED in serial using 9V battery.

Here are the specifications of this LED.

As I saw the Forward Voltage is 3.4V, but what does it really mean?

Can't I plug this LED into more than 3.4V battery without using resistor?

Also I know that max current of this 10mm LED is 300mA.

As I know during serial connection voltage is trying to split to each LED equally. But in parallel connection voltage is the same to each LED and current is growing up!

So tell me can I flash a few 10mm white LED without using a resistor?
If I can.. then tell me how many LEDs should I use?
So what is a solution?


texts: A slow-changing DC signal goes from 0-30mV and I need to shift it to 700mV-900mV. I cannot use op-amps and need a transistor-based solution. Please suggest.


texts:
I need to voltage boost my battery voltage 3V to 12V DC to power cheap RF module transmitter. The boost voltage will last until I transmit 3 or 4 bytes of serial data. Roughly 5ms time.

I read this wonderful article by olin lathrop & trying to understand it.

I need 3V to boost upto 12V. 50mA current is more than enough.
Supply battery is CR123 3V Cell.

I have some questions...!

1) Where is the boosted output voltage calculation? How to calculate it?

2) What component values need to change in the attached diagram to get 12V/50mA?

simulate this circuit – Schematic created using CircuitLab


texts: can contactor, water level sensor and heater all live in parallel on the same circuit

texts:
I want to connect my 3000w (220v) water heating element to a 220v water level sensor Automático de Nível so that the heating element won't turn on when there is no water present.

But the level sensor can't handle the load (1/2 HP max) so I'm using a contactor.. Can I rig it all up in parallel on the same circuit? Please see below schematic.

simulate this circuit – Schematic created using CircuitLab


texts: Why does the collector feedback resistance proportionally affect the amplitude accross the circuit?

texts:
This circuit is a small signal sine wave generator.

R7 and R8 are used to control the amplitude of the output as desired.

After a few simulations, it looks like the gain of the Q3 stage is constant with the collector feedback bias resistance. Also, those R7 and R8 actually end up controlling the amplitude of the oscillation in Q1's base. I've got no idea why.

Please explain this to me. At first I thought those resistances were there to create a collector feedback bias, and such high values would limit the gain significantly, but it remains constant.


texts: FET Current limiter 30A and overload detection

texts:
I plan to make a module for my motorbike to replace fuse by current limiters and overload detection system. I've heard nice things to do with J-FET. It should work up to 12V 30AMP. The detection should return the signal to a PIC Microcontroler.

I have found the explaination below in litterature. It says that when it is overload the current falls to 8mA. Is there any ways to measure it and send a return signal to microcontroler? Thanks in advance!

JFET current Limiter

JFET current limiting circuit is shown in figure.  Almost all the supply voltage therefore appears across the load. When the load current tries to increase to an excessive level (may be due to short-circuit or any other reason), the excessive load current forces the JFET into active region, where it limits the current to 8 mA. The JFET now acts as a current source and prevents excessive load current.

A manufacturer can tie the gate to the source and package the JFET as a two terminal device. This is how constant-current diodes are made. Such diodes are also called current-regulator diodes.


texts: I'm a mechanical engineer and my knowledge of electronics is letting me down please help. I'm looking to run a 1.5V led from an input signal that can vary from 0.3 to 0.5V ac. I want to make the entire circuit as small as possible. Up to now i found i probably need a full bridge rectifier with a capacitor over it connected to a small voltage regulator like a transistor regulator. Would this work? any advise would be much appreciated.


texts: I want to build a battery based DC supply for LED mirror that has AC power cable (230VAC)

texts:
I recently purchased an LED mirror that is AC powered (230VAC). The problem is there is no GPO (power outlet) in the room.

I am trying to make this wireless and wall mounted. I tried researching DC to AC inverters, however they appear to be very large/heavy and powered by a 12VDC socket. This is not practical for the space as I want it to be wall mounted and to have the cables hidden - I can’t connect it to a socket.

I am looking for suggestions on how to convert DC to 230VAC in a compact way I.e. with battery based supply or other

Could I engineer a solution with a DC to AC inverter? How could I build it to be battery based instead of a 12VDC socket input?

An example of the inverter I’m looking at can be found here: https://www.jaycar.com.au/150w-450w-surge-12vdc-to-240vac-inverter-with-usb/p/MI5130

Would it be more effective to design the whole circuit rather than using the inverter and engineering a battery based input? If so, can you please provide suggestions on where to start?


texts: How to work out this implementation of chua's diode?

texts:
The author of a book claims that this is the implementation of Chua's diode by [Kennedy, 1992], although I cannot find this article. My question here is, how does this circuit work? For me, the diagram is a terrible mess.

Note: The circuit shown misses a connection: pin 5 of the (second) opamp should be connected to the input of the device. This is pointed out in a comment.

The voltage-current graph of Chua's diode should look like the graph below. Here are my attempts in making sense of the circuit above:

It looks as if the two opamps are divided into two groups. Each group has identical configuration but different resistor value.
The output potential of an opamp is linear, but cannot surpass its input voltage: in this case 9+9=18 volts. It appears that, due to different resistor values, one opamp reaches this limit before this other: this is where the slope of the line suddenly changes in the graph below.
But what will happen if both opamps reaches this limit?

I cannot figure this out - How can I work out the voltage-current graph from the circuit diagram?


texts: Solar cell to charge LiPo through BQ24075 IC

texts:
I have a 2W solar panel with an open-circuit voltage of ~6V, when I connect it to VIN of the BQ24075, it drops to about 4.5V and the CHG LED indicates it is charging. However, there is no change in mA,mV,mW of the charge circuit (BQ27441). After about 30 minutes of charging (no load), there is no change in the State of Charge (soc %). I am using a 3.7V 2Ah LiPo battery. Is my battery charging?

I have tried all three modes on EN1, EN2… the full 1.5A does not seem to work as it loads the solar cell below the VDDO threshold of 4.35, but both 500mA and 100mA hold a steady voltage at the solar panel. The datasheet of the 24075 indicates it likes to regulate the voltage at VOUT at 5.5V, whereas the 24072 tracks VBAT + 225mV. I had assumed this chip would still be able to charge the battery as long as the VIN was above VDDO (4.35). Can anyone help me understand what is going on?


texts: SMBus is always busy after HAL_SMBUS_Master_Transmit_IT()

texts:
I'm using PMM240 power management board to control battery RRC-2054, and I have problem to use SMBus, please see the code I listed below, looks device is ready, but when you send something, it is always in busy(Master Data Transmission process is ongoing). Will this a matter of address problem, or a command problem, or others? anyway to get more info for this busy status?

if (HAL_SMBUS_IsDeviceReady(&hsmbus2, (uint16_t) PMM240_ADDRESS, 2, 2)
            != HAL_OK) {
        Error_Handler();//passed
    }
uint32_t test = HAL_SMBUS_GetState(&hsmbus2);
        if (test != HAL_SMBUS_STATE_READY) {
            Error_Handler();//passed.
        }
        ret = HAL_SMBUS_Master_Transmit_IT(&hsmbus2,
                (uint16_t) PMM240_ADDRESS, &buffertx[0], 1,
                SMBUS_OTHER_FRAME_NO_PEC);

        if (ret != HAL_OK) {
            Error_Handler();//passed
        }
        // after enough time delay, 100 or 1000 ms
          HAL_Delay(100);//not useful for the following code.
       // inserting HAL_SMBUS_Init(&hsmbus2) could reset the busy status, but info lost, right?
        test = HAL_SMBUS_GetState(&hsmbus2);
        if (test != HAL_SMBUS_STATE_READY) {
            Error_Handler();//not passed
        }


texts: Will this circuit for quiz buzzers work?

texts:
I am a student in 10th class. I have joined my school's science club and I am trying to design a circuit for buzzers to be used in quiz. With normal buzzers, it sometimes becomes difficult to tell that which team pressed the switch first. So I have made a circuit diagram in which When the first buzzer is pressed, all other swicthes will turn off.

This is the circuit diagram:

I have never made a circuit using transistors so I don't know weather it will work or not.

I have to make it on next Saturday (10th May, 2014) so can you please tell weather this will work or not? And If it does not work, then what to do to make it work?


texts:
I once read an article (source : http://ieeexplore.ieee.org/document/7561271/ ) about measure absorbance using photodiode
The formula used is :

\$A= -\log{\frac{I}{Io}} = - \log \left(\frac{V_{sample}-{V_{zero}}}{V_{solvent}-V_{zero}}\right) \$

Where Io and I are incident light intensity and transmitted light intensity

ܸVsample and Vsolvent is voltage when the light transmits a sample and solvent respectively . Vzero is the voltage at
zero light

I understand why they used Vsample - Vzero , but the substraction Vsolvent - Vzero seems to be wrong , this is true only if the solvent does not absorb the light , but in fact even water absorb light . So what did i miss here?


texts: What is the output when D and C on D flip flop are connected?

texts: What is the output when D and C on D flip flop are connected (when they are the same), what happens with set up and hold time in this case? Can someone explain this simple as possible?


texts:
I am working on samD21 MCU to control the 16 relays. I am also using a circuit to detect the input AC switch status On/OFF (Connected serially to the relays). This is connected through optocoupler circuit and buffer IC. and the Relays are driven through ULN2003.
The PCB is pretty lengthy (27cmx10cm) and traces are little lengthy. I have used so many decaps and diodes closed to the relays.
The relays output connected to a 39 ohm 0.01uF snubber circuit. I checked with connecting 440V TVS diode also.
The real problem is whenever the switching happens MCU getting hang. Currently I connected to 10W LED Bulb as load
On the same 3V3 bus I hooked up a esp32 module (same board). which is havig no issues yet (shielded, only uart communication to SAMD21. no long traces other than uart routing).
Help me to figure this out.
I have attached schematics and layout. let me know any more info needed.


texts: How to get dBc level of Cross Polarization and Sidelobe of an antenna?

texts: I literally wonder how to convert from dB to dBc or how to get dBc level of those I mentioned in the title. Specification in this link


texts: Is separation required around a 12V AC input, if its surrounded by 3.3v and logic level voltages?

texts: I personally think it does, but my colleague thinks differently, I would seriously appreciate a proper opinion on this!


texts: How does integrated displays controlled by the computer?

texts:
Consider a run off the mill pc: lcd displays connected, you have brightness control in the menu of the lcd. And some other stuff like color temp and modes.

Now consider a laptop, AIOs and kiosk PCs. Light sensors turns brightness up and down, proximity sensors switches the actual display on or off. And the OS have access to these readings and gives control over it (like a brightness slider for example).

What interface does this controller use to talk to the computer? I've been googling around and there are mentions of GPIOs, or I2C via SMBus, but it might have been deprecated in recent years. What is the current top interface for this usage?

Anyone with experience on this? Does this involves custom motherboards with gpio or extra smbus? I know some embedded Mobos have gpio and i2c header, and on laptop scene I guess the manufacturer can have anything they want. Are these interfaces simply not available on consumer Mobos?


texts:
this may be more of a geometry question than an EE one, but i'll ask it here anyway. I'm trying to build a weather vane, and am looking at using several linear hall effect sensors (such as the allegro 1324) laid out around a shaft with a free-spinning magnet on it.

how many sensors would i need? this is what i'm looking at doing now (they're the sot23w package)

i could get away with 3 laid out on the corners of an equilateral triangle, but... can i get away with half of the schematic above, and just look at the effect from the north pole vs the south pole?


texts: What certification is needed for electronic devices in Europe?

texts: I am going to be selling my project, Super OSD. It has a 3 MHz SMPS PSU and an 8 MHz crystal oscillator, but is not intended to emit radio signals. Will it be necessary to get testing to sell in Europe? I am selling from Europe, the UK to be specific.


texts: Why does a simple conductor start to emit EM waves when carrying a signal?

texts:
I understand that on circuit board traces with a clock, if the higher harmonics have sufficient power, it results in electromagnetic waves being emitted from the traces which creates EMI. What I don't understand is why this happens in the first place?

Why does a high frequency current have to pass through the conductor for it to emit EM radiation and why does this not happen with low frequency currents? What I understand is that the board trace is essentially starting to behave as an antenna in this case but I do not know the reason.


texts: Conserving battery life in a stepper motor circuit

texts:
i'm trying to design a circuit that will control two biopolar stepper motors to scan the temperature of a room.

The mechanism will look something similar to this (minus the gears, and much lighter) but a small IR sensor rather than a camera. The bottom motor will rotate 360 degrees taking measurements every 5 degrees. After the camera has finished a rotation, the top stepper motor will move up 5 degrees. The bottom motor will then begin another revolution until all of the room has been scanned with the sensor looking up at the ceiling.

This is the stepper motor that i will be using it is rated at 12V. However, I plan on running it at 5V to conserve battery life (important as the device is portable and Will send data via WiFi). I was also informed that connecting the battery directly to the drivers enable pin will waste battery life (shown in the figure below) and that I should connect all of them directly to a single GPIO of the micro controller (bearing in mind that I am using two motor drivers, so 1 GPIO to 4 Enable pins).

My first question is does this seem suitable for the application?

Secondly, if all of the enable pins on the drivers are constantly connected to 1 GPIO of the microcontroller, that power has to come from somewhere. i.e the battery, right? How would this method increase battery life? Also, I can't see how you could alternate between switching on the enable pins on the drivers if they are directly connected to 1 GPIO. I seem to be missing some understanding here. Thanks


texts:
EDIT:
I just came back from my local Conrad and replaced the MOSFET with a new one - everything works just fine.
I really just had the bad luck of having three faulty ones lying around. Good that I got that fixed.

EDIT 2:
Definitely check out the answer I've marked as best, as it gives valuable tips on the general design of my circuit and circuits in general. I thank everyone who participated in this, but that answer is one of the most helpful I've seen so far. I especially like the voltage divider, I thought about implementing one but it didn't cross my mind to do it that way. That's definitely a thing to take away from all this that will come in handy in the future.

Original question below this line

After looking around the web for a while to find a way to interface my P-channel MOSFET with my microcontroller, I've come up with the attached schematic that's currently present on my breadboard. The npn transistor is supposed to pull the gate of the MOSFET to 0V, thus making it conduct, and the resistor (10k and 1k tested, same result) is supposed to pull the gate up to 18V when the npn is not conducting. The microcontroller pin is basically running a "blink LED" five line program and works as expected. So far the theory, sadly it doesn't work. The LED between the source of the MOSFET and GND is constantly on and the NPN transistor gets really, really hot.

Should the worst-case load on the transistor not be 18V / 10k = 1.8mA (18V -> 10k resistor -> NPN -> GND)? That's way below the specs of the NPN. Same for the voltage.

Here's my really (too?) simple schematics (the 18V source and the 5V source for the microcontroller share a common ground)

simulate this circuit – Schematic created using CircuitLab

So to sum up the questions: Why does the MOSFET never turn off?
Why is my NPN getting so hot?

I'm sorry if this seems like a redundant question, as there is a lot available on this on the web, but I'm just not good enough to link my problem to any of the solutions and tutorials on the web. It seems like everyone is using this exact circuit to do the job.


texts: Smallest AES implementation for microcontrollers?

texts:
Can anyone recommend a small, free implementation of AES-128 Rijndael for microcontrollers. Ideally, for the PIC18, though a general implementation in C would be useful.

Compiling the axTLS implementation for PIC18 and encrypting/decrypting a block requires 6KB ROM and 750b of RAM.

Compiling rijndael-alg-fst.c for PIC18 and encrypting/decrypting a block requires 28KB ROM and 0.5KB RAM.

Compiling Brian Gladman's 8-bit AES for PIC18 and encrypting/decrypting a block requires 19KB of ROM and 190 bytes of RAM.

Are there better optimised PIC specific variants available?

(updated RAM requirements for axTLS version)


texts: If I incorporate a UL/NRTL listed power supply in our product, must we re-test?

texts:
We are building a product. It's a bench-top electrical testing thing, similar to a Keithley DMM or an oscilloscope in that it's something engineers would use at companies for testing stuff and occasionally would get built into other equipment.

I would like to incorporate the AC-DC power supply in the chassis so all the user plugs in is a power cable. In other words there would be no need for a wall-wart or desktop power supply.

The big concern is that we would need to get UL (or other NRTL) listed for some of our customers. But what if we purchased a UL listed power supply -- something like a PC's power supply with +12, +5, and -12 -- and incorporated it. It would bolt into our chassis and only the back side would be exposed to the customer. Could we claim UL listing?


texts: Show components in Altium schematic, but exclude from design

texts:
I am designing an I2C multiplexer circuit in Altium 17.0 which includes a reset input through a transistor.

In this particular PCB, the reset function will not be needed, and the reset pin of the mux will just be tied to ground. But, I have a small sub-circuit (input port, transistor, three resistors, output port) that generally would be included with this multiplexer.

To save myself time in the future, I would like to leave this sub-circuit on the schematic, but somehow disable it. Obviously, I could just create a copy of the schematic for future reference, but then I'd have to maintain two versions.

How can I "disable" these components so they are not annotated, compiled, or copied to the PCB, but stay on the schematic?


texts: Arduino Mega output at 2.5 Volts and how to pull-down?

texts:
In my arduino project I want to connect the output of first arduino to an input of a second Arduino. Unfortunately on trying I found that the second Arduino input was behaving as always on. On further investigation I found that pin 51 output gives 2.5 volts approximately from the time I power the first arduino. All other pins are 0 or nearly 0.
I read through the forums and found that input pins need to be pulled down for stopping them from floating, but should it be required when connected to output of the first arduino?
Should I use a pull down resistor to the rogue output? I if I add a 5kohm resistor grounded between this output and input of second Arduino should it be ok?
Weirdly in the IDE this pin (51) variable name "L" shows up as green while others are black.


texts:
I am trying to replace some electric timers with some sort of a micro-controller based solution http://www.directindustry.com/industrial-manufacturer/panel-mount-timer-154503.html. I would like to run at least 10 timers from one micro-controller, a 20x4 LCD and 4 push buttons. All these requires 38 pins (I think I counted it right). The LCD will display the timers set value. Since there are 10 timers I though a 20x4 will be ideal. The push buttons will be used to set the time. The timers will be independent from each other.

I was planning to use a PIC16F887A micro-controller but I released that the number of pins are not sufficient. An Arduino Mega would be ideal but forums suggested that it is not reliable for an industrial application. What other micro-controllers are out there for this sort of application.

The current timers has 24V inputs and 24V outputs. How can address this issue?

I am new to this micro-controller business and PCB designing. I've been trying to learn on the internet so some links would be really helpful, specially for programming.

Also, do you guys think replacing those timers with a micro-controller is a good idea?

Thanks a bunch.


texts: Switch controlled by open/closed circuit

texts: I am looking for a specific product: a type of switch that has an 2-pin remote connector. If these 2 pins are open-circuited, it should produce no (or low) voltage (on different output channel). If those 2 pins are short-circuited, it should produce around 12V. I do not have good knowledge of eletronics components. Are there any solutions for such a situation?


texts: RS485 slew rate limiting remove need for termination

texts:
In regards to the highlighted feature of "slew-rate limiting" RS485 ICs. It says in multiple brand datasheets that the slew-rate limiting helps with transmission errors when there is incorrect termination.
My questions are:

Does the slew-rate limiting remove the need for termination completely? Only at certain baud rates or cable lengths? I know 9600 baud is pretty stable as-is; I am particular curious about and 38400 to 115200 baud.

How would the RS485 bus behave if there is a mix of slew-rate limited ICs and non-limited ICs on the same bus? Does the slew-rate limiting only work if all RS485 ICs on the bus have this feature? Or can the feature be utilized locally on one PCB if it is the only one on the bus with a slew-rate limited IC.

Thanks!


texts:
A powerful thunderstorm rolled through my area yesterday and something happened that I had never noticed before.  Many times before when powerful thunderstorms with lightning rolled through, the AC mains power has either not been affected or went totally out after a nearby strike.  Yesterday something different happened...

After a very bright and loud (and most likely nearby lightning strike, but not sure where it could have hit), the AC mains dropped out (to zero I guess) and stayed out for about 5 seconds then came back ON....   What could have caused this?  I am fairly certain there are no grid substations too nearby where I live.  Furthermore, I guess to answer this question, we have to assume that my small city uses the most common or "default" type/method of electrical power distribution.


texts: Finding out the current through the battery

texts:
An electric network is formed by two hexagon and joining grid points with wires.The resistance of each side and the connecting wires  is \$R\$. An ideal battery of emf \$E\$ is joined as shown in figure.The question is to find out the current passing through the battery.(Assuming that the wire   connected with the cell is ideal).

I tried to find out the current distribution in the network.

Since the current cannot distinguish between the three branches hence it should divide equally. I have used the same symmetry arguments in other cases.However when i used kirchoff law in the outer loop i didnot get the correct answer.I couldnot understand where i have committed mistake

Here is my attempt after the answer below.

The simplified circuit in the answer can be redrawn as

which can also be manipulated as

The repeating unit in the above circuit is

and so the circuit simplifies to

which is similar to

But doing all this doesnot yields the correct result.Am I doing wrong somewhere.I tried to use star delta transformation but that complicated the circuit.Thanks.


texts: How to convert 4 wire speaker level output to 3 wire line level

texts:
I have a Shark Motorcycle Audio radio that has differential (balanced) output for the left and right channels. I wish to convert this to a 3 wire line level signal to the input of my headphone amplifier. A similar question was posed in March of 2011 under the topic: Stereo line-level converter: Odd grounding?

An answer by user3524 includes a diagram which I have a question about. What are the correct resistor values for R1, R2, and R3. In the balanced in, balanced out section, it is stated that R1 and R2 must be equal. The value of R3 is not addressed. In the balanced in, unbalanced out (which is what I need) R2 and R3 are combined and a value of 680 ohms is suggested, with a value of 4.7K suggested for R1. I don't understand how the R2/R3 combo could be less than R!, if R1 and R2 are supposed to be equal. Can anyone help explain? Thanks.


texts:
I have a homework question but no idea what this circuit does and how to make calculations. In the simulation input and output voltages are same why?

Thanks for any help


texts: Are there any guidelines to injecting power at the USB 3 device side instead of having it powered from the host? Basically making it self powered?

texts:
I am trying to power two USB 3 cameras off 24V, so I can  power a LED circuit at the same time, instead of 5V and basically put a 5V regulator at each camera side. I am wondering if there were a good way to do this or I would just have to power it from the USB port.

Left the 5V from the USB host device floating and connected the grounds together
Both the device and computer are powered from the same 24V power supply
The system works at USB 3 without dropping frames when one camera is plugged in, but drops a bunch of frames when two are plugged in
Plugging both cameras in directly with a USB 3 cable works fine

Here is a basic schematic

The SBC is powered off the same 24V as the USB3 camera
The two 4-layer PCBs are designed to have a 90 ohm differential impedance, but not impedance  controlled
The connectors are made for USB 3 speeds
Never tested the loss of the entire path
System works at full bandwidth with a single powered camera setup when the SBC is replaced with a floating laptop

Thank you


texts:
I am working on project with esp8266 UC powered with 3.7v lithium ion battery, where the reset pin is pulled low to keep it OFF.

I would like to know if my battery were to be consumed with this method or it is like powering off the MCU, and then there is no power consumption.


texts: the top cell of Li-ion battery is no longer good, its buldged out, looking for replacement info..out of a Schumacher Red fuel portable jump starter

texts:
Schumacher Red Fuel Pocket Power Jump Starter Booster Pack and Backup Power it is not in warranty..the mfg does not offer it on ipl https://www.ebay.com/i/324290187018 .i already removed the battery and the top cell is buldged out and separated when i removed the wrapping......the unit kept saying reverse polarity detected with it not connected to anything...it is in an orange wrapper has GLP7445135 5799000040 Rechargeable Li-ion Battery 3000mAh 38.4Wh 12.8v 4IFpP 34/50/155 1607141
the closest match i am able to physically see is..https://dirtcheaprc.com/shop/11-1v-6500mah-3s-cell-75c-150c-hardcase-lipo-battery-pack-w-traxxas-high-current-style-connector/ but it doesn seem to have a thermal temp sensor that has a separate plug to the board..im nor worried about that as i believe the newer ones dont require it as its built in...
i have seen 14.6v with 9000mAh but trying to find a matched size replacement..most vehicles when charging will hit 14.5vdc. i build my own vehicles as a hobby and i am a commercial HVAC tech working on units up to 460v 3 phase to 150amps so i know all about high voltage precautions and seen explosions before..  i have been bit by it also, its not fun, ya gotta be quick to pull away..
i enjoy repairing my own stuff, been doing electronics as a kid and used to make my own circuit boards way back in high school and still solder failed components to this day...
does anyone know of a suitable replacement of just the cells or a suitable replacement?


texts:
I am practising for my radio license exam. One of the questions from an old exam:

This filter belongs to a 3.7MHz transmitter. Approximate the impedance Z for a load of 50Ω.

Answers: 1kΩ; 50Ω; 10kΩ; or 10Ω.

I thought I could calculate the reactances of the inductors and capacitors (left is C1; assuming full values for the caps and 2.5uH for the inductor):

\$X_L = 2\cdot\pi\cdot3700000\cdot0.0000025 = 58.12\Omega\$
\$X_{C_1} = \frac1{2\cdot\pi\cdot3700000\cdot0.000000000463} = 92.90\Omega\$
\$X_{C_2} = \frac1{2\cdot\pi\cdot3700000\cdot0.000000001852} = 23.23\Omega\$

And then proceed to compute the substitution resistance of C2 with Rload (parallel), then combine with L (series) and finally with C1 (parallel). I do that with Pythagoras and get:

With C2 and Rload: \$Z_1 = \sqrt{50^2 + 23.23^2} = 55.13\Omega\$
With L: \$Z_2 = \sqrt{58.12^2 + 55.13^2} = 80.11\Omega\$
With C1: \$Z = \sqrt{92.90^2 + 80.11^2} = 122.67\Omega\$

This is not one of the answers. The correction model says it should be 1kΩ, but how should I calculate that?


texts: Does the charge of a battery affect its discharge voltage or current?

texts: Although I am making an electrochemical battery (1 lead acid cell), I thought that this question would be more suitable here. Would there be any difference in the voltage and current of the cell (when connected to a lightbulb) between a cell that was charged for 5 minutes vs. a cell that was charged for 10 minutes? I'm guessing that the voltage supplied and current will remain the same but only the time until the bulb runs out will be longer with a 10 minute charged cell?


texts: What is the role of the diode D1 in this ramp generator circuit?

texts:
The circuit below is a ramp generator used in switched power supplies to generate a saw-tooth signal for compensation, but I don't really understand what is the role of the diode D1 in the circuit ??

simulate this circuit – Schematic created using CircuitLab


texts: Any rules of thumb to fix this non-functioning board I just made?

texts:
I just reflowed this PCB. It is a 20 x 16 mm PCB with a Nordic nRF52832 Bluetooth Low Energy (BLE) SoC IC. I powered it on and the regulator, mounted on the back, got very hot.

I measured the Vcc and GND outputs of the 3 V regulator and read 50 ohms. That is wrong. I checked all my capacitors, since I suspected it was something connecting Vcc and GND, and they seem fine.

I found a solder bridge on the nRF chip and fixed it. I would expect to see a short if there were problems, but not 50 ohms. I have no resistors between Vcc and GND that could cause this. Where would 50 ohms come from? I accidentally connected power to the regulator backwards at first, maybe something is wrecked.

I took the suggestions here and then built another one. This one I could program and blink the LED. I was helped by your comments. Here is a photo of it working. The photo caught when the LED was on.


texts: Exchange serial messages via UART between 3.3V µController and 5V µController concrete (STM32F4 and ATMega 2560)

texts:
I would like to send messages from STM32F4Discovery board to Arduino Mega 2560 via UART.
How do I connect the Arduino to the STM32F4Discovery? Do I need any extra electronics? If I understand correctly, Arduino's UART has voltage level of 5V and the STM32F$ 3.3V.


texts:
I’m currently getting ready for an Electronic Systems Engineering exam, and going through past paper questions.

I need help with a few questions regarding the following current limited regulator.

The questions:

Find the zener voltage of Dz if the required regulated output is 12V.
Calculate the value of R for safe operation if the input voltage is 15V and the power rating of Dz is 0.5W.

My answers:

My questions to you:

Have I approached the first question correctly? Can you please confirm my answer?
In the second question: what is a “safe” current for the zener? Of course it should be less than the maximum current found from its power rating. But how much less? (I just randomly assumed 30mA)


texts:
I'm a beginner in electronics and my knowledge is pretty basic. I've been trying to understand how the Octopus Component Tester Works. I know that it's outputs should be used to plot a Current x Voltage relation in an oscilloscope, but I don't understand why we use the resistor's current and not that of the actual component that is being tested. I also don't really know how to analyse circuits where the voltage is varying. I would be really grateful if someone could explain how does it work. Here's the diagram:

The probes in the diagram are where the component to be tested should be attached to.


texts: Is there a device which acts like an accelerometer but only measures absolute velocity? I could integrate the accelerometer's output but errors quickly accumulate and cause problems. Preferably the device is available in a MEMS based chip and is low cost. I could use a GPS device (and am currently, with success), but this is expensive, bulky, and requires a GPS link, which is not available in all circumstances.


texts: Powering 4 modulated IR LEDs through transistor

texts:
I've done some research but can't seem to find an answer to my specific problem.

I'm using an Arduino as a beam-break sensor. In order to do that it modulates the IR LED at 38kHz by code and listens for this signal on the sensor pin.
Now, I want to increase the range of this system to 15m using a retroreflector on the other side. In order to do that I need more power on the LEDs than the 20mA the Arduino can output.

As I understand it I will need a transistor to do this.

I have ordered these LEDs

And these TIP120 transistors

Will I be able to accomplish having 4 LEDs running through this transistor at 100mAh each and then have the Arduino modulate the transistor at 38kHz so the combined output of all LEDs is modulated?

I already have a 12v power supply in place so that will be the supply voltage for the system.


texts: i need atmega 16 output to toggle using switch

texts:
i built remote controlled switch and connected its output to PB0 in atmega16 microcontroller

then connected pir sensor with single trigger configuration for 30 sec and connected to PB1 in atmega16

here is the circuit

my goal is to put pir sensor to detect that i entered my room so it trun on the light (this point is done in the code)

my problem in the RC switch i want it to toggle the status of PB1 so i can control turning the on and off using it

i used this code

/*
 * AVRGCC4.c
 *
 * Created: 7/9/2017 20:05:11
 *  Author: shadylap
 */

#include <avr/io.h>
#include <util/delay.h>
int main(void)
{
    DDRA= 0b11111111;
    DDRB= 0b00000000;
    DDRC= 0b00000000;
    while(1)
    {

       if (PINB == 0b00000010)
       {
           _delay_ms(500);
           PORTA = 0b00000001;

       }

       if (PINB == 0b00000001)
       {
           _delay_ms(1000);
           PORTA &= ~ (1<<PA0);
       }

          }
    return 0 ;
}

when i switch on IR switch the led keeps turning on and off but i want when i turn IR switch on led toggles its state once only

new update .....................................................................  i used this code but its not working in the Proteus simulation although it was working before why ??

    #define F_CPU 1000000UL
#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/delay.h>

int main(void)
{
    DDRA=0b11111111;
    DDRB=0b00000000;
    DDRD=0b00000000;

    MCUCR |= (1<<ISC00);
    GICR |= (1<<INT0);
    sei();

    while(1)
    {
    if (PINB == 0b00000010)
    {
        PORTA = 0b00000001;
        _delay_ms(500);
    }
        return 0;
    }

}

ISR(INT0_vect){

        PORTA ^=(1<<PA0);

    }


texts:
...hi :)
a few days back I saw this Instructables..

https://www.instructables.com/id/Using-Diode-As-a-Solar-Cell/

...so I started to experiment how this can be used to charge a cellphone or a battery. I soldered 3 block of 11 diodes in series, each soldered in parallel (as show in the picture)...

...here is it really desorganized (but it works)...

...taped the diodes to a lamp and as you can see a LED lights up (it can shine harder so I want to know how)...

...when I measure Voltage it shows up to 30 V...(!) (don't know why)
...haven't been able to measure Current.
...also I don't understand why the Led haven't burned out and why it is lightning up.

... so my question is:
If the LED lights up, does this means that Voltage and Current are flowing?

...and a more general one:
Have anyone tried to give diodes this use and how can I improve my approach?

thank you very much! :)


texts: Help to verify this power supply's isolation property from its data sheet

texts:
How can I tell whether this power supply  provides any isolation by design or not, from earth ground?  (i.e. is its output floating with respect to earth ground on the AC side)

Here is the only data sheet I could find.


texts: RP2040 Board receiving weird output from SparkFun Ublox NEO-M9N GPS Unit

texts:
I am a software engineer, but new to hardware hacking, so I apologize if this is missing any detail, I will be thorough.
I am working on a small tracking system as a personal project. I am using a SparkFun Pro Micro board based on the RP2040 that I had laying around as a microcontroller, and I want to use the SparkFun Ublox NEO-M9N as the GPS unit. I had a spare ceramic antenna that I attached to the GPS unit's antenna socket. For the software side I installed MicroPython on the MC board.
When I tested the components separately, they all work. The GPS unit works well with my macbook, and with gpsmon I can verify that it has a lock and the location is correct. It seems like it defaults to GLONASS, but once I figured that out it wasn't hard to translate the sentences.
My problem is that when I soldered the boards together and try to run code on the board to print out the serial communications across UART if gives me junk data.
I expected to see the GPS sentences you might expect i.e. $GNPLL .....
The PPS LED still blinks indicating that there is a satellite lock, and the power flows freely - no suspect sparks or smells indicating a bad burn or anything.
I have been looking around to find any support, but it doesn't look like it's out there or I know the correct search terms.
I was sure to do the following:

Attach Rx to TX and TX to RX on the boards

Check that the baud rate of the GPS and the board match (baud rate is set to 115200, compatible according to both board's data sheets. In the below example I use 4800, but 115200 gives the same junk output)

I have considered that it could be an encoding issue, I have found some references to a UBX format online, but can't find the documentation.
I also considered that I could have soldered poorly, could poor solder connections explain the output above? I also accidentally soldered the CS port closed, but didn't cause any shorts, I had assumed it would be okay.
Soldering work here:

I redid the soldering on the Yellow RX cable to improve the connection. Checking the output with a baud rate of 115200 as specified in doc sheets yields:


texts:
I am attempting to use thin, flexible solar panels to charge a battery on a plane (RC) for a school project. After fully charged, I will begin flying the plane, and the panels will hopefully extend the flight time by charging during flight. The battery is a 2100mAh, 11.1V LiPo. The solar panels will be placed on the wing, which is 7.5" x 31". I may be able to fit a couple of small panels on the tail as well. The problem I have is finding appropriately sized, lightweight panels that can produce at least 600mA of current. A few of my options are:
1.) 6.0V, 100mA, 4.5x5.9"
2.) 7.2V, 100mA, 3.0x10.0"
3.) 7.2V, 200mA, 5.9x10"
4.) 4.80V, 50mA, 3.0x3.7"
 5.) 4.20V, 22mA, 1.5x.3"
I'll need to wire two panels in series to get the necessary voltage, but then I'd need multiple sets of these in parallel to get a worthwhile current going. Would it be possible to wire the large 7.2V, 200mA panel in series with a small 4.80V, 50mA panel? Would that result in 12V and 200mA? If not, are there any better configurations with my options? Otherwise, it looks like I could only get 200-300mA with the larger panels.


texts:
I'm currently trying to count the pulses from a 555 timer. I've opted to use a 74LS590 (8-bit binary counter with output register; 3-state).

However, I can't get the counter to count anything. I've checked on the datasheet and I think I wired everything right. Am I missing something ?

Thank you.


texts: I need to connect the vcc pin to a bluetooth module but then I need to sue it again for a relay module what do I do?


texts: What would be the voltmeter reading in the following circuit?


texts:
I'm working on a circuit to turn on and off a set of lights on a vehicle.

I have to do the switching on the high side of the lights and need to use a positive voltage to trigger them on. So, I've got a little NPN transistor that grounds the gate of my P-Channel FET when it gets voltage and sends current from the battery to the light.

It works great breadboarded out but I am concerned about protecting the MOSFET and (maybe the BJT) when it's on a vehicle. Do I need a Zener or TVS diode somewhere? Where should it go? What does it need to do? What values do I need to look for when sourcing it? I am more than happy with overkill.

This is the FET I was planning on using: SQJ459EP. It has a diode built in between the drain and the source but it might need something to protect the gate?

Thank you guys for any help you can give me!

Edit: Fixed Schematic


texts: A "Dark-on" opto-isolator that is normally conducting when the LED is turned off

texts:
I brought up this question in my previous question on Connecting a Camera Hot Shoe to a homemade strobe, but there was no answer to this specific point.

Is there such thing as a "dark on" opto-isolator, that allows current to flow through pins 5 and 4 when no current flows trough pins 1 and 2, and blocks current through pins 5 and 4 when a current flows trough pins 1 and 2?

This will be like a normal opto-isolator, but it "turns on" when the LED is turned off, instead of the opposite.


texts:
I am using the Basys 2 Spartan-3E FPGA board with Xilinx. I need the pmod i/o to be at 1.8v so I am using LVCMOS18 IOSTANDARD.

You can find all of the IOSTANDARD's available for Spartan-3E in this document.

Whenever I try to compile my project it always errors out on the Place & Route phase that says:

ERROR:Place:864 - Incompatible IOB's are locked to the same bank 0
   Conflicting IO Standards are:
   IO Standard 1: Name = LVCMOS25, VREF = NR, VCCO = 2.50, TERM = NONE, DIR = INPUT, DRIVE_STR = NR
   List of locked IOB's:
    mclk
ERROR:Place:864 - Incompatible IOB's are locked to the same bank 3
   Conflicting IO Standards are:
   IO Standard 1: Name = LVCMOS25, VREF = NR, VCCO = 2.50, TERM = NONE, DIR = OUTPUT, DRIVE_STR = NR
   List of locked IOB's:
    LEDs<7>

I have done some research on that error and I believe it means that there are different IOSTANDARD's on the same bank. The pins that I directly set are on bank 1 but the conflicts are on bank 0 and bank 3. When I remove the IOSTANDARD from the pmod i/o it compiles successfully but those pins are not 1.8v then.

My constraints file looks like:

# clock pin for Basys2 Board
NET "mclk" LOC = "B8" ; # Bank = 0, Signal name = MCLK
NET "mclk" CLOCK_DEDICATED_ROUTE = FALSE;

# Pin assignment for LEDs
NET "LEDs<7>" LOC = "G1" ; # Bank = 3, Signal name = LD7
NET "LEDs<6>" LOC = "P4" ; # Bank = 2, Signal name = LD6
NET "LEDs<5>" LOC = "N4" ;  # Bank = 2, Signal name = LD5
NET "LEDs<4>" LOC = "N5" ;  # Bank = 2, Signal name = LD4
NET "LEDs<3>" LOC = "P6" ; # Bank = 2, Signal name = LD3
NET "LEDs<2>" LOC = "P7" ; # Bank = 3, Signal name = LD2
NET "LEDs<1>" LOC = "M11" ; # Bank = 2, Signal name = LD1
NET "LEDs<0>" LOC = "M5" ;  # Bank = 2, Signal name = LD0

# Loop Back only tested signals
NET "spi_si" LOC = "B2" | DRIVE = 2 | IOSTANDARD = LVCMOS18 | PULLDOWN ; # Bank = 1, Signal name = JA1
NET "spi_so" LOC = "A3" | DRIVE = 2 | IOSTANDARD = LVCMOS18 | PULLDOWN ; # Bank = 1, Signal name = JA2
NET "spi_cs" LOC = "J3" | DRIVE = 2 | IOSTANDARD = LVCMOS18 | PULLDOWN ; # Bank = 1, Signal name = JA3
NET "spi_sck" LOC = "B5" | DRIVE = 2 | IOSTANDARD = LVCMOS18 | PULLDOWN ; # Bank = 1, Signal name = JA4

NET "sw0" LOC = "P11";  # Bank = 2, Signal name = SW0

How do I fix these conflicts?

The Basys2 has the CP132 package. Here is the chip diagram and bank schematic:


texts: Effect of parameters on feedback system and some confusion regarding it

texts:
I am confused in some basic terminologies of feedback system and its requirements
1.what is difference between actual input ,reference input and disturbance input ?
2.is reference input setup by designer or its unwanted input ?
3.is output of of the feedback settle at value equal to reference input after infinite time?
4.I know feedback minimize the effect of disturbance input ,but what about other two inputs i.e actual input and reference input ,how does feedback system effect these two inputs ?
I am ok with rigorous mathematics ,if anyone wants to explain by maths by taking any particular example and even a theoretical answer would also be appreciated!
I'll add paragraph of book by Bernard Friedland for more context about question
!


texts: 2 Voltage regulator wired together to produce higher amperage possible?

texts:
I need a 12V 2.56A regulator. I happened to have 2x 2A 12V linear regulators I brought and did nothing with.

I was wondering could I wire them together and get 12V 4A or would I have divide my circuit amongst the two regulators? A schematic of how I would wire them would be much appriciated.


texts: Can a button control a 5 speed fan without a microcontroller?

texts: Is it possible to control a fan with a single button that cycles though fan speeds without using a micro controller.  Can anyone point me to some documentation on how this would work or any ideas how this could work?


texts:
I am trying to work out USART ISR's on the ATmega 328P. So far I have got the USART rx and tx working. I have come across a strange issue when it comes to the UART ISR's, though. The ISR seems to override the delays, causing the code in my main loop to run without a pause.

Consider the following code (which is complete and functioning for easy troubleshooting):

#include <avr/io.h>
#include <util/delay.h>
#include <avr/interrupt.h>

#define FOSC            16000000
#define BAUD            9600
#define BAUD_GEN_VAL    (((FOSC/BAUD)/16)-1)

void uart_tx( unsigned char data );
unsigned char uart_rx( void );

void main(void)
{
    sei();  //enable interrupts globally
    UBRR0H = (BAUD_GEN_VAL>>8);
    UBRR0L = BAUD_GEN_VAL;                  //set baud rate
    UCSR0B |= (1<<TXEN0) | (1<<RXEN0);    //enable transmitter and receiver
    //UCSR0B |= (1<<TXCIE0);              //Enable interrupt on TX (serial)
    UCSR0C |= (1<<UCSZ00) | (1<<UCSZ01);  //8 bit data

    while (1)
    {
        uart_tx('A');
        _delay_ms(2500);
    }
}

ISR(__vector_USART_TXC)
{
     //blink an led here or something similar
}

void uart_tx( unsigned char data )
{
    while ( !( UCSR0A & (1<<UDRE0)) );   //Wait for empty transmit buffer

    UDR0 = data;    //Put data into buffer, sends the data
}

This code works perfectly, printing "A" to a serial monitor every 2.5 seconds. However, if I un-comment the line UCSR0B |= (1<<TXCIE0); — which enables the interrupt on transmission completion — the microcontroller spews "A"s out so fast that the serial monitor can't even keep up.

I can't understand how this is happening, however. It is as if the ISR did nothing but override the delay! Can anyone shed light on this?


texts: What is the resistance of a low-pass filter

texts:
I'm trying to build a low-pass filter for converting the PWM output of an Arduino to a (somewhat) stable DC output with the corresponding voltage.

I'm using the RC filter design shown on this online calculator.

I have a 0.1uF capacitor at my disposal. Using this calculator I concluded that a 20kOhm resistor is enough for the ripples to become acceptable (PWM Frequency is 980Hz).

I already tested my circuit without using PWM and a low-pass filter and instead just put a resistor in (it's powering an IR LED, very simple circuit: Just one resistor and one LED). I realized that I can't put in more than 1kOhm before the LED gets too weak to be detected by my IR receiver.

The output on the linked calculator confuses me because even though there's a 20kOhm resistor connected to the source, the output can reach the full 5 volts the Arduino is supplying.

So I wonder, what resistance does this low-pass filter (resistor + capacitor) actually have? If I don't put in another resistor after the low-pass filter, will my LED burn out?

I'm sorry if this is badly worded, I'm new to the world of electrical engineering.

Background:
I'm trying to produce a square-wave, making both the voltage and frequency controllable by the Arduino. Therefore I need this low-pass filter converting the Arduinos PWM output to a steady DC output. I then feed it through a transistor which is controlled by a second Arduino output delivering a square wave (say 38kHz, produced by tone()). This will then power an IR LED used to detect distances. By changing the duty cycle of the PWM output I can then control the voltage of the 38kHz signal the LED gets, and can use this to control the sensitivity of my distance detector (I'm aware that I can also use a frequency sweep instead, but this doesn't work for reasons unrelated to this question).


texts:
Radio data system is the standard used for embedding small digital information in FM radio. I am excited for the release of the new RDS 2.0 standard. But I am not really sure if the technical standard has been finalised. If it has been finalised, can you point me to the documentation of technical specifications of RDS 2.0?

Are there FM stations or FM radio equipment that support RDS 2.0? Or are there atleast plans or announcements about any FM stations or FM radio equipment supporting RDS 2.0?


texts: How can I prevent my switching power supply from sudden voltage increases?

texts:
I'm currently using a 3kW AC/DC converter which gave 48VDC output(Switch mode power supply). The device is capable to deliver up to 62.5A current to the load.
My application is a cyclic movement driven by a motor. Due to high torque requirements, the motor draws up to 25A current from the converter. The movement completed within 1 second and after then it starts again for n-times.
When the cyclic movement is finished, the output voltage of the power supply increases up to 62VDC. Since the device has internal over-voltage protection it shuts down itself and I cannot continue to my application.
How can I overcome this problem? Is there any solution to prevent that sudden voltage increase?
Thank you all


texts: How to measure duty-cycle with Input Capture from STM32F103C8T6?

texts:
I'm trying to measure the duty-cycle of the 0-5V electrical PWM signal I have generated from the any source. How can I do this? Anyone can help me?

IDE: Keil
Microcontroller: STM32F103C8T6


texts: Designing a 6V --> 40V step up converter

texts:
I need to design a step up converter with the following requierements:

Vin = 6V - 8.4V
Vout = 35 - 40V, Iout = 2.5A

Could anyone give me some insights on how to start it? I have found some step up schematics but could not find any that could deliver 40V and 2.5A.
Any reference is well apreciated.

Best,


texts: Thermal resistance - Temperature transistor

texts:
I have a transistor with Vsupply = 24VDC, VCEO = 45VDC, ICE = 20mA. How to calculate the delta T (rise in temperature) of this transistor. I would like to know what thermal resistance I may have at maximum.

In my opinion:

Pdissipation (worst case): 24VDC*20mA = 480mW (current loop, almost all current goes through this transistor)

If the thermal resistance is for example 120 K/W (or C/W) the delta T would be: 120*0.48 = 57.6 (rise). This means my transistor will become around 25 (ambient) + 57.6 = 82.6 degrees.

Is my calculation correct, or do I need to observe other parameters as well? I need a very small transistor package, but it must be able to dissipate ~500mA and work in an ambient environment of +55 degrees.


texts: Can North American split-phase 220VAC supply power to a device designed for single phase power?

texts: In North America I know we use split-phase 220V power. I am wanting to purchase an industrial power supply that has an input rating 100-240VAC, and has 3 input terminals labeled ⏚, L, N. I know the N is for neutral, which would apply to most of the world which uses regular single-phase 220V. But can I plug split-phase power (with its two hots, 180 out of phase) into those two L, N terminals safely?


texts:
I am currently designing a product that needs to be waterproof (IP67.) The product also requires some user interaction - basically at least one push-button and one LED.
For the LED I am using these IP68 light guides.
There seems to be no easy solution for the push buttons. I would like to avoid using push buttons that have to be screwed into the front panel, like these because they would increase product cost significantly as they are expensive and complicate the assembly process a lot (because they need to be soldered after they are screwed in.)
I think the optimal solution would be one with a flexible membrane in the middle and a plastic outer ring that provides a similar snap mechanism as the light guides do so I can mount the switch on the PCB and only need to mount the seal to the case.
What are the best practices to cost-effectively add buttons to IP67 designs?


texts: Using a barrel jack with higher than rated current but lower voltage?

texts:
I have a 5V/10A power supply (with a 2.1mm DC plug) and want to use it to power four or five 5V/2A devices.
But I see that no barrel jacks are rated for 10A (they're all around 5A max - see this Digikey search).
Is this really an issue? I would have thought parts likes jacks, that are basically little more than a metal conductor, would be rated for e.g. a max wattage.
But I see on places like Digikey that instead they're rated for a max voltage and a max current (12V and 5A seem typical values).
It seems odd to have a power supply with a 2.1mm DC plug if you can't actually get a jack that can handle the supply's current. So is it OK to use a 12V/5A rated jack with a 10A power supply as long as the voltage is half the max rated? If it's not OK then what are my options and if it is OK is there anything else I need to watch out for?
I was planning to just twist the wires of my various power cables together and screw them down in a 2.1mm jack-to-screw terminal block. Or solder down a barrel jack on a proto board and then solder each power cable on separately to the same board.
These kinds of setups have always worked out for toying around with typical 5V/2A setups but will there be issues once I start dealing with higher currents?
Parts I'm using:

(source: odroid.com)


texts: Expanded standard deviation in logarithmic scale

texts:
Hello and good day to all.

Referring to picture attached I have a question.

.

I am working on different measurements and trying to find the mean and standard deviation values of these measurements. The values are given in dBuV/m so for calculating different values I have first converted them to linear scale and applied the formualas of mean and standard deviation. My problem is till calculating mean or avg value I am getting the as expected result "When I converted these linear values back to Logarithmic scale". But for standard deviation I am not getting the correct value when I converted it back to dBuV/m scale. The standard deviation after the measurement values shouldnt be more than 1-3 dB but strangely I am getting "70 dBuV/m. Do anybody has any idea where is the problem. Here below I am pasting all the formulas i have used so far.

From dBuV/m to linear scale \$=\dfrac{10^{value/20}}{1,000,000}\$
For calculating power average \$=
\sqrt{\dfrac{x_1^2+x_2^2+x_3^2+x_4^2.....x_{10}^2}{10}}\$
For standard deviation \$= \sqrt{\dfrac{\sum{(A(i)-Avg)^2}}{9}}\$
For expanded S.D I multiplied S.D with 2.228 to get 95 % of confidence level of guassian distribution.


texts: Connecting multiple LED strips in parallel to a 220v/5A power line (via 12V driver)

texts:
I would like to power 5 LED strips via a 220v/5A wall outlet (each strip is 5m in length). I will be consulting and employing the electrician for the best way to run the wiring but from the initial phone call, he said he isn't too knowledgeable about LED strips and said he would bring along a fellow professional. Until that happens, I'm hoping I can get a better understanding on this topic from the folks on this group.

The reason I would like to run all 5 strips from the same socket is so I can power them all using a single switch that already happens to be in the wall switch board. Please note that I will be using a 12V/5A driver at the head of each strip.

My concern is whether powering all 5 strips from one socket is even possible. When I look at the LED specs, it says the power consumption is 72W for 5m which I take means a current draw of 6A. WOuldn't that mean just one strip would max out a 5A mains supply line or am I wrong in my calculations?

If indeed each strip requires one 5A line, does this mean I will need to power each strip from a different wall socket (or 5A line)? AFAIK a 5A line is good for 1100W (220vx5A) but as I've described, that contradicts the 'amperage view' if I can call it that. I'm pretty sure I'm messing up something here, just hoping you knowledgeable folks can help me sort my confusion.

My end goal is to have all 5 strips controlled by a single wall switch. If there's a better way to go about this, please share your thoughts.

While we're on this subject, I would also like to run some safety fuse into each LED strip. What's a good way to do it? get a 7A fuse? Would appreciate pointers to any products or links that explain adding the fuses.


texts: Reliability and failure mode of MLCC (chip capacitors)

texts:
Recently I've been preparing to manufacture a product which exclusively uses MLCC capacitors across the board. It integrates an onboard buck converter which uses them, and MLCC are also used for local decoupling.

My prototypes have consisted of "dodgy" reflow techniques using a hot plate. Generally, 10% of the time after doing this, I find a shorted MLCC on the board, usually found because when power is applied, the cap will smoke.

However, just right now I was replacing one of these caps with a soldering iron and after I had replaced it, it was still shorted. I verified there was no other short circuit on the board (because when removed 3.3V showed a few kohms of resistance.) It seems the simple operation of soldering the cap has caused it to fail.

I've also recently repaired an LCD monitor which had a shorted MLCC on the T-con board and a few other users on a popular forum have reported this issue as being surprisingly common. Now, in this case, a monitor gets warm or hot, but no where near as hot as a soldering iron - so why could these be failing?

I am planning to offer a five year or perhaps longer warranty on these boards, but I can only do so if I am confident the board is capable of surviving normal conditions.

Caps are 0603 (100n, 10u 6.3V), 0805 (22u 6.3V) and 1206 (10u 35V). All are X5R or X7R. There are some 18pF caps for the crystal, but I've never seen those fail - I suspect they are a different technology to MLCC though.


texts: Trying to identify some small flat flex cable connectors on a Nintendo Switch motherboard

texts:
I recently bought a faulty Nintendo Switch console which somebody had already looked at - it has two broken flat flex cable connectors.

I have the tools, equipment and the skills to replace these BUT I'm not familiar with FFC connector types so am having difficulty finding replacements.

The following page has some decent photos of the motherboard -

https://www.unitechnix.de/reparaturanleitungen/nintendo-switch.php

If you look at this photo (the smaller, blown up image to the right) -

at the far left of the smaller photo you'll see one of the connectors that I'm after (it handles the FFC for the left Joycon connector) - there are eleven pins

As for the other connector, it handles the FFC for the fan - take a look at this photo -

look to the bottom of the photo at the thinner 'tongue' of the PCB (reminds me a bit of Florida!) - there's two small, white FFC connectors. One has a black locking tab, the other a grey locking tab. It's the one with the grey locking tab that I'm after. There are four pins.

What kind of connector is this and what is the process to look up a similar unknown connector in the future

Thanks


texts: Fourier transform of \$x(t) =t^2e^{-|t|}\$

texts:
I have to find the Fourier transform of this function.

(- sign exists BEFORE modulus). I thought of using this standard result.

If I split this fourier transform into this will it be correct to use this standard result.

Otherwise do I have to intergrate this by hand - I thought of using the convolution theoram but firstly I cannot work out the Fourier transform of t^2 (when I try using the fourier transfer equation I get 0) and I also cannot find
that in any standard signal processing books.

I have also sketched this function in the time domain.

Please can you advise me on this question.


texts: Temporary thermal adhesive for PCB measurement

texts:
I am making an examination on the effects of adding cooling to some existing electronics (making an comparison between having no cooling of the electronics and adding a heatsink or heatpipe + heatsink). Therefore I am taking measurements with external thermocouples on critical components and hot spots on the PCB itself. These measurements has been done before with the thermocouple leads simply touching the intended measurement points, but I would instead like to use some thermal adhesive for a better/more true/quicker reading of the temperature.

My main problem is that any such thermal adhesive I have found seems to be very strong epoxies meant for fixation for ever. (For example this) Has anyone used any thermal adhesive solution that is "semi strong" e.g. will be reasonably strong in a laboratory environment but not intended to hold for ever, e.g can be quite easily removed as well.

Or essentially any tips from people experienced on doing temperature measurements on your PCBs/components or on using thermocouples in a good way in a laboratory setting measuring electronics.

Maybe it is possible to use some kind of silicone heat pads if they are "flexible" enough e.g. if you can form them etc as some kind of dough?


texts:
What are:

"Number using O6 output only: 1,511",
"Number using O5 output only: 37",
"Number of Slice registers: 1,866",
"Number of 36k BlockRAM used : 2"

How can I find out more information about my Xilinx Design Summary? My device is XC5VFX70T.


texts: How many IR LEDs needed to get accurate remote control signals around room

texts:
I'm trying to make a stationary TV remote control and I'm not noticing the difference between using 12 IR LEDs and 1 IR LED. I still can't get the TV (for example) to get the IR message if the LEDs are not facing the IR sensor on the TV. Whereas the TV remote I already have works fine if its facing the opposite direction. Do I need to use more LEDs or different IR LEDs entirely? The LEDs I'm using are TSAL7400.

The LEDs are arranged like so (12 instead of 20 that are in the picture):

I've checked and each LED is getting 100mA when they are on so they are definitely all turning on.


texts: Q: How to use circuit analysis on a circuit ideal diodes with ideal op-amps

texts:
I have been practicing how to analyze op-amps with diodes as I never really learnt them and thought it would be a handy skill to finally learn.

I have been attempting a question on here that I found, but I am getting stuck.

Here's is the schematic

simulate this circuit – Schematic created using CircuitLab

I am doing a case where the diode is off (assuming ideal). Where I need to find the drop of the diode to be < 0, however I have no idea what is the output voltage of the op-amp. Any hints or suggestions will be helpful!

EDIT: I tried doing the negative input and it looks like the diode is both on and off?

simulate this circuit


texts: Possible to charge a LiPo battery with a 3.5mm headphone cable but also send/receive data?

texts:
If I have a device (Device A) that is plugged into a 120v wall outlet, and is connected to another device (Device B), that has a small LiPo battery, via a 3.5mm headphone cable (consider this a temporary state), is it possible to communicate (serial) with Device B as well as charge its battery, all from Device A via the cable? Neither the charging or the data communication need be very fast.

Note: I haven't worked with batteries in my Arduino projects yet, I've mostly worked with fairly basic sensors, relays, and some serial/wireless communication, so if somebody could explain if this is possible and which general components I would need to accomplish it, that would be much appreciated.

Update: Let's say I intend to use a 4 conductor wire (example: digikey #CP-43514SJTR-ND)


texts: How does a capacitive multi-touch screen capture multiple triggers?

texts:
On which principles does a capacitive touch screen work to enable detection of multiple triggers?

I understand that there are two layers; a driving layer and a sensing layer (with x or driving and y or sensing lines) that form a grid that when touched causes a trigger of some-sort.

How can it determine multiple touches, and what if your multiple touches effect the same driver or sensing line, how does it determine where those touches originated from?


texts: What to do with unused chip amp channel?

texts:
I'm planning to use STA540 in a guitar combo, because it's one of a few chip amps that can give me about 15W with 12V supply and 4ohm speaker.

My problem is that the chip has four amplifiers and I will be using only two of them (bridged). What should I do with the other two?

My ideas:

Ground the inputs and leave the outputs hanging.
Use the second pair in parallel with the first one. This probably won't help me push more power to the speaker because I think I will be limited by input voltage and not the IC itself and I don't see any other advantages of this
Find a smaller IC -- but I already tried that and didn't succeed....
Use them to drive headphones. Is this realistic, or would the headphones explode?


texts: How to create a multi-extension intercom system using wired phones?

texts:
I want to create a simple (telephone based) intercom system in our new house. Shouting between rooms is not so good, and trying to use an IM client or Facetime doesn't have the immediacy of a good shout down the corridor.

I've got a box of old wired telephones that don't have much use any more, and will be wiring the new place with cat5e for networking so running an extra wire to each room and sticking a phone into it is no real hassle.

I've seen online plenty of sites showing me how to connect two phones together so you can talk in one, and it comes out the other. This seems pretty simple - a battery, a resistor, some phone jacks to make it neat.

What if I wanted many phones (five) and also wanted them to make them ring?

I'm not trying to create my own PBX, there's no need to ring individual phones or have more than two people talking at once. Picking up a handset and having all the others ring until any other handset is picked up is enough.

Bonus points if I can do it without touching an Arduino ;-)


texts: MDB Protocol - Communication between a PC and a payment terminal

texts:
I'm working on a project where I need to create a communication channel between a standard PC (running Windows) and a payment terminal (a NFC credit card reader, an Ingenico iUC 180B). I'm a junior embedded software engineer so I have done low level communication protocols such as I2C or SPI, or serial communication between two devices, I'm not completely clueless on the subject BUT I have never worked on payment terminals before.
What I would like to do is very basic : I know on the iUC180B I can fill a price table with ID 0 corresponding to a certain amount of cents, ID 1 to an other amount etc, ok no problem. But now, I would simply like for the PC to communicate an ID to the payment terminal, the payment terminal then asks the client to put its credit card on the NFC reader for the corresponding amount, and then, when it's done, the payment terminal sends a "yes" or "no" answer to the PC depending on if the payment was accepted or not. That is basically all I need and it seems, for me, to be a very basic functionality. The trouble is I just can't understand the communication between the two devices.
I have done some researches and I'm currently reading the 313 pages of the MDB v4.2 protocol but I'm just really troubled by those researches. It seems as if a micro-controller serving as a VMC is needed between the PC and the iUC 180B, which seems very strange to me for such a simple and widespread functionality. Am I misinterpreting things ? And if a VMC is needed, does a fully functional VMC micro-controller can be bought and if so, where ? This communication is really a small part of the project I'm working on (for my company) and I simply don't have time to loose weeks on it...
Also, for such a basic task, isn't there a way to use an other communication protocol ? I heard of the executive protocol (or protocol A) but I couldn't really find ressources on this, I'm not sure what it is.
Before I started this project, I just assumed that we could plug the payment terminal to the PC via USB and just use a standard serial communication. I also assumed that high level libraries were available on Github or somewhere else to use the serial port with high level methods (such as "request_payment(price)" or something like that). I assumed that because payment terminals are so widespread so it seems a little crazy to me that this is not possible (open-source or not), but maybe it is and I'm just not looking in the right place ?
Thank you for any help you can give me !