texts: Programing another atmega8 running on 1MHZ internal RC oscillator using Arduino IDE

texts: I want to write code for another atmega8 running at 1MHz internal RC oscillator using the Arduino IDE and its libraries. I have an ISP programmer to burn the code. What are the things that I should care about? How can I compile the code for 1MHz instead of 16MHz?


texts: Convert schematic from Eagle 6 to Eagle 5

texts: Is there a way to convert a .sch file in Eagle 6 to Eagle 5?


texts: Phase difference between two waves from wave equation

texts:
I need to calculate phase angle between

$$i_1 = -4\sin(377t + 55) \hspace{0.2cm}\quad \mathrm{and}\quad \hspace{0.2cm} i_2 = 5\cos(377t - 65)$$

I need to determine which one is leading too.

My progress so far:

$$\begin{align}i_1 &= -4 \sin(377t + 55)\\ &= 4\cos(377t + 55 + 90)\\ &= 4\cos(377t + 145)\\[1em]
i_2 &= 5\cos(377t - 65)\end{align}$$

So, we get phase difference = 145 - (-65) = 210, \$i_1\$ leads \$i_2\$ by 210.

But, $$\begin{align}i_2 &= 5\cos(377t - 65)\\ &= 5\cos(377t - 65 + 360)\\ &= 5\cos(377t + 295)\end{align}$$

Now, we get phase difference = 295 - 145 = 150, \$i_2\$ leads \$i_1\$ by 150.

Are both of these correct ?


texts: Parasitic Passbands in distributed filters

texts:
it is known that if we realize a filter (for instance a low pass filter) by using distributed elements (transmission lines), there will be some parasitic passbands (which moreover show a behaviour which seems "periodic").

For instance I did this simulation of a Butterworth filter of 5 order:

Note that it behaves as a perfect low pass filter only for few GHz after the cut-off frequency. What is the cause of this phenomenon?


texts: Taking into account power factor when calculating energy savings

texts: I am attempting to calculate the energy savings of a fan motor after a new runner and inlet cone was installed which claimed to improve fan efficiency.  I have logged amp draw before and after the upgrade.  The fan is in a large pulp and paper mill and is used for supplying combustion air to a Power Boiler.  The site claims to have near unity power factor however I believe the fan motor is very old and probably has a much lower PF.  My question is, do I need to take into account the site PF when calculating the energy consumption of the fan? or simply the PF of the fan itself?


texts: Using “Video 90” spray to clean up a cell phone motherboard

texts:
Can I use Video 90 Spray with electronic motherboards, like smartphones?

My cell phone was dropped in water while the battery was out, now I have dried it out using rice and instant oat!

Before, plugging it back on, I want to use a spray cleaner on it.

Video 90 is generally available in my local market, please let know if you think this could work for electronic devices as well.

Video 90 description:

http://www.farnell.com/datasheets/318263.pdf

http://www.connector.nl/image/imagedir/kontakt_chemie/TechnicalManual_CatalogKontaktChemie2015English.pdf


texts:
I wonder why octagonal IC packages in the LQFP times have never been a thing.

In my opinion they would allow easier pcb routing, they take less space and weight for the same die size, shorter leads to the die compared to square packages as well.

Pick and place machines wouldn't have a problem with them, and EDA software is fine with 45° routing anyway, so it seems like a logical thing to do.

Yet I've never seen one.

Any idea why?


texts: Input voltage triangular wave signal with 12.7Vmax and 9.1Vmin passing thru a NPN BJT, assuming if the forward voltage of the BJT is 0.7V then why is the output Vmax is not 12.0V but way lower like 11..V. Here the graph and the part of the schematic diagram. Vout is in blue and Vin is in green. Any idea on why this happened and how to make it have a gain of 1 for the voltage?


texts:
This question might be too localized, but I try.

Is it possible to replace a variable resistor by a MOSFET, under conditions shown in the following schematic?

If yes, can someone propose a MOSFET type or the required MOSFET parameters.

simulate this circuit – Schematic created using CircuitLab

Update

What I am actually trying to accomplish is to replace R2a by something simple that I can control with a microcontroller (DAC).

I am hacking an existing device and can not replace the resistor R1.


texts: Derivation of stability criterion for type 3 digital PLL

texts:
Could anyone help to derive the following expression (4.23) which is the stability criterion for type 3 digital PLL ?

Note: Screenshots are taken from Floyd Gardner's book : Phaselock Techniques 3rd Edition


texts: How is Early effect of a BJT minimized during its construction?

texts:
Considering an NPN BJT transistor, I have read in some texts before that for a more stable control of collector current Ic by the base-emitter voltage Vbe, the effect of Vce on the width of base region is minimized. So Ic Vce curves are better to be flatter.

But how is that achieved in construction? I've read once that, it is done by making the emitter side highest doping concentration, then less concentration the base side and even less doping concentration at the collector side. Is that correct? And how does this minimize the Early effect?


texts: QPSK/QAM, digital quadrature modulation: square wave as local oscillator possible?

texts:
Goal is to build a lab exercise for students to illustrate digital IQ-modulation (QPSK, M-QAM). The bit stream for I and Q are generated by e.g. an Arduino.
Is it possible to use a square wave as local oscillator (original and 90-phase shifted) or must it be a sine wave? Most books and datasheets assume a sine-shaped local oscillator.
How would you implement it (square wave, square wave filtered, sine wave?) for a lab exercise (I'm not asking for a electric schema, although welcome, but more in principle how would you do it)? Goal of the exercise is not to show the most efficient way to transmit data but to make the students see and feel the most important principles of digital IQ modulation.


texts: Building a pseudo-solenoid electromagnet - Heat disipation

texts:
I am planning to build an electromagnet as shown in the picture below. The copper windings are coiled around a thin plastic cylinder. The goal of the setup is to attract small metal chips floating in water inside the cylindrical space to the inner wall of the plastic tube, and hold them there for a while (>20 minutes).
I am aware that the electromagnet is much weaker without a solid core, but having one is not feasible since I want to attract what is inside the cylinder to the walls, and the chips are very small so they should be able to be attracted by the coils without a core.

I have found information on how to dimension the wire diameter and length based on solenoids or electromagnet tutorials. However for most applications I have seen the devices are turned on just for a couple of seconds with a low cycle rate (e.g. 2 seconds on, 8 off). I would like to be able to turn the magnet for extended amounts of times, so I am thinking about ways to limit the generated heat

Can I limit the current into the coil by placing a resistor before it? If a given coil setup draws 1 A, and I limit that to 0.5 Amp, what would be the ballpark impact on the magnetic force (1/2, 1/10, 1/1000)?
Would it be a bad practice to place a fan or two on the coil to keep it cool?

Edit: The discussion in the comments has given me another question, what if instead of coiling on the cylinder, I coil it inside and out like in the picture below AND use an iron cylinder instead of plastic?

The field will be stronger, so I could limit the current even more.
Also the iron would act as a heatsink
Are both assumptions correct?


texts: Power supply for battery powered application with precision ADC

texts:
I’m designing battery powered application in the form of a sensor with an onboard high-precision (20 to 24 bit) sigma-delta ADC that measures a couple of load cells in a Wheatstone bridge. My question deals with how to properly power such a device to both meet the low-noise requirements of the ADC as well as long battery life for the overall product.

I intend to supply the sensor with two series connected single-cell alkaline batteries, for instance 2 x AA batteries providing a nominal voltage of 3V. Looking at the discharge curve of a typical alkaline AA battery I can see that the cell voltage ranges from 0.8V (discharged) to 1.5V (nominal). In other words, I will end up with a supply voltage of 2 x 0.8V = 1.6V when I have used the full capacity.

The ADC that I intend to use has an analog supply requirement of MIN 2.7V to MAX 3.6V. Therefore, to make full use of the battery capacity I will need to use some kind of power management circuitry that can boost my battery voltage (VBAT: 1.6V - 3V) to a stable 3V - 3.3V. To do this I have been looking at the possibility of using a DC/DC step-up regulator. The main problem I see with such a device is the large ripple it produces at the regulated output voltage which might be compromise the accuracy of the ADC.

So the dilemma I’m facing is that I would like to have as long battery life as possible and at the same time avoid compromising the accuracy of the ADC. I don’t have any previous experience in using switching type regulators. What type of power management would you recommend for my specific application? Is there a good practice?

Some details:

ADC Type: MAX11206 (20-bit single-channel delta-sigma)
Current consumption: ADC consumes 300uA during operation and 0.4uA during sleep. The rest of the board draws 400uA in average.
Voltage output: 3.3V used for AVDD, REF and VE for ADC/brige and microcontroller on the board.
ADC-Bridge Connection: Ratiometric connection (where bridge excitation voltage is the same as the reference voltage).
Sampling rate: Very low (1 sps)

Looking forward to hear your suggestions.


texts: Do I need to ground this circuit board inside my 3d printed case?

texts:
I bought a microphone amp system that has 2 mics and then outputs the audio via aux cable. I am using it for a project and 3d printed an enclosure for it and took out the circuit board from the microphone system. However I noticed the screws on it have conductive plates that go into the original enclosure which is some sort of metal.

Do I need to ground the board and how would I do it with a plastic case now?


texts: Can I burn components / short circuit by using a multimeter

texts:
It's probably not new to you, but sometimes we want to analyze a powered circuit with a multimeter. I love to do that, but I'm a little worried that I might burn some components or the whole circuit.

Are there any best practices, do's and don't for using multimeters on circuits and components ?


texts:
The book says the rds of the 2N8461 JFET can be varied from 100 ohm to 10Meg.

I went on and tried to verify this using the equation and plug values in it from the datasheet

using the minimum values for vgs(off) and Idss and a vgs = 0.799 I only get a maximum a rds of 4k ohm why is that?


texts:
In my UART communication I need to know the start byte and the stop byte of the message sent. The start byte is easy but the stop byte, not so much. I have implemented two stop bytes at the end of my message, that is \n and \r (10 and 13 decimal). UART only works on bytes 0-255 values so how fail-safe is this? I can imagine, though low probability, that my message might contain the values "10 and 13" after each other when they are not the stop bytes.

Is there a better way to implement this?


texts:
I need to convert a PWM signal with varying duty cycle from the arduino to an analog voltage from 0-5V. I used a RC filter with a time period of 3.9ms. The PWM output has a period of 2ms. I experienced loading effect at the output and therefore I used an op-amp as a buffer. However, I am still experiencing the same problem. My output is ranging from 1.2-5V. I need the output to vary across the entire range of 0-5V. Can anyone suggest a solution for this?

simulate this circuit – Schematic created using CircuitLab

The op-amp is LM358N.


texts: Changing LED brightness using PIC 16F877A

texts: I am planning to change the brightness of an LED using a PIC 16F877A. I get suggestions that the brightness can be changed by changing the time interval between two pulses. But the brightness of the LED depends on its power, and that depends only on voltage and current (which we can't change in the PIC controller). Please explain how this works, or if the suggestion is wrong please suggest some other ideas.


texts: How do data and address strobes cause input to be latched?

texts:
Often in digital systems when multiple components communicate with each other they use strobe signals. Among these are data and address strobes. The strobe signal being asserted means that the data or address is ready to be latched. However, the actual latching takes place only on the edge as the strobe signal is deasserted.

In sequential circuits a clock signal is used to latch data in the registers. How does this strobe signal relate to the clock? Is it actually fed into the clock port of the registers perhaps after inversion to match the edge with what is required by the register to latch data?


texts: External power supply design (12V to 5V and 3.3V) for arduino based system

texts:
I am designing an embedded system having following components:

One arduino uno (~300-500mA 5V=2.5W)
One nodemcu (esp8266) (~300-500mA 3.3v=~2W)
One PAM8403 based audio amp board (3W output, so on 5V it should be ~600mA)
One custom made mic preamp (2n2222A+LM358) (don't know, should be within 200 mA=1W)
One car door lock actuator (12V, running for 500ms while activated, assuming 1A required so power is 12W).

Total power=2.5+2+3+1+12=~21W

All of the above systems are connected in a same system. I want to use one PSU that would provide power to all of the modules in the system. I bought a 12V 2A switching power supply, assuming it would be enough to run all systems together.

So I made a regulator board using two 7805 (one for arduino and preamp, another for audio amp), and one lms111733 (for esp8266) (All TO220 package for high power handling), feeding them by the 12V PSU. Problem is while I connect all systems all regulators are running hot, and most hot is the one connected to the audio amp, its so hot it burnt my hand (ran only for a minute or so).

I read through couple of forum posts and found that the 7805 linear would run hot as it would dissipate the power (input power-output power) inside itself. For example if the output is 5V-1A then it would dissipate 12V*1A-5V*1A=7W in itself so the heat.

In such situation I can use one 12V PSU along with 1 5V mobile charger adapter kind of things, but I want to stick to using one PSU. Can anyone suggest how to design the power supply for such system.


texts:
I am looking for the cheapest, smallest way of charging a 50-100 mAh 3.7V Li-Ion battery through micro USB. Fast-charging is not necessary, especially if it would cause an increase in price or size.

To give you some more background on my ECE education. It has focused primarily on electrical circuits and their biological applications. A really huge gap in my education is that I have almost no knowledge regarding Li-Ion batteries, let alone how to safely charge them. In fact, I have stupidly just been soldering these kinds of batteries to my board for a DIY project without putting them through any kind of regulator. Therefore, I really am recognizing my ignorance now as I begin to research charging these kinds of batteries, and would like to pose this question to those with a more traditional ECE background to make sure I don't make such a stupid, dangerous, and wasteful mistake again.

I have found a number of interesting example circuits, but most of them involve regulators designed for much higher current uses. My circuit requires about 1-5mA. The ultimate design is a heartrate monitor, so safety is also a concern. Charging time is not a concern.

How can I find an effective battery and charger design for this particular use case? Is the MCP73831 the most appropriate IC for this design? What kind of parameters and search terms should I use to find the cheapest possible product on a site such as DigiKey?

Ideally, I would prefer something that could be easily described to a foreign circuit manufacturer should I decide to go that route. That is, I don't just want a simple, overpriced charger from Sparkfun. The ideal answer would be a number of individual components (USB connector, charging circuit, battery), or a pre-made charger that is extremely cheap and needs only a battery to connect to. I want to build it myself, in a way that can be mass manufactured later on, should I be fortunate enough to go that route.


texts: LTspice IV How can I get round value with 4 point digit?

texts:
First of all sorry if the title aren't fully describe what I want since I'm not native Eng speaker ,

In short I start taring my self on electronic using LTspice IV , since I don't want high precision output values I end up seeing xxxx.xxxxxx somthing mV which I don't need and makes diagram read so difficult(I had to decrease  font size to see the values )


texts: Draw 15V from USB C Power Delivery devices

texts:
I need to draw 15V from USB C PD capable devices such as power banks or chargers.

So I need a rather small tool or build for this I can draw about 15V 3A via usb c with.

Thanks for your help.


texts: Is there a better way to rotate through 3 different states (A, B, A+B)?

texts:
I would like to be able to rotate through 3 states (A, B, A+B) with one momentary push button (M) as follows:

starting state: A is high, B is high
after having pressed on M a 1st time : A is high, B is low
after having pressed on M a 2nd time : A is low, B is high
after having pressed on M : back to starting state

I designed a circuit achieving this behavior as a falstad simulation.
It seems to work fine, however it requires 2 flipflops, 2 OR gates, 1 NOR, 1 XOR and 1 AND gate.
Is there any way to simplify it ? Or are you aware of an IC able to achieve this kind of behavior with less parts involved ?
Thank you a lot for your help.
Note: The logic is meant to energize 2 different relays. The starting state can be different as the one above (but at least A or B must be high).


texts: Need to know the exact values for sense resistor, resistors in op-amp and power supplies

texts:
I am computer scientist and I don't know much about electronics.
In my master work, I have to design a circuit that measure the energy consumption of receiving single tweet from mobile (smartphones). I made a circuit that measure the voltage difference, amplifies it and sends it to ADC.
Kindly have a look at circuit. The problem is that I don't know exactly how much miliOhm  or Ohm resistor should I use.
I know mobile battery operates at 3.7 V. I place the sense resistor if mobile receives any text SMS or tweet. Then it will measure the difference or cost of single tweet in term of voltage

Kindly help me out, or if there is good tutorial then let me know.


texts: Verilog Case Statement evaluating all combinations of a 10-bit ADC sample

texts: I have a (hopefully) pretty easy question on case statements.  If I am sampling an incoming signal, which is returned as a 10-bit value, can I evaluate that sample in a case statement and assign a result value for the output register based on every one of the 1024 cases?  Would this eat up LUTs in the FPGA fabric? I considered just doing a large if-else chain, but I've already done it with the large case block and it synthesizes and runs just fine on the Spartan-6 FPGA after doing it for 2 inputs. But now that my design has gotten bigger and I've done that now for 4 different inputs, now the fpga only works when I flash the fpga, but if I power cycle it it boots up to some weird unknown state.


texts: How can I size the 'supply noise filtering' capacitors at the load end for this scenario?

texts:
There is this SMPS dual-power supply which needs to power a load outdoors around 100 meters far away via a 3-wire cable as shown below:

simulate this circuit – Schematic created using CircuitLab

The load will draw max around 50mA but for a better signal quality some suggested to add caps at the load terminals to filter out the power supply noise.

I guess the way caps are placed correct, but is there a way to size the capacitors here? I need to find a logical explanation why we should use the capacitors with particular capacitance. Telling "I have seen somewhere it is a rule of thumb" does not convince some people. What should be the approach?

I would like to know for this application what value should be the capacitances of course and maybe even most importantly why.


texts: Specs of HK-TR6A remote controller receiver

texts:
I'm trying to use a 2.4 GHz digital 6 channel remote controller to send signals to an Arduino UNO R3 board. The receiver is the HK-TR6A-V2.

I can't find any information on what each pin input/output is, and how the information is encoded. Since there are 3 pins for each of the 6 channels, I imagine that each channel has its own Vcc and ground, and the signal itself will be on the third pin, but I'm not sure which is which.

Also, I don't know what voltage should be supplied to the battery pins (and why there are 3 pins for the battery).

The modulation used to encode the signal in each channel seems to be PPM, but I'm also not sure about that.

Has anyone worked with this receiver (or a similar one)? Is there a manual or any information about how to interface it with an Arduino board?


texts:
I have a transfer function as follows -
$$
G(s) = \frac{320 (1-4s)e^{-3s}}{24s^2+28s+4}
$$
I calculated its time delay as 3 sec, gain as 80, but confused in finding the time constant.
I know the time constant of standard first and second order transfer function but not for non-standard. So I found its inverse laplace and got
$$
G(s) = 80(\frac{e^{0.5-t/6}}{3}-e^{3-t})
$$
and on putting
$$
\frac{e^{0.5-t/6}}{3}-e^{3-t} = \frac{1}{e}(\frac{e^{0.5}}{3}-e^3)
$$
got 2 roots, around 1 and 18. Please shed some light on how to find answer from laplace domain. TIA


texts:
I've got 15 devices each with a current of 20mA and I am interested in running them all for 10 seconds. How would I go about working out the amount of mAh a battery would need to provide for this?

I understand that to find the mAh to run something for an hour you take the current and multiply it by 1000 and so my understanding of his problem was that you could get minutes by multiplying by 100 and then seconds by 10. So What I thought I needed to do was something like this:

15 x 20mA = 300mA/0.3A

0.3 x 10 = 3

3 x 10(seconds of runtime) = 30mAh

However I am not sure if this is right, so I would be grateful if someone could look it over and point out my mistakes.


texts: Matrix switch module for electronics testing - what uses?

texts:
I'm doing a presentation about NI PXI and such test equipment for school.

And I am explaining what the multiplexer and matrix modules can be used for.

The multiplexer is simple: Connect, for example, all voltage measurement points to the multiplexer inputs, and a DMM to the output, and cycle through them in order and acquire measurements.

But what exactly is the matrix used for? I can't figure out what the advantage of this one is.

Page 13 here shows a diagram etc: enter link description here


texts:
What kind of diode is this?
What kind do I replace this with?


texts:
I am attempting to create a calculator using Keil C51 compiling for a DS89c450 target device, but I have run into an obstacle with regards to negative powers. The compiler keeps returning errors when ever I attempt to calculate the inverse of a trigonometric function and a run time error (a null response) occurs when I try negative powers. I believe the documentation states this isn't possible, is it possible with the default math.h or, if not, how would I go about achieving this?

To clarify, this is being completed in C, to assembly.

Thanks for any assistance.


texts: ADC outputs random values to constant input

texts:
I am using ADC (ADS7822) from TI and I have some strange behaviour with it. Below diagram explains the voltage inputs and connections.

I was reading strange values with this setup.

I removed signal and provided a fixed DC voltage of 2V to PIN 2 (+In). I assume I will get some value for wich the MSB will be almost close to each other on each samples. I am comparing 400 samples at a time. But I receive dynamic outputs from the ADC wich has all possible values.
The first sample is always zero (surprising). I always get sampled values for 2V from the 2nd sample onwards.
Even if I don't provide and signal to PIN 2 (floating) it still outputs some data. I am providing clock and ss low so I assume it will sample noise if no signal is present. But the output should be close to each other. I receive all values from FFF to 000. I don't see such source of noise in my system.

Can someone suggest any possible reason for this behaviour?


texts: 90 degrees phase shifted magnetic fields

texts:
If we have a closed magnetic circuit with two primary coils and one secondary coil wound on it. The primary coils are wound such that unlike poles are adjacent. Both primary coils are using rectified AC and the current in one coil is phase shifted by 90 degrees to the other coil.

This would result in an interplay of the magnetic fields where one is increasing to its peak value while at the same time the other is decreasing to zero. What would be the effect of the magnetic fields on a secondary coil? I'm not sure, however I'll take a stab at it.

If the south pole on primary1 is losing strength lenz law says the secondary will establish a north pole to arrest the waning south pole. At the same time the north pole on primary2 is gaining strength lenz law says the secondary will establish a north pole in opposition to the growing magnetic north pole. Obviously two north poles is not possible, so what is the effect on the secondary?


texts:
I want to connect a set of low power halogen lamps to a dimmer. This would be used to illuminate plants who are then monitored using a hyperspectral camera.

I was wondering whether any spurious switching behaviour of the dimmer and transformer will show up in the final image. The exposure time will be in in the order of 1/1000 seconds.

Example set-up:

HTI DALI 315 DIM (dimmer) connected to HTM or HTN (transformer) 12V, 50W lamp


texts: How are severed phone lines, the ones on utility poles, repaired when they are severed

texts: I have been searching for this answer for a long time and I haven't found any info on the way severed lines are repaired. There must be tens of thousands of tiny wires that must reconnected, and in the proper order, before the line can be put back into service. What tool and technique is required to achieve such a daunting repair?


texts: Op-amp (LM358N) half-wave rectifier and 3.3V clamp

texts:
I was wondering if I could have some feedback on this circuit.

The goal is to:

Input up to 18VAC sine waves (possibly noisy) up to 20khz.
Output 3.3V digital pulses.
Minimize discrete part count.

I have built this circuit and it seems to work fine.

The left op-amp is wired to operate as a voltage clamp. Because the LM358N is not Rail to Rail, the output of this first op-amp is max 2V (3.3V - 1.3V spec'd rail voltage offset.)

The right op-amp is wired to operate as a Comparator. This allows the circuit to output full-rail 3.3V when the input signal crosses the the threshold voltage, as defined by the two resistors shown.

In the SPICE simulation below, the black sinusoid is the input signal, the green line is from the left op-amp and the orange is the right op-amp output.

Some notes:

This circuit started off with a few more resistors and diodes, based on a bunch of other circuits on the web. I'm not sure why, but I couldn't get most of the other circuits working in SPICE, while this one both simulated properly in SPICE and works properly on the breadboard. This makes me suspicious that I'm missing something that everyone else is seeing. Yet it is working fine in reality.
I actually tested the left op-amp circuit by itself as an input to a 3.3V Arduino, and while it worked for square wave and triangle wave inputs, the Arduino interrupt handler activated two or three times the actual pulse rate when using a sine wave. That was why I added the Comparator stage.

Some cons:

Obviously, skew.


texts:
I'm working on android drivers (native code) for CH340G USB-to-serial chip.
I've successfully tested it with baudrate 115200 and Arduino Uno CH340G but for some reason it does not work with baudrate 57600 and Arduino Nano CH340G.

I've looked at linux drivers code:

static int ch341_set_baudrate(struct usb_device *dev,
121                               struct ch341_private *priv)
122 {
123         short a, b;
124         int r;
125         unsigned long factor;
126         short divisor;
127
128         if (!priv->baud_rate)
129                 return -EINVAL;
130         factor = (CH341_BAUDBASE_FACTOR / priv->baud_rate);
131         divisor = CH341_BAUDBASE_DIVMAX;
132
133         while ((factor > 0xfff0) && divisor) {
134                 factor >>= 3;
135                 divisor--;
136         }
137
138         if (factor > 0xfff0)
139                 return -EINVAL;
140
141         factor = 0x10000 - factor;
142         a = (factor & 0xff00) | divisor;
143         b = factor & 0xff;
144
145         r = ch341_control_out(dev, 0x9a, 0x1312, a);
146         if (!r)
147                 r = ch341_control_out(dev, 0x9a, 0x0f2c, b);
148
149         return r;
150 }

What's wrong? Is there any difference between 340 and 341 in terms of setting baud rate? ANy suggestions are appreciated.


texts: What happens with a parallel EEPROM data bus when the address is changed?

texts:
I have a parallel EEPROM chip (AT28C256 to be precise). I keep the OE and CE lines low. Some address is set at the address bus. What happens on the data bus when I flip one address bit?

Does it switch instantly from the old data value to the new data value, all bits at once?
Does switch bit-by-bit (some bits sooner, some bits later)?
Does it go through some random intermediate state?
Does it go through High-Z?


texts: Suppose we have an oscillating signal V(t) with V(t) >= 0. I'm looking for a circuit that averages this signal over a given time so that I can read out the average value directly using a simple voltage measurement tool.


texts: How does a computer deal with subtraction of 2 values that are in two's complement?

texts:
I'm confused how the computer calculates if there are two values A and B, both are in two's complement. Now we want do the operation D=A-B. How is this done?

Let's say A=0100110 and B=0000111

What we do now?

I would do: 0100110+0000111 but I'm really not sure.

Or maybe: 0100110+1111000? So basically A+NegationOfB

Any ideas? Please let me know as this is very confusing for me...

Edit: jonk I made table for your answer but I don't know how to make in table visible that we have cin0=1 because we have subtraction... you know? is table correct to your description?


texts:
During lecture CPU (Central Processing Unit), ASIP (Application-Specific Instruction set Processor) and DSP (Digital Signal Processor) were briefly mentioned.

Unfortunately the main differences (and use cases) weren't discussed.

In my understanding CPUs are the general purpose work horses. They are flexible, but not as efficient to specific tasks. DSPs are basically stripped down CPUs, which are really efficient at digital signalling applications. ASIPs have an custom instruction set for specific use cases.

Is this understanding correct? Could you elaborate further the differences and use cases of those devices? Is a DSP an ASIP?


texts:
How to measure input pulse signal's frequency using xilinx toolkit on matlab?

Since I'm bad at coding,I use System generator on matlab.
I'm doing a project, In which I'll be using a Proximity sensor to measure RPM of a motor. The output of the sensor is put across Schmitt trigger, so it becomes a Pulse Signal.

I need to find the frequency of this pulse signal, So I can calculate RPM.


texts:
So it looks like a capacitor but from my testing it is propably a resistor. And this is the board i removed it.
It is written VW-1 HF(OR T)


texts: Why do most microcontrollers not embed a 32k oscillator?

texts: Why do most embedded systems use an external 32k oscillator?


texts:
I'm testing on BCR12LM-14LB8XO Triac. According to its datasheet, the gate is triggered by a 1.5v.

https://alltransistors.com/scr/datasheet.php?pdf=BCR12LM-14LB

I have a 2.7VDC power source, 700mA maximum.

I'm testing the Triac while it's attached to its electric board.

On my breadboard I added a 3mm blue led (Forward voltage 2.8VDC - Max forward current
20 mA ), and connected it to T1 & T2.

It's a pretty simple circuit, nothing more was added not even a resistor.

When I connected the Gate to T2 the led turned on.

Once I disconnected the Gate from T2 the led went off.

What am I missing here, Shouldn't the circuit continue to be closed?

P.S: I'm pretty new to the electronics world.

Thank you in advance.


texts: The method to get synchronous D-flip flop with three inputs,D,CLK and reset

texts:
I want a synchronous D-flip flop with three input,reset,D and CLK,but i can't find it,only four or two inputs,and four inputs just D,CLK,Set and reset ,but find the asynchronous D-flip flop with three input on the Internet.

Can i do anything to let asynchronous D-flip flop become synchronous D-flip flop ? For example,change NAND by AND .

Someone told me : take the 4 input one and ignore the set, that is, hold it false and remove any following logic that no longer changes state as a result,but i don't know last sentence meaning and the method.


texts: Provide power if power is not present already (circuit inside)

texts:
I am designing a simple controller for an automotive application. As you can in the schematic below, they system is consisted of a sensor, a gauge and a controller. This particular sensor shorts its own power line (SIGNAL in the schematic) to ground, creating a PWM signal which represents the measured quantity. The gauge works by balancing a needle between the magnetic fields produced by two coils.

When the gauge is present, the controller's only job is to sense SIGNAL (which switches between 0 and ~6.5V). However, I also need to support the configuration where the gauge is removed from the circuit and the sensor is directly connected to the controller. In this case, I need to provide power to the SIGNAL wire (perhaps using a current limited regulator) AND sense it at the same time.

I am looking for a decent way to support both of these configurations (gauge present and not present). One solution I can think of is to use the controller MCU to monitor SIGNAL at power up and if a PWM voltage is not detected (say after 1 second), turn on a MOSFET which will provide power to SIGNAL. But I feel like there should be an easier way. Any ideas?


texts: Actually I know that voltage source is of two types AC and DC, can capacitor behave as AC voltage source for a circuit, which contains a resistance R only. If yes! Then how do we do it? .


texts: Understanding addressing and size in memory map

texts:
TM4C123 has 256 kiBytes of flash ROM as shown in the memory map. The range of memory addresses for the ROM is 0x0000.0000 to 0x0003.FFFF (a 32bit address), totaled to 3x16x16x16x16 = 196,608 number of addresses. The memory is byte addressable so that block of memory addresses adds up to 196,608 bytes instead. Why does the manufacturer claim it has 256 kiB and not 196kB ROM memory size?
Even if the range of addresses can't sum up to an exact 256k, wouldn't 0x0000.0000 - 0.0004.FFFF (4x16x16x16x16 = 262k) give a size closer to 256k than 0x0003.FFFF's 196k?


texts:
Would the voltage of a power source decrease if multiple loads / more load is added to it?
I am researching battery types, and wanted to know, if I added enough load to a battery how much / would there be any voltage drop?
Example: I have a 12 V set of batteries in series. The batteries' rated current is 48 A.
I have four loads that each require 12 V and 13 A of electricity. Would there be any voltage drop, would the load have to be significantly higher to actually see a decrease, or would the voltage stay the same?


texts: Reasons why an I2C bus requires a minimum value of capacitance on the clock to function?

texts:
I have a microcontroller (LPC1768FBD100) and am using I2C to configure a 3 port eithernet switch (KSZ8863RLLI). I’ve made about 100 boards so far and they have all worked well, except one. For some reason switch configuration (performed over the I2C interface) is failing. While probing the control signals with an oscilloscope, it all of a sudden sprung to life. On closer inspection it appears that adding the capacitance of the probe (15pF) to the clock line is enough to get it all working.

If I understand the I2C bus correctly, officially you don’t need a minimum value of line capacitance for it to work, but is there some kind of rule of thumb minimum capacitance value for reliable operation?

=======Specs/Notes=======

I2C clock speed = 370kHz.

I2C pull up resistors = 4k7.

Pull up’s are located near the microcontroller.

I2C Clock Length = 91mm.

I2C Data Length = 78mm.

There are no nearby sources of noise that may be interfering with the clock and both traces are running adjacent to a continuous ground plane.

=======Testing=======

Tried reducing clock speed to 100kHz, didn’t work.

Tried 1k, 4k7, 10k, 47k pull up resistances. None worked

Tried adding 8pF of grounding capacitance to the 4k7 clock pullup, didn’t work.

Tried adding 16pF of grounding capacitance to the 4k7 clock pullup, system works and boots reliably.

When I check the clock and data signal lines, there are no signs of ringing. Though, I guess there could potentially be some ringing which the 15pF of probe capacitance is concealing.

=========UPDATED INFO=========

We are using the hardware implementation of I2C built into the LPC1768FBD100

I don't think it is a mechanical issue. I have reflowed all the joins and when I probe the line, I am doing so on a test point, not a solder connection.

Regarding noise and cross talk, my gut is telling me that isn't the issue as the traces are not that long (~80mm), are running adjacent to a continuous ground plane and i'm using pull ups of 4k7. I could be wrong though.

Waveforms. Notations added to each screenshot.

I2C Traces. Routing is not mine. I inherited this from another engineer.


texts: Does DSB-SC signals retain original shape of the message signal \$ x(t) \$ when \$ x(t) <0 \$?

texts:
The conventional DSB-FC AM signal is given by:
\$ s(t)=[A+x(t)]\cos \omega _C t  \$
In conventional DSB-FC AM we take care of the fact that \$ |x(t) | <A\$. So that the modulated signal is not distorted when \$ x(t) <0 \$.
However, the DSB-Suppressed Carrier (DSB-SC)  is given by:
\$g(t)= x(t) A\cos \omega _C t \$
So, in a DSB-SC system, whenever \$ x(t) <0 \$ (at zero crossings), the modulated signal gets distorted and the modulated signal does not retain the original shape of the message signal \$ x(t)  \$. So, is this a disadvantage of DSB-SC system? If so, then this is a major drawback of DSB-SC system. Then how do DSB-SC systems deal with modulating signals where \$ x(t)<0 \$
DIAGRAM:
Signal distortion at zero Crossings(The original shape of the signal is not retained).


texts: Transceiver pulls both CAN wires to ground, when in standby. What does that mean for the other devices on the bus?

texts:
In a project, I am  using a CAN bus with several devices on it. The CAN bus is terminated with 120 Ohms at both ends. When all devices are booted up, the CAN waveform looks like I would expect:

When idle, both CAN wires are at about 2.5V (recessive)
When a device is sending, I see the typical square waves in opposite directions: CANL goes low and CANH goes high (dominant) and then both go back to 2.5V again.

However, when one of the microcontrollers is in JTAG mode (i.e., the device is waiting to be programmed), then a pullup on the STANDBY pin of the CAN transceiver (MCP2542) makes sure that the transceiver goes into standby mode. In that mode, both CAN wires are pulled to ground. The good old CAN square waves are no more. It looks like the other devices are trying to drive CANH high, but CANL doesn't really move.

What does it mean for the other devices, if one (or multiple) devices are (and stay) in standby mode? Are the other devices on the bus still able to communicate?

One of my concerns is, that the microcontroller is in JTAG mode. So the CAN controller is not initialized, no program is running, and thus the device cannot wakeup from standby - if that would be required.

Another concern is that the amperage used to drive both CAN wires low during standby is about twice as much as for the normal recessive level.

Is there a requirement that devices must wakeup from standby? Or can a device stay in standby for an indefinite amount of time while all other devices happily use the CAN bus?

As soon as the microcontroller is programmed, we drive the standby pin of the transceiver low and thus the transceiver exits standby mode. Then the bus starts showing normal voltage levels.


texts: What is the current capability of the common "C" wire for house thermostats

texts:
I'm not entirely sure if this belongs here, so if it belongs somewhere else let me know.

Home thermostats (in the United States at least, I'm not sure about other locations) for newer homes have a few different wires (depending on capabilities for the home) that are used for turning on the heater, turning on the AC, and turning on the fan.  There is typically two more wires, one that is the hot (connect this to the AC wire will turn on the AC, connect this to the heater to turn on the heater, etc), and one that is the "common" wire and is used for powering the thermostat itself.

These all run at 24VAC that comes from a transformer stepping down the mains voltage somewhere in the system.

Are there any building codes or product standards that would tell me what the minimum current carrying capability of this circuit is?  How much current can the transformer handle?  How much current is the wire supposed to handle?


texts:
I need to design a system on a four layer PCB. The layer stack-up from what I know would be

signal / components
ground plane
power
signal

My problem is, I have a system with a power supply of +-5V and for one part of the system I need 3.3V analog and digital supply. What would be the best practice to realize the power distribution of this system?

My idea was to have one rail at the bottom of the power plane which is VSS and one rail at the top which is VDD and then have multiple fingers from the top to the bottom and vice versa similar to intra layer capacitors in chip design. For the 3.3V I'll just have a small area within the power plane dedicated for.

Would that make sense or is there a better solution for this kind of routing?

Edit: Here is a sketch of what I mean with multiple fingers from bottom and top of the power plane. This sketch displays my intended power plane. I hope this clarifies any misconceptions.

-------------------------
|   ______    ______      VDD = +5V
|  |  __  |  |  __  |  |
|  | |  | |  | |  | |  |
|  | |  | |  | |  | |  |
|__| |  | |__| |  | |__|
     |  |      |  |
-----´  `-----´   `-----
|_______________________  VSS = -5V


texts:
I have a faulty graphics card i am trying to repair, i noticed on the back near the 12v connector that a step down converter in Q501 had a leg missing (right side, second from the bottom) and i am not sure what the cause was (possible corrosion?).

I have a few questions regarding repairing this:

What would be the easiest way to swap out the step down converter with a replacement.
What is the space in Q505 for as it looks like a step down converter in the TSOT-23-8 package would fit.

The step down converter in question: https://www.mouser.co.uk/ProductDetail/Monolithic-Power-Systems-MPS/MP1475DJ-LF-P?qs=Iq7RKQRjpgoaxnjiXuhBAA%3D%3D

Any help would be greatly appreciated, Thankyou.


texts: How to know phasor current direction in LTspice AC analysis

texts:
When one does AC analysis in ltspice at just one frequency (list option), the phasor values for current and voltage are diplayed for each element of the circuit. But i need to know the direction in which the currents are oriented. How do i do that?.I could go (V2-V1)/Z but i want to know if i can know the direction directly form ltspice. Is it always the same as the direction shown in the transient analysis (for currents)?
I found this website
https://csserver.evansville.edu/~richardson/courses/Tutorials/LTspiceIV/06_ACAnalysis/html/06_ACAnalysis.html
and in here they say that a little triangle pointing in the positive current direction appears in the resistors and that way you set the positive direction. But i dont see these apearing when placing a resistor.


texts: How to achieve positional servo control with an Atmega328P?

texts:
I am trying to drive my SG90 servo using the timers on the Atmega329P using phase correct PWM. I have set up my motor well enough that it rotates, but I cannot get it to stop - the servo motor just continues rotating.

Here's my current code:
servo.c

#define F_CPU 16000000L

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

#define TOP 500 // 1000*(64/16000000)

void servo_delay() {
   _delay_ms(1500);

}

void setup_servos() {
   DDRD = (1 << DDD5) | (1 << DDD6);
   TCCR0A |= (1 << COM0A1) | (1 << COM0A0) | (1 << WGM00) | (1 << COM0B1);
   TCCR0B |= (1 << CS00) | (1 << CS01);
   OCR0A = 0x00;

}

void move_servos() {
   for (int i = 100; i < TOP; i++) {
      OCR0A = i;
      servo_delay();
      if (OCR0A == 300) {
          PORTD &= ~ (1 << PD5);
        }

    }
}

servocontrol.h

#ifndef SERVOCONTROL_H
#define SERVOCONTROL_H

void servo_delay();

void setup_servos();

void move_servos();

#endif

main.c

#define F_CPU 16000000L

#include <avr/io.h>
#include "servocontrol.h"

int main() {
    setup_servos();
    move_servos();
}

I'm trying to use timer0 in phase correct non-inverting mode, but I exprecienced the same problem when I used timer1.
How do I get the servo to stop at the location I want? I feel like there is a part of the PWM process that I am currently missing, but I cannot seem to figure it out. I will greatly appreciate any help.


texts:
I have a micro controller (uC) with 1.8V supply and no integrated ADC.
This uC must monitor one signal, and check if it is currently 5V or below 4.2V.

I then need to be able to trigger interrupts based on the value, by sensing HIGH and LOW:

LOW for <4.2V
HIGH for 5V

Is using the a voltage divider + uC evaluation hysteresis too risky?

Thanks


texts:
I got a bunch of LM3940 to convert 5V to 3.3V. I wanted to use the same to make -3.3 V so I switched the ground and output. In the schematic the top circuit works fine and I get 3.3V out. I expect V_out in the second circuit to be -3.3V but I am getting +3.3V. Can someone help? Is this something to do with the LM3940?

simulate this circuit – Schematic created using CircuitLab


texts: Motor Speed Controller Voltage Regulator

texts:
Would this cheap Chinese voltage regulator work as a speed controller for a 3 phase 300W induction motor?

thanks.


texts: How to model electric power consumption in verilog-a?

texts:
I am modeling an analog device using verilog-a (to which I am quite new). I would like the model to match the power consumption of the physical device, for which the energy cost associated with state transitions has been measured.

What is the usually preferred way of achieving this? As this device is voltage-controlled, I could add some contribution rules to the current that roughly follow the measured power, although that would be complicated to implement. I also saw that I could add charge contribution directly, which would be easier to do given my data.

I do not need extremely high precision, especially when it comes to transient simulations: a rough estimate of electric power consumption over the whole simulation time should be enough.

These points are of particular interest to me:

What way (if any) is it usually done?
Do discontinuities in current or charge contribution (ex: Q(vin) <+ 1e3;) risk to cause convergence or stability problems for the simulator?
Is it a lot more costly to compute this? (Will it negatively impact my simulation time?)


texts: NTE941M Non-inverting OpAmp Has Non-zero Output with 0V Input

texts:
I have a non-inverting, single-supply, variable gain op-amp circuit configured in accordance with this diagram:

Vcc: +16V
Rf: 800k Ohm Potentiometer
R2: 100k Ohm

I have the potentiometer set to ~200k Ohm for a gain of:

$$
A=(1+R_f/R_2)=(1+200k/100k)=3
$$

I have confirmed that this works experimentally (A=3.07). However, what puzzles me is that when \$V_{in}\$ is left floating I get an output of 6V instead of approx. 0V. Consequently, any input below approx. 2V yields no change in output.

Per the datasheet for this OpAmp, the maximum \$V_{os}\$ is 5mV, which even when amplified by 3, is nowhere near 6V.

Edit:

Below is a drawing of my circuit.


texts: Combining two phantom power microphone capsules

texts:
I just bought a two channel wireless system for my accordion. It is two separate battery powered transmitters transmitting to a single dual channel receiver. It's good that I can have one microphone for the left hand (basses) and one for the right hand (piano keyboard). I'm using condenser microphone capsules that came with a  different devicebut it seems to work and the transmitters appear to be giving out phantom power (although a little low at only 4v measured by multi meter).

My problem is that the spread of the microphone for the right hand is not enough. To avoid feedback I need it close to the keyboard but when I do that it only picks up the five or six notes closest to it. I want to combine (cheaply!) another microphone capsule into the transmitter for the right hand so I can have two pointed at different parts of the keyboard. I don't want to buy a third transmitter.

I understand from reading online that this is a bad idea? People have asked this question and been told that one microphone will drive the other, etc etc, but would it really be that bad? Admittedly the quality of the six notes that ARE being picked up currently seems to be very good! However, I would give up some quality if it allowed the rest of the notes to be heard too!
Any thoughts?


texts: 0-12V Adjustable Home Made DC Source not working

texts:
I have a home made dc source that is made a few years ago. Solders at the back of the board are very bad so I can not track the connections very good. But it's circuit diagram is very similar to the following diagram.

Solders of connections of pot was broken off. I connected them randomly. I measured the output, the output voltage is 0 V. I changed the pin connections of pot but the output is still 0V. I did some measurements and saw the output of regulator is 0V while its input is approximately 17-18 V. Is it possible regulator is broken? What can be the reason of 0 volt at the output of the regulator? What can be the reason of 0 volt at the output of dc source?


texts: Logic gates for relay coils analogic control signals

texts:
I have 2 external signals arriving to my board, A and C. B is generated inverting A. They 3 will be used for generating 3 switch control signals: A', B', C' at every point (there will be 8x3 24 switch). Every one will be 12V or 0V. 12V state means to activate the coil of a relay, because of coil needs 12V for closing contacts.

According to the application, there can only be one active switch at the same time I thought a way for ensuring that only A', B' or C' will be ON and the other two signals: OFF.

I though about muxes and logic gates that supports input and output voltages of 12V. So I found useful products. But after thinking that I was having a good solution, I realized that:

these coils have a resistance = 150 Ohms. So Icoil = 12V/150 = 80mA -relay datasheet don't say anything about cutoff current, but drop-out voltage: 1V -
the most of existing logic gates provide a max output current = 10mA.
so, I'm afraid that coils will not be energized because 10mA < 80mA

questions:

I dont' know if my explanation and situation is correctly deduced. Is it generally only needed to have 12V or may the coils need 12V + I > 80mA?
If I can' t find AND and NOR gates with this current output features, how do you solve the situation?
Must I say bye to modifying control signals using logic gates? or can be applied some electronics to the outputs? I don't consider using current elevators due to the quantity of them that I would need.

Any information will help.


texts: How to analyze BJT amp circuit with multiple gains

texts:
Im currently trying to solve this problem for total gain, though I'm stuck right off the bat with DC analysis. I was told the emitter current for Q1 and Q2 will be 0.9 mA though I have no idea why.

Why is the emitter current for Q1 and 2 0.9mA?

Would Ic at Q1 be Ic1=(9.3--10)/22k = 0.872mA?

edit: I understand the AC portion so don't bother with that, just need help with DC.


texts: What does mean a rail to rail output opAmp?

texts:
Context : have a very similar problem to the one exposed here, and in the best rated answer (by Olin Lathrop), he says we need a rail to rail output opamp.

My question :

What is rail to rail opamp ? (In what characteristic does it differ from a regular opamp ?)
What is rail to rail output opamp ? (In what characteristic does it differ from a rail to rail opamp ?)


texts:
I am trying to find the output resistance \$Rout\$ of this circuit consisting of 3 n-type MOSFETs.

It is given that all 3 MOSFETs have \$g_m=4 mA/V^2\$ and output resistance \$R_o=100k\Omega\$.

simulate this circuit – Schematic created using CircuitLab

The given answers to the question are to use a small-signal equivalent circuit and then just use \$Rout=R_4+R_o=100.09 k\Omega\$

The method I used was different but also uses a small-signal equivalent.  My working is shown below and I get an answer of \$136.09 k\Omega\$

The equivalent MOSFET circuit has a voltage-dependent current source. I was always taught that to find the effective resistance when a dependent source is present, you can't simply add/shunt resistances together, you have to 'excite' the circuit with a voltage/current source and measure the resulting current/voltage from that source.

A quick explanation of my method:  I first set input voltage to zero and 'excite' the circuit with a 1A source between VDD and the drain of the 3rd MOSFET since this is where the R_out arrow points between.  The first two MOSFETs do nothing and then R_out is equal to the voltage across the 1A source divided by 1A which is just the voltage at the 3rd MOSFET drain.  I then just do nodal analysis on the drain and source nodes to find the drain voltage.  Note: I accidentally wrote R_out as R_o in my working.

I also simulated my circuit in PSPICE which resulted in the same drain voltage as in my answer.

Which answer is correct and if I'm wrong, where am I going wrong?  Thanks for any help.


texts: While looking into the schematic of the Nucleo STM32F767ZI, I saw a blue led driven by 3.3V, which is the GPIO voltage of the STM32. The datasheet of this led specifies a typical voltage drop of 3.3V, so how does this configuration work with that 680 limiting resistor, as almost all voltage drops on the led?


texts: Is 3.5mm jack to female Apple Lightning adapter technically possible?

texts:
I couldn't find a trustworthy source for whether Apple EarPods are digital or analog, but I'm pretty sure it is digital as most teardowns show a chip on it that might be a DAC. Should this make passive converter impossible?
Active converters with a ADC are always technically possible, but is there any on the market? Would one also need external power?

Sorry, if the description is unclear. What is described adapter used for is connecting Lightning EarPods to analog sound source that is using 3.5mm socket.


texts: Why does wire not have large capacitive reactance?

texts:
For capacitive reactance, I am presented this formula:
$$X_C = -\frac{1}{2\pi fC} $$
Where clearly, the capacitive reactance is inversely proportional to the capacitance.
This confuses me.
We usually talk about capacitive reactance in relation to capacitors, which have a rather high capacitance. From this formula, I would expect their reactive capacitance to be small, and the reactive capacitance of elements with low capacitance to become very high. That is, a simple wire should always have a much higher reactive capacitance than a capacitor.
What am I getting wrong here? Does this formula only apply to the circuit-elements we define as capacitors? If so, what makes them so special that we can apply this formula to them, but not to other elements which also have a (very small) capacitance?


texts: ESD Grounding Straps with No Chassis Ground

texts:
I've got water pump device that needs to pass ESD testing (IEC 61000-4-2, 8kV contact, 15kV air discharge).

On this device (as circled in red), there are these four metal inlets.

At 2kV with an ESD gun this device is hard resetting, on any contact with the metal inlets.  So I'm assuming the ESD is triggering the reset pin (or some other condition) on the microcontroller.

This is a friend's device, and built by a hobbyist of sorts.  He used a single layer board with no signal GND plane of sorts, and we are going to redesign the board to 4 layers with TVS, ferrites, and series resistors as needed to protect the microcontroller lines.  There'll be as large a possible signal GND plane on this board for the TVS to shunt the ESD transients.

So in the ideal, that will fix our ESD issues.

BUT, what about ground straps from each metal inlet to provide a low impedance path for the ESD transient before it even approachs the board?

The enclosure is all plastic, and there is no chassis GND.

On the four metal inlets, where could you ground those if you just have the one PCB in the system?

I'm thinking we would have an isolated area on the PCB that runs straight to signal GND with these four straps from the metal inlets?

How are folks making these types of connections to chassis ground (if we had a chassis ground)?

I'm thinking of soldering a wire to the metal inlet -- is there something off-the-shelf that works better that's commonly used for these types of connections?

Should all four straps run to one central location in the far corner of the PCB that feeds to the signal GND?

I was brainstorming a wire with a ferrite in series that would dissipate the ESD as it comes in from the metal inlets and goes to our PCB signal GND?


texts: How can I connect a sensor to two LEDs so that one will work when the sensor's output is HIGH and the other when it's LOW?

texts:
(Moved from the Arduino stackexchange)

Let OUT be the sensor's output.

If I connect

LED1 to BAT+ and OUT

LED2 to BAT- and OUT

is this Ok?

Instead of LEDs those could be units that need even less current. I am also interested to know the limits of the offered solution in terms of current and what should I do from units that draw higher current.

Anyway, I look for a solution without a MCU.


texts: Z(in) for small signal analysis with BJT for unbypassed emitter and r0 in place

texts:
I have been studying the small signal analysis of BJT with re model with the emitter terminal not bypassed. I am able to derive those Zi, Zo,Av, Ai long as ro is assumed to be infinite. But I am unable to find Zi with a finite ro. Following is the circuit diagram:

Below is the equivalent re model:

I tried with google, but have not been able to find any. Everywhere the solution is done omitting ro.Kindly help me with the analysis or provide some helpful link.  Thanks in advance.

EDIT:

let, beta=B

From my analysis, Vb=Ib[Bre+(B+1)RE]

So, Zb=Vb/Ib= [Bre+(B+1)RE]

Zi=RB||Zb

But the expression for Zb given in the book by Boylestad and Nashelsky is

Zb=Bre+[{(B+1)+RC/ro}/{1+(RC+RE)/ro}]RE

which I am not able to understand. Please explain it.


texts: Effective resistance from a random resistance network

texts:
I am trying to calculate the equivalent resistance from a random resistance network formed by carbon nanotubes (CNTs.)
I have a MATLAB program where the CNTs are randomly distributed inside a volume. The code basically calculates the distance between the CNTs and if the distance is less than the tunneling distance (user defined) it achieves percolation (meaning that two opposite faces are connected through a path.) Then with matrices, I calculated the voltage drop on every CNTs (resistor) so now I have a vector of electrical potentials which apparently with it I can calculate the electrical current inside the volume and then the equivalent resistance.
However, I have been trying to understand how can I do this.


texts: Time parameters of pressing a tact button by people

texts:
Sorry for bad English.

How fast people can press a tact button? I.e. what is minimal time of holding a button pressed people can get?
What is typical bouncing time when people press tact button?

I have no oscilloscope to check it, but maybe anyone already did it and public in the Internet?


texts: Difference between cutoff and subthreshold region of nmosfet?

texts: I understand that some current does flow from drain to source when Vgs is below vth and Vds is greater than zero. But why this has a different name?(and a different region in Cadence virtuoso tool) when cutoff and subthreshold both have same behavior? Please explain me what am I getting wrong here?


texts: IPC Specification for pad width vs. pin width (SMD)

texts:
I am working on a board that has a fine-pitch component (0.35mm). Each pin is 0.15mm wide. I received a question from the manufacturer asking if they could adjust the pad width from 0.22mm to 0.18mm +/- 20% to allow a soldermask web between the pads. However, 0.18mm - 20% is 0.144mm, which would mean a pad width that is narrower than the component pin.

I am looking for an IPC specification mentioning the minimum pad width vs. component pin width, to determine whether or not it is permissible to have a pad that is slightly narrower than the pin that will be soldered to it.

I realize 0.144mm is not much less than 0.15mm and will probably be ok, but I am looking for a concrete IPC spec saying whether or not this is allowed. I have checked IPC-SM-782 and IPC-7351 but, unless I missed it, I could not find this information.


texts:
I've bought these special upright USB Type A ports with a "Sensor Contact" (the stray pin I've marked "Sensor Contact Pin"). I've been Googling on how they work, as well as sent about a half dozen emails to the tech support guy at the company (FCI) they come from asking the same question(s) like "How does it work?" and "Do you have examples?", and gotten nothing back but "They have the same pinout as other USB A ports", but not any relevant, helpful answers.

So that's why I'm turning to you guys. My assumption is that when a device is plugged in, it provide +5V through the "sensor" contact, which I could hook to an MCU or transistor or something.

What do you guys think?

Here's the Mouser page


texts: Resistor in shunt regulator not following Ohm's law?

texts:
I was reverse engineering a power tool battery charger (21V SMPS) that derives its 5V rail from a simple shunt regulator, employing a TL431 programmable precision reference and a NPN transistor, as per my crude sketch (sorry I didn't have time to paint it). The programmable reference runs the gate of the NPN transistor, maintaining a stable 5 volts on the rail that powers the microcontroller, indicator LED. etc. (The reference is programmed to 5V by R1 and R2, but is actually running 0.6V higher, as it needs to overcome the additional Vbe of the transistor, so Vka is really 5.6V) The voltage measurements from the sketch were measured at the same time, in an idle, no load state. A SMPS 21V source feeds R4, dropping 0.577V, which per Ohm's law means about 0.0012A are flowing through R4. The transistor gate is biased by a 4.7kOhm resistor R3. The voltage drop on R3 also corresponds to Vcb, measuring 14.99V. Now I stop understanding things. With this voltage drop, R3 should be passing 0.0032A, but this is impossible since the "inrush limiting" resistor R4 is only passing 0.0012A! I also probed the points with my oscilloscope to make sure there wasn't some kind of weird wave action taking place that would mess up my multimeter reading but no, it showed a stable voltage. I understand that what is probably happening is some borderline open circuit condition, with the transistor just teetering on some kind of almost-off state 'commanded' by the reference, but this feels rather vague in my mind.
Can somebody please explain what is happening, more to the point, what current can R3 be passing if its voltage drop measures 14.99V and Ohm's law would dictate it passing 3.2mA, but the circuit is only being fed a MAXIMUM of 1.2mA?
Many thanks for any explanation! Cheers!
EDIT: as one commenter immediately mentioned, R4 I was reading as 470 Ohm was really 47 Ohm, so the currents all add up and all is good, as 12mA are coming into the circuit, and R3 is only shunting 3mA of those. Many thanks to the keenly eyed!
I would still appreciate if anyone would be so kind as to describe "boundary" operation of the transistor, teetering on dropping 15.6V as maintained by the reference.
Many thanks!


texts: Why are alkalines "required" for metal detectors?

texts: A handheld metal detector specifies only "Alkaline" batteries and not "heavy duty" or "rechargeable". Since there are li-ion 9v batteries available not at low cost I was wondering what is different that requires these in a metal-detector specifically? Is there something about the metals or magnetism reacting within the device or is it an issue of power draw?


texts: Why is the depletion region formed by minority carriers?

texts: While I was studying about the working of transistors I came across a term called the depletion region which stops the flow of electrons from one place to another. A doubt that came to me was why couldn't the majority carriers form a depletion region?


texts:
The x-axis is the current and y-axis is the voltage across the diodes

I am trying to find out with one of these lines is 1N4001 and which one is 1N4003. My intuition tells me that blue one is 1N4001, because it is heavily doped (blockage current is 50V) and the other one is naturally 1N4003 (blockage current 200V).


texts: Say one wishes to transmit a sequence of characters - "ABC". What are the steps that are invariably done to enable this transmission of information?

texts:
I would like to elaborate on the same: Naturally, one would use the ASCII representation to first encode "ABC" into raw bits. The sequence would then become (in binary) "01000001 01000010 01000011". Let us assume that this data is transmitted in the form of a Unipolar Encoded Signal (between voltage levels of 0 and 5).

What are the further steps involved in transmission and reception?

Additionally, can reception occur only real-time? In other words, can the information be picked up on the channel (can be wired or wireless) only at the same instant as when it was transmitted? Isn't there a chance that there might be some other data being transmitted at the same frequency (at the instance of time we are trying to detect/receive)?

To summarize, how do we know that the information we receive is actually the information that we are meant to receive? Do the concepts of Synchronisation and Equalisation help solve this problem?


texts: What is the purpose of input on oscillator after initializing

texts:
Perhaps that is not worded properly. But what I am wondering is given the picture below lets assume I have a 1V sinusoidal input and that the amplifier in turn gives me a 10V sinusoidal, then the feedback will attenuate that back to 1/10 of the output to give me again 1V so that it can be converted back up to 10V.
But if my input is already at 1V whats the point of the feed back? Unless you add the input to initialize it and then take it away and let the oscillator oscillate on its own.


texts: What is this white box in a battery pack?

texts:
I have an O2 Hurricane canless air system that seems not to charge anymore. I was a bit surprised because it hasn't been through much use or many charging cycles, and customer support was non-responsive, so I decided to take it apart and see if I could at least make it work with direct DC power.

Here's the inside circuit with the battery pack taken out:

The black box is the on switch. Circles 1 and 2 are the metal tabs that were connected to the battery pack, and circle 3 is the white piece I'm wondering about. Because when I plug this circuit straight into the wall (via a 12V DC adaptor), the motor twitches but doesn't spin up.

Here's a close up of the white box:

I tried for 5 minutes to get a picture where I could make out exactly what the writing above 55*C says, but I couldn't do it, even under a 4x magnifying glass. I'm hoping someone recognizes it just by shape or place in the circuit. The other sides of the box are blank.


texts: Balancing hardware to charge my DIY 13s6p 18650 LiOn from 54.6v Smart Charger?

texts:
I know the cells must be balanced though I wanted to confirm that the the 54.6v "smart" charger (which made no mention of battery prerequisites) didn't some how trickle the charge into the pack in some safe way I did not know about. I would have been VERY surprised if it could.

This is my first LiOn project and I have been researching diligently. Unfortunately confirming an author's credentials is not self evident. I have discovered http://henrysbench.capnfatz.com and http://batteryuniversity.com which seem to be solid resources, but I know there are insights to be had from members here.

Concisely, I am enquiring here for advice.

I was advised to buy something labeled as "Charger for 13S 46.8V/48V (13S 3.6V*13/3.7V*13) Li-ion/Li-Polymer or 15S 48V (15*3.2V) rechargeable battery". There was no mention of balancing, I assume I need my battery to balance itself under these conditions. (and would be surprised otherwise. Hardware recommendations or references anyone?)

I am leaning toward constructing the "Arduino 18650 Battery Charger Project" described here: http://henrysbench.capnfatz.com/henrys-bench/arduino-projects-tips-and-more/arduino-18650-battery-charger-project-1/

Have spent a relative fortune for 78 Samsung 25R batteries I want to charge them right.


texts: Is it OK to create a negative rail just by dividing voltage with resistors?

texts:
I want to build some circuits to learn about op-amps, and so I would like to set up a negative rail.
Are there any problems in creating a negative rail by using an 18 V bench supply and then simply dividing the voltage using, say, two 10 MΩ resistors and setting ground to the mid-point so I have +9 V/GND/-9 V?
Please keep in mind that I am a newbie when it comes to electronics!
EDIT:
In further reading guided by all the kind and helpful responses I received here, I just want to signpost to other newbies that there is a great overview of the implications of using a voltage divider as a power source in The Art of Electronics, Horowitz and Hall 3rd Ed Section 1.2 on the Thevenin equivalent circuit


texts: Is there any design consideration to keep in mind when switching to higher capacity lithium batteries?

texts:
Long story short, had an RC drone with 3.7V ~1400maH lithium batteries and switched to 3.7V 2.2AH battery. But now the whole electronics cut-off when the throttle is pushed beyond mid-way (i.e. Higher currents). Otherwise it works fine at low motor rotations.

What might be a consideration that I might have missed related to battery selection?


texts: Consideration when switching from 2N3904 to MMBT3904

texts:
I created a (very) basic circuit with:

simulate this circuit – Schematic created using CircuitLab

On the test board, with 2N3904 transistor, VM1 show ~12V and ~6V when SW is pushed (as expected).

When trying to go to SMD components, I am using MMBT3904, but it seem to behave differently: Showing about 6V indifferently of the state of SW1.Additionally, the collector voltage seem to contaminate the base voltage.

I tried several options:

Minimized soldering temperature up to minimum (270º) about a few seconds to solder. Is it still to much?
Created a mini pcb only for the transistor, so all the other circuit is exactly the same.

The question is: is there special considerations to switch between 2N3904 to MMBT3904, either in the circuit or the soldering process? What am I doing wrong?

EDITED:

On request, here is a a picture. I created the transistor PCB about 1h ago.

EDITED 2:


texts: Does footprint matter when selecting a part in Kicad?

texts:
When designing a circuit schematic in Kicad, does it matter what footprint or package is listed in the part name?

This is similar to this question, but I'm more confused about the naming scheme shown in Kicad's part selector in the schematic editor. As I understand Kicad's workflow, you design the circuit first and then specify footprints later when designing the pcb.

I want to place a n-channel mosfet, and I know the physical part needs to be in the 3-pin DPAK package size. When I go to select a mosfet in the schematic view, Kicad's part selector lists a lot of mosfets. Some specify no package, but a lot specify explicit packages like "SO-8" or "SOT-143". I don't see any listing "DPAK". Is DPAK not supported, or does the package listed in the parts selector not matter, and I can select the footprint later when designing the PCB?


texts: What is the simplest solution for over voltage protection?

texts:
In a small device (direct current). What is the simplest and efficient solution for over voltage protection?

Regards


texts: should land patterns match the typical or the maximum part footprint dimension?

texts:
I've read that for QFN packages at least, the width of the pads on the board should exactly match the width of the feet on the bottom of the chip.  However, the datasheet for the part I'm working with (here) shows both typical and maximum sizes for the feet.  Which is best to use?

The same question applies for the thermal pad at the center of the chip.


texts: How are poles of Bessel filter related to cutoff frequency?

texts:
For a 2nd order Bessel low pass, I have a pole-zero map which has a pole couple of the form: \$p_{1/2} = a \pm jb\$.

Can I deduce the cutoff frequency from the pole location? Does it contain any more information?

EDIT: Since the calculation of the cutoff frequency in the answer depends on the filter type I am wondering, if it is possible to determine the cutoff frequency for any kind of 2nd order low pass solely by the pole location (under the assumption they are complex conjugate)?


texts: After adding a power switch onto a LED string of lights, some still light up very slightly when switched off

texts:
I bought a string of lights made of white LEDs (SÄRDAL by that famous Swedish company) that doesn't have an on-off switch. The AC/DC converter directly plugs into the mains (220V) and I wanted to add a switch to turn it off without having to unplug it.

I bought a very simple switch from the hardware store and installed it on the leads that make up the string of lights, after the adapter since this was my only option. There are two leads on the string, and they run on 24VDC.

The switch is made so that one of the leads is interrupted mechanically when in "off" state, but the other lead is directly connected from one end to the other end of the switch by a strip of copper.

I thought this should be enough to interrupt the circuit and turn the LEDs off, which is mostly does, except some of the LEDs still light up very faintly in the "off" state.

When in the off state, I measure a very slight negative DC voltage between the two leads with my multimeter (as opposed to positive 24V when on).

Why is that? I thought it might be due to the two leads being twisted in a double helix way along the length of the string of lights, acting as inductors? Or maybe the electrical insulation between the two leads is not thick enough?

I tried connecting the negative lead to the terminals within the switch that are directly connected together (and the V+ wire on the interrupted side), as well as connecting the V+ lead to those and interrupting the negative wire, but both options still produce a faint light.

Thanks.

EDIT: this might not be important, but the LEDs are connected in parallel (I think), since there are 3 leads between any two LEDs, even though only two leads come out of the adapter.


texts: Plugging a 65W computer power plug into a 45W step down transformer

texts:
Is it safe? Would it only charge slower, or could it damage anything?

Here is the setup in more detail:
I'm in Europe, where plugs are 230V.
My computer was bought in the US, so it's a 110V appliance.
I have a step down transformer 230V-110V, with a 45W wattage.
My computer power plug has a 65W wattage.

Thank you.


texts: Component identification - MELF capacitor? inductor?

texts:
I opened a circa-2005 TV tuner VHF/UHF "can" from an 19" CRT Emerson TV and found these hollow MELF components. Can anyone identify what they are? They measure as capacitors but I initially suspected they might be bead inductors. Please see attached photos. Note that the circuit also includes multilayer ceramic capacitors.

They didn't appear hollow when soldered on the PCB because solder filled in the ends. However once they were desoldered I noticed some hollow ends. Inside one end of the component there is what appears to be a "plug" blocking the hole (I forced one out by pushing a lead through the open end). The 'plug' is round and flat like a short flat cylinder (like a hockey puck). I'm not sure of the purpose.  Since these are hollow (except for the plug) I initially suspected they might be bead inductors. However my LCR measurements don't confirm that (not confident about UNI-T readings):

2.612 nF, 0.L ohms, -- mH / measured with DER EE DE-5004 LCR

2.65 nF, 0.L ohms, 6.87 mH / measued with UNI-T UT603 LCR

The tuner PCB is labeled SMEWN870A and the can had the label UTUNNTUAL025 / TEDH9-300A / 1227CT3A. I couldn't find a schematic or datasheet.

(last image is courtesy of electronicrepairguide.com)


texts: Power supply requirements for a small brushless fan

texts:
I've found many resources on the Internet on how to drive a small two-wire brushless fan and to vary its speed. What I didn't manage to find is information on the requirements for the power supply, besides what's usually on its datasheet.

In particular, I'd like to know what are the risks, if any, of powering it using a very simple AC/DC unregulated power supply (i.e. transformer, diode bridge, filter capacitor).

Could the electronics inside the fan, e.g. the controller, misbehave if the power supply is not properly regulated (of course, assuming the unregulated supply voltage output doesn't violate the maximum required by the fan)?

The reason behind my question is that I'd like to use some of those cheap PC fans that can be purchased on Amazon or E-bay to build a ventilation mechanism to blow away soldering fumes, and I'd like to keep the power supply as simple as possible (I plan to reuse some old unregulated wall warts I've in my junk box).


texts:
I'm having a problem mapping touch pins(for touch buttons) on adafruit hazzah, because pins on the chip(for touch sensors) and board doesn't match. Does anybody knows how to connect them(to which pins) on the board itself:
 https://cdn-learn.adafruit.com/downloads/pdf/adafruit-huzzah32-esp32-feather.pdf


texts: NFC spectrum analysis, weird frequencies showing

texts:
I apologize for the picture quality, I did not have an opportunity to export the screenshots.

I have a problem properly interpreting this signal. The subcarrier peak is visible but the data seems to be noisy? I assume using a pre amplifier wouldn't get me a better result. There are also two peaks visible on the leftmost and rightmost side of the screen and I have no idea where they come from. This is the response of an ISO14443-A Tag:

Are the settings of the analyzer wrong or is this the proper spectrum?


texts: How to read a 5.5V IC push-pull output using a 3.3V microcontroller?

texts:
I have two devices that I need connect, one fed with 5V, the other fed with 3.3V,  and I also have a level-shifter, TXS0108E, that allows communication between two circuits, one working in 3.3V and the other working in 5V. This IC has internal pull-ups in both sides and the 5V side is connected to a CD4021BC 8-Stage Static Shift Register, the 3.3V side is connected to a dsPIC33EP64MC202 input that is not 5V tolerant.
The reading of the CD4021 by the dsPIC is not working, I guess it is due to the pull-up present in the level shifter IC, the pins of the CD4021 and dsPIC are push-pull. So, I was wondering, is there a way to enable the reading of the CD4021 by the dsPIC ? I mean, with another circuit, transistors etc... ?


texts: can verilog do `if defined(SOMETHING) ... `elsif defined(SOMETHING_ELSE) ... `endif?

texts:
I'm pretty sure I've done something like this in C before where I have a variety of choices but only one will be true at compile, and I'd like to do it for Verilog sims as well. I haven't found anything about it though. Here's what I'd like to do:

define on command line one of the FLASH_IS_??? names for the current run

in testbench file do:

`if defined(FLASH_IS_1MB)
    `define FLASH_TEA              19000000000 //19s max for 1MB erase cycle
`elsif defined(FLASH_IS_512KB)
    `define FLASH_TEA              12000000000 //12s max for 512KB erase cycle
`elsif defined(FLASH_IS_256KB)
    `define FLASH_TEA               6000000000 //6s max for 256KB erase cycle
`elsif defined(FLASH_IS_128KB)
    `define FLASH_TEA               4000000000 //4s max for 128KB erase cycle
`endif

...

#`FLASH_TEA; //wait for erase time

...


texts: BLDC (Brushless DC Motor) vs PMSM (Permanent Magnet Synchornous Motor)

texts:
The differences between BLDC and PMSM are very small and for what I have seen while reading about it, is not clear to many of us. Most of the articles I have read say that the main difference is that the BEMF of a BLDC motor looks more trapezoidal and the one for PMSM looks more sinusoidal, however I can't understand what is the difference on their construction; is it the wounding? their geometry?...

The main reason for my question is that I want to understand which control method should be used on each motor to have the best performance of if any control method can be used on both.


texts: How do resistive type fuel level sensors work?

texts:
Resistive type fuel level sensors which are used in fuel storage tanks(such as those at fuel stations) comprise of 2 visible parts; dual probe rods and a connecting float.

When the float is at the very bottom the output of the sensor is Vmin(possibly ~0V) and as the float progressively approaches the top the output increases upto Vmax(possibly ~Vsupp).

I would like to understand how these sensors work possibly by a simple circuit model?

For example:
XM/XT 66400 Series Continuous Level Transmitter(note the dual rod/probes)


texts: ESD Mat and wrist strap grounding - Ground hole not available in my country

texts:
I'm building my new lab and I'm not sure where to ground since I live in the Netherlands; we only have hot and neutral available, I don't see a third a hole.
I understand I should get an ESD mat and wrist strap that includes the 1Mohm resistor. And ground these 2 with a common-point ground as shown here http://documents.desco.com/pdf/tb-2000.pdf
The ESD mat should also include a 1Mohm resistor in order to soft-ground it as well, but I'm a bit confused as to why wouldn't the non-conductive top surface be considered a soft-ground for the bottom-conductive layer.
However, my question is about how should I ground the the common-point ground. Should I unscrew the third hole on my wall socket a bit and tie it there? I'm a bit lost how to continue, all the tutorials I see on the internet always include a dummy plug with ground connection to a hot-neutral-ground wall socket, which I don't have.

Any help is appreciated!
EDIT:
I've got 3 cables in the inside of the receptacle I showed above:

Is the top right cable (kinda grey-ish) the ground that I need? If so, then can I just replace with the other outlets containing a ground prong?


texts: Purpose of base-collector resistor in open-collector opto-isolated GPIO output

texts:
I've been working with an opto-isolated output for a high-speed camera I'm interfacing with and was a little puzzled by the circuit they were using for an opto-isolated open collector output. As far as I can tell, the NPN photo-transistor is configured in a darlington pair with two parallel NPN BJTs. I assume they've done this to increase the current the circuit can sink. According to other posts R67 provides a current path to switch off the second stage quicker and prevents leakage current turning the BJTs on.
What I can't figure out is why the designers of this circuit have included R66 in their design. Does anyone know why a base-collector resistor would be included when the BJTs should be acting as a switch? Or what the advantage of this configuration is?
Unfortunately I don't know the part-numbers or values for any components since the only schematic I have is from their documentation. Any thoughts would be helpful, I've ammended the original schematic with an external pull-up resistor and power supply.

EDIT
I have improved the circuit diagram because it had been laid out weirdly.


texts: Connect microphone to RN-52 Bluetooth module

texts:
My goal is to build a bluetooth hands free device, basically a speaker phone, to pair with a mobile phone. I am using the Roving Networks RN-52 Bluetooth Audio module mounted on a breakout board from Sparkfun (product). Connecting a speaker and configuring the device for Hands Free Profile (HFP) has been no problem. However, I am having difficulty connecting a microphone. I have a electret condenser mic and breakout board, also from Sparkfun (product).

The RN-52 has five audio input related pins: Mic_R+, Mic_R-, Mic_L+, Mic_L-, and M_bias. The electric mic has three pins: Audio, Ground and VCC.

I have tried connecting the audio and ground of the mic to both the + and - of left and right mic inputs on the RN-52 with no luck. (VCC is connected to 3.3v).

I am certain that the mic connection is my problem, as the module and speaker work fine for streaming audio over A2DP.

I would sincerely appreciate any help or advice.


texts:
I have only 1 pulse as input and I use qubic-spline to reshape the pulse. The user plot manually the signal inputs from a flow-image and then the signal is imported to Matlab in a ASCII form. That means that the sampling period is not uniform. Then I have a pressure pulse that are sampled at 128 Hz.

If I use same samplig period (128Hz) using qubic spline on the flow signal. If I increase the sampling to 4-8 times what will it effects of the FFT analysis?
I can see in Matlab that the amplitude changes at different up-sampling rate.

If I multiply the input signal (pulse train) e.g. 2-6 times it will also effect the FFT analysis. The bins are the same at higher pulse train but not at just one single pulse.
One pulse or many should not impact the FFT analysis?

Right know I have no filter on the signal (before and after resampling)


texts: How does this telephone circuit eliminate the sidetone?

texts:
I know that the sidetone in telephones is removed by a hybrid transformer or by differential amplifier using an op-amp.
I don't know how this circuit does the job using just 2 transistors (I took the circuit from the ebook: "200 Transistor circuits,Collin Mitchell" and we practically manufactured the circuit and it worked very good ):

This is another sidetone removal circuit using op amps. Its operation is more understandable (I took it from an answer to another question):

I want simple explanation of the transistorized circuit (the following description from the ebook is not sufficient ).


texts:
I have some doubt regarding the working of series termination resistor for impedance matching purpose.
For an example, i am feeding a 50MHz clock to the clock buffer ic PL133-37 input, i have seen the resistor selection is based on the equation R = Zo-Zd where Zd= Driver output impedance & Zo= Trace impedance.
But my doubt is whether we see any reflections at the CMOS input of the receiver when signal comes from 50ohm trace line as typical CMOS input impedance are in ~KOhm range ?? We can't avoid this ?


texts: Input Impedance of BJT CE Configuration different from Multisim simulation

texts:
So as I derived, my input impedance should be Rb||rπ. But by substituting the value I obtain via the AC analysis from Multsim, I got different values. Tried a few times but still, the input impedance calculates not equal to Probe of Rin(where expression: V(Rin)/V(Rout).
I got no idea what've I missed.
It will be great if someone can help me with this!


texts: Is it possible to use 400 kHz I2C buses with a 32 kHz slave?

texts: I am going to use a 400 kHz I2C bus, but I want to talk to a slave MCU, a PIC16F690 (datasheet), running at 32 kHz. Is it possible to do this? I think so, because the master does the clocking, but are there any unforeseen problems that might occur? (e.g. MCU can't load data into RAM quick enough.)


texts: Using an arduino to read a 5050 LED signal

texts:
I have a project right now where I have access to a header to control standard 12v 5050 LED strips.  What I'm trying to do is read that signal with an Arduino, and then use the values to control other types of RGB strips/bulbs that are connected to the Arduino.

I cannot seem to wrap my head around how to pull the signal I want. I've got a +12V, and an R, G, and B signal. The RGB ones aren't + voltage so... what are they then?  How do I go about converting them into something the arduino can read on the Analog pins?


texts: Issues with kitchen fan - how to salvage?

texts:
In my kitchen there is a fan to extract air in case it smells during cooking to not make the whole appartment stink like food. When I turn it on, it looks like it is working. But after a bit of time, the sounds it makes change - which seems unexpected.
So I took the blower unit out of its housing. This is what it looks like on its own:

The schematics look like the following (this is what I was able to figure out without opening the fan itself):

I connected it to the mains and let it run for a bit. And sadly it behaved a exactly like in its housing in the kitchen. When the unit starts up being cold, you can feel a strong air flow out of it. After a while the air flow drops to a gentle breeze. This is where I disconnected it from the mains again. I did 2 measurements: First I measured the voltage accross the capacitor: It starts at 280 V AC and slowly drops down. Around 180 V AC there was not much air flow left. What bothered me was that the capacitor heated up. I'm bad at guessing temperatures but it was well above comfortable temperature.
Since I don't have a power analyzer socket, I let it cool down and measured the current it draws. The unit starts at around 200mA. The current exponentially rises. At 350mA you could hear that the motor was spinning slower and at 400mA I disconnected power again.
The label on the fan says 36W which would translate into roughly 160mA. The label on the capacitor says 1,5 uA +/- 10% @ 320V AC.
My multi-meter did not want to measure the capacitor in situ. And since the connectors are crimped and I don't have replacements at hand, I did not want to destroy them, yet.
As the current draw is well above what the unit should have drawn and also the capacitor is getting too hot for my councious, the unit is not getting back into the kitchen anytime soon.
Question: Is this fan salvagable? And if so which component should I replace?
Date of manufacture: 10/1982
Location is Germany, so the mains voltage is 230 V
Edit:

I measured the capacitor on its own. Also made a technician at a local electronics store measure it. Both measurements came up fine. But that does not mean anything. The fan started blowing fine at first.
I bought a new capacitor and wired everything up. After 5 minutes the capacitor stayed cool and there was no audible changes in fan speed. Also the voltage across the capacitor stayed between 275V and 280V AC.

Will put everything together tonight and reinstall it. Thanks for the help.


texts: How does digital signal is propogated in channel?

texts:
As mentioned on the picture a digital signal is sent, after that it got affected by noise and disturbances and it is retrieved perfectly by the repeaters.
My question is, signal in digital is sent as electromagnetic wave right? So it is a Sinusoid, so is it a sinusoid with fixed amplitude or fixed frequency, if it is so; then in the picture shows digital pulse shape is kind of lost its shape, so how I imagine this distortion in terms of sinusoids.

For example: if I send an analog signal, it faded and AWGN added into it I can imagine the distorted analog signal, but I am having difficult time visualizing digital signal distortion from this picture, because we don't send digital pulse in space? Because waves in real life are Sinusoidal. Clarify me like I am five


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I am studying an advanced mathematics textbook. One of the examples is within the context of an electrical circuit (a series circuit, I think). The example makes the following claim:

  As we go around the circuit, the total voltage drop must equal zero.

Can someone please explain what law/principle of physics this is, and elaborate on it a bit? My research indicates that it might be Ohm's law, but I'm too inexperienced with these concepts to link the formal description of Ohm's law to the above statement.

Thank you.

P.S. I'm not sure if my tags are appropriate, so feel free to edit with the appropriate tags.


texts: How holes and electrons in the diode gets back to their original position when it is turned off?

texts: When diode is turned on the holes and electrons gets mixed that is the holes will also appear largely on the n side and electrons also appears on the p side but when turned off how electrons and holes get separated as p and n side with same as when it is not connected. Practicals explanation please


texts: Transient voltage supression for high voltage Thyristor or Avalanche TVS

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I am making a high voltage 240 VAC 60Hz voltage measurement front end and is in need of a transient suppression device. According the a table in wikipedia.

Avalanche and Thyristors are the only remaining options to choose from. Are there any other factors that i should consider aside from the one in the picture?
I am leaning to use the avalanche type because it is something that i am familiar with in low voltage applications, so choosing parts is not that difficult i already even have a tentative part from littlefuse and bournes. Thyristors on the other hand i am not familiar with the terms they are using.
Is it worth using a thyristor?
EDIT:
I have narrowed down a bit on the limits of what i want to protect, so far in my design process i have used 2000 V as my absolute maximum in term of component spacing, resistor selections, and isolation barrier. I tried to choose components beyond this where possible, but 2000V is where i draw the line. Also fits great for level 3 IEC/EN 61000-4-5 certification (im not going to certify this device)


texts: Designing of a voltage to current converter schematic

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Voltage is from a sensor (0 to 4 V), and load is within -100 nA and +100nA, where 0V should be converted to -100nA and 4V to +100nA.
Here is my last trial (picture below.)
I got the -100nA for 0V and +100nA for 4V as I wanted, but the curve is not a straight line (I assume it's supposed to be totally linear) since I use non-symmetrical power supply for the op amp (for the minus terminal I use 8V battery and 4V as a battery for + terminal of the op amp).
Do you have some hints or links for a good textbook?


texts: 555 timer as Dual Direction H-bridge driver

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I am trying to design an analog direction driver circuit for an H-bridge configuration on a small DC motor. I have a pretty tight space constraint, and a simple requirement for my design, hence why I am trying to avoid microcontrollers. What I want to happen is for the motor to travel in one direction for 2.5 seconds, then to switch directions and travel for another 2.5 seconds. That's it for right now. In my design so far I have a 555 timer driving the timing side of things, and it is giving the desired output (HI for 2.5, OFF for 2.5 seconds). I also have the motor driver circuit built and functioning such that:

Input A = LO, Input B = HI - Output=Clockwise

Input A = HI, Input B = LO - Output=Counter-Clockwise

If In A = In B, Output = Stopped

My question is: How can I use the output of the 555 timer to drive the inputs of the H-bridge in the manner mentioned above? I am missing the link between the two sides of the circuit, and was wondering what suggestions you might have.


texts: „Power circle“ - first buck then boost for converter testing

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I would like to test the efficiency of some buck converters. I am thinking of using two current sensors like INA219 (or similar) connected to an Arduino and using the serial monitor to gather data.

Vin: 12V
Vout: 5V, 3.3V for now.
Iout: 8-10A max. maybe 15-20A in future.

Instead of dissipating the output voltage of the buck converter into heat using a lamp or a power resistor, I would like to re-convert the buck output using a boost converter to be reused by the buck. It’s like a “power circle."

Can I use the output current limit of the boost converter to create gradual steps to measure efficiency over Iout?
How can I control Ilim resistor with my microcontroller or do I have to do that manually with a potetiometer?
Lastly, does Vin main act as a supplemental supply while the entire output of the boost ist being used by the buck?