texts: Class A amplifier asymmetric distortion mystery

texts:
I have an amplifier that went bad on the left channel a couple of days ago. I'm kinda intrigued by the failure and symptoms, which is also why I'm posting here and not just counting my losses.
I was under the impression that class A designs feature a single conducting element, thus no cross-over distortion and/or asymmetric behaviour should be possible, which is why I find the output very strange - I've recorded a video with the left & right channel outputs on a sweeping sine:
https://youtu.be/7JUJDubUtk4
Note that the oscilloscope input is from the headphone audio jack of the amp. The audio in the video is from a microphone in the room. Some observations:

Output distorted waveshape is frequency dependent and input volume dependent
In the frequency domain, the non linear distortion seems to be frequency invariant
Distortion is load dependent - if I turn off the speakers while recording from the jack, the distortion mostly disappears
Distortion levels seem to follow a smooth envelope - if I instantly turn the volume down, the distortion goes away but slowly creeps in again
Extreme amplifier feedback reaction - at 0:27 I touch the bass diaphragm of the bad and afterwards the good channel

I have already isolated the error to the output stage, i.e. the preamp outputs are clean. The fault occured instantly, and seemingly out of nowhere.
So while I don't have high hopes for repairing it, I would be very interested if anyone has any ideas as to what might be happening, or how one could diagnose it further.
The amplifier in question is a Denon PMA-980R.
Edit: Here's some different parts of the video - interestingly the waveshaping distortion seems to cycle around decades (e.g. from 100 hz to 1kHz cycles around):

Also, I claimed it was a class A amplifier because it says "New optical class-A" on the front, and I believe this amplifier range used to be class A, but I may be wrong.
Edit 2: Sweep with no inductive load:
https://youtu.be/jQCvrfjg_N8
Edit 3: Schematic

Here's another part, but I believe it to be mostly irrelevant:

Edit 4: Increasing volume showcasing AB behaviour:
https://youtu.be/vuVzfaQDpaA


texts: Mosfet shared diffusion Spice extraction (Magic)

texts:
I'm working on a project and try to design a layout using cmos CAD tool Magic. In a part of the project, I connect the nmos transistors in the form of shared diffusion as follows(each square represents 90nm x 90nm block):

There are four parallel transistors there. All drains and sources connected together. Drains connected to output Q and sources go to GND.

And when I extract the layout as spice, the part corresponds to the part of the layout above is like this:

M1004 GND A Q Gnd nfet w=0.36u l=0.18u
+ ad=0.3888p pd=3.6u as=0.5184p ps=5.04u
M1005 Q B GND Gnd nfet w=0.36u l=0.18u
+ ad=0p pd=0u as=0p ps=0u
M1006 GND C Q Gnd nfet w=0.36u l=0.18u
+ ad=0p pd=0u as=0p ps=0u
M1007 Q D GND Gnd nfet w=0.36u l=0.18u
+ ad=0p pd=0u as=0p ps=0u

My question is, why all the AD PD AS PS dimensions are extracted as 0? Is it an error that shows up in all cmos CAD tools or am I doing something wrong with Magic? Or is this the correct form of representing shared diffusion contacts in SPICE that I shouldn't be worrying about?


texts: Design Consideration: Cortex M0 vs Cortex M4 for IoT Applications

texts:
I'm designing an IoT Device with many sensors which are going to be integrated using serial interfaces like UART, SPI, I2C and so on. For communication capabilities, I plan to use Wi-Fi (IEEE 802.11). Does it make sense to use something like Atmel’s Wi-Fi SoC and SAM D21 ARM Cortex-M0+ MCU or use Atmel's Cortex M4 and then integrate a WiFi module using SPI or UART (not a SoC solution).

If I go with M0 option, I have the advantage of Wifi and MCU on single chip.
With M4, I will have to integrate them together using some serial interface. But the advantage is a faster processor.

Since I have many peripherals on board, does it makes sense to use a Cortex M4 CPU which is much faster and capable?

Edit:
I'm sure this is opinion based. But I'm looking for some valid design inputs which help me make this choice. For example,

I plan to integrate a SD storage, real time clock, a number of sensors - temperature, energy etc. The number of peripherals might be 10 - 12. All integrated through UART, SPI and I2C.
I also plan to have communication - Wifi, RF, GSM, Ethernet etc.
I don't need any hardcore mathematical capability. FPU unit would be nice but not compulsory.

What I'm looking for are answers to questions like --

Does having many peripherals mean I need a bigger and a faster
        processor? I know this can be handled by ATMega. I was using an 8
        bit ATMega for something similar. It worked. But I'm moving to a bigger platform with more peripherals.
Will going for bigger
processor like M4 and M7 help me handle time sensitive operations
like RF, WiFi and sensor communication?
How does one choose based
on valid design principles? Is there a set of rules?
Does faster processor speed, RAM and Flash mean easier to work with when I'm switching between different peripherals?

Also: I'm an electrical engineer with amateur/decent embedded programming skills. Not the greatest but decent.


texts: What this mosfet really needed on the STUSB4500?

texts:
I want to use STUSB4500 in a project, to have USB C PD. A MCU will also be on the same PCB and it will control the STUSB4500 via I2C.

There are two schematics in the datasheet (https://www.st.com/resource/en/datasheet/stusb4500.pdf) on page 24 and 25. One is for standalone use, one for use with a MCU. The MCU version has an additional MOSFET in the power path (T4), and I do not really understand why it's in there. Can I leave it out in my design, to save on BOM and board space? On the evaluation board, T4 can also be bridged by a 0R resistor...


texts: Does a current source have a difference in potential?

texts:
I am doing a nodal analysis of this circuit.

I have found that \$ V_A = 10 V \$ and \$ V_B = -20 V \$ is it possible to have a situation like that? I mean a difference in potential between terminals of a current source?

I have found \$ i_{R1} = 0 A \$ and \$ i_{R2} = 2 A \$

If that is true there is a difference in potential of 30V on the current source.

If all this is true, the current source is the one driving the circuit, R1 and the voltage source V1 are not having any effect. No current circulating from V1/R1.

Is this calculation wrong?


texts: How to reduce loading of JTAG lines by USB UART bridge using shared signals

texts:
I have a USB to TTL (UART bridge) that is connected permanently to a custom board with an ARM MCU. The UART lines are shared with the JTAG programming lines. The problem is that even without any activity on the UART, the presence of the USB to TTL converter loads the line and sometimes this creates problem with trying to connect with the JTAG programmer.
The most trivial solution would be to disconnect the UART lines from the UART bridge, however that is a bit complicated in the present setup. The other solution is perhaps to pulldown the lines with a large resistors, perhaps 100k? Any other thoughts?


texts:
I've been looking into energy monitoring (240VAC mains) lately and I've come across seemingly conflicting info. On the one hand, a lot of advice I've seen online stress the importance of galvanic isolation between the HV section and the MCU/logical section of the circuit, for the safety of the circuit and its designer as well. This is usually done with a low-rated transformer to reduce mains to some more manageable voltage below 12 V, for instance.

On the other hand, I've looked up a number of energy-metering ICs (like the ADE and STPM series) and all the app notes I've examined so far (such as this PDF), show circuits where the IC analog front-end is connected directly to mains live (albeit through some heavy attenuation) and the neutral is directly connected to the AGND, which in turn is linked to the DGND of the control section (sometimes through an inductor to dampen transients apparently). No galvanic isolation whatsoever.

So is all this stuff really contradictory or am I missing something? What's the 'right' way to take these measurements?


texts: Why is it said that in practical cases loop gain of an oscillator should be slightly greater than unity?

texts: Recently I read about oscillators and I noted a sentence. It is said that in practical cases the loop gain should be somewhat 5% larger than unity. Why is it said so?Will it result in increasing the amplitude to an unexpected limit?


texts: Transient protection to prevent microcontroller freeze - Selecting MOVs and TVS diodes

texts:
I have a circuit which contains an offline switching SMPS circuit (based on viper22a) converting 220V to 5V regulated down to 3.3V using linear regulator IC. This powers up an ESP wifi module and Atmega328p chip. The microcontroller is being used to control ac appliances such as tublights, bulbs, fans etc (using optically isolated triacs). The circuit goes behind the switchboard, very close to ac mains wire.

Everything works fine except for once or twice in a week when my atmega freezes and GPIO pins latch up in a random state - High, Low or Mixed (few pins high, few pins low). Since circuit is inside the switch board, the only means of bringing it back to normal operation is by cutting the power to that switchboard.

After doing some reading, I concluded that it might be due to transients in ac line (generated by switching of inductive/capacitive loads like AC, refrigerator etc) somehow reaching the micro controller. Am I correct?

I came across two possible fixes:

(1) Implementing watch dog timer in the code side (yeah I didn't do it earlier)

(2) Using some transient suppression hardware like MOVs or TVS diodes

(1) has been taken care of. For (2), I need some help.

I am planning to put a TVS diode for 3.3V line which goes to the Atmega328. I have selected a few which has a breakdown voltage in the range 4.1 - 6.8 V.

Besides this, I am planning to put another layer of protection right at the ac entry point (at the power supply circuit).

Out of TVS diode and MOV, which will be a better choice? Or should I add both in parallel?

I am more inclined towards TVS diodes because it's more reliable and has long life.

What will be more suited for this purpose? Is there anything else that I can do to improve the performance of my circuit?

Thanks

EDIT: Adding the schematic of power supply


texts: What capacitor value should I use for 3.3v from a buck converter IC?

texts:
I am relatively new to electronics and trying to design a buck converter circuit using the XL1509-ADJE1. The datasheet specifies that for the adjustable versions (which this is) you should use specific capacitor values depending on the output voltage you desire. The only issue is, I need 3.3v out and the datasheet only gives capacitor values for 2v and 4v (and upwards). What value should I use?
Another weird thing I wanted to know (just out of interest) is why the datasheet gives different capacitance values depending on the type/brand of the capacitor. I have included the table from the datasheet and as you can see it shows different values for electrolytic and tantalum capacitors.

Thanks! :)


texts: Are h- and g-parameters only applicable to two-port networks?

texts:
There are plenty of references to various ways to represent two-port networks (S, Z, Y, T, ABCD, h and g parameters).

S and T parameters are commonly generalised to N-port networks. Is the same true of h and g parameters?

If I look at the definition of h-parameters in Wikipedia:
https://en.wikipedia.org/wiki/Two-port_network#Hybrid_parameters_(h-parameters)

It seems that, if I had e.g. a 3-port network, I could get \$h_{13} = \frac{V_1}{V_3}|_{I_3=0}\$. Is this valid?

Formulas are also available to convert from S-parameters to h-parameters in the 2-port case, but I'm not sure how to generalise them if this is at all possible.


texts: How AC current is distributed to our homes?

texts:
I apologize in advance if this is a basic or a silly question. When an AC current is generated by a motor,the current is generated in the loop that is rotating in magnetic field. The current direction varies at each cycle and when it enters the circuit. as is shown here

Reference: https://www.myodesie.com/wiki/index/returnEntry/id/3081

The direction of the current that goes through R has different directions at each cycle hence we have an AC current. Now when I look at the big picture of how the AC current gets distributed to get to our homes, I can't get my head around it. Let's say we have a cable that transfers AC current, does it mean that the current direction keeps changing in the wire?


texts:
I've read that the C-Band used in optical communication ranges from 1530 – 1565 nm.  Since one nanometer corresponds to 0.000000000299792458 GHZ, this is far less than 1 GHz. However, the C-Band is divided into multiple 50 GHz channels. How can this be the case, if it's range isn't even 1 GHz?

I guess I just messed things up when converting the units but I cannot figure out what?!

Can anyone please help? Thanks!


texts: What microcontroller programming toolchains are available on mac OSX and how do they compare?

texts:
I am trying to figure which microcontroller starter kit to buy, provided i have only macs and like to code on them (and look for a solution without linux in virtualbox and the like).

It is an acceptable answer to say that all compare poorly to Linux or Windows based toolchains but has to be explained.


texts: Confusion about what should be a simple resistor-divider circuit

texts:
I'm reverse engineering a circuit in some industrial equipment, and I came across some curious behavior of the input circuit...

The circuit is pretty simple, it is a resistor divider with a capacitor going into an opto-coupler for isolation. The input voltage is 24V, and the other side of the opto-coupler is 3.3V (not shown because that part isn't confusing me). What is confusing me is that when I apply 22V to the input circuit, I measure 1.65V at the opto-coupler:

Now, I measured the resistance of the resistors (and verified by the code), that it is indeed a 3.74K ohm resistor and a 715 ohm resistor. I don't know what the value of the capacitor is, but I'm guessing it is less than 0.1uF.

To add to the confusion, the input can be wired as sinking (shown above), or sourcing, like this:

So the question is, is the capacitor modifying the resistance of the resistor-divider circuit such that the output is different? Or am I also measuring the voltage drop across the diode when I measure it? The resistor-divider should be producing about 3.5V (at 22V input) at the diode. The TLP290-4 datasheet shows the diode forward voltage at 1.25V.


texts:
So I realized that it might become a necessity for me to use a transimpedance amplifier for a pulse watch that I intend to make.

Some background:

The pulse watch shoots light at 940 and 660nm at the wrist and picks up the reflected light in a photodiode (https://dk.farnell.com/hamamatsu/s1223/photodiode-pin-to-5/dp/1495587).

Hence why the signal that the photodiode picks up may be diluted and subject to noise, if I don't treat it correctly.
The V_Out signal is supposed to go into my Arduinos analog port from which, I (hopefully) can draw a nice pulse curve.

As I'm not an electrical engineer, the primary part that I'm unsure about is the operational amplifier that I inserted into the circuit.
I tried to look around for similar applications, but I'm still unsure about the capacitors, and resistors that I've put in there (if the values are correct).

The op-amp I intend to use is this: https://dk.farnell.com/texas-instruments/op07cd/ic-op-amp-low-offset-smd-soic8/dp/9589929?st=OP07

Is this application of the operational amplifier correct, with correct resistor and capacitor values, i.e. will this provide me with a nice low-noise amplified output?
The loop after the photodiode with R3 still confuses me. Is this just to pull V_Out low when no current is flowing?


texts: Optocoupler calculate resistance on output

texts:
How do I calculate the resistance between the Anode and the Cathode of an Optocoupler (while the optocoupler is on).
I am messing aroung a little bit with optocouplers and found out using an multimeter that my optocoupler has an resistance of about 100 Ohms between the Anode and the Cathode. How do I calculate this resistance and why is it that high ?

I was using the digital pins of my Arduino Uno to turn the optocoupler on.

Thank you for every hint!


texts: Electrical Engineering Math, showing time independence? how?

texts:
I have a cheat sheet provided by the teacher about the calculation of the Coherence Time, however I get lost along the way.

There are 2 paths of a signal at:

Path 1: \$\phi_1(t) = 2\pi\frac{vt}{\lambda} = 2\pi f \frac{vt}{c}\$

Path 2: \$\phi_2(t) = 2\pi\frac{2d-vt}{\lambda}=2\pi f\frac{2d-vt}{c}\$

Phase difference at time \$t\$: \$\Delta\phi(t) = \phi_1(t)-\phi_2(t) = 2\pi f\frac{1}{c}(2vt-2d)\$

We want to find the smallest \$\Delta t\$ such that the phase difference of the two phases changes by \$\pi/2\$:

$$T_c(t) =  \arg \underset{\Delta t} \min = \{\Delta t:\Delta\phi(t+\Delta t)-\Delta\phi(t)=\frac{\pi}{2}\}$$

Showing that \$T_c(t)\$ is actually independent of \$t\$:

$$\Delta\phi(t+\Delta t)-\Delta\phi(t)=2\pi f\frac{2v}{c}\Delta t=\frac{\pi}{2}$$

$$\Leftrightarrow \Delta t = \frac{1}{8f\frac{v}{c}}=\frac{1}{4(2f\frac{v}{c})}$$

I lose it at the last equation, I can't get what happens there. It would be great if someone could explain me the idea behind the calculation there.

How do we get to this part, of the equation above:

$$2\pi f\frac{2v}{c}\Delta t$$


texts:
I purchased a 5V 8 channel realy to use with Arduino.
When the output is low the relays are on. I need to turn the relays on when the output signal is high.
Is there a way to make the board respond to a high input and to turn on the relay?


texts:
I have this question here, which I am unsure of my final answer:

Firstly, I times the numerator and denominator by the conjugate 1-jt - resulting me in the alternate form of the function

Next, I've found the Fourier Transform of the first term using duality property

And lastly, I've found the Fourier Transform of the next term

As a result, the final Fourier Transform of x(t) would be 0. Have I gone wrong somewhere in my reasoning?

The formula sheet we used for this paper is here and here


texts: In a 4 bit ripple carry adder 4 full adders are connected serially, one FA waits for the carry input from the previous FA. My question is, when calculating the propagation delay, should we assume that the subsequent FAs won't start functioning until it receives carry from previous FA, or can at least the first XOR gate compute A XOR B even without carry input from previous FA?


texts: 3.3V LDO identification similar but smaller than SOT-223

texts:
I'd like to identify or find a replacement for a LDO component in the board above:

It's a 3.3V LDO.
It reads "AMS1117 3.3 DN18".
The body is around 4mm width.
Similar to SOT-223 package, but it's smaller.

I was looking for AMS1117 but according to datasheet it is available only in SOT-223, TO-252 and SO-8 factors.
He're another photo, with a SOT-223 AMS1117 that I had at hand. I was considering bending LDO but then I saw that top "tab" pin won't fit, so it doesn't look like a viable option.


texts: Generation of 3 state signal using 2 IOs of FPGA or MCU

texts:
I need to generate a 3 state signal i.e 12 V , -12 V and 0 V square wave using 2 IOs from FPGA. I have a circuit shown below, 2 signals are generated i.e, 0 V to +12 V and -12 V to 0 V, but i need to combine these 2 signals into a single waveform so that 0 V, 12 V, 12 V states are not disturbed . when i combined these 2 outputs with a single wire, the output amplitude was -5 to +5 V but the expected is -12 V to +12 V .
I have given input of 0 to 3V3 signal from function generator and the input of 2nd opamp was exactly 180 deg out of phase (for generating this i used a inverter using transistor).
please suggest any solution for combining outputs.

IO1 : 1, IO2 : 0 --> output +12V
IO1 :0 , IO2: 1--> output -12V
IO1 : 0, IO2: 0 --> Output 0V
By uisng the above combination we can generate the 3 state signal using above circuit.
IO1 - input to non-inverting comparator
IO2 - input to inverting comparator
Frequency of the sqaure wave 32KHz


texts:
I just got embedded system CJMCU-75 which has LM75A I2C temperature sensor on top of it. I dig into the LM75A documentation and found out that it's I2C address consists of four fixed MSB and three LSB bits which can be set up externally by pulling pins A0/A1/A2 towards VCC or GND.

So I looked again at my newly bought embedded system and found that designer already took care of this on the bottom of the board where he put three pads for setting A0/A1/A2 pins:

Do you have any advice on how to solder A0/A1/A3 pads to VCC/GND in order to be able to change them easily afterwards.


texts: What would happen if I connect a battery which has lower voltage than output of battery charger

texts:
At this moment I'm building a charger for Li-ion battery based on constant current, constant voltage method. I have used IC LT3741 to build a charger.

The specs of my charger: 8,4 V, 2A

But I dont understand one thing:

When charging the battery, the voltage of battery will be lower than the output voltage of the charger (but of course greater than 6V.)  What would happen then with the output of the charger? Because we have now the situation of two "DC-sources" which are connected parallel and have different voltage. Or am I wrong?

Two DC-sources, different voltage, connect together will not be good idea, will it?


texts:
I am trying to connect my atmel atmega8 with usbasp (V0.2) to my PC.
I follow this tutorial to connect my atmega to usbasp.

I have a 6-pins connector:

o MISO   o VCC

o SCK    o MOSI

o RESET  o GND

Once I connect my usb to my PC, led turns on, and in Control Panel (win7) I see "libusb-win32 devices".
After having compiled main.c with winAVR "make" command, if I try to use "make program" command or I write in cmd this:

avrdude -p atmega8 -P m8 -c usbasp -U flash:w:main.hex

system tells me:

avrdude: error: programm enable: target doesn't answer. 1
avrdude: initialization failed, rc=-1
Double check connection and try again, or use -F to override this check

How can I solve this problem?


texts: Altium chaning footprint's origin cause shifting on pcb issue

texts:
I needed to update all of my components in my library (shown in the images below), but when I update my project to new components, all of the components are shifting because of origin change. Is it possible to do some tricks, feature, script to avoid shifting issue?

Thank you for your help!

Old component:

Updated component:


texts: How do I set a value within an if statement using logic gates?

texts:
I have a value B that I want to set if a variable A = 1.
I know how to create the if statement by applying an AND gate on a 1 constant and A, but how do I set B within that if statement using logic gates?


texts: Capacitor values for use with 78xx voltage regulators

texts: I want to get the output: 5V - 25mA from 24VDC-0.75A with IC 7805. So what should be the value of C1 and C0? I need a formula for my report. thanks in advance


texts:
I'm designing a USB3 PCB. USB3 tracks should have 90Ohm differential impedance.

The board is FR4 with 35um copper on the top layer. How can I calculate the track width / distance / distance to others?

I want to use tracks of 0.1mm or 0.2mm.


texts: Readying a New Design, would appreciate som feedback

texts:
I designed a Arduino shield compatible board around the NXP LPC4337JBD144. so far I have been unable to get the first revision to program.

In the first design the JTAG header was not setup correctly, there were no bypass capacitors, the USB did not have all the pullups/pulldowns it needed, the DBGEN and TRST pins were not broken out to jumpers, and the Ethernet section did not follow spec as strict as it should have. I have able to add all the pullups to the JTAG and pull the DBGEN high and the TRST low by modifying the PCB with external jumper wires and resisters. I am still unable to program it with my JTAG.

I should note that the rev one PCB is only populated with what is necessary to get the chip programming and running, no additional hardware passive or active. I have tested that I am getting the correct signals from the JTAG and they are going to the right pins. I checked the crystal as well but I don't get a signal because the crystal will no initialize until the chip is programmed because the first thing that runs in a system configuration routine that sets up all PLLs and external oscillator settings. Everything on the first revision PCB has been check thoroughly with an oscilloscope, JTAG signals, crystals, and power section.

That being said I have been battling with this first revision for several weeks, I have tried everthing that NXP support has recommended, I have reviewed the schematics for several evaluation boards from NXP, Keil, and Hitex modifying my PCB along the way to bring it up to the ARM standard spec to no avail.

At this point  I am convinced that the design is flawed in too many ways putting it way out of the standard specifications for an ARM Cortex M4 that it cannot be fixed with external modification to the PCB and that  second revision of the design needs to be tested. This is a very time sensitive design, I was hoping to at least get the first one working then have the second revision be a fine tuning process. That being said I need to get a new design out to the fab house to keep my professors happy. I'm looking for constructive feedback on my new design, I have spent about two weeks looking through this design on my own and with the help of others in attempts to find anything that could be a serious potential problem down the road. I have been double checking the reference schematics and datasheet and I personally haven't detected any problems so far (most of my previous design work has been with AVRs).

EDIT:
My board is 4 layers, the two outer layers are for signals and the two inner layers are a ground plane and a power plane. Right now I have the negative space on the two outersignals filled in with a ground fill polygon, could that cause some problems with the board such as ground loops?

Below I have attached the smart PDF for my Altium Project it includes the schematic and PCB design.  https://www.dropbox.com/s/qb9ptr67v6msmh0/Abstract%20Hardware%20Device.pdf

Altium PCBdoc: https://www.dropbox.com/s/s7s0aw3yuh4va3g/Abstract%20Hardware%20Device%20PCB.PcbDoc

EDIT2:
share link updated to Dropbox one.
Altium PCBdoc shared.


texts: Low noise transimpedance amplifier (TIA) - why does the addition of a feedback capacitor cause voltage noise peaking?

texts:
I am working on a low noise transimpedance amplifier (TIA) for the detection of weak optical signals. The aim is to achieve a 10MHz bandwidth with a white voltage noise floor of 10-20nV/rtHz. I am using the FGA21 photodiode and the OPA847 Op-Amp with a 10kohm feedback resistor  operating in photoconductive mode.

Key specifications include:

Gain banwidth product: GBW = 3.9GHz
Input voltage noise: e_n = 0.85nV/rtHz
Input current noise: i_n = 2.5pA/rtHz
photodiode capacitance: C_d = 100pF @ 3V bias

The PCB design followed many of the suggested layout techniques (minimising track length, passing feedback components under the op-amp, isolating sensitive tracks from the ground plane etc.). Additionally, the voltage supply was heavily filtered using decoupling capacitors and the OPA820 Op-Amp was used to buffer the output.

Two noise spectra were taken, one where the feedback capacitance was left open and one where it was set to 1.5pF:

The dashed lines represent the corresponding theoretical noise curves. Clearly the capacitor causes the noise peaking to broaden and shift in frequency, this contradicts theory which suggests that a feedback capacitor dampens the transimpedance gain and reduces high frequency noise.

To test this further a circuit was constructed without the photodiode, instead a 100pF capacitor was added to mimic the diode junction capacitance and the noise measurements were retaken:

In this circuit the addition of a feedback capacitor causes the noise to dampen similar to how the theory predicts it to, suggesting to me that the simple photodiode model of a junction capacitance and current source may not be completely accurate. However, searching through literature I have not yet found discussions of the limitations of this model, nor have I seen any examples of this behaviour.

So I am wondering if anyone else has come across this issue before or can understand how the addition of a single capacitor causes a large disparity between theory and experiment?

(Please excuse the lack of circuit diagrams, I am a new user and as of yet can only attach two links per question)

Edit: Here is the PCB layout for the TIA with photodiode:

and here is the circuit schematic (it is worth noting the low pass filter between the op-amps wasn't used, the capacitor was left open):

Edit 2: Note in the above circuit diagrams the photodiode is not reverse biased, in all noise spectra shown it is soldered in the correct bias


texts: How can I force LTspice to redraw a plot during a long simulation?

texts:
Sometimes during long simulations, the LTspice plot window will display a yellow "broken" icon, and/or simply not render parts or all of the data. Sometimes the axis are missing, sometimes it only shows the most recent data.

Once it finishes, it will redraw correctly, and do so every time you select a new signal. But during an ongoing simulation, you're just looking at a blank/broken plot window.

Is there a way to redraw the window without interrupting the simulation?


texts: Where am I going wrong with LM317 power supply circuit?

texts:
I am still learning analog electronics and possibly making a mistake here.

I am trying to build this power supply circuit but I am getting 0V as output instead of 4V.

This is the schematic

Both of them show output voltage as 0.0V and 0.06V for schematic design and breadboard design respectively.

I don't understand where am I going wrong. There is nothing wrong with the source voltage. I keep on checking it.

Is the circuit wrong?


texts: What is the correct spelling/capitalization of watt hour?

texts:
In some documentation I have commented that a field contains "the forward active power, in Wh". Which way should it be written (when I don't want to use the abbreviation)?

the forward active power, in watt hours
the forward active power, in Watt hours
the forward active power, in watt-hours
the forward active power, in Watt-hours

On the wikipedia page for kWh they seem to use both hyphenated and non-hyphenated versions. I don't see "watt" being capitalized there. Is there a standard? This may be more of a question for english.stackexchange.com, not sure.


texts: How to find the bandwidth of a function having infinite DC gain?

texts:
The transfer function of a plant is given by \$G(s) = \frac {10}{s(s+15)} \$.
After plotting the Bode Plot on Matlab, I can't find the bandwidth of this system since it has infinite DC gain.
Could someone please explain to me how am I can find the bandwidth from this transfer function?


texts: OpAmp with common-mode voltages and zero feedback current

texts:
Circuit A is a classic non-inverting amplifier with a common-mode DC voltage 1 V to both its inverting and non-inverting input. Since 1 V has to appear at the inverting input, there is no voltage drop across \$ R_i \$ and subsequently there cannot be any current through \$ R_f \$ either.  With no current and no voltage drop across \$ R_f \$, the output \$ V_{out} \$ has to hold the same voltage as that appears on the inverting input: \$ V_{out} = 1\,\text{V} \$.
I will certainly measure 1 V at the output but conceptually that doesn't feel right...
If no current passes through \$ R_f \$, the feedback loop is essentially an open circuit (circuit B). If the feedback is open, there is no feedback and the circuit is simply an open loop op-amp (circuit C): if both inputs in circuit C is 1 V, there is no potential between the inputs and the output must be \$ V_{out} = 0\,\text{V} \$! After all, an op amp by itself amplifies any potential difference with infinite gain and drives itself to saturation - but there is no potential difference, output should be zero.
To sum things up, if I go with ideal op-amp analysis, I get \$ V_{out} = 1\,\text{V} \$. But if think through the circuit conceptually from step A, B to C, then I would arrive at \$ V_{out} = 0\,\text{V} \$.
There has to be something wrong in my thought process but I don't know where it is.


texts: Powering 12V LED strip lights with a 12V deep cycle battery

texts:
I would like to run 16.4' of 12V LED strip lighting with a 12v deep cycle battery. The strip lighting says it uses 1.5W per foot so I'm expecting that I'll need to provide about 2A. I was really hoping that there would be a ready made product to regulate the current efficiently, but so far no luck (if you happen to know of a product available to do this I would really appreciate a link).  What would be a common way to accomplish this task?

Thank you,
Trevor


texts:
Imagine a circuit like this: 6 red leds with a Vf of 1.8V are wired in series with a resistor. Vcc is 12v.
To acheive a current of 10mA, you would do (12-10.8)/0.01 = 120 so 120 ohm resistor.
Now to calculate the power dissipated over that resistor I have three options:

P = VI = 12 * 0.01 = 0.12W
P = V^2 / R = (12)^2 / 120 = 1.2W
P = I^2 * R = (0.01)^2 * 120 = 0.012W

So, which one is it?


texts: Non-inverting output of transistor circuit (at NPN base) is 0.69V max. why?

texts:
I tried to make a simple NPN transistor inverter so that I can use the strobe line of the parallel port to store data in two separate flip-flop IC's. (74HC174 and 74HC574) The IC that data will be stored in is based on whether the strobe is on the falling edge or the rising edge.

I connected everything including this circuit and there is no smoke, no heat or anything. I could assume my resistor choices are terrible, but I'm not sure, especially with how many changes there are to PC port designs.

For reference, the parallel port I'm using is coming from a dell laptop and I specifically disabled ACPI.

When I tested the particular circuit shown, The voltages I get from the NPN base are 0.09 and 0.69V. However, the NPN collector voltages are acceptable (0.0 something, and 4.9 something).

What would cause the NPN base voltage to be so low in both cases and how do I fix it?


texts: ADS AEL: operand: ee_boolparameter value required whenever I try to compare voltages

texts:
I'm not very experienced with Keysight's Advanced Design System. I am trying to use the if statement in my user-defined function to compare two volage values and take an action based on the outcome.
During debugging, if I use constants as the function parameters, it works fine. But the moment I use the actual voltage value (from the simulation), I get the error message

  operand: ee_boolparameter value required

Below is a test function:

    defun Test(argument, argument2)
{
    decl x = argument;
    decl y = argument2;

    if(x == y)
    {
        return "Equal";
    }
    else
    {
        return "Not Equal";
    }
}

Now, if I use constants as the arguments passed in the equation, it works fine, but if I use the values I got via simulation, it reports the error (see the attached images).The first image is the function with constant values passed as paramters.  The next two are with the simulated values

I know it is a simple problem, but I've had sleepless nights over this, as my work is dependent on it. Please can anyone help tell me what to do?


texts: Potential Difference in the Ground plane

texts:
I am new to layout designing. I am using Eagle 9.5. Here is the layout design of my project:

Right section of the PCB is for analog circuit. middle section is for DAC and ADC and digital output of those two ICs are going to two of the long pin headers. There are two analog switch ICs which are controlled by SPI and they are in the analog section but it will be active only when there is no analog signal present. (switch will select certain resistor and capacitor for gain setting and compensation respectively). left side of the PCB for power supply. whole board will sit on Atmega development board.
I am using 4 layer board and layer stack are: top: signal
2nd layer: power supply (it's not a plane but thick traces)
3rd layer: signal layer
bottom layer: ground plane.
Analog signal frequency: 1-100khz
Digital signal frequency: upto 18Mhz
Analog and digital signals doesn't overlap on DGND and AGND plane (there are few exceptions)
I have a question about return-path/ground. I read few documents to understand how signal current will return and accordingly I have designed the ground plane. image of bottom layer:

My colleague told me that there will be potential difference between PGND in bottom layer and AGND of analog section and it is not good for the design but my understanding is that if I have intact ground plane then it will not be any potential difference. it only happens when I share ground trace with multiple components and then connect to ground plane. like this:

Please tell me, is my colleague correct or my ground plane is alright?
EDIT :  here is my load which is connected to the virtual ground of the trans-impedance amplifier. load is basically electrochemistry cell. it might not draw any current. Because of reaction in the cell it may generate few nano amperes to milli amperes.
Basically, I am implementing signal processing for impedance spectroscopy. few hundreds of millivolt signal is given to the load as a excitation signal which will be pure sine wave with dc offset. so, range of the signal could be -2.5v to +2.5V


texts:
What component is this? They have a temperature printed, and a part code, but both are pretty much erased in the purple part. The orange one is a bit more readable, but not much. I think they may be resistors, but I'm not sure.

This is the information I can read from both parts:

Orange: T1 = 169 °C; D167PHMP
Purple: 184 °C

The measured resistance on both seems to be about 3-5 Ω.


texts:
More components are only available in SMD packages.
For hobbyist assembly the options are to buy breakout boards or
solder SMD.

Since components are usually packaged in a couple of SMD
package types I am trying to put together a set of guidelines
for choosing packages that are compatible with hobbyist
skills and tools. I would consider hobbyist level tools for SMD
assembly as -- soldering iron in the $50-$100 range (new),
for magnification a $40 visor (like the B&L) and tweezers.

For the kits I make now I use the following guidelines --

Passives 0805 or larger
Min Lead Pitch for SOIC or QFP -- 0.5mm
No QFN, LGA or BGA
Prefered package for gates, BJT, FET --- SOT23
Diodes SOD123 (or larger)

I am interested in recommendations on component selection,
minimum tool requirements and assembly issues.
Specific tool changes (like solder tip size) that enabled you to do SMD assembly with your existing tools would be useful too.

Thanks.


texts: Is it practically possible to use mutually coupled capacitors as we use mutually coupled inductors?

texts:
Inductor and capacitor are dual to each other in Physics. One comes from Electric Field Theory while the other one comes from Magnetic Theory; the both theories expose strong duality with each other. Sometimes we can replace an inductor with a capacitor, or a capacitor with an inductor in a circuit in the appropriate manner.

After considering all these similarities between inductor and capacitor, the idea of "mutually coupled capacitors (MCC)" comes into my mind. How does a practical MCC system look like; what kind of Physical structure would it have? Why don't we use MCCs in practice?

After giving it a though for a while, I came up with an idea of a typical MCC structure.

I'm not an expert in Electromagnetics, but here is my explanation:

If \$A_1=A_2\$, then the voltage ratio between \$V_s\$ and \$V_p\$ will be as simple as \$\dfrac{V_p}{V_s}=\dfrac{2 \ell_1 + \ell_2}{\ell_2}\$ (similar to the one in the ideal transformer case). I can't explain why but I feel that this will only work when \$V_p\$ is AC (maybe someone can clarify this).


texts:
Is there any disadvantages in storing electronics in cold storage (min. temperature about -30 °C/-22 °F)? I am speaking about non-assembled components and assembled (consumer) electronics.

I am aware that condensation is a problem, but it can be avoided. I'd like to know what kind of effects low temperature might cause, like solder joint cracks due different thermal expansion coefficient.


texts: What is the optimal disposition of coil to maximize the magnetic field created?

texts:
I am trying to create a powerful magnetic field using coil, and possibly some ferromagnetic metal bars.

The white box with the X on it, is empty, or made of air.

Saying that I have no limits on how many metal bars I have, or their dimensions, but I have limited copper wire length that I can use, and through all examples, the current that I use is constant.

The examples in the image included, but I would gladly accept anything new you can think of, what is the best way to have the maximum possible magnetic flux go through the box?


texts:
I’ve recently acquired a modified T962A reflow oven and have been experimenting with profiles. I’ve had to really ramp up the peak temperature and time at peak temperature to even have any chance at melting and flowing the solder paste.

In the attached pictures I believe the solder paste is burnt. How can this be avoided? As mentioned I had to really increase peak temperature, even with longer soak times and temperatures to get any sort of reflow.

EDIT: Here's a link to the solder paste in question. We've only had it for a few weeks and it's been stored within the recommended temperature range.


texts: I had two doubts about the working of an s-r latch. One is, when we apply a clock signal along with the s and r inputs to the gates, how do we administer the time after which the clock signal changes again. And when the latch is set where does the electronic pulse get stored? Does it get stored in a capacitor? And if it does then how does the capacitor get discharged when the latch is reset?


texts: Do I need to restrict current to charge a dyson Li-ion battery directly with my photovoltaic system

texts:
I would like to charge my Li-ion battery from Dyson V6 vacuum cleaner with my solar system/controller (12V output voltage) with a step up converter 26.1V/3A. I already charge my apple computers and ipad pros, and all the other electronic stuff, which are all tolerant to current, as they handle current control themselves. However this one is trickier:

The original dyson poweradapter states 26,1V and 780mA. To step up to 26,1V can be easily achieved, but what about the current? My current step up module limits current to 3A. Do I need to limit the current somehow?

I appreciate any feedback. Would it be safe if I step up to 26,1V e.g. with a maximum of 1A only? Or do I need to fit the exact data stated by the original poweradapter?

Kind regards,
Alex


texts: How does a flame sensor or thermocouple operate with just one wire?

texts:
I am learning electronics and I just got stumped. I was just looking at a flame sensor and it appears to have only has one connector.

I thought sensors in general need two wires to form a complete circuit. How can current travel from the flame to the rod to create a complete circuit?  If you wanted to measure the voltage or current of the sensor on an open flame, how can this be done with a multimeter? What do you reference it against? I thought the metal collar was a grounding point, but this is used to bolt the sensor to a furnace. Is the furnace acting as a reference point?


texts: Boost converter drawing too much current

texts:
I am trying to play around with some SMPS boost converters, in order to power my Nixie tubes at around 170V (boosting from 20V to 170V). Yes, I know that there are already existing power supplies that I can buy for those if I want to, but where is the fun in that? :)

I am trying to build the circuit whose schematics I have posted below. It should be more or less straight out of the LM3478 manual. I even used their online WEBENCH to draw out the schematics for me (I just translated this to Eagle manually).

When I try to construct the circuit, I am struggling with it drawing way too much current. Somehow, it seems like something is shorted. However, when I went through with my meter, I could not find anything. Furthermore, I also built two versions of the PCB, with exactly the same problem.

So, I am beginning to suspect that there is something wrong with my approach. Not with the actual soldering itself. However, I am struggling to find where to debug.

The parts I am using are fairly straight out of the box. Of the noteworthy ones:

CD214B-R3600 -  Schottky Rectifier, 600 V, 3 A, Single, DO-214AA, 2 Pins, 1 V
IPD320N20N3GATMA1 - MOSFET Transistor, N Channel, 34 A, 200 V, 0.027 ohm, 10 V, 3 V
SRP1245A-180M -  Power Inductor (SMD), 18 µH, 7.5 A, Shielded, 11 A, SRP1245A Series

I am also attaching an image of the board layout, just in case there is something in my layout that could be the problem.


texts:
I'm building camera systems to mount on top of a TV tower.
When storm clouds roll, in the video is displayed on the TV weather report.
No one wants to climb the tower to manually pan and tilt and zoom and focus the camera during a thunderstorm, so we control them remotely.
Currently I control the systems with Pelco D protocol over RS485.

I'm building some camera systems that are capable of variable-speed pan, tilt, zoom, and focus. (PTZ).
(The prototype has an Arduino that controls the zoom and focus motors).

Alas, my ancient copy of the standard Pelco D protocol (and the earlier Pelco P protocol) doesn't have a way to tell the camera what speed to zoom or focus.
(The only variable-speed stuff it supports is variable-speed pan and tilt).
So currently I hard-wire the speed, which everyone agrees is the wrong speed.
About half the people say it's too fast, and the other say it's too slow :-).
It would be much easier to frame a shot and focus if we could take advantage of the hardware I already have to do variable-speed control.

I control both ends of the RS485 cable, so I could make up yet another random protocol.

Is there a standard or semi-standard extension to the Pelco protocol that supports variable-speed focus or zoom or both?
Is there a good way to extend the Pelco protocol in such a way that, when I add a new cameras and a new camera controller to a common RS485 bus, they don't conflict with old cameras and old camera controllers already on the bus; and are less likely to conflict with new extensions others may add later?
Is there maybe some other standard protocol for controlling TV cameras, preferably ones that support variable-speed zoom?
Wikipedia says that Pelco D is used in "infancy". Are better protocols are available? If so, how do I get the information I need to implement those protocols in my camera systems?


texts: If, for a large motor, you are given cumulative kWh values at 5-minute increments, how would you determine an instantaneous power consumption value?


texts: Find instant in which diode starts conducting in transformer full wave rectifier

texts:
We have the following circuit

V2 = Vs/a;

a = 10;

Vs = 100sin(wt);

w = 200 rad/s;

  Each of the diodes is
  modeled by a fixed 0.8 V drop when conducting, and by an open circuit when OFF. Find the
  first time instant (in ms) when diode D1 starts conducting.

I know that for a diode to be conducting there vL should have a voltage equal or higher than V2.

By KVL I found that vL = 9.2 V and put 10sin(wt) = 9.2, and solved it to get t = 0.335 (ms).

The answer however is 0.4 (ms).

What did I do wrong and how should I proceed?


texts: Most efficient way to generate 5.0 and 13.25 volts out of 2xAA

texts:
Working on an instrumentation device for some friends' lab. The MCU and most of the electronics require 5V @ ~15 mA, and 13.25 volts need to be fed to one side of a differential unity-gain opamp. The requirement is to measure a lead-acid battery's voltage very precisely, and a LT1990 is used to shift the voltage from 12-13V to 0-1V to be read by a precise ADC.

The implication is that the 13.25 V reference voltage needs to be very clean, but it doesn't need a lot of current (basically none, as this is an op-amp).

The device box can accommodate either a 9V or 2xAA batteries; I've chosen AAs, as they have better energy density. My current power-supply setup is as follows:

                           +-> LDO -> 5V
                           |
AAs -> Polulu 791 -> 8.4V -+
                           |
                           +-> TC7660 charge pump -> 16.8V -> LM317 -> 13.25V

I used the Polulu 791 step-up regulator during prototyping for ease of development. As you can imagine, the current setup is awfully inefficient; the switcher inside the polulu has some 44% efficiency at low currents and high voltages. With the current loads, the batteries are drained at 100+ mA

Is there a better way to do this? General redesign is okay (but I want to keep the 2xAAs)?


texts: Coaxial cables vs zip cords for unbalanced signalling

texts:
I was watching a short tutorial video about balanced audio, and the guy claims for unbalanced transmission even there is shield in coax cable "hum and noise still gets true". But in wiki it says: "Coaxial cable also provides protection of the signal from external electromagnetic interference."

So I was wondering does a coax cable is worthless to shield electromagnetic interference? If so what is the benefit of using it rather than a zip cord.

Basically what I'm wondering is imagine a single ended(non-differential) signalling. What kind of noise coax shield would reject better comparing to a zip cord? Or should we say coax mitigates the noise but still passes some? I observe myself 50Hz noise when I use coax cables. So why are they used instead of zip cords besides the reason impedance matching in RF?


texts:
I am going to feed 5V unresisted in through pin 3, ground out pin 2, and then read the output from pin 1. Would that be correct for this IR sensor?

Also is this analog or digital output signal?


texts:
I have searched for short channel effect in google. There are plenty of articles on that topics, but I can't somehow understand them all.

Can you please briefly explain in plain words what are they?

What is drin induced barrier lowering in plain words?


texts: What's the frequency v power relationship of an oscillator + transmitter?

texts:
I'm starting with the assumption that a higher frequency EM wave is more energetic than a lower frequency one and thus requires more energy (and thus more power) to transmit.

In my naive model of a transmitter, there's an oscillator circuit, an amplifier and an antenna. It doesn't seem to be the case that there's a proportional relationship between frequency and power in an oscillator circuit so am assuming that the extra power must be consumed by either the amplifier or antenna circuitry.

Is the power consumed by an oscillator circuit not proportional to the frequency of oscillation, ceteris paribus?

In what stage of the generation/transmission of higher frequency EM waves does the extra power get consumed ?

Assuming wide enough bandwidth in the amplifier + antenna for the frequencies under consideration (ie 3 dB point is far enough out or ideal no parasitic system), where does the extra power get consumed to justify conservation of energy and Einstein-Planck (E=hv)?


texts:
I am interfacing a Micron MT48H16M32LFCM-75 SDRAM with an Atmel AT91SAM9G20 and I need to verify on paper (as far as possible), that the timing specifications between those two devices are compatible.

However, I have trouble matching some parameters from the Atmel data sheet against the parameters from the Micron SDRAM.

AT91SAM9G20 SDRAM timings:

MT48H16M32LFCM-75 timings:

I manage to compare CKE, CS, CAS, RAS, DQM, BA, WE and Address setup and hold times (2.0ns and 1.0ns respectively) between the two tables.

What I am unsure about is:

What is Data Out Access time (Atmel specs) referring to?
What is Data Out change time (Atmel specs) referring to?
I don't find any information in the Atmel data sheet regarding the 100/133MHz clock stability / timing to check against the clock requirements of the SDRAM.


texts:
As I understand it, the ideal frequency response for a filter is that we want maximum gain in pass band, a vertical or instant cutoff and 0 in the stop band, however this is ideal and can never be achieved in real life.

Along came Butterworth and found a relationship / formula for choosing the right combination of inductors and capacitors to be able to create filters that matched a certain spec and resembled the frequency response that we want - but not ideal.

With the exact same filter structure along came Chebyshev and he worked out an even better formula to get an even tighter / more tuned relationship to give us a filter that was closer to idea than Butterworths relationship, for example a much more steeper transition band than the same design using Butterworths.

Then again, along came Cauer with his own method of calculating the relationships and values needed to get an even better and closer approximation to an idea filter. With the steepest transition yet.

With all these, they haven't discovered a new "structure" or found that by making a different connection you get a better filter, but instead each one devised a better and more accurate formula for choosing the values of your components to get your filter close and closer to ideal.

So my question is this.

Lets say we are dealing with a 5 order low pass filter. (The type doesn't really matter). With Butterworth we have a good filter, then still using a 5th order and same structure Chebyshev was able to "tune" it even more to create and even better response, and then the same with Cauer.

Now if I was to take my 5th order structure and was able to simulate for every possible inductor value and capacitor value would I find a combination that would give me the best possible / closest model to ideal, that beats all previously known filter types?

And then when someone is able to devise or work out a relationship linking all these values together and with the spec thats required it would then be a classified its own filter type such as Butterworth etc?

My second question is then,

Do mathematicians / engineers know of a "best" filter response that is physically possible for a given order but so far do not know how to create it.

Similar to saying, if NP = P was proven it would mean we know for sure that there are solution to the problems but we haven't worked out yet how to get there / havnt worked out an algorithm for it. (Sorry if thats a bad example or its wrong but its the best analogy I can think of for now)


texts:
I have a accelerometer (ILS - MPU9250) and a woojer vest. The woojer vest is a device that shakes based on audio input. (simple line in with jack)
What I would like to do, is to put this accelerometer onto my RC-Car, and convert the signal of the Z axis to a compatible audio signal, and then transmit it with a wireless audio transmitter to my vest. I do have only a very basic understanding in electronics. So my current understanding would be that the output of the sensor has to be read by a Arduino microcontroller, that takes the input signal, and outputs it via the analog port.
This outputted signal needs then to be scaled and shifted so that it is centered around 0 Volts, and based on the shock, it moves between +/-1 Volt.

Is this correct? If so, how can I scale/shift a 0-5V signal to a -1 / +1 V signal?


texts: Total Voc and Vmp with charge controller

texts:
I currently have Blue Sky 2512i charge controller. Great unit! We have three 75W panels in parallel. Blue Sky limits the Voc and Vmp to 28V and 16.5V-18.5V. We would like to get a fourth panel to get a little more charge to our system.

Can we do a series/parallel combination with this controller?

Our batteries are 12V. But, can we send 24V "nominal" to the charge controller, or is the Voc and Vmp additive when the panel are in series, thus putting us over the 28V Voc and 16.5-18.5 V Vmp limit?


texts: OK to tin soldering tip prior to shutdown?

texts: I usually clean my soldering iron's tip before turning it off. Yesterday I read an article where someone suggested to tin the tip before turning off the iron. Is this a good idea? And how would it help? My station is a Weller WSM-1 if it makes any difference.


texts:
I'm a sign writer and often need to transfer patterns / designs to paper in a perforated way. Small holes in the outline of the design allow chalk or charcoal to be applied through the paper to the final surface.
This can be a very long process involving a small pounce tool / wheel (like a mini pizza cutter). Which is rolled over the surface to create small holes.
There is an electric tool for the job called a Electro Pounce machine. It rapidly burns small holes through the paper to create a perforated outline.
See here. These are very expensive and basically I'm trying to figure out an alternative or a hack of some kind to create perforated holes through paper. I thought maybe a tattoo gun would work but have no idea if you can slow them down enough to create gaps between holes or if it would even perforate.
I'm wondering if anyone has any creative ideas that would do the job?
Might be the wrong forum but you never know :)


texts: What's the hardware and software detect mechanism of the cellphone Micro USB devices attached and detached?

texts:
What's the hardware and software detect mechanism of the Android cellphone Micro USB devices attached and detached?

simulate this circuit – Schematic created using CircuitLab

Hardware Schematic

Fig1 is my application draft, and more details are as follows:

My cellphone support OTG function and is enabled

As the picture says, my device has connected the ID pin to the ground in order to get the power of 5V.

I connect the D- pin to 5V so that it tells the phone this is a low-speed device.

I have an APP installed on my phone to supervise if there is a device plugged in.

My device is a non-standard USB device, I don't use the D+/D- pin to communicate with the phone

In my point of view, as soon as the device plugged in, firstly the ID pin of the micro USB receptacle get a falling edge and thus tell the phone there is a device plugin and the device is working as a HOST.
so, anybody familiar with the process of the detect?
I upload the PCB board photo so you can see clearly about my situation.

update : I have measured the output of VBUS when I insert the device, and the VBUS=5V, also as a power indicator a LED is mounted on the PCB, it works well.

Ultimate question: If my hardware connect is right? and then can somebody give me some instructions about the software code?


texts:
I have a samsung LTN154X3-L03 LCD screen from an old laptop. And I was trying to use it as a second display.

I bought the t.vst59.031 lcd controler board. The problem is that this board doesn't come with the LVDS cable (or inverter).

Looking at the datasheets I was able to map most of the pins, except two (pins number 6 and 7).

While trying to map the pins from the laptop's LVDS cable (FI-XB30SL-HF10) to the CN12 conector of the LCD t.vst59.031 Controller I came up with this:

But I'm struggling to map the pin 6 (CLKEDID or DDC Clock) and 7 (DATADID)

With this configuration I was able to see some noise in the screen (very dark since I don't have the inverter set up yet) but it's still not right.
Does anyone know where the CLKEDID and DDC Clock pins should go?

This might also help:


texts: How to make a ground plane for relay PCB switching mains?

texts:
I am making a PCB board with 4 relays controlled by a PIC microcontroller as shown. The board consists of components that are working on 5V DC and the relays that are connected to 110VAC. I had a few doubts regarding the ground plane:-

Q1. If I make a ground plane that covers the entire PCB, will the AC traces cause any problem in the working of the board?

Q2. Should I make a ground plane on the entire board or just for the DC portion of the board? Which will be better?


texts:
I'm designing an analog audio amp with a 6 band analog equalizer controlled via a 7" LCD touch screen. I'm wanting to preform a real time 2048 point FFT and display it on the screen in some kind of visual animation. The equalizer will have digipot that will be on a SPI bus. I was shooting for a all in one solution. Also some kind of cheap dev board to prototype with is a must. Below are the requirements that I have come up with.

min 43 GPIO
min 50Mhz clock
min 1 10 bit resolution ADC
FFT capability

This is my first large design project and I'm a little overwhelmed with the size of the market. Was looking at the Stellaris made by TI, but it turns out that the chip is still in experimental phase and not available for test are distribution. I was thinking about possible desoldering the chip and putting it on my own board but was concerned that the chip may be stressed to much. Any input are advice would help a bunch.


texts: When any layout is called High Speed Layout? What are the pins we should look for considering any board layout as a high speed design?


texts: How to identify semiconductor parameters for spice model?

texts:
I am simulating circuit which uses NPN IRFZ44N power MOSFET and MBR1560CT rectifier (used in the circuit just as a shottky diode, connecting 2 out of its 3 legs only).

Here is a circuit made in “EveryCircuit”:

This simulation application asks for parameters I can not identify:

1. For NPN MOSFET:

Width
Length
KP
VTO
Lambda

2. For Schottky diode:

Breakdown voltage
Saturation current
Ohmic resistance
Emission coefficient
Junction capacitance

Could you help me find or connect those parameters with values from the datasheet?

EDIT:
I found this page:
http://www.eecg.toronto.edu/~kphang/teaching/spice/part3.html#7.5
which explains a lot yet it is very concise. It this the best / official reference?


texts: Is possible to use Ipad touch screen with PIC16F707 MCU for DIY ?

texts:
I'm developing a project that I would like to use the Ipad capacitive touchscreen(digitizer) with mTouch controller PIC16F707 but by now I have no clue about the specifications of Ipad touch screen. I would like to use it because the OEM Ipad screen is not too expensive.

I know that mTouch controller can handle up to 32 sensor channels.
I got the details of the controller on this website http://www.microchip.com/pagehandler/en-us/technology/mtouchscreens/products.html They even offer a development kit.

Anybody know how would I get a clue ? I did find on internet but found almost nothing. I found this interesting topic here also Capacitive Touchscreen for DIY usage?


texts: Suppose we have a linear non-causal system with an input x(t) and an output y(t). If the input is zero up until t=a, must the output be zero before to because of linearity? Or can the output take nonzero value before t=a because the system can anticipate the future that x(t) will be nonzero after t=a?


texts: What is the analog bandwidth of general purpose ADCs?

texts:
I am making use of the dsPIC33FJ64GP802's ADC to do Undersampling and for that, I need to know the analog bandwidth of the ADC of this Microcontroller. My signal is around a few MHz. I have already contacted Microchip for the specs but no reply.

So would anyone know about the typical analog bandwidth of this tier of ADCs?

Note that I am using the 4 simultaneous channels option with the 10-bit ADC.

I am making a circuit to measure the analog bandwidth anyway. I just wanted to know if anyone knows beforehand maybe there's no need to go through the trouble.

Let me stress out again that I am Undersampling the few MHz signal which has a bandwidth that satisfies the Nyquist–Shannon sampling theorem.

And yes, I am aware that the sampling rate is 1.1 MS/s so a max signal BW of 550 kHz.


texts: How to drive high current transistor with Arduino?

texts:
I need to control a 6 volt 100w watt incandescent bulb with my Arduino. I was thinking of using a TIP35C transistor but I realized the 40mA(max) output of the pins on the Arduino would be inadequate.

Is it possible to use one transistor to drive another to achieve this effect? For example the Arduino switches a TIP120 which switches the TIP35C. If so how would this look?

Is this an overly complex way to do it?


texts: Is it okay to cut a 2 row 8-pin DIP socket for IC to stripboard connections?

texts:
I have a fatal short circuit (connecting 0V to 5V) on a very tedious stripboard project because I was given an 8-pin 2-row DIP socket (shown below) that has a short circuit between pins 2 and 3 (the two middle pins on the left-most side) instead of an 8-pin 2-row DIP socket where none of the pins are connected to each other.

Do I have to de-solder all ten of the sockets I have used and solder new ones in (painful) or could I simply manually cut the socket between pins 2 and 3 with some sort of razor blade (please recommend a better tool)?

Edit: it was suggested that no sockets are manufactured with short circuits so I am guessing there must be something wrong with the board. I have S-C, O-C and continuity tested the board (as well as made some extra track breaks) and still I cannot see why the top most rail is shorted to the bottom most rail... Most of this board was not by work but it is my task to finish it off (groan).

Topside and bottomside pictures shown below (shorted pins shown in red):


texts: What is the advantage of non-inverting op amp high pass filter

texts: The non-inverting op amp high-pass filter (first picture below) has a unity gain limit close to DC, while inverting op amp high-pass filter (second picture below) doesn't have such a limit. So why do people still use the non-inverting high-pass configuration?


texts:
How to hold two breadboards together in a way that they dont take apart so I can put them in my car easily and go on travel?

There are so many wires between them


texts: Help me identify this type of pin header

texts:
Can you help me identify this type of pin header?

I know it's a SIP (single in line) package, but would this type of connector be male or female since it has both gender types of connectors?

Also, could anyone suggest a distributor to purchase this type of header in bulk?


texts:
I have the next exercise:

I proceed as follows (assuming ideal op-amp):

$$C = 2 \mu F$$
$$R_{1} = 50k \Omega$$
$$R_{2}=10k \Omega$$
$$v_{2} = 0V$$

For \$t>0\$:

Node \$v1\$:

$$i_{s}=C \frac{d(v1-v2)}{dt}+ \frac{v1-v2}{R_{1}}$$
$$ \implies i_{s}=C \frac{dv1}{dt}+\frac{v1}{R_{1}}$$

Node \$v2\$:

$$ C \frac{dv1}{dt}+ \frac{v1}{R_{1}} = \frac{v2-v_{o}}{R_{2}}$$
$$ \implies R_{2}C \frac{dv1}{dt}+ \frac{R_{2}}{R_{1}}v1 = -v_{o}$$

Solving for \$v_{o}\$ using last nodal equations:

$$v_{o}(t) = -i_{s}R_{2}=-100mV$$

Based on book answers, \$v_{o}(t)=100(2e^{-10t}-1)mV\$. What I did wrong?


texts: On a Rigol DS1052E oscilloscope, what does the word "Local" mean?

texts: On the front panel of my Rigol DS1052E oscilloscope, on the "TRIGGER" column of controls, the word "Local" is written alongside the bottom button, labelled "FORCE" . What is the significance of this word, please?


texts: High speed communications on a lower speed controler

texts:
I am new to electronics, I'm trying to get my head around this concept.

As I understand it, on any processor, you will be able to switch an output on or off, at a rate no faster than the speed of that processor.  So a 8Mhz chip could (ideally) switch an input on or off at a rate of 8 million times a second.

HDMI 2.0 specification calls for a transmission rate of up to 18 Gbit/s.  How is this possible without an 18Gzh processor?


texts: Do COB LEDs usually need electrically insulating from the heatsink?

texts:
I have some Vero series LEDs from Bridgelux. I want to put multiple LEDs on 1 heatsink. I was planning to use thermal epoxy, so there is the possibility of the aluminium base of the LED touching the metal heatsink.

I have looked through the data sheet and all application notes. I can't see any reference to electrical isolation between the LED power and the heatsink. Is this because it is standard for these type of LEDs to have electrical insulation between the power connection and it's aluminium base?

I have tested with a multimeter and it is open circuit, but I will be driving the LEDs at a much higher voltage than the multimeter is using to do the test.


texts: Multiple power supplies, why link negative

texts:
I'm new to electrical engineering, and I still have many stupid questions. Here's one of them.

This is what I'm reading.  https://itp.nyu.edu/physcomp/labs/motors-and-transistors/using-a-transistor-to-control-high-current-loads-with-an-arduino

In it, it says to link the external power supply's ground (negative) to the Arduino's ground (negative). Why do we do this? Also, could you link the positives instead?

  The ground of the motor power supply should connect to the ground of the microcontroller, on the breadboard.

Also, why do we have to do this:

  Next, add a diode in parallel with the collector and emitter of the transistor, pointing away from ground. The diode to protects the transistor from back voltage generated when the motor shuts off, or if the motor is turned in the reverse direction.

Thank you.


texts: We are using one motor driver IC which can provide max 2A. The motor driver IC part no is BD6222HFP-TR. Maximum current drawing for motor is 1.5A when it got stalled. We tried to calculate the derating for this IC, but we are getting different remarks. Can anyone please guide if this IC be used for this purpose?


texts:
I had a very peculiar situation on a PCB I am working on, and the only possibility I can think of is that my assembler installed the wrong chip on my board. I'd like to present it to the forum to see if anyone has another idea.

I was testing USB on my board, which includes a TVS chip at the input - pinout below:

I had pin 1 tied to D-, pin 4 tied to D+, pin 2 & 3 to GND, pin 6 & 5 to Vbus. Pins 3 and 6 are NC, but I've used this same wiring previously and it worked no problem, and I'd prefer not to leave them floating.

When I went to test the USB communication I noticed a short from D- to VBUS and also from D+ to GND. After probing a couple copies of the board and noticing the same thing, I desoldered the chip from the board. The short on the board & the USB cable was removed, and USB worked flawlessly.

I probed the removed chip itself and saw shorts from pins 1 (IO) - 6 (NC) and 3 (NC) - 4 (IO). This explained the shorts on the board. But I can't understand why there are shorts here given the "not internally connected" statement in the function column of the table.

Is there any reasonable guess for what happened here, besides the manufacturer installing the wrong chip?


texts: Power adapter efficiency standards, any drawbacks?

texts:
Supposedly, some new federal regulation is imposing "energy efficiency" standards on small power adapters.

How is this going to affect electronics? Are the old types of adapters going away? If so, what is the difference between the old adapters and new adapters internally? I assume the new adapters will be more expensive. How much more expensive?


texts: Fibonacci LFSR - polynomial , sequence, phase shift

texts:
Hi, it's my first post here. I have a question according this picture. So let's see.

IMHO the primitive polynomial for that LFSR will be \$x^4+x+1\$ but I'm not sure if I'm thinking good. I've read somewhere that flip-flops are \$x^0
\$, \$x^1\$, \$x^2\$, \$x^3\$, \$x^4\$ starting from the input and we consider only these that are connected with XOR gate. Here I don't know which flip-flop is \$x^0\$ and which is \$x^4\$?

Starting from 1000 we will have 1000 -> 0100 -> 1010 -> 0101 -> 0010 -> 0001 -> 1000 so bits of \$m_1\$ will be 0, 0, 0, 1, 0, 1 yup?

And the part with \$m_1\$ delayed by 4 clock cycles. It's probably easy one but I don't have any ideas what's going on.


texts:
I have a LG TV (32SL8000), which has a RS232 Control Port. I tried to control it with an Arduino and a TTL to Serial Converter (MAX3232). I looked up the commands from the manual.
Serial.begin(9600);
Serial.println("ka 0 01"); //Turns on TV
Serial.println("ka 0 00"); //Turns off TV

Turning on the TV works perfectly, but any other command doesn't work.
I don't know how to fix this problem.
Thanks for your help
The Manual


texts: Can a digipot be used between an amp and speaker for volume control

texts:
Maybe someone can help me with this question.

Can I use a digipot (controlled by an Arduino) between a car radio (ISO pin) and a speaker to control it's volume (fading)?


texts: Do radio receivers use any power from a transmitter?

texts:
Someone gave me this analogy - turning on your TV or radio does not cost the broadcaster more money because the radio waves would otherwise be dissipated by the air or other objects. Is this correct? I find it difficult to believe - surely some energy must be drawn in by the receiver circuit of the radio and the fact that the radio is on or off does not change the properties of said objects.

(OK, it may only be milliwatts drawn by said devices, but I'm still curious as to how much it would make a difference.)


texts:
I have a problem:
I have a circuit with a MSP430 MCU.
I have a sensor which is supposed to be powered in 3.3V. My main power rail in my circuit is 3.3V. I need to power on and power off this sensor using a GPIO to pilot the power, so I suppose I need to use a transistor BJT being controlled by GPIO to let go the current in on/off mode into the sensor.
Problem is power rail value = sensor value and my transistor got VCEsat = 0.7V (or I can also change it to -0.7V)
So how do I manage with the Resistor value (R208) ?


texts: Looking for a high temperature potentiometer

texts: Does anyone know of any potentiometers that are rated up to 500 degrees F?


texts:
So I've got a couple servos that I would like to hook up to an Arduino Uno. The servos come with an attached circuit board which I can't identify it's purpose.

Should I try to use the circuit board? Or just scrap it and use the motor and pot directly?

Edit: Just going to find a servo driver board and hook it up to the motor and pot directly.


texts: LED in a circuit with alternating polarities

texts:
I am building a project that simplifies a dolly moving on a track.
When the dolly reaches the end of the track, it triggers a microswitch that cuts the power to the motor, and redirects the power to a LED to light up to indicate that the switch has been triggered.

My problem is that since the motor controller I am using changes the polarity of the motor to make it go left or right, I am getting positive and negative voltage every other time. (depending on if the dolly is moving right or left).
I have tried to use a 12V relay to trigger and light the LED, but the problem is relay needs at least 6 volts to latch, and when the motor is running slow, the motor controller only provides 3-4 volts.

Is there anyone that has a solution on how I can make this work? I am just starting to fiddle with electronics, and I am on a budget with this build, so therefore: Is there a relatively easy fix for this problem? Are there relays out there that has a latch range from 3V to 12V?

Schematics of the circuit with the LED (and resistor) connected directly to the microswitch. The problem here is that every other time the positive and negative switches.

Schematics of the circuit with a relay attached to the 2nd output of the microswitch. The problem here is that the relay need 6 volts to latch, and the motor controller doesnt provide that at slow speeds.


texts: Standard format for custom symbols in schematic drawings?

texts:
When drawing a circuit in a schematic editor, most of the time people are going to have to draw their own custom symbols, for example ICs.

What is the standard practice for the way in which pins are laid out on a custom symbol?

Is it better to order the pins around the block as they appear physically on the part....(I find this helps with pin identification when debugging hardware)

or
 2. Is it better to assume a non-chronological order so as to minimise cross overs of wires...(I find this helps improve readability)

Summary: Which of those two methods (or another i'm unaware of) considered standard practice?


texts:
I'm wondering how quarter wave antennas mimic half-wave antennas by using the ground plane.

I haven't touched these subjects in a bit, but here are my thoughts:

How does the mirrored return current not result in a voltage change for reference of the other half of the wave?  Why are the voltages not just shunted to ground, especially on a cell phone? I assume cell phones are designed with bypass capacitors to limit the noise on the ground plane.


texts:
im trying to write driver for EEPROM (24LC64):

page size: 32 byte
capacity: 8KB (64Kbit)

definition code:

#define E24LC64_WRITE_PAGE_SIZE 32
#define E24LC64_TOTAL_SIZE 8000
#define E24LC64_WRITE_DELAY_MS 5

class public function:

uint32_t E24LC64::eeprom_write(uint16_t address, const uint8_t* buff,int32_t length){
                        //          19      this is test. trimmed?          22
uint8_t page_head_addr ;
int32_t sent_length;
uint32_t err_val = TWI_SUCCESS;
//do we need to write next page:
while ( (length>0) && (TWI_SUCCESS == err_val) ){
    err_val = _PageWrite(address, buff, length);
    page_head_addr = (address % E24LC64_WRITE_PAGE_SIZE);
    sent_length = E24LC64_WRITE_PAGE_SIZE - page_head_addr;
    length  -=  sent_length;
    address +=  sent_length;
    buff += sent_length;
}
return err_val;

}

class private function to write pages

/*
    this function write pages
    it trims the right bytes if they exceed the page boundary.
    max length = EEPROM page size.
*/
uint32_t E24LC64::_PageWrite(uint16_t ROMADDR, const uint8_t *buff, uint8_t length){
    uint8_t send_length;

    uint8_t page_head_addr = (ROMADDR % E24LC64_WRITE_PAGE_SIZE);

    if ( (page_head_addr + length)>E24LC64_WRITE_PAGE_SIZE){
        send_length = E24LC64_WRITE_PAGE_SIZE - page_head_addr; //trim the extra
    }else{
        send_length = length;
    }

    twi_packet_t packet;
    packet.buffer = (void*) buff;
    packet.length = send_length;
    packet.chip = _I2Caddr;
    packet.addr[0] = uint8_t(ROMADDR & 0xff00);
    packet.addr[1] = uint8_t((ROMADDR >> 8) & 0x00ff);
    packet.addr_length = 2;
    uint32_t err_val = twi_master_write(_pTWI, &packet);

    if (err_val == TWI_SUCCESS)
        delay_ms(E24LC64_WRITE_DELAY_MS);
    return err_val;

}

user call:

E24LC64 ext_eeprom(TWI0, 0x50);
char mystr[] = "this is test. trimmed?";
ext_eeprom.eeprom_write(19,(uint8_t*)mystr,strlen(mystr))

the error:
the function eeprom seems to write back to address 19!

so it looks like this code didnt execute?!

address +=  sent_length;

can you spot the logical error that makes the page write overlapping?


texts: I have designed this Sallen-Key to give a 2nd order low pass circuit with a cut-off frequency of 150Hz. Another design specification is that R1=R2 and C1=C2. The issue is when simulated on LT-Spice this sallen-key returns a low pass bode plot with a cut off frequency of around 100Hz. Have I calculated the resistor and capacitor values incorrectly? What could be causing this issue?


texts: Current sense resistor - Should I consider self-heating contribution?

texts:
I am trying to implement a precision current sense amplifier. I am calculating now the tolerances introduced by the resistor.
I know the maximum drop will be 20mV and I will use a 5mΩ resistor. Max drop is 18.75mV.
I am almost sure that, if I understood well, on the amplifier side, the offset contribution will set the floor for the minimum detectable current. Then, on the resistor side, I can estimate the voltage (hence current) contribution due to resistor tolerance (let's say 1%).
But there is the TCR. Everywhere I read that is enough to multiply the ambient temperature with it to find the resistance deviation, but what about the self heating?
The resistor I choose was this one: https://eu.mouser.com/datasheet/2/303/res_fc4l-1265349.pdf
(FC4L16 serie, 5mΩ). But I see no mentioning on thermals due to self heating. I would expect a thermal resistance to allow me the temperature increase, or estimate it at least. Should I just assume that within power rating, self heating does not contribute as much as ambient temperature? The resistor will be stressed at less than 33% of its current rating (max dissipation will be 70mW, while is rated 250mW).
Hope my doubt is clear: what is the correct way to estimate errors from those resistors, if I don't get the thermal data?
EDIT: is not important how good or bad will be the performance of the resistor, I need to find out truthful error contributions, and I don't know when to make assumptions and when not, since seems I don't have full thermal data on that particular resistor - and I am not sure is normal or not.


texts:
Before doing any mistake, can you confirm me that it is not possible to connect directly UART pins of Arduino UNO on UART pint of ESP32 ?

I see on the datasheet a voltage of 3.3V. I would like to make communicating both boards by TX/RX pins.

Thank you,


texts: How to change polarity at 120V DC using DPDT?

texts:
I have a strand of LED Christmas lights. Each "bulb" has two LEDs - one is color and the other is white - the polarity on the string determines which of the two LED lights up. Pressing the button changes modes - it flips the current direction, changing from white -> color (and back) and also has fade up/down modes.

My goal is to automate this over WiFi using something like the ESP8266. I'm an electronics newbie, but here's what I've got so far.

Mains @ 120 VAC --> Rectifier (~110 VDC) --> [ ?? PWM dimmer of some sort, controlled by ESP8266 ??] --> double DPDT relay (as H-bridge?) which can swap polarity --> LEDs.

My questions:

Will this work?
Any ideas for a PWM dimmer device?
As I said, I'm a total newbie; I don't know where I should be sourcing parts. Any ideas on where to find these things? Specifically I was having trouble finding the DPDTs that can handle 110V.

Is this item: DS2Y-S-DC3V likely to work as expected above?


texts:
I am looking to install a DC 12V 6W submersible aquatic pool pump for use in a small scale hydroponic setup. The location of the beds will be too far away from mains electrical, and I would like to power this pump via a charged (via solar panels) battery.

I have a very limited knowledge on electrical power generation and discharge in a setup like this, and all the research I can find tells of calculators for larger home-scale setups.

Can anyone please point me in the right direction?
Thanks.


texts: What is the diference between concurrent 2 "when-then", sequential 2 "if-then" and "if-elsif" statements in VHDL?

texts:
I want to create an 8 bit counter with reset button on a FPGA board.
I have two signals: btn_up which is debounced and btn_center which isn't. R is an output signal which represents 8 bit counter. I want to use btn_up rising edge to increment the counter and btn_center to reset it to "00000000".
I thought there are 3 ways to do it, but only one of them works. Here is the code:

Using concurrent statement "when-else" :

R <= R + 1      when (rising_edge(clk))          else
     "00000000" when (rising_edge(btn_center))   else
     R;

if I press btn_center R incements by 1 and doesn't get set to "00000000"

Using sequential "if-elsif" statement:

process(clk, btn_center)
begin
    if rising_edge(clk) then
        R <= R + 1;
    elsif btn_center = '1' then
        R <= "00000000";
    end if;
end process;

during synthesis I get error code 9 again

Using 2 sequential "if-if" statements:

process(clk, btn_center)
begin
    if rising_edge(clk) then
        R <= R + 1;
    end if;
    if btn_center = '1' then
        R <= "00000000";
    end if;
end process;

It works.

Why aren't these 3 ways of doing this the same in this case?


texts: Identifying decoupling capacitors in schematics and routing them properly to ICs

texts:
I am a chemistry student trying to replicate a 4-layer PCB design from a pre-designed schematic , this is my first PCB project.
The design:
The stack:

Signal/component top layer (jacks,pots,buttons)

PWR internal plane

GND internal plane

Signal/component bottom layer (the layer with all the components).

General:

A audio-signal processor ( audio delay unit).
Power consumption: +12V rail: 188mA max / -12V rail: 48mA max
Digital power : 3.3 V
Audio output : +10.5V to -10.5V maximum output
Clock signal output : 0V to 8.2V

Main Components

x1 MC - STM32F427ZGT6 - x1 Dram - AS4C16M16SA-7TCN
x2 CODEC - CS4271-CZZ
x7 Dual op-amps - https://www.mouser.dk/datasheet/2/294/NJM2068_E-364244.pdf
x6 Jfet Dual op-amp - https://www.mouser.dk/datasheet/2/389/cd00000492-1795525.pdf
x1 Non-Isolated DC/DC Converters 3.3V 500MA OUT THRU - 78E-3.3-0.5 https://www.mouser.dk/datasheet/2/468/R_78E_0_5-1711129.pdf

Full schematic can be found here: https://github.com/4ms/DLD/blob/master/hardware/DLD-v1-schematic.pdf
Whilst I was routing my board I noticed that some of the capacitors where connected to both GND(from plane via) and PWR(3.3v, from plane via) and nothing else. I found this odd and then presumably learned that these are presumably decoupling capacitors used to mitigate AC noise on DC power tracks. I then checked the schematic and found some seemingly random (to me), stand alone, sets parallel connected capacitors in the schematics but thought nothing of it.
STM IC, presumed sets of parallel connected decoupling caps to the top right:

Sdram, with its presumed allocated set of decoupling caps:

Time output channel, with some presumed decouple caps:

Clockoutput channels, with presumed decouple caps for two channels but not all of them????:

PWR section with presumed decouple caps:

My questions:
How does one identify which set of decoupling capacitors should belong to a given IC/power chip? Why aren't these caps just connected straight to the IC in the schematic? Moreover, how does one route these capacitors to the pads of the IC?
My thoughts:
Bear with me...

Lets take the STM chip, it has 13 connections to that go straight (no resistor or capacitor connected in series) to 3.3V and 9 connections straight to GND. I was going to suggest that these should be placed in parallel between the 3.3V and the GND pads on the chip - but the set of parallel connected capacitors closest to the IC in the schematic consist of 2 sets of 6 parallel connected capacitors. So this seemingly doesn't add up.

A presumed example of this routing:

Route/connect the capacitors together in parallel and then parallely connect the 3.3 V/ GND input/outputs to the respective pads. One set per two IC sides.

A presumed example of this routing ( with 2 caps as an example):

Any thoughts would be greatly appreciated.


texts:
On many schematics I saw areas, which are apparently not connected to other parts of the scheme.

For example, below is a part of Arduino Uno diagram:

As you see, below are two "islands" which are not connected to other parts.

What are they mean?


texts: Two different MCU , different output but none was right?

texts:
I write this simple code to check my new burner :

#include<avr/io.h>

void main(void)
{
DDRC = 0xFF;  //high pins
PORTC=0x00;

while(1)
{

PORTC=0xFF;
}
}

I use Extreme burner software to burn . My burner seems to work fine. It burn the code (said by the burner software ) but output is not as I expected.
I burn two ATmega32 .
For first one , PC2 , PC3, PC4 give high output (around 4.3 volt) and rest is low (around 1.7 volt) .
For second one , PC0 , PC1 , PC7 pin high output and rest is low.
I can't understand why ???
anyone can explain and give me a solution ??
Thanks


texts: Can I dynamically change STM32 voltage during runtime

texts:
I'm using an STM32L151 MCU for a battery powered wireless sensor node. I came across the TPS6274x series switching regulator, who's voltage can be reconfigured at runtime by flipping it's inputs. The radio I'm using can only transmit with full power with 3.3v, but it can transmit at slightly lower power at 1.8v. All of my sensors can run down to 1.8v.

Does it make sense to use the control pins of the TPS62740 to boost up to 3.3v only during radio transmission and enjoy the power savings of the 1.8v the rest of the time? What are the implications for the RTC or clock speeds? Do I just need to update the clock configurations when boosting, or are they just good to go?


texts: Maximum limit on the Buck converter inductance value

texts:
I found the minimum inductor required for a buck converter using the following formula -

$$L_1 = \frac{V_{in\,max} - V_{out}}{I_o \times K_{ind}} \times
        \frac{V_{out}}{V_{in\,max} \times fsw}$$

We usually take 40% buffer on the calculated minimum inductance value (so that inductance at rated current will not vary much and ripple will be under control) and choose the inductor.

I think lower inductor values will have more ripple, good transient response, as inductor value increases there will be less ripple and less pressure on output capacitors.

Is there any higher limit on the inductor value for a buck converter?

My requirements are the following:

\$V_{in}\$ = 10.8 to 13.2V, typical = 12V
\$V_{out}\$ = 0.9V
\$I_{out}\$ =15A
ripple = 30%
\$V_{out}\$ ripple = 2.5%
and possible transients can occur up to 10A/2us.

I have seen in WEBENCH from TI/National Instruments where maximum value of inductor is specified, but I'm not sure how they have calculated it.


texts: How to change the highlight color in Eagle when using the show command?

texts: I want to use "show GND" and have everything highlighted show up purple. How do I achieve this?


texts: Why is zero represented by 4mA in 4 - 20 mA industrial control systems?

texts: Ideally, to drive a controller the required current must be just above 0 mA. However, practically we consider readings only taken from 4 mA as the valid data sets. Now, my question is why do we take 4 mA and not 3 mA or 2 mA? Is there any particular reason or is it a randomly chosen point for the sake of an ideal graph?


texts: Why are the pins of a ZIF socket usually wider than a normal socket?

texts: The pins of Zero Insertion Force sockets are usually wider than those of normal sockets.  This makes it difficult to piggy-back ZIF sockets on other sockets or headers.  Why are ZIF pins so wide?


texts: What's the purpose of SMA antenna connector grounding? Can I just use a copper antenna with no grounding?

texts:
I'm looking at a schematic which includes an SMA antenna connector.  I'm wondering why this connector needs grounding and whether a simple copper wire without grounding can be used instead

Would I be able to use an internal antenna like this one, with no grounding?


texts: Instrumentation amplifier output attenuation in LTSpice

texts:
My task was to design an instrumentation amplifier with given specifications and simulate it on LTSpiceXVII. We were told to only use one type of ac source, so to get the inverted signal I used a simple inverter design with unity gain. However, I noticed that keeping the resistance values small gave me the desired output, however increasing the resistance to large values, the output suffered drastically.
This is the circuit where I used 1kohm resistors in inverter.

And this is where I used 270kohm resistors.

I cannot figure out the reason why the simulation is giving me such results. The OP-AMPS are not totally ideal but still should behave ideally even for 270kohm resistors since the actual input resistance is of very large order. Any help would be appreciated.


texts: Arduino 433MHz transmission fails if falling edge is less than 122ms

texts:
I am trying to control a LED using a high-power 433MHz transmitter receiver pair, with transmitter connected to my Arduino Nano.

Here is the transmitter (XLPCF20): http://www.colorapples.com/rf-wireless-transmitter-module-315-or-43392mhz-xlpcf20-p-38493.html

Here is the receiver (CDR 5 B): http://www.amazon.co.uk/433MHZ-115dbm-Wireless-Receiver-CDR-5-B/dp/B00COD96UG

I can send HIGH to a data channel at the transmitter (it has 4 channels) and receive the HIGH input at the same channel at the receiver, successfully lighting up a LED. This is my current test sketch:

void setup(){
  pinMode(8, OUTPUT);
}

void loop(){
  digitalWrite(8, HIGH);
  delay(122); //this is the important line
  digitalWrite(8, LOW);
  delay(100);
}

This works well, however, if I change the 122ms delay at the falling edge to 121ms (or anything below that) I have no output at the receiver. The LED doesn't light at all. It's the same for all channels, there's a sharp change at that very border between 121ms and 122ms (found the exact value by trial and error). At the transmitter/Arduino, the output signal is clear so it's an error with the transmitter or receiver. I've used other, much simpler/cheaper 433MHz transmitter/receiver pairs in the past with no such issue. At the rising edge (second delay call, the one with 100ms), there's another issue when I drop below 13ms. At exactly 12ms, the LED is unstable, it sometimes blinks as expected, but sometimes just lights up. Anything below 12ms, the LED is constantly high, not a single blink.

UPDATE: If I use _delay_ms instead of regular delay, I get about 1ms more room for both edges, but below that, it's still the same.

UPDATE 2: I've tried changing to different output pins on my Nano, both PWM and non-PWM ones. Nothing changes.

What would be the problem?


texts: Is there a difference between the pins in the Arduino UNO Ethernet and the Ethernet shield?

texts: I just bought an Arduino UNO Ethernet R3, have been looking for projects that use it but can only find projects that use the old basic Arduino with an additional Ethernet shield. Any major differences between the two that become relevant when using these shield projects as a guide?


texts: Can anyone give me tips on how to proceed with this triac/optocoupler/motor circuit fix?

texts:
I'm working on a Fisher Digital Vortex Mixer that has an intermittent issue in which the AC motor is energized, but no movement occurs. By rough estimate, this will occur on one of every 8 attempts.

The circuit consists of a PIC16F73 that serves to activate a MOC3021 optocoupler that passes an AC signal to a Q4010N5 Triac. I have no access to circuit diagrams from the manufacturer, so this is my best analysis of the circuit:

As you can see, there does not appear to be any stubbing present, despite this system having an inductive load.  It is certainly possible that I missed the stubbing circuit during my analysis, but having thoroughly examined the circuit over several days, I am relatively confident that it is not present.

The signal coming from the PIC microcontroller is a clean digital signal that seems to drive the optocoupler without issue.

The signals going through the circuit at points 1, 2, and 3 (Circled in orange) are visible below.

The first row (point 1) depicts the No Button Press, the Good, and the Bad waveforms, in that order. The second (point 2) and third (point 3) rows only depict Good, then Bad waveforms.

Early in the analysis, someone else working on this circuit had replaced the Triac and Optocoupler as they were the likely suspects. There has been no change in behaviour after the replacements.

Despite my best efforts to figure out the cause of the waveforms I've witnessed in this circuit, I have not been able to find it. If you can offer any advice on how you would proceed, or if you require any additional information I haven't provided, please let me know.

Edited to remove extraneous pleasantries.


texts: Why are transmitting antennas generally larger than receiving antennas?

texts: The reasons I can think of are transmitting antenna has to be more directive also larger length will imply larger power and thus will help compensating for losses. But on contrary if receiving antenna is made larger and transmitting antenna smaller won't the advantage be still applicable due to reciprocity theorem?


texts:
I am designing a \$\Sigma\Delta\$ ADC. Most of the high level specs are already set:

order = 2
1 bit quantizer
OSR = 256 (or 512 if needed)
signal band: 100/200Hz

We expect some 16bit output, i.e. about 100dB SNR.

I have already carried some preliminary simulations with an ideal modulator, ideal integrators and switches (that's a switched cap circuit), and so on.

We are particularly concerned about DC and limit tones. As you maybe know, when a \$\Sigma\Delta\$ modulator is fed a DC signal it produces a periodic waveform and for some inputs the period may fall in the signal band, destroying the SNR around its frequency. Unfortunately this problem seems to be ignored by most of the papers that I have found and I am hoping to get some nice inputs from you.

We know we can use dithering to eliminate limit cycles but I'd love to use it only if necessary and I would like also to have some simulated (or calculated or whatever) proof of its effectiveness before this thing goes on the silicon.

The question then is: is there any standard technique to analyze a modulator robustness regarding limit cycles, and how can I get some quantitative results about it?

note: we're concerned about DC because the converter will be used with flow sensors, their output is "stairs-like" with very long steps, i.e. it stays stable for quite some time, it makes a small step, and so on.


texts: How to set a minimum distance between components in OrCAD PCB Designer?

texts:
I am using OrCAD PCB Designer Professional 17.4 and I can't setup the minimum distance between components. This is the "DFA Constraints Dialog" from Allegro in which you can make the setup, but my software doesn't have this option.

This is how my constraints menu looks, you can see that I can't choose between mils or mm, nor do I have the "Apply" button. My grid is set to mm, so I would want to have the minimum distance between components to be 0.5mm, nothing happens if I put the components closer than that, I won't get any DRC error.

This is how the error should be represented in the editor:

Here are some components that I placed, and u can see that the distance between the components is less than 0.5mm and I don't get any DRC error: