texts: How to drive 3 1/2 digit static TN LCD with ATmega328 in low power mode?

texts:
I've built this clock with a 3 1/2 digit static TN LCD (GYTN-0587). I drive the 28 LCD segments with an ATmega328 and four 74HC595N shift registers chained together.

Here are the (simplified) schematics (link to larger image):

And here's a picture of the board:

(The board also have an LT1111 regulator in boost configuration and a DS1307 RTC that are not shown in the schematics for simplicity.)

To save batteries and run the clock for several months on the same cells, I planned to run the ATmega in low power mode, waking it up only once per minute or so just to change the display and putting it back to sleep. However, I later learned that TN static LCDs must be refreshed at 10 to 30kHz (sorry, I couldn't find the document I read that - I couldn't find much information about driving TN LCDs out there).

Well, if I drive the shift registers at 30kHz it will leave me no time for the '328 to sleep. In the end that's what I'm doing, refreshing the LCD at 30kHz and the clock works ok. But the batteries run for only about 40h.

If I ignore the LCD refresh rate and leave the segments on for several seconds, the segments kind of vanish away (as in the picture below).

I couldn't find anything about the LCD power consumption and I haven't measured it, but I'm pretty sure the LCD consumes very little current (in the uA range). The '595 also won't use much current either since they are not sourcing much current and consume only 160 uA each. What's wasting all my batteries is the ATmega refreshing the LCD. I just need a different way to drive this LCD that doesn't take as much cycles from the MCU.

My questions are:

Can I drive this LCD in low power with this circuit I've built? If so, how?
If not, what changes should I make to my circuit so I can drive the LCD with minimum power consumption?
What is the Right Way (TM) of driving these LCDs?


texts: Grounding the (unused) power layer of a 4-layer PCB

texts:
I'm developing a new PCB and I realized that all my power connections are on one side of the board, easily connected with a wide trace. So, I don't really need the inner power layer of the board. I do need an inner ground, though, since the ground connections are just all over the place. I don't have the option to order a 3-layer board from my manufacturer, so I'm stuck with a 4-layer board with internal power and ground.

Since I'm not using the power layer, should it be grounded? I'm thinking of grounding it at a single point there the power enters the board.


texts:
I have created a schematic for a circuit that I wish to create. I believe the underlying circuit is pretty solid; however, I am having trouble picking parts with the right specs. I have attached the schematic of the circuit I wish to create. My question has to do with the transistor. How much voltage do I need to provide the following transistor to make it fully on. I know the data sheet says it needs 2 volts as its threshold; however, that only allows a small amount of curent to flow through the transistor. How do I know how much voltage I need to make it fully on. Also, how do I determine what type of resistor to use from the 5V GPIO pin to the gate of the transistor.

Here is my circuit:

simulate this circuit – Schematic created using CircuitLab

My other question is what do I need to look at to make sure the diode is strong enough to handle the EMF kickback. The diode I am looking at is from Jameco with model number 1000 VOLT 1 AMP SILICON RECTIFIER DIODE.


texts: USB-to-Serial chips or MCU with USB support - what are the options?

texts:
I'm looking for a cheaper alternative of the FTDI chip to add USB support to an MCU, so far I like the PL-2303HX however the problem with it is there are fake copies all over the net.
And I don't see any official distributors that allow you to buy original chips online.

Does anybody have an idea where can this chip be bought? :) Preferably from some trusted distributor, as ebay is full of the fake copies.

Or can you recommend any other lower cost alternative?

If I use an MCU with built-in USB (like this one by Atmel) is this a good choice? Do I need any windows drivers in this case?


texts: Why do ideal Op-Amps have zero offset voltage?

texts: Why does ideal operational amplifiers have zero offset voltage? Is that because it has infinite gain?


texts: What should I keep instead of this energy harvester breakout for maximum efficiency of the solar and supercaps circuit?

texts:
This is my circuit which charges the supercapacitors. The problem with the circuit is the minimum input voltage require to get 3.3 volts output. Once the input voltage goes below the certain level ( i guess ~4.2 volts ) then breakout board does not give 3.3 volts as an output. As per the circuit, I do need 3.3 volts constant.

Should I use boost converter from 2.7 volts to 3.3 volts?

Please give some suggestions of IC or circuits.

simulate this circuit – Schematic created using CircuitLab

Components:

Energy Harvester

EDIT:

This project is about powering few LEDs (let's say 3 LEDs) with the solar panel. LED specs are 2.6 volts and 2 mA. The solar panel could be of any voltage and dimension. I prefer to use 5, 6 or, 9 volts small panels. I used LDR to sense the presence of the light with the LM393 comparator and TI SPST switch IC for switching. My original goal is to be able to use it for a long time at least 16-18 hours. Thus, I used super caps to store energy.

Temperature range: -20 to 52 deg C

LED: 2.65 volts and 2 mA datasheet

Solar PV source power: 0.6 W Amazon

desired load power: 0.02 W

work time: 24 hours (after 'power-bank' is fully charged and LEDs are triggered by the sensor)

sensor: LDR (I would love to use other sensors like current as LDR could give false detection with some occlusion)

project time: 30 days


texts: I sometimes run into a problem with altera's Quartus that I would like a better solution to. Sometimes I use the graphical interface for design and I have a bus that I would like to pull off just one route it to a block. Usually I create a custom block and put one wire in and multiple wires out. This seems a little excessive, is there a better way?


texts: I need to size and build a bleeder resistor network or could be as simple as two bleed resistors....im not sure but I have an application where a we have a step up transformer from 120VAC single phase to circa 1200VAC on the O/P side. When we power up the line, and the line could be anywhere from 5 to 120km with cross sections ranging from 6mm to 25mm for each of the conductors, ie L(6mm) and N(6mm) for application 1 and L(25mm)/ N(25mm) for application 2 they obvious act like a capacitors ie when we switch the power supply off, there is still a residual charge in the line. We then have to "dump" that to earth before we can work on it or you get a shock. So, question is, where to put the bleed resistors in the circuit, on the 120VAC "input" side of the XMFR or do they have to be on the O/P side? If they have to be on the output side, how do i connect them so they are not in circuit when the transformer is on but when it is switched off they are activated? Finding relays / contactors etc for 1200VAC rating is difficult. Also, We would need to bleed the circuit within approx 5 to 10 mins, so how do we go about sizing the resistors? The 1200VAC power supply is approx 2.5kVA rated.


texts:
I'm trying to create a CPU, using 8-bit instructions, and there will be 9 or 10 of them.

I have an add, subtract, multiply, load, store, branch if zero, branch if not zero, print (to display), input (from keyboard), and return (exit program) instructions.

Addresses are 4 bits long, and I have two general purpose registers, so I only need a single bit per register; so for addition, subtraction, and multiplication, I need 2 bits for the registers (one per register, two registers) - leaving me with 6 extra bits in the instruction format.

For loading/storing/branch if zero/branch if not zero, I need one bit for the single register and 4 bits for the address, leaving me with 3 extra bits in the instruction format.

For print and return, I only need one register, so 1 bit, leaving me with 7 bits for the rest of the instruction format; and for return, I have a full 8 bits I'm not sure what to do with.

So I need to figure out the instruction format and build my control unit circuit. I've been trying to do a lot of reading and I feel pretty stuck at how to even go about this - what size my op code should be, how to implement this in a logic circuit, etc.

Any advice would be appreciated.

EDIT: I've been given these specifications and I have to work around them, though I know they're not really ideal - it's just a small project I've been assigned (however I do appreciate the additional input because I do want to learn as much as possible, just know that I can't really change the specifications).


texts: bridged emitter follower - how does it work?

texts:
I built a rough test version of the above circuit, it is intended as a bridged (i.e 'balanced') unity gain buffer for headphones.
The test circuit seems to work, as in there is sound and it is not blatantly distorted .

The op amp outputs in the circuits are from the balanced XLR output from my DAC, therefore the op amp circuit is internal to the DAC and can not be modified, it's just there for clarity.

If possible my aim is to have distortion no worse than a typical emitter follower (e.g single supply, ac coupled, dc biased) with this circuit, but with a reduced number of parts.

Would this behave like a typical emitter follower or is there any obvious issue?

There are 2 things I'm most interested to know and will be do my best to describe them:

1.  The load 'floats' between the 2 outputs it seems, how does the NPN handle negative voltage swings from the op amp?

For example, If the negative side of the load (300 ohm headphone) were connected to -12V supply instead of the output of the negative half as it's shown in circuit then the NPN would be able to source current even during negative voltage swings on the op amp output.
So what happens during negative swing when it is connected 'floating' between the negative and postive halves? can the NPN still source current during negative voltage swings from the op amp?

2. The -12V supply is treated as ground for the NPNs, this means Re is connected to the output of the negative voltage regulator, does this matter?

Would it be better/worse to instead connect Re before the regulator, to the negative output of bridge rectifier?
This would resemble a more 'normal' single ended supply for the NPN... you would never see a negative regulator on ground for a single supply.

To be clear I am not looking for a 'better' alternative to this circuit, I want to know the problems with this circuit and, if they exist, solutions.
If problems exist without solutions then my alternative will simply be to build the standard single supply, AC coupled emitter follower


texts: Capacitive power supply - Bleeding resistor reliability considerations

texts:
We are using a capacitive power supply for one of our applications.

The X2 capacitor (330nF in this case) provides good reliability with respect to failing safely/open and good over-voltage withstanding capability.

So the question came up what to consider, when choosing the parallel bleeding resistor to prevent negating the properties of the X2.

Apart from calculating the resistance value (500k for ~1s discharge choosen) and power rating (0.5W choosen) which is pretty straightforward, what else is there to consider?

What about properties like
* Flame retardant
* Fusable type
* Pulse voltage rating

I would tend to select a fusible type at least. I am unsure about the pulse voltage and peak power ratings though. The circuit will be used in an industrial environment and thus will be tested against 2kV surge L-N and falls into over-voltage category II. Resistors that withstand voltages >2kV are like 20x6mm 4W types, which seems total overkill.

PS: Our customer would prefer not using a varistor for surge protection if possible, due to very limited PCB space. So it may be a good idea to rate the resistor accordingly. And yes, they would really like to have the bleeding resistor because its easy to touch the contacts after being disconnected.


texts:
I'm trying to disable the stepper driver to allow manual operation of the lead screw it's controlling.
I've tried connecting MF+ and MF- to ground and 24V in multiple combinations but the motor was still energized. Any ideas? Thank you.


texts:
This question comes from viewing this post.

I am confused why in one of the KVL equations \$I_{C1}\$ was multiplied by \$R_{C1}\$.
Doing a quick KCL, the current through resistor would be \$I_{C1}-I_{B2}\$.
However, if solved by basically neglecting \$I_{B2}\$, \$I_{B2}\$ is very small and to some extent, it makes sense we can somewhat neglect it. But I feel that's not the reasoning behind it.
Hence, why is it (from my perspective) that \$I_{B2}\$ is being neglected when solving for \$V_{C}\$ (when \$I_{C1}\$ and \$R_{C1}\$ are being multiplied)?


texts:
I just saw this question and was wondering how this circuit actually works, since I couldn't really figure it out, I though about asking it.

This is the circuit I am talking about:

Lets label transistors from left to right as: Q1, Q2, Q3, Q4. I dont really know where to start, how to analyze this circuit to figure it out how it works. What I am especially curious about is the purpose of Q1? Or what about the diode?

If someone could give a detailed description of the circuit I would be really thankfull.


texts: Implementing a boolean function using a decoder

texts:
I am taking a course in computer organization, and currently struggling with circuits. I was stumped by the question below.

I drew the K-map for the boolean function and managed to obtain a simplified SoP expression:
W'Y' + XY + WX' (here ' refers to the complement). I noticed that this expression is independent of the boolean variable Z. We are left with 3 variables W, X and Y, so I guessed that we need to use S1, S0 and E as input signals (even though E is also an enable signal). But E must always be 0 for the decoder to be active, so I figured I had to make E correspond to a variable which was always in complemented form in the boolean expression of the function. But I couldn't find such a variable. Compounding my troubles was the fact that all the outputs are active-low, which makes things more confusing. After being stuck for ages, I decided to refer to the (extremely brief) solution, shown below.

I could not make sense of the solution. Apart from the fact that I was clueless as to how to implement the function, the boolean expression was also different from the one I had obtained. I would really appreciate a thorough explanation at this point.

EDIT: Here is the K-map which I drew, from which I derived the expression W'Y' + XY + WX'.


texts: I am getting wrong answer for the above problem. My book says R should be 23ohms. Please guide me where I am doing the mistake.


texts: Altium Designer - connection of two nets and using vias

texts:
I design a simple PCI-E riser. I need a clue, I'm stuck on a relatively simple element. I would like to connect two power supply lines + 12V (pads B1 and B2) on the top layer and then go through the three passes to the Bottom layer. In addition I wonder how to get the irregular shape of the path visible on the right in the selected rectangle (red color). Shoud I use Polygon Plane?

Thanks for your support! I did the following:

created Polygon Pour, connect it to Net +12V
selected Pour Over All Same Net Objects
selected Layer: Top Layer

Next I've set proterties of Viases: Net -> +12V.

Is this correct?

I will also use the Interactive Length Tuning function, thank you for the link!


texts:
I am controlling the voltage of a 3.6V lithium battery with a MCP112-250 (I know it is 3V but I have a diode in series with my battery).
And the output is connected to the gate of a N-channel MOSFET, IRFB7430PbF according to this schematic :

The MCP112 is doing his job by toggling his ouptup from high to low.
When Vin>2.5V I have my MCP112 output high and I have 2.5V at Vout of the LDO, and when Vin<2.5V I have my MCP112 low but I don't have 0V as expected but aproximately 1.2V when Vin=2.2V. My circuit is not shut down as expected... Theoretically when I have a 0V on the gate of a N-channel it has to be "open" so my system is off.

But why is this working like there were no MOSFET ?

EDIT:

It seems I have some current leaking from somewhere... Because when the MOSFET is removed I have Vout=~2V ...But from where ? I used a GND power plane on my board. Is it possible that current is leaking between the pads and the power plane ?


texts: How does the speed of a synchronous generator changes with load?

texts: When the generator is rotating at rated speed and let us say that the load decreases then the mechanical torque will be more than the electrical torque which will lead to increase in the speed of generator. I understand this. What I'm having problem understanding is how this happens physically, i.e., what is going on with armature and field current during such transient period and how they affect the speed.


texts: Given a battery of unknown chemistry and unknown origin, how to I tell it's a rechargeable alkaline manganese, NiMH or NiCd battery by looking at its electrical or physical properties, eg. maybe they have a different distinct capacity-weight-ratio or significantly different discharge or charge behavior. Taking them apart is not an option. I'm not sure if this might be better on the chemistry SE.


texts: EMI consideration for Microwave Sensor Module

texts: I'm using Microwave Solutions MDU1720 datasheet with recommendation that The length of leads connecting the MDU to the signal processing circuitry must be minimised, to reduce pick up of electromagnetic interference. A maximum lead length of 1.5cm is recommended and screened leads are preferred.  Due to other prototype constraints, however, I'm stuck with 15cm long 22gauge unshielded hookup wire for the +5V and GND leads.  Would it be likely enough to just twist these leads together and run perpendicularly away from the pcb?


texts: Transformation from Normalized Low-Pass Filter to Denormalized High-Pass Filter

texts:
I would like to ask a question about the a method (method number 2) to go from a normalized LPF to a HPF:
Note: normalized refers to frequency normalization for the mentioned filters.
1- One method allows to go from normalized LPF to denormalized HPF by using the transformation (refer to Figure below)

This then allows to get for example an inductor L' in the denormalized HPF by using the capacitor value C in the normalized LPF: L'= \$ \frac{1}{C\omega_{p}}\$
2- Another method allows to go from a normalized LPF to a HPF. However, I am not sure if it leads to a normalized or denormalized HPF. Here is the transformation (Figure below):

And an inductor L' in the HPF is obtained by L'= \$ \frac{1}{C\omega_{0}^{2}}\$ where C is the capacitor in the normalized LPF.
Would this L' represent the inductor in a normalized HPF or denormalized HPF in the case where we start from a normalized LPF?
Thank you


texts: How can inductance affect push pull converter?

texts:
I'm trying to figure out the effect of adding inductance to a push pull topolgy but there are many parameters and I got confused.

First of all, considering the previous basic circuit, What limits the current when one of the mosfets is one? Isn't it the inductance and the resistance (though the reistance is very small ) of the primary winding ? so what bother if I
added another inductance (I mean the inductive resistor at the bottom) to the path?

And would it change anything if I put this inductive resistor at the high side (regarding the switching speed of mosfets)?

Can't this inductance acts somehow as a lowpass filter and filters some of the high frequency components of the PWM singal (which is 10 Khz sine pwm)? and if yes, wouldn't that be a good thing for the 50 hz transformer?

I asked this question becuase of the answers of my other question about the very low value resistor and some mentioned that my resistor is inductive and can cause issues in switching circuits so I wanted to know its effect on my particualr application and it seemed to my little knowledgement of electronics that it has advantages not the opposite (electronics is really too tricky to me).


texts: Is there an actual need for the concepts "emf" and "back emf"?

texts:
Given a two-terminal element where you can only measure the voltage across terminals \$v(t)\$ [\$v_{ab}(t)\$] and the current \$i(t)\$ defined as entering the positive [a] terminal, there doesn't seem to be a need to introduce concepts as "emf" or "back emf".

Furthermore, in actual use there seems to be inconsistencies in the sign of these elements. For instance, in an inductor, it is well-known that
\$v_L=L\frac{di_L}{dt}\$. This page gives such an expression  for a solenoid (with a value of L as a function of its parameters) before talking about "back emf". However, under the title "back emf generated by an inductor" we find the sign changed \$V_L=-L\frac{di_L}{dt}\$.

So, what's the point of using the "electromotive force EMF" which, according to wikipedia is "the electrical intensity (!) developed by a source" instead of voltage?

Why is there a need to introduce "CEMF" defined, according to wikipedia "the EMF caused by magnetic induction"?

Wouldn't it be reasonable to just use the only variables which can be measured in practice, \$v(t)\$ and \$i(t)\$?


texts: What is the logical equivalent to this CMOS circuit?

texts:
I'm examining a chip die and I'm trying to figure out what this arrangement of transistors is equivalent to if it's a logic gate or what (something you could get in a 74LS chip for example).

simulate this circuit – Schematic created using CircuitLab


texts: Equivalent circuit (series capacitor on inductive pickup)

texts:
In the following circuit, does V1=V2?  It seems to be the case, because there is nothing being driven across the capacitor terminals.

The relevant application is filtering the signal received from a pickup coil, which I guess would be done by a capacitor in parallel.


texts: 4017 counter: Why do some LEDs have multiple connections in this traffic light circuit?

texts:
Schematic (from here):

Why are four legs connected to the green LED and two to the amber LED in the 4017 traffic light circuit? Shouldn't it be able to do with only one leg per LED?


texts: How to power one fan with two different power supplies individually

texts: I have two systems that run on separate power supplies and turn on independently of each other.The issue here is that each system needs to be cooled by the same cooling fan. So I need to know if there is a way that I could have either system on and the cooling fan turn on for either one. Also need to be able to have both on without overvolting the fan. I also really dont want to run another power supply just for the fan and have to turn it on independently of the systems. Thank you all for any help. The fan is rated at 12V but can be ran at about 5V. One of the power supplies is 5V and the other is 7V. Also, what would I do with the negative wire in this situation? Is it fine to have it connected to only one of the power supplies or should I have it configured a different way?


texts: Switching converter current mode control - load disconnect problem

texts:
I'm building LED driver based on current mode control buck converter. My question is quit general. If load is disconnected then output capacitor voltage shoots up. If load is reconnected it gets overcurrent spike from that charged capacitor. If output capacitor cannot be removed, what else can be done? Is there a general approach to this problem?

Thats a simplified circuit. If LED is disconnected, output capacitor charges to high voltages and can destruct the LED if it is reconnected.

My biggest worry is if I'm missing something simple and obvious? If not, thats ok, I will do my work somehow.


texts: Differential amplifier solving equations for iDS

texts:
In large signal analysis of differential amplifier there are some equations  to determine iDS.

If we simplify it looks like that :

\$ \large 2x^2+2kx+k^2-2\frac{l}{m}=o\$

Is there an easy way to solve these kind of equations. What should one study to easily solve these kind of problems?

Edit

Original equation looks like this.

Citation :

  Agarwal, Anant, Lang, Jeffrey. Foundations of Analog and Digital
  Electronic Circuits.. [edx].

Edit

Ok. I solved equation using completing the square technic.

\$ \large (x+\frac{k}{2})^2 = \frac {l} {m} - \frac{k^2}{4}\$

\$ \large x = \frac{1}{2}(\frac {\sqrt {4l-mk^2}}{\sqrt{m}} - k) \$


texts:
(this is the last of my unknown components).

It is less than 1 cm (half inch) diameter, has one wire on each end.

It has description:

CNR C8G 75L RU G12

The RU is written reversed.


texts: Crimping multiple wires to a single crimp

texts:
I need to connect a power supply to a device. The power supply provides 24V on a 2-pin Molex Mini-Fit Jr. header. The device has a 9-pin female D-Sub connector as input of which 3 pins are GND and 3 pins 24V.
My idea would be to use a 6-conductor able and crimp three conductors together into a single terminal. The conductors would be 26 AWG each (cross-section area of 0.129 mm^2); for a total cross-section area of 0.387 mm^2. I would then use a 18-24 AWG crimp terminal; which should be OK if it was a single-conductor cable.
Questions:

Is this the recommended approach? If not, what would you advice?
Should I be aware of any reliability issues? Can these be controlled or mitigated?


texts: Where should I look for transformer inductance discrepancy?

texts:
I'm experimenting with this smallish (~15VA) toroidal line transformer as
a "lab" exercise as I'm learning about transformers. Right now it has its
original 115V primary winding only; I "unwound" and removed the secondaries it
came with and will be adding new ones of various descriptions for experimental
purposes.

The primary is about 1500 turns, with a winding resistance of 28 \$\Omega\$.

The problem I'm having is I'm getting widely different values for the primary
inductance, depending on how I measure it. I have a few hypotheses why, but
wondering which might be most likely.

When I measure the primary with my Agilent U1733C LCR meter, I get a reading
of 22.7 H @ 100 Hz. There's no 60 Hz option for whatever reason, so I picked the
lowest available frequency. On the 120 Hz setting, it reads 20.4 H, so I'm
figuring the 60 Hz value is somewhat higher than 22.7 H rather than lower.

On the 100 Hz setting, it reads 7.7 nF for capacitance.
My second test is for identifying the core characteristics, specifically the
saturation curve, but it also indicates inductance. Basically I apply
a voltage (4 VDC in this case) and then observe the current curve with the
scope over a 1 \$\Omega\$ resistor. The slope of the linear portion in the first few microseconds after
voltage is applied indicate the inductance. By this measurement method I get
about 8.8 H.
The third test I performed was to measure the magnetizing current. Using my
DVM, I get 3.1 mA AC RMS through the primary when plugged in to 120 VAC.
(today the line is running about 124 VAC).

That gives an impedance of about 40 \$k\Omega\$ which would correspond to an
inductance of 106 H.

So I'm wondering why there would be so wide a variation in the inductance
measurement.

I know the LCR meter is measuring at too high a frequency, but it seems like
worst case the actual would be no more than, say, 30 \$H\$.

On the DC voltage test, I suspect there are some core magnetization hysterisis
effects going on because I get a very different (way longer) curve when
I reverse the polarity, but only the first time at the new polarity.

The magnetizing current test seems like it should be pretty darn accurate
though.

Anyway, I'm pretty stumped here about how to explain this and perhaps modify
one or more of my test procedures.

Does anyone have any ideas about how this might be explained?


texts: How the pull-up resistor settles the logic level?

texts:
According to Wikipedia,
"Pull-up resistors are used in electronic logic circuits to ensure that inputs to logic systems settle at expected logic levels if external devices are disconnected or high-impedance is introduced."

and in the above figure,
When the switch is open the voltage of the gate input is pulled up to the level of Vin. When the switch is closed, the input voltage at the gate goes to ground.

What is the point of using the pull-up resistor anyway in this circuit ?

For example, If i were to remove the pull-up resistor from the circuit above, and the switch is open, still the voltage of the gate is pulled up the level of Vin.
Why use the Pull-up resistor then ?


texts:
Principles of Electronic Materials and Devices - Hasap, pg: 585, he says:

$$\epsilon_r = \frac{Q}{Q_0} = \frac{C}{C_0} = \text{relative permittivitty}$$

Then he says:

  It is important to remember that when the dielectric medium is
  inserted, the electric field remains unchanged, provided that the
  insulator fills the whole space between the plates as shown in Figure
  7.1c. The voltage V remains the same and therefore so does the gradient V/d, which
  means that electric field E remains constant.

But I thought the reason we had absolute and relative permittivitty is because the material affects the strength of the electric field with \$\epsilon_0\$ being absolute permitivitty (free space). Also how is he getting that (above) equation, given that:
\$C = (\epsilon_0 \times A) / d\$


texts: DRV8874 fault investigation (on one unit only out of 9 sharing the same design)

texts:
I have designed a board which controls 9x DRV8874, using the exact same circuit as shown in the datasheet for the independent half-bridge example (except the control input of OUT2 is tied to GND, I'm not using it because of the current sensing topology ; and nFAULT sinks 2mA from a LED off the 5V when it's activated).
When I power up the board while no load is connected, one of the IC has FAULT activated, not the others. I looked at the VCP voltage and they're all at Vmot+5V (17.5V) except one, the one which has a fault, and this one sits annoyingly at Vmot+7.5V (20V). I can also see the CPL and CPH pins oscillate like crazy (respectively between 0.7 and 12.5V, and between 7.5 and 20V) between two values on the faulty unit, whereas they're nice and stable on the others. When I connect a load, the chip whines... I don't know why, and I don't see anything else I could test.
Then, when I disconnect the logic supply (5V and 3.3V), VCP drops to VM which is normal.
The other ICs work as expected, but this one never outputs anything. What's wrong with it?
I checked the entire PCB for shorts, nothing. They all have the same identical schematic and layout, and I populated the board P/N by P/N so no mistake there either.


texts:
Many kinds of electronic equipment use an external brick power supply unit. There are several advantages to this; it keeps heat and noise out of the product, and it reduces the scope of electrical safety considerations, as discussed in What's the reason to make power supplies external?

Nonetheless, despite early home computers tending to use external bricks, desktop PCs soon settled on internal power supply units. Why? What's the advantage of an internal unit that outweighs the disadvantages?


texts:
Given a simple circuit with one voltage generator and one other circuit element, if these values are given:

U = 200 ∠ -45° V
I = 5 ∠ 60° A

(both values are phasors - I just don't know how to underline the U and I characters)

Let's calculate the impendance (of that other circuit element):

Z = U / I = ( 200 ∠ -45° ) / ( 5 ∠ 60° ) = 200 / 5 ∠ ( -45° - 60° ) = 40 ∠ -105° Ω

Now, is this possible? I'm asking because I thought that the range for φ is [-90°, 90°]. With this value for Z, the resistance has a negative value:

R = Re Z = 40 * cos(-105°) = -9.64 Ω

What am I missing here?


texts: Recovering Dead Soldering Tip That's Not Tinned

texts:
Situation Breakdown

I've seen multiple posts regarding this certain topic, but, using all of those posts confirmed answer, the results never showed to be significant, long lasting, or even remotely yielding results in the first place.

I have a medium duty Wellers soldering iron, and I use the iron primarily for chip boards. Now before you tell me that I should learn how to solder before doing chip boards, I'd rather learn something like electronics production while learning how to solder. With that all set aside, below is the entire soldering kit. Yes I do use aluminum, but aluminum works just fine when it comes to small scale chips.

Soldering Kit

As you can see, the tip that I use for soldering things such as capacitators, switches, and resistors, on a really small scale. The soldering I use here (if it's important, that is) is a "Fine Eletrical Rosin Core Solder".

Now, the real culprit is the soldering tips. The only reason I'm confused on how to fix them is because I want to say that the black stuff you can see on the cone tip, is carbon build up. I also heard that the metal used on soldering irons tips are prone to oxidation. Now what was confusing is that I've only had this iron for a week. While my dad has NEVER tinned his soldering iron, and after almost a decade it still works as if it were brand new.

At first I thought I should simply just take a sanding block and just sand off the odd deformation my iron has created, but that didn't work. So now I tried tinning the iron, but the soldering flux wouldn't stick. So I melted a pool of soldering flux, thinking that would make it stick, and submerged my soldering tip into the molten flux pool, but to no avail. Finally I tried wiping it off several times, reapplying flux to it, and it still ended up like it is now. What's worse, is now when I apply the soldering core to the tip of the iron, it doesn't even melt it.

Soldering Tips In Question

I can return it, but it holds sentimental value to me, particularly because it was the first thing I used to solder with, which in my opinion, is worth holding onto, so I'd rather try and save the cores, and learn something from this, than return it and learn absolutely nothing from it.


texts: Time complexity of carry look ahead adder

texts: How is the time complexity of carry look ahead adder O(log n)? Can you explain in terms of gate delays?


texts: What are these wires with pre-attached connectors called?

texts: What are these connectors commonly called, and what would I search for if I wanted to buy sets of male/female pairs with a specific gauge of wire pre-attached?


texts:
We have a capacitor fully charged with some voltage. At t=0 we can find the current.
This current will change the voltage of the capacitor. However the information of the change of the voltage of the capacitor will travel at the speed of light in the dialetric material.
So for t<d/c where d is the distance of the mettalic plates and c is the speed of light in the dialetric material the electrons won't feel the change in voltage. After that time interval the information of  change of the electric field will reach the electrons.
The graph of current with respect to time while discharging a capacitor is continuous while from the above reasoning it should be quantized.
Any help?


texts: Can program FPGA but not PROM on my Spartan-3A dev board

texts:
I decided to brush the dust off my Xilinx Spartan-3A starter board that I got a while back, and learn to use Verilog.  So with the help of Pong Chu's book FPGA Prototyping By Verilog Examples: Xilinx Spartan-3 Version
 I got a simple program written and compiled using the Xilinx ISE.

I then launched their IMPACT tool so I could download the program to the board.  After a few false starts, I was able to get everything configured (I thought) and download the program to the FPGA, and it ran.  But of course if I restarted the board, the demo program that came with the board was loaded off the PROM and started running again.

So I then tried to program the PROM instead.  Even thought the IMPACT console says the part is programmed (see below), when I restart the board I still get the original demo program running again.


texts: Automotive: how to safely connect the car's power grid to the input of an intelligent switch?

texts:
I have an intelligent switch. Let's take this one as an example - it's the one I'm plan on using, unless I find a better one. What I need to do is drive it by the voltage from the car's power grid. There are two complications here:

I'd like to get 3.5-5 volts at the input of the switch, but I have no other voltage source to clamp the input to with a diode.
Whatever schematic you suggest must withstand voltage pulses up to at least 60V (better yet - 100), and keep in mind the pulses may have reverse polarity as well.

What are the simplest solutions you can think of?

I've been thinking along the lines of a high-resistance voltage divider + a suppressor diode or a Zener diode. But I have no idea if it will work, let alone - work reliably. Please keep in mind I'm not an electrical engineer, and don't beat me up if I ask how your solution works.


texts:
let's consider this logarithmic multi - stage amplifier:

Each stage is an amplifier with this mechanism: if the input signal is small (under a certain threshold), it is amplified with high gain A; if it is large (over the previous threshold), it is amplified with unitary gain.

The purpose of this multi - stage amplifier is that of getting a Voutput - Vinput curve like that in the previous picture. But I do not understand the presence of the Adder circuit. I think that simply the cascade of the previous amplifier will generate a curve like that, in which small signals are amplified a lot, and high signal are amplified less.

Can you help me on understanding the presence of the adder?

This circuit is analyzed here.


texts: Can opamps work with signal that may go higher or lower than supply voltage?

texts:
I'm trying to make a impedance meter using STM32 and I want to ask that question to make sure it work ( at least the theory).

So, Can opamps work with signal that may go higher or lower than supply voltage
(single positive supply) as long as it's output remains in Vsupply region ?

Sorry for my bad English and thanks !


texts: Re-capping old car stereo - does this affect bias?

texts:
I am refurbing a car stereo from an early-90s Volvo (stereo model HD-603) - plus replacing the cassette circuit with Bluetooth and Aux In. But this question is not about this modding per se.
The stereo itself, being 30-years-old, initially was failing due to the main input cap leaking its guts, and despite now working after that repair, there are a number of (quite a lot of) electrolytic caps on the board, and of all the ones I've pulled and tested off the board, they are drifting off and mostly high in ESR.
So - before reinstalling the stereo, I will replace the electrolytic caps with exact like-for-like, only LESR, plus there are several sub-1uF electrolytic caps which I will replace with polyesters of the same values.
My question is - might these new caps (despite being all exactly the same uF values as the originals) potentially affect biasing or possibly introduce new issues? (If so I won't do it!) (And I am a capable solderer, and won't put them in wrong!)
The car stereo board has 3 test points and 4 pots - though I don't have a schematic or much info about this board. I don't know if these pots are for bias adjustment or levels.
Also - I should add that this stereo unit appears to only output to an external power amp buried elsewhere in the dashboard, and, doesn't seem to have a 'power amp' stage itself, with larger transistors/fets and output caps. So I guess the matter of DC offset at the speakers isn't an issue.
Thanks for looking at this.


texts: How do I use a current source for a pulsed voltage in LT Spice?

texts:
For an LT Spice simulation I was doing of a transformer, I would like to set the current to 3 amps for a power supply, but I'm not sure how to use a current source for that.  I tried putting two current sources to represent the current of a pulsed power source, but the current through the resistor still isn't limited to 3 amps.  I'm not sure if it would effect the output much because it wouldn't draw much more than 3 amps, but I would like to know how to do it.
Here's the schematic and the current reading through the resistor R4:


texts: Calculating resistance for piece of metal

texts:
I have very poor understaning of electricity and usually go for "water analogy" (or Ohm's law) but it seem to have no use here:

I need to calculate a resistance of a metal disk with given diameter, thikness and conductivity but I'm also trying to understand what "actually" will go on?

Will current go in a thin channel of "least resistance"? Will it "go broadly" through all of the disk? My intuitiun tells me that it will matter what points of disk are actually in contact with the wires but why?

What is the "normal" way to calculate resistance of a complex body?


texts: Motor consumption with 1V vs 3V w/ 90% PWM

texts:
Using a DC motor, I can reach about 1200rpm using 1V/1A (laboratory style power supply)
However, if I use 3V input and a PWMized MOSFET, I need a duty cycle of about 90% to reach the same rpms and the power consumption is then 3V/1A
Why it appears that the motor needs 3W to reach the same speed using PWMized supply as compared with the 1W when not using it?


texts: Building a safe low-temperature heat box : heat sources

texts:
I'm not sure if this is more of a physics or electronics question, but here goes:

I use a heatbox with a temperature in the range of 80-100F for warming wax (for sculpture modeling). My current heatbox is a peltier-based thermoelectric wine cooler with the poles switched on the peltier and an external thermostat controlling the power to the entire unit.

I have an old 7 cubic foot freezer and am debating on which heat source would be best. The issue is (1) i don't want any heating component within the freezer to be able to get above 180F or so and (2) i want effective heat transfer (therefore I'll either have to add a fan to recirculate air or use something that already integrates a fan).

Options:

1.) I know I could use a peltier (can't reach 180F with normal ambient room temperature, too big a differential) but I am thinking it's a rather advanced solution for a rather simple problem. Also I'm not sure if it can effectively bring the heat up at this larger volume. My current heat box (maybe 2 cubic feet) heats very slowly (24 hours for the wax to reach specified temp), I am not sure if this is in part because the fan is only on when the peltier is on and the air does not recirculate once the air temperature reaches the thermostats setpoint.

2.) A lightbulb has high surface temperature and the potential for breaking, though perhaps a very low watt halogen would be more appropriate. Many people use lightbulbs for this purpose but to me it sounds risky.

3.) A low-temperature heating pad type device would have to have enough surface area for a low surface temp and enough wattage to heat the box itself. Many have integrated thermostats which may be difficult to disable (may be deeply embedded) if they prevent the heat pad from operating in an environment above 80 or 90F (just need it to get to 100F max, so it's close). I could make my own out of nichrome wire embedded in silicone or ceramic and give it just the right current to keep the heat in range, but this seems more complicated than the peltier.

4.) I have a low watt hair dryer with an output temperature under 180 (on low) which has the advantage of acting as an air circulator. If located outside of the box with a metal inlet and outlet pipe its electronics are safe from wax getting on them and the air flow pattern can be optomized. I am concerned though that in the event of a thermostat problem it could overheat from recirculating hotter and hotter air, although it has protections built in for many such conditions (both a bi-metalic safety and a heat-fuse as well as a GFCI). It is not intrinsically limited in heat, is my concern.

5.) They sell recirculating tank heaters for automotive and aquarium purposes. One of these could be rigged up to copper tubing running throughout the heat box and generate a safe surface temperature and good heat exchange (fan would still be necessary though I assume). This would absolutely guarantee a low surface temperature to all heat components but has the potential for other safety issues I imagine? This seems like a complicated solution, though, and possibly more expensive.

Recommendations?

EDIT: Note I already have a controller I'm happy with and I don't need precise temperature control (+/- 3.0F has worked fine for me in the past), so I don't need heating solutions that inherently have tight control, I'm just seeking safety/simplicity recommendations, mainly.


texts: There are multiple hFE options for BD139s, with the higher hFE being slightly more expensive. What advantages or disadvantages, if any, would the higher hFE parts have in emitter follower circuit?


texts: How to reliably and safely recreate a blue smoke monster for a workshop?

texts:
First and foremost, I'm going to say that I do and plan to continue to follow all safety best practices for working with electronics. I'm also a relative newbie, so I don't have a lot of experience diagnosing WHY things fail, and especially not in creating deliberate types of failures.

That being said, I'm helping a friend make a few short videos to augment an electronics workshop he does. The workshop is a very basic overview of electronics, more to get kids interested in the possibilities than an introduction to electrical engineering. With my background in graphic design and A/V production, he's enlisted me to make his powerpoint presentation more dynamic. I'm adding some short animations and video clips illustrating electrical concepts.

One video that I want will show power being applied to a circuit and then having the circuit smoke and fail after a short delay. We have a couple things we want to communicate:

electricity is dangerous (if this happens on a small scale, imagine the disastrous results on a larger scale),
the delay will show that failures may not be instantaneous, BUT
don't let that stop you...everyone's encountered a blue smoke monster, fix it and move on.

LED flareups (see how easy it is to burn out an LED by simply mixing up where the anode and cathode land?), aren't nearly as visually dramatic as I'd hoped, but I do recall making something from a kit about a year ago that just smoked like crazy once I plugged it. I'm not sure what component failed, and it's dead on my workbench waiting for a diagnosis...but it looks AWESOME. So I'm looking for a circuit; I envision a PCB or breadboard with a couple components, I attach a power source (AA or 9v battery), and after a few seconds, smoke. If there's an LED that blinks out after the smoking begins, illustrating that the circuit is dead...that'd be awesome. And, being the perfectionist I am, I'd like to be able to reproduce it reliably for multiple takes.

Any suggestions for a circuit that'll do this without unnecessarily endangering myself?


texts: Error in the direct approach for power flow calculation

texts:
In the famous paper [teng2003direct] on direct formulation of power flow calculation for power distribution networks, there is a simplification in converting nodal current injections to line current flows. In short, current loss along lines is ignored. I am wondering if the error introduced by this simplification is significant, which is not discussed in detail in the paper.
We can focus on radial distribution feeders only. There is an example in the paper:

The relationship between the bus current injections and branch currents can be expressed as:
$$
\left[\begin{array}{l}
B_{1} \\
B_{2} \\
B_{3} \\
B_{4} \\
B_{5}
\end{array}\right]=\left[\begin{array}{lllll}
1 & 1 & 1 & 1 & 1 \\
0 & 1 & 1 & 1 & 1 \\
0 & 0 & 1 & 1 & 0 \\
0 & 0 & 0 & 1 & 0 \\
0 & 0 & 0 & 0 & 1
\end{array}\right]\left[\begin{array}{l}
I_{2} \\
I_{3} \\
I_{4} \\
I_{5} \\
I_{6}
\end{array}\right]
$$
where \$B\$ represents complex current flows along lines and \$I\$ represents complex current injections at buses.
The relationship should be
$$
\left[\begin{array}{l}
B_{1} \\
B_{2} \\
B_{3} \\
B_{4} \\
B_{5}
\end{array}\right]=\left[\begin{array}{lllll}
1 & 1 & 1 & 1 & 1 \\
0 & 1 & 1 & 1 & 1 \\
0 & 0 & 1 & 1 & 0 \\
0 & 0 & 0 & 1 & 0 \\
0 & 0 & 0 & 0 & 1
\end{array}\right]\left[\begin{array}{l}
I_{2} + I_{\text{loss}, 1} \\
I_{3} + I_{\text{loss}, 2} \\
I_{4} + I_{\text{loss}, 3} \\
I_{5} + I_{\text{loss}, 4} \\
I_{6} + I_{\text{loss}, 5}
\end{array}\right]
$$
where \$I_{\text{loss}, k}\$ represents the current loss along line \$k\$.

In a related paper [zad2018new], the problem is mentioned when converting nodal power injections to line power flows.
$$
\left[\begin{array}{l}
P_{12} \\
P_{23} \\
P_{34} \\
P_{45} \\
P_{36}
\end{array}\right]=\left[\begin{array}{lllll}
1 & 1 & 1 & 1 & 1 \\
0 & 1 & 1 & 1 & 1 \\
0 & 0 & 1 & 1 & 0 \\
0 & 0 & 0 & 1 & 0 \\
0 & 0 & 0 & 0 & 1
\end{array}\right]\left[\begin{array}{l}
P_{2} + P_{\text{loss}, 1} \\
P_{3} + P_{\text{loss}, 2} \\
P_{4} + P_{\text{loss}, 3} \\
P_{5} + P_{\text{loss}, 4} \\
P_{6} + P_{\text{loss}, 5}
\end{array}\right]
$$

[teng2003direct]: Teng, J. H. (2003). A direct approach for distribution system load flow solutions. IEEE Transactions on power delivery, 18(3), 882-887.
[zad2018new]: Zad, B. B., Lobry, J., & Vallée, F. (2018). A New Voltage Sensitivity Analysis Method for Medium-Voltage Distribution Systems Incorporating Power Losses Impact. Electric Power Components and Systems, 46(14-15), 1540-1553.


texts: What is the maximum power a DC dummy resistive load can take, if I connect two 50 ohm 2kW power resistors in parallel? Is it 2kW or 4kW?


texts:
Is it possible to read a 4-wire PT1000 using an MCP3008, which is connected to a Raspberry Pi?
I can handle the software part; I am looking for how to wire things up.
Is this possible after all? Which additional components are required?
Thanks!
Update: adding datasheet for the MCP3008, thanks Transistor.
Update 2: adding information about the PT1000 RTD.
Update 3: I found a posting (German) showing how to wire a PT100 to the MCP3551.
Is is possible to replace the MCP3551 with the MCP3008? How would I wire this?
The MCP3008 has a resolution of 10 bits, as compared to the 22 bits of the MCP3551. This will reduce the accuracy of the readings. Anything else I need to think of?


texts:
I would like to use a car microphone for bluetooth communication.

The mic is a BMW one: 84316938762.

The wiring diagram (TIS) marks the mic's two connectors for the pin 1 and 2: TIS (X18507).

However measuring with oscilloscope on these pins, there is pretty much nothing. (Measuring in AC mode, 5-10mV range).

How can I use this microphone? (If I need a pre-amp, please post some schematics, or a specific recommendation).

The BT module which I'm using is BC127, there is not too much info about the microphone's requirements.


texts: RTOS: Why Do We Need Special Post versions for ISRs?

texts:
In some RT kernels, if you want to post to a semaphore or flag from an ISR, you need to call an special version of the method, instead of the regular one called from a normal task. Examples:

xSemaphoreGiveFromISR() instead of xSemaphoreGive() in FreeRTOS
isr_PostSem() instead of CoPostSem() in CoOS.

However there are other kernels where this is not needed. For instance:

OSSemPost() in uC/OS can be called both from tasks and ISRs.
release() in mbed-rtos, can be called from Threads and ISRs.
semGive() in VxWorks seems to be callable from an ISR according to the docs, and at first glance no special method exists for ISRs.

Why would you need to create special versions? I understand that the posting of a semaphore or flag might cause a blocked task of higher priority to be awaken. And that's why the scheduler is most likely going to run when the ISR exit callback is called (I'm talking about those functions needed to be called when you want to use kernel code inside the ISR, like portEXIT_SWITCHING_ISR() in FreeRTOS, or OSIntExit in uC/OS). So why the special post method in addition to the ISRexit call?


texts: High speed passive probe - contradiction between authors or different points of view?

texts:
In a document Hiscocks et al. describes some basics of Oscilloscope probe theory. The document is very understandable and seems coherent. Notice in particular that for him, the bad guy is the parallel capacitance of the coaxial cable and of the oscilloscope that should be compensated by adding a capacitance in parallel to the tip of the probe (so, the capacitance of the tip is increased).

Then comes d. smith with his method to build a 1 GHz passive probe. First, it is not entirely clear why he terminates his probe by a 50 ohm resistance: to avoid reflections, isn't it sufficient that one side of the probe (that is the oscilloscope side) be terminated by a 50 ohm resistance?
I presume that this is to kill even more the reflections. So, let it be.
But what is strange for me is that he does not take into account the capacitance of the cable, nor the capacitance of the oscilloscope. In particular, for him, the beast that has to be killed is the tip capacitance (so he increases the parallel capacitance of the cable), the exact converse of what says Hiscoks in the document above.
If this man were a newbie, I would say that he does not understand why his probe works, and that he actually increases the capacitance of the tip with his copper foil. But hey! this man is a guru of probes that published several articles in different journals.

And now the best of the best, The Art of Electronics, 12.2 p. 808: to do a high speed passive probe? very simple:

  ... and make your own by hooking a series resistor (we like 950 ohm) onto a length of skinny 50 ohm coax (we like RG-178); you temporarily solder the coax shield to a nearby ground, plug the other end into the scope (set for 50 ohm input) and voila - a high speed 20 x probe!.

If my understanding is right, the 950 ohm resistor with the 50 ohm characteristic impedance of the cable make a 1:20 resistor divider (up to now OK), but what about probe compensation etc.? uh!

Can someone tell me what is going on?


texts:
What are the practical differences between LVDS and MIPI?
 A little background information:
I am attempting to build my own projector on the cheap and want to use a nexus 10 LCD panel (2560 X 1600 resolution) but I have been reading mixed information on its interface, some say it is LVDS and others say it is MIPI.


texts: Controlling a DC Motor via an analog PID circuit

texts:
I am trying to design a 1 DOF copter as in this drawing:

For this circuit there is a stick connected to a DC motor and potentiometer.  The potetiometer can be rotated.  I need to control the position of the motor with analaog PID circuit using another potentiometer.
My PID circuit is as below:

The first potentiometer controls the angle.  The output potentiometer should give feedback.
I am newbie and this circuit does not work, that means my motor does not work when I supply power.
I checked without the motor connected. There is a voltage and everything is okay but after connecting the motor, the voltage is zero and the system does not work.
Because of the pandemic situation, I cannot use the lab equipment to power supply. I think there is not enough current.

How can I increase the current?
How can I make sure the PID circuit is working correctly?

Some information my circuit components:

All op-amps UA741cp
Other component same with the designed circuit in picture
My motor is 820 coreless brushed motor set 3.3V =35000-37000 RPM, 5V = 50000 RPM , Size:8 x 20mm, working current min = 0.15A, weight 6.5gr


texts: How would I condition the signal from an accelerometer for a microphone input?

texts:
I'm looking to measure vibrations using a 3-axis analogue accelerometer connected the the microphone input on a PC. Ideally I want to combine the 3 axis into one signal as I don't really care about the x,y and z components, just the amplitude and the frequencies of the vibration.

I was looking at the Freescale MMA7361L, but I imagine anything similar will suffice.

I did an Electronics degree, but after many years of only using the digital, embedded and software side, my analogue knowledge is pretty rusty.

Can I combine the signals using appropriately selected capacitors or should I buffer them first?
I'm guess I'm going to have to do some level adjustment and impedance matching for the signal to be suitable for a microphone input?
Can I use a simple passive filter to remove frequencies over 20kHz? Do I need to do this?
What other considerations are there if I want to sample signals between 20Hz and 20kHz?


texts: Safe and feasible way to multiplex CAN bus?

texts: Is there a standard method or tool to connect more than one CAN bus to a CAN controller with single CAN interface? Each CAN bus would be directly connected to individual transceivers and then the Tx,Rx of the transceivers would be multiplexed to a single CAN controller? Any suggestions? I was thinking about using Analog switch ICs but most of them are not rated for automotive use and the electrical ratings are not desirable for CAN bus.


texts: Can a weak power supply damage connected electronics?

texts:
I have an RGB LED strip which according to what I found online can eat up to 8 A at the length I am using. I bought a power supply which supplies 5 V / 8 A and the LED strip runs fine off it.

I have wondered though, if I were to connect a power supply that is able to provide only say 5 V / 1 A and drove the LED strip to shine bright white light (making it require more power), could that permanently damage my LED strip?

I'd try this but if the answer is yes I'd not like to find out another way. I am also interested in if it could damage the power supply, but I wouldn't mind that as long as the LED strip remains undamaged.

I found a related question which seems to suggest with some more complex electronics, this can be a problem, but I don't think LED strip has anything in it which may cause a permanent failure in cause it is underpowered? It's an addressable LED strip so there are logic components in it, but there are no power transistors.


texts: Reverse voltage protection for Analog Devices’ family of protection controllers

texts:
After going through several datasheets for devices from "Analog Devices’ family of high voltage surge stoppers, overvoltage protection, overcurrent protection, and circuit breaker ICs", I found that external reverse polarity protection is done by the same method but found some differences in some details.

Below are three schematics from three different datasheets. I am interested in finding out why are these schematics different as I think that they shouldn't:

An explanation on how the reverse polarity protection circuit works is present in LTC4366 datasheet (page 20). I should note that the three controllers have similar absolute maximum rating for the gate pin negative voltage of -0.3V.

When comparing the 3 circuits:

The first circuit seems ideal as the diode D1 blocks excessive positive voltage from the input supply passing to the GATE and D2 prevents damage to the LTC4366’s GATE pin by clamping it at ground when the M2’s gate is negative. The 270k resistor R4 is small which will lead to faster switching-on time of M2.

The second circuit rely on the large resistance R5 to block excessive currents from passing to the GATE pin in the event of excessive positive voltage at the input supply or negative voltages present at M2's GATE.

The third circuit uses a diode to block the excessive positive voltage at the input supply but uses nothing to protect the GATE pin from negative voltages (perhaps rely on the resistance of R4(240k).

My question is: If the three circuits are intended for the same purpose of reverse polarity protection, why am I seeing 3 different versions and most important which circuit is the best?


texts: Custom device with multiple gates tied together in Eagle

texts:
I'm trying to create a transistor array device in a small library I'm working on in Eagle. The device has five P-Channel MOSFETs. The source of each MOSFET is internally tied together and connected to pins 1 and 12 of the SIP package.

For clarification, the datasheet is here: http://www.sanken-ele.co.jp/en/prod/semicon/pdf/sla5086e.pdf

I have created a standard P-Channel MOSFET symbol in my library, and I've created an appropriate package (SIP-12 with pads and drill holes, etc). However, I can't connect these to create a "device".

I'm sure I could change my symbol to be a boring rectangle with 12 pins, but I'd like to be able to place the MOSFETs individually on my schematic like logic gates from a gate array package. The problem is that there doesn't appear to be any way to connect all of the source pins together in the "device" editor after I've placed all 5 parts in the symbol area (so it won't let me use my package because there "aren't enough pads"), and, even if I could, there doesn't seem to be a way to connect a pin from the symbol to multiple pads on the package (ie, a source pin to both pads 1 and 12).

Am I missing something, or am I going to have to create a boring rectangle symbol with 12 pins for my FET array?


texts: Why is a linear passive circuit stable, i.e. why does its impulse response approach zero over time?

texts:
This is a silly question to ask because the answer might be obvious, but I still have my doubts.

If given a circuit composed only of resistors, inductors, and capacitors, if its impulse response decays over time, there should be negative exponents in that response. But that means that the complex roots of the characteristic polynomial should have negative (or zero) real parts. I assumed this was because the characteristic polynomial has positive coefficients but I later found out that not all polynomials with positive coefficients have no positive real parts in their roots. For instance, take a look at \$s^5+s^4+s^3+s^2+s+1\$.

I know there might be some physical explanation to this even though I'm looking from a mathematical standpoint.


texts:
I'm using Logisim to make basic circuits and they have in-built things such as Counter and D Flip-Flop. The D Flip-Flop looks like this:

It however doesn't show how it's made up of the basic gates (NAND, NOT, etc). I'm wanting to know how to create a D Flip-flop that can clear if Clear is equal to 1. I've tried searching it up but only get more complicated approaches to what I'm after.


texts: Can I safely run the microwave for an extended time with just a bowl of water?

texts:
I would like to leave a microwave running for several minutes (2-5, the longer the better) as part of a research project (I'm measuring the microwave emissions).

Is it safe to put a bowl of water in the microwave to prevent the magnetron from overheating? If not is there something else I could put in.

To answer the obvious question, I do not want to put food in the microwave because I intend to be running the microwave frequently, and it is not sustainable to buy a frozen pizza every time I want to run the microwave.


texts: DDR3 RAM, FPGA connection and termination

texts:
I want to use a DDR3 RAM in conjunction with a FPGA. The FPGA will control the DDR3 RAM. I am using a XILINX 7series FPGA. XILINX has a guide for this, on p.129 is the needed termination mentioned, this can also be seen in below image.

Point 3 states that unidirectional signals need a 40Ohm VTT termination. And bidirectional signals need the termination at both ends. I have a DDR3 memory with an option for a on die termination.
So when I use this on die termination do I still need the VTT termination?
The DQ Pins (data) are bidirectional so I will need a termination at both ends. All other pins are unidirectional, right? So they will just need a termination at the receiver side.


texts: How to charge Lithium Ion with protection circuitry

texts:
I am trying to build a charger for the Ctr 003 battery for the Nintendo DS.  This battery has 3 outputs, which I call +, 0, and - for simplicity.  When I measure voltage from + to -, or from + to 0, I get the same reading of 2.54V.  However, when I apply arbitrarily small current from + to -, the voltage jumps arbitrarily high, and then trickles back down to 2.54.

I've had this happen in protected laptop batteries.  The protection circuit kept the batteries from charging, unless it thought they were inside a laptop.  This problem could be overcome by running an appropriate resistor between two non + or - ends of the battery.  However, in this case, there is only one end that's not + or -.  What other means do there exist, to fool the protection circuitry into thinking that the battery is inside a Nintendo DS?

I'm not expecting a full answer; it would be great even just to get some ideas of what I could try with other three-output protected batteries.


texts: MOSFET \$I_{ON}\$ formula in the book CMOS VLSI design

texts:
This screenshot is taken from CMOS VLSI Design by Weste and Harris. According to the square (Shockley) model, the current in saturation is given by the following equation:
$$I_{ds} = \frac{\beta}{2} \cdot V_{GD}^2$$
And according to the previously screenshotted paragraph, \$I_{ON}\$ is the current when \$V_{GS} = V_{DD}\$ and \$V_{DS} = V_{DD}\$. This means that it's the maximum current in saturation. However, using the previous equation, It can be deduced that
$$I_{on} = \frac{\beta}{2} \cdot (V_{DD} - V_t)^2$$
What am I getting wrong here?


texts: Help Powering 2x10W LED using a 15v 1A power supply

texts:
Beginner here, trying to build a lighting using two 10W SMD LED'S.
Please advise me for a better and efficient setup.

Here are my specs.

Power Supply DC 15v 1A

LED specs: Input voltage 9-12v

Forward current: 300mA

Here is the schematic, using two 7812 IC's.

Please correct me if i am doing this entirely stupid, LEDs are lighting up in full brightness but generating a lot of heat so I doubt something is wrong with the current distribution. FYI LEDs and 7812's are mounted to heatsinks.

Or should I use a switching converter with a current limiting setting like this one https://www.aliexpress.com/item/DC-DC-LM2596-HV-S-60V-3A-Buck-Constant-Current-Voltage-CC-CV-Step-Down-Module/32756952440.html


texts: I had the SainSmart UNO+LCD Keypad+Prototype Shield+HC-SR04 Distance Sensor. Didn't buy them combo.I am somewhat new working with the Arduino kits and was hoping you could show me a guide of how the boards are connected. I am using this kit for a school project and am having a bit of trouble.


texts: Why am I measuring earth to line voltage as zero? Is that what it supposed to be?

texts:
I have a confusion about the topology below:

I was wondering the potential difference between the line and earth.
So I decided to check this through a 3-prong plug.

I thought I would read the same voltage as line to neutral, since neutral and earth are supposed to be connected.

But when I measure the voltage between the line and the earth, the voltmeter shows zero volts.

What does that mean?


texts:
I have this question, which I thought I knew how to do, however my method is wrong somewhere. I converted the numbers to binary, removed 1 then inverted them to get them in normal binary format. I then added 4 leading 0's to give me a 16 bit number then converted it back to two's complement in hex giving FEF7 Hex, which is the correct answer. However applying the same method to the second number gives F7FE, which is incorrect, as the answer should be 0F7E Hex according to the mark scheme. Can you please tell me where i'm going wrong?

Thanks


texts: Anti-wind up scheme in the implementation of PID controller

texts:
I want to implement designed PID controller. But I am facing the problem of how to limit the saturation limit in both positive and negative direction? I tried using zener diode, but I would like to know if are there any design procedures to get anti-wind up scheme in the  implementation of PID controller using zener/diode combination?

EDIT:

this is the designed pid controller and i am using TL084 op-amps which has +15 volts and -15 volts as their supply. when the error is generated, due to integrator the control signal(Vc) output is going to saturation point of nearly 15 volts. I want Vc to be in the range of (0.85-3.8 volts), so that i can give this to SG3524 PWM IC to generate constant duty ratio PWM pulses. I tried by putting zener diode of 3.3 volt rating, but now Vc is coming upto 3.5 volts(basically saturation limit has come down to 3.5 volts) . The problem is how to limt the Vc to the specified range.
Can any one please suggest modifications for proper design of anti-windup  working scheme of this.
Here VFb=-3 volts and VRef= 3 volts


texts: Talking to Logic Motion Controller (LMC 300) via USB

texts:
I have a Nilan Compact-P heating system in my home and it has a USB connector. When I plug it in my Windows Laptop automatically the driver for "lmc 300" is installed and a COM Port opens up.

This is the panel where I can control temperatures and read the info from (but can't export)

My goal is to talk to the controller to read information about the heating system like Temperatures, status (currently heating or not), etc..

What I know by now:

A technician of the company said they use a software called "loader multitool" to read the data via USB. I didn't find any software by this (pretty generic) name via Google. Has anyone of you heard of it?
The Engineer also talked about some "motus module" but that also doesn't bring up many answers on Google
I tried talking to the Heating system via the COM Port and Putty. No reply whatsoever but then again I don't even know its baud rate

Has anyone of you heard of this LMC and knows how to talk to it?


texts: What does "6 V stop-start applications" mean?

texts:
I read the following in the NXP TDF8530 leaflet:

  this ultra-efficient device supports 6 V stop-start applications and delivers
  audiophile sound quality

What does that "6 V stop-start applications" mean?


texts:
I need a 3 phase power supply for Lab purpose. Since using 220 V x 3 phase is dangerous, I'm searching for a three phase step down transformer and that seems not available. Am I asking something which is not commonly used?

Input : 3 phase, RYB, 220 V AC
Output : 3 phase, RYB, 12 V AC

I'm looking for a transformer just like the power companies do - 11 kV to 220 V, 3 phase - similar transformer from 220 VAC to 12 VAC, 3 phase.

Any directions? Pros / Cons - why not available easily, any references?


texts: Does 3x22μF mean three capacitors of 22μF in parallel or series?

texts:
In the following schematic (TPS63061) several capacitors are denoted as multiples. As a newbie I am unfamiliar with this notation: does 3x22μF mean three capacitors of 22μF in parallel or series?

See figure 8 here: http://www.ti.com/lit/ds/symlink/tps63061.pdf


texts: Capacitor for TF CARD placement on PCB layout

texts:
I am currently laying out a PCB where there is a TF CARD on it. The schematic is as below. I have this capacitor to place which I suppose might be a decoupling by pass capacitor, so unless my mistake I have to put it close to the power pin which might be VCC.
However we have a connector for this TF card and the connector of the VCC pin is just below the connector/slot so I can not place the cap directly close to the pin.
What woudl you recommend :
1./ Put the cap on the same layer on the edge of the connector ?
2./ Put the cap on the other side of the PCB and create a via ?


texts: connect 2 speakers to act as a telephone

texts:
I've got this very faint memory from my childhood that my dad connected 2 pieces of old, 5 cm diameter speakers to each other with a 10 meter wire. And without any other equipment, it would transmit the sound between rooms. Not loud or anything, but volume was enough to hear what the other was saying.

Got me thinking, after all, the sound waves move the coil, that generates electricity that would move the coil in the other speaker too. If the mouth is close to the speaker, it could work.

But I never found anything like that while googling for this. Could this actually work?


texts:
When I transmit serial data on an ATmega2560 I sometimes get bit stretching, corrupting the characters:

I send character 0x55 twice at a baud rate of 115200; this is the yellow trace in the image. The red trace signals the start and end of the interrupt routine sending the characters.

The first character is fine. The falling edge is the start of the start bit, followed by 8 data bits (LSB to MSB) and then the stop bits (starting at the last rising edge).

The time for the 9 bits (start bit plus 8 data bits) is 78us; consistent with a bit time of 8.68us (115200 baud).

The second character is corrupted: two of the data bits are stretched. The start bit and the other data bits are fine.

This seems to happen randomly.

Is there anything that can cause this?


texts:
So I'm building a small audio mixer (or rather planning to do so) and I'm about to go shopping components and it's a jungle out there.

My circuit says plainly 1uF with the regular capacitor symbol. There is no plus-minus signs in the symbol, does this mean that I should not use an electrolytic capacitor?

If that is the case will any ceramic or polyester capacitor whitin specifications of voltage and Farad do the trick? How should I think about this?

simulate this circuit – Schematic created using CircuitLab


texts: Memory chips, are the bits of a long word stored contiguously?

texts:
I am reading Structured Computer Organization, 6th edition by by Andrew S. Tanenbaum and Todd Austin. Chapter 3.3.5 talks about memory chips. I'm confused about the following paragraph, which relates to the diagram on slide 17 here: http://www.iro.umontreal.ca/~boyer/IFT1227/H09/chap3-1x2.pdf

  Years ago, the largest memory chips were often organized like Fig. 3-30(b).
  As memory words have grown from 8 bits to 32 bits and beyond, 1-bit-wide chips
  began to be inconvenient. To build a memory with a 32-bit word from 4096K
  ×
  1
  chips requires 32 chips in parallel. These 32 chips have a total capacity of at least
  16 MB, whereas using 512K
  ×
  8 chips requires only four chips in parallel and al-
  lows memories as small as 2 MB. To avoid having 32 chips for memory, most chip
  manufacturers now have chip families with 4-, 8-, and 16-bit widths. And the
  situation with 64-bit words is even worse, of course.

My thinking is that memory is just one giant array of bytes, and loading a 32-bit integer just grabs 4 "adjacent" bytes. But if the memory is comprised of chips that each have 8 data lines such as in (a), does it actually read a byte at the same offset within each chip from 4 separate chips at once, and then merge the result?

Also, the book doesn't explicitly say what kind of advantage chip (b) has with its single data line, but my guess is that all of the memory can be reachable (though at less bandwidth overall?) using fewer data lines in total. A 16MiB memory of 32 (512K x 8) chips would have 256 data lines, for a density of 65KiB/dataline. A 16MiB memory using 32 (4096K x 1) chips would be able to load a 32-bit word, but with only 32 data lines at 524KiB/dataline.
Is this a possible advantage for chip (b), and is my work correct?


texts: Interface optocouper with wide voltage range

texts:
I need to interface optocopuler with my GPIO (3V Max) to detect presence of a wide voltage range in the optocopuer input (5V - 30V). After searching all different parts I have come up with this parts and circuit. Please let me know if it is a correct.

simulate this circuit – Schematic created using CircuitLab

Datasheet of VOD207T http://www.mouser.com/ds/2/427/vod205t-537247.pdf


texts: I have a small circuit board that has no mounting holes but does provide unpopulated test point pads. Is there any option for machine screws or standoffs that I could solder into these for mounting the board?


texts: Dot convention in Magnetically coupled circuits

texts: The book says that the for loop 2, the KVL is \$-j3 I_{1} + (12+j6)I_{2}=0\$ , but the loop 2 leaves the dot in its coil. Isn't it supposed to be \$-j3I_{1} + (12-j6)I_{2} =0\$ ?


texts: How I find the current and voltage in this matrix?

texts:
My book above uses nodal analysis to find the current and voltage across the resistors.

Now consider this alternate circuit:

Look at the branch that doesn't any components (the second straight line with no components). How would I find the current across it? I only know Kirchoff's Laws and Nodal Analysis so far. Can the current across it be found using these techniques?


texts:
We need to use 1PPS (pulse-per second) in our standalone system which is based on arm processor, and  has cameras input.

The 1PPS is implemented with GPIO which is injecting an interrupt (low to high) every 1 second.

The 1PPS is needed for a timetag of video captured frames.

I try to understand the motivation of using 1PPS in such a standalone cpu system:

Today cpu already have high resolution timer within its soc/processor, than what's the added value of using PPS in such system ?


texts: How to select the compatible USB to SPI IC Programmer?

texts:
I built an image of Coreboot (open source firmware) and wanted to flash it on the Minnowboard Max. SF100 is compatible to do the job (as described in this article). However, I want to be clear on the compatibility and possibly want cheaper alternatives.

SPI protocol is the standard one, so I believe except the pin layout exposed by the development board SPI IC connector, the underlying job must be same for all the SPI IC programmers. But I am still not sure.

What should I take care of, so that I am sure that the programmer will be compatible with my development board.

EDIT

I searched regarding the BIOS EEPROM chip on my SBC and I got to know its an SPI based chip. At the same time, I also came across people using Raspberry Pi / Arduino with flashrom to flash BIOS on their laptops and motherboards. So technically I should also be able to flash BIOS using a SPI master device (say raspberry pi) instead of buying dedicated costly devices (provided I follow correct connections and voltage levels recommended for the chip).

I see no technical limitations with this approach. Please correct me if I am wrong.


texts:
In a new design I would like to use the MAX682. In the datasheet I found this typical operating circuit:

I would like to use it exactly like that except that I'm going to pull /SKIP to GND.

In table 2, I find the recommended values for the capacitors: CIN should be 2.2uF, CX should be 1uF and COUT should be 47uF (tantalum) or 10uF (ceramic).

First of all, why does the needed capacity depend on the type of capacitor? And secondly: from the circuit it looks like I can't use electrolytic capacitors for CIN and CX. Is that correct? Why is it so, because it seems clear that the polarity won't change. I would prefer to use electrolytic capacitors because I have them in stock.

I actually did a quick test myself and used electrolytic capacitors everywhere. In total, the circuit drew about 110mA, while the 5V circuit drew only 2mA. And besides that, the output has about 0.4V AC noise. However, it's not entirely sure that this is just because of the capacitors, because I for example didn't use a very short trace between GND and PGND (pin 1 is top left):

So it really isn't possible. The question remains why.


texts: Industrial Control Voltages 120VAC or 24VDC

texts:
Lately I have been designing some industrialized products (Industrial Arduino / RP IO boards) for use in automation environments. I have worked in the automation field briefly when I was younger and all of our control voltages were 120VAC. I see a lot of people using 24VDC now and only a few clients ask for 120VAC compatibility.

Without this sounding like an opinion:

Is the automation and controls industry moving away from 120VAC for the safer and more world friendly 24VDC? Or should I be thorough and continue to support both 120VAC and 24VDC?


texts:
A 3 phase fully controlled bridge converter is fed through star-delta transformer. The converter is operated at a firing angle of 30 degrees. Assuming the load to be a RL load and load current to be virtually constant at 1 pu and transformer to be an ideal one, how will be the input phase current waveform look like ?

Edit:

I was expecting the following result

but to my surprise the answer is the following waveform.

Definitely I'm making some mistake, please tell me how the waveform came.


texts: Read from UART seems to overwrite while in buffer

texts:
I am reading sending data to a PIC32MX7xx using UART. The data frames are all 6 bytes long, no exception.

The problem I am facing is that when there are 6 bytes waiting to be read and I send another 6 bytes too fast, the PIC locks up.

I am reading the bytes out in packets of 6 and writing them to a buffer to be put on a CAN network (but that's not important).

typedef struct {
    WORD id;
    DWORD data;
} WiFiRXPacket;

BYTE *WiFiRXTemp = NULL;
WiFiRXPacket* WiFiRXBuffer = NULL;
int RXelements = 0;
int RXallocated = 0;

void TCPReceiving()
{
    int dataAmount = 0;
    int i = 0;
    int j = 0;
    dataAmount = DataRdyUART1();

    if(dataAmount != 0)
    {
        WiFiRXTemp = (BYTE *) malloc(6 * sizeof(BYTE));
        if(WiFiRXTemp)
        {

            while(i<6)
            {
                WiFiRXTemp[i] = getcUART1();
                i++;
            }

            WiFiRXPacket packet;
            packet.id = ((WORD)WiFiRXTemp[j]) << 8;
            packet.id += ((WORD)WiFiRXTemp[j + 1]);

            if (packet.id != 0)
            {
                packet.data = ((DWORD)WiFiRXTemp[j + 2]) << 24;
                packet.data += ((DWORD)WiFiRXTemp[j + 3]) << 16;
                packet.data += ((DWORD)WiFiRXTemp[j + 4]) << 8;
                packet.data += ((DWORD)WiFiRXTemp[j + 5]);

                PutInTXBuffer(packet.id, (QWORD)packet.data);   // Send the received command back for confirmation
            }
        }
    }
    free(WiFiRXTemp);                   // Deallocate the buffers memory
    WiFiRXTemp = NULL;                  // Re-initialize the buffer
}

Does anyone have a clue why this happens?


texts: What does "limit cycle" mean in delta-sigma modulator?

texts: Could anyone explain limit cycle related spurious tones? It is stated that a higher order modulator is better than low level one because of limit cycle related spurious tones, but I don't have picture of the limit cycle. Does it mean the tones in DC input and this tones in DC with period appear to be an increasing high frequency tones?


texts: Driving Permanent Magnet DC Motor via PWM

texts:
SUMMARY:

I am currently trying to finish up a DIY project I've been working on for a while: Building an electric potters wheel. I acquired a treadmill and salvaged quite a few good parts from it, and thought this would be a great way to put it to use. Unfortunately when I got everything together, and after a few tests I committed a terrible crime: I dropped a washer on my MC-60 motor controller board. As you guessed, on my next start-up there was magic smoke everywhere.

So I have all the physical assembly completed, and a good condition treadmill motor without power supply. So I'm venturing into salvaging and building my own, not spending $50-$100 on a new board if I can help it.

I have been doing quite a bit of reading over the past few weeks and came to the conclusion that PWM supply offers the most consistent torque, and this was what I was concerned about. I don't want the thing to be choppy and low torque, so I'm going to do some physical reductions with pulleys/gears to be able to maintain a decent amount of torque on the motor.

I've completed my PWM circuit with the quick help of Netduino isolated with Opto to drive mosfets. Everything seems to be fine, yes I'll have to adjust components to varying voltages as time moves forward.

QUESTION:

I know I don't have to drive this thing with full 90vdc to get the small amount of toque/rpm I need correct? I mean it's a pottery wheel, not a lathe. I figured I might need 30-40vdc max, or is this a bad assumption? Will this drastically lower my torque to an unusable level? I really would like to avoid dealing with 90vdc PWM, that seems like way overkill.

PROPOSAL:

My theory on the power supply is I could simply use a transformer to reduce a 110vac voltage to say ~50vac (or whatever necessary) and then rectify and smooth this resulting DC voltage to a usable limit. Then drive this through the MOSFET, to the "clutch" (which helps further smooth any ripple), to the motor. Am I headed in the right direction or am I under-thinking something here? I just really don't want to waste anymore money on components until I can be certain it's the correct way to go. I also don't want to waste money on a control board that is complete overkill for my needs. All I need is simple on/off with a little bit of speed control, nothing really specific.

Thanks for any help.

Motor Specs:

Permanent Magnet DC Motor

Electrical Rating:
    @130vdc  2.5hp  6700rpm 18amps
    Continuous Duty  @95vdc 1.5 hp

ADDED:

Just realized it would probably be better to maintain a higher voltage to keep as much torque as I can, and adjust the duty cycle. Rather than adjusting the voltage to say 60vdc and then PWM that..


texts: FPGA - What is the maximum allowed DRAM capacity on an XUPV5-LX110T Development Board?

texts:
I have purchased an XUPV5LX110T FPGA Development board and am unclear as to the size of the DRAM that can be upgraded.

Currently I have a SODIMM 256MB that I am looking to increase for the possibility of using a good portion as Frame Buffering memory for a GPU Project I am undertaking.

If expandable, what compatible chips can be used as a substitute to the default DRAM that is provided with the board?


texts: Ethernet communication with UDP/IP stack working with direct connection but doesn't work through my LAN Switch

texts:
I working on Ethernet Interface on the FPGA.  My goal is to send and receive UDP packet to my FPGA over the LAN.
I found this reference:
https://github.com/alexforencich/verilog-ethernet
this great reference provides working MAC G/MII with UDP/IP stack using Verilog on FPGA.
I instantiated this ethernet core to my project and tested the results,
in the first case, I have my FPGA with Cat6 connected to Ethernet<->USB-C adapter connected to my PC.

I configured this connection in the 'Network Connections @ Control Panel' to have an IPv4 suitable to the IP I have on the FPGA and check the result using Analyzer on the FPGA and Wireshark on PC.
I can see that I broadcast from my PC ARP request and the FPGA response to it and tell to my LAN what is his MAC address, after that I can see the FPGA using command line (arp -a).
the FPGA response is:

the dest mac address is: ---------
this is the USB-C <-> Ethernet connection MAC address,
the src mac address is: 00_01_02_03_04_05
The dest&src IP address are correct.
Everything great so far, Now I want to connect the FPGA to my room LAN, I have D-Link Switch which is connected to all the devices in the room, I want the FPGA to connect to it as well.
ok, so I connected the FPGA with Cat6 cable to the Switch, and the PC already connected to this Switch as well.

I configure the connection and added another IPv4 (besides the IP that connects to the Network) suitable to the FPGA IP.
Once again I can see the ARP request broadcast on the Wireshark, the FPGA catches this request and transmits a response which I need to arrive at my PC to successfully connect the FPGA to the LAN.
But using Wireshark the ARP response from the FPGA never arrives, its like the ethernet packet is lost inside the Switch somehow.
The FPGA response on this case:

the dest mac address: ----------
this is the Switch <-> Ethernet connection MAC address.
src mac address: 00_01_02_03_04_05
and once again the dest&src IP address right
I can see this packets go through the design till it goes out from the output pins on the FPGA (phy_txd[7:0], phy_tx_en..).
Any idea what is going on? where to investigate? I feel stuck here.
If additional information &/ code needed please reply and I add these.
Thanks!

Edit 1:
I'm using Lattice ECP3 Versa Evaluation Board with Marvell PHY 88e1111.
OK so as Alex suggested I made another testing environments:
case 1: "working case" - through USB-C adapter.
case 2: "not working case" - straight Cat cable connection.
even without a switch, cat6 from FPGA to the PC doest work either.
compare of the packet the FPGA sending between the cases:

Edit 2:

OK so that's mean the switch isn't the problem, when it connected through usb-c adapter somehow its working.. when its just rj-45 to rj-45 its not working, made me even more confused... any leads please?

Edit 3:
Alex suggested the right solution, it was a problem in the TX FCS bytes, the CRC block doesn't work well with Lattice tools, so change it to a simpler module fixes the FCS.


texts: Does solid/multi-stranded/Litz wire make a difference in binary serial output?

texts:
I'm using two shift registers to control 16 digital outputs using only 3 pins on my microcontroller. The parallel outputs carry <= 20 mA DC, their sole purpose is to power LEDs. My microcontroller pins do the following:

One is a serial binary data stream (5 or 0 Volts DC). In my case it's a 16 bit periodic pattern which mutates every second.
One is the input clock pulse for the shift registers. It sends a HIGH pulse for each bit in the data stream. Depending on how I tune the program, the frequency could be anything from 50 Hz to about 16 MHz.
One is the output latch clock pulse for the shift registers. It sends a HIGH pulse for every 16 bits in the data stream.

Does it matter whether I use solid, multi-stranded or Litz wire in this project?

I've read that the main point of Litz wire is to reduce AC resistance at high frequencies. I suppose nothing here really qualifies as AC, and I'll admit the question is mostly academical. But I'm a bit curious since there are some (possibly) high frequencies involved. This formula and these values from Wikipedia give a skin depth of 65 µm for copper at 1 MHz, so the skin effect certainly is significant, at least for true AC.


texts: My BLDC motor is stuttering and I have no idea why

texts: I'm driving 2 BLDC motors with two ESCs, the motors and the ESCs are powered by an external LiPo battery and the Arduino is powered via usb. The motors work with pulses between 1000 and 2000 microseconds but during testing (where we accelerate them from 1000 to 2000) the motors stop after about 1350 and before that they stutter like this: https://imgur.com/1HgRoIa


texts: is there a way to relate a frequency to other frequency by some circuit or mcrocontroller

texts:
A circuit that outputs a fraction of the input frequency controlled by some micro-controller or electronic circuit or component.

Say I am feeding the said circuit f-in( say 2KHz) and the circuit outputs

f-out = (1/4)*f-in ( implies 500Hz). Is there some way to do this

I couldn't find anything on google, so I came here.
so,please guide me in the right direction


texts: When should you or shouldn't you use a specific fet?

texts:
When are P channel mosfets used instead of N channel mosfets?
When should you NOT use a P channel mosfet instead of a N channel mosfet, and vice versa?
When should you use a Jfet?

I just want to get a good comparison going between the different channel mosfets.


texts:
Hi,
I have two ways of thinking about this and I don't know which is more correct:
Explanation A
There are essentially two devices there, each trying to force a different current into the same branch. The lower current device will always win, which is the PMOS M2 and cause the NMOS M1 to be driven towards the edge of the linear/saturation region, hence the VDS of M1 must fall, in other words the Vout must fall!
PMOS Current Mirror: see @BimpelRekkie's answer here.
Explanation B - this is what I think @DavideM means.
There will always be a parasitic capacitance on the output node. Thus, if M2 is injecting less current into that parasitic capacitor and M1 is sinking more current to ground from that capacitor, the voltage on the output should fall. This aligns with what Razavi says.
Explanation C - I just had a another thought, this makes a lot more sense to me as well but I'd like to confirm. Assuming that both transistors are operating in saturation, theoutput resistance (ro) is defined as 1/lambda*Id and thus the ro of each transistor is inversely proportional the square of the Vgs or Vsg in the PMOS case.
If the Vgs of the NMOS increases, the output resistance ro for the NMOS will fall, while the Vgs increase of PMOS (Vsg fall) means that the PMOS ro will increase. Thus, the output voltage formed with this voltage divider will fall!
All of these make sense to me! But I want to confirm which would be more accurate or is there a combination of the three?


texts:
I have understood that there are both input and output parasitic capacitances in real op-amps, but I am trying to understand why they are there.

As for the input capacitance, there are two types:

Differential: it is the parasitic capacitance between the inverting and non-inverting pins of an op amp
Common-mode: it is the parasitic capacitance between each input pin and ground.

Is that right?
For the output capacitance, I don't know where it comes from.
Also, I  understand that this capacitances are almost always neglected, but they may affect our circuit if the frequency becomes extremely large, right?


texts: How to find system overshoot (Mp) from Bode diagram

texts:
In some questions (in linear control theory) it is desired to design a controller to change the system overshoot (Mp), my question is:

  Is it possible to find Mp or damping factor directly from Bode diagram without estimating the transfer function of the system?


texts: Why do I get a triangle wave in this Schmitt trigger oscillator?

texts:
I'm trying to design a function generator that can generate square, triangle and sine waves, with frequency varying between 100Hz and 100kHz.

The circuit in the blue box is supposed to be a schmitt trigger with thresholds different from those of the NOT gate. the thresholds change when we change the Vb voltage and hence, the frequency changes. (I'm actually using a CD4093B NAND gate with one input in high voltage).

This part of the circuit was suggested by my professor, but I have been trying to get it to work in Proteus and instead of a square wave, I'm getting a very neat triangle wave in the output pin of the gate, which doesn't make sense to me, since I thought this pin was supposed to have either a high, or a low voltage and not much in between.

This is the simulation result from this part of the circuit. The graph shows the voltage at the output pin of the gate:

Can someone please explain why this is happening, and possibly suggest a solution to this problem?

I am only allowed to use resistors (not variable), diodes, capacitors and one CD4093B ic.

Thank you in advance


texts: frequency domain S11 convertion to time domain TDR

texts:
bellow we see the S11 plot of a transmission line the wikipedia definitions of the reflection coefficient as a function of S-params.
As i see it S-param frequency domain plot comes from time domain steady state.
TDR is time domain in every moment from the start(transient)
So how can we convert from S-param (steady state ) to TDR(transisent)
how its possible?
Thanks.


texts: STM32 - Getting HardFault when assigning uint32_t value

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Getting hard fault when assigning this 32 bit value to the shown variable(val_32);
  uint32_t val_32 = *((uint32_t *)( &buffer[0] + length - 4));

  or

  uint32_t val_32 = *((uint32_t *)( &buffer[length - 4] ));

Same thing but tried:
  uint32_t val_32 = *((uint32_t *)(buffer + length - 4));

Declarations of the variables used;
uint8_t buffer[200];
uint8_t length;
System:
MCU = STM32F072C8T6
Keil v5.23
When i debugging, hardfault occurs at stepping over this code. Though without stepping over i put that code to the watch window and get the result i expected. Dont know what is my mistake or how to fix it. Thanks for the help.


texts: What does 'L' mean in the name of motor driver IC "L293D"?

texts: i was wondering what the letter L in the name L293D stand for and what does it mean.


texts:
I have a USB to RS485 converter:

It has a CH341 chip, that is all I know about it. When I plug it in, I can see that it is bound to port ttyUSB0. I want to be able to send and receive bytes from PC (Ubuntu) to a STM32 board. The board side is not a problem, but rather the PC side.
Does someone have experience with such a device? Do I write the bytes that I want to send onto this serial port and the magic will happen, or does it have some special protocol, config bytes or command bytes or such? The datasheet is basically 1 page with literally no information in it.
I am not familiar with serial port programming under Linux, but it will be fun to learn it. I just wanted to know whether I have to pay attention to anything special before I start working on this home project.
Any information, code snippet or just advice or experience is very welcome :)


texts: Powering Pi Zero + Arduino Micro for brief interruption in supply

texts:
I have this toy I am making for my toddler that includes Arduino Micro and Raspberry Pi Zero (plus 10 APA-102 RGB LEDs and audio amplifier that feeds a 3W speaker.

This all is powered through a 5V USB power bank. It serves nicely for a battery, also when the power bank itself is changing via the supply cable. The problem is that when the power bank supply cable is disconnected from the supply (usually a power adapter in wall socket), there's a brief power loss to the output sockets that causes reboot for both Arduino and Zero.

I am looking for a reliable solution to keep the devices powered for that brief moment. Something connected in parallel to the power bank output. Perhaps a reasonably large capacitor would do? I am afraid if the capacitor would discharge too quickly and damage the devices. A small rechargeable 5V battery could do, but that seems to be an overkill.


texts: MCP41100 Power supply and grounding ? Analog ? Digital?

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I'm thinking of using an mcp41100 digital potentiometer to control an op amp gain.
My board will have a split ground plane - digital and analog grounds.

Unfortunately the mcp41100 doesn't have separate digital and analog power/ground rails.

How should I power and ground the chip ? Digital/Analog supply/ground ?