texts:
I have the UE910 cellular module from Telit. I have manufactured a PCB containing the module but it's not working (power is reaching it but serial program not communicating with the tx and rx pins). I know now that the problem maybe is that I left 2 pins ("On/OFF" and "HW_Shutdown") unconnected even though the datasheet recommends connecting them.

I attached some screenshots from the datasheet.

It is written however that the "HW_shutddown" pin can be left floating as it is internally pulled up so it might be the "ON/OFF" one that need to be connected. Can you help me state the functionality of that pin? Do you think it is the reason why the module is not working?


texts:
When I was little, the general advice for electronics hobbyists was to socket all their ICs.  Indeed you would find the word must referring to the need for sockets.  This was to prevent thermal damage to the chips. There were even sockets for transistors.

Then surface mount technology came along.  It's harder (perhaps well nigh impossible) to hand solder some of the dust like surface mount components.  Yet we automatically try to.

I realise that high frequency circuitry can suffer from parasitic impedances due to the socket.  But I'm still thinking of the super simple hobbyist like me.  I don't want to dwell on any particular chips, but consider the unremarkable LM358M op amp in SMT form.  It has a humble bandwidth of only 1 MHz so impedance is probably not of concern.  It runs on a proper 15V.  Yet if used tonight, it would be soldered directly to a PCB.  No one would flinch at a recent Elektor Magazine article telling them to do so.

Similarly I have a 6502 processor.  Advice in the day would have been absolutely to socket it.  Many people now directly solder on SMT Amtel controllers with no consideration of sockets.  And hands up, who used a transistor socket last year?

What changed? Why were hobbyists advised to socket ICs before, but not now?

(I'm focusing on hobby level PCB fabrication, not bread boarding.
I'm not really looking for a treatise on the benefits of SMT per se.)


texts: Need help identifying a component that I think is a varistor.  It is burnt so it appears black.  The circuit is part of a control module for the headlights and keyless entry on a Lincoln.  I want to replace the part but can't seem to identify it's value so I can match it up.


texts: Detect Modbus RTU start of frame and end of frame

texts: I have implemented Modbus RTU slave in PIC12F1840. My problem is I have not implemented detection of start of message in the slave device. Any guidance on how to implement it?


texts: Is there a reason not to put a beefy cap on the output of a homemade power supply?

texts:
I'm a beginner in electronics, and in the process of completing a homemade power supply would love to get some advice.

The power supply itself is fairly straightforward - I'm using a laptop power supply with an output of about 20V and it powers my circuit which consists of:

2 fixed at 3.3V and 5.0V
2 adjustable with voltage and current limit
and another 5.0V to power an arduino nano
4 INA219 breakouts to measure each channel voltage and current
an arduino nano to collect the data
and an LCD to display voltages, currents, current limits, etc.

It all works, however, when I attach my homemade (arduino based) oscilloscope to the outputs, I'm noticing some ripple on the 3.3V and 5V channels, adding a 100uF cap improved it but didn't get rid of it, so I upped it to 1000uF which got the job done, (or at least within +-0.03V which is the margin of error of my crappy home-made oscilloscope).

So, the question is - is there any reason not to put a 1000uF cap at the outputs of these channels?

I don't have a schematic because the circuit was simple enough, so I didn't make one before implementing it.

To simplify my question further, imagine just a DC power source and a step-down switching voltage regulator, would there be any reason not to put a 1000uF capacitor on the output of the regulator?

EDIT: Added line breaks, I couldn't figure out how to do it last night. Sorry for the mess.


texts: Power dissipation BJT transistor as voltage follower

texts:
Following the discussion from this thread I am finalizing my calculations. I am not sure that I am calculating the power dissipation correctly. Given the following circuit

I need to operate the opamp between 0-2.4V in 100mV steps, sometimes holding the values for 30min. With V_cc=3V and V_Bas=1V, V_Emit=0.5V. The collectorcurrent reads I_c=0.13mA and I_emit=0.043mA. At this conditions the Power loss calculates as

  P_loss = (V_cc-V_Emit)*(I_c-I_emit)

I draw the power loss with the above formula over the range of V_in

Can I choose the right transistor based on this calculation (max ~430uW)?


texts:
Microelectronic Circuits by Sedra/Smith present a method to analyze series-shunt feedback circuits by separating the 'A circuit' from the 'B circuit' in which h11 and h22 are consolidated into the 'A circuit' along with source and load resistances and h21 is neglected:

The open-loop gain A is determined by Vo/Vi:

Everything makes sense until they present the following example circuit:

They redraw the circuit so that the 'A Circuit' (on the left) and the 'B circuit' (on the right) are clearly shown:

I've highlighted the part that I don't understand. Why are R1, R2, and the input source returned to ground? If the parallel combination of R1 and R2 constitutes h11, then these resistors should not be returned to ground as per the first image I posted. What they seem to be doing is this:

So the question is: what's the justification for connecting h11 and Vi to ground when no such connection exists in the first image I posted?


texts: STM32 NVIC interrupts after a reset / power-on

texts:
I have a few active-low signals that I want to interrupt on. During normal operation, the interrupts work just fine. However, on reset / power-on only rising edge is detected.

In other words, on start-up my routine is called when the interrupt line is inactive (pulled-up to VDD). If the line is active (LOW), the function is not called on start-up.

I tried disabling the rising edge trigger, but that didn't help.

Is this expected or am I doing something wrong? What would be the best way to work around this issue?

TLDR: How do I get my interrupt routines called when the interrupt signal is in a stable LOW state at the time of power-on?

Here is my code:

#include <stm32f2xx.h>
#include "DBG.h"

void EXTI3_IRQHandler(void)
{
    DBG("EXTI3\r\n");
    EXTI->PR |= EXTI_PR_PR3;
}

void EXTI4_IRQHandler(void)
{
    DBG("EXTI4\r\n");
    EXTI->PR |= EXTI_PR_PR4;
}

void DI_interrupt_setup(void)
{
    /* enable syscfg controller clock */
    RCC->APB2ENR |= RCC_APB2ENR_SYSCFGEN;

    /* unmask relevant interrupt lines */
    EXTI->IMR |= EXTI_IMR_MR3 | EXTI_IMR_MR4;

    /* enable falling edge triggers */
    EXTI->FTSR |= EXTI_FTSR_TR3 | EXTI_FTSR_TR4;

    /* enable rising edge triggers */
    EXTI->RTSR |= EXTI_RTSR_TR3 | EXTI_RTSR_TR4;

    SYSCFG->EXTICR[0] |= SYSCFG_EXTICR1_EXTI3_PD;
    SYSCFG->EXTICR[1] |= SYSCFG_EXTICR2_EXTI4_PD;

    NVIC_EnableIRQ(EXTI3_IRQn);
    NVIC_EnableIRQ(EXTI4_IRQn);
}


texts: Is it possible to make hierarchy of constants in System Verilog?

texts:
Is it possible to make a synthesizable hierarchy of constants in System Verilog?

For example:

There is a board with FPGA and several peripheral ICs.
Each IC have some setting registers.
Each setting register has a number of parts.
And each part has some possible values.

Is it possible to get these values with some like this DEV.REG.PART.VAL (not a DEV_REG_PART_VAL)?

Structs are not so excellent for making this hierarchy because of names intersection.

For example, there is a USB IC and a stepper-motor IC on board. A USB IC has a register SPEED with possible values LOW, HIGH and FULL. Stepper-motor IC also has a register SPEED with values 1RPM, 10RPM and 100RPM.

I would like to use a hierarchy like folders in a file system where I can create two different folders with the same names. And it is valid for all cases except "two identical names in one parent folder" (even same names parent and child folders).


texts: If the order of any component is altered in a series circuit, will the total voltage be affected?

texts:
I recently posed this question to someone. I always thought that the answer was simply no because of Kirchhoff's voltage law... However, their response was... "no, the voltage is not altered due to the total resistance staying the same" ... does this have any merit? I guess I never thought about it that way, but I don't see why they'd be wrong in saying that. Would just like some clarification on this.

For example, if I had two sources in a series circuit that both produced 2V as well as two 5 Ohm resistors (also in series). No matter how I positioned the sources or resistors, there would always be a total of 4V produced and 4V dropped.


texts: How to experimentally measure damping in RLC circuits?

texts:
I know there are methods to theoretically determine the damping factor and quality factor in RLC circuits. Equations such as

$$\zeta = \frac{R_s}{2} \sqrt{\frac{C}{L}}$$

$$Q = \frac{1}{2\zeta}$$

Can tell me all about the damping behavior in a certain circuit, however, I would like to find damping experimentally. I have done some research and I know that I can experimentally find some factors which will help formulate a damping graph, but I would like more direct methods.

Is it possible to use an oscilloscope and probe the capacitor to see the actual ac signal?

I am open to using a wide range of methods.

Thank you in advance.


texts:
I currently make a system consisting of a plastic enclosure which contains an MCU talking to 7 ADCs using 2MHz SPI over wires about 5cm long.

The problem is that I'm concerned about EMI. Everything I have read suggests that any kind of digital signal that's not safely on a PCB in a grounded metal chassis will radiate too much to pass EMI testing. I guess this would include I2C as well.

Is this likely to fail EMI testing? What can I do about this?

I am looking for any kind of answers, including "Use a different bus / ADC", but not including answers that involve mechanical changes like: "Put all the ADCs on the same PCB" or "Put the whole thing in a metal box". I am especially interested in Low-EMI alternatives to SPI including differential buses.

Here is some relevant information about the application. Please let me know if you need to know more things:

6 wires go to each ADC board (Power, GND, CS, CLK, MOSI, MISO).
ADCs are currently MCP3208 (Microchip 8-channel, 12-bit)
I am working in a desperately space constrained application, so adding shielding to the wires isn't really an option.
It would be nice to use some kind of differential bus (one or two pairs only), but the only ADCs with differential communication seem to be multi-MSPS LVDS types.
CAN is probably too slow, and also kind of bulky for such a space constrained application.
Sample rate: I need to sample every channel at 1kHz.

Added:

Just to give an idea of the space constraints:

Here you can see one of the ADC PCBs. This one actually has an MCP3202 instead of an MCP3208, but it's compatible(ish). It's in a TSSOP 8 package. The PCB is 11mm x 13mm. The black cable is 2mm diameter. As you can see, there isn't even space for a connector and the wires are soldered directly to the PCB, then potted. The lack of connector is due to surrounding space constraints rather than PCB space constraints.


texts: Why Verilog doesn't introduce a FF for reg type variable in always@* block and why reg is allowed in combinational circuits

texts:
as far as I know, register (e.g., reg reg1) and register file (e.g., reg [3:0] reg2)

can be used in the always block whether it is a sequential (i.e., always @(posedge clk)) or combinational (i.e., always @*).

However, only when they are used in sequential always block, Flip-flops are inferred.

I think it's because register and register file in combinational always block are assigned continuously, so memory may not necessary.

However, I don't know why Verilog allows using register and register-files inside the always @* block which is a combinational circuit.

Is it because to enable RT level description such as if statement, case statement, etc in combinational logic?

The name 'reg' confuses me because its name implies the storage (FF), but it acts like a just wire inside the always @* block.

It seems that the 'reg' works as expected as a storage only inside the sequential always block.

Even though assign keyword allows a value to be assigned to a wire variable,
is there any other reason that the Verilog allows register and register files to be used inside always @* block as a wire?

To me, a register and register file are just declared as a reg type in combinational always block to be used at LHS of assignment, but act as a wire type variable.

I appreciate any help.


texts:
I've got few of these LEDs which are in a 3S3P configuration and rated 9-12V 900-1050mA.
I tried to power one of these with this module which I earlier set at 12V and 1A with a multimeter in short circuit.

The problem is that when I connect the LED in series with the multimeter, the latter tells me that is drawing less than 400mA.

So, out of curiosity and willing to fry one LED, I connected it directly to a power supply (a laptop brick, 12V 3A) and the LED doesn't draw more than 600mA.
More LEDs in parallel gives me these values:

2 LEDs: 1200mA
3 LEDs: 1600mA

I'd like to push the rated current through the LEDs (so to take them to full brightness), also is weird that seems like they're current-limiting themselves without the need of a constant-current circuit.

Does anyone have any explanation/experience with this behaviour?

Thanks


texts: Why would a current transformer act like a high pass filter, how can I estimate the low frequency cutoff?

texts: I am struggling to wrap my head around this. I understand that a transformer is not going to pass DC, and that every current transformer (CT) has some pass band. But what properties drive the high pass behavior, and how can I estimate what this corner frequency would be? I understand that it has something to do with the inductance of the primary, core material, etc. But if I know my turns ratio and core material is there some rule of thumb to estimate where the low frequency cutoff is? I read this article on CT design but I am still trying to grasp this. Perhaps if someone could draw an equivalent circuit for me showing whatever parasitic RLC components are in play.


texts: Can the power source for a USB device be different from the data source?

texts:
I was wondering if the data source (USB Host) for a USB device has to also deliver the power 5V circuit e.g. data and power need to have a common ground.

Or can I connect the data lines to the data source and have a separate power supply for the 5V line?


texts: Query regarding Electric Potential and Electric field intensity

texts:
We have a relation between Electric field(E) and potential(V) as

E = -∇V and V = -Integral (E)dl

In such case, V have to be equal to -E.D ::: V = -E.D but in most cases we use V=E.D. Why is this?


texts: Why doesn't the fan work when the LED is connected in series with it?

texts:
In this picture, I have connected a fan and an LED to a battery. The LED works when I switch the circuit ON but the fan doesn't. If I connect the fan directly, things work.
Fan not working

Fan works

What could be the reason? Is battery power the issue? To be honest, I don't think that an LED takes that much power that the fan doesn't move even a bit.


texts: MPC508AP as central IC on audio input selector board

texts:
I am working on audio preamp and for the input selector I've created following design:

Now, as you can see, I've chosen Texas Instrument's MPC508AP Analog Multiplexer for input switching IC. However, in its datasheet, I could not find channel crosstalk and other audio related operating parameters and I wanted to know, if this IC is even suitable for audio applications?


texts: Troublesome circuit with pull up resistors for smart power strip based on ESP8266

texts:
I'm making a WiFi power strip with a Wemos D1 mini v3 (ESP8266) microcontroller and a 4 mechanical relay board. 220v mains is converted to 5v 600mA using a HLK-PM01 which powers both the relay board and the ESP8266. Now I'm using 4 standard AC rated switches as a digital input each of which are wired to a 10k pull up resistor. The whole setup worked for some time (while I tested everything) and then I take it for a demo just then the ESP stops booting up (have tried with MongooseOS and Tasmota firmware) when plugged in the circuit made on the protoboard. Here are the schematics, sorry for the mess.. I'm new to Fritzing.

The microcontroller works just fine once it's disconnected from this circuit. I can't seem to understand what's wrong. Appreciate the help!


texts: Is it possible to use a 12V 3,35A power supply to power a 20V 2,5A device?

texts:
title says it all.. The device works with that power supply (adapter), but will it make any damage to the device or even worse (blow out or something like that)?

thanks


texts:
In the datasheet (like http://www.mouser.com/ds/2/149/NC7SZ125-98364.pdf), there is a spec of input leakage current ( +/- 10uA in this case).
I'm wondering about this current.
Is this current flow inside to the chip? or it can be out from the chip?
Why is there a -10uA current? Does it mean that the current may flow out of the pin?
And, if I have a pull-up or pull-down resistor at the input pin, should I consider the resistance, to avoid violating the VIH or VIL?
Say, if I have a 100K Ohm pull-down resistor, will the 10uA flow out (-10uA) and go through the resistor, and create a 1V voltage on the input pin? that might exceed the VIL of the input pin spec...

Thanks.

Add the picture of the reverse-bias leakage.


texts: Which software is used for producing those schematic sketch?

texts:
It's a while that in the internet I'm finding schematics with hand-made pencil drawing style. I've tried to search a little bit for the software used to make them but I didn't find it.

Any advice?

Here some examples:


texts: Problem making an OOK current signal using pvcvs

texts:
I am trying to make an OOK current signal using pvcvs in cadence (I tried pcccs but i couldn't find out what the settings were and it didn't work), and in order to change the output to current i used a vccs as seen in the figure below:

it works fine when i haven't yet added the vccs but as i add it, i get the error that i have a negative giga volts voltage somewhere and that my system is unstable. can someone please suggest a way to make a current OOK signal or help me with resolving the error?


texts: How mount IR gas detector sensor for outdoor use

texts:
I'm in search of a Gas detector sensor for outdoor use and I've found this sensor.
My only concern is how do I mount it for outdoor use as, on the datasheet, there's no information about the mounting.
Do you think I need to put inside some sort of enclosure or can I mount it with the head of the sensor in direct contact with the outside air?


texts: Why does the delay between bytes increase when I increase UART baud rate?

texts:
Something interesting to note, which I am not fully understanding. My UART is initialized with 9600 baud. I've looked at the TX on the line via logic analyzer, and the bytes I send have minimal delay. It is 36µs per byte, which is expected.

Now, if I initialize that UART with a different baud rate, say 115,200, the delay between each byte sent increases significantly. It jumps to 125µs per byte.

This is causing a problem, since I've got to increase my baud rate at some point, but have a time constraint on my response.

Shouldn't the delay decrease between bytes, since it should be sending more bits at the same frequency?

EDIT:

I am using an ATMega2560.

Two timing diagrams are attached below.

~9600 Baud Rate -

~115200 Baud Rate -


texts: Trying to interface with intercom / door phone system (Read 15 times)

texts:
I have a project idea where I want to interface with my intercom / door phone system. Its a proprietary system developed by SSS Siedle, and there is next to no documentation or research on how these devices work.

I have hooked the incoming wires onto my scope and found that the device likely uses a combination of analogue and digital signals for its operation.

From my understanding the system operates as a serial bus where each flat is connected to each-other, and not directly to the central unit.

When idle the bus sits at 30V. Whenever I submit a command (Unlock front door, or start audio/vide) the signal/bus/incoming lead drops to 0Vmin and creates a square wave signal with 9Vmax. Once "one" the signal returns to 30V (Slightly above 30v the first few ms).

I believe I should be able to interface quite simply with this by using an optocoupler or simply just some resistors as a voltage divider.

The problem however is the audio/video part. From my scoping this seems to be modulated into the 30V (carrier?) signal. Whenever there's video transmitted over the bus I can see a 20MHz sine wave that with about 100mV variation between Vmin and Vmax.

How would I best go forth and read this signal? I do not necessarily need to process it on the Arduino (or ESP* or similar), but I would use the Arduino (Or ESP* or similar) to intercept the signal before passing it on to a computer or wirelessly or something.

Would I need an external 200+MHz ADC (ie. an ST ADC120?) coupled together with a resistor voltage divider or some other smart voltage divider?
Is this at all feasible?

PS: Im no EE and I am likely not familiar with anything that go beyond EE basics.


texts:
I want to build timer or delay relay, so that after I remove 12V DC from it, it keeps pulling for 1 second, and then releases.

What are the components that I need to add to a 12VDC relay?


texts: How to do with a capacitor that i can't buy

texts:
I would like to buy only 4 capacitors like this:
750pF
1600VDC
500VAC
5% tolerance

I only find it on mouser but MOQ is 2'000; almost same as me !
How I can deal with that? Should I try to find 2 capaciters totalizing 750pF and wire them in parallel ?

Thank you


texts: Why my HB100's amplifying circuit can't generate more than a signal of 200 Hz?

texts:
I want to amplify the HB100's IF signal with the circuit shown below, but when I test my circuit I can't read more than 200 Hz, maximum 300 Hz. The circuit works with the OPA2365 integrated circuit at 5V. The first stage has a bandwith between 0.01 Hz and 7.23 kHz:

$$f_{inf1} = \frac{1}{2 \pi R6 C3} = 0.01 Hz$$
$$f_{sup1} = \frac{1}{2 \pi R5 C4} = 7.23 kHz$$

With a similar approach, the second stage has a bandwidth between 0.02 and 8.8 kHz. Are these calculations correct? What's wrong in the circuit?


texts:
I want to find the voltage V, the exercise suggests using Thevenin, I didn't learn it officially in class so I'm trying my best. The diode is ideal. This is the circuit:

simulate this circuit – Schematic created using CircuitLab

Since I'm trying to find V with respect to ground, this is my open circuit:

simulate this circuit

There is no current so V is 15, which is obviously wrong, I know I made a mistake, just want to know how to proceed if the voltage I want is inside parallel wires...


texts: LTSpice, plot a current–voltage characteristic

texts:
I have LTSpice on macOS.
I would like to plot in x-axis the voltage v(2) and in y-axis the current I(R1).
But, when I add traces to the plot pane, I cannot choose the axis. How can I plot the current–voltage characteristic?
In ngSpice the command is: plot (v(1)-v(2))/1000 vs v(2) xlimit -7 2. I don't know how to translate this on LTSpice.


texts: Is there a reason why we don't use higher rated voltage capacitors?

texts:
Recently purchased some components from a BOM for restoring an old tube radio, however it got me wondering about the capacitors and the voltage ratings..

Part of the order contained two 10uF electrolytic capacitors but at different ratings, one at 1000V and one at 630V (for what it's worth, the voltage I'm working with here is ~440V). Would it matter if I were to use just two 1000V ones? What are any downsides in using a higher rated capacitor than what is called for?

I also stumbled upon this in a similar question that was asked and would appreciate any help in understanding it:

My assumptions are: these are all the same ~4.7uF capacitance, just at varying voltage ratings; and a capacitor is inoperable at voltages higher than what it's rated for. So let's compare the two extremes, 0603 and 1812, at ~3V. It seems the capacitance of the 0603 is now ~2.5uF meanwhile the 1812 is still high up at ~4.7uF. This indicates (to me) what should be a noticeable change in behaviour when comparing the two in a 1-5V application. So what would it be?

I know this is pretty loaded and there's a lot of questions going on. I definitely digress here and there, please forgive me. I'd appreciate as much info at a noob-friendly level as possible. Thanks!

EDIT: Here is the post I've already read, also source of image used.


texts: Operation of LC circuit in Frequency Modulation with simulation and linking it to the basic principle of frequency modulation

texts:
Can somebody help how message signal (words spoken near microphone) is modulated using LC circuit and how lc circuit oscillates at particular frequency by applying dc voltage. In the below circuit l1 is 0.1 uH and capacitor is vc10-100 pf.

Actually in frequency modulation increase in voltage of message signal increases the frequency of carrier frequency and decrease in the voltage of message signal decreases the carrier frequency .I want that concept to be linked to the circuit.
Thanks in Advance


texts:
i've build 15w amp from TDA 2030 but currently i measure from input line to ground (measure are performed from audio jack), reaching 400 mV, my question is:

-is that normal? how i can remove it? even with decoupling cap it's still 400 mV and what is this called? Input offset votage and current?

-can i use another voltage divider in between 1 uF cap decoupling and pin 1 to the ground to remove it?

-how much current and voltage that emmited by amplifier circuit are acceptable for phone or any media player?

This is the image that i use, the red one is the first voltage divider that come default and i thought it was the source of problem?:


texts: IR Led & Phototransistor pair bandwidth issue

texts:
I'm trying to sense IR wave with a phototransistor circuit. The circuit operates well under DC operations (I mean 3.3V through inputs). However, if a square wave is supplied from UART input, after 2kHz output voltage waveform become noisy DC about 200mV. What should I consider to increase bandwidth to 100kHz (maximum)? There is 1cm space between IR & phototransistor in vertical axis. LED draws 20mA current.

Here are the datasheets:

bc848b: http://www.nxp.com/documents/data_sheet/BC848_SER.pdf

bc858b: http://www.nxp.com/documents/data_sheet/BC856_BC857_BC858.pdf

phototransistor: http://www.megasan.com/service/pdfhandler.ashx?fileid=3565

simulate this circuit – Schematic created using CircuitLab


texts: Why is there a capacitor in the feedback path of a comparator, why is there a resistor on the input?

texts:
I am interested in charging a supercapacitor from a solar panel. I saw a circuit on this page by David Johnson. He doesn't let you copy the circuit, but the gist of it is this:

simulate this circuit – Schematic created using CircuitLab

I understand most of this. The op-amp is acting as a comparator for V+ through a voltage divider, so that when V+ is 2.654V it will reach the comparator threshold of 1.2V (the LM385 is a 1.2V reference).

(2.654 * 61.9) / (75 + 61.9) = 1.2

When the input voltage exceeds 2.654V the op-amp will turn on the MOSFET which will conduct R5 to V-, thus shunting the input voltage to stop it exceeding 2.654V (by much). (The super-capacitor in this case is a 2.7V one).

I have two questions:

What is C1 for? I presume stability of the op-amp, but am not sure.
What is R2 for? That doesn't seem to be doing much. It isn't acting as a voltage divider, and the op-amp input is already high-impedance. I am guessing it is something to do with circuit stability, but am not sure. What is to stop you connecting the voltage reference directly to the non-inverting input of the op-amp? Why choose 10k and not some other value?


texts: why the D-FF does not use the clock assigned by me Quartus schematic

texts:
The schematic given above is a simplified version of a design. But this is enough to explain my problem. As you can see from the schematic, clock signal of second dff is connected to (Q0' & clk). But in simulations, D1 is not using the signal connected to the port. Instead, it clearly uses my_clk signal. I added CLK1 pin for more clear observation.

I wonder why does this happen? Also, I added the buffers at clock port with the hope of solving the problem but it didn't help. In case of someone offers to delete those buffers, it does not work. I also added more closer picture of the problematic area. I would really appreciate it if you explain me the problem here. Thanks in advance.

When I remove the AND gates it works fine. So, the problem is the AND gates but I need them in my overall design.


texts: Can I use a slightly bigger or smaller output capacitor in an audio amplifier?

texts:
I am currently working on building a basic audio amplifier with the Arduino Uno and am following a tutorial on how to do so.

This is the schematic:

(Source: arduino.cc)

The project calls for a 250 microfarad capacitor, but I only have either 220 or 330 microfarad capacitors. Will choosing either of those affect the circuit much? And in what way? Mind you, I'm also trying to learn about the functionality of a capacitor.


texts:
According to this tutorial on Exclusive-OR Gate

The logic or Boolean expression given for a logic OR gate is that for Logical Addition which is denoted by a plus sign, (+).

However, in my understanding
1 OR 1 =1
1 + 1 = 0 (1 carryover)
How come that logical OR is the same as logical addition?


texts: What voltage and current do I need to charge a 4V Acid Battery?

texts:
I need to charge a 4V Lead Acid battery, but it is not clear what charging current and voltage I need.

I checked many datasheets for 4V acid batteries, but I did not find anything that determines what voltage and current I need to charge it.

Is 2-3V and about 400mA enough to charge this? http://www.allbatteries.co.uk/media/pdf/AMP92108_FR.pdf


texts:
I have ua741cn and connected it to 10V.
V_+ =10V
V_- =GND
Just to verify I have a valid chip I did a little test.
I connected the non-inverting input to GND and the inverting to 10V I would expect the output be 0V but it was 2V.
The opposite test did give me 10V at the output so the error is only in low output.
Is there any explanation and how to fix it?
I tried to use different socket and chips but the same problem had occured
Thanks


texts: What is the voltage of a fully charged battery pack?

texts:
I bought a 24v lion battery pack (It is not this one but almost: 24v) and I wanted to know the SoC of my battery. Since I think there are 6 batteries in series, is the full charged voltage 4.2 x 6 = 25.2v? And then the discharged voltage, let's say 3 x 6 = 18 for a 4.2v full charged cell and 3v for a discharged cell? I'm not sure. I mean, I know there is all kinds of batteries but I'm not sure about the math
Also, do lion batteries need a balance charger like lipo chargers? My battery pack came with a round clable, like a laptop charger. It seems it has a circuit inside but i don't know.
Thanks for replying


texts: Cascade amplifiers with different corner frequency

texts: In these 2 cases I have the output of a non inversor circuit connected to the input of an inversor circuit. The only difference is the resistors. What I have noticed is that the cutoff frequency is different for both cases, but I dont know why, since both separate circuits have the same cutoff frequency and gain.


texts:
I have a 28V steady DC input, and I want to use it to charge 2x12V lead-acid batteries in series.

I want to use the LM723 IC to make an adjustable (26V to 28V) regulated output, as it has current limiting capabilities. So I used the Positive Switching Regulator figure from the datasheet with the recommended values for R1 and R2, but the circuit is not working neither in simulation nor reality.

Am I missing something? I checked multiple times.

Is my choice for the transistors right? I can't find 2N5005 and 2N5153 locally.

Can anyone help me please? Thanks.


texts: how to protect a dc-dc converter (LM2596) and an Arduino from Inrush current

texts:
I am fairly inexperienced with electronics so please bear with me.
I have an Arduino Nano 33 IoT being powered by a battery pack which at 100% outputs 40.2V and at 0% outputs 36.5V
Since the Max Vin Voltage the Arduino supports is 21V, I am using a LM2596 to reduce the input voltage from the battery(40V) to the Arduino(10V)

When I was testing the LM2596 I noticed some sparks came out, then when I started searching about it I figured it out that is was inrush current probably caused by the capacitors being charged? Correct me if I am wrong. Then I searched on how could I prevent my circuit  from frying up, and couple solutions came up with resistors or NTCs. But the main issue now is, which resistor to chose from(Ohm wise)? or the NTC Thermistor? What's the math and the calculations behind it?
Thanks in advance!


texts: What type of switch is this push switch [photos]?

texts:
I suspect this switch isn’t functioning correctly and would like to replace it but can’t find one similar. What sort of switch is it?

The front is a push with two states (in/out) and has a bulb to indicate on/off (though that’s not currently working). It’s probably from early 90s or late 80s.

This is a similar switch that I got a better photo of, though it has extra wires out. The switch of interest is in the background.


texts:
From The Basic Principles of Shielding:

Apertures, or holes, have SE. The SE of an aperture and ultimately the
entire electronic enclosure is determined by the size, shape and
number of the apertures. The formula is:

Where: λ = Wavelength k = 20 for a slit or 40 for a round hole L =
Longest dimension of the aperture If there is more than one hole, we
subtract from the original formula: the total number of holes within
half a wavelength.

Likewise, Analyse on shielding effectiveness of board level shielding with apertures says:

$$\mathrm{SE\ (dB)} = K \log_{10} \left (\frac{λ}{2 L} \right ) - 20 \log_{10}(n)$$
Where: n = numbers of apertures within a half wavelength

and Rule-of-Thumb for Calculating Aperture Size says "n=number of apertures within λ/2"
But what does this mean?  Number of holes in a circle with half-wavelength radius?  (When I try to calculate this way, the first part of the expression is 275 dB, while the second half is 277 dB, producing a negative SE.)  Number of holes along a line half a wavelength long?
Can you work through an example calculation for, say, a microwave oven door with triangularly-packed holes?


texts: Where do you find out how to program a specific microprocessor?

texts: I have experience with AVRs, by programming them through the SPI port, but right now I'm looking at a Holtek HT46R22 and I can't find anything about how to program this Microprocessor. My question is not about the Holtek, but in general.


texts: What Electronic Component Marking On A Circuit Board Is Designated For BF?

texts:
While looking at ESR values for capacitors on a failed Samsung refrigerator circuit board I was looking over other components for telltale signs of failure and spotted an unusual component that I thought was at first a fried diode, but the marking next to it is BF1 which I've never seen before in any circuit board I've worked on.

I've checked the resistance and I'm getting about .02 ohms no matter what the polarity side is + or - on the leads tested.

What is that component labeled BF1?  Is that a fried diode or something else?  It has a tiny hint of dark ring on the far right.  Where the leads come out of the component there seems to be distinct orange coloring on both ends.


texts: How Many EEPROM Write Cycles Left in My EEPROM

texts: I ordered some AT28C256 EEPROMs, but none of them were cleared, they all have some garbage programmed, probably from the last user. Obviously they're supposed to be clean and new. I wanted to ask, is there any way I can determine how many write cycles are left before the EEPROM becomes useless? I know they start with 100,000 writes from the factory, but can I figure out approximately how many writes I can have without knowing the history of the EEPROM's use? I wanted to decide whether I should return them or not. If they've been used a lot, I will. If they still have a long way to go, I'll avoid the effort of returning them.


texts: 2 speakers are playing at same volume from computer. One speaker volume is controlled by software but knob turned to maximum. Another speaker has volume knob set at 75%. Both are playing at same volume. Which method of controlling speaker volume consumes more power?


texts: Capacitor/resistor effect on audio signal

texts:
I have a pair of 20 years old electrostatic speakers that have an analog first order high-pass filter before the electrostatic panels, so there is a capacitor in the audio signal path. The original capacitors were electrolytic (I suppose the capacitors were about the same age as the speakers) with a capacitance of 100 uF which I replaced (by recommendation) with Mundorf MCap 250 MKP capacitors. After the switch I subjectively heard an improvement in the sound quality with a more refined upper end. I should note that I do use a calibration system with mic that should fix most big problems in the signal frequency response.

My question is if it just was an placebo effect or if there is actually some measurable quality in the capacitors that can cause the improvement in sound/signal quality? If so, what causes this and is it a consequence of the aging of the capacitors or have the type of capacitor a measurable effect on sound/signal quality (there are very expensive "high-end" capacitors sold by DIY speaker stores)? Does the same differences exist with different types of resistors that are in the signal path?


texts: What is the name of the pressed brass part in a plug socket?

texts:
I am designing a custom smart plug, and it's required to plug into a UK plug socket, and to expose a UK plug socket. For my first prototypes I dismantled timer sockets to get the brass parts, but now the project is moving towards production, I am trying to source them.

I have found places that supply the brass pins that go into the wall socket, but I can't manage to find a supplier of the folded brass sheet that forms the exposed socket. Can someone please tell me what this is called so I might have some more luck sourcing it?

Alternatively, if this core assembly can be sourced, the name for that would also be great.

I am assuming that they are such a standard part that I won't need to get them made custom.


texts:
I know that Thunderbolt 3 uses the USB Type-C port, and I know that you can plug a USB cable into a Thunderbolt port and it will function as USB or Thunderbolt depending on the peripheral.

However, if I have a USB 3.1 Gen 2 Type-C Port and I plug a Thunderbolt 3 peripheral into it, will I get the 10 Gbps from USB 3.1 Gen 2, or will I get a slower speed. Or, will it just not work at all?


texts: STM32 standard method for remote firmware update

texts:
My question is about a special case for Bootloader sequence for The Discovery kit for STM32F0 series with STM32F072RBT6 MCU that we currently have implemented in some of our products in the field.

I will use ST's own bootloader to update my firmware but I want to do this remotely which means there is no way of physically shorting the BOOT0 and BOOT1 pins as described in the user manuals to go in "BOOT" mode.

—> lets say the firmware I uploaded is not a good version, it’s buggy or I want to upload a newer version of my firmware later. My Issue here is that I have no way of going back to the ST’s ROM Bootloader to get new firmware AFTER I am running the User application. If I reset the board it will start executing instructions from the flash again and not the ROM. And I can't rely on the firmware to put me back in boot mode.

Is the only solution a custom bootloader?

If the solution is a custom bootloader, I have already implemented a dummy bootloader that I download to the sections 0 and 1 (and more if needed) of my flash. This Dummy bootloader will run first all the time on reset. All it does is that I will decide to jump to the User application code in sections 2-7 of the FLASH or to the ST’s original bootloader in system memory (ROM). It will do so by setting the Main Stack pointer(MSP) to the starting address of sections mentioned,  see code below.

void jumpToBootloader()
{
  resetAll();

  // Remap system memory to 0x00000000
  SYSCFG_MemoryRemapConfig(SYSCFG_MemoryRemap_SystemFlash);

  __set_MSP(*((uint32_t*) 0x00000000));
  ((void (*)(void)) *((uint32_t*) 0x00000004))();
}

void jumpToMainApp()
{
  resetAll();

  // Tell processor the address of the new vector table before jumping to the main app
  NVIC_SetVectorTable(NVIC_VectTab_FLASH, MAIN_APP_OFFSET);
  __set_MSP(*((uint32_t*) (0x8000000 + MAIN_APP_OFFSET)));
  ((void (*)(void)) *((uint32_t*) (0x8000004 + MAIN_APP_OFFSET)))();
}

This is good as if my firmware is corrupted I can just reset and I am good to upload new code if needed.

How is this done in the industry is there a standard 3rd party tool/lib I can use that provides the same functionality as my bootloader but it is much more stable?


texts: How can I determine the maximum possible current in a transformer?

texts:
I am curious how far can I go if I'd like to rework a small 12V/0.1A DC power supply to give higher current without changing the transformer inside it.

I understand that I have to upgrade the electronic part (a different linear voltage regulator, or maybe get rid of it completely to get maximum possible output). What I don't understand is what is the limit of the transformer? How can I find that limit? Should I expect that as a soft source under heavier load there will be a significat voltage drop and nothing bad happens? Or will the transformer under heavier load dangerously overheat? Is appropriate to put there a thermal fuse (e.g. 115°C) to protect if from that overheating? You know I don't want to buy a new transformer, I just want to try to use the existing one (without datasheet).

This question is probably more theoretical than practical, I just want to make things clear for me and not actually desperately need the new power supply. For example if I tried to push the same transformer to give .2 A instead of .1 A (two times more than originally designed), what result can I expect? Since it is made of a thin wire, I expect either it will give lower voltage and nothing else happen, or it will dangerously overheat.

I know that this question is similar to this: Finding maximum current experimentally
But I think they ain't the same, just similar. My question is aimed at transformers.


texts: how to connect multiple voltage supplies to a PCB

texts: I need to connect +/-5V and +/-12V supplies to a PCB and want to know the best way to design the connecting cable. Should I tie the GNDs together at the supplies and then bring a single ground wire to the PCB? I'm thinking about ground loops. The power cables also need to be shielded so should I just connect one end to ground at the power supply?


texts:
I cannot seem to upload sketches to my Duemilanov.

On Ubuntu, the arduino terminal displays: avrdud: stk500_recv(): programmer is not responding
On Windows: avrdude: avrdude: stk500_getsync(): not in sync: resp=0x00

Tried reburning the bootloader:

avrdude: error: could not find USB device "USBasp" with vid=0x16c0 pid=0x5dc

.

When I attempt to upload a new sketch, the Arduino RX/TX lights do not do anything. The "L" LED blinks once and that is all. While the IDE is "uploading" the new sketch, the Arduino begins running the previously loaded sketch as if completely ignoring the new data.

Sometimes the IDE will get stuck "uploading" and the TX light on the board will blink indefinitely.

When I first plug the board in to my PC, the "L" LED blinks 7 times after TX/RX blink a few times.

The most strange thing I have figured out is that if I completely unplug all of the data lines that are connected to the board it works fine. I am able to upload without a problem so long as nothing is plugged into the board (not even a 5V, GND, or digital pin).

I tried this and it works fine: http://forum.arduino.cc/index.php?topic=73748.0

Any suggestions? I was literally just using it without a problem 24 hours ago.

Arduino 1.0.5

Duemilanov


texts: NPN Transistor Analysis: How is collector current determined?

texts:
I'm trying to understand NPN transistors by reading the chapter on them in Razavi's "Fundamentals of Microelectronics", and it says that collector current (Ic) is a function of the base-emitter voltage (Vbe):

$$ I_c = I_s \cdot e^{\frac{V_{be}}{V_t}} $$

where Is and Vt are constants.

In the following section, the beta value is introduced and it states that the collector current is base current times beta:
$$ I_c = \beta \cdot I_b $$

I'm confused whether Ic is determined by Vbe or Ib (or both?) since both these values can be controlled independent of each other using a resistor.
Can you give an explanation of how terminal currents and/or voltages are determined?

Pic for reference:


texts: How to control braking circuit of the three phase voltage source inverter?

texts:
I have been developing a control software for the three phase voltage source inverter for three phase induction motor control. There is a requirement to implement regenerative braking algorithm where the kinetic energy of the drive is transformed into the electrical energy which is then disipated in a braking circuit (resistor along with transistor in series) in parallel to the dc link capacitor.

My question regards the control algorithm of the braking circuit. I am going to implement the control algorithm of the braking circuit in following manner:

Do you think that the suggested control algorithm could work? Does anybody know better approach how to control the braking circuit? Thanks in advance for any ideas.


texts: BCR402R - what is the purpose of Rext in this LED driver?

texts:
I'd like to know what is(are) the purpose(s) of Rext in the BCR402R LE driver circuit.

The BCR402R is a 20 mA constant current LED driver. The application circuit (see below) shows an external resistor Rext which isn't described in the datasheet. So two questions: 1. What is the purpose or Rext? 2. If I omit Rext, should I leave pin 4 open or connect to +Vs?

BCR402R old datasheet - Newer datasheet

(My thoughts: I expect that pin 4 is normally left unconnected, and Rext either allows to get more than 20 mA current from the driver, or it moves the heat out of the LED driver to an external resistor to get better cooling of the LED driver.)


texts:
When connecting a NIC (Intel I210-IS) to an gigabit ethernet switch with integrated PHYs (Marvell 88E6176) using the SGMII interface, I came across the following question:

Since SGMII is a serialized version of GMII, it should contain a serialized version of MDIO, right?

Can I therefore assume, that I will be able to configure the switch via the SGMII interface?


texts: New design with XC9500XL CPLDs, is it already obsolete?

texts:
I am in the middle of a new design for which a relatively small amount of logic is needed. This is a change to a previous version in which discrete 3.3V logic parts were used. We decided to go a CPLD route to gain some flexibility and upgradability of the hardware. (An FPGA is part of the design which is supported under Vivado, but a few CPLDs in the XC9500XL family are now being added for multiple purposes, including reliability.)
Looking at the CPLD alternatives from a pure hardware perspective, the XILINX XC9500XL CPLD family seemed the most adequate as it directly supports 3.3V logic, tolerates 5V on its inputs (which we do have to account for in some signals), and has a guaranteed 20yr configuration retention. We went ahead and put together a couple schematics with these parts.
But now, before we commit to a PCB, we decided to examine the software toolchain for these parts and we seem to be hitting against a few problems.

The new toolchains from XILINX do not support these parts
The most recent versions of the old toolchains from XILINX do not support these parts.
You have to go to older versions (pre-2015) that don't even run on modern operating systems.
That is, the supported ISE version can only be used via a VirtualBox virtual machine running an obsolete version of Oracle Linux 6.4 (the current version is 8.3)

Questions:

Is this path as problematic as it seems to be, or have we overlooked something?

If so, why are these devices still being sold and marketed instead of just being deemed obsolete?

Notes:

The question originally mentioned the XC9500 family which XILINX actually obsoleted in favor of the XC9500XL family, which is the one we are actually using.

A "more modern family" of XILINX CPLDs with a 1.8V core, the CoolRunner II, requires the exact same toolchain.


texts: Setting the cutoff frequency of an active bandpass filter (op amp) and finding the phase in LTSpice

texts:
I am doing an exercise and my op amp cutoff frequencies are: lower 1kHz, upper 10kHz.
I have found the phase shift of the filter, but since the graph I get does not make much sense for me I think it is wrong.
So my questions are:

How can I find the phase shift? (Or am I doing it right?)
How to 'set' the cutoff frequencies so I get the right ones?

Thanks in advance


texts:
Been working on this for a while. Circuits are not my strong point.
Power Source =5.5v dc
The first image is a 4093 NAND that another used helped me with. It changes a dual led from one color to the other and sounds the buzzer for 750ms each time the 5v touch pad is pressed.
The second image is the 5v relay and an NE555. This circuit will engage the coils relay and hold it until C1 discharges. What am I saying. You guys know this stuff. Let me get to the problem I'm having. Well it's more of a concern.
I've connected pin2 from the output of the touch pad and pin4 from the output of the gate (where it connects to the buzzer) when the touch pads trigger goes high it causes pin4 to go high. At the same time the output of the gate goes low sounding the buzzer and pin2 also goes low which triggers and starts the 555. In theory it works but my concern is that the two pins may trigger at the same time causing unpredictable results. My question is can pin4 be delayed? Perhaps with a simple resistor? I've tried to figure this out but not having any luck. I do thank you in advance for your help


texts: Maximum cable length for 3.3V UART signals

texts:
I would like to avoid using RS-232 converters between two microcontrollers on two different boards. For various reasons, only UARTs are supported, e.g. no SPI or I2C, and I will be using CAT5E cable to RJ45 jacks between the boards. The data rate will be 115200bps, possibly up to 921600bps. Ground is connected along with the UART signals.

While I currently have it working at the lengths I need it, for my own education, is there a way to estimate the maximum cable length at which this would be reliable?


texts: How do we calculate the Fourier Transform of Additive White Gaussian Noise? Since AWGN itself is random, does it mean that its Fourier transform is also random?


texts:
Where can I find an Eagle model for the TO-220F-4L package? Or something similar?

I'm trying to add a KA78RXXC-Series Voltage Regulator and I can't even find another component with the same pins.


texts:
Since this is my first question here, I hope this is on topic.

The power supply of one of our old CISCO Aironet 1231G wifi access point failed recently, after a power outage. I think that the power supply failure took something in the AP with it, because even using a known good supply I get nothing when I plug the device in.
I opened the device and I think I found the failed component, marked CR1006:

Considering the blackened pins and PCB traces, I think this is the most likely culprit.
I am a relative novice when dealing with electronics though, and I have no idea what this thing is (or rather was). My own research led me to believe that this is some kind of diode, other, more obvious, diodes are also marked as CRxxxx, but I don't see any polarity markings. Here is a second picture which show the markings better:

I found nothing about this using Google. Poking it with a multimeter gives me 285 ohms regardless of polarity.

This device is not anything that is really important anymore, and a professional repair is not economical (the AP is at least 8 years old), but I would like to try this repair anyway, as learning experience, and because I dislike throwing repairable equipment away.


texts: Digital Multimeter not working on higher frequency

texts:
I have an ordinary multi-meter which looks like the one below in the description. When i measure higher frequencies above 200kHZ the voltage is not showing up properly as it says on the frequency generator? Are this kind of multi-meters designed for DC voltage and have problem with high AC voltage?
I also have a related question i am not sensing the voltage on my tongue when it is at higher frequencies. Is the voltage really decreasing or it is not sensible it won't zap easily at higher frequencies?


texts: Do I need biasing resistors on the +/- lines for RS485?

texts:
I know I should have a terminating resistor on RS 485.

Do I need biasing resistors on the +/- lines of an RS485 differential signal?


texts: Is it safe to power a 3V 50mA device through a USB port?

texts:
I don’t know much about electronics and from what I read on an instructable it was doable. I’m basically trying to stop using AA batteries for my wireless keyboard and wondered if I could just solder a usb cable for it to get power from a port.

Edit: A lot of comments on why I don’t just get another keyboard and how I’ll just have a wired keyboard... I never use the keyboard I just needed one quickly and for a short while.


texts:
I have recently completed the Nand2Tetris 1 on Coursera which lets you create a basic computer. For a while now I have been trying to physically implement the things I learned to create a fully functional 16-bit computer. One thing I haven`t been able to figure out is how to implement a screen.

The course has told me how to write the values to be written to the screen on in a 8k Ram chip. Each register in the ram cab hold 16 bits. Each bit corresponds to a pixel. if the bit = 1 the pixel is black, if the bit is zero the pixel is white.

The firs register represents the first 16 pixels from the top right, the next register represents the next 16 bits from where the last register left off. When  line is completed, it continues to the next line. This continues until the entire screen has been filled, in which case it repeats the entire process from the top.

here on p.13 is a diagram to make it easier to understand.

I have 2 questions:

Is this how a normal screen works?
How do I write the values in the RAM onto the screen?


texts:
This connector is out of a Sega Dreamcast. I need a new wiring harness but can't find out what this plug is.

The plug is 6.54mm wide, 3.42mm high (excluding the "key" 4.08 with the key), 6.48mm deep.

I can just about make out the letters JST, but very small.  I can't get the camera to focus.


texts: Etching using Sodium Persulfate, Is my photosensitive board too old?

texts:
I am trying to etch my first PCB ever, I have used the inkjet transparency method to expose my photosensitive Bungard board and developed it using Sodium Peroxide. This part of the process seems to have gone well, I can see the traces clearly on the board in a darker shade. Because the printer I used didn't put a thick enough layer of ink on the transparencysheet there are some 'specks' in the pads and traces here and there, this is something I can fix later.

However, if you look at a photo of the board, there seems to appear some kind of grid, and the etching takes really long. I have been waiting (with short periods of agitating the board in the solution) for more than two hours now. I am keeping the solution at a temperature of 40 degrees celcius using an aquarium heater with built-in thermostat.

The boards are quite old, I have bought them 2,5 years ago but the photosensitive side has not been exposed to light, as I kept the boards facing eachother in storage.

Does this look like I am using boards that are too old? Or am I doing something else wrong (I know there are methods that are faster/more efficient, but this method should at least produce some better results as far as I know).

Edit after Dwayne Reid's answer

After tripling my exposure time to 15 minutes instead of 5 (I have a rather weak UV CCFL setup) and using two inkjet transparencies instead of one for better opacity I had better results.

When developing dark purple/brown-ish clouds rose from the board (in the solution), this did not happen previously. I did however make the developer solution twice as strong as need be (in error), so the board came out wrong in the end. But definitely an improvement over the previous batch! Maybe this can also be caused by the fact that I am using really old boards (2,5 years old), as Leon Heller stated in the comments.

The etching went alot faster this time, you could clearly see blue clouds rising from the board.

The board ended up looking like this:

After making my developer solution a little bit stronger, agitating the board with a brush while developing and heated up the etching solution to somewhere round 50 degrees celcius (just added a load of boiling water the the bain marie) I got even better results, still not great, but a lot better nonetheless.

I think the grainy traces are caused by using bad inkjet ink/transparencies, so that will be the next improvement, but that is out of the scope of this question.


texts: ATmega 328p arduino bootloader factory reset cause

texts:
I am using an ATmega328p with an Arduino Nano bootloader on a custom board.
We got recently an issue where the bootloader got reset. I need to return the bootloader and then the firmware in order to get the board working again.
At the moment I can only guess which can be the cause because I was not there when the issue appeared the first time.
Is it possible that an ESD can cause that issue? Anybody got the same issue or similar?
We have a metal shielded enclosure to the ground and standard TTL communication coming from outside with a JST 2mm connector.


texts:
I have a question about open loop gain. In the circuit below, I want to measure the open loop gain of the error op-amp. I'm curious if the Current Limiting op-amp will affect my gain.

What does it mean when they say Open loop voltage gain @ Rl = >= 10M, Change of Vo = 1v to 4v

simulate this circuit – Schematic created using CircuitLab


texts:
This is a total hardware noob question, but I really need an answer to this one:

I have 2 devices, A & B that are both self-powered. I would like to disable the +5VDC cord inside USB port, but still send data between devices through Data+ & Data- cables. Can this be done?


texts:
I got a LCD removed from some device. I need to check whether it is working. But the thing is I only have the LCD, no datasheet or any documentation regarding that.

I have an Arduino mega 2560. I'm trying to drive the LCD from that.But I don't know the pin-out. Is there some way to identify the pins ? (or somehow drive the LCD).

These are the details i can give about the LCD

It has 16 pins
There's this number printed on back side PVC160205Q (I tried to find a datasheet for the number. But couldn't find anything usefull)

Any help is appreciated. Thanks!

PS:

For better understanding, I've drawn following image. Hope that'll help. That's what you see when looking at the LCD from front.

In addition to the 16 pins, there are two other + and - pins (though, they haven't used) at the right edge, as shown


texts:
In the following diagram from a Redundant Emergency Stop (p.356 ref), there are two pairs of shielded cable.

At the (1) end, the two individual shields are grounded.
At the (3) end, after the Z symbol, appear a single overall shield grounded to the (1) end (not the (3) end), and do not show anything about the individual shields.

Note that being a redundant loop having a single cable with two pairs is not very plausible. These should be two separate pairs (at least not in a same cable)...

Should I use a double shielded twisted pair with overall shield, or two single shielded twisted pairs? In the first case, which is the sense of having a redundant link in a same cable?


texts: How to measure DC Operating Point of a simple transistor circuit

texts:
Could someone explain to me how to find the DC Operating point of this circuit? I need to find it by running a simulation and probing the circuit, not solving for it mathematically, and I'm not sure how to do that.

I know it has to do with the intersection of the DC load line and the Ib line on a Vce vs. Ic graph, but I'm not sure how to simulate that. I can plot the base current, but I don't know how to get the DC load line on the graph to find the intersection.

Thanks in advance.

simulate this circuit – Schematic created using CircuitLab


texts: Add a rechargeable LiPo to Arduino micro project

texts:
I'm somewhat confused by the various options, hoping someone can clarify which breakout board I need. I want to build a prop that drives a bunch of Neopixel sticks. It should:

have a rechargeable battery
work with an Arduino micro
be able to charge over USB when plugged in to a computer
be able to get new firmware over the same USB cable
be able to drive the LEDs directly off the battery and not just through the Arduino voltage regulator (there may be lots of them).

Am I correct that I could do all that with this LiPo battery charger?

Are there other options that would be better?


texts: Antenna's resistance: meaning and evaluation

texts:
When I studied elementary antenna's theory, I saw that the resistance (for simplicity let's consider only the resistive terms) of an antenna Ra is made of:

1) a parasitic resistance Rl, which causes antenna losses.

2) a radiation resistance Rr which is in practice the free space resistance, and it is like a load resistance if for instance we think at a transmitting antenna.

Now I have two questions:

about 2), from its definition it seems to me that the radiation resistance should depend on the space conditions (rain, humidity, temperature, presence of turbulences etc). If it is true, how can we design a correct matching network between an antenna and a transmission (since it is not a fixed value)?
how can I physically evaluate the impedance of an antenna? For instance a stylus antenna (I must connect it to a coaxial cable and so I thought that its knowledge is important to choice the correct matching network)?


texts: Why are discrete four-terminal MOSFETs so hard to find?

texts: I know that a MOSFET is a four-terminal device, but nearly every discrete MOSFET you can buy has its bulk/body/substrate internally connected to the source. Why is this? It makes it inconvenient to use in certain types of circuit, for example when breadboarding a basic IC design (for instructional purposes) in which all the body terminals are connected either to VCC or to ground. Are discrete 4-terminal MOSFETs just not that useful? Or is there some easy way to simulate them with a few 3-terminal MOSFETs?


texts:
Please see this diagram:

On the left is a fairly typical unbalanced to balanced circuit featuring 2 opamps.
The signal is then passed over a shielded twisted pair.
On the right, I want to use a transformer to both 'unbalance' the audio and to isolate it.
Is this possible?
All diagrams I've seen show transformers with a centre tapped primary used to unbalance audio,but that means I have to connect the centre tap to the ground of the left hand circuit.
This is only one channel. I want to use a cat6 cable to transmit and receive 3 isolated audio channels, o I can't use the shield as a ground for all three channels because they wouldn't be isolated.

Do I need the ground from the left hand circuit at all? Can't I just use a transformer with a single
primary and secondary? That is, not have any reference to the ground of the left hand circuit at all, in the right hand circuit?
I remember reading somewhere that connecting ground to chassis at both ends of a long run can cause noise. People suggest not connecting the cable shield to chassis at one end of the cable run. Is this nonsense?


texts: Using a microcontroller+BLE (Bluetooth Low Energy) +Servo with one battery source

texts:
I am currently working on a project where I was looking for a microcontroller that is capable of BLE (Bluetooth Low Energy) which determines a servo's position.
Using an Arduino the project works well on a breadboard.

To have a better design of the project and enhance the energy efficiency (I need to use batteries and no breadboard)
the Adafruit Trinket was recommended as once
covered within this forum (For a 'customized' arduino consuming less energy making use of Attiny85 vs PCB Fabrication?). As I read I need to use the Adafruit Trinket Pro since the normal trinket with an attiny85 microcontroller will not enable me to attach a BLE module.

Researching on Trinket Pro 5V I found out that the onboard 5V regulator can provide only 150mA output and not 800mA  unlike an Arduino Uno.
Therefore I cannot attach the servo(250mAh/4,8V/6V) on the Trinket.

Now I was planning to make use of ONE battery box (6V) and attach it on the Pro Trinket, BLE Module and Servo.
I don't see any other good solution given the requirement that I need to use only one 6V battery box.
I am aware of the risk that the if the Servo uses too much current the device will not work anymore due to the lack of energy. However I will make use of Sleep and interrupt functions to increase the lifetime of the device.

Given the fact that I require a collaboration of a microcontroller, a BLE module and a servo motor, is there a way to use them together in a beneficial/recommendable  way?? As of now I consider to attach all of them on an Adafruit Trinket Pro.
However I guess I am thinking too naively; especially considering the battery requirement.

There was a similar question but I cannout extract a useful answer for me from the answers provided there (Using adafruit Flora or Adafruit Trinket + MPU-6050 3-Axis Gyroscope + nRF24L01+ together)


texts: How big should battery be to power two strips of led for few hours?

texts:
I have an idea for halloween costume for upcoming Halloween. It will involve building two small sets of infinity mirrors. I am completely new to the electrical engineering. The infinity mirrors require any light source in between two one-way mirrors. I want to use a small LED strip for each sets.

How large battery would be needed to power two small LED strips for hours? Suppose I have a headset that already holds two AA batteries for speakers that I will never use, will those two batteries suffice or should I dig it out and use that space to hold other kind of battery?

Which is the best small/thin LED strip should I purchase to maximize brightness and minimize power consumption?

EDIT: Since that many LED strips have their LEDS spaced too wide on the strips. (Many offer 6 ft of LED strip, I only need like 1 foot but the same amount of LEDs crammed in it.) I decided to use electroluminescent light (EL) instead. Will that change the equation of energy consumption a lot?


texts: why does a step up transformer cause lower currents?

texts: The usual answer I hear is because power needs to be conserved, but I dont find that answer satisfying. Normally if I were to double a supply voltage in a circuit, then I would expect twice the current (assuming its a linear circuit). But if i have a 2x transformer (which AFAIK is made of inductors which are linear elements), then the output of the transformer will have twice the voltage and half the current. What exactly is going on electromagnetically that allows a transformer to violate ohms law and give lower currents with higher voltage?


texts: A question about the current value in a mains tester

texts:
After reading this question, I simulated the tester as in the below circuit along with the current passing through human body:

Even I set the R_tester to  zero, the current still will be around 10μA which is too small for a neon bulb. This is due to the Xc being huge because of tiny human body capacitance.

The only way the current to become 0.5mA is to increase the capacitance to around at least 5nF.

But the references say that the human body capacitance is around 100pF in series with 1.5k resistor.

According to these assumptions it seems something is not quite true here.

What could be the problem with the model I've drawn above?


texts:
I am working on a SMPS and wanted to size a varistor at the input to protect the rectifier against transient overvoltage (let's say a 1 ms surge).
However, by looking at datasheets the maximum clamping voltage is always related to a transient current value (because of the maximum energy that can be handled by the varistor).
How can I estimate the transient current value for a given transient voltage (stated by standards for surge tests) ? Is it only related to the line resistance ?
Thanks!


texts: Transfer function of high pass filter via impulse response function

texts:
I'm having a hard time computing the transfer function of a high pass RC filter, by taking the Fourier transform of its impulse response function:

$$
H(\omega)=\int_{-\infty}^{\infty} h(t)e^{-i\omega t}\ = \frac{-1}{1+i\omega RC},
$$
which is the transfer function corresponding to a low pass transfer function.

I obtained its impulse response function by taking the derivative of its step response function $$h(t) = \frac{d}{dt} e^{-t/RC} = \frac{-1}{RC} e^{-t/RC}\ .$$

The step function $$s(t) = e^{-t/RC}$$ is derived by solving the differential equation resulting from equating the expressions for the current through the resistor and capacitor, respectively.


texts: Signal drawing based on a constellation diagram

texts:
Constellation diagram of a communication system is given.

S1(t) -> 0, S2(t) -> 1

Φ1 and Φ2 are basis functions and Tb is the bit period.

How can I draw S1(t),S2(t) and decision boundaries?


texts: Why does my Current Regulative Diode not regulate current well?

texts:
I recently ordered several E153 CRDs from Semitec (data sheet here) to maintain a steady current to an LED (data sheet here). Mistakenly, I didn't read the "Dynamic Characteristics" portion of the data sheet before ordering which seems to suggest the E153 doesn't line regulate very well, with current peaking at 10Vin and dropping off thereafter. The "Basic characteristics" graph however gave me the impression that any Vin above 10V would maintain a steady pinch-off current.

My questions is, is this expected behavior of a CRD or is the E153 just bad? Can I still use them as a constant current source for my LED?

For my purposes I need to use a 9V power source which droops by at most 0.5V under the heaviest load we require. Temperature will range from 25C to 30C worst case. The consistency of LED brightness is crucial for its purpose; we need the LED to maintain +-0.1mA of current. We bin our LEDs to ensure they all output the same brightness at a specific current.

Sorry for the basic question, and thank you!


texts: I'm confused a bit on basic control stuff for a PID controller

texts:
I'm doing a PID controller demonstration project in which heat is applied to a K type thermocouple and I'm supposed to maintain the temperature read at 50 °C using a PWM signal. I know the basic control materials, but since this is the first time I'm supposed control an actual physical system I'm a bit overwhelmed. Can you please correct me if I'm misunderstanding something here?
The main components are: Arduino used as a controller, Nichrome wire as the heating element, a K type thermocouple and a 12 V source. I send a PWM signal to a MOSFET to switch on/off the 12 V across the nichrome wire. My step input is the 12 V(?), my system is an open loop when I manually turn off the power at 50 °C(?) and it is closed loop when I for example say if temperature > 50 °C, switch off the MOSFET(?).
This is my open-loop response:

Where I switched off manually. In the other one, the sensor output is used to turn off the MOSFET by a simple if (temperature > 50 °C) and these are the closed-loop responses:

And finally the last is where I added a proportional controller instead of on/off and this is the response:

Now I think I can add I and D to my controller just by trial and error, but I want to take a more simulation based approach. But I don't have a transfer function model of this system to do any simulation on it in MATLAB. I know how to model one if I have a stable closed loop response, but mine never reaches a steady state. Only the one with the P controller is stable. I'm so confused...


texts: What is the best approach to calculate the transfer function of this RC circuit?

texts: I want to calculate the transfer function of the circuit below. I tried to calculate the equivalent impedance of each block and work my way with voltage dividers until I get to V3, but this method is very long and I wonder if there is better way.


texts:
I'm relatively new to antennas. In most of the textbooks, it is said that we want to minimize standing waves in the transmission lines by matching the characteristic impedance of the line with the antenna's impedance.

My confusion is regarding the following two questions:

If the antenna and the line are perfectly matched there are no standing waves in the line?
If so, what happens to these traveling waves once they reach the end of the dipole antennas. Most pictures show that there are actually standing waves on two sides of the dipole. It is clearly seen here that there are standing waves:

Image source: "Animation showing the sinusoidal standing waves of voltage, V (red) and current, I (blue) on a half-wave dipole driven by an AC voltage at its resonant frequency" from Dipole characteristics on Wikipedia, Dipole antenna

Does it mean that standing waves occur in line as well?

PS. An excerpt from C. Balanis book on antennas third edition page 18, which clearly says that there are standing waves in the dipole antenna.


texts:
Question is Determine total power in the circuit and determine if the indicated power rating of each resistor is sufficient
to handle the actual power delivered to it in the circuit. If the rating of the resistor is not adequate, specify
the minimum required rating

Now what i did is i found current and than i found the actuall power in circuit which was less than total power on question.So i than found the actuall power required on each resistor
Now i dont think i did it right.Can anyone help me with it?


texts: Replicating Lidar lite what emitter to use?

texts: So, I am not advocating or trying to copy or in any way infringe on the copyright that Lidar lite is based on. That being said I would like to use something like lidar lite for a distance sensing project (Basically an rc self driving). Now I haven't found any sensors that really are in my price range, less than 100 dollars, so I was thinking I could maybe home brew together something that is at least partially functional. But Lidar lite is no longer available and there isn't really a lot of info on how to do something like that. What research can I look into to make something like it. I have been experimenting with some ir emitters and receivers but haven't had any really good results. I also know that frequency modulation is a good idea since it will give the lidar a unique signature. But past that I am not really sure what to build. Is this way out of the realm of possibility or can it be done? My main question is what IR emitter to use in order to determine the distance of an object at least 40 metres away outside.


texts: Verilog - how to overcome the fact that I cannot mixed edge and level triggers,writing to memory

texts:
I have a 32x32 ram module which i built, the simple code:

Verilog Code

module RAM32X32(
    input clk,
    input rst,
    input WE,
    input [4:0] ADDRESS,
    input [31:0] D_IN,
    output  [31:0] D_OUT
    );
//////internal////////////////
reg [31:0] mem [31:0];//,r;
wire [31:0] data ;
integer i;
/////////////////////////////

initial begin
  for (i = 0; i < 32; i = i +1) begin
      mem[i] = 32'b0;
  end
end
assign data = WE ? D_IN : 32'bz;

always @ (posedge clk) begin
    if  (WE == 1'b1) begin
        mem[ADDRESS] = data;
    end
end
assign D_OUT = mem[ADDRESS];
endmodule

now I see that when I writing to the ram, It takes time, and in the simulation I see the memory changes just the CC after, as seen below (R31 is in the last row, there i want to write):

So i changes my sensitivity list and added:

(posedge clk or data)

And I got what I wanted in the simulation.
But....synthasize didnt allowed it because of :

  No support for synthesis of mixed edge and level triggers.

So i thought of doing a level triggered ram with tri-state to protect him.
What do you think? is it even legit to use level triggered this days?
Any help will be helpful!

Thanks!!


texts: Which tools do you use to analyze waveform data from simulation or logic analyzer traces?

texts:
I need to save Xilinx ChipScope waveforms for later review/analysis with my co-workers.

Wikipedia provided a handy list of waveform tools but I am looking for user feedback on some of the strengths and weaknesses of specific tools.

To date, I have used the ChipScope export as VCD option along with the VCD->WLF conversion tools built into ModelSim for this purpose. Currenty my needs are:

Store waveform data for later inspection and analysis of control signal logic
Compare/diff waveforms to identify differences between working and failing cases
Plot amplitude data over time
Plot one datum against another (e.g. constellation plot)
Use as input to ModelSim simulation

For context, my role is that of an embedded software developer working with the FPGA team at my company and I often find it helpful to look over waveforms I capture during a debug session with a coworker who worked on the module in question, especially when I believe it can be nailed down to a specific HW/SW interface. In such cases I want to capture and save off the waveforms when I do not have the right person at hand. It is also helpful for me to work through control signal logic on my own to identify possible issues.

I have started to use ModelSim for this analysis and review purpose and would be interested in alternatives and industry standard tools for this use case. We are a Xilinx shop with some smattering of Synopsys and MentorGraphics tools.


texts: low-cost idea for Identifying passive tags by inductive coupling/pulses

texts:
Hi electronics experts,

I want to build a circuit that can identify few (4-10) tags wirelessly by proximity. No need for multiple simultaneous detection. I don't need any memory on the tags - just a simple ID - a number from 1..10 would suffice. I have a simple micro controller on board.

The circuit should be as low cost as possible, small, and run on simple AA/AAA batteries. Standard RFID reader/tags solution is not what I need here.

Case study:

I've found a similar system in a low cost plastic toy for children.
Before I dismantled (and beheaded) the product it was a "barby-style" doll which identifies when you place one of its (plastic) pet animals near it and responded with a unique speech sound for each animal. The set had a total of 3 animals.

The doll contains a circuit connected to a custom wire-wound antenna, few hundreds turns I guess and air core. It got damaged unfortunately during the dismantling process.
I checked the waveforms going to the antenna (no load) - attaching the osc screen captures
basically a ~330us (3KHz) negative pulse every couple of ms (inbetween two 1.8ms positive pulses)
The tags insides the pet dolls contain a tiny single layer PCB with just a through-hole inductor (didn't measure inductance) and two capacitors all connected in parallel. It was obvious that the coil values in each tag are different. Don't have a disponsible LC meter to check values right now.. I guess the identification is performed by reading back the effect from the variable L/C values on the tags.

The main IC on the toy was epoxy encapsulated so I can tell what it is.
I understand that this circuit works by transmitting pulses periodically and reception & measurement of the response which varies by the tag inductance/capacitance. but

How does exactly does this system work?

more elaborately:
Please help me understand how this system works, what and how to measure, how to build a similar one, or point me in the right direction. What is the max number of tags it can identify in this scheme, how to calculate all parameters, etc
which ICs/components should I look at.

tag:

simulate this circuit – Schematic created using CircuitLab

Basic controller schematic:

simulate this circuit

The main PCB and the antenna are shown here:
Main PCB

Main Antenna (was connected to the yellow-green wires)

Measure diameter/air-core:

The tags:
(top left one coil's was broken off in the process)

Osc screenshots:

zoomed out:

Many thanks!!


texts: Circuit that can replace the ideal current source in the two stage amp

texts:
I want to find a circuit that can replace the ideal current source in the two stage amp,my classmate said that i can use the bandgap to replace it,but i want to make sure of it,doesn't bandgap provide a stable voltage?why can it be a current source?so can anyone give me a suggestion?

I also find a circuit from here:

Replacing Ideal current source in two-stage opamp

but honestly,i don't know how to calculate it,so i can't use it to replace the ideal current source


texts:
I am considering the mcp390Xa series for a energy meter project.  What I am not understanding here is where the voltage part of the watt calculation is happening.  Is this up to the micro to measure voltage and apply it to the output pulses?  When used it a non micro situation, is it assumed to be 115v, or whatever may be expected in that local?

Supposing I use a decent micro, say a pic32, are there any advantages to rolling my own setup using something like an mcp3911?

See reference design


texts:
Am I getting motors correct?
I'm building a third party psu for a slot car race track.
Obviously easy bit is transforming 240Vac down to 12Vdc.
But I am unsure how thiswill react with my motor. THe motor is rated as 12Vdc at 0.42A. Am I correct in thinking that if the motor is corrected in series with rheostat (as thus to adjust the Volts suppled to the motor) it will slow down? Or will it for some reason decide to take even more than 0.42A

CHeeers
Motor in question    http://www.pendleslotracing.co.uk/scaleauto-short-can-motor-30000rpm-sc-0005.html

Also, the main issue. I've got two tracks which essentially act as uninsulated wires. On each loop the respective Rheostat will of course cause a Volt drop and therefore less p=iv into the M1. But conservation of enerhgy,that v drop will now of course go into M2. How can I make it so that the motors are independentanly speed controlled? I've heard of pwm or something but that is out of bounds.

Please help oh mighty ones


texts: Why is the resistance of the circuits input voltage not taken into account when calculating overall resistance of the circuit?

texts:
When calculating the resistance in a circuit, one uses Ohm's Law i.e. V = IR with resistors in the circuit.

But why is the resistance of the inputs not taken into account?

For example, if one has a 9V battery with 2 x resistors of 10 ohms each, we can calculate that I = .45 amps.  But why is the resistance across the terminals of the battery e.g. 50 M ohms not taken into account in the calculation?

And if it is ever taken into account, under what circumstances?

For that matter, does one take into account the resistance across other components such as capacitors, inductors, op amps, etc?


texts: Opamp Misbehaving in Constant Current Source Circuit

texts:
I'm planning to build a current regulator for a power supply and I'm prototyping a number of different regulator circuits.  First up, the op amp and transistor circuit shown below.

I felt I understood the principle well enough: negative feedback resulting in the opamp regulating the transistor in order to equalize its inputs to some given reference voltage.  So, I pulled out whatever bits and bobs I had in the box and put the circuit together.  I was aiming for a current limit of about 100mA and I wanted to keep the voltage drop across Rsense low.  I had some low ohmic resistors from another project, so I used a .010 ohm resistor as the sense.  Calculating the reference voltage to achieve 100mA gave me 1mV (100mA x .01R).  The voltage divider shown on the left in the schematic below produces 1mV at the non-inverting pin.  So far, so good... but then... many, many hours later and a lot of contemplation and confusion, I still don't understand it.

As you can see from the schematic below, the notes are the actual measurements taken using a dvm.

The opamp inputs are refusing to equalize.  What's more, the opamp seems to be driving the transistor hard into saturation, the current almost completely owing to the 22 ohm (7W) load resistance. It's almost like the opamp is using positive feedback, rather than negative feedback.  But, why so? The inverting pin is clearly reading 3mV.  I'm stumped! Any help greatly appreciated.


texts: How do we calculate the charging time of a Li-ion or a Li-Po battery if we used a fast charger?

texts:
Consider a rechargeable 7.4V 5000mAh Li-ion/Li-Po battery.
If we were to fast charge this battery what would be the charging time?
Although it is known that the general equation for charging time is:
Charging time = Battery Capacity(Ah)/Applied Current(A)
How could we be sure as the fast charging of Li-ion/Li-Po battery happens in stages(CC-CV).
It is also known that in fast charging the battery will be fast charged until a certain percentage of the total Battery capacity(Ah).
And then the charging rate decreases eventually.
Any charger capable of delivering an output power of 10W or more can be considered as a fast charger.
So wouldn't the general equation given above fall short when we consider fast chargers? If no, how? And if yes, what should be the new equation or set of equations?


texts: Programmer gives me an error in programming a big hex file

texts:
I want to download a program into an Atmega128. the programmer which I am using is this ( jamshad ISP -USB ZIF_Socket_Programmer_V5 ).

The Programmer work correctly for programming one small length hex code but when I want to program a big hex file ( which is tested by Proteus ), The programmer gives me an error and cannot programming the big hex file into the IC.

( I used ISP Connection and i am sure it's connection is correct because i could program micro by a small code and seeing the result on the LCD, but for big hex files the programmer suddenly got an error with several declaration and My PC hanging  Like This:)

You can get the hex file and Proteus simulator files from this link:

http://filepi.com/i/9zF33M4

Thanks a lot


texts: Why are core losses mechanical and not electrical in an AC power flow diagram?

texts: The power flow diagram of a generator (a) and a motor (b) are shown. But why are core losses mechanical losses?


texts: How can I break the loop and test the loop gain for a capacitive opamp?

texts:
Here is an opamp with a capacitive feedback network

I have tried two methods to break the loop and obtain the frequency response for the loop.
Method 1
Use a large inductor to break the loop at high frequencies and a large cap to provide the AC input at high frequencies. Test signal is applied at Vt and the response is obtained at Vr.
Schematic

The frequency response is "wierd"

Method 2
Remove the large cap
Schematic

The frequency response looks "normal"

So which of the above methods is a correct way to break the loop? If both are wrong, what is the right method to do so?
Thanks.


texts:
I have a DPDT relay and I would like to create a H-bridge.

How do I implement a H-bridge with a DPDT relay?


texts: How can I view a song from my iPhone jack on an oscilloscope?

texts:
I was wondering how to view a song from my Iphone on an oscilloscope. I tried doing it today but got mixed results.

I set the horizontal sweep to 1ms/div, the vertical to 1 volt/div and the coupling to AC but I don't know if what I was looking at was correct. I should have taken a picture so I will do that tomorrow.

The impedance of my oscilloscope can be set to either 50 Ohms or 1 MOhm but isn't the impedance of headphones that my iPhone would drive drastically different than this? Would this affect the results?


texts: Do I need a protection diode to prevent reverse current flow into a voltage regulator?

texts:
I have a 78L series voltage regulator that is used when a power supply is connected. When the power supply is absent, battery power is used. The battery will skip over the voltage regulator. The battery positive supplies power to the circuit at the same point as the voltage regulator output.

Do I need a reverse protection diode on the voltage regulator output to prevent damage to it when battery power is active and the regulator is not providing the power?

simulate this circuit – Schematic created using CircuitLab


texts: Non inverted OpAmp & Shunt circuit not working

texts:
I am trying to measure the output from a Hall effect sensor (LEM-LF 310-S) for a welding application.

The maximum output of the sensor is 0-0.25A when sensing 0-500A. This range I need to convert to 0-1V for my measurement equipment (Oscilloscope for testing, later RedPitaya).

So I am using a Shunt with 100mOhm which should give me an output voltage of U=R*I=0.1Ohm*0.25A =0.025V.

This voltage I wanted to amplify with a non-inverted OpAmp (MCP6292) to get 1V as Output-Voltage -> Amplify with a ratio of 40 (a=32.04dB). According to an online calculator 100Ohm & 3.9kOhm are sufficient for the required amplification.
The used OpAmp is a dual OpAmp where I just use one of the two.

The supply Voltage of my Sensor is +-15V DC and the supply voltage of my OP-AMP is +5V DC.

I tried to read 0-1V as output with the following circuit but I am receiving nothing but noise:

What I tried already:

Measuring the Hall-Sensor output directly with a 4Ohm measuring resistance -> as expected
Checked wiring with multimeter
Measured output of DC-DC Converter (15V to 5V) = Supply Voltage for OpAmp -> Output voltage is 5.6V
(Should be ok according to OpAmps datasheet?)
Measured resistance of Resistors and Shunt -> as expected

I also thought about adding a capacitor of 100nF to the OpAmps PowerSupply, but I think this is not the problem here?

Hope someone can help me figure out the problem.


texts: What circuit symbol is this? I know its a diode, but the part number leads nowhere

texts: I cant seem to find what type of schottky diode this symbol is representing. The part number listed on this reference schematic leads nowhere. If you could give me an example PN it would be greatly appreciated.


texts: Changing potentiometer from a gaming steering wheel

texts:
I have Logitech's vibration feedback wheel which has a rotation of 270 degrees. I am considering changing its potentiometer so it can rotate more (900 degrees or 1000 degrees maybe).

What potentiometer should I choose for this task? Apart from its Ohm resistance what other parameters should I keep in mind?

THank you


texts: What does a symbol with an arrow pointing to the upper right mean?

texts:
Full Circuit Below

I looked through multiple sites that includes a lot of different symbols and I have no idea what this is.


texts:
I designed a simple buck converter to meet the following specs (I have attached the schematic):

Vin = 17.4V
Vout = 12V
D = 0.69
Switching Frequency = 50kHz
Inductor Ripple Current = 20% of Output Current
Output Voltage Ripple = 2% of Vout

Background Info: All the parts and component values listed on the schematic are parts I'm implementing in the circuit. I know the inductor and capacitor values are not matched perfectly to the specs listed above, but they are the closest that I could find. The PWM signal is being generated by the Arduino Uno and I am using the TC4427 IC to drive the signal at the gate of my MOSFET.

Problem:My MOSFET is not turning on. I know for it to turn on Vgs > Vth. I am using the TC4427, because the max output voltage of the Arduino is only 5V. What I'm confused about is why my gate driver isn't supplying the necessary turn on voltage. I thought I understood how it works, but not apparently. The max output of the TC4427 is only as high as the supply voltage I feed into it (from measurements I've taken), which doesn't make sense to me. I've looked on the TC4427 datasheet, but it doesn't give me any information on the max voltage output coming from the gate driver. Does this mean I need to supply an input volts higher than V1 to the supply just to turn on my MOSFET? Or how exactly is a gate driver supposed to work?

simulate this circuit – Schematic created using CircuitLab


texts: Routing traces over traces in two layer pcb

texts:
I am kind of new to PCB Design. I have a few confusions on my board layout, in order to reduce EMI in routing. I am designing a two-layer PCB design

I am aware that when you route traces over different layer and if they cross each other, coupling occurs between the cross-sectional area where the two traces meet as they create a parasitic capacitance. But if it definitely has to cross, then it has to cross at 90 degrees. My question is: Is this applicable for all kind of traces where a power trace crosses an analog or digital trace?
Since the power trace has the lowest impedance because of its wider trace, is it possible to crossover two power traces on different layers?
How wide should be the trace length, if I am taking it all over the board for a star connection (as daisy chaining is a bad practice)?
Is it correct to add decoupling capacitors on the cross-sectional area over the weaker trace?

I am working with low power circuits, where the voltage is 3.3V and the microcontroller runs at 8 MHz, a 1 MHz buck-boost with a couple of analog and digital sensors. I have also made sure that the analog and digital ground are separated and directly meet at the origin (i.e. a battery).

Also, is there any signal integrity simulation software available as open source?

Any suggestions and tips apart from this are also welcome. Thank you.


texts:
Problem:
We design a PCB with an JTAG compatible FPGA that I need to program.
Now I want to be able to access the JTAG Interface from either a connector (_A) or an FT2232H USB controller (_B).
The main interface would be FTDI Device while the connector should act as Backup if progamming from FTDI fails for some reason.
Question:
What is a proper way to split the signals between the connector and the USB Chip ? Or do i need to split them at all ?
I have 2 ideas so far. Maybe someone has a better idea for this ?
IDEA 1

Will this add noise or any significant quality loss to the signals ?
IDEA 2

Looks like an elegant way to do it. My only concern is that the MUX will pull the signals that are not connected to ground via 6M Ohm internal pull down resistors (from Datasheet of the Mux). Does this affects the FTDI chip in any way ?
Thanks in advance


texts: How to find out the heated IC's or CMOS in a circuit automatically. Because its very hard to find the heated IC's by touching each and everything. ca anyone suggest me any method to find it out?


texts: Stripping USB Cable - What to do with shielding?

texts:
I'm new to electronics so please bear with me.

I'm stripping a USB cable that I want to connect to another component - a 5V fan for example.

On the side pictured, i'm connecting up to a 5V fan. And on the other side is a regular USB connector which will plug in to a 5V DC power supply.

After stripping, I have noticed there is a outer wire running along the cable. On the left of the picture:

From my searching i've found this is a shielding wire. Is this correct?
In the case where i'm not looking to shield and only provide power supply (not even use the data wires) what should I do with this extra wiring of the shield? I have heard that shield should be grounded. So should I:

Combine shield and ground wire
Ground shield wire separately
Leave shield wire floating


texts:
I would like to know how to drive this little e-Ink display. The company supplies a demo kit and a sort of "adaptor circuit" (basically a breakout board with a few capacitors, which allows one to use the same demo kit with several displays).

The question is, if I want to incorporate such a display into my own design, how do I go about doing it? Because I don't see an MCU anywhere on the display. So do I have to buy any driver, or is it there any MCU on the chip I don't see?

Thanks!


texts: How close should the diode be to a solenoid?

texts:
When using a diode to deal with the back EMF from a solenoid, common advice is to put the diode as close to the solenoid as possible.  Indeed, in pinball machines, I've seen diodes soldered directly to the solenoid's contacts.
I've got a solenoid valve that's sealed (IP 65).  Instead of contacts, it comes with wire leads that at are each about 15 inches (almost 40 cm) long.  I assume the diode should be closer to the solenoid, and that I should cut the leads much shorter.  Is that correct?  Or does the distance not matter as long as the diode is closer than the switching circuit that drives it?
Is there a reason solenoids aren't manufactured with snubber diodes built in?  It seems the solenoid itself generally dictates the diode selection (at least for low-frequency activation that you would expect from valves).
(I've found answers to related questions, but not one that directly addresses the distance issue, especially when the solenoid comes with long leads.)